黄水河下游地区地下水化学特征及演化规律

Hydrochemical characteristics and evolution mechanisms of the groundwater in the lower reaches of Hangshui river

选取黄水河下游地区为典型研究区,综合水文地质条件等资料,运用数理统计分析、水质图解法、饱和指数计算和反向水文地球化学模拟等方法对该地区地下水水化学组分进行分析,深入了解研究区地下水的水化学特征及演化规律。结果表明:(1)研究区地下水主要为淡水和微咸水,地下水组分中阳离子以Ca^(2+)、Mg^(2+)为主,阴离子以HCO_(3)^(-)和Cl^(-)为主。研究区由东南向西北方向,TDS和Cl浓度均逐渐升高,水质由淡水逐渐向微咸水转化,地下水的优势阴离子类型沿着HCO_(3)·SO_(4)→HCO_(3)→HCO_(3)·Cl→Cl变化。(2)碳酸盐岩、蒸发岩和硅酸盐的风化溶解是本区地下水中主要的水文地球化学过程;还存在正向阳离子交替吸附作用。(3)反向水文地球化学模拟结果进一步定量验证了中上游地下水水化学组分主要受到岩石风化作用的控制。下游地下水主要受到海水入侵的影响,同时在海水入侵的作用下发生了阳离子交换。

The lower reaches of the Huangshui river was selected as a typical study area,and the hydrochemical composition of shallow groundwater in this area was analyzed employing multivariate statistical analysis,Piper three-line diagram,Gibbs diagram,silicate stability field diagram,ion ratio,calculation of water-soluble composition and reverse hydrogeochemical simulation.The results show that:(1)From the southeast to northwest of the study area,the concentrations of TDS and Cl gradually increased,and the water quality changed from freshwater to salt water.The dominant anion types of groundwater were along HCO_(3)→HCO_(3)·Cl→Cl·HCO_(3)→Cl changes.Na^(+) and Ca^(2+) were the major cation in most regions.(2)The weathering and dissolution of carbonate rock,evaporite and aluminosilicate were the main hydrogeochemical processes in the groundwater in this area.Besides,there was the positive cation alternate adsorption.(3)The results of reverse hydrogeochemical simulation quantitatively verified that the chemical composition of groundwater in the upper and middle reaches of Huangshui river was mainly controlled by rock weathering,the groundwater in the lower reaches was mainly affected by seawater intrusion,and cation exchange occurred under the influence of seawater intrusion.