1
|
Li R, Yan J, Wang C, Yang S, Zhang L, Peng T, Zhu W, Li P, Zhang L, Feng X. Mercury sources, transport, and transformation in rainfall-runoff processes: Mercury isotope approach. WATER RESEARCH 2024; 261:122044. [PMID: 38972237 DOI: 10.1016/j.watres.2024.122044] [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: 03/21/2024] [Revised: 06/25/2024] [Accepted: 07/02/2024] [Indexed: 07/09/2024]
Abstract
Mercury (Hg) in runoff water poses significant ecological risks to aquatic ecosystems that can affect organisms. However, accurately identifying the sources and transformation processes of Hg in runoff water is challenging due to complex natural conditions. This study provides a comprehensive investigation of Hg dynamics in water from rainfall to runoff. The Hg isotope fractionation in water was characterized, which allows accurate quantification of Hg sources, transport, and transformations in rainfall-runoff processes. Δ200Hg and corrected Δ199Hg values can serve as reliable tracers for identifying Hg sources in the runoff water and the variation of δ202Hg can be explained by Hg transformation processes. During runoff migration processes, Hg from rainfall is rapidly absorbed on the land surface, while terrestrial Hg entering the water by the dissolution process becomes the primary component of dissolved mercury (DHg). Besides the dissolution and adsorption, microbial Hg(II) reduction and demethylation of MeHg were dominant processes for DHg in the runoff water that flows through the rice paddies, while photochemical Hg(II) reduction was the dominant process for DHg in the runoff water with low water exchange rates. Particulate Hg (PHg) in runoff water is dominantly originated by the terrestrial material and derived from the dissolution and adsorption process. Tracking sources and transformations of Hg in runoff water during the rainfall-runoff process provides a basis for studying Hg pollution in larger water bodies under complex environmental factors.
Collapse
Affiliation(s)
- Ruolan Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Junyao Yan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chuan Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shaochen Yang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Lin Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Puding Karst Ecosystem Research Station, Chinese Academy of Sciences, Puding 562100, China
| | - Tao Peng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Puding Karst Ecosystem Research Station, Chinese Academy of Sciences, Puding 562100, China
| | - Wei Zhu
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden
| | - Ping Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
| | - Leiming Zhang
- Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto M3H5T4, Canada
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
2
|
Song Z, Huang S, Zhang P, Yuan T, Zhang Y. Isotope Data Constrains Redox Chemistry of Atmospheric Mercury. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024. [PMID: 38810222 DOI: 10.1021/acs.est.4c02600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2024]
Abstract
The redox chemistry of mercury (Hg) in the atmosphere exerts a significant influence on its global cycle. However, our understanding of this important process remains shrouded in uncertainty. In this study, we utilize three-dimensional atmospheric Hg isotope modeling to evaluate the isotopic composition of particle-bound mercury [HgII(P)] in the global atmosphere. We investigate various chemistry mechanisms and find that they induce remarkably disparate odd-number mass-independent fractionation (odd-MIF) in HgII(P) on a global scale. The observed odd-MIF data identify the essential role of sea salt aerosol debromination in the redox chemistry of atmospheric Hg and underscore the predominant influence of Br oxidation in the marine boundary layer. The odd-MIF signatures significantly narrow the uncertainty range of redox chemistry rates and constrain the photoreduction of HgII(P) at a magnitude of 10-3 JNO2 (local photolysis frequency of NO2) in the global atmosphere. This study advances our understanding of atmospheric Hg chemistry processes and provides insights into the potential impacts of climate change on Hg cycling.
Collapse
Affiliation(s)
- Zhengcheng Song
- School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China
- Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Shaojian Huang
- School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Peng Zhang
- School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Tengfei Yuan
- School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China
| | - Yanxu Zhang
- School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China
- Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, Jiangsu 210023, China
| |
Collapse
|
3
|
Fukami Y, Ariizumi R, Ijichi Y, Ohno T, Kashiwabara T, Shibuya T, Suzuki K, Hirata T. Variation in the relationship between odd isotopes of tin in mass-independent fractionation induced by the magnetic isotope effect. Proc Natl Acad Sci U S A 2024; 121:e2321616121. [PMID: 38635630 PMCID: PMC11046578 DOI: 10.1073/pnas.2321616121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 03/19/2024] [Indexed: 04/20/2024] Open
Abstract
Experimental results are presented showing the variation in the relationship between odd isotopes of tin (Sn) in mass-independent fractionation caused by the magnetic isotope effect (MIE), which has previously only been observed for mercury. These results are consistent with the trend predicted from the difference between the magnitudes of nuclear magnetic moments of odd isotopes with a nuclear spin. However, the correlation between odd isotopes in fractionation induced by the MIE for the reaction system used in this study (solvent extraction using a crown ether) was different from that reported for the photochemical reaction of methyltin. This difference between the two reaction systems is consistent with a theoretical prediction that the correlation between odd isotopes in fractionation induced by the MIE is controlled by the relationship between the spin conversion time and radical lifetime. The characteristic changes in the correlation between odd isotopes in fractionation induced by the MIE observed for Sn in this study provide a guideline for quantitatively determining fractionation patterns caused by the MIE for elements that have multiple isotopes with a nuclear spin. These results improve our understanding of the potential impact of the MIE on mass-independent fractionation observed in natural samples, such as meteorites, and analytical artifacts of high-precision isotope analysis for heavy elements.
Collapse
Affiliation(s)
- Yusuke Fukami
- Department of Chemistry, Faculty of Science, Gakushuin University, Tokyo171-8588, Japan
| | - Ryoko Ariizumi
- Department of Chemistry, Faculty of Science, Gakushuin University, Tokyo171-8588, Japan
| | - Yuta Ijichi
- Geochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo113-0033, Japan
| | - Takeshi Ohno
- Department of Chemistry, Faculty of Science, Gakushuin University, Tokyo171-8588, Japan
| | - Teruhiko Kashiwabara
- Submarine Resources Research Center (SRRC), Japan Agency for Marine–Earth Science and Technology (JAMSTEC), Yokosuka237-0061, Japan
| | - Takazo Shibuya
- Super-cutting-edge Grand and Advanced Research (SUGAR) Program, Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine–Earth Science and Technology (JAMSTEC), Yokosuka237-0061, Japan
| | - Katsuhiko Suzuki
- Submarine Resources Research Center (SRRC), Japan Agency for Marine–Earth Science and Technology (JAMSTEC), Yokosuka237-0061, Japan
| | - Takafumi Hirata
- Geochemical Research Center, Graduate School of Science, The University of Tokyo, Tokyo113-0033, Japan
| |
Collapse
|
4
|
Zhu W, Li Z, Li P, Sommar J, Fu X, Feng X, Yu B, Zhang W, Reis AT, Pereira E. Legacy Mercury Re-emission and Subsurface Migration at Contaminated Sites Constrained by Hg Isotopes and Chemical Speciation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:5336-5346. [PMID: 38472090 DOI: 10.1021/acs.est.3c07276] [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: 03/14/2024]
Abstract
The re-emission and subsurface migration of legacy mercury (Hg) are not well understood due to limited knowledge of the driving processes. To investigate these processes at a decommissioned chlor-alkali plant, we used mercury stable isotopes and chemical speciation analysis. The isotopic composition of volatilized Hg(0) was lighter compared to the bulk total Hg (THg) pool in salt-sludge and adjacent surface soil with mean ε202HgHg(0)-THg values of -3.29 and -2.35‰, respectively. Hg(0) exhibited dichotomous directions (E199HgHg(0)-THg = 0.17 and -0.16‰) of mass-independent fractionation (MIF) depending on the substrate from which it was emitted. We suggest that the positive MIF enrichment during Hg(0) re-emission from salt-sludge was overall controlled by the photoreduction of Hg(II) primarily ligated by Cl- and/or the evaporation of liquid Hg(0). In contrast, O-bonded Hg(II) species were more important in the adjacent surface soils. The migration of Hg from salt-sludge to subsurface soil associated with selective Hg(II) partitioning and speciation transformation resulted in deep soils depleted in heavy isotopes (δ202Hg = -2.5‰) and slightly enriched in odd isotopes (Δ199Hg = 0.1‰). When tracing sources using Hg isotopes, it is important to exercise caution, particularly when dealing with mobilized Hg, as this fraction represents only a small portion of the sources.
Collapse
Affiliation(s)
- Wei Zhu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå SE-90183, Sweden
| | - Zhonggen Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- School of Resources and Environment, Zunyi Normal College, Zunyi 563006, China
| | - Ping Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jonas Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xuewu Fu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ben Yu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Wei Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Ana T Reis
- EPIUnit─Instituto de Saúde Pública, Universidade do Porto, Porto 4050-600, Portugal
- Laboratório para a Investigação Integrativa e Translacional em Saúde Populacional (ITR), Porto 4050-600, Portugal
| | - Eduarda Pereira
- LAQV-REQUIMTE─Associated Laboratory for Green Chemistry, University of Aveiro, Aveiro 3810-193, Portugal
| |
Collapse
|
5
|
Baldwin AK, Janssen SE, Tate MT, Poulin BA, Yoder AM, Naymik J, Larsen C, Hoovestol C, Krabbenhoft DP. Mercury sources and budget for the Snake River above a hydroelectric reservoir complex. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 907:167961. [PMID: 37865255 DOI: 10.1016/j.scitotenv.2023.167961] [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: 08/16/2023] [Revised: 10/13/2023] [Accepted: 10/18/2023] [Indexed: 10/23/2023]
Abstract
Understanding sources of mercury (Hg) and methylmercury (MeHg) to a water body is critical for management but is often complicated by poorly characterized Hg inputs and in situ processes, such as inorganic Hg methylation. In this study, we determined inorganic Hg and MeHg concentrations and loads (filter-passing and particulate fractions) for a semi-arid 164-kilometer stretch of the Snake River above the Hells Canyon Complex, a Hg-impaired hydroelectric reservoir complex on the Idaho-Oregon border, and used water quality measurements and Hg stable isotope ratios to create a comprehensive Hg source budget for the river. Results show that whereas most of the streamflow to the study reach comes from the main branch of the Snake River (i.e., the upstream watershed), major tributaries within the study reach contribute a greater proportion of inorganic Hg and MeHg loads. Mercury stable-isotope analyses highlight that Hg within the tributaries is predominantly associated with geologic deposits and snowmelt sources, the latter reflecting wet deposition. Surprisingly, irrigation return drains contribute 40-50 % of particulate inorganic Hg loads despite being ≤4.3 % of the overall water budget. Together, tributaries and irrigation return drains account for 97-100 % of the inorganic Hg and streamflow to the study reach, but ~65 % of the MeHg, indicating in-stream and riparian methylation may be an important and previously unrecognized source of MeHg. Streamflow, total suspended solids, dissolved organic carbon, and agricultural land cover were found to be important controls on the mobilization and transport of different Hg species and fractions. This study represents the first fluvial budget for Hg in the Snake River that accounts for particulate and filter-passing Hg species from both major tributaries and irrigation return drains, and expands our understanding of Hg sources and methylation processes within semi-arid environments. This information is critical to inform management decisions related to elevated Hg burdens in biota.
