Abstract
Abstract. The Xact 625 Ambient Metals Monitor was tested during a 3-week field campaign at the rural, traffic-influenced site Härkingen in Switzerland during the summer of 2015. The field campaign encompassed the Swiss National Day fireworks event, providing increased concentrations and unique chemical signatures compared to non-fireworks (or background) periods. The objective was to 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. Data quality was evaluated for 10 24 h averages of Xact data 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. Ten elements (S, K, Ca, Ti, Mn, Fe, Cu, Zn, Ba, Pb) showed excellent correlation between the compared methods, with r2 values ≥ 0.95. However, the slopes of the regressions between Xact 625 and ICP data varied from 0.97 to 1.8 (average 1.28) and thus indicated generally higher Xact elemental concentrations than ICP for these elements. Possible reasons for these differences are discussed, but further investigations are needed. For the remaining elements no conclusions could be drawn about their quantification for various reasons, mainly detection limit issues. An indirect intercomparison of hourly values was performed for the fireworks peak, which brought good agreement of total masses when the Xact data were corrected with the regressions from the 24 h value intercomparison. The results demonstrate that multi-metal characterization at high-time-resolution capability of Xact is a valuable and practical tool for ambient monitoring.
Highlights
The quantification of trace elements in airborne particulate matter (PM) can be achieved with various techniques, such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectrometry (XRF), and particle-induced X-ray emission spectrometry (PIXE)
Data quality was evaluated for 10 24 h averages of Xact data 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
The goals of this article are (1) to characterize the measurements of the test period in Härkingen and compare them with previous studies in Switzerland; (2) to examine the achieved data quality for the selected elements with respect to their MDLs; (3) to quantify the measurement quality based on intercomparisons between the Xact and NABEL PM10 data (1 h tapered element oscillating microbalance (TEOM) data and 24 h filter samples) for Härkingen; (4) to evaluate the applicability of the instrument at high time resolution in typical summer conditions and concentration ranges at a traffic-influenced rural site in Switzerland; and (5) to gauge the advantages of high-time-resolution sampling for a preliminary investigation of sources based on enhancement ratios and diurnal variability of elements
Summary
The quantification of trace elements in airborne particulate matter (PM) can be achieved with various techniques, such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectrometry (XRF), and particle-induced X-ray emission spectrometry (PIXE). These methods require a two-step procedure, i.e. sample collection in the field followed by laboratory analysis. Ambient pollutants are conventionally collected on filter substrate for large time duration such as 8 or 24 h sampling time to ensure that sufficient elemental mass is available for analytical analysis (ICP).
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