1
|
Oladoye PO, Wang K, Aguilar K, Liu G, Cai Y. Particles-involved photochemical processes: A review for the case of mercury reduction in relation to aquatic mercury cycling. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 931:172845. [PMID: 38685427 DOI: 10.1016/j.scitotenv.2024.172845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 04/08/2024] [Accepted: 04/26/2024] [Indexed: 05/02/2024]
Abstract
Mercury (Hg) is one of the toxic metals of global and environmental concern, with aquatic Hg cycling being central in determining the production of highly toxic methylmercury and the air-water Hg exchange influencing the long-range intercontinental atmospheric Hg transport. Both inorganic and organic forms of Hg can be bound by suspended particles, including inorganic minerals (in particular metal oxides/sulfides) and particulate organic matter. Photochemical transformation is a critical process in surface water, and the role of suspended particles in Hg redox photoreactions has increasingly emerged, albeit in limited studies in comparison to extensive studies on aqueous (homogeneous) photoreactions of Hg. The lack of understanding of what roles suspended particles play might result in inaccurate estimation of how Hg species transform and/or cycle in the environment. In view of this gap, this paper critically reviews and synthesizes information on the studies conducted on different natural surface waters with respect to the potential roles of suspended particles on Hg photo-redox reactions. It robustly discusses the various possible pathways and/or mechanisms of particle-mediated Hg (II) reduction, in enhancing or lowering the production of dissolved gaseous mercury. These processes include photo hole-electron pair formation and reactive oxygen species generation from particle excitation and their involvement in Hg photoreduction, in addition to the light attenuation effect of particles. This paper highlights the necessity of future studies exploiting these particles-mediated Hg photoreactions pathways and the implications of including these heterogeneous photoreactions (together with particulate elemental Hg species) on the air-water Hg exchange estimation.
Collapse
Affiliation(s)
- Peter Olusakin Oladoye
- Department of Chemistry and Biochemistry, Florida International University, Miami, 11200 SW 8th St, Miami, FL 33199, United States; Institute of Environment, Florida International University, 11200 SW 8th St, Miami, FL 33199, United States.
| | - Kang Wang
- Department of Chemistry and Biochemistry, Florida International University, Miami, 11200 SW 8th St, Miami, FL 33199, United States
| | - Kate Aguilar
- Department of Chemistry and Biochemistry, Florida International University, Miami, 11200 SW 8th St, Miami, FL 33199, United States
| | - Guangliang Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, 11200 SW 8th St, Miami, FL 33199, United States
| | - Yong Cai
- Department of Chemistry and Biochemistry, Florida International University, Miami, 11200 SW 8th St, Miami, FL 33199, United States; Institute of Environment, Florida International University, 11200 SW 8th St, Miami, FL 33199, United States.
| |
Collapse
|
2
|
Yang X, Yu R, Wang T, Wen X, He Y, Li Z, Ma C, Chen W, Zhang C. Algae-leached DOM inhibits the Hg(II) reduction and uptake by lettuce in aquatic environments under light conditions. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 271:106928. [PMID: 38688065 DOI: 10.1016/j.aquatox.2024.106928] [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: 12/26/2023] [Revised: 04/16/2024] [Accepted: 04/17/2024] [Indexed: 05/02/2024]
Abstract
The significant role of aquatic phytoplankton in global primary productivity, accounting for approximately 50 % on an annual basis, has been recognized as a crucial factor in the reduction of Hg(II). In this study, we compared the efficiency of Hg(II) photoreduction mediated by three types of algae leaching dissolved organic matter (DOM) and humic acid (DOM-HA). Especially, we investigated the potential effects of algae-leached DOM on the photoreduction of Hg(II) and its subsequent uptake by lettuce, which serves as an indicator of Hg bioavailability for aquatic plants. The results revealed that under light conditions, the conversion of Hg(II) to Hg(0) mediated by algae-leached DOM and DOM-HA was 6.4-39.9 % higher compared to dark condition. Furthermore, the free radical quenching experiment demonstrated that the reduction of Hg(II) mediated by DOM-HA was higher than algae-leached DOM, mainly due to its ability to generate superoxide anion (O2•-). Moreover, the photoreduction efficiences of Hg(II) mediated by algae-leached DOM were 29-18 % lower compared to DOM-HA. The FT-IR analysis revealed that the production of -SH from algae-leached DOM led to the formation of strong metal-complexes, which restricts the reduction process from Hg(II) to Hg(0). Finally, the hydroponics experiment demonstrated that algae-leached DOM inhibited the bioavailability of Hg(II) to plants more effectively than DOM-HA. Our research emphasizes the significant functional roles and potential mechanisms of algae in reducing Hg levels, thereby influencing the availability of Hg in aquatic ecosystems.
