Most of the previous researches estimate influencing factors impact on air quality average without considering the heterogeneity of influential factors on different levels of air quality. In order to detect the different effects of influencing factors on air quality index (AQI) between lower-AQI and higher-AQI cities, this study applies a spatial quantile regression model (SQRM) to investigate heterogeneity of influential factors on AQI, while accounting for spatial autocorrelation of AQI. The results show that heterogeneity effects of windspeed, terrain slope, urbanization sprawl and spatial autocorrelation on AQI are large across the entire AQI spectrum, while heterogeneity effects of precipitation, temperature, relative humidity, terrain fluctuation and urbanization intensity on AQI are not obvious. The spatial positive autocorrelation of AQI in higher-AQI cities is greater than that in lower-AQI cities. Compared with higher-AQI cities, the negative impact of terrain slope on AQI is lager in lower-AQI cities. One unit increase in wind speed contributes AQI to decrease 9.31 to 5.64 then to 5.39 for lower, medium and higher-AQI cities. One unit increase in urbanization sprawl would lead AQI increase 25.6 to 15.6 then to 10.5 for lower, medium and higher-AQI cities. The heterogeneity analysis of meteorological, topographic and socioeconomic factors effects on air quality are of guiding significance for realizing the differentiation of policy measures for air pollution prevention and control.

NO₂ oxidation of soot exhausted from engines is more efficient than O₂ under low-temperature conditions, and is crucial for diesel particulate filter to control soot pollution. To explore the principle behind accelerating soot oxidation by NO₂, this paper uses density functional theory to reveal soot oxidation process by NO₂. This study contributes to understanding rules of soot oxidation by NO₂ and perfecting soot oxidation models to develop soot emission control technologies. Results show that NO₂ oxidation of pyrene radical involves three steps. Firstly, NO₂ attacks the C∗ atom to form –C (NO₂) with reaction energy of 306.3 kJ/mol, which decomposes to produce a –C (O) compound. Secondly, another NO₂ molecule climbs over an energy barrier of 8.8 kJ/mol, and changes into a –C (ONO₂) intermediate on –C (O). Finally, the N or O atom of NO₂ attacks –C (O) for a second time to help open aromatic ring for releasing CO or CO₂. Further decomposition of –C (NO₂) and –C (ONO₂) requires activation energies of 81.6 kJ/mol, 75.7 kJ/mol, and 53.5 kJ/mol, respectively, on preferential pathways. Calculations prove that attacks of O atom from NO₂ on C∗ help open the aromatic ring more efficiently than N atom.

Waste date palm-derived biochar (DPBC) was modified with nano-zerovalent iron (BC-ZVI) and silica (BC-SiO₂) through mechanochemical treatments and evaluated for arsenate (As(V)) removal from water. The feedstock and synthesized adsorbents were characterized through proximate, ultimate, and chemical analyses for structural, surface, and mineralogical compositions. BC-ZVI demonstrated the highest surface area and contents of C, N, and H. A pH range of 2–6 was optimum for BC-ZVI (100% removal), 3–6 for DPBC (89% removal), and 4–6 for BC-SiO₂ (18% removal). Co-occurring PO₄³⁻ and SO₄²⁻ ions showed up to 100% reduction, while NO₃⁻ and Cl⁻ ions resulted in up to 26% reduction in As(V) removal. Fitness of the Langmuir, Freundlich and Redlich-Peterson isotherms to As(V) adsorption data suggested that both mono- and multi-layer adsorption processes occurred. BC-ZVI showed superior performance by demonstrating the highest Langmuir maximum adsorption capacity (26.52 mg g⁻¹), followed by DPBC, BC-SiO₂, and commercial activated carbon (AC) (7.33, 5.22, and 3.28 mg g⁻¹, respectively). Blockage of pores with silica particles in BC-SiO₂ resulted in lower As(V) removal than that of DPBC. Pseudo-second-order kinetic model fitted well with the As(V) adsorption data (R² = 0.99), while the Elovich, intraparticle diffusion, and power function models showed a moderate fitness (R² = 0.53–0.93). The dynamics of As(V) adsorption onto the tested adsorbents exhibited the highest adsorption rates for BC-ZVI. As(V) adsorption onto the tested adsorbents was confirmed through post-adsorption FTIR, SEM-EDS, and XRD analyses. Adsorption of As(V) onto DPBC, BC-SiO₂, and AC followed electrostatic interactions, surface complexation, and intraparticle diffusion, whereas, these mechanisms were further abetted by the higher surface area, nano-sized structure, and redox reactions of BC-ZVI.

