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.

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.

An integrated approach to asses origin and mobilization of As, Fe and Mn in groundwater: the case study of Cremona (northern Italy)

NASA Astrophysics Data System (ADS)

Rotiroti, Marco; Bonomi, Tullia; Fumagalli, Letizia

2013-04-01

The present work concerns the analysis of the hydrogeology and the hydrogeochemistry of the As, Fe, Mn rich groundwater of the alluvial multi-layer aquifer in the lower Po Plain of Cremona (northern Italy). In this analysis, an integrated approach is applied in order to understand the origins (natural or anthropic) and chemical mechanisms of high groundwater As, Fe and Mn concentrations found in the study area. The study area covers a 50 km2 wide area around the urban territory of Cremona. It is located near the confluence between Adda and Po rivers. The multi-aquifer system which interests the first 200-250 m of depth is investigated. The integrated approach involves the (a) collection of historical data related to water quality, water levels and well logs; (b) storage of collected data in specific databases and geographical information systems; (c) design and execution of two field surveys of water levels and water quality, realized in July 2010 and July 2012, concerning also groundwater sampling for isotope and microbiological analysis; (d) construction of a 3D model of aquifer hydrogeological properties (deposits texture, hydraulic conductivity and effective porosity), built by means of ordinary kriging interpolation of numerical values derived from the coding of well logs; (e) analysis of the hydrodynamic properties of the system on the basis of the field measurements; (f) analysis of water quality data (both field and historical data) considering the hydrogeological and hydrodynamic properties of the aquifer system; (g) analysis of isotope and microbiological measurements; (h) implementation of a 1D reactive transport model in order to better understand the hydrogeochemical mechanisms in the system; (i) elaboration of a general hydrogeochemical conceptual model concerning possible origins and chemical mechanisms for the high groundwater As, Fe, Mn and NH4 concentrations, considering also possible anthropogenic influences; (j) development of management tools, as natural background levels (NBL) derivation, supporting groundwater resources protection by public authorities. This approach allows to assume the process of natural organic matter degradation (i.e. peat) as primary control factor on high As, Fe, Mn and NH4 concentrations. Degradation of peat is associated with the consecutive reduction of O2, NO3-, Mn(IV), Fe(III), SO42-, CO2. The reductive dissolution of Mn and Fe oxides (contained in the aquifer sediments) leads to high concentrations of dissolved Fe and Mn, but also to high concentrations of dissolved As, which is generally sorbed on Mn and Fe oxides. Dissolved As concentration can be also lowered by different processes (co-precipitation of As in iron sulfides, precipitation of arsenic sulfides, sorption of As on the remaining Fe-oxides and Mn-oxides, etc.). NH4 is released from the degradation of organic nitrogen of peat. Therefore, a natural origin of As, Fe, Mn and NH4 can be assumed. In addiction, anthropogenic influences on groundwater As, Fe, Mn and NH4 concentrations are locally identified in two sites located in the study area, that are affected by hydrocarbons and organic leachate pollution.

Molecular controls on Cu and Zn isotopic fractionation in Fe-Mn crusts

NASA Astrophysics Data System (ADS)

Little, S. H.; Sherman, D. M.; Vance, D.; Hein, J. R.

2014-06-01

The isotopic systems of the transition metals are increasingly being developed as oceanic tracers, due to their tendency to be fractionated by biological and/or redox-related processes. However, for many of these promising isotope systems the molecular level controls on their isotopic fractionations are only just beginning to be explored. Here we investigate the relative roles of abiotic and biotic fractionation processes in controlling modern seawater Cu and Zn isotopic compositions. Scavenging to Fe-Mn oxides represents the principal output for Cu and Zn to sediments deposited under normal marine (oxic) conditions. Using Fe-Mn crusts as an analogue for these dispersed phases, we investigate the phase association and crystal chemistry of Cu and Zn in such sediments. We present the results of an EXAFS study that demonstrate unequivocally that Cu and Zn are predominantly associated with the birnessite (δ-MnO2) phase in Fe-Mn crusts, as previously predicted from sequential leaching experiments (e.g., Koschinsky and Hein, 2003). The crystal chemistry of Cu and Zn in the crusts implies a reduction in coordination number in the sorbed phase relative to the free metal ion in seawater. Thus, theory would predict equilibrium fractionations that enrich the heavy isotope in the sorbed phase (e.g., Schauble, 2004). In natural samples, Fe-Mn crusts and nodules are indeed isotopically heavy in Zn isotopes (at ∼1‰) compared to deep seawater (at ∼0.5‰), consistent with the predicted direction of equilibrium isotopic fractionation based on our observations of the coordination environment of sorbed Zn. Further, ∼50% of inorganic Zn‧ is chloro-complexed (the other ∼50% is present as the free Zn2+ ion), and complexation by Cl- is also predicted to favour equilibrium partitioning of light Zn isotopes into the dissolved phase. The heavy Zn isotopic composition of Fe-Mn crusts and nodules relative to seawater can therefore be explained by an inorganic fractionation during uptake. However, Cu in Fe-Mn crusts is isotopically light (at ∼0.3 to 0.5‰) compared to the dissolved phase in seawater (at ∼0.9‰). We suggest that this is because dissolved Cu in the oceans is overwhelmingly complexed to strong organic ligands, which are better competitors for the heavy isotope.

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.

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.

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

Trace metals partitioning between particulate and dissolved phases along a tropical mangrove estuary (Can Gio, Vietnam).

PubMed

Thanh-Nho, Nguyen; Strady, Emilie; Nhu-Trang, Tran-Thi; David, Frank; Marchand, Cyril

2018-04-01

Mangroves can be considered as biogeochemical reactors along (sub)tropical coastlines, acting both as sinks or sources for trace metals depending on environmental factors. In this study, we characterized the role of a mangrove estuary, developing downstream a densely populated megacity (Ho Chi Minh City, Vietnam), on the fate and partitioning of trace metals. Surface water and suspended particulate matter were collected at four sites along the estuarine salinity gradient during 24 h cycling in dry and rainy seasons. Salinity, pH, DO, TSS, POC, DOC, dissolved and particulate Fe, Mn, Cr, As, Cu, Ni, Co and Pb were measured. TSS was the main trace metals carrier during their transit in the estuary. However, TSS variations did not explain the whole variability of metals distribution. Mn, Cr and As were highly reactive metals while the other metals (Fe, Ni, Cu, Co and Pb) presented stable log K D values along the estuary. Organic matter dynamic appeared to play a key role in metals fractioning. Its decomposition during water transit in the estuary induced metal desorption, especially for Cr and As. Conversely, dissolved Mn concentrations decreased along the estuary, which was suggested to result from Mn oxidative precipitation onto solid phase due to oxidation and pH changes. Extra sources as pore-water release, runoff from adjacent soils, or aquaculture effluents were suggested to be involved in trace metal dynamic in this estuary. In addition, the monsoon increased metal loads, notably dissolved and particulate Fe, Cr, Ni and Pb. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

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 (

Characterization of iron and manganese minerals and their associated microbiota in different mine sites to reveal the potential interactions of microbiota with mineral formation.

PubMed

Park, Jin Hee; Kim, Bong-Soo; Chon, Chul-Min

2018-01-01

Different environmental conditions such as pH and dissolved elements of mine stream induce precipitation of different minerals and their associated microbial community may vary. Therefore, mine precipitates from various environmental conditions were collected and their associated microbiota were analyzed through metagenomic DNA sequencing. Various Fe and Mn minerals including ferrihydrite, schwertmannite, goethite, birnessite, and Mn-substituted δ-FeOOH (δ-(Fe 1-x , Mn x )OOH) were found in the different environmental conditions. The Fe and Mn minerals were enriched with toxic metal(loid)s including As, Cd, Ni and Zn, indicating they can act as scavengers of toxic metal(loid)s in mine streams. Under acidic conditions, Acidobacteria was dominant phylum and Gallionella (Fe oxidizing bacteria) was the predominant genus in these Fe rich environments. Manganese oxidizing bacteria, Hyphomicrobium, was found in birnessite forming environments. Leptolyngbya within Cyanobacteria was found in Fe and Mn oxidizing environments, and might contribute to Fe and Mn oxidation through the production of molecular oxygen. The potential interaction of microbial community with minerals in mine sites can be traced by analysis of microbial community in different Fe and Mn mineral forming environments. Iron and Mn minerals contribute to the removal of toxic metal(loid)s from mine water. Therefore, the understanding characteristics of mine precipitates and their associated microbes helps to develop strategies for the management of contaminated mine water. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effects of iron(II) on the kinetics of arsenic oxidation and sorption on manganese oxides.

