21 Jun 2022
21 Jun 2022
Status: this preprint is currently under review for the journal AMT.

Direct measurement of N2O5 heterogeneous uptake coefficients on ambient aerosols via an aerosol flow tube system: design, characterization and performance

Xiaorui Chen1,a, Haichao Wang3,4, Tianyu Zhai1, Chunmeng Li1, and Keding Lu1,2 Xiaorui Chen et al.
  • 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 2The State Environmental Protection Key Laboratory of Atmospheric Ozone Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 3School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, 519082, China
  • 4Guangdong Provincial Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary, Key Laboratory of Tropical Atmosphere-Ocean System, Ministry of Education, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519082, China
  • anow at: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China

Abstract. An aerosol flow tube system coupled with detailed box model was newly developed to measure N2O5 heterogeneous uptake coefficients (γ(N2O5)) on ambient aerosols directly. This system features simultaneous measurements of N2O5 concentration at the both entrance and exit of the flow tube to ensure an accurate derivation of N2O5 loss in the flow tube. Simulation and laboratory tests demonstrate that this flow tube system is able to overcome the interference from side reactions led by varying reactants (e.g., NO2, O3 and NO) and improve the robustness of results with the assistance of box model method . Factors related to γ(N2O5) derivation were extensively characterized, including particle transmission efficiency, mean residence time in the flow tube and wall loss coefficient of N2O5, for normal operating condition. The measured γ(N2O5) on (NH4)2SO4 model aerosols were in good agreement with literature values over a range of relative humidity (RH). The detection limit of γ(N2O5) was estimated to be 0.0016 at low aerosol surface concentration (Sa) condition of 200 μm2 cm-3. Given the instrument uncertainties and potential fluctuation of air mass between successive sampling modes, we estimate the overall uncertainty of γ(N2O5) that ranges from 16 to 74 % for different ambient conditions. This flow tube system was then successfully deployed for field observations at an urban site of Beijing influenced by anthropogenic emissions. The performance in field observation demonstrates that the current setup of this system is capable of obtaining robust γ(N2O5) amid the switch of air mass.

Xiaorui Chen et al.

Status: open (until 26 Jul 2022)

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Xiaorui Chen et al.

Xiaorui Chen et al.


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Short summary
N2O5 is an important reservoir of atmospheric nitrogen, the interface reaction of which on ambient particles can largely influence the fate of nitrogen oxides and air quality. In this study, we developed an approach to enable the reactions of N2O5 on ambient particles directly in a tube-reactor and thus derive the reaction rate of this process by a chemistry model. Its successful application helps complement the data scarcity and fill the knowledge gap between laboratory and field results.