1
|
Peterson BD, Poulin BA, Krabbenhoft DP, Tate MT, Baldwin AK, Naymik J, Gastelecutto N, McMahon KD. Metabolically diverse microorganisms mediate methylmercury formation under nitrate-reducing conditions in a dynamic hydroelectric reservoir. THE ISME JOURNAL 2023; 17:1705-1718. [PMID: 37495676 PMCID: PMC10504345 DOI: 10.1038/s41396-023-01482-1] [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: 03/31/2023] [Revised: 07/13/2023] [Accepted: 07/14/2023] [Indexed: 07/28/2023]
Abstract
Brownlee Reservoir is a mercury (Hg)-impaired hydroelectric reservoir that exhibits dynamic hydrological and geochemical conditions and is located within the Hells Canyon Complex in Idaho, USA. Methylmercury (MeHg) contamination in fish is a concern in the reservoir. While MeHg production has historically been attributed to sulfate-reducing bacteria and methanogenic archaea, microorganisms carrying the hgcA gene are taxonomically and metabolically diverse and the major biogeochemical cycles driving mercury (Hg) methylation are not well understood. In this study, Hg speciation and redox-active compounds were measured throughout Brownlee Reservoir across the stratified period in four consecutive years (2016-2019) to identify the location where and redox conditions under which MeHg is produced. Metagenomic sequencing was performed on a subset of samples to characterize the microbial community with hgcA and identify possible links between biogeochemical cycles and MeHg production. Biogeochemical profiles suggested in situ water column Hg methylation was the major source of MeHg. These profiles, combined with genome-resolved metagenomics focused on hgcA-carrying microbes, indicated that MeHg production occurs in this system under nitrate- or manganese-reducing conditions, which were previously thought to preclude Hg-methylation. Using this multidisciplinary approach, we identified the cascading effects of interannual variability in hydrology on the redox status, microbial metabolic strategies, abundance and metabolic diversity of Hg methylators, and ultimately MeHg concentrations throughout the reservoir. This work expands the known conditions conducive to producing MeHg and suggests that the Hg-methylation mitigation efforts by nitrate or manganese amendment may be unsuccessful in some locations.
Collapse
Affiliation(s)
- Benjamin D Peterson
- Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, 53706, USA.
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, 53706, USA.
- Department of Environmental Toxicology, University of California - Davis, Davis, CA, 95616, USA.
| | - Brett A Poulin
- Department of Environmental Toxicology, University of California - Davis, Davis, CA, 95616, USA
| | - David P Krabbenhoft
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, Madison, WI, 53726, USA
| | - Michael T Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, Madison, WI, 53726, USA
| | - Austin K Baldwin
- U.S. Geological Survey, Idaho Water Science Center, Boise, ID, 83702, USA
| | | | | | - Katherine D McMahon
- Department of Civil and Environmental Engineering, University of Wisconsin - Madison, Madison, WI, 53706, USA
- Department of Bacteriology, University of Wisconsin - Madison, Madison, WI, 53706, USA
| |
Collapse
|
2
|
Shen Z, Liu G, Guo Y, Jiang T, Liu Y, Shi J, Hu L, Yin Y, Cai Y, Jiang G. Dissolved organic matter mediated dark- and photo-aging processes of Hg(II): Critical impacts of binding sites and sulfidation on Hg(II) abiotic reduction and microbial methylation. WATER RESEARCH 2023; 242:120294. [PMID: 37429137 DOI: 10.1016/j.watres.2023.120294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 06/25/2023] [Accepted: 06/29/2023] [Indexed: 07/12/2023]
Abstract
Dissolved organic matter (DOM)-mediated divalent mercury (Hg(II)) aging kinetics play a crucial role in controlling Hg(II) transformation and bioavailability in natural aquatic environments. However, the differential environmental behaviors of new and aged Hg(II) in a same reaction system remains unknown. In this study, multi-isotope tracing was used to investigate the impacts of binding site and sulfidation during DOM-mediated Hg(II) aging processes on Hg(II) reduction and microbial methylation in the same reaction system. Stepwise reduction approach and liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) demonstrate that DOM-mediated dark aging processes are mainly driven by the rearrangement of DOM binding sites with Hg(II), but not the formation of mercury sulfide nanoparticles (HgSNP). The abundant but weaker RO/N (carboxyl and amino) Hg(II)-binding sites are replaced with stronger RSH (thiol) moieties towards Hg(II) binding with aging, resulting in a decrease in Hg(II) reduction. In contrast, besides reduction, DOM-mediated Hg(II) photoaging induces the formation of HgSNP, as revealed by LC-ICP-MS, which in turn decreases the microbial methylation potential of Hg(II). These findings help better understand and predict the kinetic characteristics of Hg(II) reactivity and its influence on Hg cycle within natural aquatic environments.
Collapse
Affiliation(s)
- Zelin Shen
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences (UCAS), Beijing 100049, China
| | - Guangliang Liu
- Institute of Environment and Health, Jianghan University, Wuhan 430056, China
| | - Yingying Guo
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Tao Jiang
- Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, College of Resources and Environment, Southwest University, Chongqing 400716, China
| | - Yanwei Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jianbo Shi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Ligang Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yongguang Yin
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences (UCAS), Beijing 100049, China; Institute of Environment and Health, Jianghan University, Wuhan 430056, China; School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China.
| | - Yong Cai
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| |
Collapse
|
3
|
Yang N, Hu J, Yin D, He T, Tian X, Ran S, Zhou X. Mercury and methylmercury in Hg-contaminated paddy soil and their uptake in rice as regulated by DOM from different agricultural sources. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023:10.1007/s11356-023-27712-9. [PMID: 37249779 DOI: 10.1007/s11356-023-27712-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 05/13/2023] [Indexed: 05/31/2023]
Abstract
In this study, from the perspectives of structural and compositional variations of soil-dissolved organic matter (DOM), we explored the effects of agricultural DOM inputs on methylmercury (MeHg) accumulation in the soil and mercury (Hg) bioaccumulation in rice grains. Pot experiments with the addition of DOMs from maize straw (MaS), rape straw (RaS), rice straw (RiS), composted rice straw (CRiS), cow dung (CD), and composted cow dung (CCD) were then conducted. Results showed that, relative to the control, the DOM amendment from each agricultural source elevated MeHg concentrations in the soil, with an increase of 18-227%, but only parts of DOMs elevated total dissolved Hg (DHg) and MeHg (DMeHg) concentrations in pore water. Among all DOM species, RiS, CRiS, and CCD significantly increased total Hg (THg) and MeHg contents in rice grains by 34-64% and 32-118%, respectively. Compared with RiS, THg and MeHg contents in rice grains in the CRiS treatment decreased slightly, which was consistent with the distributions of DHg and DMeHg concentrations in pore water and the aromaticity variation of soil DOM. In contrast, the CCD input significantly enhanced the enrichment of THg and MeHg in rice grains relative to CD because it significantly reduced the humification of soil DOM at all rice-growing stages while increasing the low-molecular-weight fractions in soil DOM. The THg and MeHg contents in the rice grains were significantly lower treated by RaS than those by MaS and RiS, which may be related to the higher sulfur-containing compounds such as sulfate and cysteine in rape straw or its DOM solution. Overall, DOM amendment from different agricultural sources resulted in significantly discriminative effects on the MeHg accumulation in soil and Hg enrichment in rice in the Hg-contaminated paddy field by shaping soil DOM properties.
Collapse
Affiliation(s)
- Ningla Yang
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
- College of Resources and Environment, Guizhou University, Guiyang, 550025, China
| | - Jie Hu
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
- College of Resources and Environment, Guizhou University, Guiyang, 550025, China
| | - Deliang Yin
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
- College of Resources and Environment, Guizhou University, Guiyang, 550025, China
| | - Tianrong He
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China.
- College of Resources and Environment, Guizhou University, Guiyang, 550025, China.
| | - Xiang Tian
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Shu Ran
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
| | - Xian Zhou
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, 550025, China
| |
Collapse
|
4
|
Wang T, Yang X, Li Z, Chen W, Wen X, He Y, Ma C, Yang Z, Zhang C. MeHg production in eutrophic lakes: Focusing on the roles of algal organic matter and iron-sulfur-phosphorus dynamics. JOURNAL OF HAZARDOUS MATERIALS 2023; 457:131682. [PMID: 37270963 DOI: 10.1016/j.jhazmat.2023.131682] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 05/20/2023] [Accepted: 05/21/2023] [Indexed: 06/06/2023]
Abstract
The mechanisms by which eutrophication affects methylmercury (MeHg) production have not been comprehensively summarized, which hinders accurately predicting the MeHg risk in eutrophic lakes. In this review, we first discussed the effects of eutrophication on biogeochemical cycle of mercury (Hg). Special attentions were paid to the roles of algal organic matter (AOM) and iron (Fe)-sulfur (S)-phosphorus (P) dynamics in MeHg production. Finally, the suggestions for risk control of MeHg in eutrophic lakes were proposed. AOM can affect in situ Hg methylation by stimulating the abundance and activities of Hg methylating microorganisms and regulating Hg bioavailability, which are dependent on bacteria-strain and algae species, the molecular weight and composition of AOM as well as environmental conditions (e.g., light). Fe-S-P dynamics under eutrophication including sulfate reduction, FeS formation and P release could also play crucial but complicated roles in MeHg production, in which AOM may participate through influencing the dissolution and aggregation processes, structural order and surface properties of HgS nanoparticles (HgSNP). Future studies should pay more attention to the dynamics of AOM in responses to the changing environmental conditions (e.g., light penetration and redox fluctuations) and how such variations will subsequently affect MeHg production. The effects of Fe-S-P dynamics on MeHg production under eutrophication also deserve further investigations, especially the interactions between AOM and HgSNP. Remediation strategies with lower disturbance, greater stability and less cost like the technology of interfacial O2 nanobubbles are urgent to be explored. This review will deepen our understanding of the mechanisms of MeHg production in eutrophic lakes and provide theoretical guidance for its risk control.
