Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

2 Scopus Citations
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Author(s)

  • Yuk‐Chun Chan
  • Mathew J. Evans
  • Pengzhen He
  • Christopher D. Holmes
  • Lyatt Jaeglé
  • Prasad Kasibhatla
  • Xue‐Yan Liu
  • Tomás Sherwen
  • Joel A. Thornton
  • Zhouqing Xie
  • Shuting Zhai
  • Becky Alexander

Related Research Unit(s)

Detail(s)

Original languageEnglish
Article numbere2021JD034688
Journal / PublicationJournal of Geophysical Research: Atmospheres
Volume126
Issue number9
Online published24 Apr 2021
Publication statusPublished - 16 May 2021

Abstract

Studies of wintertime air quality in the North China Plain (NCP) show that particulate-nitrate pollution persists despite rapid reduction in NOx emissions. This intriguing NOx-nitrate relationship may originate from non-linear nitrate-formation chemistry, but it is unclear which feedback mechanisms dominate in NCP. In this study, we re-interpret the wintertime observations of 17O excess of nitrate (∆17O(NO3)) in Beijing using the GEOS-Chem (GC) chemical transport model to estimate the importance of various nitrate-production pathways and how their contributions change with the intensity of haze events. We also analyze the relationships between other metrics of NOy chemistry and [PM2.5] in observations and model simulations. We find that the model on average has a negative bias of −0.9‰ and −36% for ∆17O(NO3) and [Ox,major] (≡ [O3] + [NO2] + [p-NO3]), respectively, while overestimating the nitrogen oxidation ratio ([NO3]/([NO3] + [NO2])) by +0.12 in intense haze. The discrepancies become larger in more intense haze. We attribute the model biases to an overestimate of NO2-uptake on aerosols and an underestimate in wintertime O3 concentrations. Our findings highlight a need to address uncertainties related to heterogeneous chemistry of NO2 in air-quality models. The combined assessment of observations and model results suggest that N2O5 uptake in aerosols and clouds is the dominant nitrate-production pathway in wintertime Beijing, but its rate is limited by ozone under high-NOx-high-PM2.5 conditions. Nitrate production rates may continue to increase as long as [O3] increases despite reduction in [NOx], creating a negative feedback that reduces the effectiveness of air pollution mitigation.

Research Area(s)

  • GEOS-Chem, heterogeneous chemistry, nitrate, NO2 uptake, winter air quality, Δ17O(NO3−)

Citation Format(s)

Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain. / Chan, Yuk‐Chun; Evans, Mathew J.; He, Pengzhen; Holmes, Christopher D.; Jaeglé, Lyatt; Kasibhatla, Prasad; Liu, Xue‐Yan; Sherwen, Tomás; Thornton, Joel A.; Wang, Xuan; Xie, Zhouqing; Zhai, Shuting; Alexander, Becky.

In: Journal of Geophysical Research: Atmospheres, Vol. 126, No. 9, e2021JD034688, 16.05.2021.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review