Moving from the home front to the river front, the studies also provide an extensive baseline of information against which planners and water managers can measure the success of strategies for reduction of nutrients and toxics in tributaries to Chesapeake Bay. Fish, streambed-sediment, and water samples were used to assess the occurrence of contaminants.
Contaminants in streambed sediment at some sites were detected at levels potentially harmful to aquatic life. Trace metals and long-banned organic contaminants are present in streambed sediment in the Lower Susquehanna and Potomac Rivers and their tributaries and have been incorporated into the food chain. These metals and contaminants were detected in clam and fish tissues. The use of PCBs, DDT, and chlordane has been banned or restricted for nearly 20 years, but these contaminants are still being detected in rivers and streams. The USGS cautioned that the fish were collected and analyzed to determine if contaminants were present, not to determine if the fish were safe to eat.
Being more specific, Ator said, "Mercury contamination from an industrial source near Waynesboro, Va., has led to measurable concentrations of mercury in sediment as far as 170 miles downstream on the Shenandoah River near Harpers Ferry, W. Va., even though the use of mercury at the Waynesboro site ended in 1950."
The studies of the Lower Susquehanna and Potomac River Basins,
two of the largest watersheds that drain into Chesapeake Bay, were
conducted by the USGS National Water-Quality Assessment (NAWQA)
Program. The full-color reports summarize USGS studies that began
in 1992 and are written to convey the technical findings to a wide
audience including water managers, policy makers, other scientists,
and the public. Details on the results of the studies an
Contact: Bruce Lindsey
United States Geological Survey