Geochemistry and mineralogy of surface pyritic tailings impoundments at two mining sites of the Iberian Pyrite Belt (SW Spain) |
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Authors: | J C Arranz González V Cala Rivero I Iribarren Campaña |
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Institution: | 1.Departamento de Investigación en Recursos Geológicos,Instituto Geológico y Minero de Espa?a,Madrid,Spain;2.Facultad de Ciencias, Departamento de Geología y Geoquímica,Universidad Autónoma de Madrid,Madrid,Spain;3.Departamento de Investigación y Prospectiva Geocientífica,Instituto Geológico y Minero de Espa?a,Madrid,Spain |
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Abstract: | Two pyritic tailings impoundments located in two mining areas of the Iberian Pyrite Belt (Cueva de la Mora and Minas de Ríotinto-Zarandas)
were selected to asses their potential environmental impact. Mineralogical (XRD diffraction study), physico-chemical characterization
(colour, particle size, pH, acid–base account, total Fe, As, Cu, Pb and Zn) as well as a speciation study (by means of a seven-step
sequential extraction procedure) were performed in superficial (0–20 cm) tailings samples. Arsenic and metal contents in soils
around the tailings impoundments were also studied. Zarandas dam, a reclaimed impoundment, which has been limed, partially
topsoiled and planted, has supported and allowed the growth of pine trees and other plants for many years. The surface of
this impoundment can be considered very acid but nonacid forming. Although total As and metal concentrations were relatively
high, it is not possible to conclude that the Zarandas tailings have polluted the surrounding soils. Tailings in Cueva de
la Mora showed high total and easily mobilizable concentration of toxic elements. The net neutralization potential was strongly
negative as a consequence of the acid generation caused by the sulphide oxidation, the presence of secondary acid-generating
minerals and the absence of neutralizing materials. Coquimbite and rhomboclase efflorescences formed during the Mediterranean
dry summers on the surface of this impoundment contained very high levels of soluble As, Cu and Zn that were easily dissolved
and released to the running water in the first rains of autumn. |
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