Methylmercury cycling in estuarine sediment pore waters (Penobscot River estuary, Maine, USA)

Merritt, Karen A.; Amirbahman, Aria

doi:10.4319/lo.2008.53.3.1064

Cited by 32 publications

(35 citation statements)

References 42 publications

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“…It shows a 1.5-3-cm thick zone where MeHg is consumed relatively fast (zone 1; R MeHg net = À0.9 Â 10 À21 mol cm À3 s À1 to À3.5 Â 10 À21 mol cm À3 s À1 ) above a zone of much slower net MeHg consumption (zone 2; R MeHg net = À0.01 Â 10 À21 mol cm À3 s À1 to À0.03 Â 10 À21 mol cm À3 s À1 ). The R MeHg net values for net MeHg removal from Lake Tantaré porewater are slightly lower than those reported by Goulet et al (2007) in Lake St. Pierre (R MeHg net = À0.1 Â 10 À21 mol cm À3 s À1 to À12.4 Â 10 À21 mol cm À3 s À1 ) and much lower than those reported by Merritt and Amirbahman (2008) for the highly contaminated Penobscot River-Estuary sediments (R MeHg net = À10 Â 10 À21 mol cm À3 s À1 to À650 Â 10 À21 mol cm À3 s À1 ).…”

Section: Modeling the [Mehg] Profilescontrasting

confidence: 73%

“…On this basis, we calculate that k demethyl varies between 0.04 d À1 and 0.3 d À1 in Basin A and between 0.1 d À1 and 0.8 d À1 in Basin B. These field-derived rate constant values are slightly lower than that (1.1 d À1 ) reported by Merritt and Amirbahman (2008) for the Penobscot River estuary. They can also be compared with those recently obtained in laboratory experiments where sediments or lake water samples were simultaneously spiked with low amounts of Hg(II) and MeHg labelled with different stable Hg isotopes and incubated.…”

Section: Modeling the [Mehg] Profilescontrasting

confidence: 50%

“…This averaging procedure likely leads to underestimate the actual spatial heterogeneity in net MeHg production and consumption rates. An important heterogeneity among replicate [MeHg] profiles, as we observed in Lake Tantaré Basin A, was also noticed in the Penobscot River Estuary (Merritt and Amirbahman, 2008). We do not have a clear explanation for this heterogeneity, which did not show in the sediments of the seasonally anoxic Basin B, but we speculate that it is related to small scale variations in the activity of benthic animals.…”

Section: Modeling the [Mehg] Profilesmentioning

confidence: 48%

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Mercury dynamics in lake sediments

Feyte

Gobeil

Tessier

et al. 2012

Geochimica et Cosmochimica Acta

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Triplicate porewater depth-profiles of pH and concentrations of total Hg (Hg T ), methylmercury (MeHg), Fe, Mn, sulfate, total sulfide, total zero-valent sulfur, organic C and major ions were determined at two sampling dates in a perennially oxygenated basin and a seasonally anoxic basin from Lake Tantaré, a Canadian Shield lake. The vertical distribution of Hg T , MeHg, acid volatile sulfide, total S, Fe, Mn, Al and organic C were also determined in dated sediment cores from the same lake basins and from the deepest site of two other lakes, one also located in the Canadian Shield and the other in the Northeastern part of the Appalachian Mountains. Application of a one-dimensional transport-reaction equation to the dissolved Hg T and MeHg profiles constrains the depth intervals (zones) where these species are produced or consumed in the sedimentary column and yields estimates of net reaction rates of Hg T or MeHg in each of the zones as well as their fluxes at the sediment-water interface.Dissolved Hg T and MeHg diffused from the overlying water into the sediments, except for MeHg at one of the sampling dates in the perennially oxygenated basin. About 97% and 50% of the MeHg flux to the sediments is presently deposited with settling particles in the perennially oxygenated and seasonally anoxic basins, respectively. Removal of porewater Hg T and MeHg occurred at all dates and sampling sites. Comparison of the consumption zones of porewater Hg T and MeHg with the profiles of ancillary parameters, coupled with thermodynamic calculations, suggest that pure Hg mineral phases do not form in the sediments, that Hg T and MeHg adsorption onto authigenic Fe oxyhydroxides occurs in minor proportions, and that the association of Hg T and MeHg to Fe sulfide phases or sulfidized organic matter is possible. Assuming that the net consumption of MeHg in the porewaters was essentially due to demethylation, an apparent first-order rate constant for MeHg demethylation of 0.04-0.8 d À1 was estimated. Production of porewater MeHg occurred only in the perennially oxygenated basin, at sediment depths where SO 4 was consumed. Assuming that the net production of porewater MeHg was essentially due to methylation, an apparent first-order rate constant for Hg methylation ranging between 0.006 d À1 and 0.1 d À1 was calculated. These field-derived Hg methylation and MeHg demethylation rate constant values are within the range of those derived from Hg-spiked experiments. We also show that the post-depositional redistribution of total Hg during the early stages of sediment diagenesis is minor and that the solid-phase Hg T record can be used to reconstruct the evolution of the anthropogenic Hg T deposition.

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Section: Modeling the [Mehg] Profilescontrasting

confidence: 73%

Section: Modeling the [Mehg] Profilescontrasting

confidence: 50%

Section: Modeling the [Mehg] Profilesmentioning

confidence: 48%

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Mercury dynamics in lake sediments

Feyte

Gobeil

Tessier

et al. 2012

Geochimica et Cosmochimica Acta

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“…Porewater As profiles were modeled assuming the absence of significant advective flux and the quasi steady-state (i.e., o[As]/ot % 0) of the system. Although the steady-state assumption may not be strictly valid for an environment subject to variations in dissolved O 2 and temperature, it has been useful to explore the parameters that cause either the sequestration or the mobilization of trace elements (Gallon et al, 2004;Chappaz et al, 2008;Merritt and Amirbahman, 2008) and the quantification of As postdepositional mobility (Couture et al, 2008). For this modeling exercise, the one-dimensional mass conservation equation provided by Boudreau (1997) at steady-state:…”

Section: Net Reaction Rates Of Porewater As Production or Consumptionmentioning

confidence: 99%

Arsenic, iron and sulfur co-diagenesis in lake sediments

Couture

Gobeil

Tessier

2010

Geochimica et Cosmochimica Acta

132

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“…Near-shore sediments may be an important source of MeHg to marine organisms, including fish consumed by humans (Chen et al, 2008). Estuaries are highly variable with respect to geochemical characteristics and have a high potential for sequestration and methylation of Hg (e.g., Hines et al, 2006; Lambertsson and Nilsson, 2006; Merritt and Amirbahman, 2008; Schartup et al, 2013; Liu et al, 2015) due to high pore-water sulfate (

{SO}_{4}^{2 -}

) concentrations, great amounts of labile sediment organic carbon, and a relatively shallow redox transition in the sediment. The fate of Hg in the sediment is dependent on sediment disturbances (e.g.…”

Section: Introductionmentioning

confidence: 99%

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA

et al. 2015

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Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by 7Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes (Nereis virens). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hgi) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hgi is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase (mer-A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments.

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Methylmercury cycling in estuarine sediment pore waters (Penobscot River estuary, Maine, USA)

Abstract: Particulate mercury (Hg)

Cited by 32 publications

References 42 publications

Mercury dynamics in lake sediments

Mercury dynamics in lake sediments

Arsenic, iron and sulfur co-diagenesis in lake sediments

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA

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