Preprints
https://doi.org/10.5194/acp-2021-289
https://doi.org/10.5194/acp-2021-289

  07 May 2021

07 May 2021

Review status: this preprint is currently under review for the journal ACP.

Ammonium nitrate promotes sulfate formation through uptake kinetic regime

Yongchun Liu1,5, Zeming Feng1, Feixue Zheng1, Xiaolei Bao2,7, Pengfei Liu3, Yanli Ge3, Yan Zhao3, Tao Jiang4, Yunwen Liao5, Yusheng Zhang1, Xiaolong Fan1, Chao Yan6, Biwu Chu3,6, Yonghong Wang6, Wei Du6, Jing Cai6, Federico Bianch6, Tuukka Petäjä6,8, Yujing Mu3, Hong He3, and Markku Kulmala1,6 Yongchun Liu et al.
  • 1Aerosol and Haze Laboratory, Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, China
  • 2Hebei Provincial Academy of Environmental Sciences, Shijiazhuang, 050037, China
  • 3State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
  • 4Hebei Provincial Meteorological Technical Equipment Center, Shijiazhuang, 050021, China
  • 5College of Chemistry and Chemical Engineering, China West Normal University, Nanchong, 637002, China
  • 6Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, P.O. Box 64, FI-00014, Finland
  • 7Hebei Chemical & Pharmaceutical College, Shijiazhuang, 050026, China
  • 8Joint International Research Laboratory of Atmospheric and Earth System Sciences (JirLATEST), University of Helsinki and Nanjing University, Nanjing 210023, China

Abstract. Although the anthropogenic emissions of SO2 have decreased significantly in China, the decrease in SO42− in PM2.5 is much smaller than that of SO2. This implies an enhanced formation rate of SO42− in the ambient air, and the mechanism is still under debate. This work investigated the formation mechanism of particulate sulfate based on statistical analysis of long-term observations in Shijiazhuang and Beijing supported with flow tube experiments. Our main finding was that the SOR was exponentially correlated with ambient RH in Shijiazhuang (SOR = 0.15 + 0.0032exp(RH/16.2)) and Beijing (SOR = −0.045 + 0.12exp(RH/37.8)). In Shijiazhuang, the SOR is linearly correlated with the ratio of aerosol water content (AWC) in PM2.5 (SOR = 0.15 + 0.40AWC/PM2.5). Kinetics studies suggest that uptake of SO2 instead of oxidation of S(IV) in particle-phase is the rate determining step for sulfate formation. NH4NO3 plays an important role in the AWC and the transition of particle phase, which is a crucial factor determining the uptake kinetics of SO2 and the enhanced SOR during haze days. Our results show that NH3 significantly promoted the uptake of SO2, subsequently, the SOR, while NO2 had little influence on SO2 uptake and SOR in the presence of NH3.

Yongchun Liu et al.

Status: open (until 02 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-289', Anonymous Referee #1, 14 Jun 2021 reply

Yongchun Liu et al.

Yongchun Liu et al.

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Short summary
The mechanisms and kinetics of particulate sulfate formation in the atmosphere are still open questions although they have been extensively discussed. We found that uptake of SO2 is the rate determining step for the conversion of SO2 to particulate sulfate. NH4NO3 plays an important role in the AWC, the phase state of aerosol particles, subsequently, the uptake kinetics of SO2 under high RH conditions. This work is a good exmple about the feedback between aerosol physics and aerosol chemistry.
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