Study on Accumulation and Transportation of Refractory Organic Materials in Terrestrial Area

全球有机碳循环的一个重要组成部分是陆地有机碳从大陆到海洋的通量。由于河流、河口和沿海地区固有的复杂性和可变性，沿海系统在全球和区域有机收支中的潜在重要性仍不清楚。因此，了解河口和海岸系统的有机质循环，特别是河流DOM和POM的特征和动态具有重要意义。但DOM和POM在大小或化学特征上并不均匀，因此我们无法评估陆地和沿海环境的联系。本研究的目的是了解溶解性有机物和颗粒性有机物从陆地区域向海洋的迁移行为。本研究使用碳同位素比率（Δ^<14>C和Δ^< 13>C值）作为有机碳的示踪剂，因为同时使用这些值为地表水生环境中碳循环的同位素研究增加了第二个维度。用XAD萃取法从苏格兰、乌克兰、日本和印度尼西亚的河水中分离出难降解的有机腐殖质物质。溶解腐殖物质的Δ^<14>C值在-316‰~ +209‰之间，具有明显的时空分布特征。为了了解POM在水系中的运移，我们选择了具有不同流域条件的三个水系（Tokachi、Ishikari和Kuji水系），并在每个水系中进行定点观测。Δ^<14>C值在北海道东北部的德胜河为-111 ~ -286‰，在北海道东南部的石kari河为-103 ~ -364‰，在关东地区的Kuji河为-18.7 ~ -94.4‰。配对的Δ^<14>C和Δ^< 13>C的分布随河流和季节而变化。这些结果表明，Δ^<14>C和Δ^< 13>C配对分布的差异可能反映了水排放和流域环境。

An important part of global organic carbon cycle is the flux of terrestrial organic carbon from the continents to the oceans. The potential importance of coastal systems in global and regional organic budgets is still unclear because of the inherent complexity and variability of rivers, estuaries and coastal zones. Therefore, it is important to understand the organic matter cycling in estuaries and coastal systems, especially characteristics and dynamics of river DOM and POM. But the DOM and POM is not homogeneous in terms of size or chemical characteristics so that we can't evaluate the linkage of terrestrial and coastal environments. The objective of this study is to understand the transport behavior of dissolved and particulate organic matter from terrestrial region to ocean. This study used carbon isotopic ratios (Δ^<14>C and δ^<13>C values) as tracers of organic carbon because the simultaneous use of these values adds a second dimension to isotopic studies of carbon cycling in surface aquatic environments.Refractory organic materials, humic substances, were isolated from the river waters in Scotland, Ukraine, Japan and Indonesia by the XAD extraction. The Δ^<14>C values of dissolved humic substances ranged from -316‰ to +209‰, indicating spatial and temporal distribution.To understand transport of POM in river systems, we selected three river systems (Tokachi, Ishikari and Kuji River systems) with different watershed conditions and carried out the observation at a fixed point in each river. The Δ^<14>C values range from -111 to -286‰ for the Tokachi River in northeast Hokkaido, -103〜-364‰ for the Ishikari River in southeast Hokkaido and -18.7〜-94.4‰ for the Kuji River in Kanto area in Japan. The paired Δ^<14>C vs. δ^<13>C distributions vary with rivers and seasons. These results suggest that the difference in paired Δ^<14>C vs. δ^<13>C distributions may reflect the water discharge and watershed environments.