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Characteristics and Formation Mechanisms of Fine Particulate Nitrate in Typical Urban Areas in China

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Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control (AEMPC), Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CIC-AEET), School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China
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State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
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State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China
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Author to whom correspondence should be addressed.
Academic Editor: Guey-Rong Sheu
Atmosphere 2017, 8(3), 62; https://doi.org/10.3390/atmos8030062
Received: 17 January 2017 / Revised: 15 March 2017 / Accepted: 20 March 2017 / Published: 22 March 2017
(This article belongs to the Section Air Quality)
Nitrate is a very important aerosol component, thus elucidation of its characteristics and formation mechanisms is essential and important for effective reduction of aerosol pollution. In this work, highly time-resolved submicron aerosol (PM1) data measured by Aerodyne aerosol mass spectrometers (AMS) in Nanjing, Beijing and Lanzhou during both summer and winter were integrated to investigate the nitrate behaviors in urban China air. Results showed that nitrate occupied 1/8–1/4 of PM1 mass, typically higher than those observed in rural/remote regions. Relative mass fractions of nitrate also varied significantly at different pollution levels. Nitrate mass fractions generally increased with the increase of PM1 loadings during summer, while the contributions during winter increased first and then decreased with the increase of pollution levels. We further propose that there are at least three mechanisms that likely govern the urban nitrate behaviors: Type I—thermodynamics driven, Type II—photochemistry driven, and Type III—planetary boundary layer (PBL) dynamics driven. Analyses of the ammonium-sulfate-nitrate data revealed that ammonium nitrate was able to form before sulfuric acid was fully neutralized in some urban areas. Our findings provide useful insights into the characterization and reduction of fine particulate nitrate pollution. View Full-Text
Keywords: fine aerosols; nitrate; aerosol mass spectrometer; diurnal variation; formation mechanism fine aerosols; nitrate; aerosol mass spectrometer; diurnal variation; formation mechanism
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Ge, X.; He, Y.; Sun, Y.; Xu, J.; Wang, J.; Shen, Y.; Chen, M. Characteristics and Formation Mechanisms of Fine Particulate Nitrate in Typical Urban Areas in China. Atmosphere 2017, 8, 62.

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