In this paper, the removal of total organic carbon (TOC) from a primary treated municipal wastewater using a new electrode configuration in electrocoagulation was evaluated. The used electrode configuration induces a dielectrophoretic (DEP) force by using an asymmetrical aluminum electrode with an alternating current power supply. The impact of applied current, electrolysis time, and interelectrode distance on the removal efficiency of TOC were evaluated. The experimental results showed that the maximum removal efficiency of TOC was obtained at 30 min electrolysis time, 600 mA applied current, and 0.5 cm interelectrode distance. Under these operating conditions, the TOC removal was 87.7% compared to 80.5% using symmetrical aluminum electrodes with no DEP effect. The energy consumption at the selected operating conditions was 3.92 kWh/m³. The experimental results were comparable with the simulation results done by COMSOL Multiphysics software.

The persistence of pathogenic Agrobacterium strains as soil-associated saprophytes may cause an inconsistency in the efficacy of the biocontrol inoculants under field condition. The study of the interaction occurring in the rhizosphere between the beneficial and the pathogenic microbes is thus interesting for the development of effective biopesticides for the management of crown gall disease. However, very little is still known about the influence of these complex interactions on the biocontrol determinants of beneficial bacteria, especially Bacillus strains. This study aimed to evaluate the effect of the soil borne pathogen Agrobacterium tumefaciens C58 on root colonization and lipopeptide production by Bacillus velezensis strain 32a during interaction with tomato plants. Results show that the presence of A. tumefaciens C58 positively impacted the root colonization level of the Bacillus strain. However, negative impact on surfactin production was observed in Agrobacterium-treated seedling, compared with control. Further investigation suggests that these modulations are due to a modified tomato root exudate composition during the tripartite interaction. Thus, this work contributes to enhance the knowledge on the impact of interspecies interaction on the ecological fitness of Bacillus cells living in the rhizosphere.

Plastics are a widespread environmental problem, particularly in the form of small particles or fragments (microplastics). With the purpose of gradually replacing the use of plastics in cosmetic products (primary microplastics), the use of paraffin in microspheres has recently been applied. Paraffin waxes are composed by organic molecules usually derived from petroleum, thus assumed to be chemically and biologically inert, having a lower (eco)toxicity and residence time compared with plastic particles. However, the low ecotoxicity of paraffin waxes may be somewhat questionable, because some paraffin constituents can be absorbed and catabolized, thus exerting biological effects. The main objective of this study was to understand the potential toxic effects of paraffin microparticles on key physiological processes of the polychaete Hediste diversicolor. To attain this objective, this work assessed the acute and chronic effects of three densities (5, 20, and 80 mg L⁻¹) of four size ranges of paraffin particles (from 100 to 1200 μm) on this epibenthic organism. Although paraffin wax can be generically considered innocuous, the present study was able to demonstrate a significant inhibition in the activity of acetylcholinesterase in acutely exposed organisms and an increase in the activity of glutathione peroxidase, catalase, and glutathione S-transferase under some specific scenarios.

We studied the effect of sand filtration with natural esker material on the removal of total organic carbon (TOC), total suspended solids (TSS), and turbidity from the effluent of an experimental recirculating aquaculture system (RAS) farm. Separate experiments were performed with the same esker sand: (1) a soil column experiment in 2017 where the effluent (mean TOC 8.14 mg L⁻¹) was percolated vertically through a 50-cm-thick sand column with the infiltration 1 m day⁻¹; (2) a sand filtration experiment with water-saturated conditions in 2018 where the effluent from the woodchip denitrification (mean TOC 26.84 mg L⁻¹) was infiltrated through a sand layer with the retention time of 1.2 days. In experiment 2, infiltration of 25 L day⁻¹ through a 31-cm sand layer and 40 L day⁻¹ through a 50-cm sand layer were studied. Both experiments were performed in association with rainbow trout (Oncorhynchus mykiss) grow-out trials. In sand filtration with vertical water flow through a soil column, the removal of TSS was 40%, while of TOC 6%, partly due to the small thickness of the soil column and coarse sand material. In water-saturated conditions, mean removal of TOC (3 mg L⁻¹ 1.2 day⁻¹), TSS (1.2 mg L⁻¹ 1.2 day⁻¹), and turbidity (0.4 FTU 1.2 day⁻¹) reached 11% (TOC), 18% (TSS), and 15% (turbidity), even with the retention time of only 1.2 days. The removal of TOC in water-saturated conditions correlated with the removal of TSS and turbidity.

