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Zhang S, Xia M, Pan Z, Wang J, Yin Y, Lv J, Hu L, Shi J, Jiang T, Wang D. Soil organic matter degradation and methylmercury dynamics in Hg-contaminated soils: Relationships and driving factors. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 356:120432. [PMID: 38479282 DOI: 10.1016/j.jenvman.2024.120432] [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: 11/06/2023] [Revised: 02/01/2024] [Accepted: 02/17/2024] [Indexed: 04/07/2024]
Abstract
Biodegradation of soil organic matter (SOM), which involves greenhouse gas (GHG) emissions, plays an essential role in the global carbon cycle. Over the past few decades, this has become an important research focus, particularly in natural ecosystems. SOM biodegradation significantly affects contaminants in the environment, such as mercury (Hg) methylation, producing highly toxic methylmercury (MeHg). However, the potential link between GHG production from SOM turnover in contaminated soils and biogeochemical processes involving contaminants remains unclear. In this study, we investigated the dynamics of GHG, MeHg production, and the relationship between biogeochemical processes in soils from two typical Hg mining sites. The two contaminated soils have different pathways, explaining the significant variations in GHG and MeHg production. The divergence of the microbial communities in these two biogeochemical processes is essential. In addition to the microbial role, abiotic factors such as Hg species can significantly affect MeHg production. On the other hand, we found an inverse relationship between CH4 and MeHg, suggesting that carbon emission reduction policies and management could inadvertently increase the MeHg levels. This highlights the need for an eclectic approach to organic carbon sequestration and contaminant containment. These findings suggest that it is difficult to establish a general pattern to describe and explain the SOM degradation and MeHg production in contaminated soils within the specific scenarios. However, this study provides a case study and helpful insights for further understanding the links between environmental risks and carbon turnover in Hg mining areas.
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Affiliation(s)
- Siqi Zhang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China
| | - Meng Xia
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China
| | - Zhaoyang Pan
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jianxu Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Yongguang Yin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, School of Environment and Health, Jianghan University, Wuhan, 430056, China
| | - Jitao Lv
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Ligang Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, School of Environment and Health, Jianghan University, Wuhan, 430056, China
| | - Jianbo Shi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, School of Environment and Health, Jianghan University, Wuhan, 430056, China
| | - Tao Jiang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China; Hubei Key Laboratory of Environmental and Health Effects of Persistent Toxic Substances, School of Environment and Health, Jianghan University, Wuhan, 430056, China.
| | - Dingyong Wang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China
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2
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Wang J, Xie Q, Xiang Y, Xue J, Jiang T, Zhang C, Li J, Wang Y, Wang D. Anthropogenic activities enhance mercury methylation in sediments of a multifunctional lake: Evidence from dissolved organic matter and mercury-methylating microorganisms. JOURNAL OF HAZARDOUS MATERIALS 2024; 466:133505. [PMID: 38280325 DOI: 10.1016/j.jhazmat.2024.133505] [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: 09/11/2023] [Revised: 12/20/2023] [Accepted: 01/09/2024] [Indexed: 01/29/2024]
Abstract
Multifunctional lakes are highly susceptible to anthropogenic influences, potentially introducing exogenous pollutants or nutrients into aquatic sediments. This, in turn, affects the mercury (Hg) methylation in the sediments. This study was conducted in the Changshou Lake, a representative multifunctional lake in southwestern China, with a specific focus on investigating the Hg variations, the potential of Hg methylation, and the influential factors affecting the methylation process within sediments across different functional areas. The results revealed significant variations in total Hg concentrations between the ecological culture area (area I), the ecological tourism area (area II), and the wetland protection area (area III), suggesting the possibility of exogenous Hg introduction associated with human activities. Furthermore, sediments from areas I and II displayed a greater potential for Hg methylation. This was ascribed to the enhanced diversity and relative abundance of Hg-methylating microorganisms, especially Geobacteraceae, induced by elevated levels of dissolved organic carbon in these two areas from human activities like historical cage culture. This study provides evidence that anthropogenic activities enhance the process of Hg methylation in the sediments of multifunctional lakes, highlighting the necessity of implementing comprehensive scientific water quality management practices to mitigate the negative impacts of human influences on these unique ecosystems.
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Affiliation(s)
- Juan Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Qing Xie
- College of Resources and Safety, Chongqing Vocational Institute of Engineering, Chongqing 402260, China
| | - Yuping Xiang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Jinping Xue
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, Institut des Sciences Analytiques et des Physico-Chimie pour l'Environnement et les Matériaux (IPREM), Pau 64000, France
| | - Tao Jiang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Cheng Zhang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Jiajia Li
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Yongmin Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China.
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
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3
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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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4
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Huang H, Mackereth RW, Mitchell CPJ. Impacts of forest harvesting on mercury concentrations and methylmercury production in boreal forest soils and stream sediment. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 341:122966. [PMID: 37981183 DOI: 10.1016/j.envpol.2023.122966] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/21/2023]
Abstract
Methylmercury (MeHg) is the most neurotoxic and bioaccumulative form of mercury (Hg) present in the terrestrial and aquatic food sources of boreal ecosystems, posing potential risks to wildlife and human health. Harvesting impacts on Hg methylation and MeHg concentrations in forest soils and stream sediment are not fully understood. In this study, a field investigation was carried out in 4 harvested and 2 unharvested boreal forest watersheds, before and after harvest, to better understand impacts on Hg methylation and MeHg concentration in soils and stream sediment, including their responses to different forest management practices. Changes in total Hg (THg) and MeHg concentrations, first-order potential rate constants for Hg methylation and MeHg demethylation (Kmeth and Kdemeth) as well as total carbon content and carbon-to-nitrogen ratio post-harvest in upland, wetland and riparian soils and stream sediment were assessed and compared. Increases in MeHg production were minimal in upland, wetland or riparian soils after harvest. Sediment in streams with minor buffer protection (∼3 m), greater fractions (>75%) of harvested watershed area and more road construction had significantly increased THg and MeHg concentrations, %-MeHg, Kmeth and total carbon content post-harvest. From these patterns, we infer that inputs of carbon and inorganic Hg into harvest-impacted stream sediment are likely sourced from the harvested upland areas and stimulate in situ MeHg production in stream sediment. These findings indicate the importance of stream sediment as potential MeHg pools in harvested forest watersheds. The findings also demonstrate that forest management practices aiming to mitigate organic matter and Hg inputs to streams can effectively alleviate harvesting impacts on Hg methylation and MeHg concentrations in stream sediment.
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Affiliation(s)
- Haiyong Huang
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada
| | - Robert W Mackereth
- Centre for Northern Forest Ecosystem Research, Ontario Ministry of Natural Resources and Forestry, Thunder Bay, ON, Canada
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.
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5
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Leclerc M, Ponton DE, Bilodeau F, Planas D, Amyot M. Enhanced Bioaccumulation and Transfer of Monomethylmercury through Periphytic Biofilms in Benthic Food Webs of a River Affected by Run-of-River Dams. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:20792-20801. [PMID: 38016692 PMCID: PMC10720379 DOI: 10.1021/acs.est.3c05585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 11/03/2023] [Accepted: 11/03/2023] [Indexed: 11/30/2023]
Abstract
Run-of-river (ROR) power plants impound limited terrestrial areas compared to traditional hydropower plants with large reservoirs and are assumed to have reduced impacts on mercury cycling. We conducted a study on periphyton and benthic communities from different habitats of the St. Maurice River (Québec, Canada) affected by two ROR power plants and their effect on the bioaccumulation and biomagnification of monomethylmercury (MMHg). Proportion of total mercury as MMHg reached maximum values about 2.9 times higher in flooded sites compared to unflooded sites. Impoundment by ROR would therefore provide favorable environments for the growth of periphyton, which can produce and accumulate MMHg. Periphyton MMHg concentrations significantly explained concentrations in some benthic macroinvertebrates, reflecting a local transfer. Through the analysis of δ13C and δ15N signatures, we found that flooding, creating scattered lenthic habitats, led to modifications in trophic structures by the introduction of new organic matter sources. The computed trophic magnification slopes did not show significant differences in the transfer efficiency of MMHg between sectors, while intercepts of flooded sectors were higher. Increases in MMHg concentrations in flooded areas are likely due to the impoundment, combined with watershed disturbances, and the creation of small habitats favorable to periphyton should be included in future predictive models.
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Affiliation(s)
- Maxime Leclerc
- GRIL,
GEOTOP, Département de Sciences Biologiques, Université de Montréal, 1375 Thérèse-Lavoie-Roux Ave., Montréal, Québec H2V 0B3, Canada
| | - Dominic E. Ponton
- GRIL,
GEOTOP, Département de Sciences Biologiques, Université de Montréal, 1375 Thérèse-Lavoie-Roux Ave., Montréal, Québec H2V 0B3, Canada
| | - François Bilodeau
- Hydro-Québec,
Direction Environnement, 800 De Maisonneuve Est Blvd., Montréal, Québec H2Z 1A4, Canada
| | - Dolors Planas
- GRIL,
GEOTOP, Département de Sciences Biologiques, Université du Québec à Montréal, 141 Président-Kennedy Ave., Montréal, Québec H2X 1Y4, Canada
| | - Marc Amyot
- GRIL,
GEOTOP, Département de Sciences Biologiques, Université de Montréal, 1375 Thérèse-Lavoie-Roux Ave., Montréal, Québec H2V 0B3, Canada
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6
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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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7
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Abdelhafiz MA, Liu J, Jiang T, Pu Q, Aslam MW, Zhang K, Meng B, Feng X. DOM influences Hg methylation in paddy soils across a Hg contamination gradient. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 322:121237. [PMID: 36758923 DOI: 10.1016/j.envpol.2023.121237] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/05/2023] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
Rice paddies provide optimum conditions for Hg methylation, and paddy soil is a hot spot for Hg methylation and the predominant source of methylmercury (MeHg) accumulated in rice grains. The role of dissolved organic matter (DOM) in controlling Hg bioavailability and methylation in rice paddy systems remains unclear. Paddy soils from eight various cultivation sites in China were chosen to investigate the variations in soil DOM and the influence of DOM concentration and optical characteristics on Hg methylation in rice paddy systems. In the present study, 151 rhizosphere soil samples were collected, and UV-Vis absorption and fluorescent spectroscopy were used to identify the optical properties of DOM. The relationship between MeHg and DOM's optical property indices revealed the production of MeHg consumes lower molecular weight DOM. Moreover, the correlation between DOM concentration and its optical characteristics highlighted the significant role of humic components on MeHg variability in paddy soil. Variation and correlation results demonstrated the allochthonous origin of DOM in the Hg-contaminated soil, with a higher molecular weight and humic character of DOM, as well as the dominant role of autochthonous DOM in promoting Hg methylation in uncontaminated soil. The current study indicated that soil organic matter and its dissolved fractions tend to limit Hg bioavailability and subsequently diminish MeHg production in contaminated paddy soils. Furthermore, the leading roles of allochthonous DOM in protecting MeHg from degradation and autochthonous DOM signatures in enhancing MeHg production in paddy soils. Overall, these findings provide insight into the correlative distributions of DOM and Hg along a Hg concentration gradient in paddy soil, thereby highlighting their potential role in controlling Hg bioavailability and regulating Hg methylation in the soil ecosystems.
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Affiliation(s)
- Mahmoud A Abdelhafiz
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Geology Department, Faculty of Science, Al-Azhar University, Assiut, 71524, Egypt
| | - Jiang Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Tao Jiang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China; Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, 400716, China
| | - Qiang Pu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Muhammad Wajahat Aslam
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Kun Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
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8
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Diverse Methylmercury (MeHg) Producers and Degraders Inhabit Acid Mine Drainage Sediments, but Few Taxa Correlate with MeHg Accumulation. mSystems 2023; 8:e0073622. [PMID: 36507660 PMCID: PMC9948709 DOI: 10.1128/msystems.00736-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Methylmercury (MeHg) is a notorious neurotoxin, and its production and degradation in the environment are mainly driven by microorganisms. A variety of microbial MeHg producers carrying the gene pair hgcAB and degraders carrying the merB gene have been separately reported in recent studies. However, surprisingly little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat, and no studies have been performed to explore to what extent these two contrasting microbial groups correlate with MeHg accumulation in the habitat of interest. Here, we collected 86 acid mine drainage (AMD) sediments from an area spanning approximately 500,000 km2 in southern China and profiled the sediment-borne putative MeHg producers and degraders using genome-resolved metagenomics. 46 metagenome-assembled genomes (MAGs) containing hgcAB and 93 MAGs containing merB were obtained, including those from various taxa without previously known MeHg-metabolizing microorganisms. These diverse MeHg-metabolizing MAGs were formed largely via multiple independent horizontal gene transfer (HGT) events. The putative MeHg producers from Deltaproteobacteria and Firmicutes as well as MeHg degraders from Acidithiobacillia were closely correlated with MeHg accumulation in the sediments. Furthermore, these three taxa, in combination with two abiotic factors, explained over 60% of the variance in MeHg accumulation. Most of the members of these taxa were characterized by their metabolic potential for nitrogen fixation and copper tolerance. Overall, these findings improve our understanding of the ecology of MeHg-metabolizing microorganisms and likely have implications for the development of management strategies for the reduction of MeHg accumulation in the AMD sediments. IMPORTANCE Microorganisms are the main drivers of MeHg production and degradation in the environment. However, little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat. We used genome-resolved metagenomics to reveal the vast phylogenetic and metabolic diversities of putative MeHg producers and degraders in AMD sediments. Our results show that the diversity of MeHg-metabolizing microorganisms (particularly MeHg degraders) in AMD sediments is much higher than was previously recognized. Via multiple linear regression analysis, we identified both microbial and abiotic factors affecting MeHg accumulation in AMD sediments. Despite their great diversity, only a few taxa of MeHg-metabolizing microorganisms were closely correlated with MeHg accumulation. This work underscores the importance of using genome-resolved metagenomics to survey MeHg-metabolizing microorganisms and provides a framework for the illumination of the microbial basis of MeHg accumulation via the characterization of physicochemical properties, MeHg-metabolizing microorganisms, and the correlations between them.
