Radiocaesium accumulation from Chernobyl fallout in nestlings of two pied flycatcher populations (aves) in central Norway; estimating ecological timelag responses and transfer mechanisms

The accumulation of caesium isotopes (134Cs and 137Cs) from the Chernobyl fallout in nestings of two breeding populations of Pied Flycatcher (Ficedula hypoleuca) in central Norway was determined from 1986 to 1992. The birds at the Luru site showed a mean accumulation of 844, 535, 383, 607, 515, 348 and 327 Bq kg-1 during these years. At Lauvsjøen, the corresponding accumulations was 102, 111, 74, 89, 293, 175 and 193 Bq kg-1. In 1996, the levels had decereased to 118 Bq kg-1 at Luru and 32 Bq kg-1 at Lauvsjøen. The mean values of radiocaesium activity in the nestlings rose a few years (1989 and 1990) after the accident in 1986. The data show large variations within and between years in the initial period of this study, suggesting that these ecosytems ere not equilibrium during this period. However, equilibrium may have been approached during the last years. The measurements from 1992 and 1996 correspond to an ecological exchange rate of 0.22 year-1 at Luru and 0.34 year-1 at Lauvsjøen (on average 0.28), implying and approximate ecological half-life equivalent for caesium transfer in the monitor organisms, the young flycatchers, of 3.2 years at Luru and 2.0 years at Lauvshøen (on average 2.6 years).