Degradation patterns of fresh and aged petroleum-contaminated soils

Biodegradation patterns were measured for fresh and aged petroleum products of similar chromatographic distribution in soil. An aerobic respirometer measured utilization of the petroleum products by indigenous soil microorganisms in soil slurries over a 40-day period. Hydrocarbon concentration changes in the soils were measured at various intervals over the 40 days using a Diesel Range Organics (DRO) method. These tests were applied to two soils with different physical characteristics, contamination profiles, and treatment histories. Results indicated greater rates of hydrocarbon loss for the soils containing the fresh petroleum product compared with the aged product, and the lower molecular weight fraction of either product. The treatment history of the two aged soils controlled their extent of further hydrocarbon loss. A simple biodegradability test may be an effective tool in screening the potential success of bioremediation and estimating the final hydrocarbon concentration achievable.