Acidophilic sulfur disproportionation

作者：Hardisty Dalton S^*; Olyphant Greg A; Bell Jonathan B; Johnson Adam P; Pratt Lisa M

来源：Geochimica et Cosmochimica Acta, 2013, 113: 136-151.

DOI：10.1016/j.gca.2013.03.013

Bacterial disproportionation of elemental sulfur (S-0) is a well-studied metabolism and is not previously reported to occur at pH values less than 4.5. In this study, a sediment core from an abandoned-coal-mine-waste deposit in Southwest Indiana revealed sulfur isotope fractionations between S-0 and pyrite (Delta(34) Ses-py) of up to -35 parts per thousand, inferred to indicate intense recycling of S-0 via bacterial disproportionation and sulfide oxidation. Additionally, the chemistry of seasonally collected pore-water profiles were found to vary, with pore-water pH ranging from 2.2 to 3.8 and observed seasonal redox shifts expressed as abrupt transitions from Fe(III) to Fe(II) dominated conditions, often controlled by fluctuating water table depths. S-0 is a common product during the oxidation of pyrite, a process known to generate acidic waters during weathering and production of acid mine drainage. The H2S product of S-0 disproportionation, fractionated by up to -8.6 parts per thousand, is rapidly oxidized to S-0 near redox gradients via reaction with Fe(III) allowing for the accumulation of isotopically light S-0 that can then become subject to further sulfur disproportionation. A mass-balance model for S-0 incorporating pyrite oxidation, S-0 disproportionation, and S-0 oxidation readily explains the range of observed Delta(34) Ses-py and emphasizes the necessity of seasonally varying pyrite weathering and metabolic rates, as indicated by the pore water chemistry. The findings of this research suggest that S-0 disproportionation is potentially a common microbial process at a pH <4.5 and can create large sulfur isotope fractionations, even in the absence of sulfate reduction.

• 出版日期2013-7-15