Collapse
Affiliation(s)
- Austin K Baldwin
- U.S. Geological Survey, Idaho Water Science Center, United States of America.
| | - Sarah E Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, United States of America
| | - Michael T Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, United States of America
| | - Brett A Poulin
- Department of Environmental Toxicology, University of California at Davis, United States of America
| | - Alysa M Yoder
- U.S. Geological Survey, Idaho Water Science Center, United States of America
| | | | | | | | - David P Krabbenhoft
- U.S. Geological Survey, Upper Midwest Water Science Center, United States of America
| |
Collapse
|
6
|
Armstrong G, Janssen SE, Poulin BA, Tate MT, Krabbenhoft DP, Hurley JP. Competition between Dissolved Organic Matter and Freshwater Plankton Control Methylmercury Isotope Fractionation during Uptake and Photochemical Demethylation. ACS EARTH & SPACE CHEMISTRY 2023; 7:2382-2392. [PMID: 38148993 PMCID: PMC10749477 DOI: 10.1021/acsearthspacechem.3c00154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 12/28/2023]
Abstract
Isotope fractionation related to photochemical reactions and planktonic uptake at the base of the food web is a major uncertainty in the biological application of mercury (Hg) stable isotopes. In freshwater systems, it is unclear how competitive interactions among methylmercury (MeHg), dissolved organic matter (DOM), and phytoplankton govern the magnitude of mass-dependent and mass-independent fractionation. This study investigated how DOM alters rates of planktonic MeHg uptake and photodegradation and corresponding Hg isotope fractionation in the presence of freshwater phytoplankton species, Raphidocelis subcapitata. Outdoor sunlight exposure experiments utilizing R. subcapitata were performed in the presence of different DOM samples using environmentally relevant ratios of MeHg-DOM thiol groups. The extent of Δ199Hg in phytoplankton incubations (2.99‰ St. Louis River HPOA, 1.88‰ Lake Erie HPOA) was lower compared to paired abiotic control experiments (4.29 and 2.86‰, respectively) after ∼30 h of irradiation, resulting from cell shading or other limiting factors reducing the extent of photodemethylation. Although the Δ199Hg/Δ201Hg ratio was uniform across experiments (∼1.4), Δ199Hg/δ202Hg slopes varied dramatically (from -0.96 to 15.4) across incubations with R. subcapitata and DOM. In addition, no evidence of Hg isotope fractionation was observed within R. subcapitata cells. This study provides a refined examination of Hg isotope fractionation markers for key processes occurring in the lower food web prior to bioaccumulation, critical for accurately accounting for the photochemical processing of Hg isotopes across a wide spectrum of freshwater systems.
Collapse
Affiliation(s)
- Grace
J. Armstrong
- U.S.
Geological Survey Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States
- Environmental
Chemistry and Technology Program, University
of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Sarah E. Janssen
- U.S.
Geological Survey Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States
| | - Brett A. Poulin
- Department
of Environmental Toxicology, University
of California Davis, Davis, California 95616 United States
| | - Michael T. Tate
- U.S.
Geological Survey Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States
| | - David P. Krabbenhoft
- U.S.
Geological Survey Upper Midwest Water Science Center, Madison, Wisconsin 53726, United States
| | - James P. Hurley
- Environmental
Chemistry and Technology Program, University
of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- University
of Wisconsin Aquatic Sciences Center, Madison, Wisconsin 53706, United States
| |
Collapse
|
7
|
Li C, Jiskra M, Nilsson MB, Osterwalder S, Zhu W, Mauquoy D, Skyllberg U, Enrico M, Peng H, Song Y, Björn E, Bishop K. Mercury deposition and redox transformation processes in peatland constrained by mercury stable isotopes. Nat Commun 2023; 14:7389. [PMID: 37968321 PMCID: PMC10652010 DOI: 10.1038/s41467-023-43164-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 11/02/2023] [Indexed: 11/17/2023] Open
Abstract
Peatland vegetation takes up mercury (Hg) from the atmosphere, typically contributing to net production and export of neurotoxic methyl-Hg to downstream ecosystems. Chemical reduction processes can slow down methyl-Hg production by releasing Hg from peat back to the atmosphere. The extent of these processes remains, however, unclear. Here we present results from a comprehensive study covering concentrations and isotopic signatures of Hg in an open boreal peatland system to identify post-depositional Hg redox transformation processes. Isotope mass balances suggest photoreduction of HgII is the predominant process by which 30% of annually deposited Hg is emitted back to the atmosphere. Isotopic analyses indicate that above the water table, dark abiotic oxidation decreases peat soil gaseous Hg0 concentrations. Below the water table, supersaturation of gaseous Hg is likely created more by direct photoreduction of rainfall rather than by reduction and release of Hg from the peat soil. Identification and quantification of these light-driven and dark redox processes advance our understanding of the fate of Hg in peatlands, including the potential for mobilization and methylation of HgII.
Collapse
Affiliation(s)
- Chuxian Li
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden.
| | - Martin Jiskra
- Environmental Geosciences, University of Basel, Basel, Switzerland
| | - Mats B Nilsson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | | | - Wei Zhu
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Dmitri Mauquoy
- School Geosciences, University of Aberdeen, Scotland, UK
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Maxime Enrico
- Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, TotalEnergies, LFCR, IPREM, Pau, France
| | - Haijun Peng
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Yu Song
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Erik Björn
- Department of Chemistry, Umeå University, Umeå, Sweden
| | - Kevin Bishop
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
| |
Collapse
|
8
|
Du H, Wang X, Yuan W, Wu F, Jia L, Liu N, Lin CJ, Gan J, Zeng F, Wang K, Feng X. Elevated Mercury Deposition, Accumulation, and Migration in a Karst Forest. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:17490-17500. [PMID: 37908057 DOI: 10.1021/acs.est.3c05409] [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: 11/02/2023]
Abstract
The karst forest is one of the extremely sensitive and fragile ecosystems in southwest China, where the biogeochemical cycling of mercury (Hg) is largely unknown. In this study, we investigated the litterfall deposition, accumulation, and soil migration of Hg in an evergreen-deciduous broadleaf karst forest using high-resolution sampling and stable isotope techniques. Results show that elevated litterfall Hg concentrations and fluxes in spring are due to the longer lifespan of evergreen tree foliage exposed to atmospheric Hg0. The hillslope has 1-2 times higher litterfall Hg concentration compared to the low-lying land due to the elevated atmospheric Hg levels induced by topographical and physiological factors. The Hg isotopic model suggests that litterfall Hg depositions account for ∼80% of the Hg source contribution in surface soil. The spatial trend of litterfall Hg deposition cannot solely explain the trend of Hg accumulation in the surface soil. Indeed, soil erosion enhances Hg accumulation in soil of low-lying land, with soil Hg concentration up to 5-times greater than the concentration on the hillslope. The high level of soil Hg migration in the karst forest poses significant ecological risks to groundwater and downstream aquatic ecosystems.
Collapse
Affiliation(s)
- Hu Du
- Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, Hunan, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huanjiang 547100, Guangxi, China
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Wei Yuan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Fei Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Longyu Jia
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Nantao Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Che-Jen Lin
- Center for Advances in Water and Air Quality, Lamar University, Beaumont, Texas 77710, United States
| | - Jiang Gan
- Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, Hunan, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huanjiang 547100, Guangxi, China
| | - Fuping Zeng
- Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, Hunan, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huanjiang 547100, Guangxi, China
| | - Kelin Wang
- Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, Hunan, China
- Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huanjiang 547100, Guangxi, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| |
Collapse
|
9
|
Wu F, Yang L, Wang X, Yuan W, Lin CJ, Feng X. Mercury Accumulation and Sequestration in a Deglaciated Forest Chronosequence: Insights from Particulate and Mineral-Associated Forms of Organic Matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:16512-16521. [PMID: 37857302 DOI: 10.1021/acs.est.3c03107] [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: 10/21/2023]
Abstract
Understanding mercury (Hg) complexation with soil organic matter is important in assessing atmospheric Hg accumulation and sequestration processes in forest ecosystems. Separating soil organic matter into particulate organic matter (POM) and mineral-associated organic matter (MAOM) can help in the understanding of Hg dynamics and cycling due to their very different chemical constituents and associated formation and functioning mechanisms. The concentration of Hg, carbon, and nitrogen contents and isotopic signatures of POM and MAOM in a deglaciated forest chronosequence were determined to construct the processes of Hg accumulation and sequestration. The results show that Hg in POM and MAOM are mainly derived from atmospheric Hg0 deposition. Hg concentration in MAOM is up to 76% higher than that in POM of broadleaf forests and up to 60% higher than that in POM of coniferous forests. Hg accumulation and sequestration in organic soil vary with the vegetation succession. Variations of δ202Hg and Δ199Hg are controlled by source mixing in the broadleaf forest and by Hg sequestration processes in the coniferous forest. Accumulation of atmospheric Hg and subsequent microbial reduction enrich heavier Hg isotopes in MAOM compared to POM due to the specific chemical constituents and nutritional role of MAOM.
