The effect of population density of waterhyacinth on the growth and the absorption of nitrate nitrogen was studied under natural condition.
The effect of population density on waterhyacinth growth could be showed by logistic equation. Based on logistic growth equation, the following linear relation between the reciplocal after growing (1/S) and initial population density (1/S₀) of waterhyacinth was derived by Shinozuka (1956) and found to satisfy the experimental results at any stage of growth of waterhyacinth,
1/S=A+B1/S
in which A and B are the constants whose values depend on time, t. The growth rate of waterhyacinth was found to be directly proportional to the absorption rate of nitrate nitrogen. Therefore the absorption rate of nitrate nitrogen by waterhyacinth was found to be approximatly showed by logistic equation.
In order to remove 1 gram of nitrate nitrogen, 300-400grams of waterhyacinth might be produced from solar energy in water.

抄録全体を表示

広島湾内の4地点でセディメント・トラップを用いて毎月水中懸濁物を捕集し,捕集物の組成や捕集量の変化について調査し,水中懸濁物の底泥への堆積速度の推定や1次生産量との比較を行った。
1) 表層におけるトラップ捕集物の有機物濃度は,広島湾の水質環境が最も悪化する夏期(6～8月)において最大となるが,トラップ捕集量は夏期に少く秋期(9～10月)に集中して増大する。
2) 捕集量の集中する秋期の懸濁物は,色素濃度に対する有機炭素の組成比が20～40で植物プランクトンの組成比とほぼ同じであることから1次生産起源の有機物であると考えられる。
3) 捕集量から推定した懸濁物の見掛け上の沈降速度は,概ね0.5m/日以下であるが,10月には4～6m/日となり,水中懸濁物の沈降が主として海水の上下混合に支配されて生じていることが認められた。
4) 表層における捕集物の組成や捕集量と1次生産量との比較から,広島湾における捕集物のほとんどが,1次生産起源のものと考えられるので,下層でのトラップ捕集物の全量が1次生産起源のものと仮定して懸濁物の物質収支を求めると,生産された水中懸濁物の約6～8割が水中での沈降過程において分解されるものと推定される。
5) 水中懸濁物の底泥への堆積速度は乾重量では沖合の方が大きいが,有機物量で比較すると沿岸も沖合もほぼ一定で,TOC,TON,T-Pで,おのおの100,14,3g/m²/yrであった。

抄録全体を表示

The characteristics of phosphorus uptake and growth were studied in cultures of water hyacinth [Eichhornia crassipes (Mart.) Solms] growing outdoors in continuously flowing nutrient solutions.
Specific growth rate of about 0.02-0.13 (1/day) was determined, which was affected significantly by mean air temperature. The maximum rate of phosphorus removal was about 164mg-P/m²/day in the summer experiment. The relationship between specific uptake rate of phosphorus and phosphate concentration in culture container offered the analogy of a Langmuir adsorption isotherm. Phosphorus contents of tops and roots of water hyacinth on a dry weight basis were 0.20-1.20(%) and 0.17-0.76(%) respectively. Phosphorus content of whole plant was related to external phosphate concentration with a hyperbolic form.

抄録全体を表示