准噶尔盆地南缘土壤水运移特征及其补给来源识别

在荒漠区,土壤水是一切陆生植物赖以生存的基础,识别荒漠区土壤水的补给来源,探索土壤水的运移机理,对于荒漠区生态修复非常必要。通过对荒漠区非饱和带剖面土壤水的含水率、易溶盐离子及稳定同位素(δD、δ~(18)O)的测定和分析,研究荒漠区土壤水的补给来源与运移机理。结果表明:荒漠区土壤含水率、易溶盐与土壤水氢氧同位素在垂向上呈现旋回变化,剖面中土壤Cl-含量与含水量成正相关;0~1.6 m为蒸发影响带,1.6~8.0 m为土壤水向下运移带,8.0 m以下为潜水影响带。从土壤水中氢氧同位素及Cl-含量信息来看,荒漠区土壤水来源于大气降水的补给。旋回中Cl-含量极低值与δD与δ~(18)O极贫值相对应,δD值贫化峰值为-124.10‰~-97.39‰,荒漠区土壤水来源于冬季大气降水或降雪的入渗补给。     

新疆霍城县水环境同位素特征及其指示作用

在分析研究区水文地质条件基础上,根据同位素测试结果,重点分析了地下水、泉水及地表水氢氧稳定同位素和氚同位素的分布特征.潜水δD变化范围为-87.71 ～-75.40‰,δ18 O为-12.80～-10.91‰.承压水δD为-90.44～-65.57‰,δ18O为-13.08～-8.17‰.地下水氚浓度主要集中在15 ～ 30TU范围内,绝大部分地下水为1953年以前所补给.地下水与地表水均起源于当地大气降水.潜水与承压水水力联系较强,潜水与承压水属于同一含水系统,在开发过程中要十分注重保护这一含水系统,防止过度开发导致含水系统遭到破坏.     

应用环境同位素识别松嫩平原西南部地下水的补给来源

识别地下水的补给来源是进行合理开发利用与科学管理地下水资源的重要前提.文中根据松嫩平原月大气降水同位素数据,建立了当地大气降水线方程δD =7.29 δ18O-0.81‰;通过分析研究区内110件地下水样品的环境同位素(2H、18O、3H)特征以及结合区域水文地质条件,识别出了研究区地下水的补给来源.结果表明:第四系潜水补给来源以当地降水为主,受蒸发作用影响强烈;第四系承压水补给来源有两种途径,一种是山前平原的侧向补给(降水来源)或上层第四系潜水的渗透补给;另一种可能是δ18O值更为贫化的山区降水入渗所形成的侧向补给.新近系泰康组与大安组承压水的补给来源为历史时期的古降水,其水汽来源特征与现今相比更加湿润.     

氢氧稳定同位素对达里湖水体蒸发与补给来源的指示作用

为了研究稳定同位素质量平衡法在寒旱区封闭型内陆湖泊水量平衡计算中的适用性,以内蒙古高原达里湖作为研究区域,基于流域水体样品中氢氧稳定同位素(δD、δ~(18)O)特征分析,讨论了δD、δ~(18)O对水体蒸发和补给来源的指示作用。结果表明:夏季达里湖水体氢氧稳定同位素值不断减小,其主要受到降水过程的影响;冬季结冰过程使得氢氧同位素在冰体中富集。达里湖湖水δ~(18)O-δD关系点落在了当地大气降水线的右下方,显示湖区水体蒸发最为强烈;部分河水和地下水δ~(18)O-δD关系点落在当地大气降水线左上方,显示当地大气降水并非其地下水的主要补给来源。利用稳定同位素质量平衡法对2018年达里湖蒸发量和地下水补给量进行估算,结果显示年蒸发量约为2.69×10~8m~3,全年地下水补给量约为1.65×10~8m~3。在考虑动力分馏和初始水体同位素组成的条件下,利用水体稳定同位素分馏过程中δD与剩余水体比例的关系,计算得到达里湖湖水蒸发损失量约为初始水体的41%～46%。     

吐鲁番盆地水环境同位素分析与应用

在吐鲁番盆地范围内进行水环境取样,运用同位素技术及分析方法,对吐鲁番盆地各类水体进行研究,分析了研究区水环境同位素特征,并讨论各类水体间的相互关系。盆地地表水的δ18O值在-13.62~-9.00‰之间,平均值为-10.31‰;δD值在-79.73~-60.09‰之间,平均值为-65.98‰。地下水的δ18O值在-12.28~-7.02‰之间,平均值为-10.30‰;δD值在-86.54~-48.98‰之间,平均值为-68.27‰。结果表明二者之间具有较强的水力联系。高昌区、鄯善县地表水、地下水起源自北部山区内水系,托克逊县地表水、地下水起源即来自北部山区内水系,又来自西部山区内水系。盆地内泉水起源即有潜水也有承压水,坎儿井水起源较为复杂,即有潜水也有人为灌溉入渗补给。     

