Search Results (681)

Polyethylene (PE) mulching has been widely practiced in agriculture for decades, but its short-term impacts on heavy metal dynamics and crop safety under field conditions remain poorly understood. In this study, a one-season field trial was carried out in Cd-contaminated paddy to evaluate how PE mulching influences rhizosphere microbial communities, soil physicochemical properties, and Cd accumulation in rice. Results showed that PE mulching improved rice performance, increasing dry grain weight by 14.47% and thousand-grain weight by 1.10 folds, while reducing grain Cd concentration from 0.2307 to 0.1727 mg/kg, below the national safety threshold of 0.2 mg/kg. These effects were closely linked to elevated soil pH, decreased redox potential, and the enrichment of metal-reducing (Geobacteraceae, Desulfuromonadia) and sulfate-reducing (Desulfosporosinus, Methanospirillum) taxa, which promoted Cd immobilization into less bioavailable forms. A structural equation model (SEM) further confirmed that microbial abundance and Cd speciation were key factors associated with Cd uptake by rice. However, PE mulching also reduced microbial diversity and functional redundancy, disrupted co-occurrence networks, and potentially weakened rhizosphere ecosystem stability and resilience in the short term. This study provides field-based evidence that PE mulching reduces food safety risks and improves yield but destabilizes soil microbial communities, highlighting its short-term double-edged ecological effects and the need for balanced management to sustain productivity and soil health. Full article

Soil contamination by organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), pesticides, pharmaceuticals, and petroleum hydrocarbons has emerged as a global environmental concern due to their persistence, bioaccumulation, and potential health risks. Biochar, a carbon-rich material derived from the pyrolysis of biomass, has attracted increasing attention as an environmentally friendly and cost-effective amendment for remediating contaminated soils. This review systematically summarizes recent advances in the application of biochar for the remediation of organic pollutants in soils to guide the development of more effective biochar-based strategies for sustainable soil remediation. The physicochemical properties of biochar influencing pollutant interactions are discussed, including surface area, pore structure, functional groups, and aromaticity. Mechanisms such as adsorption, sequestration, microbial interaction enhancement, and catalytic degradation are elucidated. Moreover, this review highlights the influence of feedstock types, pyrolysis conditions, biochar modification strategies, and environmental factors on biochar performance. The analysis reveals that biochar performance is strongly dependent on feedstock selection, pyrolysis conditions, and post-modification strategies, which jointly determine pollutant immobilization efficiency and long-term stability. Current challenges, such as long-term stability, pollutant desorption, and ecological impacts, are critically examined. Finally, future perspectives on the design of engineered biochar and its integration with other remediation technologies are proposed. Rationally engineered biochar, particularly when integrated with biological or physicochemical remediation technologies, demonstrates strong potential for efficient and sustainable soil remediation. Full article

Arsenic (As) contamination in paddy soils poses a serious risk to rice safety and human health. To mitigate this issue, we developed a low-temperature, partially pyrolyzed Fe/Mn/Mg-modified biochar (FMM-BC) and evaluated its performance and mechanisms for remediating As-contaminated soil through a pakchoi–rice rotation pot experiment, aiming to reduce As accumulation in rice grains and pakchoi. The results indicated that FMM-BC application altered soil physicochemical properties and As speciation, reducing both water-soluble and bioavailable As and promoting its transformation from exchangeable to more stable organic-bound and residual fractions. Compared with the control, FMM-BC application reduced arsenic content in rice stems, leaves, and brown rice to 1.94 mg∙kg⁻¹, 5.24 mg∙kg⁻¹, and 1.21 mg∙kg⁻¹, respectively. In contrast, unmodified biochar (BC) increased As bioavailability and plant uptake, underscoring the importance of Fe/Mn/Mg modification. FMM-BC also enhanced the translocation of Fe, Mn, and Mg within rice plants, thereby modifying internal As transport dynamics and suppressing its accumulation in aboveground tissues. Under FMM-BC treatment, arsenic content in pakchoi stems and leaves decreased to 1.19 mg∙kg⁻¹ (vs. 1.96 mg∙kg⁻¹ in the control), and brown rice declined to 0.27 mg∙kg⁻¹ (vs. 1.49 mg∙kg⁻¹ in the control)—well below the national food safety threshold (0.35 mg∙kg⁻¹). These findings demonstrate that FMM-BC effectively stabilizes As in contaminated soils and reduces its transfer to edible plant parts, with Fe/Mn/Mg playing a key role in enhancing As immobilization and limiting its mobility within the soil–plant system. Full article

