My current research focuses on assessing environmental pathogen fate and transport, carbon nanomaterial transformations, and biogeochemical cycles, especially carbon, nitrogen, and trace metal. One emphasis is on photo-chemical and photo-biological processes in aquatic and terrestrial environments, including direct and sensitized photo-reactions (of nanomaterials, pesticides, polycyclic aromatics, halogenated pollutants, metals); light-initiated free radical reactions; and photo-reactions on soil and plant surfaces. Kinetic, mechanistic and photo-product studies relevant to risk assessment are drivers of these studies.