The Development and Application of Coprecipitation/Solid Solution Models to Describe Low Temperature Trace Element Geochemistry

Jordi Bruno Intera Information Technologies, Parc Tecnologic del Vallès, E-08290 Cerdanyola, Spain

Lara Duro Intera Information Technologies, Parc Tecnologic del Vallès, E-08290 Cerdanyola, Spain

Joan de Pablo Dept. of Chemical Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain

Trace metal cycling in natural water systems is associated to the cycling of major components, particularly Fe, C, and S. The thermodynamic description of these associations is a complex but necessary task in order to understand the processes that control and regulate trace metal concentrations in low temperature aqueous systems, particularly at redox interfaces.

The kinetics and thermodynamics of the coprecipitation of trace metals with iron(III) oxihydroxide has been thoroughly studied in laboratory conditions by a combination of solution chemical and surface spectroscopic methods. The outcome of this work has allowed us to propose a simple but rigorous thermodynamic model to describe the low T interaction of trace metals with iron(III) oxyhdroxides (Bruno et al., 1995).

This model has been used to describe the co-precipitation/co-dissolution behaviour of a series of trace metals in different geochemical environments, namely:

1) Ba, Cu, Mn, Ni, Pb, Sr, Th, U and Zn in El Berrocal, a granitic batholite in Central Spain (Bruno and Duro, 1994).

2) Sr, Ni, REE, U and Zn in a sandstone medium in the Poços de Caldas complex (Brazil) (Bruno et al., 1993).

3) U mobility in the GME and Southern Nares Abyssal Plain sediments (Santschi et al., 1988)

Both the fundaments and applications of the model will be presented


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