Mobile source emissions

Air lead concentrations for purposes of determining dispersion data can be found by actual measurement over some unit of selected time, e.g., 24-hour high-volume sampling or with various dispersion models. A major factor in either air lead measurement or modehng is the type of lead emission source. Mobile sources or mixes of mobile and point lead sources when modeled within relatively broad geographic areas such as urban zones require quite different quantification approaches than modeling particular point source emissions, i.e., from a primary or secondary lead smelter. 

The atmosphere of the world cannot continue to accept greater and greater amounts of emissions from mobile sources as our transportation systems expand. The present emissions from all transportation sources in the United States exceed 50 biUion kg of carbon monoxide per year, 20 billion kg per year of unbumed hydrocarbons, and 20 billion kg of oxides of nitrogen. If presently used power sources cannot be modified to bring their emissions to acceptable levels, we must develop alternative power sources or alternative transportation systems. All alternatives should be considered simultaneously to achieve the desired result, an acceptable transportation system with a minimum of air pollution. 

Hydrogen fuel-based technologies hold great promise in reducing carbon dioxide and toxic air emissions from mobile sources in meeting current clean air standards and proposed greenhouse gas reductions. 

The published guideline VDI 3881 /2—4/ describes, how to measure odour emissions for application in dispersion models. Results obtained by this method have to be completed with physical data like flow rates etc. As olfactometric odour threshold determination is rather expensive, it is supplemented with tracer gas emissions, easy to quantify. In the mobile tracer gas emission source, fig, 2, up to 50 kg propane per hour are diluted with up to 1000 m2 3 air per hour. This blend is blown into the open atmosphere. The dilution device, including the fan, can be seperated from the trailer and mounted at any place, e.g. 

For purposes of characterization, emission sources are generally divided broadly into stationary and mobile or transportation sources. Stationary sources are further divided into point and area emitters. Typical point sources must include petroleum refineries and electric power plants. Commercial solvent emission and gasoline marketing emission may generally be represented as area sources. A third category has been defined recently—indirect sources—that takes into account hybrid sources like sports arenas and shopping centers. These have fixed locations, but the traffic that is generated by or attracted to such a facility constitutes the source of emission that is combined with the emission of the facility itself. 

Generally, catalysts are called into action to eliminate emissions from mobile (cars) and stationary (industry) sources, to take part in liquid and solid waste treatment, and contribute to the effort to reduce volatile organic compounds and gases that pose major environmental problems such as photochemical smog and (at a global level) the greenhouse effect. 

Air, water, soil, and sediment are broad categories of environmental media and each of these can be divided into several subcategories, for example, ambient air, indoor air, industrial or workplace air, and vapor emissions from mobile or stationary combustion sources. Body fluids and tissue are also relevant environmental media because... 

From all data available, it can be concluded that personal exposure cannot be estimated from ambient air concentrations. Reducing benzene emissions from mobile sources only will have a rather limited effect on total human air exposure to this compound. 

In an effort to reduce emissions from mobile sources to help address acute ozone nonattainment problems, the State of California adopted a Low Emission Vehicle/Clean Fuel program in 1990. Low Emission Vehicles, or LEVs, are designed to meet significantly stricter HC, CO and NOx standards than vehicles sold in the remainder of the U.S., and are designed to operate on a strictly controlled reformulated fuel to achieve low emissions over the vehicle s lifetime. One of the characteristics of this fuel is a low sulfur content, which averages 30-40 ppm or less. Data provided by the Auto Oil Air Quality Research Program and other studies were instrumental in the development of the low emission properties of this fuel, and vehicle manufacturers now use this fuel in the development, calibration, and certification process for Low Emission Vehicles sold in California. 

The pollution with dust is caused by emissions from industrial plants and traffic, as well as by high emissions from natural sources of dust. The main emission sources of nitrogen oxides are mainly the mobile ones such as motor vehicles. The relatively high level of pollution by ozone is determined by photo-chemical reactions in the atmosphere under the influence of solar radiation and the high level of ozone precursor compounds. 

Over the past 15 years, the atmospheric science community has developed a series of mobile platforms with highly accurate and specific fast response instrumentation that have revolutionized atmospheric chemistry field measurements. These include high-altitude aircraft, such as NASA s ER-2 and WB-57, and lower-altitude aircraft like the NASA DC-8, the National Oceanic and Atmospheric Administration (NOAA) and Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) (Naval Postgraduate School) Twin Otters, the National Center for Atmospheric Research (NCAR) C-130, and the DOE Gl. In addition, mobile surface laboratories are now being used for a wide variety of urban and regional air quality and emission source characterization studies.4 Typical configurations for the ER-2 and the mobile laboratory are shown in Figures 1 and 2. 

The performance of the Champlin SCOT unit has been tested by the Los Angeles APCD emission source test team. They found that the emission level was considerably below the statutory limits of 500 ppm sulfur dioxide. The plant has also been subject to a lengthy test by the mobile laboratory of the EPA with similar findings. Performance tests made by Shell Development Co. proved that the Champlin Plant met and exceeded its guarantee level of 500 ppm hydrogen sulfide in absorber offgas and that the selectivity of the solvent for hydrogen sulfide exceeded expectations. 

Olcese, L.E., Palancar, G.G. and Toselli, B.M. (2001) An inexpensive method to estimate carbon monoxide and nitrogen oxide emissions from mobile sources. Atmos Environ, 35 (35), 6213-6218. 

Kolb, C.E., Herndon, S.C., McManus, J.B. et al. (2004) Mobile laboratory with rapid response instruments for real-time measurements of urban and regional trace gas and particulate distributions and emission source characteristics. Environ Sci Technol, 38 (21), 5694-5703. 

In addition to the fiber sensors, there have been numerous reports on remote fiberless optical detection of pollution from stationary sources. Mobile remote sensors can have cost advantages over on-site instruments and also are much more versatile. Pollutants in smokestack emissions have been identified by irradiation with a laser from a mobile unit equipped with a telescope, a monochromator, and low-noise detection electronics. The gases and particles in the plume scatter the laser light in various directions. A fraction is scattered back to the receiver and analysed to detect the amount and type of gas in the plume. Many of these methods await their application to fiber-optic sensing schemes which are inherently safer than direct laser spectroscopic schemes. 

Emission inventory Mobile sources Stationary sources Area sources Biogenic sources... 

Pollution controls on vehicles initially were established in 1970. Vehicle controls are one of three methods used to reduce emissions from mobile sources. Inspection and maintenance of the vehicles, and cleaner burning fuels such as oxygenated fuels, also are used. 

Toxic Pollutants Emissions from Mobile Sources... 

A large majority of air polluting emissions comes from mobile sources. The automobile is an obvious example, but other vehicles, such as semi-trucks, trains, and aircraft also contribute. Emissions from mobile sources include CO2, volatile organic compounds (VOCs), NO, and particulates. The latter may also have heavy metals, such as lead or mercury, or hazardous organics attached. Stationary sources typically burn or produce fossil fuels - coal, gasolines, and natural gas. These produce gaseous sulfur compounds (H2S, SO2, etc.), nitrogen oxides (NOJ, CO2, and particulates. Fuel producers and distributors also typically produce VOCs. 

---