May 5, 2010

Fingerprinting The Dust Giants

Vast dust storms that dump millions of tons of topsoil from the Australian outback as far afield as Canberra, Sydney, the Great Barrier Reef, New Zealand and New Caledonia, with small amounts even reaching Antarctica, may also be a possible source of disease for people, crops and animals.

This phenomenon is being investigated by Professor Patrick De Deckker of the Australian National University, who is this year's winner of the Australian Academy of Science's prestigious Mawson Medal for his career contribution to understanding the forces that drive our continent.

Professor De Deckker is pioneering a new method for "Ëœfingerprinting' dust storms to identify their origins, causes and potential impacts on the places and people they affect, which he will outline in a presentation at the Academy's Shine Dome, May 6 at 10.30 am.

'On the night of October 22-23, 2002 a vast dust event took place which extended from the Victorian border to the southern Great Barrier Reef, and dropped 6 grams of dust per square meter on Canberra "“ which is a huge amount. Analysis of clay particles, pollen, trace elements and selected elemental isotopes in the dust created a "Ëœfingerprint' which has enabled us to pinpoint its origin to the region around Cobar and Bourke in NSW,' he explains.

The dust was an outcome of the severe drought in the region over the previous two years. Professor De Deckker predicts that when current inland floods across western Queensland, NSW and northern South Australia dry out, they will deposit dust as fine as talcum powder across large areas, increasing the likelihood of major dust storms in the coming spring.

He and his team plan to search for the telltale fingerprints of individual Australian dust storms in the southern hemisphere in places as far afield as New Zealand, Antarctica and possibly South America.

His research indicates that dust storms may be far more important for human and environmental health than previously thought. 'Our investigations reveal they are also laden with pollen, picked up from where they originate and along their path, as well as many soil organisms, some of which are known to cause disease to crops or even people. Using DNA analysis, we have identified a vast array of different organisms from desert soils in dust from the 2002 event,' he says.

"ËœAustralia is the largest source of airborne dust in the southern hemisphere', he says. 'One reason why we produce so much dust is that, worldwide, deserts are covered by a thin organic crust (often referred to as "Ëœdesert crust'), formed by minute plantlets and other organisms, such as cryptogams. This protects the desert soils and prevents them from blowing away. But when the crust is broken up by grazing animals or by the use of 4WD and other vehicles, it allows the land to "Ëœdeflate' and the dust escapes into the air.'


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