Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have developed a tool to quantitatively measure elusive atmospheric chemicals that play a key role in forming photochemical smog. The device measures atmospheric hydroperoxyl radicals - short-lived, highly reactive intermediates involved in forming ozone, a component of photochemical smog - in the lowest layer of Earth's atmosphere. The levels of these radicals can indicate which chemical pathways predominate in converting hydrocarbons, nitrogen oxides, and water vapor into smog in the presence of sunlight.

Previous detectors for hydroperoxyl radicals have been cumbersome and costly. The new device is comparatively small, lightweight, and inexpensive, consumes low power, and gives a sensitive, fast response. It detects 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 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, used by Brookhaven and other national laboratory scientists for various atmospheric studies.

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