The pivotal role of sulfite species in shaping the oxygen isotope composition of sulfate: new insights from a stable isotope perspective

Abstract

The oxygen isotope composition of sulfate can be used as archive for microbial and abiotic processes that prevail in the environment as sulfate does not exchange oxygen with the water under most natural conditions. The oxygen isotope composition of ancient sulfate minerals can be used to draw conclusions on the environmental conditions that prevailed in the past. This work investigated especially the influence of sulfite on the oxygen isotope composition of sulfate. Sulfite is often mentioned as final sulfoxy intermediate during the oxidation of reduced sulfur compounds and in contrast to sulfate it exchanges rapidly oxygen with water. The results of this work reveal the importance of sulfite in shaping the oxygen isotope composition of sulfate and how differences in the experimental setup (pH, oxidant) produce highly different values that accommodate for almost the entire range of oxygen isotope compositions of sulfate from natural environments.