Water qualitiy and distribution of trace elements in the Doñana aquifer (SW Spain)

The variations of groundwater quality in the unconfined zone of the Almonte-Marismas aquifer, upon which Donana National Park is located, are analysed. Most sampled points are multiple piezometers, allowing for the vertical distribution study of the hydrogeochemical characteristics in the aquifer. Temperature, pH, electrical conductivity, dissolved oxygen and redox potential were determined in the field. A large number of parameters, including major ions and a large amount of minor and trace elements, were analysed. In the southern zone, where aeolian sands crop out, water composition in the shallower part of the aquifer is of the sodium chloride type, with low pH (5.5–6) and mineralization (