Low‐Temperature Mineralization of Crude Oil in Soil

Abstract

AbstractPrudhoe Bay crude oil was added at 0,3, and 6% wt oil to wt of soil in a laboratory study designed to evaluate methods of enhancing crude oil mineralization at 10°C. Both mechanical stirring of the soil and fertilization were effective in enhancing mineralization. Under the most favorable conditions of the study at the 3 and 6% loading rates, respectively, only 18.9 and 11.9% of the added C was evolved as CO2. Nitrogen appeared to be the most stimulatory fertilizer; however, phosphorus in addition to nitrogen further enhanced C mineralization. Sulfur or a combined assortment of other macro‐ and micronutrients was not beneficial when added to nitrogen and phosphorus fertilizers. Sawdust was added to decrease the hydrophobic nature of oiled soils and to improve soil physical properties. Although added sawdust lessened aggregation of the stirred soil, degradation of the oil was not enhanced. Aerobic bacteria and actinomycetes were both initially active shortly after oil addition. This was followed somewhat later by population increases of bacteria growing anaerobically. Oil additions had no stimulatory effect on fungal populations. Doubling time of the net aerobic bacterial population was calculated to be 2.0 days in unfertilized soil receiving 6% oil. In fertilized soil receiving the same rate of oiling, the corresponding time was 1.2 days. Thus, fertilization decreased the doubling interval of indigenous bacteria by approximately 40% in this study conducted at 10°C.