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MODEL CALCULATIONS OF THE ANNUAL ATMOSPHERIC DEPOSITION OF TOXIC METALS TO LAKE MICHIGAN
Citation:
Clark, T. MODEL CALCULATIONS OF THE ANNUAL ATMOSPHERIC DEPOSITION OF TOXIC METALS TO LAKE MICHIGAN. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-92/234 (NTIS PB93120905).
Description:
The 1990 Clean Air Act Amendments include specific provisions to study significant sources of atmospheric deposition of toxic substances and their impacts on the health and welfare of the Great Lakes and other major water bodies. his act also requires an assessment of the atmospheric loadings to the Great Lakes and other major water bodies. owever, because of cost and technological limitations, spatially-integrated atmospheric deposition to a body of water can not be directly determined. ntil recently, the total annual atmospheric deposition was estimated from the product of (1) spatially-limited, land-based, rural air concentrations, (2) constant theoretical or empirical atmospheric removal rates, and (3) the surface area of the water body. lthough it is expedient, this approach, with its inherent assumptions, has several serious drawbacks that cast doubts on the spatially-integrated atmospheric loadings. omprehensive atmospheric deposition models based on future enhanced versions of currently-available regional air pollution models offcer a more accurate alternative to this traditional approach. owever, since a better understanding of the emission rates and atmospheric processes governing airborne toxic deposition is a prerequisite for the enhanced model versions, these comprehensive models will not be operational within the next several years. n the interim, the Regional Lagrangian Model of Air Pollution (RELMAP), a simple atmospheric deposition model, was applied to quantify the expected range of annual disposition amounts of toxic trace metals to Lake Michigan. hese metals are arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and Nickel (Ni).