Cadmium (Cd) contamination in agricultural systems poses significant ecotoxicological risks through bioaccumulation in food chains. While lime-based amendments are widely applied for Cd immobilization, mechanistic understanding of bioavailability control pathways remains limited. This study employed a meta-analysis methodology based on 260 datasets from 55 publications to systematically investigate the mechanisms and differences in the effectiveness of calcium hydroxide, calcium carbonate, and calcium oxide in regulating Cd migration in acidic soil–plant systems. The study revealed that lime-based materials synergistically regulated Cd migration through two processes: chemical fixation and ionic competition. Results showed lime application reduced soil available Cd by 33.0%, decreased grain Cd by 44.8%, increased soil pH by 15.6%, and enhanced exchangeable Ca by 35.2%. Chemical fixation was evidenced by Cd transformation from labile to stable forms (residual Cd: +29.5%, acid-soluble Cd: −17.5%). Ionic competition was quantitatively confirmed through strong negative correlation between exchangeable Ca and grain Cd (R² = 0.704). Among the materials, Ca(OH)₂ exhibits the highest efficiency in rapid pedogenic passivation (58.7% reduction in available Cd), whereas CaCO₃ demonstrates superior long-term grain Cd attenuation (65.7% inhibition) via sustained Ca²⁺ release and rhizosphere-regulated dissolution. This study advances mechanistic understanding of Cd bioavailability control and establishes quantitative frameworks for predicting ecotoxicological outcomes, providing scientific basis for optimizing remediation strategies to minimize Cd transfer through agricultural food chains. Full article

Arsenic (As) contamination threatens ecosystems and human health, and iron (hydr)oxides-mediated formation of Fe-As composites is a key strategy for arsenic immobilization, while the long-term stability of these composites under complex environmental conditions remains a critical concern. This study systematically investigated the interactive effects of environmental factors (temperature: 5–35 °C, pH: 4–8, competing ions: phosphate and citrate) and material intrinsic properties (ferrihydrite aging: 0–60 days, Fe/As molar ratio: 1.875 and 5.66, adsorption time) on Fe-As composite stability using multiscale characterization techniques and theoretical modeling. Results showed that temperature was the dominant controlling factor, with arsenic release increasing by 4.25% per 1 °C rise (178% higher at 35 °C vs. 20 °C) and an exponential relationship model established (R² = 0.96). Ferrihydrite aging enhanced stability, as 60-day aged composites (Fh_60d-As) exhibited minimal arsenic release (18.83%) at pH 4/20 °C, attributed to increase As(V)-O-Fe binding energy (1.2 eV) and -OH group enhancement (12.5%). Phosphate induced 2.4-fold higher arsenic release than citrate, and lower pH (4–6) reduced release via enhanced protonation. A stability prediction model was developed (R² = 0.91), and practical remediation strategies were proposed: maintaining temperatures below 25 °C in arsenic-containing waste repositories and using pre-aged iron-based materials. This work provides quantitative benchmarks and mechanistic insights for contaminated site rehabilitation. Full article