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9
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Wang B, Hu H, Bishop K, Buck M, Björn E, Skyllberg U, Nilsson MB, Bertilsson S, Bravo AG. Microbial communities mediating net methylmercury formation along a trophic gradient in a peatland chronosequence. JOURNAL OF HAZARDOUS MATERIALS 2023; 442:130057. [PMID: 36179622 DOI: 10.1016/j.jhazmat.2022.130057] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 09/05/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023]
Abstract
Peatlands are generally important sources of methylmercury (MeHg) to adjacent aquatic ecosystems, increasing the risk of human and wildlife exposure to this highly toxic compound. While microorganisms play important roles in mercury (Hg) geochemical cycles where they directly and indirectly affect MeHg formation in peatlands, potential linkages between net MeHg formation and microbial communities involving these microorganisms remain unclear. To address this gap, microbial community composition and specific marker gene transcripts were investigated along a trophic gradient in a geographically constrained peatland chronosequence. Our results showed a clear spatial pattern in microbial community composition along the gradient that was highly driven by peat soil properties and significantly associated with net MeHg formation as approximated by MeHg concentration and %MeHg of total Hg concentration. Known fermentative, syntrophic, methanogenic and iron-reducing metabolic guilds had the strong positive correlations to net MeHg formation, while methanotrophic and methylotrophic microorganisms were negatively correlated. Our results indicated that sulfate reducers did not have a key role in net MeHg formation. Microbial activity as interpreted from 16S rRNA sequences was significantly correlated with MeHg and %MeHg. Our findings shed new light on the role of microbial community in net MeHg formation of peatlands that undergo ontogenetic change.
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Affiliation(s)
- Baolin Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China; Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Haiyan Hu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China.
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Moritz Buck
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Mats B Nilsson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Stefan Bertilsson
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Andrea G Bravo
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM-CSIC), Pg Marítim de la Barceloneta 37-49, E08003 Barcelona, Catalunya, Spain
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10
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Capo E, Feng C, Bravo AG, Bertilsson S, Soerensen AL, Pinhassi J, Buck M, Karlsson C, Hawkes J, Björn E. Expression Levels of hgcAB Genes and Mercury Availability Jointly Explain Methylmercury Formation in Stratified Brackish Waters. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:13119-13130. [PMID: 36069707 PMCID: PMC9494745 DOI: 10.1021/acs.est.2c03784] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Neurotoxic methylmercury (MeHg) is formed by microbial methylation of inorganic divalent Hg (HgII) and constitutes severe environmental and human health risks. The methylation is enabled by hgcA and hgcB genes, but it is not known if the associated molecular-level processes are rate-limiting or enable accurate prediction of MeHg formation in nature. In this study, we investigated the relationships between hgc genes and MeHg across redox-stratified water columns in the brackish Baltic Sea. We showed, for the first time, that hgc transcript abundance and the concentration of dissolved HgII-sulfide species were strong predictors of both the HgII methylation rate and MeHg concentration, implying their roles as principal joint drivers of MeHg formation in these systems. Additionally, we characterized the metabolic capacities of hgc+ microorganisms by reconstructing their genomes from metagenomes (i.e., hgc+ MAGs), which highlighted the versatility of putative HgII methylators in the water column of the Baltic Sea. In establishing relationships between hgc transcripts and the HgII methylation rate, we advance the fundamental understanding of mechanistic principles governing MeHg formation in nature and enable refined predictions of MeHg levels in coastal seas in response to the accelerating spread of oxygen-deficient zones.
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Affiliation(s)
- Eric Capo
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Caiyan Feng
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
| | - Andrea G. Bravo
- Department
of Marine Biology and Oceanography, Institute of Marine Sciences, Spanish National Research Council (CSIC), Barcelona 08003, Spain
| | - Stefan Bertilsson
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Anne L. Soerensen
- Department
of Environmental Research and Monitoring, Swedish Museum of Natural History, Stockholm 104 05, Sweden
| | - Jarone Pinhassi
- Centre
for Ecology and Evolution in Microbial Model Systems—EEMiS, Linnaeus University, Kalmar 391 82, Sweden
| | - Moritz Buck
- Department
of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Camilla Karlsson
- Centre
for Ecology and Evolution in Microbial Model Systems—EEMiS, Linnaeus University, Kalmar 391 82, Sweden
| | - Jeffrey Hawkes
- Department
of Chemistry, Uppsala University, Uppsala 751 23, Sweden
| | - Erik Björn
- Department
of Chemistry, Umeå University, Umeå 901 87, Sweden
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11
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Wang J, Xiang Y, Tian X, Zhang C, Gong G, Xue J, Jiang T, Wang D, Wang Y. Role of the rhizosphere of a flooding-tolerant herb in promoting mercury methylation in water-level fluctuation zones. J Environ Sci (China) 2022; 119:139-151. [PMID: 35934459 DOI: 10.1016/j.jes.2022.05.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 04/26/2022] [Accepted: 05/06/2022] [Indexed: 06/15/2023]
Abstract
The water-level fluctuation zone (WLFZ) has been considered as a hotspot for mercury (Hg) methylation. Flooding-tolerant herbs are gradually acclimated to this water-land ecotone, tending to form substantial root systems for improving erosion resistance. Accompanying rhizosphere microzone plays crucial but unclear roles in methylmercury (MeHg) formation in the WLFZ. Thus, we conducted this study in the WLFZ of the Three Gorges Reservoir, to explore effects of the rhizosphere of a dominant flooding-tolerant herb (bermudagrass) on MeHg production. The elevated Hg and MeHg in rhizosphere soils suggest that the rhizosphere environment provides favorable conditions for Hg accumulation and methylation. The increased bioavailable Hg and microbial activity in the rhizosphere probably serve as important factors driving MeHg formation in the presence of bermudagrass. Simultaneously, the rhizosphere environments changed the richness, diversity, and distribution of hgcA-containing microorganisms. Here, a typical iron-reducing bacterium (Geobacteraceae) has been screened, however, the majority of hgcA genes detected in rhizosphere, near-, and non-rhizosphere soils of the WLFZ were unclassified. Collectively, these results provide new insights into the elevated MeHg production as related to microbial processes in the rhizosphere of perennial herbs in the WLFZ, with general implications for Hg cycling in other ecosystems with water-level fluctuations.
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Affiliation(s)
- Juan Wang
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Yuping Xiang
- Laboratory of Environmental Nanotechnology & Health Effect, Chinese Academy of Sciences, Research Center for Eco-Environmental Sciences, Beijing 100085, China
| | - Xiaosong Tian
- College of Resources and Safety, Chongqing Vocational Institute of Engineering, Chongqing 402260, China
| | - Cheng Zhang
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Guiqing Gong
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Jinping Xue
- Institut des Sciences Analytiques et des Physico-Chimie pour l'Environnement et les Matériaux (IPREM), UMR 5254, CNRS, Université de Pau et des Pays de l'Adour, Pau 64000, France
| | - Tao Jiang
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Dingyong Wang
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China.
| | - Yongmin Wang
- Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400715, China.
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12
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Huang H, Mangal V, Rennie MD, Tong H, Simpson MJ, Mitchell CPJ. Mercury methylation and methylmercury demethylation in boreal lake sediment with legacy sulphate pollution. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2022; 24:932-944. [PMID: 35532885 DOI: 10.1039/d2em00064d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Sulphate and dissolved organic matter (DOM) in freshwater systems may regulate the formation of methylmercury (MeHg), a potent neurotoxin that biomagnifies in aquatic ecosystems. While many boreal lakes continue to recover from decades of elevated atmospheric sulphate deposition, little research has examined whether historically high sulphate concentrations can result in persistently elevated MeHg production and accumulation in aquatic systems. This study used sediment from a historically sulphate-impacted lake and an adjacent reference lake in northwestern Ontario, Canada to investigate the legacy effects of sulphate pollution, as well as the effects of newly added sulphate, natural organic matter (NOM) of varying sulphur content and a sulphate reducing bacteria (SRB) inhibitor on enhancing or inhibiting the Hg methylation and demethylation activity (Kmeth and Kdemeth) in the sediment. We found that Kmeth and MeHg concentrations in sulphate-impacted lake sediment were significantly greater than in reference lake sediment. Further adding sulphate or NOM with different sulphur content to sediment of both lakes did not significantly change Kmeth. The addition of a SRB inhibitor resulted in lower Kmeth only in sulphate-impacted sediment, but methylation was not entirely depressed. Methylmercury demethylation potentials in sediment were consistent across lakes and experimental treatments, except for some impacts related to SRB inhibitor additions in the reference lake sediment. Overall, a broader community of microbes beyond SRB may be methylating Hg and demethylating MeHg in this system. This study reveals that legacies of sulphate pollution in boreal lakes may persist for decades in stimulating elevated Hg methylation in sediment.
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Affiliation(s)
- Haiyong Huang
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Ontario, Canada.
| | - Vaughn Mangal
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Ontario, Canada.
| | - Michael D Rennie
- Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada
| | - Huan Tong
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Ontario, Canada.
- Environmental NMR Centre, University of Toronto Scarborough, Ontario, Canada
| | - Myrna J Simpson
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Ontario, Canada.
- Environmental NMR Centre, University of Toronto Scarborough, Ontario, Canada
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Ontario, Canada.
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13
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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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14
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Zhao Q, Wang J, OuYang S, Chen L, Liu M, Li Y, Jiang F. The exacerbation of mercury methylation by Geobacter sulfurreducens PCA in a freshwater algae-bacteria symbiotic system throughout the lifetime of algae. JOURNAL OF HAZARDOUS MATERIALS 2021; 415:125691. [PMID: 33773254 DOI: 10.1016/j.jhazmat.2021.125691] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/15/2021] [Accepted: 03/16/2021] [Indexed: 06/12/2023]
Abstract
Mine-polluted wastewater with mercury (Hg) poses severe environmental pollution since Hg(II) can be converted to highly neurotoxic methylmercury (MeHg) under anaerobic conditions. Previous studies on Hg methylation have focused on aquatic sediments, but few have investigated the MeHg formation in water layers containing algae. In this study, we investigated the dynamic effect of algae on Hg methylation throughout the lifetime of algae. We found that Chlorella pyrenoidosa was a non-methylating alga and exhibited good tolerance to Hg stress (1-20 μg/L); thus Hg(II) could not inhibit the process of eutrophication. However, the presence of C. pyrenoidosa significantly enhanced the Hg methylation by Geobacter sulfurreducens PCA. Compared to the control sample without algae, the MeHg production rate of algae-bacteria samples remarkably exacerbated by 62.3-188.3% with the algal growth period at cell densities of 1.5 × 106-25 × 106 cells/mL. The increase of algal organic matter and thiols with the algal growth period resulted in the exacerbation of MeHg production. The Hg methylation was also enhanced with the presence of dead algae, of which the enhancement was ~62.4% lower than that with the presence of live algae. Accordingly, the potential mechanism of Hg methylation in a freshwater algae-bacteria symbiotic system throughout the algal lifetime was proposed.
