Soil-plastisphere interfacial properties enable decoding microplastics behaviour in the environment

The plastisphere extends from microplastic surfaces into a zone of surrounding soil particles. The microbial processes are studied, but the physical drivers and effects on water dynamics remain elusive. This study reveals changes in adhesion forces and interfacial properties within the plastisphere. Samples amended with polypropylene and polyethylene fibres were incubated for three and six months. Spatial measurements of the plastisphere observed lower rates of contact angle increases compared to bulk soil. Surface adhesion forces, determined by atomic force microscopy, declined by 85% for polypropylene and 30% for polyethylene. Substantial surface transformations occurred with oxygen-containing functional groups emerging on microplastics, leading to reduced hydrophobicity in contrast to increasing hydrophobicity of the bulk soil and the soil-plastisphere. These findings demonstrate the relationship between microplastic degradation and modifications in soil wettability and strength, coupled with alterations in soil and microplastic surface interaction energies. Such changes can significantly influence soil health by altering the dynamics of contaminant transport, retention, and release.