Search Results (521)

Containerized ornamental plant production requires efficient irrigation strategies to balance plant quality with water and nutrient conservation. This study evaluated four leaching fraction (LF) levels (0%, 20%, 40%, and 60%) in a completely randomized design with three replications, each consisting of three pots, to determine their effects on plant growth, ornamental quality, gas exchange, water use efficiency (WUE), and macronutrient leaching in off-season potted Curcuma cv. ‘Jasmine Pink’. Irrigation volumes were determined using crop coefficient (Kc)-based estimates derived from evaporation pan measurements. The results showed that the highest LF level (60%) significantly improved several ornamental quality traits, including flower number per cluster, leaf greenness, specific leaf area, and compactness index, while also increasing aerial dry weight and improving gas exchange parameters during the flowering stage. These improvements were associated with reduced substrate electrical conductivity, indicating lower soluble salt accumulation in the root zone under higher LF treatments and more favorable conditions for plant growth. Leaching fraction is commonly used in containerized crop production to prevent excessive salt accumulation in the root zone by allowing excess irrigation water to drain from the substrate. However, increasing LF also resulted in greater irrigation water consumption and higher macronutrient losses through leachate, particularly potassium. In contrast, lower LF treatments (0–20%) improved water use efficiency and reduced nutrient losses but were associated with higher substrate electrical conductivity, suggesting greater soluble salt accumulation in the root zone. Overall, the results indicate that a higher LF (60%) provided the greatest improvement in plant growth and ornamental quality under the conditions of the present study for off-season potted Curcuma alismatifolia production, although integrated strategies may be required to reduce water and nutrient losses. These findings provide practical insights for optimizing irrigation management in container-grown ornamental crops. Full article

With the growing severity of water pollution, conventional treatment technologies are increasingly unable to satisfy the demand for deep purification. Catalytic wastewater treatment has emerged as an effective strategy for degrading refractory pollutants because of its high efficiency, mild operating conditions, and environmentally friendly nature. This review systematically summarizes recent progress in catalytic materials for wastewater treatment, covering four major categories: metal-based materials, carbon-based materials, multicomponent composites, and photo/electrocatalytic systems. Particular attention is given to their design strategies, structural characteristics, and performance advantages. On this basis, the full mechanistic chain is discussed, from interfacial adsorption and activation to reactive-species generation, including both radical and non-radical pathways, intermediate transformation, and macroscopic reaction kinetics. The review also highlights representative applications in practical wastewater streams, including textile dyeing and pharmaceutical, chemical, landfill leachate, and municipal tailwater treatment, thereby demonstrating the engineering potential of catalytic technologies. At the same time, several critical challenges remain, including insufficient long-term material stability, incomplete mechanistic understanding in complex water matrices, limited adaptability to real wastewater, and the high cost of large-scale preparation. Future research should therefore focus on the development of highly stable, low-cost, and interference-resistant catalytic materials, deeper mechanistic elucidation through in situ characterization and theoretical calculations, stronger integration with membrane separation, biological treatment, photovoltaic or electrochemical processes, and the establishment of standardized evaluation protocols and life-cycle assessment frameworks. These efforts will accelerate the transition of catalytic wastewater treatment toward greener, smarter, and more practical engineering applications. Full article

In order to evaluate the utilization potential and environmental risk of iron tailings in ameliorating soda saline–alkali soil, a leaching experiment of iron tailings was carried out by simulating the soil acid–base environment and the saline–alkali stress environment of soda saline–alkali, and the basic physicochemical properties and the content and leaching characteristics of metal elements of iron tailings were analyzed to evaluate the environmental risk. The results showed that the iron tailings sand had a large specific surface area (0.66~0.91 m²·g⁻¹) and a rich pore structure (pore diameter 9.07~11.48 nm), which was conducive to the adsorption of salt-alkali by iron tailings sand. The main chemical composition of iron tailings is SiO₂ (33.39%~57.32%) and Fe₂O₃ (8.47%~14.94%), the content of plant nutrient elements in iron tailings is abundant, and the content of risk elements is far below the national standard limit. The leaching experiment results indicated that under acid or alkali conditions, the leaching amounts of various metal elements from the iron tailings met the national water quality standards for farmland irrigation, with Cd, Hg, Mn, Al, Ca, and others being more readily leached under acidic conditions. Under the same pH conditions, Cd, Hg, As, Al, and others were more readily leached under the soda saline–alkali environment. Unlike in the soil acid–base environment, the correlations between the leaching amounts of different metals were weaker under the combined soda saline–alkali stress, with only As and Al showing a positive correlation with the pH of the leachate, though the correlation was not significant. This study confirms that the environmental risk of using iron tailings for the improvement of soda saline–alkali soil is relatively low, and long-term changes in the contents of heavy metals such as As and Al in the soil should be given focused attention in future work. Full article

