Large Amounts Of Iron Research Articles

Absorption of Iron from Ferritin Is Independent of Heme Iron and Ferrous Salts in Women and Rat Intestinal Segments 3

AbstractFerritin iron from food is readily bioavailable to humans and has the potential for treating iron deficiency. Whether ferritin iron absorption is mechanistically different from iron absorption from small iron complexes/salts remains controversial. Here, we studied iron absorption (RBC 59Fe) from radiolabeled ferritin iron (0.5 mg) in healthy women with or without non-ferritin iron competitors, ferrous sulfate, or hemoglobin. A 9-fold excess of non-ferritin iron competitor had no significant effect on ferritin iron absorption. Larger amounts of iron (50 mg and a 99-fold excess of either competitor) inhibited iron absorption. To measure transport rates of iron that was absorbed inside ferritin, rat intestinal segments ex vivo were perfused with radiolabeled ferritin and compared to perfusion with ferric nitrilotriacetic (Fe-NTA), a well-studied form of chelated iron. Intestinal transport of iron absorbed inside exogenous ferritin was 14.8% of the rate measured for iron absorbed from chelated iron. In the steady state, endogenous enterocyte ferritin contained >90% of the iron absorbed from Fe-NTA or ferritin. We found that ferritin is a slow release source of iron, readily available to humans or animals, based on RBC iron incorporation. Ferritin iron is absorbed by a different mechanism than iron salts/chelates or heme iron. Recognition of a second, nonheme iron absorption process, ferritin endocytosis, emphasizes the need for more mechanistic studies on ferritin iron absorption and highlights the potential of ferritin present in foods such as legumes to contribute to solutions for global iron deficiency.

Maternal Iron Deficiency Heightens Fetal Susceptibility to Metabolic Syndrome in Adulthood

Iron is involved in the functional conformation of hemoglobin; it facilitates hemoglobin binding to oxygen. Iron also has a critical role in erythropoiesis. When erythroblasts proliferate and differentiate, they require large amounts of iron for hemoglobin synthesis. The heme moiety of erythroblasts requires iron for synthesis, and it regulates globin production. Thus, iron deficiency (ID) causes anemia, which is associated with many diseases. Because ID in the adult has a detrimental influence on erythrocyte function, maternal ID affects fetal development; thereafter, many physiological functions may be altered in the offspring. In rats fed a low-iron diet, although maternal ID did not cause severe anemia in the dam, brain development in the offspring was profoundly impaired; their offspring showed an increased auditory brainstem response time later in life, which suggested an impairment in brain development (1). Thus, subclinical anemia in the mother during early pregnancy may be a risk factor for abnormal central nervous system development in the fetus. The authors also showed that there was a time window for the susceptibility of brain development to ID (1). The fetal stage was thought to be the most vulnerable stage during development (2). The bottom line was that, when a fetus had experienced maternal ID, health problems become manifest in adulthood, despite adequate adult nutrition. Although animals are resistant to diet-induced obesity under normal circumstances, feeding with a high-fat diet (HFD) induces obesity in many experimental animals. Therefore, HFD is widely used as a model for the Western diet, which is thought to be an important risk factor for obesity. In turn, obesity increases the risk for metabolic syndrome, which includes cardiovascular disease. Therefore, the relationship between obesity and the Western diet has a profound impact on public health. Because the time range of highest vulnerability in brain development occurs in the fetal stage, one might expect that some abnormal development of the brain at that time could affect the adult’s susceptibility to obesity (3). In fact, the thrifty phenotype hypothesis proposed that poor nutrition in early life causes subsequent development of the metabolic syndrome in adults (4). It is now recognized that intrauterine undernutrition or excessive maternal feeding, including a HFD, affects the developmental programming of the offspring, and changes can be manifest in adulthood (5). Thus, the risk for adult health problems, particularly metabolic syndrome, can be markedly influenced by fetal and prenatal environmental exposures. Interestingly, many abnormal feeding behaviors are manifest only with the HFD. For example, heterozygote carriers of the proopiomelanocortin gene mutation are predisposed to obesity. Under normal feeding conditions, these mice maintained a normal weight; however, when fed a HFD, these mice became significantly obese (6). This also occurred with pharmacological receptor manipulations (7). Similar responses were observed in neuropeptide Y knockout mice. When fed normal chow, they look healthy, but when fed a HFD, they become obese (8). These are only a few examples, but they showed that the HFD is useful for revealing diseases. In this issue of Endocrinology, Bourque et al. (9) reported that mouse offspring exposed to maternal ID during the gestational period developed a susceptibility to HFD-induced obesity; in addition, they developed glucose intolerance and increases in blood pressure. These symptoms are indicative of metabolic syndrome. Dams fed a

