Precise measurements of /sup 234/U//sup 238/U and U concentrations in profiles of Pacific and Atlantic waters
High precision measurement of /sup 234/U//sup 238/U ratios and U concentrations in profiles of Atlantic and Pacific waters have been made in order to determine the degree of heterogeneity of these parameters in the open ocean. The measurements were made possible by the development of mass spectrometric techniques to measure /sup 234/U//sup 238/U to +/- approx. 5 per thousand (2sigma) and U concentrations to +/- 2 per thousand with 2-5 x 10/sup 9/ atoms of /sup 234/U. A /sup 233/U-/sup 236/U double spike is used to correct for instrumental mass fractionation. The average /sup 234/U//sup 238/U for 4 samples from the Pacific profile is 144 +/- 4 per thousand higher than the equilibrium atomic /sup 234/U//sup 238/U ratio (5.47 x 10/sup -5/). The average for 5 samples in the Atlantic profile is identical (144 +/- 4 per thousand). A comparison of /sup 234/U//sup 238/U values for samples above and below the thermocline shows similar homogeneity. U concentrations normalized to 35 per thousand salinity are the same within approx. 1% (3.215 +/- 6 to 3.257 +/- 6 ppb) but clearly show variation greater than the +/- 2 per thousand error. The reason for this fine scale variation requires further investigation. The authors data suggest that /sup 234/U//sup 238/U in the open ocean is homogeneous to within 8 per thousand. This is consistent with the long residence time of U and the long /sup 234/U half life compared to the residence time of water in the deep ocean. Similar measurements on marine pore fluids which can easily be done using the authors technique should provide constraints on the U flux across the sediment-water interface (524).
- Research Organization:
- California Institute of Technology, Pasadena (USA)
- OSTI ID:
- 6649858
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Aquatic-- Radioactive Materials Monitoring & Transport-- (1989)
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ACTINIDE COMPOUNDS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ALPHA DECAY RADIOISOTOPES
ATLANTIC OCEAN
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
EVEN-EVEN NUCLEI
GEOCHEMISTRY
HEAVY NUCLEI
INTERFACES
ISOTOPE RATIO
ISOTOPES
MASS SPECTROSCOPY
NUCLEI
PACIFIC OCEAN
QUANTITATIVE CHEMICAL ANALYSIS
RADIOISOTOPES
SEAS
SEDIMENT-WATER INTERFACES
SPECTROSCOPY
SURFACE WATERS
URANIUM 234
URANIUM 236
URANIUM 238
URANIUM COMPOUNDS
URANIUM ISOTOPES
WATER CHEMISTRY
YEARS LIVING RADIOISOTOPES