Observational evidence for the non-suppression effect of atmospheric chemical modification on the ice nucleation activity of East Asian dust

Abstract

Airborne mineral dust triggers ice formation in clouds and alters cloud microphysical properties by acting as ice-nucleating particles (INPs), potentially influencing weather and climate at regional and global scales. Anthropogenic pollution would modify natural mineral dust during the atmospheric transport process. However, the effects of anthropogenic pollution aging on the ice nucleation activity (INA) of mineral dust remain not well-understood. In this study, we investigated the immersion mode ice nucleation properties and particle chemical characterizations of collected size-resolved Asian dust samples (eight particle size classes ranging from 0.18 to 10.0 μm), and testified the chemical modification of aged dust particles via particle chemistry and morphology analyses including the mass concentrations of particulate matter, the water-soluble ion concentrations, the mental element concentrations, and single-particle morphology. The mass fraction of Ca2+ in element Ca and the mean relative mass proportions of supermicron Ca2+ increased by 67.0 % and 3.5–11.2 % in aged Asian dust particles, respectively, suggesting the occurrence of heterogeneous reactions. On the other hand, the total INP concentrations (total NINP) and total ice nucleation active site densities (total ns(T)) were consistent between aged and normal dust particles (0.62–1.18 times) without a statistically significant difference. And the NINP and ns(T) of chemically aged supermicron dust (1.0–10.0 μm) in each particle size class were nearly equal to or slightly higher than those of normal Asian dust, which were 0.70–2.45 times and 0.64–4.34 times at −18 °C, respectively. These results reveal that anthropogenic air pollution does not notably change the INP concentrations and does not impair the INA of Asian dust. Our work provides direct observational evidence and clarifies the non-suppression effect of anthropogenic air pollution on the INA of East Asian dust, advancing the understanding of the ice nucleation of airborne aged mineral dust.