Iron oxides in plinthic soils on sedimentary deposits in northeastern Brazil

This study was conducted to examine the distribution and nature of Fe oxides in plinthic soils on the sediments of Barreiras Group (in the state of Piauí) and Itapecuru Formation (in the state of Maranhão) in Northeastern Brazil. Four pedons were selected: a "plinthic, dystrophic, epieutrophic Gray Podzolic with low activity clay" and a "dystrophic Plinthosol with low activity clay" (both Plinthic Kandiustalfs) on the Barreiras sediments, as well as an "eutrophic Plinthosol with low activity clay" and an "allic Plinthosol with low activity clay" (both Plinthustalfs) on the Itapecuru sediments. Soil samples were fractionated into > 2 mm (pisoliths), water-stable aggregates (plinthite) and matrices; the aggregates and matrices were further fractionated into sand, silt and clay sizes. Dithionite extractable iron (Fe d) and aluminum (Al d), as well as oxalate extractable iron (Fe o), were determined for all fractions, and X-ray diffraction analyses were performed on the pisoliths. It was observed that the Plinthustalfs contain more iron oxides, exhibit more extensive plinthite development and have a greater potential for further plinthite development than the Kandiustalfs. The distribution of values for the Fe d indicates that plinthite formation and induration in all soils were accompanied by an enrichment of Fe oxides in all particle size fractions. This Fe segregation was accompanied by aggregation of particles leading to a greater degree of crystallinity, as indicated by analysis of the ratios of Al d:Fe d. Larger ratios of goethite to hematite, and relatively smaller amounts of silicates in the more mature pisoliths were revealed by X-ray diffraction analysis. Ratios of Al d:Fe d were larger in the Kandiustalfs than in the Plinthustalfs, and also larger than expected for Al-substituted Fe oxides. According to ratios of Al d:Fe d, Fe mobilization in all soils has likely occurred under reducing conditions, facilitated by organic matter on the soil surface.

Iron oxides and quality of organic matter in sugarcane harvesting systems

Improvements in working conditions, sustainable production, and competitiveness have led to substantial changes in sugarcane harvesting systems. Such changes have altered a number of soil properties, including iron oxides and organic matter, as well as some chemical properties, such as the maximum P adsorption capacity of the soil. The aim of this study was to characterize the relationship between iron oxides and the quality of organic matter in sugarcane harvesting systems. For that purpose, two 1 ha plots in mechanically and manually harvested fields were used to obtain soil samples from the 0.00-0.25 m soil layer at 126 different points. The mineralogical, chemical, and physical results were subjected to descriptive statistical analyses, such as the mean comparison test, as well as to multivariate statistical and principal component analyses. Multivariate tests allowed soil properties to be classified in two different groups according to the harvesting method: manual harvest with the burning of residual cane, and mechanical harvest without burning. The mechanical harvesting system was found to enhance pedoenvironmental conditions, leading to changes in the crystallinity of iron oxides, an increase in the humification of organic matter, and a relative decrease in phosphorus adsorption in this area compared to the manual harvesting system.

Effect of adsorbed polyaniline on the thermal stability of iron and arsenic oxides

Iron and arsenic oxide grains are coated with the conducting organic polymer polyaniline. The obtained samples were characterized by infrared spectroscopy, SEM, conducting measurements and thermogravimetry. The thermal stability of both oxides are increased. For As2O3 the sublimation temperature is increased from 165ºC in the pure oxide to 206ºC in the polymer modified sample. The pure Fe3O4 sample exhibits sublimation at 780ºC whereas the polyaniline coated oxide is stable until at least 1000ºC.

Oxochloroalkoxide of the Cerium (IV) and Titanium (IV) as oxides precursor

The Cerium (IV) and Titanium (IV) oxides mixture (CeO2-3TiO2) was prepared by thermal treatment of the oxochloroisopropoxide of Cerium (IV) and Titanium (IV). The chemical route utilizing the Cerium (III) chloride alcoholic complex and Titanium (IV) isopropoxide is presented. The compound Ce5Ti15Cl16O30 (iOPr)4(OH-Et)15 was characterized by elemental analysis, FTIR and TG/DTG. The X-ray diffraction patterns of the oxides resulting from the thermal decomposition of the precursor at 1000 °C for 36 h indicated the formation of cubic cerianite (a = 5.417Å) and tetragonal rutile (a = 4.592Å) and (c = 2.962 Å), with apparent crystallite sizes around 38 and 55nm, respectively.

Elimination of dyes from aqueous solutions using iron oxides and chitosan as adsorbents: a comparative study

This work investigates the adsorption of Alizarin, Eriochrome Blue Black R and Fluorescein using chitosan, goethite and magnetite as adsorbents. For Alizarin, the best adsorbent is chitosan with a Langmuir parameter of 15.8 mmol dye/g adsorbent. For Eriochrome Blue Black R only 1.94 mmol dye/g chitosan is adsorbed. Langmuir parameters for the Alizarin adsorption on both iron oxides display one or two orders of magnitude lower than for chitosan and two orders of magnitude lower in the case of Eriochrome Blue Black R. Fluorescein does not adsorb in appreciable amounts on chitosan and it presents the lower affinity on the iron oxides.

