CUERE Seminar: Pollutant mass balance in the Anacostia River

Abstract 

Bioaccumulation of hydrophobic organic pollutants (HOCs) such as polychlorinated biphenyls (PCBs) in aquatic organisms is a major pathway for exposure to humans. Uptake of these chemicals in aquatic food web is governed by the chemical activity in surface water and sediments. The freely dissolved concentration of HOCs in these phases has been shown to be directly related to their chemical activity and can be used to accurately predict bioaccumulation. In large environmental systems such as rivers, this freely dissolved concentration is governed by mass transfer of pollutants across the air-water and sediment-water interfaces as well as direct inputs from tributaries and overflows. Differences in chemical activity govern the direction of these mass transfer processes as well as the impact of direct inputs on the receiving water body. This research demonstrates the use of a novel passive sampling approach for time-integrated measurement of freely dissolved concentrations of pollutants in the water and sediment phases, as well as gas phase measurements. The measurements performed in the Anacostia River watershed in Washington, District of Columbia (DC), were able to provide the first accurate mass balance of freely dissolved pollutant concentrations in the river, enabling identification of a major tributary and contaminated sediment hot-spots as the sources having the most negative impact on the water body. These findings are challenging the traditional Total Maximum Daily Loads (TMDL) approach of using total mass loading of pollutants as a way of assessing management options. This research demonstrates that application of passive sampling techniques can lead to better identification and delineation of sources that raise chemical activity of the pollutants in the river and cause negative impacts through bioaccumulation in the food web, thereby improving the decision making process and leading to more efficient utilization of monetary resources.