Quantifying airborne particle compositions in the field The aim of this work package is to demonstrate the field capacity of XRF, combined with flexible particle sampling techniques, in order to establish within air quality monitoring networks novel methods for the quantification of regulated elements in ambient aerosols. In particular this includes mobile real time analytical methods with enhanced sensitivity, spatial and temporal resolution. In contrast to conventional analytical methods XRF methods are sufficiently sensitive to include ultrafine particles i.e. particles with diameter smaller than 100 nm and with negligible mass contribution which are per se not yet regulated by the European directives. A number of well-established aerosol sampling techniques (sampling heads, cascade impactors, electrostatic samplers, filters etc.) will be used for in-situ-sampling of airborne particles either integrated over size or in separate size bins from several 10 μm in diameter (PM10) down to several nm. Quantitative elemental analyses on the samples will be performed semi-automatically in-situ by mobile XRF and by Aerodyne Aerosol Chemical Speciation Monitor (ASCM). On-site sampling and analysis will be performed during at least two field campaigns at two locations in Europe with different air pollution scenarios in order to demonstrate the field capability of the methods. Parallel on-site particle size distribution measurements will complete the characterisation of the aerosols and provide data for a deeper subsequent analysis. During the campaigns aerosol samples will also be taken and stored for a later backup laboratory analysis by lab-based XRF as well as by standard methods (ICP-MS) used in current EU air monitoring practice. The comparison of in-field and lab-based results will enable the estimation of realistic uncertainty budgets for the quantification of elements in ambient aerosols: The uncertainty budget will be based in the case of XRF-techniques on calibration with model aerosols and model aerosol samples and/or instrumental and elemental fundamental parameters and in the case of ICP-MS on commercially available reference standards. Further to this, the improved sensitivity and time resolution of the XRF-based methods over the standard methods (ICP-MS) will be demonstrated and quantified. In contrast to standard field sampling methods (filter sampling), those applied in WP4 will offer in combination with XRF a particle size resolved quantification of elements in aerosol samples in order to allow the identification of individual sources of air pollutions and a size dependent study of aerosols in the environment. The work package is divided into three tasks: Task 4.1 – Demonstration of the field capability – Real-time in-field measurements with mobile devices (XRF, ASCM) for quantifying the mass concentration of regulated elements (As, Cd, Hg, Ni) in aerosol samples; Task 4.2 – Laboratory analysis: (Re)-analysis of particle compositions (using in-field samples from 4.1) with conventional techniques (ICP-MS and others) as well as lab-based calibrated XRF; Task 4.3 – Lab exercise: Establishment of an independent traceability chain for mobile XRF using lab-generated Ni-particles of selected sizes as test aerosols and lab based TXRF/GIXRF as a reference method. Task 4.1: Demonstration of the field capability – Real-time in-field measurements with mobile devices for quantifying the mass concentration of regulated elements in aerosol samples The aim of this task is to demonstrate the field capability of mobile, time-resolved and quantitative in-situ (in-field) devices for quantifying the mass concentration of regulated elements (As, Cd, Hg, Ni) in aerosol samples. Task 4.2: Backup laboratory analysis: (Re)-analysis of particle compositions with conventional techniques, lab-based calibrated XRF and comparison with field data. The aim of this task is to demonstrate equivalent (or better) uncertainty and substantially improved sensitivity of the innovative XRF-based methods used in Task 4.1 in the quantitative chemical analysis of regulated elements (As, Cd, Hg and Ni). To do this, the samples generated in A4.1.4 will be reanalysed with conventional techniques (ICP-MS etc.) and state-of-the art lab-based methods and the respective results and measurement uncertainties will be compared. Task 4.3: Laboratory activity: Establishment of an independent traceability chain for mobile XRF using lab-generated Ni-particles of selected sizes as test aerosols and lab based TXRF/GIXRF as a reference method. The aim of this task is to establish an independent traceability chain for mobile XRF as a method for the in-situ measurement of mass concentrations of an element in aerosol samples using Ni-particles of selected sizes as test aerosols and TXRF/GIXRF as a reference method.