Strong Binding Environments for Mercury in Peat
Abstract
Mercury toxicity to humans and wildlife largely originates in bacterial generation of methylmercury in the aquatic environment. Methylmercury may be inhibited from forming if mercury(II) is bound to reduced sulfur in dissolved or solid natural organic matter. Mercury(II)-reduced sulfur bonds are the strongest type of binding between mercury and natural organic matter, but the molecular configurations and binding strengths have still not been fully characterized despite many recent investigations using synchrotron-based analytical capabilities and competitive ligand experimentation. Also, at the low but toxic concentration levels of mercury(II) in the environment, characterization with these approaches is difficult. Using Extended X-ray Absorption Fine Structure spectroscopy at liquid He temperature we have obtained new information on the binding environment of mercury(II) adsorbed to peat obtained from the Florida Everglades at five mercury concentrations ranging from 60 to 99,000 ppm. These data were complemented with X-ray Absorption Near Edge Structure spectroscopy for the speciation of reduced sulfur. At mercury(II) concentrations of 60 and 350 ppm the dominant binding occurred in structures similar to those observed for some metallothioneins. At concentrations of 4000 ppm, mercury(II) occurred mainly in a linear arrangement bonded to two sulfurs. At higher concentrations, mercury(II) was bound to two oxygens in a five-membered chelate ring structure. The new binding configuration observed at 60 and 350 ppm is likely more stable than any reported previously, suggesting that peat may be a good material to apply in remediating environments contaminated with mercury.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.B44A..03N
- Keywords:
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- 0409 Bioavailability: chemical speciation and complexation