| The green roof is an important sponge city construction unit with many functions such as regulating rainwater runoff and alleviating the heat island effect.However,due to the thinner green matrix layer and insufficient capacity of water storage,the green roof needs to be watered frequently,which increases the difficulty of maintenance and limits its promotion.Super Absorbent Polymer(SAP)is a material with a wide range of sources and mature preparation process.As its excellent water absorption and water retention,SAP has been widely used in drought resistance technology of agroforestry.SAP is an excellent soil conditioner which will reduce the irrigation demand of soil,however,there are currently few studies on the use of SAP as a green roof matrix modifier.In this study,based on the investigation of the performance of SAP,the most suitable SAP for green roof was isolated,and the effect of SAP for the green matrix layer and sedium lineare was also investigated.Meanwhile,the performance of the green roof with SAP was also evaluated.In this study,the primary screening for the SAP was conducted among three common categories of SAP on the basis of water absorption performance through water experiments,and preliminary screening of SAP species was carried out.Results showed that the polyacrylic acid potassium salt type-the imported raw material SAP(A-SAP)and the acrylic-attapulgite hybridized SAP(C-SAP)had the stronger potential ability for soil improvement.A-SAP had the best water absorption and water retention capacity,and its water absorption can reach 266 g water/g SAP.The reusability and temperature resistance of C-SAP were the best.After 13 repetitions of absorption and release of water,the water absorption reduction rate and mass loss rate of C-SAP were the lowest,8.9% and 35.9%,respectively,meanwhile,the effect of SAP water absorption was also minimal.Moreover,on this basis,the effect of SAP on the physical properties of the matrix(saturated water content,field water holding capacity and bulk density)and vertical infiltration(penetration rate and permeability)were investigated by penetrant experiments.When the C-SAP application rate was 0.6?0.9% and the particle size was less than or equal to 12 mesh,the saturated water content and field water holding capacity of the substrate increased 23.8% and 24.6%,respectively.Meanwhile,the infiltration rate of the matrix also reduced.48.5%,and the wicking performance increased 39.3%.Above all,the C-SAP was the most suitable matrix improver for green roofs.This study also studied the effects of C-SAP on physiological and growth indexes of sedum lineare.Application amount and particle size of C-SAP were optimized through membership function method.The results showed that the optimal application amount of C-SAP was 0.6%,and the optimal particle size was 12 mesh.In that case,the membership function value reached the maximum value,and the most significant effect on the growth of the grass was achieved.Based on the results above,the green roof construction of the sage grass was completed and its comprehensive performance was studied.Results showed that the application of C-SAP could significantly improve the quality of green roof turf and the speed of formation,and improve the water-absorbing capacity of green roof matrix.After 8 months of growth,the total growth of the C-SAP group was 33.6% higher than that of the control group,and the growth of the sage was also improved.The application of CSAP increased the level of the chlorophyll content in the leaves and reduced the cell membrane permeability.The formation time(coverage rate was 80%)went down by 10 days.In addition,compared to the control group,the average soil moisture of the C-SAP group increased to 63.3% from 53.3%,and the runoff yield of the C-SAP treatment group went down by 7.4% to 23.1%. |
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