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Title: Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas

Abstract

The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengal suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelfmore » sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.« less

Authors:
; ;
Publication Date:
Research Org.:
Univ. of Tokyo (JP)
OSTI Identifier:
20076120
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 64; Journal Issue: 10; Other Information: PBD: May 2000; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; NEODYMIUM; ISOTOPE RATIO; RARE EARTHS; INDIAN OCEAN; ECOLOGICAL CONCENTRATION; ORIGIN; POLLUTION SOURCES

Citation Formats

Amakawa, Hiroshi, Alibo, D.S., and Nozaki, Yoshiyuki. Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas. United States: N. p., 2000. Web. doi:10.1016/S0016-7037(00)00333-1.
Amakawa, Hiroshi, Alibo, D.S., & Nozaki, Yoshiyuki. Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas. United States. doi:10.1016/S0016-7037(00)00333-1.
Amakawa, Hiroshi, Alibo, D.S., and Nozaki, Yoshiyuki. Mon . "Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas". United States. doi:10.1016/S0016-7037(00)00333-1.
@article{osti_20076120,
title = {Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas},
author = {Amakawa, Hiroshi and Alibo, D.S. and Nozaki, Yoshiyuki},
abstractNote = {The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengal suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelf sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.},
doi = {10.1016/S0016-7037(00)00333-1},
journal = {Geochimica et Cosmochimica Acta},
issn = {0016-7037},
number = 10,
volume = 64,
place = {United States},
year = {2000},
month = {5}
}