Cooperative SO2 and NOx aerosol formation in haze pollution

January 29, 2014, Science China Press
This shows a) particle number size distributions and b) fractional contributions of organics, nitrate, sulfate, ammonium, and chloride to the PM1 mass during the haze episode from 06:00 to 15:00 LT, Jan. 12, 2013. Credit: Science China Press

Air pollution in China has exhibited noticeable changes over the past 30 years, shifting from point-source pollution (around factories and industrial plants) in the 1980s to urban pollution in the 1990s. Since the start of this century, air pollution has become increasingly regional and more complex. Recent research has indicated that the cooperative transition of SO2 and NOx into secondary aerosols (sulfate and nitrate) played a critical role in the haze pollution episode in China in January 2013.

The coexistence of high concentrations of primary and secondary gaseous and particulate pollutants results in numerous heterogeneous reactions occurring on the surfaces of fine particles. These reactions change the oxidizing capacity of the atmosphere, chemical compositions, and the physicochemical and optical properties of the particulate matter. The overall effect is that and haze formation is accelerated. It is, therefore, important to explore the formation mechanisms of secondary aerosols during air episodes. The paper, "Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China", Science China: Earth Sciences, No. 1, 2014, by Professor Wang and co-workers shows that the formation of secondary sulfate aerosols from SO2 increases in the presence of NOx.

This study explores the cooperative transition of SO2 and NOx into secondary aerosols on the surfaces of carbon-containing particles through heterogeneous reactions. The formation of sulfates from SO2 is promoted by the existence of NOx. Results show that as the particle size increases, the fractional contributions of secondary inorganic ions, such as sulfate and nitrate, also increase (Figure 1). The hygroscopicity of the particles increase and the increased water content can accelerate the gas–liquid–solid reactions of SO2 and NOx, which further increases the hygroscopicity of the particles. These processes form a positive feedback mechanism that enhances the conversion of primary gas pollutants into secondary aerosols. Consequently, it is important to reduce emissions of the precursor gases of PM2.5 to reduce the overall PM2.5 concentrations in the atmosphere. The authors conclude that in central and eastern China, SO2 and NOx should be controlled synchronously to reduce PM2.5 concentrations.

Explore further: First infrared satellite monitoring of peak pollution episodes in China

More information: WANG, Y. S., YAO, L., WANG, L. L., LIU, Z. R., JI, D. S., TANG, G. Q., ZHANG, J. K., HU, B., XIN, J. Y. Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China. SCIENCE CHINA Earth Sciences, 2014, DOI: 10.1007/s11430-013-4773-4 . http://link.springer.com/article/10.1007%2Fs11430-013-4773-4

Related Stories

Conifer scent influences climate

January 9, 2014

(Phys.org) —Conifers emit volatile hydrocarbons, primarily terpenes, which we experience as the characteristic smell of the woods. In a complicated series of reactions involving ozone and sulfur dioxide, these compounds ...

Long term exposure to air pollution linked to coronary events

January 21, 2014

Long term exposure to particulate matter in outdoor air is strongly linked to heart attacks and angina, and this association persists at levels of exposure below the current European limits, suggests research conducted at ...

Beijing air pollution at dangerously high levels

January 16, 2014

Beijing's skyscrapers receded into a dense gray smog Thursday as the capital saw the season's first wave of extremely dangerous pollution, with the concentration of toxic small particles registering more than two dozen times ...

China's pollution seen from space

January 17, 2014

Scientists said on Friday they had mapped ground-level air pollution in China from space for the first time, a feat that should help the fight against a notorious health hazard.

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.