Chromium (Cr) is a highly toxic heavy metal, yet its effects on soil invertebrates—particularly Caenorhabditis elegans (C. elegans)—remain insufficiently understood, especially regarding how soil properties and Cr speciation change regulate its bioavailability and toxicity. In this study, the toxicity of Cr(VI) to the growth, fertility, and reproduction of C. elegans was assessed in six representative agricultural soils following 7, 60, and 120 days of spiked soil aging, following ISO 10872 guidelines. Substantial differences in toxicity were observed among soils after 7 days of aging, with toxicity ranking from low to high as black soil < yellowish-red soil < red soil < yellow–brown soil < fluvo-aquic soil < purple soil. After 60 days of aging, Cr(VI) toxicity decreased markedly, with EC₅₀ values for growth, fertility, and reproduction increasing by 1.04–2.32, 1.04–2.34, and 1.40–2.20 times, respectively. Organic matter (OM) and amorphous aluminum oxides (Al_AO) were identified as the principal soil properties that were significantly correlated with Cr(VI) toxicity and were useful for explaining and estimating toxicity thresholds within the range of soils examined in this study. In addition, the magnitude of the aging effect showed significant positive correlations with both amorphous aluminum oxides (Al_AO) and total aluminum (Al_total), suggesting that Al-bearing minerals may contribute to the time-dependent immobilization of Cr(VI) under the experimental conditions of this study. These findings expand the ecotoxicological database for chromium, improve the prediction of toxicity thresholds under diverse soil conditions, and provide a scientific basis for refining soil environmental quality standards and developing targeted management strategies for Cr-contaminated agricultural soils. Full article

Nanoparticles have become more widely applied in industrial, consumer, and therapeutic products over the past decade, and this trend is presumed to persist due to the rapid population growth, industry, urbanization, and intensive agriculture. The manufacturing of nanomaterials is not necessarily accomplished through eco-friendly processes. Certain nanomaterials involve heavy metals. The release of nanomaterials into the environment could result in soil and aquatic system contamination. Once released into water and soil matrices, nanoparticles undergo dynamic transformations, including aggregation, dissolution, and surface modification, which determine their transport and bioavailability and their toxicological profiles. Different studies have consistently reported adverse impacts of metal, carbon, and plastic-based nanomaterials on aquatic organisms, soil microbial community, enzymatic activities, and nutrient cycling processes, mainly through oxidative stress, disruption of the membrane, and release of metal ions. These problems have stimulated intensive research aimed at the prediction of environmental concentrations of nanoparticles in water and soil and for their ecotoxicological effect on aquatic and terrestrial ecosystems. On the other hand, nanomaterials are also showing great potential for sustainable use, such as water purification, soil remediation, immobilization of contaminants, and geotechnical soil improvement, referring to soil stabilization, strength enhancement, permeability reduction, and ground improvement, where low dosages can improve the mechanical properties and respected environmental performance. This paper deals with current research on these competing roles, examining the causes of nanotoxicity as well as their positive geotechnical and remedial applications in water and soil systems. Full article

Both organic matter and iron oxide (FeO) dynamics pose key roles in soil cadmium (Cd) bioavailability. However, the microbially driven transformation of soil organic matter and FeO and their linkages to Cd fractions remain unclear under reductive soil disinfestation (RSD) with different organic sources, which limits our mechanistic understanding of Cd immobilization by RSD. To address this gap, we conducted a 45 day microcosm experiment using a paddy soil contaminated with 22.8 mg/kg Cd. Six treatments were established: untreated control (CK), waterlogged (WF), and RSD-amended soils with 0.7% or 2.1% wheat straw (LWD, HWD) or soybean meal (LSD, HSD). We systematically assessed soil Cd fractionation, organic carbon and FeO concentrations, and bacterial community structure, aiming to clarify differences in Cd immobilization efficiency and the underlying mechanisms between wheat straw and soybean meal. For strongly extractable Cd, wheat straw RSD reduced the soil Cd concentrations from 6.02 mg/kg to 4.32 mg/kg (28.2%), whereas soybean meal RSD achieved a maximum reduction to 2.26 mg/kg (62.5%). Additionally, the soil mobility factor of Cd decreased from 44.6% (CK) to 39.2% (HWD) and 32.5% (HSD), while the distribution index increased from 58.5% (CK) to 62.2% (HWD) and 66.8% (HSD). Notably, the HWD treatment increased soil total organic carbon, humus, and humic acid concentrations by 34.8%, 24.6%, and 28.3%, respectively. Regarding amorphous FeO, their concentrations increased by 19.1% and 33.3% relative to CK. RSD treatments significantly altered soil C/N ratios (5.91–12.5). The higher C/N ratios associated with wheat straw stimulated r-strategist bacteria (e.g., Firmicutes, Bacteroidetes), which promoted carbohydrate degradation and fermentation, thereby enhancing the accumulation of humic substances. In contrast, the lower C/N ratios of soybean meal increased dissolved organic carbon and activated iron-reducing bacteria (FeRB; e.g., Anaeromyxobacter, Clostridium), driving iron reduction and amorphous iron oxide formation. PLS-PM analysis confirmed that wheat straw RSD immobilized Cd primarily through humification, whereas soybean meal RSD relied on FeRB-mediated FeO amorphization. These findings suggest that Cd immobilization in soil under RSD may be regulated by microbially mediated organic matter transformation and iron oxide dynamics, which was affected by organic materials of different C/N ratios. Full article