Collapse
Affiliation(s)
- Tantan Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Xu Yang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Zihao Li
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Wenhao Chen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Xin Wen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Yubo He
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Chi Ma
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Zhongzhu Yang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Chang Zhang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
| |
Collapse
|
5
|
Poulin BA, Tate MT, Ogorek J, Breitmeyer SE, Baldwin AK, Yoder AM, Harris R, Naymik J, Gastelecutto N, Hoovestol C, Larsen C, Myers R, Aiken GR, Krabbenhoft DP. Biogeochemical and hydrologic synergy control mercury fate in an arid land river-reservoir system. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2023; 25:912-928. [PMID: 37186129 DOI: 10.1039/d3em00032j] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Reservoirs in arid landscapes provide critical water storage and hydroelectric power but influence the transport and biogeochemical cycling of mercury (Hg). Improved management of reservoirs to mitigate the supply and uptake of bioavailable methylmercury (MeHg) in aquatic food webs will benefit from a mechanistic understanding of inorganic divalent Hg (Hg(II)) and MeHg fate within and downstream of reservoirs. Here, we quantified Hg(II), MeHg, and other pertinent biogeochemical constituents in water (filtered and associated with particles) at high temporal resolution from 2016-2020. This was done (1) at inflow and outflow locations of three successive hydroelectric reservoirs (Snake River, Idaho, Oregon) and (2) vertically and longitudinally within the first reservoir (Brownlee Reservoir). Under spring high flow, upstream inputs of particulate Hg (Hg(II) and MeHg) and filter-passing Hg(II) to Brownlee Reservoir were governed by total suspended solids and dissolved organic matter, respectively. Under redox stratified conditions in summer, net MeHg formation in the meta- and hypolimnion of Brownlee reservoir yielded elevated filter-passing and particulate MeHg concentrations, the latter exceeding 500 ng g-1 on particles. Simultaneously, the organic matter content of particulates increased longitudinally in the reservoir (from 9-29%) and temporally with stratified duration. In late summer and fall, destratification mobilized MeHg from the upgradient metalimnion and the downgradient hypolimnion of Brownlee Reservoir, respectively, resulting in downstream export of elevated filter-passing MeHg and organic-rich particles enriched in MeHg (up to 43% MeHg). We document coupled biogeochemical and hydrologic processes that yield in-reservoir MeHg accumulation and MeHg export in water and particles, which impacts MeHg uptake in aquatic food webs within and downstream of reservoirs.
Collapse
Affiliation(s)
- Brett A Poulin
- Department of Environmental Toxicology, University of California, Davis, USA.
| | - Michael T Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, USA
| | - Jacob Ogorek
- U.S. Geological Survey, Upper Midwest Water Science Center, USA
| | | | | | - Alysa M Yoder
- U.S. Geological Survey, Idaho Water Science Center, USA
| | - Reed Harris
- Reed Harris Environmental Ltd, Toronto, Canada
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Koenigsmark F, Chiu M, Rivera N, Johs A, Eskelsen J, Leonard D, Robertson BK, Szynkiewicz A, Derolph C, Zhao L, Gu B, Hsu-Kim H, Pierce EM. Crystal lattice defects in nanocrystalline metacinnabar in contaminated streambank soils suggest a role for biogenic sulfides in the formation of mercury sulfide phases. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2023; 25:445-460. [PMID: 36692344 DOI: 10.1039/d1em00549a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
At mercury (Hg)-contaminated sites, streambank erosion can act as a main mobilizer of Hg into nearby waterbodies. Once deposited into the waters, mercury from these soils can be transformed to MeHg by microorganisms. It is therefore important to understand the solid-phase speciation of Hg in streambanks as differences in Hg speciation will have implications for Hg transport and bioavailability. In this study, we characterized Hg solid phases in Hg-contaminated soils (100-1100 mg per kg Hg) collected from the incised bank of the East Fork Poplar Creek (EFPC) in Oak Ridge, TN (USA). The analysis of the soil samples by scanning electron microscopy-energy dispersive spectroscopy indicated numerous microenvironments where Hg and sulfur (S) are co-located. According to bulk soil analyses by extended X-ray absorption fine structure spectroscopy (EXAFS), the near-neighbor Hg molecular coordination in the soils closely resembled freshly precipitated Hg sulfide (metacinnabar, HgS); however, EXAFS fits indicated the Hg in the HgS structure was undercoordinated with respect to crystalline metacinnabar. This undercoordination of Hg-S observed by spectroscopy is consistent with transmission electron microspy images showing the presence of nanocrystallites with structural defects (twinning, stacking faults, dislocations) in individual HgS-bearing particles. Although the soils were collected from exposed parts of the stream bank (i.e., open to the atmosphere), the presence of reduced forms of S and sulfate-reducing microbes suggests that biogenic sulfides promote the formation of HgS nanoparticles in these soils. Altogether, these data demonstrate the predominance of nanoparticulate HgS with crystal lattice defects in the bank soils of an industrially impacted stream. Efforts to predict the mobilization and bioavailability of Hg associated with nano-HgS forms should consider the impact of nanocrystalline lattice defects on particle surface reactivity, including Hg dissolution rates and bioavailability on Hg fate and transformations.
Collapse
Affiliation(s)
- Faye Koenigsmark
- Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA
| | - Michelle Chiu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Nelson Rivera
- Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Jeremy Eskelsen
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Donovan Leonard
- Manufacturing Demonstration Facility Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Boakai K Robertson
- Department of Biological Sciences, Alabama State University, Montgomery, AL 36104, USA
| | - Anna Szynkiewicz
- Department of Earth and Planetary Sciences, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
| | - Christopher Derolph
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Linduo Zhao
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Heileen Hsu-Kim
- Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| |
Collapse
|
7
|
Guo Y, Xiang Y, Liu G, Chen Y, Liu Y, Song M, Li Y, Shi J, Hu L, Yin Y, Cai Y, Jiang G. "Trojan Horse" Type Internalization Increases the Bioavailability of Mercury Sulfide Nanoparticles and Methylation after Intracellular Dissolution. ACS NANO 2023; 17:1925-1934. [PMID: 36688800 DOI: 10.1021/acsnano.2c05657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Mercury sulfide nanoparticles (HgSNP), as natural metal-containing nanoparticles, are the dominant Hg species in anoxic zones. Although the microbial Hg methylation of HgSNP has been previously reported, the importance of this process in Hg methylation has yet to be clarified due to the lack of knowledge on the internalization and transformation of HgSNP. Here, we investigated the internalization and transformation of HgSNP in microbial methylator Geobacter sulfurreducens PCA through total Hg analysis and different Hg species quantification in medium and cytoplasm. We found that the microbial uptake of HgSNP, via a passive diffusion pathway, was significantly higher than that of the Hg2+-dissolved organic matter (Hg2+-DOM) complex. Internalized HgSNP were dissolved to Hg2+ in cytoplasm with a maximal dissolution of 41%, suggesting a "Trojan horse" mechanism. The intracellular Hg2+ from HgSNP exposure at the initial stage (8 h) was higher than that in Hg2+-DOM group, which led to higher methylation of HgSNP. Furthermore, no differences in methylmercury (MeHg) production from HgSNP were observed between the hgcAB gene knockout (ΔhgcAB) and wild-type strains, suggesting that HgSNP methylation may occur through HgcAB-independent pathways. Considering the possibility of a broad range of hgcAB-lacking microbes serving as methylators for HgSNP and the ubiquity of HgSNP in anoxic environments, this study highlights the importance of HgSNP internalization and methylation in MeHg production and demonstrates the necessity of understanding the assimilation and transformation of nutrient and toxic metal nanoparticles in general.
Collapse
Affiliation(s)
- Yingying Guo
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Yuping Xiang
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Guangliang Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Ying Chen
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanwei Liu
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Maoyong Song
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Jianbo Shi
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Ligang Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| | - Yongguang Yin
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
| | - Yong Cai
- Laboratory of Environmental Nanotechnology and Health Effect, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Guibin Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China
| |
Collapse
|
8
|
Hu H, Gao Y, Yu H, Xiao H, Chen S, Tan W, Tang J, Xi B. Mechanisms and biological effects of organic amendments on mercury speciation in soil-rice systems: A review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 251:114516. [PMID: 36628877 DOI: 10.1016/j.ecoenv.2023.114516] [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: 10/26/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Mercury (Hg) pollution is a well-recognized global environmental and health issue and exhibits distinctive persistence, neurotoxicity, bioaccumulation, and biomagnification effects. As the largest global Hg reservoir, the Hg cumulatively stored in soils has reached as high as 250-1000 Gg. Even more concerning is that global soil-rice systems distributed in many countries have become central to the global Hg cycle because they are both a major food source for more than 3 billion people worldwide and the central bridge linking atmospheric and soil Hg circulation. In this review, we discuss the form distribution, transformation, and bioavailability of Hg in soil-rice systems by focusing on the Hg methylation and demethylation pathways and distribution, uptake, and accumulation in rice plants and the effects of Hg on the community structure and ecological functions of microorganisms in soil-rice systems. In addition, we clarify the mechanisms through which commonly used humus and biochar organic amendments influence Hg and its environmental effects in soil-rice systems. The review also elaborates on the advantages of sulfur-modified biochars and their critical role in controlling Hg migration and bioavailability in soils. Finally, we provide key information about Hg pollution in soil-rice systems, which is of great significance for developing appropriate strategies and mitigation planning to limit Hg bioconcentration in rice crops and achieving key global sustainable development goals, such as the guarantee of food security and the promotion of sustainable agriculture.
Collapse
Affiliation(s)
- Hualing Hu
- Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Yiman Gao
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Hanxia Yu
- School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China
| | - Haoyan Xiao
- School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China
| | - Shuhe Chen
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Wenbing Tan
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Jun Tang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Beidou Xi
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| |
Collapse
|
9
|
Cheng Z, He T, Yin D, Tian X, Ran S, Zhou X. Effects of Composted Agricultural Organic Materials on Mercury Methylation in Paddy Soil and Mercury Enrichment in Rice. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2023; 110:38. [PMID: 36607425 DOI: 10.1007/s00128-022-03671-8] [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: 10/17/2022] [Accepted: 12/06/2022] [Indexed: 06/17/2023]
Abstract
Many studies have shown that returning fresh straw to the field can promote mercury accumulation in crops; therefore, it is necessary to find an appropriate way to use agricultural organic materials in mercury-contaminated farmlands. In this study, pot experiments were conducted to study the effects of composted agricultural organic materials on mercury bioaccumulation in the paddy field ecosystem by adding fresh rice straw (RS), composted rice straw (CRS), cow dung (CD) and composted cow dung (CCD) to the soils. Compared with RS and CD, the CRS and CCD amendments reduced dissolved organic matter (DOM) contents in soil, but increased the aromaticity and small molecule proportion of DOM, and also increased the tartaric acid contents in soil, as well as the methylation and release of mercury in soil. However, the increased available mercury and methylmercury in the soils in the CRS and CCD treatments were not effectively absorbed by rice plants. Overall, compared with fresh organic materials, composted organic materials amendments could reduce mercury accumulation in rice to a certain extent.
Collapse
Affiliation(s)
- Zongfu Cheng
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China
| | - Tianrong He
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China.
