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Wang X, Wang Y, Zhang Y, Liu Z, Ji X, Cai Y. Mercury contents and potential exposure risk of rice-containing food products. J Environ Sci (China) 2025; 148:683-690. [PMID: 39095199 DOI: 10.1016/j.jes.2024.02.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 02/07/2024] [Accepted: 02/07/2024] [Indexed: 08/04/2024]
Abstract
Mercury (Hg), especially methylmercury (MeHg), accumulation in rice grain due to rice paddy possessing conditions conducive to Hg methylation has led to human Hg exposure through consumption of rice-based daily meals. In addition to being a food staple, rice is widely used as a raw material to produce a vast variety of processed food products. Little is known about Hg levels in snacking rice-food products and potential Hg exposure from consumption of them, besides previous studies on infant rice cereals. Aiming to provide complementary information for a more complete assessment on Hg exposure risk originated from Hg-containing rice, this study determined total Hg (THg) and MeHg levels in 195 rice-containing and rice-free processed food products covering all major types of snack foods marketed in China and the estimated daily intake (EDI) of dietary Hg from the consumption of these foods. The results clearly showed THg and MeHg contents in rice-containing foods were significantly higher than rice-free products, suggesting the transfer of Hg and MeHg from the rice to the end products, even after manufacturing processes. Moreover, significant positive correlations were observed between THg, MeHg, or MeHg/THg ratio and rice content for samples containing multiple grains as ingredients, further indicating the deciding role of rice for Hg levels in the end food products. Although the EDI of THg and MeHg via rice-based food products were relatively low compared to the reference dose, it should be considered these snacking food products would contribute additive Hg intake outside of the daily regular meals.
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Affiliation(s)
- Xin Wang
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yingjun Wang
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
| | - Yaqi Zhang
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Ziyan Liu
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Xiaomeng Ji
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yong Cai
- Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China; Department of Chemistry & Biochemistry, Florida International University, Miami, FL 33199, USA
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2
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Boie F, Ducey TF, Xing Y, Wang J, Rinklebe J. Field-aged rice hull biochar stimulated the methylation of mercury and altered the microbial community in a paddy soil under controlled redox condition changes. JOURNAL OF HAZARDOUS MATERIALS 2024; 472:134446. [PMID: 38696958 DOI: 10.1016/j.jhazmat.2024.134446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/25/2024] [Accepted: 04/25/2024] [Indexed: 05/04/2024]
Abstract
Mercury (Hg) contaminated paddy soils are hot spots for methylmercury (MeHg) which can enter the food chain via rice plants causing high risks for human health. Biochar can immobilize Hg and reduce plant uptake of MeHg. However, the effects of biochar on the microbial community and Hg (de)methylation under dynamic redox conditions in paddy soils are unclear. Therefore, we determined the microbial community in an Hg contaminated paddy soil non-treated and treated with rice hull biochar under controlled redox conditions (< 0 mV to 600 mV) using a biogeochemical microcosm system. Hg methylation exceeded demethylation in the biochar-treated soil. The aromatic hydrocarbon degraders Phenylobacterium and Novosphingobium provided electron donors stimulating Hg methylation. MeHg demethylation exceeded methylation in the non-treated soil and was associated with lower available organic matter. Actinobacteria were involved in MeHg demethylation and interlinked with nitrifying bacteria and nitrogen-fixing genus Hyphomicrobium. Microbial assemblages seem more important than single species in Hg transformation. For future directions, the demethylation potential of Hyphomicrobium assemblages and other nitrogen-fixing bacteria should be elucidated. Additionally, different organic matter inputs on paddy soils under constant and dynamic redox conditions could unravel the relationship between Hg (de)methylation, microbial carbon utilization and nitrogen cycling.
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Affiliation(s)
- Felizitas Boie
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany
| | - Thomas F Ducey
- US Department of Agriculture, Coastal Plains Soil, Water, Plant Research Center, 2611 West Lucas Street, Florence, SC, USA
| | - Ying Xing
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550002, PR China
| | - Jianxu Wang
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550082 Guiyang, P.R. China
| | - Jörg Rinklebe
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water and Waste Management, Laboratory of Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany.
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3
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Dong H, Wang Y, Zhi T, Guo H, Guo Y, Liu L, Yin Y, Shi J, He B, Hu L, Jiang G. Construction of protein-protein interaction network in sulfate-reducing bacteria: Unveiling of global response to Hg. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 351:124048. [PMID: 38714230 DOI: 10.1016/j.envpol.2024.124048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 04/20/2024] [Accepted: 04/23/2024] [Indexed: 05/09/2024]
Abstract
Sulfate-reducing bacteria (SRB) play pivotal roles in the biotransformation of mercury (Hg). However, unrevealed global responses of SRB to Hg have restricted our understanding of details of Hg biotransformation processes. The absence of protein-protein interaction (PPI) network under Hg stimuli has been a bottleneck of proteomic analysis for molecular mechanisms of Hg transformation. This study constructed the first comprehensive PPI network of SRB in response to Hg, encompassing 67 connected nodes, 26 independent nodes, and 121 edges, covering 93% of differentially expressed proteins from both previous studies and this study. The network suggested that proteomic changes of SRB in response to Hg occurred globally, including microbial metabolism in diverse environments, carbon metabolism, nucleic acid metabolism and translation, nucleic acid repair, transport systems, nitrogen metabolism, and methyltransferase activity, partial of which could cover the known knowledge. Antibiotic resistance was the original response revealed by this network, providing insights into of Hg biotransformation mechanisms. This study firstly provided the foundational network for a comprehensive understanding of SRB's responses to Hg, convenient for exploration of potential targets for Hg biotransformation. Furthermore, the network indicated that Hg enhances the metabolic activities and modification pathways of SRB to maintain cellular activities, shedding light on the influences of Hg on the carbon, nitrogen, and sulfur cycles at the cellular level.
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Affiliation(s)
- Hongzhe Dong
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Sino-Danish College, University of Chinese Academy of Sciences, Beijing, 100049, China; Sino-Danish Centre for Education and Research, Beijing, 100049, China
| | - Yuchuan Wang
- Hebei Key Laboratory for Chronic Diseases, School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, Hebei, 063210, China
| | - Tingting Zhi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Hua Guo
- School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
| | - Yingying Guo
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Lihong Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Yongguang Yin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
| | - Jianbo Shi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; School of Environment and Health, Jianghan University, Wuhan, 430056, China
| | - Bin He
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
| | - Ligang Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Sino-Danish College, University of Chinese Academy of Sciences, Beijing, 100049, China; Sino-Danish Centre for Education and Research, Beijing, 100049, China; School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China.
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310024, China
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4
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Peng X, Yang Y, Yang S, Li L, Song L. Recent advance of microbial mercury methylation in the environment. Appl Microbiol Biotechnol 2024; 108:235. [PMID: 38407657 PMCID: PMC10896945 DOI: 10.1007/s00253-023-12967-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 12/02/2023] [Accepted: 12/13/2023] [Indexed: 02/27/2024]
Abstract
Methylmercury formation is mainly driven by microbial-mediated process. The mechanism of microbial mercury methylation has become a crucial research topic for understanding methylation in the environment. Pioneering studies of microbial mercury methylation are focusing on functional strain isolation, microbial community composition characterization, and mechanism elucidation in various environments. Therefore, the functional genes of microbial mercury methylation, global isolations of Hg methylation strains, and their methylation potential were systematically analyzed, and methylators in typical environments were extensively reviewed. The main drivers (key physicochemical factors and microbiota) of microbial mercury methylation were summarized and discussed. Though significant progress on the mechanism of the Hg microbial methylation has been explored in recent decade, it is still limited in several aspects, including (1) molecular biology techniques for identifying methylators; (2) characterization methods for mercury methylation potential; and (3) complex environmental properties (environmental factors, complex communities, etc.). Accordingly, strategies for studying the Hg microbial methylation mechanism were proposed. These strategies include the following: (1) the development of new molecular biology methods to characterize methylation potential; (2) treating the environment as a micro-ecosystem and studying them from a holistic perspective to clearly understand mercury methylation; (3) a more reasonable and sensitive inhibition test needs to be considered. KEY POINTS: • Global Hg microbial methylation is phylogenetically and functionally discussed. • The main drivers of microbial methylation are compared in various condition. • Future study of Hg microbial methylation is proposed.