Several issues about the quality of urban surface waters, such as the Detroit River, are becoming a concern due to the increasing detection of emerging contaminants. Although the emerging contaminants are present in low concentrations—ranging from nanograms per liter (ng/L) to micrograms per liter (µg/L)—these raise serious concerns about long-term effects on human health and aquatic ecosystems, particularly when left unregulated. Municipal wastewater effluent has been reported as one of the major pathways for these emerging contaminants. Most treatment plants are not equipped to effectively remove many emerging contaminants, allowing them to enter surface waters. To assess the presence of these emerging contaminants, water samples were collected during the summer from sites near the upstream and downstream of the Detroit wastewater treatment plant. Among the sixteen emerging contaminants analyzed were pharmaceuticals, personal care products, and pesticides. Ten of these, such as sucralose, caffeine, acetaminophen, and bisphenol A, were detected at both locations, with concentrations ranging from 42 to 4100 ug/L. Elevated contaminant levels found downstream can come from various sources, such as agricultural runoff, leachate from landfills, overland flow, and Combined Sewer Overflows (CSOs). Furthermore, local pharmaceutical usage patterns and the effectiveness of our treatment facilities play significant roles in the contaminant concentrations we see. Tracking emerging contaminants both upstream and downstream of treatment plants is crucial for pinpointing vulnerable watersheds. This vital information enables us to establish a solid baseline and craft effective strategies to lower contaminant levels. Full article

Phosphogypsum (PG) stockpiles pose a persistent threat to regional water environments, yet their differential impacts on surface water and groundwater remain unclear. This study examined the pollution characteristics, sources, mechanisms, and model-predicted trends of PG-derived contaminants in both systems within a representative PG-affected region. Results showed that total phosphorus declined sharply from surface water to groundwater due to soil retention, whereas SO₄²⁻ and F⁻ remained comparable. Nitrogen species accumulated more in groundwater, indicating distinct transport and transformation processes. Arsenic was higher in surface water but rarely exceeded limits. In contrast, lead and manganese were significantly enriched in groundwater, exceeding standards by up to 27- and 11-fold, mainly due to reductive mobilization and subsurface geochemical processes. The Nemerow Index indicated heavy pollution in 35% of surface water and 43% of groundwater samples. Principal component analysis identified PG leachate as the dominant pollution source. Model predictions further suggested that increasing stockpile capacity would intensify contamination and pose long-term environmental risks. This study provided a scientific basis for understanding the distinct pollution mechanisms of PG stockpiles and offered guidance for targeted water environment management in PG-impacted areas. These findings have broader implications for regions globally facing similar challenges from industrial solid waste storage. Full article

This study aimed to evaluate the leaching of nutrients and pathogens following the surface application of pH-modified slurry on sandy soil. Three slurry pH modification strategies—mineral and biological acidification (pH 5) and alkalinization (pH 9.5)—were tested using mineral acids or bases, paper-industry by-products, or combinations of additives. We hypothesized that: (i) acidification increases nitrogen (N) and phosphorus (P) leaching through nutrient solubilization, and (ii) effective sanitization reduces the risk of pathogen leaching. A 24-day column leaching experiment was conducted with slurry applied at 240 kg N ha⁻¹ and four weekly irrigation events. Results indicated that nitrate (NO₃⁻) leaching accounted for less than 15% of the total nitrogen applied; however, acidified slurry significantly increased ammonium (NH₄⁺) leaching by 72%. The combination of H₂SO₄ with sucrose reduced NH₄⁺ and NO₃⁻ leaching, although P leaching exceeded 35% of the total P applied. Sulphur (S) concentrations in leachates ranged from 42.3 to 112.8 mg S kg⁻¹ soil, particularly in treatments involving H₂SO₄ or SO₄²⁻—rich additives such as spent acid. Faecal coliform leaching declined throughout the study, with acidified slurry consistently maintaining levels below the threshold for irrigation water (<100 MPN/100 mL). Regarding nutrient leaching, pH-modified slurry may present a higher risk of N, P and S leaching compared to untreated slurry, which could also be interpreted as an increase in plant nutrient availability. Full article

