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Deng Y, Zhao H, Zhang X, Li X, Chi G. The dissipation of organophosphate esters mediated by ryegrass root exudate oxalic acid in soil: Analysis of enzymes activities, microorganism. CHEMOSPHERE 2024; 356:141896. [PMID: 38579949 DOI: 10.1016/j.chemosphere.2024.141896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 03/28/2024] [Accepted: 04/02/2024] [Indexed: 04/07/2024]
Abstract
Complex rhizoremediation is the main mechanism of phytoremediation in organic-contaminated soil. Low molecular weight organic acids (LMWOAs) in root exudates have been shown to increase the bioavailability of contaminants and are essential for promoting the dissipation of contaminants. The effects of root exudates on the dissipation of organophosphate esters (OPEs) in soil are unclear. Consequently, we studied the combined effects of root exudates, soil enzymes and microorganisms on OPEs (tri (1-chloro-2-propyl) phosphate (TCPP) and triphenyl phosphate (TPP)) dissipation through pot experiments. Oxalic acid (OA) was confirmed to be the main component of LMWOAs in root exudates of ryegrass. The existence of OA increased the dissipation rate of OPEs by 6.04%-25.50%. Catalase and dehydrogenase activities were firstly activated and then inhibited in soil. While, urease activity was activated and alkaline phosphatase activity was inhibited during the exposure period. More bacteria enrichment (e.g., Sphingomonas, Pseudomonas, Flavisolibacter, Pontibacter, Methylophilus and Massilia) improved the biodegradation of OPEs. In addition, the transformation paths of OPEs hydrolysis and methylation under the action of root exudates were observed. This study provided theoretical insights into reducing the pollution risk of OPEs in the soil.
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Affiliation(s)
- Yaxi Deng
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China
| | - Hongxia Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China.
| | - Xiaonuo Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China
| | - Xintong Li
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China
| | - Goujian Chi
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian, 116024, China
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2
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Wu J, Zou J, Lin J, Li S, Chen S, Liao X, Yang J, Yuan B, Ma J. Hydroxylamine enhanced the degradation of diclofenac in Cu(II)/peracetic acid system: Formation and contributions of CH 3C(O)O •, CH 3C(O)OO •, Cu(III) and •OH. JOURNAL OF HAZARDOUS MATERIALS 2023; 460:132461. [PMID: 37677972 DOI: 10.1016/j.jhazmat.2023.132461] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 08/13/2023] [Accepted: 08/31/2023] [Indexed: 09/09/2023]
Abstract
The slow reduction of Cu(II) into Cu(I) through peracetic acid (PAA) heavily limited the widespread application of Cu(II)/PAA system. Herein, hydroxylamine (HA) was proposed to boost the oxidative capacity of Cu(II)/PAA system by facilitating the redox cycle of Cu(I)/Cu(II). HA/Cu(II)/PAA system was quite rapid in the removal of diclofenac within a broad pH range of 4.5-9.5, with a 10-fold increase in the removal rate of diclofenac compared with the Cu(II)/PAA system at an optimal initial pH of 8.5. Results of UV-Vis spectra, electron paramagnetic resonance, and alcohol quenching experiments demonstrated that CH3C(O)O•, CH3C(O)OO•, Cu(III), and •OH were involved in HA/Cu(II)/PAA system, while CH3C(O)OO• was verified as the predominant reactive species of diclofenac elimination. Different from previously reported Cu-catalyzed PAA processes, CH3C(O)OO• mainly generated from the reaction of PAA with Cu(III) rather than CH3C(O)O• and •OH. Four possible elimination pathways for diclofenac were proposed, and the acute toxicity of treated diclofenac solution with HA/Cu(II)/PAA system significantly decreased. Moreover, HA/Cu(II)/PAA system possessed a strong anti-interference ability towards the commonly existent water matrix. This research proposed an effective strategy to boost the oxidative capacity of Cu(II)/PAA system and might promote its potential application, especially in copper-contained wastewater.
