Sulphur Isotope Effects in Chemical and Biological Processes

Abstract

The sulphur isotope effect in the oxidation of aqueous sodium sulphite with molecular oxygen has been measured under a variety of conditions. The observed effect is compared with theoretical calculations based on the reaction mechanism. The uncatalysed and enzyme catalyzed sulphur isotope exchange between sulphate and sulphite has been examined. The oxidation of sulphide to internally-stored sulphur and the subsequent oxidation of the sulphur to sulphate by Chromatium have been studied. Sulphur isotope fractionation in mixed cultures of Chromatium and Desulphovibrio desulphuricans has also been examined. The results are discussed in relation to the natural variations in sulphur isotope abundance.