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Volume 18, issue 1 | Copyright
Atmos. Chem. Phys., 18, 167-184, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 08 Jan 2018

Research article | 08 Jan 2018

Role of ambient ammonia in particulate ammonium formation at a rural site in the North China Plain

Zhaoyang Meng1, Xiaobin Xu1, Weili Lin2,a, Baozhu Ge3, Yulin Xie4,5, Bo Song4, Shihui Jia1,6, Rui Zhang7,8, Wei Peng1, Ying Wang1, Hongbing Cheng1, Wen Yang7, and Huarong Zhao1 Zhaoyang Meng et al.
  • 1State Key Laboratory of Severe Weather & Key Laboratory for Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China
  • 2CMA Meteorological Observation Centre, Beijing 100081, China
  • 3State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 4University of Science and Technology Beijing, Beijing 100083, China
  • 5Baotou Steel Group Mining Research Institute, Baotou 014010, China
  • 6South China University of Technology, Guangzhou 510641, China
  • 7Chinese Research Academy of Environmental Sciences, Beijing 100012, China
  • 8Beijing Municipal Research Institute of Environmental Protection, Beijing 100037, China
  • anow at: College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China

Abstract. The real-time measurements of NH3 and trace gases were conducted, in conjunction with semi-continuous measurements of water-soluble ions in PM2.5 at a rural site in the North China Plain (NCP) from May to September 2013 in order to better understand chemical characteristics of ammonia and the impact of secondary ammonium aerosols on formation in the NCP. Extremely high NH3 and NH4+ concentrations were observed after a precipitation event within 7–10 days following urea application. Elevated NH3 levels coincided with elevated NH4+, indicating that NH3 likely influenced particulate ammonium mass. For the sampling period, the average conversionoxidation ratios for NH4+ (NHR), SO42− (SOR), and NO3 (NOR) were estimated to be 0.30, 0.64, and 0.24, respectively. The increased NH3 concentrations, mainly from agricultural activities and regional transport, coincided with the prevailing meteorological conditions. The high NH3 level with NHR of about 0.30 indicates that the emission of NH3 in the NCP is much higher than needed for aerosol acid neutralisation, and NH3 plays an important role in the formation of secondary aerosols as a key neutraliser. The hourly data obtained were used to investigate gas–aerosol partitioning characteristics using the thermodynamic equilibrium model ISORROPIA-II. Modelled SO42−, NO3, and NH3 values agree well with the measurements, while the modelled NH4+ values largely underestimate the measurements. Our observation and modelling results indicate that strong acids in aerosol are completely neutralised. Additional NH4+ exists in aerosol, probably a result of the presence of a substantial amount of oxalic and other diacids.

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This paper presents simultaneous measurements of NH3, other trace gases, and water-soluble ions in PM2.5 from May to September 2013 at a rural site in the North China Plain. Atmospheric ammonia and related parameters are characterised and the impact of ammonia on formation of secondary aerosols is investigated. The results presented in this paper may improve our understanding of the role of ammonia in aerosol formation.
This paper presents simultaneous measurements of NH3, other trace gases, and water-soluble ions...