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Long-Term Study of Volatile Organic Compound Recovery from Ampulated, Dry, Fortified Soils

Lockheed Martin Services Group, Environ. Serv., 980 Kelly Johnson Drive, Las Vegas, NV 89119

Brian A. Schumacher

U.S. Environ. Protection Agency, Natl. Exposure Res. Lab., Characterization Res. Div., P.O. Box 93478, Las Vegas, NV 89193-3478

^* Corresponding author (schumacher-brian{at}wpmail.las.epa.gov).

ABSTRACT

Our objective was to evaluate the stability and extractability of volatile organic compounds (VOCs) when fortified on dry soils and stored in sealed ampules. Two desiccator-dried soils were fortified with eight neat VOCs, benzene, toluene, ethylbenzene, o-xylene, 1,1,1-trichloroethane (TCA), trichloroethene (TCE), tetrachloroethene (PCB), and 1,1,2,2-tetrachloroethane (TTCA) at 800 ng each VOC/g soil. The fortified soil was portioned into ampules, sealed, and stored in the dark at 25°C for up to 56 wk. Replicate ampules were analyzed after 2 d and 2, 4, 8, 13, 34, and 56 wk by two extraction procedures modified from the U.S. Environmental Protection Agency's (USEPA's) low- and high-level purge-and-trap procedures (SW-846 Methods 5030/8021).The modified high-level procedure (1-h methanol extraction at 25°C prior to purge-and-trap analysis) yielded significantly higher recoveries of all compounds on both soils as compared with the low-level procedure, with the exception of benzene on the Charleston soil. Moreover, when measured by the high-level procedure, concentrations of benzene, toluene, ethylbenzene, and o-xylene (BTEX) remained relatively unchanged during the 56-wk study. The results indicate that the 1-h, 25°C methanol extraction was sufficient for extraction of the BTEX compounds from these soils. For the chlorinated compounds, regression analysis demonstrated significant trends of changing concentrations over time. Recoveries of TCA decreased at a rate of 3 and 4 ng/g/week and recoveries of TTCA decreased at rates of 8 and 17 ng/g/week on the Hayesville and Charleston soils, respectively. PCE concentrations did not show any significant concentration changes, while TCE concentrations increased at 6 and 7 ng/g/week for the Hayesville and Charleston soils, respectively. We submit that the 1-h, 25°C methanol extraction was inadequate for removal of the chlorinated compounds. Additionally, we postulate that dehydrochlorination of TTCA to form TCE occurred in desiccator-dried soil.