LONG-TERM STUDY OF VOLATILE ORGANIC-COMPOUND RECOVERY FROM AMPULATED,DRY, FORTIFIED SOILS

Our objective was to evaluate the stability and extractability of vola tile organic compounds (VOCs) when fortified on dry soils and stored i n sealed ampules. Two desiccator-dried soils were fortified with eight neat VOCs, benzene, toluene, ethylbenzene, o-xylene, 1,1,1-trichloroe thane (TCA), trichloroethene (TCE), tetrachloroethene (PCE), and 1,1,2 ,2-tetrachloroethane (TTCA) at 800 ng each VOC/g soil. The fortified s oil was portioned into ampules, sealed, and stored in the dark at 25 d egrees C for up to 56 wk. Replicate ampules were analyzed after 2 d an d 2, 4, 8, 13, 34, and 56 wk by two extraction procedures modified fro m the U.S. Environmental Protection Agency's (USEPA's) low- and high-l evel purge-and-trap procedures (SW-846 Methods 5030/8021). The modifie d high-level procedure (1-h methanol extraction at 25 degrees 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, tolue ne, ethylbenzene, and o-xylene (BTEX) remained relatively unchanged du ring the 56-wk study. The results indicate that the 1-h, 25 degrees C methanol extraction was sufficient for extraction of the BTEX compound s 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 recove ries of TTCA decreased at rates of 8 and 17 ng/g/week on the Hayesvill e and Charleston soils, respectively. PCE concentrations did not show any significant concentration changes, while TCE concentrations increa sed at 6 and 7 ng/g/week for the Hayesville and Charleston soils, resp ectively. We submit that the 1-h, 25 degrees C methanol extraction was inadequate for removal of the chlorinated compounds. Additionally, we postulate that dehydrochlorination of TTCA to form TCE occurred in de siccator-dried soil.