银川平原承压水氢氧同位素组成与~(14)C年龄分布特征

利用地下水氢氧同位素(2H、3H和18O)和碳同位素(14C)方法,分析银川平原承压水的补给更新能力。在平原区采集承压水氢、氧、碳同位素样品45组,测试其氢氧同位素含量和14C年龄。据测试结果分析,地下水氢、氧、碳环境同位素分布特征存在较好的一致性,揭示了该区承压水的补给、流动的区域规律和局部变化特征。地下水14C测年结果显示,承压水年龄大多介于3000~22290 a之间,同时采用Tamers和Gonfiantinie模型对14C年龄校正进行了对比分析。沿同位素水文地质剖面计算得出:银川以北贺兰山前向平原中部地下水的流动速率为2.22~0.63 m/a,呈现由南向北递减的特征;从青铜峡冲洪积区向平原中部地下水由每年流动十余米减少至2 m。综合分析认为,银川平原承压水流动缓慢,水交替循环时间长,局部与潜水水力联系较密切,在承压水开采区,潜水越流补给量可达45%,适量开采存在一定程度的可更新性。     

滇西某铁路隧道选址区地下水同位素信息及循环模式

借助于不同水源的氘、氚、氧同位素,分析隧道选址区地下水同位素和水化学特征.利用同位素混合模型,判别研究区地表水和地下水的交替关系.定性、定量分析水体补给源及补给方式.最后结合地质背景初步推论本区地下水循环模式.为指导工程提供依据.     

北京温榆河冲洪积扇地面沉降特征及机理研究

北京区域地面沉降呈快速发展趋势,局部最大形变速率超过13cm/a,严重威胁城市安全。掌握地下水开采条件下的分层地面沉降特征,是定量揭示地面沉降机理和缓解沉降灾害的前提。以北京最大的地面沉降区温榆河冲洪积扇地区的八仙庄沉降区为研究对象,分析了该地区地下水开采、地下水位动态特征与分层压缩量的关系,基于分层沉降数据得出该地区土体释水形变以浅部地层、深部地层的弹性形变以及中深部地层的弹塑性形变为主,并从地层条件、固结历史和物理力学性质方面对压缩特性的影响因素进行了分析,得出以地面沉降为约束条件的地下水开采主要调控层分布。     

北京市平原区地下水循环特征的同位素研究

同位素技术是研究区域地下水循环规律的主要手段之一。本文对平原区地下水进行了取样分析,运用同位素技术并结合水文地质条件,研究了北京市平原区地下水循环演化规律。运用^3H和^14C的测年技术确定了地下水年龄;利用D和18^O关系曲线探讨了地下水的起源;按照是否积极参加了现代水循环的原则将第四系地下水划分为浅层水和深层水;对浅层水和深层水的更新状况进行了研究。研究表明,浅层水广泛分布于北京平原区,径流条件好,更新快;深层水主要分布于永定河、潮白河冲洪积扇下部及冲洪积平原的深部地区,补给条件相对差,与现代大气降水联系弱,径流条件差,更新慢。     

青海省格尔木山前平原区地下水动态特征分析

在格尔木山前平原区水文地质条件基础上,结合多年地下水位监测资料,对格尔木河冲洪积平原区的多年水位动态特征及其影响因素进行了分析研究,总结出该地区的地下水动态类型.格尔木山前平原区3个不同区域由于赋存条件及开发利用条件的不同,地下水动态类型分异显著.研究区地下水整体流向与地形起伏相一致,自南向北径流,区域上流场形态变化不大.冲洪积扇中上部地下水多年动态处于平衡状态,近年来由于开采力度加大,地下水位呈急速下降趋势,地下水动态类型为水文-径流型;冲洪积扇下部地下水位以区域性下降为主,地下水动态类型主要为蒸发型;冲洪积扇西翼水源地附近由于地下水调蓄能力较强,地下水位总体呈稳定并局部有上升趋势,地下水动态类型为水文-人类活动型.     

毛坝向斜核部岩溶水绕轴径流的同位素示踪分析

本文针对圆梁山隧道毛坝向斜段岩溶地下水问题,利用环境同位素及地下水氘过量参数示踪原理,探讨了该区深层岩溶水的形成、补给、循环交替等信息。结果表明,向斜核部的深部承压水,同时接受向斜东翼和西翼大气降水的补给。T1d含水层,受垂直入渗的影响较大;P2ω c含水层,受上覆地层水和向斜东翼层间水入渗的影响明显;P1q m含水层与上覆地层含水层不存在直接的水力联系,但受到来自F02断层和不整合面有限渗流的影响。向斜核部水的渗流方向是从两翼指向核部,且流速较慢,不存在绕轴迳流。     

