Agregación de sedimentos en una cuenca de llanura: utilización del Microscopio Electrónico de Barrido como herramienta de evaluación

The purpose of this study was to determine the presence of sedimentary aggregates, which affect the transport of fine sediments. This contribution explores the influence of organic matter and dissolved salts, as the main factors that determine the aggregation of particles. Bottom sediments of Negro river (tributary of the Parana River), flows in the Chaco province (North-East of Argentina), and were assessed by granulometric analysis in consecutive phases of sample processing, to evaluate the presence of aggregates. The relative abundance of the different sizes in each analyzed phase, was controlled by Scanning Electron Microscope (SEM). The obtained results represent the first quantitative set of values of sediment aggregation in a river of the Chaco Plain, and can be used as a reference for the characterization of other rivers of subtropical plains. The results of this study show that the aggregates formation was favored by the high concentration of dissolved salts, but also by the presence of organic matter, abundant in subtropical environments. It was concluded that it is not convenient to apply classical techniques of sediment particle disaggregation (chemical oxidation to remove organic matter and chemical dispersants to break down associated particles), in order to avoid misinterpretation of transport dynamics of sediments in the natural environment.