绿色、蓝色和蓝-绿屋顶径流水质特征

屋顶占据大量城市不透水面，实施生态屋顶建设，有利于缓解城市化造成的生态和环境问题.在北京市区搭建不同类型生态屋顶(绿色屋顶、蓝色屋顶和蓝-绿屋顶),基于对2019年雨季降雨特征、各类生态屋顶径流量以及径流中营养盐和重金属浓度的监测，计算不同生态屋顶径流污染负荷和径流水质指数(RQI),定量对比分析不同类型生态屋顶径流的综合水质差异.结果表明，在2019年雨季，各生态屋顶均表现出良好的雨水滞留能力，平均径流削减率在75.7%～78.9%之间，且不同生态屋顶的径流削减率无显著差异(P>0.05);相较雨水，各生态屋顶均为NH⁺₄-N、 DZn和DCd的汇，累积负荷削减率分别在63.8%～96.4%、68.6%～90.7%和39.8%～54.5%之间，但均为NO^-₃-N、 DCr、 DFe和DNi的释放源；蓝色屋顶是DCu的汇(累积负荷削减率为21.9%),但对雨水径流中PO^3-₄-P的累积负荷无明显影响，而绿色和蓝-绿屋顶均为PO^3-

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.