Identificação de origem de sedimentos de erosão utilizando sensores proximais

Abstract

Erosion is one of the main causes of soil degradation and knowing the origin of sediments and the processes that aggravate the problem is one of the objectives of soil conservation. Thus, different sensors have contributed to the research advances, enabling the determination of the source of sediments, for example, in the catchment, fundamental units in the environmental conservation. The objectives of this work were to identify the source of deposited sediments in a floodplain applying fingerprinting approach, and to evaluate two proximal sensors to identificay sediment sources: the portable X-ray fluorescence spectrometer (pXRF) and the susceptibility meter. The selection of tracer variables in the sediment, recommended by the fingerprinting approach, was based on pedological knowledge, being selected the elements Fe, Si, Al, Ti and Zr. The sediment contribution area consists of two contrasting parent materials –gabbro, and granite-gneiss–, on which a typical Red Dystrophic Latosol (LV) and a typical Red-Yellow Dystrophic Argisol (PVA) developed, respectively. In the sediment contribution area, 35 samples were collected in the soil surface layer (0-2 cm), in a regular grid of 50 meters. In the deposition area, 24 samples were collected, in a regular 7-meter mesh. The determination of sediment sources was carried out through topographic variables and cluster statistical analysis –an algorithm that classifies objects into groups (cluster) according to the similarity and difference between them. The relief and accumulated flux maps were made from a digital elevation model (DEM) generated from 1-meter contour line. Analysis of cluster and topographic variables indicated that the PVA –the most susceptible soil to erosion in the sub-basin–, was the one that most contributed as a source of sediments. The pXRF as more efficient in detecting the sediment sources when compared to the susceptibility meter. The results point to the efficiency and practicality of using proximal sensors to identify the sediment sources in small area basins. In addition, these techniques reinforce the importance of adopting conservation practices in soils that are found on steep terrain, especially in soils more susceptible to erosion, aiming to monitor, predict and control and the anthropogenic factors that cause water erosion at a basin scale.