Print Page
Recommend Page

Contact

Dr Hang Su

Max Planck Institute for Chemistry, Mainz

Phone: +49 61 3130-5426

Email: h.su@­mpic.de

Profile_image

Dr. Ulrich Pöschl

head of the aerosol research group

Max Planck Institute for Chemistry, Mainz

Phone: +49 6131 305-422
Fax: +49 6131 305-487

Email: u.poschl@­mpic.de

Original publication

Hang Su, Yafang Cheng, Robert Oswald, Thomas Behrendt, Ivonne Trebs, Franz X. Meixner, Meinrat O. Andreae, Peng Cheng, Yuanhang Zhang & Ulrich Pöschl
Soil nitrite as a source of atmospheric  HONO and OH radicals
Science, 18 August 2011, DOI: 10.1126/science.1207687

Related Links

Atmosphere cleans itself more efficiently than previously thought
Concentration of pollutant-degrading hydroxyl radicals in the air remains stable worldwide
Anthropogenic nitrogen plays a double role in climate change
Increased nitrous oxide emissions from fertilised soils offset climatic benefits from carbon sequestration

Chemistry . Earth Sciences . Ecology

Nitrogen in the soil cleans the air

Nitrogen-containing soil is a source of hydroxyl radicals that remove pollutants from the atmosphere

August 19, 2011

Eutrophication harms the environment in many ways. Unexpectedly, nitrogen fertilizer may also be positive for the environment. And even acidic soils, promoting the destruction of forests, can have a positive effect. Researchers from the Biogeochemistry Department at the Max Planck Institute for Chemistry in Mainz found out that nitrogen fertilizer indirectly strengthens the self-cleaning capacity of the atmosphere. Their study shows that nitrous acid is formed in fertilized soil and released to the atmosphere, whereby the amount increases with increasing soil acidity. In the air, nitrous acid leads to the formation of hydroxyl radicals oxidizing pollutants that then can be washed out. Previously, this nitrogen-effect has not been taken into account by geoscientists. The gap has now been closed by the Max Planck researchers.
standard Zoom Image
What is the source of nitrous acid in the atmosphere? Mainz scientists study the exchange of gases between soil samples and the air in this reaction chamber. [less]
© Su, Max Planck Institute for Chemistry.

Our air partly cleans itself as pollutants are being oxidized by hydroxyl radicals and washed out by rain. Now, researchers at the Max Planck Institute in Mainz and colleagues in Beijing have discovered the origin of a bulk part of the nitrous acid that is acting beside ozone as a source of hydroxyl radicals. According to their studies, large quantities of the acid are released into the atmosphere from soil. In nitrogen-rich soils the acid is formed from nitrite ions produced through microbiological transformations of ammonium and nitrate ions. The more acidic the soil is and the more nitrite it contains, the more nitrous acid is released. Through this pathway some of the nitrogen in fertilized soil escapes into the air.

In the latest issue of the journal Science, the Mainz researchers describe how they demonstrated the existence of this previously unnoticed pathway in the nitrogen cycle. They measured the concentration of HONO – a chemical term for gaseous nitrous acid – that escaped from a defined volume of arable soil. They added nitrite to a soil sample and varied its water content. The quantity of released HONO closely matched the researchers' estimates based on acid/base and solubility equilibria. Based on these findings they can also explain why previous studies had measured high levels of HONO in the air above fertilized agricultural soil.

 
/4400262/nitrogen_cleans_air
loading content