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Affiliation(s)
- Xuya Peng
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Yan Yang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Shu Yang
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China.
- Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China.
| | - Lei Li
- Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, No. 174, Shapingba Street, Chongqing, 400045, China
| | - Liyan Song
- School of resources and environmental engineering, Anhui University, No 111 Jiulong Road, Economic and Technology Development Zone, Hefei, 230601, People's Republic of China.
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Guo P, Rennenberg H, Du H, Wang T, Gao L, Flemetakis E, Hänsch R, Ma M, Wang D. Bacterial assemblages imply methylmercury production at the rice-soil system. ENVIRONMENT INTERNATIONAL 2023; 178:108066. [PMID: 37399771 DOI: 10.1016/j.envint.2023.108066] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/03/2023] [Accepted: 06/24/2023] [Indexed: 07/05/2023]
Abstract
The plant microbiota can affect plant health and fitness by promoting methylmercury (MeHg) production in paddy soil. Although most well-known mercury (Hg) methylators are observed in the soil, it remains unclear how rice rhizosphere assemblages alter MeHg production. Here, we used network analyses of microbial diversity to identify bulk soil (BS), rhizosphere (RS) and root bacterial networks during rice development at Hg gradients. Hg gradients greatly impacted the niche-sharing of taxa significantly relating to MeHg/THg, while plant development had little effect. In RS networks, Hg gradients increased the proportion of MeHg-related nodes in total nodes from 37.88% to 45.76%, but plant development enhanced from 48.59% to 50.41%. The module hub and connector in RS networks included taxa positively (Nitrososphaeracea, Vicinamibacteraceae and Oxalobacteraceae) and negatively (Gracilibacteraceae) correlating with MeHg/THg at the blooming stage. In BS networks, Deinococcaceae and Paludibacteraceae were positively related to MeHg/THg, and constituted the connector at the reviving stage and the module hub at the blooming stage. Soil with an Hg concentration of 30 mg kg-1 increased the complexity and connectivity of root microbial networks, although microbial community structure in roots was less affected by Hg gradients and plant development. As most frequent connector in root microbial networks, Desulfovibrionaceae did not significantly correlate with MeHg/THg, but was likely to play an important role in the response to Hg stress.
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Affiliation(s)
- Pan Guo
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, China
| | - Heinz Rennenberg
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, China
| | - Hongxia Du
- Chongqing Key Laboratory of Bio-resource for Bioenergy, College of Resources and Environment, Southwest University, Chongqing, China
| | - Tao Wang
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, China
| | - Lan Gao
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, China
| | - Emmanouil Flemetakis
- Laboratory of Molecular Biology, Department of Biotechnology, Agricultural University of Athens, 11855 Athens, Greece
| | - Robert Hänsch
- Institute for Plant Biology, Technische Universität Braunschweig, Humboldtstraße 1, D-38106 Braunschweig, Germany
| | - Ming Ma
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, China; Chongqing Key Laboratory of Bio-resource for Bioenergy, College of Resources and Environment, Southwest University, Chongqing, China.
| | - Dingyong Wang
- Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Chongqing, China
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Li Y, Dai SS, Zhao J, Hu ZC, Liu Q, Feng J, Huang Q, Gao Y, Liu YR. Amendments of nitrogen and sulfur mitigate carbon-promoting effect on microbial mercury methylation in paddy soils. JOURNAL OF HAZARDOUS MATERIALS 2023; 448:130983. [PMID: 36860084 DOI: 10.1016/j.jhazmat.2023.130983] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/05/2023] [Accepted: 02/07/2023] [Indexed: 06/18/2023]
Abstract
The imbalance of nutrient elements in paddy soil could affect biogeochemical processes; however, how the key elements input influence microbially-driven conversion of mercury (Hg) to neurotoxic methylmercury (MeHg) remains virtually unknown. Herein, we conducted a series of microcosm experiments to explore the effects of certain species of carbon (C), nitrogen (N) and sulfur (S) on microbial MeHg production in two typical paddy soils (yellow and black soil). Results showed that the addition of C alone into the soils increased MeHg production approximately 2-13 times in the yellow and black soils; while the combined addition of N and C mitigated the C- promoting effect significantly. Added S also had a buffering effect on C-facilitated MeHg production in the yellow soil despite the extent being lower than that of N addition, whereas this effect was not obvious for the black soil. MeHg production was positively correlated with the abundance of Deltaproteobactera-hgcA in both soils, and the changes in MeHg production were related to the shifts of Hg methylating community resulting from C, N, and S imbalance. We further found that the changes in the proportions of dominant Hg methylators such as Geobacter and some unclassified groups could contribute to the variations in MeHg production under different treatments. Moreover, the enhanced microbial syntrophy with adding N and S might contribute to the reduced C-promoting effect on MeHg production. This study has important implications for better understanding of microbes-driven Hg conversion in paddies and wetlands with nutrient elements input.
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Affiliation(s)
- Yunyun Li
- Fujian Provincial Key Laboratory of Ecology-Toxicological Effects & Control for Emerging Contaminants, College of Environmental and Biological Engineering, Putian University, Putian 351100, China
| | - Shu-Shen Dai
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Jiating Zhao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Department of Environmental Science, Zhejiang University, Hangzhou 310058, China.
| | - Zhi-Cheng Hu
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Qin Liu
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Jiao Feng
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Qiaoyun Huang
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuxi Gao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Yu-Rong Liu
- State Key Laboratory of Agricultural Microbiology and College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China.
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Cardona GI, Escobar MC, Acosta-González A, Marín P, Marqués S. Highly mercury-resistant strains from different Colombian Amazon ecosystems affected by artisanal gold mining activities. Appl Microbiol Biotechnol 2022; 106:2775-2793. [PMID: 35344092 PMCID: PMC8990959 DOI: 10.1007/s00253-022-11860-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 01/28/2022] [Accepted: 02/27/2022] [Indexed: 02/07/2023]
Abstract
Two sites of the Colombian Amazon region with different levels of human intervention and mercury pollution were selected for the collection of samples of river and lake water, sediments, and associated forest soils. The Tarapacá region, affected mainly by barrage mining, showed low mercury concentrations, whilst in the Taraira region, affected by underground mining, there were several points with high mercury pollution levels. A collection of 72 bacterial and 10 yeast strains with different levels of mercury resistance was isolated and characterized. Most of the highly resistant bacterial strains (MIC > 40 mg L−1 HgCl2) were isolated from soil and sediment samples and belonged to either Pseudomonas (60%) or Bacillus (20%). Most of highly resistant bacterial strains were positive for the presence of the merA gene, suggesting an active mercury resistance mechanism. This was confirmed in the two most resistant strains, Pseudomonas sp. TP30 and Burkholderia contaminans TR100 (MIC = 64 and 71 mg L−1 HgCl2, respectively), which in the presence of increasing mercury concentrations expressed the merA gene at increasing levels, concomitant with a significant mercury reduction activity. Analysis of the MerA sequences present in the different isolates suggested a high gene conservation within the taxonomic groups but also several horizontal gene transfer events between taxonomically distant genera. We also observed a positive correspondence between the presence of the merA gene and the number of antibiotics to which the strains were resistant to. The most resistant strains are good candidates for future applications in the bioremediation of mercury-contaminated sites in the Amazon. Key points • Amazon sediments affected by underground gold mining have higher Hg levels. • Highly Hg-resistant isolates belonged to Pseudomonas and Bacillus genera. • TR100 and TP30 strains showed remediation potential to be used in the Amazon region.