PubMed

Wu, Yun; Li, Wei; Sparks, Donald L

2015-11-01

In this study, As(III) oxidation kinetics by a poorly-crystalline phyllomanganate (δ-MnO2) in the presence and absence of dissolved Fe(II) was investigated using stirred-flow and batch experiments. Chemically synthetic δ-MnO2 was reacted with four influent solutions, containing the same As(III) concentration but different Fe(II) concentrations, at pH 6. The results show an initial rapid As(III) oxidation by δ-MnO2, which is followed by an appreciably slow reaction after 8h. In the presence of Fe(II), As(III) oxidation is inhibited due to the competitive oxidation of Fe(II) as well as the formation of Fe(III)-(hydr)oxides on the δ-MnO2 surface. However, the sorption of As(III), As(V) and Mn(II) are increased, for the newly formed Fe(III)-(hydr)oxides provide additional sorption sites. This study suggests that the competitive oxidation of Fe(II) and consequently the precipitation of Fe(III) compounds on the δ-MnO2 surface play an important role in As(III) oxidation and As sequestration. Understanding these processes would be helpful in developing in situ strategies for remediation of As-contaminated waters and soils. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

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.

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

2014-07-01

Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle.

Geochemistry of Dissolved Trace Metals in the Waters of Bahia Magdalena, Baja California Sur, Pacific Coast, Mexico

NASA Astrophysics Data System (ADS)

Suresh Babu, S.

2016-12-01

Forty two samples were acquired from the surface and bottom water profiles along 5 transects spread over Bahia Magdalena lagoon, Baja California Sur to assess the behavior of trace metals in a high influenced upwelling region on the Pacific coast. To elaborate the fate of metals, also the physico-chemical parameters (pH, temperature, salinity, conductivity, dissolved oxygen). Determination of the concentrations of trace metals (Fe, Mn, Cr, Cu, Co, Pb, Ni, Zn, Cd As, Hg) were measured using Atomic absorption spectrometry. The results demonstrated high values of As, Ni and Co which is attributed to the local geology and phosphate deposits. Low values of Fe and Mn are attested to the oxic conditions of the lagoon which are responsible for the oxidation of Fe and Mn. The region witnesses raised temperatures (28.92ºC) and salinities of 35.2 PSU for its arid climatic conditions and high rates of evaporation. In general, the region presented minor quantities of dissolved trace metals due to dispersion and high intense interaction with the open sea. The results were also compared with other studies to understand the enrichment pattern in this side of the pacific coast which experiences various geothermal activities and upwelling phenomenon.

In vitro and in vivo corrosion properties of new iron-manganese alloys designed for cardiovascular applications.

PubMed

Drynda, Andreas; Hassel, Thomas; Bach, Friedrich Wilhelm; Peuster, Matthias

2015-04-01

The principle of biodegradation for the production of temporary implant materials (e.g. stents) plays an important role in the treatment of congenital heart defects. In the last decade several attempts have been made with different alloy materials-mainly based on iron and magnesium. None of the currently available materials in this field have demonstrated satisfying results and have therefore not found entry into broad clinical practice. While magnesium or magnesium alloy systems corrode too fast, the corrosion rate of pure iron-stents is too slow for cardiovascular applications. In the last years FeMn alloy systems were developed with the idea that galvanic effects, caused by different electrochemical properties of Fe and Mn, would increase the corrosion rate. In vitro tests with alloys containing up to 30% Mn showed promising results in terms of biocompatibility. This study deals with the development of new FeMn alloy systems with lower Mn concentrations (FeMn 0.5 wt %, FeMn 2.7 wt %, FeMn 6.9 wt %) to avoid Mn toxicity. Our results show, that these alloys exhibit good mechanical features as well as suitable in vitro biocompatibility and corrosion properties. In contrast, the evaluation of these alloys in a mouse model led to unexpected results-even after 9 months no significant corrosion was detectable. Preliminary SEM investigations showed that passivation layers (FeMn phosphates) might be the reason for corrosion resistance. If this can be proved in further experiments, strategies to prevent or dissolve those layers need to be developed to expedite the in vivo corrosion of FeMn alloys. © 2014 Wiley Periodicals, Inc.

Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India.

PubMed

Chakraborty, Parthasarathi; Chakraborty, Sucharita; Jayachandran, Saranya; Madan, Ritu; Sarkar, Arindam; Linsy, P; Nath, B Nagender

2016-10-01

This study describes the effect of varying bottom-water oxygen concentration on geochemical fractionation (operational speciation) of Cu and Pb in the underneath sediments across the oxygen minimum zone (Arabian Sea) in the west coast of India. Both, Cu and Pb were redistributed among the different binding phases of the sediments with changing dissolved oxygen level (from oxic to hypoxic and close to suboxic) in the bottom water. The average lability of Cu-sediment complexes gradually decreased (i.e., stability increased) with the decreasing dissolved oxygen concentrations of the bottom water. Decreasing bottom-water oxygen concentration increased Cu association with sedimentary organic matter. However, Pb association with Fe/Mn-oxyhydroxide phases in the sediments gradually decreased with the decreasing dissolved oxygen concentration of the overlying bottom water (due to dissolution of Fe/Mn oxyhydroxide phase). The lability of Pb-sediment complexes increased with the decreasing bottom-water oxygen concentration. This study suggests that bottom-water oxygen concentration is one of the key factors governing stability and lability of Cu and Pb complexes in the underneath sediment. Sedimentary organic matter and Fe/Mn oxyhydroxide binding phases were the major hosting phases for Cu and Pb respectively in the study area. Increasing lability of Pb-complexes in bottom sediments may lead to positive benthic fluxes of Pb at low oxygen environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Observed and modeled seasonal trends in dissolved and particulate Cu, Fe, Mn, and Zn in a mining-impacted stream.

PubMed

Butler, Barbara A; Ranville, James F; Ross, Philippe E

2008-06-01

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 discharge directly related to snowmelt and strong seasonal storms. Additionally, conditions in the stream cause rapid precipitation of large amounts of hydrous iron oxides (HFO) that sequester metals. Because AMD-impacted systems are complex, geochemical modeling may assist with predictions and/or confirmations of processes occurring in these environments. This research used Visual-MINTEQ to determine if field data collected over a two and one-half year study would be well represented by modeling with a currently existing model, while limiting the number of processes modeled and without modifications to the existing model's parameters. Observed distributions between dissolved and particulate phases in the water column varied greatly among the metals, with average dissolved fractions being >90% for Mn, approximately 75% for Zn, approximately 30% for Cu, and <10% for Fe. A strong seasonal trend was observed for the metals predominantly in the dissolved phase (Mn and Zn), with increasing concentrations during base-flow conditions and decreasing concentrations during spring-runoff. This trend was less obvious for Cu and Fe. Within hydrologic seasons, storm events significantly influenced in-stream metals concentrations. The most simplified modeling, using solely sorption to HFO, gave predicted percentage particulate Cu results for most samples to within a factor of two of the measured values, but modeling data were biased toward over-prediction. About one-half of the percentage particulate Zn data comparisons fell within a factor of two, with the remaining data being under-predicted. Slightly more complex modeling, which included dissolved organic carbon (DOC) as a solution phase ligand, significantly reduced the positive bias between observed and predicted percentage particulate Cu, while inclusion of hydrous manganese oxide (HMO) yielded model results more representative of the observed percentage particulate Zn. These results indicate that there is validity in the use of an existing model, without alteration and with typically collected water chemistry data, to describe complex natural systems, but that processes considered optimal for one metal might not be applicable for all metals in a given water sample.

