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application/pdf, It is the purpose of this paper to assess the nitrogen load caused by yellowtail culture to the environment. The nitrogen load could be estimated on the basis of nitrogen budget, using the data concerning growth rate, food supply rate and kind of food. The fundamental equation of nitrogen budget may be represented as follows: Fn=Ln+In, In=Gn+Pn+Un, where F is the rate of food supply, L the rate of food loss in the time of supply, I the reate of food intake, G the rate of store in body, P the rate of fecal pellet excretion, and U the rate of urine et al. excretion. Suffix N indicates nitrogen. Total nitrogen load, to which the urine et al. contributed largely, was highest in September and lowest in January, showing a fairy large seasonal variation. 0-year-old and 1-year-old yellowtail were assessed to give the total nitrogen loads of 0.28 and 1.5 g/day. kg, respectively, in September, and 0.15 and 0.29 g/day. kg, respectively, in January., 養殖技術・管理などが比較的良好な養殖場を対象にして, 成長速度, 飼料給与速度, 飼料の種類, 水温に関する現場飼料を使用し, 窒素収支法により, ハマチ養殖における窒素負荷速度を推算した. 総窒素負荷速度は季節, 場所によってかなり変る. 単位体重当りでは, 0才魚でもっとも大きいのは6月で平均2.8g/day.kg, 小さいのは1月で平均0.15g/day.kgであった. 同様に, 1才魚でもっとも大きいのは7?9月で平均1.5g/day.kg,小さいのは1月で平均0.29g/day.kgであった. 総窒素負荷速度に対する尿などによる窒素負荷速度の割合がもっとも大きく(0才魚:64?89%, 1才魚:86?88%), 次いで給与時の逸散による窒素負荷速度の割合(0才魚:8?30%, 1才魚:7?8%), 糞による窒素負荷速度の割合はもとも小さかった(0才魚:4?7%, 1才魚:5?6%).

application/pdf, In Ichinotani estuary, into which the polluted water of 17.1 × 10 3 ？/day in discharge and 350 kg/day in COD load flowed, the rate of COD removal was estimated by the use of observed data concerning water temperature, chlorinity, COD, and water inflow on the basis of the two-layer box model. The area and volume of estuary were 277 × 10 3 ？ and 1160 × 10 3 ？, respectively. The rate of COD removal was 3.0g/sec as a whol. On the other hand, the rate of COD decay in estuary was also estimated at about 1.7g/sec on the basis of the results of laboratory experiments on COD decay of the polluted water flowing directly into the estuary. Accordingly, the percentage of the rate of COD decay to the rate of COD removal amounted approximately to 57%., 一ノ谷川河口域に, 2層構造のボックス・モデルを適用して, 水温, 塩素量, COD, 流入量から河口域におけるCOD除去速度を推算した. 調査当日, 一ノ谷川河口へのCOD総負荷量は約350kg/day,流入量は17.1 × 10 3 ？/dayであった. また, CODの減衰に関する実験データから河口におけるCOD減衰速度を見積った. ボックス1(上流側ボックス, 容積40 x 10 3 ？, 水面積44 x 10 3 ？)およびボックス2(下流側ボックス, 容積1120 x 10 3 ？, 水面積233 x 10 3 ？)において, COD除去速度は, それぞれ, 1.4g/sec, 1.6g/sec, COD減衰速度は, それぞれ0.7g/sec, 1.0g/secという結果を得た. したがって, COD除去速度に対するCOD減衰速度の割合はボックス1で50%, ボックス2で63%ということになる.