Oil on the beach: A laboratory investigation into the influence of temperature on oil remobilization and retention in shoreline sediments

Marine oil spills that strand on shorelines can result in prolonged ecological impacts, extended response times, and increased cleanup costs. Predicting oil penetration, remobilization, and retention can inform the selection of shoreline treatment options and improve the efficacy of shoreline response tactics. This laboratory study examined the 24-h remobilization and retention of the non-aqueous phase of Very Low Sulphur Fuel Oil and diluted bitumen in five uniform shoreline sediments across seven temperature regimes using 435 column experiments following an 8-h penetration phase and a single simulated tidal cycle. Across screened experiments, 24-h oil retention ranged from 52 to 99% of the initial loading mass and was strongly dependent on sediment type and temperature. Under both uniform and non-uniform temperature regimes, 24-hour residual oil 19 concentrations decreased exponentially with increasing sediment grain size and higher oil 20 viscosity, whether intrinsic to the product or driven by temperature and weathering. Time-resolved oil remobilization exhibited a biphasic release pattern, with 42–52% of the cumulative remobilized oil released within the first 130 min of inundation and initial release rates 6.6–13.0 times greater than those during the remainder of the 24-h flooding period. Retained oil mass increased proportionally with penetration depth. These results provide an experimentally supported mechanistic framework linking temperature, penetration, remobilization, and retention, providing insights relevant to shoreline treatment and response across climate-relevant temperature regimes.