Enrichment of Fe‐Containing Phases and Recovery of Iron and Its Oxides by Magnetic Separation from BOF Slags

AbstractSteel slag normally contains a large amount of iron and its oxides. Therefore, it is a potential renewable resource in case of inadequate iron ore supply. To recover the metals from steel slag, two types of BOF slags were remelted at 1873 K. The liquid slags were cooled using four types of cooling conditions, namely, water granulation, splashing, air cooling, and furnace cooling, to investigate the influence of cooling rate on mineral components, especially the enrichment behavior of Fe‐containing minerals. Subsequently, wet magnetic separation was conducted to examine the relations between iron recovery ratio and cooling conditions. The results show that the slags under the four cooling conditions mainly contained dicalcium silicate, RO phase, FetO, 2CaO(Fe,Al)2O3, and calcium ferrite. However, tricalcium silicate, 12CaO·7Al2O3, M‐A spinel, and free CaO and MgO were occasionally observed. The amount of glass matrix decreased, the Fe‐containing minerals increased, and the minerals more fully crystallized when the cooling rate of the liquid slag was decreased. From granulation to furnace cooling of the slags, the iron content in the recovered concentrate and the iron recovery ratio both increased. This result is in agreement with the findings on phase transformation through SEM analysis.

Crystal structures of (Mg 1- x ,Fe x )SiO 3 postperovskite at high pressures

X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg(0.9)Fe(0.1))SiO(3) and (Mg(0.6)Fe(0.4))SiO(3) at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO(3)-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density (ρ = 6.119(1) g/cm(3)) than the former (ρ = 5.694(8) g/cm(3)) due to both the larger amount of iron and the smaller ionic radius of Fe(2+) as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe(2+) also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe(2+) in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered.

Fur in Magnetospirillum gryphiswaldense influences magnetosomes formation and directly regulates the genes involved in iron and oxygen metabolism.

Magnetospirillum gryphiswaldense strain MSR-1 has the unique capability of taking up large amounts of iron and synthesizing magnetosomes (intracellular magnetic particles composed of Fe3O4). The unusual high iron content of MSR-1 makes it a useful model for studying biological mechanisms of iron uptake and homeostasis. The ferric uptake regulator (Fur) protein plays a key role in maintaining iron homeostasis in many bacteria. We identified and characterized a fur-homologous gene (MGR_1314) in MSR-1. MGR_1314 was able to complement a fur mutant of E. coli in iron-responsive manner in vivo. We constructed a fur mutant strain of MSR-1. In comparison to wild-type MSR-1, the mutant strain had lower magnetosome formation, and was more sensitive to hydrogen peroxide and streptonigrin, indicating higher intracellular free iron content. Quantitative real-time RT-PCR and chromatin immunoprecipitation analyses indicated that Fur protein directly regulates expression of several key genes involved in iron transport and oxygen metabolism, in addition it also functions in magnetosome formation in M. gryphiswaldense.

