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Xu Z, Lu Q, Xu X, Liang L, Abeysinghe KS, Chen Z, Qiu G. Aquatic methylmercury is a significant subsidy for terrestrial songbirds: Evidence from the odd mass-independent fractionation of mercury isotopes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 880:163217. [PMID: 37011675 DOI: 10.1016/j.scitotenv.2023.163217] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 03/27/2023] [Accepted: 03/28/2023] [Indexed: 05/27/2023]
Abstract
In contrast to aquatic food chains, knowledge of the origins and transfer of mercury (Hg) and methylmercury (MeHg) in terrestrial food chains is relatively limited, especially in songbirds. We collected soil, rice plants, aquatic and terrestrial invertebrates, small wild fish, and resident songbird feathers from an Hg-contaminated rice paddy ecosystem for an analysis of stable Hg isotopes to clarify the sources of Hg and its transfer in songbirds and their prey. Significant mass-dependent fractionation (MDF, δ202Hg), but no mass-independent fractionation (MIF, ∆199Hg) occurred in the trophic transfers in terrestrial food chains. Piscivorous, granivorous, and frugivorous songbirds and aquatic invertebrates were all characterized by elevated Δ199Hg values. The estimated MeHg isotopic compositions obtained using linear fitting and a binary mixing model explained both the terrestrial and aquatic origins of MeHg in the terrestrial food chains. We found that MeHg from aquatic habitats is an important subsidy for terrestrial songbirds, even those that feed mainly on seeds, fruits, or cereals. The results show that MIF of the MeHg isotope is a reliable tool to reveal MeHg sources in songbirds. Because the MeHg isotopic compositions was calculated with a binary mixing model or directly estimated from the high proportions of MeHg, compound-specific isotope analysis of Hg would be more useful for the interpretation of the Hg sources, and is highly recommended for future studies.
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Affiliation(s)
- Zhidong Xu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Qinhui Lu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; The Key Laboratory of Environment Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang 550025, China
| | - Xiaohang Xu
- College of Resources and Environmental Engineering, Guizhou University, Guiyang 550025, China; Key Laboratory of Karst Georesources and Environment (Guizhou University), Ministry of Education, Guiyang 550025, China
| | - Longchao Liang
- School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550001, China
| | - Kasun S Abeysinghe
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Zhuo Chen
- School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550001, China
| | - Guangle Qiu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
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2
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Zhou Z, Wang H, Li Y. Mercury stable isotopes in the ocean: Analytical methods, cycling, and application as tracers. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 874:162485. [PMID: 36858226 DOI: 10.1016/j.scitotenv.2023.162485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 02/22/2023] [Accepted: 02/22/2023] [Indexed: 06/18/2023]
Abstract
Mercury (Hg) has seven stable isotopes that can be utilized to trace the sources of Hg and evaluate the importance of transport and transformation processes in the cycling of Hg in the environment. The ocean is an integral part of the Earth and plays an important role in the global mercury cycle. However, there is a lack of a systematic review of Hg stable isotopes in marine environments. This review is divided into four sections: a) advances in Hg stable isotope analysis, b) the isotope ratios of Hg in various marine environmental matrices (seawater, sediment, and organisms), c) processes governing stable Hg isotope ratios in the ocean, and d) application of Hg stable isotopes to understand biotic uptake and migration. Mercury isotopes have provided much useful information on marine Hg cycling that cannot be given by Hg concentrations alone. This includes (i) sources of Hg in coastal or estuarine environments, (ii) transformation pathways and mechanisms of different forms of Hg in marine environments, (iii) trophic levels and feeding guilds of marine fish, and (iv) migration/habitat changes of marine fish. With the improvement of methods for seawater Hg isotope analysis (especially species-specific methods) and the measurement of Hg isotope fractionation during natural biogeochemical processes in the ocean, Hg stable isotopes will advance our understanding of the marine Hg cycle in the future, e.g., mercury exchange at the sea-atmosphere interface and seawater-sediment interface, contributions of different water masses to Hg in the ocean, fractionation mechanisms of Hg and MeHg transformation in seawater.
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Affiliation(s)
- Zhengwen Zhou
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, 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
| | - Huiling Wang
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, 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
| | - Yanbin Li
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, 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.
