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Title: Warming increases methylmercury production in an Arctic soil

Abstract

The rapid temperature rise in Arctic permafrost concerns not only the degradation of stored soil organic carbon (SOC) and climate feedback, but also the production and bioaccumulation of methylmercury (MeHg) that may endanger humans, as well as wildlife in terrestrial, aquatic, and marine ecosystems. Decomposition of SOC provides an energy source for microbial methylation, although little is known how rapid permafrost thaw affects Hg methylation and how SOC degradation is coupled to MeHg biosynthesis. We describe rates of MeHg production in Arctic soils from an 8-month warming microcosm experiment under anoxic conditions. MeHg production increased >10 fold in both organic- and the mineral-rich soil layers at a warmer temperature (8 C) compared to a sub-zero temperature ( 2 C). MeHg production was positively correlated to methane and ferrous ion concentrations, suggesting that Hg methylation is coupled with methanogenesis and iron reduction. Labile SOC, such as reducing sugars and alcohol, were particularly effective in fueling the initial rapid biosynthesis of MeHg. In freshly amended Hg we found that there was more bioavailable than existing Hg in the mineral soil. Finally, the data indicate that climate warming and permafrost thaw could greatly enhance MeHg production, thereby impacting Arctic aquatic and marine ecosystemsmore » through biomagnification in the food web.« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [5];  [6]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Univ. of Science and Technology of China, Hefei (China). CAS Key Lab. for Urban Pollutant Conversion
  3. Univ. of Science and Technology of China, Hefei (China). CAS Key Lab. for Urban Pollutant Conversion
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division and Biology and Soft Matter Division
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division and Climate Change Science Inst.
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1319169
Alternate Identifier(s):
OSTI ID: 1341459
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Environmental Pollution
Additional Journal Information:
Journal Volume: 214; Journal Issue: C; Journal ID: ISSN 0269-7491
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Mercury; methylmercury; permafrost; organic matter; climate warming

Citation Formats

Yang, Ziming, Fang, Wei, Lu, Xia, Sheng, Guo-Ping, Graham, David E., Liang, Liyuan, Wullschleger, Stan D., and Gu, Baohua. Warming increases methylmercury production in an Arctic soil. United States: N. p., 2016. Web. doi:10.1016/j.envpol.2016.04.069.
Yang, Ziming, Fang, Wei, Lu, Xia, Sheng, Guo-Ping, Graham, David E., Liang, Liyuan, Wullschleger, Stan D., & Gu, Baohua. Warming increases methylmercury production in an Arctic soil. United States. doi:10.1016/j.envpol.2016.04.069.
Yang, Ziming, Fang, Wei, Lu, Xia, Sheng, Guo-Ping, Graham, David E., Liang, Liyuan, Wullschleger, Stan D., and Gu, Baohua. Fri . "Warming increases methylmercury production in an Arctic soil". United States. doi:10.1016/j.envpol.2016.04.069. https://www.osti.gov/servlets/purl/1319169.
@article{osti_1319169,
title = {Warming increases methylmercury production in an Arctic soil},
author = {Yang, Ziming and Fang, Wei and Lu, Xia and Sheng, Guo-Ping and Graham, David E. and Liang, Liyuan and Wullschleger, Stan D. and Gu, Baohua},
abstractNote = {The rapid temperature rise in Arctic permafrost concerns not only the degradation of stored soil organic carbon (SOC) and climate feedback, but also the production and bioaccumulation of methylmercury (MeHg) that may endanger humans, as well as wildlife in terrestrial, aquatic, and marine ecosystems. Decomposition of SOC provides an energy source for microbial methylation, although little is known how rapid permafrost thaw affects Hg methylation and how SOC degradation is coupled to MeHg biosynthesis. We describe rates of MeHg production in Arctic soils from an 8-month warming microcosm experiment under anoxic conditions. MeHg production increased >10 fold in both organic- and the mineral-rich soil layers at a warmer temperature (8 C) compared to a sub-zero temperature ( 2 C). MeHg production was positively correlated to methane and ferrous ion concentrations, suggesting that Hg methylation is coupled with methanogenesis and iron reduction. Labile SOC, such as reducing sugars and alcohol, were particularly effective in fueling the initial rapid biosynthesis of MeHg. In freshly amended Hg we found that there was more bioavailable than existing Hg in the mineral soil. Finally, the data indicate that climate warming and permafrost thaw could greatly enhance MeHg production, thereby impacting Arctic aquatic and marine ecosystems through biomagnification in the food web.},
doi = {10.1016/j.envpol.2016.04.069},
journal = {Environmental Pollution},
number = C,
volume = 214,
place = {United States},
year = {Fri Apr 29 00:00:00 EDT 2016},
month = {Fri Apr 29 00:00:00 EDT 2016}
}

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  • The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, andmore » low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO 2 and CH 4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO 2 and CH 4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO 2 and CH 4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.« less
  • Phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models’ projections of the 2014–2100 Arctic warming under radiative forcing from representative concentration pathway 4.5 (RCP4.5) vary from 0.9° to 6.7°C. Climate models with or without a full indirect aerosol effect are both equally successful in reproducing the observed (1900–2014) Arctic warming and its trends. However, the 2014–2100 Arctic warming and the warming trends projected by models that include a full indirect aerosol effect (denoted here as AA models) are significantly higher (mean projected Arctic warming is about 1.5°C higher) than those projected by models without a full indirect aerosolmore » effect (denoted here as NAA models). The suggestion is that, within models including full indirect aerosol effects, those projecting stronger future changes are not necessarily distinguishable historically because any stronger past warming may have been partially offset by stronger historical aerosol cooling. In conclusion, the CMIP5 models that include a full indirect aerosol effect follow an inverse radiative forcing to equilibrium climate sensitivity relationship, while models without it do not.« less