Collapse
Affiliation(s)
- Xu Yang
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010070, China; College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
| | - Ruihong Yu
- Inner Mongolia Key Laboratory of River and Lake Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot 010070, China.
| | - Tantan Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Xin Wen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Yubo He
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Zihao Li
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Chi Ma
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Wenhao Chen
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China
| | - Chang Zhang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
| |
Collapse
|
3
|
Yang J, Fan Y, Lu Z, Guo Y, Huang J, Cai K, Sun Q, Wang F. Positive profile of natural small molecule organic matters on emerging antivirus pharmaceutical elimination in advance reduction process: A deep dive into the photosensitive mechanism of triplet excited state compounds. WATER RESEARCH 2024; 256:121611. [PMID: 38640567 DOI: 10.1016/j.watres.2024.121611] [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: 03/05/2024] [Accepted: 04/12/2024] [Indexed: 04/21/2024]
Abstract
Natural small molecular organic matter (NSOM), ubiquitous in natural waters and distinct from humic acid or fulvic acid, is a special type of dissolved organic matter (DOM) which is characterized as strong photosensitivity and simple molecular structure. However, little study had been directed on the role of NSOM in eliminating emerging contaminants in advanced reduction process (ARP). This study took three small molecular isomeric organic acids (p-hydroxybenzoic acid, pHBA; salicylic acid, SA; m-hydroxybenzoic acid, mHBA) as the representative substances of NSOM to explore these mechanisms on promoting Ribavirin (RBV, an anti COVID-19 medicine) degradation in ultraviolet activated sulfite (UV/Sulfite) process. The results demonstrated that the observed degradation rate constant of RBV (kobs-RBV) was 7.56 × 10-6 s-1 in UV/Sulfite process, indicating that hydrated electron (eaq-) from UV/Sulfite process could not effectively degrade RBV, while it increased by 178 and 38 times when pHBA and SA were introduced into UV/Sulfite process respectively, suggesting that pHBA and SA strongly promoted RBV degradation while mHBA had no promotion on RBV abatement in UV/Sulfite process. Transient absorption spectra and reactive intermediates scavenging experiment indicated that the triplet excited state pHBA and SA (3pHBA* and 3SA*) contributed to the degradation of RBV through non-radical process. Notably, eaq- played the role of key initiator in transforming pHBA and SA into their triplet states. The difference of kobs-RBV in UV/Sulfite/pHBA and UV/Sulfite/SA process was attributed to different generation pathways of 3pHBA* and 3SA* (high molar absorptivity at the wavelength of 254 nm and photosensitive cycle, respectively) and their second order rate constants towards RBV (kRBV-3pHBA* = 8.60 × 108 M-1 s-1 and kRBV-3SA* = 6.81 × 107 M-1 s-1). mHBA could not degrade RBV for its lack of intramolecular hydrogen bond and low molar absorptivity at 254 nm to abundantly transform into its triplet state. kobs-RBV increased as pH increased from 5.0 to 11.0 in UV/Sulfite/SA process, due to the high yield of eaq- in alkaline condition which promoted the generation of 3SA* and the stable of the absorbance of SA at 254 nm. By contrast, kobs-RBV underwent a process of first increasing and then decreasing in UV/Sulfite/pHBA process as the increase of pH, and its highest value achieved in a neutral condition. This lied in the exposure of eaq- increased as the increase of pH which promoted the generation of 3pHBA*, while the molar absorptivity of pHBA at 254 nm decreased as the increase of pH in an alkaline condition which inhibited the yield of 3pHBA*. The RBV degradation pathways and products toxicity assessment indicated that UV/Sulfite/pHBA had better detoxification performance on RBV than UV/Sulfite/SA process. This study disclosed a novel mechanism of emerging contaminants abatement through non-radical process in NSOM mediated ARP, and provide a wide insight into positive profile of DOM in water treatment process, instead of only taking DOM as a quencher of reactive intermediates.
Collapse
Affiliation(s)
- Jing Yang
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China
| | - Yongjie Fan
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China; College of the Environment & Ecology, Xiamen University, Xiamen 361102, Fujian, China
| | - Zhilei Lu
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China
| | - Yuxin Guo
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China
| | - Jintao Huang
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China
| | - Kaicong Cai
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou 350117, China; Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005, China
| | - Qiyuan Sun
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China.
| | - Feifeng Wang
- College of Environmental and Resource Sciences, College of Carbon Neutral Modern Industry, Fujian Key Laboratory of Pollution Control & Resource Reuse, Fujian Normal University, Fuzhou 350117, Fujian, China.
| |
Collapse
|
4
|
Perrot V, Ma T, Vandeputte D, Smolikova V, Bratkic A, Leermakers M, Baeyens W, Gao Y. Origin and partitioning of mercury in the polluted Scheldt Estuary and adjacent coastal zone. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 878:163019. [PMID: 36996990 DOI: 10.1016/j.scitotenv.2023.163019] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 03/04/2023] [Accepted: 03/19/2023] [Indexed: 05/13/2023]
Abstract
Estuaries and coastal zones are areas with complex biogeochemical and hydrological cycles and are generally facing intense pollution due to anthropogenic activities. An emblematic example is the Scheldt Estuary which ends up in the North Sea and has been historically heavily contaminated by multiple pollutants, including mercury (Hg). We report here Hg species and their levels in surface waters of the Scheldt Estuary and the Belgian Part of North Sea (BPNS) from different sampling campaigns in February-April 2020 and 2021. Along the estuary, Hg concentration on suspended particles ([HgSPM]) progressively decreased with increasing salinity and was strongly correlated with organic matter content (%Corg) and origin (identified with δ13Corg). While [HgSPM] drives total Hg concentration in the estuary (total dissolved Hg, HgTD is only 7 ± 6 %), annual and daily variations of total Hg levels were mostly attributed to changes in SPM loads depending on river discharge and tidal regime. In the BPNS, a significant fraction of total Hg occurs as HgTD (40 ± 21 %) and the majority of this HgTD was reducible (i.e. labile Hg), meaning potentially available for microorganisms. Compared to the '90s, a significant decrease of [HgSPM] was observed in the estuary, but this was not the case for [HgTD], which can be due to (1) still significant discrete discharges from Antwerp industrial area, and (2) higher Hg partitioning towards the dissolved phase in the water column relative to the '90s. Our results highlight the important contribution of the Scheldt estuary for the Hg budget in North Sea coastal waters, as well as the need for seasonal monitoring of all Hg species.
