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Nonpoint source pollution (NPSP) from human production and life activities causes severe destruction in river basin environments. In this study, three types of sediment samples (A, NPSP tributary samples; B, non-NPSP mainstream samples; C, NPSP mainstream samples) were collected at the estuary of the NPSP tributaries of the Jialing River. High-throughput sequencing of the fungal-specific internal transcribed spacer (ITS) gene region was used to identify fungal taxa. The impact of NPSP on the aquatic environment of the Jialing River was revealed by analysing the community structure, community diversity, and functions of sediment fungi. The results showed that the dominant phylum of sediment fungi was Rozellomycota, followed by Ascomycota and Basidiomycota (relative abundance > 5%). NPSP caused a significant increase in the relative abundances of Exosporium, Phialosimplex, Candida, Inocybe, Tausonia, and Slooffia, and caused a significant decrease in the relative abundances of Cercospora, Cladosporium, Dokmaia, Setophaeosphaeria, Paraphoma, Neosetophoma, Periconia, Plectosphaerella, Claviceps, Botrytis, and Papiliotrema. These fungal communities therefore have a certain indicator role. In addition, NPSP caused significant changes in the physicochemical properties of Jialing River sediments, such as pH and available nitrogen (AN), which significantly increased the species richness of fungi and caused significant changes in the fungal community β-diversity (P < 0.05). pH, total phosphorus (TP), and AN were the main environmental factors affecting fungal communities in sediments of Jialing River. The functions of sediment fungi mainly involved three types of nutrient metabolism (symbiotrophic, pathotrophic, and saprotrophic) and 75 metabolic circulation pathways. NPSP significantly improved the pentose phosphate pathway, pentose phosphate pathway, and fatty acid beta-oxidation V metabolic circulation pathway functions (P < 0.05) and inhibited the chitin degradation to ethanol, super pathway of heme biosynthesis from glycine, and adenine and adenosine salvage III metabolic circulation pathway functions (P < 0.05). Hence, NPSP causes changes in the community structure and functions of sediment fungi in Jialing River and has adversely affected for the stability of the Jialing River Basin ecosystem. [ABSTRACT FROM AUTHOR]

Copper (Cu) and zinc (Zn) are two heavy metal pollutants that pose a serious risk in the Jialing River. Cu and Zn are transported into the sediment primarily due to the activities of the mining and smelting industries. In this study, we employed the diffusive gradient in thin films (DGT) technique, sequential extraction, and two assessment methods to evaluate the remobilization, fractions, and environmental risk in the downstream section of the Jialing River. The total concentrations of Cu and Zn in the four study areas followed the order S3 > S2 > S4 > S1, and the assessment results indicated that Cu and Zn presented a low environmental risk in the study area. Cu and Zn were primarily bound to the Fe/Mn oxide fraction (F2) and the residual fraction (F4). The results of the DGT probe showed a clear vertical distribution of Cu and Zn in the sediment (from 3 to − 12 cm), and both elements showed obvious increasing trends at the bottom of the probe. The correlation analysis indicated that CDGT-Cu correlated well with CDGT-Zn (r = 0.834, p < 0.01). The flux results showed that the sediment in the downstream section of the Jialing River is a major source of Cu and Zn and that there is a potential risk of release to the overlying water. Further analysis found that CDGT-Fe was negatively correlated with CDGT-Cu and CDGT-Zn, indicating that Fe may influence the remobilization of these metals. In addition, a hotspot of CDGT-Cu and CDGT-Zn at the bottom of the probe corresponded with a dark area in the AgI gel measuring CDGT-S. These results indicate that Fe and S are factors that mitigate the release of Cu and Zn from sediments. [ABSTRACT FROM AUTHOR]

Eco-efficiency plays a significant role in expressing how efficient the economic activity consumes nature's goods and services. To accurately measure eco-efficiency, the method slack-based measure modified three-stage data envelopment analysis (DEA) is adopted to evaluate environmental conditions in China's 30 provinces from year 2004 to 2016. This study treats carbon emissions and three industrials wastes as undesirable outputs and excludes the influences from external environment and random errors when make adjustments. Based on the results, this study makes the following conclusions: Firstly, industrial structure, trade openness, and population have negative effects on eco-efficiency while technology investment, urbanization process, foreign direct investment, and fiscal decentralization have positive effects on eco-efficiency. Secondly, the eco-efficiency for most provinces after adjusted is lower than the pre-adjusted, which indicates the overestimation in eco-efficiency when using traditional approaches. Thirdly, the eco-efficiency in China showed a clear geographical step distribution, with the highest eco-efficiency in the east area, followed by the central, northwest, and southwest regions. [ABSTRACT FROM AUTHOR]