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Du H, Gu X, Johs A, Yin X, Spano T, Wang D, Pierce EM, Gu B. Sonochemical oxidation and stabilization of liquid elemental mercury in water and soil. JOURNAL OF HAZARDOUS MATERIALS 2023; 445:130589. [PMID: 37055993 DOI: 10.1016/j.jhazmat.2022.130589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 11/23/2022] [Accepted: 12/08/2022] [Indexed: 06/19/2023]
Abstract
Over 3000 mercury (Hg)-contaminated sites worldwide contain liquid metallic Hg [Hg(0)l] representing a continuous source of elemental Hg(0) in the environment through volatilization and solubilization in water. Currently, there are few effective treatment technologies available to remove or sequester Hg(0)l in situ. We investigated sonochemical treatments coupled with complexing agents, polysulfide and sulfide, in oxidizing Hg(0)l and stabilizing Hg in water, soil and quartz sand. Results indicate that sonication is highly effective in breaking up and oxidizing liquid Hg(0)l beads via acoustic cavitation, particularly in the presence of polysulfide. Without complexing agents, sonication caused only minor oxidation of Hg(0)l but increased headspace gaseous Hg(0)g and dissolved Hg(0)aq in water. However, the presence of polysulfide essentially stopped Hg(0) volatilization and solubilization. As a charged polymer, polysulfide was more effective than sulfide in oxidizing Hg(0)l and subsequently stabilizing the precipitated metacinnabar (β-HgS) nanocrystals. Sonochemical treatments with sulfide yielded incomplete oxidation of Hg(0)l, likely resulting from the formation of HgS coatings on the dispersed µm-size Hg(0)l bead surfaces. Sonication with polysulfide also resulted in rapid oxidation of Hg(0)l and precipitation of HgS in quartz sand and in the Hg(0)l-contaminated soil. This research indicates that sonochemical treatment with polysulfide could be an effective means in rapidly converting Hg(0)l to insoluble HgS precipitates in water and sediments, thereby preventing its further emission and release to the environment. We suggest that future studies are performed to confirm its technical feasibility and treatment efficacy for remediation applications.
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Affiliation(s)
- Hongxia Du
- College of Resources and Environment, Southwest University, Chongqing 400715, PR China; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Xin Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Xiangping Yin
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Tyler Spano
- Nuclear Nonproliferation Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Dingyong Wang
- College of Resources and Environment, Southwest University, Chongqing 400715, PR China
| | - Eric M Pierce
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States; Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN 37996, United States.
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2
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Miao C, Zhou H, Lv Y, Shang J, Mamut A. Combined effects of ferrihydrite coating and ionic type on the transport of compost-derived dissolved organic matter in saturated porous media. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 307:119501. [PMID: 35636713 DOI: 10.1016/j.envpol.2022.119501] [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: 01/31/2022] [Revised: 05/12/2022] [Accepted: 05/16/2022] [Indexed: 06/15/2023]
Abstract
Field application of manure compost introduces a large quantity of dissolved organic matter (DOM), which can affect the migration of DOM-associated contaminants. In this study, the transport of humic acid (HA) and compost-derived dissolved organic matter (CDOM) in two porous media under various conditions, including ionic types, ionic strength, and influent concentrations, were investigated by column experiments and modeling analysis. Increasing Na+ concentration did not affect the transport of CDOM and HA in quartz sands, but inhibited CDOM transport in ferrihydrite (Fh)-coated sands. The retention recoveries of CDOM in Fh-coated sands were not changed with increasing NaCl concentration, suggesting that the adsorption of CDOM on Fh-coated sands caused by increasing NaCl concentration was a reversible process. Ca2+ could reduce the mobility of CDOM and HA through bridge bonding and electrostatic interaction. CDOM had a higher mobility than HA in quartz sands under CaCl2 conditions because the aggregation stability of CDOM was stronger than that of HA. The ferrihydrite coating increased the roughness of sand surface, resulting in lower mobility of CDOM in the Fh-coated sands than in quartz sands. A part of CDOM adsorbed onto Fh-coated sand was strongly bound through ligand exchange-surface complexation. The pore volume of CDOM required to saturate adsorption sites onto the Fh-coated sand depends on the influent CDOM concentration. The influent CDOM with higher concentration required less pore volume to achieve adsorption equilibrium. Modeling analysis suggested that the types of deposition sites provided by Fh-coated sand are mainly irreversible sites. Our findings demonstrated that CDOM transport in the sand columns may change the porous medium's physicochemical properties and alter the hydrochemistry conditions. Therefore, these factors mentioned above should not be ignored when evaluating the environmental risks of CDOM.
