Accuracy improvement on quantitative analysis of the total iron content in branded iron ores by laser-induced breakdown spectroscopy combined with double back propagation artificial neural network

The rapid and accurate quantitative analysis of total iron (TFe) content in iron ores is extremely important in global iron ores trade. Due to the matrix effect among iron ores...

Remotely sensed estimation of total iron content in soil with harmonic analysis and BP neural network

Background The estimation of total iron content at the regional scale is of much significance as iron deficiency has become a routine problem for many crops. Methods In this study, a novel method for estimating total iron content in soil (TICS) was proposed using harmonic analysis (HA) and back propagation (BP) neural network model. Several data preprocessing methods of first derivative (FD), wavelet packet transform (WPT), and HA were conducted to improve the correlation between the soil spectra and TICS. The principal component analysis (PCA) was exploited to obtained three kinds of characteristic variables (FD, WPT-FD, and WPT-FD-HA) for TICS estimation. Furthermore, the estimated accuracy of three BP models based on these variables was compared. Results The results showed that the BP models of different soil types based on WPT-FD-HA had better estimation accuracy, with the highest R2 value of 0.95, and the RMSE of 0.68 for the loessial soil. It was proved that the characteristic variable obtained by harmonic decomposition improved the validity of the input variables and the estimation accuracy of the TICS models. Meanwhile, it was identified that the WPT-FD-HA-BP model can not only estimate the total iron content of a single soil type with high accuracy but also demonstrate a good effect on the estimation of TICS of mixed soil. Conclusion The HA method and BP neural network combined with WPT and FD have great potential in TICS estimation under the conditions of single soil and mixed soil. This method can be expected to be applied to the prediction of crop biochemical parameters.

Pyrrhotite–silicate melt partitioning of rhenium and the deep rhenium cycle in subduction zone

The Re-Os isotopic system serves as an important tracer of recycled crust in Earth’s deep mantle because of the large Re/Os ratios and time-integrated enrichment of radiogenic Os in Earth’s crust. However, the Re distribution in Earth’s known reservoirs is mass imbalanced, and the behavior of Re during subduction remains little understood. We performed laboratory experiments to determine the partition coefficients of Re between pyrrhotite and silicate melt (DRepo/sm) at 950–1080 °C, 1–3 GPa, and oxygen fugacities (in log units relative to the fayalite-magnetite-quartz [FMQ] buffer) of FMQ –1.3 to FMQ +2. The obtained DRepo/sm values are 200–25,000, which increase with decreasing oxygen fugacity and the total iron content (FeOtot) of silicate melt but decrease with increasing temperature or decreasing pressure. Applying DRepo/sm to constrain the behavior of Re during slab melting demonstrates that slab melts contribute minimal Re to the sub-arc mantle, with most Re dissolved in sulfides subducted into Earth’s deep mantle. Deep storage of recycled oceanic basalts and sediments can explain the mass imbalance of Re in Earth’s primitive mantle, depleted mantle, and crust.

A quantification of the effect of diagenesis on the paleoredox record in mid-Proterozoic sedimentary rocks

Iron speciation in ancient sedimentary rocks is widely used to reconstruct oceanic redox conditions over geological time, specifically to assess the extent of oxic, euxinic (anoxic containing sulfide), and ferruginous (anoxic containing iron) conditions. We explore how post-depositional sedimentary processes can skew particular geochemical signals in the rock record. One such process is when aqueous sulfide—including that produced in the sediment column—reacts with sedimentary iron, converting non-sulfide, highly reactive iron minerals to iron-sulfide minerals; this can lead to increased preservation of iron as pyrite and an overestimation of seafloor euxinia. We show that sedimentary rocks with higher (>5 wt%) total iron content are more buffered to this effect and thus are a more reliable indicator of true water-column euxinia. When considering this effect in the geological past, we estimate that true euxinia in the mid-Proterozoic may have been as much as fourfold less than previously thought—more in line with other recent paleoredox proxies not based on iron minerals. Marine iron and sulfate concentrations were more equivalent in Proterozoic–Neoproterozoic oceans, suggesting this time period was particularly susceptible to this post-depositional alteration, explaining the extent of euxinia suggested for this geological interval.

