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Discussion papers
https://doi.org/10.5194/acp-2019-1105
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2019-1105
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 28 Jan 2020

Submitted as: research article | 28 Jan 2020

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This preprint is currently under review for the journal ACP.

Measurements of traffic dominated pollutant emissions in a Chinese megacity

Freya A. Squires1, Eiko Nemitz2, Ben Langford2, Oliver Wild3, Will S. Drysdale1,4, W. Joe F. Acton3, Pingqing Fu5,6, C. Sue B. Grimmond7, Jacqueline F. Hamilton1, C. Nick Hewitt3, Michael Hollaway3,a, Simone Kotthaus7,b, James Lee1,4, Stefan Metzger8,9, Natchaya Pingintha-Durden8, Marvin Shaw1, Adam R. Vaughan1, Xinming Wang10, Ruili Wu11, Qiang Zhang11, and Yanli Zhang10 Freya A. Squires et al.
  • 1Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO10 5DD, UK
  • 2Centre for Ecology and Hydrology, Edinburgh, EH26 0QB, UK
  • 3Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK
  • 4National Centre for Atmospheric Science, University of York, York, UK
  • 5Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 6Institute of Surface-Earth System Science, Tianjin University, Tianjin, China
  • 7Department of Meteorology, University of Reading, Reading, UK
  • 8National Ecological Observatory Network Program, Battelle, 1685 38th Street, Boulder, CO 80301, USA
  • 9University of Wisconsin-Madison, Department of Atmospheric and Oceanic Sciences, 1225 West Dayton Street, Madison, WI 53706, USA
  • 10Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
  • 11Ministry of Education Key Laboratory for Earth System Modelling, Department of Earth System Science, Tsinghua University, Beijing, China
  • anow at: Centre for Ecology & Hydrology, Lancaster Environment Centre, Bailrigg, Lancaster, UK
  • bnow at: Institut Pierre Simon Laplace, École Polytechnique, Palaiseau, France

Abstract. Direct measurements of NOx, CO and aromatic VOC (benzene, toluene, C2-benzenes and C3-benzenes) flux were made for a central area of Beijing using the eddy covariance technique. Measurements were made during two intensive field campaigns in central Beijing as part of the Air Pollution and Human Health (APHH) project, the first in November–December 2016 and the second during May–June 2017, to contrast winter and summertime emission rates. There was little difference in the magnitude of NOx flux between the two seasons (mean NOx flux was 4.41 mg m−2 h−1 in the winter compared to 3.55 mg m−2 h−1 in the summer). CO showed greater seasonal variation with mean CO flux in the winter campaign (34.7 mg m−2 h−1) being over twice that of the summer campaign (15.2 mg m−2 h−1). Larger emissions of aromatic VOCs in summer were attributed to increased evaporation due to higher temperatures. The largest fluxes in NOx and CO generally occurred during the morning and evening rush hour periods indicating a major traffic source with high midday emissions of CO indicating an additional influence from cooking fuel. Measured NOx and CO fluxes were then compared to the MEIC 2013 emissions inventory which was found to significantly overestimate emissions for this region, providing evidence that proxy-based emissions inventories have positive biases in urban centres. This first set of pollutant fluxes measured in Beijing provides an important benchmark of emissions from the city which can help to inform and evaluate current emissions inventories.

Freya A. Squires et al.

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Freya A. Squires et al.

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Short summary
Megacities like Beijing in China experience significant air quality problems. In order to manage air pollution it is vital that legislators have a clear understanding of pollutant emissions. Emissions inventories however are associated with large uncertainties. Reliable field measurements of pollutant emissions are therefore required to constrain inventories and provide information about emissions. This work presents the first measurements of traffic dominated emissions for Beijing.
Megacities like Beijing in China experience significant air quality problems. In order to manage...
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