On-line determination of the chemical composition of single activated cloud condensation nuclei – a pilot study. Issue 8 (22nd June 2022)

• Record Type: Journal Article
• Authors: Dameto de España, Carmen; Wonaschuetz, Anna; Steiner, Gerhard; Schuh, Harald; Sioutas, Constantinos; Hitzenberger, Regina
• Is Part Of: Aerosol science and technology. Volume 56:Issue 8(2022)
• Page Start: 673
• Page End: 687
• Publication Date: 2022-06-22
• Subjects: Jim Smith; Aerosols -- Periodicals; Aerosol Propellants -- Periodicals; Aerosols -- Periodicals; 660.294515
• DOI: 10.1080/02786826.2022.2069545
• Languages: English
• ISSNs: 0278-6826

Abstract

Abstract: Cloud condensation nuclei (CCN), i.e., aerosol particles that undergo theoretically unlimited growth when exposed to a certain (low) water vapor supersaturation and grow to large droplets, play an important role in cloud microphysics and are crucial for the second indirect effect of aerosols on global climate. The activation and growth of particles depends not only on their size but also on their chemical composition, which determines whether a particle of a certain size will actually be activated to grow to a cloud droplet. In order to analyze the chemical composition of individual CCN, the CCN must first be separated from non-CCN particles. For this purpose, we coupled a CCN-VACES (Cloud Condensation Nuclei-Versatile Aerosol Concentration Enrichment System, a modification of the original VACES), which activates CCN at defined supersaturations and enriches their concentrations by a factor of 17 to a single particle mass spectrometer (in our case a Laser Ablation Aerosol Particle Time of Flight mass spectrometer; LAAPTOF). Supersaturations in the CCN-VACES are set to 0.035%, 0.054%, 0.1% and 0.6%, respectively. The CCN present in an aerosol flow entering the CCN-VACES are activated and grow to droplets. Droplets > 1.5 µm are enriched in the exit flow and pass directly into the LAAPTOF where the chemical composition of the droplets originating from the individual activated CCN is obtained. In this pilot study, where ambient urban aerosol as well as nebulized sea water samples were used as test aerosols, we show that the LAAPTOF is indeed able to provide ion spectra for aqueous droplets and can therefore be used to determine the chemical composition of actually activated CCN in their droplet state. Single ambient CCN were found to contain sometimes highly complex mixtures of different carbonaceous and non-carbonaceous components. Sea water derived CCN show the expected sea salt constituents, but also the presence of organic material. Copyright © 2022 American Association for Aerosol Research