I am interested in the ways in which hydrology and biogeochemistry interact in urban systems. I use stable isotopes to trace nitrogen in streams to its watershed sources and in-situ sensors to see fine temporal scale changes in water quality. Current projects include: (1) quantifying the spatial and temporal patterns of atmospheric deposition of reactive nitrogen across the Pittsburgh area and (2) continuous sensing of Nine Mile Run water quality to observe the geochemical markers of sewage contamination.