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MODELING FLUX PATHWAYS TO VEGETATION FOR VOLATILE AND SEMI-VOLATILE ORGANIC COMPOUNDS IN A MULTIMEDIA ENVIRONMENT
Citation:
Cooter, E J. AND Y. Cohen. MODELING FLUX PATHWAYS TO VEGETATION FOR VOLATILE AND SEMI-VOLATILE ORGANIC COMPOUNDS IN A MULTIMEDIA ENVIRONMENT. Presented at Sixth International Conference on Air Surface Exchange of Gases and Particles, Edinburgh, England, July 3-7, 2000.
Impact/Purpose:
The goal of this research is to develop and test appropriate chemical and physical mechanisms for use in EPA's Models-3 chemical/transport models. These models will be addressing issues of tropospheric photochemistry, fine particles, toxic and semi-volatile substances, and acid deposition. As such, scientifically credible mechanisms for atmospheric gas- and aqueous-phase chemistry as well as heterogeneous chemistry, applicable to the particular pollutant regimes must be included in Models-3.
Description:
This study evaluates the treatment of gas-phase atmospheric deposition in a screening level model of the multimedia environmental distribution of toxics (MEND-TOX). Recent algorithmic additions to MEND-TOX for the estimation of gas-phase deposition velocity over vegetated surfaces are evaluated via recently published dry deposition flux measurements. Model results are compared to similar estimates made by the NOAA multilayer dry deposition model. Results of the evaluation indicate that MEND-TOX performs quite well (r? = .74), for a screening level model, for the estimation of gas-phase dry deposition velocity of nitric acid over soybeans. As long as the stated model assumptions regarding chemical properties are met, the present study exceeds previous laboratory results for organic species to include some inorganic species and open field and dry leaf conditions.