An experimental study on the Dioaccumulation and turnover of polonium-210 and lead-210 in marine shrimp

The experimental accumulation of 210Po and 'lOPb from seawater alone and from seawater and food was studied in the laboratory with the benthic shrimp Lysrnata seticaudata.Shrimp accumulated both radionuclides from water for 21 d, reaching whole body concentration factors [CF = (Bq g-' of shrimp wet wt)/(Bq ml-' filtered water)] of 139 k 28 for "OPo and 682 + 149 for 'l0Pb.When uptake was from water only, tissue analyses revealed that radionuclide accumulation was mainly due to external adsorption.Accumulation in internal tissues also occured through the intake of seawater for osmotic regulation.Exposure of shrimp to radionuclides dissolved In water and labelled food produced a noticeable accumulation of 210Po in internal tissues which was not accompanied by an identical accumulation of 210Pb.It is concluded that in shrimp 210Po was mainly accumulated from food, whereas 210Pb was largely taken up from the fraction dissolved in seawater.A much higher digestive assimilation efficiency for 210Po, about 5-fold that of ''Opb, was observed in L. seticaudata.This difference can account for the enhancement of 2'oPo:210Pb ratios observed in the lower trophic levels of marine food chains.Turnover of 2'0Po in shnmp tissues is much slower than for 2'0Pb, a fact which also contributes to the enhanced 2'o~o:2'0Pb concentration ratios observed in marine crustaceans.