Hydrogels, as an emerging extinguishant, exhibit outstanding performance in forest fire rescues. However, the near-zero freezing point limits their application at low temperatures. Herein, a sensible candidate commercial extinguishant was selected for analysis, and its freezing point was modified based on the evaluation of water absorption rate, agglomeration, viscosity, and water dispersibility. Notably, the introduction of different antifreeze and flame retardant exhibited a significant disparate impact on the viscosity representative factor. Ten orthogonal experiments were performed to optimize the specific formulation. When ethylene glycol, urea and ammonium bicarbonate, and xanthan gum were applied as antifreeze, flame retardant, and thickener, with the addition amounts of 5 mL, 0.08 g and 0.04 g, and 0.12 g, respectively, the hydrogel extinguishant with 1% ratio in 50 mL of ultra-water featured the remarkable performance. Compared with the original extinguishant, the freezing point of the modified sample decreased from −0.3 to −9.2 °C. The sample’s viscosity was improved from 541 to 1938 cP, and the flame retardance time was more than 120 s. The results of corrosion and biotoxicity show that the optimized hydrogel extinguishant satisfies the national standards. This understanding provides a deeper insight into the application of low-temperature extinguishants in forest fires. Full article

The contents of ten heavy metals (HMs) (Cu, Pb, Zn, Cd, Ni, Cr, Hg, As, Co, and Mn) in 80 surface soil samples (0–20 cm) were investigated in the Pearl River Delta (PRD), Guangdong Province, China. The average contents of Cu, Pb, Zn, Cd, Ni, Cr, Hg, As, Co, and Mn were 16.45, 40.20, 45.10, 0.09, 12.93, 47.93, 0.13, 14.44, 5.68, and 199.66 mg/kg, respectively. The soil quality was generally good, though slightly higher levels (1.17, 1.61, 1.67, and 1.62 times) of soil Pb, Cd, Hg, and As contents were observed compared with the soil background values. The spatial distribution of soil HM pollution in the PRD showed that 36% of sample sites were evaluated as sites without soil pollution, 32% as sites with slight pollution, 20% as sites with nearly moderate pollution, 9% as sites with moderate pollution, and 3% as site with serious pollution. Source apportionment analysis showed that the source of 64.33% of soil HMs in the PRD could be explained by natural and industrial sources, 24.80% by transportation, and 10.87% by agricultural activities. Full article

To identify high-concentration contributing sources and highly dispersive pollution sources of fine particulate matter, analyze the relationship between the location and distribution shape of emission sources and the concentration contribution and dispersion of particulate matter, and realize the atmospheric environment risk simulation and the differential control of non-point sources in the mining area, taking a large mining area in Inner Mongolia as an example, we classified the emission sources of PM_2.5 (particulate matter less than 2.5 μm) and complied with the emission inventory. A CALPUFF model was used to simulate the contribution for the PM_2.5 concentration of six types of emission sources and a multi-source superposition. Through scenario simulation, we analyzed the relationship between the spatial distribution of emission sources and the emission concentration and diffusion in a large mining area. We analyzed the relative risks of six types of sources under the influence of other superimposed sources and the change of emission concentration during transmission. We established a three-dimensional evaluation model to assess the atmospheric environmental risk of PM_2.5 non-point sources in the mining area, considering the change rate of PM_2.5 concentration with migration, the relative contribution ratio of superimposed sources, and the equal contribution index of the standard concentration. The results show that the maximum equal contribution index of standard concentration of multi-source superposition was 4.40. Among them, non-paved roads, exposed surface sources of coal piles, and exposed surface sources of mine pits and dumps were the top three pollution contributors, and their maximum equal contribution indexes of standard concentration were 2.40, 2.21, and 2.10, respectively. The effect of superimposed pollution sources was affected by the wind field and the spatial distribution density of emission sources, while the dispersion was affected by the wind direction and the distribution direction of pollution sources. In the case of the same source intensity and emission area, the denser the source distribution was, the higher the emission concentration was, the smaller the contribution ratio of superimposed sources was, and the greater the relative pollution risk was. When the angle between the direction of dispersed linear pollution sources and the dominant wind direction was smaller, the emission concentration was higher, but the diffusion surface was smaller. When the angle with the direction of wind direction was larger, the emission concentration was lower, but the diffusion surface was larger. Concentrated pollution sources had the highest concentration and the diffusion surface was in the middle. Non-paved roads had the highest environmental risk, with an average risk of 5.61 × 10⁻², followed by coal piles with an average value of 2.06 × 10⁻², followed by pits and dumps with an average value of 1.89 × 10⁻²; the environmental risk of loading and unloading sources was the lowest. Unpaved roads were pollution sources with high relative pollution risk and diffusion risk, and their average relative pollution risk and diffusion risk were 2.34 × 10⁻² and 3.28 × 10⁻², respectively. In the case of multi-source superposition, the high-risk areas were mainly heavily polluted areas with intensive emission sources, while the medium-risk areas were moderately polluted areas with scattered pollution sources, and the diffusion risk was high. This research concludes that the dispersed distribution of pollution sources can reduce pollution risk, and the smaller the angle is between the linear distribution direction of pollution sources and the dominant wind direction, the smaller the diffusion risk is. Therefore, differentiated control can be carried out according to the characteristics of pollution sources. The conclusions can provide methods and theoretical support for the control of atmospheric environment risk, pollution prevention, and control planning in mining areas. Full article

