Advances in Remediation of Contaminated Sites: Volume I

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 161756

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Special Issue Editors

School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
Interests: pollution control; soil remediation; e-waste; mining area; heavy hetals; persistent organic pollutants; polybrominated diphenyl ethers
Special Issues, Collections and Topics in MDPI journals
College of Resources and Environment, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
Interests: soil remediation; photoelectrochemical catalysis; catalytic degradation; acid mine drainage; biochar; heavy metals
Special Issues, Collections and Topics in MDPI journals
School of Ecology and Environment, Hainan University, Haikou 570228, China
Interests: soil washing; photo-transformation; surfactant; e-waste; polychlorinated biphenyls; bi-metal; emerging contaminants
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the development of the social economy, the population has increased sharply, and the land area involved in production and human life is also gradually increasing. To meet the production and development needs of society, land resources have been synchronously damaged and polluted to certain extents due to human activity. As land resources are non-renewable, developing land restoration and improvement approaches with efficiency is an important approach for achieving the sustainable development of human society. Site remediation technology has developed rapidly in recent years and has brought hope for land remediation. However, after this rapid development, land remediation technology has also encountered bottlenecks, and new breakthroughs are urgently required.

This Special Issue “Advances in Remediation of Contaminated Sites: Volume I” aims to collect the latest progress in contaminated site remediation, in order to help solve the new bottleneck in the development of site remediation technology. Topics of interest include but are not limited to:

  1. Survey and assessment of contaminated sites
  2. Environmental processes and effects of pollutants
  3. Remediation technology and its application in contaminated sites
  4. Remediation strategy and management in contaminated sites

Prof. Dr. Guining Lu
Prof. Dr. Zenghui Diao
Dr. Kaibo Huang
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • contaminated sites
  • survey and assessment
  • remediation technology
  • remediation strategy
  • site management
  • heavy metals
  • organic pollutants

Published Papers (21 papers)

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Editorial

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5 pages, 774 KiB  
Editorial
Advances in Remediation of Contaminated Sites
by Kaibo Huang, Zenghui Diao and Guining Lu
Processes 2023, 11(1), 157; https://doi.org/10.3390/pr11010157 - 04 Jan 2023
Viewed by 14540
Abstract
With the development of the social economy, the population has increased sharply, and the land area involved in people’s production and life is also gradually increasing [...] Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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Research

Jump to: Editorial, Review

14 pages, 5367 KiB  
Article
Experimental and Modeling Study on Cr(VI) Migration from Slag into Soil and Groundwater
by Xiange Wu, Tiantian Ye, Chunsheng Xie, Kun Li, Chang Liu, Zhihui Yang, Rui Han, Honghua Wu and Zhenxing Wang
Processes 2022, 10(11), 2235; https://doi.org/10.3390/pr10112235 - 31 Oct 2022
Cited by 2 | Viewed by 5153
Abstract
The transport and prediction of hexavalent chromium (Cr(VI)) contamination in “slag–soil–groundwater” is one with many uncertainties. Based on the column experiments, a migration model for Cr(VI) in the slag–soil–groundwater system was investigated. The hydraulic conductivity (Kt), distribution coefficient (Kd), retardation factor (Rd), and [...] Read more.
The transport and prediction of hexavalent chromium (Cr(VI)) contamination in “slag–soil–groundwater” is one with many uncertainties. Based on the column experiments, a migration model for Cr(VI) in the slag–soil–groundwater system was investigated. The hydraulic conductivity (Kt), distribution coefficient (Kd), retardation factor (Rd), and other hydraulic parameters were estimated in a laboratory. Combining these hydraulic parameters with available geological and hydrogeological data for the study area, the groundwater flow and Cr(VI) migration model were developed for assessing groundwater contamination. Subsequently, a Cr(VI) migration model was developed to simulate the transport of Cr(VI) in the slag–soil–groundwater system and predict the effect of three different control programs for groundwater contamination. The results showed that the differences in the measured and predicted groundwater head values were all less than 3 m. The maximum and minimum differences in Cr(VI) between the measured and simulated values were 1.158 and 0.001 mg/L, respectively. Moreover, the harmless treatment of Cr(VI) slag considerably improved the quality of groundwater in the surrounding areas. The results of this study provided a reliable mathematical model for transport process analysis and prediction of Cr(VI) contamination in a slag–soil–groundwater system. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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14 pages, 2176 KiB  
Article
The Difference of Lead Accumulation and Transport in Different Ecotypes of Miscanthus floridulus
by Jianqiao Qin, Huarong Zhao, Hao Liu, Min Dai, Peng Zhao, Xi Chen and Xiange Wu
Processes 2022, 10(11), 2219; https://doi.org/10.3390/pr10112219 - 28 Oct 2022
Cited by 4 | Viewed by 4363
Abstract
Miscanthus floridulus is a plant with a high biomass and heavy metal tolerance, which is a good candidate for phytoremediation. Pot experiments were conducted to compare the growth response, Pb enrichment ability, and the effect on Pb speciation of two ecotypes of M. [...] Read more.
