W4 AM Environmental Fate of Mercury
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in Ballroom 4

(MUR-1117-814822) TRIM.FaTE and 3MRA Model Comparison of Multimedia Mercury Fate and Transport.

Murphy, R¹, Jones, B¹, Laniak, G², Murphy, D³, ¹ ICF Consulting, Research Triangle Park, NC² USEPA/ORD, Athens, GA³ USEPA/OAQPS, Research Triangle Park, NC

ABSTRACT- TRIM.FaTE, the Fate, Transport, and Ecological Exposure module of USEPA's Total Risk Integrated Methodology, is a mass-balanced, multimedia compartmental model designed to support EPA's needs in assessing non-air impacts of air pollutants. In this model comparison exercise, the results from a TRIM.FaTE case study in which mercury was emitted into the air from a single facility were compared to results derived from a customized application of another EPA multimedia fate and transport modeling system, 3MRA (Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment). 3MRA was developed originally for analysis of hazardous waste management policies and consists of multiple linked models (including several EPA legacy models, such as ISCST3 and EXAMS) to simulate the transport of pollutant from source to receptor. The two models were applied to the same site, using the same emissions data for a 30-year time period, but the majority of the input parameters were set independently by the two model teams in order to create a robust comparison of the two model applications. Estimated concentrations and deposition rates of various forms of mercury were compared for the 30-year period across a broad set of media (biotic and abiotic) in multiple locations, with focus on media and locations of particular interest (such as upper trophic-level fish in a nearby pond). Reasons for differences in various results were identified and ranged from different methods for simulating mercury fate in air and other media, to different spatial approaches underlying the two models, to differences in input values. Overall, the model comparison enhanced the confidence in both models, improved understanding of the impact of particular inputs or process models within the context of both models, helped to identify areas where further evaluation would be informative, and provided information to assist scientists with regard to future applications of these models.

Key words: multimedia model, mercury fate and transport, model comparison