T03_06

Radiocarbon in dissolved organic carbon by UV oxidation: an update of procedures and blank characterization at NOSAMS

Xu L¹, Roberts M¹, Elder K¹, Hansman R¹, Gagnon A¹, Kurz M¹

¹Woods Hole Oceanographic Institution, Woods Hole, United States

Radiocarbon measurements of dissolved organic carbon (DOC) in aquatic systems provide key insights into the age and biogeochemical cycling of this large and reactive carbon reservoir.  At the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility, we have worked extensively to reduce the procedural blank of DO¹⁴C to 3.3 ± 0.8 µg C with Fm of 0.35 ± 0.15, down from 22.0 ± 6.0 µg C in 2018.  This was achieved through modifications of sample processing that included elimination of higher blank organic carbon reagents and improved sample and reactor handling intended to reduce exposure to laboratory air (which may contribute to the DOC blank via volatile organic compounds).  Sample throughput has been improved three-fold to three samples per day by increasing the size of the UV oxidation chamber to allow for three reactors.