Numerous studies on megacities have reported less air pollution in polycentric form urban than monocentric form urban. However, findings from these studies do not imply that increasing air pollution in region or country is accompanied by the expanding megacities. Using satellite night-light data, this study investigates the impact of polycentric urban form at the provincial level on PM₂.₅ concentrations in China while controlling for variables of urban population size, energy consumption, and the weather. The results reveal that the PM₂.₅ concentrations are reduced by 1.46% to 2.67%, with a 1% increase in polycentric urban form. The similar impact has also been observed in the South China, but larger in the Central China. Further studies show that the urban form-air pollution relationship mainly influenced by transportation distance and enhanced by rising per capita income. The findings suggest that regional planning and policies favoring polycentric urban patterns should be strengthened to alleviate air pollution.

Poly(hydroxylmethyl methacrylate-co-glycidyl methacrylate) (p(HEMA-GMA)) macroporous cryogel with high density of epoxy groups was synthesized, and the epoxy groups of the cryogel were modified into phosphonate groups. The effects of dye concentrations, adsorption time, pH, salt concentration, and adsorption temperature on the adsorption of Direct Blue-53 (DB-53) and Reactive Blue-160 (RB-160) dyes were studied. The maximum adsorption capacity was found to be 245.3 and 155.8 mg/g (0.255 or 0.119 mmol/g) for the DB-53 and RB-160 dyes, respectively. The higher adsorption capacity achieved for the DB-53 compared with the RB-160 dye can result from the pendant primary amino groups of the DB-53 dye as well as the smaller size of the dye molecule. The Langmuir isotherm model and the pseudo-second-order kinetic model well described the experimental data. The p(HEMA-GMA)-PO₄²⁻ adsorbent has many operational advantages for the removal of pollutants. It could be a promising adsorbent to be used in industrial wastewater treatment.

Sheep are important livestock and a source of milk, meat, and wool globally. The increasing demand for animal protein requires increased productivity in sheep. In vitro fertilization and maturation can improve sheep productivity. The aims of this study were to evaluate the effects of honey bee addition as a supplementation medium on in vitro maturation improvement, gene expression of matured sheep oocytes, and determine the optimum concentration from honey bee for in vitro maturation of sheep oocytes. Cumulus oocyte complexes were obtained from the ovaries of slaughtered female sheep. Grade A and B oocytes were cultured for 24 h in medium without honey bee (control, G1) or medium supplemented with 5% (G2), 10% (G3), or 20% (G4) honey bee. Oocyte maturation rate, glutathione concentration, and the expression of candidate genes (GDF-9, BAX, Cyclin B, C-MOS, IGF1) were determined in the matured oocytes. The maturation rate of sheep oocyte was better in the presence of 5% and 10% honey bee; the mean number of oocytes in metaphase II stage was higher than that in G1 and G4 groups. Glutathione concentration was highest in G2 (10.93 ± 0.57). In general, gene expression levels were similar in G2 and G3, which were greater that in G1 and G4. In conclusion, the optimal concentration of black seeds honey bee that can be added to the maturation medium is 5% to obtain the highest mean MII and glutathione concentration values, and to improve gene expression in in vitro matured sheep oocytes.

Biochar was increasingly used in agriculture soil amendment and has received widespread attention due to its potential to improve soil micro-ecological environment and crop growth. The raw material of the biochar used in this study is peanut shell, which is mixed with other organics and minerals to become a mineral-enhanced biochar under heating conditions (220 °C). When the third season crop is finished, we evaluated black soil physicochemical properties, microbial communities, and crop growth in long-term agricultural trials. Four treatments were set up: no amendment (control CK), nitrogen fertilizer only (70 kg ha⁻¹ N), enhanced biochar only (5 t ha⁻¹ B), and nitrogen fertilizer (70 kg ha⁻¹) + enhanced biochar (5 t ha⁻¹) (NB). The enhanced biochar promotes crop growth and increased the richness of the bacterial community, while reducing the richness of the fungal community. Nitrogen fertilizer + enhanced biochar increased soil microbial biomass carbon, nitrate nitrogen, and ammonium nitrogen by 43.75, 7.25, and 19.28%. In addition, we found changes in bacterial community were closely related to soil organic carbon, while changes in fungal community structure were closely related to soil carbon to nitrogen ratio. And the soil organic carbon and soil carbon to nitrogen ratio of biochar treatment were increased by 5.64 and 6.25% compared with fertilizer treatment, respectively. We concluded that enhanced biochar improved the soil more effectively and made the soil more conducive to crop growth. Regulating the microbial community by improving the physicochemical properties of soil was an important way to improve the stability and condition of the soil system with biochar. An enhanced biochar was of great significance for circular development of agriculture and soil improvement in Northeast China.

