My current research interests are directed at the fate, transport, and transformation of trace metals, especially mercury, cadmium, and lead, and the metalloids (arsenic and selenium) in aquatic systems and the atmosphere. The scope of research includes the open ocean, the coastal zone and estuaries, as well as freshwater systems. The focus of current research is the important transformation processes, both in the sediment and in the water column, for metals and how these impact bioavailability and bioaccumulation into aquatic organisms. Studies are also focused on the exchange across interfaces, such as the processes controlling air-water and sediment-water exchange of metals.
The role of biota, primarily microorganisms, in mediating the chemical transformations of mercury and other metals in the environment is a current research focus. For example, recent investigations have examined the factors controlling mercury methylation and methylmercury degradation, as well as mercury redox chemistry in aquatic systems with funding through the National Science Foundation (NSF). The primarily rationale for these studies is to promote an understanding of the relationship between the input of mercury from the atmosphere, and from other sources, to aquatic systems and the amount of methylmercury in fish.
Mercury inputs come from both natural and anthropogenic sources and it appears that man’s activities have exacerbated the mercury problem globally and locally. Elevated levels of methylmercury in fish are an important human and ecosystem health concern. One project, in conjunction with Cindy Gilmour of the Smithsonian Environmental Research Institute (SERC), funded by the NSF Chemical Oceanography Program, is aimed at examining the production and fate of methylmercury in estuarine and coastal ecosystems. A number of cruises were completed in 2005/06 and currently the samples collected are being analyzed. Another project, in conjunction with Harvard University, also focused on the coastal zone, is examining the impact of hurricanes on mercury dynamics in the Gulf of Mexico. A further project, with Gilmour, and with Andrew Heyes of the Chesapeake Biological Laboratory (CBL), University of Maryland, has allowed our participation in a large program (the METAALICUS Project) within the Experimental Lakes Area in Northwestern Ontario, Canada where mercury isotopes are being added to a lake to track the rate of formation and fate of methylmercury in a freshwater ecosystem. In addition, I am involved in a project in collaboration with the USGS in California investigating mercury dynamics and differences in methylmercury fate in various parts of the San Francisco Bay delta region, where elevated mercury levels in fish occur.
In terms of the atmosphere, studies in surface waters and in the atmosphere are aimed at quantifying wet and dry deposition of mercury, as well as gas evasion, in both the coastal zone and the open ocean. We are currently air sampling at Bermuda in collaboration with the Bermuda Biological Station/Bermuda Government. These studies follow up on a long-term and extensive set of studies that have been done at CBL. The atmospheric studies are probing the importance of chemical reactions in the atmosphere and in surface waters in influencing mercury transport and chemical form, and the rate of input of mercury from the atmosphere.