Collapse
Affiliation(s)
- Fei Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Luhan Yang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Wei Yuan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Che-Jen Lin
- Center for Advances in Water and Air Quality, Lamar University, Beaumont, Texas 77710, United States
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| |
Collapse
|
10
|
Schwab L, Gallati N, Reiter SM, Kimber RL, Kumar N, McLagan DS, Biester H, Kraemer SM, Wiederhold JG. Mercury Isotope Fractionation during Dark Abiotic Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:15243-15254. [PMID: 37748105 PMCID: PMC10569049 DOI: 10.1021/acs.est.3c03703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 09/04/2023] [Accepted: 09/07/2023] [Indexed: 09/27/2023]
Abstract
Stable mercury (Hg) isotope ratios are an emerging tracer for biogeochemical transformations in environmental systems, but their application requires knowledge of isotopic enrichment factors for individual processes. We investigated Hg isotope fractionation during dark, abiotic reduction of Hg(II) by dissolved iron(Fe)(II), magnetite, and Fe(II) sorbed to boehmite or goethite by analyzing both the reactants and products of laboratory experiments. For homogeneous reduction of Hg(II) by dissolved Fe(II) in continuously purged reactors, the results followed a Rayleigh distillation model with enrichment factors of -2.20 ± 0.16‰ (ε202Hg) and 0.21 ± 0.02‰ (E199Hg). In closed system experiments, allowing reequilibration, the initial kinetic fractionation was overprinted by isotope exchange and followed a linear equilibrium model with -2.44 ± 0.17‰ (ε202Hg) and 0.34 ± 0.02‰ (E199Hg). Heterogeneous Hg(II) reduction by magnetite caused a smaller isotopic fractionation (-1.38 ± 0.07 and 0.13 ± 0.01‰), whereas the extent of isotopic fractionation of the sorbed Fe(II) experiments was similar to the kinetic homogeneous case. Small mass-independent fractionation of even-mass Hg isotopes with 0.02 ± 0.003‰ (E200Hg) and ≈ -0.02 ± 0.01‰ (E204Hg) was consistent with theoretical predictions for the nuclear volume effect. This study contributes significantly to the database of Hg isotope enrichment factors for specific processes. Our findings show that Hg(II) reduction by dissolved Fe(II) in open systems results in a kinetic MDF with a larger ε compared to other abiotic reduction pathways, and combining MDF with the observed MIF allows the distinction from photochemical or microbial Hg(II) reduction pathways.
Collapse
Affiliation(s)
- Lorenz Schwab
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
- Doctoral
School in Microbiology and Environmental Science, University of Vienna, 1030 Vienna, Austria
- Environmental
Engineering Institute IIE-ENAC, Soil Biogeochemistry Laboratory, École Polytechnique Fédérale
de Lausanne (EPFL), Route
des Ronquos 86, 1951 Sion, Switzerland
| | - Niklas Gallati
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Sofie M. Reiter
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Richard L. Kimber
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Naresh Kumar
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
- Soil
Chemistry and Chemical Soil Quality Group, Department of Environmental
Sciences, University of Wageningen, Droevendaalsesteeg 3a, 6708 Wageningen, Netherlands
| | - David S. McLagan
- Environmental
Geochemistry Group, Institute of Geoecology, Technische Universität Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
- Department
of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada
- School
of Environmental Studies, Queen’s
University, Kingston, Ontario K7L 3N6, Canada
| | - Harald Biester
- Environmental
Geochemistry Group, Institute of Geoecology, Technische Universität Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
| | - Stephan M. Kraemer
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| | - Jan G. Wiederhold
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
| |
Collapse
|
11
|
Yuan W, Wang X, Lin CJ, Song Q, Zhang H, Wu F, Liu N, Lu H, Feng X. Deposition and Re-Emission of Atmospheric Elemental Mercury over the Tropical Forest Floor. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:10686-10695. [PMID: 37437160 DOI: 10.1021/acs.est.3c01222] [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: 07/14/2023]
Abstract
Significant knowledge gaps exist regarding the emission of elemental mercury (Hg0) from the tropical forest floor, which limit our understanding of the Hg mass budget in forest ecosystems. In this study, biogeochemical processes of Hg0 deposition to and evasion from soil in a Chinese tropical rainforest were investigated using Hg stable isotopic techniques. Our results showed a mean air-soil flux as deposition of -4.5 ± 2.1 ng m-2 h-1 in the dry season and as emission of +7.4 ± 1.2 ng m-2 h-1 in the rainy season. Hg re-emission, i.e., soil legacy Hg evasion, induces negative transitions of Δ199Hg and δ202Hg in the evaded Hg0 vapor, while direct atmospheric Hg0 deposition does not exhibit isotopic fractionation. Using an isotopic mass balance model, direct atmospheric Hg0 deposition to soil was estimated to be 48.6 ± 13.0 μg m-2 year-1. Soil Hg0 re-emission was estimated to be 69.5 ± 10.6 μg m-2 year-1, of which 63.0 ± 9.3 μg m-2 year-1 is from surface soil evasion and 6.5 ± 5.0 μg m-2 year-1 from soil pore gas diffusion. Combined with litterfall Hg deposition (∼34 μg m-2 year-1), we estimated a ∼12.6 μg m-2 year-1 net Hg0 sink in the tropical forest. The fast nutrient cycles in the tropical rainforests lead to a strong Hg0 re-emission and therefore a relatively weaker atmospheric Hg0 sink.
Collapse
Affiliation(s)
- Wei Yuan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Che-Jen Lin
- Center for Advances in Water and Air Quality, Lamar University, Beaumont, Texas 77710, United States
| | - Qinghai Song
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
| | - Hui Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Fei Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Nantao Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Huazheng Lu
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| |
Collapse
|
12
|
Zheng W, Zhou A, Sahoo SK, Nolan MR, Ostrander CM, Sun R, Anbar AD, Xiao S, Chen J. Recurrent photic zone euxinia limited ocean oxygenation and animal evolution during the Ediacaran. Nat Commun 2023; 14:3920. [PMID: 37400445 DOI: 10.1038/s41467-023-39427-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 06/12/2023] [Indexed: 07/05/2023] Open
Abstract
The Ediacaran Period (~635-539 Ma) is marked by the emergence and diversification of complex metazoans linked to ocean redox changes, but the processes and mechanism of the redox evolution in the Ediacaran ocean are intensely debated. Here we use mercury isotope compositions from multiple black shale sections of the Doushantuo Formation in South China to reconstruct Ediacaran oceanic redox conditions. Mercury isotopes show compelling evidence for recurrent and spatially dynamic photic zone euxinia (PZE) on the continental margin of South China during time intervals coincident with previously identified ocean oxygenation events. We suggest that PZE was driven by increased availability of sulfate and nutrients from a transiently oxygenated ocean, but PZE may have also initiated negative feedbacks that inhibited oxygen production by promoting anoxygenic photosynthesis and limiting the habitable space for eukaryotes, hence abating the long-term rise of oxygen and restricting the Ediacaran expansion of macroscopic oxygen-demanding animals.
Collapse
Affiliation(s)
- Wang Zheng
- School of Earth System Science, Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China
| | - Anwen Zhou
- School of Earth System Science, Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China
- Department of Earth, Ocean and Atmospheric Science and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, 32306, USA
| | | | - Morrison R Nolan
- Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Chadlin M Ostrander
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
- Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, 84112, USA
| | - Ruoyu Sun
- School of Earth System Science, Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China
| | - Ariel D Anbar
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Jiubin Chen
- School of Earth System Science, Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China.
| |
Collapse
|
13
|
Zhang H, Fu X, Wu X, Deng Q, Tang K, Zhang L, Sommar J, Sun G, Feng X. Using Mercury Stable Isotopes to Quantify Bidirectional Water-Atmosphere Hg(0) Exchange Fluxes and Explore Controlling Factors. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023. [PMID: 37378655 DOI: 10.1021/acs.est.3c01273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
In this study, exchange fluxes and Hg isotope fractionation during water-atmosphere Hg(0) exchange were investigated at three lakes in China. Water-atmosphere exchange was overall characterized by net Hg(0) emissions, with lake-specific mean exchange fluxes ranging from 0.9 to 1.8 ng m-2 h-1, which produced negative δ202Hg (mean: -1.61 to -0.03‰) and Δ199Hg (-0.34 to -0.16‰) values. Emission-controlled experiments conducted using Hg-free air over the water surface at Hongfeng lake (HFL) showed negative δ202Hg and Δ199Hg in Hg(0) emitted from water, and similar values were observed between daytime (mean δ202Hg: -0.95‰, Δ199Hg: -0.25‰) and nighttime (δ202Hg: -1.00‰, Δ199Hg: -0.26‰). Results of the Hg isotope suggest that Hg(0) emission from water is mainly controlled by photochemical Hg(0) production in water. Deposition-controlled experiments at HFL showed that heavier Hg(0) isotopes (mean ε202Hg: -0.38‰) preferentially deposited to water, likely indicating an important role of aqueous Hg(0) oxidation played during the deposition process. A Δ200Hg mixing model showed that lake-specific mean emission fluxes from water surfaces were 2.1-4.1 ng m-2 h-1 and deposition fluxes to water surfaces were 1.2-2.3 ng m-2 h-1 at the three lakes. Results from the this study indicate that atmospheric Hg(0) deposition to water surfaces indeed plays an important role in Hg cycling between atmosphere and water bodies.
Collapse
Affiliation(s)
- Hui Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuewu Fu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xian Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qianwen Deng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kaihui Tang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Leiming Zhang
- Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto M3H5T4, Ontario, Canada
| | - Jonas Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Guangyi Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
14
|
Yuan W, Liu M, Chen D, Xing YW, Spicer RA, Chen J, Them TR, Wang X, Li S, Guo C, Zhang G, Zhang L, Zhang H, Feng X. Mercury isotopes show vascular plants had colonized land extensively by the early Silurian. SCIENCE ADVANCES 2023; 9:eade9510. [PMID: 37115923 PMCID: PMC10146902 DOI: 10.1126/sciadv.ade9510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The colonization and expansion of plants on land is considered one of the most profound ecological revolutions, yet the precise timing remains controversial. Because land vegetation can enhance weathering intensity and affect terrigenous input to the ocean, changes in terrestrial plant biomass with distinct negative Δ199Hg and Δ200Hg signatures may overwrite the positive Hg isotope signatures commonly found in marine sediments. By investigating secular Hg isotopic variations in the Paleozoic marine sediments from South China and peripheral paleocontinents, we highlight distinct negative excursions in both Δ199Hg and Δ200Hg at Stage level starting in the early Silurian and again in the Carboniferous. These geochemical signatures were driven by increased terrestrial contribution of Hg due to the rapid expansion of vascular plants. These excursions broadly coincide with rising atmospheric oxygen concentrations and global cooling. Therefore, vascular plants were widely distributed on land during the Ordovician-Silurian transition (~444 million years), long before the earliest reported vascular plant fossil, Cooksonia (~430 million years).
