Search Results (563)

Phytoremediation is widely acknowledged as a viable method for soil remediation; however, its efficacy remains limited in soils co-polluted with petroleum hydrocarbons and heavy metals. To overcome this constraint, the present study explored an innovative approach utilizing ferrate-modified biochar (FeBC) to augment phytoremediation efficiency. Experimental findings revealed that ferrate treatment markedly modified the physicochemical characteristics of biochar, yielding thinner, smoother-surfaced structures with pronounced iron enrichment. At a 5% application rate alongside ryegrass cultivation, FeBC exhibited superior remediation performance, achieving 52.0% degradation of petroleum hydrocarbons (notably within the meso-aggregate fraction) and a 19.2% decline in zinc bioavailability via immobilization, thereby reducing zinc uptake in ryegrass tissues. Furthermore, FeBC amendment induced significant shifts in rhizosphere soil biochemistry and microbial ecology, characterized by diminished catalase activity but elevated urease and alkaline phosphatase activities. Phospholipid fatty acid profiling indicated a substantial rise in bacterial biomass (encompassing both Gram-positive and Gram-negative groups), particularly in meso- and micro-aggregates, whereas soil bacterial α-diversity declined markedly, accompanied by distinct compositional changes across aggregate size fractions. These results offer mechanistic insights into the synergistic interaction between FeBC and ryegrass in co-contaminated soil rehabilitation, the aggregate-dependent distribution of remediation effects, and microbial community adaptations to FeBC treatment. Collectively, this study advances the understanding of ferrate-modified biochar’s role in phytoremediation enhancement and clarifies its operational mechanisms in petroleum-zinc co-contaminated soil systems. Full article

Legacy sulfur smelting has left behind complex contamination landscapes, yet the spatial structuring of microbial risks and adaptation strategies across soil profiles remains insufficiently understood. Microbial risk genes, including those conferring resistance to antibiotic resistance (ARGs), biocide and metal resistance (BRGs/MRGs), and virulence (VFGs), are increasingly recognized as co-selected under heavy metal stress, posing both ecological and public health concerns. In this study, we integrated geochemical analyses with metagenomic sequencing and functional annotation to jointly characterize the vertical (0–7 m) and horizontal (~2 km) distribution of heavy metals/metalloids, microbial communities, and functional risk genes at a historic smelting site in Zhenxiong, Yunnan. Heavy metals and metalloids such as arsenic (As), chromium (Cr), copper (Cu), and lead (Pb) showed clear accumulation with depth, while significantly lower concentrations were observed in both upstream and downstream locations, revealing persistent vertical and horizontal pollution gradients. Correspondingly, resistance and virulence genes were co-enriched at contaminated sites, suggesting potential co-selection under prolonged stress. LEfSe analysis revealed distinct ecological patterns: vertically, upper layers were dominated by nutrient-cycling and mildly stress-tolerant taxa, while deeper layers favored metal-resistant, oligotrophic, and potentially pathogenic microorganisms; horizontally, beneficial and diverse microbes characterized low-contamination zones, whereas heavily polluted areas were dominated by resistant and stress-adapted genera. These findings provide new insights into microbial resilience and ecological risk under long-term smelting stress. Full article

The effect of adding 10% biochar (B) or sludgechar (SL) on the water regime and adsorption properties of soils was tested on composites prepared by mixing two standard soils of loamy and clay type with B or SL in a 90:10 weight ratio. Water-holding capacity was assessed as initial (2 h) and equilibrium (24 h). Water retention time was estimated by evaporation from saturated samples at 20 °C to a constant weight. The composites exhibited a 60–90% increase in water absorption compared to the individual soils, retaining water up to 3–6 days longer than the individual soils. The adsorption properties were tested for cation (Pb²⁺) and anion (Sb(OH)₆⁻) adsorption and for Pb²⁺ and Sb(OH)₆⁻ co-adsorption from model solutions under laboratory conditions. All samples showed higher selectivity for Pb²⁺, with the adsorption efficiency from 40% to 99%. Sb(OH)₆⁻ adsorption achieved a maximum efficiency of only 10%. Pb²⁺ and Sb(OH)₆⁻ co-adsorptions were efficient for Sb(OH)₆⁻ adsorption, reaching efficiency levels above 95%. At prolonged reaction times, the adsorption efficiency elevated by more than 20%. Only 10% wt. addition of biochar or sludgechar enhanced not only the water regime of soils but also their adsorption capacity for ionic contaminants. Full article

