Pollution characteristics of runoff in different function area of Tianjin

The surface runoff in different function areas of Tianjin was monitored after typical rainfall to investigate the variations of pollutants concentration,event mean concentrations(EMCs) and the pollutant load of runoff caused by rainfall water.Results showed that the pollutant concentration was up to the highest value in the first 10-20 min and then descended to a stable value in a wavy pattern,which indicated an obvious scouring effect in the early step of rainfall.The EMCs of SS,COD,BOD5 were 153.15-676.21,70-314,10.27-80.65 mg/L,given the pollutant load of 793-3 369,349-1 564 and 51-402 kg/(hm2·a)separately.The runoff water quality was below grade Ⅴof surface water environment standard;More than 50% of the monitoring results were above the first-order of national overall discharge standard of sewage.The pollutant EMCs and load of Tianjin was fairly near to the monitoring results of Guangzhou city,little higher than that of Beijing and Shanghai city,but far more than the United States,France and other developed countries.Furthermore,the most serious runoff pollution in different types of land use was industrial area,which was followed by commercial area,residential area and education area.Consequently,rainwater runoff was polluted seriously in Tianjin,and the implementation of pollution control was very important.