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THE RELATIVE IMPORTANCE OF THE VADOSE ZONE IN MULTIMEDIA RISK ASSESSMENT MODELING APPLIED AT A NATIONAL SCALE: AN ANALYSIS OF BENZENE USING 3MRA
Citation:
Babendreier, J E. THE RELATIVE IMPORTANCE OF THE VADOSE ZONE IN MULTIMEDIA RISK ASSESSMENT MODELING APPLIED AT A NATIONAL SCALE: AN ANALYSIS OF BENZENE USING 3MRA. Presented at 2002 American Geophysical Union Spring Meeting, Washington, DC, May 28-31, 2002.
Impact/Purpose:
The current focus is to 1.) develop, distribute, and support the FRAMES-3MRA modeling technology, 2) to apply the FRAMES-3MRA modeling technology for the purposes of executing national and site-specific risk assessments, 3) to complete model application case studies to explore model performance issues, such as, model validation, 5) to collaborate with other Federal Agencies in an effort to leverage expertise and resources associated with common modeling interests, and 6) to monitor ongoing developments at the Office of Solid Waste and within the environmental modeling community in an effort to identify new needs for science modules and locate or develop solutions within the FRAMES 3MRA modeling system.
Description:
Evaluating uncertainty and parameter sensitivity in environmental models can be a difficult task, even for low-order, single-media constructs driven by a unique set of site-specific data. The challenge of examining ever more complex, integrated, higher-order models is a formidable one, particularly in regulatory settings applied on a national scale. Quantitative assessment of uncertainty and sensitivity within integrated, multimedia models that simulate hundreds of sites, spanning multiple geographical and ecological regions, will ultimately require a systematic, comparative approach coupled with sufficient computational power. The Multimedia, Multipathway, and Multireceptor Risk Assessment Model (3MRA) is an important code being developed by the United States Environmental Protection Agency for use in site-scale risk assessment (e.g. hazardous waste management facilities). The model currently entails over 700 variables, 185 of which are explicitly stochastic. The 3MRA can start with a chemical concentration in a waste management unit (WMU). It estimates the release and transport of the chemical throughout the environment, and predicts associated exposure and risk. The 3MRA simulates multimedia (air, water, soil, sediments), pollutant fate and transport, multipathway exposure routes (food ingestion, water ingestion, soil ingestion, air inhalation, etc.), multireceptor exposures (resident, gardener, farmer, fisher, ecological habitats and populations), and resulting risk (human cancer and non-cancer effects, ecological population and community effects). The 3MRA collates the output for an overall national risk assessment, offering a probabilistic strategy as a basis for regulatory decisions. To facilitate model execution of 3MRA for purposes of conducting uncertainty and sensitivity analysis, a PC-based supercomputer cluster was constructed. Design of SuperMUSE, a 125 GHz Windows-based Supercomputer for Model Uncertainty and Sensitivity Evaluation is described, along with the conceptual layout of an accompanying java-based paralleling software toolset. Preliminary work is also reported for a scenario involving Benzene disposal that describes the relative importance of the vadose zone in driving risk levels for ecological receptors and human health. Incorporating landfills, waste piles, aerated tanks, surface impoundments, and land application units, the site-based data used in the analysis included 201 national facilities representing 419 site-WMU combinations.