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A rapid method for quantifying single mineral phases in heterogeneous natural dusts using X-ray diffraction

Published online by Cambridge University Press:  29 February 2012

Jennifer S. Le Blond ,
Gordon Cressey ,
Claire J. Horwell  and
Ben J. Williamson
Jennifer S. Le Blond*
Affiliation:
Department of Geography, University of Cambridge, Downing Site, Cambridge CB2 3EN, United Kingdom and Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
Gordon Cressey
Affiliation:
Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
Claire J. Horwell
Affiliation:
Department of Earth Sciences, Science Laboratories, IHRR, Durham University, Durham DH1 3LE, United Kingdom
Ben J. Williamson
Affiliation:
Camborne School of Mines, School of Geography, Archaeology & Earth Resources, University of Exeter, Penryn, Cornwall TR10 9EZ, United Kingdom
*
a)Author to whom correspondence should be addressed. Present address: Department of Geography, University of Cambridge, Downing Site, Cambridge CB2 3EN, UK. Electronic mail: [email protected]
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Abstract

Quantification of potentially toxic single mineral phases in natural dusts of heterogeneous composition is critical for health hazard assessment. For example, crystalline silica, a human carcinogen, can be present as respirable particles in volcanic ash such as quartz, cristobalite, or tridymite. A method to rapidly identify the proportions of crystalline silica within mixed dust samples, such as volcanic ash, is therefore required for hazard managers to assess the potential risk of crystalline silica exposure to local populations. Here we present a rapid method for quantifying the proportions of single phases in the mineral assemblage of mixed dusts using X-ray diffraction (XRD) with a fixed curved position-sensitive detector. The method is a modified version of the whole-pattern peak-stripping (PS) method (devised by Cressey and Schofield [Powder Diffr.11, 35–39 (1996)]) using an internal attenuation standard (IAS) but, unlike the PS method, it requires no knowledge of other phases present in the sample. Ten synthetic sample mixtures were prepared from known combinations of four pure phases (cristobalite, hematite, labradorite, and obsidian), chosen to represent problematic constituents of volcanic ash, and analyzed by XRD. Results of the IAS method were directly compared with those of the PS method. The proportions of cristobalite estimated using the methods were comparable and accurate to within 3 wt %. The new IAS method involved less sample preparation and processing and, therefore, was faster than the original PS method. It therefore offers a highly accurate rapid technique for determination of the proportions of individual phases in mixed dusts.

Keywords

cristobalitecrystalline silicadustsX-ray diffractioncurved position-sensitive detectorhealth hazard
Type
Technical Articles
Information
Powder Diffraction , Volume 24 , Issue 1 , March 2009 , pp. 17 - 23
Copyright
Copyright © Cambridge University Press 2009

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