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3
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Wang B, Yang S, Li P, Qin C, Wang C, Ali MU, Yin R, Maurice L, Point D, Sonke JE, Zhang L, Feng X. Trace mercury migration and human exposure in typical mercury-emission areas by compound-specific stable isotope analysis. ENVIRONMENT INTERNATIONAL 2023; 174:107891. [PMID: 36963155 DOI: 10.1016/j.envint.2023.107891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/17/2023] [Accepted: 03/16/2023] [Indexed: 06/18/2023]
Abstract
Anthropogenic mercury (Hg) emissions have increased significantly since the Industrial Revolution, resulting in severe health impacts to humans. The consumptions of fish and rice were primary human methylmercury (MeHg) exposure pathways in Asia. However, the lifecycle from anthropogenic Hg emissions to human MeHg exposure is not fully understood. In this study, a recently developed approach, termed MeHg Compound-Specific Isotope Analysis (CSIA), was employed to track lifecycle of Hg in four typical Hg-emission areas. Distinct Δ199Hg of MeHg and inorganic Hg (IHg) were observed among rice, fish and hair. The Δ199Hg of MeHg averaged at 0.07 ± 0.15 ‰, 0.80 ± 0.55 ‰ and 0.43 ± 0.29 ‰ in rice, fish and hair, respectively, while those of IHg averaged at - 0.08 ± 0.24 ‰, 0.85 ± 0.43 ‰ and - 0.28 ± 0.68 ‰. In paddy ecosystem, Δ199Hg of MeHg in rice showed slightly positive shifts (∼0.2 ‰) from those of IHg, and comparable Δ199Hg of IHg between rice grain and raw/processed materials (coal, Hg ore, gold ore and sphalerite) were observed. Simultaneously, it was proved that IHg in fish muscle was partially derived from in vivo demethylation of MeHg. By a binary model, we estimated the relative contributions of rice consumption to human MeHg exposure to be 84 ± 14 %, 58 ± 26 %, 52 ± 20 % and 34 ± 15 % on average in Hg mining area, gold mining area, zinc smelting area and coal-fired power plant area, respectively, and positive shifts of δ202HgMeHg from fish/rice to human hair occurred during human metabolic processes. Therefore, the CSIA approach can be an effective tool for tracking Hg biogeochemical cycle and human exposure, from which new scientific knowledge can be generated to support Hg pollution control policies and to protect human health.
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Affiliation(s)
- Bo Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Health Management Center, the Affiliated Hospital of Guizhou Medical University, Guiyang 550009, China
| | - Shaochen Yang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Ping Li
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
| | - Chongyang Qin
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Chuan Wang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Muhammad Ubaid Ali
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Runsheng Yin
- State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Laurence Maurice
- Observatory Midi-Pyrénées, Geosciences Environment Toulouse Laboratory, Research Institute for the Development (IRD), University of Toulouse and CNRS, 31400, Toulouse, France
| | - David Point
- Observatory Midi-Pyrénées, Geosciences Environment Toulouse Laboratory, Research Institute for the Development (IRD), University of Toulouse and CNRS, 31400, Toulouse, France
| | - Jeroen E Sonke
- Observatory Midi-Pyrénées, Geosciences Environment Toulouse Laboratory, Research Institute for the Development (IRD), University of Toulouse and CNRS, 31400, Toulouse, France
| | - Leiming Zhang
- Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Toronto M3H 5T4, Canada
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
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4
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Lepak RF, Janssen SE, Ogorek JM, Dillman CB, Hoffman JC, Tate MT, McIntyre PB. Can preserved museum specimens be used to reconstruct fish mercury burden and sources through time? ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2023; 10:165-171. [PMID: 38357329 PMCID: PMC10866153 DOI: 10.1021/acs.estlett.3c00009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
To evaluate the utility of preserved fishes for reconstructing historical and spatial patterns of mercury (Hg) exposure, we experimentally tested the stability of Hg concentrations and Hg stable isotope ratios under standard museum practices of specimen preservation. We found that loss of unidentified constituents during preservation increased Hg concentrations in fish muscle. Low-Hg fish reared in the laboratory were susceptible to exogenous contamination with inorganic mercury (iHg) when preservative fluids were intentionally spiked or iHg leached passively from contaminated wild fishes in the same container. This contamination impacted Hg isotope values of total Hg, but the conservative nature of methylmercury allows us to quantitatively correct for iHg contamination. Our findings validate the potential to use fishes from the world's museums to generate spatiotemporal baselines for the Minamata Convention on Mercury, but we recommend a set of precautions to maximize inference strength. Selecting the largest specimens of a target species helps dilute any iHg contamination. Specimens should be drawn from lots that were not comingled with fishes from other collections to minimize risk of iHg transfer among fish with different contamination histories. Finally, focusing on low-lipid species will enhance the comparability of Hg concentrations between historical and contemporary collections.
