Divergent responses of soil nematode communities to conventional and oxidized polyethylene microplastics and their mitigation by sawdust amendment in a floodplain agricultural field

Microplastic (MP) pollution in agricultural soils poses a growing threat to soil biodiversity and ecosystem functionality. However, the ecological impacts of polyethylene MPs at various stages of environmental aging-particularly the differences between conventional and oxidized forms-are not yet fully understood. This study examined the effects of conventional low-density polyethylene microplastics (LDPE-MPs) and oxidized polyethylene microplastics (OLDPE-MPs), in conjunction with sawdust amendment, on soil nematode communities in a typical alluvial Entisol from the Yellow River Basin throughout the peanut growth cycle. The results demonstrated that MP type significantly influenced nematode community dynamics, with OLDPE-MPs causing more substantial reductions in nematode abundance (38.22 %), genus richness (25.72 %), and maturity index (11.54 %) compared to LDPE-MPs. OLDPE-MPs were associated with trophic-level-specific responses, particularly affecting bacterivorous nematodes. The addition of sawdust effectively mitigated these adverse effects by enhancing soil physicochemical properties, reducing the negative impacts of LDPE-MPs and OLDPE-MPs on Shannon diversity by 8.98 % and 8.79 %, respectively. These findings underscore that environmental aging processes play a critical role in determining the ecological consequences of microplastics and highlight the potential of organic amendments in enhancing soil ecosystem resilience. This study offers both mechanistic insights into microplastic-soil interactions and practical strategies for mitigating microplastic pollution in agricultural environments.