The Chalk Aquifers of Northern Europe
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The Cretaceous Chalk aquifers of Northern Europe underlie and support many sensitive ecosystems whilst at the same time being an important source of drinking water. This volume brings together the outcomes of numerous projects and case studies to provide the latest applied and theoretical understanding of all aspects of Chalk hydrogeology in Northern Europe.
Differentiated influence of the double porosity of the chalk on solute and heat transport
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Published:September 07, 2023
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CiteCitation
Richard Hoffmann, Pascal Goderniaux, Pierre Jamin, Philippe Orban, Serge Brouyère, Alain Dassargues, 2023. "Differentiated influence of the double porosity of the chalk on solute and heat transport", The Chalk Aquifers of Northern Europe, R. P. Farrell, N. Massei, A. E. Foley, P. R. Howlett, L. J. West
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Abstract
Chalk porosity plays a decisive role in the transport of solutes and heat in saturated chalk. From a geological point of view, there are at least two types of porosity: the porosity of pores corresponding to the micro-spaces between the fossil coccoliths that form the chalk matrix and the porosity owing to the micro- and macro-fractures (i.e. secondary porosity). For groundwater flow, the fracture porosity is a determining factor at the macroscopic scale. The multiscale heterogeneity of the porous/fractured chalk induces different effects on solute and heat transport. For solute transport considered at the macroscopic scale, tracer tests have shown that the ‘effective transport porosity’ is substantially lower than the ‘effective drainable porosity’. Moreover, breakthrough curves of tracer tests show an important influence of diffusion in a large portion of the ‘immobile water’ (‘matrix diffusion’) together with rapid preferential advection through the fractures. For heat transport, the matrix diffusion in the ‘immobile water’ of the chalk is hard to distinguish from conduction within the saturated chalk.