Miscanthus floridulus is a plant with a high biomass and heavy metal tolerance, which is a good candidate for phytoremediation. Pot experiments were conducted to compare the growth response, Pb enrichment ability, and the effect on Pb speciation of two ecotypes of M. floridulus from the Dabaoshan Mining Area and the non-mining area of Boluo County, Huizhou, in soils with different Pb contents. The results showed that two ecotypes of M. floridulus had different growth responses to Pb concentrations in soil. Under a low concentration of Pb (100 mg·kg−1) treatment, the aboveground biomass of the non-mining area plant ecotype was significantly affected, while the plants with the mining area ecotype were not significantly affected. When the concentration of Pb increased, the aboveground biomass of the non-mining ecotype was 30.2–41.1% of the control, while that of the mining ecotype was 57.8–65.0% of the control. The root biomass of the non-mining ecotype decreased with the increase of treatment concentration, accounting for 57.8–64.2% of the control, while that of the mining ecotype increased significantly, accounting for 119.5–138.6% of the control. The Pb content in the shoots and roots of the mining ecotype M. floridulus increased rapidly with the increase of the Pb treatment concentration in the soil, and the increase in speed was obviously faster than that of the non-mining ecotype. The total amount of Pb accumulated in the roots of the ecotype from the mining area was much greater than that of the ecotype from the non-mining area, and increased significantly with the increase of Pb concentration in the soil (p < 0.05). With the aggravation of Pb stress, the transfer coefficient and tolerance index of the two ecotypes decreased by different degrees. The transfer coefficient and tolerance index of the mining ecotype were significantly higher than those of the non-mining ecotype. Pearson correlation analysis showed that root biomass was positively correlated with shoot biomass, and shoot biomass was negatively correlated with Pb content in both root and shoot, indicating that Pb accumulation in root and shoot was toxic to plants and inhibited the growth of M. floridulus. The mining ecotypes showed stronger tolerance to and enrichment of Pb. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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12 pages, 5803 KiB  
Article
Straw Biochar at Different Pyrolysis Temperatures Passivates Pyrite by Promoting Electron Transfer from Biochar to Pyrite
by Xiaohua Shu, Wei Tian, Shiqing Xiong, Wenlong Zhang and Qian Zhang
Processes 2022, 10(10), 2148; https://doi.org/10.3390/pr10102148 - 21 Oct 2022
Cited by 1 | Viewed by 4847
Abstract
To control acid mine drainage (AMD) at source, biochar, a new green and environmentally friendly passivator has been introduced to passivate pyrite. However, the raw material and pyrolysis temperature largely determine the physical and chemical properties of biochar, the causal relationship between biochar [...] Read more.
To control acid mine drainage (AMD) at source, biochar, a new green and environmentally friendly passivator has been introduced to passivate pyrite. However, the raw material and pyrolysis temperature largely determine the physical and chemical properties of biochar, the causal relationship between biochar and pyrite and the underlying mechanism are still unknown. Here, biochar materials (rice-straw biochar (RSB) and sugarcane bagasse biochar (SBB)) at different pyrolysis temperatures (300–600 °C) were utilized for the passivation of pyrite. The results of our investigations revealed that the passivation ability of RSB was superior to that of SBB. The addition of RSB with higher pyrolysis temperatures could greatly enhance the passivation efficiency of pyrite. RSB-500 (produced at a pyrolysis temperature of 500 °C) achieved the best passivation effect on pyrite. RSB can form Fe-O bonds through C=O bonding with pyrite. Moreover, the addition of RSB created a reducing environment in the mixture system because of its strong electron-donation capacity (EDC) and altered the energy-band structure of pyrite, which promoted the transfer of electrons from biochar to pyrite. On the contrary, the addition of SBB did not result in the formation of Fe-O bonds with pyrite. In addition, the EDC of SBB was also lower than that of RSB and it had almost no effect on the band structure of pyrite. Hence it did not alter the direction of the electron migration. These findings shed light on the mechanism of biochar passivation of pyrite and provide a theoretical foundation for selecting suitable biochar materials for AMD prevention at source. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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18 pages, 1856 KiB  
Article
Effects of Polyethylene Microplastics and Phenanthrene on Soil Properties, Enzyme Activities and Bacterial Communities
by Shasha Liu, Kaibo Huang, Guodong Yuan and Chengfang Yang
Processes 2022, 10(10), 2128; https://doi.org/10.3390/pr10102128 - 19 Oct 2022
Cited by 9 | Viewed by 5342
Abstract
Microplastics (MPs) or polycyclic aromatic hydrocarbons (PAHs) pollution has received increasing concern due to their ubiquitous distribution and potential risks in soils. However, nothing is known about the influences of PAHs-MPs combined pollution on soil ecosystems. To address the knowledge gap, a 1-year [...] Read more.
