Advances in measuring low N2O fluxes by a portable gas analyser and manual chambers

Abstract

Nitrous oxide (N2O) is one of the most important greenhouse gases with a global warming potential of about 298 times stronger than carbon dioxide (CO2) over a period of 100 years. From 1800 to 2023, the atmospheric concentration of N2O has increased from 273 to 336 ppbv, whereby more than half of this rise is due to the addition of fertilisers and manure on agricultural soils. Whilst these managed, nutrient-rich soils have been relatively well studied, little is known about N2O fluxes in nutrient-poor ecosystems (e.g., the Arctic). Since many Arctic soils contain very low amounts of available nitrogen, in the past it has been generally assumed that Arctic soils are not a significant source of N2O. Only recently, several studies have reported significant N2O emissions from organic-rich Arctic soils; however, due to methodological challenges, extensive investigations on N2O fluxes in Arctic soils have been limited. As a result, the importance of N2O fluxes from this region to the global budget remains highly uncertain.  With the recent advances in portable GHG analyser technology, extensive manual chamber measurements based on in-situ N2O concentration measurements can provide novel information to close this knowledge gap. However, guidelines on measuring techniques (e.g., chamber closure time) and data quality (e.g., no flux vs. low flux) are still lacking. In this study, we provide new insights on N2O fluxes in a nutrient-poor ecosystem and give general practical guidelines for measuring low N2O fluxes with a portable gas analyser and manual chambers. In May, July, and September 2023, we used a portable N2O/CO2 analyser to measure N2O fluxes in a thawing sub-Arctic permafrost peatland in northern Sweden. Recommendations on practical use in the field are given to support future N2O research with portable gas analysers.