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Yu C, Peng M, Wang X, Pan X. Photochemical demethylation of methylmercury (MeHg) in aquatic systems: A review of MeHg species, mechanisms, and influencing factors. Environ Pollut 2024; 344:123297. [PMID: 38195023 DOI: 10.1016/j.envpol.2024.123297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/01/2023] [Accepted: 01/02/2024] [Indexed: 01/11/2024]
Abstract
Photodemethylation is the major pathway of methylmercury (MeHg) demethylation in surface water before uptake by the food chain, whose mechanisms and influence factors are still not completely understood. Here, we review the current knowledge on photodemethylation of MeHg and divide MeHg photolysis into three pathways: (1) direct photodemethylation, (2) free radical attack, and (3) intramolecular electron or energy transfer. In aquatic environments, dissolved organic matter is involved into all above pathways, and due to its complex compositions, properties and concentrations, DOM poses multiple functions during the PD of MeHg. DOM-MeHg complex (mainly by sulfur-containing molecules) might weaken the C-Hg bond and enhance PD through both direct and indirect pathways. In special, synergistic effects of both strong binding sites and chromophoric moieties in DOM might lead to intramolecular electron or energy transfer. Moreover, DOM might play a role of radical scavenger; while triplet state DOM, which is generated by chromophoric DOM under light, might become a source of free radicals. Apart from DOMs, transition metals, halides, NO3-, NO2-, and carbonates also act as radical initialaters or scavengers, and significantly pose effects on radical demethylation, which is generally mediated by hydroxyl radicals and singlet oxygen. Environmental factors such as pH, light wavelength, light intensity, dissolved oxygen, salinity, and suspended particles also affect the PD of MeHg. This study assessed previously published works on three major mechanisms, with the goal of providing general estimates for photodemethylation under various environment factors according to know effects, and highlighting the current uncertainties for future research directions.
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Affiliation(s)
- Chenghao Yu
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Mao Peng
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xiaonan Wang
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
| | - Xiangliang Pan
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
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2
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Liu Q, Liu S, Zhou XQ, Liu YR. Assessing microbial degradation potential of methylmercury in different types of paddy soil through short-term incubation. Environ Pollut 2023; 337:122603. [PMID: 37748640 DOI: 10.1016/j.envpol.2023.122603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Revised: 09/03/2023] [Accepted: 09/20/2023] [Indexed: 09/27/2023]
Abstract
The neurotoxic methylmercury (MeHg) in paddy soils can accumulate in rice grains. Microbial demethylation is an important pathway of MeHg degradation in soil, but the effect of soil type on microbial degradation of MeHg remains unclear. Therefore, we investigated MeHg degradation in eight typical paddy soils and analyzed the associations between soil physiochemical properties and microbial degradation efficiencies of MeHg. Results showed that MeHg was significantly degraded in unsterilized paddy soils, and the microbial degradation efficiency ranged from 10.8% to 64.6% after a 30-day incubation. The high microbial degradation efficiency of MeHg was observed in the soils with high levels of clay content, whereas relatively low degradation efficiency was found in the red paddy soils. We identified that Paenibacillaceae was the most important microbial predictor of MeHg degradation and was positively correlated with the degradation efficiency in the soils. The abundances of these microbial taxa associated with MeHg degradation were positively correlated with clay content. In addition, Eh, pH, and SOC could influence microbial degradation of MeHg by regulating certain microbial communities. Our results indicate that soil type is crucial in driving MeHg degradation, which has important implications for the mitigation of MeHg pollution in various croplands.
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Affiliation(s)
- Qin Liu
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Siyuan Liu
- College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Xin-Quan Zhou
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan, China
| | - Yu-Rong Liu
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan, China; Hubei Key Laboratory of Soil Environment and Pollution Remediation, Huazhong Agricultural University, Wuhan, 430070, China.