Collapse
Affiliation(s)
- Vincent Perrot
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Tianhui Ma
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Delphine Vandeputte
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Vendula Smolikova
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Arne Bratkic
- Universitat de Lleida, Chemistry Department, Environmental Physical Chemistry group, Av. Rovira Roure 191, 25198 Lleida, Spain
| | - Martine Leermakers
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Willy Baeyens
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium
| | - Yue Gao
- Vrije Universiteit Brussel (VUB), Analytical and Environmental Geochemistry (AMGC), Pleinlaan 2, Ixelles 1050, Belgium.
| |
Collapse
|
5
|
Wen X, Yang X, Wang T, Li Z, Ma C, Chen W, He Y, Zhang C. Photoreduction of Hg(II) by typical dissolved organic matter in paddy environments. CHEMOSPHERE 2023; 327:138437. [PMID: 36963580 DOI: 10.1016/j.chemosphere.2023.138437] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 03/10/2023] [Accepted: 03/15/2023] [Indexed: 06/18/2023]
Abstract
The photochemical behavior of dissolved organic matter (DOM) in surface water and its effect on Hg(II) photoreduction has been extensively studied, but the contribution of DOM in paddy water to Hg(II) photoreduction is largely unknown. Herein, the effect of DOM from biochar (BCDOM), rice straw (RSDOM), and chicken manure (CMDOM) on Hg(II) photoreduction were examined. The comparable reduction efficiency of Hg(II) suggested that DOM-like fraction (62.3-63.7%) contributes more than suspended particulate matter-like fraction (17.7-23.4%) and bacteria-like fraction (13.0-20.0%) in paddy water. Under irradiation, the typical DOM significantly promoted Hg(II) photoreduction, and the reduction efficiency of BCDOM (65.5 ± 2.1%) was higher than that of CMDOM (48.3 ± 2.6%) and RSDOM (32.8 ± 2.4%) in 6 h. The quenching and kinetics experiments showed that superoxide anion (O2•-) was the main reactive species for Hg(II) photoreduction. Fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry revealed that DOM with a higher degree of lignin/carboxy-rich acyclic molecules, condensed aromatics structures, and phenolic compounds could promote the formation of O2•-. These findings highlight the importance of DOM in Hg(II) photoreduction and provide new ideas for regulating Hg cycling and bioavailability in paddy environments.
Collapse
Affiliation(s)
- Xin Wen
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Xu Yang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Tantan Wang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Zihao Li
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Chi Ma
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Wenhao Chen
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Yubo He
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China
| | - Chang Zhang
- College of Environmental Science and Engineering, Hunan University, Changsha, 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, China.
| |
Collapse
|
6
|
Lotfi-Kalahroodi E, Le Bechec M, Tessier E, Pigot T, Amouroux D. Influence of oxygen, UV light and reactive dissolved organic matter on the photodemethylation and photoreduction of monomethylmercury in model freshwater. CHEMOSPHERE 2023; 330:138675. [PMID: 37076088 DOI: 10.1016/j.chemosphere.2023.138675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 04/06/2023] [Accepted: 04/10/2023] [Indexed: 05/03/2023]
Abstract
The key factors which affect the abiotic photodemethylation process of monomethylmercury (MMHg) in the freshwaters has remained unclear. Hence, this work aimed to better elucidate the abiotic photodemethylation pathway in a model freshwater. Anoxic and oxic conditions were implemented to investigate the simultaneous photodemethylation to Hg(II) and photoreduction to Hg(0). MMHg freshwater solution was irradiated through exposure to three wavelength ranges of full light (280-800 nm), without short UVB (305-800 nm), and visible light (400-800 nm). The kinetic experiments were performed following dissolved and gaseous Hg species concentrations (i.e., MMHg, iHg(II), Hg(0)). A comparison between two methods of post-irradiation purging and continuous-irradiation purging confirmed MMHg photodecomposition to Hg(0) is mainly induced by a first photodemethylation step to iHg(II) followed by a photoreduction step to Hg(0). Photodemethylation under full light extent normalized to absorbed radiation energy showed a higher rate constant in anoxic conditions at 18.0 ± 2.2 kJ-1 compared to oxic conditions at 4.5 ± 0.4 kJ-1. Moreover, photoreduction also increased up to four-fold under anoxic conditions. Normalized and wavelength-specific photodemethylation (Kpd) and photoreduction (Kpr) rate constants were also calculated for natural sunlight conditions to evaluate the role of each wavelength range. The relative ratio in wavelength-specific KPAR: Klong UVB+ UVA: K short UVB showed higher dependence on UV light for photoreduction at least ten-fold compared to photodemethylation, regardless of redox conditions. Both results using Reactive Oxygen Species (ROS) scavenging methods and Volatile Organic Compounds (VOC) measurements revealed the occurrence and production of low molecular weight (LMW) organic compounds that are as photoreactive intermediates responsible for MMHg photodemethylation and iHg(II) photoreduction in the dominant pathway. This study also supports the role of dissolved oxygen as an inhibitor for the photodemethylation pathways driven by LMW photosensitizers.
