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Title: Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation

Abstract

Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. Here we report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). Lastly, these results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.

Authors:
 [1];  [2];  [2];  [2];  [2];  [3];  [2];  [4];  [5];  [4]; ORCiD logo [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Univ. of Science and Technology of China, Hefei (China). Dept. of Chemistry
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Sun Yat-Sen University, Guangzhou (China). School of Environmental Science and Engineering
  4. Univ. of Science and Technology of China, Hefei (China). Dept. of Chemistry
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab.
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:
1343495
Alternate Identifier(s):
OSTI ID: 1397819
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Environmental Pollution
Additional Journal Information:
Journal Volume: 220; Journal Issue: PB; Journal ID: ISSN 0269-7491
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; Dissolved organic matter; Hg-DOM photolysis; Methylmercury; Biogeochemical transformation; HgS precipitation

Citation Formats

Luo, Hong-Wei, Yin, Xiangping, Jubb, Aaron M., Chen, Hongmei, Lu, Xia, Zhang, Weihua, Lin, Hui, Yu, Han-Qing, Liang, Liyuan, Sheng, Guo-Ping, and Gu, Baohua. Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation. United States: N. p., 2016. Web. doi:10.1016/j.envpol.2016.10.099.
Luo, Hong-Wei, Yin, Xiangping, Jubb, Aaron M., Chen, Hongmei, Lu, Xia, Zhang, Weihua, Lin, Hui, Yu, Han-Qing, Liang, Liyuan, Sheng, Guo-Ping, & Gu, Baohua. Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation. United States. doi:10.1016/j.envpol.2016.10.099.
Luo, Hong-Wei, Yin, Xiangping, Jubb, Aaron M., Chen, Hongmei, Lu, Xia, Zhang, Weihua, Lin, Hui, Yu, Han-Qing, Liang, Liyuan, Sheng, Guo-Ping, and Gu, Baohua. Wed . "Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation". United States. doi:10.1016/j.envpol.2016.10.099. https://www.osti.gov/servlets/purl/1343495.
@article{osti_1343495,
title = {Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation},
author = {Luo, Hong-Wei and Yin, Xiangping and Jubb, Aaron M. and Chen, Hongmei and Lu, Xia and Zhang, Weihua and Lin, Hui and Yu, Han-Qing and Liang, Liyuan and Sheng, Guo-Ping and Gu, Baohua},
abstractNote = {Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. Here we report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). Lastly, these results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.},
doi = {10.1016/j.envpol.2016.10.099},
journal = {Environmental Pollution},
number = PB,
volume = 220,
place = {United States},
year = {2016},
month = {11}
}

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