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12 pages, 2571 KiB

Open AccessArticle

Spatial Differentiation Characteristics and Evaluation of Cu and Cd in Paddy Soil around a Copper Smelter

by Yuan Ding, Li Xi, Yujing Wu, Yihong Chen, Xiaoping Guo, Hong Shi and Shuo Cai

Toxics 2023, 11(8), 647; https://doi.org/10.3390/toxics11080647 - 26 Jul 2023

Cited by 2 | Viewed by 1111

Abstract

To accurately evaluate the distribution and bioavailability of potentially toxic elements (PTEs) such as Cu and Cd in farmlands near a copper smelter, we determined the total concentrations (Cu-T and Cd-T), various speciation concentrations of Cu and Cd and physicochemical properties of 18 [...] Read more.

To accurately evaluate the distribution and bioavailability of potentially toxic elements (PTEs) such as Cu and Cd in farmlands near a copper smelter, we determined the total concentrations (Cu-T and Cd-T), various speciation concentrations of Cu and Cd and physicochemical properties of 18 paddy soil (or colloid) samples in Guixi town, Jiangxi province, China. The results showed that the concentrations of Cu-T and Cd-T in the soil around the smelter far exceeded the standard limits. Specifically, Cu ranged from 97.47 to 1294.63 mg·kg⁻¹, with a coefficient of variation (CV) of 0.95; Cd ranged from 0.14 to 9.06 mg·kg⁻¹, and the CV was 1.68. Furthermore, the pollution of PTEs continued to accumulate, posing a significant risk to the environment and human health. The findings from the analysis of soil and colloid indicated that the distribution characteristics of Cu and Cd speciations did not align with the total concentrations. The highest pollution points were found to be shifted to the residual fraction of Cu, organic fraction, and crystalline iron oxide fraction of Cd in soil. The dominant fraction of Cu in colloid was the amorphous iron oxide fraction, whereas Cd was the crystalline iron oxide fraction. The assessment of Cu and Cd migration (M_R) revealed that Cd posed a greater ecological risk. Further examination of the properties of iron oxides in soil and colloid revealed that they played a crucial role in the migration and transformation of soil PTEs. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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16 pages, 2502 KiB

Open AccessEditor’s ChoiceArticle

The Migration Mechanism of BTEX in Single- and Double-Lithology Soil Columns under Groundwater Table Fluctuation

by Jingwei Zheng, Yang Yang, Juan Li, Hao Zhang and Yan Ma

Toxics 2023, 11(7), 630; https://doi.org/10.3390/toxics11070630 - 20 Jul 2023

Cited by 2 | Viewed by 1914

Abstract

The migration of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Groundwater table fluctuation can not only affect contaminant migration but also redox conditions, bacterial communities, and contaminant degradation. Understanding LNAPLs’ (e.g., benzene, toluene, ethylbenzene, and xylene (BTEX)) [...] Read more.

The migration of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Groundwater table fluctuation can not only affect contaminant migration but also redox conditions, bacterial communities, and contaminant degradation. Understanding LNAPLs’ (e.g., benzene, toluene, ethylbenzene, and xylene (BTEX)) behavior within porous media is critical for the high efficiency of most in situ remediation systems. A laboratory study of single- and double-lithology soil column investigation of the groundwater table fluctuation effect on BTEX transport, using benzene and toluene as typical compounds, in a typical representative model of aquifers subjected to water table fluctuation was undertaken in this study. The results show that benzene and toluene migration in single-lithology soil columns packed with sand was mainly affected by flushing due to the hydraulic force induced by water table fluctuations and that the double-lithology soil column packed with sand and silt was significantly affected by retention due to the higher adsorption induced by 10 cm of silt. The dissolution mainly correlated with the BTEX migration in saturated zones, and the contaminant concentration increased when the water table fell and decreased when the water table rose. For a contaminated site with a single-lithology structure consisting of sand, more attention should be paid to organic contaminant removal within the groundwater, and a double-lithology structure containing silt is more suited to the removal of organic contaminants from the silt layer. The difference in biodegradation kinetics between the groundwater table fluctuation (GTF) zone and the saturated zone should be better understood for the remediation of BTEX compounds. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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17 pages, 5616 KiB

Open AccessArticle

Simultaneously Cationic and Anionic Dyes Elimination via Magnetic Hydrochar Prepared from Copper Slag and Pinewood Sawdust

by Huabin Wang, Yi Wu, Yi Wen, Dingxiang Chen, Jiang Pu, Yu Ding, Sailian Kong, Shuaibing Wang and Rui Xu

Toxics 2023, 11(6), 484; https://doi.org/10.3390/toxics11060484 - 25 May 2023

Cited by 3 | Viewed by 1510

Abstract

In practical wastewater, cationic and anionic dyes usually coexist, while synergistic removal of these pollutants is difficult due to their relatively opposite properties. In this work, copper slag (CS) modified hydrochar (CSHC) was designed as functional material by the one-pot method. Based on [...] Read more.

