Reducing sulfur dioxide emissions alone cannot substantially decrease air pollution

April 11, 2020

High loadings of fine particulate matter (PM2.5) during haze are mostly produced from the chemical reactions of the reactive gas precursors, including sulfur dioxide (SO2), nitrogen oxides (NOx), ammonia (NH3), and volatile organic compounds. In an ideal world, air pollution would be cured by wiping clean any one of these four PM2.5 precursors. However, in the real world, we have to go step by step, considering the technological conditions and the economic costs in the emission control strategies. Besides, these gases are subject to a certain thermodynamic equilibrium in the atmosphere. Theoretically, NH3 prefers to combine with SO2 (sulfuric acid) to form ammonium sulfate, which is stable in the atmosphere. Excessive NH3 will react with nitrogen dioxide (nitric acid) to form ammonium nitrate, which is unstable, and the formation of which is influenced by the relative abundance of NH3 and nitrogen dioxide. Consequently, a decrease in SO2 emissions leaves more NH3 to form ammonium nitrate, and it may also perturb the balance between NH3 and nitrogen dioxide.

Due to the delivery of the Air Pollution Control Action Plan, SO2 emissions have declined dramatically since 2013. It also offers us an opportunity to examine whether a reduction in SO2 will perturb the balance between NH3 and nitrogen dioxide in forming ammonium nitrate, and to decide how to make emission control strategies in the future.

Professor Xingying ZHANG from the National Satellite Meteorological Center and his coauthors have addressed this issue. They evaluated and compared the behavior of PM2.5 with respect to NOx and NH3 emission changes in high (2013) and low (2018) SO2 emission cases.

Prof. Zhang's group has found that, from 2013 to 2018, due to the changes in precursor emissions, the simulated annual mean PM2.5 concentration decreased by nearly 20%, more than half of which was driven by reduced SO2 emissions. "To evaluate the influence of a reduction in SO2 emissions on the sensitivity of PM2.5 to NOx and NH3 emissions, we conducted model sensitivity studies by separately perturbing NOx and NH3 emissions by ?25%. Then, we calculated the relative reduction of PM2.5 concentration caused by a 1% decrease in NOx and NH3 emissions," explains Professor Zhang.

According to the study of Prof. Zhang, it can be concluded that, due to the reduced emissions of SO2, and considering the high level of NH3 emissions in China, nitrogen dioxide emissions control is more effective in reducing the surface PM2.5 concentration in China. This paper has been published in .
-end-


Institute of Atmospheric Physics, Chinese Academy of Sciences

Related Air Pollution Articles from Brightsurf:

How air pollution affects homeless populations
When air quality worsens, either from the smoke and ozone of summer or the inversion of winter, most of us stay indoors.

Exploring the neurological impact of air pollution
Air pollution has become a fact of modern life, with a majority of the global population facing chronic exposure.

Spotting air pollution with satellites, better than ever before
Researchers from Duke University have devised a method for estimating the air quality over a small patch of land using nothing but satellite imagery and weather conditions.

Exposure to air pollution during pregnancy is associated with growth delays
A new study by the Barcelona Institute for Global Health (ISGlobal) has found an association between exposure to air pollution during pregnancy and delays in physical growth in the early years after birth.

Nearly half of US breathing unhealthy air; record-breaking air pollution in nine cities
Amid the COVID-19 pandemic, the impact of air pollution on lung health is of heightened concern.

Air pollution linked to dementia and cardiovascular disease
People continuously exposed to air pollution are at increased risk of dementia, especially if they also suffer from cardiovascular diseases, according to a study at Karolinska Institutet in Sweden published in the journal JAMA Neurology.

New framework will help decide which trees are best in the fight against air pollution
A study from the University of Surrey has provided a comprehensive guide on which tree species are best for combating air pollution that originates from our roads -- along with suggestions for how to plant these green barriers to get the best results.

Air pollution is one of the world's most dangerous health risks
Researchers calculate that the effects of air pollution shorten the lives of people around the world by an average of almost three years.

The world faces an air pollution 'pandemic'
Air pollution is responsible for shortening people's lives worldwide on a scale far greater than wars and other forms of violence, parasitic and insect-born diseases such as malaria, HIV/AIDS and smoking, according to a study published in Cardiovascular Research.

Air pollution in childhood linked to schizophrenia
Children who grow up in areas with heavy air pollution have a higher risk of developing schizophrenia.

Read More: Air Pollution News and Air Pollution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.