Fluctuations in the thermoluminescence signal of suspended sediment in an alpine glacial meltwater stream

Analysis of the thermoluminescence (TL) signal from suspended sediment samples from the Dora di Ferret river in northern Italy reveals two scenarios for entrainment, transport and blenching of the TL signal. In clear weather, a simple diurnal fluctuation in luminescence intensity is apparent, but the correlation with sediment concentration in the stream is very low. Storm events in contrast cause large amounts of unbleached sediment to be mobilised and entrained in the flow, producing a significant positive correlation between TL intensity and sediment concentration. Such storm events may be identified by an initial dip in the intensity of the TL signal, believed to be due to zeroed grains on the surface of valley slopes being washed off the slopes, followed by a major rise in signal as erosion starts to incorporate previously unbleached sediment into the flow. (C) 1997 Elsevier Science Ltd.