Biogeochemistry of aquatic environments, emphasizing in situ rates of and controls on microbial metabolism in anaerobic soils and sediments; role of anaerobic microbial processes in geochemical cycling and energy flow in sedimentary systems; physiology and ecology of anaerobic respiratory bacteria; influence of anaerobic microbial processes on the mobility and fate of metals and organic contaminants in soils/surface sediments and groundwater aquifer sediments.