クリーク

The activity of some creek water plants on water purification was studied. Five water plants collected for the experiment are locally called, hoteiaoi (Eichhornia crassipes), yoshi (Phragmites cornmunis), hishi (Trapa natans L.var. bispinosa), ukikusa (Spirodela polyrhi2a), suzumenohie (Paspalum Thunbergii). Additionally, anacalis originated outside of Japan was studied for comparison. The items of measured water quality were, water temperature, DO, EC, pH and NO3. Hoteiaoi was most effective on absorbing nitrate oxygen. But when this plant densely populated, the leaves impede the photosynthesis of botanical plankton and resulted in the decrease of DO. Yoshi was effective on decreasing EC. This plant can be alive up to early winter. The long life characteristic of this plant helps to purify the creek water. Hishi was most weak plant for the temperature decrease. During the experiment, started on the beginning of October and ended late December, no effective activities on X water purification were observed. Ukikusa covers creek water surface with small and thin leaves but they don't so much impede the light penetration. This plant was not effective on nutrition'absorption because of the small mass of leaves. Suzumenohie has small blade of leaves resembles to yoshi but the size are one tenth of the leaves of yoshi. The characteristic feature of this plant on water purification was almost the same with yoshi. Anacalis showed most effective activity on the DO increase. This plant is effective for creek water purification but ecological studies would be necessary because this plant is not originated in Japan.