Collapse
Affiliation(s)
- Wei Yuan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Mu Liu
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
| | - Daizhao Chen
- Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Corresponding author. (X.F.); (D.C.)
| | - Yao-Wu Xing
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
| | - Robert A. Spicer
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
- School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes, MK7 6AA, UK
- State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
| | - Jitao Chen
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China
- Nanjing College, University of Chinese Academy of Sciences, Nanjing 211135, China
| | - Theodore R. Them
- Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, USA
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Shizhen Li
- Oil and Gas Survey, China Geological Survey, Ministry of Natural Resources, Beijing 100083, China
| | - Chuan Guo
- College of Resources and Environmental Engineering, Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang 550025, China
| | - Gongjing Zhang
- Department of Earth Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Liyu Zhang
- Wuxi Research Institute of Petroleum Geology, Petroleum Exploration and Production Research Institute, SINOPEC, Wuxi 214126, China
| | - Hui Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Corresponding author. (X.F.); (D.C.)
| |
Collapse
|
15
|
Mercury isotopic evidence for the importance of particles as a source of mercury to marine organisms. Proc Natl Acad Sci U S A 2022; 119:e2208183119. [PMID: 36279440 PMCID: PMC9636975 DOI: 10.1073/pnas.2208183119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The origin of methylmercury in pelagic fish remains unclear, with many unanswered questions regarding the production and degradation of this neurotoxin in the water column. We used mercury (Hg) stable isotope ratios of marine particles and biota to elucidate the cycling of methylmercury prior to incorporation into the marine food web. The Hg isotopic composition of particles, zooplankton, and fish reveals preferential methylation of Hg within small (< 53 µm) marine particles in the upper 400 m of the North Pacific Ocean. Mass-dependent Hg isotope ratios (δ
202
Hg) recorded in small particles overlap with previously estimated δ
202
Hg values for methylmercury sources to Pacific and Atlantic Ocean food webs. Particulate compound specific isotope analysis of amino acids (CSIA-AA) yield δ
15
N values that indicate more-significant microbial decomposition in small particles compared to larger particles. CSIA-AA and Hg isotope data also suggest that large particles (> 53 µm) collected in the equatorial ocean are distinct from small particles and resemble fecal pellets. Additional evidence for Hg methylation within small particles is provided by a statistical mixing model of even mass–independent (Δ
200
Hg and Δ
204
Hg) isotope values, which demonstrates that Hg within near-surface marine organisms (0–150 m) originates from a combination of rainfall and marine particles. In contrast, in meso- and upper bathypelagic organisms (200–1,400 m), the majority of Hg originates from marine particles with little input from wet deposition. The occurrence of methylation within marine particles is supported further by a correlation between Δ
200
Hg and Δ
199
Hg values, demonstrating greater overlap in the Hg isotopic composition of marine organisms with marine particles than with total gaseous Hg or wet deposition.
Collapse
|
16
|
Zhang L, Yin Y, Li Y, Cai Y. Mercury isotope fractionation during methylmercury transport and transformation: A review focusing on analytical method, fractionation characteristics, and its application. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 841:156558. [PMID: 35710002 DOI: 10.1016/j.scitotenv.2022.156558] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/04/2022] [Accepted: 06/04/2022] [Indexed: 06/15/2023]
Abstract
Methylmercury (MeHg), a potent neurotoxin, can be formed, migrated and transformed in environmental compartments, accompanying with unique mass-dependent and mass-independent fractionation of mercury (Hg). These Hg isotope fractionation signals have great potential to probe the transformation and transport of MeHg in aquatic environments. However, the majority of studies to date have focused on total Hg isotopic composition, with less attention to the isotopic fractionation of MeHg due to technical difficulties in analysis, which severely hinders the understanding of MeHg isotopic fractionation and its applications. This review a) evaluates the reported analytical methods for Hg isotopic composition of MeHg, including online and offline measurement techniques; b) summarizes the extent and characteristics of Hg isotopic fractionation during MeHg transport and transformation, focusing on methylation, demethylation, trophic transfer and internal metabolism; and c) briefly discusses several applications of MeHg isotopic fractionation signatures in estimating the extent of photodemethylation, tracing the source of Hg species, and diagnosing reaction mechanisms. Additionally, the existing problems and future directions in MeHg isotope fractionation are highlighted to improve the analytical protocol for Hg isotope fractionation and deepen our understanding of Hg isotope fractionation in the biogeochemical cycling of MeHg.
Collapse
Affiliation(s)
- Lian Zhang
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Yong Cai
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China; Department of Chemistry & Biochemistry, Florida International University, Miami, FL 33199, United States.
| |
Collapse
|
17
|
Sun G, Feng X, Yin R, Wang F, Lin CJ, Li K, Sommar JO. Dissociation of Mercuric Oxides Drives Anomalous Isotope Fractionation during Net Photo-oxidation of Mercury Vapor in Air. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:13428-13438. [PMID: 35960609 DOI: 10.1021/acs.est.2c02722] [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: 06/15/2023]
Abstract
The atmosphere is the primary medium for long-distance transport and transformation of elemental mercury (Hg), a potent neurotoxin. The recent discovery of mass-independent fractionation (MIF) of even-mass Hg isotopes (even-MIF, measured as Δ200Hg and Δ204Hg) in the atmosphere is surprising and can potentially serve as a powerful tracer in understanding Hg biogeochemistry. Far-ultraviolet (UVC) light-induced gas-phase reactions have been suspected as a likely cause for even-MIF, yet the mechanism remains unknown. Here, we present the first experimental evidence of large-scale even-MIF caused by UVC-induced (wavelength: 254 nm) Hg oxidation in synthetic air at the pressure (46-88 kPa) and temperature (233-298 K) resembling those of the lower atmosphere. We observe negatively correlated Δ200Hg and Δ204Hg signatures with values as low as -50‰ and as high as 550‰, respectively, in the remaining atomic Hg pool. The magnitude of even-MIF signatures decreases with decreasing pressure with the Δ200Hg/Δ204Hg ratio being similar to that observed in global precipitation. This even-MIF can be explained by photodissociation of mercuric oxides that are photochemically formed in the UVC-irradiated Hg-O2 system. We propose that similar processes occurring in the atmosphere, where mercuric oxide species serve as intermediates, are responsible for the observed even-MIF in the environment.
Collapse
Affiliation(s)
- Guangyi Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian 710061, China
| | - Runsheng Yin
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Feiyue Wang
- Centre for Earth Observation Science, and Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Che-Jen Lin
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- Center for Advances in Water and Air Quality, Lamar University, Beaumont, Texas 777100, United States
| | - Kai Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100045, China
| | - Jonas Olof Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| |
Collapse
|
18
|
Gao Z, Zheng W, Li Y, Liu Y, Wu M, Li S, Li P, Liu G, Fu X, Wang S, Wang F, Cai Y, Feng X, Gu B, Zhong H, Yin Y. Mercury transformation processes in nature: Critical knowledge gaps and perspectives for moving forward. J Environ Sci (China) 2022; 119:152-165. [PMID: 35934460 DOI: 10.1016/j.jes.2022.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Revised: 07/11/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
The transformation of mercury (Hg) in the environment plays a vital role in the cycling of Hg and its risk to the ecosystem and human health. Of particular importance are Hg oxidation/reduction and methylation/demethylation processes driven or mediated by the dynamics of light, microorganisms, and organic carbon, among others. Advances in understanding those Hg transformation processes determine our capacity of projecting and mitigating Hg risk. Here, we provide a critical analysis of major knowledge gaps in our understanding of Hg transformation in nature, with perspectives on approaches moving forward. Our analysis focuses on Hg transformation processes in the environment, as well as emerging methodology in exploring these processes. Future avenues for improving the understanding of Hg transformation processes to protect ecosystem and human health are also explored.
Collapse
Affiliation(s)
- Zhiyuan Gao
- Centre for Earth Observation Science, and Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Wang Zheng
- Institute of Surface-Earth System Science, Tianjin University, Tianjin 300192, 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
| | - Yurong Liu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Mengjie Wu
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Shouying Li
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China
| | - Ping Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Guangliang Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Xuewu Fu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Shuxiao Wang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, China
| | - Feiyue Wang
- Centre for Earth Observation Science, and Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Yong Cai
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Huan Zhong
- School of the Environment, Nanjing University, State Key Laboratory of Pollution Control and Resource Reuse, Nanjing 210023, China; Environmental and Life Sciences Program (EnLS), Trent University, Peterborough, Ontario K9L 0G2, Canada.
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| |
Collapse
|
19
|
Chemical Oxidation and Reduction Pathways of Mercury Relevant to Natural Waters: A Review. WATER 2022. [DOI: 10.3390/w14121891] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mercury (Hg) pollution in the environment is a global issue and the toxicity of mercury depends on its speciation. Chemical redox reactions of mercury in an aquatic environment greatly impact on Hg evasion to the atmosphere and the methylation of mercury in natural waters. Identifying the abiotic redox pathways of mercury relevant to natural waters is important for predicting the transport and fate of Hg in the environment. The objective of this review is to summarize the current state of knowledge on specific redox reactions of mercury relevant to natural waters at a molecular level. The rate constants and factors affecting them, as well as the mechanistic information of these redox pathways, are discussed in detail. Increasing experimental evidence also implied that the structure of natural organic matter (NOM) play an important role in dark Hg(II) reduction, dark Hg(0) oxidation and Hg(II) photoreduction in the aquatic environment. Significant photooxidation pathways of Hg(0) identified are Hg(0) photooxidation by hydroxyl radical (OH•) and by carbonate radical (CO3−•). Future research needs on improving the understanding of Hg redox cycling in natural waters are also proposed.