声波测井在碎屑岩沉积压实研究中的应用

通过对塔里木盆地北部阿克库勒地区 5口钻井泥质岩的声波时差及相应的孔隙度、古地层压力研究 ,求得本区的平均压实方程。认为本区 310 0～ 350 0 m属于正常压实层 ,其下属于欠压实层段。初步分析各时代流体的封闭时间和主要目的层欠压实异常类型。结合地震勘探资料 ,提出低速异常带中的更低异常区是找油领域之一。     

罗布泊盐湖晶间卤水运动特征及其动力学分析

根据地下水运动的一般规律，阐述了罗布泊盐湖钙芒硝储卤层及富钾卤水的特性，并讨论了该卤水层的变化特性。在罗布泊干盐湖区采用^14C测年技术、人工放射性同位素技术和化学示踪技术，研究晶间卤水循环速率、卤水渗流方向及渗透流速与实际流速，揭示罗布泊盐湖晶间卤水处于缓慢的流动及交替状态。探讨了新构造活动、古气候变化、地层静压力作用、深部地层水及大气降水补给作用等因素对罗布泊盐湖晶间卤水运动的控制和影响，提出了晶间卤水的运动模式。     

黔西南郭家湾地区中三叠世坡段组幻龙化石埋藏环境 ——来自碳酸盐岩岩相与碳、氧同位素的指示

为详细刻画黔西南郭家湾一带中三叠世安尼期幻龙化石的埋藏环境,对所属地层坡段组进行岩相和碳、氧同位素分析。结果显示该组属于开阔台地、台地边缘礁和礁缘斜坡亚相,包含五种沉积微相类型。全岩碳氧同位素分析结果显示,δ18O_PDB值为-6.28‰~-2.11‰,平均值为-4.36‰;δ13C_PDB值为+0.50‰~+2.86‰,平均值为1.58‰,与黔西南及邻区同期地层碳氧同位素组成一致。获得古海水温度为16℃~20℃,盐度为125.77~131.62,指示为正常温暖的海相沉积环境。淡水的加入是导致δ13C_PDB和δ18O_PDB在化石层显示轻微负偏的主要原因。综合分析还原化石的埋藏活动表明:地震活动导致碳酸盐岩台地局部地层失稳,形成含大量幻龙骨骼的碎屑流最终于礁缘斜坡地带发生卸载,形成异地埋藏化石层。研究结果为进行黔西南及邻区三叠纪化石群特异埋藏分析提供资料。     

北京市城近郊区地下水的环境同位素研究

应用环境同位素方法,研究北京城近郊区地下水演化规律。沿北京市永定河冲洪积扇地下水流动方向取样15组(D、18O、T、14C及全分析),对所取水样进行D、18O、T、14C分析,并确定地下水同位素年龄。运用地下水14C和T含量在垂向和水平方向变化的结果,验证了地下水的流向并计算了地下水的流速变化范围为5·02~62·63m/a,从山前至平原浅层地下水径流速度逐渐变小,反映了地下水水平径流强度逐渐减弱,地下水交替逐渐变差;浅层孔隙水以垂向交替为主,深层孔隙水以水平径流为主。对地下水D、18O之间的关系进行分析,从而判断地下水的补给来源等。     

北京平原区地下水位预警初步研究

借鉴美国地质调查局在宾夕法尼亚的地下水位预警方法,从统计学的角度,探索了北京平原区地下水预警方法。对监测井多年长期监测资料进行百分位统计分析,把同一时间(月平均、旬平均、日平均)地下水水位(头)标高值的最小值至百分位5、百分位5至百分位10、百分位10至百分位25、百分位25至百分位75范围内的地下水位分别定义为红色、橙色、黄色和蓝色预警,形成地下水位预警判据。根据地下水水位实时监测数据,实时判定监测井代表区域的地下水预警等级,同时修正和完善地下水位预警判据,称之为监测井单点预警,监测井代表的同一层位的区域的集合,构成不同含水层的地下水位区域预警。对北京平原区2009年12月的地下水位预警结果为:潮白河冲洪积扇顶部和中部潜水含水层地下水位为红色预警,前缘为黄色预警,冲洪积平原为蓝色预警区;城区以南地区为红色预警,海淀山后的西北部地区为红色预警,永定河冲积扇和冲积平原大部分地区黄色和蓝色预警,大石河冲洪积扇地区均为蓝色预警;承压水含水层在潮白河冲洪积扇的前缘为红色预警,冲洪积平原为蓝色预警,北运河山前地带均为橙色预警,城区东、东南地区为橙色和黄色预警,少数地区为橙色预警,除上述地区以外,承压水均为蓝色预警。北京市平原区主要地下水开采地区地下水位已经处于历史的较低水位处,特别是潮白河冲积扇中上部地区以及平谷盆地,地下水位几乎全部处于红色预警区。该预警方法原理明确,方法简便,有望在地下水主要开采区推广应用。     

