Occurrence of microplastics in natural and farmland soil in the Qilian Mountains of the Northern Tibetan Plateau

Microplastics (MPs) become ubiquitous in soil and are an environmental and public health concern worldwide. However, the status of MPs in natural and farmland soils in remote areas remains poorly understood. In this study, we investigated the characteristics of MPs in natural and farmland soils along two transects in the Qilian Mountains of the northern Tibetan Plateau. The average abundance of MPs in natural and farmland soils was 29,778 and 56,123 items kg−1, respectively, with a detection size range of 10–1000 μm. MPs in the size range of 10–100 μm accounted for 84.1% of particles detected. Among the 21 polymers detected, polyethylene dominated in both farmland and natural soils. The shape of MPs was dominated by fragments (95.8%), followed by fibers (3.8%) and beads (0.4%). The abundance of MPs was positively correlated with increasing altitude in natural soils. There was no significant correlation between the abundance of MPs and soil physicochemical properties due to the narrow range of values of soil physicochemical properties. With the growing concern regarding MPs pollution, research on the status of MPs in high altitude and remote areas is critical to understanding their global cycle.