Moisture meters measure the moisture content in bulk solids, liquids and gases. Some devices use infrared (IR), radio frequency (RF), or microwave techniques to evaporate water from a sample. Others determine moisture content by measuring a material’s conductance, resistance, or capacitance and calculating a corresponding moisture value. Variables measured include relative humidity, absolute humidity, specific humidity, and dew point. Relative humidity is a measure of the amount of water in the air compared with the amount of water the air can hold at a measured temperature. By contrast, absolute humidity is the mass of water vapor in a given volume of air. Specific humidity is the absolute humidity divided by the total mass of the given volume of air. Dew point is a measure of the temperature to which air needs to be cooled in order for saturation to occur. Moisture meters that measure pressure and temperature are commonly available. These specialized devices often include special circuitry or additional probes.
There are several form factors for moisture meters. Many require a secondary device or instrument for data acquisition or the transmission of humidity information. Integrated circuit (IC) chips mount on printed circuit boards (PCB). Benchtop or floor-standing moisture meters include a full casing or cabinet and an integral interface. Handheld units include an integral probe and are designed to be operated while held in one hand. Gauges mount on walls, well, racks, or DIN rails and include an integral display. Both analog and digital devices are available; however, simple light emitting diode (LED) power indicators are not considered to be a display. Video display terminal (VDT) styles include cathode ray tube (CRT) monitors and flat panel display (FPD). Mounted transmitters do not include a display, but provide an integral sensor or probe.
Selecting moisture meters requires an analysis of performance specifications and output options. Humidity range and dew point range are usually expressed as linear outputs. Humidity accuracy and dew point accuracy measure the closeness of a measured or computed value to its true value. Analog current outputs include variable levels such as 0 – 20 mA or 4 – 2 mA. Common analog voltage outputs are 0 – 10 V and ±5 V. Moisture meters with frequency or pulse outputs use amplitude modulation (AM), frequency modulation (FM) or pulse width modulation (PWM). With switch-type outputs, contacts are open or closed depending on the state of the variable being monitored
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Experienced Instrumentation Engineer shares technical information and tips to be used by Instrumentation Professionals, Students and Educators.
Tuesday, December 21, 2010
Notes on EMF Testers.
EMF meters detect and monitor harmful electric, magnetic or electromagnetic fields surrounding personal or work areas. Electromagnetic fields (EMF) are invisible lines of force produced by the voltage and current which surround electrical wires or devices. These physical fields consist of two components: the electric field, which is the result of the voltage; and the magnetic field, which is the result of the current flow. One of the most common places for EMFs is near power lines; however, EMFs may also occur near electrical appliances and office equipment. In terms of human health and safety, some research indicates that elevated levels of extremely low-frequency (ELF) EMFs may cause cancer and leukemia. Consequently, electrical workers and other maintenance personnel may use EMF meters before entering a job site.
EMF meters can combine magnetic, electric and radio frequency (RF) or microwave detection in a single package. Handheld devices vary in terms of measurement speed and cost, but are reliable instruments for detecting electromagnetic pollution. Specifications for EMF meters include measurement range, frequency bandwidth, percent accuracy, sampling rate, minimum resolution, number of axes, weight, dimensions, power requirements, and operating temperature. There are two measurement ranges for EMF meters: milliGaus (mG) and micro Tesla (microT). Most Gaussmeters have a measuring of range of 0.1 to 199.9 mG . Most Tesla meters have a range of 0.01 to 19.99 microT. Choices for frequency bandwidth include 30 to 300 Hz, 1 to 200 kHz, and 11 Hz at 3 db. Typically, percent accuracy is measured at 50/60 Hz.
EMF meters vary in terms of features and applications. Some products have audible, adjustable alarms that sound when an electromagnetic field is encountered. Others provide datalogging capabilities with a date/time stamp for field use. Devices that have an RS-232 or universal serial bus (USB) interface are also commonly available. In terms of applications, EMF meters can be used to identify AC magnetic fields, AC electric fields, and RF radiation. Specialized EMF meters can detect hidden sources of extremely low-frequency (ELF) radiation from computers, kitchen appliances, television sets, vacuum cleaners, electric can openers, hair dryers, and power tools. Magnetometers are used to measure the direction and/or intensity of magnetic fields.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
EMF meters can combine magnetic, electric and radio frequency (RF) or microwave detection in a single package. Handheld devices vary in terms of measurement speed and cost, but are reliable instruments for detecting electromagnetic pollution. Specifications for EMF meters include measurement range, frequency bandwidth, percent accuracy, sampling rate, minimum resolution, number of axes, weight, dimensions, power requirements, and operating temperature. There are two measurement ranges for EMF meters: milliGaus (mG) and micro Tesla (microT). Most Gaussmeters have a measuring of range of 0.1 to 199.9 mG . Most Tesla meters have a range of 0.01 to 19.99 microT. Choices for frequency bandwidth include 30 to 300 Hz, 1 to 200 kHz, and 11 Hz at 3 db. Typically, percent accuracy is measured at 50/60 Hz.
EMF meters vary in terms of features and applications. Some products have audible, adjustable alarms that sound when an electromagnetic field is encountered. Others provide datalogging capabilities with a date/time stamp for field use. Devices that have an RS-232 or universal serial bus (USB) interface are also commonly available. In terms of applications, EMF meters can be used to identify AC magnetic fields, AC electric fields, and RF radiation. Specialized EMF meters can detect hidden sources of extremely low-frequency (ELF) radiation from computers, kitchen appliances, television sets, vacuum cleaners, electric can openers, hair dryers, and power tools. Magnetometers are used to measure the direction and/or intensity of magnetic fields.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Conductivity Meters.
Notes on Conductivity Meters.
Conductivity meters, Total Dissolved Solids (TDS) meters and resistivity meters are analytical instruments that measure the conductivity, dissolved solids, and/or resistivity of a liquid sample. They can measure a single variable, a combination of variables, or all three variables. Often, because these variables are related, combination conductivity meters, dissolved solids meters and resistivity meters used. Conductivity, a measure of water’s ability to transmit electrical current, is a gross, indirect measurement of the concentration of ions. Consequently, conductivity can be used to estimate levels of total dissolved solids (TDS), a measurement of the dry mass of dissolved solids in water. As a rule, most of the colloidal particles are included in a TDS measurement. Resistivity, another related variable, is the reciprocal of conductivity.
Specifications for conductivity meters, dissolved solids meters and resistivity meters include conductivity range, dissolved solids range, and resistivity range; conductivity accuracy, dissolved solids accuracy, and resistivity accuracy; and process media temperature. Portable, hand held, modular, lab, benchtop, field-use, and panel-mounted instruments are commonly available. These instruments have an analog meter, a digital display, or a video display such as cathode ray tube (CRT), liquid-crystal display (LCD), or flat panel display (FPD). Often, conductivity meters, dissolved meters and resistivity meters with manual controls have knobs or potentiometers. Analytical instruments with a digital front panel are programmed with a keypad. Programmable conductivity meters, dissolved solids meters and resistivity meters are also available.
Conductivity meters, dissolved solids meters and resistivity meters provide electrical outputs such as analog voltages, analog currents, and analog frequencies. Devices with a switch or alarm-relay output are also available. In terms of features, some conductivity meters, dissolved solids meters and resistivity meters are battery-powered, temperature compensated, event triggered, or designed for extreme environments. Others have filters, built-in or self-calibration, or self-test capabilities. Conductivity meters, dissolved solids meters, and resistivity meters with that provide special signal processing and/or filtering are also available. Often, these analytical instruments use Butterworth or Bessel filters. Butterworth filters provide a very flat response. There is almost no attenuation in the passband, and the roll-off rate is somewhat slower than other filters. Bessel filters have a relatively flat passband and slow roll-off.
Notes on TDS
Total Dissolved Solids (TDS) are the total amount of mobile charged ions, including minerals, salts or metals dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm). TDS is directly related to the purity of water and the quality of water purification systems and affects everything that consumes, lives in, or uses water, whether organic or inorganic, whether for better or for worse.
Why Should You Measure the TDS Level in Your Water?
Some regulations advise a maximum contamination level (MCL) of 500mg/liter (500 parts per million (ppm)) for TDS, while the World Health Organisation says 1000ppm. Numerous water supplies exceed this level. When TDS levels exceed 1000mg/L it is not considered fit for human consumption. A high level of TDS is an indicator of potential concerns, and warrants further investigation. Most often, high levels of TDS are caused by the presence of potassium, chlorides and sodium. These ions have little or no short-term effects, but toxic ions (lead arsenic, cadmium, nitrate and others) may also be dissolved in the water.
Even the best water purification systems on the market require monitoring for TDS to ensure the filters and/or membranes are effectively removing unwanted particles and bacteria from your water.
Notes on Water Hardness
Does hard water really create problems ?
Hard water can be a very costly addition to your home primarily because it leaves a residue called hard water scale on all washable surfaces.
Over a period of time, hard water scale can clog your plumbing which eventually reduces water pressure. It damages water heaters, dishwashers, washing machines, coffee makers and virtually all appliances through which water passes. This scale leaves spots or streaks on dishes and glassware, and dulls the look of clothing, floors, sinks, tubs, and even hair.
Corrosion often occurs because of highly acidic water that gradually eats away pipes, appliances, heaters, boilers and air-conditioning units.
Water Softeners are designed to soften water so that it washes brighter, rinses cleaner and feels much better.
High TDS indicates Hard water, which causes scale buildup in pipes and valves, inhibiting performance. Since TDS is related to water hardness, using a TDS meter can be your first step in determining the degree of hardness of the water. Generally speaking, the higher the level of TDS (ppm), the higher the degree of hardness.
Water hardness is typically reported in parts per million (ppm). .
Where Do Dissolved Solids Come From?
Some dissolved solids come from organic sources such as leaves, silt, plankton, and industrial waste and sewage. Other sources come from runoff from urban areas, fertilizers and pesticides used on lawns and farms.
Dissolved solids also come from inorganic materials such as rocks and air that may contain calcium bicarbonate, nitrogen, iron phosphorous, sulfur, and other minerals. Many of these materials form salts, which are compounds that contain both a metal and a nonmetal.
Salts usually dissolve in water forming ions. Ions are particles that have a positive or negative charge.
Water may also pick up metals such as lead or copper as they travel through pipes used to distribute water to consumers.
The efficacy of water purifications systems in removing total dissolved solids will be reduced over time, so it is highly recommended to monitor the quality of a filter or membrane and replace them when required.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Conductivity meters, Total Dissolved Solids (TDS) meters and resistivity meters are analytical instruments that measure the conductivity, dissolved solids, and/or resistivity of a liquid sample. They can measure a single variable, a combination of variables, or all three variables. Often, because these variables are related, combination conductivity meters, dissolved solids meters and resistivity meters used. Conductivity, a measure of water’s ability to transmit electrical current, is a gross, indirect measurement of the concentration of ions. Consequently, conductivity can be used to estimate levels of total dissolved solids (TDS), a measurement of the dry mass of dissolved solids in water. As a rule, most of the colloidal particles are included in a TDS measurement. Resistivity, another related variable, is the reciprocal of conductivity.
Specifications for conductivity meters, dissolved solids meters and resistivity meters include conductivity range, dissolved solids range, and resistivity range; conductivity accuracy, dissolved solids accuracy, and resistivity accuracy; and process media temperature. Portable, hand held, modular, lab, benchtop, field-use, and panel-mounted instruments are commonly available. These instruments have an analog meter, a digital display, or a video display such as cathode ray tube (CRT), liquid-crystal display (LCD), or flat panel display (FPD). Often, conductivity meters, dissolved meters and resistivity meters with manual controls have knobs or potentiometers. Analytical instruments with a digital front panel are programmed with a keypad. Programmable conductivity meters, dissolved solids meters and resistivity meters are also available.
Conductivity meters, dissolved solids meters and resistivity meters provide electrical outputs such as analog voltages, analog currents, and analog frequencies. Devices with a switch or alarm-relay output are also available. In terms of features, some conductivity meters, dissolved solids meters and resistivity meters are battery-powered, temperature compensated, event triggered, or designed for extreme environments. Others have filters, built-in or self-calibration, or self-test capabilities. Conductivity meters, dissolved solids meters, and resistivity meters with that provide special signal processing and/or filtering are also available. Often, these analytical instruments use Butterworth or Bessel filters. Butterworth filters provide a very flat response. There is almost no attenuation in the passband, and the roll-off rate is somewhat slower than other filters. Bessel filters have a relatively flat passband and slow roll-off.
Notes on TDS
Total Dissolved Solids (TDS) are the total amount of mobile charged ions, including minerals, salts or metals dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm). TDS is directly related to the purity of water and the quality of water purification systems and affects everything that consumes, lives in, or uses water, whether organic or inorganic, whether for better or for worse.
Why Should You Measure the TDS Level in Your Water?
Some regulations advise a maximum contamination level (MCL) of 500mg/liter (500 parts per million (ppm)) for TDS, while the World Health Organisation says 1000ppm. Numerous water supplies exceed this level. When TDS levels exceed 1000mg/L it is not considered fit for human consumption. A high level of TDS is an indicator of potential concerns, and warrants further investigation. Most often, high levels of TDS are caused by the presence of potassium, chlorides and sodium. These ions have little or no short-term effects, but toxic ions (lead arsenic, cadmium, nitrate and others) may also be dissolved in the water.
Even the best water purification systems on the market require monitoring for TDS to ensure the filters and/or membranes are effectively removing unwanted particles and bacteria from your water.
Notes on Water Hardness
Does hard water really create problems ?
Hard water can be a very costly addition to your home primarily because it leaves a residue called hard water scale on all washable surfaces.
Over a period of time, hard water scale can clog your plumbing which eventually reduces water pressure. It damages water heaters, dishwashers, washing machines, coffee makers and virtually all appliances through which water passes. This scale leaves spots or streaks on dishes and glassware, and dulls the look of clothing, floors, sinks, tubs, and even hair.
Corrosion often occurs because of highly acidic water that gradually eats away pipes, appliances, heaters, boilers and air-conditioning units.
Water Softeners are designed to soften water so that it washes brighter, rinses cleaner and feels much better.
High TDS indicates Hard water, which causes scale buildup in pipes and valves, inhibiting performance. Since TDS is related to water hardness, using a TDS meter can be your first step in determining the degree of hardness of the water. Generally speaking, the higher the level of TDS (ppm), the higher the degree of hardness.
Water hardness is typically reported in parts per million (ppm). .
Where Do Dissolved Solids Come From?
Some dissolved solids come from organic sources such as leaves, silt, plankton, and industrial waste and sewage. Other sources come from runoff from urban areas, fertilizers and pesticides used on lawns and farms.
Dissolved solids also come from inorganic materials such as rocks and air that may contain calcium bicarbonate, nitrogen, iron phosphorous, sulfur, and other minerals. Many of these materials form salts, which are compounds that contain both a metal and a nonmetal.
Salts usually dissolve in water forming ions. Ions are particles that have a positive or negative charge.
Water may also pick up metals such as lead or copper as they travel through pipes used to distribute water to consumers.
The efficacy of water purifications systems in removing total dissolved solids will be reduced over time, so it is highly recommended to monitor the quality of a filter or membrane and replace them when required.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Colour Sensors used in Analysers.
Color sensors register items by contrast, true color, or translucent index. True color sensors are based on one of the color models, most commonly the RGB model (red, green, blue). A large percentage of the visible spectrum can be created using these three primary colors.
Many color sensors are able to detect more than one color for multiple color sorting applications. Depending on the sophistication of the sensor, it can be programmed to recognize only one color, or multiple color types or shades for sorting operations.
Some types of color sensors do not recognize colors, per se, instead focusing on light wavelengths. These devices can be configured to locate wavelengths from near infrared (colors in the 750 nm to 2500 nm wavelength range), far infrared (colors in the 6.00 to 15.00 micron wavelength range), and UV (colors in the 50 to 350 and 400 nm wavelength range), in addition to the visible range. Sensors that read the visible range are the most common type of color sensors. They measure color based on an RGB color model (red, green, blue). A large percentage of the visible spectrum (380 nm to 750 nm wavelength) can be created using these three colors.
Color sensors are generally used for two specific applications, true color recognition and color mark detection. Sensors used for true color recognition are required to "see" different colors or to distinguish between shades of a specific color. They can be used in either a sorting or matching mode. In sorting mode, output is activated when the object to be identified is close to the set color. In matching mode, output is activated when the object to be detected is identical (within tolerance) to the color stored in memory. Color mark detection sensors do not detect the color of the mark, rather they "see" differences or changes in the mark in contrast with other marks or backgrounds. They are sometimes referred to as contrast sensors.
Color sensors shine light onto the object to be monitored and measure either the direct reflection or the output into color components. Many color sensors have integral light sources to achieve the desired effect. These integral light sources include LEDs, lasers, fiber optic, and halogen lamps
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Many color sensors are able to detect more than one color for multiple color sorting applications. Depending on the sophistication of the sensor, it can be programmed to recognize only one color, or multiple color types or shades for sorting operations.
Some types of color sensors do not recognize colors, per se, instead focusing on light wavelengths. These devices can be configured to locate wavelengths from near infrared (colors in the 750 nm to 2500 nm wavelength range), far infrared (colors in the 6.00 to 15.00 micron wavelength range), and UV (colors in the 50 to 350 and 400 nm wavelength range), in addition to the visible range. Sensors that read the visible range are the most common type of color sensors. They measure color based on an RGB color model (red, green, blue). A large percentage of the visible spectrum (380 nm to 750 nm wavelength) can be created using these three colors.
Color sensors are generally used for two specific applications, true color recognition and color mark detection. Sensors used for true color recognition are required to "see" different colors or to distinguish between shades of a specific color. They can be used in either a sorting or matching mode. In sorting mode, output is activated when the object to be identified is close to the set color. In matching mode, output is activated when the object to be detected is identical (within tolerance) to the color stored in memory. Color mark detection sensors do not detect the color of the mark, rather they "see" differences or changes in the mark in contrast with other marks or backgrounds. They are sometimes referred to as contrast sensors.
Color sensors shine light onto the object to be monitored and measure either the direct reflection or the output into color components. Many color sensors have integral light sources to achieve the desired effect. These integral light sources include LEDs, lasers, fiber optic, and halogen lamps
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Cable Testers.
Cable testers are handheld, benchtop, or floor-standing electronic devices that measure the electrical and physical properties of cabling. They are used to certify cabling to published standards, and as a troubleshooting tool. Cable testers are used with many different types of cables. Common types of cabling include Category 3 (Cat 3), Category 5 (Cat 5) and Category 6 (Cat 6) cables; coaxial, triaxial, and twisted pair; RG6 and RG11; fiber optic, fibre channel, and IEEE 1394; parallel, serial, and universal serial bus (USB); small computer system interface (SCSI) and general-purpose interface bus (GPIB); and Ethernet and local area network (LAN) cables. Cable testers are also used to test cabling for proprietary interfaces and architectures such FireWire®, a registered trademark of Apple Computer, Inc., and Infiniband®, a registered trademark of the InfiniBand Trade Association.
