洞庭湖湖区降水-地表水-地下水同位素特征

为探明洞庭湖湖区水体稳定同位素时间和空间上的变化规律,弄清各水体间的相互关系,分别在2012年4月和8月对区域内具有代表性的采样点进行了地表水和地下水的采样。通过对样品进行D、18O同位素分析,结合全球大气降水同位素监测网（GNIP）公布的1988—1992年间长沙降水同位素数据,发现湖区年内受不同盛行风影响,降水及地表水的同位素存在较大的季节性差异,4月份同位素富集,8月份贫化。此外,河水、湖水同位素也呈现明显的空间差异。两个时期地表水的水线斜率均小于当地降水线,地表水在两个时期均存在蒸发作用。虽然地表水和地下水的来源均为大气降水,但与地表水相比,地下水同位素季节变化较小,地下水接受地表水补给是一个较为长期的过程。     

下垫面蒸发和云中凝结分馏对降水稳定同位素影响的数值试验——空间分布的比较

利用稳定同位素大气水平衡模式（iAWBM）,在一个水平衡和水稳定同位素平衡的框架下以及在相同的气象驱动下,模拟在不同的下垫面蒸发和不同的云中凝结分馏条件下降水中稳定同位素效应的空间分布特征,并通过与GNIP实测数据的比较以及模拟试验结果之间的相互比较,揭示云中的稳定同位素分馏和从下垫面蒸发的水汽同位素δ_e对降水中稳定同位素变化的可能影响,增进对全球水循环中稳定同位素效应的理解和认识。结果显示：iAWBM的4个模拟试验均很好地再现了全球降水中平均δ¹⁸O和平均δ¹⁸O季节差的空间分布特征;很好地模拟了降水同位素的温度效应、降水量效应的分布特点以及全球的大气水线MWL;比较而言,平衡分馏假设下模拟的全球降水中平均δ¹⁸O的空间分布与根据GNIP数据得到的实际空间分布以及模拟的全球MWL与实际MWL最接近,且模拟效果亦最好;动力分馏假设下模拟的降水中δ¹⁸O平均季节差的空间分布与根据GNIP数据得到的实际分布之间的相关程度较好,且拟合水平明显提高;在动力分馏和δ_e季节性的假设下,iAWBM再现全球δ¹⁸O-T和δ¹⁸O-P相关关系空间分布的能力较强。     

Isotopes (δD and δ18O) in precipitation, groundwater and surface water in the Ordos Plateau, China: implications with respect to groundwater recharge and circulation

The characteristics of δD and δ¹⁸O in precipitation, groundwater and surface water have been used to understand the groundwater flow system in the Ordos Plateau, north-central China. The slope of the local meteoric water line (LMWL) is smaller than that of the global meteoric water line (GMWL), which signifies secondary evaporation during rainfall. The distribution of stable isotopes of precipitation is influenced by temperature and the amount of precipitation. The lake water is enriched isotopically due to evaporation and its isotopic composition is closely related to the source of recharge and location in the groundwater flow systems. River water is enriched isotopically, indicating that it suffers evaporation. The deep groundwater (more than 150?m) is depleted in heavy isotopes relative to the shallow groundwater (less than 150?m), suggesting that deep groundwater may have been recharged during the late Pleistocene and early Holocene, when the climate was wetter and colder than at present. All groundwater samples plot around the LMWL, implying groundwater is of meteoric origin. Shallow groundwater has undergone evaporation and the average evaporation loss is 53%. There are two recharge mechanisms: preferential flow, and the mixture of evaporated soil moisture and subsequent rain.     

A feather hydrogen isoscape for Mexico

Developing useful biological isoscapes for areas of the world is a priority. This is the case for Mexico that hosts a large percentage of North America's Neotropical migrant birds. Here we investigated the use of House Sparrow (Passer domesticus) feathers to create a spatially explicit feather deuterium isoscape for that country using samples (n = 461) that were collected across Mexico. Considerable and useful spatial hydrogen isotopic structure was observed, suggesting that isotopes may be a potential forensic tool for evaluating origins of Mexican derived fauna and flora. The most positive feather δD values occurred in the northeast and most negative in the south-central part of the country, roughly matching δD patterns observed in groundwater. A weak negative isotopic relationship was found with altitude in both the Pacific and Atlantic drainage systems. The most parsimonious model describing isotopic spatial variation in feathers between 300 and 3000 m a.s.l. included groundwater δD (δD_gw; precipitation proxy), sex, amount of precipitation, and the coefficient of variation in amount of precipitation. Overall, δD_gw was a poor predictor of sparrow δD_f values for all of Mexico. However, this relationship was considerably strengthened when we considered sex separately, removed the Baja peninsula from our sample, and considered the Atlantic and Pacific drainage basins separately. The strongest relationship between δD_gw and δD_f was found for female sparrows in the Atlantic drainage basin (r² = 0.464). We recommend that researchers interested in inferring origins of migratory birds and other animals in Mexico create species specific isotopic basemaps that may be guided by the isotopic patterns we have observed for House Sparrows and groundwater.     

