Analysis of dissolved nitrate stable isotopes using the one-step Ti (III) reduction method and Elementar EnvirovisION System

Identifying and quantifying sources and cycling of nitrogen is important for understanding not only aquatic ecosystems but also planning water resource management, mitigating urban and agricultural pollution, and optimizing government policy. Stable isotopes of dissolved nitrate and nitrite (δ15N, δ18O and δ17O) have been useful in distinguishing between the diverse nitrogen sources and sinks and help understand large scale global ocean processes as well as revealing major changes in agricultural land use and urbanization.Despite the strength of dissolved nitrate and nitrite stable isotope analysis, the strong barrier for uptake using the favored contemporary methods (bacterial denitrifier and Cd-azide reaction) due to the laborious multi-step methods, maintenance of anerobic bacterial cultures and use of highly toxic chemicals has limited the analysis to highly specialized laboratories. We evaluate the performance of the Elementar EnvirovisION using the new Titanium (III) reduction method (Altabet et al., 2019) for one step conversion of nitrate into N2O for IRMS analysis.The EnvirovisION has been developed for high performance analysis of CO2, N2O and CH4 and dissolved nitrate. The system has the capacity to be rapidly customized for specific needs with options for dual GC columns supporting the Weigand ‘heart-cut’ N2O method (Weigand et al., 2016) and sequential N2 and N2O analysis from a single atmospheric sample.