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Affiliation(s)
- Gladys Inés Cardona
- Instituto Amazónico de Investigaciones Científicas SINCHI, 110321, Bogotá, Colombia.
| | - María Camila Escobar
- Instituto Amazónico de Investigaciones Científicas SINCHI, 110321, Bogotá, Colombia
| | | | - Patricia Marín
- Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Environmental Protection, Granada, Spain
| | - Silvia Marqués
- Consejo Superior de Investigaciones Científicas, Estación Experimental del Zaidín, Department of Environmental Protection, Granada, Spain
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Strickman RJ, Larson S, Huang H, Kakouros E, Marvin-DiPasquale M, Mitchell CPJ, Neumann RB. The relative importance of mercury methylation and demethylation in rice paddy soil varies depending on the presence of rice plants. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2022; 230:113143. [PMID: 34998262 DOI: 10.1016/j.ecoenv.2021.113143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 12/26/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
Neurotoxic methylmercury (MeHg) accumulates in rice grain from paddy soil, where its concentration is controlled by microbial mercury methylation and demethylation. Both up- and down-regulation of methylation is known to occur in the presence of rice plants in comparison to non-vegetated paddy soils; the influence of rice plant presence/absence on demethylation is unknown. To assess the concurrent influence of rice plant presence/absence on methylation and demethylation, and to determine which process was more dominant in controlling soil MeHg concentrations, we maintained six rhizoboxes of paddy soil with and without rice plants. At the peak of plant growth, we simultaneously measured ambient MeHg, ambient inorganic mercury (IHg), and potential rate constants of methylation and demethylation (Kmeth and Kdemeth) in soil using stable isotope tracers and ID-GC-ICPMS. We also measured organic matter content, elemental S, and water-extractable sulfate. We found MeHg concentrations were differentially controlled by MeHg production and degradation processes, depending on whether plants were present. In non-vegetated boxes, MeHg concentration was controlled by Kmeth, as evidenced by a strong and positive correlation, while Kdemeth had no relation to MeHg concentration. These results indicate methylation was the dominant driver of MeHg concentration in non-vegetated soil. In vegetated boxes, Kdemeth strongly and negatively predicted MeHg concentration, indicating that demethylation was the dominant control in soil with plants. MeHg concentration, Kmeth, and % MeHg all had significantly less variance in vegetated than in non-vegetated soils due to a consistent elimination of greater values. This pattern suggests that reduced MeHg production capacity was a secondary control on MeHg concentrations in vegetated soils. We observed no difference in the magnitude or variance of Kdemeth between treatments, suggesting that demethylation was robust to soil chemical conditions influenced by the plant, perhaps because of a wider taxonomic diversity of demethylators. Our results suggest that methylation and demethylation processes could both be leveraged to alter MeHg concentrations in rice paddy soil.
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Affiliation(s)
- R J Strickman
- Department of Civil and Environmental Engineering, University of Washington, Seattle, USA.
| | - S Larson
- Department of Civil and Environmental Engineering, University of Washington, Seattle, USA
| | - H Huang
- University of Toronto Scarborough, Ontario, Canada
| | - E Kakouros
- US Geological Survey, Menlo Park, Palo Alto, CA, USA
| | | | | | - R B Neumann
- Department of Civil and Environmental Engineering, University of Washington, Seattle, USA
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9
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Du H, Guo P, Wang T, Ma M, Wang D. Significant bioaccumulation and biotransformation of methyl mercury by organisms in rice paddy ecosystems: A potential health risk to humans. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 273:116431. [PMID: 33453697 DOI: 10.1016/j.envpol.2021.116431] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 12/13/2020] [Accepted: 12/31/2020] [Indexed: 06/12/2023]
Abstract
Rice has been confirmed as one of the principal intake pathways for methylmercury (MeHg) in human, however, the impact of edible organisms, such as snails, loaches and eels, living in the rice-based ecosystem to the overall MeHg intake has been overlooked. Here, we conducted a cross-sectional ecological study, and the results showed that bioaccumulation of MeHg in these edible organisms was significantly higher than in paddy soils and rice roots (p < 0.001), even though rice roots and grains have significantly higher total Hg (THg) (p < 0.001). The MeHg/THg ratios were consistently and significantly higher in those edible organisms than in rice grains, suggesting a potential elevated MeHg exposure risk through consumption. Based on results of bioaccumulation factors (BAFs) for MeHg, it was clear that MeHg was bioaccumulated and biotransformed from paddy soils to earthworms and then to eels, as well as from paddy soils to snails and then to eels and loaches, potentially indicating that the consumption of eels and loaches was absolutely pernicious to people regularly feeding on them. Overall, MeHg was biomagnified along the food chain of the paddy ecosystem from soil to the organisms, and it was of potential higher risks for local residents to eat them, especially eels and loaches. Therefore, it is intensely indispensable for people fond of such diets to attenuate their consumption of rice, eels and loaches, thus mitigating their MeHg exposure risks.
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Affiliation(s)
- Hongxia Du
- Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Pan Guo
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Tao Wang
- Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Ming Ma
- Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China; Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing, 400715, China.
| | - Dingyong Wang
- Chongqing Key Laboratory of Bio-resource for Bioenergy, Southwest University, College of Resources and Environment, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, College of Resources and Environment, Southwest University, Chongqing, 400715, China
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10
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Wu Q, Hu H, Meng B, Wang B, Poulain AJ, Zhang H, Liu J, Bravo AG, Bishop K, Bertilsson S, Feng X. Methanogenesis Is an Important Process in Controlling MeHg Concentration in Rice Paddy Soils Affected by Mining Activities. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13517-13526. [PMID: 33084323 DOI: 10.1021/acs.est.0c00268] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Rice paddies are agricultural sites of special concern because the potent toxin methylmercury (MeHg), produced in rice paddy soils, accumulates in rice grains. MeHg cycling is mostly controlled by microbes but their importance in MeHg production and degradation in paddy soils and across a Hg concentration gradient remains unclear. Here we used surface and rhizosphere soil samples in a series of incubation experiments in combination with stable isotope tracers to investigate the relative importance of different microbial groups on MeHg production and degradation across a Hg contamination gradient. We showed that sulfate reduction was the main driver of MeHg formation and concentration at control sites, and that methanogenesis had an important and complex role in MeHg cycling as Hg concentrations increased. The inhibition of methanogenesis at the mining sites led to an increase in MeHg production up to 16.6-fold and a decrease in MeHg degradation by up to 77%, suggesting that methanogenesis is associated with MeHg degradation as Hg concentrations increased. This study broadens our understanding of the roles of microbes in MeHg cycling and highlights methanogenesis as a key control of MeHg concentrations in rice paddies, offering the potential for mitigation of Hg contamination and for the safe production of rice in Hg-contaminated areas.
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Affiliation(s)
- Qingqing Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Haiyan Hu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala SE-75007, Sweden
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
| | - Baolin Wang
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala SE-75007, Sweden
| | - Alexandre J Poulain
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Hua Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
| | - Jinling Liu
- School of Earth Sciences, China University of Geosciences, Wuhan 430074, P. R. China
| | - Andrea G Bravo
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM-CSIC), Pg Marítim de la Barceloneta 37-49, Barcelona E08003, Catalunya, Spain
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala SE-75007, Sweden
| | - Stefan Bertilsson
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala SE-75007, Sweden
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, P. R. China
- Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian 710061, P. R. China
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11
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Bishop K, Shanley JB, Riscassi A, de Wit HA, Eklöf K, Meng B, Mitchell C, Osterwalder S, Schuster PF, Webster J, Zhu W. Recent advances in understanding and measurement of mercury in the environment: Terrestrial Hg cycling. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 721:137647. [PMID: 32197286 DOI: 10.1016/j.scitotenv.2020.137647] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Revised: 02/23/2020] [Accepted: 02/28/2020] [Indexed: 06/10/2023]
Abstract
This review documents recent advances in terrestrial mercury cycling. Terrestrial mercury (Hg) research has matured in some areas, and is developing rapidly in others. We summarize the state of the science circa 2010 as a starting point, and then present the advances during the last decade in three areas: land use, sulfate deposition, and climate change. The advances are presented in the framework of three Hg "gateways" to the terrestrial environment: inputs from the atmosphere, uptake in food, and runoff with surface water. Among the most notable advances: These and other advances reported here are of value in evaluating the effectiveness of the Minamata Convention on reducing environmental Hg exposure to humans and wildlife.
