Environmental implications of interaction between humic substances and iron oxide nanoparticles: A review.

Goethite, hematite, ferrihydrite, and other iron oxides bind through various sorption reactions with humic substances (HS) in soils creating nano-, micro-, and macro-aggregates with a specific nature and stability. Long residence times of soil organic matter (SOM) have been attributed to iron-humic substance (Fe-HS) complexes due to physical protection and chemical stabilization at the organic-mineral interface. Humic acids (HA) and fulvic acids (FA) contain many acidic functional groups that interact with Fe oxides through different mechanisms. Due to the numerous interactions between mineral Fe and natural SOM, much research has led into a better identification and definition of HS. In this review, we first focus on the surface colloidal properties of Fe oxides and their reactivity toward HS. These minerals can be efficiently identified by usual techniques, such as XRD, FTIR spectroscopy, XAS, Mössbauer, diffuse reflectance spectroscopies (DRS), HRTEM, ATM, NanoSIMS. Second, we present the recent state of art regarding the adsorption/precipitation of HS onto iron mineral surfaces and their effects on binding metalloid and trace elements. Finally, we consider future research directions based on recent scientific literature, with particular focus on the ability of Fe nano-particles to increase Fe bioavailability, improve carbon sequestration, reduce greenhouse gas emissions, and decrease the impact of persistent organic and inorganic pollutants. The methodology in this field has rapidly developed over the last decade. However, new procedures to estimate the nature of Fe-HA bonds will be important contributions in clarifying the role of natural iron oxides in soil for carbon stabilization.

Combining P and Zn fertilization to enhance yield and grain quality in maize grown on Mediterranean soils.

The main aim of this study was to elucidate the effect of individual and joint fertilization with P and Zn on maize plants grown on typical Mediterranean soils with a limited Zn availability. For this purpose, we examined the effects of P and Zn fertilization individually and in combination on growth, yield and grain protein content in maize grown in pots filled with three different Mediterranean soils (LCV, FER and INM). Phosphorus and Zn translocation to grain was impaired, and aboveground dry matter and yield at harvest reduced by 8-85% (LCV and FER), in plants treated with Zn or P alone relative to unfertilized (control) plants. In contrast, joint fertilization with P and Zn enhanced translocation of these nutrients to grain and significantly increased aboveground dry matter (30% in LCV, 50% in FER and 250% in INM) and grain Zn availability in comparison with control plants. Also, joint application of both nutrients significantly increased grain P (LCV) and Zn (LCV and FER) use efficiency relative P and Zn, respectively, alone. Yield was increased between 31% in LCV and 121% in FER relative to control plants, albeit not significantly. Fertilization with P or Zn significantly influenced the abundance of specific proteins affecting grain quality (viz., storage, lys-rich and cell wall proteins), which were more abundant in mature grains from plants fertilized with Zn alone and, to a lesser extent, P + Zn. Sustainable strategies in agriculture should consider P-Zn interactions in maize grown on soils with a limited availability of Zn, where Zn fertilization is crucial to ensure grain quality.

Optimum Olsen Phosphorus/ZincDTPA ratio for the initial growth of maize in agricultural soils of the Mediterranean region.

BACKGROUND: Zinc (Zn) deficiency in crops is commonly aggravated by high levels of phosphorus (P) in soil. In this work, the initial performance of pot-growing maize in response to the available P and Zn in soils with low available Zn and to the application of P and Zn fertilizers was investigated. RESULTS: The soils (six non-calcareous and 14 calcareous) ranged widely in available P (Olsen P: 5.5-37.9 mg kg-1 ), were poor in available Zn [diethylenetriaminepentaacetic acid-extractable Zn (ZnDTPA ): 0.20-0.84 mg kg-1 ] and had an Olsen P/ZnDTPA ratio of 13 to 111 mg mg-1 . Soil P application generally increased aerial dry matter (ADM) yield; Zn increased ADM yield mostly when applied in combination with P; and the sole application of Zn increased yield only in a soil with a high (28 mg kg-1 ) Olsen P and a low (0.36 mg kg-1 ) ZnDTPA . The increase in ADM yield resulting from optimal application of P and/or Zn to the soil was modest in soils where the Olsen P/ZnDTPA ratio was 30-60 and Olsen P was >14 mg kg-1 . Zinc uptake by the control plants was correlated with the ZnDTPA of the soil. For a certain ZnDTPA value, the level of plant available Zn was higher in non-calcareous than in calcareous soils. CONCLUSION: Soil application of fertilizer P and Zn, in soils with low levels of available Zn, should not only aim at increasing the available P and Zn levels but also balancing them at the appropriate Olsen P/ZnDTPA ratio, which was found to lie in the 30-60 range in the present study. © 2020 Society of Chemical Industry.

