Estimating Oil and Grease Content of Petroleum‐Contaminated Soil

Abstract
The precision and accuracy of estimating the oil and grease content of petroleum‐contaminated soil using acidification, followed by Soxhlet extraction with trichlorotrifluoroethane (freon) and methylene chloride, are compared. Stock oil‐soil mixtures prepared with vegetable oil, no. 2 and no. 6 fuel oil, SAE 30 nondetergent motor oil, and an oily petroleum waste are analyzed. The analytical results obtained using freon are more precise. Using freon, the coefficient of variation for all oil‐soil mixtures analyzed never exceeds 4%, compared to 9% when methylene chloride was used as the solvent. Percent recovery varies with oil type, with freon providing more accurate estimates of vegetable oil and no. 2 fuel‐oil concentrations, and methylene chloride giving a more accurate estimate of no. 6 fuel‐oil concentration. Recoveries slightly exceed 100% for both motor oil using freon and the oily petroleum waste using methylene chloride. The results suggest that either freon or methylene chloride can be used to provide reasonably precise and accurate estimates of the oil and grease content of contaminated soils.

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