My Research Interests biogeochemistry of soil, sediment and water reactions controlling fate of carbon and contaminants in the critical zone environmental surface and colloid chemistry His research group explores the biogeochemistry of soil, sediment and water through laboratory and field-based experiments probed with advanced analytical chemistry techniques. Of particular interest is resolving how mineral-organic interactions influence the weathering of soils, the stabilization of organic carbon, and the speciation, mobility and bioaccessibility of pollutants. He directs a core analytical chemistry facility, the Arizona Laboratory for Emerging Contaminants and serves as PI of the UA-led, NSF-funded Santa Catalina Mountains – Jemez River Basin Critical Zone Observatory.