Risk assessment and zoning of soil microplastics in a typical megacity, China

As emerging pollutants, microplastics (MPs) may threaten urban soil and human health. Here, we used quantitative models and geostatistical analysis to evaluate MP risks and influencing factors in Nanjing, a typical megacity in China. We also identified areas with different risk control needs. Results showed spatial variability in MP risks, with higher risks in the western region compared to the eastern region. Residential, government, and industrial areas were pollution hotspots. Factors like washing-related points of interest (POIs) and soil properties significantly influenced MP risks. Risk areas were categorized based on MP concentration and polymer risks. HRCZ-CP, the highest-risk area, distributed primarily in commercial zones and other human-dense areas heavily influenced by traffic and packaging-related POIs, requires close monitoring of anthropogenic emissions. Two secondary risk categories were identified: HRCZ-NH (high concentration risk near water) and HRCZ-H (high polymer risk in public green spaces). Future efforts should focus on controlling MP runoff in HRCZ-NH and managing soil MP retention and degradation in HRCZ-H. The clean zone (CZ), with the lowest risk, should maintain environmental standards. This study provides a basis for targeted management of urban soil MP risks.