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Affiliation(s)
- Ryan F. Lepak
- 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
| | - Sarah E. Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 1 Gifford Pinchot Drive, Madison, WI 53726, USA
| | - Jacob M. Ogorek
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 1 Gifford Pinchot Drive, Madison, WI 53726, USA
| | - Casey B. Dillman
- Museum of Vertebrates, Department of Ecology and Evolutionary Biology, Cornell University, E145 Corson Hall, Ithaca, NY 14853, USA
| | - Joel C. Hoffman
- 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
| | - Michael T. Tate
- U.S. Geological Survey, Upper Midwest Water Science Center, USGS Mercury Research Laboratory, 1 Gifford Pinchot Drive, Madison, WI 53726, USA
| | - Peter B. McIntyre
- Department of Natural Resources and the Environment, Cornell University, Fernow Hall, Ithaca, NY 14853, USA
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5
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Crowther ER, Demers JD, Blum JD, Brooks SC, Johnson MW. Coupling of nitric acid digestion and anion-exchange resin separation for the determination of methylmercury isotopic composition within organisms. Anal Bioanal Chem 2023; 415:759-774. [PMID: 36472636 DOI: 10.1007/s00216-022-04468-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 11/19/2022] [Accepted: 11/28/2022] [Indexed: 12/12/2022]
Abstract
Isotope ratios of methylmercury (MeHg) within organisms can be used to identify sources of MeHg that have accumulated in food webs, but these isotopic compositions are masked in organisms at lower trophic levels by the presence of inorganic mercury (iHg). To facilitate measurement of MeHg isotope ratios in organisms, we developed a method of extracting and isolating MeHg from fish and aquatic invertebrates for compound-specific isotopic analysis involving nitric acid digestion, batch anion-exchange resin separation, and pre-concentration by purge and trap. Recovery of MeHg was quantified after each step in the procedure, and the average cumulative recovery of MeHg was 93.4 ± 2.9% (1 SD, n = 28) for biological reference materials and natural biota samples and 96.9 ± 1.8% (1 SD, n = 5) for aqueous MeHgCl standards. The amount of iHg impurities was also quantified after each step, and the average MeHg purity was 97.8 ± 4.3% (1 SD, n = 28) across all reference materials and natural biota samples after the final separation step. Measured MeHg isotopic compositions of reference materials agreed with literature values obtained using other MeHg separation techniques, and MeHg isotope ratios of aqueous standards, reference materials, and natural biota samples were reproducible. On average, the reproducibility associated with reference material process replicates (2 SD) was 0.10‰ for δ202MeHg and 0.04‰ for Δ199MeHg. This new method provides a streamlined, reliable technique that utilizes a single sample aliquot for MeHg concentration and isotopic analysis. This promotes a tight coupling between MeHg concentration, %MeHg, and Hg isotopic composition, which may be especially beneficial for studying complex food webs with multiple isotopically distinct sources of iHg and/or MeHg.
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Affiliation(s)
- Elizabeth R Crowther
- Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Ave., Ann Arbor, MI, 48109-1005, USA.
| | - Jason D Demers
- Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Ave., Ann Arbor, MI, 48109-1005, USA
- Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, 8 College Rd., Durham, NH, 03824-2600, USA
| | - Joel D Blum
- Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Ave., Ann Arbor, MI, 48109-1005, USA
| | - Scott C Brooks
- Environmental Science Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN, 37831-6038, USA
| | - Marcus W Johnson
- Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Ave., Ann Arbor, MI, 48109-1005, USA
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6
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Zhang L, Yin Y, Li Y, Cai Y. Mercury isotope fractionation during methylmercury transport and transformation: A review focusing on analytical method, fractionation characteristics, and its application. 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.
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Affiliation(s)
- Lian Zhang
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yongguang Yin
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
| | - Yanbin Li
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education and College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China
| | - Yong Cai
- School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China; Department of Chemistry & Biochemistry, Florida International University, Miami, FL 33199, United States.
