TY - JOUR
T1 - Measuring spatial variability of vapor flux to characterize vadose-zone VOC sources
T2 - Flow-cell experiments
AU - Mainhagu, J.
AU - Morrison, C.
AU - Truex, M.
AU - Oostrom, M.
AU - Brusseau, M. L.
N1 - Funding Information:
This work was funded through the Department of Energy (contract no. 110080 ) and the NIEHS Superfund Research Program grant no. P42 ESO4940 . The authors would like to thank the members of the Contaminant Transport group for their help and support and Guzel Tartakovsky from PNNL for her help. The authors would also like to thank Thomas Wietsma of PNNL for his involvement in the design and assembly of the flow cell. We thank the reviewers for their constructive comments.
PY - 2014/10/15
Y1 - 2014/10/15
N2 - 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. The results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.
AB - 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. The results illustrate that comparison of temporal concentration profiles obtained at various monitoring points gives a general indication of the source location with respect to the extraction and monitoring points.
KW - Flow cell experiment
KW - Source characterization
KW - VOC
KW - Vadose zone
KW - Vapor phase tomography
UR - http://www.scopus.com/inward/record.url?scp=84906841393&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84906841393&partnerID=8YFLogxK
U2 - 10.1016/j.jconhyd.2014.07.007
DO - 10.1016/j.jconhyd.2014.07.007
M3 - Article
C2 - 25171394
AN - SCOPUS:84906841393
VL - 167
SP - 32
EP - 43
JO - Journal of Contaminant Hydrology
JF - Journal of Contaminant Hydrology
SN - 0169-7722
ER -