The UNESCO national biosphere reserve (Marismas del Odiel, SW Spain): an area of 18,875 ha affected by mining waste.

At the mouth of the Odiel River, within the Natural Area "Marismas del Odiel", there has been for years a collection of waste from different mining sites. In the present work, an approach has been made to the problem that this supposes, quantifying the pollutants that are poured into the estuary from the mineral collection located on the banks of the river. The study carried out has been able to determine high metal concentrations, comparable with any rubble from the upstream mines, with pH value of 1.66, lower than many other areas affected by acid mine drainage in the same river, and even with concentrations of Fe and As higher than those provided by the rest of the mining facilities of the Odiel basin. This can make us understand the serious situation of the Natural Park, where a great variety of birds and plants of special ecological interest are located.