INFLUENCE OF ENVIRONMENTAL-FACTORS ON HEAVY-METAL CONCENTRATION IN LAKE-SEDIMENTS IN SOUTHERN NORWAY INDICATED BY PATH-ANALYSIS

We studied relationships between environmental factors and accumulation of Hg, Cd, Pb, and Ni in sediments in 132 lakes in southern Norway. Generally, the concentrations of Hg, Cd, and Pb in surface sediments were considerably elevated as compared with sediments deposited in preindustrial times whereas Ni concentrations showed only minor increases. By path analysis, we modelled how different environmental factors may influence the metal concentrations in surface sediments. The models indicated that both Hg and Pb were associated with sedimenting organic matter, and sediment concentrations were strongly influenced by atmospheric deposition (indirectly measured as metal concentration in mosses) and the amount of organic carrier particles in lake water. Cd behaved similarly, except for a weaker association with organic matter and a positive effect from pH, indicating that Cd is mobilized during acidification. Ni was associated with the inorganic fractions in lake sediments and seemed also to be mobilized during acidification. Geochemical contributions of Ni were larger in sediments than atmospheric deposition whereas atmospheric deposition was the major source of Pb. For the other two elements, estimates of geochemical contributions were lacking.