长江干流水体氢氧同位素空间分布特征

采用热转换元素分析同位素比值质谱法(TC/EA-IRMS)对重庆至上海段长江干流的氢氧同位素进行了监测,分析了该段长江水的氢氧同位素和氘过量参数的空间变化规律,并探讨了δ(18O)和δ(D)与大气降水氢氧同位素的关系.结果表明:长江干流不同地段水体受补给来源、大陆效应、高程效应等因素影响,其水体氢氧同位素也呈现出不同的...     

莱州湾白浪河河水和河口海水的水化学和氢氧稳定同位素特征

在海水入侵的研究中,通常将海水作为一个重要的混合端元。而一般沿海带的海水,尤其是河口海水相对于标准海水都会受到入海河流以及沿海人为活动的强烈影响,在空间和时间上的分布不断在变化。因此在研究海水入侵之前,研究河口海水、标准海水与河水成分之间的混合关系至关重要。本研究主要是对比海水和地表水的稳定同位素和水文地球化学成分。在莱州湾入海河流白浪河的下游沿岸采集5件河水样品,河口采集7件海水样品,对样品进行了水化学和稳定同位素测试,研究淡水和海水的混合关系。采用惰性示踪剂(δD、δ~(18)O、Cl~-、Br~-)和反应示踪剂(Na~+、Mg~(2+)、SO~(2-)_4、HCO~-_3、Ca~(2+)、NO~-_3)展开分析。在δD-δ~(18)O关系图上,所有的河水样品都位于全球大气水线之下,反映了上游水库水的蒸发,海水样品则位于标准海水与河水样品的混合线上。河水样品δ~(18)O—Cl~-关系表明不同程度的溶解了蒸发盐;河水样品的Ca~(2+)、HCO~-_3、SO~(2-)_4与Cl~-的比值反映了CO_2气体、碳酸盐以及硫酸盐溶解。海水样品的Br~-/Cl~-比值与海水比值基本相同,与其它主要离子与Cl~-的关系都表明海水样品源于标准海水与河水的混合。因此当河水和海水混合时,两种水体的溶剂发生机械混合,溶质中海水占主导的化学成分与Cl~-比值都接近海水比值,包括Na~+、Mg~(2+)、SO~(2-)_4、Br~-和Cl~-的比值,而大陆生成的成分在淡水中与Cl~-的比值都会大于海水比值,主要有HCO~-_3、Ca~(2+)、NO~-_3和Cl~-的比值。这种混合机理也适用于地下水。     

四川鲜水河-安宁河断裂带温泉氢氧稳定同位素特征

温泉地下水同位素特征对确定断裂带地下水来源、循环过程和断裂带活动性至关重要。为了确定青藏高原东缘温泉的地下水同位素特征和流体来源本研究采集了鲜水河-安宁河断裂带上温泉水、冷泉水、河流和积雪融水等样品,进行了氢氧稳定同位素和水化学组分测定,并进行了同位素特征的对比研究。分析结果表明,温泉水体δ¹⁸O变化范围为-19.04%~-12.71‰,平均值为-16.42‰;δ²H变化范围为-144.07‰~-88.63‰,平均值为-122.37‰。河水的δ¹⁸O变化范围为-15.90‰~-10.85‰,平均值为-13.86‰;δ²H变化范围为-118.21‰~-71.12‰,平均值为-98.99‰。康定冷泉δ¹⁸O和δ²H分别为-13.66‰和-106.74‰。道孚积雪融水的δ¹⁸O和δ²H分别为-10.27‰和-65.41‰。不同类型水体样品氢氧稳定同位素组成主要分布在全球和区域大气降水线上表明了大气降水成因,缺少明显的氧同位素漂移特征。不同类型水体同位素值差异较大显示出温泉与河水、积雪融水之间补给来源的不一致性。温泉同位素值具有明显的同位素高程效应,鲜水河-安宁河断裂带上氧同位素高程效应为-0.23‰/100m,氢同位素高程效应为-1.95‰/100m。温泉氧同位素漂移与相关离子比值、Na-K-Mg三角图、Li和Sr元素等指标表明研究区域大部分温泉的水岩作用强度弱。氢氧稳定同位素特征、水岩作用特征和循环深度揭示出温泉的成因为远距离大气降水运移补给地下水,地下水在地下热储层加热后通过断裂上升到地表形成温泉,这为认识青藏高原东缘地热水循环、断裂带活动性与演化特征提供了依据。     

