Much of the current interest in aerosols focuses on two areas, first the connections between aerosols and climate, and second the links between aerosol pollution and human disease. Interest in the aerosol-climate connection centers on the direct and cloud-mediated effects of aerosols on solar radiation. Concern over the health effects of aerosol particles < 2.5 |im in diameter (the PM-2.5 fraction) is responsible for the recently enacted standards regarding particulate matter (PM) in the United States (Federal Register, 1997). Both of these general areas of interest require accurate information on the formation, composition, chemical reactivity, and transport of aerosol particles. Models and measurements have been used to determine where aerosols are produced and what they are made of, but advances in remote sensing and analytical methods will lead to a more comprehensive picture of the sources, composition, and reactivity of the atmospheric aerosol.
Beyond these concerns, it is now recognized that understanding the chemistry of aerosols is a key to dealing with other atmospheric constituents of immediate concern, including, for example, certain photochemical oxidants (Finlayson-Pitts and Pitts, 1997). Furthermore, understanding the linkages among the chemical cycles of aerosols, VOCs, and NOv, will be required for the development of effective pollution control strategies (Meng et al., 1997). This newly recognized need for an integrated approach to understanding and controlling air pollution also will lead to improvements in the socioeconomic models that are becoming increasingly important in policy-making decisions.
Climate models are incorporating more and more information on the sources, composition, and fluxes of aerosols. Improved estimates of the quantities of gases and aerosols emitted into the atmosphere from natural and anthropogenic sources are being developed in association with the Global Emissions Inventory Activity (GEIA), a component of the International Global Atmospheric Chemistry Program (IGAC, e.g., Graedel et al., 1993). Given the global dimensions of aerosol pollution problems coupled with the heterogeneity of the aerosol distribution, it is appropriate that coordinated international efforts are being mounted to address both scientific and public health issues.
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