Coagulation behavior and floc characteristics of a novel composite poly-ferric aluminum chloride-polydimethyl diallylammonium chloride coagulant with different OH/(Fe3+ + Al3+) molar ratios.

PubMed

Sun, Cuizhen; Qiu, Jinwei; Zhang, Zhibin; Marhaba, Taha F; Zhang, Yanhao

2016-10-01

In this paper, flocculating performance and mechanisms of a new composite coagulant, poly-ferric aluminum chloride-polydimethyl diallylammonium chloride (PFAC-PD) with different OH - /(Fe 3+ + Al 3+ ) molar ratios, were investigated for humic acid (HA)-kaolin synthetic wastewater treatment. The impact of OH - /(Fe 3+ + Al 3+ ) molar ratios on the removal efficiencies of turbidity and dissolved organic carbon, specific UV absorbance, coagulation mechanisms and dynamics was explored during the coagulation process using composite coagulants. The coagulation experimental results revealed that the composite coagulants with lower OH - /(Fe 3+ + Al 3+ ) molar ratio exhibited better coagulation efficiency. When OH - /(Fe 3+ + Al 3+ ) molar ratio of the composite coagulant was 1.5, adsorption-bridging played a dominant role in coagulating HA-kaolin synthetic wastewater. The floc growth rate and floc size, increased with increasing OH - /(Fe 3+ + Al 3+ ) molar ratio and the highest peak height of the size distribution was obtained by PFAC-PD with OH - /(Fe 3+ + Al 3+ ) = 1.5. Also, the composite coagulants with higher OH - /(Fe 3+ + Al 3+ ) molar ratio formed more compact flocs, as reflected by the higher fractal dimension value. The flocs coagulated by PFAC-PD with basicity value of 1.0 gave strong strength and good recoverability.

Acidity and Alkalinity in mine drainage: Practical considerations

USGS Publications Warehouse

Cravotta, III, Charles A.; Kirby, Carl S.

2004-01-01

In this paper, we emphasize that the Standard Method hot peroxide treatment procedure for acidity determination (hot acidity) directly measures net acidity or net alkalinity, but that more than one water-quality measure can be useful as a measure of the severity of acid mine drainage. We demonstrate that the hot acidity is related to the pH, alkalinity, and dissolved concentrations of Fe, Mn, and Al in fresh mine drainage. We show that the hot acidity accurately indicates the potential for pH to decrease to acidic values after complete oxidation of Fe and Mn, and it indicates the excess alkalinity or that required for neutralization of the sample. We show that the hot acidity method gives consistent, interpretable results on fresh or aged samples. Regional data for mine-drainage quality in Pennsylvania indicated the pH of fresh samples was predominantly acidic (pH 2.5 to 4) or near neutral (pH 6 to 7); approximately 25 percent of the samples had intermediate pH values. This bimodal frequency distribution of pH was distinctive for fully oxidized samples; oxidized samples had acidic or near-neutral pH, only. Samples that had nearneutral pH after oxidation had negative hot acidity; samples that had acidic pH after oxidation had positive hot acidity. Samples with comparable pH values had variable hot acidities owing to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. The hot acidity was comparable to net acidity computed on the basis of initial pH and concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity computed from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was comparable to that computed on the basis of aqueous species and FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the hot acidities were comparable for fresh and aged samples. Thus, meaningful “net” acidity can be determined from a measured hot acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. Together, these water-quality data can be useful for evaluating the potential for toxicity, corrosion, or encrustation and can be helpful for determining the appropriate remediation. By demonstrating the measurements on fresh and aged samples, we hope to encourage (1) consistent use of the hot peroxide treatment procedure for acidity determination and (2) consistent reporting of negative acidity values.

RECOVERY OF URANIUM FROM LOW GRADE URANIUM BEARING ORES

DOEpatents

Rhodes, H.B.; Pesold, W.F.; Hirshon, J.M.

1959-06-01

Recovery of U, Fe, and Al from Chattanooga shale is described. Ground shale (-4 to +325 mesh) is roasted to remove organic and volatile matter. The heated shale is then reacted with a chlorinating agent (CCl/sub 4/, COCl/sub 2/, Cl, and SCl) at 600 to 1000 C. The metal chloride vapor is separated from entrained solids and then contacted with a liquid alkali metal chloride which removes U. The U is reeovered by cooling and dissolving the bath followed by acidification and solvent extraction. A condensed phase of Al, Fe, and K chlorides is treated to separate Al as alumina by passing through a Fe/sub 2/O/ sub 3/ bed. The remaining FeCl/sub 3/ is oxidized by O/sub 2/ at 1000 C to form Fe/sub 2/O/sub 3/ and Cl/sub 2/. Alternatively, vapor from the U separation step may be passed to a liquid KCl bath at 500 to 650 C. The resulting mixture is oxidized to form Cl/sub 2/ and Fe/sub 2/O/sub 3/ + Al/sub 2/O/sub 3/. The Al and Fe are separated by reaction with NaOH at high temperatures and pressures. (T.R.H.)

Cation-induced coagulation of aquatic plant-derived dissolved organic matter: Investigation by EEM-PARAFAC and FT-IR spectroscopy

USDA-ARS?s Scientific Manuscript database

Interaction and coagulation of plant-derived dissolved organic matter (DOM) by metal cations are important biogeochemical processes of organic matter in lake systems. Thus, coagulation and fractionation of plant-derived DOM by di- and tri-valent Ca, Al, and Fe ions were investigated. Metal ion-induc...

Adaptation Reactions of Siderophilic Cyanobacteria to High and Low Levels Of Environmental Iron: Implications for Biosphere History

NASA Technical Reports Server (NTRS)

Brown, I. I.; Bryant, D.; Sarkisova, S.; Shen, G.; Garrison, D.; McKay, D. S.

2009-01-01

Of all extant environments, iron-depositing hot springs may constitute the most appropriate natural models (Pierson and Parenteau, 2000) for analysis of the ecophysiology of ancient cyanobacteria (CB) which may have emerged in association with hydrothermal activity (Brown et al., 2007) and elevated levels of environmental Fe (Rouxel et al., 2005). Elevated environmental Fe2+ posed a significant challenge to the first oxygenic phototrophs - CB - because reduced Fe2+ induces toxic Fenton reactions (Wiedenheft et al., 2005). Ancient CB could have also been stressed by occasional migrations from the Fe2+-rich Ocean to the basaltic land which was almost devoid of dissolved Fe2+. That is why the study of the adaptation reactions of siderophilic CB, which inhabit iron-depositing hot springs, to up and down shifts in levels of dissolved Fe may shed light on the paleophysiology of ancient oxygenic prokaryotes. Methods. Siderophilic CB (Brown et al., 2007) were cultivated in media with different concentrations of added Fe3+. In some cases basaltic rocks were used as a source of Fe and trace elements. The processes of Fe mineralization and rock dissolution were studied using TEM, SEM and EDS techniques. Fluorescence spectroscopy was used for checking chlorophyll-protein complexes. Results. It was found that five siderophilic isolates Chroogloeocystis siderophila, JSC-1, JSC-3, JSC-11 and JSC-12 precipitated Fe-bearing phases on the exopolymeric sheaths of their cells if [Fe3+] was approx. 400-600 M (high Fe). Same [Fe3+] was most optimal one for the cultures proliferation rate (Brown et al., 2005; Brown et al., 2007). Higher concentrations of Fe3+ repressed the growth of some siderophilic CB (Brown et al., 2005). No mineralized Fe3+ was observed on the sheath of freshwater isolates Synechocystis sp. PCC 6803 and Phormidium aa. Scanning TEM in conjunction with thin-window energy dispersive X-ray spectroscopy (EDS) revealed intracellular Fe-rich phases within all three isolates studied JSC-1, JSC-3 and JSC-11. The elemental composition of the Fe-rich precipitates indicates P, Fe, and O as the major elements with minor amounts of Al and Ca. It was also found that the PSI:PSII ratio is higher in JSC-1 and JSC-3 isolates than in CB without detectable ability to mineralize Fe. SEM-EDS studies of the interaction of siderophilic cyanobacteria with Fe-rich minerals and rocks revealed, for the first time, their ability to leach ilmenite, olivine, FeS, ZnS and ferrosilicates, perhaps because the cyanobacteria studied can secrete 2-oxo-glutarate and malate which possess chelating properties. The draft of Cyanobacterium JSC-1 is currently being completed. This will help to verify the molecular mechanisms of Fe mineralization and Fe-rich minerals by siderophilic CB. Conclusions. The results obtained suggest that colloidal Fe3+ is transported in CB cytoplasm most likely through ABC-type Fe3+ transport system (Braun et al., 2004). The prevalence of PSI components over PSII in some species of siderophilic CB may indirectly support the Y. Cohen s hypothesis that PSI in cyanobacteria can be involved in Fe2+ oxidation (Cohen, 1984; 1989). The ability of siderophilic CB to mineralize Fe within their cytoplasms could be a protective survival mechanism induced by high levels of [Fe2+] and UV radiation, while the ability to leach Fe-rich minerals could have supported the expansion of ancient CB onto basaltic land.

Modern Dust Deposition and Dissolved Iron Residence Times in the Eastern Tropical Pacific Ocean

NASA Astrophysics Data System (ADS)

Vivancos, S. M.; Anderson, R. F.; Pavia, F. J.; Fleisher, M. Q.; Lu, Y.; Zhang, P.; Cheng, H.; Edwards, R. L.

2016-02-01

We use dissolved 230Th and 232Th data along the U.S. GEOTRACES Equatorial Pacific Zonal Transect (EPZT) from Peru to Tahiti to quantify dust input to the region. Dust in the global oceans is a mineral ballast that helps carry organic matter to depth, a reactive particle surface that scavenges trace metals such as Th and Pa from the water column, and through its dissolution dust provides essential micronutrients, such as iron, that stimulate productivity. When integrating Th inventories from the sea surface to 500 meters water depth (Hayes et al., Earth Planet. Sci. Lett., 383 (2013) 16-25), we find that dust fluxes along the EPZT are an order of magnitude lower (0.18-1.61 g/m2/yr) than along the U.S. GEOTRACES Atlantic Transect (Mauritania to Bermuda; 3.22 to 10.56 g/m2/yr). Dust fluxes decrease with distance away from the dust source (i.e., the continents). Using an Fe/Th ratio of 2660 g/g for dust and assuming a Fe/Th solubility ratio of 1.0 (Hayes et al., Geochim. Cosmochim. Acta, 169 (2015) 1-16), we calculate a dissolved iron flux of 12.06 to 109.88 µmol/m2/yr to the EPZT region. Utilizing dissolved iron data along the EPZT (Resing et al., Nature, 523 (2015) 200-203), we calculate a dissolved iron residence time integrated from the sea surface to 500 meters water depth of 4 to 11 years.

An experimental study of basaltic glass-H2O-CO2 interaction at 22 and 50 ° C: Implications for subsurface storage of CO2

NASA Astrophysics Data System (ADS)

Galeczka, Iwona; Wolff-Boenisch, Domenik; Oelkers, Eric H.; Gislason, Sigurdur R.

2014-05-01

A novel high pressure column flow reactor (HPCFR) was used to investigate the evolution of fluid chemistry along a 2.3 meter flow path during 37-104 days of pure water- and CO2-charged water- (0.3 M CO2(aq)) basaltic glass interaction experiments at 22 and 50 ° C. The scale of the HPCFR, the ability to sample a reactive fluid at discrete spatial intervals under pressure and the possibility to measure the dissolved inorganic carbon and pH in situ all render the HPCFR unique in comparison with other reactors constructed for studies of CO2-charged water-rock interaction. During the pure water-basaltic glass interaction experiment, the pH of the injected water evolved rapidly from 6.7 to 9-9.5 and most of the dissolved iron was consumed by secondary mineral formation, similar to natural basaltic groundwater systems. In contrast to natural systems, however, the dissolved aluminium concentration remained relatively high along the entire flow path. The reactive fluid was undersaturated with respect to basaltic glass and carbonate minerals, but supersaturated with respect to zeolites, clays, and Fe hydroxides. Basaltic glass dissolution in the CO2-charged water was closer to stoichiometry than in pure water. The mobility of metals increased significantly in the reactive fluid and the concentration of some metals, including Mn, Fe, Cr, Al, and As exceeded the WHO (World Health Organisation) allowable drinking water limits. Iron was mobile and the aqueous Fe2+/Fe3+ ratio increased along the flow path. Basaltic glass dissolution in the CO2-charged water did not overcome the pH buffer capacity of the fluid. The pH rose only from an initial pH of 3.4 to 4.5 along the first 18.5 cm of the column, then remained constant during the remaining 2.1 meters of the flow path. Increasing the temperature of the CO2-charged fluid from 22 to 50 ° C increased the relative amount of dissolved divalent iron along the flow path. After a significant initial increase along the first metre of the column, the dissolved aluminium concentration decreased consistent with its incorporation into secondary minerals. The dissolved chromium concentration evolution mimicked that of Al at 50 ° C, suggesting substitution of trivalent Cr for Al in secondary phases. According to PHREEQC calculations, the CO2-charged fluid was always undersaturated with respect to carbonate minerals within the column, but supersaturated with respect to clays and Fe hydroxides at 22 ° C and with respect to clays and Al hydroxides at 50 ° C. Substantial differences were found between modelled and measured dissolved element concentrations in the fluids during the experiments. These differences underscore the need to improve computational models before they can be used to predict with confidence the fate and consequences of carbon dioxide injected into the subsurface.

Distribution and flux estimates of soluble, colloidal, and leachable particulate trace metals in dynamic and oxygen depleted Mauritanian shelf waters

NASA Astrophysics Data System (ADS)

Rapp, I.; Schlosser, C.; Gledhill, M.; Achterberg, E. P.

2016-02-01

Fe availability in surface waters determines primary production, N2 fixation and microbial community structure and thus plays an important role in ocean carbon and nitrogen cycles. Eastern boundary upwelling areas with oxygen minimum zones, such as the Mauritanian shelf region, are typically associated with elevated Fe concentrations with shelf sediments as key source of Fe to bottom and surface waters. The magnitude of vertical and horizontal Fe fluxes from shelf sediments to onshore and offshore surface waters are not well constrained and there are still large uncertainties concerning the stabilisation of Fe once released from sediments into suboxic and oxic waters. Supportive data of other trace metals can be used as an indicator of sediment release, scavenging processes and biological utilisation. Here we present soluble (<0.02 µm), dissolved (<0.2 µm) and total dissolvable (unfiltered) trace metal data collected at 10 stations on a 90 nautical mile transect across the Mauritanian shelf region in June 2014 (cruise Meteor 107). The samples were pre-concentrated using an automated off-line pre-concentration device and analysed simultaneously for Cd, Pb, Fe, Ni, Cu, Zn, Mn and Co using a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). First results indicate the importance of benthic sources to the overall Fe budget in this region. Both dissolved Fe and Mn showed enhanced concentrations close to the shelf at depths between 40 and 180 m corresponding with low oxygen concentrations (<50 µmol L-1). Elevated soluble, dissolved, and total dissolvable Fe and Mn concentrations at an offshore station coincided with the location of a cyclonic Eddie that was characterised by an oxygen depleted water body. To further assess the accuracy of vertical and horizontal fluxes of Fe and other trace metals, we compare diffusivity estimates determined by a microstructure profiler and the scale length method (de Jong et al. 2012) with observed isotopic Ra data.

Cr(VI) removal by FeS-coated alumina, silica, and natural sand

NASA Astrophysics Data System (ADS)

Park, M.; Lee, S.; Jeong, H. Y.

2014-12-01

Removal of Cr(VI) was investigated using mackinawite (FeS)-coated mineral sorbents under anoxic conditions. The sorbents included alumina (Al), silica (WS), and natural sand (NS). By analysis of both solution and solid phases, all FeS-coated sorbents were found to reduce Cr(VI) into Cr(III). The sorption extent and mechanism of Cr(VI) strongly depended on the pH conditions. Only at pH 4.5, significant amounts of the dissolved Cr remained in the solution. Titration of dissolved Cr(III) and Fe(III) by NaOH solutions indicated that no bulk-phase precipitation occurred at pH 4.5. Also, the removal of Cr(VI) at pH 4.5 was the greatest by FeS-coated NS. Consistent with these, Cr-K edge EXAFS revealed that Cr was removed by FeS-coated NS via surface precipitation, and that it was immobilized by FeS-coated WS and Al by forming surface clusters. Regardless of FeS-coated sorbents, at pH 7.0 and pH 9.5, the initially added Cr(VI) was quantitatively removed from the solution phase. By EXAFS analysis, the Cr sorption by FeS-coated Al was mainly due to the bulk-phase precipitation of Cr(OH)3(s) or [Cr, Fe](OH)3(s). In case of FeS-coated WS and NS, the short Cr-Cr distance (~2.6 Å) at pH 7.0 and pH 9.5 was not simply accounted for by the bulk precipitation as either hydroxide (rCr-Cr ~ 3.0 Å), and it would rather result from the surface precipitation. Such a difference in the coordination structure among FeS-coated sorbents was likely due to in the lower surface area of the former available for the surface precipitation.

Reactive iron and manganese in estuarine sediments of the Baltic Sea: Impacts of flocculation and redox shuttling

NASA Astrophysics Data System (ADS)

Jilbert, Tom; Tiihonen, Rosa; Myllykangas, Jukka-Pekka; Asmala, Eero; Hietanen, Susanna

2016-04-01

Iron (Fe) and manganese (Mn) play important roles in sedimentary carbon cycling in both freshwater and marine systems. Dissimilatory reduction of Fe and Mn oxides is known to be a major pathway of suboxic organic matter remineralization in surface sediments, while recent studies have shown that Fe and Mn oxides may be involved in the anaerobic oxidation of methane deeper in the sediment column (e.g., Egger et al., 2015). Estuaries are transitional environments, characterized by gradients of salinity and redox conditions which impact on the mobility of Fe and Mn. In turn, the distribution of Fe and Mn in estuarine sediments, and the role of the two metals in carbon cycling, is expected to be spatially heterogeneous. However, few studies have attempted to describe the sedimentary distribution of Fe and Mn in the context of processes occurring in the estuarine water column. In particular, salinity-driven flocculation and redox shuttling are two key processes whose relative impacts on sedimentary Fe and Mn have not been clearly demonstrated. In this study we investigated the coupled water column and sedimentary cycling of Fe and Mn along a 60km non-tidal estuarine transect in the Gulf of Finland, Baltic Sea. We show that riverine Fe entering the estuary as colloidal oxides associated with dissolved organic matter (DOM) is quickly flocculated and sedimented within 5 km of the river mouth, despite the shallow lateral salinity gradient. Sediments within this range are enriched in Fe (up to twice the regional average), principally in the form of crystalline Fe oxides as determined by sequential extractions. The high crystallinity implies relative maturity of the oxide mineralogy, likely due to sustained oxic conditions and long residence time in the river catchment. Despite the reducing conditions below the sediment-water interface, Fe is largely retained in the sediments close to the river mouth. In contrast, sedimentary Mn concentrations are highest in a deep silled basin more than 10km downstream. Throughout the estuary, Mn oxides are reductively dissolved shallower in the sediment column than Fe oxides, resulting in strong effluxes of dissolved Mn from the sediments. Subsequent oxidation of bottom water dissolved Mn to particulate oxides and lateral transport ("redox shuttling") account for the sedimentary Mn enrichments in the deep silled basin. Porewater data suggest that the heterogeneity of Fe and Mn availability in the estuarine sediments may influence the relative importance of the two metals for anaerobic oxidation of methane. Egger, M. et al., Environmental Science and Technology 49(1), 277-283, 2015.

Net alkalinity and net acidity 2: Practical considerations

USGS Publications Warehouse

Kirby, C.S.; Cravotta, C.A.

2005-01-01

The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples. Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5-4) or near neutral (pH 6-7); ??? 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6. The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze. The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= -net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH < 6.3 after oxidation had positive Hot Acidity. Samples with similar pH values before oxidation had dissimilar Hot Acidities due to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. Hot Acidity was approximately equal to net acidity calculated based on initial pH and dissolved concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity calculated from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was equivalent to that calculated based on complete aqueous speciation of FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the Hot Acidities were comparable for fresh and most aged samples. A meaningful "net" acidity can be determined from a measured Hot Acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. The use of net alkalinity = (Alkalinitymeasured - Hot Aciditymeasured) to design mine drainage treatment can lead to systems with insufficient Alkalinity to neutralize metal and H+ acidity and is not recommended. The use of net alkalinity = -Hot Acidity titration is recommended for the planning of mine drainage treatment. The use of net alkalinity = (Alkalinitymeasured - Aciditycalculated) is recommended with some cautions. ?? 2005 Elsevier Ltd. All rights reserved.

The effect of volcanic eruptions on the chemistry of surface waters: The 1991 and 2000 eruptions of Mt. Hekla, Iceland

NASA Astrophysics Data System (ADS)

Flaathen, Therese K.; Gislason, Sigurdur R.

2007-08-01

The Mt. Hekla eruptions in 1991 and 2000 have provided a unique opportunity to study the local environmental effects of high latitude volcanic eruptions in the middle of winter. Both eruptions started around sunset at sub-zero temperatures. In order to define better these effects we studied the chemistry of surface waters in the vicinity of the volcano. Additionally, we describe and predict the environmental consequences of these volcanic eruptions on the chemistry of surface waters on land and in the ocean. Several dissolved elements in the polluted snow melt from the 2000 eruption (Cl, F, Al, Fe, Mn, As, Cd, Pb, Zn, and U) exceeded the limits for water intended for human consumption. The volcanic ash, the primary minerals and secondary mineral phases that commonly form in the weathering environment of Iceland were undersaturated in the polluted snow melts with the exception of fluorite, barite, goethite and amorphous FeOOH. These minerals can constrain the maximum initial concentration of the respective dissolved constituents in the meltwaters. It took few days after the first rainfall on the volcanic ash to flush out the readily soluble constituents in the vicinity of the headwaters of the Ytri-Rangá River. The polluted river waters were oversaturated with respect to several secondary minerals, resulting in precipitation of amorphous Al hydroxide and FeOOH and further, scavenging of some trace elements on the Al and Fe surfaces. Dissolved Al and F were the main contaminants in the Ytri-Rangá river water. Previous studies have shown that combined Al-F toxicity is directly related to the predominance of specific Al-F species in solution. Model calculations for mixing of a Hekla-type volcanic cloud with 4 surface water end-members shows Al-F species to be most important in rain and dilute river waters. This makes Al and F phyto-available but diminishes the concentration of the Al 3+ species, the most toxic Al species. Mixing with high alkalinity river waters or seawater results in the domination of non toxic Al(OH) 4- species at dilutions greater than 800, thus hindering Al toxicity and bioavailability. This study indicates that H 2SO 4 contamination from volcanic eruptions is time and place dependent. Volcanic eruptions that take place during winter at high latitudes result in relatively high global sulfur contamination and relatively low local sulfur contamination due to the low oxidation rate of SO 2 into H 2SO 4 because of the low solar radiation.

Interaction of exogenous refractory nanophases with antimony dissolved in liquid iron

NASA Astrophysics Data System (ADS)

Burtsev, V. T.; Anuchkin, S. N.; Samokhin, A. V.

2017-07-01

The heterophase interaction of Al2O3 refractory nanoparticles with a surfactant impurity (antimony) in the Fe-Sb (0.095 wt %)-O (0.008 wt %) system is studied. It is shown that the introduction of 0.06-0.18 wt % Al2O3 nanoparticles (25-83 nm) into a melt during isothermal holding for up to 1200 s leads to a decrease in the antimony content: the maximum degree of antimony removal is 26 rel %. The sessile drop method is used to investigate the surface tension and the density of Fe, Fe-Sb, and Fe-Sb-Al2O3 melts. The polytherms of the surface tension of these melts have a linear character, the removal of antimony from the Fe-Sb-Al2O3 melts depends on the time of melting in a vacuum induction furnace, and the experimental results obtained reveal the kinetic laws of the structure formation in the surface layers of the melts. The determined melt densities demonstrate that the introduction of antimony into the Fe-O melt causes an increase in its compression by 47 rel %. The structure of the Fe-Sb-O melt after the introduction of Al2O3 nanoparticles depends on the time of melting in a vacuum induction furnace.

Geochemical interactions between constituents in acidic groundwater and alluvium in an aquifer near Globe, Arizona

USGS Publications Warehouse

Stollenwerk, Kenneth G.

1994-01-01

Acidic water from a copper-mining area has contaminated an alluvial aquifer and stream near Globe, Arizona. The most contaminated groundwater has a pH of 3.3, and contains about 100 mmol/1 SO4, 50 mmol/1 Fe, 11 mmol/1 Al and 3 mmol/1 Cu. Reactions between alluvium and acidic groundwater were first evaluated in laboratory column experiments. A geochemical model was developed and used in the equilibrium speciation program, MINTEQA2, to simulate breakthrough curves for different constituents from the column. The geochemical model was then used to simulate the measured changes in concentration of aqueous constituents along a flow path in the aquifer.The pH was predominantly controlled by reaction with carbonate minerals. Where carbonates had been dissolved, adsorption of H+ by iron oxides was used to simulate pH. Acidic groundwater contained little or no dissolved oxygen, and most aqueous Fe was present as Fe(II). In the anoxic core of the plume, Fe(II) was oxidized by MnO2 to Fe(III), which then precipitated as Fe(OH)3. Attenuation of aqueous Cu, Co, Mn, Ni and Zn was a function of pH and could be quantitatively modeled with the diffuse-layer, surface complexation model in MINTEQA2. Aluminum precipitated as amorphous Al(OH)3 at pH < 4.7 and as AlOHSO4 at pH < 4.7. Aqueous Ca and SO4were close to equilibrium with gypsum.After the alluvium in the column had reached equilibrium with acidic groundwater, uncontaminated groundwater was eluted through the column to evaluate the effect of reactants on groundwater remediation. The concentration of Fe, Mn, Cu, Co, Ni and Zn rapidly decreased to the detection limits within a few pore volumes. All of the gypsum that had precipitated initially redissolved, resulting in elevated Ca and SO4concentrations for about 5 pore volumes. Aluminum and pH exhibited the most potential for continued adverse effects on groundwater quality. As H+ desorbed from Fe(OH)3, pH remained below 4.5 for more than 20 pore volumes, resulting in dissolution of AlOHSO4 and elevated aqueous Al.

Siderophore production in high iron environments

NASA Astrophysics Data System (ADS)

Bennett, S. A.; Hoffman, C. L.; Moffett, J. W.; Edwards, K. J.

2010-12-01

Up until recently, the geochemical cycling of Fe in deep sea hydrothermal plumes has assumed to be inorganically dominated, resulting in quantitative precipitation of all hydrothermally sourced Fe to the seafloor. Recent detection of organic Fe binding ligands within both the dissolved and particulate phase (Bennett et al., 2008; Toner et al., 2009), suggests that hydrothermally sourced Fe may be important on a global scale (Tagliabue et al., 2010). The source of these organic ligands is currently unknown; hypotheses include the possible entrainment of organic carbon from the biologically rich diffuse flow areas, or in-situ production from microbial processes. However, the microbial production of organic ligands is only expected when Fe is a limited micronutrient, which is not the case in the hydrothermal environment. The importance of Fe cycling microorganisms within hydrothermal systems was previously overlooked due to the poor energetics with regards to Fe oxidation and reduction. But their recent detection within the hydrothermal system, both around low temperature Fe rich mineral deposits and within hydrothermal plumes (Edwards et al., 2004; Sylvan et al., In prep) suggests that they may have an important role in the hydrothermal Fe cycle, potentially resulting in an interplay between Fe and organic carbon. Within the laboratory, we have carried out experiments to investigate an Fe oxidizing bacteria in a variety of high Fe environments. We have detected both the production of siderophores and an increase in reduced Fe when the Fe oxidizing bacteria is exposed to both Fe(III) and Fe(II) rich minerals. The role of these microbes in the mineral dissolution of Fe sulfides along the seafloor and within the hydrothermal plume, may have important implications on the speciation of Fe and the role of siderophores in the marine environment. Bennett, S.A. et al. 2008. EPSL, 270: 157-167. Edwards, K.J. et al. 2004. Geomicrobiology Journal, 21: 393-404. Sylvan, J.B. et al. In prep for Geobiology Tagliabue, A. et al. 2010. Nature Geoscience, 3: 252-256. Toner, B.M.,et al. 2009. Nature Geoscience, 2: 197 - 201.

New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

USGS Publications Warehouse

To, T.B.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.; McCleskey, R. Blaine

1999-01-01

A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), Al(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2/??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.

Revisiting Mn and Fe removal in humic rich estuaries

NASA Astrophysics Data System (ADS)

Oldham, Véronique E.; Miller, Megan T.; Jensen, Laramie T.; Luther, George W.

2017-07-01

Metal removal by estuarine mixing has been studied for several decades, but few studies emphasize dissolved metal speciation and organic ligand complexation. Findings from the last decade indicate that metal-humic complexation can be significant for dissolved metals including Cu(II), Al(III) and Fe(III), but little consideration is given to the precipitation of these complexes with humic material at pH < 2. Given that total soluble metal analysis involves an acidification step for sample preservation, we show that Mn and other metal concentrations may have been underestimated in estuaries, especially when humic substance concentrations are high. A competitive ligand assay of selected samples from our study site, a coastal waterway bordered by wetlands (Broadkill River, DE), showed that Mn(III)-humic complexation is significant, and that some Mn(III)-L complexes precipitate during acidification. In the oxygenated surface waters of the Broadkill River, total dissolved Mn (dMnT) was up to 100% complexed to ambient ligands as Mn(III)-L, and we present evidence for humic-type Mn(III)-L complexes. The Mn(III) complexes were kinetically stabilized against Fe(II) reduction, even when [Fe(II)] was 17 times higher than [dMnT]. Unlike typical oceanic surface waters, [Fe(II)] > [Fe(III)-L] in surface waters, which may be attributed to high rates of photoreduction of Fe(III)-L complexes. Total [Mn(III)-L] ranged from 0.22 to 8.4 μM, in excess of solid MnOx (below 0.28 μM in all samples). Filtration of samples through 0.02 μm filters indicated that all Mn(III)-L complexes pass through the filters and were not colloidal species in contrast to dissolved Fe. Incubation experiments indicated that the reductive dissolution of solid MnOx by ambient ligands may be responsible for Mn(III) formation in this system. Unlike previous studies of estuarine mixing, which demonstrated metal removal during mixing, we show significant export of dMn and dissolved Fe (dFe) in the summer and fall of 2015. Thus, we propose that estuarine removal should be considered seasonal for dMn and dFe, with export in the summer and fall and removal during the winter.

Influence of ultrasonic energy on dispersion of aggregates and released amounts of organic matter and polyvalent cations

NASA Astrophysics Data System (ADS)

Kaiser, M.; Kleber, M.; Berhe, A. A.

2010-12-01

Aggregates play important roles in soil carbon storage and stabilization. Identification of scale-dependent mechanisms of soil aggregate formation and stability is necessary to predict and eventually manage the flow of carbon through terrestrial ecosystems. Application of ultrasonic energy is a common tool to disperse soil aggregates. In this study, we used ultra sonic energy (100 to 2000 J cm-3) to determine the amount of polyvalent cations and organic matter involved in aggregation processes in three arable and three forest soils that varied in soil mineral composition. To determine the amount of organic matter and cations released after application of different amount of ultrasonic energy, we removed the coarse fraction (>250 µm). The remaining residue (<250 µm) was mixed with water and ultrasonically dispersed by application of 100, 200, 400, 500, 1000, 1500 and 2000 J cm-3 energy. After centrifugation the supernatant was filtered and the solid residue freeze dried before we analyzed the amounts of water-extracted organic carbon (OC), Fe, Al, Ca, Mn, and Mg in the filtrates. The extracted OM and solid residues were further characterized by Fourier Transformed Infra Red spectroscopy and Scanning Electron Microscopy. Our results show a linear increase in amount of dissolved OC with increasing amounts of ultra sonic energy up to 1500 J cm-3 indicating maximum dispersion of soil aggregates at this energy level independent from soil type or land use. In contrast to Mn, and Mg, the amounts of dissolved Ca, Fe, and Al increase with increasing ultra sonic energy up to 1500 J cm-3. At 1500 J cm-3, the absolute amounts of OC, Ca, Fe, and Al released were specific for each soil type, likely indicating differences in type of OM-mineral interactions involved in micro-scaled aggregation processes. The amounts of dissolved Fe, and Al released after an application of 1500 J cm-3 are not related to oxalate- and dithionite- extractable, or total Al content indicating less disintegration of pedogenic oxides or clay minerals due to high levels of ultrasonic energy.

Diel changes in metal concentrations in a geogenically acidic river: Rio Agrio, Argentina

NASA Astrophysics Data System (ADS)

Parker, Stephen R.; Gammons, Christopher H.; Pedrozo, Fernando L.; Wood, Scott A.

2008-12-01

Rio Agrio in Patagonia, Argentina is a geogenically acidic stream that derives its low-pH waters from condensation of acidic gases near its headwaters on the flanks of the active Copahue Volcano. This study reports the results of three diel (24-h) water samplings in three different pH regimes (3.2, 4.4 and 6.3) along the river. Changes in the concentration and speciation of Fe dominated the diel chemical changes at all three sites, although the timing and intensity of these cycles were different in each reach. At the two acidic sampling sites, total dissolved Fe and dissolved Fe(III) concentrations decreased during the day and increased at night, whereas dissolved Fe(II) showed the reverse pattern. These cycles are explained by Fe(III) photoreduction, as well as enhanced rates of precipitation of hydrous ferric oxide (HFO) during the warm afternoon hours. A strong correlation was observed between Fe(III) and As at the furthest upstream (pH 3.2) site, most likely due to co-precipitation of As with HFO. At the downstream (pH 6.3) location, Fe(II) concentrations increased at night, as did concentrations of rare earth elements and dissolved Al. Photoreduction does not appear to be an important process at pH 6.3, although it may be indirectly responsible for the observed diel cycle of Fe(II) due to advection of photochemically produced Fe(II) from acidic upstream waters. The results of this study of a naturally-acidic river are very similar to diel trends recently obtained from mining-impacted streams receiving acid rock drainage. The results are also used to explore the link between geochemistry and microbiology in acidic eco-systems. For example, Fe(III) photoreduction produces chemical potential energy (in the form of metastable Fe 2+) that helps support the bacterial community in this unique extreme environment.

Determination of chemical-constituent loads during base-flow and storm-runoff conditions near historical mines in Prospect Gulch, upper Animas River watershed, southwestern Colorado

USGS Publications Warehouse

Wirt, Laurie; Leib, K.J.; Bove, D.J.; Mast, M.A.; Evans, J.B.; Meeker, G.P.

1999-01-01

Prospect Gulch is a major source of iron, aluminum, zinc, and other metals to Cement Creek. Information is needed to prioritize remediation and develop strategies for cleanup of historical abandoned mine sites in Prospect Gulch. Chemical-constituent loads were determined in Prospect Gulch, a high-elevation alpine stream in southwestern Colorado that is affected by natural acid drainage from weathering of hydro-thermally altered igneous rock and acidic metal-laden discharge from historical abandoned mines. The objective of the study was to identify metal sources to Prospect Gulch. A tracer solution was injected into Prospect Gulch during water-quality sampling so that loading of geochemical constituents could be calculated throughout the study reach. A thunderstorm occurred during the tracer study, hence, metal loads were measured for storm-runoff as well as for base flow. Data from different parts of the study reach represents different flow conditions. The beginning of the reach represents background conditions during base flow immediately upstream from the Lark and Henrietta mines (samples PG5 to PG45). Other samples were collected during storm runoff conditions (PG100 to PG291); during the first flush of metal runoff following the onset of rainfall (PG303 to PG504), and samples PG542 to PG700 were collected during low-flow conditions. During base-flow conditions, the percentage increase in loads for major constituents and trace metals was more than an order of magnitude greater than the corresponding 36 % increase in stream discharge. Within the study reach, the highest percentage increases for dissolved loads were 740 % for iron (Fe), 465 % for aluminum (Al), 500 % for lead (Pb), 380 % for copper (Cu), 100 % for sulfate (SO4), and 50 % for zinc (Zn). Downstream loads near the mouth of Prospect Gulch often greatly exceeded the loads generated within the study reach but varied by metal species. For example, the study reach accounts for about 6 % of the dissolved-Fe load, 13 % of the dissolved-Al load, and 18 % of the dissolved-Zn load; but probably contributes virtually all of the dissolved Cu and Pb. The greatest downstream gains in dissolved trace-metal loads occurred near waste-rock dumps for the historical mines. The major sources of trace metals to the study reach were related to mining. The major source of trace metals in the reach near the mouth is unknown, however is probably related to weathering of highly altered igneous rocks, although an unknown component of trace metals could be derived from mining sources The late-summer storm dramatically increased the loads of most dissolved and total constituents. The effects of the storm were divided into two distinct periods; (1) a first flush of higher metal concentrations that occurred soon after rainfall began and (2) the peak discharge of the storm runoff. The first flush contained the highest loads of dissolved Fe, total and dissolved Zn, Cu, and Cd. The larger concentrations of Fe and sulfate in the first flush were likely derived from iron hydroxide minerals such as jarosite and schwertmanite, which are common on mine dumps in the Prospect Gulch drainage basin. Peak storm runoff contained the highest measured loads of total Fe, and of total and dissolved calcium, magnesium, silica and Al, which were probably derived from weathering of igneous rocks and clay minerals in the drainage basin.

Dissolution of man-made vitreous fibers in rat alveolar macrophage culture and Gamble's saline solution: influence of different media and chemical composition of the fibers.

PubMed Central

Luoto, K; Holopainen, M; Karppinen, K; Perander, M; Savolainen, K

1994-01-01

The effect of different chemical compositions of man-made vitreous fibers (MMVF) on their dissolution by alveolar macrophages (AM) in culture and in Gamble's solution was studied. The fibers were exposed to cultured rat AMs, culture medium alone; or Gamble's saline solution for 2, 4, or 8 days. The dissolution of the fibers was studied by measuring the amount of silicon (Si), iron (Fe), and aluminum (Al) in each medium. The AMs in culture dissolved Fe and Al from the fibers but the dissolution of Si was more marked in the cell culture medium without cells and in the Gamble's solution. The dissolution of Si, Fe, and Al was different for different fibers, and increased as a function of time. The Fe and Al content of the fibers correlated negatively with the dissolution of Si by AMs from the MMVF, i.e., when the content of Fe and Al of the fibers increased the dissolution of Si decreased. These results suggest that the chemical composition of MMVFs has a marked effect on their dissolution. AMs seem to affect the dissolution of Fe and Al from the fibers. This suggests that in vitro models with cells in the media rather than only culture media or saline solutions would be preferable in dissolution studies of MMVFs. PMID:7882911

Effect of Initial Iron Content in a Zinc Bath on the Dissolution Rate of Iron During a Hot Dip Galvanizing Process

NASA Astrophysics Data System (ADS)

Lee, Sang Myung; Lee, Suk Kyu; Paik, Doo-Jin; Park, Joo Hyun

2017-04-01

The mechanism of iron dissolution and the effect of initial Fe content in a Zn bath on the dissolution rate of iron were investigated using a finger rotating method (FRM). When the initial iron content, [Fe]°, in the zinc bath was less than the solubility limit, the iron content in the zinc bath showed a rapid increase, whereas a moderate increase was observed when [Fe]° was close to the solubility limit. Based on Eisenberg's kinetic model, the mass transfer coefficient of iron in the present experimental condition was calculated to be k M = 1.2 × 10-5 m/s, which was similar to the results derived by Giorgi et al. under industrial practice conditions. A dissolution of iron occurred even when the initial iron content in the zinc bath was greater than the solubility limit, which was explained by the interfacial thermodynamics in conjunction with the morphology of the surface coating layer. By analyzing the diffraction patterns using TEM, the outermost dendritic-structured coating layer was confirmed as FeZn13 ( ζ). In order to satisfy the local equilibrium based on the Gibbs-Thomson equation, iron in the dendrite-structured phase spontaneously dissolved into the zinc bath, resulting in the enrichment of iron in front of the dendrite tip. Through the diffusion boundary layer in front of the dendritic-structured layer, dissolved Fe atoms diffused out and reacted with Zn and small amounts of Al, resulting in the formation of dross particles such as FeZn10Al x ( δ). It was experimentally confirmed that the smaller the difference between the initial iron content in the zinc bath and the iron solubility limit at a given temperature, the lower the number of formed dross particles.

Characterization of dissolved organic matter during reactive transport: A column experiment with spectroscopic detection

NASA Astrophysics Data System (ADS)

Vazquez, A.; Hernández, S.; Rasmussen, C.; Chorover, J.

2010-12-01

Al and Fe oxy-hydroxide minerals have been implicated in dissolved organic matter (DOM) stabilization. DOM solutions from a Pinus ponderosa forest floor (PPDOM) were used to irrigate polypropylene columns, 3.2 cm long by 0.9 cm diameter (total volume 2.0 cm3), that were packed with quartz sand (QS), gibbsite-quartz sand (Al-QS), and goethite-quartz sand (Fe-QS) mixtures. To investigate the mobilization and fractionation of DOM during reactive transport, effluent solutions were characterized by UV-Vis absorbance and excitation-emission matrix (EEM) fluorescence spectroscopies. Magnitude of PPDOM sorption followed the trend Al-QS > Fe-QS > QS during the initial transport. Effluent pH values suggest that ligand exchange is a primary mechanism for PPDOM sorption onto oxy-hydroxide minerals. Low molar absorptivity values were observed in effluent solutions of early pore volumes, indicating preferential mobilization of compounds with low aromatic character. Compounds traditionally characterized by EEM spectroscopy as being more highly humified were favorably absorbed onto the gibbsite and goethite surfaces. Humification index values (HIX) were also correlated with DOM aromaticity. HIX results suggest that the presence of low mass fractions of oxy-hydroxide minerals affect the preferential uptake of high molar mass constituents of PPDOM during reactive transport.

Spatio-Temporal Variability of Dissolved Metals in the Surface Waters of an Agroforestry Catchment with Low Levels of Anthropogenic Activity

NASA Astrophysics Data System (ADS)

Soto-Varela, Fátima; Rodríguez-Blanco, M. Luz; Mercedes Taboada-Castro, M.; Taboada-Castro, M. Teresa

2017-12-01

Evaluation of levels and spatial variations of metals in surface waters within a catchment are critical to understanding the extent of land-use impact on the river system. The aims of this study were to investigate the spatial and temporal variations of five dissolved metals (Al, Fe, Mn, Cu and Zn) in surface waters of a small agroforestry catchment (16 km2) in NW Spain. The land uses include mainly forests (65%) and agriculture (pastures: 26%, cultivation: 4%). Stream water samples were collected at four sampling sites distributed along the main course of the Corbeira stream (Galicia, NW Spain) between the headwaters and the catchment outlet. The headwater point can be considered as pristine environment with natural metal concentrations in waters because of the absence of any agricultural activity and limited accessibility. Metal concentrations were determined by ICP-MS. The results showed that metal concentrations were relatively low (Fe > Al > Mn > Zn > Cu), suggesting little influence from agricultural activities in the area. Mn and Zn did not show significant differences between sampling points along main stream, while for Fe and Cu significant differences were found between the headwaters and all other points. Al tended to decrease from the headwaters to the catchment outlet.

Modelling removal mechanisms of Pb, Cu, Zn and Cd in acidic groundwater during the neutralization by ambient surface and ground waters

USGS Publications Warehouse

Paulson, Anthony J.; Balistrieri, Laurie S.

1999-01-01

Removal of Pb, Cu, Zn, and Cd during neutralization of acid rock drainage is examined using model simulations of field conditions and laboratory experiments involving mixing of natural drainage and surface waters or groundwaters. The simulations consider sorption onto hydrous Fe and Al oxides and particulate organic carbon, mineral precipitation, and organic and inorganic solution complexation of metals for two physical systems where newly formed oxides and particulate organic matter are either transported or retained along the chemical pathway. The calculations indicate that metal removal is a strong function of the physical system. Relative to direct discharge of ARD into streams, lower metal removals are observed where ARD enters streamwaters during the latter stages of neutralization by ambient groundwater after most of the Fe has precipitated and been retained in the soils. The mixing experiments, which represent the field simulations, also demonstrated the importance of dissolved metal to particle Fe ratios in controlling dissolved metal removal along the chemical pathway. Finally, model calculations indicate that hydrous Fe oxides and particulate organic carbon are more important than hydrous Al oxides in removing metals and that both inorganic and organic complexation must be considered when modeling metal removal from aquatic systems that are impacted by sulfide oxidation.

Humic substances and trace metals associated with Fe and Al oxides deposited in an acidic mountain stream

USGS Publications Warehouse

McKnight, Diane M.; Wershaw, R. L.; Bencala, K.E.; Zellweger, G.W.; Feder, G.L.

1992-01-01

Hydrous iron and aluminum oxides are deposited on the streambed in the confluence of the Snake River and Deer Creek, two streams in the Colorado Rocky Mountains. The Snake River is acidic and has high concentrations of dissolved Fe and Al. These metals precipitate at the confluence with the pristine, neutral pH, Deer Creek because of the greater pH (4.5-6.0) in the confluence. The composition of the deposited oxides changes consistently with distance downstream, with the most upstream oxide samples having the greatest Fe and organic carbon content. Fulvic acid accounts for most of the organic content of the oxides. Results indicate that streambed oxides in the confluence are not saturated with respect to their capacity to sorb dissolved humic substances from streamwater. The contents of several trace metals (Mn, Zn, Cu, Pb, Ni and Co) also decrease with distance downstream and are correlated with both the Fe and organic carbon contents. Strong metal-binding sites associated with the sorbed fulvic acid are more than sufficient to account for the trace metal content of the oxides. Complexation of trace metals by sorbed fulvic acid may explain the observed downstream decrease in trace metal content.

Low biodegradability of dissolved organic matter and trace metals from subarctic waters.

PubMed

Oleinikova, Olga V; Shirokova, Liudmila S; Drozdova, Olga Y; Lapitskiy, Sergey A; Pokrovsky, Oleg S

2018-03-15

The heterotrophic mineralization of dissolved organic matter (DOM) controls the CO 2 flux from the inland waters to the atmosphere, especially in the boreal waters, although the mechanisms of this process and the fate of trace metals associated with DOM remain poorly understood. We studied the interaction of culturable aquatic (Pseudomonas saponiphila) and soil (Pseudomonas aureofaciens) Gammaproteobacteria with seven different organic substrates collected in subarctic settings. These included peat leachate, pine crown throughfall, fen, humic lake, stream, river, and oligotrophic lake with variable dissolved organic carbon (DOC) concentrations (from 4 to 60mgL -1 ). The highest removal of DOC over 4days of reaction was observed in the presence of P. aureofaciens (33±5%, 43±3% and 53±7% of the initial amount in fen water, humic lake and stream, respectively). P. saponiphila degraded only 5% of DOC in fen water but did not affect all other substrates. Trace elements (TE) were essentially controlled by short-term (0-1h) adsorption on the surface of cells. Regardless of the nature of organic substrate and the identity of bacteria, the degree of adsorption ranged from 20 to 60% for iron (Fe 3+ ), 15 to 55% for aluminum (Al), 10 to 60% for manganese (Mn), 10 to 70% for nickel (Ni), 20 to 70% for copper (Cu), 10 to 60% for yttrium (Y), 30 to 80% for rare earth elements (REE), and 15 to 50% for uranium (U VI ). Rapid adsorption of organic and organo-mineral colloids on bacterial cell surfaces is novel and potentially important process, which deserves special investigation. The long-term removal of dissolved Fe and Al was generally consistent with solution supersaturation degree with respect to Fe and Al hydroxides, calculated by visual Minteq model. Overall, the biomass-normalized biodegradability of various allochthonous substrates by culturable bacteria is much lower than that of boreal DOM by natural microbial consortia. Copyright © 2017 Elsevier B.V. All rights reserved.

Fractionation of fulvic acid by iron and aluminum oxides: influence on copper toxicity to Ceriodaphnia dubia

USGS Publications Warehouse

Smith, Kathleen S.; Ranville, James F.; Lesher, Emily K.; Diedrich, Daniel J.; McKnight, Diane M.; Sofield, Ruth M.

2014-01-01

This study examines the effect on aquatic copper toxicity of the chemical fractionation of fulvic acid (FA) that results from its association with iron and aluminum oxyhydroxide precipitates. Fractionated and unfractionated FAs obtained from streamwater and suspended sediment were utilized in acute Cu toxicity tests on ,i>Ceriodaphnia dubia. Toxicity test results with equal FA concentrations (6 mg FA/L) show that the fractionated dissolved FA was 3 times less effective at reducing Cu toxicity (EC50 13 ± 0.6 μg Cu/L) than were the unfractionated dissolved FAs (EC50 39 ± 0.4 and 41 ± 1.2 μg Cu/L). The fractionation is a consequence of preferential sorption of molecules having strong metal-binding (more aromatic) moieties to precipitating Fe- and Al-rich oxyhydroxides, causing the remaining dissolved FA to be depleted in these functional groups. As a result, there is more bioavailable dissolved Cu in the water and hence greater potential for Cu toxicity to aquatic organisms. In predicting Cu toxicity, biotic ligand models (BLMs) take into account dissolved organic carbon (DOC) concentration; however, unless DOC characteristics are accounted for, model predictions can underestimate acute Cu toxicity for water containing fractionated dissolved FA. This may have implications for water-quality criteria in systems containing Fe- and Al-rich sediment, and in mined and mineralized areas in particular. Optical measurements, such as specific ultraviolet absorbance at 254 nm (SUVA254), show promise for use as spectral indicators of DOC chemical fractionation and inferred increased Cu toxicity.

Evaluating remedial alternatives for an acid mine drainage stream: Application of a reactive transport model

USGS Publications Warehouse

Runkel, R.L.; Kimball, B.A.

2002-01-01

A reactive transport model based on one-dimensional transport and equilibrium chemistry is applied to synoptic data from an acid mine drainage stream. Model inputs include streamflow estimates based on tracer dilution, inflow chemistry based on synoptic sampling, and equilibrium constants describing acid/base, complexation, precipitation/dissolution, and sorption reactions. The dominant features of observed spatial profiles in pH and metal concentration are reproduced along the 3.5-km study reach by simulating the precipitation of Fe(III) and Al solid phases and the sorption of Cu, As, and Pb onto freshly precipitated iron-(III) oxides. Given this quantitative description of existing conditions, additional simulations are conducted to estimate the streamwater quality that could result from two hypothetical remediation plans. Both remediation plans involve the addition of CaCO3 to raise the pH of a small, acidic inflow from ???2.4 to ???7.0. This pH increase results in a reduced metal load that is routed downstream by the reactive transport model, thereby providing an estimate of post-remediation water quality. The first remediation plan assumes a closed system wherein inflow Fe(II) is not oxidized by the treatment system; under the second remediation plan, an open system is assumed, and Fe(II) is oxidized within the treatment system. Both plans increase instream pH and substantially reduce total and dissolved concentrations of Al, As, Cu, and Fe(II+III) at the terminus of the study reach. Dissolved Pb concentrations are reduced by ???18% under the first remediation plan due to sorption onto iron-(III) oxides within the treatment system and stream channel. In contrast, iron(III) oxides are limiting under the second remediation plan, and removal of dissolved Pb occurs primarily within the treatment system. This limitation results in an increase in dissolved Pb concentrations over existing conditions as additional downstream sources of Pb are not attenuated by sorption.

Evaluation of Fe(II) oxidation at an acid mine drainage site using laboratory-scale reactors

NASA Astrophysics Data System (ADS)

Brown, Juliana; Burgos, William

2010-05-01

Acid mine drainage (AMD) is a severe environmental threat to the Appalachian region of the Eastern United States. The Susquehanna and Potomac River basins of Pennsylvania drain to the Chesapeake Bay, which is heavily polluted by acidity and metals from AMD. This study attempted to unravel the complex relationships between AMD geochemistry, microbial communities, hydrodynamic conditions, and the mineral precipitates for low-pH Fe mounds formed downstream of deep mine discharges, such as Lower Red Eyes in Somerset County, PA, USA. This site is contaminated with high concentrations of Fe (550 mg/L), Mn (115 mg/L), and other trace metals. At the site 95% of dissolved Fe(II) and 56% of total dissolved Fe is removed without treatment, across the mound, but there is no change in the concentration of trace metals. Fe(III) oxides were collected across the Red Eyes Fe mound and precipitates were analyzed by X-ray diffraction, electron microscopy and elemental analysis. Schwertmannite was the dominant mineral phase with traces of goethite. The precipitates also contained minor amounts of Al2O3, MgO,and P2O5. Laboratory flow-through reactors were constructed to quantify Fe(II) oxidation and Fe removal over time at terrace and pool depositional facies. Conditions such as residence time, number of reactors in sequence and water column height were varied to determine optimal conditions for Fe removal. Reactors with sediments collected from an upstream terrace oxidized more than 50% of dissolved Fe(II) at a ten hour residence time, while upstream pool sediments only oxidized 40% of dissolved Fe(II). Downstream terrace and pool sediments were only capable of oxidizing 25% and 20% of Fe(II), respectively. Fe(II) oxidation rates measured in the reactors were determined to be between 3.99 x 10-8and 1.94 x 10-7mol L-1s-1. The sediments were not as efficient for total dissolved Fe removal and only 25% was removed under optimal conditions. The removal efficiency for all sediments decreased as residence time decreased and as water column depth increased. Control reactors with Co-60 irradiated sediments showed an increase in Fe concentration as a result of dissolution of the sediments; thus, it was concluded that Fe(II) oxidation in the reactors was a result of biological processes and not abiotic oxidation. It was also concluded that Fe(II) oxidation and removal rates were dependent upon geochemical gradients (pH, Fe(II) concentration) rather than depositional facies. Fluorescent in situ hybridization was also performed on field and reactor samples to determine which microbial communities were responsible for the highest Fe(II) oxidation rates.

Stabilizing cadmium into aluminate and ferrite structures: Effectiveness and leaching behavior.

PubMed

Su, Minhua; Shih, Kaimin; Kong, Lingjun

2017-02-01

The inappropriate disposal of sludge, particularly for those enriched in heavy metals, is highly hazardous to the environment. Thermally converting sludge into useful products is a highly promising technique as heavy metals are immobilized and organic substances are mineralized. This work investigated the feasibility of stabilizing simulated cadmium-laden sludge by sintering with Al-and Fe-rich precursors. To simulate the process, cadmium oxide was alternatively mixed and sintered with γ-Al 2 O 3 and α-Fe 2 O 3 . Cadmium was crystallographically incorporated into aluminate (CdAl 4 O 7 ) monoclinic structure and ferrite (CdFe 2 O 4 ) spinel, dependent on the type of precursor used. The CdFe 2 O 4 formation was initialed at about 150-300 °C lower than that of CdAl 4 O 7 . With Rietveld refinement analysis of the collated XRD data, the weight percentages of crystalline phases in the fired samples were quantified. To evaluate the cadmium incorporation efficiency, a transformation ratio (TR) index was devised. The TR values revealed that, to effectively incorporate cadmium, 950 °C was favored by γ-Al 2 O 3 and 850 °C was for α-Fe 2 O 3 within a 3-h sintering treatment. Constant pH leaching test (CPLT) was used to assess the metal stabilization effects, revealing a remarkable reduction of cadmium by transformation into CdAl 4 O 7 and CdFe 2 O 4 . Both CdAl 4 O 7 and CdFe 2 O 4 were incongruently dissolved in an acid solution. The overall finding indicated a potentially feasible technology in cadmium-laden sludge stabilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of Aluminum on the Formation Behavior of Zn-Al-Fe Intermetallic Particles in a Zinc Bath

NASA Astrophysics Data System (ADS)

Park, Joo Hyun; Park, Geun-Ho; Paik, Doo-Jin; Huh, Yoon; Hong, Moon-Hi

2012-01-01

The shape, size, and composition of dross particles as a function of aluminum content at a fixed temperature were investigated for aluminum added to the premelted Zn-Fe melt simulating the hot-dip galvanizing bath by a sampling methodology. In the early stage, less than 30 minutes after Al addition, local supersaturation and depletion of the aluminum concentration occurred simultaneously in the bath, resulting in the nucleation and growth of both Fe2Al5Zn x and FeZn13. However, the aluminum was homogenized continuously as the reaction proceeded, and fine and stable FeZn10Al x formed after 30 minutes. An Al-depleted zone (ADZ) mechanism was newly proposed for the "η→η+ζ→δ" phase transformations. The ζ phase bottom dross partly survived for a relatively long period, i.e., 2 hours in this work, whereas the η phase disappeared after 30 minutes. In the early stage of dross formation, both Al-free large particles as well as high-Al tiny particles were formed. The dross particle size decreased slightly with increased reaction time before reaching a plateau. The opposite tendency was observed when the Al content was 0.130 mass pct; with a relatively high Al content, the nucleation of tiny η phase dross was significantly enhanced because of the high degree of supersaturation. This unstable η phase dissolved continuously and underwent simple transformation to the stable δ phase. The relationship between nucleation potential and supersaturation ratio of species is discussed based on the thermodynamics of classical nucleation theory.

Metal-fluxes characterization at a catchment scale: Study of mixing processes and end-member analysis in the Meca River watershed (SW Spain)

NASA Astrophysics Data System (ADS)

Cánovas, C. R.; Macías, F.; Olías, M.; López, R. Pérez; Nieto, J. M.

2017-07-01

Fluxes of acidity and contaminants from acid mine drainage (AMD) sources to the receiving surface water bodies were studied in a mining-impacted watershed (Meca River, SW Spain) using a novel methodology based on the joint application of EMMA and MIX codes. The application of EMMA and elemental ratios allowed delimiting the end-members responsible for water quality variations at a catchment scale. The further application of MIX quantified the significant impact of AMD on the river quality; less than 10% of AMD relative contribution is enough to maintain acidic conditions during most of the year. The mixing model also provided information about the element mobility, distinguishing those elements with a quasi-conservative behavior (e.g., Cu, Zn, Al, Co or Ni) from those affected by mineral precipitation/dissolution (e.g., K, Si, Na, Sr, Ca, Fe, Pb, or As). Floods are the main driver of dissolved and, mainly particulate, contaminants in the catchment. Thus, the first rainfall events in November only accounted for 19% of the annual Meca flow but yielded between 26 and 43% of the net acidity and dissolved metal loads (mainly, Fe, As and Pb). Concerning particulate transport, around 332 tons of particulate Fe, 49 tons of Al, 0.79 tons of As and 0.37 tons of Pb were recorded during these first floods. The particulate As concentration can be up to 34 times higher than the dissolved one during floods and between 2 and 4 times higher for Fe, Pb and Cr. This integrated modeling approach could be a promising and useful tool to face future restoration plans in derelict mines worldwide. This approach would allow prioritizing remedial measures, achieving an environmental and cost-effective restoration of degraded areas.

The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes

NASA Astrophysics Data System (ADS)

Bennett, Sarah A.; Achterberg, Eric P.; Connelly, Douglas P.; Statham, Peter J.; Fones, Gary R.; German, Christopher R.

2008-06-01

We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those samples. At 2.5 km down plume from the nearest known vent site dissolved Fe concentrations were ˜ 20 nM. This is much higher than would be predicted from a combination of plume dilution and dissolved Fe(II) oxidation rates, but consistent with stabilisation due to the presence of organic Fe complexes and Fe colloids. Using Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-CSV), stabilised dissolved Fe complexes were detected within the dissolved Fe fraction on the edges of one non-buoyant hydrothermal plume with observed ligand concentrations high enough to account for stabilisation of ˜ 4% of the total Fe emitted from the 5° S vent sites. If these results were representative of all hydrothermal systems, submarine venting could provide 12-22% of the global deep-ocean dissolved Fe budget.

Element ratios between digestive gland and gill tissues of the Antarctic bivalve Laternula elliptica as a proxy for element uptake from different environmental sources

NASA Astrophysics Data System (ADS)

Poigner, H.; Monien, D.; Monien, P.; Kriews, M.; Brumsack, H.-J.; Wilhelms-Dick, D.; Abele, D.

2012-04-01

Trace metals in bivalve carbonate shells are frequently used as environmental or paleoclimate proxies. Carbonate mineralogy and animals' physiology affect the incorporation of elements from different environmental sources into bivalve shells. Generally, metals from particulate matter are assimilated via the digestive tract; whereas dissolved metals are absorbed via gills. Therefore, measurements of element concentrations deposited in the shell matrix do not necessarily allow inference with respect to the assimilation pathways. In this study, we used element ratios between digestive gland (DG) and gills (cDG/cGill) of the Circum-Antarctic clam Laternula elliptica to identify predominating assimilation pathways and potential sources of bio-available metals. This normalization between tissues of each individual eliminates the effects of individual age and physiological condition (e.g. accumulation over lifetime, metabolic activity) on metal assimilation. These effects also minimize the reproducibility, when absolute element concentrations are compared between individuals from different locations. Therefore, an additional normalization is required. We favored "ellipsoid shell volume" over shell length or soft tissue weight as more conservative approximation for intra- and intersite comparisons. Metal concentrations in DG, gills, and hemolymph of the bivalve L. elliptica, collected at Potter Cove (King George Island, Antarctic Peninsula), were analyzed by means of inductively coupled plasma - optical emission spectroscopy and mass spectrometry after total acid digestion. The element ratios (cDG/cGill) indicate a predominant assimilation of Al, Ca, Fe, K, Mn, and Mg from the dissolved phase. These high Al and Fe concentrations in gill tissues and hemolymph are in contrast to the low solubility of Al and Fe in seawater. But high dissolved Fe concentrations in pore waters (up to 1400 μg L-1 due to suboxic sediment conditions) and glacial melt waters enriched in dissolved Al (of approx. 54 μg L-1 due to weathering processes) with respect to seawater concentrations (5.4-13.5 μg L-1) are likely bio-available sources at Potter Cove. In contrast, Cd, Cu, and Sr are mainly assimilated via the digestion of particulates. Since most studies on metal incorporation into bivalve shells have provided mathematical correlations to environmental data, this proxy-based approach provides a more causal relationship between sources and assimilation pathways. It improves the interpretation of element variations (if independent from shell mineralogy) in bivalve shells, especially, where a full characterization of the biogeochemical environment of the bivalves is lacking.

Stability of Fe-Ni hydride after the reaction between Fe-Ni alloy and hydrous phase (δ-AlOOH) up to 1.2 Mbar: Possibility of H contribution to the core density deficit

NASA Astrophysics Data System (ADS)

Terasaki, Hidenori; Ohtani, Eiji; Sakai, Takeshi; Kamada, Seiji; Asanuma, Hidetoshi; Shibazaki, Yuki; Hirao, Naohisa; Sata, Nagayoshi; Ohishi, Yasuo; Sakamaki, Tatsuya; Suzuki, Akio; Funakoshi, Ken-ichi

2012-03-01

The hydrous mineral, δ-AlOOH, is stable up to at least the core-mantle boundary, and therefore has been proposed as a water carrier to the Earth's deep mantle. If δ-AlOOH is transported down to the core-mantle boundary by a subducting slab or the mantle convection, then the reaction between the iron alloy core and δ-AlOOH is important in the deep water/hydrogen cycle in the Earth. Here we conducted an in situ X-ray diffraction study to determine the behavior of hydrogen between Fe-Ni alloys and δ-AlOOH up to near the core-mantle boundary conditions. The obtained diffraction spectra show that fcc/dhcp Fe-Ni hydride is stable over a wide pressure range of 19-121 GPa at high temperatures. Although the temperature of formation of Fe-Ni hydride tends to increase up to 1950 K with increasing pressure to 121 GPa, this reaction temperature is well below the mantle geotherm. δ-AlOOH was confirmed to coexist stably with perovskite, suggesting that δ-AlOOH can be a major hydrous phase in the lower mantle. Therefore, when δ-AlOOH contacts with the core at the core-mantle boundary, the hydrogen is likely to dissolve into the Earth's core. Based on the present results, the amount of hydrogen to explain the core density deficit is estimated to be 1.0-2.0 wt.%.

Net acidity indicates the whole effluent toxicity of pH and dissolved metals in metalliferous saline waters.

PubMed

Degens, Bradley P; Krassoi, Rick; Galvin, Lynette; Reynolds, Brad; Micevska, Tina

2018-05-01

Measurements of potential acidity in water are used to manage aquatic toxicity risks of discharge from acid sulfate soils or acid mine drainage. Net acidity calculated from pH, dissolved metals and alkalinity is a common measurement of potential acidity but the relevance of current risk thresholds to aquatic organisms are unclear. Aquatic toxicity testing was carried out using four halophytic organisms with water from four saline sources in southern Western Australia (3 acidic drains and one alkaline river; 39-40 g TDS/L) where acidity was varied by adjusting pH to 4.5-6.5. The test species were brine shrimps (Artemia salina), locally sourced ostracods (Platycypris baueri), microalgae (Dunaliella salina) and amphipods (Allorchestes compressa). Testing found the EC 10 and IC 10 of net acidity ranged from -7.8 to 10.5 mg CaCO 3 /L with no survival or growth of any species at >47 mg CaCO 3 /L. Reduced net acidity indicated reduced whole effluent toxicity more reliably than increased pH alone with organisms tolerating pH up to 1.1 units lower in the absence of dissolved metals. Variation in toxicity indicated by net acidity was mostly attributed to reduced concentrations of dissolved Al and Fe combined with higher pH and alkalinity and some changes in speciation of Al and Fe with pH. These results indicate that rapid in-field assessments of net acidity in acidic, Al dominated waters may be an indicator of potential acute and sub-chronic impacts on aquatic organisms. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Impact of chemical amendment of dairy cattle slurry on phosphorus, suspended sediment and metal loss to runoff from a grassland soil.

PubMed

Brennan, R B; Fenton, O; Grant, J; Healy, M G

2011-11-01

Emerging remediation technologies such as chemical amendment of dairy cattle slurry have the potential to reduce phosphorus (P) solubility and consequently reduce P losses arising from land application of dairy cattle slurry. The aim of this study was to determine the effectiveness of chemical amendment of slurry to reduce incidental losses of P and suspended sediment (SS) from grassland following application of dairy cattle slurry and to examine the effect of amendments on metal concentrations in runoff water. Intact grassed-soil samples were placed in two laboratory runoff boxes, each 200-cm-long by 22.5-cm-wide by 5-cm-deep, before being amended with dairy cattle slurry (the study control) and slurry amended with either: (i) alum, comprising 8% aluminium oxide (Al(2)O(3)) (1.11:1 aluminium (Al):total phosphorus (TP) of slurry) (ii) poly-aluminium chloride hydroxide (PAC) comprising 10% Al(2)O(3) (0.93:1 Al:TP) (iii) analytical grade ferric chloride (FeCl(2)) (2:1 Fe:TP), (iv) and lime (Ca(OH)(2)) (10:1 Ca:TP). When compared with the study control, PAC was the most effective amendment, reducing dissolved reactive phosphorus (DRP) by up to 86% while alum was most effective in reducing SS (88%), TP (94%), particulate phosphorus (PP) (95%), total dissolved phosphorus (TDP) (81%), and dissolved unreactive phosphorus (DUP) (86%). Chemical amendment of slurry did not appear to significantly increase losses of Al and Fe compared to the study control, while all amendments increased Ca loss compared to control and grass-only treatment. While chemical amendments were effective, the reductions in incidental P losses observed in this study were similar to those observed in other studies where the time from slurry application to the first rainfall event was increased. Timing of slurry application may therefore be a much more feasible way to reduce incidental P losses. Future work must examine the long-term effects of amendments on P loss to runoff and not only incidental losses. Copyright © 2011 Elsevier B.V. All rights reserved.

Comment on “Isotopic fractionation between Fe(III) and Fe(II) in aqueous solutions” by Clark Johnson et al., [Earth Planet. Sci. Lett. 195 (2002) 141–153

USGS Publications Warehouse

Bullen, Thomas D.; White, Arthur F.; Childs, Cyril W.

2003-01-01

In a recent contribution [1], Johnson et al. reported the equilibrium isotope fractionation factor between dissolved Fe(II) and Fe(III) in aqueous solutions at pH=2.5 and 5.5. They suggest that because the iron isotope fractionation observed in their experiments spans virtually the entire range observed in sedimentary rocks, Fe(II)–Fe(III) aqueous speciation may play a major role in determining iron isotope variations in nature where Fe(II) and Fe(III) can become physically separated. They discounted earlier conclusions by us and others [2] ;  [3] that significant equilibrium fractionation between specific coexisting Fe(II)- or Fe(III)-aqueous complexes (e.g., between aqueous Fe(II)(OH)x(aq)and Fe(II)(aq) ion) is capable of producing iron isotope contrasts that can be preserved in nature. This is an important contribution not only because the authors recognize the importance of abiotic equilibrium iron isotope fractionation in nature in contrast to previous assertions [4], but also because it will help to focus discussion on the development and evaluation of experimental approaches that can reveal abiotic fractionation mechanisms. However, in this Comment we propose that the experiments presented in this paper cannot be interpreted as straightforwardly as Johnson et al. contend. In particular, we show that in one of their critical experiments attainment of either isotope mass balance or equilibrium was not demonstrated, and thus the results of that experiment cannot be used to calculate an Fe(II)–Fe(III) equilibrium fractionation factor.

The Distribution between the Dissolved and the Particulate Forms of 49 Metals across the Tigris River, Baghdad, Iraq

PubMed Central

Hamad, Samera Hussein; Schauer, James Jay; Shafer, Martin Merrill; Abed Al-Raheem, Esam; Satar, Hyder

2012-01-01

The distribution of dissolved and particulate forms of 49 elements was investigated along transect of the Tigris River (one of the major rivers of the world) within Baghdad city and in its major tributary (Diyala River) from 11 to 28 July 2011. SF-ICP-MS was used to measure total and filterable elements at 17 locations along the Tigris River transect, two samples from the Diyala River, and in one sample from the confluence of the two rivers. The calculated particulate forms were used to determine the particle-partition coefficients of the metals. No major changes in the elements concentrations down the river transect. Dissolved phases dominated the physical speciation of many metals (e.g., As, Mo, and Pt) in the Tigris River, while Al, Fe, Pb, Th, and Ti were exhibiting high particulate fractions, with a trend of particle partition coefficients of [Ti(40) > Th(35) > Fe(15) > Al(13) > Pb(4.5)] ∗ 106 L/kg. Particulate forms of all metals exhibited high concentrations in the Diyala River, though the partition coefficients were low due to high TSS (~270 mg/L). A comparison of Tigris with the major rivers of the world showed that Tigris quality in Baghdad is comparable to Seine River quality in Paris. PMID:23304083

Dissolved trace elements in a nitrogen-polluted river near to the Liaodong Bay in Northeast China.

PubMed

Bu, Hongmei; Song, Xianfang; Guo, Fen

2017-01-15

Dissolved trace element concentrations (Ba, Fe, Mn, Si, Sr, and Zn) were investigated in the Haicheng River near to the Liaodong Bay in Northeast China during 2010. Dissolved Ba, Fe, Mn, and Sr showed significant spatial variation, whereas dissolved Fe, Mn, and Zn displayed seasonal variations. Conditions such as water temperature, pH, and dissolved oxygen were found to have an important impact on redox reactions involving dissolved Ba, Fe, and Zn. Dissolved Fe and Mn concentrations were regulated by adsorption or desorption of Fe/Mn oxyhydroxides and the effects of organic carbon complexation on dissolved Ba and Sr were found to be significant. The sources of dissolved trace elements were found to be mainly from domestic sewage, industrial waste, agricultural surface runoff, and natural origin, with estimated seasonal and annual river fluxes established as important inputs of dissolved trace elements from the Haicheng River into the Liaodong Bay or Bohai Sea. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxic limestone drains for treatment of dilute, acidic mine drainage

USGS Publications Warehouse

Cravotta, Charles A.

1998-01-01

Limestone treatment systems can be effective for remediation of acidic mine drainage (AMD) that contains moderate concentrations of dissolved O2 , Fe3+ , or A13+ (1‐5 mg‐L‐1 ). Samples of water and limestone were collected periodically for 1 year at inflow, outflow, and intermediate points within underground, oxic limestone drains (OLDs) in Pennsylvania to evaluate the transport of dissolved metals and the effect of pH and Fe‐ and Al‐hydrolysis products on the rate of limestone dissolution. The influent was acidic and relatively dilute (pH <4; acidity < 90 mg‐L‐1 ) but contained 1‐4 mg‐L‐1 Of O2 , Fe3+ , A13+ , and Mn2+ . The total retention time in the OLDs ranged from 1.0 to 3.1 hours. Effluent remained oxic (02 >1 mg‐L‐1 ) but was near neutral (pH = 6.2‐7.0); Fe and Al decreased to less than 5% of influent concentrations. As pH increased near the inflow, hydrous Fe and Al oxides precipitated in the OLDs. The hydrous oxides, nominally Fe(OH)3 and AI(OH)3, were visible as loosely bound, orange‐yellow coatings on limestone near the inflow. As time elapsed, Fe(OH)3 and AI(OH)3 particles were transported downflow. During the first 6 months of the experiment, Mn 2+ was transported conservatively through the OLDs; however, during the second 6 months, concentrations of Mn in effluent decreased by about 50% relative to influent. The accumulation of hydrous oxides and elevated pH (>5) in the downflow part of the OLDs promoted sorption and coprecipitation of Mn as indicated by its enrichment relative to Fe in hydrous‐oxide particles and coatings on limestone. Despite thick (~1 mm) hydrous‐oxide coatings on limestone near the inflow, CaCO3 dissolution was more rapid near the inflow than at downflow points within the OLD where the limestone was not coated. The rate of limestone dissolution decreased with increased residence time, pH, and concentrations of Ca2+ and HCO3‐ and decreased PCO2. The following overall reaction shows alkalinity as an ultimate product of the iron hydrolysis reaction in an OLD:Fe2+ + 0.25 O2 +CaCO3 + 2.5 H2O --> Fe(OH)3 + 2 Ca2+ + 2 HCO3-where 2 moles of CaCO3 dissolve for each mole of Fe(OH)3 produced. Hence, in an OLD, rapidly dissolving limestone surfaces are not stable substrates for Fe(OH)3 attachment and armoring. Because overall efficiency is increased by combining neutralization and hydrolysis reactions, an OLD followed by a settling pond requires less land area than needed for a two‐stage treatment system consisting of an anoxic limestone drain an oxidation‐settling pond or wetland. To facilitate removal of hydrous‐oxide sludge, a perforated‐pipe subdrain can be installed within an OLD.

Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

NASA Astrophysics Data System (ADS)

Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

2016-05-01

Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

Transformation of organo-ferric peat colloids by a heterotrophic bacterium

NASA Astrophysics Data System (ADS)

Oleinikova, Olga V.; Shirokova, Liudmila S.; Gérard, Emmanuele; Drozdova, Olga Yu.; Lapitskiy, Sergey A.; Bychkov, Andrey Yu.; Pokrovsky, Oleg S.

2017-05-01

Bacterial mineralization of allochthonous (soil) dissolved organic matter (DOM) in boreal waters governs the CO2 flux from the lakes and rivers to the atmosphere, which is one of the main factor of carbon balance in high latitudes. However, the fate of colloidal trace element (TE) during bacterial processing of DOM remains poorly constrained. We separated monoculture of Pseudomonas saponiphila from a boreal creek and allowed it to react with boreal Fe-rich peat leachate of approximate colloidal (3 kDa-0.45 μm) composition C1000Fe12Al3.3Mg2Ca3.7P1.2Mn0.1Ba0.5 in nutrient-free media. The total net decrease of Dissolved Organic Carbon (DOC) concentration over 4 day of exposure was within 5% of the initial value, whereas the low molecular weight fraction of Corg (LMW<3 kDa) yielded a 16%-decrease due to long-term bio-uptake or coagulation. There was a relative depletion in Fe over Corg of 0.45 μm, colloidal and LMW fraction in the course of peat leachate interaction with P. saponiphila. Al, Mn, Ni, Cu, Ga, REEs, Y, U were mostly affected by bacterial presence and exhibited essentially the adsorption at the cell surface over first hours of reaction, in contrast to Fe, Ti, Zr, and Nb that showed both short-term adsorption and long-term removal by physical coagulation/coprecipitation with Fe hydroxide. The low molecular weight fraction (LMW<3 kDa) of most TE was a factor of 2-5 less affected by microbial presence via adsorption or removal than the high molecular weight (HMW) colloidal fractions (<0.45 μm and <50 kDa). The climate change-induced acceleration of heterotrophic bacterial activity in boreal and subarctic waters may lead to preferential removal of Fe over DOC from conventionally dissolved fraction and the decrease of the proportion of LMW < 3 kDa fraction and the increase of HMW colloids. Enhanced heterotrophic mineralization of organo-ferric colloids under climate warming scenario may compensate for on-going "browning" of surface waters.

Iron isotope constraints on arsenic release from Mekong Delta sediments, Cambodia

NASA Astrophysics Data System (ADS)

Matsumoto, T.; Yamaguchi, K. E.; Hirata, T.; Yamagata, Y.; Yamaguchi, A.; Abe, G.

2017-12-01

Arsenic-contaminated groundwater is a world-wide environmental problem and threatens more than 100 million people living in delta areas of South, SE and East Asia. It is typically associated with reducing aquifers with organic-rich alluvial sediments, little thermal gradients, low sulfate concentrations, and slow flushing rates. Such conditions are typical for low-lying countries in Asian deltas; however, compared to Bangladesh, Cambodia has received far less attention. Upon reductive dissolution of Fe-(oxyhydr)oxides that adsorbed As, Fe and As are released into solution as dissolved Fe2+ and arsenate, respectively. Following the oxidation of dissolved Fe2+, newly-formed Fe-(oxyhydr)oxides adsorb As again. Thus, in anoxic waters, concentrations of As correlate with those of dissolved Fe2+. Fluctuating redox conditions in the aquifer are control As release, although inhibition of adsorption of arsenate and arsenite onto the Fe-(oxyhydr)oxides occurs when the concentrations of phosphate, bicarbonate, silicate, and/or organic matter become sufficiently high. Biogeochemical redox reactions of Fe result in significant isotope fractionation (e.g., Johnson et al., 2008). We hypothesized that magnitude of isotope fractionation of Fe in the aquifer sediments, reflecting repeated (incomplete) redox reactions of Fe, may be proportional to the amount of total As release. We aim to calibrate the As release from aquifer sediment by Fe isotope analysis. As a preliminary study, series of sediment samples were collected from the Mekong Delta, Cambodia, in September 2016. Based on measurements by XRF, ICP-AES and ICP-MS, concentrations of As varied significantly covering the range from 4.5 to 15.5 µg/g with a median value of 11 µg/g (higher than the average crustal value of 5 µg/g), and those of Fe is from 2.6 to 9.7 wt.% with a median value of 7.1 wt.%. Concentrations of As and Fe show positive correlation (R2 = 0.72), indicating an effective redox cycling of Fe and As as stated above. Sediment incubation experiment to explore various pathways of As release would show time-series correlated changes in the Fe isotope compositions and As concentrations. The data obtained here are essential in investigating the mechanism of As release.

DISSOLVED ORGANIC CARBON CHARACTERISTICS IN METAL-RICH WATERS AND THE IMPLICATIONS FOR COPPER AQUATIC TOXICITY

EPA Science Inventory

This research will aim to quantify the effects of fractionation between DOC, HFO, HAO, free copper and the behavior of resultant free DOC in the water column on the toxicological effects of copper. Fractionation between DOC, free metals and iron (Fe) and aluminum (Al) hydro...

Fe(II)-regulated moderate pre-oxidation of Microcystis aeruginosa and formation of size-controlled algae flocs for efficient flotation of algae cell and organic matter.

PubMed

Qi, Jing; Lan, Huachun; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

2018-06-15

The coagulation/flocculation/flotation (C/F/F) process is becoming a popular method for algae-laden water treatment. However, the efficiency of flotation is highly dependent on the ability of the preceding coagulation/flocculation process to form flocculated algae flocs. This study aims to improve the Microcystis aeruginosa flotation efficiency from algae cell and organic matter aspects by applying Fe(II)-regulated pretreatment enhanced Al coagulation process. The ability of the C/F/F process to remove cyanobacterial cells can be enhanced from 8% to 99% at a Fe(II) dose of 30 μM. The Al dose needed can be reduced by more than half while achieving successful flotation. The introduced Fe(II) after KMnO 4 can not only realize moderate pre-oxidation of cyanobacterial cells, but also form in-situ Fe(III). The DOC value can also be decreased significantly due to the formation of in-situ Fe(III), which is more efficient in dissolved organic matter (DOM) removal compared with pre-formed Fe(III). In addition, the gradually hydrolyzed in-situ Fe(III) can facilitate the hydrolysis of Al as a dual-coagulant and promote the clustering and cross-linking of Al hydrolyzates, which can enhance the formation of size-controlled algae flocs. Finally, the size-controlled algae flocs can be effectively floated by the bubbles released in the flotation process due to the efficient collision and attachment between flocs and bubbles. Therefore, the efficient flotation of algae cell and organic matter can be realized by the Fe(II) regulated moderate pre-oxidation of M. aeruginosa and formation of size-controlled algae flocs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil.

PubMed

Barbiero, Laurent; Berger, Gilles; Rezende Filho, Ary T; Meunier, Jean-François; Martins-Silva, Elisângela R; Furian, Sonia

2016-01-01

Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the literature, the study suggests that the co-existence of trioctahedral Mg-smectite and dioctahedral Fe-mica should be regarded as a standard occurrence in alkaline soil systems with organic rich waters.

Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil

PubMed Central

Meunier, Jean-François; Martins-Silva, Elisângela R.; Furian, Sonia

2016-01-01

Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the literature, the study suggests that the co-existence of trioctahedral Mg-smectite and dioctahedral Fe-mica should be regarded as a standard occurrence in alkaline soil systems with organic rich waters. PMID:27463379

Distribution and chemistry of suspended particles from an active hydrothermal vent site on the Mid-Atlantic Ridge at 26°N

NASA Astrophysics Data System (ADS)

Trocine, Robert P.; Trefry, John H.

1988-04-01

Suspended particles were collected from an area of active hydrothermal venting at the Trans-Atlantic Geotraverse (TAG) Hydrothermal Field on the Mid-Atlantic Ridge and analyzed for Fe, Mn, Cd, Zn, Cu, V, Ni, Cr, Pb, Mg, Ca, Al and Si. Rapid advection of vent-derived precipitates produced a lens with total suspended matter (TSM) loadings of 14-60 μg/l at 200-700 m above the seafloor; TSM concentrations > 60 μg/l were observed only at near-vent sites. The distribution of suspended particles correlated well with increased dissolved Mn concentrations and particulate Fe values near the vent source. Particulate Fe values decreased linearly relative to TSM concentrations as hydrothermal precipitates mixed with background suspended matter. Near-vent precipitates were characterized by up to 35% Fe, 2% Zn, 0.6% Cu and > 100 μg/g Cd. In comparison to Fe, particulate Cd, Zn and Cu values decreased dramatically away from the vent source. This trend supports differential settling and/or dissolution of Cd-, Zn- and Cu-bearing phases. Particulate Mn and Fe values were inversely related with only 50 μg Mn/g in the near-vent particles. At near-vent sites, > 99% of the total Mn was in solution; this fraction decreased to 75-80% at background TSM values. In contrast to Cd, Zn and Cu, particulate V levels show a continuous, linear decrease with particulate Fe values. This trend is explained by adsorption of V on Fe-oxides in the vent plume. Scavenging of Cr, Pb and Mg by hydrothermal precipitates is also suggested by the data. Nickel and Al values were low in near-vent particles at < 100 and < 3 μg/g, respectively. The complementary behavior of dissolved Mn and particulate trace metals provides a useful framework for studying broad aspects of hydrothermal plume processes.

Preparation and characterization of bottom ferromagnetic electrode for graphene based magnetic junction

NASA Astrophysics Data System (ADS)

Cheng, Shufan; Cobas, Enrique; van't Erve, Olaf M. J.; Jonker, Berend T.

2016-03-01

Magnetic multilayer stacks incorporating several layers of graphene have been predicted to produce very high magnetoresistance and high conductivity, a combination of properties that would be useful in magnetic sensors and future spin-based data storage and processing technologies such as MRAM. To realize the theoretically modeled heterostructures and probe their properties, a clean, high-quality graphene-ferromagnet interface, such as one that results from CVD of graphene directly on ferromagnetic films, is required. However, past works using Ni and Co films for CVD of graphene employ the ferromagnetic film as a sacrificial layer to be dissolved after graphene growth and ignore changes to its morphology and magnetic properties. Here we investigated the effect of graphene CVD growth conditions on the properties of Co, Ni, Co90Fe10 and Ni80Fe20 ferromagnetic films. The magnetic films were grown by dc magnetron sputtering with different growth conditions onto c-Al2O3, Si/AlN and MgO substrates. The crystalline orientation, surface morphology/roughness and magnetic properties of the films were measured using X-ray diffraction, atomic force microscopy and vibrating sample magnetometry, respectively. Cobalt films grown at 500 °C were found to be hcp and heteroepitaxial on c-Al2O3. CoFe, Ni, and NiFe films on c-Al2O3 were found to be fcc and to be (111) textured but with grains having in-plane rotation differing by 60°. The CoFe and NiFe films on c-Al2O3 retained their small coercivity and high remanence while the pure Co and Ni films exhibited much smaller remanence after graphene growth, making them unsuitable for magnetic memory technologies. Films on Si/AlN were found to have the same rotational domains as those on sapphire c-Al2O3. The NiFe films on (111) MgO were found to be mostly single domain.

Hydrobiogeochemical interactions in 'anoxic' limestone drains for neutralization of acidic mine drainage

USGS Publications Warehouse

Robbins, E.I.; Cravotta, C.A.; Savela, C.E.; Nord, G.L.

1999-01-01

Processes affecting neutralization of acidic coal mine drainage were evaluated within 'anoxic' limestone drains (ALDs). Influents had pH???3.5 and dissolved oxygen <2 mg/l. Even though effluents were near neutral (pH 6 and alkalinity acidity), two of the four ALDs were failing due to clogging. Mineral-saturation indices indicated the potential for dissolution of calcite and gypsum, and precipitation of Al3+ and Fe3+ compounds. Cleavage mounts of calcite and gypsum that were suspended within the ALDs and later examined microscopically showed dissolution features despite coatings by numerous bacteria, biofilms, and Fe-Al-Si precipitates. In the drain exhibiting the greatest flow reduction, Al-hydroxysulfates had accumulated on limestone surfaces and calcite etch points, thus causing the decline in transmissivity and dissolution. Therefore, where Al loadings are high and flow rates are low, a pre-treatment step is indicated to promote Al removal before diverting acidic mine water into alkalinity-producing materials. ?? 1998 Elsevier Science Ltd.

Metal loading assessment of a small mountainous sub-basin characterized by acid drainage -- Prospect Gulch, upper Animas River watershed, Colorado

USGS Publications Warehouse

Wirt, Laurie; Leib, Kenneth J.; Melick, Roger; Bove, Dana J.

2001-01-01

strongly affected by natural acidity from pyrite weathering. Metal content in the water column is a composite of multiple sources affected by hydrologic, geologic, climatic, and anthropogenic conditions. Identifying sources of metals from various drainage areas was determined using a tracer injection approach and synoptic sampling during low flow conditions on September 29, 1999 to determine loads. The tracer data was interpreted in conjunction with detailed geologic mapping, topographic profiling, geochemical characterization, and the occurrence and distribution of trace metals to identify sources of ground-water inflows. For this highly mineralized sub-basin, we demonstrate that SO4, Al, and Fe load contributions from drainage areas that have experienced historical mining?although substantial?are relatively insignificant in comparison with SO4, Al, and Fe loads from areas experiencing natural weathering of highlyaltered, pyritic rocks. Regional weathering of acid-sulfate mineral assemblages produces moderately low pH waters elevated in SO4, Al, and Fe; but generally lacking in Cu, Cd, Ni, and Pb. Samples impacted by mining are also characterized by low pH and large concentrations of SO4, Al, and Fe; but contained elevated dissolved metals from ore-bearing vein minerals such as Cu, Zn, Cd, Ni, and Pb. Occurrences of dissolved trace metals were helpful in identifying ground-water sources and flow paths. For example, cadmium was greatest in inflows associated with drainage from inactive mine sites and absent in inflows that were unaffected by past mining activities and thus served as an important indicator of mining contamination for this environmental setting. The most heavily mine-impacted reach (PG153 to PG800), contributed 8% of the discharge, and 11%, 9%, and 12% of the total SO4, Al, and Fe loads in Prospect Gulch. The same reach yielded 59% and 37% of the total Cu and Zn loads for the subbasin. In contrast, the naturally acidic inflows from the Red Chemotroph iron spring yielded 39% of the discharge and 54%, 73%, and 87% of the SO4, Al, and Fe loads; but only 4% of the total Cu and 30% of the total Zn loads in Prospect Gulch. Base flow from the Prospect Gulch sub-basin contributes about 4.8 percent of the total discharge at the mouth of Cement Creek; compared with sampled instream loads of 1.8%, 8.8%, 15.9%, 28%, and 8.6% for SO4, Al, Fe, Cu and Zn, respectively. Water-shed scale remediation efforts targeted at reducing loads of SO4, Al, and Fe at inactive mine sites are likely to fail because the major sources of these constituents in Prospect Gulch are predominantly discharged from natural sources. Remediation goals aimed at reducing acidity and loads of Cu and other base metals, may succeed, however, because changes in pH and loads are disproportionately greater than increases in discharge over the same reach, and a substantial fraction of the metal loading is from mining-impacted reaches. Whether remediation of abandoned mines in Prospect Gulch can be successful depends on how goals are defined?that is, whether the objective is to reduce loads of SO4, Al, and Fe; or whether loads of Cu and other base metals and pH are targeted.

No effect of H2O degassing on the oxidation state of hydrous rhyolite magmas: a comparison of pre- and post-eruptive Fe2+ concentrations in six obsidian samples from the Mexican and Cascade arcs

NASA Astrophysics Data System (ADS)

Waters, L.; Lange, R. A.

2011-12-01

The extent to which degassing affects the oxidation state of arc magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of magmas, and it has been proposed that degassing may induce either oxidation or reduction depending on the initial oxidation state. A commonly proposed oxidation reaction is related to H2O degassing: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt). Another mechanism by which H2O degassing can affect the iron redox state is if dissolved water affects the activity of ferrous and/or ferric iron in the melt. Although Moore et al. (1995) presented experiments showing no evidence of an affect of dissolved water on the activity of the ferric-ferrous ratio in silicate melts, other experimental results (e.g., Baker and Rutherford, 1996; Gaillard et al., 2001; 2003) indicate that there may be such an effect in rhyolite liquids. It has long been understood that rhyolites, owing to their low total iron concentrations, are more sensitive than other magma types to degassing-induced change in redox state. Therefore, a rigorous test of whether H2O degassing affects the redox state of arc magmas is best evaluated on rhyolites. In this study, a comparison is made between the pre-eruptive (pre-degassing) Fe2+ concentrations in six, phenocryst-poor (<5%), fresh, glassy obsidian samples with their post-eruptive (post-degassing) Fe2+ concentrations. Near-liquidus co-precipitation of two Fe-Ti oxides allows the pre-eruptive oxygen fugacity and temperature to be calculated in each rhyolite using the oxygen barometer and thermometer of Ghiorso and Evans (2008). Temperatures range from 793 (± 19) to 939 (± 15) °C, and ΔNNO values (log10fO2 of sample - log10fO2 of Ni-NiO buffer) range from -0.4 to +1.4. These ΔNNO values allow the ferric-ferrous ratio in the liquid to be calculated, using the experimental calibration of Kress and Carmichael (1991), which relates melt composition (not including dissolved water), oxygen fugacity and temperature to melt ferric-ferrous ratios. With temperature known, the plagioclase-liquid hygrometer of Lange et al. (2009) was applied and maximum melt water concentrations range from 4.2 to 7.5 wt%. Both the oxidation state and water concentration are known prior to eruption, at the time of phenocryst growth. After eruption, the rhyolites lost nearly all of their volatiles, as indicated by the low loss on ignition values (LOI ≤ 0.7 wt%). In order to test how much oxidation of ferrous iron occurred as a consequence of that degassing, we measured the ferrous iron concentration in the bulk samples by titration, using the Wilson (1960) method, which was successfully tested again three USGS and one Canadian Geological Survey standards. Our results indicate no detectable change within analytical error between pre- and post-eruptive FeO concentrations, with an average deviation of 0.09 wt% and a maximum deviation of 0.15 wt%. Our results show that H2O degassing has no effect on the redox state of rhyolite magmas, which requires that dissolved water has no resolvable affect on the activity ratio of the iron oxide components in melt.

X-ray photoelectron spectroscopic evidence for bacteria-enhanced dissolution of hornblende

NASA Astrophysics Data System (ADS)

Kalinowski, B. E.; Liermann, L. J.; Brantley, S. L.; Barnes, A.; Pantano, C. G.

