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Mercury Methylation Pathways in Connecticut Freshwater Wetlands

EPA Grant Number: F5B20251
Title: Mercury Methylation Pathways in Connecticut Freshwater Wetlands
Investigators: May, Cynthia
Institution: Yale University
EPA Project Officer: Thompson, Delores
Project Period: June 1, 2005 through May 1, 2006
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2005)
Research Category: Academic Fellowships

Description:

Objective:

Mercury contamination in our nation’s water is a large-scale threat to human health. Past research has identified two pathways involved in the transformation of inorganic mercury to its toxic and bioavailable form, methylmercury, in aquatic systems: biotic and abiotic methylation. Studies have indicated that organic matter type (labile or refractory organic matter) may control which pathway predominates. The purpose of this project is to measure organic matter type and methylmercury concentrations in the sediment of five freshwater wetland systems in Connecticut in an attempt to identify a dominant methylation pathway. The identification of a methylation pathway improves understanding of how methylation is occurring and, as a result, has important implications for management decisions that may impact mercury methylation rates in aquatic systems.

The objective of this research is to answer the following questions:

  1. Are DOM type and methylmercury levels significantly well-correlated to suggest a predominant mercury methylation pathway in freshwater wetland systems?
  2. How do refractory and labile concentrations of DOM in sediment pore water vary among freshwater wetland systems in south-central Connecticut?
  3. What is the significance of abiotic mercury methylation in freshwater wetlands in south-central Connecticut?

Approach:

Concentrations of DOM (labile and refractory) and methylmercury in the sediment of five freshwater wetlands in south-central Connecticut will be estimated. Sediment cores will be extracted from eight representative sites within each of the five wetland systems for a total of 40 sample cores. The particulate and pore water portions of the sediment cores will be analyzed for DOC, POC, pH, temperature, sulfate/sulfide, total mercury, and methylmercury using EPA standard methods.

Expected Results:

Significant correlations between methylmercury and labile DOM concentrations are expected, indicating primarily biotic mercury methylation in the freshwater wetland systems examined.

Supplemental Keywords:

abiotic, DOC, labile, mercury, methylation, POC, refractory, , Water, Scientific Discipline, Mercury, Environmental Chemistry, Ecology and Ecosystems, Environmental Monitoring, Geochemistry, aquatic, fate and transport, methylmercury, methylation, mercury formation in fresh waters, wetland, geochemical cycling, mercury concentration, biochemical pathway, Connecticut, biogeochemical cycling

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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