Mercury accumulation in peatbogs at Czech sites with contrasting pollution histories

Abstract

Mercury (Hg) concentrations and accumulation patterns were studied in 210Pb-dated peat cores from three ombrotrophic sites in the Czech Republic with contrasting emission histories (Novodomské rašeliniště, ND, and Bílá Smědá, BS, in the polluted northern parts of the country, and Jezerní slať, JS, in a relatively pristine southern part of the Czech Republic). The Hg concentration varied significantly between sites. Whereas the sites in the northern part of the Czech Republic yielded a range of higher Hg concentrations (50–750μgkg−1 for ND and 30–600μgkg−1 for BS), a Hg concentration range of 40–220μgkg−1 was reported at JS. At the northern localities, the highest Hg concentrations were detected at depths of 5–10cm, corresponding to the period between the early 1960s until the late 1980s. In contrast, the highest Hg values at JS were observed at a depth of 10–15cm, corresponding to the period between the early 1950s and the early 1970s. The maximum Hg accumulation rates were approximately 2× higher at the northern localities (ND: 106μgm−2yr−1, BS: 90μgm−2yr−1, JS: 43μgm−2yr−1). Although a decrease in the Hg concentration can be observed in the youngest segments of all the peat cores, a slight increase in Hg accumulation rates in the most recent peat segments (living Sphagnum moss) has been reported for all three sites (40–44μgm−2yr−1), which is approximately 2× higher than in peat bogs in western and northern Europe. This observation may either be related to a real recent increase in Hg emissions in Central Europe (active coal mining and burning and limited Hg pollution control in thermal power plants) or could indicate a preferential Hg binding mechanism in the living moss at the surface of the peat.