Scientists Discover Natural Source of Potent Greenhouse Gas

A new study from Michigan State University (MSU) has identified a new natural source of a greenhouse gas that's considered to be more potent than carbon dioxide.

The study, published in the journal Nature Geosciences, showed that decomposing leaves in the soil could promote the production of nitrous oxide.

"Most nitrous oxide is produced within teaspoon-sized volumes of soil, and these so-called hot spots can emit a lot of nitrous oxide quickly," said Sasha Kravchenko, a plant, soil and microbial scientists at MSU and lead author of the study, in a press release. "But the reason for occurrence of these hot spots has mystified soil microbiologists since it was discovered several decades ago."

For the study, the researchers solved the mechanism behind the N20 hotspots using a powerful X-ray scanner. First, they collected soil samples from the university's Kellogg Biological Station Long-term Ecological Research site. Then, they used the synchrotron scanning facilities at Argonne National Laboratory. This scanner is much more powerful version of a medical CT and can easily penetrate the soil, allowing the researchers to accurately characterize the environments where nitrous oxide is produced an emitted.

The researchers found that the size of pores in the soil play a crucial role in the potential of decomposing leaves in producing and emitting nitrous oxide. In larger pores, the researchers observed that leaf particles act as a sponge that soaks up water from the pores, creating a micro-habitat for N20-producing bacteria. On the other hand, leaf particles can't be soaked up in small pores because these pores hold water more tightly. Bactria won't be able to produce large quantities of nitrous oxide without the additional moisture. Additionally, smaller pores will make it more difficult for the gas produced to leave the soil before being consumed by bacteria.

Nitrous oxide emissions were mostly driven by agricultural practices. This greenhouse gas has about 300 times greater global warming potential than carbon dioxide.