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Palabras clave: minería, mercurio, Sudamérica, contaminación RESUMENEn este estudio se determinaron las concentraciones de Al, Co, Cu, Fe, Hg, Ni, Mn, Pb y Zn en muestras de sedimentos de fondo del río Puyango y de algunos de sus tributarios con el objeto de conocer los factores de enriquecimiento de estos elementos en los sedimentos. Las muestras de sedimento fueron sometidas a digestión ácida utilizando el método EPA 3050B, para luego ser analizadas por espectrofotometría de absorción atómica. Las muestras para el análisis de Hg total fueron digeridas con una mezcla de HNO 3 , HCl y KMNO 4 y determinadas con la técnica de arrastre de vapor frío. Las mayores concentraciones de metales pesados fueron encontradas en los sedimentos colectados en el sector localizado después de la confluencia entre los ríos Calera y Amarillo. Los altos niveles de metales pesados y las bajas concentraciones de Al en los sedimentos de este sector indican que estos últimos están compuestos principalmente de mineral polimetálico, el cual ha sido descargado por las plantas procesadoras de mineral después del proceso de extracción de oro. Los sedimentos de las secciones media y baja del río Puyango se encuentran severamente contaminados con los elementos Hg, Cu, Pb, Zn y Mn, así como moderadamente contaminados con Co y Fe. Las altas concentraciones de Hg, Cu, Pb, Zn, Mn y Fe en los sedimentos de estos ríos pueden tener un efecto adverso para la biota acuática, de acuerdo con los criterios establecidos en normas internacionales.Key words: mining, mercury, South America, contamination ABSTRACTIn this study the concentrations of Al, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn were determined in bottom sediment samples of the Puyango River and its tributaries with the goal to know the enrichment factors of these elements in the sediments. Bulk sediment samples were digested using the EPA method 3050B and then analyzed by atomic absorption spectrometry. The samples for Hg determinations were digested with a mixture of HNO 3 , HCl y KMNO 4 and then analyzed by the cold-vapor generation technique. The highest concentrations of heavy metals in sediments were found in the sector located after the Calera-Amarillo rivers confluence. The high levels of heavy metals and the low concentrations of Al in the bottom sediments of this sector indicate

Adaptation and microbial attachment mechanisms for the degradation of sulfide ores are mediated by the production of extracellular polymeric substances (EPS) and their role in biofilm formation. EPS production responds to induction mechanisms associated with environmental conditions. In this study, the double induction of EPS with galactose and high ferric iron concentrations in planktonic cells of Acidithiobacillus ferrooxidans, and their attachment on the surface of a polymetallic sulfide ore from Bella Rica-Azuay in Ecuador were evaluated. A. ferrooxidans cells were previously adapted to different concentrations of galactose [0, 0.15, and 0.25% (w/v)], using two ferrous iron concentrations as an energy source (9 and 18 g L–1) in a 9K culture medium. EPS production and its effect on mineral attachment were determined at the time point of maximal growth. The results obtained show a maximum cell attachment of 94.1% within 2 h at 0.15% of galactose and 18 g⋅L–1 of ferric iron concentration, compared to 71.4% without galactose and 9 g⋅L–1 of ferric iron. The maximum concentration of EPS was obtained with a 0.25% galactose concentration; however, it did not result in greater attachment compared to 0.15% galactose concentration. Through the combined induction of low galactose concentration and high ferric iron concentration, the percentage of bacterial attachment can be increased and, therefore, a possible increase in the rate of biooxidation and bioleaching could be obtained.