The application of phytoremediation technologies to metal-contaminated soils in Aznalcóllar

Abstract

The application of phytoremediation technologies to metal-contaminated soils in Aznalcóllar.

The spill of pyrite sludge from the Aznalcóllar mine in 1998, affected 4286 ha of land, 59.7 % of which was agricultural. The main contaminants were As, Cd, Cu, Pb and Zn, their effects being exacerbated by the soil acidification caused by the oxidation of metallic sulphides. This dramatic case of soil pollution mobilised the Spanish and international scientific communities, with the aim of applying biological techniques for soil remediation based on the use of plants (phytoremediation). These were fundamental in the development of the "Green Corridor of Guadiamar" land recuperation plan by the Andalusian regional government. Difficulties arose from the multi-element contamination, the chemical instability of the contaminants and the acidic nature of the contamination. This article briefly describes some phytoremediation experiments carried out in situ in experimental plots. The feasibility of certain phytoremediation techniques has been evaluated: phytoextraction by Indian mustard, a high-biomass crop able to accumulate metals in its aerial parts, in combination with the improvement of soil properties by the application of organic and calcareous amendments, and phytoimmobilisation using white lupin, a leguminous species tolerant of heavy metals due to their immobilisation in the roots and, to a certain degree, tolerant of soil acidity.