Estimation of the Long-range Transport of Mercury, Cadmium, and Lead to Northern Finland on the Basis of Moss Surveys

Abstract

Nation-wide surveys of the accumulation of 10 heavy metals in mosses were carried out in Finland in 1985, 1990, 1995, and 2000. Separate investigations were carried out, on the basis of these surveys, into the atmospheric deposition of Hg, Cd, and Pb beyond the Arctic Circle in northern Finland. These metals are readily distributed in the form of long-range transboundary pollution, and particular concern has been raised about the transport and accumulation of these metals into Arctic areas. The Hg, Cd, and Pb concentrations in mosses in northern Finland were low. There was a clear decrease in Cd and Pb concentrations during the period 1985–2000. The Pb concentration decreased, on the average, from 8 to 2 μg g−1, and the Cd concentration from 0.3 to 0.1 μg g−1. Hg concentrations, which were analyzed in 1995 and 2000, decreased only slightly from 0.037 to 0.031 μg g−1. The slight decrease in Hg concentrations in northern Finland appears to reflect the decreasing Hg emissions and the high mobility of this metal. Factors leading to the decrease in Pb and Cd concentrations in mosses in northern Finland include a decrease in local emissions and a decrease in transboundary air pollution. The past two decades have been characterized by decreases in heavy metal emissions of throughout Europe. The greatest reductions have been in Pb emissions, due to the introduction of unleaded fuels.