Preprints
https://doi.org/10.5194/acp-2021-576
https://doi.org/10.5194/acp-2021-576

  03 Aug 2021

03 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Free amino acids quantification in cloud water at the puy de Dôme station (France)

Pascal Renard1, Maxence Brissy2, Florent Rossi2, Martin Leremboure2, Saly Jaber2, Jean-Luc Baray1,3, Angelica Bianco1, Anne-Marie Delort2, and Laurent Deguillaume1,3 Pascal Renard et al.
  • 1Université Clermont Auvergne, Laboratoire de Météorologie Physique, OPGC/CNRS UMR 6016, Clermont-Ferrand, France
  • 2Université Clermont Auvergne, CNRS, SIGMA Clermont, Institut de Chimie de Clermont-Ferrand (ICCF), Clermont-Ferrand, France
  • 3Université Clermont Auvergne, Observatoire de Physique du Globe de Clermont-Ferrand, UAR 833, Clermont-Ferrand, France

Abstract. Eighteen free amino acids (FAAs) were quantified in cloud water sampled at the puy de Dôme station (PUY – France) during 13 cloud events. This quantification has been performed without concentration neither derivatization, using LC-MS and the standard addition method to avoid matrix effects. Total concentrations of FAAs (TCAAs) vary from 1.2 µM to 7.7 µM, Ser (Serine) being the most abundant AA (23.7 % in average) but with elevated standard deviation, followed by Glycine (Gly) (20.5 %), Alanine (Ala) (11.9 %), Asparagine (Asn) (8.7 %), and Leucine/Isoleucine (Leu/I) (6.4 %). The distribution of AAs among the cloud events reveals high variability. TCAA constitutes between 0.5 and 4.4 % of the dissolved organic carbon measured in the cloud samples. AAs quantification in cloud water is scarce but the results agree with the few studies that investigated AAs in this aqueous medium. The environmental variability is assessed through a statistical analysis. This work shows that AAs are correlated with the time spent by the air masses in the boundary layer, especially over the sea surface before reaching the PUY. The cloud microphysical properties fluctuation does not explain the AAs variability in our samples confirming previous studies at PUY. We finally assessed the sources and the atmospheric processes that potentially explain the prevailing presence of certain AAs in the cloud samples. The initial relative distribution of AAs in biological matrices (proteins extracted from bacterial cells or mammalian cells, for example) could explain the dominance of Ala, Gly and Leu/I. AA composition of aquatic organisms (i.e., diatoms species) could also explain the high concentrations of Ser in our samples. The analysis of the AAs hydropathy also indicates a higher contribution of AAs (80 % in average) that are hydrophilic or neutral revealing the fact that other AAs (hydrophobic) are less favorably incorporated into cloud droplets. Finally, the atmospheric aging of AAs has been evaluated by calculating atmospheric lifetimes considering their potential transformation in the cloud medium by biotic or abiotic (mainly oxidation) processes. The most concentrated AAs encountered in our samples present the longest atmospheric lifetimes and the less dominant are clearly efficiently transformed in the atmosphere, potentially explaining their low concentrations. However, this cannot fully explain the relative contribution of several AAs in the cloud samples. This reveals the high complexity of the bio-physico-chemical processes occurring in the multiphasic atmospheric environment.

Pascal Renard et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-576', Anonymous Referee #1, 03 Sep 2021
  • RC2: 'Comment on acp-2021-576', Anonymous Referee #2, 16 Sep 2021

Pascal Renard et al.

Pascal Renard et al.

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Short summary
Amino acids (AAs) have been quantified in cloud water collected at the puy de Dôme station (France). Concentrations and speciation of those compounds are highly variable among the samples. Sources from the sea surface and atmospheric transformations during the air mass transport, mainly in the free troposphere have been shown to modulate AAs levels in cloud water.
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