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Affiliation(s)
- Jianying Wu
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Jing Zou
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China.
| | - Jinbin Lin
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China; Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, School of Environment, Shanghai Jiao Tong University, Shanghai 200240, PR China
| | - Sheng Li
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Siying Chen
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Xiaobin Liao
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China
| | - Jingxin Yang
- Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Institute of Environmental Research at Greater Bay, Guangzhou University, Guangzhou 510006, PR China
| | - Baoling Yuan
- Xiamen Key Laboratory of Municipal and Industrial Solid Waste Utilization and Pollution Control, College of Civil Engineering, Huaqiao University, Xiamen, Fujian 361021, PR China; Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun 130118, PR China
| | - Jun Ma
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, Heilongjiang 150090, PR China
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Liu L, Du L, Lu S, Yang B, Zhao X, Wu D, Fei X, He H, Wang D. Molecular insight into DOM fate using EEM-PARAFAC and FT-ICR MS and concomitant heavy metal behaviors in biologically treated landfill leachate during coagulation: Al speciation dependence. JOURNAL OF HAZARDOUS MATERIALS 2023; 460:132374. [PMID: 37683350 DOI: 10.1016/j.jhazmat.2023.132374] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/27/2023] [Accepted: 08/22/2023] [Indexed: 09/10/2023]
Abstract
Various combined processes with pre-coagulation have been developed for biologically treated landfill leachate, but the microscopic-level processes occurring during coagulation remain largely unknown. Herein, dissolved organic matter (DOM) fate using fluorescence excitation emission matrix spectroscopy combined with parallel factor analysis and electrospray ionization coupled Fourier transform-ion cyclotron resonance mass spectrometry and concomitant heavy metal (HM) behaviors were explored at the molecular level. In addition, AlCl3 and two polyaluminum chloride (PACl) species (dominated by [AlO4Al12(OH)24(H2O)12]7+ and [(AlO4)2Al28(OH)56(H2O)26]18+, respectively) were used. The results show that all coagulants are efficient at removing DOM. PACl was found to be advantageous over AlCl3 in overcoming pH fluctuation, which is ascribed to the different dominant mechanisms, namely, entrapment and sweep flocculation for AlCl3 and charge neutralization for PACl. Consequently, PACl was more effective at removing humic substances, usually high-molecular-weight, oxygen-rich and unsaturated, than protein substances. For HM removal, PACl was likewise better and more stable, where As, Cu, Ni, Co and Hg were removed predominantly via adsorption, and Cr, Zn, Pb, Cd and Mn were removed via coprecipitation. Correlation analysis showed that humic substances tended to complex with HMs and be removed synergistically due to the ubiquitous occurrences of aromatic structures and oxygen-containing functional groups.
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Affiliation(s)
- Libing Liu
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Lei Du
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Sen Lu
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Shenzhen, Guangdong 518055, China
| | - Bo Yang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Xu Zhao
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Deli Wu
- State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science & Engineering, Tongji University, Shanghai 200092, China
| | - Xunchang Fei
- School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore
| | - Hongping He
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China.
| | - Dongsheng Wang
- College of Environmental and Resource Science, Zhejiang University, Hangzhou, Zhejiang 310058, China
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Wang Q, Zhao H, Bekele TG, Qu B, Chen J. Citric acid can enhance the uptake and accumulation of organophosphate esters (OPEs) in Suaeda salsa rhizosphere: Potential for phytoremediation. JOURNAL OF HAZARDOUS MATERIALS 2023; 443:130169. [PMID: 36257113 DOI: 10.1016/j.jhazmat.2022.130169] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 10/07/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
Bioaccumulation of organophosphate esters (OPEs) by plants has been widely studied, but how root exudates influence their bioavailability to plants is poorly understood. Here, we examined whether root exudates could promote desorption of OPEs, thereby enhancing bioavailability and subsequent accumulation potential. Root exudate components exert great influences on the sorption/desorption isotherms of OPEs in soils, resulting in activating OPEs and enhanced bioavailability. Among root exudate components, citric acid was confirmed to play a crucial role in driving OPEs, with 77.7-90.3 % attribution. Citric acid at rhizosphere levels (0.01-0.4 mM) can successfully reduce OPEs sorption to soils by decreasing electrostatic interaction, ligand exchange, and hydrophobic force. Pot experiments indicated that the addition of citric acid can significantly increase OPEs dissolution and bioaccumulation from the rhizosphere soil to Suaeda salsa. A higher level of citric acid in rhizosphere soil resulted in a higher accumulation of OPEs in Suaeda salsa, which was partly attributed to the enhanced OPEs mobility, and the increased root lengths (13.4-29.0 %) and tip numbers (60.2-120 %), promoting OPEs uptake by roots. Our findings suggest the activation process of OPEs in soils by citric acid at rhizosphere levels and provide insights into designing LMWOAs-enhanced phytoremediation techniques in natural environment.
