| Abstract: | Caesium-137 from fallout from nuclear weapons tests is adsorbed on fine sediments and becomes an effective tracer. It is hypothesised that within a drainage basin, sites undergoing little or no erosion accumulate 137 Cs in their upper layers; cultivated soils will have 137 Cs uniformly distributed within the cultivated layer; eroded soils, cultivated or not, will have relatively less l37 Cs, depending on the severity of erosion. Accumulated sediments will have characteristic 137 Cs profiles reflecting temporal fallout variations and sedimentation history. This hypothetical model is largely confirmed by results from Maluna Creek basin, where erosion and accumulation of sediments has taken place. Soils under viticulture have about one third the 137 Cs content of soils with grass cover, indicating more severe erosion under cultivation. Caesium-137 profiles in alluvial fan and flood plain deposits correlate with sediment layers and known cultivation history. |
