屋面径流水量水质变化

Variations of Roof Runoff Qualities and Quantities

为探明普通屋顶和绿化屋顶屋面径流水质和水量的变化规律,采用4个1.0×0.5 m^2木箱模拟普通屋顶和3种不同基材配方的绿化屋顶,并运用人工降雨的试验手段,相隔12个月2次对比观测屋面径流过程的水量和径流Cd、Pb、Cu、Zn、TP和TN含量。结果表明:(1)与普通屋面相比,绿化屋面的径流开始更晚,结束更迟,延时更长,径流总量更小,径流洪峰更低。(2)除初始流外,绿化屋顶屋面径流TP的含量高于普通屋面径流;试验初期,绿化屋顶屋面径流TN的含量高于普通屋面径流;使用复合肥的绿化屋顶屋面径流TN和TP含量比使用缓释肥绿化屋顶屋面径流含量高。(3)普通屋顶屋面径流重金属和TN、TP含量随着径流过程逐渐减少,绿化屋顶屋面径流中污染物含量随径流过程变化规律不明显。绿化屋顶初期屋面径流TN含量比1 a后高。(4)3种绿化屋面的径流和普通屋顶屋面径流的初始流TP、TN、Cd和Pb含量超过了GB 3838-2002规定Ⅳ类水域含量指标。研究表明不同类型和不同绿化基材的绿化屋顶屋面径流过程和水质变化规律不同。

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 m^2 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.