What a Blue Sky! – Airborne Measurements of Sulfuric Acid, Methanesulfonic Acid, C2 Amines and Natural Ions over Europe during the BLUESKY Campaign Utilizing a Newly Developed Nitrate-CI-APi-TOF-MS on the HALO Aircraft

Abstract:

Ambient trace-gas and natural-ion measurements in the free troposphere and lower stratosphere are rare although they are important to better understand chemical processes in the atmosphere. For this reason, we conducted the BLUESKY aircraft measurement campaign over Europe between the end of May and beginning of June 2020, i.e. during Europe’s COVID-19 lockdown. With a variety of meteorological, aerosol and gas-phase instruments, we performed several flights with the research aircraft HALO and FALCON, based at Oberpfaffenhofen site of DLR (German Aerospace Center). The flights covered continental and marine regions; altitudes up to 14 km; vertical profiles over urban agglomerations; and outflow air masses of deep convective clouds.

We coupled a newly developed nitrate-based chemical ionization source – the SCORPION (Switchable CORona Powered ION source) – to a time-of-flight (TOF) mass spectrometer, integrated onboard the HALO aircraft. We measured in-situ air samples continuously in chemical ionization (CI) mode, covering the whole range from ground up to maximum flight level. The CI mode was intermitted by occasional natural ion measurements in APi (Atmospheric Pressure interface) mode.

The substances analyzed in CI mode include – among others – sulfuric acid, methanesulfonic acid (MSA), and C₂ amines (i.e., ethylamine and dimethylamine, DMA). We present their ambient profiles and their behavior with regards to altitude, urban/rural/marine sites, and different meteorological circumstances. Furthermore, we present typical mass spectra of natural ions in different altitudes.

With this, we present the first results of a newly developed aircraft instrument that focuses on the detection of molecules which directly contribute to atmospheric new particle formation.