Collapse
|
20
|
Xia S, Yuan W, Lin L, Yang X, Feng X, Li X, Liu X, Chen P, Zeng S, Wang D, Su Q, Wang X. Latitudinal gradient for mercury accumulation and isotopic evidence for post-depositional processes among three tropical forests in Southwest China. JOURNAL OF HAZARDOUS MATERIALS 2022; 429:128295. [PMID: 35074747 DOI: 10.1016/j.jhazmat.2022.128295] [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: 11/19/2021] [Revised: 01/04/2022] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
Tropical forest contributes to > 50% of global litterfall mercury (Hg) inputs and surface soil Hg storage, while with limited understanding of Hg biogeochemical processes. In this study, we displayed the 5-m resolution of Hg spatial distribution in three 1-ha tropical forest plots across the latitudinal gradient in Southwest China, and determined Hg isotopic signatures to understand factors driving Hg spatial distribution and sequestration processes. Our results show that tropical forest at the lowest latitude has the highest litterfall Hg input (74.95 versus 34.14-56.59 μg m-2 yr-1 at higher latitude plots), but the smallest surface soil Hg concentration (2-3 times smaller than at higher latitude sites). Hg isotopic evidence indicates that the decreasing climate mediated microbial Hg reduction in forest floor leads to the increasing Hg accumulation along the latitudinal gradient in three tropical forests. The terrain induced indirect effects by influencing litterfall Hg inputs, soil organic matters distribution and interplays between surface and deep soils drive the heterogeneity of surface soil Hg distribution within each sampling plot. Our results highlight though the elevated litterfall Hg inputs, the distinct post-depositional reductions induced Hg loss would remarkedly decrease atmospheric Hg net sink in tropical forest.
Collapse
Affiliation(s)
- Shangwen Xia
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666300, Yunnan, China; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Menglun, Yunnan 666303, China
| | - Wei Yuan
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Luxiang Lin
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666300, Yunnan, China; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Menglun, Yunnan 666303, China; National Forest Ecosystem Research Station at Xishuangbanna, Mengla 666300, Yunnan, China
| | - Xiaodong Yang
- CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666300, Yunnan, China; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Menglun, Yunnan 666303, China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xianming Li
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Xu Liu
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Peijia Chen
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Shufang Zeng
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, China
| | - Qizhao Su
- Mengla Institute of Conservation, Xishuangbanna Administration of Nature Reserves, Mengla 666300, Yunan, China
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
| |
Collapse
|
21
|
Liu C, Fu X, Xu Y, Zhang H, Wu X, Sommar J, Zhang L, Wang X, Feng X. Sources and Transformation Mechanisms of Atmospheric Particulate Bound Mercury Revealed by Mercury Stable Isotopes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:5224-5233. [PMID: 35385257 DOI: 10.1021/acs.est.1c08065] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
This study examined the isotopic composition of particulate bound mercury (PBM) in 10 Chinese megacities and explored the associated sources and transformation mechanisms. PBM in these cities was characterized by negative δ202Hg (mean: -2.00 to -0.78‰), slightly negative to highly positive Δ199Hg (mean: -0.04 to 0.47‰), and slightly positive Δ200Hg (mean: 0.02 to 0.06‰) values. The positive PBM Δ199Hg signatures were likely caused by physiochemical reactions in aerosols. The Δ199Hg/Δ201Hg ratio varied from 0.94 to 1.39 in the cities and increased with the increase in the corresponding mean Δ199HgPBM value. We speculate that, in addition to the photoreduction of oxidized Hg, other transformation mechanisms in aerosols (e.g., isotope exchange, complexation, and oxidation, which express nuclear volume effects) also shape the Δ199HgPBM signatures in the present study. These processes are likely enhanced in the presence of strong gas-particle partitioning of gaseous oxidized Hg (GOM) and elevated levels of redox active metals (e.g., Fe), halides, and elemental carbon. Based on Δ200HgPBM data presented in this and previous studies, we estimate that large proportions (∼47 ± 22%) of PBM were sourced from the oxidation of gaseous elemental Hg followed by the partitioning of GOM onto aerosols globally, indicating the transformation of Hg(0) to PBM as an important sink of atmospheric Hg(0).
Collapse
Affiliation(s)
- Chen Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuewu Fu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Yue Xu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Hui Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xian Wu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jonas Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Leiming Zhang
- Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto M3H 5T4, Ontario, Canada
| | - Xun Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
22
|
Huang S, Jiang R, Song Q, Zhao Y, Lv S, Zhang Y, Huo Y, Chen Y. The Hg behaviors in mangrove ecosystems revealed by Hg stable isotopes: a case study of Maowei mangrove. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:25349-25359. [PMID: 34843054 DOI: 10.1007/s11356-021-17744-4] [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: 08/13/2021] [Accepted: 11/21/2021] [Indexed: 06/13/2023]
Abstract
As one of the most productive marine ecosystems in the tropics and subtropics, mangroves are an important part of the global mercury (Hg) cycling. The environmental processes and effects of Hg in mangroves are complex and affect human Hg exposure, and it is crucial to understand Hg behaviors in the mangrove ecosystem. However, clarifying Hg behaviors in the mangrove ecosystem remains difficult because of an insufficient understanding of the dominant pathways. In this study, measurements of mercury (Hg) concentration and isotope ratios in sediment and plant tissues from a mangrove wetland were used to investigate Hg isotope fractionation in mangrove plants and sediments. Spatial patterns in Hg concentration and isotope signatures indicate that Hg re-emission in the sediment was suppressed by mangrove plants. The ratio of Δ199Hg/Δ201Hg was 0.93 for all sediments, indicating that Hg mass-independent fractionation in the mangrove ecosystem was primarily affected by photoreduction, while the ratios of Δ199Hg/Δ201Hg and Δ199Hg/δ202Hg for plant tissues suggested that natural organic matter reduction of Hg(II) was occurred in the plants. The distinct positive Δ199Hg values found in mangrove plants were supposed to be the results of the unique physiological characteristics of mangroves. The exterior Hg sources from atmosphere and seawater emphasize the role of mangrove ecosystems in the global Hg biogeochemistry. Our study highlights the distinct Hg isotope signatures in the mangrove from that in forests and indicates unique Hg behaviors in the mangrove ecosystem.
Collapse
Affiliation(s)
- Shuyuan Huang
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361102, China
| | - Ronggen Jiang
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China
| | - Qingyong Song
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361102, China
| | - Yuhan Zhao
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China
- College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, China
| | - Supeng Lv
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China
| | - Yuanbiao Zhang
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China.
| | - Yunlong Huo
- Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, 361005, China
| | - Yaojin Chen
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361102, China
| |
Collapse
|
23
|
Lepak RF, Ogorek JM, Bartz KK, Janssen SE, Tate MT, Runsheng Y, Hurley JP, Young DB, Eagles-Smith CA, Krabbenhoft DP. Using carbon, nitrogen, and mercury isotope values to distinguish mercury sources to Alaskan lake trout. ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2022; 9:312-319. [PMID: 35685226 PMCID: PMC9171711 DOI: 10.1021/acs.estlett.2c00096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Lake trout (Salvelinus namaycush), collected from 13 remote lakes located in southwestern Alaska, were analyzed for carbon, nitrogen, and mercury (Hg) stable isotope values to assess the importance of migrating oceanic salmon, volcanic activity, and atmospheric deposition to fish Hg burden. Methylmercury (MeHg) bioaccumulation in phytoplankton (5.0 - 6.9 kg L-1) was also measured to quantify the basal uptake of MeHg to these aquatic food webs. Hg isotope values in lake trout revealed that while the extent of precipitation-delivered Hg was similar across the entire study area, volcanic Hg is likely an important additional source to lake trout in proximate lakes. In contrast, migratory salmon (Oncorhynchus nerka) deliver little MeHg to lake trout directly, although indirect delivery processes via decay could exist. A high level of variability in carbon, nitrogen, and Hg isotope values indicate niche partitioning in lake trout populations within each lake and that a complex suite of ecological interactions is occurring, complicating the conceptually linear assessment of contaminant source to receiving organism. Without connecting energy and contaminant isotope axes, we would not have understood why lake trout from these pristine lakes have highly variable Hg burdens despite consistently low water Hg and comparable age-length dynamics.
Collapse
Affiliation(s)
- Ryan F Lepak
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI 53706, USA
- U.S. Environmental Protection Agency Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA
| | - Jacob M Ogorek
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, 1 Gifford Pinchot Dr, Madison, WI 53726, USA
| | - Krista K Bartz
- National Park Service, Southwest Alaska Inventory and Monitoring Network, 240 West 5 Avenue, Anchorage, AK, 99501, USA
| | - Sarah E Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, 1 Gifford Pinchot Dr, Madison, WI 53726, USA
| | - Michael T Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, 1 Gifford Pinchot Dr, Madison, WI 53726, USA
| | - Yin Runsheng
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - James P Hurley
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI 53706, USA
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
- University of Wisconsin Aquatic Sciences Center, Madison, WI 53706, USA
| | - Daniel B Young
- National Park Service, Lake Clark National Park and Preserve, 240 West 5 Avenue, Anchorage, AK, 99501, USA
| | - Collin A Eagles-Smith
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR 97330, USA
| | - David P Krabbenhoft
- U.S. Geological Survey, Upper Midwest Water Science Center, Mercury Research Laboratory, 1 Gifford Pinchot Dr, Madison, WI 53726, USA
| |
Collapse
|
24
|
Bouchet S, Tessier E, Masbou J, Point D, Lazzaro X, Monperrus M, Guédron S, Acha D, Amouroux D. In Situ Photochemical Transformation of Hg Species and Associated Isotopic Fractionation in the Water Column of High-Altitude Lakes from the Bolivian Altiplano. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:2258-2268. [PMID: 35114086 DOI: 10.1021/acs.est.1c04704] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Photochemical reactions are major pathways for the removal of Hg species from aquatic ecosystems, lowering the concentration of monomethylmercury (MMHg) and its bioaccumulation in foodwebs. Here, we investigated the rates and environmental drivers of MMHg photodegradation and inorganic Hg (IHg) photoreduction in waters of two high-altitude lakes from the Bolivian Altiplano representing meso- to eutrophic conditions. We incubated three contrasting waters in situ at two depths after adding Hg-enriched isotopic species to derive rate constants. We found that transformations mostly occurred in subsurface waters exposed to UV radiation and were mainly modulated by the dissolved organic matter (DOM) level. In parallel, we incubated the same waters after the addition of low concentrations of natural MMHg and followed the stable isotope composition of the remaining Hg species by compound-specific isotope analysis allowing the determination of enrichment factors and mass-independent fractionation (MIF) slopes (Δ199Hg/Δ201Hg) during in situ MMHg photodegradation in natural waters. We found that MIF enrichment factors potentially range from -11 to -19‰ and average -14.3 ± 0.6‰ (1 SE). The MIF slope diverged depending on the DOM level, ranging from 1.24 ± 0.03 to 1.34 ± 0.02 for the low and high DOM waters, respectively, and matched the MMHg MIF slope recorded in fish from the same lake. Our in situ results thus reveal (i) a relatively similar extent of Hg isotopic fractionation during MMHg photodegradation among contrasted natural waters and compared to previous laboratory experiments and (ii) that the MMHg MIF recorded in fish is characteristic for the MMHg bonding environment. They will enable a better assessment of the extent and conditions conducive to MMHg photodegradation in aquatic ecosystems.
