底泥盐分释放对北塘水库水质成化的影响

为研究南水北调通水后,水源改变及水库调度对底泥盐分释放的影响,2005年7月,取0～60cm深度的北塘水库原状底泥样品,在实验室内模拟分析不同底泥含盐量、不同蓄水水质及水位变动和扰动条件下底泥氯化物释放规律。结果表明,底泥中Cl~-含量为0.043%,释放强度为0.12g/m~2·d,Cl~-含量越高,释放强度越大。在底泥含盐量相同的条件下,蓄去离子水的底泥Cl~-释放强度是蓄水库水的1.87倍。扰动状态下,底泥中的Cl~-有5.0%～9.5%释放出来,高于静止状态的3.2%～5.6%。水库运行水位发生变化,将影响底泥盐分的释放。1.0m水深条件下Cl~-的释放量是1.5m水深的5.8倍。水库四周地下水中Cl~-浓度为8.0×10~3～4.2×10~4mg/L,远高于目前水库水的Cl~-浓度。因此,一定要避免水库在低于设计低水位和周边地下水水位的条件下运行,防止底泥盐分释放及地下水反向补给造成水库水质的成化。

Effect of Salt Release from Sediment on Water Quality of Beitang Reservoir

To determine the effect of water storage and operation on salt release from sediment of Beitang Reservoir after water transfer project,experiment was conducted in PVC pipe loaded in original sediments of 60cm to analyze rule of Cl~- release from sediment in different salt contents,storage water quality and water level.Results showed that release intensity of Cl~- was consistent with the content in sediment.When Cl~- was 0.043% in sediment,release intensity was 0.12g/ m~2/d.In the same content condition,the release intensity in PVC pipe filled with deionized water was 1.87times with reservoir water.There was 5.0% to 9.5% of Cl~- released from sediment in disturbance,which was higher than 3.2% to 5.6% of release rate in static condition. Variation of water level also affected Cl~- release.In the PVC pipe with 1.0m depth of water,the release of Cl~- was 5.8 times in pipe with 1.5m depth of water.Concentration of Cl~- in groundwater around Beitang Reservoir were 8.0×10~3～4.2×10~4mg/L,which was far higher than Cl~- in the water.It was important to run the Reservoir with water level above lowest designed level and above ground water level surrounding to keep a press to reduce Cl~- release from sediment and prevent ground water supply.