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k`■ KLEINFELDER <br /> I <br /> I <br /> 3.1.2 THEORY OF AIR SPARGING <br /> For Physical Stripping <br /> Air sparging with the objective of physical stripping involves the injection of air into the <br /> fsaturated zone using wells screened below the groundwater surface. The air bubbles come into <br /> contact with the contaminants dissolved in the groundwater, reach natural liquid/vapor <br /> equilibrium, and are transferred into the vapor phase. Now gaseous, the contaminant portion <br /> rises into the vadose zone where it is removed by the vapor extraction system. The stripping rate <br /> is generally a function of the Henry's Law constant of the dissolved constituent(s) which is <br /> related to the following equation: <br /> PgaS=khMgas <br /> Where: <br /> Pgas= Partial pressure of the contaminant in the gas phase <br /> Mgt Solubility expressed as molarity for the contaminant <br /> kh= Henry's Law constant <br /> Henry's constant is a ratio of a compound's vapor pressure to solubility; the highest constants <br /> being those with a high vapor pressure and low solubility in water. Therefore, the greater the kh <br /> value the more readily the contaminant will leave the dissolved state and favor the vapor phase, <br /> represented by the passing air/ozone bubble. Air sparging behaves like an in situ air stripper. <br /> The compounds that respond well to air stripping will respond to air sparging. Gasoline range <br /> petroleum compounds and DCA have a relatively high Henry's constant so air sparging is <br /> expected to readily strip the contaminants from the dissolved and sorbed phases. <br /> 12280/2002R476 Page 7"of 26 <br /> f Copyright 2002 KEetnfelder,Inc, May 17,2002 <br />