This paper presents the results of the study on columnar aerosol optical and physical properties and radiative effects directly observed over Dushanbe, the capital city of Tajikistan, a NASA AERONET site (equipped with a CIMEL sunphotometer) in Central Asia. The average aerosol optical depth (AOD) and Ångström exponent (AE) during the observation period from July 2010 to April 2018 were found to be 0.28 ± 0.20 and 0.82 ± 0.40, respectively. The highest seasonal AOD (0.32 ± 0.24), accompanied by the lowest average AE (0.61 ± 0.25) and fine-mode fraction in AOD (0.39), was observed during summer due to the influence of coarse particles like dust from arid regions. Fine particles were found in significant amounts during winter. The ‘mixed aerosol’ was identified as the dominant aerosol type with presence of ‘dust aerosol’ during summer and autumn seasons. Aerosol properties like volume size distribution, single scattering albedo, asymmetry parameter and refractive index suggested the influence of coarse particles (during summer and autumn). Most of the air masses reaching this site transported local and regional emissions, including from beyond Central Asia, explaining the presence of various aerosol types in Dushanbe’s atmosphere. The seasonal aerosol radiative forcing efficiency (ARFE) in the atmosphere was found high (>100 Wm⁻²) and consistent throughout the year. Consequently, this resulted in similar seasonally coherent high atmospheric solar heating rate (HR) of 1.5 K day⁻¹ during summer-autumn-winter, and ca. 0.9 K day⁻¹ during spring season. High ARFE and HR values indicate that atmospheric aerosols could exert significant implications to regional air quality, climate and cryosphere over the central Asian region and downwind Tianshan and Himalaya-Tibetan Plateau mountain regions with sensitive ecosystems.

Nonylphenol (NP) is a chemical raw material and intermediate which is mainly used in the production of surfactants, lubricating oil additives and pesticide emulsifiers. NP is reported to be toxic on the immune system, nervous system and reproductive system due to its binding to estrogen receptors. However, the toxicity of NP on mammalian oocyte quality remains unclear. In present study, we explored the effects of NP exposure on mouse oocyte maturation. Our results showed that 4 weeks of NP exposure increased the number of atresia follicles and decreased oocyte developmental competence. Transcriptomic analysis indicated that NP exposure altered the expression of more than 800 genes in oocytes, including multiple biological pathways. Subcellular structure examination indicated that NP exposure disrupted meiotic spindle organization and caused chromosome misalignment. Moreover, aberrant mitochondrial distribution and decreased membrane potential were also observed, indicating that NP exposure caused mitochondria dysfunction. Further analysis showed that NP exposure resulted in the accumulation of reactive oxygen species (ROS), which causes oxidative stress; and the NP-exposed oocytes showed positive Annexin-V signal, indicating the occurrence of early apoptosis. In summary, our results indicated that NP exposure reduced oocyte quality by affecting cytoskeletal dynamics and mitochondrial function, which further induced oxidative stress and apoptosis in mice.

In the context of global warming, an important issue is that many pesticides become more toxic, putting non-target organisms at higher risk of pesticide exposure. Eremias argus (a native Chinese lizard) was selected as animal model in this study. As a kind of poikilothermic vertebrate, E.argus is sensitive to temperature change. The experimental design [(with or without L-Glufosinate-ammonium (L-GLA) pollution × two temperatures (25 and 30 °C)] was used in this study for 90 days to identify the chronic effects of the pesticide–temperature interaction on the lizards’ neuroendocrine-regulated reproduction. Survival rate, body weight, clutch characteristics, testicular histopathology, the content of neurotransmitters and related enzyme activity, the level of sex steroid, the expression of Heat shock protein 70 (HSP70), antioxidant system, the accumulation and degradation of L-GLA were examined. Results showed that L-GLA disrupt reproduction of lizards through hypothalamus-pituitary-gonad (HPG) axis. In addition, temperature can not only change the environmental behavior of pesticides, but also alter the physiological characteristics of lizards. Thus, our results emphasized that temperature is an essential abiotic factor that should not be overlooked in ecotoxicological studies.

