(392b) Weathering Induced Changes in Microplastic Dispersity and Pollutant Uptake Capacity

Microplastics have become ubiquitous in nature and a part of our everyday life, however their environmental fate remains poorly understood. As microplastics age and endure weathering, their surface chemistry can be altered. An accelerated weathering experiment was performed on microscopic polyethylene particles in the laboratory over a 10-day period. During this period, a change in wettability was observed, which resulted in a shift of the particles to a hydrophilic state and an overall increase of their dispersal in the water column. This change in wettability can be attributed to the destruction of hydrophobic surface groups through the photo-degradation process. To study changes in adsorption, we compared the uptake of two common pollutants onto the microplastic substrate: (1) positively charged malachite green molecules and (2) negatively charged arsenite molecules. We observed an increase in the adsorption of malachite green molecules onto weathered particles, but no significant adsorption of the arsenite molecules throughout the weathering process. This is because during weathering, the magnitude of the negative charge on the PE particles and thus results in electrostatic attraction and repulsion between the malachite green and arsenite molecules, respectively. This finding provides insight on both the transport and dispersibility of MPs in the environment, as well as further understanding their toxicity to human health.