Lessons Learned from Radon at a Chlorinated Vapor Intrusion Research House
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Indoor air and subslab soil gas volatile organic compound (VOC) samples are recognized as important lines of evidences for vapor intrusion (VI) investigations.

These samples can be confounded by temporal and spatial variability, as well as indoor and ambient VOC sources. Short-term sampling (e.g., 8- to 24-hour for indoor air samples) under natural conditions continue to be the most common sampling approach for assessing the VI pathway. Radon is a naturally occurring radioactive gas found in soil that can be used as a low-cost indicator and tracer of VOC vapors, since it may migrate along the same pathway(s) as VOCs for some sites and indoor sources are often considered negligible. More recently, radon has been proposed as a potential line of evidence for guiding VOC sampling time and location.

This study provides an evaluation of radon as an indicator and tracer for improving confidence in decision making using short-term indoor air and subslab soil gas sampling results. Concurrent real-time indoor air VOC and radon concentration data, along with monthly multi-depth soil gas surveys, were collected over a two-year period at a VI research house. Preliminary analyses show that indoor air temporal variations of TCE and radon follow similar long-term (i.e., seasonal) and short-term patterns; however, differences in subsurface distribution and soil gas-to-indoor air attenuation factors related to source characteristics and preferential VOC vapor transport have also been observed. The results of this study highlight the utility of radon as an indicator and tracer in VI investigations, as well as the limitations of radon as a surrogate for VOC measurements.

Publication Summary

  • Geosyntec Authors: Chase Holton
  • All Authors: Chase Holton
  • Title: The Association for Environmental Health and Sciences (AEHS) Foundations' 30th Annual International Conference on Soil, Water, Energy, and Air
  • Event or Publication: Event
  • Practice Areas: Vapor Intrusion Assessment and Remediation
  • Citation: Geosyntec practitioners will present at the Association for Environmental Health and Sciences (AEHS) Foundations' 30th Annual International Conference on Soil, Water, Energy, and Air on March 16-19, 2020. The conference will be held at the DoubleTree Mission Valley in San Diego, California.
  • Date: March 16-19, 2020
  • Location: San Diego, California
  • Publication Type: Platform Presentation