Kinetics of arsenic and antimony reduction and oxidation in peatlands treating mining-affected waters: Effects of microbes, temperature, and carbon substrate

Arsenic (As) and antimony (Sb) from mining-affected waters are efficiently removed in two treatment peatlands (TPs) Northern Finland. However, the exact mechanisms behind this removal not well resolved. Thus, present study combines results microcosm experiments pilot-scale TPs on effects of microbes, temperature, carbon substrate to elucidate role peat microorganisms As Sb removal. The main species TP inflow water arsenate antimonate. In microcosms, they were quantitatively reduced, however, at rates about 20–400 times lower than previously reported pure cultures, likely due excess other terminal electron acceptors, such as nitrate sulfate. Addition microbial inhibitor sodium azide inhibited reduction, indicating that it is indeed microbially mediated. Arsenite antimonite (re)oxidation, which situ limited upper, oxic layers, was likewise observed microcosms. Only for antimonite, oxidation also occurred abiotically, catalyzed by humic acids or metals. Process increased with increasing but all processes low temperatures. Monitoring revealed only minor winter conditions (i.e., temperature freezing) arsenic Formation methylated oxyarsenates increase mobility onset freezing. From different substrates tested, lactate slightly enhanced reduction antimonate stimulated acetate, lactate, formate. a maximum rate enhancement 1.8 indicates availability rate-limiting factor reduction. collective data indicate catalyze (re)oxidation TPs, even though major controlling reduction/(re)oxidation, concentrations, long residence times, presence unfrozen layers allow efficient under conditions. • Peatland microbes species. Microbial As/Sb crucial contaminant peatlands. Temperature strongly affects turnover rates. Removal possible concentrations times.