Relation between bioavailability and fuel oil hydrocarbon composition in contaminated soils

Bioavailability of oil components in contaminated soils is an important regulating factor for biodegradation rates. Changes in the composition of mineral oil can provide information regarding the bioavailability restrictions in contaminated soils. The fate of oil components was studied in a lysimeter experiment and laboratory incubations. A shift in the n-alkane ratios in the range n-C16:n-C20 was observed around 4.0 g kg(-1), indicating that two different mechanisms control the bioavailability of the oil. At higher concentrations, the bioavailability was controlled by solubilization from a non-aqueous-phase liquid into the aqueous soil water phase. The ratios remained constant with decreasing oil concentration in this stage. Below 4.0 g kg(-1), desorption and diffusion became rate-limiting factors: a shift was observed in the n-alkane ratios, showing that biodegradation rates of n-alkanes increased with decreasing carbon number. The monitoring of n-alkane ratios can be used to improve the efficiency of bioremediation treatments.