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Title: Measuring Spatial Variability of Vapor Flux to Characterize Vadose-zone VOC Sources: Flow-cell Experiments

A method termed vapor-phase tomography has recently been proposed to characterize the distribution of volatile organic contaminant mass in vadose-zone source areas, and to measure associated three-dimensional distributions of local contaminant mass discharge. The method is based on measuring the spatial variability of vapor flux, and thus inherent to its effectiveness is the premise that the magnitudes and temporal variability of vapor concentrations measured at different monitoring points within the interrogated area will be a function of the geospatial positions of the points relative to the source location. A series of flow-cell experiments was conducted to evaluate this premise. A well-defined source zone was created by injection and extraction of a non-reactive gas (SF6). Spatial and temporal concentration distributions obtained from the tests were compared to simulations produced with a mathematical model describing advective and diffusive transport. Tests were conducted to characterize both areal and vertical components of the application. Decreases in concentration over time were observed for monitoring points located on the opposite side of the source zone from the local–extraction point, whereas increases were observed for monitoring points located between the local–extraction point and the source zone. We found that the results illustrate that comparison of temporal concentrationmore » profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.« less
 [1] ;  [1] ;  [2] ;  [2] ;  [3]
  1. Univ. of Arizona, Tucson, AZ (United States). Soil, Water and Environmental Science Dept.
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Univ. of Arizona, Tucson, AZ (United States). Soil, Water and Environmental Science Dept.; Univ. of Arizona, Tucson, AZ (United States). Hydrology and Water Resources Dept.
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0169-7722; 47929; 830403000
Grant/Contract Number:
AC05-76RL01830; 110080; P42 ESO4940
Accepted Manuscript
Journal Name:
Journal of Contaminant Hydrology
Additional Journal Information:
Journal Volume: 167; Journal ID: ISSN 0169-7722
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES Contaminant transport; Intermediate-scale experiments; Vapor phase tomography; Vadose zone; Source characterization; Flow cell experiment; VOC