The Rapid Preparation of Seawater Sigma-CO2 for Radiocarbon Analysis at the National Ocean Sciences AMS Facility

Abstract

We have established a laboratory for extracting Sigma-CO2 from seawater samples for AMS analysis of the radiocarbon content. The seawater samples are collected at sea, poisoned and stored until analysis in the laboratory. Each sample is acidified; the inorganic carbon is stripped out as CO2 with an inert carrier gas and then converted to graphite. We present results for Buzzards Bay surface H2O and Na2CO3 standards that demonstrate we strip >98% of inorganic carbon from seawater. Stable isotope analyses are performed to better than 0.2 per mil, and the reproducibility of 14C measurements on Buzzards Bay seawater is better than 13 per mil. Finally, we compare data from samples collected in 1991 to those collected in the 1970s and to large volume samples.