Sandra Andrade

Iron(II) oxide determination in rocks and minerals

Abstract The determination of FeO of geologic materials by modern instrumental methods (such as atomic absorption spectroscopy (AAS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), etc.) cannot distinguish between different oxidation states of elements. In many cases, the oxidation state of Fe has to be known in order to perform several chemical calculations (norms, etc.) and discuss the reactions that occur during weathering, hydrothermal alteration and other processes. A modified Wilson method is proposed, giving reproducible results in a much shorter time than the classical method. Back-titration with potassium dichromate and an Fe(II) and ammonia sulphate solution is used, after dissolution of the sample powder in a heated HF/H 3 PO 4 mixture and an ammonium vanadate solution. This modified method, tested with several international reference materials, gives reliable results, equivalent to the ones cited in the literature for the reference materials.

Adaptation of ICP–OES routine determination techniques for the analysis of rare earth elements by chromatographic separation in geologic materials: tests with reference materials and granitic rocks

Abstract The present contribution shows the results of tests on geological materials for determination of the rare-earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, as well as Y and Sc. The samples were prepared using lithium borate fusion of powdered rock sample followed by dissolution in hydrochloric acid. A separation was performed in cationic exchange columns with resin by hydrochloric and nitric acid gradient concentration and subsequent analysis using inductively coupled plasma atomic emission spectrometry (ICP–OES) and an ultrasonic nebulizer. All potentially interfering elements, except Ba and Zr, were eliminated using this procedure. Spectral interferences generated by Zr and the REE among themselves (Ce on Gd, Nd on Sm–Ce–Er, Gd on Sm, Pr on La–Ce–Nd–Ho–Tb, Tb on Ho, Sm on Tb) were identified and corrected quantitatively. The whole procedure was tested with international geological standard reference materials AC-E and JG-3 (granitic rocks), JB-1a (basalt), JA-2 (andesite), JR-2 (rhyolite) and JGb-1 (gabbro). A Student’s statistical test showed that the obtained analytical results were mostly satisfactory. The methodology, now performed on a routine basis, was applied for the determination of the REE patterns of assorted granitic rocks occurring in the state of Sao Paulo, southeastern Brazil.

Rare earth element and yttrium geochemistry applied to the genetic study of cryolite ore at the Pitinga Mine (Amazon, Brazil)

ABSTRACT This work aims at the geochemical study of Pitinga cryolite mineralization through REE and Y analyses in dissem-inated and massive cryolite ore deposits, as well as in fluorite occurrences. REE signatures in fluorite and cryoliteare similar to those in the Madeira albite granite. The highest 6REE values are found in magmatic cryolite (677 to1345 ppm); 6REE is lower in massive cryolite. Average values for the different cryolite types are 10.3 ppm, 6.66 ppmand 8.38 ppm (for nucleated, caramel and white types, respectively). Disseminated fluorite displays higher6REE val-ues(1708and1526ppm)thanfluoriteinlateveins(34.81ppm). Yttriumconcentrationishigherindisseminatedfluoriteand in magmatic cryolite. The evolution of several parameters (REE total , LREE/HREE, Y) was followed throughoutsuccessive stages of evolution in albite granites and associated mineralization. At the end of the process, late cryolitewas formed with low REE total content. REE data indicate that the MCD was formed by, and the disseminated oreenriched by (additional formation of hydrothermal disseminated cryolite), hydrothermal fluids, residual from albitegranite. The presence of tetrads is poorly defined, although nucleated, caramel and white cryolite types show evidencefor tetrad effect.

Human bocavirus in very young infants hospitalized with acute respiratory infection in Northeast Brazil

Abstract A cross-sectional study was carried out over a period of 12 months to investigate the occurrence of human bocavirus (HBoV) infection in infants hospitalized for respiratory infections in a teaching hospital in Salvador, Brazil, and to describe the clinical manifestations of this infection. Nasopharyngeal aspirates were collected from the children and immunofluorescence and polymerase chain reaction were performed to investigate the presence of respiratory viruses. HBoV was detected in 4 out of 66 patients. Two of the HBoV-positive infants were co-infected with other viruses. The principal clinical findings in HBoV-positive children were: nasal obstruction, catarrh, cough, fever and dyspnea. This study revealed HBoV infection in children aged <2 months, suggesting that the infection may occur at a very early age.

Chlamydia trachomatis: a major agent of respiratory infections in infants from low-income families

OBJECTIVES To determine the prevalence of lower respiratory tract infection (LRTI) due to Chlamydia trachomatis in newborn infants and to describe the clinical, laboratory, and radiological characteristics of the disease. METHODS A cross-sectional study carried out over a 12-month period. All infants up to 6 months of age admitted consecutively at the Centro Pediátrico Professor Hosannah de Oliveira of the Universidade Federal da Bahia in Salvador, Brazil, and diagnosed with LRTI according to clinical and/or radiological criteria were included in the study. C. trachomatis infection was diagnosed by the enzyme-linked immunosorbent assay (ELISA) for the detection of IgM-class antibodies. The prevalence of LRTI by C. trachomatis was determined and the prevalence ratios for the infection and clinical or laboratory variables were calculated. RESULTS One hundred and fifty-one infants were submitted to serology for C. trachomatis and 15 (9.9%) tested positive. Chlamydial infection was found only in infants under 5 months of age, mainly in those aged under 2 months. Three of the infants with C. trachomatis infection were born by cesarean section. Conjunctivitis and eosinophilia had occurred in 33.3% of the cases. Chest X rays were abnormal in 92.0% of cases. There was an association between C. trachomatis infection and the duration of hospitalization exceeding 15 days (p = 0.0398) and oxygen therapy (p = 0.0484). CONCLUSIONS There was a high prevalence of C. trachomatis respiratory infection in the population studied. The infection was associated with a more severe form of the disease, emphasizing the importance of testing pregnant women for this infection to avoid infection in the newborn infant.