Microplastics (MPs) or polycyclic aromatic hydrocarbons (PAHs) pollution has received increasing concern due to their ubiquitous distribution and potential risks in soils. However, nothing is known about the influences of PAHs-MPs combined pollution on soil ecosystems. To address the knowledge gap, a 1-year soil microcosm experiment was conducted to systematically investigate the single and combined effect of polyethylene (PE) /phenanthrene (PHE) on soil chemical properties, enzymatic activities and bacterial communities (i.e., diversity, composition and function). Results showed that PE and PHE-PE significantly decreased soil pH. The available phosphorus (AP) and neutral phosphatase activity were not considerably changed by PHE, PE and PHE-PE. Significant enhancement of dehydrogenase activity in a PHE-PE amended system might be due to the degradation of PHE by indigenous bacteria (i.e., Sphingomonas, Sphingobium), and PE could enhance this stimulative effect. PHE and PHE-PE led to a slight increase in soil organic matter (SOM) and fluorescein diacetate hydrolase (FDAse) activity but a decrease in available nitrogen (AN) and urease activity. PE significantly enhanced the functions of nitrogen cycle and metabolism, reducing SOM/AN contents but increasing urease/FDAse activities. There were insignificant impacts on overall community diversity and composition in treated samples, although some bacterial genera were significantly stimulated or attenuated with treatments. In conclusion, the addition of PHE and PE influenced the soil chemical properties, enzymatic activities and bacterial community diversity/composition to some extent. The significantly positive effect of PE on the nitrogen cycle and on metabolic function might lead to the conspicuous alterations in SOM/AN contents and urease/FDAse activities. This study may provide new basic information for understanding the ecological risk of PAHs-MPs combined pollution in soils. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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15 pages, 3974 KiB  
Article
Human-Health and Environmental Risks of Heavy Metal Contamination in Soil and Groundwater at a Riverside Site, China
by Dongyuan Luo, Yuan Liang, Hao Wu, Shudi Li, Yaoye He, Junyan Du, Xixi Chen and Shengyan Pu
Processes 2022, 10(10), 1994; https://doi.org/10.3390/pr10101994 - 02 Oct 2022
Cited by 2 | Viewed by 4706
Abstract
The contaminated site is considered a high-risk pollution source due to the accumulation of industrial waste and wastewater, which affects the soil and groundwater environment. In this study, through soil and groundwater investigation, we outlined the characteristics of heavy metal contamination in the [...] Read more.
The contaminated site is considered a high-risk pollution source due to the accumulation of industrial waste and wastewater, which affects the soil and groundwater environment. In this study, through soil and groundwater investigation, we outlined the characteristics of heavy metal contamination in the soil and groundwater of the contaminated site, assessed the health risk of the contaminated site to humans, and established a numerical model to predict the ecological and environmental risks of the site. The results of the study showed that the maximum contamination concentration of pollutants (lead, arsenic, cadmium) in the soil all exceeded the Chinese environmental standard (GB36600-2018, Grade II), that the maximum contamination concentration (cadmium, Cd) of the groundwater exceeded the Chinese environmental standard (GB14848–2017, Grade IV), and that the heavy metal pollution was mainly concentrated in the production area of the site and the waste-residue stockpiles. The total carcinogenic risk and non-carcinogenic hazard quotient of the site’s soil heavy metal contaminants exceed the human acceptable limit, and there is a human health risk. However, the groundwater in the area where the site is located is prohibited from exploitation, and there is no volatility of the contaminants and no exposure pathway to the groundwater, so there is no risk to human health. The simulation prediction results show that, with the passage of time, the site groundwater pollutants as a whole migrate from south to north, affecting the northern surface water bodies after about 12 years, and there is a high ecological and environmental risk. The above findings provide a scientific basis for the study of the soil and groundwater at the riverside contaminated site. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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18 pages, 5729 KiB  
Article
Treatment of PBDEs from Soil-Washing Effluent by Granular-Activated Carbon: Adsorption Behavior, Influencing Factors and Density Functional Theory Calculation
by Yao Ma, Haoliang Li, Chunsheng Xie, Xiaodong Du, Xueqin Tao and Guining Lu
Processes 2022, 10(9), 1815; https://doi.org/10.3390/pr10091815 - 08 Sep 2022
Cited by 2 | Viewed by 10407
Abstract
Soil-washing is a potential technology for the disposal of soil contaminated by e-waste; however, the produced soil-washing effluent will contain polybrominated diphenyl ethers (PBDEs) and a large number of surfactants, which are harmful to the environment, so the treatment of PBDEs and the [...] Read more.
Soil-washing is a potential technology for the disposal of soil contaminated by e-waste; however, the produced soil-washing effluent will contain polybrominated diphenyl ethers (PBDEs) and a large number of surfactants, which are harmful to the environment, so the treatment of PBDEs and the recycling of surfactants are the key to the application of soil-washing technology. In this study, coconut shell granular-activated carbon (GAC) was applied to remove PBDEs from Triton X-100 (TX-100) surfactant which simulates soil-washing effluent. The adsorption results show that, GAC can simultaneously achieve effective removal of 4,4′-dibromodiphenyl ether (BDE-15) and efficient recovery of TX-100. Under optimal conditions, the maximum adsorption capacity of BDE-15 could reach 623.19 μmol/g, and the recovery rate of TX-100 was always higher than 83%. The adsorption process of 4,4′-dibromodiphenyl ether (BDE-15) by GAC could best be described using the pseudo-second-order kinetic model and Freundlich isothermal adsorption model. The coexistence ions had almost no effect on the removal of BDE-15 and the recovery rate of TX-100, and the solution pH had little effect on the recovery rate of TX-100; BDE-15 had the best removal effect under the condition of weak acid to weak base, indicating that GAC has good environmental adaptability. After adsorption, GAC could be regenerated with methanol and the adsorption effect of BDE-15 could still reach more than 81%. Density functional theory (DFT) calculation and characterization results showed that, Van der Waals interaction and π–π interaction are dominant between BDE-15 and GAC, and hydrogen bond interactions also exist. The existence of oxygen-containing functional groups is conducive to the adsorption of BDE-15, and the carboxyl group (-COOH) has the strongest promoting effect. The study proved the feasibility of GAC to effectively remove PBDEs and recover surfactants from the soil-washing effluent, and revealed the interaction mechanism between PBDEs and GAC, which can provide reference for the application of soil-washing technology. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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10 pages, 1243 KiB  
Article
Heavy Metal Contamination in Soils from a Major Planting Base of Winter Jujube in the Yellow River Delta, China
by Changqing Shan, Zaiwang Zhang, Deyong Zhao, Meiling Zou, Wenwen Huang, Xiangrui Wang, Jianchao Jin, Yanpeng Zhang, Qian Yang, Wenjun Xie and Jialiang Li
Processes 2022, 10(9), 1777; https://doi.org/10.3390/pr10091777 - 05 Sep 2022
Cited by 5 | Viewed by 4564
Abstract
Surface soils form a major planting base of winter jujube in China were collected and detected for six heavy metals including Co, Ni, Cu, Zn, Cd, and Pb. The concentrations of Co, Ni, Cu, Zn, Cd, and Pb were 27.6 ± 6.0, 57.9 [...] Read more.
