1. Observations of the vertical distributions of summertime atmospheric pollutants in Nam Co: OH production and source analysis.
- Author
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Xing, Chengzhi, Liu, Cheng, Ye, Chunxiang, Xue, Jingkai, Wu, Hongyu, Ji, Xiangguang, Ou, Jinping, and Hu, Qihou
- Subjects
ATMOSPHERIC chemistry ,CLIMATE change ,OPTICAL spectroscopy ,WATER vapor ,LIGHT absorption - Abstract
The Tibetan Plateau (TP) plays a key role in the regional environment and global climate change; however, the lack of vertical observations of atmospheric species, such as HONO and O 3 , hinders a deeper understanding of the atmospheric chemistry and atmospheric oxidation capacity (AOC) on the TP. In this study, we conducted multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements at Nam Co, the central TP, to observe the vertical profiles of aerosol, water vapor (H 2 O), NO 2 , HONO and O 3 from May to July 2019. In addition to NO 2 mainly exhibiting a Gaussian shape with the maximum value appearing at 300 =- 400 m, the other four species all showed an exponential shape and decreased with the increase in height. The maximum values of monthly averaged aerosol (0.17 km -1) and O 3 (66.71 ppb) occurred in May, H 2 O (3.68 × 10 17 molec. cm -3) and HONO (0.13 ppb) appeared in July, and NO 2 (0.39 ppb) occurred in June at the 200–400 m layer. H 2 O, HONO and O 3 all exhibited a multi-peak pattern, and aerosol appeared to have a bi-peak pattern for its averaged diurnal variations. The averaged vertical profiles of OH production rates from O 3 and HONO all exhibited an exponential shape decreasing with the increase in height, with maximum values of 2.61 and 0.49 ppb h -1 at the bottom layer, respectively. The total OH production rate contributed by HONO and O 3 on the TP was obviously larger than that in low-altitude areas. In addition, source analysis was conducted for HONO and O 3 at different height layers. The heterogeneous reaction of NO 2 on wet surfaces was a significant source of HONO. The maximum values of HONO / NO 2 appeared when H 2 O concentrations were approximately 1.0 × 10 17 molec. cm -3 and aerosol concentrations were larger than 0.15 km -1 below 1.0 km. The maximum values were usually accompanied by H 2 O concentrations of 1.0–2.0 × 10 17 molec. cm -3 and aerosol concentrations greater than 0.02 km -1 at 1.0–2.0 km. O 3 was potentially sourced from the South Asian subcontinent and Himalayas through long-range transport. Our results contribute to the new understanding of vertical distribution of atmospheric components and explain the strong AOC on the TP. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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