Influence of basic properties of Mg,Al-mixed oxides on their catalytic activity in knoevenagel condensation between benzaldehyde and phenylsulfonylacetonitrile

The catalytic performance of Mg,Al-mixed oxides (MO20, MO25 and MO33) derived from hydrotalcites was evaluated in the Knoevenagel reaction between benzaldehyde and phenylsulfonylacetonitrile at 373 and 383 K. The best results were obtained for the sample MO20 that presented the highest basic sites density and external area and the smallest crystallite sizes. The relative amount of basic sites with weak to intermediate strength also played an important role on catalytic performance. By increasing the catalyst content from 1 to 5 wt.% at 383 K, a complete conversion of the reactants is attained, producing α-phenylsulfonylcinnamonitrile with a selectivity of 100%.

Preparation of glasses and glass ceramics of heavy metal oxides containing silver: optical, structural and electrochemical properties

Silver containing heavy metal oxide glasses and glass ceramics of the system WO3-SbPO4-PbO-AgCl with different AgCl contents have been prepared and their thermal, structural and optical properties characterized. Glass ceramics containing metallic silver nanoparticles have been prepared by annealing glass samples at temperatures above the glass transition and analyzed by transmission electron microscopy and energy dispersive X-ray microanalysis. The presence of the metallic clusters has been also confirmed by the observation of a surface plasmon resonance band in the visible range. Cyclic voltammetric measurements indicated the presence of metallic silver into the glasses, even before to perform the thermal treatment.

Thermal decomposition of solid state compounds of lanthanide and yttrium benzoates in CO2 atmosphere

Solid-state Ln-Bz compounds, where Ln stands for trivalent lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetric and differential thermal analysis in a CO2 atmosphere were used to study the thermal decomposition of these compounds.

Synthesis and magnetic studies of copper(II)-lanthanide(III) 5-bromosalicylideneglycylglycine

The physico-chemical properties of the new 3d-4f heteronuclear complexes with general formula LnCu3(C11H8N2 O4Br)3·13H2O (where Ln = Pr, Eu, Gd, Tb, Er, Yb and H3(C11H8N2 O4Br) - 5-bromosalicylideneglycylglycine) were studied. The compounds were characterized by elemental, spectral and thermal analyses and magnetic measurements. The formation of Schiff base is evidenced by a strong band at ca. 1646-1650 cm-1 attributable to C=N stretching mode. The presence of water molecules is confirmed by broad absorptions with maximum at 3360 - 3368 cm-1. The Cu(II)-Ln(III) complexes are stable up to ca. 318 K. During dehydration process the water molecules are lost probably in two stages. The magnetic susceptibility data for these complexes change with temperature according to the Curie-Weiss law.

Synthesis, characterization and thermal behaviour of heavy trivalent lanthanide malonates

Solid-state Ln-L compounds, where Ln stands for heavy trivalent lanthanides (Tb-Lu) and L is malonate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The dehydration of the compounds begins at 303 K and the anhydrous compounds are stable up to 548 K. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds.

Nitric oxide, cholesterol oxides and endothelium-dependent vasodilation in plasma of patients with essential hypertension

The objective of the present study was to identify disturbances of nitric oxide radical (·NO) metabolism and the formation of cholesterol oxidation products in human essential hypertension. The concentrations of·NO derivatives (nitrite, nitrate, S-nitrosothiols and nitrotyrosine), water and lipid-soluble antioxidants and cholesterol oxides were measured in plasma of 11 patients with mild essential hypertension (H: 57.8 ± 9.7 years; blood pressure, 148.3 ± 24.8/90.8 ± 10.2 mmHg) and in 11 healthy subjects (N: 48.4 ± 7.0 years; blood pressure, 119.4 ± 9.4/75.0 ± 8.0 mmHg).Nitrite, nitrate and S-nitrosothiols were measured by chemiluminescence and nitrotyrosine was determined by ELISA. Antioxidants were determined by reverse-phase HPLC and cholesterol oxides by gas chromatography. Hypertensive patients had reduced endothelium-dependent vasodilation in response to reactive hyperemia (H: 9.3 and N: 15.1% increase of diameter 90 s after hyperemia), and lower levels of ascorbate (H: 29.2 ± 26.0, N: 54.2 ± 24.9 µM), urate (H: 108.5 ± 18.9, N: 156.4 ± 26.3 µM), ß-carotene (H: 1.1 ± 0.8, N: 2.5 ± 1.2 nmol/mg cholesterol), and lycopene (H: 0.4 ± 0.2, N: 0.7 ± 0.2 nmol/mg cholesterol), in plasma, compared to normotensive subjects. The content of 7-ketocholesterol, 5alpha-cholestane-3ß,5,6ß-triol and 5,6alpha-epoxy-5alpha-cholestan-3alpha-ol in LDL, and the concentration of endothelin-1 (H: 0.9 ± 0.2, N: 0.7 ± 0.1 ng/ml) in plasma were increased in hypertensive patients. No differences were found for ·NO derivatives between groups. These data suggest that an increase in cholesterol oxidation is associated with endothelium dysfunction in essential hypertension and oxidative stress, although ·NO metabolite levels in plasma are not modified in the presence of elevated cholesterol oxides.

