Iron Enrichment Research Articles

Displacement cloud point extraction procedure for preconcentration of iron(III) in water and fruit samples prior to spectrophotometric determination

ABSTRACT. For the enrichment of iron(III) prior to spectrophotometric determination, displacement cloud point extraction (D-CPE) technique was applied depending on the difference in stability constant of metal complexes. Zinc(II) as gallic acid complex was first separated into a Triton X-100 surfactant. Then, once the aqueous phase has been removed, the sample containing Fe(III) is added, and another CPE process is performed. Because Fe-GA has a higher stability than Zn-GA, Fe(III) can displace Zn(II) from the pre-extracted Zn-GA, allowing for Fe(III) separation from the complex sample matrix and its spontaneous spectrophotometric determination at 560 nm. The effects of pH, ligand, and surfactant quantities, temperature and heating time, centrifuge processes, and interferences were all studied. At the optimal conditions, the calibration graph was linear from 0.5 to 500 µg L-1 with enrichment factor of 75.0. The LOD was 0.15 µg L-1 and the RSD was 1.3% for 60 µg L-1 of Fe(III), n = 10. Accuracy was also evaluated using the standard reference substance (SRS) and flame atomic absorption spectroscopy (FAAS) approaches. This procedure was used for separation and micro-determination of Fe(III) in water and fruit tests (banana, strawberry, lemon, orange, and peaches) with recoveries ranged from 96.5 to 105%.
 
 KEY WORDS: Displacement cloud point extraction, Iron, Spectrophotometry, Fruit samples
 
 Bull. Chem. Soc. Ethiop. 2023, 37(1), 1-10. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i1.1 

Paleo‐stratigraphic permeability anisotropy controls supergene mimetic martite goethite deposits

AbstractThe Hamersley Basin in Western Australia is one of the world's largest iron ore‐producing regions, hosting two types of ore in banded iron formations: the high‐grade martite‐microplaty haematite and the supergene martite‐goethite ores. With the high‐grade ores almost entirely mined in the last decade, the supergene ores have more recently become the dominant resource of interest. Consequently, understanding the genesis of these martite‐goethite deposits is a critical step for exploration. Yet, although various models exist, there is still no consensus on how these mineral resources formed, complicating the prediction of resource volume and location. Here, we show that the paleo‐stratigraphic permeability anisotropy (with higher permeability along strata than across) controls the supergene mimetic enrichment transport process and, subsequently, the mineralisation distribution. We introduce a flow model that implicitly represents strata with a potential function that orients the permeability tensor accurately. The numerical solver uses automatic mesh adaptivity to deliver robust solutions. By accurately reproducing the mineralisation patterns in specific deposits, we identify and quantify the paleo‐water table level and permeability anisotropy ratio as the two main controlling parameters for the mineralisation distribution. These insights provide new timing constraints for the mineralisation and the physical process of iron enrichment, suggesting much more potential mineralisation volume in the paleo‐reconstructed zones than previously anticipated. These flow models allow us to draw geological conclusions with few a priori assumptions required for the genetic model in which the transport component is dominant. The predictive power of this methodology will allow targeted drilling to narrow down the prospective areas and lower exploration costs. Furthermore, the methodology's generality applies to other commodities in sedimentary basins involving supergene processes and will improve our understanding of various genetic models.

Apparent shifts in the microplankton community in response to zinc and iron enrichments in the Northeastern Subarctic Pacific