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Affiliation(s)
- Chuanghe Miao
- College of Land Science and Technology, China Agricultural University, Beijing 100193, PR China
| | - Hu Zhou
- College of Land Science and Technology, China Agricultural University, Beijing 100193, PR China; Key Laboratory of Arable Land Conservation (North China), MARA, Beijing 100193, PR China
| | - Yizhong Lv
- College of Land Science and Technology, China Agricultural University, Beijing 100193, PR China; Key Laboratory of Arable Land Conservation (North China), MARA, Beijing 100193, PR China.
| | - Jianying Shang
- College of Land Science and Technology, China Agricultural University, Beijing 100193, PR China; Key Laboratory of Arable Land Conservation (North China), MARA, Beijing 100193, PR China
| | - Ajigul Mamut
- College of Land Science and Technology, China Agricultural University, Beijing 100193, PR China
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Liu J, Zhao L, Kong K, Abdelhafiz MA, Tian S, Jiang T, Meng B, Feng X. Uncovering geochemical fractionation of the newly deposited Hg in paddy soil using a stable isotope tracer. JOURNAL OF HAZARDOUS MATERIALS 2022; 433:128752. [PMID: 35364530 DOI: 10.1016/j.jhazmat.2022.128752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 03/08/2022] [Accepted: 03/19/2022] [Indexed: 06/14/2023]
Abstract
The newly deposited mercury (Hg) is more readily methylated to methylmercury (MeHg) than native Hg in paddy soil. However, the biogeochemical processes of the newly deposited Hg in soil are still unknown. Here, a field experimental plot together with a stable Hg isotope tracing technique was used to demonstrate the geochemical fractionation (partitioning and redistribution) of the newly deposited Hg in paddy soils during the rice-growing period. We showed that the majority of Hg tracer (200Hg, 115.09 ± 0.36 μg kg-1) was partitioned as organic matter bound 200Hg (84.6-89.4%), followed by residual 200Hg (7.6-8.1%), Fe/Mn oxides bound 200Hg (2.8-7.2%), soluble and exchangeable 200Hg (0.05-0.2%), and carbonates bound 200Hg (0.04-0.07%) in paddy soils. Correlation analysis and partial least squares path modeling revealed that the coupling of autochthonous dissolved organic matter and poorly crystalline Fe (oxyhydr)oxides played a predominant role in controlling the redistribution of the newly deposited Hg among geochemical fractions (i.e., fraction changes). The expected aging processes of the newly deposited Hg were absent, potentially explaining the high bioavailability of these Hg in paddy soil. This study implies that other Hg pools (e.g., organic matter bound Hg) should be considered instead of merely soluble Hg pools when evaluating the environmental risks of Hg from atmospheric depositions.
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Affiliation(s)
- Jiang Liu
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
| | - Lei Zhao
- School of Management Science, Guizhou University of Finance and Economics, Guiyang 550025, China; Guizhou Key Laboratory of Big Data Statistical Analysis (No. [2019]5103), Guiyang 550025, China.
| | - Kun Kong
- 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
| | - Mahmoud A Abdelhafiz
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China; Geology Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt
| | - Shanyi Tian
- Soil Ecology Lab, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Tao Jiang
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Interdisciplinary Research Centre for Agriculture Green Development in Yangtze River Basin, Department of Environmental Sciences and Engineering, College of Resources and Environment, Southwest University, Chongqing 400716, China
| | - Bo Meng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
| | - Xinbin Feng
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
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Tan B, Liu C, Tan X, You X, Dai C, Liu S, Li J, Li N. Heavy metal transport driven by seawater-freshwater interface dynamics: The role of colloid mobilization and aquifer pore structure change. WATER RESEARCH 2022; 217:118370. [PMID: 35405553 DOI: 10.1016/j.watres.2022.118370] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/13/2022] [Accepted: 03/25/2022] [Indexed: 06/14/2023]
Abstract
Co-transport of colloidal substances and pollutants is a pivotal link that significantly affects the environment of coastal groundwater. The effect of colloid mobilization and aquifer pore structure change on heavy metal transport driven by seawater-freshwater interface dynamics is not fully understood. In this study, packed column experiments were conducted to model the seawater intrusion (SWI) and freshwater replenishment (FWR) processes using a sampled medium from a coastal sandy aquifer. Hydrodynamic, hydrochemical variables, and heavy metal (Pb, Cu, Cd) transport during the propagation of the seawater-freshwater interface were tested and analyzed. During the SWI stage, cation exchange induced heavy metal liberations, and it developed peak concentrations synchronized with the seawater-freshwater interface at the pore volume of 1.00. The colloid-facilitated transport for heavy metals was the predominant mechanism in the FWR stage, characterized by a peak release lagging the interface propagation by approximately 0.5 pore volumes. Because the colloidal fraction was mobilized during aquifer desalination, it lagged behind the decline of the salinity gradient. Furthermore, Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations explained that the replenishment decreased the depth of the secondary energy minimum of the colloids; meanwhile, the thickness of the electrical double layer increased from 0.63 nm to 10.14 nm, resulting in a repulsive energy barrier up to 3,213 kT. The transport of colloids led to a reduction in porosity from 18.16% to 2.28% of the total immobile domain. At these times, the dimension of the transported colloids evolved, showing a size-selective transport and therefore regulating the total emission fluxes of the heavy metals. These mechanisms were proposed to be incorporated in colloid filtration theory for targeting the coastal scenario.