2000-04-01

An Arthrobacter species capable of extracting Fe from hornblende was isolated from a soil from the Adirondacks, NY (USA). This bacteria isolate, used in batch experiments with hornblende, accelerated the release of Fe from hornblende without measurably affecting Al release. The isolate produces both low molecular weight organic acids (LMWOA) and a catecholate siderophore. Polished hornblende (glass and crystal) discs were analyzed with X-ray photoelectron spectroscopy (XPS) before and after incubation with growing Arthrobacter sp. to investigate whether the bacteria caused a distinguishable chemical signature on the upper 100 Å of mineral surface. After removal of the arthrobacter grown on hornblende crystal or glass substrates using lysozyme, XPS revealed surface depletion of Fe for samples grown for several days in buffered (crystal) and unbuffered (crystal and glass) media. Fe/Si ratios of hornblende surfaces dissolved under biotic conditions are significantly lower than Fe/Si ratios on surfaces dissolved under abiotic conditions for similar amounts of time. Enhanced Fe release and the formation of Fe-depleted surfaces is inferred to be caused by catechol complexation at the mineral surface. Because natural siderophore was not isolated in sufficient quantities to run bacteria-free leaching experiments, parallel investigations were run with a commercially available siderophore (desferrioxamine B). Desferrioxamine B was observed to enhance release of Fe, Si, and Al from hornblende both with and without added bacteria. Formation of desferrioxamine-Fe surface complexes were probed by studying the multiple splitting and shift in intensities of the N 1s line analyzed by XPS on siderophore ± Fe on gold surfaces and siderophore + hornblende crystal surfaces. Based upon the observed formation of an hydroxamate (desferrioxamine) surface complex on hornblende, we infer that catecholate siderophores, such as those produced by the arthrobacter, also complex on the hornblende surface. Surface complexation is favored because of the extremely high association constants for siderophore + Fe(III). X-ray photoelectron spectroscopic data is therefore consistent with a model wherein enhanced Fe release by these bacteria or desferrioxamine B is caused by Fe-siderophore complexation at the silicate surface. Such complexation presumably weakens bonds between the Fe and the oxide lattice, causing enhanced Fe leaching and an Fe-depleted surface. Some leaching may also be due to LMWOA, although this is interpreted to be of secondary importance.

The effect of membrane filtration on dissolved trace element concentrations

USGS Publications Warehouse

Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

1996-01-01

The almost universally accepted operational definition for dissolved constituents is based on processing whole-water samples through a 0.45-??m membrane filter. Results from field and laboratory experiments indicate that a number of factors associated with filtration, other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample), can produce substantial variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. These variations result from the inclusion/exclusion of colloidally- associated trace elements. Thus, 'dissolved' concentrations quantitated by analyzing filtrates generated by processing whole-water through similar pore- sized membrane filters may not be equal/comparable. As such, simple filtration through a 0.45-??m membrane filter may no longer represent an acceptable operational definition for dissolved chemical constituents. This conclusion may have important implications for environmental studies and regulatory agencies.

Year-round record of dissolved and particulate metals in surface snow at Dome Concordia (East Antarctica).

PubMed

Grotti, Marco; Soggia, Francesco; Ardini, Francisco; Magi, Emanuele; Becagli, Silvia; Traversi, Rita; Udisti, Roberto

2015-11-01

From January to December 2010, surface snow samples were collected with monthly resolution at the Concordia station (75°06'S, 123°20'E), on the Antarctic plateau, and analysed for major and trace elements in both dissolved and particulate (i.e. insoluble particles, >0.45 μm) phase. Additional surface snow samples were collected with daily resolution, for the determination of sea-salt sodium and not-sea-salt calcium, in order to support the discussion on the seasonal variations of trace elements. Concentrations of alkaline and alkaline-earth elements were higher in winter (April-October) than in summer (November-March) by a factor of 1.2-3.3, in agreement with the higher concentration of sea-salt atmospheric particles reaching the Antarctic plateau during the winter. Similarly, trace elements were generally higher in winter by a factor of 1.2-1.5, whereas Al and Fe did not show any significant seasonal trend. Partitioning between dissolved and particulate phases did not change with the sampling period, but it depended only on the element: alkaline and alkaline-earth elements, as well as Co, Cu, Mn, Pb and Zn were for the most part (>80%) in the dissolved phase, whereas Al and Fe were mainly associated with the particulate phase (>80%) and Cd, Cr, V were nearly equally distributed between the phases. Finally, the estimated marine and crustal enrichment factors indicated that Cd, Cr, Cu, Pb and Zn have a dominant anthropogenic origin, with a possible contribution from the Concordia station activities. Copyright © 2014 Elsevier Ltd. All rights reserved.

Microbial Transport Mechanisms in Silty, Sandy Media as Inferred From Short Core Experiments Performed in the Field.

NASA Astrophysics Data System (ADS)

Mailloux, B.; Hall, j; Fuller, M.; Scheibe, T.; DeFlaun, M.; Onstott, T.

2001-12-01

A novel approach to examining the mechanisms controlling the velocity and attachment of bacteria in porous media was developed for the South Oyster Bacterial Transport Field Site. Instead of performing bacterial transport experiments in the lab using repacked materials and artificial water, samples of sediment core, 7 cm. in length, were connected to multi-level samplers at the field site, the groundwater from select levels in the aquifer was pumped through the cores, and an aliquot of cells stained with a viable, fluorescent dye was injected with Br into the influent end of the cores. The same cells, Br and groundwater were simultaneously passed through repacked cores composed of sieved sand of varying grain size fractions (100 to 600  diameter) and a single grain size fraction coated with Fe and Al synthetic oxides. The grain size of the coated sand and the Fe and Al concentrations of the coated sand (500 to 1000 ppm) were representative of the average value of the aquifer. By using this approach, the parameters that are difficult to reproduce in the lab, e.g., the dissolved gas concentrations, pH, temperature, dissolved organic matter, the indigenous bacterial and protist populations, could be replicated. One of the results derived from 29 short core experiments indicate that the enhanced velocity of adhesion deficient DA001 that has been reported in laboratory experiments was greatly reduced in the field experiments for the Fe and Al coated sands and greatly enhanced for the fine grained sands.

Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

DOE PAGES

Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; ...

2017-05-19

Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here in this work, we have measured themore » redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). Lastly, we present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.« less

Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.

Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here in this work, we have measured themore » redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). Lastly, we present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.« less

Accumulation of Fe oxyhydroxides in the Peruvian oxygen deficient zone implies non-oxygen dependent Fe oxidation

NASA Astrophysics Data System (ADS)

Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-Mi; Toner, Brandy M.; Marcus, Matthew A.

2017-08-01

Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). We present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.

Tungsten solution kinetics and amorphization of nickel in mechanically alloyed Ni-W alloys

NASA Technical Reports Server (NTRS)

Aning, A. O.; Wang, Z.; Courtney, T. H.

1993-01-01

The kinetics of solution of W, and the subsequent amorphization of Ni, in mechanically alloyed Ni-W alloys has been investigated. As W is a highly abrasive material in the energy intensive devices used for mechanical alloying, we studied the above reactions in different mills. One used hardened steel balls as the grinding media, and the other Al2O3. Abrasion is common to both mills, but Fe wear debris from the hardened steel enters into solution in the Ni rich phases whereas Al2O3 debris is present as small dispersoids. The kinetics of W solution and those of subsequent amorphization do not appear strongly affected by the Fe in solution or the Al2O3 dispersoid. Tungsten dissolves in crystalline Ni in amounts in excess of the equilibrium solubility during alloying. Amorphization of the Ni phase occurs if the W content in this phase exceeds ca. 28 at. pct.

Trace element fractionation and transport in boreal rivers and soil porewaters of permafrost-dominated basaltic terrain in Central Siberia

NASA Astrophysics Data System (ADS)

Pokrovsky, O. S.; Schott, J.; Dupré, B.

2006-07-01

The chemical status of ˜40 major and trace elements (TE) and organic carbon (OC) in pristine boreal rivers draining the basaltic plateau of Central Siberia (Putorana) and interstitial solutions of permafrost soils was investigated. Water samples were filtered in the field through progressively decreasing pore size (5 μm → 0.22 μm → 0.025 μm → 10 kDa → 1 kDa) using cascade frontal filtration technique. Most rivers and soil porewaters exhibit 2-5 times higher than the world average concentration of dissolved (i.e., <0.22 μm) iron (0.03-0.4 mg/L), aluminum (0.03-0.4 mg/L), OC (10-20 mg/L) and various trace elements that are usually considered as immobile in weathering processes (Ti, Zr, Ga, Y, REEs). Ultrafiltration revealed strong relationships between concentration of TE and that of colloidal Fe and Al. According to their partition during filtration and association with colloids, two groups of elements can be distinguished: (i) those weakly dependent on ultrafiltration and that are likely to be present as truly dissolved inorganic species (Li, Na, K, Si, Mn, Mo, Rb, Cs, As, Sb) or, partially (20-30%) associated with small size Fe- and Al-colloids (Ca, Mg, Sr, Ba) and to small (<1-10 kDa) organic complexes (Co, Ni, Cu, Zn), and (ii) elements strongly associated with colloidal iron and aluminum in all ultrafiltrates largely present in 1-100 kDa fraction (Ga, Y, REEs, Pb, V, Cr, Ti, Ge, Zr, Th, U). TE concentrations and partition coefficients did not show any detectable variations between different colloidal fractions for soil porewaters, suprapermafrost flow and surface streams. TE concentration measurements in river suspended particles demonstrated significant contribution (i.e., ⩾30%) of conventionally dissolved (<0.22 μm) forms for usually "immobile" elements such as divalent transition metals, Cd, Pb, V, Sn, Y, REEs, Zr, Hf, Th. The Al-normalized accumulation coefficients of TE in vegetation litter compared to basalts achieve 10-100 for B, Mn, Zn, As, Sr, Sn, Sb, and the larch litter degradation is able to provide the major contribution to the annual dissolved flux of most trace elements. It is hypothesized that the decomposition of plant litter in the topsoil horizon leads to Fe(III)-, Al-organic colloids formation and serves as an important source of elements in downward percolating fluids.

The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer

USGS Publications Warehouse

Kent, D.B.; Fox, P.M.

2004-01-01

We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 ??M dissolved oxygen (DO), pH 5.9]; (2) the suboxic zone (5 ??M DO, pH 6.2, elevated concentrations of sewage-derived phosphate and nitrate); and (3) the anoxic zone [dissolved iron(II) 100-300 ??M, pH 6.5-6.9, elevated concentrations of sewage-derived phosphate]. Sediments are comprised of greater than 90% quartz but the surfaces of quartz and other mineral grains are coated with nanometer-size iron (Fe) and aluminum (Al) oxides and/or silicates, which control the adsorption properties of the sediments. Uncontaminated groundwater with added phosphate (620 ??M) was pumped into the uncontaminated zone while samples were collected 0.3 m above the injection point. Concentrations of As(V) increased from below detection (0.005 ??M) to a maximum of 0.07 ??M during breakthrough of phosphate at the sampling port; As(III) concentrations remained below detection. These results are consistent with the hypothesis that naturally occurring As(V) adsorbed to constituents of the coatings on grain surfaces was desorbed by phosphate in the injected groundwater. Also consistent with this hypothesis, vertical profiles of groundwater chemistry measured prior to the tracer test showed that dissolved As(V) concentrations increased along with dissolved phosphate from below detection in the uncontaminated zone to approximately 0.07 and 70 ??M, respectively, in the suboxic zone. Concentrations of As(III) were below detection in both zones. The anoxic zone had approximately 0.07 ??M As(V) but also had As(III) concentrations of 0.07-0.14 ??M, suggesting that release of As bound to sediment grains occurred by desorption by phosphate, reductive dissolution of Fe oxides, and reduction of As(V) to As(III), which adsorbs only weakly to the Fe-oxide-depleted material in the coatings. Results of reductive extractions of the sediments suggest that As associated with the coatings was relatively uniformly distributed at approximately 1 nmol/g of sediment (equivalent to 0.075 ppm As) and comprised 20%-50% of the total As in the sediments, determined from oxidative extractions. Quartz sand aquifers provide high-quality drinking water but can become contaminated when naturally occurring arsenic bound to Fe and Al oxides or silicates on sediment surfaces is released by desorption and dissolution of Fe oxides in response to changing chemical conditions. ?? 2004 American Institute of Physics.

Diverse stoichiometry of dissolved trace metals in the Indian Ocean

PubMed Central

Thi Dieu Vu, Huong; Sohrin, Yoshiki

2013-01-01

Trace metals in seawater are essential to organisms and important as tracers of various processes in the ocean. However, we do not have a good understanding of the global distribution and cycling of trace metals, especially in the Indian Ocean. Here we report the first simultaneous, full-depth, and basin-scale section-distribution of dissolved (D) Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the Indian Ocean. Our data reveal widespread co-limitation for phytoplankton production by DFe and occurrence of redox-related processes. The stoichiometry of the DM/phosphorus ratio agrees within a factor of 5 between deep waters in the Indian and Pacific, whereas it shows variability up to a factor of 300 among water masses within the Indian Ocean. This indicates that a consistent mechanism controls the stoichiometry in the deep waters, which are significantly depleted in Mn, Fe, and Co compared to requirements for phytoplankton.

Mass-size distribution and concentration of metals from personal exposure to arc welding fume in pipeline construction: a case report.

PubMed

Yang, Show-Yi; Lin, Jia-Ming; Young, Li-Hao; Chang, Ching-Wen

2018-04-07

We investigate exposure to welding fume metals in pipeline construction, which are responsible for severe respiratory problems. We analyzed air samples obtained using size-fractioning cascade impactors that were attached to the welders performing shielded metal and gas tungsten arc welding outdoors. Iron, aluminum, zinc, chromium, manganese, copper, nickel, and lead concentrations in the water-soluble (WS) and water-insoluble (WI) portions were determined separately, using inductively coupled plasma mass spectrometry. The mass-size distribution of welding fume matches a log-normal distribution with two modes. The metal concentrations in the welding fume were ranked as follows: Fe > Al > Zn > Cr > Mn > Ni > Cu > Pb. In the WS portion, the capacities of metals dissolving in water are correlated with the metal species but particle sizes. Particularly, Zn, Mn, and Pb exhibit relatively higher capacities than Cu, Cr, Al, Fe, and Ni. Exposure of the gas-exchange region of the lungs to WS metals were in the range of 4.9% to 34.6% of the corresponding metals in air by considering the particle-size selection in lungs, metal composition by particle size, and the capacities of each metal dissolving in water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fan; Parker, Jack C.; Brooks, Scott C

This study investigated sorption of uranium and technetium onto aluminum and iron hydroxides during titration of a contaminated groundwater using both Na hydroxide and carbonate as titrants. The contaminated groundwater has a low pH of 3.8 and high concentrations of NO3-, SO42-, Al, Ca, Mg, Mn, trace metals such as Ni and Co, and radionuclides such as U and Tc. During titration, most Al and Fe were precipitated out at pH above ~4.5. U as well as Tc was found to be removed from aqueous phase at pH below ~5.5, but to some extent released at higher pH values. Anmore » earlier geochemical equilibrium reaction path model that considered aqueous complexation and precipitation/dissolution reactions predicted mineral precipitation and adequately described concentration variations of Al, Fe and some other metal cations, but failed to predict sulfate, U and Tc concentrations during titration. Previous studies have shown that Fe- and Al-oxyhydroxides strongly sorb dissolved sulfate, U and Tc species. Therefore, an anion exchange model was developed for the sorption of sulfate, U and Tc onto Al and Fe hydroxides. With the additional consideration of the anion exchange reactions, concentration profiles of sulfate, U and Tc were more accurately predicted. Results of this study indicate that consideration of complex reactions such as sorption/desorption on mixed mineral phases, in addition to hydrolysis and precipitation, could improve the prediction of various contaminants during pre- and post-groundwater treatment practices.« less

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

PubMed

Bae, Yeunook; Kim, Dooil; Cho, Hyun-Hee; Singhal, Naresh; Park, Jae-Woo

2012-12-01

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Detection of Remarkably Low Isotopic Ratio of Iron in Anthropogenic Aerosols and Evaluation of its Contribution to the Surface Ocean

NASA Astrophysics Data System (ADS)

Kurisu, M.; Iizuka, T.; Sakata, K.; Uematsu, M.; Takahashi, Y.

2015-12-01

It has been reported that phytoplankton growth in the High Nutrient-Low Chlorophyll (HNLC) regions is limited by dissolved iron (DFe) concentration (e.g., Martin and Fitzwater, 1988). Aerosol is known as one of the dominant sources of DFe to the ocean and classified into two origins such as anthropogenic and natural. A series of recent studies showed that Fe in anthropogenic aerosols is more soluble than that in natural aerosols (Takahashi et al., 2013) and has lower isotopic ratio (Mead et al., 2013). However, the difference between Fe isotopic ratio　(δ56Fe: [(56Fe/54Fe)sample/(56Fe/54Fe)IRMM-14]-1) of two origins reported in Mead et al. (2013) is not so large compared with the standard deviation. Therefore, the aim of this study is to determine Fe species and δ56Fe in anthropogenic aerosols more accurately and to evaluate its contribution to the ocean surface. Iron species were determined by X-ray absorption fine structure (XAFS) analysis, while δ56Fe in size-fractionated aerosols were measured by MC-ICP-MS (NEPTUNE Plus) after chemical separation using anion exchange resin. Dominant Fe species in the samples were, ferrihydrite, hematite, and biotite. It was also revealed that coarse particles contained a larger amount of biotite and that fine particles contained a larger amount of hematite, which suggested that anthropogenic aerosols were emitted during combustion processes. In addition, results of Fe isotopic ratio analysis suggested that δ56Fe of coarse particles were around +0.25‰, whereas that of fine particles were -0.5 ˜ -2‰, which was lower than the δ56Fe in anthropogenic aerosol by Mead et al. (2013). The size-fractionated sampling made it possible to determine the δ56Fe in anthropogenic aerosol. Soluble component in fine particles extracted by simulated rain water also showed much lower δ56Fe (δ56Fe = -3.9±0.12‰), suggesting that anthropogenic Fe has much lower isotopic ratio. The remarkably low δ56Fe may be caused by the anthropogenic combustion process. The δ56Fe in anthropogenic aerosols measured here is important to model the budget of iron in the surface ocean.

Nanoscale Titanium Dioxide (nTiO2) Transport in Water-Saturated Natural Sediments: Influence of Soil Organic Matter and Fe/Al Oxyhydroxides

NASA Astrophysics Data System (ADS)

Fisher-Power, L.; Cheng, T.

2017-12-01

Transport of engineered nanoparticles (ENP) in subsurface environments has important implications to water quality and soil contamination. Although extensive research has been conducted to understand the effects of water chemistry on ENP transport, less attention has been paid to influences from the transport medium/matrix. The objective of this research is to investigate the effects of natural organic matter (NOM) and Fe/Al oxyhydroxides in a natural sediment on ENP transport. A sediment was collected and separated into four portions, one of which was unmodified, and the others treated to remove specific components (organic matter, Fe/Al oxyhydroxides, or both organic matter and Fe/Al oxyhydroxides). Transport of nanoscale titanium dioxide (nTiO2) in columns packed with quartz sand and each of the four types of the sediment under water-saturated conditions was studied. Our results showed that nTiO2 transport was strongly influenced by pH and sediment composition. When influent pH = 5, nTiO2 transport in all the sediments was low, as positively-charged nTiO2 was attracted to negatively charged NOM, quartz, and other minerals. nTiO2 transport was slightly enhanced in columns packed with untreated sediment or Fe/Al oxyhydroxides removed sediment due to dissolved organic matter generated by the partial dissolution of NOM, which adsorbed onto nTiO2 surface and reversed its zeta potential to negative. When influent pH = 9, nTiO2 transport was generally high since negatively-charged nTiO2 was repelled by negatively charged transport medium. However, in columns packed with the organic matter removed sediment or the Fe/Al oxyhydroxides removed sediment, nTiO2 transport was low. This was attributable to pH buffering by the sediment, which decreased pore water pH in the column, resulting in zeta potential change and electrostatic attraction between Fe/Al oxyhydroxides and nTiO2. This research demonstrates that electrostatic forces between nTiO2 and mineral/organic components in natural sediments is a key factor that controls nTiO2 retention and transport, and that both NOM and Fe/Al oxyhydroxides may substantially influence nTiO2 transport.

Problems associated with using filtration to define dissolved trace element concentrations in natural water samples

USGS Publications Warehouse

Horowitz, A.J.; Lum, K.R.; Garbarino, J.R.; Hall, G.E.M.; Lemieux, C.; Demas, C.R.

1996-01-01

Field and laboratory experiments indicate that a number of factors associated with filtration other than just pore size (e.g., diameter, manufacturer, volume of sample processed, amount of suspended sediment in the sample) can produce significant variations in the 'dissolved' concentrations of such elements as Fe, Al, Cu, Zn, Pb, Co, and Ni. The bulk of these variations result from the inclusion/exclusion of colloidally associated trace elements in the filtrate, although dilution and sorption/desorption from filters also may be factors. Thus, dissolved trace element concentrations quantitated by analyzing filtrates generated by processing whole water through similar pore-sized filters may not be equal or comparable. As such, simple filtration of unspecified volumes of natural water through unspecified 0.45-??m membrane filters may no longer represent an acceptable operational definition for a number of dissolved chemical constituents.

Magnetite Authigenesis and the Ancient Martian Atmosphere

NASA Astrophysics Data System (ADS)

Tosca, N. J.; Ahmed, I. A.; Ashpitel, A.; Hurowitz, J.

2017-12-01

Although the Curiosity rover has documented lacustrine sediments at Gale Crater, how liquid water became physically stable is unknown. The early Martian atmosphere is thought to have been dominated by CO2 [1], but the Curiosity rover has provided only ambiguous detections of carbonate minerals at abundances significantly less than 1 wt. % [2, 3], and climate models indicate that in the absence of additional components, multi-bar CO2 atmospheres could not have maintained surface temperatures above freezing. To constrain the composition of the ancient Martian atmosphere, we experimentally investigated the nucleation and growth kinetics of authigenic Fe(II)-minerals in Gale Crater mudstones. Experiments show that as basaltic waters experience pH increases above 8.0, a series of anoxic mineral transformations generates magnetite in days. Electrochemical and dissolved gas analyses show that one stage of this process, the conversion of Fe(OH)2 to green rust, generates H2(g). Experiments including dissolved CO2 show that, despite magnetite formation, Fe(II)-carbonate does not nucleate until significant supersaturation is reached, at PCO2 levels far above previous estimates. Our experimental observations imply that Gale Crater lakes could have been in contact with a CO2-rich atmosphere. In addition, geochemical calculations show that groundwater infiltration into lacustrine sediments triggered magnetite and H2(g) generation at Gale Crater (instead of Fe(II)-carbonate cementation). Groundwater infiltration is consistent with data from the Sheepbed member mudstones, and deep-water mudstones of the Murray formation, both of which contain abundant authigenic magnetite [2, 4]. Low temperature H2 production may have provided a globally significant but transient feedback for stabilizing liquid water on early Mars. Data collected to date by the Curiosity rover are consistent with both estimated timescales and climatic shifts associated with H2-induced warming. Low temperature H2 production also implies that a wide range of biologically relevant chemical reactions may have been operative on the early Martian surface. [1] J. Pollack, et al. (1987) Icarus 71, 203-24. [2] D. Vaniman et al., (2014) Science 343, 8. [3] D. Ming, et al., (2014) Science 343, 1245267. [4] J. Hurowitz, et al. (2017) Science 356, 922.

Effect of adsorbed metals ions on the transport of Zn- and Ni-EDTA complexes in a sand and gravel aquifer

USGS Publications Warehouse

Kent, D.B.; Davis, J.A.; Anderson, L.C.D.; Rea, B.A.; Coston, J.A.

2002-01-01

Adsorption, complexation, and dissolution reactions strongly influenced the transport of metal ions complexed with ethylenediaminetetraacetic acid (EDTA) in a predominantly quartz-sand aquifer during two tracer tests conducted under mildly reducing conditions at pH 5.8 to 6.1. In tracer test M89, EDTA complexes of zinc (Zn) and nickel (Ni), along with excess free EDTA, were injected such that the lower portion of the tracer cloud traveled through a region with adsorbed manganese (Mn) and the upper portion of the tracer cloud traveled through a region with adsorbed Zn. In tracer test S89, Ni- and Zn-EDTA complexes, along with excess EDTA complexed with calcium (Ca), were injected into a region with adsorbed Mn. The only discernable chemical reaction between Ni-EDTA and the sediments was a small degree of reversible adsorption leading to minor retardation. In the absence of adsorbed Zn, the injected Zn was displaced from EDTA complexes by iron(III) [Fe(III)] dissolved from the sediments. Displacement of Zn by Fe(III) on EDTA became increasingly thermodynamically favorable with decreasing total EDTA concentration. The reaction was slow compared to the time-scale of transport. Free EDTA rapidly dissolved aluminum (Al) from the sediments, which was subsequently displaced slowly by Fe. In the portion of tracer cloud M89 that traveled through the region contaminated with adsorbed Zn, little displacement of Zn complexed with EDTA was observed, and Al was rapidly displaced from EDTA by Zn desorbed from the sediments, in agreement with equilibrium calculations. In tracer test S89, desorption of Mn dominated over the more thermodynamically favorable dissolution of Al oxyhydroxides. Comparison with results from M89 suggests that dissolution of Al oxyhydroxides in coatings on these sediment grains by Ca-EDTA was rate-limited whereas that by free EDTA reached equilibrium on the time-scale of transport. Rates of desorption are much faster than rates of dissolution of Fe oxyhydroxides from sediment-grain surfaces and, therefore, adsorbed metal ions can strongly influence the speciation of ligands like EDTA in soils and sediments, especially over small temporal and spatial scales. Copyright ?? 2002 Elsevier Science Ltd.

Biological versus mineralogical chromium reduction: potential for reoxidation by manganese oxide.

PubMed

Butler, Elizabeth C; Chen, Lixia; Hansel, Colleen M; Krumholz, Lee R; Elwood Madden, Andrew S; Lan, Ying

2015-11-01

Hexavalent chromium (Cr(vi), present predominantly as CrO4(2-) in water at neutral pH) is a common ground water pollutant, and reductive immobilization is a frequent remediation alternative. The Cr(iii) that forms upon microbial or abiotic reduction often co-precipitates with naturally present or added iron (Fe), and the stability of the resulting Fe-Cr precipitate is a function of its mineral properties. In this study, Fe-Cr solids were formed by microbial Cr(vi) reduction using Desulfovibrio vulgaris strain RCH1 in the presence of the Fe-bearing minerals hematite, aluminum substituted goethite (Al-goethite), and nontronite (NAu-2, Clay Minerals Society), or by abiotic Cr(vi) reduction by dithionite reduced NAu-2 or iron sulfide (FeS). The properties of the resulting Fe-Cr solids and their behavior upon exposure to the oxidant manganese (Mn) oxide (birnessite) differed significantly. In microcosms containing strain RCH1 and hematite or Al-goethite, there was significant initial loss of Cr(vi) in a pattern consistent with adsorption, and significant Cr(vi) was found in the resulting solids. The solid formed when Cr(vi) was reduced by FeS contained a high proportion of Cr(iii) and was poorly crystalline. In microcosms with strain RCH1 and hematite, Cr precipitates appeared to be concentrated in organic biofilms. Reaction between birnessite and the abiotically formed Cr(iii) solids led to production of significant dissolved Cr(vi) compared to the no-birnessite controls. This pattern was not observed in the solids generated by microbial Cr(vi) reduction, possibly due to re-reduction of any Cr(vi) generated upon oxidation by birnessite by active bacteria or microbial enzymes. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential for rapid (re)formation of dissolved Cr(vi) above regulatory levels.

Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

NASA Astrophysics Data System (ADS)

Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

2015-12-01

In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

Phosphate reactivity in long-term poultry litter-amended southern Delaware sandy soils

USGS Publications Warehouse

Arai, Y.; Livi, K.J.T.; Sparks, D.L.

2005-01-01

Eutrophication caused by dissolved P from poultry litter (PL)-amended agricultural soils has been a serious environmental concern in the Delaware-Maryland-Virginia Peninsula (Delmarva), USA. To evaluate state and federal nutrient management strategies for reducing the environmental impact of soluble P from long-term PL-amended Delaware (DE) soils, we investigated (i) inorganic P speciation; (ii) P adsorption capacity; and (iii) the extent of P desorption. Although the electron microprobe (EMP) analyses showed a strong correlation between P and Al/Fe, crystalline Al/Fe-P precipitates were not detected by x-ray diffraction (XRD). Instead, the inorganic P fractionation analyses showed high levels of oxalate extractable P, Al, and Fe fractions (615-858, 1215-1478, and 337-752 mg kg-1, respectively), which were susceptible to slow release during the long-term (30-d) P desorption experiments at a moderately acidic soil pHwater. The labile P in the short-term (24-h) desorption studies was significantly associated with oxalate and F extractable Fe and Al, respectively. This was evident in an 80% reduction maximum in total desorbable P from NH4 oxalate/F pretreated soils. In the adsorption experiments, P was strongly retained in soils at near targeted pH of lime (???6.0), but P adsorption gradually decreased with decreasing pH near the soil pHwater (???5.0). The overall findings suggest that P losses from the can be suppressed by an increase in the P retention capacity of soils via (i) an increase in the number of lime applications to maintain soil pHwater at near targeted pH values, and/or (ii) alum/iron sulfate amendments to provide additional Al- and Fe-based adsorbents. ?? Soil Science Society of America.

Characterisation of urban catchment suspended particulate matter (Auckland region, New Zealand); a comparison with non-urban SPM.

PubMed

Bibby, Rebecca L; Webster-Brown, Jenny G

2005-05-01

Suspended particulate matter (SPM) is an important transport agent for metal contaminants in streams, particularly during high flow periods such as storm events. For highly contaminated urban catchments in the greater Auckland (New Zealand) area, trace metal partitioning between the dissolved phase and SPM was determined, and SPM characterised in terms of its Si, Al, Fe, Mn, Zn, Cu, Pb, TOC, TON and PO(4) concentrations, as well as particle size, abundance, type and surface area. This data was compared to similar data from representative non-urban catchments in the Auckland region, the Kaipara River and Waikato River catchments, to identify any significant differences in the SPM and its potential trace metal adsorption capacity. Trace metal partitioning was assessed by way of a distribution coefficient: K(D)=[Me(SPM)]/[Me(DISS)]. Auckland urban SPM comprises quartz, feldspars and clay minerals, with Fe-oxides and minor Mn-oxides. No particles of anthropogenic origin, other than glass shards, were observed. No change in urban SPM particle size or SSA was observed with seasonal change in temperature, but the nature of the SPM was observed to change with flow regime. The abundance of finer particles, SSA and Al content of the SPM increased under moderate flow conditions; however, Si/Al ratios remained constant, confirming the importance of aluminosilicate detrital minerals in surface run-off. The SPM Fe content was observed to decrease with increased flow and was attributed to dilution of SPM Fe-oxide of groundwater origin. The Kaipara River SPM was found to be mineralogically, chemically and biologically similar to the urban SPM. However, major differences between urban catchment SPM and SPM from the much larger (non-urban) Waikato River were observed, and attributed to a higher abundance of diatoms. The Fe content of the Waikato River SPM was consistently lower (<5%), and the Si/Al ratio and Mn content was higher. Such differences observed between urban and non-urban SPM did not appear to affect the partitioning of Zn and Cu; however, Pb in the Kaipara and Waikato Rivers was found to be more associated with the dissolved phase. This is likely to reflect higher particulate Pb inputs to urban systems.

Mechanisms controlling lateral and vertical porewater migration of depleted uranium (DU) at two UK weapons testing sites.

PubMed

Graham, Margaret C; Oliver, Ian W; MacKenzie, Angus B; Ellam, Robert M; Farmer, John G

2011-04-15

Uranium associations with colloidal and truly dissolved soil porewater components from two Ministry of Defence Firing Ranges in the UK were investigated. Porewater samples from 2-cm depth intervals for three soil cores from each of the Dundrennan and Eskmeals ranges were fractionated using centrifugal ultrafiltration (UF) and gel electrophoresis (GE). Soil porewaters from a transect running downslope from the Dundrennan firing area towards a stream (Dunrod Burn) were examined similarly. Uranium concentrations and isotopic composition were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), respectively. The soils at Dundrennan were Fe- and Al-rich clay-loam soils whilst at Eskmeals, they were Fe- and Al-poor sandy soils; both, however, had similar organic matter contents due to the presence of a near-surface peaty layer at Eskmeals. These compositional features influenced the porewater composition and indeed the associations of U (and DU). In general, at Dundrennan, U was split between large (100kDa-0.2μm) and small (3-30kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10cm depth, association with large Fe/Al/organic colloids was considered to be a precursor to the removal of U from the Dundrennan porewaters to the solid phase. In contrast, the association of U with small organic colloids was largely responsible for inhibiting attenuation in the Eskmeals soils. Lateral migration of U (and DU) through near-surface Dundrennan soils will involve both large and small colloids but, at depth, transport of the smaller amounts of U remaining in the porewaters may involve large colloids only. For one of the Dundrennan cores the importance of redox-related processes for the re-mobilisation of DU was also indicated as Mn(IV) reduction resulted in the release of both Mn(II) and U(VI) into the truly dissolved phase. Copyright © 2011 Elsevier B.V. All rights reserved.

Characterization of elemental release during microbe granite interactions at T = 28 °C

NASA Astrophysics Data System (ADS)

Wu, Lingling; Jacobson, Andrew D.; Hausner, Martina

2008-02-01

This study used batch reactors to characterize the mechanisms and rates of elemental release (Al, Ca, K, Mg, Na, F, Fe, P, Sr, and Si) during interaction of a single bacterial species ( Burkholderia fungorum) with granite at T = 28 °C for 35 days. The objective was to evaluate how actively metabolizing heterotrophic bacteria might influence granite weathering on the continents. We supplied glucose as a C source, either NH 4 or NO 3 as N sources, and either dissolved PO 4 or trace apatite in granite as P sources. Cell growth occurred under all experimental conditions. However, solution pH decreased from ˜7 to 4 in NH 4-bearing reactors, whereas pH remained near-neutral in NO 3-bearing reactors. Measurements of dissolved CO 2 and gluconate together with mass-balances for cell growth suggest that pH lowering in NH 4-bearing reactors resulted from gluconic acid release and H + extrusion during NH 4 uptake. In NO 3-bearing reactors, B. fungormum likely produced gluconic acid and consumed H + simultaneously during NO 3 utilization. Over the entire 35-day period, NH 4-bearing biotic reactors yielded the highest release rates for all elements considered. However, chemical analyses of biomass show that bacteria scavenged Na, P, and Sr during growth. Abiotic control reactors followed different reaction paths and experienced much lower elemental release rates compared to biotic reactors. Because release rates inversely correlate with pH, we conclude that proton-promoted dissolution was the dominant reaction mechanism. Solute speciation modeling indicates that formation of Al-F and Fe-F complexes in biotic reactors may have enhanced mineral solubilities and release rates by lowering Al and Fe activities. Mass-balances further reveal that Ca-bearing trace phases (calcite, fluorite, and fluorapatite) provided most of the dissolved Ca, whereas more abundant phases (plagioclase) contributed negligible amounts. Our findings imply that during the incipient stages of granite weathering, heterotrophic bacteria utilizing glucose and NH 4 only moderately elevate silicate weathering reactions that consume atmospheric CO 2. However, by enhancing the dissolution of non-silicate, Ca-bearing trace minerals, they could contribute to high Ca/Na ratios commonly observed in granitic watersheds.

Source and fate of inorganic solutes in the Gibbon River, Yellowstone National Park, Wyoming, USA. II. Trace element chemistry

USGS Publications Warehouse

McCleskey, R. Blaine; Nordstrom, D. Kirk; Susong, David D.; Ball, James W.; Taylor, Howard E.

2010-01-01

The Gibbon River in Yellowstone National Park receives inflows from several geothermal areas, and consequently the concentrations of many trace elements are elevated compared to rivers in non-geothermal watersheds. Water samples and discharge measurements were obtained from the Gibbon River and its major tributaries near Norris Geyser Basin under the low-flow conditions of September 2006 allowing for the identification of solute sources and their downstream fate. Norris Geyser Basin, and in particular Tantalus Creek, is the largest source of many trace elements (Al, As, B, Ba, Br, Cs, Hg, Li, Sb, Tl, W, and REEs) to the Gibbon River. The Chocolate Pots area is a major source of Fe and Mn, and the lower Gibbon River near Terrace Spring is the major source of Be and Mo. Some of the elevated trace elements are aquatic health concerns (As, Sb, and Hg) and knowing their fate is important. Most solutes in the Gibbon River, including As and Sb, behave conservatively or are minimally attenuated over 29 km of fluvial transport. Some small attenuation of Al, Fe, Hg, and REEs occurs but primarily there is a transformation from the dissolved state to suspended particles, with most of these elements still being transported to the Madison River. Dissolved Hg and REEs loads decrease where the particulate Fe increases, suggesting sorption onto suspended particulate material. Attenuation from the water column is substantial for Mn, with little formation of Mn as suspended particulates.

Pyrite oxidation in the presence of hematite and alumina: I. Batch leaching experiments and kinetic modeling calculations.

PubMed

Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi

2017-02-15

Pyrite is one of the most common and geochemically important sulfide minerals in nature because of its role in the redox recycling of iron (Fe). It is also the primary cause of acid mine drainage (AMD) that is considered as a serious and widespread problem facing the mining and mineral processing industries. In the environment, pyrite oxidation occurs in the presence of ubiquitous metal oxides, but the roles that they play in this process remain largely unknown. This study evaluates the effects of hematite (α-Fe 2 O 3 ) and alumina (α-Al 2 O 3 ) on pyrite oxidation by batch-reactor type experiments, surface-sensitive characterization of the oxidation layer and thermodynamic/kinetic modeling calculations. In the presence of hematite, dissolved sulfur (S) concentration dramatically decreased independent of the pH, and the formation of intermediate sulfoxy anionic species on the surface of pyrite was retarded. These results indicate that hematite minimized the overall extent of pyrite oxidation, but the kinetic model could not explain how this suppression occurred. In contrast, pyrite oxidation was enhanced in the alumina suspension as suggested by the higher dissolved S concentration and stronger infrared (IR) absorption bands of surface-bound oxidation products. Based on the kinetic model, alumina enhanced the oxidative dissolution of pyrite because of its strong acid buffering capacity, which increased the suspension pH. The higher pH values increased the oxidation of Fe 2+ to Fe 3+ by dissolved O 2 (DO) that enhanced the overall oxidative dissolution kinetics of pyrite. Copyright © 2016 Elsevier B.V. All rights reserved.

Combining cross flow ultrafiltration and diffusion gradients in thin-films approaches to determine trace metal speciation in freshwaters

NASA Astrophysics Data System (ADS)

Liu, Ruixia; Lead, Jamie R.; Zhang, Hao

2013-05-01

Cross flow ultrafiltration (CFUF) and diffusive gradients in thin films (DGT) with open pore gel (OP) and restricted pore gel (RP) were used to measure trace metal speciation in selected UK freshwaters. The proportions of metals present in particulate forms (>1 μm) varied widely between 40-85% Pb, 60-80% Al, 7-56% Mn, 10-49% Cu, 0-55% Zn, 20-38% Cr, 20-30% Fe, 6-25% Co, 5-22% Cd and <7% Ni. In the colloidal fraction (2 kDa-1 μm) values varied between 53-91% Pb, 33-55% Al, 21-55% Cu, 20-44% Fe, 34-36% Cr, 20-40% Cd, 7-28% Co and Ni, 2-32% Zn and <8% Mn. Wide variations were also observed in the ultrafiltered fraction (<2 kDa). These results indicated that colloids indeed influenced the occurrence and transport of Al, Fe, Cr, Co, Ni, Cu, Zn, Cr and Pb metals in rivers, while inorganic or organic colloids did not exert an important control on Mn transport in the selected freshwaters. Of total species, total labile metal measured by DGT-OP accounted for 1.4-50% for Al, Fe, Co, Ni, Cu, Cd and Pb in all selected waters. Of these metals total labile Pb concentration was the lowest with value less than 1.4% although this value slightly increased after deducting particulate fractions. In some waters, a majority of total Mn, Zn and Cr is DGT labile, in which the DGT labile Mn fraction accounted for 98-118% of the total dissolved phase. In most cases, the inorganic labile concentration measured by DGT-RP was lower than the total labile metal concentration. By the combination of CFUF and DGT techniques, the concentrations of total labile and inorganic labile metal species in CFUF-derived truly dissolved phase were measured in four water samples. 100% of ultrafiltered Mn species was found to be total DGT labile. The proportions of total labile metal species were lower than those of ultrafiltered fraction for Al, Fe, Co, Ni, Cu, Cd and Pb in all selected waters, and Cr and Zn in some cases, indicating a large amount of natural complexing ligands with smaller size for the metals to form kinetically inert species or thermodynamically stable complexes. Observed discrepancies in metal speciation between metals and within sampling sites were related to the differences in the characteristics of the metals and the nature of water sources.

Characteristics and source identification of dissolved trace elements in the Jinshui River of the South Qinling Mts., China.

PubMed

Bu, Hongmei; Wang, Weibo; Song, Xianfang; Zhang, Quanfa

2015-09-01

Dissolved trace elements and physiochemical parameters were analyzed to investigate their physicochemical characteristics and identify their sources at 12 sampling sites of the Jinshui River in the South Qinling Mts., China from October 2006 to November 2008. The two-factor ANOVA indicated significant temporal variations of the dissolved Cu, Fe, Sr, Si, and V (p < 0.001 or p < 0.05). With the exception of Sr (p < 0.001), no significant spatial variations were found. Distributions and concentrations of the dissolved trace elements displayed that dissolved Cu, Fe, Sr, Si, V, and Cr were originated from chemical weathering and leaching from the soil and bedrock. Dissolved Cu, Fe, Sr, As, and Si were also from anthropogenic inputs (farming and domestic effluents). Correlation and regression analysis showed that the chemical and physical processes of dissolved Cu was influenced by water temperature and dissolved oxygen (DO) to some degree. Dissolved Fe and Sr were affected by colloid destabilization or sedimentary inputs. Concentrations of dissolved Si were slightly controlled by biological uptake. Principal component analysis confirmed that Fe, Sr, and V resulted from domestic effluents, agricultural runoff, and confluence, whereas As, Cu, and Si were from agricultural activities, and Cr and Zn through natural processes. The research results provide a reference for ecological restoration and protection of the river environment in the Qinling Mts., China.

Major ions, nutrients, and trace elements in the Mississippi River near Thebes, Illinois, July through September 1993

USGS Publications Warehouse

Taylor, Howard E.; Antweiler, Ronald C.; Brinton, Terry I.; Roth, David A.; Moody, John A.

1994-01-01

Extensive flooding in the upper Mississippi River Basin during summer 1993 had a significant effect on the water quality of the Mississippi River. To evaluate the change in temporal distribution and transport of dissolved constituents in the Mississippi River, six water samples were collected by a discharge-weighted method from July through September 1993 near Thebes, Illinois. Sampling at this location provided water-quality information from the upper Mississippi, the Missouri, and the Illinois River Basins. Dissolved major constituents that were analyzed in each of the samples included bicarbonate, calcium (Ca), carbonate (C03), chloride (Cl), dissolved organic carbon, magnesium (Mg), potassium (K), silica NOD, sodium (Na), and sulfate (S04). Dissolved nutrients included ammonium ion (NH4), nitrate (N03), nitrite (N02), and orthophosphate (P04) . Dissolved trace elements included aluminum (Al), arsenic (As), barium (Ba), boron (B), beryllium (Be), bromide (Br), cadmium (Cd), chromium (Cr), cobalt, (Co), copper (Cu), fluoride (F), iron (Fe), lead, lithium (Li), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), strontium (Sr), thallium, uranium (U), vanadium (V), and zinc (Zn). Other physical properties of water that were measured included specific conductance, pH and suspended-sediment concentration (particle size, less than 63 micrometers). Results of this study indicated that large quantities of dissolved constituents were transported through the river system. Generally, pH, alkalinity, and specific conductance and the concentrations of B, Br, Ca, Cl, Cr, K, Li, Mg, Mo, Na, S04, Sr, U, and V increased as water discharge decreased, while concentrations of F, Hg, and suspended sediment sharply decreased as water discharge decreased after the crest of the flood. Concentrations of other constituents, such as Al, As, Ba, Be, Co, Cu, Ni, N03, N02, NH4, P04, and Si02, varied with time as discharge decreased after the crest of the flood. For most constituents, the load transported during floods generally is much greater than that transported during low-flow conditions. How ever, for Cd, Cr, Fe, Mn, V, and Zn, loads increased substantially as water discharge decreased after the crest of the flood.

Characterization of metal adsorption variability in a sand and gravel aquifer, Cape Cod, Massachusetts, U.S.A

USGS Publications Warehouse

Fuller, C.C.; Davis, J.A.; Coston, J.A.; Dixon, E.

1996-01-01

Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb2+) and zinc (Zn2+) adsorption at constant chemical conditions (pH 5.3) varied by a factor of 2 and 4, respectively. Pb2+ and Zn2+ were adsorbed primarily by Fe- and Al-oxide coatings on quartz-grain surfaces. Per unit surface area, both Pb2+ and Zn2+ adsorption were significantly correlated with the amount of Fe and Al that dissolved from the aquifer material in a partial chemical extraction. The variability in conditional binding constants for Pb2+ and Zn2+ adsorption (log KADS) derived from a simple non-electrostatic surface complexation model were also predicted by extracted Fe and Al normalized to surface area. Because the abundance of Fe- and Al-oxide coatings that dominate adsorption does not vary inversely with grain size by a simple linear relationship, only a weak, negative correlation was found between the spatial variability of Pb2+ adsorption and grain size in this aquifer. The correlation between Zn2+ adsorption and grain size was not significant. Partial chemical extractions combined with surface-area measurements have potential use for estimating metal adsorption variability in other sand and gravel aquifers of negligible carbonate and organic carbon content.

Investigation of Pb Li compatibility issues for the dual coolant blanket concept

NASA Astrophysics Data System (ADS)

Pint, B. A.; Moser, J. L.; Tortorelli, P. F.

2007-08-01

One proposed blanket concept uses advanced ferritic alloys and a SiC/SiC composite flow channel insert with both Pb-17 at.%Li and He coolants. As the first step in determining the long-term compatibility of SiC/SiC in Pb-Li, specimens of high-purity, chemical vapor deposited (CVD) SiC were exposed in capsules for up to 5000 h at 800 °C and 1000 h at 1200 °C. Dissolved Si was detected in the Pb-Li after the highest temperature exposures suggesting that SiC may be limited to <1100 °C in Pb-Li. Aluminide coatings are being considered for corrosion resistant coatings for the tubing between the first wall and the heat exchanger. Initial results indicate that, in Pb-Li at 700 °C, FeCrAl, Fe 3Al and NiAl form a protective alumina layer which reduces dissolution compared to type 316 stainless steel.

The chemistry of iron, aluminum, and dissolved organic material in three acidic, metal-enriched, mountain streams, as controlled by watershed and in-stream processes

USGS Publications Warehouse

McKnight, Diane M.; Bencala, Kenneth E.

1990-01-01

Several studies were conducted in three acidic, metal-enriched, mountain streams, and the results are discussed together in this paper to provide a synthesis of watershed and in-stream processes controlling Fe, Al, and DOC (dissolved organic carbon) concentrations. One of the streams, the Snake River, is naturally acidic; the other two, Peru Creek and St. Kevin Gulch, receive acid mine drainage. Analysis of stream water chemistry data for the acidic headwaters of the Snake River shows that some trace metal solutes (Al, Mn, Zn) are correlated with major ions, indicating that watershed processes control their concentrations. Once in the stream, biogeochemical processes can control transport if they occur over time scales comparable to those for hydrologic transport. Examples of the following in-stream reactions are presented: (1) photoreduction and dissolution of hydrous iron oxides in response to an experimental decrease in stream pH, (2) precipitation of Al at three stream confluences, and (3) sorption of dissolved organic material by hydrous iron and aluminum oxides in a stream confluence. The extent of these reactions is evaluated using conservative tracers and a transport model that includes storage in the substream zone.

Trace elements records from vermetids aragonite as millennial paleo-oceanographic archives in the South-East Mediterranean

NASA Astrophysics Data System (ADS)

Jacobson, Yitzhak; Yam, Ruth; Shemesh, Aldo

2017-04-01

The Mediterranean Sea is a region under high anthropogenic stress, thus a hotspot for climate change studies. Natural conditions, such as SST, productivity, precipitation and dust fluxes along with human induced activity affect seawater chemistry. We study millennial variability of trace elements in East Mediterranean Sea high-resolution records, in attempt to connect them to environmental factors. The Mediterranean reef builder Vermetid, D. petraeum is a sessile gastropod, secreting its aragonite shells in tidal zones. Cores of Vermetid reefs from the South Eastern Mediterranean (Israel) were previously analyzed by Sisma?Ventura et al. (2014) to reconstruct seawater surface temperature (SST) and δ13C of dissolved inorganic carbon (DIC). In this study we analyzed trace elements of these vermetid cores, and reconstructed millennial records of elements to calcium (el/Ca) molar ratios. Vermetid trace element contents from recent decades are mostly in agreement with known values for marine biogenic aragonites from corals and mollusk. We divide vermetid trace element records into three element groups: 1) Sr and U are related to SST and DIC. These elements correlate with major climatic events of the last millennium, such as the Medieval Warm Period (900-1300 AD) and the Little Ice Age (1450-1850 AD). 2) Pb and Cd are related to anthropogenic pollution and demonstrate industrial sourced trends throughout the anthropocene (since 1750 AD). 3) Terrogenous elements, including Fe, Al, Mn and V. Al in seawater and sediments has been used to trace water masses and land derived sediment source. We observe a major change in average vermetid Al/Fe ratios from 0.5 to 2.5 over the recorded period (n=72). This vermetid Al/Fe change points at a possible shift from Nilotic sediments (0.1-0.5 Al/Fe molar ratio) to Saharan dust ratio (2-4 Al/Fe molar ratio). Mn and V show a similar variability to Fe. Understanding the variability of vermetid TE can help us interpret the relative dominance of different climate systems and anthropogenic processes on the East Mediterranean environment.

Laboratory and field evaluation of a flushable oxic limestone drain for treatment of net-acidic drainage from a flooded anthracite mine, Pennsylvania, USA

USGS Publications Warehouse

Cravotta, C.A.

2008-01-01

This paper demonstrates the use of dissolution-rate data obtained in the laboratory to indicate the potential quality of effluent from a field-scale oxic limestone drain (OLD) treatment system for neutralization of dilute acidic mine drainage (AMD). Effluent from the Reevesdale Mine South Dip Tunnel, a large source of AMD and base flow to the Wabash Creek and Little Schuylkill River in the Southern Anthracite Coalfield of east-central Pennsylvania, is representative of AMD with low concentrations but high loadings of dissolved Fe, Al and other metals because of a high flow rate. In January 2003, rapid neutralization of the AMD from the Reevesdale Mine was achieved in laboratory tests of its reaction rate with crushed limestone in closed, collapsible containers (Cubitainers). The tests showed that net-alkaline effluent could be achieved with retention times greater than 3 h and that effluent alkalinities and associated dissolution rates were equivalent for Fe(OH)3-coated and uncoated limestone. On the basis of the laboratory results, a flushable OLD containing 1450 metric tons of high-purity calcitic limestone followed by two 0.7-m deep wetlands were constructed at the Reevesdale Mine. During the first year of operation, monthly data at the inflow, outflow and intermediate points within the treatment system were collected (April 2006-2007). The inflow to the treatment system ranged from 6.8 to 27.4 L/s, with median pH of 4.7, net acidity of 9.1 mg/L CaCO3, and concentrations of dissolved Al, Fe and Mn of 1.0, 1.9 and 0.89 mg/L, respectively. The corresponding effluent from the OLD had computed void-volume retention times of 4.5-18 h, with median pH of 6.6, net acidity of -93.2 mg/L CaCO3, and concentrations of dissolved Al, Fe and Mn of <0.1, 0.08 and 0.52 mg/L, respectively. The wetlands below the OLD were effective for retaining metal-rich solids flushed at monthly or more frequent intervals from the OLD, but otherwise had little effect on the effluent quality. During the first year of operation, approximately 43 metric tons of limestone were dissolved and 2 metric tons of Al, Fe and Mn were precipitated within the OLD. However, because of the accumulation of these metals within the OLD and possibly other debris from the mine, the effectiveness of the treatment system declined. Despite the installation of a flush-pipe network at the base of the OLD to remove precipitated solids, the limestone bed clogged near the inflow. Consequently, a large fraction of the AMD bypassed the treatment system. To promote flow through the OLD, the flush pipes were open continuously during the last 4 months of the study; however, this effluent was only partially treated because short-circuiting through the pipes decreased contact between the effluent and limestone. A reconfiguration of the flow path through the limestone bed from horizontal to vertical upward could increase the limestone surface area exposed to the metal-laden influent, increase the cross-sectional area perpendicular to flow, decrease the flow path for solids removal, and, consequently, decrease potential for clogging.

Contrasted response of colloidal, organic and inorganic dissolved phosphorus forms during rewetting of dried riparian soils

NASA Astrophysics Data System (ADS)

Gu, Sen; Gruau, Gérard; Malique, François; Dupas, Rémi; Gascuel-Odoux, Chantal; Petitjean, Patrice; Bouhnik-Le Coz, Martine

2017-04-01

Riparian vegetated buffer strip (RVBS) are currently used to protect surface waters from phosphorus (P) emissions because of their ability to retain P-enriched soil particles. However, this protection role may be counterbalanced by the development in these zones of conditions able to trigger the release of highly mobile dissolved or colloidal P forms. Rewetting after drying is one of these conditions. So far, the potential sources of P mobilized during rewetting after drying are not clearly identified, nor are clearly identified the chemical nature of the released dissolved P species, or the role of the soil P speciation on these forms. In this study, two riparian soils (G and K) showing contrasting soil P speciation (65% of inorganic P species in soil G, as against 70% of organic P) were submitted to three successive dry/wet cycles in the laboratory. Conventional colorimetric determination of P concentrations combined with ultrafiltration, and measurements of iron (Fe) and aluminum (Al) and dissolved organic carbon (DOC) contents using ICP-MS and TOC analyzers, respectively, were used to study the response of the different P forms to rewetting after drying and also their release kinetics during soil leaching. For both soils, marked P release peaks were observed at the beginning of each wet cycles, with the organic-rich K soils giving, however, larger peaks than the inorganic one (G soil). For both soils also, concentrations in molybdate reactive P (MRP) remained quite constant throughout each leaching episode, contrary to the molybdate unreactive P (MUP) concentrations which were high immediately after rewetting and then decreased rapidly during leaching. A speciation change was observed from the beginning to the end of all leaching cycles. Colloidal P was found to be a major fraction of the total P immediately after rewetting (up to 50-70%) and then decreased to the end of each wet cycle where most of the eluted P was true dissolved inorganic P. Colloidal-P exhaustion was tightly associated with DOC, Fe and Al exhaustions. Colloids were larger in size at the beginning than at the end of all cycles. Peak at the beginning of each wet cycles remained quite constant even after two drying/leaching cycles, evidencing the existence of mechanisms able to rebuild a pool of leachable P during drying process. Thus, there was clearly a control of soil characteristics on the released P forms in leachates. Colloidal P carriers appeared to consist of Fe and/or Al oxyhydroxide nano/microparticles associated with organic matter. Most importantly, a survey of colloidal size distribution during leaching indicated that the rapidly exhausted MUP pool consisted of larger size MUP and colloidal P phases, which probably originated from soil macropores, while the relatively infinite MRP pool consisted of smaller size colloidal P and true dissolved MRP phases, which was mobilized from soil micropores. These results further demonstrate the ability of rewetting after drying to lead to pulses of dissolved and colloidal P in riparian soils, thereby evidencing the risks that P-enriched soil particles accumulated in RVBS could constitute a long-term threat for surface water.

Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

NASA Astrophysics Data System (ADS)

Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

2017-04-01

Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past hydrothermalism from ocean sediment records.

Distribution of dissolved labile and particulate iron and copper in Terra Nova Bay polynya (Ross Sea, Antarctica) surface waters in relation to nutrients and phytoplankton growth

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Ianni, Carmela; Massolo, Serena; Abelmoschi, M. Luisa; De Vittor, Cinzia; Frache, Roberto

2011-05-01

The distribution of the dissolved labile and of the particulate Fe and Cu together with dissolved oxygen, nutrients, chlorophyll a and total particulate matter was investigated in the surface waters of Terra Nova Bay polynya in mid-January 2003. The measurements were conducted within the framework of the Italian Climatic Long-term Interactions of the Mass balance in Antarctica (CLIMA) Project activities. The labile dissolved fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The dissolved labile Fe ranges from below the detection limit (0.15 nM) to 3.71 nM, while the dissolved labile Cu from below the detection limit (0.10 nM) to 0.90 nM. The lowest concentrations for both metals were observed at 20 m depth (the shallowest depth for which metals were measured). The concentration of the particulate Fe was about 5 times higher than the dissolved Fe concentration, ranging from 0.56 to 24.83 nM with an average of 6.45 nM. The concentration of the particulate Cu ranged from 0.01 to 0.71 nM with an average of 0.17 nM. The values are in agreement with the previous data collected in the same area. We evaluated the role of the Fe and Cu as biolimiting metals. The N:dissolved labile Fe ratios (18,900-130,666) would or would not allow a complete nitrate removal, on the basis of the N:Fe requirement ratios that we calculated considering the N:P and the C:P ratios estimated for diatoms. This finding partially agrees with the Si:N ratio that we found (2.29). Moreover we considered a possible influence of the dissolved labile Cu on the Fe uptake process.

Iron [Fe(0)]-rich substrate based on iron-carbon micro-electrolysis for phosphorus adsorption in aqueous solutions.

PubMed

Deng, Shihai; Li, Desheng; Yang, Xue; Xing, Wei; Li, Jinlong; Zhang, Qi

2017-02-01

The phosphorus (P) adsorption properties of an iron [Fe(0)]-rich substrate (IRS) composed of iron scraps and activated carbon were investigated based on iron-carbon micro-electrolysis (IC-ME) and compared to the substrates commonly used in constructed wetlands (CWs) to provide an initial characterization of the [Fe(0)]-rich substrate. The results showed that P was precipitated by Fe(III) dissolved from the galvanic cell reactions in the IRS and the reaction was suppressed by the pH and stopped when the pH exceeded 8.90 ± 0.09. The adsorption capacity of the IRS decreased by only 4.6% in the second round of adsorption due to Fe(0) consumption in the first round. Substrates with high Ca- and Mg-oxide contents and high Fe- and Al-oxide contents had higher P adsorption capacities at high and low pH values, respectively. Substrates containing high Fe and Al concentrations and low Ca concentrations were more resistant to decreases in the P adsorption capacity resulting from organic matter (OM) accumulation. The IRS with an iron scrap to activated carbon volume ratio of 3:2 resulted in the highest P adsorption capacity (9.34 ± 0.14 g P kg -1 ), with minimal pH change and strong adaptability to OM accumulation. The Fe(0)-rich substrate has the considerable potential for being used as a CW substrate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of sea level rise on iron diagenesis in an east Florida subterranean estuary

USGS Publications Warehouse

Roy, M.; Martin, J.B.; Cherrier, J.; Cable, J.E.; Smith, C.G.

2010-01-01

Subterranean estuary occupies the transition zone between hypoxic fresh groundwater and oxic seawater, and between terrestrial and marine sediment deposits. Consequently, we hypothesize, in a subterranean estuary, biogeochemical reactions of Fe respond to submarine groundwater discharge (SGD) and sea level rise. Porewater and sediment samples were collected across a 30-m wide freshwater discharge zone of the Indian River Lagoon (Florida, USA) subterranean estuary, and at a site 250. m offshore. Porewater Fe concentrations range from 0.5 ??M at the shoreline and 250. m offshore to about 286 ??M at the freshwater-saltwater boundary. Sediment sulfur and porewater sulfide maxima occur in near-surface OC-rich black sediments of marine origin, and dissolved Fe maxima occur in underlying OC-poor orange sediments of terrestrial origin. Freshwater SGD flow rates decrease offshore from around 1 to 0.1. cm/day, while bioirrigation exchange deepens with distance from about 10. cm at the shoreline to about 40. cm at the freshwater-saltwater boundary. DOC concentrations increase from around 75 ??M at the shoreline to as much as 700 ??M at the freshwater-saltwater boundary as a result of labile marine carbon inputs from marine SGD. This labile DOC reduces Fe-oxides, which in conjunction with slow discharge of SGD at the boundary, allows dissolved Fe to accumulate. Upward advection of fresh SGD carries dissolved Fe from the Fe-oxide reduction zone to the sulfate reduction zone, where dissolved Fe precipitates as Fe-sulfides. Saturation models of Fe-sulfides indicate some fractions of these Fe-sulfides get dissolved near the sediment-water interface, where bioirrigation exchanges oxic surface water. The estimated dissolved Fe flux is approximately 0.84 ??M Fe/day per meter of shoreline to lagoon surface waters. Accelerated sea level rise predictions are thus likely to increase the Fe flux to surface waters and local primary productivity, particularly along coastlines where groundwater discharges through sediments. ?? 2010 Elsevier Ltd.

Role of hydrous iron oxide formation in attenuation and diel cycling of dissolved trace metals in a stream affected by acid rock drainage

USGS Publications Warehouse

Parker, S.R.; Gammons, C.H.; Jones, Clain A.; Nimick, D.A.

2007-01-01

Mining-impacted streams have been shown to undergo diel (24-h) fluctuations in concentrations of major and trace elements. Fisher Creek in south-central Montana, USA receives acid rock drainage (ARD) from natural and mining-related sources. A previous diel field study found substantial changes in dissolved metal concentrations at three sites with differing pH regimes during a 24-h period in August 2002. The current work discusses follow-up field sampling of Fisher Creek as well as field and laboratory experiments that examine in greater detail the underlying processes involved in the observed diel concentration changes. The field experiments employed in-stream chambers that were either transparent or opaque to light, filled with stream water and sediment (cobbles coated with hydrous Fe and Al oxides), and placed in the stream to maintain the same temperature. Three sets of laboratory experiments were performed: (1) equilibration of a Cu(II) and Zn(II) containing solution with Fisher Creek stream sediment at pH 6.9 and different temperatures; (2) titration of Fisher Creek water from pH 3.1 to 7 under four different isothermal conditions; and (3) analysis of the effects of temperature on the interaction of an Fe(II) containing solution with Fisher Creek stream sediment under non-oxidizing conditions. Results of these studies are consistent with a model in which Cu, Fe(II), and to a lesser extent Zn, are adsorbed or co-precipitated with hydrous Fe and Al oxides as the pH of Fisher Creek increases from 5.3 to 7.0. The extent of metal attenuation is strongly temperature-dependent, being more pronounced in warm vs. cold water. Furthermore, the sorption/co-precipitation process is shown to be irreversible; once the Cu, Zn, and Fe(II) are removed from solution in warm water, a decrease in temperature does not release the metals back to the water column. ?? 2006 Springer Science+Business Media B.V.

Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater.

PubMed

Jeong, Sanghyun; Sathasivan, Arumugam; Kastl, George; Shim, Wang Geun; Vigneswaran, Saravanamuthu

2014-01-01

Coagulation removes colloidal matters and dissolved organic carbon (DOC) which can cause irreversible membrane fouling. However, how DOC is removed by coagulant is not well-known. Jar test was used to study the removal of hydrophobic and hydrophilic DOC fractions at various doses (0.5-8.0 mg-Fe(+3) L(-1)) of ferric chloride (FeCl3) and pH (5.0-9.0). Natural organic matter (NOM) in seawater and treated seawater were fractionated by liquid chromatography-organic carbon detector (LC-OCD). Compared to surface water, the removal of DOC in seawater by coagulation was remarkably different. Majority of DOC could be easily removed with very low coagulant dose (<5.0 mg-Fe(+3) L(-1)) and the removal efficiency did not vary with pH, but the DOC composition in treated water had significantly changed. Hydrophobic fraction (HB) was better removed at high pH while hydrophilic fraction (HF) was better removed at low pH. A modified model of Kastl et al. (2004) which assumed that the removal occurred by adsorption of un-dissociated compounds onto ferric hydroxide was formulated and successfully validated against the jar test data. Copyright © 2013 Elsevier Ltd. All rights reserved.

Enhancing Corrosion and Wear Resistance of AA6061 by Friction Stir Processing with Fe78Si9B13 Glass Particles

PubMed Central

Guo, Lingyu; Liu, Yan; Shen, Kechang; Song, Chaoqun; Yang, Min; Kim, Kibuem; Wang, Weimin

2015-01-01

The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix. The XRD results indicated that the lattice parameter of α-Al increases and the preferred orientation factors F of (200) plane of α-Al reduces after friction stir processing. The coefficient of thermal expansion (CTE) for FSP samples increases at first with the temperature but then decreases as the temperature further increased, which can be explained by the dissolving of Mg and Si from β phase and Fe78Si9B13 particles. The corrosion and wear resistance of FSP samples have been improved compared with that of base metal, which can be attributed to the reduction of grain size and the CTE mismatch between the base metal and reinforced particles by FSP, and the lubrication effect of Fe78Si9B13 particles also plays a role in improving wear resistance. In particular, the FSP sample with reinforced particles in amorphous state exhibited superior corrosion and wear resistance due to the unique metastable structure. PMID:28793492

Chemical characteristics of dissolved organic matter (DOM) in relation to heavy metal concentrations in soil water from boreal peatlands after clear-cut harvesting

NASA Astrophysics Data System (ADS)

Kiikkilä, O.; Nieminen, T.; Starr, M.; Ukonmaanaho, L.

2012-04-01

Boreal peatlands form an important terrestrial carbon reserve and are a major source of dissolved organic matter (DOM) to surface waters, particularly when disturbed through forestry practices such as draining or timber harvesting. Heavy metals show a strong affinity to organic matter and so, along with DOM, heavy metals can be mobilized and transported from the soil to surface waters and sediments where they may become toxic to aquatic organisms and pass up the food chain. The complexation of heavy metals with DOM can be expected to be related and determined by the chemical characteristics of DOM and oxidation/reducing conditions in the peat. We extracted interstitial water from peat samples and determined the concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and Al, Cu, Zn and Fe in various fractions of DOM isolated by adsorption properties (XAD-8 fractionation) and molecular-weight (ultrafiltration). The peat samples were taken from 0-30 and 30-50 cm depth in drained peatland catchments two years after whole-tree or stem-only clear-cut harvesting (Scots pine or Norway spruce) had been carried out. The samples from the upper layer had been subject to alternating saturation/aeration conditions while the deeper layer had been continuously under the water table. The fractionation of DOC and DON according to both adsorption properties and molecular-weight fractions clearly differed between the upper and lower peat layers. While the hydrophobic acid fraction contained proportionally more DOC and DON than the hydrophilic acid fraction in the upper peat layer the results were vice versa in the lower peat layer. High-molecular-weight compounds (> 100 kDa) were proportionally more abundant in the upper and low-molecular-weight compounds (< 1 kDa) in the lower peat layer. These differences are assumed to reflect differences in the aerobic/ anaerobic conditions and degree of decomposition between the two layers. The concentrations of Zn, Al, Fe and DON correlated positively with DOC concentrations whereas the concentration Cu did not correlate with DOC concentrations. Heavy metal concentrations in different molecular-weight fractions indicated that Al, Cu, Zn and Fe were mostly associated with high-molecular-weight compounds and only a small fraction existed as free metal ions in solution. There were no clear differences in the chemical characteristics of DOC or DON or heavy metal concentrations between the two harvesting treatments.

Decoupling of As and Fe release to Bangladesh groundwater under reducing conditions. Part I: Evidence from sediment profiles

NASA Astrophysics Data System (ADS)

Horneman, A.; van Geen, A.; Kent, D. V.; Mathe, P. E.; Zheng, Y.; Dhar, R. K.; O'Connell, S.; Hoque, M. A.; Aziz, Z.; Shamsudduha, M.; Seddique, A. A.; Ahmed, K. M.

2004-09-01

This study reexamines the notion that extensive As mobilization in anoxic groundwater of Bangladesh is intimately linked to the dissolution of Fe oxyhydroxides on the basis of analyses performed on a suite of freshly collected samples of aquifer material. Detailed sediment profiles extending to 40 to 70 m depth below the surface were obtained at six sites where local groundwater As concentrations were known to span a wide range. The sediment properties that were measured include (1) the proportion of Fe(II) in the Fe fraction leached in hot 1.2 N HCl, (2) diffuse spectral reflectance, and (3) magnetic susceptibility. In parallel with local concentrations of dissolved As ranging from <5 to 600 μg/L, Fe(II)/Fe ratios in shallow (gray) Holocene sands tended to gradually increase with depth from values of 0.3 to 0.5 to up to 0.9. In deeper (orange) aquifers of presumed Pleistocene age that were separated from shallow sands by a clay layer and contained <5 μg/L dissolved As, leachable Fe(II)/Fe ratios averaged ˜0.2. There was no consistent relation between sediment Fe(II)/Fe and dissolved Fe concentrations in groundwater in nearby wells. The reflectance measurements indicate a systematic linear relation (R 2 of 0.66; n = 151) between the first derivative transform of the reflectance at 520 nm and Fe(II)/Fe. The magnetic susceptibility of the shallow aquifer sands ranged from 200 to 3600 (x 10 -9 m 3/kg SI) and was linearly related (R 2 of 0.75; n = 29) to the concentrations of minerals that could be magnetically separated (0.03 to 0.79% dry weight). No systematic depth trends in magnetic susceptibility were observed within the shallow sands, although the susceptibility of deeper low-As aquifers was low (up to ˜200 × 10 -9 m 3/kg SI). This set of observations, complemented by incubation results described in a companion paper by van Geen et al. (this volume), suggests that the release of As is linked to the transformation of predominantly Fe (III) oxyhydroxide coatings on sand particles to Fe(II) or mixed Fe(II/III) solid phases with a flatter reflectance spectrum such as siderite, vivianite, or magnetite, without necessarily resulting in the release of Fe to groundwater. The very low As/Fe ratio of magnetically separated minerals compared to the As/Fe of bulk acid leachate (2 vs. 40 10 -6, respectively) suggests that such a transformation could be accompanied by a significant redistribution of As to a mobilizable phase on the surface of aquifer particles.

Iron Cycling in Marine Sediments - New Insights from Isotope Analysis on Sequentially Extracted Fe Fractions

NASA Astrophysics Data System (ADS)

Henkel, S.; Kasten, S.; Poulton, S.; Hartmann, J.; Staubwasser, M.

2014-12-01

Reactive Fe (oxyhydr)oxides preferentially undergo early diagenetic cycling and may cause a diffusive flux of dissolved Fe2+ from sediments towards the sediment-water interface. The partitioning of Fe in sediments has traditionally been studied by applying sequential extractions based on reductive dissolution of Fe minerals. We complemented the sequential leaching method by Poulton and Canfield [1] in order to be able to gain δ56Fe data for specific Fe fractions, as such data are potentially useful to study Fe cycling in marine environments. The specific mineral fractions are Fe-carbonates, ferrihydrite + lepidocrocite, goethite + hematite, and magnetite. Leaching was performed with acetic acid, hydroxylamine-HCl, Na-dithionite and oxalic acid. The processing of leachates for δ56Fe analysis involved boiling the samples in HCl/HNO3/H2O2, Fe precipitation and anion exchange column chromatography. The new method was applied to short sediment cores from the North Sea and a bay of King George Island (South Shetland Islands, Antarctica). Downcore mineral-specific variations in δ56Fe revealed differing contributions of Fe (oxyhydr)oxides to redox cycling. A slight decrease in easily reducible Fe oxides correlating with a slight increase in δ56Fe for this fraction with depth, which is in line with progessive dissimilatory iron reduction [2,3], is visible in the top 10 cm of the North Sea core, but not in the antarctic sediments. Less reactive (dithionite and oxalate leachable) fractions did not reveal isotopic trends. The acetic acid-soluble fraction displayed pronounced δ56Fe trends at both sites that cannot be explained by acid volatile sulfides that are also extracted by acetic acid [1]. We suggest that low δ56Fe values in this fraction relative to the pool of easily reducible Fe oxides result from adsorbed Fe(II) that was open to isotopic exchange with oxide surfaces, affirming the experimental results of Crosby el al. [2]. Hence, δ56Fe analyses on marine sediments appear to be particularly useful when targeting specific Fe pools, rather than the total highly reactive Fe fraction, since isotopic trends may be masked within the latter pool. [1] Poulton and Canfield (2005), Chemical Geology 214, 209-221. [2] Crosby et al., Geobiology 5 (2007), 169-189. [3] Staubwasser et al., Geology 34 (2006), 629-632.

Aquifer geochemistry at potential aquifer storage and recovery sites in coastal plain aquifers in the New York city area, USA

USGS Publications Warehouse

Brown, C.J.; Misut, P.E.

2010-01-01

The effects of injecting oxic water from the New York city (NYC) drinking-water supply and distribution system into a nearby anoxic coastal plain aquifer for later recovery during periods of water shortage (aquifer storage and recovery, or ASR) were simulated by a 3-dimensional, reactive-solute transport model. The Cretaceous aquifer system in the NYC area of New York and New Jersey, USA contains pyrite, goethite, locally occurring siderite, lignite, and locally varying amounts of dissolved Fe and salinity. Sediment from cores drilled on Staten Island and western Long Island had high extractable concentrations of Fe, Mn, and acid volatile sulfides (AVS) plus chromium-reducible sulfides (CRS) and low concentrations of As, Pb, Cd, Cr, Cu and U. Similarly, water samples from the Lloyd aquifer (Cretaceous) in western Long Island generally contained high concentrations of Fe and Mn and low concentrations of other trace elements such as As, Pb, Cd, Cr, Cu and U, all of which were below US Environmental Protection Agency (USEPA) and NY maximum contaminant levels (MCLs). In such aquifer settings, ASR operations can be complicated by the oxidative dissolution of pyrite, low pH, and high concentrations of dissolved Fe in extracted water.The simulated injection of buffered, oxic city water into a hypothetical ASR well increased the hydraulic head at the well, displaced the ambient groundwater, and formed a spheroid of injected water with lower concentrations of Fe, Mn and major ions in water surrounding the ASR well, than in ambient water. Both the dissolved O2 concentrations and the pH of water near the well generally increased in magnitude during the simulated 5-a injection phase. The resultant oxidation of Fe2+ and attendant precipitation of goethite during injection provided a substrate for sorption of dissolved Fe during the 8-a extraction phase. The baseline scenario with a low (0.001M) concentration of pyrite in aquifer sediments, indicated that nearly 190% more water with acceptably low concentrations of dissolved Fe could be extracted than was injected. Scenarios with larger amounts of pyrite in aquifer sediments generally resulted in less goethite precipitation, increased acidity, and increased concentrations of dissolved Fe in extracted water. In these pyritic scenarios, the lower amounts of goethite precipitated and the lower pH during the extraction phase resulted in decreased sorption of Fe2+ and a decreased amount of extractable water with acceptably low concentrations of dissolved Fe (5.4??10-6M). A linear decrease in recovery efficiency with respect to dissolved Fe concentrations is caused by pyrite dissolution and the associated depletion of dissolved O2 (DO) and increase in acidity. Simulations with more than 0.0037M of pyrite, which is the maximum amount dissolved in the baseline scenario, had just over a 50% recovery efficiency. The precipitation of ferric hydroxide minerals (goethite) at the well screen, and a possible associated decrease in specific capacity of the ASR well, was not apparent during the extraction phase of ASR simulations, but the model does not incorporate the microbial effects and biofouling associated with ferric hydroxide precipitation.The host groundwater chemistry in calcite-poor Cretaceous aquifers of the NYC area consists of low alkalinity and moderate to low pH. The dissolution of goethite in scenarios with unbuffered injectate indicates that corrosion of the well could occur if the injectate is not buffered. Simulations with buffered injectate resulted in greater precipitation of goethite, and lower concentrations of dissolved Fe, in the extracted water. Dissolved Fe concentrations in extracted water were highest in simulations of aquifers (1) in which pyrite and siderite in the aquifer were in equilibrium, and (2) in coastal areas affected by saltwater intrusion, where high dissolved-cation concentrations provide a greater exchange of Fe2+ (FeX2). Results indicate that ASR in pyrite-beari

The effect of oxygen on density of liquid iron at high pressure

NASA Astrophysics Data System (ADS)

Takubo, Y.; Terasaki, H.; Shimoyama, Y.; Urakawa, S.; Suzuki, A.; Nishida, K.; Kamuro, R.; Kishimoto, S.; Kondo, T.; Ohtani, E.; Yoshinori, K.

2012-12-01

The Earth's outer core has been thought to be composed of liquid iron alloys with 10 % of light elements, such as sulfur, carbon, silicon and oxygen. Density of liquid iron alloy is one of the key parameters to understand the composition and structure of the Earth's outer core. The effect of various light elements (e.g., S, Si, and C) on the density of liquid iron at high pressure and high temperature has been studied (Nishida et al., 2011; Tateyama et al., 2011 Sanloup et al., 2011; Terasaki et al., 2010). It was revealed that the density depression is quite different depending on dissolving light element. However the effect of oxygen on the density of liquid iron has not been investigated due to high liquidus temperature of Fe-O system, although oxygen is one of the major candidates of the light elements in the Earth's outer core (e.g., Ringwood, 1977). Oxygen could be incorporated into the core during early terrestrial evolution (Corgne et al., 2009). In this study, we have measured the density of liquid Fe-O in the pressure and temperature ranges of 2.3-3.0 GPa and 2000-2250 K using X-ray absorption method. High pressure experiment was performed using a cubic-type multi-anvil press installed at BL22XU of the SPring-8 synchrotron radiation facility in Japan. Monochromatic X-ray of 35 keV was used. Mixture of Fe and FeO powders with 0.5 wt% oxygen, which corresponds to the eutectic composition at 3 GPa (Ohtani et al., 1984) was used as a sample. The sample was inserted in a single crystal sapphire capsule. The obtained density of this study is 6.7 g/cm3 at 3 GPa and 2005 K. Compared to the density of pure liquid iron (Anderson and Ahrens, 1994) at the present experimental condition, the density of liquid Fe-O is about 5.3 % smaller than that of pure liquid iron. On the other hand, thermal expansion coefficient of liquid Fe-O shows similar value to that of liquid iron.

Evidence of degassing-induced oxidation of relatively oxidized K-rich magmas caused by degassing of dissolved SO­42- (S6+) component in the melt to SO2 (S4+) in the gas phase

NASA Astrophysics Data System (ADS)

Pu, X.; Lange, R. A.; Moore, G. M.

2016-12-01

Near Volcán Colima in the Mexican volcanic arc, nine cones erupted minette, leucite basanite and basanite. These K-rich lavas have high post-eruptive Fe3+/FeT ratios (≤0.63) and sulfur contents (≤ 1004 ppm) (Carmichael et al., 2006). Olivine-hosted melt inclusions record ≤ 6.2wt% H2O and ≤ 6700ppm sulfur (Vigouroux et al., 2008). Here, we test whether the post-eruptive Fe3+/FeT ratios, measured by titration on fresh lavas, reflect magmatic values or a change in oxidation state during degassing. To constrain pre-eruptive fO2 (ilmenite is absent), the most Mg-rich olivine analyzed in each sample, together with a Fe-Mg KD (olivine-melt) of 0.355 (from hydrous experiments of Righter and Carmichael (1996) on a minette and the Jayasuriya et al. (2004) model to relate melt Fe2+/Fe3+ ratio to melt temperature and fO2), were used to obtain the Fe3+/FeT ratio at the onset of olivine crystallization. The resulting Fe3+/FeT ratios (0.31-0.41) and ΔNNO values (1.2-2.4) for the nine K-rich magmas are systematically lower than the post-eruptive values, which suggests that degassing induced oxidation may have occurred. In addition, the pre-eruptive Fe3+/FeT ratios and ΔNNO values are higher than those (0.19-0.31 and -0.2 to +1.2, respectively) documented for calc-alkaline basalts from Michoacán-Guanajuato Volcanic Field (MGVF) using a similar method (Pu et al., 2016). Because a similar increase between pre- and post-eruptive Fe3+/FeT ratios is not found in the MGVF samples, we infer that the increase between the pre- and post-eruptive Fe3+/FeT ratios in the K-rich samples is caused by the relatively high solubility of sulfate (S6+ in CaSO4 component) in the relatively oxidized (ΔNNO ≤ 2.4) potassic melts, which then degassed as S4+ (SO2). We deduce that oxidation caused by degassing of sulfur can only occur in melts that were already relatively oxidized, because the degassing-induced oxidation process requires an initial high concentration of sulfate in the melt phase.

2015 Progress Report/July 2016: Iron Oxide Redox Transformation Pathways: The Bulk Electrical Conduction Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scherer, Michelle M.; Rosso, Kevin M.

Despite decades of research on the reactivity and stable isotope properties of Fe oxides, the ability to describe the redox behavior of Fe oxides in the environment is still quite limited. This is due, in large part, to the analytical and spatial complexities associated with studying microscopic processes at the Fe oxide-water interface. This project had the long-term vision of filling this gap by developing a detailed understanding of the relationship between interfacial ET processes, surface structure and charge, and mineral semiconducting properties. We focused on the Fe(III)-oxides and oxyhydroxides because of their geochemical preponderance, versatility in synthesis of compositionally,more » structurally, and morphologically tailored phases, and because they are amenable to a wide range of surface and bulk properties characterization. In particular, reductive transformation of phases such as hematite (α-Fe 2O 3) and goethite (α-FeOOH) in aqueous solution can serve as excellent model systems for studies of electron conduction processes, as well as provide valuable insights into effect of nanoscale conductive materials on contaminant fate at DOE sites. More specifically, the goal of the Iowa component of this project was to use stable Fe isotope measurements to simultaneously measure isotope specific oxidation states and concentrations of Fe at the hematite-water and goethite-water interface. This work builds on our previous work where we used an innovative combination of 57Fe Mössbauer spectroscopy and high precision isotope ratio measurements (MC-ICP-MS) to probe the dynamics of the reaction of aqueous Fe(II) with goethite. Mössbauer spectroscopy detects 57Fe only among all other Fe isotopes and we have capitalized on this to spectroscopically demonstrate Fe(II)-Fe(III) electron transfer between sorbed Fe(II) and Fe(III) oxides (Handler, et al., 2009; Gorski, et al. 2010; Rosso et al., 2010). By combining the Mössbauer spectroscopy and stable isotopes measurements, we have been able to simultaneously track the oxidation state and isotope concentration of the bulk Fe oxide and aqueous Fe. One of our most compelling findings is that despite the apparent stability of the Fe(II)-goethite system, there is actually a tremendous amount of Fe atom cycling occurring between the aqueous phase and the bulk goethite as indicated by the isotopic composition of both phases approaching the mass balance average (Handler et al., 2009). How such extensive re-crystallization and Fe atom exchange can occur with no significant morphological change is a fascinating question. Based on previous work from PI Rosso’s group showing that a potential gradient across hematite crystal faces leads to conduction through hematite and growth and dissolution at separate crystal faces we proposed that a redox-driven recrystallization could be occurring that would explain the extensive mixing observed with the isotope data. From our previous studies utilizing Mössbauer spectroscopy, we know that sorption of Fe(II) onto goethite results in electron transfer between the sorbed Fe(II) and the structural Fe(III) in goethite. Oxidation of the sorbed Fe(II) produces growth of goethite on goethite (i.e., homoepitaxy), as well as injection of an electron into goethite. It is possible that electron transfer from sorbed Fe(II) occurs across a potential gradient, and that Fe(II) atoms are dissolved at a different location on the goethite surface. These newly-reduced Fe(II) atoms could then dissolve into the aqueous phase, exposing fresh Fe(III) goethite to the aqueous phase. Through a repeated series of these five steps of sorption–electron transfer–crystal growth–conduction– dissolution, a redox-driven conveyor belt, could be established that would allow all of the goethite to be eventually exposed to the aqueous phase and exchanged. This surface-mediated recrystallization process would result in similar Fe isotope distributions in the aqueous phase and goethite particle, as we have observed here. It would also result in a stable aqueous Fe(II) concentration, if there were equal rates of goethite growth and dissolution.« less

Quantitative evaluation of the effect of H2O degassing on the oxidation state of magmas

NASA Astrophysics Data System (ADS)

Lange, R. A.; Waters, L.

2014-12-01

The extent to which degassing of the H2O component affects the oxidation state of hydrous magmas is widely debated. Several researchers have examined how degassing of mixed H-C-O-S-Cl fluids may change the Fe3+/FeT ratio of various magmas, whereas our focus is on the H2O component. There are two ways that degassing of H2O by itself may cause oxidation: (1) the reaction: H2O (melt) + 2FeO (melt) = H2 (fluid) + Fe2O3 (melt), and/or (2) if dissolved water preferentially enhances the activity of ferrous vs. ferric iron in magmatic liquids. In this study, a comparison is made between the pre-eruptive oxidation states of 14 crystal-poor, jet-black obsidian samples (obtained from two Fe-Ti oxides) and their post-eruptive values (analyzed with the Wilson 1960 titration method tested against USGS standards). The obsidians are from Medicine Lake (CA), Long Valley (CA), and the western Mexican arc; all have low FeOT (1.1-2.1 wt%), rendering their Fe2+/Fe3+ ratios highly sensitive to the possible effects of substantial H2O degassing. The Fe-Ti oxide thermometer/oxybarometer of Ghiorso and Evans, (2008) gave temperatures for the 14 samples that range for 720 to 940°C and ΔNNO values of -0.9 to +1.4. With temperature known, the plagioclase-liquid hygrometer was applied and show that ≤ 6.5 wt% H2O was dissolved in the melts prior to eruption. In addition, pre-eruptive Cl and S concentrations were constrained on the basis of apatite analyses (Webster et al., 2009) and sulfur concentrations needed for saturation with pyrrhotite (Clemente et al., 2004), respectively. Maximum pre-eruptive chlorine and sulfur contents are 6000 and 200 ppm, respectively. After eruption, the rhyolites lost nearly all of their volatiles. Our results indicate no detectable change between pre- and post-eruptive Fe2+ concentrations, with an average deviation of ± 0.1 wt % FeO. Although degassing of large concentrations of S and/or Cl may affect the oxidation state of magmas, at the pre-eruptive levels in these 14 rhyolitic magmas, no effect is detected. Therefore, it can be robustly concluded that degassing of substantial amounts of the H2O component (≤ 6.5 wt%), by itself, does not induce oxidation in erupted magmas, particularly those more iron-rich than rhyolites (e.g., arc basalts).

Acid Mine Drainage and Metal Sulfate Minerals in the Shasta Mining District, California

NASA Astrophysics Data System (ADS)

Livingston, J. D.; Murphy, W. M.; Miller, R. M.; Ayars, E. J.

2005-12-01

Metal sulfate minerals were collected at four surface water drainage sites during September and October of 2004 in the Shasta Mining District, southern Klamath Mountains, Shasta County, California and analyzed by X-ray fluorescence, atomic absorption spectroscopy, and X-ray diffraction to determine elements present, quantities of Fe, Cu, and Zn, and mineralogy. The Shasta Mining District produced major quantities of Cu, Zn, and pyrite (S) with minor amounts of Au, Ag, and Fe from massive sulfide bodies (Kinkel et al., 1956). Three study sites are located on Iron Mountain and one study site is at Bully Hill. Although mining occurred during a period of just over 100 years, it is estimated that acid mine drainage (AMD) will continue from Iron Mountain for over 3,200 years (Nordstrom and Alpers, 1998). AMD at the study sites produces blooms of metal sulfates during California's Mediterranean climate summer. The minerals readily dissolve in the "first flush" of seasonal rain creating runoff water of low pH with high amounts of dissolved metals (Bayless and Olyphant, 1993; Jambor et al., 2000). Data were examined for mineralogical changes in time and space and for zoning of minerals on a scale of centimeters. Sulfate mineral samples are complex with some samples composed of over a dozen different minerals. Site 1 is located on Spring Creek downstream from the Iron Mountain superfund remediation site, so levels of Fe, Cu, and Zn in the sulfates at this site are lower than at the other sites. Two site 1 samples from the same location taken a month apart show Ca, Fe, Cu, Sr, Y, and Sn, and the first sample also has detectable Br. The metal sulfates identified from the first visit are celestine, cesanite, chessexite, hectorfloresite, and ungemachite, and the mineralogy of the second visit is bilinite, epsomite, millosevichite, and anhydrite. The Fe bearing sulfate mineral during the first visit is ungemachite, but bilinite was the Fe bearing mineral at the time of the second visit. Analyses indicate a dynamic evolution of sulfate minerals at individual locations over time, mineralogical and chemical differences among individual locations at a site, and mineralogical zonations in individual samples.

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

NASA Astrophysics Data System (ADS)

Xiao, Jian; He, Xinhua; Hao, Jialong; Zhou, Ying; Zheng, Lirong; Ran, Wei; Shen, Qirong; Yu, Guanghui

2016-06-01

Mineral binding is a major mechanism for soil carbon (C) stabilization. However, the submicron information about the in situ mechanisms of different fertilization practices affecting organo-mineral complexes and associated C preservation remains unclear. Here, we applied nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS) to examine differentiating effects of inorganic versus organic fertilization on interactions between highly reactive minerals and soil C preservation. To examine such interactions, soils and their extracted colloids were collected during a 24-year long-term fertilization period (1990-2014) (no fertilization, control; chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization, NPK; and NPK plus swine manure fertilization, NPKM). The results for different fertilization conditions showed a ranked soil organic matter concentration with NPKM > NPK > control. Meanwhile, oxalate-extracted Al (Alo), Fe (Feo), short-range ordered Al (Alxps), Fe (Fexps), and dissolved organic carbon (DOC) ranked with NPKM > control > NPK, but the ratios of DOC / Alxps and DOC / Fexps ranked with NPKM > NPK > control. Compared with the NPK treatment, the NPKM treatment enhanced the C-binding loadings of Al and Fe minerals in soil colloids at the submicron scale. Furthermore, a greater concentration of highly reactive Al and Fe minerals was presented under NPKM than under NPK. Together, these submicron-scale findings suggest that both the reactive mineral species and their associations with C are differentially affected by 24-year long-term inorganic and organic fertilization.

Biogeochemical Activity of Siderophilic Cyanobacteria and Insights from their Genomes Implications for the Development of New Biosignatures

NASA Technical Reports Server (NTRS)

Brown, I. I.; Bryant, D. A.; Thomas,-Keprta, K. L.; Tringe, S. G.; Sarkisova, S. A.; Galindo, C., Jr.; Malley, K.; Sosa, O.; Garrison, D. H.; McKay, David S.

2010-01-01

Verifying the links between genomie features in living organisms and their mineralization/demineralization activity will help to reveal traces of life on Earth and beyond. Among contemporary environments, iron-depositing hot springs (IDHS) may represent one of the most appropriate natural models for insights into ancient life since organisms may have originated on Earth and possibly Mars in association with hydrothennal activity and high [Fe(2+)]. Siderophilic or "iron-loving" cyanobacteria (CB) inhabiting IDHS may have genomic features and properties similar to those of ancient organisms because abundant Fe(2+) in IDHS has a strong potential to increase the magnitude of oxidative stress. That is why specific and/or additional proteins involved in Fe mineralization by siderophilic CB are expected. Inorganic polyphosphates (PPi) are known to increase the viability of prokaryotes Linder heavy metal concentrations and UV stress conditions. PPi have also been proposed as biosignatures. Ancient CB could have also been stressed by occasional migrations from the Fe(2+) rich Ocean to the basaltic land which was almost devoid of dissolved Fe(2+). Thus, the study of the adaptation reactions of siderophilic CB to fluctuation of dissolved Fe level may shed light on the paleophysiology of ancient oxygenic prokaryotes. Moreover, bioweathered Fe, Al, P, Cu, Ti and rare earth elements can be thought of as candidate organomarkers that document the effects of or ganic molecules in weathered rocks. However, the molecular mechanisms of the maintenance of Fe homeostasis in siderophilic CB, the role of PPi for this process and bioweathering activities are poorly understood. Here we present preliminary results describing a new mechanism of Fe mineralization in siderophilic CB, the effect of Fe on the generation of PPi bodies in siderophilic CB, their bioweathering activity and preliminary analysis of the diversity of proteins involved in the prevention of oxidative stress in phototrophs inhabiting IDHS.

Effect of membrane filtration artifacts on dissolved trace element concentrations

USGS Publications Warehouse

Horowitz, Arthur J.; Elrick, Kent A.; Colberg, Mark R.

1992-01-01

Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one; only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

The effect of membrane filtration artifacts on dissolved trace element concentrations

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Colberg, M.R.

1992-01-01

Among environment scientists, the current and almost universally accepted definition of dissolved constituents is an operational one only those materials which pass through a 0.45-??m membrane filter are considered to be dissolved. Detailed laboratory and field studies on Fe and Al indicate that a number of factors associated with filtration, other than just pore size, can substantially alter 'dissolved' trace element concentrations; these include: filter type, filter diameter, filtration method, volume of sample processed, suspended sediment concentration, suspended sediment grain-size distribution, concentration of colloids and colloidally-associated trace elements and concentration of organic matter. As such, reported filtered-water concentrations employing the same pore size filter may not be equal. Filtration artifacts may lead to the production of chemical data that indicate seasonal or annual 'dissolved' chemical trends which do not reflect actual environmental conditions. Further, the development of worldwide averages for various dissolved chemical constituents, the quantification of geochemical cycles, and the determination of short- or long-term environmental chemical trends may be subject to substantial errors, due to filtration artifacts, when data from the same or multiple sources are combined. Finally, filtration effects could have a substantial impact on various regulatory requirements.

Fe-Impregnated Mineral Colloids for Peroxide Activation: Effects of Mineral Substrate and Fe Precursor.

