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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 6 | Copyright
Atmos. Meas. Tech., 11, 3541-3557, 2018
https://doi.org/10.5194/amt-11-3541-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Jun 2018

Research article | 20 Jun 2018

Field and laboratory evaluation of a high time resolution x-ray fluorescence instrument for determining the elemental composition of ambient aerosols

Anja H. Tremper1, Anna Font1, Max Priestman1, Samera H. Hamad2, Tsai-Chia Chung3, Ari Pribadi1, Richard J. C. Brown4, Sharon L. Goddard4, Nathalie Grassineau3, Krag Petterson5, Frank J. Kelly1, and David C. Green1 Anja H. Tremper et al.
  • 1MRC-PHE Centre for Environment and Health, King's College London, London, SE1 9NH, UK
  • 2Department of Behavioural and Community Health, School of Public Health, the University of Maryland, College Park, MD 20742, USA
  • 3Earth Sciences Department, Royal Holloway University of London, Egham TW20 0EX, UK
  • 4Chemical, Medical and Environmental Science Department, National Physical Laboratory, Teddington, TW11 0LW, UK
  • 5Cooper Environmental Services, LLC, 9403 SW Nimbus Ave. Beaverton, OR 97062, USA

Abstract. Measuring the chemical composition of airborne particulate matter (PM) can provide valuable information on the concentration of regulated toxic metals, support modelling approaches for source detection and assist in the identification and validation of abatement techniques. Undertaking these at a high time resolution (1h or less) enables receptor modelling techniques to be more robustly linked to emission processes. This study describes a comprehensive laboratory and field evaluation of a high time resolution x-ray fluorescence (XRF) instrument (CES XACT 625) for a range of elements (As, Ba, Ca, Cd, Ce, Cl, Cr, Cu, Fe, K, Mn, Mo, Ni, Pb, Pt, S, Sb, Se, Si, Sr, Ti, V and Zn) against alternative techniques: high time resolution mass measurements, high time resolution ion chromatography, aerosol mass spectrometry, and established filter-based, laboratory analysis using inductively coupled plasma mass spectrometry (ICP-MS).

  1. Laboratory evaluation was carried out using a novel mass-based calibration technique to independently assess the accuracy of the XRF against laboratory generated aerosols, which resulted in slopes that were not significantly different from unity. This demonstrated that generated particles can serve as an alternative calibration method for this instrument.

  2. The XACT was evaluated in three contrasting field deployments; a heavily trafficked roadside site (PM10 and PM2.5), an industrial location downwind of a nickel refinery (PM10) and an urban background location influenced by nearby industries and motorways (PM10). The XRF technique agreed well with the ICP-MS measurements of daily filter samples in all cases with a median R2 of 0.93 and a median slope of 1.07 for the elements As, Ba, Ca, Cr, Cu, Fe, K, Mn, Ni, Pb, Se, Sr, Ti, V and Zn. Differences in the results were attributed to a combination of inlet location and sampling temperature, variable blank levels in filter paper and recovery rates from acid digestion. The XRF technique also agreed well with the other high time resolution measurements but showed a clear positive difference (slopes between 1.41 and 4.6), probably due to differences in the size selection methodology, volatility and water solubility of the PM in aerosol mass spectrometry (SO4) and ion chromatography (Ca, Cl, K and SO4), respectively.

  3. A novel filter analysis technique using the XACT showed promising initial results: filters analysed off-line with the XACT compared well to in situ XACT measurements with a median R2 of 0.96 and median slope of 1.07. The resulting range of slopes was comparable to slopes produced in the ICP-MS comparison. This technique provides an opportunity to use the XACT when it is not deployed in the field; thus expanding the potential use of this instrument in future studies.

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Measuring the chemical composition of airborne particulates can provide valuable information on the concentration of regulated toxic metals and their sources and assist in the identification and validation of abatement techniques. Undertaking these measurements at a high time resolution enables computer modelling techniques to be more robustly linked to emission processes. This study describes a comprehensive laboratory and field evaluation of a high time resolution metal monitoring instrument.
Measuring the chemical composition of airborne particulates can provide valuable information on...
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