title: Using vapor phase tomography to measure the spatial distribution of vapor concentrations and flux for vadose-zone VOC sources.
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.
authors.affiliation: Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ 85721, United States.
authors.forename: J
authors.initials: J
authors.lastname: Mainhagu
authors.affiliation: Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ 85721, United States.
authors.forename: C
authors.initials: C
authors.lastname: Morrison
authors.affiliation: Soil, Water and Environmental Science Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ 85721, United States; Hydrology and Water Resources Department, School of Earth and Environmental Sciences, University of Arizona, Tucson, AZ 85721, United States. Electronic address: Brusseau@email.arizona.edu.
authors.forename: M L
authors.initials: ML
authors.lastname: Brusseau
mesh_terms: D001130:Arizona; D005740:Gases; D060587:Groundwater; D010539:Permeability; D012997:Solvents / Q000032:analysis / Q000737:chemistry; D014054:Tomography / Q000379:methods*; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry; D060986:Water Wells
chemical_list: D005740:Gases; D012997:Solvents; D055549:Volatile Organic Compounds; D014874:Water Pollutants, Chemical
keywords: DNAPL; Remediation; SVE; Tomography; VOC
references.citation: Vadose Zone J. 2013 Nov 1;12(4):null
references.pmid: 25383058
references.citation: J Contam Hydrol. 2013 Jun;149:1-12
references.pmid: 23528743
references.citation: Ground Water Monit Remediat. 2010 Summer;30(3):57-64
references.pmid: 23516336
references.citation: Chemosphere. 2013 Jan;90(2):459-63
references.pmid: 22921434
references.citation: Ground Water Monit Remediat. 2014 Fall;34(4):23-32
references.pmid: 26069436
references.citation: J Contam Hydrol. 2014 Oct 15;167:32-43
references.pmid: 25171394
references.citation: Environ Sci Technol. 2010 Nov 15;44(22):8609-14
references.pmid: 20954708