Aging of Microplastics across a Constructed Wetland

In constructed wetland ecosystems, physical, chemical, and biological processes work together to weather microplastics over time. In this study, the aging of five microplastic polymer types (low-density polyethylene, high-density polyethylene, polypropylene, polystyrene [PS], and polyethylene terephthalate [PET]) was contextualized in four habitats within a wastewater constructed (treatment) wetland over 18 months. This is the first study to analyze the weathering and microorganism colonization of different types of microplastics as they age within a constructed wetland. A multistep analysis approach was employed to assess microplastic aging. Microorganisms quickly and abundantly colonized all polymer types, with the highest biomass and cell counts being found on particles at the wetland cell outlet. Overall, the wetland cell outlet showed the highest metrics of weathering, and PET and PS were found to be the most weathered within this system. No complete disintegration was found in this study, underscoring the durability of microplastics in aquatic ecosystems. As microplastics abundantly flow through wastewater treatment streams and receiving constructed wetlands have demonstrated strong retention potential, it is important that environmental managers better contextualize the aging abilities of these systems.