Investigating the effects of particle shape and biofilm growth on microplastics settling velocity

Session: 46. - Plastics in the Great Lakes: Characterizing the Problem and Finding Solutions

Patricia Semcesen, University of Toronto, [email protected]
Roberta Fulthorpe, University of Toronto Scarborough, [email protected]
Mathew Wells, University of Toronto Scarborough, [email protected]

Abstract

Easy to manufacture and durable, plastics are used in every day products, but these plastics enter and pollute out Great Lakes as microplastics. Microplastics pollution is a growing global concern as it can negatively impact ecosystems and humans. Field observations have revealed that microplastics pollution is not localized near its urban and industrial sources, but can disperse to remote areas of the Great Lakes (Ballent et al., 2016). Since microplastics distribution and dispersal ability are not well understood, laboratory experiments were conducted to investigate how particle morphology and density affect microplastics settling velocity. Granules and shavings of LDPE, HDPE, PP, and PS were added to tanks of lake water for biofilm development on the microplastics. Particle settling velocities were quantified using a camera and particle tracking velocimetry software. Results supported the hypothesis that biofilm growth can cause plastics less dense than water (i.e. LDPE, HDPE, PP) to become negatively buoyant while plastics denser than water (i.e. PS) can become positively buoyant. It was also found that more spherical particles settled faster that flake-like particles. Quantified effects of microplastics settling ability will improve Great Lakes Hydrodynamic model estimates for microplastics pollution dispersal.

1. Keyword
microplastics

2. Keyword
hydrodynamics

3. Keyword
biofilm