不同配置绿色屋顶径流水质特征及综合评价

绿色屋顶是海绵城市建设的重要措施之一，但植被和基质等配置因素对其径流水质的综合影响尚不清楚，这限制了绿色屋顶的推广.通过在北京市区搭建3种植被类型［佛甲草（Sedum lineare）、大花马齿苋（Portulaca grandiflora，马齿苋）和无植被（对照）］、3种基质类型［田园土、改良土和轻质生长基质（轻质基）］和2种基质厚度（15 cm和10 cm）的12个绿色屋顶，基于2019年雨季降雨特征、各绿色屋顶径流量以及径流中营养盐和重金属浓度的监测，构建绿色屋顶径流水质指数（RQI）定量分析不同绿色屋顶配置对径流水质的综合影响.结果表明，植被可提高绿色屋顶径流削减率和有效降低径流中NO₃^--N的浓度，佛甲草和马齿苋绿色屋顶的RQI接近，径流水质均优于对照绿色屋顶；基质材料显著影响绿色屋顶径流削减率和径流中污染物浓度，轻质基绿色屋顶的径流削减率最低且径流中NH₄⁺-N、DFe、DMn和DZn的浓度均值最高，其径流水质劣于改良土和田园土绿色屋顶；基质厚度为15 cm的绿色屋顶径流削减率更高，其径流水质优于10 cm的绿色屋顶.研究结果可为绿色屋顶设计及径流水质综合评价提供科学依据.

Integrated Assessment of Runoff Quality from Green Roofs with Different Configurations

Green roofs are regarded as one of the important measures for the sponge city construction. However, the comprehensive impacts of configuration factors (e.g., vegetation and substrates) on runoff quality from green roofs are not clear, which limits the promotion of green roofs. In this study, 12 green roofs with three vegetation types (i.e., Sedum lineare, Portulaca grandiflora, and non-vegetated substrates), three substrate types (i.e., local planting soil, engineered soil, and light growing medium), and two substrate depths (i.e., 10 cm and 15 cm) were set up in Beijing. During the rainy season of 2019, the rainfall characteristics, runoff volumes, and concentrations of nutrients and heavy metals of runoff from the green roofs were monitored. Based on the measured data, a runoff quality index (RQI) was developed to evaluate the comprehensive influences of configurations on runoff quality of the green roofs. The results showed that vegetation could improve runoff reduction rate and decrease the concentrations of NO₃^--N in runoff of green roofs. The RQIs of green roofs planted with S. linear and P. grandiflora were similar, and the evaluation results of runoff quality were better than those with non-vegetated substrates. The materials of substrates had significant influences on the runoff reduction rate and pollutant concentrations in runoff from green roofs. The green roofs with light growing medium, which had the lowest runoff reduction rates and the highest concentrations of NH₄⁺-N, DFe, DMn, and DZn in the runoff, showed poorer runoff quality than the green roofs with local planting soil and engineered soil. The green roofs with a substrate depth of 15 cm had higher runoff reduction rates than those with 10 cm deep substrate, and the runoff quality was better than those with a substrate depth of 10 cm. The results of this study provide scientific reference for the design and integrated assessment of green roofs.