New device to understand smog formation

Scientists have developed a new tool for quantitatively measuring elusive atmospheric chemicals that play a key role in the formation of photochemical smog.

Washington, Nov 20 : Scientists have developed a new tool for quantitatively measuring elusive atmospheric chemicals that play a key role in the formation of photochemical smog.

Developed at the U.S. Department of Energy's Brookhaven National Laboratory, the device measures atmospheric hydroperoxyl radicals (short-lived, highly reactive intermediates involved in the formation of ozone, a component of photochemical smog) in the lowest layer of Earth's atmosphere.

The levels of these radicals can indicate which of a variety of chemical pathways is predominant in converting basic starting ingredients like hydrocarbons, nitrogen oxides, and water vapor, into smog in the presence of sunlight.

Better measurements will improve scientists' understanding of the mechanisms of smog formation and their ability to select and predict the effectiveness of various mitigation strategies.

"Understanding the relative importance of the various pathways can help you tailor your mitigation strategies," said Brookhaven atmospheric chemist Stephen Springston, one of the inventors.

"Our measurements will help predict which strategy would be most successful for a particular set of atmospheric conditions and make modifications to the strategy as those conditions change," said co-inventor Judy Lloyd of the State University of New York at Old Westbury.

But a major problem lies in getting accurate measurements because of the extreme reactivity of hydroperoxyl radicals.

"These chemicals are so fragile you cannot take a bottle home with you," said Springston. "You have to measure them where they form, in the atmosphere, before they react and disappear," he added.

Though various groups have developed detectors for hydroperoxyl radicals, these have been mostly cumbersome and costly.

But the new device is comparatively small, lightweight, inexpensive, has low power requirements, and gives a sensitive, fast response.

It works by detecting a 'glowing' signal from a chemiluminescent compound (similar to the compound that makes fireflies glow) when it reacts with the hydroperoxyl radicals in atmospheric samples fed into the device during flight.

"The chemiluminescence produced in solution creates a strong and readily detectable signal without the need for complex amplification procedures," said Lloyd.

The device has been tested in a mountaintop setting, but has not yet been deployed on an aircraft for a sampling mission. It is designed to be flown on atmospheric sampling aircraft, such as the Department of Energy's Gulfstream 1.

ANI