Impact of Microplastics on Oil Dispersion Efficiency in the Marine Environment

Role of light microplastics in the dispersion process of spilled crude oil in the marine environment

Oil spill and microplastic (MP) pollution are the main problems in the marine environment. After an oil spill, the oil film may be dispersed into the water column in the form of droplets under the action of ocean waves. In this study, the sea condition was simulated through the batch conical flask oscillation experiment. Merey crude oil was selected as experimental oil, and polyethylene (PE) and polystyrene (PS) were used as experimental MP. The effects of MP properties (type, concentration and size) on the dispersion of spilled oil were investigated. It is found that for each MP, the oil dispersion efficiency (ODE) increased rapidly at first and then tended to be stable, which all reached the maximum at 360 min. When the concentrations of PE and PS increased from 0 to 100 mg/L, the maximum ODE decreased from 32.64 % to 13.72 % and 10.75 %, respectively, indicating that the presence of MP inhibits the oil dispersion. At the same oscillation time, the volumetric mean diameter (VMD) of dispersed oil increased with the MP concentration. When the particle size of PE and PS increased from 13 to 1000 μm, the maximum ODE increased from 24.74 % to 31.49 % and 28.60 %, respectively. However, the VMD decreased with the size of MP. In addition, the time series of the oil adsorption rate by the MP were well fitted by the kinetic models. The results of this research deepen the understanding of the migration law of spilled oil to the marine environment in the presence of MP, and may further improve the ability of marine environmental scientists to predict the fate of oil spill.

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Impact of mixing energy and dispersant dosage on oil dispersion and sedimentation with microplastics in the marine environment

Recently, the fate of spilled oil in the presence of microplastics (MPs) in the sea has attracted attention of researchers. Merey crude oil and polyethylene terephthalate (PET) were used as the experimental materials in this study. The effects of mixing energy and dispersant dosage on oil dispersion and sedimentation in the presence of MPs in the water column were investigated by laboratory experiments simulating actual sea conditions. The increase of mixing energy showed a promoting effect on oil dispersion. When the oscillation frequency increased from 140 rpm to 180 rpm, the oil dispersion efficiency (ODE) ranged from 2.1 %-3.7 % to 17.4 %-30.8 %, and the volumetric mean diameter (VMD) of the suspended oil droplets/MPs-oil agglomerates (MOA) decreased from 99.9-131.4 μm to 76.6-88.2 μm after 2 h oscillation. The application of chemical dispersant led to an increase in both the quantity and size of the formed sunken MPs-oil-dispersant agglomerates (MODA). At the dispersant-to-oil ratio (DOR) of 1:5, the ODE declined from 77.7 % to 62.6 % when the MPs concentration increased from 0 to 150 mg/L, while the oil sinking efficiency (OSE) rose from 3.4 % to 15.6 % when the MPs increased from 25 to 150 mg/L; the maximum size of the sunken MODA reached 13.0 mm, and the total volume of the MODA formed per unit volume oil reached 389.7 μL/mL oil at the MPs concentration of 150 mg/L. Meanwhile, the results showed that the presence of MPs inhibited the oil dispersion by increasing the oil-water interfacial tension. The outcomes of this work may provide assistance in predicting the transport of spilled oil and developing emergency measures.

Transport of Microplastic and Dispersed Oil Co-contaminants in the Marine Environment

Microplastics (MPs) and oil pollution are major concerns in oceans. Although their coexistence in oceans and the associated MP-oil-dispersant agglomerates (MODAs) have been reported, limited attention is given to the behavior of the co-contaminants. This study investigated MODA transport in a simulated ocean system and explored related mechanisms under various oil types, salinities, and mineral concentrations. We found that more than 90% of the heavy oil-formed MODAs stayed at the seawater surface, while the light oil-formed MODAs were widely distributed throughout the seawater column. The increased salinity promoted MODAs formed by 7 and 90 μm MPs to transport from the seawater surface to the column. This was elucidated by the Derjaguin-Landau-Verwey-Overbeek theory as more MODAs formed under higher salinities and dispersants kept them stable in the seawater column. Minerals facilitated the sinking of large MP-formed MODAs (e.g., 40 μm) as minerals were adsorbed on the MODA surface, but their impact on small MP-formed MODAs (e.g., 7 μm) was negligible. A MODA-mineral system was proposed to explain their interaction. Rubey's equation was recommended to predict the sinking velocity of MODAs. This study is the first attempt to reveal MODA transport. Findings will contribute to the model development to facilitate their environmental risk evaluation in oceans.

Microplastic and oil pollutant agglomerates synergistically intensify toxicity in the marine fish, Asian seabass, Lates calcalifer

Asian seabass, Lates calcarifer frys were exposed to polystyrene (MP: 0.5 mg/l), oil (0.83 ml/l) and agglomerates (MP + oil + Corexit) as eight treatments in three replicates, and fresh synthetic marine water (control) for 15 days. The synergistic effect was confirmed (P ˂ 0.05) by bio-indicators including RBC count, total plasma protein, aspartate aminotransferase (AST), catalase (CAT), glutathione S-transferase (GST), basophils, thrombocyte and eosinophils percentages. Most of the significant and synergistic effects were observed in the highest doses (5 mg/l MP and 5 mg/l MP-oil-dispersant). Exposure to MP and a combination of MP+ oil caused tissue lesions in gill, liver and intestine. Our results suggest there are no critical health issues for Asian seabass in natural environments. However, the bioaccumulation of MPs, oil, and their agglomerates in consumers' bodies may remain a concern.

Microplastic and oil pollution in oceans: Interactions and environmental impacts

Microplastics (MPs) have been found in oil-polluted oceans, but studies on MPs and oil were still focused on their respective transport, biodegradation, and bioaccumulation. The interactions between MPs and oil in the marine environment remain unknown. MPs would incorporate with oil to form MP-oil agglomerate (MOA), the behaviors of MOA were thus discussed in this study. It was found that the MOA formation resulted in the decreased oil dispersion efficacy and affect marine oil spill response operations. Moreover, oil biodegradation rate would be changed when oil existed as the form of MOA. The slow vertical transport of MOA might lead to wider ocean contamination. MOA would cause much worse impacts on phytoplankton, zooplankton, and high trophic species in the marine environment than MPs or oil individually. MOA assembling with phytoplankton in oceans may reduce carbon dioxide (CO₂) transport to deep seas. Exploring the interactions between MPs and oil in the marine environment opened a door for understanding MPs and oil as co-contaminants.

Recent advances in chemical and biological degradation of spilled oil: A review of dispersants application in the marine environment

Growing concerns over the risk of accidental releases of oil into the marine environment have emphasized our need to improve both oil spill preparedness and response strategies. Among the available spill response options, dispersants offer the advantages of breaking oil slicks into small oil droplets and promoting their dilution, dissolution, and biodegradation within the water column. Thus dispersants can reduce the probability of oil slicks at sea from reaching coastal regions and reduce their direct impact on mammals, sea birds and shoreline ecosystems. To facilitate marine oil spill response operations, especially addressing spill incidents in remote/Arctic offshore regions, an in-depth understanding of the transportation, fate and effects of naturally/chemically dispersed oil is of great importance. This review provides a synthesis of recent research results studies related to the application of dispersants at the surface and in the deep sea, the fate and transportation of naturally and chemically dispersed oil, and dispersant application in the Arctic and ice-covered waters. Future perspectives have been provided to identify the research gaps and help industries and spill response organizations develop science-based guidelines and protocols for the application of dispersants application.