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Affiliation(s)
- Qingzhi Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Hongxia Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
| | - Tadiyose Girma Bekele
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Baocheng Qu
- College of Marine Technology and Environment, Dalian Ocean University, Dalian 116023, China
| | - Jingwen Chen
- Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
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5
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Chen L, Zhuang WE, Yang L. Critical evaluation of the interaction between fluorescent dissolved organic matter and Pb(II) under variable environmental conditions. CHEMOSPHERE 2022; 307:135875. [PMID: 35932920 DOI: 10.1016/j.chemosphere.2022.135875] [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: 06/22/2022] [Revised: 07/12/2022] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
Dissolved organic matter (DOM) can strongly influence the behavior and risk of metal pollutants in aquatic ecosystems. However, a comprehensive study on the effects of DOM level and environmental factors on the binding of DOM with Pb(II) is lacking. This study examined the DOM-Pb(II) interaction in the river water under variable DOM level, pH, and major ions, using fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Four humic-like and one protein-like component were identified, and the abundant humic-like components showed higher Pb(II)-binding fractions (f) than the protein-like component. The f of PARAFAC components decreased while the conditional stability constants (logKM) increased for the diluted DOM, indicating the influence of DOM level on its metal binding. The DOM-Pb(II) interaction was sensitive to changes in pH, with generally higher f and lower logKM at the alkaline condition due to changes in the DOM conformation. The addition of major ions significantly decreased the fluorescence quenching by Pb(II), due to competitive effects and potential DOM conformation changes at elevated ions. Overall, our results show that the DOM-Pb(II) complexation is highly dependent on both the DOM properties and environmental factors, which have implications for optimizing the experimental conditions and for comparing the results in different environments.
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Affiliation(s)
- Linwei Chen
- Fujian Provincial Engineering Research Center for High-value Utilization Technology of Plant Resources, College of Environment and Safety Engineering, Fuzhou University, Fuzhou, Fujian, PR China
| | - Wan-E Zhuang
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
| | - Liyang Yang
- Fujian Provincial Engineering Research Center for High-value Utilization Technology of Plant Resources, College of Environment and Safety Engineering, Fuzhou University, Fuzhou, Fujian, PR China.
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6
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Gao Y, Zhu J, He A. Effect of dissolved organic matter on the bioavailability and toxicity of cadmium in zebrafish larvae: Determination based on toxicokinetic-toxicodynamic processes. WATER RESEARCH 2022; 226:119272. [PMID: 36283231 DOI: 10.1016/j.watres.2022.119272] [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: 06/16/2022] [Revised: 10/14/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
The presence of dissolved organic matter (DOM) strongly influences the bioavailability of metals in aquatic environments; however, the association between the binding activities and the concentrations of DOM compositions is not well documented, leading to uncertainties in metal toxicity assessment. We creatively quantify the mitigation and acceleration effects of DOM compositions on cadmium (Cd) bioaccumulation and toxicity in zebrafish larvae using abiotic ligand (ABLs) and biotic ligand (BLs) in a toxicokinetic-toxicodynamic (TK-TD) model. The BL-TK-TD model could accurately predict the protective effect of fulvic acid while overestimating the complexing capacity of citric acid. The model also could successfully simulate the protective effects of native DOM in most cases from 32 natural water bodies in China. The observed LC50 values of Cd showed a peak effect for the native DOM fraction comprising hydrophilic acidic contents (3.55 ± 0.44 mg L - 1) in natural water from 32 sites. The BL-TK-TD model provides practically useful information to identify the effect of different DOM compositions on metal bioavailability and toxicity in aquatic environments and guides future water management policies aimed at controlling aquatic heavy metal pollution.
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Affiliation(s)
- Yongfei Gao
- College of Ecology, Taiyuan University of Technology, Taiyuan 030024, PR China.
