Desorption kinetics of soil sorbed carbazole, fluorene, and dibenzothiophene by P. aeruginosa RS1 from single and multicomponent systems and elucidation of their interaction effects

This study explored the utilization of soil sorbed carbazole (CBZ), fluorene (FLU), and dibenzothiophene (DBT) by an efficient polynuclear aromatic hydrocarbon (PAH) and heterocyclic PAH degrading bacterial strain, Pseudomonas aeruginosa RS1, inoculated in soil microcosms. Biotic and abiotic microcosm studies were set up with Tenax beads, which sequestered the desorbed compounds from the aqueous phase. Soil phase decay profiles obtained for single, binary and ternary systems containing soil sorbed CBZ, FLU, and DBT under both biotic and abiotic conditions were fitted using a first-order decay model. Across all compounds, the first-order decay coefficient under biotic condition (kb, varying from 5.77 ×10−4 to 40 ×10−4 hr−1) was 2–5.2 times higher than the corresponding values obtained under abiotic condition (ka, varying from 1.3 ×10−4 to 13.4 ×10−4 hr−1), indicating direct interfacial uptake of soil sorbed compounds by P. aeruginosa. Although the model fitted the abiotic decay profiles well, the model fits were not consistently good for the biotic profiles. In abiotic systems, the mass of the compounds was conserved, while in biotic systems, microbial degradation of both desorbed and sorbed compounds caused loss of CBZ, FLU, and DBT, and sequestration in Tenax was 1.3–5-fold lower.