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Affiliation(s)
- Qingxia Zhao
- School of Environment, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou 510006, China
| | - Jinting Wang
- Department of Civil and Environmental Engineering, Water Technology Lab, Hong Kong Branch of Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Shenyu OuYang
- School of Environment, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou 510006, China
| | - Laiguo Chen
- State Environmental Protection Key Laboratory of Urban Ecological Environment Simulation and Protection, South China Institute of Environmental Sciences, Ministry of Ecology and Environment of the People's Republic of China, Guangzhou 510655, China
| | - Ming Liu
- State Environmental Protection Key Laboratory of Urban Ecological Environment Simulation and Protection, South China Institute of Environmental Sciences, Ministry of Ecology and Environment of the People's Republic of China, Guangzhou 510655, China
| | - Yu Li
- School of Environment, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Theoretical Chemistry of Environment, South China Normal University, Guangzhou 510006, China.
| | - Feng Jiang
- School of Environmental Science & Engineering, Sun Yat-sen University, Guangzhou 510275, China.
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15
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AŽdajić M, Yumvihoze E, Blais JM, Poulain AJ. The effect of legacy gold mining on methylmercury cycling and microbial community structure in northern freshwater lakes. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2021; 23:1220-1230. [PMID: 34318847 DOI: 10.1039/d1em00129a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Smelting activities at Giant Mine (Yellowknife, NWT, Canada) have resulted in high sulfate and arsenic concentrations in nearby lakes. Here we tested whether historic smelting affects current mercury (Hg) cycling in 35 freshwater lakes over a 2800 km2 area around the former gold mine. We sampled lake water and sediment over three consecutive years (2015-2017) using a factorial sampling design that accounted for different environmental variables known to affect the net methylmercury (MeHg) levels in water. Stable Hg(ii) and MeHg isotope tracers were used to quantify Hg methylation and demethylation rate constants in sediments, and 16S rRNA gene amplicon sequencing was used to characterize microbial community structure. This study reveals that the fraction of methylated total Hg (% MeHg) found in surface water is positively correlated to the sulfate gradient, while the rate at which Hg is methylated (Km) in sediments is negatively correlated with total arsenic, and positively correlated with dissolved organic carbon, total phosphorous, and % MeHg in the water. Furthermore, 6 of the 28 lakes that had detectable demethylation rate constants (Kd) also had significantly lower DOC concentrations than lakes with non-detectable Kd. Our results also show that legacy pollution from smelting activities is affecting the structure of microbial communities in lake sediments. This study reveals the complex dynamics of Hg cycling in this northern environment, highlighting the importance of large-scale studies in which the effect of multiple pollution gradients (e.g. arsenic and sulfate) must be taken into consideration.
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Affiliation(s)
- Mija AŽdajić
- Department of Biology, University of Ottawa, 30 Marie-Curie, Ottawa, Ontario K1N 6N5, Canada.
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16
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Yu C, Xiao W, Xu Y, Sun X, Li M, Lin H, Tong Y, Xie H, Wang X. Spatial-temporal characteristics of mercury and methylmercury in marine sediment under the combined influences of river input and coastal currents. CHEMOSPHERE 2021; 274:129728. [PMID: 33540304 DOI: 10.1016/j.chemosphere.2021.129728] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 01/01/2021] [Accepted: 01/18/2021] [Indexed: 06/12/2023]
Abstract
Mercury, especially in the form of methylmercury (MeHg), is a global pollutant, and aquatic products are considered the main sources of Hg exposure to humans. The Bohai and Yellow seas are two important epicontinental seas for marine fisheries and aquaculture in China. A decreasing trend of the THg in the Yellow River Estuary toward the outer edge was reported according to 83 surface sediments (27.3 ± 15.0 ng g-1) and 3 sediment cores from the Bohai Sea and Yellow Sea. The relatively higher THg levels in the central Yellow Sea can be primarily attributed to higher organic carbon levels and finer-grained sediment sizes and partly to the particulates from the riverine input of the Yellow River driven by the currents. An increasing trend in THg levels since industrialization in north China around the Bohai and Yellow seas, and a decreasing trend of Yellow River THg input in recent years were recorded by sediment cores. The spatial distribution pattern of surface sediments MeHg (161 ± 130 pg g-1) was different from that of THg. A higher MeHg content and MeHg/THg ratio were found in the Bohai and Yellow seas compared to the East China Sea, and extremely high MeHg levels (714 pg g-1) were found in the Yellow Sea Cold Water Mass (YSCWM) area, which is considered an important region for fishery and marine breeding, suggesting that more attention should be paid to the potential ecological and human health risks in the region due to mercury exposure.
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Affiliation(s)
- Chenghao Yu
- Ministry of Education Laboratory of Earth Surface Process, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Wenjie Xiao
- College of Marine Sciences, Shanghai Ocean University, Shanghai, 201306, China; Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China; Shenzhen Key Laboratory of Marine Archaea Geo-Omics, Shenzhen, 518055, China
| | - Yunping Xu
- College of Marine Sciences, Shanghai Ocean University, Shanghai, 201306, China
| | - Xuejun Sun
- Key Laboratory of Tibetan Environmental Changes and Land Surface Process, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing, 100101, China
| | - Mingyue Li
- Key Laboratory of Tibetan Environmental Changes and Land Surface Process, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing, 100101, China
| | - Huiming Lin
- Ministry of Education Laboratory of Earth Surface Process, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Yindong Tong
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300072, China
| | - Han Xie
- Ministry of Education Laboratory of Earth Surface Process, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Xuejun Wang
- Ministry of Education Laboratory of Earth Surface Process, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.
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17
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Millera Ferriz L, Ponton DE, Storck V, Leclerc M, Bilodeau F, Walsh DA, Amyot M. Role of organic matter and microbial communities in mercury retention and methylation in sediments near run-of-river hydroelectric dams. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 774:145686. [PMID: 33609815 DOI: 10.1016/j.scitotenv.2021.145686] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 01/08/2021] [Accepted: 02/03/2021] [Indexed: 06/12/2023]
Abstract
Run-of-river power plants (RoRs) are expected to triple in number over the next decades in Canada. These structures are not anticipated to considerably promote the mobilization and transport of mercury (Hg) and its subsequent microbial transformation to methylmercury (MeHg), a neurotoxin able to biomagnify in food webs up to humans. To test whether construction of RoRs had an effect on Hg transport and transformation, we studied Hg and MeHg concentrations, organic matter contents and methylating microbial community abundance and composition in the sediments of a section of the St. Maurice River (Quebec, Canada). This river section has been affected by the construction of two RoR dams and its watershed has been disturbed by a forest fire, logging, and the construction of wetlands. Higher total Hg (THg) and MeHg concentrations were observed in the surface sediments of the flooded sites upstream of the RoRs. These peaks in THg and MeHg were correlated with organic matter proportions in the sediments (r2 = 0.87 and 0.82, respectively). In contrast, the proportion of MeHg, a proxy for methylation potential, was best explained by the carbon to nitrogen ratio suggesting the importance of terrigenous organic matter as labile substrate for Hg methylation in this system. Metagenomic analysis of Hg-methylating communities based on the hgcA functional gene marker indicated an abundance of methanogens, sulfate reducers and fermenters, suggesting that these metabolic guilds may be primary Hg methylators in these surface sediments. We propose that RoR pondages act as traps for sediments, organic matter and Hg, and that this retention can be amplified by other disturbances of the watershed such as forest fire and logging. RoR flooded sites can be conducive to Hg methylation in sediments and may act as gateways for bioaccumulation and biomagnification of MeHg along food webs, particularly in disturbed watersheds.
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Affiliation(s)
- L Millera Ferriz
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - D E Ponton
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - V Storck
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada
| | - M Leclerc
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - F Bilodeau
- Hydro-Québec Production, Environment Department, Montreal, QC, Canada
| | - D A Walsh
- Biology Department, Concordia University, Montreal H4B 1R6, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada
| | - M Amyot
- Département de sciences biologiques, Université de Montréal, Montreal H2V 2S9, QC, Canada; GRIL, Groupe de Recherche Interuniversitaire en Limnologie, Département de sciences biologiques, Université de Montréal, Campus MIL, Montreal H3C 3J7, QC, Canada.
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18
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Yu C, Xu Y, Yan Y, Xiao W, Liu M, Cheng M, He W, Xu F, Wang X. Mercury and methylmercury in China's lake sediments and first estimation of mercury burial fluxes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 770:145338. [PMID: 33517014 DOI: 10.1016/j.scitotenv.2021.145338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 01/17/2021] [Accepted: 01/17/2021] [Indexed: 06/12/2023]
Abstract
Lake sediments are key materials for mercury deposition and methylation. To understand the mercury concentrations in China's lakes, 100 lake surface sediment samples were collected from 35 lakes in 2014. Total mercury (THg), methylmercury (MeHg) concentrations and the annual Hg burial rates in lake sediments were measured. THg and MeHg concentrations in the sediment ranged from 13.6 to 1488 ng‧g-1 and 0.05 to 1.70 ng‧g-1, respectively, and urban lakes reported most high values, indicating direct anthropogenic inputs. The Inner Mongolia-Xinjiang Region (MX) and Qinghai-Tibet Plateau Region (QT) reported relatively lower mercury burial rates, while the Eastern Plain Region (EP), Northeast Mountain and Plain Region (NE), and Yunnan-Guizhou Plateau Region (YG) reported higher mercury burial rates. Regional variances of THg burial fluxes were dominated by atmospheric deposition, terrestrial input, and sediment accumulation rates in different lakes. In 2014, the estimated average THg burial rate in China's lakes was 139 μg‧m-2‧yr-1, comparable to the average in mid-latitude North America in recent years; however, due to China's much smaller lake area relative to NA, the annual THg burial flux in China was much lower than that in North America. EP and NE, where most freshwater aquatic products in China are harvested, accounted for 58.2% and 22.9%, respectively, of the THg burial flux. High sedimentary MeHg concentrations and MeHg:THg ratios were reported in most of the NE but low MeHg concentrations and MeHg:THg ratios were reported in EP. MeHg concentrations and MeHg:THg ratios were positively correlated with water COD levels and negatively correlated with average temperature. The results of this study indicate that in addition to the adjacent seas, lake sediments are an important mercury sink in China's aquatic environment, which could cause health risks due to MeHg intake, especially in NE.
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Affiliation(s)
- Chenghao Yu
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Yunping Xu
- College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China
| | - Yunyun Yan
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Wenjie Xiao
- College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China; Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China; Shenzhen Key Laboratory of Marine Archaea Geo-Omics, Shenzhen 518055, China
| | - Maodian Liu
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; School of the Environment, Yale University, New Haven, CT 06511, USA
| | - Menghan Cheng
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Wei He
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Fuliu Xu
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
| | - Xuejun Wang
- Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
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19
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Dai SS, Yang Z, Tong Y, Chen L, Liu SY, Pan R, Li Y, Zhang CJ, Liu YR, Huang Q. Global distribution and environmental drivers of methylmercury production in sediments. JOURNAL OF HAZARDOUS MATERIALS 2021; 407:124700. [PMID: 33333388 DOI: 10.1016/j.jhazmat.2020.124700] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 11/11/2020] [Accepted: 11/25/2020] [Indexed: 06/12/2023]
Abstract
Neurotoxic methylmercury (MeHg) in environments poses substantial risks to human health. Saturated sediments are basic sources of MeHg in food chains; however, distribution patterns and environmental drivers of MeHg at a global scale remain largely unexplored. Here, we characterized global patterns of MeHg distribution and environmental drivers of MeHg production based on 495 sediment samples across five typical ecosystems from the literature (1995-2018) and our own field survey. Our results showed the MeHg concentration ranged from 0.009 to 55.7 μg kg-1 across the different ecosystems, and the highest MeHg concentration and Hg methylation potential were from the sediments of paddy and marine environments, respectively. Further, using combined analysis of random forest and structural equation modeling, we identified temperature and precipitation as important regulators of MeHg production after accounting for the well-known drivers including Hg availability and sediment geochemistry. More importantly, we found increased MeHg production in sediments with elevated mean annual Hg precipitation, and warmer temperature could also accelerate MeHg production by facilitating activities of microbial methylators. Together, this work advances our understanding of global MeHg distribution in sediments and environmental drivers, which are fundamental to the prediction and management of MeHg production and its potential health risk globally.