Collapse
Affiliation(s)
- Sylvain Bouchet
- Universite de Pau et des Pays de l'Adour, E2S/UPPA, CNRS, Institut des sciences analytiques et de physico-chimie pour l'environnement et les matériaux (IPREM), 64000 Pau, France
| | - Emmanuel Tessier
- Universite de Pau et des Pays de l'Adour, E2S/UPPA, CNRS, Institut des sciences analytiques et de physico-chimie pour l'environnement et les matériaux (IPREM), 64000 Pau, France
| | - Jeremy Masbou
- Géosciences Environnement Toulouse (GET), Univ. Paul Sabatier, CNRS, IRD, Observatoire Midi Pyrénées (OMP), 14 avenue Edouard Belin, 31400 Toulouse, France
- Institut Terre et Environnement de Strasbourg (ITES), Université de Strasbourg/EOST/ENGEES, CNRS UMR 7063, 5 rue Descartes, Strasbourg F-67084, France
| | - David Point
- Géosciences Environnement Toulouse (GET), Univ. Paul Sabatier, CNRS, IRD, Observatoire Midi Pyrénées (OMP), 14 avenue Edouard Belin, 31400 Toulouse, France
- Unidad de Calidad Ambiental (UCA) - Instituto de Ecologia - Universidad Mayor de San Andres, Campus Universitario de Cota Cota, Calle 27, 3161 La Paz, Bolivia
| | - Xavier Lazzaro
- Unidad de Calidad Ambiental (UCA) - Instituto de Ecologia - Universidad Mayor de San Andres, Campus Universitario de Cota Cota, Calle 27, 3161 La Paz, Bolivia
- Unité Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Muséum National d'Histoire Naturelle, Sorbonne Université, Université Caen-Normandie, Université des Antilles, CNRS, IRD. 61 rue Buffon, 75231 Paris CEDEX 5, France
| | - Mathilde Monperrus
- Universite de Pau et des Pays de l'Adour, E2S/UPPA, CNRS, Institut des sciences analytiques et de physico-chimie pour l'environnement et les matériaux (IPREM), 64000 Pau, France
| | - Stéphane Guédron
- Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, 38000 Grenoble, France
- Laboratorio de Hidroquímica - Instituto de Investigaciones Químicas - Universidad Mayor de San Andrés, Campus Universitario de Cota-Cota, Casilla, 3161 La Paz, Bolivia
| | - Dario Acha
- Unidad de Calidad Ambiental (UCA) - Instituto de Ecologia - Universidad Mayor de San Andres, Campus Universitario de Cota Cota, Calle 27, 3161 La Paz, Bolivia
| | - David Amouroux
- Universite de Pau et des Pays de l'Adour, E2S/UPPA, CNRS, Institut des sciences analytiques et de physico-chimie pour l'environnement et les matériaux (IPREM), 64000 Pau, France
| |
Collapse
|
25
|
Priyadarshanee M, Chatterjee S, Rath S, Dash HR, Das S. Cellular and genetic mechanism of bacterial mercury resistance and their role in biogeochemistry and bioremediation. JOURNAL OF HAZARDOUS MATERIALS 2022; 423:126985. [PMID: 34464861 DOI: 10.1016/j.jhazmat.2021.126985] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 08/17/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
Mercury (Hg) is a highly toxic element that occurs at low concentrations in nature. However, various anthropogenic and natural sources contribute around 5000 to 8000 metric tons of Hg per year, rapidly deteriorating the environmental conditions. Mercury-resistant bacteria that possess the mer operon system have the potential for Hg bioremediation through volatilization from the contaminated milieus. Thus, bacterial mer operon plays a crucial role in Hg biogeochemistry and bioremediation by converting both reactive inorganic and organic forms of Hg to relatively inert, volatile, and monoatomic forms. Both the broad-spectrum and narrow-spectrum bacteria harbor many genes of mer operon with their unique definitive functions. The presence of mer genes or proteins can regulate the fate of Hg in the biogeochemical cycle in the environment. The efficiency of Hg transformation depends upon the nature and diversity of mer genes present in mercury-resistant bacteria. Additionally, the bacterial cellular mechanism of Hg resistance involves reduced Hg uptake, extracellular sequestration, and bioaccumulation. The presence of unique physiological properties in a specific group of mercury-resistant bacteria enhances their bioremediation capabilities. Many advanced biotechnological tools also can improve the bioremediation efficiency of mercury-resistant bacteria to achieve Hg bioremediation.
Collapse
Affiliation(s)
- Monika Priyadarshanee
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology Rourkela, Rourkela 769 008, Odisha, India
| | - Shreosi Chatterjee
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology Rourkela, Rourkela 769 008, Odisha, India
| | - Sonalin Rath
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology Rourkela, Rourkela 769 008, Odisha, India
| | - Hirak R Dash
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology Rourkela, Rourkela 769 008, Odisha, India
| | - Surajit Das
- Laboratory of Environmental Microbiology and Ecology (LEnME), Department of Life Science, National Institute of Technology Rourkela, Rourkela 769 008, Odisha, India.
| |
Collapse
|
26
|
Zhu W, Fu X, Zhang H, Liu C, Skyllberg U, Sommar J, Yu B, Feng X. Mercury Isotope Fractionation during the Exchange of Hg(0) between the Atmosphere and Land Surfaces: Implications for Hg(0) Exchange Processes and Controls. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:1445-1457. [PMID: 34964623 DOI: 10.1021/acs.est.1c05602] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Atmosphere-surface exchange of elemental mercury (Hg(0)) is a vital component in global Hg cycling; however, Hg isotope fractionation remains largely unknown. Here, we report Hg isotope fractionation during air-surface exchange from terrestrial surfaces at sites of background (two) and urban (two) character and at five sites contaminated by Hg mining. Atmospheric Hg(0) deposition to soils followed kinetic isotope fractionation with a mass-dependent (MDF) enrichment factor of -4.32‰, and negligible mass-independent fractionation (MIF). Net Hg(0) emission generated average MDF enrichment factors (ε202Hg) of -0.91, -0.59, 1.64, and -0.42‰ and average MIF enrichment factors (E199Hg) of 0.07, -0.20, -0.14, and 0.21‰ for urban, background, and Hg mining soils and cinnabar tailing, respectively. Positive correlations between ε202Hg and ambient Hg(0) concentration indicate that the co-occurring Hg(0) deposition (accounting for 10-39%) in a regime of net soil emission grows with ambient Hg(0). The MIF of Hg(0) emission from soils (E199Hg range -0.27 to 0.14‰, n = 8) appears to be overall controlled by the photochemical reduction of kinetically constrained Hg(II) bonded to O ligands in background soils, while S ligands may have been more important in Hg mining area soils. In contrast, the small positive MIF of Hg(0) emission from cinnabar ore tailing (mean E199Hg = 0.21‰) was likely controlled by abiotic nonphotochemical reduction and liquid Hg(0) evaporation. This research provides critical observational constraints on understanding the Hg(0) isotope signatures released from and deposited to terrestrial surfaces and highlight stable Hg isotopes as a powerful tool for resolving atmosphere-surface exchange processes.
Collapse
Affiliation(s)
- Wei Zhu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Xuewu Fu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China
| | - Hui Zhang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chen Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ulf Skyllberg
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden
| | - Jonas Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Ben Yu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China
| |
Collapse
|
27
|
Huang Q, He X, Huang W, Reinfelder JR. Mass-Independent Fractionation of Mercury Isotopes during Photoreduction of Soot Particle Bound Hg(II). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:13783-13791. [PMID: 34623141 DOI: 10.1021/acs.est.1c02679] [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: 06/13/2023]
Abstract
Soot and mercury (Hg) are two notorious air pollutants, and the fate and transport of Hg may be affected by soot at various scales in the environment as soot may be both a carrier and a reactant for active Hg species. This study was designed to quantify photoreduction of Hg(II) in the presence of soot and the associated Hg isotope fractionation under both atmospheric aerosol and aqueous conditions (water-saturated). Photoreduction experiments were conducted with diesel soot particulate matter under controlled temperature and relative humidity (RH) conditions using a flow-through semibatch reactor system. Mass-dependent fractionation resulted in the enrichment of heavier Hg isotopes in the remaining Hg(II) with enrichment factors (ε202Hg) of 1.48 ± 0.02‰ (±2 standard deviation) to 1.75 ± 0.05‰ for aerosol-phase reactions (RH 28-68%) and from 1.26 ± 0.11 to 1.50 ± 0.04‰ for aqueous-phase reactions. Positive odd mass-independent fractionation (MIF) was observed in aqueous-phase reactions, resulting in Δ199Hg values for reactant Hg(II) as high as 5.29‰, but negative odd-MIF occurred in aerosol-phase reactions, in which Δ199Hg values of reactant Hg(II) varied from -1.02 to 0‰. The average ratio of Δ199Hg/Δ201Hg (1.1) indicated that under all conditions, MIF was dominated by magnetic isotope effects during photoreduction of Hg(II). Increasing RH resulted in higher reduction rates but lower extents of negative MIF in the aerosol-phase experiments, suggesting that the reduction of soot particle-bound Hg(II) was responsible for the observed negative odd-MIF. Our results suggest that mass-independent Hg isotope fractionation during Hg(II) photoreduction varies with soot aerosol water content and that Hg-stable isotope ratios may be used to understand the transformational histories of aerosol-bound Hg(II) in the environment.