| | - Jingxue Zhu
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, PR China
| | - An He
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, PR China
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Li X, Zhang J, Jin Y, Liu Y, Li N, Wang Y, Du C, Xue Z, Zhang N, Chen Q. Effect of pH-Dependent Homo/Heteronuclear CAHB on Adsorption and Desorption Behaviors of Ionizable Organic Compounds on Carbonaceous Materials. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:12118. [PMID: 36231423 PMCID: PMC9566536 DOI: 10.3390/ijerph191912118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 09/19/2022] [Accepted: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Herein, the adsorption/desorption behaviors of benzoic acid (BA) and phthalic acid (PA) on three functionalized carbon nanotubes (CNTs) at various pH were investigated, and the charge-assisted H-bond (CAHB) was verified by DFT and FTIR analyses to play a key role. The results indicated that the adsorption order of BA and PA on CNTs was different from Kow of that at pH 2.0, 4.0, and 7.0 caused by the CAHB interaction. The strength of homonuclear CAHB (≥78.96 kJ·mol-1) formed by BA/PA on oxidized CNTs is stronger than that of heteronuclear CAHB formed between BA/PA and amino-functionalized CNTs (≤51.66 kJ·mol-1). Compared with the heteronuclear CAHB (Hysteresis index, HI ≥ 1.47), the stronger homonuclear CAHB leads to clearly desorption hysteresis (HI ≥ 3.51). Additionally, the contribution of homonuclear CAHB (≥52.70%) was also greater than that of heteronuclear CAHB (≤45.79%) at pH 7.0. These conclusions were further confirmed by FTIR and DFT calculation, and the crucial evidence of CAHB formation in FTIR was found. The highlight of this work is the identification of the importance and difference of pH-dependent homonuclear/heteronuclear CAHB on the adsorption and desorption behaviors of ionizable organic compounds on carbonaceous materials, which can provide a deeper understanding for the removal of ionizable organic compounds by designed carbonaceous materials.
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Affiliation(s)
- Xiaoyun Li
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
- International Joint Research Centre of Shaanxi Province for Pollutants Exposure and Eco-Environmental Health, Xi’an 710119, China
| | - Jinlong Zhang
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Yaofeng Jin
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Yifan Liu
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Nana Li
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Yue Wang
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Cong Du
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Zhijing Xue
- Department of Environmental Science, School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, China
| | - Nan Zhang
- Environmental Protection Department of Mahe Town, Yuyang District, Yulin 719000, China
| | - Qin Chen
- Northwest Land and Resource Research Center, Shaanxi Normal University, Xi’an 710119, China
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8
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Wan X, Liao Z, He H, Shi M, Yu G, Zhao F, Lai C, Wang Y, Huang B, Pan X. The desorption mechanism of dissolved organic matter on pollutants and the change of biodiversity during sediment dredging. ENVIRONMENTAL RESEARCH 2022; 212:113574. [PMID: 35636464 DOI: 10.1016/j.envres.2022.113574] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/15/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Sediment dredging is an effective means to control the endogenous pollution of lakes, which could significantly change the concentration and composition of organic matter, especially dissolved organic matter (DOM) in the lake. DOM is particularly important for the release of endogenous pollutants, which will inevitably bring an impact on aquatic biodiversity. Nevertheless, in recent research little attention has been paid to the desorption mechanism of DOM on pollutants and the change of biodiversity during dredging. This study investigated the physicochemical properties of DOM in the sediment by taking a sediment dredging project in Dianchi Lake in China for example. The correlations of DOM properties with the desorption behavior of nitrogen (N), phosphorus (P), cadmium (Cd), lead (Pb) and the biodiversity of aquatic organisms were analyzed. The results show that the aromaticity and humification of DOM were improved after dredging, and the high molecular weight DOM was degraded into low molecular weight substance. The desorption amount of N, P and heavy metals (Cd, Pb) were decreased as the pH values increased. Moreover, NH4+-N promoted the release of Pb2+ from DOM, while the release of PO43--P was inhibited. Correlation analysis shows that the physicochemical properties of DOM exactly affected the release of N, P, Cd and Pb. It was easier to desorb pollutants with low aromaticity and humification of DOM, leading to a decrease in the diversity of aquatic organisms. This study identified the desorption mechanism of endogenous pollutants in DOM and the ecological risk to aquatic organisms, providing a theoretical basis for the prevention and control of water pollution.
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Affiliation(s)
- Xing Wan
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Zhicheng Liao
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Huan He
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China.
| | - Min Shi
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Guoxi Yu
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Fenqing Zhao
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Chaochao Lai
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China
| | - Yan Wang
- Key Laboratory of Ecological Environment Evolution and Pollution Control in Mountainous and Rural Areas of Yunnan Province, Kunming, 650224, China
| | - Bin Huang
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China.