Selecting cable testers requires an analysis of product specifications and features. Important specifications for cable testers include test points, test resistance, maximum voltage, and maximum current. The number of test points is the number of wires, tracings or contact points that a cable tester can test simultaneously. Test resistance is the resistance value of the object being tested. Maximum voltage is the number of volts (V) applied to each test circuit. Maximum current is the number of amperes (A) applied to each test point. In terms of features, cable testers may include capacitors, diodes, or resistors in the test circuit. Some products can perform high potential or hipot tests to determine conformance with isolation requirements. Others include a trigger for a time domain reflectometer (TDR) view or option.
Cable testers are used to certify cabling according to published standards from organizations such as the American National Standards Institute (ANSI), the Electronic Industry Association (EIA), the Telecommunications Industry Association (TIA), the National Fire Protection Association (NFPA), the Canadian Standards Association (CSA), and the International Standards Organization (ISO). Cable testers are also used to troubleshoot connectivity problems and determine whether an existing link can support specific network speeds and technologies. These qualification testers are more powerful than verification tools, but do not perform the battery of tests that meet certification requirements.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Selecting cable testers requires an analysis of product specifications and features. Important specifications for cable testers include test points, test resistance, maximum voltage, and maximum current. The number of test points is the number of wires, tracings or contact points that a cable tester can test simultaneously. Test resistance is the resistance value of the object being tested. Maximum voltage is the number of volts (V) applied to each test circuit. Maximum current is the number of amperes (A) applied to each test point. In terms of features, cable testers may include capacitors, diodes, or resistors in the test circuit. Some products can perform high potential or hipot tests to determine conformance with isolation requirements. Others include a trigger for a time domain reflectometer (TDR) view or option.
Cable testers are used to certify cabling according to published standards from organizations such as the American National Standards Institute (ANSI), the Electronic Industry Association (EIA), the Telecommunications Industry Association (TIA), the National Fire Protection Association (NFPA), the Canadian Standards Association (CSA), and the International Standards Organization (ISO). Cable testers are also used to troubleshoot connectivity problems and determine whether an existing link can support specific network speeds and technologies. These qualification testers are more powerful than verification tools, but do not perform the battery of tests that meet certification requirements.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Thermocouples & RTD Simulators.
Thermocouple simulators and RTD simulators provide precise standard values of resistance or voltage for simulation and calibration. Thermocouples are bimetallic temperature probes used in a variety of temperature sensing applications. Resistance temperature detectors (RTDs) are wire windings or other thin-film serpentines that exhibit changes in resistance with changes in temperature. RTD simulators provide a resistance value simulating the output of a resistance temperature detector (RTD) at a particular temperature. In some cases, resistance decade boxes can be used as RTD simulators. Thermocouple simulators provide a voltage value simulating the millivolt (mV) drop output of a thermocouple at a particular temperature. Some voltage sources can be used as thermocouple simulators.
Selecting thermocouple simulators and RTD simulators requires an analysis of performance specifications such as temperature resolution and simulation type. The types of temperature-sensing devices that can be simulated include K type thermocouples, J type thermocouples, E type thermocouples, T type thermocouples, platinum RTDs, copper RTDs, nickel RTDs, and proprietary devices. Additional considerations include number of decades and temperature coefficient, the rate at which the nominal resistance value changes as a function of temperature. With thermocouple simulators and RTD simulators, temperature coefficient is expressed in parts per million per degree Celsius (ppm/C).
Thermocouple simulators and RTD simulators differ in terms of resistance specifications and voltage specifications. Resistance specifications include resistance range and resistance resolution per step. Resolution is the digital value represented by one bit in the display of a digital measure. For example, a decade box where one bit on the display represents 10 amps has a resolution of 10 amps. Voltage specifications for thermocouple simulators and RTD simulators include voltage range, voltage resolution per step, and voltage accuracy. Like resistance resolution, voltage resolution is the digital value represented by one bit in the display of a digital measure.
Thermocouple simulators and RTD simulators provide many different features. Some products offer calibration that can be traced to the National Institute of Standards and Technology (NIST). Others have low values of zero, residual impedance resistance, inductance or capacitance. Programmable thermocouple simulators and RTD simulators have a computer interface for programming, control or data acquisition. Stand-alone devices are packaged in a case with binding posts. Rack mounted devices have options for both front and rear outputs.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Selecting thermocouple simulators and RTD simulators requires an analysis of performance specifications such as temperature resolution and simulation type. The types of temperature-sensing devices that can be simulated include K type thermocouples, J type thermocouples, E type thermocouples, T type thermocouples, platinum RTDs, copper RTDs, nickel RTDs, and proprietary devices. Additional considerations include number of decades and temperature coefficient, the rate at which the nominal resistance value changes as a function of temperature. With thermocouple simulators and RTD simulators, temperature coefficient is expressed in parts per million per degree Celsius (ppm/C).
Thermocouple simulators and RTD simulators differ in terms of resistance specifications and voltage specifications. Resistance specifications include resistance range and resistance resolution per step. Resolution is the digital value represented by one bit in the display of a digital measure. For example, a decade box where one bit on the display represents 10 amps has a resolution of 10 amps. Voltage specifications for thermocouple simulators and RTD simulators include voltage range, voltage resolution per step, and voltage accuracy. Like resistance resolution, voltage resolution is the digital value represented by one bit in the display of a digital measure.
Thermocouple simulators and RTD simulators provide many different features. Some products offer calibration that can be traced to the National Institute of Standards and Technology (NIST). Others have low values of zero, residual impedance resistance, inductance or capacitance. Programmable thermocouple simulators and RTD simulators have a computer interface for programming, control or data acquisition. Stand-alone devices are packaged in a case with binding posts. Rack mounted devices have options for both front and rear outputs.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Videoscopes, Borescopes or Endoscopes
Videoscopes, Borescopes or endoscopes are inspection tools that capture images from inside holes, bores or cavities. They are combination bundles of optical devices and light sources that can be used in normally inaccessible locations. Images are displayed in real time, recorded onto tape, and/or stored digitally. Videoscopes resemble fiberscopes in appearance and operation. However, instead of deriving a fiber optic image from a bundle in the probe, videoscopes use a charged couple device (CCD) in the distal tip to capture the image and transmit it back as electronic pulses. A connected CCU converts these pulses, into real time video images, which may be displayed on a monitor for viewing, in addition to storage. Generally, videoscopes provide sharper and more detailed images than fiberscopes produce, and these images can be transmitted over greater distances with a low level of image degradation.
Videoscopes are available in a wide range of configurations, with many optional features that may allow for easier use and more clearly produced images. Some of the more common configurations include the viewing angle of the device, its resolution, frame production rate, and video format and color output type. Optional features include whether the device has a 2-way or 4-way articulating tip, or whether it can accommodate interchangeable tips; whether the tip can rotate or is fixed; is the entire device flexible or just its neck and tip; and the adjustability of the light source to provide brighter, higher resolution images without edge fading or hot spots.
Video Scopes are widely used in medical fields, including cardiology, dentistry, and reproductive analysis. In industrial applications, videoscopes are often used for visual inspection of the internal surfaces, or inner diameter (I.D.) of tubes, piping, cylinders and castings, and for examination of engines and structures, and quality assurance testing.
Video Scopes are also be found in security applications, most notably airport security. Other applications would include gun barrel inspection, Automotive and Diesel mechanics, HVAC Technicians, Electricians, Plumbers, Law Enforcement Inspectors, Welders, Carpenters and Architects
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Videoscopes are available in a wide range of configurations, with many optional features that may allow for easier use and more clearly produced images. Some of the more common configurations include the viewing angle of the device, its resolution, frame production rate, and video format and color output type. Optional features include whether the device has a 2-way or 4-way articulating tip, or whether it can accommodate interchangeable tips; whether the tip can rotate or is fixed; is the entire device flexible or just its neck and tip; and the adjustability of the light source to provide brighter, higher resolution images without edge fading or hot spots.
Video Scopes are widely used in medical fields, including cardiology, dentistry, and reproductive analysis. In industrial applications, videoscopes are often used for visual inspection of the internal surfaces, or inner diameter (I.D.) of tubes, piping, cylinders and castings, and for examination of engines and structures, and quality assurance testing.
Video Scopes are also be found in security applications, most notably airport security. Other applications would include gun barrel inspection, Automotive and Diesel mechanics, HVAC Technicians, Electricians, Plumbers, Law Enforcement Inspectors, Welders, Carpenters and Architects
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Barometers and Weather Instruments.
Barometers are for the measurement of atmospheric pressure and can be labeled into the category of weather Instruments. Weather instruments are designed to measure one or multiple components of weather including wind speed and direction, rain or snow fall, solar radiation, temperature, pressure and humidity. In some cases, these instruments are designed for incorporation into a weather station arrangement and can be mounted on a pole or base and remotely monitored. In other cases, these are individual sensors or instruments that can measure one aspect of weather. In all cases, the instruments and sensors are designed for environmental type applications, and often housings are rugged for these and other applications.
Output options for weather instruments can include analog voltage, analog current, frequency or pulse signal and switch or alarm. These instruments can be connected to computers via serial, parallel, or other digital means for signal acquisition. Some models even have built-in modems and thus can act as event-triggered devices or can be programmed remotely in some cases. They can have local or remote analog, digital or video style displays. The user interfaces on weather instruments can be analog front panel type controls with switches, dials, potentiometers, etc.; digital interfaces with keypads, buttons and menus; or controlled by a remote computer with the same interfaces stated above.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Output options for weather instruments can include analog voltage, analog current, frequency or pulse signal and switch or alarm. These instruments can be connected to computers via serial, parallel, or other digital means for signal acquisition. Some models even have built-in modems and thus can act as event-triggered devices or can be programmed remotely in some cases. They can have local or remote analog, digital or video style displays. The user interfaces on weather instruments can be analog front panel type controls with switches, dials, potentiometers, etc.; digital interfaces with keypads, buttons and menus; or controlled by a remote computer with the same interfaces stated above.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Air Velocity Sensors in Anemometers.
Anemometers can be handheld instruments and are used for air velocity measurements using air velocity sensors. Air velocity flow sensors can be inserted into a duct or pipe through an access hole to measure air velocity. In other instances a capture hood is used to measure volumetric flow from a grill or exhaust diffuser. Air velocity or volume measurements can often be used with engineering handbook data or design information to reveal proper or improper performance of an airflow system.
Two types of air velocity flow sensors are the insertion probes and balometers or flow hoods. Insertion probes go directly into a duct to gauge the effectiveness of ventilation by measuring air velocity. Flow hoods and balometers measure air volume flow at the air supply or exhaust outlets.
Different technologies are used with air velocity flow sensors. A thermal anemometer is a body that is heated up to a fixed temperature and then exposed to the air velocity. By measuring how much more air is required to maintain the original temperature, indication of the air speed is gained. The higher the air speed, the more energy required to keep the temperature at a set level. Differential pressure type sensors have Pitot tubes, averaging tubes and other velocity pressure measurement devices. The velocity pressure is the difference between the total pressure and the static pressure. A Pitot tube has two pressure sampling points, static pressure and back pressure. Used with a differential pressure transmitter, the difference between these pressures is a measure of the velocity. Vane anemometers have a proximity switch that counts the revolutions of the vane and supplies a pulse sequence that is converted by the measuring instrument to a flow rate. This is based on the conversion of rotation into electrical signal and can be either a rotating or swinging vane.
Measurement ranges are important specifications, whether measuring air velocity, volume or pressure. Accuracy for air velocity flow sensors is usually expressed as a percentage of full-scale measurement. These instruments can be either handheld devices, for ease in moving from one location to another, or permanent fixtured units.
Some models of air velocity flow sensors can have selectable measuring ranges. Another option is time or multi-point averaging functions to compensate for non-uniform air velocity across the duct cross-section. They can also measure temperature and be temperature compensated.
Outputs for air velocity flow sensors can be analog voltage, current or frequency. They can also have switched or alarm output and can even be connected to computers for data collection and programming. Other control and programming options are through an analog or digital front panel. Displays for these sensors can be analog, digital or video terminals.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Two types of air velocity flow sensors are the insertion probes and balometers or flow hoods. Insertion probes go directly into a duct to gauge the effectiveness of ventilation by measuring air velocity. Flow hoods and balometers measure air volume flow at the air supply or exhaust outlets.
Different technologies are used with air velocity flow sensors. A thermal anemometer is a body that is heated up to a fixed temperature and then exposed to the air velocity. By measuring how much more air is required to maintain the original temperature, indication of the air speed is gained. The higher the air speed, the more energy required to keep the temperature at a set level. Differential pressure type sensors have Pitot tubes, averaging tubes and other velocity pressure measurement devices. The velocity pressure is the difference between the total pressure and the static pressure. A Pitot tube has two pressure sampling points, static pressure and back pressure. Used with a differential pressure transmitter, the difference between these pressures is a measure of the velocity. Vane anemometers have a proximity switch that counts the revolutions of the vane and supplies a pulse sequence that is converted by the measuring instrument to a flow rate. This is based on the conversion of rotation into electrical signal and can be either a rotating or swinging vane.
Measurement ranges are important specifications, whether measuring air velocity, volume or pressure. Accuracy for air velocity flow sensors is usually expressed as a percentage of full-scale measurement. These instruments can be either handheld devices, for ease in moving from one location to another, or permanent fixtured units.
Some models of air velocity flow sensors can have selectable measuring ranges. Another option is time or multi-point averaging functions to compensate for non-uniform air velocity across the duct cross-section. They can also measure temperature and be temperature compensated.
Outputs for air velocity flow sensors can be analog voltage, current or frequency. They can also have switched or alarm output and can even be connected to computers for data collection and programming. Other control and programming options are through an analog or digital front panel. Displays for these sensors can be analog, digital or video terminals.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Gas Sensors and Detectors.
Gas detectors and gas sensors interact with a gas to initiate the measurement of its concentration. The gas detector of gas sensor then provides output to a gas instrument to display the measurements. Common gases measured by gas detectors and gas sensors include ammonia, aerosols, arsine, bromine, carbon dioxide, carbon monoxide, chlorine, chlorine dioxide, Diborane, dust, fluorine, germane, halocarbons or refrigerants, hydrocarbons, hydrogen, hydrogen chloride, hydrogen cyanide, hydrogen fluoride, hydrogen selenide, hydrogen sulfide, mercury vapor, nitrogen dioxide, nitrogen oxides, nitric oxide, organic solvents, oxygen, ozone, phosphine, silane, sulfur dioxide, and water vapor.
Important measurement specifications to consider when looking for gas detectors and gas sensors include the response time, the distance, and the flow rate. The response time is the amount of time required from the initial contact with the gas to the sensors processing of the signal. Distance is the maximum distance from the leak or gas source that the sensor can detect gases. The flow rate is the necessary flow rate of air or gas across the gas detectors or gas sensors to produce a signal.
Gas detectors and gas sensors can output a measurement of the gases detected in a number of ways. These include percent LEL, percent volume, trace, leakage, consumption, density, and signature or spectra. The lower explosive limit (LEL) or lower flammable limit (LFL) of a combustible gas is defined as the smallest amount of the gas that will support a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified in terms of % LEL: 0% LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the gas is at its lower flammable limit. The relationship between % LEL and % by volume differs from gas to gas. Also called volume percent or percent by volume, percent volume is typically only used for mixtures of liquids. Percent by volume is simply the volume of the solute divided by the sum of the volumes of the other components multiplied by 100%. Trace gas sensors given in units of concentration: ppm. Leakage is given as a flow rate like ml/min. Consumption may also be called respiration. Given in units of ml/L/hr. Density measurements are given in units of density: mg/m^3. A signature or spectra measurement is a spectral signature of the gases present; the output is often a chromatogram.
Common outputs from gas detectors and gas sensors include analog voltage, pulse signals, analog currents and switch or relays. Operating parameters that are important to consider for gas detectors and gas sensors include operating temperature and humidity.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Important measurement specifications to consider when looking for gas detectors and gas sensors include the response time, the distance, and the flow rate. The response time is the amount of time required from the initial contact with the gas to the sensors processing of the signal. Distance is the maximum distance from the leak or gas source that the sensor can detect gases. The flow rate is the necessary flow rate of air or gas across the gas detectors or gas sensors to produce a signal.
Gas detectors and gas sensors can output a measurement of the gases detected in a number of ways. These include percent LEL, percent volume, trace, leakage, consumption, density, and signature or spectra. The lower explosive limit (LEL) or lower flammable limit (LFL) of a combustible gas is defined as the smallest amount of the gas that will support a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified in terms of % LEL: 0% LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the gas is at its lower flammable limit. The relationship between % LEL and % by volume differs from gas to gas. Also called volume percent or percent by volume, percent volume is typically only used for mixtures of liquids. Percent by volume is simply the volume of the solute divided by the sum of the volumes of the other components multiplied by 100%. Trace gas sensors given in units of concentration: ppm. Leakage is given as a flow rate like ml/min. Consumption may also be called respiration. Given in units of ml/L/hr. Density measurements are given in units of density: mg/m^3. A signature or spectra measurement is a spectral signature of the gases present; the output is often a chromatogram.
Common outputs from gas detectors and gas sensors include analog voltage, pulse signals, analog currents and switch or relays. Operating parameters that are important to consider for gas detectors and gas sensors include operating temperature and humidity.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Notes on Gas Instruments in General.
Gas instruments detect, monitor or analyze gases present in an environment. Detectors sense situations outside normal operating parameters and are set to alarm when these conditions are violated. Monitors are also set up to alarm, but their role is to determine which gases are in the stream being measured, and in what quantity they are present. Analyzers provide a breakdown of what is found, log the information, and can download it to a computer where further analysis and record keeping can be performed. Gas instruments and air instruments can sense sometimes just one gas or else can sense multiple types of gases with one instrument.
When analyzing gases there are a few basic types of measurements that can be made. Percent LEL or lower explosive limit or lower flammable limit (LFL) of a combustible gas is defined as the smallest amount of the gas that will support a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified in terms of % LEL: 0% LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the gas is at its lower flammable limit. The relationship between % LEL and % by volume differs from gas to gas. Another measurement is percent volume, which measures the amount of a specific gas within a sample. Trace measurement is usually given in units of ppm or ppb. Leakage and consumption rates can also be measured, as can gas density and signature or spectra, which is the spectral signature of the gases present.
Specifications for gas instruments are first what type of gas the application requires sensing and second how many channels the instrument needs to sense through. This can be for multiple types of gas sensors, redundant sensors for the same gas, or for placing sensors throughout a location to get sampling at many different spots. Other factors to consider are response time, maximum distance from leak that the detector can detect gases, and flow rate through the sensor.
Gas instruments can be detectors, monitors or analyzers. A gas detector will detect situations outside normal operating parameters. It is set up to alarm of this situation and covers gas leak detectors as well. A monitor is set up to alarm and determine which gases are present and in what amounts. An analyzer will analyze what is found, log the information and has the ability to download to a computer for further analysis.
These instruments can typically be handheld, larger portable devices or permanently mounted instruments. They have four primary purposes: personal exposure monitoring, air quality monitoring, confined space monitoring, and process gas monitoring.