Collapse
Affiliation(s)
- Elaheh Lotfi-Kalahroodi
- Universite de Pau et des Pays de L'Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-chimie pour L'environnement et Les Matériaux (IPREM), 64000, Pau, France.
| | - Mickael Le Bechec
- Universite de Pau et des Pays de L'Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-chimie pour L'environnement et Les Matériaux (IPREM), 64000, Pau, France
| | - Emmanuel Tessier
- Universite de Pau et des Pays de L'Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-chimie pour L'environnement et Les Matériaux (IPREM), 64000, Pau, France
| | - Thierry Pigot
- Universite de Pau et des Pays de L'Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-chimie pour L'environnement et Les Matériaux (IPREM), 64000, Pau, France
| | - David Amouroux
- Universite de Pau et des Pays de L'Adour, E2S/UPPA, CNRS, Institut des Sciences Analytiques et de Physico-chimie pour L'environnement et Les Matériaux (IPREM), 64000, Pau, France
| |
Collapse
|
7
|
Zhang J, Li C, Tang W, Wu M, Chen M, He H, Lei P, Zhong H. Mercury in wetlands over 60 years: Research progress and emerging trends. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 869:161862. [PMID: 36716881 DOI: 10.1016/j.scitotenv.2023.161862] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 01/04/2023] [Accepted: 01/23/2023] [Indexed: 06/18/2023]
Abstract
Wetlands are considered the hotspots for mercury (Hg) biogeochemistry, garnering global attention. Therefore, it is important to review the research progress in this field and predict future frontiers. To achieve that, we conducted a literature analysis by collecting 15,813 publications about Hg in wetlands from the Web of Science Core Collection. The focus of wetland Hg research has changed dramatically over time: 1) In the initial stage (i.e., 1959-1990), research mainly focused on investigating the sources and contents of Hg in wetland environments and fish. 2) For the next 20 years (i.e., 1991-2010), Hg transformation (e.g., Hg reduction and methylation) and environmental factors that affect Hg bioaccumulation have attracted extensive attention. 3) In the recent years of 2011-2022, hot topics in Hg study include microbial Hg methylators, Hg bioavailability, methylmercury (MeHg) demethylation, Hg stable isotope, and Hg cycling in paddy fields. Finally, we put forward future research priorities, i.e., 1) clarifying the primary factors controlling MeHg production, 2) uncovering the MeHg demethylation process, 3) elucidating MeHg bioaccumulation process to better predict its risk, and 4) recognizing the role of wetlands in Hg circulation. This research shows a comprehensive knowledge map for wetland Hg research and suggests avenues for future studies.
Collapse
Affiliation(s)
- Jin Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Chengjun Li
- Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University, Guangzhou 510006, China
| | - Wenli Tang
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Mengjie Wu
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing 210023, China
| | - Mingying Chen
- School of Environment, Nanjing Normal University, Nanjing 210023, China
| | - Huan He
- School of Environment, Nanjing Normal University, Nanjing 210023, China
| | - Pei Lei
- School of Environment, Nanjing Normal University, Nanjing 210023, China.
| | - Huan Zhong
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing 210023, China; Environmental and Life Science Program (EnLS), Trent University, Peterborough, Ontario, Canada
| |
Collapse
|
8
|
Clarke RG, Klapstein SJ, Keenan R, O'Driscoll NJ. Mercury photoreduction and photooxidation kinetics in estuarine water: Effects of salinity and dissolved organic matter. CHEMOSPHERE 2023; 312:137279. [PMID: 36402352 DOI: 10.1016/j.chemosphere.2022.137279] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 06/16/2023]
Abstract
Net photoreduction of divalent mercury (Hg(II)) and volatilization of photoreduction products (i.e., elemental mercury (Hg(0))/dissolved gaseous mercury (DGM)) is a mechanism by which mercury burdens in ecosystems are lessened. The effects of salinity on mercury photoreactions were investigated while controlling the concentration of DOM (>1 kDa) using natural surface water from the tidal Jijuktu'kwejk (Cornwallis River) and processed with a tangential ultrafiltration-dilution technique. Pseudo first-order rate constants in estuarine water salinity dilutions ranged between 0.22 h-1 and 0.73 h-1. The amount of mercury available for photoreduction (Hg(II)RED) ranged between 67.2 and 265.9 pg. Pseudo first-order rate constants decreased with increasing salinity treatments (0-13.5 g L-1), with minimal change in rate constants occurring in higher salinity treatments (e.g. 20.3 or 26.8 g L-1), while Hg(II)RED increased with salinity. In lower salinity treatments, DOM was more photoactive. Taken together, results suggest changes in the mercury photoreduction mechanism from DOM-bound electron transfer to photochemically produced secondary reduction products with increasing salinity. Experiments examining photooxidation showed decreases in Hg (0) with longer exposure time, suggesting transformation of Hg(II)RED into a non-reducible form. This research highlights the importance of salinity and DOM interactions in estuarine surface water and their effects on mercury photochemistry.
Collapse
Affiliation(s)
- Rachel G Clarke
- Department of Earth & Environmental Science. Acadia University, Wolfville, Nova Scotia, B4P 2R6, Canada
| | - Sara J Klapstein
- Department of Earth & Environmental Science. Acadia University, Wolfville, Nova Scotia, B4P 2R6, Canada
| | - Robert Keenan
- Environment and Climate Change Canada, Dartmouth, Nova Scotia, B2Y 2N6, Canada
| | - Nelson J O'Driscoll
- Department of Earth & Environmental Science. Acadia University, Wolfville, Nova Scotia, B4P 2R6, Canada.
