Distribución y Especiación de Mercurio en Suelos del Distrito Minero de Almadén
Abstract
Almost no environmental data on mercury distribution and speciation in soils have been published so far for the Almadén mining district (central Spain), despite its huge size and historic importance. The mercury distribution in soils of the district reveals the existence of high and extremely high mercury values (up to ~9000 ppm Hg).
The Hg-thermodesorption curves for soils from a decommissioned metallurgical precinct (Almadenejos) and a phytoremediation site show that mercury occurs in the forms of cinnabar and as mercury bound to organic matter. The TEM-EDX study of the highly contaminated anthrosols from Almadenejos (samples with Hg >5000 ppm) shows the existence of cinnabar particles adsorbed to the surface of chlorite grains.
Given the generally pyrite-poor character of the ores, and the presence of carbonates in the host rocks, cinnabar solubilization is limited, which in turn mitigates environmental hazards in the district. The only by-product of cinnabar leaching in the mineral dumps is schuetteite (Hg3SO4O2). Preliminary results on local plants (Asparagus acutifolius, Dittrichia graveolens, Marrubium vulgare) show that mercury gets incorporated into roots, stems, and leaves, with values of up to about 300 ppm Hg.
Resumen
En el distrito minero de Almadén, se encontraron altos niveles de mercurio en los suelos, principalmente en forma de cinabrio y mercurio ligado a materia orgánica. Se identificaron partículas de cinabrio en suelos altamente contaminados, y se observó que la solubilidad del cinabrio está limitada.
La fitorremediación ha sido utilizada en el área para mitigar los peligros ambientales. Además, se encontró que las plantas locales incorporan mercurio en raíces, tallos y hojas.