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Affiliation(s)
- Shu-Shen Dai
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Ziming Yang
- Department of Chemistry, Oakland University, Rochester, MI 48309, United States
| | - Yindong Tong
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China
| | - Long Chen
- Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai 200241, China
| | - Si-Yuan Liu
- College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Rong Pan
- College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
| | - Cui-Jing Zhang
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Yu-Rong Liu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China; Hubei Key Laboratory of Soil Environment and Pollution Remediation, Wuhan 430070, China.
| | - Qiaoyun Huang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China; College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China; Hubei Key Laboratory of Soil Environment and Pollution Remediation, Wuhan 430070, China
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20
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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: 4] [Impact Index Per Article: 1.3] [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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21
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Cai W, Jin J, Dang F, Shi W, Zhou D. Mercury methylation from mercury selenide particles in soils. JOURNAL OF HAZARDOUS MATERIALS 2020; 400:123248. [PMID: 32585526 DOI: 10.1016/j.jhazmat.2020.123248] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 05/17/2020] [Accepted: 06/16/2020] [Indexed: 06/11/2023]
Abstract
Selenium-inhibited monomethylmercury (MeHg) production is an attractive strategy for mitigating the risks of MeHg exposure. However, it is poorly understood the methylation potential of mercury selenide (HgSe) particles during their aging in soils and sediments. Net MeHg production in three floodplain soils amended with different geochemical species of mercury selenides, i.e., dissolved inorganic mercury freshly mixed with selenite (Hg(II)+Se(IV)), HgSe nanoparticles (45.2 ± 0.5 nm) and microparticles (> 1 μm) is examined. Among mercury types, the methylation from nanoparticulate HgSe was similar to (0.05 - 0.5 % vs. 0.1 - 0.4 %, yellow brown soil) or 12.9 - 21.0 times lower (0.02 - 0.1 vs. 0.6 - 1.5 %, black soil) than that from Hg(II)+Se(IV); however, net MeHg production from HgSe nanoparticles (0.02 - 0.5 %) was 1.9 - 15.5 times greater than HgSe microparticles (< 0.05 %) in all soils. Furthermore, net MeHg production from nanoparticulate HgSe varied significantly among soil types, attributable to differences in soil organic matter contents (2.4-5.8%) and microbial methylator community among soils. These results address the importance of geochemical intermediates of mercury selenide precipitation reactions and soil properties in MeHg production, and develop Se-based remediation strategy to minimize negative effects of MeHg on environmental and human health.
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Affiliation(s)
- Weiping Cai
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Jingmei Jin
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; College of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - Fei Dang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Weilin Shi
- College of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - Dongmei Zhou
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
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22
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Burke SM, Zimmerman CE, Laske SM, Koch JC, Derry AM, Guernon S, Branfireun BA, Swanson HK. Fish growth rates and lake sulphate explain variation in mercury levels in ninespine stickleback (Pungitius pungitius) on the Arctic Coastal Plain of Alaska. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 743:140564. [PMID: 32758814 DOI: 10.1016/j.scitotenv.2020.140564] [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: 04/15/2020] [Revised: 06/24/2020] [Accepted: 06/25/2020] [Indexed: 06/11/2023]
Abstract
Mercury concentrations in freshwater food webs are governed by complex biogeochemical and ecological interactions that spatially vary and are often mediated by climate. The Arctic Coastal Plain of Alaska (ACP) is a heterogeneous, lake-rich landscape where variability in mercury accumulation is poorly understood. Earlier research indicated that the level of catchment influence on lakes varied spatially on the ACP, and affected mercury accumulation in lake sediments. This work sought to determine drivers of spatial variation in mercury accumulation in lake food webs on the ACP. Three lakes that were a priori identified as "high catchment influence" (Reindeer Camp region) and three lakes that were a priori identified as "low catchment influence" (Atqasuk region) were sampled, and variability in water chemistry, food web ecology, and mercury accumulation was investigated. Among-lake differences in ninespine stickleback (Pungitius pungitius) length-adjusted methylmercury concentrations were significantly explained by sulphate concentration in lake water, a tracer of catchment runoff input. This effect was mediated by fish growth, which had no pattern between regions. Together, lake water sulphate concentration and fish age-at-size (proxy for growth) accounted for nearly all of the among-lake variability in length-adjusted methylmercury concentrations in stickleback (R2adj = 0.94, p < 0.01). The percentage of total mercury as methylmercury (a proxy for net Hg methylation) was higher in sediments of more autochthonous, "low catchment influence" lakes (p < 0.05), and in the periphyton of more allochthonous, "high catchment influence" lakes (p < 0.05). The results indicate that dominant sources of primary production (littoral macrophyte/biofilm vs. pelagic phytoplankton) and food web structure (detrital vs. grazing) are regulated by catchment characteristics on the ACP, and that this ultimately influences the amount of methylmercury in the aquatic food web. These results have important implications for predicting future mercury concentrations in fish in lakes where fish growth rates and catchment inputs may change in response to a changing climate.
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Affiliation(s)
- S M Burke
- Department of Biology and Water Institute, University of Waterloo, 200 University Ave. West, Waterloo, Ontario N2L 3G1, Canada; Environment and Climate Change Canada (ECCC), Aquatic Contaminants Research Division, 867 Lakeshore Rd., Burlington, ON L7S 1A1, Canada.
| | - C E Zimmerman
- U. S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK 99508, USA
| | - S M Laske
- U. S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK 99508, USA
| | - J C Koch
- U. S. Geological Survey, Alaska Science Center, 4210 University Dr., Anchorage, AK 99508, USA
| | - A M Derry
- Département des sciences biologiques, Université du Québec à Montréal (UQAM), P.O. Box 8888, Succ. Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - S Guernon
- Département des sciences biologiques, Université du Québec à Montréal (UQAM), P.O. Box 8888, Succ. Centre-Ville, Montréal, Québec H3C 3P8, Canada
| | - B A Branfireun
- Western University, Department of Biological Sciences, London, Ontario N6A 3K7, Canada
| | - H K Swanson
- Department of Biology and Water Institute, University of Waterloo, 200 University Ave. West, Waterloo, Ontario N2L 3G1, Canada
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23
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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: 33] [Impact Index Per Article: 8.3] [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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24
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Apler A, Snowball I, Josefsson S. Dispersal of cellulose fibers and metals from contaminated sediments of industrial origin in an estuary. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 266:115182. [PMID: 32673976 DOI: 10.1016/j.envpol.2020.115182] [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: 05/07/2020] [Revised: 07/02/2020] [Accepted: 07/03/2020] [Indexed: 06/11/2023]
Abstract
The boreal forest's pulp and paper industry plays a major role in economic prosperity but, historically, caused an environmental burden. Remnants of discharges of contaminated suspended solids (fiberbanks) are continuously being discovered on the beds of shallow seas, rivers and lakes in the northern hemisphere. We investigated the dispersion of Cd, Cr, Cu, Hg, Ni, Pb and Zn from deeper to surficial layers in fiberbanks in a Swedish estuary and the larger-scale transport of the same metals to distal areas of sediment accumulation. We also tested the C:N ratio as a common denominator for these anthropogenic, cellulose-rich deposits. Sampling and analyses of three fiberbanks located in the inner part of the estuary and from sediment accumulation sites outside and along the estuary reveals that metal concentrations are regressing to background levels towards the surface at the accumulation sites. The fiberbanks show a higher degree of contamination and C:N ratios demonstrate inclusion of cellulose fibers. C:N ratios also indicate that there is currently no significant transport of fiberbank material into the distal areas. A ∼10 cm natural cap of recently settled fine-grained sediment covering one of the fiberbanks seems to prevent metals dispersing into overlying water whereas the other two fiberbanks show signs of metal enrichment and potential mercury methylation in surficial layers. Although the estuarine system seems to recover from the impact of industrial waste, there is no evidence that the fiberbanks will be remediated naturally but instead will continue to threaten the aquatic environment.
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Affiliation(s)
- Anna Apler
- Geological Survey of Sweden, Box 670, 751 28, Uppsala, Sweden; Department of Earth Sciences, Uppsala University, Villavägen 16, 751 36, Uppsala, Sweden.
| | - Ian Snowball
- Department of Earth Sciences, Uppsala University, Villavägen 16, 751 36, Uppsala, Sweden
| | - Sarah Josefsson
- Geological Survey of Sweden, Box 670, 751 28, Uppsala, Sweden
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25
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Azaroff A, Goñi Urriza M, Gassie C, Monperrus M, Guyoneaud R. Marine mercury-methylating microbial communities from coastal to Capbreton Canyon sediments (North Atlantic Ocean). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 262:114333. [PMID: 32443198 DOI: 10.1016/j.envpol.2020.114333] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 03/01/2020] [Accepted: 03/04/2020] [Indexed: 06/11/2023]
Abstract
Microbial mercury (Hg) methylation transforms inorganic mercury to neurotoxic methylmercury (MeHg) mainly in aquatic anoxic environments. Sampling challenges in marine ecosystems, particularly in submarine canyons, leads to a lack of knowledge about the Hg methylating microbia in marine sediments. A previous study showed an enrichment of mercury species in sediments from the Capbreton Canyon where both geochemical parameters and microbial activities constrained the net MeHg production. In order to characterize Hg-methylating microbial communities from coastal to deeper sediments, we analysed the diversity of microorganisms' (16S rDNA-based sequencing) and Hg methylators (hgcA based cloning and sequencing). Both, 16S rDNA and hgcA gene analysis demonstrated that the putative Hg-methylating prokaryotes were likely within the Deltaproteobacteria, dominated by sulfur-compounds based reducing bacteria (mainly sulfate reducers). Additionally, others clades were also identified as carrying HgcA gene, such as, Chloroflexi, Spirochaetes, Elusimicrobia, PVC superphylum (Plantomycetes, Verrucomicrobia and Chlamydiae) and Euryarchaea. Nevertheless, 61% of the hgcA sequences were not assigned to specific clade, indicating that further studies are needed to understand the implication of new microorganisms carrying hgcA in the Hg methylation in marine environments. These first results suggest that sulfur cycle drives the Hg-methylation in marine ecosystem.
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Affiliation(s)
- Alyssa Azaroff
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA, UMR 5254, 64600 Anglet, France
| | - Marisol Goñi Urriza
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France
| | - Claire Gassie
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France
| | - Mathilde Monperrus
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA, UMR 5254, 64600 Anglet, France
| | - Rémy Guyoneaud
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM-MIRA Environmental Microbiology, UMR 5254, 64000, Pau, France.
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26
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Liu J, Wang D, Zhang J, Liem-Nguyen V, Huang R, Jiang T. Evaluation of Hg methylation in the water-level-fluctuation zone of the Three Gorges Reservoir region by using the MeHg/Hg T ratio. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 195:110468. [PMID: 32200146 DOI: 10.1016/j.ecoenv.2020.110468] [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: 12/16/2019] [Revised: 03/05/2020] [Accepted: 03/09/2020] [Indexed: 06/10/2023]
Abstract
In the recent decade, the hydroelectric reservoir is identified as a methylmercury (MeHg) hotspot and gained much attention. The artificial water level management in the Three Gorges Reservoir (TGR) in China formed a water-level-fluctuation zone (WLFZ) undergoing flooding drying rotations annually. However, the mercury (Hg) methylation and major geochemical driving factors at different elevations in the WLFZ remain unclear. Here we use total Hg (HgT) normalized MeHg (MeHg/HgT ratio) to evaluate Hg methylation degree in a one-year field study at 155, 165 m elevations in the WLFZ and with >175 m elevation as the reference. Results demonstrate that MeHg/HgT ratio at the WLFZ could reach 4.1% in soils, and both 155 and 165 m elevations have a higher Hg methylation degree than the >175 m elevation. However, the differences in MeHg/HgT ratios both in soils and waters between 155 and 165 m elevations are not significant. This indicates the influence of different submerging periods on the MeHg/HgT at the WLFZ elevations is not observed. The significant correlation between the MeHg/HgT ratio and soil organic carbon (SOC) content implies a MeHg retention in re-exposed soils after flooding. Decoupling of MeHg/HgT ratios between submerged soil and overlying water are found at both elevations and therefore make MeHg/HgT in waters alone cannot be used to evaluate Hg methylation degree in this study. The calculation of HgT and MeHg partitioning coefficient (Kd) found an immobilization of MeHg by submerged soils at the WLFZ during the flooding period. Major geochemical factors, determined through principal component analysis (PCA), in affecting Hg methylation are the redox cycling of sulfur and the distribution of organic matters in the WLFZ.
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Affiliation(s)
- Jiang Liu
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, 400716, China; Centre for Earth Observation Science, Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
| | - Dingyong Wang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, 400716, China.
| | - Jinzhong Zhang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, 400716, China.
| | - Van Liem-Nguyen
- Laboratory of Advanced Materials Chemistry, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam; Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam.
| | - Rong Huang
- College of Resources, Sichuan Agricultural University, Chengdu, 611130, China.
| | - Tao Jiang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing, 400716, China.
