Abstract

In October 1966, an intense precipitation event (190 mm in 24 h) broke an old tailings retaining structure in the “El Segundo” mining district in the western sector of Spain’s Sierra de Gador, generating a contaminated flood. The Pb-F rich mixture flowed for more than 12 km through the dry riverbeds, damaging infrastructures and crops. In March, 2010, over 40 years later, 41 samples were collected from boreholes and springs, along with eight sediment samples from near the tailings pond and along the dry riverbeds. The fluoride levels in the area’s groundwater were close to 1 ppm, surpassing the area’s normal geogenic levels, and in some cases exceeding the WHO maximum recommended value for drinking water, despite the time that has elapsed since the event. Less mobile elements, such as Pb and Zn, also had higher concentrations in the area affected by the sludge contamination, but did not significantly exceed the background geogenic values.