Soil-aged microplastics exhibit stronger effects than air- and rainwater-aged ones on the network complexity and assembly process of soil microbial community

Divergence in aging characteristics of plastic mulching film (PMF)-derived microplastics (MPs) exposure to air, rainwater and soil and their effects on soil microbial community characteristics were investigated in this work. During the application, soil contributed more to the aging of PMF than air and rainwater, which was linked with the attachment of soil particles and abundant microbes in the soil. As expected, after entering the soil, natural-aged PMF-derived MPs exhibited more significant erosion features than the pristine ones. Meanwhile, the addition of these natural-aged MPs enhanced the network complexity of soil bacterial communities, and the effect followed in an order of soil-aged MPs > air-aged MPs > rainwater-aged MPs > the pristine ones. Bacterial community assembly was predominantly governed by stochastic processes rather than deterministic ones. Among these MPs treatments, the addition of soil-aged MPs increased the proportion of stochastic processes, which concurred with a more complex microbial community network in soil added with soil-aged MPs. Overall, the response of microbial community characteristics to PMF-derived MPs was related to the changes in their surface roughness. This work could provide new insights into the impacts of PMF-derived MPs on soil ecosystems from the microbial ecology perspective.