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.

Soils have the ability to modify contaminant bioavailability and toxicity. Prediction the modifying effect of soil on arsenic phytoaccumulation and phytoavailability using either soil property data or soil chemical extraction data in risk assessment of contaminated soil is highly desirable. In this study, plant bioassays important to ecological receptors, were conducted with 20 soils with a wide range in chemical and physical soil properties to determine the relationships between As measured by soil chemical extraction (soil pore water, Bray-1, sodium phosphate solution, hydroxylamine hydrochloride, and acid ammonium oxalate) or soil physico/chemical properties on arsenic phytotoxicity and phytoaccumulation. Soil pore water As and Bray-1 extracted As were significantly (P < 0.01) correlated with lettuce tissue As and those extractants and sodium phosphate were correlated with ryegrass tissue As. Hydroxylamine and acid ammonium oxalate extractions did not correlate with plant bioassay endpoints. Simple regression results showed that lettuce tissue relative dry matter growth (RDMG) was inversely related to tissue As concentration (r² = 0.85, P < 0.01), with no significant relationship for ryegrass. Soil clay exhibited strong adsorption for As and significantly reduce tissue As for lettuce and ryegrass. In addition to clay content, reactive aluminum oxide (AlOx), reactive Fe oxide (FeOx) and eCEC was inversely related to ryegrass tissue As. Multiple regression equation was strongly predictive (r² = 0.83) for ryegrass tissue As (log transformed) using soil AlOx, organic matter, pH, and eCEC as variables. Soil properties can greatly reduce contaminant phytoavailability, plant exposure and risk, which should be considered when assessing contaminant exposure and site-specific risk in As-contaminated soils.

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.

The determination of the spatiotemporal patterns and driving factors of PM₂.₅ is of great interest to the atmospheric and climate science community, who aim to understand and better control the atmospheric linkage indicators. However, most previous studies have been conducted on pollution-sensitive cities, and there is a lack of large-scale and long-term systematic analyses. In this study, we investigated the spatiotemporal evolution of PM₂.₅ and its influencing factors by using an exploratory spatiotemporal data analysis (ESTDA) technique and spatial econometric model based on remote sensing imagery inversion data of the Yangtze River Economic Belt (YREB), China, between 2000 and 2016. The results showed that 1) the annual value of PM₂.₅ was in the range of 23.49–37.67 μg/m³ with an inverted U-shaped change trend, and the PM₂.₅ distribution presented distinct spatial heterogeneity; 2) there was a strong local spatial dependence and dynamic PM₂.₅ growth process, and the spatial agglomeration of PM₂.₅ exhibited higher path-dependence and spatial locking characteristics; and 3) the endogenous interaction effect of PM₂.₅ was significant, where each 1% increase in the neighbouring PM₂.₅ levels caused the local PM₂.₅ to increase by at least 0.4%. Natural and anthropogenic factors directly and indirectly influenced the PM₂.₅ levels. Our results provide spatial decision references for coordinated trans-regional air pollution governance as well as support for further studies which can inform sustainable development strategies in the YREB.

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 series of phosphorus containing ZnO (P–ZnO) photocatalysts with various percentages of phosphorus were successfully synthesized using the hydrothermal method. The structural, physical and optical properties of the obtained microparticles were investigated using diverse techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible diffusion reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and N₂ adsorption-desorption analysis. The photocatalytic activities of the pure and P–ZnO samples were evaluated for the degradation of Rhodamine B (RhB) under visible light irradiation. The parameters such as pH, catalyst dosage, contaminant concentration and effect of persulfate as an oxidant were studied. It was found that the P–ZnO1.8% photocatalyst could destroy 99% of RhB (5 ppm) in 180 min at pH = 7; furthermore, it degraded ∼100% of 5 and 10 ppm of the RhB pollutant in 120 and 180 min, respectively, only by adding 0.01 g of persulfate into the reaction solution. To determine the photocatalytic mechanism, 2-propanol, benzoquinone and EDTA were used and it was indicated that hydroxyl radicals, superoxide ions and holes, all had major roles in the photocatalytic degradation but the hydroxyl radical effect was the most significant. The phenol degradation was also investigated using the P–ZnO1.8% optimum photocatalyst which could destroy 53% of the phenol (5 ppm) in 180 min. According to the reusability test, it was proved that after 5 cycles, the catalyst activity was not highly changed and it was potentially capable of pollutant degradation.

Microplastics (MPs) are an emerging threat to ecosystem functioning and biota. The major sources of MPs are terrestrial and agricultural lands. But their fate, concentration in the terrestrial environment, and effects on soil and biota are poorly understood. There is a growing body of concern about the adverse effects of MPs on soil-dwelling organisms such as microbes in mycorrhizae and earthworms that mediate essential ecosystem services. Environmental concentrations and effects of MPs are considered to increase with increasing trend of its global production. MPs in the soil could directly impact plants through blocking the seed pore, limiting the uptake of water and nutrient through roots, aggregation, and accumulation in the root, shoot, and leaves. However, MPs can also indirectly impact plants by affecting soil physicochemical characteristics, soil-dwelling microbes, and fauna. An affected soil could impact plant community structure and perhaps primary production. In this article, we have assessed the potential direct and indirect impacts of MPs on plants. We have discussed both the positive and negative impacts of MPs on plants in terrestrial systems based on currently available limited literature on this topic and our hypothetical understandings. We have summarized the most current progress in this regard highlighting the future directions on microplastic research in terrestrial systems.

