A comprehensive study was carried out to evaluate the occurrence, significance of concentrations and spatial distribution of heavy metals (Cr, Cd, Ni, Cu, Pb, Hg, Zn and As) in sediments along the Valencia coastline (Spain). The sampling campaign covered 476 km of the coastline in a 4-year period. The highest concentrations of metals in the sediments were mainly Cr, Ni, Zn and Cd (up to 28.93 mg Cr kg⁻¹ dw, 15.80 mg Ni kg⁻¹ dw, 57.13 mg Zn kg⁻¹ dw and 0.293 mg Cd kg⁻¹ dw), obtained in the northern areas, some central areas and in an isolated area on the southern coastline. The Sediment Quality Guidelines applied reveal that for all metals studied, none of them reached, or exceed, the “effects of median range” or the “probable effect level”. The pollution index reveals that 75% of the stretch coastline has a low priority risk level and the rest “medium-low priority risk level”. And, lastly, Potential Ecological Risk Index shows that all but one zone have low ecological risk.

This study investigates the validity of the EKC (environmental Kuznets curve) hypothesis for the 50 US states and a Federal District (Washington, D.C.). To this aim, the common correlated effects (CCE) and the augmented mean group (AMG) estimation procedures are applied between 1980 and 2015. While the CCE estimation does not support EKC hypothesis, the AMG does. The empirical findings of the AMG estimation indicate that only 14 states verify the EKC hypothesis. Additionally, the expected negative impacts of fossil energy consumption on the environment (CO₂ emissions) are strongly detected in all states except Texas. However, the expected positive impacts of renewable energy consumption on the CO₂ emissions are detected only in 13 states. Furthermore, the expected negative impacts of the population are not detected in some mostly populated states like New York, Texas, and Ohio. The overall findings of this study may help the US state-level policy makers in two ways: first, to understand whether their economic growths are sustainable (eco-friendly); second, to see how their fossil and renewable energy consumptions affect their environments and to review their energy policies.

Oxytetracycline (OTC), a type of tetracycline, was used widely as feeding additive to promote animal growth in breeding industry in the world. Its residue has been found in soils. Based on potted maize experiments, the influences of OTC on soil enzyme activity, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and soil fertility were investigated during the growth stages of maize receiving different fertilizers (spent mushroom substrate, worm manure, and biochar, among others, with single applications and combined applications with their cooperating microbial inoculants). The results showed that OTC negatively affected the soil enzyme activity, MBC, MBN, and cation exchange capacity (CEC). Enzyme activity, MBC, and MBN were more sensitive to OTC than soil fertility. The significant negative correlations were found between OTC concentrations and catalase, MBC, and CEC (p < 0.05). This indicated that the effects of OTC on soil can be alleviated by different fertilizers, and the effects of T6 (microbial inoculants), T7 (microbial inoculants + worm manure), T8 (microbial inoculants + SMS), and T9 (microbial inoculants + biochar) were the best among those of all treatments. During the mature stage of maize, the content of OTC in the soil of T7 was the lowest compared with other treatments. The results provide a good basis for the development of methods to remediate OTC-contaminated soils.

The Environmental Kuznets Curve hypothesis is a theoretical proposition explicating the link between a locality’s income level and environmental degradation. Previous studies estimated the current relationship with an unchanging parameter. However, due to changes in global conomic and political conditions, natural disasters, technological shocks, and implemented policies, the link between income and environmental degradation is about to change. The study investigates the income-pollution nexus for G7 countries—Canada, France, Germany, Italy, Japan, the UK, and the USA—from 1970 to 2014 using a novel methodology: bootstrap panel rolling window causality. In this context, this approach is advantageous for determining the link between income and pollution level in sub-sample periods, rather than assuming an unchanging parameter, and captures the hidden causal linkages between income and environmental pollution. The results confirm the validity of the EKC hypothesis in Japan and the USA, whereas in the other countries, the relationship between EF and GDP exhibits no evidence for an inverted U-shaped pattern.

Although the Chinese government emphasizes the significance of public transportation development and encourages green travel, no empirical study has examined whether the expansion of public transportation facilitates the mitigation of carbon emissions. To this end, we employ a panel quantile regression to test the endogenous relationship between public transportation scale and carbon emissions. The results suggest that the effect of public transportation scale on carbon emissions is heterogeneous across China’s provinces based on the level of carbon emissions. Even so, the results still support a stable inverted U-shaped relationship between public transportation scale and carbon emissions for provinces with different levels of carbon emissions. That is, when public transportation scale exceeds a threshold value, the relationship between public transportation and carbon emissions will turn from positive to negative. Our findings provide evidence advocating for public transportation development and green travel. It is of great significance for China to respond to climate changes.

The tailings produce acid mine drainage (AMD) due to sulfide minerals, especially pyrite oxidation. AMD has caused serious pollution to the surrounding aquatic and terrestrial ecosystems because of its famous low pH value and high metal and sulfate concentration, which is an urgent environmental problem faced by the world’s ore mining industry. Here, we show that silicic protective surface films can suppress the oxidation of pyrite-bearing tailings for AMD control at-source without pre-oxidation of pyrite and solution pH adjuster and buffer. We found that the silicic protective surface films formed by calcium silicate can inhibit the oxidation of pyrite-bearing tailings and reduce the production of AMD through chemical leaching tests. Fourier transform infrared (FTIR) analyses and scanning electron microscopy with energy-dispersive spectrometry (SEM/EDS) confirmed the presence of silicic protective surface films of calcium silicate on the surface of pyrite-bearing tailings.

