High Levels of Daytime Molecular Chlorine and Nitryl Chloride at a Rural Site on the North China Plain

Molecular chlorine (Cl2) and nitryl chloride (ClNO2) concentrations were measured using chemical ionization mass spectrometry at a rural site over the North China Plain during June 2014. High levels of daytime Cl2 up to ∼450 pptv were observed. The average diurnal Cl2 mixing ratios showed a maximum...

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Bibliographic Details
Published in:Environmental science & technology 2017-09, Vol.51 (17), p.9588-9595
Main Authors: Liu, Xiaoxi, Qu, Hang, Huey, L. Gregory, Wang, Yuhang, Sjostedt, Steven, Zeng, Limin, Lu, Keding, Wu, Yusheng, Hu, Min, Shao, Min, Zhu, Tong, Zhang, Yuanhang
Format: Article
Language:English
Subjects:
Air Pollutants
Alkanes
Chemical compounds
China
Chlorides
Chlorine
Daytime
Diurnal
Electric power generation
Electric power plants
Environmental Monitoring
Free radicals
Ionization
Mass spectrometry
Mass spectroscopy
Maxima
Mixing ratio
Molecules
Nitrites
Noon
Ozone
Peroxy radicals
Photochemicals
Power plants
Rural areas
Sulfur
Sulfur dioxide
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Summary:Molecular chlorine (Cl2) and nitryl chloride (ClNO2) concentrations were measured using chemical ionization mass spectrometry at a rural site over the North China Plain during June 2014. High levels of daytime Cl2 up to ∼450 pptv were observed. The average diurnal Cl2 mixing ratios showed a maximum around noon at ∼100 pptv. ClNO2 exhibited a strong diurnal variation with early morning maxima reaching ppbv levels and afternoon minima sustained above 60 pptv. A moderate correlation (R 2 = 0.31) between Cl2 and sulfur dioxide was observed, perhaps indicating a role for power plant emissions in the generation of the observed chlorine. We also observed a strong correlation (R 2 = 0.83) between daytime (10:00–20:00) Cl2 and ClNO2, which implies that both of them were formed from a similar mechanism. In addition, Cl2 production is likely associated with a photochemical mechanism as Cl2 concentrations varied with ozone (O3) levels. The impact of Cl2 and ClNO2 as Cl atom sources is investigated using a photochemical box model. We estimated that the produced Cl atoms oxidized slightly more alkanes than OH radicals and enhanced the daily concentrations of peroxy radicals by 15% and the O3 production rate by 19%.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.7b03039