Strange molecule in sky cleans acid rain

August 13th, 2008 - 3:29 pm ICT by IANS  

Washington, Aug 13 (IANS) Researchers have stumbled upon an unusual molecule that helps break down pollutants, especially the compounds that cause acid rain. Marsha Lester and Joseph Francisco, of Pennsylvania and Purdue Universities, found the molecule that had exercised scientists for more than 40 years.

Somewhat like a human body metabolising food, the earth’s atmosphere has the ability to “burn,” or oxidise pollutants, especially nitric oxides emitted by factories and automobiles. What doesn’t get oxidised in the air falls back to earth in the form of acid rain.

“The chemical details of how the atmosphere removes nitric acid have not been clear,” Francisco said. “This gives us important insights into this process. Without that knowledge we really can’t understand the conditions under which nitric acid is removed from the atmosphere.”

“This becomes important in emerging industrial nations such as China, India and Brazil where there are automobiles and factories that are unregulated,” Francisco said. “This chemistry will give us insight into the extent that acid rain will be a future concern.”

Lester said the molecule had been theorised by atmospheric chemists for 40 years and that she and Francisco had pursued it for the past several years.

“We’ve speculated about this unusual atmospheric species for many years, and then to actually see it and learn about its properties was very exciting,” she said.

What makes the molecule so unusual is its two hydrogen bonds, which are similar to those found in water. Chemists know that although water is one of the most common substances found on the planet, it has unusual properties.

Hydrogen bonds are usually weaker than the normal bonds between atoms in a molecule, which are known as covalent bonds. In fact, covalent bonds are 20 times stronger than hydrogen bonds. But in this case, these two hydrogen bonds are strong enough to affect atmospheric chemistry, Francisco said.

The study appears in this week’s special edition of the Proceedings of the National Academy of Science.

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