Gaseous emissions, source control

There are many types of emissions to atmosphere, and these can be characterized as particulate (solid or liquid), vapor and gaseous. Overall, the control of atmospheric emissions is difficult because the majority of emissions come from small sources that are difficult to regulate and control. Legislators therefore control emissions from sources that are large enough to justify monitoring and inspection. Industrial emissions of major concern are as follows. 

There are three main types of practical problems to which the contents of this book can be applied How are aerosols formed at pollution sources How can we remove particles from gaseous emission,s to prevent them from becoming an air pollution problem How can we relate air quality to emission sources and thereby devise effective pollution control strategies The fundamentals of aerosol behavior necessary to deal with these problems are developed in this text. Although fundamentals are stressed, examples of practical problems are included throughout. 

Industrial plants have been relying on a form of SCR since the 1960s [19], however, the controlled and stable nature of industrial plant operation allows several degrees of freedom that are not possible on a vehicle. Industrial plants have relatively steady emissions output, are able to introduce gaseous NH3, can control the temperature of the catalyst to a very narrow window, and readily employ cleanup catalysts as the space constraints are not as limiting as on a vehicle. With these factors in mind, the low-cost vanadium and tungsten oxides supported on titania are the most widely used catalysts employed to selectively reduce NOx from stationary sources [20]. These catalysts have also been implemented for diesel vehicles in Europe, but they have limited thermal durability as well as the potential to emit harmful gaseous vanadium [21-23]. 

This completely automated spectrum analysis procedure represents the final element in our effort to reduce to routine practice the quantitative analysis of similarly constituted gaseous samples by FTIR. It has seen wide and successful application within our laboratory, having been the principle analytic method for two extensive hydrocarbon species-specific auto exhaust catalyst efficiency studies, a comprehensive study of the gases emitted by passive-restraint air bag inflators, several controlled furnace atmosphere analyses, several stationary source stack emission checks and several health-related ambient atmosphere checks. 

NH3 and to a lesser extent mono-, di-, and trimethylamines are the only significant gaseous bases in the atmosphere, and there has been considerable interest in whether the oceans are a source or sink of these gases. Early attempt to assess the air-sea flux from concentration measurements are probably suspect because of the ease with which sample contamination can occur during laboratory processing and analysis. It should be noted here that due to its high solubihty (low value of Henry s law constant), the air-water transfer of NH3 (and the methylamines for the same reason) is under gas phase control (see Section 6.03.2.1.1). The first reliable measurements were probably from the North and South Pacific and indicated that the flux of NH3 from sea to air is of a size similar to that for emission of DMS (Quinn et al., 1990, 1988). Indeed, the authors showed that this similarity was mirrored in the molar ratio of (non-sea-salt) sulfate to ammonium (1.3 0.7) in atmospheric aerosol particles collected on the cruise, indicating that for clean marine air remote from terrestrial sources, the emission of DMS and NH3 from the sea appears to control the composition of the aerosol. 

Monaci et al. (1997) performed a lichen-biomonitoring study in Siena by means of two different methods. The pattern of air quality in the study area was examined on the basis of the in situ frequency of different species of epiphytic lichens, i.e. using their species-specific sensitivity to the complex mixture of phytotoxic pollutants in the urban environment. The distribution of trace elements was evaluated quantitatively by an analysis of thalli of a tolerant species, P. caperata, known to be a reliable bioaccumulator of persistent atmospheric pollutants. The values obtained for Al, Ba, Cr, Cu, Fe, Pb and S were significantly higher in Sienese lichens over and above controls. Traffic was found to be the major source of atmospheric pollution. The pattern of trace-elemental deposition did not always coincide with air quality. lAP values were found to reflect essentially the emission of gaseous phytotoxic pollutants in the urban environment. 

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