Contributions to OH reactivity from unexplored volatile organic compounds measured by PTR-ToF-MS &ndash; A case study in a suburban forest of the Seoul Metropolitan Area during KORUS-AQ 2016

Sanchez, Dianne; Seco, Roger; Gu, Dasa; Guenther, Alex; Mak, John; Lee, Youngjae; Kim, Danbi; Ahn, Joonyoung; Blake, Don; Herndon, Scott; Jeong, Daun; Sullivan, John T.; Mcgee, Thomas; Kim, Saewung

doi:https://doi.org/10.5194/acp-2020-174

Preprints

https://doi.org/10.5194/acp-2020-174
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Preprints

24 Mar 2020

Contributions to OH reactivity from unexplored volatile organic compounds measured by PTR-ToF-MS – A case study in a suburban forest of the Seoul Metropolitan Area during KORUS-AQ 2016

Dianne Sanchez¹, Roger Seco^1,a,b, Dasa Gu¹, Alex Guenther¹, John Mak², Youngjae Lee³, Danbi Kim³, Joonyoung Ahn³, Don Blake⁴, Scott Herndon⁵, Daun Jeong¹, John T. Sullivan⁶, Thomas Mcgee⁶, and Saewung Kim¹ Dianne Sanchez et al.

¹Department of Earth System Science, University of California, Irvine, Irvine CA 92697, USA
²School of Marine and Atmospheric Sciences, Stony Brooke University, Stony Brook, NY 1111794, USA
³National Institute of Environmental Research, Inchoen 22689, South Korea
⁴Department of Chemistry, University of California, Irvine, Irvine CA 92697, USA
⁵Aerodyne Research Inc., Billerica MA 01821, USA
⁶NASA Goddard Space Flight Center, Chemistry and Dynamics Laboratory, Greenbelt, MD 20771, USA
^anow at: Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark
^bnow at: Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management , University of Copenhagen, Copenhagen, Denmark

Received: 23 Feb 2020 – Accepted for review: 20 Mar 2020 – Discussion started: 24 Mar 2020

Abstract. We report OH reactivity observations by a chemical ionization mass spectrometer – comparative reactivity method (CIMS-CRM) instrument in a suburban forest of the Seoul Metropolitan Area (SMA) during Korea US Air Quality Study (KORUS-AQ 2016) from mid-May to mid-June of 2016. A comprehensive observational suite was deployed to quantify reactive trace gases inside of the forest canopy including a high-resolution proton transfer reaction time of flight mass spectrometer (PTR-ToF-MS). An average OH reactivity of 30.7 ± 5.1 s⁻¹ was observed, while the OH reactivity calculated from CO, NO + NO₂ (NO_x), ozone (O₃), sulfur dioxide (SO₂), and 14 volatile organic compounds (VOCs) was 11.8 ± 1.0 s⁻¹. An analysis of 346 peaks from the PTR-ToF-MS accounted for an additional 6.0 ± 2.2 s⁻¹ of the total measured OH reactivity, leaving 42.0 % missing OH reactivity. The missing OH reactivity most likely comes from VOC oxidation products of both biogenic and anthropogenic origin.