A study of the radionuclides in the Scheldt estuary was undertaken. The Western Scheldt is characterized by a long residue time of water and particles in the brackish zone where almost permanent anoxic conditions prevail. It is thus possible to investigate in this system the influence of the redox conditions on the behaviour of the radionuclides. Furthermore, the region of Antwerp receives an important load of organic matter which allows the study of complexation of radionuclides in water and on particulate matter. The artificial radionuclides can also be used as a tool to study estuarine hydrodynanic processes.
Considerable variation is size of suspended particles was found, with no difference between fresh water and salt water suspensions. The variation seems to be regulated by local conditions of turbulence and particle settling. Organic matter content was in general higher in fresh water.
Distribution of radionuclides depended on their mode of introduction into the estuary. The distribution of antimony-125, rubidium-106, plutonium-239, plutonium-240 and caesium-137 increases seawards, indicating a marine source (the contaminated coastal waters of the North Sea). Cobalt-60 and plutonium-238 originate in nuclear plants up river. Radionuclides released by the Chernobyl incident had a predominantly continental origin.
The behaviour of radionuclides in the estuary was studied. The activity of plutonium-239 and plutonium-240 was found to be higher in marine samples from the mouth of the estuary than in samples collected within the estuary. This is similar to behaviour noted in four United States estuaries.
The sorption of radionuclides on suspended matter on short time scales was investigated.
TRANSFER PROCESSES AND MODELLING OF PLUTONIUM SPECIES AND GAMMA EMITTERS IN THE SCHELDT ESTUARY; REDOX AND ORGANIC SPECIATION IN RELATION TO AQUEOUS AND PARTICULATE FRACTIONATION.