Mercury dynamics in the pore water of peat columns during experimental freezing and thawing

Sirota, Jennie I.; Kolka, Randall K.; Sebestyen, Stephen D.; Nater, Edward A.

doi:10.1002/jeq2.20046

Cited by 4 publications

(6 citation statements)

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“…It is mostly oxic above the water table and includes living plants and the majority of roots . The catotelm is a deeper zone of permanently saturated and higher density peat with lower hydraulic conductivity and permanently anoxic conditions. , Between the acrotelm and catotelm is the mesotelm (approximately 30–50 cm below the surface), a transitional area characterized by a fluctuating water table. ,,, The mesotelm is periodically oxic, corresponding to low water tables, or anoxic, corresponding to high water tables.…”

Section: Methodsmentioning

confidence: 99%

“…44,45 Between the acrotelm and catotelm is the mesotelm (approximately 30−50 cm below the surface), a transitional area characterized by a fluctuating water table. 35,40,45,46 The mesotelm is periodically oxic, corresponding to low water tables, or anoxic, corresponding to high water tables.…”

Section: Methodsmentioning

confidence: 99%

“…Most lab and field studies to date have focused on inorganic sulfate as a driver for mercury methylation, ,,, but bogs have little inorganic sulfur. , Our objective was to investigate the role of organic sulfur species, as opposed to inorganic sulfur species, in peatland soil as important reactants and products in mercury methylation. In a climate with an increasingly variable water table (i.e., longer drought with deeper water table position) a greater volume of peat may be exposed to biogeochemical processes that are able to generate ester sulfate and MeHg. ,− …”

Section: Introductionmentioning

confidence: 99%

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Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Pierce

Furman

Nicholas

et al. 2022

Environ. Sci. Technol.

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We examined the composition and spatial correlation of sulfur and mercury pools in peatland soil profiles by measuring sulfur speciation by 1s X-ray absorption near-edge structure spectrocopy and mercury concentrations by cold vapor atomic fluorescence spectroscopy. Also investigated were the methylation/demethylation rate constants and the presence of hgcAB genes with depth. Methylmercury (MeHg) concentration and organic disulfide were spatially correlated and had a significant positive correlation (p < 0.05). This finding is consistent with these species being products of dissimilatory sulfate reduction. Conversely, a significant negative correlation between organic monosulfides and MeHg was observed, which is consistent with a reduction in Hg(II) bioavailability via complexation reactions. Finally, a significant positive correlation between ester sulfate and instantaneous methylation rate constants was observed, which is consistent with ester sulfate being a substrate for mercury methylation via dissimilatory sulfate reduction. Our findings point to the importance of organic sulfur species in mercury methylation processes, as substrates and products, as well as potential inhibitors of Hg(II) bioavailability. For a peatland system with sub-μmol L–1 porewater concentrations of sulfate and hydrogen sulfide, our findings indicate that the solid-phase sulfur pools, which have a much larger sulfur concentration range, may be accessible to microbial activity or exchanging with the porewater.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Pierce

Furman

Nicholas

et al. 2022

Environ. Sci. Technol.

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“…The PEATCOSM Study, hosted by USDA Forest Service and Michigan Technological University in Houghton, MI, investigated the effect of varying water tables and changes in plant communities anticipated with climate change [22]. Finally, results from a mesocosm study simulating winter responses on the effects of warming on freeze/thaw cycles on THg and MeHg in peatland pore waters from Jennie's Bog at the MEF were also considered [23]. We do not thoroughly address the implications of climate change on import ions and microorganisms responsible for methylation (e.g., sulfate-and iron-reducing bacteria and methanogens) and Hg transport (e.g., DOC: dissolved organic carbon), though generally, it does not appear that climate change will limit the availability of reducers and associated ions, and there are likely increases in peatland-derived DOC fluxes as a result of greater decomposition with warming [24].…”

Section: Review Of Boreal Peatland Climate Studiesmentioning

confidence: 99%

Review of the Influence of Climate Change on the Hydrologic Cycling and Gaseous Fluxes of Mercury in Boreal Peatlands: Implications for Restoration

