Metal contamination of streams in relation to catchment silvicultural practices: a comparative study in Finnish and Russian headwaters

We studied metal contamination of streams in the forestry dominated and close-on pristine subcatchments in Finland and Russian Karelia. In this area, atmospheric deposition and point loading are insignificant as sources of metals, while geochemical sources and silvicultural activities are important. Aquatic moss Fontinalis antipyretica Hedw. was used as a sentinel organism measuring the metal contamination. Tufts of Fontinalis were collected at 10 Russian and 8 Finnish stream sites for the measurement of whole-plant Al, Fe, Cd, Zn, Cu, Pb and Ni concentrations. The average Al, Fe, Cd, Cu, Zn and Ni concentrations were statistically significantly higher in the Finnish moss samples than in the Russian ones. In particular, concentrations of Al, Fe, Cu, Ni and Zn in many Finnish streams clearly exceeded natural background concentrations and were comparable to the earlier results from streams affected by metal loading from point and non-point sources. The results suggest that silvicultural practices in combination with specific geochemical features may cause metal contamination of streams in areas considered otherwise unpolluted. We stress the importance of taking precautions against forestry-induced metal contamination.