Hydrogeochemical processes in an arid region of Europe (Almeria, SE Spain)

In the Lower Andarax river basin 3 aquifer units have been defined, namely the Carbonate Aquifer, the Deep Aquifer and the Detrital Aquifer, which bet ween them contain a wide variety of water types. Identification of hydrogeo chemical processes has been performed by studying a series of ionic ratios, comprising the principal constituents together with B and Li (Cl vs SO4, C l vs Mg, Cl vs Li, B vs Li). Among the processes detected, the circulation of groundwaters with high concentrations of SO4 was found to have significa nt effects. Moreover, in the coastal region, naturally occurring processes related to the flushing of saline waters from sediments of marine origin oc cur in conjunction with others, clearly of human origin, that are related t o saltwater intrusion. A further factor is the entry, from overlying deposi ts, of waters with a high saline content; this salinity is related to the f lushing of sediments of marine origin. The use of B and Li together enables waters in which salinity is related to seawater to be distinguished from o thers in which salinity is related to evaporitic layers or to thermal areas . The concentration of Li is directly related to water temperature, while t hat of B is greater in the most saline sectors, of gypsiferous and/or seawa ter origin. (C) 1999 Elsevier Science Ltd. All rights reserved.