Amirbahman, A. ., University of Maine, Orono, USA, aria@umit.maine.edu
Merritt, K. A., ENVIRON International Corp., Portland, USA, kmerritt1@gmail.com
Voytek, M. A., US Geological Survey, Reston, USA, mavoytek@usgs.gov
Chen, C. Y., Dartmouth College, Hanover, USA, celia.chen@dartmouth.edu

CYCLING OF METHYLMERCURY IN THE SEDIMENTS OF THE PENOBSCOT RIVER ESTUARY (MAINE, USA)

Due to the presence of high concentrations of organic matter and sulfate, estuarine sediments may produce a great deal of methylmercury (MeHg). Using equilibrium dialysis samplers and molecular analysis of the resident microbial population in contaminated sediments of Penobscot estuary, we observed a correspondence between the density of the sediment sulfate reducing bacteria and methylation in porewaters. We also observed rapid MeHg demethylation close to the sediment-water interface (SWI) that may be due to the presence of iron reducing bacteria that are dominant close to the SWI, or to the presence of mer-A genes that may be expressed in contaminated sediments, such as the ones studied here. We studied Hg methylation in intact sediment cores by manipulating the location of the redoxcline in laboratory. Induced shoaling of the redoxcline was correlated with a shoaling of the net MeHg production zone and an increase in net MeHg production rate. Based on this, environments such as salt pannes, where the shallow redoxcline leads to the shoaling of the MeHg front, are likely to be Hg methylation and release hotspots in coastal environments.

Poster presentation

Presentation is given by student: No
Session #:187
Date: 03-03-2008
Time: 17:30 - 19:30