## 2 Materials and Methods
#### 2.1.3 The FP Technique to Evaluate Soil and Water Resources' Degradation
However, the accuracy and precision of tracer selection procedures for unmixed sediment sources is an area that needs to be investigated in terms of sediment FP [73]. The novel CSSI technique was introduced in 2008 in Ireland to study the origin of sediments in estuaries [46; 92] and was introduced in Latin America and the Caribbean in 2014 [31]. The method can be applied to several biomarkers (FAs, n-alkanes, etc.) and different isotopes (\(\delta^{13}\)C and \(\delta^{2}\)H), and its use is valid to reconstruct changes in the contributions of land use sources from sedimentary records, correcting isotopic values of \(\delta^{13}\)C [45; 46; 50; 74]. [PERSON], in 2019 [48], combined two nuclear techniques: FRN to document soil redistribution, and CSSI to identify sediment sources in central Argentina. [PERSON], in 2020 [90], used the soil organic biomarkers to trace the origin of eroded sediment in Petzenkirchen (Austria). The \(\delta^{13}\)C of saturated long-chain FAs (i.e., C24:0 and C26:0) allowed the best discrimination, to establish the contributions of sources to sediment collected at the watershed outlet, confirming that information from \(\delta\) C-FA analysis could provide a unique support to enable effective agroecosystem management. The CSSI technique allows the identification of soil erosion sources and deposition sites by studying the isotopic signature (\(\delta^{13}\)C) of long-chain FAs [93]. It is not a quantitative technique, so combining it with other sediment load estimation techniques is recommended. Knowledge of the sources of soil erosion provides the necessary information for us to take preventive measures to preserve this natural resource and mitigate adverse ex situ effects. In this way, joint efforts can be made to improve soil fertility and provide ecosystem services [94]. The CSSI technique is widely used around the world; one can mention the work developed by [PERSON] in 2021 [95] to understand sedimentation and track soil organic carbon and nitrogen sources in highly eroded mountain watersheds controlled by a dam; the results provided scientific insights into how to develop effective management practices for soil erosion and nutrient loss control in highly eroded agricultural watersheds. [PERSON], in 2022 [96], modeled water erosion and sediment transport in a reservoir with WaTEM/SEDEM v.2006 software; their results supported the idea that introducing green areas within farmland benefits the landscape and reduces soil erosion and reservoir sedimentation. This idea is corroborated in the research developed by [PERSON] in 2022 [97], where they demonstrate the effect of agricultural intensity on the contribution of nutrients and sediments in hydrographic basins, e.g., the absence of green areas makes the landscape vulnerable to degradation due to water erosion. [PERSON] further confirmed these statements in 2022 [98], where land use was shown to be the most dominant factor in land degradation. The impacts of the land use change associated with the area of this change and runoff on the sediment production of the watershed were evaluated. Initially, it was proposed that an uncontrolled sediment flow destabilizes a dam, and the sediments produced are influenced by the predominant types of land use and land cover, along with the amount and intensity of precipitation. Subsequently,results obtained using Soil and Water Assessment (SWAT v.2012 10_4.19) software affirmed that land use types exert more dominant control over runoff and sediment production than land cover areas without ruling out a climatic influence. In the authors' experience, land use is a critical parameter in soil and water degradation assessments. The authors also support the idea that soil cover is essential and cannot be downplayed as a crucial conservation measure to minimize the effects of water erosion. This confirms the ideas of [PERSON] in 2022 [96], who stated that soil cover reduces soil degradation and the consequent loss of water quality.