Characterisation of the major dust storm that traversed over eastern Australia in September 2009; a multidisciplinary approach

Abstract

In September 2009, a major dust storm passed over the southeast coast of Australia and covered the large city of Sydney that is located on the eastern coast of Australia. It was referred to as the 'Red Dawn' event. Along its course across the state of New South Wales, the dust plume passed over Canberra, the capital of Australia located some 300. km from Sydney. In this study we identified the sources of the dust and tracked the progression of the dust storm using satellite imagery. We also examined the meteorological conditions that led to the formation of the dust plume. We also investigated the microbial and lipid composition, grain-size distribution, pollen content and geochemical composition of several samples of the dust that fell in Canberra (called 'Canberra dust'), with particular attention paid to the ratio of some rare earth elements as well as strontium and neodymium isotopes. This was done to identify a geochemical and palynological 'fingerprint' of this dust to determine the source of the material. Collectively, the meteorological and fingerprinting analyses identified the principal location of dust entrainment as between the large playa Lakes Gairdner and Torrens in arid South Australia, some 1600. km away from Canberra. We also determined through Sr isotope analyses and other elements measured in the dust that fell in Canberra and the township of Eden, located south of Sydney, that the dust changed composition slightly over a few hours, being the consequence of local dust entrainment along the path of the dust plume across South Australia and New South Wales. In addition, we present a scenario which explains dust transport away from the direction of the major dust plume. Those investigations carried out on the Canberra dust are compared with a previously documented event when dust was also sampled in Canberra in 2002. The origin and composition of the 2002 dust plume was clearly different from that which occurred in 2009, as demonstrated by the different chemical (organic and inorganic) composition, grain-size characteristics and palynological fingerprints, as well as microbial composition.