21 Oct 2021

21 Oct 2021

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

The formation and mitigation of nitrate pollution: Comparison between urban and suburban environments

Suxia Yang1,2, Bin Yuan1,2, Yuwen Peng1,2, Shan Huang1,2, Wei Chen3, Weiwei Hu3, Chenglei Pei3,4,5,6, Jun Zhou1,2, David Parrish1, Wenjie Wang7, Xianjun He1,2, Chunlei Cheng2,8, Xiaobing Li1,2, Xiaoyun Yang1,2, Yu Song7, Haichao Wang9, Jipeng Qi1,2, Baolin Wang10, Chen Wang10, Chaomin Wang1,2, Zelong Wang1,2, Tiange Li1,2, E Zheng1,2, Sihang Wang1,2, Caihong Wu1,2, Mingfu Cai1,2, Chenshuo Ye7, Wei Song3, Peng Cheng7, Duohong Chen6, Xinming Wang3, Zhanyi Zhang1,2, Xuemei Wang1,2, Junyu Zheng1,2, and Min Shao1,2 Suxia Yang et al.
  • 1Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
  • 2Guangdong-Hongkong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, Jinan University, Guangzhou 511443, China
  • 3State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
  • 4CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China
  • 5University of Chinese Academy of Sciences, Beijing 100049, China
  • 6Guangzhou Ecological and Environmental Monitoring Center of Guangdong Province, Guangzhou 510060, China
  • 7State Joint Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
  • 8Institute of Mass Spectrometry and Atmospheric Environment, Guangdong Provincial Engineering Research Center for on-line Source Apportionment System of Air Pollution, Jinan University, Guangzhou 510632, China
  • 9School of Atmospheric Sciences, Sun Yat-Sen University, Guangzhou 510275, China
  • 10School of Environmental Science and Engineering, Qilu University of Technology, Jinan 250353, China

Abstract. Ambient nitrate has been of increasing concern in PM2.5, while there are still large uncertainties in quantifying the formation of nitrate aerosol. The formation pathways of nitrate aerosol at an urban site and a suburban site in the Pearl River Delta (PRD) are investigated using an observation-constrained box model. Throughout the campaigns, aerosol pollution episodes were constantly accompanied with the increase of nitrate concentrations and fractions at both urban and suburban sites. The simulations demonstrate that chemical reactions in the daytime and at night both contributed significantly to formation of nitrate in the boundary layer at the two sites. However, nighttime reactions predominately occurred aloft in the residual layer at the urban site and downward transport from the residual layer in the morning are important source (53 %) for surface nitrate at the urban site, whereas similar amounts of nitrate were produced in the nocturnal boundary layer and residual layer at the suburban site, which results in little downward transport of nitrate from the residual layer to the ground at the suburban site. We show that nitrate formation was in the volatile organic compounds (VOCs)-limited regime at the urban site, and in the transition regime at the suburban site, identical to the response of ozone at both sites. The reduction of VOCs emissions can be an efficient approach to mitigate nitrate in both urban and suburban areas through influencing hydroxyl radical (OH) and N2O5 production, which will also be beneficial for the synergistic control of regional ozone pollution. The results highlight that the relative importance of nitrate formation pathways can be site-specific, and the quantitative understanding of various pathways of nitrate formation will provide insights for developing nitrate mitigation strategies.

Suxia Yang et al.

Status: open (until 02 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-730', Anonymous Referee #3, 28 Oct 2021 reply
  • RC2: 'Comment on acp-2021-730', Anonymous Referee #2, 09 Nov 2021 reply
  • RC3: 'Comment on acp-2021-730', Anonymous Referee #1, 11 Nov 2021 reply
  • RC4: 'Comment on acp-2021-730', Anonymous Referee #4, 12 Nov 2021 reply

Suxia Yang et al.


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Short summary
We use a model constrained using observations to study the formation of nitrate aerosol in and downwind of a representative megacity. We found different contributions of various chemical reactions to ground-level nitrate concentrations between urban and suburban regions. We also show that controlling VOCs emissions are effective for decreasing nitrate formation in both urban and regional environments, although VOCs are not direct precursors of nitrate aerosol.