Vertical distributions of microplastics in long-term mulched soils and their potential impacts on soil properties and...

Microplastics (MPs) pose a significant threat to soil ecosystem. However, the vertical distribution characteristics of MPs and their effects on soil physicochemical properties and microorganisms in arid farmlands soils in West China are not well understood. In this study, the vertical distribution of MPs in soils of different crop types was investigated from 14 soil profiles (0-50 cm) of plastic-mulched farmlands. The results indicated that the average MPs abundance in the entire soil profile was highest in the corn field (13.1 ×10⁵ items kg^-1), followed by the rapeseed field (9.55 ×10⁵ items kg^-1) and the vegetable field (5.15 ×10⁵ items kg^-1). The MPs abundance declined with increased soil depth, dominated by fragments (93.46 %), MPs with size < 50 μm accounted for 58.04 %. Fibers exhibited a relatively higher vertical migration rate. The length of crop roots played an important role in the vertical migration ability and depth distribution of MPs. In addition, the Chao1 and Shannon indices were negatively correlated with MPs abundance. MPs may impact the microbial community structure and diversity by altering soil physicochemical properties. This study will enhance our understanding of the MPs vertical migration in farmland soil and their potential impact on soil physicochemical properties and microbial diversity in arid regions.