The environmental challenges posed by heavy metal contamination in sludge leachate are becoming increasingly severe, necessitating the development of highly efficient remediation technologies. Among various treatment approaches, magnetic adsorbents have garnered significant attention as a promising solution due to their outstanding adsorption performance, convenient magnetic separation characteristics, and potential for regeneration. This paper systematically reviews the latest research progress on magnetic adsorbents designed for the complex system of sludge leachate, covering synthesis methods, surface functionalization, adsorption mechanisms, and performance evaluation. Key synthesis strategies are analyzed, including magnetic core preparation, inorganic coating, carbon composites, organic polymer grafting, functional molecule impregnation, and metal–organic framework (MOF) composites. The mechanisms by which these strategies influence material adsorption capacity, selectivity, and stability are elucidated. Despite significant achievements in laboratory studies, practical applications still face challenges such as large-scale synthesis, regeneration efficiency, cyclic stability, and adaptability to complex water bodies. Future research should focus on green synthetic pathways to advance the industrial application of structurally functional magnetic composite materials, providing systematic solutions from material design to process optimization for the sustainable remediation of heavy metal contamination in sludge leachate. Full article

Per- and polyfluoroalkyl substances (PFASs) include thousands of fluorinated organic compounds of anthropogenic origin. Their extensive use, combined with their high stability, has led to the widespread contamination of water and soil resources. Here, single-step foam fractionation enhanced soil washing was carried out for the remediation of PFAS-contaminated soil. Concentrations of target Perfluoroalkyl Carboxylic Acids (PFCAs) and Perfluoroalkane Sulfonic Acids (PFSAs) were monitored in foam and leachate along the duration of the treatment. Among PFCAs, only long-chain compounds peaked in foam at the beginning of the treatment. This was consistent with the increase in the sorption affinity to the air–water interface with chain length. The same behavior was observed also in PFSAs by comparing PFHXs, PFHpS and PFOS. The fraction of PFCAs still in the leachate after 40 min of treatment was found to decrease with chain length, with PFSAs showing a similar trend. PFAS removal significantly increased with soil particle size, ranging from 48.2 ± 3.2% (fraction < 0.063 µm) to 64.1 ± 1.9% (fraction > 2 mm). Final mass balance analyses detail PFAS distribution among soil, leachate, and foam, providing valuable information for the additional treatment required to destroy the PFAS load extracted from the contaminated soil. Full article

Landfills are complex repositories where macroplastics degrade into MPs. This review examines mechanical, chemical, and biological pathways of plastic fragmentation, as well as the occurrence, characteristics, and removal efficiency of MPs in landfill leachate. We also explore the landfill plastisphere from the perspective of this complex matrix, considering how plastic surfaces and microbial life may potentially converge to form a key biogeochemical interface that could influence carbon and nitrogen transformations. The plastisphere’s complex surface structure drives microbial differentiation. Given its established links to GHG production in soil and water, we propose it likely represents a key contributor to GHG emissions in the more complex landfill environment. To bridge this conceptual gap, we review a mathematical scaffolding encompassing biofilm growth, polymer degradation kinetics, and gas flux, which can as a theoretical baseline requiring future in situ parameterization to evaluate plastisphere-driven biogeochemical interactions. Building on recent advances in monitoring and remote sensing technologies, including IOT networks, UAV imagery, and AI analysis, we outline a low-carbon landfill framework designed to optimize operational controls. This framework is described to simultaneously mitigate MP release and reduce GHG emissions, lowering carbon footprints. Amid surging plastic pollutants, this review underscores the necessity of holistic, integrated mitigation strategies. Full article

Municipal solid waste disposed of in open dumpsites and unlined landfills contaminates groundwater, soils, and air across urban areas of low- and middle-income countries. Nevertheless, impacts across all three environmental media have not been systematically assessed together. We conducted a PRISMA 2020-compliant systematic review of 286 peer-reviewed studies from PubMed, Dimensions, and OpenAlex, applying structured eligibility screening and quality appraisal using an adapted JBI checklist. Heavy metals—lead, cadmium, chromium, and zinc—were the most frequently detected contaminants in leachate and groundwater, commonly exceeding WHO drinking water guidelines by one to three orders of magnitude. Soil contamination by potentially toxic elements was documented at virtually all open dumpsites studied, persisting for decades after site closure. Particulate matter at South Asian MSW sites reached up to 41 times the WHO 2021 annual guideline. Microplastics acting as heavy metal carriers and dumpsite leachate as a source of antimicrobial resistance genes were identified as emerging risks outside standard monitoring frameworks. Non-carcinogenic hazard indices exceeded acceptable thresholds in the majority of health risk studies reviewed. Engineered containment was the strongest predictor of contamination severity across all sites. Phytoremediation, constructed wetlands, and biofiltration showed promise as mitigation approaches. Critical evidence gaps remain for Central Asia, harmonized reporting standards, and longitudinal monitoring data. Full article

