Copyright © 1993 Published by Elsevier Ltd.
The role of the Ganges-Brahmaputra mixing zone in supplying barium and226Ra to the Bay of Bengal
Received 17 February 1992;
Abstract
The Ganges-Brahmaputra river system is ranked fourth among world rivers as a source of freshwater to the oceans and is believed to supply more sediment to the ocean than any other; 1.5 × 1012 kg/yr (Milliman and Meade, 1983). Barium and226Ra are typically enriched in waters where sediment-laden rivers enter the ocean. As such, the Ganges-Brahmaputra is likely to produce globally significant barium and226Ra fluxes to the ocean.
Water samples for barium and226Ra were collected within four major channels of the Ganges-Brahmaputra mixing zone during a period of low sediment and freshwater discharge. The data suggest that, in addition to suspended sediments supplied directly from rivers, river sediments deposited during high discharge in mangroves and on islands are desorbing barium and226Ra to seawater. The release of barium and226Ra from these sediment deposits is out-of-phase with the direct supply of sediments from the rivers. Estimates of the annual fluxes of barium and226Ra from the Ganges-Brahmaputra mixing zone were also derived. The fluxes of barium and226Ra are 5.3 × 108 mol barium/yr and 9.5 × 1014 dpm radium/yr. The first silicate and phosphate mixing profiles for this system are reported.






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