Mining and metallurgical activities negatively impact ecosystems due to the release of potentially toxic elements (PTEs). This study assesses PTE pollution and accumulation in native plant species that have spontaneously colonized a historical mining site (Michaly, site A) and a nearby metallurgical smelter site (Varvara, site B) on the Lavreotiki Peninsula, Attika, Greece. Soils were analyzed for As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, and Zn. A total of 89 native plant taxa across 28 families were identified. The aerial parts from dominant species were analyzed for PTE concentrations, and bioconcentration factors (BCFs) were calculated. One-way ANOVA and principal component analysis (PCA) using R were used for statistical evaluation. Soils at both sites showed elevated As, Cd, Cr, Cu, Ni, Pb, Sb, and Zn; Mn was high only at site B, while Co and Fe remained at background levels. Several plant species, especially at Michaly, had elevated concentrations of As, Cd, Co, Cr, Fe, Pb, Sb, and Zn in their aerial parts. BCFs indicated general PTE exclusion from aerial parts, particularly at site B. Native vegetation on these contaminated sites shows resilience and PTE exclusion, highlighting their potential for phytoremediation, especially phytostabilization, and ecological restoration in similarly polluted Mediterranean environments. Full article

This study employs Geographic Information Systems (GIS) combined with multivariate statistical techniques to evaluate soil contamination at two landfill sites in Al-Kharj, Saudi Arabia. A total of 32 soil samples were collected and analyzed for heavy metals and metalloids (HMs) using a range of contamination indices and established soil quality standards. GIS mapping revealed that the Al-Kharj landfill 1 (Kj1) experienced a steady area expansion from 2014 through 2025, while landfill Kj2 expanded from 2014 until 2022, after which its area contracted following the construction of additional facilities. The average values of HMs observed were as follows: Fe (9909 mg/kg), Al (6709 mg/kg), Mn (155.9 mg/kg), Zn (36.4 mg/kg), Cr (24.1 mg/kg), V (22.2 mg/kg), Ni (19.5 mg/kg), Cu (8.20 mg/kg), Pb (7.91 mg/kg), Co (4.32 mg/kg), and As (2.29 mg/kg). Notably, Kj2 exhibited overall higher HM concentrations than Kj1, with particularly elevated levels of Cr, Ni, and Pb. Although most HMs remained within internationally accepted safety limits, only three samples (9.4% of the total) exceeded the WHO threshold for Pb (>30 mg/kg). An analysis using contamination and enrichment factors pointed to increased concentrations of Pb, Zn, and Cr, suggesting localized anthropogenic contributions. Additionally, all samples recorded an ecological risk index (Eri) below 40, and the levels of As, Cr, and Pb consistently stayed under their respective effects range-low (ERL) thresholds, indicating minimal contamination risks. The variations in HM contamination between the sites are likely attributable to differences in the sources of metal inputs and removal processes. These findings highlight the need for continuous monitoring and localized remediation strategies to ensure environmental safety and sustainable landfill management. Full article

This study examined the temporal dynamics of metal(loid) concentrations in agricultural soils, fern Amauropelta rivularioides, and surface waters in a peri-urban region on the Brazil–Paraguay border during 2019–2020. Elevated levels of As, Se, Co, Mn, Cu, and Zn raised concerns about environmental and human health risks, especially when compared to international guidelines. Post-harvest and pre-harvest periods, particularly during corn cultivation, revealed higher concentrations of toxic metals, suggesting cumulative effects of agrochemical use. Principal Component Analysis indicated significant geochemical variation, with particular emphasis on the Collection 1 period (1 June 2019). The fern A. rivularioides demonstrated metal accumulation, especially for As, Pb, Cr, and Ba, reflecting the influence of agrochemical residues and seasonal runoff. Surface waters displayed metal concentrations below detection limits, but phosphorus levels surpassed USEPA thresholds for eutrophication risk. Risk assessments indicated moderate to high contamination in soils, particularly for P, As, Mg, and Se. Hazard Quotient and Hazard Index values suggested chronic health risks, and Incremental Lifetime Cancer Risk values for dermal exposure to As, Pb, and Cr indicated an elevated cancer risk. Full article

