Atmospheric pollutant dispersion

So far in discussing motion in the atmosphere, we have been emphasizing only horizontal motions. Although of much smaller magnitude than horizontal motions, vertical motions are important both to daily weather formation and to the transport and dispersion of pollutants. 

Clouds cover roughly two-thirds of our earth s surface and play an important role in influencing global climate by affecting the radiation budget. Cirrus clouds are one example of a cloud type whose optical properties are not accurately known. Cirrus clouds form in the upper troposphere and are composed almost exclusively of non-spherical ice crystal particles. The impact of cloud coverage on dispersion of pollution in the atmosphere is an area of great concern and intensive study. 

If the sphere of air mass moves upward in an adiabatic process but in an atmosphere with a subadiabatic lapse rate, the sphere follows a temperature change given by the adiabatic slope but when it arrives at point Zj, it is at a lower temperature than its surroundings, but at the same pressure. As a result, it is heavier than the surroundings and tends to fall back to its original position. This condition is called stable. In a stable atmosphere pollutants will only slowly disperse, and turbulence is suppressed. 

The unique appearance of an infrared spectrum has resulted in the extensive use of infrared spectrometry to characterize such materials as natural products, polymers, detergents, lubricants, fats and resins. It is of particular value to the petroleum and polymer industries, to drug manufacturers and to producers of organic chemicals. Quantitative applications include the quality control of additives in fuel and lubricant blends and to assess the extent of chemical changes in various products due to ageing and use. Non-dispersive infrared analysers are used to monitor gas streams in industrial processes and atmospheric pollution. The instruments are generally portable and robust, consisting only of a radiation source, reference and sample cells and a detector filled with the gas which is to be monitored. 

HEINES, T.S., L.K.PETERS An analytical investigation of effect of a first order chemical reaction on the dispersion of pollutants in the atmosphere. Atmospheric Environment 7 (1972) S. 153-162. 

The wavelength-dispersive x-ray spectroscopy method (ASTM D6376) provides a rapid means of measuring metallic elements in coke and provides a guide for determining conformance to material specifications. A benefit of this method is that the sulfur content can also be used to evaluate potential formation of sulfur oxides, a source of atmospheric pollution. This test method specifically determines sodium, aluminum, silicon, sulfur, calcium, titanium, vanadium, manganese, iron, and nickel. 

Radiotracers have been employed in studies of physical and biological processes in the atmosphere and the hydrosphere. Among the quantities that have been measured in atmospheric studies are the natural airflow patterns in large- and small-scale investigations, the dispersion of atmospheric pollutants from various sources, and the identification of the sources of various pollutants. In studies of... 

In general, diffusion is most useful for fundamental studies where we want to know the details about the system. For example, if we were concerned with a plastisizer inside a polymer film, we might want to know where and when the plasticizer is located. Diffusion will tell us. Dispersion can be important when there is convection, as in chromatography or atmospheric pollution. Mass transfer, on the other hand, tends to be useful in less fundamental, more practical problems. For example, if we want to know how to humidify and ventilate a house, we probably will use mass transfer coefficients. 

In these discussions we will thus use the following explicit definition of a chemical measurement in the atmosphere the collection of a definable atmospheric phase as well as the determination of a specific chemical moiety with definable precision and accuracy. This definition is required since most atmospheric pollutants are not inert gaseous and aerosol species with atmospheric concentrations determined by source strength and physical dispersion processes alone. Instead they may undergo gas-phase, liquid-phase, or surface-mediated conversions (some reversible) and, in certain cases, mass transfer between phases may be kinetically limited. Analytical methods for chemical species in the atmosphere must transcend these complications from chemical transformations and microphysical processes in order to be useful adjuncts to atmospheric chemistry studies. 

In atmospheric pollution the impact of point source (e.g., a chimney stock) or a continuous source in an area (e.g. industrial area or urban motorway) is usually modeled. Different models exist based on different mathematical assumptions. Many, such as AERMOD, CALPUFF, BLP, CALINE3, are developed or accepted for use by the US EPA and more information can be found at US EPA Web site [55]. The current technology allows environmental modeling based on physicomathematical processing of mass flux in the diffusion and dispersion of pollutants that can migrate from emission sources to the environment, both in the air near the ground and in the atmosphere, in general. 

Many urban features can influence the atmospheric flow, its turbulence regime, the microclimate, and, accordingly modify the transport, dispersion, and deposition of atmospheric pollutants within urban areas, namely ... 

The distribution and dispersal of pollutants within the atmospheric boundary layer have been thoroughly discussed elsewhere, and will not be elaborated here. 

Additives may be used to improve the fuel performance, and additives such as alkyl nitrates and nitrites (ASTM D-1839, ASTM D-4046) can improve ignition quality. Pour point depressants can improve low-temperature performance. Antismoke additives reduce exhaust smoke, which is of growing concern as more and more attention is paid to atmospheric pollution. Antioxidant and sludge dispersants may also be used, particularly with fuels formulated with cracked components, to prevent the formation of insoluble compounds that could cause line and filter plugging (ASTM D-2068, ASTM D-6371, IP 309). 

