Determining 'Availability' of BTEX and PAHs from Soils and Sediments Using Selective Supercritical Fluid Extraction

摘要

The availability of BTEX and PAHs on 15 MGP soils was determined using mildrnsupercritical carbon dioxide extraction (SFE) and compared to uptake by terrestrial worms. Thernpattern of PAH release obtained using mild SFE was shown to be correlated with PAH uptake byrnworms. BTEX concentrations on the same soils were typically 100 to 1000-fold lower than PAHrnconcentrations, and conventional EPA purge and trap methods for BTEX underestimated thernactual concentrations (determined by SFE and sonication) of benzene by two to three orders ofrnmagnitude. However, characterization of benzene availability using SFE for BTEX and PAHsrndemonstrated that benzene was highly unavailable with extraction rates much slower than thernPAHs. Since benzene is much more soluble in supercritical carbon dioxide than PAHs, thesernresults indicate that benzene present in these soils is very tightly bound. Initial determinations ofrnbenzene soil/water Kds are in the range of 10~5 to 10~6, which is several orders of magnitudernhigher than typical soil/water Kds for benzene. These results indicate that BTEX and PAHs inrnsoil may have a large range in partitioning behavior to groundwater and soil biota and that mildrnSFE may provide a tool for estimating this variability in partitioning behavior