Release of polycyclic aromatic hydrocarbons from contaminated soils by surfactant and remediation of this effluent byPenicilliumspp

Studies in which surfactants have been employed to increase the bioavailability of soil-bound polycyclic aromatic hydrocarbons (PAHs) have not yielded consistent results. Surfactant mobilization of high molecular weight (MW) PAHs from contaminated soils has not been extensively studied; therefore, the purpose of this research was to compare the extent of release of freshly added high MW 14C-PAH with aged PAH from four different PAH-contaminated soils using a nonionic detergent, Tween 80, and to determine whether Tween 80-solubilized 14C-PAH in soil washings could be degraded by indigenous microorganisms or by added Penicillium spp. Only very high concentrations of Tween 80 (>1,000 times the critical micelle concentration [CMC] for 3 of 4 soils) were able to mobilize bound 14C-pyrene, -chrysene, and -benzo[a]pyrene. The concentration of surfactant required to release 50% of bound 14C-PAH (the SC50 value) ranged from 5 to 30 g/L depending on soil type; a modest correlation was found (0.512) between the fraction of organic carbon in the soil and the SC50 value. At 104 × CMC, Tween 80 released an average of 75% of bound 14C-PAH and 64% of the aged PAH, indicating that the 14C-PAH release only slightly overestimated PAH mobilization from weathered soil. An exception was one soil that had been previously remediated in which <30% of the PAHs were released. The PAH structure had a negligible effect on the mobilization by surfactant because the solubilization curves for all three PAHs were very similar. Tween 80-solubilized 14C-pyrene readsorbed to soil when the surfactant concentration dropped below 103 × CMC. Greater than 90% of the 14C-pyrene in the soil washing effluent could be removed by the addition of spores of active PAH-oxidizing Penicillium spp. plus nutrients. In contrast, <10% of 14C-pyrene was oxidized by the indigenous soil bacteria under the same conditions.