Events

Deemed “emerging contaminants” by the U.S. EPA, microplastics (MPs) are plastic particles less than 5 mm in size. MPs come in many different sizes, shapes, and polymer types. They can be categorized as Primary MPs (particles specifically designed for commercial use) or Secondary MPs (particles that are derived from primary plastics). These contaminants are increasingly found in surface waters due to a rise in commercial and industrial use, affecting ecosystems and drinking water sources alike. Due to the challenges of detecting and quantifying MPs in the environment, strong predictive fate and transport models are critical for risk assessment. However, current models are largely based on experiments with “pristine” particles. For example, microsphere analogs are often used in current MP research. Plastics are more commonly found as fragments, fibers, and films as opposed to these microspheres. In this preliminary work, secondary polystyrene MPs were produced from household plastics to identify differences between these generated MP fragments and manufactured 5 um polystyrene microspheres. Although cryo-milling is a common method to make plastic particles, these MPs aren’t always easily suspended. In this work, sonication in alkaline suspension was used to fragment the parent plastic into MPs. Microscopic imaging and particle sizing techniques were employed to compare these particle types. The MP fragments made were less uniform in both shape and sizes compared to the microspheres. While as the microspheres were mostly 5 um in diameter, the diameter of the fragment particles where between 25 and 2 um. Future work will involve more comprehensive chemical and physical characterization of the polystyrene MPs, extensions to other commonly found polymer types in surface waters, and aggregation experiments with natural organic matter (NOM), a key interaction for particles in the environment. The aim of these MP experiments is to incorporate major identifiable differences between these particles and integrate these parameters to bridge the gap between realistic complex systems and simplified systems for more reliable contaminant modeling.

This project presenter is available for live video chat on Sept. 1, 2020 from 10:15 a.m. - 12:00 p.m. PDT.