(super 14) C analysis of annual tree rings from the vicinity of the Chernobyl NPP.

Abstract

Samples of >40 pine trees were collected from around the Chernobyl NPP for radiocarbon measurement, to determine the spatial distribution of excessive (super 14) C in tree rings from 1986 consequent upon accidental radiocarbon release. Tree samples were collected during 1995-1996 from sites situated at distances >2.5 km from the NPP and covering a variety of directions in relation to the NPP. To evaluate Delta (super 14) C for 1986 annual rings, we compared (super 14) C levels for separate 1985-1987 annual rings, taking into account the trend of operational releases. Early and late wood samples for 1986 annual tree rings were measured separately to increase the sensitivity and precision of measurements. The maximum value observed for excessive accidental radiocarbon levels (Delta (super 14) C) was found to be 124 pMC (281.6 Bq kg (super -1) C). We present Delta (super 14) C values for examined sites; their spatial distribution shows a high irregularity of atmospheric (super 14) C depending on direction from the NPP. Using obtained data, we reconstruct the temporal behavior of (super 14) C release during the Chernobyl accident with the aid of atmospheric transport modeling. The total amount of (super 14) C released from 26 April to 5 May 1986 has been estimated as 44 TBq.