About: Isotope fractionation is a(n) research topic. Over the lifetime, 4138 publication(s) have been published within this topic receiving 209991 citation(s).
•23 Jul 1997
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.
•01 Jan 1973
Abstract: Theoretical and Experimental Principles.- Isotope Fractionation Processes of Selected Elements.- Variations of Stable Isotope Ratios in Nature.
Marion H. O'Leary1•Institutions (1)
Abstract: Plants with the C 3 , C 4 , and crassulacean acid metabolism (CAM) photosynthetic pathways show characteristically different discriminations against 13 C during photosynthesis. For each photosynthetic type, no more than slight variations are observed within or among species. CAM plants show large variations in isotope fractionation with temperature, but other plants do not. Different plant organs, subcellular fractions and metabolises can show widely varying isotopic compositions. The isotopic composition of respired carbon is often different from that of plant carbon, but it is not currently possible to describe this effect in detail. The principal components which will affect the overall isotope discrimination during photosynthesis are diffusion of CO 2 , interconversion of CO 2 and HCO − 3 , incorporation of CO 2 by phosphoenolpyruvate carboxylase or ribulose bisphosphate carboxylase, and respiration. Theisotope fractionations associated with these processes are summarized. Mathematical models are presented which permit prediction of the overall isotope discrimination in terms of these components. These models also permit a correlation of isotope fractionations with internal CO 2 concentrations. Analysis of existing data in terms of these models reveals that CO 2 incorporation in C 3 plants is limited principally by ribulose bisphosphate carboxylase, but CO 2 diffusion also contributes. In C 4 plants, carbon fixation is principally limited by the rate of CO 2 diffusion into the leaf. There is probably a small fractionation in C 4 plants due to ribulose bisphosphate carboxylase.
TL;DR: The fractionation of carbon isotopes that occurs during photosynthesis is one of the most useful techniques for investigating the efficiency of CO2 uptake and indicates that different strategies are needed for improving wateruse efficiency in different kinds of plants.
Abstract: he efficiency of photosynthesis continues to interest biochemists, biologists, and plant physiologists. Scientists interested in CO2 uptake are concerned about the extent to which the uptake rate is limited by such factors as stomatal diffusion and the chemistry of the CO2 absorption process. The fractionation of carbon isotopes that occurs during photosynthesis is one of the most useful techniques for investigating the efficiency of CO2 uptake. Atmospheric carbon dioxide contains approximately 1.1% of the nonradioactive isotope carbon-13 and 98.9% of carbon-12. During photosynthesis, plants discriminate against C because of small differences in chemical and physical properties imparted by the difference in mass. This discrimination can be used to assign plants to various photosynthetic groups. The isotope fractionation also reflects limitations on photosynthetic efficiency imposed by the various diffusional and chemical components of CO2 uptake. When analyzed in detail, this fractionation provides information .about water use efficiency and indicates that different strategies are needed for improving wateruse efficiency in different kinds of plants. Isotope fractionation in simple physical and chemical processes is well understood and is commonly Current studies include
Abstract: Changes of the isotopic composition of water within the water cycle provide a recognizable signature, relating such water to the different phases of the cycle. The isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes. As a result, meteoric waters are depleted in the heavy isotopic species of H and O relative to ocean waters, whereas waters in evaporative systems such as lakes, plants, and soilwaters are relatively enriched. During the passage through the aquifers, the isotope composition of water is essentially a conservative property at ambient temperatures, but at elevated temperatures, interaction with the rock matrix may perturb the isotope composition. These changes of the isotope composition in atmospheric waters, surface water, soil, and groundwaters, as well as in the biosphere, are applied in the characterization of hydrological system as well as indicators of paleo-climatological conditions in proxy materials in climatic archives, such as ice, lake sediments, or organic materials.