Mercury deposition/accumulation rates in the vicinity of a lead smelter as recorded by a peat deposit

Mercury (Hg) concentration profiles and historical accumulation rates were determined in three ²¹⁰Pb-dated cores from a peat deposit in the vicinity of a lead (Pb) smelter at Příbram, Czech Republic. The Hg concentrations in peat samples ranged from 66 to 701 μg kg⁻¹. Cumulative Hg inventories from each core (for the past 150 yr) varied by a factor of 1.4 (13.6–18.5 mg Hg m⁻²), indicating variations of net Hg accumulation rate within the peat deposit. Historical changes in vegetation cover (leading to variable interception by trees) are probably responsible for this variation in space and time. The uncorrected Hg accumulation rates peaked between the 1960s and 1980s (up to 226 μg m⁻² yr⁻¹). Recent findings show that Hg records from peat tend to overestimate historical levels of Hg deposition. Therefore we used the mass loss compensation factor (MLCF) to normalize Hg accumulation rates. These corrected Hg accumulation rates were significantly lower (maximum 129 μg m⁻² yr⁻¹) and better corresponded to changes in historical smelter emissions, which were highest in the 1960s. The agreement between the corrected Hg accumulation rates in the uppermost peat sections (2–38 μg m⁻² yr⁻¹) and biomonitoring of atmospheric deposition by mosses in several recent years (4.7–34.4 μg m⁻² yr⁻¹) shows the usefulness of MLCF application on Hg accumulation in peat archives. However, the MLCF correction was unsuitable for Pb. The recent Pb deposition rates obtained by an independent biomonitoring study using mosses (0.5–127 mg m⁻² yr⁻¹) were better correlated with net Pb accumulation rates recorded in peat (7–145 mg m⁻² yr⁻¹) than with corrected rates obtained by the MLCF approach (1–28 mg m⁻² yr⁻¹).