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Evaluation of nutrient impact from river to coastal biogeochemical systems as an aspect from material transport processes

作为物质运输过程的一个方面，评估从河流到沿海生物地球化学系统的养分影响

基本信息

批准号：
16201001
负责人：
MINAGAWA Masao
金额：
$ 32.12万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2007
项目状态：
已结题

项目摘要

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.

我们在北海道、本州中部和四国地区的几个地点调查了河流径流的生物地球化学作用，并评估了这些河流水对处理海洋碳循环的沿海生物生产的贡献。通过对竹内河、阿部河、新代渡河和岛岛河的营养物和同位素的地球化学观测，我们发现了以下结果。(1)高知河DIN和DIP的营养盐负荷分别为1.3m ol/m~2/a和0.009 m o l/m~2/a。(2)这些营养物质的排放与光合作用有关，其N/P和Si/N比值可能有利于硅藻的生产。(3)强降水的零星事件可以提供较大的影响，主要是氮素，可能相当于年平均输送通量的8%的DIN供应。(4)融雪季节的河流径流提供海岸生物生产所需营养物质的30%~40%，颗粒有机碳不到固碳量的1/10，不到PON氮的1/2。(5)静冈县一级河流的含氮量相对较低，为27~98μM，而二级河流的含氮量较高，为82~504 mm，变化幅度较大。磷酸盐和硅酸盐的浓度范围分别为0.21~9.2μM和109~413μM，反映了流域面积、土地利用格局和文明程度等环境条件的差异。