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Impact of Hurricanes, Tropical Storms, and Coastal Extratropical Storms on Indoor Air VOC Concentrations
Citation:
Lutes, C., V. Boyd, G. Buckley, L. Levy, K. Bronstein, J. Zimmerman, A. Williams, AND B. Schumacher. Impact of Hurricanes, Tropical Storms, and Coastal Extratropical Storms on Indoor Air VOC Concentrations. Groundwater Monitoring & Remediation. Wiley-Blackwell Publishing, Hoboken, NJ, 44(2):101-117, (2024). https://doi.org/10.1111/gwmr.12642
Impact/Purpose:
This paper examines the causes of temporal variability of volatile organic compound (VOC) concentrations in indoor air (IA) samples collected as part of vapor intrusion (VI) investigations. The analyses presented herein rely on a high-resolution VOC dataset obtained from an industrial warehouse-type building located in coastal Virginia, below which elevated VOC concentrations in the subsurface were identified. This paper focuses on short-term variations over timelines of hours to days that may be attributable to hurricanes, tropical storms, or extratropical coastal storms. Through measurements of radon and VOC VI under various conditions, several studies have provided insights on the complexity of temporal variability of indoor air concentrations attributable to VI. State and federal guidance documents tend to emphasize the role of the differential temperature–driven stack effect in controlling seasonal indoor air concentration changes (US EPA 2012a, 2015a, Levy 2019). Two radon studies have demonstrated that barometric pressure fluctuations can affect the transport of soil gas into buildings (Nazaroff et al. 1987, Robinson and Sextro 1997). The impact of barometric pressure fluctuations on indoor air is influenced by the interaction of the building’s structures and conditions, as well as other concurrent factors, such as wind (Luo et al. 2009). Changes in atmospheric conditions (e.g., pressure, wind) and building conditions (e.g., open doors and windows) may temporarily over- or under-pressurize a building. Based on long-term differential pressure datasets at an Indianapolis study site at which radon and VOCs were measured in subslab and indoor air, other factors that can influence temporal and spatial variability in soil gas and indoor air concentrations include (US EPA 2012b, 2015b, 2015c): Fluctuations in building air exchange rates due to resident behavior/HVAC operations Fluctuations in outdoor/indoor temperature difference Rainfall events and resultant infiltration and fluctuations in the water table elevation Snow/ice events. Thus, VI has been shown to be a multifactorial process and a strong correlation between any one independent variable and indoor air VOC concentration is generally not expected. Furthermore, the same factors that increase the entry rate of soil gas into the building and thus increase indoor air concentrations can often increase the air exchange rate, counteracting the effect on indoor air concentrations. The relative strength of those two effects depends on building envelope–specific factors.
Description:
Understanding vapor intrusion (VI) temporal variability is key for the design of sampling strategies intended to assess reasonable maximum exposure of indoor air concentrations of volatile organic compounds (VOCs) as well as risk evaluation and mitigation planning. VI temporal variability has previously been shown to be dependent on the complex interactions of multiple independent variables—meteorological, hydrogeological, and human behavioral. Several meteorological variables, including barometric pressure, wind speed, and rainfall, are linked during tropical and extratropical storm events. High-frequency meteorological and indoor VOC data from a series of seven tropical storms and four extratropical storms were collected at a single industrial building with multiple heating, ventilation, and air conditioning (HVAC) zones. The storms and sampling zones showed a variety of effects on trichloroethylene (TCE) concentrations in indoor air. In one zone (supply room), increases in TCE concentrations often, but not always, closely coincided with decreasing barometric pressure, sustained wind speeds over 32 km/h (20 mph), and differential pressures indicating subslab to indoor flow. A second zone, in a restroom, did not show a consistent pattern of temporal correlation between meteorological factors and indoor air concentrations. While peak indoor air concentrations may be associated with the passage of cyclonic storms at some sampling locations, this does not appear to be generalizable to all sampling locations. The observed increase in indoor air concentration potentially attributable to these storms is typically less than an order of magnitude and the duration ranges from a day to a week.
URLs/Downloads:
DOI: Impact of Hurricanes, Tropical Storms, and Coastal Extratropical Storms on Indoor Air VOC Concentrations