Prediction of microplastic transport in oil-contaminated waters

Microplastics (MPs) are pervasive in marine environments and pose potential risks to marine ecosystems. MPs can transport from the surface to the deep layers, raising concerns about their impact on vulnerable deep-sea species. Scientists believe MPs are present in oceans around the world. Recent studies on the application of oil spill treating agents at sea have shown that MPs can interact with oil in the presence of chemical dispersants to form MP-oil-dispersant agglomerates (MODAs). To advance our knowledge on the behavior and transport of MPs, this study investigated the distribution of MPs under different salinities and mineral concentrations in oil-contaminated marine environments. Results indicated that the presence of oil and chemical dispersants promoted the downward transport of MPs. Minerals significantly enhanced the sinking of larger MPs through adsorption. A causal analysis identified specific surface area (SSA) as the dominant factor influencing MP transport in oil-contaminated marine environments. Model predictions further revealed that sinking velocity increased with agglomerate size and density. Our findings provide important experimental data to support the development of predictive MP transport models that are needed for environmental risk assessments and the selection of the most appropriate oil spill response measures in oil-contaminated waters.