Judith L. Sims

Polycyclic Aromatic Hydrocarbon Biodegradation as a Function of Oxygen Tension in Contaminated Soil

Abstract Laboratory tests were conducted to determine the effect of soil gas oxygen concentration on the degradation and mineralization of spiked 14C-pyrene and nonspiked 16 priority pollutant polycyclic aromatic hydrocarbons (PAH) present in the soil. The soil used for the evaluation was taken from a prepared-bed land treatment unit at the Champion International Superfund Site in Libby, Montana. This soil was contaminated with wood preserving wastes including creosote (composed primarily of polycyclic aromatic hydrocarbons and pentachlorophenol). Degradation rates of 14C-pyrene and PAH compounds were found to be enhanced under soil gas oxygen concentrations between 2% and 21% in the contaminated soil. Between 45% and 55% of 14C-pyrene spiked onto the soil was mineralized after 70 days at soil gas oxygen levels between 2% and 21%. No statistically significant mineralization was found to occur at 0% oxygen concentrations. Mineralization of 14C-pyrene in contaminated soil poisoned with mercuric chloride was determined to be less than 0.5%. Degradation of indigenous nonradiolabeled PAH in non-poisoned soil was statistically significantly greater than in poisoned soil. These results indicated that the degradation of 14C-pyrene and PAH compounds was biological and would occur under low oxygen concentrations. For example, the use of soil aeration technology in order to achieve continued treatment for buried lifts of soil while new lifts are added will decrease the total time for soil remediation of the prepared-bed.

Fate of Pyrene in Contaminated Soil Amended with Alternate Electron Acceptors

Creosote-contaminated soil samples from the Libby Ground Water Contamination Superfund Site in Libby, MT, were amended with the potential alternate electron acceptors (AEA) nitrate (KNO3), manganese oxide (MnO2), and amorphous iron oxyhydroxide (FeOOH) and incubated at low oxygen tensions (0-6% O2). The fate of 14C-pyrene was evaluated with respect to the different soil amendments. The fate of 14C from the radiolabeled pyrene with regard to mineralization and bound residue formation within soil humic fractions was not significantly different from controls for the iron and manganese amended soils. Nitrate amendments appeared to stimulate 14C-pyrene mineralization at a level of 170 mg NO3-N kg(-1), and inhibit mineralization at 340 mg NO3-N kg(-1). The stimulatory effect did not appear to be the result of nitrate serving as an electron acceptor. Although AEA amendments did not significantly affect the rate or extent of 14C-pyrene mineralization, results of oxygen-deprived incubations (purged with N2) indicate that AEA may be utilized by the microbial community in the unsaturated contaminated soil system.

Pentachlorophenol and phenanthrene biodegradation in creosote contaminated aquifer material

Contamination of the subsurface environment at the Libby Superfund Site, Montana, includes polycyclic aromatic hydrocarbons and f1p4achlorophenol due to accidental spills and improper disposal of wood preserving wastes. Biodegradation is a treatment technology gaining wide application in the treatment of hazardous waste sites. A microcosm study was conducted to evaluate the effect of temperature, sampling depth, nutrient addition, and oxygen on the biodegradation potential of phenanthrene and pentachlorophenol in aquifer samples using radiolabeled chemicals. Mineralization of phenanthrene reached 14% but was less than 1% for pentachlorophenol over the 56 day incubation period. Phenanthrene mineralization in microcosms at 10 degrees C was not significantly different from those at 20 degrees C. This may have been due to microbial community acclimation to lower temperatures at the site. Average volatilization was less than 2% for both phenanthrene and pentachlorophenol. After 56 days, most of the radiolabeled chemical was either solvent extractable or soil bound.

Distribution and biomagnification of hexachlorophene in urban drainage areas

Hexachlorophene (HCP) n has been a widely used bacteriostatic agent for the last twenty years. Until the recent ban on its use, other than as a preservative in cosmetics and as a prescription antibacterial drug (EDWARDS, 1972), HCP was a ubiquitous Ingredient in soaps, creams, lotions, disinfectants, deodorants, and various other products. The use of HCP was curtailed when a subacute toxicity was demonstrated (KIMBROUGH and GAINES, 1971; LOCKHART, 1972), in addition to the long known fact that HCP was toxic in high concentrations (GUCKLHORN, 1969; GffMP, 1969; KIMBROUGH, 1971). Thou~h HCP bas been widely studied in terms of its medical usefulness and safety, the environmental effects, or even the presence of HCP in the envlronment have not beel well studled, desplte its structural similarity to chlorinated hydrocarbon pesticides. In response to this lack of information a study was undertaken to determine the presence and distribution of HCP in the waterways of the Upper Haw River Basin near Greensboro, North Carolina. HCP is thought to be a pollutant whose source is the urban environment, and would therefore be round in municipal effluents, as has recently been substantiated by BUHLER et al. (1973).

Fugacity Framework: Web Access And Implementation For Site Assessment And Rehabilitation

The fugacity-framework addresses multiple-media and multiple contaminant aspects of environmental site assessment. A U.S. EPA database of priority chemicals has been linked to the fugacity model for assessment of contaminant sources, transport and transformation, and exposure. Site-specific data are provided by the user. This tool provides a way for managers to visualize the behavior of toxic chemicals at a contaminated site, the effect of site-specific characteristics on contaminant distribution, the behavior of daughter products of degradation, and the associated risks to humans and the environment. The framework can be used to make decisions regarding protection of public health and the environment, site rehabilitation, and the sustainable development and economic recovery of impacted sites, The fugacity framework can be accessed at http://www,engineering .usu.eduluwrY, Utah Water Research Laboratory.