21 Apr 2022
21 Apr 2022
Status: this preprint is currently under review for the journal ACP.

Mass spectrometric measurements of ambient ions and estimation of gaseous sulfuric acid in the free troposphere and lowermost stratosphere during the CAFE-EU/BLUESKY campaign

Marcel Zauner-Wieczorek1, Martin Heinritzi1, Manuel Granzin1, Timo Keber1, Andreas Kürten1, Katharina Kaiser2, Johannes Schneider2, and Joachim Curtius1 Marcel Zauner-Wieczorek et al.
  • 1Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt am Main, Frankfurt am Main, 60629, Germany
  • 2Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55128, Germany

Abstract. Ambient ions play an important role in atmospheric processes such as ion-induced new particle formation. While there are several studies of ambient ions for different layers of the atmosphere, data coverage for the free troposphere and especially the upper troposphere and lower stratosphere (UTLS) region is scarce. Here, we present the first airborne measurements of ambient ions using a High Resolution-Atmospheric Pressure interface-Time Of Flight-Mass Spectrometer (HR-APi-TOF-MS) in the free troposphere and lower stratosphere above Europe on board the HALO aircraft during the CAFE-EU/BLUESKY campaign in May and June 2020. In negative measurement mode, we observed nitrate and hydrogen sulfate and their related ion clusters in an altitude range of 4.7 to 13.4 km. The horizontal profiles for those ions reveal an increasing count rate for NO3– and (HNO3)NO3– towards higher altitudes, but no significant trend for HSO4–. From the count rates of the nitrate (NO3–) and hydrogen sulfate (HSO4–) core ions, we inferred the number concentration of gaseous sulfuric acid. The lowest average value was found to be 1.8 · 105 cm–3 at the maximum altitude bin, i.e. 13.4 km. The highest average value of 9.1 · 105 cm–3 was observed in the 8.7–9.2 km altitude bin. During the transit through a liquid water cloud, we observed an event of enhanced ion count rates and aerosol particle concentrations that can largely be assigned to nitrate ions and particles, respectively; this may have been caused by the shattering of cloud droplets on the surface of the aircraft or the inlet. Furthermore, we report the proof of principle for the measurement of ambient cations and the identification of protonated pyridine.

Marcel Zauner-Wieczorek et al.

Status: open (until 08 Jun 2022)

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Marcel Zauner-Wieczorek et al.

Marcel Zauner-Wieczorek et al.


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Short summary
We present measurements of ambient ions in the free troposphere and lower stratosphere over Europe in spring 2020. We observed nitrate and hydrogen sulfate, amongst others. From their ratio, the number concentrations of gaseous sulfuric acid were inferred. Nitrate increased towards the stratosphere, whilst sulfuric acid was slightly decreased there. The average values for sulfuric acid were 1.8 to 9.1E5 cm–3. Protonated pyridine was identified in an altitude range of 4.6 to 8.5 km.