Sources, Distribution and Fate of Mercury at Contaminated Sites in Penobscot Bay, Maine
Mercury contamination is a high profile, significant environmental problem throughout the U.S., especially in the Northeast. Continued atmospheric deposition and discharges from point sources make this persistent problem even more critical in the region, especially in aquatic ecosystems. More information is becoming known about the extent and concentration of mercury in marine environments, but little is known about the fate, transformation, bioavailability and effects of mercury relative to estuarine and marine organisms. In particular, little information is available on the fraction of mercury that is bioavailable in marine and estuarine environments. The ability to assess impacts on biota by measuring bioexposure in indigenous organisms can be complicated at some contaminated sites, and the proposed approach of using highly adaptable bacterial communities as one measure of bioavailability and biological response to mercury is a potentially useful approach worthy of evaluation.
The intent of the project is to determine the extent of contamination and availability of mercury to organisms in aquatic environments near suspected mercury sources. The areal and subsurface distribution of mercury will be measured at two sites, one in a low salinity tidal river next to an industrial point source and the other in a small, active fishing harbor on the Atlantic Ocean with sediments contaminated from unknown sources. The potential for bacterial transformation of ionic mercury to volatile elemental and organic forms, and the degree of resistance in bacteria will be determined using samples from the most contaminated sediment areas at both sites. The bioexposure of blue mussels to mercury will also be determined at the harbor site.
Development and application of this unique combination of approaches will help environmental management and public health agencies assess the significance of trace metal contamination. The project is timely in that it coincides with ongoing and new related research projects on mercury in estuarine environments in New Hampshire, and ongoing analysis of the extent of mercury contamination throughout Penobscot Bay by the principal investigators. The results should also provide needed fate and contamination information that compliments other ongoing studies on mercury in Penobscot Bay.
The overall goal of the project is to determine the extent and impacts of mercury contamination at two sites at extreme ends of the Penobscot River watershed. The specific objectives are to:
1) Determine distribution of Hg contamination in surface sediments in Stonington Harbor and the associated dredge dump site
2) Establish the historical chronology of mercury deposition and burial at both sites via analysis of sediment cores
3) Determine Hg bioavailability at both sites by assessing mercury volatilization rates and degree of bacterial Hg resistance
4) Determine Hg bioexposure at Stonington Harbor sites using transplanted mussels.
Experiments will be carried out at various UNH labs and at two sites in Penobscot Bay and River. Surface sediments and cores will be sampled and mercury concentrations will be measured to determine the distribution and historical deposition of mercury at the two sites.
Long- and short-term bioexposure of blue mussels to mercury will be determined at the oceanic site; bacterial resistance to mercury and detoxification processes will be measured from water and sediment samples at both sites. The project will provide useful information on mercury bioavailability.
The project relates particularly to Sea Grant priorities on determination of existing levels of sediment pollutants, estimating the assimilative capacity of the marine environment, relating pollutant concentrations to ecosystem degradation, effects of dredging, and the impacts of coastal development ecosystem health. The project addresses mercury pollution, which is an important national issue. Mercury pollution is probably the number one environmental quality issue in the Gulf of Maine, and there are acute problems on the Maine coast, particularly in Penobscot Bay.
Available from the National Sea Grant Library (use NHU number to search) or NH Sea Grant
- Getchell, S. (2002). The spatial and temporal distribution of Cu, Pb, Zn, and Cd in marine sediments of Boothbay, Maine. Master's Thesis, University of New Hampshire.