Atrazine contamination is of great concern due to its widespread occurrence in shallow lakes. Here, the distribution and degradation of atrazine in acidic and alkaline lake systems were investigated. Meanwhile, the bacterial communities in different sediments and the effects of environmental factors on atrazine-degrading bacteria were evaluated. In the lake systems without plants, atrazine levels in sediment interstitial water reached peak concentrations on the 4th d. More than 90% of atrazine was then degraded in all sediment interstitial water by day 30. Meanwhile, the degradation rate of atrazine in alkaline sediments was faster than that in acidic sediments. Values of hydroxylated metabolites in the acidic lake sediments tended to be greater. Moreover, the amounts of Proteobacteria, Actinobacteria, Firmicute, Nitrospinae, Aminicenantes, Ignavibacteriae and Saccharibacteria in acidic Tangxunhu Lake sediments were significantly different from alkaline Honghu Lake sediments, while the amounts of Cyanobacteria and Saccharibacteria in sediments treated with atrazine were significantly greater than those in sediments without atrazine (P < 0.05). Notably, pH was the most relevant environmental factor in the quantitative variation of atrazine-degrading bacteria, including in Clostridium-sensu-stricto, Pseudomonas, Comamonas and Rhodobacter. The Mantel test results indicated that the degradation of atrazine in different sediments was mainly affected by the sediment physicochemical properties rather than by the addition of atrazine and the cultivation of hydrophytes.

In recent years, the Chinese government has made great efforts to jointly control and prevent air pollution, especially fine particulate matter (PM₂.₅). However, these efforts are challenged by technical constraints due to the significant temporal and spatial heterogeneity of PM₂.₅ across China. In this study, the Affinity Zone Identification Approach (AZIA), which combines rotated principal component analysis (RPCA) with revised clustering analysis, was developed and employed to regionalize PM₂.₅ pollution in China based on data from 1496 air quality monitoring sites recorded from 2013 to 2017. Two clustering methods, cluster analysis with statistical test (CAST) and K-center-point (K-medoids) clustering, were compared and revised to eliminate unspecified sites. Site zonation was finally extended to the municipality scale for the convenience of the controlling measures. The results revealed that 17 affinity zones with 5 different labels from clean to heavily polluted areas could be identified in China. The heavily polluted areas were mainly located in central and eastern China as well as Xinjiang Province, with regional average annual PM₂.₅ concentrations higher than 66 μg/m³. The new approach provided more comprehensive and detailed affinity zones than obtained in a previous study (Wang et al., 2015b). The North China Plain and Northeastern China were both further divided into northern and southern parts based on different pollution levels. In addition, five affinity zones were first recognized in western China. The findings provide not only a theoretical basis to further display the temporal and spatial variations in PM₂.₅ but also an effective solution for the cooperative control of air pollution in China.

Mitigation of air pollution by plants is a well-established phenomenon. Trees planted on the roadside are known to reduce particulate matter pollution by about 25%. In an urban ecosystem, especially in a metropolitan city such as Delhi, roadside trees are constantly exposed to air pollution. We, therefore, evaluated the effect of air pollution on a common Indian roadside tree, Neem (Azadirachta indica), and its associated microbes in areas with high and low levels of particulate matter (PM) pollution in Delhi. We hypothesized that alteration in the air quality index not only influences plant physiology but also its microbiome.A 100-fold increase in the number of epiphytic and 10–100 fold increase in endophytic colonies were found with 1.7 times increase in the level of pollutants. Trees in the polluted areas had an abundance of Salmonella, Proteus and Citrobacter, and showed increased secondary metabolites such as phenols and tannins as well as decreased chlorophyll and carotenoid. The number of unique microbes was positively correlated with increased primary metabolites.Our study thus indicates that, alteration in air quality affects the natural micro-environment of plants. These results may be utilized as sustainable tools for studying plant adaptations to the urban ecosystem.

