Pollution of a river basin impacted by acid mine drainage in the Iberian Pyrite Belt (SW Spain)

Abstract

The Iberian Pyrite Belt (IPB) is one of the most famous sulfide mining regions in the world. Mining activity in the IPB dates back to prehistoric times, and though today there is no active mining, the pollution continues to generate. The result is acidic drainage containing elevated concentration of sulfate and heavy metals. This is responsible for the pollution and degradation of the Odiel River basin in south-western Spain. In this work we have conducted a study along the entire Odiel basin. During the years 2002 and 2003 we have collected water samples at 69 points in order to characterize and quantify the pollutants that the Odiel River receives as a consequence of the AMD inputs within its watershed. The contaminant load transported by the Odiel River into the Huelva Estuary has also been calculated. Due to the great quantity of samples and analyses, the use of statistical multivariate techniques (Principal Component Analysis) was used to interpret the results. PCA of the samples showed strong interrelationships between the generation of acid by sulfide mineral weathering and metal loads. In downstream reaches, the rock forming elements (K, Ca, Na, Mg, etc.) dominate as the acidic waters dissolve the rocks in the stream bed. The contaminant load transported by the Odiel River to the Huelva Stuary is dominated by SO 42-, Al and Fe, with lesser quantities of Zn, Cu, Cd, etc.