Hydrochemistry and flow modelling of the Aveiro multilayer Cretaceous aquifer

Detailed hydrogeochemical studies, including the analysis of major, minor a nd trace elements, and groundwater modelling of the Aveiro Cretaceous coast al aquifer are used to give a better understanding of groundwater flow cond itions and the natural geochemical processes within the groundwater flow sy stem. The results show evidence of an aquifer with a very slow chemical kin etics for water-rock interactions as a consequence of the dominant silicicl astic composition of the aquifer sediments. The geochemical evolution of th e groundwater composition clearly reflects the silicate nature of the sedim ents, determined by the very slow dissolution-rate mechanisms of silicate m inerals. Feldspar dissolution and cation exchange with the aquifer clay min erals control the groundwater chemical composition. Flow modelling has been used to test the validity of the conceptual model of the aquifer and contr ibuted to interpret the regional patterns of the flow system, confirming th at the aquifer has limited natural recharge. (C) 1999 Elsevier Science Ltd. All rights reserved.