Analise multielementar quantitativa de solos e sedimentos por espectrometria de fluorescencia de raios X

AUTOR(ES)

Fabio Roberto Zambello

DATA DE PUBLICAÇÃO

2001

RESUMO

This dissertation evaluates wavelength-dispersive X-ray fluorescence spedrometry (XRF) as an analytical tool of soils and sediments, for economic geology and environmental geochemistry applications. The multi-element capacity and the analytical speed of XRF are of interest to elemental geochemical mapping projects, in mineral deposits prospects and in the evaluation of the environmental contamination by heavy metais. A difficulty found in the analysis of soils and sediments by XRF is instrument calibration, for a wide range of elemental concentration, using reference samples. Those are rarely characterised for ali the elements of interest, may present inhomogeneities in some degree, mainly when the samples are simply pressed as pellets. The instrumental progress of the last years and the wide interest in the fast analysis of such matrices justify the development and the evaluation of analytical programs for this application. A quantitative analytical program for determination of major (Si, AI, Fe, Mg, Ca, K, Na, Mn, Ti and P) and trace elements (As, Ba, Cd, Co, Cr, Cu, Ga, Mo, Nb, Ni, Pb, Rb, S, Sb, Sn, Sr, Th, U, V, Y, 20, and Zr) in pressed pellets of soils and sediments was prepared and the associated figures of merit (precision, accuracy and detection limits) were evaluated. For the two stages (calibration and evaluation) more than sixty reference materiais of soils and sediments from intemational suppliers a sequential X-rays fluorescence spectrometer were used. The detection limits for trace elements (1-5 J.19g-1) indicate that the analytical program is fit-for-purpose, i.e., the considered elements can be analysed in most cases in such matrices. Exceptions are Cd and Sb, whose detection limits (1,6 and 1,9 J1g g-1, respectively) are too high, considering their average concentrations in soils and sediments, but would still be useful to detect anomalous concentrations. The reference samples used in the evaluation of the accuracy were others than those used for instrument calibration. Three methods were used to evaluate the results. The results of trace elements fali within the confidence interval of the certifted values or are very close of the recommended values. Due to the mineralogical effects, the calibration of the major elements was more complex, but the results, in general were in goOO agreement with recommended values. Eventual discrepancies were useful to improve calibrations and contributed to a better knowledge of the used reference samples and as criteria to choose the calibration samples

ASSUNTO(S)

metais pesados - aspectos ambientais espectroscopia de fluorescencia sedimentos (geologia) geologia economica fluorescencia de raio x geoquimica analitica

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