| Project/Area Number |
20310003
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | Hokkaido University |
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Principal Investigator |
TSUNOGAI Urumu Hokkaido University, 大学院・理学研究院, 准教授 (50313367)
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| Co-Investigator(Kenkyū-buntansha) |
TANIMOTO Hiroshi 独立行政法人国立環境研究所, 大気圏環境研究領域・大気化学研究室, 室長 (30342736)
KANDA Jota 東京海洋大学, 海洋科学部, 教授 (60202032)
NOGUCHI Izumi 北海道環境科学研究センター, 環境科学部, 主任研究員兼環境科学科長 (10442617)
KOMATSU Daisuke 北海道大学, 大学院・理学研究院, 博士研究員 (70422011)
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| Project Period (FY) |
2008 – 2010
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| Project Status |
Completed (Fiscal Year 2010)
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| Budget Amount *help |
¥18,590,000 (Direct Cost: ¥14,300,000、Indirect Cost: ¥4,290,000)
Fiscal Year 2010: ¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2009: ¥6,630,000 (Direct Cost: ¥5,100,000、Indirect Cost: ¥1,530,000)
Fiscal Year 2008: ¥8,060,000 (Direct Cost: ¥6,200,000、Indirect Cost: ¥1,860,000)
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| Keywords | 一次生産 / 三酸素同位体 / 大気化学 / 栄養塩 / 水環境 / 窒素沈着 / 陸水学 / 海洋化学 |
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| Research Abstract |
The stable isotopic compositions of nitrate in precipitation (wet deposition) and groundwater (spring, lake, and stream water) were determined for the island of Rishiri, Japan, so as to use the ^<17>O anomalies (Δ^<17>O) to trace the fate of atmospheric nitrate that had deposited onto the island ecosystem, which is a representative background forest ecosystem for eastern Asia. The deposited nitrate had large ^<17>O anomalies with Δ^<17>O values with +26.2 ‰ being the annual average. On the other hand, nitrate in groundwater had small Δ^<17>O values ranging from +0.9‰ to 3.2‰, which corresponds to an average mixing ratio of atmospheric nitrate to total nitrate of 7%. Thus, we estimated that the direct drainage accounts for 10.5 ± 5.2% of atmospheric nitrate that has deposited on the island and that the residual portion has undergone biological processing before being exported from the forest ecosystem. The stable isotopic compositions of nitrate were determined in the oligotrophic water column of Lake Mashu, Japan, as well. These data were then used to quantify the geochemical dynamics of nitrate in the lake, by using the deposition rate of the atmospheric nitrate onto the entire catchment area of the lake.
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