Distribution Characteristics and Control Measures of Nitrogen Composition in Urban Stormwater Runoff from Different Underlying Surfaces

Nitrogen composition in urban stormwater runoff from five underlying surfaces was studied and discussed. It is shown that the highest EMCs of TN(Total Nitrogen) came from urban traffic road(i.e. 10.6 mg/L), and the lowest was from campus catchment areas(i.e. 2.4 mg/L). Meanwhile, EMCs of NH3-N from traffic road and commercial district (i.e. 3.4~4.6 mg/L) were much higher than that from concrete roofs and tile roofs(i.e. 1.2~1.6 mg/L). Although PEMC10 of TN was greater than EMCs, the proportion of nitrogen was still similar. Nitrogen in stormwater was predominantly dissolved (73%~82%), with DIN (Dissolved Inorganic Nitrogen) the abundant form (63%~82% of TN). The highest concentrations of nitrogen species form commercial district, concrete roofs, campus catchment and tile roofs were NO3-N, which made up of 39%, 39%, 44% and 52% of TN respectively. However, it was NH3-N that had greatest concentration in runoff from urban traffic road, and the ratio of NH3-N /TN was as high as 43%. The removal of TN could be enhanced through improvement of stormwater management measures. The key factor was that conditions to drive nitrification must be created, retention time of stormwater runoff in treatment systems should be increased and material with low nitrogen content should be selected as construction media.