Abstract
We report the role of particle composition and lateral particle movement that influences the oceanic distribution of 231Pa and 230Th. Settling particles were collected during sediment trap experiments. These and surface sediments were obtained from five stations along 38 to 44°N in the northwestern North Pacific. The high total mass flux and seasonal variations in the marginal area of the western North Pacific are controlled by the supply of lithogenic materials and primary productivity. The high content of the lithogenic material in the settling particles in this area contributes to 230Thex fluxes that exceed the local rate of supply. The lithogenic materials are important as a carrier of 230Th and contribute to the fractionation between 230Th and 231Pa in the ocean, as the 231Paex/230Thex ratio in the settling particles decreases with increasing 232Th concentration. The 231Paex/230Thex ratio in the settling particles collected in the abyssal basin decreases with water depth, which indicates that lateral transport of the lithogenic particles from the marginal area and/or shallower depth plays an important role in determining the 231Paex/230Thex ratio in a population of settling particles and remineralization. This indicates that lateral redistribution of particles and sediment focusing influence the 231Paex/230Thex ratios in surface sediments. Thus, the observations reported here mean that the use of the sediment 231Paex/230Thex ratio as a paleoproductivity proxy will be problematic in the northwestern North Pacific.
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Anderson, R. F., M. P. Bacon and P. G. Brewer (1983a): Removal of 230Th and 231Pa in the open ocean. Earth Planet. Sci. Lett., 62, 7–23.
Anderson, R. F., M. P. Bacon and P. G. Brewer (1983b): Removal of 230Th and 231Pa in the ocean margins. Earth Planet. Sci. Lett., 66, 73–90.
Anderson, R. F., Y. Lao, W. S. Broecker, S. E. Trumore, H. J. Hofmann and W. Wolfi (1990): Boundary scavenging in the Pacific Ocean: a comparison of 10Be and 231Pa. Earth Planet. Sci. Lett., 96, 287–304.
Anderson, R. F., M. Q. Fleisher, P. E. Biscaye, N. Kumar, B. Dittrich, P. Kubik and M. Suter (1994): Anomalous boundary scavenging in Middle Atlantic Bight: evidence from 230Th, 231Pa, 10Be and 210Pb. Deep-Sea Res. II, 41, 537–561.
Bacon, M. P. (1988): Tracers of chemical scavenging in the ocean: boundary effects and large scale chemical fractionation. Philosoph. Trans. Roy. Soc. London A, 320, 187–200.
Bacon, M. P., D. W. Spencer and P. G. Brewer (1976): 210Pb/ 226Ra and 210Po/210Pb disequilibria in seawater and particulate matter. Earth Planet. Sci. Lett., 32, 277–296.
Bacon, M. P., C.-A. Huh, A. P. Fleer and W. G. Deuser (1985): Seasonality in flux of natural radionuclides and plutonium in the deep Sargasso Sea. Deep-Sea Res., 32, 273–286.
Brewer, P. G.,Y. Nozaki, D. W. Spencer and A. P. Fleer (1980): Sediment trap experiments in the deep North Atlantic: isotopic and elemental fluxes. J. Mar. Res., 38, 703–728.
Craig, H., S. Krishnaswami and B. L. K. Somayajulu (1973): 210Pb-226Ra: Radioactive disequilibrium in the deep sea. Earth Planet. Sci. Lett., 17, 295–305.
Guo, L., P. Santschi, M. Baskaran and A. Zindler (1995): Distribution of dissolved and particulate 230Th and 232Th in seawater from the Gulf of Mexico and off Cape Hatteras as measured by SIMS. Earth Planet. Sci. Lett., 133, 117–128.
Honda, M. C., K. Imai, Y. Nojiri, F. Hoshi, T. Sugawara and M. Kusakabe (2002): The biological pump in the northwestern North Pacific based on fluxes and major components of particulate matter obtained by sediment-trap experiments (1997-2000). Deep-Sea Res. II, 49, 5595–5625.
Huh, C.-A. andT. M. Beasley (1987): Profiles of dissolved and particulate thorium isotopes in the water column of coastal Southern California. Earth Planet. Sci. Lett., 85, 1–10.
Kumar, N.,R. F. Anderson, R. A. Mortlock and P. N. Froelich (1993): 231Pa/230Th ratios in sediments as a proxy for the past changes in the Southern Ocean productivity. Nature, 362, 45–48.
Lao, Y., R. F. Anderson, W. S. Broecker, H. J. Hofrmann and W. Wolfli (1993): Particulate fluxes of 230Th, 231Pa and 10Be in the northeastern Pacific. Geochim. Cosmochim. Acta, 57, 205–217.
Luo, S. and T.-L. Ku (1999): Oceanic 231Pa/230Th ratio influenced by particle composition and remineralization. Earth Planet. Sci. Lett., 167, 183–195.
McCabe, W. J., R. G. Ditchburn and N. E. Whitehead (1979): The quantitative separation, electrode positron and alpha spectrometry of Uranium, Thorium and Protactinium in silicates and carbonates. Inst. Nucl. Sci. (NZ) Rep. INS-R-262, 29 pp.
