CHRONOLOGY AND SOURCES OF ANTHROPOGENIC TRACE-METALS IN SEDIMENTS FROM SMALL, SHALLOW ARCTIC LAKES

Fluxes of Pb, Cd, Zn, and Cu are measured in sediment cores from two arctic lakes. One lake is undisturbed by direct human activity, and the other is used for sewage disposal. Sediment layers were analyzed for metals and dated with Pb-210. Sediment focusing was measured by using a ratio of observed to expected Cs-137. Focus-corrected metal fluxes are compared between lakes and show consistent background levels until the 1940s. Following World War II, atmospheric fluxes of Pb, Cd, and Zn increased until the early 1980s when a trend toward lower levels was observed. Atmospheric inputs of anthropogenic trace metals account for no more than 26% of total mass of any of these four metals in sediment. Sewage inputs account for 33% of total Cd mass in sediment, 30% of Zn, and less than 25% of Pb and Cu.