the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Measurement report: Molecular-level investigation of atmospheric cluster ions at the tropical high-altitude research station Chacaltaya (5240 m a.s.l.) in the Bolivian Andes
- 1Institute for Atmospheric and Earth System Research /Physics, University of Helsinki, Helsinki, Finland
- 2Department of Environmental Science & Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
- 3Institut des Géosciences de l'Environnement, Univ Grenoble Alpes, CNRS, IRD, Grenoble INP, Grenoble, France
- 4Department of Chemistry & Molecular Biology, University of Gothenburg, Sweden
- 5Federal University of Uberlândia, Uberlândia, MG, Brazil
- 6Institute for Ion and Applied Physics, University of Innsbruck, Innsbruck, Austria
- 7Joint International Research Laboratory of Atmospheric and Earth System Sciences, Nanjing University, Nanjing, China
- 8Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China
- 9Aerodyne Research, Inc., Billerica, MA, USA
- 10Laboratory for Atmospheric Physics, Institute for Physics Research, Universidad Mayor de San Andrés, La Paz, Bolivia
- 11Department of Atmospheric and Oceanic Sciences, University of Maryland, College Park, MD, 25 USA
- 1Institute for Atmospheric and Earth System Research /Physics, University of Helsinki, Helsinki, Finland
- 2Department of Environmental Science & Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
- 3Institut des Géosciences de l'Environnement, Univ Grenoble Alpes, CNRS, IRD, Grenoble INP, Grenoble, France
- 4Department of Chemistry & Molecular Biology, University of Gothenburg, Sweden
- 5Federal University of Uberlândia, Uberlândia, MG, Brazil
- 6Institute for Ion and Applied Physics, University of Innsbruck, Innsbruck, Austria
- 7Joint International Research Laboratory of Atmospheric and Earth System Sciences, Nanjing University, Nanjing, China
- 8Aerosol and Haze Laboratory, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, China
- 9Aerodyne Research, Inc., Billerica, MA, USA
- 10Laboratory for Atmospheric Physics, Institute for Physics Research, Universidad Mayor de San Andrés, La Paz, Bolivia
- 11Department of Atmospheric and Oceanic Sciences, University of Maryland, College Park, MD, 25 USA
Abstract. Air ions are the key components for a series of atmospheric physicochemical interactions, such as ion-catalyzed reactions, ion-molecule reactions, and ion-induced new particle formation. They also control atmospheric electrical properties with effects on global climate. We performed molecular-level measurements of cluster ions at the high-altitude research station Chacaltaya (CHC; 5240 m a.s.l.), located in the Bolivian Andes, from January to May 2018 using an atmospheric pressure interface time-of-flight mass spectrometer. The negative ions mainly consisted of (H2SO4)0–3•HSO4−, (HNO3)0–2•NO3−, SO5−, (NH3)1–6•(H2SO4)3–7•HSO4−, malonic acid-derived, and CHO/CHON•(HSO4−/NO3−) cluster ions. Their temporal variability exhibited distinct diurnal and seasonal patterns due to the changes in the corresponding neutral species’ molecular properties (such as electron affinity and proton affinity) and concentrations resulting from the air masses arriving at CHC from different source regions. The positive ions were mainly composed of protonated amines and organic cluster ions, but exhibited no clear diurnal variation. H2SO4-NH3 cluster ions likely contributed to the new particle formation process, particularly during wet-to-dry transition period and dry season when CHC was more impacted by air masses originating from source regions with elevated SO2 emissions. Our study provides new insights into the chemical composition of atmospheric cluster ions and their role in new particle formation in the high-altitude mountain environment of the Bolivian Andes.
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Qiaozhi Zha et al.
Status: final response (author comments only)
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RC1: 'Comment on egusphere-2022-1182', Anonymous Referee #1, 04 Jan 2023
This manuscript presents a large dataset of atmospheric cluster ions at a high-altitude station in the Sothern Hemisphere over a 5-month campaign, which is important. This work is one of the few existing studies reporting cluster ion composition at high altitudes, and probably the only one in the Southern Hemisphere. The chemical composition of the cluster ions was determined by using state-of-the-art instrumentation. The authors show interesting seasonal variations of the observed ions and attribute them to the properties of parent neutral molecules and different source origins by combing the results from the FLEXPART model. The potential link between the observed cluster ions and aerosol nucleation is also discussed. The manuscript is well-written and within the scope of ACP as a measurement report. I recommend it be accepted after the authors address several (minor) comments listed below:
- While the authors attributed the variations of some cluster ions (e.g., NO3- and HSO4-) to the abundance and properties of their parent neutral molecules in a convincing way, it would be better to show the observed concentrations of, e.g., NOx and SO2.
- This reviewer understands that the seasonality of positively charged ions could not be determined because they were only measured in wet season. A significant fraction of the discussion in the manuscript is thus based on measurements of negatively charged cluster ions. However, as mentioned in line 554, the increase of large positive ions was found concurrently with NPF events. It would be better if the authors could specify the chemical composition of the NPF-related positive ions instead of the sum of the signals over a certain mass range.
- It is odd to see the fraction of SA-NH3 and SA cluster ions started increasing before the onset of nucleation (line 530), and an explanation for this may be needed. The reviewer suggests the authors make sure the aerosol data in Fig. 10 are synchronized with cluster ion data.
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RC2: 'Comment on egusphere-2022-1182', Anonymous Referee #2, 20 Jan 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/egusphere-2022-1182/egusphere-2022-1182-RC2-supplement.pdf
Qiaozhi Zha et al.
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Figure data of "Measurement report: Molecular-level investigation of atmospheric cluster ions at the tropical high-altitude research station Chacaltaya (5240 m a.s.l.) in the Bolivian Andes" Qiaozhi Zha https://doi.org/10.5281/zenodo.7271286
Qiaozhi Zha et al.
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