Site “S-7”, Location: Piedrafita de Cebreiro (Lugo, Spain) Abandoned Pb/Zn mine UTM 29T 660781/4726800
The Pb/Zn mine of Rubiais (Lugo, NW Spain) was active from 1977 to 1992, during which time a total of 18.6 Mt of Pb and Zn sulphide ores were extracted. Metal deposits are rich in sulphides, principally in the form of sphalerite (PbS) and galena (ZnS). Extraction was predominantly done by the vertical crater retreat method and minerals were separated by flotation. The altitude is 1070 m and the climate of the region is Oceanic, with a mean annual precipitation of 2000 mm and annual temperature of 8–9ºC. Sludges generated during mineral processing were deposited in tailing ponds, which cover a surface area of approximately 30 ha. Large areas of the tailings were covered with topsoil and re-planted with birch as a reclamation method at the time of the mine closure. Alumi-umbric Leptosols and Regosols are the most frequent natural soils in the area. Colonising plant species, which can be found across the tailings, include Cytisus scoparius (L.) Link, Betula celtiberica Rothm. & Vasc., Cytisus multiflorus (L´ Hér.) Sweet, Salix atrocinerea Brot., and Lotus corniculatus L.
The field trial was established in 2011 and forms part of the PhytoSUDOE network of phytomanaged sites. A short rotation coppicing system is being evaluated for its Cd/Zn phytoextraction capacity and potential for biomass production. Cd/Zn-accumulating Salix smithiana BOKU 03 CZ-001 was planted in monoculture (10000 cuttings ha-1) or co-cropped with Alnus glutinosa to evaluate possible benefits to plant growth and nutrition from incorporating plants which form associations with N-fixing microorganisms. Inorganic fertilisation is also being compared with the addition of composted municipal solid wastes (added at a rate of 5% w/w).