The offshore Gulf of Alaska—in the northeastern subarctic Pacific—is a high-nitrate, low-chlorophyll (HNLC) oceanic region where concentrations of dissolved iron (DFe) and zinc (DZn) are of the order ~0.1 nmol kg−1 in surface waters. At the average winter mixed layer depth of ~120 m, DFe and DZn are of the orders ~0.1–0.2 nmol kg−1 and ~1–2 nmol kg−1, respectively. Vertical supply of Fe to surface waters is therefore limited, with phytoplankton blooms driven by episodic atmospheric and lateral inputs of Fe. In contrast, DZn is presumably replenished through seasonal vertical mixing, though maintained at low levels in surface waters, even in winter, implying that removal processes are in operation. Previous supplementation experiments have demonstrated that phytoplankton biomass (chl-a), growth, and drawdown of nitrate (NO3-) are stimulated strongly by Fe but only minimally, if at all, by Zn alone. Using on-deck bioassay incubations of surface waters, we confirm that the addition of Fe stimulates significant increases in chl-a and large diatoms, and drawdown of NO3- and silicic acid [Si(OH)4]. Associated drawdown of DZn and dissolved cadmium (DCd) indicated Zn stress in the control and +Fe treatment. Supplementation with Zn alone had no significant impact on NO3- and commonly monitored pigments such as chl-a and fucoxanthin. However, in the +Zn treatment, DFe and coccolithophore abundance were significantly lower, and the concentration of particulate organic carbon (POC) and that of the pigments alloxanthin and chlorophyll c1+2 were significantly higher than those in control incubations. Our experiment corroborates previously observed relationships between DZn and alloxanthin and chlorophyll c across the subarctic north Pacific and Bering Sea and could help to explain the low or undetectable concentrations of alloxanthin frequently observed in this region. Alloxanthin is a pigment specific to the cryptophytes, either within free-living cells or within functional plastids retained by mixotrophic protists. Both cryptophytes and mixotrophic ciliates, such as Laboea sp. and Strombidium spp., make a variable but significant contribution to phytoplankton biomass in this area. In the absence of Fe supply to surface waters, Zn could play a hitherto unsuspected role in shaping plankton communities in the HNLC Gulf of Alaska.

Individual enrichment of titanium and iron from low-titanium beach titanomagnetite via preconcentration-reduction roasting and magnetic separation with calcium fluoride

Reduction roasting-magnetic separation realizes the separation of titanium and iron in high-titanium beach titanomagnetite. However, the TiO 2 grade in titanium concentrate is low, and few studies have investigated low-titanium beach titanomagnetite. The preconcentration-reduction roasting and magnetic separation process was developed to utilize the low-titanium beach titanomagnetite. The effects of graphite dosage, reduction temperature, calcium fluoride dosage, and time on the product indices were optimized. The direct reduction iron containing 94.95% iron and 0.75% TiO 2 , titanium concentrate assaying 31.10% TiO 2 were produced under optimal conditions, and metal recovery for both products exceeded 80%. Calcium fluoride increased the liquid phase and reduced the viscosity of the slag system, thereby improving the growth of iron particles. However, an excess liquid phase produced by adding more calcium fluoride inhibited the reduction of iron minerals and promoted the formation of low-titanium minerals, which affected the iron recovery and the quality of the titanium concentrate. • The process was proposed for efficient recovery of iron and titanium. • Direct reduction iron and titanium concentrate were produced. • Calcium fluoride reduced the liquidus temperature and viscosity.

Imaging the Whole‐Lithosphere Architecture of a Mineral System—Geophysical Signatures of the Sources and Pathways of Ore‐Forming Fluids

AbstractMineral systems can be thought of as a combination of several critical elements, including the whole‐lithosphere architecture, favorable geodynamic/tectonic events, and fertility. Because they are driven by processes across various scales, exploration benefits from a scale‐integrated approach. There are open questions regarding the source of ore‐forming fluids, the depth of genesis, and their transportation through the upper crust to discrete emplacement locations. In this study, we investigate an Au–Cu metal belt located at the margin of an Archean‐Paleoproterozoic microcontinent. We explore the geophysical signatures by analyzing three‐dimensional models of the electrical resistivity and shear‐wave velocity throughout the lithosphere. Directly beneath the metal belt, narrow, vertical, finger‐like low‐resistivity features are imaged within the resistive upper‐middle crust and are connected to a large low‐resistivity zone in the lower crust. A broad low‐resistivity zone is imaged in the lithospheric mantle, which is well aligned with a zone of low shear‐wave velocity, examined with a correlation analysis. In the upper‐middle crust, the resistivity signatures give evidence for ancient pathways of fluids, constrained by a structure along a tectonic boundary. In the lower lithosphere, the resistivity and velocity signatures are interpreted to represent a fossil fluid source region. We propose that these signatures were caused by a combination of factors related to refertilization and metasomatism of the lithospheric mantle by long‐lived subduction at the craton margin, possibly including iron enrichment, F‐rich phlogopite, and metallic sulfides. The whole‐lithosphere architecture controls the genesis, evolution, and transport of ore‐forming fluids and thus the development of the mineral system.

