Uranium groundwater contamination due to U mining and processing affects numerous sites globally. Bioreduction of soluble, mobile U(VI) to U(IV)-bearing solids is potentially a very effective remediation strategy. Uranium isotopes (238U/235U) have been utilized to track the progress of microbial reduction, with laboratory and field studies finding a ∼1‰ isotopic fractionation, with the U(IV) pr...

The productivity of the biosphere leaves its imprint on the isotopic composition of atmospheric oxygen. Ultimately, atmospheric oxygen, through photosynthesis, originates from seawater. Fractionations during the passage from seawater to atmospheric O2 and during respiration affect δ17O approximately half as much as δ18O. An “anomalous” (also termed mass independent) fractionation process change...

Oxygen and iron isotope analyses of low-Ti and high-Timare basalts are presented to constrain their petrogenesis and to assess stable isotope variations within lunar mantle sources. An internally-consistent dataset of oxygen isotope compositions of mare basalts encompasses five types of low-Ti basalts from the Apollo 12 and 15 missions and eight types of high-Ti basalts from the Apollo 11 and 1...

The D/H ratios of hydrogen gas in equilibrium with aqueous alkali halide solutions were determined at 25 °C, using a hydrophobic platinum catalyst. The hydrogen isotope effect between the solution and pure water changes linearly with the molality of the solution at low concentrations, but deviates from this linearity at higher concentration for all alkali halide solutions. The magnitude of the ...

In this study, we present the first experimental results for stable barium (Ba) isotope ((137)Ba/(134)Ba) fractionation during low-temperature formation of the anhydrous double carbonate BaMn[CO(3)](2). This investigation is part of an ongoing work on Ba fractionation in the natural barium cycle. Precipitation at a temperature of 21±1°C leads to an enrichment of the lighter Ba isotope described...

Signatures of mass-independent isotope fractionation (MIF) are found in the oxygen ((16)O,(17)O,(18)O) and sulfur ((32)S, (33)S, (34)S, (36)S) isotope systems and serve as important tracers of past and present atmospheric processes. These unique isotope signatures signify the breakdown of the traditional theory of isotope fractionation, but the physical chemistry of these isotope effects remain...

Introduction: While it is well known that igneous CAIs tend to have high Si/Si and Mg/Mg relative to chondritic values, there have been few systematic studies that relate observed isotope fractionations in CAIs to their conditions and timescales of formation. Together with a wealth of information about the physical chemistry associated with evaporation and condensation of CAI-like liquids [1] w...

Introduction: Recently, the classic theory of stable isotope fractionation of the Bigeleisen-Mayer equation [1] has been expanded by the original author to include the mass-independent term named the nuclear field shift effect [2]. The improved theory successfully explained the observed non-linear isotope effect on U in a chemical exchange system [2]. Since then, researchers have applied the ne...

Swart, P.K., 1983. Carbon and oxygen isotope fractionation in scleractinian corals: a review. Earth-Sci. Rev., 19: 51-80. The present theories on the fractionation of stable isotopes in scleractinian corals are critically discussed in the light of data available on primary productivity, respiration and stable isotope chemistry. These data support a model of fractionation in which the carbon and...

RATIONALE Potential post-mortem alteration to the oxygen isotope composition of biogenic silica is critical to the validity of palaeoclimate reconstructions based on oxygen isotope ratios (δ18 O values) from sedimentary silica. We calculate the degree of oxygen isotope alteration within freshly cultured diatom biogenic silica in response to heating and storing in the laboratory. METHODS The e...