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7
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Li ML, Kwon SY, Poulin BA, Tsui MTK, Motta LC, Cho M. Internal Dynamics and Metabolism of Mercury in Biota: A Review of Insights from Mercury Stable Isotopes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:9182-9195. [PMID: 35723432 PMCID: PMC9261262 DOI: 10.1021/acs.est.1c08631] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Monitoring mercury (Hg) levels in biota is considered an important objective for the effectiveness evaluation of the Minamata Convention. While many studies have characterized Hg levels in organisms at multiple spatiotemporal scales, concentration analyses alone often cannot provide sufficient information on the Hg exposure sources and internal processes occurring within biota. Here, we review the decadal scientific progress of using Hg isotopes to understand internal processes that modify the speciation, transport, and fate of Hg within biota. Mercury stable isotopes have emerged as a powerful tool for assessing Hg sources and biogeochemical processes in natural environments. A better understanding of the tissue location and internal mechanisms leading to Hg isotope change is key to assessing its use for biomonitoring. We synthesize the current understanding and uncertainties of internal processes leading to Hg isotope fractionation in a variety of biota, in a sequence of better to less studied organisms (i.e., birds, marine mammals, humans, fish, plankton, and invertebrates). This review discusses the opportunities and challenges of using certain forms of biota for Hg source monitoring and the need to further elucidate the physiological mechanisms that control the accumulation, distribution, and toxicity of Hg in biota by coupling new techniques with Hg stable isotopes.
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Affiliation(s)
- Mi-Ling Li
- School
of Marine Science and Policy, University
of Delaware, 201 Robinson Hall, Newark, Delaware 19716, United
States
| | - Sae Yun Kwon
- Division
of Environmental Science and Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro,
Nam-Gu, Pohang 37673, South Korea
- Institute
for Convergence Research and Education in Advanced Technology, Yonsei University, 85 Songdogwahak-Ro, Yeonsu-Gu, Incheon 21983, South Korea
| | - Brett A. Poulin
- Department
of Environmental Toxicology, University
of California Davis, One Shields Avenue, Davis, California 95616, United States
| | - Martin Tsz-Ki Tsui
- School
of Life Sciences, State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR 999077, China
| | - Laura C. Motta
- Department
of Chemistry, University at Buffalo, 359 Natural Sciences Complex, Buffalo, New York 14260-3000, United States
| | - Moonkyoung Cho
- Division
of Environmental Science and Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro,
Nam-Gu, Pohang 37673, South Korea
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Manceau A, Brossier R, Janssen SE, Poulin BA. Response to Comment on "Mercury Isotope Fractionation by Internal Demethylation and Biomineralization Reactions in Seabirds: Implications for Environmental Mercury Science": Principles and Limitations of Source Tracing and Process Tracing with Stable Isotope Signatures. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:2065-2068. [PMID: 35060387 DOI: 10.1021/acs.est.2c00052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Alain Manceau
- Université Grenoble Alpes, ISTerre, CNRS, 38000 Grenoble, France
| | - Romain Brossier
- Université Grenoble Alpes, ISTerre, CNRS, 38000 Grenoble, France
| | - Sarah E Janssen
- U.S. Geological Survey, Upper Midwest Water Science Center, Middleton, Wisconsin 53562, United States
| | - Brett A Poulin
- Department of Environmental Toxicology, University of California Davis, Davis, California 95616, United States
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Manceau A, Brossier R, Janssen SE, Rosera TJ, Krabbenhoft DP, Cherel Y, Bustamante P, Poulin BA. Mercury Isotope Fractionation by Internal Demethylation and Biomineralization Reactions in Seabirds: Implications for Environmental Mercury Science. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:13942-13952. [PMID: 34596385 DOI: 10.1021/acs.est.1c04388] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
A prerequisite for environmental and toxicological applications of mercury (Hg) stable isotopes in wildlife and humans is quantifying the isotopic fractionation of biological reactions. Here, we measured stable Hg isotope values of relevant tissues of giant petrels (Macronectes spp.). Isotopic data were interpreted with published HR-XANES spectroscopic data that document a stepwise transformation of methylmercury (MeHg) to Hg-tetraselenolate (Hg(Sec)4) and mercury selenide (HgSe) (Sec = selenocysteine). By mathematical inversion of isotopic and spectroscopic data, identical δ202Hg values for MeHg (2.69 ± 0.04‰), Hg(Sec)4 (-1.37 ± 0.06‰), and HgSe (0.18 ± 0.02‰) were determined in 23 tissues of eight birds from the Kerguelen Islands and Adélie Land (Antarctica). Isotopic differences in δ202Hg between MeHg and Hg(Sec)4 (-4.1 ± 0.1‰) reflect mass-dependent fractionation from a kinetic isotope effect due to the MeHg → Hg(Sec)4 demethylation reaction. Surprisingly, Hg(Sec)4 and HgSe differed isotopically in δ202Hg (+1.6 ± 0.1‰) and mass-independent anomalies (i.e., changes in Δ199Hg of ≤0.3‰), consistent with equilibrium isotope effects of mass-dependent and nuclear volume fractionation from Hg(Sec)4 → HgSe biomineralization. The invariance of species-specific δ202Hg values across tissues and individual birds reflects the kinetic lability of Hg-ligand bonds and tissue-specific redistribution of MeHg and inorganic Hg, likely as Hg(Sec)4. These observations provide fundamental information necessary to improve the interpretation of stable Hg isotope data and provoke a revisitation of processes governing isotopic fractionation in biota and toxicological risk assessment in wildlife.
