Usage of Proximal Sensing to Trace the Origin of Deposited Sediments in a Drainage Subbasin

Usage of proximal sensors in soil and water conservation are still scarce. The objective of this study was to identify the origin of sediments deposited in the lower portion of a drainage subbasin using the fingerprinting approach based on two proximal sensors: the portable X-ray fluorescence spectrometer (pXRF), and the magnetic susceptibility (MS) meter. Five sediment tracing elements were selected: Fe, Si, Al, Ti and Zr. In addition, MS measurements were utilized as auxiliary data for the characterization, and discrimination of deposited sediments. The sediment contributing area had two contrasting parent materials, upon which two soil classes were formed: Anionic Acrudox (LV), and Typic Hapludult (PVA), respectively. The lower area where the sediments accumulated corresponded to an area with Typic Udifolists (OX). In the contributing area, 35 samples were collected from the topsoil layer (0 – 2 cm), using a regular grid of 50 m x 50 m. In the deposition area, 24 samples were collected in a regular grid of 7 m x 7 m. The source of sediments was determined via cluster analysis using data provided by the proximal sensors and topographic attributes. Cluster models using the elements Fe, Si, and Al (Figure 1a), and Fe, Si, Al, and Ti/Zr (Figure 1b) presented the best performance in defining the origin of sediments. Contrarywise, models using only MS data showed poor performance. Misclassification of sediment samples was most likely due to naturally occurring high organic matter contents causing a positive correlation between sediments of the upper areas and Typic Udifolist samples. Results indicated that the Typic Hapludult, which is more susceptible to erosion, contributed the most with sediment deposition on the lower areas. These findings showed the efficacy of using pXRF data for the discrimination of sediment samples and predicting their source via cluster analysis of elemental contents of the soils in the contributing area. This can be a useful to identify areas that are sources of large amounts of sediments.