著者

呉 佳紅 西島 好美 佐竹 洋

出版者

日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.42, no.1, pp.1-11, 2008

参考文献数

37

被引用文献数

1

---

Nitrogen isotope ratio of nitrate ion in precipitation at Toyama was traced from June 2003 to December 2005 to investigate the behavior of nitrate ion inassociation with precipitation. δ¹⁵N value varied from -7.8 to + 1.6%o and showed seasonal variation; i.e., it was higher in winter than in summer. δ¹⁵N value negatively correlated to solar radiation. Negative correlation was also observed between δ¹⁵N value and concentration of atmospheric oxidant, which converted NO₂ to HNO₃. Such correlations suggest that the δ¹⁵N value of nitrate ion decreases with increasing conversion rate from atmospheric NO₂ to HNO₃. Based on an equation obtained from the relationship between the conversion rate and δ¹⁵N value according to the Rayleigh distillation model, 78-98% (av. ±1σ, 90±5%) NO₂ exhausted into the atmosphere were estimated to be converted into HNO₃. The similar seasonal variation was also observed at Nagoya, although the δ¹⁵N values are systematically higher than those of Toyama. The NO₂ concentration at Nagoya istwice as high as the concentration at Toyama, suggesting that the conversion rate from NO₂ to HNO₃ is lower in Nagoya (av. ±1σ, 86±6%) than in Toyama.