- College of Resources and Environment, Guizhou University, 550025, Guiyang, China.
| | - Deliang Yin
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China
- College of Resources and Environment, Guizhou University, 550025, Guiyang, China
| | - Xiang Tian
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China
| | - Shu Ran
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China
| | - Xian Zhou
- Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, 550025, Guiyang, China
| |
Collapse
|
10
|
Li H, Li Y, Tang W, Zhong H, Zhao J, Bai X, Sha S, Xu D, Lei P, Gao Y. Assessment of the Bioavailability of Mercury Sulfides in Paddy Soils Using Sodium Thiosulfate Extraction - Results from Microcosm Experiments. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2022; 109:764-770. [PMID: 35305130 DOI: 10.1007/s00128-022-03483-w] [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: 11/28/2021] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Mercury sulfides (HgS), one of the largest Hg sinks in the lithosphere, has long been considered to be highly inert. Recently, several HgS speciation (e.g., nano- or micro-sized HgS particles) in paddy soils have been found to be reactive and bioavailable, increasing the possibility of methylation and bioaccumulation and posing a potential risk to humans. However, a simple and uniform method for investigating HgS bioavailability is still lacking. To address this issue, we extracted dissolved Hg from HgS particles by sodium thiosulfate (Na2S2O3) in paddy soils and analyzed the correlation between extracted Hg and soil methylmercury (MeHg). Results showed that the amounts of Hg extracted by Na2S2O3 had a strong positive correlation with the levels of soil MeHg (R 2 adj = 0.893, p < 0.05). It is suggested that Na2S2O3 extraction may be a good method of predicting Hg bioavailability in paddy soils. Our results would help to give clues in better predicting Hg risk in natural environments.
Collapse
Affiliation(s)
- Hong Li
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
- Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
| | - Yunyun Li
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
| | - Wenli Tang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, 210023, Nanjing, China
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, 210023, Nanjing, China
| | - Jiating Zhao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
| | - Xu Bai
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Shengnan Sha
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Diandou Xu
- Research Center of Radiographic Techniques and Equipment, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China
| | - Pei Lei
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, 210023, Nanjing, China.
| | - Yuxi Gao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, 100049, Beijing, China.
| |
Collapse
|
11
|
Janssen SE, Tate MT, Poulin BA, Krabbenhoft DP, DeWild JF, Ogorek JM, Varonka MS, Orem WH, Kline JL. Decadal trends of mercury cycling and bioaccumulation within Everglades National Park. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156031. [PMID: 35595135 DOI: 10.1016/j.scitotenv.2022.156031] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/11/2022] [Accepted: 05/13/2022] [Indexed: 06/15/2023]
Abstract
Mercury (Hg) contamination has been a persistent concern in the Florida Everglades for over three decades due to elevated atmospheric deposition and the system's propensity for methylation and rapid bioaccumulation. Given declines in atmospheric Hg concentrations in the conterminous United States and efforts to mitigate nutrient release to the greater Everglades ecosystem, it was vital to assess how Hg dynamics responded on temporal and spatial scales. This study used a multimedia approach (water and biota) to examine Hg and methylmercury (MeHg) dynamics across a 76-site network within the southernmost portion of the region, Everglades National Park (ENP), from 2008 to 2018. Hg concentrations across matrices showed that air, water, and biota from the system were inextricably linked. Temporal patterns across matrices were driven primarily by hydrologic and climatic changes in the park and no evidence of a decline in atmospheric Hg deposition from 2008 to 2018 was observed, unlike other regions of the United States. In the Shark River Slough (SRS), excess dissolved organic carbon and sulfate were also consistently delivered from upgradient canals and showed no evidence of decline over the study period. Within the SRS a strong positive correlation was observed between MeHg concentrations in surface water and resident fish. Within distinct geographic regions of ENP (SRS, Marsh, Coastal), the geochemical controls on MeHg dynamics differed and highlighted regions susceptible to higher MeHg bioaccumulation, particularly in the SRS and Coastal regions. This study demonstrates the strong influence that dissolved organic carbon and sulfate loads have on spatial and temporal distributions of MeHg across ENP. Importantly, improved water quality and flow rates are two key restoration targets of the nearly 30-year Everglades restoration program, which if achieved, this study suggests would lead to reduced MeHg production and exposure.
Collapse
Affiliation(s)
- Sarah E Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, USA.
| | - Michael T Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, USA
| | - Brett A Poulin
- University of California-Davis, Department of Environmental Toxicology, Davis, CA, USA
| | - David P Krabbenhoft
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, USA
| | - John F DeWild
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, USA
| | - Jacob M Ogorek
- U.S. Geological Survey, Upper Midwest Water Science Center, Madison, WI, USA
| | - Matthew S Varonka
- U.S. Geological Survey, Geology, Energy & Minerals Science Center, Reston, VA, USA
| | - William H Orem
- U.S. Geological Survey, Geology, Energy & Minerals Science Center, Reston, VA, USA
| | - Jeffrey L Kline
- South Florida Natural Resources Center, Everglades National Park, Homestead, FL, USA
| |
Collapse
|
12
|
Lei P, Zou N, Liu Y, Cai W, Wu M, Tang W, Zhong H. Understanding the risks of mercury sulfide nanoparticles in the environment: Formation, presence, and environmental behaviors. J Environ Sci (China) 2022; 119:78-92. [PMID: 35934468 DOI: 10.1016/j.jes.2022.02.017] [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: 10/24/2021] [Revised: 01/16/2022] [Accepted: 02/10/2022] [Indexed: 06/15/2023]
Abstract
Mercury (Hg) could be microbially methylated to the bioaccumulative neurotoxin methylmercury (MeHg), raising health concerns. Understanding the methylation of various Hg species is thus critical in predicting the MeHg risk. Among the known Hg species, mercury sulfide (HgS) is the largest Hg reservoir in the lithosphere and has long been considered to be highly inert. However, with advances in the analytical methods of nanoparticles, HgS nanoparticles (HgS NPs) have recently been detected in various environmental matrices or organisms. Furthermore, pioneering laboratory studies have reported the high bioavailability of HgS NPs. The formation, presence, and transformation (e.g., methylation) of HgS NPs are intricately related to several environmental factors, especially dissolved organic matter (DOM). The complexity of the behavior of HgS NPs and the heterogeneity of DOM prevent us from comprehensively understanding and predicting the risk of HgS NPs. To reveal the role of HgS NPs in Hg biogeochemical cycling, research needs should focus on the following aspects: the formation pathways, the presence, and the environmental behaviors of HgS NPs impacted by the dominant influential factor of DOM. We thus summarized the latest progress in these aspects and proposed future research priorities, e.g., developing the detection techniques of HgS NPs and probing HgS NPs in various matrices, further exploring the interactions between DOM and HgS NPs. Besides, as most of the previous studies were conducted in laboratories, our current knowledge should be further refreshed through field observations, which would help to gain better insights into predicting the Hg risks in natural environment.
Collapse
Affiliation(s)
- Pei Lei
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Nan Zou
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Yujiao Liu
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - 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
| | - Mengjie Wu
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Wenli Tang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China; Environmental and Life Sciences Program (EnLS), Trent University, Peterborough Ontario, K9L 0G2, Canada.
| |
Collapse
|
13
|
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.
Collapse
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.
| |
Collapse
|
14
|
Stenzler BR, Zhang R, Semrau JD, DiSpirito AA, Poulain AJ. Diffusion of H 2 S from anaerobic thiolated ligand biodegradation rapidly generated bioavailable mercury. Environ Microbiol 2022; 24:3212-3228. [PMID: 35621051 DOI: 10.1111/1462-2920.16078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/27/2022]
Abstract
Methylmercury (MeHg) is a potent neurotoxin that biomagnifies through food webs and which production depends on anaerobic microbial uptake of inorganic mercury (Hg) species. One outstanding knowledge gap in understanding Hg methylation is the nature of bioavailable Hg species. It has become increasingly obvious that Hg bioavailability is spatially diverse and temporally dynamic but current models are built on single thiolated ligand systems, mostly omitting ligand exchanges and interactions, or the inclusion of dissolved gaseous phases. In this study, we used a whole-cell anaerobic biosensor to determine the role of a mixture of thiolated ligands on Hg bioavailability. Serendipitously, we discovered how the diffusion of trace amounts of exogenous biogenic H2 S, originating from anaerobic microbial ligand degradation, can alter Hg speciation - away from H2 S production site - to form bioavailable species. Regardless of its origins, H2 S stands as a mobile mediator of microbial Hg metabolism, connecting spatially separated microbial communities. At a larger scale, global planetary changes are expected to accelerate the production and mobilization of H2 S and Hg, possibly leading to increased production of the potent neurotoxin; this work provides mechanistic insights into the importance of co-managing biogeochemical cycle disruptions. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Benjamin R Stenzler
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada
| | - Rui Zhang
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada
| | - Jeremy D Semrau
- Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Alan A DiSpirito
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA
| | - Alexandre J Poulain
- Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada
| |
Collapse
|
15
|
Li Y, Lu C, Zhu N, Chao J, Hu W, Zhang Z, Wang Y, Liang L, Chen J, Xu D, Gao Y, Zhao J. Mobilization and methylation of mercury with sulfur addition in paddy soil: Implications for integrated water-sulfur management in controlling Hg accumulation in rice. JOURNAL OF HAZARDOUS MATERIALS 2022; 430:128447. [PMID: 35158248 DOI: 10.1016/j.jhazmat.2022.128447] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/28/2022] [Accepted: 02/06/2022] [Indexed: 06/14/2023]
Abstract
Sulfur-fertilizer is commonly applied in croplands and in immobilizing Hg in contaminated soil. However, there is still great uncertainty and controversy concerning Hg transportability and transformation when supplying sulfur in paddies with complex conditions. Herein, we explored the effect of adding sulfate in paddy soil at different rice growth stages on soil Hg release and MeHg accumulation in rice and uncovered the correlation between sulfur induced MeHg production and the dynamically changed soil Eh, dissolved Fe, and dissolved organic carbon (DOC). In specific, sulfate addition at early stages (flooding period) triggered the decrease of Eh and increase of DOC and dissolved Fe, which in turn promoted Hg release and favored MeHg generation (increased by 235.19-555.07% vs control). Interestingly, adding sulfate at late stages (drainage condition), as compared with that at early stages, alleviated Hg release and MeHg production accompanied by the increase of Eh and decrease of dissolved Fe and DOC. The microcosmic experiment further confirmed the reduction of sulfate to sulfide promoted the change of Eh, thereby stimulating HgS dissolution in soil extract. The results give clues on the rational application of sulfur-fertilizer and through the water-sulfur fertilizer management considering the correspondingly changed soil conditions to diminish Hg bioavailability and MeHg production in paddies and paddy-like environments.
