WATER QUALITY RESTORATION IN LAKES AND RESERVOIRS USING NATURAL ENERGY

富营养化湖泊和水库中常见的溶解氧（DO）耗竭会破坏天然底栖生物，并增加沉积物中营养盐的释放。作为解决这些问题的对策，提出了将含有大量DO的地表水注入DO经常耗尽的底层的方法。通过在面积为100 m^2的围隔系统和面积为15000 m^2、最大水深为5 m的水库中进行的野外试验，研究了连续或间歇注入地表水后水体的水质恢复情况。通过室内试验研究了该系统对沉积物质量的恢复效果，结果表明，即使在溶解氧（DO）被沉积物需氧量（SOD）消耗的情况下，该系统仍能抑制沉积物中营养盐和溶解态金属的释放。实验室实验结果还显示，手术后测得的SOD值小于手术前测得的值。这可能是由于2000年夏季表层水的持续注入促进了沉积物中有机质溶解氧的持续消耗。实验和观测结果表明，该系统是一种很有前途的封闭水域水沙质量恢复方法。

Dissolved oxygen (DO) depletion, which is usually observed in eutrophic lakes and reservoirs, damages natural benthic organisms and enhances nutrient release from the sediment. As a countermeasure aganist these problems, a method which injects surface water including a large amount of DO into the bottom layer, in which DO is often depleted, was proposed. In this study, the water quality restoration in case of continuous or intermittently injection of surface water into hypolimnion was investigated by field experiments performed in an enclosure system which is 100m^2 in area, and in a reservoir which is 15000m^2 in area and 5m in maximum depth. Furthermore, the effect of this system on sediment quality restoration was also investigated by a laboratory experiment.Field experimental results revealed that this system suppressed nutrient and dissolved metals release from the sediment even when DO was depleted by sediment oxygen demand (SOD). Laboratory experimental results also revealed that SOD measured after the procedure had smaller values than those measured before the procedure. This might be due to the continuous DO consumption of organinc materials in the sediment during summer in 2000, promoted by continuous injection of surface water. The experimental and observational results indicate that this system is a promising method to restore water and sediment qualities in enclosed water areas.