Experimental approaches to the study of technetium transfers to sediments and benthic marine species

Laboratory experiments have been undertaken to evaluate the technetium-fixing capacity of sediments and marine species sampled on the English Channel coast. Water-to-sediment transfers of 99Tc and 95sup(m)Tc were studied on a range of marine sediments with various geochemical properties. It seems to be the reducing sediments, or sediments heavily loaded with organic matter, which fix technetium most readily. However, the distribution coefficients obtained are relatively small and the contamination kinetics very slow. Bacteria appear to play an important role, sorption being inhibited by sterilization. Bioaccumulation kinetics were studied on algae, annelids, crustaceans, one mollusc and a fish with the help of 95sup(m)Tc. For most species the concentration factors remain very slight, ranging from 1 to 10. However, for brown algae (Fucus serratus) and for certain annelids (Perinereis cultrifera) and crustaceans (Homarus vulgaris), concentration factors of 1000 and more have been observed after one month of contamination. Some of these results have been confirmed by analyses of 99Tc concentrations in species sampled near the La Hague reprocessing plant. (author)