Pre-deliquescent water uptake in deposited nanoparticles observed with in situ ambient pressure X-ray photoelectron spectroscopy

Creators: Lin, Jack J.; Raj R., Kamal; Wang, Stella; Kokkonen, Esko; Mikkelä, Mikko-Heikki; Urpelainen, Samuli; Prisle, Nønne L.

Abstract

We study the adsorption of water onto deposited inorganic sodium chloride and organic malonic acid and sucrose nanoparticles at ambient water pressures corresponding to relative humidities (RH) from 0 % to 16 %. To obtain information about water adsorption at conditions which are not accessible with typical aerosol instrumentation, we use surface-sensitive ambient pressure X-ray photoelectron spectroscopy (APXPS), which has a detection sensitivity starting at parts per thousand. Our results show that water is already adsorbed on sodium chloride particles at RH well below deliquescence and that the chemical environment on the particle surface is changing with increasing humidity. While the sucrose particles exhibit only very modest changes on the surface at these relative humidities, the chemical composition and environment of malonic acid particle surfaces is clearly affected. Our observations indicate that water uptake by inorganic and organic aerosol particles could already have an impact on atmospheric chemistry at low relative humidities. We also establish the APXPS technique as a viable tool for studying chemical changes on the surfaces of atmospherically relevant aerosol particles which are not detected with typical online mass- and volume-based methods.

Additional Information

© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 6 April 2020 – Discussion started: 29 April 2020; Revised: 1 February 2021 – Accepted: 3 February 2021 – Published: 26 March 2021. Code availability: The SPANCF fitting package is available from Edwin Kukk, ekukk@utu.fi. Data availability: Data for the XPS spectra are available at https://doi.org/10.5281/zenodo.4624072 (Prisle, 2021). Supplement: The supplement related to this article is available online at: https://doi.org/10.5194/acp-21-4709-2021-supplement. Author contributions: Conceptualization, funding acquisition, supervision and project administration were performed by NLP. The experiments were carried out by JJL, KRR, SW, EK, MHM and SU. Data analysis was done by SU, JJL, SW and NLP. The first draft of the paper was written by JJL, SU and NLP with input from all co-authors. The authors' response was written by JJL, NLP and SU with input from all co-authors. The revised draft was written by JJL and NLP with input from all co-authors. The authors declare that they have no conflict of interest. We acknowledge MAX IV Laboratory for time on beamline SPECIES. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research Council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969 and Formas under contract 2019-02496. We warmly thank Jenny Rissler and Birgitta Svenningsson for assistance with preparation of samples and estimation of surface coverage. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program, project SURFACE (grant agreement no. 717022). The authors also gratefully acknowledge the financial contribution from the Academy of Finland, including grant nos. 308238, 314175, 335649, 290145, 326291 and 331532. Review statement: This paper was edited by Thorsten Bartels-Rausch and reviewed by two anonymous referees.

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