Beta particle counting of sediments from Lac du Bouchet and Meerfelder Maar

A plastic scintillator system for beta particle counting, with automatic sample changer, has been employed to determine the depth dependence of radioactivity at approx. 2 cm intervals along a 6.5 sediment core from Lac du Bouchet in France. The reliability and reproducibility of measurements from the system are assessed. The data are compared with detailed alpha particle measurements made previously on the same samples as used in the present work and with an earlier smaller set of beta activity measurements from a different core from the same lake. Fifty two out of the 222 samples from the core were also subject to gamma ray spectrometry to aid the discussion. The relative merits of alpha particle counting, beta particle counting and gamma ray spectrometry to assess the depth dependence of radioactivity in a sediment core are considered. The interpretation of the activity distribution down the Lac du Bouchet core and in some sediment samples from Meerfelder Maar in Germany is discussed, particularly in relation to possible climatic influence.