The impact of carbonaceous and inorganic aerosols on haze dynamics: Insights from size-resolved analysis

초록

Understanding size-resolved physicochemical characteristics of atmospheric aerosols is pivotal for elucidating their formation mechanisms, behavior, and atmospheric fate. However, most aerosol studies rely on mass-based methods, which often underestimate the contribution of ultrafine and submicron particles due to their low mass fractions. Despite their small mass, these particles dominate the aerosol number concentrations and play a critical role in atmospheric chemical processes. Herein, we investigate the size-resolved characteristics of submicron aerosols, focusing on three major components: carbon, nitrate, and sulfate, using an integrated analytical approach that combines particle size distribution (PSD) and chemical composition analytical analysis. Online PSD measurements and offline size-segregated aerosol sampling were simultaneously performed using an electrical low-pressure impactor (ELPI+), covering aerodynamic diameters from 6 nm to 1.64 mu m. Raman spectroscopy was applied to investigate the chemical composition of size-resolved samples. This integrated approach was applied during a winter haze event. Our results indicate that ultrafine carbonaceous particles, primarily from local traffic emissions, dominated the concentration of submicron aerosols. In contrast, secondary inorganic aerosols (sulfate and nitrate) were prominent in the accumulation mode, forming heterogeneously on preexisting particles' surfaces. Nitrate concentrations were particularly elevated during daytime haze periods and coexisted with highly oxidized carbonaceous particles. The observed evolution in carbonaceous aerosol oxidation states and mixing characteristics contributed to enhanced atmospheric reactions, light absorption and scattering modification, and reduced visibility, which are key drivers of haze formation. These findings demonstrate the effectiveness of the integrated analytical approach for advancing our understanding of submicron aerosol behavior and their role in air pollution and climate.

키워드