新疆库车盆地盐泉水水化学特征、来源及找钾指示意义

库车盆地是塔里木盆地的一个次级凹陷,位于新疆塔里木陆块北缘与西南天山之间。文章介绍了库车盆地盐泉水的化学特征、来源及其找钾指示意义。对库车盆地几个代表性盐泉出露区进行盐泉水样品(21件)采集和分析,研究了其化学组成特征、水化学类型和氢氧同位素组成,同时根据收集的129件盐泉水化学数据资料,生成了盐泉水水化学分布图。新采自库车盆地的21件盐泉水样品矿化度范围为120.216~305.322g/L,水型以氯化物型(瓦里亚什科分类法)为主,具有明显的深部地层氯化钙型卤水的特征。氢氧同位素组成分析发现,盐泉水δ18 O范围为-9.1‰~4.7‰,δ2 H值范围为-75‰~-28‰,投点偏离大气降水线且δ18 O和δ2 H具有一定的正相关关系(r=0.81),表明该区盐泉水曾受到强烈蒸发作用影响,同时也受水—岩作用影响,存在一定的δ18 O漂移现象。库车盆地盐泉水组成特征与深部岩层岩性有密切关系,而断裂控制盐泉水出露与分布,盐泉水形成的地表地球化学异常对于该区找钾有一定的指示意义。     

九江地震台地下水氢氧稳定同位素变化特征及意义

在地震地下流体研究中,地下水补给及循环过程是重要的研究内容之一,氢氧同位素示踪技术是目前研究该过程的常用手段。通过对九江地震台2井地下水、大气降水及周边天花井水库水、马尾水高山泉水的样品进行氢氧同位素测定分析,结果表明,与降水相比地下水氢氧同位素变化更为稳定。夏半年,大气降水氢氧同位素与降水量呈显著的负相关关系,具有明显的降水量效应;冬半年,与温度成显著的正相关关系,具有明显的温度效应,地下水氢氧同位素并未表现出明显的降水效应和温度效应。氢氧同位素及过量氘揭示地下水在下渗补给前经历了明显的蒸发分馏作用,并与围岩进行~(18)O交换,δ~(18)O与δD计算的补给高程分别约为647m、440m。九江台地下水总体属于大气成因型,循环过程为较稳定的裂隙水补给形成承压自流井。     

莱州湾南岸卤水的稳定同位素与地球化学特征

莱州湾南岸卤水的开发利用始于20世纪50年代,如今卤水的含盐量比海水高出3～6倍。本文采用稳定同位素和水化学分析来鉴定卤水的盐分来源,为此在研究区内采集了9件卤水样品,采样井深度为30～80m。首先根据同位素盐效应,对卤水的δD和δ~(18)O值进行了校正。校正后的δD和δ~(18)O值关系图表明卤水的水分子来源于大气降水,而不是海水。δ~(18)O—Cl~-和Br~-—Cl~-关系表明卤水的盐分不同于海水蒸发的余留水。根据化学分水岭原理,卤水的Ca~(2+)/SO_(-4)~2和Ca~(2+)/Mg~(2+)值演化提示溶解盐起源不是蒸发的海水卤水。其它化学成分关系也证实了卤水的盐分源于海水蒸发盐的反复溶解。本研究说明卤水样品与海水盐分有关,但是与海水的水分子无关。     

香溪河流域大气降水稳定氢氧同位素时空分布特征

香溪河流域地处不同地理、气候、岩溶地貌分区的重要过渡位置,研究其大气降水氢氧同位素时空分布特征,是利用氢氧同位素示踪技术研究流域水循环特征的基础。本文通过不同高程布设的观测点,获取到研究区大气降水稳定氢氧同位素(D、~(18)O及17O)观测数据,由此首次建立了香溪河流域大气降水线(δD=8.17δ~(18)O+13.38),氧同位素间的关系式(δ'17O=0.512δ'~(18)O+0.024),并深入分析氢氧同位素时空分布特征。     

