2007 Fiscal Year Final Research Report Summary
Evaluation of nutrient impact from river to coastal biogeochemical systems as an aspect from material transport processes
| Project/Area Number |
16201001
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 |
MINAGAWA Masao Hokkaido University, 大学院・地球環境科学研究院, Professor (10250507)
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| Co-Investigator(Kenkyū-buntansha) |
NAGAO Seiya Hokkaido University, Faculty.Env.Earth Sci., Associate Professor (20343014)
IRINO Tomohisa Hokkaido University, Faculty.Env.earth Sci., Assist.Prof. (70332476)
KATO Yoshisa Tokai University, Dept.Oceanography, Professor (00152752)
NARITA Hisashi Tokai University, Dept.Oceanography, Associate Professor (50250501)
MURAYAMA Masafumi Kochi University (50261350)
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| Project Period (FY) |
2004 – 2007
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| Keywords | Tokachi river / Abe river / Shimanto river / Niyodo river / nitrate / phosphate / silicate / coastal biological production |
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| Research Abstract |
We have investigated biogeochemical role of river runoff at several locations in Hokkaido, Central Honshu and Shikoku districts and have evaluated the contribution of these river water for the coastal biological production that is dealing with the marine carbon cycling. Based on geochemical observations including nutrient and isotopic analyses at Tokachi river, Abe river, Niyodo river, and Shimanto river, we found following results. (1) Nutrient loadings from Tokachi river were estimated as 1.3 and 0.009 mol/m^2/yr for DIN, and DIP, respectively. (2) These nutrient discharge can have dealings with 8.4 molC/m^2/yr as photosynthesis and may benefit for diatom production by their N/P and Si/N ratios. (3) Sporadic events with heavy precipitation can supply large effect mainly for nitrogen which provides potentially corresponding to 8% DIN supply of mean annual transport flux. (4) River discharge in the snow melting season would supply 30 to 40% of nutrient needed for coastal biological production, on the other hand particulate organic carbon make for less than one tenth of carbon fixation and less than a half of PON nitrogen. (5) The first class rivers in Shizuoka prefecture tend to have relatively lower nitrogen content ranging from 27 to 98 μM, but those in the second class rivers showed higher concentrations ranging from 82 to 504 mM and even wide variations. The phosphate and silicate concentrations are ranging from 0.21 to 9.2 μM and from 109 to 413 μM, respectively, reflecting difference of local environmental conditions such as water shed area, land utilization pattern and degree of civilizations.
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[Presentation] 古海洋学研究と微量元素・同位体2005
Author(s)
加藤義久, ら
Organizer
2005年度日本海洋学会秋季大会シンポジウム
Place of Presentation
仙台市 戦災復興記念会館
Year and Date
2005-09-27
Description
「研究成果報告書概要(和文)」より
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