In practical wastewater, cationic and anionic dyes usually coexist, while synergistic removal of these pollutants is difficult due to their relatively opposite properties. In this work, copper slag (CS) modified hydrochar (CSHC) was designed as functional material by the one-pot method. Based on characterizations, the Fe species in CS can be converted to zero-valent iron and loaded onto a hydrochar substrate. The CSHC exhibited efficient removal rates for both cationic dyes (methylene blue, MB) and anionic dyes (methyl orange, MO), with a maximum capacity of 278.21 and 357.02 mg·g⁻¹, respectively, which was significantly higher than that of unmodified ones. The surface interactions of MB and MO between CSHC were mimicked by the Langmuir model and the pseudo-second-order model. In addition, the magnetic properties of CSHC were also observed, and the good magnetic properties enabled the adsorbent to be quickly separated from the solution with the help of magnets. The adsorption mechanisms include pore filling, complexation, precipitation, and electrostatic attraction. Moreover, the recycling experiments demonstrated the potential regenerative performance of CSHC. All these results shed light on the co-removal of cationic and anionic contaminates via these industrial by-products derived from environmental remediation materials. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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12 pages, 3437 KiB

Open AccessArticle

The Treatment of Aquaculture Wastewater with Biological Aerated Filters: From the Treatment Process to the Microbial Mechanism

by Jiafeng Ding, Yunjuan Meng, Shihuan Lu, Yiwen Peng, Wen Yan, Wenbing Li, Jinchun Hu, Ting Ye, Yuchi Zhong and Hangjun Zhang

Toxics 2023, 11(6), 478; https://doi.org/10.3390/toxics11060478 - 25 May 2023

Cited by 2 | Viewed by 2062

Abstract

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the [...] Read more.

Algal cell proliferation has posed significant problems for traditional water treatment facilities; these problems are attributed to surface hydrophilicity and electrostatic repulsion. Biological aerated filters (BAFs) have been extensively used in wastewater treatment to remove pollutants such as algal cells by utilizing the adsorption and separation capabilities of the filter media. In this study, a BAF was supplemented with biological filter medium (Marchantia polymorpha) to assess its effectiveness of pretreating aquaculture wastewater. In terms of process performance, steady and consistent treatment was achieved by the BAF with M. polymorpha (BAF2) under an algal cell density as high as 1.65 × 10⁸ cell/L, with average removal rates for NH₄⁺-N and algae cells of 74.4% and 81.9%, respectively. The photosynthetic activity parameters (rETRmax, α, Fv/Fm, and I_k) of the influent and effluent were quantitatively assessed, and M. polymorpha was found to remove algae by disrupting the photosynthetic system of the algal cells. Furthermore, the addition of the M. polymorpha filter medium enhanced the community structure of the functional microbes in the BAF system. The highest microbial community richness and diversity were observed in the BAF2. Meanwhile, M. polymorpha promoted an increase in the abundance of denitrifying bacteria, including Bdellovibrio and Pseudomonas. Overall, this work offers a unique perspective on the aquaculture wastewater pretreatment process and BAF design. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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16 pages, 2652 KiB

Open AccessArticle

Mercury Biogeochemical Cycle in Yanwuping Hg Mine and Source Apportionment by Hg Isotopes

by Xingang Jin, Junyao Yan, Muhammad Ubaid Ali, Qiuhua Li and Ping Li

Toxics 2023, 11(5), 456; https://doi.org/10.3390/toxics11050456 - 14 May 2023

Cited by 3 | Viewed by 1645

Abstract

Although mercury (Hg) mining activities in the Wanshan area have ceased, mine wastes remain the primary source of Hg pollution in the local environment. To prevent and control Hg pollution, it is crucial to estimate the contribution of Hg contamination from mine wastes. [...] Read more.

Although mercury (Hg) mining activities in the Wanshan area have ceased, mine wastes remain the primary source of Hg pollution in the local environment. To prevent and control Hg pollution, it is crucial to estimate the contribution of Hg contamination from mine wastes. This study aimed to investigate Hg pollution in the mine wastes, river water, air, and paddy fields around the Yanwuping Mine and to quantify the pollution sources using the Hg isotopes approach. The Hg contamination at the study site was still severe, and the total Hg concentrations in the mine wastes ranged from 1.60 to 358 mg/kg. The binary mixing model showed that, concerning the relative contributions of the mine wastes to the river water, dissolved Hg and particulate Hg were 48.6% and 90.5%, respectively. The mine wastes directly contributed 89.3% to the river water Hg contamination, which was the main Hg pollution source in the surface water. The ternary mixing model showed that the contribution was highest from the river water to paddy soil and that the mean contribution was 46.3%. In addition to mine wastes, paddy soil is also impacted by domestic sources, with a boundary of 5.5 km to the river source. This study demonstrated that Hg isotopes can be used as an effective tool for tracing environmental Hg contamination in typical Hg-polluted areas. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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25 pages, 12380 KiB