Surface soils form a major planting base of winter jujube in China were collected and detected for six heavy metals including Co, Ni, Cu, Zn, Cd, and Pb. The concentrations of Co, Ni, Cu, Zn, Cd, and Pb were 27.6 ± 6.0, 57.9 ± 12.8, 67.1 ± 10.3, 102.6 ± 23.4, 0.24 ± 0.07, and 25.1 ±5.9 mg/kg, respectively, showing an order of Zn > Cu > Ni > Co > Pb > Cd. The contents of the investigated metals were frequently observed higher than their related background values, suggesting that extra metal inputs occurred. Levels of all elements were below the associated risk screening values of agricultural soil in China, indicating healthy planting conditions for the winter jujube cultivation. Nemerow comprehensive pollution indexes of the metals in all the sampling stations were lower than 0.7, revealing a non-pollution status of the soils. Geo-accumulation indexes suggested that Zn and Pb caused no pollution, and Co, Ni, Cu, and Cd seemed to result in slight pollution. Co, Ni, Zn, Cd, and Pb had similar sources, which might be related to some natural processes and the use of fertilizers. Extra Cu might be mainly from the use of copper-containing pesticides. Based on our observations, the soils from the planting base of winter jujube in the Yellow River Delta were safe for the cultivation of winter jujube, and the rational utilization of pesticide and fertilizer were proposed to control the new inputs of heavy metals. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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12 pages, 2338 KiB  
Article
Migration Behavior and Influencing Factors of Petroleum Hydrocarbon Phenanthrene in Soil around Typical Oilfields of China
by Hao Chen, Mengfan Lang, Changjun Liao and Xuetao Guo
Processes 2022, 10(8), 1624; https://doi.org/10.3390/pr10081624 - 17 Aug 2022
Cited by 3 | Viewed by 4893
Abstract
Petroleum spills and land contamination are becoming increasingly common around the world. Polycyclic aromatic hydrocarbons (PAHs) and other pollutants found in petroleum are constantly migrating underground, making their migration in soil a hot research topic. Therefore, it is of great significance to evaluate [...] Read more.
Petroleum spills and land contamination are becoming increasingly common around the world. Polycyclic aromatic hydrocarbons (PAHs) and other pollutants found in petroleum are constantly migrating underground, making their migration in soil a hot research topic. Therefore, it is of great significance to evaluate the migratory process of petroleum hydrocarbons in petroleum-polluted soil to clarify its ecological and environmental risks. In this study, Phenanthrene (PHE) was used as a typical pollutant of PAHs. The soil was gathered from three typical oilfields in China, and a soil column apparatus was built to simulate the vertical migration of PHE in the soil. The migration law and penetration effect of PHE in various environmental conditions of soil were investigated by varying the ionic strength (IS), pH, particle size, and type of soil. According to the literature, pH has no discernible effect on the migration of PHE. The migration of PHE was adversely and positively linked with changes in IS and soil particle size, respectively. The influence of soil type was mainly manifested in the difference of organic matter and clay content. In the Yanchang Oilfield (YC) soil with the largest soil particle size and the least clay content, the mobility of PHE was the highest. This study may reveal the migration law of PAHs in soils around typical oilfields, establish a new foundation for PAH migration in the soil, and also provide new ideas for the management and control of petroleum pollution in the soil and groundwater. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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17 pages, 23259 KiB  
Article
Improvement of Ecological Risk Considering Heavy Metal in Soil and Groundwater Surrounding Electroplating Factories
by Hong Fang, Xiujuan Wang, Di Xia, Jianting Zhu, Weida Yu, Yaoming Su, Jingwen Zeng, Yuanling Zhang, Xiaojun Lin, Yutao Lei and Jinrong Qiu
Processes 2022, 10(7), 1267; https://doi.org/10.3390/pr10071267 - 27 Jun 2022
Cited by 7 | Viewed by 4926
Abstract
Heavy metals in groundwater and soil are toxic to humans. An accurate risk assessment of heavy metal contamination can aid in environmental security decision making. In this study, the improved ecological risk index (RI) is used to comprehensively investigate the influence [...] Read more.
