Development and application of a multimedia model to assess fate and transport of organic chemicals in a South Texas Lake

The coastal bend region of South Texas has undergone significant changes in recent times. Increased agricultural activities, industrialization, and population growth have enhanced the releases of organic chemicals in South Texas environments. Several classes of organic contaminants have been detected in air, water, and sediment samples collected in this region. There is a growing concern that this increased usage may lead to unacceptable exposures and pollute surface-water bodies used for water supply purposes. A study was to develop a two-compartment mathematical model to assess the fate and distribution of benzene (or similar aromatics) in the vicinity of Choke Canyon reservoir, TX. Data for model inputs were complied from several sources. A Geographic Information System (GIS) was to identify the fraction of total emissions that actually pass-over the reservoir. The amount of available data did not allow development of site-specific probability distribution functions to statistically characterize uncertainty and variability in the inputs. Therefore, fuzzy set theoretic approaches were used to assess imprecision in estimated steady-state water and air phase benzene concentrations in the lake. The analysis suggests that for the assumed conditions, exposure to benzene either through vapor or aqueous pathways is most likely insignificant. Geographic information systems and fuzzy set theory were seen to be useful tools to manage data and characterize uncertainty. This is an abstract of a paper presented at the conference on Contaminated Soils, Sediments and Water: Success and Challenges (Massachusetts Fall 2005).