Atmospheric aerosols transportation

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

Nickel releases to the atmosphere are mainly in the form of aerosols that cover a broad spectrum of sizes. Particulates from power plants tend to be associated with smaller particles than those from smelters (Cahill 1989 Schroeder et al. 1987). Atmospheric aerosols are removed by gravitational settling and dry and wet deposition. Submicron particles may have atmospheric half-lives as long as 30 days (Schroeder et al. 1987). Monitoring data confrrm that nickel can be transported far from its source (Pacyna and Ottar 1985). Nickel concentrations in air particulate matter in remote, rural, and U.S. urban areas are 0.01-60, 0.6-78, and 1-328 ng/m, respectively (Schroeder et al. 1987). 

Alfheim, I., and M. Moller, Mutagenicity of Long-Range Transported Atmospheric Aerosols, Sci. Total Environ., 13, 275-278 (1979). 

Hansen, J. E., W. C. Wang, and A. A. Lacis, 1979. Climatic effects of atmospheric aerosols, Proc. Conf. on Aerosols Urban and Rural Characteristics, Source and Transport Studies, New York Academy of Sciences, New York. 

Pacific cyclones represent the major source of precipitation over the western United States. Therefore, they also represent a major source of deposition of contaminant aerosols in the waters of these states. The examination of radioactive aerosols in precipitation resulting from Pacific cyclones is thus of interest in understanding the transport of atmospheric aerosols to the ground by precipitation. 

The observational program included getting information about the content and properties of atmospheric aerosol and most substantial optically active MGCs (03, CO, NOx, S02, etc.), but concentrated on aerosol studies to retrieve data on direct and indirect aerosol RF (ARF). The most interesting (and in many respects unexpected) results were connected with detection of a thick aerosol layer in the troposphere (an important feature of aerosol chemical composition consisted in the presence of a considerable black carbon component) and distinct manifestations of the long-range transport of both aerosol and MGCs. 

An increase of C02 concentration in the atmosphere does not determine substantial fertilization of marine bioproductivity—but does lead to pH decrease. As temperature grows, C02 assimilation by the ocean decreases, but C02 emissions due to upwellings are reduced and the transport of excess carbon to deep layers of the ocean diminishes. The anthropogenically induced input of nutrients to the oceans through river run-off and deposition of atmospheric aerosols (especially nitrate and iron as elements of atmospheric aerosols) can affect bioproductivity. 

An important current problem is attaining sufficient understanding of atmospheric aerosol dynamics to develop mathematical models capable of relating emission reductions of primary gaseous and particulate pollutants to changes in ambient aerosol loadings and thereby to improvements in visibility and health effects. These models involve thermodynamics, transport phenomena, and chemical kinetics in an intricate equilibrium and... 

The on-line integration of meso-scale meteorological models and atmospheric aerosol and chemical transport models enables the utilization of all meteorological 3D fields in ACTMs at each time step and the consideration of the feedbacks of air pollution (e.g. urban aerosols) on meteorological processes and climate forcing. 

The Atmospheric Chemistry-Aerosol-Transport models/modules depend on applicable meteorological driver as well as selected domain of interest and hence, different meteorological operational or re-analysed archived datasets from NWP (such as DMI-HIRLAM (Unden et al. 2002 Sass et al. 2002) or ECMWF) models (or climate models) can be used. At present, output from several nested versions of DMl-HlRLAM is applied (Fig. 16.2) ... 

The principal processes that govern the concentration and properties of atmospheric aerosols are emission of aerosol particles and precursor gases, gas-to-particle conversion and other pertinent atmospheric chemical reactions, transport, and processes by which particles are removed from the atmosphere. There is a substantial hterature on the characterization of these processes from laboratory studies and field measurements (cf. Section 4.04.1), so only a brief overview is provided here. 

Understanding the processes that control atmospheric aerosol concentrations and representing these processes in chemical transport models rests in large part on the accuracy of emissions inventories of aerosols and gaseous precursors. The most widely applied approach to developing such inventories is characterization of emissions per unit of activity (called emission factors ) combined with characterization of the intensity and geographic distribution of these activities. This approach is well developed for some gas-phase species. Emission of SO2 from fossil fuel combustion provides an example. Most sulfur in... 

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