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- Kim, Hyunji, et al.
(författare)
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Methylmercury Mass Budgets and Distribution Characteristics in the Western Pacific Ocean
- 2017
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 51:3, s. 1186-1194
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Tidskriftsartikel (refereegranskat)abstract
- Methylmercury (MeHg) accumulation in marine organisms poses serious ecosystem and human health risk, yet the sources of MeHg in the surface and subsurface ocean remain uncertain. Here, we report the first MeHg mass budgets for the Western Pacific Ocean estimated based on cruise observations. We found the major net source of MeHg in surface water to be vertical diffusion from the subsurface layer (1.8-12 nmol m(-2) yr(-1)). A higher upward diffusion in the North Pacific (12 nmol m(-2) yr(-1)) than in the Equatorial Pacific (1.8-5.7 nmol m(-2) yr(-1)) caused elevated surface MeHg concentrations observed in the North Pacific. We furthermore found that the slope of the linear regression line for MeHg versus apparent oxygen utilization in the Equatorial Pacific was about 2-fold higher than that in the North Pacific. We suggest this could be explained by redistribution of surface water in the tropical convergence-divergence zone, supporting active organic carbon decomposition in the Equatorial Pacific Ocean. On the basis of this study, we predict oceanic regions with high organic carbon remineralization to have enhanced MeHg concentrations in both surface and subsurface waters.
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| 2. |
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| 3. |
- Kim, Jihee, et al.
(författare)
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Mass Budget of Methylmercury in the East Siberian Sea: The Importance of Sediment Sources
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 1086-931X .- 1520-6912 .- 0013-936X .- 1520-5851.
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Tidskriftsartikel (refereegranskat)abstract
- Biological concentrations of methylmercury(MeHg) are elevated throughout the Arctic Ocean; however, to date, the major sources and the spatial variability of MeHg are not well quantified. To identify the major inputs and outputs of MeHg to the Arctic shelf water column, we measured MeHg concentrations in the seawater and sediment samples from the East Siberian Sea collected from August to September 2018. We found that the MeHg concentrations in seawater and pore water were higher on the slope than on the shelf, while the MeHg concentrations in the sediment were higher on the shelf than on the slope. We created a mass budget for MeHg and found that the benthic diffusion and resuspension largely exceed other sources, such as atmospheric deposition and river water input. The major sinks of MeHg in the water column were dark demethylation and evasion. When we extrapolated our findings on benthic diffusion to the entire Arctic shelf system, the annual MeHg diffusion from the shelf sediments was estimated to be 23,065 ± 939 mol yr−1, about 2 times higher than previously proposed river discharges. Our study suggests that the MeHg input from shelf sediments in the Arctic Ocean is significant and has been previously underestimated.
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| 4. |
- Yang, Jisook, et al.
(författare)
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The role of fluorescent dissolved organic matter on mercury photoreduction rates : A case study of three temperate lakes
- 2020
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 277, s. 192-205
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Tidskriftsartikel (refereegranskat)abstract
- The formation of dissolved gaseous mercury (DGM) in lake water is mainly attributed to photochemical processes mediated by dissolved organic matter (DOM). In this study, we explored how different DOM components influence the Hg(II) photoreduction rate constant (kr) in lake surface water. For this purpose, the kr and the fluorescence properties of DOM were obtained from three Korean lakes with different trophic states. Three major fluorophores were identified by excitation-emission matrix fluorescence spectroscopy combined with a parallel factor analysis: plant-derived terrigenous humic-like DOM (C1), autochthonous DOM (C2), and soil fulvic-like DOM (C3). The principal component analysis (PCA) loading matrix demonstrated that kr increases when bulk DOM has high flavin-like and soil-derived fulvic-like fractions. The results of a Pearson’s correlation agreed with the outcome of the PCA analysis: kr showed a strong positive correlation with the soil fulvic-like DOM component (r = 0.92) and the redox index (r = 0.92). This was further confirmed by a partial least squares-regression model that predicted kr (r = 0.99) using multiple DOM components. Overall, our results suggest that kr can be modeled using fluorescence intensities of diverse DOM components, which in turn has the potential to be incorporated into Hg biogeochemical models to better predict the variability of Hg redox rates across lake systems.
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