Open AccessArticle

Efficient Calibration of Groundwater Contaminant Transport Models Using Bayesian Optimization

by Hao Deng, Shengfang Zhou, Yong He, Zeduo Lan, Yanhong Zou and Xiancheng Mao

Toxics 2023, 11(5), 438; https://doi.org/10.3390/toxics11050438 - 6 May 2023

Cited by 8 | Viewed by 2162

Abstract

Numerical modeling is a significant tool to understand the dynamic characteristics of contaminants transport in groundwater. The automatic calibration of highly parametrized and computationally intensive numerical models for the simulation of contaminant transport in the groundwater flow system is a challenging task. While [...] Read more.

Numerical modeling is a significant tool to understand the dynamic characteristics of contaminants transport in groundwater. The automatic calibration of highly parametrized and computationally intensive numerical models for the simulation of contaminant transport in the groundwater flow system is a challenging task. While existing methods use general optimization techniques to achieve automatic calibration, the large numbers of numerical model evaluations required in the calibration process lead to high computing overhead and limit the efficiency of model calibration. This paper presents a Bayesian optimization (BO) method for efficient calibration of numerical models of groundwater contaminant transport. A Bayes model is built to fully represent calibration criteria and derive the objective function for model calibration. The efficiency of model calibration is made possible by the probabilistic surrogate model and the expected improvement acquisition function in BO. The probabilistic surrogate model approximates the computationally expensive objective function with a closed-form expression that can be computed efficiently, while the expected improvement acquisition function proposes the most promising model parameters to improve the fitness to the calibration criteria and reduce the uncertainty of the surrogate model. These schemes allow us to find the optimized model parameters effectively by using a small number of numerical model evaluations. Two case studies for the calibration of the Cr(VI) transport model demonstrate that the BO method is effective and efficient in the inversion of hypothetical model parameters, the minimization of the objective function, and the adaptation of different model calibration criteria. Specifically, this promising performance is achieved within 200 numerical model evaluations, which substantially reduces the computing budget for model calibration. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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16 pages, 2233 KiB

Open AccessArticle

Water Management Impacts on Chromium Behavior and Uptake by Rice in Paddy Soil with High Geological Background Values

by Zeting Guan, Ran Wei, Ting Liu, Jingjing Li, Ming Ao, Shengsheng Sun, Tenghaobo Deng, Shizhong Wang, Yetao Tang, Qingqi Lin, Zhuobiao Ni and Rongliang Qiu

Toxics 2023, 11(5), 433; https://doi.org/10.3390/toxics11050433 - 5 May 2023

Cited by 1 | Viewed by 1832

Abstract

Chromium (Cr) is an expression toxic metal and is seriously released into the soil environment due to its extensive use and mining. Basalt is an important Cr reservoir in the terrestrial environment. Cr in paddy soil can be enriched by chemical weathering. Therefore, [...] Read more.

Chromium (Cr) is an expression toxic metal and is seriously released into the soil environment due to its extensive use and mining. Basalt is an important Cr reservoir in the terrestrial environment. Cr in paddy soil can be enriched by chemical weathering. Therefore, basalt-derived paddy soils contain extremely high concentrations of Cr and can enter the human body through the food chain. However, the water management conditions’ effect on the transformation of Cr in basalt-derived paddy soil with high geological background values was less recognized. In this study, a pot experiment was conducted to investigate the effects of different water management treatments on the migration and transformation of Cr in a soil–rice system at different rice growth stages. Two water management treatments of continuous flooding (CF) and alternative wet and dry (AWD) and four different rice growth stages were set up. The results showed that AWD treatment significantly reduced the biomass of rice and promoted the absorption of Cr in rice plants. During the four growth periods, the root, stem and leaf of rice increased from 11.24–16.11 mg kg⁻¹, 0.66–1.56 mg kg⁻¹ and 0.48–2.29 mg kg⁻¹ to 12.43–22.60 mg kg⁻¹, 0.98–3.31 mg kg⁻¹ and 0.58–2.86 mg kg⁻¹, respectively. The Cr concentration in roots, stems and leaves of AWD treatment was 40%, 89% and 25% higher than CF treatment in the filling stage, respectively. The AWD treatment also facilitated the potential bioactive fractions conversion to the bioavailable fraction, compared with the CF treatment. In addition, the enrichment of iron-reducing bacteria and sulfate-reducing bacteria with AWD treatment also provided electron iron for the mobilization of Cr, thus affecting the migration and transformation of Cr in the soil. We speculated that the reason for this phenomenon may be the bioavailability of Cr was affected by the biogeochemical cycle of iron under the influence of alternating redox. This indicates that AWD treatment may bring certain environmental risks in contaminated paddy soil with high geological background, and it is necessary to be aware of this risk when using water-saving irrigation to plant rice. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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16 pages, 3310 KiB