Heavy metal accumulation in agricultural land causes crop production losses worldwide. Metal homeostasis within cells is tightly regulated. However, homeostasis breakdown leads to accumulation of reactive oxygen species (ROS). Overall plant fitness under stressful environment is determined by coordination between roots and shoots. But little is known about organ specific responses to heavy metals, whether it depends on the metal category (redox or non-redox reactive) and if these responses are associated with heavy metal accumulation in each organ or there are driven by other signals. Maize seedlings were subjected to sub-lethal concentrations of four metals (Zn, Ni, Cd and Cu) individually, and were quantified for growth, ABA level, and redox alterations in roots, mature leaves (L1,2) and young leaves (L3,4) at 14 and 21 days after sowing (DAS). The treatments caused significant increase in endogenous metal levels in all organs but to different degrees, where roots showed the highest levels. Biomass was significantly reduced under heavy metal stress. Although old leaves accumulated less heavy metal content than root, the reduction in their biomass (FW) was more pronounced. Metal exposure triggered ABA accumulation and stomatal closure mainly in older leaves, which consequently reduced photosynthesis. Heavy metals induced oxidative stress in the maize organs, but to different degrees. Tocopherols, polyphenols and flavonoids increased specifically in the shoot under Zn, Ni and Cu, while under Cd treatment they played a minor role. Under Cu and Cd stress, superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR) activities were induced in the roots, however ascorbate peroxidase (APX) activity was only increased in the older leaves. Overall, it can be concluded that root and shoot organs specific responses to heavy metal toxicity are not only associated with heavy metal accumulation and they are specialized at the level of antioxidants to cope with.

Environmental exposure to 2,3,7,8-tetrachlorodibenzofuran (TCDF), one of typical persistent organic pollutants (POPs) produced from municipal waste combustion, exerts toxic effects on human healthy. In the current study, we mainly used targeted metabolomics combined with untargeted ¹H NMR-based metabolomics to investigate the effects of TCDF exposure on lipid homeostasis in mice. We found that TCDF exposure induced hepatic lipogenesis, the early-stage of non-alcoholic fatty liver disease, manifested by excessive lipids including triglycerides, fatty acids and lipotoxic ceramides accumulated in the liver together with elevated serum very low-density lipoprotein by activating the aryl hydrocarbon receptor (AHR) and its target genes such as Cyp1a1 and Cd36. We also found that TCDF exposure induced alteration of phospholipids and choline metabolites and endoplasmic reticulum (ER) markers in the liver of mice, indicating that disruption of host cell membrane structural integrity and ER stress leading to hepatic steatosis. In addition, complementary information was also obtained from histopathologic assessments and biological assays, strongly supporting toxic effects of TCDF. These results provide new evidence of TCDF toxicity associated with fatty liver disease and further our understanding of health effects of environmental pollutants exposure.

A novel denitrifying bacterium YSF15 was isolated from the Lijiahe Reservoir in Xi’an and identified as Comamonas sp. It exhibited excellent nitrogen removal ability under low C/N conditions (C/N = 2.5) and 94.01% of nitrate was removed in 18 h, with no accumulation of nitrite. PCR amplification and nitrogen balance experiments were carried out, showing that 68.92% of initial nitrogen was removed as gas products and the nitrogen removal path was determined to be NO3−-N→NO2−-N→NO→N2O→N2. Scanning electron microscopy and three-dimensional fluorescence spectroscopy were used to track extracellular polymeric substances (EPS). The results show that complete-denitrification under low C/N conditions is associated with EPS, which may provide a reserve carbon source in extreme environments. These findings reveal that Comamonas sp. YSF15 can provide novel basic materials and a theoretical basis for wastewater bioremediation under low C/N conditions.

Exhaust emissions from diesel vehicles are significant sources of air pollution. In this study, particle number emissions and size distributions of a modern Euro 5b -compliant diesel passenger car exhaust were measured under the NEDC and US06 standard cycles as well as during different transient driving cycles. The measurements were conducted on a chassis dynamometer; in addition, the transient cycles were repeated on-road by a chase method. Since the diesel particulate filter (DPF) removed practically all particles from the engine exhaust, it was by-passed during most of the measurements in order to determine effects of lubricant on the engine-out exhaust aerosol. Driving conditions and lubricant properties strongly affected exhaust emissions, especially the number emissions and volatility properties of particles. During acceleration and steady speeds particle emissions consisted of non-volatile soot particles mainly larger than ∼50 nm independently of the lubricant used. Instead, during engine motoring particle number size distribution was bimodal with the modes peaking at 10–20 nm and 100 nm. Thermal treatment indicated that the larger mode consisted of non-volatile particles, whereas the nanoparticles had a non-volatile core with volatile material condensed on the surfaces; approximately, 59–64% of the emitted nanoparticles evaporated. Since during engine braking the engine was not fueled, the origin of these particles is lubricant oil. The particle number emission factors over the different cycles varied from 1.0 × 10¹⁴ to 1.3 × 10¹⁵ #/km, and engine motoring related particle emissions contributed 12–65% of the total particle emissions. The results from the laboratory and on-road transient tests agreed well. According to authors’ knowledge, high particle formation during engine braking under real-world driving conditions has not been reported from diesel passenger cars.