Current study deals with the surface modification of acid activated carbon (prepared from Pongamia pinnata shells) with Cetyltrimethylammonium bromide (CTAB) and its role as an adsorbent in eliminating anionic azo dyes viz. Congo red (CR) and Direct blue 6 (DB) from single and binary adsorptive systems. Binary adsorptive system involved the synergistic and antagonistic influence of one dye over the adsorption of other dye. Physico-chemical alterations due to surfactant modification and post adsorption were studied using atomic force microscopy (AFM), Zeta Potential, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), surface area analysis and Fourier-transformed infrared spectroscopy (FTIR). Process parameters influencing efficient adsorption of CR and DB species viz. initial pH of dye solution, adsorbent dosage, incubation temperature and initial concentration of dye species were optimised. Sorbate-sorbent interaction studies for single adsorptive system revealed sorbate’s monolayer formation over adsorbent’s surface and the involvement of chemisorption, as verified by Langmuir isotherm model and pseudo-second order model, respectively. Langmuir maximum adsorption capacity of the adsorbent was 555.56 mg/g for CR and 625.00 mg/g for DB. Meanwhile, for binary adsorptive system, competitive Langmuir model verified both CR and DB had antagonistic/competitive effect over each other’s adsorption. Thermodynamic analysis revealed the adsorptive process as exothermic, spontaneous and thermodynamically favourable with an elevated degree of dis-orderedness. Co-existing cations and anions has nominal effect on the adsorption capacity of dyes. Recyclability studies verified a modest efficiency of 62.52% for CR and 50.47% for DB species after the end of 4th adsorption-desorption cycle; thus affirming its recyclability potential. Phytotoxic assay affirmed the effectivity of the adsorbent in adsorbing dye species from aqueous solutions using Vigna mungo seeds as the model.

Sulfitobacter porphyrae ZFX1, isolated from surface seawater of the East China Sea during a Prorocentrum donghaiense bloom recession, exhibits high algicidal activity against P. donghaiense. To evaluate the algicidal effect of ZFX1, the algicidal mode and stability were investigated. The results showed that ZFX1 indirectly attacked algae by secreting algicidal compounds, and the algicidal activity of the ZFX1 supernatant was insensitive to different temperatures, light intensities and pH values (pH 3–12). To explore the algicidal mechanism of the ZFX1 supernatant, its effects on the morphological and ultrastructural alterations, photosynthetic capacity, reactive oxygen species (ROS) and antioxidative system of P. donghaiense were investigated. Scanning and transmission electron microscopy revealed that the ZFX1 supernatant destroyed the algal cell membrane structure and caused intracellular leakage. The decrease in the chlorophyll a content and the marked declines in both the photosynthetic efficiency (Fv/Fm) and the electron transport rate (rETR) indicated that the ZFX1 supernatant could damage the photosynthetic system of P. donghaiense. The excessive production of ROS in algal cells demonstrated the oxidative damage triggered by the ZFX1 supernatant. Although the antioxidant defense system of P. donghaiense was activated to scavenge excessive ROS, lipid oxidation occurred. The fatty acid composition profile indicated that the ZFX1 supernatant markedly increased the contents of two saturated fatty acids and a monounsaturated fatty acid and decreased the proportion of two polyunsaturated fatty acids, which resulted in lipids with a lower degree of unsaturation (DU). The decline in the DU decreased the lipid fluidity and rigidified the membrane system, and these effects destroyed the function of the membrane system and ultimately resulted in algal cell death. Therefore, ZFX1 probably plays a key role in mitigating P. donghaiense bloom by inducing lipid oxidation, decreasing the DU of lipids and ultimately destroying the membrane systems of algal cells.

Erhai Lake in the Yunnan-Guizhou Plateau, a typical subtropical deep lake, experienced long-time input of nutrients and pollutants, which provides beneficial conditions for evolution and spread of resistance genes. In this study, the profile of bacterial community, antibiotic and metal resistance genes in sediments of Erhai Lake were analyzed via high-thought sequencing of 16S rRNA and metagenomic DNA. Proteobacteria, Firmicutes, Nitrospirae, and Bacteroidetes were found to be the main composition of the bacterial community. Multidrug-, bacitracin-, macrolide-lincosamide-streptogramin (MLS)- and tetracycline resistance genes were the primary antibiotic resistance gene (ARG) types with high relative abundance, whereas Multi-metal-, and arsenic- resistance genes were the primary metal resistance gene (MRG) types. The effects of nitrogen and phosphorus on the abundance of ARGs and MRGs depended on the different types. Some specific ARG (fosmidomycin resistance genes) and MRG types (multi-metal resistance genes) also showed significant geographic distribution. Bacterial community was the main driver shaping the resistome. Nutrients also played an essential role in structuring the bacterial community and resistome in the sediments of Erhai Lake. This study sheds light on the distribution and fate of resistome under a high load of nitrogen and phosphorus in a deep lake.