Current velocity, temperature and oil thickness as determinants of the refloating process of stranded oil in the Bohai Sea

Abstract

After oil spill accidents, weathered oil slicks can drift to coastal areas and interact with shoreline substrates. This process has been demonstrated to be the cause of the formation of stranded oil, which has attracted much attention. However, the refloating process of stranded oil when coastal hydrodynamic conditions change has been little investigated. This study evaluated the effects of current velocity, temperature and oil thickness on the refloating process of a simulated oil patty in a flow-through tank. The oil refloating efficiency (ORE) was used to quantitatively examine the degree of refloating. Non-linear fitting results indicated that the ORE increased gradually over time and then plateaued. Both observations and measurements indicated that higher current velocity brought about more oil refloat and enhanced the oil refloating rate. Furthermore, both the mass of refloating oil and the oil refloating rate showed a positive linear correlation with current velocity. The effects of temperature on the oil refloating process were determined by the effects of temperature on oil viscosity. In addition, the ORE at equilibrium increased linearly with increasing oil thickness. An empirical model was introduced and found to be closely consistent with the experimental data. This information is useful in predicting the fate and transport of stranded oil in the Bohai Sea.