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Preprints
https://doi.org/10.5194/egusphere-2024-3804
https://doi.org/10.5194/egusphere-2024-3804
14 Jan 2025
 | 14 Jan 2025
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Direct measurement of N2O5 heterogeneous uptake coefficients on atmospheric aerosols in southwestern China and evaluation of current parameterizations

Jiayin Li, Tianyu Zhai, Xiaorui Chen, Haichao Wang, Shuyang Xie, Shiyi Chen, Chunmeng Li, Huabin Dong, and Keding Lu

Abstract. The heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) is a critical process in assessing NOx fate and secondary pollutants (e.g. particulate nitrate) formation. However, accurate quantification of the N2O5 uptake coefficient (γ(N2O5)) in the ambient conditions is a challenging problem which can causes unpredictable uncertainties in the predictions of the air quality models. Here, the γ(N2O5) values were directly measured using an improved aerosol flow tube system in a city located on the plateau in southwestern China to investigate its influencing factors and the performance of current γ(N2O5) parameterization under this typical environmental condition. The nocturnal mean γ(N2O5) value ranged from 0.0018 to 0.12 with an average of 0.023±0.021. The aerosol water significantly promoted N2O5 uptake, while particulate organic and nitrate generally showed suppression effect. We found that median γ(N2O5) predicted by some parameterizations agreed well with observation, whereas the parameterizations failed to reproduce the range of observed values and showed poor correlations (R2=0.00~0.09). Elevated differences between prediction and observation specifically occurred at high aerosol liquid water content (ALWC) with an underestimation by -37 %~-1 % and low ALWC with an overestimation by 34~189 %, respectively. Such differences between the measured and parameterized γ(N2O5) would lead to biased estimation (-77 %~74 %) on particulate nitrate production potential. Our findings suggest the need for more direct field quantifications of γ(N2O5) and the laboratory measurements under extreme ALWC conditions to re-evaluate the response coefficients between γ(N2O5) and aerosol chemical compositions.

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Short summary
We directly measured the dinitrogen pentoxide (N2O5) uptake coefficient which critical impact...