T03_P08

A new UV-Oxidation set up for AMS radiocarbon analysis for small dissolved organic carbon in marine and fresh water samples

Haghipour N^1,2, Lupker M¹, Wacker L², Eglinton T¹

¹Geological Institute, ETH Zurich, Zurich, Switzerland, ²Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland

Radiocarbon measurements of dissolved organic carbon (DOC) can give us valuable information about origin and age of DOC, a major, yet little understood component in the global carbon cycle. One way to measure DOC in water is to remove dissolved inorganic carbon first, oxidize organic carbon with UV irradiation and ultimately analyses the formed inorganic CO₂ for ¹⁴C. The main challenge of UV-Oxidation (UVox) methods is to extract the typically low concentrations of DOC with low blanks required for relatively high precision ¹⁴C measurements. A disadvantage of currently used UVox methods is that only one sample can be oxidized in a laborious process at the same time. Here we present a UV-Oxidation system where up to 12 water samples can be oxidized simultaneously in 12 separate quartz reactors arranged around a single UV lamp in a compact setup. The simple setup further uses helium instead of vacuum typically used by conventional extraction lines to speed up the extraction of the formed CO₂ after oxidation. The key improvements of the new UVox setup are: 1) Reduced amount of water needed (30- 60 ml) as samples are measured for ¹⁴C with the Micadas gas ion source, 2) UV oxidation efficiency for standards is high (96%), 3) No KI trap is needed,4) Required time for sample preparation of up to 12 samples is 4-6 h. To test the oxidation efficiency, reproducibility  and blank assessment we used different reference materials. Here we discuss the preliminary results from the performance of UVox extraction line.