Evolución mineralógica en medios afectados por contaminación ácida

Resumo

Contaminated soils and surface waters, from copper mining in Galicia, are acidic, high in sulphate and increase appreciably in the concentration of elements such as Al, Fe, Ca, Mg, K, Mn, Cu and Zn. Application of activity data to mineral equilibrium diagrams illustrates the instability of Al-hydroxides and aluminosilicates compared to Al-sulphates of the alunite and jurbanite type, in the waters which are most acid and display sulphate activities close to 10-2 M. The solution extracted from soils around the spoil heaps reflects the strong influence of the most heavily contaminated run-off waters, with little or no buffering by the solid phase. Neoformation of Al-sulphate (and Fe-sulphate) is observed both in soils and in the channels of the contaminated streams, above all the points of contact with non-acid or slightly acid waters.