A comprehensive characterisation of Asian dust storm particles: chemical composition, reactivity to SO₂, and hygroscopic property

Abstract. Mineral dust comprises of a significant fraction of the globe's aerosol loading. Yet it remains the largest uncertainty in future climate predictions due to the complexity in its components and physico-chemical properties. Multi-analysis methods, including SEM-EDX, FTIR, BET, TPD/mass, and Knudsen cell/mass, were used in the present study to characterise Asian dust storm particles. The morphology, element fraction, source distribution, true uptake coefficient of SO₂ and hygroscopic behaviour were studied. The major components of Asian dust storm particles were found to consist of aluminosilicate, SiO₂, and CaCO₃, which were coated with organic compounds and inorganic nitrate. The dust storm particles have a low reactivity to SO₂ (true uptake coefficient of 5.767×10⁻⁶) which limits the conversion of SO₂ to sulfate during a dust storm period. The low reactivity also demonstrated that the heterogeneous reaction of SO₂, in both dry and humid air conditions, had little effect on the hygroscopic behaviour of the dust particles. These results indicate that the impact of dust storms on atmospheric SO₂ removal should not be overestimated.