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Affiliation(s)
- Alain Manceau
- Université Grenoble Alpes, ISTerre, CNRS, 38000 Grenoble, France
| | - Romain Brossier
- Université Grenoble Alpes, ISTerre, CNRS, 38000 Grenoble, France
| | - Sarah E Janssen
- Upper Midwest Water Science Center, U.S. Geological Survey, Middleton, Wisconsin 53562, United States
| | - Tylor J Rosera
- Upper Midwest Water Science Center, U.S. Geological Survey, Middleton, Wisconsin 53562, United States
| | - David P Krabbenhoft
- Upper Midwest Water Science Center, U.S. Geological Survey, Middleton, Wisconsin 53562, United States
| | - Yves Cherel
- Centre d'Etudes Biologiques de Chizé (CEBC), CNRS, La Rochelle Université, 79360 Villiers-en-Bois, France
| | - Paco Bustamante
- Littoral Environnement et Sociétés (LIENSs), CNRS-La Rochelle Université, 17000 La Rochelle, France
| | - Brett A Poulin
- Department of Environmental Toxicology, University of California Davis, Davis, California 95616, United States
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10
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Janssen SE, Patnode KA, Pluta BR, Krabbenhoft DP. Insights into Mercury Source Identification and Bioaccumulation Using Stable Isotope Approaches in the Hannibal Pool of the Ohio River, USA. INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT 2021; 17:233-242. [PMID: 32633881 PMCID: PMC8043245 DOI: 10.1002/ieam.4308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 02/03/2020] [Accepted: 07/06/2020] [Indexed: 06/11/2023]
Abstract
Mercury contamination in river systems due to historic and current Hg releases is a persistent concern for both wildlife and human health. In larger rivers, like the Ohio River, USA, it is difficult to directly link Hg discharges to bioaccumulation due to the existence of multiple industrial Hg sources as well as the varied dietary and migratory habits of biota. To better understand how industrial effluent influences the cycling and bioaccumulation of Hg within the Ohio River, Hg stable isotope analysis was applied to various nonbiological and biological media. High Hg concentrations in suspended particulate matter suggest this vector was the largest contributor of Hg to the water column, and distinct Hg source signatures were observed in effluent particulates from different industrial processes, such as chlor-alkali activity (δ202 Hg = -0.52‰) and coal power plant discharge (δ202 Hg = -1.39‰). Despite this distinction, average sediments (δ202 Hg = -1.00 ± 0.23‰) showed intermediate isotopic signatures that suggest the accumulation of a mixed Hg source driven by multiple industrial discharges. Biota in the system were shown to have a conserved range of δ202 Hg and estimation approaches related these signatures back to particulate matter within Hannibal Pool. Mussels were found to conserve Hg isotopes signatures independently of food web drivers and served as ideal water column indicators of bioaccumulated Hg sources. This study highlights the complexity of Hg cycling within an industrialized river and shows that an isotope tracer approach can provide insight to water column sources of Hg. Integr Environ Assess Manag 2021;17:233-242. Published 2020. This article is a US Government work and is in the public domain in the USA.
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Affiliation(s)
- Sarah E Janssen
- United States Geological Survey, Upper Midwest Water Science Center, Middleton, Wisconsin
| | | | - Bruce R Pluta
- United States Environmental Protection Agency, Hazardous Site Cleanup Division, Philadelphia, Pennsylvania
| | - David P Krabbenhoft
- United States Geological Survey, Upper Midwest Water Science Center, Middleton, Wisconsin
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