Use of hydrogeochemistry and environmental isotopes for evaluation of groundwater in Qingshuihe Basin,northwestern China

Hydrogeochemistry and environmental isotope data were utilized to understand origin, geochemical evolution, hydraulic interconnection, and renewability of groundwater in Qingshuihe Basin, northwestern China. There are four types of groundwater: (1) shallow groundwater in the mountain front pluvial fans, originating from recent recharge by precipitation, (2) deep paleo-groundwater of the lower alluvial plains, which was formed long ago, (3) shallow groundwater in the lower alluvial plains, which has undergone evaporation during the recharge process, and (4) mixed groundwater (shallow and deep groundwater in the plain). The main water types are Na–HCO₃, which dominates type (1), and Na–SO₄, which dominates types (2) and (3). Geochemical evolution in the upper pluvial fans is mainly the result of CO₂ gas dissolution, silicates weathering and cation exchange; in the lower alluvial plains, it is related to mineral dissolution. The evaporative enrichment only produces significant salinity increases in the shallow groundwater of the lower alluvial plains. Shallow groundwater age in the upper plain is 10 years or so, showing a strong renewability. Deep groundwater ages in the lower plain are more than 200 years, showing poor renewability. In the exploitation areas, the renewability of groundwater evidently increases and the circulation period is 70–100 years.     

北京市永定河流域地下水^14C年龄的初步分析

应用同位素方法初步分析北京郊区永定河流域地下水的演化特点。沿永定河冲洪积扇地下水流动方向布置取样剖面，共有取样点14个，对采集的水样进行^14C和氚含量分析，并确定地下水同位素年龄。浅层孔隙水的^14C年龄的变化范围为730～4900a，深层孔隙水为13420-22480a；^14C年龄在垂直方向上由浅部至深部逐渐增大，最大变化幅度为从3010a增至22480a；浅层孔隙水的氚含量都在14．99～30．56TU之间，深层孔隙水大部分在0．51～4．71TU之间。运用地下水^14C和氚年龄在垂向和水平方向变化的结果，验证了地下水的流向并计算了地下水的流速变化范围为5．02～62．63m／a，从山前至平原浅层地下水径流速度逐渐变小，反映了地下水水平径流强度逐渐减弱，地下水交替逐渐变差，浅层孔隙水以垂向交替为主，深层孔隙水以水平径流为主。     

乌鲁木齐河流域北部平原地下水流模拟

本文运用数字水文地质概念模型的方法建立了乌鲁木齐河流域北部平原的地下水流模型,并用流量边界与柴窝堡盆地和河谷区的地下水流模型相接,构成一个统一的流域地下水模型,为乌鲁木齐河流域水资源整体规划利用提供了模拟分析工具。北部平原的南部倾斜平原为砂卵砾石组成的大厚度潜水含水层,北部细土平原为多层结构。地下水总体上由南向北径流,天然状态下在交界地带溢出成泉或流入沙漠。目前,地下水循环基本上由人为控制。农田灌溉回归补给量与河流和山前侧向补给量持平;而开采量已是绝对的排泄量。季节性开采造成地下水位季节性大幅度变化。水位的下降使蒸发蒸腾量减少,减轻了由于灌溉造成的土壤盐碱化问题。     

Recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system,southwest of North China Plain

Many cities around the world are developed at alluvial fans. With economic and industrial development and increase in population, quality and quantity of groundwater are often damaged by over-exploitation in these areas. In order to realistically assess these groundwater resources and their sustainability, it is vital to understand the recharge sources and hydrogeochemical evolution of groundwater in alluvial fans. In March 2006, groundwater and surface water were sampled for major element analysis and stable isotope (oxygen-18 and deuterium) compositions in Xinxiang, which is located at a complex alluvial fan system composed of a mountainous area, Taihang Mt. alluvial fan and Yellow River alluvial fan. In the Taihang mountainous area, the groundwater was recharged by precipitation and was characterized by Ca–HCO₃ type water with depleted δ¹⁸O and δD (mean value of −8.8‰ δ¹⁸O). Along the flow path from the mountainous area to Taihang Mt. alluvial fan, the groundwater became geochemically complex (Ca–Na–Mg–HCO₃–Cl–SO₄ type), and heavier δ¹⁸O and δD were observed (around −8‰ δ¹⁸O). Before the surface water with mean δ¹⁸O of −8.7‰ recharged to groundwater, it underwent isotopic enrichment in Taihang Mt. alluvial fan. Chemical mixture and ion exchange are expected to be responsible for the chemical evolution of groundwater in Yellow River alluvial fan. Transferred water from the Yellow River is the main source of the groundwater in the Yellow River alluvial fan in the south of the study area, and stable isotopic compositions of the groundwater (mean value of −8.8‰ δ¹⁸O) were similar to those of transferred water (−8.9‰), increasing from the southern boundary of the study area to the distal end of the fan. The groundwater underwent chemical evolution from Ca–HCO₃, Na–HCO₃, to Na–SO₄. A conceptual model, integrating stiff diagrams, is used to describe the spatial variation of recharge sources, chemical evolution, and groundwater flow paths in the complex alluvial fan aquifer system.     

