Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Australie → Physical and chemical properties of Australian continental aerosols

University of New South Wales (2010)

Physical and chemical properties of Australian continental aerosols

Radhi, Majed

Titre : Physical and chemical properties of Australian continental aerosols

Auteur : Radhi, Majed

Université de soutenance : University of New South Wales

Grade : Doctor of Philosophy (2010)

Résumé
This thesis has examined the characteristics of Australia’s two major continental aerosol types - mineral dust and biomass burning - using both remote sensing data, and the laboratory analysis of field samples.Australia is the dominant mineral dust source in the southern hemisphere, yet the physical, chemical and optical properties of Australian dust aerosol are presently poorly understood. In this study three field campaigns have been conducted within the Lake Eyre Basin in order to collect size resolved aerosol particles using a 12 stage impactor. The physical properties (size distribution) of these aerosols have been investigated by studying the mass of aerosol on each filter, which showed that the fine fraction made approximately 50% of the TSP during non dust storm conditions. The chemical properties of these aerosols have been investigated by using a range of different analysis methods. Ion Beam Analysis was used to determine the elemental composition of all filter samples and as expected, Si is a strongly abundant element in all size fractions during all sampling events at all sites. Ion Chromatography provides good information about secondary aerosol components, and about the soluble and insoluble components of elements such as sodium and chlorine. A new technique, QEMSCAN, has been used for the first time to determine the mineralogy of dust aerosols in the atmosphere. This showed that Australian dust particles are an internal mixture, and that much of the Fe is not in the form of iron oxide minerals.The scatter plot slopes of Fe against Al were found to be in the range 0.77 - 0.94 within LEB, which higher than the values have been reported for the North Hemisphere sites (0.4-0.7) and higher than the global crustal average, confirming that Australian dusts are comparatively rich in Fe. The fraction of salt in transported dust was found to be in the range 0.2-1% during non dust storm days, and somewhat less during dust storms.Evidence of the contribution of marine biogenic aerosol to the total atmospheric aerosol over the LEB is provided by the presence of MSA, and also nssSO42-Ground-based remote sensing measurements of aerosol optical depth have been used to investigate the optical and physical properties of aerosol and their variation with time for three regions across the Australian continent. The results show that the tropical north sites show seasonal cycles in AOD and α with fine fraction aerosol dominating during spring month due to biomass burning activities, while for the desert site the coarse fraction dominates during dust storm activity. A careful analysis of AOD data during a recent bushfire season showed clear evidence of smoke aging.

Mots-clés : Aerosols ; Australian mineral dust ; Ion Beam Analysis ; Size-resolved chemistry ; Mineralogy ; Lake Eyre Basin ; Bushfire ; Biomass Burning Aerosol

Présentation

Version intégrale

Page publiée le 30 janvier 2012, mise à jour le 3 juillet 2017