Experts comment on the dust storm that has blanketed much of NSW, ACT, southern Queensland and northern South Australia.
ANSTO is currently analysing the dust from all along the Australian east coast. See here for more information.
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Dr Christel Hassler is a chemical and biological oceanographer from the Plant Functional Biology and Climate Change Cluster at the University of Technology Sydney (UTS).
“Because dust is known to bring essential nutrients, such as iron, that are required for the growth of marine algae, this storm will probably have significant short-term impact to our coastal waters and the Tasman Sea. An important spring bloom might be induced from this dust storm which could be followed from space using satellite images. Algal blooms are important for our fisheries as algae are the base of the marine food-web but they are also important to our climate, as algae fixe up to 40% of the global atmospheric carbon. This event nicely illustrates the tight bond between natural processes amongst terrestrial, atmospheric and marine environments.”
Dr Craig Strong is northern coordinator of DustWatch based at Griffith University, Queensland. DustWatch is a community-based project set up to monitor the extent and severity of wind erosion across Australia.
“What’s interesting about this event is that we’ve got a combination of factors which have been building for 10 months already. Floods, droughts and strong winds. Early on in the year a large flood transported sediment down the Diamantina River and deposited into Lake Eyre region. Big floods bring fresh sediment which is deposited, eventually dries out, and then becomes available for wind erosion. Combine this new source of available sediment with the passage of cold fronts (and their associated troughs), there is the mechanism for dust movement. Cold fronts commonly occur around this time of year and move across the country, passing over the Lake Eyre region and the Channel Country. Add to these factors the prevailing drought conditions that reduce the vegetation cover and the soil surface is at its most vulnerable to wind erosion.
Because of these circumstances this area is quite rich and quite ripe for wind erosion. Even last weekend there was an event in which the pre-frontal northerly winds picked up the sediment and transported it across the South Australian coastline across the ocean and off to New Zealand. This weekend we’ve had two very close events within 24 hours both picking sediment up from that region. The approach of a cold front brings different winds directions. Before the front actually hits an area, pre-frontal northerly winds prevail, so that’s usually associated with the hot, dry winds coming from the northerly direction. This weekend dust from east of Lake Eyre was entrained and transported in a south easterly direction over Tibboburra and Canberra and off the coast. As the front moves in, winds change direction from a pre-frontal northerly to a westerly. Now the westerly winds associated with this front were quite strong and vigorous and we actually produced a line of rolling dust storm, which are sometimes known as Bedouries or Haboob’s. Early on Tuesday morning this dust storm front was around 600 - 800km long. So now we have a westerly wind which is picking up this dust material and moving it in a easterly direction. It is this material which has impacted Sydney. The northern part of it is impacting western Queensland at the moment and will continue in an easterly direction.
Depending on how far north the dust front impacts there is the possibility of dust recirculation, in which once the dust is off shore it can sometimes be picked up on the south-east trade winds and then brought back across the northern coastline of Queensland. An event of this magnitude i would probably expect that we would see some sort of dust hazes along the eastern Queensland seaboard over the next couple of days. Essentially that’s material that’s made it into the South Pacific ocean and then picked up and then moved up along the coastline again.
Wind erosion is common to the Australian continent; there is a fine mix between natural rates of wind erosion and accelerated erosion, and accelerated predominantly being removal of vegetation, whether that’s inappropriate land management or just bad luck land management with the prevailing wind conditions. In terms of the cycle of wind erosion, it does follow the El Niño/La Niña cycle. So at the moment, this particular area is quite dry and exacerbated by the fact that we have a whole new load of new sediment down there ready for removal. So over the next couple of years, as this material has been deflated and removed, it will require more wind strength to remove what’s left.”
Professor Mark Harris is Executive Director of the Centre for Primary Health Care and Equity at the University of New South Wales.
“Dust storms may contain plant materials, smoke from fires as well as soil (giving the sky its red tinge and leaving residues on cars etc). These irritants may precipitate an asthma attack and is a concern especially for parents with children with asthma in rural areas (who may be exposed to dust storms more regularly) and older people with chronic lung diseases such as emphysema. They may also affect patients with heart disease or those. Dust storms have been associated with increased rates of presentation in general practice and to hospitals (especially in the large dust storms in Asia). Patients with respiratory disease should stay indoors during dust storms.”
Dr Ross Mitchell is from CSIRO Marine and Atmospheric Research
“We run a couple of monitoring stations in the outback, one at Birdsville and another at a more remote site at Tinga Tingana in the southern Strzelecki desert - about 400kms south of Birdsville. They are both within the Lake Eyre Basin, the main Australian dust source region.
What we have seen over the last 24 hours is really quite unusual. At the Tinga Tingana there was elevated dust through the whole day at a level usually associated with a major dust storm. The units we use in this measurement are ‘inverse mega metres’, and a number of about 1000 constitutes a really severe dust storm. Normally you will see an event that will peak at this level and then drop back. What we saw yesterday was a signal that remained at about that level for the whole day.