东亚水循环中水稳定同位素的GCM模拟和相互比较

利用引入稳定同位素循环的ECHAM4、GISS E和HadCM3模式的模拟,对东亚降水中年平均δD和过量氘d的空间分布以及大气水线（MWL）进行了分析.根据模拟的空间分布,降水同位素在很大程度上反映不同气团的地理背景以及它们之间的相互作用,模拟结果很好地再现了由GNIP实测资料得到的降水稳定同位素的纬度效应、大陆效应和...     

Quantification of the water balance and hydrogeological processes of groundwater–lake interactions in the Pampa Plain, Argentina

This paper gives an account of the assessment and quantification of the water balance and the hydrogeological processes related to lake–groundwater interaction in the Pampa Plain by using hydrogeochemical, isotopic and flow numerical modeling techniques. La Salada is a permanent shallow lake, with an area of 5.8 km², located on the SE of Buenos Aires Province. A total of 29 lake water samples and 15 groundwater samples were collected for both hydrochemical analysis and environmental stable isotope determination. Water table depths were measured in wells closed to the lake. Groundwater samples appear grouped on the Local Meteoric Water Line, suggesting a well-mixed system and that rainfall is the main recharge source to the aquifer. Water evaporation process within La Salada is also corroborated by its isotopic composition. The model that best adjusts to La Salada Lake hydrochemical processes includes evaporation from groundwater, calcite precipitation with CO₂ release and cationic exchange. The annual water balance terms for the lake basin indicates for each hydrological component the following values: 1.16 E⁰⁸ m³ rainfall, 8.15 E⁰⁷ m³ evapotranspiration, 1.90 E⁰⁶ m³ runoff, 1.55 E⁰⁷ m³ groundwater recharge, 6.01 E⁰⁶ m³ groundwater discharge to the lake, 9.54 E⁰⁶ m³ groundwater discharge to the river, 5.00 E⁰⁵ m³ urban extraction and 4.90 E⁰⁶ m³ lake evaporation. Integrated analysis of hydrochemical and isotopic information helped to calibrate the groundwater flow model, to validate the conceptual model and to quantitatively assess the basin water balance.     

气候变化对陆地水循环影响研究的问题

简要地回顾了现存的由气候情景驱动水文模型研究气候变化对陆地水循环影响的方法。指出这种单向连接方法很难将气候变暖及人类活动引起的陆地水循环变化反馈给大气。这既影响对降雨的预测精度,又不能正确地描写陆地水循环的变化。近10年来气候学家对大气环流模型中陆面过程模型的改进以及水文气候学家对大尺度水文模型研究所取得的进展,展现了它们之间的互补性,以及未来用水文-气候耦合模型方法研究气候变化与人类活动对陆地水循环影响及水资源预测的可能性。     

Spatio-temporal variations of δ<Superscript>2</Superscript>H and δ<Superscript>18</Superscript>O in precipitation and shallow groundwater in the Hilly Loess Region of the Loess Plateau,China

Groundwater is of utmost significance to socio-economic development and ecological recovery for the Loess Plateau. However, studies regarding the mechanism governing groundwater recharge over this area appear to be inadequate. This study is to examine the spatio-temporal variations of δ²H and δ¹⁸O in precipitation and shallow groundwater. On the basis of this, the mechanisms governing shallow groundwater recharge were explored. Precipitation and groundwater were sampled monthly from May to October during the period 2004–2006 at 13 sites in the Chabagou Catchment (187 km²). In the Caopingxigou Experimental Watershed (0.1 km²), meteorological variables were observed and rainfall larger than 5 mm was sampled immediately after each rain event. Across the area, 90% of the precipitation occurred from May to September primarily in the form of heavy rains or rainstorms with great spatial variability. There were about 30 localized rains in each year. It was indicated that there existed notable seasonality and pronounced spatial variability in precipitation isotopic compositions. Contributing factors and indications of isotopic compositions, as well as their climatic indications such as monsoon intensities and mixing processes of water vapor, were investigated. The δ²H–δ¹⁸O relation of groundwater was found to be δ²H = 3.22 × δ¹⁸O − 38.1, deviating from the local meteoric water line δ²H = 7.57 × δ¹⁸O + 3.9. The range of δ values in groundwater is shrunken to be 15–21% of that in individual precipitations, and groundwater in the middle reaches shows a wider range of δ values. Isotopic results showed that groundwater originates from precipitation with hydrogen and oxygen isotopic compositions being −69 and −9.7‰, respectively, and most groundwater experiences serious evaporation and adequate mixing with old water during infiltration or percolation in the aerated zone. It was also founded that obvious fluctuations of isotopic compositions in groundwater mainly appear in the middle reaches especially at sites that are close to valleys, suggesting varying sources of groundwater from precipitation, precipitation runoff, isotopically enriched surface water and/or lateral recharge of adjacent groundwater.     