Mohamed, C. A. R. andS. Tsunogai (1998): 231Pa in hemipelagic sediments: Is it affected by boundary scavenging? Geochem. J., 32, 11–20.
Mohamed, C. A. R., H. Narita, K. Harada and S. Tsunogai (1996): Sedimentation of natural radionuclides on the seabed across the northern North Pacific. Geochem. J., 30, 217–229.
Narita, H., K. Harada, W. C. Burnett, S. Tsunogai and W. J. McCabe (1989): Determination of 210Pb, 210Bi and 210Po in natural waters and other materials by electrochemical separation. Talanta, 36, 925–929.
Narita, H., K. Harada and S. Tsunogai (1990): Lateral transport of particles in the Okinawa Trough determined by natural radionuclides. Geochem. J., 24, 207–216.
Narita, H., S. Sato, S. Tsunogai, M. Murayama, M. Ikehara, T. Nakatsuka, M. Wakatsuchi, N. Harada and Y. Ujiie (2002): Biogenic opal indicating less productive northwestern North Pacific. Geophys. Res. Lett., 29, l10.1029/2001GL014320.
Noriki, S. and S. Tsunogai (1986): Particulate fluxes and major components of settling particles from sediment trap experiments in the Pacific-Ocean. Deep-Sea Res., 33, 903–912.
Nozaki, Y. and T. Nakanishi (1985): 231Pa and 230Th profiles in the open ocean water column. Deep-Sea Res., 32, 1209–1220.
Nozaki, Y. and M. Yamada (1987): Thorium and protactinium isotope distributions in waters of the Japan Sea. Deep-Sea Res., 34, 1417–1430.
Nozaki, Y., J. Thomson and K. K. Turekian (1976): The distribution of 210Pb and 210Po in the surface water of the Pacific Ocean. Earth Planet. Sci. Lett., 32, 304–312.
Nozaki, Y., Y. Horibe and H. Tsubota (1981): The water column distributions of thorium isotopes in the western North Pacific. Earth Planet. Sci. Lett., 54, 203–216.
Otosaka, S. and S. Noriki (2000): REEs and Mn/Al ratio of settling particles: horizontal transport of particulate material in the northern Japan Trench. Mar. Chem., 72, 329–342.
Saito, C., S. Noriki and S. Tsunogai (1992): Particlulate flux of Al, a component of land, in the western North Pacific. Deep-Sea Res., 39, 1315–1327.
Taguchi, K., K. Harada and S. Tsunogai (1989): Particulate removal of 230Th and 231Pa in the biological productive northern North Pacific. Earth Planet. Sci. Lett., 93, 223–232.
Tsunogai, S. and S. Noriki (1991): Particulate fluxes of carbonate and organic carbon in the ocean. Is the marine biological activity working as a sink of the atmospheric carbon? Tellus, 43B, 256–266.
Tsunogai, S., M. Uematsu, S. Noriki, N. Tanaka and M. Yamada (1982): Sediment trap experiment in the northern North Pacific: Undulation of settling particles. Geochem. J., 16, 129–147.
Tsunogai, S., S. Noriki, K. Harada and K. Tate (1990): Vertical change index for the particulate transport of chemical and isotopic composition in the ocean. Geochem. J., 24, 229–243.
Turekian, K. K. (1977):The fate of metals in the ocean. Geochim. Cosmochim. Acta, 41, 1139–1144.
Yang, H.-S., Y. Nozaki, H. Sakai and A. Masuda (1986a): The distribution of 230Th and 231Pa in the deep-sea surface sediments of the Pacific Ocean. Geochim. Cosmochim. Acta, 50, 81–89.
Yang, H.-S., Y. Nozaki, H. Sakai, Y. Nagaya and K. Nakamura (1986b): Natural and man-made radionuclide distributions in Northwest Pacific deep-sea sediments: rates of sedimentation, bioturbation and 226Ra migration. Geochem. J., 20, 29–40.
Walter, H.-J., M. M. Rutgers van der Loeff and H. Hoeltzen (1997): Enhanced scavenging of 231Pa relative to 230Th in the South Atlantic south of the Polar Front. Implications for the use of the 231Pa/230Th ratio as a paleoproducivity proxy. Earth Planet. Sci. Lett., 149, 85–100.
Walter, H.-J., W. Geibert, M. M. Rutgers van der Loeff, G. Fischeer and U. Bathmann (2001): Shallow vs. deep-water scavenging of 231Pa and 230Th in radionuclide enriched waters of the Atlantic sector of the Southern Ocean. Deep-Sea Res. I, 48, 471–493.
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Narita, H., Abe, R., Tate, K. et al. Anomalous Large Scavenging of 230Th and 231Pa Controlled by Particle Composition in the Northwestern North Pacific. Journal of Oceanography 59, 739–750 (2003). https://doi.org/10.1023/B:JOCE.0000009602.16947.74
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DOI: https://doi.org/10.1023/B:JOCE.0000009602.16947.74