Evidence for regulation of monomethyl mercury by nitrate in a seasonally stratified, eutrophic lake.
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.
Todorova
Svetoslava G
SG
Department of Civil and Environmental Engineering, Syracuse University, Syracuse, New York 13244, USA. stodorov@maxwell.syr.edu
Driscoll
Charles T
CT
Matthews
David A
DA
Effler
Steven W
SW
Hines
Mark E
ME
Henry
Elizabeth A
EA
D004784:Environmental Monitoring; D005068:Eutrophication; D005618:Fresh Water / Q000737:chemistry* / Q000382:microbiology; D008767:Methylmercury Compounds / Q000032:analysis / Q000737:chemistry*; D009518:New York; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis / Q000737:chemistry; D012621:Seasons; D013431:Sulfates / Q000032:analysis / Q000737:chemistry; D013440:Sulfides / Q000032:analysis / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
D008767:Methylmercury Compounds; D009566:Nitrates; D013431:Sulfates; D013440:Sulfides; D014874:Water Pollutants, Chemical; D010100:Oxygen