Sorption and dissipation of current-use pesticides and personal-care products on high-density polyethylene microplastics in seawater

Sorption kinetics and the desorption of three current-use pesticides (CUPs: methyl-chlorpyrifos - m-CPF -, pendimethalin and propyzamide) and three personal-care products (PCPs: triclosan - TCS-, tonalide and galaxolide) on high-density polyethylene (HDPE) in seawater were characterised in this study. Sorption kinetic equilibrium and mass balance were determined for all contaminants, evidencing simultaneous dissipation processes (degradation, volatilization, etc.) after 72 h, particularly for propyzamide, pendimethalin, galaxolide and tonalide. However, they were lower than 24 % for TCS and m-CPF, getting the steady-state for all considered analytes in 24 h. The concentration of contaminants sorbed on HDPE increased with the hydrophobicity from 13.9 ng g⁻¹ to 35.1 ng g⁻¹ for m-CPF and TCS, respectively. No clear effect of temperature was observed for m-CPF sorption, and apparently the sorption of TCS was higher at 15 °C than at 25 °C, but it can be affected by the higher dissipation at 25 °C for this compound. This study confirmed the desorption of TCS and m-CPF from HDPE, being higher than 30 % in all cases during the first 24 h, especially for the highest tested concentrations (200 ng L⁻¹). Sorption of TCS and m-CPF were favoured (4–7 times) on HDPE with the highest specific surface (estimated in an increase of 49-fold times).