Lead zirconate titanate (PZT) has been widely used because of its electrochemical effect, but its effect on soil microorganisms is rarely studied. In this study, laboratory soil microcosms with different soil moisture content and pH were established to explore the effects of the PZT-5H bimorph with different quantities and states on soil microorganisms after 49 days. Plate counting was used to study the number changes of soil bacteria, fungi and actinomycetes. Isothermal microcalorimetry was used to evaluate microbial activity. High-throughput sequencing was used to analyze soil microbial diversity and community structure. The results showed that the number and activity of microorganisms could be significantly promoted by two vibrating PZT bimorphs under the appropriate soil moisture content (20%) and pH (7). At the same time, it promoted the growth of non- dominant microorganisms and increased the diversity of microorganisms. These results indicate that it is possible for PZT bimorphs to be used in soil field. Full article

Dodecamethylcyclohexasiloxane (D6) is widely used daily in the chemical industry and exists in the environment; however, its eco-toxicity is not well documented. A hydroponic experiment was performed to investigate the effects of D6 exposure (10–1000 mg L⁻¹) on oxidative stress induction and gene expression changes in crayfish (Procambarus clarkii). The results showed that superoxide dismutase (SOD) activity was enhanced by 20–32% at low D6 exposure (10 mg L⁻¹) in muscle but reduced in gill tissue at high D6 exposure (1000 mg L⁻¹). High D6 (1000 mg L⁻¹) also increased catalase (CAT) and peroxidase (POD) activities in muscle tissue by 14–37% and 14–45%, respectively, and the same trend was observed in the carapace and gill tissue of crayfish. The Malondialdehyde (MDA), ascorbate (AsA), and glutathione (GSH) contents were increased by 16–31%, 19–31%, and 21–28% in the muscle of crayfish under D6 exposure. Additionally, silicon (Si) content increased in three organs (gill, carapace, and muscle) of crayfish. Related genes involved in enzyme and nonenzyme activities were detected, and when crayfish was exposed to D6, genes such as Sod3, Cat3, Pod3, and Gsh3 were up-regulated, while Asa3 and Oxido3 were significantly down-regulated in the muscle. The research results help us to understand the toxicity of D6 in crayfish and provide a basis for further research on the mechanism of D6-induced stress in crayfish and other aquatic organisms. Full article

The bio-flocculation ability of UTEX 2341 was studied for the purpose of improving microalgae harvesting efficiency to cut the high cost of biofuel production. The algae cells of UTEX 2341 cultured under heterotrophic and municipal wastewater conditions were found to have better self-flocculation ability, with flocculation rates of 92% and 85% at 2 h, respectively. Moreover, the flocculation rates of 16 freeze-dried microalgae powder samples cultured under different stress conditions were 0~72% with an algae powder dosage of 35 mg L⁻¹. The flocculation efficiency of DIM, DCd1, DT28, and L6S was stable under different pH of 3~9 and temperatures of 15~50 °C. For samples of IM, LCd0.6, LMn2, and LZn2, the flocculation efficiency decreased or increased respectively with increased pH or temperatures. Though the flocculation properties of the eight samples showed wide differences, their flocculant compositions were almost the same with unknown components occupying large proportions. More studies needed to be further carried out to reveal the flocculation mechanisms and analyze the flocculation abilities in practical application, which would be conducive to future large-scale application of the bio-flocculation method and also cost reduction. Full article