Application of γ-ray spectrometry to the study of grain size distribution of beach and river sands

Changes in the relative values of radionuclide content with respect to shallow subsurface depth of intertidal estuarine and coastal beach sands, from east and west coast localities near Auckland, New Zealand, were studied using a high-purity germanium gamma -ray detector. It was found that differences in gamma -ray activity from the natural distribution of radionuclides varied up to 35%. This permitted detection of grain size differences as a result of hydraulic separation and sorting processes. Grain size measurements on the same samples were also made using a laser sediment size analyzer. Comparison between the gamma -ray and the laser scattering methods of grain size determination suggests that in these nearshore systems the former is a more sensitive measure of textural variations with sub-surface depth in these sandy sediments than the latter. The gamma -ray technique can be relatively rapid and involves little sample preparation. It may warrant wider application. (C) 2001 Elsevier Science B.V. All rights reserved.