7Be analyses in seawater by low background gamma-spectroscopy

Oceanographers use the cosmogenic radionuclide 7Be (T1/2 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 7Be from seawater. The scavenging efficiency of Fe(OH)3 for each sample is measured by ICP-MS using stable 9Be 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 7Be in the Sargasso Sea. (author)