ECN publication
A generic approach to geochemical multi-surface modelling of the leaching of contaminated materials
Published by: Publication date:
ECN Environment & Energy Engineering 7-2-2014
ECN report number: Document type:
ECN-M--14-006 Conference Paper
Number of pages: Full text:
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Geochemical modelling is increasingly being used in both scientific research and environmental risk assessment of contaminated materials. In this presentation an overview will be given of the development of a generic multi-surface geochemical modelling approach, to describe the speciation and solid/liquid partitioning (leaching) of major and trace elements in both soils and waste materials. The approach is based on the premise that the major reactive organic and mineral surfaces that are being considered, play a generic and determining role in the speciation and leaching of elements in these different materials. The geochemical modelling approach is based on individual adsorption models for which generic binding parameters have been published for a wide range of elements. It currently includes reactions for aqueous speciation and mineral solubility, combined with sorption to organic matter (NICA-Donnan model), Fe/Al-(hydr)oxides (Generalized Two-Layer Model) and clay (Donnan model). As such, the model is fully based on published generic thermodynamic parameters for these different types of processes and used without any parameter fitting. Methods for the estimation of essential modelling parameters such as the potentially available/reactive fraction of elements of interest, and the type and amounts of reactive mineral and organic surfaces will be discussed. The performance of this modelling approach has been tested for a range of different elements and contaminated materials, particularly by comparing measurements and model predictions of the solid/liquid partitioning of elements over a wide pH range. Examples will be presented of different model applications, illustrating similarities and differences in controlling processes and element speciation. These applications suggest very similar properties and contributions of the considered reactive mineral and organic surfaces in the speciation and leaching of elements among very different waste and soil materials. Finally, an outlook will be given on current work and ambitions to further develop and improve this modelling approach.

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