Characteristics of soil microplastics and ecological risks in the Qilian Mountains region, Northeast Tibetan Plateau.

Microplastics (MPs) pollution has become a vital global environmental issue. However, comprehensive understanding of the ecological risks of MPs in soils of Northeast Tibetan Plateau still requires further study. In this study, we used the Agilent 8700 Laser Direct Infrared (LDIR) spectroscopy to analyze the characteristics of 10-1000 μm MPs in soils of different vegetation types throughout the Qilian Mountains basin, and to comprehensively explore the ecological risks of MPs in various ecological environments. The results indicate that MPs abundance is highest in soil of shrub areas (26,369 ± 32,147 items kg-dry weight (dw)), followed by woodland (22,215 ± 22,544 items kg-dw), desert (17,769 ± 9,040 items kg-dw), grassland (16,462 ± 12,872 items kg-dw), and forest (15,662 ± 13,857 items kg-dw). MPs in soils of different vegetation types show similar physical and chemical characteristics, with the shape dominated by fragments (93%-96%), followed by fibers and a few beads, with dominant sizes of 10-30 μm (63%-76%), and polymers dominated by polyamide (PA) and polyethylene terephthalate (PET). Additionally, the environmental risks posed by the fundamental characteristics of MPs have been quantified through the Pollution Load Index (PLI), Pollution Hazard Index (PHI), and Potential Ecological Risk Index (PERI) models. According to the PLI assessment, the current levels of MPs in the environment have not yet imposed significant burdens on the ecosystem. However, the results of PHI and PERI indicate a higher risk of MPs pollution in the Qilian Mountains. This study offers vital information for MPs pollution in the whole Qilian Mountains regions and their potential environmental risks in remote areas' soil.