氢氧稳定同位素指示的呼和浩特地区土壤水的补给特征

土壤水中的氢氧稳定同位素特征包含了水在包气带中的迁移信息,因此,分析土壤水中的氢氧稳定同位素的变化特征可以追踪土壤水的迁移过程.文中主要对呼和浩特地区西南部两个孔的包气带土壤剖面中氢氧稳定同位素随深度的变化特征进行了分析,并对呼和浩特地区降水、土壤水和地下水之间的同位素组成进行了比较.结果表明:该区土壤表层的水中的δ2H和δ18O受到降水中的δ2H和δ18O的直接影响,同时受到蒸发作用的影响,同位素值产生富集,之后变化幅度逐渐减小,逐渐接近地下水中的同位素值,显示出土壤底部的水分与地下水的交换比较活跃;通过对比该区降水、土壤水和地下水的同位素值,发现该区土壤水的补给来源主要为降水,且降水的补给为季节性补给,补给季节主要是秋季.     

石羊河下游青土湖大气降水氢氧同位素特征及水汽来源

青土湖属于季风边缘区内陆河尾闾封闭湖泊,以其生态脆弱性和气候敏感性是古气候、古环境等全球变化环境研究的理想区域。降水是干旱区生态系统水循环的重要输入因子,研究降水氢氧同位素特征及水汽来源对全球气候变化背景下青土湖水资源管理具有重要的理论和实践意义。基于氢氧稳定同位素技术,通过分析青土湖5月～10月6个月21个大气降水氢氧同位素组成及与环境因子的关系,结合HYSPLIT模型模拟大气降水气团传输途径和过程,判定该地区水汽来源。结果表明:5月-10月大气降水氢氧稳定同位素关系的线性方程LMWL为δD=6. 67δ~(18)O-1. 01(n=21,R2=0. 95);大气降水的δ~(18)O变化范围为-16. 97‰～3.23‰,平均值为-5. 36‰。δD的变化范围为-118. 36‰～15. 63‰,平均值为-36. 82‰。过量氘(d-excess)介于-23. 64～21. 93‰,均值为6. 03‰,低于全球平均值(10‰)。降水δ~(18)O与降雨量显著相关,但温度效应不显著。受西风水汽、局地人工季节性湖面蒸发和亚洲季风的影响,青土湖大气降水水汽来源的季节性明显,夏季主要来源于西风环流、东南季风及局地蒸发,秋季来源于西伯利亚和蒙古的极地大陆气团。连续多年生态补水形成的人工季节性湖面蒸发成为夏季降水水汽来源之一,对改善湖区生态环境具有重要的意义。     

包头地区大气降水δD和δ~(18)O变化特征浅析

大气降水中氢氧稳定同位素包含着水循环演化过程中的历史信息,对揭示水资源的形成及演化机制具有重要的意义。文中根据包头站大气降水中稳定同位素和气象资料,分析了包头地区(1986-1992年)大气降水的氢氧稳定同位素的变化特征及其与气温和降水之间的关系,发现该区氘盈余值(d)具有冬季高夏季低的特点,且d值接近全球大部分地区降水的d值(10‰)。该区大气降水中δ18O值具有夏季高冬季低,δ18O的温度效应显著,而降水量效应只在夏半年(4-9月)间显著。同时提出了包头地区当地大气降水线方程为δD=6.4δ18O-4.07,与全国及全球降水线方程相比,反映出干旱的气候特征。     

西部降水氢氧稳定同位素温度及地理效应

本文基于IAEA和WMO建立的GNIP网降水资料,得出中国西部地区大气降水线方程(LMWL)为δ2H=7.56δ18O+5.05‰(VSMOW)。分析了降水中氢氧稳定同位素温度效应、地理效应,确定了降水中δ18O和δ2H与月平均气温、降水量、海拔高度、纬度的相关关系。根据张掖站降水δ18O与温度之间的相关关系和民勤地下水14C年龄和δ18O特征,初步重建了晚更新世以来民勤盆地地下水补给温度,并与惰性气体补给温度(NGT)进行了比较,其相关系数为0.65,晚更新世地下水的补给温度(据δ-T关系)较大,可能是没有考虑降水量效应的缘故。     

