Iron, sulfur, and dissolved carbon dynamics in a northern peatland
Blodau, Christian; Roehm, Charlotte L.; Moore, Tim R.
published: Aug 7, 2002
ArtNo. ESP141015404002, Price: 29.00 €
We examined the aqueous and solid-phase biogeochemistry of three different types of northern peatland sediments (oligotrophic bog, beaver pond, and transition site) along a peatland transect in Ontario, Canada. Pore water concentrations (pH, Fe2+ Fe3+ SO42-, H2S, CH4, CO2 and fatty acids) we monitored seasonally, solid phase profiles (Fe (II), Fe (III), reduced inorganic sulfur) measured, and potential rates of CO2, CH4, Fe2+, and H2S production determined in slurries of peat. Dissolved CO2 (up to 6 mmol/L) and CH4 (up to 1 mmol/L) were the predominant species at all sites. In the acidic bog acetate (up to 1 mmol/L) and smaller quantities of propionate and butyrate were present in the pore water. Dissolved Fe2+ (<5-150 µmol/l), so42- (10-50 µmol/L), and H2S (0 to 10µmol/L) concentrations were much lower in comparison. The Fe (II) production rates (0.6-7.2 mmol m-2 d-1) were small compared to production rates of CO2 (38-46 mmol m-2 d-1) and CH4 (14-29 mmol m-2 d-1). Low concentrations of reactive Fe (III) (5-75 µmol/g) suggested that the Fe (II) reduction rate was limited by reactive Fe (III). In slurries amended with sulfate (0.5 mM) the potential for sulfate reduction was substantial and rates of CH4 production decreased by 48-86%. The in situ accumulation of acetate, propionate and butyrate in the acidic bog was consistent with a lack of stimulation of CO2 and CH4 production during anaerobic incubation amended with acetate. Despite differences between sites Fe reduction was overall of little significance for the carbon flow. Sulfate reduction might have been more important based on the results from the incubations. In the bog, the accumulation of acetate and propionate confirmed the decoupling of anaerobic metabolic processes and the important role of fatty acid dynamics in the carbon cycle of acidic northern peatlands.