PubMed

Li, Yue; Machala, Libor; Yan, Weile

2016-02-02

Heterogeneous iron species at the mineral/water interface are important catalysts for the generation of reactive oxygen species at circumneutral pH. One significant pathway leading to the formation of such species arises from deposition of dissolved iron onto mineral colloids due to changes in redox conditions. This study investigates the catalytic properties of Fe impregnated on silica, alumina, and titania nanoparticles (as prototypical mineral colloids). Fe impregnation was carried out by immersing the mineral nanoparticles in dilute Fe(II) or Fe(III) solutions at pH 6 and 3, respectively, in an aerobic environment. The uptake of iron per unit surface area follows the order of nTiO2 > nAl2O3 > nSiO2 for both types of Fe precursors. Impregnation of mineral particles in Fe(II) solutions results in predominantly Fe(III) species due to efficient surface-mediated oxidation. The catalytic activity of the impregnated solids to produce hydroxyl radical (·OH) from H2O2 decomposition was evaluated using benzoic acid as a probe compound under dark conditions. Invariably, the rates of benzoic acid oxidation with different Fe-laden particles increase with the surface density of Fe until a critical density above which the catalytic activity approaches a plateau, suggesting active Fe species are formed predominantly at low surface loadings. The critical surface density of Fe varies with the mineral substrate as well as the aqueous Fe precursor. Fe impregnated on TiO2 exhibits markedly higher activity than its Al2O3 and SiO2 counterparts. The speciation of interfacial Fe is analyzed with diffuse reflectance UV-vis analysis and interpretation of the data in the context of benzoic oxidation rates suggests that the surface activity of the solids for ·OH generation correlates strongly with the isolated (i.e., mononuclear) Fe species. Therefore, iron dispersed on mineral colloids is a significant form of reactive iron surfaces in the aquatic environment.

Synthesis of trevorite to capture Tc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsui, Colin

2011-09-02

Spinel containing technetium can be used to prevent Tc volatilization during vitrification of radioactive waste. Spinel dissolves in glass at elevated temperatures. This study focuses on the synthesis of spinel and the retention of rhenium, a nonradioactive surrogate for Tc in the crystals. To produce trevorite, a nickel-iron spinel (NiFe2O4), Fe and Ni nitrates were mixed with alkali nitrates along with Al(OH)3 and heated to 500 to 800°C. The trevorite content in samples (up to 40 mass%) was measured with x-ray diffraction. Viable samples were rerun with KReO4. Scanning electron microscopy-energy dispersive spectroscopy detected that Re became partly immobilized inmore » spinel-forming crystals.« less

Uranium chloride extraction of transuranium elements from LWR fuel

DOEpatents

Miller, W.E.; Ackerman, J.P.; Battles, J.E.; Johnson, T.R.; Pierce, R.D.

1992-08-25

A process of separating transuranium actinide values from uranium values present in spent nuclear oxide fuels containing rare earth and noble metal fission products as well as other fission products is disclosed. The oxide fuel is reduced with Ca metal in the presence of Ca chloride and a U-Fe alloy which is liquid at about 800 C to dissolve uranium metal and the noble metal fission product metals and transuranium actinide metals and rare earth fission product metals leaving Ca chloride having CaO and fission products of alkali metals and the alkali earth metals and iodine dissolved therein. The Ca chloride and CaO and the fission products contained therein are separated from the U-Fe alloy and the metal values dissolved therein. The U-Fe alloy having dissolved therein reduced metals from the spent nuclear fuel is contacted with a mixture of one or more alkali metal or alkaline earth metal halides selected from the class consisting of alkali metal or alkaline earth metal and Fe or U halide or a combination thereof to transfer transuranium actinide metals and rare earth metals to the halide salt leaving the uranium and some noble metal fission products in the U-Fe alloy and thereafter separating the halide salt and the transuranium metals dissolved therein from the U-Fe alloy and the metals dissolved therein. 1 figure.

Uranium chloride extraction of transuranium elements from LWR fuel

DOEpatents

Miller, William E.; Ackerman, John P.; Battles, James E.; Johnson, Terry R.; Pierce, R. Dean

1992-01-01

A process of separating transuranium actinide values from uranium values present in spent nuclear oxide fuels containing rare earth and noble metal fission products as well as other fission products is disclosed. The oxide fuel is reduced with Ca metal in the presence of Ca chloride and a U-Fe alloy which is liquid at about 800.degree. C. to dissolve uranium metal and the noble metal fission product metals and transuranium actinide metals and rare earth fission product metals leaving Ca chloride having CaO and fission products of alkali metals and the alkali earth metals and iodine dissolved therein. The Ca chloride and CaO and the fission products contained therein are separated from the U-Fe alloy and the metal values dissolved therein. The U-Fe alloy having dissolved therein reduced metals from the spent nuclear fuel is contacted with a mixture of one or more alkali metal or alkaline earth metal halides selected from the class consisting of alkali metal or alkaline earth metal and Fe or U halide or a combination thereof to transfer transuranium actinide metals and rare earth metals to the halide salt leaving the uranium and some noble metal fission products in the U-Fe alloy and thereafter separating the halide salt and the transuranium metals dissolved therein from the U-Fe alloy and the metals dissolved therein.

Corrosion behavior of oxide dispersion strengthened ferritic steels in supercritical water

NASA Astrophysics Data System (ADS)

Gao, Wenhua; Guo, Xianglong; Shen, Zhao; Zhang, Lefu

2017-04-01

The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer.

Atmospheric wet deposition of dissolved trace elements to Jiaozhou Bay, North China: Fluxes, sources and potential effects on aquatic environments.

PubMed

Xing, Jianwei; Song, Jinming; Yuan, Huamao; Wang, Qidong; Li, Xuegang; Li, Ning; Duan, Liqin; Qu, Baoxiao

2017-05-01

To analyze the fluxes, seasonal variations, sources and potential ecological effects of dissolved trace elements (TEs) in atmospheric wet deposition (AWD), one-year wet precipitation samples were collected and determined for nine TEs in Jiaozhou Bay (JZB) between June 2015 and May 2016. Both the volume-weighted mean (VWM) concentration and flux sequence for the measured TEs was Al > Mn > Zn > Fe > Pb > Se > Cr > Cd > Co. Al was the most abundant TE with a VWM concentration and wet flux of 33.8 μg L -1 and 29.2 mg m -2  yr -1 , which were 2 and 3 orders of magnitude higher than those of Co, respectively. The emission intensities of pollutants, rainfall amount and wind speed were the dominating factors influencing seasonal variations of TEs in AWD. Based on enrichment factors, correlation analysis and principal component analysis, most of the TEs in AWD were primarily originated from anthropogenic activities except for Al and Fe, which are typically derived from re-suspended soil dusts. Although the TE inputs by AWD were significantly lower than those by rivers, the TE inputs via short-term heavy rains would distinctly increase surface seawater TE concentrations and then pollute the marine environment of JZB. AWD would have both profound impacts on the biogeochemical cycles of TEs and dual ecological effects (nutrient and toxicity) on aquatic organisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Molecular fractionation of dissolved organic matter with metal salts.

PubMed

Riedel, Thomas; Biester, Harald; Dittmar, Thorsten

2012-04-17

Coagulation of dissolved organic matter (DOM) by hydrolyzing metals is an important environmental process with particular relevance, e.g., for the cycling of organic matter in metal-rich aquatic systems or the flocculation of organic matter in wastewater treatment plants. Often, a nonremovable fraction of DOM remains in solution even at low DOM/metal ratios. Because coagulation by metals results from interactions with functional groups, we hypothesize that noncoagulating fractions have a distinct molecular composition. To test the hypothesis, we analyzed peat-derived dissolved organic matter remaining in solution after mixing with salts of Ca, Al, and Fe using 15 T Electrospray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FT-ICR-MS). Addition of metals resulted in a net removal of DOM. Also a reduction of molecular diversity was observed, as the number of peaks from the ESI-FT-ICR-MS spectra decreased. At DOM/metal ratios of ∼9 Ca did not show any preference for distinct molecular fractions, while Fe and Al removed preferentially the most oxidized compounds (O/C ratio >0.4) of the peat leachate. Lowering DOM/metal ratios to ∼1 resulted in further removal of less oxidized as well as more aromatic compounds ("black carbon"). Molecular composition in the residual solution after coagulation was more saturated, less polar, and less oxidized compared to the original peat leachate and exhibited a surprising similarity with DOM of marine origin. By identifying more than 9200 molecular formulas we can show that structural properties (saturation and aromaticity) and oxygen content of individual DOM molecules play an important role in coagulation with metals. We conclude that polyvalent cations not only alter the net mobility but also the very molecular composition of DOM in aquatic environments.

Coating transformations in the early stages of hot-dip galvannealing of steel sheet

NASA Astrophysics Data System (ADS)

McDevitt, Erin Todd

The present, comprehensive study of the reactions occurring early in galvanneal processing under conditions typical of commercial production represents the first detailed investigation of the microstructural evolution of the coating in the early stages of galvannealing and the results shed new light on the course of the coating microstructural development. During hot dipping, an Fe2Al5 inhibition layer formed on the surface of the steel substrate in the first instants of immersion in Zn baths containing as low as 0.10 wt.% Al. When hot-dipping in a 0.14 wt.% Al, the as-dipped coating microstructure consisted of an Fe2Al 5 layer on the steel surface. That layer was covered by a layer of the Fe-Zn compound Gamma1, which was covered by the zeta phase or unalloyed Zn. Substrate chemistry did not affect coating microstructure development in the bath. Thermodynamic predictions of the precipitation behavior during the bath reactions agrees well with experimental observations. A mechanism for coating microstructure development in the Zn bath which is consistent with all the experimental results is proposed. From this information, the metallurgical variables which govern inhibition layer formation are discerned. The breakdown of the Fe2Al5 inhibition layer during galvannealing at 500°C occurred without the formation of outbursts. Instead, the grain boundary diffusion of Al into the steel substrate accounted for dissolution of the inhibition layer in the first second of galvannealing. A mechanism for inhibition layer breakdown is presented. P-additions affected only the rate at which the inhibition layer dissolved and did not affect the rate of Fe-Zn compound formation. P in the substrate blocked grain boundary diffusion of Al into the substrate thus slowing inhibition layer dissolution. The slower overall galvannealing behavior often observed on P-bearing substrates is due to a longer period of inhibition layer survival which results in a longer incubation period for the initiation of the formation of Fe-Zn compounds. The coating solidified after inhibition layer dissolution by the continuous formation of new delta grains from the liquid at the solidification front. The microstructural evolution of the entire coating, including the formation of Gamma and Gammal, during solidification is also presented.

Contrasting Effects of Carbon and Sulfur on Fe-Isotope Fractionation between Metal and Silicate Melt during Planetary Core Formation

NASA Astrophysics Data System (ADS)

Elardo, S. M.; Shahar, A.

2015-12-01

There are numerous studies that show well-resolved Fe isotope fractionations in igneous materials from different planetary bodies. Potential explanations for these fractionations include a non-chondritic bulk planetary Fe isotopic composition, and equilibrium fractionation between Fe-alloys or minerals and silicate melts during planetary differentiation, mantle melting, or fractional crystallization. This is further complicated by the fact that these processes are not mutually exclusive, making the interpretation of Fe isotope data a complex task. Here we present new experimental results investigating the effect of C on Fe isotope fractionation between molten peridotite and an Fe-alloy. Experiments were conducted at 1 GPa and 1850° C for 0.5 - 3 hours on a mixture of an 54Fe-spiked peridotite and Fe-metal with and without Ni metal in an end-loaded piston cylinder at the Geophysical Laboratory. Carbon saturation was achieved with a graphite capsule, and resulted in C contents of the Fe-alloy in our experiments ranging from 3.8 - 4.9 wt. %. The metal and silicate phases from half of each experiment were separated manually and dissolved in concentrated acids. Iron was separated from matrix elements by anion exchange chromatagraphy. Iron-isotopic compositions were determined with the Nu Plasma II MC-ICP-MS at GL. The other half of each experiment was used for quantitative microbeam analysis. Equilibrium was assessed with a time series and the three-isotope exchange method. The Ni-free experiments resulted in no resolvable Fe isotope fractionation between the Fe-C-alloy and molten silicate. This is in contrast to the results of Shahar et al. (2015) which showed a fractionation for Δ57Fe of ~0.18 ‰ between a peridotite and an Fe-alloy with a similar S abundance to C in these experiments. The one experiment thus far that contained Ni (~4 wt. % in the alloy) showed a resolvable fractionation between the Fe-Ni-C alloy and silicate of ~0.10 ‰. Shahar et al. found a similar magnitude fractionation to our Ni bearing experiment in experiments with no C or S. The difference in temperature (1650° C in Shahar et al. vs. 1850° C here) may be partially responsible for these discrepancies. Ongoing experiments will further investigate the effects of C and other light elements on Fe isotope fractionation during core segregation.

Distribution of dissolved and labile particulate trace metals in the overlying bottom water in the Vistula River plume (southern Baltic Sea).

PubMed

Sokolowski, A; Wolowicz, M; Hummel, H

2001-10-01

Overlying bottom water samples were collected in the Vistula River plume, southern Baltic Sea, (Poland) and analysed for dissolved and labile particulate (1 M HCl extractable) Cu, Pb, Zn, Mn, Fe and Ni, hydrological parameters being measured simultaneously. Particulate organic matter (POM), chlorophyll a and dissolved oxygen are key factors governing the chemical behaviour of the measured metal fractions. For the dissolved Cu, Pb, Zn, Fe and Ni two maxima, in the shallow and in the deeper part of the river plume, were found. In the shallow zone desorption from seaward fluxing metal-rich riverine particles account for markedly increased metal concentrations, as confirmed also by high particulate metal contents. For Pb, atmospheric inputs were also considered to have contributed to the elevated concentrations of dissolved Pb adjacent to the river mouth. In the deep zone desorption from detrital and/or resuspended particles by aerobic decomposition of organic material may be the main mechanism responsible for enrichment of particle-reactive metals (Cu, Pb, Zn) in the overyling bottom waters. The increased concentrations of dissolved Fe may have been due to reductive dissolution of Fe oxyhydroxides within the deep sediments by which dissolved Ni was released to the water. The distribution of Mn was related to dissolved oxygen concentrations, indicating that Mn is released to the water column under oxygen reduced conditions. However, Mn transfer to the dissolved phase from anoxic sediments in deeper part of the Vistula plume was hardly evidenced suggesting that benthic flux of Mn occurs under more severe reductive regime than is consistent with mobilization of Fe. Behaviour of Mn in a shallower part has been presumably affected by release from porewaters and by oxidization into less soluble species resulting in seasonal removal of this metal (e.g. in April) from the dissolved phase. The particulate fractions represented from about 6% (Ni) and 33% (Mn, Zn, Cu) to 80% (Fe) and 89% (Pb) of the total (labile particulate plus dissolved) concentrations. The affinity of the metals for particulate matter decreased in the following order: Pb > Fe > Zn > or = > Cu > Mn > Ni. Significant relationships between particulate Pb-Zn-Cu reflected the affinity of these metals for organic matter, and the significant relationship between Ni-Fe reflected the adsorption of Ni onto Fe-Mn oxyhydroxides. A comparison of metal concentrations with data from other similar areas revealed that the river plume is somewhat contaminated with Cu, Pb and Zn which is in agreement with previous findings on anthropogenic origin of these metals in the Polish zone of southern Baltic Sea.

Solubility of reduced C-O-H volatiles in basalt as a function of fCO: Implications for the early Earth, the moon, and Mars

NASA Astrophysics Data System (ADS)

Armstrong, L. S.; Hirschmann, M. M.

2013-12-01

Magmatic C-O-H volatiles influence the evolution of planetary atmospheres and, when precipitated and stored in solidified mantles, the dynamical evolution of planetary interiors. In the case of the Earth, the fO2 of the mantle near the end of core formation should have been ~IW-2, and subsequently increased to present-day values [1]. In experiments with fO2 ≤ IW, a variety of reduced volatile species have been found dissolved in magmas, including H2, CH4, CO, Fe(CO)5 and possibly Fe(CO)62+. However, there remains significant disagreement regarding the identity and concentrations of these volatiles in natural magmas, as well as their dependencies on intensive variables (T, P, fO2, fCO, fH2)[2-6]. Previous experiments document the importance of CO-related species [2,6], but were conducted over a limited range of fCO and had potentially interfering effects from poorly controlled variations in H2O. We aim to experimentally determine the solubility of C-O-H volatiles in basaltic magmas under reduced, C-saturated conditions while minimizing water content. The relationship between volatile speciation, fO2, and fCO at 1.2 GPa and 1400°C are constrained, laying the groundwork for a more extensive study at a range of conditions relevant to the interiors of the terrestrial planets and the moon. Both MORB and a martian basalt were studied, contained in Pt-C capsules with Fe × Pt × Si metal added to generate reducing conditions and to monitor fO2. A nominal amount of H2O is unavoidable in experimental charges, but was minimized by drying capsules prior to welding. Phase compositions were determined by electron microprobe and volatile concentrations were measured by FTIR spectroscopy. In preliminary experiments with fO2 of IW-0.70 to +1.75 (corresponding to log fCO of 3.3-4.5), H2O and CO2 concentrations as determined by FTIR are 113-13283 and 12-721 ppm, respectively. Most experiments also display a small FTIR peak at 2205 cm-1, whereas the most reduced experiments lack this peak but have peaks at 3370 and/or 1615 cm-1. The 2205 cm-1 peak was previously observed in similar experiments [6], and attributed to a C=O bond, possibly in the Fe-carbonyl Fe(CO)62+ [7]. The normalized intensity of the 2205 cm-1 peak is zero at IW -0.70 and increases with greater fO2 and fCO. This suggests that over a small fO2 and fCO range with the CCO buffer as an upper limit, CO-bearing species account for a portion of the dissolved C in reduced, graphite-saturated magmas. These volatiles could play an important role in martian magmatism, in the early Earth's mantle post-core formation, and in more oxidized regions of the lunar mantle. However, the fO2 during terrestrial core formation would have been too low for CO2 or the CO-bearing species to dissolve in a magma ocean. Ongoing work will extend the study to more reducing conditions and determine total C and H2O concentrations by SIMS. References: [1] Frost et al. (2008) Phil. Trans. R. Soc. A 366, 4315-4337. [2] Wetzel D. et al. (2013) PNAS, doi:10.1073/pnas.1219266110. [3] Dasgupta et al. (2013) GCA 102, 191-212. [4] Hirschmann et al. (2012) EPSL 345, 38-48. [5] Ardia et al. (2013) GCA 114, 52-71. [6] Stanley et al. (in review), GCA. [7] Bley et al. (1997) Inorg. Chem. 36, 158-160.

Prediction of the thermodynamic properties of metal-arsenate and metal-arsenite aqueous complexes to high temperatures and pressures and some geological consequences

NASA Astrophysics Data System (ADS)

Marini, Luigi; Accornero, Marina

2007-07-01

The standard thermodynamic properties at 25°C, 1 bar (Δ G {f/o}, Δ H {f/o}, S o, C {P/o}, V o, ω) and the coefficients of the revised Helgeson-Kirkham-Flowers equations of state were evaluated for several aqueous complexes formed by dissolved metals and either arsenate or arsenite ions. The guidelines of Shock and Helgeson (Geochim Cosmochim Acta 52:2009-2036, 1988) and Sverjensky et al. (Geochim Cosmochim Acta 61:1359-1412, 1997) were followed and corroborated with alternative approaches, whenever possible. The SUPCRT92 computer code was used to generate the log K of the destruction reactions of these metal-arsenate and metal-arsenite aqueous complexes at pressures and temperatures required by the EQ3/6 software package, version 7.2b. Apart from the AlAsO{4/o} and FeAsO{4/o} complexes, our log K at 25°C, 1 bar are in fair agreement with those of Whiting (MS Thesis, Colorado School of Mines, Golden, CO, 1992). Moreover, the equilibrium constants evaluated in this study are in good to fair agreement with those determined experimentally for the Ca-dihydroarsenate and Ca-hydroarsenate complexes at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) and for Fe(III)-hydroarsenate complex at 25°C (Raposo et al., J Sol Chem 35:79-94, 2006), whereas the disagreement with the log K measured for the Ca-arsenate complex at 40°C (Mironov et al., Russ J Inorg Chem 40:1690, 1995) might be due to uncertainties in this measured value. The implications of aqueous complexing between dissolved metals and arsenate/arsenite ions were investigated for seawater, high-temperature geothermal liquids and acid mine drainage and aqueous solutions deriving from mixing of acid mine waters and surface waters.

Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hein, James R.; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe J.; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah R.; Till, Claire P.

2017-11-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, and HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits. The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ˜15 Myr ago.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

USGS Publications Warehouse

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

Reactive Iron Delivery to the Central Gulf of Alaska via Two Mesoscale Eddies (Invited)

NASA Astrophysics Data System (ADS)

Lippiatt, S. M.; Brown, M. T.; Lohan, M. C.; Bruland, K. W.

2010-12-01

Coastal waters in the northern Gulf of Alaska (GoA) are considered Fe-rich and nitrate-poor, in contrast to the Fe-poor, high-nitrate, low chlorophyll (HNLC) waters of the central GoA. Mixing between these two regimes can lead to enhanced primary productivity. Mesoscale anticyclonic eddies are an important mechanism for cross-shelf exchange of coastal and HNLC waters. This presentation will discuss findings from a cruise in the GoA during late summer 2007, namely dissolved Fe, leachable particulate Fe (defined as the portion of the particulate Fe that is solubilized with a two hour, 25% acetic acid leach with a short heating step and a reducing agent), and nitrate. Leachable particulate Fe concentrations in coastal surface waters between Yakutat, AK and the Kenai Peninsula ranged from over 1 uM in the Alsek River plume to less than 5 nM at the base of Cook Inlet, and were more variable and at least an order of magnitude higher than dissolved Fe concentrations. Relatively low and consistent dissolved Fe (~2 nM) suggests that the system’s ability to solubilize this large concentration of leachable particulate Fe is overwhelmed by the massive input of glacial-derived particulate Fe. Suspended leachable particulate Fe is available for exchange to the dissolved phase and is suggested to maintain a relatively constant 2 nM concentration of dissolved Fe in the coastal GoA. Glacial meltwaters were not a significant source of nitrate compared to central GoA HNLC or upwelled waters. The work completed in the coastal GoA set the stage for assessing the delivery of this glacial-derived coastal Fe to HNLC waters via mesoscale eddies. Two mesoscale eddies were sampled during this study: a Sitka eddy located off Yakutat, Alaska and a Kenai eddy sampled off the shelf break near Kodiak Island. The temperature and salinity structures of the eddies reflected their coastal origin; core waters were warmer and fresher than surrounding basin waters, coincident with elevated dissolved and leachable particulate Fe. In the core of the Yakutat eddy at 50 - 100 m depth there was on average 0.8 nM reactive Fe (dissolved + leachable particulate Fe), approximately five times more reactive Fe compared to adjacent GoA basin waters (0.16 nM). At the same depths in the core of the Kenai eddy there was on average 1.9 nM reactive Fe, ten times more reactive Fe than the basin waters (0.19 nM). In addition, for a given density, core waters had elevated nitrate and silicate compared to outside the eddy. Storms can mix Fe-enriched eddy core waters to the surface. Furthermore, anticyclonic GoA eddies can be a significant source of Fe to HNLC waters when they propagate into the central GoA and eventually relax with the Fe and nutrient rich subsurface waters rebounding or upwelling towards the surface. The transport of coastal waters into central GoA waters via mesoscale eddies is shown to be an important mechanism for Fe delivery into this HNLC region.

Attenuation and colloidal mobilization of bacteriophages in natural sediments under anoxic as compared to oxic conditions.

PubMed

Klitzke, Sondra; Schroeder, Jendrik; Selinka, Hans-Christoph; Szewzyk, Regine; Chorus, Ingrid

2015-06-15

Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge conditions. Under anoxic conditions, attenuation of bacteriophages was dominated by sorption over inactivation, with MS2 showing a higher degree of sorption than PhiX174. Inactivation in water was low under anoxic conditions for both bacteriophages with about one log10 decrease in concentration during 16 h. Increased Fe/Al concentrations and a low organic carbon content of the sediment led to enhanced bacteriophage removal under anoxic conditions. However, even in the presence of sufficient Fe/A-(hydr)oxides on the solid phase, bacteriophage sorption was low. We presume that organic matter may limit the potential retention of sesquioxides in anoxic sediments and should thus be considered for the risk assessment of virus breakthrough in the subsurface. Copyright © 2015 Elsevier B.V. All rights reserved.

Reconstructing the Mineralogy and Bioavailability of Dust-Borne Iron Deposited to the Southern Ocean through the Last Glacial Cycle

NASA Astrophysics Data System (ADS)

Shoenfelt, E. M.; Winckler, G.; Lamy, F.; Bostick, B. C.

2017-12-01

The iron (Fe) in dust deposited to the Fe-limited Southern Ocean plays an important role in ocean biogeochemistry and global climate. For instance, increases in dust-borne Fe deposition in the subantarctic Southern Ocean have been linked to increases in productivity and part of the CO2 drawdown of the last glacial cycle [1]. Notably, bioavailable Fe impacts productivity rather than total Fe. While it has long been understood that Fe mineralogy impacts Fe bioavailability in general, our understanding of the mineralogy of Fe in dust in specific is limited to that in modern dust sources. Reduced mineral Fe in dust has been shown to be more bioavailable than oxidized mineral iron, as it is more readily dissolved [2], and it is more easily utilized directly by a model diatom [3]. Our previous work focusing on South American dust sources shows that glacial activity is associated with higher Fe(II) fractions in dust-borne minerals, due to the physical weathering of Fe(II)-rich silicates in bedrock [3]. Thus, we hypothesize that there were higher Fe(II) fractions in dust deposited during cold glacial periods where ice sheets were more widespread. Using synchrotron-based X-ray absorption spectroscopy, we have reconstructed the mineralogy of Fe deposited to Southern Ocean sediment cores from the subantarctic South Atlantic (TN057-6/ODP Site 1090) and South Pacific (PS7/56-1) through the last glacial cycle, creating the first paleorecord of Fe mineralogy and its associated bioavailability. During cold glacial periods there is a higher fraction of reduced Fe - in the form of Fe(II) silicates - deposited to the sediments compared to warm interglacial periods. Thus, Fe(II) content is directly correlated with dust input. The presence of Fe(II) silicates rather than products of diagenesis such as pyrite suggests that these Fe(II) minerals are physically weathered from bedrock and preserved rather than produced in the sediment. This result suggests that not only was there more dust and Fe deposited to the Southern Ocean during glacial periods, glacial Fe was also more bioavailable due to the importance of glacial activity to high latitude dust formation. [1] A. Martinez-Garcia et al., Science 343 (2014). [2] A. W. Schroth et al., Nat. Geosci. 2 (2009). [3] E. M. Shoenfelt et al., Sci. Adv. 3(6), DOI:10.1126/sciadv.1700314 (2017).

Benzyl and Methyl Fatty Hydroxamic Acids Based on Palm Kernel Oil as Chelating Agent for Liquid-Liquid Iron(III) Extraction

PubMed Central

Haron, Md Jelas; Jahangirian, Hossein; Silong, Sidik; Yusof, Nor Azah; Kassim, Anuar; Rafiee-Moghaddam, Roshanak; Mahdavi, Behnam; Peyda, Mazyar; Abdollahi, Yadollah; Amin, Jamileh

2012-01-01

Liquid-liquid iron(III) extraction was investigated using benzyl fatty hydroxamic acids (BFHAs) and methyl fatty hydroxamic acids (MFHAs) as chelating agents through the formation of iron(III) methyl fatty hydroxamate (Fe-MFHs) or iron(III) benzyl fatty hydroxamate (Fe-BFHs) in the organic phase. The results obtained under optimized conditions, showed that the chelating agents in hexane extract iron(III) at pH 1.9 were realized effectively with a high percentage of extraction (97.2% and 98.1% for MFHAs and BFHAs, respectively). The presence of a large amount of Mg(II), Ni(II), Al(III), Mn(II) and Co(II) ions did affect the iron(III) extraction. Finally stripping studies for recovering iron(III) from organic phase (Fe-MFHs or Fe-BFHs dissolved in hexane) were carried out at various concentrations of HCl, HNO3 and H2SO4. The results showed that the desired acid for recovery of iron(III) was 5 M HCl and quantitative recovery of iron(III) was achieved from Fe(III)-MFHs and Fe(III)-BFHs solutions in hexane containing 5 mg/L of Fe(III). PMID:22408444

Secondary mineral formation associated with respiration of nontronite, NAu-1 by iron reducing bacteria

PubMed Central

O'Reilly, S Erin; Watkins, Janet; Furukawa, Yoko

2005-01-01

Experimental batch and miscible-flow cultures were studied in order to determine the mechanistic pathways of microbial Fe(III) respiration in ferruginous smectite clay, NAu-1. The primary purpose was to resolve if alteration of smectite and release of Fe precedes microbial respiration. Alteration of NAu-1, represented by the morphological and mineralogical changes, occurred regardless of the extent of microbial Fe(III) reduction in all of our experimental systems, including those that contained heat-killed bacteria and those in which O2, rather than Fe(III), was the primary terminal electron acceptor. The solid alteration products observed under transmission electron microscopy included poorly crystalline smectite with diffuse electron diffraction signals, discrete grains of Fe-free amorphous aluminosilicate with increased Al/Si ratio, Fe-rich grains, and amorphous Si globules in the immediate vicinity of bacterial cells and extracellular polymeric substances. In reducing systems, Fe was also found as siderite. The small amount of Fe partitioned to the aqueous phase was primarily in the form of dissolved Fe(III) species even in the systems in which Fe(III) was the primary terminal electron acceptor for microbial respiration. From these observations, we conclude that microbial respiration of Fe(III) in our laboratory systems proceeded through the following: (1) alteration of NAu-1 and concurrent release of Fe(III) from the octahedral sheets of NAu-1; and (2) subsequent microbial respiration of Fe(III).

Spatiotemporal evaluation of the groundwater quality in Gharbiya Governorate, Egypt.

PubMed

Masoud, Alaa A; El Bouraie, Mohamed M; El-Nashar, Wafaa; Mashaly, Hamdy

2017-03-01

Groundwater quality indicators were monitored over 6 years (2007-2012) from 55 drinking water supply wells in Gharbiya Governorate (Egypt). The prime objective was to characterize, for the first time, the governorate-wide significant and sustained trends in the concentrations of the groundwater pollutants. Quality indicators included turbidity, pH, total dissolved solid (TDS), electric conductivity (EC), Cl - , SO 4 2- , Na + , total alkalinity, hardness (total, Mg, and Ca), Fe 2+ , Mn 2+ , Cu 2+ , Zn 2+ , F - , NH 4 + , NO 2 - , NO 3 - , PO 4 3- , dissolved oxygen (DO), and SiO 2 contents. Detection and estimation of trends and magnitude were carried out applying the non-parametric Mann-Kendall and Thiel-Sen trend statistical tests, respectively. Factor analysis was applied to identify significant sources of quality variation and their loads. Violation of groundwater quality standards clarified emergence of Mn 2+ (46%), Fe 2+ (35%), and NH 4 + (33%). Out of the 55 wells, notable upward trends (deterioration) were significant (>95% level) for TDS (89%), NO 3 - (85), PO 4 3- (75%), NH 4 + (65%), total alkalinity (62%), Fe 2+ (58%), NO 2 - (47%), Mg hardness (36%), turbidity (25%), and Mn 2+ (24%). Ranges of attenuation rates (mg/l/year) varied for TDS (24.3, -0.7), Mg hardness (3.8, -0.85), total alkalinity (1.4, -1.2), NO 3 - (0.52, -0.066), PO 4 3- (0.069, -0.064), NH 4 + (0.038, -0.019), Mn 2+ (0.015, -0.044), Fe 2+ (0.006, -0.014), and NO 2 - (0.006, -0.00003). Highest rates marked Tanta (total alkalinity and Fe 2+ ), Al-Mehala Al-Kubra (TDS, Mg hardness, and NO 3 - ), Kafr Al-Zayat (NH 4 + ), Zifta (Mn 2+ ), Bassyun (NO 2 - ), and Qutur (PO 4 3- ). Precision of the trend estimate varied in goodness of fit, for TDS (86%), Mg hardness (76%), total alkalinity (73%), PO 4 3- (67.4%), NH 4 + (66.8%), Mn 2+ (55%), and Fe 2+ (49.6%), arranged in decreasing order. Two main varimax-rotated factors counted for more than 55% of the quality variance and, in particular, significant loads of salinity (TDS, EC, Cl - , Na + , and SO 4 2- ), followed by the alkalinity, hardness, redox potentials (Mn 2+ and Fe 2+ ), and NH 4 + , in decreasing order were identified. The spatial-temporal variation in pollutants originated from organic matter degradation, either naturally from the aquifer peaty sediments or anthropogenic due to improper well head protection in the urban centers or from the agricultural drains in low relief areas. Considering the latest contents of indicators and their rate of increase, the time that the permissible limits would be reached can be accurately estimated and alleviative actions could be effectively set.

Insights into iron sources and pathways in the Amazon River provided by isotopic and spectroscopic studies

NASA Astrophysics Data System (ADS)

Mulholland, Daniel Santos; Poitrasson, Franck; Boaventura, Geraldo Resende; Allard, Thierry; Vieira, Lucieth Cruz; Santos, Roberto Ventura; Mancini, Luiz; Seyler, Patrick

2015-02-01

The present study investigated the weathering and transport mechanisms of Fe in the Amazon River. A particular emphasis was placed on Fe partitioning, speciation, and isotopic fractionation in the contrasting waters of the Solimões and Negro rivers and their mixing zone at the beginning of the Amazon River. Samples collected in the end-member rivers and thirteen sites distributed throughout the mixing zone were processed through frontal vacuum filtration and tangential-flow ultrafiltration to separate the different suspended solid fractions, i.e., particulate (P > 0.45 μm and P > 0.22 μm), colloidal (0.22 μm > C > 5 kDa) and truly dissolved elements (TD < 5 kDa). The Fe isotopic composition and electron paramagnetic resonance (EPR) species were measured on these different pore-sized fractions. The acidic and organo-Fe-rich waters of the Negro River displayed dissolved and colloidal fractions enriched in heavy isotopes (∼1.2‰, in δ57Fe values relative to IRMM-14), while the particulate fractions yielded light isotopic compositions of -0.344‰ for P > 0.22 μm and -0.104‰ for P > 0.45 μm fractions). The mineral particulate-rich waters of the Solimões River had dissolved and colloidal fractions with light isotopic composition (-0.532‰ and -0.176‰, respectively), whereas the particulate fractions yielded δ57Fe values close to those of the continental crust (i.e., -0.029‰ for P > 0.22 μm and 0.028‰ for P > 0.45 μm). Ten kilometers downstream from the Negro and Solimões junction, the concentrations of colloidal and dissolved Fe species deviate markedly from conservative mixing. A maximum Fe loss of 43 μg/L (i.e., 50% of the dissolved and colloidal Fe) is observed 110 km downstream from the rivers junction. The contrasting Negro and Solimões Rivers isotopic compositions along the pore-sized water fractions is attributable to the biogeochemical processes involving different types of upland soils and parental materials. For instance, the isotopic composition of colloidal and dissolved Fe from the Negro River are consistent with Fe oxidation and complexation mechanisms at the interface between waterlogged podzols and river networks, as supported by strong organo-Fe complexes signals observed by EPR. Conversely, the particulate and colloidal fractions from the Solimões River have δ57Fe consistent with strong mechanical erosion in the Andean Cordillera and upland soils, as evidenced by high concentrations of Fe3+-oxides sensu lato measured by EPR. The massive dissolved and colloidal Fe removal is associated with the evolution of the physical and chemical composition of the waters (i.e., ionic strength) during mixing, which influences organo-Fe3+ and Fe3+-oxyhydroxides stability. Several models are discussed to explain Fe non-conservative behavior, including dissociation of organo-Fe complexes and the subsequent formation of solid Fe3+-oxyhydroxides and semiquinone free radicals, as evidenced by EPR spectra demonstrating that organo-Fe signals decrease as Fe3+-oxyhydroxides and free radicals signals increase. As in estuarine regions, the mechanisms involving Fe transfer and loss in the mixing zone has a negligible effect on the bulk water Fe isotopic composition. This result suggests that a tropical basin similar to the Amazon River Basin delivers to the ocean waters with an Fe isotopic composition similar to that of the Earth's continental crust.

Characteristics of water obtained by dewatering cyanobacteria-containing sludge formed during drinking water treatment, including C-, N-disinfection byproduct formation.

PubMed

Xu, Hangzhou; Pei, Haiyan; Jin, Yan; Xiao, Hongdi; Ma, Chunxia; Sun, Jiongming; Li, Hongmin

2017-03-15

This is the first study to systematically investigate the characteristics of the water obtained by dewatering cyanobacteria-containing sludge generated in the drinking water treatment plant, including formation of C- and N-disinfection by-products (DBPs). Results showed that this 'dewatering water' (DW) had different properties when the sludge was stored at different times. The content of dissolved organic matter (DOM) and microcystins (MCs) in the DW were low when the sludge was treated or disposed of within 4 days; correspondingly, the C-, N-DBP production was also low. However, due to the damage of algal cells to some extent, the DOM and MC levels increased significantly for storage time longer than 4 days; the production of C-, N-DBPs also increased. There were also obvious differences in the characteristics of the DW from sludges generated with different coagulant species. Due to the better protective effect of FeCl 3 and polymeric aluminium ferric chloride (PAFC) flocs, the DOM and MC levels and the production of C-, N-DBPs in the DW with FeCl 3 and PAFC coagulation were lower than those with AlCl 3 coagulation, even though the sludges were stored for the same amount of time. Furthermore, because of the formation of Al and Fe hydroxides, precipitated onto the surface of flocs, the soluble Al and Fe in the DW decreased with increased storage time, especially in the first four days. Overall, this study revealed the trends in variation of DW quality for cyanobacteria-containing sludges formed with different coagulants, then FeCl 3 and PAFC coagulants are recommended and sludge should be treated or disposed of within 4 days. Copyright © 2017 Elsevier Ltd. All rights reserved.

Response of Phytoplankton Iron Contents to Gradients in Iron Availability in the California Current System

NASA Astrophysics Data System (ADS)

Twining, B. S.; Jacquot, J. E.; Rauschenberg, S.; Enright, J.; Marchetti, A.; Cohen, N.; Brown, M.; Parker, C.; Bruland, K. W.

2016-02-01

Iron is a critical micronutrient that controls primary production in large swaths of the global ocean. Experiments with laboratory cultures indicate that phytoplankton differ in their ability to compete for and store Fe in response to varying ambient Fe concentrations. However there are very few measurements of the physiological responses of natural phytoplankton populations to gradients in Fe availability. Incubation experiments were conducted off the coast of California and Oregon at two sites characterized by a 10-fold difference in dissolved Fe (0.3 and 3 nM). In each experiment, incubation water was amended with either dissolved Fe (5-10 nM), the model siderophore desferrioxamine B (DFB; 200 nM), or left unamended. Iron contents of three abundant diatom groups (Chaetoceros sp. and large and small pennate diatoms) were monitored by synchrotron X-ray fluorescence, along with dissolved and bulk particulate trace metals and macronutrients over the course of 3 days. Transcriptomic samples were also collected at daily timepoints to assess molecular responses. Added dissolved Fe was drawn down in both experiments, while DFB appeared to solubilize a fraction of ambient particulate Fe in the high-Fe experiment. Iron quotas of unamended diatoms were nearly 10-fold higher under high-Fe conditions. Quotas increased in response to added Fe in both experiments, but the magnitude of changes varied between diatom taxa. DFB additions resulted in reduced Fe quotas in the low-Fe incubation, since cells were presumably forced to use internal Fe stores to support growth. These data demonstrate significant plasticity in the abilities of phytoplankton to take advantage of changing micronutrient inputs. Quota data will be compared to transcript abundance data to ascertain mechanisms of Fe quota maintenance.

Transformation products of submicron-sized aluminum-substituted magnetite: Color and reductant solubility

NASA Technical Reports Server (NTRS)

Golden, D. C.; Ming, D. W.; Lauer, H. V., Jr.

1991-01-01

Magnetite, when present as fine particles, is soluble in acid ammonium oxalate (pH equals 3). However, the commonly used extractant for free iron oxides (i.e., citrate dithionite-bicarbonate (CDB) is not very effective in dissolving magnetite in soils and geologic materials. Upon oxidation, magnetite transforms to maghemite; at elevated temperatures, maghemite inverts to hematite. This transformation causes a change in color from black to red and may affect the reductant solubility as well. The objectives here were to examine the color and reflectance spectral characteristics of products during the transformation of magnetite to maghemite to hematite and to study the effect of Al-substitution in magnetite on the above process. Reductant solubility of Al-substituted magnetite, maghemite, and hematite was also studied. In summary, the transformation of magnetite to maghemite was accompanied by a change in color from black to red because of the oxidation of Fe2(+) to Fe3(+). The phase change maghemite to hematite had a relatively minor effect on the color and the reflectance spectra.

Effect of Thermomechanical Processing on Texture and Superelasticity in Fe-Ni-Co-Al-Ti-B Alloy

NASA Astrophysics Data System (ADS)

Lee, Doyup; Omori, Toshihiro; Han, Kwangsik; Hayakawa, Yasuyuki; Kainuma, Ryosuke

2018-03-01

The texture and superelasticity were investigated in austenitic Fe-Ni-Co-Al-Ti-B alloy with various reduction ratios of cold rolling and heating ratios in annealing. The rolled sheets show the {110} <112> deformation texture at a reduction ratio higher than 80%, while the texture hardly changes in the primary recrystallization at 1000 °C. The β (B2) precipitates inhibit the grain growth at this temperature, but they dissolve during heating, and secondary recrystallization occurs due to decreased pinning force at temperatures higher than 1100 °C, resulting in texture change to {210} <001> . The recrystallization texture is more strongly developed when the reduction ratio and heating rate are high and slow, respectively. The 90% cold-rolled and slowly heated sheet shows the recrystallization texture and high fraction of low-angle boundaries. As a result, ductility and superelasticity can be drastically improved in the 90% cold-rolled sheet, although superelasticity was previously obtained only in thin sheets with 98.5% reduction.

Equilibrium isotopic fractionation of copper during oxidation/reduction, aqueous complexation and ore-forming processes: Predictions from hybrid density functional theory

NASA Astrophysics Data System (ADS)

Sherman, David M.

2013-10-01

Copper exists as two isotopes: 65Cu (∼30.85%) and 63Cu (∼69.15%). The isotopic composition of copper in secondary minerals, surface waters and oxic groundwaters is 1-12‰ heavier than that of copper in primary sulfides. Changes in oxidation state and complexation should yield substantial isotopic fractionation between copper species but it is unclear to what extent the observed Cu isotopic variations reflect equilibrium fractionation. Here, I calculate the reduced partition function ratios for chalcopyrite (CuFeS2), cuprite (Cu2O), tenorite (CuO) and aqueous Cu+, Cu+2 complexes using periodic and molecular hybrid density functional theory to predict the equilibrium isotopic fractionation of Cu resulting from oxidation of Cu+ to Cu+2 and by complexation of dissolved Cu. Among the various copper(II) complexes in aqueous environments, there is a significant (1.3‰) range in the reduced partition function ratios. Oxidation and congruent dissolution of chalcopyrite (CuFeS2) to dissolved Cu+2 (as Cu(H2O)5+2) yields 65-63δ(Cu+2-CuFeS2) = 3.1‰ at 25 °C; however, chalcopyrite oxidation/dissolution is incongruent so that the observed isotopic fractionation will be less. Secondary precipitation of cuprite (Cu2O) would yield further enrichment of dissolved 65Cu since 65-63δ(Cu+2-Cu2O) is 1.2‰ at 25 °C. However, precipitation of tenorite (CuO) will favor the heavy isotope by +1.0‰ making dissolved Cu isotopically lighter. These are upper-limit estimates for equilibrium fractionation. Therefore, the extremely large (9‰) fractionations between dissolved Cu+2 (or Cu+2 minerals) and primary Cu+ sulfides observed in supergene environments must reflect Rayleigh (open-system) or kinetic fractionation. Finally the previously proposed (Asael et al., 2009) use of δ65Cu in chalcopyrite to estimate the oxidation state of fluids that transported Cu in stratiform sediment-hosted copper deposits is refined.

Chemistry and phytotoxicity of arsenic in soils. II. Effects of time and phosphorus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woolson, E.A.; Axley, J.H.; Kearney, P.C.

Arsenate from sodium arsenate changes to less soluble compounds in soils with time. To study these changes, the arsenic soluble in 1N NH/sub 4/Cl, 0.5N NH/sub 4/F, 0.1N NaOH, and 0.5N H/sub 2/SO/sub 4/ solutions was determined. These dissolved arsenates, were designated as WS-As (water soluble, Al-As, Fe-As, or Ca-As, respectively. The percent of WS-As present was proportional to As added and inversely proportional to time, and to the Fe and Al content. Fe-As was the predominant form of As in Hagerstown silty clay loam while Al-As predominated in Lakeland loamy sand. Growth of corn (Zea mays) increased with increasemore » in time of As incubation in the soil before planting. Arsenic phytotoxicity and As in the plant were altered by P additions. Arsenic residues in the Lakeland soil became more phytotoxic, while residues in the Hagerstown soil became less phytotoxic with P additions. This plant response was related to the availability of As and P in these soils. Leaching with 0.05 M KH/sub 2/PO/sub 4/ removed 77% of the total As from a contaminated Dunkirk fine sand. The distribution of the forms of As in this soil changed during leaching. 26 references, 3 figures, 4 tables.« less

Bioleaching of ilmenite and basalt in the presence of iron-oxidizing and iron-scavenging bacteria

NASA Astrophysics Data System (ADS)

Navarrete, Jesica U.; Cappelle, Ian J.; Schnittker, Kimberlin; Borrok, David M.

2013-04-01

Bioleaching has been suggested as an alternative to traditional mining techniques in extraterrestrial environments because it does not require extensive infrastructure and bulky hardware. In situ bioleaching of silicate minerals, such as those found on the moon or Mars, has been proposed as a feasible alternative to traditional extraction techniques that require either extreme heat and/or substantial chemical treatment. In this study, we investigated the biotic and abiotic leaching of basaltic rocks (analogues to those found on the moon and Mars) and the mineral ilmenite (FeTiO3) in aqueous environments under acidic (pH ˜ 2.5) and circumneutral pH conditions. The biological leaching experiments were conducted using Acidithiobacillus ferrooxidans, an iron (Fe)-oxidizing bacteria, and Pseudomonas mendocina, an Fe-scavenging bacteria. We found that both strains were able to grow using the Fe(II) derived from the tested basaltic rocks and ilmenite. Although silica leaching rates were the same or slightly less in the bacterial systems with A. ferrooxidans than in the abiotic control systems, the extent of Fe, Al and Ti released (and re-precipitated in new solid phases) was actually greater in the biotic systems. This is likely because the Fe(II) leached from the basalt was immediately oxidized by A. ferrooxidans, and precipitated into Fe(III) phases which causes a change in the equilibrium of the system, i.e. Le Chatelier's principle. Iron(II) in the abiotic experiment was allowed to build up in solution which led to a decrease in its overall release rate. For example, the percentage of Fe, Al and Ti leached (dissolved + reactive mineral precipitates) from the Mars simulant in the A. ferrooxidans experimental system was 34, 41 and 13% of the total Fe, Al and Ti in the basalt, respectively, while the abiotic experimental system released totals of only 11, 25 and 2%. There was, however, no measurable difference in the amounts of Fe and Ti released from ilmenite in the experiments with A. ferrooxidans versus the abiotic controls. P. mendocina scavenged some Fe from the rock/mineral substrates, but the overall amount of leaching was small (<2% of total Fe in rocks) when compared with the acidophilic systems. Although the mineralogy of the tested basaltic rocks was roughly similar, the surface areas of the lunar and Mars simulants varied greatly and thus were possible factors in the overall amount of metals released. Overall, our results indicate that the presence of bacteria does not increase the overall silica leaching rates of basaltic rocks; however, the presence of A. ferrooxidans does lead to enhanced release of Fe, Al and Ti and subsequent sequestration of Fe (and other metals) in Fe(III)-precipitates.

The geochemical cycling of trace elements in a biogenic meromictic lake

NASA Astrophysics Data System (ADS)

Balistrieri, Laurie S.; Murray, James W.; Paul, Barbara

1994-10-01

The geochemical processes affecting the behavior and speciation of As, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn in Hall Lake, Washington, USA, are assessed by examining dissolved and acid soluble particulate profiles of the elements and utilizing results from thermodynamic calculations. The water column of this meromictic lake is highly stratified and contains distinctive oxic, suboxic, and anoxic layers. Changes in the redox state of the water column with depth affect the distribution of all the elements studied. Most noticeable are increases in dissolved Co, Cr, Fe, Mn, Ni, Pb, and Zn concentrations across the oxic-suboxic boundary, increases in dissolved As, Co, Cr, Fe, Mn, and V concentrations with depth in the anoxic layer, significant decreases in dissolved Cu, Ni, Pb, and Zn concentrations in the anoxic region below the sulfide maximum, and large increases in acid soluble particulate concentrations of As, Cr, Cu, Fe, Mo, Ni, Pb, V, and Zn in the anoxic zone below the sulfide maximum. Thermodynamic calculations for the anoxic region indicate that all redox sensitive elements exist in their reduced forms, the primary dissolved forms of Cu, Ni, Pb, and Zn are metal sulfide solution complexes, and solid sulfide phases of Cu, Fe, Mo, and Pb are supersaturated. Calculations using a vertical diffusion and reaction model indicate that the oxidation rate constant for Mn(II) in Hall Lake is estimated to be 0.006 d -1 and is at the lower end of the range of microbial oxidation rates observed in other natural systems. The main geochemical processes influencing the distribution and speciation of trace elements in Hall Lake appear to be transformations of dissolved elements between their oxidation states (As, Cr, Cu, Fe, Mn, V), cocycling of trace elements with Mn and Fe (As, Co, Cr, Cu, Mo, Ni, Pb, V, Zn), formation of soluble metal sulfide complexes (Co, Cu, Ni, Pb, Zn), sorption (As, Co, Cr, Ni, V), and precipitation (Cu, Fe, Mn, Mo, Pb, Zn).

The geochemical cycling of trace elements in a biogenic meromictic lake

USGS Publications Warehouse

Balistrieri, L.S.; Murray, J.W.; Paul, B.

1994-01-01

The geochemical processes affecting the behavior and speciation of As, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn in Hall Lake, Washington, USA, are assessed by examining dissolved and acid soluble particulate profiles of the elements and utilizing results from thermodynamic calculations. The water column of this meromictic lake is highly stratified and contains distinctive oxic, suboxic, and anoxic layers. Changes in the redox state of the water column with depth affect the distribution of all the elements studied. Most noticeable are increases in dissolved Co, Cr, Fe, Mn, Ni, Pb, and Zn concentrations across the oxic-suboxic boundary, increases in dissolved As, Co, Cr, Fe, Mn, and V concentrations with depth in the anoxic layer, significant decreases in dissolved Cu, Ni, Pb, and Zn concentrations in the anoxic region below the sulfide maximum, and large increases in acid soluble particulate concentrations of As, Cr, Cu, Fe, Mo, Ni, Pb, V, and Zn in the anoxic zone below the sulfide maximum. Thermodynamic calculations for the anoxic region indicate that all redox sensitive elements exist in their reduced forms, the primary dissolved forms of Cu, Ni, Pb, and Zn are metal sulfide solution complexes, and solid sulfide phases of Cu, Fe, Mo, and Pb are supersaturated. Calculations using a vertical diffusion and reaction model indicate that the oxidation rate constant for Mn(II) in Hall Lake is estimated to be 0.006 d-1 and is at the lower end of the range of microbial oxidation rates observed in other natural systems. The main geochemical processes influencing the distribution and speciation of trace elements in Hall Lake appear to be transformations of dissolved elements between their oxidation states (As, Cr, Cu, Fe, Mn, V), cocycling of trace elements with Mn and Fe (As, Co, Cr, Cu, Mo, Ni, Pb, V, Zn), formation of soluble metal sulfide complexes (Co, Cu, Ni, Pb, Zn), sorption (As, Co, Cr, Ni, V), and precipitation (Cu, Fe, Mn, Mo, Pb, Zn). ?? 1994.

Assessment of Young Dong tributary and Imgok Creek impacted by Young Dong coal mine, South Korea.

PubMed

Lee, Byung-Tae; Ranville, James F; Wildeman, Thomas R; Jang, Min; Shim, Yon Sik; Ji, Won Hyun; Park, Hyun Sung; Lee, Hyun Ju

2012-01-01

An initial reclamation of the Young Dong coal mine site, located in northeastern South Korea, was completed in 1995. Despite the filling of the adit with limestone, acid rock drainage (ARD) enters Young Dong tributary and is then discharged to Imgok Creek. This ARD carries an average of 500 mg CaCO(3)/l of mineral acidity, primarily as Fe(II) and Al. Before spring runoff, the flow of Imgok Creek is 3.3-4 times greater than that of the tributary and has an alkalinity of 100 mg CaCO(3)/l, which is sufficient to eliminate the mineral acidity and raise the pH to about 6.5. From April through September 2008, there were at least two periods of high surface flow that affects the flow of ARD from the adit. Flow of ARD reaches 2.8 m(3)/min during spring runoff. This raised the concentrations of Fe and Al in the confluence with Imgok Creek. However, by 2 km downstream the pH of the Imgok Creek is 6.5 and only dissolved Fe is above the Korean drinking water criteria (0.30 mg/l). This suggests only a minor impact of Young Dong Creek water on Imgok Creek. Acid digestion of the sediments in Imgok Creek and Young Dong Tributary reveals considerable abundances of heavy metals, which could have a long-term impact on water quality. However, several water-based leaching tests, which better simulate the bioavailable metals pool, released only Al, Fe, Mn, and Zn at concentrations exceeding the criteria for drinking water or aquatic life.

Temporal variability of dissolved iron species in the mesopelagic zone at Ocean Station PAPA

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; Ross, Andrew R. S.; Davidson, Ashley B.; Stewart, Gillian M.; Cullen, Jay T.

2017-08-01

Deposition of atmospheric aerosols to the surface ocean is considered an important mechanism for the supply of iron (Fe) to remote ocean regions, but direct observations of the oceanic response to aerosol deposition are sparse. In the high nutrient, low chlorophyll (HNLC) subarctic Pacific Ocean we observed a dissolved Fe and Fe(II) anomaly at depth that is best explained as the result of aerosol deposition from Siberian forest fires in May 2012. Interestingly, there was no evidence of enhanced dFe concentrations in surface waters, nor was there a detectable phytoplankton bloom in response to the suspected aerosol deposition. Dissolved Fe (dFe) and Fe(II) showed the strongest enhancement in the subsurface oxygen deficient zone (ODZ), where oxygen concentrations <50 μmol kg-1 are prevalent. In the upper 200 m, dFe concentrations were at or below historic background levels, consistent with a short residence time of aerosol particles in surface waters and possible scavenging loss of dFe. Aerosol toxicity and/or dominance of particle scavenging over dissolution of Fe in the upper water column may have contributed to the lack of a strong phytoplankton response.

Aluminum anode for aluminum-air battery - Part I: Influence of aluminum purity

NASA Astrophysics Data System (ADS)

Cho, Young-Joo; Park, In-Jun; Lee, Hyeok-Jae; Kim, Jung-Gu

2015-03-01

2N5 commercial grade aluminum (99.5% purity) leads to the lower aluminum-air battery performances than 4N high pure grade aluminum (99.99% purity) due to impurities itself and formed impurity complex layer which contained Fe, Si, Cu and others. The impurity complex layer of 2N5 grade Al declines the battery voltage on standby status. It also depletes discharge current and battery efficiency at 1.0 V which is general operating voltage of aluminum-air battery. However, the impurity complex layer of 2N5 grade Al is dissolved with decreasing discharge voltage to 0.8 V. This phenomenon leads to improvement of discharge current density and battery efficiency by reducing self-corrosion reaction. This study demonstrates the possibility of use of 2N5 grade Al which is cheaper than 4N grade Al as the anode for aluminum-air battery.

REE geochemistry of 3.2 Ga BIF from the Mapepe Formation, Barberton Greenstone Belt, South Africa

NASA Astrophysics Data System (ADS)

Yahagi, T. R.; Yamaguchi, K. E.; Haraguchi, S.; Sano, R.; Teraji, S.; Kiyokawa, S.; Ikehara, M.; Ito, T.

2012-12-01

Banded iron formations (BIFs) are chemical sediments interbedded with Fe- and Si-rich layers, characteristically present in the early history of the Earth. A popular hypothesis for the formation of BIFs postulates that dissolved oxygen produced by photosynthesizers such as cyanobacteria oxidized dissolved ferrous Fe supplied by submarine hydrothermal activities. During precipitation of Fe-oxide minerals, phosphorus and rare earth elements (REEs) were most likely adsorbed on their surface. Therefore, chemical compositions of REEs that adsorbed onto Fe-oxide have useful information on the seawater chemistry at the time of deposition. Especially, information on the redox state of seawater and the extent of the contribution of hydrothermal activity during BIF deposition are expected to have been recorded. Occurrence of BIF has been traditionally tied to the chemical evolution of the atmosphere. Rise of atmospheric oxygen, or as known as GOE (Great Oxidation Event: e.g., Holland, 1994), has been widely believed to have occurred at around 2.4 Ga ago. Contrary, however, some studies have suggested that such oxygenation could have occurred much earlier (e.g., Hoashi et al., 2009). In this study, we used 3.2 Ga old BIF from the Mapepe Formation at the bottom of the Fig Tree Group of the Swaziland Supergroup in the northeastern part of the Barberton Greenstone Belt, South Africa. We aimed to constrain the marine environment, and by inference atmospheric environment, at the time of BIF deposition from REE geochemistry. Major elements and REE compositions of 37 samples were measured using XRF and ICP-MS, respectively. Samples with less than 1.0 wt% Al2O3 are considered to be "pure" BIFs with minimal amount of continental contamination, and are expected to have inherited marine REE signatures. Abundance of REE normalized by C1 chondrite for the analyzed samples commonly exhibits positive Eu anomaly and LREE

Iron limitation of microbial phosphorus acquisition in the tropical North Atlantic

NASA Astrophysics Data System (ADS)

Browning, Thomas; Achterberg, Eric; Yong, Jaw Chuen; Rapp, Insa; Utermann, Caroline; Engel, Anja; Moore, Mark

2017-04-01

Growth-limitation of marine phytoplankton by fixed nitrogen (N) has been demonstrated for most of the low-latitude oceans; however, in the (sub)tropical North Atlantic enhanced N2 fixation leads to secondary/(co-)limitation by phosphorus (P). The dissolved organic P pool is rarely fully depleted in the modern ocean and potentially represents a substantial additional P source. Microbes can use a variety of alkaline phosphatase enzymes to access P from a major fraction of this pool. In contrast to the relatively well studied PhoA family of alkaline phosphatases that utilize zinc (Zn) as a cofactor, the recent discovery of iron (Fe) as a cofactor in the more widespread PhoX[1] and PhoD[2] enzymes imply potential for a complex, biochemically-dependant interplay between oceanic Zn, Fe and P cycles. Here we demonstrate enhanced natural community alkaline phosphatase activity (APA) following Fe amendment within the low Zn and moderately low Fe western tropical North Atlantic. In contrast, beneath the Saharan dust plume in the Eastern Atlantic no APA response to trace metal addition was observed. This is the first demonstration of intermittent Fe limitation of microbial P acquisition, providing an additional facet in the argument for Fe control of the coupling between oceanic N and P cycles. 1. Yong, S. C. et al. A complex iron-calcium cofactor catalyzing phosphotransfer chemistry. Science 345, 1170-3 (2014). 2. Rodriguez, F. et al. Crystal structure of the Bacillus subtilis phosphodiesterase PhoD reveals an iron and calcium-containing active site. J. Biol. Chem. 289, 30889-30899 (2014).

Importance of interlayer H bonding structure to the stability of layered minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conroy, Michele; Soltis, Jennifer A.; Wittman, Rick S.

Layered (oxy) hydroxide minerals often possess out-of-plane hydrogen atoms that form hydrogen bonding networks which stabilize the layered structure. However, less is known about how the ordering of these bonds affects the structural stability and solubility of these minerals. Here, we report a new strategy that uses the focused electron beam to probe the effect of differences in hydrogen bonding networks on mineral solubility. In this regard, the dissolution behavior of boehmite (γ-AlOOH) and gibbsite (γ-Al(OH)3) were compared and contrasted in real time via liquid cell electron microscopy. Under identical such conditions, 2D-nanosheets of boehmite (γ-AlOOH) exfoliated from the bulkmore » and then rapidly dissolved, whereas gibbsite was stable. Further, substitution of only 1% Fe(III) for Al(III) in the structure of boehmite inhibited delamination and dissolution. Factors such as pH, radiolytic species, and knock on damage were systematically studied and eliminated as proximal causes for boehmite dissolution. Instead, the creation of electron/hole pairs was considered to be the mechanism that drove dissolution. The widely disparate behaviors of boehmite, gibbsite, and Fe-doped boehmite are discussed in the context of differences in the OH bond strengths, hydrogen bonding networks, and the presence or absence of electron/hole recombination centers.« less

Importance of interlayer H bonding structure to the stability of layered minerals

DOE PAGES

Conroy, Michele; Soltis, Jennifer A.; Wittman, Rick S.; ...

2017-10-16

Layered (oxy) hydroxide minerals often possess out-of-plane hydrogen atoms that form hydrogen bonding networks which stabilize the layered structure. However, less is known about how the ordering of these bonds affects the structural stability and solubility of these minerals. Here, we report a new strategy that uses the focused electron beam to probe the effect of differences in hydrogen bonding networks on mineral solubility. In this regard, the dissolution behavior of boehmite (γ-AlOOH) and gibbsite (γ-Al(OH)3) were compared and contrasted in real time via liquid cell electron microscopy. Under identical such conditions, 2D-nanosheets of boehmite (γ-AlOOH) exfoliated from the bulkmore » and then rapidly dissolved, whereas gibbsite was stable. Further, substitution of only 1% Fe(III) for Al(III) in the structure of boehmite inhibited delamination and dissolution. Factors such as pH, radiolytic species, and knock on damage were systematically studied and eliminated as proximal causes for boehmite dissolution. Instead, the creation of electron/hole pairs was considered to be the mechanism that drove dissolution. The widely disparate behaviors of boehmite, gibbsite, and Fe-doped boehmite are discussed in the context of differences in the OH bond strengths, hydrogen bonding networks, and the presence or absence of electron/hole recombination centers.« less

Elevated concentrations of dissolved Ba, Fe and Mn in a mangrove subterranean estuary: Consequence of sea level rise?

NASA Astrophysics Data System (ADS)

Sanders, Christian J.; Santos, Isaac R.; Barcellos, Renato; Silva Filho, Emmanoel V.

2012-07-01

Groundwater underlying a mangrove habitat was studied to determine the geochemical nature of Ba, Fe and Mn as related to dissolved organic carbon (DOC), SO4 and salinity (Sepetiba Bay, Brazil). Wells were placed across geobotanic facies and sampled monthly for a year. We observed non-conservative behavior and elevated concentrations of dissolved metals relative to local end-members (i.e., fresh river water and seawater). Average Ba concentrations were near 2000 nM in an area with low salinity (˜5.3). Dissolved Fe (up to 654 μM) was two orders of magnitude greater in fresh groundwater than in the seaward sampling stations. Manganese concentrations were greatest (112 μM) in the high salinity (˜65) zone, being directly influenced by salinity. Groundwater Ba, Fe and Mn showed differing site specific concentrations, likely related to ion exchange processes and redox-controlled cycling along distinct mangrove facies. The results of this work show that metal concentrations are altered relative to conservative mixing between terrestrial and marine endmembers, illustrating the importance of mangrove subterranean estuaries as biogeochemical reactors. Roughly-estimated submarine groundwater discharge-derived dissolved Ba, Fe and Mn fluxes were at least one order of magnitude greater than river-derived fluxes into Sepetiba Bay.

Combined effects of hydrographic structure and iron and copper availability on the phytoplankton growth in Terra Nova Bay Polynya (Ross Sea, Antarctica)

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Luisa Abelmoschi, Maria; Grotti, Marco; Ianni, Carmela; Magi, Emanuele; Margiotta, Francesca; Massolo, Serena; Saggiomo, Vincenzo

2012-04-01

Surface water (<100 m) samples were collected from the Terra Nova Bay polynya region of the Ross Sea (Antarctica) in January 2006, with the aim of evaluating the individual and combined effects of hydrographic structure, iron and copper concentration and availability on the phytoplankton growth. The measurements were conducted within the framework of the Climatic Long Term Interaction for the Mass-balance in Antarctica (CLIMA) Project of the Programma Nazionale di Ricerca in Antartide activities. Dissolved oxygen, nutrients, phytoplankton pigments and concentration and complexation of dissolved trace metals were determined. Experimental data were elaborated by Principal Component Analysis (PCA). As a result of solar heating and freshwater inputs from melting sea-ice, the water column was strongly stratified with an Upper Mixed Layer 4-16 m deep. The integrated Chl a in the layer 0-100 m ranged from 60 mg m-2 to 235 mg m-2, with a mean value of 138 mg m-2. The pigment analysis showed that diatoms dominated the phytoplankton assemblage. Major nutrients were generally high, with the lowest concentration at the surface and they were never fully depleted. The Si:N drawdown ratio was close to the expected value of 1 for Fe-replete diatoms. We evaluated both the total and the labile dissolved fraction of Fe and Cu. The labile fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The total dissolved Fe ranged from 0.48 to 3.02 nM, while the total dissolved Cu from 3.68 to 6.84 nM. The dissolved labile Fe ranged from below the detection limit (0.15 nM) to 1.22 nM, and the dissolved labile Cu from 0.31 to 1.59 nM, respectively. The labile fractions measured at 20 m were significantly lower than values in 40-100 m samples. As two stations were re-sampled 5 days later, we evaluated the short-term variability of the physical and biogeochemical properties. In particular, in a re-sampled station at 20 m, the total dissolved Fe increased and the total dissolved Cu decreased, while their labile fraction was relatively steady. As a result of the increase in total Fe, the percentage of the labile Fe decreased. An increase of the Si:N, Si:P and Si:FUCO ratios was measured also in the re-sampled station. On this basis, we speculated that a switch from a Fe-replete to a Fe-deplete condition was occurring.

Size-fractionation of groundwater arsenic in alluvial aquifers of West Bengal, India: the role of organic and inorganic colloids.

PubMed

Majumder, Santanu; Nath, Bibhash; Sarkar, Simita; Chatterjee, Debashis; Roman-Ross, Gabriela; Hidalgo, Manuela

2014-01-15

Dissolved organic carbon (DOC) and Fe mineral phases are known to influence the mobility of arsenic (As) in groundwater. Arsenic can be associated with colloidal particles containing organic matter and Fe. Currently, no data is available on the dissolved phase/colloidal association of As in groundwater of alluvial aquifers in West Bengal, India. This study investigated the fractional distribution of As (and other metals/metalloids) among the particulate, colloidal and dissolved phases in groundwater to decipher controlling behavior of organic and inorganic colloids on As mobility. The result shows that 83-94% of As remained in the 'truly dissolved' phases (i.e., <0.05 μm size). Strong positive correlation between Fe and As (r(2) between 0.65 and 0.94) is mainly observed in the larger (i.e., >0.05 μm size) colloidal particles, which indicates the close association of As with larger Fe-rich inorganic colloids. In smaller (i.e., <0.05 μm size) colloidal particles strong positive correlation is observed between As and DOC (r(2)=0.85), which highlights the close association of As with smaller organic colloids. As(III) is mainly associated with larger inorganic colloids, whereas, As(V) is associated with smaller organic/organometallic colloids. Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy confirm the association of As with DOC and Fe mineral phases suggesting the formation of dissolved organo-Fe complexes and colloidal organo-Fe oxide phases. Attenuated total reflectance-Fourier transform infrared spectroscopy further confirms the formation of As-Fe-NOM organometallic colloids, however, a detailed study of these types of colloids in natural waters is necessary to underpin their controlling behavior. © 2013 Elsevier B.V. All rights reserved.

Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 1: Constituent quantities and correlations

USGS Publications Warehouse

Cravotta, C.A.

2008-01-01

Complete hydrochemical data are rarely reported for coal-mine discharges (CMD). This report summarizes major and trace-element concentrations and loadings for CMD at 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania. Clean-sampling and low-level analytical methods were used in 1999 to collect data that could be useful to determine potential environmental effects, remediation strategies, and quantities of valuable constituents. A subset of 10 sites was resampled in 2003 to analyze both the CMD and associated ochreous precipitates; the hydrochemical data were similar in 2003 and 1999. In 1999, the flow at the 140 CMD sites ranged from 0.028 to 2210 L s-1, with a median of 18.4 L s-1. The pH ranged from 2.7 to 7.3; concentrations (range in mg/L) of dissolved (0.45-??m pore-size filter) SO4 (34-2000), Fe (0.046-512), Mn (0.019-74), and Al (0.007-108) varied widely. Predominant metalloid elements were Si (2.7-31.3 mg L-1), B ( C > P = N = Se) were not elevated in the CMD samples compared to average river water or seawater. Compared to seawater, the CMD samples also were poor in halogens (Cl > Br > I > F), alkalies (Na > K > Li > Rb > Cs), most alkaline earths (Ca > Mg > Sr), and most metalloids but were enriched by two to four orders of magnitude with Fe, Al, Mn, Co, Be, Sc, Y and the lanthanide rare-earth elements, and one order of magnitude with Ni and Zn. The ochre samples collected at a subset of 10 sites in 2003 were dominantly goethite with minor ferrihydrite or lepidocrocite. None of the samples for this subset contained schwertmannite or was Al rich, but most contained minor aluminosilicate detritus. Compared to concentrations in global average shale, the ochres were rich in Fe, Ag, As and Au, but were poor in most other metals and rare earths. The ochres were not enriched compared to commercial ore deposits mined for Au or other valuable metals. Although similar to commercial Fe ores in composition, the ochres are dispersed and present in relatively small quantities at most sites. Nevertheless, the ochres could be valuable for use as pigment.

Hydrochemical evaluation of the influences of mining activities on river water chemistry in central northern Mongolia.

PubMed

Batsaikhan, Bayartungalag; Kwon, Jang-Soon; Kim, Kyoung-Ho; Lee, Young-Joon; Lee, Jeong-Ho; Badarch, Mendbayar; Yun, Seong-Taek

2017-01-01

Although metallic mineral resources are most important in the economy of Mongolia, mining activities with improper management may result in the pollution of stream waters, posing a threat to aquatic ecosystems and humans. In this study, aiming to evaluate potential impacts of metallic mining activities on the quality of a transboundary river (Selenge) in central northern Mongolia, we performed hydrochemical investigations of rivers (Tuul, Khangal, Orkhon, Haraa, and Selenge). Hydrochemical analysis of river waters indicates that, while major dissolved ions originate from natural weathering (especially, dissolution of carbonate minerals) within watersheds, they are also influenced by mining activities. The water quality problem arising from very high turbidity is one of the major environmental concerns and is caused by suspended particles (mainly, sediment and soil particles) from diverse erosion processes, including erosion of river banks along the meandering river system, erosion of soils owing to overgrazing by livestock, and erosion by human activities, such as mining and agriculture. In particular, after passing through the Zaamar gold mining area, due to the disturbance of sediments and soils by placer gold mining, the Tuul River water becomes very turbid (up to 742 Nephelometric Turbidity Unit (NTU)). The Zaamar area is also the contamination source of the Tuul and Orkhon rivers by Al, Fe, and Mn, especially during the mining season. The hydrochemistry of the Khangal River is influenced by heavy metal (especially, Mn, Al, Cd, and As)-loaded mine drainage that originates from a huge tailing dam of the Erdenet porphyry Cu-Mo mine, as evidenced by δ 34 S values of dissolved sulfate (0.2 to 3.8 ‰). These two contaminated rivers (Tuul and Khangal) merge into the Orkhon River that flows to the Selenge River near the boundary between Mongolia and Russia and then eventually flows into Lake Baikal. Because water quality problems due to mining can be critical, mining activities in central northern Mongolia should be carefully managed to minimize the transboundary movement of aquatic contaminants (in particular, turbidity, dissolved organic carbon, Fe and Al) from mining activities.

Comparison study of phosphorus adsorption on different waste solids: Fly ash, red mud and ferric-alum water treatment residues.

PubMed

Wang, Ying; Yu, Yange; Li, Haiyan; Shen, Chanchan

2016-12-01

The adsorption of phosphorus (P) onto three industrial solid wastes (fly ash, red mud and ferric-alum water treatment residual (FAR)) and their modified materials was studied systematically via batch experiments. Compared with two natural adsorbents (zeolite and diatomite), three solid wastes possessed a higher adsorption capacity for P because of the higher Fe, Al and Ca contents. After modification (i.e., the fly ash and red mud modified by FeCl 3 and FARs modified by HCl), the adsorption capacity increased, especially for the modified red mud, where more Fe bonded P was observed. The P adsorption kinetics can be satisfactorily fitted using the pseudo-second-order model. The Langmuir model can describe well the P adsorption on all of the samples in our study. pH and dissolved organic matter (DOM) are two important factors for P adsorption. Under neutral conditions, the maximum adsorption amount on the modified materials was observed. With the deviation from pH7, the adsorption amount decreased, which resulted from the change of P species in water and surface charges of the adsorbents. The DOM in water can promote P adsorption, which may be due to the promotion effects of humic-Fe(Al) complexes and the pH buffer function exceeds the depression of competitive adsorption. Copyright © 2016. Published by Elsevier B.V.

An experimental study on ferrous iron photo-oxidation: Effect of the solar spectrum on the surface for acidification of surface water in the early Hesperian Mars

NASA Astrophysics Data System (ADS)

Tabata, H.; Sekine, Y.; Kanzaki, Y.; Sugita, S.; Murakami, T.

2017-12-01

Geochemical evidence obatined by Mars Opportunity rover suggests that the pH of Martian surface water shifted to highly acidic, i.e., pH 2-4, in the early Hesperian (e.g., Tosca et al., 2005). Hurowitz et al. (2010) proposed that solar UV light may have promoted the acidification through photo-oxidation of ferrous iron dissolved in upwelling groundwater on early Mars. However, the trigger for the acidification in the early Hesperian remains unclear. The photo-oxidation of Fe2+ occurs under acidic conditions, i.e., pH < 3 (Jortner et al., 1962); however, the pH of upwelling groundwater would be neutral to alkaline (Zolotov et al., 2016). At neutral to alkaline pH, FeOH+ can exist together with Fe2+ in a solution. While both Fe2+ and FeOH+ are photo-oxidized only by UV light (< 300 nm), FeOH+ can also be photo-oxidized by long UV/visible light (300-400 nm). Thus, the efficiency of acidification through photo-oxidation on early Mars should have depended on the solar spectrum on the surface at that time which is determined by the atmospheric composition. To investigate the effect of UV spectrum on the acidification, we conducted two types of laboratory experiments: One used a Xe lamp as the light source for photo-oxidation of ferrous iron to irradiate light with continuous spectrum from 250 to 400 nm, and the other used the Xe lamp with an optical filter that cuts off UV light shorter than 300 nm. The pH value of the starting solution was around 7. Upon the UV irradiation covering full wavelength range (250-400 nm), the pH value of the solution decreases down to less than 4, consistent with the proposed pH of the Hesperian acidic water on Meridiani Planum (Tosca et al., 2005). This occurs because Fe2+ is stable at pH < 5, and because Fe2+ can be continuously photo-oxidized in the acidic solution by UV light in 250-300 nm. When the UV irradiation covering 300-400 nm, the pH value of the solution also decreases to pH 5 immediately after the UV irradiation. However, it does not decrease less than pH 5 and reaches a steady state. This is the case because FeOH+ is converted into Fe2+ at low pH, which prevents further photo-oxidation by light in 300-400 nm. These results suggest that a change in the atmospheric composition and consequent reaching of UV light in the wavelength < 300 nm may have played a key role for triggering the acidification in the early Hesperian.

Key sources and distribution patterns of particulate material in the South Atlantic: data from the UK GEOTRACES A10 cruise

NASA Astrophysics Data System (ADS)

Milne, A.; Palmer, M.; Lohan, M. C.

2016-02-01

Particles play a fundamental role in the biogeochemical cycling of both major- and micro-nutrients in marine systems, including trace elements and isotopes. However, knowledge of particulate distributions, and their potential to regulate dissolved elemental concentrations, remains limited and poorly understood. The paradox is, that the oceanic inventory of trace metals is dominated by particulate inputs (e.g. aerosol deposition, shelf sediment resuspension). Moreover the labile fraction of particulate trace elements could be an important regulator of dissolved concentrations. Here we present particulate data from the UK GEOTRACES South Atlantic transect (GA10) from South Africa to Uruguay. Data from a range of elements (e.g. Fe, Al, Mn) revealed a greater input of particulate metals from the Argentine shelf (up to 290 nM of pFe) in comparison to the South African shelf (< 40 nM of pFe). Overall, higher concentrations of all metals were observed in the bottom waters of the Argentine basin and penetrated deeper up the water column (up to 1300 m), a result of intense benthic storms. The imprint of leakage from the Agulhas Current, identified through temperature and salinity, was observed in the upper water column profile of numerous particulate data (e.g. Pb, Ni, Cd). Measured elemental gradients, combined with measurements from a vertical mixing-profiler, will allow estimates of particulate fluxes to be calculated.

Development of a SREX Flowsheet for the Separation of Strontium from Dissolved INEEL Zirconium Calcine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Law, Jack Douglas; Wood, David James; Todd, Terry Allen

1999-02-01

Laboratory experimentation has indicated that the SREX process is effective for partitioning 90 Sr from acidic radioactive waste solutions located at the Idaho Nuclear Technology and Engineering Center. These laboratory results were used to develop a flowsheet for countercurrent testing of the SREX process with dissolved pilot plant calcine. Testing was performed using 24 stages of 2-cm diameter centrifugal contactors which are installed in the Remote Analytical Laboratory hot cell. Dissolved Run #64 pilot plant calcine spiked with 85 Sr was used as feed solution for the testing. The flowsheet tested consisted of an extraction section (0.15 M 4',4'(5')-di-(tert-butylcyclohexo)-18-crown-6 andmore » 1.5 M TBP in Isopar-L.), a 1.0 M NaNO3 scrub section to remove extracted K from the SREX solvent, a 0.01 M HNO3 strip section for the removal of Sr from the SREX solvent, a 0.25 M Na2CO3 wash section to remove degradation products from the solvent, and a 0.1 M HNO3 rinse section. The behavior of 85 Sr, Na, K, Al, B, Ca, Cr, Fe, Ni, and Zr was evaluated. The described flowsheet successfully extracted 85 Sr from the dissolved pilot plant calcine with a removal efficiency of 99.6%. Distribution coefficients for 85 Sr ranged from 3.6 to 4.5 in the extraction section. With these distribution coefficients a removal efficiency of approximately >99.99% was expected. It was determined that the lower than expected removal efficiency can be attributed to a stage efficiency of only 60% in the extraction section. Extracted K was effectively scrubbed from the SREX solvent with the 1.0 M NaNO3 resulting in only 6.4% of the K in the HLW strip product. Sodium was not extracted from the dissolved calcine by the SREX solvent; however, the use of a 1.0 M NaNO3 scrub solution resulted in a Na concentration of 70 mg/L (12.3% of the feed concentration) in the HLW strip product. Al, B, Ca, Cr, Fe, Ni, and Zr were determined to be essentially inextractable.« less

Development of a SREX flowsheet for the separation of strontium from dissolved INEEL zirconium calcine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Law, J.D.; Wood, D.J.; Todd, T.A.

1999-01-01

Laboratory experimentation has indicated that the SREX process is effective for partitioning {sup 90}Sr from acidic radioactive waste solutions located at the Idaho Nuclear Technology and Engineering Center. These laboratory results were used to develop a flowsheet for countercurrent testing of the SREX process with dissolved pilot plant calcine. Testing was performed using 24 stages of 2-cm diameter centrifugal contactors which are installed in the Remote Analytical Laboratory hot cell. Dissolved Run No.64 pilot plant calcine spiked with {sup 85}Sr was used as feed solution for the testing. The flowsheet tested consisted of an extraction section (0.15 M 4{prime},4{prime}(5{prime})-di-(tert-butylcyclohexo)-18-crown-6 andmore » 1.5 M TBP in Isopar-L.), a 1.0 M NaNO{sub 3} scrub section to remove extracted K from the SREX solvent, a 0.01 M HNO{sub 3} strip section for the removal of Sr from the SREX solvent, a 0.25 M Na2CO{sub 3} wash section to remove degradation products from the solvent, and a 0.1 M HNO{sub 3} rinse section. The behavior of {sup 85}Sr, Na, K, Al, B, Ca, Cr, Fe, Ni, and Zr was evaluated. The described flowsheet successfully extracted {sup 85}Sr from the dissolved pilot plant calcine with a removal efficiency of 99.6%. Distribution coefficients for {sup 85}Sr ranged from 3.6 to 4.5 in the extraction section. With these distribution coefficients a removal efficiency of approximately >99.99% was expected. It was determined that the lower than expected removal efficiency can be attributed to a stage efficiency of only 60% in the extraction section. Extracted K was effectively scrubbed from the SREX solvent with the 1.0 M NaNO{sub 3} resulting in only 6.4% of the K in the HLW strip product. Sodium was not extracted from the dissolved calcine by the SREX solvent; however, the use of a 1.0 M NaNO{sub 3} scrub solution resulted in a Na concentration of 70 mg/L (12.3% of the feed concentration) in the HLW strip product. Al, B, Ca, Cr, Fe, Ni, and Zr were determined to be essentially inextractable.« less

Evolution of concentration-discharge relations revealed by high frequency diurnal sampling of stream water during spring snowmelt

NASA Astrophysics Data System (ADS)

Olshansky, Y.; White, A. M.; Thompson, M.; Moravec, B. G.; McIntosh, J. C.; Chorover, J.

2017-12-01

Concentration discharge (C-Q) relations contain potentially important information on critical zone (CZ) processes including: weathering reactions, water flow paths and nutrient export. To examine the C-Q relations in a small (3.3 km2) headwater catchment - La Jara Creek located in the Jemez River Basin Critical Zone Observatory, daily, diurnal stream water samples were collected during spring snow melt 2017, from two flumes located in outlets of the La Jara Creek and a high elevation zero order basin within this catchment. Previous studies from this site (McIntosh et al., 2017) suggested that high frequency sampling was needed to improve our interpretation of C-Q relations. The dense sampling covered two ascending and two descending limbs of the snowmelt hydrograph, from March 1 to May 15, 2017. While Na showed inverse correlation (dilution) with discharge, most other solutes (K, Mg, Fe, Al, dissolved organic carbon) exhibited positive (concentration) or chemostatic trends (Ca, Mn, Si, dissolved inorganic carbon and dissolved nitrogen). Hysteresis in the C-Q relation was most pronounced for bio-cycled cations (K, Mg) and for Fe, which exhibited concentration during the first ascending limb followed by a chemostatic trend. A pulsed increase in Si concentration immediately after the first ascending limb in both flumes suggests mixing of deep groundwater with surface water. A continual increase in Ge/Si concentrations followed by a rapid decrease after the second rising limb may suggest a fast transition between soil water to ground water dominating the stream flow. Fourier transform infrared spectroscopy of selected samples across the hydrograph demonstrated pronounced changes in dissolved organic matter molecular composition with the advancement of the spring snow melt. X-ray micro-spectroscopy of colloidal material isolated from the collected water samples indicated a significant role for organic matter in the transport of inorganic colloids. Analyses of high frequency diurnal sampling greatly improve our ability to probe rapid CZ changes occurring during spring snowmelt, and provide useful information for evaluation and modeling of CZ processes in other snow melt dominated regions.

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils

NASA Astrophysics Data System (ADS)

Sauerwein, Meike; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

2010-05-01

Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils Meike Sauerwein1, Alexander Hanke2, Klaus Kaiser3, Karsten Kalbitz2 1) Dept. of Soil Ecology, Bayreuth Centre of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany, meike.sauerwein@gmail.com 2) Institute of ecosystem dynamics and biodiversity, University of Amsterdam, 1018 WV, Netherlands, a.hanke@uva.nl, k.kalbitz@uva.nl 3) Soil Sciences, Martin Luther University Halle, 06099 Halle, Germany, klaus.kaiser@landw.uni-halle.de Current knowledge on dissolved organic matter (DOM) in soils is based mainly on observations and experiments in aerobic environments. Adsorption to soil minerals is an important mechanism of DOM retention and stabilization against microbial decay under oxic conditions. Under anoxic conditions where hydrous iron oxides, the potential main adsorbents of DOM, possibly dissolve, the importance of adsorption seems questionable. Therefore, we studied the adsorption of DOM to selected soil minerals and to mineral soils under oxic and anoxic conditions. In detail, we tested the following hypotheses: 1. Minerals and soils adsorb less DOM under anoxic conditions than under oxic ones. 2. The reduced adsorption under anoxic conditions is result of the smaller adsorption to hydrous Fe oxides whereas adsorption to clay minerals and Al hydroxides is not sensitive to changes in redox conditions 3. DOM adsorption will increase with the number of redox cycles, thus time of soil formation, due to increasing contents of poorly crystalline Fe oxides. This will, however, cause a stronger sensitivity to redox changes as poor crystalline Fe oxides are more reactive. 4. Aromatic compounds, being preferentially adsorbed under oxic conditions, will be less strongly adsorbed under anoxic conditions. We chose paddy soils as models because their periodically and regular exposure to changing redox cycles, with anoxic conditions during the rice growing period and oxic conditions during harvest and growth of other crops. Soils of a unique chronosequence of paddy soils (50, 300, 700 and 2000 years) in China were studied in direct comparison to non-paddy soils of the same age. In additions, selected soil minerals (goethite, ferrihydrite, amorphous Al hydroxide, hydrobiotite, nontronite and ripodolite), differing in their response to changes in redox conditions, were studied in order to indentify those mineral constituents responsible for redox-induced changes in DOM adsorption to the test soils. The DOM for the adsorption was extracted from composted rice straw as a surrogate for DOM percolating in paddy soils. Batch adsorption experiments were carried out with DOM pre-incubated to give oxic and anoxic conditions and maintaining these redox conditions during the whole procedure. The redox potential resulting from anoxic pre-incubation was about 100 mV, thus in the range of Fe reduction. Besides of dissolved organic carbon (DOC), we determined changes in the composition of DOM by the specific UV absorbance. We also analyzed main cations, anions and redox-sensitive elements to give a comprehensive picture of the effects of changing redox conditions on the dynamics of organic C, N, P, S, Fe and Al. First results indicated indeed less adsorption of DOM to Fe oxides under anoxic than under oxic conditions, with a more pronounced effect for ferrihydrite than for goethite. Maximum adsorption of DOM was more than 50% larger under oxic than under anoxic conditions. The effect was less pronounced but still detectable for clay minerals such as hydrobiotite, nontronite, and ripodolite. The specific UV absorbance of DOM contact with minerals was 20-50% stronger under anoxic than under oxic conditions. These changes in DOM composition indicated that preferential adsorption of aromatic compounds might be limited to aerated soils. We conclude that adsorption, although less strong than under oxic conditions, is an important mechanism of DOM retention also under anoxic conditions. Decreasing amounts of adsorbed DOM and changes in its composition might result in a less effective sorptive stabilization against microbial decay under anoxic than under oxic conditions.

Photoreduction fuels biogeochemical cycling of iron in Spain's acid rivers

USGS Publications Warehouse

Gammons, C.H.; Nimick, D.A.; Parker, S.R.; Snyder, D.M.; McCleskey, R. Blaine; Amils, R.; Poulson, S.R.

2008-01-01

A number of investigations have shown that photoreduction of Fe(III) causes midday accumulations of dissolved Fe(II) in rivers and lakes, leading to large diel (24-h) fluctuations in the concentration and speciation of total dissolved iron. Less well appreciated is the importance of photoreduction in providing chemical energy for bacteria to thrive in low pH waters. Diel variations in water chemistry from the highly acidic (pH 2.3 to 3.1) Ri??o Tinto, Ri??o Odiel, and Ri??o Agrio of southwestern Spain (Iberian Pyrite Belt) resulted in daytime increases in Fe(II) concentration of 15 to 66????M at four diel sampling locations. Dissolved Fe(II) concentrations increased with solar radiation, and one of the stream sites showed an antithetic relationship between dissolved Fe(II) and Fe(III) concentrations; both results are consistent with photoreduction. The diel data were used to estimate rates of microbially catalyzed Fe(II) oxidation (1 to 3??nmol L- 1 s- 1) and maximum rates of Fe(III) photoreduction (1.7 to 4.3??nmol L- 1 s- 1). Bioenergetic calculations indicate that the latter rates are sufficient to build up a population of Fe-oxidizing bacteria to the levels observed in the Ri??o Tinto in about 30??days. We conclude that photoreduction plays an important role in the bioenergetics of the bacterial communities of these acidic rivers, which have previously been shown to be dominated by autotrophic Fe(II)-oxidizers such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans. Given the possibility of the previous existence of acidic, Fe(III)-rich water on Mars, photoreduction may be an important process on other planets, a fact that could have implications to astrobiological research. ?? 2008 Elsevier B.V. All rights reserved.

Solubility, Partitioning, and Speciation of Carbon in Shallow Magma Oceans of Terrestrial Planets Constrained by High P-T Experiments

NASA Astrophysics Data System (ADS)

Chi, H.; Dasgupta, R.; Shimizu, N.

2011-12-01

Deep planetary volatile cycles have a critical influence on planetary geodynamics, atmospheres, climate, and habitability. However, the initial conditions that prevailed in the early, largely molten Earth and other terrestrial planets, in terms of distribution of volatiles between various reservoirs - metals, silicates, and atmosphere - remains poorly constrained. Here we investigate the solubility, partitioning, and speciation of carbon-rich volatile species in a shallow magma ocean environment, i.e., in equilibrium with metallic and silicate melts. A series of high pressure-temperature experiments using a piston cylinder apparatus were performed at 1-3 GPa, 1500-1800 °C on synthetic basaltic mixtures + Fe-Ni metal powders contained in graphite capsules. All the experiments produced glassy silicate melt pool in equilibrium with quenched metal melt composed of dendrites of cohenite and kamacite. Major element compositions of the resulting phases and the carbon content of metallic melts were analyzed by EPMA at NASA-JSC. Carbon and hydrogen concentrations of basaltic glasses were determined using Cameca IMS 1280 SIMS at WHOI and speciation of dissolved volatiles was constrained using FTIR and Raman spectroscopy at Rice University. Based on the equilibria - FeO (silicate melt) = Fe (metal alloy melt) + 1/2O2, we estimate the oxygen fugacity of our experiments in the range of ΔIW of -1 to -2. FTIR analysis on doubly polished basaltic glass chips suggests that the concentrations of dissolved CO32- or molecular CO2 are negligible in graphite and metal saturated reduced conditions, whereas the presence of dissolved OH- is evident from the asymmetric peak at 3500 cm-1. Collected Raman spectra of basaltic glasses in the frequency range of 200-4200 cm-1 suggest that hydrogen is present both as dissolved OH- species (band at 3600 cm-1) and as molecular H2 (band near 4150 cm-1) for all of our experiments. Faint peaks near 2915 cm-1 and consistent peaks near 740 cm-1 suggest that possible carbon species in our reduced glasses are likely minor CH4 and Si-C, respectively and are consistent with the recent solubility studies at reduced conditions [1,2]. Carbon solubility (calibrated using 12C/30Si) at graphite saturation in our reduced basaltic glasses is only in the range 20-100 ppm C, with H2O contents in the range of 0.2-0.7 wt.%. In contrast to the low dissolved carbon concentration in the basaltic silicate melts, carbon solubility in quenched metallic melts vary in the range of 5-7 wt.%. Our preliminary work indicates that the solubility of carbon in reduced basaltic melts relevant for early magma conditions may be several orders of magnitude lower compared to the solubility of carbon in modern terrestrial basalts. This coupled with significant solubility of carbon in Fe-Ni metallic melt suggests that most of magma ocean carbon was likely partitioned into deep metallic melts. Further metal-silicate experiments with more depolymerized basaltic melts of variable compositions are underway and will be presented. [1] Kadik et al. JPetrol 45, 1297-1310, 2004; [2] Kadik et al. Geochem Int 44, 33-47, 2006.

In-situ arsenic remediation by aquifer iron coating: Field trial in the Datong basin, China

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Xianjun; Pi, Kunfu; Liu, Yaqing

2016-01-01

In situ As removal from groundwater used for water supply has been performed in Daying village of Shanyin County where mild alkaline groundwater contains high dissolved As concentration. The objective of this study was to evaluate in situ As treatment by aquifer Fe coating technology. The groundwater in the studied aquifer contains As dominated by aqueous As(III) and low dissolved Fe(II) concentration, which are unfavorable conditions for forming Fe-oxides/hydroxides for As removal. In addition, high As(III) concentration limits As adsorption onto Fe-oxides/hydroxides. Accordingly, dissolved Fe(II) (5mM) and NaClO (5mM) were injected into the studied aquifer to form Fe-oxides/hydroxides and oxidizemore » As(III) to As(V), creating favorable conditions for As removal via adsorption and/or co-precipitation. During alternatively cycled injection of Fe(II) and NaClO, the As concentration in groundwater from the pumping well significantly decreased to below drinking water standard. The developed approach can be applied similarly in many parts of the world containing high As concentrations.« less

Iron: A Biogeochemical Engine That Drives Carbon, Nitrogen, and Phosphorus Cycling in Humid Tropical Forest Soils

NASA Astrophysics Data System (ADS)

Silver, W. L.; Hall, S. J.; Thompson, A.; Yang, W. H.

