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Reactive Oxidized Nitrogen at a High Mountain Site in the North China Plain: Chemical Speciation and Temporal Variations During 2007–2023.

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Title: Reactive Oxidized Nitrogen at a High Mountain Site in the North China Plain: Chemical Speciation and Temporal Variations During 2007–2023.
Authors: Xue, Likun1 (AUTHOR) xuelikun@sdu.edu.cn, Jiang, Ying1 (AUTHOR), Li, Hongyong1 (AUTHOR), Liu, Qingqing1 (AUTHOR), Zhang, Ji1 (AUTHOR), Shen, Hengqing1 (AUTHOR), Zhao, Yong2 (AUTHOR), Guo, Zhaoxin2 (AUTHOR), Chen, Tianshu1 (AUTHOR), Wen, Liang3 (AUTHOR), Liu, Yuhong1 (AUTHOR), Mu, Jiangshan1 (AUTHOR), Wang, Xinfeng1 (AUTHOR), Gao, Jian3 (AUTHOR), Wang, Tao4 (AUTHOR), Wang, Wenxing1 (AUTHOR)
Source: Journal of Geophysical Research. Atmospheres. 4/16/2025, Vol. 130 Issue 7, p1-17. 17p.
Subject Terms: *Atmospheric chemistry, *Tropospheric ozone, Atmospheric boundary layer, Particulate nitrate, Chemical speciation, Peroxyacetyl nitrate, Reactive nitrogen species
Abstract: Total reactive oxidized nitrogen (NOy) and its speciated compounds, such as nitric oxide (NO), nitrogen dioxide (NO2), peroxyacetyl nitrate (PAN), and particulate nitrate (pNO3−), play a major role in tropospheric chemistry, regional air quality, and climate change. However, little is known regarding the chemical speciation and long‐term trends of NOy in China. In this study, we analyzed the temporal variations in NOy and speciated compounds during eight intensive field campaigns and 6 years of continuous measurements during 2007–2023 at Mount Tai in the North China Plain (NCP). The measured concentration levels of NOy were significantly higher than those at other remote high‐altitude sites globally. NO2 was the most abundant species (24%–42%), followed by pNO3− (18%–34%) and PAN (7%–12%). Over the study period, the concentrations of NOx, NOy, and NOz exhibited a significant downward trend, while pNO3− exhibited a significant upward trend. Vertical transport from the planetary boundary layer (PBL) substantially influences the atmosphere at Mount Tai, with air masses from both PBL and free troposphere containing different chemical compositions of NOy. The lower free troposphere above the NCP contained relatively high abundances of PAN and pNO3−. This study represents the first comprehensive analysis of decadal trends in NOy and its chemical speciation in China's high‐altitude atmosphere. Our findings underscore the necessity for additional efforts to mitigate photochemical and secondary aerosol pollution caused by nitrogen species at high altitudes in China. Plain Language Summary: Reactive nitrogen oxides are key players in atmospheric chemistry, air quality, and climate change, but understandings about their chemical speciation and long‐term variations have long been lacking in China. By analyzing a comprehensive set of observations at the highest mountain in the North China Plain during 2007–2023, this study fills a gap in the long‐term characterizations of reactive nitrogen chemistry in the regional atmospheres of China. It also presents useful research data for better understanding atmospheric chemistry in the free troposphere, and emphasizes the interplay of reactive substances between planetary boundary layer and free troposphere. Key Points: At Mt. Tai, total reactive oxidized nitrogen is dominated by nitrogen dioxide, followed by particulate nitrate and peroxyacetyl nitrateFrom 2007 to 2023, concentrations of NOy, NOx, and organic NOz trended downward, while concentrations of pNO3− trended upwardPAN and pNO3− are abundant in the lower free troposphere over the North China Plain [ABSTRACT FROM AUTHOR]
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Abstract:Total reactive oxidized nitrogen (NOy) and its speciated compounds, such as nitric oxide (NO), nitrogen dioxide (NO2), peroxyacetyl nitrate (PAN), and particulate nitrate (pNO3−), play a major role in tropospheric chemistry, regional air quality, and climate change. However, little is known regarding the chemical speciation and long‐term trends of NOy in China. In this study, we analyzed the temporal variations in NOy and speciated compounds during eight intensive field campaigns and 6 years of continuous measurements during 2007–2023 at Mount Tai in the North China Plain (NCP). The measured concentration levels of NOy were significantly higher than those at other remote high‐altitude sites globally. NO2 was the most abundant species (24%–42%), followed by pNO3− (18%–34%) and PAN (7%–12%). Over the study period, the concentrations of NOx, NOy, and NOz exhibited a significant downward trend, while pNO3− exhibited a significant upward trend. Vertical transport from the planetary boundary layer (PBL) substantially influences the atmosphere at Mount Tai, with air masses from both PBL and free troposphere containing different chemical compositions of NOy. The lower free troposphere above the NCP contained relatively high abundances of PAN and pNO3−. This study represents the first comprehensive analysis of decadal trends in NOy and its chemical speciation in China's high‐altitude atmosphere. Our findings underscore the necessity for additional efforts to mitigate photochemical and secondary aerosol pollution caused by nitrogen species at high altitudes in China. Plain Language Summary: Reactive nitrogen oxides are key players in atmospheric chemistry, air quality, and climate change, but understandings about their chemical speciation and long‐term variations have long been lacking in China. By analyzing a comprehensive set of observations at the highest mountain in the North China Plain during 2007–2023, this study fills a gap in the long‐term characterizations of reactive nitrogen chemistry in the regional atmospheres of China. It also presents useful research data for better understanding atmospheric chemistry in the free troposphere, and emphasizes the interplay of reactive substances between planetary boundary layer and free troposphere. Key Points: At Mt. Tai, total reactive oxidized nitrogen is dominated by nitrogen dioxide, followed by particulate nitrate and peroxyacetyl nitrateFrom 2007 to 2023, concentrations of NOy, NOx, and organic NOz trended downward, while concentrations of pNO3− trended upwardPAN and pNO3− are abundant in the lower free troposphere over the North China Plain [ABSTRACT FROM AUTHOR]
ISSN:2169897X
DOI:10.1029/2024JD042479