09:45 〜 10:00
[ACC29-04] 北極圏氷床コア中の硝酸窒素安定同位体組成から復元する過去の人間活動の変遷
キーワード：同位体、硝酸、人間活動、窒素循環、窒素酸化物
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 NO3− concentration, 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 NO3− concentrations 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.
Nitrogen and oxygen isotopic compositions of NO3− provide information on changes in the nitrogen source and its formation pathways, but ice core records for NO3− concentrations 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.