Recently, there has been renewed interest in the relationship between economic globalization and environmental pollution since various globalization indices are developed. Although several attempts have been made to investigate the impact of globalization on the environment, no known empirical research has focused on exploring the causal relationship between ecological footprint and economic globalization index (provided by KOF Swiss Economic Institute) considering also its subcomponents—trade and financial globalization indices. In this study, a new panel data technique for the causality analysis is developed (namely, panel Fourier Toda-Yamamoto approach) and applied to ecological footprint-economic globalization nexus in 14 MENA (Middle East and North Africa) countries during the period 1981–2016. The empirical results highlight that ecological footprint Granger causes economic, trade, and financial globalization for the panel. Besides, it is found that financial globalization has a predictive power to predict further values of environmental degradation in the MENA countries. The empirical results of this paper have a number of practical implications for policymakers. Especially, policymakers should be careful about implementing environmental policies since they may affect economic (trade and financial) activities negatively.

The present work describes the synthesis of α-MnO₂ nanorods using a natural extract of Brassica oleracea (cabbage) and the formulation of its nanohybrids with polycarbazole, i.e., α-MnO₂/PCz. Synergistic interaction between PCz and MnO₂ is revealed from infrared spectroscopy (IR) studies while the composition is determined by X-ray photoelectron spectroscopy (XPS). The formation of α-MnO₂ nanorods is confirmed via high-resolution transmission electron microscopy (HRTEM). The indirect bandgap of α-MnO₂ is reported as 2.5 eV while for the nanohybrids it is found to be ranging between 2.3 and 2.5 eV. Results show that 91% and 89% of degradation is achieved within 30 min and 90 min under the microwave and UV irradiation respectively. Hydroxyl radicals (•OH) and superoxide (•O₂⁻) radicals are responsible for photocatalytic degradation of the drug Bactrim DS which is confirmed by radical scavenging experiments. The nanohybrids show promising catalytic activity under UV as well as microwave irradiation.

Silver contamination of soil systems has been shown to have significant negative effects on soil microbial communities and key functional processes. However, few studies to date have addressed the influence that soil physico-chemical characteristics may have on silver toxicity. In this study, the influence of soil pH soil was investigated on the toxicity of both silver nano-(NP) and micron-(MP) particles to microbial communities and community functioning in a pastureland soil. An acidic soil, pH 5.1, was harvested from an agricultural pastureland and divided into two batches, one of which was adjusted with calcium carbonate to a neutral pH of 7. The effect of 50 mg kg⁻¹ of AgNP and AgMP amendment on the acidic soil and the neutral soil microbial communities was then examined in a microcosm-based experiment. Our results found dehydrogenase activity, which was used as a proxy measure for microbial activity, to be far more susceptible to both AgNP and AgMP contamination in the acidic soil than in the neutral soil. Additionally, both AgNPs and AgMPs significantly affected bacterial and fungal community structures in the acidic soil; however, community structures in the pH-neutral soil amended with AgNPs and AgMPs remained similar to those in the unamended control. The results from this study indicate that soil pH was an influential factor affecting AgNP toxicity in our soil system with the acidic soils far more susceptible to silver contamination than the neutral soil.

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 copper pots with an inner coating layer of tin have been remarkably used in many countries for a long time. In this study, leaching of some metals from tin-lined copper pots into food simulators at different pHs (4, 5.5, 7, and 8.5) during boiling processing (95 °C for 1, 2, and 3 h) or refrigerated storage (4 °C for 1, 2, and 3 days) was investigated. Citric acid and sodium hydroxide were used to adjust the pH of food simulators. The leaching concentrations of metals were analyzed by inductively coupled plasma optical emission spectrometers (ICP-OES). Scanning electron microscopy (SEM) was used to indicate the surface morphological properties of cookware. Based on the preliminary experiments, metals including Al, Sn, Cu, Mn, Fe, Ca, Na, Cr, Mg, and Zn were selected to analyze in acidic treatments. Furthermore, Al, Cu, Sn, Na, and Ca were analyzed for neutral and alkaline ones. Results showed that the boiling temperature for 3 h resulted in a much higher migration of metals compared with cold storage for 3 days. Mn and Cr showed the lowest metal concentration during cooking and cold storage, respectively. The concentration of Sn in acidic simulators was remarkably higher than the other metals during both cooking and refrigerated storage. However, Ca during cold storage, as well as Na during both cooking and cold storage, showed the most migration in alkaline solutions, among the other pHs. An acidic simulator with pH 4 showed the most considerable release of metals from copper pots. SEM results indicated more intense surface corrosion by acidic solution (pH 4) than alkaline one. In general, longer cooking and cold storage durations led to increasing metals release. The migration of the studied metals demonstrates the impurities of the tin layer of these cookwares that may lead to acute and/or chronic diseases.