Isotope composition of sulphates generated by bacterial and abiological oxidation

Abstract

Oxygen isotope compositions of secondary sulphates provide a potentially powerful tool for elucidating mechanisms of sulphur oxidation. Such studies should reveal the consequences of various anthropogenic sulphur contributions to the environment, including gaseous emissions, aqueous solutions and elemental sulphur dust. At mining sites, metal sulphides may be oxidized in situ, giving rise to acid mine waters. The environment can receive these compounds from natural sources also, for example volcanoes, sulphurous springs and sour-gas seeps. There are many fundamental questions concerning the specific oxidation reactions and associated kinetics. In principle, isotope data from appropriate experiments can be used to address such questions. In the case of acid mine drainage, the approach of Taylor et al.¹ is noteworthy. Here we present a critical examination of their results and suggest a novel method of determining the kinetic isotope effects identified with the incorporation of O₂ and H₂O-oxygen by SO₄²⁻.