Using the radium quartet Ra-228, Ra-226, Ra-224, and Ra-223 to estimate water mixing and radium inputs in Loch Etive, ScotlandReportar como inadecuado




Using the radium quartet Ra-228, Ra-226, Ra-224, and Ra-223 to estimate water mixing and radium inputs in Loch Etive, Scotland - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1 Department of Earth Sciences 2 School of Geosciences Edinburgh 3 SAMS - Scottish Association for Marine Science 4 GEOMAR LEGOS LEGOS - Laboratoire d-études en Géophysique et océanographie spatiales

Abstract : The radium Ra quartet Ra-228, Ra-226, Ra-224, and Ra-223 has been investigated in Loch Etive, a Scottish fjord, to provide new constraints on water mixing rates and on the inputs of Ra from sediments. Maximum water transport rates for the inflowing estuarine layer at 5 m depth, determined from the excess Ra-223 Ra-223ex, indicate that this water travels at no more than 2.4 +- 0.2 cm s-1 net and that it takes 17 +- 2 d for waters to travel from the mouth to the head of the loch if no horizontal mixing is taken into account. Alternatively, neglecting advection, the short-lived Ra distribution could be explained by horizontal mixing rates of 6.1 x 106 cm2 s-1 Ra-223ex or 9.1 x 106 cm2 s-1 Ra-224ex. Periodic overturning circulation plays an important role in resetting chemical cycles in the isolated deep basin of the inner loch. Sediment in this deep basin provides the major input of Ra-228 to the isolated deep water, and the accumulation of Ra-228 in deep waters allows an assessment of sedimentary fluxes of Ra-228, a poorly constrained aspect of the Ra-228 input to the global ocean. The calculated sedimentary Ra-228 flux of 2.1 +- 0.2 x 109 atoms m-2 yr-1 in the inner deep basin is comparable with previous measurements of sedimentary Ra-228 inputs from shelf sediments, supporting existing global Ra-228 budgets, which are used to assess global rates of groundwater discharge to the ocean.

Keywords : SCOTTISH FJORD GROUNDWATER DISCHARGE EQUATORIAL PACIFIC MASS-SPECTROMETRY COASTAL WATERS WORLD OCEAN DEEP-SEA ISOTOPES SEDIMENTS DYNAMICS





Autor: Y. T. Hsieh - W. Geibert - P. Van-Beek - H. Stahl - D. Aleynik - G. M. Henderson -

Fuente: https://hal.archives-ouvertes.fr/



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