Time-series stable carbon isotope monitoring of volatile organic compounds (VOCs) atthe Idaho National Engineering and Environmental Laboratory's (INEEL) field site Test Area North (TAN) was conducted during a pilot study to investigate the treatment potential of using lactate to stimulate in situ biologic reductive dechlorination of trichloroethene (TCE). The isotope ratios of TCE and its biod...

The radiogenic neodymium (Nd) isotope composition of foraminiferal shells provides a powerful archive to investigate past changes in sources and mixing of water masses. However, seawater Nd isotope ratios extracted from foraminiferal shells can be biased by contaminant phases such as organic matter, silicates, or ferromanganese coatings, the removal of which requires rigorous multiple step clea...

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 ...

Despite the widespread use of carbon stable isotopes to distinguish among potential energy pathways in food webs, their usefulness is limited where potential basal carbon sources are numerous and diverse. We measured carbon isotope values of the major fisheries species, the mostly carnivorous Scylla serrata (giant mud crab), and potential basal, autotrophic sources supporting the food web. Conv...

To further validate the doubly labeled water method for measurement of CO2 production and energy expenditure in humans, we compared it with near-continuous respiratory gas exchange in nine healthy young adult males. Subjects were housed in a respiratory chamber for 4 days. Each received 2H2(18)O at either a low (n = 6) or a moderate (n = 3) isotope dose. Low and moderate doses produced initial ...

Data from a combination of laboratory and fieldwork is presented to initiate testing of stable carbon and nitrogen isotope ratios to trace sources of TNT in contaminated soil and groundwater. Evaluation of these extraction methods resulted in 99.9 and 99.8% recovery of TNT with Soxhlet and solid-phase extraction (SPE), respectively. As a result of the high extraction efficiency, isotope fractio...

We have investigated Mo and W isotope compositions in acid leachates and an insoluble residue from the Murchison carbonaceous chondrite. The new data reveal variable enrichments of sand r-process isotopes and demonstrate that several isotopically diverse presolar components are present in Murchison. The insoluble residue is enriched in s-process Mo and W, evidently due to the enrichment s-proce...

In response to the CMAJ news article, “Uncertainties shroud medical isotope supply,” we at Nordion would like to clarify the record with regard to the statement: Isotope supplier MDS Nordion has begun importing isotopes from Russia as part of broader, “multi-source” approach to isotope supply. To state that Nordion is importing isotopes from Russia that would be available to the market is misle...

Redox processes are ubiquitous in Earth science and are often associated with large isotope fractionations. In a previous study, voltage-dependent amplification of stable isotope fractionation was observed for an Fe reduction process. Here, we describe experiments showing a similar effect for a second transition metal, zinc. After electrochemical reduction, the composition of plated Zn metal is...

bentonite deposits of economic interest are widespread in tashtab mountains (khur), east of isfahan province, iran. several bentonite deposits have been developed in this area as a result of eocene volcanic alteration. these deposits are classified as khur bentonite horizon. xrd analyses reveal that alteration products consist of na-montmorillonite, kaolinite, quartz, calcite, and crystobalite....