The association between temperature and mortality has been widely reported. However, it remains largely unclear whether inflammation-related diseases, caused by excessive or inappropriate inflammatory reaction, may be affected by ambient temperature, particularly in low-income areas.To explore the association between ambient temperature and clinical visits for inflammation-related diseases in rural villages in the Ningxia Hui Autonomous Region, China, during 2012─2015.Daily data on inflammation-related diseases and weather conditions were collected from 258 villages in Haiyuan (161 villages) and Yanchi (97 villages) counties during 2012─2015. A Quasi-Poisson regression with distributed lag non-linear model was used to examine the association between temperature and clinical visits for inflammation-related diseases. Stratified analyses were performed by types of diseases including arthritis, gastroenteritis, and gynecological inflammations.During the study period, there were 724,788 and 288,965 clinical visits for inflammation-related diseases in Haiyuan and Yanchi, respectively. Both exposure to low (RR: 2.045, 95% CI: 1.690, 2.474) and high temperatures (RR: 1.244, 95% CI: 1.107, 1.399) were associated with increased risk of total inflammation-related visits in Haiyuan county. Low temperatures were associated with increased risks of all types of inflammation-related diseases in Yanchi county (RR: 4.344, 95% CI: 2.887, 6.535), while high temperatures only affected gastroenteritis (RR: 1.274, 95% CI: 1.040, 1.561). Moderate temperatures explained approximately 26% and 33% of clinical visits due to inflammation-related diseases in Haiyuan and Yanchi, respectively, with the burden attributable to cold exposure higher than hot exposure. The reference temperature values ranged from 17 to 19 in Haiyuan, and 12 to 14 in Yanchi for all types of clinical visits.Our findings add additional evidence for the adverse effect of suboptimal ambient temperature and provide useful information for public health programs targeting people living in rural villages.

Adding exogenous low-molecular weight organic acids is an effective technique to improve phytoremediation of Cd-contaminated soil and has been well documented, but how acid application rate affects remediation efficiency and its underlying limiting factors remains elusive. We investigated this using pot experiments with rapeseed (Brassica napus L.) as the model plant. Plastic pots packed with a sandy loam contaminated by Cd at 4.838 mg/kg were amended with acetic acid, oxalic acid, citric acid, malic acid and tartaric acid, respectively, at an application rate gradient varying from 0.0 to 12.0 mmol/kg. Plants in each pot were harvested after growing for five months, and we then measured the exchangeable, carbonate, Fe–Mn oxide, organic and residual Cd in the rhizosphere, as well as Cd in both roots and shoots. The results showed that all organic acids improved plant uptake of Cd and, compared with the control without acid addition, they could improve Cd uptake by more than 100%. The enhanced Cd extraction was due to the increase in exchangeable Cd in the rhizosphere. Plant Cd was weakly correlated to the amount of Cd lost from a unit volume of the rhizosphere due to root extraction (R² = 0.06), but a good negative correlation was found between them after normalizing the lost Cd by root biomass (R² = 0.36). Mass balance analysis revealed that the average Cd content in soil (rhizosphere and bulk soils combined) was much higher than the Cd content in the rhizosphere, and the improved Cd mobility after acid addition was thus due to the increased chelation. As diffusion of ligands in water is one order in magnitude smaller than diffusion of Cd ions, our results suggested that Cd migration from the bulk soil into the rhizosphere was a major factor limiting Cd phytoextraction by rapeseed after adding the exogenous organic acids.

Phytoextraction using Celosia argentea Linn. can potentially decontaminate Cd-contaminated soils. However, most earlier studies have been conducted at laboratory scale and for a relatively short remediation period. To evaluate the phytoextraction efficiency of C. argentea combined with different soil amendments (ammonium chloride, Bacillus megaterium, and citric acid), an 18-month field experiment was carried out in a farmland soil contaminated with 3.68 mg kg⁻¹ Cd by mine tailings in southern China. Soil Cd concentrations were decreased by 6.34 ± 0.73% after the three harvestings (with no amendments), which was 2.27 times that of the no-planting control (p < 0.05). Application of ammonium chloride, B. megaterium, and citric acid increased the overall Cd reduction rate in soil by 40.5%, 46.1%, and 105%, respectively. The application of citric acid decreased total Cd in soil by up to 16.9% in the rhizosphere soil and 13.0% in the bulk soil. The highest annual shoot biomass yield and Cd extraction amount reached 8.79 t ha⁻¹ and 273 g ha⁻¹. Acid-soluble Cd fraction in the rhizosphere was significantly lower compared to that in the bulk soil (p < 0.05), which indicates that mobile Cd in the rhizosphere was taken up by the roots vastly. C. argentea phytoextraction also improved soil metabolic functions by increasing the activities of soil enzymes (urease, invertase, phosphatase, and catalase). These findings demonstrate that Cd phytoextraction using C. argentea with the application of soil amendments can greatly improve the quality of Cd-contaminated soils.

