The Cu/TiO₂ catalysts with the addition of Eu were developed by the sol-gel way for the selective catalytic reduction (SCR) of NOₓ by NH₃. Activity tests revealed that CuEu/TiO₂-0.15 catalyst showed the optimal de-NOₓ performance in a wide temperature range (150–300 °C), along with an admirable SO₂ tolerance. According to characterization analysis, the relationship between the NH₃-SCR performance and physicochemical characters of samples was explored. The adjunction of Eu on Cu/TiO₂ catalyst can contribute to the formation of a large amount of Cu²⁺, adsorbed oxygen, and acid sites on the catalyst surface. Moreover, the Eu addition on Cu/TiO₂ is favorable to the generation of activated NOₓ and NH₃ substances adsorbed on the catalyst surface, which would conduce to the NH₃-SCR process by Langmuir-Hinshelwood (L-H) mechanism effectively.

The feasibility and performance of Jicama peroxidase (JP) immobilized Buckypaper/polyvinyl alcohol (BP/PVA) membrane for methylene blue (MB) dye removal was investigated in a customized multi-stage filtration column under batch recycle mode. The effect of independent variables, such as influent flow rate, ratio of H₂O₂/MB dye concentration, and contact time on the dye removal efficiency, were investigated using response surface methodology (RSM). To capture the inherent characteristics and better predict the removal efficiency, a data-driven adaptive neuro-fuzzy inference system (ANFIS) is implemented. Results indicated that the optimum dye removal efficiency of 99.7% was achieved at a flow rate of 2 mL/min, 75:1 ratio of H₂O₂/dye concentration with contact time of 183 min. The model predictions of ANFIS are significantly good compared with RSM, thus resulting in R² values of 0.9912 and 0.9775, respectively. The enzymatic kinetic parameters, Kₘ and Vₘₐₓ, were evaluated, which are 1.98 mg/L and 0.0219 mg/L/min, respectively. Results showed that JP-immobilized BP/PVA nanocomposite membrane can be promising and cost-effective biotechnology for the practical application in the treatment of industrial dye effluents.

Identifying the magnitude and seasonal variability of groundwater nitrogen (N) under various land use types and quantifying the contribution of their environmental factors are of great importance when attempting to implement prioritizing effective strategies for mitigating groundwater N pollution. In this study, hydrochemical investigation was used to assess the magnitude and temporal variability of groundwater N in arid regions. Spatial distributions of N species (total N (TN), nitrate-N (NO₃––N), ammonium-N (NH₄⁺–N), and nitrous-N (NO₂––N)) were mapped using geostatistical techniques. Redundancy analysis (RDA) was conducted to determine environmental factors controlling hydrochemistry. The results showed that residential areas (town and village) and cropland had higher groundwater N concentrations than natural (forest and grassland) and unused land. And the concentrations of N species in rain season (August) were greater than those in the dry season (March) and normal season (November). The N species spatial patterns showed that there is a risk of TN and NO₃––N pollution in groundwater of town and surrounding developed cropland, and that NH₄⁺–N and NO₂––N pollution were negligible. Selected environmental factors explained a total of 77.4% of data variance in N concentrations. These factors indicated that water environmental factors (dissolved oxygen (DO), oxidation–reduction potential (ORP), water temperature (WT), and pH) affect groundwater concentrations and forms of N by influencing the process of nitrification and denitrification, which explained about 60% of the variance of the data. Approximately 10.8 and 8.3% of the variability was explained by shallow groundwater depth and soil texture, indicating that N concentrations in groundwater had heterogeneous influence. The high N excessive pollution ratio was observed in towns and cropland indicating that artificial N input is the main reason for groundwater N pollution in the study area. Hence, ameliorating anthropogenic agricultural practices and reducing N input in urban areas are critical to alleviating groundwater N pollution in the research area.

