Removal of benzo( a)pyrene in soil composting systems amended with the white rot fungus Phanerochaete chrysosporium

Abstract

Inoculation of the benzo( a)pyrene (B( aP) contaminated soil composting system with the white rot fungus Phanerochaete chrysosporium increased the rate of bound residue formation of contaminant carbon from 0.73 mg B( a)P/kg-day to 1.58 mg B( a)P/kg-day over the first 30 days of investigation. Despite this initial enhancement in contaminant removal, fungal inoculation was found to be ineffective in significantly enhancing the extent of benzo( a)pyrene during the 95 day composting study. The extent of contaminant removal was 62.8 ± 5.9%, 65.6 ± 1.2% and 49.3 ± 0.5% for the fungal inoculated, fungal uninoculated and poisoned compost reactors, respectively. First order modeling of removal kinetics yielded contaminant half lives of 11.5, 8.6 and 230 days for the fungal inoculated, uninoculated and poisoned compost reactor systems, respectively. Analysis of soil systems revealed appreciable numbers of PAH degrading fungi ( > 1 × 10 4 CFU/gm) in the uninoculated compost systems at the end of the 95 day treatment period. Analysis of volatile traps indicated that neither mineralization nor vapor partitioning of benzo( a)pyrene (or its chemical intermediates) was significant during the soil composting process. Bound residue formation was found to be the predominant transformation mechanism for benzo( a)pyrene in the microbially active compost systems accounting for nearly 100% of the benzo( a)pyrene removed.