Evidence for regulation of monomethyl mercury by nitrate in a seasonally stratified, eutrophic lake

Svetoslava G. Todorova, Charles T. Driscoll, David A. Matthews, Steven W. Effler, Mark E. Hines, Elizabeth A. Henry

Research output: Contribution to journalArticle

54 Scopus citations

Abstract

The accumulation of monomethyl mercury (CH3Hg+) in aquatic ecosystems is a redox sensitive process that is accelerated under sulfate-reducing conditions. While nitrate (NO3-) reduction is energetically favored over sulfate reduction, the influence of NO3- on the accumulation of CH3Hg+ has not been reported in the literature. We examined temporal and vertical patterns in redox constituents and CH3Hg+ concentrations in the hypolimnion of a dimictic lake, Onondaga Lake, prior to and following increases in NO3- inputs. Detailed water-column profiles and a long-term record revealed marked decreases in the accumulation of CH 3Hg+ in the anoxic hypolimnion coinciding with long-term decreases in the deposition of organic matter coupled with recent increases in NO3- concentrations. CH3Hg+ concentrations in the hypolimnion were substantially abated when NO 3- was present above the sediment-water interface. A decrease in the peak hypolimnetic mass of CH3Hg+ and shortening of the period of elevated CH3Hg+ concentrations resulted in more than a 50% decline in the accumulated CH3Hg +. NO3- regulation of CH3Hg + accumulation may be a widespread phenomenon in oxygen-limited freshwater and terrestrial environments, and could have an important, not previously recognized, effect on the biogeochemistry of mercury.

Original languageEnglish (US)
Pages (from-to)6572-6578
Number of pages7
JournalEnvironmental Science and Technology
Volume43
Issue number17
DOIs
StatePublished - Sep 1 2009

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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