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, [email protected]


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.