TENDENCIES IN THE CONTENT CHANGE OF HEAVY METALS IN LAKE SEDIMENTS IN NORTHERN FENNOSCANDIA OVER THE LAST CENTURIES

To study trends in the heavy metal load on lake catchments in Northern Fennoscandia and their ecological status, lake sediment cores were collected in the border area between Russia, Norwayand Finlandwithin the impact zone of the "Pechenganikel" smelter emissions. Age determination by 210Pb chronology was carried out in the sediment samples. The average sedimentation rate in the studied lakes was found to be fairly constant and range within 0.7–1.6 mm/year. A rise Ni, Cu and Co levels in lake sediments was generally found in the layers dates to the 1920s–1930s, and the greatest increase happened in the 1970s–1980s as a result of mining and metal processing in the region. A marked increase in Pb concentrations in the dated sediments was recorded at the beginning of the 18th century. Pb amounts in the surface layer of the sediments have been decreasing in most of the lakes over the past one or two decades. Hg, As and Cd also serve as markers of contamination of the catchments. According to our datings, contamination by the latter elements began in the early or mid-19th century.