A comprehensive evaluation of water uptake on atmospherically relevant mineral surfaces: DRIFT spectroscopy, thermogravimetric analysis and aerosol growth measurements

[摘要] The hygroscopicity of mineral aerosol samples has been examined by threeindependent methods: diffuse reflectance infrared Fourier transformspectroscopy, thermogravimetric analysis and differential mobility analysis.All three methods allow an evaluation of the water coverage of two samples,CaCO₃ and Arizona Test dust, as a function of relative humidity. Forthe first time, a correlation between absolute gravimetric measurements andthe other two (indirect) methods has been established. Water uptakeisotherms were reliably determined for both solids which at 298 K and 80%relative humidity exhibited similar coverages of ~4 monolayers.However, the behaviour at low relative humidity was markedly different inthe two cases, with Arizona Test Dust showing a substantially higheraffinity for water in the contact layer. This is understandable in terms ofthe chemical composition of these two materials. The mobility analysisresults are in good accord with field observations and with our ownspectroscopic and gravimetric measurements. These findings are of value foran understanding of atmospheric chemical processes.

[学科分类] 大气科学