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27
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Wang B, Nilsson MB, Eklöf K, Hu H, Ehnvall B, Bravo AG, Zhong S, Åkeblom S, Björn E, Bertilsson S, Skyllberg U, Bishop K. Opposing spatial trends in methylmercury and total mercury along a peatland chronosequence trophic gradient. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 718:137306. [PMID: 32087589 DOI: 10.1016/j.scitotenv.2020.137306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 02/11/2020] [Accepted: 02/12/2020] [Indexed: 06/10/2023]
Abstract
Peatlands are abundant elements of boreal landscapes where inorganic mercury (IHg) can be transformed into bioaccumulating and highly toxic methylmercury (MeHg). We studied fifteen peatlands divided into three age classes (young, intermediate and old) along a geographically constrained chronosequence to determine the role of biogeochemical factors and nutrient availability in controlling the formation of MeHg. In the 10 cm soil layer just below the average annual growing season water table, concentrations of MeHg and %MeHg (of total Hg) were higher in younger, more mesotrophic peatlands than in older, more oligotrophic peatlands. In contrast, total mercury (THg) concentrations were higher in the older peatlands. Partial least squares (PLS) analysis indicates that the net MeHg production was positively correlated to trophic demands of vegetation and an increased availability of potential electron acceptors and donors for Hg methylating microorganisms. An important question for further studies will be to elucidate why there is less THg in the younger peatlands compared to the older peatlands, even though the age of the superficial peat itself is similar for all sites. We hypothesize that ecosystem features which enhance microbial processes involved in Hg methylation also promote Hg reduction that makes previously deposited Hg more available for evasion back to the atmosphere.
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Affiliation(s)
- Baolin Wang
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Mats B Nilsson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Karin Eklöf
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Haiyan Hu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China; Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden.
| | - Betty Ehnvall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Andrea G Bravo
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM-CSIC), Pg Marítim de la Barceloneta 37-49, E08003 Barcelona, Catalunya, Spain
| | - Shunqing Zhong
- College of City and Tourism, Hengyang Normal University, 421002 Hengyang, China
| | - Staffan Åkeblom
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden
| | - Stefan Bertilsson
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden; Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
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Tsui MTK, Blum JD, Kwon SY. Review of stable mercury isotopes in ecology and biogeochemistry. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 716:135386. [PMID: 31839301 DOI: 10.1016/j.scitotenv.2019.135386] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/21/2019] [Accepted: 11/04/2019] [Indexed: 06/10/2023]
Abstract
Due to the advent of cold vapor-multicollector-inductively coupled plasma mass spectrometry (CV-MC-ICP-MS) in the past two decades, many research groups studying mercury (Hg) biogeochemistry have integrated stable Hg isotopes into their research. Currently, >200 studies using this technique have been published and this has greatly enhanced our understanding of the Hg biogeochemical cycle beyond what Hg concentration and speciation analyses alone can provide. These studies are largely divided into two groups: (i) controlled experiments investigating fractionation of Hg isotopes and refining tools of isotopic analyses, and (ii) studies of natural variations of Hg isotopes. It is now known that Hg isotopes undergo both mass dependent fractionation (MDF; reported as the ratio of mass 202Hg to 198Hg) and mass independent fractionation (MIF), with MIF occurring at odd masses (199Hg, 201Hg) to a larger magnitude and at even masses (200Hg, 204Hg) to a much smaller magnitude. The two types of MIF are controlled by different photochemical processes. The range of isotopic variations of MDF, odd-MIF, and even-MIF are now well documented in a diverse set of environmental samples, and researchers are continuing to explore how the field of Hg isotope biogeochemistry can be further developed and taken to the next level of understanding. One application that has received considerable attention is the use of Hg isotopes to examine the environmental controls on the production and degradation of methylmercury (MeHg), the most toxic and bioaccumulative form of Hg. Since MeHg is efficiently assimilated and biomagnified along food chains, MeHg has the potential to be a robust ecological tracer. In this review, we give an updated overview of the field of Hg isotopes and focus on how Hg isotopes of MeHg can be used to address fundamental ecological questions, including energy transfer across ecosystem interfaces and as a tracer for animal movements.
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Affiliation(s)
- Martin Tsz-Ki Tsui
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27402, USA.
| | - Joel D Blum
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sae Yun Kwon
- Division of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang 37673, South Korea
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Bravo AG, Cosio C. Biotic formation of methylmercury: A bio-physico-chemical conundrum. LIMNOLOGY AND OCEANOGRAPHY 2020; 65:1010-1027. [PMID: 32612306 PMCID: PMC7319479 DOI: 10.1002/lno.11366] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 09/17/2019] [Accepted: 10/02/2019] [Indexed: 05/11/2023]
Abstract
Mercury (Hg) is a natural and widespread trace metal, but is considered a priority pollutant, particularly its organic form methylmercury (MMHg), because of human's exposure to MMHg through fish consumption. Pioneering studies showed the methylation of divalent Hg (HgII) to MMHg to occur under oxygen-limited conditions and to depend on the activity of anaerobic microorganisms. Recent studies identified the hgcAB gene cluster in microorganisms with the capacity to methylate HgII and unveiled a much wider range of species and environmental conditions producing MMHg than previously expected. Here, we review the recent knowledge and approaches used to understand HgII-methylation, microbial biodiversity and activity involved in these processes, and we highlight the current limits for predicting MMHg concentrations in the environment. The available data unveil the fact that HgII methylation is a bio-physico-chemical conundrum in which the efficiency of biological HgII methylation appears to depend chiefly on HgII and nutrients availability, the abundance of electron acceptors such as sulfate or iron, the abundance and composition of organic matter as well as the activity and structure of the microbial community. An increased knowledge of the relationship between microbial community composition, physico-chemical conditions, MMHg production, and demethylation is necessary to predict variability in MMHg concentrations across environments.
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Affiliation(s)
- Andrea G. Bravo
- Department of Marine Biology and Oceanography, Institute of Marine SciencesSpanish National Research Council (CSIC)BarcelonaSpain
| | - Claudia Cosio
- Université de Reims Champagne Ardennes, UMR‐I 02 INERIS‐URCA‐ULH SEBIO, Unité Stress Environnementaux et BIOsurveillance des milieux aquatiquesReimsFrance
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Ji X, Liu C, Zhang M, Yin Y, Pan G. Mitigation of methylmercury production in eutrophic waters by interfacial oxygen nanobubbles. WATER RESEARCH 2020; 173:115563. [PMID: 32059129 DOI: 10.1016/j.watres.2020.115563] [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: 09/03/2019] [Revised: 01/17/2020] [Accepted: 01/28/2020] [Indexed: 06/10/2023]
Abstract
In mercury (Hg)-polluted eutrophic waters, algal blooms are likely to aggravate methylmercury (MeHg) production by causing intensified hypoxia and enriching organic matter at the sediment-water interface. The technology of interfacial oxygen (O2) nanobubbles is proven to alleviate hypoxia and may have potential to mitigate the risks of MeHg formation. In this study, incubation column experiments were performed using sediment and overlying water samples collected from the Baihua Reservoir (China), which is currently suffering from co-contamination of Hg and eutrophication. The results indicated that after the application of O2 nanobubbles, the %MeHg (ratio of MeHg to total Hg) in the overlying water and surface sediment decreased by up to 76% and 56% respectively. In addition, the MeHg concentrations decreased from 0.54 ± 0.15 to 0.17 ± 0.01 ng L-1 in the overlying water and from 56.61 ± 9.23 to 25.48 ± 4.08 ng g-1 in the surface sediment. The decline could be attributed to the alleviation of anoxia and the decrease of labile organic matter and bioavailable Hg. In addition, hgcA gene abundances in the overlying water and surface sediment decreased by up to 69% and 44% after the addition of O2 nanobubbles, as is consistent with MeHg occurrence in such areas. Accordingly, this work proposed a promising strategy of using interfacial oxygen nanobubbles to alleviate the potentially enhanced MeHg production during algal bloom outbreaks in Hg-polluted eutrophic waters.
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Affiliation(s)
- Xiaonan Ji
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Chengbin Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, PR China
| | - Meiyi Zhang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China.
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China
| | - Gang Pan
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China; Beijing Advanced Science and Innovation Center, Chinese Academy of Sciences, Beijing, 101407, PR China; Center of Integrated Water-Energy-Food Studies (iWEF), School of Animal, Rural, and Environmental Sciences, Nottingham Trent University, Brackenhurst Campus, NG25 0QF, UK.
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31
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Hu H, Wang B, Bravo AG, Björn E, Skyllberg U, Amouroux D, Tessier E, Zopfi J, Feng X, Bishop K, Nilsson MB, Bertilsson S. Shifts in mercury methylation across a peatland chronosequence: From sulfate reduction to methanogenesis and syntrophy. JOURNAL OF HAZARDOUS MATERIALS 2020; 387:121967. [PMID: 31901845 DOI: 10.1016/j.jhazmat.2019.121967] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/07/2019] [Accepted: 12/23/2019] [Indexed: 06/10/2023]
Abstract
Peatlands are globally important ecosystems where inorganic mercury is converted to bioaccumulating and highly toxic methylmercury, resulting in high risks of methylmercury exposure in adjacent aquatic ecosystems. Although biological mercury methylation has been known for decades, there is still a lack of knowledge about the organisms involved in mercury methylation and the drivers controlling their methylating capacity. In order to investigate the metabolisms responsible for mercury methylation and methylmercury degradation as well as the controls of both processes, we studied a chronosequence of boreal peatlands covering fundamentally different biogeochemical conditions. Potential mercury methylation rates decreased with peatland age, being up to 53 times higher in the youngest peatland compared to the oldest. Methylation in young mires was driven by sulfate reduction, while methanogenic and syntrophic metabolisms became more important in older systems. Demethylation rates were also highest in young wetlands, with a gradual shift from biotic to abiotic methylmercury degradation along the chronosequence. Our findings reveal how metabolic shifts drive mercury methylation and its ratio to demethylation as peatlands age.
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Affiliation(s)
- Haiyan Hu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China; Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden.
| | - Baolin Wang
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Andrea G Bravo
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (ICM-CSIC), Pg Marítim de la Barceloneta 37-49, E08003 Barcelona, Catalunya, Spain
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - David Amouroux
- CNRS/Univ Pau & Pays Adour/ E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Materiaux-mira, UMR5254, 64000, Pau, France
| | - Emmanuel Tessier
- CNRS/Univ Pau & Pays Adour/ E2S UPPA, Institut des Sciences Analytiques et de Physicochimie pour l'Environnement et les Materiaux-mira, UMR5254, 64000, Pau, France
| | - Jakob Zopfi
- Department of Environmental Sciences, Biogeochemistry, University of Basel, CH-4056 Basel, Switzerland
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Mats B Nilsson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Stefan Bertilsson
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden; Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
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Ji X, Liu C, Pan G. Interfacial oxygen nanobubbles reduce methylmercury production ability of sediments in eutrophic waters. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 188:109888. [PMID: 31706242 DOI: 10.1016/j.ecoenv.2019.109888] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/23/2019] [Accepted: 10/27/2019] [Indexed: 06/10/2023]
Abstract
Eutrophication can induce hypoxia/anoxia and rich organic matter at the sediment-water interface in surface waters. When eutrophic waters are impacted with mercury (Hg) pollution, methylmercury (MeHg) production ability (MPA) of surface sediment would increase and more MeHg might be produced. To tackle this risk, this study firstly collected samples of surface sediment and overlying water from a typical eutrophic lake-Taihu Lake. Then from a sediment-water simulation system, we demonstrated that eutrophic waters were able to methylate Hg spontaneously, and that sediment is the major Hg sink in the system. After the addition of HgCl2 solution (approximately 1 mg L-1 in the slurry), MeHg concentrations in the sediment increased by 11.7 times after 48 h. The subsequent column experiments proved that O2 nanobubbles could significantly decrease the MPA of surface sediment, by up to 48%. Furthermore, we found that O2 nanobubbles could remediate anoxia mainly by increasing dissolved oxygen (from 0 to 2.1 mg L-1), oxidation-reduction potentials (by 37% on average), and sulfate (by 31% on average) in the overlying water. In addition, O2 nanobubbles could also help decrease organic matter concentration, as was revealed by the decline of dissolved organic carbon in the overlying water (by up to 57%) and total organic carbon in surface sediment (by up to 37%). The remediation of anoxia and reduction of organic matter could contribute to the decrease of hgcA gene abundance (by up to 86%), and thus result in the reduction of MPA after the addition of O2 nanobubbles. This study revealed the risk of MeHg production in case Hg pollution occurs in eutrophic waters and proposed a feasible solution for MeHg remediation.
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Affiliation(s)
- Xiaonan Ji
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Chengbin Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, PR China
| | - Gang Pan
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China; Beijing Advanced Science and Innovation Center, Chinese Academy of Sciences, Beijing, 101407, PR China; Center of Integrated Water-Energy-Food Studies (iWEF), School of Animal, Rural, and Environmental Sciences, Nottingham Trent University, Brackenhurst Campus, NG25 0QF, UK.