Photochemical emission and fixation of NOX gases in soils.

Gaseous nitrogen oxides (NOx), which result from the combustion of fossil fuels, volcanic eruptions, forest fires, and biological reactions in soils, not only affect air quality and the atmospheric concentration of ozone, but also contribute to global warming and acid rain. Soil NOx emissions have been largely ascribed to soil microbiological processes; but there is no proof of abiotic catalytic activity affecting soil NO emissions. We provide evidence of gas exchange in soils involving emissions of NOx by photochemical reactions, and their counterpart fixation through photocatalytic reactions under UV-visible irradiation. The catalytic activity promoting NOx capture as nitrate varied widely amongst different soil types, from low in quartzitic sandy soils to high in iron oxide and TiO2 rich soils. Clay soils with significant amounts of smectite also exhibited high rates of NOx sequestration and fixed amounts of N comparable to that of NO (nitric oxide) losses through biotic reactions. In these soils, a flux of 100 µg NNO m-2 h-1, as usually found in most ecosystems, could be reduced by these photochemical reactions by more than 60%. This mechanism of N fixation provides new insight into the nitrogen cycle and may inspire alternative strategies to reduce NO emissions from soils.

Entamoeba Histolytica: Updates in Clinical Manifestation, Pathogenesis, and Vaccine Development.

Entamoeba histolytica is the responsible parasite of amoebiasis and remains one of the top three parasitic causes of mortality worldwide. With increased travel and emigration to developed countries, infection is becoming more common in nonendemic areas. Although the majority of individuals infected with E. histolytica remain asymptomatic, some present with amoebic colitis and disseminated disease. As more is learned about its pathogenesis and the host's immune response, the potential for developing a vaccine holds promise. This narrative review outlines the current knowledge regarding E. histolytica and E. dispar and insight in the development of a vaccine.

Phosphorus reduces the zinc concentration in cereals pot-grown on calcareous Vertisols from southern Spain.

BACKGROUND: Zinc deficiency, a major problem in crops grown on soils low in available Zn, is even more important in phosphorus-rich soils. This work aimed to elucidate the effects of soil P and Zn levels, and of fertilizer application, on yield and Zn concentration in cereal grains. RESULTS: Wheat and barley were successively pot-grown on 20 calcareous Vertisols low in available Zn and ranging widely in available P. Grain yield in the plants grown on the native soils was positively correlated with Olsen P but not with diethylenetriaminepentaacetic acid (DTPA)-extractable Zn except for wheat on P-rich soils. Grain Zn concentration was negatively correlated with Olsen P. Grain Zn uptake differed little among soils. Application of P to the soils increased grain yield insignificantly and P concentration significantly; however, it reduced grain Zn concentration (particularly at low Olsen P values). Applying Zn alone only increased grain Zn concentration, whereas applying P and Zn in combination increased yield and grain Zn concentration at low and high Olsen P values, respectively. CONCLUSION: Applying P alone to plants grown on calcareous Vertisols low in available P and Zn may in practice reduce grain Zn concentrations while not increasing grain yield significantly. © 2016 Society of Chemical Industry.

Chromium Displacement in Subtropical Soils Fertilized with Hydrolysed Leather: A Laboratory Study.

Prolonged use of biosolids with high metal content may result in diffuse pollution across large regions, especially if such ions can move freely through the soil profile and reach underground water sources. The objective of this study was to verify whether Cr added to the soil surface in the form of hydrolysed leather or a soluble salt would migrate over significant distances in four subtropical soils differing in physical, chemical and mineralogical properties. Horizontal and vertical mobility were assessed in Petri dishes and small pots, respectively, using low (12 mg kg-1 soil) and high Cr levels (150 mg kg-1 soil) added to the soil surface. Irrespective of concentration, soluble Cr salts were found to move more easily in soils with low organic matter and clay content. Contrarily, Cr added as hydrolysed leather exhibited negligible mobility and tended to accumulate in the vicinity of application.

