Sulfur Metabolism in Polluted Sphagnum Peat Bogs: A Combined 34S-35S-210Pb Study

The size and isotopic behavior of sulfur pools in210Pb-dated peat cores were investigated to obtain an insight into retention mechanisms of pollutant S in two mountain-top peatlands of the Northern Czech Republic, CentralEurope. The bogs were situated 40 km apart in an area which between the years 1985 and 1995 received as much as 130 kg Sha-1 yr-1 from the atmosphere. Vertical peat accretion was faster at Pod Jeleni horou (JH) than at Velky mocal (VM). Organic carbon-bonded S was the most abundant sulfur pool, constituting 77 and 65 wt. % at JHand VM, respectively. At JH both the S concentration maximum and the highest annual S deposition rate were displaced downward by more than 20 years (from 1987 to the 1960s)indicating that the buried S is vertically mobile. At VM the Sconcentration was the highest in the topmost 2-cm section even though atmospheric S deposition peaked in 1987. Different mechanisms of S isotope redistribution prevailed in the topmost peat layers at JH, where a negative δ34Sshift occurred, and at VM, where a positive δ34Sshift occurred. Bacterial sulfate reduction was responsible for the negative δ34S shift at JH. One possible explanation of the positive δ34S shift at VM is release of 32S-enriched products of mineralization during peat diagenesis. There was a strong positive correlation between the abundance of total and pyrite S along the profiles.The presence of pyrite S at VM (526 ± 60 ppm) suggested that even at VM bacterial sulfate reduction occurred. Ananaerobic incubation of JH peat indicated sulfate reduction rate of 600 nmol g-1 day-1. The turnover times for inorganic S pools were shorter than for the organic S pools.Cumulative S contents in the Czech peat bogs were found to be significantly lower than in similar sites in the NortheasternU.S., even though the atmospheric S inputs were more than three times higher at the Czech sites. Possible causes of such discrepancy are discussed