The removal of Acid Orange 51 (AO 51) dye in aqueous solution by microscale zero-valent iron (m-ZVI) was investigated. The m-ZVI powder was characterized granulometrically by laser particle sizer and morphologically by transmission electron microscopy (TEM). The effects of pH, m-ZVI concentration, H₂O₂ addition, and dye concentration on the decolorization of AO 51 were experimentally investigated. Results indicate that the removal efficiency is independent from pH values, increases with increasing ZVI dosage, and decreases with dye concentration. With 1 g/L of m-ZVI, AO 51 was effectively removed without and with addition of 25 mM H₂O₂, yielding a decolorization efficiency of around 70% and 98%, respectively, at pH 3 within 60 min of reaction time. The involvement of ˙OH in oxidizing AO 51 was examined by measuring the removal rates based on ˙OH scavenging molecule. Finally, the disappearance of AO 51 was estimated by monitoring the UV–Vis spectral evolution after 120 min of treatment while the Fourier-Transform Infrared spectroscopy (FT-IR) was performed to verify the occurrence of organic sorption on m-ZVI surface. The scanning electron microscope (SEM) images before and after the reaction illustrated morphological changes on m-ZVI surface. The detoxification of the treated solution was demonstrated using phytotoxicity test.

Mechanochemical degradation (MCD) technology has shown its remarkable potential in the disposal of persistent organochlorines in a non-combustion manner. In the present study, endosulfan, as the newly listed persistent organic pollutants (POPs) in the Stockholm Convention, was investigated for its feasibility of mechanochemical destruction using high-energy ball milling. Using calcium oxide (CaO) as a co-milling reagent, the degradation efficiency of endosulfan was nearly 100% after ball milling for 60 min, while the dechlorination efficiency and the sulfate formation efficiency were delayed for endosulfan degradation. After ball milling for 120 min, the dechlorination efficiency and sulfate formation efficiency reached 87.55% and 26.28%, respectively. Based on the measurement results from various material characterization approaches, the main degradation pathway of endosulfan was proposed as sequential dechlorination followed by the destruction of hydrocarbon skeleton. The GC-MS analysis confirmed that complete desulfurization and dechlorination had been realized finally. This study provides an option for the way toward the efficient and rapid destruction of endosulfan as a new POPs using mechanochemical technology.

Nowadays, the extensive use of pesticides in crops production puts a significant challenge to minimize its side effects along with safe production, storage, and after-use treatment. This paper reports results related to the emission of certain pesticide formulations through the PET containers, as well as, their mitigation to the PET containers during their storage. The influence of storage time on cypermethrin migration to and through the PET was studied in short-term Collaborative International Pesticides Analytical Council test lasting up to 30 days. The PET containers were filled with pure xylene and pesticide formulations, where the amount of active substance, cypermethrin (CY), varied from 5 to 20 wt%, while the amount of emulsifier was kept constant. The results indicate that pesticide formulations diffuse to PET containers with an average increase of its initial mass up to 1.5%. The most intensive diffusion is in the first 24 months of storage, after its rate significantly decreases. It should be noted that the diffusion studied pesticide formulations are also very dependent on CY concentration. Besides the migration to the PET containers, it was also found that pesticide formulation was emitted through the PET containers in the first 17 to 24 months of storage depending on CY concentration. Emission rates were also dependent on CY concentration and were in the range of 15.3 to 38.0 mg/month·container. The emission through the PET containers was successfully predicted using artificial neural networks with R² = 0.94 and the mean absolute percentage error (MAPE) of only 6.2% on testing.

Milk can be considered as an indicator of the degree of environmental contamination of the place where it is produced and this is especially important when assessing its content in toxic metals. Therefore, 36 bovine milk samples from 7 farms with a semi-extensive grazing system were analysed, located in Asturias (Spain), in an area with high probability of being highly contaminated due to a mining zone, with important industrial activity and near high-density highway traffic. The samples were lyophilised to achieve total dehydration, further analysed using inductively coupled plasma mass spectrometry (ICP-MS). The metals titrated were aluminium (Al), arsenic (As), molybdenum (Mo) and mercury (Hg) in the lyophilised samples and subsequently extrapolated their values to whole milk. All samples analysed showed levels of Al and Mo above the limit of detection, with mean values of Al of 140.89 ± 157.07 in liquid milk and 1065.76 ± 1073.45 in lyophilised milk and Mo of 20.72 ± 14.61 μg/kg and 152.26 ± 96.82 μg/kg in whole and lyophilised milk. Only As was detected in four samples with mean values of 18.45 ± 6.89 and 166.45 ± 42.30 μg/kg in liquid and lyophilised milk, respectively, and no Hg was found in any of them. In no case do the values found indicate a significant hazard to the population and are in agreement with those found in other investigations. Although the various anthropogenic activities of the area (industrial, mining, traffic density) could, a priori, indicate a possibly contaminated area.