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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- 作者：Lilian D. V. Abreu and Paul C. Johnson
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：June 15, 2005
- 年：2005
- 卷：39
- 期：12
- 页码：4550 - 4561
- 全文大小：409K
- 年卷期：v.39,no.12(June 15, 2005)
- ISSN：1520-5851
文摘
A three-dimensional numerical model of the soil vapor-to-indoor air pathway is developed and used as a tool toanticipate not-yet-measured relationships between the vaporattenuation coefficient, 
(indoor air concentration/source vapor concentration), and vapor source-buildinglateral separation, vapor source depth, and buildingconstruction characteristics (depth of building foundation)for nondegrading chemicals. The numerical modelallows for diffusive and advective transport, multicomponentsystems and reactions, spatially distributed foundationcracks, and transient indoor and ambient pressurefluctuations. Simulations involving different lateral separationsbetween the vapor source and building show decreasing values with increasing lateral separation. For example, is 2 orders of magnitude less when a 30 m × 30 msource located 8 m below ground surface is displacedfrom the edge of the building by 20 m. The decrease in with increasing lateral separation is greater for shallowersource depths. For example, is ~5 orders of magnitudeless when a 30 m × 30 m source located 3 m belowground surface is displaced from the edge of the buildingby 20 m. To help visualize the effects of changing vaporsource-building separations, normalized vapor concentrationcontour plots for both horizontal and vertical crosssections are presented for a sequence of lateral separationsranging from the case in which the 30 m × 30 m sourceand 10 m × 10 m building footprint centers are collocatedto shifting of the source positioning by 50 m. Simulationsinvolving basement and slab-on-grade constructions producesimilar trends. In addition, when buildings are overpressurized to create outflow to soil gas on the order of 1-3L/min, emissions to indoor air are reduced by over 5 ordersof magnitude relative to intrusion rates at zero buildingunderpressurization. The results are specific to simulationsinvolving homogeneous soil properties, nondegradingchemicals, steady source concentrations and buildingunderpressurizations, and the geometries studied in thiswork.
(indoor air concentration/source vapor concentration), and vapor source-buildinglateral separation, vapor source depth, and buildingconstruction characteristics (depth of building foundation)for nondegrading chemicals. The numerical modelallows for diffusive and advective transport, multicomponentsystems and reactions, spatially distributed foundationcracks, and transient indoor and ambient pressurefluctuations. Simulations involving different lateral separationsbetween the vapor source and building show decreasing values with increasing lateral separation. For example, is 2 orders of magnitude less when a 30 m × 30 msource located 8 m below ground surface is displacedfrom the edge of the building by 20 m. The decrease in with increasing lateral separation is greater for shallowersource depths. For example, is ~5 orders of magnitudeless when a 30 m × 30 m source located 3 m belowground surface is displaced from the edge of the buildingby 20 m. To help visualize the effects of changing vaporsource-building separations, normalized vapor concentrationcontour plots for both horizontal and vertical crosssections are presented for a sequence of lateral separationsranging from the case in which the 30 m × 30 m sourceand 10 m × 10 m building footprint centers are collocatedto shifting of the source positioning by 50 m. Simulationsinvolving basement and slab-on-grade constructions producesimilar trends. In addition, when buildings are overpressurized to create outflow to soil gas on the order of 1-3L/min, emissions to indoor air are reduced by over 5 ordersof magnitude relative to intrusion rates at zero buildingunderpressurization. The results are specific to simulationsinvolving homogeneous soil properties, nondegradingchemicals, steady source concentrations and buildingunderpressurizations, and the geometries studied in thiswork.