We investigate the validity of the environmental Kuznets curve (EKC) hypothesis for the NAFTA countries. In this investigation, we approach this hypothesis from a different methodology and propose employing the ARMEY curve hypothesis since the mathematical-functional propositions of both hypotheses were constructed on the same inverted U-shaped relationships. Thus, for the first time, it can be interpreted that the EKC hypothesis is empirically tested through a transmission mechanism of the ARMEY curve hypothesis in a single composite model. Therefore, this approach makes our study different from all empirical studies in the relevant literature. We apply the Augmented Mean Group (AMG) estimator to this aim. Empirical findings indicate that the ARMEY curve hypothesis was verified only for the USA. However, this new approach proposed in this study cannot test the EKC hypothesis through the ARMEY curve model for any NAFTA country since this approach requires verification of the ARMEY curve hypothesis and a significant composite model for the same NAFTA country. If our composite model was significant, it might make it possible to numerically determine a maximum real GDP per capita level that would minimize or maximize CO₂ emission levels for the USA. Therefore, this study introduces-proposes this new methodology as an alternative way of testing the EKC hypothesis in the relevant literature for future empirical studies.

Cold recycling techniques emerged in road construction to recycle deteriorated pavements as bases and surfaces. A detailed review is carried out in the current study on the design, evaluation, performance, and advances in the emulsified asphalt-treated bases (EATB). The mix-design of EATB is a complex procedure in which the performance is based on optimizing water, additives, and emulsified asphalt contents. This paper covers the design methods, compaction characteristics, curing periods, additive contents, strength development, strength parameters, determination of the optimum emulsified asphalt content, and finally, the performance evaluation of EATB. From the detailed review, indirect tensile strength (ITS) is the most influencing parameter considered in the mix design of the EATB. Maximum dry density, Marshall Stability, and ITS are considered as primary performance indicators of the EATB. Modulus, rutting, and fatigue being consider secondary performance indicators. Overall, the recycled bases using emulsified asphalt proved sustainable and economical compared with the natural aggregates (NA).

Mineralogy was an important driver for the environmental release of heavy metals. Therefore, the present work was conducted by coupling mineral liberation analyzer (MLA) with complementary geochemical tests to evaluate the geochemical behaviors and their potential environmental risks of heavy metals in the smelter contaminated soil. MLA analysis showed that the soil contained 34.0% of quartz, 17.15% of biotite, 1.36% of metal sulfides, 19.48% of metal oxides, and 0.04% of gypsum. Moreover, As, Pb, and Zn were primarily hosted by arsenopyrite (29.29%), galena (88.41%), and limonite (24.15%), respectively. The integrated geochemical results indicated that among the studied metals, Cd, Cu, Mn, Pb, and Zn were found to be more bioavailable, bioaccessible, and mobile. Based on the combined mineralogical and geochemical results, the environmental release of smelter–driven elements such as Cd, Cu, Mn, Pb, and Zn were mainly controlled by the acidic dissolution of minerals with neutralizing potential, the reductive dissolution of Fe/Mn oxides, and the partial oxidation of metal sulfide minerals. The present study results have confirmed the great importance of mineralogy analysis and geochemical approaches to explain the contribution of smelting activities to soil pollution risks.

In this study, lanthanum copper oxide was synthesized under hydrothermal techniques and characterized for doxycycline degradation. The catalyst exhibited enhanced photocatalytic doxycycline degradation under visible light owing to its compatible bandgap energy (1.7 eV). The XRD data revealed high crystallinity of the material with no noticeable impurities. Three-dimensional microspheres of varying sizes (average diameter of 2.52 μm) were observed from SEM. EDX confirms the successful synthesis of La₂CuO₄. The effect of DC concentration, catalyst dosage, and initial pH on the degradation rate of DC was studied methodically. Interestingly, about 85% of doxycycline (10 mg/L) was degraded within 120 min of light-emitting diode irradiation at pH 10. Oxygen vacancies and surface defects were determined through photoluminescence spectra. The recyclability experiments suggested that the catalyst is capable of degrading DC for three consecutive runs. Radical trapping trials suggested that holes (h⁺), superoxide radicals (●O₂⁻), and hydroxyl radicals (●OH) are involved in the photodegradation of DC. Herein, the novel approach of La₂CuO₄ synthesis and the efficient visible-light harvesting capability of as-prepared catalyst reveal the potentiality for DC degradation thereby opening a new horizon of research employing La₂CuO₄ used for various environmental applications.

Surplus tetracycline in the water body causes damage to the ecology balance and human health. Therefore, this work established an efficient strategy, namely, the BFO-based UV-heterogeneous Fenton-like system, to eliminate TC pollution. The photocatalytic oxidation system has been integrated with the heterogeneous Fenton-like system, cooperated with the photolysis of H₂O₂. These synergistic effects could boost the generation of reactive species for the TC degradation and mineralization, due to the reduction of Fe(III) to Fe(II) by photogenerated electrons and the separation of photogenerated electron–hole pairs. The prepared BFO was stable with no secondary pollution, and could be recovered by an extra magnet to reuse. Compared with other single oxidation systems, this coupled system showed an outstanding performance in TC disposal, and TC and TOC removal efficiencies could reach 100% and 74.92%, respectively. Moreover, the mechanisms for TC degradation involved that TC was degraded by oxidation species, such as superoxide radicals, hydroxyl radicals, and positive holes, and intermediate products in the TC degradation process mainly were products at m/z = 459, m/z = 445, and m/z = 134. The promising TC disposal efficiency achieved by the integration between BFO-based photocatalytic and heterogeneous Fenton-like system sheds light on applying BFO to control water pollution.

