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M-1 W I.E <br /> WE W__ <br /> Wlkj �Z <br /> WNW "M-59"'MI <br /> ORION` MMMM-''WRN <br /> a ffiwlm I'VE <br /> PRINCIPLES OF SOIL VAPOR CONTA11:11ANT ASSESSMENT <br /> The soil vapor survey, or SVC-A, technique taken advantage of the <br /> behavior of hydrocarbon mixtures and the physicochemical proper- <br /> ticu of tne individual components in the aub5urface. Following a <br /> subsurfaces gasoline release, free product will migrate downwards <br /> towards the ground water, some of the gasoline will volatilize, <br /> and come will adsorb to the coils. In the case of a spill of <br /> sufficient volume to exceed the coil binding capacity, free <br /> liquid will reach ground water, at which point it will float and <br /> may begin to vaporize and solubilize. <br /> Like most hydrocarbon licrjidg, gasoline is a complex mixture of <br /> me.ny comptt,nd5, each with its own physicochemical properties. <br /> The contaminants found in ground water located beneath a layer of <br /> f?aating hydrocarbon are generally Ica* hydrophobic and are <br /> generally found in cc:centrations pro;:-ortiortal to the hydro <br /> carbon/water partition coefficient (i.e., the relative solubility <br /> of a given compound in the bulk hy4rocarbon to its solubility in <br /> -Ater) tnd to their percencorn:%oaition in the gasoline. It may <br /> be noted that concentration of total benzene, toluene, and <br /> xl-loner in proeict-sa%;urated water may exceed 10-20 mg/L (AFI <br /> 1985). <br /> Hydrocarbons wil) also volatilize into the air- or gas-filled <br /> soil interstices. Volatilization is largely a !unction of vapor <br /> pressure. The natures of thea contaminant mixtures, in terms of <br /> specific compor.ent mixtures, in either the aqueous or vapor <br /> phase, are distinctly different from each other and from the <br /> gasoline. That is, the more hydrophilic hydrocarbons will be <br /> more likely to move into ground water, while the more volatile <br /> compounds are more likely_._;o_rmve_.into the v porphape,and the <br /> compounds that areboth IC33 volatile and more hydrophobic are <br /> more Akely to remain in the free product or be adsorbed to soils <br /> (Hinchee and Reisinger 1987) . <br /> CHV82A.apa 1 <br />