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Search Results (1,228)

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Keywords = contaminated soil remediation

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21 pages, 1245 KiB  
Article
Geochemical Behaviour of Trace Elements in Diesel Oil-Contaminated Soil During Remediation Assisted by Mineral and Organic Sorbents
by Mirosław Wyszkowski and Natalia Kordala
Appl. Sci. 2025, 15(15), 8650; https://doi.org/10.3390/app15158650 (registering DOI) - 5 Aug 2025
Abstract
The topic of environmental pollution by petroleum products is highly relevant due to rapid urbanisation, including industrial development, road infrastructure and fuel distribution. Potential threat areas include refineries, fuel stations, pipelines, warehouses and transshipment bases, as well as sites affected by accidents or [...] Read more.
The topic of environmental pollution by petroleum products is highly relevant due to rapid urbanisation, including industrial development, road infrastructure and fuel distribution. Potential threat areas include refineries, fuel stations, pipelines, warehouses and transshipment bases, as well as sites affected by accidents or fuel spills. This study aimed to determine whether organic and mineral materials could mitigate the effects of diesel oil pollution on the soil’s trace element content. The used materials were compost, bentonite and calcium oxide. Diesel oil pollution had the most pronounced effect on the levels of Cd, Ni, Fe and Co. The levels of the first three elements increased, while the level of Co decreased by 53%. Lower doses of diesel oil (2.5 and 5 cm3 per kg of soil) induced an increase in the levels of the other trace elements, while higher doses caused a reduction, especially in Cr. All materials applied to the soil (compost, bentonite and calcium oxide) reduced the content of Ni, Cr and Fe. Compost and calcium oxide also increased Co accumulation in the soil. Bentonite had the strongest reducing effect on the Ni and Cr contents of the soil, reducing them by 42% and 53%, respectively. Meanwhile, calcium oxide had the strongest reducing effect on Fe and Co accumulation, reducing it by 12% and 31%, respectively. Inverse relationships were recorded for Cd (mainly bentonite), Pb (especially compost), Cu (mainly compost), Mn (mainly bentonite) and Zn (only compost) content in the soil. At the most contaminated site, the application of bentonite reduced the accumulation of Pb, Zn and Mn in the soil, while the application of compost reduced the accumulation of Cd. Applying various materials, particularly bentonite and compost, limits the content of certain trace elements in the soil. This has a positive impact on reducing the effect of minor diesel oil pollution on soil properties and can promote the proper growth of plant biomass. Full article
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26 pages, 3020 KiB  
Review
Fabrication of Cellulose-Based Hydrogels Through Ionizing Radiation for Environmental and Agricultural Applications
by Muhammad Asim Raza
Gels 2025, 11(8), 604; https://doi.org/10.3390/gels11080604 - 2 Aug 2025
Viewed by 160
Abstract
Hydrogels exhibit remarkable physicochemical properties, including high water absorption and retention capacities, as well as controlled release behavior. Their inherent biodegradability, biocompatibility, and non-toxicity make them suitable for a wide range of applications. Cellulose, a biodegradable, renewable, and abundantly available polysaccharide, is a [...] Read more.
Hydrogels exhibit remarkable physicochemical properties, including high water absorption and retention capacities, as well as controlled release behavior. Their inherent biodegradability, biocompatibility, and non-toxicity make them suitable for a wide range of applications. Cellulose, a biodegradable, renewable, and abundantly available polysaccharide, is a viable source for hydrogel preparation. Ionizing radiation, using electron-beam (EB) or gamma (γ) irradiation, provides a promising approach for synthesizing hydrogels. This study reviews recent advancements in cellulose-based hydrogels, focusing on cellulose and its derivatives, brief information regarding ionizing radiation, comparison between EB and γ-irradiation, synthesis and modification through ionizing radiation technology, and their environmental and agricultural applications. For environmental remediation, these hydrogels have demonstrated significant potential in water purification, particularly in the removal of heavy metals, dyes, and organic contaminants. In agricultural applications, cellulose-based hydrogels function as soil conditioners by enhancing water retention and serving as carriers for agrochemicals. Full article
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16 pages, 1365 KiB  
Article
Immobilization of Cd Through Biosorption by Bacillus altitudinis C10-4 and Remediation of Cd-Contaminated Soil
by Tianyu Gao, Chenlu Zhang, Xueqiang Hu, Tianqi Wang, Zhitang Lyu and Lei Sun
Microorganisms 2025, 13(8), 1798; https://doi.org/10.3390/microorganisms13081798 - 1 Aug 2025
Viewed by 159
Abstract
In this study, a highly cadmium (II)-resistant bacterium strain, C10-4, identified as Bacillus altitudinis, was isolated from a sediment sample collected from Baiyangdian Lake, China. The minimum inhibitory concentration (MIC) of Cd(II) for strain C10-4 was 1600 mg/L. Factors such as the [...] Read more.
