乌苏里江流域左岸地下水水化学特征成因解析

Analysis of Hydrochemical Characteristics and Genesis of Groundwater on the Left Bank of Wusuli River Basin

为明晰三江平原水环境特征,以乌苏里江流域左岸地下水为研究对象,通过对44组地下水样品进行水化学组分测试及水化学特征分析,探讨氧化还原条件对地下水水化学组分的控制作用,并利用反向水文地球化学模型解释地下水水化学组分的变化规律。结果表明:(1)乌苏里江流域左岸地下水呈弱酸性,浅层地下水阴离子以HCO3型、Cl-HCO3型和Cl-SO4型为主,阳离子以Ca-Mg型、Ca-Mg-Na型和Ca-Na型为主,而深层地下水阴离子以HCO3型为主,阳离子以Ca-Mg型为主;(2)地下水离子组成受岩石风化过程和大气降水因素的影响,浅层地下水中Na^(+)主要来源于岩盐的溶解,深层地下水中Na^(+)主要来源于钠长石的风化溶解,地下水中发生了阳离子交换作用,主要为Ca^(2+)和Mg^(2+)置换Na^(+)进入地下水中;(3)地下水处于弱氧化或还原环境,pH值与Eh值共同控制着氧化还原环境,反硝化作用显著;(4)水文地球化学模拟结果显示,浅层地下水中氧化-还原反应显著,地下水处于弱氧化环境时,水中铁锰矿物主要以游离态Fe^(2+)、Mn^(^(2+))存在,深层地下水处于较稳定的弱氧化-还原环境中,Eh值是控制地下水中Fe、Mn含量的主要因素。该研究结果可为三江平原东部乌苏里江流域左岸区域水土环境利用与保护、农业商品粮基地可持续发展提供依据。

In order to clarify the characteristics of water environment in Sanjiang Plain,this paper takes groundwater on the left bank of Wusuli River Basin as the research object,and tests and analyzes 44 groups of samples to explore the control effect of redox conditions on the hydrochemical composition of groundwater,and explains the change law by the reverse hydrogeochemical model.The results are as follows:(1)The groundwater of Wusuli River is weakly acidic,the anions in shallow groundwater are mainly HCO3,Cl-HCO3 and Cl-SO4,and the cations are mainly Ca-Mg,Ca-Mg-Na and Ca-Na;the anions in deep groundwater are mainly HCO3,and the cations are mainly Ca-Mg.(2)The ion composition of groundwater is affected by the weathering process of rocks and atmospheric precipitation.The Na^(+)in shallow groundwater mainly comes from the dissolution of rock salt,and the Na^(+)in deep groundwater mainly comes from the weathering dissolution of albite.The cation exchange occurs,mainly for the replacement of Na^(+)by Ca^(2+)and Mg^(2+).(3)Groundwater is in weak oxidation or reduction environment,Eh value and pH value jointly control the oxidation-reduction environment,and denitrification is significant.(4)Hydrogeochemical simulation results show that the oxidation and reduction reactions are significant in shallow groundwater.When the groundwater is in a weak oxidation environment,iron and manganese minerals in water mainly exist as free Fe^(2+)and Mn^(2+).Deep groundwater is in a relatively stable weak oxidation-reduction environment,and the change of Eh mainly causes the change of Fe and Mn contents.The results can provide basis for the research of the left bank of Wusuli River Basin,in the east of Sanjiang Plain,such as utilization and protection of water and soil environment,and the sustainable development of agricultural commodity grain gathering area.