EFFECTS OF TYPICAL MICROPLASTICS ON SOIL PROPERTIES AND MICROBIAL COMMUNITIES

Abstract

Microplastics can significantly alter the physicochemical properties and biological characteristics of soil, and their potential impacts on agroecosystems have become a major research hotspot in environmental science and agroecology. In this work, soil was fractionated into three aggregate size classes using the dry-sieving method: >250 μm (macroaggregates, MA), 53-250 μm (microaggregates, MI), and <53 μm (silt and clay, SC). Polyethylene microplastics (<200 mesh) were utilized in soil incubation studies to examine how particle dimensions influenced agroecosystem contamination dynamics. Results showed that polyethylene microplastics reduced soil nutrient contents and affected soil functional performance, with the most pronounced effects observed in the SC fraction. Additionally, diminished soil enzymatic activities suggested microplastic interference with biochemical processes, potentially impeding C, N, and P cycling and consequently compromising soil fertility and quality. Microbial community profiling further demonstrated that polyethylene microplastics substantially diminished both diversity and abundance of soil aggregate-associated microorganisms (bacterial and fungal), while markedly restructuring dominant phyla composition-Actinobacteria supplanted Proteobacteria as the prevalent bacterial group. Structural equation model analysis indicated that soil physicochemical properties can directly affect microbial phyla and can also indirectly influence microbial diversity through their effects on enzyme activities.