Comparison of microplastics and heavy metal contamination in soils of typical plateau lake basins: Distribution patterns, potential sources, and driving factors.

As typical emerging pollutants, Microplastics (MPs) pose growing threats to fragile terrestrial and aquatic ecosystems. However, the co-occurrence patterns, sources, and driving factors of MPs and heavy metals (HMs) remain poorly constrained. 50 topsoil samples were collected from three latitudinally different lake basins on China's Inner Mongolia Plateau. Combined positive matrix factorization (PMF), partial least squares structural equation modeling (PLS-SEM) and HYSPLIT models were applied to analyze MPs spatial distribution, sources and MPs-HMs co-occurrence. The results revealed a distinct latitudinal gradient in MPs abundance, which decreased with rising latitude. The average MPs abundance in the soils was 4693 n/kg, 2902 n/kg, and 2147 n/kg in the Daihai (DH), Dalinor (DLH), and Ulagai (WLG) basins, respectively. HMs concentrations exhibited significant basin-specific heterogeneity. Mixed daily-life related and agricultural activities were the predominant source of soil MPs, contributing 87.4% of the MPs pollution. PLS-SEM results elucidated the complex driving mechanisms governing the distribution of MPs in plateau soils, and grazing intensity was identified as the primary influencing factor. This study establishes a robust framework for exploring the sources and driving mechanisms of coupled MPs and HMs in soil ecosystems.