| |
Collapse
|
9
|
Chemical Oxidation and Reduction Pathways of Mercury Relevant to Natural Waters: A Review. WATER 2022. [DOI: 10.3390/w14121891] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mercury (Hg) pollution in the environment is a global issue and the toxicity of mercury depends on its speciation. Chemical redox reactions of mercury in an aquatic environment greatly impact on Hg evasion to the atmosphere and the methylation of mercury in natural waters. Identifying the abiotic redox pathways of mercury relevant to natural waters is important for predicting the transport and fate of Hg in the environment. The objective of this review is to summarize the current state of knowledge on specific redox reactions of mercury relevant to natural waters at a molecular level. The rate constants and factors affecting them, as well as the mechanistic information of these redox pathways, are discussed in detail. Increasing experimental evidence also implied that the structure of natural organic matter (NOM) play an important role in dark Hg(II) reduction, dark Hg(0) oxidation and Hg(II) photoreduction in the aquatic environment. Significant photooxidation pathways of Hg(0) identified are Hg(0) photooxidation by hydroxyl radical (OH•) and by carbonate radical (CO3−•). Future research needs on improving the understanding of Hg redox cycling in natural waters are also proposed.
Collapse
|
10
|
Liang X, Zhu N, Johs A, Chen H, Pelletier DA, Zhang L, Yin X, Gao Y, Zhao J, Gu B. Mercury Reduction, Uptake, and Species Transformation by Freshwater Alga Chlorella vulgaris under Sunlit and Dark Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:4961-4969. [PMID: 35389633 DOI: 10.1021/acs.est.1c06558] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
As a major entry point of mercury (Hg) to aquatic food webs, algae play an important role in taking up and transforming Hg species in aquatic ecosystems. However, little is known how and to what extent Hg reduction, uptake, and species transformations are mediated by algal cells and their exudates, algal organic matter (AOM), under either sunlit or dark conditions. Here, using Chlorella vulgaris (CV) as one of the most prevalent freshwater model algal species, we show that solar irradiation could enhance the reduction of mercuric Hg(II) to elemental Hg(0) by both CV cells and AOM. AOM reduced more Hg(II) than algal cells themselves due to cell surface adsorption and uptake of Hg(II) inside the cells under solar irradiation. Synchrotron radiation X-ray absorption near-edge spectroscopy (SR-XANES) analyses indicate that sunlight facilitated the transformation of Hg to less bioavailable species, such as β-HgS and Hg-phytochelatins, compared to Hg(Cysteine)2-like species formed in algal cells in the dark. These findings highlight important functional roles and potential mechanisms of algae in Hg reduction and immobilization under varying lighting conditions and how these processes may modulate Hg cycling and bioavailability in the aquatic environment.
Collapse
Affiliation(s)
- Xujun Liang
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- School of Resources and Environment Science, Quanzhou Normal University, Quanzhou 362000, China
| | - Nali Zhu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- School of Environment, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Hongmei Chen
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Dale A Pelletier
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Lijie Zhang
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Xixiang Yin
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Yuxi Gao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Jiating Zhao
- CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee 37996, United States
| |
Collapse
|
11
|
Li L, Wang X, Fu H, Qu X, Chen J, Tao S, Zhu D. Dissolved Black Carbon Facilitates Photoreduction of Hg(II) to Hg(0) and Reduces Mercury Uptake by Lettuce ( Lactuca sativa L.). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:11137-11145. [PMID: 32804493 DOI: 10.1021/acs.est.0c01132] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Here, we investigated the photoreduction of Hg(II) (Hg(NO3)2) mediated by dissolved black carbon (DBC, <0.45 μm size fraction) collected from water extracts of biochar derived by pyrolyzing crop residues (rice, soybean, and peanut). Under simulated sunlight conditions, the presence of 5 mg C/L DBC significantly facilitated the production of Hg(0) from Hg(II) (initially at 10 nmol/L) with a reduction ratio of 73 ± 4% in 5.3 h. Inhibition of photolysis-induced reactive oxygen species by a quencher or removal of dissolved oxygen indicated that Hg(II) was mainly reduced by superoxide anion (O2•-). Reduction by electrons transferred from photoexcited DBC components or by organic free radicals produced from photo-Fenton-like reactions was also proposed to play a role. Contrary to dissolved humic substances, the DBC-mediated photoreduction of Hg(II) led to unique positive mass-independent isotopic fractionation (MIF) of Hg(0) (Δ199Hg = 1.8 ± 0.3‰), which was attributed to the dominance of secondary Hg(II) reduction by O2•-. The leachate from soil amended with rice biochar at 1-5% mass ratios exhibited significantly higher photocatalytic efficiency than that from unamended soil (wherein the reduced Hg(0) increased from 27 ± 1 to 63 ± 2% in maximum), and the efficiency positively correlated with the percentage of amended biochar. Under natural illumination conditions, the total mercury and/or methylmercury uptake by roots, shoots, and leaves of lettuce (Lactuca sativa L.) grown in water extracts of rice biochar-amended soil was consistently lower (up to 70 ± 20%) than that without the biochar amendment. The findings highlight that DBC might play an important and previously unrecognized role in the biogeochemical cycle and the environmental impact of mercury.