Ironstone as a proxy of Paleozoic ocean oxygenation

Marine ironstone is a Phanerozoic biochemical sedimentary rock that contains abundant primary iron. Although rare, ironstone is conspicuous in the Paleozoic sedimentary record. Its iron source remains contentious, with traditional models invoking a continentally derived source. Increasing sedimentologic evidence suggests that many Paleozoic ironstones formed along favourably oriented continental margins where coastal upwelling delivered ferruginous waters, with the postulated source of iron being deep-ocean hydrothermal fluids. Thus, deep-water redox conditions are potentially a critical control on the concentration of iron in early Phanerozoic seawater and the accumulation of ironstone. We report novel in situ strontium isotopic and europium anomaly data from five geographically and temporally distinct Ordovician-Silurian ironstones from the Rheic and Iapetus oceans to test the emerging ferruginous upwelling model. These data provide robust evidence that ironstone formed from marine fluids with a component of mid-ocean ridge hydrothermal waters that remained largely unmixed during transport to the locations of ironstone accumulation. These results imply that the deep oceans must have been oxygen deficient to allow local or regional enrichment in hydrothermal iron. Such conditions are interpreted to have been associated with a spatiotemporally variable redox-stratified global ocean with anoxia beneath an oxic surface layer. Thus, sedimentologic and geochemical data presented herein agree with other paleoredox proxies that suggest rising oxygen levels in the Neoproterozoic gave way to early Paleozoic oceans with dynamic redox conditions. The temporal record of Paleozoic ironstone suggests redox stratification, poor deep-ocean ventilation, and upwelling-related ironstone genesis persisted until the Devonian but not into the Carboniferous.

Complete Genome Sequence of Vibrio maritimus BH16, a Siderophore-Producing Mutualistic Bacterium Isolated from Diatom Skeletonema costatum.

Complete Genome Sequence of Vibrio maritimus BH16, a Siderophore-Producing Mutualistic Bacterium Isolated from Diatom Skeletonema costatum.

Distribution Characteristics and Genesis of Marine Anoxic Conditions in the Southwest of the Upper Yangtze Basin During the Late Ordovician–Early Silurian, South China

The distribution characteristics and formation of marine anoxic conditions through the Late Ordovician–Early Silurian (O–S) remain poorly resolved despite their importance in the preservation of sedimentary organic matter and the formation of black shale. In this study, the major, trace, and pyrite δ34S (δ34Spy) contents of 36 shale samples at the edge of the southwest depocenter of the Upper Yangtze Basin (Tianlin and Changhebian sections) were analyzed to understand the redox conditions, terrigenous clastic inputs, and primary productivity changes. The iron speciation and enrichment factor of U and Mo show that the range of anoxic conditions gradually expanded from the sedimentation center to the edge during the late Katian stage, peaked in the early Hirnantian stage followed by a rapid decrease, and expanded again during the early Rhuddanian stage. Comprehensive index analysis showed that the increase of terrigenous clastic input and the relative decrease of primary productivity due to tectonism and sea level change controlled the transformation of the water column from anoxic, especially euxinic, to suboxic-oxic conditions. This is reflected in the correlation between paleo-salinity, δ34Spy, chemical index of alteration, and the organic carbon accumulation rate. This work emphasizes the control of terrigenous clastic input and sulfate availability on the transformation of marine redox conditions during the O-S period in semi-restricted basins.

Biogeochemistry of Iron Enrichment in Groundwater: An Indicator of Environmental Pollution and Its Management

Iron (Fe) is one of the most biochemically active and widely distributed elements and one of the most important elements for biota and human activities. Fe plays important roles in biological and chemical processes. Fe redox reactions in groundwater have been attracting increasing attention in the geochemistry and biogeochemistry fields. This study reviews recent research into Fe redox reactions and biogeochemical Fe enrichment processes, including reduction, biotic and abiotic oxidation, adsorption, and precipitation in groundwater. Fe biogeochemistry in groundwater and the water-bearing medium (aquifer) often involves transformation between Fe(II) and Fe(III) caused by the biochemical conditions of the groundwater system. Human activities and anthropogenic pollutants strongly affect these conditions. Generally speaking, acidification, anoxia and warming of groundwater environments, as well as the inputs of reducing pollutants, are beneficial to the migration of Fe into groundwater (Fe(III)→Fe(II)); conversely, it is beneficial to the migration of it into the media (Fe(II)→Fe(III)). This study describes recent progress and breakthroughs and assesses the biogeochemistry of Fe enrichment in groundwater, factors controlling Fe reactivity, and Fe biogeochemistry effects on the environment. This study also describes the implications of Fe biogeochemistry for managing Fe in groundwater, including the importance of Fe in groundwater monitoring and evaluation, and early groundwater pollution warnings.

