Study provides new evidence of cooling properties of atmospheric molecule

Apr 24, 2013

(Phys.org) —Scientists have discovered further evidence for the existence of new molecules in the atmosphere that have the potential to off-set global warming by reacting with airborne pollutants.

Researchers from The University of Manchester, Bristol University, Southampton University and Sandia National Laboratories in California have detected the second simplest Criegee intermediate molecule – acetaldehyde oxide – and measured its reactivity.

Intermediates are molecules that are formed during a chemical reaction and react further to produce the final chemicals of the reaction. Criegee intermediates – carbonyl oxides – were first identifies by the team in January last year and shown to be powerful oxidisers, reacting with pollutants such as nitrogen dioxide and sulphur dioxide.

The authors, whose latest study is again published in the journal Science, believe Criegee intermediates have the potential to cool the planet by converting these pollutants into sulphate and nitrate compounds that will lead to aerosol and .

Professor Carl Percival, who led the Manchester team in the University's School of Earth, Atmospheric and Environmental Sciences, said: "We have carried out the first ever studies on the second simplest Criegee intermediate and were able to show that it also reacts extremely quickly with sulphur dioxide to produce under experimental conditions.

"We can therefore say that the reaction of these intermediates with sulphur dioxide will have a significant impact on sulphuric acid production in the atmosphere if they follow the pattern established by these two studies.

The paper is titled "Direct Measurements of Conformer-Dependent Reactivity of the Criegee Intermediate CH3COOH," published in Science.

He continued: "One of the main questions from our first study was if this increased reactivity would be observed for other Criegee intermediates, so with these findings we now have additional evidence that Criegee intermediates are indeed powerful oxidisers of pollutants such as and .

"What this study suggests is that the biosphere could have a significant impact on aerosol production and thus potentially climate cooling via the formation of Criegee intermediates. The next steps will be to carry out modelling studies to quantify the impact of Criegee intermediates on climate and to quantify the level of alkene present in various environments."

The formation of Criegee intermediates or biradicals was first postulated by the German chemist Rudolf Criegee in the 1950s but, despite their importance, it had not been possible to study the chemicals in the laboratory. The detection of the molecules was made possible through a unique apparatus that uses light from a third-generation synchrotron facility at the Lawrence Berkeley National Laboratory.

The latest study has also revealed which of the two isomers of acetaldehyde oxide is the most reactive. Isomers are molecules that contain the same atoms but arranged in different combinations, while conformational isomerism refers to the way the atoms of a molecule are rotated around a single chemical bond.

"In this new paper we have been able to show that the reactivity depends on the conformer of acetaldehyde oxide in a dramatic way," said Professor Percival. "The 'anti' conformer is much more reactive than the 'syn' conformer, which we believe more likely to be formed in the atmosphere. This enabled us to measure the rate coefficient for reaction with water for the first time; the removal, via reaction with water, is of vital importance if we want to understand the role of Criegee intermediates in the atmosphere."

Sandia combustion chemist Craig Taatjes, the lead author on the paper, added: "Observing conformer-dependent represents the first direct experimental test of theoretical predictions. The work will be of tremendous importance in validating the theoretical methods that are needed to accurately predict the kinetics for reactions of Criegee intermediates that still cannot be measured directly."

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User comments : 3

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Claudius
1 / 5 (5) Apr 24, 2013
Here's one cooling gas they failed to mention:

New Discovery: NASA Study Proves Carbon Dioxide Cools Atmosphere

http://principia-...facebook
Mike_Massen
5 / 5 (3) Apr 24, 2013
You Claudius are GUILTY of intellectual dishonesty and should be banned from any scientific forum !

From the actual (NASA) source of the article, its also NOT a new discovery re CO2/NO, unlike the solar flare energies.
"..Infrared radiation from CO2 and NO, the two most efficient coolants in the thermosphere.."

Claudius FFS, another propagandist hiding behind a vain nickname !
Get your facts straight and in context with the location of the thermosphere. If you were actually more than just a propagandist mouthpiece you SHOULD have the integrity to check the comparative mass of CO2 in the thermosphere vs the regions it acts as a greenhouse gas, you are wasting valuable time, you dunderhead Claudius !

Claudius, You should be ashamed and if not for your ignorance and obvious need to get an education you should be embarrassed you did not educate yourself first even a little !

Save me and the human race for the hubris of feeble intellects such as Claudius, Please...
NikFromNYC
1 / 5 (4) Apr 24, 2013
If the current negative phase of natural climate cycles are adequate to stall warming
for 16 years, how much of previous warming did their positive phase contribute to?

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