This paper proposes a quantitative method to optimize the existing river monitoring network based on a modified approaching degree model, T test, and Euclidean distance. In this study, the Liaohe River located in Liaoning province, China, was taken as a research object. Samples were collected from 8 sampling sites throughout the monitoring network, and water quality parameters were analyzed every 2 months from January 2009 to December 2010. The results show that the average concentrations of the ammonia nitrogen (NH₄⁺-N) and chemical oxygen demand (COD) were beyond grade III of the Environmental Quality Standards for Surface Water of China (GB3838-2002), and they were the main water quality parameters. After optimization, the number of monitoring sections along the Liaohe River was reduced to five from the original eight, thus saving 37.5% of the monitoring cost; meanwhile, there is no significant difference between the un-optimized and optimized monitoring networks, and the optimized monitoring network remains to be able to perform as good as the original one. In addition, the total data attainment rate was improved greatly, and the duplicate setting degree of monitoring points decreased significantly compared with other optimal methods. The optimized monitoring network proves to be more efficient, reasonable, and economically feasible, so this quantitative method can help optimize the changing orderly river monitoring networks.

Some researches have shown the associations between air pollution and hospital-based emergency department visits, while the evidence about the acute effects of air pollution on emergency ambulance dispatches for the whole population is rarely available, especially on an hourly time scale. This paper aimed to investigate the effects of hourly concentrations of ambient air pollution on hourly number of ambulance emergency call-outs (AECOs) in Shenzhen, China. AECO data were collected from Shenzhen Emergency Center from January 2013 to December 2016. A time-stratified case-crossover design with conditional Poisson regression was performed to fit the relationship between hourly air pollution and AECOs. The distributed lag model was applied to determine lag structure of the effects of air pollutants. There were a total of 502,862 AECOs during the study period. The significant detrimental effects of SO₂, PM₂.₅, and PM₁₀ appeared immediately with a following harvesting effect after 5 h and the effects lasted for about 96 h. The cumulative effect estimates of four pollutants over 0–96 h were 13.99% (95% CI 7.52–20.85%), 2.07% (95% CI 0.72–3.43%), 1.20% (95% CI 0.54–1.87%), and 2.46% (95% CI 1.63–3.29%), respectively. We did not observe significant effects of O₃. This population-based study quantifies the adverse effects of air pollution on ambulance dispatches and provides evidence of the lag structure of the effects on an hourly time scale.

Uses of iron oxide nanoparticles have increased in the last decade. The increased application marked a concern regarding their fate and behavior in the environment. Especially towards the aquatic ecosystems, as the ultimate descend of these iron oxide nanoparticles are aquatic bodies. The greater surface area per mass compared with larger-sized materials of the same chemistry renders these nanoparticles biologically more active. Therefore, it is imperative to assess their eco-toxicogical impact on aquatic eco-systems. In the present study, comparative assessment of iron oxide nanoparticles and their bulk counterpart have been monitored using Coelastrella terrestris up to 40 days. Interestingly, study reveals the potential of Coelastrella terrestris as tool for the bioremediation of iron nanoparticles to combat nano-pollution. Adsorption/absorption kinetics measured after 25 days of treatments with iron oxide nanoparticle and its bulk counterpart revealed higher absorption levels in comparison to the adsorption with maximum accumulation factor (AF) of 2.984 at 50 mg L⁻¹ in nano-form. Iron oxide absorption was found linearly related with concentration in both cases (y = 11.313x-12.165, R² = 0.8691 in nano; y = 6.35x-5.74, R² = 0.8128 in bulk). However, 50-mg L⁻¹ nanoparticle concentration was perceived sub-lethal for the algae with 33.33% algal growth reduction under nano and 27.77% under bulk counterpart. Other biochemical parameters, i.e., SOD, CAT, MDA, and lipid quantification, were also quantified to correlate the state of metabolism of treated algal cells in comparison to the control and these exhibited reduction in algal growth due to oxidative stress. Morphological changes were monitored through SEM and TEM.

