Absorção e fracionamento dos elementos terras raras por vegetais: estudo comparativo em plantas ocorrentes em diferentes contextos geológicos

Abstract

This work investigates the behavior of REE in some plant species in relation to the concentration levels of these elements in the substratum, independent of the metabolic and physiological specificities of each type of plant and of the nature of the geochemical environment. REE concentrations of leaf ashes determined by ICP-MS e ICP-3500 techniques had been compared with the concentrations of the soil or rock samples of different geologic contexts such as carbonatitic, syenitic and ultramafic environments. In the syenitic environment the REE patterns in leaf ash are similar to those of the whole rock, reproducing the LREE enrichment. In the ultramafic environment the leaf ash contents are higher than those of soils, with REE patterns displaying the W-type tetrad effect. In the lateritic covering of the carbonatite leaf ash patterns have lower REE contents and lack positive Ce anomalies. The results show that the diverse species reflect the REE patterns of the substratum with some variations, such as the tetrad effect, resulting from the fractionation of the elements of the series by the plants.