石羊河下游青土湖白刺灌丛水分来源及其对生态输水的响应

通过测定人工湖面不同距离白刺灌丛生长季降水、土壤水、地下水、植物水的稳定氢氧同位素变化特征,结合IsoSource模型,定量分析了白刺灌丛生长季的水分利用策略。结果表明:随样地与人工湖面距离的增加,0-200m水平范围白刺灌丛各土层平均土壤水分逐渐减小,其中0m样地最高为10.02%,200m样地最小为5.24%,对250m-600m样地各土层平均土壤水分的影响不大。受蒸发及降水季节变化的影响,白刺灌丛0-70cm土壤水及其δ~(18)O变化剧烈。土壤水的δ~(18)O介于-8.78‰～16.39‰,平均值为0.14‰。地下水的δ~(18)O介于-4.19‰～-3.55‰,平均值为-3.89‰。降水的δ~(18)O介于-17.31‰～3.37‰,平均值为-6.36‰。湖水的δ~(18)O介于-1.84‰～11.66‰,平均值为3.02‰。木质部水的δ~(18)O介于-5.98‰～2.74‰,平均值为-3.59‰,各样地不同土层土壤水分δ~(18)O差异显著(P<0.05)。随样地与人工湖面距离的增加,白刺灌丛逐渐利用更深层次的土壤水及地下水。     

Distribution of isotopes and chemicals in precipitation in Shule River Basin,northwestern China:an implication for water cycle and groundwater recharge

The distribution of stable isotopes and ions in precipitation in the Shule River Basin,northwestern China,were investigated to understand the regional water cycle and precipitation input to groundwater recharge.The study found that the mean annual concentrations of Ca2+,Na+,SO42–,Cl–,Mg2+,NO3–,and K+ in the basin were lower than those in other arid areas of northwestern China.The average concentrations of ions in the lower reaches of the Shule River were higher than those in the upper reaches.The results showed that the main ionic concentrations decreased with the increase of precipitation amount,indicating that heavy precipitation cannot only wash crustal aerosols out of the atmosphere,but also create a dilution effect.Cl– and Na+ in precipitation had a strong and positive correlation,suggesting a common origin for the two ions.However,the excess of Na+,combined with non-marine SO42– and NO3–,indicated that some ions were contributed by terrestrial origins.In the extremely arid regions of northwestern China,the evaporation process obviously changes the original relationship between δ2H and δ18O in precipitation,and leads to dexcess values 8‰.δ18O and temperature were significantly correlated,suggested that temperature strongly affected the characteristics of isotopes in the study area.The δ18O value indicates a dominant effect of westerly air masses and southwest monsoon in warm months,and the integrated influence of westerly and Siberian-Mongolian polar air masses in cold months.The d-excess values were generally lower in warm months than those in cold months,indicating that post-condensation processes played a significant role in the water cycle.The results provide reliable precipitation input information that can be used in future groundwater recharge calculations in the study area.     

西藏雨季主要水体氢、氧同位素特征

通过对2014年雨季西藏境内63处水体中δD和δ~(18)O值的测定,分析其中氢、氧稳定同位素组成特征。结果表明:水体δD和δ~(18)O的取值范围分别为-152.06‰~-19.05‰和-16.96‰~4.66‰,δD较δ~(18)O的标准差大,平均值分别为-101.38‰和-9.67‰;3种水体的δD和δ~(18)O值关系为湖泊δD相对河流δD富集,河流δD相对沼泽δD富集,湖泊δ~(18)O相对河流δ~(18)O和沼泽δ~(18)O富集,河流δ~(18)O和沼泽δ~(18)O无差异;蒸发趋势方程分别为δD湖泊=6.14δ~(18)O-45.48(n=22,R2=0.855),δD河流=7.83δ~(18)O-26.22(n=32,R2=0.858),δD沼泽=5.93δ~(18)O-52(n=9,R2=0.723),河流相比湖泊和沼泽水体的δD与δ~(18)O更易受大气降水的影响;氘过量参数特征为湖泊-79‰~-17‰,河流-40‰~-5‰,湿地沼泽-34‰~-7‰,表现出蒸发强烈的水体特征;沼泽水体δ~(18)O与纬度的一元线性回归方程为y=1.67x-63.23。     

Source identification of nitrate in the upper aquifer system of the Wadi Shueib catchment area in Jordan based on stable isotope composition

