Oil-water interactions play a crucial role in everyday life, such as in food emulsions like salad dressing and over-the-counter medications. However, these stable mixtures can also pose significant environmental concerns when it comes to oil spills in large bodies of water. Historically, oil is naturally present in oceans, but increased reliance on and transportation of oil have amplified the prevalence and impact of oil spills. Researchers have extensively studied oil behavior in water, including how oil droplets rise to the surface, accumulate on the water surface, and separate from the water. Surprisingly, the transition of an oil drop rising through the ocean to form an oil layer after reaching the surface is crucial for our understanding of oil spills because droplets that don’t accumulate on the oil layer cannot be easily removed during ocean cleanups.

Turbulent waves in the ocean generate entrapped air bubbles that rise to the water’s surface. However, the opposite effect is observed if there are oil droplets. Researchers from the University of Illinois found that when there is an ocean oil spill, oil droplets do not always form a continuous oil layer on the surface ; instead, upon reaching the surface, they burst into smaller daughter droplets that are pushed downward by the turbulence in the waves. This phenomenon results in an undesirable effect where progressively smaller oil droplets drop deep into the ocean, making them easily missed by oil clean-up efforts. To see if they could reduce the formation of these daughter oil droplets, the authors added glycerol, a thickening agent, to water which successfully slowed down the motion of the waves and minimized the formation of smaller oil droplets. 

This study shows that oil drops bursting at the surface of the water can disperse daughter droplets deep into the ocean, potentially prolonging oil droplet lifetimes and hampering oil spill cleanup efforts. This finding has significant implications for understanding oil spill behavior and developing remediation strategies. Moreover, the presence of marine biosurfactants like glycerol can influence the droplet generation, highlighting areas for future research. These insights are valuable not only for environmental management but also for various industries where oil-water interactions are essential.

This study was led by researchers at the University of Illinois, Chicago, with corresponding author Sushant Anand.

Managing Correspondent: Gurminder K. Paink 

Press article: Bursting of underwater oil drops: How pollution may remain in water after oil spill cleanups (phys.org)

Original Journal Article: Bursting of Underwater Oil Drops (Physical Review Letters)

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