## 2 Materials and Methods
#### 2.1.2 The FRN Technique for Assessing Soil and Water Resources' Degradation
In China, [PERSON], in 2021 [58], applied radioactive radionuclides (FRNs), such as \({}^{137}\)Cs and \({}^{210}\)Pb, as a rapid and economical tool to estimate erosion rates at a wide range of spatial and temporal scales. [PERSON], in 2021 [59], summarized the combined use of \({}^{137}\)Cs and \({}^{210}\)Pbex isotopes to establish the chronology of sediment cores, providing a specialized synthesis with a unique worldwide compilation for the characterization of FRN sources and levels on a global scale. This provides a reference of \({}^{137}\)Cs peak attribution for improved dating of sediment cores. It outlines the main issues that deserve attention in future research and the regions where additional \({}^{137}\)Cs fallout investigations should be prioritized. To understand the effect of past practices and current agricultural management, [PERSON] in 2022 [60; 61] combined the strength of empirical data and spatially distributed modeling in a medium-sized catchment representative of agroforestry landscapes of NE Spain, developing an ensemble technique composed of \({}^{137}\)Cs-derived soil redistribution rates with specific point values and a grid-based-setup calibration for the WaTEM/SEDEM model. Research conducted in Palestine by [PERSON] in 2022 [62] used the FRN technique with \({}^{137}\)Cs for the first time to evaluate the impact of terracing on soil erosion and deposition rates in the northern West Bank. Research carried out in Cuba by [PERSON] in 2022 [12] showed the application of FRN at a nationally demonstrative site for soil, water, and forest conservation, using \({}^{137}\)Cs to determine the impacts of soil erosion and the feasibility of measures taken for its preservation and improvement. Current works, such as the investigation of [PERSON] in 2023 [63] in northern Morocco, evaluate the impact of cropping systems based on zero tillage on soil erosion using two indicators: le Biossonnais soil aggregate stability test and the activities of \({}^{7}\)Be and \({}^{137}\)Cs radionuclides using FRN. Another work, carried out in 2023 by [PERSON] and [PERSON]. [64], based on the use of \({}^{137}\)Cs, confirmed that over the past four decades, theoretical models have proven to be very effective in identifying areas at risk of land degradation. [PERSON] in 2023 [65] studied the effects of cropland abandonment and post-land abandonment management (through natural revegetation and afforestation) on soil redistribution rates using fallout \({}^{137}\)Cs measurements in the Araguas catchment in the Spanish Pyrenees. The work developed by [PERSON] in 2023 [66] applied 137 Cs as a tracer to estimate the impacts of various silvicultural systems on soil redistribution and achieve greater efficiency in their conservation in Iran. [PERSON], in 2023 [67], in the Himalayan hills and mountains, used \({}^{137}\)Cs FRNs for reliable measurement of long-term soil erosion rates to suggest suitable conservation measures. In 2023 [68], [PERSON] combined \({}^{137}\)Cs and \({}^{210}\)Pbex to study soil redistribution rates and the variability of lithogenic radionuclides by contrasting two watersheds with different land uses in the Uruguayan Pampa grassland. [PERSON] in 2023 [69] used \({}^{137}\)Cs and soil organic carbon inventories from watersheds spanning different climates to identify the relationship between climate change and erosion-induced disturbance of soil organic carbon cycling. [PERSON] in 2023 [70] utilized two nuclear techniques, cosmic-ray neutron sensors (CRNSs) and fallout \({}^{137}\)Cs, confirming that the integration provides a more comprehensive understanding of how the water content varies in soils, its relationships with other soil properties, and how soil moisture affects the process of soil degradation.