Uptake of acid pollutants by mineral dust and their effect on aerosol solubility

Due to the implications caused by mineral dust and sea-salt heterogeneous reactions with SO2, NOx and NH3 derivatives, this study aims to understand the interaction between gaseous and particulate phases; PM10 and PM2.5, in dust-rich and dust-poor environments. During dust outbreaks, the increase in PM10 and PM2.5 mass concentrations by 80 and 75%, respectively, was accompanied with approximately 30% decrease in water soluble inorganic ions. However, nitrate ion concentration, which increased by 36% during dust-rich episodes, was correlated with a 96% increase in gaseous HONO concentration. This implies a significant impact of dust storms on the tropospheric NO2 to HONO conversion and consequently the formation of nitrate in PMs. Products of the reaction between HONO and mineral dust render atmospheric aerosols more soluble and consequently higher nitrogen deposition fluxes were calculated.

► In dust-rich episodes; Increase in PM10 (80%) and PM2.5 (75%) mass concentrations.
► Increase in PM10-nitrate (36%), and -chloride (30%) and PM2.5-nitrate (54%).
► Reaction rate of HNO3–CaCO3 becomes in the same order of magnitude as SO2–NaCl.
► A 96% increase in HONO(g) is accompanied by a 36% increase in particle nitrate.
► Conversion of calcite to soluble nitrate particles is enhanced over urban areas.