Elucidating the Geochemical Dynamics of Arsenite and Pyrite in Aquatic Systems

oxidizes As(III) via an inner-sphere electron transfer process. This heterogeneous oxidation likely proceeds through a ternary surface complexation involving arsenite and Fe sites. These findings challenge both the conventional radical-dominated pathway and the assumed mechanism of natural arsenopyrite formation. By elucidating the dominant As(III) sorption/oxidation pathway on pyrite surfaces, our findings reshape our current understanding of arsenic geochemistry. They also inform risk assessment and remediation strategies for arsenic-impacted environments.