Remoção de Pb2+ e Cr3+ em solução por zeólitas naturais associadas a rochas eruptivas da formação serra geral, bacia sedimentar do Paraná

The capacity of natural zeolites and its host rock (dacite) to remove Pb2+ and Cr3+ from aqueous solutions has been investigated. Results showed that both samples prefer to remove Pb2+ instead of Cr3+. Almost 100% of Pb2+ was removed from solutions with concentration until 50 mg L-1 and 100 mg L-1 of this metal, respectively by dacite and zeolite. The equilibrium of metals adsorption process was reached during the first 30 min by both materials. Na+ can be used to recover Pb2+, but not to remove Cr3+ from the treated samples. The Sips model showed a good fit for experimental data of this study.

Assinatura química de óxidos de ferro associados ao enriquecimento em ferro na Formação Ferrífera Bandada Cauê - Depósito de Esperança, Quadrilátero Ferrífero, Brasil: um estudo por ablação a laser ICP-MS

Manuscript ID: 30190. Received: 10/27/2014. Approved: 04/24/2015. ABSTRACT: Chemical signatures of iron oxides from dolomitic itabirite and high-grade iron ore from the Esperança deposit, located in the Quadrilátero Ferrífero, indicate that polycyclic processes involving changing of chemical and redox conditions are responsible for the iron enrichment on Cauê Formation from Minas Supergroup. Variations of Mn, Mg and Sr content in different generations of iron oxides from dolomitic itabirite, high-grade iron ore and syn-mineralization quartz-carbonate-hematite veins denote the close relationship between high-grade iron ore formation and carbonate alteration. This indicates that dolomitic itabirite is the main precursor of the iron ore in that deposit. Long-lasting percolation of hydrothermal fluids and shifts in the redox conditions have contributed to changes in the Y/Ho ratio, light/heavy rare earth elements ratio and Ce anomaly with successive iron oxide generations (martite-granular hematite), as well as lower abundance of trace elements including rare earth elements in the younger specularite generations.Chemical signatures of iron oxides from dolomitic itabirite and high-grade iron ore from the Esperanca deposit, located in the Quadrilatero Ferrifero, indicate that polycyclic processes involving changing of chemical and redox conditions are responsible for the iron enrichment on Caue Formation from Minas Supergroup. Variations of Mn, Mg and Sr content in different generations of iron oxides from dolomitic itabirite, high-grade iron ore and syn-mineralization quartz-carbonate-hematite veins denote the close relationship between high-grade iron ore formation and carbonate alteration. This indicates that dolomitic itabirite is the main precursor of the iron ore in that deposit. Long-lasting percolation of hydrothermal fluids and shifts in the redox conditions have contributed to changes in the Y/Ho ratio, light/heavy rare earth elements ratio and Ce anomaly with successive iron oxide generations (martite-granular hematite), as well as lower abundance of trace elements including rare earth elements in the younger specularite generations.

Efeito da adição de zeólita e vermiculita na lixiviação de potássio do solo

This study aimed to investigate the leaching of potassium (K+) from the soil (Oxisol) and to evaluate the efficiency of uptake of this ion with the addition of minerals with high cation exchange capacity (CEC), such as vermiculite and zeolite. Oxisol samples collected in Araraquara (SP) were physically, chemically and mineralogically characterized. The leaching of potassium from the soil was performed using two tests: (1) K+ leaching using columns filled with soil, in the presence of vermiculite or zeolite, and (2) incubating soils with vermiculite and zeolite for 30 days to analyze the interaction between these minerals and the K+ added to the soil in the presence/ absence of Ca2+ (as CaCO3). The soil has clay texture and low acidity, and is poor in nutrients and mineral sources of K+. Tests in soil columns proved that the texture and mineralogy of the soil play an important role in the retention of K+, promoting its rapid transfer from the soluble to the exchangeable phase. The Oxisol released, on average, only 2% of the K+ added to the soil, and this value decreased to 1.6% in the presence of vermiculite and to 1.2% in the presence of zeolite. In the incubation test, it was also noted that the K+ added to the soil is rapidly transferred to the exchangeable phase, and that the retention rate of this cation increases in the soil in the presence of vermiculite and zeolite. However, the presence of calcium in the soil does not favor the retention of K+ by vermiculite - which retains preferably cations of higher valence, such as Ca2+. The same is not true for zeolite, since its exchange sites hold preferably lower valence cations, such as K+. In general, it was found that the addition of minerals with high CEC increases the amount of K+ in the fixed phase, which can serve as a reserve of this ion, and decreases the loss by leaching of this nutrient from the soil.

SEM/EDS-Assisted LAM-ICPMS Analyses of Tourmaline of Tourmalinites Hosted in Serpentinites of the Paso Del Dragón Complex, Northeastern Uruguay

Tourmaline has successfully been applied in the interpretation of geologic processes. Thanks to certain characteristics, tourmaline can acquire a chemical signature from the rock in which it develops and can retain that signature through geologic time [2]. As a contribution to the understanding of the still debatable origin of Paso del Dragón Complex mafic-ultramafic rocks [3, 4], we started a SEM/EDSassisted LAM-ICPMS study of the Cerro La Tuna tourmaline, aiming at its chemical characterization.