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r 4.0 CONCLUSIONS Laboratory testing demonstrated that treatment of soil and groundwater with H2O2, acid and/or chelated or acidified iron could remove GRO from the groundwater. However, removal was due primarily to volatilization, especially when the initial H2O2 concentration was as high as 5%. The best degree of GRO destruction was achieved with acidified H202and with acidified H202+iron (classical Fenton' s reagent). PRIMA does not recommend using H2O2/FeEDTA in the field due to the nearly instantaneous and extremely vigorous reaction. All treatments generated Cr(VI�–up to 0. 11 mg/L. . The ability of this Cr(VI) to attenuate naturally was not evaluated in this study. The concentration of Cr(VI) that might be generated during a field application of a peroxide-based treatment at this site is uncertain due to differences between laboratory and field conditions. However, the presence of Cr(VI) at relatively high concentrations in all laboratory tests indicates a high potential for Cr(VI) formation in the field and any proposed in situ treatment should have a contingency for Cr(VI) formation. Treatments employing acid and/or iron increased the concentrations of several metals. The concentrations of vanadium, magnesium, calcium, chromium, iron, manganese, cobalt, and nickel increased in tests using acid and acidified iron, while the concentration of barium decreased. The concentrations of chromium, iron, cobalt, nickel and copper increased in tests using iron (chelated or acidified), while the concentration of arsenic decreased to < 0.005 mg/L The pH did not change by more than one pH unit, even in the tests to which acid was added. Buffering tests indicate that site soil is highly buffering-100 mmol W (50 mL of pH 1 solution) was neutralized within about 24 hours when combined with 50 g soil. PRIMA Environmental, Inc. 18 Eval of Peroxide February 8, 2007 Cambria--G Street, Davis