Open AccessEditor’s ChoiceArticle

The Adsorption Behaviors and Mechanisms of Humic Substances by Thermally Oxidized Graphitic Carbon Nitride

by Hongxin Li, Jianlong Wang, Dongbei Yue, Jianchao Wang, Chu Tang and Lingyue Zhang

Toxics 2023, 11(4), 369; https://doi.org/10.3390/toxics11040369 - 12 Apr 2023

Cited by 4 | Viewed by 1892

Abstract

Thermal oxidation is efficient for enhancing the photocatalysis performance of graphitic carbon nitride (g-C₃N₄), while its effect on adsorption performance has not been fully studied, which is crucial to the application of g-C₃N₄ as adsorbents and [...] Read more.

Thermal oxidation is efficient for enhancing the photocatalysis performance of graphitic carbon nitride (g-C₃N₄), while its effect on adsorption performance has not been fully studied, which is crucial to the application of g-C₃N₄ as adsorbents and photocatalysts. In this study, thermal oxidation was used to prepare sheet-like g-C₃N₄ (TCN), and its application for adsorption of humic acids (HA) and fulvic acids (FA) was evaluated. The results showed that thermal oxidation clearly affected the properties of TCN. After thermal oxidation, the adsorption performance of TCN was enhanced significantly, and the adsorption amount of HA increased from 63.23 (the bulk g-C₃N₄) to 145.35 mg/g [TCN prepared at 600 °C (TCN-600)]. Based on fitting results using the Sips model, the maximum adsorption amounts of TCN-600 for HA and FA were 327.88 and 213.58 mg/g, respectively. The adsorption for HA and FA was markedly affected by pH, alkaline, and alkaline earth metals due to electrostatic interactions. The major adsorption mechanisms included electrostatic interactions, π-π interactions, hydrogen bonding, along with a special pH-dependent conformation (for HA). These findings implied that TCN prepared from environmental-friendly thermal oxidation showed promising prospects for humic substances (HSs) adsorption in natural water and wastewater. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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12 pages, 3042 KiB

Open AccessArticle

Spatial and Temporal Variations of Heavy Metals’ Bioavailability in Soils Regulated by a Combined Material of Calcium Sulfate and Ferric Oxide

by Chi Zhang, Jie Li, Yuxia Dai, Williamson Gustave, Weiwei Zhai, Zhong Zhong and Jianmeng Chen

Toxics 2023, 11(4), 296; https://doi.org/10.3390/toxics11040296 - 24 Mar 2023

Viewed by 1718

Abstract

Heavy metal pollution in soils threatens food safety and human health. Calcium sulfate and ferric oxide are commonly used to immobilize heavy metals in soils. However, the spatial and temporal variations of the heavy metals’ bioavailability in soils regulated by a combined material [...] Read more.

Heavy metal pollution in soils threatens food safety and human health. Calcium sulfate and ferric oxide are commonly used to immobilize heavy metals in soils. However, the spatial and temporal variations of the heavy metals’ bioavailability in soils regulated by a combined material of calcium sulfate and ferric oxide (CSF) remain unclear. In this work, two soil column experiments were conducted to investigate the spatial and temporal variations of CSF immobilized Cd, Pb, and As. In the horizontal soil column, the results showed that CSF’s immobilization range for Cd increased over time, and adding CSF in the center of the soil column decreased the concentrations of bioavailable Cd significantly, up to 8 cm away by day 100. The CSF immobilization effect on Pb and As only existed in the center of the soil column. The CSF’s immobilization depths for Cd and Pb in the vertical soil column increased over time and extended to 20 cm deep by day 100. However, the CSF’s immobilization depths for As only extended to between 5 and 10 cm deep after 100 days of incubation. Overall, the results from this study can serve as a guide to determine the CSF application frequency and spacing distance for the in-situ immobilization of heavy metals in soils. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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18 pages, 7303 KiB

Open AccessArticle

Quantitative Source Apportionment of Potentially Toxic Elements in Baoshan Soils Employing Combined Receptor Models

by Chunyu Dong, Hao Zhang, Haichan Yang, Zhaoxia Wei, Naiming Zhang and Li Bao

Toxics 2023, 11(3), 268; https://doi.org/10.3390/toxics11030268 - 14 Mar 2023

Cited by 2 | Viewed by 1862

Abstract

Arable soils are crucial for national development and food security; therefore, contamination of agricultural soils from potentially toxic elements (PTEs) is a global concern. In this study, we collected 152 soil samples for evaluation. Considering the contamination factors and using the cumulative index [...] Read more.

