Thorium isotopes in the surface air of the Western North Pacific Ocean |
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| Institution: | 1. UMR 5199 PACEA, Université de Bordeaux, bâtiment B18, Allée Geoffroy Saint-Hilaire, 33615 Pessac CEDEX, France;2. Service de Préhistoire, Université de Liège, Place du XX Août, 4000 Liège, Belgium;3. SARL Paléotime, 6173 Rue Jean Séraphin Achard Picard, 38350 Villard-de-Lans, France;4. 21 rue du Général Ferrié, 38100 Grenoble, France;5. UMR 5140 Archéologie des sociétés méditerranéennes, Université de Montpellier 3, Route de Mende, 34199 Montpellier, France;6. UMR 6042 GEOLAB, Université Clermont Auvergne, Université Blaise Pascal, 4 Rue Ledru, 63052 Clermont-Ferrand cedex 1, France;7. Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany;2. Department of Biochemistry, Faculty of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan;3. Department of Regenerative Medicine & Transplantation, Faculty of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan;1. Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA;2. Bermuda Institute of Ocean Sciences, Ferry Reach, Bermuda;3. Department of Ocean and Earth Science, University of Southampton, Southampton, UK |
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| Abstract: | The concentrations and activity ratios of thorium isotopes in maritime airborne particles, collected over the western North Pacific along 137° E during cruises in January 1982 and 1983 and in March 1983, are reported here. The 232Th concentration in air is high at mid-latitude, near the Japanese islands and decreases southwards further from land. The 232Th concentration ranges from 0·036 to 0·22 μBq m−3. The 230Th/232Th activity ratio in the maritime air is almost unity, reflecting the U/Th activity ratio coupled with the crustal abundance. The 228Th/232Th activity ratio ranges from 3 to 69·5 and is, in general, higher than that in air over land. The results indicate the importance of the aeolian flux of the thorium isotopes, especially for 232Th and 228Th, in the geochemical cycle of thorium in the marine environment. |
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