陕西省现代大气降水氢氧同位素组成特征研究

陕西地处我国东部湿润气候与西部干冷气候的过渡地区,气候偏冷,偏旱,降水偏少,蒸发量远大于降水量。全境呈南北狭长状,分属三个不同气候带。本文根据自然地理分区(陕北、关中、陕南)的大气降水氢氧同位素组成的逐月变化,求得陕西地区大气降水的雨水线公式:δD=8.36δ~(?)O 14.5。又根据气象要素——温度(t)、降水量(L)、蒸发量(1)对降水的氢氧同位素组成的影响,通过回归分析得出,影响δ值变化的主要因素是降水量,且为负相关,其次是温度和蒸发量。大气降水δ值与综合气象要素的回归方程式为:δD=-46.382 2.0438t-0.3084L-0.05451,δ~(18)O=-7.8436 0.2677t-0.0335L-0.00611。进而根据全省大气降水和由降水补给的地下水氢氧同位素组成之间的关系,通过相关计算,求得地下水δ值与大气降水δ值的相关关系式:δD_(地下水)=0.3062δD_(降水)-51.00,δ~(?)O_(地下水)=0.1411δ~(18)O_(降水)-8.14。     

漳州盆地水热系统的氢氧稳定同位素研究

本文对我国东南沿海地区温度最高的典型花岗岩裂隙热水盆地——漳州盆地水热系统的地下热水及各类相关的其它类型天然水的氢氧稳定同位素(δD和δ~(18)O)特征进行了研究。对漳州地区的大气降水线、地下热水起源、地下热水的补给源(区)以及影响地下热水同位素成分的形成与演化的海水与大气降水的混合等地球化学作用问题进行讨论。     

运城盆地地下水同位素年龄特征及其演化过程和可持续利用

通过分析运城盆地地下水的碳同位素组成,结合水化学特征,揭示了盆地深层承压地下水的补给期为22～3 ka BP （现代碳百分比(a¹⁴C) 6~38 pmC）。浅层地下水（71~89 pmC）由现代水或现代水和老水混合组成。深层地下水氢氧同位素组成特征（δ¹⁸O~-10‰; δ²H~-70‰）表明地下老水在气候较冷的环境下受到补给,而浅层地下水的氢氧同位素组成（δ¹⁸O~-8‰; δ²H～-51‰）特征与现代西安降水组成相似。浅层地下水NO^-₃平均含量（31mg/L）比深层地下水（1.8 mg/L）高,硝酸盐的δ¹⁵N－δ¹⁸O_NO3 组成 (0‰～5‰）揭示了硝酸盐的主要来源为综合肥料。此外,浅层地下水的TDS由于蒸散发、矿物溶解,可达8.5 g/L（平均2.0 g/L）,深层地下老水TDS可达1.8 g/L（平均1.1g/L）水质相对较好。研究区目前主要开采深层地下水,受断裂带影响,浅层地下水已经侵入中深层地下水并与之发生混合,严重影响了中深层地下水的水质。如果发生大规模的浅层地下水与中深层地下水混合,会造成中深层地下老水的NO^-₃、TDS等含量越来越高。     

An assessment of groundwater salinization in Haryana state in India using hydrochemical tools in association with GIS

Unplanned abstraction of groundwater due to various land use land cover activities and variations in monsoonal rainfall have greatly affected the availability and quality of groundwater resources in semi-arid regions of India. In the present study, a study of the hydrogeochemical characteristics of groundwater was undertaken in the Sonipat district of Haryana in India together with the use of stable isotope (δ¹⁸O and δD) measurements and GIS analysis. A total of 53 groundwater samples were collected from seven blocks of the district, and 14 water quality parameters and stable isotopes (δ¹⁸O and δD) were analysed to infer hydrogeochemical processes taking place in the area. The integration of hydrochemistry with GIS is very helpful to understand the factors governing in the area. The majority of the samples showed Na–Cl type of hydrochemical facies. The trilinear plot for major cations and anions in groundwater indicates dominance of sodium, calcium, chloride and bicarbonate ions. Nitrate plumes in the groundwater appear to be migrating in groundwater from the central and south-western parts of the area towards the urbanized areas. A total of 64% of the samples exceed the maximum permissible limit of 1.5 mg/L given by WHO for fluoride. Besides natural sources such as silicate and carbonate weathering, ion exchange, and reverse ion exchange, the leaching of surficial salts and untreated industrial wastes along with unregulated abstraction are contributing to poor groundwater quality in the study area. An assessment of saturation indices has shown that groundwater in the area is unsaturated with respect to anhydrite, halite and gypsum suggesting significant contribution of Ca²⁺, Mg²⁺ and other ions in the groundwater. A scatter plot of δ¹⁸O versus Cl also suggests mixing of saline water with fresh groundwater.     