In this study, a highly cadmium (II)-resistant bacterium strain, C10-4, identified as Bacillus altitudinis, was isolated from a sediment sample collected from Baiyangdian Lake, China. The minimum inhibitory concentration (MIC) of Cd(II) for strain C10-4 was 1600 mg/L. Factors such as the contact time, pH, Cd(II) concentration, and biomass dosage affected the adsorption of Cd(II) by strain C10-4. The adsorption process fit well to the Langmuir adsorption isotherm model and the pseudo-second-order kinetics model, based on the Cd(II) adsorption data obtained from the cells of strain C10-4. This suggests that Cd(II) is adsorbed by strain C10-4 cells via a single-layer homogeneous chemical adsorption process. According to the Langmuir model, the maximum biosorption capacity was 3.31 mg/g for fresh-strain C10-4 biomass. Cd(II) was shown to adhere to the bacterial cell wall through SEM-EDS analysis. FTIR spectroscopy further indicated that the main functional sites for the binding of Cd(II) ions on the cell surface of strain C10-4 were functional groups such as N-H, -OH, -CH-, C=O, C-O, P=O, sulfate, and phosphate. After the inoculation of strain C10-4 into Cd(II)-contaminated soils, there was a significant reduction (p < 0.01) in the exchangeable fraction of Cd and an increase (p < 0.01) in the sum of the reducible, oxidizable, and residual fractions of Cd. The results show that Bacillus altitudinis C10-4 has good potential for use in the remediation of Cd(II)-contaminated soils. Full article
(This article belongs to the Section Environmental Microbiology)
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16 pages, 1706 KiB  
Article
Biochar-Immobilized Pseudomonas aeruginosa Enhances Copper Remediation and Growth of Chinese Milk Vetch (Astragalus sinicus)
by Yunkai Hu, Chuan Wang and Youbao Wang
Microorganisms 2025, 13(8), 1793; https://doi.org/10.3390/microorganisms13081793 - 31 Jul 2025
Viewed by 173
Abstract
Heavy metal-contaminated soil poses a severe threat to environmental quality and human health, calling for eco-friendly and efficient remediation strategies. This study explored the use of biochar-immobilized copper-resistant Pseudomonas aeruginosa to remediate copper-contaminated soil and promote growth of Chinese milk vetch (Astragalus [...] Read more.
Heavy metal-contaminated soil poses a severe threat to environmental quality and human health, calling for eco-friendly and efficient remediation strategies. This study explored the use of biochar-immobilized copper-resistant Pseudomonas aeruginosa to remediate copper-contaminated soil and promote growth of Chinese milk vetch (Astragalus sinicus L.). Indoor pot experiments compared four groups: copper-contaminated soil (control), soil with biochar, soil with free bacteria, and soil with biochar-immobilized bacteria (IM). Results showed IM had the most significant effects on soil properties: it raised pH to 7.04, reduced bioavailable copper by 34.37%, and increased catalase (3.48%) and urease (78.95%) activities. IM also altered soil bacterial communities, decreasing their richness and evenness (alpha diversity) while shifting community composition. For Chinese milk vetch, IM reduced leaf malondialdehyde (a marker of oxidative stress) by 15%, increased total dry weight by 90%, and lowered copper accumulation in roots (18.62%) and shoots (60.33%). As a nitrogen-fixing plant, the vetch’s nitrogen fixation in roots and shoots rose by 82.70% and 57.08%, respectively, under IM. These findings demonstrate that biochar-immobilized Pseudomonas aeruginosa is a promising in situ amendment for remediating copper-contaminated soil and boosting plant growth. Full article
(This article belongs to the Section Environmental Microbiology)
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22 pages, 2576 KiB  
Review
Essential Per- and Polyfluoroalkyl Substances (PFAS) in Our Society of the Future
by Rudy Dams and Bruno Ameduri
Molecules 2025, 30(15), 3220; https://doi.org/10.3390/molecules30153220 - 31 Jul 2025
Viewed by 163
Abstract
Per- or polyfluoroalkyl substances (PFASs) are man-made compounds involved in compositions of many industrial processes and consumer products. The largest-volume man-made PFAS are made up of refrigerants and fluoropolymers. Major concerns for our society related to these substances are their contribution to global [...] Read more.
