Distribution and variation of typical contaminant species in short-term storm runoff from different urban land surfaces

The pollutants in urban storm runoff, which lead to non-point source contamination of water environment around cities, are of great concerns. The distributions of typical contaminants and the variations of their species in short term storm runoff from different land surfaces in a seaside city in South China were investigated. The concentrations of various contaminants, including organic matter, nutrients (i.e., N and P) and heavy metals, were significantly higher in parking lot and road runoff than those in roof and lawn runoff. The early runoff samples from traffic road and parking lot contained much high total nitrogen (TN 6-19 mg/L) and total phosphorus (TP 1-3 mg/L). A large proportion (around 60%) of TN appeared as the species of total dissolved nitrogen (TDN) in most kinds of runoff. The percentage of TDN (%TDN) or percentage of total dissolved phosphorus (%TDP) remained relatively stable in runoff during the rain events and did not decrease as dramatically as TN or TP. In addition, only parking lot and road runoff were contaminated by heavy metals, in which only Pb (25-120 μg/L) and Zn (0.1-1.2 mg/L) were the significant heavy metal contaminants. Soluble Pb and Zn were predominantly existed as labile complex species (50%-99%), which are adsorbed on the surface of suspended particles and could be easily re-released out when ambient pH decreased. This indicates that the labile complex pb and Zn in urban runoff would have the largest impact on the aquatic environment.