2014-12-01

The abundance of redox active Fe minerals has the potential to alter the storage and loss of C, contribute to gaseous N emissions, and control P retention in upland tropical forest soils. High concentrations of short-range order Fe minerals led to Fe(II) production rates of 26-206 μg g d-1 under short-term low redox conditions (Chacón et al. 2006, Liptzin and Silver 2009, Dubinsky et al. 2010). Potential C mineralization from Fe(II) reduction was 34-263 g CO2-C m-2 y-1, C losses equivalent to approximately 10-60 % of annual litterfall production in this forest. Decreased acidity during Fe reduction can destabilize soil aggregates and lead to C losses. Iron is rapidly reoxidized during aerobic periods, which can subsequently lead to C stabilization via complexation reactions. Fe oxidation can also stimulate C losses via pH-driven dissolved organic C production and directly via Fenton reactions. In laboratory experiments, rates of CO2 production were strongly linearly correlated with Fe(II) loss under aerobic conditions, increasing by 0.51 ± 0.02 µg CO2-C g soil h-1 respired for each mg of Fe(II) g-1 soil oxidized or sorbed (Hall and Silver 2013). Iron oxidation has also been linked to dissimilatory NO3- reduction to NH4+ leading to N retention in ecosystems. Fe(III) reduction coupled with NH4+ oxidation (Feammox) can lead to N losses as dinitrogen gas (N2) or nitrous oxide (N2O), a potent greenhouse gas. Estimates suggest that Feammox resulted in gaseous N losses of 1-4 kg N ha-1 y-1 (Yang et al. 2012), rates equivalent to total denitrification in this forest. Oxidized Fe can strongly bind P decreasing it's availability to plant roots. While this is commonly cited as a potential limitation to net primary production in tropical forests, it also helps to retain P in ecosystems with high rainfall and potential leaching losses. Microbial biomass P availability increased significantly with Fe(II) production, suggesting the P mobilized during Fe(II) reduction was rapidly immobilized into biological pools (Liptzin and Silver 2009). Data suggest that Fe-redox cycling may decrease P limitation to NPP, and help maintain forest nutrient stocks. In summary, our results highlight the biogeochemical significance of Fe cycling in upland soils environments and its important role in the dynamics of humid tropical forests.

Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation

USGS Publications Warehouse

Schroth, A.W.; Crusius, John; Chever, F.; Bostick, B.C.; Rouxel, O.J.

2011-01-01

Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic composition is indicative of mechanical weathering as the Fe source. Conversely, Fe fluxes from boreal-forested systems have higher dissolved Fe concentrations corresponding to higher DOC concentrations. Iron colloids and suspended sediment consist of Fe (hydr)oxides and organic complexes. These watersheds have an iron isotopic composition indicative of an internal chemical processing source. We predict that as the GoA watershed evolves due to deglaciation, so will the source, flux, and chemical nature of riverine Fe loads, which could have significant ramifications for Alaskan marine and freshwater ecosystems.

Diurnal variations in, and influences on, concentrations of particulate and dissolved arsenic and metals in the mildly alkaline Wallkill River, New Jersey, USA

NASA Astrophysics Data System (ADS)

Barringer, Julia L.; Wilson, Timothy P.; Szabo, Zoltan; Bonin, Jennifer L.; Fischer, Jeffrey M.; Smith, Nicholas P.

2008-01-01

Diurnal variations in particulate and dissolved As and metal concentrations were observed in mildly alkaline water from a wetlands site on the Wallkill River in northwestern New Jersey. The site, underlain by glacial sediments over dolomite bedrock, is 10 km downstream from a mined area of the Franklin Marble, host to Zn ores, also As and Mn minerals. In mid-September 2005, maxima and minima in dissolved-oxygen-concentration and pH, typically caused by photosynthesis and respiration, occurred at 2000 and 0800 hours. Concentrations of dissolved As (1.52-1.95 μg/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 μg/L, respectively) were lowest at dusk and peaked at 1000 hours. These opposing cycles probably reflect sorption and desorption of As (an anion), and Mn and Zn (cations) as pH varied throughout the 24-h period. Doubly-peaked cycles of B, Cl, SO4, and nutrients also were observed; these may result from upstream discharges of septic-system effluent. Both recoverable amd particulate Al, Fe, Mn, and Zn concentrations peaked between 0200 and 0600 hours. The particulate metals cycle, with perturbations at 0400 hours, may be influenced by biological activity.

Influence of Dissolved Organic Matter and Fe (II) on the Abiotic Reduction of Pentachloronitrobenzene

EPA Science Inventory

Nitroaromatic pesticides (NAPs) are hydrophobic contaminants that can accumulate in sediments by the deposition of suspended solids from surface waters. Fe(II) and dissolved organic matter (DOM), present in suboxic and anoxic zones of freshwater sediments, can transform NAPs in n...

Orientation relationship of eutectoid FeAl and FeAl2.

PubMed

Scherf, A; Kauffmann, A; Kauffmann-Weiss, S; Scherer, T; Li, X; Stein, F; Heilmaier, M

2016-04-01

Fe-Al alloys in the aluminium range of 55-65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl 2 , which is caused by a eutectoid decomposition of the high-temperature Fe 5 Al 8 phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl 2 has previously been studied by Bastin et al. [ J. Cryst. Growth (1978 ▸), 43 , 745] and Hirata et al. [ Philos. Mag. Lett. (2008 ▸), 88 , 491]. Since both results are based on different crystallographic data regarding FeAl 2 , the data are re-evaluated with respect to a recent re-determination of the FeAl 2 phase provided by Chumak et al. [ Acta Cryst. (2010 ▸), C 66 , i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl 2 crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉 FeAl || solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl 2 was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by ([Formula: see text]01) FeAl || (114)[Formula: see text] and [111] FeAl || [1[Formula: see text]0][Formula: see text]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe 5 Al 8 , FeAl and FeAl 2 in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be accommodated at the interface of FeAl and FeAl 2 .

Assessing bioavailability levels of metals in effluent-affected rivers: effect of Fe(III) and chelating agents on the distribution of metal speciation.

PubMed

Han, Shuping; Naito, Wataru; Masunaga, Shigeki

To assess the effects of Fe(III) and anthropogenic ligands on the bioavailability of Ni, Cu, Zn, and Pb, concentrations of bioavailable metals were measured by the DGT (diffusive gradients in thin films) method in some urban rivers, and were compared with concentrations calculated by a chemical equilibrium model (WHAM 7.0). Assuming that dissolved Fe(III) (<0.45 μm membrane filtered) was in equilibrium with colloidal iron oxide, the WHAM 7.0 model estimated that bioavailable concentrations of Ni, Cu, and Zn were slightly higher than the corresponding values estimated assuming that dissolved Fe(III) was absent. In contrast, lower levels of free Pb were predicted by the WHAM 7.0 model when dissolved Fe(III) was included. Estimates showed that most of the dissolved Pb was present as colloidal iron-Pb complex. Ethylene-diamine-tetra-acetic acid (EDTA) concentrations at sampling sites were predicted from the relationship between EDTA and the calculated bioavailable concentration of Zn. When both colloidal iron and predicted EDTA concentrations were included in the WHAM 7.0 calculations, dissolved metals showed a strong tendency to form EDTA complexes, in the order Ni > Cu > Zn > Pb. With the inclusion of EDTA, bioavailable concentrations of Ni, Cu, and Zn predicted by WHAM 7.0 were different from those predicted considering only humic substances and colloidal iron.

In situ arsenic removal in an alkaline clastic aquifer

USGS Publications Warehouse

Welch, A.H.; Stollenwerk, K.G.; Paul, A.P.; Maurer, D.K.; Halford, K.J.

2008-01-01

In situ removal of As from ground water used for water supply has been accomplished elsewhere in circum-neutral ground water containing high dissolved Fe(II) concentrations. The objective of this study was to evaluate in situ As ground-water treatment approaches in alkaline ground-water (pH > 8) that contains low dissolved Fe (

Ocean Compositions on Europa and Ganymede

NASA Astrophysics Data System (ADS)

Leitner, M. A.; Bothamy, N.; Choukroun, M.; Pappalardo, R. T.; Vance, S.

2014-12-01

The ocean compositions of icy Galilean satellites Europa and Ganymede are highly uncertain. Spectral observations of the satellites' surfaces provide clues for the interior composition. Putative sulfate hydration features in Galileo near-infrared reflectance spectra suggest fractionation of Na and Mg sulfates from a subsurface reservoir (McCord et al. 1998, Sci. 278, 271; McCord et al. 1998, Sci. 280, 1242; Dalton et al. 2005, Icarus, 177, 472). Recent spatially resolved spectral mapping of Europa hints at possible partitioning of near-surface brines in Europa's low-lying planes (Shirley et al. 2010; Icarus, 210, 358; Dalton et al. 2012; J. Geophys. Res. 117, E03003). Surface materials can be modified by the delivery of material from impacts and Io's active volcanoes as well as intense irradiation from Jupiter's magnetic field interaction with the jovian magnetosphere. These factors, combined with observations of high Cl/K ratios in Europa's exosphere, have led other investigators to suggest that Europa's ocean is dominated by dissolved chloride rather than sulfate (Brown and Hand 2013; Astr. J. 145, 110). There is still much uncertainty regarding how well the surface composition approximates the interior ocean composition. Exogenic materials, seafloor hydrothermal processes, and fractional crystallization during ice formation will determine the abundances of species in the ocean and by extension those present on Europa's surface. We develop a bottom-up model for oceans on Europa and Ganymede, assuming initial compositions of chondritic and cometary materials including an Fe core for Europa and an Fe-FeS eutectic core for Ganymede. We calculate an ocean composition by employing a Bulk Silicate Earth approach, also used by Zolotov and Shock (2001; J. Geophys. Res. 106, 32815) at Europa, which assess element partitioning between the rocky mantle, Fe-rich core, and water ocean. Partitioning factors are based on terrestrial estimates for Earth. The resulting ocean composition is used to assess solid precipitation into the ocean and ice shell using FREZCHEM modeling software (Marion et al. 2010; Icarus, 207, 675). These results are then compared with measured compositions of brines on Europa's surface. We develop the model in a way that permits ready application to other icy satellites, such as Titan or Enceladus.

Thorium distributions in high- and low-dust regions and the significance for iron supply

NASA Astrophysics Data System (ADS)

Hayes, Christopher T.; Rosen, Jeffrey; McGee, David; Boyle, Edward A.

2017-02-01

Thorium and uranium isotopes (232Th, 230Th, 238U, and 234U) were investigated to refine their use for estimating mineral dust deposition and Fe delivery to the ocean. U concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published U-salinity relationships and global average seawater isotopic composition. Near Barbados, waters affected by the Amazon outflow contained elevated 232Th. This signals one region where the thorium-dust method is inaccurate because of a confounding continental input. Dissolved 232Th fluxes in this region suggest that Amazonian Fe supply to the adjacent open ocean is much larger than local atmospheric deposition. The colloidal content of dissolved Th south of Bermuda was found to be quite small (2-6%), similar to that found north of Hawaii, despite the order of magnitude higher dust deposition in the Atlantic. This finding supports the assumption that dissolved 232Th and 230Th are scavenged at the same rate despite their different sources and also sheds light on the increase of dissolved 232Th fluxes with integrated depth. Outside the region influenced by Amazon River waters, dissolved 232Th fluxes are compared with Bermudan aerosol Fe deposition to estimate that fractional Th solubility is around 20% in this region. Finally, new dissolved and soluble Fe, Mn, and Cr data from the subtropical North Pacific support the idea that Fe concentrations in the remote ocean are highly buffered, whereas 232Th has a larger dynamic range between high- and low-dust regions.

Water vapor effect on high-temperature oxidation behavior of Fe3Al intermetallics

PubMed Central

Chevalier, Sebastian; Juzon, Pitor; Przybylski, Kazimierz; Larpin, Jean-Pierre

2009-01-01

Fe3Al intermetallics (Fe3Al, Fe3Al-Zr, Fe3Al-Zr,Mo and Fe3Al-Zr, Mo, Nb) were oxidized at 950 °C in dry and humid (11 vol% water) synthetic air. Thermogravimetric measurements showed that the oxidation rates of the tested intermetallics were lower in humid air than in dry air (especially for Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb). The addition of small amounts of Zr, Mo or Nb improved the kinetics compared with that of the undoped Fe3Al. Fe3Al showed massive spallation, whereas Fe3Al-Zr, Fe3Al-Zr, Mo and Fe3Al-Zr, Mo, Nb produced a flat, adherent oxide layer. The rapid transformation of transient alumina into alpha alumina may explain the decrease in the oxidation rate in humid air. PMID:27877306

The 3D Distribution of Dissolved and Colloidal Fe, Mn, Zn, Cu, Ni, Cd and Pb in the Western Antarctic Peninsula Shelf Region; Implications for Natural Fe Fertilization

NASA Astrophysics Data System (ADS)

Sherrell, R. M.; Fitzsimmons, J. N.; Roccanova, J.; Schofield, O.; Meredith, M. P.

2016-02-01

The Western Antarctic Peninsula (WAP) shelf region is is a natural Fe fertilization zone where primary production exceeds that of the adjacent open Southern Ocean. Until recently, however, distributions of Fe and of other bioactive metals were completely lacking for the WAP, and the sources and delivery mechanisms of Fe to the euphotic zone were only speculated upon. We have previously presented surface water (2m) dissolved (dTM, <0.2µm) and particulate (pTM, >0.45µm) distributions for Fe and a suite of other bioactive metals over the WAP shelf, covering the Palmer LTER sampling grid for Jan. 2010, 2011 and 2012. We now report the first complete 3D distribution of dissolved and colloidal Fe (and Mn, Zn, Cu, Ni, Cd and Pb) over the LTER grid in Jan. 2015, allowing assessment of dFe size speciation, sources and transport pathways in this dynamic shelf system. Dissolved metals were analyzed by automated offline preconcentration (seaFAST-pico, ESI) followed by sector-field ICP-MS. We confirm previous findings of low ( 0.1nM) dFe in surface waters on the mid-outer shelf in the northern portion of the grid, and now find that concentrations at this level or below persist through the euphotic zone. However, dFe increases rapidly with depth, with low surface values underlain by substantially higher concentrations even at 50m. Inner shelf surface waters are generally substantially > 0.1nM, suggesting Fe replete conditions in this region. Vertical profiles reveal that dFe generally increases with depth, much moreso in the inner shelf (dFe up to 5.0nM) than the outer shelf. A general N-S gradient in dFe is also evident, with concentrations higher in the southern WAP, especially in Marguerite Bay. In addition, shelf stations often show a dFe maximum suggesting remineralization from sinking biogenic particles. These findings for dFe and for the other metals, will be used to help unravel the biogeochemical workings of natural Fe fertilization in this region.

Arsenic release by indigenous bacteria Bacillus cereus from aquifer sediments at Datong Basin, northern China

NASA Astrophysics Data System (ADS)

Xie, Zuoming; Wang, Yanxin; Duan, Mengyu; Xie, Xianjun; Su, Chunli

2011-03-01

Endemic arsenic poisoning due to long-term drinking of high arsenic groundwater has been reported in Datong Basin, northern China. To investigate the effects of microbial activities on arsenic mobilization in contaminated aquifers, Bacillus cereus ( B. cereus) isolated from high arsenic aquifer sediments of the basin was used in our microcosm experiments. The arsenic concentration in the treatment with both bacteria and sodium citrate or glucose had a rapid increase in the first 18 d, and then, it declined. Supplemented with bacteria only, the concentration could increase on the second day. By contrast, the arsenic concentration in the treatment supplemented with sodium citrate or glucose was kept very low. These results indicate that bacterial activities promoted the release of arsenic in the sediments. Bacterial activities also influenced other geochemical parameters of the aqueous phase, such as pH, Eh, and the concentrations of dissolved Fe, Mn, and Al that are important controls on arsenic release. The removal of Fe, Mn, and Al from sediment samples was observed with the presence of B. cereus. The effects of microbial activities on Fe, Mn, and Al release were nearly the same as those on As mobilization. The pH values of the treatments inoculated with bacteria were lower than those without bacteria, still at alkaline levels. With the decrease of Eh values in treatments inoculated with bacteria, the microcosms became more reducing and are thus favorable for arsenic release.

A lower trophic ecosystem model including iron effects in the Okhotsk Sea

NASA Astrophysics Data System (ADS)

Okunishi, Takeshi; Kishi, Michio J.; Ono, Yukiko; Yamashita, Toshihiko

2007-09-01

We applied a three-dimensional ecosystem-physical coupled model including iron the effect to the Okhotsk Sea. In order to clarify the sources of iron, four dissolved iron compartments, based on the sources of supply, were added to Kawamiya et al.'s [1995, An ecological-physical coupled model applied to Station Papa. Journal of Oceanography, 51, 635-664] model (KKYS) to create our ecosystem model (KKYS-Fe). We hypothesized that four processes supply iron to sea water: atmospheric loadings from Northeastern Asia, input from the Amur River, dissolution from sediments and regeneration by zooplankton and bacteria. We simulated one year, from 1 January 2001 to 31 December 2001, using both KKYS-Fe and KKYS. KKYS could not reproduce the surface nitrate distribution after the spring bloom, whereas KKYS-Fe agreed well with observations in the northwestern Pacific because it includes iron limitation of phytoplankton growth. During the spring bloom, the main source of iron at the sea surface is from the atmosphere. The contribution of riverine iron to the total iron utilized for primary production is small in the Okhotsk Sea. Atmospheric deposition, the iron flux from sediment and regeneration of iron in the water column play important roles in maintaining high primary production in the Okhotsk Sea.

Experimental and simulation studies of iron oxides for geochemical fixation of CO2-SO2 gas mixtures

USGS Publications Warehouse

Garcia, Susana; Rosenbauer, Robert J.; Palandri, James; Maroto-Valer, M. Mercedes

2011-01-01

Iron-bearing minerals are reactive phases of the subsurface environment and could potentially trap CO2–SO2gas mixtures derived from fossil fuel combustion processes by their conversion to siderite (FeCO3) and dissolved sulfate. Changes in fluid and mineral compositions resulting from reactions, involving the co-injection of SO2 with CO2 were observed both theoretically and experimentally. Experiments were conducted with a natural hematite (α-Fe2O3) sample. A high pressure-high temperature apparatus was used to simulate conditions in geologic formations deeper than 800 m, where CO2 is in the supercritical state. Solid samples were allowed to react with a NaCl–NaOH brine and SO2-bearing CO2-dominated gas mixtures. The predicted equilibrium mineral assemblage at 100 °C and 250 bar became hematite, dawsonite (NaAl(OH)2CO3), siderite (FeCO3) and quartz (SiO2). Experimentally, siderite and dawsonite, derived from the presence of kaolinite (Al2Si2O5(OH)4) in the parent material, were present in residual solids at longer reaction time intervals, which agreed well with results from the modelling work.

A Geochemical and Mineralogical Model for Formation of Layered Sulfate Deposits at Meridiani Planum by Hydrothermal Acid-sulfate Alteration of Pyroclastic Basalt

NASA Astrophysics Data System (ADS)

McCollom, T. M.; Hynek, B. M.

2012-12-01

The Mars Exploration Rover (MER) Opportunity has extensively characterized sulfate-rich, hematite-bearing bedrock exposed at Meridiani Planum, Mars. Based on various measurements, the mineral composition of the bedrocks has been interpreted to include: amorphous silica/glass/phyllosilicates, Mg-, Ca-, and Fe-bearing sulfates including jarosite, minor amounts of igneous phases including plagioclase, pyroxene, olivine, and magnetite, and hematite [1,2]. Chemically, the bedrocks closely resemble the composition of pristine martian basalt with addition of S and O, and minor variations of Mg and Cl with depth [3,4]. Based on these and other observations, the MER team has proposed that the bedrocks represent chemically altered siliciclastic sediments combined with sulfate salts formed by evaporation of sulfate-bearing fluids, modified by transport and multiple stages of infiltrating groundwater [3,5]. Several alternative scenarios have been proposed for the origin of the rocks including large impacts [6], evaporating glacial deposits [7], acid-fog alteration [8], and hydrothermal acid-sulfate alteration of basalt [4]. In order to further evaluate the potential contribution of hydrothermal proceeses to the deposits, we performed numerical geochemical models of acid-sulfate alteration of martian basalt based on constraints provided by recent laboratory experiments. Experimental studies of alteration of basalt conducted in our lab [9] indicate that the initial stages of acid-sulfate alteration of pyroclastic basalt are characterized by rapid decomposition of igneous crystalline phases including plagioclase, pyroxene, and olivine, while the glass (and igneous phases protected within the glass) remain unreactive. Elements released by dissolving minerals are precipitated primarily as amorphous silica and Ca-, Al-, Fe- and Mg-bearing sulfates, while precipitation of phyllosilicates and Fe-oxides/oxyhydroxides (FeOx) is kinetically inhibited. Based on these constraints, models of acid-sulfate alteration of martian pyroclastic basalt predict that the early stages of alteration will produce amorphous silica, anhydrite (or gypsum at lower temperature), Fe-bearing natroalunite, and kieserite as predominant secondary phases, along with relict glass and silicates protected within the glass. Hematite may form with continued heating through partial decomposition of Fe-bearing natroalunite [9], and some of the glass phase may partially devitrify to form minor phyllosilicates such as nontronite and nanophase Fe oxides. The resulting rock would have a chemical and mineralogical composition closely resembling that observed at Meridiani Planum. We conclude that hydrothermal acid-sulfate alteration of pyroclastic basalt provides the most parsimonious explanation for the composition of the sulfate deposits. References: [1] Glotch et al., JGR (2006). [2] Klingelhöfer et al. Science (2004). [3] McLennan et al., EPSL (2005). [4] McCollom & Hynek, Nature (2005). [5] Squyres et al. Science (2006). [6] Knauth et al. Nature (2005). [7] Niles & Michalski, Nat. Geosci. (2009). [8] Berger et al. Am. Mineral. (2009). [9] McCollom et al. JGR-Planets (submitted ms.)

Distribution patterns of particulate trace metals in the water column and nepheloid layer of the Gulf of Riga.

PubMed

Poikāne, Rita; Carstensen, Jacob; Dahllöf, Ingela; Aigars, Juris

2005-07-01

The dynamics (fate) of trace metals in suspended particulate matter within the Gulf of Riga has not yet been adequately addressed in the scientific literature. Therefore, during a two year period (2001-2002) samples of suspended particulate matter and surface sediments for trace metal analysis were collected in the Gulf of Riga and the Daugava river, and these data were combined with background information from the national marine monitoring program in Latvia. This paper presents a descriptive study of solid phase trace metals (aluminium, iron, cadmium, chromium, copper, manganese, nickel, lead and zinc) dynamics and their spatial distribution within the Gulf of Riga based on Principal Component Analysis and Cluster analysis. Fluvial particulate matter and particulate Al, Fe, Cr and Ni were brought into the Gulf of Riga mainly during spring flood and thereafter quickly diluted by the water masses of the Gulf of Riga. Fine-grained suspended material and particulate Al and Fe were well mixed and evenly distributed through all deepwater basins of the Gulf of Riga. The increase of particulate Mn below the thermocline in August and a strong negative correlation with dissolved oxygen concentrations suggested that particulate Mn in the water column and the sediments were regulated mainly by changing oxic-anoxic conditions in the sediments of the Gulf of Riga. The observed correlation between Al and Fe in the water column is in contrast to that observed in the nepheloid layer where Fe correlated with Mn, obviously due to fast diagenetic processes on sediment surface. The observed negative correlation of Cd and Zn with total carbon and total nitrogen in the nepheloid layer might indicate different sedimentation mechanisms of these elements, however, this assumption is still inconclusive.

EFFECT OF Mg AND TEMPERATURE ON Fe-Al ALLOY LAYER IN Fe/(Zn-6%Al-x%Mg) SOLID-LIQUID DIFFUSION COUPLES

NASA Astrophysics Data System (ADS)

Liang, Liu; Liu, Ya-Ling; Liu, Ya; Peng, Hao-Ping; Wang, Jian-Hua; Su, Xu-Ping

Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe-Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe-Al alloy layer. It was found that the Fe2Al5Znx phase layer forms close to the iron sheet and the FeAl3Znx phase layer forms near the side of the melted Zn-6%Al-3%Mg in diffusion couples. When the Fe/(Zn-6%Al-3%Mg) diffusion couple is kept at 510∘C for more than 15min, a continuous Fe-Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples, the Fe-Al alloy layer on the interface of the Fe/(Zn-6% Al-3% Mg) diffusion couple is the thinnest. The Fe-Al alloy layer forms only when the diffusion temperature is above 475∘. These results show that the Fe-Al alloy layer in Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples is composed of Fe2Al5Znx and FeAl3Znx phase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe-Al alloy layer. When the Mg content in the Fe/(Zn-6%Al-x%Mg) diffusion couples is 3%, the growth of the Fe-Al alloy layer is inhibited. These results may explain why there is no obvious Fe-Al alloy layer formed on the interface of steel with a Zn-6%Al-3%Mg coating.

Evolution of the chemistry of Fe bearing waters during CO2 degassing

USGS Publications Warehouse

Geroni, J.N.; Cravotta, C.A.; Sapsford, D.J.

2012-01-01

The rates of Fe(II) oxidation and precipitation from groundwater are highly pH dependent. Elevated levels of dissolved CO2 can depress pH and cause difficulty in removing dissolved Fe and associated metals during treatment of ferruginous water. This paper demonstrates interdependent changes in pH, dissolved inorganic C species, and Fe(II) oxidation rates that occur as a result of the removal (degassing) of CO2 during aeration of waters discharged from abandoned coal mines. The results of field monitoring of aeration cascades at a treatment facility as well as batchwise aeration experiments conducted using net alkaline and net acidic waters in the UK are combined with geochemical modelling to demonstrate the spatial and temporal evolution of the discharge water chemistry. The aeration cascades removed approximately 67% of the dissolved CO2 initially present but varying the design did not affect the concentration of Fe(II) leaving the treatment ponds. Continued removal of the residual CO2 by mechanical aeration increased pH by as much as 2 units and resulted in large increases in the rates of Fe(II) oxidation and precipitation. Effective exsolution of CO2 led to a reduction in the required lime dose for removal of remaining Fe(II), a very important factor with regard to increasing the sustainability of treatment practices. An important ancillary finding for passive treatment is that varying the design of the cascades had little impact on the rate of CO2 removal at the flow rates measured.

Sulfide mineralization: Its role in chemical weathering of Mars

NASA Technical Reports Server (NTRS)

Burns, Roger G.

1988-01-01

Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produced degradation products in the Martian regolith. By analogy with terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato- and hydroxo-complex ions and sols formed gossans above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite) and silica (opal). Underlying groundwater, now permafrost, contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, etc., which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates and phyllosilicates during dust storms on Mars.

Weathering of sulfides on Mars

NASA Technical Reports Server (NTRS)

Burns, Roger G.; Fisher, Duncan S.

1987-01-01

Pyrrhotite-pentlandite assemblages in mafic and ultramafic igneous rocks may have contributed significantly to the chemical weathering reactions that produce degradation products in the Martian regolith. By analogy and terrestrial processes, a model is proposed whereby supergene alteration of these primary Fe-Ni sulfides on Mars has generated secondary sulfides (e.g., pyrite) below the water table and produced acidic groundwater containing high concentrations of dissolved Fe, Ni, and sulfate ions. The low pH solutions also initiated weathering reactions of igneous feldspars and ferromagnesian silicates to form clay silicate and ferric oxyhydroxide phases. Near-surface oxidation and hydrolysis of ferric sulfato-and hydroxo-complex ions and sols formed gossan above the water table consisting of poorly crystalline hydrated ferric sulfates (e.g., jarosite), oxides (ferrihydrite, goethite), and silica (opal). Underlying groundwater, now permafrost contains hydroxo sulfato complexes of Fe, Al, Mg, Ni, which may be stabilized in frozen acidic solutions beneath the surface of Mars. Sublimation of permafrost may replenish colloidal ferric oxides, sulfates, and phyllosilicates during dust storms on Mars.

Trace metals in the Ob and Yenisei Rivers' Estuaries (the Kara Sea).

NASA Astrophysics Data System (ADS)

Demina, L. L.

2014-12-01

Behavior of some trace metals (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb) in water column (soluble <0.45 µm and particulate fractions) and bottom sediments (surface and cores) along the two transects from the Ob River and Yenisei River Estuaries to the Kara Sea was studied. The length of both transects was about 700 km. Water depth was 12-63 m, O2 dissolved :5.36-9.55 ml l-1. Along the transects salinity increased from 0.07 to 34.2 psu, while the SPM' concentration decreased from 10.31 to 0.31 mg/l. Total suspended particulate matter load is more than one order of magnitude higher in the Ob River Estuary comparing to that of the Yenisei River. It has led to a significant difference between the suspended trace metals' concentrations (µg/l) in water of the two estuaries. With salinity increase along transects Fe susp., Mn susp. and Zn susp. decreased by a factor of 100-500, that has led to a growth of a relative portion of dissolved trace metals followed by their bioaccumulation (Demina et al., 2010). A strong direct correlation between suspended Cu, Fe and SPM mass concentration was found. For the first time along the Yenisei River' Estuary -the Kara Sea transect a direct positive correlation between Cu suspended and volume concentration of SPM (mg/ml3) was found, that was attributed to contribution of phytoplankton aggregates in the SPM composition. A trend of relationship between content of suspended As and pelitic fraction (2-10 µm) of SPM was firstly found in theses basins also. Study of trace metal speciation in the bottom sediments (adsorbed, associated with Fe-Mn (oxyhydr)oxides, organic matter and fixed in the mineral lattice or refractory) has revealed the refractory fraction to be prevailing (70-95% total content) for Fe, Zn, Cu, Co, Ni, Cr, Cd and Pb. That means that toxic heavy metals were not available for bottom fauna. Mn was predominantly found in the adsorbed and (oxyhydr)oxides geochemically labile forms, reflecting the redox condition change along both transects and within the sedimentary cores. References. Demina L.L., Gordeev V.V., Galkin S.V., Kravchishina M.D. Biogeochemistry of some heavy metals and metalloids along the transect the Ob River Estuary - the Kara Sea. Oceanology, 2010, vo. 50, No 5, pp. 729- 742.

Suspended particulate matter determines physical speciation of Fe, Mn, and trace metals in surface waters of Loire watershed.

PubMed

Baalousha, Mohamed; Stoll, Serge; Motelica-Heino, Mikaël; Guigues, Nathalie; Braibant, Gilles; Huneau, Frédéric; Le Coustumer, Philippe

2018-02-10

This study investigates the spatiotemporal variability of major and trace elements, dissolved organic carbon (DOC), total dissolved solids (TDS), and suspended particulate matter (SPM) in surface waters of several hydrosystems of the Loire River watershed in France. In particular, this study aims to delineate the impact of the abovementioned water physicochemical parameters on natural iron and manganese physical speciation (homoaggregation/heteroaggregation) among fine colloidal and dissolved (< 10 nm), colloidal (10-450 nm) and particulate (> 450 nm) phases in Loire River watershed. Results show that the chemistry of the Loire River watershed is controlled by two end members: magmatic and metamorphic petrographic context on the upper part of the watershed; and sedimentary rocks for the middle and low part of the Loire. The percentage of particulate Fe and Mn increased downstream concurrent with the increase in SPM and major cations concentration, whereas the percentage of colloidal Fe and Mn decreased downstream. Transmission electron microscopy analyses of the colloidal and particulate fractions (from the non-filtered water sample) revealed that heteroaggregation of Fe and Mn rich natural nanoparticles and natural organic matter to the particulate phase is the dominant mechanism. The heteroaggregation controls the partitioning of Fe and Mn in the different fractions, potentially due to the increase in the ionic strength, and divalent cations concentration downstream, and SPM concentration. These findings imply that SPM concentration plays an important role in controlling the fate and behavior of Fe and Mn in various sized fractions. Graphical abstract Physical speciation by heteroaggregation of (Fe-Mn) compounds: high [SPM] → [Fe-Mn] particulate faction; low {SPM] → [Fe-Mn] colloid-dissolved fraction.

Coupled cycling of Fe and organic carbon in submarine hydrothermal systems: Modelling approach

NASA Astrophysics Data System (ADS)

Legendre, Louis; German, Christopher R.; Sander, Sylvia G.; Niquil, Nathalie

2014-05-01

It has been recently proposed that hydrothermal plumes may be a significant source of dissolved Fe to the oceans. In order to assess this proposal, we investigated the fate of dissolved Fe released from hydrothermal systems to the overlying ocean using an approach that combined modelling and field values. We based our work on a consensus conceptual model developed by members of SCOR-InterRidge Working Group 135. The model was both complex enough to capture the main processes of dissolved Fe released from hydrothermal systems and chemical transformation in the hydrothermal plume, and simple enough to be parameterized with existing field data. It included the following flows: Fe, water and heat in the high temperature vent fluids, in the fluids diffusing around the vent, and in the entrained seawater in the buoyant plume; Fe precipitation in polymetallic sulphides near the vent; transport of Fe in the non-buoyant plume, and both its precipitation in particles onto the sea bottom away from the vent and dissolution into deep-sea waters. In other words, there were three Fe input flows into the buoyant hydrothermal plume (vent-fluids; entrained diffuse flow; entrained seawater) and three Fe output flows (sedimentation from the buoyant plume as polymetallic sulfides; sedimentation from the non-buoyant plume in particulate form; export to the deep ocean in dissolved or nanoparticulate form). The output flows balanced the input flows. We transformed the conceptual model into equations, and parameterized these with field data. To do so, we assumed that all hydrothermal systems, globally, can be represented by the circumstances that prevail at the EPR 9°50'N hydrothermal field, although we knew this assumption not to be accurate. We nevertheless achieved, by following this approach, two important goals, i.e. we could assemble into a coherent framework, for the first time, several discrete data sets acquired independently over decades of field work, and we could obtain model results that were consistent with recent field observations. We used our model to explore scenarios of Fe emissions and transformations under various constraints. The modelling exercises indicated that the provision of significant amounts of dissolved Fe to the oceans by hydrothermal plumes was consistent with realistic model parameters. This supported the proposition that hydrothermal systems play significant roles in the global biogeochemical Fe cycle.

Sulfide oxidation and distribution of metals near abandoned copper mines in coastal environments, Prince William Sound, Alaska, USA

USGS Publications Warehouse

Koski, R.A.; Munk, L.; Foster, A.L.; Shanks, Wayne C.; Stillings, L.L.

2008-01-01

The oxidation of sulfide-rich rocks, mostly leftover debris from Cu mining in the early 20th century, is contributing to metal contamination of local coastal environments in Prince William Sound, Alaska. Analyses of sulfide, water, sediment, precipitate and biological samples from the Beatson, Ellamar, and Threeman mine sites show that acidic surface waters generated from sulfide weathering are pathways for redistribution of environmentally important elements into and beyond the intertidal zone at each site. Volcanogenic massive sulfide deposits composed of pyrrhotite and (or) pyrite + chalcopyrite + sphalerite with subordinate galena, arsenopyrite, and cobaltite represent potent sources of Cu, Zn, Pb, As, Co, Cd, and Hg. The resistance to oxidation among the major sulfides increases in the order pyrrhotite ??? sphalerite < chalcopyrite ??? pyrite; thus, pyrrhotite-rich rocks are typically more oxidized than those dominated by pyrite. The pervasive alteration of pyrrhotite begins with rim replacement by marcasite followed by replacement of the core by sulfur, Fe sulfate, and Fe-Al sulfate. The oxidation of chalcopyrite and pyrite involves an encroachment by colloform Fe oxyhydroxides at grain margins and along crosscutting cracks that gradually consumes the entire grain. The complete oxidation of sulfide-rich samples results in a porous aggregate of goethite, lepidocrocite and amorphous Fe-oxyhydroxide enclosing hydrothermal and sedimentary silicates. An inverse correlation between pH and metal concentrations is evident in water data from all three sites. Among all waters sampled, pore waters from Ellamar beach gravels have the lowest pH (???3) and highest concentrations of base metals (to ???25,000 ??g/L), which result from oxidation of abundant sulfide-rich debris in the sediment. High levels of dissolved Hg (to 4100 ng/L) in the pore waters probably result from oxidation of sphalerite-rich rocks. The low-pH and high concentrations of dissolved Fe, Al, and SO4 are conducive to precipitation of interstitial jarosite in the intertidal gravels. Although pore waters from the intertidal zone at the Threeman mine site have circumneutral pH values, small amounts of dissolved Fe2+ in the pore waters are oxidized during mixing with seawater, resulting in precipitation of Fe-oxyhydroxide flocs along the beach-seawater interface. At the Beatson site, surface waters funneled through the underground mine workings and discharged across the waste dumps have near-neutral pH (6.7-7.3) and a relatively small base-metal load; however, these streams probably play a role in the physical transport of metalliferous particulates into intertidal and offshore areas during storm events. Somewhat more acidic fluids, to pH 5.3, occur in stagnant seeps and small streams emerging from the Beatson waste dumps. Amorphous Fe precipitates in stagnant waters at Beatson have high Cu (5.2 wt%) and Zn (2.3 wt%) concentrations that probably reflect adsorption onto the extremely high surface area of colloidal particles. Conversely, crystalline precipitates composed of ferrihydrite and schwertmannite that formed in the active flow of small streams have lower metal contents, which are attributed to their smaller surface area and, therefore, fewer reactive sorption sites. Seeps containing precipitates with high metal contents may contribute contaminants to the marine environment during storm-induced periods of high runoff. Preliminary chemical data for mussels (Mytilus edulis) collected from Beatson, Ellamar, and Threeman indicate that bioaccumulation of base metals is occurring in the marine environment at all three sites.

Concentrations and distributions of metals associated with dissolved organic matter from the Suwannee River (GA, USA)

USGS Publications Warehouse

Kuhn, M. Keshia; Neubauer, Elisabeth; Hofmann, Thilo; von der Kammer, Frank; Aiken, George R.; Maurice, Patricia A.

2015-01-01

Concentrations and distributions of metals in Suwannee River (SR) raw filtered surface water (RFSW) and dissolved organic matter (DOM) processed by reverse osmosis (RO), XAD-8 resin (for humic and fulvic acids [FA]), and XAD-4 resin (for “transphilic” acids) were analyzed by asymmetrical flow field-flow fractionation (AsFlFFF). SR samples were compared with DOM samples from Nelson's Creek (NLC), a wetland-draining stream in northern Michigan; previous International Humic Substances Society (IHSS) FA and RO samples from the SR; and an XAD-8 sample from Lake Fryxell (LF), Antarctica. Despite application of cation exchange during sample processing, all XAD and RO samples contained substantial metal concentrations. AsFlFFF fractograms allowed metal distributions to be characterized as a function of DOM component molecular weight (MW). In SR RFSW, Fe, Al, and Cu were primarily associated with intermediate to higher than average MW DOM components. SR RO, XAD-8, and XAD-4 samples from May 2012 showed similar MW trends for Fe and Al but Cu tended to associate more with lower MW DOM. LF DOM had abundant Cu and Zn, perhaps due to amine groups that should be present due to its primarily algal origins. None of the fractograms showed obvious evidence for mineral nanoparticles, although some very small mineral nanoparticles might have been present at trace concentrations. This research suggests that AsFlFFF is important for understanding how metals are distributed in different DOM samples (including IHSS samples), which may be key to metal reactivity and bioavailability.

The effect of annealing on structure and hardness of (Fe-Cr)-50 at.% Al coatings synthesized by mechanical alloying

NASA Astrophysics Data System (ADS)

Ciswandi, Aryanto, Didik; Irmaniar, Tjahjono, Arif; Sudiro, Toto

2018-05-01

In this research, the deposition of (Fe-Cr)-50at.% Al coatings on low carbon steel was carried out by a mechanical alloying (MA) technique. The MA was performed in a shaker mill for 4 hours. Two types of Fe-Cr powders as starting material were used, high purity Fe-Cr powders: (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al, and Fe-Cr lump powder: (50FeCr)-50Al (in at.%). The coated samples were then annealed in a vacuum furnace at 700°C for 1h. The characterizations of coating structure before and after annealing were studied by XRD and SEM-EDX, while the coating hardness was measured by micro-Vickers hardness tester. Before annealing, all of coating composition were composed mainly of (Fe,Cr)Al phase. After annealing, the FeAl and Fe0.99Cr0.02Al0.99 intermetallic phases was formed in the (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al coatings. In addition, Fe2CrAlwas also found in the (Fe-25Cr)-50Al coating. Whilethe AlCr2 intermetallic phase was detected as the main phase of (50FeCr)-50Al coating. The cross-sectional microstructure showed that the (Fe-12.5Cr)-50Al and (Fe-25Cr)-50Al coatings have a smoother structure compared to (50FeCr)-50Al coating. The annealing led to intermetallic phase formation and an increasing coating hardness.

Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

NASA Astrophysics Data System (ADS)

Shi, Z.; Bonneville, S.; Krom, M. D.; Carslaw, K. S.; Jickells, T. D.; Baker, A. R.; Benning, L. G.

2010-11-01

We investigated the iron (Fe) dissolution kinetics of African (Tibesti) and Asian (Beijing) dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust (<20 μm: PM20; <10 μm: PM10; and <2.5 μm: PM2.5) were dissolved at pH 1, 2 and/or 3 for up to 1000 h. In the first 10 min, all dust samples underwent an extremely fast Fe solubilisation. Subsequently, the Fe dissolution proceeded at a much slower rate before reaching a stable dissolution plateau. The time-dependant Fe dissolution datasets were best described by a model comprising three acid-extractable Fe pools each dissolving according to first-order kinetics. The dissolution rate constant k of each pool was independent of the source (Saharan or Asian) and the size (PM20, PM10 or PM2.5) of the dust but highly dependent on pH. The "fast" Fe pool had a k (25 h-1 at pH=1) of a similar magnitude to "dry" ferrihydrite nanoparticles and/or poorly crystalline Fe(III) oxyhydroxide, while the "intermediate" and "slow" Fe pools had k values respectively 50-60 times and 3000-4000 times smaller than the "fast" pool. The "slow" Fe pool was likely to consist of both crystalline Fe oxide phases (i.e., goethite and/or hematite) and Fe contained in the clay minerals. The initial mass of the "fast", "intermediate" and "slow" Fe pools represented respectively about 0.5-2%, 1-3% and 15-40% of the total Fe in the dust samples. Furthermore, we showed that in systems with low dust/liquid ratios, Fe can be dissolved from all three phases, whereas at high dust/liquid ratios (e.g., in aerosols), sufficient Fe is solubilised from the "fast" phase to dominate the Fe dissolved and to suppress the dissolution of Fe from the other Fe pools. These data demonstrated that dust/liquid ratio and pH are fundamental parameters controlling Fe dissolution kinetics in the dust. In order to reduce errors in atmospheric and climate models, these fundamental controlling factors need to be included.

Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

NASA Astrophysics Data System (ADS)

Shi, Z.; Bonneville, S.; Krom, M. D.; Carslaw, K. S.; Jickells, T. D.; Baker, A. R.; Benning, L. G.

2011-02-01

We investigated the iron (Fe) dissolution kinetics of African (Tibesti) and Asian (Beijing) dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust (<20 μm: PM20; <10 μm: PM10; and <2.5 μm: PM2.5) were dissolved at pH 1, 2 and/or 3 for up to 1000 h. In the first 10 min, all dust samples underwent an extremely fast Fe solubilisation. Subsequently, the Fe dissolution proceeded at a much slower rate before reaching a stable dissolution plateau. The time-dependant Fe dissolution datasets were best described by a model comprising three acid-extractable Fe pools each dissolving according to first-order kinetics. The dissolution rate constant k (h-1) of each pool was independent of the source (Saharan or Asian) and the size (PM20, PM10 or PM2.5) of the dust but highly dependent on pH. The "fast" Fe pool had a k (25 h-1 at pH = 1) of a similar magnitude to "dry" ferrihydrite nanoparticles and/or poorly crystalline Fe(III) oxyhydroxide, while the "intermediate" and "slow" Fe pools had k values respectively 50-60 times and 3000-4000 times smaller than the "fast" pool. The "slow" Fe pool was likely to consist of both crystalline Fe oxide phases (i.e., goethite and/or hematite) and Fe contained in the clay minerals. The initial mass of the "fast", "intermediate" and "slow" Fe pools represented respectively about 0.5-2%, 1-3% and 15-40% of the total Fe in the dust samples. Furthermore, we showed that in systems with low dust/liquid ratios, Fe can be dissolved from all three pools, whereas at high dust/liquid ratios (e.g., in aerosols), sufficient Fe may be solubilised from the "fast" phase to dominate the Fe dissolved and to suppress the dissolution of Fe from the other Fe pools. These data demonstrated that dust/liquid ratio and pH are fundamental parameters controlling Fe dissolution kinetics in the dust. In order to reduce errors in atmospheric and climate models, these fundamental controlling factors need to be included.

Enhanced coagulation for improving coagulation performance and reducing residual aluminum combining polyaluminum chloride with diatomite.

PubMed

Hu, Wenchao; Wu, Chunde

2016-01-01

The feasibility of using enhanced coagulation, which combined polyaluminum chloride (PAC) with diatomite for improving coagulation performance and reducing the residual aluminum (Al), was discussed. The effects of PAC and diatomite dosage on the coagulation performance and residual Al were mainly investigated. Results demonstrated that the removal efficiencies of turbidity, dissolved organic carbon (DOC), and UV254 were significantly improved by the enhanced coagulation, compared with PAC coagulation alone. Meaningfully, the five forms of residual Al (total Al (TAl), total dissolved Al (TDAl), dissolved organic Al (DOAl), dissolved monomeric Al (DMAl), and dissolved organic monomeric Al (DOMAl)) all had different degrees of reduction in the presence of diatomite and achieved the lowest concentrations (0.185, 0.06, 0.053, 0.014, and 0 mg L(-1), respectively) at a PAC dose of 15 mg L(-1) and diatomite dose of 40 mg L(-1). In addition, when PAC was used as coagulant, the majority of residual Al existed in dissolved form (about 31.14-70.16%), and the content of DOMAl was small in the DMAl.

Microstructure and Properties of Fe3Al-Fe3AlC x Composite Prepared by Reactive Liquid Processing

NASA Astrophysics Data System (ADS)

Verona, Maria Nalu; Setti, Dalmarino; Paredes, Ramón Sigifredo Cortés

2018-04-01

A Fe3Al-Fe3AlC x composite was prepared using reactive liquid processing (RLP) through controlled mixture of carbon steel and aluminum in the liquid state. The microstructure and phases of the composite were assessed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, optical microscopy, and differential scanning calorimetry. In addition, the density, hardness, microhardness, and elastic modulus were evaluated. The Fe3Al-Fe3AlC x composite consisted of 65 vol pct Fe3Al and 35 vol pct Fe3AlC x ( κ). The κ phase contained 10.62 at. pct C, resulting in the stoichiometry Fe3AlC0.475. The elastic modulus of the Fe3Al-Fe3AlC0.475 composite followed the rule of mixtures. The RLP technique was shown to be capable of producing Fe3Al-Fe3AlC0.475 with a microstructure and properties similar to those achieved using other processing techniques reported in the literature.

Assessing element distribution and speciation in a stream at abandoned Pb-Zn mining site by combining classical, in-situ DGT and modelling approaches.

PubMed

Omanović, Dario; Pižeta, Ivanka; Vukosav, Petra; Kovács, Elza; Frančišković-Bilinski, Stanislav; Tamás, János

2015-04-01

The distribution and speciation of elements along a stream subjected to neutralised acid mine drainage (NAMD) effluent waters (Mátra Mountain, Hungary; Toka stream) were studied by a multi-methodological approach: dissolved and particulate fractions of elements were determined by HR-ICPMS, whereas speciation was carried out by DGT, supported by speciation modelling performed by Visual MINTEQ. Before the NAMD discharge, the Toka is considered as a pristine stream, with averages of dissolved concentrations of elements lower than world averages. A considerable increase of element concentrations caused by effluent water inflow is followed by a sharp or gradual concentration decrease. A large difference between total and dissolved concentrations was found for Fe, Al, Pb, Cu, Zn and As in effluent water and at the first downstream site, with high correlation factors between elements in particulate fraction, indicating their common behaviour, governed by the formation of ferri(hydr)oxides (co)precipitates. In-situ speciation by the DGT technique revealed that Zn, Cd, Ni, Co, Mn and U were predominantly present as a labile, potentially bioavailable fraction (>90%). The formation of strong complexes with dissolved organic matter (DOM) resulted in a relatively low DGT-labile concentration of Cu (42%), while low DGT-labile concentrations of Fe (5%) and Pb (12%) were presumably caused by their existence in colloidal (particulate) fraction which is not accessible to DGT. Except for Fe and Pb, a very good agreement between DGT-labile concentrations and those predicted by the applied speciation model was obtained, with an average correlation factor of 0.96. This study showed that the in-situ DGT technique in combination with model-predicted speciation and classical analysis of samples could provide a reasonable set of data for the assessment of the water quality status (WQS), as well as for the more general study of overall behaviour of the elements in natural waters subjected to high element loads. Copyright © 2014 Elsevier B.V. All rights reserved.

A Re-evaluation of the Ferrozine Method for Dissolved Iron: The Effect of Organic Interferences

NASA Astrophysics Data System (ADS)

Balind, K.; Barber, A.; Gelinas, Y.

2016-12-01

Among the most commonly used analytical methods in geochemistry is the ferrozine method for determining dissolved iron concentration in water (1). This cheap and easy-to-use spectrophotometric method involves a complexing agent (ferrozine), a reducing agent (hydroxylamine-HCl) and buffer (ammonium acetate with ammonium hydroxide). Previous studies have demonstrated that complex organic matter (OM) originating from the Suwannee River did not lead to a significantly underestimation of the measured iron content in OM amended iron solutions (2). The authors concluded that this method could be used even in organic rich (i.e., 25 mg/L) waters. Here we compare the concentration of Fe measured using this spectrophotometric method to the total Fe as measured by ICP-MS in the presence/absence of specific organic molecules to ascertain if they interfere with the ferrozine method. We show that certain molecules with hydroxyl and carboxyl functional groups as well as multi-dentate chelating species have a significant effect on the measured iron concentrations. Two possible mechanisms likely are responsible for the inefficiency of this method in the presence of specific organic molecules; 1) incomplete reduction of Fe(III) bound to organic molecules, or 2) competition between the OM and ferrozine for the available iron. We address these possibilities separately by varying the experimental conditions. These methodological artifacts may have far reaching implications due to the extensive use of this method. Stookey, L. L., Anal. Chem., 42, 779 (1970). Viollier, E., et al., Applied Geochem., 15, 785 (2000).

Geochemical evolution of acidic ground water at a reclaimed surface coal mine in western Pennsylvania

USGS Publications Warehouse

Cravotta,, Charles A.

1991-01-01

Concentrations of dissolved sulfate and acidity in ground water increase downflow in mine spoil and underlying bedrock at a reclaimed surface coal mine in the bituminous field of western Pennsylvania. Elevated dissolved sulfate and negligible oxygen in ground water from bedrock about 100 feet below the water table suggest that pyritic sulfur is oxidized below the water table, in a system closed to oxygen. Geochemical models for the oxidation of pyrite (FeS2) and production of sulfate (SO42-) and acid (H+) are presented to explain the potential role of oxygen (O2) and ferric iron (Fe3+) as oxidants. Oxidation of pyrite by O2 and Fe3+ can occur under oxic conditions above the water table, whereas oxidation by Fe3+ also can occur under anoxic conditions below the water table. The hydrated ferric-sulfate minerals roemerite [Fe2+Fe43+(SO4)4·14H2O], copiapite [Fe2+Fe43+(SO4)6(OH)2·20H20], and coquimbite [Fe2(SO4)3·9H2O] were identified with FeS2 in coal samples, and form on the oxidizing surface of pyrite in an oxic system above the water table. These soluble ferric-sulfate 11 salts11 can dissolve with recharge waters or a rising water table releasing Fe3+, SO42-. and H+, which can be transported along closed-system ground-water flow paths to pyrite reaction sites where O2 may be absent. The Fe3+ transported to these sites can oxidize pyritic sulfur. The computer programs WATEQ4F and NEWBAL were used to compute chemical speciation and mass transfer, respectively, considering mineral dissolution and precipitation reactions plus mixing of waters from different upflow zones. Alternative mass-balance models indicate that (a) extremely large quantities of O2, over 100 times its aqueous solubility, can generate the observed concentrations of dissolved SO42- from FeS2, or (b) under anoxic conditions, Fe3+ from dissolved ferric-sulfate minerals can oxidize FeS2 along closed-system ground-water flow paths. In a system open to O2, such as in the unsaturated zone, the aqueous solubility of O2 is not limiting, and oxidation of pyrite by O2 and Fe3+ accounts for most SO42- and Fe2+ observed in acidic ground water. However, in a system closed to O2, such as in the saturated zone, O2 solubility is limiting; hence, ferric oxidation of pyrite is a reasonable explanation for the observed elevated SO42- with increasing depth below the water table.

Iron oxidation kinetics and phosphorus immobilization at the groundwater-surface water interface

NASA Astrophysics Data System (ADS)

van der Grift, Bas; Rozemeijer, Joachim; Griffioen, Jasper; van der Velde, Ype

2014-05-01

Eutrophication of freshwater environments following diffuse nutrient loads is a widely recognized water quality problem in catchments. Fluxes of non-point P sources to surface waters originate from surface runoff and flow from soil water and groundwater into surface water. The availability of P in surface waters is controlled strongly by biogeochemical nutrient cycling processes at the soil-water interface. The mechanisms and rates of the iron oxidation process with associated binding of phosphate during exfiltration of anaerobic Fe(II) bearing groundwater are among the key unknowns in P retention processes in surface waters in delta areas where the shallow groundwater is typically pH-neutral to slightly acid, anoxic, iron-rich. We developed an experimental field set-up to study the dynamics in Fe(II) oxidation and mechanisms of P immobilization at the groundwater-surface water interface in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. The exfiltrating groundwater was captured in in-stream reservoirs constructed in the ditch. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we quantified Fe(II) oxidation kinetics and P immobilization processes across the seasons. This study showed that seasonal changes in climatic conditions affect the Fe(II) oxidation process. In winter time the dissolved iron concentrations in the in-stream reservoirs reached the levels of the anaerobic groundwater. In summer time, the dissolved iron concentrations of the water in the reservoirs are low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into the reservoirs. Higher discharges, lower temperatures and lower pH of the exfiltrated groundwater in winter compared to summer shifts the location of the redox transition zone, with Fe(II) oxidation taking place in the soil surrounding the ditch during summer and in the surface water during winter. The dynamics in Fe(II) oxidation did not affect the dissolved P concentrations. The dissolved P concentrations of the in-stream reservoirs water were an order of magnitude lower than observed in the groundwater and have no seasonal trend. Our data showed preferential binding of P during initial stage of the Fe(II) oxidation process, indicating the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at the groundwater-surface water interface is an important geochemical mechanism in the transformation of dissolved phosphate to particulate phosphate and therefore a major control on the P retention in natural waters that drain anaerobic aquifers.

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernández-Trincado, J. G.; Geisler, D.; Tang, B.

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similarmore » metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.« less

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

NASA Astrophysics Data System (ADS)

Fernández-Trincado, J. G.; Zamora, O.; García-Hernández, D. A.; Souto, Diogo; Dell'Agli, F.; Schiavon, R. P.; Geisler, D.; Tang, B.; Villanova, S.; Hasselquist, Sten; Mennickent, R. E.; Cunha, Katia; Shetrone, M.; Allende Prieto, Carlos; Vieira, K.; Zasowski, G.; Sobeck, J.; Hayes, C. R.; Majewski, S. R.; Placco, V. M.; Beers, T. C.; Schleicher, D. R. G.; Robin, A. C.; Mészáros, Sz.; Masseron, T.; García Pérez, Ana E.; Anders, F.; Meza, A.; Alves-Brito, A.; Carrera, R.; Minniti, D.; Lane, R. R.; Fernández-Alvar, E.; Moreno, E.; Pichardo, B.; Pérez-Villegas, A.; Schultheis, M.; Roman-Lopes, A.; Fuentes, C. E.; Nitschelm, C.; Harding, P.; Bizyaev, D.; Pan, K.; Oravetz, D.; Simmons, A.; Ivans, Inese I.; Blanco-Cuaresma, S.; Hernández, J.; Alonso-García, J.; Valenzuela, O.; Chanamé, J.

2017-09-01

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ -1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.

Trace element distributions in the water column near the Deepwater Horizon well blowout.

PubMed

Joung, DongJoo; Shiller, Alan M

2013-03-05

To understand the impact of the Deepwater Horizon well blowout on dissolved trace element concentrations, samples were collected from areas around the oil rig explosion site during four cruises in early and late May 2010, October 2010, and October 2011. In surface waters, Ba, Fe, Cu, Ni, Mn, and Co were relatively well correlated with salinity during all cruises, suggesting mixing with river water was the main influence on metal distributions in these waters. However, in deep oil/gas plumes (1000-1400 m depth), modestly elevated concentrations of Co and Ba were observed in late May, compared with postblowout conditions. Analysis of the oil itself along with leaching experiments confirm the oil as the source of the Co, whereas increased Ba was likely due to drilling mud used in the top kill attempt. Deep plume dissolved Mn largely reflected natural benthic input, though some samples showed slight elevation probably associated with the top kill. Dissolved Fe concentrations were low and also appeared largely topographically controlled and reflective of benthic input. Estimates suggest that microbial Fe demand may have affected the Fe distribution but probably not to the extent of Fe becoming a growth-limiting factor. Experiments showed that the dispersant can have some limited impact on dissolved-particulate metal partitioning.

Release of 226Ra from uranium mill tailings by microbial Fe(III) reduction

USGS Publications Warehouse

Landa, E.R.; Phillips, E.J.P.; Lovley, D.R.

1991-01-01

Uranium mill tailings were anaerobically incubated in the presence of H2 with Alteromonas putrefaciens, a bacterium known to couple the oxidation of H2 and organic compounds to the reduction of Fe(III) oxides. There was a direct correlation between the extent of Fe(III) reduction and the accumulation of dissolved 226Ra. In sterile tailings in which Fe(III) was not reduced, there was negligible leaching of 226Ra. The behavior of Ba was similar to that of Ra in inoculated and sterile systems. These results demonstrate that under anaerobic conditions, microbial reduction of Fe(III) may result in the release of dissolved 226Ra from uranium mill tailings. ?? 1991.

In situ analysis of oxygen consumption and diffusive transport in high-temperature acidic iron-oxide microbial mats.

PubMed

Bernstein, Hans C; Beam, Jacob P; Kozubal, Mark A; Carlson, Ross P; Inskeep, William P

2013-08-01

The role of dissolved oxygen as a principal electron acceptor for microbial metabolism was investigated within Fe(III)-oxide microbial mats that form in acidic geothermal springs of Yellowstone National Park (USA). Specific goals of the study were to measure and model dissolved oxygen profiles within high-temperature (65-75°C) acidic (pH = 2.7-3.8) Fe(III)-oxide microbial mats, and correlate the abundance of aerobic, iron-oxidizing Metallosphaera yellowstonensis organisms and mRNA gene expression levels to Fe(II)-oxidizing habitats shown to consume oxygen. In situ oxygen microprofiles were obtained perpendicular to the direction of convective flow across the aqueous phase/Fe(III)-oxide microbial mat interface using oxygen microsensors. Dissolved oxygen concentrations dropped from ∼ 50-60 μM in the bulk-fluid/mat surface to below detection (< 0.3 μM) at a depth of ∼ 700 μm (∼ 10% of the total mat depth). Net areal oxygen fluxes into the microbial mats were estimated to range from 1.4-1.6 × 10(-4)  μmol cm(-2)  s(-1) . Dimensionless parameters were used to model dissolved oxygen profiles and establish that mass transfer rates limit the oxygen consumption. A zone of higher dissolved oxygen at the mat surface promotes Fe(III)-oxide biomineralization, which was supported using molecular analysis of Metallosphaera yellowstonensis 16S rRNA gene copy numbers and mRNA expression of haem Cu oxidases (FoxA) associated with Fe(II)-oxidation. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

Geochemical drivers of organic matter decomposition in Arctic tundra soils

DOE PAGES

Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; ...

2015-12-07

Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO 2) and methane (CH 4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonalmore » patterns of dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH 4 increased relative to dissolved CO 2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.« less

Development of phase analysis methods of impurity elements in alloys based on iron and nickel

NASA Astrophysics Data System (ADS)

Andreeva, N. A.; Anuchkin, S. N.; Volchenkova, V. A.; Kazenas, E. K.; Penkina, T. N.; Fomina, A. A.

2018-04-01

Using the method of AES with ICP, new methods have been developed for quantifying the content of various forms of existence of impurity elements: Al-Al2O3; Zr-ZrO2 in alloys based on iron (Fe-Sn) and nickel (Ni-Sn). Open systems were used to dissolve Al and Zr. To translate difficult-to-open aluminum oxides (corundum) and zirconium oxide (baddeleyite) into the solution, accelerated techniques were developed using the microwave system Mars 5. To confirm the completeness of the dissolution of oxides, a classical scheme of alloy fusion with alkali metal salts was used. Optimal analytical parameters for determining the elements: Al and Zr were chosen. The influence of matrix elements (iron and nickel) and methods of its elimination were studied. This made it possible to determine the elements in a wide concentration range from 1 • 10-3 to n% Al and from 1 • 10-4 to n% Zr without preliminary separation of the matrix with good metrological characteristics. The relative standard deviation (Sr) does not exceed 0,2. The separate determination of the contents of aluminum and aluminium oxide in the model melt of Fe-Sn-Al2O3 and zirconium and zirconium oxide in the Ni-Sn-ZrO2 model melt allowed us to estimate the number of nanoparticles participating in the heterophase interaction with tin and retired to the interface in the form of ensembles and the number of nanoparticles present in the melt and affecting the crystallization process and the structure of the metal.

Size and elemental distributions of nano- to micro-particulates in the geochemically-stratified Great Salt Lake

USGS Publications Warehouse

Diaz, X.; Johnson, W.P.; Fernandez, D.; Naftz, D.L.

2009-01-01

The characterization of trace elements in terms of their apportionment among dissolved, macromolecular, nano- and micro-particulate phases in the water column of the Great Salt Lake carries implications for the potential entry of toxins into the food web of the lake. Samples from the anoxic deep and oxic shallow brine layers of the lake were fractionated using asymmetric flow field-flow fractionation (AF4). The associated trace elements were measured via online collision cell inductively-coupled plasma mass spectrometry (CC-ICP-MS). Results showed that of the total (dissolved + particulate) trace element mass, the percent associated with particulates varied from negligible (e.g. Sb), to greater than 50% (e.g. Al, Fe, Pb). Elements such as Cu, Zn, Mn, Co, Au, Hg, and U were associated with nanoparticles, as well as being present as dissolved species. Particulate-associated trace elements were predominantly associated with particulates larger than 450 nm in size. Among the smaller nanoparticulates (<450 nm), some trace elements (Ni, Zn, Au and Pb) showed higher percent mass (associated with nanoparticles) in the 0.9-7.5 nm size range relative to the 10-250 nm size range. The apparent nanoparticle size distributions were similar between the two brine layers; whereas, important differences in elemental associations to nanoparticles were discerned between the two layers. Elements such as Zn, Cu, Pb and Mo showed increasing signal intensities from oxic shallow to anoxic deep brine, suggesting the formation of sulfide nanoparticles, although this may also reflect association with dissolved organic matter. Aluminum and Fe showed greatly increased concentration with depth and equivalent size distributions that differed from those of Zn, Cu, Pb and Mo. Other elements (e.g. Mn, Ni, and Co) showed no significant change in signal intensity with depth. Arsenic was associated with <2 nm nanoparticles, and showed no increase in concentration with depth, possibly indicating dissolved arsenite. Mercury was associated with <2 nm nanoparticles, and showed greatly increased concentration with depth, possibly indicating association with dissolved organic matter. ?? 2009 Elsevier Ltd.

Fate of colloids during estuarine mixing in the Arctic

NASA Astrophysics Data System (ADS)

Pokrovsky, O. S.; Shirokova, L. S.; Viers, J.; Gordeev, V. V.; Shevchenko, V. P.; Chupakov, A. V.; Vorobieva, T. Y.; Candaudap, F.; Causserand, C.; Lanzanova, A.; Zouiten, C.

2014-02-01

The estuarine behavior of organic carbon (OC) and trace elements (TE) was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river has a deltaic estuary covered in ice during several hydrological seasons: summer (July 2010, 2012) and winter (March 2009) baseflow, and the November-December 2011 ice-free period. Colloidal forms of OC and TE were assessed for three pore size cutoffs (1, 10, and 50 kDa) using an in situ dialysis procedure. Conventionally dissolved (< 0.22 μm) fractions demonstrated clear conservative behavior for Li, B, Na, Mg, K, Ca, Sr, Mo, Rb, Cs, and U during the mixing of freshwater with the White Sea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. Si and OC also displayed conservative behavior but with a pronounced decrease in concentration seawards. Rather conservative behavior, but with much smaller changes in concentration (variation within ±30%) over a full range of salinities, was observed for Ti, Ni, Cr, As, Co, Cu, Ga, Y, and heavy REE. Strong non-conservative behavior with coagulation/removal at low salinities (< 5‰) was exhibited by Fe, Al, Zr, Hf, and light REE. Finally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (~ 2-5‰, Ba, Mn) or intermediate (~ 10-15‰, Ba, Zn, Pb, Cd) salinities, which is most likely linked to TE desorption from suspended matter or sediment outflux. The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW< 1 kDa fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved (< 0.22 μm) pool as the salinity increases. Similarly, the relative proportion of colloidal (1 kDa-0.22 μm) pool for the OC and insoluble TE bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (< 5‰) salinities. Overall, the observed decrease in the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa-0.22 μm portion by the LMW< 1 kDa fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW< 1 kDa ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate versus dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either conservative (OC and related elements such as divalent metals) or non-conservative, coagulation-controlled (Fe, Al, and insoluble TE associated with organo-ferric colloids) behavior. The climate warming at high latitudes is likely to intensify the production of LMW< 1 kDa organic ligands and the associated TE; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.

Observed And Modeled Seasonal Trends In Dissolved And Particulate Cu, Fe, Mn, And Zn In A Mining-Impacted Stream

EPA Science Inventory

North Fork Clear Creek (NFCC) in Colorado, an acid-mine drainage (AMD) impacted stream, was chosen to examine the distribution of dissolved and particulate Cu, Fe, Mn, and Zn in the water column, with respect to seasonal hydrologic controls. NFCC is a high-gradient stream with d...

Characterization and evolution of dissolved organic matter in acidic forest soil and its impact on the mobility of major and trace elements (case of the Strengbach watershed)

NASA Astrophysics Data System (ADS)

Gangloff, Sophie; Stille, Peter; Pierret, Marie-Claire; Weber, Tiphaine; Chabaux, François

2014-04-01

Dissolved Organic Carbon (DOC) plays an important role in the behavior of major and trace elements in the soil and influences their transfer from soil to soil solution. The first objective of this study is to characterize different organic functional groups for the Water Extractable Organic Carbon (WEOC) fractions of a forest soil as well as their evolution with depth. The second objective is to clarify the influence of these organic functional groups on the migration of the trace elements in WEOC fractions compared to those in the soil solution obtained by lysimeter plates. All experiments have been performed on an acidic forest soil profile (five depths in the first meter) of the experimental spruce parcel in the Stengbach catchment. The Infra-red spectra of the freeze-dried WEOC fractions show a modification of the molecular structure with depth, i.e. a decrease of the polar compounds such as polysaccharides and an increase of the less polar hydro-carbon functional groups with a maximum value of the aromaticity at 30 cm depth. A Hierarchical Ascending Classification (HAC) of the evolution of Water Extractable Chemical Elements (WECE) with the evolution of the organic functional groups in the organic matter (OM) enriched soil compartments permits recognition of relationships between trace element behavior and the organic functional group variations. More specifically, Pb is preferentially bound to the carboxylic acid function of DOC mainly present in the upper soil compartment and rare earth elements (REE) show similar behavior to Fe, V and Cr with a good affinity to carboxy-phenolic and phenolic groups of DOC. The experimental results show that heavy REE compared to light REE are preferentially bound to the aromatic functional group. This different behavior fractionates the REE pattern of soil solutions at 30 cm depth due to the here observed aromaticity enrichment of DOC. These different affinities for the organic functional groups of the DOC explain some aspects of the behavior of trace elements in soil solutions and in the soil profile but, also the competition between trace elements in complexation with DOC. The results of this study are important for the understanding of the mobility and the migration of pollutants (as heavy metals or radionuclides) as well as nutrients in natural ecosystems. WE PrN/YbN is constant between 3 and 16 cm depth whereas SS PrN/YbN slightly decreases from 0.80 at 5 cm depth to 0.74 at 10 cm depth. This results from Pr (LREE) enrichment in the soil solution of the upper soil compartment caused by vegetation controlled LREE recycling and/or atmospheric depositions (see above). WE PrN/YbN and SS PrN/YbN show similar depth dependent distributions including the enrichment at 30 cm depth. It results from Yb depletion at this depth and enrichment in the deeper soil compartment compared to Pr. Similar to Marsac et al. (2012, 2013) one might suggest that there is competition between Fe3+, Al3+ and REE for the binding with DOC. They have a high affinity with the same organic functional groups which is confirmed by the classification scheme (Fig. 8). The studies of Marsac et al. suggest that at acidic pH and low metal/DOC ratios, Fe3+and Al3+ compete more with HREE than LREE; moreover, at high metal/DOC ratios and acidic pH, Al3+ competes with LREE. The Fig. 13 showing the variations of WECEN for Al and Fe in function of WECEN LREE and HREE confirms Marsac et al.’s observations. The slope of the extrapolation line resulting from WECEN Al and HREE values remains rather unchanged for the OM depleted and enriched soil compartments; thus, the change in the metal/DOC ratio in the soil does not change the extraction behavior of Al and HREE. However, the WECEN Fe strongly increase compared to the corresponding HREE values in the OM enriched compartment pointing to the competition between Fe and HREE. Alternatively, one observes that the WECEN Fe and LREE values in the OM enriched compartment plot on the extrapolation line derived from OM depleted soil samples. Thus, in this case, the change in the metal/DOC ratio does not affect the extraction behavior of Fe and LREE. However, the WECEN values for Al and corresponding LREE of samples from the OM enriched soil compartment plot below the extrapolation line and point to the competition between Al and LREE. These results are also in agreement with the REE distribution pattern of the soil solutions from the same site which are at greater depth LREE depleted (Stille et al., 2009).

Microstructure and mechanical properties of Al-3Fe alloy processed by equal channel angular extrusion

NASA Astrophysics Data System (ADS)

Fuxiao, Yu; Fang, Liu; Dazhi, Zhao; Toth, Laszlo S.

2014-08-01

Al-Fe alloys are attractive for applications at temperatures beyond those normally associated with the conventional aluminum alloys. Under proper solidification condition, a full eutectic microstructure can be generated in Al-Fe alloys at Fe concentration well in excess of the eutectic composition of 1.8 wt.% Fe. The microstructure in this case is characterized by the metastable regular eutectic Al-Al6Fe fibers of nano-scale in diameter, instead of the equilibrium eutectic Al-Al3Fe phase. In this study, the microstructure and mechanical properties of the Al-3Fe alloy with metastable Al6Fe particles deformed by equal channel angular extrusion were investigated. Severe plastic deformation results in a microstructure consisting of submicron equiaxed Al grains with a uniform distribution of submicron Al6Fe particles on the grain boundaries. The room temperature tensile properties of the alloy with this microstructure will be presented.

An experimental study of ^{{{{Fe}}^{2 + } {-}{{Mg}}}} K_{{D}} between orthopyroxene and rhyolite: a strong dependence on H2O in the melt

NASA Astrophysics Data System (ADS)

Waters, Laura E.; Lange, Rebecca A.

2017-06-01

The effect of temperature, pressure, and dissolved H2O in the melt on the Fe2+-Mg exchange coefficient between orthopyroxene and rhyolite melt was investigated with a series of H2O fluid-saturated phase-equilibrium experiments. Experiments were conducted in a rapid-quench cold-seal pressure vessel over a temperature and pressure range of 785-850 °C and 80-185 MPa, respectively. Oxygen fugacity was buffered with the solid Ni-NiO assemblage in a double-capsule assembly. These experiments, when combined with H2O-undersaturated experiments in the literature, show that ^{{{{Fe}}^{2 + } {-}{{Mg}}}} K_{{D}} between orthopyroxene and rhyolite liquid increases strongly (from 0.23 to 0.54) as a function of dissolved water in the melt (from 2.7 to 5.6 wt%). There is no detectable effect of temperature or pressure over an interval of 65 °C and 100 MPa, respectively, on the Fe2+-Mg exchange coefficient values. The data show that Fe-rich orthopyroxene is favored at high water contents, whereas Mg-rich orthopyroxene crystallizes at low water contents. It is proposed that the effect of dissolved water in the melt on the composition of orthopyroxene is analogous to its effect on the composition of plagioclase. In the latter case, dissolved hydroxyl groups preferentially complex with Na+ relative to Ca2+, which reduces the activity of the albite component, leading to a more anorthite-rich (calcic) plagioclase. Similarly, it is proposed that dissolved hydroxyl groups preferentially complex with Mg2+ relative to Fe2+, thus lowering the activity of the enstatite component, leading to a more Fe-rich orthopyroxene at high water contents in the melt. The experimental results presented in this study show that reversely zoned pyroxene (i.e., Mg-rich rims) in silicic magmas may be a result of H2O degassing and not necessarily the result of mixing with a more mafic magma.

Bactericidal Effect of Zero-Valent Iron Nanoparticles on Escherichia coli

PubMed Central

Lee, Changha; Kim, Jee Yeon; Lee, Won Il; Nelson, Kara L.; Yoon, Jeyong; Sedlak, David L.

2008-01-01

Zero-valent iron nanoparticles (nano-Fe0) in aqueous solution rapidly inactivated Escherichia coli (E. coli). A strong bactericidal effect of nano-Fe0 was found under deaerated conditions, with a linear correlation between log inactivation and nano-Fe0 dose (0.82 log inactivation / mg/L nano-Fe0 · hr). The inactivation of E. coli under air saturation required much higher nano-Fe0 doses due to the corrosion and surface oxidation of nano-Fe0 by dissolved oxygen. Significant physical disruption of the cell membranes was observed in E. coli exposed to nano-Fe0, which may have caused the inactivation, or enhanced the biocidal effects of dissolved iron. The reaction of Fe(II) with intracellular oxygen or hydrogen peroxide also may have induced oxidative stress by producing reactive oxygen species. The bactericidal effect of nano-Fe0 was a unique property of nano-Fe0, which was not observed in other types of iron-based compounds. PMID:18678028

Diurnal variations in, and influences on, concentrations of particulate and dissolved arsenic and metals in the mildly alkaline Wallkill River, New Jersey, USA

USGS Publications Warehouse

Barringer, J.L.; Wilson, T.P.; Szabo, Z.; Bonin, J.L.; Fischer, J.M.; Smith, N.P.

2008-01-01

Diurnal variations in particulate and dissolved As and metal concentrations were observed in mildly alkaline water from a wetlands site on the Wallkill River in northwestern New Jersey. The site, underlain by glacial sediments over dolomite bedrock, is 10 km downstream from a mined area of the Franklin Marble, host to Zn ores, also As and Mn minerals. In mid-September 2005, maxima and minima in dissolved-oxygen-concentration and pH, typically caused by photosynthesis and respiration, occurred at 2000 and 0800 hours. Concentrations of dissolved As (1.52-1.95 ??g/L) peaked at dusk (2000 hours), whereas dissolved Mn and Zn concentrations (76.5-96.9 and 8.55-12.8 ??g/L, respectively) were lowest at dusk and peaked at 1000 hours. These opposing cycles probably reflect sorption and desorption of As (an anion), and Mn and Zn (cations) as pH varied throughout the 24-h period. Doubly-peaked cycles of B, Cl, SO4, and nutrients also were observed; these may result from upstream discharges of septic-system effluent. Both recoverable amd particulate Al, Fe, Mn, and Zn concentrations peaked between 0200 and 0600 hours. The particulate metals cycle, with perturbations at 0400 hours, may be influenced by biological activity. ?? 2007 Springer-Verlag.

Effects of alloying elements (Mn, Co, Al, W, Sn, B, C and S) on biodegradability and in vitro biocompatibility of pure iron.

PubMed

Liu, B; Zheng, Y F

2011-03-01

Pure iron was determined to be a valid candidate material for biodegradable metallic stents in recent animal tests; however, a much faster degradation rate in physiological environments was desired. C, Mn, Si, P, S, B, Cr, Ni, Pb, Mo, Al, Ti, Cu, Co, V and W are common alloying elements in industrial steels, with Cr, Ni, Mo, Cu, Ti, V and Si being acknowledged as beneficial in enhancing the corrosion resistance of iron. The purpose of the present work (using Fe-X binary alloy models) is to explore the effect of the remaining alloying elements (Mn, Co, Al, W, B, C and S) and one detrimental impurity element Sn on the biodegradability and biocompatibility of pure iron by scanning electron microscopy, X-ray diffraction, metallographic observation, tensile testing, microhardness testing, electrochemical testing, static (for 6 months) and dynamic (for 1 month with various dissolved oxygen concentrations) immersion testing, cytotoxicity testing, hemolysis and platelet adhesion testing. The results showed that the addition of all alloying elements except for Sn improved the mechanical properties of iron after rolling. Localized corrosion of Fe-X binary alloys was observed in both static and dynamic immersion tests. Except for the Fe-Mn alloy, which showed a significant decrease in corrosion rate, the other Fe-X binary alloy corrosion rates were close to that of pure iron. It was found that compared with pure iron all Fe-X binary alloys decreased the viability of the L929 cell line, none of experimental alloying elements significantly reduced the viability of vascular smooth muscle cells and all the elements except for Mn increased the viability of the ECV304 cell line. The hemolysis percentage of all Fe-X binary alloy models were less than 5%, and no sign of thrombogenicity was observed. In vitro corrosion and the biological behavior of these Fe-X binary alloys are discussed and a corresponding mechanism of corrosion of Fe-X binary alloys in Hank's solution proposed. As a concluding remark, Co, W, C and S are recommended as alloying elements for biodegradable iron-based biomaterials. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fractionation of Fe isotopes by soil microbes and organic acids

USGS Publications Warehouse

Brantley, Susan L.; Liermann, Laura; Bullen, Thomas D.

2001-01-01

Small natural variations in Fe isotopes have been attributed to biological cycling. However, without understanding the mechanism of fractionation, it is impossible to interpret such variations. Here we show that the δ56Fe of Fe dissolved from a silicate soil mineral by siderophore-producing bacteria is as much as 0.8% lighter than bulk Fe in the mineral. A smaller isotopic shift is observed for Fe released abiotically by two chelates, and the magnitude of the shift increases with affinity of the ligand for Fe, consistent with a kinetic isotope effect during hydrolysis of Fe at the mineral surface. Fe dissolved abiotically without chelates shows no isotopic shift. The δ56Fe of the exchange fraction on soil grains is also lighter by ~0.6%-1% than Fe from both hornblende and iron oxyhydroxides. The kinetic isotope effect is therefore preserved in open systems such as soils. when recorded in the rock record, Fe isotopic fractionation could document Fe transport by organic molecules or by microbes where such entities were present in the geologic past.

Chemical removal of nitrate from water by aluminum-iron alloys.

PubMed

Xu, Jie; Pu, Yuan; Qi, Wei-Kang; Yang, Xiao Jin; Tang, Yang; Wan, Pingyu; Fisher, Adrian

2017-01-01

Zero-valent iron has been intensively investigated in chemical reduction of nitrate in water, but the reduction requires acidic or weak acidic pH conditions and the product of the reduction is exclusively ammonium, an even more toxic substance. Zero-valent aluminum is a stronger reductant than iron, but its use for the reduction of aqueous nitrate requires considerably alkaline pH conditions. In this study, aluminum-iron alloys with an iron content of 10%, 20% and 58% (termed Al-Fe10, Al-Fe20 and Al-Fe58, respectively) were investigated for the reduction of aqueous nitrate. Al-Fe alloys were efficient to reduce nitrate in water in an entire pH range of 2-12 and the reduction proceeded in a pseudo-first order at near neutral pH conditions. The observed reaction rate constant (K obs ) of Al-Fe10 was 3 times higher than that of Fe and the K obs of Al-Fe20 doubled that of Al-Fe10. The nitrogen selectivity of the reduction by Al-Fe10, Al-Fe20 and Al-Fe58 was 17.6%, 23.9% and 40.3%, respectively at pH 7 and the nitrogen selectivity by Al-Fe20 increased from 18.9% at pH 2-60.3% at pH 12. The enhanced selectivity and reactivity of Al-Fe alloys were likely due to the presence of an intermetallic Al-Fe compound (Al 13 Fe 4 ). Copyright © 2016 Elsevier Ltd. All rights reserved.

Rapid removal of chloroform, carbon tetrachloride and trichloroethylene in water by aluminum-iron alloy particles.

PubMed

Xu, Jie; Pu, Yuan; Yang, Xiao Jin; Wan, Pingyu; Wang, Rong; Song, Peng; Fisher, Adrian

2017-09-05

Water contamination with chlorinated hydrocarbons such as chloroform (CHCl 3 ), carbon tetrachloride (CCl 4 ) and trichloroethylene (TCE) is one of the major public health concerns. In this study, we explored the use of aluminum-iron alloys particles in millimeter scale for rapid removal of CHCl 3 , CCl 4 and TCE from water. Three types of Al-Fe alloy particles containing 10, 20 and 58 wt% of Fe (termed as Al-Fe10, Al-Fe20 and Al-Fe58) were prepared and characterized by electrochemical polarization, X-ray diffraction and energy dispersive spectrometer. For concentrations of 30-180 μg/L CHCl 3 , CCl 4 and TCE, a removal efficiency of 45-64% was achieved in a hydraulic contact time of less than 3 min through a column packed with 0.8-2 mm diameter of Al-Fe alloy particles. The concentration of Al and Fe ions released into water was less than 0.15 and 0.05 mg/L, respectively. Alloying Al with Fe enhances reactivity towards chlorinated hydrocarbons' degradation and the enhancement is likely the consequence of galvanic effects between different phases (Al, Fe and intermetallic Al-Fe compounds such as Al 13 Fe 4 , Fe 3 Al and FeAl 2 ) and catalytic role of these intermetallic Al-Fe compounds. The results demonstrate that the use of Al-Fe alloy particles offers a viable and green option for chlorinated hydrocarbons' removal in water treatment.

Tracing anthropogenic aerosol Fe sources in the North Atlantic Ocean using dissolved Fe isotope ratios

NASA Astrophysics Data System (ADS)

Conway, T. M.; Shelley, R.; Aguilar-Islas, A. M.; Landing, W. M.; Mahowald, N. M.; John, S.

2016-02-01

Supply of iron (Fe) to the surface ocean from atmospheric deposition plays a vital role in marine biogeochemical cycles, especially in Fe-limited areas or regions close to dust sources. However, large uncertainties remain over the fluxes, solubility and bioavailability of Fe supplied by aerosol dust. Additionally, aerosol Fe is likely to consist of a mixture of natural and anthropogenic (urban, biomass burning and combustion) components, which may have very different solubilities in seawater [e.g. 1]. To constrain soluble Fe supply to the oceans, it is thus vitally important to understand the relative contributions of different types of aerosol Fe, their solubilities and spatial distributions. Stable Fe isotopes (δ56Fe) may offer a way to discriminate between different dust sources [2], because of differential fractionation during a range of chemical processes. In this study, we measured δ56Fe in North Atlantic marine aerosols collected during two US GEOTRACES GA03 cruises (Lisbon to Woods Hole via Cape Verde, 2010-11) and we present δ56Fe measurements (relative to IRMM-014) from both the bulk aerosol (HF-HNO3 digested) and the water-soluble (10s ultrapure water leach) fractions. Aerosols collected from different air-masses (Saharan, European and N. American) allowed us to investigate the variability in δ56Fe due to different regional dust sources. The bulk phase was characterized by near-crustal δ56Fe values of +0.1±0.2‰, indicating the dominance of mineral dust. In contrast, the water-soluble fraction showed great variability; aerosols from European and North American air-masses were very isotopically light (-1.2±0.2‰ and -1.1±0.7‰) while those from Saharan air-masses were crustal (+0.1‰). Comparison of this data with isotope-informed model predictions of soluble Fe from mineral and anthropogenic sources (combustion, biofuels and biomass burning) [1], suggests that the data is consistent with mixing of either 1) Fe from mineral dust (+0.1‰) and a distinctly light anthropogenic Fe (-1.6‰), or 2) Fe from crustal mineral dust, isotopically heavy combustion Fe (+0.1 to +0.3‰), and biomass Fe that is both isotopically light (-1.6‰) and very soluble (>50%). [1] Luo, C. et al. (2008), Glob. Biogeochem. Cyc., 22, GB1012. [2] Mead, C. et al. (2013), Geophys. Res. Lett., 40, 5722-5727.

Influence of Oxalate on Ni Fate during Fe(II)-Catalyzed Recrystallization of Hematite and Goethite.

PubMed

Flynn, Elaine D; Catalano, Jeffrey G

2018-06-05

During biogeochemical iron cycling at redox interfaces, dissolved Fe(II) induces the recrystallization of Fe(III) oxides. Oxalate and other organic acids promote dissolution of these minerals and may also induce recrystallization. These processes may redistribute trace metals among the mineral bulk, mineral surface, and aqueous solution. However, the impact of interactions among organic acids, dissolved Fe(II), and iron oxide minerals on trace metal fate in such systems is unclear. The present study thus explores the effect of oxalate on Ni release from and incorporation into hematite and goethite in the absence and presence of Fe(II). When Ni is initially structurally incorporated into the iron oxides, both oxalate and dissolved Fe(II) promote the release of Ni to aqueous solution. When both species are present, their effects on Ni release are synergistic at pH 7 but inhibitory at pH 4, indicating that cooperative and competitive interactions vary with pH. In contrast, oxalate suppresses Ni incorporation into goethite and hematite during Fe(II)-induced recrystallization, decreasing the proportion of Ni substituting in a mineral structure by up to 36%. These observations suggest that at redox interfaces oxalate largely enhances trace metal mobility. In such settings, oxalate, and likely other organic acids, may thus enhance micronutrient availability and inhibit contaminant sequestration.

The reduction mechanism of chromite in the presence of a silica flux

NASA Astrophysics Data System (ADS)

Weber, P.; Eric, R. H.

1993-12-01

The reduction behavior of a natural chromite from the Bushveld Complex of South Africa was studied at 1300 °C to 1500 °C. Reduction was by graphite in the presence of silica. Thermo-gravimetric analysis, X-ray diffraction (XRD) analysis, energy-dispersive X-ray analysis (EDAX), and metallographic analysis were the experimental techniques used. Silica affected the reduction at and above 1400 °C. A two-stage reduction mechanism was established. The first stage, up to a reduction level of about 40 pct, is primarily confined to iron metallization, and zoning is observed in partially reduced chromites. In this stage, silica does not interfere with the reduction, which proceeds by an outward diffusion of Fe2+ ions and an inward diffusion of Mg2+ and Cr2+ ions. The second stage is primarily confined to chromium metallization, and formation of a silicate slag alters the reduction mechanism. The slag phase agglomerates and even embeds partially reduced chromite particles. An ion-exchange reaction between the re-ducible cations (Cr3+ and Fe2+) in the spinel and the dissolved cations (Al3+ and Mg2+) in the slag allows further reduction. Once the reducible cations are dissolved in the slag phase, they are reduced to the metallic state at sites where there is contact with the reductant.

Chemical characterization of iron-mediated soil organic matter stabilization in tropical subsoils

NASA Astrophysics Data System (ADS)

Coward, E.; Plante, A. F.; Thompson, A.

2015-12-01

Tropical forest soils contribute disproportionately to the poorly-characterized and persistent deep soil carbon (C) pool. Highly-weathered and often extending one to two meters deep, these soils also contain an abundance of semicrystalline, Fe- and Al-containing short-range-order (SRO) minerals, metastable derivatives of framework silicate and ferromagnesian parent materials. SRO minerals are capable of soil organic matter (SOM) stabilization through sorption or co-precipitation, a faculty enhanced by their high specific surface area (SSA). As such, SRO-mediated organomineral associations may prove a critical, yet matrix-selective, driver of SOM stabilization capacity in tropical soils, particularly at depth. Surface (0-20 cm) and subsoil (50-80 cm) samples were taken from 20 quantitative soil pits dug in the Luquillo Critical Zone Observatory, located in northeast Puerto Rico. Soils were stratified across granodiorite and volcaniclastic parent materials, spanning primary mineral contents of 5 to 40%. Selective dissolution procedures were used to isolate distinct forms of Fe-C interactions: (1) sodium pyrophosphate to isolate organo-mineral complexes, (2) hydroxylamine and (3) oxalate to isolate SRO phases, and (4) inorganic dithionite to isolate crystalline Fe oxides. Extracts were analysed for dissolved organic C (DOC) and Fe and Al concentrations to estimate SOM associated with each mineral phase. Soils were also subjected to SSA analysis, 57Fe-Mössbauer spectroscopy and X-ray diffraction before and after extraction to determine the contribution of extracted mineral phases to SOM stabilization capacity. Preliminary results indicate a dominance of secondary (hydr)oxides and kaolin minerals in surface soils, strongly driven by parent material. With depth, however, we observe a marked shift towards SRO mineral phases across both parent materials, suggesting that SRO-mediated organomineral associations are significant contributors to observed C storage in tropical subsoils.

Fe-Al interface intermixing and the role of Ti, V, and Zr as a stabilizing interlayer at the interface

NASA Astrophysics Data System (ADS)

Priyantha, W.; Smith, R. J.; Chen, H.; Kopczyk, M.; Lerch, M.; Key, C.; Nachimuthu, P.; Jiang, W.

2009-03-01

Fe-Al bilayer interfaces with and without interface stabilizing layers (Ti, V, Zr) were fabricated using dc magnetron sputtering. Intermixing layer thickness and the effectiveness of the stabilizing layer (Ti, V, Zr) at the interface were studied using Rutherford backscattering spectrometry (RBS) and x-ray reflectometry (XRR). The result for the intermixing thickness of the AlFe layer is always higher when Fe is deposited on Al as compared to when Al is deposited on Fe. By comparing measurements with computer simulations, the thicknesses of the AlFe layers were determined to be 20.6 Å and 41.1 Å for Al/Fe and Fe/Al bilayer systems, respectively. The introduction of Ti and V stabilizing layers at the Fe-Al interface reduced the amount of intermixing between Al and Fe, consistent with the predictions of model calculations. The Zr interlayer, however, was ineffective in stabilizing the Fe-Al interface in spite of the chemical similarities between Ti and Zr. In addition, analysis suggests that the Ti interlayer is not effective in stabilizing the Fe-Al interface when the Ti interlayer is extremely thin (˜3 Å) for these sputtered metallic films.

Influence of testing environment on the room temperature ductility of FeAl alloys

NASA Technical Reports Server (NTRS)

Gaydosh, D. J.; Nathal, M. V.

1990-01-01

The effects of testing atmospheres (air, O2, N2, and vacuum) on the room-temperature ductility of Fe-40Al, Fe-40Al-0.5B, and Fe-50Al alloys were investigated. The results confirmed the decrease in room-temperature ductility of Fe-rich FeAl alloys by the interaction of the aluminide with water vapor, reported previously by Liu et al. (1989). The highest ductilities were measured in the atmosphere with the lowest moisture levels, i.e., in vacuum. It was found that significant ductility is still restricted to Fe-rich alloys (Fe-40Al), as the Fe-50Al alloy remained brittle under all testing conditions. It was also found that slow cooling after annealing was beneficial, and the effect was additive to the environmental effect. The highest ductility measurements in this study were 9 percent elongation in furnace-cooled Fe-40Al and in Fe-40Al-0.5B, when tested in vacuum.

Macroalgal biomonitors of trace metal contamination in acid sulfate soil aquaculture ponds.

PubMed

Gosavi, K; Sammut, J; Gifford, S; Jankowski, J

2004-05-25

Earthen shrimp aquaculture ponds are often impacted by acid sulfate soils (ASS), typically resulting in increased disease and mortality of cultured organisms. Production losses have been attributed to either low pH or to elevated concentrations of toxic metals, both direct products of pyrite oxidation in ASS. The standard farm management practice to minimise effects of pyrite oxidation is to maintain pH of pond waters above 5, based on the assumption that dissolved metal bioavailability is negligible at this pH. This study aimed to test the validity of this assumption, and therefore elucidate a possible role of toxic heavy metals in observed decreases in farm productivity. Metal bioaccumulation in four genera of macroalgae, Ulva sp., Enteromorpha sp., Cladophora sp. and Chaetomorpha sp., sampled from ASS-affected shrimp aquaculture ponds were measured using inductively coupled plasma-optical emission spectroscopy (ICP-OES) to assess the relative bioavailability of dissolved metals within the system. Results showed that all four genera of macroalgae accumulated appreciable quantities of Fe, Al, Zn, Cd, Cu, As and Pb. Iron and Al, the most common metals mobilised from ASS, were both accumulated in all algal genera to concentrations three orders of magnitude greater than all other metals analysed. These findings indicate that dissolved heavy metals are indeed bioavailable within the aquaculture pond system. A literature search of heavy metal bioaccumulation by these algal genera revealed concentrations recorded in this study are comparable to highly contaminated environments, such as those exposed to urban, industrial and mining pollution. The results of this study indicate that dissolved metal bioavailability in many earthen shrimp aquaculture ponds may be higher than previously thought.

