Wednesday, 16 March 2011

CASANZ 2011 presentation on silica in ambient air


The scientific community and general public are becoming increasingly aware that mineralogy of airborne particulates matters as much as size and shape. The latest paper on this topic will be presented by Anthony Morrison at the 20th Clean Air Society of Australia and New Zealand Conference CASANZ 2011 in Christchurch 5-8th July 2011. It characterises silica and silicon concentrations in ambient air in the vicinity of open cut coal mining operations in the Hunter Valley, New South Wales, Australia. FEI’s automated scanning electron microscopy and energy- dispersive x-ray spectroscopy (SEM-EDS) solution QEMSCAN is used to quantify the proportion of quartz in the particulate matter (PM) samples, identify other silicon containing species for provenance interpretation, and to determine the degree of liberation of quartz in the dust samples.

This study is among the first to apply Automated Mineralogy to the investigation of the public health impacts of airborne particulates to inform the discussion of air quality management plans. It is also pioneering a direct sampling to measurement process, using a Micro Orifice Uniform Deposit Impactor (MOUDI) allowing the dust samples to be collected on polycarbonate discs specially prepared for transferral into the QEMSCAN sample holder. Finally, the study is involving the world’s first attempt at measuring loosely bound particles, thus avoiding sectioning or polishing. The QEMSCAN Particle View screenshot above demonstrates that the surface covered by silt-sized particles is flat enough to be measured.

Have a look at the abstract below and make sure to attend the conference to get a copy of the full paper.

"Quantifying respirable crystalline silica in the ambient air of the Hunter Valley, NSW - sorting the silica from the silicon"
by Anthony Morrison, Peter F. Nelson, Eduard Stelcer, David Cohen, David Haberlah

Crystalline forms of silica are known to cause lung damage for which there is no effective treatment. Silicon is abundant in crustal material and silicates are the single largest mineral grouping, with silica (SiO2) being the most abundant crustal compound. Media reports of high levels of silicon in particles in the air in the vicinity of Hunter Valley open-cut coal mines have caused community anxiety and concerns about potential health impacts on local populations. An extensive sampling campaign using continuous air quality monitoring and targeted collection of particles has been carried out in an area close to mining operations. It was determined that silicon as silica was present in the ambient air, although the concentrations of crystalline silica measured suggest that it should not should cause health problems even for sensitive individuals within the general population. The results of the research should inform more rigorous discussions of air quality management plans for fine particles in the Hunter Valley and aid discussions of community concerns over the potential health impacts of coal mining

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