There is an urgent need to develop sustainable approaches for the remediation of contaminated soil as well as to promote sustainable practices for waste management. Here, we provide the first evaluation of the performance of two types of iron nanoparticles (NA and NH) obtained from olive mill wastewater for the remediation of an acidic multi-contaminated soil, including metal(loid)s, PCBs, and a flame retardant (TCPP). Their efficiency was then compared against that of a commercial nanoscale zero-valent iron (NS) through a one-month microcosm experiment employing two doses of each nanomaterial. The impact of the treatments on key soil physicochemical properties, metal(loid) availability, PCB and TCPP concentrations, and soil phytotoxicity was assessed. All treatments reduced soil acidity. Regarding organic contaminants, bioremediation of TCPP was enhanced by all nanomaterials, particularly NH, whereas NA was the only treatment that significantly reduced PCB concentration under the tested conditions. NS achieved the highest rates of metal(loid) immobilization (63–100%); NH was most beneficial for soil fertility and immobilized As, Ni, and Pb (100, 38, and 53%, respectively), whereas NA was only effective for Pb (21–49%). The low dose of both NA and NH improved the germination index (66 and 61%, respectively), reducing soil phytotoxicity. These results highlight the potential of valorizing olive mill wastewater for soil remediation, thereby contributing to the principles of the Circular Economy. Full article

Pb²⁺ and Cd²⁺ represent common heavy metal contaminants in aquatic environments, posing significant risks to ecosystem stability and human health. To develop efficient adsorbents for removing Cd²⁺ and Pb²⁺ while achieving resource utilization of industrial by-products (red mud and distiller’s grains), this study synthesized a novel composite biochar—red mud–Lactobacillus plantarum composite biochar (RM)—by immobilizing red mud and Lactobacillus plantarum onto biochar derived from distiller’s grains. The structural and chemical properties of RM were characterized using SEM-EDS, XRD, and FTIR. Batch adsorption experiments were conducted to evaluate the effects of various experimental factors on Cd²⁺ and Pb²⁺ adsorption. The adsorption process was further elucidated through kinetic and isothermal models, revealing that it follows the pseudo-second-order kinetic model. Equilibrium data were best described by the Langmuir model for Cd²⁺ and the Freundlich model for Pb²⁺. The maximum adsorption capacities reached 12.13 mg/g for Cd²⁺ and 130.10 mg/g for Pb²⁺. The primary mechanisms involved in Cd²⁺ and Pb²⁺ adsorption by RM include surface complexation, cation–π interactions, ion exchange, and coprecipitation. These findings demonstrate that RM represents a promising and effective adsorbent for the remediation of heavy metal-contaminated water. Full article