General available features for gas instruments can include temperature and humidity measurements, external or internal sampling “sniffer” pump, interchangeable probes, alarm settings, controller functionality, self-calibration, data storage or logging, and usability in hazardous environments.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
When analyzing gases there are a few basic types of measurements that can be made. Percent LEL or lower explosive limit or lower flammable limit (LFL) of a combustible gas is defined as the smallest amount of the gas that will support a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified in terms of % LEL: 0% LEL being a combustible gas-free atmosphere and 100% LEL being an atmosphere in which the gas is at its lower flammable limit. The relationship between % LEL and % by volume differs from gas to gas. Another measurement is percent volume, which measures the amount of a specific gas within a sample. Trace measurement is usually given in units of ppm or ppb. Leakage and consumption rates can also be measured, as can gas density and signature or spectra, which is the spectral signature of the gases present.
Specifications for gas instruments are first what type of gas the application requires sensing and second how many channels the instrument needs to sense through. This can be for multiple types of gas sensors, redundant sensors for the same gas, or for placing sensors throughout a location to get sampling at many different spots. Other factors to consider are response time, maximum distance from leak that the detector can detect gases, and flow rate through the sensor.
Gas instruments can be detectors, monitors or analyzers. A gas detector will detect situations outside normal operating parameters. It is set up to alarm of this situation and covers gas leak detectors as well. A monitor is set up to alarm and determine which gases are present and in what amounts. An analyzer will analyze what is found, log the information and has the ability to download to a computer for further analysis.
These instruments can typically be handheld, larger portable devices or permanently mounted instruments. They have four primary purposes: personal exposure monitoring, air quality monitoring, confined space monitoring, and process gas monitoring.
General available features for gas instruments can include temperature and humidity measurements, external or internal sampling “sniffer” pump, interchangeable probes, alarm settings, controller functionality, self-calibration, data storage or logging, and usability in hazardous environments.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Global Warming
Global warming is the gradual rise of the earth's near-surface temperature over approximately the last hundred years. The best available scientific evidence—based on continuous satellite monitoring and data from about 2,000 meteorological stations around the world—indicates that globally averaged surface temperatures have warmed by about 0.3 to 0.6°C since the late nineteenth century. Different regions have warmed—some have even cooled—by different amounts. Generally, the Northern Hemisphere has warmed to a greater extent than the Southern Hemisphere, and mid to high latitudes have generally warmed more than the tropics.
Since the advent of satellites, it has become possible for scientists to thoroughly monitor the earth's climate on a global scale. To examine the historical climate record, however, scientists have to use earlier, sparser forms of measurement, such as long-standing temperature records and less exact "proxy" data, such as the growth of coral, tree rings, as well as information from ice cores, which contain trapped gas bubbles and dust grains representative of the climate in which they were deposited. The bubbles in these cores contain oxygen, particularly oxygen isotopes 180 to 160, which are sensitive to variations in temperature. From the ratio between these isotopes at varying ice depths scientists can reconstruct a picture of the temperature variations over time in specific locations. Greater measurement uncertainty surrounds the earlier parts of this record because of sparse coverage (especially in ocean regions). Despite this uncertainty, the balance of scientific evidence confirms that there has been a discernable warming over the last century.
Causes
Gases such as water vapor, methane, and carbon dioxide allow short-wave radiation from the sun to pass through to the surface of the earth, but do not allow long-wave radiation reflected from the earth to travel back out into space. This naturally occurring insulation process—dubbed the greenhouse
LEADING COAL-BURNING STATES FOR ELECTRIC POWER GENERATION IN THE UNITED STATES Rank State Use (million tons)
SOURCE: Adapted from U.S. Department of Energy. Electric Power Annual 2000 , vol. 1. Available from http://www.eia.doe.gov/cneaf/electricity/epav1.
1 Texas 99.7
2 Indiana 59.5
3 Ohio 55.9
4 Pennsylvania 52.1
5 Illinois 46.6
6 Kentucky 40.2
7 Missouri 37.3
8 West Virginia 37.0
9 Alabama 35.6
10 Michigan 33.7
11 Georgia 33.5
12 North Carolina 29.9
13 Florida 29.9
14 Wyoming 26.5
15 Tennessee 26.1
16 North Dakota 25.1
Other States 322.4
Total 990.966
Global Mean Surface Air Temperature
Percent Reduction in June-August Soil Moisture
effect—keeps the earth warm: In its absence, the earth would be about 33°C cooler than it is now. However, as the concentration of greenhouse gases increases (due largely to human activities), most scientists agree that the effect is expected to intensify, raising average global temperatures.
The Antarctic Larsen B shelf is breaking up, as shown in these photographs from February and March 2002, causing fears of global warming. Seen in these photographs is the loss of 500 billion tons of ice. (
© Reuters NewMedia Inc./Corbis. Reproduced by permission.
)
However, the earth's climate is known to vary on long timescales. The existence of naturally occurring ice ages and warm periods in the distant past demonstrates that natural factors such as solar variability, volcanic activity, and fluctuations in greenhouse gases play important roles in regulating the earth's climate. A minority of scientists believe that purely natural variations in these factors can account for the observed global warming.
Climate in the Twenty-first Century
Climate forecasts are inherently imprecise largely because of two different sorts of uncertainty: incomplete knowledge about how the system works—understandable for a system governed by processes the spatial scales of which range from the molecular to the global and uncertainty about how important climate factors will evolve in the future. A variety of factors affect temperature near the surface of the earth, including variability in solar output, volcanic activity, and dust and other aerosols, in addition to concentrations of greenhouse gases.
However, this uncertainty does not stop one from making some broad statements about (1) the likelihood of the sources of observed global warming and (2) the likely effects of continued warming. In the first case, attempts by climate modelers to reproduce the observed global near-surface temperature
Sea Level Rise. (
GFDL climate model
)
record using only natural variability in climate models have proved inadequate. The Third Assessment Report (2001) of the Intergovernmental Panel on Climate Change (IPCC) attributes some 80 percent of recent rises in global temperature to human activities, with other important contributions coming from volcanic and solar sources. Over the coming century, likely effects of continued warming include higher daily maximum and minimum temperatures, more hot days over most land areas, fewer frosts in winter, fewer cold days over most land areas, a reduced daily range of temperatures, more extreme precipitation events (all very likely), increased risk of drought, increases in cyclone peak wind, and precipitation intensity (likely). Other effects, such as the disintegration of Antarctic ice sheets, carry potentially enormous implications, but are considered very unlikely.
Responses to Climate Change
These effects are likely to be beneficial in some places, but disruptive in most, and as a consequence, governments around the world have begun planning responses to climate change. These fall into two categories: mitigation, which involves taking action to prevent climate change (usually by cutting greenhouse gas emissions) and adaptation, which involves adapting to the effects as and after they happen. For example, if sea levels rise in the next century due to thermal expansion of the oceans, low lying areas such as the Netherlands and Bangladesh may be flooded. A mitigation strategy would involve trying to cut emissions to forestall the heat-driven sea level rise, whereas an adaptation strategy might be to build large barriers to prevent the sea level rise from flooding these countries. In wealthy countries such as the Netherlands this is perhaps a viable option. It is not so clear that Bangladesh—one of the world's poorest countries—will be in a position to implement this sort of strategy.
Surface Air Warming. (
GFDL R15 Climate Model; CO 2 transient experiments, years 401-500
)
Because of the potentially serious ramifications of continued global warming, the World Meteorological Organisation and United Nations Environment Programme jointly established the IPCC in 1988. It assesses scientific and socioeconomic information on climate change and related impacts, and provides advice on the options for either mitigating climate change by limiting the emissions of greenhouse gases, or adapting to expected changes through developments such as building higher flood defenses.
In the wake of the general increase in the awareness of environmental issues in the Western world since the 1970s, global warming has become an important political issue in the last decade. Following the successful implementation of the Montréal Protocol (1987) that prohibited the production of ozone-depleting gases (i.e., chlorofluorocarbons [CFCs], halons, and carbon tetrachloride) starting in 2000, the international community sought to address the problem of global warming in the Kyoto Protocol (1992). This involves industrialized countries taking the lead on cutting greenhouse gas emissions. The protocol requires them to decrease their emissions to 90 percent of their 1990 levels. The Kyoto Protocol comes into effect if fifty-five parties to the convention ratify the protocol, with "annex 1" (or industrialized) parties accounting for 55 percent of that group's carbon dioxide emissions in 1990.
This approach has proved controversial for a variety of reasons: (1) It applies primarily to industrialized countries, freeing some of the world's worst polluters, such as China and Saudi Arabia, from having to comply; (2) the reductions are arbitrarily fixed at 10 percent of a country's 1990 level, irrespective of whether that country is a big polluter, like the United States, or a relatively small polluter, like Sweden; (3) disagreements about whether the cuts imposed by the treaty will actually be worth the economic costs; (4) the treaty targets only gross emissions rather than net emissions—during the negotiations key differences emerged between a group of nations that favored the use of man-made forests as "carbon sinks" planted to soak up carbon emissions, and countries that believed this to be an inadequate response.
Although the Kyoto Protocol has been enthusiastically backed by European countries, various wealthy countries remain outside the treaty, most notably Australia and the United States. The U.S. decision to not sign the Kyoto Protocol has proved particularly controversial, as the United States emits some 23 percent of global greenhouse emissions, while only containing 5 percent of the global population. The current Bush administration does not intend to ratify the agreement on the grounds "that the protocol is not sound policy," according to U.S. Undersecretary of State Paula Dobriansky.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Since the advent of satellites, it has become possible for scientists to thoroughly monitor the earth's climate on a global scale. To examine the historical climate record, however, scientists have to use earlier, sparser forms of measurement, such as long-standing temperature records and less exact "proxy" data, such as the growth of coral, tree rings, as well as information from ice cores, which contain trapped gas bubbles and dust grains representative of the climate in which they were deposited. The bubbles in these cores contain oxygen, particularly oxygen isotopes 180 to 160, which are sensitive to variations in temperature. From the ratio between these isotopes at varying ice depths scientists can reconstruct a picture of the temperature variations over time in specific locations. Greater measurement uncertainty surrounds the earlier parts of this record because of sparse coverage (especially in ocean regions). Despite this uncertainty, the balance of scientific evidence confirms that there has been a discernable warming over the last century.
Causes
Gases such as water vapor, methane, and carbon dioxide allow short-wave radiation from the sun to pass through to the surface of the earth, but do not allow long-wave radiation reflected from the earth to travel back out into space. This naturally occurring insulation process—dubbed the greenhouse
LEADING COAL-BURNING STATES FOR ELECTRIC POWER GENERATION IN THE UNITED STATES Rank State Use (million tons)
SOURCE: Adapted from U.S. Department of Energy. Electric Power Annual 2000 , vol. 1. Available from http://www.eia.doe.gov/cneaf/electricity/epav1.
1 Texas 99.7
2 Indiana 59.5
3 Ohio 55.9
4 Pennsylvania 52.1
5 Illinois 46.6
6 Kentucky 40.2
7 Missouri 37.3
8 West Virginia 37.0
9 Alabama 35.6
10 Michigan 33.7
11 Georgia 33.5
12 North Carolina 29.9
13 Florida 29.9
14 Wyoming 26.5
15 Tennessee 26.1
16 North Dakota 25.1
Other States 322.4
Total 990.966
Global Mean Surface Air Temperature
Percent Reduction in June-August Soil Moisture
effect—keeps the earth warm: In its absence, the earth would be about 33°C cooler than it is now. However, as the concentration of greenhouse gases increases (due largely to human activities), most scientists agree that the effect is expected to intensify, raising average global temperatures.
The Antarctic Larsen B shelf is breaking up, as shown in these photographs from February and March 2002, causing fears of global warming. Seen in these photographs is the loss of 500 billion tons of ice. (
© Reuters NewMedia Inc./Corbis. Reproduced by permission.
)
However, the earth's climate is known to vary on long timescales. The existence of naturally occurring ice ages and warm periods in the distant past demonstrates that natural factors such as solar variability, volcanic activity, and fluctuations in greenhouse gases play important roles in regulating the earth's climate. A minority of scientists believe that purely natural variations in these factors can account for the observed global warming.
Climate in the Twenty-first Century
Climate forecasts are inherently imprecise largely because of two different sorts of uncertainty: incomplete knowledge about how the system works—understandable for a system governed by processes the spatial scales of which range from the molecular to the global and uncertainty about how important climate factors will evolve in the future. A variety of factors affect temperature near the surface of the earth, including variability in solar output, volcanic activity, and dust and other aerosols, in addition to concentrations of greenhouse gases.
However, this uncertainty does not stop one from making some broad statements about (1) the likelihood of the sources of observed global warming and (2) the likely effects of continued warming. In the first case, attempts by climate modelers to reproduce the observed global near-surface temperature
Sea Level Rise. (
GFDL climate model
)
record using only natural variability in climate models have proved inadequate. The Third Assessment Report (2001) of the Intergovernmental Panel on Climate Change (IPCC) attributes some 80 percent of recent rises in global temperature to human activities, with other important contributions coming from volcanic and solar sources. Over the coming century, likely effects of continued warming include higher daily maximum and minimum temperatures, more hot days over most land areas, fewer frosts in winter, fewer cold days over most land areas, a reduced daily range of temperatures, more extreme precipitation events (all very likely), increased risk of drought, increases in cyclone peak wind, and precipitation intensity (likely). Other effects, such as the disintegration of Antarctic ice sheets, carry potentially enormous implications, but are considered very unlikely.
Responses to Climate Change
These effects are likely to be beneficial in some places, but disruptive in most, and as a consequence, governments around the world have begun planning responses to climate change. These fall into two categories: mitigation, which involves taking action to prevent climate change (usually by cutting greenhouse gas emissions) and adaptation, which involves adapting to the effects as and after they happen. For example, if sea levels rise in the next century due to thermal expansion of the oceans, low lying areas such as the Netherlands and Bangladesh may be flooded. A mitigation strategy would involve trying to cut emissions to forestall the heat-driven sea level rise, whereas an adaptation strategy might be to build large barriers to prevent the sea level rise from flooding these countries. In wealthy countries such as the Netherlands this is perhaps a viable option. It is not so clear that Bangladesh—one of the world's poorest countries—will be in a position to implement this sort of strategy.
Surface Air Warming. (
GFDL R15 Climate Model; CO 2 transient experiments, years 401-500
)
Because of the potentially serious ramifications of continued global warming, the World Meteorological Organisation and United Nations Environment Programme jointly established the IPCC in 1988. It assesses scientific and socioeconomic information on climate change and related impacts, and provides advice on the options for either mitigating climate change by limiting the emissions of greenhouse gases, or adapting to expected changes through developments such as building higher flood defenses.
In the wake of the general increase in the awareness of environmental issues in the Western world since the 1970s, global warming has become an important political issue in the last decade. Following the successful implementation of the Montréal Protocol (1987) that prohibited the production of ozone-depleting gases (i.e., chlorofluorocarbons [CFCs], halons, and carbon tetrachloride) starting in 2000, the international community sought to address the problem of global warming in the Kyoto Protocol (1992). This involves industrialized countries taking the lead on cutting greenhouse gas emissions. The protocol requires them to decrease their emissions to 90 percent of their 1990 levels. The Kyoto Protocol comes into effect if fifty-five parties to the convention ratify the protocol, with "annex 1" (or industrialized) parties accounting for 55 percent of that group's carbon dioxide emissions in 1990.
This approach has proved controversial for a variety of reasons: (1) It applies primarily to industrialized countries, freeing some of the world's worst polluters, such as China and Saudi Arabia, from having to comply; (2) the reductions are arbitrarily fixed at 10 percent of a country's 1990 level, irrespective of whether that country is a big polluter, like the United States, or a relatively small polluter, like Sweden; (3) disagreements about whether the cuts imposed by the treaty will actually be worth the economic costs; (4) the treaty targets only gross emissions rather than net emissions—during the negotiations key differences emerged between a group of nations that favored the use of man-made forests as "carbon sinks" planted to soak up carbon emissions, and countries that believed this to be an inadequate response.
Although the Kyoto Protocol has been enthusiastically backed by European countries, various wealthy countries remain outside the treaty, most notably Australia and the United States. The U.S. decision to not sign the Kyoto Protocol has proved particularly controversial, as the United States emits some 23 percent of global greenhouse emissions, while only containing 5 percent of the global population. The current Bush administration does not intend to ratify the agreement on the grounds "that the protocol is not sound policy," according to U.S. Undersecretary of State Paula Dobriansky.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Alcohol Breath Tester
DESCRIPTION:
The MTI-0001 Alcohol Breath Tester is commonly used at home, bar, laboratory, Police or while you are on the road.
Device provided with extra mouthpieces for convenience.
Units activated through a micro switch, after a brief internal self test; the test subject blows through the sensor and result are converted and read within few seconds.
SPECIFICATIONS
Built in DSP microprocessor technology
CE approval by FIMKO
Warm up time: less then 20 seconds (typical)
Unique 4 digits LCD display
Auto adjust/reset, with reset button
Illumination button for use in dark ( Auto shut off after 10 seconds)
Power source: 3 X 1.5V AA regular batteries or rechargeable batteries. Also 12 volts DC adapter cable allow user test in the car or recharging the batteries.
Size: 175 X 60 X 25 mm.
Accuracy: 15% @ 0.01% BAC
Blowing time: 4 to 5 seconds continuously.
Automatic switch off after 30 seconds.
Calibration: Availed upon request (recommended every 12 months).
Removable mouthpiece, easy to clean and replace.
Breath Tester used as a monitor, it can indicate when equivalent blood alcohol percentages are above the legal limits.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
The MTI-0001 Alcohol Breath Tester is commonly used at home, bar, laboratory, Police or while you are on the road.
Device provided with extra mouthpieces for convenience.
Units activated through a micro switch, after a brief internal self test; the test subject blows through the sensor and result are converted and read within few seconds.
SPECIFICATIONS
Built in DSP microprocessor technology
CE approval by FIMKO
Warm up time: less then 20 seconds (typical)
Unique 4 digits LCD display
Auto adjust/reset, with reset button
Illumination button for use in dark ( Auto shut off after 10 seconds)
Power source: 3 X 1.5V AA regular batteries or rechargeable batteries. Also 12 volts DC adapter cable allow user test in the car or recharging the batteries.
Size: 175 X 60 X 25 mm.
Accuracy: 15% @ 0.01% BAC
Blowing time: 4 to 5 seconds continuously.
Automatic switch off after 30 seconds.
Calibration: Availed upon request (recommended every 12 months).
Removable mouthpiece, easy to clean and replace.
Breath Tester used as a monitor, it can indicate when equivalent blood alcohol percentages are above the legal limits.
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Carbon Monoxide
Carbon monoxide is an invisible, odorless, and poisonous gas with the chemical formula CO. Because of its toxicity, the U.S. Environmental Protection Agency (EPA) regulates CO. The gas is a by-product of incomplete combustion (burning with insufficient oxygen). Its major source is vehicle exhaust (60 percent). Other sources include water heaters and furnaces, gas-powered
Sources of Carbon Monoxide in the Home
engines (boats and lawn mowers), charcoal and wood fires, agricultural burning, and tobacco smoke.
CO is classified as an indirect greenhouse gas. It does not contribute to global warming directly, but leads to the formation of ozone. Ozone is the major air pollutant formed in photochemical smog and a potent greenhouse gas.
Human exposure to elevated CO impairs oxygen uptake in the bloodstream. Under CO-free conditions, oxygen is transported from the lungs to tissues by hemoglobin. When CO is present, it mimics the shape of oxygen and binds instead to the hemoglobin. The molecule is not easily released, blocking further oxygen uptake, and ultimately depriving organs and tissues of life-sustaining oxygen. The symptoms of CO poisoning range from dizziness, mild headaches, and nausea at lower levels to severe headaches, seizures, and death at higher levels.
