International Journal of Environmental Research最新文献

This study aimed to evaluate the effect of nanoclay (NC), zeolite (Z), biochar (B), municipal waste compost (MWC), and farmyard manure (FYM) at two application levels of 1% and 3% (w/w) on the saturated hydraulic conductivity (K_S) and sodification process of a calcareous soil under leaching by waters with different electrical conductivity (EC) and sodium absorption ratio (SAR) values. Columns containing control and amended soils were washed in three separate experiments using 20 pore volumes of three solutions classified in C3S1, C4S3, and C4S4 classes. The incorporation of the amendments led to a significant decrease in soil sodification because of decreasing exchangeable sodium and increasing exchangeable calcium. The exchangeable sodium percentage (ESP) of soils after leaching by solutions C3S1, C4S3, and C4S4 varied in the ranges of 1.80–5.79%, 2.78–7.85%, and 3.66–15.6%, respectively. The highest and lowest ESP values were obtained for control and 3% FYM treatment, respectively. For each leaching solution, the K_S was significantly higher in the control compared to the amended soils (P ≤ 0.05). The lowest value of K_S was obtained for the 3% B treatment. Furthermore, K_S values increased with an increase in SAR of water. This was likely due to the simultaneous increase in EC and concentration of divalent cations (calcium and magnesium). The most effective amendments in controlling soil sodification were FYM, B, and MWC at the application level of 3%.

PM_2.5 is a main air pollutant in China. Considering the unevenly distributed PM_2.5 and population in China, an accurate assessment of PM_2.5 exposure is needed. In this study, the population-weighted exposure (PWE) is used to measure the overall PM_2.5 exposure based on 2766 counties across mainland China. The population exposure risk (PER) is used to better assess the partial PM_2.5 exposure risk level for residents at the county level. The PM_2.5 PWE and PER are calculated with the latest 2020 census data and the predicted concentrations estimated by spatial models considering both the geographic similarities and aggregation. The PWE differed from the concentrations across China, especially in four heavily polluted regions and three detected high-concentration clusters. In China, the average PM_2.5 PWE in 2019 was 39.46 μg/m³, 2.41 μg/m³ higher than the mean concentration (37.05 μg/m³). The exposure in three detected clusters was much higher than in the Sichuan Basin (SCB), the Pearl River Delta (PRD), and the Yangtze River Delta (YRD), suggesting the focus of environmental governance should not only be the traditional heavily polluted areas according to administrative divisions. Regions with high concentrations also differed from regions with high PM_2.5 exposure risk. The counties with higher PM_2.5 PER were located in east-central and eastern coastal China, different from the distribution of concentrations. This study clarified the necessity of considering spatial aggregation of PM_2.5 in LUR models and also emphasized the importance of calculating PM_2.5 PWE as exposures in further health effect assessments.

Implementing nutrient recycling in wastewater treatment plants is essential for sustainable agriculture. In this study, we investigated a biphasic treatment system for anaerobic liquid digestate, which involved natural and K-enriched zeolite for NH₄⁺ recovery (phase 1), followed by struvite crystallization under two conditions: NH₄⁺ excess and Mg²⁺ excess (phase 2). The adsorption of NH₄⁺ by natural zeolite enabled saving Mg and P reagents, used to achieve target Mg:NH₄:PO₄ ratios. The reagent use efficiency of struvite precipitation was highest with natural zeolite under NH₄⁺ excess conditions (96%), whereas the other treatments exhibited lower yields. In this condition, the digestate enriched in Ca²⁺ released by zeolite; however, no P interferences occurred (Ca²⁺/Mg²⁺ < 0.5). Fractions of Ca²⁺ precipitated as CaCO₃. Both the isomorphic NH₄- and K-struvite occurred, distinguished by calibrating XRPD data (total struvite) with N contents (indicative of NH₄⁺-struvite). The precipitates comprised NH₄- and K-struvite at 60% and 30% (calcite at 9%) in the treatment that involved natural zeolite, 65% and 35% with the K-exchanged zeolite, due to higher presence of K⁺. Concerning the chemical evolution of the treated digestate, fewer alterations occurred for inorganic ions in the treatment that involved natural zeolite (phase 1) with NH₄⁺ excess condition (phase 2), besides for unreacted SO₄^2– derived from the Mg reagent. The recovered zeolite was enriched in N at 0.5%. Struvite precipitates met the EU regulations regarding permissible levels of organic C, P content, and heavy metal impurities, thereby potentially enabling its use as a fertilizer.

