Quantifying the Dynamics of Polystyrene Microplastics UV-Aging Process

Massive amounts of plastic waste have been released into ecosystems, generating huge amounts of microplastics (MPs) and nanoplastics (NPs) during the environmental aging process. However, particle size and number dynamics along the aging process have not been quantitatively assessed, which can greatly influence their fate and environmental risk assessment. We applied single particle inductively coupled plasma mass spectroscopy (spICP-MS) to quantitatively analyze the polystyrene (PS) MPs aging process with a wide particle size range (800 nm–5 μm) as well as particle number concentration at an environmentally relevant value (down to 7.1 × 106 particles/L). We investigated the UV-light accelerated aging dynamics of PS MPs and revealed the generation of large amounts of nano/microsize PS MPs fragments. PS MPs showed a rapid size downtrend along the aging process, shrinking from 5 to 1 μm. At the same time, PS MPs particle number concentration increased 3 times. Furthermore, pristine PS MPs may induce acute toxicity in feeding behavior, growth, and survival, while aged ones caused marked chronic toxicity on the reproduction inhibition of Daphnia magna, both at environmentally relevant concentrations. Overall, the research uncovered and quantified MPs particle size and concentration during the aging process, which is essential to assessing ecotoxicological risks of MPs/NPs.