TY - JOUR
T1 - Vertical profiles of the transport fluxes of aerosol and its precursors between Beijing and its southwest cities
AU - Hu, Qihou
AU - Liu, Cheng
AU - Li, Qihua
AU - Liu, Ting
AU - Ji, Xiangguang
AU - Zhu, Yizhi
AU - Xing, Chengzhi
AU - Liu, Haoran
AU - Tan, Wei
AU - Gao, Meng
N1 - Funding Information:
This research was supported by the National Natural Science Foundation of China (No. 41977184 and U21A2027 ), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA23020301 ), the Key Research and Development Project of Anhui Province ( 202104i07020002 ), the Major Projects of High Resolution Earth Observation Systems of National Science and Technology ( 05-Y30B01-9001-19/20-3 ), the Youth Innovation Promotion Association of CAS ( 2021443 ), and the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment, CAS ( CERAE202004 ), the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Sciences (No. XDPB1901 ).
Publisher Copyright:
© 2022 Elsevier Ltd
Copyright © 2022 Elsevier Ltd. All rights reserved.
PY - 2022/11/1
Y1 - 2022/11/1
N2 - The influence of regional transport on aerosol pollution has been explored in previous studies based on numerical simulation or surface observation. Nevertheless, owing to inhomogeneous vertical distribution of air pollutants, vertical observations should be conducted for a comprehensive understanding of regional transport. Here we obtained the vertical profiles of aerosol and its precursors using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) at the Nancheng site in suburban Beijing on the southwest transport pathway of the Beijing-Tianjin-Hebei (BTH) region, China, and then estimated the vertical profiles of transport fluxes in the southwest-northeast direction. The maximum net transport fluxes per unit cross-sectional area, calculated as pollutant concentration multiply by wind speed, of aerosol extinction coefficient (AEC), NO2, SO2 and HCHO were 0.98 km−1 m s−1, 24, 14 and 8.0 μg m−2 s−1 from southwest to northeast, which occurred in the 200–300 m, 100–200 m, 500–600 m and 500–600 m layers, respectively, due to much higher pollutant concentrations during southwest transport than during northeast transport in these layers. The average net column transport fluxes were 1200 km−1 m2 s−1, 38, 26 and 15 mg m−1 s−1 from southwest to northeast for AEC, NO2, SO2 and HCHO, respectively, in which the fluxes in the surface layer (0–100 m) accounted for only 2.3%–4.2%. Evaluation only based on surface observation would underestimate the influence of the transport from southwest cities to Beijing. Northeast or weak southwest transports dominated in clean conditions with PM2.5 <75 μg m−3 and intense southwest transport dominated in polluted conditions with PM2.5 >75 μg m−3. Southwest transport through the middle boundary layer was a trigger factor for aerosol pollution events in urban Beijing, because it not only directly bringing air pollutants, but also induced an inverse structure of aerosols, which resulted in stronger atmospheric stability and aggravated air pollution in urban Beijing.
AB - The influence of regional transport on aerosol pollution has been explored in previous studies based on numerical simulation or surface observation. Nevertheless, owing to inhomogeneous vertical distribution of air pollutants, vertical observations should be conducted for a comprehensive understanding of regional transport. Here we obtained the vertical profiles of aerosol and its precursors using ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) at the Nancheng site in suburban Beijing on the southwest transport pathway of the Beijing-Tianjin-Hebei (BTH) region, China, and then estimated the vertical profiles of transport fluxes in the southwest-northeast direction. The maximum net transport fluxes per unit cross-sectional area, calculated as pollutant concentration multiply by wind speed, of aerosol extinction coefficient (AEC), NO2, SO2 and HCHO were 0.98 km−1 m s−1, 24, 14 and 8.0 μg m−2 s−1 from southwest to northeast, which occurred in the 200–300 m, 100–200 m, 500–600 m and 500–600 m layers, respectively, due to much higher pollutant concentrations during southwest transport than during northeast transport in these layers. The average net column transport fluxes were 1200 km−1 m2 s−1, 38, 26 and 15 mg m−1 s−1 from southwest to northeast for AEC, NO2, SO2 and HCHO, respectively, in which the fluxes in the surface layer (0–100 m) accounted for only 2.3%–4.2%. Evaluation only based on surface observation would underestimate the influence of the transport from southwest cities to Beijing. Northeast or weak southwest transports dominated in clean conditions with PM2.5 <75 μg m−3 and intense southwest transport dominated in polluted conditions with PM2.5 >75 μg m−3. Southwest transport through the middle boundary layer was a trigger factor for aerosol pollution events in urban Beijing, because it not only directly bringing air pollutants, but also induced an inverse structure of aerosols, which resulted in stronger atmospheric stability and aggravated air pollution in urban Beijing.
KW - Aerosol
KW - Flux
KW - Gaseous pollutant
KW - Regional transport
KW - Vertical profile
KW - Environmental Monitoring/methods
KW - Nitrogen Dioxide/analysis
KW - Aerosols/analysis
KW - Air Pollution/analysis
KW - Beijing
KW - Air Pollutants/analysis
KW - China
KW - Particulate Matter/analysis
KW - Cities
UR - http://www.scopus.com/inward/record.url?scp=85136632122&partnerID=8YFLogxK
U2 - 10.1016/j.envpol.2022.119988
DO - 10.1016/j.envpol.2022.119988
M3 - Journal article
C2 - 36028076
AN - SCOPUS:85136632122
SN - 0269-7491
VL - 312
JO - Environmental Pollution
JF - Environmental Pollution
M1 - 119988
ER -