Radiometric sand-mud characterisation in the Rhine-Meuse estuary part A. Fingerprinting

The composition of the underwater sediment bed is often defined in terms of the mud (63 and 63 mum) and sand (>63 mum) as: 46.2 +/- 1.9 Bq/kg U-238 and 9.3 +/- 0.9 Bq/kg U-238 and 45.6 +/- 1.9 Bq/kg Th-232 and 9.7 +/- 0.9 Bq/kg Th-231, respectively. The assessed radiometric fingerprint allows a quantitative interpretation of the mud and sand content through the total U-238 + Th-232 activity. This interpretation is confirmed by the high correlation (R-2 = 0.96) for the mud percentages obtained from radiometric analysis and those by laser diffraction in the laboratory. It can be concluded that radiometric sedimentology provides a tool for reliable sediment characterisation. New perspectives are opened when radiometric fingerprints are combined with in situ radiometric characterisation of sediments, which will be presented in part B of this paper (this issue). (C) 2002 Elsevier Science B.V. All rights reserved.