Assessment of the dissolved pollutant flux of the Odiel River (SW Spain) during a wet period

The abandoned mining districts of the Iberian Pyrite Belt (IPB, SW Spain) are an extreme source of pollution by acid mine drainage (AMD) to the Tinto and Odiel rivers. The pollutant flux transported by the Odiel River during a high stage period was assessed using concentration-discharge relationships and concentration-conductivity relationships, for the hydrological year 2009/10 (which was especially wet). Both correlations were high (R2 > 0.80) for most of the elements studied. The two methods for flux calculation gave similar results with differences generally lower than 10%. The dissolved contaminant flux transported by the Odiel River just before its mouth mainly includes sulphate (257,534 ± 13,464 t/yr), Al (13,259 ± 1071 t/yr), Zn (4265 ± 242 t/yr), Mn (2532 ± 146 t/yr) and Cu (1738 ± 136 t/yr), and minor amounts of other elements. These findings confirm that, up to our knowledge, the Odiel River can be considered to be the largest contributor of mining-related pollutants to the world's oceans.