In this paper, we are reporting a simple hydrothermal technique for preparation of MoSe₂ nanostructures (nanourchins and nanosheets) using selenium and sodium molybdate as precursors. Samples are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, UV-Vis spectroscopy, Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The FESEM revealed that the morphology of materials was varying significantly by changing pH value during synthesis. Photocatalytic degradation of anionic dye (MO), cationic dye (MB), and reduction of Cr(VI) into Cr(III) were performed. Nanosheets and nanourchins showed higher photocatalytic activity, enhanced photocatalytic degradation efficiency is correlated with the higher •OH radical concentration, crystallinity of material, and large surface area as evident through XPS, XRD, and BET, respectively. Photocatalysis mechanism along with role of reactive species (•OH and holes) were explained using trapping experiments. Identification of degraded products was carried out using high-performance liquid chromatography (HPLC). Reaction kinetics and reusability of materials were also studied; wherein, it was observed that the materials have reusable properties.

Quaternary ammonium salt type cotton linter (QCL) was synthesized by radiation grafting of dimethylaminoethyl methacrylate (DMAEMA) onto cotton linter and subsequent quaternization. Batch and column adsorption experiments were used to evaluate the adsorption behaviors of the QCL for phosphate. The adsorption kinetics of QCL for phosphate were well obeyed pseudo-second-order mode. The adsorption isotherms were well fitted by Langmuir, Temkin, and Dubinin–Radushkevich model. Column experiments showed that the breakthrough curves were dependent on the inlet concentration and flow rate but independent on space velocity. Moreover the QCL can be effectively regenerated for further repeated use at least 10 cycles. And QCL exhibited good selective adsorption for phosphate. Such high adsorption and desorption efficiency of QCL made it employing for phosphate adsorption in practical application.

This study examines the Environmental Kuznets Curve (EKC) hypothesis in the context of 12 members of the OPEC by utilizing data on both the aggregate gross value added and the services’ sectoral value-added between 1992 and 2015. This empirical work contributes to the literature by applying the panel spatial techniques which resulted in the findings as follows. Firstly, the results verify the authenticity of the EKC hypothesis for the aggregate level of gross value added as perceived from its inverted-U shaped association with CO2 emissions. Secondly, the disaggregated analysis affirms the heterogeneity of the validity of the EKC hypothesis across the subsectors within the services sector; this justifies the importance of analyzing the EKC hypothesis from a comprehensive (disaggregated) perspective for unearthing key sector-specific policy implications. The results reveal that the EKC hypothesis holds only in the context of construction services only but not for the cases of restaurant services, tourism and transportation services. These key findings call for effective measures to be undertaken to address the adverse environmental impacts that can be attributed to thse three sub-sectors for which the EKC did not hold. In line with the overall findings from the empirical exercises, it is recommended that the concerned OPEC members reduce their monotonic dependency on the consumption of fossil fuels, oil in particular, and gradually incorporate renewable energy resources into the energy-mix particularly within their respective services sector.

This study investigates the heterogeneous causal linkages between urbanization, the intensity of electric power consumption, water-based pollutant emissions, and GRP in regional China by developing an urbanization-augmented “Stochastic Impacts by Regression on Population, Affluence, and Technology” (STIRPAT) model. A whole country panel of 29 provinces as well as region sub-panels of China, for the period 1999 to 2018, are estimated employing common correlated effects mean group approach (CCEMGA), which offers robustness against heterogeneous characteristics and cross-sectionally dependent series. From the theoretic modeling aspect, the intensity of electric power consumption and urbanization have been introduced as the determinants of water-based pollutant emissions in the STIRPAT modeling framework. Based on empirical results, first, GRP growth has shown appealing behavior in the form of its heterogeneous impacts on water-based pollutant emissions growth in the case of different regions. For instance, its impact is noted to be positive and statistically significant for the western region, which turned positive but statistically insignificant for the intermediate region. And it further turned significantly negative in the case of the eastern region. We call this phenomenon as “development level-based emission mitigation effect.” Second, in terms of the impact of GRP growth on urbanization, the “development-based urbanization ladder effect” has been found. Based on heterogeneous causal links, firstly, the existence of a positive bilateral causal link between the intensity of electric power consumption and GRP growth and urbanization and GRP growth has been validated. Secondly, a positive unidirectional causal link emerged from urbanization to the intensity of electric power consumption and water-based pollutant emissions growth. Thirdly, the causal connection between GRP growth and water-based pollutant emissions growth remained very interesting and of mixed nature. Based on empirical findings, useful policies are extended. Graphical abstract

