Preprints
https://doi.org/10.5194/gmd-2020-387
https://doi.org/10.5194/gmd-2020-387

Submitted as: model description paper 07 Dec 2020

Submitted as: model description paper | 07 Dec 2020

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

APFoam-1.0: integrated CFD simulation of O3–NOx–VOCs chemistry and pollutant dispersion in typical street canyon

Luolin Wu1, Jian Hang1, Xuemei Wang2, Min Shao2, and Cheng Gong3 Luolin Wu et al.
  • 1School of Atmospheric Sciences, Sun Yat-sen University, Guangzhou 510275, P. R. China
  • 2Institute for Environmental and Climate Research, Jinan University, Guangzhou 510632, P. R. China
  • 3China Aerodynamics Research and Development Center, Mianyang 621000, P. R. China

Abstract. Urban air quality issues are closely related to the human health and economic development. In order to improve the resolution and numerical accuracy of urban air quality simulation, this study has developed the Atmospheric Photolysis calculation framework (APFoam-1.0), an open-source CFD code based on OpenFOAM, which can be used to examine the micro-scale reactive pollutant formation and dispersion in the urban area. The chemistry module of the newly APFoam has been modified by adding five new types of reaction, which implements the coupling with atmospheric photochemical mechanism (full O3–NOx–VOCs chemistry) and CFD model. Additionally, numerical model has been validated and shows the good agreement with wind tunnel experimental data, indicating that the APFoam has sufficient ability to study urban turbulence and pollutant dispersion characteristics. By applying the APFoam, O3–NOx–VOCs formation processes and dispersion of the reactive pollutants are analyzed in an example of typical street canyon (aspect ratio H / W = 1). Chemistry mechanism comparison shows that O3 and NO2 are underestimated while NO is overestimated if the VOCs reactions are not considered in the simulation. Moreover, model sensitivity cases reveal that 82 %–98 % and 75 %–90 % of NO and NO2 are related to the local vehicle emissions which are verified as the dominated contributors to local reactive pollutant concentration in contrast to their background conditions.

Besides, a large amount of NOx emission, especially NO emission, is beneficial to reduce the O3 concentrations since NO consumes O3. Background precursors (NOx/VOCs) from boundary conditions only contribute 2 %–16 % and 12 %–24 % of NO and NO2 concentrations and raise O3 concentration by 5 %–9 %. Weaker ventilation conditions lead to accumulation of NOx and higher NOx concentration, but a lower O3 concentrations due to the stronger NO titration effect consuming O3. Furthermore, in order to reduce the reactive pollutant concentrations under the odd-even license plate policy (reduce 50 % of the total vehicle emissions), vehicle VOCs emissions should be reduced by at least another 30 % to effectively lower O3, NO and NO2 concentrations at the same time. These results indicate that the examination of the precursors (NOx/VOCs) from both traffic emissions and background boundaries is the key point for better understanding O3–NOx–VOCs chemistry mechanisms in street canyons and providing effective guidelines for the joint prevention and control of local street air pollution.

Luolin Wu et al.

 
Status: open (until 01 Feb 2021)
Status: open (until 01 Feb 2021)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement

Luolin Wu et al.

Model code and software

Atmospheric Photolysis calculation framework (APFoam-1.0) Luolin Wu https://doi.org/10.5281/zenodo.4279172

Luolin Wu et al.

Viewed

Total article views: 264 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
186 76 2 264 4 2
  • HTML: 186
  • PDF: 76
  • XML: 2
  • Total: 264
  • BibTeX: 4
  • EndNote: 2
Views and downloads (calculated since 07 Dec 2020)
Cumulative views and downloads (calculated since 07 Dec 2020)

Viewed (geographical distribution)

Total article views: 178 (including HTML, PDF, and XML) Thereof 174 with geography defined and 4 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 22 Jan 2021
Download
Short summary
In order to improve the resolution and numerical accuracy of urban air quality simulation, this study has developed the APFoam-1.0 to examine the micro-scale reactive pollutant formation and dispersion in the urban area. The model has been validated and shows the good agreement with wind tunnel experimental data. Model sensitivity cases reveal that the vehicle emissions, background concentrations and wind conditions are the key factors affecting the photochemical reaction process.