Microplastic and dispersed oil co-contaminants in the simulated marine environment: formation, transport, and fate

Yang, Min (2023) Microplastic and dispersed oil co-contaminants in the simulated marine environment: formation, transport, and fate. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Microplastics (MPs) and oil spills are two major concerns in the marine environment with negative effects on marine ecosystems. Each year, more than 700 million liters of oil enter oceans from thousands of oil spills during oil extraction, transportation, and consumption. Chemical dispersants are widely adopted as oil spill treating agents to break oil into tiny droplets and facilitate their biodegradation. Dispersant efficiency could be affected by mixing energy, seawater salinity, dispersant-to-oil volumetric ratio (DOR), and suspended particles such as minerals. However, there is extremely limited information on how MPs affect oil dispersion as well as dispersed oil transport and transformation although MPs are frequently detected in oil-polluted oceans. This thesis thus focuses on the interaction between MPs and crude oil in the presence of chemical dispersants and the formation, transport, and fate of MP-oil-dispersant agglomerates (MODAs) in the marine environment. It includes the following objectives: 1) to conduct a viewpoint to summarize the knowledge gaps regarding MP and crude oil interactions; 2) to explore the interaction between MPs and crude oil in the presence of dispersants under diverse conditions (MP concentration, aging degree, and DOR); 3) to reveal MODA formation mechanism under various MP sizes using the surface free energy minimization principle, and evaluate the impacts of MODAs on oil dispersion under different ocean conditions (seawater salinity and mixing energy); 4) to evaluate the transport of MODAs in seawater layers (surface and column) under various conditions (MP size, crude oil type, seawater salinity, and mineral concentration), and predict the sinking velocity of MODAs; and 5) to investigate the degradation efficiency of ii dispersed oil in the presence of biofilm-developed MPs (B-MPs) in seawater layers, and uncover the degradation mechanism. This thesis reported the existence of MODAs in the marine environment for the first time and revealed the formation of two types of MODAs. It suggested a transport model (Rubey’s equation) for MODA sinking velocity prediction and demonstrated that minerals could enhance the downward transport of MODAs. The combined effects of oil evaporation, B-MODA formation, and biodegradation (EBB effects) were proposed for the first time to explain the degradation mechanisms of dispersed oil. This thesis established a comprehensive framework for exploring the MP and oil co-contaminants in marine environments. Findings would guide decision-making on oil spill response strategies and operations in the presence of MPs and contribute to marine MP and oil pollution control.

Item Type: Thesis (Doctoral (PhD))
URI: http://research.library.mun.ca/id/eprint/16351
Item ID: 16351
Additional Information: Includes bibliographical references (pages 208-232) -- Restricted until February 1, 2026
Keywords: microplastics, oil pollution, marine environment, transport and fate
Department(s): Engineering and Applied Science, Faculty of
Date: December 2023
Date Type: Submission
Digital Object Identifier (DOI): https://doi.org/10.48336/PTYP-5X64
Library of Congress Subject Heading: Microplastics--Biodegradation; Oil pollution of water; Marine pollution; Dispersing agents

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