Urban smog adds a lot to ozone on the ground

March 25th, 2008 - 1:32 pm ICT by admin  


Washington, March 25 (IANS) Bringing down alarming ozone levels might be a possibility now with the identification of an atmospheric chemical reaction that plays a crucial role in its formation, contributing to smog and pollution. The finding would help benefit more than 100 million people worldwide, particularly in cities grappling with major air and urban smog problems, even as they fail to meet international standards, said Amitabha Sinha of University of California (UC).

Ozone at the ground level is a major pollutant, though the ozone layer at the top of the earth’s atmosphere protects us from the harmful ultraviolet rays of the sun.

“It shows us that the chemistry of urban ozone is even more complicated than we initially assumed. With improved knowledge of how ozone is produced, we should be in a better position to control the air quality of large urban areas across the United States as well as around the world,” said Sinha, who led the research.

Urban ozone levels peak over large cities after being generated through a complex chemical reactions involving the interaction of sunlight with hydrocarbons and nitrogen oxides from automobile exhaust, reports Sciencedaily.

Ozone production is initiated when hydroxyl radicals are produced from water vapour. These radicals subsequently attack hydrocarbons and resulting products combine through a series of chemical reactions with nitric oxide to produce nitrogen dioxide and eventually ozone.

“Identifying the sources of atmospheric hydroxyl radical production is important to understanding how to control the ozone problem, since it is the reaction of these radicals with hydrocarbons that ultimately leads to urban ozone,” Sinha said.

German scientists first proposed this method of producing hydroxyl radicals in 1997. Their measurements, however, did not detect any radicals being formed and, as a result, they suggested that the reaction would play a fairly insignificant role in the atmosphere.

The study has been detailed in the March 21 issue of the journal Science.

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