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Nitrogen forms three-quarters of our atmosphere. In its principal atmospheric form, it is inert. A process called nitrogen fixation, which is accomplished by soil microbes or by combustion, converts nitrogen to reactive compounds. In these reactive forms, such as nitrogen oxides, nitrogen is an important plant nutrient.
But reactive nitrogen can also be an environmental hazard. Nitrogen oxides react with other compounds in the presence of sunlight to create ground-level ozone, a pollutant that contributes to asthma and other respiratory ailments. In forests, excess nitrogen can acidify soils and cause damage to the roots of plants. In water, it can contribute to dead zones and red tides that harm our fisheries.
The same atom of nitrogen can cause all of these problems—at different times and different places. It’s what scientists refer to as the “nitrogen cascade.”
Nitrogen has been a research focus of forest ecologist Gary Lovett at the Cary Institute…
“When this atom of nitrogen is released into the atmosphere it can cause smog and it can cause acid rain. Then when it lands on the forest, it can cause acidification of the soil and changes in species composition. And then it moves on through the forests into the lakes and streams, it can cause acidification there and also over-enrichment of nutrients.”
The flip side of the nitrogen cascade is that if we could reduce the types of combustion that create reactive nitrogen, we can help to solve at least three environmental problems at once: air pollution, soil acidification, and water pollution. That’s another good reason to reduce reactive nitrogen emissions from power plants and internal combustion engines.
Web Links
http://www.msnbc.msn.com/id/24653839/ns/us_news-environment/t/nitrogen-cascade-called-threat-ecosystems/
Nitrogen Pollution: From the Sources to the Sea
Hubbard Brook Research Foundation
http://hubbardbrookfoundation.org/12-2/nitrogen-pollution/
Photo, taken on June 5, 2006 in Kleinmönchhof, North Rhine-Westphalia, DE, courtesy of Bruno D. Rodrigues via Flickr.