I have been a scientist with the U.S. Geological Survey since 1984, and with the New York Water Science Center since 1987. My principal general interests are in biogeochemistry and hydrology, with specific interests in describing and quantifying the processes that affect the cycling of nutrients and metals through watersheds. Much of my work has focused on the effects of acid deposition on ecosystems, but I also study the effects of human land use and landscape disturbance on water quality and hydrology.

In October 2006, I was appointed Director of the National Acid Precipitation Assessment Program, for which I will be lead author of a quadrennial report to the U.S. Congress. I also recently joined a team of scientists who are studying and modeling the processes that control the transformations and transport of mercury in watersheds as part of the USGS National Water Quality Assessment Program. Another recent interest is documenting changes in climate over the past 50+ years and trying to better understand the implications of climate change on water resources.

I hold a B.A. in Geology from Hope College, an M.S. in Environmental Sciences from the University of Virginia, and a PhD in Water Resources from the State University of New York, College of Environmental Science and Forestry. I am also the author of more than 50 scientific papers and reports on topics such as the effects of acid rain on stream chemistry and nitrogen cycling processes in small watersheds.