TY - JOUR
T1 - Investigating the sources of atmospheric nitrous acid (HONO) in the megacity of Beijing, China
AU - Gu, Rongrong
AU - Shen, Hengqing
AU - Xue, Likun
AU - Wang, Tao
AU - Gao, Jian
AU - Li, Hong
AU - Liang, Yutong
AU - Xia, Men
AU - Yu, Chuan
AU - Liu, Yiming
AU - Wang, Wenxing
N1 - Funding Information:
This work was supported by the National Natural Science Foundation of China ( 41922051 and 91844301 ), the Shandong Provincial Science Foundation for Distinguished Young Scholars ( ZR2019JQ09 ), the Hong Kong Research Grants Council ( T24-504/17-N ), and the Jiangsu Collaborative Innovation Center for Climate Change .
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/3/15
Y1 - 2022/3/15
N2 - Nitrous acid (HONO) can powerfully influence atmospheric photochemistry by producing hydroxyl radical ([rad]OH), which is a crucial oxidant that controls the fate of atmospheric trace species. To deduce HONO formation mechanisms in polluted regions, two field observations were conducted in urban Beijing during the early summer of 2017 and the winter of 2018. These two seasons bore distinguishing pollution characteristics with a higher degree of ageing and heavier aerosol loading in the early summer and more abundant NOx (NOx = NO + NO2) in the winter. Elevated concentrations of HONO were observed during these two seasons, with the mean ± standard deviation (maximum) concentrations of 1.25 ± 0.94 (6.69) ppbv and 1.04 ± 1.27 (9.55) ppbv in early summer and winter, respectively. The observed daytime (08:00–17:00 h, local time) HONO production rate was several times higher in early summer than in winter (4.44 ± 1.93 ppbv h−1 vs. 0.88 ± 0.49 ppbv h−1). Budget analysis revealed distinct daytime HONO formation mechanisms during these two seasons. Photo-induced heterogeneous conversion of NO2 on the ground surface dominated in early summer, and homogeneous reaction of NO + [rad]OH was dominant in winter. Photolysis of HONO was the major source of primary [rad]OH in both seasons, and thus, played a key role in the regulation of atmospheric oxidising capacity. This study demonstrates the significant seasonal variations in HONO budget and underlines the predominant role of HONO in primary [rad]OH production in Beijing. Our findings will be helpful to gain an understanding of the chemical mechanisms underlying the formation of secondary pollution in metropolitan areas.
AB - Nitrous acid (HONO) can powerfully influence atmospheric photochemistry by producing hydroxyl radical ([rad]OH), which is a crucial oxidant that controls the fate of atmospheric trace species. To deduce HONO formation mechanisms in polluted regions, two field observations were conducted in urban Beijing during the early summer of 2017 and the winter of 2018. These two seasons bore distinguishing pollution characteristics with a higher degree of ageing and heavier aerosol loading in the early summer and more abundant NOx (NOx = NO + NO2) in the winter. Elevated concentrations of HONO were observed during these two seasons, with the mean ± standard deviation (maximum) concentrations of 1.25 ± 0.94 (6.69) ppbv and 1.04 ± 1.27 (9.55) ppbv in early summer and winter, respectively. The observed daytime (08:00–17:00 h, local time) HONO production rate was several times higher in early summer than in winter (4.44 ± 1.93 ppbv h−1 vs. 0.88 ± 0.49 ppbv h−1). Budget analysis revealed distinct daytime HONO formation mechanisms during these two seasons. Photo-induced heterogeneous conversion of NO2 on the ground surface dominated in early summer, and homogeneous reaction of NO + [rad]OH was dominant in winter. Photolysis of HONO was the major source of primary [rad]OH in both seasons, and thus, played a key role in the regulation of atmospheric oxidising capacity. This study demonstrates the significant seasonal variations in HONO budget and underlines the predominant role of HONO in primary [rad]OH production in Beijing. Our findings will be helpful to gain an understanding of the chemical mechanisms underlying the formation of secondary pollution in metropolitan areas.
KW - Atmospheric oxidation capacity
KW - Budget analysis
KW - Hydroxyl radical ([rad]OH)
KW - Nitrous acid (HONO)
KW - Seasonal variation
UR - http://www.scopus.com/inward/record.url?scp=85121828692&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2021.152270
DO - 10.1016/j.scitotenv.2021.152270
M3 - Journal article
AN - SCOPUS:85121828692
SN - 0048-9697
VL - 812
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 152270
ER -