A bench-scale aerobic microbial degradation study of soil contaminated with Saudi Arabian crude oil was conducted. The effects of nutrient additions and seeding with naturally-occurring microorganisms were evaluated, through comparison of results from a control reactor, a second reactor with nutrients, and a third reactor with nutrients and seed microorganisms. A separate weathering experiment was conducted under identical environmental conditions for evaluation of abiotic weathering losses of the crude oil The total petroleum hydrocarbon (TPH) content of soil contaminated with crude oil was measured as a function of time. During a five-week evaluation period, a TPH reduction of 60 to 70% was observed for the nutrient evaluation. Based on the weathering tests, approximately 17% of the TPH loss was attributed to abiotic losses For the specific environmental conditions, crude oil, seawater, and soil evaluated, the addition of nutrients stimulated the biodegradation of crude oil over the test period. Due to the availability of indigenous bacteria, seeding with naturally-occurring bacteria did not improve the rate of TPH loss
