Lead-210 Dating and Heavy Metal Concentration in Recent Sediments of Lama Lake (Norilsk Area, Siberia)

Abstract

Lama Lake is situated in the Noril’sk district of the southern Taymyr Peninsula, Siberia (69°N, 88°E) and covers an area of 466 km2. The geology of the catchment is dominated by Permo-Triassic Continental Flood Basalts (CFB). Cu-Ni sulfides have been mined in the Noril’sk area since 1930. Radiochemical 210Pb and geochemical investigations were carried out on a 0.52 m core from Lama Lake. A mean accumulation rate of 0.04 g cm−2 a−1 was calculated from the 210Pb data. The chemical composition of the lake sediments identifies the CFB formations as the main source of the sediment. The Cd, Cu, Pb, Ni and Zn concentrations show a progressive increase from 4 cm depth up to the sediment-water interface. With the identification of the geogenic source of the sediments, enrichment factors (EFM) of the heavy metals can be calculated as: EFcd (2.5) > EFpb (2.0) > EFzn (1.3) = EFCu (1.3) = EFNi (1.3). The Cd, Pb and Zn enrichment factors display the same pattern as those determined in other arctic regions (e.g. Greenland), whereas Cu and Ni are more enriched in Lama Lake. According to the 210Pb ages, the onset of heavy metal enrichment took place in 1940, coinciding with the start of mining of Cu-Ni sulfide deposits in the Noril’sk area. This supports the assumption of an anthropogenic source for the enriched heavy metals in the sediment core.