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Jia X, Wang Y, Zhao M, Zhang F, Li C, Ma D. Migration and morphological transformation patterns of heavy metals on sludge cells and extracellular polymeric substances (EPS) under the influence of different treatments. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:21578-21590. [PMID: 38393566 DOI: 10.1007/s11356-024-32398-8] [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: 09/13/2023] [Accepted: 02/03/2024] [Indexed: 02/25/2024]
Abstract
The impediment of sludge resource utilization stems from the presence of heavy metals within the sludge matrix. To optimize heavy metal removal techniques from undried sludge, it is essential to study the distribution of heavy metals in the sludge flocs structure and the changes in morphology in the sludge cells after different treatments. In this study, the sludge was subjected to chemical treatments using citric acid (CA), EDTA, and saponin, as well as electrokinetic treatment at 2 V/cm. The distribution and migration of Cu, Ni, and Zn in sludge flocs after various treatment methods were analyzed. The heavy metals were found to migrate from intracellular to extracellular polymeric substances (EPS) without causing extensive sludge cell lysis. They gradually diffused outward with the dispersion of the EPS layer. The migration efficiency of the three heavy metals in the sludge flocs was Zn, Ni, and Cu. This was mainly related to the initial distribution and morphology of the heavy metals. Under the influence of chemicals and an electric field, the acid-soluble and reducible heavy metals in the cells partially migrated to the EPS, while the stable heavy metals transformed into an unstable state. Furthermore, the order of chemical reagents in terms of their effect on the migration efficiency of heavy metals was CA > EDTA > Saponin, owing to the varying binding strengths of heavy metals and their impact on the degree of loosening of the EPS. Especially after CA treatment a greater proportion of Cu, Ni, and Zn were transferred from the cells to the EPS. The acidification effect near the anode during electrokinetic treatment intensifies the migration of heavy metals. This study provides basic research for subsequent engineering optimization aimed at removing heavy metals from sludge.
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Affiliation(s)
- Xiaoyu Jia
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China
| | - Yuxin Wang
- Lianhe Equator Environmental Impact Assessment Co Ltd, Tianjin, 300350, People's Republic of China
| | - Miaomiao Zhao
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China
| | - Fan Zhang
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China
| | - Chen Li
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China
| | - Degang Ma
- School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China.
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Sun J, Luo J, Ma R, Lin J, Fang L. Effects of microwave and plastic content on the sulfur migration during co-pyrolysis of biomass and plastic. CHEMOSPHERE 2023; 305:135457. [PMID: 36584830 DOI: 10.1016/j.chemosphere.2022.135457] [Citation(s) in RCA: 55] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 06/19/2022] [Accepted: 06/20/2022] [Indexed: 05/25/2023]
Abstract
In order to reduce the risks of sulfur-containing contaminants present in biofuels, the effects of microwave and content of hydrogen donor on the cracking of C-S bonds and the migration of sulfur were studied by co-pyrolysis of biomass and plastic. The synergistic mechanism of microwave and hydrogen donor was explored from the perspective of deducing the evolution of sulfur-containing compounds based on microwave thermogravimetric analysis. By combining temperature-weight curves, it was found that microwaves and hydrogen radicals promoted the cracking of sulfur-containing compounds and increased the mass loss of biomass during pyrolysis. The mixing ratio of hydrogen donor (plastic) was the key parameter resulting in the removal of sulfur from oil. By adjusting the mixing ratio, the yield of co-pyrolyzed oil was three times higher than that of cow dung pyrolysis alone and the relative removal rate of sulfur reached 73.67%. The relative content of sulfur in the oil was reduced by 73.77% due to the escape of sulfur-containing gases (H2S, COS and C2H5SH) and the formation of sulfate crystals in the char. Microwave selectively heated sulfur-containing organics and hydrogen radicals stimulated the breaking of C-S bonds, which improved the cracking efficiency of the oil. This breaking will provide a theoretical and technological reference for the environmentally friendly treatment of biomass and biofuels.
