A multivariate approach to estimate the degradation age of plastics in marine environments

This study quantifies plastic aging in the marine environment using a multivariate approach. Plastic samples exposed to simulated seawater conditions for 1.8–10 years were analyzed using complementary analytical techniques, including Fourier Transform Infrared Spectroscopy, Raman spectroscopy, and Elemental Analyzer-Isotope Ratio Mass Spectrometry. Additionally, this study introduces the novel application of Rock-Eval ® to characterize polymer aging. Results show that polymer properties and environmental conditions influence plastic degradation. This study proposes to use principal component analysis to construct a single multivariate Aging Index (AI) to quantify degradation. To validate this, a regression model relating AI to exposure time of polyethylene (PE) pellets from the microcosm was used to estimate the degradation age of PE pellets from the Pacific Ocean. Results indicate that the investigated pellets were degraded over 1–2.5 years. Acknowledging the limitations, this study emphasizes that the dataset and this method could be explored across different environments and polymer types.