Nitrous oxide (N2O), commonly known as laughing gas, traps heat in the atmosphere 300 times more effectively than carbon dioxide and destroys the ozone layer, making the gas no laughing matter when it escapes into the environment, primarily from farming.
Certain bacteria, known as denitrifiers, inhale nitrous oxide and render the gas harmless when they exhale nitrogen. However, more nitrous was disappearing from the environment than could be accounted for by these bacteria. While greenhouse gases disappearing mysteriously may sound like the type of problem scientists want to have, it also made it difficult to accurately model the long term effects of artificially elevated nitrous oxide levels on the Earth.
A recent study published in the Proceedings of the National Academy of Science found the microbial magicians responsible for the the atmospheric enigma. By analyzing the genomes of a wide range of microbes, a team led by Frank Loeffler of the University of Tennessee – Knoxville found the genetic codes for versions of the enzymes used by denitrifiers to break down nitrous, were common to many soil microorganisms.
"Before we did this study, there was an inconsistency in nitrous oxide emission predictions based on the known processes contributing to nitrous oxide consumption, suggesting the existence of an unaccounted nitrous oxide sink," said Loeffler in a press release. "The new findings potentially reconcile this discrepancy."
For billions of years, nitrous oxide was produced mostly by bacterial and fungal decomposition of plant material. Once human farmers started plowing the soil, growing nitrogen fixing crops such as beans and adding nitrogen-rich fertilizers, the production of nitrous oxide increased as the soil organisms were giving a smorgasbord of nitrogen compounds to feast upon, according to the U.S. Environmental Protection Agency. Internal combustion engines are another major human source of nitrous oxide, Loeffler's research will help atmospheric scientists understand what happens to the gas.
"This will allow us to better describe and predict the consequences of human activities on ozone layer destruction and global warming," said Loeffler. "Our results imply that the analysis of the typical denitrifier populations provides an incomplete picture and is insufficient to account for or accurately predict the true nitrous oxide emissions."
Farm tractor cultivating soil. (Will Lovell, Wikimedia Commons)
Medical grade nitrous oxide tanks (William Rafti, Wikimedia Commons)