Optical properties and mineralogical composition of differentSaharan mineral dust samples: a laboratory study

[摘要] In aerosol chamber experiments optical properties of resuspended mineraldust samples of defined size distributions were measured. Extinctioncoefficients (b_ext) and mass specific extinction cross sections(σ_ext) were determined for Saharan dust samples from differentlocations. The results for σ_ext were not very sensitive to thetype of dust and varied at λ=550 nm between 3.3±0.4 m² g⁻¹ and 3.7±0.4 m² g⁻¹. The absorptioncoefficients (b_abs) and mass specific absorption cross sections(σ_abs) were determined with a novel multi-wavelengthphoto-acoustic absorption spectrometer (PAS). The single scattering albedowas close to 1 (0.98 to 0.99) at 532 nm and 1064 nm, but significantly lower(0.63 to 0.76) at 266 nm. Additionally the chemical and mineralogicalcomposition of the dust samples were analysed with special regard to theiron oxide phases hematite and goethite. At λ=266 nm the mineraldust sample without any detectable iron oxides showed a significantly higherSSA compared to the sample with a hematite content of 0.6 wt-%.

[学科分类] 大气科学