柴达木盆地东北部巴音河小流域水化学特征及来源

Hydrochemical Characteristics and Sources of Small Bayin River Watershed in the Northeast of Qaidam Basin,China

水化学特征是流域气候特征与环境的重要指示器,可用于揭示流域内河流、湖泊的补给方式及物质来源。以青藏高原柴达木盆地东北部巴音河小流域为研究对象,分析了巴音河—可鲁克湖—托素湖小流域生态系统的水化学组成,探讨了其主要的离子来源及控制因素。结果表明:水体pH、电导率(EC)及溶解性总固体(TDS)沿流向均呈升高的趋势,巴音河、可鲁克湖及托素湖水化学类型分别为HCO_(3)-Cl^(-)Na-Ca-Mg型/HCO_(3)-Cl^(-)Na-Mg型、HCO_(3)-Cl^(-)Na-Mg型及SO_(4)-Cl^(-)Na-Mg型;托素湖作为封闭的咸水湖,主要受到蒸发浓缩作用的控制,而巴音河、可鲁克湖则受到岩石风化作用、蒸发浓缩作用以及钠盐淋溶作用等的共同控制;受蒸发作用的影响,水体碳酸盐矿物达到饱和状态并发生沉淀,从而导致Ca^(2+)质量浓度沿流向下降;巴音河、可鲁克湖Mg^(2+)/Ca^(2+)摩尔浓度比值较低,推测形成文石、方解石等碳酸盐沉淀,而托素湖Mg^(2+)/Ca^(2+)摩尔浓度比值较高,则可能形成高镁方解石、原白云石等碳酸盐沉淀;研究区水体中Na^(+)、K^(+)、Cl^(-)主要来源于石盐(NaCl)和钾盐(KCl)等蒸发岩的溶解;而Mg^(2+)、SO_(4)^(2-)主要来源于蒸发岩(MgSO_(4))风化;Ca^(2+)及高质量浓度的HCO_(3)^(-)可能来源于碳酸盐矿物的快速溶解,此过程也是水体Mg^(2+)来源之一。

Hydrochemistry characteristics,which are indicators of the regional climate and environment,can reveal recharge mode and material sources of lakes and rivers in the basin.To investigate the hydrochemical characteristics and the sources of major ions of the small Bayin river watersheds in the northeast of Qaidam Basin,Qinghai-Tibet Plateau,the water samples from Bayin river,Hurleg lake,and Tosen lake were collected during May 2021.The results show that pH,EC,and TDS increase along the flow direction;according to the Sukalev classification,the hydrochemical types of Bayin river,Hurleg lake,and Tosen lake are HCO_(3)-Cl^(-)Na-Ca-Mg/HCO_(3)-Cl^(-)Na-Mg,HCO_(3)-Cl^(-)Na-Mg,and SO_(4)-Cl^(-)Na-Mg,respectively;as a typical closed inland brackish lake,water chemistry of Tosen lake is primarily dominated by evaporation-crystallization processes;while Bayin river and Hurleg lake are jointly influenced by weathering,evaporation-crystallization processes,and sodium salt leaching;owing to the enhanced evaporation,carbonate minerals are always the first phase to precipitate,resulting in the decrease of Ca^(2+)mass concentration along the flow direction;the Mg^(2+)/Ca^(2+)molar concentration ratios of Bayin river and Hurleg lake are low,indicating that aragonite or calcite is probably formed;while the Mg^(2+)/Ca^(2+)molar concentration ratio of Tosen lake is high,indicating that high magnesium calcite or protodolomite might be formed;the main sources of Na^(+),K^(+)and Cl^(-)in the water body are the evaporate dissolution such as halite(NaCl)and potash(KCl);moreover,Mg^(2+)and SO_(4)^(2-)are mainly derived from the evaporate(MgSO_(4))weathering;HCO_(3)^(-)with high mass concentration and Ca^(2+)may result from rapid dissolution of carbonate minerals,which is also one of the sources of Mg^(2+).