Oil on the beach: A laboratory investigation into the influence of temperature on oil penetration into shoreline sediments

When oil reaches shorelines during a marine oil spill, it can persist in the sediment for decades, extending well beyond on-water operations and can become a significant expense to the overall response. Oil's persistence on beaches is initially driven by its ability to penetrate sediment, a process heavily influenced by a suite of in situ shoreline conditions as well as the oil's properties. One property of note is viscosity, which undergoes non-linear changes under the influence of temperature and influences oil's ability to penetrate shoreline sediments. Through 435 column experiments, this study systematically examines the penetration behaviour of diluted bitumen (dilbit) and a distillate very low-sulphur fuel oil (VLSFO) in unsaturated, coarse-grained, inorganic beach sediments under seven temperature regimes (Polar to Equatorial), five sediment types and two oil types. Results indicate that the sediment's temperature significantly influences oil penetration, while the presence of temperature gradients within the sediments exerts minimal influence on its penetration. Low temperatures limited oil penetration, concentrating oil near the sediment's surface. In contrast, higher temperatures in those same sediments resulted in deeper penetration and increased the net volume of oil-contaminated sediment. These findings confirm the temperature-viscosity feedback as a key control on oil migration in marine beach sediments and provide new empirical insights that directly inform shoreline response strategies and waste management planning across diverse climatic regions.