Arable soils are crucial for national development and food security; therefore, contamination of agricultural soils from potentially toxic elements (PTEs) is a global concern. In this study, we collected 152 soil samples for evaluation. Considering the contamination factors and using the cumulative index and geostatistical methods, we investigated the contamination levels of PTEs in Baoshan City, China. Using principal component analysis, absolute principal component score-multivariate linear regression, positive matrix factorization, and UNMIX, we analyzed the sources and quantitatively estimated their contributions. The average Cd, As, Pb, Cu, and Zn concentrations were 0.28, 31.42, 47.59, 100.46, and 12.36 mg/kg, respectively. The Cd, Cu, and Zn concentrations exceeded the corresponding background values for Yunnan Province. The combined receptor models showed that natural and agricultural sources contributed primarily to Cd and Cu and As and Pb inputs, accounting for 35.23 and 7.67% pollution, respectively. Industrial and traffic sources contributed primarily to Pb and Zn inputs (47.12%). Anthropogenic activities and natural causes accounted for 64.76 and 35.23% of soil pollution, respectively. Industrial and traffic sources contributed 47.12% to pollution from anthropogenic activities. Accordingly, the control of industrial PTE pollution emissions should be strengthened, and awareness should be raised to protect arable land around roads. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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15 pages, 3192 KiB

Open AccessArticle

Isolation and Identification of Mercury-Tolerant Bacteria LBA119 from Molybdenum-Lead Mining Soils and Their Removal of Hg²⁺

by Hanyue Yao, Hui Wang, Jiangtao Ji, Aobo Tan, Yang Song and Zhi Chen

Toxics 2023, 11(3), 261; https://doi.org/10.3390/toxics11030261 - 12 Mar 2023

Cited by 6 | Viewed by 2217

Abstract

Aims: To screen heavy metal-tolerant strains from heavy metal-contaminated soil in mining areas and determine the tolerance of the strains to different heavy metals and their removal rates through experiments. Methods: Mercury-resistant strain LBA119 was isolated from mercury-contaminated soil samples in Luanchuan County, [...] Read more.

Aims: To screen heavy metal-tolerant strains from heavy metal-contaminated soil in mining areas and determine the tolerance of the strains to different heavy metals and their removal rates through experiments. Methods: Mercury-resistant strain LBA119 was isolated from mercury-contaminated soil samples in Luanchuan County, Henan Province, China. The strain was identified by Gram staining, physiological and biochemical tests, and 16S rDNA sequences. The LBA119 strain showed good resistance and removal rates to heavy metals such as Pb²⁺, Hg²⁺, Mn²⁺, Zn²⁺, and Cd²⁺ using tolerance tests under optimal growth conditions. The mercury-resistant strain LBA119 was applied to mercury-contaminated soil to determine the ability of the strain to remove mercury from the soil compared to mercury-contaminated soil without bacterial biomass. Results: Mercury-resistant strain LBA119 is a Gram-positive bacterium that appears as a short rod under scanning electron microscopy, with a single bacterium measuring approximately 0.8 × 1.3 μm. The strain was identified as a Bacillus by Gram staining, physiological and biochemical tests, and 16S rDNA sequence analysis. The strain was highly resistant to mercury, with a minimum inhibitory concentration (MIC) of 32 mg/L for mercury. Under a 10 mg/L mercury environment, the optimal inoculation amount, pH, temperature, and salt concentration of the LBA119 strain were 2%, 7, 30 °C, and 20 g/L, respectively. In the 10 mg/L Hg²⁺ LB medium, the total removal rate, volatilization rate, and adsorption rate at 36 h were 97.32%, 89.08%, and 8.24%, respectively. According to tolerance tests, the strain showed good resistance to Pb²⁺, Mn²⁺, Zn²⁺, Cd²⁺, and other heavy metals. When the initial mercury concentration was 50 mg/L and 100 mg/L, compared with the mercury-contaminated soil that contained an LB medium without bacterial biomass, LBA119 inoculation increased 15.54–37.67% after 30 days of culture. Conclusion: This strain shows high bioremediation potential for mercury-contaminated soil. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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14 pages, 2999 KiB

Open AccessArticle

Microbial Removal of Petroleum Hydrocarbons from Contaminated Soil under Arsenic Stress

by Qu Su, Jiang Yu, Kaiqin Fang, Panyue Dong, Zheyong Li, Wuzhu Zhang, Manxia Liu, Luojing Xiang and Junxiong Cai

Toxics 2023, 11(2), 143; https://doi.org/10.3390/toxics11020143 - 1 Feb 2023

Cited by 10 | Viewed by 2795

Abstract

The contamination of soils with petroleum and its derivatives is a longstanding, widespread, and worsening environmental issue. However, efforts to remediate petroleum hydrocarbon-polluted soils often neglect or overlook the interference of heavy metals that often co-contaminate these soils and occur in petroleum itself. [...] Read more.

