H43F-1572
Using Vapor Phase Tomography to Measure the Spatial Distribution of Vapor Concentrations and Flux for Vadose-Zone VOC Sources
Thursday, 17 December 2015
Poster Hall (Moscone South)
Jon Mainhagu, University of Arizona, Tucson, AZ, United States, Mark L Brusseau, University of Arizona, Soil, Water, and Environmental Science Department and Hydrology and Water Resource Department, Tucson, AZ, United States and Candice N Morrison, University of Arizona, Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, Tucson, AZ, United States
Abstract:
A test was conducted at a chlorinated-solvent contaminated site in Tucson, AZ, to evaluate the effectiveness of vapor-phase tomography (VPT) for characterizing the distribution of volatile organic contaminants (VOC) in the vadose zone. A soil vapor extraction (SVE) system has been in operation at the site since 2007. Vapor concentration and vacuum pressure were measured at four different depths in each of the four monitoring wells surrounding the extraction well. The test provided a 3D characterization of local vapor concentrations under induced-gradient conditions. Permeability data obtained from analysis of borehole logs were used along with pressure and the vapor-concentration data to determine VOC mass flux within the test domain. A region of higher mass flux was identified in the deepest interval of the S–SW section of the domain, indicating the possible location of a zone with greater contaminant mass. These results are consistent with the TCE-concentration distribution obtained from sediment coring conducted at the site. In contrast, the results of a standard soil gas survey did not indicate the presence of a zone with greater contaminant mass. These results indicate that the VPT test provided a robust characterization of VOC concentration and flux distribution at the site.
