Bioavailability of phenanthrene sorbed to mineral-associated humic acid

Phenanthrene, a 3-ring aromatic hydrocarbon, was used as a model substrate to analyze the effect of sorption on the bioavailability of polycyclic aromatic hydrocarbons (PAHs). This study focused on sorption to mineral-associated humic acid (HA). Batch sorption analyses of phenanthrene to mineral-HA complexes were performed as integral part of the bioavailability experiments to account for the sorbed fraction under the various experimental conditions. A mixed culture that was enriched from a coal tar contaminated soil dominated by Pseudomonas sp. served as an inoculum. Phenanthrene mineralization was substantially enhanced upon sorption to mineral-HA complexes and the degree of enhancement was positively correlated with the fraction of sorbed phenanthrene. This stimulation is thought to be related to sorption of both the microorganisms and phenanthrene to the colloidal surfaces. This study suggests that when sorbed contaminants are still bioavailable, the presence of surfaces may stimulate mineralization.