Negative pH values in an open-air radical environment affected by acid mine drainage. Characterization and proposal of a hydrogeochemical model

Aguasanta M Sarmiento; José Antonio Grande; Ana T Luís; José Miguel Dávila; Juan Carlos Fortes; María Santisteban; Jesús Curiel; María Luisa de la Torre; Eduardo Ferreira da Silva

doi:10.1016/j.scitotenv.2018.06.381

Negative pH values in an open-air radical environment affected by acid mine drainage. Characterization and proposal of a hydrogeochemical model

Sci Total Environ. 2018 Dec 10:644:1244-1253. doi: 10.1016/j.scitotenv.2018.06.381. Epub 2018 Jul 13.

Authors

Aguasanta M Sarmiento¹, José Antonio Grande², Ana T Luís³, José Miguel Dávila², Juan Carlos Fortes², María Santisteban², Jesús Curiel⁴, María Luisa de la Torre², Eduardo Ferreira da Silva⁵

Affiliations

¹ Department of Water, Mining and Environment, Scientific and Technological Center of Huelva, University of Huelva, 21004 Huelva, Spain; Sustainable Mining Engineering Research Group, Department of Mining, Mechanic, Energetic and Construction Engineering, Higher Technical School of Engineering, University of Huelva, 21819 Palos de la Frontera, Huelva, Spain. Electronic address: aguasanta.miguel@dgeo.uhu.es.
² Department of Water, Mining and Environment, Scientific and Technological Center of Huelva, University of Huelva, 21004 Huelva, Spain; Sustainable Mining Engineering Research Group, Department of Mining, Mechanic, Energetic and Construction Engineering, Higher Technical School of Engineering, University of Huelva, 21819 Palos de la Frontera, Huelva, Spain.
³ GeoBioTec Research Unit, Department of Geosciences, Campus de Santiago, 3810-193 Aveiro, Portugal; CESAM Associated Lab, Department of Biology, Campus de Santiago, 3810-193 Aveiro, Portugal.
⁴ Environmental Geochemical and Engineering Laboratory (LI2GA), Polytechnic University of Madrid, c/Alenza 4, 28003 Madrid, Spain.
⁵ GeoBioTec Research Unit, Department of Geosciences, Campus de Santiago, 3810-193 Aveiro, Portugal.

PMID: 30743837
DOI: 10.1016/j.scitotenv.2018.06.381

Abstract

This paper presents the finding of a singular environment polluted by acid mine drainage in the Iberian Pyrite Belt. This situation is regulated by particular conditions, thus the analysed values can be considered as extreme, not only because of the high concentrations of toxic elements, but also due to the extreme low pH, reaching an average negative pH of -1.56, never found before in open-air environments contaminated by acid mine drainage. Concentrations up to 59 g/L of Fe, 2.4 g/L of Al, 740 mg/L of As, 4.3 mg/L of Co, 5.3 mg/L of Ge, 4.8 mg/L of Sb, inter alia, can be found dissolved in these polluted waters. The main aims of the present work are the physicochemical characterization and the toxicity assessment of these radical polluted waters. In addition, a hydrogeochemical model of the system will be proposed, which justifies the extreme pH value and the extraordinarily high concentrations of toxic elements, even for acid mine drainage polluted environments. Extreme acidity and metal and sulphate concentrations in the Radical Environment are due to several processes of different nature, mainly driven by the geochemistry of the minerals presents in the endorheic character of the basin. The extremely acidic nature of these waters control the Fe species present in them, being FeHSO₄⁺ the mainly Fe specie representing 94% of total. High toxicity of these waters has been detected due to the absence of any diatoms species.

Keywords: Acid Mine Drainage; Iberian Pyrite Belt; Negative pH values.