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Xiao C, Zhang M, Ding L, Qiu X, Guo X. New sight of microplastics aging: Reducing agents promote rapid aging of microplastics under anoxic conditions. J Hazard Mater 2023; 451:131123. [PMID: 36871465 DOI: 10.1016/j.jhazmat.2023.131123] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/16/2023] [Accepted: 03/01/2023] [Indexed: 06/18/2023]
Abstract
The aging of microplastics (MPs) occurs extensively in the environment, and understanding the aging mechanisms of MPs is essential to study the properties, fate and environmental impact of MPs. We proposed a creative hypothesis that polyethylene terephthalate (PET) can be aged by reducing reactions with reducing agents. Simulation experiments based on the principle of reduction of carbonyl by NaBH4 were conducted to test the correctness of this hypothesis. The results showed that after 7 days of experiments, physical damage and chemical transformation occurred in the PET-MPs. The particle size of MPs was reduced by 34.95-55.93 %, and the C/O ratio was increased by 2.97-24.14 %. The changing order of surface functional groups (CO > C-O > C-H > C-C) was obtained. The occurrence of reductive aging and electron transfer of MPs was further supported by electrochemical characterization experiments. These results together reveal the reductive aging mechanism of PET-MPs: CO is firstly reduced to C-O by BH4- attack, and then further reduced to ·R. The resulting ·R recombines to form new C-H and C-C. This study is beneficial to deepen the understanding of the chemical aging of MPs, and can provide a theoretical basis for further research on the reactivity of oxygenated MPs with reducing agents.
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Affiliation(s)
- Chuanqi Xiao
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Mengwei Zhang
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Ling Ding
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Xinran Qiu
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, PR China
| | - Xuetao Guo
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, PR China; Key Laboratory of Plant Nutrition and the Agri-Environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, PR China.
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Yang Q, Guo Y, Xiang Y, Chen L, Liu G, Liu Y, Shi J, Hu L, Liang Y, Yin Y, Cai Y, Jiang G. Toward efficient bioremediation of methylmercury in sediment using merB overexpressed Escherichia coli. Water Res 2023; 229:119502. [PMID: 36549184 DOI: 10.1016/j.watres.2022.119502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 11/26/2022] [Accepted: 12/16/2022] [Indexed: 06/17/2023]
Abstract
Sediment is the primary hotspot for microbial production of toxic and bio-accumulative methylmercury (MeHg). Common remediation strategies such as sediment dredging and capping can be too expensive and cannot degrade MeHg efficiently. Here, we constructed an Escherichia coli strain overexpressing merB gene (DH5α J23106) and assessed the effectiveness of this recombinant strain in degradation of MeHg in culture medium and sediment. DH5α J23106 can efficiently degrade MeHg (with initial concentration from 0.01 to 50 ng/mL) to more than 81.6% in a culture medium under anoxic and oxic conditions. Enriched isotope addition (199HgCl2) revealed that this recombinant strain can degrade 78.6% of newly produced Me199Hg in actual sediment, however the biodegradation decreased to 36.3% for intrinsic MeHg. Degradation of spiked MeHg after aging in anoxic and oxic sediments further demonstrated DH5α J23106 can efficiently degrade newly produced MeHg and the degradation decreased with aging significantly, especially for oxic sediment. Eight sediments were further assessed for the biodegradation of aged MeHg by DH5α J23106 under oxic conditions, with degradation ratios ranging from 9.0% to 66.9%. When combined with (NH4)2S2O3 leaching, the degradation of MeHg increased by 15.8-38.8% in on-site and off-site modes through enhanced MeHg bioavailability in some of these sediments. Thus, this recombinant strain DH5α J23106 can degrade MeHg efficiently and have the potential for remediating bioavailable MeHg in contaminated sediments.
