Collection and Measurement of Carbon Isotopes in Seawater DIC.

Abstract

The stable and radio-carbon isotopic content of seawater dissolved inorganic carbon (DI13C and DI14C, respectively) is measured by extracting the inorganic carbon as CO2 gas. A small portion of the gas is analyzed on a stable isotope ratio mass spectrometer and most of the gas is converted to graphite and inserted into an accelerator mass spectrometer where the number of 14C atoms are counted. The sampling procedure described below is straightforward, but it is important to stress the need for clean, careful sampling techniques to ensure an uncompromised sample. In order to minimize exchange with atmospheric CO2 , sample transfers must be as rapid as possible. The use of an accelerator mass spectrometer to measure 14C in seawater samples has greatly reduced the size of the sample required for the measurement, but it has also greatly increased the importance of collecting the sample in a clean, 14C-free, environment....