| | - Xuejun Pan
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
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9
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Zhang G, Yang B, Shao L, Li F, Leng Y, Chen X. Differences in bioaccumulation of Ni and Zn by microalgae in the presence of fulvic acid. CHEMOSPHERE 2022; 291:132838. [PMID: 34762892 DOI: 10.1016/j.chemosphere.2021.132838] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 10/04/2021] [Accepted: 11/07/2021] [Indexed: 06/13/2023]
Abstract
In the presence of dissolved organic matter, the mechanism of algal bioaccumulation of different metals is complex, and its significance goes far beyond the alga-metal binary system. In the presence of 10 and 20 mg L-1 fulvic acid (FA), the maximum tolerance concentrations of Chlorella pyrenoidosa to Ni were 0.25 and 0.26 mmol L-1, and to Zn were 0.62 and 0.68 mmol L-1, respectively. Within the maximum tolerance concentration ranges, the bioaccumulation behaviors of Ni and Zn were systematically compared in the presence of FA. The presence of FA shortened the adsorption equilibrium time and decreased the maximum bioaccumulation capacity of Ni and Zn. The bioaccumulation mechanism of Ni by C. pyrenoidosa was more inclined to monolayer adsorption, while the bioaccumulation mechanism of Zn was more inclined to multilayer adsorption. More details were revealed after the bioaccumulated metals were separated into adsorption and internalization states by 0.01 M EDTA elution. The presence of FA decreased more adsorbed Zn than the adsorbed Ni, due to the different competitive roles of FA in the ternary system of Ni and Zn, but the presence of FA increased the internalized Ni might due to the stronger complexation of Ni-FA. This research indicated that algae had unique bioaccumulation mechanisms for different metals in the presence of FA, which is of great significance to accurately evaluate the ecological risk posed by heavy metals.
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Affiliation(s)
- Gaoxiang Zhang
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China
| | - Boxuan Yang
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China
| | - Luze Shao
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China
| | - Feili Li
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China.
| | - Yaling Leng
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China
| | - Xiaoling Chen
- College of Environment, Zhejiang University of Technology, 310032, Hangzhou, China
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10
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Chen G, Han K, Liu C, Yan B. Quantitative research on heavy metal removal of flue gas desulfurization-derived wastewater sludge by electrokinetic treatment. JOURNAL OF HAZARDOUS MATERIALS 2021; 414:125561. [PMID: 34030412 DOI: 10.1016/j.jhazmat.2021.125561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 02/27/2021] [Accepted: 02/27/2021] [Indexed: 06/12/2023]
Abstract
Flue gas desulfurization-derived wastewater sludge (FGD-WWS) has been produced increasingly in China and India etc., and its content of heavy metals (HMs) including Cd, Cr, Cu, Hg, Ni and Zn seriously exceeds the limits allowed. Developing the suitable disposal of FGD-WWS is therefore significantly important and necessary. The novel process of electrokinetic treatment combined with chemical pretreatment of HMs in FGD-WWS were proposed here to improve the removal efficiency. Results indicate that the effects of different pretreatment agents (citric acid (CA), ammonia, tetrasodium of N, N-bis (carboxymethyl) glutamic acid (GLDA), and rhamnolipid) on the ET of HMs were different. To investigate the mechanism of combined process, the transformation potential (TP), exchange potential (EP) and removal potential (RP) were calculated. Correlation analysis shows the correlation between TP and RP was higher than that between EP and RP, indicating that the removal efficiency is mainly affected by the fraction transformation of HMs. Electric field, pH and pretreatment agents are main factors causing fraction transformation and affecting TP. Focusing on fraction transformation is an efficient way to improve further the removal efficiency. The work is promisingly valuable for developing the technology of treating FGD-WWS.
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Affiliation(s)
- Guanyi Chen
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China; School of Mechanical Engineering, Tianjin University of Commerce, Lhasa 850012, China; School of Science, Tibet University, Lhasa 850012, China; Tianjin Engineering Research Center for Organic Wastes Safe Disposal and Energy Utilization, Tianjin 300072, China
| | - Kexuan Han
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China
| | - Caixia Liu
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China; Tianjin Engineering Research Center for Organic Wastes Safe Disposal and Energy Utilization, Tianjin 300072, China.
