The break in a retaining wall of Aznalcóllar´s mines caused one of the most important ecological catastrophes in Spain in the last years. The dumping was calculated at 2 million cubic metres of toxic mud and 4 million acid water and put the Natural Reserve of Doñana in risk.
A group of scientists of the University of Granada has worked, together with experts of different Spanish universities and the Higher Council of Scientific Research (CSIC), evaluating the damage caused by the dumping in soils of the area, which became contaminated after the accident with heavy metals like arsenic, lead, zinc, thallium, copper or cadmium.
The team of scientists, coordinated by Professor José Aguilar Ruiz (Dpt. of Edaphology and Agricultural Chemistry), integrated in the PICOVER (Research Program of the Green Corridor of the river Guadiamar) set up by the Andalusian Council as a result of the disaster. Specifically, their plan of action centres around the monitoring, control and disposal of contamination.
The method pointed out by experts to improve soils is the block technique consisting of the addition of certain substances to cancel out the action the pollutants and, therefore, their toxic action.
“The two materials which blocked the pollutant effect of heavy metals contained in soil the most were, on the one hand, calcium carbonate and, on the other hand, iron oxide”, points out Professor Aguilar.
The novelty of the method is that these materials offer the possibility of recycling waste from other industries to use them to decontaminante, since calcium carbonate is present in waste materials like wood pulp, sewage sludge or sugar scum.
Liming is the most common disposal practice in recovery works. The effect on soils is the rise in the pH which must be distributed in soil in a homogeneous way. It must be added in small doses and to a minimum depth of 25 cm. In addition a continuous soil removal must be carried out to destroy iron and aluminium covers that form on the surface.
The study has had great social and scientific repercussions and has been published in several scientific journals like Geoderma, Enviromental Pollution, The Sciencie of total Enviroment or Water, Air and Soil Pollution. All the lecturers of the Department of Edaphology and Agricultural Chemistry have taken part in the study.
Information: Prof. José Aguilar Ruiz
Department of Edaphology and Agricultural Chemistry
Phone number: 958243393 958248537
E-mail: aguilar@ugr.es
