Radionuclide Fluxes in the Arabian Sea: The role of particle composition

• Published in: Earth and Planetary Science Letters
• Main Authors: Scholten, Jan, Fietzke, Jan, Mangini, A., Stoffers, Peter, Rixen, T., Gaye- Haake, B., Blanz, T., Ramaswamy, V., Siricko, F., Schulz, H., Ittekkot, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2005
• Subjects: Pacific; Southern Ocean; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/8025/; https://oceanrep.geomar.de/id/eprint/8025/1/1-s2.0-S0012821X04006727-main.pdf; https://doi.org/10.1016/j.epsl.2004.11.003

We investigated the influence of the composition of the vertical particle flux on the removal of particle reactive natural radionuclides (Th-230 and Pa-231) from the water column to the sediments. Radionuclide concentrations determined in sediment traps moored in the western, central and eastern Arabian Sea were related to the major components (carbonate, particulate organic matter (POC), opal, lithogenic material) of the particle flux. These data were combined with sediment trap data previously published from the Southern Ocean, Equatorial Pacific and North Atlantic [Z. Chase, R.F. Anderson, M.Q. Fleisher, P.W. Kubik, The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean, Earth Planet. Sci. Lett. 204 (2002) 215-229; J.C. Scholten, F. Fietzke, S. Vogler, M. Rutgers van der Loeff, A. Mangini, W Koeve, J. Waniek. P. Stoffers, A. Antia, J. Kass, Trapping efficiencies of sediment traps from the deep eastern North Atlantic: The Th-230 calibration, Deep Sea Research 1148 (2001) 2383-2408]. The correlations observed between the particle-dissolved distribution coefficients (K-d) of Th-230 and Pa-231 and the concentrations of the particle types depend on the sediment trap data set used. This result suggests that scavenging affinities of the nuclides differ between oceanic regions. Several factors (K-d values, reactive surface areas of particles, inter-correlations in closed data set) can, however, influence the observed relationships and thus hamper the interpretation of these correlation coefficients as a measure of relative scavenging affinities of the nuclides to the particle types investigated. The mean fractionation factor (F(Pa/Th)=K-d(Pa)/(K)d(Th)) from the Equatorial Pacific (F=0.11+/-0.03) is similar to that from the North Atlantic (F(Pa/Th)=0.077+/-0.026), and both are lower than the factors from the Arabian Sea (F(Pa/Th)=0.35+/-0.12) and from the Southern Ocean (F(Pa/Th) 0.87+/-0.4). For opal concentrations exceeding similar to60%, an increase in the fractionation ...