Principal component analysis and hierarchical cluster analyses of arsenic groundwater geochemistry in the Hetao basin,Inner Mongolia

Although high As groundwater has been observed in shallow groundwater of the Hetao basin, little is known about As distribution in deep groundwater. Quantitative investigations into relationships among chemical properties and among samples in different areas were carried out. Ninety groundwater samples were collected from deep aquifers of the northwest of the basin. Twenty-two physicochemical parameters were obtained for each sample. Statistical methods, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to analyze those data. Results show that As species were highly correlated with Fe species, NH₄-N and pH. Furthermore, result of PCA indicates that high As groundwater was controlled by geological, reducing and oxic factors. The samples are classified into three clusters in HCA, which corresponded to the alluvial fans, the distal zone and the flat plain. Moreover, the combination of PCA with HCA shows the different dominant factors in different areas. In the alluvial fans, groundwater is influenced by oxic factors, and low As concentrations are observed. In the distal zone, groundwater is under suboxic conditions, which is dominated by reducing and geological factors. In the flat plain, groundwater is characterized by reducing conditions and high As concentrations, which is dominated by the reducing factor. This investigations indicate that deep groundwater in the alluvial fans mostly contains low As concentrations but high NO₃ and U concentrations, and needs to be carefully checked prior to being used for drinking water sources.     

保定平原区地下水生态水位阈值的探讨

地下水具有重要的生态价值,地下水生态系统中的地下水位、水质和包气带含水率与含盐量的变化驱动着表生生态格局的演变,但目前对各变量的生态阈值研究尚处于起步阶段,理论与方法体系还不完善。以保定平原区为例,采用地下水位及地下水生态环境的历史回归法、GIS法、差分网格计算法等方法,从时空角度分析了地下水位变化的驱动力以及生态效应,在此基础上确定不同水文地质单元的生态水位阈值。研究表明:（1）20世纪50—60年代,研究区依赖于地下水的生态格局基本维持着天然状态;1959—2000年,地下水位持续下降,局部地段出现降落漏斗;2000—2008年,地下水位骤降,降落漏斗迅速扩张,地下水与地表水补排关系发生变异;2008年至今,部分区域地下水位逐渐上升。（2）研究区内山前地带地下水生态水位埋深为10~15?m,拒马河冲洪积扇群与漕河—瀑河冲洪积扇群为5~10?m,唐河—大沙河冲洪积扇群为3~5?m,冲积平原中定州—望都范围为3~5?m,保定市为10~15?m,其余均为5~10?m,冲湖积平原环淀区域小于3?m。（3）以确定的地下水生态水位为标准,初步估算研究区现状地下水位恢复至生态水位的需水量为57.14×108?m3。研究成果对恢复当地地下水生态环境格局有重要意义,对华北平原地下水生态水位的确定也具有借鉴意义。     

Impact of transferred water on the hydrochemistry and water quality of surface water and groundwater in Baiyangdian Lake,North China

The hydrochemical composition of surface water and groundwater is a key parameter for understanding the evolution of water and its quality.In particular, little is known about the impact of transferred water on surface water and groundwater.In this study, Baiyangdian Lake was selected as a typical area for extensive groundwater exploration and surface water transfer in the North China Plain.Surface water and groundwater samples were sampled in dry/wet seasons and then analyzed before/after the water transfer, respectively.Generally, surface water and groundwater are extensively hydrologically connected based on hydrochemical evidence.It was found that the hydrochemical composition of the shallow groundwater is affected by the surface water and that the water quality of the deep groundwater is stable.However, inter-aquifer recharge processes from the shallow groundwater to the deep groundwater existed in the anthropogenic region impacted with high nitrate-ion concentrations.Also, the hydrochemical composition of the surface water and groundwater was dominated by rock-weathering and evaporation-precipitation processes.Due to the existence of the deep vadose zone in the alluvial fan, Na~+was exchanged into soil matrices during the leakage of the surface water.In addition, the transferred water resulted in surface water with good quality, and it also played as an important recharge source to groundwater.As the most important water resource for irrigation and drinking, deep groundwater should be paid more attention in the alluvial fan with frequent water transfer and extensive groundwater exploration.     

Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain,Uttarakhand, India

The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels.