Humification of Pyrene in Contami- Nated Soil during Land Farming

252 Pyrene, a polycyclic aromatic hydrocarbon (PAH) compound present in contaminated soil at the Champion International Superfund site in Libby, Montana, a site presently undergoing land farming/preparedbed bioremediation, was evaluated with regard to incorporation into soil components (humification) in biologically active and poisoned treatments under varying environmental conditions including soil moisture, incubation temperature, and electron acceptor concentrations. The methyl isobutyl ketone (MIBK) humic fractionation method was used to separate soil organic matter (SOM) into fulvic acid, humic acid, bound humic acid, bound lipid, and mineral associated fractions. A radiolabeled chemical mass balance approach was used to evaluate the distribution of humified C among humic fractions. This is the first application of the MIBK fractionation method to a soil previously contaminated with a complex waste mixture. Humification, or nonsolvent extractable incorporation, of C associated with C-pyrene, was significantly higher in biologically active treatments with the humic acid fraction of SOM being the primary sink. The bound lipid SOM fraction was the primary sink for C in poisoned microcosms. Treatments incubated at a soil matric potential of -1 bar demonstrated significantly more C humification than those incubated at -16 bars. Total humified C in treatments incubated at 10° C was equal to that of treatments incubated at 20° and 30° C at the end of 365 days of incubation. Addition of alternate electron acceptors did not significantly affect the extent or distribution of humified C compared to the unamended control with only native electron acceptors. Pyrene or pyrene transformation products associated with SOM fractions are likely to present a low risk to environmental receptors due to their difficulty of extraction. Because of this, humification of pyrene and other hydrophobic organic compounds (HOC) may be an acceptable endpoint in soil systems. Data generated from this project will be applied to the management of the Champion International Superfund site. HUMIFICATION OF PYRENE IN CONTAMINATED SOIL DURING LAND FARMING