Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-CC Cryospheric Sciences & Cold District Environment

[A-CC29] Ice cores and paleoenvironmental modeling

Tue. May 22, 2018 9:00 AM - 10:30 AM 201A (2F International Conference Hall, Makuhari Messe)

convener:Ryu Uemura(University of the Ryukyus), Kenji Kawamura(National Institute of Polar Research, Research Organization of Information and Systems), Ayako Abe-Ouchi(東京大学大気海洋研究所, 共同), Nozomu Takeuchi(Chiba University), Chairperson:Takeuchi Nozomu(千葉大学), Hattori Shohei(東工大)

9:45 AM - 10:00 AM

[ACC29-04] Nitrogen isotope of nitrate in Arctic ice core and its relation to past anthropogenic energy shift

*Shohei Hattori1, Asuka Tsuruta1, Iizuka Yoshinori2, Koji Fujita4, Ryu Uemura3, Sumito Matoba2, Naohiro Yoshida1,5 (1.Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2.Hokkaido University, Japan, 3.University of Ryukyus, 4.Nagoya University, Japan, 5.Earth-Life Science Institute)

Keywords:isotope, nitrate, anthropogenic activity, nitrogen cycle, Nitrogen oxides

Nitrate is one of the major anions found in snow. Nitrate (NO3) deposition results from reactions between nitrogen oxides (NOx = NO + NO2) and atmospheric oxidants. Global main sources of NOx are fossil fuel, biomass burning, biogenic soil emissions, and lightning. A recent increase in NO3 in ice cores has been associated with increasing anthropogenic emissions of NOx. Based on the changes in NO3concentration, however, it is not easy to identify specific sources of NOx which takes into account for the changes in NO3 concentrations, hindering the development of mitigation policy of anthropogenic pollution and its effect on the environment.
Nitrogen and oxygen isotopic compositions of NO3 provide information on changes in the nitrogen source and its formation pathways, but ice core records for NO3concentrations and its isotopic compositions are problematic because of post depositional loss of NO3 via photolysis. In this study, we analyzed isotopic compositions of NO3 preserved in the high-accumulation dome ice core, South East Greenland, which has a dome with high accumulation rate (about 1 m yr -1 ) in water equivalent. In this study, delta15N value of NO3 was measured by the bacterial method coupled with N2O decomposition via microwave-induced plasma (MIP).
The nitrogen isotopic compositions for NO3 were generally lower than those reported in Summit, Greenland, suggesting that some extent of NO3 deposited in Summit is removed via photolysis. Based on the trend of reconstructed delta15N values and NOx emission inventory, switches from coal to oil combustion mainly in North
America was likely a factor changing the nitrogen cycle in the Arctic environments.