Understanding long-term groundwater flow at Pahute Mesa and vicinity,Nevada National Security Site,USA, from naturally occurring geochemical and isotopic tracers

Recently collected naturally occurring geochemical and isotopic groundwater tracers were combined with historic data from the Pahute Mesa area of the Nevada National Security Site (NNSS), Nevada, USA, to provide insights into long-term regional groundwater flow patterns, mixing and recharge. Pahute Mesa was the site of 85 nuclear detonations between 1965 and 1992, many of them deeply buried devices that introduced radionuclides directly into groundwater. The dataset examined included major ions and field measurements, stable isotopes of hydrogen (δ²H), oxygen (δ¹⁸O), carbon (δ¹³C) and sulfur (δ³⁴S), and radioisotopes of carbon (¹⁴C) and chloride (³⁶Cl). Analysis of the patterns of groundwater ¹⁴C data and the δ²H and δ¹⁸O signatures indicates that groundwater recharge is predominantly of Pleistocene age, except for a few localized areas near major ephemeral drainages. Steep gradients in sulfate (SO₄) and chloride (Cl) define a region near the western edge of the NNSS where high-concentration groundwater flowing south from north of the NNSS merges with dilute groundwater flowing west from eastern Pahute Mesa in a mixing zone that coincides with a groundwater trough associated with major faults. The ³⁶Cl/Cl and δ³⁴S data suggest that the source of the high Cl and SO₄ in the groundwater was a now-dry, pluvial-age playa lake north of the NNSS. Patterns of groundwater flow indicated by the combined data sets show that groundwater is flowing around the northwest margin of the now extinct Timber Mountain Caldera Complex toward regional discharge areas in Oasis Valley.

     

Tracing ionic sources and geochemical evolution of groundwater in the Intermountain Una basin in outer NW Himalaya,Himachal Pradesh,India

The present research aims to identify sources of ions and factors controlling the geochemical evolution of groundwater in an intermountain basin, comprising hill and valley fill region, of Outer Himalaya in Himachal Pradesh, India. The groundwater samples collected from 81 tubewells and handpumps are analyzed for major ions, trace metals and stable isotopes (δ¹⁸O and δD). Geochemically the dominant hydrochemical facies in the Una basin are Ca–HCO₃, Ca–Mg–HCO₃ and Na–Cl types at few locations. A relatively lower ionic concentration in the valley fills indicates dilution and low residence time of water to interact with the aquifer mass due to high porosity and permeability. The ionic ratios of 0.9, 0.8 and 3.8 to 5.7, respectively, for (Ca?+?Mg): HCO₃, (Ca?+?Mg): (HCO₃?+?SO₄) and Na: Cl, suggests that ionic composition of groundwater is mainly controlled by rock weathering of, particularly by dissolution/precipitation of calcrete and calcite hosted in rock veins and Ca–Na feldspar hosted in conglomerate deposits derived from the Higher and Lesser Himalaya during the formation of Siwalik rocks. Although Na, K, NO₃ and SO₄ are introduced in the groundwater through agricultural practices, Na has also been introduced through ion exchange processes that have occurred during water–rock interaction, as indicated by negative CAI values. Factor analysis further suggests three major factors affecting the water chemistry of the area. The first two factors are associated with rock weathering while the third is anthropogenic processes associated with high nitrate and iron concentration. High concentrations of Fe and Mn ions that are exceeded that of WHO and BIS standards are also present at few locations. The recharge of groundwater in the Outer Himalaya is entirely through Indian Southwest Monsoon (ISM) and depleted ratios of δ¹⁸O/δD in valley region indicate infiltration from irrigation in recharging the groundwater and fractionation of isotopes of precipitation due to evaporation before infiltration. High d-excess values and inverse relation with δ¹⁸O are indicative of secondary evaporation of precipitation during recharge of groundwater.     

