Windscale effluent in the waters and sediments of the Minch

Abstract

A SYSTEMATIC intrusion of water of high ¹³⁷Cs content into the north-eastern North Sea has been reported by the German Hydrographic Office¹. Jefferies et al.² later confirmed that a stream of water rich in radioactive caesium from Windscale passes northwards through the Hebridean Channel, around the north of Scotland and into the North Sea. Although the circulation pattern with respect to ¹³⁷Cs has been significantly refined in recent reports³ and from German data for 1975 (ref. 4) and 1976 (Kautsky, personal communication) little attention has been paid to the status of other radionuclides in this stream. Such a study offers, however, an excellent opportunity of looking at the geochemical discrimination between, for example, ¹³⁷Cs and the transuranic α-emitting nuclides; it seemed also that an examination of the changes of the ratio of ¹³⁴Cs to ¹³⁷Cs during this passage would give a good basis for estimation of the travel time. As a part of the Flex Programme (Fladen Ground Experiment—part of Jonsdap 76 international programme on the interplay of environment and a plankton bloom) in the North Sea in May–June 1976, we collected a series of sediment, water and biota samples for that purpose. We report here our analyses of samples from a large-volume water station and a 21-cm diameter sediment core taken in the Minch, 27 May 1976.