Major advances in our understanding of the sources, distribution and fate of contaminants in natural systems have resulted from studies of geochemical tracers. An ideal tracer is a substance with a well-defined source and environmental chemistry. The distribution of the tracer provides insight into the fate of environmental contaminants with similar geochemical behavior. A perfect example is Cs-137. This radionuclide was distributed worldwide with global fallout from the atmospheric testing of large nuclear weapons. The profile of Cs-137 activity with depth in sediment cores from natural water systems provides a relatively simple method for dating sediments -- determining the rate of accumulation over the past several decades. Dated sediment cores contain a historical record of the levels of particle-associated contaminants in the system. Such contaminants include PCBs, dioxins, hydrocarbon pesticides -- some of our most significant environmental pollutants.
Often the pollutants themselves can serve as tracers. DDT-derived compounds are useful indicators of atmospheric sources of contamination. Dissolved phosphate from municipal wastewater discharges in the New York Metropolitan Area is a good tracer of water mass mixing in the lower Hudson Estuary. Copper and lead trace the fate of particle-associated contaminants from these same sources. Chloroform, produced during chlorination of drinking water and waste water, is a tracer of gas exchange between natural waters and the atmosphere. Chlorinated solvent contaminants have significant potential as groundwater flow tracers. Ongoing research has centered on the Hudson River and contiguous waters. Some of the topics under investigation are the PCB problem in the upper Hudson, nutrient cycling in the Hudson Estuary, local sources of contaminants to New York Harbor, dioxins in Newark Bay, contaminants in the vicinity of the nearshore dredge material disposal site and atmospheric inputs of contaminants to the continental slope.
The future of tracer geochemistry is most exciting. As a discipline, it combines the basic scientific investigation of natural systems with the practical appeal of addressing specific environmental problems through the use of creative chemical measurements.
The focus of tracer geochemistry is to gain a better understanding of both the natural system and the behavior of chemical constituents, including contaminants. My general interests lie in the field of environmental geochemistry. At Columbia, I developed and taught graduate courses in Organic Geochemistry and Diffusion and Gas Exchange. On the undergraduate level at Columbia and Barnard, I created courses entitled Chemical Cycles in the Environment, Environmental Measurements, and Environmental Case Studies. I also taught introductory Environmental Science. At Rensselaer, I am teaching Oceanography and Chemistry of the Hudson River, and developing graduate and undergraduate offerings in environmental geochemistry.
My research activities are focused on the Hudson River and surrounding waters. At present I am most involved with sediment core dating and the development of particle-associated pollutant chronologies. Other interests include particle-water partitioning of contaminants, nutrient cycling, gas exchange, atmospheric transport of contaminants and the use of halogenated organic compounds as tracers in surface and groundwater systems. My research has been applied to issues such as the transport and fate of PCBs in the Hudson, the effects of wastewater discharge to New York Harbor, and the impacts of offshore disposal of sewage sludge and dredged material. In the near future I will be addressing the effects of acid deposition on Adirondack lakes, through a program at Rensselaer's Fresh Water Institute.