Biofumigation is an effective, non-chemical method to control soil-borne pests and diseases and to maximize crop yield. We studied the responses of soil bacterial and fungal communities, the soil’s nutritional state and strawberry yield, when the soil was biofumigated each year for five consecutive years using fresh chicken manure (BioFum). BioFum significantly increased the soil’s NH4+-N, NO3−-N, available P and K and organic matter. Fusarium spp. and Phytophthora spp. which are known to cause plant disease, were significantly decreased after BioFum. In addition, Biofum increased the soil’s temperature, enhanced chlorophyll levels in the leaves of strawberry plants, and the soluble sugar and ascorbic acid content in strawberry fruit. We used high-throughput gene sequencing to monitor changes in the soil’s bacterial and fungal communities. Although BioFum significantly decreased the diversity of these communities, it increased the relative abundance of some biological control agents in the phylum Actinobacteria and the genera Pseudomonas, Bacillus and Chaetomium. An increase in these biological control agents would reduce the incidence of soil-borne pathogens and plant disease. Although strawberry marketable yield using BioFum was higher in the first three years, the decline in the final two years could be due to the accumulation of P and K which may have delayed flowering and fruiting. Methods to overcome yield losses using BioFum need to be developed in the future. Our research, however, showed that BioFum enhanced soil fertility, reduced the presence of soil pathogens, increased the relative abundance of beneficial bacteria and fungi and improved strawberry quality. Unlike chemical soil treatments that can cause pest and disease resistance when used continuously over many years, our multi-year research program on BioFum showed that this treatment provided significant benefits to the soil, plant and strawberry fruit.

China and the UK use different risk-based approaches to derive soil screening or guideline values (SSVs; SGVs) for contaminants. Here we compare the approaches and the derived values for 6 illustrative contaminants. China’s SSVs are derived using an approach developed in the US as follows: for carcinogens, acceptable level of risk (ACR) is set at 10−6 and the SSVs calculated as 10−6 divided by the soil exposure and toxicity data; for non-carcinogens, the hazard quotient is 1 and the SSV is calculated as 1 divided by the soil exposure and toxicity data. The UK’s SGVs are calculated by the CLEA model, for which the Average Daily Exposure (ADE) from soil sources by a specific exposure route equals the health criteria values (HCVs) for that route, whether for carcinogens or a non-carcinogens. The UK’s CLEA model is also used here to derive SSVs with Chinese input parameters. China’s SSVs, the UK’s SGVs and values for Chinese conditions derived using the UK approach were as follows (mg/kg): As, <1, 35, 20; Cd, 20, 18, 11; Cr (VI), <1, 14, 29; benzene, 1, 1, 2; toluene, 1200, 3005, 3800; ethyl-benzene, 7, 930, 1200. By comparing the differences in toxicity assessment and risk characterization, exposure assessment and parameter types in the methodologies to obtain SSVs in China and the UK, and by combining the CLEA model with Chinese parameterisation, these comparisons highlight that the difference in toxicity assessment and risk characterization methods of carcinogens results in the biggest difference in SSVs between the 2 countries. However, for non-carcinogenic substances, the difference of SSVs calculation method and SSVs is small. The difference in SSVs for carcinogenic substances is also related to the route of exposure. For volatile organic compounds, the presence of indoor respiratory exposure pathways greatly reduces the differences caused by toxicity assessment and risk characterization methods. For non-volatile substances such as heavy metals, the effects of toxicity assessment and risk characterization methods are significant. The SSV of As obtained by the CLEA model with Chinese parameters is closer to the background value of soil in China. In the management of non-volatile contaminated sites such as heavy metals in China, the CLEA model can be used for risk assessment and calculation of site specific SSVs. In the future, China can use the UK method to strengthen its toxicity assessment and risk characterization methods for carcinogenic substances, to reduce the uncertainty in the risk assessment of contaminated sites and improve the scientific management of contaminated sites.

Dibutyl phthalate (DBP), an important plastic contaminant in the environment, is known to cause organ toxicity. Although current research has shown that DBP-induced organ toxicity is associated with oxidative stress, the toxic effect of DBP on the lungs have not been fully elucidated. Therefore, we investigated the potential mechanism by which DBP induces pulmonary toxicity using a model of DBP-induced allergic airway inflammation in rats. The results showed that chronic exposure to DBP induced histopathological damage, inflammation, oxidative stress, apoptosis, and increased the protein levels of thymic stromal lymphopoietin (TSLP) and its downstream protein Janus kinase 1 (JAK1) and signal transducer and activator of transcription 6 (STAT6). Moreover, DBP exposure inhibited nuclear factor-erythroid-2-related factor 2 (Nrf2) and levels of its target genes NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Additionally, using in vitro experiments, we found that DBP induced oxidative stress, reduced cell viability, and inhibited the Nrf2/HO-1/NQO1 pathway in mouse alveolar type II epithelial cell line. Overall, these data demonstrate that DBP induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway.