Uptake and depuration of 131I by the edible periwinkle Littorina littorea:: uptake from seawater

Uptake and depuration experiments for the edible periwinkle Littorina littorea have been performed using I-131-labelled seawater. Throughout the experimental phase the winkles were fed on unlabelled Chondrus crispus. I-131 concentrations in winkles during uptake followed linear first-order kinetics with an uptake half-time of 11 days, whereas for depuration a triphasic sequence with biological half-lives of 4, 23 and 56 days was determined. In general, iodine turnover in winkles via labelled seawater appears to be slower than observed for other molluscs (2-3 days). Most of the activity prior to and after deputation is found to be in the shell, with indications that shell and soft parts accumulate and depurate I-131 at a similar rate. The operculum displays the highest specific activity of all fractions with a concentration factor of 750 l kg(-1). Concentration factors for whole winkle, shell, soft parts and digestive gland are in the order of 40-60 l kg(-1), higher than the IAEA recommended CF value for iodine in molluscs of 10 l kg(-1). The I-131 CF in winkles is closer to that of the conservative radionuclides Tc-99 and Cs-137 than the CF of the particle reactive radionuclides Pu-239,Pu-240 and Am-241. (C) 2004 Elsevier Ltd. All rights reserved.