鄂尔多斯盆地北部浅层地下水水化学特征及形成机制分析

发布时间：2018-02-28 00:26

本文关键词： 鄂尔多斯盆地地下水化学特征形成机制多元统计　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：位于中国西北部干旱半干旱缺水地区的鄂尔多斯盆地,地下水资源是该地区居民生活、工农业用水的主要来源。盆地北部煤炭资源大规模开采、地下水资源过度、农业生产频繁等人类活动对该地区地下水产生一定影响,因此分析该区域地下水的化学特征及其形成机制对了解地下水与环境的相互关系及更合理地利用地下水资源尤为重要。本文基于中国地质调查局“鄂尔多斯盆地地下水污染调查评价”项目,利用2014年采集的盆地北部石炭系-侏罗系碎屑岩含水系统的84个浅层地下水样品和白垩系碎屑岩裂隙孔隙含水系统的134个浅层地下水样品数据,通过各水质指标的统计特征分析,将聚类分析、判别分析等多元统计分析方法与离子比例关系图、水化学类型、Gibbs图相结合,研究鄂尔多斯盆地北部两个不同含水系统地下水的化学特征、水化学过程及其形成机制。结果表明,石炭系-侏罗系碎屑岩含水系统中地下水主要为矿化度中等偏低的中性-弱碱性淡水,整体上水质良好,仅有个别采样点发现水质超标现象;地下水化学类型为Ca-Mg-HCO_3型,硅酸盐的风化作用是主要水化学成因,另外还伴随有蒸发浓缩和阳离子交替吸附作用,硝酸盐是主要污染因子。白垩系裂隙孔隙含水系统地下水为中性-弱碱性水,矿化度偏高,整体水质较差,其中硫酸盐、氟化物、氯离子和三氮超标现象最为严重。地下水化学类型混杂,包括Ca·Mg-SO_4·Cl型、Ca·Mg-HCO_3型、Na-SO_4·Cl型和Na-SO_4型。该含水系统地下水离子成分形成的原因是水岩作用和蒸发-分馏结晶作用,地下水中存在硅酸盐风化溶解、硫酸盐溶解、土壤中芒硝溶解等作用,该含水系统的主要污染因子同样是硝酸盐,而个别采样点含量异常高的硫酸根可能是由地层中存在的黄铁矿氧化、石油天然气开采及农业施肥等造成的。
[Abstract]:The Ordos Basin is located in the arid and semi-arid region of northwest China. Groundwater resources are the main source of water for people living in the area and for industry and agriculture. Coal resources in the northern part of the basin are exploited on a large scale and groundwater resources are excessive. The frequent agricultural production and other human activities have a certain impact on the groundwater in this area. Therefore, it is very important to analyze the chemical characteristics and formation mechanism of groundwater in this area in order to understand the relationship between groundwater and environment and to utilize groundwater resources more reasonably. This paper is based on the "Ordos Basin" of China Geological Survey. Investigation and Evaluation of groundwater pollution, Based on the data collected in 2014 from 84 shallow groundwater samples of Carboniferous Jurassic clastic rock water-bearing system and 134 shallow groundwater samples of Cretaceous clastic rock fissure pore water system collected in 2014. Through the statistical characteristic analysis of each water quality index, the multivariate statistical analysis methods, such as cluster analysis, discriminant analysis and so on, are combined with the ion ratio diagram and the Gibbs diagram of water chemistry type. The chemical characteristics, hydrochemical process and formation mechanism of groundwater in two different water-bearing systems in northern Ordos Basin are studied. The groundwater in the water system of Carboniferous Jurassic clastic rocks is mainly neutral and weak alkaline fresh water with medium and low mineralization degree, and the water quality is good on the whole, only a few sampling points find water quality exceeding the standard, and the chemical type of groundwater is Ca-Mg-HCO_3 type. The weathering of silicate is the main hydrochemical origin, in addition, it is accompanied by evaporative concentration and cation alternate adsorption. Nitrate is the main pollution factor. The groundwater of the Cretaceous fissure pore water system is neutral and weak alkaline water. The salinity is on the high side and the overall water quality is poor, among which sulfate, fluoride, chloride ion and trinitrogen are the most serious phenomena. It includes Ca 路Mg-SO_4 路Cl, Ca 路Mg-HCO_3, Na-SO _ 4 路Cl and Na-SO_4. The reasons for the formation of ion composition in the water system are water-rock action and evaporation-fractionation crystallization, silicate weathering dissolution, sulfate dissolution, and nitrate dissolution in soil, etc. The main pollution factor of this water bearing system is also nitrate, and the sulphate radical with high content in individual sampling sites may be caused by pyrite oxidation, oil and gas exploitation and agricultural fertilization.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P641.3

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