Colonization of Aquatic Insects and Water Purification of a Pond Using Umbrella Plant (Cyperus alternifolius L. )

摘要

The umbrella plant (Cyperus alternifolius L.) was planted in an eutrophic pond for water purification and restoration of ecosystem. The effluent pH value was reduced to about 7 from 9 by efficiency of shading the light. The plant removed 6 for T-N and 15 for T-P of influent nutrient. Since the number of aquatic insects increased two times in one year, aquatic insects in the pond gradually colonized by planting. The 4.3 growth rate for summer was a second value as compared with that of water hyacinth. The annual mean growth rate of the plant was 1.6. Nevertheless, the plant is suitable for water purification because it doesn't die in winter and could be used in all seasons. The plant was planted in the developed pot with emerging and floating culture system and harvested at 60cm high from the surface of the pond water. We found this was the most efficient method of nutrient removal. The nutrient removal rates were 0.363g· m~(-2)·d~(-1) for T-N and 0.089g·m~(-2)·d~(-1) for T-P.