Study on spatial distribution of pollutants and total amount reduction in the Duliujian River (Tianjin, China)

Abstract

Abstract The Duliujian River is the largest river in the downstream area of the Haihe River. In order to further clarify the main pollutant load and load contribution of the basin, and analyze the watershed pollution control unit, key pollution sources and their spatial distribution characteristics, this study divides the control unit of the basin, which is based on the digital elevation model (DEM), and applies the expansion template of Arc Map–Arc Hydro tools software. On the basis of water environment capacity and total maximum daily load (TMDL) theory, water quality standards are set in accordance with the requirements of the water body function. Considering seasonal influence and the pollution load contribution rate, a total pollution load control plan and a load optimization allocation plan are proposed, in order to realize the distribution of pollution load among point source, non-point source and safety margin. According to the calculations, TMDL of chemical oxygen demand (COD) and NH3-N in the flood season (June–September) in the Duliujian River is the largest, about 27,005 kg/d and 2,296 kg/d, respectively. During the dry season (December–March), the reduction of COD and NH3-N is the largest, reaching 50.74% and 90.14%, respectively. And Duliujian River is dominated by non-point source pollution.