6533b7d7fe1ef96bd1268cd9

RESEARCH PRODUCT

Accuracy of 210Pb dating in two annually laminated lake sediments with high Cs background

subject

description

Abstract A low-background gamma ray spectroscopy system has been used for nondestructive determination of 210Pb, 226Ra, 134Cs and 137Cs in lake sediment samples. Two Finnish sediment cores with high 137Cs activity originating from the Chernobyl accident have been analysed and dated using 210Pb. The accuracy of the 210Pb dating method was checked by varve counting of replicate samples. In one lake the 210Pb method gave similar dating results as varves, but in the other lake significant differences were detected. It was found that a high Cs concentration significantly impairs the accuracy of the 210Pb activity measurement. However, tha reliability of the dating result depends mostly on the constancy of the Pb flux into the sediment. Human activity has greatly increased the variability of 210Pb flux, reducing the reliability of 210Pb dating. Independent support by other methods is required to improve dating results.