Determination of mercury methylation potentials in the water column of lakes across Canada

Eckley, Chris S.; Hintelmann, Holger

doi:10.1016/j.scitotenv.2005.09.042

Cited by 168 publications

(123 citation statements)

References 35 publications

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“…S1). Rapid methylation has been observed in measurements of labeled Hg(II) additions to lake water (Eckley and Hintelmann, 2006), and in previous incubations of unfiltered seawater (Lehnherr et al, 195 2011). Previous marine methylation rate measurements with isotopes have exclusively used unfiltered waters or filters that allow bacteria to pass through (Monperrus et al, 2007;Lehnherr et al, 2011), which prevented distinction between bacterial and non-bacterial methylation in those experiments.…”

mentioning

confidence: 72%

Dynamic mercury methylation and demethylation in oligotrophic marine water

Munson¹,

Lamborg²,

Boiteau³

et al. 2018

Preprint

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Monomethylmercury bioaccumulation in open ocean food webs depends on the net rate of inorganic mercury conversion to monomethylmercury in the water column. We measured significant methylation rates across large gradients in oxygen utilization in the oligotrophic central Pacific Ocean. Overall, methylation rates over 24 hour incubation periods were comparable to those previously published 20 from Arctic and Mediterranean waters despite differences in productivity between these marine environments. In contrast to previous studies that have attributed Hg methylation to heterotrophic bacteria, we measured higher methylation rates in filtered water compared to unfiltered water. Furthermore, we observed enhanced demethylation of newly produced methylated mercury in incubations of unfiltered water relative to filtered water. The addition of station-specific bulk suspended particulate matter, a Biogeosciences Discuss., https://doi

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mentioning

confidence: 72%

Dynamic mercury methylation and demethylation in oligotrophic marine water

Munson¹,

Lamborg²,

Boiteau³

et al. 2018

Preprint

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“…The most intense sites of methylmercury production in ecosystems are in wetlands, lake sediments, and anoxic bottom waters (13,20). In the Lake 658 catchment, the wetland exported ambient methylmercury at a rate of 0.2-0.4 g⅐m Ϫ2 ⅐year Ϫ1 , which is at the high end of the range of methylmercury export rates from wetlands at the ELA (14).…”

Section: Resultsmentioning

confidence: 99%

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Harris

Rudd²,

Amyot

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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404

333

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Methylmercury contamination of fisheries from centuries of industrial atmospheric emissions negatively impacts humans and wildlife worldwide. The response of fish methylmercury concentrations to changes in mercury deposition has been difficult to establish because sediments/soils contain large pools of historical contamination, and many factors in addition to deposition affect fish mercury. To test directly the response of fish contamination to changing mercury deposition, we conducted a whole-ecosystem experiment, increasing the mercury load to a lake and its watershed by the addition of enriched stable mercury isotopes. The isotopes allowed us to distinguish between experimentally applied mercury and mercury already present in the ecosystem and to examine bioaccumulation of mercury deposited to different parts of the watershed. Fish methylmercury concentrations responded rapidly to changes in mercury deposition over the first 3 years of study. Essentially all of the increase in fish methylmercury concentrations came from mercury deposited directly to the lake surface. In contrast, <1% of the mercury isotope deposited to the watershed was exported to the lake. Steady state was not reached within 3 years. Lake mercury isotope concentrations were still rising in lake biota, and watershed mercury isotope exports to the lake were increasing slowly. Therefore, we predict that mercury emissions reductions will yield rapid (years) reductions in fish methylmercury concentrations and will yield concomitant reductions in risk. However, a full response will be delayed by the gradual export of mercury stored in watersheds. The rate of response will vary among lakes depending on the relative surface areas of water and watershed.bioaccumulation ͉ mercury methylation ͉ stable isotopes ͉ whole-ecosystem experimentation ͉ methylmercury

