[pam-users] Xu et al., AMT, 2024

[pam-users]

$@,Da

On Wed, Jul 17, 2024, 11:10 AM pam-users <
aerodyne-pam-users at lists.aerodyne.com> wrote:

> Xu, N., Le, C., Cocker, D. R., Chen, K., Lin, Y.-H., and Collins, D. R.:
> An oxidation flow reactor for simulating and accelerating secondary aerosol
> formation in aerosol liquid water and cloud droplets, Atmos. Meas. Tech.,
> 17, 4227–4243, https://doi.org/10.5194/amt-17-4227-2024, 2024.
>
>
>
> *Abstract. *Liquid water in cloud droplets and aqueous aerosols serves as
> an important reaction medium for the formation of secondary aerosol through
> aqueous-phase reactions (aqSA). Large uncertainties remain in estimates of
> the production and chemical evolution of aqSA in the dilute solutions found
> in cloud droplets and the concentrated solutions found in aerosol liquid
> water, which is partly due to the lack of available measurement tools and
> techniques. A new oxidation flow reactor (OFR), the Accelerated Production
> and Processing of Aerosols (APPA) reactor, was developed to measure
> secondary aerosol formed through gas- and aqueous-phase reactions, both for
> laboratory gas mixtures containing one or more precursors and for ambient
> air. For simulating in-cloud processes, ∼ 3.3 µm diameter droplets formed
> on monodisperse seed particles are introduced into the top of the reactor,
> and the relative humidity (RH) inside it is controlled to 100 %. Similar
> measurements made with the RH in the reactor < 100 % provide contrasts
> for aerosol formation with no liquid water and with varying amounts of
> aerosol liquid water.
>
> The reactor was characterized through a series of experiments and used to
> form secondary aerosol from known concentrations of an organic precursor
> and from ambient air. The residence time distributions of both gases and
> particles are narrow relative to other OFRs and lack the tails at long
> residence time expected with laminar flow. Initial cloud processing
> experiments focused on the well-studied oxidation of dissolved SO2 by O3,
> with the observed growth of seed particles resulting from the added
> sulfuric acid agreeing well with estimates based on the relevant set of
> aqueous-phase reactions. The OH exposure (OHexp) for low RH, high RH, and
> in-cloud conditions was determined experimentally from the loss of SO2 and
> benzene and simulated from the KinSim chemical kinetics solver with inputs
> of the measured 254 nm UV intensity profile through the reactor and loss of
> O3 due to photolysis. The aerosol yield for toluene at high OHexp ranged
> from 21.4 % at low RH with dry seed particles present in the reactor to
> 78.1 % with cloud droplets present. Measurement of the composition of the
> secondary aerosol formed from ambient air using an aerosol mass
> spectrometer showed that the oxygen-to-carbon ratio (O : C) of the organic
> component increased with increasing RH (and liquid water content).
>
> PAM Wiki - Publications Using Other Oxidation Flow Reactors (google.com)
> <https://sites.google.com/site/pamwiki/publications-using-other-oxidation-flow-reactors>
>
>
>
> Andrew Lambe
>
> Principal Scientist
>
> Aerodyne Research, Inc.
>
>
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