Soil and water contamination with high nutrient concentrations from swine farms poses a risk to human and animal health. This study investigated the effects of biochar derived from young aromatic coconut husk (CH), coconut shell (CS), and their mixture (CHCS) on nutrient retention in biochar-amended soil columns for variable synthetic swine wastewater (SW) loading based on water use for piglets and fattening stalls. A 0.9 L leaching test column contained 3 g of each biochar type mixed with 300 g of soil. It was loaded daily with synthetic SW for 42 days at loading rates of 30 mL/day (piglet SW) and 60 mL/day (fattening SW). CH-amended soil was then selected to investigate the effect of rainfall rates at 0 (R0), 25 (R25), 70 (R70) and 140 (R140) mL/4 days on soil nutrient retention. Leachate was collected every 7 days to analyze nitrogen and phosphorus concentrations. The results showed that CH-amended soil had the highest retention of total nitrogen (TN) and phosphate among all treatments. For piglet SW, TN retention in CH-amended soil was 1.4–1.6 times higher than with CS and CHCS treatments, probably due to enhanced ammonium retention on exchangeable sites associated with the high cation exchange capacity of CH. High phosphate retention in CH-amended soil was linked to Ca²⁺ release from CH, facilitating phosphate precipitation. Moreover, CH-amended soil at R25 showed the highest ammonium retention but inhibited seed germination. Overall, CH-amended soil effectively retained nutrients and was suitable as a seedling growth medium, except under the R25 rainfall condition. Full article

In this work, iron–phosphorus-based composite biochar (FPBC) was prepared by modification with the leachate of spent LiFePO₄ batteries. The effects of solution pH, dosage, adsorption time, initial concentration, and temperature on the adsorption performance of FPBC were investigated by batch adsorption experiments with Pb(II) and Sb(III) as the target pollutants, and the adsorption mechanism was explored using SEM, BET, XPS, FTIR and XRD characterization. The results indicated that as the initial pH of the solution increased, the removal efficiency of FPBC for Pb(II) gradually increased, while the removal efficiency for Sb(III) remained largely unchanged. The removal of Pb(II) and Sb(III) by FPBC fitted the pseudo-second-order kinetic model and the three-step intraparticle diffusion model, indicating that their removal was primarily controlled by chemical adsorption. Isothermal adsorption studies revealed that FPBC adsorption of Pb(II) better fitted the Langmuir and D-R models, suggesting a monolayer-dominated adsorption process. In contrast, adsorption of Sb(III) fitted the Langmuir, Freundlich, and Temkin models, suggesting a combination of monolayer and multilayer adsorption characteristics. The maximum adsorption capacities of FPBC for Pb(II) and Sb(III) were 312.54 mg·g⁻¹ and 219.20 mg·g⁻¹ at 30 °C, which were approximately 12.85 and 3.37 times those of commercial corn stalk biochar (BC). Thermodynamic analysis confirmed that the removal of Pb(II) and Sb(III) by FPBC was a spontaneous and endothermic process. In addition, FPBC demonstrated strong selective adsorption of Pb(II) in the binary co-adsorption system of Pb(II) and Sb(III). Mechanism studies indicated that Pb(II) removal primarily occurred through co-precipitation, complexation, ion exchange, and electrostatic adsorption, while Sb(III) was mainly adsorbed by FPBC via redox reactions and complexation. Therefore, this work not only provides a low-cost, high-performance adsorbent for the remediation of water contaminated with Pb(II) and Sb(III), but also opens up new avenues for the resource recovery of the leachate of spent LiFePO₄ batteries. Full article

