Verifica sperimentale di due modelli di conversione della perdita di cesio-137 in erosione netta per un bacino forestato

In Ihis paper two different approaches proposed by Garcia-Oliva el al. and Yang el al. To convert caesium-137 measuremenls lo quantitative estimates of erosion and deposition rales for uncultivated soii are firstly reviewed. The rainfall and sediment yield data from 1978 to 1994 in a small Calabrian basin, reafforested wilh eucalyptus trees, are used lo calibrate the Revised Universal Soil Loss Equation compled wilh a sediment delivery distributed approach Using the model of Garcia-Oliva el al. showed that net soil erosion values lend to overestimate the calculated sediment yield values both at morphological unit and basin scale, because the model of Garcia-Oliva et al. neglects selective remove of fine particles. A particle size correction factor was introduced for taking into account that the mobilized sediment is enriched in 137CS respectto the originai soil. Applying the mass balance model of Yang et al., for converting the caesium-137 measurements carried out at 55 sites well distributed over the basin area, three different caesium-137 depth distributions and two temporal distributions of the 137Cs input fallout were assumed The analysis showed that the effect of the temporal distribution of fallout deposition is negligible and that the best agreement, at the two investigated scales, between sediment yield and the corresponding net soil erosion values can be obtained using the potential caesium-137 depth distribution.