New mobile, field based continuous-flow isotope ratio mass spectrometer system for automated denitrification studies

Daniel I. Warner1, Clemens Scheer1, David W. Rowlings1, Peter R. Grace1

1 Institute of Future Environments, Queensland University of Technology, Brisbane, QLD 4000 Australia,


Terrestrial denitrification, the reduction of oxidized nitrogen (N) to nitrous oxide (N2O) and dinitrogen (N2), is considered the least well understood process in the global nitrogen cycle. This study introduces a novel continuous-flow isotope ratio mass spectrometer (IR-MS) system that can be deployed in the field and continuously measure N2 and N2O emissions. Utilizing the 15N gas flux method this system can provide a better understanding of terrestrial denitrification. The system was tested over 14 days on 2 different agricultural soils (vertosol and ferrosol) which were fertilized with the equivalent of 100 kg ha-1 of N added in the form of KNO3 where the N was 60 at.% 15N. Total gaseous N losses over the 14 day monitoring period resulted in 14.1± 0.53 kg ha-1 and 5.7± 0.92 kg ha-1 for the ferrosol and vertosol soils, respectively. These results clearly demonstrate the ability of the field based IR-MS to measure N2 and N2O emissions from denitrification under field conditions. This system has the potential to improve our understanding of terrestrial denitrification and improve efforts to reduce gaseous N emissions from agricultural systems.