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Yin Y, Yang S, Liu F, Wang X, Chen Y, Luo X. Effect mechanism of low-molecular-weight organic acids during sulfidation of As(V)-bearing ferrihydrite. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2025; 372:126031. [PMID: 40086781 DOI: 10.1016/j.envpol.2025.126031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/01/2025] [Revised: 02/28/2025] [Accepted: 03/08/2025] [Indexed: 03/16/2025]
Abstract
Sulfide induces the reductive dissolution of iron (oxyhydr) oxides, the primary host phases for arsenic (As), thereby triggering As release. We investigates the physicochemical mechanisms of three types of low molecular weight organic acids (LMWOAs) on sulfide-mediated reductive dissolution of As(V)-ferrihydrite and As release using batch experiments combined with hydro-chemical, spectroscopic, and microscopic analyses. Arsenate dominated the aqueous (97.2-100 %) and solid phases throughout the experiment. LMWOAs accelerated S(-II) consumption and As release by inhibiting FeS formation, with rates ordered as citric acid (CA) > oxalic acid (OA) > malic acid (MA) > control (Kb). At S(-II): Fe = 0.5, maximum As release was 11.78 % (Kb) and 14.60 % (CA); at S(-II): Fe = 1, it was 27.58 % (Kb) and 30.71 % (OA). LMWOAs enhanced As release via non-reductive ligand dissolution of As(V)-ferrihydrite. Secondary mineral formation in later stages re-immobilized As, with mineral layers ≥50 nm thick. LMWOAs interacted differently with secondary minerals: CA primarily adsorbed on surfaces, while MA integrated into the matrix. LMWOAs influenced As redistribution in secondary minerals, increasing contamination risks. Thus, the complex effects of organic matter (OM) on Fe, S, and As biogeochemistry must be considered in risk assessments and remediation strategies for As-contaminated sites in sulfidic environments.
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Affiliation(s)
- Yitong Yin
- School of Ocean Sciences, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Shanshan Yang
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Fei Liu
- Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Xue Wang
- School of Ocean Sciences, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Yue Chen
- School of Ocean Sciences, China University of Geosciences (Beijing), Beijing, 100083, China.
| | - Ximing Luo
- School of Ocean Sciences, China University of Geosciences (Beijing), Beijing, 100083, China.
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Gao M, Ning Y, Liu C, Song X, Xu J, Cui L, Liu J. The "Fe-S wheel": A new perspective on methylmercury production dynamics in subalpine peatlands. JOURNAL OF HAZARDOUS MATERIALS 2025; 493:138401. [PMID: 40306242 DOI: 10.1016/j.jhazmat.2025.138401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2024] [Revised: 03/18/2025] [Accepted: 04/23/2025] [Indexed: 05/02/2025]
Abstract
The cycling of iron (Fe) and sulfur (S) in peatland ecosystems plays a pivotal role in modulating methylmercury (MeHg) formation. This study integrates data on Fe and S fractions, geochemical factors, microbial communities, and statistical modeling to propose the novel "Fe-S wheel" conceptual framework. This framework explores the coupled cycling of Fe, S, and Hg in the Dajiuhu peatland (DJH), an exemplary natural laboratory in central China. Through this framework, we demonstrate that the "Fe-S wheel" exerts a strong direct inhibitory effect on MeHg formation. However, when the S/Fe molar ratio is less than 0.25, the "Fe-S wheel", influenced by microbial communities, can indirectly enhance MeHg generation by promoting humic acid-bound Hg. Conversely, when the S/Fe molar ratio exceeds 0.25, the "Fe-S wheel", under the influence of dissolved oxygen, suppresses MeHg formation by inhibiting strong-complexed Hg and sulfide-bound Hg. Global peatland data corroborate these findings, showing a significant negative correlation between the S/Fe ratio and MeHg concentrations. Given the uncertainties in the interaction and transformation mechanisms between Fe and S, the S/Fe molar ratio is likely to serve as a key parameter reflecting their coupled effects on MeHg. This study highlights the critical role of Fe and S interactions in regulating MeHg generation within peatland ecosystems.
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Affiliation(s)
- Mingyuan Gao
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Yongqiang Ning
- Kunming General Survey of Natural Resources Center, China
| | - Chutong Liu
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Xiannong Song
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Jiale Xu
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
| | - Liwei Cui
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Jinling Liu
- Hubei Key Laboratory of Critical Zone Evolution, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China.
