Three-dimensional vapor intrusion modeling approach that combines wind and stack effects on indoor, atmospheric, and subsurface domains

Abstract

Vapor intrusion exposure risks are difficult to characterize due to the role of atmospheric, building and subsurface processes. This study presents a three-dimensional VI model that extends the common subsurface fate and transport equations to incorporate wind and stack effects on indoor air pressure, building air exchange rate (AER) and indoor contaminant concentration to improve VI exposure risk estimates. The model incorporates three modeling programs: 1) COMSOL Multiphysics to model subsurface fate and transport processes, 2) CFD0 to model atmospheric air flow around the building, and 3) CONTAM to model indoor air quality. The combined VI model predicts AER values, zonal indoor air pressures and zonal indoor air contaminant concentrations as a function of wind speed, wind direction and outdoor and indoor temperature. Steady state modeling results for a single-story building with a basement demonstrate that wind speed, wind direction and opening locations in a building play important roles in changing the AER, indoor air pressure, and indoor air contaminant concentration. Calculated indoor air pressures ranged from approximately −10Pa to +4Pa depending on weather conditions and building characteristics. AER values, mass entry rates and indoor air concentrations vary depending on weather conditions and building characteristics. The presented modeling approach can be used to investigate the relationship between building features, AER, building pressures, soil gas concentrations, indoor air concentrations and VI exposure risks.

Observation of Conditions Preceding Peak Indoor Air Volatile Organic Compound Concentrations in Vapor Intrusion Studies

“…The dominant effect can be determined by the balance in leakage area between ceiling, walls, flue and floor (Song et al 2014). Recent three‐dimensional modeling efforts have also shown that indoor concentrations vary in complex ways with wind speed, direction and the location of major openings in the building envelope (Shirazi and Pennell 2017; Shirazi et al 2020).…”

Chlorinated vapor intrusion indicators, tracers, and surrogates (ITS): Supplemental measurements for minimizing the number of chemical indoor air samples—Part 1: Vapor intrusion driving forces and related environmental factors

“…This evidence could be understood considering CSM of CVI where wind speed and direction is only one component of VI driving forces and the number of other features along the pathway affecting indoor concentrations, including for example, details of the building condition and behavior as well as other VI driving forces discussed previously. The evidence for wind as a unitary indicator of VI concentrations is complex in that localized building‐specific winds and their effects can be influenced by topography, vegetation, building design and condition, orientation to the wind (Shirazi & Pennell, ; U.S. EPA, ), and, possibly, fluctuation of winds (DeVaull, ; Luo, ; Luo, Dahlen, Johnson, Peargin, & Creamer, ; U.S. EPA, ).…”

Temporal Variability in an Industrial Building—Time Series and Machine Learning Analysis

“…Furthermore, buildings do not have a significant capacity to “store” or delay static pressure changes (that would be analogous to heat capacity), but soils do. DPs are influenced by many factors other than changes in static pressure, such as temperature differences and winds that are generated by meteorological processes at a great distance away from the building (U.S. EPA 2012b; Shirazi and Pennell 2017).…”