滨海水库沉积物盐分释放水化学特征变化

Variations in hydrochemical during the process of sediment salt release in coastal reservoirs

以北大港水库为研究区,通过野外实地采样和批试验相结合的方法,对滨海水库库水和沉积物混合后盐分和各主要离子指标的变化规律进行分析,探究库水和沉积物之间的水文地球化学作用,揭示水库咸化机理。结果表明:库水和沉积物在混合条件下,沉积物中的盐分会释放到库水中,各水化学指标能够快速地达到平衡;各采样点溶解性总固体(TDS)均先快速增加,而后盐分释放达到平衡,平衡后TDS释放量整体呈现出水库下游采样点>水库上游采样点的规律;Na+和Cl-是库水和沉积物水文地球化学作用过程中发生变化的主要离子,Na^(+)、Cl^(-)最大释放量分别为7597.25 mg/kg和11097.00 mg/kg。在库水和沉积物相互作用中各采样点的Na^(+)、K^(+)、Mg^(2+)、Ca^(2+)和SO_(4)^(2-)发生着不同程度的增加或减少,Cl^(-)均有所升高,HCO_(3)^(-)略有降低;除HCO_(3)^(-)和Ca^(2+)外,其他离子的变化均呈现水库下游采样点>水库上游采样点的规律。

Completion of the Binhai Reservoir may experience serious salinization or sudden brackishness,thus affecting the normal water supply function.The research on reservoir water salinization mainly focuses on total salinity,chloride ion,or other single indicators,but the release of sediment salt is a complex process.In fact,during the hydrogeochemical process of sediments and reservoir water,various ions may change to different degrees,and the changes of ions will affect the TDS content,which in turn affects the salinity content of the reservoir water.Therefore,the research on the regularity of salt release also needs to carry out a full analysis of ion indicators,to provide theoretical support for the hydrogeochemical interactions between sediments and reservoir water.Taking Beidagang Reservoir as the research area,through the method of combining field sampling and batch experiment,the change law of salinity and main ion indexes after the mixing of coastal reservoir water and sediment is analyzed to explore reservoir water and sediment.The hydrogeochemical interaction between the objects reveal the mechanism of reservoir salinization.Illation condition of reservoir water and sediment,the water chemical indexes can quickly reach equilibrium.The TDS mass concentration of each sampling point increased rapidly at first,and the salt release reached equilibrium after 30 s.Na^(+)and Cl^(-)were the main ions involved in water-rock interaction;the maximum release amounts of Na+and Cl^(-)were 7597.25 mg/kg,11097.00 mg/kg.The Na^(+),K^(+),Mg^(2+),Ca^(2+),SO_(4)^(2-)of each sampling point increased or decreased in different degrees in the sediment-reservoir water interaction.Cl^(-)was increased,HCO_(3)^(-)decreased slightly.Except for HCO_(3)^(-)and Ca^(2+),the changes of other ions showed the rule of sampling points in the downstream of the reservoir>sampling points in the upstream of the reservoir.During the hydrogeochemical process of sediment-reservoir water,the total salt in the sediment was released,and the changes of each ion in the process of salt release were related to the mass concentration difference of each ion in the sediment and the reservoir water.After mixing with the reservoir water,it will be released into the water,and the ions with very low content in the sediment will be adsorbed into the sediment after mixing with the reservoir water,resulting in the reduction of the ion content in the reservoir water.It can be seen from the experiment that the release of salt from sediments can lead to an increase in the salinity of the reservoir water,resulting in the salinization of the reservoir.In the process of salinization of the reservoir water,Na^(+),and Cl^(-)are the main ions involved in water-rock interaction.The change in salinity showed the rule of sampling points downstream of the reservoir>sampling points upstream of the reservoir.