A comprehensive evaluation of water uptake on atmospherically relevant mineral surfaces: DRIFT spectroscopy, thermogravimetric analysis and aerosol growth measurements R. J. Gustafsson, A. Orlov, C. L. Badger, P. T. Griffiths, R. A. Cox, and R. M. Lambert Chemistry Department, Cambridge University, Lensfield Road, Cambridge CB2 1EW, UK
Abstract. The hygroscopicity of mineral aerosol samples has been examined by three
independent methods: diffuse reflectance infrared Fourier transform
spectroscopy, 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. For
the first time, a correlation between absolute gravimetric measurements and
the other two (indirect) methods has been established. Water uptake
isotherms 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 in
the two cases, with Arizona Test Dust showing a substantially higher
affinity for water in the contact layer. This is understandable in terms of
the chemical composition of these two materials. The mobility analysis
results are in good accord with field observations and with our own
spectroscopic and gravimetric measurements. These findings are of value for
an understanding of atmospheric chemical processes.
Citation: Gustafsson, R. J., Orlov, A., Badger, C. L., Griffiths, P. T., Cox, R. A., and Lambert, R. M.: A comprehensive evaluation of water uptake on atmospherically relevant mineral surfaces: DRIFT spectroscopy, thermogravimetric analysis and aerosol growth measurements, Atmos. Chem. Phys., 5, 3415-3421, doi:10.5194/acp-5-3415-2005, 2005.