| | - Beibei Yan
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China; Tianjin Key Lab of Biomass/waste Utilization, Tianjin 300072, China; Tianjin Engineering Research Center for Organic Wastes Safe Disposal and Energy Utilization, Tianjin 300072, China
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11
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Gao Y, Feng J, Zhu J, Zhu L. Predicting copper toxicity in zebrafish larvae under complex water chemistry conditions by using a toxicokinetic-toxicodynamic model. JOURNAL OF HAZARDOUS MATERIALS 2020; 400:123205. [PMID: 32585514 DOI: 10.1016/j.jhazmat.2020.123205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
Multiple water chemistry parameters influence metal toxicity in natural waters and accurate quantification of those influences may accelerate the development of site-specific water quality criteria (WQC) and further execute metal risk assessment for better protection of aquatic biota. Here, we investigated the effects of water chemistry parameters on copper (Cu) toxicity of larval zebrafish (Danio rerio) and then incorporated the effects of key parameters in a Toxicokinetic and Toxicodynamic (TK-TD) model. Further, the proposed TK-TD model was used to predict Cu toxicity in laboratory artificial waters as well as natural water samples. The predictive performance of the TK-TD model was evaluated in comparison to the biotic ligand model (BLM). The results showed that increasing Ca, Mg, pH, and fulvic acid (FA) levels significantly mitigated Cu toxicity in larvae, while K and Na levels had no significant effect on Cu toxicity. A predictive TK-TD model based on these data described 91 % of Cu accumulation and 87 % of survival of larvae exposed to Cu under 0, 2.5, 5, 10 mg/L FA. Compared with BLM, TK-TD model predicted better Cu accumulation and toxicity for an independent dataset in low DOC concentration (<10.95 mg L-1) of 9 sites in Haihe river (Tianjin, China) media during 96 h exposure. The BLM under-predicted the acute Cu toxicity to larvae when compared with observed values. In high DOC concentration (13.12-17.78 mg L-1) among three field sites, BLM and TK-TD model both under-predicted the acute Cu toxicity to larvae when compared with observed values. Our research provides a TK-TD approach for predicting Cu toxicity under complex water chemistry conditions and deriving Cu-WQC in different scenarios where there exist limits for using the BLM.
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Affiliation(s)
- Yongfei Gao
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China
| | - Jianfeng Feng
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China.
| | - Jingxue Zhu
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China
| | - Lin Zhu
- Key Laboratory of Pollution Process and Environmental Criteria of Ministry of Education and Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, China
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12
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Xiang L, Chen XT, Yu PF, Li XH, Zhao HM, Feng NX, Li YW, Li H, Cai QY, Mo CH, Li QX. Oxalic Acid in Root Exudates Enhances Accumulation of Perfluorooctanoic Acid in Lettuce. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13046-13055. [PMID: 33030897 DOI: 10.1021/acs.est.0c04124] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Perfluorooctanoic acid (PFOA) is bioaccumulative in crops. PFOA bioaccumulation potential varies largely among crop varieties. Root exudates are found to be associated with such variations. Concentrations of low-molecular-weight organic acids (LMWOAs) in root exudates from a PFOA-high-accumulation lettuce variety are observed significantly higher than those from PFOA-low-accumulation lettuce variety (p < 0.05). Root exudates and their LMWOAs components exert great influences on the linear sorption-desorption isotherms of PFOA in soils, thus activating PFOA and enhancing its bioavailability. Among root exudate components, oxalic acid is identified to play a key role in activating PFOA uptake, with >80% attribution. Oxalic acid at rhizospheric concentrations (0.02-0.5 mM) can effectively inhibit PFOA sorption to soils by decreasing hydrophobic force, electrostatic attraction, ligand exchange, and cation-bridge effect. Oxalic acid enhances dissolution of metallic ions, iron/aluminum oxides, and organic matters from soils and forms oxalate-metal complexes, based on nuclear magnetic resonance spectra, ultraviolet spectra, and analyses of metal ions, iron/aluminum organometallic complexes, and dissolved organic carbon. The findings not only reveal the activation process of PFOA in soils by root exudates, particularly oxalic acid at rhizospheric concentrations, but also give an insight into the mechanism of enhancing PFOA accumulation in lettuce varieties.