Hydrologic and geologic factors controlling groundwater geochemistry in the Turonian aquifer (southern Tunisia)

Water in the fissured limestone and dolomite of the Turonian aquifer of Tunisia has been investigated using geochemical (major ions) and isotopic (δ¹⁸O, δ²H, ¹⁴C) data. To carry out a characterization of aquifer behaviour, 48 representative samples were collected at the end of the humid season. The evolution of chemical composition of groundwater from recharge areas to discharge areas is characterized by increasing sodium, chloride and sulphate contents as a result of leaching of evaporite rock. In the study, three distinct chemical trends in groundwater were identified. The major reactions responsible for the chemical evolution of groundwater in the investigated area fall into three categories: (1) calcite precipitation, (2) gypsum and halite dissolution, and (3) ion exchange. The stable isotope composition of water samples indicates large-scale interaction between the Continental Intercalaire and the Turonian aquifer and the presence of a young local component which probably enters the system via faults and/or fractures.     

淮河下游地区地表水与地下水同位素特征分析

为探明淮河下游地区地表水与地下水稳定同位素的组成特征,于2020年11月对该区域进行代表性采样,共采集地表水样13个,地下水样82个.结合全球大气降水同位素监测网(GNIP)公布的南京降水同位素数据,根据最小二乘法得出当地大气降水线(LMWL)方程为:δD=8.49δ18O+17.71,其斜率和截距高于全球大气降水线(...     

Evaluation of boron isotopes in halite as an indicator of the salinity of Qarhan paleolake water in the eastern Qaidam Basin,western China

In this study, nineteen brine samples from the Qarhan Salt Lake (QSL) in western China were collected and analyzed for boron (B) and chlorine (Cl) concentrations, total dissolved solids (TDS), pH values and stable B isotopic compositions. The B concentrations and δ¹¹B values of brines in the QSL range from 51.6 mg/L to 138.4 mg/L, and from +9.32‰ to +13.08‰, respectively. By comparison of B concentrations and TDS of brines in QSL with evaporation paths of brackish water, we found that B enrichment of brines primarily results from strong evaporation and concentration of Qarhan lake water. Combining with comparisons of B concentrations, TDS, pH values and δ¹¹B values of brines, previously elemental ratios (K/Cl, Mg/Cl, Ca/Cl, B/Cl) and δ¹¹B values of halite from a sediment core (ISL1A), we observe good correlations between B concentrations and TDS, TDS and pH values, pH and δ¹¹B values of brines, which demonstrate that higher B concentrations and more positive δ¹¹B values of halite indicate higher salinity of the Qarhan paleolake water as well as drier paleoclimatic conditions. Based on this interpretation of the δ¹¹B values of halite in core ISL1A, higher salinity of the Qarhan paleolake occurred during two intervals, around 46–34 ka and 26–9 ka, which are almost coincident with the upper and lower halite-dominated salt layers in core ISL1A, drier climate phases documented from the δ¹⁸O record of carbonate in core ISL1A and the paleomoisture record in monsoonal central Asia, and a higher solar insolation at 30°N. These results demonstrate that the δ¹¹B values of halite in the arid Qaidam Basin could be regarded as a new proxy for reconstructing the salinity record of paleolake water as well as paleoclimate conditions.     

长江流域降水稳定同位素的云下二次蒸发效应

对长江流域443个GNIP的降水样品同位素原始资料,分降雪和降雨进行δ2H和δ18O线性回归,得到降雪样品的相关方程为δ2H=7.965δ18O+17.114,有最大的斜率和截距;而降雨样品根据降水量大小从<10mm至>300mm分为4组后,得到的相关方程随着降水量的减小,斜率和截距均减小,斜率从7.701减小为5.705,截距从7.812×10-3减小为-5.479×10-3。δ2H~δ18O相关方程的斜率及截距与气温、水汽压之间的关系表明,在降水从云层底部降落到地面的过程中,仅较小降雨事件有明显的二次蒸发现象,并伴随着同位素的分馏。长江流域较小降雨事件占有比例很小,仅为所有降水事件的6.32%,所以二次蒸发效应仅引起地区大气降水方程斜率和截距的微弱减小。研究表明,单个降水原始资料的同位素分析,能产生长期加权平均降水同位素分析得不到的宝贵信息。     

