Temporal change of PM10 and its mass fraction during a dust storm in September 2009 in Australia

Frequent dust storms are a major concern in Australia due to associated human health risks and potential economic losses. From 23 to 24 September 2009, a dust storm passed over many east coast regions of Australia. This blanketed them with dust and reduced the visibility to a few hundred meters for several hours. The respirable particulate matter less than 10 mu m (PM10) was monitored at 22 locations across New South Wales (NSW) by the Environmental Protection Agency. In addition, samples were collected in Sydney using a nine-stage cascade impactor both during and after the dust storm. The PM10 concentration over most of NSW jumped from less than 50 mu g/m(3) to more than 10,000 mu g/m(3) within a couple of hours and then dropped again to more normal levels (< 50 mu g/m(3)). The normal bimodal particle size distribution was observed to change to a multimodal distribution during a dust storm event. Also, the elemental ratio of Al to Si increased from 0.14 to 0.39 during the storm. An Al/Si ratio > 0.3 indicates that the dust originated from inland desert areas and indeed was closely matched to Lake Eyre Basin crustal element data indicating it had travelled from central Australia to the eastern coasts.