Manganese minerals and associated fine particulates in the streambed of Pinal Creek, Arizona, U.S.A.: a mining-related acid drainage problem

USGS Publications Warehouse

Lind, Carol J.; Hem, J.D.

1993-01-01

The Pinal creek drainage basin in Arizona is a good example of the principal non-coal source of mining-related acid drainage in the U.S.A., namely copper mining. Infiltration of drainage waters from mining and ore refining has created an acid groundwater plume that has reacted with calcite during passage through the alluvium, thereby becoming less acid. Where O2 is present and the water is partially neutralized, iron oxides have precipitated and, farther downstream where the pH of the stream water is near neutral, high-Mn crusts have developed. Trace metal composition of several phases in the Pinal Creek drainage basin illustrates the changes caused by mining activities and the significant control Mn-crusts and iron oxide deposits exert on the distribution and concentration of trace metals. The phases and locales considered are the dissolved phase of Webster Lake, a former acid waste disposal pond; selected sections of cores drilled in the alluvium within the intermittent reach of Pinal Creek; and the dissolved phase, suspended sediments, and streambed deposits at specified locales along the perennial reach of Pinal creek. In the perennial reach of Pinal Creek, manganese oxides precipitate from the streamflow as non-cemented particulates and coatings of streambed material and as cemented black crusts. Chemical and X-ray diffraction analyses indicate that the non-cemented manganese oxides precipitate in the reaction sequence observed in previous laboratory experiments using simpler solution composition, Mn3O4 to MnOOH to an oxide of higher oxidation number usually <4.0, i.e. Na-birnessite, and that the black cemented crusts contain (Ca,Mn,Mg)CO3 and a 7-A?? phyllomanganate mixture of rancieite ((Ca,Mn)Mn4O9 ?? (3H2O)) and takanelite ((Mn,Ca)Mn4O9 ?? (3H2O)). In the laboratory, aerating and increasing the pH of Pinal Creek water to 9.00 precipitated (Ca,Mn,Mg)CO3 from an anoxic groundwater that contained CO2 HCO3, and precipitated Mn3O4 and subsequently MnOOH from an oxic surface water from which most of the dissolved CO2 had been removed. It is suggested that the black cemented crusts form by precipitation of Fe on the Mn-enriched carbonates, creating a site for the MnFe oxidation cycle and thus encouraging the conversion of the carbonates to 7-A?? physllomanganates. The non-magnetic <63-??m size-fractions of the black cemented crusts consisted mostly of the manganese-calcium oxides but also contained about 20% (Ca,Mn,Mg)CO3, 5% Fe (calculated as FeOOH), 2-4% exchangeable cations, and trace amounts of several silicates. ?? 1992.

Design of template-stabilized active and earth-abundant oxygen evolution catalysts in acid† †Electronic supplementary information (ESI) available: CVs for unary metal oxides deposition, electrochemical stability at higher current densities for unary metal oxides at pH 2.5, EDS maps for CoMnOx and CoPbOx, STEM images and PXRD of CoMnOx and CoFePbOx, high-resolution XPS of Fe 2p for CoFePbOx, Pourbaix diagrams (of Mn, Co, Pb, and Fe), and elemental analysis. See DOI: 10.1039/c7sc01239j Click here for additional data file.

PubMed Central

Huynh, Michael; Ozel, Tuncay; Liu, Chong; Lau, Eric C.

2017-01-01

Oxygen evolution reaction (OER) catalysts that are earth-abundant and are active and stable in acid are unknown. Active catalysts derived from Co and Ni oxides dissolve at low pH, whereas acid stable systems such as Mn oxides (MnOx) display poor OER activity. We now demonstrate a rational approach for the design of earth-abundant catalysts that are stable and active in acid by treating activity and stability as decoupled elements of mixed metal oxides. Manganese serves as a stabilizing structural element for catalytically active Co centers in CoMnOx films. In acidic solutions (pH 2.5), CoMnOx exhibits the OER activity of electrodeposited Co oxide (CoOx) with a Tafel slope of 70–80 mV per decade while also retaining the long-term acid stability of MnOx films for OER at 0.1 mA cm–2. Driving OER at greater current densities in this system is not viable because at high anodic potentials, Mn oxides convert to and dissolve as permanganate. However, by exploiting the decoupled design of the catalyst, the stabilizing structural element may be optimized independently of the Co active sites. By screening potential–pH diagrams, we replaced Mn with Pb to prepare CoFePbOx films that maintained the high OER activity of CoOx at pH 2.5 while exhibiting long-term acid stability at higher current densities (at 1 mA cm–2 for over 50 h at pH 2.0). Under these acidic conditions, CoFePbOx exhibits OER activity that approaches noble metal oxides, thus establishing the viability of decoupling functionality in mixed metal catalysts for designing active, acid-stable, and earth-abundant OER catalysts. PMID:29163926

Simplified sample treatment for the determination of total concentrations and chemical fractionation forms of Ca, Fe, Mg and Mn in soluble coffees.

PubMed

Pohl, Pawel; Stelmach, Ewelina; Szymczycha-Madeja, Anna

2014-11-15

A simpler, and faster than wet digestion, sample treatment was proposed prior to determination of total concentrations for selected macro- (Ca, Mg) and microelements (Fe, Mn) in soluble coffees by flame atomic absorption spectrometry. Samples were dissolved in water and acidified with HNO3. Precision was in the range 1-4% and accuracy was better than 2.5%. The method was used in analysis of 18 soluble coffees available on the Polish market. Chemical fractionation patterns for Ca, Fe, Mg and Mn in soluble coffees, as consumed, using a two-column solid-phase extraction method, determined Ca, Mg and Mn were present predominantly as cations (80-93% of total content). This suggests these elements are likely to be highly bioaccessible. Copyright © 2014 Elsevier Ltd. All rights reserved.

Heavy metal distributions in Peru Basin surface sediments in relation to historic, present and disturbed redox environments

NASA Astrophysics Data System (ADS)

Koschinsky, Andrea

Heavy metal distributions in deep-sea surface sediments and pore water profiles from five areas in the Peru Basin were investigated with respect to the redox environment and diagenetic processes in these areas. The 10-20-cm-thick Mn oxide-rich and minor metal-rich top layer is underlain by an increase in dissolved Mn and Ni concentrations resulting from the reduction of the MnO 2 phase below the oxic zone. The mobilised associated metals like Co, Zn and Cu are partly immobilised by sorption on clay, organic or Fe compounds in the post-oxic environment. Enrichment of dissolved Cu, Zn, Ni, Co, Pb, Cd, Fe and V within the upper 1-5 cm of the oxic zone can be attributed to the degradation of organic matter. In a core from one area at around 22-25 cm depth, striking enrichments of these metals in dissolved and solid forms were observed. Offset distributions between oxygen penetration and Mn reduction and the thickness of the Mn oxide-rich layer indicate fluctuations of the Mn redox boundary on a short-term time scale. Within the objectives of the German ATESEPP research programme, the effect of an industrial impact such as manganese nodule mining on the heavy metal cycle in the surface sediment was considered. If the oxic surface were to be removed or disturbed, oxygen would penetrate deep into the formerly suboxic sediment and precipitate Mn 2+ and metals like Ni and Co which are preferably scavenged by MnO 2. The solid enrichments of Cd, V, and other metals formed in post-oxic environments would move downward with the new redox boundary until a new equilibrium between oxygen diffusion and consumption is reached.

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.

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.

Calcium carbonate-based permeable reactive barriers for iron and manganese groundwater remediation at landfills.

