Soil-plant system of pastures from an agrosilvopastoral system implemented on abandoned Fe–Mn mine

In the Iberian Pyrite Belt there are several small Mn abandoned mines, where soils developed on contaminated materials as well as those adjacent to contaminated areas have been converted by the local population into traditional agrosilvopastoral systems without any evaluation of their environmental risk.

Although no visual symptoms of phytotoxicy have been observed in vegetation, there is no information about the potential environmental risk of these soils and vegetation, especially in the herbaceous cover grazed by domestic animals. The Fe–Mn mine located in Ferragudo (Portugal) was exploited between 1959 and 2001. Posteriorly this area was converted in an agrosilvopastoral system with Quercus ilex woodland with small tree density and cultivated grass species. In the present study a biogeochemical characterization of this abandoned mine area was done in order to evaluate the potential environmental risk of the grassland. Soil samples were collected in two depths until a maximum of 20 cm as well as the aerial part of grassland. Soils were analysed to potentially hazardous elements (PHE) concentrations in total and available fraction as well as to other classical parameters. In plants was also determined the PHE concentrations being these values compared to the maximum allowed value for domestic animals.

Soils had a pH close to neutral and a good fertility. The concentrations of some PHE (e.g. Mn and Fe) in total soil fraction were higher than the average concentrations in non-contaminated soils of the region. However, the available concentrations were small. The elements concentrations in plants depended on element. In general, this agrosilvopastoral system did not pose a significant environmental risk.