Sea-to-land transfer of technetium-99 through the use of contaminated seaweed as an agricultural soil conditioner

The use of seaweed as an agricultural soil conditioner gives rise to a potential pathway for the transfer of Technetium-99 (99Tc) from marine to terrestrial ecosystems and thence to man. However, to date there is little information on the extent of the release of 99Tc from seaweed into soil and the mechanisms involved. This pot experiment has shown that 99Tc is released fairly rapidly from Fucus vesiculosus into a sandy coastal soil. Despite low temperature conditions, 60% of the 99Tc added with the seaweed had accumulated in the soil 15 weeks after addition. Concurrent CO2 monitoring (used as a measure of microbial decomposition or catabolism) suggested that the initial 99Tc release (up to 40% in the first 8 weeks) was due to leaching from the seaweed and that microbial decomposition was responsible for the release of the remaining 99Tc in the latter phase (12–15 weeks).