An Accurate Method to Evaluate Non-point Source Pollution in a Typical Area of Beijing

Abstract:

Nonpoint source (NPS) pollutants have been recognized as major threats to water resources throughout the world. Thus evaluating NPS pollution becomes an issue of increasing importance. In urban-rural transition areas, the accuracy of the NPS pollution assessment decides the success rate of water ecological restoration. However, the method to estimate and verify NPS pollution inflow rivers in these areas is not accurate enough. Therefore, in this study, the EcoHAT-NPS model was used to simulate the typical NPS pollution load based on multiple sampling data of NPS pollution in Beijing, from 2017 to 2018. And the amount of NPS inflow into rivers was obtained combined with the NPS land-river transition model. Then, a method for quickly determining the quasi-true value of NPS inflow was proposed based on the one-dimensional river water quality model, control area of the waterlogging point and length of the road. Finally, the uncertainty of the simulation results of the NPS inflow in urban-rural transition areas was analyzed by using the quasi-true value of the NPS inflow. A real case study was performed in a typical area of Beijing, China. The result shows that the simulation of the NPS pollution load and NPS inflow in urban-rural transition areas is satisfactory (average R² = 0.88, average relative error = 18.09%); the NPS pollution load is in general agreement with the distribution of rainfall and population; NPS pollution is severe in months of July and August due to the rainfall increases; the NPS pollution from agricultural areas has the highest impact on the river water quality, whereas that from high-altitude mountain areas has the lowest impact. This study will provide theoretical guidance for the selection of key NPS pollution control areas and river water quality restoration by proposing a method for clarifying the distribution characteristics of pollutants from generation to river inflow. Therefore, the health of water resources can be improved.