The long-term accumulation of phosphogypsum (PG) stacks has caused combined pollution of total phosphorus (TP), fluoride (F⁻), metals and metalloids (MMs), posing a severe threat to regional ecological security. To clarify the migration characteristics of pollutants in PG stacks, water leaching experiments and environmental risk assessment were conducted in 21 typical PG stacks in Southwest China. The spatial differentiation and vertical migration characteristics of pollutants under various coverage measures (high-density polyethylene (HDPE) film covering, soil covering, a composite of film–soil covering, and open-air storage) at different pH conditions were systematically analyzed. Results indicated that under open-air stockpiling conditions, the surface accumulation of TP and F⁻ was the most significant among all covering measures, corresponding to the highest environmental risk. In contrast, the membrane–soil composite covering exhibited the optimal inhibitory effect on the surface diffusion of TP and F⁻, but was less effective for metal and metalloid enrichment. Under acidic conditions (pH < 6), the vertical migration capacity of TP, F⁻, and MMs (Cu, Cd, Cr, Pb, and Zn) increased, leading to enrichment in the deep layers of the stack. With the increase in pH, the calcium-mediated precipitation–adsorption effect created a “geochemical barrier”, facilitating the solid-phase fixation of pollutants. A significant positive correlation among pollutants indicates synergistic release and fixation behaviors. In addition, a pH-controlled P-F-MM source-to-sink conceptual model was established, outlining the dissolution, precipitation, adsorption, fixation and re-enrichment pathway from fresh stock to leachate. This work provides insights for optimizing cover designs and pollution control strategies. Full article

Landfill leachate is considered one of the most recalcitrant wastewaters due to its high organic strength, elevated ammonia concentrations, and complex chemical composition. This study evaluates integrated technologies for treating highly loaded landfill leachate from the Wadi Al-Asla landfill, Jeddah Saudi Arabia, using GPS-X^TM modeling combined with regulatory compliance and techno-economic assessment (TEA). The characterized mature leachate exhibited extremely high average concentrations of COD (17,050 mg L⁻¹), BOD₅ (10,058 mg L⁻¹), ammonia-N (989 mg L⁻¹), and total nitrogen (1223 mg L⁻¹), indicating severe pollution levels requiring integrated treatment technologies. Five (5) different scenarios involving integrated biological, physicochemical, and membrane-based processes were modelled, simulated and evaluated against local discharge standards complaince. Conventional and municipality-proposed upgrade configurations achieved ~80–83% COD removal, producing effluent COD > 2900 mg L⁻¹ and 1790–1801 mg L⁻¹ BOD₅, indicating persistent non-compliance for organic pollutants. Nitrogen removal improved substantially (93.7–95.7% ammonia-N and 91–93% total nitrogen removal), yet residual ammonia-N (44–63 mg L⁻¹) and total nitrogen (92–108 mg L⁻¹) remained above regulatory limits. Advanced hybrid systems achieved complete TSS removal and strong phosphorus control (TP ≤ 0.42 mg L⁻¹), while three(3) compartmental aerobic–anoxic membrane bioreactor coupled with reverse osmosis (MBR + RO) achieved near-complete nitrogen removal and reduced 90% COD removal. The lifecyle economic assessment indicated OPEX ranging from USD 1.1 to 5.6 m⁻³ of treated leachate with the aerobic–anoxic MBR + RO configuration yieding footprint advantage, lower CAPEX and moderate OPEX By combining process modeling, regulatory compliance evaluation, and economic assessment, this study provides a practical screening framework for selecting sustainable treatment strategies for high-strength landfill leachate and wastewater matices. Full article

The compliant discharge of landfill leachate constitutes a pivotal factor for the effective implementation of integrated water resource management. Aged landfill leachate exhibits complex composition and an imbalanced carbon-to-nitrogen ratio. Electrocatalytic oxidation technology, as an efficient advanced oxidation process, demonstrates promising application potential. This study employed Ti/RuO₂–IrO₂ Anodes for the electrocatalytic oxidation treatment of aged landfill leachate. The removal efficiencies and variation patterns of chemical oxygen demand (COD), ammonia nitrogen, and total nitrogen at different current densities and reaction times were systematically investigated, along with an analysis of energy consumption and current efficiency. The degradation and transformation processes of organic matter were elucidated using Three-dimensional Excitation–Emission Matrix (EEM) Spectra. Fresh anodes and those used for 1000 h were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) to elucidate their failure mechanisms. The results demonstrate that electrocatalytic oxidation achieves efficient pollutant removal. At a current density of 1000 A/m² and a reaction time of 30 min, the effluent concentrations of ammonia nitrogen and total nitrogen satisfied the discharge standards, while COD complied with emission requirements after 60 min. The pollutant removal efficiencies were positively correlated with current density and reaction time. EEM analysis revealed that the electrocatalytic process effectively disrupts the structure of macromolecular organic matter, degrading it into smaller molecules and eventually achieving complete mineralization. Electrode characterization identified titanium substrate corrosion due to coating cracks and coating detachment as the primary causes of electrode failure. This study confirms the effectiveness of electrocatalytic oxidation technology for treating aged landfill leachate, and provides a theoretical foundation and technical support for its practical engineering application. The technology exhibits considerable theoretical significance and promising application potential in the treatment of landfill leachate. Full article