First determination on two kinds of microplastic-air partition coefficients of seven per- and polyfluoroalkyl substances under environmentally relative conditions: Experiment measurement and model prediction

Microplastics (MPs) in the environment are the sink and vector of organic contaminants, including per- and polyfluoroalkyl substances (PFASs). Although PFASs are low- and non-volatile compounds, they have the potential to partition and diffuse from MP into the gas phase in the environmental functions. Herein, the MP-air partition coefficient (K) of seven PFASs was measured using a solid-fugacity meter. The PFAS K values in two MPs (high-density polyethylene (HDPE) and thermoplastic polyurethane (TPU)) were determined under different times, temperatures, and relative humidities (RH), and a model was developed to predict the PFAS K values based on the measured data. The results showed that the K of PFASs increased with the prolonged partition time until 90 mins, and higher temperature and RH facilitated the distribution of PFASs in MPs into the air phase, leading to smaller K values. Moreover, the derived equation for predicting PFAS log K values was robust with 0.79 of an adjusted square of correlation coefficient (R = 0.79) and 0.35 of root mean squared error (RMSE = 0.35). These findings provided the first knowledge for understanding the partition behavior and fate of PFASs in the MP-air microenvironment.