Ex-situ process for treating PAH-contaminated soil with Phanerochaete chrysosporium

Based on the known ability of the white rot fungus Phanerochaete chrysosporium to metabolize PAHs, a fungal reactor system with separate soil extraction and fungal incubation units was constructed. The design of the system allowed samples to be easily removed at strategic positions and to ascertain mineralization. The highly contaminated soil (1-2 mm particle diameter), with a total EPA Method 610 concentration of 41 g of PAHs kg^-1, was spiked with [7,10-¹⁴C]benzo[a]pyrene in order to follow the fate of this tracer by HPLC and high-performance gel permeation chromatography. While mineralization amounted to only 2.5%, it was observed that the fungus reduced the total soil PAH concentration by 45% through polymerization processes. For [7,10-¹⁴C]benzo[a]pyrene, a value of 4.9 mg kg^-1 day^-1 or overall 5.5% was obtained. The polymers remained associated with soil, and no monomeric PAHs were detected in the medium. In parallel experiments without soil, high molecular weight polymers could be found in the medium. Sterile soil and medium controls revealed no polymerization. The results were consistent with literature reports that P. chrysosporium converts PAHs primarily to quinones, which have a strong tendency to polymerize. On the basis of the success of this system, scaling up appears to be justifiable.