Per- or polyfluoroalkyl substances (PFASs) are man-made compounds involved in compositions of many industrial processes and consumer products. The largest-volume man-made PFAS are made up of refrigerants and fluoropolymers. Major concerns for our society related to these substances are their contribution to global warming as greenhouse gasses and the potential for adverse effects on living organisms, particularly by long-chain perfluoroalkyl acid derivatives. Restrictions on manufacturing and applications will increase in the near future. The full remediation of historical and current contaminations of air, soil and water remains problematic, especially for ultra-short PFASs, such as trifluoroacetic acid. Future monitoring of PFAS levels and their impact on ecosystems remains important. PFASs have become integrated in the lifestyle and infrastructures of our modern worldwide society and are likely to be part of that society for years to come in essential applications by closing the fluorine loop. Full article
(This article belongs to the Special Issue Insights for Organofluorine Chemistry, 2nd Edition)
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16 pages, 1981 KiB  
Article
Computational Design of Mineral-Based Materials: Iron Oxide Nanoparticle-Functionalized Polymeric Films for Enhanced Public Water Purification
by Iustina Popescu, Alina Ruxandra Caramitu, Adriana Mariana Borș, Mihaela-Amalia Diminescu and Liliana Irina Stoian
Polymers 2025, 17(15), 2106; https://doi.org/10.3390/polym17152106 - 31 Jul 2025
Viewed by 262
Abstract
Heavy metal contamination in natural waters and soils poses a significant environmental challenge, necessitating efficient and sustainable water treatment solutions. This study presents the computational design of low-density polyethylene (LDPE) films functionalized with iron oxide (Fe3O4) nanoparticles (NPs) for [...] Read more.
Heavy metal contamination in natural waters and soils poses a significant environmental challenge, necessitating efficient and sustainable water treatment solutions. This study presents the computational design of low-density polyethylene (LDPE) films functionalized with iron oxide (Fe3O4) nanoparticles (NPs) for enhanced water purification applications. Composite materials containing 5%, 10%, and 15% were synthesized and characterized in terms of adsorption efficiency, surface morphology, and reusability. Advanced molecular modeling using BIOVIA Pipeline was employed to investigate charge distribution, functional group behaviour, and atomic-scale interactions between polymer chains and metal ions. The computational results revealed structure–property relationships crucial for optimizing adsorption performance and understanding geochemically driven interaction mechanisms. The LDPE/Fe3O4 composites demonstrated significant removal efficiency of Cu2+ and Ni2+ ions, along with favourable mechanical properties and regeneration potential. These findings highlight the synergistic role of mineral–polymer interfaces in water remediation, presenting a scalable approach to designing multifunctional polymeric materials for environmental applications. This study contributes to the growing field of polymer-based adsorbents, reinforcing their value in sustainable water treatment technologies and environmental protection efforts. Full article
(This article belongs to the Special Issue Polymer-Based Coatings: Principles, Development and Applications)
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16 pages, 3327 KiB  
Article
Development and Evaluation of Selenium-Enriched Compound Fertilizers for Remediation of Mercury-Contaminated Agricultural Soil
by Yuxin Li, Guangpeng Pei, Yanda Zhang, Shuyun Guan, Yingzhong Lv, Zhuo Li and Hua Li
Agronomy 2025, 15(8), 1842; https://doi.org/10.3390/agronomy15081842 - 30 Jul 2025
Viewed by 305
Abstract
Agricultural soil contaminated with mercury (Hg) poses a serious threat to ecosystems and human health. Although adding an appropriate amount of selenium (Se) can reduce the toxicity and mobility of Hg in soil, Se alone is prone to leaching into groundwater through soil [...] Read more.