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Affiliation(s)
- Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, 75007 Uppsala, Sweden.
| | | | - Ami Riscassi
- Department of Environmental Sciences, University of Virginia, P.O. Box 400123, Charlottesville, VA 22904-4123, USA.
| | - Heleen A de Wit
- Norwegian Institute for Water Research, Gaustadalléen 21, NO-0349, Norway.
| | - Karin Eklöf
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, 75007 Uppsala, Sweden.
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
| | - Carl Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
| | - Stefan Osterwalder
- Institut des Géosciences de l'Environnement, Université Grenoble Alpes, CNRS, IRD, Grenoble 18 INP, 38000 Grenoble, France.
| | - Paul F Schuster
- U.S. Geological Survey, 3215 Marine Street, Suite E-127, Boulder, CO 80303-1066, USA.
| | - Jackson Webster
- Department of Civil Engineering, California State University, 400 W. 1st Street, 21 95929-0930 Chico, CA, USA.
| | - Wei Zhu
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
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12
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Zhao L, Meng B, Feng X. Mercury methylation in rice paddy and accumulation in rice plant: A review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 195:110462. [PMID: 32179234 DOI: 10.1016/j.ecoenv.2020.110462] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/07/2020] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
The bioavailability and toxicity of mercury (Hg) are dependent on its chemical speciation, in which methylmercury (MeHg) is the most toxic compound. Inorganic Hg can be transformed into MeHg in anaerobic conditions. Subsequent accumulation and biomagnification in the food chain pose a potential threat to human health. Previous studies have confirmed that paddy soil is an important site for MeHg production, and rice fields are an important source of MeHg in terrestrial ecosystems. Rice (Oryza sativa L.) is recently confirmed as a potential bioaccumulator plant of MeHg. Understanding the behaviour of Hg in rice paddies is important, particularly the mechanisms involved in Hg sources, uptake, toxicity, detoxification, and accumulation in crops. This review highlights the issue of MeHg-contaminated rice, and presents the current understanding of the Hg cycling in the rice paddy ecosystem, including the mechanism and processes of Hg species accumulation in rice plants and Hg methylation/demethylation processes in rice paddies and the primary controlling factors. The review also identified various research gaps in previous studies and proposes future research objectives to reduce the impact of Hg-contamination in rice crops.
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Affiliation(s)
- Lei Zhao
- School of Management Science, Guizhou University of Finance and Economics, Guiyang, 550025, PR China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, PR China.
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13
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Li Y, He X, Wang Y, Guan J, Guo J, Xu B, Chen YH, Wang G. Organic fertilizer amendment increases methylmercury accumulation in rice plants. CHEMOSPHERE 2020; 249:126166. [PMID: 32062560 DOI: 10.1016/j.chemosphere.2020.126166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/05/2020] [Accepted: 02/08/2020] [Indexed: 06/10/2023]
Abstract
Rice grains are a methylmercury (MeHg) intake route for humans, especially in certain mercury (Hg)-contaminated areas. For rice plant growth, animal manure is commonly used as an organic fertilizer; however, its role in the formation of MeHg in paddy soils remains poorly understood. The aims of this study were thus to explore 1) the effect of chicken manure (CH) and cow manure (CO) addition on the production of soil MeHg and the accumulation of MeHg in rice plants and 2) the mechanism by which CH and CO addition affect the bioaccumulation of MeHg in grains. A pot experiment with different levels of CH and CO was carried out with newly deposited Hg-contaminated paddy soil. Two microcosm experiments were performed to explore the associated mechanisms. The results of the pot experiment showed that 0.1-1% CH and CO addition promoted the biomass of rice plants by 10-23% and increased the soil MeHg concentration by 34-143%, which exhibited a significant positive correlation with brown rice MeHg content. Organic fertilizer addition significantly increased MeHg bioaccumulation in rice plants and the ratio of MeHg to total Hg (THg) in brown rice. Organic fertilizer also increased the abundance of microbial methylators. The results of the microcosm experiments showed that organic fertilizer addition enhanced dissolved THg concentrations in soil and consequently increased the soil MeHg concentration. These results suggested that applying organic fertilizer to newly deposited Hg-contaminated soil may increase MeHg accumulation in grains due to enhanced Hg release and microbial methylator activity, leading to environmental health concerns.
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Affiliation(s)
- Yunyun Li
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Xucheng He
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Yongjie Wang
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, PR China
| | - Jiaxun Guan
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Jingxia Guo
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Bo Xu
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Yan-Hui Chen
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Guo Wang
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China.
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14
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Du H, Sun T, Wang D, Ming M. Bacterial and archaeal compositions and influencing factors in soils under different submergence time in a mercury-sensitive reservoir. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 191:110155. [PMID: 31972452 DOI: 10.1016/j.ecoenv.2019.110155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 12/27/2019] [Accepted: 12/30/2019] [Indexed: 06/10/2023]
Abstract
Soils in the water-level-fluctuating zone (WLFZ) of Three Gorges Reservoir (TGR) inundated by water for different periods of time are confirmed to have disparate characteristics to mercury (Hg), and thus it is of great significance to further investigate microbial compositions and influencing factors. The objective of this study was to compare bacterial and archaeal richness, α-diversities and compositions, as well as affecting variables, especially Hg concentrations, among soils under different submergence time-SI (inundated soil), SS (semi-inundated soil), SN(non-inundated soil) and SSe (sediment)-based on high throughput sequencing. Results showed that sediment had significantly higher bacterial and archaeal richness and α-diversities than the other soil types. Anaerolinea and Aeromonas, as well as Altiarchaeales, Nitrosoarchaeum, and Methanosarta were dominant in SSe, while sharply decreasing in the other soil types, with significant difference among groups. An unclassified genus in SCG critically predominating in SI, SS and SN, drastically reduced in SSe, with extremely significant difference among groups. Bathyarchaeota and Nitrososphaera, both dominating in SSe, decreased dramatically and almost vanished in SI and SN. All the variables except pH posed a significant positive effect on bacterial and archaeal compositions in SSe, while opposite effect in the other three soil types. MeHg and THg concentrations had relatively weaker effects on microbial compositions comparing to variables like NH4+, CEC, OM and SO42+.
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Affiliation(s)
- Hongxia Du
- College of Resources and Environment, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Bioresource for Bioenergy, Southwest University, Chongqing, 400715, China
| | - Tao Sun
- College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing, 400715, China
| | - Ma Ming
- College of Resources and Environment, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Bioresource for Bioenergy, Southwest University, Chongqing, 400715, China.
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15
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Yuan K, Chen X, Chen P, Huang Y, Jiang J, Luan T, Chen B, Wang X. Mercury methylation-related microbes and genes in the sediments of the Pearl River Estuary and the South China Sea. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 185:109722. [PMID: 31577991 DOI: 10.1016/j.ecoenv.2019.109722] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 09/14/2019] [Accepted: 09/23/2019] [Indexed: 05/16/2023]
Abstract
Methylmercury (MeHg) is a toxicant that mainly originates from in situ microbial methylation of inorganic mercury (Hg) in the environment and poses a severe health risk to the public. However, the characteristics of the Hg-methylating microbial community and its relationship with MeHg production in various environments remain to be understood. In the present study, Hg-methylating microbial communities and genes (hgcAB cluster) in the sediments of the Pearl River (PR), Pearl River Estuary (PRE) and South China Sea (SCS) were investigated at a large spatial scale using high-throughput sequencing-based approaches. The results showed that sulfur-reducing bacteria (SRB) and iron-reducing bacteria (IRB) were consistently the dominant microbial strains responsible for the methylation of inorganic Hg in all three regions investigated. The abundance and diversity of Hg-methylating communities and genes were both found to be higher in the PR sediments compared to that in the PRE and SCS sediments, and in good agreement with the spatial distribution of MeHg. Furthermore, a significant correlation was observed between the MeHg concentration and the abundance of both hgcA and hgcB genes in the sediments of the PR, PRE and SCS regions. Overall, the present study suggested that there was the presence of a close link between MeHg and Hg-methylating communities or genes in the ambient aquatic environment, which could be used to reflect the potential of in situ MeHg production.
