Elemental composition of ambient aerosols measured with high temporal resolution using an online XRF spectrometer
Markus Furger1, María Cruz Minguillón2, Varun Yadav3, Jay G. Slowik1, Christoph Hüglin4, Roman Fröhlich1, Krag Petterson3, Urs Baltensperger1, and André S. H. Prévôt11Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, 5232 Villigen 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 4Laboratory for Air Pollution/Environmental Technology, Empa, Überlandstrasse 129, 8600 Dübendorf, Switzerland
Received: 23 Nov 2016 – Accepted for review: 10 Jan 2017 – Discussion started: 11 Jan 2017
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 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 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 (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 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.
Furger, M., Minguillón, M. C., Yadav, V., Slowik, J. G., Hüglin, C., Fröhlich, R., Petterson, K., Baltensperger, U., and Prévôt, A. S. H.: Elemental composition of ambient aerosols measured with high temporal resolution using an online XRF spectrometer, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-383, in review, 2017.