The other component is directed toward estimation of the capacity of the region to accept industrial development—the regional carrying capacity—based on the meteorological characteristics of the region. More specific needs are (1) more accurate atmospheric models to predict the transport and dispersion of atmospheric pollutants, (2) determining rates at which pollutants are removed from the atmosphere, and (3) quantitative information on the effects of air pollutants on critical atmospheric processes related to undesirable effects, e.g., precipitation quality, decreased visibility, and local climate modification. ... 

In order to achieve any one or a combination of the previously listed objectives, it is necessary to measure ambient air concentrations of dioxin. In order to interpret variations in the distribution of air pollution concentrations, the on-site measurement of meteorology and a basic understanding of the role of the atmosphere in transporting and dispersing air pollutants is needed. Sampling Site Selection... 

The city of Veles, with its geographical position, atmospheric characteristics, urban and industrial concentration, and its improperly located the Lead and Zinc Smelter Plant upstream to the north wind opposite to the Wind Rose (north wind is dominant and dispersion of pollutants is going directly to the city), multiplied by inconvenient climate-meteorological, hydro-topographic factors has a huge and continuous air pollution problem. The Lead Smelter Plant, built in Veles in 1973, is located on the north of the city only 200-300 m away from first households. 

An important factor in determining the extent of air pollution in urban areas is whether the atmosphere is stable (poor mixing, accumulation of pollutants) or unstable (good mixing and dispersion of pollutants). Whether the atmosphere is stable or unstable depends on how the temperature profile (the so-called lapse rate) in the atmosphere near ground level compares with the adiabatic lapse rate. The adiabatic lapse... 

Yeh, J. T. "Modeling Atmospheric Dispersion of Pollutants." In). Air Pollution Control and Design for Industry, edited by R N. Cheremisinoff. New York Marcel Dekker, 1993. 

Each of these scales of atmospheric motion plays a role in air pollution, although over different periods of time. For example, the microscale meteorological effects determine the dispersion of a plume from an industrial stack or a highway over timescales on the order of minutes to a few hours. On the other hand, mesoscale phenomena take place over hours or days and influence the transport and dispersal of pollutants to areas that are hundreds of kilometers from their sources. 

A k-e atmospheric dispersion model POLLUT was developed at the TU Munchen [93] to describe hot gas plumes escaping from stacks of power plants. The code was used in a DLR study [45] to investigate hydrogen dispersion upon accidents with LH2 powered cars releasing their tank contents both in open terrain and in a road tuimel. 

Given the new European laws concerning air pollution, it is important nowadays to model the effect of conveying and dispersing these atmospheric pollutants. To resolve these problems it is necessary to use many databases and, subsequently, many measuring points. 

The problem of florescences is germane to atmospheric pollution. First of all, the florescences may originate in the attack of atmospheric gases on masonry materials. Once they have formed, they increase the concentration of ions in solution and thereby increase the solubility of potential efflorescences dispersed in the matrix of the stone, and thus concentrate them in the near-surface regions where they are most effective in causing the disintegration of the stone. 

An inversion occurs when air temperature increases with altitude. Temperature inversions (extreme cases of atmospheric stability) create a virtual lid on the upward movement of atmospheric pollution. This situation occurs frequently but is generally confined to a relatively shallow layer. Plumes emitted into air layers that are experiencing an inversion (inverted layer) do not disperse very much as they are transported with the wind. Plumes that are emitted above or below an inverted layer do not penetrate that layer rather, these plumes are trapped either above or below that inverted layer. High concentrations of air pollufants are often associated with inversions, as they inhibit plume dispersions. Two types of inversions are important from an air quality standpoint radiation and subsidence inversions. 

There is no simple relationship between the source strength and ambient concentration of an atmospheric pollutant, since dispersion of the pollutant between source and receptor is a process which is dependent upon meteorological conditions and is hence very variable. For this reason, concentrations measured over a short time period at only one site may not be representative of ambient concentrations in that region, and longer-term average concentrations measured at carefully selected sites are to be greatly preferred. 

Develop an order-of-magnitude solution for the dispersion of atmospheric pollutants. The most commonly used models of atmospheric dispersion from continuous sources are the Gaussian plume models. For an infinite-line source such as might be used to simulate automotive emissions on a freeway, the model takes the form... 

In solution analysis, the use of MC-ICP-MS has allowed the precision to be significantly increased, as discussed in previous sections. This has been also demonstrated in this particular context for the analysis of lichens, used as biotracers for mapping the dispersion of atmospheric pollutants in urban areas [77], and for monitoring the evolution of sources of anthropogenic Pb in Iceland, after analysis of a sediment monoUth [78]. However, in addition, the major advantage of this technique is that it opens doors for measuring other isotopic systems that are also of environmental interest. 

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