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Affiliation(s)
- Jiaman Sun
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Juan Luo
- School of Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Rui Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China.
| | - Junhao Lin
- School of Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Lin Fang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, 518060, China
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Noller C, Friesl-Hanl W, Hood-Nowotny R, Watzinger A. Remediating Garden Soils: EDTA-Soil Washing and Safe Vegetable Production in Raised Bed Gardens. TOXICS 2022; 10:652. [PMID: 36355942 PMCID: PMC9696853 DOI: 10.3390/toxics10110652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 10/26/2022] [Accepted: 10/27/2022] [Indexed: 06/16/2023]
Abstract
Soil remediation is an important practice in the restoration of heavy metal-contaminated soils and reduce the heavy metal exposure of the local population. Here, we investigated the effect of an ex-situ soil washing technique, based on ethylenediaminetetraacetic acid (EDTA) as a chelating agent, on a contaminated Cambisol. Lead, Cd and Zn were investigated in different soil fractions, drainage water and four vegetables from August 2019 to March 2021. Three treatments consisting of (C) contaminated soil, (W) washed soil and (WA) washed soil amended with vermicompost and biochar were investigated in an outdoor raised bed set up. Our results showed that the total and bioavailable metal fractions were significantly reduced but failed to meet Austrian national guideline values. Initial concentrations in the soil leachate increased significantly, especially for Cd. Vegetables grown on the remediated soil took up significantly lower amounts of all heavy metals and were further reduced by the organic amendment, attaining acceptable values within EU guideline values for food safety. Only spinach exceeded the thresholds in all soil treatments. The increase in soil pH and nutrient availability led to significantly higher vegetable yields.
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Jez E, Bravo C, Lestan D, Gluhar S, Martin-Neto L, De Nobili M, Contin M. Changes in organic matter composition caused by EDTA washing of two soils contaminated with toxic metals. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:65687-65699. [PMID: 34322798 PMCID: PMC8636399 DOI: 10.1007/s11356-021-15406-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
Two soils contaminated with potentially toxic metals (PTMs) contrasting in pH and mineralogy were remediated with CaEDTA, and changes in soil organic matter (SOM) composition were investigated. Previous studies showed no significant loss of SOM from CaEDTA-treated soils, but the results of our study reflected significant decreases (from 46 to 49%) in the free fraction of humic acids (HAs). Remediation affected the composition of the free HA fraction via disturbance of intermolecular bonds - an increase in phenolic and aromatic groups with a simultaneous decrease in carbohydrates - which was confirmed by FTIR spectroscopy in both soils. Because non-radical molecules such as carbohydrates were selectively removed, the concentration of free radicals in the free HA fraction increased in acidic soil. The bound fraction of HAs and fulvic acids (FAs) in SOM, which are important due to their stability and the permanent effects they have on the soil's physical properties, remained unchanged in both remediated soils. The effect of soil recultivation was observed only in the excitation emission matrix (EEM) fluorescence spectra of HAs. In terms of SOM, CaEDTA soil washing can be considered moderately conservative; however, the restoration of free humic fractions is likely to be a long-term process.
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Affiliation(s)
- Erika Jez
- Wine Research Centre, University of Nova Gorica, Vipavska cesta 13, 5000, Nova Gorica, Slovenia
| | - Carlo Bravo
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Via delle Scienze 206, 33100, Udine, Italy
| | - Domen Lestan
- Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000, Ljubljana, Slovenia
| | - Simon Gluhar
- Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000, Ljubljana, Slovenia
| | | | - Maria De Nobili
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Via delle Scienze 206, 33100, Udine, Italy
| | - Marco Contin
- Department of Agricultural, Food, Environmental and Animal Sciences, University of Udine, Via delle Scienze 206, 33100, Udine, Italy.