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Affiliation(s)
- Bo Tan
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China
| | - Chao Liu
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China
| | - Xiao Tan
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China
| | - Xueji You
- Department of Hydraulic Engineering, College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Chaomeng Dai
- Department of Hydraulic Engineering, College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Shuguang Liu
- Department of Hydraulic Engineering, College of Civil Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China
| | - Jun Li
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China.
| | - Naiwen Li
- State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resource & Hydropower, Sichuan University, 610065 Chengdu, Sichuan, China
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Li Y, Guo N, Xian D, Zhou W, Shi Y, Wang J, Chen Y, Liu C. Bentonite colloids immobilization and release in quartz column and its influence on selenite migration. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 820:152833. [PMID: 35007589 DOI: 10.1016/j.scitotenv.2021.152833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 12/08/2021] [Accepted: 12/28/2021] [Indexed: 06/14/2023]
Abstract
Immobilization and release of colloids are important for colloids-facilitated migrations, and in the safety assessment of geological disposal for high-level radioactive waste, the association between the immobilization and release process of the bentonite colloids with selenite migration has not been well revealed. In this work, the migration of bentonite colloids under different conditions is evaluated, and the effects of colloids immobilization and release on selenite migration are studied. In addition, the cases of in-migration (colloids are immobilized in the quartz sand, and then selenite migrates through the quartz sand with immobilized colloids) and co-migration (colloids bearing selenite are immobilized in the quartz sand) are investigated. The results show that in the systems containing 3.0 mM Mg2+, the mobility of the colloids is highly hindered and the colloids are immobilized in the quartz sand mainly by straining effect. The immobilization of bentonite colloids affects selenite migration differently according to the immobilization process (in-migration or co-migration). A more significant retardation effect is observed in the co-migration process than in-migration due to the additional inner-sphere complexed selenite in the co-migration. The immobilized colloids can be more easily released by alkaline DI-water (pH 11.0) than acidic one (pH 6.0) as a result of the more negative surface charges of the immobilized bentonite colloids. The average size of the released colloids is larger than the initial colloids at the same pH. Selenite is found to be released ahead of colloids in either in- or co-migration process, and part of selenite is discovered migrating with released colloids in co-migration process. Since colloids immobilization and release would influence radionuclides migration, further research about colloids immobilization and release with broad range of pH and ionic strength in the host rock and its influence on the migration of other radionuclides are needed.
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Affiliation(s)
- Yao Li
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Ning Guo
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Dongfan Xian
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Wanqiang Zhou
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Yanling Shi
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Jingyi Wang
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Yawen Chen
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Chunli Liu
- Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
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6
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Mao M, Zheng X, Chen C, Zhao K, Yan C, Sharma P, Shang J. Coupled effect of flow velocity and structural heterogeneity on transport and release of kaolinite colloids in saturated porous media. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:35065-35077. [PMID: 32583117 DOI: 10.1007/s11356-020-09806-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 06/18/2020] [Indexed: 06/11/2023]
Abstract
Understanding the behavior and fate of clay colloids in water-saturated porous media is critical to assess its environmental impact and potential risk since clay is commonly a carrier of many contaminants. Column experiments with four-packing configurations were designed to understand the coupled effects of column structural heterogeneity and the flow velocity on the transport and fate of kaolinite colloids in the saturated porous media. The results showed that the structural heterogeneity could have facilitated the transport of kaolinite colloids in saturated porous media. For the columns with strong heterogeneity, the preferential flow paths led to an early breakthrough of kaolinite. Only few kaolinite colloids were released with slow flow rate; however, the released peak concentration and release percentage of kaolinite colloids had further increased with the high flow velocity. In the layered column, there was significant kaolinite's retention at the interface where water passed from fine to coarse quartz sand. All results indicated that both flow rates and media characteristics played an important role in controlling kaolinite's fate and transport in porous media. A thorough understanding of these processes had an important significance for pollution control in subsurface natural environment where heterogeneous soil and variation in flow pattern are usually common.
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Affiliation(s)
- Meng Mao
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China
| | - Xiaoli Zheng
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China
| | - Chong Chen
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China
| | - Kang Zhao
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China
| | - Chaorui Yan
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China
| | - Prabhakar Sharma
- School of Ecology and Environment Studies, Nalanda University, Nalanda, Rajgir, Bihar, India.
| | - Jianying Shang
- College of Land Science and Technology, Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, China Agricultural University, Beijing, 100193, China.
