Hydrochemistry and flow modelling of the Aveiro multilayer Cretaceous aquifer

Detailed hydrogeochemical studies, including the analysis of major, minor and trace elements, and groundwater modelling of the Aveiro Cretaceous coastal aquifer are used to give a better understanding of groundwater flow conditions and the natural geochemical processes within the groundwater flow system. The results show evidence of an aquifer with a very slow chemical kinetics for water-rock interactions as a consequence of the dominant siliciclastic composition of the aquifer sediments. The geochemical evolution of the groundwater composition clearly reflects the silicate nature of the sediments, determined by the very slow dissolution-rate mechanisms of silicate minerals. Feldspar dissolution and cation exchange with the aquifer clay minerals control the groundwater chemical composition. Flow modelling has been used to test the validity of the conceptual model of the aquifer and contributed to interpret the regional patterns of the flow system, confirming that the aquifer has limited natural recharge. (C) 1999 Elsevier Science Ltd. All rights reserved.