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Thiol-Grafted Chitosan Membranes as a Tool for Monitoring the Biogeochemical Cycling of Porewater Inorganic and Organic (Methyl) Mercury

EPA Grant Number: FP916432
Title: Thiol-Grafted Chitosan Membranes as a Tool for Monitoring the Biogeochemical Cycling of Porewater Inorganic and Organic (Methyl) Mercury
Investigators: Merritt, Karen A.
Institution: University of Maine
EPA Project Officer: Willett, Stephanie H.
Project Period: January 1, 2004 through December 31, 2004
Project Amount: $88,120
RFA: STAR Graduate Fellowships (2004)
Research Category: Academic Fellowships , Fellowship - Environmental Chemistry and Environmental Material Science , Engineering and Environmental Chemistry

Description:

Objective:

This objective of this research is focused on monitoring both the porewater flux and biological availability of mercury (Hg) through the use of a reactive, Hg-specific membrane. Membranes are based on chitosan, a chemical derivative of crustacean chitin modified to enhance Hg-binding potential. Specific modifications include surface area enhancement (via the addition and subsequent dissolution of silica gel porogen) and functional group grafting (including both –SH and –NH2 groups). Membranes, secured within Teflon frames, will be deployed vertically within estuarine sediments to assess the standing stock burden and transport potential of Hg within sediment porewater. As chitosan membranes possess high affinity and specificity for Hg and have demonstrated rapid uptake kinetics, accurate porewater measurements will be attainable with a high degree of spatial (<1 cm depth increment) and temporal (6 hours) resolution. Understanding Hg dynamics within sediments is important as porewater exposure may play a significant role in Hg uptake by benthic and epibenthic organisms.

Approach:

Chitosan membranes will be utilized initially to study Hg mobilization within the sediments of the Penobscot River estuary in Maine. By matching membrane deployment times to tidal stage, we will assess the extent to which variations in ambient geochemistry (including salinity and dissolved O2) affect the potential mobility of porewater Hg. In a comparative sense, deploying chitosan membranes in environments with comparable contaminant burdens but differing geochemistry may allow the exploration of factors (including relative frequency or extent of tidal inundation and/or the effects of vegetation type on contaminant storage) that influence the biological availability of porewater Hg species. Chitosan membranes ultimately may function as an assessment tool for the potential remediation of contaminated coastal and estuarine sediments.

Supplemental Keywords:

fellowship, mercury, coastal waters, estuarine waters, chitosan membranes, porewater, benthic organisms, water pollution, coastal sediments, estuarine sediments, Maine, ME, biogeochemical cycling, mercury-specific membrane , Water, Scientific Discipline, Mercury, Environmental Engineering, Environmental Chemistry, aquatic, mercury measurement, sediment porewater, monitoring, ecosystem restoration, mercury loading, chitosan membrane, biogeochemical cycling
Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 177KB, about PDF)

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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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