EFFECT OF AQUATIC PLANTS ON WATER QUALITIES IN SMALL CLOSED WATERS

摘要

Water quality purification by use of an aquatic plant is proposed in a closed water body. In order to make use of the method in a water body with floating aquatic plants, we have to transport the nutritive salt from the bottom to the surface of the water. In this study, a field observation was conducted in order to consider the effects of the abundance of aquatic plants on the water quality and water flow in a small water body, such as an agricultural pond. As the results, it is reveals that the fluid exchange was performed by thermal convection between the area with and without an abundance of vegetation at nighttime. Then, though the nutrients decreased due to the absorption and adsorption from the vegetation during the flowering period in the summer, these nutrients increased in reversal due to the elution from the bottom of water body after the vegetation decayed in the winter. From the above results, it can be concluded that aquatic plants should be adequately controlled to exert its effect sufficiently on the eutrophied water body.