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Hemmat-Jou MH, Safari-Sinegani AA, Che R, Mirzaie-Asl A, Tahmourespour A, Tahmasbian I. Toxic trace element resistance genes and systems identified using the shotgun metagenomics approach in an Iranian mine soil. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:4845-4856. [PMID: 32949366 DOI: 10.1007/s11356-020-10824-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 09/13/2020] [Indexed: 05/27/2023]
Abstract
This study aimed to identify the microbial communities, resistance genes, and resistance systems in an Iranian mine soil polluted with toxic trace elements (TTE). The polluted soil samples were collected from a mining area and compared against non-polluted (control) collected soils from the vicinity of the mine. The soil total DNA was extracted and sequenced, and bioinformatic analysis of the assembled metagenomes was conducted to identify soil microbial biodiversity, TTE resistance genes, and resistance systems. The results of the employed shotgun approach indicated that the relative abundance of Proteobacteria, Firmicutes, Bacteroidetes, and Deinococcus-Thermus was significantly higher in the TTE-polluted soils compared with those in the control soils, while the relative abundance of Actinobacteria and Acidobacteria was significantly lower in the polluted soils. The high concentration of TTE increased the ratio of archaea to bacteria and decreased the alpha diversity in the polluted soils compared with the control soils. Canonical correspondence analysis (CCA) demonstrated that heavy metal pollution was the major driving factor in shaping microbial communities compared with any other soil characteristics. In the identified heavy metal resistome (HV-resistome) of TTE-polluted soils, major functional pathways were carbohydrates metabolism, stress response, amino acid and derivative metabolism, clustering-based subsystems, iron acquisition and metabolism, cell wall synthesis and capsulation, and membrane transportation. Ten TTE resistance systems were identified in the HV-resistome of TTE-polluted soils, dominated by "P-type ATPases," "cation diffusion facilitators," and "heavy metal efflux-resistance nodulation cell division (HME-RND)." Most of the resistance genes (69%) involved in resistance systems are affiliated to cell wall, outer membrane, periplasm, and cytoplasmic membrane. The finding of this study provides insight into the microbial community in Iranian TTE-polluted soils and their resistance genes and systems.
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Affiliation(s)
| | | | - Rongxiao Che
- Institute of International Rivers and Eco-security, Yunnan University, Kunming, 650091, China
| | - Asghar Mirzaie-Asl
- Department of Biotechnology, Bu-Ali Sina University, Hamedan, 6517838695, Iran
| | - Arezoo Tahmourespour
- Department of Basic Medical Sciences, Islamic Azad University (Isfahan Branch), Isfahan, Iran
| | - Iman Tahmasbian
- Department of Agriculture and Fisheries, Queensland Government, Toowoomba, QLD, 4350, Australia
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Fukushi K, Yamaguchi J, Shibasaki Y, Fujimori A. Tracking and Recovery of Metal Desorption from Organized Films of Polyguanamine Derivatives having Cyclic Moieties. ChemistrySelect 2020. [DOI: 10.1002/slct.202003172] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Keito Fukushi
- Graduate School of Science and Engineering Saitama University, 255 Shimo-okubo, Sakura-ku Saitama 338-8570 Japan
| | - Junto Yamaguchi
- Faculty of Engineering Saitama University, 255 Shimo-okubo, Sakura-ku Saitama 338-8570 Japan
| | - Yuji Shibasaki
- Department of Chemistry and Biological Sciences, Faculty of Science and Engineering Iwate University, 4–3-5 Ueda, Morioka Iwate 020-8551 Japan
| | - Atsuhiro Fujimori
- Graduate School of Science and Engineering Saitama University, 255 Shimo-okubo, Sakura-ku Saitama 338-8570 Japan
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Wang T, Wang S, Tang X, Fan X, Yang S, Yao L, Li Y, Han H. Isolation of urease-producing bacteria and their effects on reducing Cd and Pb accumulation in lettuce (Lactuca sativa L.). ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:8707-8718. [PMID: 31912394 DOI: 10.1007/s11356-019-06957-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 11/04/2019] [Indexed: 06/10/2023]
Abstract
