College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.
Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
Environ Sci Pollut Res Int. 2020 Oct;27(28):35416-35427. doi: 10.1007/s11356-020-09746-5. Epub 2020 Jun 27.
Vapor intrusion (VI) risk assessments determine the cleanup level of groundwater in the absence of ingestion. In recent VI investigations, the building pressure cycling (BPC) method has been applied to help minimize ambiguity caused by temporal variability of indoor air samples that are important to risk assessments, and, consequently, determine groundwater cleanup level accurately. In this study, we use a three-dimensional numerical model to examine the dynamic migration of VOCs from groundwater after the application of BPC. First, we validated the numerical model with field measurements. Then, the verified model is used to investigate the effects of site-specific features in determining the performance of BPC operation. At last, we summarize past field applications of BPC to examine the simulated results. Our study indicates that the BPC-induced indoor depressurization can increase the building loading rate in the first 2-3 h, which would then drop to 2-3 times of that with natural conditions in most cases of groundwater contamination. In some cases involving a strong source, e.g., a vapor source above the capillary fringe or a groundwater source with sandy soil above the groundwater level, the normalized building loading rates can be maintained as high as 4-9 without decrease after the first 2-3 h. Significantly higher increase in building loading rate may indicate a potential presence of a preferential pathway between the groundwater contamination and concerned building.
蒸气入侵 (VI) 风险评估在没有摄入的情况下确定地下水的清理水平。在最近的 VI 调查中，建筑压力循环 (BPC) 方法已被应用于帮助最小化室内空气样本的时间变异性引起的歧义，这对于风险评估很重要，从而准确确定地下水清理水平。在这项研究中，我们使用三维数值模型来研究 BPC 应用后地下水中 VOCs 的动态迁移。首先，我们使用现场测量来验证数值模型。然后，使用经过验证的模型来研究确定 BPC 操作性能的特定地点特征的影响。最后，我们总结了过去 BPC 的现场应用，以检验模拟结果。我们的研究表明，BPC 引起的室内减压会在最初的 2-3 小时内增加建筑加载率，然后在大多数地下水污染的情况下降至自然条件下的 2-3 倍。在涉及强源的情况下，例如毛细带上方的蒸气源或高于地下水位的含沙土壤上的地下水源，归一化的建筑加载率在最初的 2-3 小时后可能保持高达 4-9 倍不变。建筑加载率的显著增加可能表明地下水污染与相关建筑物之间存在潜在的优先途径。
