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

To investigate the spatial and vertical distribution of atmospheric pollutants (SO2, NOx, CO and O-), 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, NOx, CO) were generally present in Beijing, Tianjin, Langfang and Tangshan areas, while high values of O-3 frequently appeared in areas far from the city The flights at noon and dusk measured higher O-3 concentrations at 600 m and lower O concentrations at higher altitudes, implying a strong influence by photochemical production. Back trajectory analysis suggested that Lhe 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 Lenin-al balloon were concluded in Gaocun (a rural site between Beijing and Tianjin) on June 17th. The results indicated that an inversion layer at Lhe Lop of Lhe planetary boundary layer (PBL) significantly suppressed vertical exchange hrough he PBL and resulted in a L wo-layer vertical distribution of pollutants above and below the PBL. Additionally, a residual high O-3 layer (79.9 +/- 2.5 ppb, 500-1000 m) was observed above the PBL, and it contributed to the surface peak O-3 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. (C) 2021 Elsevier B.V. All rights resented.

Automated summary

Aircraft-based measurements were conducted to investigate the spatial and vertical distribution of atmospheric pollutants over the Beijing-Tianjin-Hebei region. The results showed high concentrations of primary gaseous pollutants in urban areas, with high ozone values appearing further from the city. The study highlights the importance of considering both horizontal and vertical transport effects in future research on chemical transport models in the region.