Studies on Mitigation of Shallow water Pollution by Organic Deposits in Semi-closed Bay

浅水污染是由于养殖鱼类所需的有机物质的运输或沉积造成的。事实上，在半封闭海湾，底部沉积物的熵化趋势是显著的。近年来，养鱼用水环境恶化问题日益严重。本野外研究在北田半封闭海湾进行了如下考察：2.检查海湾的水质和底部沉积物。3.海湾地形；3 .潮汐和风浪观测；5.海湾利用信息研究；6.海底沉积物耗氧实验；7.海底沉积物有机质含量分析。8.沉积物物理试验实地考察底栖生物等。研究结果证明：1。夏季水质的恶化主要是由于水体浑浊和淡水的作用导致水温密度的上升，而DO的外流对密度流的影响、鱼类的增加、有效波的交换水的减少、底栖动物的死亡、海湾层的影响和鱼类养殖的拥挤等因素又加速了水温密度的上升。2. 鱼用湿丸和干丸有效地改善了水质。3. 有机质在短时间内与底沉积物耗氧量无关。因此，有必要通过Eh测量来检测底沉积状况。4. Eh与短周期耗氧量有关。BOD和Eh都是耗氧量的一个特征。5. 在初始阶段，底沉积氧化还原条件发生较快，Eh指数随之上升。6. 与12年前的结果相比，有机污染扩散到整个北田半封闭海湾地区。7. 仅西北方向风的波浪在海湾流中受到有效影响。8. 潮汐力的递减效应有利于海湾水的交换。9. 因此，有必要在海水交换后将海水的DO保持在4ppm以上，并且底部沉积物的Eh必须保持在-150 mv以上。少

The shallow water pollution has been caused by the transport or deposits of organic materials for breeding fish. In fact, the trend of entrophication by the bottom deposits is remarkable in semiclosed bay. The superannuation of water circumstance for fish culture has become serious recently. This field study has been examined in Kitanada semi-closed bay as following: 1. Examinations of water qualities and bottom deposits in the bay, 2. Bay topography, 3. Observation of tide and wind wave, 4. Information research for utilization of the bay, 5. Experiments on consumed oxygen by bottom deposit, 6. Analysis of bottom deposits for organic matter content, 7. Physical test of sediments and 8. Field research of benthos et al.The results of studies has been proved that: 1. Getting worse of water qualities in summer are caused by the encouraged temperature densitocline by muddiness and by fresh water, which are accelerated by an phenomenon of DO flowout on density current, an increasing of fish … More food, decrease of exchange water on effective wave, death of benthos, influence of the bay lay and crowded fish culture. 2. Moist-pellets and dry-pellets for fish have made the effective improvement of water qualities. 3. Organic matters are not related to the consumed oxygen of bottom deposit during short period. Therefore, it is necessary to examine about the condition of bottom deposit by Eh measurement. 4. Eh has been related to the consumed oxygen of short period. Both BOD and Eh are to be a characteristic about the consumed oxygen together. 5. At the incipient stage, reducing condition of bottom deposit oxidation take place fairly fast, and then the Eh indexing go up too. 6. As compared with the results 12 years ago, the organic pollution spreaded out the whole area of Kitanada semi-closed bay. 7. The wave from NW direction wind only has been influenced in the bay current effectively. 8. The decreasing effects depended on tidal forces are useful to exchange of the bay water. 9. Consequently, it is necessary that the sea water's DO have to be kept over 4 ppm after sea water exchange, and that bottom deposit's Eh have to be kept over -150 mv. Less