This study examines the production of metallized biochar as a cost-effective and sustainable adsorbent with a high carbon dioxide (CO₂) uptake at ambient temperature. Leucaena wood (LW)-derived biochar was prepared at various pyrolysis temperatures (500, 700, and 900 °C) for 90 min. Among all, highly microporous LW biochar, pyrolyzed at 900 °C, showed the highest CO₂ adsorption capacity of 52.18 mg/g at 30 °C, 1 bar This biochar was further impregnated with ammonium metavanadate solution at different concentrations (1, 3, 4, 5 and 8 wt%) and then heated at 500 °C to obtain vanadium oxide-deposited biochar. The metal deposition of 3 wt% increased the CO₂ adsorption capacity of the biochar to 71.85 mg/g under the same adsorption conditions, which can be attributed to the significant contribution of vanadium oxide to CO₂ chemisorption. Here, vanadium oxide could create oxygen vacancy on the LW surface which further react with CO₂ in the atmosphere. Kinetic studies revealed that the Avrami model could accurately predict the CO₂ adsorption behaviour, indicating both physisorption and chemisorption contributed to the adsorption. The activation energy for CO₂ uptake was calculated at around − 8.04 kJ/mol. The sustainable performance of metallized biochar was demonstrated in several cycles of CO₂ adsorption–desorption. In addition, this adsorbent showed high affinity towards CO₂ over air, CH₄ and N₂. The results of this study present the prospective potential of this sustainable adsorbent for large-scale post-combustion CO₂ capture.

Due to the increased demand for agricultural products, the agricultural industry has become intensified, resulting in a homogenization of the rural landscape. Our study defines rural landscape types at three scales (national, regional, and local) using a multi-scale method. We generated three landscape element datasets using literature and gray statistical analysis. Subsequently, we used the overlay approach and two-step cluster analysis to identify landscape regions, types, and subtypes. The findings indicate the presence of 47 landscape regions at the national scale, 448 landscape types at the regional scale, and 44 landscape subtypes at the local scale with Dahongshan Mountain Region serving as the empirical study site. Furthermore, we have developed a novel method to evaluate landscape diversity index (LDI) which utilizes the proportion of land area occupied by landscape elements in various landscape types. This method incorporates diverse elements, such as topography, landform, land cover/use, vegetation, and agroforestry industries. To examine the role of LDI in landscape planning, we analyzed the relationship between LDI and recreation services using the geographically weighted regression model. The result facilitates landscape planning and management at different administrative levels.

Chromium hydroxide is an important form present in chromium chemicals and a major product in the reduction of hexavalent chromium pollutants, and the study of chromium hydroxide re-oxidation process is crucial in controlling chromium pollution. The aim of this research was to investigate the re-oxidation performance of different forms of chromium hydroxide in air: crystalline chromium hydroxide (C-Cr(OH)₃), amorphous chromium hydroxide (A-Cr(OH)₃), chromium hydroxide obtained by reduction (R-Cr(OH)₃), and aged R-Cr(OH)₃ (Aged-R-Cr(OH)₃). The results showed that A-Cr(OH)₃ had the highest re-oxidation efficiency and the largest re-oxidation rate constant (k), followed by R-Cr(OH)₃, Aged-R-Cr(OH)₃, and C-Cr(OH)₃. The study found that the re-oxidation rate of chromium hydroxide was mainly affected by the surface Cr–O bond energy and physical water. The advantageous re-oxidation of chromium hydroxide could be attributed to its diminutive bond energy of Cr–O and the presence of physical water on its surface. It was observed that increasing the temperature and adding salt (Na₂SO₄ and Na₂CO₄) promoted the re-oxidation of Cr(III) for different chromium hydroxides. This effect was particularly noticeable under alkaline conditions induced by Na₂CO₃ or at a reaction temperature of 200 °C. The re-oxidation rate constant of chromium hydroxides was up to 39.4 times higher at a reaction temperature of 200 °C than at 80 °C. This would be of great significance for chromium contamination removal by controlling the hexavalent chromium reduction products and environmental conditions.

The purpose of this study was to determine twelve potentially toxic elements (PTEs), encompassing aluminum (Al), arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V), and zinc (Zn), in 120 samples of bottled water (mineral and drinking) collected from the market in Tehran, Iran, during the winter and summer seasons. The bottled water samples were assessed using an inductively coupled plasma optical emission spectroscopy (ICP-OES). Furthermore, non-carcinogenic and carcinogenic health risks were evaluated for adults and children using hazard quotient (HQ), hazard index (HI), and cancer risk (CR). The maximum content of PTEs was attributed to Zn in bottled drinking water in winter, and the minimum content was attributed to V in bottled mineral water in summer. There was a significant difference in the concentration of Cu and Zn in the summer and winter (p < 0.05). Also, the concentration of Ni, V, and Zn in bottled drinking water and bottled mineral water revealed a statistically significant difference (p < 0.05). In all cases, the values of THQ and HI were less than one and were acceptable. CR values for Cr and Ni were unacceptable.

