Browsing by Author "Box, MA"

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    Physical and chemical properties of Australian desert dust, Aeolian dust: its potential role as a carrier of terrestrial salt in Australia
    (Australian Nuclear Science and Technology Organisation, 2008-07) Radhi, M; Box, MA; Box, GP; Mitchell, RM; Keywood, D; French, D; Cohen, DD; Stelcer, E
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    Physical, chemical and optical properties of Australian desert dust: a multiple analysis from several sites
    (3rd International Workshop on Mineral Dust, 2008-09) Radhi, M; Box, MA; Box, GP; Mitchell, RM; Keywood, MD; French, D; Cohen, DD; Stelcer, E
    Australian dust aerosol was sampled at two desert locations, Birdsville (25.54 S, 139.20 E) and Muloorina (29.14 S, 137.64 E), using a 12-stage MOUDI sampler. Backgound TSP levels were 15.8 ± 3 μg/m3 at Birdsville, and 244 ± 10 μg/m3 at Muloorina. Ion beam analysis shows that the following elements are dominant at both sites: Na, Al, Si, Cl, K, Ca, Ti and Fe. Sulphur is the only pollutant element that occurred in the Muloorina analysis due to local vegetation burning. Weather conditions during sampling at Birdsville were classified as non-dusty to weak dust. At Muloorina we had different weather conditions: non-dust, weak dust and dust storm. The concentrations of the element loading in the atmosphere varied with weather conditions. The mass ratio of the other elements to Al also varied with the weather conditions. For both sites Fe occurred in fine and coarse size ranges, appearing strongly in the size range 1.8 to 10 μm in all events. The Fe/Al mass ratio was 1.97, 2.5, 0.96 and 1.02 for non dust, weak dust and north and south dust storm respectively at Muloorina, while at Birdsville the value was in the range 0.45 to 0.65, indicating Muloorina is rich in Fe. Both Na and Cl demonstrated a good correlation with Al as Australian desert dust also contains a mixture of salts from dry saline lakes. Selected filters are currently undergoing electron microscopy analysis in order to determine the mineralogical content, especially hematite vs. goethite. The monthly mean of the aerosol optical depth at Birdsville shows maximum values during summer (Feb. 0.06 ± 0.05) and spring (Oct. 0.11 ± 0.05), and minimum values in June (0.02 ± 0.001). The Ångström exponent was low (suggesting coarse particles) during summer and spring. The relationship between AOD and Ångström exponent shows a good pattern of decreasing α with increasing AOD, indicating the effects of dust particles.
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    Size-resolved chemical composition of the September 2009 Sydney dust storm
    (Clean Air Society of Australia and New Zealand, 2010-11-01) Radhi, M; Box, MA; Box, GP; Cohen, DD
    In September 2009, a major dust storm crossed eastern Australia, blanketing Sydney on two occasions. We collected size-resolved aerosol samples on both days, and also on the following days, for comparison. The size distribution during the dust storm showed a strong coarse mode, as expected. We subjected these samples to Ion Beam Analysis at ANSTO, obtaining their size-resolved chemical composition. In this paper we present these results, and compare them with some of the analysis of similar samples obtained in field trips to the Lake Eyre Basin of central Australia, the source region for much of the dust. In particular, the Fe/Al ratios (roughly 0.9) are similar to LEB values (roughly 0.8 - 1.0), and higher than northern hemisphere values (roughly 0.55). Salt entrainment indicates a contribution from dry lakes. © 2010, Clean Air Society of Australia and New Zealand
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    Size-resolved mass and chemical properties of dust aerosols from Australia's Lake Eyre Basin
    (Elsevier, 2010-09) Radhi, M; Box, MA; Box, GP; Mitchell, RM; Cohen, DD; Stelcer, E; Keywood, MD
    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. We have investigated the properties of Australian aerosol at a site near Lake Eyre in central Australia, which is strongly influenced by mineral dust. During a field campaign in November 2007 we collected eight sets of size-resolved aerosol samples for laboratory analysis: six during quiescent conditions, and two during dust storms. Ion Beam Analysis was used to determine the elemental composition of all filter samples. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and hence soil-derived. The Fe/Si ratio was consistently higher than the global crustal average, confirming that Australian dusts are comparatively rich in Fe. Scatter plots for Na and Cl against Si showed clear evidence of a second aerosol population, associated with maritime advection. Profiles of water soluble ions for two sample sets, showed the importance of marine influences on both the fine and coarse modes, as well as the presence of organic acids. Estimates of the mass fraction of NaCl in our samples suggest that, for quiescent days, roughly 0.5% of the sample mass was NaCl. © 2010, Elsevier Ltd.
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    Size-resolved properties of atmospheric aerosols in Sydney and Regional NSW
    (Department of the Environment and Water Resources, 2007-09-13) Hallal, T; Box, GP; Radhi, M; Box, MA; Cohen, DD; Stelcer, E
    In recent years it has become evident that size-resolved chemical composition of atmospheric aerosols is important in determining optical properties such as refractive index, scattering and absorption coefficients, extinction and hygroscopicity. These properties affect the way radiation is scattered and absorbed as it passes through the atmosphere, and thus are important for the calculation of aerosol radiative forcing and "atmospheric correction" of satellite images, as well as local air quality and visibility. We report results from a study of the size-resolved chemistry of atmospheric aerosols in Sydney and regional NSW, and their relationship to optical properties. PM2.5 and PM10 samples were collected at four sites during the summer, autumn, winter and spring of 2003. These were analysed using Ion Beam Analysis (IBA) and selected samples have also been analysed by Scanning Electron Microscopy (SEM). The elemental chemistry, in combination with meteorological parameters and a chemical thermodynamic model, was then used to determine the aerosol refractive index for each of the sites and size fractions. IBA results show seasonal differences within sites and between sites, as well as differences between PM2.5 and PM10 composition at particular sites. Refractive index values also show seasonal and spatial differences. Further PM2.5 and PM10 measurements were made during winter 2006 in Sydney, and Wagga Wagga in regional NSW. A second set of measurements, including using a 10-stage MOUDI sampler for better size-resolution of the chemistry is planned and similarly analysed.