CONICET | Buscador de Institutos y Recursos Humanos

The chemical composition, granulometry and mineralogy of sediments, together with their phosphate content and association are key factors to assess the role played by sediments in the phosphorous cycle. Phosphate association is very important in this respect because the stability and mobility of phosphate will eventually depend on the chemical nature and properties of its associated material. The simplest and more applied methodology to determine association is sequential extraction, which imply successive treatments of the sediment with acid, alkaline or complexing solutions in order to sequentially dissolve oxides and salts and extract its associated phosphate. A more sophisticated technique is electron microscopy combined with electron microprobe analysis, which allows to evaluate the spatial distribution of different elements in a solid sample. By comparing the mapping of the target element with those of other elements, association can be assessed. This work reports the general characteristics of sediments from two dams of the province of Córdoba, Argentina, together with a study of phosphate association by the two mentioned methodologies. Both, sequential extraction and microprobe analysis reveal that phosphate is associated to iron, aluminum and calcium containing solids at different degrees depending on the sediment location. In addition, the good correlation among clay content, surface area and phosphate content, and the fact that phosphate is detected at the surface of micaceous minerals, suggest that phosphate is also associated to the basal surface of phyllosilicates, perhaps bridged by iron, aluminum and/or calcium cations. Acknowledgements: This work is partially financed by SECyT-UNC, CONICET and FNDACIÓN ANTORCHAS

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