Variations of Roof Runoff Qualities and Quantities

YE Jianjun; ZHU Zhaohua; LIU Defu; XIAO Henglin; XU Guogang; XU Weisheng; WANG Hongying; WAN Juan

doi:10.3969/j.issn.1003-6504.2017.04.020

Abstract：To figure out the varying principles of runoff qualities and quantities from conventional and green roofs,four wooden crates with dimensions of 1.0×0.5 m2 were firstly built to simulate one conventional roof and three green roofs with different substrates.And then two artificial rainfalls with 12 months apart were sprayed on them,and in each rainfall event the water quantities during roof runoff processes and Cd,Pb,Cu,Zn,TP and TN concentrations in roof runoffs were comparatively investigated.Results showed that runoff processes from conventional roof and green roofs all have a greatest initial runoff quantities,and then decreased gradually till disappeared.Compared with runoff from conventional roof,runoffs from green roofs started later,lasted longer,and had smaller volumes and lower peaks.Except for initial runoffs,TP concentrations in runoffs from green roofs were higher than those from conventional roof.And at the early stage,TN concentrations in runoffs from green roofs were also higher than those from conventional roof;and runoffs from green roofs with substrates made of compound fertilizer had higher TP and TN concentrations than those from conventional roof.While heavy metals,TN and TP concentrations in runoffs from conventional roof decreased along with the runoff processes,the pollutant concentrations in runoffs from green roofs were not related with runoff processes.Green roofs produced runoffs with higher TN concentrations at the early stage than a year later.TP,TN,Cd and Pb concentrations in runoff from the three green roofs and in initial runoff from conventional roof were all beyond the stipulated values of GB 3838-2002.This study proved that runoffs from different types of roofs or from green roofs with different substrates had different runoff processes and different quality varying modes.