Determination of reactivity rates of silicate particle-size fractions

The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves), and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides) was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

Reconnaissance study of macrofossils from the upper purus river - Western Amazônia.

Fossils of wood, bone and teeth found along the Upper Purus River οf Amazonia. were studied using conventional microscopy and scanning electron microscopy. Mass spectometry was also used to investigate minor and trace element signatures of bone samples.The microsopy studies showed that there was little alteration of original textures. In the fossil wood samples, identified In thin section as tropical hardwood trees, the replacement of the original material with siderite suggests that fossilization occured in shallow sediments in which interstitial waters were saturated with respect to iron carbenate. In samples of both fossilized bone and wood, precipitation of secondary iron phases was commonly observed in cracks and voids. Other secondary phases Included silica, iron oxides, manganese carbonate. The intimate assοciation οf these secondary phases with the original biological structures could be evidence for a microbiological role in the formation of these phases. The similarity in rare earth element (REE) signatures for 2 fossil bone samples from different modern locations indicates their having shared similar diagenetic histories.The virtually complete preservation of original textures suggests that microscοpic studies could be useful in classifying fossil and even in identifying original materials. Rare carth signatures in fossilized bone may reflect ground water compositions at the time of fossilization.

Lipid peroxidation and nitric oxide inactivation in postmenopausal women

OBJECTIVE: To assess the effect of endogenous estrogens on the bioavailability of nitric oxide (·NO) and in the formation of lipid peroxidation products in pre- and postmenopausal women. METHODS: NOx and S-nitrosothiols were determined by gaseous phase chemiluminescence, nitrotyrosine was determined by ELISA, COx (cholesterol oxides) by gas chromatography, and cholesteryl linoleate hydroperoxides (CE18:2-OOH), trilinolein (TG18:2-OOH), and phospholipids (PC-OOH) by HPLC in samples of plasma. RESULTS: The concentrations of NOx, nitrotyrosine, COx, CE18:2-OOH, and PC-OOH were higher in the postmenopausal period (33.8±22.3 mM; 230±130 nM; 55±19 ng/mL; 17±8.7 nM; 2775±460 nM, respectively) as compared with those in the premenopausal period (21.1±7.3 mM; 114±41 nM; 31±13 ng/mL; 6±1.4 nM; 1635±373 nM). In contrast, the concentration of S-nitrosothiols was lower in the postmenopausal period (91±55 nM) as compared with that in the premenopausal p in the premenopausal period (237±197 nM). CONCLUSION: In the postmenopausal period, an increase in nitrotyrosine and a reduction of S-nitrosothiol formation, as well as an increase of COx, CE18:2-OOH and PC-OOH formation occurs. Therefore, •NO inactivation and the increase in lipid peroxidation may contribute to endothelial dysfunction and to the greater risk for atherosclerosis in postmenopausal women.

Avaliação da capacidade de fixação de fósforo pelo solo

Phosphate "fixation" is the convertion of soluble into insoluble phosphate in the soil. There are many factors conditioning phosphate fixation by soil such as reactions originating less soluble compounds (phosphates of iron, aluminum, calcium, magnesium, etc.), PO4-3 adsorption by the colloidal fraction of soils, PO4-3 absorption by the soil microflora, etc. Certain soils of the state of São Paulo (Brazil) are relatively rich in both iron and aluminum oxides. PO4-3 fixation, using P31 and P32 has been verified by researchers, specially with "Terra Roxa". The known methods for fixation evaluation are conventional as this depends on phosphate solution concentration, pH, time of contact between soil and solution, relation of sample weight to solution volume, shaking time, etc. In this experiment, the following conventional method was used: 4 g of soil were shaken for 15 minutes at 30-40 rpm, in 300 ml Erlenmeyer flask in a Wagner shaking machine, together with 100 ml of 0,03 normal phosphate solution (being 0,01 normal as PO4-3 contributed by H8PO4 and 0,02 normal as PO4-3 from KH2PO4). After shaking it was set aside for 24 hours and then filtered. Phosphate was determined in a suitable aliquot of both the original solution (blank) and the soil extract, by the vanadomolibidic-phosphoric acid method. From phosphate concentration in the blank minus phosphate concentration in the soil stract the rate of fixation by 100 g of soil was calculated. The data obtained show that "Terra Roxa" and "Terra Roxa Misturada" have a fairly high PO4-3 fixation capacity, varying from 10 to 24 milliequivalents of PO4-3 per 100 g of soil.