Studies of Tropospheric and Stratospheric Aerosol using Ion Beam Analysis

Detta är en avhandling från Div. of Nuclear Physics, Dept. of Physics, Lund Institute of Technology, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden

Sammanfattning: Atmospheric aerosol particles are believed to have an impact on the radiative forcing of the earth's surface. The predicted results indicate a net cooling effect on the global climate, however there are few studies available to substantiate this and experimental data are needed. This work deals with the collection and the analysis of aerosol particles in various environments, specifically in the upper tropospheric and lower stratospheric region (the tropopause). As a part of the joint European CARIBIC project, aerosols have been sampled systematically during a two year period from a commercial aircraft during intercontinental flights. The main flight route has been from Germany to Sri Lanka/Maldives. 31 flights have been investigated regarding elemental composition with particle-induced X-ray emission (PIXE). From each flight, both total samples covering the full distance and time resolved samples (2.5 hours time resolution), have been collected. The sampling methodology developed for the special experimental environment at these altitudes is presented in paper I and the first results from this large-scale systematic study are presented in papers II and III. PIXE is multi-elemental and several elements have been detected (e.g. S, K, Fe, Ca, Ti, As, Br) and concentrations of these are presented. Sulphur is the main element of interest and its expected domination is assessed, being a factor of 50 greater in concentration compared to potassium. Seasonal trends have been obtained for sulphur, potassium and iron. The sulphur concentration is also investigated regarding latitude and a clear dependency is found, with a factor of 4 increase from 5 to 50 degrees north in latitude. The stratospheric influence is estimated and found to be significant. The chemical speciation tool Ion Beam Thermography (IBT), combining four elemental ion beam analysis techniques (PIXE, PESA, cPESA and pNRA) with thermography, has been characterised with respect to a number of parameters in paper IV. The chemical compound system sulfuric acid - ammonium sulphate in aerosol samples has been investigated in detail in paper V and the ability of IBT to distinguish the different chemical states of these important constituents of the atmospheric aerosol is assessed.

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