The interaction of heavy metals and metalloids in the soil-plant system in the São Domingos mining area (Iberian Pyrite Belt, Portugal).

São Domingos belongs among the most important historic Iberian Pyrite Belt Cu mines. The anthrosoil is contaminated by a very high content of heavy metals and metalloids. The study was focused on evaluating the interaction of some chemical elements (Ca, Mg, Fe, Mn, Cu, Pb, Zn, Ag, Cd, Ni, Co, As, Sb) in the system soil vs. five autochthonous dominant plant species: Pinus pinaster Aiton, Quercus rotundifolia Lam., Agrostis sp., Juncus conglomeratus L. and Juncus effusus L. The plants are heavily contaminated by Cu, Pb, As and Zn. The bioconcentration factor proved that they exhibit features of metal tolerant excluders. The trees are accumulators of Ag, whereas the graminoids are hyper-accumulators of Ag and Juncus effusus of Co. The translocation factor confirmed that the selected elements are immobilised in the roots except for Mn and Zn in Pinus pinaster and Mn in Quercus rotundifolia and Juncus conglomeratus. The bioaccumulation of Mn, Zn and Cu at low pH increases. The increased content of Ca and Mg in the soil inhibits, in the case of some metals and metalloids, their intake to plants. Although the studied plants, despite their fitness and vitality at the contaminated sites, are not suitable for phytoextraction (except Co and Ag), they can be used for phytostabilisation at the mining habitats.

Source and pathway analysis of lead and polycyclic aromatic hydrocarbons in Lisbon urban soils.

One hundred soil samples were collected from urban spaces, in Lisbon, Portugal, in two surveys that were carried out in consecutive years, to assess the potential adverse human health effects following exposure to potentially toxic elements and organic compounds in the urban soils. The study hereby described follows on from the earlier work of the authors and aims at performing a source-pathway-fate analysis of lead (Pb) and polycyclic aromatic hydrocarbons (PAHs) in the urban soils in order to increase current knowledge on factors influencing exposure of the population. Various techniques were combined to achieve the proposed goal. Geogenic and anthropogenic sources were apportioned by means of Pb isotope mixing models. Isotope data was further coupled with geographic information system mapping to assess local mixed sources of Pb and PAHs. Unleaded vehicle exhaust and cement production show the largest relative contribution to the total soil-Pb, but their respective importance depends on factors such as location and urban landscape. The primary sources of PAHs to the urban soils are probably air and land traffic. Multivariate analysis was used to investigate which soil properties could influence mobility and fate of the contaminants. Whilst principal components analysis indicates carbonates and other calcium phases as probable factors controlling the dispersion of Pb in the urban soils, the linear models obtained from stepwise multiple regression analysis show that soil phosphorous (P) and manganese (Mn) are good predictors of the total soil Pb content. No robust model was obtained for the PAHs, impeding identifying environmental factors most likely to influence their dispersion in the urban soils. The solid-phase distribution study provided critical information to untangle the, at a first glance, contradictory results obtained by the multivariate analysis. Carbonates and other calcium phases, having these a probable anthropogenic origin, are soil components containing major fractions of Pb, P, and Mn.