Kolka,

Pierce,

Garrioch

et al. 2024

Water

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Mercury (Hg) is a pollutant that bioaccumulates in the food web, leading to health issues in humans and other fauna. Although anthropogenic Hg deposition has decreased over the past 20 years, our watersheds continue to be sources of Hg to downstream communities. Wetlands, especially peatlands in the Boreal Region of the globe, play a vital role in the formation of bioaccumulative methylmercury (MeHg). Few studies have assessed how increases in temperatures such as those that have already occurred and those predicted will influence the hydrologic transport of Hg to downstream communities or the net fluxes of gaseous Hg. The results indicate that peatland pore water concentrations of MeHg are increasing with ecosystem warming, and to some degree with elevated carbon dioxide (eCO2) in the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment at the Marcell Experimental Forest (MEF) in northern Minnesota, USA. Similar to SPRUCE, in the Biological Response to A Changing Environment (BRACE) experiment in Canada, mesocosm pore water MeHg concentrations increased with soil warming. However, long-term peatland watershed streamflow fluxes of MeHg at the MEF indicate that the competing effects of climate warming and decreased atmospheric deposition have led to overall decreases in watershed MeHg transport. Mesocosm studies in the PEATCOSM experiment in Upper Michigan, USA, indicate that simulated fluctuating water tables led to higher concentrations of MeHg in peatland pore water that is available for downstream transport when water tables rise and the next runoff event occurs. Results from a winter peatland soil freeze/thaw simulation from large mesocosm cores from Jennie’s Bog at the MEF indicate higher total Hg (THg) upon soil thawing but lower MeHg, likely a result of cold temperatures limiting methylation during thawing. Although there are lower MeHg concentrations after thawing, more THg is available for methylation once soils warm. Results from PEATCOSM and the literature also suggest that plant community changes that result in higher densities of sedges also lead to elevated MeHg in pore water. From a climate warming perspective, it appears that two complementary mechanisms, both related to decomposition, are at play that lead to increased pore water MeHg concentrations with warming. First, warming increases decomposition rates, leading to a higher availability of many ions, including Hg (and sulfur) species. Higher decomposition rates also lead to increases in soluble carbon which complexes with Hg species and assists in downstream hydrologic transport. However, if streamflow is decreasing with climate change as a result of landscape-level changes in evapotranspiration as suggested at MEF, the combination of less direct watershed Hg deposition and lower streamflow results in decreases in the watershed transport of MeHg. Given changes already occurring in extreme events and the rewetting and restoration of hydrology during peatland restoration, it is likely that methylation and pore water MeHg concentrations will increase. However, the landscape-level hydrologic cycle will be key to understanding the connection to downstream aquatic communities. Finally, gaseous Hg fluxes increase with warming and lead to decreases in peatland pools of Hg that may influence future availability for downstream transport.

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“…Thus, risks for humans and ecosystems are highly variable and require different management strategies to reduce them. A recent JEQ article by Sirota et al (2020) presents research on cycling of Hg in peat under freezing and thawing conditions. They observed that freeze-thaw cycles increase risks for Hg transport, which is especially relevant given global climate change conditions.…”

Section: Trace Element Contaminant Sources and Sitesmentioning

confidence: 99%

Fifty years of articles in JEQ on trace elements in the environment and future outlook

Strawn

Hettiarachchi

2021

J of Env Quality

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Fifty years ago, the Journal of Environmental Quality (JEQ) was launched to provide an outlet for publication of research on the impacts of agriculture on the environment, and vice versa. A core concept of JEQ is advancement of environmental science, with emphasis on understanding factors that affect the fate, risks, and quality of soil, water, and atmospheric systems, and how these system processes affect plants, microbes, and animals. Trace elements are a focus area of JEQ because when present at higher than natural concentrations, they may pose risks to environmental quality and ecosystem health, depending on their bioavailability. Trace element biogeochemical cycling is affected by anthropogenic influences on land, air, and water, including land management practices such as agriculture and mining. The Journal of Environmental Quality has published a prolific catalog of scientific research publications on trace elements and their risks to humans, soil health, water quality, and the environment. In this review, research on trace elements and their impacts on environmental quality is presented, with a special focus on work published in JEQ.

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Mercury dynamics in the pore water of peat columns during experimental freezing and thawing

Cited by 4 publications

References 50 publications

Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Review of the Influence of Climate Change on the Hydrologic Cycling and Gaseous Fluxes of Mercury in Boreal Peatlands: Implications for Restoration

Fifty years of articles in JEQ on trace elements in the environment and future outlook

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