Metal concentrations in sediments in acidifying lakes in Finnish Lapland

Fifteen lakes in the Finnish Lapland were investigated to study acidification and pollution effects on metal concentrations in sediments. In four lakes the pH was lower than 6.0 and the alkalinity was lower than 50 meq l–1. Contamination factor (Cf, ratio of metal concentration of the top layer to the bottom layer in a sediment core) of Pb (Cf = 10.1–10.4) was high in comparison to other investigated heavy metals, particularly in acidic lakes. Lake acidification results in decreasing Ni, Cu, Zn, Cd, and Al concentrations towards the sediment surface. Reduction of organic material content (loss on ignition) in upper sediments of acidic lakes was also noticed. The buffer capacity index (BCI, ratio of sum of alkaline and alkaline-earth metals (K, Na, Ca, Mg) to Al) was lower in the acidic lakes (0.12–0.36) than in the other studied lakes (0.42–1.34)