Collaborative Research: CAS-MNP: Understand and Predict the Adsorption of Organic Contaminants by Aging Microplastics

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This award from the Environmental Chemical Sciences Program in the Division of Chemistry supports Professors Francois Perreault and Jay Oswald at Arizona State University and Professor Onur Apul at the University of Maine for research on microplastics. These small plastic particles form during the breakdown of waste plastic. Because of their small size, microplastics accumulate more organic contaminants on their surface than larger plastic pieces. Microplastics age in the environment due to the action of sunlight or microorganisms, which changes their surface characteristics. To predict the environmental effects of microplastics, it is important to understand how aging of microplastics by sunlight or microorganisms affect contaminant adsorption. This project focuses on the aging of low-density polyethylene, one of the most abundant plastics. The exploratory scope of this project leads to insights for future in-depth studies of the nature of microplastics aging and their effect in complex natural systems. Graduate and undergraduate students at the two institutions have the opportunity to learn about interdisciplinary research, including experimental and theoretical work. The team also engages in age-appropriate outreach activities on the topic of plastic pollution for K-12 students in their communities. This project combines experimental and theoretical approaches to identify the molecular-level mechanisms involved in organic contaminant adsorption on pristine and aged low-density polyethylene microplastics. Laboratory-based aging procedures, simulating the effect of sunlight or surface biofilms, are used to produce well-characterized low-density polyethylene microparticles representative of environmental microplastics. Using these model microplastics, adsorption isotherms are measured for a range of model organic contaminants to determine how biofilms or the change in surface chemistry affect the adsorption of different classes of contaminant. Molecular dynamics simulations are used to identify, based on the aged microplastics characterization, the molecular-level changes in surface chemistry that occur during environmental aging. This multidisciplinary approach provides a mechanistic insight into how environmental aging by sunlight or biofilms affect the role of microplastics as vectors of organic contaminants in the environment. The experimental framework developed in this project can be applied to a wide range of microplastic materials or mechanism of environmental aging to provide a comprehensive understanding of how organic contaminants will interact with microplastics in the environment over time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.