ABSTRACT

Investigations are made to determine molybdenum species in sea-water samples collected from the Seto Inland Sea, the Japan Sea, the Bering Sea, and the western North Pacific. A large portion of the molybdenum species in sea waters exists as a hexavalent oxoacid anion (MoO^2-₄), but an appreciable amount of molybdenum was found as an unextractable species with an 8-quinolinol-DIBK system in the high-molecular weight species. Total dissolved molybdenum was uniformly distributed in oceanic waters at a concentration level of 8.10 to 12.0 μg/l (average, 10.2±0.90 μg/l). In coastal waters, however, great spatial and temporal variations were observed. The concentration of unextractable molybdenum was relatively high in the coastal waters (0.60±0.52 μg/l) and in the shallow waters of the open oceans (0.40±0.33 μg/l), while it was not large in the deep waters (0.28±0.27 μg/l). High molecular-weight molybdenum, which has a molecular weight over 10, 000, was sometimes observed. The molybdenum was randomly distributed and not related to the distribution of the unextractable species. The unextractable and/or high molecular-weight molybdenum, which is probably associated with organic substances, may significantly contribute to the biological cycle of molybdenum in a productive area.