Premium
The marine geochemistry of actinium‐227: Evidence for its migration through sediment pore water
Author(s) -
Nozaki Yoshiyuki,
Yamada Masatoshi,
Nikaido Hirofumi
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i011p01933
Subject(s) - bioturbation , sediment , water column , pore water pressure , geology , radionuclide , oceanography , bottom water , tracer , sediment–water interface , flux (metallurgy) , geochemistry , geomorphology , chemistry , physics , geotechnical engineering , organic chemistry , quantum mechanics , nuclear physics
227 Ac with a half life of 21.8 years has a potential utility as a tracer of deep water circulation and mixing studies on time scales less than 100 years. Here we present the first measurement of 227 Ac profile in the pore water of Northwest Pacific deep‐sea sediment and in the ∼ 10,000 m long water column of Izu‐Ogasawara Trench. The results clearly show that 227 Ac is supplied from the sediment to the overlying water through migration in the pore water. The model calculation indicates that the molecular diffusion alone through sediment porewater can support only a half of the standing crop of excess 227 Ac in the water column and the enhanced supply of 227 Ac by particle mixing is necessary to account for the remainder. Thus, bioturbation in the deep sea plays an important role in controlling the flux of some short‐lived radionuclides such as 227 Ac and 228 Ra across the sediment‐water interface.