Heavy metals in groundwater and soil are toxic to humans. An accurate risk assessment of heavy metal contamination can aid in environmental security decision making. In this study, the improved ecological risk index (RI) is used to comprehensively investigate the influence of heavy metals in soil and groundwater within electroplating factories and their surrounding regions. In the non-overlapping area, the RI of soil and groundwater is computed individually, and in the overlapping area, the greater RI of soil and groundwater is employed. Two typical electroplating factories are used to examine the heavy metal distribution pattern. The heavy metal concentrations are compared between Factory A, which is in operation, and Factory B, which is no longer in operation, in order to analyze the heavy metal concentrations and associated ecological risks. Heavy metals continue to spread horizontally and vertically after Factory B was closed. Heavy metal concentrations in groundwater surrounding Factory B are substantially greater, and the maximum concentration exists deeper than in Factory A. Because Cr, Cu, and Hg in soil contribute significantly to the RI, the primary high RI region is observed at Factory A and the region to the southwest. The RI of Factory B demonstrates a broad, moderate risk zone in the west and southwest. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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15 pages, 919 KiB  
Article
Speciation Distribution and Influencing Factors of Heavy Metals in Rhizosphere Soil of Miscanthus Floridulus in the Tailing Reservoir Area of Dabaoshan Iron Polymetallic Mine in Northern Guangdong
by Jianqiao Qin, Huarong Zhao, Ming Dai, Peng Zhao, Xi Chen, Hao Liu and Baizhou Lu
Processes 2022, 10(6), 1217; https://doi.org/10.3390/pr10061217 - 18 Jun 2022
Cited by 11 | Viewed by 5389
Abstract
Through field investigation and experimental analysis, the forms, contents and distribution of heavy metals (Zn, Pb, Cu, Cd, Ni, Cr) in rhizosphere and non-rhizosphere soils of Miscanthus floridulus growing everywhere in Tielongwei mine pond (sample plot 1), Caoduikeng tailings pond (sample plot 2), [...] Read more.
Through field investigation and experimental analysis, the forms, contents and distribution of heavy metals (Zn, Pb, Cu, Cd, Ni, Cr) in rhizosphere and non-rhizosphere soils of Miscanthus floridulus growing everywhere in Tielongwei mine pond (sample plot 1), Caoduikeng tailings pond (sample plot 2), Donghua tailings pond (sample plot 3) and Small tailings pond (sample plot 4) in Dabaoshan, Guangdong Province were studied. The results showed that the main forms and distributions of heavy metals in rhizosphere and non-rhizosphere soils are basically the same, which shows that the mineral content accounts for most of the total amount of heavy metals, while the exchange content is low. Compared with non-rhizosphere soil, the proportion of exchangeable and organic heavy metals in rhizosphere soil increased significantly, in which the proportion of organic-bound Cu increased by 53.25%, the proportion of organic-bound Cd and Pb increased by more than 17%, and the proportion of Zn increased by 5.67%. At the same time, the contents of carbonate-bound and iron manganese oxide-bound decreased. Statistical analyses showed that the morphological distribution of Zn, Pb, Cu, Cd, Ni and Cr in rhizosphere soil was closely related to soil pH value, organic matter content, plant growth and other factors. The results of this study provided a basis for the restoration of heavy metal-contaminated sites by Miscanthus. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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13 pages, 3101 KiB  
Article
Effects of Tetracycline and Copper on Water Spinach Growth and Soil Bacterial Community
by Jiadan Tao, Jiayu Wang, Xiongkai Zheng, Aiping Jia, Mengyao Zou, Jinlian Zhang and Xueqin Tao
Processes 2022, 10(6), 1135; https://doi.org/10.3390/pr10061135 - 06 Jun 2022
Cited by 3 | Viewed by 10144
Abstract
The effects of tetracycline (TC) and copper (Cu) on the growth of water spinach and the bacterial community structure in soil were examined in this study. The results revealed that a single Cu treatment decreased water spinach development more severely than TC, and [...] Read more.
The effects of tetracycline (TC) and copper (Cu) on the growth of water spinach and the bacterial community structure in soil were examined in this study. The results revealed that a single Cu treatment decreased water spinach development more severely than TC, and that the toxic effects of TC and Cu on water spinach were synergistic at low doses and antagonistic at high concentrations. The single Cu treatment had the largest influence on the activities of three antioxidant enzymes (Superoxide Dismutase (SOD), Peroxidase (POD), Catalase (CAT)) and the content of Malondialdehyde (MDA) in water spinach leaves, followed by the TC and Cu composed treatment, with the single TC treatment having the least effect. The results of 16Sr RNA sequence analysis showed that the richness and diversity of soil bacterial communities were reduced by either a single TC or Cu treatment. Cu had a greater effect on the composition of the microbial community at genus level than TC. In conclusion, Cu had a greater influence on the growth of water spinach and soil microbial community composition than TC. TC and Cu exhibited synergistic effects at low concentrations and antagonistic effects at high concentrations on relevant indicators when Cu concentration was fixed. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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10 pages, 3308 KiB  
Article
Contamination of Heavy Metals in Sediments from an Estuarine Bay, South China: Comparison with Previous Data and Ecological Risk Assessment
by Zaiwang Zhang, Jianchao Jin, Jiqiang Zhang, Deyong Zhao, He Li, Changping Yang and Yingbang Huang
Processes 2022, 10(5), 837; https://doi.org/10.3390/pr10050837 - 24 Apr 2022
Cited by 8 | Viewed by 4670
Abstract
Heavy metal contamination is an elevating threat to the aquatic environment of estuarine bays. In the present study, surface sediments from Shantou Bay in South China were collected and detected for the concentrations of heavy metals including copper (Cu), zinc (Zn), chromium (Cr), [...] Read more.