The contamination of soils with petroleum and its derivatives is a longstanding, widespread, and worsening environmental issue. However, efforts to remediate petroleum hydrocarbon-polluted soils often neglect or overlook the interference of heavy metals that often co-contaminate these soils and occur in petroleum itself. Here, we identified Acinetobacter baumannii strain JYZ-03 according to its Gram staining, oxidase reaction, biochemical tests, and FAME and 16S rDNA gene sequence analyses and determined that it has the ability to degrade petroleum hydrocarbons. It was isolated from soil contaminated by both heavy metals and petroleum hydrocarbons. Strain JYZ-03 utilized diesel oil, long-chain n-alkanes, branched alkanes, and polycyclic aromatic hydrocarbons (PAHs) as its sole carbon sources. It degraded 93.29% of the diesel oil burden in 7 days. It also had a high tolerance to heavy metal stress caused by arsenic (As). Its petroleum hydrocarbon degradation efficiency remained constant over the 0–300 mg/L As(V) range. Its optimal growth conditions were pH 7.0 and 25–30 °C, respectively, and its growth was not inhibited even by 3.0% (w/v) NaCl. Strain JYZ-03 effectively bioremediates petroleum hydrocarbon-contaminated soil in the presence of As stress. Therefore, strain JYZ-03 may be of high value in petroleum- and heavy-metal-contaminated site bioremediation. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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21 pages, 3508 KiB

Open AccessArticle

Adsorption Characteristics of Indigenous Chromium-Resistant Aspergillus niger Strain Isolated from Red Soil for Remediation of Toxic Chromium in Red Soil Environments

by Jiwei Xu, Lumeng Li, Huabin Wang, Zhanyuan Gao, Chuanshu Wang, Rong Sun, Yong Zhang, Wumei Xu, Xiying Hou and Rui Xu

Toxics 2023, 11(1), 31; https://doi.org/10.3390/toxics11010031 - 29 Dec 2022

Cited by 3 | Viewed by 2286

Abstract

The microbial treatment of soil has great potential to reduce chromium pollution. Here, an indigenous chromium-resistant Aspergillus niger strain (A1) was isolated and screened from heavily chromium-contaminated red soil in Yunnan Province, China using a traditional isolation method and a selective culture experiment. [...] Read more.

The microbial treatment of soil has great potential to reduce chromium pollution. Here, an indigenous chromium-resistant Aspergillus niger strain (A1) was isolated and screened from heavily chromium-contaminated red soil in Yunnan Province, China using a traditional isolation method and a selective culture experiment. The molecular identification of A1 was achieved using 18S rRNA sequencing. The tolerance of the strain to toxic chromium was evaluated through pure laboratory culture. The adsorption effect and mechanism of A1 on chromium in red soil were further studied. The study concluded that A1 exhibited strong activity with exposure to 500 mg·L⁻¹ Cr⁶⁺. Chromium adsorption by A. niger occurred mainly through intracellular metabolism, surface complexations with EPS, and chemical reduction with -C=C-, -OXuH, NH₂, and -C=0. The optimized results showed that A1 had the best Cr⁶⁺ removal effect at pH 4, 40 °C, and a 60 h culture time. Compared with the inoculating of exogenous microbial agents, after inoculating A1 into the chromium-contaminated red soil, Cr⁶⁺ content was significantly reduced, and the high-toxicity chromium state (water-soluble and exchange states) decreased, whereas the low-toxicity chromium state (precipitation and residue states) increased. The results of red soil ITS also showed that the inoculation of indigenous microorganisms can better colonize the red soil. This study proves the feasibility of the application of indigenous A. niger to address red soil chromium pollution and provides a new idea and theoretical support for red soil remediation. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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12 pages, 1891 KiB

Open AccessArticle

Novel Insights into the Influence of Soil Microstructure Characteristics on the Migration and Residue of Light Non-Aqueous Phase Liquid

by Xiaodong Li, Qian Zhang, Xueli Zhang, Jialun Shen, Zongquan Sun, Fujun Ma, Bin Wu and Qingbao Gu

Toxics 2023, 11(1), 16; https://doi.org/10.3390/toxics11010016 - 24 Dec 2022

Cited by 1 | Viewed by 1817

Abstract

Understanding the influence of soil microstructure on light non-aqueous phase liquids (LNAPLs) behavior is critical for predicting the formation of residual LNAPLs under spill condition. However, the roles of soil particle and pore on LNAPLs migration and residue remains unclear. Here, the experiment [...] Read more.

