ASSESSMENT OF LAKE ECOSYSTEM RESPONSE TO TOXIC EVENTS WITH THE AQUATOX MODEL

摘要

The EPA aquatic ecosystem model AQUATOX can be used to describe food web dynamics and characterize bioaccumulation under the condition of a toxic event, such as a terrorist attack to a water system. AQUATOX predicts the partitioning of a toxicant among water, sediment, and biota, and includes processes of microbial degradation, photolysis, hydrolysis, and volatilization. The user will most likely be interested in the effects and recovery of two endpoints: fish biomass and bioaccumulation of the chemical in fish tissue. In general, a toxic event will result in a decrease in biomass and an increase in toxicant concentration in biota for a period of time, followed by recovery of both measures to their initial states. However, as illustrated by an example for Coralville Reservoir in Iowa, USA, the response depends on the several factors: the octanol-water partition coefficient of the toxicant, which determines the rate of bioaccumulation; the characteristics of the species present, where less sensitive species may actually increase due to a release from competition; and the time of year, since a spill in a high-flow season will have less effect on biota. For valued water resources, a parameterized and calibrated AQUATOX model could be a useful tool in the response to a toxic event.