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Affiliation(s)
- Ke Yuan
- Southern Marine Science and Engineering Guangdong Laboratory, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
| | - Xin Chen
- Southern Marine Science and Engineering Guangdong Laboratory, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
| | - Ping Chen
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Yongshun Huang
- Guangdong Provincial Hospital for Occupational Diseases Prevention and Treatment, Guangzhou, 510300, China
| | - Jie Jiang
- Shenzhen Center for Disease Control and Prevention, Shenzhen, 518055, China
| | - Tiangang Luan
- Southern Marine Science and Engineering Guangdong Laboratory, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China; State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Baowei Chen
- Southern Marine Science and Engineering Guangdong Laboratory, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China.
| | - Xiaowei Wang
- Southern Marine Science and Engineering Guangdong Laboratory, School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China.
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16
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Li Y, Hu W, Zhao J, Chen Q, Wang W, Li B, Li YF. Selenium decreases methylmercury and increases nutritional elements in rice growing in mercury-contaminated farmland. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 182:109447. [PMID: 31325809 DOI: 10.1016/j.ecoenv.2019.109447] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/04/2019] [Accepted: 07/13/2019] [Indexed: 05/09/2023]
Abstract
Methylmercury (MeHg) in rice grains grown in Hg-contaminated areas has raised environmental health concerns. Pot experiments found that selenium (Se) could reduce MeHg levels in rice grains. However, relatively high levels of Se (up to 6 mg/kg) were applied in these pot experiments, which may have adverse effects on the soil ecology due to the toxicity of Se. The aims of this work were thus to study 1) the effect of low levels of Se on the accumulation and distribution of Hg, especially MeHg, in rice plants grown in a real Hg-contaminated paddy field and 2) the effect of Se treatment on Se and other nutritional elements (e.g., Cu, Fe, Zn) in grains. A field study amended with different levels of Se was carried out in Hg-contaminated paddy soil in Qingzhen, Guizhou, China. The levels of MeHg and total Hg were studied using cold vapor atomic fluorescence spectrometry (CVAFS) and inductively coupled plasma mass spectrometry (ICP-MS). The distribution and relative quantification of elements in grains were examined by synchrotron radiation X-ray fluorescence analysis (SR-XRF). This field study showed that low levels of Se (0.5 μg/mL, corresponding to 0.15 mg Se/kg soils) could significantly reduce total Hg and MeHg in rice tissues. Se treatment also reduced Hg distribution in the embryo and endosperm and increased the levels of Fe, Cu, Zn and Se in grains and especially embryos. This field study implied that treatment with an appropriate level of Se is an effective approach to not only decrease the level of MeHg but to also increase the levels of nutritional elements such as Fe, Cu, Zn and Se in rice grains, which could bring beneficial effects for rice-dependent residents living in Hg-contaminated areas.
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Affiliation(s)
- Yunyun Li
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China; CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, And HKU-IHEP Joint Laboratory on Metallomics, And State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Wenjun Hu
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Jiating Zhao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, And HKU-IHEP Joint Laboratory on Metallomics, And State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Qimin Chen
- College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China
| | - Wei Wang
- College of Engineering, China Agricultural University, Beijing, 100083, China.
| | - Bai Li
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, And HKU-IHEP Joint Laboratory on Metallomics, And State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
| | - Yu-Feng Li
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, And HKU-IHEP Joint Laboratory on Metallomics, And State Environmental Protection Engineering Center for Mercury Pollution Prevention and Control, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
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17
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Liu J, Wang J, Ning Y, Yang S, Wang P, Shaheen SM, Feng X, Rinklebe J. Methylmercury production in a paddy soil and its uptake by rice plants as affected by different geochemical mercury pools. ENVIRONMENT INTERNATIONAL 2019; 129:461-469. [PMID: 31154148 DOI: 10.1016/j.envint.2019.04.068] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 04/15/2019] [Accepted: 04/28/2019] [Indexed: 06/09/2023]
Abstract
The formation of neurotoxic methylmercury (MeHg) in paddy fields and its accumulation by rice plants is of high environmental concern. The contribution of different geochemical mercury (Hg) pools in paddy soils to MeHg production and its accumulation by rice seedlings is not well-studied up to now. Therefore, we investigated the impact of different inorganic Hg forms, including HgCl2, nano-particulated HgS (nano-HgS), Hg bound with dissolved organic matter (Hg-DOM), β-HgS, and α-HgS, at levels of 5 mg Hg/kg soil and 50 mg Hg/kg soil, on the production of MeHg in the soil during rice growing season. Further, we studied the uptake of MeHg by the roots, stalks, leaves, and grains of rice in the tillering, panicle formation, and ripening growth stages, and compared these treatments to a non-polluted soil (control). MeHg contents in HgCl2 polluted soil were the highest, and were 13.5 times and 36.1 times higher than control in 5 and 50 mg/kg Hg treatments, respectively. MeHg contents in α-HgS, β-HgS, nano-HgS, and Hg-DOM polluted soil were 3.9, 2.6, 2.4, and 1.7 times, and 4.4, 15.1, 6.7, and 10.9 times higher than control in 5 and 50 mg/kg Hg treatments, respectively, suggesting the mobilization and methylation of these Hg complexes. The ratio of MeHg to total Hg in the pore water (indication of methylation potential) in HgCl2 and β-HgS treatments were higher than in Hg-DOM, α-HgS, and nano-HgS treatments. HgCl2 treatment resulted in significantly higher MeHg contents in the root, stalk, leaf, and brown rice than nano-HgS, Hg-DOM, β-HgS, and α-HgS treatments both in 5 and 50 mg/kg Hg polluted soils. Rice grain in HgCl2 treatment showed a potential hazard to human health, as indicated by high health risk index (HRI > 1) of MeHg. Current results improve our understanding of MeHg production in soil polluted with different Hg forms, and the assessment of human health risks from consumption of MeHg-laden rice grain at Hg polluted sites with different Hg forms in soils.
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Affiliation(s)
- Jinling Liu
- School of Earth Sciences, China University of Geosciences, Wuhan 430074, China.
| | - Jianxu Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China.
| | - Yongqiang Ning
- School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Shaochen Yang
- School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Pengcong Wang
- School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Sabry M Shaheen
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; King Abdulaziz University, Faculty of Meteorology, Environment, and Arid Land Agriculture, Department of Arid Land Agriculture, 21589 Jeddah, Saudi Arabia; University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33516 Kafr El-Sheikh, Egypt.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Jörg Rinklebe
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; University of Sejong, Department of Environment, Energy and Geoinformatics, 98 Gunja-Dong, Guangjin-Gu, Seoul, South Korea.
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18
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Wang R, Xu S, Jiang C, Zhang Y, Bai N, Zhuang G, Bai Z, Zhuang X. Impacts of Human Activities on the Composition and Abundance of Sulfate-Reducing and Sulfur-Oxidizing Microorganisms in Polluted River Sediments. Front Microbiol 2019; 10:231. [PMID: 30809217 PMCID: PMC6379298 DOI: 10.3389/fmicb.2019.00231] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 01/28/2019] [Indexed: 11/30/2022] Open
Abstract
Water system degradation has a severe impact on daily life, especially in developing countries. However, microbial changes associated with this degradation, especially changes in microbes related to sulfur (S) cycling, are poorly understood. In this study, the abundance, structure, and diversity of sulfate-reducing microorganisms (SRM) and sulfur-oxidizing microorganisms (SOM) in the sediments from the Ziya River Basin, which is polluted by various human interventions (urban and agricultural activities), were investigated. Quantitative real-time PCR showed that the S cycling-related (SCR) genes (dsrB and soxB) were significantly elevated, reaching 2.60 × 107 and 1.81 × 108 copies per gram of dry sediment, respectively, in the region polluted by human urban activities (RU), and the ratio of dsrB to soxB abundance was significantly elevated in the region polluted by human agricultural activities (RA) compared with those in the protected wildlife reserve (RP), indicating that the mechanisms underlying water system degradation differ between RU and RA. Based on a 16S rRNA gene analysis, human interventions had substantial effects on microbial communities, particularly for microbes involved in S cycling. Some SCR genera (i.e., Desulfatiglans and Geothermobacter) were enriched in the sediments from both RA and RU, while others (i.e., Desulfofustis and Desulfonatronobacter) were only enriched in the sediments from RA. A redundancy analysis indicated that NH4+-N and total organic carbon significantly influenced the abundance of SRM and SOM, and sulfate significantly influenced only the abundance of SRM. A network analysis showed high correlation between SCR microorganisms and other microbial groups for both RU and RA, including those involved in carbon and metal cycling. These findings indicated the different effects of different human interventions on the microbial community composition and water quality degradation.
