Experimental study of uranium isotope fractionation of rock material from two aquifers

This paper presents results of a study carried out in order to estimate the uranium isotope fractionation ²³⁴U/²³⁸U in groundwater from laboratory experiments. Matrix rock from borcholes in a Triassic sandstone aquifer and a Pleistocene sand aquifer was leached with 1 N HCl, 0.1 N HCl and deionized water.

Additionally, the uranium isotope composition of the bulk rock (index “R”) and several groundwater samples of corresponding horizons were analysed. The results indicate the relation between the portion of leached uranium (index “L”) and the observed activity ratio ²³⁴U/²³⁸U (AU)

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If this relation can be confirmed by further investigations new possibilities of using uranium isotopes in hydrogeology would be made available

Die Arbeit stellt Ergebnisse einer Studie vor, die zur Abschützung der Uranium-Isotopenfraktionierung ²³⁴U/²³⁸U im Grundwasser aus Laborexperimenten durchgeführt wurde. Matrixgestein von Bohrlöchern in einem Triassischen Sandstein-Grundwasserleiter und einem aus pleislozänen Sanden bestehenden Grundwasserleiter wurde mit 1 N HCl, 0,1 HCl und entionisiertem Wasser gelaugt. Auβerdem wurden die Uranium-Isotopenzusammensetzung des Gesteins (Index “R”) und einige Grundwasserproben zugehöriger Horizonte analysiert. Die Ergebnisse zeigen cine Beziehung zwischen dem Anteil des gelaugten Uraniums (Index “L”) und dem Aktivitätsverhältnis ²³⁴U/²³⁸U (AU)

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Wenn diese Relation durch weitere Untersuchungen bestäligt werden kann, eröffnen sich neue Möglichtkeiten für die Nutzung der Uraniumisotope in der Hydrogeologie.     

西安市沪河下游湿地水文水质特征的初步分析

目的 针对西安浐河下游地区进行的湿地恢复工程,调查研究湿地恢复区的生态环境状况以及湿地水文水质特性,为中国西北地区湿地的恢复与重建提供基础数据和实践经验.方法 采用野外实地观测获得水文资料和湿地恢复区的水质监测数据,分析研究湿地恢复区的水文水质变化情况.结果 湿地水文过程受到浐河径流特性的影响,需要工程清淤措施来调控补给水源,湿地出水流量6×106 m3/y,湿地水位在进水流量变化的影响下,呈现出阶段性涨落变化的趋势;湿地对浐河水质改善明显,总氮、总磷、化学需氧量等6项监测指标从原来的V类或劣V类水质改善达到或接近Ⅲ类地表水水质标准.结论 以浐河为水源,将分布在河道外侧的采砂坑重建为湖泊湿地的方案可行,在恢复湿地地表径流的基础上,湖泊湿地得以重建,恢复区生态环境效益显著,为西北地区的湿地恢复提供了参考.     

同位素水文学的若干回顾与展望

从降水径流、非饱和带水分运移、地下水来源及年龄测定、古洪水研究等方面回顾了同位素水文学研究的现状,认为同位素示踪技术可以从更微观的角度研究径流形成、流域汇流过程中的水分转换关系等;概述了河海大学近年来在同位素水文学研究方面的相关进展,指出其研究主要包括同位素水文数学模型、平原区同位素径流组分划分试验、同位素在地下水中的应用、"引江济太"水量分配、流域氮源示踪等方面。在综述同位素水文学研究进展基础上,对当前同位素水文学研究存在的问题进行了分析,并对同位素方法在水文学中的应用前景进行了展望。     

Compound-specific stable isotope analysis of organic contaminants in natural environments: a critical review of the state of the art,prospects, and future challenges

Compound-specific stable isotope analysis (CSIA) using gas chromatography-isotope ratio mass spectrometry (GC/IRMS) has developed into a mature analytical method in many application areas over the last decade. This is in particular true for carbon isotope analysis, whereas measurements of the other elements amenable to CSIA (hydrogen, nitrogen, oxygen) are much less routine. In environmental sciences, successful applications to date include (i) the allocation of contaminant sources on a local, regional, and global scale, (ii) the identification and quantification of (bio)transformation reactions on scales ranging from batch experiments to contaminated field sites, and (iii) the characterization of elementary reaction mechanisms that govern product formation. These three application areas are discussed in detail. The investigated spectrum of compounds comprises mainly n-alkanes, monoaromatics such as benzene and toluene, methyl tert-butyl ether (MTBE), polycyclic aromatic hydrocarbons (PAHs), and chlorinated hydrocarbons such as tetrachloromethane, trichloroethylene, and polychlorinated biphenyls (PCBs). Future research directions are primarily set by the state of the art in analytical instrumentation and method development. Approaches to utilize HPLC separation in CSIA, the enhancement of sensitivity of CSIA to allow field investigations in the µg L^–1 range, and the development of methods for CSIA of other elements are reviewed. Furthermore, an alternative scheme to evaluate isotope data is outlined that would enable estimates of position-specific kinetic isotope effects and, thus, allow one to extract mechanistic chemical and biochemical information.Abbreviations BTEX benzene, toluene, ethylbenzene, xylenes - MTBE methyl tert-butyl ether - PAHs polycyclic aromatic hydrocarbons - VOCs volatile compounds - PCBs polychlorinated biphenyls - CSIA compound-specific (stable) isotope (ratio) analysis - GC-IRMS, GC/IRMS or GCIRMS gas chromatography-isotope ratio mass spectrometry - GC-C-IRMS, GC/C/IRMS or GCC-IRMS gas chromatography-combustion-isotope ratio mass spectrometry - irmGC/MS isotope ratio monitoring gas chromatograph-mass spectrometry - GC/P/IRMS gas chromatography-pyrolysis-isotope ratio mass spectrometry (used for D/H) - KIE kinetic isotope effect - PSIA position-specific isotope analysis (for intramolecular isotope distribution) - SNIF-NMR site-specific natural isotopic fractionation by nuclear magnetic resonance spectroscopy     