Collapse
Affiliation(s)
- Langlang Li
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Xuejun Wang
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Heyun Fu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046, China
| | - Xiaolei Qu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Jiangsu 210046, China
| | - Jiubin Chen
- Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
| | - Shu Tao
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Dongqiang Zhu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| |
Collapse
|
12
|
Luo H, Cheng Q, Pan X. Photochemical behaviors of mercury (Hg) species in aquatic systems: A systematic review on reaction process, mechanism, and influencing factor. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 720:137540. [PMID: 32143045 DOI: 10.1016/j.scitotenv.2020.137540] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/23/2020] [Accepted: 02/23/2020] [Indexed: 06/10/2023]
Abstract
The fate and transport of Hg species in natural aquatic environment are strongly affected by photochemical transformation of Hg0, Hg2+, and MeHg. Migration of Hg is determined by its complexation with organic and inorganic ligands that are widely present in the water. The presence of dissolved organic matter (DOM) is closely related to photochemical reactions of Hg. DOM can strongly bind to mercury (e.g., Hg2+ and MeHg), thus affecting its speciation, mobility and toxicity, eventually dominating its bioavailability. This review summarizes extensive studies on photochemical behaviors of Hg including: (1) photo-oxidation; (2) photo-reduction; (3) photochemical methylation; and (4) MeHg photo-degradation. Photo-oxidation of Hg0 is mostly caused by oxidative free radicals (e.g., •OH, CO3•-, O3, and 1O2), while photo-reduction of Hg2+ is more complicated and it involves two pathways: (1) primary processes (direct photolysis of Hg2+ or ligand-metal charge transfer of Hg2+-DOM complex); and (2) secondary processes (reduction of Hg2+-DOM complex induced by free radicals derived from DOM photolysis). Photochemical methylation of inorganic Hg occurs as follows: (1) Hg2+ complexes with methyl donors (e.g., acetic acid, tert-butyl, alcohols, etc.) to form intermediates, followed by (2) an intramolecular methyl transfer. MeHg photo-degradation is the leading pathway for MeHg demethylation and it primarily proceeds via four different pathways. The information on DOM was also mentioned, but DOM is not the only factor that affects the photochemical behaviors of Hg. Other influencing factors such as: (1) pH value; (2) dissolved oxygen; (3) cations (Fe3+, K+) and anions (NO3-, HCO3-, CO32-, Cl-); and (4) suspended substance cannot be ignored.
Collapse
Affiliation(s)
- Hongwei Luo
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Qianqian Cheng
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Xiangliang Pan
- Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
| |
Collapse
|
13
|
Soto Cárdenas C, Diéguez MDC, Queimaliños C, Rizzo A, Fajon V, Kotnik J, Horvat M, Ribeiro Guevara S. Mercury in a stream-lake network of Andean Patagonia (Southern Volcanic Zone): Partitioning and interaction with dissolved organic matter. CHEMOSPHERE 2018; 197:262-270. [PMID: 29353676 DOI: 10.1016/j.chemosphere.2018.01.048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 01/10/2018] [Accepted: 01/11/2018] [Indexed: 06/07/2023]
Abstract
Lake Nahuel Huapi (NH) is a large, ultraoligotrophic deep system located in Nahuel Huapi National Park (NHNP) and collecting a major headwater network of Northwestern Patagonia (Argentina). Brazo Rincón (BR), the westernmost branch of NH, is close to the active volcanic formation Puyehue-Cordón Caulle. In BR, aquatic biota and sediments display high levels of total Hg (THg), ranging in contamination levels although it is an unpolluted region. In this survey, Hg species and fractionation were assessed in association with dissolved organic matter (DOM) in several aquatic systems draining to BR. THg varied between 16.8 and 363 ng L-1, with inorganic Hg (Hg2+) contributing up to 99.8% and methyl mercury (MeHg) up to 2.10%. DOC levels were low (0.31-1.02 mg L-1) resulting in high THg:DOC and reflecting in high Hg2+ availability for binding particles (partitioning coefficient log Kd up to 6.03). In streams, Hg fractionation and speciation related directly with DOM terrestrial prints, indicating coupled Hg-DOM inputs from the catchment. In the lake, DOM quality and photochemical and biological processing drive Hg fractionation, speciation and vertical levels. Dissolved gaseous Hg (Hg0) reached higher values in BR (up to 3.8%), particularly in upper lake layers where solar radiation enhances the photoreduction of Hg2+ and Hg-DOM complexes. The environmental conditions in BR catchment promote Hg2+ binding to abiotic particles and bioaccumulation and the production of Hg0, features enhancing Hg mobilization among ecosystem compartments. Overall, the aquatic network studied can be considered a "natural Hg hotspot" within NHNP.
Collapse
Affiliation(s)
- Carolina Soto Cárdenas
- Grupo de Ecología de Sistemas Acuáticos a escala de Paisaje, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue- CCT Patagonia Norte CONICET), Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina.
