The distribution of the chemical element during weathering of trachyandesite in S. Miguel Island (Azores, Portugal), and in
mosses and lichens growing on these rocks, was studied using instrumental neutron activation analysis. A general enrichment
of rare earth elements (REEs), a Ce positive anomaly (partial oxidation after primary apatite dissolution) and a Eu negative
anomaly (Eu2+ in plagioclases/clay minerals) are observed with increasing weathering. Mosses and lichens are Ce and Eu depleted, indicating
that the main REE uptake is done via absorption from REE3+ secondary phosphates, probably together with P (essential nutrient). Zn, Br and Sb show higher enrichment factors in lichens
We report instrumental neutron activation analysis results for 15 elements (K, Fe, Sc, Cr, Co, Zn, As, Rb, Sb, Cs, Ba, Hf, Ta, Th, and U) in 16 geochemical reference samples, namely SDC-1, SCo-1, SGR-1, STM-1, RGM-1, BIR-1, MAG-1 and BHVO-1 from USGS (United States Geological Survey, Reston), Soil-5, Soil-7 and SL-1 from IAEA (International Atomic Energy Agency, Vienna), and GSS-1, GSS-4, GSS-7, GSR-2 and GSR-3 from IGGE Institute of Geophysical and Geochemical Prospecting, People's Republic of China), The results are compared with literature values. In general our results agree well with recommended or proposed values.
Eight rare-earth elements (REE), namely La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu, as well as other elements (Na, K, Sc, Cr, Fe, Co, Rb, Cs, Ba, Hf, Ta, and Th), have been determined in fifteen cretaceous clay samples of continental facies by instrumental neutron activation analysis. It was found that the REE contents are variable in absolute and relative values, but the means of these values are similar to those of European, shales. Analyses have also been made of the fractions <38 m and <2 m (clay-sized). The mineral contents of the clay-sized fraction were determined semi-quantitatively by X-ray diffraction. The results suggest the preferential presence of REE, Hf, and Th in fractions 2–38 m, which can be explained by the presence of apatite, monazite, and zircon. A correlation study of chemical and mineralogical data of the clay-sized fraction showed that kaolinite is correlated with REE, specially the lighter ones; illite with K, Rb, and Cs; and smectite with Na.
Three Canadian reference rocks, syenites SY-2 and SY-3, and gabbro MRG-1 have been analysed for Na, K, Sc, Cr, Fe, Co, Zn, As, Rb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta and Th, by instrumental neutron activation analysis. The results are reported and compared with usable values. In general the agreement is good.
Authors:M. Gouveia, M. Prudencio, M. Freitas, E. Martinho, and J. Cabral
A numerical procedure is given to correct for the interference of U in the determination of the light rare earths, Zr, and Ru. The corresponding interference factors were calculated and their values compared with experimental results. The agreement is favourable in most cases.
Authors:M. Gouveia, M. Prudencio, I. Morgado, M. Magalhaes, and J. Cabral
Trace element data (Sc, Cr, Co, Hf, Ta and Th) are reported for a weathering profile of gabbroic rocks located near Serpa, Portugal. The results obtained for the whole rock samples showed that: (i) Co and Sc contents decrease upwards the profile. Co appears to be mobilized in the soil probably as soluble cation; (ii) Cr tends to remain in the profile; and (iii) Hf and Th concentrate in the upper horizons. Trace element distribution in different size fractions of the upper horizons revealed: (i) Sc, Cr and Co have a more uniform distribution than Hf, Ta and Th; (ii) Hf and Ta are concentrated in the intermediate fractions; and (iii) Th is concentrated in the finer fractions, probably due to incorporation in weathering resistant minerals, specially in the initial stages of weathering.
Authors:M. Gouveia, M. Prudêncio, J. Barros, L. Morgado, and J. Cabral
Instrumental neutron activation analysis, atomic absorption spectrometry and conventional methods were used on five USGS Geochemical Exploration Reference Materials: GXR-1, 2, 3, 4 and 6. The concentrations of 35 elements are reported and compared with available literature values. In general the agreement is good.
Authors:M. Gouveia, M. Prudêncio, I. Morgado, and J. Cabral
Two reference rocks of the Geological Survey of Japan have been analyzed for Na, K, Sc, Cr, Fe, Co, Zn, Rb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U, using instrumental neutron activation analysis. The results are reported and compared with consensus values proposed in the literature. In general, the agreement is good except for Cs.
Authors:M. Freitas, F. De Corte, M. Gouveia, M. Prudêncio, and J. Cabral
The Ree contents in lichens and plants determined by k0-standardized NAA with LEPD and HPGe are compared. We obtain similar values for Sm, Eu, Tb and Yb and better values for Ce and Nd by using LEPD Besides, LEPD allows the determination of Gd, Tm and Lu. The study of REE concentrations in the neighbourhood of two coal power stations show that: i) in the station under construction (C. T. Pego), the index of accumulation of each REE by the lichens and olive tree leaves is identical in two sampling loci where the soils have different REE concentration; and ii) in the station in operation (C. T. Sines), the REE contents in the soils is identical and the differences observed in the lichens and wild terrestrial plants are most probably due to the fly-ashes emmission from the station.
Authors:S.M. Silveira, A. Cunha Jr., M. Maraschin, S. Verruck, F.L. Secchi, G. Scheuermann, E.S. Prudencio, N. Fronza, and C.R.W. Vieira
The antioxidant and antimicrobial activities of extracts of 12 plant species growing in Brazil were determined. Antimicrobial activity against 12 food-related bacterial species was studied using the disc-diffusion, MIC, and MBC methods. Campomanesia eugenioides extract was the most active against the tested Gram-positive bacteria, whereas Parapiptadenia rigida bark extract presented the highest activity against the evaluated Gram-negative bacteria (MIC and MBC of 0.075 and 0.62 mg ml−1, respectively, against Pseudomonas aeruginosa). Those two extracts also presented high phenolic content and high DPPH and ABTS radical scavenging ability. C. eugenioides extract presented high Fe2+ chelating capacity. The results of the present study demonstrate that, among the evaluated extracts, P. rigida bark and C. eugenioides, both Brazilian native species, presented the highest potential of application as natural antimicrobial and antioxidant agents.