Analysis of the β-cyclodextrin enhancing Bio-denitrification from the Perspective of Substrate Metabolism, Electron Transfer, and Iron Acquisition

Denitrification is widely applied in wastewater treatment systems for nitrogen removal, but it is still disturbed by unsatisfactory efficiency, nitrite accumulation, and nitrous oxide emission. In this study, the presence of 0.5 mM β-cyclodextrin (β-CD), an oligosaccharide chemical compound, effectively promoted the nitrate reduction by Paracoccus denitrificans from 68.02% to 82.78% after 20 h of cultivation. Meanwhile, the exogenous addition of β-CD significantly up-regulated the expression of denitrification-related genes (narG, nirS, norB, and nosZ), and mitigated the accumulation of nitrite and nitrous oxide emission. Notably, different from traditional organic substances for enhancing denitrification, this study not only identified β-CD increased electron generation and ATP synthesis from glucose metabolism of P. denitrificans instead of being utilized as an external carbon source, but also observed the relative promotion of β-CD on electron transfer and denitrification were positively correlated with ambient iron concentration. The addition of β-CD stimulated bacterial EPS secretion and indirectly enriched peripheral iron, and simultaneously benefited the iron transmembrane transportation and intracellular iron concentration. Given the whole process of iron enrichment and transportation, β-CD was demonstrated to improve denitrification and electron transfer via promoting iron acquisition. This study first revealed the enhancement of β-CD on bio-denitrification via iron acquisition, which provided a novel basis for its application in nitrogen removal.

Effects of iron and light on microbial nitrogen cycles in the primary nitrite maxima of the eastern Indian Ocean

To elucidate the effect of light and iron on the dynamics of nitrogen at the primary nitrite maximum (PNM), observed at the bottom of the euphotic zone of the eastern Indian Ocean, we conducted high-resolution sampling and incubation experiments at three stations. The stations were located at the Bay of Bengal, equatorial region, and South Indian subtropical gyre. The PNM was observed below the subsurface chlorophyll maximum and around the nitracline at all three stations; its magnitude was largest (>1.5 μM) in the Bay of Bengal. The results of the iron enrichment experiments under two different light regimes demonstrated that the growth of phytoplankton communities at the PNM was limited by light availability at all three stations. In the subtropical gyre, co-imitation by iron and light was observed, whereas iron was the secondary limiting factor at the other two stations, suggesting widespread iron limitation on phytoplankton growth in the subsurface waters of the open ocean. However, the changes in the concentrations of ammonium, nitrite, and nitrate suggest that the effect of light and iron deficiency on the release of nitrite by phytoplankton is relatively minor. Instead, active ammonium oxidization by shallow-clade ammonium-oxidizing archaea was observed around the PNM, suggesting that nitrite supply via the tight coupling of ammonium regeneration sustained by high surface productivity and ammonium oxidization maintains the distinct PNM in the subsurface water of the eastern Indian Ocean.

Hyperspectral and Geochemical Analysis of Chlorites at the Gongchangling High-Grade Magnetite Deposit, NE China: Implications for Alteration Processes

The Gongchangling deposit is a representative banded iron formation (BIF) in China, in which developed several high-grade magnetite ores. The surrounding alteration rocks recorded the genesis information of the high-grade ores. However, the study related to alteration processes remains poor. In this study, we investigate the sub-types and formation temperature of chlorite using hyperspectral imaging and electronic probe microanalysis (EPMA), and deciphered the elemental migration trend during alteration processes by whole-rock geochemistry. The chlorites in the alteration rocks were divided into three sub-types according to the spectral features of the Fe-OH band near 2250 nm. The range of wavelength position is approximately 2250–2255 nm for chlorite-I, 2255–2260 nm for chlorite-II, and 2260–2265 nm for chlorite-III. The variation in Mg# is 0.32–0.44 in chlorite-I, 0.20–0.34 in chlorite-II, and 0.15–0.23 in chlorite-III, which is consistent with the range of wavelength position. The hydrothermal alteration resulted in the enrichment of iron and the depletion of silicon. The results shed new light on the recognition of chlorite sub-types and deciphered the hydrothermal alteration processes of high-grade magnetite ores, which proposed an effective method for mineralogical mapping.

