Release potential of nanofibers and additives during mask aging among different soils

The extensive use of masks has raised concerns about soil contamination. However, the soil properties that determine risks from released nanofibers and plastic additives during mask aging remain unclear. We investigated the release kinetics of nanofibers and plastic additives from masks in six different soils across China to clarify the dominant soil factors and the associated release mechanisms, and to predict their exposure risks worldwide. There were approximately 6.10-201.24 × 10¹² particles/(piece aged mask) nanofibers and 5.64-215.64 mg/(piece aged mask) plastic additives released from masks after 48 h of aging. Dominants of soil properties on nanofiber releases were in order of chemical properties (0.72) > biological properties (0.66) > physical properties (0.45). In addition, acidic soils enhanced the release of inorganic additives from masks, and high dissolved organic carbon and low electrical conductivity of soils enhanced the release of organic additives from masks. Using in-situ Zymography and soil metabolomics, the contribution of microbial metabolism to mask aging and the resultant disrupted soil metabolic stability have been confirmed. The predicted global maps suggested high risks from mask contaminants in densely populated areas with acidic and highly organic clay soils. This study warns us that the pandemic COVID-19 ends but the resulting soil contaminants should be much concern in the future.