Landfill: time capsule of plastic waste but microplastic generation source.

Landfills act as critical terrestrial sources of microplastics, functioning as "leaky time capsules" continuously releasing pollutants into surrounding ecosystems. Here, we establish a prediction model to dynamically quantify microplastic generation in landfills. By calibrating 31 years of in-situ tracking at a large-scale landfill together with a nationwide field investigation across 37 landfills, we systematically identify the spatial patterns of microplastic generation in China. East China acts as a primary hotspot contributing 45.6% of the total microplastic stock. Landfills in coastal areas account for nearly one-third of the national microplastic stock despite representing only 8.3% of the total sites. Although aggressive source reduction and in-situ remediation reduce the national microplastic by 46.4% by 2050, high-risk landfills in coastal areas remain insensitive to these measures. These findings highlight the necessity of differentiated regional control measures to effectively mitigate landfill-sourced microplastic pollution.