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Caesium in aquatic systems and fish

A single catchment area, chosen from a group identified as having high levels of secondary input of radionuclides, has been studied. The change in caesium activity with time was obtained for the lake and six contributory streams. Two streams had much higher activity levels than the others and significant relationships with flow and time form the initial Chernobyl fallout. The two emanated from saturated peat catchments; the others from either ranker or thin podsolic soils. Five mechanisms of caesium release have been suggested. Firstly, that the lack of illite in the catchment area prevents long term storing of caesium. Secondly, that flooding of peat soils allows the caesium to be washed out easily. Thirdly, that humic compounds in the peat soils chelate the caesium and hold it in solution. Fourthly, that low concentrations of ammonia in rainfall displace caesium from frayed edge sites on the small quantity of illite particles in the catchment area. Lastly, that low molecular weight humic acids, formed by oxidation of humic material, deform the frayed edge sites on the small quantities of illite particles, thus releasing the caesium.

Data on fish size and caesium activity have been obtained from several lakes in the United Kingdom. The data show considerable scatter and it is not possible to observe any trend after Chernobyl. A power relationship exists between activity per unit mass in the flesh and fish size (weight or length)

Reported by

Natural Environment Research Council
East Stoke
BH20 6BB Wareham
United Kingdom
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