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33
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Chen CF, Ju YR, Lim YC, Chen CW, Wu CH, Lin YL, Dong CD. Dry and wet seasonal variation of total mercury, inorganic mercury, and methylmercury formation in estuary and harbor sediments. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2020; 253:109683. [PMID: 31666210 DOI: 10.1016/j.jenvman.2019.109683] [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: 03/09/2019] [Revised: 09/17/2019] [Accepted: 10/05/2019] [Indexed: 06/10/2023]
Abstract
This study analyzed the seasonal variations and the spatial distributions of total mercury (THg), inorganic divalent mercury (IHg), and methylmercury (MeHg) in sediments of river mouth (RM), main channel (MC), and entrance (E) of the Port of Kaohsiung, Taiwan. The THg, IHg, and MeHg concentrations were, respectively, 198-9130, 2.6-3164, and <0.3-42.6 μg/kg in the wet season and 362-2264, 11.0-790, and 3.3-65.6 μg/kg in the dry season. As for seasonal variations, the concentrations of THg and IHg for RM sediment were higher in the wet season than in the dry season, whereas for MC and E was converse. Generally, MeHg in sediment was higher in the dry season than in the wet season. THg and IHg were mainly transported from the river, whereas MeHg was generated by onsite microbes transforming the local available IHg. Results indicated that the formation of MeHg in sediment may be mainly influenced by the concentration of IHg and seasonal variations.
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Affiliation(s)
- Chih-Feng Chen
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan
| | - Yun-Ru Ju
- Department of Safety, Health and Environmental Engineering, National United University, Miaoli, 36063, Taiwan
| | - Yee Cheng Lim
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan
| | - Chiu-Wen Chen
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan.
| | - Chung-Hsin Wu
- Department of Chemical and Materials Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 80778, Taiwan
| | - Yi-Li Lin
- Department of Safety, Health and Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 82445, Taiwan
| | - Cheng-Di Dong
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung, 81157, Taiwan.
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34
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Chen CF, Ju YR, Chen CW, Dong CD. The distribution of methylmercury in estuary and harbor sediments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 691:55-63. [PMID: 31319258 DOI: 10.1016/j.scitotenv.2019.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 06/24/2019] [Accepted: 07/01/2019] [Indexed: 06/10/2023]
Abstract
Methylmercury (MeHg) presents high toxicity to humans and can be accumulated to organisms via the food chains. In aquatic environments, MeHg is mainly formed by microorganism using the bioavailable inorganic mercury in sediment. In this study, a total of 120 surface sediments from 20 sites in the Kaohsiung Harbor were collected quarterly in the period from July 2016 to October 2017 and analyzed for total mercury (THg), bioavailable inorganic mercury (BIHg), MeHg, and several geochemical parameters. The concentrations of THg, BIHg, and MeHg in sediment were 455-5108, 7.0-1021, and 0.84-24.1 μg/kg dw, respectively. Results indicated that the percentage of MeHg to THg (MeHg ratio) in most sediment (85%) is <1.2%. Correlation analysis showed that MeHg in sediment was mainly controlled by BIHg (r = 0.759, p < 0.01), while the concentration of BIHg in sediment was mainly related to TOC (r = 0. 480, p < 0.01) and THg (r = 0.435, p < 0.01). The relationship between total bioavailable inorganic mercury (containing BIHg and the bioavailable inorganic mercury used in the synthesis of MeHg) and MeHg concentration in the sediments that collected from the estuary, harbor channel, and the entrance was established by a Michaelis-Menten model to predict the maximum value of MeHg. The efficiency of Hg methylation in the sediments of Kaohsiung Harbor is significantly affected by the total bioavailable inorganic mercury and the related environmental factors. In addition, changes in environmental conditions caused by local seasonality should also be an important factor to consider when assessing the efficiency of Hg methylation.
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Affiliation(s)
- Chih-Feng Chen
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan
| | - Yun-Ru Ju
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan
| | - Chiu-Wen Chen
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan.
| | - Cheng-Di Dong
- Department of Marine Environmental Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 81157, Taiwan.
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Liu YR, Yang Z, Zhou X, Qu X, Li Z, Zhong H. Overlooked Role of Putative Non-Hg Methylators in Predicting Methylmercury Production in Paddy Soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:12330-12338. [PMID: 31603332 DOI: 10.1021/acs.est.9b03013] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Rice ingestion has been recognized as an important route of dietary exposure to neurotoxic methylmercury (MeHg) that is commonly synthesized in rice paddy soils. Although Hg methylators are known to regulate soil MeHg formation, the effect of non-Hg methylating communities on MeHg production remains unclear. Here, we collected 141 paddy soil samples from main rice-producing areas across China to identify associations between bacterial community composition (including both Hg and putative non-Hg methylators) and MeHg production. Results showed that the MeHg content in the paddy soils varied from 0.11 to 8.36 ng g-1 at a national spatial scale, which could be due to the shifts of soil microbial community composition across different areas. Our structure equation modeling suggested a strong link between bacterial community composition and MeHg content and %MeHg. More importantly, random forest analyses suggested a more significant role of putative non-Hg methylators than Hg methylators in predicting variations of soil MeHg content. The relative abundance of putative non-Hg methylators such as unclassified Xanthomonadales and Chitinophagaceae were strongly correlated with soil MeHg contents. Further, microbial network analysis revealed strong co-occurrence patterns between the putative non-Hg and Hg methylators. These findings highlight an overlooked role of non-Hg methylating communities in predicting MeHg production in paddy soils.
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Affiliation(s)
| | - Ziming Yang
- Department of Chemistry , Oakland University , Rochester , Michigan 48309 , United States
| | | | | | - Zizhu Li
- School of the Environment , Nanjing University , Nanjing 210023 , China
| | - Huan Zhong
- School of the Environment , Nanjing University , Nanjing 210023 , China
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Poulin BA, Ryan JN, Tate MT, Krabbenhoft DP, Hines ME, Barkay T, Schaefer J, Aiken GR. Geochemical Factors Controlling Dissolved Elemental Mercury and Methylmercury Formation in Alaskan Wetlands of Varying Trophic Status. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:6203-6213. [PMID: 31090422 DOI: 10.1021/acs.est.8b06041] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The transformations of aqueous inorganic divalent mercury (Hg(II)i) to volatile dissolved gaseous mercury (Hg(0)(aq)) and toxic methylmercury (MeHg) govern mercury bioavailability and fate in northern ecosystems. This study quantified concentrations of aqueous mercury species (Hg(II)i, Hg(0)(aq), MeHg) and relevant geochemical constituents in pore waters of eight Alaskan wetlands that differ in trophic status (i.e., bog-to-fen gradient) to gain insight on processes controlling dark Hg(II)i reduction and Hg(II)i methylation. Regardless of wetland trophic status, positive correlations were observed between pore water Hg(II)i and dissolved organic carbon (DOC) concentrations. The concentration ratio of Hg(0)(aq) to Hg(II)i exhibited an inverse relationship to Hg(II)i concentration. A ubiquitous pathway for Hg(0)(aq) formation was not identified based on geochemical data, but we surmise that dissolved organic matter (DOM) influences mercury retention in wetland pore waters by complexing Hg(II)i and decreasing the concentration of volatile Hg(0)(aq) relative to Hg(II)i. There was no evidence of Hg(0)(aq) abundance directly limiting mercury methylation. The concentration of MeHg relative to Hg(II)i was greatest in wetlands of intermediate trophic status, and geochemical data suggest mercury methylation pathways vary between wetlands. Our insights on geochemical factors influencing aqueous mercury speciation should be considered in context of the long-term fate of mercury in northern wetlands.
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Affiliation(s)
- Brett A Poulin
- U.S. Geological Survey , Boulder , Colorado 80303 , United States
- Department of Civil, Environmental, and Architectural Engineering , University of Colorado Boulder , Boulder , Colorado 80309 , United States
| | - Joseph N Ryan
- Department of Civil, Environmental, and Architectural Engineering , University of Colorado Boulder , Boulder , Colorado 80309 , United States
| | - Michael T Tate
- U.S. Geological Survey , Middleton , Wisconsin 53562 , United States
| | | | - Mark E Hines
- Department of Biological Sciences , University of Massachusetts Lowell , Lowell , Massachusetts 01854 , United States
| | - Tamar Barkay
- Department of Biochemistry and Microbiology , Rutgers University , New Brunswick , New Jersey 08901 , United States
| | - Jeffra Schaefer
- Department of Environmental Sciences , Rutgers University , New Brunswick , New Jersey 08901 , United States
| | - George R Aiken
- U.S. Geological Survey , Boulder , Colorado 80303 , United States
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Xu Z, Fan W, Shi Z, Tan C, Cui M, Tang S, Qiu G, Feng X. Mercury and methylmercury bioaccumulation in a contaminated bay. MARINE POLLUTION BULLETIN 2019; 143:134-139. [PMID: 31789148 DOI: 10.1016/j.marpolbul.2019.04.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 04/04/2019] [Accepted: 04/12/2019] [Indexed: 06/10/2023]
Abstract
The bioaccumulation and the main source of total Hg (THg) and methylmercury (MMHg) in the deposit-feeding polychaete Neanthes japonica collected in Jinzhou Bay, China, were investigated. Compared with the historical data, THg bioaccumulation in polychaetes collected in sediment of Jinzhou Bay was distinctly higher due to higher sediment THg concentration, but MMHg bioaccumulation was significantly lower. THg accumulation in polychaetes mainly derived from its accumulation in sediment. However, MMHg bioaccumulation in polychaetes did not correlate with Hg concentration in sediment. Besides sediment ingestion, MMHg accumulation in polychaetes may partially source from the process of in vivo transformation. The in vivo Hg methylation may take place in polychaetes, according to the excellent correlation between MMHg concentration and THg and inorganic Hg concentration in polychaetes. The biochemical characters in polychaete body, the oxidation-reduction environment and the microbial activity in polychaete gut may be beneficial to in vivo Hg methylation.
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Affiliation(s)
- Zhizhen Xu
- Key Laboratory of Occupational Safety and Health, Beijing Municipal Institute of Labor Protection, Beijing 100054, PR China
| | - Wenhong Fan
- School of Space and Environment, Beihang University, Beijing 100191, PR China; Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, Beihang University, Beijing 100191, PR China.
| | - Zhiwei Shi
- School of Space and Environment, Beihang University, Beijing 100191, PR China
| | - Cheng Tan
- School of Space and Environment, Beihang University, Beijing 100191, PR China
| | - Minming Cui
- School of Space and Environment, Beihang University, Beijing 100191, PR China
| | - Shichuan Tang
- Key Laboratory of Occupational Safety and Health, Beijing Municipal Institute of Labor Protection, Beijing 100054, PR China
| | - Guangle Qiu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, PR China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, PR China.
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Mercury methylating microbial communities of boreal forest soils. Sci Rep 2019; 9:518. [PMID: 30679728 PMCID: PMC6345997 DOI: 10.1038/s41598-018-37383-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/29/2018] [Indexed: 02/05/2023] Open
Abstract
The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is also linked to the composition of non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.
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39
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Regnell O, Watras CJ. Microbial Mercury Methylation in Aquatic Environments: A Critical Review of Published Field and Laboratory Studies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4-19. [PMID: 30525497 DOI: 10.1021/acs.est.8b02709] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Methylmercury (MeHg) is an environmental contaminant of concern because it biomagnifies in aquatic food webs and poses a health hazard to aquatic biota, piscivorous wildlife and humans. The dominant source of MeHg to freshwater systems is the methylation of inorganic Hg (IHg) by anaerobic microorganisms; and it is widely agreed that in situ rates of Hg methylation depend on two general factors: the activity of Hg methylators and their uptake of IHg. A large body of research has focused on the biogeochemical processes that regulate these two factors in nature; and studies conducted within the past ten years have made substantial progress in identifying the genetic basis for intracellular methylation and defining the processes that govern the cellular uptake of IHg. Current evidence indicates that all Hg methylating anaerobes possess the gene pair hgcAB that encodes proteins essential for Hg methylation. These genes are found in a large variety of anaerobes, including iron reducers and methanogens; but sulfate reduction is the metabolic process most often reported to show strong links to MeHg production. The uptake of Hg substrate prior to methylation may occur by passive or active transport, or by a combination of both. Competitive inhibition of Hg uptake by Zn speaks in favor of active transport and suggests that essential metal transporters are involved. Shortly after its formation, MeHg is typically released from cells, but the efflux mechanisms are unknown. Although methylation facilitates Hg depuration from the cell, evidence suggests that the hgcAB genes are not induced or favored by Hg contamination. Instead, high MeHg production can be linked to high Hg bioavailability as a result of the formation of Hg(SH)2, HgS nanoparticles, and Hg-thiol complexes. It is also possible that sulfidic conditions require strong essential metal uptake systems that inadvertently bring Hg into the cytoplasm of Hg methylating microbes. In comparison with freshwaters, Hg methylation in open ocean waters appears less restricted to anoxic environments. It does seem to occur mainly in oxygen deficient zones (ODZs), and possibly within anaerobic microzones of settling organic matter, but MeHg (CH3Hg+) and Me2Hg ((CH3)2Hg) have been shown to form also in surface water samples from the euphotic zone. Future studies may disclose whether several different pathways lead to Hg methylation in marine waters and explain why Me2Hg is a significant Hg species in oceans but seemingly not in most freshwaters.
