Abiotic nitrous oxide emission from the hypersaline Don Juan Pond in Antarctica

Nitrous oxide is a potent atmospheric greenhouse gas(1) that contributes to ozone destruction(2). Biological processes such as nitrification and denitrification are thought to drive nitrous oxide production in soils, which comprise the largest source of nitrous oxide to the atmosphere(1). Here we present measurements of the concentration and isotopic composition of nitrous oxide in soil pore spaces in samples taken near Don Juan Pond, a metabolically dormant hypersaline pond in Southern Victoria Land, Antarctica in 2006, 2007 and 2008, together with in situ fluxes of nitrous oxide from the soil to the atmosphere. We find fluxes of nitrous oxide that rival those measured in fertilized tropical soils(3). Laboratory experiments -in which nitrite-rich brine was reacted with a variety of minerals containing Fe(II)-reveal a new mechanism of abiotic water-rock reaction that could support nitrous oxide fluxes at Don Juan Pond. Our findings illustrate a dynamic and unexpected link between the geosphere and atmosphere.