Elemental composition of ambient aerosols measured with high temporal resolution using an online XRF spectrometer

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Courtesy of Cooper Environmental Services

Markus Furger1,*, María Cruz Minguillón2, Varun Yadav3, Jay G. Slowik1, Christoph Hüglin4, Roman
Fröhlich1, Krag Petterson3, Urs Baltensperger1, André S. H. Prévôt1
1Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen 5 PSI, Switzerland
2Institute of Environmental Assessment and Water Research (IDAEA), Consejo Superior de Investigaciones Científicas
(CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain
3Cooper Environmental Services (CES), 9403 SW Nimbus Avenue, Beaverton, OR 97008, USA
4 Laboratory for Air Pollution / Environmental Technology, Empa, Überlandstrasse 129, 8600 Dübendorf, Switzerland
10 * Correspondence to: Markus Furger (markus.furger@psi.ch)

Abstract.An Xact 625 ambient metals monitor was tested during a three-week field campaign at the rural, traffic-influenced
site Härkingen in Switzerland during summer of 2015. The objective was to characterize the handling and operation of the
instrument, evaluate the data quality by intercomparison with other independent measurements, and test its applicability for
aerosol source quantification. The Xact was configured to measure 24 elements in PM10 with 1-h time resolution. Hourly
15 element concentrations ranged from a few ng m-3 for trace elements in background conditions to tens of μg m-3 for major
elements during a high-emission event (fireworks). The total Xact element mass comprised approximately 20 % of the total
PM10 mass. The six major elements Si, S, Cl, K, Ca, and Fe contributed 95 % to the Xact PM10 mass, the remaining 5 %
were attributed to the trace elements. Data quality was evaluated by intercomparison with 24-h PM10 filter data analysed with
ICP-OES for major elements, ICP-MS for trace elements, and gold amalgamation atomic absorption spectrometry for Hg. 10
20 elements (S, K, Ca, Ti, Mn, Fe, Cu, Zn, Ba, Pb) showed an excellent correlation between the compared methods, with r2
values ≥ 0.95, even though the Xact 625 yielded approximately 28% higher elemental concentrations than ICP for these
elements. These elements demonstrate the high precision of the Xact instrument. An average 28 percent difference to ICP
analyses might in part be attributed to the differences in the sampling systems (inlets), the geographic distance between the
inlets and between the inlets and the freeway, and to uncertainties in the different analysis methods. 10 additional elements
25 (Cr, V, Co, Ni, As, Se, Cd, Sn, Hg, Bi) could not be compared to a reference, because their concentrations were close to or
below the minimum detection limits of at least one of the analysis methods. Sb revealed a calibration issue with the Xact,
which requires correction. Si, Cl and Pt were not analysed with ICP, and thus could not be evaluated. The well-quantified
elements were further used for a simple investigation of sources. The field campaign encompassed the Swiss National Day
fireworks event, providing increased concentrations and unique chemical signatures compared to non-fireworks (or
30 background) periods. Fireworks and traffic or rural background emissions could clearly be identified with their element
mixture. The results demonstrate that multi-metal characterization at high-time resolution capability of Xact is a valuable
and practical tool for ambient monitoring, exhibiting significant advantages compared to traditional elemental analysis
methods.

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