Impacts of metal-enriched microplastics on plant and soil properties

Abstract

Microplastics (MPs) are now known to be a significant source of water pollution worldwide. Significantly less is known, however, regarding the ability of terrestrial and aquatic plants to tolerate pollution by microplastics. The effects of MPs exposed to Cd, Pb, and Zn on wheat (Triticum aestivum) and oat (Avena sativa) and a species of sedge (Carex scoparia) were assessed during 30 days of incubation in a growth chamber. Particles were analyzed for changes to surface characteristics by FTIR and light microscopic analysis. After a 30-day exposure to metal enriched MPs, Cd-treated MPs had a slightly toxic effect on plant growth and health while Zn-treated MPs sometimes promoted growth and health. Visual analysis of MPs after the 30-day period showed differences in surface texture and color, suggesting weathering or the presence of a biofilm. ATR-FTIR analysis found that MP exposure to metals affects the chemical bonds in PP and PE pellets and that metal groups may directly bond to PE at the 1472 cm-1 CH2 bend. The reported study shows that metal sorption to microplastics alters certain reactive groups; in addition, plants differ in their tolerance to metals sorbed to MPs. This has long-term implications in locations where microplastics pollution is an on-going issue.