Assessing the role of spent fuel surfaces during leaching in presence of hydrogen by using Cr(VI) as a redox marker

ABSTRACTIn many deep repository concepts spent nuclear fuel (SNF) will be disposed in canisters containing large amounts of iron. Intrusion of groundwater in a failed canister may occur under the presence of hydrogen, expected to be produced by the anoxic corrosion of iron. Compelling evidence now exists that hydrogen inhibits oxidative dissolution of SNF, the mechanism is however not fully understood. Hydrogen generally requires a catalyst in order to operate as a reductant. The metallic inclusions (ε-particles) present in SNF are a likely catalyst for this process due to their noble metal content. There is also evidence that the SNF UO2 matrix or doping of the UO2 with fission products can activate hydrogen. In most spent fuel experiments carried out under hydrogen, a decrease in concentration of all redox sensitive nuclides originating from a pre-oxidized layer is observed. Given their low concentrations and abundance in the fuel, it has however been difficult to detect any reductive precipitation on the fuel surfaces.In this study, Cr(VI) oxyanions were employed as a redox sensitive marker, as Cr(VI) is expected to precipitate as Cr(III) oxide on the catalyst that activates hydrogen.In the experiments PWR spent fuel (43 MWd/kgU) was leached in simulated groundwater (10 mM NaCl, 2 mM NaHCO3) at 25 and 70 ◦C under 5 MPa of hydrogen and dissolved Cr(VI). Dark green, Cr(III)-oxide was found to precipitate; mapping by electron microscopy (SEM-WDS) evidenced a Cr rich layer covering the fuel, suggesting that the whole fuel surface is catalyzing the reduction of chromium.

Leaky lysosomes in lung transplant macrophages: azithromycin prevents oxidative damage

BackgroundLung allografts contain large amounts of iron (Fe), which inside lung macrophages may promote oxidative lysosomal membrane permeabilization (LMP), cell death and inflammation. The macrolide antibiotic azithromycin (AZM) accumulates 1000-fold inside the acidic lysosomes and may interfere with the lysosomal pool of Fe.ObjectiveOxidative lysosomal leakage was assessed in lung macrophages from lung transplant recipients without or with AZM treatment and from healthy subjects. The efficiency of AZM to protect lysosomes and cells against oxidants was further assessed employing murine J774 macrophages.MethodsMacrophages harvested from 8 transplant recipients (5 without and 3 with ongoing AZM treatment) and 7 healthy subjects, and J774 cells pre-treated with AZM, a high-molecular-weight derivative of the Fe chelator desferrioxamine or ammonium chloride were oxidatively stressed. LMP, cell death, Fe, reduced glutathione (GSH) and H-ferritin were assessed.ResultsOxidant challenged macrophages from transplants recipients without AZM exhibited significantly more LMP and cell death than macrophages from healthy subjects. Those macrophages contained significantly more Fe, while GSH and H-ferritin did not differ significantly. Although macrophages from transplant recipients treated with AZM contained both significantly more Fe and less GSH, which would sensitize cells to oxidants, these macrophages resisted oxidant challenge well. The preventive effect of AZM on oxidative LMP and J774 cell death was 60 to 300 times greater than the other drugs tested.ConclusionsAZM makes lung transplant macrophages and their lysososomes more resistant to oxidant challenge. Possibly, prevention of obliterative bronchiolitis in lung transplants by AZM is partly due to this action.

Investigation on Properties of Bentonite Type in Cold Bonded Pelletization of Flue Dust

In the integrated steel mills fabrication processes, the by-product of flue dust and electrostatic precipitator dust were found to be rich with large amounts of iron and carbon content and it could be recycled as a raw material for blast furnaces. In this study, we use the “Cold-bonded Pellet; CBP” technique to prepare the recycling samples for subsequent processing. Therefore, this study investigated under a fixed amount of bentonite added, the choice of different types of bentonite on the powder granulation performance and strength of particle duration effects, bentonite used as a basis for adjustment. The results showed that Bentonite samples of the granulation efficiency increase, relative to its yield and the rate of sticky increase. In general, CBP particle compressive strength increased, duration have increased, and found that curing condition B are large than the A method. In addition, by particle size analysis results show that, bentonite average particle size of 11-12μm have better compressive strength. Comprehensive assessment of granulation and mechanical properties, of which A label in four Bentonite can be preferred.