River basin landscape pattern and its modern earth surface process of the LRGR

Directing at the the longitudinal rangegorge region＇s special constituting condition of river basin geography landscape, the authors synthetically used the data analyses and spatial information treatment technique, selected corresponding measurable homology indicators, comparatively analyzed the characteristic difference of different river basin＇s landscape constitution patterns in the longitudinal range-gorge region, researched into different river net patterns and land cover conditions of each river basin landscape, and explored the river basin＇s landscape form and its spatial distributed chracters. Based on the analyses on river basin＇s landscape composition and its spatial distribution characters, this study researched into the main driving factor of modern earth surface process in the longitudinal range-gorge region, analyzed the relationship between the basin landscape changing and its modern earth surface process, finally completed a series of the potential ecological hydrology effect analyses.     

龙脉水库除险加固设计洪水分析研究

采用实测暴雨资料进行设计洪水复核,为龙脉水库除险方案和加固措施提供依据.复核中,通过对暴雨特性、暴雨频率分析,以设计点暴雨、设计雨型和设计面暴雨,采用扣损法进行产流复核分析,并进行时程分配,利用瞬时单位线法进行汇流复核计算,从而确定了水库除险加固设计洪水.通过与推理公式、经验公式和原设计成果比较分析,采用瞬时单位线法的洪水复核成果更为合理.     

Estimation of snow and glacier melt contribution to Liddar stream in a mountainous catchment,western Himalaya: an isotopic approach

Snow- and glacier-dominated catchments in the Himalayas are important sources of fresh water to more than one billion people. However, the contribution of snowmelt and glacier melt to stream flow remains largely unquantified in most parts of the Himalayas. We used environmental isotopes and geochemical tracers to determine the source water and flow paths of stream flow draining the snow- and glacier-dominated mountainous catchment of the western Himalaya. The study suggested that the stream flow in the spring season is dominated by the snowmelt released from low altitudes and becomes isotopically depleted as the melt season progressed. The tracer-based mixing models suggested that snowmelt contributed a significant proportion (5–66?%) to stream flow throughout the year with the maximum contribution in spring and summer seasons (from March to July). In 2013 a large and persistent snowpack contributed significantly (～51?%) to stream flow in autumn (September and October) as well. The average annual contribution of glacier melt to stream flow is little (5?%). However, the monthly contribution of glacier melt to stream flow reaches up to 19?% in September during years of less persistent snow pack.     

Tightly bound soil water introduces isotopic memory effects on mobile and extractable soil water pools

Cryogenic vacuum extraction is the well-established method of extracting water from soil for isotopic analyses of waters moving through the soil–plant–atmosphere continuum. We investigate if soils can alter the isotopic composition of water through isotope memory effects, and determined which mechanisms are responsible for it. Soils with differing physicochemical properties were re-wetted with reference water and subsequently extracted by cryogenic water distillation. Results suggest some reference waters bind tightly to the soil and not all of this tightly bound water is removed during cryogenic vacuum extraction. Kinetic isotopic fractionation occurring when reference water binds to the soil is likely responsible for the ¹⁸O-depletion of re-extracted reference water, suggesting an enrichment of the tightly bound soil water pool. Further re-wetting of cryogenically extracted soils indicates an isotopic memory effect of tightly bound soil water on water added to the soil. The data suggest tightly bound soil water can influence the isotopic composition of mobile soil water. Findings show that soils influence the isotope composition of soil water by (i) kinetic fractionation when water is bound to the soil and (ii) equilibrium fractionation between different soil water pools. These findings could be relevant for plant water uptake investigations and complicate ecohydrological and paleohydrological studies.     

模糊水文学的基本理论模型与应用

水文学中引入模糊集理论有十分重要的意义。根据笔者１９８７年提出的 模糊水文学关于成因、概率统计与模糊集分析相结合的新观点与研究方法 论，进而提出模糊水文学的基本理论模型与应用。本文提出的模糊划分、识 别、判决相统一的理论模型．更能够适应新学科进一步发展的需要。     

分布式冰雪融水雨水混合水文模型

在以冰雪融水雨水混合补给为主的流域中，产流空间分布的不均匀性十分突出。为此，建议一种基于数字高程模型（DEM）和地理信息系统（GIS）的网格式空间分布水文模型。该模型可在分别考虑不同网格的热量和水分状态的基础上计算产流和汇流，并在乌鲁木齐河山区流域上得到应用，取得了良好效果。