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MODEL DEVELOPMENT AND TESTING FOR SEMI-VOLATILES (ATRAZINE)
Citation:
Hutzell, W T. MODEL DEVELOPMENT AND TESTING FOR SEMI-VOLATILES (ATRAZINE). Presented at 1999 POP and Heavy Metals Workshop, Durham, NC, October 10-11, 1999.
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:
The Community Multi-Scale Air Quality (CMAQ) model, air quality model within EPA's Models-3 system, can be adapted to simulate the fate of semi-volatile compounds that are emitted into the atmosphere. "Semi-volatile" refers to compounds that partition their mass between two phases within the atmosphere. One phrase is gaseous. The other phase is sorbed onto atmospheric particulate matter. The fate of such compounds has relevance toward assessing environmental health because several toxic compounds fall into the category.
This presentation discusses progress in adapting CMAQ to simulate atmospheric concentrations and deposition of semi-volatile compounds. It first outlines changes to the model to accomplish the goal. The presentation then focuses on applying the revised model to Atrazine, a widely used agricultural pesticide. The application illustrates how concentrations in gas and sorbed phases change based on the algorithm used to partition mass between the phases. The result implies that water vapor greatly affects the partitioning Atrazine. The presentation concludes on future research and model development that will improve modeling Atrazine and other semi-volatile compounds.