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Affiliation(s)
- Qingqing Yang
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Institute of Environment and Health, Jianghan University, Wuhan, China; School of Environment and Health, Jianghan University, Wuhan 430056, China
| | - Yingying Guo
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yuping Xiang
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Lufeng Chen
- Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Institute of Environment and Health, Jianghan University, Wuhan, China; School of Environment and Health, Jianghan University, Wuhan 430056, China
| | - Guangliang Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, United States
| | - Yanwei Liu
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jianbo Shi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Ligang Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yong Liang
- Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Institute of Environment and Health, Jianghan University, Wuhan, China; School of Environment and Health, Jianghan University, Wuhan 430056, China
| | - Yongguang Yin
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, Institute of Environment and Health, Jianghan University, Wuhan, China.
| | - Yong Cai
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, United States
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
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Zhang L, Song Y, Li Y, Yin Y, Cai Y. Role of light in methylmercury photodegradation: From irradiation to absorption in the presence of organic ligands. Sci Total Environ 2022; 848:157550. [PMID: 35907539 DOI: 10.1016/j.scitotenv.2022.157550] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/07/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
Photochemical degradation acts as the principal sink for methylmercury (MeHg) in surface water, which is regulated by light and solution matrix (especially the presence of dissolved organic matter, DOM). The spectral composition of light irradiation and the light absorption properties of reaction media (often exerted by DOM) are important in MeHg photodegradation, which has not yet been clearly resolved. Aiming to understand the role of light in MeHg photodegradation from the perspectives of both light irradiation and absorption, we investigated the photodegradation of MeHg under different simulated sunlight sources, with and without DOM model compounds of different molecular structures. The results show that the photodegradation of MeHg under different sunlight irradiation yields distinct first-order date constant, mainly due to the slight difference in UVB composition. The degradation of MeHg without DOM under a light source with high intensity in the UV region and no MeHg degradation under the UV-filtered light even in the presence of DOM showed the importance of UV lights in MeHg photodegradation. The use of ultrapure water as a reaction medium may be subject to MeHg loss through vessel adsorption, not just photolysis. Additionally, this work found that the type and position of coexisting substituents on aromatic thiols play a critical role in improving the photodegradation of MeHg, following amino > hydroxyl > carboxyl, para > meta > ortho. Based on the characterization of ultraviolet-visible absorption spectra and our previous work, it was concluded that the presence of DOM could induce red-shift in light absorption and reduce the electronic transition energy of the CHg bond, facilitating MeHg photodegradation. The structures of DOM affect the light absorption properties, which are related to MeHg photodegradation.
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Affiliation(s)
- Lian Zhang
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yue Song
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yong Cai
- Department of Chemistry & Biochemistry, Florida International University, Miami, FL 33199, United States
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Zhang L, Yin Y, Li Y, Cai Y. Mercury isotope fractionation during methylmercury transport and transformation: A review focusing on analytical method, fractionation characteristics, and its application. Sci Total Environ 2022; 841:156558. [PMID: 35710002 DOI: 10.1016/j.scitotenv.2022.156558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/04/2022] [Accepted: 06/04/2022] [Indexed: 06/15/2023]
Abstract
Methylmercury (MeHg), a potent neurotoxin, can be formed, migrated and transformed in environmental compartments, accompanying with unique mass-dependent and mass-independent fractionation of mercury (Hg). These Hg isotope fractionation signals have great potential to probe the transformation and transport of MeHg in aquatic environments. However, the majority of studies to date have focused on total Hg isotopic composition, with less attention to the isotopic fractionation of MeHg due to technical difficulties in analysis, which severely hinders the understanding of MeHg isotopic fractionation and its applications. This review a) evaluates the reported analytical methods for Hg isotopic composition of MeHg, including online and offline measurement techniques; b) summarizes the extent and characteristics of Hg isotopic fractionation during MeHg transport and transformation, focusing on methylation, demethylation, trophic transfer and internal metabolism; and c) briefly discusses several applications of MeHg isotopic fractionation signatures in estimating the extent of photodemethylation, tracing the source of Hg species, and diagnosing reaction mechanisms. Additionally, the existing problems and future directions in MeHg isotope fractionation are highlighted to improve the analytical protocol for Hg isotope fractionation and deepen our understanding of Hg isotope fractionation in the biogeochemical cycling of MeHg.
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Affiliation(s)
- Lian Zhang
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Yong Cai
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China; Department of Chemistry & Biochemistry, Florida International University, Miami, FL 33199, United States.
