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Biominerals play an active role in controlling metal dispersion in polluted water and soil systems. At the Ingurtosu Pb Zn mine (SW Sardinia), heavy metal concentration in waters of the Naracauli stream, the main stream of the area, is abated by the seasonal bioprecipitation of hydrozincite. Hydrozincite could be used in a controlled process to attenuate metal pollution in mining waters. Information on environmental conditions that promote the biomineralization process is fundamental for the development of remediation strategies. According to field observations, correlated with speciation and equilibrium calculations, the optimum condition for hydrozincite precipitation occurs in late spring of rainy years, when the hydraulic regime in the stream reaches stationary conditions, and Saturation Index values with respect to hydrozincite and pH reach the highest values, in agreement with the higher stability of the hydrozincite solid phase in contact with slightly alkaline waters. Obtained results suggest that the bioprecipitation of hydrozincite could be applied to attenuate metal pollution in mining environments where no problems of water acidi cation exist.

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Daniela Medas has a Doctoral Degree in Earth Sciences from University of Cagliari (Italy). She has a thorough knowledge of harmful metals pollution of waters and soils, and biomineralization processes with particular reference to mining environment.Presently working as research assistant at the Department of Chemical and Geological Sciences (Italy)

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