Nonpoint Source Pollution (NPSP) Induces Structural and Functional Variation in the Fungal Community of Sediments in the Jialing River, China

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 tributary 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, Chytridiomycota, Basidiomycota, Mortierellomycota and Zoopagomycota (relative abundance>1%). NPSP caused a significant increase in the relative abundances of Rozellomycota, Saccharomycetes, Microascales, Saccharomycetales, Branch02 and Branch03. In addition, it caused a significant decrease in the relative abundances of Chytridiomycota, Dothideomycetes, Capnodiales, Glomerellales, Xylariales and Chaetothyriales. Moreover, 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 Jialing River sediments. 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 NONOXIPENT-PWY, PENTOSE-P-PWY, and PWY-6837 metabolic circulation pathway functions (P<0.05) and inhibited the PWY-7118, PWY-5920, and PWY-6609 metabolic circulation pathway functions (P<0.05). Hence, NPSP causes changes in the community structure and functions of sediment fungi in Jialing River and destroys the stability of the Jialing River Basin ecosystem.

Effects of land use and nutrients on the characteristics of dissolved organic matter in the Nanchong Section of Jialing River, China in December 2019

Chromophoric dissolved organic matter (CDOM) in aquatic ecosystems can reflect the impacts of human activities on the carbon-cycling process. However, direct evidence of the combined effect of land use and anthropogenic nutrients on CDOM characteristics in river ecosystems is limited. Herein, we collected water samples from 18 sites in the Nanchong section of Jialing River in December 2019 to elucidate how the land use and nutrients affect the source and composition of CDOM through parallel factor (PARAFAC) analysis of excitation–emission matrices (EEMs). First, the absorption coefficient a254 (r2=0.29, p&lt;0.01) and three fluorescence components (humic-like C1 and C2 and protein-like C3) (r2=0.31–0.37, p&lt;0.01) significantly increased with increased urban area, and the four parameters were higher in the urban than in the suburb (p&lt;0.05). The correlation between small CDOM molecule and cropland land was positive (p&lt;0.01). Second, the increase in nutrient levels increased the a254 (r2=0.84 and 0.33, p&lt;0.01) and three fluorescence components (r2=0.30–0.84, p&lt;0.01 or p&lt;0.05). Third, allochthonous CDOM were prevalent in the Nanchong Section of Jialing River, and the proportions of C1 and C2 were 42 and 41%, respectively. Our findings indicated that the variability of source and composition of CDOM significantly depended on urbanization and increased nutrients in the Nanchong Section of Jialing River.

Hydrological simulation of the Jialing River Basin using the MIKE SHE model in changing climate

Climate change and human activities have an important impact on the changing environment, leading to significant changes in the basin water cycle process. The Jialing River Basin, the largest tributary of the upper Yangtze River, is selected as the study area. Three different rainfall datasets, the China Meteorological Assimilation Driving (CMAD) dataset, the Tropical Rainfall Measuring Mission data, and gauged observation data, were used as inputs for the MIKE System Hydrological European (MIKE SHE) model. By comparing the simulation results driven by various meteorological data, the applicability of the MIKE SHE model at four stations is evaluated, and the sensitivity and uncertainty of model parameters are analyzed. Meanwhile, the impact of large hydropower stations on the runoff of the Jialing River Basin is assessed, and the influence of human activities on the runoff change is determined. The future climate change of the watershed was analyzed by using the typical representative concentration pathway (RCP) 4.5 and RCP8.5 climate scenarios. Based on the MIKE SHE model, the runoff of the Jialing River Basin in the future climate scenario is predicted, and the corresponding response of the Jialing River Basin is analyzed quantitatively. The results show that the CMAD data-driven model has better Nash–Sutcliffe efficiency and correlation coefficient for each period. By analyzing the influence of the hydropower station on the runoff process at the outlet of the basin, it is found that the hydropower station has a certain regulating effect on the runoff process at the outlet of the basin. In addition, the RCP4.5 scenario is more consistent with the future scenario, indicating that the Jialing River Basin will become colder and drier.

Multi-objective optimal operation of reservoir group in Jialing River based on DREAM algorithm

With the implementation of the most stringent water resources management system and the advancement of the construction process of reservoir terrace basins, the research and application of the theory and method of joint operation of reservoir groups are becoming more and more important. The Differential Evolution Adaptive Metropolis (DREAM) algorithm is a sampling algorithm based on the Markov Chain Monte Carlo method proposed in recent years. The algorithm satisfies ergodicity and is good at handling problems with multivariate nonlinearity, high dimensionality, and multi-peaks, and as such the algorithm is a new global optimization solution. This paper elaborated the solution mechanism of the standard DREAM algorithm, and the algorithm was applied to the optimal operation model of the reservoir group in Jialing River. First, we optimized and analyzed the multi-objective supply operation model of the reservoir group water in Jialing River. Then the multi-attribute decision-making and evaluation index system of water supply operation rules for the reservoir group to assess the optimization of the operation model was adopted. Finally based on the results of the evaluation, the best water supply operation scheme for the reservoir group of Jialing River was selected. The results show that the Baozhusi Reservoir can fully meet the planned water supply requirements in dry years, while the two reservoirs, Shengzhong and Tingzikou, need to be weighed against the evaluation indexes of water supply operation. The research provides a theoretical basis for the DREAM algorithm in the optimal operation of the reservoir group and the actual operation scheme for the reservoir group of Jialing River.

Study on the Installation and Construction Technology of the Transfer Stairway on the Track Platform on Bridge—— Taking the Construction of the Jialing River Bridge in Zengjiayan of Chongqing City as an Example

The bridge deck on the Yuzhong side of Zengjiayan Jialing River Bridge is close to subway lines and light rail stations. It is necessary to set up transfer stairways on both sides of the bridge. The construction technology of installing and replacing with tunnel under special conditions is discussed to provide reference for bridge construction.