Heavy metal contamination is an elevating threat to the aquatic environment of estuarine bays. In the present study, surface sediments from Shantou Bay in South China were collected and detected for the concentrations of heavy metals including copper (Cu), zinc (Zn), chromium (Cr), nickel (Ni), cadmium (Cd), and lead (Pb) using ICP-MS. Spatial distribution, temporal trend, and potential ecological risks for the metal pollution were discussed. The results showed that levels of metals generally decreased by the order of Zn > Pb > Cr > Cu > Ni > Cd. Spatial variation of metal contents was observed with an order of Rongjiang River > Niutian Bay > Shanthou Harbor for Zn and Cd. Sediments of the Niutian Bay were observed with higher levels of Cu, Cr, Ni, and Pb. Compared with reported data from the same region at different sampling periods, a low–high–low trend was observed for the concentrations of the six elements, suggesting a great improvement of sediment quality in Shantou Bay. The average Igeo values suggested moderate pollution of Cu, Zn, Pb, and Cd. The potential ecological risks of Cu, Pb, Zn, Ni, and Cr were in low levels. More attention should be paid to the Cd pollution, considering its great values of potential ecological risk index. Our findings provided better understanding of heavy metal pollution in estuarine environments. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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14 pages, 2082 KiB  
Article
Heavy Metal Distribution in Surface Sediments of the Coastal Pearl Bay, South China Sea
by Changping Yang, Gang Yu, Yan Liu, Binbin Shan, Liangming Wang, Dianrong Sun and Yingbang Huang
Processes 2022, 10(5), 822; https://doi.org/10.3390/pr10050822 - 21 Apr 2022
Cited by 12 | Viewed by 4699
Abstract
Six heavy metals (As, Cu, Cd, Zn, Cr, and Pb) in surface sediments (0–5 cm) from the twenty selected sites of the coastal Pearl Bay (South China Sea) were analyzed to assess the distribution pattern and potential ecological risk. Overall concentrations (mg/kg, dw) [...] Read more.
Six heavy metals (As, Cu, Cd, Zn, Cr, and Pb) in surface sediments (0–5 cm) from the twenty selected sites of the coastal Pearl Bay (South China Sea) were analyzed to assess the distribution pattern and potential ecological risk. Overall concentrations (mg/kg, dw) in the sediment samples were: As (10.88 ± 6.50), Cu (24.16 ± 18.63), Cd (0.55 ± 0.78), Zn (48.53 ± 30.06), Cr (35.78 ± 28.66), Pb (31.28 ± 18.50). Results showed that the overall mean values of Cd concentrations exceeded the standard of China Marine Sediment Quality, caused by significantly high levels of Cd contents in five sites (S8, S11, S13, S16, and S17) at the offshore area of Pearl Bay. Generally, the metal concentrations showed a decreasing trend from the offshore area to the inner bay. Various index values such as the geo-accumulation index (Igeo), the ecological risk index (Eri), and the contamination factor (CF) demonstrated that the coastal Pearl Bay was not polluted by the examined metals except for Cd, which might cause contamination and ecological risk in the region. Principal component analysis (PCA) results indicated that Cu, Zn, and Cr might originate from natural sources inland, and Pb and As might come from the gasoline and diesel fuel from engine boats. It is recommended that further research should focus on detecting the acute source and transferring mechanisms of the toxic metal Cd. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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13 pages, 2428 KiB  
Article
Photodegradation of Decabrominated Diphenyl Ether in Soil Suspensions: Kinetics, Mechanisms and Intermediates
by Kaibo Huang, Haozhong Lin, Xueqin Tao, Mengyao Zou and Guining Lu
Processes 2022, 10(4), 718; https://doi.org/10.3390/pr10040718 - 08 Apr 2022
Cited by 3 | Viewed by 9861
Abstract
Pollution by polybrominated diphenyl ethers (PBDEs) is a major concern due to their bioaccumulation, persistence, and carcinogenicity. This study aimed to investigate the decabrominated diphenyl ether (BDE-209) photodegradation in soil suspensions. The results indicate BDE-209 can degrade in soil suspensions and its degradation [...] Read more.
Pollution by polybrominated diphenyl ethers (PBDEs) is a major concern due to their bioaccumulation, persistence, and carcinogenicity. This study aimed to investigate the decabrominated diphenyl ether (BDE-209) photodegradation in soil suspensions. The results indicate BDE-209 can degrade in soil suspensions and its degradation follows pseudo-first-order kinetics. The light sources and intensity effects were studied and the photodegradation rates were 500 W Mercury Lamp > 300 W Mercury Lamp > 500 W Xenon Lamp > 300 W Xenon Lamp, which indicates UV light is the main reason for BDE-209 degradation. Soil particle inhibits BDE-209 photodegradation due to the light-shielding effect. BDE-209 photodegradation rates increased from 0.055 to 0.071 h−1 with pH value increasing from 3.5 to 9.5. This may be because the products are more easily produced in higher pH soil suspensions. The presence of humic acid (HA) may inhibit BDE-209 photodegradation by photo-shielding. Fe3+ and Cu2+ have an adverse effect on BDE-209 photodegradation due to the photo competition. The •OH and 1O2 were detected in soil solutions. Analysis of the photoproducts of BDE-209 by gas chromatography mass spectrometry (GC-MS) and liquid chromatography time of flight mass spectrometry (LC-TOF-MS) showed that BDE-209 was mainly debrominated to the lower-brominated BDEs and the reactive oxygen radicals may not lead to BDE-209 degradation. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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14 pages, 4544 KiB  
Article
Sorption of Cd2+ on Bone Chars with or without Hydrogen Peroxide Treatment under Various Pyrolysis Temperatures: Comparison of Mechanisms and Performance
by Qing Guo, Hongmei Tang, Lu Jiang, Meiqing Chen, Nengwu Zhu and Pingxiao Wu
Processes 2022, 10(4), 618; https://doi.org/10.3390/pr10040618 - 22 Mar 2022
Cited by 11 | Viewed by 5145
Abstract
In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd2+ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and [...] Read more.