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Affiliation(s)
- Rui Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Shengjun Xu
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Cancan Jiang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Yang Zhang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Na Bai
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,School of Safety and Environmental Engineering, Capital University of Economics and Business, Beijing, China
| | - Guoqiang Zhuang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Zhihui Bai
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Xuliang Zhuang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
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Zhao JY, Ye ZH, Zhong H. Rice root exudates affect microbial methylmercury production in paddy soils. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 242:1921-1929. [PMID: 30072222 DOI: 10.1016/j.envpol.2018.07.072] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 07/16/2018] [Accepted: 07/16/2018] [Indexed: 06/08/2023]
Abstract
Microbial methylmercury (MeHg) production in contaminated soil-rice systems and its accumulation in rice pose health risks to consumers, especially those in Asia. However, the mechanism responsible for microbial MeHg production in paddy soils is far from clear. While previous studies examined the effect of soil and microbial factors on soil MeHg levels, in this work we explored the impact of rice cultivation itself on microbial MeHg production, focusing on the root exudate organic matter as a potential source of electron donors for microbial methylators. Effects of the cultivation of two rice cultivars, Heigu246 (H-rice) and Neiwuyou8015 (N-rice), on MeHg production in soils were therefore investigated in pot and batch incubation experiments. Soil MeHg levels measured in H-rice treatment during the heading and harvest stages were 18-49% higher than in the control and 23-108% higher than in N-rice treatment. Consequently, MeHg levels in grain, straw, and root were 38%, 81%, and 40% higher in H-rice than those in N-rice, which was mainly attributed to cultivar-specific MeHg production in soils. Results of the batch experiments suggested that root exudate organic matter could be responsible for MeHg production in soils during rice cultivation, by increasing the abundances of potential microbial methylators. For instance, root exudate organic matter increased copy numbers of Hg methylation genes (hgcA) in soils 4.1-fold. Furthermore, the 211% higher concentration of acetate (a key electron donor for microbial methylators) in the root exudate of H-rice could account for the higher MeHg production under H-rice than N-rice cultivation. Our results suggest that root exudate organic matter, especially acetate, as its key component, contributes to the elevated soil MeHg concentrations during rice cultivation. The proposed mechanism provides new insights into the elevated risk of MeHg production in contaminated soil-rice systems, as well as cultivar-specific MeHg bioaccumulation.
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Affiliation(s)
- Jia-Yin Zhao
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, PR China
| | - Zhi-Hong Ye
- State Key Laboratory for Bio-control and Guangdong Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510006, PR China
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, PR China; Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada.
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20
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Yang J, Takaoka M, Sano A, Matsuyama A, Yanase R. Vertical Distribution of Total Mercury and Mercury Methylation in a Landfill Site in Japan. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:ijerph15061252. [PMID: 29899229 PMCID: PMC6025181 DOI: 10.3390/ijerph15061252] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/05/2018] [Accepted: 06/08/2018] [Indexed: 11/25/2022]
Abstract
Mercury is a neurotoxin, with certain organic forms of the element being particularly harmful to humans. The Minamata Convention was adopted to reduce the intentional use and emission of mercury. Because mercury is an element, it cannot be decomposed. Mercury-containing products and mercury used for various processes will eventually enter the waste stream, and landfill sites will become a mercury sink. While landfill sites can be a source of mercury pollution, the behavior of mercury in solid waste within a landfill site is still not fully understood. The purpose of this study was to determine the depth profile of mercury, the levels of methyl mercury (MeHg), and the factors controlling methylation in an old landfill site that received waste for over 30 years. Three sampling cores were selected, and boring sampling was conducted to a maximum depth of 18 m, which reached the bottom layer of the landfill. Total mercury (THg) and MeHg were measured in the samples to determine the characteristics of mercury at different depths. Bacterial species were identified by 16S rRNA amplification and sequencing, because the methylation process is promoted by a series of genes. It was found that the THg concentration was 19–975 ng/g, with a geometric mean of 298 ng/g, which was slightly less than the 400 ng/g concentration recorded 30 years previously. In some samples, MeHg accounted for up to 15–20% of THg, which is far greater than the general level in soils and sediments, although the source of MeHg was unclear. The genetic data indicated that hgcA was present mostly in the upper and lower layers of the three cores, merA was almost as much as hgcA, while the level of merB was hundreds of times less than those of the other two genes. A significant correlation was found between THg and MeHg, as well as between MeHg and MeHg/THg. In addition, a negative correlation was found between THg and merA. The coexistence of the three genes indicated that both methylation and demethylation processes could occur, but the lack of merB was a barrier for demethylation.
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Affiliation(s)
- Jing Yang
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Masaki Takaoka
- Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
- Graduate School of Global Environmental Studies, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Akira Sano
- Graduate School of Global Environmental Studies, Kyoto University, C-kluster, Kyotodaigakukatsura, Nishikyo-ku, Kyoto 6158540, Japan.
| | - Akito Matsuyama
- National Institute for Minamata Disease, 4058-18 Hama, Minamata-City, Kumamoto 8670008, Japan.
| | - Ryuji Yanase
- Environmental Protection Center, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 8140180, Japan.
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21
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Yin D, He T, Yin R, Zeng L. Effects of soil properties on production and bioaccumulation of methylmercury in rice paddies at a mercury mining area, China. J Environ Sci (China) 2018; 68:194-205. [PMID: 29908739 DOI: 10.1016/j.jes.2018.04.028] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Revised: 04/30/2018] [Accepted: 04/30/2018] [Indexed: 06/08/2023]
Abstract
Rice paddy soil is recognized as the hotspot of mercury (Hg) methylation, which is mainly a biotic process mediated by many abiotic factors. In this study, effects of key soil properties on the production and bioaccumulation of Hg and methylmercury (MeHg) in Hg-contaminated rice paddies were investigated. Rice and soil samples were collected from the active Hg smelting site and abandoned Hg mining sites (a total of 124 paddy fields) in the Wanshan Mercury Mine, China. Total Hg (THg) and MeHg in soils and rice grains, together with sulfur (S), selenium (Se), organic matter (OM), nitrogen (N), phosphorus (P), mineral compositions (e.g., SiO2, Al2O3 and Fe2O3) and pH in soils were quantified. The results showed that long-term Hg mining activities had resulted in THg and MeHg contaminations in soil-rice system. The newly-deposited atmospheric Hg was more readily methylated relative to the native Hg already in soils, which could be responsible for the elevated MeHg levels in soils and rice grains around the active artificial Hg smelting site. The MeHg concentrations in soils and rice grains showed a significantly negative relationship with soil N/Hg, S/Hg and OM/Hg ratio possibly due to the formation of low-bioavailability Hg-S(N)-OM complexes in rhizosphere. The Hg-Se antagonism undoubtedly occurred in soil-rice system, while its role in bioaccumulation of MeHg in the MeHg-contaminated rice paddies was minor. However, other soil properties showed less influence on the production and bioaccumulation of MeHg in rice paddies located at the Wanshan Mercury Mine zone.
