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The Bothnian Sea which is located between Finland and Sweden represents an important source of fresh water to the Baltic Sea. We here present new data on the radioactive isotope I species from water samples collected in December 2009 at different depths in the Bothnian Sea. Concentrations of I (iodide) in the Bothnian Sea range from 14 × 10 to 32 × 10 atoms/L, while IO (iodate) concentrations are relatively low and fluctuating at 1 × 10 atoms/L. For nutrients data determined in the same samples as I, significant correlations could be found between I and total P, NO-N, SiO-Si, but rather poor with NH-N. The correlations suggest comparable source pathway of I and nutrient parameters, while the source of NH-N may be different. The small amounts and negligible change of IO indicate prevailing extensive reduction of iodate in the Baltic Sea. [ABSTRACT FROM AUTHOR]

Abstract: To improve the throughput of sample preparation for AMS 14C measurements, we made improvements to a manually operated system for CO2 reduction at the Graduate School of Environmental Studies, Nagoya University. Most of the processes of the CO2 reduction procedure were automated, and a CO2 sample containing 0.3–1mg carbon was credibly reduced to graphite within a few hours by hydrogen gas with catalytic iron powder in a 7.4ml reactor consisting of a quartz reduction tube, a pressure transducer gauge and a cold finger trap equipped with a temperature-controllable trap device for trapping CO2 and H2O. The improved system has the potential to easily carry out graphitization of more than 100 CO2 samples per week. The 14C values of graphite produced from 14C-free CO2 (>0.3mg C) were 0.0028±0.0010 fraction modern carbon (FMC) on average (n =8, 1std), which are almost the same as the black level of 1-MV HVEE Tandetron installed at the Korea Institute of Geoscience and Mineral Resources (KIGAM). [Copyright &y& Elsevier]

Abstract: The original sealed tube zinc reduction graphitization process was first developed for rapid low-precision measurements of biomedical tracer samples and later also applied for high precision measurements of not too old samples. In this study we tested the MICADAS (mini radiocarbon dating system [1]) radiocarbon measurements of targets prepared by sealed tube graphitization process. We found the optimal iron catalyst and reagents (TiH2 and Zn) amount whereby we can reach a relatively low background level, and minimized the overall δ13C fractionation during the graphitization. Repeated measurements of normalization standards and real samples with known 14C activities were very well reproduced. Finally, we demonstrated the applicability of the sealed tube graphitization on real environmental samples covering a wide range of 14C concentrations. [Copyright &y& Elsevier]

Abstract: Most laboratories prepare carbonates samples for radiocarbon analysis by acid decomposition in evacuated glass tubes and subsequent reduction of the evolved CO2 to graphite in self-made reduction manifolds. This process is time consuming and labor intensive. In this work, we have tested a new approach for the preparation of carbonate samples, where any high-vacuum system is avoided and helium is used as a carrier gas. The liberation of CO2 from carbonates with phosphoric acid is performed in a similar way as it is often done in stable isotope ratio mass spectrometry where CO2 is released with acid in septum sealed tube under helium atmosphere. The formed CO2 is later flushed in a helium flow by means of a double-walled needle mounted from the tubes to the zeolite trap of the automated graphitization equipment (AGE). It essentially replaces the elemental analyzer normally used for the combustion of organic samples. The process can be fully automated from sampling the released CO2 in the septum-sealed tubes with a commercially available auto-sampler to the graphitization with the automated graphitization. The new method yields in low sample blanks of about 50000years. Results of processed reference materials (IAEA-C2, FIRI-C) are in agreement with their consensus values. [Copyright &y& Elsevier]

Abstract: The first application of 39Ar Accelerator Mass Spectrometry (AMS) at the ATLAS facility of Argonne National Laboratory was to date ocean water samples relevant to oceanographic studies using the gas-filled magnet technique to separate the 39K–39Ar isobars. In particular the use of a quartz liner in the plasma chamber of the electron cyclotron resonance ion source enabled a 39K reduction of a factor ∼130 compared to previous runs without liners, and allowed us to reach a detection sensitivity of 39Ar/Ar=4×10−17. In order to improve this sensitivity and allow the measurement of lower ratios, higher ion source currents and a lower overall 39K background are necessary. This paper summarizes our efforts to investigate new methods combining low level potassium cleaning techniques with the use of ultra-pure aluminum liners in the plasma chamber of the ion source. The aim of the study was to improve by 1–2 orders of magnitude the 39Ar detection sensitivity required in the selection of ultra-pure materials for detectors used in weakly interacting massive particle dark matter searches. [Copyright &y& Elsevier]

Abstract: Previous work has demonstrated that the sealed tube Zn reduction method for converting CO2 to graphite for AMS 14C measurements produces targets that can be measured with high precision and low background for samples of about 1mgC down to approximately 0.1mgC at the Keck Carbon Cycle AMS facility at the University of California, Irvine (KCCAMS). Now a modified method has been developed to prepare small-mass samples ranging from 0.015 to 0.1mgC. In this modified method, the volume of the sealed reactor tube is reduced to ∼1.9cm3, and the amounts of Zn and TiH2 reagents are reduced proportionally. The amount of Fe catalyst used remains the same to ensure a long lasting current in the AMS. Small-mass samples prepared by this method generally yield 12C+1 currents of about 0.5μA per 1μgC. An in situ simultaneous AMS δ13C measurement allows for correction of both graphitization and machine-induced isotopic fractionation, and is a prerequisite for high precision and accurate measurements using the Zn reducing method. Corrections for modern-carbon and dead-carbon background components are applied to samples based on small-mass samples of a 14C free material and of a modern standard covering the sample size range. It was discovered during additional investigation into lowering the modern-carbon background component that baking assembled reactor tubes at 300°C for 1h prior to use resulted in significantly lower modern-carbon background values. The accuracy and precision of small-mass samples prepared by this method are size dependent, but is usually±10–15‰ for the smallest samples (0.015–0.02mgC), based on duplicate measurements of primary and secondary standards. [Copyright &y& Elsevier]

Abstract: A CO2 laser decomposition method enabled the efficient preparation of carbonate samples for AMS 14C measurement. Samples were loaded in a vacuum chamber and thermally decomposed using laser emission. CO2 liberated from the carbonate was directly trapped in the cold finger trap of a small CO2 reduction reactor and graphitized by a hydrogen gas reduction method using catalytic iron powder. The fraction modern values for 0.07–0.57mg of carbon, obtained from 200μm-diameter spots of IAEA-C1, varied with sample size in the range of 0.00072±0.00003 to 0.00615±0.00052. The contamination induced by the laser decomposition method and the following graphite handling was estimated to be 0.53±0.21μg of modern carbon, assuming a constant amount of extraneous carbon contamination. This method could also make it possible to avoid the time-consuming procedures of the conventional acid dissolution method that involves multiple complex steps for the preparation of carbonate samples. [Copyright &y& Elsevier]