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Sun Q, Burton ED, Yu Z, Chen L, Bi L, Cui P, Wang Y. Iron, Sulfur, and Carbon Dynamics Collectively Regulate the Fate of Cadmium over the Sulfidation-Reoxidation Cycle. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2025; 59:7297-7309. [PMID: 40189937 DOI: 10.1021/acs.est.4c13365] [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: 04/16/2025]
Abstract
Cadmium bioavailability is sensitive to redox fluctuations, with its fate linked to the coupled dynamics of Fe, S, and C. This study examines the behavior of Cd-loaded ferrihydrite (Fh) with/without organic matter (OM) undergoing S(-II)-induced reduction followed by O2-induced reoxidation. During sulfidation, S(-II) was fully consumed, and Fh was partially reduced to Fe(II) species, with some OM released from the Fh surface. Meanwhile, Cd initially adsorbed on Fh was completely converted to CdS, regardless of Cd loading or the presence of OM. Upon reoxidation, Fe(II) species were reoxidized to Fe(III) oxides, which recaptured OM, while solid-phase S(-II) was oxidized to S0 and sulfate. Concurrently, partial oxidation of CdS occurred, mainly driven by H2O2 generated during Fe(II) oxidation, with minor contributions from •OH and O2, but OM inhibited CdS oxidation, primarily by scavenging H2O2. Released Cd from CdS oxidation was predominantly readsorbed on Fe(III) oxides. Additionally, released Cd was partially structurally incorporated into newly formed Fe(III) oxides while some CdS was encapsulated within Fe(III) oxide aggregates. However, OM interactions with Fe(III) oxides reduced the formation of these Cd species. These findings provide insights into the molecular-scale mechanisms governing Cd dynamics in redox-dynamic environments.
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Affiliation(s)
- Qian Sun
- College of Agricultural Sciences and Engineering, Hohai University, Nanjing 210098, China
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Edward D Burton
- Faculty of Science and Engineering, Southern Cross University, Lismore 2480, New South Wales, Australia
| | - Zhenghong Yu
- College of Agricultural Sciences and Engineering, Hohai University, Nanjing 210098, China
| | - Lina Chen
- College of Agricultural Sciences and Engineering, Hohai University, Nanjing 210098, China
| | - Lidong Bi
- College of Agricultural Sciences and Engineering, Hohai University, Nanjing 210098, China
| | - Peixin Cui
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Yujun Wang
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Xu Z, Huang Z, Li H, Zhu S, Lei Z, Liu C, Meng F, Chen JL, Chen TY, Feng C. Sulfidation-reoxidation enhances heavy metal immobilization by vivianite. WATER RESEARCH 2024; 263:122195. [PMID: 39116713 DOI: 10.1016/j.watres.2024.122195] [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: 03/09/2024] [Revised: 07/24/2024] [Accepted: 07/30/2024] [Indexed: 08/10/2024]
Abstract
Iron minerals in nature are pivotal hosts for heavy metals, significantly influencing their geochemical cycling and eventual fate. It is generally accepted that, vivianite, a prevalent iron phosphate mineral in aquatic and terrestrial environments, exhibits a limited capacity for adsorbing cationic heavy metals. However, our study unveils a remarkable phenomenon that the synergistic interaction between sulfide (S2-) and vivianite triggers an unexpected sulfidation-reoxidation process, enhancing the immobilization of heavy metals such as cadmium (Cd), copper (Cu), and zinc (Zn). For instance, the combination of vivianite and S2- boosted the removal of Cd2+ from the aqueous phase under anaerobic conditions, and ensured the retention of Cd stabilized in the solid phase when shifted to aerobic conditions. It is intriguing to note that no discrete FeS formation was detected in the sulfidation phase, and the primary crystal structure of vivianite largely retained its integrity throughout the whole process. Detailed molecular-level investigations indicate that sulfidation predominantly targets the Fe(II) sites at the corners of the PO4 tetrahedron in vivianite. With the transition to aerobic conditions, the exothermic oxidation of CdS and the S sites in vivianite initiates, rendering it thermodynamically favorable for Cd to form multidentate coordination structures, predominantly through the Cd-O-P and Cd-O-Fe bonds. This mechanism elucidates how Cd is incorporated into the vivianite structure, highlighting a novel pathway for heavy metal immobilization via the sulfidation-reoxidation dynamics in iron phosphate minerals.
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Affiliation(s)
- Zhangyi Xu
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China
| | - Ziyuan Huang
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China
| | - Han Li
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China
| | - Shishu Zhu
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China
| | - Zhenchao Lei
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China
| | - Chengshuai Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, PR China.
| | - Fangyuan Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, PR China
| | - Jeng-Lung Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Tsung-Yi Chen
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, ROC
| | - Chunhua Feng
- Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, School of Environment and Energy, South China University of Technology, Guangzhou 510006, PR China.
