Superfund Research Program
Indoor Air Concentration Dynamics and Vapor Intrusion
Project Leader: Eric M. Suuberg
Grant Number: P42ES013660
Funding Period: 2009-2021
Studies and Results
Work proceeded on all of the specific aims, as shown in the corresponding points below:
- New vapor pressure information was obtained on halogenated PACs and on a new class of compounds for the researchers - brominated flame retardants. Also, a summary of information was prepared.
- Modeling work continued and focused on what the implications were for the data contained in the US EPA VI database, and approximation methods were developed to describe key aspects of vapor intrusion.
- The influence of moisture in soil has been examined - in particular, the effects of rainfall.
- The researchers have continued to have close relations to the RI DEM. The researchers are also writing up the field data obtained from the related ARRA project based in Somerville, MA (which is really a MA DEP project).
The significance of this project continues to be in providing fundamental thermodynamic property data on SVOC compounds of environmental health interest. In many cases, no earlier data exist; in other instances, the researchers are contributing to a limited literature database. The researchers have continued to work on the properties of mixtures of PAH and PAC. It has turned out that the phase behavior of mixtures of PAH is far more complicated than they had originally anticipated. As a result of increasing environmental health concerns regarding the brominated flame retardants, the researchers continued to extend their work to this class of compounds. The thermodynamic properties obtained are of significance in the prediction of fate and transport of these materials in the environment.
The second major focus of this project is in the area of vapor intrusion (VI) modeling. As opposed to the SVOC interest in the other portion of this project, this portion of the project has focused mainly on the VI problem associated with VOCs (chlorinated solvents and hydrocarbons). The researchers have incorporated biodegradation into their existing 3-D modeling code, to explore how these processes might influence what is observed. They have been examining the EPA database of VI results in an effort to establish where existing models fail to predict key features of the data. The researchers believe that neglect of a significant diffusional resistance in the capillary zone has resulted in a failure to predict the spread of actual field results. Also, there has been an under-appreciation of the influence of non-uniformity of contaminant concentration in the groundwater plume. They have developed simple semi-empirical approximations to the full 3-D codes so that a computationally simple (but more robust) screening tool be made available to practitioners who must now rely on the 1-D Johnson and Ettinger approach. The researchers have also explored the question of whether rainfall events significantly affect measured soil gas concentrations. They are also in the process of modeling field results from the Somerville, MA vapor intrusion site. Some of these field results have been obtained as part of a related ARRA project (headed by Kelly Pennell of UMASS Dartmouth).