Collapse
Affiliation(s)
- Yunyun Li
- College of Resources and Environment, Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Chang Lu
- College of Resources and Environment, Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Nali Zhu
- School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
| | - Jiang Chao
- College of Resources and Environment, Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Wenjun Hu
- College of Resources and Environment, Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Zhiyuan Zhang
- College of Resources and Environment, Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China.
| | - Yongjie Wang
- School of Geographic Sciences, East China Normal University, Shanghai 200241, China
| | - Lichun Liang
- Agricultural and rural Bureau of Dehua County, 362500, Fujian China
| | - Jinkan Chen
- Agricultural and rural Bureau of Dehua County, 362500, Fujian China
| | - Diandou Xu
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Yuxi Gao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Jiating Zhao
- CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, Division of Nuclear Technology and Applications, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
| |
Collapse
|
16
|
Kneer ML, Lazarcik J, Ginder-Vogel M. Investigation of ICP-MS/MS for total sulfur quantification in freshwater dissolved organic matter. JOURNAL OF ENVIRONMENTAL QUALITY 2021; 50:1476-1485. [PMID: 34559900 DOI: 10.1002/jeq2.20291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 09/10/2021] [Indexed: 06/13/2023]
Abstract
Sulfur-containing functional groups in dissolved organic matter (DOM) interact with trace metals, which in turn affects trace metal mobility and bioavailability in aquatic environments. Typical methods for identification and quantification of sulfur in DOM are costly, complex, and time intensive. Triple quadrupole inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) is capable of part per billion-level sulfur quantification in environmental samples and is a more accessible analytical technique compared with other available methods. This study is the first published investigation of ICP-MS/MS for the direct quantification of sulfur in freshwater DOM. Sulfur (32 S) detection occurs at a mass-to-charge ratio of 48 as 32 S16 O+ after removal of interferences and reaction with oxygen gas. We compare three commonly used DOM preparation methods to assess variability among replicate samples. Preparation of freshwater DOM samples by solid phase extraction followed by evaporation overnight and dissolution in 2% nitric acid results in the most accurate quantification of sulfur. Analysis of sulfur in Suwannee River Fulvic Acid standard serves as method validation, measuring a carbon-normalized sulfur concentration that is ∼20% higher than previously reported methods. We apply the ICP-MS/MS analysis method to determine sulfur concentrations in DOM from nine lakes in the northern Midwest. Carbon-normalized sulfur concentrations in the selected lakes are in general agreement with previously reported percentages of sulfur-containing formulas in DOM found by Fourier transform-ion cyclotron resonance-mass spectroscopy.
Collapse
Affiliation(s)
- Marissa L Kneer
- Dep. of Civil and Environmental Engineering, Environmental Chemistry and Technology Program, Univ. of Wisconsin-Madison, 660 N. Park St., Madison, WI, 53705, USA
- Current address: U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Rd, Vicksburg, MS, 39180, USA
| | - James Lazarcik
- Dep. of Civil and Environmental Engineering, Environmental Chemistry and Technology Program, Univ. of Wisconsin-Madison, 660 N. Park St., Madison, WI, 53705, USA
| | - Matthew Ginder-Vogel
- Dep. of Civil and Environmental Engineering, Environmental Chemistry and Technology Program, Univ. of Wisconsin-Madison, 660 N. Park St., Madison, WI, 53705, USA
| |
Collapse
|
17
|
Mukherjee S, Kumar M. Cycling of black carbon and black nitrogen in the hydro-geosphere: Insights on the paradigm, pathway, and processes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 770:144711. [PMID: 33508667 DOI: 10.1016/j.scitotenv.2020.144711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 12/20/2020] [Accepted: 12/21/2020] [Indexed: 06/12/2023]
Abstract
The provenance, preponderance, mobilization/export potential, and environmental health effects of charred residues have been reviewed and discussed in the context of decoupling of biogeochemical DOC (and DON) cycling. The present review suggests that high anthropogenic inputs and enrichment of marine sediments by bulk terrigenous DOC (δ13C ~ -20‰ to -25‰) lead to high DOC/DON ratios (≥10), which correlate with seasonal hydrology and diagenetic events. The stability of refractory residues like pyrrole for black nitrogen (BN) and aromatic hydrocarbons for (BC) under pedogenic and diagenetic processes needs to be addressed, considering time lags between production and resuspension events. A variation in absolute values of δ15N (2.0 to 7.0‰) in organically sequestered marine sediments indicates complex sources of various nitrogen-enriched organic carbon (OC) and dynamic erosion processes. These natural events are signified by an OC/DBN ratio of 13.3 ± 3.5, often explained by variations in precursor organic materials. Complex biogeochemical evolution at forest and agricultural ecosystem levels, coupled with anthropogenic influences, renders δ15N values between -10 and 10‰, which are lower than in marine ecosystems (6-10‰). This article focuses on the interrelationship between DBC and DBN, their global features relative to transport and movement to aquatic bodies, and current methodologies that specifically explore aquatic and terrestrial cycling of DBC/DBN. The review also takes into account critical research gaps and highlights the challenges and opportunities for research on BC and BN dynamics in the environment. The quantitative contribution of BC and BN in the DOC of the hydrosphere and the corresponding pathway of DBC may be studied further to have more insight into the distribution of dissolved matter in the global ocean system.
Collapse
Affiliation(s)
- Santanu Mukherjee
- School of Agriculture, Shoolini University of Biotechnology and Management Sciences, Solan 173229, India; Discipline of Earth Science, Indian Institute of Technology Gandhinagar, Gujarat 382-355, India
| | - Manish Kumar
- Discipline of Earth Science, Indian Institute of Technology Gandhinagar, Gujarat 382-355, India.
| |
Collapse
|
18
|
Wang Y, Zhang Y, Ok YS, Jiang T, Liu P, Shu R, Wang D, Cao X, Zhong H. Biochar-impacted sulfur cycling affects methylmercury phytoavailability in soils under different redox conditions. JOURNAL OF HAZARDOUS MATERIALS 2021; 407:124397. [PMID: 33183839 DOI: 10.1016/j.jhazmat.2020.124397] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 10/19/2020] [Accepted: 10/26/2020] [Indexed: 06/11/2023]
Abstract
Recently, there has been increasing interest in reducing methylmercury (MeHg) phytoavailability using biochar, although the underlying mechanisms are not fully understood. By combining lab-scale batch incubation with pot and field validations, we demonstrate that biochar-impacted sulfur cycling in soils and MeHg-soil binding play key roles in controlling MeHg phytoavailability. (1) Under anoxic conditions, biochar-associated sulfate and biochar-facilitated microbial sulfate reduction enhanced the production of reduced inorganic sulfur species as acid-volatile sulfide (AVS) in soils by 122%, facilitating MeHg binding with soils and thus reducing MeHg phytoavailability. (2) In contrast, under oxic conditions, the reduced inorganic sulfur was oxidized (resulting in a 68-91% decrease in AVS), which released soil-bound MeHg and increased MeHg phytoavailability. The proposed mechanisms could explain the distinct effects of biochar amendment on MeHg bioaccumulation observed under anoxic (10-88% lower in rice grains) and oxic conditions (48-84% higher in wheat grains). Our results dispute the commonly held assumption that reduced MeHg phytoavailability under biochar amendment can be primarily attributed to MeHg-biochar binding. Therefore, the potential increased risk of MeHg in oxic soils following biochar amendment should be evaluated in more detail.
Collapse
Affiliation(s)
- Yongjie Wang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China; Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai 200241, PR China
| | - Yue Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China
| | - Yong Sik Ok
- Korea Biochar Research Center, O-Jeong Eco-Resilience Institute (OJERI) & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Tao Jiang
- College of Resources Environment, Southwest University, Chongqing 400716, PR China
| | - Peng Liu
- School of Environmental Studies, China University of Geosciences, 388 Lumo Rd., Wuhan 430074, PR China
| | - Rui Shu
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China
| | - Dingyong Wang
- College of Resources Environment, Southwest University, Chongqing 400716, PR China
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, PR China; Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario, Canada.
| |
Collapse
|
19
|
Manceau A, Nagy KL, Glatzel P, Bourdineaud JP. Acute Toxicity of Divalent Mercury to Bacteria Explained by the Formation of Dicysteinate and Tetracysteinate Complexes Bound to Proteins in Escherichia coli and Bacillus subtilis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:3612-3623. [PMID: 33629845 DOI: 10.1021/acs.est.0c05202] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Bacteria are the most abundant organisms on Earth and also the major life form affected by mercury (Hg) poisoning in aquatic and terrestrial food webs. In this study, we applied high energy-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy to bacteria with intracellular concentrations of Hg as low as 0.7 ng/mg (ppm) for identifying the intracellular molecular forms and trafficking pathways of Hg in bacteria at environmentally relevant concentrations. Gram-positive Bacillus subtilis and Gram-negative Escherichia coli were exposed to three Hg species: HgCl2, Hg-dicysteinate (Hg(Cys)2), and Hg-dithioglycolate (Hg(TGA)2). In all cases, Hg was transformed into new two- and four-coordinate cysteinate complexes, interpreted to be bound, respectively, to the consensus metal-binding CXXC motif and zinc finger domains of proteins, with glutathione acting as a transfer ligand. Replacement of zinc cofactors essential to gene regulatory proteins with Hg would inhibit vital functions such as DNA transcription and repair and is suggested to be a main cause of Hg genotoxicity.
Collapse
Affiliation(s)
- Alain Manceau
- Université Grenoble Alpes, CNRS, ISTerre, CS 40700, 38058 Grenoble, France
| | - Kathryn L Nagy
- Department of Earth and Environmental Sciences, University of Illinois at Chicago, MC-186, 845 West Taylor Street, Chicago, Illinois 60607, United States
| | - Pieter Glatzel
- European Synchrotron Radiation Facility (ESRF), 71 Rue des Martyrs, 38000 Grenoble, France
| | - Jean-Paul Bourdineaud
- Institut Européen de Chimie et Biologie, Université de Bordeaux, CNRS, UMR 5234, 2 rue Escarpit, 33607 Pessac, France
| |
Collapse
|
20
|
Manceau A, Bourdineaud JP, Oliveira RB, Sarrazin SLF, Krabbenhoft DP, Eagles-Smith CA, Ackerman JT, Stewart AR, Ward-Deitrich C, Del Castillo Busto ME, Goenaga-Infante H, Wack A, Retegan M, Detlefs B, Glatzel P, Bustamante P, Nagy KL, Poulin BA. Demethylation of Methylmercury in Bird, Fish, and Earthworm. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:1527-1534. [PMID: 33476127 DOI: 10.1021/acs.est.0c04948] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Toxicity of methylmercury (MeHg) to wildlife and humans results from its binding to cysteine residues of proteins, forming MeHg-cysteinate (MeHgCys) complexes that hinder biological functions. MeHgCys complexes can be detoxified in vivo, yet how this occurs is unknown. We report that MeHgCys complexes are transformed into selenocysteinate [Hg(Sec)4] complexes in multiple animals from two phyla (a waterbird, freshwater fish, and earthworms) sampled in different geographical areas and contaminated by different Hg sources. In addition, high energy-resolution X-ray absorption spectroscopy (HR-XANES) and chromatography-inductively coupled plasma mass spectrometry of the waterbird liver support the binding of Hg(Sec)4 to selenoprotein P and biomineralization of Hg(Sec)4 to chemically inert nanoparticulate mercury selenide (HgSe). The results provide a foundation for understanding mercury detoxification in higher organisms and suggest that the identified MeHgCys to Hg(Sec)4 demethylation pathway is common in nature.
