Heterogeneous Reaction of CaCO ₃ With NO ₂ at Different Relative Humidities: Kinetics, Mechanisms, and Impacts on Aerosol Hygroscopicity

Heterogeneous reaction of NO2 with CaCO3, an abundant and reactive component in mineral dust aerosol, was investigated this work at different relative humidifies (RH, up to 80%), using a fixed-bed reactor. Ion chromatograph vapor sorption analyzer were employed measure changes particulate nitrate water time (up 24 h). When concentration ∼10 ppmv (∼2.5 × 1014 molecule cm−3), CaCO3 showed very low reactivity toward <1% RH, γ(NO2) estimated be <2 10−8; consequently, no significant change hygroscopicity particles observed after for h as the amount formed limited. significantly enhanced elevated RH (20%–80%), during covered deliquesced layer resulting from uptake by nitrate; addition, average determined (1.21 ± 0.45) 10−7, independent (20%–80%) (3–24 After 10 mass associated reacted 90% equal ∼45% unreacted suggesting that heterogeneous 20%–80% could substantially increase its hygroscopicity. Overall, our laboratory study suggested may impact composition particles.