Remotely Sensed Estimation of Total Iron Content in Soil With Harmonic Analysis and BP Neural Network

Background: The estimation of total iron content at the regional scale is much of significance as iron deficiency has become a routine problem for many crops. Methods: In this study, a novel method for estimating total iron content in soil (TICS) was proposed using harmonic analysis (HA) and back propagation (BP) neural network model. Several data preprocessing methods of first derivative (FD), wavelet packet transform (WPT), and HA were conducted to improve the correlation between the soil spectra and TICS. The principal component analysis (PCA) was exploited to obtained three kinds of characteristic variables (FD-PCA, WPT-FD-PCA, and WPT-FD-HA-PCA) for TICS estimation. Furthermore, the estimated accuracy of three BP models based on these variables was compared. Results: The results showed that the BP models of different soil types based on WPT-FD-HA-PCA had better estimation accuracy, with the highest R2 value of 0.95, and the RMSE of 0.68 of the loessial soil. It was proved that the characteristic variable obtained by harmonic decomposition improved the validity of the input variables and the estimation accuracy of the TICS models. Meanwhile, it was identified that the WPT-FD-HA-PCA-BP model can not only estimate the total iron content of a single soil type with high accuracy but also demonstrate a good effect on the estimation of TICS of mixed soil.Conclusion: The HA method and BP neural network combined with WPT and FD have great potential in TICS estimation under the conditions of single soil and mixed soil. This method can be expected to be applied to the prediction of crop biochemical parameters.

Iron Content in Deep Gray Matter as a Function of Age Using Quantitative Susceptibility Mapping: A Multicenter Study

PurposeTo evaluate the effect of resolution on iron content using quantitative susceptibility mapping (QSM); to verify the consistency of QSM across field strengths and manufacturers in evaluating the iron content of deep gray matter (DGM) of the human brain using subjects from multiple sites; and to establish a susceptibility baseline as a function of age for each DGM structure using both a global and regional iron analysis.MethodsData from 623 healthy adults, ranging from 20 to 90 years old, were collected across 3 sites using gradient echo imaging on one 1.5 Tesla and two 3.0 Tesla MR scanners. Eight subcortical gray matter nuclei were semi-automatically segmented using a full-width half maximum threshold-based analysis of the QSM data. Mean susceptibility, volume and total iron content with age correlations were evaluated for each measured structure for both the whole-region and RII (high iron content regions) analysis. For the purpose of studying the effect of resolution on QSM, a digitized model of the brain was applied.ResultsThe mean susceptibilities of the caudate nucleus (CN), globus pallidus (GP) and putamen (PUT) were not significantly affected by changing the slice thickness from 0.5 to 3 mm. But for small structures, the susceptibility was reduced by 10% for 2 mm thick slices. For global analysis, the mean susceptibility correlated positively with age for the CN, PUT, red nucleus (RN), substantia nigra (SN), and dentate nucleus (DN). There was a negative correlation with age in the thalamus (THA). The volumes of most nuclei were negatively correlated with age. Apart from the GP, THA, and pulvinar thalamus (PT), all the other structures showed an increasing total iron content despite the reductions in volume with age. For the RII regional high iron content analysis, mean susceptibility in most of the structures was moderately to strongly correlated with age. Similar to the global analysis, apart from the GP, THA, and PT, all structures showed an increasing total iron content.ConclusionA reasonable estimate for age-related iron behavior can be obtained from a large cross site, cross manufacturer set of data when high enough resolutions are used. These estimates can be used for correcting for age related iron changes when studying diseases like Parkinson’s disease, Alzheimer’s disease, and other iron related neurodegenerative diseases.

Ecological Assessment of the State of Drinking Water Within the United Territorial Communities of the Enlarged Zhytomyr District

Purpose. Assess the quality of drinking water of sources of decentralized water supply of rural settlements of Berezivka united territorial community of the enlarged Zhytomyr district. Methods. Field, laboratory-analytical, statistical. Results. As a result of research it is established that the greatest contribution to the pollution of drinking water is made by nitrates, the excess content of which was recorded on average in 50.7% of the selected samples, and in 57% of the studied settlements water belongs to quality class 4, "Limited" given undesirable quality. A critical situation was recorded in Bolyarka, Bondartsi, Dubovets and Cheremoshne villages, in which well water had increased content of nitrates in all selected samples. On average, 34% of the selected water samples do not meet the standard for the pH value in the direction of its reduction. In terms of pH, quality classes vary from "excellent", very clean to "good", clean water with a bias to the class of "satisfactory", slightly contaminated acceptable quality). The total iron content exceeded the standard by 6.6% of the selected samples. Conclusion. It is proved that the formation of the general class of water quality is significantly influenced by a group of general sanitary indicators, which is primarily due to the high content of nitrates in the studied sources of decentralized water supply. The calculation of the integrated ecological index of development of rural settlements according to the indicators of drinking water quality showed that such rural settlements as: Zamozhne and Sadky need priority attention; 11 settlements need improvement; only village of Vasylivka needs support at the same level.