Major and trace element partitioning between dissolved and particulate phases in Antarctic surface snow.

PubMed

Grotti, M; Soggia, F; Ardini, F; Magi, E

2011-09-01

In order to provide a new insight into the Antarctic snow chemistry, partitioning of major and trace elements between dissolved and particulate (i.e. insoluble particles, >0.45 μm) phases have been investigated in a number of coastal and inland snow samples, along with their total and acid-dissolvable (0.5% nitric acid) concentrations. Alkaline and alkaline-earth elements (Na, K, Ca, Mg, Sr) were mainly present in the dissolved phase, while Fe and Al were predominantly associated with the particulate matter, without any significant difference between inland and coastal samples. On the other hand, partitioning of trace elements depended on the sampling site position, showing a general decrease of the particulate fraction by moving from the coast to the plateau. Cd, Cu, Pb and Zn were for the most part in the dissolved phase, while Cr was mainly associated with the particulate fraction. Co, Mn and V were equally distributed between dissolved and particulate phases in the samples collected from the plateau and preferentially associated with the particulate in the coastal samples. The correlation between the elements and the inter-sample variability of their concentration significantly decreased for the plateau samples compared to the coastal ones, according to a change in the relative contribution of the metal sources and in good agreement with the estimated marine and crustal enrichment factors. In addition, samples from the plateau were characterised by higher enrichment factors of anthropogenic elements (Cd, Cr, Cu, Pb and Zn), compared to the coastal area. Finally, it was observed that the acid-dissolvable metal concentrations were generally lower than the total concentration values, showing that the acid treatment can dissolve only a given fraction of the metal associated with the particulate (<20% for iron and aluminium).

Removal of H 2S via an iron catalytic cycle and iron sulfide precipitation in the water column of dead end tributaries

NASA Astrophysics Data System (ADS)

Ma, Shufen; Noble, Abigail; Butcher, Derek; Trouwborst, Robert E.; Luther, George W., III

2006-11-01

The oxidation and precipitation of H 2S were investigated in Torquay Canal and Bald Eagle Creek, two tributaries of northern Rehoboth Bay, one of the Delaware Inland Bays. These man-made dead end canals develop seasonal anoxia and have been the site of past fish kills and harmful algal blooms. The canals have multiple holes over 5.5 m deep compared to an average low tide depth of 2 m. In situ determination for dissolved O 2, H 2S and other Fe and S redox species were conducted with a solid-state Au/Hg microelectrode in 2003 and 2004. Laboratory analyses of discrete samples were also performed to measure dissolved and particulate Fe, Mn, and S 8 to follow the seasonal dynamics of O, S, Fe and Mn redox species. Our results indicate that the water in the holes becomes stratified with O 2 decreasing with depth and H 2S increasing with depth. Dissolved Fe was as high as 30 μM whereas dissolved Mn was only 0.2 μM in the water column, indicating that Fe is the dominant metal involved in S redox cycling and precipitation. In surface oxic waters, the dominant form of Fe was particulate Fe(III) (oxy)hydroxides. When seasonal anoxia developed, Fe(III) (oxy)hydroxides were reduced by H 2S to Fe(II) at the oxic-anoxic interface. The Fe(II) reduced from particulate Fe can be re-oxidized to Fe(III) by O 2 above and at the interface to form a catalytic cycle to oxidize H 2S. Elemental S is the predominant oxidation product and was as high as 30 μM level (as S 0) at the interface. When the system was stable, the Fe catalytic cycle prevented H 2S from being released into surface waters during seasonal anoxia. However, when storms came, the water column was overturned and H 2S was released to the surface water. The reaction rates for the Fe catalytic cycle are not fast enough and the concentration of Fe was not high enough to regulate the high concentration of H 2S in surface waters during storm and mixing events.

Transport and cycling of iron and hydrogen peroxide in a freshwater stream: Influence of organic acids

USGS Publications Warehouse

Scott, Durelle T.; Runkel, Robert L.; McKnight, Diane M.; Voelker, Bettina M.; Kimball, Briant A.; Carraway, Elizabeth R.

2003-01-01

An in-stream injection of two dissolved organic acids (phthalic and aspartic acids) was performed in an acidic mountain stream to assess the effects of organic acids on Fe photoreduction and H2O2 cycling. Results indicate that the fate of Fe is dependent on a net balance of oxidative and reductive processes, which can vary over a distance of several meters due to changes in incident light and other factors. Solution phase photoreduction rates were high in sunlit reaches and were enhanced by the organic acid addition but were also limited by the amount of ferric iron present in the water column. Fe oxide photoreduction from the streambed and colloids within the water column resulted in an increase in the diurnal load of total filterable Fe within the experimental reach, which also responded to increases in light and organic acids. Our results also suggest that Fe(II) oxidation increased in response to the organic acids, with the result of offsetting the increase in Fe(II) from photoreductive processes. Fe(II) was rapidly oxidized to Fe(III) after sunset and during the day within a well-shaded reach, presumably through microbial oxidation. H2O 2, a product of dissolved organic matter photolysis, increased downstream to maximum concentrations of 0.25 ??M midday. Kinetic calculations show that the buildup of H2O2 is controlled by reaction with Fe(III), but this has only a small effect on Fe(II) because of the small formation rates of H2O2 compared to those of Fe(II). The results demonstrate the importance of incorporating the effects of light and dissolved organic carbon into Fe reactive transport models to further our understanding of the fate of Fe in streams and lakes.

A Thermodynamic Model to Estimate the Formation of Complex Nitrides of Al x Mg(1- x)N in Silicon Steel

NASA Astrophysics Data System (ADS)

Luo, Yan; Zhang, Lifeng; Li, Ming; Sridhar, Seetharaman

2018-06-01

A complex nitride of Al x Mg(1- x)N was observed in silicon steels. A thermodynamic model was developed to predict the ferrite/nitride equilibrium in the Fe-Al-Mg-N alloy system, using published binary solubility products for stoichiometric phases. The model was used to estimate the solubility product of nitride compound, equilibrium ferrite, and nitride compositions, and the amounts of each phase, as a function of steel composition and temperature. In the current model, the molar ratio Al/(Al + Mg) in the complex nitride was great due to the low dissolved magnesium in steel. For a steel containing 0.52 wt pct Als, 10 ppm T.Mg., and 20 ppm T.N. at 1100 K (827 °C), the complex nitride was expressed by Al0.99496Mg0.00504N and the solubility product of this complex nitride was 2.95 × 10-7. In addition, the solution temperature of the complex nitride increased with increasing the nitrogen and aluminum in steel. The good agreement between the prediction and the detected precipitate compositions validated the current model.

Kinetics of homogeneous and surface-catalyzed mercury(II) reduction by iron(II)

USGS Publications Warehouse

Amirbahman, Aria; Kent, Douglas B.; Curtis, Gary P.; Marvin-DiPasquale, Mark C.

2013-01-01

Production of elemental mercury, Hg(0), via Hg(II) reduction is an important pathway that should be considered when studying Hg fate in environment. We conducted a kinetic study of abiotic homogeneous and surface-catalyzed Hg(0) production by Fe(II) under dark anoxic conditions. Hg(0) production rate, from initial 50 pM Hg(II) concentration, increased with increasing pH (5.5–8.1) and aqueous Fe(II) concentration (0.1–1 mM). The homogeneous rate was best described by the expression, rhom = khom [FeOH+] [Hg(OH)2]; khom = 7.19 × 10+3 L (mol min)−1. Compared to the homogeneous case, goethite (α-FeOOH) and hematite (α-Fe2O3) increased and γ-alumina (γ-Al2O3) decreased the Hg(0) production rate. Heterogeneous Hg(0) production rates were well described by a model incorporating equilibrium Fe(II) adsorption, rate-limited Hg(II) reduction by dissolved and adsorbed Fe(II), and rate-limited Hg(II) adsorption. Equilibrium Fe(II) adsorption was described using a surface complexation model calibrated with previously published experimental data. The Hg(0) production rate was well described by the expression rhet = khet [>SOFe(II)] [Hg(OH)2], where >SOFe(II) is the total adsorbed Fe(II) concentration; khet values were 5.36 × 10+3, 4.69 × 10+3, and 1.08 × 10+2 L (mol min)−1 for hematite, goethite, and γ-alumina, respectively. Hg(0) production coupled to reduction by Fe(II) may be an important process to consider in ecosystem Hg studies.

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

USGS Publications Warehouse

Brown, C.J.; Schoonen, M.A.A.; Candela, J.L.

2000-01-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO4/2- in the aerobic zone, and to the reduction of SO4/2- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55 x 10-4 to 48.6 x 10-4 mmol 1-1 yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO4/2- (1.31 x 10-4 to 15 x 10-4 mmol 1-1 yr-1). The overall increase in SO4/2- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO4/2- loss through microbial reduction is exceeded by SO4/2- gain through diffusion from sediments and through the oxidation of FeS2. Geochemichal and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO4/2- -rich zones have localized SO4/2- -reducing zones in which the formation of iron disulfides been depleted by microbial reduction and resulted in decreases dissolved iron concentrations. These localized zones of SO4/2- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling. (C) 2000 Elsevier Science B.V.Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO42- in the aerobic zone, and to the reduction of SO42- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55??10-4 to 48.6??10-4mmol l-1yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO42- (1.31??10-4 to 15??10-4mmol l-1yr-1). The overall increase in SO42- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO42- loss through microbial reduction is exceeded by SO42- gain through diffusion from sediments and through the oxidation of FeS2. Geochemical and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO42--rich zones have been depleted by microbial reduction and resulted in localized SO42--reducing zones in which the formation of iron disulfides decreases dissolved iron concentrations. These localized zones of SO42- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling.

Significance of floods in metal dynamics and export in a small agricultural catchment

NASA Astrophysics Data System (ADS)

Roussiez, Vincent; Probst, Anne; Probst, Jean-Luc

2013-08-01

High-resolution monitoring of water discharge and water sampling were performed between early October 2006 and late September 2007 in the Montoussé River, a permanent stream draining an experimental agricultural catchment in Gascogne region (SW France). Dissolved and particulate concentrations of major elements and trace metals (i.e. Al, Fe, Mn, As, Cd, Cr, Cu, Ni, Pb, Sc and Zn) were examined. Our results showed that contamination levels were deficient to moderate, as a result of sustainable agricultural practices. Regarding dynamics, metal partitioning between particulate and dissolved phases was altered during flood conditions: the particulate phase was diluted by coarser and less contaminated particles from river bottom and banks, whereas the liquid phase was rapidly enriched owing to desorption mechanisms. Soluble/reactive elements were washed-off from soils at the beginning of the rain episode. The contribution of the flood event of May 2007 (by far the most significant episode over the study period) to the annual metal export was considerable for particulate forms (72-82%) and moderate for dissolved elements (0-20%). The hydrological functioning of the Montoussé stream poses dual threat on ecosystems, the consequences of which differ from both temporal and spatial scales: (i) desorption processes at the beginning of floods induce locally a rapid enrichment (up to 3.4-fold the pre-flood signatures on average for the event of May 2007) of waters in bioavailable metals, and (ii) labile metals - enriched by anthropogenic sources - associated to particles (mainly via carbonates and Fe/Mn oxides), were predominantly transferred during floods into downstream-connected rivers.

Iron dynamics: Transformation of Fe(II)/Fe(III) during injection of natural organic matter in a sandy aquifer

NASA Astrophysics Data System (ADS)

Liang, Liyuan; McCarthy, John F.; Jolley, Louwanda W.; McNabb, J. Andrew; Mehlhorn, Tonia L.

1993-05-01

The dynamics of dissolved, colloidal, and deposited iron phases were examined during a forced-gradient field experiment. The experiment involved the injection of oxygenated water containing high levels of natural organic matter (NOM) into a sandy aquifer. The initial redox potential of the aquifer favored Fe(II) in the groundwater. The changes in the concentrations of Fe(II) and Fe(III) were observed in sampling wells. Under the increased dissolved oxygen (DO) conditions, Fe(II) oxygenation was rapid, resulting in the formation of Fe(III) (hydr) oxide colloids. The oxidation follows the rate law as given in STUMM and MORGAN (1981): d[ Fe(II)] /dt = - k obs[ O2( aq)] /[ H+] 2[ Fe(II)] , with a rate constant, kobs to be 1.9 × 10 -12 M min -1. For an averaged pH and DO of the groundwater, the half time of Fe(II) oxidation is 49 h. The NOM was postulated to stabilize the newly formed colloids, thereby increasing the turbidity in the groundwater. The additional increase in the colloidal fraction of Fe(III) oxide suggested that transport of the colloidal particles was occurring. At those locations where DO remained constantly low, the turbidity increase was moderate, and up to 80% of Fe(III) was in the dissolved phase (< 3000 mol. wt). The latter observation was attributed to the presence of NOM, forming Fe(III)-organic complexes. In addition, NOM may play a role in the oxygen consumption through a Fe(II)/Fe(III) catalyzed oxidation of organic matter as outlined by STUMM and MORGAN (1981, p. 469). In this mechanism, Fe(II) oxidation is slow, maintaining a near constant Fe(II) concentration, in agreement with field data. The overall increase in Fe(III) under low DO conditions was postulated to be a combination of (1) slow oxidation, (2) ligand-promoted and catalytic dissolution of deposited iron phases, and (3) the transport of newly formed iron oxide colloids along flow paths.

Origin of Fe-Ti Oxide Mineralization in the Middle Paleoproterozoic Elet'ozero Syenite-Gabbro Intrusive Complex (Northern Karelia, Russia)

NASA Astrophysics Data System (ADS)

Sharkov, E. V.; Chistyakov, A. V.; Shchiptsov, V. V.; Bogina, M. M.; Frolov, P. V.

2018-03-01

Magmatic oxide mineralization widely developed in syenite-gabbro intrusive complexes is an important Fe and Ti resource. However, its origin is hotly debatable. Some researchers believe that the oxide ores were formed through precipitation of dense Ti-magnetite in an initial ferrogabbroic magma (Bai et al., 2012), whereas others consider them as a product of immiscible splitting of Fe-rich liquid during crystallization of Fe-Ti basaltic magma (Zhou et al., 2013). We consider this problem with a study of the Middle Paleoproterozoic (2086 ± 30 Ma) Elet'ozero Ti-bearing layered intrusive complex in northern Karelia (Baltic Shield). The first ore-bearing phase of the complex is mainly made up of diverse ferrogabbros, with subordinate clinopyroxenites and peridotites. Fe-Ti oxides (magnetite, Ti-magnetite, and ilmenite) usually account for 10-15 vol %, reaching 30-70% in ore varieties. The second intrusive phase is formed by alkaline and nepheline syenites. Petrographical, mineralogical, and geochemical data indicate that the first phase of the intrusion was derived from a moderately alkaline Fe-Ti basaltic melt, while the parental melt of the second phase was close in composition to alkaline trachyte. The orebodies comprise disseminated and massive ores. The disseminated Fe-Ti oxide ores make up lenses and layers conformable to general layering. Massive ores occur in subordinate amounts as layers and lenses, as well as cross-cutting veins. Elevated Nb and Ta contents in Fe-Ti oxides makes it possible to consider them complex ores. It is shown that the Fe-Ti oxide mineralization is related to the formation of a residual (Fe,Ti)-rich liquid, which lasted for the entire solidification history of the first intrusive phase. The liquid originated through multiple enrichment of Fe and Ti in the crystallization zone of the intrusion owing to the following processes: (1) precipitation of silicate minerals in the crystallization zone with a corresponding increase in the Fe and Ti contents in an interstitial melt; and (2) periodic accumulation of the residual melt in front of this zone. Unlike liquid immiscibility leading to melt splitting into two phases, this liquid dissolved the residual components of the melt. Correspondingly, such an Fe-rich liquid has unusual properties and requires further study.

An empirical method for estimating instream pre-mining pH and dissolved Cu concentration in catchments with acidic drainage and ferricrete

USGS Publications Warehouse

Nimick, D.A.; Gurrieri, J.T.; Furniss, G.

2009-01-01

Methods for assessing natural background water quality of streams affected by historical mining are vigorously debated. An empirical method is proposed in which stream-specific estimation equations are generated from relationships between either pH or dissolved Cu concentration in stream water and the Fe/Cu concentration ratio in Fe-precipitates presently forming in the stream. The equations and Fe/Cu ratios for pre-mining deposits of alluvial ferricrete then were used to reconstruct estimated pre-mining longitudinal profiles for pH and dissolved Cu in three acidic streams in Montana, USA. Primary assumptions underlying the proposed method are that alluvial ferricretes and modern Fe-precipitates share a common origin, that the Cu content of Fe-precipitates remains constant during and after conversion to ferricrete, and that geochemical factors other than pH and dissolved Cu concentration play a lesser role in determining Fe/Cu ratios in Fe-precipitates. The method was evaluated by applying it in a fourth, naturally acidic stream unaffected by mining, where estimated pre-mining pH and Cu concentrations were similar to present-day values, and by demonstrating that inflows, particularly from unmined areas, had consistent effects on both the pre-mining and measured profiles of pH and Cu concentration. Using this method, it was estimated that mining has affected about 480 m of Daisy Creek, 1.8 km of Fisher Creek, and at least 1 km of Swift Gulch. Mean values of pH decreased by about 0.6 pH units to about 3.2 in Daisy Creek and by 1-1.5 pH units to about 3.5 in Fisher Creek. In Swift Gulch, mining appears to have decreased pH from about 5.5 to as low as 3.6. Dissolved Cu concentrations increased due to mining almost 40% in Daisy Creek to a mean of 11.7 mg/L and as much as 230% in Fisher Creek to 0.690 mg/L. Uncertainty in the fate of Cu during the conversion of Fe-precipitates to ferricrete translates to potential errors in pre-mining estimates of as much as 0.25 units for pH and 22% for dissolved Cu concentration. The method warrants further testing in other mined and unmined watersheds. Comparison of pre-mining water-quality estimates derived from the ferricrete and other methods in single watersheds would be particularly valuable. The method has potential for use in monitoring remedial efforts at mine sites with ferricrete deposits. A reasonable remediation objective might be realized when the downstream pattern of Fe/Cu ratios in modern streambed Fe-precipitates corresponds to the pattern in pre-mining alluvial ferricrete deposits along a stream valley.

Phase constitution characteristics of the Fe-Al alloy layer in the HAZ of calorized steel pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Yajiang; Zou Zengda; Wei Xing

1997-09-01

Mechanical properties of the welding region and phase constitution characteristics in the iron-aluminum (Fe-Al) alloy layer of calorized steel pipes were researched by means of metallography, which included the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and an X-ray diffractometer. Experimental results indicated that the Fe-Al alloy layer of calorized steel pipe was mainly composed of an FeAl phase, an Fe{sub 3}Al phase and an {alpha}-Fe(Al) solid solution, and the microhardness in the Fe-Al coating was 600--310 HM from the surface layer to the inside. There were no higher aluminum content phases, suchmore » as brittle FeAl{sub 2}, Fe{sub 2}Al{sub 5} and FeAl{sub 3}. By controlling the aluminizing process parameters, the ability to bear deformation and weld-ability of the calorized steel pipe were remarkably improved.« less

Geochemical characteristics of dissolved rare earth elements in acid mine drainage from abandoned high-As coal mining area, southwestern China.

PubMed

Li, Xuexian; Wu, Pan

2017-09-01

Acid mine drainage (AMD) represents a major source of water pollution in the small watershed of Xingren coalfield in southwestern Guizhou Province. A detailed geochemical study was performed to investigate the origin, distribution, and migration of REEs by determining the concentrations of REEs and major solutes in AMD samples, concentrations of REEs in coal, bedrocks, and sediment samples, and modeling REEs aqueous species. The results highlighted that all water samples collected in the mining area are identified as low pH, high concentrations of Fe, Al, SO 4 2- and distinctive As and REEs. The spatial distributions of REEs showed a peak in where it is nearby the location of discharging of AMD, and then decrease significantly with distance away from the mining areas. Lots of labile REEs have an origin of coal and bedrocks, whereas the acid produced by the oxidation of pyrite is a prerequisite to cause the dissolution of coal and bedrocks, and then promoting REEs release in AMD. The North American Shale Composite (NASC)-normalized REE patterns of coal and bedrocks are enriched in light REEs (LREEs) and middle REEs (MREEs) relative to heavy REEs (HREEs). Contrary to these solid samples, AMD samples showed slightly enrichment of MREEs compared with LREEs and HREEs. This behavior implied that REEs probably fractionate during acid leaching, dissolution of bedrocks, and subsequent transport, so that the MREEs is primarily enriched in AMD samples. Calculation of REEs inorganic species for AMD demonstrated that sulfate complexes (Ln(SO 4 ) + and Ln(SO 4 ) 2 - ) predominate in these species, accounting for most of proportions for the total REEs species. The high concentrations of dissolved SO 4 2- and low pH play a decisive role in controlling the presence of REEs in AMD, as these conditions are necessary for formation of stable REEs-sulfate complexes in current study. The migration and transportation of REEs in AMD are more likely constrained by adsorption and co-precipitation of Fe-Al hydroxides/hydroxysulfate. In addition, the MREEs is preferentially captured by poorly crystalline Fe-Al hydroxides/hydroxysulfate, which favors that sediments also preserve NASC-normalized patterns with MREEs enrichment in the stream.

Determining the Pollution Parameters of Degirmendere Stream (Trabzon, NE TURKEY)

NASA Astrophysics Data System (ADS)

Sunnetci, M. O.; Hatipoglu, E.; Firat Ersoy, A.; Gultekin, F.

2013-12-01

The pollution parameters of Degirmendere Stream (Trabzon, TURKEY) are determined in this study. The study area is located between Maçka, 26 km to the south of Trabzon city, and the Black Sea. The area consists of Late Cretaceous volcano-sedimentary rocks, dacite, and basalt, overlain by Eocene volcanic rocks. Quaternary alluvium overlay all geological units following Degirmendere Stream bed. In-situ physical parameter measurements, anion-cation analysis, and heavy and pollutant element analysis on water samples were carried out for four months at four different locations on the stream. The stream's water temperature values were between 4.7 and 9.7oC, pH values were between 6.01 and 7.98, dissolved oxygen (DO) values were between 7.03 and 12.38 mg/l, electrical conductivity (EC) values were between 86 and 254 μS/cm. According to the Piper diagram, the stream water is classified as Ca-HCO3 type water. In the Schoeller diagram, the lines combining mek/l values of the ions in stream water are parallel. Al concentration in the stream water varied from 0.06 to 0.22 mg/l, Mn concentration varied from 0.1 to 0.36 mg/l, and Fe concentration varied from 0.01 to 0.12 mg/l. The stream water is classified as first class in point of temperature, pH, DO, total dissolved solids (TDS), NO3-, P, Pb, Fe, and Al; first and second class in point of NH4+; second class in point of Cu; and third class in point of NO2-, according to the Water Pollution Control Regulation of the Turkish Republic's Criteria for Inland Surface Water Classification. Results indicate waters of the Degirmendere Stream is very good-good for irrigation use according to the Wilcox diagram.

Effects of Al content and annealing on the phases formation, lattice parameters, and magnetization of A l x F e 2 B 2 ( x = 1.0 , 1.1 , 1.2 ) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levin, E. M.; Jensen, B. A.; Barua, R.

AlFe 2B 2 is a ferromagnet with the Curie temperature around 300 K and has the potential to be an outstanding rare-earth free candidate for magnetocaloric applications. However, samples prepared from the melt contain additional phases which affect the functional response of the AlFe 2B 2 phase. Here, we report on the effects of Al content in samples with the initial (nominal) composition of Al xFe 2B 2 where x=1.0, 1.1, and 1.2 prepared by arc-melting followed by suction casting and annealing. The as-cast Al xFe 2B 2 alloys contain AlFe 2B 2 as well as additional phases including themore » primary solidifying FeB and Al 13Fe 4 compounds which are ferromagnetic and paramagnetic, respectively, at 300 K. The presence of these phases makes it difficult to extract the intrinsic magnetic properties of AlFe 2B 2 phase. Annealing of Al xFe 2B 2 alloys at 1040°C for 3 days allows for reaction of the FeB with Al 13Fe 4 to form the AlFe 2B 2 phase, significantly reduces the amount of additional phases, and results in nearly pure AlFe 2B2 phase as confirmed with XRD, magnetization, scanning electron microscopy, and electronic transport. The values of the magnetization, effective magnetic moment per Fe atom, specific heat capacity, electrical resistivity and Seebeck coefficient for the AlFe 2B 2 compound have been established.« less

Effects of Al content and annealing on the phases formation, lattice parameters, and magnetization of A l x F e 2 B 2 ( x = 1.0 , 1.1 , 1.2 ) alloys

DOE PAGES

Levin, E. M.; Jensen, B. A.; Barua, R.; ...

2018-03-26

AlFe 2B 2 is a ferromagnet with the Curie temperature around 300 K and has the potential to be an outstanding rare-earth free candidate for magnetocaloric applications. However, samples prepared from the melt contain additional phases which affect the functional response of the AlFe 2B 2 phase. Here, we report on the effects of Al content in samples with the initial (nominal) composition of Al xFe 2B 2 where x=1.0, 1.1, and 1.2 prepared by arc-melting followed by suction casting and annealing. The as-cast Al xFe 2B 2 alloys contain AlFe 2B 2 as well as additional phases including themore » primary solidifying FeB and Al 13Fe 4 compounds which are ferromagnetic and paramagnetic, respectively, at 300 K. The presence of these phases makes it difficult to extract the intrinsic magnetic properties of AlFe 2B 2 phase. Annealing of Al xFe 2B 2 alloys at 1040°C for 3 days allows for reaction of the FeB with Al 13Fe 4 to form the AlFe 2B 2 phase, significantly reduces the amount of additional phases, and results in nearly pure AlFe 2B2 phase as confirmed with XRD, magnetization, scanning electron microscopy, and electronic transport. The values of the magnetization, effective magnetic moment per Fe atom, specific heat capacity, electrical resistivity and Seebeck coefficient for the AlFe 2B 2 compound have been established.« less

Atrazine sorption by hydroxy-interlayered clays and their organic complexes.

PubMed

Indraratne, Srimathie P; Farenhorst, Annemieke; Goh, Tee Boon

2008-01-01

This study examined the sorption of atrazine by hydroxy-Fe interlayered montmorillonite (FeMt) and its hydroquinone (FeMtHQ), citrate (FeMtCt) and catechol (FeMtCC) complexes as well as by hydroxy-Al interlayered montmorillonite (AlMt) and its hydroquinone (AlMtHQ) and citrate (AlMtCt) complexes. Found among the clays were sorption distribution coefficients (K(d)) ranging from 24 to 123 mL g(-1) and maximum sorption (M) ranging from 2.2 to 16.8 microg g(-1). Both K(d) and M decreased in the order of FeMtCC > FeMtHQ > AlMtHQ > (AlMt = FeMt) > (AlMtCt = FeMtCt). The pH was negatively correlated with both K(d) (r = -0.90, p < 0.001) and M (r = -0.81, p < 0.001). When interlayered clays were associated with humified material (FeMtCC, FeMtHQ, AlMtHQ), both K(d) (r > 0.96, p < 0.01) and M (r > 0.94, p < 0.01) were highly positively correlated with total organic C and alkali-soluble C. However, clays with non-humified organic compounds (FeMtCt and AlMtCt) sorbed less atrazine than clays without any organic C (FeMt and AlMt). This suggests that functional groups of Fe-OH and Al-OH in FeMt and AlMt reduced the available sorption sites for atrazine by making complexes with citrate ions while forming FeMtCt and AlMtCt. The atrazine was sorbed through the hydrophobic interactions with organic compound surfaces as well as through H-bonding and ionic bonding with clay-mineral surfaces.

Dissolved and particulate Barium in the Ganga (Hooghly) River estuary, India: Solute-particle interactions and the enhanced dissolved flux to the oceans

NASA Astrophysics Data System (ADS)

Samanta, Saumik; Dalai, Tarun K.

2016-12-01

In this study, the sources and the cycling of Ba have been evaluated in the Ganga (Hooghly) River estuary using the composition of the suspended sediments and the water samples collected during six seasons of contrasting water discharge over two years (2012 and 2013). In addition, the data on the samples of groundwater from areas adjacent to the estuary, and the industrial effluent water and urban wastewater draining into the estuary are presented. Selective extraction experiments were also performed on the suspended particulate matter of two seasons to assess the distribution of exchangeable concentrations of major ions and Ba. In the mixing zone, the variation patterns of the dissolved Ba concentrations show mid-salinity maxima and are similar to the patterns of variation of the particulate Mg/Al and Mg/Fe, suggesting that the production of dissolved Ba is linked to the adsorption of major ions on to the clay minerals and Fe-Mn oxyhydroxides in the particulate matter. The inference of coupled adsorption-desorption processes is supported by the observations that the particulate Ba/Mg and Ba/K ratios exhibit significant to strong negative correlations with the concentrations of Al, Fe and Mn. The observations of mid-salinity maxima for the concentrations of exchangeable Mg and K, and of the exchangeable Ba concentrations that decrease with salinity provide strong evidence that the solute-particle interactions is the major driver in regulating the dissolved Ba distributions in the estuary. The estimates of the quantity of desorbed Ba based on three different approaches suggest that desorption is sufficient to account for the calculated excess Ba (Baxs) concentrations. The contribution of Ba to the dissolved load via dissolution of the particulate carbonate phases is minor, up to 3% of the maximum Baxs concentrations. The estimates of anthropogenic contributions are insignificant, and account for ⩽2% of maximum Baxs in the estuary. Groundwater contributions are less significant and account for up to 5% of the annual Ba flux from the Hooghly estuary. The estimates of Ba flux show that annually (1.5-1.9) × 107 moles of Ba is transported by the Hooghly River. About (3.6-4.3) × 107 moles of Ba is generated annually in the estuary through desorption. Added together, the desorbed and riverine Ba fluxes generate a total Ba flux of (5.1-6.2) × 107 moles per year. Thus, the solute-particle interactions enhance the riverine Ba flux by >300%. A compilation of the available data shows that the enhancement of the riverine Ba flux and the fractions of desorbed Ba flux scale with (particulate matter flux/water flux) ratio in several estuaries of the world, suggesting that the process of solute-particle interactions is a major driver for the estuarine production of Ba on a global scale. Among the rivers considered in this study, the estuaries of the Hooghly River and the Ganges-Brahmaputra rivers, characterized by very high (sediment flux/water flux) ratio, depict the highest increase in the riverine Ba flux. This unique feature of the Ganga River system is inferred to be resulting from the collective impact of the tectonic activity and the monsoonal rainfall in the catchment areas.

TEM/STEM study of Zircaloy-2 with protective FeAl(Cr) layers under simulated BWR environment and high-temperature steam exposure

NASA Astrophysics Data System (ADS)

Park, Donghee; Mouche, Peter A.; Zhong, Weicheng; Mandapaka, Kiran K.; Was, Gary S.; Heuser, Brent J.

2018-04-01

FeAl(Cr) thin-film depositions on Zircaloy-2 were studied using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) with respect to oxidation behavior under simulated boiling water reactor (BWR) conditions and high-temperature steam. Columnar grains of FeAl with Cr in solid solution were formed on Zircaloy-2 coupons using magnetron sputtering. NiFe2O4 precipitates on the surface of the FeAl(Cr) coatings were observed after the sample was exposed to the simulated BWR environment. High-temperature steam exposure resulted in grain growth and consumption of the FeAl(Cr) layer, but no delamination at the interface. Outward Al diffusion from the FeAl(Cr) layer occurred during high-temperature steam exposure (700 °C for 3.6 h) to form a 100-nm-thick alumina oxide layer, which was effective in mitigating oxidation of the Zircaloy-2 coupons. Zr intermetallic precipitates formed near the FeAl(Cr) layer due to the inward diffusion of Fe and Al. The counterflow of vacancies in response to the Al and Fe diffusion led to porosity within the FeAl(Cr) layer.

A phytoremediation approach using Calamagrostis ligulata and Juncus imbricatus in Andean wetlands of Peru.

PubMed

Miguel, Bobadilla; Edell, Aliaga; Edson, Yupanqui; Edwin, Palomino

2013-01-01

Emergent plant species growing in Andean natural wetlands have shown efficient phytoremediation capabilities in wetlands polluted by acid mine drainage. However, the types and amounts of heavy metals accumulated by native plant species are not well understood. In this study, we focused on determining heavy metal concentrations and bioaccumulation factors in Calamagrostis ligulata and Juncus imbricatus. Two acid wetlands located above 3,500 m a.s.l. in Ancash, Peru were assessed. Physico-chemical parameters and heavy metals concentrations in control and experimental plant samples were measured in dry and rainy seasons. Results indicated that C. ligulata and J. imbricatus aerial parts accumulated higher amounts of Fe, Zn, As and Al. Also, bioaccumulation factors revealed notable increases in As, Pb and Al, but less so in Cd, Fe and Zn. On the other hand, physico-chemical parameters of water quality (pH, temperature, dissolved oxygen, sulphides) between inflow and outflow of wetlands indicated significant differences in the presence of metals in comparison with their maximum permissible limits. Both emergent plant species showed an accumulation of heavy metals and thus the ability to recovery of water quality in wetland outflows.

Tuning the reactivity of Al/Fe{sub 2}O{sub 3} nanoenergetic materials via an approach combining soft template self-assembly with sol–gel process process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Tianfu; Wang, Zhen; Li, Guoping

2015-10-15

A bottom-up approach combining soft template self-assembly with sol–gel process, was adopted to prepare the assembled Al/Fe{sub 2}O{sub 3} nanoenergetic materials, assembly-Al/Fe{sub 2}O{sub 3} sample. The other two unassembled Al/Fe{sub 2}O{sub 3}a nanoenergetic materials, sol–gel–Al/Fe{sub 2}O{sub 3} sample and mixing-Al/Fe{sub 2}O{sub 3} sample, were prepared by sol–gel method and physical mixing method respectively. The assembly process within the preparation of the assembly-Al/Fe{sub 2}O{sub 3} sample was analyzed through the changes in the average hydrodynamic diameters of the particles and the micelles in solution. SEM, EDS and TEM tests were performed to demonstrate a significant improvement regarding to dispersity and arrangementsmore » of the Al and Fe{sub 2}O{sub 3} particles in the assembled samples, compared to that of the unassembled Al/Fe{sub 2}O{sub 3} samples. DSC test was employed to characterize the reactivity of the samples. The heat release of the assembled Al/Fe{sub 2}O{sub 3} sample was 2088 J/g, about 400 and 990 J/g more than that of the sol–gel–Al/Fe{sub 2}O{sub 3} sample and mixing-Al/Fe{sub 2}O{sub 3} sample, respectively. - Graphical abstract: Modified aluminum (Al) nanoparticles with hydrophobic surface assembled into the Brij S10 micelle in Fe(III) sol, then the well dispersed system was transformed into Al/Fe{sub 2}O{sub 3} nanoenergetic materials with high reactivity. - Highlights: • An approach combining soft template self-assembly with sol–gel process was adopted. • The aggregation of Al nanoparticles in the final product was reduced significantly. • The reactivity of Al/Fe{sub 2}O{sub 3} nanoenergetic materials was improved to a large extent.« less

Evaluation of air sparging and vadose zone aeration for remediation of iron and manganese-impacted groundwater at a closed municipal landfill.

PubMed

Pleasant, Saraya; O'Donnell, Amanda; Powell, Jon; Jain, Pradeep; Townsend, Timothy

2014-07-01

High concentrations of iron (Fe(II)) and manganese (Mn(II)) reductively dissolved from soil minerals have been detected in groundwater monitoring wells near many municipal solid waste landfills. Air sparging and vadose zone aeration (VZA) were evaluated as remedial approaches at a closed, unlined municipal solid waste landfill in Florida, USA. The goal of aeration was to oxidize Fe and Mn to their respective immobile forms. VZA and shallow air sparging using a partially submerged well screen were employed with limited success (Phase 1); decreases in dissolved iron were observed in three of nine monitoring wells during shallow air sparging and in two of 17 wells at VZA locations. During Phase 2, where deeper air sparging was employed, dissolved iron levels decreased in a significantly greater number of monitoring wells surrounding injection points, however no radial pattern was observed. Additionally, in wells affected positively by air sparging (mean total iron (FeTOT) <4.2mg/L, after commencement of air sparging), rising manganese concentrations were observed, indicating that the redox potential of the groundwater moved from an iron-reducing to a manganese-reducing environment. The mean FeTOT concentration observed in affected monitoring wells throughout the study was 1.40 mg/L compared to a background of 15.38 mg/L, while the mean Mn concentration was 0.60 mg/L compared to a background level of 0.27 mg/L. Reference wells located beyond the influence of air sparging areas showed little variation in FeTOT and Mn, indicating the observed effects were the result of air injection activities at study locations and not a natural phenomenon. Air sparging was found effective in intercepting plumes of dissolved Fe surrounding municipal landfills, but the effect on dissolved Mn was contrary to the desired outcome of decreased Mn groundwater concentrations. Copyright © 2014 Elsevier B.V. All rights reserved.

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume

USGS Publications Warehouse

Ziegler, Brady A.; Schreiber, Madeline E.; Cozzarelli, Isabelle M.

2017-01-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011–2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich “iron curtain,” associated with the anoxic-suboxic transition zone, migrated 30 m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter.

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume.

PubMed

Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M

2017-09-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011-2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich "iron curtain," associated with the anoxic-suboxic transition zone, migrated 30m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of Low-Symmetry Structures from Phase Equilibrium of Fe-Al System—Microstructures and Mechanical Properties

PubMed Central

Matysik, Piotr; Jóźwiak, Stanisław; Czujko, Tomasz

2015-01-01

Fe-Al intermetallic alloys with aluminum content over 60 at% are in the area of the phase equilibrium diagram that is considerably less investigated in comparison to the high-symmetry Fe3Al and FeAl phases. Ambiguous crystallographic information and incoherent data referring to the phase equilibrium diagrams placed in a high-aluminum range have caused confusions and misinformation. Nowadays unequivocal material properties description of FeAl2, Fe2Al5 and FeAl3 intermetallic alloys is still incomplete. In this paper, the influence of aluminum content and processing parameters on phase composition is presented. The occurrence of low-symmetry FeAl2, Fe2Al5 and FeAl3 structures determined by chemical composition and phase transformations was defined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) examinations. These results served to verify diffraction investigations (XRD) and to explain the mechanical properties of cast materials such as: hardness, Young’s modulus and fracture toughness evaluated using the nano-indentation technique. PMID:28787979

Weathering controls on mechanisms of carbon storage in grassland soils

USGS Publications Warehouse

Masiello, C.A.; Chadwick, O.A.; Southon, J.; Torn, M.S.; Harden, J.W.

2004-01-01

On a sequence of soils developed under similar vegetation, temperature, and precipitation conditions, but with variations in mineralogical properties, we use organic carbon and 14C inventories to examine mineral protection of soil organic carbon. In these soils, 14C data indicate that the creation of slow-cycling carbon can be modeled as occurring through reaction of organic ligands with Al3+ and Fe3+ cations in the upper horizons, followed by sorption to amorphous inorganic Al compounds at depth. Only one of these processes, the chelation Al3+ and Fe3+ by organic ligands, is linked to large carbon stocks. Organic ligands stabilized by this process traverse the soil column as dissolved organic carbon (both from surface horizons and root exudates). At our moist grassland site, this chelation and transport process is very strongly correlated with the storage and long-term stabilization of soil organic carbon. Our 14C results show that the mechanisms of organic carbon transport and storage at this site follow a classic model previously believed to only be significant in a single soil order (Spodosols), and closely related to the presence of forests. The presence of this process in the grassland Alfisol, Inceptisol, and Mollisol soils of this chronosequence suggests that this process is a more significant control on organic carbon storage than previously thought. Copyright 2004 by the American Geophysical Union.

Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy.

PubMed

Slenkamp, Karla M; Lynch, Michael S; Van Kuiken, Benjamin E; Brookes, Jennifer F; Bannan, Caitlin C; Daifuku, Stephanie L; Khalil, Munira

2014-02-28

Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (νCN) vibrations found in [(NH3)5Ru(III)NCFe(II)(CN)5](-) (FeRu) dissolved in D2O and formamide and [(NC)5Fe(II)CNPt(IV)(NH3)4NCFe(II)(CN)5](4-) (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the νCN modes in the electronic ground state. The FTIR spectra of the νCN modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic νCN modes. The vibrational mode anharmonicities of the individual νCN modes range from 14 to 28 cm(-1). The mixed-mode anharmonicities range from 2 to 14 cm(-1). In general, the bridging νCN mode is most weakly coupled to the radial νCN mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four νCN modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D2O. The νCN modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm(-1). This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the νCN modes in cyanide-bridged transition metal mixed valence complexes.

Menzerite-(Y) a New Species {(Y REE)(Ca Fe2plus)2}[(Mg Fe2plus)(Fe3plus Al)](Si3)O12 from a Felsic Granulite Parry Sound Ontario and a New Garnet End-member (Y2Ca)Mg2(SiO4)3

DOE Office of Scientific and Technical Information (OSTI.GOV)

E Grew; J Marsh; M Yates

2011-12-31

Menzerite-(Y), a new mineral species, forms reddish brown cores, n = 1.844 (20), up to 70 {micro}m across, rimmed successively by euhedral almandine containing up to 2.7 wt% Y{sub 2}O{sub 3} and by K-feldspar in a felsic granulite on Bonnet Island in the interior Parry Sound domain, Grenville Orogenic Province, Canada. It is named after Georg Menzer (1897-1989), the German crystallographer who solved the crystal structure of garnet. Single-crystal X-ray-diffraction results yielded space group Ia3d, a = 11.9947(6) {angstrom}. An electron-microprobe analysis of the grain richest in Y (16.93 wt% Y{sub 2}O{sub 3}) gave the following formula, normalized to eightmore » cations and 12 oxygen atoms: {l_brace}Y{sub 0.83}Gd{sub 0.01}Dy{sub 0.05}Ho{sub 0.02}Er{sub 0.07}Tm{sub 0.01}Yb{sub 0.06}Lu{sub 0.02}Ca{sub 1.37}Fe{sub 0.49}{sup 2+}Mn{sub 0.07}{r_brace} [Mg{sub 0.55}Fe{sub 0.42}{sup 2+}Fe{sub 0.58}{sup 3+}Al{sub 0.35} V{sub 0.01}Sc{sub 0.01}Ti{sub 0.08}](Si{sub 2.82}Al{sub 0.18})O{sub 12}, or {l_brace}(Y,REE)(Ca,Fe{sup 2+}){sub 2}{r_brace}[(Mg,Fe{sup 2+})(Fe{sup 3+},Al)](Si{sub 3})O{sub 12}. Synchrotron micro-XANES data gave Fe{sup 3+}/{Sigma}Fe = 0.56(10) versus 0.39(2) calculated from stoichiometry. The scattering power refined at the octahedral Y site, 17.68 epfu, indicates that a relatively light element contributes to its occupancy. Magnesium, as determined by electron-microprobe analyses, would be a proper candidate. In addition, considering the complex occupancy of this site, the average Y-O bond length of 2.0244(16) {angstrom} is in accord with a partial occupancy by Mg. The dominance of divalent cations with Mg > Fe{sup 2+} and the absence of Si at the octahedral Y site (in square brackets) are the primary criteria for distinguishing menzerite-(Y) from other silicate garnet species; the menzerite-(Y) end-member is {l_brace}Y{sub 2}Ca{r_brace}[Mg{sub 2}](Si{sub 3})O{sub 12}. The contacts of menzerite-(Y) with almandine are generally sharp and, in places, cuspate. It is interpreted to have equilibrated with ferrosilite, augite, quartz, oligoclase, allanite-(Ce), magnetite, ilmenite and fluorapatite, in the absence of almandine, on the prograde path at 7-8.5 kbar and T {approx} 700-800 C, and subsequently dissolved incongruently in an anatectic melt to form almandine, most likely, at P {approx} 8.5-9.5 kbar and T {approx} 800-850 C.« less

Flavins secreted by roots of iron-deficient Beta vulgaris enable mining of ferric oxide via reductive mechanisms.

PubMed

Sisó-Terraza, Patricia; Rios, Juan J; Abadía, Javier; Abadía, Anunciación; Álvarez-Fernández, Ana

2016-01-01

Iron (Fe) is abundant in soils but generally poorly soluble. Plants, with the exception of Graminaceae, take up Fe using an Fe(III)-chelate reductase coupled to an Fe(II) transporter. Whether or not nongraminaceous species can convert scarcely soluble Fe(III) forms into soluble Fe forms has deserved little attention so far. We have used Beta vulgaris, one among the many species whose roots secrete flavins upon Fe deficiency, to study whether or not flavins are involved in Fe acquisition. Flavins secreted by Fe-deficient plants were removed from the nutrient solution, and plants were compared with Fe-sufficient plants and Fe-deficient plants without flavin removal. Solubilization of a scarcely soluble Fe(III)-oxide was assessed in the presence or absence of flavins, NADH (nicotinamide adenine dinucleotide, reduced form) or plant roots, and an Fe(II) trapping agent. The removal of flavins from the nutrient solution aggravated the Fe deficiency-induced leaf chlorosis. Flavins were able to dissolve an Fe(III)-oxide in the presence of NADH. The addition of extracellular flavins enabled roots of Fe-deficient plants to reductively dissolve an Fe(III)-oxide. We concluded that root-secretion of flavins improves Fe nutrition in B. vulgaris. Flavins allow B. vulgaris roots to mine Fe from Fe(III)-oxides via reductive mechanisms. © 2015 CSIC New Phytologist © 2015 New Phytologist Trust.

RETRACTED ARTICLE: Precipitation behavior of B2-ordered aluminide

NASA Astrophysics Data System (ADS)

Han, Chang-Suk

2006-12-01

Fine dispersion of disordered phases is obtained in Ni-Al-Cr and Fe-Al-Co temary systems. A transmission electron microscope investigation has been performed on the precipitation of α-Cr in B2-ordered β-NiAl with different stoichiometry and α-Fe in B2-FeAl(Co) compound. Precipitation behavior and hardening were investigated by measuring the hardness variation. The hardness of NiAl and FeAl increases appreciably with the fine precipitation of α-Cr and α-Fe, and over-age softening occurs after prolonged aging. In the case of B2-NiAl(Cr), perfect lattice coherency is maintained at the interfaces between the α-Cr particles and the matrix during the initial stage of aging. After prolonged aging, a loss of coherency occurs by the attraction of matrix dislocations to the particle/matrix interface, followed by climbing around the particles. On the other hand, in the case of B2-FeAl(Co), the disordered α-Fe phase is present as a precipitate in the B2-FeAl(Co) matrix and has a cubic-cubic orientation with the matrix. At the early aging periods, prismatic dislocation loops formed in the B2-FeAl(Co) matrix. B2-FeAl(Co) matrix is typically hardened by the precipitation of α-Fe.

Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use.

PubMed

Yu, Changxun; Peltola, Pasi; Nystrand, Miriam I; Virtasalo, Joonas J; Österholm, Peter; Ojala, Antti E K; Hogmalm, Johan K; Åström, Mats E

2016-01-15

This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Rönnskär smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter. Copyright © 2015 Elsevier B.V. All rights reserved.

EXAFS Reveals the Mechanism of U Isotope Fractionation During Adsorption to Mn Oxyhydroxide

NASA Astrophysics Data System (ADS)

Wasylenki, L. E.; Brennecka, G.; Bargar, J.; Weyer, S.; Anbar, A. D.

2010-12-01

Natural variations in the ratio of 238U/235U due to “stable” isotope fractionation have now been reported for a range of geological samples [1-3]. Among the observed variations are a small difference in 238U/235U between seawater and ferromanganese sediments (seawater slightly heavier) and a larger difference, with opposite sense, between seawater and black shales (seawater lighter). These variations suggest that long-term changes in the proportions of oxic and anoxic/sulfidic sinks for U in the ocean over Earth’s history may be recorded as shifts in the isotopic compositions of marine sediments. Thus U isotopes are a potential paleoredox proxy for the oceans, as suggested by [4]. In order to investigate the mechanism behind fractionation of U isotopes in oxidizing marine environments, we previously conducted simple adsorption experiments in which an isotopically known pool of dissolved U partly adsorbed onto synthetic birnessite, a common Mn oxyhydroxide in hydrogenetic ferromanganese crusts. Our experimental result agreed very well with that observed between seawater and natural ferromanganese sediments: δ238U/235U of adsorbed U was 0.2‰ lighter than δ238U/235U of dissolved U [5]. The magnitude of fractionation is constant as a function of experimental duration and fraction of U adsorbed, suggesting an equilibrium isotope effect. Many metal isotope effects are driven by changes in oxidation state for the metal of interest. Because both dissolved and adsorbed U are hexavalent in this system, a redox reaction cannot be causing isotope fractionation. We therefore hypothesized that a difference in uranium’s coordination environment between dissolved and adsorbed U is likely responsible for the isotope effect. We analyzed a sample from our experimental study with extended X-ray absorption fine structure (EXAFS) spectroscopy. Comparison of the EXAFS spectrum of U adsorbed on birnessite with the spectra of aqueous U species (UO22+ and UO2(CO3)34-) reveals subtle, but important differences in the U-O coordination shell between dissolved and adsorbed U. In particular, there is an increase in disorder in the bond distances to equatorial oxygens in the adsorbed complex. Our EXAFS data support our hypothesis that a difference in coordination chemistry drives the isotope effect observed in our experiments. The same mechanism may well explain the U isotope fractionation observed between seawater and hydrogenetic ferromanganese nodules, although a similar investigation of U isotope behavior during adsorption to Fe oxyhydroxides should be undertaken. [1] Weyer et al. (2008) GCA 72, 345. [2] Stirling et al. (2007) EPSL 264, 208. [3] Bopp et al. (2009) Geology, 37, 611. [4] Montoya-Pino et al. (2010) Geology 38, 315. [5] Brennecka et al. (2008) GCA 72(12) Suppl., A114.

The cycling of iron, zinc and cadmium in the North East Pacific Ocean - Insights from stable isotopes

NASA Astrophysics Data System (ADS)

Conway, Tim M.; John, Seth G.

2015-09-01

Dissolved stable isotope ratios of the transition metals provide useful information, both for understanding the cycling of these bioactive trace elements through the oceans, and tracing their marine sources and sinks. Here, we present seawater dissolved Fe, Zn and Cd concentration and stable isotope ratio (δ56Fe, δ66Zn, and δ114Cd) profiles from two stations in the Pacific Ocean, the SAFe Station (30°N 140°W) in the subtropical North East Pacific from the GEOTRACES IC2 cruise, and the marginal San Pedro Basin (33.8°N 118.4°W) within the South California Bight. These data represent, to our knowledge, the first full-water column profiles for δ66Zn and δ56Fe from the open-ocean North Pacific, and the first observations of dissolved δ66Zn and δ114Cd in a low-oxygen marginal basin. At the SAFe station, δ56Fe is isotopically lighter throughout the water column (-0.6 to +0.1‰, relative to IRRM-014) compared to the North Atlantic, suggesting significant differences in Fe sources or Fe cycling between these two ocean basins. A broad minimum in δ56Fe associated with the North Pacific oxygen minimum zone (OMZ; <75 μmol kg-1 dissolved oxygen; ∼550-2000 m depth) is consistent with reductive sediments along the California margin being an important source of dissolved Fe to the North Pacific. Other processes which may influence δ56Fe at SAFe include biological cycling in the upper ocean, and input of Fe from hydrothermal vents and oxic sediments below the OMZ. Zn and Cd concentration profiles at both stations broadly match the distribution of the macronutrients silicate and phosphate, respectively. At SAFe, δ114Cd increases towards the surface, reflecting the biological preference for assimilation of lighter Cd isotopes, while negative Cd∗ (-0.12) associated with low oxygen waters supports the recently proposed hypothesis of water-column CdS precipitation. In contrast to δ114Cd, δ66Zn at SAFe decreases towards the surface ocean, perhaps due to scavenging of isotopically heavy Zn, while at intermediate depths δ66Zn provides further evidence of a mid-depth dissolved δ66Zn maximum. We suggest this may be a global feature of Zn biogeochemistry related to either regeneration of heavy adsorbed Zn, or to ZnS formation and removal within the water column. Data from San Pedro shows that anoxic sediments can be a source of isotopically light Zn to the water column (δ66Zn of ∼-0.3‰ relative to JMC Lyon), though evidence of this signal is not observed being transported to SAFe. Within North Pacific Intermediate Water at SAFe (NPIW; ∼500 m) elevated Cd∗ and Zn∗ and a focused minimum in δ56Fe suggest possible transport of Fe, Zn, and Cd over thousands of km from subpolar waters, meaning that NPIW may have a strong influence on the subsurface distribution of trace metals throughout the North Pacific.

Room temperature luminescence and ferromagnetism of AlN:Fe

NASA Astrophysics Data System (ADS)

Li, H.; Cai, G. M.; Wang, W. J.

2016-06-01

AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR) method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe2+ state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV) and 598 nm (2.07 eV) are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

Aluminum Coprecipitates with Fe (hydr)oxides: Does Isomorphous Substitution of Al3plus for Fe3plus in Goethite Occur

DOE Office of Scientific and Technical Information (OSTI.GOV)

E Bazilevskaya; D Archibald; M Aryanpour

2011-12-31

Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitatesmore » were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with {<=}20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with {>=}25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with {<=}25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with 30 mol% Al (at pH {approx}2.25 for Fe{sup 3+} and at pH {approx}4 for Al{sup 3+}), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 Mol% Al) in clustered arrangement (i.e., the formation of diaspore-like clusters) were in good agreement with available experimental data whereas optimized unit cell parameters for isolated Al atoms were not, and (ii) Al-substituted goethites with Al in diaspore-like clusters resulted in more energetically favored structures. Combined experimental and DFT results are consistent with the coprecipitation of Al with Fe (hydr)oxides and with the formation of diaspore-like clusters, whereas DFT results suggest isomorphous Al for Fe substitution within goethite is unlike at 8 mol% Al substitution.« less

Effect of nano-oxide layers on giant magnetoresistance in pseudo-spin-valves using Co 2FeAl electrodes

NASA Astrophysics Data System (ADS)

Zhang, D. L.; Xu, X. G.; Wu, Y.; Miao, J.; Jiang, Y.

2011-03-01

We studied the pseudo-spin-valves (PSVs) with a structure of Ta/Co 2FeAl/NOL 1/Co 2FeAl/Cu/Co 2FeAl/NOL 2/Ta, where NOL represents the nano-oxide layer. Compared with the normal Co 2FeAl (CFA) PSV with a structure of Ta/Co 2FeAl/Cu/Co 2FeAl/Ta, which shows only a current-in-plane (CIP) giant magnetoresistance (GMR) of 0.03%, the CFA PSV with NOLs shows a large CIP-GMR of 5.84%. The enhanced GMR by the NOLs inserted in the CFA PSV is due to the large specular reflection caused by [(CoO)(Fe 2O 3)(Al 2O 3)] in NOL 1 and [(Fe 2O 3)(Al 2O 3)(Ta 2O 5)] in NOL 2. Another reason is that the roughness of the interface between Ta and CFA is improved by the oxidation procedure.

Distinct Siderophores Contribute to Iron Cycling in the Mesopelagic at Station ALOHA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bundy, Randelle M.; Boiteau, Rene M.; McLean, Craig

The distribution of dissolved iron (Fe), total organic Fe-binding ligands, and siderophores were measured between the surface and 400 m at Station ALOHA, a long term ecological study site in the North Pacific Subtropical Gyre. Dissolved Fe concentrations were low throughout the water column and strong organic Fe-binding ligands exceeded dissolved Fe at all depths; varying from 0.9 nmol L -1 in the surface to 1.6 nmol L -1 below 150 m. Although Fe does not appear to limit microbial production, we nevertheless found siderophores at nearly all depths, indicating some populations of microbes were responding to Fe stress. Ferrioxaminemore » siderophores were most abundant in the upper water column, with concentrations between 0.1-2 pmol L -1, while a suite of amphibactins were found below 200 m with concentrations between 0.8-11 pmol L -1. The distinct vertical distribution of ferrioxamines and amphibactins may indicate disparate strategies for acquiring Fe from dust in the upper water column and recycled organic matter in the lower water column. Amphibactins were found to have conditional stability constants (log ) ranging from 12.0-12.5, while ferrioxamines had much stronger conditional stability constants ranging from 14.0-14.4, within the range of observed L1 ligands by voltammetry. We used our data to calculate equilibrium Fe speciation at Station ALOHA to compare the relative concentration of inorganic and siderophore complexed Fe. The results indicate that the concentration of Fe bound to siderophores was up to two orders of magnitude higher than inorganic Fe, suggesting that even if less bioavailable, siderophores were nevertheless a viable pathway for Fe acquisition by microbes at our study site. Finally, we observed rapid production of ferrioxamine E by particle-associated bacteria during incubation of freshly collected sinking organic matter. Fe-limitation may therefore be a factor in regulating carbon metabolism and nutrient regeneration in the mesopelagic.« less

Distinct Siderophores Contribute to Iron Cycling in the Mesopelagic at Station ALOHA

DOE PAGES

Bundy, Randelle M.; Boiteau, Rene M.; McLean, Craig; ...

2018-03-01

The distribution of dissolved iron (Fe), total organic Fe-binding ligands, and siderophores were measured between the surface and 400 m at Station ALOHA, a long term ecological study site in the North Pacific Subtropical Gyre. Dissolved Fe concentrations were low throughout the water column and strong organic Fe-binding ligands exceeded dissolved Fe at all depths; varying from 0.9 nmol L -1 in the surface to 1.6 nmol L -1 below 150 m. Although Fe does not appear to limit microbial production, we nevertheless found siderophores at nearly all depths, indicating some populations of microbes were responding to Fe stress. Ferrioxaminemore » siderophores were most abundant in the upper water column, with concentrations between 0.1-2 pmol L -1, while a suite of amphibactins were found below 200 m with concentrations between 0.8-11 pmol L -1. The distinct vertical distribution of ferrioxamines and amphibactins may indicate disparate strategies for acquiring Fe from dust in the upper water column and recycled organic matter in the lower water column. Amphibactins were found to have conditional stability constants (log ) ranging from 12.0-12.5, while ferrioxamines had much stronger conditional stability constants ranging from 14.0-14.4, within the range of observed L1 ligands by voltammetry. We used our data to calculate equilibrium Fe speciation at Station ALOHA to compare the relative concentration of inorganic and siderophore complexed Fe. The results indicate that the concentration of Fe bound to siderophores was up to two orders of magnitude higher than inorganic Fe, suggesting that even if less bioavailable, siderophores were nevertheless a viable pathway for Fe acquisition by microbes at our study site. Finally, we observed rapid production of ferrioxamine E by particle-associated bacteria during incubation of freshly collected sinking organic matter. Fe-limitation may therefore be a factor in regulating carbon metabolism and nutrient regeneration in the mesopelagic.« less

Physical versus chemical effects on bacterial and bromide transport as determined from on site sediment column pulse experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, James A.; Mailloux, Brian J.; Onstott, Tullis C.

2005-02-01

Twenty eight bacterial and Br transport experiments were performed in the field to determine the effects of physical and chemical heterogeneity of the aquifer sediment. The experiments were performed using groundwater from two field locations to examine the effects of groundwater chemistry on transport. Groundwater was extracted from multilevel samplers and pumped through 7 cm long columns of intact sediment or re-packed sieved and coated or uncoated sediment from the underlying aquifer. Two bacterial strains, Comamonas sp. DA001 and Paenibacillus polymyxa FER-02, were injected along with Br into the influent end of the columns to examine the effect of cellmore » morphology and surface properties on bacterial transport. The effect of column sediment grain size and mineral coatings coupled with groundwater geochemistry were also delineated. Significant irreversible attachment of DA001 was observed in the Fe oxyhydroxide coated columns, but only in the sub-oxic groundwater where the concentrations of dissolved organic carbon (DOC) were ca. 1 ppm. In the oxic groundwater where DOC was ca. 8 ppm, little attachment of DA001 to the Fe oxyhydroxide coated columns was observed. This indicates that DOC can significantly reduce bacterial attachment due electrostatic interactions. The larger and more negatively charged FER-02 displayed increasing attachment with decreasing grain size regardless of DOC concentration, and modeling of FER-02 attachment revealed that the presence of Fe and Al coatings on the sediment also promoted attachment. Finally, the presence of Al coatings and Al containing minerals appeared to significantly retard the Br tracer regardless of the concentration of DOC. These findings suggest that DOC in shallow oxic groundwater aquifers can significantly enhance the transport of bacteria by reducing attachment to Fe, Mn and Al oxyhydroxides. This effect is profound for weakly charged, hydrophilic bacteria and may contribute to differences in observations between laboratory experiments verses field-scale investigations particularly if the groundwater pH remains circum-neutral and Fe oxyhydroxide phases exist. These observations validate the novel approach taken in the experiments outlined here of performing laboratory-scale experiments on site to facilitate the use of fresh groundwater and thus be more representative of in situ groundwater conditions.« less

Synthesis, microstructure and magnetic properties of Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jian, E-mail: snove418562@163.com; Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081; Fan, Xi’an, E-mail: groupfxa@163.com

2015-11-15

Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by insulating SiO{sub 2} using the modified stöber method. The Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO{sub 2}=2α-Al{sub 2}O{sub 3}+3Si took place during the sintering process. As a result the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{submore » 3} composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe{sub 3}Si{sub 0.7}Al{sub 0.3} core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties. - Graphical abstract: In Fe{sub 3}Si/Al{sub 2}O{sub 3} composite, Fe{sub 3}Si phases are separated by Al{sub 2}O{sub 3} layers and the eddy currents are confined in Fe{sub 3}Si phases, thus increasing resistivity and reducing core loss. - Highlights: • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores were prepared. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by nano-sized SiO{sub 2} clusters. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores showed good soft magnetic properties. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than Fe{sub 3}Si{sub 0.7}Al{sub 0.3} cores.« less

Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Süle, P.; Horváth, Z. E.; Kaptás, D.

2015-10-07

The chemical mixing at the “Al on Fe” and “Fe on Al” interfaces was studied by molecular dynamics simulations of the layer growth and by {sup 57}Fe Mössbauer spectroscopy. The concentration distribution along the layer growth direction was calculated for different crystallographic orientations, and atomically sharp “Al on Fe” interfaces were found when Al grows over (001) and (110) oriented Fe layers. The Al/Fe(111) interface is also narrow as compared to the intermixing found at the “Fe on Al” interfaces for any orientation. Conversion electron Mössbauer measurements of trilayers—Al/{sup 57}Fe/Al and Al/{sup 57}Fe/Ag grown simultaneously over Si(111) substrate by vacuummore » evaporation—support the results of the molecular dynamics calculations.« less

Corrosion study of AA2024-T3 by scanning Kelvin probe force microscopy and in situ atomic force microscopy scratching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmutz, P.; Frankel, G.S.

1998-07-01

The localized corrosion of AA2024-T3, and the behavior of intermetallic particles in particular, were studied using different capabilities of the atomic force microscope (AFM). The role of intermetallic particles in determining the locations and rates of localized corrosion was determined using scanning Kelvin probe force microscopy in air after exposure to chloride solutions. Al-Cu-Mg particles, which have a noble Volta potential in air because of an altered surface film, are actively dissolved in chloride solution after a certain induction time. Al-Cu(Fe, Mn) particles are heterogeneous in nature and exhibit nonuniform dissolution in chloride solution as well as trenching of themore » matrix around the particles. Light scratching of the surface by rastering with the AFM tip in contact mode in chloride solution results in accelerated dissolution of both pure Al and alloy 2024-T3. The abrasion associated with contact AFM in situ resulted in the immediate dissolution of the Al-Cu-Mg particles because of a destabilization of the surface film.« less

Acid attack on hydrated cement — Effect of mineral acids on the degradation process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutberlet, T.; Hilbig, H.; Beddoe, R.E., E-mail: robin.beddoe@tum.de

During acid attack on concrete structural components, a degraded layer develops whose properties as a protective barrier are decisive for durability. {sup 29}Si NMR spectroscopy and {sup 27}Al NMR spectroscopy were used with XRD to investigate the degraded layer on hardened cement paste exposed to HCl and H{sub 2}SO{sub 4}. The layer comprises an amorphous silica gel with framework silicates, geminate and single silanol groups in which Si is substituted by Al. Amorphous Al(OH){sub 3} and Fe(OH){sub 3} are present. The gel forms by polycondensation and cross-linking of C-A-S-H chains at AlO{sub 4} bridging tetrahedra. In the transition zone betweenmore » the degraded layer and the undamaged material, portlandite dissolves and Ca is removed from the C-A-S-H phases maintaining their polymer structure at first. With HCl, monosulphate in the transition zone is converted into Friedel's salt and ettringite. With H{sub 2}SO{sub 4}, gypsum precipitates near the degradation front reducing the thickness of the transition zone and the rate of degradation.« less

Trace metals in bulk precipitation and throughfall in a suburban area of Japan

NASA Astrophysics Data System (ADS)

Hou, H.; Takamatsu, T.; Koshikawa, M. K.; Hosomi, M.

Throughfall and bulk precipitation samples were collected monthly for 1.5 years over bare land and under canopies of Japanese cedar ( Cryptomeria japonica), Japanese red pine ( Pinus densiflora), Japanese cypress ( Chamaecyparis obtusa), and bamboo-leafed oak ( Quercus myrsinaefolia) in a suburban area of Japan. Samples were analyzed for dissolved Al, Mn, Fe, Cu, Zn, Ag, In, Sn, Sb and Bi by ICP-AES and ICP-MS. The metal concentrations were higher in throughfall, especially that of C. japonica, than bulk precipitation. Enrichment ratios (ERs: ratios of metal concentrations in throughfall to those in bulk precipitation) ranged from 2.5 (Zn) to 5.3 (Ag) (3.9 on average), and ERs for slightly soluble metals were generally higher than those for easily soluble metals. Concentrations of Mn, Fe, Cu, and Zn accounted for 99% of the total concentration of heavy metals in rainwater, whereas those of rare metals such as Ag, In, Sn, and Bi totaled <0.23%. Average concentrations of rare metals were 0.002 and 0.010 μg l -1 for Ag, 0.001 and 0.005 μg l -1 for In, 0.062 and 0.21 μg l -1 for Sn, and 0.006 and 0.023 μg l -1 for Bi in bulk precipitation and throughfall, respectively. The metal concentrations in rainwater were negatively correlated to the volume of rainwater, indicating that washout is the main mechanism that incorporates metals into rainwater. From the enrichment factors, that is, (X/Al) rain/(X/Al) crust, metals other than Fe were shown to be more enriched in rainwater than in the Earth's crust, including those present as a result of leaching from soil dust (Mn) and from anthropogenic sources (Cu, Zn, Ag, In, Sn, Sb, and Bi).

Responses of soil buffering capacity to acid treatment in three typical subtropical forests.

PubMed

Jiang, Jun; Wang, Ying-Ping; Yu, Mengxiao; Li, Kun; Shao, Yijing; Yan, Junhua

2016-09-01

Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0-40cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH≈4.5; pH=3.5; pH=2.5). We found that pH3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH2.5 treatment significantly increased concentrations of NO3(-), SO4(2-), Ca(2+), Mg(2+), Al(3+), Fe(3+) and DOC in leachate from the pioneer forest soil, and also concentrations of NO3(-), SO4(2-), Mg(2+), Al(3+), Fe(3+) and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future. Copyright © 2016 Elsevier B.V. All rights reserved.

Hydrothermal Alteration Promotes Humic Acid Formation in Sediments: A Case Study of the Central Indian Ocean Basin

NASA Astrophysics Data System (ADS)

Sarma, Nittala S.; Kiran, Rayaprolu; Rama Reddy, M.; Iyer, Sridhar D.; Peketi, A.; Borole, D. V.; Krishna, M. S.

2018-01-01

Anomalously high concentrations of humic-rich dissolved organic matter (DOM) in extant submarine hydrothermal vent plumes traveled far from source are increasingly being reported. This DOM, able to mobilize trace metals (e.g., Fe2+) has been hypothesized as originating from organic matter produced by thermogenic bacteria. To eliminate a possible abiogenic origin of this DOM, study is required of well-preserved organic compounds that can be attributed to thermogenic bacteria. The Central Indian Ocean Basin (CIOB) is part of a diffuse plate boundary and an intraplate deformation zone. Coarse fraction (>63 µ) characteristics, mineralogy, magnetic susceptibility, and geochemistry were examined in sediments of a core raised close to a north-south fracture zone near the Equator. Two horizons of distinctly brown-colored sediments were shown as hydrothermally altered from their charred fragments and geochemistry (CaCO3, Corg, Ti/Al, Al/(Al + Fe + Mn), Sr/Ba, Mg/Li, Mn micronodules, Fe/Mn). We examined whether humic substances were preserved in these sediments, and if so whether their carbon isotope distribution would support their hydrothermal origin. Alkali extraction of sediments afforded humic acids (HA) in yields up to 1.2% in the brown sediments. The remaining portions of the core had nil or low concentrations of HA. The carbon of hydrothermal HA is isotopically heavier (average δ13C, ˜ -16.3‰) compared to nonhydrothermal HA (-18.1‰), suggesting that they were probably formed from organic matter that remained after elimination of lighter carbon enriched functional groups during diagenesis. The results provide compelling evidence of HA formation from lipids originating from thermogenic bacteria.

Net alkalinity and net acidity 1: Theoretical considerations

USGS Publications Warehouse

Kirby, C.S.; Cravotta, C.A.

2005-01-01

Net acidity and net alkalinity are widely used, poorly defined, and commonly misunderstood parameters for the characterization of mine drainage. The authors explain theoretical expressions of 3 types of alkalinity (caustic, phenolphthalein, and total) and acidity (mineral, CO2, and total). Except for rarely-invoked negative alkalinity, theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined "CO 2-acidity" is closely related to most standard titration methods with an endpoint pH of 8.3 used for determining acidity in mine drainage, but it is unfortunately named because CO2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/mass- action approach and employing graphs to illustrate speciation with changes in pH, the authors explore the concept of principal components and how to assign acidity contributions to aqueous species commonly present in mine drainage. Acidity is defined in mine drainage based on aqueous speciation at the sample pH and on the capacity of these species to undergo hydrolysis to pH 8.3. Application of this definition shows that the computed acidity in mg L -1 as CaCO3 (based on pH and analytical concentrations of dissolved FeII, FeIII, Mn, and Al in mg L -1):aciditycalculated=50{1000(10-pH)+[2(FeII)+3(FeIII)]/56+2(Mn)/ 55+3(Al)/27}underestimates contributions from HSO4- and H+, but overestimates the acidity due to Fe3+ and Al3+. However, these errors tend to approximately cancel each other. It is demonstrated that "net alkalinity" is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. Further, it is shown that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: (1) alkalinity and acidity values based on aqueous speciation, (2) measured alkalinity minus calculated acidity, or (3) taking the negative of the value obtained in a standard method "hot peroxide" acidity titration, provided that labs report negative values. The authors recommend the third approach; i.e., net alkalinity = -Hot Acidity. ?? 2005 Elsevier Ltd. All rights reserved.

Experiment on infrared radiation characteristic of colloid Fe/Al thermite

NASA Astrophysics Data System (ADS)

Zhen, Jian-wei; Li, Jin-ming; Guo, Meng-meng; Liu, Guo-qing; Wang, Guo-dong

2016-01-01

The Fe/Al thermite was made as bulk material. Mixed proportion with liquid energetic colloid, the Fe/Al thermite was made to be collid Fe/Al thermite combustible agent. Then, combustion test sample was got. The combustion process and the infrared radiation characteristic of colloid Fe/Al thermite was experiment by thermal infrared imager. It was showed that collid Fe/Al thermite combustible agent had better infrared radiation characteristic. It could be as based agentia of infrared decoy with the characteristic of persistent and wide spectral range.

Assessing the concentration, speciation, and toxicity of dissolved metals during mixing of acid-mine drainage and ambient river water downstream of the Elizabeth Copper Mine, Vermont, USA

USGS Publications Warehouse

Balistrieri, L.S.; Seal, R.R.; Piatak, N.M.; Paul, B.

2007-01-01

The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd + Co + Cu + Ni + Pb + Zn) concentrations decreases from 6270 to 100 ??g/L in the dynamic mixing and reaction zone that is downstream of the river's confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates. The uptake of dissolved metals by aquatic organisms is dependent on the aqueous speciation of the metals and kinetics of complexation reactions between metals, ligands and solid surfaces. Dissolved speciation of Cd, Cu, Ni and Zn in the mixing and reaction zone is assessed using the diffusive gradients in thin films (DGT) technique and results of speciation calculations using the Biotic Ligand Model (BLM). Data from open and restricted pore DGT units indicate that almost all dissolved metal species are inorganic and that aqueous labile or DGT available metal concentrations are generally equal to total dissolved concentrations in the mixing zone. Exceptions occur when labile metal concentrations are underestimated due to competition between H+ and metal ions for Chelex-100 binding sites in the DGT units at low pH values. Calculations using the BLM indicate that dissolved Cd and Zn species in the mixing and reaction zone are predominantly inorganic, which is consistent with the DGT results. Although the DGT method indicates that the majority of aqueous Cu species are inorganic, BLM calculations indicate that dissolved Cu is inorganic at pH 5.5. Integrated dissolved labile concentrations of Cd, Cu and Zn in the mixing and reaction zone are compared to calculated acute toxicity concentrations (LC50 values) for fathead minnows (Pimephales promelas) (Cd, Cu and Zn) and water fleas (Ceriodaphnia dubia) (Cd and Cu) using the BLM, and to national recommended water quality criteria [i.e., criteria maximum concentration (CMC) and criterion continuous concentration (CCC)]. Observed labile concentrations of Cd and Zn are below LC50 values and CMC for Cd, but above CCC and CMC for Zn at sites <30 m downstream of the confluence. In contrast, labile Cu concentrations exceed LC50 values for the organisms as well as CCC and CMC at sites <30 m downstream of the confluence. These results suggest that environmental conditions at sites closest to the confluence of the river and acid-mine drainage should not support healthy aquatic organisms. ?? 2007 Elsevier Ltd. All rights reserved.

Phase constitution in the interfacial region of laser penetration brazed magnesium–steel joints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, Yugang; Han, Duanfeng, E-mail: handuanfeng@gmail.com; Xu, Xiangfang

2014-07-01

The phase constitution in the interfacial region of laser penetration brazed magnesium–steel joints was investigated using electron microscopy. From the distribution of elements, the transition zone was mainly composed of elements Mg and Fe along with some Al and O. Furthermore, the transition layer consisted mainly of intermetallic compounds and metal oxides. The compounds were identified as Al-rich phases, such as Mg{sub 17}Al{sub 12}, Mg{sub 2}Al{sub 3}, FeAl and Fe{sub 4}Al{sub 13}. More noteworthy was that the thickness of the transition layer was determined by Fe–Al compounds. The presence of FeAl and Fe{sub 4}Al{sub 13} was a result of themore » complex processes that were associated with the interfacial reaction of solid steel and liquid Mg–Al alloy. - Highlights: • A technology of laser penetration brazed Mg alloy and steel has been developed. • The interface of Mg/Fe dissimilar joints was investigated using electron microscopy. • The transition layer consisted of intermetallic compounds and metal oxides. • Moreover, the thickness of transition layer was determined by Fe/Al compounds. • The presence of FeAl and Fe{sub 4}Al{sub 13} was associated with the interfacial reaction.« less

Novel mesoporous FeAl bimetal oxides for As(III) removal: Performance and mechanism.

PubMed

Ding, Zecong; Fu, Fenglian; Cheng, Zihang; Lu, Jianwei; Tang, Bing

2017-02-01

In this study, novel mesoporous FeAl bimetal oxides were successfully synthesized, characterized, and employed for As(III) removal. Batch experiments were conducted to investigate the effects of Fe/Al molar ratio, dosage, and initial solution pH values on As(III) removal. The results showed that the FeAl bimetal oxide with Fe/Al molar ratio 4:1 (shorten as FeAl-4) can quickly remove As(III) from aqueous solution in a wide pH range. The FeAl-4 before and after reaction with As(III) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), Brunauer-Emmett-Teller (BET) surface area measurement, and X-ray photoelectron spectroscopy (XPS). The BET results showed that the original FeAl-4 with a high surface area of 223.9 m 2 /g was a mesoporous material. XPS analysis indicated that the surface of FeAl-4 possessed a high concentration of M-OH (where M represents Fe and Al), which was beneficial to the immobility of As(III). The excellent performance of FeAl-4 makes it a potentially attractive material for As(III) removal from aqueous solution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Magnetite/Fe-Al-montmorillonite as a Fenton catalyst with efficient degradation of phenol.

PubMed

Wei, Xipeng; Wu, Honghai; Sun, Feng

2017-10-15

A Fe-Al-MPM material assembled from nanosized magnetite and Fe-Al-pillared montmorillonite (Fe-Al-Mt) was characterized by XRD, XPS, BET, SEM and TEM. Fe-Al-Mt was proven to be capable of facilitating the dispersion of magnetite nanoparticles and inhibiting their aggregation. The coupling of Fe-Al-Mt with magnetite in Fe-Al-MPM improved its Fenton catalytic activity. Complete conversion of phenol within 80min with a high TOC removal rate (>78%) was achieved using Fe-Al-MPM as a heterogeneous Fenton catalyst under optimized conditions. The Fenton process first underwent a slow induction reaction, followed by the rapid oxidative decomposition of phenol. The existence of the induction reaction period was attributed to the need for activation of the iron species on the catalyst surfaces, and the duration depended on the solution temperature, pH and catalyst's nature. More importantly, Fe-Al-MPM showed high stability, with a low iron-release even after it was recycled 5 times. The minimal iron-leaching from Fe-Al-MPM was ascribed to the competitive adsorption of the incorporated aluminum and all the iron species for the residual (low ecotoxicity) organic ligands. These organic acids were among the main products that remained at the end of the Fenton process. Also important was the ease of separation of Fe-Al-MPM under a magnetic field. Copyright © 2017 Elsevier Inc. All rights reserved.

Fe-As sludge stability and effluent quality for a two-stage As-contaminated water treatment with Fe(II) and aeration.

PubMed

Zhuang, J Ming; Hobenshield, Evan; Walsh, Tony

2009-02-01

A two-stage (I and II) lab-scale treatment system has been studied for arsenic removal from water using Fe(II) and lignosulphonates with aeration. In stage I, using an Fe/As mole ratio of 1.5-2.5 at a pH of around 6.5-7.5, the dissolved arsenic can be reduced with Fe(II) oxidation-precipitation from an initial 72 mg L(-1) to < 2 mg L(-1). The generated sludge is entirely recycled to the second tank of stage II. In the first tank of stage II, the water is further treated with the same amount of Fe(II) as that used in stage I, in the presence of lignosulphonates and aeration. The air-oxidization of Fe(II) to Fe(III) is continued for about 30 minutes at a pH of around 7.0-8.0. The water output from the first tank is transferred to the second tank in which mixing under aeration occurs with the sludge recycled from stage I. Accordingly, the dissolved arsenic in the effluent is reduced to < 0.1 mg L(-1). The results show that this two-stage process can save more than 50% of total chemical costs, and reduce the amount of sludge by more than 50%, in comparison with the conventional Fe(III)/lime-treatment process. According to US EPA regulations, the final Fe-As sludge is classified as non-hazardous materials by the Toxicity Characteristic Leaching Procedure. But, the study shows that the instability of Fe-As sludge could be influenced by some factors, such as higher pH levels, a longer water-leaching time and larger water-leaching volume, leading to the liberation of more dissolvable As species. After being treated with Ligmet stabilizer, the Fe-As sludge showed an improved stability under varying pH conditions and large amounts of water leaching. The treated Fe-As sludge is suitable for landfill disposal.

Room temperature luminescence and ferromagnetism of AlN:Fe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, H., E-mail: lihui@mail.iee.ac.cn, E-mail: wjwang@aphy.iphy.ac.cn; Cai, G. M.; Wang, W. J., E-mail: lihui@mail.iee.ac.cn, E-mail: wjwang@aphy.iphy.ac.cn

2016-06-15

AlN:Fe polycrystalline powders were synthesized by a modified solid state reaction (MSSR) method. Powder X-ray diffraction and transmission electron microscopy results reveal the single phase nature of the doped samples. In the doped AlN samples, Fe is in Fe{sup 2+} state. Room temperature ferromagnetic behavior is observed in AlN:Fe samples. Two photoluminescence peaks located at about 592 nm (2.09 eV) and 598 nm (2.07 eV) are observed in AlN:Fe samples. Our results suggest that AlN:Fe is a potential material for applications in spintronics and high power laser devices.

Critical evaluation and modeling of algal harvesting using dissolved air flotation. DAF Algal Harvesting Modeling

DOE PAGES

Zhang, Xuezhi; Hewson, John C.; Amendola, Pasquale; ...

2014-07-14

In our study, Chlorella zofingiensis harvesting by dissolved air flotation (DAF) was critically evaluated with regard to algal concentration, culture conditions, type and dosage of coagulants, and recycle ratio. Harvesting efficiency increased with coagulant dosage and leveled off at 81%, 86%, 91%, and 87% when chitosan, Al 3+, Fe 3+, and cetyl trimethylammonium bromide (CTAB) were used at dosages of 70, 180, 250, and 500 mg g -1, respectively. The DAF efficiency-coagulant dosage relationship changed with algal culture conditions. In evaluating the influence of the initial algal concentration and recycle ratio revealed that, under conditions typical for algal harvesting, wemore » found that it is possible that the number of bubbles is insufficient. A DAF algal harvesting model was developed to explain this observation by introducing mass-based floc size distributions and a bubble limitation into the white water blanket model. Moreover, the model revealed the importance of coagulation to increase floc-bubble collision and attachment, and the preferential interaction of bubbles with larger flocs, which limited the availability of bubbles to the smaller sized flocs. The harvesting efficiencies predicted by the model agree reasonably with experimental data obtained at different Al 3+ dosages, algal concentrations, and recycle ratios. Based on this modeling, critical parameters for efficient algal harvesting were identified.« less

Critical evaluation and modeling of algal harvesting using dissolved air flotation. DAF Algal Harvesting Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xuezhi; Hewson, John C.; Amendola, Pasquale

In our study, Chlorella zofingiensis harvesting by dissolved air flotation (DAF) was critically evaluated with regard to algal concentration, culture conditions, type and dosage of coagulants, and recycle ratio. Harvesting efficiency increased with coagulant dosage and leveled off at 81%, 86%, 91%, and 87% when chitosan, Al 3+, Fe 3+, and cetyl trimethylammonium bromide (CTAB) were used at dosages of 70, 180, 250, and 500 mg g -1, respectively. The DAF efficiency-coagulant dosage relationship changed with algal culture conditions. In evaluating the influence of the initial algal concentration and recycle ratio revealed that, under conditions typical for algal harvesting, wemore » found that it is possible that the number of bubbles is insufficient. A DAF algal harvesting model was developed to explain this observation by introducing mass-based floc size distributions and a bubble limitation into the white water blanket model. Moreover, the model revealed the importance of coagulation to increase floc-bubble collision and attachment, and the preferential interaction of bubbles with larger flocs, which limited the availability of bubbles to the smaller sized flocs. The harvesting efficiencies predicted by the model agree reasonably with experimental data obtained at different Al 3+ dosages, algal concentrations, and recycle ratios. Based on this modeling, critical parameters for efficient algal harvesting were identified.« less

Effects of Metals Associated with Wildfire Ash on Water Quality

NASA Astrophysics Data System (ADS)

Cerrato, J.; Clark, A.; Correa, N.; Ali, A.; Blake, J.; Bixby, R.

2015-12-01

The forests of the western United States are impacted dramatically by climate change and have suffered from large-scale increases in wildfire activity. This rise in wildfires introduces additional ash to ecosystems and can represent a serious and ongoing threat to water quality in streams and rivers from storm event runoff in burn areas. The effect of metals associated with wildfire ash (from wood collected from the Valles Caldera National Preserve, Jemez Mountains, New Mexico) on solution pH and dissolved oxygen was assessed through a series of laboratory experiments. Microscopy and spectroscopy analyses were conducted to characterize the elemental content and oxidation state of metals in unreacted and reacted ash. Certain metals (e.g., Ca, K, Al, Mg) were detected in ash from ponderosa pine, one of the dominant species in the Valles Caldera, with mean concentrations ranging from 400-1750 mg kg-1. Other metals (e.g., Na, Fe, Mn, V, Zn, Ni) were present at lower mean concentrations ranging from 12-210 mg kg-1. The initial pH after conducting batch experiments reacting ash with water started at 9.9 and the alkalinity of the water was 110 mg L-1 as CaCO3. Solution pH decreased to 8.0 after 48 hours of reaction, which is almost a delta of two pH units. Dissolved oxygen concentrations decreased by 2 mg L-1 over the course of 12 hours before the rate of reaeration surpassed the rate of consumption. This presentation will discuss how redox-active metals, such as Fe and Mn, could contribute to the increased dissolved oxygen demand and fluctuation of the oxidation/reduction potential in the system.

Surface chemistry of bulk nanocrystalline pure iron and electrochemistry study in gas-flow physiological saline.

PubMed

Nie, F L; Zheng, Y F

2012-07-01

Conventional microcrystalline pure iron (MC-Fe) becomes a new candidate as biodegradable metals, which has the insufficient physical feature and inferior biodegradation behavior. Novel bulk nanocrystalline pure iron (NC-Fe) was fabricated via equal channel angular pressing technique in the present work to overcome these problems. The contact angle test with water and glycerol droplets shows a smaller angle (though >90°) of NC-Fe than that of MC-Fe, which implies a lower surface energy of NC-Fe. The surface roughness of NC-Fe increased greatly than that of MC-Fe. A further comparative study of corrosion and electrochemistry performance between NC-Fe and its original MC-Fe was investigated in physiological saline with different dissolved oxygen concentration, aiming to in vitro simulate the corrosion process of coronary stent occurred in physiological environment. The electrochemical impedance spectra analysis and anodic polarization measurements indicated that the NC-Fe exhibited higher corrosion resistance than that of the MC-Fe; meanwhile obvious enhanced corrosion resistance with the decrement of dissolved oxygen concentration was observed. Related equivalent circuit model and surface reconstruction process were further discussed, and the degradation mechanism of the MC-Fe and NC-Fe were finally established. Copyright © 2012 Wiley Periodicals, Inc.

Predicting organic matter, nitrogen, and phosphorus concentrations in runoff from peat extraction sites using partial least squares regression

NASA Astrophysics Data System (ADS)

Tuukkanen, T.; Marttila, H.; Kløve, B.

2017-07-01

Organic matter and nutrient export from drained peatlands is affected by complex hydrological and biogeochemical interactions. Here partial least squares regression (PLSR) was used to relate various soil and catchment characteristics to variations in chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) concentrations in runoff. Peat core samples and water quality data were collected from 15 peat extraction sites in Finland. PLSR models constructed by cross-validation and variable selection routines predicted 92, 88, and 95% of the variation in mean COD, TN, and TP concentration in runoff, respectively. The results showed that variations in COD were mainly related to net production (temperature and water-extractable dissolved organic carbon (DOC)), hydrology (topographical relief), and solubility of dissolved organic matter (peat sulfur (S) and calcium (Ca) concentrations). Negative correlations for peat S and runoff COD indicated that acidity from oxidation of organic S stored in peat may be an important mechanism suppressing organic matter leaching. Moreover, runoff COD was associated with peat aluminum (Al), P, and sodium (Na) concentrations. Hydrological controls on TN and COD were similar (i.e., related to topography), whereas degree of humification, bulk density, and water-extractable COD and Al provided additional explanations for TN concentration. Variations in runoff TP concentration were attributed to erosion of particulate P, as indicated by a positive correlation with suspended sediment concentration (SSC), and factors associated with metal-humic complexation and P adsorption (peat Al, water-extractable P, and water-extractable iron (Fe)).

Urban wastewater photobiotreatment with microalgae in a continuously operated photobioreactor: growth, nutrient removal kinetics and biomass coagulation-flocculation.

PubMed

Mennaa, Fatima Zahra; Arbib, Zouhayr; Perales, José Antonio

2017-11-03

The aim of this study was to investigate the growth, nutrient removal and harvesting of a natural microalgae bloom cultivated in urban wastewater in a bubble column photobioreactor. Batch and continuous mode experiments were carried out with and without pH control by means of CO 2 dosage. Four coagulants (aluminium sulphate, ferric sulphate, ferric chloride and polyaluminium chloride (PAC)) and five flocculants (Chemifloc CM/25, FO 4498SH, cationic polymers Zetag (Z8165, Z7550 and Z8160)) were tested to determine the optimal dosage to reach 90% of biomass recovery. The maximum volumetric productivity obtained was 0.11 g SS L -1  d -1 during the continuous mode. Results indicated that the removal of total dissolved nitrogen and total dissolved phosphorous under continuous operation were greater than 99%. PAC, Fe 2 (SO 4 ) 3 and Al 2 (SO 4 ) 3 were the best options from an economical point of view for microalgae harvesting.

Trace Metals in Urban Stormwater Runoff and their Management

NASA Astrophysics Data System (ADS)

Li, T.; Hall, K.; Li, L. Y.; Schreier, H.

2009-04-01

In past decades, due to the rapid urbanization, land development has replaced forests, fields and meadows with impervious surfaces such as roofs, parking lots and roads, significantly affecting watershed quality and having an impact on aquatic systems. In this study, non-point source pollution from a diesel bus loop was assessed for the extent of trace metal contamination of Cu, Mn, Fe, and Zn in the storm water runoff. The study was carried out at the University of British Columbia (UBC) in the Greater Vancouver Regional District (GVRD) of British Columbia, Canada. Fifteen storm events were monitored at 3 sites from the diesel bus loop to determine spatial and temporal variations of dissolved and total metal concentrations in the storm water runoff. The dissolved metal concentrations were compared with the provincial government discharge criteria and the bus loop storm water quality was also compared with previous studies conducted across the GVRD urban area. To prevent storm water with hazardous levels of contaminants from being discharged into the urban drainage system, a storm water catch basin filter was installed and evaluated for its efficiency of contaminants removal. The perlite filter media adsorption capacities for the trace metals, oil and grease were studied for better maintenance of the catch basin filter. Dissolved copper exceeded the discharge criteria limit in 2 out of 15 cases, whereas dissolved zinc exceeded the criteria in 4 out of 15 cases, and dissolved manganese was below the criteria in all of the events sampled. Dissolved Cu and Zn accounted for 36 and 45% of the total concentration, whereas Mn and Fe only accounted for 20 and 4% of their total concentration, respectively. Since they are more mobile and have higher bioaccumulation potentials, Zn and Cu are considered to be more hazardous to the aquatic environment than Fe and Mn. With high imperviousness (100%) and intensive traffic at the UBC diesel bus loop, trace metal concentrations were 3, 0.7, 9, and 3.2 times higher than the GVRD urban area limits for Cu, Mn, Fe, and Zn, respectively. The filter showed high and stable capture efficiencies in total metals (Cu 62%, Mn 75%, Fe 83%, Zn 62%), dissolved metals (Cu 39%, Mn 37%, Fe 47%, Zn 32%), turbidity (72%), and suspended solids (74%) removal during the first month of operation. After that, there was gradual degradation. The catch basin filter performance improved significantly for the suspended solids and total metal removal after cleaning. However, the perlite filter medium showed poor performance for dissolved metal removal in the second study period. Based on the findings, a catch basin filter is effective in storm water management to control suspended solids loading from storm water runoff.

Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water

NASA Astrophysics Data System (ADS)

van der Grift, B.; Rozemeijer, J. C.; Griffioen, J.; van der Velde, Y.

2014-06-01

The retention of phosphorus in surface waters though co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater to surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than one week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilisation of dissolved P during the initial stage of the Fe(II) oxidation proces which results in P-depleted water before Fe(II) is competly depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to particulate phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.

Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water

NASA Astrophysics Data System (ADS)

van der Grift, B.; Rozemeijer, J. C.; Griffioen, J.; van der Velde, Y.

2014-11-01

The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to structural phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.

Composition and source apportionment of dust fall around a natural lake.

PubMed

Latif, Mohd Talib; Ngah, Sofia Aida; Dominick, Doreena; Razak, Intan Suraya; Guo, Xinxin; Srithawirat, Thunwadee; Mushrifah, Idris

2015-07-01

The aim of this study was to determine the source apportionment of dust fall around Lake Chini, Malaysia. Samples were collected monthly between December 2012 and March 2013 at seven sampling stations located around Lake Chini. The samples were filtered to separate the dissolved and undissolved solids. The ionic compositions (NO3-, SO4(2-), Cl- and NH4+) were determined using ion chromatography (IC) while major elements (K, Na, Ca and Mg) and trace metals (Zn, Fe, Al, Ni, Mn, Cr, Pb and Cd) were determined using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the average concentration of total solids around Lake Chini was 93.49±16.16 mg/(m2·day). SO4(2-), Na and Zn dominated the dissolved portion of the dust fall. The enrichment factors (EF) revealed that the source of the trace metals and major elements in the rain water was anthropogenic, except for Fe. Hierarchical agglomerative cluster analysis (HACA) classified the seven monitoring stations and 16 variables into five groups and three groups respectively. A coupled receptor model, principal component analysis multiple linear regression (PCA-MLR), revealed that the sources of dust fall in Lake Chini were dominated by agricultural and biomass burning (42%), followed by the earth's crust (28%), sea spray (16%) and a mixture of soil dust and vehicle emissions (14%). Copyright © 2015. Published by Elsevier B.V.

