International Journal of Environmental Research最新文献

Abstract

The search for potent plastic-degrading bacteria has been a focal point of research over the recent decades to develop sustainable methods for plastic waste management. Despite promising results at the laboratory scale, replicating the same at the field scale has been limited. Natural extremophilic conditions of the landfill host many plastic-degrading bacteria, and recently, culture-independent Next-Generation Sequencing metagenomics approaches are being adopted to screen them and exploit their utilities. However, one of the main challenges is the difficulty in designing the optimum artificial test conditions for understanding the growth and metabolic activities of the concerned microorganisms. In the current study using precision metagenomics, genes coding for PET and PHA degrading enzymes were screened from a landfill-mined soil-like fraction (LMSF) sample, with landfill soil under a freshly deposited waste dump acting as the control. Subsequently, thorough geoenvironmental characterization of the samples was performed to generate an understanding of the growth conditions of the microorganisms. Genes encoding for MHETase outpopulated the genes encoding for PETase in LMSF, while the reverse trend was observed in the control. The abundance and taxonomic distribution of the hosts containing genes of PETase and MHETase enzymes in the samples, when co-related with the FTIR spectra of the samples, indicated that the PET residues might have possibly degraded to MHET under natural conditions. Usually, commercial composts, which are already a market-ready product for the agriculture sector, are used for polymer composting, which is not sustainable in the long run. The structural and functional patterns of the microbes obtained in the metagenomics study and permissible levels of leachable heavy metals generate promise for the landfill-mined soil-like fractions to be potentially used for polymer degradation. Alongside this, the presence of a monotypic oceanic genus Plesiocystis in the landfill environment was confirmed, which is of utmost importance to the field of microbial ecology.

Graphical Abstract

The development of stable electrodes with significant capacitance is necessary for the commercial viability of supercapacitors, which have generated a lot of interest. Metal oxides are a promising material because they have multiple valence shells for charge transfer, a high theoretical specific capacitance, and variable redox properties. Because of this, we explore, for the first time to the best of our knowledge, the effects of Copper (Cu) doping on the super capacitive performance of tin oxide (SnO₂). The pure, 2%, 7%, and 15% Cu-doped SnO₂ are synthesised by facile coprecipitation. We demonstrate a maximum electrochemical performance for 2% Cu-doped sample with a specific capacitance of 27.099 F/g at a sweep rate of 10 mV s⁻¹, while further increase in doping levels had a negative impact on the capacitive performance of SnO₂. The specific capacitance vale was found to be decreased with an increase in Cu concentration, which could be explained by the increasing trend found in the charge transfer resistance upon doping as observed from electrochemical impedance spectroscopy, the resistance increased from 5.85 to 7.19 Ω. The perfect reversible behaviour of a pseudocapacitor is estimated from the highly symmetric nature of chronopotentiometry (GCD) curves and the pseudo behaviour is further confirmed from the cyclic voltammetry curve with an excellent potential window of 1.3 V.

An investigation was conducted in the vicinity of a sustainable pig farm to assess the presence of antibiotics through SPE-HPLC/MS/MS, microbial communities via Illumina high-throughput sequencing, and antibiotic resistance genes using SmartChip technology. The study revealed that tetracyclines were the predominant antibiotics detected in the soil and sediment surrounding the pig farm, with residual concentrations ranging from 33.3 to 1244.2 μg∙kg⁻¹. The most prevalent phyla identified at various sampling sites were Firmicutes, Chloroflexi, Proteobacteria, Actinobacteria, and Acidobacteria. A total of 188 antibiotic resistance genes (ARGs) and 9 mobile genetic elements were found in the sediment, with aminoglycoside (particularly aadA2-03), sulfonamide (specifically sul2), and tetracycline (particularly tetX) resistance genes being the most frequently observed. The presence of tetracycline residue was observed to influence the composition of the microbial community, whereas no significant association was found between antibiotics and ARGs. Examination of the correlation between ARGs and bacteria at the phylum level demonstrated that Cyanobacteria, Acidobacteria, Planctomycetota, and Gemmatimonadota were the predominant phyla associated with ARG presence near an intensive pig farm. Notably, Cyanobacteria may function as a continual reservoir and/or shelter for ARGs, thereby potentially contributing to the dissemination of ARGs in the sediment environment in close proximity to a pig farm. This study presents evidence of the ecological risks posed by antibiotics in a pig farm-cropland system, highlighting the connection between microbial community structure and ARGs. Therefore, the issue of antibiotic residues must be factored into the sustainability of animal husbandry practices.

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.