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Ting Y, Ch'ng BL, Chen C, Ou MY, Cheng YH, Hsu CJ, Hsi HC. A simulation study of mercury immobilization in estuary sediment microcosm by activated carbon/clay-based thin-layer capping under artificial flow and turbation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 708:135068. [PMID: 31780157 DOI: 10.1016/j.scitotenv.2019.135068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/10/2019] [Accepted: 10/18/2019] [Indexed: 06/10/2023]
Abstract
In-situ thin layer capping (TLC) is a promising sediment remediation approach that has been shown effective in immobilizing contaminants from releasing to natural biotas and human beings. This research intended to comprehend the effectiveness of Hg immobilization by TLC under turbation condition via a microcosm study. Three TLC caps with different activated carbon (AC)/clay combinations were applied to actual Hg-contaminated estuary sediment (76.0 ± 2.6 mg-Hg/kg). The caps with AC (3%) + bentonite (3%) and AC (3%) + kaolin (3%) were efficient in reducing both total mercury (THg) and methylmercury (MeHg) concentrations in overlying water by 75-95% and 64-98%, respectively, in the later stage of 75-d operation. In contrast, the AC (3%) + montmorillonite (3%) cap did not show a significant reduction on THg and MeHg in the overlying water, probably due to the unstable, suspension property of montmorillonite. The stable caps showed higher resistance to Hg breakthrough under occasional turbation events; however, a labile cap appeared to have dramatic Hg breakthrough when turbation occurred. It is therefore essential to note that with unstable caps, turbation events may result in unwanted secondary resuspension of contaminants.
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Affiliation(s)
- Yu Ting
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Boon-Lek Ch'ng
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Chi Chen
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Meng-Yuan Ou
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Yung-Hua Cheng
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Che-Jung Hsu
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan
| | - Hsing-Cheng Hsi
- Graduate Institute of Environmental Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
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8
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Yan C, Cheng T, Shang J. Effect of bovine serum albumin on stability and transport of kaolinite colloid. WATER RESEARCH 2019; 155:204-213. [PMID: 30849734 DOI: 10.1016/j.watres.2019.02.022] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 01/29/2019] [Accepted: 02/12/2019] [Indexed: 06/09/2023]
Abstract
The stability and transport of clay colloids in groundwater are strongly influenced by colloid interactions with dissolved organic matter (DOM). Protein is an important DOM component that is ubiquitous in natural water, reclaimed water, and soil solutions. To date, the interactions between clay colloids and proteins have not been fully studied. The objective of this study was to examine the effect of bovine serum albumin (BSA), a representative protein, on the stability, aggregation, and transport of kaolinite colloids under neutral pH conditions. Hydrodynamic diameter and ζ-potential measurements, stability tests, and column transport experiments were performed in salt solutions with a range of ionic strengths and different BSA concentrations at pH 7. Additionally, BSA-kaolinite colloid interactions were studied using TEM and batch adsorption experiments. The experimental results showed that BSA prevented colloid aggregation and increased the stability and transport of colloids, especially at high ionic strength, even though the charges of kaolinite colloids were less negative in the presence of BSA. Theoretical calculation of the interaction energies indicated that XDLVO theory, in which the steric force is considered due to BSA adsorption, could correctly quantify the interaction energies in the presence of BSA. This study demonstrated that the role of protein needs to be determined in order to better predict the overall effect of DOM on particle aggregation and transport in the soil environment.
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Affiliation(s)
- Chaorui Yan
- Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, PR China
| | - Tao Cheng
- Department of Earth Sciences, Memorial University St. John's, Newfoundland and Labrador, A1B 3X5, Canada
| | - Jianying Shang
- Department of Soil and Water Sciences, China Agricultural University, Beijing, 100193, PR China.
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O'Connor D, Hou D, Ok YS, Mulder J, Duan L, Wu Q, Wang S, Tack FMG, Rinklebe J. Mercury speciation, transformation, and transportation in soils, atmospheric flux, and implications for risk management: A critical review. ENVIRONMENT INTERNATIONAL 2019; 126:747-761. [PMID: 30878870 DOI: 10.1016/j.envint.2019.03.019] [Citation(s) in RCA: 168] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 02/13/2019] [Accepted: 03/08/2019] [Indexed: 05/24/2023]
Abstract
Mercury (Hg) is a potentially harmful trace element in the environment and one of the World Health Organization's foremost chemicals of concern. The threat posed by Hg contaminated soils to humans is pervasive, with an estimated 86 Gg of anthropogenic Hg pollution accumulated in surface soils worldwide. This review critically examines both recent advances and remaining knowledge gaps with respect to cycling of mercury in the soil environment, to aid the assessment and management of risks caused by Hg contamination. Included in this review are factors affecting Hg release from soil to the atmosphere, including how rainfall events drive gaseous elemental mercury (GEM) flux from soils of low Hg content, and how ambient conditions such as atmospheric O3 concentration play a significant role. Mercury contaminated soils constitute complex systems where many interdependent factors, including the amount and composition of soil organic matter and clays, oxidized minerals (e.g. Fe oxides), reduced elements (e.g. S2-), as well as soil pH and redox conditions affect Hg forms and transformation. Speciation influences the extent and rate of Hg subsurface transportation, which has often been assumed insignificant. Nano-sized Hg particles as well as soluble Hg complexes play important roles in soil Hg mobility, availability, and methylation. Finally, implications for human health and suggested research directions are put forward, where there is significant potential to improve remedial actions by accounting for Hg speciation and transportation factors.