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“…Higher MeHg concentrations were observed in the hypoxic and anoxic bottom layers. Enhanced MeHg levels in anoxic hypolimnion has been reported for several stratified freshwater systems (Chadwick et al 2006;Eckley and Hintelmann 2006), but there have been fewer reports of this phenomenon occurring in marine systems (Lu et al 1986;Pempkowiak et al 1998) (Table 1). A similar trend was also observed for inorganic Hg (discussed previously), which we speculated arose from a ''particle concentration effect.''…”

Section: Resultsmentioning

confidence: 99%

Chemical and physical speciation of mercury in Offatts Bayou: A seasonally anoxic bayou in Galveston Bay

Han

Lehman

Choe

et al. 2007

Limnology & Oceanography

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A chemical equilibrium model was used to predict the solution speciation of dissolved mercury (Hg) in the stratified water column of Offatts Bayou, a subestuary in Galveston Bay, Texas, which undergoes seasonal anoxia in bottom waters. Chemical equilibrium modeling was conducted using conditional stability constants and concentrations of Hg-complexing organic ligands experimentally determined by competitive ligand equilibration methods. Dissolved Hg complexation was dominated by interactions with sulfide and dissolved organic matter (DOM) (HOHgHS 0 , HOHgHS(DOM), HgSHS 2 , and HgS 2{ 2 ) at all depths. Sulfide and glutathione competed for methylmercury (MeHg) complexation in oxic layers; in anoxic waters, sulfide complexation dominated MeHg speciation. The particle-water distribution coefficient (K d ) of Hg decreased in the anoxic layer of the water column, where the dissolved sulfide concentration increased, providing evidence that sulfide complexation influences the solubility of Hg. The solubility of MeHg was elevated in the anoxic as compared to the oxic layers, and this distributional feature was coincident with a change in the solution speciation of dissolved MeHg from glutathione/sulfide complexation in the oxic layers to a predominantly sulfide complexation in the anoxic layers. Maximum enrichment of Hg, MeHg, and iron (Fe) in suspended particulate matter was observed in the lower layer of the pycnocline, most likely resulting from formation of insoluble Fe oxide, which scavenged dissolved Hgsulfide and MeHg-sulfide species. The concomitant decrease in dissolved inorganic Hg, Fe, and sulfide in the anoxic layers is suggested to result from scavenging of inorganic Hg by FeS, which is in accordance with the Hg speciation model. Overall, Hg cycling in the water column of Offatts Bayou was associated with sulfide and DOM complexation, Fe dissolution/precipitation, water column production of MeHg, and/or efflux of MeHg from anoxic sediment.Determining the aqueous chemical speciation of mercury (Hg) under various redox conditions is important for understanding the methylmercury (MeHg) production process, which occurs in redox transition zones, mainly via sulfate-reducing bacteria (King et al. 1999). Neutral monosulfide (HOHgHS 0 ) and polysulfide species (HgS 5 ) are predicted to be bioavailable to sulfate-reducing bacteria (Benoit et al. 1999a,b;Jay et al. 2000). Thermodynamic equilibrium modeling calculations predict that the HOHgHS 0 concentration decreases with increasing sulfide concentration. This prediction is consistent with observed patterns of MeHg production in estuarine and freshwater sediments (Benoit et al. 1999a,b). While the solution speciation of dissolved Hg is critical for understanding MeHg production, most experimental studies of Hg speciation in redox transition zones have been limited to the determination of MeHg and total Hg in sediment pore water.The presence of dissolved sulfide and dissolved organic matter (DOM) in anoxic water is known to increase the solubility of particul...

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Determination of mercury methylation potentials in the water column of lakes across Canada

Cited by 168 publications

References 35 publications

Dynamic mercury methylation and demethylation in oligotrophic marine water

Dynamic mercury methylation and demethylation in oligotrophic marine water

Whole-ecosystem study shows rapid fish-mercury response to changes in mercury deposition

Chemical and physical speciation of mercury in Offatts Bayou: A seasonally anoxic bayou in Galveston Bay

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