Agricultural soil contaminated with mercury (Hg) poses a serious threat to ecosystems and human health. Although adding an appropriate amount of selenium (Se) can reduce the toxicity and mobility of Hg in soil, Se alone is prone to leaching into groundwater through soil runoff. Therefore, Se-enriched compound fertilizers were developed, and their remediation effect on Hg-contaminated agricultural soil was determined. The Se-enriched compound fertilizers were prepared by combining an organic fertilizer (vinegar residue, biochar, and potassium humate), inorganic fertilizer (urea, KH2PO4, ZnSO4, and Na2SeO3), and a binder (attapulgite and bentonite). A material proportioning experiment showed that the optimal granulation rate, organic matter content, and compressive strength were achieved when using 15% attapulgite (Formulation 1) and 10% bentonite (Formulation 2). An analysis of Se-enriched compound fertilizer particles showed that the two Se-enriched compound fertilizers complied with the standard for organic–inorganic compound fertilizers (China GB 18877-2002). Compared with the control, Formulation 1 and Formulation 2 significantly reduced the Hg content in bulk and rhizosphere soil following diethylenetriaminepentaacetic acid (DTPA) extraction by 40.1–47.3% and 53.8–56.0%, respectively. They also significantly reduced the Hg content in maize seedling roots and shoots by 26.4–29.0% and 57.3–58.7%, respectively, effectively limiting Hg uptake, transport, and enrichment. Under the Formulation 1 and Formulation 2 treatments, the total and DTPA-extractable Se contents in soil and maize seedlings were significantly increased. This study demonstrated that Se-enriched compound fertilizer effectively remediates Hg-contaminated agricultural soil and can promote the uptake of Se by maize. The results of this study are expected to positively contribute to the sustainable development of the agro-ecological environment. Full article
(This article belongs to the Section Innovative Cropping Systems)
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8 pages, 172 KiB  
Editorial
Toxicity Characterization, Detection and Remediation of Contaminants in Soils and Groundwater
by Bowen Liu, Haoyang Xiong, Junhao Qin, Peidong Su, Feng Zhu and Lin Ding
Toxics 2025, 13(8), 635; https://doi.org/10.3390/toxics13080635 - 28 Jul 2025
Viewed by 186
Abstract
Soil and groundwater contamination remains a critical environmental and public health challenge worldwide [...] Full article
18 pages, 1555 KiB  
Review
Immobilization of Cadmium, Lead, and Copper in Soil Using Bacteria: A Literature Review
by Saulius Vasarevičius and Vaida Paliulienė
Land 2025, 14(8), 1547; https://doi.org/10.3390/land14081547 - 28 Jul 2025
Viewed by 315
Abstract
The heavy metal contamination of soils is a global environmental challenge threatening water quality, food safety, and human health. Using a systematic literature review approach, this study aimed to assess the potential of bacterial strains to immobilize cadmium (Cd2+), lead (Pb [...] Read more.
The heavy metal contamination of soils is a global environmental challenge threatening water quality, food safety, and human health. Using a systematic literature review approach, this study aimed to assess the potential of bacterial strains to immobilize cadmium (Cd2+), lead (Pb2+), and copper (Cu2+) in contaminated soils. A total of 45 articles were analyzed, focusing on studies that reported heavy metal concentrations before and after bacterial treatment. The analysis revealed that bacterial genera such as Bacillus, Pseudomonas, and Enterobacter were most commonly used for the immobilization of these metals. Immobilization efficiencies ranged from 25% to over 98%, with higher efficiencies generally observed when microbial consortia or amendments (e.g., phosphate compounds and biochar) were applied. The main immobilization mechanisms included biosorption, bioprecipitation (such as carbonate-induced precipitation), bioaccumulation, and biomineralization, which convert mobile metal ions into more stable, less bioavailable forms. These findings highlight the promising role of microbial-assisted immobilization in mitigating heavy metal pollution and reducing ecological risks. Further laboratory and field studies are needed to optimize the use of these microbial strains under site-specific conditions to ensure effective and sustainable soil remediation practices. Full article
(This article belongs to the Section Land Use, Impact Assessment and Sustainability)
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22 pages, 6926 KiB  
Article
Exploring Heavy Metals Exposure in Urban Green Zones of Thessaloniki (Northern Greece): Risks to Soil and People’s Health
by Ioannis Papadopoulos, Evangelia E. Golia, Ourania-Despoina Kantzou, Sotiria G. Papadimou and Anna Bourliva
Toxics 2025, 13(8), 632; https://doi.org/10.3390/toxics13080632 - 27 Jul 2025
Viewed by 989
Abstract
This study investigates the heavy metal contamination in urban and peri-urban soils of Thessaloniki, Greece, over a two-year period (2023–2024). A total of 208 composite soil samples were systematically collected from 52 sites representing diverse land uses, including high-traffic roadsides, industrial zones, residential [...] Read more.
