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Use of quantitative mineralogical variables in identifying sources of sediment in a watershed do Rio Grande do Sul

The use of mineralogy as a tool for assessment of soil mineral properties is extremely important for understanding the different chemical and physical relationships in the soil. These variables/properties in the identification of sources of suspended sediments may help elucidate the factors and processes that govern the transfer of sediments and pollutants from terrestrial to aquatic systems. The aim of this study was to quantitatively characterize the mineralogy of the soil of the sources and suspended sediments in a watershed and to identify which mineralogical variables have tracer properties. For identification of sources, the fingerprinting method was used, which compares soils from different sources and the suspended sediments found in the drainage channel, using tracer elements. The soil and sediment sources are mainly composed of kaolinite, 2:1 layer minerals, and hematite and goethite. Among the oxides, hematite was predominant in the samples. The mineralogical variables, kaolinite and hematite contents showed discriminating capacity and were able to be used as tracers in identification of sediment production sources and in estimation of the contribution of each one, increasing the predictive power of the model. The greatest contribution to sediment production was from river channels, followed by the sampling grid and unpaved roads.

fingerprinting; tracer elements; mineralogy


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