"The soil emissions were much larger than we expected," she said. "The biggest areas were the dry topical regions like the Sahel, and in the mid-latitude regions where there is a lot of agriculture."
During summer in North America, Europe and Asia, nitrogen oxides emitted from soil can reach half the emissions from fossil fuel combustion.
"And this is at a time when there are already problems with air pollution," Jaeglé said.
Nitrogen oxides comprise a group of highly reactive gases containing nitrogen and oxygen in varying amounts. Besides producing ozone smog, they help form the dirty brown clouds that often hang over major cities, they contribute to acid rain and they play a role in global climate change.
In addition to equatorial Africa, hot spots for soil emissions include the central plains of the United States; southwestern Europe, primarily the Iberian Peninsula; much of India; and the northern plains of Asia, she said. All of those areas are highly agricultural.
The new research was published in May in Faraday Discussions, a journal of England's Royal Society of Chemistry. Co-authors are Linda Steinberger of the UW; Randall Martin of Dalhousie University in Halifax, Nova Scotia; and Kelly Chance of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. The work was funded by the National Aeronautics and Space Administration's New Investigator Program in Earth Science.
Jaeglé noted that agricultural activity i