Preprints
https://doi.org/10.5194/acp-2021-948
https://doi.org/10.5194/acp-2021-948

  21 Dec 2021

21 Dec 2021

Review status: this preprint is currently under review for the journal ACP.

Seasonal characteristics of atmospheric peroxyacetyl nitrate (PAN) in a coastal city of Southeast China: Explanatory factors and photochemical effects

Taotao Liu1,2,3, Gaojie Chen1,2,3, Jinsheng Chen1,2, Lingling Xu1,2, Mengren Li1,2, Youwei Hong1,2, Yanting Chen1,2, Xiaoting Ji1,2,3, Chen Yang1,2,3, Yuping Chen1,2,3, Weiguo Huang4, Quanjia Huang5, and Hong Wang6 Taotao Liu et al.
  • 1Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
  • 2Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
  • 3University of Chinese Academy of Sciences, Beijing, China
  • 4State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, China
  • 5Xiamen Environmental Monitoring Station, Xiamen, China
  • 6Fujian Meteorological Science Institute, Fujian Key Laboratory of Severe Weather, Fuzhou, China

Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical pollution can redistribute NOx and modulate O3 production. Coupled with the observation-based model (OBM) and a generalized additive model (GAM), the intensive observation campaigns were conducted to reveal the pollution characteristics of PAN and its impact on O3, the contributions of influencing factors to PAN formation were also quantified in this paper. The F-values of GAM results reflecting the importance of the influencing factors showed that ultraviolet radiation (UV, F-value = 60.64), Ox (Ox = NO2+O3, 57.65), and air temperature (T, 17.55) were the main contributors in the PAN pollution in spring, while the significant effects of Ox (58.45), total VOCs (TVOCs, 21.63) and T (20.46) were found in autumn. The PAN formation rate in autumn was 1.58 times higher than that in spring, relating to the intense photochemical reaction and meteorological conditions. Without considering the transformation of peroxyacetyl radical (PA) and PAN, acetaldehyde contributed to the dominant production of PA (46 ± 4 %), followed by methylglyoxal (28 ± 3 %) and radical cycling (19 ± 3 %). The PAN formation was highly VOC-sensitive, and sufficient NOx (compared with VOCs abundance) would not be the limited factor for atmospheric photochemistry. PAN could promote or inhibit O3 formation under high or low ROx levels, respectively. The PAN promoting O3 formation mainly occurred during the periods of 11:00–16:00 (local time) when the favorable meteorological conditions (high UV and T) stimulated the photochemical reactions to offer ROx radicals, which accounted for 17 % of the whole monitoring periods in spring and 31 % in autumn. In this study, the formation mechanism of PAN and its effect on ozone were identified, which might be helpful to improve the scientific understanding of photochemical pollution in coastal areas.

Taotao Liu et al.

Status: open (until 10 Feb 2022)

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Taotao Liu et al.

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Short summary
We clarified the seasonal variations of PAN pollution, influencing factors, its mechanisms and impacts on O3 based on OBM and GAM model. PAN presented inhibition and promotion effects on O3 under low and high ROx levels. The monitoring of PAN and its precursors and the quantification of its impacts on O3 formation have significant guidance on photochemical pollution control.The analysis methods used in this study provide a reference for study on formation mechanism of PAN and O3 in other regions.
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