Nitrous oxide, also known as laughing gas, has largely been replaced by other anesthetics in the dentist’s office. This odorless and colorless gas makes up only a scant 320 parts per billion in Earth’s atmosphere. But it will play a big role in our planet’s future.
Most nitrous oxide in the atmosphere is derived from soil microbes. When they break down nitrogen compounds in the soil, nitrous oxide is a byproduct, and a small amount diffuses to the atmosphere.
When we add nitrogen fertilizers to agricultural crops, the amount of nitrogen processed by soil microbes increases, and so do nitrous oxide emissions. Between 1 and 2% of nitrogen fertilizer applied is returned to the atmosphere as nitrous oxide.
Each molecule of nitrous oxide is about 200 times more effective in warming the atmosphere than a molecule of carbon dioxide. And concentrations are increasing at about a half a percent per year.
Adding to the problem, nitrous oxide offers a double-whammy. When it diffuses to the stratosphere, it also destroys ozone, which protects us from the Sun’s ultraviolet radiation. Since the chlorofluorocarbon ban, nitrous oxide has been the leading cause of human-derived stratospheric ozone destruction.
Recent work at the Cary Institute shows that the destruction of nitrous oxide by soil bacteria is small—mostly they produce it. The only major way that the gas is removed from the atmosphere is by the ozone-destroying reactions in the stratosphere.
So, if we are worried about global warming and ozone losses, we will need to take actions to reduce the use of nitrogen fertilizers, which are driving excess nitrous oxide production in soils.
***********
Web Links
For more information, see Schlesinger, 2013, An estimate of the global sink for nitrous oxide in soils, published in Global Change Biology
Photo, taken March 31, 2010, courtesy of P177 | WikiMedia Commons via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.