Influences of iron, manganese, and dissolved organic carbon on the hypolimnetic cycling of amended mercury

Chadwick, Shawn P.; Babiarz, Chris L.; Hurley, James P.; Armstrong, David E.

doi:10.1016/j.scitotenv.2005.09.039

Cited by 72 publications

(46 citation statements)

References 36 publications

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“…Where Fe oxide precipitates, Hg-sulfide and MeHg-sulfide complexes are scavenged, resulting in increases in K d of inorganic Hg and MeHg in the lower pycnocline. The role of Fe oxide in the transport and cycling of Hg and MeHg was also reported in the hypolimnion of a freshwater lake (Chadwick et al 2006). In anoxic and high-sulfidic layers, the Hg speciation model provides evidence that a FeS-Hg association is more important than that for a POM-Hg association.…”

Section: Resultsmentioning

confidence: 70%

“…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%

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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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Section: Resultsmentioning

confidence: 70%

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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“…However, our state-of-the-art knowledge on Hg thermodynamics and kinetics predict that all these chemical forms would rapidly form Hg(SR-NOM) 2 and MeHgSR-NOM complexes in the oxic humic-rich brackish water of the estuary and our mesocosm systems. Previous whole-lake experiments have also indicated a rapid association of added Hg II tracers with NOM in the water column 46 . In contrast, the solid/adsorbed phase Hg tracers used in our study needed to be synthesized to thermodynamically favoured chemical forms before addition to the sediment.…”

Section: Discussionmentioning

confidence: 92%

Differentiated availability of geochemical mercury pools controls methylmercury levels in estuarine sediment and biota

et al. 2014

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Neurotoxic methylmercury (MeHg) formed from inorganic divalent mercury (Hg II ) accumulates in aquatic biota and remains at high levels worldwide. It is poorly understood to what extent different geochemical Hg pools contribute to these levels. Here we report quantitative data on MeHg formation and bioaccumulation, in mesocosm water-sediment model ecosystems, using five Hg II and MeHg isotope tracers simulating recent Hg inputs to the water phase and Hg stored in sediment as bound to natural organic matter or as metacinnabar. Calculations for an estuarine ecosystem suggest that the chemical speciation of Hg II solid/adsorbed phases control the sediment Hg pool's contribution to MeHg, but that input of MeHg from terrestrial and atmospheric sources bioaccumulates to a substantially greater extent than MeHg formed in situ in sediment. Our findings emphasize the importance of MeHg loadings from catchment runoff to MeHg content in estuarine biota and we suggest that this contribution has been underestimated.

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“…This may result from a variety of other conditions in sediments and the water column, which are also dependant on pH, such as decreased reduction and volatilization of Hg, decreased availability of binding sites on organic matter, and redox conditions (Ullrich et al, 2001). When oxygen is limited, inorganic Hg may be released from binding with oxyhydroxide compounds of iron and manganese and thereby increase the pool of Hg 2+ available to methylating bacteria (Chadwick et al, 2006), which may in turn be more abundant in anoxic conditions (Morel et al, 1998;Ullrich et al, 2001;Fleming et al, 2006). A few studies have demonstrated a positive relationship between dissolved iron and Hg in fish such as yellow perch (Gabriel et al, 2009), northern pike (Esox lucius), and walleye (Sander vitreus; Wren et al, 1991).…”

Section: Bioavailability In Aqueous Environmentsmentioning

confidence: 99%

Bioaccumulation and Biomagnification of Mercury through Food Webs

Kidd

Clayden

Jardine

2011

Environmental Chemistry and Toxicology of Mercury

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Influences of iron, manganese, and dissolved organic carbon on the hypolimnetic cycling of amended mercury

Cited by 72 publications

References 36 publications

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

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

Differentiated availability of geochemical mercury pools controls methylmercury levels in estuarine sediment and biota

Bioaccumulation and Biomagnification of Mercury through Food Webs

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