The expanding production and widespread application of acrylamide caused inevitable release to aquatic ecosystems. Contrary to its extensive attention to human and animal health, the hazards of acrylamide to the aquatic primary productivity have been rarely studied. The potential effects of acrylamide on the marine algae (Nitzschia closterium) and the limnetic algae (Scenedesmus quadricauda) were investigated by monitoring cell abundance, total chlorophyll content, maximum photosystem II (PSII) quantum yield (Fv/Fm), and reactive oxygen species (ROS). The growth of two algae was significantly inhibited by acrylamide. The 96 h EC₅₀ of acrylamide on N. closterium and S. quadricauda were 5.50 mg L⁻¹ and 45.3 mg L⁻¹, and no observed effect concentration (NOEC) were 1.07 mg L⁻¹ and 6.97 mg L⁻¹, respectively. After 96 h exposure to 50 mg L⁻¹ of acrylamide, the total chlorophyll content declined to approximate 18% (N. closterium) and 48% (S. quadricauda), and Fv/Fm was observed to be 0.35 and 0.32 for N. closterium and S. quadricauda, respectively. ROS was significantly increased following higher exposure concentrations, and its levels increased around 2.1-fold and 1.4-fold following exposure to 5 mg L⁻¹ of acrylamide. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the visible cell plasmolysis, rupture of the plasma membrane, cell vacuolization, and disintegration of chloroplasts of the algae caused acrylamide.

A novel ZnO-CeO₂-rGO (ZCG) ternary nanocomposite with varying ZnO/CeO₂ weight proportions was synthesized by a hydrothermal process for photoelectrochemical water splitting and photocatalytic application. XRD diffraction peaks of ZCG nanocomposites displayed the patterns of ZnO and CeO₂ nanoparticles, and SEM revealed irregular flake-like particles, which were uniformly decorated on the rGO matrix. Increase in the intensity ratio of D and G bands from Raman spectra revealed changes in oxygen bonding in the ZnO-rGO (ZG) and ZCG nanocomposites. The shift in the band edge positions and the decrease in the band gap with increase in the cerium oxide content in ZCG composites were observed from UV-Vis and Mott-Schottky plots. XPS results showed that Ce³⁺ fraction increased with an increase in the cerium oxide content in ZCG nanocomposites. The ZCG3 (85:15) nanocomposite exhibited decreased electron-hole recombination rate as evidenced from the photoluminescence and electrochemical impedance spectroscopy Nyquist plots. The characteristic frequency in Bode’s plot shifted to a lower frequency for the ZCG3 electrode demonstrating low interfacial charge transfer resistance, and ZCG3 photoelectrode displayed a higher photocurrent density of 0.69 mA/cm² at 1.5 V compared with other photoelectrode. The optimized and highly efficient ZCG3 nanocomposite exhibited improved photocatalytic degradation of methylene blue (MB) with a reaction rate constant of 0.0201 min⁻¹. Combination of defects in the form of Ce³⁺ ion and surface oxygen vacancies coupled with rGO as the electron acceptor improved the charge carrier density and carrier transport in addition to the formation Schottky-type junction and the presence of an internal electric field.

The removal of organic micro-pollutants (OMPs) from landfill leachate in constructed wetland (CW) media having different material mixtures of sand (S), clay (C), and iron powder (Fe) was investigated using experimental column study. The use of S:C:Fe media consisting of 60:30:10% (w/w) and cattail as vegetation was found optimum for the removals of 2,6-DTBP, BHT, DEP, DBP, and DEHP at 67.5–75.4% during long-term operation of 373 days. Adsorption and biodegradation were confirmed as predominant mechanisms for their removal in CW media but their contribution in total removal varied depending on chemical properties of OMPs. Adsorption kinetic could be well explained by pseudo-second-order whereas biodegradation kinetic followed first-order reaction. The adsorption affinity of OMPs to CW media was S:C:Fe > S:C > S in descending order. This study demonstrated high and sustainable removal of OMPs during long-term operation of CW with the optimized reactive media.

