Mechanism of sinuosity effect on self-purification capacity of rivers.

As one of the important characteristics of river morphology, river sinuosity has a direct impact on the river water quality and self-purification capacity. In the present study, 4 physical river channel simulation models using circulating water with a sinuosity of 2.2, 1.8, 1.4, and 1.0, respectively, were established in our laboratory. Related hydraulic tests and detection were performed, including the detection of microbial communities in overlying water, monitoring of the river flow velocity and depth, and observation of the river flow line and bank scouring. The results show that the TN reduction rate at a sinuosity of 2.2 was 1.09, 1.20, and 1.75 times that at a sinuosity of 1.8, 1.4, and 1.0, respectively. And the total plate count for the set of tests with a sinuosity of 2.2 was 3.32 times that for the set of tests with a straight channel. The sinuous rivers have more complex flow regimes, more suitable hydraulic conditions, larger hyporheic zone areas, better microbial environments, and longer river flow paths, giving them a higher purification capacity against pollution. These findings can provide a theoretical basis for the optimization of water system layout and the restoration of river environments in the process of urbanization in China.