The EPA national outdoor air quality standard for CO is nine parts per million or ppm (0.0009 percent) averaged over an eight-hour period. The gas is life-threatening after three hours at 400 ppm (0.04 percent) and within minutes at 1.28 percent. In 1996, 525 deaths in the United States were attributed to unintentional and 1,988 deaths to intentional CO poisoning.
Exposure to CO can be reduced by assuring adequate ventilation when near any combustion source. Indoor cooking with charcoal and running gaspowered engines inside a garage are both dangerous and should be avoided. Fuel-burning appliances and fireplaces ought to be routinely inspected.
CO detectors are available to detect less obvious sources, such as a malfunctioning furnace. The sensors operate in one of three ways: They mimic the body's response to CO (biomimetic detectors), they allow a heated metal oxide to react with the gas (metal oxide detectors), or they facilitate a reaction using platinum electrodes immersed in an electrolyte solution (electrochemical detectors). The lowest level that a CO alarm can detect is 70 ppm.
Read more: Carbon Monoxide - water, environmental, United States, EPA, human, sources, life http://www.pollutionissues.com/Br-Co/Carbon-Monoxide.html#ixzz18jhmJHEs
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Sources of Carbon Monoxide in the Home
engines (boats and lawn mowers), charcoal and wood fires, agricultural burning, and tobacco smoke.
CO is classified as an indirect greenhouse gas. It does not contribute to global warming directly, but leads to the formation of ozone. Ozone is the major air pollutant formed in photochemical smog and a potent greenhouse gas.
Human exposure to elevated CO impairs oxygen uptake in the bloodstream. Under CO-free conditions, oxygen is transported from the lungs to tissues by hemoglobin. When CO is present, it mimics the shape of oxygen and binds instead to the hemoglobin. The molecule is not easily released, blocking further oxygen uptake, and ultimately depriving organs and tissues of life-sustaining oxygen. The symptoms of CO poisoning range from dizziness, mild headaches, and nausea at lower levels to severe headaches, seizures, and death at higher levels.
The EPA national outdoor air quality standard for CO is nine parts per million or ppm (0.0009 percent) averaged over an eight-hour period. The gas is life-threatening after three hours at 400 ppm (0.04 percent) and within minutes at 1.28 percent. In 1996, 525 deaths in the United States were attributed to unintentional and 1,988 deaths to intentional CO poisoning.
Exposure to CO can be reduced by assuring adequate ventilation when near any combustion source. Indoor cooking with charcoal and running gaspowered engines inside a garage are both dangerous and should be avoided. Fuel-burning appliances and fireplaces ought to be routinely inspected.
CO detectors are available to detect less obvious sources, such as a malfunctioning furnace. The sensors operate in one of three ways: They mimic the body's response to CO (biomimetic detectors), they allow a heated metal oxide to react with the gas (metal oxide detectors), or they facilitate a reaction using platinum electrodes immersed in an electrolyte solution (electrochemical detectors). The lowest level that a CO alarm can detect is 70 ppm.
Read more: Carbon Monoxide - water, environmental, United States, EPA, human, sources, life http://www.pollutionissues.com/Br-Co/Carbon-Monoxide.html#ixzz18jhmJHEs
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Vehicular Pollution
The large majority of today's cars and trucks travel by using internal combustion engines that burn gasoline or other fossil fuels. The process of burning gasoline to power cars and trucks contributes to air pollution by releasing a variety of emissions into the atmosphere. Emissions that are released directly into the atmosphere from the tailpipes of cars and trucks are the primary source of vehicular pollution. But motor vehicles also pollute the air during the processes of manufacturing, refueling, and from the emissions associated with oil refining and distribution of the fuel they burn.
Primary pollution from motor vehicles is pollution that is emitted directly into the atmosphere, whereas secondary pollution results from chemical reactions between pollutants after they have been released into the air.
Despite decades of efforts to control air pollution, at least 92 million Americans still live in areas with chronic smog problems. The U.S. Environmental Protection Agency (EPA) predicts that by 2010, even with the benefit of current and anticipated pollution control programs, more than 93 million people will live in areas that violate health standards for ozone (urban smog), and more than 55 million Americans will suffer from unhealthy levels of fine-particle pollution, which is especially harmful to children and senior citizens.
While new cars and light trucks emit about 90 percent fewer pollutants than they did three decades ago, total annual vehicle-miles driven have increased by more than 140 percent since 1970 and are expected to increase another 25 percent by 2010. The emission reductions from individual vehicles have not adequately kept pace with the increase in miles driven and the market trend toward more-polluting light trucks, a category that includes sports utility vehicles (SUVs). As a result, cars and light trucks are still the largest single source of air pollution in most urban areas, accounting for onequarter of emissions of smog-forming pollutants nationwide.
Ingredients of Vehicular Pollution
The following are the major pollutants associated with motor vehicles:
•Ozone (O 3 ). The primary ingredient in urban smog, ozone is created when hydrocarbons and nitrogen oxides (NO x )—both of which are chemicals released by automobile fuel combustion—react with sunlight. Though beneficial in the upper atmosphere, at the ground level ozone can irritate the respiratory system, causing coughing, choking, and reduced lung capacity.
•Particulate matter (PM). These particles of soot, metals, and pollen give smog its murky color. Among vehicular pollution, fine particles (those less than one-tenth the diameter of a human hair) pose the most serious threat to human health by penetrating deep into lungs. In addition to direct emissions of fine particles, automobiles release nitrogen oxides, hydrocarbons, and sulfur dioxide, which generate additional fine particles as secondary pollution.
•Nitrogen oxides (NO x ). These vehicular pollutants can cause lung irritation and weaken the body's defenses against respiratory infections such as pneumonia and influenza. In addition, they assist in the formation of ozone and particulate matter. In many cities, NO x pollution accounts for one-third of the fine particulate pollution in the air.
During the morning rush hour, the Miguel Hidalgo area of Mexico City is clogged with traffic and smog. (
©Stephanie Maze/Corbis. Reproduced by permission.
)
•Carbon monoxide (CO). This odorless, colorless gas is formed by the combustion of fossil fuels such as gasoline. Cars and trucks are the source of nearly two-thirds of this pollutant. When inhaled, CO blocks the transport of oxygen to the brain, heart, and other vital organs in the human body. Newborn children and people with chronic illnesses are especially susceptible to the effects of CO.
•Sulfur dioxide (SO 2 ). Motor vehicles create this pollutant by burning sulfur-containing fuels, especially diesel. It can react in the atmosphere to form fine particles and can pose a health risk to young children and asthmatics.
•Hazardous air pollutants (toxics). These chemical compounds, which are emitted by cars, trucks, refineries, gas pumps, and related sources, have been linked to birth defects, cancer, and other serious illnesses. The EPA estimates that the air toxics emitted from cars and trucks account for half of all cancers caused by air pollution.
Vehicular Emissions That Contribute to Global Warming
Carbon monoxide, ozone, particulate matter, and the other forms of pollution listed above can cause smog and other air quality concerns, but there are vehicular emissions that contribute to a completely different pollution issue: global warming.
Morning rush hour traffic waiting to pay the toll to cross the Oakland Bay Bridge in August 1989. (
©James A. Sugar/Corbis. Reproduced by permission.
)
The gases that contribute to global warming are related to the chemical composition of the Earth's atmosphere. Some of the gases in the atmosphere function like the panes of a greenhouse. They let some radiation (heat) in from the sun but do not let it all back out, thereby helping to keep the Earth warm. The past century has seen a dramatic increase in the atmospheric concentration of heat-trapping gasses, due to human activity. If this trend continues, scientists project that the earth's average surface temperature will increase between 2.5°F and 10.4°F by the year 2100.
One of these important heat-trapping gasses is carbon dioxide (CO 2 ). Motor vehicles are responsible for almost one-quarter of annual U.S. emissions of CO 2 . The U.S. transportation sector emits more CO 2 than all but three other countries' emissions from all sources combined.
Curbing Vehicular Pollution
Vehicular emissions that contribute to air quality problems, smog, and global warming can be reduced by putting better pollution-control technologies on
Fuel Economy by Model Year
cars and trucks, burning less fuel, switching to cleaner fuels, using technologies that reduce or eliminate emissions, and reducing the number of vehicle-miles traveled.
Pollution Control Technology
Federal and California regulations require the use of technologies that have dramatically reduced the amount of smog-forming pollution and carbon monoxide coming from a vehicle's tailpipe. For gasoline vehicles, "threeway" catalysts, precise engine and fuel controls, and evaporative emission controls have been quite successful. More advanced versions of these technologies are in some cars and can reduce smog-forming emissions from new vehicles by a factor of ten. For diesel vehicles, "two-way" catalysts and engine controls have been able to reduce hydrocarbon and carbon monoxide emissions, but nitrogen oxide and toxic particulate-matter emissions remain very high. More advanced diesel-control technologies are under development, but it is unlikely that they will be able to clean up diesel to the degree already achieved in the cleanest gasoline vehicles.
Added concerns surround the difference between new vehicle emissions and the emissions of a car or truck over a lifetime of actual use. Vehicles with good emission-control technology that is not properly maintained can become "gross polluters" that are responsible for a significant amount of existing air-quality problems. New technologies have also been developed to identify emission-equipment control failures, and can be used to help reduce the "gross polluter" problem.
Burning Less Fuel
The key to burning less fuel is making cars and trucks more efficient and putting that efficiency to work in improving fuel economy. The U.S. federal government sets a fuel-economy standard for all passenger vehicles. However, these standards have remained mostly constant for the past decade. In addition, sales of lower-fuel-economy light trucks, such as SUVs, pickups, and minivans, have increased dramatically. As a result, on average, the U.S. passenger-vehicle fleet actually travels less distance on a gallon of gas than it did twenty years ago. This has led to an increase in heat-trapping gas emissions from cars and trucks and to an increase in smog-forming and toxic emissions resulting from the production and transportation of gasoline to the fuel pump.
This trend can be reversed through the use of existing technologies that help cars and trucks go farther on a gallon of gasoline. These include more efficient engines and transmissions, improved aerodynamics, better tires, and high strength steel and aluminum. More advanced technologies, such as hybrid-electric vehicles that use a gasoline engine and an electric motor plus a battery, can cut fuel use even further. These technologies carry with them additional costs, but pay for themselves through savings at the gasoline pump.
Zero-Emission Vehicles
As more cars and trucks are sold and total annual mileage increases, improving pollution-control technology and burning less fuel continues to be vital, especially in rapidly growing urban areas. However, eliminating emissions from the tailpipe goes even further to cut down on harmful air pollutants.
Hydrogen fuel-cell and electric vehicles move away from burning fuel and use electrochemical processes instead to produce the needed energy to drive a car down the road. Fuel-cell vehicles run on electricity that is produced directly from the reaction of hydrogen and oxygen. The only byproduct is water—which is why fuel-cell cars and trucks are called zero-emission vehicles. Electric vehicles store energy in an onboard battery, emitting nothing from the tailpipe.
The hydrogen for the fuel cell and the electricity for the battery must still be produced somewhere, so there will still be upstream emissions associated with these vehicles. These stationary sources, however, are easier to control and can ultimately be converted to use wind, solar, and other renewable energy sources to come as close as possible to true zero-emission vehicles.
Cleaner Fuels
The gasoline and diesel fuel in use today contains significant amounts of sulfur and other compounds that make it harder for existing control technology to keep vehicles clean. Removing the sulfur from the fuel and cutting down on the amount of light hydrocarbons helps pollution-control technology to work better and cuts down on evaporative and refueling emissions.
Further large-scale reductions of other tailpipe pollution and CO 2 can be accomplished with a shift away from conventional fuels. Alternative fuels such as natural gas, methanol, ethanol, and hydrogen can deliver benefits to the environment while helping to move the United States away from its dependence on oil. All of these fuels inherently burn cleaner than diesel and gasoline, and they have a lower carbon content—resulting in less CO 2 . Most of these fuels are also more easily made from renewable resources, and fuels such as natural gas and methanol help provide a bridge to producing hydrogen for fuel-cell vehicles.
Reducing Driving
Because we are still dependent on fossil fuels and the number of cars on the road is expected to double, a significant reduction in vehicular pollution requires more than gains in fuel efficiency. Measures that encourage us to drive less can help curb vehicular pollution and protect natural resources and public health.
Alternatives that can reduce the number of vehicle-miles traveled include
•providing transportation alternatives to cars, including mass transit, bicycle, and pedestrian routes;
•promoting transit-oriented, compact developments in and around cities and towns; and adopting policies to improve existing roads and infrastructure.
Personal Contributions
Individuals can also make a difference in the effort to reduce pollution from cars and trucks. How we drive and how we take care of our vehicles affects fuel economy and pollution emissions. The following are several ways people can reduce the harmful environmental impact of cars.
•Driving as little as possible is the best way to reduce the harmful environmental impact of transportation needs. Carpooling, mass transit, biking, and walking are ways to limit the number of miles we drive. Choosing a place to live that reduces the need to drive is another way.
•Driving moderately and avoiding high-speed driving and frequent stopping and starting can reduce both fuel use and pollutant emissions.
•Simple vehicle maintenance—such as regular oil changes, air-filter changes, and spark plug replacements—can lengthen the life of your car as well as improve fuel economy and minimize emissions.
•Keeping tires properly inflated saves fuel by reducing the amount of drag a car's engine must overcome.
•During start-up, a car's engine burns extra gasoline. However, letting an engine idle for more than a minute burns more fuel than turning off the engine and restarting it.
•During warm periods with strong sunlight, parking in the shade keeps a car cooler and can minimize the evaporation of fuel.
Read more: Vehicular Pollution - water, effects, environmental, pollutants, impact, EPA, chemicals, toxic, human, power, sources, use, life, health, oil http://www.pollutionissues.com/Ve-Z/Vehicular-Pollution.html#ixzz18jhZG4lU
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Primary pollution from motor vehicles is pollution that is emitted directly into the atmosphere, whereas secondary pollution results from chemical reactions between pollutants after they have been released into the air.
Despite decades of efforts to control air pollution, at least 92 million Americans still live in areas with chronic smog problems. The U.S. Environmental Protection Agency (EPA) predicts that by 2010, even with the benefit of current and anticipated pollution control programs, more than 93 million people will live in areas that violate health standards for ozone (urban smog), and more than 55 million Americans will suffer from unhealthy levels of fine-particle pollution, which is especially harmful to children and senior citizens.
While new cars and light trucks emit about 90 percent fewer pollutants than they did three decades ago, total annual vehicle-miles driven have increased by more than 140 percent since 1970 and are expected to increase another 25 percent by 2010. The emission reductions from individual vehicles have not adequately kept pace with the increase in miles driven and the market trend toward more-polluting light trucks, a category that includes sports utility vehicles (SUVs). As a result, cars and light trucks are still the largest single source of air pollution in most urban areas, accounting for onequarter of emissions of smog-forming pollutants nationwide.
Ingredients of Vehicular Pollution
The following are the major pollutants associated with motor vehicles:
•Ozone (O 3 ). The primary ingredient in urban smog, ozone is created when hydrocarbons and nitrogen oxides (NO x )—both of which are chemicals released by automobile fuel combustion—react with sunlight. Though beneficial in the upper atmosphere, at the ground level ozone can irritate the respiratory system, causing coughing, choking, and reduced lung capacity.
•Particulate matter (PM). These particles of soot, metals, and pollen give smog its murky color. Among vehicular pollution, fine particles (those less than one-tenth the diameter of a human hair) pose the most serious threat to human health by penetrating deep into lungs. In addition to direct emissions of fine particles, automobiles release nitrogen oxides, hydrocarbons, and sulfur dioxide, which generate additional fine particles as secondary pollution.
•Nitrogen oxides (NO x ). These vehicular pollutants can cause lung irritation and weaken the body's defenses against respiratory infections such as pneumonia and influenza. In addition, they assist in the formation of ozone and particulate matter. In many cities, NO x pollution accounts for one-third of the fine particulate pollution in the air.
During the morning rush hour, the Miguel Hidalgo area of Mexico City is clogged with traffic and smog. (
©Stephanie Maze/Corbis. Reproduced by permission.
)
•Carbon monoxide (CO). This odorless, colorless gas is formed by the combustion of fossil fuels such as gasoline. Cars and trucks are the source of nearly two-thirds of this pollutant. When inhaled, CO blocks the transport of oxygen to the brain, heart, and other vital organs in the human body. Newborn children and people with chronic illnesses are especially susceptible to the effects of CO.
•Sulfur dioxide (SO 2 ). Motor vehicles create this pollutant by burning sulfur-containing fuels, especially diesel. It can react in the atmosphere to form fine particles and can pose a health risk to young children and asthmatics.
•Hazardous air pollutants (toxics). These chemical compounds, which are emitted by cars, trucks, refineries, gas pumps, and related sources, have been linked to birth defects, cancer, and other serious illnesses. The EPA estimates that the air toxics emitted from cars and trucks account for half of all cancers caused by air pollution.
Vehicular Emissions That Contribute to Global Warming
Carbon monoxide, ozone, particulate matter, and the other forms of pollution listed above can cause smog and other air quality concerns, but there are vehicular emissions that contribute to a completely different pollution issue: global warming.
Morning rush hour traffic waiting to pay the toll to cross the Oakland Bay Bridge in August 1989. (
©James A. Sugar/Corbis. Reproduced by permission.
)
The gases that contribute to global warming are related to the chemical composition of the Earth's atmosphere. Some of the gases in the atmosphere function like the panes of a greenhouse. They let some radiation (heat) in from the sun but do not let it all back out, thereby helping to keep the Earth warm. The past century has seen a dramatic increase in the atmospheric concentration of heat-trapping gasses, due to human activity. If this trend continues, scientists project that the earth's average surface temperature will increase between 2.5°F and 10.4°F by the year 2100.
One of these important heat-trapping gasses is carbon dioxide (CO 2 ). Motor vehicles are responsible for almost one-quarter of annual U.S. emissions of CO 2 . The U.S. transportation sector emits more CO 2 than all but three other countries' emissions from all sources combined.
Curbing Vehicular Pollution
Vehicular emissions that contribute to air quality problems, smog, and global warming can be reduced by putting better pollution-control technologies on
Fuel Economy by Model Year
cars and trucks, burning less fuel, switching to cleaner fuels, using technologies that reduce or eliminate emissions, and reducing the number of vehicle-miles traveled.
Pollution Control Technology
Federal and California regulations require the use of technologies that have dramatically reduced the amount of smog-forming pollution and carbon monoxide coming from a vehicle's tailpipe. For gasoline vehicles, "threeway" catalysts, precise engine and fuel controls, and evaporative emission controls have been quite successful. More advanced versions of these technologies are in some cars and can reduce smog-forming emissions from new vehicles by a factor of ten. For diesel vehicles, "two-way" catalysts and engine controls have been able to reduce hydrocarbon and carbon monoxide emissions, but nitrogen oxide and toxic particulate-matter emissions remain very high. More advanced diesel-control technologies are under development, but it is unlikely that they will be able to clean up diesel to the degree already achieved in the cleanest gasoline vehicles.
