QUANTITATIVE EVALUATION OF WATER PURIFICATION ABILITY IN AN AQUATIC PLANT

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In this study, two experiments in a water culture inhibiting the nitrification and denitrification were conducted to evaluate the ability of nitrogen and phosphorus absorption by Zizania latifolia from May to December in 2001 and 2002 (32 weeks). The results were as follows : The wet weight, the amount of water absorption, the amounts of Total Inorganic Nitrogen (TIN) and phosphorus (PO4-P) absorption by Zizania latifolia increased along with growth of Zizania latifolia. The maximum wet weight was taken in October (636g) or September (562g). The maximum dry weight was taken in October, 2002 (78.5g) and the amount of the whole experimental period (2001) of water absorption was 74.5kg. The maximum amount of TIN and PO4-P absorption of Zizania latifolia were taken in September, which value were 629mg・4weeks-1 and 133mg・4weeks-1, respectively. The amounts of the whole experimental period of TIN and PO4-P absorption were 3150mg and 631mg, respectively. Finally, the results showed that 5.4mg … More of TIN and 1.1mg of PO4-P were required for Zizania latifolia to grow 1g of wet weight. In 2002, The N and P content of a Zizania latifolia was increased from May to October, and the maximum values taken were about 2080mg and about 400mg, respectively. The N and P mass balance of the content of Zizania latifolia and the amount of removal from the culture solution from May to October (except September) was evaluated as 70%〜110%.In this study, an experiment was conducted to evaluate the ability of accumulation of nutrients and metals by Zizania latifolia. The results are as follows : It became clear the distribution of elements inside the body change with the season and the variation of the elements. The amounts of fixed elements in a Zizania latifolia were evaluated, and the maximum values of the C, N, P, K, Mg, Ca, Mn, Fe, and B content in a Zizania latifolia were 28690mg, 1756mg, 354mg, 954mg, 204mg, 149mg, 37.3mg, 15.9mg and 4.5mg, respectively.The following facts became clear through the experiments conducted in 2001, 2002, 2003 and 2004. The amount N and P absorption of Zizania latifolia was increased significantly in the early growth stage (from May to Jul.) and the maximum value of them was taken in September, the values were 680mg and 154mg, respectively. The amount of N and P absorption per wet weight of Zizania latifolia were changed from 15mg/g, 2.7mg/g (in May) to 0.03mg/g, 0.01mg/g (in Jan.), respectively. The amount of N and P absorption for whole year was calculated as about 3,600mg and 720mg, respectively. Less