Natural and anthropogenic impacts on the composition of lake sediments

摘要

Lake sediments were studied from four lakes in environmentally different areas in northern Finland. Lakes Pyykosjarvi and Kuivasjarvi are situated near roads with heavy traffic and the city of Oulu. Lakes Martinlampi and Umpilampi are small lakes in a forest area with no immediate human impact nearby. The concentration of Pb increases in the upper parts of the sedimentary columns of Lake Kuivasjarvi and Lake Pyykosjarvi. This is interpreted as being an anthropogenic effect related to heavy traffic in the area and use of Lake Pyykosjarvi as an airport during World War II. High Ni and Zn concentrations in the Lake Umpilampi sediments are caused by weathered black schists. Sediments in Lake Martinlampi show high Pb and Zn contents with increasing Pb concentrations up through the sedimentary column. The sources of these elements are probably Pb-Zn mineralization in the bedrock, Pb-Zn-rich boulders and anomalous Pb and Zn contents in till in the catchment area of the lake.