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Abstract
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 (CH4) 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 long-recognized 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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Affiliation(s)
- Tamar Barkay
- Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey 08901, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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Liu H, Guo Y, Wang Y, Zhang H, Ma X, Wen S, Jin J, Song W, Zhao B, Ozaki Y. A nanozyme-based enhanced system for total removal of organic mercury and SERS sensing. J Hazard Mater 2021; 405:124642. [PMID: 33301972 DOI: 10.1016/j.jhazmat.2020.124642] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/15/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Total removal of organic mercury in industrial wastewater is a crucially important task facing environmental pollution in the current world. Herein, we demonstrate the fabrication of Au-NiFe layered double hydroxide (LDH)/rGO nanocomposite as not only an efficient nanozyme with oxidase-like activity but also an efficient surface-enhanced Raman spectroscopy (SERS) substrate to determine organic mercury, with the minimum detection concentration as low as 1 × 10-8 M. According to the binding energy of X-Ray photoelectron spectrometer (XPS) and the free radicals of electron paramagnetic resonance (EPR) spectra, the mechanism of catalytic enhanced degradation is the production of Au-amalgam on Au surface, accelerating the electron transfer and the generation of O2•- radicals from oxygen molecules and •CH3 radicals from the methyl group in MeHg to participate the oxidase-like reaction. Furthermore, the Au-NiFe LDH/rGO nanocomposite is able to degrade and remove 99.9% of organic mercury in two hours without the secondary pollution by Hg2+. In addition, the material can be used for the multiple degradation-regeneration cycles in actual applications, which is significant in terms of the environmental and economic point of view. This work may open a new horizon for both highly sensitive detection and thorough degradation of organic mercury in environmental science and technology.
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Affiliation(s)
- Hao Liu
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Yue Guo
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Yunxin Wang
- Jilin Provincial Center for Disease Control and Prevention, 3145 Jingyang Street, Changchun 130062, PR China
| | - Huidan Zhang
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Xiaowei Ma
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Sisi Wen
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Jing Jin
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Wei Song
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China.
| | - Bing Zhao
- State Key Laboratory of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Street, Changchun 130012, PR China
| | - Yukihiro Ozaki
- School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 660-1337, Japan; Toyota Physical and Chemical Research Institute, Yokomichi, Nagakute, Aichi 480-1192, Japan
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Xie M, Zhang C, Liao X, Huang C. The influence of wetting-drying alternation on methylmercury degradation in Guangzhou soil. Environ Pollut 2020; 259:113866. [PMID: 31891907 DOI: 10.1016/j.envpol.2019.113866] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 12/20/2019] [Accepted: 12/20/2019] [Indexed: 06/10/2023]
Abstract
In one of our previous studies, the mechanisms of radical-initiated methylmercury (MeHg) degradation in soil with coexisting Fe and Cu have been reported. In this work, various environmental factors, including water table fluctuation, pH and major ions, are discussed to clarify the behavior of MeHg in subsurface environments. Soil column experiments were set up to simulate the degradation of MeHg in the soil with an iron-bearing mineral (annite), which has often undergone repeating wetting-drying cycles, resulting from the local climate. The results indicate that wetting-drying alternation can initiate MeHg degradation in the soil with the annite mineral. Additionally, the majority of the major ions (K+, Na+, Mg2+, Fe3+, Cl-, SO42-, NO3-) in the interstitial soil had little effect in the degradation of MeHg with the exception of Cu, which improved the degradation depending on the pH. At acidic pHs Cu increased the production of hydroxyl radical while at more alkaline pHs there was oxidation to Cu(III). The products including Hg(II) and Hg(0) of MeHg degradation were also identified in this work. This study reveals that the geochemical cycle of MeHg is closely linked to local climate and pedosphere processes.
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Affiliation(s)
- Mengying Xie
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, PR China
| | - Caixiang Zhang
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, 430074, PR China.
| | - Xiaoping Liao
- School of Chemistry and Environmental Engineering, Wuhan Institute of Technology, Wuhan, 430074, PR China
| | - Changsheng Huang
- Wuhan Center of China Geological Survey, Wuhan, 430205, Hubei, China
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