Understanding the influence of soil microstructure on light non-aqueous phase liquids (LNAPLs) behavior is critical for predicting the formation of residual LNAPLs under spill condition. However, the roles of soil particle and pore on LNAPLs migration and residue remains unclear. Here, the experiment simulated an LNAPLs (diesel) spill that was performed in fourteen types of soils, and the key factors affecting diesel behavior are revealed. There were significant differences between fourteen types of soils, with regard to the soil particle, soil pore, and diesel migration and residue. After 72 h of leakage, the migration distance of diesel ranged from 3.42 cm to 8.82 cm in the soils. Except for sandy soil, diesel was mainly distributed in the 0–3 cm soil layer, and the residual amounts were 7.85–26.66 g/kg. It was further confirmed from microstructure that the consistency of soil particle and volume of soil macropores (0.05–7.5 μm) are important for diesel residue in the 0–1 cm soil layer and migration distance. The large soil particles corresponding to 90% of volume fraction and volume of soil mesopores (<0.05 μm) are key factors affecting diesel residue in the 1–3 cm soil layer. The result helps to further comprehend the formation mechanism of residual LNAPLs in the soil. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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15 pages, 7110 KiB

Open AccessArticle

Rapid and Effective Lead Elimination Using Cow Manure Derived Biochar: Balance between Inherent Phosphorus Release and Pollutants Immobilization

by Huabin Wang, Yi Wen, Yu Ding, Zhiqiang Yue, Dan Xu, Ying Liu, Yong Zhang, Rui Xu and Weiqing Zeng

Toxics 2023, 11(1), 1; https://doi.org/10.3390/toxics11010001 - 20 Dec 2022

Cited by 4 | Viewed by 2249

Abstract

Cow manure derived biochar (CMBC) can serve as a promising functional material, and CMBC can be regarded as an ecofriendly approach compared to conventional ones. CM bioadsorbent can be employed for heavy metal immobilization (such as for lead) as well as an amendment [...] Read more.

Cow manure derived biochar (CMBC) can serve as a promising functional material, and CMBC can be regarded as an ecofriendly approach compared to conventional ones. CM bioadsorbent can be employed for heavy metal immobilization (such as for lead) as well as an amendment to increase soil fertility (e.g., phosphorus). Few studies have examined the surface interactions between pollutants and bioadsorbents when inherent nutrient release is present. In this work, CMBC was prepared and applied for Pb(II) removal, and the vital roles of released phosphorus from CMBC were comprehensively disclosed. Furthermore, CMBC could immobilize part of the Pb(II) in soil and promote plant growth. CM400 was an effective adsorbent whose calculated Q_e reached 691.34 mg·g⁻¹, and it rapidly adsorbed 98.36 mg·g⁻¹ of Pb(II) within 1 min. The adsorption mechanisms of Pb(II) by CMBC include ion exchange, physical adsorption, electrostatic attraction, chemical precipitation, surface complexation, and cation–π bond interaction. Based on the residual phosphorus content and adsorption effect, complexation rather than the chemical precipitation had a greater contribution toward adsorption. Besides, as the concentration of Pb(II) increased, the main adsorption mechanisms likely transformed from chemical precipitation to ion exchange and complexation. CMBC not only had a good effect on Pb(II) removal in the solution, but also immobilized the Pb(II) in soil to restrain plant uptake as well as promote plant growth. The main novelty of this work is providing more insights to the cow manure bio adsorbent on Pb immobilization and phosphorus release. This study is expected to serve as a basis and reference for analyzing the release effects of inherent nutrients and the interfacial behaviors with heavy metals when using CMBC and other nutrient–rich carbon–based fertilizers for pollution control. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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29 pages, 11502 KiB

Open AccessReview

Toxicity of Heavy Metals and Recent Advances in Their Removal: A Review

by Manar K. Abd Elnabi, Nehal E. Elkaliny, Maha M. Elyazied, Shimaa H. Azab, Shawky A. Elkhalifa, Sohaila Elmasry, Moustafa S. Mouhamed, Ebrahim M. Shalamesh, Naira A. Alhorieny, Abeer E. Abd Elaty, Ibrahim M. Elgendy, Alaa E. Etman, Kholod E. Saad, Konstantina Tsigkou, Sameh S. Ali, Michael Kornaros and Yehia A.-G. Mahmoud

Toxics 2023, 11(7), 580; https://doi.org/10.3390/toxics11070580 - 3 Jul 2023

Cited by 120 | Viewed by 23272

Abstract

Natural and anthropogenic sources of metals in the ecosystem are perpetually increasing; consequently, heavy metal (HM) accumulation has become a major environmental concern. Human exposure to HMs has increased dramatically due to the industrial activities of the 20th century. Mercury, arsenic lead, chrome, [...] Read more.

