长三角地区填埋场ET封顶系统的性能评价
Evaluation of evapotranspiration covers of landfills in Yangtze River delta region
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摘要: 从ET(evapotranspiration,腾发)封顶系统工作机理出发,根据苏州市气象资料,首先用Penman公式计算ET封顶的潜在腾发量,然后依次求解植被截留量、土面蒸发量、植被蒸腾量和地表径流量,从而求得净入渗量;将净入渗量作为边界条件,选取典型参数分别建立单一土层型ET封顶和毛细阻滞型ET封顶的非饱和渗流模型,分析得到这两种封顶内的水分运移规律,并对其性能进行评价。分析结果表明,蒸发蒸腾对ET封顶中的水分运移起决定性作用,封顶中浅部土体含水率受降雨和腾发作用影响显著,而底部含水率不变化或变化很小,蓄水–释水循环主要发生在植被根系发育区。植被良好、根系深度50 cm的ET封顶系统累积透水量很小,在长三角地区气象条件下能满足设计要求,其中毛细阻滞型ET封顶的累积透水量小于单一土层型,这两种ET封顶减小降雨入渗的性能均优于传统压实黏土封顶。Abstract: Based on the mechanism of evapotranspiration(ET) covers,the plant interception,soil evaporation,ET,runoff and net infiltration are calculated considering the Penman’s potential ET.The calculated net infiltration is input into unsaturated flow models as boundary conditions to simulate the moisture transport and evaluate the performance of a monolithic cover and a capillary cover.The analytic results show that the ET is crucial to the moisture transport in ET covers.The moisture content of shallow soils is sensitive to the variation of rainfall and ET,whereas the moisture content of soils in the bottom remains almost unchanged.The storage and release of infiltrated water happen mainly within the root depth.The ET covers with a good stand of plants and a root depth of 50 cm are applicable to the Yangtze River delta region.The ET covers have advantages over conventional landfill covers in reducing rainfall percolation.