Control of Earth-like magnetic fields on the transformation of ferrihydrite to hematite and goethite.

Hematite and goethite are the two most abundant iron oxides in natural environments. Their formation is controlled by multiple environmental factors; therefore, their relative concentration has been used widely to indicate climatic variations. In this study, we aimed to test whether hematite and goethite growth is influenced by ambient magnetic fields of Earth-like values. Ferrihydrite was aged at 95 °C in magnetic fields ranging from ~0 to ~100 µT. Our results indicate a large influence of the applied magnetic field on hematite and goethite growth from ferrihydrite. The synthesized products are a mixture of hematite and goethite for field intensities <~60 µT. Higher fields favour hematite formation by accelerating ferrimagnetic ferrihydrite aggregation. Additionally, hematite particles growing in a controlled magnetic field of ~100 µT appear to be arranged in chains, which may be reduced to magnetite keeping its original configuration, therefore, the presence of magnetic particles in chains in natural sediments cannot be used as an exclusive indicator of biogenic magnetite. Hematite vs. goethite formation in our experiments is influenced by field intensity values within the range of geomagnetic field variability. Thus, geomagnetic field intensity could be a source of variation when using iron (oxyhydr-)oxide concentrations in environmental magnetism.

The severity of iron chlorosis in sensitive plants is related to soil phosphorus levels.

BACKGROUND: Iron (Fe) deficiency chlorosis, a major nutritional problem in plants growing on calcareous soils, is related to the content and reactivity of soil iron oxides and carbonates. The effects of other soil components, however, need elucidation. In this paper we tested the hypothesis that application of high doses of phosphorus (P) to the soil can aggravate Fe chlorosis. RESULTS: Lupin and sorghum were grown on 24 calcareous soils. Leaf chlorophyll concentration (LCC) in lupin decreased with increasing available P/available Fe ratio in the native soil but LCC in sorghum was unaffected by that ratio. Application of P to the soil resulted in significant reduction of LCC and dry weight in lupin. In sorghum, LCC and dry weight were positively affected by P fertilisation for soils poor in available P whereas the opposite effect was generally observed for the P-rich soils. In another experiment where olive plants were pot-grown on two soils during the 2009­2011 period, P fertilisation affected LCC negatively only in 2009 and 2011 and in the soil that was poorer in iron oxides. CONCLUSION: Application of fertiliser P to Fe chlorosis-inducing soils is likely to aggravate this deficiency. However, this effect depends on the plant and the Fe and P statuses of the soil.

Pot evaluation of synthetic nanosiderite for the prevention of iron chlorosis.

BACKGROUND: Iron chlorosis is a problem that affects crops grown on calcareous soils. In this work, we assessed the effectiveness of nanosized siderite (FeCO3) to prevent iron chlorosis, the underlying hypothesis being that the oxidation products of siderite in soil are poorly crystalline, and hence plant-available, iron oxides. RESULTS: Nanosized siderite was prepared by mixing FeSO4 and K2CO3 solutions, either pure or doped with phosphate (siderite SID and SIDP, respectively). The average specific surface area was ∼140 m² g⁻¹ for SID and ∼220 m² g⁻¹ for SIDP. Experimental oxidation in a calcite suspension yielded goethite for SID and a mixture of lepidocrocite and goethite for SIDP. Two pot experiments in which a SID or SIDP suspension was applied to a calcareous soil at a rate of ∼2 g Fe kg⁻¹ showed nanosiderite to prevent iron chlorosis in chickpea. In a pot experiment with five successive crops, one initial application of ∼0.7 g Fe kg⁻¹ soil in the form of SID or SIDP was as effective as FeEDDHA in preventing Fe chlorosis. The residual effect of nanosiderite when applied to the first crop alone clearly exceeded that of FeEDDHA. CONCLUSION: Nanosiderite suspensions applied at rates of ∼0.7 g Fe kg⁻¹ soil were highly effective in preventing iron chlorosis and have a great residual effect.

Ordered ferrimagnetic form of ferrihydrite reveals links among structure, composition, and magnetism.

