貧〜中栄養小規模ダムにおける栄養塩の動態 : 岐阜県岩村ダムの事例

概要

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To clarify the change in water quality caused by impoundment in a small oligotrophic to mesotrophic reservoir, we report monthly data on dissolved components at the Iwamura Dam, Gifu Prefecture, Central Japan, from April 2004 to November 2005. Concentrations of dissolved SiO_2 and NO_3^- in the dam water tended to be 10 to 20% lower than those in the inflow water. Concentrations of PO_4^<3-> in both the inflow and the dam waters were below the detection limit (0.1μmol/l). The degrees of decrease in SiO_2 and NO_3^- concentrations tended to be larger from spring to summer than in other seasons. This seasonal change is attributed to the blooming of phytoplankton, in particular diatom. Concentrations of dissolved Fe and Mn increased in the dam especially in November December, to ten times those in inflow water, reaching 2300 and 1500 nmol/l, respectively. This increase is attributed to the regeneration of Fe and Mn from sediment and/or suspended material in oxygen-deficient bottom water below thermocline.
2007-09-04