Effects of aging and temperature on the desorption of polychlorinated biphenyls from microplastics in simulated digestive fluids

Ingestion of microplastics by various organisms has been widely evidenced. Chemicals associated with microplastics (MPs) may be released to digestive tracts upon ingestion. However, the effect of aging and temperature on the chemical desorption for MPs remains poorly understood. The exposure of polyethylene (PE) particles to UV radiation in dry air, tap water, and sea water was conducted to mimic the aging process of MPs in different environments. Polychlorinated biphenyls (PCBs), as a typical hydrophobic organic contaminant, were preloaded in these aged and pristine PE. The desorption was performed by exposing preloaded PE particles in simulated gastric and gut fluids at 25 °C and 40 °C. After UV aging, the average diameter of PE particles decreased rapidly with aging time, indicating continuously fragmentation of PE under UV exposure. The desorption of PCBs from PE particles under different conditions varied from 7% to 40%, and that from aged PE in gut fluid at 37 °C was significantly higher than those under other conditions (P<0.05). Furthermore, a clear declining trend was observed as lgK_ow (octanol-water partition coefficient) value increased. The aging process, hydrophobicity of chemicals, and incubation temperature were important factors on the desorption of PCBs from PE. The present study helps understand the desorption of PCBs from microplastics and the potential risks of microplastics ingestion by organisms.