Collapse
Affiliation(s)
- Alain Manceau
- Université Grenoble Alpes, ISTerre, CNRS, Grenoble 38000, France
| | - Jean-Paul Bourdineaud
- Université de Bordeaux, Institut Européen de Chimie et Biologie, CNRS, Pessac 33600, France
| | - Ricardo B Oliveira
- Universidade Federal do Oeste Pará, LabBBEx, Santarém 68180-000, Pará, Brazil
| | - Sandra L F Sarrazin
- Universidade Federal do Oeste Pará, LabBBEx, Santarém 68180-000, Pará, Brazil
| | - David P Krabbenhoft
- Upper Midwest Water Science Center, U.S. Geological Survey, Middleton 53562, Wisconsin, United States
| | - Collin A Eagles-Smith
- Forest and Rangeland Ecosystem Science Center, U.S. Geological Survey, Corvallis 97330, Oregon, United States
| | - Joshua T Ackerman
- Western Ecological Research Center, U.S. Geological Survey, Dixon Field Station, Dixon 95620, California, United States
| | - A Robin Stewart
- U.S. Geological Survey, Water Resources Mission Area, Menlo Park 94025, California, United States
| | | | | | | | - Aude Wack
- Université Grenoble Alpes, ISTerre, CNRS, Grenoble 38000, France
| | - Marius Retegan
- European Synchrotron Radiation Facility (ESRF), Grenoble 38000, France
| | - Blanka Detlefs
- European Synchrotron Radiation Facility (ESRF), Grenoble 38000, France
| | - Pieter Glatzel
- European Synchrotron Radiation Facility (ESRF), Grenoble 38000, France
| | - Paco Bustamante
- Université La Rochelle, CNRS, Littoral Environnement et Sociétés, La Rochelle 17000, France
| | - Kathryn L Nagy
- Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago 60607, Illinois, United States
| | - Brett A Poulin
- U.S. Geological Survey, Water Resources Mission Area, Boulder 80303, Colorado, United States
- Department of Environmental Toxicology, University of California Davis, Davis 95616, California, United States
| |
Collapse
|
21
|
Fuhrmann BC, Beutel MW, O'Day PA, Tran C, Funk A, Brower S, Pasek J, Seelos M. Effects of mercury, organic carbon, and microbial inhibition on methylmercury cycling at the profundal sediment-water interface of a sulfate-rich hypereutrophic reservoir. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 268:115853. [PMID: 33120160 DOI: 10.1016/j.envpol.2020.115853] [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: 05/09/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 06/11/2023]
Abstract
Methylmercury (MeHg) produced by anaerobic bacteria in lakes and reservoirs, poses a threat to ecosystem and human health due to its ability to bioaccumulate in aquatic food webs. This study used 48-hr microcosm incubations of profundal sediment and bottom water from a sulfate-rich, hypereutrophic reservoir to assess seasonal patterns of MeHg cycling under various treatments. Treatments included addition of air, Hg(II), organic carbon, and microbial inhibitors. Both aeration and sodium molybdate, a sulfate-reducing bacteria (SRB) inhibitor, generally decreased MeHg concentration in microcosm water, likely by inhibiting SRB activity. The methanogenic inhibitor bromoethanesulfonate increased MeHg concentration 2- to 4- fold, suggesting that methanogens were potent demethylators. Pyruvate increased MeHg concentration under moderately reduced conditions, likely by stimulating SRB, but decreased it under highly reduced conditions, likely by stimulating methanogens. Acetate increased MeHg concentration, likely due to the stimulation of acetotrophic SRB. Results suggest that iron-reducing bacteria (IRB) were not especially prominent methylators and MeHg production at the sediment-water interface is elevated under moderately reduced conditions corresponding with SRB activity. In contrast, it is suppressed under oxic conditions due to low SRB activity, and under highly reduced conditions (<-100 mV) due to enhanced demethylation by methanogens.
Collapse
Affiliation(s)
- Byran C Fuhrmann
- University of California, Environmental Systems Graduate Program, 5200 North Lake Road, Merced, CA, 95340, USA.
| | - Marc W Beutel
- University of California, Environmental Systems Graduate Program, 5200 North Lake Road, Merced, CA, 95340, USA
| | - Peggy A O'Day
- University of California, Environmental Systems Graduate Program, 5200 North Lake Road, Merced, CA, 95340, USA
| | - Christian Tran
- Environmental Analytical Laboratory, University of California, 5200 North Lake Rd, Merced, CA, 95340, USA
| | - Andrew Funk
- City of San Diego, Public Utilities Department, 9192 Topaz Way, San Diego, CA, 92123, USA
| | - Sarah Brower
- City of San Diego, Public Utilities Department, 9192 Topaz Way, San Diego, CA, 92123, USA
| | - Jeffery Pasek
- City of San Diego, Public Utilities Department, 9192 Topaz Way, San Diego, CA, 92123, USA
| | - Mark Seelos
- University of California, Environmental Systems Graduate Program, 5200 North Lake Road, Merced, CA, 95340, USA
| |
Collapse
|
22
|
Bland GD, Rao B, Reible D. Evaluating the transport of Hg(II) in the presence of natural organic matter through a diffusive gradient in a thin-film passive sampler. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 749:141217. [PMID: 32827812 DOI: 10.1016/j.scitotenv.2020.141217] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 07/22/2020] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
The effects of a model natural organic matter (NOM) on the transport of Hg(II) into diffusive gradient in thin-film devices (DGTs) was evaluated in order to better understand their ability to measure colloidal Hg species in porewater. The presence of NOM significantly reduced the diffusivity of the Hg(II) species and the reduction was dependent upon NOM to Hg(II) ratio. This relationship was modeled by determining the Hg(II) partition coefficients (Kd) of size fractionated NOM obtained by ultrafiltration and estimating the Hg diffusivity through the DGT for the different NOM size fractions across a range of Hg-NOM ratios. The estimated diffusivities were consistent with experimental observations of uptake into the DGT. Overall, this study indicated that Hg(II) associated with NOM passes into a DGT, however the transport is slowed in accordance with the diffusivity of the NOM to which the Hg(II) is associated. Thus, the Hg-NOM association and complex diffusivities need to be considered when relating DGT uptake to Hg porewater concentration. The results also suggest that Hg(II) associated with colloidal or larger particles of negligible diffusivity are unlikely to contribute significantly to DGT measurements.
Collapse
Affiliation(s)
- Garret D Bland
- Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States; Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409, United States
| | - Balaji Rao
- Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409, United States
| | - Danny Reible
- Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Lubbock, TX 79409, United States.
| |
Collapse
|
23
|
Wang AO, Ptacek CJ, Paktunc D, Mack EE, Blowes DW. Application of biochar prepared from ethanol refinery by-products for Hg stabilization in floodplain soil: Impacts of drying and rewetting. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 267:115396. [PMID: 32882459 DOI: 10.1016/j.envpol.2020.115396] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 06/11/2023]
Abstract
This study evaluated three biochars derived from bioenergy by-products - manure-based anaerobic digestate (DIG), distillers' grains (DIS), and a mixture thereof (75G25S) - as amendments to stabilize Hg in contaminated floodplain soil under long-term saturated (up to 200 d) and cyclic drying and rewetting conditions. Greater total Hg (THg) removal (72 to nearly 100%) and limited MeHg production (<65 ng L-1) were observed in digestate-based biochar-amended systems under initial saturated conditions. Drying and rewetting resulted in limited THg release, increased aqueous MeHg, and decreased solid MeHg in digestate-based biochar-amended systems. Changes in Fe and S chemistry as well as microbial communities during drying and rewetting potentially affected MeHg production. Digestate-based biochars may be more effective as amendments to control Hg release and minimize MeHg production in floodplain soils under long-term saturated and drying and rewetting conditions compared to distillers' grains biochar.
Collapse
Affiliation(s)
- Alana O Wang
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, N2L 3G1, Canada
| | - Carol J Ptacek
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, N2L 3G1, Canada.
| | - Dogan Paktunc
- CanmetMINING, Natural Resource Canada, Ottawa, ON, K1A 0G1, Canada
| | - E Erin Mack
- Formerly E. I. du Pont de Nemours and Company, 974 Centre Road, Wilmington, DE, 19805, USA
| | - David W Blowes
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, N2L 3G1, Canada
| |
Collapse
|
24
|
Jones DS, Johnson NW, Mitchell CPJ, Walker GM, Bailey JV, Pastor J, Swain EB. Diverse Communities of hgcAB+ Microorganisms Methylate Mercury in Freshwater Sediments Subjected to Experimental Sulfate Loading. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:14265-14274. [PMID: 33138371 DOI: 10.1021/acs.est.0c02513] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Methylmercury (MeHg) is a bioaccumulative neurotoxin produced by certain sulfate-reducing bacteria and other anaerobic microorganisms. Because microorganisms differ in their capacity to methylate mercury, the abundance and distribution of methylating populations may determine MeHg production in the environment. We compared rates of MeHg production and the distribution of hgcAB genes in epilimnetic sediments from a freshwater lake that were experimentally amended with sulfate levels from 7 to 300 mg L-1. The most abundant hgcAB sequences were associated with clades of Methanomicrobia, sulfate-reducing Deltaproteobacteria, Spirochaetes, and unknown environmental sequences. The hgcAB+ communities from higher sulfate amendments were less diverse and had relatively more Deltaproteobacteria, whereas the communities from lower amendments were more diverse with a larger proportion of hgcAB sequences affiliated with other clades. Potential methylation rate constants varied 52-fold across the experiment. Both potential methylation rate constants and % MeHg were the highest in sediments from the lowest sulfate amendments, which had the most diverse hgcAB+ communities and relatively fewer hgcAB genes from clades associated with sulfate reduction. Although pore water sulfide concentration covaried with hgcAB diversity across our experimental sulfate gradient, major changes in the community of hgcAB+ organisms occurred prior to a significant buildup of sulfide in pore waters. Our results indicate that methylating communities dominated by diverse anaerobic microorganisms that do not reduce sulfate can produce MeHg as effectively as communities dominated by sulfate-reducing populations.