RCW 86: A TYPE Ia SUPERNOVA IN A WIND-BLOWN BUBBLE

We report results from a multi-wavelength analysis of the Galactic SNR RCW 86, the proposed remnant of the supernova of 185 A.D. We report new infrared observations from {\it Spitzer} and {\it WISE}, where the entire shell is detected at 24 and 22 $\mu$m. We fit the infrared flux ratios with models of collisionally heated ambient dust, finding post-shock gas densities in the non-radiative shocks of 2.4 and 2.0 cm$^{-3}$ in the SW and NW portions of the remnant, respectively. The Balmer-dominated shocks around the periphery of the shell, large amount of iron in the X-ray emitting ejecta, and lack of a compact remnant support a Type Ia origin for this remnant. From hydrodynamic simulations, the observed characteristics of RCW 86 are successfully reproduced by an off-center explosion in a low-density cavity carved by the progenitor system. This would make RCW 86 the first known case of a Type Ia supernova in a wind-blown bubble. The fast shocks ($> 3000$ km s$^{-1}$) observed in the NE are propagating in the low-density bubble, where the shock is just beginning to encounter the shell, while the slower shocks elsewhere have already encountered the bubble wall. The diffuse nature of the synchrotron emission in the SW and NW is due to electrons that were accelerated early in the lifetime of the remnant, when the shock was still in the bubble. Electrons in a bubble could produce gamma-rays by inverse-Compton scattering. The wind-blown bubble scenario requires a single-degenerate progenitor, which should leave behind a companion star.

Iron-dependent formation of reactive oxygen species and glutathione depletion after accumulation of magnetic iron oxide nanoparticles by oligodendroglial cells

Magnetic iron oxide nanoparticles (IONP) are currently used for various neurobiological applications. To investigate the consequences of a treatment of brain cells with such particles, we have applied dimercaptosuccinate (DMSA)-coated IONP that had an average hydrodynamic diameter of 60 nm to oligodendroglial OLN-93 cells. After exposure to 4 mM iron applied as DMSA–IONP, these cells increased their total specific iron content within 8 h 600-fold from 7 to 4,200 nmol/mg cellular protein. The strong iron accumulation was accompanied by a change in cell morphology, although the cell viability was not compromized. DMSA–IONP treatment caused a concentration-dependent increase in the iron-dependent formation of reactive oxygen species and a decrease in the specific content of the cellular antioxidative tripeptide glutathione. During a 16 h recovery phase in IONP-free culture medium following exposure to DMSA–IONP, OLN-93 cells maintained their high iron content and replenished their cellular glutathione content. These data demonstrate that viable OLN-93 cells have a remarkable potential to deal successfully with the consequences of an accumulation of large amounts of iron after exposure to DMSA–IONP.

Immunocytochemical analysis of the subcellular distribution of ferritin in Imperata cylindrica (L.) Raeuschel, an iron hyperaccumulator plant

Ferritin is of interest at the structural and functional level not only as storage for iron, a critical element, but also as a means to prevent cell damage produced by oxidative stress. The main objective of this work was to confirm by immunocytochemistry the presence and the subcellular distribution of the ferritin detected by Mösbauer spectroscopy in Imperata cylindrica, a plant which accumulates large amounts of iron. The localization of ferritin was performed in epidermal, parenchymal and vascular tissues of shoots and leaves of I. cylindrica. The highest density of immunolabeling in shoots appeared in the intracellular space of cell tissues, near the cell walls and in the cytoplasm. In leaves, ferritin was detected in the proximity of the dense network of the middle lamella of cell walls, following a similar path to that observed in shoots. Immunolabeling was also localized in chloroplasts. The abundance of immunogold labelling in mitochondria for I. cylindrica was rather low, probably because the study dealt with tissues from old plants. These results further expand the localization of ferritin in cell components other than chloroplasts and mitochondria in plants.