Potassium (K) fertilizer plays an important role in increasing crop yield, quality, and nitrogen use efficiency. However, little is known about its environmental impacts, such as its effects on emissions of the greenhouse gas nitrous oxide (N₂O). A nitrogen-15 (¹⁵N) tracer laboratory experiment was therefore performed in an acidic agricultural soil in the suburbs of Wuhan, central China, to determine the effects of K fertilizer on N₂O emissions and nitrification/denitrification product ratios under N fertilization. During 15-d incubation periods with a fixed initial N concentration (80 mg kg⁻¹), K application increased average N₂O emission rates significantly (1.6–10.8-fold) compared to the control treatment. N₂O emissions derived from nitrification and denitrification both increased in K-treated soil, and denitrification contributed more to the increase; its contribution ratio rose from 32% without K fertilizer to 53% with 300 mg kg⁻¹ of K applied. The increase in N₂O emissions under K fertilization is probably due to an increase in the activity of denitrifying microorganisms and acid-resistant nitrifying microorganisms caused by higher K⁺ concentrations and lower soil pH. Combined treatment with potassium chloride (KCl) and N fertilizer produced lower N₂O emissions than combined treatment with potassium sulfate (K₂SO₄) and N fertilizer during 15-d incubation periods. Our results imply that there are significant interaction effects between N fertilizers and K fertilizers on N₂O emissions. In particular, combining N fertilizers with fertilizers that reduce soil acidity or contain Cl or K ions may significantly affect agricultural N₂O emissions.

Via the thermal sintering, a nanocrystalline IrO₂ coating was formed on the Ti substrate to successfully prepare a Ti/IrO₂ electrode. Based on the electrochemical analysis, the prepared Ti/IrO₂ electrode was found to have powerful oxidation effect on the organics in the TNT red water, where the nitro compound was oxidized through an irreversible electrochemical process at 0.6 V vs. SCE. According to the analysis of the nitro compound content, the UV–vis spectra, and the FTIR spectra of 2,4,6-trinitrotoluene (TNT) red water with electrolytic periods, the degradation mechanism of the dinitrotoluene sulfonate (DNTS) was developed. And the intermediates were characterized by UPLC-HRMS. The DNTS mainly occurred one electron transfer reaction on the Ti/IrO₂ electrode. At the early stage of the electrolysis, the polymerization of DNTS was mainly dominated. The generated polymer did not form a polymer film on the electrode surface, but instead it promoted a further reduction. After electrolyzing for 30 h, all NO₂ function group in the TNT red water was degraded completely.

Particulate matter (PM) pollution is an urgent urban environmental problem. However, plants can mitigate this pollution by filtering the air. Combining the PM capture capacity with the air pollution tolerance could be better evaluate the suitability of greenbelt plants. We selected nine dominant roadside plants growing at two sites in Beijing, and compared their PM capture capacity, morphological characteristics, biochemical characteristics, and air pollution tolerance index (APTI). Sophora japonica had the highest PM capture capacity (362.98 μg cm⁻²), and its wax layers could trap large amounts of PM₂.₅; this high efficiency is important for successful phytoremediation. Sophora japonica. Sabina chinensis, Ulmus pumila, and Euonymus japonicus also showed relatively high PM capture capacity. This is due to their complex cuticular wax layers, short petioles, rough surfaces, high stomata density, and dense canopy structures which reduce the possibility of resuspension of captured PM. Amount of PM captured per unit leaf area had a significant positive effect on the degree of membrane lipid peroxidation, indicating that species with high PM capture capacity suffered higher oxidative stresses. Air pollution showed the strongest negative effect size on chlorophyll contents of E. japonicas. While, S. japonica, S. chinensis, and U. pumila could prevent chlorophyll content decline under severe oxidative stress. Sophora japonica also had the highest APTI at both sites, indicating this species had the greatest tolerance to air pollution. Our findings suggest that S. japonica would be the most suitable species for greenbelt construction in Beijing, followed by S. chinensis, E. japonicus, and U. pumila.

Our understanding of colloidal biochar (CB) transport and release is largely unknown in environments with transient chemical conditions, e.g., ionic strength (IS), pH, and especially humic acid (HA). In this study, column experiments were conducted to investigate CB transport and retention in the presence and absence of HA, and CB release under transient IS and pH conditions in saturated sand. Step reductions in solution IS from 25 to 0.01 mM produced significant release peaks of CB due to a reduction in the depth of the primary minima on rough surfaces with small energy barriers. In contrast, step increases of solution pH from 4 to 10 only slightly increased CB release presumably due to the strong buffering capacity of CB. The CB retention was diminished by HA during the deposition phase. However, the release of CB with transients in IS and pH was not influenced much when deposition occurred in the presence of HA. These observations indicate that HA increased the energy barrier during deposition but did not have a large influence on the depth of the interacting minimum during transient release. Potential explanations for these effects of HA on CB retention and transient release include enhanced repulsive electrostatic interactions and/or altering of surface roughness properties. Our findings indicated that the release of retained CB is sensitive to transient IS conditions, but less dependent on pH increases and CB deposition in the presence of HA. This information is needed to quantify potential benefits and/or adverse risks of mobile CB in natural environments.