The oxygen isotope equilibrium fractionation between sulfite species and water

Our results provide new insights into the oxygen isotope fractionation during reductive and oxidative sulfur cycling. They demonstrate that isotope exchange between sulfite and water during dissimilatory sulfate reduction (DSR) alone is too small to be responsible for the apparent oxygen isotope equilibrium fractionation between sulfate and water mediated by DSR. Our estimates also provide a basis for tracing and quantifying the transformation of sulfoxy intermediates during the oxidation of reduced sulfur compounds to sulfate.