Collapse
Affiliation(s)
- Daniel S Jones
- BioTechnology Institute, University of Minnesota, Saint Paul 55108, Minnesota, United States
- Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis 55455, Minnesota, United States
- Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro 87801, New Mexico, United States
- National Cave and Karst Research Institute, Carlsbad, New Mexico 88220, United States
| | - Nathan W Johnson
- Department of Civil Engineering, University of Minnesota Duluth, Duluth, Minnesota 55812, United States
| | - Carl P J Mitchell
- Department of Physical and Environmental Sciences, University of Toronto-Scarborough, Toronto, Ontario M1C 1A4, Canada
| | - Gabriel M Walker
- Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - Jake V Bailey
- Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis 55455, Minnesota, United States
| | - John Pastor
- Department of Biology, University of Minnesota Duluth, Duluth, Minnesota 55812, United States
| | - Edward B Swain
- Minnesota Pollution Control Agency, Saint Paul, Minnesota 55155, United States
| |
Collapse
|
25
|
Wang P, Peng H, Liu J, Zhu Z, Bi X, Yu Q, Zhang J. Effects of exogenous dissolved organic matter on the adsorption-desorption behaviors and bioavailabilities of Cd and Hg in a plant-soil system. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 728:138252. [PMID: 32335403 DOI: 10.1016/j.scitotenv.2020.138252] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 06/11/2023]
Abstract
Dissolved organic matter (DOM) is one of the most active soil components and plays critical direct and indirect roles in heavy metal migration, transformation, bioavailability, and toxicity in soils. In this study, isothermal adsorption/desorption experiments and pot experiments were performed and samples were physically characterized to study the effects of different sources of DOM on adsorption and desorption behavior and bioavailability of Cd and Hg in a plant-soil system. The results showed that microbial DOM promoted Cd and Hg adsorption in soil and decreased Cd and Hg bioavailability to pak choi (Brassica chinensis Linn.). In contrast, straw DOM and farmyard manure DOM decreased Cd and Hg adsorption and improved Cd and Hg migration and bioavailability. These results might be explained by the different types of DOM having different molecular weights and degrees of aromaticity. Cd was more readily desorbed by the soil and was more phytoavailable than Hg. We concluded that exogenous microbial DOM can inhibit Cd and Hg migration and bioavailability in soil but straw DOM and farmyard manure DOM can activate Cd and Hg in soil and promote Cd and Hg accumulation in plants. The results could help in developing rational agricultural fertilization regimes.
Collapse
Affiliation(s)
- Pengcong Wang
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Huan Peng
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
| | - Jinling Liu
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China.
| | - Zhenli Zhu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
| | - Xiangyang Bi
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China
| | - Qianqian Yu
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Jie Zhang
- Institute of Mathematical Geology & Remote Sensing, China University of Geoscience, Wuhan 430074, China
| |
Collapse
|
26
|
Zhang Z, Si R, Lv J, Ji Y, Chen W, Guan W, Cui Y, Zhang T. Effects of Extracellular Polymeric Substances on the Formation and Methylation of Mercury Sulfide Nanoparticles. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:8061-8071. [PMID: 32511902 DOI: 10.1021/acs.est.0c01456] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Growing evidence has suggested that microbial biofilms are potential environmental "hotspots" for the production and accumulation of a bioaccumulative neurotoxin, methylmercury. Here, we demonstrate that extracellular polymeric substances (EPS), the main components of biofilm matrices, significantly interfere with mercury sulfide precipitation and lead to the formation of nanoparticulate metacinnabar available for microbial methylation, a natural process predominantly responsible for the environmental occurrence of methylmercury. EPS derived from mercury methylating bacteria, particularly Desulfovibrio desulfuricans ND132, substantially increase the methylation potential of nanoparticulate mercury. This is likely due to the abundant aromatic biomolecules in EPS that strongly interact with mercury sulfide via inner-sphere complexation and consequently enhance the short-range structural disorder while mitigating the aggregation of nanoparticulate mercury. The EPS-elevated bioavailability of nanoparticulate mercury to D. desulfuricans ND132 is not induced by dissolution of these nanoparticles in aqueous phase, and may be dictated by cell-nanoparticle interfacial reactions. Our discovery is the first step of mechanistically understanding methylmercury production in biofilms. These new mechanistic insights will help incorporate microbial EPS and particulate-phase mercury into mercury methylation models, and may facilitate the assessment of biogeochemical cycling of other nutrient or toxic elements driven by EPS-producing microorganisms that are prevalent in nature.
Collapse
Affiliation(s)
- Zhanhua Zhang
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| | - Rui Si
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, P. R. China
| | - Jitao Lv
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China
| | - Yunyun Ji
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| | - Wenshan Chen
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| | - Wenyu Guan
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| | - Yuxiao Cui
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| | - Tong Zhang
- College of Environmental Science and Engineering, Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300350, P. R. China
| |
Collapse
|
27
|
Wang AO, Ptacek CJ, Blowes DW, Finfrock YZ, Paktunc D, Mack EE. Use of hardwood and sulfurized-hardwood biochars as amendments to floodplain soil from South River, VA, USA: Impacts of drying-rewetting on Hg removal. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 712:136018. [PMID: 32050399 DOI: 10.1016/j.scitotenv.2019.136018] [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: 09/09/2019] [Revised: 11/24/2019] [Accepted: 12/07/2019] [Indexed: 06/10/2023]
Abstract
Periodic flooding and drying conditions in floodplains affect the mobility and bioavailability of Hg in aquatic sediments and surrounding soils. Sulfurized materials have been recently proposed as Hg sorbents due to their high affinity to bind Hg, while sulfurizing organic matter may enhance methylmercury (MeHg) production, offsetting the beneficial aspects of these materials. This study evaluated hardwood biochar (OAK) and sulfurized-hardwood biochar (MOAK) as soil amendments for controlling Hg release in a contaminated floodplain soil under conditions representative of periodic flooding and drying in microcosm experiments in three stages: (1) wet biochar amended-systems with river water in an anoxic environment up to 200 d; (2) dry selected reaction vessels in an oxic environment for 90 d; (3) rewet such vessels with river water in an anoxic environment for 90 d. In Stage 1, greater Hg removal (17-98% for unfiltered total Hg (THg) and 47-99% for 0.45-μm THg) and lower MeHg concentrations (<20 ng L-1) were observed in MOAK-amended systems (10%MOAKs). In Stage 3, release of Hg in 10%MOAKs was eight-fold lower than in soil controls (SedCTRs), while increases in aqueous (up to 21 ng L-1) and solid (up to 88 ng g-1) MeHg concentrations were observed. The increases in MeHg corresponded to elevated aqueous concentrations of Mn, Fe, SO42-, and HS- in Stage 3. Results of S K-edge X-ray absorption near edge structure (XANES) analysis suggest oxidation of S in Stage 2 and formation of polysulfur in Stage 3. Results of pyrosequencing analysis indicate sulfate-reducing bacteria (SRB) became abundant in Stage 3 in 10%MOAKs. The shifts in biogeochemical conditions in 10%MOAKs in Stage 3 may increase the bioavailability of Hg to methylating bacteria. The results suggest limited impacts on Hg removal during drying and rewetting, while changes in biogeochemical conditions may affect MeHg production in sulfurized biochar-amended systems.
Collapse
Affiliation(s)
- Alana O Wang
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada
| | - Carol J Ptacek
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada.
| | - David W Blowes
- Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada
| | - Y Zou Finfrock
- CLS@APS, Sector 20, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA; Science Division, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada
| | - Dogan Paktunc
- CanmetMINING, Natural Resource Canada, Ottawa, ON K1A 0G1, Canada
| | - E Erin Mack
- Formerly E. I. du Pont de Nemours and Company, 974 Centre Road, Wilmington, DE 19805, USA
| |
Collapse
|
28
|
Thomas SA, Mishra B, Myneni SCB. Cellular Mercury Coordination Environment, and Not Cell Surface Ligands, Influence Bacterial Methylmercury Production. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:3960-3968. [PMID: 32097551 DOI: 10.1021/acs.est.9b05915] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The conversion of inorganic mercury (Hg(II)) to methylmercury (MeHg) is central to the understanding of Hg toxicity in the environment. Hg methylation occurs in the cytosol of certain obligate anaerobic bacteria and archaea possessing the hgcAB gene cluster. However, the processes involved in Hg(II) biouptake and methylation are not well understood. Here, we examined the role of cell surface thiols, cellular ligands with the highest affinity for Hg(II) that are located at the interface between the outer membrane and external medium, on the sorption and methylation of Hg(II) by Geobacter sulfurreducens. The effect of added cysteine (Cys), which is known to greatly enhance Hg(II) biouptake and methylation, was also explored. By quantitatively blocking surface thiols with a thiol binding ligand (qBBr), we show that surface thiols have no significant effect on Hg(II) methylation, regardless of Cys addition. The results also identify a significant amount of cell-associated Hg-S3/S4 species, as studied by high energy-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy, under conditions of high MeHg production (with Cys addition). In contrast, Hg-S2 are the predominant species during low MeHg production. Hg-S3/S4 species may be related to enhanced Hg(II) biouptake or the ability of Hg(II) to become methylated by HgcAB and should be further explored in this context.
Collapse
Affiliation(s)
- Sara A Thomas
- Department of Geosciences, Princeton University, Guyot Hall, Princeton, New Jersey 08544, United States
| | - Bhoopesh Mishra
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, U.K
| | - Satish C B Myneni
- Department of Geosciences, Princeton University, Guyot Hall, Princeton, New Jersey 08544, United States
| |
Collapse
|
29
|
Wang X, Seelen EA, Mazrui NM, Kerns P, Suib SL, Zhao J, Mason RP. The interaction of mercury and methylmercury with chalcogenide nanoparticles. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 255:113346. [PMID: 31627051 DOI: 10.1016/j.envpol.2019.113346] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 09/30/2019] [Accepted: 10/03/2019] [Indexed: 06/10/2023]
Abstract
Mercury (Hg) and methylmercury (CH3Hg) bind strongly to micro and nano (NP) particles and this partitioning impacts their fate and bioaccumulation into food webs, and, as a result, potential human exposure. This partitioning has been shown to influence the bioavailability of inorganic Hg to methylating bacteria, with NP-bound Hg being more bioavailable than particulate HgS, or organic particulate-bound Hg. In this study we set out to investigate whether the potential interactions between dissolved ionic Hg (HgII) and CH3Hg and NPs was due to incorporation of Hg into the core of the cadmium selenide and sulfide (CdSe; CdS) nanoparticles (metal exchange or surface precipitation), or due purely to surface interactions. The interaction was assessed based on the quenching of the fluorescence intensity and lifetime observed during HgII or CH3Hg titration experiments of these NP solutions. Additional analysis using inductively coupled plasma mass spectrometry of CdSe NPs and the separated solution, obtained after HgII additions, showed that there was no metal exchange, and X-ray photoelectron spectroscopy confirmed this and further indicated that the Hg was bound to cysteine, the NP capping agent. Our study suggests that Hg and CH3Hg adsorbed to the surfaces of NPs would have different bioavailability for release into water or to (de)methylating organisms or for bioaccumulation, and provides insights into the behavior of Hg in the environment in the presence of natural or manufactured NPs.
