Yiting Qi

Under the background of increasingly serious global environmental pollution, ensuring the safety of drinking water has become one of the focuses of global attention. In this study, Meihu Reservoir, a drinking water source, was selected as the research object, and the main pollution problems and their sources were revealed through conventional water quality analysis, suitability evaluation of the drinking water source and eutrophication evaluation of the reservoir. Using modern water quality monitoring technology and methods, the paper monitors and analyzes various water quality parameters of the Meihu Reservoir. The results showed that the water quality indexes, except total nitrogen, met the class II–III standard of drinking water, and the comprehensive nutrient state index method (TLI) evaluated the reservoir, and its index met $30\le \mathrm{TLI}(\sum )\le 50$, indicating that the reservoir belongs to the medium nutrition category. Therefore, the water quality of the reservoir has been affected by different degrees of agricultural, domestic and livestock pollution, mainly reflected in the serious excess of the total nitrogen index (the peak has reached 2.99 mg/L). The results of the on-site investigation showed that the main sources of nitrogen in the reservoir included agricultural non-point-source pollution, domestic sewage pollution, domestic garbage pollution and livestock and poultry pollution, accounting for 50.09%, 23.99%, 14.13% and 11.80% of the total load, respectively. On this basis, this paper puts forward some countermeasures for pollution control in order to provide a scientific basis and practical path for water quality protection and improvement of the Meihu Reservoir and other similar reservoirs.

As an ecological measure to deal with river water quality problems, artificial floating islands have been widely used all over the world, but the research on root deformation and shear vortex width under the action of artificial floating islands is rare. In this paper, the relationship between the deformation of vegetation roots and parameters of vegetation roots under different hydrodynamic conditions is experimentally studied. The results show that the Cauchy number ($C_a$) value gradually increases with the increase of velocity, and that the smaller the diameter is, the greater the $C_a$ value is. The value of the buoyancy number ($B$) will increase with the increase of root length and will decrease with the increase of root diameter. The corresponding deformation formula of flexible root systems under hydrodynamic conditions is obtained, and has high simulation accuracy. Based on theoretical analysis and machine learning, a formula for the shear vortex width of flexible vegetation is established, $\delta =\frac{0.361+0.0738\frac{l_e}{l}}{\alpha C_{df}}$. The research results can provide a theoretical basis for hydrodynamic and solute transport in artificial floating island channels.