An experimental study on microplastic settling velocities in different water environments: Which factors shape the...

Area of Science:

• Environmental Science
• Oceanography
• Polymer Science

Background:

• Microplastics are prevalent pollutants in aquatic ecosystems.
• Their behavior, including settling rates, impacts ecological risk assessments.
• Biofilm formation and weathering are hypothesized to alter microplastic fate.

Purpose of the Study:

• To investigate the influence of biofilm formation and weathering on microplastic settling velocities.
• To compare experimental settling data with theoretical models.
• To assess the role of polymer type, size, and surface characteristics.

Main Methods:

• Examined nine polymer types across three size categories.
• Tested microplastics in pristine, biofilm-coated, aged, and weathered/biofilm-coated conditions.
• Measured settling velocities and compared experimental data with two established theoretical models.

Main Results:

• Settling velocities ranged from 0.012 to 0.154 m/s.
• Polybutylene terephthalate and polyethylene terephthalate settled fastest; acrylonitrile butadiene styrene settled slowest.
• Biofilm formation varied with surface texture; weathering altered surface morphology.
• Water matrix, biofilm, and weathering did not significantly affect settling rates in this study.
• Experimental data closely aligned with theoretical models for irregular microplastics.

Conclusions:

• Microplastic size and density are key determinants of settling velocity.
• Theoretical models provide reliable predictions for microplastic settling behavior.
• Findings support the use of models for assessing microplastic transport and fate in aquatic systems.