Comparative evaluation of the impacts of different microplastics on greenhouse gas emissions, microbial community structure, and ecosystem multifunctionality in paddy soil

Abstract

Although the increasing accumulation of microplastics (MPs) in terrestrial soil ecosystems has aroused worldwide concern, research remains limited on their potential impacts on soil processes and ecosystem functionality. Here, through a 41-day microcosm experiment, we found that polylactic acid (PLA), low-density polyethylene (LDPE), and polypropylene (PP) MPs consistently increased soil carbon nutrients and pH but had varying effects on soil nitrogen nutrients and the chemodiversity of dissolved organic matter (DOM). Different treatments led to notable shifts in the α-diversity and composition of soil microbial community, with phyla Proteobacteria and Ascomycota consistently enriched by MPs regardless of polymer type. The emissions of CO2 and N2O were suppressed by MPs in most cases, which in combination led to a decline in global warming potential. LDPE and 1 – 1.5% of PLA MPs significantly improved the multifunctionality of the soil ecosystem, while PP and 0.5% of PLA MPs exerted an opposite effect. Soil total organic carbon, pH, DOM molecular mass and condensation degree, and CO2 emissions were identified as the most important variables for predicting soil ecosystem multifunctionality. Results of this study can extend the current understanding of the impacts of MPs on soil biogeochemical cycling and ecosystem functionality. Environmental ImplicationSoils are the largest recipient of MPs. Due to their diverse origins, MPs in the soil are typically present in different polymer types, shapes, and concentrations, which may induce complex impacts on soil ecosystem. This study highlighted that polymer types and concentrations were two important factors influencing the specific impacts of MPs on soil carbon and nitrogen turnover, microbial community composition, and ecosystem multifunctionality. Biodegradable MPs can also profoundly affect soil processes and functionality, raising questions about their ecological benefits. Results of this study can improve the current understanding of the ecological risks of MPs contamination in the soil.