20 Sep 2022
20 Sep 2022
Status: this preprint is open for discussion.

Evaluation of Transport Processes over North China Plain and Yangtze River Delta using MAX-DOAS Observations

Yuhang Song1,, Chengzhi Xing2,, Cheng Liu1,2,3,4, Jinan Lin2, Hongyu Wu5, Ting Liu7, Hua Lin5, Chengxin Zhang1, Wei Tan2, Xiangguang Ji5, Haoran Liu6, and Qihua Li6 Yuhang Song et al.
  • 1Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, China
  • 2Key Lab of Environmental Optics & Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China
  • 3Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
  • 4Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei, 230026, China
  • 5School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei, 230026, China
  • 6Institute of Physical Science and Information Technology, Anhui University, Hefei, 230601, China
  • 7School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China
  • These two authors contributed equally to this work.

Abstract. The transport of pollutants has a substantial impact on the atmospheric environment in megacity clusters. However, owing to the lack of knowledge of the vertical pollutant structure, our quantification of transport processes and understanding of their impacts on the environment remain inadequate. In this study, we retrieved the vertical profiles of aerosol, NO2, and HCHO using multi-axis differential optical absorption spectroscopy (MAX-DOAS) and analyzed three typical transport phenomena. We found as follows: (1) The main transport layer (MTL) of aerosol, NO2 and HCHO along the southwest–northeast transport pathway in the Jing-Jin-Ji region were approximately 400–800 m, 0–400 m and 400–1400 m, respectively. The maximum transport flux of HCHO appeared in Wangdu (WD), oppositely, the minimum transport fluxes of aerosol and NO2 also occurred in this station. (2) The North China Plain (NCP) was usually affected by severe dust transport. The transported dust suppressed dissipation and boosted pollutant accumulation, converting the vertical profiles into an exponential shape. Furthermore, dust can indirectly affect trace gas concentrations by weakening optical intensity. For stations with higher optical intensity, the reduced NO2 levels were closely associated with its heterogeneous reactions on dust and aerosol surfaces. Comparatively, for other stations with low solar radiation, the decreased optical intensity favored NO2 concentration increase by inhibiting NO2 photolysis. The reduced solar radiation favored local HCHO accumulation in Shijiazhuang (SJZ) due to the dominant contribution of primary HCHO. (3) A back-and-forth transboundary transport between the NCP and Yangtze River Delta (YRD) was found. The YRD-to-NCP and NCP-to-YRD transport processes mainly occurred in the 500–1500 m and 0–1000 m layers, respectively. This transport, accompanied by the dome effect of aerosol, produced a large-scale PM2.5 concentration increase, further validating the haze-amplifying mechanism by practical observations.

Yuhang Song et al.

Status: open (until 01 Nov 2022)

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  • RC1: 'Comment on egusphere-2022-653', Anonymous Referee #1, 27 Sep 2022 reply
  • RC2: 'Comment on egusphere-2022-653', Anonymous Referee #2, 29 Sep 2022 reply

Yuhang Song et al.


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Short summary
Using the MAX-DOAS network, we successfully analyzed three typical transport types (regional, dust, and transboundary long-range transport), emphasizing the unique advantages provided by the network in monitoring pollutant transport. We think that our findings provide the public with a thorough understanding of pollutant transport phenomena and a reference for designing collaborative air pollution control strategies.