大苏干湖湖水蒸发过程中析盐规律及pH值变化

The Salt Precipitation Sequence and Variation of pH Values during the Evaporation Process of Dasugan Lakewater

中文关键词:  大苏干湖  微咸水  蒸发实验  析盐规律  pH值

英文关键词:Dasugan lake  Brackish water  Evaporation experiment  Salt evolution law  pH

中文摘要:

      卤水蒸发实验多集中在矿化度较高的后期阶段的盐湖,其矿物主要为氯化物及镁的硫酸盐。为了获得碳酸盐—硫酸盐—氯化物整个盐湖演化阶段的析盐及pH值变化规律,使用大苏干湖微咸水(矿化度为26.5 g/L)在28±2 ℃的恒温室内进行蒸发实验。结果表明,在整个蒸发过程矿物结晶析出顺序为单水方解石—石盐—三水碳酸镁—白钠镁矾—泻利盐—六水泻盐—碳酸钠矾,共有七组盐类析出序列,不同于其它硫酸钠亚型的盐湖蒸发沉积规律,大苏干湖微咸水蒸发沉积过程中未见芒硝析出,可能与其特殊的水化学组成有关；pH值由8.82持续降低到6.29。其pH值的变化主要受控于矿物相的析出,在碳酸盐析出过程中pH由8.79迅速降低到7.38,而后以白钠镁矾为主的硫酸盐析出阶段pH降低到6.65,之后在石盐析出阶段pH缓慢降低到6.29。通过微咸水湖的蒸发实验,对于盐湖演化过程中的结晶析盐规律及各析盐阶段的pH值变化规律有了更加全面的认识。

英文摘要:

      Previously reported evaporation experiments of salt lake brine focused on the later period of brine evolution,and the minerals were mainly chloride and magnesium sulfate salts.In order to obtain the regularity of salt precipitation sequence and pH value variation in the whole salt lake evolution stage,the evaporation experiment of brackish water was carried out in a constant temperature chamber at (28±2) ℃.Dasugan lake belongs to the brackish lake(the salinity is 26.5 g/L).During the entire evaporation process,the sequence of mineral precipitation is calcite monohydrate,halite,carborundum trihydrate,astrakhanite,epsomite and sodium carbonate.There are seven groups of salt precipitation sequences,which is different from the evaporation and crystallization rules of other sodium sulfate subtypes.There is no mirabilite precipitation during the evaporation of brackish water in Dasugan lake.It may be due to its special hydrochemical compositions.And the pH values decrease from 8.82 to 6.29 continually.The variation of pH values is mainly controlled by the precipitation of mineral phase.The pH values rapidly decrease from 8.79 to 7.38 during the process of carbonate precipitation,and then the pH values continue to decrease to 6.65 at the sulfate precipitation which is mainly composed of astrakhanite.During the halite precipitation stage,the pH values slowly decrease to 6.29.According to the evaporation experiment of the brackish water lake,it is benefit to get more comprehensive understanding of the law of salt precipitation,brine evolution,and pH variation in each salt precipitation stage during the evaporation and concentration process of the salt lakes.