N.Z. Plans To Survey Ocean Radioactivity

Press, Volume CI, Issue 29871, 11 July 1962, Page 15

N.Z. Plans To Survey Ocean Radioactivity

New Zealand has applied to the International Atomic Energy Agency for a grant to make possible a survey of the radioactive-isotope content of seawater at various depths off the New Zealand coast, Mr T. A. Rafter, director of the Institute of Nuclear Sciences, Department of Scientific and Industrial Research, Gracefield, said yesterday. The object of the proposed survey, said Mr Rafter, was to find how long it was since water at various depths had been on the surface, and to trace ocean currents. The work wgs on lines pioneered by American scientists, particularly those of the Woods Hole Oceanographic Institute

The number of isotopes examined would depend on the size of the grant, he said. It was hoped that at least car-bon-14, strontium-90, caesium--137, cerium-144, and prome-thium-147 would be included. The latter four were entirely the result of bombtesting, while carbon-14 was partly of bomb and partly of natural origin. New Zealand was a very suitable base for studies of this kind, because ocean depths reached so near the coast, Mr Rafter said. There wkre (tenths of 3000 metres

not far off the east coast of the North Island, and of 4000 metres off Fiordland, while the Kermadec Trench reached down more than 9000 metres. Carbon-14 studies of waters in the New Zealand area, from the equator to the Antarctic, had already been made by the institute. Mr Rafter added. The pattern emerging was similar to that found in corresponding surveys overseas. Deep ocean water off the east coast was of the order of 1000 years old, with lower ages at intermediate depths. Surface Antarctic water showed the same general age by carbon-14 dating as the deep ocean water of other regions—an anomaly recorded elsewhere, but as yet unexplained. The samples had been collected by the New Zealand Oceanographic Institute.

The carbon-14 dating, said Mr Rafter, had been carried out by Mr H. S. Jansen, of his institute, but the assay of the other radioactive isotopes would be in the hands of another member of the staff, Mr W J. Mason, who was now preparing for the work. Mr Mason had already measured the radioisotopes in seawater he had collected from Makara and Day's Bay, and the results were consistent with those from New Zealand land stations