The presence of PET (polyethylene terephthalate) in the environment is a global problem due to soil and water microplastic contamination. There is a constant demand for new technologies that expand the possibilities of PET disposal or recycling while reducing energy consumption and anthropogenic carbon footprint. In this study, we developed a comprehensive zero-waste management system for PET recycling (rPET) to cyclic ketals and terephthalic acid. The developed method is based on the hydrolysis of rPET flakes in an inert environment with the separation and purification of terephthalic acid and the dehydration of ethylene glycol. For the first time, we present the use of cheap and readily available Cr/SiO₂ and Fe/SiO₂ nanocatalysts for direct acetalization of ethylene glycol without organic co-solvents. The catalysts were characterized by EDXRF, XPS and TEM techniques. The 2,2-dimethyl-1,3-dioxolane (DMD), a product of ethylene glycol’s direct acetalization with acetone, was tested as a solvent for polymers with satisfactory results in the solubility of epoxy resins. The addition of unpurified terephthalic acid and residues constituting post-production waste to concrete allows for a reduction in the mass of concrete in the range of 11.3–23.4% and the material modified in this way allows for a reduction in concrete consumption. This rPET waste management methodology is consistent with the assumptions of the circular economy and allows for a significant reduction of anthropogenic CO₂ emissions. Full article

Soil co-contamination with antimony (Sb) and arsenic (As) presents significant ecological and human health risks, demanding effective stabilization solutions. This study evaluated iron–manganese-modified hydrochar (FMHC) for synergistic Sb-As stabilization in contaminated smelter soils. Through 60-day natural aging and 30 accelerated aging cycles, we assessed stabilization performance using toxicity leaching tests (acid/water/TCLP), bioavailable fraction analysis, bioaccessibility assessment, and Wenzel sequential extraction. The key findings reveal that FMHC (5 wt%) achieves durable stabilization: (1) leaching concentrations remained stable post-aging (Sb: 0.3–4.5 mg·L⁻¹, >70% stabilization; As: <0.4 mg·L⁻¹, >94% stabilization); (2) bioavailable fractions showed maximum reductions of 64% (Sb) and 53% (As), though with some fluctuation; and (3) bioaccessible As was consistently reduced (55–77%), while Sb exhibited greater variability (maximum 58% reduction). Speciation analysis revealed similar stabilization pathways: Sb stabilization resulted from decreased non-specifically and specifically adsorbed fractions, while As stabilization involved the reduction in non-specifically/specifically adsorbed and amorphous to poorly crystalline Fe/Al hydrous oxide-bound fractions. These transformation mechanisms explain FMHC’s superior performance in converting labile Sb/As into stable forms, offering a sustainable solution for the green remediation of Sb-As co-contaminated soils in mining areas. Full article

Arsenic (As) contamination has significantly increased in recent decades due to anthropogenic activities. This is a serious challenge for human health, environmental quality, and crop productivity. Biochar (BC) is an important practice used globally to remediate polluted soils. Likewise, melatonin (MT) has also shown tremendous results in mitigating metal toxicity and improving crop productivity. Nevertheless, the mechanism of combined BC and MT in alleviating As toxicity in rice (Oryza sativa L.) remains unexplored. In this study, we investigated how As affected rice and how the combined BC and MT facilitated As tolerance. The study comprised a control, As stress (100 mg kg⁻¹), As stress (100 mg kg⁻¹) + BC (2%), As stress (100 mg kg⁻¹) + MT (100 µM) and As stress (100 mg kg⁻¹) + BC (2%) + MT (100 µM). Arsenic significantly decreased rice growth and yield by increasing electrolyte leakage (EL), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂). Co-applying BC and MT substantially enhanced rice growth and yield by increasing chlorophyll synthesis (48.12–92.42%) leaf water contents (40%), antioxidant activities (ascorbate peroxide: 56.43%, catalase: 55.14%, peroxidase: 57.77% and superoxide dismutase: 57.52%), proline synthesis (41.35%), MT synthesis (91.53%), and phytochelatins synthesis (125%) nutrient accumulation in rice seedlings and soil nutrient availability. The increased rice yield with BC + MT was also linked with reduced H₂O₂ production, As accumulation, soil As availability, and an increase in OsAPx6, OsCAT, OsPOD, OsSOD OsASMT1, and OsASMT2 and a decrease in expression of OsABCC1. Biochar + MT enhanced residual OM- and Fe, ((Fe₂As) and Mn (Mn₃(AsO₄)₂) bound forms of As leading to a substantial increase in rice growth and yield. Thus, the combination of BC and MT is an eco-friendly approach to mitigate As toxicity and improve rice productivity. Full article

