Author's personal copy Assessment of the dissolved pollutant flux of the Odiel River (SW Spain) during a wet period L. Galván a, ⁎, M. Olías a,b , J.C. Cerón a , C.R. Cánovas a , R. Pérez-López c , J.M. Nieto c a Department of Geodynamics and Palaeontology, University of Huelva, Campus El Carmen s/n, 21071 Huelva, Spain b Department of Physical, Chemical and Natural Systems, University Pablo de Olavide, Ctra. de Utrera km 1, 41013 Sevilla, Spain c Department of Geology, University of Huelva, Campus El Carmen s/n, 21071 Huelva, Spain HIGHLIGHTS • The Odiel River is a clear example of basin extremely affected by acid mine drainage. • Its pollutant load was quantified for an especially wet year. • Two relationships were used: concentration–flow and concentration–conductivity. • Flood events main controlled the discharge of contaminants into the Atlantic Ocean. • This river can be the main contributor of mining-pollutants to the world's oceans. abstract article info Article history: Received 19 April 2013 Received in revised form 14 June 2013 Accepted 14 June 2013 Available online xxxx Editor: D. Barcelo Keywords: Element flux Flow rate–concentration relationship River monitoring Mining pollution 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 (R 2 N 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. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The extraction and processing of sulphide-bearing ores leads to the production of acid mine drainage (AMD) due to the oxidation of the sulphide minerals in contact with water and oxygen. Typically, worldwide AMD refers to acidic leachates with high concentrations of sulphates and potentially hazardous elements, which constitute a major environmental concern (Nordstrom, 2011; Silva et al., 2011; Younger et al., 2002). The Odiel River (Fig. 1) flows across the Iberian Pyrite Belt (IPB), which contains original reserves in the order of 1700 Mt (Pinedo-Vara, 1963; Sáez et al., 1999). Mining activity at the IPB dates back to the Third Millennium B.C. for the extraction of gold, silver and copper (Leblanc et al., 2000; Nocete et al., 2005) and, mainly, from 1850 until the end of the 20th century for the extraction of sulphur, copper, lead and zinc (Olías and Nieto, 2012). As a result, huge amounts of mining wastes have been generated and, due to the longevity of AMD processes (Younger, 1997), the pollution in the area still continues (Sánchez España et al., 2005; Sarmiento et al., 2009). The most well-known example of AMD in the IPB is the Tinto River, which has been the focus of much research (e.g. Cánovas et al., 2007, 2010; Fernández-Remolar et al., 2005; Ferris et al., 2004; Grande et al., 2010a,b, 2011). Although the Odiel River is less polluted than the Tinto River, the length of AMD-affected streams within its drainage basin is much larger and, due to its higher flow rate, it is the main pollutant contributor into the Ría of Huelva estuary and the Gulf of Cadiz (Nieto et al., 2007; Olías et al., 2006). Along its course, the Odiel River collects leachates from over 30 old mining districts. Amongst the most important mines, Tharsis and Rio Tinto should be stressed (Fig. 1). The Odiel River has an average pH close to 3.5 and high concentrations of dissolved metals before it reaches the Ría of Huelva estuary (Cánovas et Science of the Total Environment 463–464 (2013) 572–580 ⁎ Corresponding author. Tel.: +34 95 921 9872; fax: +34 95 921 9440. E-mail addresses: laura.galvan@dgyp.uhu.es (L. Galván), manuel.olias@dgyp.uhu.es (M. Olías). 0048-9697/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2013.06.067 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv