Near-infrared spectroscopy for the prediction of rare earth elements in soils from the largest uranium-phosphate deposit in Brazil using PLS, iPLS, and iSPA-PLS models.

The largest uranium-phosphate deposit in Brazil also contains considerable levels of rare earth elements (REEs), which allows for the co-mining of these three ores. The most common methods for REE determination are time-consuming and demand complex sample preparation and use of hazardous reagents. Thus, the development of a safer and faster method to predict REEs in soil could aid in the assessment of these elements. We investigated the efficiency of near-infrared (NIR) spectroscopy to predict REEs in the soil of the uranium-phosphate deposit of Itataia, Brazil. We collected 50 composite topsoil samples in a well-distributed sampling grid along the deposit. The NIR measures in the soils ranged from 750 to 2500 nm. Three partial least squares regressions (PLSR) were selected to calibrate the spectra: full-spectrum partial least squares (PLS), interval partial least squares (iPLS), and successive projections algorithms for interval selection in partial least squares (iSPA-PLS). The concentrations of REEs were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). In addition to raw spectral data, we also used spectral pretreatments to investigate the effects on prediction results: multiplicative scatter correction (MSC), Savitzky-Golay derivatives (SG), and standard normal variate transformation (SNV). Positive results were obtained in PLS for La and ΣLREE using MSC pretreatment and in iSPA-PLS for Nd and Ce using raw data. The accuracy of the measurements was related to the REE concentration in soil; i.e., elements with higher concentrations tended to present more accurate results. The results obtained here aim to contribute to the development of NIR spectroscopy techniques as a tool for mapping the concentrations of REEs in topsoil.

Spatial variability and geochemistry of rare earth elements in soils from the largest uranium-phosphate deposit of Brazil.

The Itataia uranium-phosphate deposit is the largest uranium reserve in Brazil. Rare earth elements (REEs) are commonly associated with phosphate deposits; however, there are no studies on the concentrations of REEs in soils of the Itataia deposit region. Thus, the objective of the research was to evaluate the concentration and spatial variability of REEs in topsoils of Itataia phosphate deposit region. In addition, the influence of soil properties on the geochemistry of REEs was investigated. Results showed that relatively high mean concentrations (mg kg-1) of heavy REEs (Gd 6.01; Tb 1.25; Ho 1.15; Er 4.05; Tm 0.64; Yb 4.61; Lu 0.65) were found in surface soils samples. Soil properties showed weak influence on the geochemical behavior of REEs in soils, except for the clay content. On the other hand, parent material characteristics, such as P and U, had strong influence on REEs concentrations. Spatial distribution patterns of REEs in soils are clearly associated with P and U contents. Therefore, geochemical surveys aiming at the delineation of ore-bearing zones in the region can benefit from our data. The results of this work reinforce the perspective for co-mining of P, U and REEs in this important P-U reserve.

Estaquia de Croton zehntneri Pax et Hoffm. com diferentes concentrações de ácido indol butírico / Cuttings of Croton zehntneri Pax et Hoffm. At different concentrations of indole butyric acid

Croton zehntneri Pax et Hoffm. (canela de cunhã) é nativa do nordeste do Brasil, tem efeito antioxidante e atividade antinociceptiva e antidepressiva. O estudo da propagação vegetativa é importante por causa da baixa produção de sementes e existência de diferentes quimiotipos da espécie. O objetivo do presente trabalho foi verificar o efeito de ácido indolbutirico (AIB) na produção de mudas por estacas de C. zehntneri. Os tratamentos foram as concentrações zero, 1.000, 2.000, 3.000, 4.000 e 5.000mg L-1 de AIB. O delineamento experimental foi em blocos ao acaso, com seis tratamentos e quatro repetições de 10 estacas por parcela. Foram analisadas aos 40 dias as seguintes características: porcentagem de enraizamento, número e comprimento das raízes por estaca, número de brotações, número de folhas, massa seca foliar e de raízes. A porcentagem de enraizamento foi maior nas maiores concentrações de AIB 3.000, 4.000 e 5.000mg L-1 (80, 90 e 100%). A porcentagem de enraizamento, o número e comprimento das raízes e o número de folhas apresentaram comportamento linear em relação às concentrações de AIB, quanto maior a concentração maior o valor da característica. O número de brotações diminuiu com a maior concentração de AIB. A massa seca das raízes foi maior nos pré-tratamentos com 4.000 e 5.000mg L-1 AIB (0,35g). O pré-tratamento das estacas de C. zehntneri com solução de AIB na concentração de 4.000mg L-1 por 10 segundos é recomendado para a propagação vegetativa.

Croton zehntneri Pax et Hoffm. (canela de cunhã) is native to northeastern Brazil, has antioxidant, antinociceptive and antidepressant properties. The study of vegetative propagation is important because of the low seeds production and the existence of different chemotypes in the species. The aim of this study was to assess the effect of indole butyric acid (IBA) in plant propagation by cuttings of C. zehntneri. The experimental design was randomized blocks with six treatments and four replications of 10 cuttings. The treatments were zero concentrations, 1,000, 2,000, 3,000, 4,000 and 5,000mg L-1 IBA. It was analyzed the following characteristics: rooting percentage, root number per cutting, root length, shoot number, number of leaves, leaf dry mass and roots dry mass. The rooting percentage was higher for higher concentrations of IBA 3,000, 4,000 and 5,000mg L-1 (80, 90 and 100%). The percentage of rooting, root number, root length and number of leaves showed linear behavior in relation to concentrations of IBA, the higher the concentration the greater the value of the variable. The number of shoots decreased at higher concentration. The dry mass of roots was higher in pre-treatment with 4,000 and 5,000mg L-1 IBA (0.35g). Pre-treatment of cuttings of C. zehntneri with a solution of IBA at a concentration of 4,000mg L-1 for 10 seconds is recommended for vegetative propagation of the species.