Characteristics of non-point source pollution based on monitoring experiment in the Yingwugou small watershed, China

Identifying the main pollutants of non-point source pollution within the scope of small watersheds, carrying out load estimation, and probing its mechanism and characteristics can provide a basis for water quality control and management. The nutrient loss char-acteristics, load, and reduction rate of nutrients under different land use types were an-alyzed through the runoff plot monitoring experiment, and the non-point source pollu-tion load in the watershed was further calculated. Results showed that the loss of nutri-ents in each runoff plot was farmland > grassland> orchard in each runoff plot. Under the same slope, the loss of nutrient performance was maize > sweet potato > grassland > orchard. Taking S12 as the control group, the best reduction rate was orchard > grassland > sweet potato > maize > peanut. In runoff plot, the pollutant concentration under a single rainfall increased first and then decreased with the rainfall time. The pollutant concentrations sharply increased with the increase in flow, then gradually decreased, and finally stabi-lized at the outlet of the small watershed under a single rainfall. At this time, the shallow nutrients on the surface were easy to scour into the river, resulting in the sharp rise of pollutants in the river. In 2020, the losses of ammonia nitrogen (NH3-N), nitrate nitrogen (NO3-N), total nitrogen (TN), orthophosphate (SRP), and total phosphorus (TP) in the basin were 41.77, 296.93, 494.51, 33.87, and 44.03 kg/km2, respectively. TN and TP were the pri-mary nutrients in this area. The research results can provide a reference for the study of non-point source pollution in similar areas. (c) 2022 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.