Heavy metal surveys in Nordic lakes; concentrations, geographic patterns and relation to critical limits.

In the autumn of 1995, coordinated national lake surveys were conducted in the Nordic countries, including Russian Kola. The 11 metals (Pb, Cd, As, Zn, Cu, Ni, Co, Fe, Mn, Cr, V) investigated in nearly 3000 lakes have generally low concentrations and distinct geographical patterns. Direct and indirect influence of long-range transported air pollution is the major important factor for distribution of Pb, Cd, Zn and to a certain degree Co. Total organic carbon (TOC) concentrations in lakes are important for Fe and Mn but also to a certain degree for As, Cr and V. Bedrock geology is the major controlling factor for Cu and Ni, with the exception of areas around the smelters in the Kola peninsula, where the Cu and Ni concentrations in lakes are very high due to local airborne pollution. Bedrock and surficial geology is also an important factor for controlling the concentrations of As, Co, Cr and V. The results indicate that heavy metal pollution in lakes is a minor ecological problem on a regional scale in the Nordic countries.