Variación estacional en la especiación y movilidad de Fe y As en aguas afectadas por drenajes ácidos de mina en la cuenca del río Odiel (Huelva)

Abstract

The Odiel river drains the central part of the Iberian Pyrite Belt, one of the oldest and most important massive sulphide districts in the world. In these massive sulphide deposits, arsenic can be found in arsenical pyrite (with up to 0.4 % of As), and in some accessory minerals such as arsenopyrite. The oxidative dissolution of these sulphides releases to the Odiel river acidic waters rich in sulphates, metals and metalloids, including considerable amounts of As. Speciation and mobility of Fe and As in these waters show important seasonal variations, especially in samples not very close to the pollution sources. Although in the wet season the concentration of total As tends to be lower because of dilution with rain water, the toxicity of the waters is higher due to an increase in the concentration of As3+