Mercury methylation and demethylation potentials in Arctic lake sediments

Hudelson, Karista; Drevnick, Paul E.; Wang, Fei; Armstrong, Debbie; Fisk, Aaron T.

doi:10.1016/j.chemosphere.2020.126001

Cited by 33 publications

(14 citation statements)

References 63 publications

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“…The role of microorganisms in Hg methylation was discovered in the 1960s and, shortly afterward, followed the first reports on the degradation of MeHg, or demethylation. , These reports documented the disappearance of MeHg from sediment incubations and the isolation of bacterial cultures that degraded MeHg. , The authors of these early studies concluded that microorganisms in environments where MeHg was formed degraded MeHg, and they suggested that this activity was equally important for the accumulation of MeHg in the environment. , These competitive, simultaneous methylation and demethylation reactions have since been studied and widely observed in diverse environmental systems, such as freshwater lakes, wetlands, periphyton biofilms, marine water, and sediments. − Nevertheless, throughout the decades, much more attention has been paid to, and consequently knowledge gained on, methylation as compared to demethylation. A recent Google Scholar search with “mercury methylation” as a query resulted in 50 900 citations and with “methylmercury degradation” in 30 200 citations.…”

Section: Introductionmentioning

confidence: 99%

Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review

Barkay

2021

ACS Environ. Au

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The public and environmental health consequences of mercury (Hg) methylation have drawn much attention and considerable research to Hg methylation processes and their dynamics in diverse environments and under a multitude of conditions. However, the net methylmercury (MeHg) concentration that accumulates in the environment is equally determined by the rate of MeHg degradation, a complex process mediated by a variety of biotic and abiotic mechanisms, about which our knowledge is limited. Here we review the current knowledge on MeHg degradation and its potential pathways and mechanisms. We describe detoxification by resistant microorganisms that employ the Hg resistance (mer) system to reductively break the carbon− mercury (C−Hg) bond producing methane (CH 4 ) and inorganic mercuric Hg(II), which is then reduced by the mercuric reductase to elemental Hg(0). Very recent research has begun to elucidate a mechanism for the longrecognized mer-independent oxidative demethylation, likely involving some strains of anaerobic bacteria as well as aerobic methane-oxidizing bacteria, i.e., methanotrophs. In addition, photochemical and chemical demethylation processes are described, including the roles of dissolved organic matter (DOM) and free radicals as well as dark abiotic demethylation in the natural environment about which little is currently known. We focus on mechanisms and processes of demethylation and highlight the uncertainties and known effects of environmental factors leading to MeHg degradation. Finally, we suggest future research directions to further elucidate the chemical and biochemical mechanisms of biotic and abiotic demethylation and their significance in controlling net MeHg production in natural ecosystems.

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Section: Introductionmentioning

confidence: 99%

Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review

Barkay

2021

ACS Environ. Au

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“…Density-driven stratification could also result in localized meromictic conditions and subsequent sediment anoxia (Brahney et al 2008a(Brahney et al , 2008b. The potential combination of anoxic conditions and labile sulfur compounds in the hypolimnion, combined with potential increases in organic matter in the water column, from both the catchment and increased autochthonous primary production, could produce biogeochemical conditions that result in a release of Hg that had accumulated in the sediments over decades (Branfireun et al 2020;Hudelson et al 2020), but ongoing research is required to monitor and test this. Because the hydroecological future of Kluane Lake is uncertain, further study and ongoing monitoring are critical to understanding changes in Hg delivery and relative contributions from potential Hg sources to Kluane Lake in this new hydrological period, as well as the effect on mercury concentrations in aquatic organisms and valued fish species.…”

Section: Discussionmentioning

confidence: 99%

Mercury accumulation in sediments of Lhù’ààn Mânʼ (Kluane Lake, YT): Response to past hydrological change

Zabel

Hall

Branfireun

et al. 2021

Arctic, Antarctic, and Alpine Research

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Northern lakes provide many ecosystem services, including the provision of traditional foods and clean water. These systems are vulnerable to climate-driven changes in hydrology and contaminant accumulation, but the direction and magnitude of projected changes are poorly constrained. One contaminant of concern is mercury; currently, we cannot accurately predict how mercury accumulation in lakes will respond to climate-induced changes, especially in lakes with glacial inflows and complex hydrology. Sediment cores collected from two regions of a glacially fed lake (Lhù'ààn Mân'; Kluane Lake, Yukon, Canada) were analyzed to investigate controls on sediment mercury accumulation in the context of previously described hydrological changes. Differences in catchment contributions drove differences in sediment mercury accumulation between lake regions during the Duke River hydrological period (ca. 750-1650). During the more recent Slims River hydrological period (ca. 1650-2015), mercury accumulation did not differ between regions, and mercury was delivered to the lake primarily via catchment organic matter and carbonate-rich sediments from the largest, glacially derived inflow (Slims River). Recent climate-induced geomorphic change caused loss of the main lake inflow (Slims River) in 2016, making Kluane Lake an ideal system for future investigations of how loss of glacial inflow will affect mercury accumulation in northern lakes.

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“…It was noticed that the process of methylation in lake sediments intensified, as a result of increased primary production caused by temperature increase. Consequently, this high productivity could promote Hg accumulation in lakes, accelerating the rate of Hg removal from the water column and subsequent accumulation in bottom sediments (Hudelson et al, 2020;Stern et al, 2012). St Pierre et al (2018) indicated that glacial rivers are the most important source of Hg for Lake Hazen (Nunavut, Canada).…”

Section: Heavy Metalsmentioning

confidence: 99%

Sources, fate and distribution of inorganic contaminants in the Svalbard area, representative of a typical Arctic critical environment–a review

Rudnicka-Kępa

Zaborska

2021

Environ Monit Assess

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Global environmental changes not only contribute to the modification of global pollution transport pathways but can also alter contaminant fate within the Arctic. Recent reports underline the importance of secondary sources of pollution, e.g. melting glaciers, thawing permafrost or increased riverine run-off. This article reviews reports on the European Arctic–we concentrate on the Svalbard region–and environmental contamination by inorganic pollutants (heavy metals and artificial radionuclides), including their transport pathways, their fate in the Arctic environment and the concentrations of individual elements in the ecosystem. This review presents in detail the secondary contaminant sources and tries to identify knowledge gaps, as well as indicate needs for further research. Concentrations of heavy metals and radionuclides in Svalbard have been studied, in various environmental elements since the beginning of the twentieth century. In the last 5 years, the highest concentrations of Cd (13 mg kg−1) and As (28 mg kg−1) were recorded for organic-rich soils, while levels of Pb (99 mg kg−1), Hg (1 mg kg−1), Zn (496 mg kg−1) and Cu (688 mg kg−1) were recorded for marine sediments. Increased heavy metal concentrations were also recorded in some flora and fauna species. For radionuclides in the last 5 years, the highest concentrations of 137Cs (4500 Bq kg−1), 238Pu (2 Bq kg−1) and 239 + 240Pu (43 Bq kg−1) were recorded for cryoconites, and the highest concentration of 241Am (570 Bq kg−1) was recorded in surface sediments. However, no contamination of flora and fauna with radionuclides was observed.

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Mercury methylation and demethylation potentials in Arctic lake sediments

Cited by 33 publications

References 63 publications

Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review

Demethylation─The Other Side of the Mercury Methylation Coin: A Critical Review

Mercury accumulation in sediments of Lhù’ààn Mânʼ (Kluane Lake, YT): Response to past hydrological change

Sources, fate and distribution of inorganic contaminants in the Svalbard area, representative of a typical Arctic critical environment–a review

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