The Hot Zone

Nitrous oxide from streams contributing to climate change at three times rate previous expected

Posted by Alison Hawkes on December 20, 2010
Category : Climate Science and Scientists, The Oceans

Carbon dioxide is bad for global warming, but nitrous oxide (N2O) may be one of the worst chemical compounds you can pump up into the air. Not only does it have 300 times the potency of CO2, but it also destroys stratospheric ozone (the good kind) — a double whammy on the atmosphere.

That’s why it’s unnerving to read a new study out of the Biological Sciences department of the University of Notre Dame that found N2O emissions coming from streams and rivers at three times the rate of IPCC estimates. Waterways may be responsible for some 10 percent of human-caused NO2 in the atmosphere, which from all sources accounts for 6 percent of global warming.

Nitrogen gets into rivers and streams as runoff from agricultural areas, where it’s applied as fertilizers, and from urban areas. Once it gets there microbes go to work and in a process call denitrification convert the nitrogen into nitrous oxide and another gas called dinitrogen (we worry less about the latter).

In the study, published in the Dec. 20 online edition of the Proceedings of the National Academy of Sciences, 72 streams were tested along different land-use types in the U.S. Those streams with the highest  nitrous oxide emissions were also those closest to urban and agricultural areas. That suggests humans are loading the streams and stimulating the production of NO2, the authors claim.

It all goes back to the way people have freed up the availability of Nitrogen in the biosphere, largely through growing crops. Nitrogen in waterways has been the source of other problems, too, namely nutrient loading of water bodies that causes sudden algae blooms that then strip away oxygen for other species.

NO2 production is a less known problem emanating from waterways, but as the study shows, no less important.

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