UI researcher helps map nitrogen footprint


Light particles interact with ammonium nitrate, a fertilizer, to form the potent greenhouse gas. Credit: USDA

A large contribution to the study of greenhouse gases

Nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide, accounts for about six percent of human-induced climate change, but researchers don’t know where 30 percent its global emissions come from.

Now, a CGRER study, led by UI chemistry professor Vicki Grassian, sheds more light on that question.   

The study found that light interacts with aerosol ammonium nitrate–one of the largest components of particle pollution in the Midwest–as well as with solid fertilizer ammonium nitrate.

Vicki Grassian

Chemical and Engineering News reports:

One known source is ammonium nitrate fertilizer. Microbes chew through the compound, emitting N2O from farm lands. But Vicki Grassian of the University of Iowa and her colleagues wondered if there was a non-biological route to the gas from ammonium nitrate. They knew that particles in the atmosphere can be composed of ammonium nitrate from fertilizers applied to agricultural fields. The surface of those particles could provide surfaces for chemical reactions in the atmosphere, Grassian thought.

The study looms as a large contribution to the study of greenhouse gases, as C&E News reports:

Grassian’s proposed mechanism for creating N2O is “straightforward” but has been “really hard to measure,” says Mark Thiemens, an atmospheric chemist at the University of California, San Diego. By using isotope tagging to follow the reactions triggered by light, Grassian’s experimental method gives an unambiguous result, he says. Armed with these results, he says, researchers now can hone their monitoring strategies to track this potent greenhouse gas.

“We talk about the carbon footprint; nitrogen footprints are important too,” Thiemens says. “If you know what the problem is, you have a chance of dealing with it.”

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