Excess Cd and Pb in agricultural soils enter the food chain and adversely affect all organisms. Therefore, it is important to find an eco-friendly way to reduce heavy metal accumulation in vegetables. We used urea agar plates to isolate urease-producing bacteria from the rhizosphere soil of lettuce in Cd- and Pb-contaminated farmland and investigated their ability to produce urease and immobilize heavy metals. The effects of these strains on the biomass, quality, and Cd and Pb accumulation of lettuce were also studied. The results showed that two urease-producing bacteria, Enterobacter bugandensis TJ6 and Bacillus megaterium HD8, were screened from the rhizosphere soil of lettuce. They had a high ability to produce urease (44.5 mS cm-1 min-1 OD600-1 and 54.2 mS cm-1 min-1 OD600-1, respectively) and IAA (303 mg L-1 and 387 mg L-1, respectively). Compared with the control, inoculation with strains TJ6 and HD8 reduced the Cd (75.3-85.8%) and Pb (74.8-87.2%) concentrations and increased the pH (from 6.92 to 8.13-8.53) in solution. A hydroponic experiment showed that the two strains increased the biomass (31.3-55.2%), improved the quality (28.6-52.6% for the soluble protein content and 34.8-88.4% for the vitamin C (Vc) content), and reduced the Cd (25.6-68.9%) and Pb (48.7-78.8%) contents of lettuce shoots (edible tissue). In addition, strain HD8 had a greater ability than strain TJ6 to reduce lettuce Cd and Pb uptake and water-soluble Cd and Pb levels in solution. These data show that the urease-producing bacteria protect lettuce against Cd and Pb toxicity by extracellular adsorption, Cd and Pb immobilization, and increased pH. The effects of heavy metal immobilization by the two strains can guarantee vegetable safety in situ for the bioremediation of heavy metal-polluted farmland.
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Affiliation(s)
- Tiejun Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, People's Republic of China
| | - Shilin Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, People's Republic of China
| | - Xingchun Tang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, People's Republic of China
| | - Xianpeng Fan
- Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan, 430062, People's Republic of China
| | - Sheng Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, People's Republic of China
| | - Lunguang Yao
- Collaborative Innovation of Water Security for the Water Source Region of Mid-line of the South-to-North Diversion Project of Henan Province, College of Agricultural Engineering, Nanyang Normal University, Nanyang, 473061, People's Republic of China
| | - Yadong Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, People's Republic of China.
| | - Hui Han
- Collaborative Innovation of Water Security for the Water Source Region of Mid-line of the South-to-North Diversion Project of Henan Province, College of Agricultural Engineering, Nanyang Normal University, Nanyang, 473061, People's Republic of China.
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Ma Q, Li J, Lee CCC, Long X, Liu Y, Wu QT. Combining potassium chloride leaching with vertical electrokinetics to remediate cadmium-contaminated soils. ENVIRONMENTAL GEOCHEMISTRY AND HEALTH 2019; 41:2081-2091. [PMID: 30838487 DOI: 10.1007/s10653-019-00259-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 01/30/2019] [Indexed: 06/09/2023]
Abstract
This study evaluated the feasibility of combining potassium chloride (KCl) leaching and electrokinetic (EK) treatment for the remediation of cadmium (Cd) and other metals from contaminated soils. KCl leaching was compared at three concentrations (0.2%, 0.5%, and 1% KCl). EK treatment was conducted separately to migrate the metals in the topsoil to the subsoil. The combined approach using KCl leaching before or after EK treatment was compared. For the single vertical EK treatment, the removal of Cd, lead (Pb), copper (Cu) and zinc (Zn) from the topsoil (0-20 cm) was 9.38%, 4.80%, 0.95%, and 10.81%, respectively. KCl leaching at 1% KCl removed 84.06% Cd, 9.95% Pb, 4.34% Cu, and 19.93% Zn from the topsoil, with higher removal efficiency than that of the 0.2% and 0.5% KCl leaching treatments. By combining the KCl leaching and EK treatment, the removal efficiency of heavy metals improved, in particular for the 1% KCl + EK treatment, where the removal rate of Cd, Pb, Cu, and Zn from the upper surface soil reached 97.79%, 17.69%, 14.37%, and 41.96%, respectively. Correspondingly, the soil Cd content decreased from 4 to 0.21 mg/kg, and was below the Chinese standard limit of 0.3 mg/kg soil. These results indicate that 1% KCl + EK treatment is a good combination technique to mitigate Cd pollution from contaminated soils used for growing rice and leafy vegetables.