Recent hydrological behavior of the East African great lakes region inferred from GRACE,satellite altimetry and rainfall observations

We have jointly analysed space gravimetry data from the GRACE space mission, satellite altimetry data and precipitation over the East African Great Lakes region, in order to study the spatiotemporal variability of hydrological parameters (total water storage, lake water volume and rainfall). We find that terrestrial water storage (TWS) from GRACE and precipitation display a common mode of variability at interannual time scale, with a minimum in late 2005, followed by a rise in 2006–2007. We argue that this event is due to forcing by the strong 2006 Indian Ocean Dipole (IOD) on East African rainfall. We also show that GRACE TWS is linked to the El Niño-Southern Oscillation cycle. Combination of the altimetry-based lake water volume with TWS from GRACE over the lakes drainage basins allows estimating soil moisture and groundwater volume variations. Comparison with the WGHM hydrological model outputs is performed and discussed.     

Relationships between precipitation,soil water and groundwater at Chongling catchment with the typical vegetation cover in the Taihang mountainous region,China

Vegetation cover plays an important role in the process of evaporation and infiltration. To explore the relationships between precipitation, soil water and groundwater in Taihang mountainous region, China, precipitation, soil water and water table were observed from 2004 to 2006, and precipitation, soil water and groundwater were sampled in 2004 and 2005 for oxygen-18 and deuterium analysis at Chongling catchment. The soil water was sampled at three sites covered by grass (Carex humilis and Carex lanceolata), acacia and arborvitae respectively. Precipitation is mainly concentrated in rainy seasons and has no significant spatial variance in study area. The stable isotopic compositions are enriched in precipitation and soil water due to the evaporation. The analysis of soil water potential and isotopic profiles shows that evaporation of soil water under arborvitae cover is weaker than under grass and acacia, while soil water evaporation under grass and acacia showed no significant difference. Both δ¹⁸O profiles and soil water potential dynamics reveal that the soil under acacia allows the most rapid infiltration rate, which may be related to preferential flow. In the process of infiltration after a rainstorm, antecedent water still takes up over 30% of water in the topsoil. The soil water between depths of 0–115 cm under grass has a residence time of about 20 days in the rainy season. Groundwater recharge from precipitation mainly occurs in the rainy season, especially when rainstorms or successive heavy rain events happen.     

河套灌区西部浅层地下水咸化机制

浅层地下水水位埋深浅、含盐量高,是导致河套灌区土壤次生盐渍化的重要原因.以河套灌区西部地区为研究区,通过对浅层地下水的水化学和氢氧同位素特征分析以及水文地球化学模拟,探讨了灌区浅层地下水的补给来源和主控水-岩作用过程,并定量估算了蒸发作用对浅层地下水含盐量的影响.研究区内浅层地下水为弱碱性咸水,pH为7.23~8.45,总溶解性固体（total dissolved solids,TDS）变化范围为371~7 599 mg/L;随着地下水咸化程度增大,水化学类型由HCO₃-Na·Mg·Ca型向Cl-Na型过渡.引黄灌溉和大气降水是浅层地下水的主要补给来源,径流过程中浅层地下水受蒸发作用和植物蒸腾作用影响,地下水化学组分主要来源于蒸发盐溶解和硅酸盐风化水解,并受强烈的蒸发作用和离子交换作用影响.水文地球化学模拟和主成分分析结果显示,蒸发作用和岩盐溶解作用对区内浅层地下水咸化贡献最大,石膏和白云石等矿物的溶解、硅酸盐的水解、Na-Ca离子交换以及局部地形起伏对地下水咸化过程也有较大贡献.      

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(...     