PubMed

Wang, Yu; Pleasant, Saraya; Jain, Pradeep; Powell, Jon; Townsend, Timothy

2016-07-01

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. Two in situ permeable reactive barriers (PRBs), comprised of limestone and crushed concrete, were installed downgradient of a closed, unlined landfill in Florida, USA, to remediate groundwater containing high concentrations of these metals. Influent groundwater to the PRBs contained mean Fe and Mn concentrations of approximately 30mg/L and 1.62mg/L, respectively. PRBs were constructed in the shallow aquifer (maximum depth 4.6m below land surface) and groundwater was sampled from a network of nearby monitoring wells to evaluate barrier performance in removing these metals. PRBs significantly (p<0.05) removed dissolved Fe and Mn from influent groundwater; Fe was removed from influent water at average rates of 91% and 95% (by mass) for the limestone and crushed concrete PRBs, respectively, during the first year of the study. The performance of the PRBs declined after 3years of operation, with Fe removal efficiency decreasing to 64% and 61% for limestone and concrete PRBs, respectively. A comparison of water quality in shallow and deep monitoring wells showed a more dramatic performance reduction in the deeper section of the concrete PRB, which was attributed to an influx of sediment into the barrier and settling of particulates from the upper portions of the PRBs. Although removal of Fe and Mn from redox impacts was achieved with the PRBs, the short time frame of effectiveness relative to the duration of a full-scale remediation effort may limit the applicability of these systems at some landfills because of the construction costs required. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

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.

Metal discharges by Sinaloa Rivers to the coastal zone of NW Mexico.

PubMed

Frías-Espericueta, M G; Mejía-Cruz, R; Osuna López, I; Muy-Rangel, M D; Rubio-Carrasco, W; Aguilar-Juárez, M; Voltolina, D

2014-02-01

The aim of this work was to survey the discharges of dissolved and particulate Cd, Cu, Fe, Mn, Pb and Zn of the eight main rivers of Sinaloa State to the Mexican coastal environment. Zn was the most abundant dissolved metal and Fe was the most abundant particulate (8.02-16.90 and 51.8-1,140.3 μg/L, respectively). Only particulate Mn had significantly (p = 0.028) higher values in summer-fall (rainy season), whereas the significantly (p = 0.036) higher values of dissolved Zn were observed in winter and spring. The highest annual total discharges to Sinaloa coastal waters were those of the rivers San Lorenzo and Piaxtla (>2 × 10(3) m.t.) and the lowest those of rivers Baluarte and El Fuerte (349 and 119 m.t., respectively). Pb concentrations may become of concern, because they are higher than the value recommended for the welfare of aquatic communities of natural waters.

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.

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.

The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

NASA Technical Reports Server (NTRS)

Canfield, Donald E.; Thamdrup, BO; Hansen, Jens W.

1993-01-01

A combination of porewater and solid phase analysis as well as a series of sediment incubations are used to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). Solid phase data are integrated with incubation results to define the zones of the various oxidation processes. At S(9), surface Mn enrichments of up to 3.5 wt pct were found, and with such a ready source of Mn, dissimilatory Mn reduction was the only significant anaerobic process of carbon oxidation in the surface 10 cm of the sediment. At S(4) and S(6), active Mn reduction occurred; however, most of the Mn reduction may have resulted from the oxidation of acid volatile sulfides and Fe(2+) rather than by a dissimilatory sulfate. Dissolved Mn(2+) was found to completely adsorb onto sediment containing fully oxidized Mn oxides.

Strontium and Trace Metals in the Mississippi River Mixing Zone

NASA Astrophysics Data System (ADS)

Xu, Y.; Marcantonio, F.

2001-12-01

Strontium is generally believed to be a conservative element, i.e., it is assumed that dissolved Sr moves directly from rivers through estuaries to the ocean. More recently, however, detailed sampling of rivers suggests a weak non-conservative behavior for Sr. Here, we present dissolved and suspended load Sr and trace metal data for samples retrieved along salinity transects in the estuarine mixing zone of the Mississippi River. Our cruises took place during times representing high, falling, and low Mississippi River discharge. Sr concentration and isotopic composition were analyzed for both dissolved particulate loads. Selected particle-reactive or redox-sensitive trace metals (Mn, Fe, U, V, Mo, Ti, and Pb) were analyzed simultaneously. In the dissolved load, Sr showed conservative behavior in both high- and low- discharge periods. Non-conservative behavior of Sr predominated during falling discharge in the summer. Significant positive correlations were found between Sr, Mo and Ti. U and V distributions were found to be essentially controlled by mixing of river water and seawater, but with significantly lower riverine concentrations during high-flow stage. Particulate element concentrations can be quite variable and heterogeneous. In this study, strong correlations were found between particulate Mn (and Fe) concentrations and particulate concentrations of Ti, U, V, and Pb. No such correlations with Mn (or Fe) were found for particulate Sr and Mo. There is a vast hypoxic zone along the coast of Louisiana in the Gulf of Mexico that exists during the summer months. Based on the Sr isotope systematics and the relationships between Sr and trace metals, we believe that this eutrophication may contribute to the non-conservative behaviors of Sr and other trace metals. We discuss the potential implications of this hypothesis on the Sr mass balance of present-day and past seawater.

Reactive transport modeling of geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

USGS Publications Warehouse

Ng, Gene-Hua Crystal.; Bekins, Barbara A.; Cozzarelli, Isabelle M.; Baedecker, Mary Jo; Bennett, Philip C.; Amos, Richard T.; Herkelrath, William N.

2015-01-01

Anaerobic biodegradation of organic amendments and contaminants in aquifers can trigger secondary water quality impacts that impair groundwater resources. Reactive transport models help elucidate how diverse geochemical reactions control the spatiotemporal evolution of these impacts. Using extensive monitoring data from a crude oil spill site near Bemidji, Minnesota (USA), we implemented a comprehensive model that simulates secondary plumes of depleted dissolved O2 and elevated concentrations of Mn2+, Fe2+, CH4, and Ca2+ over a two-dimensional cross section for 30 years following the spill. The model produces observed changes by representing multiple oil constituents and coupled carbonate and hydroxide chemistry. The model includes reactions with carbonates and Fe and Mn mineral phases, outgassing of CH4 and CO2 gas phases, and sorption of Fe, Mn, and H+. Model results demonstrate that most of the carbon loss from the oil (70%) occurs through direct outgassing from the oil source zone, greatly limiting the amount of CH4 cycled down-gradient. The vast majority of reduced Fe is strongly attenuated on sediments, with most (91%) in the sorbed form in the model. Ferrous carbonates constitute a small fraction of the reduced Fe in simulations, but may be important for furthering the reduction of ferric oxides. The combined effect of concomitant redox reactions, sorption, and dissolved CO2 inputs from source-zone degradation successfully reproduced observed pH. The model demonstrates that secondary water quality impacts may depend strongly on organic carbon properties, and impacts may decrease due to sorption and direct outgassing from the source zone.

Geochemical characterisation of shallow aquifer sediments of Matlab Upazila, Southeastern Bangladesh — Implications for targeting low-As aquifers

NASA Astrophysics Data System (ADS)

von Brömssen, Mattias; Häller Larsson, Sara; Bhattacharya, Prosun; Hasan, M. Aziz; Ahmed, Kazi Matin; Jakariya, M.; Sikder, Mohiuddin A.; Sracek, Ondra; Bivén, Annelie; Doušová, Barbora; Patriarca, Claudio; Thunvik, Roger; Jacks, Gunnar

2008-07-01

High arsenic (As) concentrations in groundwater pose a serious threat to the health of millions of people in Bangladesh. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilisation of As. The distribution of As is extremely heterogeneous both laterally and vertically. Groundwater abstracted from oxidised reddish sediments, in contrast to greyish reducing sediments, contains significantly lower amount of dissolved arsenic and can be a source of safe water. In order to study the sustainability of that mitigation option, this study describes the lithofacies and genesis of the sediments within 60 m depth and establishes a relationship between aqueous and solid phase geochemistry. Oxalate extractable Fe and Mn contents are higher in the reduced unit than in the oxidised unit, where Fe and Mn are present in more crystalline mineral phases. Equilibrium modelling of saturation indices suggest that the concentrations of dissolved Fe, Mn and PO43--tot in groundwater is influenced by secondary mineral phases in addition to redox processes. Simulating AsIII adsorption on hydroferric oxides using the Diffuse Layer Model and analytical data gave realistic concentrations of dissolved and adsorbed AsIII for the reducing aquifer and we speculate that the presence of high PO43--tot in combination with reductive dissolution results in the high-As groundwater. The study confirms high mobility of As in reducing aquifers with typically dark colour of sediments found in previous studies and thus validates the approach for location of wells used by local drillers based on sediment colour. A more systematic and standardised colour description and similar studies at more locations are necessary for wider application of the approach.

