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CLOUD AND CHEMICAL PATHWAY CHARACTERIZATION OF THE NONLINEAR RESPONSE OF SULFUR DEPOSITION AND SULFATE AIR CONCENTRATIONS TO CHANGES IN SO2 EMISSIONS IN THE RADM
Citation:
McHenry, J. AND R. Dennis. CLOUD AND CHEMICAL PATHWAY CHARACTERIZATION OF THE NONLINEAR RESPONSE OF SULFUR DEPOSITION AND SULFATE AIR CONCENTRATIONS TO CHANGES IN SO2 EMISSIONS IN THE RADM. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-93/288 (NTIS PB94130101).
Description:
The aqueous-phase chemistry that occurs in both precipitating and nonprecipitating clouds provides a major mechanism for the conversion of S02 to sulfate in the troposphere. ccording to the Regional Acid Deposition Model (RADM), cloud production of sulfate dominates over gas-phase production throughout most of eastern North America (McHenry and Dennis, 1993). onprecipitating clouds are a major source of atmospheric ambient aerosol, which contributes to the degradation of visibility near the earth's surface, and is available for entrainment by subsequent clouds. recipitating clouds produce wet sulfate (acidic) deposition both by entraining ambient sulfate aerosol and by converting S02 to sulfate before and during precipitation. n previous and ongoing studies (Dennis et al., 1990), the RADM and the RADM/Engineering Models (RADM/EMs) have been used to assess the likely impact of proposed and/or legislated S02 source controls on sulfur deposition and ambient sulfate air concentrations. ike other acidic deposition models (Venkatram and Karamchandani, 1986; Misra et al., 1989; Shin and Carmichael, 1992; Carmichael et al., 1991), the RADM has shown the potential for a nonlinear response to such source controls on an annual basis, that is, a less than one-to-one reduction in sulfur deposition and sulfate air concentrations. ield studies regarding this issue have also been conducted (Meagher et al., 1990).