TRACE METALS IN THE SEDIMENTS OF AN URBANIZED REGION OF LAKE CHAMPLAIN

Sediment cores record regional contamination histories and can be used to assess the magnitude of anthropogenic inputs over time and to evaluate the effectiveness of environmental regulations. The spatial distribution of contaminants in Lake Champlain is provided through the analysis of metal concentrations in surface sediments. Grain size and trace metal data were combined with radiometric dating and pollen stratigraphy to provide an assessment of the history of contamination over the last 350 years in the Burlington region of Lake Champlain. Historical trends in metal inputs in the Burlington region from the seventeenth through the twentieth centuries are reflected in downcore variations in metal concentrations and accumulation rates. Metal concentrations increase above background values in the early to mid nineteenth century. The metal input rate to the sediments increases around 1920 and maximum concentrations and accumulation rates are observed in the late 1960s. Decreases in concentration and accumulation rate between 1970 and the present are observed for most metals. The observed trends are primarily a function of variations in anthropogenic inputs and not variations in sediment grain size. Grain size data were used to remove texture variations from the metal profiles and results show trends in the anthropogenic metal signals remain. Trace metal and grain size data were also measured in surface sediments in order to see the overall distribution of contaminants in the Lake Champlain basin. The surface sediment samples were taken to evaluate the spatial distribution of the metals and to look for potential sources and localized accumulation in the lake.