利用EARTH模型计算河北栾城地下水垂向补给量

准确计算地下水的垂向入渗补给量是合理评价和利用地下水资源的基础.EARTH模型是一种集中参数的水文模型,可刻画水流在包气带中的运移过程,弥补黑箱模型的不足.以中国科学院栾城农业生态试验站的地下水位观测资料以及气象资料为基础,综合运用降水、蒸发、土壤水、地下水动态观测资料,利用EARTH模型计算了河北平原地下水垂向入渗补给量.计算结果表明,2003年1月1日至2005年8月31日期间,栾城农业生态试验站在降水量1404.1 mm、灌溉量1050.0 mm的条件下地下水入渗补给量为487.2 mm,平均年入渗补给量为182.6 mm, 占降水和灌溉总量(2454.1 mm)的19.9%.在模拟结果的基础上,对不同年份的降水量(含灌溉)和入渗补给量分布的对比分析表明,河北栾城地下水补给滞后现象明显,在研究时间段内峰值滞后18～35 d.     

鄂尔多斯白垩系地下水盆地天然水体环境同位素组成及其水循环意义

鄂尔多斯白垩系地下水盆地天然水体的环境同位素组成表明,区内各种地表水体（河流和湖淖）在δ18O和δD图上主要分布在雨水线右侧,其关系线的斜率明显小于雨水线的蒸发线,集中反映蒸发作用对地表水体的影响。盆地内地下水大致集中沿雨水线分布,反映了白垩系盆地内地下水为大气降水成因。盆地南北两区地下水的环境同位素具有明显差异性特点,集中体现了盆地南北两区水循环条件的差异。盆地北区各含水岩组间地下水垂向水力联系比较密切,垂向运动特点比较明显,现代水积极循环带的深度为200 m;南区地下水分层性明显,以水平径流为主,现代水积极循环带的深度为160 m。区内浅层地下水以富氚和高¹⁴C含量为特征,反映为现代水补给;而中、深层地下水则以贫氚和低¹⁴C含量为特征,反映为地质历史时期补给。     

若尔盖高原典型泥炭湿地水量平衡计算

若尔盖泥炭湿地具有蓄水、固碳和生态的重要功能,其地下水水位变化决定泥炭湿地面积维持或萎缩,但是其泥炭湿地的地下水水文过程和水量动态变化缺少系统的野外监测和研究。结合红原站气象资料,并于2017年5月、7月和9月在若尔盖黑河上游泥炭湿地典型小流域开展野外原位监测,利用MODFLOW模型建立小流域三维动态地下水运动模型,模拟地下水运动过程并计算水量动态平衡变化以及沟道排水能力。结果表明:泥炭湿地的主要补水方式是降雨,占补水总量的60%,其主要出流方式是沟道排水,排水比例最高达到53%;其次是潜水蒸发,出流比例为26%。切穿泥炭层的沟道排水能力是未切穿泥炭层沟道的2.5倍。若尔盖泥炭地的地下水位受降雨影响呈现季节性波动,在雨季其涨幅约为0.5 m。     

Α high-resolution late Holocene speleothem record from Kaite Cave, northern Spain: δO variability and possible causes

A high-resolution calcite oxygen stable isotopic (δ¹⁸O) record, covering the past 4000 years, was obtained from Kaite Cave, northern Spain. The record has a mean δ¹⁸O value of -6.25‰ VPDB and a range of 2‰. Spectral analysis of the δ¹⁸O data shows significant periodicities of 2400–1900, 600, 150, 27, and 22 years. The amplitudes during these periods range from 0.2‰ to 2‰. Factors controlling the isotopic ratio in the speleothem were evaluated. The calcite is most likely precipitated under equilibrium conditions, with the cave calcite δ¹⁸O interpreted as a proxy of oxygen isotopic composition in local rainwater. Other factors such as temperature or fractionation in the karst system prior to calcite precipitation are considered of negligible or of minor importance. Mechanisms affecting rainfall isotopic composition were also investigated on different time scales. Precipitation amount is the primary factor controlling the high-frequency δ¹⁸O oscillations. Other climate parameters, such as changes of storm tracks may have significant contributions on centennial and millennial time scales.     

典型井灌区农田土壤和地下水库调蓄汛雨径流的研究

针对80年代以来,北京市平原区地下水资源日益匮乏,必须减少径流流失与燕发消耗,利用汛雨与径流增加可用水资源,对在北京市东南郊天堂河流域水资源试验区取得的近20年的降水、地下水位等资料进行了较全面地整理;分析计算了不同水文年度0-3m层土壤水库的蓄水容量和调蓄能力;揭示了流域内不同层次地下水间的水力联系;研究了潜水、承压水随降水的多年变化关系,并证明在当前地下水埋深条件下,降水对浅层地下水位变化的影响是跨年度完成的.     

