Methylmercury production in sediments of Chesapeake Bay and the mid-Atlantic continental margin

Hollweg, Terill A.; Gilmour, Cynthia C.; Mason, Robert P.

doi:10.1016/j.marchem.2009.04.004

Cited by 137 publications

(182 citation statements)

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“…On average, MeHg made up 11% of HgT in interstitial waters. Porewater Hg and MeHg concentrations were similar to those measured in the sediments of the nearby Chesapeake Bay Hollweg et al 2009) and in other shelf sediments (Hammerschmidt and Fitzgerald 2006;Liu et al 2009). Similar to bulk-phase Hg concentrations, the partitioning of Hg between the solid phase and pore water, defined as the distribution coefficient (K D ), varied by about two orders of magnitude, and was strongly correlated with OM content in sediments (Tables 4, 5).…”

Section: Resultssupporting

confidence: 74%

“…However, both distance from sources and changes in the chemistry of SOM with aging could contribute to these trends. For example, sediment organic S : C ratios decrease with distance offshore on the mid-Atlantic shelf (Hollweg et al 2009), which could result in decreased Hg binding capacity. Additionally, the S : C ratio of Baltimore Harbor sediments (, 0.1) is even higher than that of the Chesapeake Bay ).…”

Section: Discussionmentioning

confidence: 99%

“…1, Table 1). Three of these sites were sampled during four previous cruises (April 2006 andMay, July, andSeptember 2005;Hollweg et al 2009). …”

Section: Methodsmentioning

confidence: 99%

“…Detailed methods for additional analyses are given in Mitchell and Gilmour (2008) and Hollweg et al (2009).…”

Section: Methodsmentioning

confidence: 99%

“…Although MeHg concentrations and production rate constants are negatively correlated with pore-water sulfide in estuarine sediments Hammerschmidt et al 2008;Hollweg et al 2009), many saline sediments have a surface layer that is anoxic, but with little or no (low micromolar) dissolved sulfide, above the deeper, more sulfidic zones. These zones often support high levels of microbial sulfate or iron-reducing activity.…”

mentioning

confidence: 99%

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Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Hollweg

Gilmour

Mason

2010

Limnology & Oceanography

101

115

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We present a detailed study of the biogeochemical factors controlling mercury (Hg) distribution, methylmercury (MeHg) production, and MeHg efflux in sediments of the mid-Atlantic continental shelf and slope. The mildly reduced surface sediments of the shelf and slope provide ideal conditions for MeHg production. They are sufficiently reduced to support microbial sulfate reduction, but contain very low dissolved sulfide concentrations. The redox zonation of sediments determined the depth distribution of MeHg production, whereas the bioavailability of inorganic Hg for methylation appeared to be the dominant driver of spatial patterns across the shelf and slope. Sediment total Hg concentrations were well predicted by sediment organic matter (SOM) content, with the highest concentrations of Hg and MeHg in the fine-grained organic clays of the slope. However, SOM-normalized Hg concentrations decreased with distance from shore. The changing character of organic matter with distance from shore appeared to affect Hg partitioning and bioavailability for methylation. The percentage of Hg in sediments as MeHg was well predicted by measured methylation rates, but not by demethylation rates. On the basis of measured concentrations in bottom waters and surficial pore waters, the average diffusive efflux of Hg(II) and MeHg from sediments to coastal waters was estimated to be 26 and 0.8 pmol m 22 d 21 , respectively. Extrapolated globally, the diffusive input of MeHg from shelf and slope sediments is estimated to be 0.01 Mmol per year. As the actual fluxes can be substantially higher than diffusive fluxes, we suggest that shelf and upper slope sediments are a major source of MeHg to the coastal ocean.

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Section: Resultssupporting

confidence: 74%

Section: Discussionmentioning

confidence: 99%

“…1, Table 1). Three of these sites were sampled during four previous cruises (April 2006 andMay, July, andSeptember 2005;Hollweg et al 2009). …”

Section: Methodsmentioning

confidence: 99%

“…Detailed methods for additional analyses are given in Mitchell and Gilmour (2008) and Hollweg et al (2009).…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Hollweg

Gilmour

Mason

2010

Limnology & Oceanography

101

115

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Evaluation of mercury cycling and hypolimnetic oxygenation in mercury-impacted seasonally stratified reservoirs in the Guadalupe River watershed, California

McCord¹,

Beutel

Dent

et al. 2016

Water Resour. Res.

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Surface water reservoirs trap inorganic mercury delivered from their watersheds, create conditions that convert inorganic mercury to highly toxic methylmercury (MeHg), and host sportfish in which MeHg bioaccumulates. The Santa Clara Valley Water District (District) actively manages and monitors four mercury‐impaired reservoirs that help to serve communities in South San Francisco Bay, California. The Guadalupe River watershed, which contains three of those reservoirs, also includes the New Almaden mercury‐mining district, the largest historic mercury producer in North America. Monthly vertical profiles of field measurements and grab samples in years 2011–2013 portray annual cycling of density stratification, dissolved oxygen (DO), and MeHg. Monitoring results highlight the role that hypolimnetic hypoxia plays in MeHg distribution in the water column, as well as the consistent, tight coupling between MeHg in ecological compartments (water, zooplankton, and bass) across the four reservoirs. Following the 2011–2013 monitoring period, the District designed and installed hypolimnetic oxygenation systems (HOS) in the four reservoirs in an effort to repress MeHg buildup in bottom waters and attain regulatory targets for MeHg in water and fish tissue. Initial HOS operation in Calero Reservoir in 2014 enhanced bottom water DO and depressed hypolimnetic buildup of MeHg, but did not substantially decrease mercury levels in zooplankton or small fish.

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Mercury in the Black Sea: New Insights From Measurements and Numerical Modeling

Rosati

Heimbürger

Canu

et al. 2018

Global Biogeochemical Cycles

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Redox conditions and organic matter control marine methylmercury (MeHg) production. The Black Sea is the world's largest and deepest anoxic basin and is thus ideal to study Hg species along the extended redox gradient. Here we present new dissolved Hg and MeHg data from the 2013 GEOTRACES MEDBlack cruise (GN04_leg2) that we integrated into a numerical 1‐D model, to track the fate and dynamics of Hg and MeHg. Contrary to a previous study, our new data show highest MeHg concentrations in the permanently anoxic waters. Observed MeHg/Hg percentage (range 9–57%) in the anoxic waters is comparable to other subsurface maxima in oxic open‐ocean waters. With the modeling we tested for various Hg methylation and demethylation scenarios along the redox gradient. The results show that Hg methylation must occur in the anoxic waters. The model was then used to simulate the time evolution (1850–2050) of Hg species in the Black Sea. Our findings quantify (1) inputs and outputs of Hg T (~31 and ~28 kmol yr −1 ) and MeHg T (~5 and ~4 kmol yr −1 ) to the basin, (2) the extent of net demethylation occurring in oxic (~1 kmol yr −1 ) and suboxic water (~6 kmol yr −1 ), (3) and the net Hg methylation in the anoxic waters of the Black Sea (~11 kmol yr −1 ). The model was also used to estimate the amount of anthropogenic Hg (85–93%) in the Black Sea.

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Methylmercury production in sediments of Chesapeake Bay and the mid-Atlantic continental margin

Cited by 137 publications

References 87 publications

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Evaluation of mercury cycling and hypolimnetic oxygenation in mercury-impacted seasonally stratified reservoirs in the Guadalupe River watershed, California

Mercury in the Black Sea: New Insights From Measurements and Numerical Modeling

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