TY - JOUR
T1 - A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces
AU - Jellali, Salah
AU - Benremita, Hocine
AU - Muntzer, Paul
AU - Razakarisoa, Olivier
AU - Schäfer, Gerhard
N1 - Funding Information:
Support of this research work by the Zone Atelier Franco-Allemande no. 2 (ZAFA2) group of the Institut Franco-Allemand de Recherche sur l'Environnement (IFARE), by the Institut Français de Pétrole (IFP), by Bureau d'études de Géologie Appliquée (BURGEAP), by the German Universities of Stuttgart and Karlsruhe and especially by the Geological Institute of the University of Tübingen is gratefully acknowledged. Financial assistance was given by the Agence de l'Eau Rhin Meuse (AERM), by the “Contrat de Plan Etat (ULP, CNRS, Ministère de l'Aménagement du Territoire et de l'Environnement)-Région Alsace”, and by the “Programme National de Recherche en Hydrologie (PNRH/INSU)”. Special thanks go to D. Berthault, M. Blanchard, C. Ott, J. Rapp and L. Zilliox for their contribution to this work, and thanks are extended to D. Nayagum for checking the English phrasing of the manuscript. Furthermore, the authors would like to thank G. Davis and M.O. Rivett for their valuable comments and suggestions that helped to improve the paper significantly.
PY - 2003/1
Y1 - 2003/1
N2 - A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 l of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary zone into underlying groundwater. The mass transfer of TCE vapors from the vadose zone to the atmosphere was quantified using a vertical flux chamber. A special soil water sampler was used to monitor transport across the capillary fringe. Experimental data indicated that TCE in the unsaturated zone was mainly transported to the atmosphere and this exchange reduced significantly the potential for groundwater pollution. The maximum measured TCE flux to the atmosphere was about 3 g/m2/day. Observed and calculated fluxes based on vertical TCE vapor concentration gradients and Fick's law were in good agreement. This confirms that TCE vapor transport under the experimental conditions was governed essentially by molecular diffusion. TCE vapors also caused a lower, but significant contamination of the underlying groundwater by dispersion across the capillary fringe with a corresponding maximum flux of about 0.1 g/m2/day. This mass transfer to groundwater is partly uncertain due to an inadvertent entry of some nonaqueous phase liquid (NAPL) from the source area into the saturated zone. Application of an analytical solution to estimate the TCE flux from the unsaturated zone to the groundwater indicated that this phenomenon is not only influenced by molecular diffusion but also by vertical dispersion. The mass balance indicates that, under the given experimental conditions (e.g. proximity of the source emplacement relative to the soil surface, relatively high permeable porous medium), nearly 95% of the initial TCE mass was transferred to the atmosphere.
AB - A large-scale experiment was conducted to investigate the transport of trichloroethylene (TCE) vapors in the unsaturated zone and to determine the mass transfer to the groundwater and the atmosphere. The experiment involved injection of 5 l of TCE in the unsaturated zone under controlled conditions, with multidepth sampling of gas and water through the unsaturated zone and across the capillary zone into underlying groundwater. The mass transfer of TCE vapors from the vadose zone to the atmosphere was quantified using a vertical flux chamber. A special soil water sampler was used to monitor transport across the capillary fringe. Experimental data indicated that TCE in the unsaturated zone was mainly transported to the atmosphere and this exchange reduced significantly the potential for groundwater pollution. The maximum measured TCE flux to the atmosphere was about 3 g/m2/day. Observed and calculated fluxes based on vertical TCE vapor concentration gradients and Fick's law were in good agreement. This confirms that TCE vapor transport under the experimental conditions was governed essentially by molecular diffusion. TCE vapors also caused a lower, but significant contamination of the underlying groundwater by dispersion across the capillary fringe with a corresponding maximum flux of about 0.1 g/m2/day. This mass transfer to groundwater is partly uncertain due to an inadvertent entry of some nonaqueous phase liquid (NAPL) from the source area into the saturated zone. Application of an analytical solution to estimate the TCE flux from the unsaturated zone to the groundwater indicated that this phenomenon is not only influenced by molecular diffusion but also by vertical dispersion. The mass balance indicates that, under the given experimental conditions (e.g. proximity of the source emplacement relative to the soil surface, relatively high permeable porous medium), nearly 95% of the initial TCE mass was transferred to the atmosphere.
KW - Aquifer
KW - Capillary fringe
KW - Experimental site
KW - Mass transfer
KW - Trichloroethylene
KW - Vapors
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UR - http://www.scopus.com/inward/citedby.url?scp=0037210240&partnerID=8YFLogxK
U2 - 10.1016/S0169-7722(02)00062-1
DO - 10.1016/S0169-7722(02)00062-1
M3 - Article
C2 - 12498573
AN - SCOPUS:0037210240
SN - 0169-7722
VL - 60
SP - 31
EP - 53
JO - Journal of Contaminant Hydrology
JF - Journal of Contaminant Hydrology
IS - 1-2
ER -