Accelerated Weathering of Microplastics: A Systematic Approach to Model Microplastic Production

As microplastics (MP) are omnipresent in the environment, there is an increasing need to understand these emerging contaminants and their potential risks to health and the environment. However, no reliable experimental protocol exists for generating environmentally representative model MPs in sufficient quantities for toxicity and environmental fate studies across various polymer types, as uniform environmental samples are difficult to obtain due to technical and practical challenges. Additionally, there is a lack of focus on mimicking the surface characteristics of environmental microplastics in laboratory weathered samples. In this work, an accelerated method of MP generation from macroplastics was investigated to synthesize MPs that mimic key surface properties of environmental MP samples. A three-step methodology consisting of cryo-milling, UV-O exposure, and mechanochemical persulfate-based surface modification was used to create artificially weathered MPs matching the properties of environmentally found ones. The production of relevant microplastic models has the potential to allow for more quantitative experimental studies on the toxicity, fate, and behavior of these anthropogenic particles. The accelerated weathering method generated MPs in the hundreds of milligrams to grams scales, with controllable and tunable degree of oxidation (measured as carbonyl indices from 0.06 to 1.84), particle size (between 15.8 and 365.4 μm), and surface features. We found these properties to be comparable with MPs found in the ocean, making this report a unique example of scalable and tunable model MP synthesis.