Freshwater lakes, especially eutrophic ones, have become a hotspot of methanogenesis. However, the effects of eutrophication and seasonality on methanogenesis activity and methanogenic microbial community remain unclear. In the current study, for two adjacent lakes at different trophic status, their methanogenesis potential in different seasons was evaluated using incubation experiments. The density, diversity, and community structure of methanogens were analyzed based on the mcrA gene. Correlation analysis and redundancy analysis were carried out to identify the environmental factors driving the variations of methanogenesis potential and methanogen community. The results showed that eutrophication could result in active methanogenesis with relatively high seasonal variance. The methanogenesis variation could be well explained by carbon input in association with algal growth, as well as the change of methanogen population density. With the dominance of Methanomicrobiales in both lakes, the hydrogenotrophic pathway had a major contribution to total methane production. The considerable proportion of Methanomassiliicocales in eutrophic lake implied that methylotrophic methanogenesis might be previously underestimated. These results added new insights towards methanogenesis process in eutrophic freshwater lakes.

Cerium oxide (CeO2) nanoparticles are used as in-fuel catalysts and in manufacturing processes, creating a potential for release to aquatic environments. Exposures at 1 and 10 μg/L CeO2-nanoparticles were made to assess effects during the development of river biofilm communities. Scanning transmission x-ray microscopy (STXM) indicated extensive sorption of nanoparticles to the community and co-localization with lipid moieties. Following 8 weeks of development, polycarbonate coupons were removed from the reactors and used for molecular analyses, denaturing gradient gel electrophoresis analysis (DGGE-16S rRNA) and 16S rRNA amplicon sequencing. Microscopic imaging of the biofilm communities (bacterial, photosynthetic biomass, exopolymer composition, thickness, protozoan numbers), as well as carbon substrate utilization fingerprinting was performed. There was a trend toward reduced photosynthetic biomass, but no significant effects of CeO2 exposure were found on photosynthetic and bacterial biomass or biofilm thickness. Sole carbon source utilization analyses indicated increased utilization of 10 carbon sources in the carbohydrate, carboxylic acid and amino acids categories related to CeO2 exposures; however, predominantly, no significant effects (p < 0.05) were detected. Measures of microbial diversity, lectin binding affinities of exopolymeric substances and results of DGGE analyses, indicated significant changes to community composition (p < 0.05) with CeO2 exposure. Increased binding of the lectin Canavalia ensiformis was observed, consistent with changes in bacterial-associated polymers. Whereas, no significant changes were observed in binding to residues associated with algal and cyanobacterial exopolymers. 16S rRNA amplicon sequencing of community DNA indicated changes in diversity and shifts in community composition; however, these did not trend with increasing CeO2 exposure. Counting of protozoans in the biofilm communities indicated no significant effects on this trophic level. Thus, based on biomass and functional measures, CeO2 nanoparticles did not appear to have significant effects; however, there was evidence of selection pressure resulting in significant changes in microbial community composition.

The microparticle content of 37 common facial and body scrubs commercially available in the United Arab Emirates was analyzed. The chemical composition, ash content, physical characteristics, loading, particle size and shape of the microparticles were determined. Only 11 out of 37 products were found to have microplastic content. Many of the remaining products exhibited microparticles composed of microcrystalline cellulose and crushed walnut shells. Differential scanning calorimetry showed that microplastic products had softening points as low as 84 °C. Plastic microbeads of 2 products were found to fuse at 100 °C. The fusion altered the flotation characteristics of the microbeads of one product. Heat treatment of the product at 100 °C in the presence of silica gel led to entrainment of the silica and partial fragmentation of the beads upon cooling. This may be understood as one mechanism of fragmentation of a microplastic with a low softening point in the presence of hard soil particles under temperature cycling.

Nitrogen (N) deposition in China may increase due to urbanization and economic growth. Current research has considered the ecological significance under the assumption of increasing N deposition. Atmospheric N deposition tending toward levelling or declining has been observed in China. Such potential recovery and responses of high N loads ecosystems under decreasing atmospheric N deposition scenarios have yet to be adequately investigated. This work reviews existing literature to consider possible responses of carbon (C) sequestration, biodiversity and species composition, soil acidification, and greenhouse emissions in ecosystems responding to recent patterns of N deposition. Potential effects of N composition and internal ratios may be further explored through state-of-the-art N addition experiments and model development.

