| The load of external pollutants into the river and the contribution rate of each source of pollution were obtained by classification method and calculating the pollution load in the watershed using improved pollution output coefficient model, based on the investigation of pollution source, taking the Erheng ditch watershed in the upstream Qinhuai River in Nanjing as example. The results showed that the total pollutant discharge load in that watershed was: COD 229.9 t/a, TN 25.8 t/a, NH3-N 22.4 t/a, TP 1.7 t/a. The load into the river was: COD 47.1 t/a, TN 5.5 t/a, NH3-N 4.6 t/a, TP 0.36 t/a. Non point source pollution was the main pollution, while point source pollution was relatively weak. The annual contribution rate of domestic non point source pollution into the river was the highest of 44.5%, the annual contribution rate of forest non point source pollution into the river was the lowest of 0.1%. The annual contribution rates of aquaculture non point source, road non point source, paddy field non point source and dry land non point source into the river were 31.6%, 16.2%, 6.2% and 1.4%, respectively. |
