Showing papers on "Environmental isotopes published in 1997"

Environmental Isotopes in Hydrogeology

Abstract: The Environmental Isotopes Environmental Isotopes in Hydrogeology Stable Isotopes: Standards and Measurement Isotope Ratio Mass Spectrometry Radioisotopes Isotope Fractionation Isotope Fractionation (a), Enrichment (e), and Separation (D) Tracing the Hydrological Cycle Craig's Meteoric Relationship in Global Fresh Waters Partitioning of Isotopes Through the Hydrological Cycle Condensation, Precipitation, and the Meteoric Water Line A Closer Look at Rayleigh Distillation Effects of Extreme Evaporation Precipitation The T - d18O Correlation in Precipitation Local Effects on T - d18O Ice Cores and Paleotemperature Groundwater Recharge in Temperate Climates Recharge in Arid Regions Recharge from River-Connected Aquifers Hydrograph Separation in Catchment Studies Groundwater Mixing Tracing the Carbon Cycle Evolution of Carbon in Groundwaters Carbonate Geochemistry Carbon-13 in the Carbonate System Dissolved Organic Carbon Methane in Groundwaters Isotopic Composition of Carbonates Chapter 6. Groundwater Quality Sulphate, Sulphide and the Sulphur Cycle Nitrogen Cycles in Rural Watersheds The "Fuhrberger Feld" Study Source of Chloride Salinity Landfill Leachates Degredation of Chloro-organics and Hydrocarbon Sensitivity of Groundwater to Contamination Summary of Isotopes in Contaminant Hydrology Identifying and Dating Modern Groundwaters The "Age" of Groundwater Stable Isotopes Tritium in Precipitation Dating Groundwaters with Tritium Groundwater Dating with 3H -3He Chlorofluorocarbons (CFCs) Thermonuclear 36Cl Detecting Modern Groundwaters with 85Kr Submodern Groundwater Age Dating Old Groundwaters Stable Isotopes and Paleogroundwaters Groundwater Dating with Radiocarbon Correction for Carbonate Dissolution Some Additional Complications to 14C Dating 14C Dating with Dissolved Organic Carbon (DOC) Case Studies for 14C dating with DOC and DIC Chlorine-36 and Very Old Groundwater The Uranium Decay Series Water-Rock Interaction Mechanisms of Isotope Exchange High Temperature Systems Low Temperature Water-Rock Interaction Strontium Isotopes in Water and Rock Isotope Exchange in Gas-Water Reactions High pH Groundwaters-The Effect of Cement Reactions Field Methods for Sampling Groundwater Water in the Unsaturated Zone Precipitation Gases Geochemistry References Index Each chapter has Problems sections.

Two Decades of Environmental Isotope Records in Croatia: Reconstruction of the Past and Prediction of Future Levels

Abstract: A two-decade-long record of environmental isotopes (2H, 3H, 14C, 18O) in Croatia is presented and the data are statistically analyzed. The atmospheric 14C activity for the period before the actual measurements started is reconstructed by measuring tree rings from the clean-air sites, and the past tritium activity in precipitation is estimated by the correlation of our data with the Vienna station record. The long-term 3H record helped to determine a locally contaminated sampling site, and new clean sites are put into operation. The 14C data were fitted by an analytical function and the prediction of future levels is given assuming that the rate of the 14C releases remains constant. From the long-term stable isotope data record, the local meteoric water line and the temperature gradient of δ18O in precipitation are determined.

Contribution of environmental isotopes to the understanding of complex hydrologic systems. A case study: Sierra de Gador, SE Spain

Abstract: Determining the content of 18O and deuterium in the groundwater at the southern edge of the Sierra de Gador, between October 1991 and March 1993, has enabled identification of the flow system of the waters, the recharge and mixing processes and the possible mechanisms of salinization. Analysis of the precipitation indicates the dominant source and direction of the air masses. The local meteoric water line that is established indicates a primarily Mediterranean origin for the precipitation recharging the aquifers. The variation of 18O content with altitude (−0·35 per mille per 100 m) enables an estimation of the principal recharge area, which corresponds to a zone between 1200 and 1800 m a.s.l. © 1997 John Wiley & Sons, Ltd.

Critical evaluation of the use and analysis of stable isotopes (Technical Report)

Abstract: In this paper the methodology of isotopic analysis is discussed. In the first instance because a choice of analytical methods often conditions the success of research carried out with stable isotopes. The methodology of use is treated in two different chapters according to their resting or not on measurements of isotope effects. In the second case, stable isotopes are specially usef'bl for isotope dilution analysis, studies of transport phenomena, medical diagnoses. Advantages and drawbacks of their use with respect to that of radioactive isotopes are described and examples are given. Usage of isotope effects is a specificity of stable isotope work. Methods of measuring equilibrium and kinetic effects are explained. A discussion is given of tenets of applications in research in pharmacology, geochemical processes, and of kinetic effects in studies of reaction mechanisms, especially in biology. Utilisations of nuclear properties, particularly in medicine, are mentioned. This report does not cover techniques of isotope separation, preparation of labeled compounds, uses of isotopes in dating methods or in nuclear industries.

