摘要
弱透水层对含水层水质具有重要的影响,识别弱透水层孔隙水的水文地球化学成因对揭示含水层中元素的来源有重要意义。以长江中游江汉平原沉湖地区为研究区,根据沉积物粒度,将研究区48个沉积物样品划分为25个粉质黏性土和23个粉砂土(分别属于弱透水层透镜体和孔隙潜水含水岩组),通过对沉积物孔隙水中K^(+)、Na^(+)、Ca^(2+)、Mg^(2+)、HCO_(3)^(-)、SO_(4)^(2)、Cl^(-)、TFe、TMn等含量和pH值、ORP进行测试分析,利用Gibbs图、相关性分析、离子比值分析等方法对沉湖地区黏性土弱透水层孔隙水的水文地球化学成因进行了研究。结果表明:(1)沉湖地区弱透水层孔隙水的水化学类型为Ca-SO_(4)型(0~3 m)和Ca-HCO3型(>3 m),pH值的变化范围为6.90~8.65,ORP的变化范围为-106~317 mV;(2)黏性土孔隙水的水化学成分主要受矿物溶解、阳离子交换等的影响,影响黏性土孔隙水水化学组成的矿物种类包括方解石、白云石、含钙镁硅酸盐矿物等,黏性土孔隙水明显受到阳离子交换作用的影响,而粉砂土孔隙水中该作用不明显;(3)黏性土孔隙水中TFe(平均值为0.74 mg/L)和TMn(平均值为0.55 mg/L)均超过了饮用水质量标准,超标率分别为44%和84%,与孔隙水的碱性还原赋存环境、地层富含铁锰结核有关。本研究识别了沉湖地区弱透水层孔隙水水化学成分受矿物溶解和阳离子交换作用等过程的影响,为区域地下水成因和水质演化提供了新认识。
Aquitard has an important effect on the quality of groundwater.It is of great significance to identify the hydrogeochemical origin of pore water in aquitard for revealing the source of elements in groundwater.Taking Chenhu Lake area in Jianghan plain in middle Yangtze River as the study area,according to sediment particle size,this study divides the 48 sediments in the study area into 25 silty clay and 23 sandy sediment,and tests the content of K^(+)、Na^(+)、Ca^(2+)、Mg^(2+)、HCO_(3)^(-)、SO_(4)^(2)、Cl^(-),TFe and TMn,etc,and pH,ORP in the pore water.Then the study explores the hydrogeochemical process through the Gibbs figure,correlation analysis and ion ratio analysis and other methods.The results are as follows:(1)The chemical types of pore water in aquitard of Chenhu area are Ca-SO_(4) type(0-3 m)and Ca-HCO3 type(>3 m),the pH is 6.90-8.65,and the ORP range is-106 to 317 mV.(2)The chemical composition of clayey pore water is mainly affected by mineral dissolution and cation exchange.The mineral types that affect the chemical composition of pore water include calcite,dolomite,calcium and magnesium silicate minerals,etc.The pore water of clayey aquitard is obviously affected by cation exchange,but that of pore water of silt is not obvious.(3)The Fe(~0.74 mg/L)and Mn(~0.55 mg/L)in the pore water of clay exceed the quality standard of drinking water,and the exceeding rates are 44%and 84%,respectively,which are related to the alkaline reduction environment of pore water and the rich Fe-Mn nodules in the stratum in the study area.The study identifies the influence of mineral dissolution and ion exchange on the pore water hydrochemical components of aquitard in Chenhu lake area,and provides new understanding for the origin of groundwater and the evolution of water quality.
作者
刘欣
马腾
张刘梦
刘锐
吴心宇
杜尧
LIU Xin;MA Teng;ZHANG Liumeng;LIU Rui;WU Xinyu;DU Yao(School of Environmental Studies,China University of Geosciences(Wuhan),Wuhan 430078,China)
出处
《安全与环境工程》
CAS
CSCD
北大核心
2021年第3期61-70,共10页
Safety and Environmental Engineering
基金
国家自然科学基金项目(41630318)。
关键词
弱透水层
孔隙水
水化学特征
水文地球化学成因
沉湖地区
aquitard
pore water
hydrochemical characteristic
hydrogeochemical origin
Chenhu Lake area