Added concerns surround the difference between new vehicle emissions and the emissions of a car or truck over a lifetime of actual use. Vehicles with good emission-control technology that is not properly maintained can become "gross polluters" that are responsible for a significant amount of existing air-quality problems. New technologies have also been developed to identify emission-equipment control failures, and can be used to help reduce the "gross polluter" problem.
Burning Less Fuel
The key to burning less fuel is making cars and trucks more efficient and putting that efficiency to work in improving fuel economy. The U.S. federal government sets a fuel-economy standard for all passenger vehicles. However, these standards have remained mostly constant for the past decade. In addition, sales of lower-fuel-economy light trucks, such as SUVs, pickups, and minivans, have increased dramatically. As a result, on average, the U.S. passenger-vehicle fleet actually travels less distance on a gallon of gas than it did twenty years ago. This has led to an increase in heat-trapping gas emissions from cars and trucks and to an increase in smog-forming and toxic emissions resulting from the production and transportation of gasoline to the fuel pump.
This trend can be reversed through the use of existing technologies that help cars and trucks go farther on a gallon of gasoline. These include more efficient engines and transmissions, improved aerodynamics, better tires, and high strength steel and aluminum. More advanced technologies, such as hybrid-electric vehicles that use a gasoline engine and an electric motor plus a battery, can cut fuel use even further. These technologies carry with them additional costs, but pay for themselves through savings at the gasoline pump.
Zero-Emission Vehicles
As more cars and trucks are sold and total annual mileage increases, improving pollution-control technology and burning less fuel continues to be vital, especially in rapidly growing urban areas. However, eliminating emissions from the tailpipe goes even further to cut down on harmful air pollutants.
Hydrogen fuel-cell and electric vehicles move away from burning fuel and use electrochemical processes instead to produce the needed energy to drive a car down the road. Fuel-cell vehicles run on electricity that is produced directly from the reaction of hydrogen and oxygen. The only byproduct is water—which is why fuel-cell cars and trucks are called zero-emission vehicles. Electric vehicles store energy in an onboard battery, emitting nothing from the tailpipe.
The hydrogen for the fuel cell and the electricity for the battery must still be produced somewhere, so there will still be upstream emissions associated with these vehicles. These stationary sources, however, are easier to control and can ultimately be converted to use wind, solar, and other renewable energy sources to come as close as possible to true zero-emission vehicles.
Cleaner Fuels
The gasoline and diesel fuel in use today contains significant amounts of sulfur and other compounds that make it harder for existing control technology to keep vehicles clean. Removing the sulfur from the fuel and cutting down on the amount of light hydrocarbons helps pollution-control technology to work better and cuts down on evaporative and refueling emissions.
Further large-scale reductions of other tailpipe pollution and CO 2 can be accomplished with a shift away from conventional fuels. Alternative fuels such as natural gas, methanol, ethanol, and hydrogen can deliver benefits to the environment while helping to move the United States away from its dependence on oil. All of these fuels inherently burn cleaner than diesel and gasoline, and they have a lower carbon content—resulting in less CO 2 . Most of these fuels are also more easily made from renewable resources, and fuels such as natural gas and methanol help provide a bridge to producing hydrogen for fuel-cell vehicles.
Reducing Driving
Because we are still dependent on fossil fuels and the number of cars on the road is expected to double, a significant reduction in vehicular pollution requires more than gains in fuel efficiency. Measures that encourage us to drive less can help curb vehicular pollution and protect natural resources and public health.
Alternatives that can reduce the number of vehicle-miles traveled include
•providing transportation alternatives to cars, including mass transit, bicycle, and pedestrian routes;
•promoting transit-oriented, compact developments in and around cities and towns; and adopting policies to improve existing roads and infrastructure.
Personal Contributions
Individuals can also make a difference in the effort to reduce pollution from cars and trucks. How we drive and how we take care of our vehicles affects fuel economy and pollution emissions. The following are several ways people can reduce the harmful environmental impact of cars.
•Driving as little as possible is the best way to reduce the harmful environmental impact of transportation needs. Carpooling, mass transit, biking, and walking are ways to limit the number of miles we drive. Choosing a place to live that reduces the need to drive is another way.
•Driving moderately and avoiding high-speed driving and frequent stopping and starting can reduce both fuel use and pollutant emissions.
•Simple vehicle maintenance—such as regular oil changes, air-filter changes, and spark plug replacements—can lengthen the life of your car as well as improve fuel economy and minimize emissions.
•Keeping tires properly inflated saves fuel by reducing the amount of drag a car's engine must overcome.
•During start-up, a car's engine burns extra gasoline. However, letting an engine idle for more than a minute burns more fuel than turning off the engine and restarting it.
•During warm periods with strong sunlight, parking in the shade keeps a car cooler and can minimize the evaporation of fuel.
Read more: Vehicular Pollution - water, effects, environmental, pollutants, impact, EPA, chemicals, toxic, human, power, sources, use, life, health, oil http://www.pollutionissues.com/Ve-Z/Vehicular-Pollution.html#ixzz18jhZG4lU
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Acid Rain
Acid rain is any form of atmospherically deposited acidic substance containing strong mineral acids of anthropogenic origin. It was reportedly first described in England by Robert Angus Smith in 1872. Acid rain is more properly called acidic deposition, which occurs in both wet and dry forms. Wet deposition usually exists in the form of rain, snow, or sleet but also may occur as fog, dew, or cloud water condensed on plants or the earth's surface. Dry deposition includes solid particles (aerosols) that fall to the earth's surface. Condensation of fog, dew, or cloud water is referred to as occult deposition.
The most common acidic substances are compounds containing hydrogen (H + ), sulfates (SO = 4 ), and nitrates (NO 3 ). The chief source of these compounds is the combustion of fossil fuels such as coal, petroleum, and petroleum by-products, primarily gasoline. Agriculture is also a major source of nitrates. Power plants that burn coal contribute over 50 percent of sulfates to the atmosphere and 25 percent of nitrates.
Prior to the Clean Air Act of 1970, acid deposition was mostly a local problem confined to the immediate vicinity of the pollution source. After 1970, emitters of acidifying pollutants increased the height of smokestacks to reduce local pollution by diluting pollutants in larger volumes of air. The result was the regional transport of acid deposition to remote locations. Acid rain has adversely affected large areas of the mountainous regions of the eastern United States and Canada, Scandinavia, central and Eastern Europe, and parts of China. Areas that are downwind of heavy concentrations of power plants receive the most deposition.
Acid rain acidifies soils with low calcium carbonate levels, which results in the acidification of water passing through the soil to streams and lakes. Calcium carbonate soil-buffering capacity is related to soil origin. Soils weathered from rocks high in calcium carbonate have high calcium carbonate buffer capacity. Fish and other aquatic life have been eliminated from streams and lakes by acid deposition. Continued acid deposition leaches calcium and magnesium from the soil and results in the increased mobility of aluminum, which is toxic to both animals and plants. Aluminum is always present in soils, but it is innocuous until mobilized into soil water by acidic deposition. Its presence in water in small amounts will cause the outright
Spatial Patterns of Sulfur Dioxide and Nitrogen Oxide Emissions in the Eastern United States. (
Driscoll, C.T.; G.B. Lawrence; A.J. Bulger; T.J. Butler; C.S. Cronan; C. Eager; K.F. Lambert; G.E. Likens; J. L. Stoddard; and K.C. Weathers. (2001) Acid Rain Revisited: Advances in Scientific Understanding since the Passage of the 1970 Clean Air Act Amendments. Hubbard Brook Research Foundation. Science Links TM Publication, Vol. 1, No. 1.
)
Long-Term Trends in Sulfate Nitrate, and Ammonium Concentrations and pH in wet deposition at the HBEF, 1963-1994. (
Driscoll, C.T.; G.B. Lawrence; A.J. Bulger; T.J. Butler; C.S. Cronan; C. Eager; K.F. Lambert; G.E. Likens; J. L. Stoddard; and K.C. Weathers. (2001) Acid Rain Revisited: ADvances in Scientific Understanding since the Passage of the 1970 Clean Air Act Amendments. Hubbard Brook REsearch Foundation. Science Links TM Publication, Vol. 1, No. 1.
)
death of fish and other aquatic life, disrupt normal fish spawning, and reduce populations of many species of aquatic insects.
Acid forest soils are thought to cause forests to decline and grow more slowly. Soil acidity causes nutrient deficiencies in trees and other plants and predisposes them to attack by pathogens such as insects and fungi. Soil acidity also increases photo-oxidant stress in plants. Monuments and buildings made of marble or other forms of calcium carbonate and statuary made of certain metals such as copper are also damaged by acid deposition. The acidification of waters leads to increases in mercury uptake by fish, causing them to be unsafe to eat.
The governments of the European Economic Community, Canada, and the United States have taken steps to reduce the emissions of sulfate and nitrates. The Clean Air Act Amendments of 1990 were designed to reduce U.S. emissions of sulfate by about 40 percent through a program of emissions trading between emissions generators, use of low-sulfur coals (fuel switching), and controls on power plant smokestack emissions. Although this program has significantly reduced acidic deposition in many parts of the northeastern United States, many scientists agree that additional reductions will be required to prevent continued damage and allow for meaningful recovery of affected lakes and streams.
Read more: Acid Rain - water, pollutants, United States, causes, soil, toxic, power, use, life http://www.pollutionissues.com/A-Bo/Acid-Rain.html#ixzz18jhML97d
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
The most common acidic substances are compounds containing hydrogen (H + ), sulfates (SO = 4 ), and nitrates (NO 3 ). The chief source of these compounds is the combustion of fossil fuels such as coal, petroleum, and petroleum by-products, primarily gasoline. Agriculture is also a major source of nitrates. Power plants that burn coal contribute over 50 percent of sulfates to the atmosphere and 25 percent of nitrates.
Prior to the Clean Air Act of 1970, acid deposition was mostly a local problem confined to the immediate vicinity of the pollution source. After 1970, emitters of acidifying pollutants increased the height of smokestacks to reduce local pollution by diluting pollutants in larger volumes of air. The result was the regional transport of acid deposition to remote locations. Acid rain has adversely affected large areas of the mountainous regions of the eastern United States and Canada, Scandinavia, central and Eastern Europe, and parts of China. Areas that are downwind of heavy concentrations of power plants receive the most deposition.
Acid rain acidifies soils with low calcium carbonate levels, which results in the acidification of water passing through the soil to streams and lakes. Calcium carbonate soil-buffering capacity is related to soil origin. Soils weathered from rocks high in calcium carbonate have high calcium carbonate buffer capacity. Fish and other aquatic life have been eliminated from streams and lakes by acid deposition. Continued acid deposition leaches calcium and magnesium from the soil and results in the increased mobility of aluminum, which is toxic to both animals and plants. Aluminum is always present in soils, but it is innocuous until mobilized into soil water by acidic deposition. Its presence in water in small amounts will cause the outright
Spatial Patterns of Sulfur Dioxide and Nitrogen Oxide Emissions in the Eastern United States. (
Driscoll, C.T.; G.B. Lawrence; A.J. Bulger; T.J. Butler; C.S. Cronan; C. Eager; K.F. Lambert; G.E. Likens; J. L. Stoddard; and K.C. Weathers. (2001) Acid Rain Revisited: Advances in Scientific Understanding since the Passage of the 1970 Clean Air Act Amendments. Hubbard Brook Research Foundation. Science Links TM Publication, Vol. 1, No. 1.
)
Long-Term Trends in Sulfate Nitrate, and Ammonium Concentrations and pH in wet deposition at the HBEF, 1963-1994. (
Driscoll, C.T.; G.B. Lawrence; A.J. Bulger; T.J. Butler; C.S. Cronan; C. Eager; K.F. Lambert; G.E. Likens; J. L. Stoddard; and K.C. Weathers. (2001) Acid Rain Revisited: ADvances in Scientific Understanding since the Passage of the 1970 Clean Air Act Amendments. Hubbard Brook REsearch Foundation. Science Links TM Publication, Vol. 1, No. 1.
)
death of fish and other aquatic life, disrupt normal fish spawning, and reduce populations of many species of aquatic insects.
Acid forest soils are thought to cause forests to decline and grow more slowly. Soil acidity causes nutrient deficiencies in trees and other plants and predisposes them to attack by pathogens such as insects and fungi. Soil acidity also increases photo-oxidant stress in plants. Monuments and buildings made of marble or other forms of calcium carbonate and statuary made of certain metals such as copper are also damaged by acid deposition. The acidification of waters leads to increases in mercury uptake by fish, causing them to be unsafe to eat.
The governments of the European Economic Community, Canada, and the United States have taken steps to reduce the emissions of sulfate and nitrates. The Clean Air Act Amendments of 1990 were designed to reduce U.S. emissions of sulfate by about 40 percent through a program of emissions trading between emissions generators, use of low-sulfur coals (fuel switching), and controls on power plant smokestack emissions. Although this program has significantly reduced acidic deposition in many parts of the northeastern United States, many scientists agree that additional reductions will be required to prevent continued damage and allow for meaningful recovery of affected lakes and streams.
Read more: Acid Rain - water, pollutants, United States, causes, soil, toxic, power, use, life http://www.pollutionissues.com/A-Bo/Acid-Rain.html#ixzz18jhML97d
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Air Pollution
Air pollution is a phenomenon by which particles (solid or liquid) and gases contaminate the environment. Such contamination can result in health effects on the population, which might be either chronic (arising from long-term exposure), or acute (due to accidents). Other effects of pollution include damage to materials (e.g., the marble statues on the Parthenon are corroded as a result of air pollution in the city of Athens), agricultural damage (such as reduced crop yields and tree growth), impairment of visibility (tiny particles scatter light very efficiently), and even climate change (certain gases absorb energy emitted by the earth, leading to global warming).
Air pollution is certainly not a new phenomenon. Early references to it date back to the Middle Ages, when smoke from burning coal was already such a serious problem that in 1307 King Edward I banned its use in lime kilns in London. More recently, there have been major episodes of air pollution, such as the 1930 catastrophe in the Meuse Valley, Belgium, where SO 2 and particulate matter, combined with a high relative humidity, caused sixty-three excess deaths in five days. In 1948 similar conditions in Donora, Pennsylvania, a small industrial city, caused twenty excess deaths in five days,
The New York City skyline on a smoggy day in the 1960s. (
©Roger Wood/Corbis. Reproduced by permission
.)
U.S. National Pollutant Emission Estimates for 1999 (
Adapted from http://www.epa.gov/ttn/chief/trends/trends99/tier3_1999emis.pdf
)
U.S. NATIONAL POLLUTANT EMISSION ESTIMATES FOR 1999
(thousand short tons) Source Category CO NO x VOC SO 2 PM 10 PM 2.5 Total
SOURCE: Adapted from http://www.epa.gov/ttn/chief/trends/trends99/tier3_1999emis.pdf .
On-road Vehicles 49,989 8,590 5,297 363 295 229 64,763
Non-road Vehicles 25,162 5,515 3,232 936 458 411 35,714
Miscellaneous 9,378 320 716 12 20,634 4,454 35,514
Fuel Combustion 5,322 10,026 904 16,091 1,029 766 34,138
Electric Utilities 445 5,715 56 12,698 255 128 19,267
Industrial 1,178 3,136 178 2,805 236 151 7,684
Other 3,699 1,175 670 588 568 487 7,187
Waste Disposal and Recycling 3,792 91 586 37 587 525 5,618
Solvent Utilization 2 3 4,825 1 6 6 4,843
Metals Processing 1,678 88 77 401 147 103 2,494
Other Industrial Processes 599 470 449 418 343 191 2,470
Chemical Manufacturing 1,081 131 395 262 66 40 1,975
Storage and Transport 72 16 1,240 5 85 31 1,449
Petroleum Industries 366 143 424 341 29 17 1,320
Total 97,441 25,393 18,145 18,867 23,679 6,773 190,298
and in the early 1950s in London, England, two episodes of "killer fogs" claimed the lives of more than 6,000 people.
Classification of Air Pollutants
Not all pollutants are a result of human activity. Natural pollutants are those that are found in nature or are emitted from natural sources. For example, volcanic activity produces sulfur dioxide, and particulate pollution may derive from forest fires or windblown dust. Anthropogenic pollutants are those that are produced by humans or controlled processes. For example, sulfur dioxide is produced by fossil fuel combustion and particulate matter comes from diesel engines.
Air pollutants also are classified as primary or secondary. Primary pollutants are those that are emitted directly into the atmosphere from an identifiable source. Examples include carbon monoxide and sulfur dioxide. Secondary pollutants are those that are produced in the atmosphere by chemical and physical processes from primary pollutants and natural constituents. For example, ozone is produced by hydrocarbons and oxides of nitrogen (both of which may be produced by car emissions) and sunlight. See the table for a listing of estimated pollutant emissions in the United States in 1999.
Air Pollution Control Laws and Regulations
The earliest programs to manage air quality in the United States date to the late 1880s; they attempted to regulate emissions from smokestacks using nuisance law municipal ordinances. Little progress was made in air pollution control during the first half of the twentieth century.
In the 1950s there was a shift away from nuisance law and municipal ordinances as the basis for managing air quality toward increased federal involvement. The Air Pollution Control Act of 1955 established a program for federally funded research grants in the area of air pollution, but the role of the federal government remained a limited one.
National Ambient Air Quality Standards (
U.S. Environmental Protection Agency
)
NATIONAL AMBIENT AIR QUALITY STANDARDS Pollutant Standard Value* Standard Type
*Parenthetical value is an approximately equivalent concentration.
SOURCE: U.S. Environmental Protection Agency
Carbon Monoxide (CO)
8-hour Average 9 ppm (10 mg/m 3 ) Primary
1-hour Average 35 ppm (40 mg/m 3 ) Primary
Nitrogen Dioxide (NO 2 )
Annual Arithmetic Mean 0.053 ppm (100 μg/m 3 ) Primary & Secondary
Ozone (O 3 )
1-hour Average 0.12 ppm (235 μg/m 3 ) Primary & Secondary
8-hour Average 0.08 ppm (157 μg/m 3 ) Primary & Secondary
Lead (Pb)
Quarterly Average 1.5 μg/m 3 Primary & Secondary
Particulate (PM 10) Particles with diameters of 10 micrometers or less
Annual Arithmetic Mean 50 μg/m 3 Primary & Secondary
24-hour Average 150 μg/m 3 Primary & Secondary
Particulate (PM 2.5) Particles with diameters of 2.5 micrometers or less
Annual Arithmetic Mean 15 μg/m 3 Primary & Secondary
24-hour Average 65 μg/m 3 Primary & Secondary
Sulfur Dioxide (SO 2 )
Annual Arithmetic Mean 0.030 ppm (80 μg/m 3 ) Primary
24-hour Average 0.14 ppm (365 μg/m 3 ) Primary
3-hour Average 0.50 ppm (1300 μg/m 3 ) Secondary
It was the Clean Air Act (CAA) of 1963 that further extended the federal government's powers in a significant way, allowing direct federal intervention to reduce interstate pollution.
The Clean Air Act Amendments (CAAA) of 1970 continued many of the programs established by prior legislation; however, several aspects of it represented major changes in strategy by expanding the role of the federal government. The 1970 CAAA defined two types of pollutants that were to be regulated: criteria and hazardous pollutants.
