POLYCYCLIC AROMATIC HYDROCARBON BIODEGRADATION AS A FUNCTION OF OXYGEN-TENSION IN CONTAMINATED SOIL

Laboratory tests were conducted to determine the effect of soil gas ox ygen concentration on the degradation and mineralization of spiked C-1 4-pyrene and nonspiked 16 priority pollutant polycyclic aromatic hydro carbons (PAH) present in the soil. The soil used for the evaluation wa s taken from a prepared-bed land treatment unit at the Champion Intern ational Superfund Site in Libby, Montana. This soil was contaminated w ith wood preserving wastes including creosote (composed primarily of p olycyclic aromatic hydrocarbons and pentachlorophenol). Degradation ra tes of C-14-pyrene and PAH compounds were found to be enhanced under s oil gas oxygen concentrations between 2% and 21% in the contaminated s oil. Between 45% and 55% of C-14-pyrene spiked onto the soil was miner alized after 70 days at soil gas oxygen levels between 2% and 21%. No statistically significant mineralization was found to occur at 0% oxyg en concentrations. Mineralization of C-14-pyrene in contaminated soil poisoned with mercuric chloride was determined to be less than 0.5%. D egradation of indigenous nonradiolabeled PAH in non-poisoned soil was statistically significantly greater than in poisoned soil. These resul ts indicated that the degradation of C-14-pyrene and PAH compounds was biological and would occur under low oxygen concentrations. For examp le, the use of soil aeration technology in order to achieve continued treatment for buried lifts of soil while new lifts are added will decr ease the total time for soil remediation of the prepared-bed.