Study of the dispersion/settling of oil-mineral-aggregates using particle tracking model and assessment of their potential risks

Abstract

A random walk particle tracking model was used to simulate the motions of oil-mineral-aggregates (OMAs) under hydrodynamic conditions involving wave-induced velocities, random velocities due to turbulence, and the settling velocity due to gravity. Wave-induced and settling velocities for OMAs determined from the application of Stokes’s theory and empirical equations derived from experimental data were used in a series of simulations to evaluate the effects of wave characteristics, particle size distribution, and settling/floating velocity on the transport of OMAs formed from two different types of minerals. The study found that the wave effect on advection/diffusion is of secondary importance when compared to tidal currents and turbulence induced velocity. To assess the risk of OMAs to benthic organisms, predicted environmental concentrations (PEC) was compared to the benchmark concentration (BC) derived for eight different hydrocarbon groups. The simulation results indicate that no risk from both aliphatic and aromatic hydrocarbons can be found for the two cases described in this paper with a 1,000 tonnes spill. The study also showed that aromatic hydrocarbons posed more risk than aliphatic hydrocarbons. For both aliphatic and aromatic hydrocarbons, the C9–C12 group posed greater risk than other groups.