A team of young scientists yesterday unveiled the results of their research into Criegee intermediates (CIs, also known as carbonyl oxides) — a transient molecule in the atmosphere that is linked to the generation of acid rain and suspended particulates — becoming the first scientists in the world to determine the reaction between CIs and water molecules, providing a solid basis for future atmospheric studies.
Academia Sinica research fellow Lin Chih-min (林志民), who led the project, said CIs are an extremely short-lived oxidant and scientists had been unable to observe them in action.
Previous attempts by international research teams at observing the molecule used a combination of mass spectrometry and synchrotron radiation, but the results had been confined to observing the CIs at less than 10 percent atmospheric pressure, he said.
By incorporating an ultraviolet absorption spectroscope and a series of prisms, the team was able to create an environment where the air pressure was close to atmospheric pressure, thereby gaining an understanding of how the CIs react with other molecules in the atmosphere.
By observing the reactions at various relative humidity levels — up to 85 percent at 298 Kelvin — the research discovered that CIs begin to decay extremely rapidly at high humidity, indicating that they interact with water at high concentration levels.
In addition, the research found that the higher the humidity, the less likely it was that CIs would interact with sulfur dioxide and nitrogen dioxide — chemicals known to be related to the generation of acid rain and major air pollutants.
Lin said that the age of his team made the success of the research even more remarkable.
Chao Wen (趙?), the first author of the article on the research, is a senior at National Taiwan University’s Department of Chemistry, while coauthors Hsieh Chun-ting (謝郡庭) is a sophomore at Stanford University and Chang Chun-hung (張俊宏) a postgraduate student at National Tsing Hua University.
When asked whether the research would lead to an effective way of tackling the problem of acid rain, Lin said that there are hundreds types of chemical reactions taking place in the atmosphere and that those involving CIs are just some of them.
“I think effective management of the sources of pollutants would be a more effective way to solve the problem of acid rain,” Lin said.
The team’s research has been accepted by international journal Science and was published on its Web site on Thursday last week.
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