Chemie der Grubenwässer
Für die Kontamination von Grubenwässer ist weniger der Bergbau im eigentlichen Sinne verantwortlich als vielmehr die massiven hydrogeologischen bzw. hydro-chemischen Veränderungen, die damit verbunden sind (DEGNER 2003). Wie bereits in den vorherigen Abschnitten dargestellt, ist in erster Linie die Verwitterung der Mineralien für die chemische Beschaffenheit der Wässer ver-antwortlich. Diese können in Abhängigkeit von der geologischen Situation, Art und Größe der Lagerstätte und dem geochemischen Milieu teils einen sehr diffe-renzierten Charakter besitzen. Zu den hauptsächlich auftretenden Verwitterungsprozessen zählen die Oxidati-on von Sulfiden, die Lösung von Silikaten und Karbonaten. Über Sickerwässer werden die Reaktionsprodukte in das Grubenwasser transportiert. Das Gruben-wasser kann sowohl sauer als auch alkalisch aber auch neutral sein. Sauerwasser bzw. Acid Mine Drainage (AMD) ist durch niedrige pH-Werte und Netto-Acidität (Acidität > Alkaliät) gekennzeichnet (YOUNGER et. al 2002). Die zur Entstehung von sauren Grubenwässern notwendigen Komponenten sind Sulfidminerale, Wasser bzw. eine feuchte Atmosphäre und ein Oxidations-mittel (i.d.R Sauerstoff). Die ablaufenden Prozesse und chemischen Reaktionen sind stark miteinander verknüpft (HELMS 1995).

Chemistry of Mine Drainage
The massive hydrogeological and hydrochemical changes associated with mining play a much greater role in contamination due to mine drainage than do the mining activities per se (Degner, 2003). As described in the previous sections, the weathering of minerals is primarily responsible for the chemical composition of the waters, which may vary greatly, as a function of the geological conditions, type and size of the deposit and the geochemical environment. The most commonly occurring weathering processes include the oxidation of sulfides and the dissolution of silicates and carbonates. The reaction products are carried into the mine water through leachate, and the mine drainage can be acidic, alkaline or neutral. Acid mine drainage (AMD) is characterized by low pH and net acidity (acidity > alkalinity) (Younger et al. 2002). The components necessary for the formation of acid mine drainage are sulfide minerals, water or a humid environment, and an oxidant (usually oxygen). The ongoing processes and chemical reactions are strongly interrelated (Helms, 1995).

Prospezione Geofisica

La prospezione geofisica eseguita con il metodo dei (S.E.) ha permesso di constatare che la resistività della coltre vulcanica è nettamente superiore a quella dei terreni sedimentari sottostanti e i diagrammi dei S.E. mostrano la sovrapposizione di 2 mezzi elettricamente differenziati:
a) un ricoprimento resistente, con resistività quasi sempre compresa fra 400 e 2000 ohm.m, corrispondente, in linea di massima, alle formazioni vulcaniche;
b) un substrato conduttore identificabile con il basamento sedimentario.
Nel ricoprimento gli intervalli di resistività più elevati indicherebbero il forte sviluppo di lave o di tufi compatti, prevalentemente asciutti o con il livello statico piuttosto profondo. Per arrivare ad un utilizzo il più possibile esauriente delle informazioni ottenibili dalla prospezione geofisica, tenuto conto anche dei risultati del precedente studio idrogeologico e delle perforazioni eseguite, i diagrammi di S.E. sono stati elaborati per ottenere documenti che venissero a chiarire oltre alla situazione geolitologica anche quella idrogeologica e idrodinamica dell' acquifero delle vulcaniti.

Geophysical Survey

The geophysical survey carried out using electrical resistivity soundings has shown that the resistivity of the volcanic layer is substantially higher than that of the underlying soils, and the resistivity diagrams show the superposition of two electrically differentiated media:

a) a resistant top layer, with resistivity values almost always between 400 and 2000 ohm-m, corresponding, in principle, to the volcanic formations;

b) a conductive substrate identified with the sedimentary basement.

In the top layer, zones of higher resistivity would indicate the strong development of compact lava or tuff which is predominantly dry or has a relatively deep water table. In order to optimize the utilization of the information obtained from geophysical surveys, the results of the previous hydrogeologic study and the drilling program were also taken into consideration. The resistivity diagrams were designed to clarify the geolithological situation as well as the hydrogeology and hydrodynamics of the aquifer in the volcanic material.

La cuenca del Guadalquivir se desarrolla en un valle abierto a los vientos dominantes del SO, flanqueado al Norte por la cordillera Mariánica o Cierra Morena y al Sur por el complejo Sistema Bético. Las sierras Béticas son abruptas y en ellas se encuentran las mayores altitudes de la cuenca (Mulhacén y Veleta). Cierra Morena es menos elevada. El gran valle Bético de topografía suave, asciende desde el nivel del mar hasta unos 400 m de altitud.

Los ríos de la margen derecha presentan un acusado carácter torrencial y suelen llegar a secarse en verano, dado que discurren por terrenos con escasa capacidad de retención en régimen estrictamente pluvial. Los de la margen izquierda, por el contrario, alimentados por las aportaciones de los terrenos permeables que atraviesan, no presentan estiajes tan acusados.

Hidrogeológicamente, la Meseta se caracteriza por la existencia de acuíferos detríticos aislados, y en menor medida, calcáreos. Generalmente presentan escasa extensión y baja permeabilidad, siendo interesantes sólo a nivel local. En las Cordilleras Béticas existe un gran número de acuíferos con características muy dispares, derivadas de la diversidad litológica y complejidad estructural de esta unidad. En su mayor parte, son acuíferos de importancia, desarrollados en materiales calcáreos y/o dolomíticos, con mayor o menor grado de karstificación, cuyo substrato impermeable suele estar constituido por materiales triásicos (margas y arcillas yesíferas), con intercalaciones de carniolas y dolomías. En la Depresión del Guadalquivir, y en las Depresiones Internas de las Cordilleras Béticas, así como en las de Guadix-Baza, Granada y Ronda, los materiales detríticos constituyen los acuíferos más importantes.

The Guadalquivir watershed lies within a valley that is open to prevailing southwesterly winds and is flanked on the north by the Marianic range or the Sierra Morena, and on the south by the Betic System complex. The Betic mountains are steep and include the highest peaks of the basin (Mulhacén and Veleta). The Sierra Morena is lower in elevation. The great Betic Valley, with its gentle topography, rises from sea level to approximately 400 m in elevation.

The rivers on the right flank of the watershed are of a marked torrential nature and tend to dry out in the summer, as they run through a landscape with little capacity for retention in a strictly pluvial system. Those on the left flank, however, which are fed by contributions from the permeable soils through which they flow, do not suffer from such severe droughts.

Hydrogeologically, the Plateau is characterized by the existence of isolated detritic, and to a lesser extent, calcareous aquifers. They are generally of limited extent and low permeability, and are, therefore, of interest only at a local level. In the Betic Range, there are a great number of aquifers with very disparate characteristics derived from the lithologic and structural complexity of this unit. For the most part, they are important aquifers composed of calcareous materials and/or dolomites, with a greater or lesser degree of karstification, whose impermeable substrate tends to be composed of Triassic materials (gypsiferous marls and clays) with intercalations of carniola and dolomites. In the Guadalquivir Trough, and in the internal troughs of the Betic Range, as well as in those of Guadix-Baza, Granada and Ronda, the most important aquifers are composed of detritic materials.