Spatiotemporal variations, source apportionment, and cross-regional impacts of microplastics in surface seawater of Chinese Marginal Seas

Microplastics (MPs) are widely distributed as a global pollutant, with dynamic patterns driven by horizontal diffusion and vertical mixing in marine ecosystems across different hydrological seasons and regions. This study employed MATLAB for image processing and interactive operations to extract data from existing studies on the Chinese Marginal Seas conducted from 2016 to 2022, focusing on the distribution, sources, and transport processes of MPs. The results revealed that the Bohai Sea exhibited the highest pollution levels during both the rainy (9328.30 particles/m³) and dry (8665.80 particles/m³) seasons. The Yangtze River Estuary, the Pearl River Estuary, and the Bohai Bay are three hotspot regions that may significantly contribute to the enrichment of MPs in surrounding seas. The distance-similarity decay relationship indicated stronger correlations in the South China Sea and Bohai Sea during the rainy season, and in the East China Sea during the dry season. Derived from the analysis using the Positive Matrix Factorization model, it was found that, apart from the South China Sea where PE and PAN proportions were higher, PE and PP dominated the MP composition. Highly polluting and difficult-to-degrade industrial manufacturing and plastic packaging were identified as the primary sources, while the Bohai Sea and Yellow Sea posed higher transport risks, may serve as sources of pollution to the surrounding regions.