金佛山地区地下水与地表水水文地球化学及氢氧同位素特征分析

发布时间：2018-07-14 16:53

【摘要】：水是人类赖以生存的宝贵资源,地下水是水资源的一个重要组成部分。在可利用的水资源中,地下水占98.5%。赋存于各种岩溶空隙中的地下水便是岩溶水,岩溶地区占全球陆地面积的15%,全球至少10亿人口居住于岩溶区或者以岩溶水作为主要的供水水源。伴随着人类活动的增加,岩溶水的污染和水资源的浪费问题日渐凸显,合理开发利用及保护地下水资源变得愈发重要,这就要求人们需要弄清地下水的时空变化规律及水循环模式。本文选取重庆市南川区金佛山地区作为研究对象,以区域自然地理及水文地质条件为基础,结合水文地球化学及环境稳定同位素的方法,系统地对金佛山地区水化学特征的变化规律及氢氧同位素的空间分布进行分析,并进一步探究该地区存在的地下水及地表水的补给形式及循环特征,得出主要结果如下：(1)区内水体水文地球化学组成表明水化学类型为HCO3-Ca型和Ca(Mg)-HC03型,体现出了区内碳酸盐岩广布的特点。金佛山地区地表水与地下水的水化学组成分布于岩石风化控制端元附近,表明金佛山水体受到岩石风化控制作用较为显著,这与区内水体阴阳离子组成表现出了一致性。区内地下水pH值呈弱碱性,金佛山自然保护区外总硬度与总碱度比值整体高于保护区内,表明区内可溶岩的溶解过程受到其他酸类影响,个别取样点受到人为酸影响较为明显。与上世纪70年代比较,金佛山地区保护区内外的地下水总硬度与总碱度比值均存在上升的情况,保护区外上升幅度较大。Ca2+及Mg2+含量明显受到排泄点地质背景控制,分布于灰岩地层的地下水排泄点Ca2+明显较高,地质背景为白云岩地层的地下水排泄点Mg2+含量明显高于其他地区,可见影响金佛山地下水阳离子浓度的因素主要为地质背景,其次为人类活动影响。金佛山地区地下水HCO3-、Cl-、 N03-、SO42-等阴离子浓度较上世纪70年代均产生了不同程度的变化,其主要的影响因素为人类活动。(2)金佛山地区地表河水及地下水氢氧同位素组成沿重庆市大气降水线与全球大气降水线附近分布,受同位素动力分馏效应影响,存在着不同程度的偏离,而位于其左上方,地下水位置较为集中而河水较为分散,表明金佛山地区地表水及地下水主要补给来源为大气降水及冰雪融水。通过分析区内地下水d值(氘过量值)发现,区内山下低海拔地区地下水与山上高海拔地区地下水相比d值较小,说明高海拔地区地下水由于受到冰雪融水补给,体现出冰雪融水氢氧同位素偏负的特点。分析沿地表径流方向选取的流域径流系统水体,在溶滤作用、阳离子交换作用及同位素高程效应影响下,地下水变化表现为电导率沿径流方向逐渐升高而氧同位素逐渐偏重。其中地下水的电导率(EC)总体上高于地表水,主要原因是地下水在循环过程中对围岩的溶滤作用及阳离子交换作用与地表水相比较更容易进行,导致电导率上升。(3)通过水化学及氢氧同位素数据分析建立金佛山地区水体循环概念模型：在金佛山1267m～2133m的高海拔地区,大气降水以降雨及降雪的形式进入金佛山水体循环系统。降水在下渗补给地下水的过程中受蒸发效应影响,使得地下水逐渐富集重同位素。地下水运移过程中,部分地下水经过浅循环形成冷泉出露于地表,而部分地下水则继续下渗,逆着地温梯度进行渗透,随着温度升高导致水分子平均运动速度加快,水体出现同位素分馏,最终在深部形成同位素组成偏负的地下热水,地下热水随后上升与其他冷水混合出露地表形成温泉。高山地区下渗的部分地下水通过较长跨度的运移过程,在山下较远区域出露,与当地降水补给的地下水表现出较大的同位素组成差异。
[Abstract]:Water is a valuable resource for human survival, and groundwater is an important part of water resources. In the available water resources, ground water, which accounts for 98.5%. in various karst spaces, is karst water, and the karst area accounts for 15% of the global land area. At least 1 billion people live in the karst area or take the karst water as a part of the world. The main water supply source. With the increase of human activities, the pollution of karst water and the waste of water resources are becoming more and more important. It is becoming more and more important to rationally exploit and protect the groundwater resources. This requires people to find out the temporal and spatial variation of groundwater and the mode of water circulation. This paper selects the Jinfo Mountain area of Nanchuan District, Chongqing. On the basis of regional natural geography and hydrogeological conditions, combined with hydrogeochemical and environmental stable isotopes, the change law of hydrochemical characteristics and the spatial distribution of hydrogen and oxygen isotopes in the Jinfo Mountain area are systematically analyzed, and the recharge form of groundwater and surface water in this area is further explored. The main results are as follows: (1) the hydrogeochemical composition of the water body in the region shows that the hydrochemical type is HCO3-Ca and Ca (Mg) -HC03, which embodies the characteristics of the wide distribution of carbonate rocks in the area. The Hydrochemical Composition of the surface water and the groundwater in the Jinfo Mountain area is distributed near the end of the rock weathering control, indicating the water body of the Jinfo Mountain. The effect of rock weathering is more obvious, which shows the consistency with the composition of the ions and yang ions in the water body. The pH value in the inland water is weak alkaline, the ratio of the total hardness to the total alkalinity outside the Jinfo Mountain natural reserve is higher than that in the protection area, indicating that the dissolution process of the soluble rock in the area is affected by other acids, and the individual sampling points are subject to people. Compared with the 