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

Abstract

Abstract. Measuring the chemical composition of airborne particulate matter (PM) 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 at a high time resolution (1 hour 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) 5 for a range of elements (As, Ba, Ca, Cd, Ce, Cl, Cr, Cu, Fe, K, Mn, Mo, Ni, Pb, Pd, Pt, S, Sb, Se, Si, Sr, Ti, V, 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 massbased calibration technique to independently assess the accuracy of the XRF against laboratory generated 10 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 (PM 10 and PM 2.5 ), an industrial location downwind of a nickel refinery (PM 10 ) and an urban background location influenced by nearby industries and motorways (PM 10 ). The XRF technique agreed well with the ICP-MS measurements of 15 daily filter samples in all cases with a median R 2 of 0.93 and a median slope of 1.07. Differences were likely due to recovery rates from the sample digestion as well as filter sampling artefacts and matrix effects in the XRF technique. The XRF technique also agreed well with the other high time resolution measurements but showed a significant positive bias (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 and ion chromatography, 20 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 R 2 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. 25 IntroductionIt has long been known that increased air pollution, and specifically particle pollution is associated with adverse health effects (Brunekreef and Holgate, 2002;Kelly et al., 2012). Particulate matter (PM) also affects atmospheric visibility and radiative forcing (Fuzzi et al., 2015). PM is not a homogenous air pollutant but rather a complex mixture; it varies in chemical and physical co...

PM2.5 on the London Underground

“…Both these methodologies are reference procedures for ambient regulatory purposes. PM and TSP were also sampled onto mixed cellulose esters filter media (GN-4 Metricel, 0.8 μm pore) filters every four hours (Thermo Scientific Partisol 2025) and subsequently analysed for 30 elements, including Fe and other indicators of wear products in the LU using hydrofluoric acid digestion and inductively coupled plasma mass spectroscopy (Tremper et al, 2018). Twelve PM 2.5 and 10 TSP samples were analysed.…”

Non-exhaust vehicle emissions of particulate matter and VOC from road traffic: A review

“…Semi-continuous analysis of these particles is possible using in situ XRF analysis, as used in the XACT monitor (Tremper et al, 2018;Furger et al, 2017). This has the advantage over offline analysis in that it produces data in near real time and can produce data on an hourly basis.…”

Levels and sources of hourly PM2.5-related elements during the control period of the COVID-19 pandemic at a rural site between Beijing and Tianjin

“…V was retained as it is an important tracer of oil combustion (Liu et al, 2018;Wang et al, 2018). The Xact 625 has already been used in several studies (Chang et al, 2018;Gao et al, 2016;Phillips-Smith et al, 2017;Tremper et al, 2018). Due to malfunction of the instrument, data from the period of 11 February to 21 March are not available.…”