The natural nanomineral ferrihydrite is an important component of many environmental and soil systems and has been implicated as the inorganic core of ferritin in biological systems. Knowledge of its basic structure, composition, and extent of structural disorder is essential for understanding its reactivity, stability, and magnetic behavior, as well as changes in these properties during aging. Here we investigate compositional, structural, and magnetic changes that occur upon aging of "2-line" ferrihydrite in the presence of adsorbed citrate at elevated temperature. Whereas aging under these conditions ultimately results in the formation of hematite, analysis of the atomic pair distribution function and complementary physicochemical and magnetic data indicate formation of an intermediate ferrihydrite phase of larger particle size with few defects, more structural relaxation and electron spin ordering, and pronounced ferrimagnetism relative to its disordered ferrihydrite precursor. Our results represent an important conceptual advance in understanding the nature of structural disorder in ferrihydrite and its relation to the magnetic structure and also serve to validate a controversial, recently proposed structural model for this phase. In addition, the pathway we identify for forming ferrimagnetic ferrihydrite potentially explains the magnetic enhancement that typically precedes formation of hematite in aerobic soil and weathering environments. Such magnetic enhancement has been attributed to the formation of poorly understood, nano-sized ferrimagnets from a ferrihydrite precursor. Whereas elevated temperatures drive the transformation on timescales feasible for laboratory studies, our results also suggest that ferrimagnetic ferrihydrite could form naturally at ambient temperature given sufficient time.

[Update on pediatric cardiology and congenital heart disease]. / Actualización en cardiología pediátrica y cardiopatías congénitas.

The fields of pediatric cardiology and congenital heart disease have experienced considerable progress in the last few years, with advances in new diagnostic and therapeutic techniques that can be applied at all stages of life from the fetus to the adult. This article reviews scientific publications in a number of areas that appeared between August 2007 and September 2008. In developed countries, congenital heart disease is becoming increasingly prevalent in nonpediatric patients, including pregnant women. Actions aimed at preventing coronary heart disease must be started early in infancy and should involve the promotion of a healthy diet and lifestyle. Recent developments in echocardiography include the introduction of three-dimensional echocardiography and of new techniques such as two-dimensional speckle tracking imaging, which can be used for both anatomical and functional investigations in patients with complex heart disease, including a univentricular heart. Progress has also occurred in fetal cardiology, with new data on prognosis and prognostic factors and developments in intrauterine interventions, though indications for these interventions have still to be established. Heart transplantation has become a routine procedure, supplemented in some cases by circulatory support devices. In catheter interventions, new devices have become available for the closure of atrial or ventricular septal defects and patent ductus arteriosus as well as for percutaneous pulmonary valve implantation. Surgery is also advancing, in some cases with hybrid techniques, particularly for the treatment of hypoplastic left heart syndrome. The article ends with a review of publications on cardiomyopathy, myocarditis and the treatment of bacterial endocarditis.

Experimental oxidative dissolution of sphalerite in the Aznalcollar sludge and other pyritic matrices.

After the collapse on 25 Apr. 1998 of the Aznalcóllar mine tailings dike in southwestern Spain, 45 km2 of the Guadiamar valley were covered by a pyritic sludge containing up to 2% sphalerite (ZnS). Later, the sludge was mechanically removed and calcium carbonate was plowed into the soil to immobilize heavy metals. By June 2001 more than 60% of the sulfides in the residual sludge had oxidized and soil Zn contents reached locally phytotoxic levels. Therefore, the oxidative dissolution of sphalerite in the sludge and other pyritic samples was examined. Flow-through oxidation experiments showed that: (i) about 5 and 17% of the sludge Fe and Zn were in soluble form, respectively, because the sludge sample had been partly oxidized in the field; (ii) the oxidation rates of the residual pyrite and sphalerite were similar; (iii) the overall sulfide oxidation rate was relatively unaffected by the addition of calcite; and (iv) poorly crystalline Fe (hydr)oxides containing Zn in occluded form and Zn (hydroxi)carbonates were formed in the presence of calcite. The rate of oxidation of reference sphalerite greatly increased when it was incorporated in the sludge or in a reference pyrite matrix. This enhancement was due to galvanic interaction because pyrite oxidation was depressed in the presence of sphalerite. Oxidation by Fe3+ ions was less important because the oxidation rates of native sphalerite were not greater at low than at high pH. The fast oxidation rate of sphalerite in the Aznalcóllar sludge indicates a need for quick adoption of remediation measures in similar accidents elsewhere. The use of calcite amendments has little influence on the oxidation rate but does result in the accumulation of Zn in relatively insoluble forms.

