Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: Based on Δ15N and Δ17O measurements

Saehee Lim, Meehye Lee, Joel Savarino, Paolo Laj

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

PM2.5 haze pollution driven by secondary inorganic NO-3 has been a great concern in East Asia. It is, therefore, imperative to identify its sources and oxidation processes, for which nitrogen and oxygen stable isotopes are powerful tracers. Here, we determined the Δ15N (NO-3 ) and Δ117O (NO-3 ) of PM2.5 in Seoul during the summer of 2018 and the winter of 2018-2019 and estimated quantitatively the relative contribution of oxidation pathways for particulate NO-3 and investigated major NOx emission sources. In the range of PM2.5 mass concentration from 7.5 μgm-3 (summer) to 139.0 μgm-3 (winter), the mean Δ15N was -0.7‰±3.3‰ and 3:8‰±3.7 ‰, and the mean Δ117O was 23:2‰±2.2‰ and 27:7‰±2.2‰ in the summer and winter, respectively. While OH oxidation was the dominant pathway for NO-3 during the summer (87 %), nighttime formation via N2O5 and NO3 was relatively more important (38 %) during the winter, when aerosol liquid water content (ALWC) and nitrogen oxidation ratio (NOR) were higher. Interestingly, the highest Δ117O was coupled with the lowest Δ15N and highest NOR during the record-breaking winter PM2.5 episodes, revealing the critical role of photochemical oxidation process in severe winter haze development. For NOx sources, atmospheric Δ15N (NOx ) estimated from measured Δ15N (NO-3 ) considering isotope fractionation effects indicates vehicle emissions as the most important emission source of NOx in Seoul. The contribution from biogenic soil and coal combustion was slightly increased in summer and winter, respectively. Our results built on a multiple-isotope approach provide the first explicit evidence for NO-3 formation processes and major NOx emission sources in the Seoul megacity and suggest an effective mitigation measure to improve PM2.5 pollution.

Original languageEnglish
Pages (from-to)5099-5115
Number of pages17
JournalAtmospheric Chemistry and Physics
Volume22
Issue number8
DOIs
Publication statusPublished - 2022 Apr 19

Bibliographical note

Funding Information:
Acknowledgements. This research was supported by the National Strategic Project Fine Particle of the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (MSIT), Ministry of Environment (ME), and Ministry of Health and Welfare (MOHW) (grant no. 2017M3D8A1092015). Funding to Saehee Lim was provided by the National Research Foundation of Korea (NRF) from the Ministry of Science and ICT (grant no. 2018R1D1A1B07050849). Meehye Lee thanks for the support from NRF (grant no. 2020R1A2C3014592). Joel Savarino thanks the French National Research Agency (Investissements d’avenir grant no. ANR-15-IDEX-02) and the INSU program LEFE-CHAT for supporting the stable isotope laboratory. This is publication 4 of PANDA platform on which isotope analyses were performed. The authors especially thank Nicolas Caillon for performing the analysis of the ammonium–nitrogen isotope ratio. The authors thank the Korea National Institute of Environmental Research (NIER) and Korea Meteorological Administration (KMA) for their monitoring data used in this study.

Funding Information:
Financial support. This research has been supported by the National Research Foundation of Korea (grant nos. 2017M3D8A1092015, 2018R1D1A1B07050849, and 2020R1A2C3014592).

Publisher Copyright:
© Copyright:

ASJC Scopus subject areas

  • Atmospheric Science

Fingerprint

Dive into the research topics of 'Oxidation pathways and emission sources of atmospheric particulate nitrate in Seoul: Based on Δ15N and Δ17O measurements'. Together they form a unique fingerprint.

Cite this