Hydrogeochemical and Isotopic Study of Groundwater in a Semi-arid Region: Yeniceoba Plain (Cihanbeyli-KONYA), Central Anatolia,Turkey

Groundwater is the most important source of water supply in the Yeniceoba Plain in Central Anatolia,Turkey.An understanding of the geochemical evolution of groundwater is important for the sustainable development of water resources in this region.A hydrogeochemical investigation was conducted in the Plio-Quaternary aquifer system using stable isotopes(δ~(18)O andδD),tritium(~3H),major and minor elements(Ca,Na,K,Mg,Cl,SO_4,NO_3,HCO_3 and Br)in order to identify groundwater chemistry patterns and the processes affecting groundwater mineralization in this system.The chemical data reveal that the chemical composition of groundwater in this aquifer system is mainly controlled by rock/water interactions including dissolution of evaporitic minerals,weathering of silicates,precipitation/dissolution of carbonates,ion exchange,and evaporation.Based on the values of Cl/Br ratio(300 mg/l)in the Plio-Quaternary groundwater,dissolution of evaporitic minerals in aquifer contributes significantly to the high mineralization.The stable isotope analyses indicate that the groundwater in the system was influenced by evaporation of rainfall during infiltration.Low tritium values(generally1 tritium units)of groundwater reflect a minor contribution of recent recharge and groundwater residence times of more than three or four decades.     

Characterisation of chlorinated hydrocarbons from chlorine and carbon isotopic compositions: scope of application to environmental problems

A set of chlorinated hydrocarbons (TCE, PCE, DCM, 1,1,1-TCA, chloroform) provided by four manufacturers has been isotopically characterised for both C and Cl, using a new sensitive method. A very large range of δ¹³C (from −51.66 to −24.07‰/PDB) associated with a very large range of δ³⁷Cl (from −2.7 to +3.4‰/SMOC) was obtained. This range of δ³⁷Cl is much larger than that of inorganic Cl (±1‰ SMOC) and most individual solvents show a very distinct δ³⁷Cl compared to inorganic Cl isotopic signatures. Moreover, δ³⁷Cl/δ¹³C pairs are distinct from one solvent/manufacturer to another. In a δ¹³C versus δ³⁷Cl diagram, δ³⁷Cl / δ¹³C pairs show different trends for the products of a single manufacturer compared to another. This suggests that Cl isotopic compositions are probably highly fractionated during organic synthesis. The δ³⁷Cl values can be interpreted in terms of the probable manufacturing processes. Unlike the data published previously, with one exception, all the new results for samples reported here have positive δ³⁷Cl values which might differentiate natural Cl from that derived from degradation. This method has significant potential as a tool for investigating environmental pollution problems; in particular, it offers the possibility for validating models of transport and fate of pollutants.     

Hydrochemical characteristics and controlling factors for waters’ chemical composition in the Tarim Basin,Western China

This paper covers the chemical and isotopic composition of river water, groundwater from wells (15–25 m), saline spring water and stagnant surface water providing evidence for controlling factors of water composition and water evolution process in the Tarim Basin, Xinjiang, western China. Analytical data for major and minor ions of totaling 537 water samples were obtained from both years of teamwork and old reference materials. It is found that the ion background value ratio SO₄/Cl for river water (2.75) of the Tarim Basin is two times higher than that of the Qaidam Basin (0.88) and 18 times higher than seawater (0.14); K/Cl of these two basins (0.06 and 0.07) are all two times higher than seawater (0.02). This reveals that material sources of Lop Nur are relatively richer in potassium and sulfate, while poorer in chloride. Gradual changes of stable isotopic compositions in waters clearly indicate the effect of evaporation on water evolution of the basin. Besides evaporation and weathering of surrounding rocks, wide distribution of chloride type water, which commonly exist in saline springs/brines and seldom exist in other waters, indicates that hydrothermal Ca–Cl brines discharged from deep within the earth join water evolution of the basin.