Historical deposition rates of mercury in scandinavia estimated by dating and measurement of mercury in cores of peat bogs

Abstract

Historical deposition rates of Hg were determined in 7 ombrotrophic bogs located far from direct sources in Sweden and Norway. The peat bog cores were dated using 210Pb. Based on the dating result 10 to 12 slices from each core were analyzed for Hg. In Southwestern Scandinavia (Rorvik) the deposition rate has increased from about 10 to about 30 μg Hg m−2 yr−1 since the beginning of this century. In Northwestern Norway (Overbygd) the deposition rate has increased from about 10 to about 35 μg Hg m−2 yr−1 since the 1960's. In Southeast Sweden (Aspvreten) the deposition rate decreased since the beginning of this century. There are no significant trends in the historical deposition rates at the two other stations in middle Scandinavia. A comparison between recent Hg deposition rates measured by peat bog analysis, wet precipitation and mosses shows good agreement at all stations except those in Northern Norway were local dry deposition of Hg may be an important source of Hg.