Groundwater forms the main freshwater supply in arid and semi-arid areas,and contamination of this precious resource is complicated by the slow rate of recharge in these areas.Nitrate contamination of groundwater is a global water quality problem,as it entails threat to human health as well as aquatic ecosystems.Source identification of contamination is the cornerstone and a prerequisite for any effective management program of water quality.Stable isotope composition of the dissolved nitrate(δ¹⁵N-NO₃-andδ¹⁸O-NO₃-)has been applied to identify NO₃-sources and the main transformation processes in the upper aquifer system(A1/2,A4,and B2/A7 aquifers)in the Wadi Shueib catchment area,Jordan.Moreover,the stable isotope compositions of the groundwater(δ²H-H₂O andδ¹⁸O-H₂O)in conjunction with the groundwater hydrochemistry were integrated to investigate the origin and evolution of the groundwater.Results revealed that groundwater in the study area is fresh and hard-very hard water,and mainly a Ca-Mg-Cl type.NO₃-concentration was in the range of 7.0-74.0 mg/L with an average of 37.0 mg/L.Most of the samples showed concentration higher than the natural background concentration of NO₃-(5.0-10.0 mg/L).Theδ²H-H₂O andδ¹⁸O-H₂O values indicated that the groundwater is meteoric,and of Mediterranean origin,with a strong evaporation effect.Theδ¹⁵N-NO₃-values ranged between 6.0‰and 11.3‰with an average of 8.7‰,and theδ¹⁸O-NO₃-values ranged between 1.6‰and 5.9‰with an average of 3.4‰.These values are in conformity with the stable isotope composition of nitrate derived the nitrification of wastewater/manure,and soil NH4.Nitrification and denitrification are the main transformation processes affecting nitrogen species.Statistical analysis revealed no significant differences in theδ²H-H₂O andδ¹⁸OH₂O values,andδ¹⁵N-NO₃-andδ¹⁸O-NO₃-values for the three aquifers(A1/2,A4,and B2/A7),indicating that the groundwater of these aquifers has the same origin,and a common source of pollution.     

闪电河流域“三水”季节变化特征

分析水体中氢(H)、氧(O)稳定同位素(δD、δ~(18)O)的变化,可以判断出不同水体的变化特征及相互关系。通过2014年5、8、10月对内蒙古正蓝旗境内闪电河流域地表水、浅层地下水及大气降水等样品的连续采集,得到地表水样21个、地下水样69个、大气降水样21个,在对"三水"样品δD、δ~(18)O值测试分析的基础,进一步讨论了"三水"变化特征及相互关系,结果显示:1闪电河流域"大气降水线"表达式为:δD=8.01δ~(18)O+6.83‰(r=0.962 1),反映了研究区蒸发量远大于降水量的气候特征。而不同月份d(氘盈余参数)出现差异,降水最多的8月d值最低,降水最少的10月d值最高,显示了大气降水次数或强度对二次蒸发作用产生了一定程度的影响。2闪电河流域地下水与地表水中δD、δ~(18)O值,不仅位于"大气降水线"之下,而且不同月份地表水与地下水中δD、δ~(18)O值的变化区间也出现差异。5月,各断面地下水与地表水中δD、δ~(18)O值差异不大,说明地下水与地表水得到充分混合;8月和10月,地表水中δD、δ~(18)O值比地下水明显偏重且各断面中大气降水所占比例较高,显示了大气降水过程对地表水H、O同位素变化的影响。此外,闪电河流域自上游到下游地表水中δD、δ~(18)O值在8月相近,而在10月逐渐出现偏大,指示了10月强烈蒸发作用对地表水中δD、δ~(18)O值变化的影响。     

中国西北中小型盆地天然地下水水化学特征——以公婆泉盆地为例

研究分析干旱气候条件下甘肃北山公婆泉盆地天然地下水水化学成分特征,结合水文地质条件与水化学特征Piper三线图表明:研究区存在4种类型地下水,白垩系深层水中钙镁离子含量相对高于其他类型水.地下水氚同位素结合水化学特征较好地区分了水源点的水文地质属性.氢氧同位素表明,该区地下水来源于大气降水,第四系浅层水受到强烈的蒸发作用,发生了一定程度的氧漂移,并影响"混合水"的同位素组成.最后分析了地下水主要离子的来源,以及地下水形成过程中所受到的溶滤、沉积和蒸发等水文地球化学作用.     