Fe(II) sorption on pyrophyllite: Effect of structural Fe(III) (impurity) in pyrophyllite on nature of layered double hydroxide (LDH) secondary mineral formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starcher, Autumn N.; Li, Wei; Kukkadapu, Ravi K.

Fe(II)-Al(III)-LDH (layered double hydroxide) phases have been shown to form from reactions of aqueous Fe(II) with Fe-free Al-bearing minerals (phyllosilicate/clays and Al-oxides). To our knowledge, the effect of small amounts of structural Fe(III) impurities in “neutral” clays on such reactions, however, were not studied. In this study to understand the role of structural Fe(III) impurity in clays, laboratory batch studies with pyrophyllite (10 g/L), an Al-bearing phyllosilicate, containing small amounts of structural Fe(III) impurities and 0.8 mM and 3 mM Fe(II) (both natural and enriched in 57Fe) were carried out at pH 7.5 under anaerobic conditions (4% H2 – 96%more » N2 atmosphere). Samples were taken up to 4 weeks for analysis by Fe-X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy. In addition to the precipitation of Fe(II)-Al(III)-LDH phases as observed in earlier studies with pure minerals (no Fe(III) impurities in the minerals), the analyses indicated formation of small amounts of Fe(III) containing solid(s), most probably hybrid a Fe(II)-Al(III)/Fe(III)-LDH phase. The mechanism of Fe(II) oxidation was not apparent but most likely was due to interfacial electron transfer from the sorbed Fe(II) to the structural Fe(III) and/or surface-sorption-induced electron-transfer from the sorbed Fe(II) to the clay lattice. Increase in the Fe(II)/Al ratio of the LDH with reaction time further indicated the complex nature of the samples. This research provides evidence for the formation of both Fe(II)-Al(III)-LDH and Fe(II)-Fe(III)/Al(III)-LDH-like phases during reactions of Fe(II) in systems that mimic the natural environments. Better understanding Fe phase formation in complex laboratory studies will improve models of natural redox systems.« less

Solubility of copper in a sulfur-free mafic melt

NASA Astrophysics Data System (ADS)

Ripley, Edward M.; Brophy, James G.

1995-12-01

The solubility of Cu in S-free mafic melts has been measured at a series of ƒ O2 values and temperatures of 1245 and 1300°C. At constant temperature Cu solubility increases from 0.04 wt% at log ƒ O2 = -11.9 to 1.10 wt% at log ƒ O 2 = -7.4 . Copper solubilities were in excess of 8 wt% in two runs controlled at very high ƒ O2 conditions of 10 -1.4 and 10 -22 Partitioning of Cu between metal and glass shows a strong ƒ O2 dependence, with D Cumet/gl ranging from 90 at log ƒ O2 = -7.4 to 2190 at log ƒ O2 = -11.9 . Slopes of Cu solubility and DCumet/gl vs. log ƒ O2 suggest that Cu dissolves predominantly in the +1 valence state. Copper solubility decreases with increasing temperature at constant ƒ O2, similar to experimental results for Ni, Co, and Mo (Dingwell et al., 1994; Holzheid et al., 1994). The data are consistent with Cu dissolution as an oxide (represented by CuO 0.5) and suggest that changes in ƒ O2 ( Fe2+/Fe3+ variations and Cu 1+ complexation with Fe 3+) may have large effects on the distribution of Cu between silicate and sulfide magmas. Results also suggest that the extraction of oxide-bonded Cu in mafic magmas by externally derived S may be an important mechanism in the generation of Cu-rich sulfide ores.

Importance of doping and frustration in itinerant Fe-doped Cr 2Al

DOE PAGES

Susner, M. A.; Parker, D. S.; Sefat, A. S.

2015-05-12

We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr 2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr 1-xFe x) 2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing T N to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which T N gradually decreases followed by the appearance ofmore » a ferromagnetic state. Theoretical calculations explain that the Cr 2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr 2Al. In pure-phase Cr 2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr 2Al and Fe-doped Cr 2Al.« less

Study on Preparing Al2O3 Particles Reinforced ZL109 Composite by in Situ Reaction of Fe2O3/Al System

NASA Astrophysics Data System (ADS)

Zhang, Jing; Yu, Huashun; Zhao, Qi; Wang, Haitao; Min, Guanghui

Al2O3 particles reinforced ZL109 composite was prepared by in situ reaction between Fe2O3 and Al. The phases were identified by XRD and the microstructures were observed by SEM and TEM. The Al2O3 particles in sub-micron size distribute uniformly in the matrix and Fe displaced from the in situ reaction forms net-like alloy phases with Cu, Ni, Al, Mn ect. The hardness and the tensile strength at room temperature of the composites have a small increase compared with the matrix. However, the tensile strength at 350°C can reach 92.18 MPa, which is 18.87 MPa higher than that of the matrix. The mechanism of the reaction in the Fe2O3/Al system was studied by DSC. The reaction between Fe2O3 and Al involves two steps. The first step in which Fe2O3 reacts with Al to form FeO and Al2O3 takes place at the matrix alloy melting temperature. The second step in which FeO reacts with Al to form Fe and Al2O3 takes place at a higher temperature.

Coercivity Recovery Effect of Sm-Fe-Cu-Al Alloy on Sm2Fe17N3 Magnet

NASA Astrophysics Data System (ADS)

Otogawa, Kohei; Asahi, Toru; Jinno, Miho; Yamaguchi, Wataru; Takagi, Kenta; Kwon, Hansang

2018-03-01

The potential of a Sm-Fe-Cu-Al binder for improvement of the magnetic properties of Sm2Fe17N3 was examined. Transmission electron microscope (TEM) observation of a Sm-Fe-Cu-Al alloy-bonded Sm2Fe17N3 magnet which showed high coercivity revealed that the Sm-Fe-Cu-Al alloy had an effect of removing the surface oxide layer of the Sm2 Fe17N3 grains. However, the Sm-Fe-Cu-Al binder was contaminated by carbon and nitrogen, which originated from the organic solvent used as the milling medium during pulverization. To prevent carbon and nitrogen contamination, the Sm-Fe- Cu-Al alloy was added directly on the surface of the Sm2Fe17N3 grains by sputtering. Comparing the recovered coercivity per unit amount of the added binder the uncontaminated binder-coated sample had a higher coercivity recovery effect than the milled binder-added sample. These results suggested that sufficient addition of the contamination-free Sm-Fe-Cu-Al binder has the possibility to reduce the amount of binder necessary to produce a high coercive Sm2Fe17N3 magnet.

Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.

2015-09-18

FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO 2 or ZrO 2. Themore » new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.« less

Iron in the aquifer system of Suffolk County, New York, 1990–98

USGS Publications Warehouse

Brown, Craig J.; Walter, Donald A.; Colabufo, Steven

1999-01-01

High concentrations of dissolved iron in ground water contribute to the biofouling of public-supply wells, and the treatment and remediation of biofouling are costly. Water companies on Long Island, N.Y., spend several million dollars annually to recondition, redevelop, and replace supply wells and distribution lines; treat dissolved iron with sequestering agents or by filtration; and respond to iron-related complaints by customers. This report summarizes the results of studies done by the U.S. Geological Survey, in cooperation with the Suffolk County Water Authority, to characterize the geochemistry and microbiology of iron in the aquifer system of Suffolk County. This information should be helpful for the siting and operation of supply wells.Concentrations of dissolved iron in Long Island's ground water, and the frequency of iron biofouling of wells, are highest in ground-water-discharge zones, particularly near the south shore. Ground water along a deep north-south flowpath of the Magothy aquifer in southwestern Suffolk County becomes anaerobic (oxygen deficient) and Fe(III) reducing at a distance of 8 to 10 kilometers south of the ground-water divide, and this change coincides with the downgradient increase in dissolved iron concentrations. The distribution of organic carbon, and the distribution and local variations in reactivity of Fe(III), in Magothy aquifer sediments have resulted in localized differences in redox microenvironments. For example, Fe(III)-reducing zones are associated with anaerobic conditions, where relatively large amounts of Fe(III) oxyhydroxide grain coatings are present, whereas sulfate-reducing zones are associated with lignite-rich lenses of silt and clay and appear to have developed in response to the depletion of available Fe(III) oxyhydroxides. The sulfate-reducing zones are characterized by relatively low concentrations of dissolved iron (resulting from iron-disulfide precipitation) and may be large enough to warrant water-supply development.Specific-capacity and water-quality data from wells screened in the Magothy aquifer indicate that water from biofouled wells contains higher median concentrations of total and dissolved iron and manganese, total phosphate, and dissolved sulfate, and lower median concentrations of dissolved oxygen and alkalinity, and lower pH, than does water from unaffected wells. Corresponding data from wells screened in the upper glacial aquifer indicate that water from biofouled wells contains higher median concentrations of total and dissolved manganese and dissolved sulfate, and lower pH, than does water from unaffected wells.Filamentous bacteria were detected in 31 (or 72 percent) of the 43 biofilm samples obtained from biofouled wells during reconditioning. The predominant filamentous organism was Gallionella ferruginea, a major biofouling agent in the upper glacial and Magothy aquifers throughout Suffolk County. Mineral-saturation indices indicate that most of the well-encrusting material is deposited when the wells are shut down. Furthermore, the use of treated water (which has a high pH and sometimes high concentrations of dissolved iron) for pump prelubrication when wells are shut down could greatly increase the rate of iron oxidation.

Evidence of cross-cutting and redox reaction in Khatyrka meteorite reveals metallic-Al minerals formed in outer space.

PubMed

Lin, Chaney; Hollister, Lincoln S; MacPherson, Glenn J; Bindi, Luca; Ma, Chi; Andronicos, Christopher L; Steinhardt, Paul J

2017-05-09

We report on a fragment of the quasicrystal-bearing CV3 carbonaceous chondrite Khatyrka recovered from fine-grained, clay-rich sediments in the Koryak Mountains, Chukotka (Russia). We show higher melting-point silicate glass cross-cutting lower melting-point Al-Cu-Fe alloys, as well as unambiguous evidence of a reduction-oxidation reaction history between Al-Cu-Fe alloys and silicate melt. The redox reactions involve reduction of FeO and SiO 2 to Fe and Fe-Si metal, and oxidation of metallic Al to Al 2 O 3 , occurring where silicate melt was in contact with Al-Cu-Fe alloys. In the reaction zone, there are metallic Fe and Fe-Si beads, aluminous spinel rinds on the Al-Cu-Fe alloys, and Al 2 O 3 enrichment in the silicate melt surrounding the alloys. From this and other evidence, we demonstrate that Khatyrka must have experienced at least two distinct events: first, an event as early as 4.564 Ga in which the first Al-Cu-Fe alloys formed; and, second, a more recent impact-induced shock in space that led to transformations of and reactions between the alloys and the meteorite matrix. The new evidence firmly establishes that the Al-Cu-Fe alloys (including quasicrystals) formed in outer space in a complex, multi-stage process.

Manganese micro-nodules on ancient brick walls.

PubMed

López-Arce, P; García-Guinea, J; Fierro, J L G

2003-01-20

Romans, Jews, Arabs and Christians built the ancient city of Toledo (Spain) with bricks as the main construction material. Manganese micro-nodules (circa 2 microm in diameter) have grown under the external bio-film surface of the bricks. Recent anthropogenic activities such as industrial emissions, foundries, or traffic and housing pollution have further altered these old bricks. The energy-dispersive X-ray microanalyses (XPS) of micro-nodules show Al, Si, Ca, K, Fe and Mn, with some carbon species. Manganese atoms are present only as Mn(4+) and iron as Fe(3+) (FeOOH-Fe(2)O(3) mixtures). The large concentration of alga biomass of the River Tagus and the Torcón and Guajaraz reservoirs suggest manganese micro-nodules are formed either from water solutions rich in anthropogenic MnO(4)K in a reduction environment (from Mn(7+) to Mn(4+)) or by oxidation mechanisms from dissolved Mn(2+) (from Mn(2+) to Mn(4+)) linked to algae biofilm onto the ancient brick surfaces. Ancient wall surfaces were also studied by scanning electron microscopy (SEM-EDS) and X-ray diffraction (XRD). Chemical and biological analyses of the waters around Toledo are also analysed for possible sources of manganese. Manganese micro-nodules on ancient brick walls are good indicators of manganese pollution. Copyright 2002 Elsevier Science B.V.

Use of induced fluorescence measurements to assess aluminum-organic interactions in acidified lakes

NASA Technical Reports Server (NTRS)

Vodacek, A.; Philpot, W. D.

1985-01-01

The application of laser fluorosensing to the tracing of metals in acid lakes is proposed. The effects of the metals on the dissolving organic carbon (DOC) fluorescence is studied using laboratory mixed water samples and natural water samples from Hamilton and Big Moose Lakes in New York. The operation of the laser fluorosensing system employed in the experiment is described. The DOC fluorescence was quenched by Al, Cu, and Fe, and the relation between pH and the quenching rate is examined. The humic substances fluorescence spectra are analyzed to estimate the concentrations of DOC in water and the relative concentration of Al. The interference problems caused by chemical competition between metal ions and ligands, and changes in the background DOC fluorescence are discussed. It is noted that an airborne laser fluorescence is useful for detecting elevated concentrations of metals.

Dry (Mg,Fe)SiO 3 perovskite in the Earth's lower mantle

DOE PAGES

Panero, Wendy R.; Pigott, Jeffrey S.; Reaman, Daniel M.; ...

2015-02-26

Combined synthesis experiments and first-principles calculations show that MgSiO 3-perovskite with minor Al or Fe does not incorporate significant OH under lower mantle conditions. Perovskite, stishovite, and residual melt were synthesized from natural Bamble enstatite samples (Mg/(Fe+Mg) = 0.89 and 0.93; Al 2O 3 < 0.1 wt% with 35 and 2065 ppm wt H 2O, respectively) in the laser-heated diamond anvil cell at 1600-2000 K and 25-65 GPa. Combined Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and ex-situ transmission electron microscopy (TEM) analysis demonstrates little difference in the resulting perovskite as a function of initial water content. Four distinct OHmore » vibrational stretching bands are evident upon cooling below 100 K (3576, 3378, 3274, and 3078 cm -1), suggesting 4 potential bonding sites for OH in perovskite with a maximum water content of 220 ppm wt H 2O, and likely no more than 10 ppm wt H 2O. Complementary, Fe-free, first-principles calculations predict multiple potential bonding sites for hydrogen in perovskite, each with significant solution enthalpy (0.2 eV/defect). We calculate that perovskite can dissolve less than 37 ppm wt H 2O (400 ppm H/Si) at the top of the lower mantle, decreasing to 31 ppm wt H 2O (340 ppm H/Si) at 125 GPa and 3000 K in the absence of a melt or fluid phase. Here, we propose that these results resolve a long-standing debate of the perovskite melting curve and explain the order of magnitude increase in viscosity from upper to lower mantle.« less

High-temperature corrosion of iron-aluminum and iron-aluminum-yttrium alloys

NASA Astrophysics Data System (ADS)

Insoo, Kim

The high-temperature corrosion behavior of Fe3Al alloy has been investigated by conducting two studies: (1) corrosion of Fe 3Al and Fe3Al-Y alloys in oxidizing atmosphere and (2) corrosion of Fe3Al in mixed chlorine/oxygen environments. In the first study, oxidation of the two alloys, Fe-14.3 wt% Al and Fe-14.1 wt% Al-0.3 wt% Y, was carried out in the temperature range of 800 to 1100°C to investigate the general oxidation behavior of Fe3Al and the effect of yttrium on the oxidation of Fe3Al in terms of oxidation kinetics, oxide scale adhesion and microstructure. At lower temperatures (<1000°C), the oxidation rate of the two alloys was nearly identical, and the parabolic rate constant obtained as a function of temperature was Kp = 5128 exp[--39500 (cal/mol)/RT] mg2/cm4 h. At higher temperatures, however, yttrium-added Fe3Al alloy exhibited lower oxidation rate and much more improved oxide adhesion. The lower oxidation rate observed in Fe3Al-Y alloy seems to be due to the followings: (1) a decrease in aluminum diffusion through alumina scale and (2) modification of the scale growth mechanism from simultaneous countercurrent diffusion of aluminum and oxygen to predominant inward diffusion of oxygen, which generates less growth stress and thus prevents the formation of fast diffusion paths such as microcracks. The adhesion improvement of alumina scale formed on the Fe3Al-Y was attributed to the modification of alumina growth mechanism by the addition of Y to the Fe3Al alloy. The change of growth mechanism leads to the formation of pegs, decrease of the oxide growth stress, and decrease of voids formation, which enhances the adhesion of alumina scale to the Fe3Al alloy. The second study has focused on the corrosion of Fe3Al in the temperature range of 600--800°C in Cl2-Ar gas mixtures containing traces of oxygen as an impurity. Weight gain was observed during the corrosion of Fe3Al at 600°C in 0.25% Cl2-Ar, which is due to the formation of Fe2O3, while continuous weight loss of the specimen in 5% Cl2-Ar at 800°C was observed because of the formation of volatile metal chlorides, FeCl2, FeCl 3, and AlCl3. Meanwhile, three distinct stages of weight change during the corrosion of Fe3Al at 700°C in 1% Cl 2-Ar were observed: (1) weight gain, (2) linear weight loss, and (3) gradual decrease of weight loss. Initial weight gain is due to the formation of Fe2O3, and the weight loss in the subsequent two stages is due to the formation of volatile metal chlorides, FeCl 2, FeCl3, and AlCl3. Based on the kinetic and microstructural analyses, a reaction mechanism is proposed for each stage.

Assessment of phase constitution on the Al-rich region of rapidly solidified Al-Co-Fe-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, W., E-mail: witorw@gmail.com

The formation of quasicrystalline approximants in rapidly solidified Al-Co-Fe-Cr alloys was investigated. Alloys of atomic composition Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8}, Al{sub 77}Co{sub 11}Fe{sub 6}Cr{sub 6} and Al{sub 76}Co{sub 19}Fe{sub 4}Cr{sub 1} were produced using melt spinning and arc melting methods and their microstructural characterization was carried out by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Up to the present there is no consensus in the literature regarding the formation of quasicrystalline phase or quasicrystalline approximants in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy. This work presents, for the first time, a detailed structural characterization of selected alloysmore » in the Al-Co-Fe-Cr system close to the atomic composition Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8}. The results indicated the samples to be composed, mostly, by two intermetallic phases, which are quaternary extensions of Al{sub 5}Co{sub 2} and Al{sub 13}Co{sub 4} and are quasicrystalline approximants. Although the Al{sub 5}Co{sub 2} phase has already been reported in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy, the presence of the monoclinic Al{sub 13}Co{sub 4} is now identified for the first time in the as cast state. In the binary Al-Co system a quasicrystalline phase is known to form in a rapidly solidified alloy with composition close to the monoclinic and orthorhombic Al{sub 13}Co{sub 4} phases. This binary quasicrystalline phase presents an average valence electron per atom (e/a) between 1.7 and 1.9; thus, in addition to the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} alloy, the compositions Al{sub 77}Co{sub 11}Fe{sub 6}Cr{sub 6} and Al{sub 76}Co{sub 19}Fe{sub 4}Cr{sub 1} were chosen to be within the region of formation of the quaternary extension of the Al{sub 13}Co{sub 4} phase and also within the (e/a) of 1.7 to 1.9. However, no quasicrystalline phase is present in any of the studied alloys. The Al-Co-Fe-Cr system, around the compositions studied, is composed of quaternary extensions of Al-Co intermetallic phases, which present solubility of Fe and Cr at Co atomic sites. - Highlights: •The Al rich region of the AlCoFeCr system is studied concerning phase formation on rapidly solidified alloys. •The alloys were composed mostly by quaternary extensions of Al-Co intermetallic phases. •Al{sub 5}Co{sub 2} and Al{sub 13}Co{sub 4} were the major phases observed in the alloys and are approximants of a quasicrystalline phase. •No quasicrystalline phase was observed in the Al{sub 71}Co{sub 13}Fe{sub 8}Cr{sub 8} composition.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhary, Renu; Department of Physics and Astronomy and NCMN, University of Nebraska, Lincoln, NE 68588; Kharel, Parashu

Disordered CoFeCrAl and CoFeCrSi{sub 0.5}Al{sub 0.5} alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi{sub 0.5}Al{sub 0.5} is predicted to increasemore » from 2.01 μ{sub B} to 2.50 μ{sub B} per formula unit, in good agreement with experiment.« less

Factors influencing the dissolved iron input by river water to the open ocean

NASA Astrophysics Data System (ADS)

Krachler, R.; Jirsa, F.; Ayromlou, S.

The influence of natural metal chelators on the bio-available iron input to the ocean by river water was studied. Ferrous and ferric ions present as suspended colloidal particles maintaining the semblance of a dissolved load are coagulated and settled as their freshwater carrier is mixed with seawater at the continental boundary. However, we might argue that different iron-binding colloids become sequentially destabilized in meeting progressively increasing salinities. By use of a 59Fe tracer method, the partitioning of the iron load from the suspended and dissolved mobile fraction to storage in the sediments was measured with high accuracy in mixtures of natural river water with artificial sea water. The results show a characteristic sequence of sedimentation. Various colloids of different stability are removed from a water of increasing salinity, such as it is the case in the transition from a river water to the open sea. However, the iron transport capacities of the investigated river waters differed greatly. A mountainous river in the Austrian Alps would add only about 5% of its dissolved Fe load, that is about 2.0 µg L-1 Fe, to coastal waters. A small tributary draining a sphagnum peat-bog, which acts as a source of refractory low-molecular-weight fulvic acids to the river water, would add approximately 20% of its original Fe load, that is up to 480 µg L-1 Fe to the ocean's bio-available iron pool. This points to a natural mechanism of ocean iron fertilization by terrigenous fulvic-iron complexes originating from weathering processes occurring in the soils upstream.

Factors influencing the dissolved iron input by river water to the open ocean

NASA Astrophysics Data System (ADS)

Krachler, R.; Jirsa, F.; Ayromlou, S.

2005-05-01

The influence of natural metal chelators on the bio-available iron input to the ocean by river water was studied. Ferrous and ferric ions present as suspended colloidal particles maintaining the semblance of a dissolved load are coagulated and settled as their freshwater carrier is mixed with seawater at the continental boundary. However, we might argue that different iron-binding colloids become sequentially destabilized in meeting progressively increasing salinities. By use of a 59Fe tracer method, the partitioning of the iron load from the suspended and dissolved mobile fraction to storage in the sediments was measured with high accuracy in mixtures of natural river water with artificial sea water. The results show a characteristic sequence of sedimentation. Various colloids of different stability are removed from a water of increasing salinity, such as it is the case in the transition from a river water to the open sea. However, the iron transport capacities of the investigated river waters differed greatly. A mountainous river in the Austrian Alps would add only about 5% of its dissolved Fe load, that is about 2.0 µg L-1 Fe, to coastal waters. A small tributary draining a sphagnum peat-bog, which acts as a source of refractory low-molecular-weight fulvic acids to the river water, would add approximately 20% of its original Fe load, that is up to 480 µg L-1 Fe to the ocean's bio-available iron pool. This points to a natural mechanism of ocean iron fertilization by terrigenous fulvic-iron complexes originating from weathering processes occurring in the soils upstream.

Aluminum alloy anode materials for Li-ion batteries

NASA Astrophysics Data System (ADS)

Sun, Z. H.; Chen, Z. F.; Fu, Q. W.; Jiang, X. Y.

2017-03-01

Aluminum has larger theoretical capacity of 2235 mAh/g than that of graphite (372 mAh/g), but it has big disadvantages including shorter cycle life and higher irreversible capacity loss. Improving cycle performance can be obtained via alloying of aluminum. In this paper, two ternary aluminum alloy, Al7Cu2Fe and Al73Cu5Fe22 were prepared. The main phase of Al7Cu2Fe alloy was Al7Cu2Fe. The heat treatment increased the proportion of Al7Cu2Fe. The main phase of Al73Cu5Fe22 alloy was Al60Cu30Fe10. The heat treatment reduced the proportion of Al60Cu30Fe10. For two alloys, the heat treatment could increase discharge capacity compared with cast alloy. The discharge capacity was improved by 50%. The content of aluminum in alloys has little effect on improving cycle performance, and it has obvious influence on the phase structure of alloy with heat treatment.

An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3

NASA Astrophysics Data System (ADS)

Walker, James D. S.; Grosvenor, Andrew P.

2013-01-01

Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.

Natural quasicrystal with decagonal symmetry

NASA Astrophysics Data System (ADS)

Bindi, Luca; Yao, Nan; Lin, Chaney; Hollister, Lincoln S.; Andronicos, Christopher L.; Distler, Vadim V.; Eddy, Michael P.; Kostin, Alexander; Kryachko, Valery; MacPherson, Glenn J.; Steinhardt, William M.; Yudovskaya, Marina; Steinhardt, Paul J.

2015-03-01

We report the first occurrence of a natural quasicrystal with decagonal symmetry. The quasicrystal, with composition Al71Ni24Fe5, was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite. Icosahedrite, Al63Cu24Fe13, the first natural quasicrystal to be identified, was found in the same meteorite. The new quasicrystal was found associated with steinhardtite (Al38Ni32Fe30), Fe-poor steinhardtite (Al50Ni40Fe10), Al-bearing trevorite (NiFe2O4) and Al-bearing taenite (FeNi). Laboratory studies of decagonal Al71Ni24Fe5 have shown that it is stable over a narrow range of temperatures, 1120 K to 1200 K at standard pressure, providing support for our earlier conclusion that the Khatyrka meteorite reached heterogeneous high temperatures [1100 < T(K) <= 1500] and then rapidly cooled after being heated during an impact-induced shock that occurred in outer space 4.5 Gya. The occurrences of metallic Al alloyed with Cu, Ni, and Fe raises new questions regarding conditions that can be achieved in the early solar nebula.

Phase Constituents and Microstructure of Ti3Al/Fe3Al + TiN/TiB2 Composite Coating on Titanium Alloy

NASA Astrophysics Data System (ADS)

Li, Jianing; Chen, Chuanzhong; Zhang, Cuifang

Laser cladding of the Fe3Al + B4C/TiN + Al2O3 pre-placed powders on the Ti-6Al-4V alloy can form the Ti3Al/Fe3Al + TiN/TiB2 composite coating, which improved the wear resistance of the Ti-6Al-4V alloy surface. In this study, the Ti3Al/Fe3Al + TiN/TiB2 composite coating has been researched by means of X-ray diffraction and scanning electron microscope. It was found that during the laser cladding process, Al2O3 can react with TiB2, leading to the formations of Ti3Al and B. This principle can be used to improve the Fe3Al + B4C/TiN laser-cladded coating on the Ti-6Al-4V alloy. Furthermore, during the cladding process, C consumed the oxygen in Fe3Al + B4C /TiN + Al2O3 molten pool, which retarded the productions of the redundant metal oxides.

Atmospheric Processing of Volcanic Glass: Effects on Iron Solubility and Redox Speciation.

PubMed

Maters, Elena C; Delmelle, Pierre; Bonneville, Steeve

2016-05-17

Volcanic ash from explosive eruptions can provide iron (Fe) to oceanic regions where this micronutrient limits primary production. Controls on the soluble Fe fraction in ash remain poorly understood but Fe solubility is likely influenced during atmospheric transport by condensation-evaporation cycles which induce large pH fluctuations. Using glass powder as surrogate for ash, we experimentally simulate its atmospheric processing via cycles of pH 2 and 5 exposure. Glass fractional Fe solubility (maximum 0.4%) is governed by the pH 2 exposure duration rather than by the pH fluctuations, however; pH 5 exposure induces precipitation of Fe-bearing nanoparticles which (re)dissolve at pH 2. Glass leaching/dissolution release Fe(II) and Fe(III) which are differentially affected by changes in pH; the average dissolved Fe(II)/Fetot ratio is ∼0.09 at pH 2 versus ∼0.18 at pH 5. Iron release at pH 2 from glass with a relatively high bulk Fe(II)/Fetot ratio (0.5), limited aqueous Fe(II) oxidation at pH 5, and possibly glass-mediated aqueous Fe(III) reduction may render atmospherically processed ash a significant source of Fe(II) for phytoplankton. By providing new insight into the form(s) of Fe associated with ash as wet aerosol versus cloud droplet, we improve knowledge of atmospheric controls on volcanogenic Fe delivery to the ocean.

Al-Fe interactions and growth enhancement in Melastoma malabathricum and Miscanthus sinensis dominating acid sulphate soils.

PubMed

Watanabe, Toshihiro; Jansen, Steven; Osaki, Mitsuru

2006-12-01

Plants growing in acid sulphate soils are subject to high levels of Al availability, which may have effects on the growth and distribution of these species. Although Fe availability is also high in acid sulphate soils, little is known about the effect of Fe on the growth of native plants in these soils. Two species dominating this soil type in Asia, viz. Melastoma malabathricum and Miscanthus sinensis were grown hydroponically in a nutrient solution with different concentrations of Al and Fe. Melastoma malabathricum is found to be sensitive to Fe (40 and 100 microm). Application of 500 microm Al, however, completely ameliorates Fe toxicity and is associated with a decrease of Fe concentration in shoots and roots. The primary reason for the Al-induced growth enhancement of M. malabathricum is considered to be the Al-induced reduction of toxic Fe accumulation in roots and shoots. Therefore, Al is nearly essential for M. malabathricum when growing in acid sulphate soils. In contrast, application of both Fe and Al does not reduce the growth of M. sinensis, and Al application does not result in lower shoot concentrations of Fe, suggesting that this grass species has developed different mechanisms for adaptation to acid sulphate soils.

Structure and high temperature oxidation of mechanical alloyed Fe-Al coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aryanto, Didik, E-mail: Didik-phys@yahoo.co.id, E-mail: didi027@lipi.go.id; Sudiro, Toto; Wismogroho, Agus S.

2016-04-19

The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5 Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatingsmore » exhibit high oxidation resistance compared to the uncoated steel. After 60 h exposure, the uncoated steel formed mainly Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} layers with the total thickness of around 75.93 µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al){sub 2}O{sub 3}. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The obtained results suggest that the deposition of Fe-Al coating on low carbon steel can improve the oxidation resistance of low carbon steel.« less

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

NASA Astrophysics Data System (ADS)

Brown, C. J.; Schoonen, M. A. A.; Candela, J. L.

2000-11-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O 2 and SO 42- in the aerobic zone, and to the reduction of SO 42- in the anaerobic zone; estimated rates of CO 2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO 2 production calculated from dissolved inorganic carbon mass transfer (2.55×10 -4 to 48.6×10 -4 mmol l -1 yr-1) generally were comparable to the calculated rates of CO 2 production by the combined reduction of O 2, Fe(III) and SO 42- (1.31×10 -4 to 15×10 -4 mmol l -1 yr-1). The overall increase in SO 42- concentrations along the flow path, together with the results of mass-balance calculations, and variations in δ34S values along the flow path indicate that SO 42- loss through microbial reduction is exceeded by SO 42- gain through diffusion from sediments and through the oxidation of FeS 2. Geochemical and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO 42--rich zones have been depleted by microbial reduction and resulted in localized SO 42--reducing zones in which the formation of iron disulfides decreases dissolved iron concentrations. These localized zones of SO 42- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling.

Introduction to project DUNE, a DUst experiment in a low Nutrient, low chlorophyll Ecosystem

NASA Astrophysics Data System (ADS)

Guieu, C.; Dulac, F.; Ridame, C.; Pondaven, P.

2014-01-01

The main goal of project DUNE was to estimate the impact of atmospheric deposition on an oligotrophic ecosystem based on mesocosm experiments simulating strong atmospheric inputs of eolian mineral dust. Our mesocosm experiments aimed at being representative of real atmospheric deposition events onto the surface of oligotrophic marine waters and were an original attempt to consider the vertical dimension after atmospheric deposition at the sea surface. This introductory paper describes the objectives of DUNE and the implementation plan of a series of mesocosm experiments conducted in the Mediterranean Sea in 2008 and 2010 during which either wet or dry and a succession of two wet deposition fluxes of 10 g m-2 of Saharan dust have been simulated based on the production of dust analogs from erodible soils of a source region. After the presentation of the main biogeochemical initial conditions of the site at the time of each experiment, a general overview of the papers published in this special issue is presented. From laboratory results on the solubility of trace elements in dust to biogeochemical results from the mesocosm experiments and associated modeling, these papers describe how the strong simulated dust deposition events impacted the marine biogeochemistry. Those multidisciplinary results are bringing new insights into the role of atmospheric deposition on oligotrophic ecosystems and its impact on the carbon budget. The dissolved trace metals with crustal origin - Mn, Al and Fe - showed different behaviors as a function of time after the seeding. The increase in dissolved Mn and Al concentrations was attributed to dissolution processes. The observed decrease in dissolved Fe was due to scavenging on sinking dust particles and aggregates. When a second dust seeding followed, a dissolution of Fe from the dust particles was then observed due to the excess Fe binding ligand concentrations present at that time. Calcium nitrate and sulfate were formed in the dust analog for wet deposition following evapocondensation with acids for simulating cloud processing by polluted air masses under anthropogenic influence. Using a number of particulate tracers that were followed in the water column and in the sediment traps, it was shown that the dust composition evolves after seeding by total dissolution of these salts. This provided a large source of new dissolved inorganic nitrogen (DIN) in the surface waters. In spite of this dissolution, the typical inter-elemental ratios in the particulate matter, such as Ti / Al or Ba / Al, are not affected during the dust settling, confirming their values as proxies of lithogenic fluxes or of productivity in sediment traps. DUNE experiments have clearly shown the potential for Saharan wet deposition to modify the in situ concentrations of dissolved elements of biogeochemical interest such as Fe and also P and N. Indeed, wet deposition yielded a transient increase in dissolved inorganic phosphorus (DIP) followed by a very rapid return to initial conditions or no return to initial conditions when a second dust seeding followed. By transiently increasing DIP and DIN concentrations in P- and N-starved surface waters of the Mediterranean Sea, wet deposition of Saharan dust can likely relieve the potential P and/or N limitation of biological activity; this has been directly quantified in terms of biological response. Wet deposition of dust strongly stimulated primary production and phytoplanktonic biomass during several days. Small phytoplankton (< 3 μm) was more stimulated after the first dust addition, whereas the larger size class (> 3 μm) significantly increased after the second one, indicating that larger-sized cells need further nutrient supply in order to be able to adjust their physiology and compete for resource acquisition and biomass increase. Among the microorganisms responding to the atmospheric inputs, diazotrophs were stimulated by both wet and dry atmospheric deposition, although N2 fixation was shown to be only responsible for a few percent of the induced new production. Dust deposition modified the bacterial community structure by selectively stimulating and inhibiting certain members of the bacterial community. The microbial food web dynamics were strongly impacted by dust deposition. The carbon budget indicates that the net heterotrophic character (i.e., ratio of net primary production to bacteria respiration < 1) of the tested waters remained (or was even increased) after simulated wet or dry deposition despite the significant stimulation of autotrophs after wet events. This indicates that the oligotrophic tested waters submitted to dust deposition are a net CO2 source. Nonetheless, the system was able to export organic material, half of it being associated with lithogenic particles through aggregation processes between lithogenic particles and organic matter. These observations support the "ballast" hypothesis and suggest that this "lithogenic carbon pump" could represent a major contribution of the global carbon export to deep waters in areas receiving high rates of atmospheric deposition. Furthermore, a theoretical microbial food web model showed that, all other things being equal, carbon, nitrogen and phosphorus stoichiometric mismatch along the food chain can have a substantial impact on the ecosystem response to nutrient inputs from dusts, with changes in the biomass of all biological compartments by a factor of ~ 2-4, and shifts from net autotrophy to net heterotrophy. Although the model was kept simple, it highlights the importance of stoichiometric constrains on the dynamics of microbial food webs.

Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange

NASA Astrophysics Data System (ADS)

Fitzsimmons, Jessica N.; John, Seth G.; Marsay, Christopher M.; Hoffman, Colleen L.; Nicholas, Sarah L.; Toner, Brandy M.; German, Christopher R.; Sherrell, Robert M.

2017-02-01

Hydrothermally sourced dissolved metals have been recorded in all ocean basins. In the oceans' largest known hydrothermal plume, extending westwards across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4,000 km from the vent source. Both dissolved and particulate iron deepen by more than 350 m relative to 3He--a non-reactive tracer of hydrothermal input--crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5-10 m yr-1. Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe(III) oxyhydroxides, whereas dissolved iron consists of nanoparticulate Fe(III) oxyhydroxides and an organically complexed iron phase. The descent of plume-dissolved iron is best explained by reversible exchange onto slowly sinking particles, probably mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles.

High strength cast aluminum alloy development

NASA Astrophysics Data System (ADS)

Druschitz, Edward A.

The goal of this research was to understand how chemistry and processing affect the resulting microstructure and mechanical properties of high strength cast aluminum alloys. Two alloy systems were investigated including the Al-Cu-Ag and the Al-Zn-Mg-Cu systems. Processing variables included solidification under pressure (SUP) and heat treatment. This research determined the range in properties that can be achieved in BAC 100(TM) (Al-Cu micro-alloyed with Ag, Mn, Zr, and V) and generated sufficient property data for design purposes. Tensile, stress corrosion cracking, and fatigue testing were performed. CuAl2 and Al-Cu-Fe-Mn intermetallics were identified as the ductility limiting flaws. A solution treatment of 75 hours or longer was needed to dissolve most of the intermetallic CuAl 2. The Al-Cu-Fe-Mn intermetallic was unaffected by heat treatment. These results indicate that faster cooling rates, a reduction in copper concentration and a reduction in iron concentration might increase the ductility of the alloy by decreasing the size and amount of the intermetallics that form during solidification. Six experimental Al-Zn-Mg-Cu series alloys were produced. Zinc concentrations of 8 and 12wt% and Zn/Mg ratios of 1.5 to 5.5 were tested. Copper was held constant at 0.9%. Heat treating of the alloys was optimized for maximum hardness. Al-Zn-Mg-Cu samples were solution treated at 441°C (826°F) for 4 hours before ramping to 460°C (860°F) for 75 hours and then aged at 120°C (248°F) for 75 hours. X-ray diffraction showed that the age hardening precipitates in most of these alloys was the T phase (Mg32Zn 31.9Al17.1). Tensile testing of the alloys showed that the best mechanical properties were obtained in the lowest alloy condition. Chilled Al-8.2Zn-1.4Mg-0.9Cu solidified under pressure resulted in an alloy with a yield strength of 468MPa (68ksi), tensile strength of 525MPa (76ksi) and an elongation of 9%.

High Magnetic Susceptibility in a Highly Saline Sulfate-Rich Aquifer Undergoing Biodegradation of Hydrocarbon Results from Sulfate Reduction.

NASA Astrophysics Data System (ADS)

Atekwana, E. A.; Enright, A.; Ntarlagiannis, D.; Slater, L. D.; Bernier, R.; Beaver, C. L.; Rossbach, S.

2016-12-01

We investigated the chemical and stable carbon isotope composition of groundwater in a highly saline aquifer contaminated with hydrocarbon. Our aim to evaluate hydrocarbon degradation and to constrain the geochemical conditions that generated high anomalous magnetic susceptibility (MS) signatures observed at the water table interface. The occurrence of high MS in the water table fluctuating zone has been attributed to microbial iron reduction, suggesting the use of MS as a proxy for iron cycling. The highly saline aquifer had total dissolved solids concentrations of 3.7 to 29.3 g/L and sulfate concentrations of 787 to 37,100 mg/L. We compared our results for groundwater locations with high hydrocarbon contamination (total petroleum hydrocarbon (TPH) >10 mg/L), at lightly contaminated (TPH <10 mg/L) and locations with no contaminations. Our results for the terminal electron acceptors (TEAs) dissolved oxygen (DO), nitrate (NO3-), dissolved iron (Fe2+) , dissolved manganese (Mn2+), sulfate (SO42-) and methane (CH4) suggest a chemically heterogeneous aquifer, probably controlled by heterogeneous distribution of TEAs and contamination (type of hydrocarbon, phase and age of contamination). The concentrations of dissolved inorganic carbon (DIC) ranged from 67 to 648 mg C/L and the stable carbon isotope (δ13CDIC) ranged from -30.0‰ to 1.0 ‰ and DIC-δ13CDIC modeling indicates that the carbon in the DIC is derived primarily from hydrocarbon degradation. The concentrations of Fe2+ in the aquifer ranged from 0.1 to 55.8 mg/L, but was mostly low, averaging 2.7+10.9 mg/L. Given the low Fe2+ [AE1] in the aqueous phase and the high MS at contaminated locations, we suggest that the high MS observed does not arise from iron reduction but rather from sulfate reduction. Sulfate reduction produces H2S which reacts with Fe2+ to produce ferrous sulfide (Fe2+S) or the mixed valence greigite (Fe2+Fe3+2S4). We conclude that in highly saline aquifers with high concentrations of sulfate and contaminated with hydrocarbon, dominance of sulfate reduction as the TEA is responsible for iron cycling and therefore the high MS associated with biodegradation. [AE1]What about sulfate concentrations? And the range in salinity? You need to add these values to the bastrcat

Single Electron Delivery to Lewis Pairs: An Avenue to Anions by Small Molecule Activation.

PubMed

Liu, Liu Leo; Cao, Levy L; Shao, Yue; Stephan, Douglas W

2017-07-26

Single electron transfer (SET) reactions are effected by the combination of a Lewis acid (e.g., E(C 6 F 5 ) 3 E = B or Al) with a small molecule substrate and decamethylferrocene (Cp* 2 Fe). Initially, the corresponding reactions of (PhS) 2 and (PhTe) 2 were shown to give the species [Cp* 2 Fe][PhSB(C 6 F 5 ) 3 ] 1 and [Cp* 2 Fe][(μ-PhS)(Al(C 6 F 5 ) 3 ) 2 ] 2 and [Cp* 2 Fe][(μ-PhTe)(Al(C 6 F 5 ) 3 ) 2 ] 3, respectively. Analogous reactions with di-tert-butyl peroxide yielded [Cp* 2 Fe][(μ-HO)(B(C 6 F 5 ) 3 ) 2 ] 4 with isobutene while with benzoyl peroxide afforded [Cp* 2 Fe][PhC(O)OE(C 6 F 5 ) 3 ] (E = B 5, Al 6). Evidence for a radical pathway was provided by the reaction of Ph 3 SnH and p-quinone afforded [Cp* 2 Fe][HB(C 6 F 5 ) 3 ] 7 and [Cp* 2 Fe] 2 [(μ-O 2 C 6 H 4 )(E(C 6 F 5 ) 3 ) 2 ] (E = B 8, Al 9). In addition, the reaction of TEMPO with Lewis acid and Cp* 2 Fe afforded [Cp* 2 Fe][(C 5 H 6 Me 4 NOE(C 6 F 5 ) 3 ] (E = B 10, Al 11). Finally, reactions with O 2 , Se, Te and S 8 gave [Cp* 2 Fe] 2 [((C 6 F 5 ) 2 Al(μ-O)Al(C 6 F 5 ) 3 ) 2 ] 2 12, [Cp* 2 Fe] 2 [((C 6 F 5 ) 2 Al(μ-Se)Al(C 6 F 5 ) 3 ) 2 ] 2 13, [Cp* 2 Fe][(μ-Te) 2 (Al(C 6 F 5 ) 2 ) 3 ] 14 and [Cp* 2 Fe] 2 [(μ-S 7 )B(C 6 F 5 ) 3 ) 2 ] 15, respectively. The mechanisms of these SET reactions are discussed, and the ramifications are considered.

Chemical transformations during aging of zerovalent iron nanoparticles in the presence of common groundwater dissolved constituents.

PubMed

Reinsch, Brian C; Forsberg, Brady; Penn, R Lee; Kim, Christopher S; Lowry, Gregory V

2010-05-01

Nanoscale zerovalent iron (NZVI) that was aged in simulated groundwater was evaluated for alterations in composition and speciation over 6 months to understand the possible transformations NZVI could undergo in natural waters. NZVI was exposed to 10 mN of various common groundwater anions (Cl(-), NO(3)(-), SO(4)(2-), HPO(4)(2-), and HCO(3)(-)) or to dissolved oxygen (saturated, approximately 9 mg/L). Fresh and exposed NZVI samples, along with Fe-oxide model compounds, were then analyzed using synchrotron radiation X-ray absorption spectroscopy (XAS) to yield both relative oxidation state, using the X-ray absorption near edge structure (XANES), and quantitative speciation information regarding the types and proportions of mineral species present, from analysis of the extended X-ray absorption fine structure (EXAFS). Over 1 month of aging the dissolved anions inhibited the oxidation of the NZVI to varying degrees. Aging for 6 months, however, resulted in average oxidation states that were similar to each other regardless of the anion used, except for nitrate. Nitrate passivated the NZVI surface such that even after 6 months of aging the particles retained nearly the same mineral and Fe(0) content as fresh NZVI. Linear least-squares combination fitting (LCF) of the EXAFS spectra for 1 month-aged samples indicated that the oxidized particles remain predominantly a binary phase system containing Fe(0) and Fe(3)O(4), while the 6 month aged samples contained additional mineral phases such as vivianite (Fe(3)(PO(4))(2).8H(2)O) and iron sulfate species, possibly schwertmannite (Fe(3+)(16)O(16)(OH,SO(4))(12-13).10-12H(2)O). The presence of these additional mineral species was confirmed using synchrotron-based X-ray diffraction (XRD). NZVI exposed to water saturated with dissolved oxygen showed a rapid (<24 h) loss of Fe(0) and evolved both magnetite and maghemite (gamma-Fe(2)O(3)) within the oxide layer. These findings have implications toward the eventual fate, transport, and toxicity of NZVI used for groundwater remediation.

Investigating vibrational anharmonic couplings in cyanide-bridged transition metal mixed valence complexes using two-dimensional infrared spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slenkamp, Karla M.; Lynch, Michael S.; Van Kuiken, Benjamin E.

2014-02-28

Using polarization-selective two-dimensional infrared (2D IR) spectroscopy, we measure anharmonic couplings and angles between the transition dipole moments of the four cyanide stretching (ν{sub CN}) vibrations found in [(NH{sub 3}){sub 5}Ru{sup III}NCFe{sup II}(CN){sub 5}]{sup −} (FeRu) dissolved in D{sub 2}O and formamide and [(NC){sub 5}Fe{sup II}CNPt{sup IV}(NH{sub 3}){sub 4}NCFe{sup II}(CN){sub 5}]{sup 4−} (FePtFe) dissolved in D{sub 2}O. These cyanide-bridged transition metal complexes serve as model systems for studying the role of high frequency vibrational modes in ultrafast photoinduced charge transfer reactions. Here, we focus on the spectroscopy of the ν{sub CN} modes in the electronic ground state. The FTIR spectramore » of the ν{sub CN} modes of the bimetallic and trimetallic systems are strikingly different in terms of frequencies, amplitudes, and lineshapes. The experimental 2D IR spectra of FeRu and FePtFe and their fits reveal a set of weakly coupled anharmonic ν{sub CN} modes. The vibrational mode anharmonicities of the individual ν{sub CN} modes range from 14 to 28 cm{sup −1}. The mixed-mode anharmonicities range from 2 to 14 cm{sup −1}. In general, the bridging ν{sub CN} mode is most weakly coupled to the radial ν{sub CN} mode, which involves the terminal CN ligands. Measurement of the relative transition dipole moments of the four ν{sub CN} modes reveal that the FeRu molecule is almost linear in solution when dissolved in formamide, but it assumes a bent geometry when dissolved in D{sub 2}O. The ν{sub CN} modes are modelled as bilinearly coupled anharmonic oscillators with an average coupling constant of 6 cm{sup −1}. This study elucidates the role of the solvent in modulating the molecular geometry and the anharmonic vibrational couplings between the ν{sub CN} modes in cyanide-bridged transition metal mixed valence complexes.« less

Sulfuric acid baking and leaching of spent Co-Mo/Al2O3 catalyst.

PubMed

Kim, Hong-In; Park, Kyung-Ho; Mishra, Devabrata

2009-07-30

Dissolution of metals from a pre-oxidized refinery plant spent Co-Mo/Al(2)O(3) catalyst have been tried through low temperature (200-450 degrees C) sulfuric acid baking followed by mild leaching process. Direct sulfuric acid leaching of the same sample, resulted poor Al and Mo recoveries, whereas leaching after sulfuric acid baking significantly improved the recoveries of above two metals. The pre-oxidized spent catalyst, obtained from a Korean refinery plant found to contain 40% Al, 9.92% Mo, 2.28% Co, 2.5% C and trace amount of other elements such as Fe, Ni, S and P. XRD results indicated the host matrix to be poorly crystalline gamma- Al(2)O(3). The effect of various baking parameters such as catalyst-to-acid ratio, baking temperature and baking time on percentage dissolutions of metals has been studied. It was observed that, metals dissolution increases with increase in the baking temperature up to 300 degrees C, then decreases with further increase in the baking temperature. Under optimum baking condition more than 90% Co and Mo, and 93% Al could be dissolved from the spent catalyst with the following leaching condition: H(2)SO(4)=2% (v/v), temperature=95 degrees C, time=60 min and Pulp density=5%.

Cu-Ni-Fe anodes having improved microstructure

DOEpatents

Bergsma, S. Craig; Brown, Craig W.

2004-04-20

A method of producing aluminum in a low temperature electrolytic cell containing alumina dissolved in an electrolyte. The method comprises the steps of providing a molten electrolyte having alumina dissolved therein in an electrolytic cell containing the electrolyte. A non-consumable anode and cathode is disposed in the electrolyte, the anode comprised of Cu--Ni--Fe alloys having single metallurgical phase. Electric current is passed from the anode, through the electrolyte to the cathode thereby depositing aluminum on the cathode, and molten aluminum is collected from the cathode.

Dissolution flowsheet for high flux isotope reactor fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foster, T.

2016-09-27

As part of the Spent Nuclear Fuel (SNF) processing campaign, H-Canyon is planning to begin dissolving High Flux Isotope Reactor (HFIR) fuel in late FY17 or early FY18. Each HFIR fuel core contains inner and outer fuel elements which were fabricated from uranium oxide (U 3O 8) dispersed in a continuous Al phase using traditional powder metallurgy techniques. Fuels fabricated in this manner, like other SNF’s processed in H-Canyon, dissolve by the same general mechanisms with similar gas generation rates and the production of H 2. The HFIR fuel cores will be dissolved and the recovered U will be down-blendedmore » into low-enriched U. HFIR fuel was previously processed in H-Canyon using a unique insert in both the 6.1D and 6.4D dissolvers. Multiple cores will be charged to the same dissolver solution maximizing the concentration of dissolved Al. The objective of this study was to identify flowsheet conditions through literature review and laboratory experimentation to safely and efficiently dissolve the HFIR fuel in H-Canyon. Laboratory-scale experiments were performed to evaluate the dissolution of HFIR fuel using both Al 1100 and Al 6061 T6 alloy coupons. The Al 1100 alloy was considered a representative surrogate which provided an upper bound on the generation of flammable (i.e., H 2) gas during the dissolution process. The dissolution of the Al 6061 T6 alloy proceeded at a slower rate than the Al 1100 alloy and was used to verify that the target Al concentration in solution could be achieved for the selected Hg concentration. Mass spectrometry and Raman spectroscopy were used to provide continuous monitoring of the concentration of H 2 and other permanent gases in the dissolution offgas allowing the development of H 2 generation rate profiles. The H 2 generation rates were subsequently used to evaluate if a full HFIR core could be dissolved in an H-Canyon dissolver without exceeding 60% of the calculated lower flammability limit (LFL) for H 2 at a given Hg concentration.« less

PROGRESS ON THE STUDY OF THE URANIUM-ALUMINUM-IRON CONSTITUTION DIAGRAM FOR THE PERIOD APRIL 1-AUGUST 31, 1963

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.

Progress is reported of a research program on deterinining the U--Al-- Fe constitution diagram up to approximates 1000 ppm each of Al and Fe. Results are reported of metallographic examinations of U--Al, U--Fe, and U--Al--Fe alloys, and tentative phase diagrams are given for all three systems. Lattice parameters and electrical resistances were measured in an effort to determine the solid solubilities of Al and Fe in U. (D.L.C.)

Formation of the Fe-Containing Intermetallic Compounds during Solidification of Al-5Mg-2Si-0.7Mn-1.1Fe Alloy

NASA Astrophysics Data System (ADS)

Que, Zhongping; Wang, Yun; Fan, Zhongyun

2018-06-01

Iron (Fe) is the most common and the most detrimental impurity element in Al alloys due to the formation of Fe-containing intermetallic compounds (IMCs), which are harmful to mechanical performance of the Al-alloy components. In this paper we investigate the formation of Fe-containing IMCs during solidification of an Al-5Mg-2Si-0.7Mn-1.1Fe alloy under varied solidification conditions. We found that the primary Fe-containing intermetallic compound (P-IMC) in the alloy is the BCC α-Al15(Fe,Mn)3Si2 phase and has a polyhedral morphology with {1 1 0} surface termination. The formation of the P-IMCs can be easily suppressed by increasing the melt superheat and/or cooling rate, suggesting that the nucleation of the α-Al15(Fe,Mn)3Si2 phase is difficult. In addition, we found that the IMCs with a Chinese script morphology is initiated on the {1 0 0} surfaces of the P-IMCs during the binary eutectic reaction with the α-Al phase. Both the binary and ternary eutectic IMCs are also identified as the BCC α-Al15(Fe,Mn)3Si2 phase. Furthermore, we found that the Fe content increases and the Mn content decreases in the Fe-containing intermetallic compounds with the decrease of the formation temperature, although the sum of the Fe and Mn contents in all of the IMCs is constant.

[Determination of twenty one elements in lithium hexafluorophosphate by ICP-AES].

PubMed

Fang, Yi-wen; Hao, Zhi-feng; Song, Yi-bing; Sun, Chang-yong; Yu, Jian; Yu, Lin

2005-02-01

One gram (+/- 0.0001 g) of lithium hexafluorophosphate was weighed exactly under dry atmosphere and was dissolved with an adequate amount of dimethyl carbonate (DMC). After the sample solution was pretreated with a series of methods, Be, Cu, Pb, Ca, Zr, Co, Mg, V, Ti, Mo, Ni, Mn, Sr, Zn, K, Al, Ba, Cd, Fe, Cr and Na were determined by ICP-AES. The results show that the recoveries of standard addition were 93.3%-102.1%, and the relative standard deviations (n = 11) were 0%-3.56%. The method is efficient, accurate and easy to operate. It has been applied to the determination of lithium hexafluorophosphate products with satisfactory results.

Photochemical Reactivity of Dissolved Organic Matter in Boreal Lakes

NASA Astrophysics Data System (ADS)

Gu, Y.; Vuorio, K.; Tiirola, M.; Perämäki, S.; Vahatalo, A.

2016-12-01

Boreal lakes are rich in dissolved organic matter (DOM) that terrestrially derived from forest soil and wetland, yet little is known about potential for photochemical transformation of aquatic DOM in boreal lakes. Transformation of chromophoric dissolved organic matter (CDOM) can decrease water color and enhance microbial mineralization, affecting primary production and respiration, which both affect the CO2 balance of the lakes. We used laboratory solar radiation exposure experiments with lake water samples collected from 54 lakes located in Finland and Sweden, representing different catchment composition and watershed location to assess photochemical reactivity of DOM. The pH of water samples ranged from 5.4 to 8.3, and the concentrations of dissolved iron (Fe) were between < 0.06 and 22 μmol L-1. The filtered water samples received simulated solar radiation corresponding to a daily dose of sunlight, and photomineralization of dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC) was measured for determination of spectral apparent quantum yields (AQY). During irradiation, photobleaching decreased the absorption coefficients of CDOM at 330 nm between 4.9 and 79 m-1 by 0.5 to 11 m-1. Irradiation generated DIC from 2.8 to 79 μmol C L-1. The AQY at 330 nm ranged between 31 and 273 ×10-6 mol C mol photons-1 h-1, which was correlated positively with concentration of dissolved Fe, and negatively with pH. Further statistical analyze indicated that the interaction between pH and Fe may explain much of the photochemical reactivity of DOM in the examined lakes, and land cover concerns main catchment areas also can have impact on the photoreaction process. This study may suggest how environmental conditions regulate DOM photomineralization in boreal lakes.

The occurrence and distribution of trace metals in the Mississippi River and its tributaries

USGS Publications Warehouse

Taylor, Howard E.; Garbarino, J.R.; Brinton, T.I.

1990-01-01

Quantitative and semiquantitative analyses of dissolved trace metals are reported for designated sampling sites on the Mississippi River and its main tributaries utilizing depth-integrated and width-integrated sampling technology to collect statistically representative samples. Data are reported for three sampling periods, including: July-August 1987, November-December 1987, and May-June 1988. Concentrations of Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Pb, Sr, Tl, U, V, and Zn are reported quantitatively, with the remainder of the stable metals in the periodic table reported semiquantitatively. Correlations between As and V, Ba and U, Cu and Zn, Li and Ba, and Li and U are significant at the 99% confidence level for each of the sampling trips. Comparison of the results of this study for selected metals with other published data show generally good agreement for Cr, Cu, Fe, and Zn, moderate agreement for Mo, and poor agreement for Cd and V.

Alternate cathodes for sodium-metal chloride batteries

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Attia, A. I.; Halpert, G.

1991-01-01

Various metal chlorides were tested as possible cathode materials for sodium-metal batteries (in addition to Fe and Ni chlorides, which have been already developed to a stage of commercialization), using an electrochemical cell consisting of a pyrex tube, heated to 250 C, with the metal wire as working electrode, concentric Ni foil as counterelectrode, and high-purity Al as reference electrode. In particular, the aim of this study was to identify metal chlorides insoluble even in neutral melts, possible at the interface during overcharge, in order to eliminate the failure mode of the cell through a cationic exchange of the dissolved metal ions with sodium beta-double-prime alumina solid electrolyte. Results indicate that Mo and Co are likely alternatives to FeCl2 and NiCl2 cathodes in sodium batteries. The open circuit voltages of Na/CoCl(x) and Na/MoCl(x) cells at 250 C would be 2.55 V and 2.64 V, respectively.

Large magnetization and high Curie temperature in highly disordered nanoscale Fe2CrAl thin films

NASA Astrophysics Data System (ADS)

Dulal, Rajendra P.; Dahal, Bishnu R.; Forbes, Andrew; Pegg, Ian L.; Philip, John

2017-02-01

We have successfully grown nanoscale Fe2CrAl thin films on polished Si/SiO2 substrates using an ultra-high vacuum deposition with a base pressure of 9×10-10 Torr. The thickness of thin films ranges from 30 to 100 nm. These films exhibit cubic crystal structure with lattice disorder and display ferromagnetic behavior. The Curie temperature is greater than 400 K, which is much higher than that reported for bulk Fe2CrAl. The magnetic moments of the films varies from 2.5 to 2.8 μB per formula unit, which is larger than the reported bulk values. Thus, the disordered nanoscale Fe2CrAl films exhibit strong Fe-Fe exchange interactions through Fe-Cr-Fe and Fe-Al-Fe layers, resulting in both a large magnetization and a high Curie temperature.

Transformation of organic carbon, trace element, and organo-mineral colloids in the mixing zone of the largest European Arctic river

NASA Astrophysics Data System (ADS)

Pokrovsky, O. S.; Shirokova, L. S.; Viers, J.; Gordeev, V. V.; Shevchenko, V. P.; Chupakov, A. V.; Vorobieva, T. Y.; Candaudap, F.; Casseraund, C.; Lanzanova, A.; Zouiten, C.

2013-10-01

The estuarine behavior of organic carbon (OC) and trace elements (TE) was studied for the largest European sub-Arctic river, which is the Severnaya Dvina; this river is a deltaic estuary covered in ice during several hydrological seasons: summer (July 2010, 2012) and winter (March 2009) baseflow, and the November-December 2011 ice-free period. Colloidal forms of OC and TE were assessed using three pore size cutoff (1, 10, and 50 kDa) using an in-situ dialysis procedure. Conventionally dissolved (< 0.22 μm) fractions demonstrated clear conservative behavior for Li, B, Na, Mg, K, Ca, Sr, Mo, Rb, Cs, and U during the mixing of freshwater with the White Sea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. Si and OC also displayed conservative behavior but with a pronounced decrease of concentration seawards. Rather conservative behavior, but with much smaller changes in concentration (variation within ±30%) over a full range of salinities, was observed for Ti, Ni, Cr, As, Co, Cu, Ga, Y, and heavy REE. Strong non-conservative behavior with coagulation/removal at low salinities (< 5‰) was exhibited by Fe, Al, Zr, Hf, and light REE. Finally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (~2-5‰, Ba, Mn) or intermediate (~10-15‰, Ba, Zn, Pb, Cd) salinities, which is most likely linked to TE desorption from suspended matter or sediment outflux. The most important result of this study is the elucidation of the behavior of the "truly" dissolved low molecular weight LMW< 1 kDa fraction containing Fe, OC, and a number of insoluble elements. The concentration of the LMW fraction either remains constant or increases its relative contribution to the overall dissolved (< 0.22 μm) pool as the salinity increases. Similarly, the relative proportion of colloidal (1 kDa-0.22 μm) pool for the OC and insoluble TE bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (< 5‰) salinities. Overall, the observed decrease of the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the HMW1 kDa-0.22 μm portion by the LMW< 1 kDa fraction. These patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the OC, Fe and insoluble TE. The size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. In particular, LMW< 1 kDa ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous DOM and/or photodestruction. Given the relatively low concentration of particulate vs. dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. As a result, the majority of dissolved components exhibited either a conservative (OC and related elements such as divalent metals) or non-conservative, coagulation-controlled (Fe, Al, and insoluble TE associated with organo-ferric colloids) behavior. The climate warming in high latitudes is likely to intensify the production of LMW< 1 kDa organic ligands and the associated TE; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.

Importance of allochthonous and autochthonous dissolved organic matter in Fe(II) oxidation: A case study in Shizugawa Bay watershed, Japan.

PubMed

Lee, Ying Ping; Fujii, Manabu; Kikuchi, Tetsuro; Natsuike, Masafumi; Ito, Hiroaki; Watanabe, Toru; Yoshimura, Chihiro

2017-08-01

Ferrous iron (Fe[II]) oxidation by dissolved oxygen was investigated in the Shizugawa Bay watershed with particular attention given to the effect of dissolved organic matter (DOM) properties on Fe(II) oxidation. To cover a wide spectrum of DOM composition, water samples were collected from various water sources including freshwater (e.g., river water and wastewater effluent) and coastal seawater. Measurement of nanomolar Fe(II) oxidation by using luminol chemiluminescence under dark, air-saturated conditions at 25 °C indicated that spatio-temporal variation of the second-order rate constant (6.7-74.5 M -1  s -1 ) was partially explained by the variation of the sample pH (7.5-8.6). However, at comparable pH values, the oxidation rates for freshwater were generally greater than those for coastal seawater. The substantial decline in oxidation rate constant after the removal of humic-type (allochthonous) DOM suggested that this hydrophobic DOM is a key factor that accelerates the Fe(II) oxidation in the freshwater samples. Observed lower oxidation rates for coastal seawater compared with freshwater and organic ligand-free seawater were likely associated with microbially derived autochthonous DOM, and the variation of Fe(II) oxidation at a fixed pH was best described by fluorescence index that represents the proportion of autochthonous and allochthonous DOM in natural waters. Consistently, Fe(II) oxidation was found to be slower in the presence of cellular exudates from phytoplankton. The present study highlighted the significant effect of DOM composition on the Fe(II) oxidation in inland and coastal waters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reactive-transport modeling of iron diagenesis and associated organic carbon remineralization in a Florida (USA) subterranean estuary

USGS Publications Warehouse

Roy, Moutusi; Martin, Jonathan B.; Smith, Christopher G.; Cable, Jaye E.

2011-01-01

Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10-8 s-1 to 0.64 × 10-8 s-1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10-2 mg/cm2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.

The preferential orientation and lattice misfit of the directionally solidified Fe-Al-Ta eutectic composite

NASA Astrophysics Data System (ADS)

Cui, Chunjuan; Wang, Pei; Yang, Meng; Wen, Yagang; Ren, Chiqiang; Wang, Songyuan

2018-01-01

Fe-Al intermetallic compound has been paid more attentions recently in many fields such as aeronautic, aerospace, automobile, energy and chemical engineering, and so on. In this paper Fe-Al-Ta eutectic was prepared by a modified Bridgman directional solidification technique, and it is found that microstructure of the Fe-Al-Ta eutectic alloy transforms from the broken-lamellar eutectic to cellular eutectic with the increase of the solidification rate. In the cellular eutectic structure, the fibers are parallel to each other within the same grain, but some fibers are deviated from the original orientation at the grain boundaries. To study the crystallographic orientation relationship (OR) between the two phases, the preferential orientation of the Fe-Al-Ta eutectic alloy at the different solidification rates was studied by Selected Area Electron Diffraction (SAED). Moreover, the lattice misfit between Fe2Ta(Al) Laves phase and Fe(Al,Ta) matrix phase was calculated.

Structural investigation of the (010) surface of the Al13 Fe4 catalyst.

PubMed

Ledieu, J; Gaudry, É; Loli, L N Serkovic; Villaseca, S Alarcón; de Weerd, M-C; Hahne, M; Gille, P; Grin, Y; Dubois, J-M; Fournée, V

2013-02-15

We have investigated the structure of the Al(13)Fe(4)(010) surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered (P) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as "glue" atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk P plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the Al(13)Fe(4) catalytic properties recently reported in line with the site-isolation concept [M. Armbrüster et al., Nat. Mater. 11, 690 (2012)].

Aluminum-Stabilized Magnesium Diboride Superconductors

NASA Astrophysics Data System (ADS)

Dou, S. X.; Collings, E. W.; Shcherbakova, O.; Shcherbakov, A.

2006-03-01

Use of aluminum as stabilizer and iron as reaction barrier for fabrication of MgB2 superconductor wires was studied. The MgB2/Fe/Al or SiC doped MgB2/Fe/Al composite wires were made using Mg+ 2 B powder or SiC doped Mg+2 B powder in Fe/Al tube technique. The composites were processed at 600°C to 650°C for 30 minutes to 3 hours to study the interaction between Fe and Al sheath and the formation of MgB2. No reaction between Fe and Al was found until annealing temperature at 620°C for 30 minutes. A thin layer of alloy, FeAl3 is formed for samples annealed at 620°C for 90 minutes and the reaction layer increases with increasing annealing temperature. Annealing at 650°C resulted in cracks in the Al sheath. Our results show that the Fe/Al sheathed wires achieved the same performance in magnetic and electrical properties as those using an all-Fe sheath. Comparing with the standard NbTi/Cu conductors, the MgB2/Fe/Al conductor having low structural mass, greater thermal conductivity and high efficient stabilization will make a tremendous difference especially for airborne, aerospace, and other applications when weight is important.

Dislocation loop evolution during in-situ ion irradiation of model FeCrAl alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haley, Jack C.; Briggs, Samuel A.; Edmondson, Philip D.

Model FeCrAl alloys of Fe-10%Cr-5%Al, Fe-12%Cr-4.5%Al, Fe-15%Cr-4%Al, and Fe-18%Cr-3%Al (in wt %) were irradiated with 1 MeV Kr++ ions in-situ with transmission electron microscopy to a dose of 2.5 displacements per atom (dpa) at 320 °C. In all cases, the microstructural damage consisted of dislocation loops with ½< 111 > and <100 > Burgers vectors. The proportion of ½< 111 > dislocation loops varied from ~50% in the Fe-10%Cr-5%Al model alloy and the Fe-18Cr%-3%Al model alloy to a peak of ~80% in the model Fe-15%Cr-4.5%Al alloy. The dislocation loop volume density increased with dose for all alloys and showed signsmore » of approaching an upper limit. The total loop populations at 2.5 dpa had a slight (and possibly insignificant) decline as the chromium content was increased from 10 to 15 wt %, but the Fe-18%Cr-3%Al alloy had a dislocation loop population ~50% smaller than the other model alloys. As a result, the largest dislocation loops in each alloy had image sizes of close to 20 nm in the micrographs, and the median diameters for all alloys ranged from 6 to 8 nm. Nature analysis by the inside-outside method indicated most dislocation loops were interstitial type.« less

Dislocation loop evolution during in-situ ion irradiation of model FeCrAl alloys

DOE PAGES

Haley, Jack C.; Briggs, Samuel A.; Edmondson, Philip D.; ...

2017-07-06

Model FeCrAl alloys of Fe-10%Cr-5%Al, Fe-12%Cr-4.5%Al, Fe-15%Cr-4%Al, and Fe-18%Cr-3%Al (in wt %) were irradiated with 1 MeV Kr++ ions in-situ with transmission electron microscopy to a dose of 2.5 displacements per atom (dpa) at 320 °C. In all cases, the microstructural damage consisted of dislocation loops with ½< 111 > and <100 > Burgers vectors. The proportion of ½< 111 > dislocation loops varied from ~50% in the Fe-10%Cr-5%Al model alloy and the Fe-18Cr%-3%Al model alloy to a peak of ~80% in the model Fe-15%Cr-4.5%Al alloy. The dislocation loop volume density increased with dose for all alloys and showed signsmore » of approaching an upper limit. The total loop populations at 2.5 dpa had a slight (and possibly insignificant) decline as the chromium content was increased from 10 to 15 wt %, but the Fe-18%Cr-3%Al alloy had a dislocation loop population ~50% smaller than the other model alloys. As a result, the largest dislocation loops in each alloy had image sizes of close to 20 nm in the micrographs, and the median diameters for all alloys ranged from 6 to 8 nm. Nature analysis by the inside-outside method indicated most dislocation loops were interstitial type.« less

Ferric iron in sediments as a novel CO2 mineral trap: CO 2-SO2 reaction with hematite

USGS Publications Warehouse

Palandri, J.L.; Rosenbauer, R.J.; Kharaka, Y.K.

2005-01-01

Thermodynamic simulations of reactions among SO2-bearing CO 2-dominated gas, water and mineral phases predict that Fe III in sediments should be converted almost entirely to dissolved FeII and siderite (FeCO3), and that SO2 should simultaneously be oxidized to dissolved sulfate. The reactions are however, subject to kinetic constraints which may result in deviation from equilibrium and the precipitation of other metastable mineral phases. To test the prediction, a laboratory experiment was carried out in a well stirred hydrothermal reactor at 150??C and 300 bar with hematite, 1.0 m NaCl, 0.5 m NaOH, SO2 in quantity sufficient to reduce much of the iron, and excess CO2. The experiment produced stable siderite and metastable pyrite and elemental S. Changes in total dissolved Fe are consistent with nucleation of pyrite at ???17 h, and nucleation of siderite at ???600 h. Dissolution features present on elemental S at the conclusion of the experiment suggest nucleation early in the experiment. The experiment did not reach equilibrium after ???1400 h, as indicated by coexistence of hematite with metastable pyrite and elemental sulfur. However, the results confirm that FeIII can be used to trap CO2 in siderite if partly oxidized S, as SO2, is present to reduce the Fe with CO2 in the gas phase. ?? 2005 Elsevier Ltd. All rights reserved.

Microstructural Evolution of Al-1Fe (Weight Percent) Alloy During Accumulative Continuous Extrusion Forming

NASA Astrophysics Data System (ADS)

Wang, Xiang; Guan, Ren-Guo; Tie, Di; Shang, Ying-Qiu; Jin, Hong-Mei; Li, Hong-Chao

2018-04-01

As a new microstructure refining method, accumulative continuous extrusion forming (ACEF) cannot only refine metal matrix but also refine the phases that exist in it. In order to detect the refinements of grain and second phase during the process, Al-1Fe (wt pct) alloy was processed by ACEF, and the microstructural evolution was analyzed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results revealed that the average grain size of Al-1Fe (wt pct) alloy decreased from 13 to 1.2 μm, and blocky Al3Fe phase with an average length of 300 nm was granulated to Al3Fe particle with an average diameter of 200 nm, after one pass of ACEF. Refinement of grain was attributed to continuous dynamic recrystallization (CDRX), and the granulation of Al3Fe phase included the spheroidization resulting from deformation heat and the fragmentation caused by the coupling effects of strain and thermal effect. The spheroidization worked in almost the entire deformation process, while the fragmentation required strain accumulation. However, fragmentation contributed more than spheroidization. Al3Fe particle stimulated the formation of substructure and retarded the migration of recrystallized grain boundary, but the effect of Al3Fe phase on refinement of grain could only be determined by the contrastive investigation of Al-1Fe (wt pct) alloy and pure Al.

Parametric and experimentally informed BWR Severe Accident Analysis Utilizing FeCrAl - M3FT-17OR020205041

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ott, Larry J.; Howell, Michael; Robb, Kevin R.

Iron-chromium-aluminum (FeCrAl) alloys are being considered as advanced fuel cladding concepts with enhanced accident tolerance. At high temperatures, FeCrAl alloys have slower oxidation kinetics and higher strength compared with zirconium-based alloys. FeCrAl could be used for fuel cladding and spacer or mixing vane grids in light water reactors and/or as channel box material in boiling water reactors (BWRs). There is a need to assess the potential gains afforded by the FeCrAl accident-tolerant-fuel (ATF) concept over the existing zirconium-based materials employed today. To accurately assess the response of FeCrAl alloys under severe accident conditions, a number of FeCrAl properties and characteristicsmore » are required. These include thermophysical properties as well as burst characteristics, oxidation kinetics, possible eutectic interactions, and failure temperatures. These properties can vary among different FeCrAl alloys. Oak Ridge National Laboratory has pursued refined values for the oxidation kinetics of the B136Y FeCrAl alloy (Fe-13Cr-6Al wt %). This investigation included oxidation tests with varying heating rates and end-point temperatures in a steam environment. The rate constant for the low-temperature oxidation kinetics was found to be higher than that for the commercial APMT FeCrAl alloy (Fe-21Cr-5Al-3Mo wt %). Compared with APMT, a 5 times higher rate constant best predicted the entire dataset (root mean square deviation). Based on tests following heating rates comparable with those the cladding would experience during a station blackout, the transition to higher oxidation kinetics occurs at approximately 1,500°C. A parametric study varying the low-temperature FeCrAl oxidation kinetics was conducted for a BWR plant using FeCrAl fuel cladding and channel boxes using the MELCOR code. A range of station blackout severe accident scenarios were simulated for a BWR/4 reactor with Mark I containment. Increasing the FeCrAl low-temperature oxidation rate constant (3 times and 10 times that of the rate constant for APMT) had a negligible impact on the early stages of the accident and minor impacts on the accident progression after the first relocation of the fuel. At temperatures below 1,500°C, increasing the rate constant for APMT by a factor of 10 still resulted in only minor FeCrAl oxidation. In general, the gains afforded by the FeCrAl enhanced ATF concept with respect to accident sequence timing and combustible gas generation are consistent with previous efforts. Compared with the traditional Zircaloy-based cladding and channel box system, the FeCrAl concept could provide a few extra hours of time for operators to take mitigating actions and/or for evacuations to take place. A coolable core geometry is retained longer, enhancing the ability to stabilize an accident. For example, a station blackout was simulated in which cooling water injection was lost 36 hours after shutdown. The timing to first fuel relocation was delayed by approximately 5 h for the FeCrAl ATF concept compared with that of the traditional Zircaloy-based cladding and channel box system.« less

Amelioration of iron toxicity: A mechanism for aluminum-induced growth stimulation in tea plants.

PubMed

Hajiboland, Roghieh; Barceló, Juan; Poschenrieder, Charlotte; Tolrà, Roser

2013-11-01

Tea plants (Camellia sinensis) are well adapted to acid soils with high Al availability. These plants not only accumulate high leaf Al concentrations, but also respond to Al with growth stimulation. Decreased oxidative stress has been associated with this effect. Why tea plants not exposed to Al suffer from oxidative stress has not been clarified. In this study, hydroponically grown tea plants treated with 0 to 300 μM Al were analyzed for growth, Al and Fe accumulation, and Al distribution by means of morin and hematoxylin staining. Roots of control plants stained black with hematoxylin. This indicates the formation of a Fe-hematoxylin complex. Young leaves of controls accumulated more than 1000 mg Fe kg(-1) dry weight. This concentration is above the Fe-toxicity threshold in most species. Supply of Al stimulated growth and reduced Fe uptake and transport. These results indicate that Al-induced growth stimulation might be due to alleviation of a latent Fe toxicity occurring in tea plants without Al supply. © 2013.

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

USGS Publications Warehouse

Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

2008-01-01

Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

Phase equilibria in the nominally Al65Cu23Fe12 system at 3, 5 and 21 GPa: Implications for the quasicrystal-bearing Khatyrka meteorite

NASA Astrophysics Data System (ADS)

Stagno, Vincenzo; Bindi, Luca; Steinhardt, Paul J.; Fei, Yingwei

2017-10-01

Two of the three natural quasiperiodic crystals found in the Khatyrka meteorite show a composition within the Al-Cu-Fe system. Icosahedrite, with formula Al63Cu24Fe13, coexists with the new Al62Cu31Fe7 quasicrystal plus additional Al-metallic minerals such as stolperite (AlCu), kryachkoite [(Al,Cu)6(Fe,Cu)], hollisterite (AlFe3), khatyrkite (Al2Cu) and cupalite (AlCu), associated to high-pressure phases like ringwoodite/ahrensite, coesite, and stishovite. These high-pressure minerals represent the evidence that most of the Khatyrka meteoritic fragments formed at least at 5 GPa and 1200 °C, if not at more extreme conditions. On the other hand, experimental studies on phase equilibria within the representative Al-Cu-Fe system appear mostly limited to ambient pressure conditions, yet. This makes the interpretation of the coexisting mineral phases in the meteoritic sample quite difficult. We performed experiments at 3, 5 and 21 GPa and temperatures of 800-1500 °C using the multi-anvil apparatus to investigate the phase equilibria in the Al65Cu23Fe12 system representative of the first natural quasicrystal, icosahedrite. Our results, supported by single-crystal X-ray diffraction and analyses by scanning electron microscopy, confirm the stability of icosahedrite at high pressure and temperature along with additional coexisting Al-bearing phases representative of khatyrkite and stolperite as those found in the natural meteorite. One reversal experiment performed at 5 GPa and 1200 °C shows the formation of the icosahedral quasicrystal from a pure Al, Cu and Fe mixture, a first experimental synthesis of icosahedrite under those conditions. Pressure appears to not play a major role in the distribution of Al, Cu and Fe between the coexisting phases, icosahedrite in particular. Results from this study extend our knowledge on the stability of icosahedral AlCuFe at higher temperature and pressure than previously examined, and provide a new constraint on the stability of icosahedrite.

Iron in solution with aluminum matrix after non-equilibrium processing: an atom probe tomography study

NASA Astrophysics Data System (ADS)

Saller, Brandon D.; Sha, Gang; Yang, Li Mei; Liu, Fan; Ringer, Simon P.; Schoenung, Julie M.

2017-03-01

In this paper, we report on the influence of rapid solidification and severe plastic deformation on the solid solubility of Fe in Al. Atom probe tomography, for the first time, was performed on fine (3-4 μm diameter) and coarse ( 100 μm) as-atomised Al-5 at.% Fe powder and cryomilled Al-5 at.% Fe powder. The atomised powders exhibited negligible Fe in solution with Al, whereas the cryomilled powder contained 2 at.% Fe in solution. Moreover, our results suggest that severe plastic deformation is preferable to atomisation/rapid solidification for increasing the non-equilibrium solid solubility of Fe in Al.

Influence of humic acid imposed changes of ferrihydrite aggregation on microbial Fe(III) reduction

NASA Astrophysics Data System (ADS)

Amstaetter, Katja; Borch, Thomas; Kappler, Andreas

2012-05-01

Microbial reduction of Fe(III) minerals at neutral pH is faced by the problem of electron transfer from the cells to the solid-phase electron acceptor and is thought to require either direct cell-mineral contact, the presence of Fe(III)-chelators or the presence of electron shuttles, e.g. dissolved or solid-phase humic substances (HS). In this study we investigated to which extent the ratio of Pahokee Peat Humic Acids (HA) to ferrihydrite in the presence and absence of phosphate influences rates of Fe(III) reduction by Shewanella oneidensis MR-1 and the identity of the minerals formed. We found that phosphate generally decreased reduction rates by sorption to the ferrihydrite and surface site blocking. In the presence of low ferrihydrite concentrations (5 mM), the addition of HA helped to overcome this inhibiting effect by functioning as electron shuttle between cells and the ferrihydrite. In contrast, at high ferrihydrite concentrations (30 mM), the addition of HA did not lead to an increase but rather to a decrease in reduction rates. Confocal laser scanning microscopy images and ferrihydrite sedimentation behaviour suggest that the extent of ferrihydrite surface coating by HA influences the aggregation of the ferrihydrite particles and thereby their accessibility for Fe(III)-reducing bacteria. We further conclude that in presence of dissolved HA, iron reduction is stimulated through electron shuttling while in the presence of only sorbed HA, no stimulation by electron shuttling takes place. In presence of phosphate the stimulation effect did not occur until a minimum concentration of 10 mg/l of dissolved HA was reached followed by increasing Fe(III) reduction rates up to dissolved HA concentrations of approximately 240 mg/l above which the electron shuttling effect ceased. Not only Fe(III) reduction rates but also the mineral products changed in the presence of HA. Sequential extraction, XRD and 57Fe-Mössbauer spectroscopy showed that crystallinity and grain size of the magnetite produced by Fe(III) reduction in the presence of HA is lower than the magnetite produced in the absence of HA. In summary, this study shows that both the concentration of HA and Fe(III) minerals strongly influence microbial Fe(III) reduction rates and the mineralogy of the reduction products. Thus, deviations in iron (hydr)oxide reactivity with changes in aggregation state, such as HA induced ferrihydrite aggregation, need to be considered within natural environments.

Heterotrophic bacterium Pseudomonas saponiphila and sunlight as impact factors on organo-mineral colloids transformations in boreal humic waters

NASA Astrophysics Data System (ADS)

Oleinikova, Olga; Drozdova, Olga; Shirokova, Liudmila; Lapitskiy, Sergey; Bychkov, Andrew; Pokrovsky, Oleg

2017-04-01

Two of the main factors of carbon balance in high latitudes, known to govern the CO2 flux from the lakes and rivers to the atmosphere, are bacterial mineralization (respiration) of allochthonous dissolved organic matter (DOM) and photochemical degradation of DOM. Yet, in contrast to large numbers of experimental and field studies on these factors impact on the utilization of DOM of different origin, the fate of metals bound to colloids during bacterial processing of DOM and behavior of trace element (TE) during photodegradation of DOM remains poorly constrained. This is especially important in view of essentially organic and organo-mineral colloidal status of TE in most boreal waters. To answer this questions, a monoculture of Pseudomonas saponiphila from a boreal creek in NW Karelia (Russia) was separated and allowed to interact with boreal peat leachate in nutrient-free media. We quantified colloidal transformation of the peat leachate during 5-days activity of live bacteria using 3 kDa, 50 kDa Amicon® centrifugal filtration and 0.45 µm syringe filtration. The total net decrease of the concentration of Dissolved Organic Carbon (DOC) over 93 h of exposure was within 5% of the initial value for all fractions except low molecular weight one (< 3 kDa), which yielded a 16%-decrease due to long-term bio-uptake or coagulation. Elements most affected by bacterial presence were Al, Mn, (Ni), Cu, Ga, REEs, Y, U which exhibited essentially the adsorption at the cell surface over first hrs of reaction, and Fe, Ti, (Zr), and Nb showing short-term adsorption and long-term assimilation. Towards a better understanding of concentration, size fractionation and speciation change of TE in boreal waters subjected to solar radiation, we conducted on-site photo-degradation experiments in stream and bog water from pristine zone of Northern Karelia (Russian subarctic). After 5 days of exposure, the DOM in stream photodegraded in a much smaller degree than that in the bog water with 25 and 60% removal of initial DOC, respectively. Specific UV absorption (SUVA254) decreased by a factor of 1.75 and 5 over 200 h of exposure in stream and bog water, respectively. The removal of Fe and Al occurred only in the bog water (90 % and 50% respectively, over 5 days of reaction), whereas no detectable decrease of Al and Fe concentration (< 0.22 µm) was observed in the boreal stream. The majority of colloidal constituents including DOC, Fe, Al, metal micronutrients are weakly affected by heterotrophic bacterial activity and as such the stability of peat soil colloids in boreal waters is expected to be high. In contrast to this, in bog waters, alkali, alkaline-earth metals and divalent metal micornutrients, present in the form of organic complexes (50-80%), may be completely degraded over a week of sunlight exposure. We acknowledge support from a RFBR research projects №№ 16-55-150002 HЦHИ_a, 15-05-05000_a, 14-05-00430_a, 16-05-00542_a. Experimental study was supported by RSF № 14-50-00029.

Iron Speciation in the Subtropical Waters East of New Zealand using Multi Detection Window CLE-AdCSV Titrations.

NASA Astrophysics Data System (ADS)

Chandrasekhar, Anoop; Sander, Sylvia; Milnes, Angie; Boyd, Philip

2015-04-01

Iron plays a significant role in the ocean productivity as a micro nutrient that facilitates the growth of marine phytoplankton and microbes. The bioavailability of iron in the ocean depends on it speciation. Iron is bio available in its dissolved form and about 99.9% of dissolved iron in seawater is organically complexed with natural ligands. The competitive ligand equilibration - adsorptive cathodic stripping voltammetry (CLE-AdCSV) is the widely used technique to examine Fe speciation. The method has its own limitations. The analytical window employed in this technique has a distinct impact on Fe speciation results (Buck, Moffett et al. 2012). Recently, (Pizeta, Sander et al. in preparation) have shown that the accuracy of complexometric titrations improve if multiple analytical windows (MAW) are solved as a united dataset. Several programs are now available that enable this approach with the KMS (Kineteql.xls , Hudson 2014), which is based on an Excel application based on speciation calculation (Hudson, Rue et al. 2003, Sander, Hunter et al. 2011), being one of them. In the present work, the unified MAW data analysis method is applied to determine iron speciation by CLE-AdCSV with salicyl aldoxime (SA) (Abualhaija and van den Berg 2014) in real seawater samples from the Spring bloom FeCycle III voyage, which took place in an anticyclonic eddy in subtropical waters east of New Zealand in spring 2012. Two different analytical windows (5 and 15µM SA) were applied to samples from depth profiles taken during this cruise. The data obtained was analysed using the program KMS (Kineteql.xls). Most samples only returned one Fe-binding ligands class. Higher ligand concentrations were observed in the upper water column and the stability constants were above 22 (e.g. 22.25 ± 0.21 for station 63). Our results will be discussed in the context of microbial community distribution as well as other biogeochemical parameters. Abualhaija, M. M. and C. M. G. van den Berg (2014). "Chemical speciation of iron in seawater using catalytic cathodic stripping voltammetry with ligand competition against salicylaldoxime." Marine Chemistry 164(0): 60-74. Buck, K. N., J. Moffett, K. A. Barbeau, R. M. Bundy, Y. Kondo and J. Wu (2012). "The organic complexation of iron and copper: an intercomparison of competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) techniques " Limnology and Oceanography: Methods 10: 496-515. Hudson, R. J. M., E. L. Rue and K. W. Bruland (2003). "Modeling Complexometric Titrations of Natural Water Samples." Environ. Sci. Tech. 37: 1553-1562. Pizeta, I., S. G. Sander, O. Baars, K. Buck, R. Bundy, G. Carrasco, P. Croot, C. Garnier, L. Gerringa, M. Gledhill, K. Hirose, D. R. Hudson, Y. Kondo-Jacquot, L. Laglera, D. Omanovic, M. Rijkenberg, B. Twining and M. Wells (in preparation). "Intercomparison of estimating metal binding ligand parameters from simulated titration data using different fitting approaches." for Limnology and Oceanography: Methods. Sander, S. G., K. A. Hunter, H. Harms and M. Wells (2011). "Numerical approach to speciation and estimation of parameters used in modeling trace metal bioavailability." Environmental Science and Technology 45(15): 6388-6395.

Solid-state transformation of Fe-rich intermetallic phases in Al–5.0Cu–0.6Mn squeeze cast alloy with variable Fe contents during solution heat treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Bo; School of Mechanical Engineering, Gui Zhou University, Guiyang 550000; Zhang, Weiwen, E-mail: mewzhang@scut.edu.cn

2015-06-15

The Al–5.0 wt.% Cu–0.6 wt.% Mn alloys with a variable Fe content were prepared by squeeze casting. Optical microscopy (OM), Deep etching technique, scanning electron microscopy(SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the solid-state transformation of Fe-rich intermetallics during the solution heat treatment. The results showed that the Chinese script-like α-Fe, Al{sub 6}(FeMn) and needle-like Al{sub 3}(FeMn) phases transform to a new Cu-rich β-Fe (Al{sub 7}Cu{sub 2}(FeMn)) phase during solution heat treatment. The possible reaction and overall transformation kinetics of the solid-state phase transformation for the Fe-rich intermetallics were investigated. - Graphical abstract: Displaymore » Omitted - Highlights: • The α-Fe, Al{sub 6}(FeMn) and Al{sub 3}(FeMn) phases change to the β-Fe phases. • Possible reactions of Fe phases during solution heat treatment are discussed. • The overall fractional transformation rate follows an Avrami curve.« less

Magnesium transport extraction of transuranium elements from LWR fuel

DOEpatents

Ackerman, John P.; Battles, James E.; Johnson, Terry R.; Miller, William E.; Pierce, R. Dean

1992-01-01

A process of separating transuranium actinide values from uranium values present in spent nuclear oxide fuels which contain rare earth and noble metal fission products. The oxide fuel is reduced with Ca metal in the presence of CaCl.sub.2 and a U-Fe alloy containing not less than about 84% by weight uranium at a temperature in the range of from about 800.degree. C. to about 850.degree. C. to produce additional uranium metal which dissolves in the U-Fe alloy raising the uranium concentration and having transuranium actinide metals and rare earth fission product metals and the noble metal fission products dissolved therein. The CaCl.sub.2 having CaO and fission products of alkali metals and the alkali earth metals and iodine dissolved therein is separated and electrolytically treated with a carbon electrode to reduce the CaO to Ca metal while converting the carbon electrode to CO and CO.sub.2. The Ca metal and CaCl.sub.2 is recycled to reduce additional oxide fuel. The U-Fe alloy having transuranium actinide metals and rare earth fission product metals and the noble metal fission products dissolved therein is contacted with Mg metal which takes up the actinide and rare earth fission product metals. The U-Fe alloy retains the noble metal fission products and is stored while the Mg is distilled and recycled leaving the transuranium actinide and rare earth fission products isolated.

A tale of two gyres: Contrasting distributions of dissolved cobalt and iron in the Atlantic Ocean during an Atlantic Meridional Transect (AMT-19)

NASA Astrophysics Data System (ADS)

Shelley, Rachel U.; Wyatt, Neil J.; Tarran, Glenn A.; Rees, Andrew P.; Worsfold, Paul J.; Lohan, Maeve C.

2017-11-01

Cobalt (Co) and iron (Fe) are essential for phytoplankton nutrition, and as such constitute a vital link in the marine biological carbon pump. Atmospheric deposition is an important, and in some places the dominant, source of trace elements (TEs) to the global ocean. Dissolved cobalt (dCo) and iron (dFe) were determined along an Atlantic Meridional Transect (AMT-19; Oct/Nov 2009) between 50°N and 40°S in the upper 150 m in order to investigate the behaviour and distribution of these two essential, bioactive TEs. During AMT-19, large differences in the distributions of dCo and dFe were observed. In the North Atlantic gyre provinces, extremely low mixed layer dCo concentrations (23 ± 9 pM) were observed, which contrasts with the relatively high mixed layer dFe concentrations (up to 1.0 nM) coincident with the band of highest atmospheric deposition (∼5-30°N). In the South Atlantic gyre, the opposite trend was observed, with relatively high dCo (55 ± 18 pM) observed throughout the water column, but low dFe concentrations (0.29 ± 0.08 nM). Given that annual dust supply is an order of magnitude greater in the North than the South Atlantic, the dCo distribution was somewhat unexpected. However, the distribution of dCo shows similarities with the distribution of phosphate (PO43-) in the euphotic zone of the Atlantic Ocean, where the North Atlantic gyre is characterised by chronically low PO4, and higher concentrations are observed in the South Atlantic gyre (Mather et al., 2008), suggesting the potential for a similar biological control of dCo distributions. Inverse correlations between dCo and Prochlorococcus abundance in the North Atlantic gyre provinces, combined with extremely low dCo where nitrogen fixation rates were highest (∼20-28°N), suggests the dominance of biological controls on dCo distributions. The contrasting dCo and dFe distributions in the North and South Atlantic gyres provides insights into the differences between the dominant controls on the distribution of these two bioactive trace metals in the central Atlantic Ocean.

Streaming potential method for characterizing interaction of electrical double layers between rice roots and Fe/Al oxide-coated quartz in situ.