The combustion of fossil fuels has resulted in rapidly increasing emissions of nitrogen oxide (NOₓ), which has caused serious human health and environmental problems. NO capture has become a research focus in gas purification because NO accounts for more than 90% of NOₓ and is difficult to remove. Advanced oxidation processes (AOPs), features the little secondary pollution and the broad-spectrum strong oxidation of hydroxyl radicals (•OH), are effective and promising strategies for NO removal from coal-fired flue gas. This review provides the state of the art of NO removal by AOPs, highlighting several methods for producing •OH and SO₄•⁻. According to the main radicals responsible for NO removal, these processes are classified into two categories: hydroxyl radical-based AOPs (HR-AOPs) and sulfate radical-based AOPs (SR-AOPs). This paper also reviews the mechanisms of NO capture by reactive oxygen species (ROS) and SO₄•⁻ in various AOPs. A HiGee (high-gravity) enhanced AOP process for improving NO removal, characterized by intensified gas-liquid mass transfer and efficient micro-mixing, is then proposed and discussed in brief. We believe that this review will be useful for workers in this field. Graphical abstract

The leachate (pH = 14) from alumina production changes the mechanical properties of red clay, and the shear strength parameters of the system vary due to the multiple-dimensional interactions of the microscopic parameters. In this paper, the alumina production liquid and the concentrations of the NaOH solution were designed to contaminate the red clay during 80 days. The cohesion and friction angle of the alkaline-contaminated red clay were obtained from direct shear tests. Through qualitative and quantitative analyses using scanning electron microscopy (SEM), the microstructure was observed. Based on the rock engineering systems (RES) theory, interactions among microscopic parameters were analysed, and the relationships between shear strength parameters and microscopic parameters of alkaline-contaminated red clay were established. Results show that both of the cohesion and friction angle of alkaline-contaminated red clay are increased in general; the adsorption in alumina production liquid and dispersing effect of 0.7% NaOH concentration are noticeable, and the interactions of the microscopic parameters are intense; the ratio of the intra-aggregate pore number, the probability distribution index and the number of particles can significantly influence cohesion; the particle morphology fractal dimension, aspect and probability entropy have a severe effect on friction angle. This work is expected to serve as a reference for future research on the relationship between macroscopic properties and microcosmic structure of soil.

Materials held within mine tailings pose a serious risk to the environment in cases of tailings dam failure. Collapse of the tailing dam at the Stolice antimony mine in West Serbia caused a spilling of tailing slurry into the nearby river watersheds. Medium-term effects of As, Pb, Sb, Zn, and Cd from the tailings material that remained in the flooded zone 3 years after the initial exposure were evaluated. Mobility of these elements was determined by analyzing their distribution between exchangeable, reducible, oxidizable, and residual phases. Results indicate that Fe-Mn oxides represent important sinks for As, Cd, Pb, and Sb. Multivariate statistical analysis revealed that concentrations of the analyzed elements were related to sand-sized fractions, as they tended to adsorb or co-precipitate as coatings on larger particles (particularly feldspar and quartz) upon the change of redox conditions. Assessment of the most relevant physico-chemical factors, metal(loid) concentration, and mobility can be used as tool to characterize the degree of contamination of impacted sites. Percentage of sand-sized particles, content of investigated metal(loid)s, and their amount in the reducible fractions are factors determining the best remediation techniques for the area impacted by tailing spill.

The basic purpose of this study is to scrutinize the asymmetric effect of oil price changes on environmental pollution in Canada, China, India, Iran, Germany, Japan, Russia, South Korea, Saudi Arabia, and the USA. The study uses time series annual data of selected courtiers from 1981 to 2018 and applies non-linear ARDL (NARDL) model to examine the long- and short-run asymmetries. The results show that positive shocks in diesel prices in the USA, India, Japan, Germany, South Korea, Iran, and Canada, while negative shocks in China and India reduce carbon emissions in the long run. However, an increase in gasoline prices in Russia and Iran while the decrease in gasoline prices in the USA, Russia, Japan, and Canada decreases in carbon emissions in the long run. Asymmetric findings also suggest that positive and negative changes in oil prices affect carbon emissions differently in China, the USA, India, Russia, Japan, Germany, South Korea, Iran, Saudi Arabia, and Canada in the short and long run. However, sign and magnitude of positive and negative shocks of oil prices are more important in environmental economics polices. Therefore, based on sign and magnitude, more taxation of fossil fuel and clean energy subsidies are recommended for the top carbon-emitting economies.

Our study aimed to uncover the functions of two species of arbuscular mycorrhizal fungi (AMF) in soil aggregation and plant water content regulation under wetting–drying climate conditions. The climatic characteristics of seasonal drought in karst areas were simulated. Two watering periods were established in a controlled greenhouse to compare the different effects of two genetically different AMF species (Funneliformis mosseae and Rhizophagus intraradices) on the water content of 90-day-old mulberry seedlings and on soil aggregates. Our results showed that inoculation with the Rhizophagus intraradices (R.i) strain was more effective at improving mulberry growth performance than Funneliformis mosseae (F.m) inoculation under semiarid conditions. The AMF remained highly infective and continuously increased the proportion of soil macroaggregates under soil drought stress. As a result, our study showed the potential of AMF to promote sustainable mulberry plantations and the rehabilitation of degraded soil in karst areas of southwestern China.

The objective of the work was to study behavioural change of Cyclope neritea (sea snail) and Nassarius mutabilis (land snail) upon exposure to different levels of PAHs. Snail’s behaviour was translated and expressed in Behavioural State Score (BSS) where the score ranged from “0” to “5” points refers to the ascending level of locomotion of a snail. A significant difference was found in snail’s behaviour in 25.0 mg/L than in 0.5 mg/L with p value smaller than 0.01. BSS scores appear most frequent on the treatment and control group were 5 (61.5–64.5%) and 2 (41.0–45.0%), respectively. Intersex behaviour was found in all species (i.e. the same sex was grouped together) regardless of PAH concentrations. This is the first reported to study the behavioural change of snail sampled in Hong Kong area when exposed to PAHs. Further studies should be carried on the impact of snail’s behaviour exposure on each congener in the family of PAHs.