Effect of vapor source - building separation and building construction on soil vapor intrusion as studied with a three-dimensional numerical model
Effect of vapor source - building separation and building construction on soil vapor intrusion as studied with a three-dimensional numerical model
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DOI：
10.1021/eso049781k
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发表时间：
2005-06-15
影响因子：
11.4
通讯作者：
Johnson, PC
中科院分区：
文献类型：
--
作者：
Abreu, LDV;Johnson, PC
土壤蒸气室内空气通路的三维数值模型的开发和使用作为一种工具，以预期尚未测量的蒸气衰减系数，α（室内空气浓度/源蒸气浓度），和蒸气源建筑物的横向分离，蒸气源深度，和建筑结构特性（建筑物基础的深度）的非降解化学品之间的关系。数值模型考虑了扩散和平流输送、多组分系统和反应、空间分布的地基裂缝以及瞬态室内和环境压力波动。涉及蒸汽源和建筑物之间不同横向间距的模拟显示，随着横向间距的增加，α值减小。例如，当位于地面以下8 m处的30 m x 30 m源从建筑物边缘移位20 m时，α小2个数量级。对于较浅的源深度，随着横向间隔的增加，a的减小更大。例如，当位于地面以下3米处的30米x 30米的源从建筑物边缘移位20米时，α类似于小5个数量级。为了帮助可视化改变蒸汽源-建筑物间隔的影响，针对从30 m x 30 m源和10 m x 10 m建筑物占地面积中心并置到源定位偏移50 m的情况的一系列横向间隔，给出了水平和垂直横截面的归一化蒸汽浓度等值线图。模拟涉及地下室和楼板上的等级建设产生类似的趋势。此外，当建筑物被过压以产生1-3 L/min量级的土壤气体流出时，相对于零建筑物欠压下的侵入率，室内空气的排放减少了超过5个数量级。结果是特定的模拟，涉及均匀的土壤性质，非降解化学品，稳定的源浓度和建筑物欠压，以及在这项工作中研究的几何形状。
A three-dimensional numerical model of the soil vapor-to-indoor air pathway is developed and used as a tool to anticipate not-yet-measured relationships between the vapor attenuation coefficient, alpha (indoor air concentration/source vapor concentration), and vapor source-building lateral separation, vapor source depth, and building construction characteristics (depth of building foundation) for nondegrading chemicals. The numerical model allows for diffusive and advective transport, multicomponent systems and reactions, spatially distributed foundation cracks, and transient indoor and ambient pressure fluctuations, Simulations involving different lateral separations between the vapor source and building show decreasing alpha values with increasing lateral separation. For example, alpha is 2 orders of magnitude less when a 30 m x 30 m source located 8 m below ground surface is displaced from the edge of the building by 20 m. The decrease in a with increasing lateral separation is greater for shallower source depths. For example, alpha is similar to 5 orders of magnitude less when a 30 m x 30 m source located 3 m below ground surface is displaced from the edge of the building by 20 m. To help visualize the effects of changing vapor source-building separations, normalized vapor concentration contour plots for both horizontal and vertical cross sections are presented for a sequence of lateral separations ranging from the case in which the 30 m x 30 m source and 10 m x 10 m building footprint centers are collocated to shifting of the source positioning by 50 m. Simulations involving basement and slab-on-grade constructions produce similar trends. In addition, when buildings are overpressurized to create outflow to soil gas on the order of 1-3 L/min, emissions to indoor air are reduced by over 5 orders of magnitude relative to intrusion rates at zero building underpressurization. The results are specific to simulations involving homogeneous soil properties, nondegrading chemicals, steady source concentrations and building underpressurizations, and the geometries studied in this work.