Interactions between microplastics and oil dispersion in the marine environment.

Microplastics (MPs) and spilled oil are both major concerns in the marine environment. In this study, we investigated if and how MPs would interact with crude oil and potentially reduce the effectiveness of oil dispersants applied during oil spill response operations. With the addition of dispersant, MPs and oil (covered by dispersants through their hydrophobic tails) formed MPs-oil-dispersant agglomerates that were found to exist from the surface layer to the bottom of the seawater column. Their resurfacing and sinking led to a decrease in oil dispersion effectiveness. Effects of MP concentration, MP aging, and dispersant-to-oil volumetric ratios (DORs) on oil dispersion were examined. We found that the dispersion effectiveness of light oil and heavy oil decreased 38.26 % and 38.25 %, respectively, with an increased MP concentration. The dispersion effectiveness of light oil and heavy oil was 82.86 ± 10.87 % and 40.39 ± 4.96 % with pristine MPs and increased up to 109.75 ± 0.71 % and 58.30 ± 0.00 % when using MPs aged for 56 days. MPs reduced oil dispersion effectiveness under different DORs. The findings of this first report to understand the interactions among MPs, oil and dispersants have provided fundamental insights that may influence future decision making on the selection and use of oil spill response strategies.