Isotope implications of groundwater recharge,residence time and hydrogeochemical evolution of the Longdong Loess Basin,Northwest China

Groundwater plays a dominant role in the eco-environmental protection of arid and semi-arid regions.Understanding the sources and mechanisms of groundwater recharge,the interactions between groundwater and surface water and the hydrogeochemical evolution and transport processes of groundwater in the Longdong Loess Basin,Northwest China,is of importance for water resources management in this ecologically sensitive area.In this study,71 groundwater samples(mainly distributed at the Dongzhi Tableland and along the Malian River)and 8 surface water samples from the Malian River were collected,and analysis of the aquifer system and hydrological conditions,together with hydrogeochemical and isotopic techniques were used to investigate groundwater sources,residence time and their associated recharge processes.Results show that the middle and lower reaches of the Malian River receive water mainly from groundwater discharge on both sides of valley,while the source of the Malian River mainly comes from local precipitation.Groundwater of the Dongzhi Tableland is of a HCO3-Ca-Na type with low salinity.The reverse hydrogeochemical simulation suggests that the dissolution of carbonate minerals and cation exchange between Ca²⁺,Mg²⁺and Na+are the main water-rock interactions in the groundwater system of the Dongzhi Tableland.Theδ¹⁸O(from-11.70‰to-8.52‰)andδ2H(from-86.15‰to-65.75‰)values of groundwater are lower than the annual weighted average value of precipitation but closer to summer-autumn precipitation and soil water in the unsaturated zone,suggesting that possible recharge comes from the summer-autumn monsoonal heavy precipitation in the recent past(≤220 a).The corrected 14C ages of groundwater range from 3,000 to 25,000 a old,indicating that groundwater was mainly from precipitation during the humid and cold Late Pleistocene and Holocene periods.Groundwater flows deeper from the groundwater table and from the center to the east,south and west of the Dongzhi Tableland with estimated migration rate of 1.29-1.43 m/a.The oldest groundwater in the Quaternary Loess Aquifer in the Dongzhi Tableland is approximately 32,000 a old with poor renewability.Based on theδ¹⁸O temperature indicator of groundwater,we speculate that temperature of the Last Glacial Maximum in the Longdong Loess Basin was 2.4℃-6.0℃ colder than the present.The results could provide us the valuable information on groundwater recharge and evolution under thick loess layer,which would be significative for the scientific water resources management in semi-arid regions.     

Groundwater hydrochemistry and isotope geochemistry in the Turpan Basin,northwestern China

The Turpan Basin is located in the arid zone of northwestern China and is a typical closed inland basin surrounded by high mountains. It is one of the most arid regions in the world and, as a result, the groundwater in this area is very important for both domestic and agricultural uses. In the present study, the relationships of major elements（K＋, Na＋, Ca2＋, Mg2＋, HCO3-, SO42- and Cl-） and environmental isotopes（δ18O, δ2H and T） in groundwater were analyzed to investigate the evolution of the regional hydrochemistry within the Turpan Basin. The hydrochemistry results demonstrate that groundwater with high total dissolved solids（TDS） concentration is dominated by sodium chloride（Na-Cl） and sodium sulfate（Na-SO4） type water, whereas that with low TDS concentration（typically from near mountain areas） is dominated by calcium bicarbonate（Ca-HCO3） type water. The evolution of groundwater hydrochemistry within the Turpan Basin is a result of calcium carbonate precipitation, evaporation concentration, cation exchange and dissolution of evaporites（i.e. halite, mirabilite and gypsum）. Furthermore, evaporite dissolution associated with irrigation practice plays a key role in the groundwater salinization, especially in the central part of the basin. Environmental isotopes reveal that the groundwater is recharged by precipitation in the mountain areas and fast vertical infiltration of irrigation return flow. In the southern sub-basin the shallow groundwater and the deep groundwater is separated at a depth of about 40 m, with substantial differences in terms of hydrochemical and isotopic characteristics. The results are useful for decision making related to sustainable water resource utilization in the Turpan Basin and other regions in northwestern China.     

地下水位下降对区域气候影响的虚拟试验

利用数值模拟方法,研究我国西北地区地下水位大幅度下降对干旱、半干旱气候变化的影响,并对地下水位变化和大气降水相互作用的反馈机制进行探讨.结果表明,地下水位大幅降落可以引发显著的气候效应,不仅引起降水的大幅度减少和近地面的增温,而且通过对土壤水状况的改变,引起了边界层结构和陆-气通量交换的变化.这些变化引起了局地对流层中低层大气环流的调整,进一步影响干旱气候.通过虚拟试验,反映了地下水变化对土壤水和大气降水等水分循环过程和干旱气候的巨大影响.