|Distribution of radioisotopes between phytoplankton, sediment and sea water in a dialysis compartement system|
Dawson, R.; Duursma, E.K. (1974). Distribution of radioisotopes between phytoplankton, sediment and sea water in a dialysis compartement system. Neth. J. Sea Res. 8(4): 339-353
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
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The distribution of the radioisotopes 36Cl, 54Mn, 59Fe, 60CO, 65Zn, 90Sr, 106Ru, 109Cd, 110mAg, 137CS, 144Ce, 147Pm and 204Ti between seawater, Mediterranean sediment in suspension, and the phytoplankton species Phaeodactylum tricornutum was studied by using a competitive technique in which the various phases were separated by dialysis membranes. The radioisotopes were introduced into the seawater compartment and the radionuclide uptake by sediment and phytoplankton occurred in the adjoining compartments after the isotopes had diffused through the membranes. The diffusion through membranes is time dependent and related to the hydrated ion radii of the elements in solution. Chelation of the elements by organic matter from sewage may hamper this diffusion, although the complexing molecules themselves can pass through the membrane. The laboratory experiments showed that the uptake ofradionuclides by sediments and phytoplankton in suspension did not occur independently of each other but in competition relative to the different affinities to the sediment and phytoplankton and relative to the concentrations of the particulate materials themselves. On examination of the distribution coefficients, the isotopes 90Sr, 110mAg, 204Ti and in particular 109Cd, had higher affinities towards Phaeodactylum tricornutum than towards the Mediterranean sediment. The isotopes 54Mn, 60CO and 137CS had lower distribution coefficients with the phytoplankton than with sediment and in the case of 59Fe, 65Zn, 106Ru, 144Ce and 147Pm the distribution coefficients were similar for both phytoplankton and sediment. Taking into account that many more factors play a roll in the natural aquatic environment, the distribution pattern between water, plankton and sediment in suspension can be approximated by calculating the percentage distribution in the 3 phases. Those percentages are dependent on 2 parameters, being the distribution coefficients and the concentrations of the sediment and plankton in suspension. Predictions of the amounts of radionuclides or trace metals which will find their way into the biological food chain and the amounts removed by sediments can be made.