Collapse
Affiliation(s)
- Qiang Huang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, Guizhou, China
- Department of Environmental Sciences, Rutgers University, New Brunswick 08901, New Jersey, United States
| | - Xiaoshuai He
- Department of Environmental Sciences, Rutgers University, New Brunswick 08901, New Jersey, United States
| | - Weilin Huang
- Department of Environmental Sciences, Rutgers University, New Brunswick 08901, New Jersey, United States
| | - John R Reinfelder
- Department of Environmental Sciences, Rutgers University, New Brunswick 08901, New Jersey, United States
| |
Collapse
|
28
|
Zhao H, Meng B, Sun G, Lin CJ, Feng X, Sommar J. Chemistry and Isotope Fractionation of Divalent Mercury during Aqueous Reduction Mediated by Selected Oxygenated Organic Ligands. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:13376-13386. [PMID: 34520177 DOI: 10.1021/acs.est.1c03171] [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: 06/13/2023]
Abstract
We have investigated the chemistry and Hg isotope fractionation during the aqueous reduction of HgII by oxalic acid, p-quinone, quinol, and anthraquinone-2,6-disulfonate (AQDS), a derivate of anthraquinone (AQ) that is found in secondary organic aerosols (SOA) and building blocks of natural organic matter (NOM). Each reaction was examined for the effects of light, pH, and dissolved O2. Using an excess of ligand, UVB photolysis of HgII was seen to follow pseudo-first-order kinetics, with the highest rate of ∼10-3 s-1 observed for AQDS and oxalic acid. Mass-dependent fractionation (MDF) occurs by the normal kinetic isotope effect (KIE). Only the oxalate ion, rather than oxalic acid, is photoreactive when present in HgC2O4, which decomposes via two separate pathways distinguishable by isotope anomalies. Upon UVB photolysis, only the reduction mediated by AQDS results in a large odd number mass-independent fractionation (odd-MIF) signified by enrichment of odd isotopes in the reactant. Consistent with the rate, MDF, and odd-MIF reported for fulvic acid, our AQDS result confirms previous assumptions that quinones control HgII reduction in NOM-rich waters. Given the magnitude of odd-MIF triggered via a radical pair mechanism and the significant rate in the presence of air, reduction of HgII by photoproducts of AQDS may help explain the positive odd-MIF observed in ambient aerosols depleted of HgII.
Collapse
Affiliation(s)
- Huifang Zhao
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- School of Geography & Environmental Science, Guizhou Normal University, Guiyang 550025, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Guangyi Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Che-Jen Lin
- Center for Advances in Water and Air Quality, Lamar University, Beaumont, Texas 77710, United States
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
- Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian 710061, China
| | - Jonas Sommar
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| |
Collapse
|
29
|
Stable Isotope Fractionation Reveals Similar Atomic-Level Controls during Aerobic and Anaerobic Microbial Hg Transformation Pathways. Appl Environ Microbiol 2021; 87:e0067821. [PMID: 34232740 DOI: 10.1128/aem.00678-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mercury (Hg) is a global pollutant and potent neurotoxin that bioaccumulates in food webs as monomethylmercury (MeHg). The production of MeHg is driven by anaerobic and Hg redox cycling pathways, such as Hg reduction, which control the availability of Hg to methylators. Anaerobes play an important role in Hg reduction in methylation hot spots, yet their contributions remain underappreciated due to how challenging these pathways are to study in the absence of dedicated genetic targets and low levels of Hg0 in anoxic environments. In this study, we used Hg stable isotope fractionation to explore Hg reduction during anoxygenic photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. We show that cells preferentially reduce lighter Hg isotopes in both metabolisms, leading to mass-dependent fractionation, but mass-independent fractionation commonly induced by UV-visible light is absent. Due to the variability associated with replicate experiments, we could not discern whether dedicated physiological processes drive Hg reduction during photosynthesis and fermentation. However, we demonstrate that fractionation is affected by the interplay between pathways controlling Hg recruitment, accessibility, and availability alongside metabolic redox reactions. The combined contributions of these processes lead to isotopic enrichment during anoxygenic photosynthesis that is in between the values reported for anaerobic respiratory microbial Hg reduction and abiotic photoreduction. Isotope enrichment during fermentation is closer to what has been observed in aerobic bacteria that reduce Hg through dedicated detoxification pathways. Our work suggests that similar controls likely underpin diverse microbe-mediated Hg transformations that affect Hg's fate in oxic and anoxic habitats. IMPORTANCE Anaerobic and photosynthetic bacteria that reduce mercury affect mercury delivery to microbes in methylation sites that drive bioaccumulation in food webs. Anaerobic mercury reduction pathways remain underappreciated in the current view of the global mercury cycle because they are challenging to study, bearing no dedicated genetic targets to establish physiological mechanisms. In this study, we used stable isotopes to characterize the physiological processes that control mercury reduction during photosynthesis and fermentation in the model anaerobe Heliobacterium modesticaldum Ice1. The sensitivity of isotope analyses highlighted the subtle contribution of mercury uptake to the isotope signature associated with anaerobic mercury reduction. When considered alongside the isotope signatures associated with microbial pathways for which genetic determinants have been identified, our findings underscore the narrow range of isotope enrichment that is characteristic of microbial mercury transformations. This suggests that there are common atomic-level controls for biological mercury transformations across a broad range of geochemical conditions.
Collapse
|
30
|
Kurz AY, Blum JD, Johnson MW, Nadelhoffer K, Zak DR. Isotopic composition of mercury deposited via snow into mid-latitude ecosystems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 784:147252. [PMID: 34088049 DOI: 10.1016/j.scitotenv.2021.147252] [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: 02/01/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 06/12/2023]
Abstract
Atmospheric deposition of mercury (Hg) to terrestrial and aquatic ecosystems has significant implications for human and animal exposure. Measurements of Hg isotopic composition can be utilized to trace sources of Hg, but outside of the Arctic there has been little Hg isotopic characterization of snow. To better understand deposition pathways at mid-latitudes, five time series of snowfall were collected at two sites (Dexter and Pellston, Michigan, USA) to investigate the Hg isotopic composition of snowfall, how it changes after deposition, and how it compares to rain. The Hg isotopic composition of a subset of fresh snow samples revealed the influence of reactive surface uptake of atmospheric Hg(0). The first time series collected at Dexter occurred during a polar vortex, demonstrating Hg isotopic fractionation dynamics similar to those in Arctic snow, with increasingly negative Δ199Hg as snow aged with exposure to sunlight. All other time series revealed an increase in Δ199Hg as snow aged, with values reaching up to 3.5‰. This characterization of Hg isotopes in snow suggests a strong influence of oxidants and binding ligands in snow that may mediate Hg isotope fractionation. Additionally, isotopic characterization of Hg in snow deposited to natural ecosystems at mid-latitudes allows for better understanding of atmospheric mercury sources that are deposited to lakes and forests and that may become available for methylation and transfer to food webs.
Collapse
Affiliation(s)
- Aaron Y Kurz
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Joel D Blum
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA
| | - Marcus W Johnson
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA
| | - Knute Nadelhoffer
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Donald R Zak
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA; School of the Environment and Sustainability, University of Michigan, Ann Arbor, MI 48109, USA
| |
Collapse
|
31
|
Fu X, Jiskra M, Yang X, Marusczak N, Enrico M, Chmeleff J, Heimbürger-Boavida LE, Gheusi F, Sonke JE. Mass-Independent Fractionation of Even and Odd Mercury Isotopes during Atmospheric Mercury Redox Reactions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:10164-10174. [PMID: 34213316 DOI: 10.1021/acs.est.1c02568] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mass-independent fractionation (MIF) of stable even mass number mercury (Hg) isotopes is observed in rainfall and gaseous elemental Hg0 globally and is used to quantify atmospheric Hg deposition pathways. The chemical reaction and underlying even-Hg MIF mechanism are unknown however and speculated to be caused by Hg photo-oxidation on aerosols at the tropopause. Here, we investigate the Hg isotope composition of free tropospheric Hg0 and oxidized HgII forms at the high-altitude Pic du Midi Observatory. We find that gaseous oxidized Hg has positive Δ199Hg, Δ201Hg, and Δ200Hg and negative Δ204Hg signatures, similar to rainfall Hg, and we document rainfall Hg Δ196Hg to be near zero. Cloud water and rainfall Hg show an enhanced odd-Hg MIF of 0.3‰ compared to gaseous oxidized HgII, potentially indicating the occurrence of in-cloud aqueous HgII photoreduction. Diurnal MIF observations of free tropospheric Hg0 show how net Hg0 oxidation in high-altitude air masses leads to opposite even- and odd-MIF in Hg0 and oxidized HgII. We speculate that even-Hg MIF takes place by a molecular magnetic isotope effect during HgII photoreduction on aerosols that involves magnetic halogen nuclei. A Δ200Hg mass balance suggests that global Hg deposition pathways in models are likely biased toward HgII deposition. We propose that Hg cycling models could accommodate the Hg-isotope constraints on emission and deposition fluxes.
