230Th,226Ra and222Rn in abyssal sediments Article

Kadko, D. (1980). 230Th,226Ra and222Rn in abyssal sediments . EARTH AND PLANETARY SCIENCE LETTERS, 49(2), 360-380. 10.1016/0012-821X(80)90079-5

cited authors

  • Kadko, D



  • A model that predicts the flux of222Rn out of deep-sea sediment is presented. The radon is ultimately generated by230Th which is stripped from the overlying water into the sediment. Data from many authors are compared with the model predictions. It is shown that the continental contribution of ionium is not significant, and that at low sedimentation rates, biological mixing and erosional processes strongly affect the surface concentration of the ionium. Two cores from areas of slow sediment accumulation, one from a manganese nodule region of the central Pacific and one from the Rio Grande Rise in the Atlantic were analyzed at closely spaced intervals for230Th,226Ra, and210Pb. The Pacific core displayed evidence of biological mixing down to 12 cm and had a sedimentation rate of only 0.04 cm/kyr. The Atlantic core seemed to be mixed to 8 cm and had a sedimentation rate of 0.07 cm/kyr. Both cores had less total excess230Th than predicted. Radium sediment profiles are generated from the230Th model. Adsorbed, dissolved, and solid-phase radium is considered. According to the model, diffusional losses of radium are especially important at low sedimentation rates. Any particulate, or excess radium input is ignored in this model. The model fits the two analyzed cores if the fraction of total radium available for adsorption-desorption is about 0.5-0.7, and ifK, the distribution coefficient, is about 1000. Finally, the flux of radon out of the sediments is derived from the model-generated radium profiles. It is shown that the resulting standing crop of222Rn in the overlying water may be considered as an added constraint in budgeting230Th and226Ra in deep-sea sediments. © 1980 Elsevier Scientific Publishing Company.

publication date

  • January 1, 1980

published in

Digital Object Identifier (DOI)

start page

  • 360

end page

  • 380


  • 49


  • 2