地理学报 ›› 2000, Vol. 67 ›› Issue (2): 209-218.doi: 10.11821/xb200002009

• 论文 • 上一篇    下一篇

长江河口地区第四系地下水化学演化机制

宋保平1, 张先林2, 方正2, 陈中原3   

  1. 1. 华东师范大学城市与环境考古遥感开放研究实验室,上海200062;
    2. 上海市城市地质研究院,上海200062;
    3. 华东师范大学地理系,上海200062
  • 收稿日期:1999-08-25 修回日期:1999-11-20 出版日期:2000-03-15 发布日期:2000-03-15
  • 基金资助:
    上海市教委重点学科基金资助(B990305);国家教育部跨世纪人才培养计划

Mechanism of Chemical Evolution for Quaternary Groundwater in Yangtze River Estuarine Region

SONG Bao ping1, ZHANG Xian lin2, FANG Zheng2, CHEN Zhong yuan3   

  1. 1. Open Research Lab. of Remote Sensing in Urban and Environmental Archaeology, East China Normal University, Shanghai 200062;
    2. Shanghai Institute of Urban Geology, Shanghai 200062;
    3. Department of Geography,East China Normal University,Shanghai 200062
  • Received:1999-08-25 Revised:1999-11-20 Online:2000-03-15 Published:2000-03-15
  • Supported by:
    The Key Subject Foundation of Shanghai Educational Committee,No.B990305;Trass-centrury Training Program Foundation for Talents of State Education Ministry

摘要: 长江河口地区第四系沉积体系的发育很大程度上受到海面波动的控制,其中地下水化学场也不可避免地受此影响,从而具有独特的演化模式。本文根据研究区的水文地质条件,划分出3个含水系统:全新统、中上更新统和下更新统含水系统;利用Piper图解区分了更新统2个含水系统中的水化学类型;同时探讨了地下水形成后所发生的演化。研究发现,区内地下水化学演化主要通3三种作用进行:1后期补给淡水对咸水的稀释作用;2地下水中钙离子对含水层沉积物中吸咐钠离子的交换作用;3不同类型地下水通过越流等形式发生的混合作用。另外,本区地下水中的Ca2+和CO32-离子对方解石来说已达过饱和。

关键词: 水化学演化, 第四系含水系统, 长江口区

Abstract: Quaternary sea level fluctuation had played important role in affecting the spatial and temporal distribution of top Holocene phreatic aquifer and 5 (Ⅰ-Ⅴ) underlying late to early Pleistocene aquifers in the Yangtze estuary region. Inevitably, the evolution of groundwater chemical field of the region was closely associated with transgression and the occurrence of aquifuge in Quaternary stratigraphy. Present database was established primarily on 245 water samples obtained from these aquifers in 78 selected Quaternary hydrogeological boreholes. The analytic items included the concentrations of K +, Na+, Ca2+, Mg 2+, NH 4+, Al3+, Cl-, HCO3-, CO32-, and SO42-, and the values of PH and temperatures. Using hydrogeochemical methods, this paper deals with the nature of groundwater chemical types and chemical evolution. The results are showed as below: (1) One phreatic aquifer and five confined aquifers in study area belong to three aquifer systems, i. e. Holocene aquifer system (phreatic aquifer), mid and upper Pleistocene aquifer system (Ⅰ-Ⅲ confined aquifers), and lower Pleistocene aquifer system (Ⅳ-Ⅴ confined aquifers). (2) Spatial and temporal distributions of brackish water and salt water in sedimentary system of the study area were controlled by Quaternary transgressions. (3) There are two main types of aquifer system can be differentiated by Piper diagram, i. e. Ⅰ-Ⅲ aquifer system and Ⅳ-Ⅴ aquifers system. The former is characterized by salt water (Cl—Na·Ca and Cl—Na), and the later is dominated by fresh water (HCO3—Na and Cl·HCO3—Na) and brackish water (Cl—Na). (4) There are four types of groundwater chemical evolution in study area: ① dilution of salt water by fresh water recharge through atmospheric replacement taking place only in phreatic aquifer. ② exchange of sodium absorbed in aquifer medium by calcium in water. The ratios Na/(Na+Cl), used as an indicator of ion exchange, demonstrate that the degree of exchange in Ⅳ-Ⅴ aquifers (0 65 on average) is more intensifying than that of Ⅰ-Ⅲ aquifers (0 45 on average). ③ mixture of different water types through leaky system in the Quaternary aquifers system. The groundwater composition reveals that the mixture of brackish water character due to leaky system is of the transition in chemical property between salt water in upper aquifers and fresh water in lower aquifers. Through thermodynamical calculation, we proposed that the groundwater in study area is super saturated with calcite ( SI >0).

Key words: Water chemical evolution Quaternary aquifer system, Yangtze river estuarine Region

中图分类号: 

  • P641.3