SEDIMENT CHRONOLOGY TO AID IN HISTORICAL ANALYSIS OF SEDIMENTATION RATES, PCB AND TRACE METAL INFLUXES IN LAKE ANNA SEDIMENTS, VIRGINIA

Damming of the North Anna River in 1972 created Lake Anna, a cooling water source for the Dominion nuclear power plant as well as a popular recreation site in Spotsylvania and Orange counties, Virginia. Sediment cores from seven locations within the lake and three locations in the adjoining Waste Heat Treatment Facilities (WHTF) were analyzed for 210Pb and polychlorinated biphenyls (PCBs) to examine the environmental evolution of the reservoir system. Given the history of mining in the watershed, sediment samples were also analyzed for Al, Ba, Zn, Cd, Cu, Fe, Mn, and Pb to establish their distribution and loading history in the lake sediments. Based on previous studies, increased concentrations of PCBs were found in fish tissue from Lake Anna. The source of PCBs in the lake is still unknown; therefore, dated sediment cores provide ability of historical analysis and information about possible upland erosion and source sites for both PCBs and trace metals.

210Pb results suggest that sediment accumulation in the lake has been relatively low, but varies from 0.082 g cm^-2y^-1 at core 1 in the upper sections to 0.054 g cm^-2y^-1 at core 7 in the mid-lower reaches. The CRS model results display steady increase in accumulation rates with a slightly higher modern rates probably reflection the modern changes in the watershed. In addition, the 210Pb results shows that sediments above 13 cm represent post inundation lacustrine deposits whereas below are predominantly pre-1972 fluvial deposits.