PubMed

Liu, Zhao-Dong; Wang, Hai-Cui; Li, Jiu-Yu; Xu, Ren-Kou

2017-10-01

The interaction between rice roots and Fe/Al oxide-coated quartz was investigated through zeta potential measurements and column leaching experiments in present study. The zeta potentials of rice roots, Fe/Al oxide-coated quartz, and the binary systems containing rice roots and Fe/Al oxide-coated quartz were measured by a specially constructed streaming potential apparatus. The interactions between rice roots and Fe/Al oxide-coated quartz particles were evaluated/deduced based on the differences of zeta potentials between the binary systems and the single system of rice roots. The zeta potentials of the binary systems moved in positive directions compared with that of rice roots, suggesting that there were overlapping of diffuse layers of electric double layers on positively charged Fe/Al oxide-coated quartz and negatively charged rice roots and neutralization of positive charge on Fe/Al oxide-coated quartz with negative charge on rice roots. The greater amount of positive charges on Al oxide led to the stronger interaction of Al oxide-coated quartz with rice roots and the more shift of zeta potential compared with Fe oxide. The overlapping of diffuse layers on Fe/Al oxide-coated quartz and rice roots was confirmed by column leaching experiments. The greater overlapping of diffuse layers on Al oxide and rice roots led to more simultaneous adsorptions of K + and NO 3 - and greater reduction in leachate electric conductivity when the column containing Al oxide-coated quartz and rice roots was leached with KNO 3 solution, compared with the columns containing rice roots and Fe oxide-coated quartz or quartz. When the KNO 3 solution was replaced with deionized water to flush the columns, more K + and NO 3 - were desorbed from the binary system containing Al oxide-coated quartz and rice roots than from other two binary systems, suggesting that the stronger electrostatic interaction between Al oxide and rice roots promoted the desorption of K + and NO 3 - from the binary system and enhanced overlapping of diffuse layers on these oppositely charged surfaces compared with other two binary systems. In conclusion, the overlapping of diffuse layers occurred between positively charged Fe/Al oxides and rice roots, which led to neutralization of opposite charge and affected adsorption and desorption of ions onto and from the charged surfaces of Fe/Al oxides and rice roots.

Two MATE Transporters with Different Subcellular Localization are Involved in Al Tolerance in Buckwheat.

PubMed

Lei, Gui Jie; Yokosho, Kengo; Yamaji, Naoki; Ma, Jian Feng

2017-12-01

Buckwheat (Fagopyrum esculentum) shows high tolerance to aluminum (Al) toxicity, but the molecular mechanisms responsible for this high Al tolerance are still poorly understood. Here, we investigated the involvement of two MATE (multi-drug and toxic compound extrusion) genes in Al tolerance. Both FeMATE1 and FeMATE2 showed efflux transport activity for citrate, but not for oxalate when expressed in Xenopus oocytes. A transient assay with buckwheat leaf protoplasts using green fluorescent protein (GFP) fusion showed that FeMATE1 was mainly localized to the plasma membrane, whereas FeMATE2 was localized to the trans-Golgi and Golgi. The expression of FeMATE1 was induced by Al only in the roots, but that of FeMATE2 was up-regulated in both the roots and leaves. Furthermore, the expression of both genes only responded to Al toxicity, but not to other stresses including low pH, cadmium (Cd) and lanthanum (La). Heterologous expression of FeMATE1 or FeMATE2 in the Arabidopsis mutant atmate partially rescued its Al tolerance. Expression of FeMATE1 also partially recovered the Al-induced secretion of citrate in the transgenic lines, whereas expression of FeMATE2 did not complement the citrate secretion. Further physiological analysis showed that buckwheat roots also secreted citrate in addition to oxalate in response to Al in a dose-responsive manner. Taken together, our results indicate that FeMATE1 is involved in the Al-activated citrate secretion in the roots, while FeMATE2 is probably responsible for transporting citrate into the Golgi system for the internal detoxification of Al in the roots and leaves of buckwheat. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Possible Association of Ferrous Phosphates and Ferric Sulfates in S-rich Soil on Mars

NASA Astrophysics Data System (ADS)

Mao, J.; Schroeder, C.; Haderlein, S.

2012-12-01

NASA Mars Exploration Rover (MER) Spirit explored Gusev Crater to look for signs of ancient aqueous activity, assess past environmental conditions and suitability for life. Spirit excavated light-toned, S-rich soils at several locations. These are likely of hydrothermal, possibly fumarolic origin. At a location dubbed Paso Robles the light-toned soil was also rich in P - a signature from surrounding rock. While S is mainly bound in ferric hydrated sulfates [1], the mineralogy of P is ill-constrained [2]. P is a key element for life and its mineralogy constrains its availability. Ferrous phases observed in Paso Robles Mössbauer spectra may represent olivine and pyroxene from surrounding basaltic soil [1] or ferrous phosphate minerals [3]. Phosphate is well-known to complex and stabilize Fe 2+ against oxidation to Fe 3+ . Schröder et al. [3] proposed a formation pathway of ferrous phosphate/ferric sulfate associations: sulfuric acid reacts with basalt containing apatite, forming CaSO4 and phosphoric acid. The phosphoric and/or excess sulfuric acid reacts with olivine, forming Fe2+-phosphate and sulfate. The phosphate is less soluble and precipitates. Ferrous sulfate remains in solution and is oxidized as pH increases. To verify this pathway, we dissolved Fe2+-chloride and Na-phosphate salts in sulfuric acid inside an anoxic glovebox. The solution was titrated to pH 6 by adding NaOH when a first precipitate formed, which was ferrous phosphate according to Mössbauer spectroscopy (MB). At that point the solution was removed from the glovebox and allowed to evaporate in the presence of atmospheric oxygen, leading to the oxidation of Fe2+. The evaporation rate was controlled by keeping the suspensions at different temperatures; pH was monitored during the evaporation process. The final precipitates were analyzed by MB and X-Ray Fluorescence (XRF), comparable to MER MB and Alpha Particle X-ray Spectrometer instrument datasets, and complementary techniques such as X-ray diffraction. Fourier Transform Infrared spectroscopy measurements to compare to MER miniature thermal emission spectrometer data are planned. We observed differences depending on the heat source during evaporation. The closest match to Martian data on the basis of Mössbauer spectra was achieved with a suspension evaporated at 80°C on a hot plate, i.e. heated from below with a temperature gradient in the bottle. The Fe2+/FeT ratio matched, and ferrous phases were all phosphate. When heated in a water bath, i.e. without a temperature gradient in the bottle, Fe2+/FeT ratios increased and ferrous sulfates precipitated also. These results indicate that the Martian light-toned S-rich deposits formed by evaporation on the surface where temperature gradients would be expected rather than underground. They confirm that ferrous phosphate/ferric sulfate associations are possible on Mars and could be preserved in the oxygen-free Martian atmosphere. References: [1] Morris et al., J.Geophys. Res. 111 (2006) E02S13; [2] Ming et al., J. Geophys. Res. 111 (2006) E02S12; [3] Schröder et al., GSA Annual Meeting 2008, Paper No. 171-3.

Application of iron and zinc isotopes to track the sources and mechanisms of metal loading in a mountain watershed

USGS Publications Warehouse

Borrok, D.M.; Wanty, R.B.; Ian, Ridley W.; Lamothe, P.J.; Kimball, B.A.; Verplanck, P.L.; Runkel, R.L.

2009-01-01

Here the hydrogeochemical constraints of a tracer dilution study are combined with Fe and Zn isotopic measurements to pinpoint metal loading sources and attenuation mechanisms in an alpine watershed impacted by acid mine drainage. In the tested mountain catchment, ??56Fe and ??66Zn isotopic signatures of filtered stream water samples varied by ???3.5??? and 0.4???, respectively. The inherent differences in the aqueous geochemistry of Fe and Zn provided complimentary isotopic information. For example, variations in ??56Fe were linked to redox and precipitation reactions occurring in the stream, while changes in ??66Zn were indicative of conservative mixing of different Zn sources. Fen environments contributed distinctively light dissolved Fe (<-2.0???) and isotopically heavy suspended Fe precipitates to the watershed, while Zn from the fen was isotopically heavy (>+0.4???). Acidic drainage from mine wastes contributed heavier dissolved Fe (???+0.5???) and lighter Zn (???+0.2???) isotopes relative to the fen. Upwelling of Fe-rich groundwater near the mouth of the catchment was the major source of Fe (??56Fe ??? 0???) leaving the watershed in surface flow, while runoff from mining wastes was the major source of Zn. The results suggest that given a strong framework for interpretation, Fe and Zn isotopes are useful tools for identifying and tracking metal sources and attenuation mechanisms in mountain watersheds. ?? 2009 Elsevier Ltd.

Opposite effects of dissolved oxygen on the removal of As(III) and As(V) by carbonate structural Fe(II).

PubMed

Tian, Zeyuan; Feng, Yong; Guan, Yiyi; Shao, Binbin; Zhang, Yalei; Wu, Deli

2017-12-05

Freshly prepared carbonate structural Fe(II) (CSF) was used to immobilize As(III) and As(V) in wastewater under oxic and anoxic conditions. Dissolved oxygen was found to exert opposite effects on these two arsenic species. The sorption density of As(III) was higher under oxic conditions, whereas that of As(V) was higher under anoxic conditions. X-ray diffraction and infrared spectroscopic analyses indicated that crystalline parasymplesite (Fe(II) 3 (AsO 4 ) 2 ·8H 2 O) was formed when As(V) was removed under anoxic conditions, while an amorphous Fe-As-containing precipitate was formed when As(III) was removed under oxic conditions. The distribution of arsenic and iron between the solution and sediments suggested that the oxidation of structural Fe(II) promoted coprecipitation process and inhibited surface complexation. X-ray photoelectron spectroscopic analyses revealed that more As(III) was oxidized under oxic condition, which contributed to a higher sorption capacity for As(III). The formation of parasymplesite through surface complexation/precipitation was proposed to be more effective for the removal of As(V) by CSF, while As(III) was more efficiently removed through coprecipitation. Together, the results suggest that CSF may be an effective material for sequestering both As(III) and As(V). In addition, attention should be paid to the dissolved oxygen content when remediating different arsenic species.

Influence of Homogenization on Microstructural Response and Mechanical Property of Al-Cu-Mn Alloy.

PubMed

Wang, Jian; Lu, Yalin; Zhou, Dongshuai; Sun, Lingyan; Li, Renxing; Xu, Wenting

2018-05-29

The evolution of the microstructures and properties of large direct chill (DC)-cast Al-Cu-Mn alloy ingots during homogenization was investigated. The results revealed that the Al-Cu-Mn alloy ingots had severe microsegregation and the main secondary phase was Al₂Cu, with minimal Al₇Cu₂Fe phase. Numerous primary eutectic phases existed in the grain boundary and the main elements were segregated at the interfaces along the interdendritic region. The grain boundaries became discontinuous, residual phases were effectively dissolved into the matrix, and the segregation degree of all elements was reduced dramatically during homogenization. In addition, the homogenized alloys exhibited improved microstructures with finer grain size, higher number density of dislocation networks, higher density of uniformly distributed θ' or θ phase (Al₂Cu), and higher volume fraction of high-angle grain boundaries compared to the nonhomogenized samples. After the optimal homogenization scheme treated at 535 °C for 10 h, the tensile strength and elongation% were about 24 MPa, 20.5 MPa, and 1.3% higher than those of the specimen without homogenization treatment.

Characterization of Fe(II) oxidizing bacterial activities and communities at two acidic Appalachian coalmine drainage-impacted sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senko, John M.; Wanjugi, Pauline; Lucas, Melanie

2008-06-12

We characterized the microbiologically mediated oxidative precipitation of Fe(II) from coalminederived acidic mine drainage (AMD) along flow-paths at two sites in northern Pennsylvania. At the Gum Boot site, dissolved Fe(II) was efficiently removed from AMD whereas minimal Fe(II) removal occurred at the Fridays-2 site. Neither site received human intervention to treat the AMD. Culturable Fe(II) oxidizing bacteria were most abundant at sampling locations along the AMD flow path corresponding to greatest Fe(II) removal and where overlying water contained abundant dissolved O2. Rates of Fe(II) oxidation determined in laboratory-based sediment incubations were also greatest at these sampling locations. Ribosomal RNA intergenicmore » spacer analysis and sequencing of partial 16S rRNA genes recovered from sediment bacterial communities revealed similarities among populations at points receiving regular inputs of Fe(II)-rich AMD and provided evidence for the presence of bacterial lineages capable of Fe(II) oxidation. A notable difference between bacterial communities at the two sites was the abundance of Chloroflexi-affiliated 16S rRNA gene sequences in clone libraries derived from the Gum Boot sediments. Our results suggest that inexpensive and reliable AMD treatment strategies can be implemented by mimicking the conditions present at the Gum Boot field site.« less

Effects of Be, Sr, Fe and Mg interactions on the microstructure and mechanical properties of aluminum based aeronautical alloys

NASA Astrophysics Data System (ADS)

Ibrahim, Mohamed Fawzy

The present work was carried out on a series of heat-treatable aluminum-based aeronautical alloys containing various amounts of magnesium (Mg), iron (Fe), strontium (Sr) and beryllium (Be). Tensile test bars (dendrite arm spacing ~ 24mum) were solutionized for either 5 or 12 hours at 540°C, followed by quenching in warm water (60°C). Subsequently, these quenched samples were aged at 160°C for times up to 12 hours. Microstructural assessment was performed. All heat-treated samples were pulled to fracture at room temperature using a servo-hydraulic tensile testing machine. The results show that Be causes partial modification of the eutectic silicon (Si) particles similar to that reported for Mg addition. Addition of 0.8 wt.% Mg reduced the eutectic temperature by ~10°C. During solidification of alloys containing high levels of Fe and Mg, without Sr, a peak corresponding to the formation of a Be-Fe phase (Al8Fe2BeSi) was detected at 611°C. The Be-Fe phase precipitates in a script-like morphology. A new quinary eutectic-like reaction was observed to take place near the end of solidification of high Mg, high Fe, Be-containing alloys. This new reaction is composed mainly of fine particles of Si, Mg2Si, pi-Al 8Mg3FeSi6 and (Be-Fe) phases. The volume fraction of this reaction decreased with the addition of Sr. The addition of Be has a noticeable effect on decreasing the beta-phase length, or volume fraction, this effect may be limited by adding Sr. Beryllium addition also results in the precipitation of the beta-phase in a nodular form, which reduces the harmful effects of these intermetallics on the alloy mechanical properties. Increasing both Mg and Fe levels led to an increase in the amount of the pi-phase; increasing the iron content led to an increase in the volume fraction of the partially soluble beta- and pi-phases, while Mg2Si particles were completely dissolved. The beta-phase platelets were observed to undergo changes in their morphology due to the dissolution, thinning, necking and fragmentation of these platelets upon increasing the solutionizing time. The pi-phase was observed to dissolve and/or transform into a cluster of very fine beta-phase platelets. In the as-cast conditions, increasing the Mg content leads to increased transformation of beta-phase platelets into Chinese-script pi-phase, regardless of the Fe content. This, in turn, decreases the harmful effect of the beta-phase. Increasing the solutionizing time leads to a decomposition of the pi-phase to the beta-phase, fragmentation of the beta-phase and spheroidization of both the eutectic Si and the pi-phase particles, thus improving alloy tensile properties. Two mechanisms of Mg2Si precipitate coarsening were observed to occur: (1) Ostwald ripening in the solution heat-treated samples and (2) clustering. Coarsening increases with increased solution heat treatment time, increased aging time, as well as with greater Mg contents. Increased Fe levels decrease the alloy quality index (Q) values, whereas adding Mg increases them. Introducing Be, in spite of it being a toxic material, Sr, or both, simultaneously improves the alloy quality index values, regardless of solutionizing time or Fe and Mg levels. Quality index values increase with solution heat treatment time from 5 to 12 hours. Higher Mg contents lead to an increase in alloy ductility, ultimate tensile strength (UTS) and yield strength (YS), while higher Fe levels can drastically decrease these properties. For the same levels of Fe and/or Mg, Be and Sr have significant effects in improving alloy mechanical properties; these effects can be readily observed in low levels of Fe and high Mg contents. Beryllium addition is beneficial in the case of high Fe contents as it lowers the harmful effects of Fe-phases in Al-Si alloys. In the case of high Fe contents, it seems that the addition of 500 ppm of Be is not sufficient for all interactions with other alloying elements. During the melting process the formation of Be-Sr phase (probably SrBe3O4 compound) decreases the free Be content and hence the alloy mechanical properties. The role of Be in preventing the oxidation of Mg and in changing the chemistry and morphology of the Fe-intermetallics is observed through improved mechanical properties of Be-containing alloys. The partial modification effect of both Mg and Be appears to improve the alloy tensile properties. Solutionizing and aging times are important parameters affecting the alloy tensile properties. The Mg2Si precipitates were confirmed to be the main hardening components of the 356 and 357 alloys investigated. The yield strength increases with greater Mg levels, reduced Fe levels, addition of Be, Sr-modification, solution heat treatment time and aging time. The present work was extended to include an investigation of the experimental 7073 aluminum alloy. (Abstract shortened by UMI.).

Biogeochemical effects of seawater restoration to diked salt marshes

USGS Publications Warehouse

Portnoy, J.W.; Giblin, A.E.

1997-01-01

We conducted greenhouse microcosm experiments to examine the biogeochemical effects of restoring seawater to historically diked Cape Cod salt marshes. Peat cores from both seasonally flooded and drained diked marshes were waterlogged with seawater, and porewater chemistry was subsequently monitored for 21 mo. The addition of seawater to highly organic, seasonally flooded peat caused the death of freshwater wetland plants, 6-8 cm of sediment subsidence, and increased N and P mineralization. Also, sulfides and alkalinity increased 10-fold, suggesting accelerated decomposition by sulfate reduction. Addition of seawater to the low-organic-content acidic peat from the drained marsh increased porewater pH, alkalinity, PO4-P, and Fe(II), which we attribute to the reestablishment of SO4 and Fe(III) mineral reduction. Increased cation exchange contributed to 6-fold increases in dissolved Fe(II) and Al and 60-fold increases in NH4-N within 6 mo of sail-nation. Seawater reintroductions to seasonally flooded diked marshes will cause porewater sulfides to increase, likely reducing the success of revegetation efforts. Sulfide toxicity is of less concern in resalinated drained peats because of the abundance of Fe(II) to precipitate sulfides, and of NH4-N to offset sulfide inhibition of N uptake. Restoration of either seasonally flooded or drained diked marshes could stimulate potentially large nutrient and Fe(II) releases, which could in turn increase primary production and lower oxygen in receiving waters. These findings suggest that tidal restoration be gradual and carefully monitored.

Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.

1997-04-01

A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductilitymore » and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.« less

Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

DOE PAGES

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; ...

2017-03-28

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloysmore » with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). Finally, the results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.« less

Novel yolk-shell-structured Fe3O4@γ-AlOOH nanocomposite modified with Pd nanoparticles as a recyclable catalyst with excellent catalytic activity

NASA Astrophysics Data System (ADS)

Cui, Xueliang; Zheng, Yunfeng; Tian, Meng; Dong, Zhengping

2017-09-01

A novel yolk-shell-structured material (Fe3O4@γ-AlOOH-YSMs) with hierarchical γ-AlOOH flakes as the mesoporous shell and Fe3O4 nanoparticles (NPs) in the hollow core was prepared by using Fe3O4@SiO2 NPs as the seeds as well as NaAlO2 and urea as the precursor. The prepared Fe3O4@γ-AlOOH-YSMs were used as a catalyst support for fabricating a Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst with no obvious aggregation of the Pd NPs. The Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst was utilized for the catalytic reduction of the widely used and highly toxic 4-nitrophenol, rhodamine B, methylene blue, and methyl orange; and showed excellent catalytic activity as compared with other noble-metal-based catalysts. Furthermore, the Pd/Fe3O4@γ-AlOOH-YSMs nanocatalyst also can be easily separated from the reaction mixture and reused for at least ten times without any obvious decrease in the catalytic activity, indicating its reusability and stability.

Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

NASA Astrophysics Data System (ADS)

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; Howard, Richard H.; Yamamoto, Yukinori

2017-06-01

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloys with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). The results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.

Spatial characterization of dissolved trace elements and heavy metals in the upper Han River (China) using multivariate statistical techniques.

PubMed

Li, Siyue; Zhang, Quanfa

2010-04-15

A data matrix (4032 observations), obtained during a 2-year monitoring period (2005-2006) from 42 sites in the upper Han River is subjected to various multivariate statistical techniques including cluster analysis, principal component analysis (PCA), factor analysis (FA), correlation analysis and analysis of variance to determine the spatial characterization of dissolved trace elements and heavy metals. Our results indicate that waters in the upper Han River are primarily polluted by Al, As, Cd, Pb, Sb and Se, and the potential pollutants include Ba, Cr, Hg, Mn and Ni. Spatial distribution of trace metals indicates the polluted sections mainly concentrate in the Danjiang, Danjiangkou Reservoir catchment and Hanzhong Plain, and the most contaminated river is in the Hanzhong Plain. Q-model clustering depends on geographical location of sampling sites and groups the 42 sampling sites into four clusters, i.e., Danjiang, Danjiangkou Reservoir region (lower catchment), upper catchment and one river in headwaters pertaining to water quality. The headwaters, Danjiang and lower catchment, and upper catchment correspond to very high polluted, moderate polluted and relatively low polluted regions, respectively. Additionally, PCA/FA and correlation analysis demonstrates that Al, Cd, Mn, Ni, Fe, Si and Sr are controlled by natural sources, whereas the other metals appear to be primarily controlled by anthropogenic origins though geogenic source contributing to them. 2009 Elsevier B.V. All rights reserved.

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al based intermetallic phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samolyuk, G. D.; Stocks, G. M.; Újfalussy, B.

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.« less

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

DOE PAGES

Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

2014-11-07

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

Microstructure, Tensile and Fatigue Properties of Al-5 wt.%Mg Alloy Manufactured by Twin Roll Strip Casting

NASA Astrophysics Data System (ADS)

Heo, Joon-Young; Baek, Min-Seok; Euh, Kwang-Jun; Lee, Kee-Ahn

2018-04-01

This study investigated the microstructure, tensile and fatigue properties of Al-5 wt.%Mg alloy manufactured by twin roll strip casting. Strips cast as a fabricated (F) specimen and a specimen heat treated (O) at 400 °C/5 h were produced and compared. In the F specimen, microstructural observation discovered clustered precipitates in the center area, while in the O specimen precipitates were relatively more evenly distributed. Al, Al6(Mn, Fe), Mg2Al3 and Mg2Si phases were observed. However, most of the Mg2Al3 phase in the heat-treated O specimen was dissolved. A room temperature tensile test measured yield strength of 177.7 MPa, ultimate tensile strength of 286.1 MPa and elongation of 11.1% in the F specimen and 167.7 MPa (YS), 301.5 MPa (UTS) and 24.6% (EL) in the O specimen. A high cycle fatigue test measured a fatigue limit of 145 MPa in the F specimen and 165 MPa in the O specimen, and the O specimen achieved greater fatigue properties in all fatigue stress conditions. The tensile and fatigue fracture surfaces of the above-mentioned specimens were observed, and this study attempted to investigate the tensile and fatigue deformation behavior of strip cast Al-5 wt.%Mg based on the findings.

Morphological and XPS study of ball milled Fe1-xAlx (0.3≤x≤0.6) alloys

NASA Astrophysics Data System (ADS)

Rajan, Sandeep; Kumar, Anil; Vyas, Anupam; Brajpuriya, Ranjeet

2018-05-01

The paper presents mechanical and XPS study of ball milled Fe1-xAlx (0.3≤x≤0.6) alloys. The author prepared the solid solution of Fe(Al) with different composition of Al by using mechanical alloying (MA) technique. The MA process induces a progressive dissolution of Al into Fe, resulted in the formation of an extended Fe(Al) solid solution with the bcc structure after 5 hr of milling. The SEM Images shows that the initial shape of particles disappeared completely, and their structure became a mixture of small and large angular-shaped crystallites with different sizes. The TEM micrograph also confirms the reduction in crystallite size and alloy formation. XPS study shows the shift in the binding energy position of both Fe and Al Peaks provide strong evidence of Fe(Al) phase formation after milling.

Estimating production and consumption of solid reactive Fe phases in marine sediments from concentration profiles

EPA Science Inventory

1D diffusion models may be used to estimate rates of production and consumption of dissolved metabolites in marine sediments, but are applied less often to the solid phase. Here we used a numerical inverse method to estimate solid phase Fe(III) and Fe(II) consumption and product...

Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

NASA Astrophysics Data System (ADS)

Krupińska, Izabela

2017-09-01

One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

CFA Films in Amorphous Substrate: Structural Phase Induction and Magnetization Dynamics

NASA Astrophysics Data System (ADS)

Correa, M. A.; Bohn, F.; Escobar, V. M.

We report a systematic study of the structural and quasi-static magnetic properties, as well as of the dynamic magnetic response through MI effect, in Co2FeAl and MgO//Co2FeAl single layers and a MgO//Co2FeAl/Ag/Co2FeAl trilayered film, all grown onto an amorphous substrate. We present a new route to induce the crystalline structure in the Co2FeAl alloy and verify that changes in the structural phase of this material leads to remarkable modifications of the magnetic anisotropy and, consequently, dynamic magnetic behavior. Considering the electrical and magnetic properties of the Co2FeAl, our results open new possibilities for technological applications of this full-Heusler alloy in rigid and flexible spintronic devices.

Microstructural characteristics and aging response of Zn-containing Al-Mg-Si-Cu alloy

NASA Astrophysics Data System (ADS)

Cai, Yuan-hua; Wang, Cong; Zhang, Ji-shan

2013-07-01

Al-Mg-Si-Cu alloys with and without Zn addition were fabricated by conventional ingot metallurgy method. The microstructures and properties were investigated using optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), tensile test, hardness test, and electrical conductivity measurement. It is found that the as-cast Al-Mg-Si-Cu-Zn alloy is composed of coarse dendritic grains, long needle-like β/δ-AlFeSi white intermetallics, and Chinese script-like α-AlFeSi compounds. During high temperature homogenization treatment, only harmful needle-like β-AlFeSi phase undergoes fragmentation and spheroidizing at its tips, and the destructive needle-like δ-phase does not show any morphological and size changes. Phase transitions from β-AlFeSi to α-AlFeSi and from δ-AlFeSi to β-AlFeSi are also not found. Zn addition improves the aging hardening response during the former aging stage and postpones the peak-aged hardness to a long aging time. In T4 condition, Zn addition does not obviously increase the yield strength and decrease the elongation, but it markedly improves paint-bake hardening response during paint-bake cycle. The addition of 0.5wt% Zn can lead to an increment of 99 MPa in yield strength compared with the value of 69 MPa for the alloy without Zn after paint-bake cycle.

Effects of adhesions of amorphous Fe and Al hydroxides on surface charge and adsorption of K+ and Cd2+ on rice roots.

PubMed

Liu, Zhao-Dong; Wang, Hai-Cui; Zhou, Qin; Xu, Ren-Kou

2017-11-01

Iron (Fe) and aluminum (Al) hydroxides in variable charge soils attached to rice roots may affect surface-charge properties and subsequently the adsorption and uptake of nutrients and toxic metals by the roots. Adhesion of amorphous Fe and Al hydroxides onto rice roots and their effects on zeta potential of roots and adsorption of potassium (K + ) and cadmium (Cd 2+ ) by roots were investigated. Rice roots adsorbed more Al hydroxide than Fe hydroxide because of the greater positive charge on Al hydroxide. Adhesion of Fe and Al hydroxides decreased the negative charge on rice roots, and a greater effect of the Al hydroxide. Consequently, adhesion of Fe and Al hydroxides reduced the K + and Cd 2+ adsorption by rice roots. The results of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and desorption of K + and Cd 2+ from rice roots indicated that physical masking by Fe and Al hydroxides and diffuse-layer overlapping between the positively-charged hydroxides and negatively-charged roots were responsible for the reduction of negative charge on roots induced by adhesion of the hydroxides. Therefore, the interaction between Fe and Al hydroxides and rice roots reduced negative charge on roots and thus inhibited their adsorption of nutrient and toxic cations. Copyright © 2017 Elsevier Inc. All rights reserved.

Fe, Zn, and Cd stable isotopes from the eastern tropical South Pacific from GEOTRACES cruise GP16 - Methods and data

NASA Astrophysics Data System (ADS)

Helgoe, J. M.; Townsend, E.; John, S.

2014-12-01

A new method has been developed for the rapid analysis of metal concentrations and stable isotope ratios using a prepFAST automated sample processing robot. Although concentrations and isotopes are processed separately, similar methods are used for both. Initially all seawater is acidified to pH 2. Then Nobias resin with EDTA/IDA functional groups is added to either 10mL of sample for concentrations or ~1L samples for isotopes. Fe binds to the resin at low pH, and the pH is subsequently raised to allow Zn and Cd to bind. For concentration analyses, all subsequent chemistry is automated on the prepFAST including removal of seawater, rinsing of resin, and elution of resin into acid. For isotope samples these extraction techniques are performed manually, but the subsequent purification of Fe, Zn, and Cd by anion exchange chromatography is automated using the prepFAST. With these new methods, samples from the US GEOTRACES cruise GP16, in the eastern tropical South Pacific, are being analyzed. High concentrations of dissolved Fe are observed near the continental shelf and near submarine hydrothermal vents. Interestingly, isotope data show that dissolved Fe near the continental shelf generally has a δ56Fe close to 0 ‰. This δ56 Fe signature is suggestive of a non-reductive dissolution source for Fe, as Fe(II) released by reductive dissolution is typically closer to -2 ‰. Preliminary data show nutrient-type profiles for Zn and Cd, with Zn matching Si and Cd having a similar distribution to P. An increase in dissolved Zn near hydrothermal vents suggests a possible hydrothermal zinc source to the deep ocean. Continuing analysis of isotope data will reveal more about the source and biogeochemical cycling of these three chemically and biologically important trace metals throughout the eastern tropical Pacific Ocean.

Studies of the surface reactivity of metal oxyhydroxides and sulfides with relevance to environmental chemistry

NASA Astrophysics Data System (ADS)

Pierre-Louis, Andro-Marc

With the benefits of an ever increasing advance of industrialization around the globe come formidable environmental problems. Three environmental problems that have relevance to the research described in this thesis are the 1) buildup of atmospheric CO2 gas through the burning of fossil fuels, 2) eutrophication of aquatic systems, and 3) the acidification of environments from acid mine drainage (AMD) resulting from coal-mining activities. In particular research is presented in this thesis that investigated the surface chemistry of CO2 and phosphate (PO43-) on a suite of environmentally relevant iron oxyhydroxide materials and the chemistry of phospholipid molecules on environmentally relevant iron sulfide surfaces to suppress AMD. To develop a microscopic understanding of the surface chemistry of the different systems, an array of experimental and computational techniques were used in the research. Techniques included X-ray photoelectron spectroscopy, atomic adsorption, X-ray diffraction, scanning transmission microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), ion chromatography (IC), and attenuated total reflectance Fourier transform Infrared (ATR-FTIR). Results from the latter technique were interpreted with the aid of density function theory (DFT) calculations. Iron oxyhydroxides, which consisted of ferrihydrite (FeOOH), goethite (α-FeOOH), ferrimagnetic ferrihydrite (FerriFh), and aluminum-doped iron oxyhydroxide (content from 0-100 mol%) were synthesized and studied before and after exposure to gaseous CO2, CO32-, and PO43- species. FeOOH and mixed Al/Fe oxyhydroxide surfaces showed high affinities for the formation of carbonate and bicarbonate species upon exposure to gaseous CO2. Within the Al/Fe oxyhydroxide circumstance, a low Al level of incorporation in the iron oxyhydroxide structure caused a slight increase in surface area and increase in the amount of oxyanion (e.g., CO32- or PO43-) adsorption up to an Al level of 30 mol%. Significant changes were observed in the binding geometry of the adsorbed complexes on the Al/Fe mineral compared to single phase α-FeOOH, AlOOH, and FeOOH surfaces. ATR-FTIR results combined with vibrational frequency (DFT) calculations suggested the formation of multiple phosphate surface complexes via a variety of configurations such as inner-sphere/outer-sphere bidentate, monodentate depending on the solution pH and the Al mol% substituted into the Fe-oxyhydroxide. Studies investigated the adsorption of CO2 on FerriFh and compared those results to CO2 on ferrihydrite. The CO2 pressures used in these particular studies ranged from 1 to 57.8 bars. It is found that citrate bound species, resulting from the synthesis conditions used to make FerriFh, blocked surface sites for the formation of carbonate and bicarbonate species on the magnetic FerriFh and ferrihydrite oxyhydroxide minerals upon CO2(gas) exposure. A bicarbonate or bent-CO 2 like species (~1220 cm-1) formed at lower CO2 pressures (≤ 3.5 bars) but was absent at the higher pressures. Additional studies investigated the adsorption of various phospholipid molecules on pyrite, and iron sulfide with FeS2 stoichiometry. These studies were focused on suppressing the oxidative decomposition of pyrite to sulfuric acid, the root cause of AMD. Batch and column studies were employed to investigate the ability of phospholipids to reduce AMD over an extended period of time (up to 3 years). In studies that used actual coal mining refuse, which contained significant amount of pyrite, it was shown that the rate of acid production from pyrite decomposition could be reduced by as much as 70% due to the presence of surface bound phospholipid. Assembly of the phospholipid into a bilayer motif on the sulfide surface was hypothesized to form a hydrophobic barrier that kept dissolved O2 and bacteria from facilitating the oxidation of FeS2. Column experiments showed that when water at pH 7 was flowed over the coal mining waste, the effluent had a pH close to 3. In contrast when water at pH 7 was flowed over the pyrite containing waste, which was pretreated with lipid, the effluent had a pH closer to 7, and the total amount of Fe (Fe2+/Fe3+) and SO42- in the effluent waters was also reduced relative to the untreated pyrite containing waste circumstance. These studies showed that the application of phospholipid to pyrite containing coal mining waste could potentially be an environmentally friendly remediation technique.

Iron Mineralogy and Speciation in Clay-Sized Fractions of Chinese Desert Sediments

NASA Astrophysics Data System (ADS)

Lu, Wanyi; Zhao, Wancang; Balsam, William; Lu, Huayu; Liu, Pan; Lu, Zunli; Ji, Junfeng

2017-12-01

Iron released from Asian desert dust may be an important source of bioavailable iron for the North Pacific Ocean and thereby may stimulate primary productivity. However, the Fe species of the fine dusts from this source region are poorly characterized. Here we investigate iron species and mineralogy in the clay-sized fractions (<2 μm), the size fraction most prone to long-distance transport as dust. Samples were analyzed by sequential chemical extraction, X-ray diffraction, and diffuse reflectance spectrometry. Our results show that Fe dissolved from easily reducible iron phases (ferrihydrite and lepidocrocite) and reducible iron oxides (dominated by goethite) are 0.81 wt % and 2.39 wt %, respectively, and Fe dissolved from phyllosilicates extracted by boiling HCl (dominated by chlorite) is 3.15 wt %. Dusts originating from deserts in northwestern China, particularly the Taklimakan desert, are relatively enriched in easily reducible Fe phases, probably due to abundant Fe contained in fresh weathering products resulting from the rapid erosion associated with active uplift of mountains to the west. Data about Fe speciation and mineralogy in Asian dust sources will be useful for improving the quantification of soluble Fe supplied to the oceans, especially in dust models.

On the early fate of hydrothermal iron at deep-sea vents: A reassessment after in situ filtration

NASA Astrophysics Data System (ADS)

Waeles, M.; Cotte, L.; Pernet-Coudrier, B.; Chavagnac, V.; Cathalot, C.; Leleu, T.; Laës-Huon, A.; Perhirin, A.; Riso, R. D.; Sarradin, P.-M.

2017-05-01

Deep-sea hydrothermal venting is now recognized as a major source of iron (Fe), an essential trace element that controls marine productivity. However, the reactions occurring during dispersal from buoyant plumes to neutrally buoyant hydrothermal plumes are still poorly constrained. Here we report for the first time on the dissolved-particulate partition of Fe after in situ filtration at the early stage of mixing at different hydrothermal discharges, i.e., Lucky Strike (37°N), TAG (26°N), and Snakepit (23°N) on the Mid-Atlantic Ridge. We found that hydrothermal iron is almost completely preserved (>90%) in the dissolved fraction, arguing for low iron-bearing sulfide precipitation of iron in basalt-hosted systems with low Fe:H2S ratios. This result can only be explained by a kinetically limited formation of pyrite. The small part of Fe being precipitated as sulfides in the mixing gradient (<10%) is restricted to the inclusion of Fe in minerals of high Cu and Zn content. We also show that secondary venting is a source of Fe-depleted hydrothermal solutions. These results provide new constrains on Fe fluxes from hydrothermal venting.

Sintering of (Ni,Mg)(Al,Fe)2O4 Materials and their Corrosion Process in Na3AlF6-AlF3-K3AlF6 Electrolyte

NASA Astrophysics Data System (ADS)

Xu, Yibiao; Li, Yawei; Yang, Jianhong; Sang, Shaobai; Wang, Qinghu

2017-06-01

The application of ledge-free sidewalls in the Hall-Héroult cells can potentially reduce the energy requirement of aluminum production by about 30 pct (Nightingale et al. in J Eur Ceram, 33:2761-2765, 2013). However, this approach poses great material challenges since such sidewalls are in direct contact with corrosive electrolyte. In the present paper, (Ni,Mg)(Al,Fe)2O4 materials were prepared using fused magnesia, reactive alumina, nickel oxide, and iron oxide powders as the starting materials. The sintering behaviors of specimens as well as their corrosion resistance to molten electrolyte have been investigated by means of X-ray diffraction and scanning electron microscope. The results show that after firing at temperature ranging from 1673 K (1400 °C) up to 1873 K (1600 °C), all the specimens prepared are composed of single-phase (Ni,Mg)(Al,Fe)2O4 composite spinel, the lattice parameter of which increases with increasing Fe3+ ion concentration. Increasing the iron oxide content enhances densification of the specimens, which is accompanied by the formation of homogeneously distributed smaller pores in the matrix. The corrosion tests show that corrosion layers consist of fluoride and Ni(Al,Fe)2O4 composite spinel grains are produced in specimens with Fe/Al mole ratio no more than 1, whereas dense Ni(Al,Fe)2O4 composite spinel layers are formed on the surface of the specimens with Fe/Al mole ratio more than 1. The dense Ni(Al,Fe)2O4 composite spinel layers formed improve the corrosion resistance of the specimens by inhibiting the infiltration of electrolyte and hindering the chemical reaction between the specimen and electrolyte.

Microstructure and mechanical properties of aluminium matrix composites reinforced by Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} melt spun ribbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lityńska-Dobrzyńska, Lidia, E-mail: l.litynska@imim.pl; Mitka, Mikołaj; Góral, Anna

Aluminium matrix composites containing 15, 30 and 50 vol.% of pulverized Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} (in at.%) melt spun ribbons have been prepared by a vacuum hot pressing (T = 673 K, P = 600 MPa). The microstructure of the initial ribbon and the composites was investigated using X-ray, scanning and transmission electron microscopy. In the as-spun ribbon the quasicrystalline icosahedral phase (i-phase) coexisted with the cubic copper rich β-Al(Cu, Fe) intermetallic compound. The phase composition of Al-Cu-Fe particles changed after consolidation process and the i-phase transformed partially to the ω-Al{sub 70}Cu{sub 20}Fe{sub 10} phase. Additionally, the Θ-Al{sub 2}Cu phasemore » formed at the α(Al)/Al-Cu-Fe particle interfaces. With an increase in volume fraction of the reinforcement the hardness of the composites increased up to HV = 180 for the highest amount of added particles. The ultimate compression strength of the same sample reached the value of 545 MPa. - Highlights: • Al and 15, 30, 50% of pulverized Al{sub 62}Cu{sub 25.5}Fe{sub 12.5} melt spun ribbon were consolidated. • The initial ribbon consisted of the icosahedral i-phase and copper rich β-Al(Cu, Fe). • The i-phase partially transforms to ω-Al{sub 7}Cu{sub 2}Fe phase in all composites. • Increase of microhardness and compressive strength with content of reinforcement • Ultimate compression strength 545 MPa for 50% of added particles.« less

Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

1996-01-01

A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

Oxidation behavior of FeAl+Hf,Zr,B

NASA Technical Reports Server (NTRS)

Smialek, James L.; Doychak, Joseph

1988-01-01

The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

Investigation of the weldability of iron-aluminum-chromium overlay coatings for corrosion protection in oxidizing/sulfidizing environments

NASA Astrophysics Data System (ADS)

Regina, Jonathan R.

The current study investigated the effect of chromium additions on the hydrogen cracking susceptibility of Fe-Al weld overlay claddings containing chromium additions. It was found that the weldability of FeAlCr claddings was a function of both the aluminum and chromium concentrations of the weld coatings. Weld overlay compositions that were not susceptible to hydrogen cracking were identified and the underlying mechanism behind the hydrogen cracking phenomenon was investigated further. It was concluded that the cracking behavior of the FeAlCr welds depended strongly on the microstructure of the weld fusion zone. Although it was found that the cracking susceptibility was influenced by the presence of Fe-Al intermetallic phases (namely Fe3 Al and FeAl), the cracking behavior of FeAlCr weld overlay claddings also depended on the size and distribution of carbide and oxide particles present within the weld structure. These particles acted as hydrogen trapping sites, which are areas where free hydrogen segregates and can no longer contribute to the hydrogen embrittlement of the metal. It was determined that in practical applications of these FeAlCr weld overlay coatings, carbon should be present within these welds to reduce the amount of hydrogen available for hydrogen cracking. Based on the weldability results of the FeAlCr weld claddings, coating compositions that were able to be deposited crack-free were used for long-term corrosion testing in a simulated low NOx environment. These alloys were compared to a Ni-based superalloy (622), which is commonly utilized as boiler tube coatings in power plant furnaces for corrosion protection. It was found that the FeAlCr alloys demonstrated superior corrosion resistance when compared to the Ni-based superalloy. Due to the excellent long-term corrosion behavior of FeAlCr weld overlays that were immune to hydrogen cracking, it was concluded that select FeAlCr weld overlay compositions would make excellent corrosion resistant coatings for boiler tubes located in low NOx burning environments.

Metal transports and enrichments in iron depositions hosted in basaltic rocks. II: Metal rich fluids and Fe origin

NASA Astrophysics Data System (ADS)

Zhang, Ronghua; Zhang, Xuetong; Hu, Shumin

2015-12-01

This study focuses on revealing the mechanism of metal transport, enrichment and Fe origin of iron deposition during water basalt interactions occurred in basaltic rocks. Observations of the iron deposits (anhydrite-magnetite-pyroxene type deposits) hosted in K-rich basaltic rocks in the Mesozoic volcanic area of the Middle-Lower Yangtze River valley, China, indicate that the mechanism of metal transport and enrichment for those deposits are significant objective to scientists, and the Fe origin problem is not well resolved. Here the metal transport, enrichment and iron origin have been investigated in high temperature experiments of water basaltic interactions. These deposits were accompanying a wide zone with metal alteration. The effects of hydrothermal alteration on major rock-forming element concentrations in basaltic rock were investigated by systematically comparing the chemical compositions of altered rocks with those of fresh rocks. In the deposits, these metals are distributed throughout altered rocks that exhibit vertical zoning from the deeper to the shallow. Then, combined with the investigations of the metal-alterations, we performed kinetic experiments of water-basaltic rock interactions using flow-through reactors in open systems at temperatures from 20 °C to 550 °C, 23-34 MPa. Release rates for the rock-forming elements from the rocks have been measured. Experiments provide the release rates for various elements at a large temperature range, and indicate that the dissolution rates (release rates) for various elements vary with temperature. Si, Al, and K have high release rates at temperatures from 300 °C to 500 °C; the maximum release rates (RMX) for Si are reached at temperatures from 300 °C to 400 °C. The RMXs for Ca, Mg, and Fe are at low temperatures from 20 °C to 300 °C. Results demonstrate that Fe is not released from 400 °C to 550 °C, and indicate that when deep circling fluids passed through basaltic rocks, Fe was not mobile, and fixed in the rocks at temperatures from 400 °C to 550 °C. Significance of the results is to provide evidence that the Fe of ores originated from basalt, and Fe-oxides precipitated across the critical state of water. Simultaneously, Ca, Mg and Fe are fixed in the deeper altered rocks (mafic minerals). But, Fe was dissolved at relatively low temperatures (100-300 °C). Si, Al, and K were easily mobile from basalt by upward flowing fluids from 300 °C to 400 °C and transported to the upper part (silicified and argillized rock).

Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS

NASA Astrophysics Data System (ADS)

Stolpe, Björn; Guo, Laodong; Shiller, Alan M.; Aiken, George R.

2013-03-01

Water samples were collected from six small rivers in the Yukon River basin in central Alaska to examine the role of colloids and organic matter in the transport of trace elements in Northern high latitude watersheds influenced by permafrost. Concentrations of dissolved organic carbon (DOC), selected elements (Al, Si, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Ba, Pb, U), and UV-absorbance spectra were measured in 0.45 μm filtered samples. 'Nanocolloidal size distributions' (0.5-40 nm, hydrodynamic diameter) of humic-type and chromophoric dissolved organic matter (CDOM), Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb were determined by on-line coupling of flow field-flow fractionation (FFF) to detectors including UV-absorbance, fluorescence, and ICP-MS. Total dissolved and nanocolloidal concentrations of the elements varied considerably between the rivers and between spring flood and late summer base flow. Data on specific UV-absorbance (SUVA), spectral slopes, and the nanocolloidal fraction of the UV-absorbance indicated a decrease in aromaticity and size of CDOM from spring flood to late summer. The nanocolloidal size distributions indicated the presence of different 'components' of nanocolloids. 'Fulvic-rich nanocolloids' had a hydrodynamic diameter of 0.5-3 nm throughout the sampling season; 'organic/iron-rich nanocolloids' occurred in the <8 nm size range during the spring flood; whereas 'iron-rich nanocolloids' formed a discrete 4-40 nm components during summer base flow. Mn, Co, Ni, Cu and Zn were distributed between the nanocolloid components depending on the stability constant of the metal (+II)-organic complexes, while stronger association of Cr to the iron-rich nanocolloids was attributed to the higher oxidation states of Cr (+III or +IV). Changes in total dissolved element concentrations, size and composition of CDOM, and occurrence and size of organic/iron and iron-rich nanocolloids were related to variations in their sources from either the upper organic-rich soil or the deeper mineral layer, depending on seasonal variations in hydrological flow patterns and permafrost dynamics.

Annual suspended sediment and trace element fluxes in the Mississippi, Columbia, Colorado, and Rio Grande drainage basins

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Smith, J.J.

2001-01-01

Suspended sediment, sediment-associated, total trace element, phosphorus (P), and total organic carbon (TOC) fluxes were determined for the Mississippi, Columbia, Rio Grande, and Colorado Basins for the study period (the 1996, 1997, and 1998 water years) as part of the US Geological Survey's redesigned National Stream Quality Accounting Network (NASQAN) programme. The majority (??? 70%) of Cu, Zn, Cr, Ni, Ba, P, As, Fe, Mn, and Al are transported in association with suspended sediment; Sr transport seems dominated by the dissolved phase, whereas the transport of Li and TOC seems to be divided equally between both phases. Average dissolved trace element levels are markedly lower than reported during the original NASQAN programme; this seems due to the use of 'clean' sampling, processing, and analytical techniques rather than to improvements in water quality. Partitioning between sediment and water for Ag, Pb, Cd, Cr, Co, V, Be, As, Sb, Hg, and Ti could not be estimated due to a lack of detectable dissolved concentrations in most samples. Elevated suspended sediment-associated Zn levels were detected in the Ohio River Basin and elevated Hg levels were detected in the Tennessee River, the former may affect the mainstem Mississippi River, whereas the latter probably do not. Sediment-associated concentrations of Ag, Cu, Pb, Zn, Cd, Cr, Co, Ba, Mo, Sb, Hg, and Fe are markedly elevated in the upper Columbia Basin, and appear to be detectable (Zn, Cd) as far downstream as the middle of the basin. These elevated concentrations seem to result from mining and/or mining-related activities. Consistently detectable concentrations of dissolved Se were found only in the Colorado River Basin. Calculated average annual suspended sediment fluxes at the mouths of the Mississippi and Rio Grande Basins were below, whereas those for the Columbia and Colorado Basins were above previously published annual values. Downstream suspended sediment-associated and total trace element fluxes increase in the Mississippi and Columbia Basins, whereas fluxes markedly decrease in the Colorado Basin. No consistent pattern in trace element fluxes was detected in the Rio Grande Basin.

Estimates of atmospheric O2 in the Paleoproterozoic from paleosols

NASA Astrophysics Data System (ADS)

Kanzaki, Yoshiki; Murakami, Takashi

2016-02-01

A weathering model was developed to constrain the partial pressure of atmospheric O2 (PO2) in the Paleoproterozoic from the Fe records in paleosols. The model describes the Fe behavior in a weathering profile by dissolution/precipitation of Fe-bearing minerals, oxidation of dissolved Fe(II) to Fe(III) by oxygen and transport of dissolved Fe by water flow, in steady state. The model calculates the ratio of the precipitated Fe(III)-(oxyhydr)oxides from the dissolved Fe(II) to the dissolved Fe(II) during weathering (ϕ), as a function of PO2 . An advanced kinetic expression for Fe(II) oxidation by O2 was introduced into the model from the literature to calculate accurate ϕ-PO2 relationships. The model's validity is supported by the consistency of the calculated ϕ-PO2 relationships with those in the literature. The model can calculate PO2 for a given paleosol, once a ϕ value and values of the other parameters relevant to weathering, namely, pH of porewater, partial pressure of carbon dioxide (PCO2), water flow, temperature and O2 diffusion into soil, are obtained for the paleosol. The above weathering-relevant parameters were scrutinized for individual Paleoproterozoic paleosols. The values of ϕ, temperature, pH and PCO2 were obtained from the literature on the Paleoproterozoic paleosols. The parameter value of water flow was constrained for each paleosol from the mass balance of Si between water and rock phases and the relationships between water saturation ratio and hydraulic conductivity. The parameter value of O2 diffusion into soil was calculated for each paleosol based on the equation for soil O2 concentration with the O2 transport parameters in the literature. Then, we conducted comprehensive PO2 calculations for individual Paleoproterozoic paleosols which reflect all uncertainties in the weathering-relevant parameters. Consequently, robust estimates of PO2 in the Paleoproterozoic were obtained: 10-7.1-10-5.4 atm at ∼2.46 Ga, 10-5.0-10-2.5 atm at ∼2.15 Ga, 10-5.2-10-1.7 atm at ∼2.08 Ga and more than 10-4.6-10-2.0 atm at ∼1.85 Ga. Comparison of the present PO2 estimates to those in the literature suggests that a drastic rise of oxygen would not have occurred at ∼2.4 Ga, supporting a slightly rapid rise of oxygen at ∼2.4 Ga and a gradual rise of oxygen in the Paleoproterozoic in long term.

Water-chemistry data for selected springs, geysers, and streams in Yellowstone National Park, Wyoming, 1999-2000

USGS Publications Warehouse

Ball, James W.; McCleskey, R. Blaine; Nordstrom, D. Kirk; Holloway, JoAnn M.; Verplanck, Philip L.; Sturtevant, Sabin A.

2002-01-01

Sixty-seven water analyses are reported for samples collected from 44 hot springs and their overflow drainages and two ambient-temperature acid streams in Yellowstone National Park (YNP) during 1990-2000. Thirty-seven analyses are reported for 1999, 18 for June of 2000, and 12 for September of 2000. These water samples were collected and analyzed as part of research investigations in YNP on microbially mediated sulfur oxidation in stream water, arsenic and sulfur redox speciation in hot springs, and chemical changes in overflow drainages that affect major ions, redox species, and trace elements. Most samples were collected from sources in the Norris Geyser Basin. Two ambient-temperature acidic stream systems, Alluvium and Columbine Creeks and their tributaries in Brimstone Basin, were studied in detail. Analyses were performed at or near the sampling site, in an on-site mobile laboratory truck, or later in a USGS laboratory, depending on stability of the constituent and whether or not it could be preserved effectively. Water temperature, specific conductance, pH, Eh, dissolved oxygen (D.O.), and dissolved H2S were determined on-site at the time of sampling. Alkalinity, acidity, and F were determined within a few days of sample collection by titration with acid, titration with base, and ion-selective electrode or ion chromatography (IC), respectively. Concentrations of S2O3 and SxO6 were determined as soon as possible (minutes to hours later) by IC. Concentrations of Br, Cl, NH4, NO2, NO3, SO4, Fe(II), and Fe(total) were determined within a few days of sample collection. Densities were determined later in the USGS laboratory. Concentrations of Li and K were determined by flame atomic absorption spectrometry. Concentrations of Al, As(total), B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe(total), K, Li, Mg, Mn, Na, Ni, Pb, Se, Si, Sr, V, and Zn were determined by inductively-coupled plasma-optical emission spectrometry. Trace concentrations of Cd, Cr, Cu, Pb, and Sb were determined by Zeeman-corrected graphitefurnace atomic-absorption spectrometry. Trace concentrations of As(total) and As(III) were determined by hydride generation atomic-absorption spectrometry using a flow-injection analysis system. Concentrations of Cl, NO3, Br, and SO4 were determined by IC. Concentrations of Fe(II) and Fe(total) were determined by the ferrozine colorimetric method. Concentrations of NO2 were determined by colorimetry using matrix-matched standards. Concentrations of NH4 were determined by IC, with reanalysis by colorimetry where separation of Na and NH4 peaks was poor. Dissolved organic carbon (DOC) concentrations were determined by the wet persulfate oxidation method.

Effects of dissolved oxygen on dye removal by zero-valent iron.

PubMed

Wang, Kai-Sung; Lin, Chiou-Liang; Wei, Ming-Chi; Liang, Hsiu-Hao; Li, Heng-Ching; Chang, Chih-Hua; Fang, Yung-Tai; Chang, Shih-Hsien

2010-10-15

Effects of dissolved oxygen concentrations on dye removal by zero-valent iron (Fe(0)) were investigated. The Vibrio fischeri light inhibition test was employed to evaluate toxicity of decolorized solution. Three dyes, Acid Orange 7 (AO7, monoazo), Reactive Red 120 (RR120, diazo), and Acid Blue 9 (AB9, triphenylmethane), were selected as model dyes. The dye concentration and Fe(0) dose used were 100 mg L(-1) and 30 g L(-1), respectively. Under anoxic condition, the order for dye decolorization was AO7>RR120>AB9. An increase in the dissolved oxygen concentrations enhanced decolorization and chemical oxygen demand (COD) removal of the three dyes. An increase in gas flow rates also improved dye and COD removals by Fe(0). At dissolved oxygen of 6 mg L(-1), more than 99% of each dye was decolorized within 12 min and high COD removals were obtained (97% for AO7, 87% for RR120, and 93% for AB9). The toxicity of decolorized dye solutions was low (I(5)<40%). An increase in DO concentrations obviously reduced the toxicity. When DO above 2 mg L(-1) was applied, low iron ion concentration (13.6 mg L(-1)) was obtained in the decolorized AO7 solution. 2010 Elsevier B.V. All rights reserved.

Rates of arsenopyrite oxidation by oxygen and Fe(III) at pH 1.8-12.6 and 15-45 degrees C.

PubMed

Yu, Yunmei; Zhu, Yongxuan; Gao, Zhenmin; Gammons, Christopher H; Li, Denxian

2007-09-15

The oxidation rate of arsenopyrite by dissolved oxygen was measured using a mixed flow reactor at dissolved O2 concentrations of 0.007-0.77 mM, pH 1.8-12.6, and temperatures of 15-45 degrees C. As(III) was the dominant redox species (>75%) in the experimental system, and the As(III)/As(V) ratio of effluent waters did not change with pH. The results were used to derive the following rate law expression (valid between pH 1.8 and 6.4): r = 10((-2211 +/- 57)T) (mO2)(0.45 +/- 0.05), where r is the rate of release of dissolved As in mol m(-2) s(-1) and T is in Kelvin. Activation energies (Ea) for oxidation of arsenopyrite by 02 at pH 1.8 and 5.9 are 43 and 57 kJ/mol, respectively, and they compare to an Ea value of 16 kJ/mol for oxidation by Fe(III) at pH 1.8. Apparent As release rates passed through a minimum in the pH range 7-8, which may have been due to oxidation of Fe2+ to hydrous ferric oxide (HFO) with attenuation of dissolved As onto the freshly precipitated HFO.

High purity Fe3O4 from Local Iron Sand Extraction

NASA Astrophysics Data System (ADS)

Gunanto, Y. E.; Izaak, M. P.; Jobiliong, E.; Cahyadi, L.; Adi, W. A.

2018-04-01

Indonesia has a long coastline and is rich with iron sand. The iron sand is generally rich in various elements such as iron and titanium. One of the products processing of the iron sand mineral is iron (II) (III) oxide (magnetite Fe3O4). The stages of purification process to extracting magnetite phase and discarding the other phases has been performed. Magnetite phase analysis of ironsand extraction retrieved from Indonesia have been investigated. The result of analysis element of iron sand shows that it consists of majority Fe around 65 wt%. However, there are still 17 impurities such as Ti, Al, Ce, Co, Cr, Eu, La, Mg, Mn, Na, Sc, Sm, Th, V, Yb, and Zn. After extraction process, Fe element content increases up to 94%. The iron sand powder after milling for 10 hours and separating using a magnetic separator, the iron sand powders are dissolved in acid chloride solution to form a solution of iron chloride, and this solution is sprinkled with sodium hydroxide to obtain fine powders of Fe3O4. The fine powders which formed were washed with de-mineralization water. The X-ray diffraction pattern shows that the fine powders have a single phase of Fe3O4. The analysis result shows that the sample has the chemical formula: Fe3O4 with a cubic crystal system, space group: Fd-3m and lattice parameters: a = b = c = 8.3681 (1) Å, α = β = γ = 90°. The microstructure analysis shows that the particle of Fe3O4 homogeneously shaped like spherical. The magnetic properties using vibrating sample magnetometer shows that Fe3O4 obtained have ferromagnetic behavior with soft magnetic characteristics. We concluded that this purification of iron sand had been successfully performed to obtain fine powders of Fe3O4 with high purity.

Ferric iron partitioning between plagioclase and silicate liquid: thermodynamics and petrological applications

NASA Astrophysics Data System (ADS)

Sugawara, Toru

2001-06-01

A series of Fe and Mg partition experiments between plagioclase and silicate liquid were performed in the system SiO2-Al2O3-Fe2O3-FeO-MgO-CaO-Na2O under oxygen fugacities from below the IW buffer up to that of air. A thermodynamic model of plagioclase solid solution for the (CaAl,NaSi,KSi)(Fe3+,Al3+)Si2O8-Ca(Fe2+,Mg)Si3O8 system is proposed and is calibrated by regression analysis based on new and previously reported experimental data of Fe and Mg partitioning between plagioclase and silicate liquid, and reported thermodynamic properties of end members, ternary feldspar and silicate liquid. Using the derived thermodynamic model, FeOt, MgO content and Mg/(Fet+Mg) in plagioclase can be predicted from liquid composition with standard deviations of +/-0.34 wt% (relative error =9%) and +/-0.08 wt% (14%) and +/-0.7 (8%) respectively. Calculated Fe3+-Al exchange chemical potentials of plagioclase, $μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Pl} agree with those calculated using reported thermodynamic models for multicomponent spinel, μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Sp} and clinopyroxene, μ { Fe{ 3 + } ( {Al} ){ - 1} }{ Cpx} $ . The FeOt content of plagioclase coexisting with spinel or clinopyroxene is affected by Fe3+/(Fe3++Al) and Mg/(Fe+Mg) of spinel or clinopyroxene and temperature, while it is independent of the anorthite content of plagioclase. Three oxygen barometers based on the proposed model are investigated. Although the oxygen fugacities predicted by the plagioclase-liquid oxygen barometer are scattered, this study found that plagioclase-spinel-clinopyroxene-oxygen and plagioclase-olivine-oxygen equilibria can be used as practical oxygen barometers. As a petrological application, prediction of plagioclase composition and fO2 are carried out for the Upper Zone of the Skaergaard intrusion. The estimated oxygen fugacities are well below QFM buffer and consistent with the estimation of oxidization states in previous studies.

The Distribution of Dissolved Iron in the West Atlantic Ocean

PubMed Central

Rijkenberg, Micha J. A.; Middag, Rob; Laan, Patrick; Gerringa, Loes J. A.; van Aken, Hendrik M.; Schoemann, Véronique; de Jong, Jeroen T. M.; de Baar, Hein J. W.

2014-01-01

Iron (Fe) is an essential trace element for marine life. Extremely low Fe concentrations limit primary production and nitrogen fixation in large parts of the oceans and consequently influence ocean ecosystem functioning. The importance of Fe for ocean ecosystems makes Fe one of the core chemical trace elements in the international GEOTRACES program. Despite the recognized importance of Fe, our present knowledge of its supply and biogeochemical cycle has been limited by mostly fragmentary datasets. Here, we present highly accurate dissolved Fe (DFe) values measured at an unprecedented high intensity (1407 samples) along the longest full ocean depth transect (17500 kilometers) covering the entire western Atlantic Ocean. DFe measurements along this transect unveiled details about the supply and cycling of Fe. External sources of Fe identified included off-shelf and river supply, hydrothermal vents and aeolian dust. Nevertheless, vertical processes such as the recycling of Fe resulting from the remineralization of sinking organic matter and the removal of Fe by scavenging still dominated the distribution of DFe. In the northern West Atlantic Ocean, Fe recycling and lateral transport from the eastern tropical North Atlantic Oxygen Minimum Zone (OMZ) dominated the DFe-distribution. Finally, our measurements showed that the North Atlantic Deep Water (NADW), the major driver of the so-called ocean conveyor belt, contains excess DFe relative to phosphate after full biological utilization and is therefore an important source of Fe for biological production in the global ocean. PMID:24978190

Dissolved and Colloidal Trace Elements in the Mississippi River Delta Outflow after Hurricanes Katrina and Rita

NASA Astrophysics Data System (ADS)

Shim, M.; Swarzenski, P. W.; Shiller, A. M.

2010-12-01

The Mississippi River (MR) plays an important role as a major fluvial source of dissolved and particulate materials for the Gulf of Mexico (GOM). This region is periodically disturbed by tropical weather systems including major hurricanes. Such storms have the potential to stir up the normally stratified water column of the Louisiana Shelf and thus can serve as a mechanism for the abrupt termination of seasonal bottom water hypoxia. Additionally, strong tropical systems can cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, two major hurricanes, Katrina and Rita, passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we participated in a survey of the waters of the Mississippi River delta outflow, examining the distributions of trace elements (including Ba, Co, Cr, Cs, Cu, Fe, Mn, Ni, Re, U, V, and Zn) in a comparison with previous results in this area. We indeed observed that there was limited stratification on the shelf and that bottom waters were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn-O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 µm) from colloidal (0.02 - 0.45 µm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity of the Fe in estuarine systems.

Seasonality of major redox constituents in a shallow subterranean estuary

NASA Astrophysics Data System (ADS)

O'Connor, Alison E.; Krask, Julie L.; Canuel, Elizabeth A.; Beck, Aaron J.

2018-03-01

The subterranean estuary (STE), the subsurface mixing zone of outflowing fresh groundwater and infiltrating seawater, is an area of extensive geochemical reactions that determine the composition of groundwater that flows into coastal environments. This study examined the porewater composition of a shallow STE (<5 m depth) in Gloucester Point, VA (USA) over two years to determine seasonal variations in dissolved organic carbon (DOC) and the reduced metabolites Fe, Mn, and sulfide. An additional aim of this study was to investigate the relative importance of salinity gradients (which have great geochemical influence in surface estuaries) versus redox gradients on STE geochemistry. Two freshwater endmembers were identified, between which redox potential and composition varied with depth-a shallow freshwater endmember was oxidizing and high in DOC, whereas a deep freshwater endmember was reducing, lower in DOC, and high in sulfide. Results showed that dissolved Fe, Mn, and sulfide varied along a redox gradient distinct from the salinity gradient, and that three-endmember mixing was required to quantify non-conservative chemical addition/removal in the STE. In addition to salinity, humic carbon was used as a quasi-conservative tracer to quantify mixing according to a three-endmember model. The vertical distributions of DOC and reduced metabolites remained approximately constant over time, but concentrations varied with season. Dissolved organic carbon concentrations were greatest in the summer, and shallow meteoric groundwater supplied the majority of DOC to the STE. In summer, there was additional evidence for shallow non-conservative addition of DOC. Dissolved Fe and Mn were highest in a subsurface plume through the middle of the STE (100-140 cm below sediment surface at the high tide line) which was characterized by higher concentrations and greater non-conservative addition in the winter. In contrast, sulfide was higher in summer at depths within the Fe and Mn plume (100-140 cm). We attribute the contrasting seasonal patterns of dissolved Fe, Mn, and sulfide to differences in microbial response to temperature changes and organic matter availability, and to competition at the ferrous-sulfidic transition zone between dissimilatory metal reduction and sulfate reduction, leading to sulfate/sulfur reducing bacteria (SRB) being more active in summer and metal reducers being more active in winter. Throughout the STE, seasonal temperature and DOC variations determined the spatial distribution and geochemical cycling of Fe, Mn, and sulfur.

Preliminary CFA measurements of Al and Fe "available" fraction in EPICA-Dome C ice core (East Antarctica)

NASA Astrophysics Data System (ADS)

Udisti, R.; Barbante, C.; Cozzi, G.; Fattori, I.; Largiuni, O.; Magaldi, L.; Traversi, R.

2003-04-01

Aerosol load of Al and Fe allows estimating the crustal contribution to the primary aerosol sources. While continental dust is the only significant source for Al, Fe takes part also to metabolic processes of living species as an essential oligo-element. For this reason, it has been assumed that atmospheric deposition of desert dust on the oceanic surface can constitute a phytoplanktonic growth factor. Besides, Fe content in aerosol during glacial/interglacial transitions is believed to play a relevant role in controlling oceanic phytoplanktonic uptake of atmospheric CO2. A detailed stratigraphy of Al and Fe in ice cores is basic in understanding the correlation between environmental and climatic changes. Here we report preliminary results of CFA methods able to determine, in field, the "available" (free form and labile complexes) fraction of Al and Fe in ice cores with high sensitivity (D.L. of 10 ppt for Al and 300 ppt for Fe) and reproducibility (around 2 % at ppb level). The two methods were applied to 32 selected sections coming from the EPICA-Dome C ice core (EDC96): 10 sections belonging to Holocene, 10 to the transition and 12 to the LGM. Though Al and Fe determined by CFA is representative of the only soluble fraction (or "available" in the measurement conditions after filtration on 5.0 um), a comparison with the Al and Fe "total" content, as measured by ICP-MS, was made. "Available" fractions represent a minor contribution to the ICP-MS Fe and Al content in the LGM, but this contribution increases during the transition. In the Holocene, the two different analytical methods give similar values. Anyway, also CFA Fe and Al profiles show a sharp concentration decrease in the glacial/interglacial transition, reflecting the lowering dust aerosol load. Fe, especially, shows a very high sensitivity for the ACR climatic change. Whereas CFA-Fe in the LGM is more than 10 times lower than ICP-MS-Fe, ACR values are similar. This evidence could be explained considering that during the LGM the insoluble continental dust is the main Fe source, while a sort of oceanic-recycled Fe, mainly distributed in the fine particles and as more soluble species, becomes more important during the ACR and in the Holocene. Further measurements, with a very higher temporal resolution, are necessary to confirm the observed behaviour.

Literature review report on atomistic modeling tools for FeCrAl alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yongfeng; Schwen, Daniel; Martinez, Enrique

2015-12-01

This reports summarizes the literature review results on atomistic tools, particularly interatomic potentials used in molecular dynamics simulations, for FeCrAl ternary alloys. FeCrAl has recently been identified as a possible cladding concept for accident tolerant fuels for its superior corrosion resistance. Along with several other concepts, an initial evaluation and recommendation are desired for FeCrAl before it’s used in realistic fuels. For this purpose, sufficient understanding on the in-reactor behavior of FeCrAl needs to be grained in a relatively short timeframe, and multiscale modeling and simulations have been selected as an efficient measure to supplement experiments and in-reactor testing formore » better understanding on FeCrAl. For the limited knowledge on FeCrAl alloys, the multiscale modeling approach relies on atomistic simulations to obtain the missing material parameters and properties. As a first step, atomistic tools have to be identified and this is the purpose of the present report. It was noticed during the literature survey that no interatomic potentials currently available for FeCrAl. Here, we summarize the interatomic potentials available for FeCr alloys for possible molecular dynamics studies using FeCr as surrogate materials. Other atomistic methods such as lattice kinetic Monte Carlo are also included in this report. A couple of research topics at the atomic scale are suggested based on the literature survey.« less

Iron's Role in Aluminum: A Powder Metallurgy and Sustainability Approach

NASA Astrophysics Data System (ADS)

Saller, Brandon Dale

The family of Al-Fe alloys is both scientifically and technologically interesting for several reasons. First, the low equilibrium solid solubility (0.03 at.%) and diffusivity of Fe in Al suggest that the alloys containing these two elements should be thermally stable. Many studies have tried to extend this low solubility value via non-equilibrium processing routes. Second, published results suggest that there is a range of intermetallic phases, including the metastable orthorhombic Al6Fe and the equilibrium monoclinic Al13Fe4, for example, the formation of which depends on solidification and subsequent processing conditions. Third, from a sustainability standpoint, both Al and Fe are present in bauxite (aluminum ore), however up to 40 wt.% Fe-oxide present in bauxite is discarded as a waste product, creating red mud pits. In order to understand the multiple facets and implications of iron's role in aluminum, a systematic investigation was performed into the precipitates that form as a function of thermal exposure and their subsequent effect on the tensile behavior of the alloy. In this study, Al-2at.% Fe and Al-5at.% Fe powders were synthesized via helium gas atomization and argon gas atomization, respectively. Cooling rates upwards of 106 K/s were achieved resulting in an intermetallic-free starting structure. Powders were subsequently severely plastically deformed via either cryomilling or high-pressure torsion to obtain nanostructured/ultrafine-grained powder or a consolidated specimen, respectively. Characterization via electron microscopy established a map of the powder microstructure as a function of atomization cooling rate. In addition, electron backscatter diffraction revealed a large number of low-angle grain boundaries, which influenced nucleation and precipitation of the metastable Al6Fe phase. X-ray diffraction and atom probe tomography results provide the most comprehensive evidence to date of forcing of 2at.% Fe into solution with the Al matrix via cryomilling. With respect to the powder, a differential scanning calorimetry and activation energy analysis elucidated the formation and phase transformation temperatures of the relevant intermetallic phases, and the microstructural factors that influenced them. With an understanding of the fundamental science behind the intermetallic formation in the Al-Fe system, the composition of helium atomized Al-2at.% Fe was chosen combined with high-pressure torsion processing to yield a bulk alloy that demonstrated an ultimate tensile strength of 488 MPa. This strength was achieved via a combination of two mechanisms: grain refinement (Hall-Petch) and dislocation-Al6Fe interactions (Orowan strengthening), with notable thermal stability present up until 450°C. Finally, the potential for Al-Fe as a sustainable alloy was studied and a link established between current environmental literature and metallurgy literature on the potential for incorporation of Fe into Al to create a structural alloy.

Solid-State Reaction Between Fe-Al-Ca Alloy and Al2O3-CaO-FeO Oxide During Heat Treatment at 1473 K (1200 °C)

NASA Astrophysics Data System (ADS)

Liu, Chengsong; Yang, Shufeng; Li, Jingshe; Ni, Hongwei; Zhang, Xueliang

2017-04-01

The aim of this study was to control the physicochemical characteristics of inclusions in steel through appropriate heat treatment. Using a confocal scanning laser microscope (CSLM) and pipe furnace, the solid-state reactions between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide during heat treatment at 1473 K (1200 °C) and the influence of these reactions on the compositions of and phases in the alloy and oxide were investigated by the diffusion couple method. Suitable pretreatment of the oxide using a CSLM and production of the diffusion couple of Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide gave good contact between the alloy and oxide. The diffusion couple was then sealed in a quartz tube with a piece of Ti foil to lower oxygen partial pressure and a block of Fe-Al-Ca alloy was introduced to conduct heat treatment experiments. Solid-state reactions between the alloy and oxide during heat treatment at 1473 K (1200 °C) were analyzed and discussed. A dynamic model to calculate the width of the particle precipitation zone based on the Wagner model of internal oxidation of metal was proposed. This model was helpful to understand the solid-state reaction mechanism between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide.

Microstructural control of FeCrAl alloys using Mo and Nb additions

DOE PAGES

Sun, Zhiqian; Bei, Hongbin; Yamamoto, Yukinori

2017-08-14

The effects of Mo and Nb additions on the microstructure and mechanical properties of two FeCrAl alloys were studied in this paper. Fine and uniform recrystallized grain structures (~ 20–30 μm) were achieved in both alloys through suitable annealing after warm-rolling. The formation of Fe 2Nb-type Laves phase precipitates in the Nb-containing FeCrAl alloy effectively stabilized the deformed and recrystallized microstructures. The Mo-containing FeCrAl alloy exhibited strong γ texture fiber after annealing at 650–900 °C, whereas the annealed Nb-containing FeCrAl alloy had much weaker texture. Finally, both strength and ductility decreased as the grain size increased in both alloys.

Investigating vibrational relaxation in cyanide-bridged transition metal mixed-valence complexes using two-dimensional infrared and infrared pump-probe spectroscopies

PubMed Central

Slenkamp, Karla M.; Lynch, Michael S.; Brookes, Jennifer F.; Bannan, Caitlin C.; Daifuku, Stephanie L.; Khalil, Munira

2016-01-01

Using polarization-selective two-dimensional infrared (2D IR) and infrared pump-probe spectroscopies, we study vibrational relaxation of the four cyanide stretching (νCN) vibrations found in [(NH3)5RuIIINCFeII(CN)5]− (FeRu) dissolved in D2O or formamide and [(NC)5FeIICNPtIV(NH3)4NCFeII(CN)5]4− (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as models for understanding the role high frequency vibrational modes play in metal-to-metal charge transfers over a bridging ligand. However, there is currently little information about vibrational relaxation and dephasing dynamics of the anharmonically coupled νCN modes in the electronic ground state of these complexes. IR pump-probe experiments reveal that the vibrational lifetimes of the νCN modes are ∼2 times faster when FeRu is dissolved in D2O versus formamide. They also reveal that the vibrational lifetimes of the νCN modes of FePtFe in D2O are almost four times as long as for FeRu in D2O. Combined with mode-specific relaxation dynamics measured from the 2D IR experiments, the IR pump-probe experiments also reveal that intramolecular vibrational relaxation is occurring in all three systems on ∼1 ps timescale. Center line slope dynamics, which have been shown to be a measure of the frequency-frequency correlation function, reveal that the radial, axial, and trans νCN modes exhibit a ∼3 ps timescale for frequency fluctuations. This timescale is attributed to the forming and breaking of hydrogen bonds between each mode and the solvent. The results presented here along with our previous work on FeRu and FePtFe reveal a picture of coupled anharmonic νCN modes where the spectral diffusion and vibrational relaxation dynamics depend on the spatial localization of the mode on the molecular complex and its specific interaction with the solvent. PMID:27158634

Investigating vibrational relaxation in cyanide-bridged transition metal mixed-valence complexes using two-dimensional infrared and infrared pump-probe spectroscopies.

PubMed

Slenkamp, Karla M; Lynch, Michael S; Brookes, Jennifer F; Bannan, Caitlin C; Daifuku, Stephanie L; Khalil, Munira

2016-03-01

Using polarization-selective two-dimensional infrared (2D IR) and infrared pump-probe spectroscopies, we study vibrational relaxation of the four cyanide stretching (νCN) vibrations found in [(NH3)5Ru(III)NCFe(II)(CN)5](-) (FeRu) dissolved in D2O or formamide and [(NC)5Fe(II)CNPt(IV)(NH3)4NCFe(II)(CN)5](4-) (FePtFe) dissolved in D2O. These cyanide-bridged transition metal complexes serve as models for understanding the role high frequency vibrational modes play in metal-to-metal charge transfers over a bridging ligand. However, there is currently little information about vibrational relaxation and dephasing dynamics of the anharmonically coupled νCN modes in the electronic ground state of these complexes. IR pump-probe experiments reveal that the vibrational lifetimes of the νCN modes are ∼2 times faster when FeRu is dissolved in D2O versus formamide. They also reveal that the vibrational lifetimes of the νCN modes of FePtFe in D2O are almost four times as long as for FeRu in D2O. Combined with mode-specific relaxation dynamics measured from the 2D IR experiments, the IR pump-probe experiments also reveal that intramolecular vibrational relaxation is occurring in all three systems on ∼1 ps timescale. Center line slope dynamics, which have been shown to be a measure of the frequency-frequency correlation function, reveal that the radial, axial, and trans νCN modes exhibit a ∼3 ps timescale for frequency fluctuations. This timescale is attributed to the forming and breaking of hydrogen bonds between each mode and the solvent. The results presented here along with our previous work on FeRu and FePtFe reveal a picture of coupled anharmonic νCN modes where the spectral diffusion and vibrational relaxation dynamics depend on the spatial localization of the mode on the molecular complex and its specific interaction with the solvent.

Influence of Cu on modifying the beta phase and enhancing the mechanical properties of recycled Al-Si-Fe cast alloys.

PubMed

Basak, C B; Babu, N Hari

2017-07-18

High iron impurity affects the castability and the tensile properties of the recycled Al-Si alloys due to the presence of the Fe containing intermetallic β-Al 9 Fe 2 Si 2 phase. To date only Mn addition is known to transform the β-Al 9 Fe 2 Si 2 phase in the Al-Si-Fe system. However, for the first time, as reported here, it is shown that β-phase transforms to the ω-Al 7 Cu 2 Fe phase in the presence of Cu, after solutionization at 793 K. The ω-phase decomposes below 673 K resulting into the formation of θ-Al 2 Cu phase. However, the present thermodynamic description of the Al-Si-Fe-Cu system needs finer tuning to accurately predict the stability of the ω-phase in these alloys. In the present study, an attempt was made to enhance the strength of Al-6wt%Si-2wt%Fe model recycled cast alloy with different amount of Cu addition. Microstructural and XRD analysis were carried out in detail to show the influence of Cu and the stability range of the ω-phase. Tensile properties and micro-hardness values are also reported for both as-cast and solutionized alloys with different amount of Cu without and with ageing treatment at 473 K. The increase in strength due to addition of Cu, in Fe-rich Al-Si alloys is promising from the alloy recyclability point of view.

Iron Biogeochemistry in the High Latitude North Atlantic Ocean.

PubMed

Achterberg, Eric P; Steigenberger, Sebastian; Marsay, Chris M; LeMoigne, Frédéric A C; Painter, Stuart C; Baker, Alex R; Connelly, Douglas P; Moore, C Mark; Tagliabue, Alessandro; Tanhua, Toste

2018-01-19

Iron (Fe) is an essential micronutrient for marine microbial organisms, and low supply controls productivity in large parts of the world's ocean. The high latitude North Atlantic is seasonally Fe limited, but Fe distributions and source strengths are poorly constrained. Surface ocean dissolved Fe (DFe) concentrations were low in the study region (<0.1 nM) in summer 2010, with significant perturbations during spring 2010 in the Iceland Basin as a result of an eruption of the Eyjafjallajökull volcano (up to 2.5 nM DFe near Iceland) with biogeochemical consequences. Deep water concentrations in the vicinity of the Reykjanes Ridge system were influenced by pronounced sediment resuspension, with indications for additional inputs by hydrothermal vents, with subsequent lateral transport of Fe and manganese plumes of up to 250-300 km. Particulate Fe formed the dominant pool, as evidenced by 4-17 fold higher total dissolvable Fe compared with DFe concentrations, and a dynamic exchange between the fractions appeared to buffer deep water DFe. Here we show that Fe supply associated with deep winter mixing (up to 103 nmol m -2 d -1 ) was at least ca. 4-10 times higher than atmospheric deposition, diffusive fluxes at the base of the summer mixed layer, and horizontal surface ocean fluxes.

Long-term effects of drinking-water treatment residuals on dissolved phosphorus export from vegetated buffer strips.

PubMed

Habibiandehkordi, Reza; Quinton, John N; Surridge, Ben W J

2015-04-01

The export of dissolved phosphorus (P) in surface runoff from agricultural land can lead to water quality degradation. Surface application of aluminium (Al)-based water treatment residuals (Al-WTRs) to vegetated buffer strip (VBS) soils can enhance P removal from surface runoff during single runoff events. However, the longer-term effects on P removal in VBSs following application of products such as Al-WTR remain uncertain. We used field experimental plots to examine the long-term effects of applying a freshly generated Al-WTR to VBSs on dissolved P export during multiple runoff events, occurring between 1 day and 42 weeks after the application of Al-WTR. Vegetated buffer strip plots amended with Al-WTR significantly reduced soluble reactive P and total dissolved P concentrations in surface runoff compared to both unamended VBS plots and control plots. However, the effectiveness of Al-WTR decreased over time, by approximately 70% after 42 weeks compared to a day following Al-WTR application. Reduced performance did not appear to be due to drying of Al-WTR in the field. Instead, the development of preferential flow paths as well as burying of Al-WTR with freshly deposited sediments may explain these observations. Better understanding of the processes controlling long-term P removal by Al-WTR is required for effective management of VBSs.

Geochemical study of stream waters affected by mining activities in the SE Spain

NASA Astrophysics Data System (ADS)

Garcia-Lorenzo, Maria Luz; Perez-Sirvent, Carmen; Martinez-Sanchez, Maria Jose; Bech, Jaime

2015-04-01

Water pollution by dissolved metals in mining areas has mainly been associated with the oxidation of sulphide-bearing minerals exposed to weathering conditions, resulting in low quality effluents of acidic pH and containing a high level of dissolved metals. According to transport process, three types of pollution could be established: a) Primary contamination, formed by residues placed close to the contamination sources; b) Secondary contamination, produced as a result of transport out of its production areas; c) Tertiary contamination. The aim of this work was to study trace element in water samples affected by mining activities and to apply the MINTEQ model for calculating aqueous geochemical equilibria. The studied area constituted an important mining centre for more than 2500 years, ceasing activity in 1991. The ore deposits of this zone have iron, lead and zinc as the main metal components. As a result, a lot of contaminations sources, formed by mining steriles, waste piles and foundry residues are present. For this study, 36 surficial water samples were collected after a rain episode in 4 different areas. In these samples, the trace element content was determined by by flame atomic absorption spectrometry (Fe and Zn), electrothermal atomization atomic absorption spectrometry (Pb and Cd), atomic fluorescence spectrometry (As) and ICP-MS for Al. MINTEQA2 is a geochemical equilibrium speciation model capable of computing equilibria among the dissolved, adsorbed, solid, and gas phases in an environmental setting and was applied to collected waters. Zone A: A5 is strongly influenced by tailing dumps and showed high trace element content. In addition, is influenced by the sea water and then showed high bromide, chloride, sodium and magnesium content, together with a basic pH. The MINTEQ model application suggested that Zn and Cd could precipitate as carbonate (hidrocincite, smithsonite and otavite). A9 also showed acid pH and high trace element content; is influenced by tailing dumps and also by waters from gully watercourses, transporting materials from Sierra Minera. The MINTEQ simulation showed that Pb and Ca could precipitate as sulphates (anglesite and gypsum). Waters affected by secondary contamination have been mixed with carbonate materials, present in the zone increasing the pH. Some elements have precipitated, such as Cu and Pb, while Cd, Zn and As are soluble. The MINTEQ model results showed that in A10 and A14, Al could precipitate as diaspore but also carbonates could be formed, particularly dolomite. These model in A12 sample showed that soluble Zn could precipitate as carbonate and Al as oxyhydroxide, similarly than in A13. A2 and A6 waters are affected by tertiary contamination and showed basic pH, soluble carbonates and lower trace element content. Only Zn, Cd and Al are present. The speciation model showed that in A2, Cd and Zn could precipitate as carbonates while Al as oxihydroxide. In A6, the model suggested that soluble Pb could precipitate as carbonate (hidrocerusite and cerusite) or as hydroxide; Al as diaspore, Ca as calcite and Fe as hematite. Zone B: All waters are strongly affected by mining activities and showed acid pH, high trace element content and high content of soluble sulphates. The MINTEQ results showed that in B8, Fe could precipitate as hydroxychloride and in B12 could form alunite. In B9, B10, B13 y B14, the model estimates the precipitation of anglesite, gypsum and Fe hydroxichloride (B9 and B10), diaspore in B13 and B14, and gypsum and Fe hydroxychloride in B13. All the sampling points collected in Zone C are affected by primary contamination, because there are a lot of tailing dumps. C1 showed high trace element content because is a reception point of a lot of tailing dumps. Water samples from C3 to C8 also had acid pH and high trace element content, particularly As, Zn and Cd. In addition, they showed high soluble sulphates. C2 water showed neutral pH, soluble carbonate and low trace element content because is influenced by a stabilised tailing dump. In all samples, except C2, the MINTEQ model showed that a lot of efflorescences could be formed, mainly sulphates. Zone D: All waters collected in this zone showed acid pH and high trace element content, mainly Zn, Cd and As. MINTEQ model results showed that elements could precipitate as jarosite but also anglesite in D8 and gypsum in D9, D11 and D12. D1 is affected by secondary contamination, which showed higher pH (still acid) and lower content in soluble salts and trace elements. The MINTEQ model suggested that Al could precipitate as diaspore, gibbsite and alunite. The applied model is an appropriate tool for the analysis of waters affected by mining activities. The obtained simulations confirm natural attenuation processes.

Investigation into the morphology and structure of magnetic bentonite nanocomposites with their catalytic activity

NASA Astrophysics Data System (ADS)

Wan, Dong; Wang, Guanghua; Li, Wenbing; Wei, Xiaobi

2017-08-01

Al pillared bentonite-Fe3O4 nanocomposites (Fe3O4/Al-B) with controllable Fe3O4 particle sizes and loadings were synthesized by a simple in situ oxidation-precipitation method. The obtained samples were characterized by XRD, SEM, TEM, FTIR, XPS, VSM and N2 sorption. These results suggested that Fe3O4 was chemically anchored to the bentonite sheets via Fe-O-Si bonds, resulting in the formation of secondary pore structure. Three types of structure of Fe3O4/Al-B nanocomposites were proposed at different Fe3O4 loadings, varying from 40 to 80 wt%. The catalytic activity of the Fe3O4/Al-B nanocomposites was investigated in the heterogeneous Fenton-like oxidation of rhodamine B (RhB). The 50 nm Fe3O4/Al-B nanocomposite showed enhanced degradation of RhB over the control catalyst, benefited from its greater surface area and pore volume. The highest catalytic activity was found to be at Fe3O4 loading of 60 wt%, which was attributed to the synergistic effects between both increased surface area and formed Fe-O-Si bonds. These findings offer a better understanding on structural and morphological relationships of Fe3O4/Al-B nanocomposites with their heterogeneous Fenton-like catalytic activity.

Evaluation of Eurasian Watermilfoil Control Techniques Using Aquatic Herbicides in Fort Peck Lake, Montana

DTIC Science & Technology

2015-07-01

19 Table 3. Temperature , dissolved oxygen , pH, and wind...21 Table 4. Temperature , dissolved oxygen , and pH measured in the study plots following treatment, Fort Peck Lake, MT, 2012...quality, particularly temperature , pH, dissolved oxygen , and nutrient cycling (Prentki et al. 1979; Carpenter and Lodge 1986, Frodge et al. 1990; Boylen

Analysis of the FeCrAl Accident Tolerant Fuel Concept Benefits during BWR Station Blackout Accidents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robb, Kevin R

2015-01-01

Iron-chromium-aluminum (FeCrAl) alloys are being considered for fuel concepts with enhanced accident tolerance. FeCrAl alloys have very slow oxidation kinetics and good strength at high temperatures. FeCrAl could be used for fuel cladding in light water reactors and/or as channel box material in boiling water reactors (BWRs). To estimate the potential safety gains afforded by the FeCrAl concept, the MELCOR code was used to analyze a range of postulated station blackout severe accident scenarios in a BWR/4 reactor employing FeCrAl. The simulations utilize the most recently known thermophysical properties and oxidation kinetics for FeCrAl. Overall, when compared to the traditionalmore » Zircaloy-based cladding and channel box, the FeCrAl concept provides a few extra hours of time for operators to take mitigating actions and/or for evacuations to take place. A coolable core geometry is retained longer, enhancing the ability to stabilize an accident. Finally, due to the slower oxidation kinetics, substantially less hydrogen is generated, and the generation is delayed in time. This decreases the amount of non-condensable gases in containment and the potential for deflagrations to inhibit the accident response.« less

Occurrence and behaviour of dissolved, nano-particulate and micro-particulate iron in waste waters and treatment systems: new insights from electrochemical analysis.

PubMed

Matthies, R; Aplin, A C; Horrocks, B R; Mudashiru, L K

2012-04-01

Cyclic-, Differential Pulse- and Steady-state Microdisc Voltammetry (CV, DPV, SMV) techniques have been used to quantify the occurrence and fate of dissolved Fe(ii)/Fe(iii), nano-particulate and micro-particulate iron over a 12 month period in a series of net-acidic and net-alkaline coal mine drainages and passive treatment systems. Total iron in the mine waters is typically 10-100 mg L(-1), with values up to 2100 mg L(-1). Between 30 and 80% of the total iron occurs as solid phase, of which 20 to 80% is nano-particulate. Nano-particulate iron comprises 20 to 70% of the nominally "dissolved" (i.e. <0.45 μm) iron. Since coagulation and sedimentation are the only processes required to remove solid phase iron, these data have important implications for the generation or consumption of acidity during water treatment. In most waters, the majority of truly dissolved iron occurs as Fe(ii) (average 64 ± 22%). Activities of Fe(ii) do not correlate with pH and geochemical modelling shows that no Fe(ii) mineral is supersaturated. Removal of Fe(ii) must proceed via oxidation and hydrolysis. Except in waters with pH < 4.4, activities of Fe(iii) are strongly and negatively correlated with pH. Geochemical modelling suggests that the activity of Fe(iii) is controlled by the solubility of hydrous ferric oxides and oxyhydroxysulfates, supported by scanning and transmission electron microscopic analysis of solids. Nevertheless, the waters are generally supersaturated with respect to ferrihydrite and schwertmannite, and are not at redox equilibrium, indicating the key role of oxidation and hydrolysis kinetics on water treatment. Typically 70-100% of iron is retained in the treatment systems. Oxidation, hydrolysis, precipitation, coagulation and sedimentation occur in all treatment systems and - independent of water chemistry and the type of treatment system - hydroxides and oxyhydroxysulfates are the main iron sinks. The electrochemical data thus reveal the rationale for incomplete iron retention in individual systems and can thus inform future design criteria. The successful application of this low cost and rapid electrochemical method demonstrates its significant potential for real-time, on-site monitoring of iron-enriched waters and may in future substitute traditional analytical methods.

In situ removal of dissolved and suspended contaminants from a eutrophic pond using hybrid sand-filter.

PubMed

Vijayaraghavan, K; Joshi, Umid Man; Ping, Han; Reuben, Sheela; Burger, David F

2014-01-01

In this study, in situ hybrid sand filters were designed to remove dissolved and suspended contaminants from eutrophic pond. Currently, there are no attempts made to eradicate dissolved as well as suspended contaminants from eutrophic water system in a single step. Monitoring studies revealed that examined pond contain high chlorophyll-a content (101.8 μg L(-1)), turbidity (39.5 NTU) and total dissolved solids concentration (0.04 g L(-1)). Samples were further exposed to extensive water quality analysis, which include examining physicochemical parameters (pH, conductivity, total dissolved solids, salinity, turbidity and chlorophyll-a), metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Cr, and Ni) and anions (NO3, NO2, PO4, SO4, Cl, F and Br). To tackle pollutants, filtration system was designed to comprise of several components including fine sand, coarse sand/sorbent mix and gravel from top to bottom loaded in fiberglass tanks. All the filters (activated carbon, Sargassum and zeolite) completely removed algal biomass and showed potential to decrease pH during entire operational period of 20 h at 120 L h(-1). To examine the efficiency of filters in adverse conditions, the pond water was spiked with heavy metals (Cu, Cd, Pb, Zn, Cr, and Ni). Of the different filter systems, Sargassum-loaded filter performed exceedingly well with concentrations of heavy metals never exceeded the Environmental protection agency regulations for freshwater limits during total operational period. The total uptake capacities at the end of the fifth event were 24.9, 20.5, 0.58, 5.2, 0.091 and 2.8 mg/kg for Cr, Ni, Cu, Zn, Cd and Pb, respectively.

Effect of Mn and Fe on the Formation of Fe- and Mn-Rich Intermetallics in Al–5Mg–Mn Alloys Solidified Under Near-Rapid Cooling

PubMed Central

Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

2016-01-01

Mn was an important alloying element used in Al–Mg–Mn alloys. However, it had to be limited to a low level (<1.0 wt %) to avoid the formation of coarse intermetallics. In order to take full advantage of the benefits of Mn, research was carried out to investigate the possibility of increasing the content of Mn by studying the effect of cooling rate on the formation of Fe- and Mn-rich intermetallics at different content levels of Mn and Fe. The results indicated that in Al–5Mg–Mn alloy with low Fe content (<0.1 wt %), intermetallic Al6(Fe,Mn) was small in size and amount. With increasing Mn content, intermetallic Al6(Fe,Mn) increased, but in limited amount. In high-Fe-containing Al–5Mg–Mn alloys (0.5 wt % Fe), intermetallic Al6(Fe,Mn) became the dominant phase, even in the alloy with low Mn content (0.39 wt %). Cooling rate played a critical role in the refinement of the intermetallics. Under near-rapid cooling, intermetallic Al6(Fe,Mn) was extremely refined. Even in the high Mn and/or high-Fe-containing alloys, it still demonstrated fine Chinese script structures. However, once the alloy composition passed beyond the eutectic point, the primary intermetallic Al6(Fe,Mn) phase displayed extremely coarse platelet-like morphology. Increasing the content of Fe caused intermetallic Al6(Fe,Mn) to become the primary phase at a lower Mn content. PMID:28787888

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality.

