Measurements of 137Cs in the food-chain of lamb in the Faroe Islands in the period 1990-99

Radiocaesium has been measured in the food-chain of lamb in nine uncultivated pastures in the Faroe Islands since 1990. The sampling programme includes soil from the uppermost 10 cm, mixed grass and lamb meat. Lamb faeces have been included since 1995. The results for the period 1990-99 show the following averages across the nine pastures: the 137Cs deposition decreased from 5.8 kBqIm2 in 1990 to 5.1 kBq/m2 in 1999; the 137Cs concentration in mixed grass decreased from 155 Bq/kg(dw) in 1990 to 51 Bq/kg(dw) in 1999; the 137Cs concentration in lamb meat decreased from 26.0 Bq/kg(ww) in 1990 to 10.4 Bq/kg(ww) in 1999. Large variations are, however, observed between as well as within the pastures. Averaged across the pastures, the soil-to-grass transfer factor decreased from 3010-3 m2/kg(dw) in 1990 to 1310-3 m2/kg(dw) in 1999, and the aggregated soil-to-lamb (meat) transfer factor decreased from 5.5 10-3 m2/kg(ww) in 1990 to 2.0 10-3 m2/kg(ww) in 1999. The effective
ecological half-life of 137Cs in mixed grass and in lamb meat is estimated to be in the range 2.8-4.3 and 6.6-8.0 years, respectively.