Non-point source pollution transport and photocatalytic degradation effect in the Mudong River basin of Huixian Wetland based on WASP model

Agricultural activities are one of the important sources of water pollution in small agricultural watersheds. It is of great significance to understand the current status of water quality and non-point source pollution in small agricultural watersheds, estimate their pollution load, and explore pollutant reduction methods for sustainable water environment management and protection. In this paper, the small watershed of Mudong River in Huixian Wetland was taken as the study area, and the water quality monitoring indicators were dynamically simulated by the WASP model. Combined with the preparation of nano-titanium dioxide films and photocatalytic degradation experiments, the water quality reduction of each river section was systematically evaluated. Then, based on the simulation results, the reduction of pollution load into the river was estimated, which provided a scheme for the field reduction of pollutants in agricultural watersheds. The results showed that the WASP model was effective in simulating the water quality of the upper Mudong River in a typical karst area. The simulation inverted the reduction in pollution loads in the upper Mudong River for each indicator. Moreover, it calculated non-point source pollution reduction rates of ammonia nitrogen (NH ₃ -N) (31%, 9.91%, 2.18%), total nitrogen (TN) (24.59%, 21.95%, 10.58%), total phosphorus (TP) (26.64%, 29.39%, 25.15%), dichromate oxidizability (CODcr) (46.46%, 13.39%, 0.99%), and biochemical oxygen demand (BOD ₅ ) (37.67%, 31.04%, 23.09%) at 24, 12, and 6 h of the reaction, respectively. In short, this method will improve river water quality if nano-titanium dioxide material is promoted for outdoor use.