Temporal chances in the bioavailability of PAHs in soils

A study was conducted to investigate the ageing of phenanthrene in soil, and in particular how the ageing process was influenced by the presence and concentration of hydroxypropyl-beta-cyclodextrin (HPCD). [9-C-14]Phenanthrene-spiked soil was aged in the presence and absence of HPCD. In general, an increase in the soil-phenanthrene contact time resulted in decreased extractability and mineralization. It was noted that the highest concentration of HPCD resulted in enhanced loss from the system and there was an observed increase in the recalcitrant fraction of the soil-associated PAH. Lower HPCD concentrations retarded ageing with respect to both bioavailability and mineralization with only small changes observed between time 0 and 84 d. Additionally, this study showed a high degree of agreement between HPCD extraction of phenanthrene with its mineralization by catabolically active microorganisms. In terms of the assessment of the bioavailability of phenanthrene, extraction of contaminated soils with 50 mM HPCD can predict the bioavailability of the PAH to degrading microorganisms. Ultimately, this predictive tool may prove useful for determining the success or failure of bioremediation strategies in the field.