Iron enrichment from hypoxic hypolimnion supports the blooming of Raphidiopsis raciborskii in a tropical reservoir

Occurring worldwide, blooms of Raphidiopsis raciborskii threaten the use of water resources especially in tropical and subtropical waterbodies. Its high flexibility in the uses of light and macronutrients (C, N, P) frustrates any bloom prediction and control based on macronutrients regulation. To identify the critical factors promoting periodic blooms of R. raciborskii, the trends of meteorological, hydrodynamic, physical, and chemical variables (including macro- and micronutrients: N, P, Fe) were analyzed in a Chinese tropical large reservoir (Dashahe reservoir) over five years. It was hypothesized that Fe availability, mediated by the mixing pattern of the reservoir, played a crucial role in the periodic blooms of the cyanobacterium. To have a more complete understanding, the effects of Fe on growth of a local R. raciborskii strain were tested in a monoculture experiment. The biomass and relative abundance of R. raciborskii in the reservoir showed a clear seasonal trend, with relative abundance > 50% in summer/autumn (July to October). Three habitat types along a dominance gradient were identified in the reservoir and 17 variables were used to compare them. Statistical analysis and habitat comparison showed that temperature and stratification, dissolved Fe and N concentrations in the epilimnion, and dissolved Fe and oxygen concentrations in the hypolimnion were the critical factors driving the dynamics of R. raciborskii in the study reservoir. The habitat dominated by R. raciborskii was characterized by a relatively low availability of macro resources (Zeu/Zm < 1, SRP < 0.01 mg/L, DIN < 0.3 mg/L) and by a high Fe availability supplemented from hypoxic hypolimnion. The dependence of growth on Fe concentration increase was confirmed in culture where the maximum was reached at 0.689 mg Fe /L. Our results suggest that a high Fe bioavailability, also originating from the hypoxic hypolimnion, influences the dynamics R. raciborskii and favors the blooms of the species. As a consequence, Fe concentrations in the water column as well as oxygen measurements along the water column should be routinely included in the monitoring programs aimed at predicting and controlling R. raciborskii blooms.

Fetal iron uptake from recent maternal diet and the maternal RBC iron pool

During pregnancy iron can be obtained from the diet, body iron stores, or iron released from RBC catabolism. Little is known about the relative use of these sources to support fetal iron acquisition. To describe longitudinal change in iron absorption and enrichment across gestation and partitioning of RBC iron to the fetus. Fifteen pregnant women ingested an oral stable iron isotope (57Fe) in the second trimester (T2) of pregnancy (weeks 14-16) to label the RBC pool, and a second oral stable isotope (58Fe) in the third trimester (T3) (weeks 32-35). Absorption was measured at T2 and T3. Change in RBC 57Fe enrichment was monitored (18.8-26.6 wk) to quantify net iron loss from this pool. Iron transfer to the fetus was determined based on RBC 57Fe and 58Fe enrichment in umbilical cord blood at delivery. Iron absorption averaged 9% at T2 and increased significantly to 20% (P=0.01) by T3. The net increase in iron absorption from T2 to T3 was strongly associated with net loss in maternal total body iron (TBI) from T2 to T3 (P=0.01). Mean time for the labeled RBC 57Fe turnover based on change in RBC enrichment was 94.9 d (95% CI: 43.5, 207.1 d), and a greater decrease in RBC 57Fe enrichment was associated with higher iron absorption in T2 (P=0.001). Women with a greater decrease in RBC 57Fe enrichment transferred more RBC-derived iron to their fetus (P<0.05). Iron absorption doubled from T2 to T3 as maternal TBI declined. Women with low TBI had a greater decrease in RBC iron enrichment and transferred more RBC-derived iron to their neonate. These findings suggest maternal RBC iron serves as a significant source of iron for the fetus, particularly in women with depleted body iron stores.

