| To solve the contradiction between the urban construction and urban greening, and the urban rainwater utilization problem, two kinds of roof greening was constructed as the research object. The paper studies and analyses the performance of rainwater utilization of roof greening. Firstly, select plants which are common in Kunming. Then select planting matrix and proportion according to the research results of other researchers, to construct lawn-style roof greening and shrub-style roof greening.Saturated moisture of two kinds of roof greening are 77.8248L, 161.1605L, based on storage properties of planting matrix and ceramsite of roof greening. Wet bulk density of light whight anthropogenic soil is 1196.832kg/m3, when planting matrix of roof greening absorbs water saturation. It meets Code for Roof Greening of Beijing about wet bulk density of planting matrix which should not exceed the requirements of 1300kg/m3. Loads is 297.9884kg/m2,531.8762kg/m2 respectively, when two kinds of roof greening absorb water saturation. Load of lawn-style roof greening meet safety requirements of building construction; while load of shrub-style roof greening don’t meet safety requirements of building construction. It must put forward the relevant requirements sbout load of roof when shrubs-style roof greening is constructed. In order to compare the differences between actual storage capacity and theory storage capacity of roof greening, the study simulates different intensity rainfall. The results show that actual storage capacity of both roof greening is less than theory storage capacity in the actual rainfall process, and actual storage capacity increases with the decrease of the rainfall intensity.The minimum rainfall which made two kinds of roof greening have rainwater runoff is respectively 19.4mm,31.9mm based on theoretical calculation. According to the situation of rainfall in Kunming, natural rainfall usually doesn’t make the roof greening produces rainwater runoff. There will be roof runoff when roof without roof greening. Roof greening constructed can decrease roof runoff and pollutants in rainwater effectively. This paper chooses the roof rainwater as the research object and simulates natural rainfall. Then the paper studies purification capacity of roof greening and reduction amout of pollutants. Lawn-style roof greening can reduce pH from roof rainwater 11.8%-28.5%, the turbidity: 59.8%-68.0%, the SS:63.2%～68.8%,the COD:50.5%～58.4%,the NH3-N:36.5%～ 69.3%, the TN:42.5%～52.9%, the TP:37.0%-54.0%. Shrub-style roof greening can reduce pH from roof rainwater 11.4%-18.9%, the turbidity:48.2%～61.2%%, the SS: 57.8%～66.9%,the COD:48.5%～60.7%, the NH3-N:31.2%～64.8%,the TN:37.3%～ 53.6%, the TP:48.1%～68.3%.Kunming has obvious rainy season and dry season. During the rainy season, the roof greening basic need not be irrigation. During the dry season, human need irrigate roof greening to maintain water plants survival. The 21st century will fight for fresh water, so roof greening must avoid increase burden of freshwater resources. Use reclaimed water for roof greening during the dry season, then study feasibility of reclaimed water irrigate roof greening. The experiment show that lawn-style roof greening can reduce pH from reclaimed water 1.0%, the turbidity:44.0%, the SS:80.3%, the COD:-7.1%, the NH3-N: 51.5%, the TN:2.6%, the TP:47.2%. Shrub-style roof greening can reduce pH from reclaimed water -0.3%, the turbidity:6.9%, the SS:73.4%, the COD:-2.4%, the NH3-N: 49.7%, the TN:1.4%, the TP:57.3%. Pollutants except the COD of water are declined, the overall water quality is slightly worse. Then reclaimed water can be used for roof greening, but should not be watered too much make the roof greening produces water runoff. |
