Nonpoint source pollutants in urban basins include heavy metals, oil and other toxic chemicals. Among these, heavy metal contamination is of concern due to their high toxicity and bioavailability. Therefore, this study aims to analyze the characteristics of heavy metal dynamics within urban stormwater runoff in Gwanpyeong-stream basin, Daejeon. The overall and dynamic correlations between rainfall characteristics and heavy metals were examined. SWMM simulation of TSS and Zn was carried out to understand their effect better.

With point source pollutants in control, managing non-point source pollutants is drawing more attention. Climate change has influenced the rainfall characteristics which led to direct and indirect changes in stormwater runoff. Water being an excellent media for non-point source pollutants, a study on the relationship between rainfall and stormwater runoff is required. This study analyzed seven heavy metal species (Ni, As, Cr, Cu, Zn, Pb) in an urban stream and stormwater runoff. The results have shown that the study area shared some similarities with the results of previous studies concerning urban basin. The stream samples showed that Zn is the highest followed by Cu and Cr. In all rainfall events, the fluctuation of TSS and heavy metals concentrations were found to be similar.

The overall and dynamic correlation between rainfall characteristics and heavy metals were analyzed. Maximum rainfall intensity, runoff volume and total metal load showed statistically significant correlation except for Cu and Zn. Antecedent dry days (ADD) had correlation with even mean concentration (EMC) of all seven elements. The result implies that the longer dry days continue, the higher concentration of metals is released to the water. With TSS and metal concentrations having similar dynamic patterns throughout the rainfall event and partition coefficient of metals in runoff being high, the analysis results suggest that the removal of suspended solids will show high efficiency in heavy metal reduction. Street sweeping with different time intervals was simulated using SWMM, and it showed good TSS removal efficiency. The findings of this study will be useful reference for the heavy metal management measures in urban basins in Korea.