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Observation of Conditions Preceding Peak Indoor Air Volatile Org Compound Concentrations in Vapor Intrusion Studies
Citation:
Lutes, C., C. Holton, B. Schumacher, J. Zimmerman, A. Kondash, AND R. Truesdale. Observation of Conditions Preceding Peak Indoor Air Volatile Org Compound Concentrations in Vapor Intrusion Studies. Groundwater Monitoring & Remediation. Wiley-Blackwell Publishing, Hoboken, NJ, 41(2):99-111, (2021). https://doi.org/10.1111/gwmr.12434
Impact/Purpose:
This paper focuses on events preceding observations of the upper end of the indoor air VOC concentration distribution and on the primary research question of whether the temporal trend of any of the candidate indicators (T, indoor/outdoor ΔT, indoor/outdoor ΔP, subslab/indoor ΔP, or indoor radon) reliably predict volatile organic chemical vapor intrusion in a given structure and site. Other questions include 1) whether those relationships have the same form or shape for different VI conceptual site models and, 2) can the ΔP driver be predicted based on observed or forecasted barometric pressure? Observation of these indicators and tracers in parallel with fewer chemical measurements of indoor air concentration can provide greater evidence-based understanding of vapor intrusion processes in a specific building and thus improve site management.
Description:
Temporal and spatial variability of indoor air volatile organic compound (VOC) concentrations can complicate vapor intrusion (VI) assessment and decision-making. Indicators and tracers (I&T) of VI, such as differential temperature, differential pressure, and indoor radon concentration, have been proposed as low-cost lines of evidence to support sample collection scheduling and interpretation of indoor air VOC sampling results. This study compares peak, temporal indoor air chlorinated VOC concentrations and I&T conditions before and during those peaks at five residential and industrial VI sites. The sites differ geographically and in their VI conceptual site models. Relative to site-specific baseline values, the results show that cold or falling outdoor temperatures, rising cross slab differential pressure, and increasing indoor radon concentrations can be predictive of peak indoor air VOC concentrations. However, cold outdoor air temperature was not useful at one site where elevated shallow soil temperature was a better predictor. Correlations of peak VOC concentrations to elevated or rising barometric pressure and low wind speed were also observed, but with exceptions. This study shows how the independent variables that control peak indoor air VOC concentrations at VI sites are specific to building types, climates, and VI conceptual site models. More I&T measurements are needed to identify scenario-specific baseline and peak related I&T conditions to improve future VI decision-making.
URLs/Downloads:
DOI: Observation of Conditions Preceding Peak Indoor Air Volatile Org Compound Concentrations in Vapor Intrusion Studies