Hydrogeochemical and isotopic study of groundwater in the Habor Lake Basin of the Ordos Plateau,NW China

Hydrogeochemistry and isotopes were used to understand the origin and geochemical evolution in the Habor Lake Basin, northwestern China. Groundwater samples were taken, and the isotopic compositions δD, δ¹⁸O and major ions were analyzed. The groundwater can be divided into three types: the Quaternary groundwater, the shallow Cretaceous groundwater and the deep Cretaceous groundwater. The groundwater chemistry is mainly controlled by the feldspar weathering and dolomite weathering, the dissolution of Glauber’s salt, and cation exchange. Chemistry of lake water is mainly controlled by evaporation and precipitation. The stable isotopes of oxygen and hydrogen in groundwater cluster along the local meteoric water line, indicating that groundwater is of meteoric origin. Comparing with shallow groundwater, deep groundwater is depleted in heavy isotopes indicating that deep groundwater was recharged during late Pleistocene and Holocene, during which the climate was more wetter and colder than today.     

Determining Spatial and Temporal Inputs of Freshwater,Including Submarine Groundwater Discharge,to a Subtropical Estuary Using Geochemical Tracers,Biscayne Bay,South Florida

Geochemical mixing models were used to decipher the dominant source of freshwater (rainfall, canal discharge, or groundwater discharge) to Biscayne Bay, an estuary in south Florida. Discrete samples of precipitation, canal water, groundwater, and bay surface water were collected monthly for 2 years and analyzed for salinity, stable isotopes of oxygen and hydrogen, and Sr²⁺/Ca²⁺ concentrations. These geochemical tracers were used in three separate mixing models and then combined to trace the magnitude and timing of the freshwater inputs to the estuary. Fresh groundwater had an isotopic signature (δ ¹⁸O = −2.66‰, δD −7.60‰) similar to rainfall (δ ¹⁸O = −2.86‰, δD = −4.78‰). Canal water had a heavy isotopic signature (δ ¹⁸O = −0.46‰, δD = −2.48‰) due to evaporation. This made it possible to use stable isotopes of oxygen and hydrogen to separate canal water from precipitation and groundwater as a source of freshwater into the bay. A second model using Sr²⁺/Ca²⁺ ratios was developed to discern fresh groundwater inputs from precipitation inputs. Groundwater had a Sr²⁺/Ca²⁺ ratio of 0.07, while precipitation had a dissimilar ratio of 0.89. When combined, these models showed a freshwater input ratio of canal/precipitation/groundwater of 37%:53%:10% in the wet season and 40%:55%:5% in the dry season with an error of ±25%. For a bay-wide water budget that includes saltwater and freshwater mixing, fresh groundwater accounts for 1–2% of the total fresh and saline water input.     

黄土中水分迁移规律现场试验研究

黄土地区降雨诱发滑坡是不争的事实,但黄土地区地下水位很深,降雨入渗地面后如何运移,与地下水有无直接联系,目前还不是很清楚。为此设计了人工滴水试验模拟天然降雨条件,通过在一深度为10 m的探井井壁上埋设土壤水分计,观测人工滴水入渗过程中不同深度土体含水率随时间的变化情况,以确定其入渗影响深度。监测结果显示：降雨量为3.82 mm/d (小雨)时,0.5 m内土体含水率变化明显,0.5 m以下土层含水率几乎没有变化;降雨量为10.31 mm/d(中雨)时,1 m内土体含水率有所增加;降雨量达25.21 mm/d(大雨)时,1 m内土体含水率增长明显,1.0～1.6 m范围内有微弱增长;随着深度增加,土体含水率变化逐渐滞后,增幅逐渐减小。这说明在干旱的黄土地区,若无明显入水通道,短期内降雨的入渗深度有限,很难到达地下水位;但深部古土壤层的观测结果表明,即使在其上部黄土中含水率变化极其微弱的情况下,古土壤中的含水率上升明显,表明黄土中非饱和渗流或水汽迁移是存在的。通过试验还表明,陇东黄土高原地区土壤中水分循环主要发生在浅层0.7 m以内的蒸发带。降雨入渗到蒸发带以内,若无后续降雨补给,则向上蒸发排泄;若入渗至蒸发带以下,则不受蒸发影响,得以继续向下迁移;当遇到不透水面时,会在层面附近富集,有限元模拟也较好地反映了这一规律。