What we saw 400km further north at Birdsville was even more surprising. The pre-frontal dust level was just under 1000 inverse megametres, and then when the front came through at about 2pm local time, the reading peaked at 7200, the highest reading we have ever observed at either station over the last 10 years.
We have been observing at these places since 1997 and if you look at the ten years from 1997 to 2007 there was a big change in dust source emission following the 2002 drought. The dust season runs from spring to summer - essentially from September through to March . Iif you take an average dust level from 2002-2007 and compare that with 1997- 2002 there is about a factor of 2 difference, 2002-07 is about two times higher than the preceding five years , a significant increase on a decadal time scale.
The persistence of this storm is unusual, both the source region and here in Canberra where the dust lingered all day yesterday.”
Professor Nigel Tapper is Professor of Environmental Science and Head of the School of Geography and Environmental Science at Monash University in Melbourne.
“We currently have an ARC Discovery grant looking at Australian dust sources, composition, transport and impacts. These dust storms are some of the largest in the last 70 years. Improved pastoral management has been largely responsible for this lack of recent dust storms. However 10 very dry years over inland southern Australia and very strong westerlies have conspired to produce these recent storms. One storm last week passed over Melbourne to New Zealand and we are currently analysing dust collected last week from the Southern Alps of NZ. We are particularly interested in the impacts of dust in terms of ocean/ecosystem fertilisation and the microbes that are co-transported - with potential implications for ecosystem health (e.g. potentially the Great Barrier Reef, etc).”
Associate Professor Michael Box is from the School of Physics at the University of New South Wales.
“The Lake Eyre Basin area of central Australia is a dusty place, especially in early spring. Dust storms originating in this region are common, although it is far less common that the dust is carried the 1,500 km to Sydney, and beyond. However, with winds of sufficient strength and the right direction dust may be carried off the Australian coast - even as far as New Zealand.
The sky is ‘red’ because of sunlight absorption by the suspended dust. Australian desert dust is much redder than, say, Saharan dust due to its higher iron oxide content, which absorbs blue light. In storm events like these, Australia “freely exports” large quantities of iron to the oceans, which can fertilize plankton blooms. These blooms may play a beneficial role in climate change, absorbing carbon dioxide from the atmosphere.
Dust concentrations in Sydney are likely to be at least 10 to 20 times the recommended air quality goal. The sizes of the suspended particles are likely to be around one to a few micrometres, which are probably too large to penetrate deep into the lungs. Nevertheless they are small enough to enter airways, irritating the lungs of healthy people and adding to breathing difficulties in people who already have such problems.
Desert dust particles are relatively insoluble and so are not as easily removed by rain as are sulphate particles from fuel burning. They are likely to settle out on hard surfaces, and may find their way into hard to clean places.”
Dr Phillip Thompson is Director of the Centre for Asthma, Allergy and Respiratory Research at the University of Western Australia.
“Dust storms are particularly hazardous for anyone with chronic lung disease or sinus disease. Once the particles per cubic metre are above 300 dust storms pose a risk to lung health. Large particles are trapped in the nose and sinuses and can worsen sinusitis for those who suffer from this debilitating condition. Smaller particles reach the lower airways and act as an irritant and can trigger asthma in those whose asthma is unstable.
The nature of the dust can also be a major problem. It can contain a lot of plant materials such as pollen particles and cause severe allergic reactions or if it contains a lot of fine mineral dusts you can clog up the airway defense systems and increase the risks from infections and if a sustained exposure occurs it can lead to lung damage and scarring.
Patients with asthma, emphysema, bronchitis, COPD, Bronchiectasis or anyone with a current chest infection are at risk and should take preventative measures such as staying in doors with windows and doors closed, increasing medication where this is part of their self care plan and/or seek medical advice if they worsen. Repetitive/seasonal dust storms as occurs in parts of China can cause impairment in lung development in children. It is important to know the size of particles, the mineral and organic content of the dust to truly advise on the risk of dust exposure.”
Professor Guy Marks is Respiratory Physician and Clinical Professor at the University of Sydney and Head of Respiratory and Environmental Epidemiology, Woolcock Institute of Medical Research.
“There are very high levels of fine particles in the air in Sydney at present. The effect of fine particle pollution on respiratory health is at least partly influenced by their composition. For example, during thunderstorms ruptured pollen grains in the air can cause severe epidemics of asthma. The common source of particulate pollution is combustion products - vehicle and industrial emissions. These are associated with worsening of respiratory and cardiovascular disease, causing excess hospitalisations and deaths. The effect of earth (crustal) particles on health is less well studied. Several publications from Taiwan have shown small but non-significant increases in respiratory and cardiovascular admissions in the day or two after dust storm events.
Hence, the likely impact of the current event in Sydney is rather uncertain. The best advice is caution. People with severe respiratory disease (asthma or COPD) would be wise to stay indoors with the windows closed and to have their reliever inhalers available. “