| | - María Del Carmen Diéguez
- Grupo de Ecología de Sistemas Acuáticos a escala de Paisaje, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue- CCT Patagonia Norte CONICET), Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina
| | - Claudia Queimaliños
- Grupo de Ecología de Sistemas Acuáticos a escala de Paisaje, Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA, UNComahue- CCT Patagonia Norte CONICET), Quintral 1250, 8400, San Carlos de Bariloche, Río Negro, Argentina
| | - Andrea Rizzo
- Laboratorio de Análisis por Activación Neutrónica, Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, Av. Bustillo km 9.5, 8400 Bariloche, Argentina; CCT Patagonia Norte CONICET Av. Pioneros 2350, 8400, Bariloche, Argentina
| | - Vesna Fajon
- Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Jože Kotnik
- Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Milena Horvat
- Department of Environmental Sciences, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
| | - Sergio Ribeiro Guevara
- Laboratorio de Análisis por Activación Neutrónica, Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, Av. Bustillo km 9.5, 8400 Bariloche, Argentina
| |
Collapse
|
14
|
Enhanced Two Dimensional Hydrodynamic and Water Quality Model (CE-QUAL-W2) for Simulating Mercury Transport and Cycling in Water Bodies. WATER 2017. [DOI: 10.3390/w9090643] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
15
|
Pan S, Feng C, Lin J, Cheng L, Wang C, Zuo Y. Occurrence and photodegradation of methylmercury in surface water of Wen-Rui-Tang River network, Wenzhou, China. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:11289-11298. [PMID: 28299570 DOI: 10.1007/s11356-017-8708-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 02/27/2017] [Indexed: 06/06/2023]
Abstract
The spatial distribution and seasonal variations of methylmercury (MeHg) in Wen-Rui-Tang (WRT) River network were investigated by monitoring the MeHg concentrations in surface water samples collected from 30 sites across the river network over four seasons. Detection frequencies and concentrations of MeHg were generally higher in January, indicating that low sunlight irradiation, wind speed, and temperature conditions might enhance the persistence of MeHg in surface water. The MeHg levels varied with sampling locations, with the highest concentrations being observed in the industrial area especially around wastewater outfall, revealing that the mercury contamination in WRT River mainly comes from the industrial wastewater. Photodegradation of MeHg in WRT River surface water and the effects of natural constituents such as fulvic acid (FA), ferric ions (Fe3+), nitrate (NO3-), and dissolved oxygen on the MeHg photodegradation in aqueous solutions were studied under the simulated sunlight. The experimental data indicated that the indirect photodecomposition of MeHg occurred in WRT River surface water. Photodegradation of MeHg in FA solution was initiated by triplet 3FA* or MeHg-FA* via electron transfer interaction under light irradiations. The Fe3+ and NO3- can absorb light energy to produce ·OH and enhance the photochemical degradation of MeHg. The MeHg photodecompositions in FA, nitrate, and Fe3+ solutions were markedly accelerated after removing the dissolved oxygen.
Collapse
Affiliation(s)
- Shuihong Pan
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chuchu Feng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Jialu Lin
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Lidong Cheng
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
| | - Chengjun Wang
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China.
| | - Yuegang Zuo
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA.
| |
Collapse
|
16
|
Rubinos DA, Barral MT. Sorptive removal of Hg II by red mud (bauxite residue) in contaminated landfill leachate. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2017; 52:84-98. [PMID: 27737613 DOI: 10.1080/10934529.2016.1229938] [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] [Indexed: 06/06/2023]
Abstract
The ability of red mud (RM) (bauxite residue) to remove HgII from landfill leachate (LL) was assessed. The studied aspects comprised the effects of time, pH, HgII concentration and the sorption isotherm, besides the influence of chloride and representative organic ligands. HgII removal by RM exhibited a complex kinetics where initial rapid sorption was followed by desorption at longer times. The sorption of HgII on RM was strongly pH-dependent. Outstanding maximum sorption was observed at pH∼4-5 (≥99.6%), while it abruptly dropped at higher pH values down to a minimum ∼28% at pH∼10.5. Chloride decreased HgII sorption at acid pH and shifted the pHmax towards higher pH∼9.4, which opposes to sorption in LL and suggests Cl- did not primarily control the process in LL. Amongst the organic ligands, acetate and salicylate slightly affected HgII sorption. Conversely, glycine affected sorption in a pH-dependent manner resembling that in LL, which suggests the relevant role of the organic nitrogenated compounds of LL. EDTA suppressed HgII sorption at any pH. HgII speciation modelling and dissolved organic matter (DOM) sorption support complexation of HgII by DOM as the primary factor governing the removal of HgII in LL. The sorption isotherm was better described by the Freundlich equation, which agrees with the heterogeneous composition of RM. The results indicate that HgII sorption on RM is favorable, but reveal differences in sorption and reduced efficiency, in LL media. Notwithstanding, RM possesses a notable capacity to remove HgII, even under the unhelpful complexing and competing conditions of LL.
Collapse
Affiliation(s)
- David A Rubinos
- a Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy , University of Santiago de Compostela , Santiago de Compostela , Spain
| | - María T Barral
- a Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy , University of Santiago de Compostela , Santiago de Compostela , Spain
| |
Collapse
|
17
|
Luo HW, Yin X, Jubb AM, Chen H, Lu X, Zhang W, Lin H, Yu HQ, Liang L, Sheng GP, Gu B. Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 220:1359-1365. [PMID: 27836473 DOI: 10.1016/j.envpol.2016.10.099] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 10/04/2016] [Accepted: 10/31/2016] [Indexed: 06/06/2023]
Abstract
Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. We report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). These results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.
Collapse
Affiliation(s)
- Hong-Wei Luo
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Xiangping Yin
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Aaron M Jubb
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Hongmei Chen
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Xia Lu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Weihua Zhang
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou, 510006, China
| | - Hui Lin
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Han-Qing Yu
- Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Liyuan Liang
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Guo-Ping Sheng
- Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| |
Collapse
|
18
|
He F, Gao J, Pierce E, Strong PJ, Wang H, Liang L. In situ remediation technologies for mercury-contaminated soil. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:8124-8147. [PMID: 25850737 DOI: 10.1007/s11356-015-4316-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/02/2015] [Indexed: 06/04/2023]
Abstract
Mercury from anthropogenic activities is a pollutant that poses significant risks to humans and the environment. In soils, mercury remediation can be technically challenging and costly, depending on the subsurface mercury distribution, the types of mercury species, and the regulatory requirements. This paper introduces the chemistry of mercury and its implications for in situ mercury remediation, which is followed by a detailed discussion of several in situ Hg remediation technologies in terms of applicability, cost, advantages, and disadvantages. The effect of Hg speciation on remediation performance, as well as Hg transformation during different remediation processes, was detailed. Thermal desorption, electrokinetic, and soil flushing/washing treatments are removal technologies that mobilize and capture insoluble Hg species, while containment, solidification/stabilization, and vitrification immobilize Hg by converting it to less soluble forms. Two emerging technologies, phytoremediation and nanotechnology, are also discussed in this review.
