Using repeated Cs-137 and Pb-210(ex) measurements to establish sediment budgets for different time windows and explore the effect of connectivity on soil erosion rates in a small experimental catchment in Southern Italy

作者：Porto Paolo^*; Walling Desmond E; Callegari Giovanni

来源：Land Degradation & Development, 2018, 29(6): 1819-1832.

DOI：10.1002/ldr.2815

• Cs-137 measurements
• Pb-210(ex) measurements
• connectivity
• resampling approach
• sediment budget

Over the last 50years, different approaches have been employed in order to predict environmental risk due to soil erosion and to propose effective strategies to control erosion and sedimentation. The use of fallout radionuclides, mainly caesium-137 (Cs-137) and excess lead-210 (Pb-210(ex)), has proved to be a very effective complement to existing traditional methods, especially if a resampling strategy is employed. The resampling approach involves repeating soil sampling and radionuclide measurements within the same site, after a known amount of time (generally 10 to 15years). This strategy, in the light of the possibility to obtain independent estimates of soil erosion for different periods, makes it possible to establish sediment budgets for different time windows. The use of sediment budgets represents an important tool for providing information on catchment behaviour regarding the relationship between the sediment output at the catchment outlet and rates of sediment redistribution within the catchment. For this reason, this approach can provide important indications of possible changes of sediment connectivity at the catchment scale. The study reported here focuses on the W1 catchment (1.47 ha), located in Calabria, Southern Italy, for which long-term measurements of sediment yield are also available. The W1 catchment supports a rangeland vegetation cover, and no change in land use occurred during the last 100years. The catchment was sampled for Cs-137 and Pb-210(ex) analyses in 2001 and resampled in 2014 to provide estimates of soil erosion and deposition for different time windows. The uncertainty associated with these estimates is also discussed, and some guidelines for the application of Pb-210(ex) as a soil erosion tracer are provided. The results provided by the measurements of sediment yield at the catchment outlet provide evidence of a general increase of soil erosion rates during the last 15-20 years. The estimates of sediment redistribution provided by the measurements of Pb-210(ex) demonstrated that these results reflect an increase in the sediment delivery ratio and also emphasized how the presence of some small depositional areas associated with the occurrence of high-magnitude events influences the change in sediment connectivity at the catchment scale.

• 出版日期2018-6