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Fixing nitrogen: the flash-fry way.

Fixing nitrogen: The flash-fry way

Nitrogen accounts for roughly 78 percent of the air that we breathe. But this nitrogen is useless to the living cells of almost all plants and animals, which rely on a select group of organisms--most notably blue-green algae and the bacteria on the roots of alfalfa and peanuts -- that can "fix" nitrogen, or combine it with other elements into a biologically useful form. Traditionally, atmospheric scientists have thought that these organisms were the major source of fixed nitrogen (other significant sources include industrially produced fertilizers and auto pollution). But one group of researchers has found that lightning may be doing as much as half of the job.

As the strokes of electrical energy jump from cloud to ground and cloud to cloud, they ionize the air, producing nitrogen oxide (NO) in the process. Then ozone (O.sub.3.) reacts with the NO, generating NO.sub.2 and molecular oxygen. Previous studies had estimated that these reactions accounted for around 3 percent of the fixed nitrogen in the atmosphere, says Edward Franzblau of the New Mexico Institute of Mining and Technology in Socorro.

However, he and his colleagues measured the nitrogen compounds produced by lightning and found that each lightning flash fixed more nitrogen than had been previously predicted. And by multiplying the molecules fixed per flash by the average number of lightning flashes on earth -- approximately 100 per second -- they calculated that lightning produces about half the store of fixed atmospheric nitrogen.

The measurements are difficult and even dangerous. On one occasion, Franzblau had to grab his instrument and run for cover when a storm veered toward his mountaintop position. Because these measurements are unconfirmed and contradict airborne measurements of nitrogen compounds produced by lightning, some scientists question the new conclusions. But others believe the findings warrant attention. If they are confirmed, says Ralph Cicerone of the National Center for Atmospheric Research in Boulder, Colo., "it's going to force us to take a much more realistic look at lightning."
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Title Annotation:role of lightning in nitrogen fixing
Author:Monastersky, Richard
Publication:Science News
Date:Jan 2, 1988
Words:334
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