BIOREMEDIATION EFFECTIVENESS FOLLOWING THE EXXON VALDEZ SPILL

Abstract

ABSTRACT Statistical analyses of changes in the composition of oil residues remaining on beaches following the Exxon Valdez oil spill in Prince William Sound have demonstrated that bioremediation was effective in accelerating oil removal. Extensive data were obtained in a joint bioremediation monitoring program conducted during the summer of 1990 by the U.S. Environmental Protection Agency (EPA), the State of Alaska, and Exxon. Composition changes in the oil relative to hopane, a trace oil component very resistant to biodegradation, provided the basis for accurately determining rates and extent of biodegradation. Results show that on fertilized beaches the rate of oil biodegradation was from three to more than five times faster than on adjacent, unfertilized control beaches. Further, most hydrocarbon components of the oil were biodegraded simultaneously, although at different rates. On one beach studied, about 60 percent of the total hydrocarbons detectable by gas chromatograph and 45 percent of the total PAH were biodegraded in three months. Bioremediation effectiveness was determined to depend primarily on the amount of nitrogen fertilizer delivered to the sediment per unit of oil present, time, and the extent of oil degradation prior to fertilizer application. The results suggest ways to improve future bioremediation application strategies and monitoring.