Resumo

MANASSERO, Marcelo; CAMILION, Cecilia  e  RONCO, Alicia. Textures, clay minerals and heavy metals in river bottom sediments from southern río de la Plata. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.1, pp.105-111. ISSN 0004-4822.

River bottom sediments from distal positions of El Pescado, Cañada Arregui, Buriñigo, Juan Blanco, El Destino streams, and Samborombón and Salado rivers from the southern coastal area of the río de la Plata estuary were studied. Grain size analysis, clay mineralogy (X ray diffraction), organic matter content (by acid digestion followed by tritrimetric analysis) and metal concentration (by atomic absorption spectometry) were carried using standardized methods. Most of the analysed samples were classified as silty clays, silts and clays. In the Salado, El Pescado and El Destino water courses the bottom sediments show a greater proportion of sand. Clay mineral composition suggests that southern tributaries of the río de la Plata have a predominant illite composition with high proportions of smectite and kaolinite. Kaolinite rich litho-facies were detected in the Sam-borombón and Salado rivers, due to the influence of the open estuary to the South of the study area. Iron and manganese were the metals that show greater abundance and variability within the studied water courses. The physicochemical conditions infuence these metal concentrations in the depositional environments. The sequence of abundance detected for the rest of the analysed metals is Zn> Pb=Cu>Cr>Ni>Cd, with higher concentrations within the area of the estuary, showing a similar pattern as the major metals.

Palavras-chave : Bottom sediments; Heavy metals; Buenos Aires province southern coastal sector.

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