Odontoma mandibulart con inclusión de incisivo y canino permanentes / Mandibular odontoma with inclusion of permanent incisor and canine. Clinical case

Los odontomas son anomalías del desarrollo resultado del crecimiento y diferenciación epitelial de células mesenquimales. Estas células forman cantidades variables de esmalte, dentida y tejido pulpar. Algunos autores afirman que actualmente los dontomas son los tumores más frecuentes de los maxilares y representan entre un 22 por ciento y un 67 por ciento de todos los tumores odontogénicos de los maxilares. Sin embargo, la presencia de un dontoma en el sector anterior de la mandíbula es poco frecuente. En este artículo presentamos un caso de impactación de un incisivo con un quiste folicular y la inclusión del canino del lado afectado por la presencia de un odotoma mandibular

Can the presence of structural phosphorus help to discriminate between abiogenic and biogenic magnetites?

The influence of phosphate on the competitive formation of magnetite and lepidocrocite and the properties of magnetite prepared from mixtures of Fe(II) and Fe(III) salts were studied. Products were prepared at 90 degrees C and pH 12.5 (series 1), 50 degrees C and pH 7 (series 2) and 20 degrees C and pH 8 (series 3). The P/Fe atomic ratio in the initial solution ranged from 0 to 3% and the pH was kept at the desired value with NaOH or KOH. Air was used as oxidant in series 2 and 3. All products, which were characterized by X-ray diffraction, transmission electron microscopy, chemical analysis and IR spectroscopy, contained a phase intermediate between magnetite and maghemite (referred to as magnetite in this paper). The products of series 1 consisted only of magnetite at all P/Fe ratios, whereas both magnetite and lepidocrocite formed in series 2 and 3 above a certain P/Fe ratio. On increasing the P/Fe ratio in the initial solution, the magnetite crystals became smaller and more oxidized (i.e. closer to maghemite) and the lepidocrocite/magnetite ratio increased. The P associated with magnetite was partly in the form of occluded P, i.e. non-surface-adsorbed phosphate. IR spectra suggested this P to be structural and occurring as low-symmetry PO(4) units. Because abiogenic magnetites produced in various environments incorporate structural P but some well-characterized biogenic magnetites seem to contain no P or be formed in P-poor environments, we hypothesize that natural magnetites containing occluded P are unlikely to be biogenic. However, more studies are needed to discard the presence of P in biogenic magnetites.

[Value of NTproBNP concentration in an out-of-hospital adult population]. / Valor del nivel de NTproBNP en población adulta extrahospitalaria.

INTRODUCTION: The diagnosis of chronic heart failure (CHF) is based on demonstrating the cardiac origin of clinical manifestations. Echocardiography is the method of choice for the detection of left ventricular systolic dysfunction (LVSD). Brain natriuretic peptide (BNP) rises during LVSD. OBJECTIVES: To analyze the plasma concentration of N-terminal brain natriuretic propeptide (NTproBNP) in a general adult population in relation to different spontaneous circumstances and to study its capacity for identifying patients with LVSD.Methods. A cardiological examination was made and plasma NTproBNP levels were measured in a randomized group of 203 people (49-81 years old) from the Community of Valencia. RESULTS: The average NTproBNP concentration was 52.2 98.2 pmol/l. NTproBNP levels varied with age, gender and functional stage (NYHA). The highest NTproBNP values were observed in people who had previously suffered from acute pulmonary edema or who had an ejection fraction (EF) of less than 40%. There was also a significant elevation in patients with nocturnal dyspnea, orthopnea, atrial fibrillation, EF < or = 50%, angina, and ankle edema. The best concentration of NTproBNP for differentiating EF < or = 50% was 37.7 pmol/l, with 92% sensitivity and 68% specificity. CONCLUSIONS: The elevation of NTproBNP concentration indicates the cardiac origin of clinical manifestations and serves to select patients for echocardiographic examination. Low NTproBNP concentrations help to rule out LVSD.