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Environ Sci Technol

Title:		Equilibrium partitioning of chlorinated solvents in the vadose zone: low f(oc) geomedia
Author(s):		Silva JA; Bruant RG; Conklin MH; Corley TL;
Address:		"Intera, Inc., Austin, Texas 78758, USA"
Journal Title:		Environ Sci Technol
Year:		2002
Volume:		36
Issue:		7
Page Number:		1613 - 1619
DOI:		10.1021/es010812a
ISSN/ISBN:		0013-936X (Print) 0013-936X (Linking)
Abstract:		"A series of gas (vapor)-advecting water-unsaturated column experiments using a low organic content (f(oc)) silica sand was conducted to determine mass distributions of chlorinated-volatile hydrophobic organic compounds (C-VHOCs) in a natural sorbent system. C-VHOCs used were trichloroethene (TCE), tetrachloroethene (PCE), chlorobenzene (CB), and 1,3-dichlorobenzene (DCB). Four volumetric water contents (theta(w) = 0.07, 0.12, 0.17, 0.20) and several influent gas-phase C-VHOC (solute) concentrations were considered. The method of temporal first moments was applied to complete breakthrough curve data to determine total C-VHOC gas-phase retardation and associated gas-phase C-VHOC mass fraction. Results were compared to an equilibrium partitioning advective-dispersive formulation of total gas-phase retardation. Literature-derived values of Henry's law constants and independent measurements of gas/water interface areal extent and interface phase adsorption allowed quantification of C-VHOC mass fractions in the aqueous and gas/water interface phases. Unaccounted C-VHOC mass, derived from comparison of measured C-VHOC retardation to independent phase prediction, was attributed to solid-phase sorption. Results indicate that for all conditions tested, gas/water interfacial adsorption exhibited only a small effect on C-VHOC vapor retardation (accounting for < or = 10% of the total C-VHOC distributions). Solid-phase association was the dominant uptake mechanism, accounting for 46-91% of the total C-VHOC mass in the porous system. Evaluation of the solid-phase C-VHOC uptake results in terms of a modified form of the Dubinin-Radushkevich (DR) isotherm equation provided strong evidence supporting the mechanism of pore-filling in this natural, low f(oc) sorbent"
Keywords:		"Adsorption Gases Hydrocarbons, Chlorinated/*chemistry *Models, Theoretical Silicon Dioxide Soil Pollutants/*analysis Solvents/*chemistry Volatilization Water;"
Notes:		"MedlineSilva, Jeff A K Bruant, Robert G Jr Conklin, Martha H Corley, Timothy L eng P42 ESO4949/ES/NIEHS NIH HHS/ Research Support, U.S. Gov't, Non-P.H.S. Research Support, U.S. Gov't, P.H.S. 2002/05/15 Environ Sci Technol. 2002 Apr 1; 36(7):1613-9. doi: 10.1021/es010812a"