One hundred presumptive Pseudomonas isolates, recovered from 15 sites impacted by anthropogenic activity in the Foggia district (Italy), were screened for key adaptive and functional traits important for environmental applications. The isolates were phenotypically characterized for their ability to grow under combined pH (5.0–8.0) and temperature (15–37 °C) conditions, to produce proteolytic enzymes, pigments, and exopolysaccharides, and to tolerate SDS. Moreover, the resistance to six environmentally relevant heavy metals (Cd, Co, Cu, Ni, Zn, As) was qualitatively assessed. The results highlighted wide inter-strain variability, with distinct clusters of isolates showing unique combinations of stress tolerance, enzymatic potential, and resistance profile. PERMANOVA analysis revealed significant effects of both the isolation site and the metal type, as well as their interaction, on the observed resistance patterns. A subset of isolates showed co-tolerance to elevated temperatures and heavy metals. These findings offer an initial yet insightful overview of the adaptive diversity of soil-derived Pseudomonas, laying the groundwork for the rational selection of strains for bioaugmentation in contaminated soils. Full article

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

This study demonstrated that application of the particular plant growth-promoting rhizobacteria (PGPR) strains Erwinia sp. and Serratia sp. (named C15 and C20, respectively) significantly enhanced tea plant resilience in Zn (zinc)-, Pb (lead)-, and Zn + Pb-contaminated soils by the improving survival rates (over 60%) and chlorophyll content of tea plants, and by reducing the accumulation of these metals in tea plants’ tissues (by 19–37%). The PGPRs elevated key soil nutrients organic carbon (OC), total nitrogen (TH), hydrolysable nitrogen (HN), and available potassium (APO) and phosphorus (APH) contents. Compared to non-PGPR controls, both strains consistently increased microbial α-diversity (Chao1 index: +28–42% in Zn/Pb soils; Shannon index: +19–33%) across all contamination regimes. PCoA/UniFrac analyses confirmed distinct clustering of PGPR-treated communities, with strain-specific enrichment of metal-adapted taxa, including Pseudomonas (LDA = 6) and Bacillus (LDA = 4) under Zn stress; Rhodanobacter (LDA = 4) under Pb stress; and Lysobacter (LDA = 5) in Zn + Pb co-contamination. Fungal restructuring featured elevated Mortierella (LDA = 6) in Zn soils and stress-tolerant Ascomycota dominance in co-contaminated soils. Multivariate correlations revealed that the PGPR-produced auxin was positively correlated with soil carbon dynamics and Mortierellomycota abundance (r = 0.729), while the chlorophyll content in leaves was closely associated with Cyanobacteria and reduced by Pb accumulation. These findings highlighted that PGPR could mediate and improve in tea plant physiology, soil fertility, and stress-adapted microbiome recruitment under heavy metal contaminated soil and stress. Full article

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 investigation examines the influence of P. dabryanus density on the growth performance of P. nigromaculatus and the structural and functional dynamics of paddy soil microbial communities within a rice–frog–loach integrated aquaculture system. Field experiments were conducted with five density gradients of P. dabryanus (0.5, 1.0, 1.5, 2.0, and 2.5 × 10⁴ individuals/667 m²), designated as RFLS0.5, RFLS1.0, RFLS1.5, RFLS2.0, and RFLS2.5, respectively. Control treatments included rice monoculture (RM) and rice–frog co-culture (RFS). These findings demonstrated that as the density of loach increased, the weight gain ratio of P. nigromaculatus showed a unimodal pattern, reaching its peak in RFLS1. Metagenomic analysis on paddy soil revealed that the RFLS1 facilitated the enrichment of nitrogen-fixing bacteria (Proteobacteria), while concurrently suppressing proliferation of the potential pathogen Pseudomonas aeruginosa and microbial markers in metal-contaminated environments of Usitatibacter rugosus. Further, functional profiling indicated that RFLS1 group reached a peak activity in amino acid metabolism (14.52 ± 0.09%) and carbohydrate metabolism (14.44 ± 0.06%) and showed a higher proportion of glycosyltransferase (GT) abundance (41.93 ± 0.02%) than other groups. In summary, the optimal stocking density of P. dabryanus in rice–frog–loach integrated systems was determined to be 1.0 × 10⁴ individuals/667 m². This density not only promotes the growth of P. nigromaculatus but also improves the structure of paddy soil microbial communities. Full article

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 (I_geo), 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