NOx promotion of SO2 conversion to sulfate: An important mechanism for the occurrence of heavy haze during winter in Beijing

Jinzhu Ma; Biwu Chu; Jun Liu; Yongchun Liu; Hongxing Zhang; Hong He

doi:10.1016/j.envpol.2017.10.103

NO_x promotion of SO₂ conversion to sulfate: An important mechanism for the occurrence of heavy haze during winter in Beijing

Environ Pollut. 2018 Feb:233:662-669. doi: 10.1016/j.envpol.2017.10.103. Epub 2017 Nov 6.

Authors

Jinzhu Ma¹, Biwu Chu¹, Jun Liu², Yongchun Liu¹, Hongxing Zhang³, Hong He⁴

Affiliations

¹ State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China.
³ Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
⁴ State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: honghe@rcees.ac.cn.

PMID: 29121601
DOI: 10.1016/j.envpol.2017.10.103

Abstract

In this study, concentrations of NO_x, SO₂, O₃ and fine particles (PM_2.5) were measured at three monitoring stations in Beijing during 2015. For extreme haze episodes during 25 Nov. - 3 Dec. 2015, observation data confirmed that high concentrations of NO_x promoted the conversion of SO₂ to sulfate. Annual data confirmed that this is an important mechanism for the occurrence of heavy haze during winter in Beijing. Furthermore, in situ perturbation experiments in a potential aerosol mass (PAM) reactor were carried out at Shengtaizhongxin (STZX) station during both clean and polluted days. The concentrations of SO₄^2-, NH₄⁺, NO₃^- and organic aerosol were positively related to the concentration of added NO₂. These results provide definitive evidence that NO₂ can promote the conversion of SO₂ to sulfate. At the same time, we found that NO₂ can promote the formation of NH₄⁺ and organic compounds in the aerosols. Our results illustrate that strengthened controls of nitrogen oxides is a key step in reducing the fine particles level in China.

Keywords: Haze; NO(x); Promoting effects; Sulfate.

MeSH terms

Aerosols / analysis
Air Pollutants / analysis*
Beijing
China
Environmental Monitoring*
Environmental Pollution
Nitrogen / analysis
Nitrogen / chemistry*
Oxygen / analysis
Oxygen / chemistry*
Particulate Matter / analysis*
Seasons
Sulfates / analysis*
Sulfur Dioxide / analysis
Sulfur Dioxide / chemistry*

Substances

Aerosols
Air Pollutants
Particulate Matter
Sulfates
Sulfur Dioxide
nitrox
Nitrogen
Oxygen