Grantee Research Project Results
Biogeochemical Factors Influencing the Rate of Mercury Methylation and Methylmercury Demethylation in the Chesapeake Bay and the Mid-Atlantic Continental ShelfEPA Grant Number: F5B20268
Title: Biogeochemical Factors Influencing the Rate of Mercury Methylation and Methylmercury Demethylation in the Chesapeake Bay and the Mid-Atlantic Continental Shelf
Investigators: Hollweg, Terill A.
Institution: University of Connecticut
EPA Project Officer: Jones, Brandon
Project Period: May 1, 2005 through September 1, 2007
Project Amount: $74,172
RFA: STAR Graduate Fellowships (2005)
Research Category: Academic Fellowships
We are determining mercury and methylmercury concentration and distribution in sediments, as well as mercury methylation and methylmercury demethylation rates (along with the measurement of other chemical and biochemical factors) in the sediment of the Chesapeake Bay and the mid-Atlantic continental shelf over the spring, summer and fall of 2005 and 2006.
The objective of the study is to quantify mercury methylation and methylmercury demethylation rates, spatially and temporally, in the mid-Atlantic coastal region. There is a paucity of data available on the rates of methylation and demethylation for estuarine and coastal systems, and the factors influencing these conversions are poorly known. This study will provide information necessary to examine and explain the variations in methylation rates due to changing biochemical factors from the changing season and aquatic environment.Approach:
Sediment cores will be collected from nine stations in the Chesapeake Bay and the mid-Atlantic continental shelf during various cruises occurring in the spring, summer and fall of 2005 and 2006. From each station we are conducting stable isotope core incubations to determine methylation and demethylation rates, as well as radioisotope core incubations to determine sulfate reduction rates. In addition, the following parameters will be analyzed from the sediment: total mercury, methylmercury, percent organic carbon, total C/N/S, FeII/FeIII, CO2/CH4, and chlorophyll a; and total mercury, methylmercury, anions, pH, sulfide, nitrite, nitrate, manganese, iron and dissolved organic carbon will be determined from the pore water of the sediment core.Expected Results:
We expect to find large variations in mercury methylation and methylmercury demethylation rates throughout the study, both spatially and temporally. The results will allow us to examine the relative importance of the chemical speciation of mercury, which influences its rate of uptake by the methylating and demethylating bacteria, compared to microbial activity, which will vary seasonally and with changes in substrate supply. We hope to explain what is controlling methylmercury levels in sediments and its potential bioavailability to the food chain.Supplemental Keywords:
Scientific Discipline, Water, Environmental Chemistry, Biochemistry, Environmental Monitoring, Ecology and Ecosystems, Mercury, fate and transport, monitoring, mercury measurement, food chain, bioavailability, chemical flux, mercury cycling, methylmercury demethylation, biogeochemical cycling, methylmercury, methylation, marine environment, Chesapeake Bay, mercury concentrations