TNF-α-stimulated macrophages protect A549 lung cells against iron and oxidation

Previously, we have shown that TNF-α protects iron-exposed J774 macrophages against iron-catalyzed oxidative lysosomal disruption and cell death by increasing reduced glutathione and H-ferritin in cells. Because J774 cells are able to harbor large amounts of iron, which is potentially harmful in a redox-active state, we hypothesized that TNF-α-stimulated J774 macrophages will prevent iron-driven oxidative killing of alveolar epithelial A549 cells in co-culture. In the present study, iron trichloride (which is endocytosed by cells as hydrated iron-phosphate complexes) was mainly deposited inside the lysosomes of J774 macrophages, while A549 cells, equally iron exposed, accumulated much less iron. When challenged by oxidants, however, reactive lysosomal iron in A549 cells promoted lysosomal disruption and cell death, particularly in the presence of TNF-α. This effect resulted from an elevation in ROS generation by TNF-α, while a compensatory upregulation of protective molecules (H-ferritin and/or reduced glutathione) by TNF-α was absent. A549 cell death was particularly pronounced when iron and TNF-α were present in the conditioned medium during oxidant challenge; thus, iron-driven oxidative reactions in the culture medium were a much greater hazard to A549 cells than those taking place inside their lysosomes. Consequently, the iron chelator, deferoxamine, efficiently prevented A549 cell death when added to the culture medium during an oxidant challenge. In co-cultures of TNF-α-stimulated lung cells, J774 macrophages sequestered iron inside their lysosomes and protected A549 cells from oxidative reactions and cell death. Thus, the collective effect of TNF-α on co-cultured lung cells was mainly cytoprotective.

Artificial mycorrhization does not influence the effects of iron availability on Fe, Zn, Cu, Pb and Cd accumulation in leaves of a heavy metal tolerant white poplar clone

In this study, the phytoextraction capacity of a heavy metal tolerant white poplar clone, grown in the presence of high iron availability and/or mycorrhizas was evaluated. A large amount of iron in available form was determined in initial high concentrations in leaf, which declined along time and affected Cd, Cu, Pb and Zn accumulation. Natural and artificial mycorrhization did not influence these dynamics.

A New Role for Heme, Facilitating Release of Iron from the Bacterioferritin Iron Biomineral

Bacterioferritin (BFR) from Escherichia coli is a member of the ferritin family of iron storage proteins and has the capacity to store very large amounts of iron as an Fe(3+) mineral inside its central cavity. The ability of organisms to tap into their cellular stores in times of iron deprivation requires that iron must be released from ferritin mineral stores. Currently, relatively little is known about the mechanisms by which this occurs, particularly in prokaryotic ferritins. Here we show that the bis-Met-coordinated heme groups of E. coli BFR, which are not found in other members of the ferritin family, play an important role in iron release from the BFR iron biomineral: kinetic iron release experiments revealed that the transfer of electrons into the internal cavity is the rate-limiting step of the release reaction and that the rate and extent of iron release were significantly increased in the presence of heme. Despite previous reports that a high affinity Fe(2+) chelator is required for iron release, we show that a large proportion of BFR core iron is released in the absence of such a chelator and further that chelators are not passive participants in iron release reactions. Finally, we show that the catalytic ferroxidase center, which is central to the mechanism of mineralization, is not involved in iron release; thus, core mineralization and release processes utilize distinct pathways.

