【作者】 李云；

【导师】 姜月华；

【作者基本信息】 中国地质科学院 ， 地质工程， 2010， 硕士

【摘要】 扬(州)泰(州)靖(江)地区位于长江三角洲的长江北岸,包括扬州和泰州的南部及如皋地区,区内第四系赋存丰富的孔隙地下水。由于以往对研究区地下水的补径排条件、地下水成因等研究的不足,致使难以合理开发利用及有效管理其地下水资源,地下水长期过量开采、水位大幅度持续下降,极易造成浅层地下水对深层地下水的越流补给与污染。同时,扬泰靖地区作为整个长江三角洲的顶部地区,属于地下水系统的补给区及始径流区,其地下水的污染势必会对整个长江三角洲地区地下水产生威胁。因此,本文依据地下水中的同位素和水化学组分具有丰富水循环信息的特性,采用同位素水文学及水文地球化学等方法对地下水进行综合分析。通过对氘氧氚同位素以及水化学特征研究表明潜水接受大气降水与长江水的共同补给,与地表水水力联系密切；而承压水则主要接受古水的补给,与长江水及潜水的水力联系较差。潜水与大气降水具有相近的氢氧同位素均值(潜水：-45.5‰、-7.43‰；大气降水：-44.83‰、-7.36‰),与长江水的氢氧同位素值具有很好的相关性(R2=0.93)。在沿江地段,由于受到了长江水的侧向补给与稀释作用,潜水中60mg/L的Cl-等值线与长江岸线近似平行。地表水与潜水之间离子浓度共振现象明显,水化学类型一致,主要为HCO3-Ca型。承压水与潜水的同位素特征和水化学特征则存在一定差异。各层位承压水的水化学类型呈现逐步演化的特点,由Ⅰ承压水的HCO3-Ca型渐变至Ⅱ承压水的HCO3-Ca-Na型及Ⅲ承压水的HCO3-Na型。结合水化学数据,对硫同位素分析表明地表水与潜水遭受了一定程度的污染,硫同位素值约为10‰；而承压水则基本未受污染,硫同位素值的大小与不同地段的水文地质条件密切相关。在研究区顶部及沿江地段,承压含水层径流条件好、封闭性差并处于氧化环境,承压水中的硫酸盐主要来源于硫化物的氧化,硫同位素值为负值；在中部地区,承压含水层径流条件差、封闭性好、处于还原环境,硫同位素值均大于20‰,而且由于经受了硫酸盐的还原作用,硫同位素值最高可达70‰之多。承压水中硫酸盐浓度与硫同位素值之间呈现正相关的特点,表明中部地区的硫酸盐主要来源于沿程径流补给和滞留海源硫酸盐的补给。利用碳-14进行年龄计算并结合水化学剖面分析显示承压水整体的流向自西往东,伴随着明显的离子交换作用。沿程往东水动力情况变缓,Na+、Cl-易溶成分增加而Ca2+、Mg2+、HCO3-等难溶成分减少,年龄逐渐增大。在研究区顶部及沿江地段Ⅰ、Ⅱ承压水年龄小于5000年,在研究区中东部Ⅲ承压水年龄达到20000多年。更多还原

【Abstract】 Yangzhou-Taizhou-Jingjiang area, located in the northern part of the Yangtze River Delta, includes the southern part of Yangzhou and Taizhou region and Rugao region, with abundant pore water in the Quaternary deposits. Since the previous studies on the conditions of recharge, runoff and discharge and the origin of groundwater were insufficient, it is difficult to rationally exploit and effectively manage groundwater resource, and has resulted in long-term over-exploitation of groundwater and continuous drop of water table, which would easily cause leakage recharge and contamination from shallow groundwater to deep groundwater system. Meanwhile, as the top section of the Yangtze River Delta, Yangzhou-Taizhou-Jingjiang area belongs to the recharge area and the initial runoff area of groundwater system. Therefore, contamination of groundwater will inevitably threaten groundwater quality of the entire Yangtze River Delta. According to the isotopic and hydrochemical components in groundwater with rich information on water cycle, it had been analyzed comprehensively with methods of isotope hydrology and hydrogeochemistry in this paper.Through analyzing the characteristics of D, 18O, T and hydrochemical components, the results indicate that in Yangzhou-Taizhou-Jingjiang area phreatic water receives recharge both from local precipitation and Yangtze River water, and has close hydraulic connection with surface water; confined water is mainly recharged from ancient water, and has poor hydraulic connection with phreatic water and Yangtze River water. The average values of D and 18O in phreatic water (-45.5‰,-7.43‰) are similar with that of precipitation (-44.83‰,-7.36‰), and has good correlation with that of Yangtze River water (R2=0.93). In the section along the Yangtze River, phreatic water has been laterally recharged and diluted, and the contour line of Cl-concentration (60mg/L) is almost parallel to the coastline of the Yangtze River. The hydrochemical types of surface water and phreatic water is similar, mainly HCO3-Ca water, with significant resonance in concentrations between them. The isotopic and hydrochemical characteristics of confined water are different with phreatic water, and the hydrochemical types gradually change from HCO3-Ca water in the 1st confined aquifer to HCO3-Ca·Na water in the 2nd confined aquifer and to HCO3-Na water in the 3rd confined aquifer.According to the study of sulfur isotope and hydrochemistry, it shows that Surface water and phreatic water are subjected to a certain degree of contamination, withδ34S values about 10‰, and confined water is basically not contaminated, withδ34S values closely related to the hydrogeological conditions in different sections of the studied area. In shallow confined water along the Yangtze River and at the top of the study area, sulfates with negativeδ34S values originate from oxidation of sulfides, which is related to the sand-dominated lithologic character, good runoff condition, poor sealing property and aerobic environment. In deep confined water of the central section, sulfates withδ34S values more than 20‰are related to the clay-dominated lithologic character, poor runoff condition, good sealing property and anaerobic environment. And due to reduction of sulfates, someδ34S values is up to 70‰. The positive correlation between sulfate concentrations andδ34S values proves that sulfates in the central section recharge from runoff and detained marine sulfate.By means of calculating 14C age of groundwater and hydrochemical profile analysis, it illustrates that the overall flow direction of the confined water is from west to east with hydrodynamic situation gradually slowing, contents of soluble components, such as Na+ and Cl-, increasing, contents of insoluble components, such as Ca2+, Mg2+ and HCO3-, decreasing, and groundwater age increasing. Ion exchange occurred significantly in the process of groundwater runoff. Along the Yangtze River and at the top of the study area, age of the 1st and 2nd confined water was less than 5000 years, and gradually increased to 20,000 years of the 3rd confined water in the eastern part of the study area.更多还原