In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd2+ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and the number of oxygen-containing functional groups on the bone char surface increased. After being pyrolyzed, the specific surface area and the negative charge of the material were further improved. The adsorption kinetics and isotherms of Cd2+ adsorption were studied, and the influence of solution pH and the presence of ionic species were investigated. The experimental results showed that the samples with lower crystallinity exhibited less organic matter content and more surface oxygen-containing functional groups, resulting in stronger adsorption capacity. After being treated with hydrogen peroxide and pyrolyzed at 300 °C, the maximum adsorption capacity of bone char was 228.73 mg/g. The bone char sample with the lowest adsorption capacity(47.71 mg/g) was pyrolyzed at 900 °C without hydrogen peroxide pretreatment. Ion exchange, surface complexation, and electrostatic interactions were responsible for the elimination of Cd2+ by the bone char samples. Overall, this work indicates that hydrogen peroxide-treated pyrolytic bone char is a promising material for the immobilization of Cd2+. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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17 pages, 3774 KiB  
Article
Prediction of Heavy Metal Concentrations in Contaminated Sites from Portable X-ray Fluorescence Spectrometer Data Using Machine Learning
by Feiyang Xia, Tingting Fan, Yun Chen, Da Ding, Jing Wei, Dengdeng Jiang and Shaopo Deng
Processes 2022, 10(3), 536; https://doi.org/10.3390/pr10030536 - 09 Mar 2022
Cited by 8 | Viewed by 9321
Abstract
Portable X-ray fluorescence (pXRF) spectrometers provide simple, rapid, nondestructive, and cost-effective analysis of the metal contents in soils. The current method for improving pXRF measurement accuracy is soil sample preparation, which inevitably consumes significant amounts of time. To eliminate the influence of sample [...] Read more.
Portable X-ray fluorescence (pXRF) spectrometers provide simple, rapid, nondestructive, and cost-effective analysis of the metal contents in soils. The current method for improving pXRF measurement accuracy is soil sample preparation, which inevitably consumes significant amounts of time. To eliminate the influence of sample preparation on PXRF measurements, this study evaluates the performance of pXRF measurements in the prediction of eight heavy metals’ contents through machine learning algorithm linear regression (LR) and multivariate adaptive regression spline (MARS) models. Soil samples were collected from five industrial sites and separated into high-value and low-value datasets with pXRF measurements above or below the background values. The results showed that for Cu and Cr, the MARS models were better than the LR models at prediction (the MARS-R2 values were 0.88 and 0.78; the MARS-RPD values were 2.89 and 2.11). For the pXRF low-value dataset, the multivariate MARS models improved the pXRF measurement accuracy, with the R2 values improved from 0.032 to 0.39 and the RPD values increased by 0.02 to 0.37. For the pXRF high-value dataset, the univariate MARS models predicted the content of Cu and Cr with less calculation. Our study reveals that machine learning methods can better predict the Cu and Cr of large samples from multiple contaminated sites. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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15 pages, 2421 KiB  
Article
Chromium Distribution, Leachability and Speciation in a Chrome Plating Site
by Jiacong Sun, Yating Luo, Jien Ye, Chunhui Li and Jiyan Shi
Processes 2022, 10(1), 142; https://doi.org/10.3390/pr10010142 - 10 Jan 2022
Cited by 13 | Viewed by 9570
Abstract
Hexavalent chromium (Cr(VI)) waste produced by chrome plating activities pollutes the surrounding environment and harms human health. However, information about the chromium (Cr) pollution characteristics of actual electroplating sites is still lacking. In this study, the concentration, leachability and speciation of Cr in [...] Read more.
Hexavalent chromium (Cr(VI)) waste produced by chrome plating activities pollutes the surrounding environment and harms human health. However, information about the chromium (Cr) pollution characteristics of actual electroplating sites is still lacking. In this study, the concentration, leachability and speciation of Cr in soils from a typical chrome plating site were analyzed. Our results showed that this site was severely contaminated by Cr (7.2 to 7735.2 mg/kg) and Cr(VI) reached the mean concentration of 138.7 mg/kg. The spatial distribution of Cr(VI) was related to the plating processes. Chrome plating and sewage treatment areas could be considered as the hot spots of contaminated sites. The vertical distribution of Cr(VI) was mainly affected by soil properties, where the loam layer retained and reduced a large amount of Cr(VI) due to its high content of iron minerals and finer particle fractions. Additionally, the chemical extraction results showed that Cr was mainly in non-residual fractions and the existence of Cr(VI) led to a high leaching toxicity based on the toxicity characteristic leaching procedure (TCLP) results. Moreover, X-ray photoelectron spectroscopy (XPS) results revealed the speciation of Cr in the long-term contaminated soils. A large amount of Cr(VI) was reduced into Cr(III) and mainly existed as Cr(OH)3 and Cr2O3. Furthermore, Cr(VI) tended to precipitate as CaCrO4 and persisted in soils. Therefore, it is necessary to find appropriate strategies to remediate these contaminated soils. Overall, these findings strengthen our understanding of Cr(VI) behaviors and lay a foundation for the future pollution investigation, ecological remediation and risk assessment of sites contaminated by electroplating. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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16 pages, 2685 KiB  
Article
Effect of a Passivator Synthesized by Wastes of Iron Tailings and Biomass on the Leachability of Cd/Pb and Safety of Pak Choi (Brassica chinensis L.) in Contaminated Soil
by Yang Zhou and Lili Li
Processes 2021, 9(11), 1866; https://doi.org/10.3390/pr9111866 - 20 Oct 2021
Cited by 5 | Viewed by 8464
Abstract
Cadmium (Cd) and lead (Pb) carry a high heavy-metal-toxic risk for both animals and plants in soil. In this study, iron-based biochar (T-BC) was prepared by co-pyrolysis using wastes of iron tailings and biomass with urea as the functioning agents. Field-emission scanning electron [...] Read more.
