As part of the European ACTRIS project, the first
large Quadrupole Aerosol Chemical Speciation Monitor (QACSM)
intercomparison study was conducted in the region
of Paris for 3 weeks during the late-fall – early-winter period
(November–December 2013). The first week was dedicated
to the tuning and calibration of each instrument, whereas the
second and third were dedicated to side-by-side comparison
in ambient conditions with co-located instruments providing
independent information on submicron aerosol optical,
physical, and chemical properties. Near real-time measurements
of the major chemical species (organic matter, sulfate,
nitrate, ammonium, and chloride) in the non-refractory submicron
aerosols (NR-PM1/ were obtained here from 13 QACSM.
The results show that these instruments can produce
highly comparable and robust measurements of the NR-PM1
total mass and its major components. Taking the median of
the 13 Q-ACSM as a reference for this study, strong correlations
(r2 > 0:9) were observed systematically for each
individual Q-ACSM across all chemical families except for
chloride for which three Q-ACSMs showing weak correlations
partly due to the very low concentrations during the
study. Reproducibility expanded uncertainties of Q-ACSM
concentration measurements were determined using appropriate
methodologies defined by the International Standard
Organization (ISO 17025, 1999) and were found to be 9,
15, 19, 28, and 36% for NR-PM1, nitrate, organic matter,
sulfate, and ammonium, respectively. However, discrepancies
were observed in the relative concentrations of the constituent
mass fragments for each chemical component. In
particular, significant differences were observed for the organic
fragment at mass-to-charge ratio 44, which is a key
parameter describing the oxidation state of organic aerosol.
Following this first major intercomparison exercise of a large
number of Q-ACSMs, detailed intercomparison results are
presented, along with a discussion of some recommendations
about best calibration practices, standardized data processing,
and data treatment.