Integration of PMF and explainable machine learning for source apportionment and ecological risk of microplastics in urban greenspaces

Microplastics (MPs) have emerged as a global environmental concern due to their widespread distribution and potential ecological risks. Urban greenspaces play a vital role in improving the quality of life for urban residents, and are threatened by MPs pollution. While previous studies on MPs have predominantly focused on agriculture soils, MPs pollution in urban greenspaces remains insufficiently explored. To address this gap, this study investigated the spatial distribution, source apportionment, and both current and future ecological risks of MPs pollution in urban greenspaces. The results showed that MPs abundance ranged from 141 to 1258 items/kg. Nearly half of MPs were predominantly fragments (54.3 %), and were smaller than 100 μm (49.2 %). The major types were polypropylene (32.6 %), polyethylene (27.9 %), and polyethylene terephthalate (12.0 %). Source apportionment indicated that MPs primarily originated from agriculture activities (29.6 %), mixed domestic-industrial emissions (24.1 %), and traffic-related sources (23.5 %). Although the current ecological risk of MPs to urban greenspaces was generally low, economic growth and transportation development are projected to drive future risk to reach moderate level by 2030. This study comprehensively identified the sources and ecological risks of MPs in urban greenspaces, providing valuable insights for developing targeted MPs pollution management strategies in urban systems.