Influence of shape on heteroaggregation of model microplastics: a simulation study

Area of Science:

• Environmental Science
• Materials Science
• Computational Chemistry

Background:

• Microplastics pose a significant threat to aquatic ecosystems.
• Understanding microplastic aggregation with natural organic matter is crucial for environmental fate assessment.
• The influence of particle shape and flow dynamics on microplastic heteroaggregation remains poorly understood.

Purpose of the Study:

• To investigate the effect of microplastic particle shape on aggregation with organic matter.
• To analyze the stability of microplastic aggregates under varying shear flow conditions.

Main Methods:

• Molecular dynamics simulations were employed.
• Simulations modeled interactions between different microplastic shapes and smaller spherical organic matter.
• Aggregate behavior under shear flow was analyzed.

Main Results:

• Smooth microplastics formed compact aggregates with numerous weak connections and higher fractal dimensions.
• Sharp-edged microplastics formed more fractal structures with fewer, stronger connections.
• Aggregate breakup under shear flow was significantly higher for sharp-edged particles compared to rounded shapes.
• Rounded cube aggregates showed unexpected resistance to shear-induced breakup due to their compact structure and flexible connections.

Conclusions:

• Microplastic shape critically dictates aggregate structure, strength, and stability in aqueous environments.
• Flow conditions and aggregate morphology determine the mechanisms of aggregate breakup and restructuring.
• Findings provide insights into the environmental fate and transport of microplastics.