The spatial and vertical distributions of radon and uranium are evaluated in relation to the hydrogeology, geomorphology, and hydrochemistry of southwest Punjab. Radon activity of the groundwater ranges from 580 to 3633 Bq/m³ (shallow groundwater 580 to 2438 Bq/m³ and deep groundwater 964 to 3633 Bq/m³), and uranium concentration varies from 24.4 to 253 μg/L (shallow groundwater 24.4 to 253 μg/L and deep groundwater 27.6 to 76.3 μg/L). Shallow groundwater shows higher U concentration compared with deeper ones, which can be attributed to the presence of dissolved oxygen (DO) and NO₃⁻ as oxidants and HCO₃⁻ as stabilizing agent in shallow zone. Unlike uranium, the radon activities were found to be similar in both shallow and deep groundwater. Rnₑₓcₑₛₛ over secular equilibrium was used to confirm the possibility of additional sources of radon, such as secondary minerals present in the subsurface. Surface manifestations show significant influence on radon and uranium distributions in the shallow zone but not in deep zone due to limited hydraulic connectivity. Depth profiles and correlations of radon and uranium with trace elements and hydrochemical parameters indicate that groundwater exhibits different redox characteristics in shallow (younger and oxidizing) and deep zones (older and reducing). The present study provides critical information that can be helpful for planning sustainable groundwater development in this region and other similar regions without contaminating the relatively safer deep aquifers.

Vapor intrusion (VI) risk assessments determine the cleanup level of groundwater in the absence of ingestion. In recent VI investigations, the building pressure cycling (BPC) method has been applied to help minimize ambiguity caused by temporal variability of indoor air samples that are important to risk assessments, and, consequently, determine groundwater cleanup level accurately. In this study, we use a three-dimensional numerical model to examine the dynamic migration of VOCs from groundwater after the application of BPC. First, we validated the numerical model with field measurements. Then, the verified model is used to investigate the effects of site-specific features in determining the performance of BPC operation. At last, we summarize past field applications of BPC to examine the simulated results. Our study indicates that the BPC-induced indoor depressurization can increase the building loading rate in the first 2–3 h, which would then drop to 2–3 times of that with natural conditions in most cases of groundwater contamination. In some cases involving a strong source, e.g., a vapor source above the capillary fringe or a groundwater source with sandy soil above the groundwater level, the normalized building loading rates can be maintained as high as 4–9 without decrease after the first 2–3 h. Significantly higher increase in building loading rate may indicate a potential presence of a preferential pathway between the groundwater contamination and concerned building.

Small geographically isolated ponds provide a multitude of ecological functions and services, but water table fluctuations alter the magnitude of these services. Understanding temporal and spatial changes of surface water levels in the watershed, and their spatial variability, is critical for restoration and protection of small ponds. A biweight spatial consistency test was employed to quantify the seasonal variability of surface water tables for 50 ponds and hydrological connectivity models, and land use metrics, topographic characteristics, and irrigation needs, for groundwater, were introduced into the model to identify influencing factors. The spatial difference of water level changes in the rice season was greater than the wheat season while water table increased in the wheat season and declined in the rice season. Continuous runoff with complete surface hydrological connectivity of ponds, which was strongly related to precipitation, occurred only one time during the study period. Water level dynamics were largely uncorrelated to surface hydrological connectivity but were linked to watershed and pond size. By evaluating irrigation water requirements, irrigation was a primary human management factor affecting the water table changes in ponds. Groundwater also enriched influence factors that estimated water level variation in ponds, and these results will provide support for improved water resource management and ponds protection purposes.