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Affiliation(s)
- David O'Connor
- School of Environment, and State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing 100084, China; National Engineering Laboratory for Site Remediation Technologies, China
| | - Deyi Hou
- School of Environment, and State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing 100084, China; National Engineering Laboratory for Site Remediation Technologies, China.
| | - Yong Sik Ok
- Korea Biochar Research Center, OJeong Eco-Resilience Institute & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Jan Mulder
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway
| | - Lei Duan
- School of Environment, and State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing 100084, China
| | - Qingru Wu
- School of Environment, and State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing 100084, China
| | - Shuxiao Wang
- School of Environment, and State Key Joint Laboratory of Environmental Simulation and Pollution Control, Tsinghua University, Beijing 100084, China
| | - Filip M G Tack
- Department of Green Chemistry and Technology, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - Jörg Rinklebe
- University of Wuppertal, School of Architecture and Civil Engineering, Institute of Foundation Engineering, Water- and Waste-Management, Laboratory of Soil- and Groundwater-Management, Pauluskirchstraße 7, Wuppertal 42285, Germany; Department of Environment, Energy and Geoinformatics, Sejong University, 98 Gunja-Dong, Seoul, Republic of Korea
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10
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Dołęgowska S, Michalik A. The use of a geostatistical model supported by multivariate analysis to assess the spatial distribution of mercury in soils from historical mining areas: Karczówka Mt., Miedzianka Mt., and Rudki (south-central Poland). ENVIRONMENTAL MONITORING AND ASSESSMENT 2019; 191:302. [PMID: 31020409 PMCID: PMC6482127 DOI: 10.1007/s10661-019-7368-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Accepted: 03/01/2019] [Indexed: 06/01/2023]
Abstract
For the purpose of this study, 181 soil samples were collected from three post-mining areas (Miedzianka Mt. (62), Karczówka Mt. (61), and Rudki (58)) in the Holy Cross Mountains, south-central Poland. Collected samples were dried, disaggregated, and digested in a closed microwave system. All solutions were analyzed for Hg concentrations with cold vapor-atomic absorption spectroscopy (CV-AAS) technique using a continuous flow vapor accessory. The average Hg concentrations and the upper limits of geochemical background (UBG) were as follows: Miedzianka Mt. Hg 0.501 mg kg-1, UBG 0.312 mg kg-1; Karczówka Mt. Hg 0.150 mg kg-1, UBG 0.180 mg kg-1; Rudki area Hg 0.216 mg kg-1, UBG 0.193 mg kg-1. The use of a spatial distribution map of mercury concentrations integrated with computed geochemical factors and results of cluster analysis showed a direct relationship between mercury contents and mining activity conducted in these areas. Only in the case of Miedzianka Mt., this relationship was visible and probably resulted from the presence of tennantite (Cu,Fe)12As4S13 in soil samples, which was also confirmed with the factor analysis. Higher Hg concentrations in soil samples from Karczówka Mt. and Rudki resulted from the presence of clay and other secondary minerals that increase the mercury adsorption from atmospheric deposition. Fossil fuel and biomass combustion was classified as the main anthropogenic source of the metal, but the neighborhood of a cement factory may be taken under consideration. Our results showed that the use of integrated geostatistical models allows for better data visualization and interpretation.
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Affiliation(s)
- Sabina Dołęgowska
- Geochemistry and the Environment Division, Institute of Chemistry, Jan Kochanowski University, 15G Świętokrzyska St., 25-406, Kielce, Poland
| | - Artur Michalik
- Geochemistry and the Environment Division, Institute of Chemistry, Jan Kochanowski University, 15G Świętokrzyska St., 25-406, Kielce, Poland.
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Chotpantarat S, Kiatvarangkul N. Facilitated transport of cadmium with montmorillonite KSF colloids under different pH conditions in water-saturated sand columns: Experiment and transport modeling. WATER RESEARCH 2018; 146:216-231. [PMID: 30268883 DOI: 10.1016/j.watres.2018.09.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 08/31/2018] [Accepted: 09/04/2018] [Indexed: 06/08/2023]
Abstract
This study investigated the impact of pH on the migration of cadmium(II) ions (Cd2+) in relation to montmorillonite KSF colloids through a water-saturated sand column (WSSC). The sorption isotherms of Cd2+ on colloids and sand at pH values of 3, 6, and 8 were characterized by batch experiments. Cd2+ sorption by colloids and sand fit well with the Freundlich model. In the column experiments, increasing the pH increased the retardation factors and KF values of Cd2+ both with and without the presence of the colloids. The amount of Cd2+ sorbed onto the montmorillonite KSF colloids in the column effluent increased from 0.29 to 0.97 mg as the pH increased. The colloid increased Cd2+ mobility and acted as a carrier at a high solution pH. The increasing level of Cd2+ sorbed on colloids as the pH increased resulted in a long tailing of the breakthrough curve (BTC) of the total Cd, indicating that the total Cd was controlled by rate-limited reactions. These findings indicate that when the solution pH was greater than the point of zero charge (PZC) of the colloids (pH > 6), the system tended to follow a nonequilibrium two-site (TSM) model rather than an equilibrium (CDeq) model. This implies that the PZC of the colloids in the groundwater system is the main factor in predicting facilitated Cd2+ transport.