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.

Role of Dissolved Organic Matter and Geochemical Controls on Arsenic Cycling from Sediments to Groundwater along the Meghna River, Bangladesh: Tracking possible links to permeable natural reactive barrier

NASA Astrophysics Data System (ADS)

Datta, S.; Berube, M.; Knappett, P.; Kulkarni, H. V.; Vega, M.; Jewell, K.; Myers, K.

2017-12-01

Elevated levels of dissolved arsenic (As), iron (Fe) and manganese (Mn) are seen in the shallow groundwaters of southeast Bangladesh on the Ganges Brahmaputra Meghna River delta. This study takes a multi disciplinary approach to understand the extent of the natural reactive barrier (NRB) along the Meghna River and evaluate the role of the NRB in As sequestration and release in groundwater aquifers. Shallow sediment cores, and groundwater and river water samples were collected from the east and west banks of the Meghna. Groundwater and river water samples were tested for FeT, MnT, and AsT concentrations. Fluorescence spectroscopic characterization of groundwater dissolved organic matter (DOM) provided insight into the hydro geochemical reactions active in the groundwater and the hyporheic zones. Eight sediment cores of 1.5 m depth were collected 10 m away from the edge of the river. Vertical solid phase concentration profiles of Fe, Mn and As were measured via 1.2 M HCl digestion which revealed solid phase As accumulation along the riverbanks up to concentrations of 1500 mg/kg As. Microbial interactions with DOM prompts the reduction of Fe3+ to Fe2+, causing As to mobilize into groundwater and humic-like DOM present in the groundwater may catalyze this process. The extent to which microbially mediated release of As occurs is limited by labile dissolved organic carbon (DOC) availability. Aqueous geochemical results showed the highest dissolved As concentrations in shallow wells (<30 m depth), where organic matter was fresh, humic-like, and aromatic. Based on fluorescence characterization, shallow groundwater was found to contain microbial and terrestrial derived DOC, and decomposed, humified and aromatic DOM. Deeper aquifers had a significantly larger microbial OM signature than the shallower aquifers and was less aromatic, decomposed and humified. The results from this study illustrate the potential for humic substances to contribute to As cycling and quantify the extent of As accumulation in the sediments and groundwater along a 1 km stretch of the Meghna. These findings contribute to the overall understanding of geochemical processes involved in As release into groundwaters from sediments within a fluvial deltaic environment and close proximity to a possible permeable natural reactive barrier.

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.

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.

How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II), mn(II), and S(−II) in undisturbed soils and sediments using voltammetry

USGS Publications Warehouse

Slowey, Aaron J.; Marvin-DiPasquale, Mark

2012-01-01

Conclusions - Despite their intrinsic variability, Hg/Au electrodes fabricated by hand can be used to quantify O2, S(−II), Fe(II), and Mn(II) without calibrating every electrode for every constituent of interest. The pilot ion method can achieve accuracies to within 20% or less, provided that the underlying principle—the independence of slope ratios—is demonstrated for all voltammetric techniques used, and effects of the physicochemical properties of the system on voltammetric signals are addressed through baseline subtraction.

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

Harriman, D.A.; Sargent, B.P.

Groundwater quality was evaluated in seven confined aquifers and the water table aquifer in east-central New Jersey based on 237 analyses of samples collected in 1981-82, and 225 older analyses. Investigation of the effect of land use on water quality and several sampling network proposals for the region are reported. Iron (Fe) and manganese (Mn) concentrations exceed US EPA drinking water standards in some wells screened in the Potomac-Raritan-Magothy aquifer system. Sodium (Na) concentrations in samples from three wells more than 800 ft deep in the Englishtown aquifer exceed the standard. Iron and Mn concentrations in this aquifer may alsomore » exceed the standards. Iron concentrations in the Wenonah-Mount Laurel aquifer exceed the standard. Based on 15 analyses of water from the Vincetown aquifer, Mn is the only constituent that exceeds the drinking water standard. In the Manasquan aquifer, 4 of the 16 Na determinations exceed the standard, and 8 of 16 Fe determinations exceed the standard. Water quality in the Atlantic City 800-ft sand is generally satisfactory. However, 12 Fe and 1 of 12 Mn determinations exceed the standards. For the Rio Grande water-bearing zone, 1 of 3 Fe determinations exceed the standard. The Kirkwood-Cohansey aquifer system was the most thoroughly sampled (249 chemical analyses from 209 wells). Dissolved solids, chloride, Fe, nitrate, and Mn concentrations exceed drinking water standards in some areas. 76 refs., 36 figs., 12 tabs.« less

Effect of flood events on transport of suspended sediments, organic matter and particulate metals in a forest watershed in the Basque Country (Northern Spain).

PubMed

Peraza-Castro, M; Sauvage, S; Sánchez-Pérez, J M; Ruiz-Romera, E

2016-11-01

An understanding of the processes controlling sediment, organic matter and metal export is critical to assessing and anticipating risk situations in water systems. Concentrations of suspended particulate matter (SPM), dissolved (DOC) and particulate (POC) organic carbon and metals (Cu, Ni, Pb, Cr, Zn, Mn, Fe) in dissolved and particulate phases were monitored in a forest watershed in the Basque Country (Northern Spain) (31.5km(2)) over three hydrological years (2009-2012), to evaluate the effect of flood events on the transport of these materials. Good regression was found between SPM and particulate metal concentration, making it possible to compute the load during the twenty five flood events that occurred during the study period at an annual scale. Particulate metals were exported in the following order: Fe>Mn>Zn>Cr>Pb>Cu>Ni. Annual mean loads of SPM, DOC and POC were estimated at 2267t, 104t and 57t, respectively, and the load (kg) of particulate metals at 76 (Ni), 83 (Cu), 135 (Pb), 256 (Cr), 532 (Zn), 1783 (Mn) and 95170 (Fe). Flood events constituted 91%-SPM, 65%-DOC, 71%-POC, 80%-Cu, 85%-Ni, 72%-Pb, 84%-Cr, 74%-Zn, 87%-Mn and 88%-Fe of total load exported during the three years studied. Flood events were classified into three categories according to their capacity for transporting organic carbon and particulate metals. High intensity flood events are those with high transport capacity of SPM, organic carbon and particulate metals. Most of the SPM, DOC, POC and particulate metal load was exported by this type of flood event, which contributed 59% of SPM, 45% of organic carbon and 54% of metals. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean

PubMed Central

Fitzsimmons, Jessica N.; Boyle, Edward A.; Jenkins, William J.

2014-01-01

Until recently, hydrothermal vents were not considered to be an important source to the marine dissolved Fe (dFe) inventory because hydrothermal Fe was believed to precipitate quantitatively near the vent site. Based on recent abyssal dFe enrichments near hydrothermal vents, however, the leaky vent hypothesis [Toner BM, et al. (2012) Oceanography 25(1):209–212] argues that some hydrothermal Fe persists in the dissolved phase and contributes a significant flux of dFe to the global ocean. We show here the first, to our knowledge, dFe (<0.4 µm) measurements from the abyssal southeast and southwest Pacific Ocean, where dFe of 1.0–1.5 nmol/kg near 2,000 m depth (0.4–0.9 nmol/kg above typical deep-sea dFe concentrations) was determined to be hydrothermally derived based on its correlation with primordial 3He and dissolved Mn (dFe:3He of 0.9–2.7 × 106). Given the known sites of hydrothermal venting in these regions, this dFe must have been transported thousands of kilometers away from its vent site to reach our sampling stations. Additionally, changes in the size partitioning of the hydrothermal dFe between soluble (<0.02 µm) and colloidal (0.02–0.4 µm) phases with increasing distance from the vents indicate that dFe transformations continue to occur far from the vent source. This study confirms that although the southern East Pacific Rise only leaks 0.02–1% of total Fe vented into the abyssal Pacific, this dFe persists thousands of kilometers away from the vent source with sufficient magnitude that hydrothermal vents can have far-field effects on global dFe distributions and inventories (≥3% of global aerosol dFe input). PMID:25349389

Partitioning of Dissolved Metals (Fe, Mn, Cu, Cd, Zn, Ni, and Pb) into Soluble and Colloidal Fractions in Continental Shelf and Offshore Waters, Northern California

NASA Astrophysics Data System (ADS)

Fitzsimmons, J. N.; Parker, C.; Sherrell, R. M.

