Polar metabolites of polycyclic aromatic compounds from fungi are potential soil and groundwater contaminants

This study investigated the sorption to soil of water-soluble metabolites from polycyclic aromatic compounds (PACs). The soil fungus Cunninghamella elegans was used to produce PAC metabolites from two un-substituted PACs (phenanthrene, pyrene), three alkyl-substituted PACs (2-methylnaphthalene, 1-methylphenanthrene, 1-methylpyrene), and one sulfur-containing heterocyclic PAC (dibenzothiophene). Fifty-eight metabolites were tentatively identified; metabolites from the un-substituted PACs were hydroxylated and sulfate conjugated, whereas metabolites from alkyl-substituted PACs were sulfate conjugated and either hydroxylated or oxidized to carboxylic acids at the methyl group. The metabolism of the sulfur-containing heterocyclic PAC resulted in sulfate conjugates. The sorption of the PAC metabolites to three soils was determined using a batch equilibrium method, and partition coefficients (K _d's) were calculated for fourteen representative metabolites. Sulfate conjugated metabolites displayed K _d's below 70 whereas the metabolites with both a sulfate and a carboxylic acid group had K _d's below 2.8. The low K _d's of water-soluble PAC metabolites indicate high mobility in soil and a potential for leaching to surface- and groundwaters.