Use of chlorine-36 as tracer for the evolution of waters in geothermal and tectonically active areas in Western Turkey

Abstract: Problems frequently arise in the determination of residence times for groundwaters of tectonically active regions. The commonly applied isotope techniques are often not appropriate because i) the high amount of water-rock interaction, ii) the underground production of nuclides in crystalline fissured rocks under geothermal conditions, iii) the occurrence of highly saline waters at boiling temperature affected by water-rock interaction processes, and iv) the high fluxes of CO2. Therefore the application of the chlorine-36 method looks very promising. By considering the sources of chlorine-36 and the water-rock interactions with respect to the chloride cycle for each area additional information on the ongoing processes of groundwater circulation and evolution as meet as the ranges of residence times of these waters were gained. Additional information, from independent hydrodynamic and coupled geothermal modeling and measurements of other environmental isotopes give additional support to our interpretation.

Environmental isotopes as tracers in catchments

Abstract: ‘Environmental isotopes’ are those isotopes that are widespread in nature and are part of the hydrological and/or geological cycle. This chapter describes the use of oxygen, hydrogen, carbon, nitrogen and sulphur isotopes. The selection is based on the fact that these isotopes are the ones most frequently studied in catchments, and very applicable for the study of catchments where the storage time of water is relatively short. Northern catchments such as in Scandinavia often are characterised by rather rugged topography, and well-defined catchment boundaries. River discharges have strong seasonal variations with snow melt as the main flood event. Rather thin unconsolidated glacial sediments, mostly tills, cover the lithified bedrock. In isotopic hydrograph separation the streamwater is normally separated into flows of new water (event water) and old water. Old water is water that was already in the catchment before the runoff event.

Estimation of groundwater velocities from Yucca Flat to the Amargosa Desert using geochemistry and environmental isotopes

Abstract: Geochemical and isotopic data from groundwater sampling locations can be used to estimate groundwater flow velocities for independent comparison to velocities calculated by other methods. The objective of this study was to calculate groundwater flow velocities using geochemistry and environmental isotopes from the southern end of Yucca Flat to the Amargosa Desert, considering mixing of different groundwater inputs from sources each and southeast of the Nevada Test Site (NTS). The approach used to accomplish the objective of this study consisted of five steps: (1) reviewing and selecting locations where carbon isotopic groundwater analyses, reliable ionic analysis, and well completion information are available; (2) calculating chemical speciation with the computer code WATEQ4F (Ball and Nordstrom, 1991) to determine the saturation state of mineral phases for each ground water location; (3) grouping wells into reasonable flowpaths and mixing scenarios from different groundwater sources; (4) using the computer code NETPATH (Plummer et al., 1991) to simulate mixing and the possible chemical reactions along the flowpath, and to calculate the changes in carbon-13/carbon-12 isotopic ratios ({delta}{sup 13}C) as a result of these reactions; and (5) using carbon-14 ({sup 14}C) data to calculate velocity.

Deuterium and oxygen-18 isotopes on groundwater salinization of adjoining salt pans in Porbandar coast, Gujarat, India

Abstract: Water quality deterioration, mainly salinization, has occurred to groundwater adjacent to reservoirs used for salt manufacturing on the Porbandar coast, Gujarat, India. The cause of deterioration was studied using environmental isotopes of water; namely deuterium and oxygen-18 (measured as o H and S 18 0) and hydrochemical data. Water samples were collected from salt pans, sea water and groundwater. Results indicate both higher enrichment of heavier isotopes and higher chloride concentration in water samples from salt pans than in water samples from other sources. In addition to chloride concentrations, variation of 5*H and S'°0 vis-a-vis the corresponding anions and cations, were analyzed for possible relationships. Both laboratory and field data do not indicate that the groundwater contamination is caused by seepage from the salt pans. These data further suggest that seepage will not cause additional groundwater deterioration in the future under normal climatic conditions or under current operating procedures of the salt pans. INTRODUCTION Studies of groundwater salinization by sea water intrusion in coastal areas in general, deals with the measurements of soil composition, chemical parameters of soil and water, hydraulic gradient among others. Conventionally, the source of salinization in a water body could be deduced from the variation of the characteristic solute-concentration ratio such as Na/Cl, Ca/Mg, and S0