2016-02-01

The physicochemical speciation of trace metals in seawater influences their cycling as essential micronutrients for microorganisms or as tracers of anthropogenic influences on the marine environment. While chemical speciation affects lability, the size of metal complexes influences their ability to be accessed biologically and also influences their fate in the aggregation pathway to marine particles. In this study, we show that multiple trace metals in shelf and open ocean waters off northern California (IRN-BRU cruise, July 2014) have colloidal-sized components. Colloidal fractions were operationally defined using two ultrafiltration methods: a 0.02 µm Anopore membrane and a 10 kDa ( 0.003 µm) cross flow filtration (CFF) system. Together these two methods distinguished small (0.003 - 0.02 µm) and large (0.02 µm - 0.2 µm) colloids. As has been found previously for seawater in other ocean regimes, dissolved Fe had a broad size distribution with 50% soluble (<10 kDa) complexes and both small and large colloidal species. Dissolved Mn had no measurable colloidal component, consistent with its predicted chemical speciation as free Mn(II). Dissolved Cu, which like Fe is thought to be nearly fully organically bound in seawater, was only 25% colloidal, and these colloids were all small. Surprisingly Cd, Ni, and Pb also showed colloidal components (8-20%, 25-40%, and 10-50%) despite their hypothesized low organic speciation. Zn and Pb were nearly completely sorbed onto the Anopore membrane, making CFF the only viable ultrafiltration method for those elements. Zn suffered incomplete recovery ( 50-75%) through the CFF system but showed 30-85% colloidal contribution; thus, verifying a Zn colloidal phase with these methods is challenging. Conclusions will reveal links between the physical and chemical speciation for these metals and what role these metal colloids might have on trace metal exchange between the ocean margin and offshore waters.

Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: A better understanding of biogeochemical processes for safe environmental management.

PubMed

Shaheen, Sabry M; Frohne, Tina; White, John R; DeLaune, Ron D; Rinklebe, Jörg

2017-01-15

Studies about the mobilization of potentially toxic elements (PTEs) in deltaic soils can be challenging, provide critical information on assessing the potential risk and fate of these elements and for sustainable management of these soils. The impact of redox potential (E H ), pH, iron (Fe), manganese (Mn), sulfate (SO 4 2- ), chloride (Cl - ), aliphatic dissolved organic carbon (DOC), and aromatic dissolved organic carbon (DAC) on the mobilization of copper (Cu), selenium (Se), and zinc (Zn) was studied in two soils collected from the Nile and Mississippi Rivers deltaic plains focused on increasing our understanding of the fate of these toxic elements. Soils were exposed to a range of redox conditions stepwise from reducing to oxidizing soil conditions using an automated biogeochemical microcosm apparatus. Concentrations of DOC and Fe were high under reducing conditions as compared to oxidizing conditions in both soils. The proportion of DAC in relation to DOC in solution (aromaticity) was high in the Nile Delta soil (NDS) and low in the Mississippi Delta soil (MDS) under oxidizing conditions. Mobilization of Cu was low under reducing conditions in both soils which was likely caused by sulfide precipitation and as a result of reduction of Cu 2+ to Cu 1+ . Mobilization of Se was high under low E H in both soils. Release of Se was positively correlated with DOC, Fe, Mn, and SO 4 2- in the NDS, and with Fe in the MDS. Mobilization of Zn showed negative correlations with E H and pH in the NDS while these correlations were non-significant in the MDS. The release dynamics of dissolved Zn could be governed mainly by the chemistry of Fe and Mn in the NDS and by the chemistry of Mn in the MDS. Our findings suggest that a release of Se and Zn occurs under anaerobic conditions, while aerobic conditions favor the release of Cu in both soils. In conclusion, the release of Cu, Se, and Zn under different reducing and oxidizing conditions in deltaic wetland soils should be taken into account due to increased mobilization and the potential environmental risks associated with food security in utilizing these soils for flooded agricultural and fisheries systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

A mass balance approach to investigating geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

USGS Publications Warehouse

Ng, Gene-Hua Crystal; Bekins, Barbara A.; Cozzarelli, Isabelle M.; Baedecker, Mary Jo; Bennett, Philip C.; Amos, Richard T.

2014-01-01

Secondary water quality impacts can result from a broad range of coupled reactions triggered by primary groundwater contaminants. Data from a crude-oil spill research site near Bemidji, MN provide an ideal test case for investigating the complex interactions controlling secondary impacts, including depleted dissolved oxygen and elevated organic carbon, inorganic carbon, CH4, Mn, Fe, and other dissolved ions. To better understand these secondary impacts, this study began with an extensive data compilation of various data types, comprising aqueous, sediment, gas, and oil phases, covering a 260 m cross-sectional domain over 30 years. Mass balance calculations are used to quantify pathways that control secondary components, by using the data to constrain the sources and sinks for the important redox processes. The results show that oil constituents other than BTEX (benzene, toluene, ethylbenzene, o-, m- and p-xylenes), including n-alkanes and other aromatic compounds, play significant roles in plume evolution and secondary water quality impacts. The analysis underscores previous results on the importance of non-aqueous phases. Over 99.9% of the Fe2+ plume is attenuated by immobilization on sediments as Fe(II) and 85–95% of the carbon biodegradation products are outgassed. Gaps identified in carbon and Fe mass balances and in pH buffering mechanisms are used to formulate a new conceptual model. This new model includes direct out-gassing of CH4 and CO2 from organic carbon biodegradation, dissolution of directly produced CO2, and sorption with H+ exchange to improve pH buffering. The identification of these mechanisms extends understanding of natural attenuation of potential secondary impacts at enhanced reductive dechlorination sites, particularly for reduced Fe plumes, produced CH4, and pH perturbations.

A mass balance approach to investigating geochemical controls on secondary water quality impacts at a crude oil spill site near Bemidji, MN

NASA Astrophysics Data System (ADS)

Ng, G.-H. Crystal; Bekins, Barbara A.; Cozzarelli, Isabelle M.; Baedecker, Mary Jo; Bennett, Philip C.; Amos, Richard T.

2014-08-01

Secondary water quality impacts can result from a broad range of coupled reactions triggered by primary groundwater contaminants. Data from a crude-oil spill research site near Bemidji, MN provide an ideal test case for investigating the complex interactions controlling secondary impacts, including depleted dissolved oxygen and elevated organic carbon, inorganic carbon, CH4, Mn, Fe, and other dissolved ions. To better understand these secondary impacts, this study began with an extensive data compilation of various data types, comprising aqueous, sediment, gas, and oil phases, covering a 260 m cross-sectional domain over 30 years. Mass balance calculations are used to quantify pathways that control secondary components, by using the data to constrain the sources and sinks for the important redox processes. The results show that oil constituents other than BTEX (benzene, toluene, ethylbenzene, o-, m- and p-xylenes), including n-alkanes and other aromatic compounds, play significant roles in plume evolution and secondary water quality impacts. The analysis underscores previous results on the importance of non-aqueous phases. Over 99.9% of the Fe2 + plume is attenuated by immobilization on sediments as Fe(II) and 85-95% of the carbon biodegradation products are outgassed. Gaps identified in carbon and Fe mass balances and in pH buffering mechanisms are used to formulate a new conceptual model. This new model includes direct out-gassing of CH4 and CO2 from organic carbon biodegradation, dissolution of directly produced CO2, and sorption with H+ exchange to improve pH buffering. The identification of these mechanisms extends understanding of natural attenuation of potential secondary impacts at enhanced reductive dechlorination sites, particularly for reduced Fe plumes, produced CH4, and pH perturbations.

