Results of the first-ever ACSM intercomparison study from the ACTRIS-ACSM network

As part of the EU-FP7 ACTRIS program, a large international intercomparison study of 15 aerosol mass spectrometers (13 Q-ACSM, 1 ToF-ACSM and 1 HR-ToF-AMS) has been performed from 15 Nov. to 2 Dec. 2013 at the LSCE in-situ atmospheric platform which is part of the French SIRTA observatory (http://sirta.ipsl.fr) located at 20km southwest of Paris. During this period, each instrument measured the major non-refractory submicron aerosols (NR-PM1) components (organic matter, nitrate, sulfate, and ammonium) in ambient air. The accuracy of Q-ACSM instruments was determined by comparison with various co-located instruments (TEOM-FDMS, SMPS, OPC, OC-EC Sunset Field analyzer, PILS-IC, aethalometers, nephelometers, and filter sampling). The measurement precision was also evaluated by intercomparing the correlation of absolute mass concentrations for all the NR-PM1 species. The ACSM analytical uncertainties were then estimated by applying a statistical approach in order to evaluate the analytical standard deviations between ACSMs and to highlight any bias or influencing factor on the ACSM measurements. For this purpose, the Z-score indicator representing performance criteria was used making it possible to measure its relative deviation to the assigned value. Fig. 1 summarizes the Z-Score results applied to the 13 Q-ACSM datasets for the major chemical species of the NR-PM1. All the ACSMs present satisfactory Z-Score values (a Z-Score value of 3 is considered as the limit value) whatever the considered parameter highlighting the instrument precision.