Collapse
Affiliation(s)
- Xudong Wang
- Department of Chemistry, University of Connecticut, 55 North Eagleville Rd., Storrs, USA
| | - Emily A Seelen
- Department of Marine Sciences, University of Connecticut, Groton, CT, USA
| | - Nashaat M Mazrui
- Department of Chemistry, University of Connecticut, 55 North Eagleville Rd., Storrs, USA; Department of Marine Sciences, University of Connecticut, Groton, CT, USA
| | - Peter Kerns
- Department of Chemistry, University of Connecticut, 55 North Eagleville Rd., Storrs, USA
| | - Steven L Suib
- Department of Chemistry, University of Connecticut, 55 North Eagleville Rd., Storrs, USA; Institute of Materials Science, University of Connecticut, 97 North Eagleville Rd., Storrs, USA
| | - Jing Zhao
- Department of Chemistry, University of Connecticut, 55 North Eagleville Rd., Storrs, USA; Institute of Materials Science, University of Connecticut, 97 North Eagleville Rd., Storrs, USA
| | - Robert P Mason
- Department of Marine Sciences, University of Connecticut, Groton, CT, USA.
| |
Collapse
|
30
|
Pavitt AS, Tratnyek PG. Electrochemical characterization of natural organic matter by direct voltammetry in an aprotic solvent. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:1664-1683. [PMID: 31576393 DOI: 10.1039/c9em00313d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The complex and indeterminant composition of NOM makes characterization of its redox properties challenging. Approaches that have been taken to address this challenge include chemical probe reactions, potentiometric titrations, chronocoulometry, and voltammetry. In this study, we revisit the use of direct voltammetric methods in aprotic solvents by applying an expanded and refined suite of methods to a large set of NOM samples and model compounds (54 NOM samples from 10 different sources, 7 NOM model compounds, and 2 fresh extracts of plant materials that are high in redox-active quinonoid model compounds dissolved in DMSO). Refinements in the methods of fitting the data obtained by staircase cyclic voltammetry (SCV) provided improved definition of peaks, and square wave voltammetry (SWV), performed under the same conditions as SCV, provided even more reliable identification and quantitation of peaks. Further evidence is provided that DMSO improves the electrode response by unfolding some of the tertiary structure of NOM polymers, thereby allowing greater contact between redox active functional groups and the electrode surface. We averaged experimental peak potentials for all NOM compounds and calculated potentials in water. Average values for Epa1, Epc1, and Ep1 in DMSO were -0.866 ± 0.069, -1.35 ± 0.071, and -0.831 ± 0.051 V vs. Ag/Ag+, and -0.128, -0.613, and -0.0930 V vs. SHE in water. In addition to peak potentials, the breadth of SCV peaks was quantified as a way to characterize the degree to which the redox activity of NOM is due to a continuum of contributing functional groups. The average breadth values were 1.63 ± 0.24, 1.28 ± 0.34, and 0.648 ± 0.15 V for Epa1, Epc1, and Ep1 respectively. Comparative analysis of the overall dataset-from SCV and SWV on all NOMs and model compounds-revealed that NOM redox properties vary over a narrower range than expected based on model compound properties. This lack of diversity in redox properties of NOM is similar to conclusions from other recent work on the molecular structure of NOM, all of which could be the result of selectivity in the common extraction methods used to obtain the materials.
Collapse
Affiliation(s)
- Ania S Pavitt
- OHSU-PSU School of Public Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
| | | |
Collapse
|
31
|
Rivera NA, Bippus PM, Hsu-Kim H. Relative Reactivity and Bioavailability of Mercury Sorbed to or Coprecipitated with Aged Iron Sulfides. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:7391-7399. [PMID: 31173690 PMCID: PMC8412064 DOI: 10.1021/acs.est.9b00768] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The potential for inorganic mercury (Hg) to be converted to methylmercury depends, in part, on the chemical form of Hg and its bioavailability to anaerobic microorganisms that can methylate Hg. In anaerobic settings, Hg can be associated with sulfide phases, including ferrous iron sulfide (FeS), which can sorb or be coprecipitated with Hg. The objective of this study was to determine if the aging state of FeS alters the Hg coordination environment as well as the reactivity and bioavailability of sorbed and coprecipitated Hg species. FeS particles were synthesized with and without Hg2+ and aged in anaerobic conditions for multiple time frames spanning from 1 h to 1 month. For FeS particles synthesized without Hg, Hg2+ was subsequently sorbed to the FeS for 1 day. Analysis of Hg speciation of these materials by X-ray absorption near edge spectroscopy revealed a predominance of four-coordinate Hg-S species in the sorbed Hg-FeS solids and a mixture of two- and four-coordinate Hg-S in the coprecipitated Hg-FeS. The leaching potential of the Hg was assessed by exposing the particles to a solution of dissolved glutathione (a thiolate-based Hg chelator). As expected, the sorbed Hg-FeS released more soluble Hg compared to the coprecipitated Hg-FeS. However, when these particles were exposed to Desulfovibrio desulfuricans ND132 (a known Hg methylator), more Hg was methylated from the coprecipitated Hg-FeS than the sorbed Hg-FeS, consistent with expectations from the Hg-S coordination state and inconsistent with the selective leaching results. Overall, these results suggest that the bioavailability of particulate Hg cannot be easily discerned by its leaching potential into bulk solution. Rather, bioavailability entails more subtle interactions at particle-cell interfaces and perhaps correlates with the local Hg-S coordination state in the particles.
Collapse
Affiliation(s)
- Nelson A. Rivera
- Department of Civil and Environmental Engineering, Box 90287, Duke University, Durham, North Carolina 27708, USA
| | - Paige M. Bippus
- Department of Civil and Environmental Engineering, Box 90287, Duke University, Durham, North Carolina 27708, USA
| | - Heileen Hsu-Kim
- Department of Civil and Environmental Engineering, Box 90287, Duke University, Durham, North Carolina 27708, USA
| |
Collapse
|
32
|
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.
Collapse
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
| |
Collapse
|
33
|
Zhang L, Wu S, Zhao L, Lu X, Pierce EM, Gu B. Mercury Sorption and Desorption on Organo-Mineral Particulates as a Source for Microbial Methylation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:2426-2433. [PMID: 30702880 DOI: 10.1021/acs.est.8b06020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In natural freshwater and sediments, mercuric mercury (Hg(II)) is largely associated with particulate minerals and organics, but it remains unclear under what conditions particulates may become a sink or a source for Hg(II) and whether the particulate-bound Hg(II) is bioavailable for microbial uptake and methylation. In this study, we investigated Hg(II) sorption-desorption characteristics on three organo-coated hematite particulates and a Hg-contaminated natural sediment and evaluated the potential of particulate-bound Hg(II) for microbial methylation. Mercury rapidly sorbed onto particulates, especially the cysteine-coated hematite and sediment, with little desorption observed (0.1-4%). However, the presence of Hg-binding ligands, such as low-molecular-weight thiols and humic acids, resulted in up to 60% of Hg(II) desorption from the Hg-laden hematite particulates but <6% from the sediment. Importantly, the particulate-bound Hg(II) was bioavailable for uptake and methylation by a sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 under anaerobic incubations, and the methylation rate was 4-10 times higher than the desorption rate of Hg(II). These observations suggest direct contacts and interactions between bacterial cells and the particulate-bound Hg(II), resulting in rapid exchange or uptake of Hg(II) by the bacteria. The results highlight the importance of Hg(II) partitioning at particulate-water interfaces and the role of particulates as a significant source of Hg(II) for methylation in the environment.
Collapse
Affiliation(s)
- Lijie Zhang
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Shan Wu
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- School of Resource, Environmental and Chemical Engineering , Nanchang University , Nanchang 330031 , China
| | - Linduo Zhao
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Xia Lu
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Eric M Pierce
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
| | - Baohua Gu
- Environmental Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- Department of Biosystems Engineering and Soil Science , University of Tennessee , Knoxville , Tennessee 37996 , United States
| |
Collapse
|
34
|
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.
Collapse
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
| |
Collapse
|
35
|
Grigg ARC, Kretzschmar R, Gilli RS, Wiederhold JG. Mercury isotope signatures of digests and sequential extracts from industrially contaminated soils and sediments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 636:1344-1354. [PMID: 29913595 DOI: 10.1016/j.scitotenv.2018.04.261] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/12/2018] [Accepted: 04/20/2018] [Indexed: 05/24/2023]
Abstract
Environmental mercury (Hg) pollution is a matter of global concern. Mercury speciation controls its environmental behaviour, and stable isotope ratios can potentially trace Hg movement through environmental compartments. Here we investigated Hg in industrially contaminated soils and sediments (Visp, Valais, Switzerland) using concentration and stable isotope analysis (CV-MC-ICP-MS) of total digests, and a four-step sequential extraction procedure. The sequential extraction employed (1) water (labile Hg species), (2) NaOH or Na4P2O7 (organically-bound Hg), (3) hydroxylamine-HCl (Hg bound to Mn and Fe (oxyhydr)oxides), and (4) aqua regia (residual Hg pools). The majority of Hg was extracted in step 4 and up to 36% in step 2. Mercury bound to organic matter was the dominant source of Hg in water, NaOH and Na4P2O7 extracts. Sulfides and colloidal oxide minerals were possible additional sources of Hg in some samples. The inconsistent comparative performance of NaOH and Na4P2O7 extractions showed that these classical extractants may not extract Hg exclusively from the organically-bound pool. Samples taken at the industrial facility displayed the greatest isotopic variation (δ202Hg: -0.80‰ ± 0.14‰ to 0.25‰ ± 0.13‰, Δ199Hg: -0.10‰ ± 0.03‰ to 0.02‰ ± 0.03‰; all 2SD) whereas downstream of the facility there was much less variation around average values of δ202Hg = -0.47‰ ± 0.11‰ and Δ199Hg = -0.05‰ ± 0.03‰ (1SD, n = 19). We interpret the difference as the result of homogenisation by mixing of canal sediments containing Hg from the various sources at the industrial facility with preservation of the mixed industrial Hg signature downstream. In contrast to previous findings, Hg isotopes in the sequential extracts were largely similar to one another (2SD < 0.14‰), likely demonstrating that the Hg speciation was similar among the extracts. Our results reveal that Hg resides in relatively stable soil pools which record an averaged isotope signature of the industrial sources, potentially facilitating source tracing studies with Hg isotope signatures at larger spatial scales further downstream.
