The effects of surface pollution on urban river water quality under rainfall events in Wuqing district, Tianjin, China

A large quantity of pollutants is washed off by stormwater during rainfall events. Polluted storm runoff deteriorates the water quality of receiving water bodies, which is becoming a main threat to urban water environment. In this work, five rainfall events were monitored to clarify the characteristics of land surface pollution in Wuqing district, China. Four pollutant indicators of storm runoff samples, including chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN) and ammonia nitrogen (NH3-N), were analyzed and then used to validate the parameters of a model established by Infoworks integrated catchment modeling (ICM). The land surface pollutant loads of metropolitan area for four different rainfall scenarios and the variations in pollutants concentration in urban rivers were illustrated based on the model. The simulated results showed that the volume of runoff increased from 31.8 x 10(4) m(3 )to 139.7 x 10(4) m(3) with the increase in the return period. The EMCs (Event Mean Concentration) of pollutants, however, were negatively correlated with return periods and the maximum drop was approximately 67%. Furthermore, the increased runoff enhanced the dilution effect and reduced the residence time of pollutants in rivers, which were the main reasons for the decrease of the pollutants concentrations. The results suggested that the runoff should be taken into account when considering the effects of surface pollution on urban river water quality. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study monitored five rainfall events to clarify the characteristics of land surface pollution and pollution variation in urban rivers. The simulated results showed that with an increase in return period, the volume of runoff increased while the concentration of pollutants decreased, mainly due to dilution effects and reduced residence time of pollutants in rivers.