The rising levels of Co(II) in aquatic environments present considerable risks, thereby necessitating the development of effective remediation strategies. This study introduces an innovative pre-hydration method for synthesizing carbonated calcined clay dolomite (CCCD) to efficiently remove Co(II) from contaminated water. This pre-hydration treatment successfully reduced the complete carbonation temperature of the material from 500 °C to 400 °C, significantly enhancing energy efficiency. The Co(II) removal performance was systematically investigated by varying key parameters such as contact time, initial Co(II) concentration, pH, and solid/liquid ratio. Optimal removal was achieved at 318 K with pH of 4 and a solid/liquid ratio of 0.5 g·L⁻¹. Continuous flow column experiments confirmed the excellent long-term stability of CCCD, maintaining a consistent Co(II) removal efficiency of 99.0% and a stable effluent pH of 8.5 over one month. Isotherm and kinetic models were used to empirically describe concentration-dependent and time-dependent uptake behavior. The equilibrium data were best described by the Langmuir model, while kinetics followed a pseudo-second-order model. An apparent maximum removal capacity of 621.1 mg g⁻¹ was obtained from Langmuir fitting of equilibrium uptake data. Mechanistic insights from Visual MINTEQ calculations and solid phase characterizations (XRD, XPS, and TEM) indicate that Co(II) removal is dominated by mineral water interface precipitation. The gradual hydration of periclase (MgO) forms Mg(OH)₂, which creates localized alkaline microenvironments at particle surfaces and drives Co(OH)₂ formation. Carbonate availability further favors CoCO₃ formation and retention on CCCD. Importantly, this localized precipitation pathway maintains a stable, mildly alkaline effluent pH (around 8.5), reducing downstream pH adjustment demand and improving operational compatibility. Overall, CCCD combines high Co(II) immobilization efficiency, strong long-term stability, and an energy-efficient preparation route, supporting its potential for scalable remediation of Co(II) contaminated water. Full article

Photocatalytic membrane reactors (PMRs) are an innovative technology for water treatment, effectively combining membrane filtration and photocatalysis to enhance contaminant removal while enabling the regeneration of fouled membranes. In this study, a new porous film of chitosan that was impregnated with TiO₂ was developed and coated onto a ceramic support by spin coating to form a new porous immobilized PMR. The formed membrane was tested for two reasons: the removal of methylene blue dye by a dead-end filtration process and to demonstrate its ability to self-regenerate under UV exposure. The selective layer of the membrane was characterized using FTIR spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and water permeability tests. The results confirmed the formation of an amorphous film with no chemical interaction between chitosan and TiO₂. The membrane exhibited an average water permeability of 10.72 L/m²·h·bar, classifying it as either ultrafiltration (UF) or nanofiltration (NF). Dead-end filtration of methylene blue (10 mg L⁻¹) achieved 99% dye removal based on UV–vis analysis of the permeate, while flux declined rapidly due to fouling. Subsequent UV irradiation removed the deposited dye layer and restored approximately 50% of the initial flux, indicating partial self-regeneration. Overall, spin-coated chitosan–TiO₂ layers on ceramic supports provide high dye removal and photocatalytically assisted flux recovery, and further work should quantify photocatalytic degradation during regeneration. Full article

Metal-organic frameworks (MOFs) offer high porosity for water remediation but face challenges in handling as powders. We address these limitations by physically immobilizing Fe–BTC MOF within calcium-crosslinked low-methoxyl pectin matrices (PE–Ca–MOF). Solvent-cast films and freeze-dried foams were fabricated using water-based and polyvinylpyrrolidone (PVP)-assisted Fe–BTC dispersions, preserving MOF and pectin structures confirmed by FT–IR. PVP improved Fe–BTC dispersion and reduced particle size, enhancing distribution and plasticizing the matrix proved by DSC. Incorporation of water-dispersed Fe–BTC increased the equilibrium adsorption capacity but reduced the initial adsorption rate, while the PVP-assisted foam further enhanced uptake in comparative batch tests through its more open porous structure. At pH 7, PE–Ca–5%MOF films showed high adsorption capacities and removal efficiencies for paraquat (35.5 mg/g, 70.6%) and tetracycline (14.5 mg/g, 46.8%), while maintaining Zn²⁺ uptake compared to calcium-pectin films without MOF. Adsorption followed pseudo-first-order kinetics and Langmuir isotherms. Green regeneration with acetic acid enabled >80% capacity retention over five adsorption–desorption cycles. Foam architectures increased porosity and active-site accessibility (SEM), improving performance even at lower MOF loadings. Overall, controlling MOF dispersion and composite morphology enables efficient, reusable, and environmentally friendly bio-based adsorbents for water purification. Full article