Perfluorooctane Sulfonate (PFOS) is widely used in various commercial applications, including food packaging, fabrics, and fire-fighting foams. This toxic and carcinogenic compound could be present in water and food products, which could be fatal to living beings. Zeolite-based materials are promising PFOS sorbents due to their high anion exchange capacity and specific surface area. In this study, a natural Clinoptilolite-type zeolite was modified with Hexadecyl Trimetilammonium Bromide (HDTMA) for PFOS remediation in aqueous solutions. The modification introduced an inversion of Clinoptilolite's natural surface net charge, i.e., from negative to positive, making it effective in capturing PFOS. At pH 7, the modified material (Clinop_HDTMA) showed ~ 96–98% removal of PFOS at a low concentration range of 0.5–1 mg L⁻¹. The adsorption isotherm and kinetic data followed the Freundlich and pseudo second-order model, respectively, which suggested the involvement of physicochemical forces in the adsorption process. Thus, this study demonstrates a viable and cost-effective solution to remove PFOS ions from wastewater.

Graphical Abstract

With the increased activity from humans in agriculture and industry, a growing amount of waste containing heavy metals is discharged into the environment, which brings great risk to human health. Biochar, as a great absorbent for heavy metals remediation, has been extensively studied. The adsorption capability of biochar is affected by many factors, such as the species and properties of raw materials, the preparation methods (temperature, heating rate, and residence time), and functional sites introduced by the modification agent. However, how these factors determine the adsorption of heavy metals on biochar is not clear. The present work thoroughly reviewed the traditionally used methods for biochar preparation such as pyrolysis, hydrothermal carbonization and gasification, meanwhile, the emerging biochar preparation techniques (retort carbonization and torrefaction) are also explored. Accordingly, the commonly used modification methods (alkali modification, acid modification, ferromagnetic modification, microbial modification, etc.) are comprehensively investigated. The adsorption kinetics and isotherms are also discussed to demonstrate the adsorption mechanism from a theoretical basis. Notably, to facilitate the large-scale biochar application in practice, a discussion focusing on the factors associated with practical utilization is provided. Consequently, the review of environmental risk and the challenge regarding biochar disposal safety, a thorough economic analysis, detailed exploration of industrial-scale implementation challenges, enhanced life cycle assessment and sustainability analysis are included, aiming to contribute a better understanding of the practical implications of engineering biochar for application in heavy metals remediation.

This study explores the utilization of electrospun polysulfone (PSF) as a thin-film support in the pressure-retarded osmosis (PRO) system, leveraging its notable thermal, chemical, and oxidative stability. To enhance the efficiency of the PRO system, the inherently hydrophobic PSF surface is modified through functionalization with benzenesulfonamide groups (BSA-PSF). The modification process involves chloromethylation of PSF, followed by substitution with BSA, and subsequent electrospinning to produce BSA-PSF fibers. A thin-film composite forward osmosis membrane, composed of an electrospun BSA-PSF support layer and a polyamide thin layer synthesized through interfacial polymerization (BSA-PSF/PA), is developed. The incorporation of BSA improves the hydrophilicity of the membrane surface, while also imparting antibacterial features to the electrospun BSA-PSF. Comparative analyses with pristine PSF membranes reveal that the pure water flux of the BSA-PSF membrane achieves a notable 65 LMH, surpassing the pristine PSF membrane’s flux of 45 LMH. Moreover, protein absorption is significantly reduced in the BSA-PSF membrane (40.6 μg cm⁻²) compared to the unmodified PSF membrane (64.2 μg cm⁻²). The establishment of a hydration layer near the surface, facilitated by hydrogen interactions between water units and the hydrophilic sulfonamide chains in the polymer, contributes to lower protein adsorption than observed in the pristine PSF membrane. Notably, the prepared BSA-PSF/PA membrane exhibits advanced surface hydrophilicity, commendable antibacterial properties, exceptional fouling resistance, and high water permeability. These attributes position it as a promising candidate for widespread applications in power generation and large-scale water treatment.

Graphical Abstract

BSA functionalized the electrospun PSF used as the PRO membrane’s thin-film support. The introduction of BSA to PSF improved the hydrophilicity, water flux, antibacterial properties, and fouling resistance of thin-film composite PRO membrane