Measurement report: Dust Transport and Local Anthropogenic Emissions Differently Shape Atmospheric Ice-Nucleating Particles in an Industrial Urban Atmosphere

Atmospheric ice-nucleating particles (INPs) are vital for cloud formation, yet the importance of INPs from anthropogenic sources remains poorly understood. We conducted a month-long winter field campaign in Taiyuan (China), a heavily industrialized city, to quantify INP concentrations (NINP) and ice nucleation active site density (ns) of immersion mode INPs, alongside particle size distributions and chemical compositions. Our results indicate that NINP ranged from 0.05 to 13.37 L−1 at and above −15 °C, corresponding to ns values of 105–107 m−2. During the identified desert dust event, both NINP (7.47 L−1; 95 % confidence interval (CI): 6.64–8.41 L−1) and ns (1.57×107 m−2) were substantially higher than during the remaining observation periods without clear desert-dust intrusion (0.61 L−1 and 9.52×105 m−2, respectively), highlighting the strong influence of long-range transported desert dust. In contrast, during pollution periods, NINP showed only weak correlations with urban aerosol components such as sulfate (SO42-), nitrate (NO3-), and organic carbon (OC) (|r|<0.3). Positive matrix factorization (PMF) identified five PM2.5 source factors: industrial emissions, dust-related particles, secondary aerosols, coal combustion and traffic emissions, and fireworks. Although these factors dominated the PM2.5 mass, they showed no significant covariation with NINP. During this winter campaign, NINP variability in Taiyuan was characterized by strong enhancement during the identified desert dust event and weak associations with the major PM2.5 source factors during the remaining observation periods.