Persistent sulfate formation from London Fog to Chinese haze

Research Highlight

Lifting the fog on the Great Smog

© Wenjie Dong/E+/Getty

© Wenjie Dong/E+/Getty

The ‘Great Smog’ that killed thousands of people in London in 1952 was triggered by a chemical process currently causing hazy days in China’s megacities.

A major culprit behind London’s fatal fog was sulfate (SO42-) that built up due to increased sulfur dioxide (SO2) from burning coal. How the sulfate formed and why it became so lethal was less clear. A team including researchers from the CAS Key Laboratory of Aerosol Chemistry and Physics in Xi’an, China, studied hazy air in Beijing and Xi’an and found that sulfate forms when nitrogen dioxide (NO2) oxidizes SO2 under specific atmospheric conditions. The reaction occurs either on tiny airborne particles in the presence of ammonia (NH3), or on cloud droplets.

The authors conclude that ammonia from agriculture contributes to China’s pollution problem, yet also prevents sulfates in Beijing and Xi’an from becoming dangerously acidic, whereas in London’s smog, the cloud droplets evaporated each day, leaving behind particles of toxic sulfuric acid.

Supported content

  1. PNAS 113, 13630–13635 (2016). doi: 10.1073/pnas.1616540113
Institutions FC
Department of Atmospheric Sciences, TAMU, United States of America (USA) 0.30
State Key Joint Laboratory of Environmental Simulation and Pollution Control (SKJLESPC), China 0.16
State Key Laboratory of Loess and Quaternary Geology, IEE CAS, China 0.11
CAS Key Laboratory of Aerosol Chemistry and Physics (KLACP), IEE CAS, China 0.11
University of Chinese Academy of Sciences (UCAS), China 0.04
Department of Chemistry, TAMU, United States of America (USA) 0.04
Jet Propulsion Laboratory (JPL), United States of America (USA) 0.02
Chinese Research Academy of Environmental Sciences (CRAES), China 0.02
Department of Chemistry and Biochemistry, UC San Diego, United States of America (USA) 0.02
Institute of Atmospheric Physics (IAP), CAS, China 0.02
Beijing Normal University (BNU), China 0.02
School of Environmental Science and Engineering, SDU, China 0.01
MOE Key Laboratory for Semi-Arid Climate Change, LZU, China 0.01
State Key Laboratory of Marine Environmental Science, XMU, China 0.01
School of Electrical Engineering, WHU, China 0.01
Institute of Environmental Health and Pollution Control, GDUT, China 0.01
Fredy and Nadine Herrmann Institute of Earth Sciences, HUJI, Israel 0.01
School of Environmental Sciences, UEA, United Kingdom (UK) 0.01
Aerodyne Research, Inc. (ARI), United States of America (USA) 0.01
Department of Chemistry and Biochemistry, FIU, United States of America (USA) 0.01
State Key Laboratory for Structural Chemistry for Unstable and Stable Species, ICCAS, China 0.01
Beijing National Laboratory for Molecular Sciences (BNLMS), China 0.01
Xi'an Jiaotong University (XJTU), China 0.01
School of Geographic Sciences, ECNU, China 0