Evaluation of aerosol chemical speciation monitor response to different mixtures of organic and inorganic aerosols
Résumé
As national air quality networks and international research infrastructures, such as ACTRIS
(EU) and ASCENT (US), continue to expand, the deployment of online aerosol chemistry
measurements increases worldwide. These research infrastructures are focused on the ability
to compare atmospheric properties from one region to another, making it crucial to understand
instrument operation in various settings. This paper is part of a series of publications
dedicated to better understanding the operation of these instruments using a series of
laboratory tests. A particular focus was made on evaluating the organic aerosol (OA) measurement
performance of six Aerosol Chemical Speciation Monitors (ACSMs) when sampling
known mixtures of organic and inorganic aerosols and in ambient air. The study focuses on
assessing the impact of instrument-to-instrument variability on ACSM data processing as
well as identifying and quantifying the previously identified m/z44/NO3 artifacts that can
affect the accuracy of the measurements. A high degree of variability was observed in
instrument measurements of the m/z44/NO3 artifact when compared to results obtained
two years earlier (e.g., an increase from �0 in 2016 to 0.16 in 2018 or a decrease from 0.12
in 2016 to 0.05 in 2018), confirming the need for frequent evaluation and quantification
during calibration. This study underlines that the product between organic aerosol relative
ionization efficiency and the instrument collection efficiency value is instrument dependent
and that the variability in these values (1.78 ± 0.35) should be considered when estimating
the measurement uncertainties. Using a range of specific compounds, an average RIEOA for
levoglucosan (1.29 ± 0.23) close to the default value commonly used in ACSM was determined,
obtaining a value more specific to each instrument. This study provides valuable
information for the calibration and operation of ACSM instruments, ensuring that future
studies can build on this work to evaluate and improve instrument performance.
Domaines
Sciences de l'environnement
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