7Be analyses in seawater by low background gamma-spectroscopy

Oceanographers use the cosmogenic radionuclide Be-7 (T-1/2 53 days) as a tracer for atmospheric input and a conservative tracer of mixing in the open ocean. This paper elucidates a method for improving the analysis of Be-7 from seawater. The scavenging efficiency of Fe(OH)(3) for each sample is measured by ICP-MS using stable Be-9 as a yield monitor. Samples are gamma-counted in a large diameter (28 mm) well detector. The high purity germanium well detector is coupled with an active anti-coincidence cosmic guard to reduce the spectra background. The improved overall accuracy of the method and lower detection limit of the detector results in a lower volume of seawater needed for analyses. Results will be shown from a study of Be-7 in the Sargasso Sea.