Assessment of Microplastic Release and Rate of Release Over Time from Various Plastic Polymers Under Environmental Exposure in a Humid Subtropical Environment

Despite being one of humanity's most important materials, plastic, specifically plastic waste, has become a major environmental concern. This study aimed to determine the degradation rates of plastic polymers in a subtropical soil environment over time. With the growth of plastic use comes the risk of microplastics (MPs), small plastic pieces less than 5 millimeters in size, that break off from larger items (NOAA, 2021). It was hypothesized that polyvinyl chloride (PVC) would exhibit the slowest degradation rate due to its weather-resistant properties. This study investigated degradation rates and MP release from various plastic polymers, including both single-use plastics (SUPs) and non-SUPs, in a humid subtropical environment. Four different plastic polymers, polyethylene terephthalate (PET), high-density polyethylene (HDPE), PVC, and polystyrene (PS), were exposed to environmental conditions in controlled soil environments over eight weeks. MP concentrations were measured biweekly through a microscopic analysis following a density separation. A two-way ANOVA revealed a significant effect of time (p = .0003) on MP release, while the effect of polymer type approached significance (p = .091). PET showed the highest MP release, followed closely by PS. HDPE and PVC showed moderate increases, with control samples showing minimal change. The interaction between time and polymer type was not significant (p = .1809), suggesting similar degradation rates/patterns across all tested polymers. These findings provide insight into the degradation rates of different polymer types in terrestrial environments, contributing to our understanding of plastic pollution and informing policy decisions regarding plastic use and management.