[Microplastic Pollution in Groundwater of the Xingyun Lake Plateau Watershed: Characterization， Source Apportionment，...

To investigate the spatial distribution characteristics and pollution sources of microplastics in groundwater within a plateau lake watershed， this study focused on a typical agricultural and village-aggregated area on the western shore of Xingyun Lake. Groundwater samples were collected and analyzed using digestion， flotation， microscopic observation， and micro-Fourier transform infrared spectroscopy （μ-FTIR） to systematically examine microplastic abundance， morphological characteristics， and sources. The ecological risks were assessed using the pollution load index （PLI_zone） and the polymer hazard index （PHI）. The results indicated that the numerical abundance of microplastics in the groundwater of the study area ranged from 3 330 to 7 660 n·m^-3， while the mass abundance ranged from 1.16 to 3.30 mg·m^-3. The spatial distribution exhibited a significant pattern of downstream > midstream > upstream， primarily attributable to human activities. Microplastics were predominantly characterized by a particle size of 0.2-0.5 mm （50.55%）， a fibrous shape （93.06%）， and colors dominated by black （39.98%） and blue （29.03%）. The main polymer types identified were RY （66.10%） and PES （15.25%）. The primary sources of microplastics were domestic wastewater discharge and agricultural activities. Risk assessment results showed a PLI_zone value of 72.6， indicating an extremely high-risk level in the study area， while the PHI value was 3.2 ±2.5， corresponding to a low-risk level. This study provides a scientific basis for the prevention and control of microplastic pollution in groundwater within plateau lake watersheds.