Influence of natural and manmade processes of the geochemical composition of lake sediments, northeast Estonia

Causal relationships between environmental changes and features of lake ecosystems in north-eastern Estonia were studied. Geochemical data were used to reconstruct changes in concentrations of elements in lake sediments during various time intervals. An attempt was made to distinguish the effects of natural and anthropogenic processes. The lakes were characterized by differing hydrological regimes and trophic states. The results suggested that biogeochemical cycling was strongly influenced by the hydrological regime, and particularly by changes in lake water levels. Anthropogenic impacts were observable in the past century, but varied with proximity to sources of pollution.