基于水化学演化规律的盆地地下水循环研究

发布时间：2018-01-23 20:14

本文关键词： 多级次地下水流系统水化学与同位素电阻率地表水地下水交换鄂尔多斯盆地　出处：《中国地质大学(北京)》2016年博士论文　论文类型：学位论文

【摘要】：地下水循环是水循环的重要环节,地下水在循环过程中与介质相互作用会改变其水化学特征。地下水化学组分的变化规律可以指示地下水循环过程。区域地下水流理论较好的建立了盆地内部地下水化学演化规律与循环模式之间的联系,是研究区域地下水流的理论基础与有效工具。本论文基于盆地内部地下水化学特征与音频大地电磁信息识别了盆地内部地下水流循环模式与演化规律;通过地表水与地下水演化阶段所表现出的水化学组分特征,研究了盆地内部地表水与地下水的交换规律。前人多是通过水动力学特征研究区域地下水流系统的多级次性,但对多级次水流的演化规律鲜有涉及。盆地排泄基准面附近可能存在多级次地下水流的集中排泄。基于不同深度样品的水化学指标,利用聚类分析法将采样点分为具有显著水化学差异的五类(C1至C5)。利用采样点水化学、同位素信息与采样点深度关系图,识别出C1(中间流动系统)、C2(区域流动系统)、C3、C4、C5(局部流动系统)的循环深度。利用Cl-,SO42-与,氯碱指数识别出地下水演化过程的阶段性特征。地下水化学类型与矿化度的区域性变化蕴含着地下水循环演化的重要信息。通过研究区水化学类型与矿化度面状分区图,发现从上游至下游研究区地下水化学类型整体呈现HCO3-型SO42-型Cl-型的变化过程;矿化度呈现出逐渐升高的趋势。对研究区内电阻率信息进行了定量统计,发现研究区内白垩系与侏罗系地层间、白垩系地层内部上游与下游地区存在明显的电阻率差异,表明研究区内不同位置的地下水处于不同的演化阶段。多级次地下水的演化过程可能受其循环路径、滞留时间以及补给区地质条件影响。利用研究区地下水三维数值模型得到水化学取样点与音频大地电磁物探数据点相应深度地下水径流距离、循环时间以及补给区位置。研究表明:浅层地下水的径流路径与循环时间相对较短,深层地下水的径流路径与循环时间相对较长。结合研究区岩相古地理信息推断造成研究区水化学演化差异的可能原因。地下水是干旱-半干旱地区河流的重要补给源。根据研究区河水采样点与地下水采样点水化学特征的关系,判断出都思兔河上游河段为研究区内浅层与深层地下水共同补给,而下游河段主要为深层地下水补给。利用多元统计分析中的主成分分析法,判断出上游河段地表水与地下水交换过程发生的水化学反应类型。本博士论文提出了通过水化学信息识别多级次地下水流系统循环与演化规律的方法,丰富并完善了区域地下水流理论。
[Abstract]:Groundwater circulation is an important part of water circulation. The variation of groundwater chemical composition can indicate the process of groundwater circulation. The theory of regional groundwater flow is a good method to establish the underground water in the basin. The relationship between the evolution of hydrochemistry and the cycle model. It is the theoretical basis and effective tool for the study of regional groundwater flow. Based on the chemical characteristics of groundwater and audio magnetotelluric information in the basin, the circulation pattern and evolution law of groundwater flow in the basin are identified in this paper. The characteristics of water chemical components in the evolution stage of surface water and groundwater. The exchange law of surface water and groundwater in the basin is studied. Most of the predecessors studied the multistage subcharacteristics of regional groundwater flow system through hydrodynamic characteristics. However, the evolution law of multistage secondary flow is seldom concerned. There may be centralized discharge of multistage subgroundwater flow near the drainage datum level in the basin, based on the hydrochemical indexes of samples with different depths. Cluster analysis was used to divide the sampling points into five categories: C1 to C5, which had significant hydrochemical differences. Using the hydrochemistry of the sampling points, the relationship between the isotopic information and the depth of the sampling points was obtained. The cycle depth of C _ 1 (intermediate flow system) C _ 2 (regional flow system C _ 3N _ 4C _ 4 and C _ 5) was identified. The chlor-alkali index identifies the stage characteristics of groundwater evolution process. The regional variation of groundwater chemical type and salinity contains important information of groundwater cycling evolution. Zoning. It is found that the chemical types of groundwater in the study area from upstream to downstream show the variation process of HCO _ 3-type so _ 4 _ 2-type Cl _ (-) type as a whole. The resistivity information in the study area is quantitatively counted and it is found that the Cretaceous and Jurassic strata in the study area are interbedded. There are obvious resistivity differences between upper and lower reaches of the Cretaceous strata, indicating that groundwater in different locations in the study area is in different stages of evolution, and the evolution process of multistage subgroundwater may be affected by its circulation path. Based on the 3D numerical model of groundwater in the study area, the groundwater runoff distance of the corresponding depth between the sampling point and the Audio magnetotelluric geophysical data point is obtained. The results show that the runoff path and circulation time of shallow groundwater are relatively short. The runoff path and circulation time of deep groundwater is relatively long. Combined with lithofacies paleogeographic information in the study area, the possible reason for the difference of hydrochemical evolution in the study area is that groundwater is an important supplement of rivers in arid and semi-arid areas. According to the relationship between water chemical characteristics of river water sampling sites and groundwater sampling sites in the study area. It is concluded that the upper reaches of Dusiyu River are recharge of shallow and deep groundwater in the study area, while the downstream reach is mainly recharge of deep groundwater. The principal component analysis method in multivariate statistical analysis is used. The types of hydrochemical reactions in the process of surface water and groundwater exchange in upstream reach are determined. A method to identify the circulation and evolution of multistage subgroundwater flow system by hydrochemical information is proposed in this paper. The theory of regional groundwater flow is enriched and perfected.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P641.2

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