Impact/Purpose:

Resources for cleaning up Superfund Sites are running out; therefore, alternate methods must be developed. A patent for the de-halogenation of halogenated hydrocarbons in waters and soils using a zero valent iron and pyrite system (ZVI system) was successfully obtained by the EPA National Exposure Research Laboratory (NERL), Ecosystem Research Divison (ERD), Athens, GA. Roger Carlton, Region 4 Science and Ecosystem Support Division (SESD), Athens, GA, teamed up with Dr. Lee Wolfe, ERD, in order to demonstrate, by means of conducting a feasibility study, the value of applying this technology to remediate soils contaminated with Toxaphene along with a host of other chlorinated pesticides (e.g., DDT, DDE, dieldrin, etc.).

Description:

The project consisted of a preliminary laboratory study; an outdoor bench scale study and an in situ field Pilot Study to which the zero valent iron and pyrite system (ZVI system) was applied. Several beakers were filled with contaminated soil, the ZVI system and a solvent then stirred constantly. A solvent was added to assist in overcoming the mass transfer. The reaction rate (half-life) for the laboratory study was calculated to be on the order of a few hours. A three cubic foot (ft3) residential type cement mixer was used in the bench scale study to stir the aqueous matrix. The half-life for this method was determined to be on the order of seventy-two hours. The in situ study presented several obstacles that were not overcome, thus the half-life for Atotal@ de-chlorinated pesticides was calculated to be somewhere between three hundred sixty-five and four hundred thirty-three days. Samples were collected during the each study, extracted using RCRA Method 3545 and analyzed using EPA Method 8081A. In lieu of identifying the individual peaks or attempting to identify the break down products, an interpretation of the chromatogram was conducted by integrating the total area under the curve. These data were qualified as Screening Data because no compounds were identified. As a quality assurance step, a percentage of the samples were analyzed by the SESD Laboratory to confirm the findings of the screening data. These data were qualified as Definitive Data because several chlorinated compounds were identified. In summary, as the chlorine atoms came off of the compounds, the amplitude of the individual peaks changed as did the entire “integrated area under the curve.” Analytically speaking, there was no notable change in the “toxaphene window.”

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