Iron catalyst supported over magnesium oxide had been synthesized with different percentages of Fe, i.e., 0.5, 1, and 5% employing the method of impregnation. These fabricated catalysts were used to grow carbon nanotubes (CNTs) using a chemical vapor deposition (CVD) method in the CVD reactor. The 5% Fe/MgO catalyst showed the maximum growth of CNTs. The synthesized novel CNTs (5Fe-CNTs) were investigated for their adsorption capabilities for the removal of parts per million levels of hexavalent chromium from electroplating effluent. The 5Fe-CNTs were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and Zeta analyzer. The 5Fe-CNTs showed remarkable adsorption capacity of 63.3 mg g⁻¹ toward Cr(VI) in water. The effects of various operating conditions on the removal of Cr(VI) from wastewater have been evaluated. Kinetic and thermodynamic studies were performed, and it was observed that the experimental data is in best agreement with pseudo-second-order kinetics. Besides the synthesized CNTs exhibited good recyclability for adsorbing Cr(VI) as even after 3 adsorption cycles, the adsorption capacity was reduced by less than 10%.

In tropical environments, nutrient-poor soils are commonly found, leading to high fertilizers application rates to support agricultural activities. In contrast, anthropogenic activities generate large amounts of effluents containing nitrogen. In this study, two minerals (natural zeolite and vermiculite) were tested to remove NH₄⁺ from an industrial effluent with high pH and contents in Na⁺ and K⁺. Afterwards, they were tested as an alternative slow-release fertilizer in the soil. To verify the best conditions to adsorb NH₄⁺, batch tests were conducted using synthetic solutions and an industrial effluent. In general, the efficiency of both minerals in removing NH₄⁺ was high (85% for zeolite and almost 70% for vermiculite) as well as the ability to decrease the industrial effluent pH. In this process, more NH₄⁺ and K⁺ ions were removed in comparison with Na⁺, which remained in solution. These minerals were tested as slow-release fertilizers by leaching with distilled water (both minerals releasing 2 mg L⁻¹ NH₄⁺) and with an acid solution (releasing 10 mg L⁻¹ NH₄⁺ from zeolite and 50 mg L⁻¹ NH₄⁺ from vermiculite—corresponding only to 12% of total NH₄⁺ retained by zeolite and 29% by vermiculite). During the test of soil incubation with zeolite-NH₄⁺, the NH₄⁺ ions of the exchangeable sites were retained for a longer period, minimizing their loss by leaching and biological nitrification. Consequently, soil acidification was prevented. Therefore, both minerals showed high efficiency in removing NH₄⁺ from solution which can then be slowly released as a nutrient in the soil.

CO pretreatment was found to effectively improve the SCR performance of CeO₂, with over 90% at about 300 °C. The larger specific area and the decrease of CeO₂ crystallization indicated the modification of the surface structure after CO pretreatment. Abundant Ce³⁺ species and active oxygen, better reducibility, and the higher surface adsorption capacity were mainly responsible for its enhanced SCR performance. DRIFT analysis revealed the presumed coexistence of two reaction routes that the L-H mechanism was related to the reaction temperature, while the reaction rate of E-R route was almost directly proportional to the NO concentration at a certain temperature, based on the kinetic calculation. In addition, the CO-pretreated CeO₂ also exhibited a better poisoning tolerance for SO₂ and H₂O and excellent thermal stability and circularity. Graphical abstract The process of NH₃-SCR reaction over CeO₂-CO catalyst.

In this modern era, environmental pollution is the biggest problem attached to industrialization. This study tries to ensure the relationship between industrialization and CO2 emissions in Pakistan for the time period 1980–2018 by using nonlinear ARDL model while controlling for urbanization, GDP, and human capital variables as a likely factor of CO2 emissions. Our foremost study objective is to examine whether or not the outcome of industrialization on CO2 emissions is symmetric or asymmetric for Pakistan that is one of the core suppliers to CO2 in South Asia, as the emissions were 0.82 million tons in 2018. Our result approves the presence of an asymmetric effect of industrialization shocks on CO2 emissions both in the short run and long run. The results reveal that industrialization increases emissions and deindustrialization decrease emissions, in short as well as long run, in Pakistan. Moreover, our finding also advises that urbanization and GDP variables have exerted a positive impact on CO2 emissions. Based on the findings, some policy suggestions are proposed for Pakistan.