My research divides into two broad areas: (1) the environmental chemistry of trace metals, and (2) watershed based studies of water quality and its relation to land use and other human-environment interactions.
(1) The trace metal research investigates the sources, distribution, speciation, transport, behavior, and fate of trace metals (Hg, Cu, Co, Pb) in aquatic environments. This work emphasizes field investigations in order to encompass and examine the full spectrum of environmentally-relevant processes that influence metal cycling at a range of temporal and spatial scales. All components of watersheds are investigated, from soils and rivers, to lakes and sediments, but the waters themselves are emphasized because this is where our understanding is currently weakest. As the ultimate recipient of metals exported from terrestrial watersheds, estuaries are included, but freshwater environments are stressed, as they have received much less attention in the past. Understanding metal behavior is important not only because of their biological significance (as possible toxicants or micronutrients), but also because they can serve to trace a range of environmentally important processes, thereby revealing information about how ecosystems function. I am especially interested in metal speciation (chemical form), its influence on bioavailability, and the possibility that metal scarcity can control planktonic population distributions and functioning. This work helps to close a serious knowledge gap, as contamination artifacts (caused by inadequate use of clean techniques) have compromised most of the past (pre-1990) data record on trace metals in fresh waters.
(2) Watershed-based water quality studies have immediate applicability, and indeed, their goal often is to actually clean up streams. Contaminants of special concern include excess nutrients, eroded sediment, bacteria, and toxic metals, such as mercury. The challenge, increasingly, is to identify and reduce impacts from nonpoint sources, pollution caused by how we use land. Research in my group tackles this problem on three fronts. First, we conduct surveys of water quality with high resolution in space (location on a stream and its tributaries) and time (variations with season, time of day, and during storms). From this information we pinpoint critical events and pollution hotspots and design management strategies to control them. Second, we seek novel tracers to help identify sources of pollution. For example, we currently are investigating caffeine as a tracer of sewage contamination. Once perfected, this tool could be used to identify defective septic systems, leaking sewer lines, or illegal discharges. Finally, we work to design recommendations for developing land in a way that will cause the least environmental harm. My work in this area will be summarized in a book to be published in March 2007 by John Wiley Publishers.