Intellection noun: “the action or process of understanding” www.intellection.com.au Minerals Engineering Conferences - Automated Mineralogy 06 Brisbane, Australia How QEMSCANTM technology can contribute to an understanding of the possible climate impacts of atmospheric dust By Christa Pudmenzky*, Alan Butcher*, Al Cropp* and Grant McTainsh# *Intellection Pty Ltd, Australia #Griffith University, Australia Intellection noun: “the action or process of understanding”

Australia is a major dust source region in the Southern Hemisphere. Dust storms contribute large quantities of dust to the atmosphere. The 23 October, 2002 event described by McTainsh et al. (2004) picked up ~ 4.85 Mt of dust along a 2,400 km front which swept across eastern Australia. Australia is a major dust source region in the Southern Hemisphere. The climate of 75% of the continent is arid to semi-arid. Dust storms contribute large quantities of dust to the atmosphere. A dust storm event on the 23rd of October 2002 picked up approximately 4.85 Mega tonnes of dust along a 2,400 km front which swept across eastern Australia as can be seen on this satellite picture.

Recent Dust Storm Events in Australia Birdsville, Queensland, 26 January 2006 Courtesy of The Australian newspaper Moolawatana, South Australia, 25 January 2005 A Haboob passing through Thargomindah, Queensland

Dust samples are collected using a range of methods High volume air sampler Directional semi-isokinetic dust sampler Dust samples are collected using a range of different devices. Wind vane sampler

Radiative Forcing by Dust Aeolian dust influences the attenuation of sunlight by scattering and/or absorbing incoming solar radiation. Radiative forcing is change in the balance between radiation coming in the atmosphere and radiation going out. A positive radiative forcing tends to warm the surface of the Earth whereas a negative forcing tends to cool the surface. The direction and degree of radiative forcing by dust depend upon dust particle-size, aggregation, shape and mineralogy. Smaller particles are more effective in scattering energy than larger particles and the scattering also depends on particle shape and density, which are related to dust mineralogy. Dust consists of mixtures of minerals, each with characteristic optical properties, occurring as either individual mineral grains or as pure or mixed-mineral aggregates, but quantitative data on dust mineralogy are rare. Dust in the atmosphere has the potential to impact on climate. Aeolian dust influences the attenuation of sunlight by scattering and/or absorbing incoming solar radiation. Radiative forcing is the change in the balance between radiation coming in the atmosphere and radiation going out. A positive radiative forcing tends to warm the surface of the Earth and a negative forcing tends to cool the surface. The direction and degree of radiative forcing by dust depend upon dust particle-size, aggregation, shape and mineralogy. Smaller particles are more effective in scattering energy than larger particles and the scattering also depends on particle shape and density, which are related to dust mineralogy. Dust consists of mixtures of minerals, each with characteristic optical properties, occurring as either individual mineral grains or as pure or mixed-mineral aggregates, but quantitative data on dust mineralogy are rare.

Dust is the only atmospheric aerosol that could either increase or decrease global temperature by similar amounts as CO2, yet few climate models even consider it. - 0.4 to + 0.6 W/m2 Dust is the only atmospheric aerosol that could either increase or decrease global temperature by similar amounts as CO2, yet few climate models even consider it. The scientific understanding of the impact of radiative forcing by mineral dust is very low.

The main radiative dust characteristics are: Mineralogy Particle-size Particle shape Aggregation To gain a better understanding of the impact of atmospheric dust on climate it is important to determine the mineralogy, particle-size, particle shape and aggregation of dust.

How can QEMSCAN contribute to the understanding of the possible climate impact of atmospheric dust? The question arises: How can QEMSCAN contribute to the understanding of the possible climate impacts of atmospheric dust?

Research questions QEMSCANTM technology can contribute to: What is the mineralogy of Australian dust? Dust deposit Brisbane, November 1965 QEMSCAN can analyse airborne particulates and quantify the modal mineralogy and elemental composition but also provide valuable information on the grain and particle size, shape and other textural information.

What is the mineralogy of Australian dust at the source? Dust storms can pick up dust from a number of different source areas. Therefore the mineralogy of the entrained dust can vary greatly as can be seen on this slide. Here we can see analysed dust samples from Birdsville, Charleville, Thargomindah (western Queensland) and Buronga (northern NSW).

What is the mineralogy of Australian dust at the source? Quartz Kaolinite Feldspar Al-Fe-Silicate Chlorite Mica Resistates Other silicates Apatite Iron Oxides Calcite Dolomite Ankerite Gypsum Rutile Iron Sulphides Other 43 % Kaolinite 26 % Feldspar 5 % Al-Fe-Silicate 18 % Mica 3 % Quartz Others Birdsville 1995 3.0 µm 8.5 µm The QEMSCAN results of the Birdsville dust sample show that the dust in this region is rich in Kaolinite with 43%. The dust on the filter is extremely fine. Particle size analysis was done using the Coulter Multisizer 3. The dust was analysed minimally and fully dispersed. Prior to dispersion the particle-size mode is at 8.5 µm and changes to 3.0 µm after dispersion. From these results we can conclude that the Birdsville dust is highly aggregated.

What is the mineralogy of Australian dust at the source? Birdsville 1995 These are SEM images of Birdsville dust and a photo of the heavy loaded filter paper. The SEM images show that the dust is highly aggregated.

Dust samples on Carbon Tape Dust particles with cellulose fibre Dust particles Dust particles with glass fibre

What is the mineralogy of Australian dust at the sink? Al-Fe-Silicate Suspended dust can travel thousands of kilometres. During transport larger particles settle out first and therefore the mineralogy of dust changes as it travels further from the source.

What is the mineralogy of Australian dust at the sink? Brisbane 1965 17.9 µm 13.9 µm The November 1965 dust storm is regarded as the most destructive dust storm Australia ever encountered. The event affected most of Queensland, northern New South Wales and parts of central Australia, and covered more than 1 294 994 km2 with red dust. The results shown here are from a deposited dust sample collected off a glass house roof at the University of Queensland during the November 1965 event. The deposited dust was rich in Feldspar (39%), Quartz (25%) and Kaolinite (18%) but less aggregated.

Fox Glacier, NZ dust deposit Feb. 2003 Where does the dust come from? 70% Australian / 30% NZ dust [Source: SW NSW, SA?] The chemical analysis of atmospheric dust can be used to provenance the origin of dust. QEMSCAN is an ideal tool to identify different source areas.

Where does the dust come from? Red Australian dust deposit on Franz Josef Glacier, Jan. 2000 This images shows a band of red dust in the snow which travelled from South Australia to New Zealand.

Concluding Remarks Dust storms contribute large quantities of dust to the atmosphere. This dust influences the attenuation of sunlight by scattering and/or absorbing solar radiation, which can result in negative (cooling) or positive (heating) radiative forcing. The direction and degree of radiative forcing is dependent on mineralogy, particle size, shape and aggregation. QEMSCANTM technology is ideal to measure the properties of Australian dust and therefore throw new light on how dust affects global climate. The information gained from QEMSCANTM can be used in Global Climate Models to provide a more detailed understanding of the impacts of atmospheric dust on global climate.