Heterogeneous Chlorine Reactions on Mineral Dust During Dust Storm Events in the Coastal City of Qinhuangdao

Heterogeneous reactions on mineral dust surfaces during dust storm events significantly influence atmospheric chemistry by modifying aerosol composition. This study employed high-resolution scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) to investigate the morphology and elemental composition of dust particles collected during four dust events in Qinhuangdao, a coastal city in Northern China. The results revealed that clay minerals were the most abundant (53.5% ± 13.7%), followed by feldspar (12.0% ± 3.6%), quartz (11.9% ± 3.2%) and carbonate minerals (7.3% ± 4.1%). In contrast, sulfate and NaCl particles constituted only a minor fraction, representing 1.1% and 0.9% of the particles, respectively. Elemental analysis indicated that sulfur (S)-containing particles, although scarce during the initial stages, increased as the dust storms evolved, eventually accounting for about half of the particles by the end of the events. This trend suggests increasing heterogeneous processing on dust particle surfaces. Furthermore, single-particle analysis demonstrated a marked increase in chlorine (Cl)-containing particles (excluding NaCl) from 2.4% at the onset to 30.9% ± 16.5% by the end of the dust events. In contrast to studies conducted in inland cities, where Cl-containing particles are seldom observed, our findings underscore the crucial role of marine aerosols in facilitating the chlorine enrichment of dust particles in coastal atmospheric environments. Overall, these findings provide new insights into the aging processes of mineral dust in coastal atmospheres and suggest potential interactions between dust particles and marine aerosols during heterogeneous halogen and sulfur processing in dust events.