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Be-10 and Cl-36 interlaboratory comparisons: Implications for terrestrial production rates?
Merchel, S.; Bremser, W.; Alfimov, V.; Arnold, M.; Aumaître, G.; Benedetti, L.; Bourlès, D. L.; Braucher, R.; Caffee, M.; Christl, M.; Fifield, L. K.; Finkel, R. C.; Freeman, S. P. H. T.; Ruiz-Gómez, A.; Kubik, P. W.; Rood, D. H.; Sasa, K.; Steier, P.; Tims, S. G.; Wallner, A.; Wilcken, K. M.; Xu, S.
Driven by the progress in accelerator mass spectrometry (AMS) and its spreading application within geosciences, the number of samples with low isotopic ratios will increase. Therefore, we have examined the linearity of 10Be/9Be as a function of isotope ratio by distributing three secondary standards (dilutions of NIST4325: 10-12-10-14) to nine AMS labs. The problem of low ratio samples is even more crucial for 36Cl. Thus, we have prepared large quantities of three 36Cl/Cl solutions from a certified 36Cl activity (NIST4943) by dilution with NaCl. AgCl precipitated from these solutions (10-11-10-13) has been distributed to nine AMS labs. We are still awaiting some final results, but first results from eight labs for each nuclide show that these interlaboratory exercises are very valuable, as they show maximum differences between individual AMS labs up to 35% for 10Be, and 25% for 36Cl, respectively.
Our data indicate that actual 36Cl measurements at LLNL, PRIME Lab and ANU can differ by more than 10%. The implications of this for 36Cl in-situ production rates, determined earlier at these facilities, cannot be ignored. Some, although not all, of the current disagreement concerning 36Cl production rates may result from these discrepancies. However, we are assuming that our new data at the 10-12-10-13 level are still representative for earlier measurements of in-situ samples at that level.
This work was partially funded by CRONUS-EU (Marie-Curie Action, 6th FP #511927).
Keywords: accelerator mass spectrometry
Abstract in refereed journal
Geochimica et Cosmochimica Acta 73(2009)13, A871
19th V.M. Goldschmidt conference, 21.-26.06.2009, Davos, Schweiz