Formatted Title
Modeling the Interaction of Crude Oil Hydrocarbons with Polyethylene Microplastics in Aquatic Environments
Background/Objectives
Crude oil as a primary global energy source poses major environmental threats due to potential spills leading to water contamination. Oil spill accidents are primarily linked to anthropogenic sources such as maritime transportation and oil exploration activities, and despite mitigation efforts, the intentional and unintentional dispersal of crude oil in waterbodies persists. The spilled oil undergoes a complex series of physical, chemical, and biological changes that determine its fate. The prevalence of plastic and microplastic pollution in waterbodies can potentially play a role in the redistribution of petroleum hydrocarbons due to the capacity of microplastics to sorb and concentrate hydrophobic organic micropollutants. This study aims to investigate and quantify the uptake of petroleum hydrocarbons available in light crude oil by polyethylene microplastics, following their co-occurrence within the same aquatic matrix.
Approach/Activities
To fulfill the mentioned objectives, adsorption experiments were conducted in water loaded with environmentally relevant amounts of polyethylene microplastic particles and crude oil. Isotherm experiments to evaluate the adsorbent performance under constant temperature and pH conditions, and kinetic experiments to determine the rate at which adsorption occurs were conducted. Results were fitted to several kinetic and isotherm models to find the model that best describes the interaction. Gas chromatography-mass spectrometry was used to measure the concentrations of multiple polycyclic aromatic hydrocarbons, alkanes, and isoalkanes available in the crude oil used for the experiments.
Results/Lessons Learned
The study sheds light on the potential of microplastics to affect the post-spill mass balance of crude oil hydrocarbons in water, thereby enhancing our understanding of the fate of spilled oil in aquatic environments in the era of plastic accumulation. The findings of the study revealed favorable adsorptions for all the target components confirmed by both the Langmuir and the Freundlich models. The derived maximum adsorption capacity of hydrocarbons of around 365 mg.g-1 led up to an estimated 5.75 mg of hydrocarbons/m2 of polyethylene microplastics’ surface within the size range of 300-600 μm. This surpasses adsorption values reported in many studies where the removal of hydrocarbons was tested using sand, commercial activated carbon, and bentonite clay. This research underscores the significance of considering the adsorption of hydrocarbon components onto microplastics when modeling the fate of spilled oil in future predictive models, as these interactions may influence the spreading rates and natural dispersion processes.