Geochemistry of ferromanganese nodules from DOMES site a, Northern Equatorial Pacific: Multiple diagenetic metal sources in the deep sea

USGS Publications Warehouse

Calvert, S.E.; Piper, D.Z.

1984-01-01

The major and minor element composition of ferromanganese nodules from DOMES Site A has been determined by X-ray fluorescence methods. Three phases appear to control the bulk compositions: Mn and Fe oxyhydroxides and aluminosilicates. Relatively wide compositional variations are evident throughout the area. Nodules with high Mn/Fe ratios, high Cu, Mg, Mo, Ni and Zn concentrations and high todorokite/??-MnO2 ratios have granular surface textures and are confined to an east-west trending depression with thin Quaternary sediment cover. Nodules with low Mn/Fe ratios, high concentrations of As, Ca, Ce, Co, La, P, Sr, Ti, V, Y and Zr and low todorokite/??-MnO2 ratios have smooth surfaces and are confined to shallower areas with relatively thick Quaternary sediment to the north and south of the depression. All nodules in the area have compositions which are influenced by diagenesis, but those with the most marked diagenetic signature (high Mn/Fe and Cu/Ni ratios, low Ce/La ratios and more todorokite) are found in areas of very slow or non-existent sedimentation; many of these nodules are actually in contact with outcropping Tertiary sediment. This paradox may be resolved by postulating, by analogy with some shallow-water occurrences, that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation. The metals are supplied in a bottom flow (probably Antarctic Bottom Water) which also erodes, or prevents modern sedimentation in, the depression. Nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying Quaternary sediment. Apparently, abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source. Metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form. ?? 1984.

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.

Analysis of total and dissolved heavy metals in surface water of a Mexican polluted river by total reflection X-ray fluorescence spectrometry

NASA Astrophysics Data System (ADS)

Zarazua, G.; Ávila-Pérez, P.; Tejeda, S.; Barcelo-Quintal, I.; Martínez, T.

2006-11-01

The present area of study is located in the Upper Course of the Lerma River (UCLR). The Lerma is one of the most important rivers of Mexico, where it drains highly populated and industrialized regions. The aim of the present study is to determine the heavy metal concentration of Cr, Mn, Fe, Cu and Pb in dissolved and total phases of the UCLR by means of Total Reflection X-ray Fluorescence Spectrometry (TXRF). The surface water samples were collected at 8 sites distributed following the stream flow direction of the river. Four sampling campaigns were carried out in each site in a 1-year period. A sample preparation method was applied in order to obtain the total and dissolved fraction and to destroy the organic matter. The total heavy metal average concentration decrease in the following order: Fe (2566 μg/L) > Mn (300 μg/L) > Cu (66 μg/L) > Cr (21 μg/L) > Pb (15 μg/L). In general, the heavy metal concentrations in water of the UCLR are below the maximum permissible limits.

Diffusion of cations in chromia layers grown on iron-base alloys

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

Lobnig, R.E.; Hennesen, K.; Grabke, H.J.

Diffusion of the cations Cr, Fe, Mn, and Ni in Cr{sub 2}O{sub 3} has been investigated at 1,173 K. The diffusion measurements were performed on chromia layers grown on the model alloys Fe-20Cr and Fe-20Cr-12Ni in order to consider effects of small amounts of dissolved alien cations in Cr{sub 2}O{sub 3}. The samples were diffusion annealed in H{sub 2}-H{sub 2}O at an oxygen partial pressure close to the Cr{sub 2}O{sub 3}/Cr equilibrium. For all tracers the lattice-diffusion coefficients are 3-5 orders of magnitude smaller than the grain-boundary diffusion coefficients. The lattice diffusivity of Mn is about two orders of magnitudemore » greater than the other lattice-diffusion coefficients, especially in Cr{sub 2}O{sub 3} grown on Fe-20Cr-12Ni. The values of the diffusion coefficients for Cr, Fe, and Ni are in the same range. Diffusion of the tracers in Cr{sub 2}O{sub 3} grown on different alloys did not show significant differences with the exception of Mn.« less

Distribution of dissolved manganese in the Peruvian Upwelling and Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Vedamati, Jagruti; Chan, Catherine; Moffett, James W.

2015-05-01

The geochemistry of manganese (Mn) in seawater is dominated by its redox chemistry, as Mn(II) is soluble and Mn(IV) forms insoluble oxides, and redox transformations are mediated by a variety of processes in the oceans. Dissolved Mn (DMn) accumulates under reducing conditions and is depleted under oxidizing conditions. Thus the Peruvian upwelling region, characterized by highly reducing conditions over a broad continental shelf and a major oxygen minimum zone extending far offshore, is potentially a large source of Mn to the eastern Tropical South Pacific. In this study, DMn was determined on cruises in October 2005 and February 2010 in the Peruvian Upwelling and Oxygen Minimum Zone, to evaluate the relationship between Mn, oxygen and nitrogen cycle processes. DMn concentrations were determined using simple dilution and matrix-matched external standardization inductively coupled mass spectrometry. Surprisingly, DMn was depleted under the most reducing conditions along the Peruvian shelf. Concentrations of dissolved Mn in surface waters increased offshore, indicating that advection of Mn offshore from the Peruvian shelf is a minor source. Subsurface Mn maxima were observed within the oxycline rather than within the oxygen minimum zone (OMZ), indicating they arise from remineralization of organic matter rather than reduction of Mn oxides. The distribution of DMn appears to be dominated by non-redox processes and inputs from the atmosphere and from other regions associated with specific water masses. Lower than expected DMn concentrations on the shelf probably reflect limited fluvial inputs from the continent and efficient offshore transport. This behavior is in stark contrast to Fe, reported in a companion study which is very high on the shelf and undergoes dynamic redox cycling.

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.

THE EFFECTS OF ELEVATED METALS ON BENTHIC COMMUNITY METABOLISM IN A ROCKY MOUNTAIN STREAM

EPA Science Inventory

The effects of elevated metals (dissolved Zn, Mn and/or Fe) in a Rocky Mountain stream were assessed using measures of primary productivity, community respiration and water-column toxicity. Primary productivity was measured as rates of O2 evolution from natural substrates incubat...

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.

Stability Behavior and Thermodynamic States of Iron and Manganese in Sandy Soil Aquifer, Manukan Island, Malaysia

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

Lin, Chin Yik, E-mail: cy_lin_ars@hotmail.com; Abdullah, Mohd. Harun; Musta, Baba

2011-03-15

A total of 20 soil samples were collected from 10 boreholes constructed in the low lying area, which included ancillary samples taken from the high elevation area. Redox processes were investigated in the soil as well as groundwater in the shallow groundwater aquifer of Manukan Island, Sabah, Malaysia. Groundwater samples (n = 10) from each boreholes were also collected in the low lying area to understand the concentrations and behaviors of Fe and Mn in the dissolved state. This study strives to obtain a general understanding of the stability behaviors on Fe and Mn at the upper unsaturated and themore » lower-saturated soil horizons in the low lying area of Manukan Island as these elements usually play a major role in the redox chemistry of the shallow groundwater. Thermodynamic calculations using PHREEQC showed that the groundwater samples in the study area are oversaturated with respect to goethite, hematite, Fe(OH){sub 3} and undersaturated with respect to manganite and pyrochroite. Low concentrations of Fe and Mn in the groundwater might be probably due to the lack of minerals of iron and manganese oxides, which exist in the sandy aquifer. In fact, high organic matters that present in the unsaturated horizon are believed to be responsible for the high Mn content in the soil. It was observed that the soil samples collected from high elevation area (BK) comprises considerable amount of Fe in both unsaturated (6675.87 mg/kg) and saturated horizons (31440.49 mg/kg) compared to the low Fe content in the low lying area. Based on the stability diagram, the groundwater composition lies within the stability field for Mn{sup 2+} and Fe{sup 2+} under suboxic condition and very close to the FeS/Fe{sup 2+} stability boundary. This study also shows that both pH and Eh values comprise a strong negative value thus suggesting that the redox potential is inversely dependent on the changes of pH.« less

Effects of metal ions on the reactivity and corrosion electrochemistry of Fe/FeS nanoparticles.

