Real-Time Detection of Urban Atmospheric Micro-Nanoplastics and Their Chemical Mixing State Using Bioaerosol Single-Particle Mass Spectrometry.

Atmospheric micro-nanoplastics (MNPs) serve as key vectors for the global dispersion of plastic pollutants and act as reactive interfaces for atmospheric species, modifying their physicochemical properties and influencing environmental transport dynamics. However, existing methods lack the temporal resolution and specificity to characterize MNP mixing states and pollutant interactions in real time. To address this gap, we developed an innovative approach employing bioaerosol single-particle mass spectrometry (Bio-SPAMS) for simultaneous detection of polystyrene MNPs (PS MNPs; 0.3-2 μm) and their chemical associations with co-pollutants. Three diagnostic tracer ions, 91[C7H7+], 104[C8H8+], and 115[C9H7+], were identified as unambiguous markers of PS MNPs, enhancing their discrimination from ambient aerosols. Field measurements in a Chinese megacity revealed that PS MNPs constitute 1.04% of total aerosols (n = 51 045 particles), predominantly within the 0.3-0.8 μm size range. Approximately 76.4% of PS MNPs exhibited co-detection of nitrate and sulfate signatures, and in particles with PS characteristics, the relative peak areas of nitrate and sulfate are 14.30 and 4.06%, respectively, demonstrating active atmospheric aging via secondary pollutant uptake. This work established a new methodology for real-time MNP tracking in atmospheric matrices, providing critical insights into their lifecycle and risks.