70s, the ratio of the total hardness and total alkalinity of the groundwater in the Jinfo Mountain area protected area increased. The increase of.Ca2+ and Mg2+ content outside the protected area was obviously controlled by the geological background of the excretory point, and the groundwater excretion point in the limestone stratum was obviously higher in Ca2+. The Mg2+ content of groundwater excretion point in the background of dolomite is obviously higher than that in other areas. It can be seen that the factors affecting the ion concentration in the underground water and Yang of Jinfo Mountain are mainly geological background, followed by the influence of human activity. The anion concentration of groundwater HCO3-, Cl-, N03- and SO42- in the Jinfo Mountain area has been changed to different degrees in different degrees than in the 70s of the last century. The main influencing factor is human activity. (2) the hydrogen and oxygen isotopes of the water and groundwater in the ground water and groundwater in the Jinfo Mountain area are distributed along the Chongqing city's atmospheric precipitation line and the global atmospheric precipitation line, and are affected by isotopic dynamic fractionation, and there are different degrees of deviation, but the location of the groundwater is more concentrated and the river water is more concentrated. The main source of surface water and groundwater recharge in Jinfo Mountain area is atmospheric precipitation and ice snow melting water. Through the analysis of the D value of the groundwater (deuterium excess) in the area, it is found that the groundwater is smaller than the D value in the high altitude area of the mountain area, and the groundwater is supplementing with ice and snow melting water. Under the influence of filtration, cation exchange and isotope height effect, the change of groundwater change shows that the conductivity of the groundwater is gradually rising along the direction of runoff while the oxygen isotope is gradually heavier. The main reason is that the conductivity (EC) is higher than the surface water in general. The main reason is that the filtration and cation exchange of the ground water to the surrounding rock and the surface water phase are more easy to be carried out in the process of circulation. (3) the concept model of water circulation in Jinfo Mountain area is established through hydrochemistry and hydrogen oxygen isotope data analysis: in Jinfo Mountain 1267m In the high altitude area of 2133m, the atmospheric precipitation enters the circulation system of the Jinfo Mountain water in the form of rainfall and snowfall. Precipitation is influenced by the evaporation effect during the process of subsurface groundwater recharge, which causes the groundwater to accumulate heavy isotopes gradually. During the process of groundwater migration, some underground water passes through the shallow circulation and forms cold springs to the surface and part of the ground. The water continues to infiltrate and permeates through the geothermal gradient. As the temperature rises, the average velocity of water molecules is accelerated. Isotopic fractionation in the water body appears in the water. Finally, the isotopic composition of the underground hot water is formed in the deep part, and the underground hot water then rises with other cold water and forms the hot spring. The water is exposed in a relatively long distance from the mountain area through the long span migration process, showing a larger isotopic composition difference with the groundwater recharged by the local precipitation.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641.3;P342

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