Iron solid-phase differentiation along a redox gradient in basaltic soils

Iron compounds in soil are multifunctional, providing physical structure, ion sorption sites, catalytic reaction-centers, and a sink for respiratory electrons. Basaltic soils contain large quantities of iron that reside in different mineral and organic phases depending on their age and redox status. We investigated changes in soil iron concentration and its solid-phase speciation across a single-aged (400 ky) lava flow subjected to a gradient in precipitation (2200–4200 mm yr −1) and hence redox history. With increasing rainfall and decreasing Eh, total Fe decreased from about 25% to <1% of the soil mass. Quantitative speciation of soil solid-phase iron was constrained by combining 57Fe Mössbauer spectroscopy (MBS) at 295 and 4.2 K with powder X-ray diffraction, selective chemical extractions, and magnetic susceptibility measurements. This approach allowed us to partition iron into (1) nanoparticulate and microcrystalline Fe III-(oxy)hydroxides, (2) microcrystalline and bulk Fe III-oxides, (3) organic/silicate bound Fe III, and (4) ferrous iron. The Fe III-(oxy)hydroxide fraction dominated solid-phase Fe, exhibiting a crystallinity continuum based on magnetic ordering temperature. The continuum extended from well-ordered microcrystalline goethite through nanocrystalline Fe III-(oxy)hydroxides to a nano Fe III-(oxy)hydroxide phase of extremely low crystallinity. Magnetic susceptibility was correlated ( R 2 = 0.77) with Fe III-oxide concentration, consistent with a contribution of maghemite to the otherwise hematite dominated Fe-oxide fraction. The Fe III-(oxy)hydroxide fraction of total Fe decreased with increasing rainfall and was replaced by corresponding increase in the organic/silicate Fe III fraction. The crystallinity of the Fe III-(oxy)hydroxides also decreased with increasing rainfall and leaching, with the most disordered members of the crystallinity continuum, the nano Fe III-(oxy)hydroxides, gaining proportional abundance in the wetter sites. This finding runs counter to the conventional kinetic expectation of preferential removal of the most disordered minerals in a reductive dissolution-dominated environment. We suggest the persistence of highly disordered Fe phases reflects the dynamic redox conditions of these upland soils in which periods of anoxia are marked by high water-throughput and Fe 2+(aq) removal, while periodic Fe oxidation events occur in the presence of high concentrations of organic matter. Our 57Fe Mössbauer study shows basalt-derived nano-scale Fe III phases are more disordered than current synthetic analogs and have nano-structural characteristics that are linked to their formation environment.

GROWTH AND IRON-MANGANESE RELATIONSHIPS IN DRY BEAN AS AFFECTED BY FOLIAR AND SOIL APPLICATIONS OF IRON AND MANGANESE IN A CALCAREOUS SOIL

Manganese (Mn) deficiency may be induced by adding large quantities of iron (Fe), provided that soil manganese is marginally deficient. Results of a greenhouse study showed that iron soil application did not influence shoot dry matter yield of dry bean due to the fact that the iron:manganese ratio in aerial parts of dry bean was higher than 0.4. A foliar spray of 2% iron sulfate significantly reduced it probably due to the high level of shoot iron and iron:manganese ratio greater than 4. Iron application decreased concentration/uptake of shoot manganese due to the iron-manganese antagonistic relationships. Mangenese soil application is not an effective method in correction of manganese deficiency induced by iron fertilizers. Iron did not affect root manganese uptake, indicating that manganese absorption was not affected by iron application. Both manganese/iron soil tests are recommended in calcareous soils with manganese soil test in marginal range.

