Abstract: Use of Co-Located Data in the Field Validation of Vapor Flux Models for the Estimation of Exposure to Volatile Organic Compounds

SULLIVAN, MICHAEL J., ALEXANDER C. KOPF, RICHARD ANDRACHEK, and PETER J. RAFTERY, Fluor-Daniel-GTI

Volatile organic compounds (VOCs) are present in soil and groundwater at many environmentally-impaired sites throughout the United States. Human exposure to the VOCs can generally occur either through direct media contact (e.g., ingestion of groundwater or soil) or indirectly through inhalation (e.g., volatilization of VOCs from groundwater to indoor air). This paper discusses the use of co-located data in the validation of a vapor flux model for the purpose of estimating indirect exposure to VOCs in contaminated soil and non-potable groundwater. Co-located VOC concentrations were measured as (1) dissolved in groundwater, (2) adsorbed to soil, (3) soil vapor, and (4) surface flux. Geophysical and geochemical properties of soil were also collected for input into the model. The vapor flux model was run to estimate surface VOC flux rates based upon either of three types of sources: soil only, groundwater only, and soil and groundwater. Predicted flux rates were compared to measured flux rates. Measured and predicted flux rates were comparable. The model was then used to predict flux rates at other locations at the contaminated site and potential exposures were estimated. The value of having the co-located data for use in model field validation is discussed in terms of the confidence afforded the reliance upon model-predicted flux rates and exposures.

AAPG Search and Discovery Article #90935©1998 AAPG Pacific Section Meeting, Ventura, California