Element analysis on Change and origin of streamwater chemistry

水流线中径流组分的分离是水文学研究的最终目标之一。从水化学的角度看，这相当于评价河水中所含物质的来源。对于来自森林流域的径流，内部元素循环参与决定了河流的化学性质。为了证实元素循环与河流水化学之间的联系，在筑波实验森林中，除了对河流水和土壤水化学进行实验外，还对森林土壤中的元素含量进行了检测。证明在森林长期形成过程中，由于系统内循环，氮、钙等营养物质在表层土壤中大量积累，与此相反，与元素循环无关的物质在表层土壤中由于有机物的混合而减少。土壤中这些元素的含量决定了单个溶质浓度不同的土壤水化学性质，土壤水淋滤使暴雨径流退潮期的径流发生了ⅰ型和ⅱ型两种化学变化。结果表明，森林生态系统的元素循环在土壤水淋滤测定径流化学中起着重要作用。

Separation of the runoff components in hydrograph is one of the final targets in the hydrological science. From the hydrochemical point of view, this is equivalent to evaluating the origin of the materials involved in the river water. Regarding the runoff from the forested basin, the inner element cycle participates in determining the streamwater chemistry.To substantiate the link between the element cycle and the streamwater chemistry, the element content in the forest soil was examined in the Tsukuba Experimental forest, in addition to the experiments for the streamwater and soilwater chemistries. It proves that such nutrients as nitrogen and calcium are highly accumulated in the surface soil due to the recycle within the intrasystem during the long formative process of the forest, contrary to this, the materials nonrelated to the element cycle become lowered in the surface soil due to blending the organic substances. These element contents in soil make out the soilwater chemistry containing the different concentration in the individual solute, and the soilwater leaching gives to the chemical changes of the streamwater in two ways of Type I and Type II during the recession period of the storm runoff. It is concluded that the element cycle in the forest ecosystem plays a prominent role in the determination of the streamwater chemistry by the soilwater leaching.