This study aims to investigate the role of arbuscular mycorrhizal (AM) symbiosis in reducing N loss from paddy fields, using two rice lines: a mycorrhiza-defective rice line (non-mycorrhizal) and its mycorrhizal progenitor. Two rice lines were grown in the presence of an AM fungal isolate. In this study, N loss of runoff, leaching, N₂O emission, and NH₃ volatilization were measured, and in addition, N uptake of rice, soil aggregates, and plant available N concentration of soil. The results obtained suggest that N loss via runoff, leaching, NH₃ volatilization, and N₂O emission of mycorrhizal rice was 11%, 8%, 6%, and 1%, lower than that of non-mycorrhizal rice, respectively. Meanwhile, mycorrhizal rice has higher biomass and plant N uptake. Our study shows that the AM symbiosis contributes to the sustainability of rice production by reducing N loss, enhancing soil aggregation and increasing plant N uptake.

This study investigates economic convergence and sustainable development in Africa. By introducing an aggregate production technology and directional distance function, it examines the productivity growth of 28 African economies from 1990 to 2019. The proposed approach considers all decision-making units (countries) as a whole, and the productivity gains are then estimated under a nonparametric framework. In the empirical analysis, the carbon emissions are included in the Luenberger productivity measurement, called green productivity. The results show that the annual average growth rate of green productivity is 1.51% in African, and different types of club convergence for green productivity indicator and its decomposition are observed during the sample period. The decomposition of the Luenberger indicator shows that green African growth is mainly driven by technological progress, not efficiency change. Furthermore, the overall inefficiency is decomposed into technical and structural effects. The latter measure the potential improvement in terms of resource reallocation. Structural inefficiency is larger than technical inefficiency, suggesting that African countries could improve their economic and environmental performances by optimizing input/output mixes.

Pollution from livestock and poultry is the main source of rural pollution, which directly affects the rural ecological environment as well as the quality and safety of agricultural products. Based on field experiment data on broiler farmers in China, this paper analyzes farmers’ cleaner production behavior from the perspective of incomplete contracts and social trust. We find that social trust can promote farmers’ cleaner production behavior. Moreover, our evidence suggests that contract farming (CF) has a significant positive effect on farmers’ social trust and cleaner production behaviors. Further analysis indicates that CF not only directly promotes farmers’ cleaner production, but can also indirectly promote farmers’ cleaner production by improving their interpersonal trust and institutional trust. Overall, this paper offers a new point of view for improving the rural environment and sheds light upon how the government can formulate relevant policies to promote farmers’ cleaner production behavior.

This study analyzes the relationship between wind energy consumption, coal energy consumption, globalization, economic growth, and carbon emissions. Data from 37 countries for the period 2000–2019 are included in the analysis. To examine the long-term relationship between the variables, the AMG method, which considers the cross-section dependence and slope homogeneity, was used. According to the long-term coefficient estimates of the cointegrated variables, wind energy consumption has a statistically significant and negative effect on carbon emissions in the long run. For example, a 1% increase in wind energy consumption reduces carbon emissions by 0.018%. On the other hand, the variable of globalization has a statistically significant and positive effect on carbon emissions in the long run. A 1% increase in globalization increases carbon emissions by 0.107%. These findings show the importance of wind energy consumption in reducing carbon emissions.

It is widely recognized that environmental factors substantially influence on the seasonal and inter-annual variability of bacterioplankton communities, yet little is known about the seasonality of bacterioplankton communities in subtropical estuaries at longer-term time scales. Here, the bacterioplankton communities from the eight major outlets of the subtropical Pearl River Estuary were investigated across 3 years (2017–2019) using full-length 16S rRNA gene sequencing. Significant seasonal and inter-annual variation was observed in bacterioplankton community compositions across the 3 years (p < 0.05). In addition, the inferred functional composition of the communities varied with seasons, although not significantly, suggesting that functional redundancy existed among communities and across seasons that could help to cope with environmental changes. Five evaluated environmental parameters (temperature, salinity, pH, total dissolved solids (TDS), total phosphorus (TP)) were significantly correlated with community composition variation, while only three environmental parameters (temperature, pH, and TDS) were correlated with variation in inferred functional composition. Moreover, community composition tracked the seasonal temperature gradients, indicating that temperature was a key environmental factor that affected bacterioplankton community’s variation along with seasonal succession patterns. Gammaproteobacteria and Alphaproteobacteria were the most dominant classes in the surface waters of Pearl River Estuary, and their members exhibited divergent responses to temperature changes, while several taxa within these group could be indicators of low and high temperatures that are associated with seasonal changes. These results strengthen our understanding of bacterioplankton community variation in association with temperature-dependent seasonal changes in subtropical estuarine ecosystems.