Comportamiento de la vetiveria ("Chrysopogon zizanioides" L. Roberty) como extractora de metales pesados en suelos contaminados

Resumo

Soils from mining areas in Spain often contain a high level of heavy metal contamination. Traditionally have been used decontamination techniques that result very aggressive for the soil. These techniques can produce alterations in the soil characteristics and avoid its recovery and rehabilitation. Phytoremedation is a set of techniques more economical an environmentally friendly than the conventional ones, which mixes plants with certain amendments and agronomic practices to reduce the toxicity of pollutants. Among these techniques, we can highlight phytoextraction, which is based on the absorption of metals from the soil by the plant roots and translocation to the aerial parts of plants. Vetiver (Chrysopogon zizanioides (L.) Roberty) species is commonly known for its effectiveness as a barrier to control erosion, for its tolerance in soils with extreme conditions and to produce a large biomass even in contaminated areas. This paper studies the possibility of recovery of soils exposed to high contamination with heavy metals by phytoextraction techniques assisted by chelating agents. The effect of an specific type of humic acid obtained from leonardite was analyzed on the solubility of the metals Cd, Cu, Mn and Zn in three soils miners through the absorption by Vetiveria. The essay consisted on installing containers under greenhouse conditions using three different soils from the mining areas of La Unión (Murcia), Cuadrón, and Bustarviejo (Madrid). A factorial design was used with three levels of humic acid applications: 0, 2, 10 and 20 g/kg of soil with ten repetitions. The amount of metals (Cu, Cd, Zn and Mn) was evaluated in the vetiver plant, extracting the plant tissue by cutting at 4 and 8 months. It was observed that the humic acid made more available to the plant the processing of the heavy metals; this was specially observed in the soil Cuadrón with relatively low heavy metal content. On the other hand, in more contaminated soils with higher levels of humic acid there was immobilization of heavy metals.