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: Lee, Sonja
Project Period: June 1, 2005 through May 1, 2006
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


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?


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,, Scientific Discipline, Water, Environmental Chemistry, Geochemistry, Environmental Monitoring, Ecology and Ecosystems, Mercury, aquatic, fate and transport, freshwater ecosystems, geochemical cycling, Connecticut, mercury formation in fresh waters, biogeochemical cycling, methylmercury, methylation, wetland, biochemical pathway

Progress and Final Reports:

  • Final