This study investigates the heavy metal contamination in urban and peri-urban soils of Thessaloniki, Greece, over a two-year period (2023–2024). A total of 208 composite soil samples were systematically collected from 52 sites representing diverse land uses, including high-traffic roadsides, industrial zones, residential neighborhoods, parks, and mixed-use areas, with sampling conducted both after the wet (winter) and dry (summer) seasons. Soil physicochemical properties (pH, electrical conductivity, texture, organic matter, and calcium carbonate content) were analyzed alongside the concentrations of heavy metals such as Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn. A pollution assessment employed the Geoaccumulation Index (Igeo), Contamination Factor (Cf), Pollution Load Index (PLI), and Potential Ecological Risk Index (RI), revealing variable contamination levels across the city, with certain hotspots exhibiting a considerable to very high ecological risk. Multivariate statistical analyses (PCA and HCA) identified distinct anthropogenic and geogenic sources of heavy metals. Health risk assessments, based on USEPA models, evaluated non-carcinogenic and carcinogenic risks for both adults and children via ingestion and dermal contact pathways. The results indicate that while most sites present low to moderate health risks, specific locations, particularly near major transport and industrial areas, pose elevated risks, especially for children. The findings underscore the need for targeted monitoring and remediation strategies to mitigate the ecological and human health risks associated with urban soil pollution in Thessaloniki. Full article
(This article belongs to the Special Issue Distribution and Behavior of Trace Metals in the Environment)
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15 pages, 2134 KiB  
Article
Integrated Characterization of Sediments Contaminated by Acid Mine Drainage: Mineralogical, Magnetic, and Geochemical Properties
by Patrícia Gomes, Teresa Valente and Eric Font
Minerals 2025, 15(8), 786; https://doi.org/10.3390/min15080786 - 26 Jul 2025
Viewed by 245
Abstract
Acid mine drainage, a consequence of exposure of sulfide mining waste to weathering processes, results in significant water, sediment, and soil contamination. This contamination results in acidophilic ecosystems, with low pH values and elevated concentrations of sulfate and potentially toxic elements. The São [...] Read more.
Acid mine drainage, a consequence of exposure of sulfide mining waste to weathering processes, results in significant water, sediment, and soil contamination. This contamination results in acidophilic ecosystems, with low pH values and elevated concentrations of sulfate and potentially toxic elements. The São Domingos mine, an abandoned site in the Iberian Pyrite Belt, lacks remediation measures and has numerous waste dumps, which are a major source of contamination to local water systems. Therefore, this study examines sediment accumulation in five mine dams along the São Domingos stream that traverses the entire mine complex. Decades of sediment and waste transport since mine closure have resulted in dam-clogging processes. The geochemical, mineralogical, and magnetic properties of the sediments were analyzed to evaluate the mineralogical controls on the mobilization of potentially toxic elements. The sediments are dominated by iron oxides, oxyhydroxides, and hydroxysulfates, with jarosite playing a key role in binding high concentrations of iron and toxic elements. However, no considerable correlation was found between potentially toxic elements and magnetic parameters, highlighting the complex behavior of these contaminants in acid mine drainage-affected systems. Full article
(This article belongs to the Section Environmental Mineralogy and Biogeochemistry)
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19 pages, 722 KiB  
Review
Karst Multi-Source Organic Solid Waste Bio-Enhanced Composting: The Potential of Circular Utilization to Enhance Soil Quality and Control Contaminants
by Chen Huang, Xinyu Zhao, Hui Zhang, Zihan Wang and Beidou Xi
Fermentation 2025, 11(8), 426; https://doi.org/10.3390/fermentation11080426 - 24 Jul 2025
Viewed by 440
Abstract
The dual environmental challenges of karst areas lie in organic solid waste’s (OSW) massive generation scale and diffuse dispersion, which accelerate bedrock exposure and soil contamination, while simultaneously representing an underutilized resource for soil amendments through optimized composting. Bio-enhanced composting of multi-source OSW [...] Read more.