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Zhang Y, Xie X, Sun S, Wang Y. Coupled redox cycling of arsenic and sulfur regulates thioarsenate enrichment in groundwater. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 943:173776. [PMID: 38862046 DOI: 10.1016/j.scitotenv.2024.173776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Revised: 06/02/2024] [Accepted: 06/03/2024] [Indexed: 06/13/2024]
Abstract
High‑arsenic groundwater is influenced by a combination of processes: reductive dissolution of iron minerals and formation of secondary minerals, metal complexation and redox reactions of organic matter (OM), and formation of more migratory thioarsenate, which together can lead to significant increases in arsenic concentration in groundwater. This study was conducted in a typical sulfur- and arsenic-rich groundwater site within the Datong Basin to explore the conditions of thioarsenate formation and its influence on arsenic enrichment in groundwater using HPLC-ICPMS, hydrogeochemical modeling, and fluorescence spectroscopy. The shallow aquifer exhibited a highly reducing environment, marked by elevated sulfide levels, low concentrations of Fe(II), and the highest proportion of thioarsenate. In the middle aquifer, an optimal ∑S/∑As led to the presence of significant quantities of thioarsenate. In contrast, the deep aquifer exhibited low sulfide and high Fe(II) concentration, with arsenic primarily originating from dissolved iron minerals. Redox fluctuations in the sediment driven by sulfur‑iron minerals generated reduced sulfur, thereby facilitating thioarsenate formation. OM played a crucial role as an electron donor for microbial activities, promoting iron and sulfate reduction processes and creating conditions conducive to thioarsenate formation in reduced and high‑sulfur environments. Understanding the process of thioarsenate formation and the influencing factors is of paramount importance for comprehending the migration and redistribution of arsenic in groundwater systems.
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Affiliation(s)
- Yuyao Zhang
- School of Environmental Studies, China University of Geosciences, Wuhan 430074, China
| | - Xianjun Xie
- School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, China University of Geosciences, Wuhan 430078, China.
| | - Shutang Sun
- School of Resource and Environmental Sciences, Wuhan University, 430072, China
| | - Yanxin Wang
- School of Environmental Studies, China University of Geosciences, Wuhan 430074, China; State Environmental Protection Key Laboratory of Source Apportionment and Control of Aquatic Pollution, China University of Geosciences, Wuhan 430078, China
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Huang H, Tian Z, Guo D, Tang Z, Li R, Ali A, Cao Z, Lu H, Shen Y, Zhu Y, Han J. Rice straw returning enhances cadmium activation by accelerating iron cycling thus hydroxyl radical production in paddy soils during drainage. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 923:171543. [PMID: 38453068 DOI: 10.1016/j.scitotenv.2024.171543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 02/19/2024] [Accepted: 03/04/2024] [Indexed: 03/09/2024]
Abstract
Straw returning is widely found elevating the bioavailability of cadmium (Cd) in paddy soils with unclear biogeochemical mechanisms. Here, a series of microcosm incubation experiments were conducted and spectroscopic and microscopic analyses were employed. The results showed that returning rice straw (RS) efficiently increased amorphous Fe and low crystalline Fe (II) to promote the production of hydroxyl radicals (OH) thus Cd availability in paddy soils during drainage. On the whole, RS increased OH and extractable Cd by 0.2-1.4 and 0.1-3.3 times, respectively. While the addition of RS effectively improved the oxidation rate of structural Fe (II) mineral (i.e., FeS) to enhance soil Cd activation (up to 38.5 %) induced by the increased OH (up to 69.2 %). Additionally, the existence of CO32- significantly increased the efficiency level on OH production and Cd activation, which was attributed to the improved reactivity of Fe (II) by CO32- in paddy soils. Conclusively, this study emphasizes risks of activating soil Cd induced by RS returning-derived OH, providing a new insight into evaluating the safety of straw recycling.
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Affiliation(s)
- Hui Huang
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
| | - Zhuoqi Tian
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Di Guo
- School of Petroleumn Engineering and Environmental Engineering, Yan'an University, Yan'an, Shaanxi 716000, China
| | - Zhixian Tang
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
| | - Ronghua Li
- College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi 712100, China.
| | - Amjad Ali
- School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, Shaanxi 710055, China.
| | - Zhengxian Cao
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Haiying Lu
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
| | - Yu Shen
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Yongli Zhu
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Jiangang Han
- College of Ecology and Environment and Co-Innovation Center for the Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; School of Chemical Engineering and Materials, Changzhou Institute of Technology, Changzhou, Jiangsu 213032, China.
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