Historical trace metal accumulation in the sediments of an urbanized region of the Lake Champlain watershed, Burlington, Vermont

This study documents the history of pollution inputs in the Burlington regi on of Lake Champlain, Vermont using measurements of anthropogenic metals (C u, Zn, Cr, Pb, Cd, and Ag) in four age-dated sediment cores. Sediments reco rd a history of contamination in a region and can be used to assess the cha nging threat to biota over time and to evaluate the effectiveness of discha rge regulations on anthropogenic inputs. Grain size, magnetic susceptibilit y, radiometric dating and pollen stratigraphy were combined with trace meta l data to provide an assessment of the history of contamination over the la st 350 yr in the Burlington region of Lake Champlain. Magnetic susceptibili ty was initially used to identify land-use history for each site because it is a proxy indicator of soil erosion. 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 accumulat ion rates. Metal concentrations increase above background values in the ear ly to mid nineteenth century. The metal input rate to the sediments increas es around 1920 and maximum concentrations and accumulation rates are observ ed in the late 1960s. Decreases in concentration and accumulation rate betw een 1970 and the present are observed for most metals. The observed trends are primarily a function of variations in anthropogenic inputs and not vari ations in sediment grain size. Grain size data were used to remove texture variations from the metal profiles and results show trends in the anthropog enic metal signals remain. Radiometric dating and pollen stratigraphy provi de well-constrained dates for the sediments thereby allowing the metal prof iles to be interpreted in terms of land-use history.