The dual environmental challenges of karst areas lie in organic solid waste’s (OSW) massive generation scale and diffuse dispersion, which accelerate bedrock exposure and soil contamination, while simultaneously representing an underutilized resource for soil amendments through optimized composting. Bio-enhanced composting of multi-source OSW yields compounds with dual redox/adsorption capabilities, effectively improving soil quality and restoring ecological balance. The recycling and circular utilization of OSW resources become particularly critical in karst regions with vulnerable soil ecosystems, where sustainable resource management is urgently needed to maintain ecological balance. This review elucidates the ecological impacts of multi-source OSW compost applications on soil environments in ecologically fragile karst regions, specifically elucidating the mechanisms of heavy metals (HMs) migration–transformation and organic contaminant degradation (with emphasis on emerging pollutants), and the functional role of microbial carbon pumps in these processes. Furthermore, establishing a sustainable “multi-source OSW−compost−organic matter (adsorption and redox sites)−microorganisms−pollution remediation” cycle creates a green, low-carbon microenvironment for long-term soil remediation. Finally, this study evaluates the application prospects of the refined composting technology utilizing multi-objective regulation for OSW resource recycling and utilization in karst areas. This review provides critical insights for optimizing soil remediation strategies in karst ecosystems through organic waste valorization. Full article
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19 pages, 2173 KiB  
Article
The Effect of Slow-Release Fertilizer on the Growth of Garlic Sprouts and the Soil Environment
by Chunxiao Han, Zhizhi Zhang, Renlong Liu, Changyuan Tao and Xing Fan
Appl. Sci. 2025, 15(15), 8216; https://doi.org/10.3390/app15158216 - 24 Jul 2025
Viewed by 354
Abstract
To address the issue of excessive chemical fertilizer use in agricultural production, this study conducted a pot experiment with four treatments: CK (no fertilization), T1 (the application of potassium magnesium sulfate fertilizer), T2 (the application of slow-release fertilizer equal to T1), and T3 [...] Read more.
To address the issue of excessive chemical fertilizer use in agricultural production, this study conducted a pot experiment with four treatments: CK (no fertilization), T1 (the application of potassium magnesium sulfate fertilizer), T2 (the application of slow-release fertilizer equal to T1), and T3 (the application of slow-release fertilizer with the same fertility as T1). The effects of these treatments on garlic seedling yield, growth quality, chlorophyll content, photosynthetic characteristics, and the soil environment were investigated to evaluate the feasibility of replacing conventional fertilizers with slow-release formulations. The results showed that compared with CK, all three fertilized treatments (T1, T2, and T3) significantly increased the plant heights and stem diameters of the garlic sprouts (p < 0.05). Plant height increased by 14.85%, 17.81%, and 27.75%, while stem diameter increased by 9.36%, 8.83%, and 13.96%, respectively. Additionally, the chlorophyll content increased by 4.34%, 7.22%, and 8.05% across T1, T2, and T3, respectively. Among the treatments, T3 exhibited the best overall growth performance. Compared with those in the CK group, the contents of soluble sugars, soluble proteins, free amino acids, vitamin C, and allicin increased by 64.74%, 112.17%, 126.82%, 36.15%, and 45.43%, respectively. Furthermore, soil organic matter, available potassium, magnesium, and phosphorus increased by 109.02%, 886.25%, 91.65%, and 103.14%, respectively. The principal component analysis indicated that soil pH and exchangeable magnesium were representative indicators reflecting the differences in the soil’s chemical properties under different fertilization treatments. Compared with the CK group, the metal contents in the T1 group slightly increased, while those in T2 and T3 generally decreased, suggesting that the application of slow-release fertilizer exerts a certain remediation effect on soils contaminated with heavy metals. This may be attributed to the chemical precipitation and ion exchange capacities of phosphogypsum, as well as the high adsorption and cation exchange capacity of bentonite, which help reduce the leaching of soil metal ions. In summary, slow-release fertilizers not only promote garlic sprout growth but also enhance soil quality by regulating its chemical properties. Full article
(This article belongs to the Section Ecology Science and Engineering)
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20 pages, 1612 KiB  
Review
Phytoremediation Potential of Silicon-Treated Brassica juncea L. in Mining-Affected Water and Soil Composites in South Africa: A Review
by Kamogelo Katlego Motshumi, Awonke Mbangi, Elmarie Van Der Watt and Zenzile Peter Khetsha
Agriculture 2025, 15(15), 1582; https://doi.org/10.3390/agriculture15151582 - 23 Jul 2025
Viewed by 274
Abstract
Heavy metal pollution due to mining activities poses a significant threat to agricultural production, ecosystem health, and food security in South Africa. This review integrates current knowledge on the use of mustard spinach (Brassica juncea (L.) Czern.) for the bioremediation of polluted [...] Read more.