Application of the reaction of oxidation of N-methyl-p-aminophenol with hydrogen peroxide, catalyzed by Fe(II) and Fe(III) ions in flow-injection analysis of tap water

The article presents the results of the application of the oxidation reaction of N-methyl-p-aminophenol with hydrogen peroxide, catalyzed by Fe(II) and Fe(III) ions in the flow injection analysis (FIA) of tap water. Using a commercially available system for FIA with spectrophotometric detection, an optimal scheme for conducting an indicator catalytic reaction in a liquid stream was proposed, which was used to determine the total iron content in tap water. Spectrophotometric detection of colored products of the indicator catalytic reaction of the oxidation of N-methyl-p-aminophenol with hydrogen peroxide is carried out at the absorption maximum of the absorption spectrum in the visible region at λmax = 490 nm. It was shown that, under nonequilibrium FIA conditions, it is possible to significantly minimize the contribution of the noncatalytic reaction to the total analytical signal. The latter is accompanied by the expansion of the range of determined catalyst contents to lower concentrations. Taking into account the proposed FIA scheme for determining the total iron content in tap water by the oxidation of N-methyl-p-aminophenol with hydrogen peroxide, catalyzed by Fe(II) and Fe(III) ions, the linearity range of the analytical signal remains in the range of 0.05-0.4 μg/ml. The lower limit of the determined iron content is 0.02 μg/ml with a productivity of 40 samples per hour. Sample preparation of tap water consists in filtering and maintaining the required pH for the catalytic indicator reaction and subsequent FIA. The cations Al, Zn, Ni, V(V), Pb, Cd, Mn(II), and Cr(VI) do not have a significant interfering effect; only the presence of complexing agents can reduce the rate of the catalytic reaction, which, accordingly, affects the analysis results.

Free Rather Than Total Iron Content Is Critically Linked to the Fur Physiology in Shewanella oneidensis

Ferric uptake regulator (Fur) is a transcriptional regulator playing a central role in iron homeostasis of many bacteria, and Fur inactivation commonly results in pleiotropic phenotypes. In Shewanella oneidensis, a representative of dissimilatory metal-reducing γ-proteobacteria capable of respiring a variety of chemicals as electron acceptors (EAs), Fur loss substantially impairs respiration. However, to date the mechanism underlying the physiological phenomenon remains obscure. This investigation reveals that Fur loss compromises activity of iron proteins requiring biosynthetic processes for their iron cofactors, heme in particular. We then show that S. oneidensis Fur is critical for maintaining heme homeostasis by affecting both its biosynthesis and decomposition of the molecule. Intriguingly, the abundance of iron-containing proteins controlled by H2O2-responding regulator OxyR increases in the fur mutant because the Fur loss activates OxyR. By comparing suppression of membrane-impermeable, membrane-permeable, and intracellular-only iron chelators on heme deficiency and elevated H2O2 resistance, our data suggest that the elevation of the free iron content by the Fur loss is likely to be the predominant factor for the Fur physiology. Overall, these results provide circumstantial evidence that Fur inactivation disturbs bacterial iron homeostasis by altering transcription of its regulon members, through which many physiological processes, such as respiration and oxidative stress response, are transformed.

Removal of Metallic Iron from Reduced Ilmenite by Aeration Leaching

Aeration leaching was used to obtain synthetic rutile from a reduced ilmenite. The reduced ilmenite, obtained from the carbothermic reduction of ilmenite concentrate in a rotary kiln at about 1100 °C, contained 62.88% TiO2 and 28.93% Metallic iron. The particle size was about 200 μm and the size distribution was uniform. The effects of NH4Cl and HCl concentrations, stirring speed, and aeration leaching time on the extent of removal of metallic iron from the reduced ilmenite were studied at room temperature. The results revealed that aeration leaching is feasible at room temperature. When using the NH4Cl system, the metallic iron content was reduced to 1.98% in synthetic rutile, but the TiO2 content only reached 69.16%. Higher NH4Cl concentration did not improve the leaching. Using 2% NH4Cl with 3% HCl, we were able to upgrade the synthetic rutile to 75%, with a metallic iron content as low as 0.14% and a total iron content of about 4%. Synthetic rutile could be upgraded to about 90% using HCl solution alone. HCl and NH4Cl are both effective on the aeration leaching process. However, within the scope of this experiment, hydrochloric acid is more efficient in aeration leaching.