Aircraft-based observation of gaseous pollutants in the lower troposphere over the Beijing-Tianjin-Hebei region

Ruojie Zhao; Baohui Yin; Nan Zhang; Jing Wang; Chunmei Geng; Xinhua Wang; Bin Han; Kangwei Li; Peng Li; Hao Yu; Wen Yang; Zhipeng Bai

doi:10.1016/j.scitotenv.2020.144818

Aircraft-based observation of gaseous pollutants in the lower troposphere over the Beijing-Tianjin-Hebei region

Sci Total Environ. 2021 Jun 15:773:144818. doi: 10.1016/j.scitotenv.2020.144818. Epub 2021 Jan 27.

Authors

Ruojie Zhao¹, Baohui Yin¹, Nan Zhang¹, Jing Wang¹, Chunmei Geng², Xinhua Wang¹, Bin Han¹, Kangwei Li¹, Peng Li³, Hao Yu¹, Wen Yang⁴, Zhipeng Bai¹

Affiliations

¹ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, PR China.
² State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, PR China. Electronic address: gengcm@craes.org.cn.
³ Tianjin Eco-Environmental Monitoring Center, Tianjin 300191, PR China.
⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, PR China. Electronic address: yangwen@craes.org.cn.

PMID: 33592482
DOI: 10.1016/j.scitotenv.2020.144818

Abstract

To investigate the spatial and vertical distribution of atmospheric pollutants (SO₂, NO_x, CO and O₃), aircraft-based measurements (model: Yun-12, 12 flights, 27 h total flight time) were conducted from near the surface up to 2400 m over the Beijing-Tianjin-Hebei (BTH) region between June 17th and July 22nd 2016. The results showed that high concentrations of primary gaseous pollutants (SO₂, NO_x, CO) were generally present in Beijing, Tianjin, Langfang and Tangshan areas, while high values of O₃ frequently appeared in areas far from the city. The flights at noon and dusk measured higher O₃ concentrations at 600 m and lower O₃ concentrations at higher altitudes, implying a strong influence by photochemical production. Back trajectory analysis suggested that the high levels of gaseous pollutants, especially at 600 m, were associated with pollution sources transported from the southerly direction during the observation period. The first simultaneous vertical distribution measurements using aircraft and tethered balloon were conducted in Gaocun (a rural site between Beijing and Tianjin) on June 17th. The results indicated that an inversion layer at the top of the planetary boundary layer (PBL) significantly suppressed vertical exchange through the PBL and resulted in a "two-layer" vertical distribution of pollutants above and below the PBL. Additionally, a residual high O₃ layer (79.9 ± 2.5 ppb, 500-1000 m) was observed above the PBL, and it contributed to the surface peak O₃ level at noon through downward transport along with the opening up of the PBL. These results indicate that coupled effects of horizontal and vertical transport should be investigated in future studies to improve the chemical transport models used to study the vertical distribution and regional transport over the BTH region.

Keywords: Aircraft measurement; Beijing-Tianjin-Hebei (BTH) region; Gaseous pollutants; Vertical distribution.