Efficient enrichment and mechanism analyses of MXene-supported nanoscale zero-valent iron towards uranium(VI)

Efficient enrichment and mechanism analyses of MXene-supported nanoscale zero-valent iron towards uranium(VI)

Iron Fortification in Yoghurt: Methods and Processes, as well as their Influence on Physico-chemical and Sensory Qualities

It has been stated that anaemia affects 30% of the world’s population, according to the World Health Organization. Iron fortification in food is the most efficient approach of relieving iron deficiency condition, according to research. Because iron fortification manifests itself in food in the form of colour, flavour, and general acceptability, researchers are attempting to increase the nutritional value of food without compromising the sensory aspects of iron fortified food products. A large number of researches have shown that yoghurt is the most effective vehicle for iron fortification in this approach. This study discusses the fortification techniques and diverse sources of iron utilised in the development of iron fortified yoghurt, as well as the influence of these methods and sources of iron on the physico-chemical and sensory aspects of the yoghurt. It is anticipated that the general concept of iron enrichment in yoghurt will lead to improvements in iron fortification in the near future

High pressure-temperature phase relations of basaltic crust up to mid-mantle conditions

A substantial amount of subducted basaltic crusts may exist in the lower mantle. It features distinct chemical composition from the peridotitic mantle and plays important roles in the chemical and dynamic evolution of Earth's interior. However, the chemical composition of mineral phases present in basaltic crust in the lower mantle is still poorly constrained. Here, we determined phase relations of normal mid-ocean ridge basalt (MORB) up to 52 GPa at 2000 K by multi-anvil press. Throughout our experiments, the mineral assemblages consist of five phases including bridgmanite, stishovite, calcium perovskite (davemaoite), calcium ferrite and new hexagonal aluminous phases. The density of MORB calculated from our phase assemblages and previously published thermoelastic data is 2-3% higher than that of the average mantle, which is consistent with literature. The new hexagonal aluminous phase is a host of potassium but only occupies 1-2 vol.% due to limited abundance of potassium in normal MORB. This indicates that the new hexagonal aluminous phase doesn't affect the elastic properties of basalt. Electron energy-loss spectra of recovered basaltic Al-rich bridgmanite show significant enrichment of ferrous iron (75-85%) compared with peridotitic Al-poor bridgmanite (∼30%), which is against previous studies showing that ferric iron ratio in bridgmanite increases with Al content. Ferric iron exhibits strong partitioning into the new hexagonal aluminous phase (41-64%), whereas bridgmanite (14-28%) and calcium ferrite phase (5-27%) remain Fe2+-enriched. The oxygen vacancy component of MgAlO2.5 in bridgmanite is ∼11% up to 40 GPa, which is much higher than that in peridotitic bridgmanite (2-3%), possibly producing a viscosity contrast in the mid-mantle that would explain slab stagnation and plume thinning between 660 km and 1000 km depth. The presence of ferrous iron-rich bridgmanite in the deep lower mantle may contribute to seismic features of large low-shear-velocity provinces.

Iron oxide chemistry supports a multistage hydrothermal genesis of BIF-hosted hematite ore in the Mt. Tom Price and Mt. Whaleback deposits