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Affiliation(s)
- Srilert Chotpantarat
- Center of Excellence for Environmental and Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand; Department of Geology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand; Research Program of Toxic Substance Management in the Mining Industry, Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand; Research Unit of Green Mining (GMM), Chulalongkorn University, Bangkok, Thailand.
| | - Niruch Kiatvarangkul
- Center of Excellence for Environmental and Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand; International Postgraduate Programs in Environmental Management, Graduate School, Chulalongkorn University, Bangkok, 10330, Thailand.
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12
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Chen C, Zhao K, Shang J, Liu C, Wang J, Yan Z, Liu K, Wu W. Uranium (VI) transport in saturated heterogeneous media: Influence of kaolinite and humic acid. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 240:219-226. [PMID: 29747106 DOI: 10.1016/j.envpol.2018.04.095] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 03/31/2018] [Accepted: 04/22/2018] [Indexed: 05/13/2023]
Abstract
Natural aquifers typically exhibit a variety of structural heterogeneities. However, the effect of mineral colloids and natural organic matter on the transport behavior of uranium (U) in saturated heterogeneous media are not totally understood. In this study, heterogeneous column experiments were conducted, and the constructed columns contained a fast-flow domain (FFD) and a slow-flow domain (SFD). The effect of kaolinite, humic acid (HA), and kaolinite/HA mixture on U(VI) retention and release in saturated heterogeneous media was examined. Media heterogeneity significantly influenced U fate and transport behavior in saturated subsurface environment. The presence of kaolinite, HA, and kaolinite/HA enhanced the mobility of U in heterogeneous media, and the mobility of U was the highest in the presence of kaolinite/HA and the lowest in the presence of kaolinite. In the presence of kaolinite, there was no difference in the amount of U released from the FFD and SFD. However, in the presence of HA and kaolinite/HA, a higher amount of U was released from the FFD. The findings in this study showed that medium structure and mineral colloids, as well as natural organic matter in the aqueous phase had significant effects on U transport and fate in subsurface environment.
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Affiliation(s)
- Chong Chen
- Key Laboratory of Plant-Soil Interactions, The Ministry of Education, Key Laboratory of Arable Land Conservation in North China, The Ministry of Agriculture, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Kang Zhao
- Key Laboratory of Plant-Soil Interactions, The Ministry of Education, Key Laboratory of Arable Land Conservation in North China, The Ministry of Agriculture, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
| | - Jianying Shang
- Key Laboratory of Plant-Soil Interactions, The Ministry of Education, Key Laboratory of Arable Land Conservation in North China, The Ministry of Agriculture, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
| | - Chongxuan Liu
- School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jin Wang
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China
| | - Zhifeng Yan
- Institute of Surface-Earth System Science, Tianjin University, Tianjin, 300072, China
| | - Kesi Liu
- Department of Grassland Science, China Agricultural University, Beijing, 100193, China
| | - Wenliang Wu
- Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China
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Chen M, Alim N, Zhang Y, Xu N, Cao X. Contrasting effects of biochar nanoparticles on the retention and transport of phosphorus in acidic and alkaline soils. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 239:562-570. [PMID: 29698906 DOI: 10.1016/j.envpol.2018.04.050] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/09/2018] [Accepted: 04/09/2018] [Indexed: 05/24/2023]
Abstract
Land application of biomass-derived biochar has been increasingly recommended as a beneficial soil amendment for nutrients (such as N, P) retention. However, the small-scale biochar particles, especially those in the nano-scale range, may carry nutrients downward the soil profile, reducing nutrition retention and posing a potential risk to the groundwater. In this study, column experiments were conducted to investigate the retention and transport of phosphorus (P) in two acidic and two alkaline soils as affected by wood chip-derived biochar nanoparticles (NPs). In acidic paddy and red soils, biochar NPs facilitated the retention of P, increasing by about 24% and 16%, respectively, compared to the biochar absence. It is because biochar NPs stabilize soil Fe/Al oxides and dissolved organic carbon (DOC), thereby reducing the release of Fe/Al oxides- and DOC-associated P. In contrast, in alkaline huangmian and chao soils, retention of P was reduced in the presence of biochar NPs, decreasing by about 23% and 18%, respectively. It was mainly due to the increased transport of Fe/Al oxides-associated P in effluents. Moreover, biochar NPs could also act as a P carrier, mediating the retention of P. The diffusive gradients in thin films provided in-suit measurement of labile P in soil profiles, showing much lower labile P from retained P in acidic soils than that from alkaline soils though the labile P with biochar NPs presence was increased in all soils. Our findings indicate that biochar NPs have contrasting effects on the retention of P in acidic and alkaline soils, implying the cautious land applications of biochar for nutrients retention in soils with different acidities.
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Affiliation(s)
- Ming Chen
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Nurguzal Alim
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yitao Zhang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Nan Xu
- Jiangsu Key Laboratory of Environmental Functional Materials, School of Chemistry Biology and Material Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - Xinde Cao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, China.