The concentration and isotopic composition of mercury (Hg) were studied in frozen soils along a southwest-northeast transect over the Himalaya-Tibet. Soil total Hg (HgT) concentrations were significantly higher in the southern slopes (72 ± 54 ng g−1, 2SD, n = 21) than those in the northern slopes (43 ± 26 ng g−1, 2SD, n = 10) of Himalaya-Tibet. No significant relationship was observed between HgT concentrations and soil organic carbon (SOC), indicating that the HgT variation was not governed by SOC. Soil from the southern slopes showed significantly negative mean δ202Hg (−0.53 ± 0.50‰, 2SD, n = 21) relative to those from the northern slopes (−0.12 ± 0.40‰, 2SD, n = 10). The δ202Hg values of the southern slopes are more similar to South Asian anthropogenic Hg emissions. A significant correlation between 1/HgT and δ202Hg was observed in all the soil samples, further suggesting a mixing of Hg from South Asian anthropogenic emissions and natural geochemical background. Large ranges of Δ199Hg (−0.45 and 0.24‰) were observed in frozen soils. Most of soil samples displayed negative Δ199Hg values, implying they mainly received Hg from gaseous Hg(0) deposition. A few samples had slightly positive odd-MIF, indicating precipitation-sourced Hg was more prevalent than gaseous Hg(0) in certain areas. The spatial distribution patterns of HgT concentrations and Hg isotopes indicated that Himalaya-Tibet, even its northern part, may have been influenced by transboundary atmospheric Hg pollution from South Asia.

Microbial assemblages such as biofilms around aquatic plants play a major role in arsenic (As) cycling, which has often been overlooked in previous studies. In this study, arsenite (As(III))-oxidizing, arsenate (As(V))-reducing and As(III)-methylating bacteria were found to coexist in the phyllosphere of Hydrilla verticillata, and their relative activities were shown to determine As speciation, accumulation and efflux. When exposed to As(III), As(III) oxidation was not observed in treatment H(III)-B, whereas treatment H(III)+B showed a significant As(III) oxidation ability, thereby indicating that epiphytic bacteria displayed a substantial As(III) oxidation ability. When exposed to As(V), the medium only contained 5.89% As(III) after 48 h of treatment H(V)-B, while an As(III) content of 86.72% was observed after treatment H(V)+B, thereby indicating that the elevated As(III) in the medium probably originated from As(V) reduction by epiphytic bacteria. Our data also indicated that oxidizing bacteria decreased the As accumulation (by approximately 64.44% compared with that of treatment H(III)-B) in plants, while reducing bacteria played a critical role in increasing As accumulation (by approximately 3.31-fold compared with that of treatment H(V)-B) in plants. Regardless of whether As(III) or As(V) was supplied, As(III) was dominant in the plant tissue (over 75%). Furthermore, the presence of epiphytic bacteria enhanced As efflux by approximately 9-fold. Metagenomic analysis revealed highly diverse As metabolism genes in epiphytic bacterial community, particularly those related to energetic metabolism (aioAB), and As resistance (arsABCR, acr3, arsM). Phylogenetic analysis of As metabolism genes revealed evidence of both vertical inheritance and horizontal gene transfer, which might have contributed to the evolution of the As metabolism genes. Taken together, our research suggested that the diversity of As metabolism genes in epiphytic bacterial community is associated with aquatic submerged macrophytes which may play an important role in As biogeochemistry in aquatic environments.

Micronutrient deficiencies are prevalent health problems worldwide. The maintenance of adequate concentrations of micronutrients in maize grain is crucial for human health. We investigated the overall status and geospatial variation of micronutrients in Chinese maize grains and identified their key drivers. A field survey was conducted in four major maize production areas of China in 2017 with 980 pairs of soil and grain samples collected from famers’ fields. At a national scale, grain zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) concentrations varied substantially, with average values of 17.4, 17.3, 4.9, and 1.5 mg kg⁻¹, respectively, suggesting a solid gap between grain Zn and Fe concentrations and the biofortification target values. Significant regional difference in the concentrations of Zn, Mn and Cu, but not Fe, were observed in grain, with much higher levels in Southwest China. The nutritional yields of Zn, Fe and Cu were lower than the energy and Mn yields, indicating an unbalanced output between energy and micronutrients in current maize production system. Grain Zn, Fe, Mn and Cu correlated negatively with maize yield in most test regions. Increased nitrogen (N) rate positively affected grain Zn and Cu, while increased phosphorus (P) rate negatively affects grain Zn and Fe. Apart from Fe, available Zn, Mn and Cu in soil exerted significant positive effects on grain Zn, Mn and Cu concentrations, respectively. Decrease in soil pH and increase in the organic matter content may increase the accumulation of Fe and Mn in grain. Grain Zn and Cu concentrations increased as available soil P decreased. Of the factors considered in this study, grain yield, N and P rates, soil pH and organic matter were the main factors that affect grain micronutrient status and should be more extensively considered in the production and nutritional quality of maize grain.