Preliminary investigation on characterization of urban roof runoff in Macau

Four roof catchments in the city of Macao were selected for sampling and study. Water quality parameters such as pH, Turbidity, COD_ Cr , SS, TN, Zn, Pb, Fe and Cu were analyzed. The results obtained show that the average Zinc concentrations in the roof runoff from the galvanized-iron roof is about 2 times of the class V of water quality standard China. Average TN and COD_ Cr concentration also exceeds the criteria. Based on the water quality analysis from roof runoff in 3 rainfall events, the heavy metals including Zn and Pb are in the following order: galvanized-iron roof ( rusted greatly) galvanized-iron roof (rusted slightly) galvanized-iron roof (new installed) concrete roof . From the pollutographs analysis, the roof runoff discharge shows great uncertainties which depends on the length of dry weather period and storm intensity.