Collapse
Affiliation(s)
- Andrew R C Grigg
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zurich, Zurich, Switzerland; Environmental Geochemistry Group, Department of Environmental Geosciences, University of Vienna, Vienna, Austria
| | - Ruben Kretzschmar
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zurich, Zurich, Switzerland
| | - Robin S Gilli
- Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, CHN, ETH Zurich, Zurich, Switzerland
| | - Jan G Wiederhold
- Environmental Geochemistry Group, Department of Environmental Geosciences, University of Vienna, Vienna, Austria.
| |
Collapse
|
36
|
Thomas SA, Rodby KE, Roth EW, Wu J, Gaillard JF. Spectroscopic and Microscopic Evidence of Biomediated HgS Species Formation from Hg(II)-Cysteine Complexes: Implications for Hg(II) Bioavailability. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:10030-10039. [PMID: 30078312 DOI: 10.1021/acs.est.8b01305] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We investigated the chemistry of Hg(II) during exposure of exponentially growing bacteria ( Escherichia coli, Bacillus subtilis, and Geobacter sulfurreducens) to 50 nM, 500 nM, and 5 μM total Hg(II) with and without added cysteine. With X-ray absorption spectroscopy, we provide direct evidence of the formation of cell-associated HgS for all tested bacteria. The addition of cysteine (100-1000 μM) promotes HgS formation (>70% of total cell-associated Hg(II)) as a result of the biodegradation of added cysteine to sulfide. Cell-associated HgS species are also detected when cysteine is not added as a sulfide source. Two phases of HgS, cinnabar (α-HgS) and metacinnabar (β-HgS), form depending on the total concentration of Hg(II) and sulfide in the exposure medium. However, α-HgS exclusively forms in assays that contain an excess of cysteine. Scanning transmission electron microscopy images reveal that nanoparticulate HgS(s) is primarily located at the cell surface/extracellular matrix of Gram-negative E. coli and G. sulfurreducens and in the cytoplasm/cell membrane of Gram-positive B. subtilis. Intracellular Hg(II) was detected even when the predominant cell-associated species was HgS. This study shows that HgS species can form from exogenous thiol-containing ligands and endogenous sulfide in Hg(II) biouptake assays under nondissimilatory sulfate reducing conditions, providing new considerations for the interpretation of Hg(II) biouptake results.
Collapse
Affiliation(s)
- Sara A Thomas
- Department of Civil and Environmental Engineering , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Kara E Rodby
- Department of Civil and Environmental Engineering , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Eric W Roth
- Department of Materials Science and Engineering, NU ANCE Center , Northwestern University , Evanston , Illinois 60208 , United States
| | - Jinsong Wu
- Department of Materials Science and Engineering, NU ANCE Center , Northwestern University , Evanston , Illinois 60208 , United States
| | - Jean-François Gaillard
- Department of Civil and Environmental Engineering , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| |
Collapse
|
37
|
Ndu U, Christensen GA, Rivera NA, Gionfriddo CM, Deshusses MA, Elias DA, Hsu-Kim H. Quantification of Mercury Bioavailability for Methylation Using Diffusive Gradient in Thin-Film Samplers. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:8521-8529. [PMID: 29920204 PMCID: PMC6085726 DOI: 10.1021/acs.est.8b00647] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/03/2018] [Accepted: 06/19/2018] [Indexed: 05/25/2023]
Abstract
Mercury-contaminated sediment and water contain various Hg species, with a small fraction available for microbial conversion to the bioaccumulative neurotoxin monomethylmercury (MeHg). Quantification of this available Hg pool is needed to prioritize sites for risk management. This study compared the efficacy of diffusive gradient in thin-film (DGT) passive samplers to a thiol-based selective extraction method with glutathione (GSH) and conventional filtration (<0.2 μm) as indicators of Hg bioavailability. Anaerobic sediment slurry microcosms were amended with isotopically labeled inorganic Hg "endmembers" (dissolved Hg2+, Hg-humic acid, Hg-sorbed to FeS, HgS nanoparticles) with a known range of bioavailability and methylation potentials. Net MeHg production (expressed as percent of total Hg as MeHg) over 1 week correlated with mass accumulation of Hg endmembers on the DGTs and only sometimes correlated with the 0.2 μm filter passing Hg fraction and the GSH-extractable Hg fraction. These results suggest for the first time that inorganic Hg uptake in DGTs may indicate bioavailability for methylating microbes. Moreover, the methylating microbial community assessed by hgcA gene abundance was not always consistent with methylation rates between the experiments, indicating that knowledge of the methylating community should target the transcript or protein level. Altogether, these results suggest that DGTs could be used to quantify the bioavailable Hg fraction as part of a method to assess net MeHg production potential in the environment.
Collapse
Affiliation(s)
- Udonna Ndu
- Department
of Civil and Environmental Engineering, Duke University, Box 90287, Durham, North Carolina 27708, United States
| | - Geoff A. Christensen
- Biosciences
Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6036, Oak Ridge, Tennessee 37831-6036, United States
| | - Nelson A. Rivera
- Department
of Civil and Environmental Engineering, Duke University, Box 90287, Durham, North Carolina 27708, United States
| | - Caitlin M. Gionfriddo
- Biosciences
Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6036, Oak Ridge, Tennessee 37831-6036, United States
| | - Marc A. Deshusses
- Department
of Civil and Environmental Engineering, Duke University, Box 90287, Durham, North Carolina 27708, United States
| | - Dwayne A. Elias
- Biosciences
Division, Oak Ridge National Laboratory, P.O. Box 2008, MS-6036, Oak Ridge, Tennessee 37831-6036, United States
| | - Heileen Hsu-Kim
- Department
of Civil and Environmental Engineering, Duke University, Box 90287, Durham, North Carolina 27708, United States
| |
Collapse
|
38
|
Song Y, Jiang T, Liem-Nguyen V, Sparrman T, Björn E, Skyllberg U. Thermodynamics of Hg(II) Bonding to Thiol Groups in Suwannee River Natural Organic Matter Resolved by Competitive Ligand Exchange, Hg L III-Edge EXAFS and 1H NMR Spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:8292-8301. [PMID: 29983050 DOI: 10.1021/acs.est.8b00919] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A molecular level understanding of the thermodynamics and kinetics of the chemical bonding between mercury, Hg(II), and natural organic matter (NOM) associated thiol functional groups (NOM-RSH) is required if bioavailability and transformation processes of Hg in the environment are to be fully understood. This study provides the thermodynamic stability of the Hg(NOM-RS)2 structure using a robust method in which cysteine (Cys) served as a competing ligand to NOM (Suwannee River 2R101N sample) associated RSH groups. The concentration of the latter was quantified to be 7.5 ± 0.4 μmol g-1 NOM by Hg LIII-edge EXAFS spectroscopy. The Hg(Cys)2 molecule concentration in chemical equilibrium with the Hg(II)-NOM complexes was directly determined by HPLC-ICPMS and losses of free Cys due to secondary reactions with NOM was accounted for in experiments using 1H NMR spectroscopy and 13C isotope labeled Cys. The log K ± SD for the formation of the Hg(NOM-RS)2 molecular structure, Hg2+ + 2NOM-RS- = Hg(NOM-RS)2, and for the Hg(Cys)(NOM-RS) mixed complex, Hg2+ + Cys- + NOM-RS- = Hg(Cys)(NOM-RS), were determined to be 40.0 ± 0.2 and 38.5 ± 0.2, respectively, at pH 3.0. The magnitude of these constants was further confirmed by 1H NMR spectroscopy and the Hg(NOM-RS)2 structure was verified by Hg LIII-edge EXAFS spectroscopy. An important finding is that the thermodynamic stabilities of the complexes Hg(NOM-RS)2, Hg(Cys)(NOM-RS) and Hg(Cys)2 are very similar in magnitude at pH values <7, when all thiol groups are protonated. Together with data on 15 low molecular mass (LMM) thiols, as determined by the same method ( Liem-Ngyuen et al. Thermodynamic stability of mercury(II) complexes formed with environmentally relevant low-molecular-mass thiols studied by competing ligand exchange and density functional theory . Environ. Chem. 2017 , 14 , ( 4 ), 243 - 253 .), the constants for Hg(NOM-RS)2 and Hg(Cys)(NOM-RS) represent an internally consistent thermodynamic data set that we recommend is used in studies where the chemical speciation of Hg(II) is determined in the presence of NOM and LMM thiols.
Collapse
Affiliation(s)
- Yu Song
- Department of Forest Ecology and Management , Swedish University of Agricultural Science , SE-901 83 Umeå , Sweden
| | - Tao Jiang
- Department of Forest Ecology and Management , Swedish University of Agricultural Science , SE-901 83 Umeå , Sweden
| | - Van Liem-Nguyen
- Department of Forest Ecology and Management , Swedish University of Agricultural Science , SE-901 83 Umeå , Sweden
- School of Science and Technology , Örebro University , SE-701 82 Örebro , Sweden
| | - Tobias Sparrman
- Department of Chemistry , Umeå University , SE-901 87 Umeå , Sweden
| | - Erik Björn
- Department of Chemistry , Umeå University , SE-901 87 Umeå , Sweden
| | - Ulf Skyllberg
- Department of Forest Ecology and Management , Swedish University of Agricultural Science , SE-901 83 Umeå , Sweden
| |
Collapse
|
39
|
Speciation and Mobility of Mercury in Soils Contaminated by Legacy Emissions from a Chemical Factory in the Rhône Valley in Canton of Valais, Switzerland. SOIL SYSTEMS 2018. [DOI: 10.3390/soilsystems2030044] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Legacy contamination of soils and sediments with mercury (Hg) can pose serious threats to the environment and to human health. Assessing risks and possible remediation strategies must consider the chemical forms of Hg, as different Hg species exhibit vastly different environmental behaviors and toxicities. Here, we present a study on Hg speciation and potential mobility in sediments from a chemical factory site, and soils from nearby settlement areas in the canton of Valais, Switzerland. Total Hg ranged from 0.5 to 28.4 mg/kg in the soils, and 3.5 to 174.7 mg/kg in the sediments, respectively. Elemental Hg(0) was not detectable in the soils by thermal desorption analysis. Methylmercury, the most toxic form of Hg, was present at low levels in all soils (<0.010 mg/kg; <0.8% of total Hg). Sequential extractions and thermal desorption analyses suggested that most of the Hg in the soils was present as “matrix-bound Hg(II)”, most likely associated with soil organic matter. For factory sediments, which contained less organic matter, the results suggested a higher fraction of sulfide-bound Hg. Batch extractions in different CaCl2 solutions revealed that Hg solubility was low overall, and there was no Hg-mobilizing effects of Ca2+ or Cl− in solution. Only in some of the factory sediments did high CaCl2 concentrations result in increased extractability of Hg, due to the formation of Hg-chloride complexes. Additional experiments with soil redox reactors showed that even mildly reducing conditions led to a sharp release of Hg into solution, which may be highly relevant in soils that are prone to periodic water saturation of flooding.
Collapse
|