Criteria pollutants, regulated to achieve the attainment of the National Ambient Air Quality Standards (NAAQS), including primary standards for the protection of public health, ". . . the attainment and maintenance of which, . . . allowing an adequate margin of safety, are requisite to protect public health," and secondary standards for the protection of public welfare. The first six criteria pollutants were carbon monoxide (CO), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), total suspended particulate matter (TSP), hydrocarbons, and photochemical oxidants. Lead was added to the list in 1976. In 1979 the photochemical oxidants standard was replaced by one for ozone (O 3 ), and in 1983 the hydrocarbons standard was dropped altogether. In 1987 TSP was changed to PM 10 , and in 1997 PM 2.5 was added to the official list and the ozone standard revised.
National Emission Standards for Hazardous Air Pollutants (NESHAP) were established. A hazardous air pollutant (HAP) was defined as one "to which no ambient air standard is applicable and that . . . causes, or contributes to, air pollution which may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible or incapacitating reversible illness." Examples include asbestos, mercury, benzene, arsenic, and radionuclides.
Estimated Pollutant Emissions in the United States in 2000
ESTIMATED POLLUTANT EMISSIONS IN THE UNITED STATES IN 2000
(Thousand short tons) Source Category CO NO x VOC SO 2 PM 10 PM 2.5
SOURCE: EPA data available from http://www.epa.gov/ttn
Fuel combustion
Electric utilities 445 5,266 64 11,389 270 141
Industrial 1,221 3,222 185 2,894 244 157
Other 2,924 1,161 957 593 483 458
Chemical manufacturing 1,112 134 407 268 67 41
Metals processing 1,735 91 79 411 152 107
Petroleum industries 369 146 433 346 30 17
Other industrial processes 620 487 480 432 355 198
Solvent utilization 2 3 4,827 1 7 6
Storage and transport 74 17 1,225 5 87 32
Waste disposal and recycling 3,609 89 582 35 544 514
On-road vehicles 48,469 8,150 5,035 314 273 209
Nonroad vehicles 29,956 5,558 3,404 1,492 436 400
Miscellaneous 20,806 576 2,710 21 21,926 5,466
Total 109,342 24,899 20,384 18,201 24,875 7,746
Even though the CAAA of 1970 and 1977 placed deadlines on the dates for compliance with the NAAQS, as of 1990 in many areas of the United States, a variety of criteria pollutants existed in concentrations greater than the standards allowed.
As a result, the CAAA of 1990 were passed. They contain eleven major divisions, referred to as titles, the most important of which are the following: Title I: Provisions for Attainment and Maintenance of NAAQS, Title II: Provisions Relating to Mobile Sources, Title III: Hazardous Air Pollutants, Title IV: Acid Deposition Control, Title V: Permits, and Title VI: Stratospheric Ozone Protection, Title VII: Provisions Relating to Enforcement, Title VIII: Miscellaneous Provisions, Title IX: Clean Air Research, Title X: Disadvantaged Business Concerns, and Title XI: Clean Air Employment Transition Assistance.
International Nature of the Problem
Air pollution and the problems it causes are not confined by any geopolitical boundaries. For example, the radioactive cloud resulting from the Chernobyl nuclear accident in 1986 traveled as far as Ireland. A United Nations report warns that haze produced by the burning of wood and fossil fuels is creating a two-mile-thick "Asian browncloud" that covers southeastern Asia and may be responsible for hundreds of thousands of respiratory deaths a year.
In the United States, federal pollution laws and regulations apply to all states, even though some states, such as California, have adopted more stringent standards. Similarly, in the European Union (EU) existing laws apply equally to all members. Countries such as Denmark and Germany, however, have elected to imposed stricter standards than those set by the EU.
International agreements aimed at reducing various pollutants have been signed by various countries. The Montreal Protocol was signed in 1987; its purpose is the reduction of chlorofluorocarbons (CFC), a class of compounds that destroy the stratospheric ozone layer. More recently, in 1997, a conference convened in Kyoto, Japan, to discuss ways of reducing carbon dioxide emissions and other greenhouse gases . The United States has not signed the Kyoto Protocol, arguing that such an agreement would impede its economic progress. It has, however, publicly stated its intention to embark on voluntary reductions of carbon dioxide and other greenhouse gases.
Air Pollutants
In general, air pollutants are divided into two classes: those for which a NAAQS may be set (in other words, the criteria pollutants), and those for which NAAQS are not appropriate (the HAPs). If the ambient concentration of the criteria pollutants is kept below the NAAQS value, then there will be no health damage due to air pollution. The HAP (mostly known or suspected carcinogens), on the other hand, are those that, even in low concentrations, cause significant damage.
Particulate Matter. Particulate matter (PM) is the term used to describe solid or liquid particles that are airborne and dispersed (i.e., scattered, separated). PM originates from a variety of anthropogenic sources, including diesel trucks, power plants, wood stoves, and industrial processes.
The original NAAQS for PM was set in 1970. In 1987, the total suspended particulate matter, TSP, was revised, and a PM 10 (particulate matter with an aerodynamic diameter of 10 μm or less) standard was set. PM 10 , sometimes known as respirable particles, was felt to provide a better correlation of particle concentration with human health.
In 1997 the particulate matter standard was updated, to include the PM2.5 standard. These particles, known as "fine" particles, a significant fraction of which is secondary in nature, are especially detrimental to human health because they can penetrate deep into the lungs. Scientific studies show a link between PM 2.5 (alone, or combined with other pollutants in the air) and a series of significant health effects, even death.
Fine particles are the major cause of reduced visibility in parts of the United States, including many of the national parks. Also, soils, plants, water, or materials are affected by PM. For example, particles containing nitrogen and sulfur that are deposited as acid rain on land or water bodies may alter the nutrient balance and acidity of those environments so that species composition and buffering capacity change. PM causes soiling and erosion damage to materials, including culturally important objects such as carved monuments and statues.
Carbon Monoxide. Carbon monoxide (CO) is a colorless, odorless, and at high levels a poisonous gas that is fairly unreactive. It is formed when carbon in fuels is not burned completely. The major source of CO is motor vehicle exhaust. In cities, as much as 95 percent of all CO emissions result from vehicular (automobile) emissions. Other sources of CO emissions include industrial processes, nontransportation-related fuel combustion, and natural sources such as wildfires.
CO has serious health effects on humans. An exposure to 50 ppm of CO for eight hours can cause reduced psychomotor performance, while CO is lethal to humans when concentrations exceed approximately 750 ppm. Hemoglobin, the part of blood that carries oxygen to body parts, has an affinity of CO that is about 240 times higher than that for oxygen, forming carboxyhemoglobin, COHb. Moreover, the release of oxygen by hemoglobin is reduced in the presence of COHb. However, the effects of CO poisoning are reversible once the CO source has been removed.
Sulfur Dioxide. Sulfur dioxide (SO 2 ) is colorless, nonflammable, nonexplosive gas. Almost 90 percent of anthropogenic SO 2 emissions are the result of fossil fuel combustion (mostly coal) in power plants and other stationary sources. A natural source of sulfur oxides is volcanic activities.
In general, exposure to SO 2 irritates the human upper respiratory tract. The most serious air pollution episodes occurred when there was a synergistic effect of SO 2 with PM and water vapor (fog). Because of this, it has proven difficult to isolate the effects of SO 2 alone.
SO 2 is one of the precursors of acid rain (the term used to describe the deposition of acidic substances from the atmosphere). Also, SO 2 is the precursor of secondary fine sulfate particles, which in turn affect human health and reduce visibility. Prolonged exposure to SO 2 and sulfate PM causes serious damage to materials such as marble, limestone, and mortar. The carbonates (e.g., limestone, CaCO 3 ) in these materials are replaced by sulfates (e.g., gypsum, CaSO 4 ) that are water-soluble and may be washed away easily by rain. This results in an eroded surface.
Nitrogen Dioxide. Nitrogen dioxide (NO 2 ) is a reddish-brown gas. It is a lung irritant and is present in the highest concentrations among other oxides of nitrogen in ambient air. Nitric oxide (NO) and NO 2 are collectively known as NO x .
Anthropogenic emissions of NO x come from high-temperature combustion processes, such as those occurring in automobiles and power plants. Natural sources of NO 2 are lightning and various biological processes in soil. The oxides of nitrogen, much like sulfur dioxide, are precursors of acid rain and visibility-reducing fine nitrate particles.
Ozone. Ozone (O 3 ) is a secondary pollutant and is formed in the atmosphere by the reaction of molecular oxygen, O 2 , and atomic oxygen, O, which comes from the photochemical decomposition of NO 2 . Volatile organic compounds or VOCs (e.g., what one smells when refuelling the car) must also be present if O 3 is to accumulate in the atmosphere.
O 3 occurs naturally in the stratosphere and provides a protective layer from the sun's ultraviolet rays high above the earth. However, at ground level, O 3 is a lung and eye irritant and can cause asthma attacks, especially in young children or other susceptible individuals. O 3 , being a powerful oxidant, also attacks materials and has been found to cause reduced crop yields and stunt tree growth.
Lead. The major sources of lead (Pb) in the atmosphere in the United States are industrial processes from metals smelters. Thirty years ago, the major emissions of Pb resulted from cars burning leaded gasoline. In 2002 only aviation fuels contain relatively large amounts of Pb. The United States is currently working with the World Bank to eliminate the use of leaded gasoline in all countries still using such fuel.
Pb is a toxic metal and can accumulate in the blood, bones, and soft tissues. Even low exposure to Pb can cause mental retardation in children.
Hazardous Air Pollutants. Hazardous air pollutants (HAPs), commonly referred to as air toxics or toxic air pollutants, are pollutants known to cause or suspected of causing cancer or other serious human health effects or damage to the ecosystem.
EPA lists 188 HAPs and regulates sources emitting significant amounts of these identified pollutants. Examples of HAPs are heavy metals (e.g., mercury), volatile chemicals (e.g., benzene), combustion by-products (e.g., dioxins), and solvents (e.g., methylene chloride). HAPs are emitted from many sources, including large stationary industrial facilities (e.g., electric power plants), smaller-area sources (e.g., dry cleaners), mobile sources (e.g., cars), indoor sources (e.g., some building materials and cleaning solvents), and other sources (e.g., wildfires).
Potential human health effects of HAPs include headache, dizziness, nausea, birth defects, and cancer. Environmental effects of HAPs include toxicity to aquatic plants and animals as well as the accumulation of pollutants in the food chain.
Because of the potential serious harmful effects of the HAPs, even at very low concentrations, NAAQS are not appropriate. The EPA has set National Emission Standards for Hazardous Air Pollutants, NESHAP, for only eight of the HAP, including asbestos and vinyl chloride. The EPA regulates HAP by requiring each HAP emission source to meet Maximum Achievable Control Technology (MACT) standards. MACT is defined as "not less stringent than the emission control that is achieved in practice by the best controlled similar source."
Control of Air Pollutants
In general, control of pollutants that are primary in nature, such as SO 2 , NO 2 , CO, and Pb, is easier than control of pollutants that are either entirely secondary (O 3 ) or have a significant secondary component (PM 2.5 ). Primary pollutants may be controlled at the source. For example, SO 2 is controlled by the use of scrubbers, which are industrial devices that remove SO 2 from the exhaust gases from power plants. SO 2 emissions are also reduced by the use of low-sulfur coal or other fuels, such as natural gas, that contain lower amounts of sulfur. NO 2 from industrial sources also may be minimized by scrubbing. NO 2 from cars, as well as CO, are controlled by the use of catalytic converters, engine design modifications, and the use of cleaner burning grades of gasoline. Lead emissions have been reduced significantly since the introduction of lead-free gasoline.
Ozone and particulate matter are two of the most difficult pollutants to control. Reduction of oxides of nitrogen emissions, together with a reduction of VOC emissions is the primary control strategy for minimizing ozone concentrations. Because a large portion of PM 2.5 is secondary in nature, its control is achieved by control of SO 2 , NO 2 , and VOC (which are the precursors of sulfates, nitrates, and carbon-containing particulates).
Read more: Air Pollution - water, effects, environmental, pollutants, United States, types, causes, EPA, soil, chemicals, industrial, liquid, toxic, world, human, power, sources, disposal http://www.pollutionissues.com/A-Bo/Air-Pollution.html#ixzz18jh8mwnS
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Air pollution is certainly not a new phenomenon. Early references to it date back to the Middle Ages, when smoke from burning coal was already such a serious problem that in 1307 King Edward I banned its use in lime kilns in London. More recently, there have been major episodes of air pollution, such as the 1930 catastrophe in the Meuse Valley, Belgium, where SO 2 and particulate matter, combined with a high relative humidity, caused sixty-three excess deaths in five days. In 1948 similar conditions in Donora, Pennsylvania, a small industrial city, caused twenty excess deaths in five days,
The New York City skyline on a smoggy day in the 1960s. (
©Roger Wood/Corbis. Reproduced by permission
.)
U.S. National Pollutant Emission Estimates for 1999 (
Adapted from http://www.epa.gov/ttn/chief/trends/trends99/tier3_1999emis.pdf
)
U.S. NATIONAL POLLUTANT EMISSION ESTIMATES FOR 1999
(thousand short tons) Source Category CO NO x VOC SO 2 PM 10 PM 2.5 Total
SOURCE: Adapted from http://www.epa.gov/ttn/chief/trends/trends99/tier3_1999emis.pdf .
On-road Vehicles 49,989 8,590 5,297 363 295 229 64,763
Non-road Vehicles 25,162 5,515 3,232 936 458 411 35,714
Miscellaneous 9,378 320 716 12 20,634 4,454 35,514
Fuel Combustion 5,322 10,026 904 16,091 1,029 766 34,138
Electric Utilities 445 5,715 56 12,698 255 128 19,267
Industrial 1,178 3,136 178 2,805 236 151 7,684
Other 3,699 1,175 670 588 568 487 7,187
Waste Disposal and Recycling 3,792 91 586 37 587 525 5,618
Solvent Utilization 2 3 4,825 1 6 6 4,843
Metals Processing 1,678 88 77 401 147 103 2,494
Other Industrial Processes 599 470 449 418 343 191 2,470
Chemical Manufacturing 1,081 131 395 262 66 40 1,975
Storage and Transport 72 16 1,240 5 85 31 1,449
Petroleum Industries 366 143 424 341 29 17 1,320
Total 97,441 25,393 18,145 18,867 23,679 6,773 190,298
and in the early 1950s in London, England, two episodes of "killer fogs" claimed the lives of more than 6,000 people.
Classification of Air Pollutants
Not all pollutants are a result of human activity. Natural pollutants are those that are found in nature or are emitted from natural sources. For example, volcanic activity produces sulfur dioxide, and particulate pollution may derive from forest fires or windblown dust. Anthropogenic pollutants are those that are produced by humans or controlled processes. For example, sulfur dioxide is produced by fossil fuel combustion and particulate matter comes from diesel engines.
Air pollutants also are classified as primary or secondary. Primary pollutants are those that are emitted directly into the atmosphere from an identifiable source. Examples include carbon monoxide and sulfur dioxide. Secondary pollutants are those that are produced in the atmosphere by chemical and physical processes from primary pollutants and natural constituents. For example, ozone is produced by hydrocarbons and oxides of nitrogen (both of which may be produced by car emissions) and sunlight. See the table for a listing of estimated pollutant emissions in the United States in 1999.
Air Pollution Control Laws and Regulations
The earliest programs to manage air quality in the United States date to the late 1880s; they attempted to regulate emissions from smokestacks using nuisance law municipal ordinances. Little progress was made in air pollution control during the first half of the twentieth century.
In the 1950s there was a shift away from nuisance law and municipal ordinances as the basis for managing air quality toward increased federal involvement. The Air Pollution Control Act of 1955 established a program for federally funded research grants in the area of air pollution, but the role of the federal government remained a limited one.
National Ambient Air Quality Standards (
U.S. Environmental Protection Agency
)
NATIONAL AMBIENT AIR QUALITY STANDARDS Pollutant Standard Value* Standard Type
*Parenthetical value is an approximately equivalent concentration.
SOURCE: U.S. Environmental Protection Agency
Carbon Monoxide (CO)
8-hour Average 9 ppm (10 mg/m 3 ) Primary
1-hour Average 35 ppm (40 mg/m 3 ) Primary
Nitrogen Dioxide (NO 2 )
Annual Arithmetic Mean 0.053 ppm (100 μg/m 3 ) Primary & Secondary
Ozone (O 3 )
1-hour Average 0.12 ppm (235 μg/m 3 ) Primary & Secondary
8-hour Average 0.08 ppm (157 μg/m 3 ) Primary & Secondary
Lead (Pb)
Quarterly Average 1.5 μg/m 3 Primary & Secondary
Particulate (PM 10) Particles with diameters of 10 micrometers or less
Annual Arithmetic Mean 50 μg/m 3 Primary & Secondary
24-hour Average 150 μg/m 3 Primary & Secondary
Particulate (PM 2.5) Particles with diameters of 2.5 micrometers or less
Annual Arithmetic Mean 15 μg/m 3 Primary & Secondary
24-hour Average 65 μg/m 3 Primary & Secondary
Sulfur Dioxide (SO 2 )
Annual Arithmetic Mean 0.030 ppm (80 μg/m 3 ) Primary
24-hour Average 0.14 ppm (365 μg/m 3 ) Primary
3-hour Average 0.50 ppm (1300 μg/m 3 ) Secondary
It was the Clean Air Act (CAA) of 1963 that further extended the federal government's powers in a significant way, allowing direct federal intervention to reduce interstate pollution.
The Clean Air Act Amendments (CAAA) of 1970 continued many of the programs established by prior legislation; however, several aspects of it represented major changes in strategy by expanding the role of the federal government. The 1970 CAAA defined two types of pollutants that were to be regulated: criteria and hazardous pollutants.
Criteria pollutants, regulated to achieve the attainment of the National Ambient Air Quality Standards (NAAQS), including primary standards for the protection of public health, ". . . the attainment and maintenance of which, . . . allowing an adequate margin of safety, are requisite to protect public health," and secondary standards for the protection of public welfare. The first six criteria pollutants were carbon monoxide (CO), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), total suspended particulate matter (TSP), hydrocarbons, and photochemical oxidants. Lead was added to the list in 1976. In 1979 the photochemical oxidants standard was replaced by one for ozone (O 3 ), and in 1983 the hydrocarbons standard was dropped altogether. In 1987 TSP was changed to PM 10 , and in 1997 PM 2.5 was added to the official list and the ozone standard revised.
National Emission Standards for Hazardous Air Pollutants (NESHAP) were established. A hazardous air pollutant (HAP) was defined as one "to which no ambient air standard is applicable and that . . . causes, or contributes to, air pollution which may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible or incapacitating reversible illness." Examples include asbestos, mercury, benzene, arsenic, and radionuclides.
