A Review on the Factors Affecting the Deposition, Retention, and Biodegradation of Oil Stranded on Beaches and Guidelines for Designing Laboratory Experiments

The distribution and persistence of oil within the matrix of a beach depends on the oil and beach properties, the presence of fines in the water column, and beach hydrodynamics and biochemistry. In this review, we attempted to provide an assessment of the journey of oil from offshore oil spills until it deposits within beaches. In particular, we addressed the disparity of spatial scales between microscopic processes, such as the formation of oil particle aggregates and oil biodegradation, and large-scale forcings, such as the tide. While aerobic biodegradation can remove more than 80% of the oil mass from the environment, its rate depends on the pore water concentration of oxygen and nutrients, both of them vary across the beach and with time. For this reason, we discussed in details the methods used for measuring water properties in situ and ex situ. We also noted that existing first-order decay models for oil biodegradation are expedient, but might not capture impacts of water chemistry on oil biodegradation. We found that there is a need to treat the beach–nearshore system as one unit rather than two separate entities. Scaling down large-scale hydrodynamics requires a coarser porous medium in the laboratory. Unfortunately, this implies that microscopic-scale processes cannot be reproduced in such a setup, and one needs a separate system for simulating small-scale processes. Our findings of large spatio-temporal variability in pore-water properties suggest that major advancements in addressing oil spills on beaches require holistic approaches that combine hydrodynamics with biochemistry and oil chemistry.