Oxidative Roasting of Low Grade Zinc Sulfide Concentrate from Gagok Mine in Korea

A new process for utilizing low grade zinc sulfide concentrate containing a large amount of iron as a zinc and iron resource has been developed in Korea. The process largely consists of oxidative roasting and reduction-volatilization processes. In this process, zinc is recovered as zinc oxide form in the gas phase and iron is concentrated as partially reduced iron oxide compounds in the residue phase. In the present work, a kinetic study on the oxidative roasting of low grade zinc sulfide concentrate rich in iron obtained after several mineral separation processes at Gagok mine in Korea was experimentally investigated. The experiments were carried out to understand the oxidative roasting process of the zinc concentrate over a temperature range of 998 to 1073 K under air using a thermogravimetric method. The oxidative roasting rate of the zinc concentrate was found to be relatively fast under the whole temperature range and almost 95% of sulfur contained in the concentrate was removed after the oxidative roasting at 1073 K for 20 min. Sulfur removal ratio as a function of time has been analyzed by using a spherical shrinking-core model.

Periodic bioleaching of refractory gold-bearing pyrite ore

The main characteristics of a periodic bioleaching of the refractory gold-bearing pyrite ore from the Tandzut deposit (Armenia) with the help of moderate thermophilic bacterium Sulfobacillus thermosulfidooxi-dans subsp. asporogenes and original thermotolerant strains Leptospirillum spp. were studied. The optimal pH for oxidizing the ore by S. thermosulfidooxidans subsp. asporogenes was 1.8; the pulp density providing maximal iron leaching rate was 10%. The intensity of oxidation processes decreased at higher ore concentrations. When using S. thermosulfidooxidans subsp. asporogenes, the largest amount of iron passed into the solution at the initial oxidant (Fe3+) concentration of 1.3 g/l. Cocultivation of S. thermosulfidooxidans subsp. asporogenes and Leptospirillum spp. increased the degree of pyrite ore leaching to 98.4% vs. 34.1% in the case of the former bacterium alone.

Surface reactivity and layer analysis of chemisorbed reaction films in the surface-chemical environment of alkyl octadecenoates

Studies on surface reactivity of substrate iron (Fe-particles) were made in the tribo-chemical environment of alkyl octadecenoates. Two alkyl octadecenoates namely ethyl octadecenoate and methyl 12-hydroxy octadecenoate, slightly different in their chemical nature, were taken for preparing the chemisorbed reaction films (CRF) at the temperature 100 ± 5°C. The reaction products collected in the composite (amorphous) phase were isolated into three different solvent-soluble fractions (sub-layer films) using polar solvents of increasing polar strength. The FTIR analysis of these films showed that these were primarily organic in nature and were composed of alkyl and/or aryl hydroxy ethers, unsaturated hydroxy ketones, and aromatic structures chemically linked with iron surface. These reaction films also contained large amount of iron (Fe). Further, these film fractions also showed varying thermal behaviour during thermal decomposition in the temperature range of 50–800°C when thermally evaluated in the nitrogen environment.

Total carbon measurement in whole tropical soil sample

Soils are an important component in the biogeochemical cycle of carbon, storing about four times more carbon than biomass plants and nearly three times more than the atmosphere. Moreover, the carbon content is directly related on the capacity of water retention, fertility, among other properties. Thus, soil carbon quantification in field conditions is an important challenge related to carbon cycle and global climatic changes. Nowadays, Laser Induced Breakdown Spectroscopy (LIBS) can be used for qualitative elemental analyses without previous treatment of samples and the results are obtained quickly. New optical technologies made possible the portable LIBS systems and now, the great expectation is the development of methods that make possible quantitative measurements with LIBS. The goal of this work is to calibrate a portable LIBS system to carry out quantitative measures of carbon in whole tropical soil sample. For this, six samples from the Brazilian Cerrado region (Argisoil) were used. Tropical soils have large amounts of iron in their compositions, so the carbon line at 247.86 nm presents strong interference of this element (iron lines at 247.86 and 247.95). For this reason, in this work the carbon line at 193.03 nm was used. Using methods of statistical analysis as a simple linear regression, multivariate linear regression and cross-validation were possible to obtain correlation coefficients higher than 0.91. These results show the great potential of using portable LIBS systems for quantitative carbon measurements in tropical soils.