ISOTOPIC AND EXPERIMENTAL INSIGHTS ON THE MECHANISMS OF PYRITE OXIDATION

Pyrite oxidation is one of the major consumers of atmospheric oxygen. The oxidation of pyrite to ferric iron and sulfate involves multiple intermediate reactions, making the overall process complex. Due to this, little is known about what determines the isotopic composition of oxygen in sulfate during pyrite oxidation. A series of pyrite oxidation experiments were performed at pH 2, 7, and 10 in order to measure sulfate and thiosulfate concentrations over the course of 28 days, as well as determine the isotopic composition of sulfate. Oxidation experiments were also performed with isotopically labeled hydrogen peroxide, an intermediate formed during pyrite oxidation, isotopically labeled water, and isotopically labeled oxygen in order to determine what influences the isotopic composition of oxygen in sulfate. This study aims to provide insight as to how much of the labeled oxygen species is incorporated into sulfate, providing a further understanding of the mechanisms controlling pyrite oxidation. Better understanding pyrite oxidation allows us to better predict how pyrite oxidation has affected atmospheric O₂ concentrations over time.