Debra Ressler, Effects Of UV Radiation On The Degradation Capabilities Of Two Strains Of Oil Degrading Bacteria
Faculty Chair: Dr. Henry Spratt
The relative effect of UV radiation exposure on two strains of oil degrading bacteria was determined using mesocosm experiments. Twelve mesocosms were constructed out of 10 gallon glass aquaria into which 12.5 kg of sieved (2mm) and
autoclaved soil was added. Used waste crankcase oil was added to eight mesocosms (1.25L/12.5 kg soil). Anthracene, suspended in DMSO, was added to the remaining four mesocosms (25mg/kg soil) as a source of control for PAH degradation. The mesocosms were maintained in a 32°C temperature controlled chamber. Soils were inoculated with either a commercially marketed bacterial product or an oil degrading species isolated from local oil contaminated surface soils. One-half of the mesocosms were exposed to UV-B radiation. Quantification of the degradation of PAHs contained in the waste crankcase oil and the anthracene controls was assessed using EPA Method 8270. A hexane/acetone extraction procedure was designed to gravimetrically determine the concentration of waste oil present in soil mesocosms. Results of EPA Method 8270 indicated LMW PAHs declined more rapidly in UV exposed mesocosms. However, HMW PAHs tended to persist in all mesocosms throughout the eight-week study. Hexane/acetone extractions revealed a consistent level of oil recovery over time. There appeared to be no significant difference between the different bacterial species with regards to both the level of PAHs and the amount of used waste crankcase oil recovered. Exposure to UV radiation did not have a significant effect on the viability of bacterial cells or the amount of oil recovered via extraction. The results suggest further investigation and modification of analytical and experimental design procedures to account for soil adsorption, bacterial mineralization, and volatilization.