Evaluación de la movilización del As procedente de los residuos mineros abandonados de una zona semiárida (Rodalquilar, Almería)

Abstract

Navarro, A., Martin, A. 2015. Evaluation of As mobilization from abandoned mine wastes of a semi-arid area (Rodalquilar, Almeria). Ecosistemas 24(2): 76-89. Doi.: 10.7818/ECOS.2014.24-2.12 Field and laboratory studies and mathematical modeling were used in order to assess the long-term mobilization of As from an uncontrolled tailings deposit, located next to the old mine of Rodalquilar (Almeria). Leaching mine wastes by column experiments indicates the possible movement of As at concentrations ranging between 30.9 and 1.2 mg /L, and pH values between 8.24 and 7.9, in a saline leachate character and showed electrical conductivities of 425-22 100 µS/cm. The mobility of some metalloids such as arsenic may be produced by the weathering of arsenian pyrite, present in the mine wastes in appreciable amounts, and jarosite and Fe oxy-hydroxides, where the arsenic appears in appreciable amounts. In this area groundwater showed high concentrations of Al, As, Cd, Fe, Hg , Mn, Ni, Pb, Se, Sb and Zn, which exceed water quality criteria for human consumption. Highlights the extent reached by As contamination detected throughout the aquifer and with concentrations reaching 0.2 mg /L. The dissolution of Fe oxy- hydroxides in areas of low redox potential could explain the existence of appreciable amounts of As, Fe and other metals dissolved in groundwater. MODFLOW modeling code simulated the transport of As in the aquifer of Rodalquilar and indicated that the main pollutant control mechanism, in addition to the hydrodynamic dispersion is adsorption on Fe oxy- hydroxides. The results suggest a progressive increase in the concentrations of As in groundwater for years.