[S-GL21] Geochronology and Isotope Geology

[SGL21-04] Recent advances in atmospheric chemistry and biogeochemistry using natural stable isotopes as tracers

★Invited Papers

*Urumu Tsunogai¹, Fumiko Nakagawa¹, Takashi Sambuichi¹, Weitian Ding¹, Ito Masanori¹ (1.Graduate School of Environmental Studies, Nagoya University)

Keywords: Stable isotope geochemistry, Nitrate, Phosphate, Triple oxygen isotopes

In this talk, recent advances in using the ¹⁷O-excess of nitrate and phosphate in the studying fields of atmospheric chemistry and biogeochemistry were summarized, together with the possible applications in the studying field of Earth and Planetary Sciences in general. Within the possible sources of nitrate in the natural environment, only atmospheric nitrate that is produced from atmospheric NO through photochemical reactions can be characterized by the anomalous enrichment in ¹⁷O, reflecting the transfer of an oxygen atom from ozone. In addition, ¹⁷O-excess is stable during partial metabolism - such as denitrification and assimilation, so by using these characteristics of ¹⁷O-excess, the author and co-workers were able to trace the fate of atmospheric nitrate deposited onto surface ecosystems. This also allowed the author and co-workers to propose a new method to quantify nitrate dynamics - production rate through nitrification and metabolic rate through assimilation and denitrification - in aquatic environments, using the ¹⁷O-excess of nitrate. The ¹⁷O-excess method is considered to offer an alternative to the traditional artificial tracer techniques for the determination of nitrate dynamics, including temporal variations.