Heavy metal pollution due to mining activities poses a significant threat to agricultural production, ecosystem health, and food security in South Africa. This review integrates current knowledge on the use of mustard spinach (Brassica juncea (L.) Czern.) for the bioremediation of polluted water and soil, focusing on enhancing phytoremediation efficiency through the use of silicon-based biostimulant treatments. Mustard spinach is known for its capacity to accumulate and tolerate high levels of toxic metals, such as Pb, Cd, and Hg, owing to its strong physiological and biochemical defense mechanisms, including metal chelation, antioxidant activity, and osmotic adjustment. However, phytoremediation potential is often constrained by the negative impact of heavy metal stress on plant growth. Recent studies have shown that silicon-based biostimulants can alleviate metal toxicity by reducing metal bioavailability, increasing metal immobilization, and improving the antioxidative capacity and growth of plants. Combining silicon amendments with mustard spinach cultivation is a promising, eco-friendly approach to the remediation of mining-impacted soils and waters, potentially restoring agricultural productivity and reducing health risks to the resident populations. This review elucidates the multifaceted mechanisms by which silicon-enhanced phytoremediation operates, including soil chemistry modification, metal sequestration, antioxidant defense, and physiological resilience, while highlighting the practical, field-applicable benefits of this combined approach. Furthermore, it identifies urgent research priorities, such as field validation and the optimization of silicon application methods. Full article
(This article belongs to the Special Issue The Role of Silicon in Improving Crop Growth Under Abiotic Stress)
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20 pages, 2411 KiB  
Article
Influencing Factors of Hexavalent Chromium Speciation Transformation in Soil from a Northern China Chromium Slag Site
by Shuai Zhu, Junru Chen, Yun Zhu, Baoke Zhang, Jing Jia, Meng Pan, Zhipeng Yang, Jianhua Cao and Yating Shen
Molecules 2025, 30(15), 3076; https://doi.org/10.3390/molecules30153076 - 23 Jul 2025
Viewed by 275
Abstract
Chromium slag sites pose severe environmental risks due to hexavalent chromium (Cr(VI)) contamination, characterized by high mobility and toxicity. This study focused on chromium-contaminated soil from a historical chromium slag site in North China, where long-term accumulation of chromate production residues has led [...] Read more.
Chromium slag sites pose severe environmental risks due to hexavalent chromium (Cr(VI)) contamination, characterized by high mobility and toxicity. This study focused on chromium-contaminated soil from a historical chromium slag site in North China, where long-term accumulation of chromate production residues has led to serious Cr(VI) pollution, with Cr(VI) accounting for 13–22% of total chromium and far exceeding national soil risk control standards. To elucidate Cr(VI) transformation mechanisms and elemental linkages, a combined approach of macro-scale condition experiments and micro-scale analysis was employed. Results showed that acidic conditions (pH < 7) significantly enhanced Cr(VI) reduction efficiency by promoting the conversion of CrO42− to HCrO4/Cr2O72−. Among reducing agents, FeSO4 exhibited the strongest effect (reduction efficiency >30%), followed by citric acid and fulvic acid. Temperature variations (−20 °C to 30 °C) had minimal impact on Cr(VI) transformation in the 45-day experiment, while soil moisture (20–25%) indirectly facilitated Cr(VI) reduction by enhancing the reduction of agent diffusion and microbial activity, though its effect was weaker than chemical interventions. Soil grain-size composition influenced Cr(VI) distribution unevenly: larger particles (>0.2 mm) in BC-35 and BC-36-4 acted as main Cr(VI) reservoirs due to accumulated Fe-Mn oxides, whereas BC-36-3 showed increased Cr(VI) in smaller particles (<0.074 mm). μ-XRF and correlation analysis revealed strong positive correlations between Cr and Ca, Fe, Mn, Ni (Pearson coefficient > 0.7, p < 0.01), attributed to adsorption–reduction coupling on iron-manganese oxide surfaces. In contrast, Cr showed weak correlations with Mg, Al, Si, and K. This study clarifies the complex factors governing Cr(VI) behavior in chromium slag soils, providing a scientific basis for remediation strategies such as pH adjustment (4–6) combined with FeSO4 addition to enhance Cr(VI) reduction efficiency. Full article
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