Environmental geochemistry of a highly polluted area: The La Union Pb–Zn mine (Castilla-La Mancha region, Spain) B. González-Corrochano a , J.M. Esbrí a , J. Alonso-Azcárate b , A. Martínez-Coronado a , V. Jurado c , P. Higueras a,d, ⁎ a Instituto de Geología Aplicada (IGeA), Universidad de Castilla-La Mancha, Plaza Manuel Meca 1, 13400 Almadén, Spain b Departamento de Química-Física, Facultad de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha, Av. Carlos III s/n, 45071 Toledo, Spain c C. Piélago nº41, 13002, Ciudad Real, Spain d Departamento de Ingeniería Geológica y Minera, Escuela Universitaria Politécnica de Almadén, Universidad de Castilla-La Mancha, Plaza Manuel Meca 1, 13400 Almadén, Spain abstract article info Article history: Received 19 July 2013 Accepted 8 February 2014 Available online xxxx Keywords: Availability Heavy metal La Union mine Single extraction procedure Toledo, Spain Speciation This paper presents the results of a study concerning the total and extractable concentrations of eight elements (As, Cd, Cr, Cu, Ni, Pb, Se and Zn) in soils and sediments from La Union mine (Toledo province, Castilla-La Mancha region, central Spain). It also presents the extent of the heavy metal contamination produced by the mining activities. Our results show that the study area can be considered as a heavily polluted site as consequence of the mining process carried out locally. This is demonstrated by the total concentrations of all studied elements, which are much higher than the World's and the Castilla-La Mancha's averages for soils. The elements that present the highest concentrations (total and extractable) are zinc and lead. Sediments show higher mean total concentrations than soils for all the studied elements. They also show the highest extractable concentrations due to the influence of the stream in the weathering of this type of materials. The areas affected by high concen- trations of arsenic and heavy metals depend on the studied element, reaching the maximum extension and importance for lead and zinc. In the study area, the environmental damage can be increased by the low pH obtained since it implies an increase in the mobility of most of the studied elements. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Metal ions can cause multiple toxic effects in plants, wildlife and/or humans when they are present in soils under wrong conditions and/ or in excess. Human activities can alter the concentrations of metalloids and heavy metals in the environmental compartments and facilitate their dispersion from the mineral reserves in which they are naturally confined (Moreno Grau, 2003). One of the most important and persistent causes of environmental degradation and/or contamination by arsenic (As) and heavy metals are mining activities, such as raw material extraction and grinding, ore refining and waste disposal. Less than 1% of the treated mining material is recovered as useful elements (Fields, 2003). Wastes with high risk to acid generation and As and heavy metal leaching may cause contamina- tion even long time after mine closure. Among the solid wastes, mine tailings are one of the highest worrisome, especially when they have high concentration of these potentially toxic elements and low pH (Shu et al., 2001). In old mining areas, little or no vegetation exists, pro- moting water and wind erosion that continually increases the metal dis- persion (Pierzynsky et al., 1994). The heavy metal contamination around the mining areas varies from site to site and it depends on the geochemical characteristic of tailings and soils (Jung, 2001). Total concentrations are usually evaluated, but they do not provide information about the mobility, availability and tox- icity of metals. This is because elements are present in the environmen- tal compartments (soils, sediments, etc.) in several geochemical forms or bound to different geochemical fractions, showing different mobility depending on changes in the environmental conditions, which cause se- lective release of the total metal content (Sahuquillo et al., 2003). Heavy metals are rarely 100% available, i.e. available to organism (Arnold et al., 2003). Chemical fractionation and mobility of metalloids and heavy metals in sediments and soils, and hence their availability, depend on different types of reactions: i) ion-exchange, adsorption/desorption and complex formation reactions; ii) heavy metal precipitation with anions such as carbonates and sulfates; iii) isomorphic exchange with cations in the crystalline structure of minerals; iv) biological immobilization and mo- bilization (Levy et al., 1992). The availability and toxic effects of the metals can only be studied by determining their chemical partitioning Journal of Geochemical Exploration xxx (2014) xxx–xxx Abbreviations: EC, electric conductivity; ISRIC, International Soil Reference and Information Centre; FPXRF, Field Portable X-Ray Fluorescence; ICP-MS, Inductively coupled plasma-mass spectroscopy; WRLD, World's average; CLMR, Castilla-La Mancha region's mean; rs, Spearman correlation coefficients; SD, Standard Deviation; b.d.l, below the detection limit. ⁎ Corresponding author at: Departamento de Ingeniería Geológica y Minera, Escuela Universitaria Politécnica de Almadén, Universidad de Castilla-La Mancha, Plaza Manuel Meca 1, 13400 Almadén, Spain. Tel.: +34 926 295 300; fax: +34 902 204 130. E-mail address: pablo.higueras@uclm.es (P. Higueras). GEXPLO-05322; No of Pages 10 http://dx.doi.org/10.1016/j.gexplo.2014.02.014 0375-6742/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Geochemical Exploration journal homepage: www.elsevier.com/locate/jgeoexp Please cite this article as: González-Corrochano, B., et al., Environmental geochemistry of a highly polluted area: The La Union Pb–Zn mine (Castilla-La Mancha region, Spain), J. Geochem. Explor. (2014), http://dx.doi.org/10.1016/j.gexplo.2014.02.014