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Abstract  

This work addresses the chemical features of topsoils from São Domingos mine, Portugal, an abandoned mining area since middle of twentieth century. The fractions below 1 mm of the surface-soil samples (0–15 cm) were measured by k0-standardized, instrumental neutron activation analysis in order to determine the levels of rare earth element concentrations in comparison to control soils. A fractionation between the heavy and light rare-earth elements (REEs) occurred, with the latter enriched relatively to the first ones. The REEs pattern is similar in all sites with higher concentrations in the mine area as compared to the control site. The ratios between REEs are conventional for three subsamples but slightly diverge for the other sites. The REEs pattern is similar to one of the volcanic islands still with activity as Sao Miguel in Azores, Portugal, and similar to the one of an industrial area containing coal power plant and refinery.

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Abstract  

This study aims to find out a vascular plant species that accumulate relatively high concentrations of arsenic (As) for its use as phytoremediator at abandoned and contaminated mining areas, such as São Domingos mines (Portugal). The assessment of As contamination levels in soils and plants of other similar sites in the north of the country (Castromil and Poço de Freitas) was also conducted; and the sample analyses were made by instrumental neutron activation analysis. Agrostis genera have shown higher As transfer coefficients than other studied plant species and, in particular, Agrostis curtisii has shown a reasonable ability to accumulate high concentration of this toxic element.

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Abstract  

The drying process of fresh plant materials may affect the porous structure, dehydration and a number of quality characteristics of these materials. Therefore, this study has investigated the effect of different drying processes on the variation of metal and metalloid concentrations in the dried plant materials. Seven varieties of native plant species collected from São Domingos mine were analyzed by instrumental neutron activation analysis (INAA) to investigate the effects of freeze-drying (FD), ambient air-drying (AAD) and oven-drying (OD) process on the concentrations of metals and metalloids in the plant biomass. Comparison of ambient air-dried, oven-dried and freeze-dried preparations allows a phenomenological description of the dehydration artefacts. In the quantitative analysis of metals and metalloids, FD and OD plant samples show the higher concentrations of metals and metalloids when compared to those in the AAD plant biomass. The freeze-drying process is comparatively reliable for determination of metals and metalloids concentrations in plant materials.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Freitas, A. Pacheco, H. Anawar, I. Dionísio, H. Dung, N. Canha, A. Bettencourt, F. Henriques, C. Pinto-Gomes, and S. Capelo

Abstract  

This study has determined contamination levels in soils and plants from the São Domingos mining area, Portugal, by k 0-INAA. Total concentrations of As, Sb, Cr, Hg, Cu, Zn and Fe in soils were very high, exceeding the maximum limits in Portuguese legislation. Concentrations of toxic elements like As, Sb and Zn were highest in roots of Erica andevalensis, Juncus acutus, Agrostis castellana and Nicotiana glauca. Additionally, As, Br, Cr, Fe, Sb and Zn in all organs of most plants were above toxicity levels. Those species that accumulated relatively high concentrations of toxic elements in roots (and tops) may be cultivated for phytostabilisation of similar areas.

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