Heavy metal contamination of agricultural soils represents a critical environmental and agronomic challenge, particularly in regions exposed to intensive land use and transport-related emissions. This study presents a detailed assessment of soil contamination in the Dargov cadastral area (Eastern Slovakia), where elevated concentrations of Cu, Zn, Pb, Ni, As, Cd, and Cr were detected through multi-depth sampling near the I/19 first-class road. Analytical results confirmed exceedances of Slovak regulatory thresholds (Decree No. 59/2013), with persistent contamination observed even in the deepest sampling interval (20–40 cm), indicating vertical migration and long-term accumulation. Concentrations of Pb (85–210 mg·kg⁻¹), Cd (2.1–5.4 mg·kg⁻¹), Zn (120–340 mg·kg⁻¹), and Ni (45–95 mg·kg⁻¹) exceeded Slovak regulatory thresholds. The highest values were consistently detected in the 0–10 cm layer and within 3 m of the I/19 road, with a gradual decline at greater depths and distances. Nevertheless, Cd and Ni remained above permissible limits even in the deepest sampling interval (20–40 cm), confirming vertical migration and long-term persistence of contamination. The spatial distribution of contaminants suggests a dominant influence of road traffic, with implications for crop safety, soil fertility, and rural land management. Based on the findings, the study proposes context-sensitive remediation strategies, including phytoremediation and chemical immobilization, and emphasizes the need for integrated monitoring systems and land-use planning to mitigate risks. The case study contributes to the broader discourse on sustainable soil management in Central European agricultural landscapes affected by diffuse pollution. Full article

The Mianhuakeng deposit, located within the Zhuguangshan batholith in the Nanling area, is currently recognized as the largest granite-related uranium deposit in China. A portion of the uranium ore bodies is spatially associated with NE-trending mafic veins within the granite. In this study, the field investigation, zircon U-Pb dating, S and Pb isotope analysis, and whole-rock geochemical analysis were conducted on these mafic veins to explore their crystallization age, petrogenesis, tectonic setting, and relationships with uranium mineralization. The weighted mean result of zircon U-Pb is 189 ± 3 Ma, suggesting that the mafic dyke was crystallized during the Early Jurassic. The whole-rock geochemistry and isotopes exhibit characteristics of intraplate basalts, suggesting that the mafic dykes originate from an enriched mantle source consisting of garnet–spinel lherzolite, with an estimated partial melting of 1%–5%. Mafic magmas underwent low-degree contamination from the lower crust during upwelling, induced by the extension of the lithosphere during the Early Jurassic. The analyses of pyrite sulfur isotopes in mafic samples vary between −2.9‰ and 1.8‰, significantly different from that of pyrite (−14.4‰ to −7.8‰) formed during the uranium mineralization. Furthermore, the ages of the pitchblende of 127–54 Ma are much younger than the crystallization ages of mafic dykes, indicating that the mafic magmas did not contribute to the uranium mineralization of Mianhuakeng deposit during magmatism. However, the abundant reducing minerals (e.g., pyrite, hornblende, and Fe²⁺-bearing minerals) in the mafic dykes can act as a redox barrier, reducing mobile U⁶⁺ to immobile U⁴⁺ during fluid–rock interaction, thereby facilitating uranium precipitation from the hydrothermal ore-forming fluids. The secondary fractures created by the intrusion of mafic magma probably provided favorable pathways for the movement of hydrothermal fluids. Full article