Rehabilitation of mercury contaminated soils: strategies for the Almaden area

Abstract

Rehabilitation of mercury contaminated soils: strategies for the Almaden area.

Hg mining has been carried out in the Almaden area for more than 2,000 years. The recent abandonment of mining activites makes it necessary to find alternative uses for the soil and provide profitable activities for local populations. The evaluation of different strategies for soil rehabilitation, and the identification of alternative uses for the soil are the objective of this work. The first step in our study was the soil and plant characterization of the area, followed by the study of the contamination levels, and the selection of wild plant species showing some degree of Hg resistance. As an alternative use for the soils, some agricultural plant species were grown under controlled conditions on Almaden soil. Hg transfer from soil to plant was evaluated in wild and cultivated plants. Soil contamination level was better described by the bioavailable fraction than by total Hg. Regarding agricultural plant species, eggplant, lentil, lupin and chickpea can be safely cultivated on Almaden soils, and they can be used in human diet with low potential risk for the health. Vetch can not be recommended as green fodder, as it reaches Hg concentrations close to the maximum allowable limit, but the seeds can be commercialized. These crops can be proposed as an alternative soil use in Almaden. Some of the wild plants collected in the Almaden can be used in phytostabilization or revegetation of degraded areas, but they can not be recommended for phytoextraction.