Geochemical controls on arsenic mobility in spring waters around Mammoth Mountain, CA

Mammoth Mountain, CA is a volcanic region with elevated CO2 emissions from a sub-surface source, which are likely inducing mineral weathering that is leading to varied As concentrations in the surrounding springs. This study examines possible geochemical parameters responsible for the As variation by looking at redox geochemistry and major/trace element chemistry. Analysis shows As ranging from 0.22 to 409 µg/L, which exhibited strong correlations to temperature and local lithology, suggesting geothermal influence. Major/minor elements revealed strong geologic controls with contributions from weathering of felsic and basaltic lithologic units. Evaluation of Fe and S showed minimal redox influence with As concentrations varying because of contributions from other sources rather than redox conditions. Adaptation of the ion exchange method for As(III) and As(V) species separation revealed As(V) was dominant, indicating oxidizing conditions. As speciation experiments also revealed that effective separation is dependent on the column length to volume ratio.