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Nitrogen in soil helps clean the atmosphere

August 20, 2011 - Washington

A new study has found that the nitrogen in fertilized soil strengthens the self-cleaning capacity of the atmosphere.

The study by Researchers from the Biogeochemistry Department at the Max Planck Institute for Chemistry in Mainz shows that nitrous acid is formed in fertilized soil and released into 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.

Previous research has established that up to one third of the hydroxyl radicals formed in the lower atmosphere come from the photochemical breakdown of nitrous acid (HONO).

The latest study turned to the soil after previous research showed that the ground could act as a surface on which the chemical conversion of nitrite into HONO can take place.

To test their idea, 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.

The fact that soil emits HONO is not just locally, but also globally significant for air quality and the nitrogen cycle.

The study has been published in the journal Science.


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