Mercury species concentrations and fluxes in the Central Tropical Pacific Ocean

Munson, Kathleen M.; Lamborg, Carl H.; Swarr, Gretchen J.; Saito, Mak A.

doi:10.1002/2015gb005120

Cited by 91 publications

(159 citation statements)

References 59 publications

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“…In order to gain insight into the mechanism of Hg methylation in the ocean, we measured methylation rates using tracer level stable isotope additions across gradients in concentrations of methylated Hg, total dissolved Hg (THg), dissolved oxygen, and apparent oxygen utilization (AOU) (Munson et al, 2015) in waters from the central Pacific Ocean collected between Hawai'i (17 °N) and American Samoa (12 °S) during the "Metzyme" cruise (Munson et al, 2015). Across this region, low (Sunderland et al, 2009) from regions of low (<100 fM) concentrations in the central and south Pacific, with the exception of relatively elevated concentrations centered around the Equator (Munson et al, 2015).…”

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confidence: 99%

“…Across this region, low (Sunderland et al, 2009) from regions of low (<100 fM) concentrations in the central and south Pacific, with the exception of relatively elevated concentrations centered around the Equator (Munson et al, 2015). The cruise track included regions of the North Pacific where intermediate waters incorporate…”

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confidence: 99%

“…Water filtration, decanting, and treatment additions were performed under positive pressure from HEPA filter laminar flow hoods within clean 85 bubbles constructed from plastic sheeting. Concentrations of dissolved Hg species were measured throughout the cruise transect (Munson et al, 2015), with the exception of 17°N, where no MMHg samples were preserved. as well as the conversion of MMHg to DMHg (Lehnherr et al, 2011).…”

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confidence: 99%

“…However, unamended methylation rates were lowest at 17 °N along the cruise transect despite water from this station displaying the greatest drawdown of dissolved oxygen (AOU = 283 µmol kg -1 ; We amended incubation water with suspended particulate matter, carbon (as succinate), and cobalt additions. Suspended particulate matter was collected from oxygen minimum depths at each station using in situ pumps (Munson et al, 2015). This bulk particulate matter was tested for its ability to increase methylation by adding ½ of a 2 cm circular "punch" of the pump filter to incubation bottles.…”

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confidence: 99%

“…Intermediate Water and intermediate waters south of 17 °N (Sunderland et al, 2009;Munson et al, 2015).…”

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confidence: 99%

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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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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

“…Intermediate Water and intermediate waters south of 17 °N (Sunderland et al, 2009;Munson et al, 2015).…”

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Dynamic mercury methylation and demethylation in oligotrophic marine water

Munson¹,

Lamborg²,

Boiteau³

et al. 2018

Preprint

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Development of a global ocean mercury model with a methylation cycle: Outstanding issues

Semeniuk

Dastoor

2017

Global Biogeochemical Cycles

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We present a newly developed global ocean mercury (Hg) transport and biogeochemistry model and use preanthropogenic equilibrium simulations to highlight physical and chemical processes which reveal significant knowledge gaps that need to be addressed. As with previous 3‐D ocean Hg model work we use a bulk chemistry scheme based on particulate organic carbon remineralization. We also include an explicit methylation cycle based on available reaction rates. The methylation to demethylation rate ratio based on various field studies is found to be inconsistent with the concentration ratios measured in the Southern Ocean around Antarctica and in the Arctic. There is also model‐measurement disagreement in the old waters of the tropical and North Pacific Ocean. The model produces an intermediate water maximum in total Hg in this region reflecting the higher age of water which is absent in observations. The model also underestimates total Hg concentrations in the deepest waters in this region. These disagreements in depth profile shape point to an inadequate representation of scavenging and sedimentation and possibly seabed emission or remobilization of Hg. In addition, the total Hg distribution differences compared to previous model work reflect sensitivity to ocean model transport characteristics and in particular the tracer diffusion. The residence time of Hg in the global ocean and the surface evasion flux of elemental Hg is sensitive to such model aspects. We find a global ocean Hg turnover time against sediment burial to be about 1100 years which is within the range of previous studies.

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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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Mercury species concentrations and fluxes in the Central Tropical Pacific Ocean

Cited by 91 publications

References 59 publications

Dynamic mercury methylation and demethylation in oligotrophic marine water

Dynamic mercury methylation and demethylation in oligotrophic marine water

Development of a global ocean mercury model with a methylation cycle: Outstanding issues

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

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