Comparison of selected non-exhaustive extraction techniques to assess PAH availability in dissimilar soils

Recently, it has become apparent that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate and that bioavailability of contaminants is a better measure of potential exposure. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. In this study, phenanthrene extractability using hydroxypropyl-beta-cyclodextrin (HPCD) and desorption kinetics using butan-1-ol (BuOH) were determined in three dissimilar spiked soils. The soils were extracted after 1 d, 40 d and 80 d of soil-compound contact time. The amount of phenanthrene extracted by HPCD was compared to the rapidly desorbed fraction removed by BuOH. Further experiments using the same soils and extraction methods to assess the relative extractability of phenanthrene, pyrene and benzo(a)pyrene were conducted. Overall, the extraction methods used in this study had different extraction efficiencies. Results suggest that as compound hydrophobicity increased, BuOH became a more exhaustive extractant with respect to HPCD, especially for soils with high clay and organic matter content. These results are important as they highlight differences between two contrasting non-exhaustive extraction techniques both of which have been suggested to be appropriate in the assessment of bioavailability.