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Affiliation(s)
- Deliang Yin
- The Key Laboratory of Karst Environment and Geohazard Prevention, Guizhou University, Guiyang 550003, China; College of Resources and Environments, Southwest University, Chongqing 400715, China
| | - Tianrong He
- The Key Laboratory of Karst Environment and Geohazard Prevention, Guizhou University, Guiyang 550003, China.
| | - Runsheng Yin
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China; Department of Civil and Environmental Engineering, Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Lingxia Zeng
- The Key Laboratory of Karst Environment and Geohazard Prevention, Guizhou University, Guiyang 550003, China
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22
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Jia Q, Zhu X, Hao Y, Yang Z, Wang Q, Fu H, Yu H. Mercury in soil, vegetable and human hair in a typical mining area in China: Implication for human exposure. J Environ Sci (China) 2018; 68:73-82. [PMID: 29908747 DOI: 10.1016/j.jes.2017.05.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/09/2017] [Accepted: 05/12/2017] [Indexed: 06/08/2023]
Abstract
Concentrations of total mercury (T-Hg) and methylmercury (MeHg) in soil, vegetables, and human hair were measured in a mercury mining area in central China. T-Hg and MeHg concentrations in soil ranged from 1.53 to 1054.97mg/kg and 0.88 to 46.52μg/kg, respectively. T-Hg concentrations was correlated with total organic carbon (TOC) content (R2=0.50, p<0.01) and pH values (R2=0.21, p<0.05). A significant linear relationship was observed between MeHg concentrations and the abundance of sulfate-reducing bacteria (SRB) (R2=0.39, p<0.05) in soil. Soil incubation experiments amended with specific microbial stimulants and inhibitors showed that Hg methylation was derived from SRB activity. T-Hg and MeHg concentrations in vegetables were 24.79-781.02μg/kg and 0.01-0.18μg/kg, respectively; levels in the edible parts were significantly higher than in the roots (T-Hg: p<0.05; MeHg: p<0.01). Hg species concentrations in rhizosphere soil were positively correlated to those in vegetables (p<0.01), indicating that soil was an important source of Hg in vegetables. Risk assessment indicated that the consumption of vegetables could result in higher probable daily intake (PDI) of T-Hg than the provisional tolerable daily intake (PTDI) for both adults and children. In contrast, the PDI of MeHg was lower than the reference dose. T-Hg and MeHg concentrations in hair samples ranged from 1.57 to 12.61mg/kg and 0.04 to 0.94mg/kg, respectively, and MeHg concentration in hair positively related to PDI of MeHg via vegetable consumption (R2=0.39, p<0.05), suggesting that vegetable may pose health risk to local residents.
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Affiliation(s)
- Qin Jia
- College of Water Sciences, Beijing Normal University, Beijing 100875, China; Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Xuemei Zhu
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Yaqiong Hao
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Ziliang Yang
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Qi Wang
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Haihui Fu
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Hongjin Yu
- Research Institute of Solid Waste Management, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
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Liu X, Ma A, Zhuang G, Zhuang X. Diversity of microbial communities potentially involved in mercury methylation in rice paddies surrounding typical mercury mining areas in China. Microbiologyopen 2018. [PMID: 29527815 PMCID: PMC6079176 DOI: 10.1002/mbo3.577] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Mercury can be a serious hazard to human health, especially in paddy soils surrounding mining areas. In this study, mercury (Hg)‐methylating microbes with the potential biomarker gene hgcA were obtained from 45 paddy soil samples in mercury mining areas in Fenghuang, Wanshan, and Xunyang. In different areas, the abundance of the hgcA gene was affected by different environmental factors, including organic matter, pH, total carbon content, total nitrogen content, and total mercury content. Phylogenetic analysis showed that hgcA microbes in paddy soils were potentially members of the phyla Proteobacteria, Euryarchaeota, Chloroflexi, and two unnamed groups. Canonical correspondence analysis showed that pH and organic matter impacted the hgcA gene diversity and the microbial community structures in paddy soils. The identification of Hg‐methylating microbes may be crucial for understanding mercury methylation/demethylation processes, which would be helpful in assessing the risk of methylmercury contamination in the food chain.
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Affiliation(s)
- Xin Liu
- University of Sciences and Technology of China, Hefei, China.,CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China
| | - Anzhou Ma
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Guoqiang Zhuang
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Xuliang Zhuang
- CAS, Research Center for Eco-Environmental Sciences, Key Laboratory of Environmental Biotechnology, Chinese Academy of Sciences, Beijing, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
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24
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Du H, Ma M, Sun T, Dai X, Yang C, Luo F, Wang D, Igarashi Y. Mercury-methylating genes dsrB and hgcA in soils/sediments of the Three Gorges Reservoir. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:5001-5011. [PMID: 28000068 DOI: 10.1007/s11356-016-8213-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/06/2016] [Indexed: 05/04/2023]
Abstract
Previous research found that the water-level fluctuating zone (WLFZ) of the Three Gorges Reservoir (TGR) was an Hg-sensitive area. However, little research has been conducted on the distribution of Hg-methylating microorganisms in this area. The goal of this research was to provide an initial description of the distribution of the dsrB (for sulfate-reducing bacteria) and hgcA (one gene confirmed for Hg methylation) genes. Different types of soil were selected to analyze the abundance of the dsrB and hgcA in different periods, in inundated soil (SI, ≤155 m, which becomes sediment during the wet period, SS) and in non-inundated soil (≥175 m, SN) from Shibao, a typical WLFZ of the TGR. A significant positive correlation was observed between dsrB and hgcA abundance and MeHg concentrations, suggesting that microorganisms with these genes contribute to Hg methylation. Principal component analysis (PCA) indicated that dsrB diversity was highest in SI, followed by SS; SS had the highest diversity of hcgA. Six phylogenetic trees were constructed and showed that more strains were present in SI than in SS. HgcA sequences in SS were confined to three evolutionarily distant clades, δ-Proteobacteria, a methanogen group, and a Clostridia group, which was relatively rare among most clades.
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Affiliation(s)
- Hongxia Du
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Research Center of Bioenergy and Bioremediation, Southwest University, Chongqing, 400715, China
| | - Ming Ma
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing, 400715, China
| | - Tao Sun
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing, 400715, China
| | - Xianzhu Dai
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Research Center of Bioenergy and Bioremediation, Southwest University, Chongqing, 400715, China
| | - Caiyun Yang
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Research Center of Bioenergy and Bioremediation, Southwest University, Chongqing, 400715, China
| | - Feng Luo
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China
- Research Center of Bioenergy and Bioremediation, Southwest University, Chongqing, 400715, China
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China.
- Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing, 400715, China.
| | - Yasuo Igarashi
- College of Resources and Environment, Southwest University, No. 2, Tiansheng Road, Beibei District, Chongqing, 400715, People's Republic of China.
- Research Center of Bioenergy and Bioremediation, Southwest University, Chongqing, 400715, China.
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25
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Zhao L, Qiu G, Anderson CWN, Meng B, Wang D, Shang L, Yan H, Feng X. Mercury methylation in rice paddies and its possible controlling factors in the Hg mining area, Guizhou province, Southwest China. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 215:1-9. [PMID: 27176759 DOI: 10.1016/j.envpol.2016.05.001] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/24/2016] [Accepted: 05/01/2016] [Indexed: 06/05/2023]
Abstract
Understanding mercury (Hg) methylation/demethylation processes and the factors controlling methylmercury (MeHg) production within the rice paddy ecosystem of Hg mining areas is critical to assess the risk of MeHg contamination in rice grain. Two typical Hg-contaminated mining sites, a current-day artisanal site (Gouxi) and an abandoned site (Wukeng), were chosen in this study. We qualified the in situ specific methylation/demethylation rate constants in rice paddy soil during a complete rice-growing season. Our results demonstrate that MeHg levels in rice paddy soil were a function of both methylation and demethylation processes and the net methylation potential in the rice paddy soil reflected the measured MeHg production at any time point. Sulfate stimulating the activity of sulfate-reducing bacteria was a potentially important metabolic pathway for Hg methylation in rice paddies. We suggest that bioavailable Hg derived from new atmospheric deposition appears to be the primary factor regulating net MeHg production in rice paddies.
