A laboratory and field study of 210Po depuration by edible winkles (Littorina littorea L.) from the Cumbrian Coast (north-eastern Irish Sea)

Edible winkles from Saltom Bay, Cumbria (north-eastern Irish Sea) had flesh 210Po concentrations in excess of 200 Bq kg−1 (wet). This came from liquid waste discharged under authorization from a chemical plant producing phosphoric acid. This labelling of the winkles under natural conditions was exploited to determine the 210Po depuration rate and biological half-time. Winkles transferred to Lowestoft and depurated in flowing seawater had biological half-times ranging from 82 to 119 days depending on temperature. These values seem long from the few data available in the literature. Cadmium was also discharged in the liquid waste and cadmium was measured in the depurating winkles. The hypothesis is put forward that the long half-times were due to 210Po binding to sub-cellular proteins induced by the presence of cadmium. After the chemical plant was shut, changes in Saltom Bay winkle flesh contents of 210Po, 210Pb and cadmium were followed by monthly samples. The biological half-time in the environment for the decrease in 210Po after the plant closed was estimated at about 92 days.