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EVALUATION OF VADOSE ZONE AND SORUCE MODULES FOR MULTI-MEDIA, MULTI-PATHWAY, AND MULTI-RECEPTOR RISK ASSESSMENT USING LARGE-SOIL-COLUMN EXPERIMENTAL DATA
Citation:
Schmelling*, S G., M. Wang, AND K. Liu. EVALUATION OF VADOSE ZONE AND SORUCE MODULES FOR MULTI-MEDIA, MULTI-PATHWAY, AND MULTI-RECEPTOR RISK ASSESSMENT USING LARGE-SOIL-COLUMN EXPERIMENTAL DATA. Presented at Air & Waste Mgmt. Assn. 2003 RCRA Nat'l. Mtg, Washington, DC, 08/12-15/2003.
Description:
The United States Environmental Protection Agency (EPA) is developing a comprehensive environmental exposure and risk analysis software system for agency-wide application using the methodology of a Multi-media, Multi-pathway, Multi-receptor Risk Assessment (3MRA) model. This software system will have application to the technical assessment of exposures and risks relevant for national waste management rules to protect the health of humans and other living organisms. Evaluation of the suitability and applicability of the component modules used for 3MRA is critical. The Ground Water and Ecosystems Restoration Division (GWERD) of EPA's National Risk Management Research Laboratory previously conducted a large-soil-column study to investigate the behavior of organic pollutants, including halogenated aliphatic hydrocarbons, substituted benzenes, and phenols, during infiltration of municipal wastewater into soil. Based on the feasibility study, the data from this study were used to directly evaluate two modules of 3MRA: the LAU (Land Application Units) source module and the VZ (Vadose Zone) module. The Generic Soil Column sub-module, which is a fundamental component for LAU, waste piles, and landfills, was also evaluated indirectly through the evaluation of the LAU source module. Moreover, since the LAU and VZ modules are sequentially implemented in the 3MRA model, the overall performance of the two combined modules was evaluated. In general the LAU and VZ modules function quite well in simulating the fate and transport of organic constituents in source areas and vadose zones, although noticeable differences were observed between the simulated and observed results for highly volatile organics. Finally, the ways for enhancing appropriate applications of those modules are suggested.