Microplastics (MPs) are ubiquitous in terrestrial systems, where they act as vectors of environmental contaminants. The impact of MPs on the transformation or chemical speciation of trace metal contaminants is, however, unknown, restricting a comprehensive understanding of environmental risks of MPs.

A research team led by Prof. Yujun Wang from the Institute of Soil Sciences (ISS), Chinese Academy of Sciences recently published a paper entitled “Weathered microplastics induce silver nanoparticle formation” in Environmental Science & Technology Letters (DOI:10.1021/acs.estlett.1c00766).

They show that polystyrene (PS) weathered under natural sunlight reduces Ag(I) to Ag(0)-NPs in both surface freshwater and sand matrix. The reduction rate constants range from 2.3 to 6.1×10^-3  h^-1 in simulated experimental system. ATR-FTIR and XPS identify the carbonyl groups on the weathered PS as a key determinant of Ag(0)-NPs formation. Tentative estimates show an unexpectedly large pool of reductive PS in natural environment (18.1-39.4 MT per day), and they play a significant uncharacterized role that will impact the biogeochemistry of silver and other environmental contaminants reactive with surface carbonyl groups. These findings offer novel insights into the risk assessments of MPs, where their transformation and interactions with environmental contaminants determine the long-term exposure scenario of organisms and ecosystems.  

The research was supported by the National Natural Science Foundation of China (41977355, 41671484 and 42022049) and the Youth Innovation Promotion Association, CAS (2020314).