USGS Grant Number:
Year Established: 2004 Start Date: 2004-09-01 End Date: 2008-08-31
Total Federal Funds: $170,956 Total Non-Federal Funds: $176,261
Principal Investigators: Charles Werth, Barbara Mahler, Peter Van Metre
Abstract: Problem: Particle-associated contaminants (PACs) are an important contributor to urban non-point source pollution across the Nation. PACs, which include organochlorine compounds, metals, and PAHs, pose a threat to biota in aquatic systems and humans because many are persistent, bioaccumulative, and toxic. Occurrence of PACs has resulted in the impairment of thousands of streams, lakes, and reservoirs. Numerous researchers have relied on analysis of sediment cores from lakes to document changes in water, but to what degree the concentrations and trends seen in sediment cores reflect actual historical concentrations of PACs in influent streams is not well known. Recent research by the USGS RTNS team indicates that in small urban watersheds, concentrations of some PACs on suspended sediment in influent streams can greatly exceed those in bed surface sediment in the downstream reservoir. The team?s research also suggests that, for some PACs, trends may not be preserved in cores. This presents a problem because sediment monitoring programs often rely on streambed sediments and lake cores to describe the occurrence of PACs, and to evaluate the effectiveness of best management practices for mitigating PAC occurrence. Methods: The proposed study, a collaborative effort between Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, and the USGS NAWQA program (RTNS team), will investigate the influence of carbonaceous material (CM) on the transport and fate of PACs in an urban watershed. The study will investigate the evolution of CM, and the associated PACs and sorption mechanisms, as they move from the land surface (soils and street dust) into the water column as suspended sediment to their deposition in the receiving water body and subsequent burial. Suspended sediment and bed sediment will be collected from Lake Como and its influent streams, a man-made lake in Fort Worth, Texas. Soil and road dust samples will be collected from nearby areas. Lake Como has been previously cored by the NAWQA RTNS Team, and this sampling effort is scheduled for additional investigation as part of the USGS NAWQA program in 2004. Samples will be split; one split will be analyzed for PACs (trace elements, organochlorine compounds, and PAHs) at the USGS National Water Quality Lab (NWQL), and the second split made available for investigation of CM and sorption at the University of Illinois. All samples will be subject to a series of treatment steps to obtain sub-samples enriched in different CM fractions. These CM fractions will be quantified, and used in isotherm studies to identify mechanisms that control the sorption and persistence of PACs. Objectives: The overall goal of this work is to determine how CM fractions in urban reservoir sediments affect the persistence of PACs. We hypothesize that with depth, less condensed CMs are mineralized. As a result, and because sorption to less condensed CM is less favorable than sorption to more condensed CM, the fraction of PACs sorbed to the latter and the persistence of PACs increases. The specific objectives of this work are 1) to determine the persistence of different CM fractions in sediments during suspension, sedimentation, and burial, 2) to determine the CM fractions that control the sorption and persistence of PACs in urban reservoirs, and 3) to develop a model to predict PAC sorption to urban sediments.