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https://doi.org/10.5194/egusphere-2025-164
https://doi.org/10.5194/egusphere-2025-164
07 Mar 2025
 | 07 Mar 2025

The Critical Role of Volatile Organic Compounds Emission in Nitrate Formation in Lhasa, Tibetan Plateau: Insights from Oxygen Isotope Anomaly Measurements

Xueqin Zheng, Junwen Liu, Nima Chuduo, Bian Ba, Pengfei Yu, Phu Drolgar, Fang Cao, and Yanlin Zhang

Abstract. Atmospheric particulate nitrate aerosol (NO3-), produced via the oxidation of nitrogen oxides (NOx = NO + NO2), plays an important role in atmospheric chemistry and air quality, yet its formation mechanism still poorly constrained the plateau region. In this study, we first reported the yearly variation of the signatures for the stable oxygen isotope anomaly (∆17O = δ17O - 0.52 × δ18O) in NO3- collected in the urban region of Lhasa city (3650 m a.s.l), Tibetan Plateau, China. Our results show that NO2 + OH is the largest contributor to NO3- formation (46 %), followed by NO3 + VOC (26 %), and N2O5 + H2O (28 %) using the Bayesian Isotope Mixture Model. Notably, there are significant differences in the NO2 + OH, NO3 + VOC, and N2O5 + H2O pathways between spring and other three seasons (p < 0.05). Our results highlight the influence of VOC emissions from regions such as Afghanistan and northern India, which enhance NO3- concentrations in Lhasa during spring. Furthermore, the diurnal distribution of NO3- oxidation pathways varied distinctly across seasons, suggesting that these difference in NO3- pathways are attributed to ALWC, VOC concentration, and pollution levels.

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Xueqin Zheng, Junwen Liu, Nima Chuduo, Bian Ba, Pengfei Yu, Phu Drolgar, Fang Cao, and Yanlin Zhang

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Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-164', Anonymous Referee #2, 26 Mar 2025
  • RC2: 'Comment on egusphere-2025-164', Anonymous Referee #1, 03 Apr 2025

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2025-164', Anonymous Referee #2, 26 Mar 2025
  • RC2: 'Comment on egusphere-2025-164', Anonymous Referee #1, 03 Apr 2025
Xueqin Zheng, Junwen Liu, Nima Chuduo, Bian Ba, Pengfei Yu, Phu Drolgar, Fang Cao, and Yanlin Zhang
Xueqin Zheng, Junwen Liu, Nima Chuduo, Bian Ba, Pengfei Yu, Phu Drolgar, Fang Cao, and Yanlin Zhang

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Short summary
In this study, we present the first report on the annual variation of stable oxygen isotope anomalies (∆17O = δ17O - 0.52 × δ18O) in NO3- collected from the urban area of Lhasa , on the Tibetan Plateau, China. Using a Bayesian isotope mixture model, we found that the relative contribution of the NO3+VOC pathway to NO3- formation in spring in Lhasa was several times higher than in urban cities, highlighting the significant influence of VOC transported from outside the Tibetan Plateau.
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