Abstract
We report results of duplicate measurements of dissolved organic carbon concentrations ([DOC] as µM) and Δ14C in seawater in order to assess the total uncertainty of reported [DOC] and Δ14C measurements via the UV oxidation method. In addition, pure International Atomic Energy Agency standards analyzed over a 4-yr period are evaluated. We find the total uncertainty of Δ14C measurements to be ±4.0‰. However, in samples that were thawed, subsampled, and refrozen prior to UV oxidation, the total uncertainty of Δ14C measurements is on the order of ±10‰. The [DOC] measurements of these samples were also higher by 1.8 ± 0.3 µM. The reason(s) for these documented increases in total [DOC] and Δ14C uncertainty are unclear. In order to minimize any effects on sample measurements, we recommend the following: 1) regular monitoring of duplicate samples, DOC standards, and diluent (Milli-Q™) water for Δ14C and [DOC] measurements; 2) thawing a sample immediately and only once prior to UV oxidation; 3) avoid the use of DOC-leachable plumbing (such as PVC pipe) in both water systems feeding and within Milli-Q systems; and 4) consider the use of DOC-free diluents (i.e. pre-UV oxidized Milli-Q or sample water).
Highlights
Few global measurements of dissolved organic carbon (DOC) 14C have been made in the ocean despite its central importance for evaluating the source and cycling of this largest of organic carbon pools in the ocean
We report results of duplicate measurements of dissolved organic carbon concentrations ([DOC] as μM) and 14C in seawater in order to assess the total uncertainty of reported [DOC] and 14C measurements via the UV oxidation method
With the advent of accelerator mass spectrometry (AMS) analysis of 14C, the amount of seawater needed for a measurement of DOC was reduced to 5 L (Williams and Druffel 1987)
Summary
Few global measurements of dissolved organic carbon (DOC) 14C have been made in the ocean despite its central importance for evaluating the source and cycling of this largest of organic carbon pools in the ocean. With the advent of accelerator mass spectrometry (AMS) analysis of 14C, the amount of seawater needed for a measurement of DOC was reduced to 5 L (Williams and Druffel 1987). Samples as small as 0.03 L can be analyzed for DOC 14C (Beaupré et al 2007). Oxidation using ultraviolet (UV) irradiation is currently the chosen method for seawater DOC 14C analysis. Small samples (0.03–0.65 L) were diluted with pre-irradiated Milli-QTM (MQ) water prior to UV oxidation. Griffin et al (2010) reported a revised technique that used MQ water without pre-irradiation to dilute small samples that reduced the amount of time required to run a diluted sample from 2 days to 1 day Small samples (0.03–0.65 L) were diluted with pre-irradiated Milli-QTM (MQ) water prior to UV oxidation. Griffin et al (2010) reported a revised technique that used MQ water without pre-irradiation to dilute small samples that reduced the amount of time required to run a diluted sample from 2 days to 1 day
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
