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Creologkal ncwa IHC. Page 4 ' IRAP—Pilot Test Project No. 425.2 March 21,2005 ' Comparison of relative strength of oxidants ' Std. Redox Potential Relative Oxidizing Oxidant E° (Volts) Powerl Fluorine (F2) 3.0 2.23 ' Hydroxyl Radical ('OH) 2.8 2.06 -Oxygen Radical ('0) (Superoxide) 2.4 1.76 Ozone (03) 2.1 1.54 ' Hydrogen Peroxide (H2O2) 1.8 1.31 -Permanganate n04' 1.7 1.24 Chlorine Dioxide C102 1.6 1.15 ' Chlorine C12) 1.4 1.00 -Oxygen (02) 1.2 0.86 Bromine (Br2) 1.1 0.80 ' Iodine (I2) 0.8 0.54 1 =Normalized to Chlorine,where C12= 1.0 ' Ozone sparging is an in situ treatment technology that involves pumping gaseous ozone into the saturated zone. The species generated during the ozone oxidation reaction include 03, -OH and 02. The"OH radical captures a hydrogen atom (as stated above) from a molecule of ' petroleum hydrocarbon contaminant, which then causes the contaminant molecule to become unstable and breakdown. The presence of gaseous oxygen (02) and air also causes a phase transfer (partitioning) of volatile organics from a dissolved state in water to a vapor phase. Soil geology is heterogeneous in nature; therefore, soil vapors will..11ot escape to the upper and/or lower hers of soil, and the continuous sparging of ozone will oxidize the contamination. On the other hand if the soil vapory will move towards the excavation area, ' the soil vapor extraction system will extract these vapors to treat. A second effect of ozone sparging is to enhance the biodegradation process of hydrocarbons by supplying oxygen to an otherwise anaerobic environment. By pulsing the system on and off, soil micro-channels ' repeatedly empty and then fill up with water/vapor thereby creating in-situ reactors. Ozone (with oxygen) is repeatedly introduced into the channels and this augments natural biodegradation. ' 2.2 Concerns and Limitations ' Problems associated with the use and design of an ozone sparging system include those generic to any gaseous sparging system and those relating to the chemical properties of ozone: ' Gaseous sparging system: • The movement of vapor¢ in the subsurface is influenced by the permeability of the soil. Fine grained and/or heterogeneous geology can prevent the upward migration of the vapor. • The presence of low permeability soils could cause preferential channeling of vapor ' movement thereby limitirig the radius of influence from sparge points.