Collapse
Affiliation(s)
- Feng He
- College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, 310014, Zhejiang, China,
| | | | | | | | | | | |
Collapse
|
19
|
Tai C, Li Y, Yin Y, Scinto LJ, Jiang G, Cai Y. Methylmercury photodegradation in surface water of the Florida Everglades: importance of dissolved organic matter-methylmercury complexation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:7333-40. [PMID: 24901379 DOI: 10.1021/es500316d] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Photodegradation is the major pathway of methylmercury (MeHg) degradation in many surface waters. However, the mechanism of MeHg photodegradation is still not completely understood. Dissolved organic matter (DOM) is expected to play a critical role in MeHg photodegradation. By using several techniques, including N2/O2 purging and the addition of stable isotope (Me(201)Hg), scavengers, competing ligands, and a singlet oxygen ((1)O2) generator, the role played by MeHg-DOM complexation in MeHg photodegradation of Everglades surface water was investigated. DOM appeared to be involved in MeHg photodegradation via the formation MeHg-DOM complexes based on three findings: (1) MeHg was quickly photodegraded in solutions containing DOM extracts; (2) degradation of MeHg did not occur in deionized water; and (3) addition of competing complexation reagents (dithiothreitol-DTT) dramatically prohibited the photodegradation of MeHg in Everglades water. Further experiments indicated that free radicals/reactive oxygen species, including hydroxyl radical (·OH), (1)O2, triplet excited state of DOM ((3)DOM*), and hydrated electron (e(-)aq), played a minor role in MeHg photodegradation in Everglades water, based on the results of scavenger addition, (1)O2 generator addition and N2/O2 purging. A pathway, involving direct photodegradation of MeHg-DOM complexes via intramolecular electron transfer, is proposed as the dominant mechanism for MeHg photodegradation in Everglades water.
Collapse
Affiliation(s)
- Chao Tai
- Institute of Resources and Environment, Henan Polytechnic University , Jiaozuo, 454000, China
| | | | | | | | | | | |
Collapse
|
20
|
Zheng W, Lin H, Mann BF, Liang L, Gu B. Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:12827-34. [PMID: 24138581 DOI: 10.1021/es402697u] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Mercuric ion, Hg(2+), forms strong complexes with thiolate compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved aqueous elemental mercury (Hg(0)aq) and organic ligands in general, and thiol compounds in particular, are not well studied although these reactions likely affect Hg speciation and cycling in the environment. In this study, we compared the reaction rates between Hg(0)aq and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states in dark, anoxic conditions to assess the role of these ligands in Hg(0)aq oxidation. Significant Hg(0)aq oxidation was observed with all thiols but not with ligands containing no S. Compounds with oxidized S (e.g., disulfide) exhibited little or no reactivity toward Hg(0)aq either at pH 7. The rate and extent of Hg(0)aq oxidation varied greatly depending on the chemical and structural properties of thiols, thiol/Hg ratios, and the presence or absence of electron acceptors. Smaller aliphatic thiols and higher thiol/Hg ratios resulted in higher Hg(0)aq oxidation rates than larger aromatic thiols at lower thiol/Hg ratios. The addition of electron acceptors (e.g., humic acid) also led to substantially increased Hg(0)aq oxidation. Our results suggest that thiol-induced oxidation of Hg(0)aq is important under anoxic conditions and can affect Hg redox transformation and bioavailability for microbial methylation.
Collapse
Affiliation(s)
- Wang Zheng
- Environmental Sciences Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37830, United States
| | | | | | | | | |
Collapse
|
21
|
Guo HB, He F, Gu B, Liang L, Smith JC. Time-dependent density functional theory assessment of UV absorption of benzoic acid derivatives. J Phys Chem A 2012; 116:11870-9. [PMID: 23134517 DOI: 10.1021/jp3084293] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Benzoic acid (BA) derivatives of environmental relevance exhibit various photophysical and photochemical characteristics. Here, time-dependent density functional theory (TDDFT) is used to calculate photoexcitations of eight selected BAs and the results are compared with UV spectra determined experimentally. High-level gas-phase EOM-CCSD calculations and experimental aqueous-phase spectra were used as the references for the gas-phase and aqueous-phase TDDFT results, respectively. A cluster-continuum model was used in the aqueous-phase calculations. Among the 15 exchange-correlation (XC) functionals assessed, five functionals, including the meta-GGA hybrid M06-2X, double hybrid B2PLYPD, and range-separated functionals CAM-B3LYP, ωB97XD, and LC-ωPBE, were found to be in excellent agreement with the EOM-CCSD gas-phase calculations. These functionals furnished excitation energies consistent with the pH dependence of the experimental spectra with a standard deviation (STDEV) of ∼0.20 eV. A molecular orbital analysis revealed a πσ* feature of the low-lying transitions of the BAs. The CAM-B3LYP functional showed the best overall performance and therefore shows promise for TDDFT calculations of processes involving photoexcitations of benzoic acid derivatives.
Collapse
Affiliation(s)
- Hao-Bo Guo
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Tennessee 37831, United States
| | | | | | | | | |
Collapse
|