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k «, A in the presence of iron. Iron is naturally occurring in soil and groundwater or can be added during the injection process, if needed. The reaction is based on the principle of Fenton's Chemistry where iron and hydrogen peroxide react to form hydroxyl radicals and other by-products as shown in the equations below. Please note that these reactions are approximations. Suthersan (2002) and Suthersan and Payne (2005) describe some of these reactions. Equations: Fez+ + 11202 --> Fe3+ + OH- + HO* Fe3+ + 11202 --> Fe2+ + W + HOz•/•Oz Fe3+ + HOZ•/•02 ---> Fez+ + W + OZ (iron catalyst gets regenerated) H2O2 + HO* --> HOZ•/•Oz + H2O Fez+ + HO* --> Fe3+ + OH" Fez+ + HO2•/•O2 --> Fe3+ + W + H2O2 HO• = hydroxyl radical •OZ — superoxide ion radical j Residual H202not used in the oxidation process breaks down to water and oxygen in a matter of hours. In addition to the reaction described in the first equation, there are also a large number of competing reactions. The competing reactions include the free radical scavengers, most importantly, carbonate and bicarbonate alkalinity, which will greatly _ affect the overall reaction and dilute the oxidant effectiveness. Hydrogen peroxide can also serve as an oxygen source for microbes in the subsurface to enhance aerobic biodegradation of contaminants. Table 1 shows the relative strength of selected chemical oxidizers. The chemical oxidizers used in soil and groundwater remediation are summarized in Table 2. The properties of two commonly used chemical oxidizers, hydrogen peroxide and potassium permanganate, are compared in Table 3 . OVERVIEW OF FENTON'S REAGENT BENCH TESTING The purpose of bench testing is to perform several chemistry experiments in the laboratory using representative soil and groundwater from the Subject Property. During the bench test, the pH, the concentration of treatment chemicals, and other factors will be c, mged and evaluated to optimize conditions for a Pilot-Scale Testing and Full-Scale Remediation, if appropriate. Modifications or updates to these procedures will be used, as needed, based on site-specific soil and groundwater samples. 2