TY - JOUR
T1 - Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China
AU - Wang, Qingqing
AU - Sun, Yele
AU - Xu, Weiqi
AU - Du, Wei
AU - Zhou, Libo
AU - Tang, Guiqian
AU - Chen, Chen
AU - Cheng, Xueling
AU - Zhao, Xiujuan
AU - Ji, Dongsheng
AU - Han, Tingting
AU - Wang, Zhe
AU - Li, Jie
AU - Wang, Zifa
N1 - Funding Information:
Acknowledgements. This work was supported by the National Key Project of Basic Research (2014CB447900), the National Natural Science Foundation of China (41575120, 41571130034), the Beijing Natural Science Foundation (8161004), National Postdoctoral Program for Innovative Talents (BX201600157), and the General Financial Grant from the China Postdoctoral Science Foundation (2017M610972).
Publisher Copyright:
© Author(s) 2018.
PY - 2018/2/20
Y1 - 2018/2/20
N2 - We conducted the first real-Time continuous vertical measurements of particle extinction (bext/, gaseous NO2, and black carbon (BC) from ground level to 260m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: (1) uniform vertical distributions (37% of the time) with vertical differences less than 5 %, (2) higher values at lower altitudes (29 %), (3) higher values at higher altitudes (16 %), and (4) significant decreases at the heights of ∼100-150m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ∼20-30% higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2 D 0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext =NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.
AB - We conducted the first real-Time continuous vertical measurements of particle extinction (bext/, gaseous NO2, and black carbon (BC) from ground level to 260m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: (1) uniform vertical distributions (37% of the time) with vertical differences less than 5 %, (2) higher values at lower altitudes (29 %), (3) higher values at higher altitudes (16 %), and (4) significant decreases at the heights of ∼100-150m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ∼20-30% higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2 D 0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext =NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China.
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U2 - 10.5194/acp-18-2495-2018
DO - 10.5194/acp-18-2495-2018
M3 - Article
AN - SCOPUS:85042275173
SN - 1680-7316
VL - 18
SP - 2495
EP - 2509
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 4
ER -