Cadmium (Cd) and lead (Pb) carry a high heavy-metal-toxic risk for both animals and plants in soil. In this study, iron-based biochar (T-BC) was prepared by co-pyrolysis using wastes of iron tailings and biomass with urea as the functioning agents. Field-emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and toxicity-characteristic leaching procedure (TCLP) methods were employed to analyze the physicochemical characteristics of T-BC. Additionally, a pot trial was conducted to examine the effects of T-BC on the physiological characteristics of pak choi (Brassica campestris L.), the availability of heavy metals, and enzyme activities in the soils. The results show that toxic metals have been volatilized by the roasting process and immobilized within T-BC via the formation of stable metal-compounds during the co-pyrolysis process, which satisfies the requirements of a soil passivator. Incubation experiments showed that the DTPA-extractable Cd and Pb in contaminated soils decreased with an increasing amendment rate. Moreover, in the pot experiments, by adding 1% (w/w) T-BC into soils, the soils benefited from its large adsorption, complex precipitation, and immobilization capacity. Approximately 36% Cd and 29% Pb concentrations of edible parts in pak choi were reduced. The amendment proved promising for the stabilization of Cd and Pb in contaminated soils, while providing a strategy for solving the residual waste of tailings and biomass. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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Review

Jump to: Editorial, Research

24 pages, 1620 KiB  
Review
Efficient Remediation of Cadmium Contamination in Soil by Functionalized Biochar: Recent Advances, Challenges, and Future Prospects
by Yichang Lu, Jiaqi Cheng, Jieni Wang, Fangfang Zhang, Yijun Tian, Chenxiao Liu, Leichang Cao and Yanmei Zhou
Processes 2022, 10(8), 1627; https://doi.org/10.3390/pr10081627 - 17 Aug 2022
Cited by 9 | Viewed by 10271
Abstract
Heavy metal pollution in soil seriously harms human health and animal and plant growth. Among them, cadmium pollution is one of the most serious issues. As a promising remediation material for cadmium pollution in soil, functionalized biochar has attracted wide attention in the [...] Read more.
Heavy metal pollution in soil seriously harms human health and animal and plant growth. Among them, cadmium pollution is one of the most serious issues. As a promising remediation material for cadmium pollution in soil, functionalized biochar has attracted wide attention in the last decade. This paper summarizes the preparation technology of biochar, the existing forms of heavy metals in soil, the remediation mechanism of biochar for remediating cadmium contamination in soil, and the factors affecting the remediation process, and discusses the latest research advances of functionalized biochar for remediating cadmium contamination in soil. Finally, the challenges encountered by the implementation of biochar for remediating Cd contamination in soil are summarized, and the prospects in this field are highlighted for its expected industrial large-scale implementation. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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25 pages, 1166 KiB  
Review
Application of Magnetic Composites in Removal of Tetracycline through Adsorption and Advanced Oxidation Processes (AOPs): A Review
by Beibei Fan, Yi Tan, Jingxin Wang, Bangxi Zhang, Yutao Peng, Chengpeng Yuan, Chungyu Guan, Xing Gao and Shihao Cui
Processes 2021, 9(9), 1644; https://doi.org/10.3390/pr9091644 - 13 Sep 2021
Cited by 22 | Viewed by 13525
Abstract
Water pollution induced by the tetracycline (TC) has caused global increasing attention owing to its extensive use, environmental persistence, and potential harm for human health. Adsorption and advanced oxidation processes (AOPs) have been promising techniques for TC removal due to ideal effectiveness and [...] Read more.
Water pollution induced by the tetracycline (TC) has caused global increasing attention owing to its extensive use, environmental persistence, and potential harm for human health. Adsorption and advanced oxidation processes (AOPs) have been promising techniques for TC removal due to ideal effectiveness and efficiency. Magnetic composites (MCs) which exploit the combined advantages of nano scale, alternative sources, easy preparation, and separation from wastewater are widely used for catalysis and adsorption. Herein, we intensively reviewed the available literature in order to provide comprehensive insight into the applications and mechanisms of MCs for removal of TC by adsorption and AOPs. The synthesis methods of MCs, the TC adsorption, and removal mechanisms are fully discussed. MCs serve as efficient adsorbents and photocatalysts with superior performance of photocatalytic performance in TC degradation. In addition, the TC can be effectively decomposed by the Fenton-based and SO4•− mediated oxidation under catalysis of the reported MCs with excellent catalytic performance. Based on the existing literature, we further discuss the challenge and future perspectives in MCs-based adsorption and AOPs in removing TC. Full article
(This article belongs to the Special Issue Advances in Remediation of Contaminated Sites: Volume I)
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