Exploring the relationship between sediment and fallout radionuclide output for two small Calabrian catchments

In southern Italy, several investigations have documented values of soil loss greater than 100 t ha-1 year-1, especially when including periods with extreme rainfall events. There is an increasing need to develop an improved understanding of erosion and sediment delivery dynamics in this environment. The use of environmental radionuclides, particularly 137Cs and 210Pb, to investigate sediment dynamics at the catchment scale has been shown to possess several important advantages over conventional monitoring techniques, and can provide valuable information on the functioning of the erosion and sediment delivery system. The study reported here is based on two small catchments for which storm-period suspended sediment loads have been documented for a range of storm events. In addition to quantifying the storm-period sediment loads at the catchment outlets, information on the radionuclide content of the sediment output and the storm-period radionuclide fluxes has also been obtained. Surface soil samples were collected within the catchments, in order to document source material properties. The relationships between suspended sediment output and the radionuclide flux for individual storm events, as well as the variation of the 137Cs and 210Pb activity of the suspended sediment, have been explored in order to obtain an improved understanding of the sediment dynamics and functioning of the two catchments. This analysis has emphasized the close relationship between the storm-period sediment and radionuclide fluxes from the two catchments, which provides valuable confirmation of the validity of existing approaches for using environmental radionuclides to document soil erosion and soil redistribution rates.