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Affiliation(s)
- Olof Regnell
- Department of Biology/Aquatic Ecology , Lund University , SE-223 62 Lund , Sweden
| | - Carl J Watras
- Bureau of Water Quality , Wisconsin Department of Natural Resources , Madison , Wisconsin 53703 , United States
- Center for Limnology , University of Wisconsin-Madison , 3110 Trout Lake Station Drive , Boulder Junction , Wisconsin 54512 , United States
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Jiang T, Bravo AG, Skyllberg U, Björn E, Wang D, Yan H, Green NW. Influence of dissolved organic matter (DOM) characteristics on dissolved mercury (Hg) species composition in sediment porewater of lakes from southwest China. WATER RESEARCH 2018; 146:146-158. [PMID: 30243058 DOI: 10.1016/j.watres.2018.08.054] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 08/20/2018] [Accepted: 08/25/2018] [Indexed: 06/08/2023]
Abstract
The origin and composition of dissolved organic matter (DOM) in porewater of lake sediments is intricate and decisive for fate of pollutants including mercury (Hg). While there are many reports on the relationship between dissolved organic carbon concentration (DOC) and mercury (Hg) concentrations in aquatic systems, there are few in which DOM compositional properties, that may better explain the fate of Hg, have been the focus. In this study, porewaters from sediments of three lakes, Caihai Lake (CH), Hongfeng Lake (HF) and Wujiangdu Lake (WJD), all located in southwest China, were selected to test the hypothesis that DOM optical properties control the fate of Hg in aquatic ecosystems. Porewater DOM was extracted and characterized by UV-Vis absorption and fluorescence spectroscopy. A two end-member (autochthonous and allochthonous DOM) mixing model was used to unveil the origin of DOM in porewaters of the three lakes. Our results show a higher input of terrestrial DOM in the pristine lake CH, as compared to lakes HF and WJD lakes, which were both influenced by urban environments and enriched in autochthonous DOM. While the relationships between the concentrations of DOC and the different chemical forms of Hg forms were quite inconsistent, we found important links between specific DOM components and the fate of Hg in the three lakes. In particular, our results suggest that allochthonous, terrestrial DOM inhibits Hg(II) availability for Hg methylating micro-organisms. In contrast, autochthonous DOM seems to have been stimulated MeHg formation, likely by enhancing the activity of microbial communities. Indeed, DOM biodegradation experiments revealed that differences in the microbial activity could explain the variation in the concentration of MeHg. While relationships between concentrations of DOC and Hg vary among different sites and provide little information about Hg cycling, we conclude that the transport and transformation of Hg (e.g. the methylation process) are more strongly linked to DOM chemical composition and reactivity.
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Affiliation(s)
- Tao Jiang
- Department of Environment Science and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China; Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden
| | - Andrea G Bravo
- Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA), Spanish National Research Council (CSIC), Barcelona, 08034, Spain
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-901-87, Umeå, Sweden
| | - Dingyong Wang
- Department of Environment Science and Engineering, College of Resources and Environment, Southwest University, Chongqing, 400716, China
| | - Haiyu Yan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
| | - Nelson W Green
- School of Chemical and Biomolecular Engineering, Atlanta, GA, 30332, United States
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Bravo AG, Kothawala DN, Attermeyer K, Tessier E, Bodmer P, Ledesma JLJ, Audet J, Casas-Ruiz JP, Catalán N, Cauvy-Fraunié S, Colls M, Deininger A, Evtimova VV, Fonvielle JA, Fuß T, Gilbert P, Herrero Ortega S, Liu L, Mendoza-Lera C, Monteiro J, Mor JR, Nagler M, Niedrist GH, Nydahl AC, Pastor A, Pegg J, Gutmann Roberts C, Pilotto F, Portela AP, González-Quijano CR, Romero F, Rulík M, Amouroux D. The interplay between total mercury, methylmercury and dissolved organic matter in fluvial systems: A latitudinal study across Europe. WATER RESEARCH 2018; 144:172-182. [PMID: 30029076 DOI: 10.1016/j.watres.2018.06.064] [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: 01/30/2018] [Revised: 06/27/2018] [Accepted: 06/28/2018] [Indexed: 05/16/2023]
Abstract
Large-scale studies are needed to identify the drivers of total mercury (THg) and monomethyl-mercury (MeHg) concentrations in aquatic ecosystems. Studies attempting to link dissolved organic matter (DOM) to levels of THg or MeHg are few and geographically constrained. Additionally, stream and river systems have been understudied as compared to lakes. Hence, the aim of this study was to examine the influence of DOM concentration and composition, morphological descriptors, land uses and water chemistry on THg and MeHg concentrations and the percentage of THg as MeHg (%MeHg) in 29 streams across Europe spanning from 41°N to 64 °N. THg concentrations (0.06-2.78 ng L-1) were highest in streams characterized by DOM with a high terrestrial soil signature and low nutrient content. MeHg concentrations (7.8-159 pg L-1) varied non-systematically across systems. Relationships between DOM bulk characteristics and THg and MeHg suggest that while soil derived DOM inputs control THg concentrations, autochthonous DOM (aquatically produced) and the availability of electron acceptors for Hg methylating microorganisms (e.g. sulfate) drive %MeHg and potentially MeHg concentration. Overall, these results highlight the large spatial variability in THg and MeHg concentrations at the European scale, and underscore the importance of DOM composition on mercury cycling in fluvial systems.
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Affiliation(s)
- Andrea G Bravo
- Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDAEA), Spanish National Research Council (CSIC), Barcelona, Spain.
| | - Dolly N Kothawala
- Limnology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Katrin Attermeyer
- Limnology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Emmanuel Tessier
- CNRS/ UNIV PAU & PAYS ADOUR, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Materiaux, UMR5254, MIRA, Pau, France
| | - Pascal Bodmer
- Institute for Environmental Sciences, University of Koblenz-Landau, Landau, Germany; Chemical Analytics and Biogeochemistry, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - José L J Ledesma
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Joachim Audet
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | | | - Núria Catalán
- Catalan Institute for Water Research (ICRA), Girona, Spain
| | | | - Miriam Colls
- Catalan Institute for Water Research (ICRA), Girona, Spain
| | - Anne Deininger
- Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
| | - Vesela V Evtimova
- Department of Aquatic Ecosystems, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Jérémy A Fonvielle
- Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany
| | - Thomas Fuß
- Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany; WasserCluster Biological Station Lunz, Lunz am See, Austria
| | - Peter Gilbert
- The Environmental Research Institute, North Highland College, University of Highlands and Islands, Thurso, Scotland, UK
| | - Sonia Herrero Ortega
- Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany
| | - Liu Liu
- Institute for Environmental Sciences, University of Koblenz-Landau, Landau, Germany
| | - Clara Mendoza-Lera
- IRSTEA, UR RiverLy, Centre de Lyon-Villeurbanne, Villeurbanne, Cedex, France
| | - Juliana Monteiro
- Research Centre in Biodiversity and Genetic Resources (CIBIO), University of Porto, Porto, Portugal
| | - Jordi-René Mor
- Catalan Institute for Water Research (ICRA), Girona, Spain; Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, University of Barcelona (UB), Barcelona, Spain
| | - Magdalena Nagler
- Microbial Resource Management, Institute of Microbiology, University of Innsbruck, Innsbruck, Austria
| | - Georg H Niedrist
- River and Conservation Research, Institute of Ecology, University of Innsbruck, Innsbruck, Austria
| | - Anna C Nydahl
- Limnology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Ada Pastor
- Catalan Institute for Water Research (ICRA), Girona, Spain
| | - Josephine Pegg
- Department of Life and Environmental Sciences, Bournemouth University, UK; University Centre Sparsholt, Winchester, UK
| | | | - Francesca Pilotto
- Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
| | - Ana Paula Portela
- Research Centre in Biodiversity and Genetic Resources (CIBIO), University of Porto, Porto, Portugal
| | | | - Ferran Romero
- Catalan Institute for Water Research (ICRA), Girona, Spain
| | - Martin Rulík
- Department of Ecology and Environmental Sciences, Palacky University in Olomouc, Olomouc, Czech Republic
| | - David Amouroux
- CNRS/ UNIV PAU & PAYS ADOUR, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Materiaux, UMR5254, MIRA, Pau, France.
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Xiang Y, Wang Y, Zhang C, Shen H, Wang D. Water level fluctuations influence microbial communities and mercury methylation in soils in the Three Gorges Reservoir, China. J Environ Sci (China) 2018; 68:206-217. [PMID: 29908740 DOI: 10.1016/j.jes.2018.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 03/03/2018] [Accepted: 03/09/2018] [Indexed: 06/08/2023]
Abstract
Reservoirs tend to have enhanced methylmercury (MeHg) concentrations compared to natural lakes and rivers, and water level fluctuations can promote MeHg production. Until now, little research has been conducted on the effects of microorganisms in soils for the formation of MeHg during different drying and flooding alternating conditions in the Three Gorges Reservoir (TGR). This study aimed to understand how water level fluctuations affect soil microbial composition and mercury concentrations, and if such microbial variations are related to Hg methylation. The results showed that MeHg concentrations and the ratios of MeHg to THg (MeHg%) in soils were higher in the seasonally drying and flooding alternating areas (DFAs, 175-155m) than those in the non-inundated (NIAs, >175m) and inundated areas (IAs, <145m). However, MeHg% in all samples was less than 1%, indicating that the Hg methylation activity in the soils of the TGR was under a low level. 454 high-throughput sequencing of 16S rRNA gene amplicons showed that soil bacterial abundance and diversity were relatively higher in DFA compared to those in NIA and IA, and microbial community composition varied in these three areas. At the family level, those groups in Deltaproteobacteria and Methanomicrobia that might have many Hg methylators were also showed a higher relative abundance in DFA, which might be the reason for the higher MeHg production in these areas. Overall, our results suggested that seasonally water level fluctuations can enhance the microbial abundance and diversity, as well as MeHg production in the TGR.
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Affiliation(s)
- Yuping Xiang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Yongmin Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China
| | - Cheng Zhang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China
| | - Hong Shen
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400715, China.
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China; Chongqing Engineering Research Center for Agricultural Non-point Source Pollution Control in the Three Gorges Reservoir Area, Chongqing 400715, China; Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400715, China.
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43
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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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Olsen TA, Muller KA, Painter SL, Brooks SC. Kinetics of Methylmercury Production Revisited. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:2063-2070. [PMID: 29376334 DOI: 10.1021/acs.est.7b05152] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Laboratory measurements of the biologically mediated methylation of mercury (Hg) to the neurotoxin monomethylmercury (MMHg) often exhibit kinetics that are inconsistent with first-order kinetic models. Using time-resolved measurements of filter passing Hg and MMHg during methylation/demethylation assays, a multisite kinetic sorption model, and reanalyses of previous assays, we show that competing kinetic sorption reactions can lead to time-varying availability and apparent non-first-order kinetics in Hg methylation and MMHg demethylation. The new model employing a multisite kinetic sorption model for Hg and MMHg can describe the range of behaviors for time-resolved methylation/demethylation data reported in the literature including those that exhibit non-first-order kinetics. Additionally, we show that neglecting competing sorption processes can confound analyses of methylation/demethylation assays, resulting in rate constant estimates that are systematically biased low. Simulations of MMHg production and transport in a hypothetical periphyton biofilm bed illustrate the implications of our new model and demonstrate that methylmercury production may be significantly different than projected by single-rate first-order models.
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Affiliation(s)
- Todd A Olsen
- Environmental Sciences Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, United States
| | - Katherine A Muller
- Environmental Sciences Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, United States
| | - Scott L Painter
- Environmental Sciences Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, United States
| | - Scott C Brooks
- Environmental Sciences Division, Oak Ridge National Laboratory , P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, United States
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Eklöf K, Bishop K, Bertilsson S, Björn E, Buck M, Skyllberg U, Osman OA, Kronberg RM, Bravo AG. Formation of mercury methylation hotspots as a consequence of forestry operations. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 613-614:1069-1078. [PMID: 28950669 DOI: 10.1016/j.scitotenv.2017.09.151] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 05/16/2023]
Abstract
Earlier studies have shown that boreal forest logging can increase the concentration and export of methylmercury (MeHg) in stream runoff. Here we test whether forestry operations create soil environments of high MeHg net formation associated with distinct microbial communities. Furthermore, we test the hypothesis that Hg methylation hotspots are more prone to form after stump harvest than stem-only harvest, because of more severe soil compaction and soil disturbance. Concentrations of MeHg, percent MeHg of total Hg (THg), and bacterial community composition were determined at 200 soil sampling positions distributed across eight catchments. Each catchment was either stem-only harvested (n=3), stem- and stump-harvested (n=2) or left undisturbed (n=3). In support of our hypothesis, higher MeHg to THg ratios was observed in one of the stump-harvested catchments. While the effects of natural variation could not be ruled out, we noted that most of the highest % MeHg was observed in water-filled cavities created by stump removal or driving damage. This catchment also featured the highest bacterial diversity and highest relative abundance of bacterial families known to include Hg methylators. We propose that water-logged and disturbed soil environments associated with stump harvest can favor methylating microorganisms, which also enhance MeHg formation.