PubMed

Chae, Gi-Tak; Yun, Seong-Taek; Choi, Byoung-Young; Yu, Soon-Young; Jo, Ho-Young; Mayer, Bernhard; Kim, Yun-Jong; Lee, Jin-Yong

2008-10-23

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m3 year(-1)) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH4+, NO3(-), turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L(-1), max. 5.58 mg L(-1)), in addition to dissolved Fe, NH4+, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes. Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.

Fast synthesis and consolidation of porous FeAl by pressureless Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Dudina, D. V.; Brester, A. E.; Anisimov, A. G.; Bokhonov, B. B.; Legan, M. A.; Novoselov, A. N.; Skovorodin, I. N.; Uvarov, N. F.

2017-07-01

We report one-step fast synthesis and consolidation of iron aluminide FeAl of high open porosity by pressureless reactive Spark Plasma Sintering (SPS). The starting material of the Fe-40at.%Al composition was a mixture of an iron powder with an average particle diameter of 4 μm and an aluminum powder with an average particle diameter of 6 μm. The rationale behind the choice of the SPS as a processing technique and fine and comparable sizes of the two reactants for the synthesis of high-open porosity FeAl was realization of fast full chemical conversion of Fe and Al into single-phase FeAl reducing the time available for the compact shrinkage. According to the XRD phase analysis, single-phase FeAl compacts formed after SPS at 800 and 900°C. These compacts had open porosities of 41 and 46%, respectively. The transverse rupture strength of the compacts sintered at 700-900°C was found to change little with the sintering temperature in the selected range.

Viability of thin wall tube forming of ATF FeCrAl

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maloy, Stuart Andrew; Aydogan, Eda; Anderoglu, Osman

Fabrication of thin walled tubing of FeCrAl alloys is critical to its success as a candidate enhanced accident-tolerant fuel cladding material. Alloys that are being investigated are Generation I and Generation II FeCrAl alloys produced at ORNL and an ODS FeCrAl alloy, MA-956 produced by Special Metals. Gen I and Gen II FeCrAl alloys were provided by ORNL and MA-956 was provided by LANL (initially produced by Special Metals). Three tube development efforts were undertaken. ORNL led the FeCrAl Gen I and Gen II alloy development and tube processing studies through drawing tubes at Rhenium Corporation. LANL received alloys frommore » ORNL and led tube processing studies through drawing tubes at Century Tubing. PNNL led the development of tube processing studies on MA-956 through pilger processing working with Sandvik Corporation. A summary of the recent progress on tube development is provided in the following report and a separate ORNL report: ORNL/TM-2015/478, “Development and Quality Assessments of Commercial Heat Production of ATF FeCrAl Tubes”.« less

RFe{sub 2}Mg{sub x}Al{sub 8−x} (R=La–Nd and Sm; x≈0.8): Flux synthesis, structure, magnetic and electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Xiaowei; Chai, Ping; Chen, Banghao

2015-09-15

Single crystals of Mg-substituted CeFe{sub 2}Al{sub 8} type intermetallics RFe{sub 2}Mg{sub x}Al{sub 8–x} (R=La–Nd and Sm; x≤1) were grown by reacting iron and rare earth metals in 1:1 Mg/Al mixed flux. The structure features mono-capped and bi-capped trigonal prismatic FeAl{sub 6} units. Electronic structure calculations indicate that magnesium substitution reduces the valence electron count, shifting the Fermi level away from a pseudo-gap. This changes the electronic nature of the cerium analog; the previously reported ternary CeFe{sub 2}Al{sub 8} shows strong hybridization between the cerium states and the conduction electrons, resulting in no magnetic moment on Ce atoms. On the othermore » hand, magnetic susceptibility measurements on CeFe{sub 2}Mg{sub x}Al{sub 8–x} indicates a localized moment on cerium. The newly synthesized Pr, Nd and Sm analogs exhibit antiferromagnetic ordering at 2.8 K, 7.8 K and 12 K respectively. Solid state {sup 27}Al NMR of LaFe{sub 2}Mg{sub x}Al{sub 8–x} exhibits a broad Knight shift at ~1200 ppm, consistent with the metallic behavior shown by electrical resistivity data. - Graphical abstract: Mg substitution into CeFe{sub 2}Al{sub 8} modifies cerium valence due to changing valence electron count. - Highlights: • RFe{sub 2}Mg{sub x}Al{sub 8−x} (R=La–Nd, Sm) grow as large crystals from reactions in Mg/Al flux. • Products are magnesium-substituted variants of CeFe{sub 2}Al{sub 8}, with CaCo{sub 2}Al{sub 8} structure. • Ce magnetic moment in CeFe{sub 2}Mg{sub x}Al{sub 8−x} varies from that in CeFe{sub 2}Al{sub 8} due to VEC change. • Antiferromagnetic ordering observed for Pr, Nd, Sm analogs of RFe{sub 2}Mg{sub x}Al{sub 8−x}.« less

Dependence of catalytic properties of Al/Fe{sub 2}O{sub 3} thermites on morphology of Fe{sub 2}O{sub 3} particles in combustion reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Ningning; He, Cuicui; Liu, Jianbing

2014-11-15

Three Fe{sub 2}O{sub 3} particle samples with the same crystal structure but different morphologies were prepared by the hydrothermal method and then combined with Al nanoparticles to produce Al/Fe{sub 2}O{sub 3} thermites using ultrasonic mixing. The properties of Fe{sub 2}O{sub 3} and Al/Fe{sub 2}O{sub 3} were studied using a combination of experimental techniques including scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The influences of the three Al/Fe{sub 2}O{sub 3} thermites on the combustion properties of the AP/HTPB (ammonium perchlorate/hydroxyl-terminated polybutadiene) composite propellant were investigated in comparisonmore » to those of Fe{sub 2}O{sub 3}. The results show that the Al/Fe{sub 2}O{sub 3} thermites are better than Fe{sub 2}O{sub 3} in enhancing the combustion performance of AP/HTPB. Furthermore, the surface area, which depends on size and mophology, of Fe{sub 2}O{sub 3} particles was found to play a vital role in improving the burning rate of the thermites-containing propellant formulation, with the smallest particles with the largest surface-to-volume (S/V) ratio performing the best. The enhanced catalytic property of the granular-shape Fe{sub 2}O{sub 3} and the corresponding thermite is attributed to the large specific surface area of Fe{sub 2}O{sub 3}. The different thermal behaviors of these three superthemites were supposed to be attributed to the surface site of Fe{sub 2}O{sub 3} particles. This work provides a better understanding on the catalytic properties of thermites that are important for combustion applications. - Graphical abstract: Effects of Fe{sub 2}O{sub 3} and Al/Fe{sub 2}O{sub 3} have been compared for the first time by analyzing combustion properties of formulations containing them, suggesting their potential application in AP/HTPB composite propellant systems. - Highlights: • Three Fe{sub 2}O{sub 3} particles with different morphologies (polyhedral, oval and granular) were prepared by the hydrothermal method. • Thermal behaviors of thermites Al/Fe{sub 2}O{sub 3} are studied upon DSC data. • Effects of Fe{sub 2}O{sub 3} and Al/Fe{sub 2}O{sub 3} on the combustion properties of the AP/HTPB composite propellant are first investigated.« less

Imaging of Al/Fe ratios in synthetic Al-goethite revealed by nanoscale secondary ion mass spectrometry.

PubMed

Pohl, Lydia; Kölbl, Angelika; Werner, Florian; Mueller, Carsten W; Höschen, Carmen; Häusler, Werner; Kögel-Knabner, Ingrid

2018-04-30

Aluminium (Al)-substituted goethite is ubiquitous in soils and sediments. The extent of Al-substitution affects the physicochemical properties of the mineral and influences its macroscale properties. Bulk analysis only provides total Al/Fe ratios without providing information with respect to the Al-substitution of single minerals. Here, we demonstrate that nanoscale secondary ion mass spectrometry (NanoSIMS) enables the precise determination of Al-content in single minerals, while simultaneously visualising the variation of the Al/Fe ratio. Al-substituted goethite samples were synthesized with increasing Al concentrations of 0.1, 3, and 7 % and analysed by NanoSIMS in combination with established bulk spectroscopic methods (XRD, FTIR, Mössbauer spectroscopy). The high spatial resolution (50-150 nm) of NanoSIMS is accompanied by a high number of single-point measurements. We statistically evaluated the Al/Fe ratios derived from NanoSIMS, while maintaining the spatial information and reassigning it to its original localization. XRD analyses confirmed increasing concentration of incorporated Al within the goethite structure. Mössbauer spectroscopy revealed 11 % of the goethite samples generated at high Al concentrations consisted of hematite. The NanoSIMS data show that the Al/Fe ratios are in agreement with bulk data derived from total digestion and demonstrated small spatial variability between single-point measurements. More advantageously, statistical analysis and reassignment of single-point measurements allowed us to identify distinct spots with significantly higher or lower Al/Fe ratios. NanoSIMS measurements confirmed the capacity to produce images, which indicated the uniform increase in Al-concentrations in goethite. Using a combination of statistical analysis with information from complementary spectroscopic techniques (XRD, FTIR and Mössbauer spectroscopy) we were further able to reveal spots with lower Al/Fe ratios as hematite. Copyright © 2018 John Wiley & Sons, Ltd.

Structural Investigation of the (010) Surface of the Al13Fe4 Catalyst

NASA Astrophysics Data System (ADS)

Ledieu, J.; Gaudry, É.; Loli, L. N. Serkovic; Villaseca, S. Alarcón; de Weerd, M.-C.; Hahne, M.; Gille, P.; Grin, Y.; Dubois, J.-M.; Fournée, V.

2013-02-01

We have investigated the structure of the Al13Fe4(010) surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered (P) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as “glue” atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk P plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the Al13Fe4 catalytic properties recently reported in line with the site-isolation concept [M. Armbrüster , Nat. Mater. 11, 690 (2012)NMAACR1476-1122].

Improvement of thermal stability of nano-granular TMR films by using a Mg-Al-O insulator matrix

NASA Astrophysics Data System (ADS)

Kanie, S.; Koyama, S.

2018-05-01

A new metal-insulator nano-granular tunneling magnetoresistance (TMR) film made of (Fe-Co)-(Mg-Al-O) has been investigated. It is confirmed that the film has granular structure in which crystal Fe-Co granules are surrounded by an amorphous Mg-Al-O matrix. A large MR ratio of 11.8 % at room temperature is observed for a 42 vol.%(Fe0.6Co0.4)-(Mg-Al-O) film annealed at 395 °C. The electrical resistivity increases rapidly by annealing at above the changing point (500 °C). The changing point is about 300 °C higher than that of conventional (Fe-Co)-(Mg-F) nano-granular TMR films. The 42 vol.%(Fe0.6Co0.4)-(Mg-Al-O) film also exhibits less degradation in the MR ratio at high annealing temperatures such as 600 °C. These results suggest the (Fe-Co)-(Mg-Al-O) film is superior to the (Fe-Co)-(Mg-F) film in thermal stability.

Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

PubMed

Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

2015-04-01

There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters.

Electronic structure and properties of magnetic defects in Co(1+x)Al(1-x) and Fe(1+x)Al(1-x) alloys. Ph.D. Thesis - Paris Univ.

NASA Technical Reports Server (NTRS)

Abbe, D.

1984-01-01

CoAl and FeAl compounds are developed along two directions. Magnetic susceptibility and specific heat at low temperature on (NiCo)Al and (CoFe)Al ternary alloys are in good agreement with band calculations. Results on magnetization and specific heat under field at low temperature on nonstoichiometric compounds show clearly the importance of the nearest neighbor effects. In the case of CoAl, the isolated cobalt atoms substituting aluminum are characterized by a Kondo behavior, and, for FeAl, the isolated extra iron atoms are magnetic and polarize the matrix. Moreover, for the two compounds, clusters of higher order play a considerable part in the magnetic properties for CoAl, these clusters also seem to be characterized by a Kondo behavior, for FeAl, these clusters whose moment is higher than in the case of isolated atoms, could be constituted of excess parts of iron atoms.

High-Strength Nanotwinned Al Alloys with 9R Phase.

PubMed

Li, Qiang; Xue, Sichuang; Wang, Jian; Shao, Shuai; Kwong, Anthony H; Giwa, Adenike; Fan, Zhe; Liu, Yue; Qi, Zhimin; Ding, Jie; Wang, Han; Greer, Julia R; Wang, Haiyan; Zhang, Xinghang

2018-03-01

Light-weight aluminum (Al) alloys have widespread applications. However, most Al alloys have inherently low mechanical strength. Nanotwins can induce high strength and ductility in metallic materials. Yet, introducing high-density growth twins into Al remains difficult due to its ultrahigh stacking-fault energy. In this study, it is shown that incorporating merely several atomic percent of Fe solutes into Al enables the formation of nanotwinned (nt) columnar grains with high-density 9R phase in Al(Fe) solid solutions. The nt Al-Fe alloy coatings reach a maximum hardness of ≈5.5 GPa, one of the strongest binary Al alloys ever created. In situ uniaxial compressions show that the nt Al-Fe alloys populated with 9R phase have flow stress exceeding 1.5 GPa, comparable to high-strength steels. Molecular dynamics simulations reveal that high strength and hardening ability of Al-Fe alloys arise mainly from the high-density 9R phase and nanoscale grain sizes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particulate Trace Element Cycling in a Diatom Bloom at Station ALOHA

NASA Astrophysics Data System (ADS)

Weisend, R.; Morton, P. L.; Landing, W. M.; Fitzsimmons, J. N.; Hayes, C. T.; Boyle, E. A.

2014-12-01

Phytoplankton in oligotrophic marine deserts depend on remote sources to supply trace nutrients. To examine these sources, marine particulate matter samples from the central North Pacific (Station ALOHA) were collected during the July-August 2012 HOE-DYLAN cruises and analyzed for a suite of trace (e.g., Fe, Mn) and major (e.g. Al, P) elements. Daily surface SPM samples were examined for evidence of atmospheric deposition and biological uptake, while five vertical profiles were examined for evidence of surface vertical export and subsurface horizontal transport from nearby sources (e.g., margin sediments, hydrothermal plumes). Maxima in surface particulate P (a biological tracer) corresponded with a diatom bloom, and surprisingly also coincided with maxima in particulate Al (typically a tracer for lithogenic inputs). The surface particulate Al distributions likely result from the adsorption of dissolved Al onto diatom silica frustules, not from atmospheric dust deposition. In addition, a subsurface maximum in particulate Al and P was observed four days later at 75m, possibly resulting from vertical export of the surface diatom bloom. The distributions of other bioactive trace elements (e.g. Cd, Co, Cu) will be presented in the context of the diatom bloom and other biological, chemical and physical features. A second, complementary poster is also being presented which examines the cycling of trace elements in lithogenic particles (Morton et al., "Trace Element Cycling in Lithogenic Particles at Station ALOHA").

The Effect of Nb Addition on the Microstructure and the High-Temperature Strength of Fe3Al Aluminide

NASA Astrophysics Data System (ADS)

Kratochvíl, Petr; Švec, Martin; Král, Robert; Veselý, Jozef; Lukáč, Pavel; Vlasák, Tomáš

2018-02-01

The microstructural and high-temperature mechanical properties of Fe-26Al-xNb (x = 3 and 5 at. pct) are compared. The alloys were investigated "as cast" and after hot rolling at 1473 K (1200 °C). Scanning electron microscopes equipped with EDS and EBSD were used for the microstructure and phase identification. The addition of 3 at. pct of Nb into the Fe3Al matrix leads to the formation of C14 λ—Laves phase (Fe,Al)2Nb (LP) particles spread in the Fe3Al matrix, while an eutectic with thin lamellae of LP C14 λ—Laves phase (Fe,Al)2Nb and matrix is also formed in the iron aluminide with 5 at. pct of Nb. The presence of incoherent precipitates is connected with the enhancement of the high-temperature strength and creep resistance.

Electronic structure and magnetic properties in T 2 AlB 2 ( T = Fe, Mn, Cr, Co, and Ni) and their alloys

DOE PAGES

Ke, Liqin; Harmon, Bruce N.; Kramer, Matthew J.

2017-03-20

In this study, the electronic structure and intrinsic magnetic properties of Fe 2AlB 2-related compounds and their alloys have been investigated using density functional theory. For Fe 2AlB 2, the crystallographic a axis is the easiest axis, which agrees with experiments. The magnetic ground state of Mn 2AlB 2 is found to be ferromagnetic in the basal ab plane, but antiferromagnetic along the c axis. All 3d dopings considered decrease the magnetization and Curie temperature in Fe 2AlB 2. Electron doping with Co or Ni has a stronger effect on the decreasing of Curie temperature in Fe 2AlB 2 thanmore » hole doping with Mn or Cr. However, a larger amount of Mn doping on Fe 2AlB 2 promotes the ferromagnetic to antiferromagnetic transition. A very anisotropic magnetoelastic effect is found in Fe 2AlB 2: the magnetization has a much stronger dependence on the lattice parameter c than on a or b, which is explained by electronic-structure features near the Fermi level. Dopings of other elements on B and Al sites are also discussed.« less

The Organic Complexation of Iron in the Marine Environment: A Review

PubMed Central

Gledhill, Martha; Buck, Kristen N.

2012-01-01

Iron (Fe) is an essential micronutrient for marine organisms, and it is now well established that low Fe availability controls phytoplankton productivity, community structure, and ecosystem functioning in vast regions of the global ocean. The biogeochemical cycle of Fe involves complex interactions between lithogenic inputs (atmospheric, continental, or hydrothermal), dissolution, precipitation, scavenging, biological uptake, remineralization, and sedimentation processes. Each of these aspects of Fe biogeochemical cycling is likely influenced by organic Fe-binding ligands, which complex more than 99% of dissolved Fe. In this review we consider recent advances in our knowledge of Fe complexation in the marine environment and their implications for the biogeochemistry of Fe in the ocean. We also highlight the importance of constraining the dissolved Fe concentration value used in interpreting voltammetric titration data for the determination of Fe speciation. Within the published Fe speciation data, there appear to be important temporal and spatial variations in Fe-binding ligand concentrations and their conditional stability constants in the marine environment. Excess ligand concentrations, particularly in the truly soluble size fraction, seem to be consistently higher in the upper water column, and especially in Fe-limited, but productive, waters. Evidence is accumulating for an association of Fe with both small, well-defined ligands, such as siderophores, as well as with larger, macromolecular complexes like humic substances, exopolymeric substances, and transparent exopolymers. The diverse size spectrum and chemical nature of Fe ligand complexes corresponds to a change in kinetic inertness which will have a consequent impact on biological availability. However, much work is still to be done in coupling voltammetry, mass spectrometry techniques, and process studies to better characterize the nature and cycling of Fe-binding ligands in the marine environment. PMID:22403574

Substantiation of Epitaxial Growth of Diamond Crystals on the Surface of Carbide Fe3AlC0.66 Phase Nanoparticles.

PubMed

Dzevin, Ievgenij M; Mekhed, Alexander A

2017-12-01

Samples of Fe-Al-C alloys of varying composition were synthesized under high pressures and temperatures. From X-ray analysis data, only K-phase with usual for it average parameter of elemental lattice cell, a = 0.376 nm, carbide Fe 3 C and cubic diamond reflexes were present before and after cooling to the temperature of liquid nitrogen.Calculations were made of the parameters of unit cells, the enthalpy of formation of the Fe 3 AlC, Fe 3.125 Al 0.825 C 0.5 , Fe 3.5 Al 0.5 C 0.5 , Fe 3.5 Al 0.5 C, Fe 3 Al 0.66 C 0.66 , and Fe 3 AlC 0.66 unit cells and crystallographic planes were identified on which epitaxial growth of the diamond phase was possible, using density functional theory as implemented in the WIEN2k package.The possibility of epitaxial growth of diamond crystals on Fe 3 AlC 0.66 (K-phase) nanoparticles was, therefore, demonstrated. The [200] plane was established to be the most suitable plane for diamond growth, having four carbon atoms arranged in a square and a central vacancy which can be occupied by carbon during thermal-and-pressure treatment. Distances between carbon atoms in the [200] plane differ by only 5% from distances between the carbon atoms of a diamond. The electronic structure and energetic parameters of the substrate were also investigated. It was shown that the substrate with at least four intermediate layers of K-phase exhibits signs of stability such as negative enthalpy of formation and the Fermi level falling to minimum densities of states.

Preservation of water samples for arsenic(III/V) determinations: An evaluation of the literature and new analytical results

USGS Publications Warehouse

McCleskey, R. Blaine; Nordstrom, D. Kirk; Maest, A.S.

2004-01-01

Published literature on preservation procedures for stabilizing aqueous inorganic As(III/V) redox species contains discrepancies. This study critically evaluates published reports on As redox preservation and explains discrepancies in the literature. Synthetic laboratory preservation experiments and time stability experiments were conducted for natural water samples from several field sites. Any field collection procedure that filters out microorganisms, adds a reagent that prevents dissolved Fe and Mn oxidation and precipitation, and isolates the sample from solar radiation will preserve the As(III/V) ratio. Reagents that prevent Fe and Mn oxidation and precipitation include HCl, H 2SO4, and EDTA, although extremely high concentrations of EDTA are necessary for some water samples high in Fe. Photo-catalyzed Fe(III) reduction causes As(III) oxidation; however, storing the sample in the dark prevents photochemical reactions. Furthermore, the presence of Fe(II) or SO 4 inhibits the oxidation of As(III) by Fe(III) because of complexation reactions and competing reactions with free radicals. Consequently, fast abiotic As(III) oxidation reactions observed in the laboratory are not observed in natural water samples for one or more of the following reasons: (1) the As redox species have already stabilized, (2) most natural waters contain very low dissolved Fe(III) concentrations, (3) the As(III) oxidation caused by Fe(III) photoreduction is inhibited by Fe(II) or SO4.

Passive aerobic treatment of net-alkaline, iron-laden drainage from a flooded underground anthracite mine, Pennsylvania, USA

USGS Publications Warehouse

Cravotta, C.A.

2007-01-01

This report evaluates the results of a continuous 4.5-day laboratory aeration experiment and the first year of passive, aerobic treatment of abandoned mine drainage (AMD) from a typical flooded underground anthracite mine in eastern Pennsylvania, USA. During 1991-2006, the AMD source, locally known as the Otto Discharge, had flows from 20 to 270 L/s (median 92 L/s) and water quality that was consistently suboxic (median 0.9 mg/L O2) and circumneutral (pH ??? 6.0; net alkalinity >10) with moderate concentrations of dissolved iron and manganese and low concentrations of dissolved aluminum (medians of 11, 2.2, and <0.2 mg/L, respectively). In 2001, the laboratory aeration experiment demonstrated rapid oxidation of ferrous iron (Fe 2+) without supplemental alkalinity; the initial Fe2+ concentration of 16.4 mg/L decreased to less than 0.5 mg/L within 24 h; pH values increased rapidly from 5.8 to 7.2, ultimately attaining a steady-state value of 7.5. The increased pH coincided with a rapid decrease in the partial pressure of carbon dioxide (PCO2) from an initial value of 10 -1.1atm to a steady-state value of 10-3.1atm. From these results, a staged aerobic treatment system was conceptualized consisting of a 2 m deep pond with innovative aeration and recirculation to promote rapid oxidation of Fe2+, two 0.3 m deep wetlands to facilitate iron solids removal, and a supplemental oxic limestone drain for dissolved manganese and trace-metal removal. The system was constructed, but without the aeration mechanism, and began operation in June 2005. During the first 12 months of operation, estimated detention times in the treatment system ranged from 9 to 38 h. However, in contrast with 80-100% removal of Fe2+ over similar elapsed times during the laboratory aeration experiment, the treatment system typically removed less than 35% of the influent Fe2+. Although concentrations of dissolved CO2 decreased progressively within the treatment system, the PCO2 values for treated effluent remained elevated (10-2.4 to 10-1.7atm). The elevated PCO 2 maintained the pH within the system at values less than 7 and hence slowed the rate of Fe2+ oxidation compared to the aeration experiment. Kinetic models of Fe2+ oxidation that consider effects of pH and dissolved O2 were incorporated in the geochemical computer program PHREEQC to evaluate the effects of detention time, pH, and other variables on Fe2+ oxidation and removal rates. These models and the laboratory aeration experiment indicate that performance of this and other aerobic wetlands for treatment of net-alkaline AMD could be improved by aggressive, continuous aeration in the initial stage to decrease PCO 2, increase pH, and accelerate Fe2+ oxidation. ?? 2007 Springer-Verlag.

Heavy-ion damage of an amorphous metallic alloy

NASA Astrophysics Data System (ADS)

Chaki, T. K.; Li, J. C. M.

1986-09-01

A Ni base amorphous alloy BN12 (Ni 69.2Cr 6.6Si 13.7B 7.9Fe 2.6 supplied by Allied Corporation), with its shiny surface polished and covered with a 20-30 nm Al film to avoid contamination and sputtering, was irradiated with 70 MeV Ni +6 ions at a dose of about {10 16}/{cm 2}. The Al film was removed by 2 g NaOH dissolved in 1 liter water solution. A Dektak surface profilometer showed surface swelling of the irradiated spot by about 200 nm surrounded by higher ridges. Optical and scanning electron microscopic observations revealed considerable roughness within the irradiated spot. Annealing for 3 h at each 50 K. increment of temperature between 500 and 800 K did not remove the swelling. However, transmission electron microscopic studies gave no indication of voids. It seems that swelling may not associate with structural damage. This important possibility is discussed in the light of generation and disappearance of point defects.

Downstream composition changes of acidic volcanic waters discharged into the Banyupahit stream, Ijen caldera, Indonesia

NASA Astrophysics Data System (ADS)

Delmelle, P.; Bernard, A.

2000-04-01

The crater lake of Kawah Ijen volcano contains extremely low pH (<0.4) waters with high SO4 (∼70000 mg/kg), Cl (∼21000 mg/kg), F (∼1500 mg/kg), Al (∼5000 mg/kg), Fe (∼2000 mg/kg) and trace metal (Cu ∼0.5, Zn ∼4, Pb ∼3 mg/kg) contents. These brines seep outward through the western crater rim and reappear on the other side as streamlets, which form the headwaters of the Banyupahit stream. The Banyupahit first mixes with fresh rivers and thermal springs in the Ijen caldera and then irrigates a coastal agricultural plain which is 30 km from the summit crater. We discuss the downstream composition changes affecting the Banyupahit waters by using stable isotope, chemical and mineralogical data collected from sites along the stream length. The saturation of the stream waters with respect to minerals was evaluated with SOLVEQ and WATEQ4F and compared with the geochemical observations. An aluminous mineralogy (alunogen, pickeringite, tamarugite and kalinite) develops in the upper part of the Banyupahit due to concentration of the headwaters by evaporation. Downstream attenuation of dissolved element concentrations results principally from dilution and from mineral precipitation. The stream pH changes from ∼0 at the source to >4 close to the mouth. The δD and δ18O values and the relative SO4-Cl-F contents of the Banyupahit waters indicate that the tributaries are mostly meteoric. Dissolved SO4 in the acidic stream come only from the crater lake seepages and are not involved later in microbially mediated reactions, as shown by their δ34S and δ18O values. Re-equilibration of the stream SO4 oxygen-isotope composition with H2O from tributaries does not occur. Calcium, SiO2, Al, Fe, K and SO4 behave non-conservatively in the stream waters. Gypsum, silica (amorphous or poorly ordered), a basic aluminum hydroxysulfate (basaluminite?), K-jarosite and amorphous ferric hydroxide may exert a solubility control on these elements along the entire stream length, or in certain stream sections, consistent with the thermochemical model results. Downstream concentration trends and mineral saturation levels suggest that precipitation of Sr-, Pb-rich barite and celestite consume Ba, Sr and Pb, whereas dissolved Cu, Pb and Zn may adsorb onto solid particles, especially after the junctions of the acidic stream with non-acidic rivers. We calculated that significant fluxes of SO4, F, Cl, Al, SiO2, Ti, Mn and Cu may reach the irrigation system, possibly causing serious environmental impacts such as soil acidification and induration.

Removal of nitrate and phosphate using chitosan/Al2O3/Fe3O4 composite nanofibrous adsorbent: Comparison with chitosan/Al2O3/Fe3O4 beads.

PubMed

Bozorgpour, Farahnaz; Ramandi, Hossein Fasih; Jafari, Pooya; Samadi, Saman; Yazd, Shabnam Sharif; Aliabadi, Majid

2016-12-01

In the present study the chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibrous adsorbent was prepared by electrospinning process and its application for the removal of nitrate and phosphate were compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite bead adsorbent. The influence of Al 2 O 3 /Fe 3 O 4 composite content, pH, contact time, nitrate and phosphate initial concentrations and temperature on the nitrate and phosphate sorption using synthesized bead and nanofibrous adsorbents was investigated in a single system. The reusability of chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers after five sorption-desorption cycles were carried out. The Box-Behnken design was used to investigate the interaction effects of adsorbent dosage, nitrate and phosphate initial concentrations on the nitrate and phosphate removal efficiency. The pseudo-second-order kinetic model and known Freundlich and Langmuir isotherm models were used to describe the kinetic and equilibrium data of nitrate and phosphate sorption using chitosan/Al 2 O 3 /Fe 3 O 4 composite beads and nanofibers. The influence of other anions including chloride, fluoride and sulphate on the sorption efficiency of nitrate and phosphate was examined. The obtained results revealed the higher potential of chitosan/Al 2 O 3 /Fe 3 O 4 composite nanofibers for nitrate and phosphate compared with chitosan/Al 2 O 3 /Fe 3 O 4 composite beads. Copyright © 2016 Elsevier B.V. All rights reserved.

Ionic substitution of Mg2+ for Al3+ and Fe3+ with octahedral coordination in hydroxides facilitate precipitation of layered double hydroxides

NASA Astrophysics Data System (ADS)

Paikaray, Susanta; Essilfie-Dughan, Joseph; Hendry, M. Jim

2018-01-01

Precipitation of hydrotalcite-like layered double hydroxides (HT-LDHs) from CO32--SO42--rich acidic and alkaline aqueous media through ionic substitution of Mg2+ for Al3+ + Fe3+ and vice versa was investigated under ambient conditions. Diffractogram, spectroscopic, microprobe, microscopic, and synchrotron techniques were used to examine the mechanisms involved. The cations facilitated rapid precipitation of HT-LDH in alkaline conditions (pH ≥ 8.2) with SO42- and CO32- as the counter charge balancing interlayer anions, while initial formation of Fe3+- and Al3+-hydroxides in acidic conditions (pH ≥ 2.4) with subsequent transformation to MgAlFe-type HT-LDH (pH ≥ 8.2) occurred through substitution of Mg2+ for Al3+ and Fe3+. Substitution of Al3+ and Fe3+ in Mg2+-hydroxides did not yield HT-LDH, while the reverse, i.e., Mg2+ substitution in Al3+ and Fe3+-hydroxides, produced initial poorly ordered amorphous HT-LDH that gained better crystallinity and crystallite size upon neutralization. Linear combination fit analyses of XANES data suggest schwertmannite constituted the predominant Fe-phase until pH ∼3.7 followed by ferrihydrite and eventually HT-LDH after pH ≥ 10; basaluminite and epsomite constituted the predominant Al and Mg phases until pH ∼4.5, after which HT-LDH with minor Al(OH)3 and HT-LDH with brucite, respectively, predominated. The study highlights that Mg2+ substitution in Al- and Fe-precipitates is the governing mechanism for HT-LDH precipitation in oxic environments through neutralization of acidic cationic aqueous residues.

Iron and aluminum solid phase dynamics and carbon storage across a water balance gradient in volcanic soils

NASA Astrophysics Data System (ADS)

Bateman, J. B.; Fendorf, S. E.; Vitousek, P.

2017-12-01

Iron (Fe) and Aluminum (Al) are major components of volcanic soils, and strongly influence the stability of soil carbon (C). The stability of Fe and Al phases is dictated by the redox conditions and pH of soils, respectively. The water balance of a soil, defined as annual precipitation minus evapotranspiration, ultimately controls pH and redox conditions. Consequently, we hypothesize that water balance influences Fe/Al solid phase dynamics in volcanic soils when the climatic regime has persisted on timescales of 20 ky. To test this hypothesis, we collected soils from a naturally occurring water balance gradient on the windward side of Mauna Kea Volcano in Hawaii, across which water balance ranges from -1270 mm/y to +2000 mm/y. Sampling included complete soil profiles, and 30 cm surface soil samples. We determined the solid phases of Fe/Al with selective extractions and total C via combustion. Extracted Fe/Al were then partitioned into operational pools: organically bound, amorphous, crystalline, primary mineral, primary glass, and residual. All soils in the study were acidic, with pH between 3.4 and 6.4. Soil C varied considerably across the gradient, from <1% C to >15% C by weight. Across sites, soil pH, Fe in primary minerals and glasses, and residual Al are negatively correlated with water balance, while soil C, organic Fe and Al, and crystalline Fe correlated positively with water balance. Organically bound Al increases linearly with water balance, while organically bound Fe is uncorrelated with water balance in soils where water balance is negative and is positively correlated with water balance in wetter sites. These results show that soils developing from the same parent material, though under different water balance regimes, range from lightly weathered ash deposits with little C accumulation in the driest regions, to heavily weathered soils composed of crystalline Fe, organic matter, and organically bound Fe/Al in the wettest regions. Al appears to be the primary stabilizer for organic matter in many of these soils, though Fe plays a role when both water availability and soil C are high. The pattern of organic Fe/Al indicate that pH is a stronger controller on C storage in these soils when water balance is low or negative, and that redox reactions become increasingly important as water balance becomes more positive.

Fragipan Horizon Fragmentation in Slaking Experiments with Amendment Materials and Ryegrass Root Tissue Extracts

PubMed Central

Karathanasis, A. D.; Murdock, L. W.; Matocha, C. J.; Grove, J.; Thompson, Y. L.

2014-01-01

Slaking experiments were conducted of fragipan clods immersed in solutions of poultry manure, aerobically digested biosolid waste (ADB), fluidized bed combustion byproduct (FBC), D-H2O, CaCO3, NaF, Na-hexa-metaphosphate, and ryegrass root biomass. The fragipan clods were sampled from the Btx horizon of an Oxyaquic Fragiudalf in Kentucky. Wet sieving aggregate analysis showed significantly better fragmentation in the NaF, Na-hexa-metaphosphate, and ryegrass root solutions with a mean weight diameter range of 15.5–18.8 mm compared to the 44.2–47.9 mm of the poultry manure, ADB, and FBC treatments. Dissolved Si, Al, Fe, and Mn levels released in solution were ambiguous. The poor efficiency of the poultry manure, ADB, and FBC treatments was attributed to their high ionic strength, while the high efficiency of the NaF, Na-hexa-metaphosphate, and rye grass root solutions to their high sodium soluble ratio (SSR). A slaking mechanism is proposed suggesting that aqueous solutions with high SSR penetrate faster into the fragipan capillaries and generate the critical swelling pressure and shearing stress required to rupture the fragipan into several fragments. Additional fragmentation occurs in a followup stage during which potential Si, Al, Fe, and Mn binding agents may be released into solution. Field experiments testing these findings are in progress. PMID:25254233

Effects of electric potential, NaCl, pH and distance between electrodes on efficiency of electrolysis in landfill leachate treatment.

PubMed

Erabee, Iqbal K; Ahsan, Amimul; Jose, Bipin; Arunkumar, T; Sathyamurthy, R; Idrus, Syazwani; Daud, N N Nik

2017-07-03

This study investigated the effects of different parameters on the removal efficiencies of organic and inorganic pollutants in landfill leachate treatment by electrolysis. Different parameters were considered such as the electric potential (e.g., 24, 40 and 60 V), hydraulic retention time (HRT) (e.g., 40, 60, 80, 100 and 120 min), sodium chloride (NaCl) concentration (e.g., 1, 3, 5 and 7%), pH (e.g., 3, 7 and 9), electrodes materials [e.g., aluminum (Al) and iron (Fe)] and distance between electrodes (e.g., 1, 2 and 3 cm). The best operational condition of electrolysis was then recommended. The electric potential of 60 V with HRT of 120 min at 5% of NaCl solution using Al as anode and Fe as cathode (kept at a distance of 3 cm) was the most efficient condition which increased the removal efficiencies of various parameters such as turbidity, salinity, total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and heavy metals (e.g., Zn and Mn). The higher removal percentages of many parameters, especially COD (94%) and Mn (93%) indicated that the electrolysis is an efficient technique for multi-pollutants (e.g., organic, inorganic and heavy metals) removal from the landfill leachate.

Developmental phytotoxicity of metal oxide nanoparticles to Arabidopsis thaliana.

PubMed

Lee, Chang Woo; Mahendra, Shaily; Zodrow, Katherine; Li, Dong; Tsai, Yu-Chang; Braam, Janet; Alvarez, Pedro J J

2010-03-01

Phytotoxicity is an important consideration to understand the potential environmental impacts of manufactured nanomaterials. Here, we report on the effects of four metal oxide nanoparticles, aluminum oxide (nAl(2)O(3)), silicon dioxide (nSiO(2)), magnetite (nFe(3)O(4)), and zinc oxide (nZnO), on the development of Arabidopsis thaliana (Mouse-ear cress). Three toxicity indicators (seed germination, root elongation, and number of leaves) were quantified following exposure to each nanoparticle at three concentrations: 400, 2,000, and 4,000 mg/L. Among these particles, nZnO was most phytotoxic, followed by nFe(3)O(4), nSiO(2), and nAl(2)O(3), which was not toxic. Consequently, nZnO was further studied to discern the importance of particle size and zinc dissolution as toxicity determinants. Soluble zinc concentrations in nanoparticle suspensions were 33-fold lower than the minimum inhibitory concentration of dissolved zinc salt (ZnCl(2)), indicating that zinc dissolution could not solely account for the observed toxicity. Inhibition of seed germination by ZnO depended on particle size, with nanoparticles exerting higher toxicity than larger (micron-sized) particles at equivalent concentrations. Overall, this study shows that direct exposure to nanoparticles significantly contributed to phytotoxicity and underscores the need for eco-responsible disposal of wastes and sludge containing metal oxide nanoparticles.

Sources and fluxes of atmospheric trace elements to the Gulf of Aqaba, Red Sea

NASA Astrophysics Data System (ADS)

Chen, Ying; Paytan, Adina; Chase, Zanna; Measures, Christopher; Beck, Aaron J.; SañUdo-Wilhelmy, Sergio A.; Post, Anton F.

2008-03-01

We present the first comprehensive investigation of the concentrations, fluxes and sources of aerosol trace elements over the Gulf of Aqaba. We found that the mean atmospheric concentrations of crustally derived elements such as Al, Fe and Mn (1081, 683, and 16.7 ng m-3) are about 2-3 times higher than those reported for the neighboring Mediterranean area. This is indicative of the dominance of the mineral dust component in aerosols over the Gulf. Anthropogenic impact was lower in comparison to the more heavily populated areas of the Mediterranean. During the majority of time (69%) the air masses over the Gulf originated from Europe or Mediterranean Sea areas delivering anthropogenic components such as Cu, Cd, Ni, Zn, and P. Airflows derived from North Africa in contrast contained the highest concentrations of Al, Fe, and Sr but generally lower Cu, Cd, Ni, Zn, and P. Relatively high Pb, Ni, and V were found in the local and Arabian airflows suggesting a greater influence of local emission of fuel burning. We used the data and the measured trace metal seawater concentrations to calculate residence times of dissolved trace elements in the upper 50 m surface water of the Gulf (with respect to atmospheric input) and found that the residence times for most elements are in the range of 5-37 years while Cd and V residence times are longer.

Magma storage conditions of historic Plinian eruptions of Volcán de Colima, México

NASA Astrophysics Data System (ADS)

Macias, J.; Arce, J.; Sosa, G.; Gardner, J. E.; Saucedo, R.

2013-12-01

Volcán de Colima has a historical record with major explosive eruptions occurring every ~100 years (1606, 1690, 1818, and 1913) followed by intra-Plinian effusive activity. The 1818 and 1913 Plinian eruptions erupted andesitic magmas (Pl > Opx > Cpx >> Hbl + Fe-Ti oxides + Ap and rare resorbed Ol) with homogeneous bulk compositions (1913; 58.3 × 0.5 wt.% SiO2, 1818; 58.9 × 0.2 wt.% SiO2; Saucedo et al., 2010). Instead, intra-Plinian magmas are devoid of hornblende and have compositions of 59-61 wt. % in silica (Savov et al., 2008). Pre-eruptive temperatures of oxide Fe-Ti pairs in 1818 and 1913 products yielded temperatures of 830×20°C colder than intra-Plinian magmas usually >970°C (Luhr et al., 2002) depending on the mineral phase analyzed. Amphibole in 1818 and 1913 products consists of two populations: a) large xenocrysts, with plag-px-Fe-Ti oxide rims with equilibrium pressures and temperatures of 380 MPa and 950 °C (Ridolfi et al., 2010), and b) microphenocryst with equilibrium pressures and temperatures of 190-280 MPa and 870-910 °C, respectively. Some phenocrysts in the 1818 magma have a high pressure core overgrowth by a low pressure rim. In order to understand the storage conditions of Colima explosive magmas we carried out a set of hydrothermal experiments with a 1818 pumice sample. Experiments were water oversaturated and close to the oxygen fugacity of the NNO buffer. Experiments show that amphibole is stable at pressures greater than 75 MPa at 850°C, and greater than 100 MPa at 925°C. For the same range of temperature, plagioclase is stable at pressures below ~210 MPa and 100 MPa, respectively. Experimental plagioclase and experimental glass were analyzed and compared to those from the natural sample, yielding an approximate storage pressure of 210 MPa. This pressure is confirmed by the chemical equilibrium of microphenocrystic amphibole of the natural sample. Given the nearly equivalent composition of the most recent Plinain magmas is possible to assume the storage pressure of the 1913 Plinian magma. Previous studies found ~6 wt. % of water dissolved in orthopyroxene melt inclusions in the 1913 magma (Luhr, 2006). That water concentration would be dissolved in a melt with the 1913 composition at ~200 MPa (Papale et al., 2006). Equilibrium pressure of 1913 amphiboles, microphenocrysts, and xenocrysts (280-380 MPa), overall, are deeper than those of the 1818 suggesting a deeper 1913 reservoir. Therefore, the 1818 amphiboles with lower pressure rims found in the natural sample could have been inherited from a previous magma (>280 MPa) seated at similar depths than the 1913 reservoir from which were taped. Luhr, J.F., 2002 JVGR 117, 169-194. Ridolfi, F., Renzulli, A., Puerini, M., 2010. Cont Min Petrol 160, 45-66. R. Saucedo, J.L. Macías, J.C. Gavilanes, J.L. Arce, J.C. Komorowski, J.E. Gardner, G. Valdez-Moreno JVGR 191, 149-166 Savov, I.P., Luhr, J.F., Navarro-Ochoa, C., 2008. JVGR 174: 241-256.

Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe

NASA Astrophysics Data System (ADS)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-08-01

The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

Interactions between magnetite and humic substances: redox reactions and dissolution processes.

PubMed

Sundman, Anneli; Byrne, James M; Bauer, Iris; Menguy, Nicolas; Kappler, Andreas

2017-10-19

Humic substances (HS) are redox-active compounds that are ubiquitous in the environment and can serve as electron shuttles during microbial Fe(III) reduction thus reducing a variety of Fe(III) minerals. However, not much is known about redox reactions between HS and the mixed-valent mineral magnetite (Fe 3 O 4 ) that can potentially lead to changes in Fe(II)/Fe(III) stoichiometry and even dissolve the magnetite. To address this knowledge gap, we incubated non-reduced (native) and reduced HS with four types of magnetite that varied in particle size and solid-phase Fe(II)/Fe(III) stoichiometry. We followed dissolved and solid-phase Fe(II) and Fe(III) concentrations over time to quantify redox reactions between HS and magnetite. Magnetite redox reactions and dissolution processes with HS varied depending on the initial magnetite and HS properties. The interaction between biogenic magnetite and reduced HS resulted in dissolution of the solid magnetite mineral, as well as an overall reduction of the magnetite. In contrast, a slight oxidation and no dissolution was observed when native and reduced HS interacted with 500 nm magnetite. This variability in the solubility and electron accepting and donating capacity of the different types of magnetite is likely an effect of differences in their reduction potential that is correlated to the magnetite Fe(II)/Fe(III) stoichiometry, particle size, and crystallinity. Our study suggests that redox-active HS play an important role for Fe redox speciation within minerals such as magnetite and thereby influence the reactivity of these Fe minerals and their role in biogeochemical Fe cycling. Furthermore, such processes are also likely to have an effect on the fate of other elements bound to the surface of Fe minerals.

Deconvolution of trace element (As, Cr, Mo, Th, U) sources and pathways to surface waters of a gold mining-influenced watershed.

PubMed

Grosbois, C; Schäfer, J; Bril, H; Blanc, G; Bossy, A

2009-03-01

The Upper Isle River (SW France) drains the second most productive gold-mining district of France. A high resolution survey during one hydrological year of As, Cl(-), Cr, Fe, Mn, Mo, SO(4)(2-), Th and U dissolved concentrations in surface water aimed to better understand pathways of trace element export to the river system downstream from the mining district. Dissolved concentrations of As (up to 35000 ng/L) and Mo (up to 292 ng/L) were about 3-fold higher than the regional dissolved background and showed a negative logarithmic relation with discharge. Dissolved concentrations of Cr (up to 483 ng/L), Th (up to 48 ng/L) and U (up to 184 ng/L) increased with discharge. Geochemical relationships between molar ratios in surface water, geochemical background as well as rain- and groundwater data were combined. The contrasting behavior of distinct element groups was explained by a scenario involving three seasonal components: (i) The high flow component is poorly concentrated in As and Mo but highly concentrated in Cr, Th, U. This has been attributed to diffuse sources such as water-soil interactions, atmospheric inputs, bedrock and bed sediment weathering. Although this component probably also includes a contribution by weathering of sulfide veins, this signal is masked by dilution. (ii) One low flow component presents high SO(4)(2-), Fe, As and Mo and moderate Cr, Th and U concentrations. This component has been attributed to point sources such as mine gallery effluents, mining waste weathering and groundwater inputs from natural and/or mining-induced sulfide oxidation in the ore deposit. (iii) A second low flow component showing high As plus Mo concentrations associated with very low SO(4)(2-), Fe, Cr, Th and U concentrations, probably reflects trace element scavenging by ferric oxyhydroxide formation in the adjacent aquifer. This is supported by the decrease of Fe, Cr, Th and U in surface waters. Flux estimates suggest contrasting element-specific impacts on annual dissolved fluxes. Runoff may account for the major part of annual dissolved As, Mo, Th and U fluxes in the Upper Isle River. Inputs related to sulfide oxidation respectively contributed approximately 30% and approximately 24% to annual As and Mo fluxes. The formation of ferric oxyhydroxides strongly retained Cr, Th and U during the low flow, limiting their dissolved concentrations in surface waters. If this process may eventually decrease As mobility, its impact on dissolved As concentrations in surface water may be limited or/and counterbalanced by As release during sulfide oxidation.

Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter.

PubMed

Chen, Chunmei; Thompson, Aaron

2018-01-16

Abiotic Fe(II) oxidation by O 2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al 2 O 3 ) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO 2 at pH 6. We tracked Fe dynamics by adding 57 Fe(II) to 56 Fe-labeled goethite and γ-Al 2 O 3 and characterized the resulting solids using 57 Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO 2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II) (aq) alone, both goethite and γ-Al 2 O 3 surfaces increased Fe(II) oxidation rates regardless of pO 2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al 2 O 3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II) aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO 2 , and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al 2 O 3 , but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.

Strength anomaly in B2 FeAl single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshimi, K.; Hanada, S.; Yoo, M.H.

1994-12-31

Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). Themore » orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.« less

Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

NASA Astrophysics Data System (ADS)

Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

2015-10-01

A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

Enhanced photoelectrocatalytic performance of α-Fe2O3 thin films by surface plasmon resonance of Au nanoparticles coupled with surface passivation by atom layer deposition of Al2O3.

PubMed

Liu, Yuting; Xu, Zhen; Yin, Min; Fan, Haowen; Cheng, Weijie; Lu, Linfeng; Song, Ye; Ma, Jing; Zhu, Xufei

2015-12-01

The short lifetime of photogenerated charge carriers of hematite (α-Fe2O3) thin films strongly hindered the PEC performances. Herein, α-Fe2O3 thin films with surface nanowire were synthesized by electrodeposition and post annealing method for photoelectrocatalytic (PEC) water splitting. The thickness of the α-Fe2O3 films can be precisely controlled by adjusting the duration of the electrodeposition. The Au nanoparticles (NPs) and Al2O3 shell by atom layer deposition were further introduced to modify the photoelectrodes. Different constructions were made with different deposition orders of Au and Al2O3 on Fe2O3 films. The Fe2O3-Au-Al2O3 construction shows the best PEC performance with 1.78 times enhancement by localized surface plasmon resonance (LSPR) of NPs in conjunction with surface passivation of Al2O3 shells. Numerical simulation was carried out to investigate the promotion mechanisms. The high PEC performance for Fe2O3-Au-Al2O3 construction electrode could be attributed to the Al2O3 intensified LSPR, effective surface passivation by Al2O3 coating, and the efficient charge transfer due to the Fe2O3-Au Schottky junctions.

Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

NASA Astrophysics Data System (ADS)

Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

2017-01-01

Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

PubMed

Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

2016-04-01

In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited.

Behavior of tritium permeation induced by water corrosion of alpha iron around room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otsuka, T.; Hashizume, K.

2015-03-15

Tritium (T) permeation leakage to surroundings is a great safety concern in fission and fusion reactor systems. T permeation potentially occurs from T contaminated water through cooling tubes or storage tank made of metals which dissolve some T evolved by water corrosion. In order to understand behaviors of hydrogen uptake and permeation in pure α-iron (αFe) during water corrosion around room temperature, hydrogen permeation experiments for an αFe membrane have been conducted by means of tritium tracer techniques. The present study suggests that hydrogen produced by water corrosion of αFe is trapped in product oxide layers to delay hydrogen uptakemore » in αFe for a moment. However, the oxide layers do not work as a sufficient barrier for hydrogen uptake. Some of hydrogen dissolved in αFe normally diffuses and permeates through the bulk in the early stage of permeation. In a later stage, hydrogen permeation could be apparently stopped by the disappearance of concentration difference of tritium. Hydrogen partial pressure at the water/αFe interface could be ranged from 0.7 to 9.5 kPa around room temperature.« less

Structure of the orthorhombic form of Mn(2)Al(7), Fe(2)Al(7), and (Mn(0.7)Fe(0.3))(2)Al(7) that by twinning produces grains with decagonal point-group symmetry.

PubMed

Pauling, L

1988-04-01

Analysis of electron diffraction photographs of grains of Mn(2)Al(7), Fe(2)Al(7), and (Mn(0.7)Fe(0.3))(2)Al(7) leads to the conclusion that they are 5-fold twins of a 1664-atom orthorhombic crystal with a = 32.86 A, b = 31.23 A, and c = 24.80 A and with 16 icosahedral clusters of 104 atoms in positions shifted by small amounts from those of the cubic beta-tungsten structure.

Structure of the orthorhombic form of Mn2Al7, Fe2Al7, and (Mn0.7Fe0.3)2Al7 that by twinning produces grains with decagonal point-group symmetry

PubMed Central

Pauling, Linus

1988-01-01

Analysis of electron diffraction photographs of grains of Mn2Al7, Fe2Al7, and (Mn0.7Fe0.3)2Al7 leads to the conclusion that they are 5-fold twins of a 1664-atom orthorhombic crystal with a = 32.86 Å, b = 31.23 Å, and c = 24.80 Å and with 16 icosahedral clusters of 104 atoms in positions shifted by small amounts from those of the cubic β-tungsten structure. PMID:16593921

The environmental impacts of one of the largest tailing dam failures worldwide.

PubMed

Hatje, Vanessa; Pedreira, Rodrigo M A; de Rezende, Carlos Eduardo; Schettini, Carlos Augusto França; de Souza, Gabriel Cotrim; Marin, Danieli Canaver; Hackspacher, Peter Christian

2017-09-06

The impacts of the SAMARCO iron tailing spill along more than 650 km, between the dam and the plume of the Doce River in the Atlantic, were assessed by the determination of toxic metals. The tailing spill caused a substantial increase in suspended sediment loads (up to 33,000 mg L -1 ), in addition to large depositions of waste along the Doce basin. The highest estimated transport of dissolved metals was observed for Fe (58.8 μg s -1 ), Ba (37.9 μg s -1 ) and Al (25.0 μg s -1 ). Sediments reached the highest enrichment factors (EFs) for Hg (4,234), Co (133), Fe (43), and Ni (16), whereas As (55), Ba (64), Cr (16), Cu (17), Mn (41), Pb (38) and Zn (82) highest EFs were observed for suspended particulate matter (SPM). Iron, As, Hg, Mn exceeded sediment quality guidelines. Therefore, the risk of occurrence of adverse effects is highly possible, not only due to the dam failure, but also due to the Fe mining and the artisan Au mining. Heavy rain episodes will likely cause enhanced erosion, remobilization, and transport of contaminated particles, sustaining high inputs of SPM and metals for the years to come and threatening the ecosystem services.

Low-Energy Bead-Mill Dispersion of Agglomerated Core-Shell α-Fe/Al₂O₃ and α″-Fe₁₆N₂/Al₂O₃ Ferromagnetic Nanoparticles in Toluene.

PubMed

Zulhijah, Rizka; Suhendi, Asep; Yoshimi, Kazuki; Kartikowati, Christina Wahyu; Ogi, Takashi; Iwaki, Toru; Okuyama, Kikuo

2015-06-09

Magnetic materials such as α″-Fe16N2 and α-Fe, which have the largest magnetic moment as hard and soft magnetic materials, are difficult to produce as single domain magnetic nanoparticles (MNPs) because of quasistable state and high reactivity, respectively. The present work reports dispersion of agglomerated plasma-synthesized core-shell α″-Fe16N2/Al2O3 and α-Fe/Al2O3 in toluene by a new bead-mill with very fine beads to prepare single domain MNPs. As a result, optimization of the experimental conditions (bead size, rotation speed, and dispersion time) enables the break-up of agglomerated particles into primary particles without destroying the particle structure. Slight deviation from the optimum conditions, i.e., lower or higher dispersion energy, gives undispersed or broken particles due to fragile core-shell structure against stress or impact force of beads. The dispersibility of α″-Fe16N2/Al2O3 is more restricted than that of α-Fe/Al2O3, because of the preparation conditions. Especially for α″-Fe16N2/Al2O3, no change on crystallinity (98% α″-Fe16N2) or magnetization saturation after dispersion was observed, showing that this method is appropriate to disperse α″-Fe16N2/Al2O3 MNPs. A different magnetic hysteresis behavior is observed for well-dispersed α″-Fe16N2/Al2O3 MNPs, and the magnetic coercivity of these NPs is constricted when the magnetic field close to zero due to magnetic dipole coupling among dispersed α″-Fe16N2 MNPs.

On local structural changes in lizardite-1 T: {Si4+/Al3+}, {Si4+/Fe3+}, [Mg2+/Al3+], [Mg2+/Fe3+] substitutions

NASA Astrophysics Data System (ADS)

Scholtzová, Eva; Smrčok, Ľubomír

2005-09-01

Geometrical changes induced by cation substitutions {Si4+/Al3+}[Mg2+/Al3+], {2Si4+/2Al3+} [2Mg2+/2Al3+], {Si4+/Fe3+} [Mg2+/Al3+] or [Mg2+/Fe3+], where {} and [] indicate tetrahedral and octahedral sheet in lizardite 1 T, are studied by ab-initio quantum chemistry calculations. The majority of the models are based on the chemical compositions reported for various lizardite polytypes with the amount of Al in the tetrahedral sheets reported to vary from 3.5% to 8% in the 1 T and 2 H 1, up to 30% in the 2 H 2 polytype. Si4+ by Fe3+ substitution in the tetrahedral sheet with an Al3+ (Fe3+) in the role of a charge compensating cation in the octahedral sheet is also examined. The cation substitutions result in the geometrical changes in the tetrahedral sheets, while the octahedral sheets remain almost untouched. Substituted tetrahedra are tilted and their basal oxygens pushed down from the plane of basal oxygens. Ditrigonal deformation of tetrahedral sheets depends on the substituting cation and the degree of substitution.

Different Effects of Al Substitution for Mn or Fe on the Structure and Electrochemical Properties of Na0.67Mn0.5Fe0.5O2 as a Sodium Ion Battery Cathode Material.

PubMed

Wang, Huibo; Gao, Rui; Li, Zhengyao; Sun, Limei; Hu, Zhongbo; Liu, Xiangfeng

2018-05-07

P2-type layered oxides based on the elements Fe and Mn have attracted great interest as sodium ion battery (SIB) cathode materials owing to their inexpensive metal constituents and high specific capacity. However, they suffer from rapid capacity fading and complicated phase transformations. In this study, we modulate the crystal structure and optimize the electrochemical performances of Na 0.67 Mn 0.5 Fe 0.5 O 2 by Al doping for Mn or Fe, respectively, and the roles of Al in the enhancement of the rate capability and cycling performance are unraveled. (1) The substitution of Al for Mn or Fe decreases the lattice parameters a and c but enlarges d spacing and lengthens Na-O bonds, which enhances Na + diffusion and rate capability especially for Na 0.67 Mn 0.5 Fe 0.47 Al 0.03 O 2 . (2) Al doping reduces the thickness of TMO 2 and strengthens TM-O/O-O bonding. This enhances the layered structure stability and the capacity retention. (3) Al doping mitigates Mn 3+ and Jahn-Teller distortion, mitigating the irreversible phase transition. (4) Al doping also alleviates the lattice volume variation and the structure strain. This further improves the stability of the layered structure and the cycling performances particularly in the case of Al doping for Fe. The in-depth insights into the roles of Al substitution might be also useful for designing high-performance cathode materials for SIBs through appropriate lattice doping.

High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering.

PubMed

Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

2016-11-30

In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al 15 (Fe,Cr)₃Si₂ or α-Al 15 (Fe,Mn)₃Si₂ phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5.

High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering

PubMed Central

Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

2016-01-01

In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al15(Fe,Cr)3Si2 or α-Al15(Fe,Mn)3Si2 phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5. PMID:28774094

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloysmore » with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). Finally, the results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.« less

Hydrogen permeation in FeCrAl alloys for LWR cladding application

NASA Astrophysics Data System (ADS)

Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

2015-06-01

FeCrAl, an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In this study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. The total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

Handbook of the Materials Properties of FeCrAl Alloys For Nuclear Power Production Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, Yukinori; Snead, Mary A.; Field, Kevin G.

FeCrAl alloys are a class of alloys that have seen increased interest for nuclear power applications including as accident tolerant fuel cladding, structural components for fast fission reactors, and as first wall and blanket structures for fusion reactors. FeCrAl alloys are under consideration for these applications due to their inherent corrosion resistance, stress corrosion cracking resistance, radiation-induced swelling resistance, and high temperature oxidation resistance. A substantial amount of research effort has been completed to design, develop, and begin commercial scaling of FeCrAl alloys for nuclear power applications over the past half a century. These efforts have led to the developmentmore » of an extensive database on material properties and process knowledge for FeCrAl alloys but not within a consolidated format. The following report is the first edition of a materials handbook to consolidate the state-of-the-art on FeCrAl alloys for nuclear power applications. This centralized database focuses solely on wrought FeCrAl alloys, oxide dispersion strengthened alloys, although discussed in brief, are not covered. Where appropriate, recommendations for applications of the data is provided and current knowledge gaps are identified.« less

Metal(loid)s behaviour in soils amended with nano zero-valent iron as a function of pH and time.

PubMed

Vítková, Martina; Rákosová, Simona; Michálková, Zuzana; Komárek, Michael

2017-01-15

Nano zero-valent iron (nZVI) is currently investigated as a stabilising amendment for contaminated soils. The effect of pH (4-8) and time (48 and 192 h) on the behaviour of nZVI-treated Pb-Zn and As-contaminated soil samples was assessed. Additionally, soil leachates were subsequently used to study the direct interaction between soil solution components and nZVI particles in terms of mineralogical changes and contaminant retention. A typical U-shaped leaching trend as a function of pH was observed for Cd, Pb and Zn, while As was released predominantly under alkaline conditions. Oxidising conditions prevailed, so pH was the key controlling parameter rather than redox conditions. Generally, longer contact time resulted in increased soluble concentrations of metal(loid)s. However, the stabilisation effect of nZVI was only observed after the direct soil leachate-nZVI interactions, showing enhanced redox and sorption processes for the studied metals. A significant decrease of dissolved As concentrations was observed for both experimental soils, but with different efficiencies depending on neutralisation capacity, organic matter content or solid fractionation of As related to the origin of the soils. Scorodite (FeAsO 4 ·2H 2 O) was predicted as a potential solubility-controlling mineral phase for As. Sorption of metal(loid)s onto secondary Fe- and Al-(oxyhydr)oxides (predicted to precipitate at pH > 5) represents an important scavenger mechanism. Moreover, transmission electron microscopy confirmed the retention of Zn and Pb under near-neutral and alkaline conditions by newly formed Fe oxides or aluminosilicates. This study shows that the efficiency of nZVI application strongly depends not only on soil pH-Eh conditions and contaminant type, but also on the presence of organic matter and other compounds such as Al/Fe/Mn oxyhydroxides and clay minerals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigation on the Microstructure and Ductility-Dip Cracking Susceptibility of the Butt Weld Welded with ENiCrFe-7 Nickel-Base Alloy-Covered Electrodes

NASA Astrophysics Data System (ADS)

Qin, Renyao; Wang, Huang; He, Guo

2015-03-01

The weld metal of the ENiCrFe-7 nickel-based alloy-covered electrodes was investigated in terms of the microstructure, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility. Besides the dendritic gamma-Ni(Cr,Fe) phase, several types of precipitates dispersed on the austenitic matrix were observed, which were determined to be the Nb-rich MC-type carbides with "Chinese script" morphology and size of approximately 3 to 10 µm, the Mn-rich MO-type oxides with size of approximately 1 to 2 µm, and the spherical Al/Ti-rich oxides with size of less than 1 µm. The discontinuous Cr-rich M23C6-type carbides predominantly precipitate on the grain boundaries, which tend to coarsen during reheating but begin to dissolve above approximately 1273 K (1000 °C). The threshold strain for DDC at each temperature tested shows a certain degree of correlation with the grain boundary carbides. The DDC susceptibility increases sharply as the carbides coarsen in the temperature range of 973 K to 1223 K (700 °C to 950 °C). The growth and dissolution of the carbides during the welding heat cycles deteriorate the grain boundaries and increase the DDC susceptibility. The weld metal exhibits the minimum threshold strain of approximately 2.0 pct at 1323 K (1050 °C) and the DTR less than 873 K (600 °C), suggesting that the ENiCrFe-7—covered electrode has less DDC susceptibility than the ERNiCrFe-7 bare electrode but is comparable with the ERNiCrFe-7A.

Dissolved and colloidal trace elements in the Mississippi River Delta outflow after Hurricanes Katrina and Rita

USGS Publications Warehouse

Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

2012-01-01

The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn–O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02–0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity of the Fe in estuarine systems.

Dissolved and colloidal trace elements in the Mississippi River delta outflow after Hurricanes Katrina and Rita

NASA Astrophysics Data System (ADS)

Shim, Moo-Joon; Swarzenski, Peter W.; Shiller, Alan M.

2012-07-01

The Mississippi River delta outflow region is periodically disturbed by tropical weather systems including major hurricanes, which can terminate seasonal bottom water hypoxia and cause the resuspension of shelf bottom sediments which could result in the injection of trace elements into the water column. In the summer of 2005, Hurricanes Katrina and Rita passed over the Louisiana Shelf within a month of each other. Three weeks after Rita, we collected water samples in the Mississippi River delta outflow, examining the distributions of trace elements to study the effect of Hurricanes Katrina and Rita. We observed limited stratification on the shelf and bottom waters that were no longer hypoxic. This resulted, for instance, in bottom water dissolved Mn being lower than is typically observed during hypoxia, but with concentrations still compatible with Mn-O2 trends previously reported. Interestingly, for no element were we able to identify an obvious effect of sediment resuspension on its distribution. In general, elemental distributions were compatible with previous observations in the Mississippi outflow system. Co and Re, which have not been reported for this system previously, showed behavior consistent with other systems: input for Co likely from desorption and conservative mixing for Re. For Cs, an element for which there is little information regarding its estuarine behavior, conservative mixing was also observed. Our filtration method, which allowed us to distinguish the dissolved (<0.02 μm) from colloidal (0.02-0.45 μm) phase, revealed significant colloidal fractions for Fe and Zn, only. For Fe, the colloidal phase was the dominant fraction and was rapidly removed at low salinity. Dissolved Fe, in contrast, persisted out to mid-salinities, being removed in a similar fashion to nitrate. This ability to distinguish the smaller Fe (likely dominantly organically complexed) from larger colloidal suspensates may be useful in better interpreting the bioavailablity of the Fe in estuarine systems.

Meta-omic signatures of microbial metal and nitrogen cycling in marine oxygen minimum zones

PubMed Central

Glass, Jennifer B.; Kretz, Cecilia B.; Ganesh, Sangita; Ranjan, Piyush; Seston, Sherry L.; Buck, Kristen N.; Landing, William M.; Morton, Peter L.; Moffett, James W.; Giovannoni, Stephen J.; Vergin, Kevin L.; Stewart, Frank J.

2015-01-01

Iron (Fe) and copper (Cu) are essential cofactors for microbial metalloenzymes, but little is known about the metalloenyzme inventory of anaerobic marine microbial communities despite their importance to the nitrogen cycle. We compared dissolved O2, NO3−, NO2−, Fe and Cu concentrations with nucleic acid sequences encoding Fe and Cu-binding proteins in 21 metagenomes and 9 metatranscriptomes from Eastern Tropical North and South Pacific oxygen minimum zones and 7 metagenomes from the Bermuda Atlantic Time-series Station. Dissolved Fe concentrations increased sharply at upper oxic-anoxic transition zones, with the highest Fe:Cu molar ratio (1.8) occurring at the anoxic core of the Eastern Tropical North Pacific oxygen minimum zone and matching the predicted maximum ratio based on data from diverse ocean sites. The relative abundance of genes encoding Fe-binding proteins was negatively correlated with O2, driven by significant increases in genes encoding Fe-proteins involved in dissimilatory nitrogen metabolisms under anoxia. Transcripts encoding cytochrome c oxidase, the Fe- and Cu-containing terminal reductase in aerobic respiration, were positively correlated with O2 content. A comparison of the taxonomy of genes encoding Fe- and Cu-binding vs. bulk proteins in OMZs revealed that Planctomycetes represented a higher percentage of Fe genes while Thaumarchaeota represented a higher percentage of Cu genes, particularly at oxyclines. These results are broadly consistent with higher relative abundance of genes encoding Fe-proteins in the genome of a marine planctomycete vs. higher relative abundance of genes encoding Cu-proteins in the genome of a marine thaumarchaeote. These findings highlight the importance of metalloenzymes for microbial processes in oxygen minimum zones and suggest preferential Cu use in oxic habitats with Cu > Fe vs. preferential Fe use in anoxic niches with Fe > Cu. PMID:26441925

Dissolved iron and iron(II) distributions beneath the pack ice in the East Antarctic (120°E) during the winter/spring transition

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; van der Merwe, Pier; Chever, Fanny; Cullen, Jay T.; Lannuzel, Delphine; Bowie, Andrew R.

2016-09-01

Distributions of dissolved iron (dFe) and its reduced form, Fe(II), to a depth of 1000 m were investigated under the seasonal pack ice off East Antarctica during the Sea Ice Physics and Ecosystem experiment (SIPEX-2) sea-ice voyage in September-October 2012. Concentrations of dFe were elevated up to five-fold relative to Southern Ocean background concentrations and were spatially variable. The mean dFe concentration was 0.44±0.4 nM, with a range from 0.09 to 3.05 nM. Profiles of dFe were more variable within and among stations than were macronutrients, suggesting that coupling between these biologically-essential elements was weak at the time of the study. Brine rejection and drainage from sea ice are estimated to be the dominant contributors to elevated dFe concentrations in the mixed layer, but mass budget considerations indicate that estimated dFe fluxes from brine input alone are insufficient to account for all observed dFe. Melting icebergs and shelf sediments are suspected to provide the additional dFe. Fe(II) was mostly below the detection limit but elevated at depth near the continental shelf, implying that benthic processes are a source of reduced Fe in bottom waters. The data indicate that dFe builds up under the seasonal sea-ice cover during winter and that reduction of Fe may be hampered in early spring by several factors such as lack of electron donors, low biological productivity and inadequate light below the sea ice. The accumulated dFe pool in the mixed layer is expected to contribute to the formation of the spring bloom as the ice retreats.

Meta-omic signatures of microbial metal and nitrogen cycling in marine oxygen minimum zones.

PubMed

Glass, Jennifer B; Kretz, Cecilia B; Ganesh, Sangita; Ranjan, Piyush; Seston, Sherry L; Buck, Kristen N; Landing, William M; Morton, Peter L; Moffett, James W; Giovannoni, Stephen J; Vergin, Kevin L; Stewart, Frank J

2015-01-01

Iron (Fe) and copper (Cu) are essential cofactors for microbial metalloenzymes, but little is known about the metalloenyzme inventory of anaerobic marine microbial communities despite their importance to the nitrogen cycle. We compared dissolved O2, NO[Formula: see text], NO[Formula: see text], Fe and Cu concentrations with nucleic acid sequences encoding Fe and Cu-binding proteins in 21 metagenomes and 9 metatranscriptomes from Eastern Tropical North and South Pacific oxygen minimum zones and 7 metagenomes from the Bermuda Atlantic Time-series Station. Dissolved Fe concentrations increased sharply at upper oxic-anoxic transition zones, with the highest Fe:Cu molar ratio (1.8) occurring at the anoxic core of the Eastern Tropical North Pacific oxygen minimum zone and matching the predicted maximum ratio based on data from diverse ocean sites. The relative abundance of genes encoding Fe-binding proteins was negatively correlated with O2, driven by significant increases in genes encoding Fe-proteins involved in dissimilatory nitrogen metabolisms under anoxia. Transcripts encoding cytochrome c oxidase, the Fe- and Cu-containing terminal reductase in aerobic respiration, were positively correlated with O2 content. A comparison of the taxonomy of genes encoding Fe- and Cu-binding vs. bulk proteins in OMZs revealed that Planctomycetes represented a higher percentage of Fe genes while Thaumarchaeota represented a higher percentage of Cu genes, particularly at oxyclines. These results are broadly consistent with higher relative abundance of genes encoding Fe-proteins in the genome of a marine planctomycete vs. higher relative abundance of genes encoding Cu-proteins in the genome of a marine thaumarchaeote. These findings highlight the importance of metalloenzymes for microbial processes in oxygen minimum zones and suggest preferential Cu use in oxic habitats with Cu > Fe vs. preferential Fe use in anoxic niches with Fe > Cu.

Estimation of the degree of soil P saturation from Brazilian Mehlich-1 P data and field investigations on P losses from agricultural sites in Minas Gerais.

PubMed

Fischer, P; Pöthig, R; Gücker, B; Venohr, M

The degree of phosphorus saturation (DPS) of agricultural soils is studied worldwide for risk assessment of phosphorus (P) losses. In previous studies, DPS could be reliably estimated from water-soluble P (WSP) for European and Brazilian soils. In the present study, we correlated measured WSP and Mehlich-1 P (M1P) from soils of Minas Gerais (MG) and Pernambuco (PE) (R(2) = 0.94, n = 59) to create a DPS map from monitoring data. The resulting DPS map showed high spatial variability and low values of DPS (54 ± 22%, mean and standard deviation; n = 1,827). Measured soil DPS values amounted to 63 ± 14% and resulted in relatively low dissolved P concentrations measured in a surface runoff study in MG. However, fertilizer grains on the soil surface led to high WSP values (>30 mg/kg) indicating high risks of dissolved P losses. We suppose that small Oxisol particles with Fe and Al hydroxides sorbed most of the dissolved fertilizer P in runoff so that P was mainly exported in particulate form. In soils with lower contents of P sorption and binding partners, e.g. Entisols in PE, this effect may be less dominant. Consequently, superficial fertilizer effects have to be considered in addition to DPS in risk assessment of P losses from agricultural areas in Brazil.

Dependence of catalytic properties of Al/Fe2O3 thermites on morphology of Fe2O3 particles in combustion reactions

NASA Astrophysics Data System (ADS)

Zhao, Ningning; He, Cuicui; Liu, Jianbing; Gong, Hujun; An, Ting; Xu, Huixiang; Zhao, Fengqi; Hu, Rongzu; Ma, Haixia; Zhang, Jinzhong

2014-11-01

Three Fe2O3 particle samples with the same crystal structure but different morphologies were prepared by the hydrothermal method and then combined with Al nanoparticles to produce Al/Fe2O3 thermites using ultrasonic mixing. The properties of Fe2O3 and Al/Fe2O3 were studied using a combination of experimental techniques including scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The influences of the three Al/Fe2O3 thermites on the combustion properties of the AP/HTPB (ammonium perchlorate/hydroxyl-terminated polybutadiene) composite propellant were investigated in comparison to those of Fe2O3. The results show that the Al/Fe2O3 thermites are better than Fe2O3 in enhancing the combustion performance of AP/HTPB. Furthermore, the surface area, which depends on size and mophology, of Fe2O3 particles was found to play a vital role in improving the burning rate of the thermites-containing propellant formulation, with the smallest particles with the largest surface-to-volume (S/V) ratio performing the best. The enhanced catalytic property of the granular-shape Fe2O3 and the corresponding thermite is attributed to the large specific surface area of Fe2O3. The different thermal behaviors of these three superthemites were supposed to be attributed to the surface site of Fe2O3 particles. This work provides a better understanding on the catalytic properties of thermites that are important for combustion applications.

The Dart estuary, Devon, UK: a case study of chemical dynamics and pollutant mobility

NASA Astrophysics Data System (ADS)

Schuwerack, P.-M. M.; Neal, M.; Neal, C.

2007-01-01

Water, sediments and gill and digestive gland tissues of adult common shore crab (Carcinus maenas), collected at Noss Marina, Sandquay (Britannia Royal Naval College), the Dartmouth Pier, Warfleet Cove and Sugary Cove in the Dart estuary, Devon, UK, were analysed for major, minor and trace elements in spring 2004. Total acid-available measurements analysed included the truly dissolved component and acid-available sediments. Trace metal concentrations are associated largely with particulate and micro-particulate/colloidal phases, the latter being able to pass through standard filter papers. Wide ranges of chemical concentrations were found in the water, sediments and tissues at all the locations. In the water column, 48% of the variance is linked to the sea-salt component (Cl, Na, K, Ca, Mg, B, Li and Sr) and the sediment-associated acid-available fractions are linked to Fe-rich lithogenous materials (Ba, Co, Cu, Fe, Mn, V and Zn). In the sediments, trace elements of Cd, Co, Cr, Fe, Pb, Mn, Ni and V are correlated with the sea salts and associated with the fraction of fine sediments within the total sediment. In the gills and the digestive gland tissues of crabs, high concentrations of Al, Cu and Fe are found and there are correlations between acid-available trace metals of Cu, Cr, Fe, Mn, Ni, Sr and Zn. The relationships between trace metal contaminants, their site-specific concentrations, their temporal and spatial variability and the effects of human activities, such as moorland/agriculture with historic mining and recreational activities in the lower Dart estuary, are discussed.

Synthesis and structural characterization of ferrous trioctahedral smectites: Implications for clay mineral genesis and detectability on Mars

NASA Astrophysics Data System (ADS)

Chemtob, Steven M.; Nickerson, Ryan D.; Morris, Richard V.; Agresti, David G.; Catalano, Jeffrey G.

2015-06-01

Widespread detections of phyllosilicates in Noachian terrains on Mars imply a history of near-surface fluid-rock interaction. Ferrous trioctahedral smectites are thermodynamically predicted products of basalt weathering on early Mars, but to date only Fe3+-bearing dioctahedral smectites have been identified from orbital observations. In general, the physicochemical properties of ferrous smectites are poorly studied because they are susceptible to air oxidation. In this study, eight Fe2+-bearing smectites were synthesized from Fe2+-Mg-Al silicate gels at 200°C under anoxic conditions. Samples were characterized by inductively coupled plasma optical emission spectrometry, powder X-ray diffraction, Fe K-edge X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy, and visible/near-infrared (VNIR) reflectance spectroscopy. The range of redox states was Fe3+/ΣFe = 0 to 0.06 ± 0.01 as determined by both XAS and, for short integration times, Mössbauer. The smectites have 060 distances (d(060)) between 1.53 and 1.56 Å, indicating a trioctahedral structure. d(060) and XAS-derived interatomic Fe-(Fe,Mg,Al) distance scaled with Fe content. Smectite VNIR spectra feature OH/H2O absorption bands at 1.4 and 1.9 µm, (Fe2+,Mg,Al)3-OH stretching bands near 1.4 µm, and Fe2+Fe2+Fe2+-OH, MgMgMg-OH, AlAl(Mg,Fe2+)-OH, and AlAl-OH combination bands at 2.36 µm, 2.32 µm 2.25 µm, and 2.20 µm, respectively. The spectra for ferrous saponites are distinct from those for dioctahedral ferric smectites, permitting their differentiation from orbital observations. X-ray diffraction patterns for synthetic high-Mg ferrosaponite and high-Mg ferrian saponite are both consistent with the Sheepbed saponite detected by the chemistry and mineralogy (CheMin) instrument at Gale Crater, Mars, suggesting that anoxic basalt alteration was a viable pathway for clay mineral formation on early Mars.

Dissolved and particulate 230Th-232Th in the Central Equatorial Pacific Ocean: Evidence for far-field transport of the East Pacific Rise hydrothermal plume

NASA Astrophysics Data System (ADS)

Lopez, Grecia I.; Marcantonio, Franco; Lyle, Mitch; Lynch-Stieglitz, Jean

2015-12-01

We assess the distribution of 230Th and 232Th along a latitudinal gradient in the Central Equatorial Pacific Ocean (∼155°W-159°W) at two sites: 8°N and the equator. The dissolved 230Th concentration profile at 8°N increases nearly linearly from the surface to 2000 m, exhibiting behavior consistent with thermodynamic reversible scavenging. However, from 2000 m to 3000 m, the dissolved 230Th concentrations exhibit little change, before increasing slightly from 3000 m to the bottom. At this site dissolved 230Th concentrations range from 1.1 fg/kg at 100 m to 55.2 fg/kg at 4600 m. At the equator, dissolved 230Th concentrations are slightly lower, and range from undetectable at 25 m to 19.1 fg/kg at 3038 m. The pattern in the dissolved 230Th concentration profile at the equator is indistinguishable from that at 8°N. The mid-depth-water deviation from equilibrium reversible scavenging between 2 and 3 km in the 230Th profiles (lower concentrations than expected) at both sites occurs in the interval of the water column that is consistent with an interval that has high concentrations of 3He and dissolved Fe at other nearby sites. This 3He- and Fe-rich signal has been traced to hydrothermal plumes from the East Pacific Rise, thousands of kilometers away. We hypothesize that the lower concentrations of 230Th in mid-depth waters of the Central Equatorial Pacific are a result of a 5000-km transit of waters that have had their 230Th scavenged by Fe-Mn particulates close to the EPR. Oceanic residence times of thorium combined with dissolved 232Th concentrations suggest dust fluxes of about ∼ 0.5- 0.6 gm-2yr-1 to the sea surface. These fluxes are in agreement with other empirical studies in the Pacific, but are higher than those suggested by global atmospheric circulation models.

Microstructure and improved magnetocaloric properties: LaFeSi/LaAl magnets prepared by spark plasma sintering technique

NASA Astrophysics Data System (ADS)

Fan, W. B.; Hou, Y. H.; Ge, X. J.; Huang, Y. L.; Luo, J. M.; Zhong, Z. C.

2018-03-01

Bulk LaFeSi magnets with the addition of LaAl alloy showing excellent performance were prepared by the spark plasma sintering (SPS) technique. The effects of heat treatment and various amounts of LaAl on the microstructure and magnetocaloric properties were investigated in details. It was found that appropriate amounts of LaAl can promote the peritectic reaction, and LaFeSi magnets with a high 1:13 phase amount can be obtained. Due to the unfavorable effects of Al in the peritectic reaction, excess addition of LaAl alloy was not beneficial to the formation of the 1:13 phase. The addition of 5 wt.% LaAl was most favorable to the formation of the 1:13 phase. Furthermore, heat treatment had important effects on the formation of the 1:13 phase and magnetocaloric performance. For SPSed LaFeSi magnets with 5 wt.% LaAl, the maximum values of magnetic entropy change (-ΔS M)max and refrigerating capacity (RC) are 18.07 J · kg-1 · K-1 and 327.55 J · kg-1 under the field changes of 0-5 T, respectively. The variation of Curie temperature (T C) depended on the joint effects from the antiferromagnetic interaction between Fe-Al atoms and the ferromagnetic interaction between Fe-Fe atoms.

Interdiffusion behaviors of iron aluminide coatings on China low activation martensitic steel

NASA Astrophysics Data System (ADS)

Zhu, X. X.; Yang, H. G.; Yuan, X. M.; Zhao, W. W.; Zhan, Q.

2014-12-01

The iron aluminide coating on China Low Activation Martensitic (CLAM) steel was prepared by pack cementation and subsequent heat treatment. A surface Fe2Al5 layer was formed on CLAM substrate by pack cementation process with Fe2Al5 donor powder and NH4Cl activator. Diffusion heat treatment was performed in order to allow the phase transformation from Fe2Al5 to a phase with lower aluminum content. Morphology and composition of the coatings were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). There is a need to study the interdiffusion behaviors in these Al containing systems, as a basis for controlling the formation and subsequent degradation of the coating. In this paper, a predictive model was developed to describe the phase transformation of Fe2Al5 as a function of processing parameters. The Wagner's equation was used to calculate the interdiffusion coefficients based on the analysis of the Al concentration profiles. The results showed that the interdiffusion coefficients in the FeAl and α-Fe(Al) phase strongly depends on Al content and showed a maximum at about 28 at.% Al.

Observational restrictions on sodium and aluminium abundance variations in evolution of the galaxy

NASA Astrophysics Data System (ADS)

Menzhevitski, V. S.; Shimanskaya, N. N.; Shimansky, V. V.; Sakhibullin, N. A.

2013-07-01

In this paper we construct and analyze the uniform non-LTE distributions of the aluminium ([Al/Fe]-[Fe/H]) and sodium ([Na/Fe]-[Fe/H]) abundances in the sample of 160 stars of the disk and halo of our Galaxy with metallicities within -4.07 ≤ [Fe/H] ≤ 0.28. The values of metallicity [Fe/H] and microturbulence velocity ξ turb indices are determined from the equivalent widths of the Fe II and Fe I lines. We estimated the sodium and aluminium abundances using a 21-level model of the Na I atom and a 39-level model of the Al I atom. The resulting LTE distributions of [Na/Fe]-[Fe/H] and [Al/Fe]-[Fe/H] do not correspond to the theoretical predictions of their evolution, suggesting that a non-LTE approach has to be applied to determine the abundances of these elements. The account of non-LTE corrections reduces by 0.05-0.15 dex the abundances of sodium, determined from the subordinate lines in the stars of the disk with [Fe/H] ≥ -2.0, and by 0.05-0.70 dex (with a strong dependence on metallicity) the abundances of [Na/Fe], determined by the resonance lines in the stars of the halo with [Fe/H] ≤ -2.0. The non-LTE corrections of the aluminium abundances are strictly positive and increase from 0.0-0.1 dex for the stars of the thin disk (-0.7 ≤ [Fe/H] ≤ 0.28) to 0.03-0.3 dex for the stars of the thick disk (-1.5 ≤ [Fe/H] ≤ -0.7) and 0.06-1.2 dex for the stars of the halo ([Fe/H] ≤ -2.0). The resulting non-LTE abundances of [Na/Fe] reveal a scatter of individual values up to Δ[Na/Fe] = 0.4 dex for the stars of close metallicities. The observed non-LTE distribution of [Na/Fe]-[Fe/H] within 0.15 dex coincides with the theoretical distributions of Samland and Kobayashi et al. The non-LTE aluminium abundances are characterized by a weak scatter of values (up to Δ[Al/Fe] = 0.2 dex) for the stars of all metallicities. The constructed non-LTE distribution of [Al/Fe]-[Fe/H] is in a satisfactory agreement to 0.2 dex with the theoretical data of Kobayashi et al., but strongly differs (up to 0.4 dex) from the predictions of Samland.

THE EFFECT OF PH AND DISSOLVED INORGANIC CARBON ON THE PROPERTIES OF IRON COLLOIDAL SUSPENSIONS

EPA Science Inventory

Discolored water resulting from suspended iron particles is a relatively common drinking water consumer complaint. These particles result from the oxygenation of Fe(II), and this study shows that pH and dissolved inorganic carbon (DIC) have important effects on their properties....

Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Brady, M. P.; Lu, Z. P.; Liu, C. T.; Takeyama, M.; Maziasz, P. J.; Pint, B. A.

2007-11-01

Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.

Concentration, solubility and deposition flux of atmospheric particulate nutrients over the Yellow Sea

NASA Astrophysics Data System (ADS)

Shi, Jin-Hui; Zhang, Jing; Gao, Hui-Wang; Tan, Sai-Chun; Yao, Xiao-Hong; Ren, Jing-Ling

2013-12-01

Satellite images showed that two large dust storms swept over the Yellow Sea from 31 Mach to 1 April 2007; both were accompanied by precipitation. Three to four days after the dust episodes, blooms occurred in the Yellow Sea. As an important and potential controlling factor of the bloom, nutrients in the total suspended particle (TSP) and size-segregated particle samples during the cruise campaign were measured and their atmospheric deposition fluxes of nutrients are reported in this paper. Concentrations of total P and TIN (NH4+, NO2- and NO3-) in TSP varied from 0.01 to 1.05 μg m-3, and from 1.21 to 22.28 μg m-3, with the maximum occurring concurrently with the dust storm events. In addition, the measured solubility of Fe in these particles varied from 1.0 to 20.1%, while it ranged from 0.8 to 15% for Al. The total deposition fluxes of Asian dust as well as the contained nutrients were estimated on the basis of an episodic increment of the measured concentration of dissolved Al in the surface ocean during the dust events. The estimated fluxes of atmospheric deposition of soluble Fe, P and inorganic nitrogen over the Yellow Sea during the dust episodes were 42.5±10.9, 10.3±2.6 and 772.0±198.0 mg m-2, respectively. The estimated fluxes of nutrients via dry atmospheric deposition accounted for only ~2% of the total fluxes. The deposition fluxes of particulate Fe and P during the two dust storm events associated with precipitation were about 500-1000 times of that daily averaged flux during non-dust days, indicating the importance of the episodic inputs to the annual budget of these metals deposited into the ocean.

Transmission of atmospherically derived trace elements through an undeveloped, forested Maryland watershed

USGS Publications Warehouse

Scudlark, J.R.; Rice, Karen C.; Conko, Kathryn M.; Bricker, Owen P.; Church, T.M.

2005-01-01

The transmission of atmospherically derived trace elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Se, and Zn) was evaluated in a small, undeveloped, forested watershed located in north-central Maryland. Atmospheric input was determined for wet-only and vegetative throughfall components. Annual throughfall fluxes were significantly enriched over incident precipitation for most elements, although some elements exhibited evidence of canopy release (Mn) or preferential uptake (As, Cr, and Se). Stream export was gauged based on systematic sampling under varied flow regimes. Particle loading appears to contribute significantly to watershed export (> 10%) for only As, Pb, and Fe, and then only during large precipitation/runoff events. The degree of watershed transmission for each trace element was evaluated based on a comparison of total, net atmospheric input (throughfall) to stream export over an annual hydrologic cycle. This comparison indicates that the atmospheric input of some elements (Al, Cd, Ni, Zn) is effectively transmitted through the watershed, but other elements (Pb, As, Se, Fe, Cr, Cu) appear to be strongly sequestered, in the respective orders noted. Results suggest that precipitation and subsequent soil pH are the primary factors that determine the mobility of sequestered trace element phases.To further resolve primary atmospheric and secondary weathering components, the geochemical model NETPATH was applied. Results indicate that minerals dissolved include chlorite, plagioclase feldspar, epidote, and potassium feldspar; phases formed were kaolinite, pyrite, and silica. The model also indicates that weathering processes contribute negligible amounts of trace elements to stream export, indicative of the unreactive orthoquartzite bedrock lithology underlying the watershed. Thus, the stream export of trace elements primarily reflects atmospheric deposition to the local watershed.

Association with pedogenic iron and aluminum: effects on soil organic carbon storage and stability in four temperate forest soils

DOE PAGES

Porras, Rachel C.; Hicks Pries, Caitlin E.; McFarlane, Karis J.; ...

2017-05-13

Soil organic carbon (SOC) can be stabilized via association with iron (Fe) and aluminum (Al) minerals. Fe and Al can be strong predictors of SOC storage and turnover in soils with relatively high extractable metals content and moderately acidic to circumneutral pH. Here we test whether pedogenic Fe and Al influence SOC content and turnover in soils with low Fe and Al content and acidic pH. In soils from four sites spanning three soil orders, we quantified the amount of Fe and Al in operationally-defined poorly crystalline and organically-complexed phases using selective chemical dissolution applied to the soil fraction containingmore » mineral-associated carbon. We evaluated the correlations of Fe and Al concentrations, mean annual precipitation (MAP), mean annual temperature (MAT), and pH with SOC content and 14C-based turnover times. We found that poorly crystalline Fe and Al content predicted SOC turnover times (p < 0.0001) consistent with findings of previous studies, while organically-complexed Fe and Al content was a better predictor of SOC concentration (p < 0.0001). Greater site-level MAP (p < 0.0001) and colder site-level MAT (p < 0.0001) were correlated with longer SOC turnover times but were not correlated with SOC content. Our results suggest that poorly crystalline Fe and Al effectively slow the turnover of SOC in these acidic soils, even when their combined content in the soil is less than 2% by mass. However, in the strongly acidic Spodosol, organo-metal complexes tended to be less stable resulting in a more actively cycling mineral-associated SOC pool.« less

Association with pedogenic iron and aluminum: effects on soil organic carbon storage and stability in four temperate forest soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Porras, Rachel C.; Hicks Pries, Caitlin E.; McFarlane, Karis J.

Soil organic carbon (SOC) can be stabilized via association with iron (Fe) and aluminum (Al) minerals. Fe and Al can be strong predictors of SOC storage and turnover in soils with relatively high extractable metals content and moderately acidic to circumneutral pH. Here we test whether pedogenic Fe and Al influence SOC content and turnover in soils with low Fe and Al content and acidic pH. In soils from four sites spanning three soil orders, we quantified the amount of Fe and Al in operationally-defined poorly crystalline and organically-complexed phases using selective chemical dissolution applied to the soil fraction containingmore » mineral-associated carbon. We evaluated the correlations of Fe and Al concentrations, mean annual precipitation (MAP), mean annual temperature (MAT), and pH with SOC content and 14C-based turnover times. We found that poorly crystalline Fe and Al content predicted SOC turnover times (p < 0.0001) consistent with findings of previous studies, while organically-complexed Fe and Al content was a better predictor of SOC concentration (p < 0.0001). Greater site-level MAP (p < 0.0001) and colder site-level MAT (p < 0.0001) were correlated with longer SOC turnover times but were not correlated with SOC content. Our results suggest that poorly crystalline Fe and Al effectively slow the turnover of SOC in these acidic soils, even when their combined content in the soil is less than 2% by mass. However, in the strongly acidic Spodosol, organo-metal complexes tended to be less stable resulting in a more actively cycling mineral-associated SOC pool.« less

Triphenylamine based reactive coloro/fluorimetric chemosensors: Structural isomerism and solvent dependent sensitivity and selectivity

NASA Astrophysics Data System (ADS)

Kundu, Anu; Anthony, Savarimuthu Philip

2018-01-01

Triphenyl amine based chemosensors, (2-(((2-(9H-carbazol-9-yl)phenyl)imino)methyl)-5-(diphenylamino)phenol (ortho-CPDP) and 2-(((4-(9H-carbazol-9-yl)phenyl)imino)methyl)-5-(diphenylamino)phenol (para-CPDP), showed solvent and isomerism dependent selective coloro/fluorometric sensing of multiple metal ions (Fe3 +, Al3 + and Zn2 +) with distinguishable responses. In CH3CN, ortho and para-CPDP selectively produced yellow color upon addition of Al3 + and Fe3 + that was slowly disappeared. The yellow color of ortho and para-CPDP in DMF was decolourised selectively by adding Al3 + and Fe3 +. Both ortho and para-CPDP in CH3CN showed nearly similar rate of decolourization for Fe3 + and Al3 +. However, the rate of decolourization of ortho and para-CPDP in DMF was different for Fe3 + (10 μM, 8 min) and Al3 + (5 × 10- 4 M, 40 min) ions. The limit of detection of para-CPDP for Fe3 + is 10 μM and Al3 + 500 μM. The mechanistic studies revealed the imine hydrolysis of ortho and para-CPDP in presence of Lewis acidic Fe3 + and Al3 +. The reactivity based sensing lead to high selectivity for Al3 + and Fe3 + ions. Further, para-CPDP exhibited selective fluorescence turn-on for Zn2 + in DMF (λmax = 513 nm) and detection limit of 6.0 μM. Thus, reactive chemosensors, ortho and para-CPDP, exhibited selective and distinguishable colorimetric sensing of Fe3 + and Al3 + ions and isomerism and solvent dependent fluorescence sensing of Zn2 +.