RELATION BETWEEN BIOAVAILABILITY AND FUEL-OIL HYDROCARBON COMPOSITIONIN CONTAMINATED SOILS

Bioavailability of oil components in contaminated soils is an importan t regulating factor for biodegradation rates. Changes in the compositi on of mineral oil can provide information regarding the bioavailabilit y restrictions in contaminated soils. The fate of oil components was s tudied in a lysimeter experiment and laboratory incubations. A shift i n 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 bioava ilability of the oil. At higher concentrations, the bioavailability wa s controlled by solubilization from a non-aqueous-phase liquid into th e aqueous soil water phase. The ratios remained constant with decreasi ng 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 increas ed with decreasing carbon number. The monitoring of n-alkane ratios ca n be used to improve the efficiency of bioremediation treatments.