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Affiliation(s)
- Karin Eklöf
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden.
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
| | - Stefan Bertilsson
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Moritz Buck
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden; National Bioinformatics Infrastructure Sweden, Uppsala SE-75236, Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
| | - Omneya A Osman
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
| | - Rose-Marie Kronberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden
| | - Andrea G Bravo
- Department of Ecology and Genetics, Limnology and Science for Life Laboratory, Uppsala University, SE-75236 Uppsala, Sweden
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Olsen M, Schaanning MT, Braaten HFV, Eek E, Moy FE, Lydersen E. The influence of permanently submerged macrophytes on sediment mercury distribution, mobility and methylation potential in a brackish Norwegian fjord. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 610-611:1364-1374. [PMID: 28851156 DOI: 10.1016/j.scitotenv.2017.08.136] [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: 04/13/2017] [Revised: 08/06/2017] [Accepted: 08/14/2017] [Indexed: 06/07/2023]
Abstract
Macrophytes are shown to affect the microbial activity in different aqueous environments, with an altering of the sediment cycling of mercury (Hg) as a potential effect. Here, we investigated how a meadow with permanently submerged macrophytes in a contaminated brackish fjord in southern Norway influenced the conditions for sulfate reducing microbial activity, the methyl-Hg (MeHg) production and the availability of MeHg. Historically discharged Hg from a chlor-alkali plant (60-80tons, 1947-1987) was evident through high Hg concentrations (491mgTot-Hgkg-1, 268μgMeHgkg-1) in intermediate sediment depths (10-20cm) outside of the meadow, with reduced concentrations within the meadow. Natural recovery of the fjord was revealed by lower sediment surface concentrations (1.9-15.5mgTot-Hgkg-1, 1.3-3.2μgMeHgkg-1). Within the meadow, vertical gradients of sediment hydrogen sulfide (H2S) Eh and pH suggested microbial sulfate reduction in 2-5cm depths, coinciding with peak values of relative MeHg levels (0.5% MeHg). We assume that MeHg production rates was stimulated by the supply and availability of organic carbon, microbial activity and a sulfide oxidizing agent (e.g. O2) within the rhizosphere. Following this, % MeHg in sediment (0-5cm) within the meadow was approximately 10× higher compared to outside the meadow. Further, enhanced availability of MeHg within the meadow was demonstrated by significantly higher fluxes (p<0.01) from sediment to overlying water (0.1-0.6ngm-2d-1) compared to sediment without macrophytes (0.02-0.2ngm-2d-1). Considering the productivity and species richness typical for such habitats, submerged macrophyte meadows located within legacy Hg contaminated sediment sites may constitute important entry points for MeHg into food webs.
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Affiliation(s)
- Marianne Olsen
- University College of Southeast Norway, Gullbringvegen 36, N-3800 Bø, Norway; The Norwegian Institute for Water Research, Gaustadalléen 21, N-0349 Oslo, Norway.
| | | | | | - Espen Eek
- Norwegian Geotechnical Institute, NGI, PB 3930, Ullevål Stadion, 0806 Oslo, Norway
| | - Frithjof E Moy
- Institute of Marine Research, Nye Flødevigveien 20, 4817 His, Norway
| | - Espen Lydersen
- University College of Southeast Norway, Gullbringvegen 36, N-3800 Bø, Norway
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Buckman K, Taylor V, Broadley H, Hocking D, Balcom P, Mason R, Nislow K, Chen C. Methylmercury bioaccumulation in an urban estuary: Delaware River USA. ESTUARIES AND COASTS : JOURNAL OF THE ESTUARINE RESEARCH FEDERATION 2017; 40:1358-1370. [PMID: 28970741 PMCID: PMC5621658 DOI: 10.1007/s12237-017-0232-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Spatial variation in mercury (Hg) and methylmercury (MeHg) bioaccumulation in urban coastal watersheds reflects complex interactions between Hg sources, land use, and environmental gradients. We examined MeHg concentrations in fauna from the Delaware River estuary, and related these measurements to environmental parameters and human impacts on the waterway. The sampling sites followed a north to south gradient of increasing salinity, decreasing urban influence, and increasing marsh cover. Although mean total Hg in surface sediments (top 4cm) peaked in the urban estuarine turbidity maximum and generally decreased downstream, surface sediment MeHg concentrations showed no spatial patterns consistent with the examined environmental gradients, indicating urban influence on Hg loading to the sediment but not subsequent methylation. Surface water particulate MeHg concentration showed a positive correlation with marsh cover whereas dissolved MeHg concentrations were slightly elevated in the estuarine turbidity maximum region. Spatial patterns of MeHg bioaccumulation in resident fauna varied across taxa. Small fish showed increased MeHg concentrations in the more urban/industrial sites upstream, with concentrations generally decreasing farther downstream. Invertebrates either showed no clear spatial patterns in MeHg concentrations (blue crabs, fiddler crabs) or increasing concentrations further downstream (grass shrimp). Best-supported linear mixed models relating tissue concentration to environmental variables reflected these complex patterns, with species specific model results dominated by random site effects with a combination of particulate MeHg and landscape variables influencing bioaccumulation in some species. The data strengthen accumulating evidence that bioaccumulation in estuaries can be decoupled from sediment MeHg concentration, and that drivers of MeHg production and fate may vary within a small region.
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Affiliation(s)
- Kate Buckman
- Department of Biological Sciences, Dartmouth College, Hanover NH
- Corresponding Authors: , phone: 603-646-8768, , phone: 603-646-2376
| | - Vivien Taylor
- Department of Earth Sciences, Dartmouth College, Hanover NH
| | - Hannah Broadley
- Department of Biological Sciences, Dartmouth College, Hanover NH
| | - Daniel Hocking
- Department of Biology, Frostburg State University, Frostburg MD
| | - Prentiss Balcom
- Department of Marine Sciences, University of Connecticut, Groton CT
- Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge MA
| | - Rob Mason
- Department of Marine Sciences, University of Connecticut, Groton CT
| | - Keith Nislow
- Northern Research Station, USDA Forest Service, Amherst MA
| | - Celia Chen
- Department of Biological Sciences, Dartmouth College, Hanover NH
- Corresponding Authors: , phone: 603-646-8768, , phone: 603-646-2376
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Cesário R, Hintelmann H, Mendes R, Eckey K, Dimock B, Araújo B, Mota AM, Canário J. Evaluation of mercury methylation and methylmercury demethylation rates in vegetated and non-vegetated saltmarsh sediments from two Portuguese estuaries. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 226:297-307. [PMID: 28390703 DOI: 10.1016/j.envpol.2017.03.075] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 02/23/2017] [Accepted: 03/31/2017] [Indexed: 06/07/2023]
Abstract
Neurotoxic methylmercury (MMHg) is formed from inorganic divalent mercury (Hg2+). However, it is poorly understood to what extent different mercury (Hg) pools contribute to existent MMHg levels. In this study, ambient concentrations of total Hg (THg) and MMHg as well as rates of methylation and demethylation were measured simultaneously in sediments with and without salt-marsh plant vegetation, which were collected in Guadiana and Tagus estuaries, Portugal. Concurrent processes of Hg methylation and MMHg demethylation were directly monitored and compared by spiking sediments cores with stable isotope tracers of 199Hg2+ and CH3201Hg+ followed by gas chromatographic separation and isotope-specific detection using inductively coupled plasma mass spectrometry. Compared to the Guadiana estuary, where concentrations were comparatively low, THg and MMHg levels varied between vegetated and non-vegetated sediments collected at the Rosário site (ROS) of the Tagus estuary. Methylation (KM) and demethylation rates (KD) were also different between estuaries being dependent on the presence of vegetation. In addition, the type of macrophyte species influenced KM and KD values. In fact, the highest KM value was found in Sarcocornia fruticosa vegetated sediments at the Castro Marim site in Guadiana (CM, 0.160 day-1) and the lowest KM was observed in non-vegetated sediments at the Alcochete site in Tagus (ALC, 0.009 day-1). KD varied by a factor of three among sites with highest rates of demethylation observed in non-vegetated sediments in Guadiana (12 ± 1.3 day-1, corresponding to a half-life of 1.4 ± 0.2 h). This study clearly shows that the presence of vegetation in sediments favors the formation of MMHg. Moreover, this effect might be site specific and further studies are needed to confirm the findings reported here.
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Affiliation(s)
- Rute Cesário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal; IPMA-Instituto Português do Mar e Atmosfera, Av. Brasília, 1449-006 Lisboa, Portugal
| | - Holger Hintelmann
- Water Quality Centre, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada
| | - Ricardo Mendes
- IPMA-Instituto Português do Mar e Atmosfera, Av. Brasília, 1449-006 Lisboa, Portugal
| | - Kevin Eckey
- Institute of Inorganic and Analytical Chemistry, University of Muenster, Schlossplatz 2, 48149 Munster, Germany
| | - Brian Dimock
- Water Quality Centre, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada
| | - Beatriz Araújo
- Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense, Av. Alberto Lamego, 2000, Horto, Campus dos Goytacazes, Rio de Janeiro, Brazil
| | - Ana Maria Mota
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal
| | - João Canário
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, Lisboa 1, 1049-001 Lisboa, Portugal.
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49
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Paranjape AR, Hall BD. Recent advances in the study of mercury methylation in aquatic systems. Facets (Ott) 2017. [DOI: 10.1139/facets-2016-0027] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.
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Affiliation(s)
- Avnee R. Paranjape
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
| | - Britt D. Hall
- Department of Biology, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
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Bailey LT, Mitchell CPJ, Engstrom DR, Berndt ME, Coleman Wasik JK, Johnson NW. Influence of porewater sulfide on methylmercury production and partitioning in sulfate-impacted lake sediments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 580:1197-1204. [PMID: 28024742 DOI: 10.1016/j.scitotenv.2016.12.078] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 12/12/2016] [Accepted: 12/12/2016] [Indexed: 06/06/2023]
Abstract
In low-sulfate and sulfate-limited freshwater sediments, sulfate loading increases the production of methylmercury (MeHg), a potent and bioaccumulative neurotoxin. Sulfate loading to anoxic sediments leads to sulfide production that can inhibit mercury methylation, but this has not been commonly observed in freshwater lakes and wetlands. In this study, sediments were collected from sulfate-impacted, neutral pH, surface water bodies located downstream from ongoing and historic mining activities to examine how chronic sulfate loading produces porewater sulfide, and influences MeHg production and transport. Sediments were collected over two years, during several seasons from lakes with a wide range of overlying water sulfate concentration. Samples were characterized for in-situ solid phase and porewater MeHg, Hg methylation potentials via incubations with enriched stable Hg isotopes, and sulfur, carbon, and iron content and speciation. Porewater sulfide reflected historic sulfur loading and was strongly related to the extractable iron content of sediment. Overall, methylation potentials were consistent with the accumulation of MeHg on the solid phase, but both methylation potentials and MeHg were significantly lower at chronically sulfate-impacted sites with a low solid-phase Fe:S ratio. At these heavily sulfate-impacted sites that also contained elevated porewater sulfide, both MeHg production and partitioning are influenced: Hg methylation potentials and sediment MeHg concentrations are lower, but occasionally porewater MeHg concentrations in sediment are elevated, particularly in the spring. The dual role of sulfide as a ligand for inorganic mercury (decreasing bioavailability) and methylmercury (increasing partitioning into porewater) means that elucidating the role of iron and sulfur loads as they define porewater sulfide is key to understanding sulfate's influence on MeHg production and partitioning in sulfate-impacted freshwater sediment.
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Affiliation(s)
- Logan T Bailey
- Water Resources Science Program, University of Minnesota, United States
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Canada
| | - Daniel R Engstrom
- St. Croix Watershed Research Station, Science Museum of Minnesota, United States
| | - Michael E Berndt
- Minnesota Department of Natural Resources, Division of Lands and Minerals, United States
| | - Jill K Coleman Wasik
- St. Croix Watershed Research Station, Science Museum of Minnesota, United States
| | - Nathan W Johnson
- Water Resources Science Program, University of Minnesota, United States; Department of Civil Engineering, University of Minnesota Duluth, United States.
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