绿色屋面截流减污效应及机理研究

The technology of green roof has received increasingly important recently. Previous studies more focus on energy conservation and landscape value of green roof, rather than the mechanism of its role on runoff intercepting and pollution reducing, which resulted in difficultly of evaluating the effect of green roof for non-point pollution control. In this study, specific to the contamination of rainfall runoff that cause by urbanization, basing on screening and optimizing the substrates of green roof and conducting the green roof with different thickness substrates and control roof, we will carry out systematic study on hydrological dynamic processes, water quality, sources apportionment, and runoff intercepting and pollution reducing of rainfall runoff on green roof by both sampling natural rainfall and artificial simulation of rainfall. We aim at the points below: 1) Exploring the influencing mechanism of composition of substrates to runoff water quality and processes. 2) Clarifying the characteristic of sources and sinks for water quality parameters of green roof runoff. 3) Identifying the pollution sources of the C and N in the green roof runoff. 4) Analyzing the key factors which influence the water quality of rainfall runoff and capacity of runoff intercepting and pollution reducing of green roof. 5) Revealing the mechanism of runoff intercepting and pollution reducing of green roof. The results in the study would provide the scientific basis to control non-point pollution, to design and apply green roof, and then to offer the practical basis for water source conservation and water contamination control of the water shortage cities in Northern, China.

绿色屋面技术越来越受到重视。以往研究更多关注于绿色屋面的节能和景观价值，而对其截流减污机理的研究较少，很难正确评价绿色屋面对面源污染的控制效果。本项目针对城市化造成的降雨径流污染，首先筛选和优化绿色屋面基质，并自制不同厚度基质层的绿色屋面和控制屋面，通过对自然降雨和人工模拟降雨下的绿色屋面径流采样观测分析，系统开展绿色屋面降雨径流的水文动态过程、径流水质特点、污染源解析以及截流减污特性的研究，探讨绿色屋面基质层组成对降雨径流水质及径流过程的影响机制，阐明绿色屋面径流各水质参数的源汇特征，定量解析绿色屋面径流中C和N的污染来源，分析影响绿色屋面径流水质及截流减污能力的关键因素，揭示绿色屋面截流减污的机理，为面源污染的控制、绿色屋面结构设计及推广应用提供科学依据，进而也为北方缺水城市的水源地保护和污染控制提供依据。

随着城市化的快速发展，不透水地表面积所占比例越来越高，改变了原有的水文循环过程，增加了地表径流量，对城市雨洪管理带来了巨大冲击，由暴雨径流引发的城市面源污染问题逐渐成为人们关注的热点问题。绿色屋面技术具有多重生态效益，在城市雨洪管理中能够发挥重要作用。本项目针对城市化造成的降雨径流污染，系统开展绿色屋面降雨径流的水文动态过程、径流水质特点、污染源解析以及截流减污特性的研究，结果表明：1）商业基质的径流滞留率最高，达到48.6%，商业基质屋面能够有效地中和实验水的pH，且径流中EC、TP和TSS浓度与火山岩基质屋面径流无明显差异。因此，商业基质是较为适宜的绿色屋面基质。2）商业基质添加生物炭对屋面径流滞留率无显著影响；但是，商业基质中添加生物炭可以显著的降低径流中营养物质（TN）和有机污染物（COD）的浓度和污染负荷。3)基于监测的93场降雨事件分析表明：绿色屋面的平均径流滞留率达到53.4%；基于径流水质，绿色屋面对径流中pH、TSS、TN、NO3--N的浓度无显著影响，但是，绿色屋面是径流中EC和NH4+-N的汇，是COD和TP的污染源；基于污染负荷，绿色屋面1与沥青屋面相比，径流中TN、NH4+-N、NO3--N和TSS的污染负荷分别消减了43%、58%、35%和71%，但是COD和TP的污染负荷增加了227%和400%；绿色屋面1和降雨相比，径流中TN、NH4+-N、NO3--N和TSS的污染负荷分别消减了64%、76%、77%和48%，但是COD和TP的污染负荷增加了5139%和400%；降雨特征对绿色屋面径流滞留率呈现显著影响，但对径流水质影响不显著。研究结果可以为绿色屋面的科学构建和城市暴雨径流管理与控制提供科学依据，并为我国海绵城市的建设提供重要的数据支撑