北大港水库水-土界面盐分释放规律

Law of Salt Release at Soil-water Interface in Beidagang Reservoir

为了研究天津北大港水库水质咸化机理,采用野外取样与室内土柱试验相结合的方法,研究了北大港水库蓄水时底质与上覆水体之间盐分的释放规律。结果表明:底质向上覆水体释放盐分时水体中存在一个明显的盐分渐变区(扩散边界层),该层位于水-土界面以上10cm的范围,底质中释放出的盐分有60%集中在边界层,边界层以上水体盐分垂直变化较小;底质中盐分的累积释放量随时间的变化符合对数函数形式,试验运行前50天中盐分累积释放量占底质盐分总释放量的80%左右;水-土界面处盐分释放通量的变化趋势存在周期性,每个周期内均呈现先迅速增加后缓慢下降。

In order to investigate the water salinization mechanism in Beidagang reservoir of Tianjin,field sampling method and laboratory column experiment were conducted to examine the rule of salt release between the bed sediment and overlying water body under reservoir filling.The results showed that（1）a salinity variation zone（diffusion boundary layer）exists in the water body of 10cm above the sediment and water interface when salt is released from bed sediment.About 60%of the total released salt accumulates in the diffusion boundary layer,and the vertical variation of water salinity is insignificant above the diffusion boundary layer;（2）the accumulative amount of salt released from the bed sediment conforms to the form of logarithmic function with time,and the accumulative amount of released salt in the first 50days of the experiment can reach 80%of the total amount;and（3）the variation of salt flux at the sediment and water interface shows periodic characteristics with a rapidly initial increasing and then a slow decline within each period.