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Affiliation(s)
- Lei Xiang
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Xiao-Ting Chen
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Peng-Fei Yu
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Xin-Hong Li
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Hai-Ming Zhao
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Nai-Xian Feng
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Yan-Wen Li
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Hui Li
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Quan-Ying Cai
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Ce-Hui Mo
- Guangdong Provincial Research Center for Environment Pollution Control and Remediation Materials, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
| | - Qing X Li
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
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Liu S, Liu Y, Pan B, He Y, Li B, Zhou D, Xiao Y, Qiu H, Vijver MG, Peijnenburg WJGM. The promoted dissolution of copper oxide nanoparticles by dissolved humic acid: Copper complexation over particle dispersion. CHEMOSPHERE 2020; 245:125612. [PMID: 31864948 DOI: 10.1016/j.chemosphere.2019.125612] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 09/04/2019] [Accepted: 12/09/2019] [Indexed: 05/10/2023]
Abstract
Humic substances are the dominant dissolved organic matter fraction in the aqueous phase of environmental media. They would inevitably react with chemicals released into the environment. The influence of dissolved humic acid (DHA) on the dissolution and dispersion of copper oxide nanoparticles (CuO NPs, 50 nm, 49.57 mg L-1) was therefore investigated in the present study. In addition to dispersing CuO NPs and reducing the size of the aggregates, the amount of released Cu from CuO NPs was found to increase over time with increasing concentrations of DHA, 96% of which was present as organic complexes after 72 h. At DHA concentrations exceeding 16.09 mg C L-1, the complexation coefficients of DHA with Cu and the adsorptivity of CuO NPs to DHA were both reduced due to increased homo-conjugation of DHA as promoted by negative charge-assisted H-bond. Although the adsorption capacity of DHA kept increasing up to 57.07 mg C L-1, the hydrodynamic diameter and ζ-potential were similar and the percentages of total released Cu continued to increase linearly to 4.92% at higher levels of DHA (30.13-57.07 mg C L-1). Thereupon, DHA promoted the dissolution of CuO NPs in a concentration-dependent fashion. The driving force was complexation of Cu by DHA, rather than the balancing between the exposed and the covered surface area of the CuO NPs due to DHA adsorption. Our findings facilitate understanding the underlying mechanisms on how DHA impacts the CuO NPs environmental behavior (or fate) as well as on their kinetics.
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Affiliation(s)
- Siqian Liu
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
| | - Yang Liu
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China.
| | - Bo Pan
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
| | - Ying He
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
| | - Bowen Li
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
| | - Dandan Zhou
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, China; Yunnan Provincial Key Laboratory of Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, China
| | - Yinlong Xiao
- College of Environmental Sciences, Sichuan Agricultural University, Wenjiang, 611130, China
| | - Hao Qiu
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Martina G Vijver
- Institute of Environmental Sciences (CML), Leiden University, Leiden, 2300, RA, the Netherlands
| | - Willie J G M Peijnenburg
- Institute of Environmental Sciences (CML), Leiden University, Leiden, 2300, RA, the Netherlands; National Institute of Public Health and the Environment (RIVM), Center for Safety of Substances and Products, Bilthoven, 3720, BA, the Netherlands
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Chu D, Ye ZL, Chen S. Interactions among low-molecular-weight organics, heavy metals, and Fe(III) during coagulation of landfill leachate nanofiltration concentrate. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 104:51-59. [PMID: 31962217 DOI: 10.1016/j.wasman.2020.01.015] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/08/2020] [Accepted: 01/11/2020] [Indexed: 06/10/2023]
Abstract
The generation of landfill leachate nanofiltration concentrate (LLNC) has been a dilemma for leachate treatment plants because it contains large amounts of refractory organics with low molecular weight (LMWO), as well as heavy metals (HMs), and is difficult to handle. The coagulation removal of LMWOs is a significant challenge, as is the removal of HMs bonded to LMWOs. In this study, coagulation through the dosing of FeCl3 was used to remove LMWOs and HMs from LLNC. The results interestingly demonstrated that the removal rates of dissolved organic carbon (DOC), Cr, Ni, and As reached up to 84.1% ± 3.9%, 91.0 ± 1.1%, 73.1 ± 2.2%, and 96.9 ± 1.5%, respectively. The partition of LMWO components, as well as the interactions among the LMWOs, HMs, and Fe(III) were investigated to determine the mechanism behind the LMWO and HM removal. LMWOs with a high degree of humification, including humic and fulvic acid-like components, were preferentially removed through aggregation and electrostatic attraction originating from the specialistic adsorption of Fe2(OH)24+ and Fe3(OH)45+. In addition to being removed, a portion of these two components was dissociated into aromatic protein I, aromatic protein II, and soluble microbial by-product-like materials due to an acid effect and the formation of inner-sphere complexes. A redundancy analysis revealed that As, Cr, and Ni are mainly removed through the electrostatic attraction of Fe(III), bonding to humic substances and hydrophilic organics, respectively. The outcomes provide a new understanding on the coagulation removal of LMWOs and HMs.
