Stable Isotope Fractionation of Nitrogen between Gas and Hydrate Phases

Stable isotope ratios of nitrogen gas in ice core air samples represent a valuable tool for studying the past climate change. In this study, we investigated the stable isotope fractionation of nitrogen between the gas and hydrate phases during nitrogen hydrate formation. Nitrogen hydrate samples were formed in the temperature range of 225-271 K and pressure range of 13-19 MPa. The isotopic compositions of the original, residual (unreacted), and hydrate-bound gases were measured. The nitrogen isotope ratio of the hydrate-bound gas was greater than that of the residual gas by 0.2 parts per thousand , indicating that the nitrogen hydrate was slightly more susceptible to (NN)-N-14-N-15 inclusion. This suggests that the equilibrium pressure of the (NN)-N-14-N-15 hydrate is slightly lower than that of the N-14(2) hydrate.

Automated summary

Stable isotope ratios of nitrogen gas in ice core air samples are important for studying past climate change. This study investigated the stable isotope fractionation of nitrogen during hydrate formation, finding that the nitrogen hydrate was slightly more susceptible to (NN)-N-14-N-15 inclusion. The results suggest that the equilibrium pressure of (NN)-N-14-N-15 hydrate is slightly lower than that of N-14(2) hydrate.