Column experiments with sediments in the Beidagang reservoir for the coastal region of Tianjin were conducted to elucidate the dynamic characteristics of colloid release and salt release or retention of sediments in different positions in the exchange process of saline groundwater and reservoir water, and to discuss the mechanism of colloid release, salt release or retention for different sediments. > Results indicate that the fates of salinity in different locations in the reservoir were different in the exchange process of saline groundwater and reservoir water. Salinity was intercepted by the sediments at the entrance to the reservoir, and released from the sediments and transferred to the water at the reservoir outlet. The cumulative release capacity of colloids from the sediments increased gradually with increasing pore volumes, and the accumulation adsorption curve of colloids conformed to a straight line by the sediments with pore volume; the release rate of the colloids was stable. Hie maximum cumulative release capacity of colloids from the sediments of the entrance, center and outlet of the reservoir were 3.275 mg/g, 0.386 mg/g and 1.382 mg/g respectively. The release or retention of salt from the sediments in the reservoir was related to many factors, such as particle size, colloid content and salt content. The water salinity andsediments in the reservoir were in dynamic equilibrium. When the salinity of the sediments was higher than that of the equilibrium concentration, the salt from the sediments was released into the water. The salt adsorbed by the colloid was released into the water with the release of the colloid. Contrarily, the salt in the water was intercepted by the sediments. The smaller the particle size of the sediment, the easier the salt in the water was adsorbed. The law of colloid release can be explained using this double layer theory.%以天津滨海地区北大港水库为研究对象,采用室内柱试验,研究地下咸水与水库水体交换过程中不同位置沉积物胶体释放以及盐分释放/截留的动态特征,同时对沉积物胶体释放、盐分释放/截留机理进行了探讨.研究结果表明:水库不同位置地下咸水与水库水体交换过程中,盐分的归宿不同:接近水库入口处的沉积物能将盐分截留下来,而出水口沉积物却将盐分释放转移到水体.随孔隙体积数的增加,沉积物胶体累计释放量逐渐增加,入库口、库中心、出库口最大累计释放量分别为3.275 mg/g、0.386 mg/g和1.382 mg/g；胶体累计释放量随孔隙体积数的变化曲线符合直线型,胶体释放速率变化很小.盐分的释放或截留是沉积物颗粒的粒径、胶体含量、含盐量等多种因素作用的结果,水库水体与沉积物中的盐分处于动态平衡状态,当沉积物中含盐量高于平衡浓度时,其盐分会向水体中释放,同时吸附在胶体上的盐分也会随着胶体的释放而释放；反之,水体中的盐分会向沉积物中迁移被截留下来,沉积物粒径越小,越易吸附水中的盐分.胶体的释放规律可以用双电层理论得到很好的解释.
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