This study demonstrates the great value of iron oxide chemistry in low-temperature systems. Hematite records elemental signatures of structural control, partial inheritance of pre-existing alteration, and allows chemical fingerprinting of multistage BIF-hosted ore.Mt. Whaleback and Mt. Tom Price are Western Australia’s largest banded iron formation (BIF) hosted hematite ore deposits. The mechanisms and timing of iron enrichment from BIF (with ∼20–40 wt% Fe) to high-grade iron ore (with up to 69 wt% Fe) are still controversially debated. In-situ iron oxide chemistry support post-metamorphic, structurally controlled, hydrothermal hematite ore formation via multiple stages of hydrothermally altered BIF.Iron oxides in two hydrothermal alteration zones in BIF at Mt. Tom Price (distal alteration assemblages: magnetite-siderite-stilpnomelane ± pyrite and intermediate alteration assemblages: hematite-magnetite-ankerite-chlorite) show similar trace element patterns that are distinct from metamorphic magnetite in least-altered magnetite-quartz ± hematite ± Fe-carbonate ± Fe-silicates BIF. At Mt. Whaleback, the hydrothermal alteration is completely eradicated by subsequent microplaty-martite hematite ore formation, and solely recorded in hematite composition by the inheritance of various conservative element abundances.Petrographically indistinct zones within a given orebody are chemically distinct and demonstrate formation via contrasting structurally controlled hydrothermal fluid flow: At Mt. Whaleback, specifically in the vicinity of Central Fault and Whaleback Fault, systematic trace element group abundance trends are recorded: major controls are fO2, pH, and acquired country rock signatures, i.e., evolved (Al, Mn, Mo, Pb, U) at Central Fault, and primitive (Al, Cr, Ti, V, Cu, Ni, Co) at Whaleback fault. Complex zoned growth textures and element distribution in microplaty hematite support precipitation during protracted hydrothermal fluid/rock interaction. In combination, our results falsify the importance of alternative hematite crystallisation models, including goethite dehydration and coalescent nanoparticles.

Top-heavy stellar mass distribution in galactic nuclei inferred from the universally high abundance ratio of [Fe/Mg

ABSTRACT Recent observations of active galactic nuclei (AGNs) have shown a high Fe ii/Mg ii line-flux ratio in their broad-line regions, nearly independent of redshift up to z ≳ 6. The high flux ratio requires rapid production of iron in galactic nuclei to reach an abundance ratio of [Fe/Mg] ≳ 0.2 as high as those observed in matured galaxies in the local universe. We propose a possible explanation of rapid iron enrichment in AGNs by massive star formation that follows a top-heavy initial mass function (IMF) with a power-law index of Γ larger than the canonical value of Γ = −2.35 for a Salpeter IMF. Taking into account metal production channels from different types of SNe, we find that the high value of [Fe/Mg] ≳ 0.2 requires the IMF to be characterized with Γ ≳ −1 (Γ ≳ 0) and a high-mass cutoff at Mmax ≃ 100–150 M⊙ (Mmax ≳ 250 M⊙). Given the conditions, core-collapse SNe with M* ≳ 70 M⊙ and pair-instability SNe give a major contribution for iron enrichment. Such top-heavy stellar IMFs would be a natural consequence from mass growth of stars formed in dense AGN discs under Bondi-like gas accretion that is regulated by feedback at M* ≳ 10 M⊙. The massive stellar population formed in AGN discs also leave stellar-mass black hole remnants, whose mergers associated with gravitational-wave emission account for at most 10 per cent of the merger rate inferred from LIGO/Virgo observations to simultaneously explain the high [Fe/Mg] ratio with metal ejection.

Environmental risk of (heavy) metal release from urns into cemetery soils

Cremation of the deceased has become the most common funeral type in many countries in the world, including Germany. The ashes of the cremated human body (cremains) are transferred in an urn and most commonly buried in the soil. However, the possible environmental impacts of cremains on soils and groundwater have been rarely studied. In this context, it is still unclear whether or not the release of (heavy) metals like chromium, zinc, copper, nickel and lead from cremains and urns poses an environmental problem in urn grave soils.The aims of the study were to analyze the (heavy) metal content of two cremains from a 74-year-old male and 70-year-old female, and of soils in 6 cemeteries with urn graves in North and West Germany. Soil samples were taken from below the burial depth of 42 urns (upon expiry of the resting time) and from reference soils without urn burials (same cemetery site and depth).The two cremains differed significantly in their heavy metal content (zinc, nickel, copper, chromium), which originated from metal components of the deceased's clothing or burial objects or may have resulted from contrasting occupational exposure during the deceased's lives. Investigations at the cemetery sites revealed a high variability in (heavy) metal contents in the soil samples from below the buried urns. As expected, the accumulation of some element (e.g., lead and tin) in the soil increased with a higher degradation degree of the urns, but an enrichment in copper, chromium, nickel, and iron was also detected below only slightly corroded but not yet perforated urns, which were often made out of copper-bearing material and other alloying agents. This demonstrated that heavy metal releases into cemetery soils originated from both cremains and urn material.