EPA Grant Number: R827015-01-0
Title: Anaerobic Intrinsic Bioremediation of Whole Gasoline
Investigators: Joseph Suflita
Institution: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: February 1, 1999 to January 31, 2000 (N/C Ext. to
February 28, 2001)
Project Amount: $130,036
Research Category: Intrinsic bioremediation/natural attenuation
In addition to examining the susceptibility of whole gasoline to decay under methanogenic, sulfate-reducing, and nitrate-reducing conditions, we have extended our study to include a crude oil, representing a much heavier petroleum mixture and an important environmental contaminant. For this study, we chose artificially-weathered Alaska North Slope (ANS) crude oil. This mixture mimics crude oil which has undergone extensive abiotic loss, and it contains a large amount of long chain alkanes (C13-C34) and polycyclic aromatic hydrocarbons (C10-C20).
Unlike the gasoline amendment, the ANS amendment has led to a stimulation of both methanogenesis and sulfate reduction above both the unamended and the gasoline-amended incubations. We are surprised by this finding as the resident microorganisms have been not been exposed to crude oil but to gasoline condensate, a much lighter petroleum mixture. The stimulation of anaerobic respiration by ANS indicates that despite the exposure of this site to the C5-C12 alkanes that are found in gasoline condensate, the resident microorganisms harbor much broader biodegradative activities.
Hydrocarbon analysis of the residual ANS in both sulfate-reducing and methanogenic incubations showed complete biodegradation of n-alkanes under both sulfate-reducing and methanogenic conditions by Ft. Lupton's resident microbiota. This is in contrast to our results under nitrate-reducing conditions in which no significant n-alkane degradation (<5%) was observed. The highly branched alkanes, phytane and pristane, demonstrated 20-30% loss under methanogenic conditions and less 10% loss under sulfate-reducing conditions. Although their seems to be some biological fate process for these compounds, the n-alkanes are much more labile. Additionally, no significant biodegradation (<5%) of the polycyclic aromatic fraction of the ANS was observed under any condition.