Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2020 Mar 25;710:136309. doi: 10.1016/j.scitotenv.2019.136309. Epub 2019 Dec 30.
In this study, we examine the impact of a building's indoor pressure fluctuations in drawing subsurface volatile contaminants into the building, and how the presence of an impervious pavement surrounding the building influences this. Even in the absence of communication between the subsurface soil gas and ambient air fluctuations of building indoor pressure can cause upward advection of contaminated soil gas from the subfoundation zone into a building. For cases with the paved ground surface, the simulated volumetric soil gas entry rates are lower than steady-state cases with constant -5 indoor-outdoor pressure difference, by at least half an order of magnitude. When the indoor pressure fluctuation rate exceeds about 5 Pa/h (which corresponds a sinusoidal fluctuation with a period of 2 h), the predicted indoor air concentration of paved scenarios will be higher than the conventional case. When both the building foundation and surrounding pavement block diffusional escape of the volatile soil gas contaminants to the atmosphere, high subfoundation soil gas contaminant concentrations can exist, and contaminant entry into the building through foundation breaches is enhanced beyond what would be expected from diffusion as the building undergoes normal pressure cycling. Upward advection into the building may be induced even when the indoor pressure appears, based on limited measurements, to be higher than that in the subslab, particularly when the indoor pressure in the building quickly fluctuates. This represents a limitation on VI mitigation approaches that rely on indoor pressurization, if those approaches cannot at the same time control significant fluctuation of indoor pressure.
在本研究中，我们研究了建筑物内部压力波动对将地下挥发性污染物吸入建筑物的影响，以及建筑物周围不透水路面的存在如何影响这种情况。即使在地下土壤气体与建筑物内部压力波动之间没有沟通的情况下，建筑物内部压力的波动也会导致受污染的土壤气体从基础区域向上对流到建筑物中。对于铺面地面的情况，模拟的体积土壤气体进入率比具有恒定-5 室内外压差的稳态情况低至少一个数量级。当室内压力波动率超过约 5 Pa/h（对应于周期为 2 h 的正弦波动）时，预测的铺面情况下的室内空气浓度将高于常规情况。当建筑物基础和周围铺面阻止挥发性土壤气体污染物扩散到大气中时，可能会存在高的基础下土壤气体污染物浓度，并且当建筑物经历正常的压力循环时，通过基础裂缝进入建筑物的污染物进入量会超过扩散所预期的量。即使根据有限的测量，建筑物内的压力似乎高于地下板下的压力，尤其是当建筑物内的压力快速波动时，也可能会诱导向上进入建筑物的对流。如果 VI 缓解方法不能同时控制室内压力的大幅波动，那么这代表了依赖室内加压的 VI 缓解方法的局限性。
