[Effects of Green, Blue, and Blue-green Roofs on Runoff Quality]

Roofs occupy a great proportion of urban impervious surfaces, and the implementation of eco-roof construction in urban areas is beneficial to alleviate the ecological and environmental problems caused by rapid urbanization. In this study, different eco-roofs (i.e., 68.6%-90.7%, and 39.8%-54.5%, respectively. However, all the eco-roofs were sources of NO^-₃-N, DCr, DFe, and DNi. The blue roof was a sink of DCu (with a pollutant load reduction rate of 21.9%) and did not affect the cumulative load of PO^3-₄-P in runoff. However, the green roof and blue-green roof were the sources of PO^3-₄-P and DCu. The RQI value of the blue roof was the highest, followed by that of the blue-green roof and green roof. The RQI value of the green roof was significantly lower than that of the blue and blue-green roofs (P<0.05). These results indicated that the runoff quality of the blue roof was the best, whereas that of the green roof was the worst. Adding a storage layer to the green roofs could significantly improve the runoff quality. The results of this study provide scientific references for the selection and design of eco-roof facilities.