Dynamics of suspended atmospheric microplastics and their wet deposition in the Qilian Mountains, Northeast Tibetan Plateau

The Earth's environment is full of microplastics, but the characteristics of atmospheric microplastics in remote areas are still limited to constrain the understanding of the life cycle of microplastics. Hence, we conducted quantitative characteristics of suspended atmospheric microplastics (SAMPs) and wet deposition microplastics (WDMPs) in the Qilian Mountains, northeast Tibetan Plateau. The concentrations of SAMPs (> 50 µm) ranged from 0.05 to 1.36 items/m with a mean of 0.33 ± 0.35 items/m. The fluxes of WDMPs (> 50 µm) ranged from 14.94 to 450.04 items/(m·day) with a mean of 124.06 ± 115.67 items/(m·day). In general, microplastic abundance in this remote area was lower than that in high-density population areas. SAMPs and WDMPs were dominated by fragments (> 70 %). Polymers were dominated by polyamide, polyethylene, polyethylene terephthalate, polyurethane, and polyvinyl chloride. In detail, polyamide was higher in WDMPs, and polyurethane was higher in SAMPs. These differences may be attributed to the distinct wettability and aging behaviors of the polymers. The conditional fragmentation-based model revealed that the size range of SAMPs was larger and more fragmented than that of WDMPs. While SAMPs were more irregular than WDMPs, further indicating that irregular morphology favored the suspension of microplastics. Concentration-weighted trajectory revealed that sphericity is a key indicator for revealing potential source regions of microplastics. This study provided insights into the dynamics of SAMPs and WDMPs in remote mountain regions. It highlighted the need to unify the assessment of microplastic transport capacity across different shapes and sizes.