SINKS FOR TRACE-METALS, NUTRIENTS, AND SEDIMENTS IN WETLANDS OF THE CHICKAHOMINY RIVER NEAR RICHMOND, VIRGINIA

The Chickahominy River drains 790 km2 in southeastern Virginia, includ ing approximately 155 kM2 of dense commercial, industrial, and urban d evelopment in the upper basin near Richmond, Virginia. Previous studie s have shown that total stream concentrations of trace metals and nutr ients increased during storms, suggesting resuspension of contaminated sediments and (or) stormwater influxes of pollutants. The possible ro le of wetlands in maintaining water quality is of concern because the river furnishes about 46 percent of the water supply for the City of N ewport News. Particle sizes of sediments and their corresponding total concentrations of carbon, nitrogen, copper, nickel, lead, and zinc we re determined to assess their distribution within wetlands adjacent to the river. Except for Zn, concentrations of all measured constituents in the <63-mum-particle fraction were lower downstream of Richmond, s uggesting that most contaminants are retained in the upper basin. Zinc concentrations increased along downstream reaches, peaking at 5 1 0 m g kg-1 approximately 8 km below the confluence of Upham Brook with the Chickahominy River. Lead concentrations up to 192 mg kg-1 were measur ed in sediments along Upham Brook near Richmond. Concentrations of Zn and Cu were highest in streambed sediments and lowest in elevated fore sted wetlands. The results suggest that the developing regions of the basin have a significant effect on sediment chemistry within the basin and that wetlands play a role in retaining these sediment-borne conta minants in upper reaches of the basin. Studies are underway to assess the stablity of these sediments and the capacity of these contaminated wetlands to continue to assimilate them.