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Gai K, Hoelen TP, Hsu-Kim H, Lowry GV. Mobility of Four Common Mercury Species in Model and Natural Unsaturated Soils. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:3342-51. [PMID: 26949999 DOI: 10.1021/acs.est.5b04247] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Mercury (Hg) occurs as a myriad of species in environmental media, each with different physicochemical properties. The influence of Hg speciation on its transport in unsaturated soils is not well studied. Transport of four Hg species (dissolved inorganic Hg (II) species, a prepared Hg(II) and dissolved organic matter (DOM) complex, Hg(0), and HgS nanoparticles) was measured in sand and soil packed columns with partial water saturation under simulated rainfall (low ionic strength solution without DOM) and landfill leachate (high DOM content and high ionic strength) influent conditions. The Hg(II)-DOM species had the highest mobility among the four Hg species evaluated, and HgS particles (∼230 nm hydrodynamic diameter) had the poorest mobility, for all soil and influent conditions tested. The addition of 2 wt % clay particles to sand greatly retarded the transport of all Hg species, especially under simulated rainfall. DOM in the column influent facilitated the transport of all four Hg species in model and natural soils. For simulated rainfall, the transport trends observed in model sands were consistent with those measured in a sandy soil, except that the mobility of dissolved inorganic Hg(II) species was significantly lower in natural soils. For simulated rainfall, Hg transport was negligible in a high organic content (∼3.72 wt %) soil for all species except Hg-DOM. This work suggests that the Hg-DOM species presents the greatest potential for vertical migration to groundwater, especially with DOM in the influent solution.
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Affiliation(s)
- Ke Gai
- Civil & Environmental Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Thomas P Hoelen
- Chevron Energy Technology Company , San Ramon, California 94583, United States
| | | | - Gregory V Lowry
- Civil & Environmental Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
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15
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Leterme B, Jacques D. A reactive transport model for mercury fate in contaminated soil--sensitivity analysis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:16830-16842. [PMID: 26099598 DOI: 10.1007/s11356-015-4876-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/10/2015] [Indexed: 06/04/2023]
Abstract
We present a sensitivity analysis of a reactive transport model of mercury (Hg) fate in contaminated soil systems. The one-dimensional model, presented in Leterme et al. (2014), couples water flow in variably saturated conditions with Hg physico-chemical reactions. The sensitivity of Hg leaching and volatilisation to parameter uncertainty is examined using the elementary effect method. A test case is built using a hypothetical 1-m depth sandy soil and a 50-year time series of daily precipitation and evapotranspiration. Hg anthropogenic contamination is simulated in the topsoil by separately considering three different sources: cinnabar, non-aqueous phase liquid and aqueous mercuric chloride. The model sensitivity to a set of 13 input parameters is assessed, using three different model outputs (volatilized Hg, leached Hg, Hg still present in the contaminated soil horizon). Results show that dissolved organic matter (DOM) concentration in soil solution and the binding constant to DOM thiol groups are critical parameters, as well as parameters related to Hg sorption to humic and fulvic acids in solid organic matter. Initial Hg concentration is also identified as a sensitive parameter. The sensitivity analysis also brings out non-monotonic model behaviour for certain parameters.
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Affiliation(s)
- Bertrand Leterme
- Performance Assessments, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400, Mol, Belgium.
| | - Diederik Jacques
- Performance Assessments, Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400, Mol, Belgium.
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Wikiniyadhanee R, Chotpantarat S, Ong SK. Effects of kaolinite colloids on Cd²⁺ transport through saturated sand under varying ionic strength conditions: Column experiments and modeling approaches. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 182:146-156. [PMID: 26387033 DOI: 10.1016/j.jconhyd.2015.08.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 08/19/2015] [Accepted: 08/24/2015] [Indexed: 06/05/2023]
Abstract
Column experiments were performed under various ionic strengths (0.0-0.9 mM) using 10 mg L(-1) of Cd(2+) without kaolinite colloids and 10 mg L(-1) Cd(2+) mixed with 100 mg L(-1) kaolinite colloids. The nonequilibrium two-site model (TSM) described the behavior of both Cd(2+) transport and Cd(2+) co-transported with kaolinite colloids better than the equilibrium model (CD(eq)) (R(2)=0.978-0.996). The results showed that an increase in ionic strength negatively impacted the retardation factors (R) of both Cd(2+) and Cd(2+) mixed with kaolinite colloids. The presence of kaolinite colloids increased the retardation factors of Cd(2+) from 7.23 to 7.89, 6.76 to 6.61 and 3.79 to 6.99 for ionic strengths of 0.225, 0.45 and 0.9 mM, respectively. On the other hand, the presence of kaolinite colloids decreased the retardation factor of Cd(2+) from 8.13 to 7.83 for ionic strength of 0.0 mM. The fraction of instantaneous sorption sites (f) parameters, kinetic constant for sorption sites (α) and Freundlich constant (K(f)) were estimated from HYDRUS-1D of TSM for Cd(2+) transport. The fraction of instantaneous sorption sites was found to increase for an increase in ionic strength. K(f) values of Cd(2+) transport without kaolinite colloids for 0.0, 0.225 and 0.45 mM were found to be higher than those of Cd(2+) transport with kaolinite colloids, except for ionic strength of 0.9 mM. Hence, the presence of kaolinite colloids probably retarded the mobility of Cd(2+) in porous media for higher ionic strengths. Furthermore, retardation factors and K(f) values of both Cd(2+) transport and Cd(2+) co-transport were shown to decrease when ionic strength increased. Interestingly, according to TSM, the fraction of instantaneous sorption sites tends to increase for an increase in ionic strength, which imply that the mechanism of Cd(2+) sorption onto quartz sand can be better described using equilibrium sorption rather than nonequilibrium sorption for an increase in ionic strength.
