Pollution Characteristics and Discharging Process in the Direct Runoff from Suburb Areas in Dianchi Lake Catchments

Direct runoff is recognized as one of the major causes of water quality deterioration in the receiving water bodies.Two typical suburb representative resident areas,a Residential area and a Residential-Commercial mixing area,around the Dianchi Lake were chosen to study the concentrations and discharging process of pollutants in the direct runoff.The results showed the total concentrations of major pollutants in the direct runoff in the two studied areas of Dianchi Lake catchment were:2.18～29.40 mg·L-1 for total N;0.18～3.90 mg·L-1 for totalP;0.87～18.48 mg·L-1 for NH3-N;0.02～3.64 mg·L-1 for NO3-N;and the chemical oxygen demand (CODC)rand total suspended solids(TSS) were 22.51～362.92 mg·L-1 and 7.00～882.00 mg·L-1,respectively.The concentration of each pollutant in the direct runoff was well above the value of Class V in the surface water quality standard.The major nitrogen pollutants were NH3-N,particle-N and dissolved organic-N.The major phosphorus pollutants were particle-P and PO34--P.The pollutant concentration in the direct runoff of Residential-Commercial Area was higher than that of Residential Area,which was higher than that in roof runoff.The pollutant concentration in the direct runoff varied with time.Concentrations of pollutants at the beginning of the runoff were very high,and then decreased sharply with the time to the stable stage.The Event Mean Concentration(EMC)of the Residential-Commercial Area was higher than that of Residential Area,with greater randomness.