Desert microbes release greenhouse gases

Scientists have long known that wet soils in agricultural areas sometimes emit nitrous oxide – a strong greenhouse gas also known as laughing gas. The explanation is that soil microbes convert nitrogen based fertilizers into nitrous oxide when the soil is wet. A new study published in the journal Biogeochemistry shows that microbes in desert soils do the same thing after a heavy rain.    

“It only happens in waterlogged soils. Since the desert is dry most of the year, we didn’t think this process could occur in arid soils,” explained study first author Alex Krichels, an environmental scientist at UC Riverside. “This is a strategy for the bacteria to survive after a ton of water is added and there’s no oxygen for them in the soil. When that happens, instead of oxygen they use nitrate, and breathe out nitrous oxide, a process called denitrification.”

Obviously, the source of nitrates in desert soil isn’t farm-applied fertilizer. Instead scientists suspect the nitrates could be coming from exhaust, such as that from automobiles driving through a desert landscape. 

“Nitrate pollution in deserts originates from fossil fuel combustion, not fertilization,” said Krichels. “Combustion releases pollution that hangs around, gets deposited into soils over time, and re-emerges after a rain as N2O.”

A few different forms of nitrogen are created by cars and other processes. “Combined, they’re called NOx, and they can produce tropospheric ozone, which is bad for your lungs and is also a greenhouse gas,” explained study co-author Peter Homyak. “It is not to be confused with good ozone higher up in the stratosphere that protects us from UV rays,” 

The scientists who carried out the study say they hope that their work brings more awareness to the problem.  

“On a broader scale, a lot of people don’t know these processes happen in soils in general, or that the nitrogen humans add to the atmosphere can end up affecting climate change and human health in this way,” said Krichels. “There’s a lot of life in these soils, and it can affect the entire globe.”

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By Zach Fitzner, Earth.com Staff Writer