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Affiliation(s)
- Dongyuan Chu
- Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, No. 1799 Jimei Road, Xiamen City, Fujian 361021, China; University of Chinese Academy of Sciences, No. 19 (A) Yuquan Road, Beijing 100049, China.
| | - Zhi-Long Ye
- Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, No. 1799 Jimei Road, Xiamen City, Fujian 361021, China.
| | - Shaohua Chen
- Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, No. 1799 Jimei Road, Xiamen City, Fujian 361021, China.
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Li H, Wei C, Zhang D, Pan B. Adsorption of bisphenol A on dispersed carbon nanotubes: Role of different dispersing agents. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 655:807-813. [PMID: 30481707 DOI: 10.1016/j.scitotenv.2018.11.310] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 11/16/2018] [Accepted: 11/20/2018] [Indexed: 06/09/2023]
Abstract
Although the adsorption of organic contaminants on carbon nanotubes (CNTs) and the dispersion of CNTs have been extensively investigated separately, the adsorption behavior of organic contaminants on dispersed CNTs, which may be a missing link to understanding their environmental behavior and risks, remain unclear yet rarely studied. In this study, the effect of the dispersing agent structure on the adsorption characteristics of BPA (a representative organic contaminant) on dispersed CNTs were investigated using tannic acid (TA), sodium dodecylbenzenesulfonate (SDBS), and gallic acid (GA) as model dispersing agents. Our results showed that at low dispersing agent concentrations, adsorption of TA could lead to higher CNT suspension than adsorption of SDBS and GA due to greater steric hindrance. However, the presence of TA reduced the adsorption of BPA due to strong competitive adsorption on dispersed CNTs. At high concentrations of TA, the suspension of CNTs was reduced by the "bridging effect," in which adjacent dispersed CNTs form hydrogen bonds and re-aggregate. However, the adsorption of BPA dramatically increased due to the enhanced partition of BPA into pseudomicelles of TA on dispersed CNTs, as indicated by the significantly increased index of heterogeneity at high TA concentration. Transmission electron microscopy images confirmed the formation of TA pseudomicelles. This study highlights the key role of the dispersing agent structure on CNT dispersion and adsorption of organic contaminants. The high mobility and transport of CNT-adsorbed contaminants may lead to higher environmental risks compared with aggregated CNTs.
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Affiliation(s)
- Hao Li
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming 650500, China
| | - Chaoxian Wei
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming 650500, China
| | - Di Zhang
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming 650500, China.
| | - Bo Pan
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming 650500, China
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17
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Ni J, Pignatello JJ. Charge-assisted hydrogen bonding as a cohesive force in soil organic matter: water solubility enhancement by addition of simple carboxylic acids. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2018; 20:1225-1233. [PMID: 30084855 DOI: 10.1039/c8em00255j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Weak bonds between molecular segments and between separate molecules of natural organic matter (OM) govern OM solubility, adsorption, supramolecular association in solution, and complexation with metal ions and oxides. We tested the hypothesis that especially strong hydrogen bonds, known as (negative) charge-assisted hydrogen bonds, (-)CAHB, contribute significantly to OM cohesion and play a role in the water solubility of solid-phase OM. The (-)CAHB, exemplified by structures such as (-CO2HO2C-)- and (-CO2HO-)-, may form between weak acids with similar proton affinity, and is shorter, more covalent, and much stronger than ordinary hydrogen bonds. Using a high-organic reference soil, we show that (-)CAHBs within the solid OM phase (intra-OM) are disrupted by solutions of aliphatic and aromatic acids, resulting in enhanced solubility of OM. The aromatic acids included naturally occurring plant exudate compounds. At constant pH and ionic strength, OM solubility increased with added organic acid concentration and molecular weight. Polar compounds incapable of forming (-)CAHBs, such as alkanols, acetonitrile, and dimethyl sulfoxide, were ineffective. Solubility enhancement showed behavior consistent with (-)CAHB theory and published observations-namely, (i) that formate is more effective than acetate due to its tendency to form stronger (-)CAHBs; (ii) that solubility enhancement peaks at pH ∼5-6, where the product of the concentration of the interacting carboxylate ions reaches a maximum; and (iii) that elution of acetate or formate through soil columns releases hydroxide ion, consistent with formation of (-)CAHBs between added acid and free weak acid groups on the solid OM. The results support the hypothesis that the (-)CAHB contributes to the cohesion of OM in the solid state.
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Affiliation(s)
- Jinzhi Ni
- Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, 123 Huntington St., New Haven, Connecticut 06504-1106, USA.
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