RADIOCESIUM (137CS) FROM THE CHERNOBYL REACTOR IN EURASIAN WOODCOCK AND EARTHWORMS IN NORWAY

To understand the ecological effects of the Chernobyl reactor accident , we investigated radiocesium (Cs-137) levels in Eurasian woodcock (Sc olopax rusticola), earthworms (Lumbricidae), litter (dead organic mate rials lying on the ground), humus (beneath litter 2 em deep), and mine ral soil samples (3-6 cm deep) from a heavily effected (20-60 kBq/m2 [ 1 Bq = 1 nuclear fission/sec]) area in Norway. The highest concentrati ons measured in earthworms (1988 median = 142 Bq/kg) and woodcock (198 6 median = 730 Bq/kg) were below levels that should affect animal heal th. Values above the European Economic Community's limit for human foo d (600 Bq/kg fresh mass) only were found in woodcock during 1986. Radi ocesium concentrations decreased (P < 0.001) in earthworms (40%) and w oodcock (95%) from 1986 to 1990, There was no reduction in total radio cesium in soil over the same period. The relatively high radiocesium c oncentrations in woodcock during 1986 and the decreasing radiocesium r atio in woodcock to earthworms during the first years following fallou t could have been caused by woodcock ingesting abiotic radiocesium wit h earthworms. The decrease in radiocesium in woodcock and earthworms d uring the study (1986-90) probably resulted from decreasing bioavailab ility of radiocesium during the first years after fallout rather than by radiocesium disappearing from the ecosystem.