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Affiliation(s)
- Rakkreat Wikiniyadhanee
- International Postgraduate Programs in Environmental Management, Graduate School, Chulalongkorn University, Bangkok, Thailand; Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand
| | - Srilert Chotpantarat
- Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, Thailand; Department of Geology, Faculty of Science, Chulalongkorn University, Phayathai Road, Pathumwan, Bangkok 10330, Thailand.
| | - Say Kee Ong
- Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, IA, USA
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17
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Leterme B, Blanc P, Jacques D. A reactive transport model for mercury fate in soil--application to different anthropogenic pollution sources. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:12279-12293. [PMID: 24928379 DOI: 10.1007/s11356-014-3135-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 05/30/2014] [Indexed: 06/03/2023]
Abstract
Soil systems are a common receptor of anthropogenic mercury (Hg) contamination. Soils play an important role in the containment or dispersion of pollution to surface water, groundwater or the atmosphere. A one-dimensional model for simulating Hg fate and transport for variably saturated and transient flow conditions is presented. The model is developed using the HP1 code, which couples HYDRUS-1D for the water flow and solute transport to PHREEQC for geochemical reactions. The main processes included are Hg aqueous speciation and complexation, sorption to soil organic matter, dissolution of cinnabar and liquid Hg, and Hg reduction and volatilization. Processes such as atmospheric wet and dry deposition, vegetation litter fall and uptake are neglected because they are less relevant in the case of high Hg concentrations resulting from anthropogenic activities. A test case is presented, assuming a hypothetical sandy soil profile and a simulation time frame of 50 years of daily atmospheric inputs. Mercury fate and transport are simulated for three different sources of Hg (cinnabar, residual liquid mercury or aqueous mercuric chloride), as well as for combinations of these sources. Results are presented and discussed with focus on Hg volatilization to the atmosphere, Hg leaching at the bottom of the soil profile and the remaining Hg in or below the initially contaminated soil layer. In the test case, Hg volatilization was negligible because the reduction of Hg(2+) to Hg(0) was inhibited by the low concentration of dissolved Hg. Hg leaching was mainly caused by complexation of Hg(2+) with thiol groups of dissolved organic matter, because in the geochemical model used, this reaction only had a higher equilibrium constant than the sorption reactions. Immobilization of Hg in the initially polluted horizon was enhanced by Hg(2+) sorption onto humic and fulvic acids (which are more abundant than thiols). Potential benefits of the model for risk management and remediation of contaminated sites are discussed.
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Affiliation(s)
- Bertrand Leterme
- Performance Assessments, Institute for Environment, Health, and Safety, Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, 2400, Mol, Belgium,
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Zhu Y, Ma LQ, Dong X, Harris WG, Bonzongo JC, Han F. Ionic strength reduction and flow interruption enhanced colloid-facilitated Hg transport in contaminated soils. JOURNAL OF HAZARDOUS MATERIALS 2014; 264:286-292. [PMID: 24316802 DOI: 10.1016/j.jhazmat.2013.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/22/2013] [Accepted: 11/04/2013] [Indexed: 06/02/2023]
Abstract
The effects of ionic strength (IS) reduction (5-0.05mM) and flow interruption (FI, flow stopped for 7d) on colloid and Hg release in the leachate were examined in column experiment. Two Hg contaminated soils (13.9 and 146mg/kg) were used, with Hg concentrations in colloids being 2-4 times greater than bulk soils. Based on sequential extraction, Hg concentrations in organic matter (OM) fraction were the most abundant in soils (31-48%). Column leaching after IS reduction and FI released large amounts of colloidal Hg, accounting for 44-48% of released Hg. The highest colloidal Hg concentrations at 27.8 and 360μg/L were observed at ∼1 pore volume after FI. Concentration distribution of colloidal OM and colloidal Fe was similar to colloidal Hg in the leachate, showing peak concentrations after IS reduction and FI. Most of the released colloidal Hg was in OM fraction (37-53%), with some in Fe/Mn oxide fraction (11-19%). Based on composition of released colloids and Hg fractionation in soils and colloids, colloidal OM could serve as an important carrier for Hg transport in soils.
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Affiliation(s)
- Yingjia Zhu
- Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA
| | - Lena Q Ma
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046, China; Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA.
| | - Xiaoling Dong
- Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA
| | - Willie G Harris
- Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA
| | - J C Bonzongo
- Department of Environmental Engineering and Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Fengxiang Han
- Department of Chemistry and Biochemistry, Jackson State University, MS 39217, USA
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