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

Environ Sci Technol. 2009 Sep 1;43(17):6572-8. doi: 10.1021/es900887b.


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 CH3Hg+ 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 No3 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+. N03- regulation of CH3Hg+ accumulation may be a widespread phenomenon in oxygen-limited freshwater and terrestrial environments, and could have an important notpreviously recognized, effect on the biogeochemistry of mercury.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Environmental Monitoring
  • Eutrophication*
  • Fresh Water / chemistry*
  • Fresh Water / microbiology
  • Methylmercury Compounds / analysis
  • Methylmercury Compounds / chemistry*
  • New York
  • Nitrates / chemistry*
  • Oxidation-Reduction
  • Oxygen / analysis
  • Oxygen / chemistry
  • Seasons*
  • Sulfates / analysis
  • Sulfates / chemistry
  • Sulfides / analysis
  • Sulfides / chemistry
  • Water Pollutants, Chemical / analysis
  • Water Pollutants, Chemical / chemistry*


  • Methylmercury Compounds
  • Nitrates
  • Sulfates
  • Sulfides
  • Water Pollutants, Chemical
  • Oxygen