A stochastic model to predict the formation of oil-mineral aggregates

Theories for the natural attenuation of shores oiled by accidental spills have changed over the years. A new hypothesis has emerged which links the formation of oil-mineral aggregates (OMA) to improved rates of removal and biodegradation of stranded oil, but no model exists for this process. This paper proposes a new stochastic model based on the Monte Carlo method to calculate the formation time and the concentration of OMA in a typical turbulent estuarine environment. In particular, the model determines the effect of sediment size and concentration on OMA concentration. The assessment of both light and heavy oils showed that sedimentation is the main factor responsible for the formation of stable OMAs. Ideal conditions are when the size ratio varies between 0.1 and 0.4. At lower concentrations, the percentage of stabilized oil is negligible. Modeling results were found to be in good agreement with experimental data. For concentration ratios larger than 3, three minutes was found to be sufficient to stabilize all of the oil. Future work will concentrate on the effects of floc breakage, aggregation due to differential settling, and the real size distribution of sediment grains and oil droplets. 32 refs., 7 figs