Estimated Pollutant Emissions in the United States in 2000
ESTIMATED POLLUTANT EMISSIONS IN THE UNITED STATES IN 2000
(Thousand short tons) Source Category CO NO x VOC SO 2 PM 10 PM 2.5
SOURCE: EPA data available from http://www.epa.gov/ttn
Fuel combustion
Electric utilities 445 5,266 64 11,389 270 141
Industrial 1,221 3,222 185 2,894 244 157
Other 2,924 1,161 957 593 483 458
Chemical manufacturing 1,112 134 407 268 67 41
Metals processing 1,735 91 79 411 152 107
Petroleum industries 369 146 433 346 30 17
Other industrial processes 620 487 480 432 355 198
Solvent utilization 2 3 4,827 1 7 6
Storage and transport 74 17 1,225 5 87 32
Waste disposal and recycling 3,609 89 582 35 544 514
On-road vehicles 48,469 8,150 5,035 314 273 209
Nonroad vehicles 29,956 5,558 3,404 1,492 436 400
Miscellaneous 20,806 576 2,710 21 21,926 5,466
Total 109,342 24,899 20,384 18,201 24,875 7,746
Even though the CAAA of 1970 and 1977 placed deadlines on the dates for compliance with the NAAQS, as of 1990 in many areas of the United States, a variety of criteria pollutants existed in concentrations greater than the standards allowed.
As a result, the CAAA of 1990 were passed. They contain eleven major divisions, referred to as titles, the most important of which are the following: Title I: Provisions for Attainment and Maintenance of NAAQS, Title II: Provisions Relating to Mobile Sources, Title III: Hazardous Air Pollutants, Title IV: Acid Deposition Control, Title V: Permits, and Title VI: Stratospheric Ozone Protection, Title VII: Provisions Relating to Enforcement, Title VIII: Miscellaneous Provisions, Title IX: Clean Air Research, Title X: Disadvantaged Business Concerns, and Title XI: Clean Air Employment Transition Assistance.
International Nature of the Problem
Air pollution and the problems it causes are not confined by any geopolitical boundaries. For example, the radioactive cloud resulting from the Chernobyl nuclear accident in 1986 traveled as far as Ireland. A United Nations report warns that haze produced by the burning of wood and fossil fuels is creating a two-mile-thick "Asian browncloud" that covers southeastern Asia and may be responsible for hundreds of thousands of respiratory deaths a year.
In the United States, federal pollution laws and regulations apply to all states, even though some states, such as California, have adopted more stringent standards. Similarly, in the European Union (EU) existing laws apply equally to all members. Countries such as Denmark and Germany, however, have elected to imposed stricter standards than those set by the EU.
International agreements aimed at reducing various pollutants have been signed by various countries. The Montreal Protocol was signed in 1987; its purpose is the reduction of chlorofluorocarbons (CFC), a class of compounds that destroy the stratospheric ozone layer. More recently, in 1997, a conference convened in Kyoto, Japan, to discuss ways of reducing carbon dioxide emissions and other greenhouse gases . The United States has not signed the Kyoto Protocol, arguing that such an agreement would impede its economic progress. It has, however, publicly stated its intention to embark on voluntary reductions of carbon dioxide and other greenhouse gases.
Air Pollutants
In general, air pollutants are divided into two classes: those for which a NAAQS may be set (in other words, the criteria pollutants), and those for which NAAQS are not appropriate (the HAPs). If the ambient concentration of the criteria pollutants is kept below the NAAQS value, then there will be no health damage due to air pollution. The HAP (mostly known or suspected carcinogens), on the other hand, are those that, even in low concentrations, cause significant damage.
Particulate Matter. Particulate matter (PM) is the term used to describe solid or liquid particles that are airborne and dispersed (i.e., scattered, separated). PM originates from a variety of anthropogenic sources, including diesel trucks, power plants, wood stoves, and industrial processes.
The original NAAQS for PM was set in 1970. In 1987, the total suspended particulate matter, TSP, was revised, and a PM 10 (particulate matter with an aerodynamic diameter of 10 μm or less) standard was set. PM 10 , sometimes known as respirable particles, was felt to provide a better correlation of particle concentration with human health.
In 1997 the particulate matter standard was updated, to include the PM2.5 standard. These particles, known as "fine" particles, a significant fraction of which is secondary in nature, are especially detrimental to human health because they can penetrate deep into the lungs. Scientific studies show a link between PM 2.5 (alone, or combined with other pollutants in the air) and a series of significant health effects, even death.
Fine particles are the major cause of reduced visibility in parts of the United States, including many of the national parks. Also, soils, plants, water, or materials are affected by PM. For example, particles containing nitrogen and sulfur that are deposited as acid rain on land or water bodies may alter the nutrient balance and acidity of those environments so that species composition and buffering capacity change. PM causes soiling and erosion damage to materials, including culturally important objects such as carved monuments and statues.
Carbon Monoxide. Carbon monoxide (CO) is a colorless, odorless, and at high levels a poisonous gas that is fairly unreactive. It is formed when carbon in fuels is not burned completely. The major source of CO is motor vehicle exhaust. In cities, as much as 95 percent of all CO emissions result from vehicular (automobile) emissions. Other sources of CO emissions include industrial processes, nontransportation-related fuel combustion, and natural sources such as wildfires.
CO has serious health effects on humans. An exposure to 50 ppm of CO for eight hours can cause reduced psychomotor performance, while CO is lethal to humans when concentrations exceed approximately 750 ppm. Hemoglobin, the part of blood that carries oxygen to body parts, has an affinity of CO that is about 240 times higher than that for oxygen, forming carboxyhemoglobin, COHb. Moreover, the release of oxygen by hemoglobin is reduced in the presence of COHb. However, the effects of CO poisoning are reversible once the CO source has been removed.
Sulfur Dioxide. Sulfur dioxide (SO 2 ) is colorless, nonflammable, nonexplosive gas. Almost 90 percent of anthropogenic SO 2 emissions are the result of fossil fuel combustion (mostly coal) in power plants and other stationary sources. A natural source of sulfur oxides is volcanic activities.
In general, exposure to SO 2 irritates the human upper respiratory tract. The most serious air pollution episodes occurred when there was a synergistic effect of SO 2 with PM and water vapor (fog). Because of this, it has proven difficult to isolate the effects of SO 2 alone.
SO 2 is one of the precursors of acid rain (the term used to describe the deposition of acidic substances from the atmosphere). Also, SO 2 is the precursor of secondary fine sulfate particles, which in turn affect human health and reduce visibility. Prolonged exposure to SO 2 and sulfate PM causes serious damage to materials such as marble, limestone, and mortar. The carbonates (e.g., limestone, CaCO 3 ) in these materials are replaced by sulfates (e.g., gypsum, CaSO 4 ) that are water-soluble and may be washed away easily by rain. This results in an eroded surface.
Nitrogen Dioxide. Nitrogen dioxide (NO 2 ) is a reddish-brown gas. It is a lung irritant and is present in the highest concentrations among other oxides of nitrogen in ambient air. Nitric oxide (NO) and NO 2 are collectively known as NO x .
Anthropogenic emissions of NO x come from high-temperature combustion processes, such as those occurring in automobiles and power plants. Natural sources of NO 2 are lightning and various biological processes in soil. The oxides of nitrogen, much like sulfur dioxide, are precursors of acid rain and visibility-reducing fine nitrate particles.
Ozone. Ozone (O 3 ) is a secondary pollutant and is formed in the atmosphere by the reaction of molecular oxygen, O 2 , and atomic oxygen, O, which comes from the photochemical decomposition of NO 2 . Volatile organic compounds or VOCs (e.g., what one smells when refuelling the car) must also be present if O 3 is to accumulate in the atmosphere.
O 3 occurs naturally in the stratosphere and provides a protective layer from the sun's ultraviolet rays high above the earth. However, at ground level, O 3 is a lung and eye irritant and can cause asthma attacks, especially in young children or other susceptible individuals. O 3 , being a powerful oxidant, also attacks materials and has been found to cause reduced crop yields and stunt tree growth.
Lead. The major sources of lead (Pb) in the atmosphere in the United States are industrial processes from metals smelters. Thirty years ago, the major emissions of Pb resulted from cars burning leaded gasoline. In 2002 only aviation fuels contain relatively large amounts of Pb. The United States is currently working with the World Bank to eliminate the use of leaded gasoline in all countries still using such fuel.
Pb is a toxic metal and can accumulate in the blood, bones, and soft tissues. Even low exposure to Pb can cause mental retardation in children.
Hazardous Air Pollutants. Hazardous air pollutants (HAPs), commonly referred to as air toxics or toxic air pollutants, are pollutants known to cause or suspected of causing cancer or other serious human health effects or damage to the ecosystem.
EPA lists 188 HAPs and regulates sources emitting significant amounts of these identified pollutants. Examples of HAPs are heavy metals (e.g., mercury), volatile chemicals (e.g., benzene), combustion by-products (e.g., dioxins), and solvents (e.g., methylene chloride). HAPs are emitted from many sources, including large stationary industrial facilities (e.g., electric power plants), smaller-area sources (e.g., dry cleaners), mobile sources (e.g., cars), indoor sources (e.g., some building materials and cleaning solvents), and other sources (e.g., wildfires).
Potential human health effects of HAPs include headache, dizziness, nausea, birth defects, and cancer. Environmental effects of HAPs include toxicity to aquatic plants and animals as well as the accumulation of pollutants in the food chain.
Because of the potential serious harmful effects of the HAPs, even at very low concentrations, NAAQS are not appropriate. The EPA has set National Emission Standards for Hazardous Air Pollutants, NESHAP, for only eight of the HAP, including asbestos and vinyl chloride. The EPA regulates HAP by requiring each HAP emission source to meet Maximum Achievable Control Technology (MACT) standards. MACT is defined as "not less stringent than the emission control that is achieved in practice by the best controlled similar source."
Control of Air Pollutants
In general, control of pollutants that are primary in nature, such as SO 2 , NO 2 , CO, and Pb, is easier than control of pollutants that are either entirely secondary (O 3 ) or have a significant secondary component (PM 2.5 ). Primary pollutants may be controlled at the source. For example, SO 2 is controlled by the use of scrubbers, which are industrial devices that remove SO 2 from the exhaust gases from power plants. SO 2 emissions are also reduced by the use of low-sulfur coal or other fuels, such as natural gas, that contain lower amounts of sulfur. NO 2 from industrial sources also may be minimized by scrubbing. NO 2 from cars, as well as CO, are controlled by the use of catalytic converters, engine design modifications, and the use of cleaner burning grades of gasoline. Lead emissions have been reduced significantly since the introduction of lead-free gasoline.
Ozone and particulate matter are two of the most difficult pollutants to control. Reduction of oxides of nitrogen emissions, together with a reduction of VOC emissions is the primary control strategy for minimizing ozone concentrations. Because a large portion of PM 2.5 is secondary in nature, its control is achieved by control of SO 2 , NO 2 , and VOC (which are the precursors of sulfates, nitrates, and carbon-containing particulates).
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With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Pollution Issues
Scientists collect samples of air, water, soil, plants, and tissue to detect and monitor pollution. Pollutants are most often extracted from samples, then isolated by a technique called chromatography and analyzed by appropriate detection methods. Many pollutants are identified by their spectral fingerprints, unique patterns of absorbed or emitted radiation in the ultraviolet (UV), visible, or infrared (IR) region of the electromagnetic spectrum . Biomonitoring and technologies including satellite observation, sidescan sonar, and bioluminescent reporter chips are also used for pollution monitoring. In the United States, the U.S. Environmental Protection Agency (EPA) approves the methods for monitoring regulated pollutants such as pesticide residues and those in air and drinking water.
Sampling and Extraction
Air can be actively or passively sampled. Actively sampled air is pumped through a filter or chemical solution. For example, airborne lead, mostly originating from metals processing plants, is collected on filters by active sampling and then analyzed spectroscopically. Air that is not pumped but allowed to flow or diffuse naturally is passively sampled. Nitrogen oxides, resulting from vehicle emissions and combustion, can be monitored in passive sampling tubes by their reaction with triethanolamine to form nitrates. The tubes are taken to a laboratory and the amount of nitrate analyzed.
Liquid or solid extraction removes a mix of pollutants from samples. In liquid extraction, samples are shaken with a solvent that dissolves the pollutants. Solid extraction involves the adherence or absorption of pollutants to a solid that is then heated to release a mix of vaporized pollutants which are subsequently analyzed.
SELECTED INSTRUMENTAL DETECTION METHODS Chemical Method
Anions in water (e.g., nitrate, phosphate, sulfate, bromide, fluoride, chloride) Ion exchange chromatography/conductivity detector
Criteria pollutants sulfur dioxide, ozone, nitrogen oxides Ultraviolet absorption spectroscopy
Dioxins and furans High-resolution gas chromatography/high-resolution mass spectrometry
Greenhouse gases carbon dioxide, methane and nitrous oxide Infrared absorption spectroscopy
Herbicides diquat and paraquat in drinking water High-performance liquid chromatography/ultraviolet spectroscopy
Chlorinated disinfection by-products, haloacetic acids Gas chromatography/electron capture detector or mass spectrometry
Hydrocarbons in vehicle emissions Infrared absorption spectroscopy
Metals Inductively coupled plasma–atomic emission spectrometry or mass spectrometry or graphite furnace atomic absorption spectrometry for trace amounts (e.g. arsenic and lead)
Mercury Cold vapor atomic absorption spectrometry
Organophosphate pesticides (e.g. malathion, parathion) Gas chromatography/nitrogen/phosphorus detector
PCBs, chlorinated pesticides (e.g. DDT, lindane) and herbicides in water Gas chromatography/electron capture detector or mass spectrometry
Phthalates in water or biological samples Gas chromatography/electron capture or photoionization detector or mass spectrometry
Toxic gases such as hydrogen sulfide, ammonia, styrene, hydrogen fluoride Ultraviolet or infrared absorption spectroscopy
Volatile organic compounds (VOCs) in water Gas chromatography/photoionization and electrolytic conductivity detectors in series
Volatile organic compounds in air Fourier transform infrared spectroscopy
Chromatography
Chromatography is the method most often used in environmental chemistry to separate individual pollutants from mixtures. The mixture to be analyzed is added to a liquid or gas, depending on whether liquid or gas chromatography is employed. The liquid or gas, called the mobile phase, is then forced through a stationary phase, often a column packed with solid material that can be coated with a liquid. The stationary and mobile phases are chosen so that the pollutants in the mixture will have different solubilities in each of them. The greater the affinity of a pollutant for the stationary phase, the longer it will take to move through the column. This difference in the migration rate causes pollutants to separate.
A chromatogram is a graph of intensity peaks that are responses to a detection method, indicating the presence of a pollutant, plotted against time.
Diagram of a Gas Chromatograph
Individual pollutants are identified by comparing their chromatogram to one for the suspected compounds under the same conditions. The pollutant concentration is determined from the height of the peaks and area under them.
Different kinds of chromatography work best for different pollutants. Gas chromatography separates organic chemicals that vaporize easily (VOCs). Benzene and ethylbenzene are VOCs in vehicle exhaust and are monitored in drinking water. Many pesticides, polychlorinated biphenyls (PCBs), and dioxin are separated by gas chromatography. Less volatile substances such as the herbicide diquat are isolated by high-performance liquid chromatography (HPLC). Ion exchange chromatography separates inorganic ions such as nitrates that can pollute water when excess fertilizer or leaking septic tanks wash into it.
Detectors
Chromatographic methods are routinely automated. A detector that responds to the pollutants' physical or chemical properties analyzes the gas or liquid leaving the column. Detectors can be specific for individual pollutants or classes of pollutants, or nonspecific.
Nonspecific Detectors. Flame ionization, thermal conductivity, and mass spectrometry are common nonspecific detection methods that detect all molecules containing carbon and hydrogen. In mass spectrometry, molecules of a gas are energized in a variety of ways, such as bombardment with electrons or rapid heating, causing them to gain or lose electrons. Because they have different masses and charges, the resulting ions are separated when they pass through magnetic and electric fields. The size and distribution of peaks for ions with different mass-to-charge ratios, known as the mass spectrum, identify the gas and determine its concentration. Gas chromatography coupled with high-resolution mass spectrometry definitively identifies PCBs and is the most accurate way to determine their concentration. Portable gas chromatograph/mass spectrometers can measure VOCs in soil and water to parts per billion (ppb).
Specific Detectors. Methods that detect classes of pollutants include nitrogen/phosphorous detectors for organophosphate pesticides, thermionic ionization detectors that detect molecules containing NO 2 , nitro groups, such as dinitrotoluene and electron capture. Electron capture is particularly sensitive to compounds, such as organohalide pesticides that contain the halogen atoms, chlorine, bromine, or fluorine. These atoms strongly attract electrons. The electron capture detector emits electrons that are captured by the halogens atom. The reduction in electric current corresponds to the concentration of pollutant. Chlorinated disinfection by-products, haloacetic acid, and phthalates in drinking water can be separated by gas chromatography and measured by electron capture. Sulfur hexafluoride, an ozone-depleting gas, can be measured to parts per trillion (ppt) by electron capture. Spectroscopic detection methods including IR, UV, and atomic absorption and emission spectroscopy are unique for specific compounds.
Spectroscopic Detection. The electromagnetic spectrum encompasses all forms of electromagnetic radiation from the most energetic cosmic and gamma rays to the least energetic radio waves. The part of the spectrum that is particularly useful in identifying and measuring pollutants consists of radiation that interacts with the atoms and molecules that make up life on Earth. This includes radiation in the UV, visible, and IR regions.
Atomic Spectra. Atoms of different elements may be thought of as having different arrangements of electrons around the nucleus in increasing energy levels. When metals such as lead, copper, and cadmium are vaporized at high temperatures, some electrons jump to higher energy levels. When the electrons drop to their original levels, the metal atoms emit radiation in a range of wavelengths from IR to UV, including visible light. The colors in fireworks result from such emissions. The wavelengths emitted constitute a unique "fingerprint" for each element and their intensity reflects the metal concentration. Inductively coupled plasma emission spectra (ICP–AES), in which a high-temperature gas or plasma excites metal atoms, are used to identify and quantify heavy metal contamination.
The same spectral fingerprint is obtained from the wavelengths of light that each element absorbs. Trace amounts of certain metals such as mercury and arsenic are more accurately measured from their absorption, rather than their emission spectra.
UV and IR Spectra. Many pollutants can be identified by their UV and IR spectra because all molecules that absorb strongly at specific wavelengths exhibit spectral fingerprints. Pollutants separated by liquid chromatography are often detected by spectroscopy. Gases such as those from vehicle emissions, landfills, industrial manufacturing plants, electric power plants, and hazardous incineration smokestacks can be monitored by spectroscopic methods. Gas and chemical leaks may also be monitored by spectroscopy.
UV Absorption Spectra. Toxic gases such as hydrogen sulfide, ammonia, and styrene can be monitored by their UV absorption spectra. Open path monitors emit UV radiation from a source, such as a bulb containing excited xenon gas, across the area to be monitored. Detectors record the absorbed wavelengths to produce a spectral fingerprint for each gas. Ammonia is often used as a coolant for turbine generators in power plants. It can be monitored for worker safety by its UV spectrum. The EPA has established National Ambient Air Quality standards for the six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide.
Diagram of the Electromagnetic Spectrum
Satellite instruments monitoring stratospheric ozone generally measure the decrease in intensity in UV solar radiation due to ozone absorption. The total ozone mapping spectrometer on the Earth probe satellite (TOMS/EP) scans back and forth beneath the satellite to detect six individual frequencies of UV light that are scattered by air molecules back through the stratosphere. The more ozone in the stratosphere, the more "backscattered" UV radiation will be absorbed compared to UV radiation directly from the sun.
