Publication Date:
2018-02-19
Description:
The sources and atmospheric chemistry of gas-phase organic acids are currently poorly understood due in part to the limited range of measurement techniques available. In this work, we evaluated the use of SF6− as a sensitive and selective chemical ionization reagent ion for real-time measurements of gas-phase organic acids. Field measurements are made using a chemical ionization mass spectrometer (CIMS) at a rural site in Yorkville, Georgia from September to October 2016 to investigate the capability of this measurement technique. Our measurements demonstrate that SF6− can be used to measure a range of organic acids in the atmosphere. Ambient concentrations of organic acids ranged from a few parts per trillion by volume (ppt) to several parts per billion by volume (ppb). Assuming that these organic acids are completely water-soluble, the carbon mass fraction of gas-phase water-soluble organic carbon (WSOCg) comprised of these organic acids ranged from 7 to 100 % with a study average of 30 %. All the organic acids displayed similar strong diurnal behaviors, reaching maximum concentrations between 5 and 7 pm local time. The organic acid concentrations are dependent on ambient temperature, with higher organic acid concentrations being measured during warmer periods.
Electronic ISSN:
1867-8610
Topics:
Geosciences