Natural and anthropogenic sources of metals in the ecosystem are perpetually increasing; consequently, heavy metal (HM) accumulation has become a major environmental concern. Human exposure to HMs has increased dramatically due to the industrial activities of the 20th century. Mercury, arsenic lead, chrome, and cadmium have been the most prevalent HMs that have caused human toxicity. Poisonings can be acute or chronic following exposure via water, air, or food. The bioaccumulation of these HMs results in a variety of toxic effects on various tissues and organs. Comparing the mechanisms of action reveals that these metals induce toxicity via similar pathways, including the production of reactive oxygen species, the inactivation of enzymes, and oxidative stress. The conventional techniques employed for the elimination of HMs are deemed inadequate when the HM concentration is less than 100 mg/L. In addition, these methods exhibit certain limitations, including the production of secondary pollutants, a high demand for energy and chemicals, and reduced cost-effectiveness. As a result, the employment of microbial bioremediation for the purpose of HM detoxification has emerged as a viable solution, given that microorganisms, including fungi and bacteria, exhibit superior biosorption and bio-accumulation capabilities. This review deals with HM uptake and toxicity mechanisms associated with HMs, and will increase our knowledge on their toxic effects on the body organs, leading to better management of metal poisoning. This review aims to enhance comprehension and offer sources for the judicious selection of microbial remediation technology for the detoxification of HMs. Microbial-based solutions that are sustainable could potentially offer crucial and cost-effective methods for reducing the toxicity of HMs. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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14 pages, 863 KiB

Open AccessReview

A Review of Antibiotics, Antibiotic Resistant Bacteria, and Resistance Genes in Aquaculture: Occurrence, Contamination, and Transmission

by Xia Yuan, Ziqing Lv, Zeyu Zhang, Yu Han, Zhiquan Liu and Hangjun Zhang

Toxics 2023, 11(5), 420; https://doi.org/10.3390/toxics11050420 - 30 Apr 2023

Cited by 42 | Viewed by 7864

Abstract

Antibiotics are commonly used to prevent and control diseases in aquaculture. However, long-term/overuse of antibiotics not only leaves residues but results in the development of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Antibiotics, ARB, and ARGs are widespread in aquaculture ecosystems. [...] Read more.

Antibiotics are commonly used to prevent and control diseases in aquaculture. However, long-term/overuse of antibiotics not only leaves residues but results in the development of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Antibiotics, ARB, and ARGs are widespread in aquaculture ecosystems. However, their impacts and interaction mechanisms in biotic and abiotic media remain to be clarified. In this paper, we summarized the detection methods, present status, and transfer mechanisms of antibiotics, ARB, and ARGs in water, sediment, and aquaculture organisms. Currently, the dominant methods of detecting antibiotics, ARB, and ARGs are UPLC−MS/MS, 16S rRNA sequencing, and metagenomics, respectively. Tetracyclines, macrolides, fluoroquinolones, and sulfonamides are most frequently detected in aquaculture. Generally, antibiotic concentrations and ARG abundance in sediment are much higher than those in water. Yet, no obvious patterns in the category of antibiotics or ARB are present in organisms or the environment. The key mechanisms of resistance to antibiotics in bacteria include reducing the cell membrane permeability, enhancing antibiotic efflux, and structural changes in antibiotic target proteins. Moreover, horizontal transfer is a major pathway for ARGs transfer, including conjugation, transformation, transduction, and vesiculation. Identifying, quantifying, and summarizing the interactions and transmission mechanisms of antibiotics, ARGs, and ARB would provide useful information for future disease diagnosis and scientific management in aquaculture. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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13 pages, 2254 KiB

Open AccessReview

Recent Advances and Future Prospects on the Tailing Covering Technology for Oxidation Prevention of Sulfide Tailings

by Meiyan Si, Yunjian Chen, Chen Li, Yichao Lin, Jianhong Huang, Feng Zhu, Senlin Tian and Qun Zhao

Toxics 2023, 11(1), 11; https://doi.org/10.3390/toxics11010011 - 22 Dec 2022

Cited by 7 | Viewed by 2937

Abstract

Acid mine drainage, produced from sulfur-containing mine waste exposed to air, water, and bacteria, is considered as a serious environmental pollutant because of its extremely low pH and excessive heavy metals. In order to solve the ecological environment problems caused by the acid [...] Read more.

Acid mine drainage, produced from sulfur-containing mine waste exposed to air, water, and bacteria, is considered as a serious environmental pollutant because of its extremely low pH and excessive heavy metals. In order to solve the ecological environment problems caused by the acid mine drainage, treatment methods such as neutralization, adsorption, passivation, bio-inhibition, and physical coverage have been developed. Nevertheless, these methods are terminal treatment methods, which are unable to prevent the generation of acid mine drainage at the source. Recently, it is noteworthy that the tailing covering technology is particularly emphasized, owing to its superior source control capability. By reducing the contact with air, water, and bacteria, the oxidation of sulfide tailings is significantly reduced, thus avoiding the production of acid mine drainage. To date, massive research has been studied and parts of technologies have been applied, but the review on the principles, processes, and applications of these technologies are still lacking. Thus, the present review aims to increase the knowledge related to the most relevant application of tailing covering technology with the following aspects: (i) the background, concepts, and performance of tailing covering technology; (ii) the applicable conditions for each tailings coverage system and their advantages and limitations; and (iii) the future perspective of this technology. Full article

(This article belongs to the Special Issue Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater)

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