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Affiliation(s)
- Qiang Ma
- Key Laboratory on Soil Environment and Waste Reuse in Agriculture of Guangdong Higher Education Institutes, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, China
| | - Jun Li
- Key Laboratory on Soil Environment and Waste Reuse in Agriculture of Guangdong Higher Education Institutes, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, China
| | - Charles C C Lee
- School of Environmental and Life Sciences, University of Newcastle (Australia) Singapore, 6 Temasek Blvd, Singapore, 038986, Singapore
| | - Xinxian Long
- Key Laboratory on Soil Environment and Waste Reuse in Agriculture of Guangdong Higher Education Institutes, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, China
| | - Yongmao Liu
- Inner Mongolia Research Institute of Metallurgy, Hohhot, 010010, China
| | - Qi-Tang Wu
- Key Laboratory on Soil Environment and Waste Reuse in Agriculture of Guangdong Higher Education Institutes, College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, China.
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Xu Y, Li J, Xia W, Sun Y, Qian G, Zhang J. Enhanced remediation of arsenic and chromium co-contaminated soil by eletrokinetic-permeable reactive barriers with different reagents. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:3392-3403. [PMID: 30511220 DOI: 10.1007/s11356-018-3842-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/23/2018] [Indexed: 06/09/2023]
Abstract
The present work focused on the effects of different reagents on the remediation of arsenic and chromium co-contaminated soil by electrokinetic technology coupled with permeable reactive barrier (EK-PRB). In a running of EK-PRB, reductant (ascorbic acid, sodium citrate) and chelating agent (EDTA-2Na) were used to pretreat contaminated soil together with CaAl-LDH as reactive materials for PRB. As a result, the chelating agent improved the removals of As and Cr in co-contaminated soil. However, the reducing agent only increased As removal. When 0.05 M sodium citrate was used in pretreatment, the As removal attained the maximum of 50.5%, although Cr removal was only 44.1% at the same time. When the contaminated soil was pretreated with 0.01 M EDTA-2Na, the Cr removal increased to 54.28%, although As removal was only 26.3%. After EK-PRB, the As and Cr were efficiently captured by CaAl-LDH, resulting in maximal fixed amounts of 126.5 mg/kg (As) and 1507.6 mg/kg (Cr). The XRD and FITR analyses of LDH indicated that As was mainly adsorbed on the surface of LDH. As for Cr, it was mainly intercalated into interlayer of LDH.
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Affiliation(s)
- Yunfeng Xu
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China
| | - Jiangpeng Li
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China
| | - Wei Xia
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China
| | - Ying Sun
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China
| | - Guangren Qian
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China
| | - Jia Zhang
- School of Environmental and Chemical Engineering, Shanghai University, No. 99 Shangda Rd., Shanghai, 200444, People's Republic of China.
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Evaluation of Acid Leaching on the Removal of Heavy Metals and Soil Fertility in Contaminated Soil. J CHEM-NY 2018. [DOI: 10.1155/2018/5036581] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heavy metal-contaminated soils were leached with various acid reagents, and a series of treatments was assessed to understand soil fertility after acid leaching. Aqua regia digestion and a five-step sequential extraction procedure were applied to determine heavy metal distribution. The average total concentrations of Zn, Cd, Cu, and Pb for contaminated soil were 1334, 25, 263, and 525 mg·kg−1 based on the ICP/AES quantitative analysis. Other than Pb extracted by H2SO4, over 50% removal efficiency of other heavy metals was achieved. A five-step sequential extraction revealed that the bound-to-carbonate and bound-to-Fe-Mn oxides were the major forms of the heavy metals in the soil. The addition of organic manure considerably promoted soil fertility and increased soil pH after acid leaching. Seed germination experiments demonstrated that after acid leaching, the soil distinctly inhibited plant growth and the addition of manure enhanced seed germination rate from 35% to 84%. Furthermore, the procedure of soil turnover after acid leaching and manure addition greatly increased seed germination rate by 61% and shortened the initial germination time. Seed germination in untreated soil was superior to that in acid-leached soil, illustrating that the phytotoxic effect of acid leaching is more serious than that of heavy metals.
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