Concentration of gaseous sulfuric acid measured over the Southern Ocean in the austral summer of 2016/2017, during the Antarctic Circumnavigation Expedition (ACE).

Dataset abstract

The authors would highly appreciate being contacted if the data is used for any purpose.

We measured sulfuric acid concentration in the gas phase with a nitrate chemical ionization mass spectrometer (we used an APi-HTOF mass spectrometer produced by Tofwerk AG coupled with a Chemical ionization inlet A70 produced by Airmodus). Sulfuric acid is detected in the mass spectrometer either as a deprotonated ion or as a cluster with the reagent ion (NO3-). The concentration is calculated as the area of these two peaks normalized to the concentration of the reagent ions (monomer, dimer and trimer) and multiplied by a calibration factor that was experimentally derived at Paul Scherrer Institute in the summer 2017, after the campaign. In the atmosphere, sulfuric acid is produced by the oxidation of sulfur dioxide that could have both a natural or anthropogenic origin (e.g. phytoplankton emission or fossil fuel combustion). Sulfuric acid in the atmosphere is responsible for a very large fraction of the newly formed particles, therefore it is important to have accurate measurements of this vapour in remote places like the Southern Ocean to better understand secondary aerosol sources and processes.

The data have been cleaned from the influence of the exhaust of the research vessel. Temporal coverage is from January 22, 2017 to March 19, 2017. There are no data for the first leg of the expedition because the instrument was not on the ship. The instrument was operated during leg 4 but data has not been processed yet as they require additional work due to some instrumental issues that affects their quality. Data were collected with one-second time resolution but integrated to five minutes to increase the signal to noise ratio.

Concentrations are reported as molecules per cubic centimeter. The lower limit of detection is in the ppq (part per quadrillion) range but was not determined exactly as it varies with the integration time and background noise.

Dataset contents

• gas_sulfuric_acid_concentration_data.csv, data file, comma-separated values
• data_file_header.txt, metadata, text format
• README.txt, metadata, text format
• change_log.txt, metadata, text format

Data that were missing or bad because of instrumental problems were simply removed from the file (no entry).

Change log

v1.1 - data files updated

• re-analysis of the raw data with an improved mass spectra peak fitting routine, a different calibration factor was also applied to the data following a more detailed analysis of the calibration experiment
• use updated, corrected GPS data

v1.0 - initial release of dataset