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Affiliation(s)
- Lei Zhao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China; College of Resources Environment, Southwest University, Chongqing 400716, PR China
| | - Guangle Qiu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China
| | - Christopher W N Anderson
- Soil and Earth Sciences, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China.
| | - Dingyong Wang
- College of Resources Environment, Southwest University, Chongqing 400716, PR China
| | - Lihai Shang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China
| | - Haiyu Yan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China
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26
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Wang H, Guo C, Yang C, Lu G, Chen M, Dang Z. Distribution and diversity of bacterial communities and sulphate-reducing bacteria in a paddy soil irrigated with acid mine drainage. J Appl Microbiol 2016; 121:196-206. [DOI: 10.1111/jam.13143] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 03/13/2016] [Accepted: 03/16/2016] [Indexed: 11/28/2022]
Affiliation(s)
- H. Wang
- School of Environment and Energy; South China University of Technology; Guangzhou China
| | - C.L. Guo
- School of Environment and Energy; South China University of Technology; Guangzhou China
- The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters; Ministry of Education; South China University of Technology; Guangzhou China
| | - C.F. Yang
- School of Environment and Energy; South China University of Technology; Guangzhou China
| | - G.N. Lu
- School of Environment and Energy; South China University of Technology; Guangzhou China
- The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters; Ministry of Education; South China University of Technology; Guangzhou China
| | - M.Q. Chen
- School of Environment and Energy; South China University of Technology; Guangzhou China
- School of Environmental and Biological Engineering; Guangdong University of Petrochemical Technology; Maoming China
| | - Z. Dang
- School of Environment and Energy; South China University of Technology; Guangzhou China
- The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters; Ministry of Education; South China University of Technology; Guangzhou China
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27
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Wang Y, Dang F, Zhong H, Wei Z, Li P. Effects of sulfate and selenite on mercury methylation in a mercury-contaminated rice paddy soil under anoxic conditions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:4602-4608. [PMID: 26520099 DOI: 10.1007/s11356-015-5696-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/26/2015] [Indexed: 06/05/2023]
Abstract
Biogeochemical cycling of sulfur and selenium (Se) could play an important role in methylmercury (MeHg) dynamics in soil, while their potential effects on MeHg production in rice paddy soil are less understood. The main objective of this study was to explore the effects of sulfate and selenite on net MeHg production in contaminated rice paddy soil, characterized with massive MeHg production and thus MeHg accumulation in rice. A series of microcosm incubation experiments were conducted using a contaminated paddy soil amended with sulfate and/or selenite, in which sulfate-reducing bacteria were mainly responsible for MeHg production. Our results demonstrated that sulfate addition reduced solid and dissolved MeHg levels in soils by ≤18 and ≤25 %, respectively. Compared to sulfate, selenite was more effective in inhibiting net MeHg production, and the inhibitory effect depended largely on amended selenite doses. Moreover, sulfate input played a dual role in affecting Hg-Se interactions in soil, which could be explained by the dynamics of sulfate under anoxic conditions. Therefore, the effects of sulfate and selenium input should be carefully considered when assessing risk of Hg in anoxic environments (e.g., rice paddy field and wetland).
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Affiliation(s)
- Yongjie Wang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, People's Republic of China
| | - Fei Dang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, People's Republic of China
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, People's Republic of China.
- Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada.
| | - Zhongbo Wei
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, People's Republic of China
| | - Ping Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, People's Republic of China
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28
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Liu YR, Dong JX, Han LL, Zheng YM, He JZ. Influence of rice straw amendment on mercury methylation and nitrification in paddy soils. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 209:53-59. [PMID: 26629646 DOI: 10.1016/j.envpol.2015.11.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/09/2015] [Accepted: 11/16/2015] [Indexed: 06/05/2023]
Abstract
UNLABELLED Currently, rice straw return in place of burning is becoming more intensive in China than observed previously. However, little is known on the effect of returned rice straw on mercury (Hg) methylation and microbial activity in contaminated paddy fields. Here, we conduct a microcosm experiment to evaluate the effect of rice straw amendment on the Hg methylation and potential nitrification in two paddy soils with distinct Hg levels. Our results show that amended rice straw enhanced Hg methylation for relatively high Hg content soil, but not for low Hg soil, spiking the same additional fresh Hg. methylmercury (MeHg) concentration was significantly correlated to the dissolved organic carbon (DOC) content and relative abundance of dominant microbes associated with Hg methylation. Similarly, amended rice straw was found to only enhance the potential nitrification rate in soil with relatively high Hg content. These findings provide evidence that amended rice straw differentially modulates Hg methylation and nitrification in Hg contaminated soils possibly resulting from different characteristics in the soil microbial community. This highlights that caution should be taken when returning rice straw to contaminated paddy fields, as this practice may increase the risk of more MeHg production. MAIN FINDING Rice straw amendment enhanced both Hg methylation and nitrification potential in the relatively high, but not low, Hg soil.
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Affiliation(s)
- Yu-Rong Liu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| | - Ji-Xin Dong
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Li-Li Han
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yuan-Ming Zheng
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Ji-Zheng He
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Faculty of Veterinary and Agricultural Sciences, the University of Melbourne, Parkville 3010, Victoria, Australia
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29
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Liu YR, Wang JJ, Zheng YM, Zhang LM, He JZ. Patterns of bacterial diversity along a long-term mercury-contaminated gradient in the paddy soils. MICROBIAL ECOLOGY 2014; 68:575-583. [PMID: 24827389 DOI: 10.1007/s00248-014-0430-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 05/01/2014] [Indexed: 06/03/2023]
Abstract
Mercury (Hg) pollution is usually regarded as an environmental stress in reducing microbial diversity and altering bacterial community structure. However, these results were based on relatively short-term studies, which might obscure the real response of microbial species to Hg contamination. Here, we analysed the bacterial abundance and community composition in paddy soils that have been potentially contaminated by Hg for more than 600 years. Expectedly, the soil Hg pollution significantly influenced the bacterial community structure. However, the bacterial abundance was significantly correlated with the soil organic matter content rather than the total Hg (THg) concentration. The bacterial alpha diversity increased at relatively low levels of THg and methylmercury (MeHg) and subsequently approached a plateau above 4.86 mg kg(-1) THg or 18.62 ng g(-1) MeHg, respectively. Contrasting with the general prediction of decreasing diversity along Hg stress, our results seem to be consistent with the intermediate disturbance hypotheses with the peak biological diversity under intermediate disturbance or stress. This result was partly supported by the inconsistent response of bacterial species to Hg stress. For instance, the relative abundance of Nitrospirae decreased, while that of Gemmatimonadetes increased significantly along the increasing soil THg and MeHg concentrations. In addition, the content of SO(4)(2-), THg, MeHg and soil depth were the four main factors influencing bacterial community structures based on the canonical correspondence analysis (CCA). Overall, our findings provide novel insight into the distribution patterns of bacterial community along the long-term Hg-contaminated gradient in paddy soils.
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Affiliation(s)
- Yu-Rong Liu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
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Analysis of the microbial community structure by monitoring an Hg methylation gene (hgcA) in paddy soils along an Hg gradient. Appl Environ Microbiol 2014; 80:2874-9. [PMID: 24584244 DOI: 10.1128/aem.04225-13] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Knowledge of the diversity of mercury (Hg)-methylating microbes in the environment is limited due to a lack of available molecular biomarkers. Here, we developed novel degenerate PCR primers for a key Hg-methylating gene (hgcA) and amplified successfully the targeted genes from 48 paddy soil samples along an Hg concentration gradient in the Wanshan Hg mining area of China. A significant positive correlation was observed between hgcA gene abundance and methylmercury (MeHg) concentrations, suggesting that microbes containing the genes contribute to Hg methylation in the sampled soils. Canonical correspondence analysis (CCA) showed that the hgcA gene diversity in microbial community structures from paddy soils was high and was influenced by the contents of total Hg, SO4(2-), NH4(+), and organic matter. Phylogenetic analysis showed that hgcA microbes in the sampled soils likely were related to Deltaproteobacteria, Firmicutes, Chloroflexi, Euryarchaeota, and two unclassified groups. This is a novel report of hgcA diversity in paddy habitats, and results here suggest a link between Hg-methylating microbes and MeHg contamination in situ, which would be useful for monitoring and mediating MeHg synthesis in soils.
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