This paper presents model simulation results of vapor intrusion into structures built atop sites contaminated with volatile or semi-volatile chemicals of concern. A three-dimensional finite element model was used to investigate the importance of factors that could influence vapor intrusion when the site is characterized by non-homogeneous soils. Model simulations were performed to examine how soil layers of differing properties alter soil gas concentration profiles and vapor intrusion rates into structures. The results illustrate difference in soil gas concentration profiles and vapor intrusion rates between homogeneous and layered soils. The findings support the need for site conceptual models to adequately represent the site's geology when conducting site characterizations, interpreting field data and assessing the risk of vapor intrusion at a given site. For instance, in layered geologies, a lower permeability and diffusivity soil layer between the source and building often limits vapor intrusion rates, even if a higher permeability layer near the foundation permits increased soil gas flow rates into the building. In addition, the presence of water-saturated clay layers can considerably influence soil gas concentration profiles. Therefore, interpreting field data without accounting for clay layers in the site conceptual model could result in inaccurate risk calculations. Important considerations for developing more accurate conceptual site models are discussed in light of the findings.

中文翻译：

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使用三维数值模型模拟非均质土壤的蒸汽侵入过程。

本文介绍了蒸汽侵入在受关注的挥发性或半挥发性化学品污染的场地上建造的结构的模型模拟结果。当场地为非均质土壤时，使用三维有限元模型研究可能影响蒸汽侵入的因素的重要性。进行模型模拟以检查不同性质的土壤层如何改变土壤气体浓度分布和蒸汽侵入结构的速率。结果说明了均质土壤和层状土壤之间土壤气体浓度分布和蒸汽侵入率的差异。研究结果支持在进行场地特征描述时需要场地概念模型来充分代表场地的地质，解释现场数据并评估给定地点的蒸汽侵入风险。例如，在分层地质中，源和建筑物之间较低渗透率和扩散率的土壤层通常会限制蒸汽侵入率，即使地基附近较高的渗透率层允许增加进入建筑物的土壤气体流速。此外，水饱和粘土层的存在会显着影响土壤气体浓度分布。因此，解释现场数据而不考虑场地概念模型中的粘土层可能会导致风险计算不准确。根据调查结果讨论了开发更准确的概念站点模型的重要考虑因素。源和建筑物之间较低渗透性和扩散性的土壤层通常会限制蒸汽侵入率，即使地基附近较高的渗透性层允许增加进入建筑物的土壤气体流速。此外，水饱和粘土层的存在会显着影响土壤气体浓度分布。因此，解释现场数据而不考虑场地概念模型中的粘土层可能会导致风险计算不准确。根据调查结果讨论了开发更准确的概念站点模型的重要考虑因素。源和建筑物之间较低渗透性和扩散性的土壤层通常会限制蒸汽侵入率，即使地基附近较高的渗透性层允许增加进入建筑物的土壤气体流速。此外，水饱和粘土层的存在会显着影响土壤气体浓度分布。因此，解释现场数据而不考虑场地概念模型中的粘土层可能会导致风险计算不准确。根据调查结果讨论了开发更准确的概念站点模型的重要考虑因素。水饱和粘土层的存在会显着影响土壤气体浓度分布。因此，解释现场数据而不考虑场地概念模型中的粘土层可能会导致风险计算不准确。根据调查结果讨论了开发更准确的概念站点模型的重要考虑因素。水饱和粘土层的存在会显着影响土壤气体浓度分布。因此，解释现场数据而不考虑场地概念模型中的粘土层可能会导致风险计算不准确。根据调查结果讨论了开发更准确的概念站点模型的重要考虑因素。