Metals in surface specific urban runoff in Beijing

Metals are among the most toxic pollutants in urban stormwater. To investigate the concentration of dissolved and particulate fractions, the temporal variation during rain events, the effect of wash-off surface, and to assess the pollution status of metals in urban runoff, a total of 155 samples were collected mainly from trafficked areas, roofs and parking lots in Beijing from March to November 2015. Most of the metals were found mainly in the particulate fraction (68-96%) from trafficked surfaces, while for roof runoff Cd, Fe, Mn and Zn were found more equally in dissolved and particulate fractions. Metal concentrations were higher during start of a rain event than later (p < 0.05), and also were higher the longer the period of antecedent dry days. The mean concentration of all metals in trafficked areas exceeded both the Chinese standard Level III (swimming and fishery waters) and the European standards (surface water). Mean concentrations of Cd, Mn, Zn, Al, Fe, Pb and Ni from trafficked areas were 2-10 times higher due to higher traffic intensity and substantial atmospheric deposition, while Sb was 20 times higher than in any other reported data for urban runoff. Cluster analysis (CA) and principal component analysis (PCA) together with Pearson's correlation co-efficient suggested that Cd, Cr, Cu, Mn, Ni, Pb, and Zn mainly originates from vehicular activities, while Mn and Zn in roof runoff is due to atmospheric deposition. The geo-accumulation and pollution indices show that runoff from trafficked areas are moderately to heavily polluted by most metals, except Cu and Zn. Thus, Beijing urban runoff presents an environmental risk towards lakes, bathing water and drinking water. The results can be used as basis for development of stormwater and pollution control strategies. (C) 2019 Elsevier Ltd. All rights reserved.