Application of fallout-derived 239+240Pu for estimating soil redistribution rates at an olive orchard under Mediterranean climate

Soil erosion significantly threatens soil health in semiarid regions such as the Mediterranean. Fallout radionuclides (FRNs), deposited from atmospheric fallout, accumulate in the soil profile and their redistribution patterns can be used to estimate soil erosion and deposition rates.  While ¹³⁷Cs has been traditionally used for soil redistribution studies, this research explores the application of fallout-derived ^239+240Pu in an olive orchard under Mediterranean climate conditions (Montefrío, Granada, Spain). The spatial variability of the reference profiles was assessed by replicating the sampling four times. Soil redistribution rates, estimated using the MODERN model, were compared with the inventory method for eroded sites, demonstrating excellent agreement (Pearson’s r = 0.9995, slope = 0.993 ± 0.006 t ha^-1·yr^-1)/(t·ha^-1·yr^-1)). Estimated  erosion and deposition rates ranged from 0 to -76 t ha^-1 yr^-1 and from 0 to +29.9 t ha^-1·yr^-1, respectively, indicating a significant soil degradation. These results highlight the potential of Pu isotopes as a valuable tool for assessing soil dynamics in Mediterranean agricultural systems.