本文以北京市平原区永定河冲洪积扇地下水化学场的演化机理及地下水水循环规律为研究目的,根据水化学特征的水平分布及典型剖面上的演化过程研究,得到以下结论:1)从永定河冲洪积扇顶部补给区到扇缘排泄区,地下水水化学类型呈现水平分带性,潜水水化学类型由Ca-HCO3过渡到Ca·Mg-HCO3、Mg·Na-SO4,局部因人类活动影响出现Ca·Na-HCO3·SO4、Na·Ca-CI或Ca·Mg-SO4型水;中深层承压水水化学类型由Ca·Mg·Na-HCO3或Ca·Na-HCO3过渡到Na-HCO3或Na-HCO3·SO4.2)永定河冲洪积扇上不同深度的地下水化学场受到了水岩相互作用影响,从冲洪积扇顶端到冲积扇扇缘的径流过程中主要发生了硫酸盐、硅酸盐和碳酸盐的溶滤作用和Na-Mg和Na-Ca离子交换作用.3)地下水流速从扇顶补给区向扇缘排泄区逐渐减小,硅酸盐、碳酸盐、硫酸盐和岩盐的水岩相互作用强度逐渐增强,地下水更新速度减慢.%This study intends to find out the evolutionary mechanism of groundwater geochemical field and groundwater cycle in the Yongding River alluvial fan of Beijing. Based on the horizontal distribution of geochemical characteristics and groundwater evolutionary process in typical profiles, the authors have reached the following conclusions: 1) From the recharge area to the discharge area of Yongding River alluvial fan, different zones of groundwater chemical types can be recognized. The chemical type of phreatic groundwater changes from Ca-HCO3 to Ca·Mg-HCO3 and Mg·Na-SO4 while the type of deep groundwater changes from Ca·Mg·Na-HCO3 and Ca·Na-HCO3 to Na-HCO3 and Na-HCO3·SO4. Groundwater with chemical types of Ca·Na-HCO3·SO4,Na· Ca-Cl or Ca· Mg-SO4 in the recharge area have been affected by human activities. In general, the distribution of groundwater chemical zones is consistent with that of groundwater flow zones, especially in the unconfined and moderate-deep confined aquifer. 2) The groundwater chemical field in different depths is affected by water-rock interaction, which includes the dissolution/deposition of sulfate, silicate, carbonate and halite and the cation exchange of Ca-Na and Ca-Mg. 3) From the recharge areas to the downstream discharge areas of the Yongding River alluvial fan, the groundwater velocity decreases gradually while the amount of dissolution/deposition for silicate, carbonate, sulfate and halite grows gradually. Therefore, the renewable velocity of groundwater decreases.
展开▼