Some IR open path monitors use a tunable diode laser source in the near IR. The laser emits the specific frequency at which a monitored gas absorbs, so there is no interference from other gases or particles such as rain or snow. Such lasers are widely employed in the telecommunications industry. Pollutants that absorb at specific wavelengths in this range include hydrogen fluoride, an extremely toxic gas used in the aluminum smelting and petroleum industries. Hydrogen fluoride can be monitored to one part per million (ppm) for worker safety by this method.
The greenhouse gases carbon dioxide, nitrous oxide, and methane may also be monitored by IR spectroscopy. Currently, emissions of carbon dioxide from power plants are not generally measured directly but are estimated. However, the amount of carbon dioxide in the atmosphere over Mauna Loa has been measured continuously by IR spectroscopy since 1958. The Mauna Loa Observatory is located on the earth's largest active volcano on the island of Hawaii. It is relatively remote from human activity and changes in carbon dioxide concentration above it are considered a reliable indicator of the trend of carbon dioxide concentration in the troposphere. Data from Mauna Loa show a 17.4 percent increase in carbon dioxide concentration from 315.98 parts per million (ppm) by volume of dry air in 1959 to 370.9 ppm in 2001.
Remote sensors for vehicle emissions contain units that detect and measure carbon monoxide, carbon dioxide, and hydrocarbons by their IR spectra. Because IR absorption bands from water and other gases found in car exhaust interfere with the IR spectrum of NO x , the sensor also contains a unit that measures NO x from their UV absorption spectra.
Fourier transform IR spectroscopy (FTIR) analyzes the absorption spectrum of a gas mixture to detect as many as twenty gases simultaneously. The technique involves analyzing the spectra mathematically and then comparing the observed fingerprints with calibrated reference spectra stored on the hard drive of the computer to be used for analysis. Reference spectra for more than one hundred compounds are stored, including most of the VOCs considered hazardous by the EPA. Instruments that use UV Fourier transform analysis are now available. The instruments are generally installed at one location, but are portable and can be battery operated for short-term surveys. Multiple gas-monitoring systems are used in a variety of industries, including oil and gas, petrochemical, pulp and paper, food and beverage, public utility, municipal waste, and heavy industrial manufacturing.
Biomonitoring
Biomonitoring is the study of plants, vertebrate, and invertebrate species to detect and monitor pollution. Moss and lichens absorb heavy metals, mainly from air, and have been analyzed by scientists studying air pollution.
Water pollution can be studied by recording changes in the number and type of species present and in specific biochemical or genetic changes in individual organisms. Blue mussels accumulate metals in certain tissues over time and are monitored in the United States and international waters for changes in pollution levels. The index of biotic integrity (IBI), first developed by James Karr in 1981 to assess the health of small warmwater streams, uses fish sampling data to give a quantitative measure of pollution. Twelve indicators of stream health, appropriate to the geographical area, including the total number of fish, the diversity of species, and food chain interactions, are numerically rated with a maximum of five points each. An IBI close to sixty corresponds to a healthy stream, whereas a rating between twenty and twelve implies a considerable pollution. Versions of the IBI with appropriate indicators are used to assess rivers and streams in France, Canada, and different regions of the United States.
Bioluminescent Reporter Technology
In bioluminescent reporter technology, bacteria that break down pollutants are genetically modified to emit blue green light during the degradation process. The bacteria are embedded in a polymer porous to water and combined with a light sensor integrated with a silicon computer chip. The sensor measures the intensity of the glow to determine the amount of pollution, and that information is transmitted to a central computer.
Bioluminescent reporter technology is still being studied by researchers, but is currently employed in some wastewater treatment plants in the United Kingdom. Incoming wastewater is monitored for chemicals that inhibit the bacterial activity necessary for efficient wastewater treatment. The incoming water is automatically sampled and mixed with freeze-dried luminescent bacteria from the treatment plant. A reduction in light intensity compared to a control with pure water indicates the chemical inhibition of wastewater microorganisms. This technology is also being used to identify petroleum pollutants, such as napthelene.
Sidescan Sonar
Sidescan sonar instruments bounce sound off surfaces both vertically and at an angle to produce images of sea and riverbeds. Because PCBs tend to stick preferentially to organic matter, there is a greater possibility of finding them in small-grain aquatic sediments, since these contain more organic material. The EPA has analyzed sound reflection patterns from sidescan sonar data to identify areas of small grain size and selectively sample for PCBs in the Hudson River, New York. Sidescan sonars are also used to detect sea grass, an indicator of marine health, and sewage or oil leaks from underwater pipelines.
Regulations
Once a potentially harmful pollutant is measured in trace amounts, then regulators, such as the EPA, have to decide on a safe limit. Risk analysis is the method used to set limits on harmful pollutants in the United States. Risk is calculated based on laboratory tests, sometimes on animals, and epidemiological studies that relate human health to exposure.
Risk analysis is conducted for individual pollutants, but people can be exposed to multiple pollutants simultaneously, such as pesticides, heavy metals, dioxins, and PCBs. Even though a person's exposure to individual chemicals may fall within regulated limits, the pollutants may interact to cause as yet unknown adverse health effects. It is known, for instance, that exposure to both asbestos and tobacco smoke geometrically increases the risk of cancer. Because there are so many potentially harmful chemicals in the environment scientists cannot predict all their possible interactions and consequent health effects on the body.
Read more: Science - water, effects, environmental, pollutants, United States, causes, EPA, soil, pesticide, chemicals, industrial, liquid, toxic, human, power, use, life file:///C:/Documents%20and%20Settings/User/Desktop/Technical/Science%20-%20water,%20effects,%20environmental,%20pollutants,%20United%20States,%20causes,%20EPA,%20soil,%20pesticide,%20chemicals,%20industrial,%20liquid,%20toxic,%20human,%20power,%20use,%20life.mht#ixzz18jglATLO
With Regards,
Sebastian
G.M. Technical
Nunes Instruments
645 Hundred Feet Road,
Coimbatore. 641012.
Tamil Nadu
India,
Web: www.nunesinstruments.com
Mail: info@nunesinstruments.com
Mobile: 09345226022
Sampling and Extraction
Air can be actively or passively sampled. Actively sampled air is pumped through a filter or chemical solution. For example, airborne lead, mostly originating from metals processing plants, is collected on filters by active sampling and then analyzed spectroscopically. Air that is not pumped but allowed to flow or diffuse naturally is passively sampled. Nitrogen oxides, resulting from vehicle emissions and combustion, can be monitored in passive sampling tubes by their reaction with triethanolamine to form nitrates. The tubes are taken to a laboratory and the amount of nitrate analyzed.
Liquid or solid extraction removes a mix of pollutants from samples. In liquid extraction, samples are shaken with a solvent that dissolves the pollutants. Solid extraction involves the adherence or absorption of pollutants to a solid that is then heated to release a mix of vaporized pollutants which are subsequently analyzed.
SELECTED INSTRUMENTAL DETECTION METHODS Chemical Method
Anions in water (e.g., nitrate, phosphate, sulfate, bromide, fluoride, chloride) Ion exchange chromatography/conductivity detector
Criteria pollutants sulfur dioxide, ozone, nitrogen oxides Ultraviolet absorption spectroscopy
Dioxins and furans High-resolution gas chromatography/high-resolution mass spectrometry
Greenhouse gases carbon dioxide, methane and nitrous oxide Infrared absorption spectroscopy
Herbicides diquat and paraquat in drinking water High-performance liquid chromatography/ultraviolet spectroscopy
Chlorinated disinfection by-products, haloacetic acids Gas chromatography/electron capture detector or mass spectrometry
Hydrocarbons in vehicle emissions Infrared absorption spectroscopy
Metals Inductively coupled plasma–atomic emission spectrometry or mass spectrometry or graphite furnace atomic absorption spectrometry for trace amounts (e.g. arsenic and lead)
Mercury Cold vapor atomic absorption spectrometry
Organophosphate pesticides (e.g. malathion, parathion) Gas chromatography/nitrogen/phosphorus detector
PCBs, chlorinated pesticides (e.g. DDT, lindane) and herbicides in water Gas chromatography/electron capture detector or mass spectrometry
Phthalates in water or biological samples Gas chromatography/electron capture or photoionization detector or mass spectrometry
Toxic gases such as hydrogen sulfide, ammonia, styrene, hydrogen fluoride Ultraviolet or infrared absorption spectroscopy
Volatile organic compounds (VOCs) in water Gas chromatography/photoionization and electrolytic conductivity detectors in series
Volatile organic compounds in air Fourier transform infrared spectroscopy
Chromatography
Chromatography is the method most often used in environmental chemistry to separate individual pollutants from mixtures. The mixture to be analyzed is added to a liquid or gas, depending on whether liquid or gas chromatography is employed. The liquid or gas, called the mobile phase, is then forced through a stationary phase, often a column packed with solid material that can be coated with a liquid. The stationary and mobile phases are chosen so that the pollutants in the mixture will have different solubilities in each of them. The greater the affinity of a pollutant for the stationary phase, the longer it will take to move through the column. This difference in the migration rate causes pollutants to separate.
A chromatogram is a graph of intensity peaks that are responses to a detection method, indicating the presence of a pollutant, plotted against time.
Diagram of a Gas Chromatograph
Individual pollutants are identified by comparing their chromatogram to one for the suspected compounds under the same conditions. The pollutant concentration is determined from the height of the peaks and area under them.
Different kinds of chromatography work best for different pollutants. Gas chromatography separates organic chemicals that vaporize easily (VOCs). Benzene and ethylbenzene are VOCs in vehicle exhaust and are monitored in drinking water. Many pesticides, polychlorinated biphenyls (PCBs), and dioxin are separated by gas chromatography. Less volatile substances such as the herbicide diquat are isolated by high-performance liquid chromatography (HPLC). Ion exchange chromatography separates inorganic ions such as nitrates that can pollute water when excess fertilizer or leaking septic tanks wash into it.
Detectors
Chromatographic methods are routinely automated. A detector that responds to the pollutants' physical or chemical properties analyzes the gas or liquid leaving the column. Detectors can be specific for individual pollutants or classes of pollutants, or nonspecific.
Nonspecific Detectors. Flame ionization, thermal conductivity, and mass spectrometry are common nonspecific detection methods that detect all molecules containing carbon and hydrogen. In mass spectrometry, molecules of a gas are energized in a variety of ways, such as bombardment with electrons or rapid heating, causing them to gain or lose electrons. Because they have different masses and charges, the resulting ions are separated when they pass through magnetic and electric fields. The size and distribution of peaks for ions with different mass-to-charge ratios, known as the mass spectrum, identify the gas and determine its concentration. Gas chromatography coupled with high-resolution mass spectrometry definitively identifies PCBs and is the most accurate way to determine their concentration. Portable gas chromatograph/mass spectrometers can measure VOCs in soil and water to parts per billion (ppb).
Specific Detectors. Methods that detect classes of pollutants include nitrogen/phosphorous detectors for organophosphate pesticides, thermionic ionization detectors that detect molecules containing NO 2 , nitro groups, such as dinitrotoluene and electron capture. Electron capture is particularly sensitive to compounds, such as organohalide pesticides that contain the halogen atoms, chlorine, bromine, or fluorine. These atoms strongly attract electrons. The electron capture detector emits electrons that are captured by the halogens atom. The reduction in electric current corresponds to the concentration of pollutant. Chlorinated disinfection by-products, haloacetic acid, and phthalates in drinking water can be separated by gas chromatography and measured by electron capture. Sulfur hexafluoride, an ozone-depleting gas, can be measured to parts per trillion (ppt) by electron capture. Spectroscopic detection methods including IR, UV, and atomic absorption and emission spectroscopy are unique for specific compounds.
Spectroscopic Detection. The electromagnetic spectrum encompasses all forms of electromagnetic radiation from the most energetic cosmic and gamma rays to the least energetic radio waves. The part of the spectrum that is particularly useful in identifying and measuring pollutants consists of radiation that interacts with the atoms and molecules that make up life on Earth. This includes radiation in the UV, visible, and IR regions.
Atomic Spectra. Atoms of different elements may be thought of as having different arrangements of electrons around the nucleus in increasing energy levels. When metals such as lead, copper, and cadmium are vaporized at high temperatures, some electrons jump to higher energy levels. When the electrons drop to their original levels, the metal atoms emit radiation in a range of wavelengths from IR to UV, including visible light. The colors in fireworks result from such emissions. The wavelengths emitted constitute a unique "fingerprint" for each element and their intensity reflects the metal concentration. Inductively coupled plasma emission spectra (ICP–AES), in which a high-temperature gas or plasma excites metal atoms, are used to identify and quantify heavy metal contamination.
The same spectral fingerprint is obtained from the wavelengths of light that each element absorbs. Trace amounts of certain metals such as mercury and arsenic are more accurately measured from their absorption, rather than their emission spectra.
UV and IR Spectra. Many pollutants can be identified by their UV and IR spectra because all molecules that absorb strongly at specific wavelengths exhibit spectral fingerprints. Pollutants separated by liquid chromatography are often detected by spectroscopy. Gases such as those from vehicle emissions, landfills, industrial manufacturing plants, electric power plants, and hazardous incineration smokestacks can be monitored by spectroscopic methods. Gas and chemical leaks may also be monitored by spectroscopy.
UV Absorption Spectra. Toxic gases such as hydrogen sulfide, ammonia, and styrene can be monitored by their UV absorption spectra. Open path monitors emit UV radiation from a source, such as a bulb containing excited xenon gas, across the area to be monitored. Detectors record the absorbed wavelengths to produce a spectral fingerprint for each gas. Ammonia is often used as a coolant for turbine generators in power plants. It can be monitored for worker safety by its UV spectrum. The EPA has established National Ambient Air Quality standards for the six criteria pollutants: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide.
Diagram of the Electromagnetic Spectrum
Satellite instruments monitoring stratospheric ozone generally measure the decrease in intensity in UV solar radiation due to ozone absorption. The total ozone mapping spectrometer on the Earth probe satellite (TOMS/EP) scans back and forth beneath the satellite to detect six individual frequencies of UV light that are scattered by air molecules back through the stratosphere. The more ozone in the stratosphere, the more "backscattered" UV radiation will be absorbed compared to UV radiation directly from the sun.
Some IR open path monitors use a tunable diode laser source in the near IR. The laser emits the specific frequency at which a monitored gas absorbs, so there is no interference from other gases or particles such as rain or snow. Such lasers are widely employed in the telecommunications industry. Pollutants that absorb at specific wavelengths in this range include hydrogen fluoride, an extremely toxic gas used in the aluminum smelting and petroleum industries. Hydrogen fluoride can be monitored to one part per million (ppm) for worker safety by this method.
The greenhouse gases carbon dioxide, nitrous oxide, and methane may also be monitored by IR spectroscopy. Currently, emissions of carbon dioxide from power plants are not generally measured directly but are estimated. However, the amount of carbon dioxide in the atmosphere over Mauna Loa has been measured continuously by IR spectroscopy since 1958. The Mauna Loa Observatory is located on the earth's largest active volcano on the island of Hawaii. It is relatively remote from human activity and changes in carbon dioxide concentration above it are considered a reliable indicator of the trend of carbon dioxide concentration in the troposphere. Data from Mauna Loa show a 17.4 percent increase in carbon dioxide concentration from 315.98 parts per million (ppm) by volume of dry air in 1959 to 370.9 ppm in 2001.
Remote sensors for vehicle emissions contain units that detect and measure carbon monoxide, carbon dioxide, and hydrocarbons by their IR spectra. Because IR absorption bands from water and other gases found in car exhaust interfere with the IR spectrum of NO x , the sensor also contains a unit that measures NO x from their UV absorption spectra.
Fourier transform IR spectroscopy (FTIR) analyzes the absorption spectrum of a gas mixture to detect as many as twenty gases simultaneously. The technique involves analyzing the spectra mathematically and then comparing the observed fingerprints with calibrated reference spectra stored on the hard drive of the computer to be used for analysis. Reference spectra for more than one hundred compounds are stored, including most of the VOCs considered hazardous by the EPA. Instruments that use UV Fourier transform analysis are now available. The instruments are generally installed at one location, but are portable and can be battery operated for short-term surveys. Multiple gas-monitoring systems are used in a variety of industries, including oil and gas, petrochemical, pulp and paper, food and beverage, public utility, municipal waste, and heavy industrial manufacturing.
Biomonitoring
Biomonitoring is the study of plants, vertebrate, and invertebrate species to detect and monitor pollution. Moss and lichens absorb heavy metals, mainly from air, and have been analyzed by scientists studying air pollution.
Water pollution can be studied by recording changes in the number and type of species present and in specific biochemical or genetic changes in individual organisms. Blue mussels accumulate metals in certain tissues over time and are monitored in the United States and international waters for changes in pollution levels. The index of biotic integrity (IBI), first developed by James Karr in 1981 to assess the health of small warmwater streams, uses fish sampling data to give a quantitative measure of pollution. Twelve indicators of stream health, appropriate to the geographical area, including the total number of fish, the diversity of species, and food chain interactions, are numerically rated with a maximum of five points each. An IBI close to sixty corresponds to a healthy stream, whereas a rating between twenty and twelve implies a considerable pollution. Versions of the IBI with appropriate indicators are used to assess rivers and streams in France, Canada, and different regions of the United States.
Bioluminescent Reporter Technology
In bioluminescent reporter technology, bacteria that break down pollutants are genetically modified to emit blue green light during the degradation process. The bacteria are embedded in a polymer porous to water and combined with a light sensor integrated with a silicon computer chip. The sensor measures the intensity of the glow to determine the amount of pollution, and that information is transmitted to a central computer.
Bioluminescent reporter technology is still being studied by researchers, but is currently employed in some wastewater treatment plants in the United Kingdom. Incoming wastewater is monitored for chemicals that inhibit the bacterial activity necessary for efficient wastewater treatment. The incoming water is automatically sampled and mixed with freeze-dried luminescent bacteria from the treatment plant. A reduction in light intensity compared to a control with pure water indicates the chemical inhibition of wastewater microorganisms. This technology is also being used to identify petroleum pollutants, such as napthelene.
Sidescan Sonar
Sidescan sonar instruments bounce sound off surfaces both vertically and at an angle to produce images of sea and riverbeds. Because PCBs tend to stick preferentially to organic matter, there is a greater possibility of finding them in small-grain aquatic sediments, since these contain more organic material. The EPA has analyzed sound reflection patterns from sidescan sonar data to identify areas of small grain size and selectively sample for PCBs in the Hudson River, New York. Sidescan sonars are also used to detect sea grass, an indicator of marine health, and sewage or oil leaks from underwater pipelines.
Regulations
Once a potentially harmful pollutant is measured in trace amounts, then regulators, such as the EPA, have to decide on a safe limit. Risk analysis is the method used to set limits on harmful pollutants in the United States. Risk is calculated based on laboratory tests, sometimes on animals, and epidemiological studies that relate human health to exposure.
Risk analysis is conducted for individual pollutants, but people can be exposed to multiple pollutants simultaneously, such as pesticides, heavy metals, dioxins, and PCBs. Even though a person's exposure to individual chemicals may fall within regulated limits, the pollutants may interact to cause as yet unknown adverse health effects. It is known, for instance, that exposure to both asbestos and tobacco smoke geometrically increases the risk of cancer. Because there are so many potentially harmful chemicals in the environment scientists cannot predict all their possible interactions and consequent health effects on the body.
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