April 3, 2020

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Elham Shirazi and Chase Holton Co-Authored Vapor Intrusion Modeling Study Published in Environmental Science: Processes & Impacts

Elham Shirazi, Ph.D. (California) and Chase Holton, Ph.D., P.E. (Colorado) coauthored a paper entitled "Comparison of Modeled and Measured Indoor Air Trichloroethene (TCE) Concentrations at a Vapor Intrusion Site: Influence of Wind, Temperature, and Building Characteristics" that was recently published in the Royal Society of Chemistry's Environmental Science: Processes & Impacts journal. Elham and Chase's coauthors were the University of Kentucky's Kelly G Pennell, Ph.D., Gregory S. Hawk, and Arnold Stromberg, Ph.D.

Elham Shirazi is a Senior Staff Professional based in California with a focus on modeling approaches to address the vapor intrusion pathways. Chase Holton is a Senior Environmental Engineer based in Colorado focused on environmental research and consulting, with expertise and experience in vapor intrusion, site characterization, and soil and groundwater remediation.

The Royal Society of Chemistry connects scientists with each other and society as a whole, so they can do their best work and make discoveries and innovation happen. The society publishes the Environmental Science: Processes & Impacts journal which presents high quality papers in all areas of the environmental chemical sciences, including chemistry of the air, water, soil and sediment. The journal welcome studies on the environmental fate and effects of anthropogenic and naturally occurring contaminants, both chemical and microbiological, as well as related natural element cycling processes.


There is a lack of vapor intrusion (VI) models that reliably account for weather conditions and building characteristics, especially at sites where active alternative pathways, such as sewer connections and other preferential pathways, are present. Here, a method is presented to incorporate freely available models, CONTAM, and CFD0, to estimate site-specific building air exchange rates (AERs) and indoor air contaminant concentrations by accounting for weather conditions and building characteristics at a well-known VI site with a land drain preferential pathway. To account for uncertainty in model input parameters that influence indoor air chlorinated volatile organic compound (CVOC) concentration variability, this research incorporated Monte Carlo simulations and compared model results with retrospective field data collected over approximately 1.5 years from the study site. The results of this research show that mass entry rates for TCE are likely influenced by indoor air pressures that can be modeled as a function of weather conditions (over seasons) and building characteristics. In addition, the results suggest that temporal variability in indoor air TCE concentrations is greatest (modeled and measured) due to the existence of a land drain, which acts as a preferential pathway, from the subsurface to the granular fill beneath the floor slab. The field data and modeling results are in good agreement and provide a rare comparison of field data and modeling results for a VI site. The modeling approach presented here offers a useful tool for decision makers and VI practitioners as they assess these complex and variable processes that have not been incorporated within other VI models.

More Information

Learn more about the article: https://pubs.rsc.org/en/content/articlelanding/2020/em/c9em00567f#!divAbstract
Learn more about the journal: Environmental Science: Processes & Impacts
Learn more about the Royal Society of Chemistry: https://www.rsc.org/about-us/
For consultation regarding vapor intrusion modeling, contact Elham Shirazi  at This email address is being protected from spambots. You need JavaScript enabled to view it. or Chase Holton at This email address is being protected from spambots. You need JavaScript enabled to view it..
Learn more about Elham Shirazi: https://www.linkedin.com/in/elham-shirazi-57092195/
Learn more about Chase Holton: https://www.linkedin.com/in/chase-holton-59617559/