[Impacts of Vegetation on Quantity and Quality of Runoff from Green Roofs].

As a key component of green roofs, vegetation may have significant impacts on both the quantity and quality of runoff. In this study, the effects of vegetation on both the quantity and quality of runoff from green roofs are investigated through monitoring the rainfall and runoff processes of green roofs with four different types of vegetation cover (, , , and a non-vegetated bed as control) during 2017. The growth characteristics of the vegetation were also monitored, and the nutrients (NH-N, NO-N, NO-N, and PO-P) and heavy metals (Cr, Cd, Cu, and Ni) in the rainwater and runoff were measured. The results show that the average rainfall event-based runoff reduction rates for the four green roof types were 51.3%, 41.5%, 36.3%, and 33.0%, respectively. Furthermore, the runoff reduction rates of the green roof planted with were significantly higher than both the green roof and the non-vegetated bed (<0.05). The green roofs planted with and both acted as sinks for the nutrients. The green roof, which had a higher biomass, provides higher nutrient load reduction rates (59.6%, 99.9%, 82.5%, and 25.7% for NH-N, NO-N, NO-N, and PO-P, respectively) than the green roof (52.5%, 89.3%, 75.3%, and 7.8%, respectively). The green roof and the non-vegetation bed acted as sinks for NH-N and NO-N but were sources of NO-N and PO-P. All four of the green roofs were sinks for DCd, with pollution load reduction rates of 19.2%, 41.5%, 38.4%, and 31.1%, respectively. However, all the green roofs acted as the sources of DCr, DCu, and DNi.