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A DYNAMIC SIMULATOR OF ENVIRONMENTAL CHEMICAL PARTITIONING
Citation:
Cooter, E J. AND Y. Cohen. A DYNAMIC SIMULATOR OF ENVIRONMENTAL CHEMICAL PARTITIONING. Presented at 2000 Annual Meeting of the American Institute of Chemical Engineers, Los Angeles, CA, November 12-17, 2000.
Impact/Purpose:
This task has the following objectives:
Improve modelers' ability to focus on scientific and policy issues in modeling studies by providing software that supports composing, applying, and evaluating complex systems of models.
Improve the understanding of the interaction of the atmosphere and the underlying surface, especially the flux of mass in both directions, and EPA's ability to simulate that interaction.
Contribute to multimedia studies and assessments by applying state-of-the-art atmospheric models, estimating atmospheric contributions to multimedia issues and the sources of those contributions, and evaluating the models' strengths and weaknesses.
Description:
A version of the Community Multiscale Air Quality (CMAQ) model has been developed by the U.S. EPA that is capable of addressing the atmospheric fate, transport and deposition of some common trace toxics. An initial, 36-km rectangular grid-cell application for atrazine has been developed for the United States and southern Canada for a continuous 120 day period during the Spring and Summer of 1995. The principle focus of the analysis is Lake Michigan and its surrounding watershed. Grid-cell average model results are compared to total ambient atmospheric measurements reported by the U.S. EPA Lake Michigan Mass Balance (LMMB) Study and the USGS National Weather Quality Assessment program for 1995. Grid-averaged weekly and monthly aggregate wet deposition model results are compared to observations reported by the LMMB, USGS and Environment Canada. Special attention is given to gas/particle partitioning mechanisms when modeling ambient atmospheric concentration since expected partitioning behavior, based only on direct particle sorption, does not appear to adequately explain most field observations. Inclusion of additional sorption mechanisms (i.e., liquid film and film pH) results in model estimates that more closely resemble reported values. In the future, a second, 12 km rectangular grid domain, centered over Lake Michigan itself, will be nested within the larger model domain for a sub-set of the 120 day period to obtain more spatially resolved wet and dry chemical deposition patterns over the Lake surface.