This paper applies new information concerning the process blank for radiocarbon analysis of dissolved organic carbon using UV-oxidation and subsequent accelerator mass spectrometry analysis. Recent analyses at the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility show that reported values for such samples should be updated to reflect a process blank of 22 ± 6 micrograms of carbon with a fraction modern of 0.3 ± 0.2. The effects of this blank upon δ13C were also assessed and found to be generally less than 0.2‰. While this process blank does not change interpretations of stable carbon isotope results, it does affect interpretations of carbon cycling in Lake Superior, with the lake's bulk dissolved organic carbon (Bulk DOC, <0.7 µm), initial DOC (Init DOC, <0.2 μm) and low molecular weight DOC (LMW DOC, <1000 kDa) appearing more enriched in bomb radiocarbon than previously reported. This paper also applies a previously published process blank to particulate organic carbon data, and this application generally, but not always, leads to more enriched Δ14C values.
Bibliographical noteFunding Information:
This work was funded by the National Science Foundation , OCE0825600 to E.C.M. and J.P.W. We thank NOSAMS for providing the revised blank-corrected DOC data, particularly Kathy Elder, Li Xu, and Mark Roberts.
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