Co‐Occurrence of Heavy Metals and Microplastics in Farmland Soils of Xizang (Tibet), China: Implications for Ecological Integrity in Plateau Agroecosystems

ABSTRACT Although the coexistence of microplastics and heavy metals in the environment has been observed in the environment, evidence for their joint occurrence in farmland soils remains limited, particularly in the Xizang (Tibet) Plateau region. In this study, cultivated soil samples were collected from Lhasa, Xigaze, and Shannan to investigate the occurrence of microplastics and heavy metals in farmland soils and their relationships with soil properties and microbial communities. The abundance of microplastics in Xigaze soils reached up to 2652.0 n g −1 , whereas that in Shannan ranged from 15.0 to 593.0 n g −1 . Arsenic (As) contents ranged from 30.7 to 63.9 mg kg −1 , generally exceeding the permissible limit for heavy metals in cultivated soils in China. Ethylene‐vinyl acetate (EVA) and polyacetal microplastics occured at relatively low proportions but exerted the greatest influences on soil microbial communities and chemical properties. Polyacetal significantly increased soil microbial diversity ( p < 0.05), whereas EVA significantly reduced it. Both EVA and polyacetal contents were positively correlated with soil organic matter and available phosphorus, while polyacetal showed a significant negative correlation with available nitrogen. Overall microplastics abundance showed relatively weak correlations with Proteobacteria and Firmicutes . Whereas As was significantly negatively correlated with Bacteroidota . Funcational associations suggested that Actinobacteriota may enhance available nitrogen through urease (UE) production, Firmicutes may increase available phosphorus through alkaline phosphatase (AKP) activity, and Acidobacteriota may contribute to organic matter accumulation through the production of β‐glucosidase (β‐GC) and protease (Pro). In general, this study confirms the co‐occurrence of microplastics and As contamination in farmlands of Xizang and elucidates potential mechanisms linking these pollutants with soil nutrient dynamics, thereby providing a theoretical basis for alleviating their adverse impacts on soil fertility.