Collapse
Affiliation(s)
- Xuewu Fu
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Martin Jiskra
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
- Environmental Geosciences, University of Basel, Basel 4001, Switzerland
| | - Xu Yang
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
| | - Nicolas Marusczak
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
| | - Maxime Enrico
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
| | - Jérôme Chmeleff
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
| | - Lars-Eric Heimbürger-Boavida
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
- Mediterranean Institute of Oceanography, Aix Marseille Université, CNRS/IRD, Université de Toulon, IRD, Marseille 13288, France
| | - François Gheusi
- Laboratoire d'Aérologie, CNRS/IRD/Université de Toulouse, Toulouse 31000, France
| | - Jeroen E Sonke
- Géosciences Environnement Toulouse, CNRS/IRD/CNRS/Université de Toulouse, Toulouse 31000, France
| |
Collapse
|
32
|
Enrico M, Balcom P, Johnston DT, Foriel J, Sunderland EM. Simultaneous combustion preparation for mercury isotope analysis and detection of total mercury using a direct mercury analyzer. Anal Chim Acta 2021; 1154:338327. [PMID: 33736793 DOI: 10.1016/j.aca.2021.338327] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 02/11/2021] [Accepted: 02/14/2021] [Indexed: 10/22/2022]
Abstract
Mercury (Hg) stable isotope signatures are widely used to understand Hg cycling in the environment. Sample preparation methods for determining Hg isotope ratios by CV-MC-ICP-MS vary widely among laboratory facilities and sample types. Here, we present a novel and rapid method for preparing solid samples prior to determining Hg isotope composition. We use a direct Hg analyzer (that measures total Hg) for sample combustion, amalgamation and analysis. During the thermal release of Hg from the amalgamator and following detection, the analyte gas enters a trapping solution consisting of 10% HCl/BrCl (5:1, vol/vol). We find Hg blank values are less than 1% of the Hg introduced during sample analysis, Hg detection is not altered by modifying the system, and more than 90% of the introduced Hg is recovered in the trapping solution. Hg isotope results are statistically indistinguishable from accepted values for previously published certified reference materials and uncertainty of 2σ (0.05-0.12‰) is similar to the solution standard RM8610 (2σ = 0.09‰). This new method allows for solid sample preparation for Hg isotope analysis in under 15 min. It has the additional advantage of minimizing use of sample mass during simultaneous detection and preparation.
Collapse
Affiliation(s)
- Maxime Enrico
- Harvard John A. Paulson School of Engineering & Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA, 02138, USA.
| | - Prentiss Balcom
- Harvard John A. Paulson School of Engineering & Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA, 02138, USA
| | - David T Johnston
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St, Cambridge, MA, 02138, USA
| | - Julien Foriel
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St, Cambridge, MA, 02138, USA
| | - Elsie M Sunderland
- Harvard John A. Paulson School of Engineering & Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA, 02138, USA; Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St, Cambridge, MA, 02138, USA
| |
Collapse
|
33
|
Bonsignore M, Manta DS, Barsanti M, Conte F, Delbono I, Horvat M, Quinci EM, Schirone A, Shlyapnikov Y, Sprovieri M. Mercury isotope signatures in sediments and marine organisms as tracers of historical industrial pollution. CHEMOSPHERE 2020; 258:127435. [PMID: 32947671 DOI: 10.1016/j.chemosphere.2020.127435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 06/09/2020] [Accepted: 06/14/2020] [Indexed: 06/11/2023]
Abstract
Isotopic composition of mercury (Hg) in marine organisms and sediment cores was used to identify sources and reconstruct historical trends of contamination in the coastal-marine area of Rosignano Solvay (Italy), affected by Hg pollution from a chlor-alkali plant on the near land. Sediments show a wide range of Hg concentration and Hg isotope signatures. Particularly, coupled Hg concentration and δ202Hg values trace inputs from different sources. The two depth-profiles clearly indicate three distinct periods: "pre-industrial" (before 1941), "industrial" (between 1941 and 2007) and "post-industrial" (after 2007) ages. This is also corroborated by sediment chronology, using 210Pb dating method, validated through 137Cs. Marine organisms are characterized by Hg isotope signatures comparable to "post-industrial" surface sediments. Notably, specimens of Mullus spp. evidence isotope composition comparable to the "industrial" sediments, thus suggesting a still active role of those sediments as source of Hg for the benthic fish compartment. The small amount of MIF and the Δ199Hg/Δ201Hg ratio recorded in organisms are reasonably consistent with limited processes of MMHg demethylation in the water column.
Collapse
Affiliation(s)
- Maria Bonsignore
- IAS-CNR - National Research Council of Italy IAS - Institute of Anthropic Impacts and Sustainability in marine environment, Capo Granitola, Italy.
| | - Daniela Salvagio Manta
- IAS-CNR - National Research Council of Italy IAS - Institute of Anthropic Impacts and Sustainability in marine environment, Lungomare Cristoforo Colombo 452, 90149 Palermo, Italy
| | - Mattia Barsanti
- ENEA - Italian National Agency for new technologies, energy and sustainable economic development, SSPT - Department for Sustainability of Production and Territorial Systems, La Spezia, Italy
| | - Fabio Conte
- ENEA - Italian National Agency for new technologies, energy and sustainable economic development, SSPT - Department for Sustainability of Production and Territorial Systems, La Spezia, Italy
| | - Ivana Delbono
- ENEA - Italian National Agency for new technologies, energy and sustainable economic development, SSPT - Department for Sustainability of Production and Territorial Systems, La Spezia, Italy
| | - Milena Horvat
- Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
| | - Enza Maria Quinci
- IAS-CNR - National Research Council of Italy IAS - Institute of Anthropic Impacts and Sustainability in marine environment, Capo Granitola, Italy
| | - Antonio Schirone
- ENEA - Italian National Agency for new technologies, energy and sustainable economic development, SSPT - Department for Sustainability of Production and Territorial Systems, La Spezia, Italy
| | | | - Mario Sprovieri
- IAS-CNR - National Research Council of Italy IAS - Institute of Anthropic Impacts and Sustainability in marine environment, Capo Granitola, Italy
| |
Collapse
|
34
|
Lepak RF, Janssen SE, Engstrom DR, Krabbenhoft DP, Tate MT, Yin R, Fitzgerald WF, Nagorski SA, Hurley JP. Resolving Atmospheric Mercury Loading and Source Trends from Isotopic Records of Remote North American Lake Sediments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:9325-9333. [PMID: 32597170 PMCID: PMC7781044 DOI: 10.1021/acs.est.0c00579] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The strongest evidence for anthropogenic alterations to the global mercury (Hg) cycle comes from historical records of mercury deposition preserved in lake sediments. Hg isotopes have added a new dimension to these sedimentary archives, promising additional insights into Hg source apportionment and biogeochemical processing. Presently, most interpretations of historical changes are constrained to a small number of locally contaminated ecosystems. Here, we describe changes in natural Hg isotope records from a suite of dated sediment cores collected from various remote lakes of North America. In nearly all cases, the rise in industrial-use Hg is accompanied by an increase in δ202Hg and Δ199Hg values. These trends can be attributed to large-scale industrial emission of Hg into the atmosphere and are consistent with positive Δ199Hg values measured in modern-day precipitation and modeled increases in δ202Hg values from global emission inventories. Despite similar temporal trends among cores, the baseline isotopic values vary considerably among the different study regions, likely attributable to differences in the fractionation produced in situ as well as differing amounts of atmospherically delivered Hg. Differences among the study lakes in precipitation and watershed size provide an empirical framework for evaluating Hg isotopic signatures and global Hg cycling.
Collapse
Affiliation(s)
- Ryan F. Lepak
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 N. Park Street, Madison, WI 53706, USA
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 8505 Research Way, Middleton, WI 53562, USA
- U.S. Environmental Protection Agency Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA
- corresponding author: Ryan Lepak, U.S. EPA Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, 6201 Congdon Blvd, Duluth, MN 55804, USA –
| | - Sarah E. Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 8505 Research Way, Middleton, WI 53562, USA
| | - Daniel R. Engstrom
- St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd St. N., Marine on St. Croix, MN 55047, USA
| | - David P. Krabbenhoft
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 8505 Research Way, Middleton, WI 53562, USA
| | - Michael T. Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 8505 Research Way, Middleton, WI 53562, USA
| | - Runsheng Yin
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 99 Lincheng West Road, Guanshanhu District, Guiyang, Guizhou 550081, China
| | | | - Sonia A. Nagorski
- University of Alaska Southeast, Department of Natural Sciences, Juneau, AK 99801, USA
| | - James P. Hurley
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 N. Park Street, Madison, WI 53706, USA
- University of Wisconsin Aquatic Sciences Center, 1975 Willow Dr., Madison, WI 53706, USA
| |
Collapse
|
35
|
Motta LC, Chien AD, Rask AE, Zimmerman PM. Mercury Magnetic Isotope Effect: A Plausible Photochemical Mechanism. J Phys Chem A 2020; 124:3711-3719. [PMID: 32314920 DOI: 10.1021/acs.jpca.0c00661] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Large mass-independent fractionation signatures in Hg have been observed in the laboratory and the environment, prompting deep questions about the chemical reasons behind these signatures. Since the relative lack of mechanistic information about Hg chemistry in the environment has precluded explanations of these isotope effects, the present study uses high-level electronic structure methods to evaluate the possible photochemical mechanisms of mass-independent isotope effects (MIEs) in HgX2 and CH3HgX (X = Cl, Br, I, and SCH3). The results show that spin-orbit coupling wipes out the potential of MIEs for Hg bound to Br or I, but that complexes involving lighter elements, HgX2 and CH3HgX (X = Cl and SCH3), have relatively small spin-orbit couplings upon photolysis. This unexpected finding shows that magnetic isotope fractionation due to hyperfine coupling is possible, depending on the identity of the Hg complex. By examination of the photolysis potential energy profiles, this study shows that HgX2 complexes can have a positive or a negative MIE (depending on reaction conditions), while CH3HgX complexes exclusively result in a positive MIE. These findings agree with MIE recorded in natural samples, demonstrating a plausible mechanism for the surprising mass-independent fractionation of Hg in the environment.
Collapse
Affiliation(s)
- Laura C Motta
- Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| | - Alan D Chien
- Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| | - Alan E Rask
- Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| | - Paul M Zimmerman
- Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109, United States
| |
Collapse
|