PubMed

Kim, Eun-Ju; Kim, Jae-Hwan; Chang, Yoon-Seok; Turcio-Ortega, David; Tratnyek, Paul G

2014-04-01

Nano-zerovalent iron (nZVI) formed under sulfidic conditions results in a biphasic material (Fe/FeS) that reduces trichloroethene (TCE) more rapidly than nZVI associated only with iron oxides (Fe/FeO). Exposing Fe/FeS to dissolved metals (Pd(2+), Cu(2+), Ni(2+), Co(2+), and Mn(2+)) results in their sequestration by coprecipitation as dopants into FeS and FeO and/or by electroless precipitation as zerovalent metals that are hydrogenation catalysts. Using TCE reduction rates to probe the effect of metal amendments on the reactivity of Fe/FeS, it was found that Mn(2+) and Cu(2+) decreased TCE reduction rates, while Pd(2+), Co(2+), and Ni(2+) increased them. Electrochemical characterization of metal-amended Fe/FeS showed that aging caused passivation by growth of FeO and FeS phases and poisoning of catalytic metal deposits by sulfide. Correlation of rate constants for TCE reduction (kobs) with electrochemical parameters (corrosion potentials and currents, Tafel slopes, and polarization resistance) and descriptors of hydrogen activation by metals (exchange current density for hydrogen reduction and enthalpy of solution into metals) showed the controlling process changed with aging. For fresh Fe/FeS, kobs was best described by the exchange current density for activation of hydrogen, whereas kobs for aged Fe/FeS correlated with electrochemical descriptors of electron transfer.

Effects of electron acceptors on soluble reactive phosphorus in the overlying water during algal decomposition.

PubMed

Wang, Jinzhi; Jiang, Xia; Zheng, Binghui; Niu, Yuan; Wang, Kun; Wang, Wenwen; Kardol, Paul

2015-12-01

Endogenous phosphorus (P) release from sediments is an important factor to cause eutrophication and, hence, algal bloom in lakes in China. Algal decomposition depletes dissolved oxygen (DO) and causes anaerobic conditions and therefore increases P release from sediments. As sediment P release is dependent on the iron (Fe) cycle, electron acceptors (e.g., NO3 (-), SO4 (2-), and Mn(4+)) can be utilized to suppress the reduction of Fe(3+) under anaerobic conditions and, as such, have the potential to impair the release of sediment P. Here, we used a laboratory experiment to test the effects of FeCl3, MnO2, and KNO3 on soluble reactive phosphorus (SRP) concentration and related chemical variables in the overlying water column during algal decomposition at different algal densities. Results showed that algal decomposition significantly depleted DO and thereby increased sediment Fe-bound P release. Compared with the control, addition of FeCl3 significantly decreased water SRP concentration through inhibiting sediment P release. Compared with FeCl3, addition of MnO2 has less potential to suppress sediment P release during algal decomposition. Algal decomposition has the potential for NO3 (-) removal from aquatic ecosystem through denitrification and by that alleviates the suppressing role of NO3 (-) on sediment P release. Our results indicated that FeCl3 and MnO2 could be efficient in reducing sediment P release during algal decomposition, with the strongest effect found for FeCl3; large amounts of NO3 (-) were removed from the aquatic ecosystem through denitrification during algal decomposition. Moreover, the amounts of NO3 (-) removal increased with increasing algal density.

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.

Formation of Fe-Mn crusts within a continental margin environment

USGS Publications Warehouse

Conrad, Tracey A.; Hein, James R.; Paytan, Adina; Clague, David A.

2017-01-01

This study examines Fe-Mn crusts that form on seamounts along the California continental-margin (CCM), within the United States 200 nautical mile exclusive economic zone. The study area extends from approximately 30° to 38° North latitudes and from 117° to 126° West longitudes. The area of study is a tectonically active northeast Pacific plate boundary region and is also part of the North Pacific Subtropical Gyre with currents dominated by the California Current System. Upwelling of nutrient-rich water results in high primary productivity that produces a pronounced oxygen minimum zone. Hydrogenetic Fe-Mn crusts forming along the CCM show distinct chemical and mineral compositions compared to open-ocean crusts. On average, CCM crusts contain more Fe relative to Mn than open-ocean Pacific crusts. The continental shelf and slope release both Fe and Mn under low-oxygen conditions. Silica is also enriched relative to Al compared to open-ocean crusts. This is due to the North Pacific silica plume and enrichment of Si along the path of deep-water circulation, resulting in Si enrichment in bottom and intermediate waters of the eastern Pacific.The CCM Fe-Mn crusts have a higher percentage of birnessite than open-ocean crusts, reflecting lower dissolved seawater oxygen that results from the intense coastal upwelling and proximity to zones of continental slope pore-water anoxia. Carbonate fluorapatite (CFA) is not present and CCM crusts do not show evidence of phosphatization, even in the older sections. The mineralogy indicates a suboxic environment under which birnessite forms, but in which pH is not high enough to facilitate CFA deposition. Growth rates of CCM crusts generally increase with increasing water depth, likely due to deep-water Fe sources mobilized from reduced shelf and slope sediments.Many elements of economic interest including Mn, Co, Ni, Cu, W, and Te have slightly or significantly lower concentrations in CCM crusts relative to crusts from the Pacific Prime Crust Zone and other open-ocean basins. However, concentrations of total rare earth elements and yttrium average only slightly lower contents and in the future may be a strategic resource for the U.S.

Acid volatile sulfides oxidation and metals (Mn, Zn) release upon sediment resuspension: laboratory experiment and model development.

PubMed

Hong, Yong Seok; Kinney, Kerry A; Reible, Danny D

2011-03-01

Sediment from the Anacostia River (Washington, DC, USA) was suspended in aerobic artificial river water for 14 d to investigate the dynamics of dissolved metals release and related parameters including pH, acid volatile sulfides (AVS), and dissolved/solid phase Fe(2+). To better understand and predict the underlying processes, a mathematical model is developed considering oxidation of reduced species, dissolution of minerals, pH changes, and pH-dependent metals' sorption to sediment. Oxidation rate constants of elemental sulfur and zinc sulfide, and a dissolution rate constant of carbonate minerals, were adjusted to fit observations. The proposed model and parameters were then applied, without further calibration, to literature-reported experimental observations of resuspension in an acid sulfate soil collected in a coastal flood plain. The model provided a good description of the dynamics of AVS, Fe(2+), S(0)((s)), pH, dissolved carbonates concentrations, and the release of Ca((aq)), Mg((aq)), and Zn((aq)) in both sediments. Accurate predictions of Mn((aq)) release required adjustment of sorption partitioning coefficient, presumably due to the presence of Mn scavenging by phases not accounted for in the model. The oxidation of AVS (and the resulting release of sulfide-bound metals) was consistent with a two-step process, a relatively rapid AVS oxidation to elemental sulfur (S(0)((s))) and a slow oxidation of S(0)((s)) to SO(4)(2-)((aq)), with an associated decrease in pH from neutral to acidic conditions. This acidification was the dominant factor for the release of metals into the aqueous phase. Copyright © 2010 SETAC.

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.

Iron Cycling in Sediment of the North Atlantic: Preliminary Results from R/V Knorr Expedition 223

NASA Astrophysics Data System (ADS)

Anderson, C. H.; Estes, E. R.; Dyar, M. D.; Murray, R. W.; Spivack, A. J.; Sauvage, J.; McKinley, C. C.; Present, T. M.; Homola, K.; Pockalny, R. A.; D'Hondt, S.

2015-12-01

Iron (Fe) in marine sediments is a significant microbial electron acceptor [Fe(III)] in suboxic conditions and is an electron donor [Fe(II)] in oxic conditions. In the transition from oxic to suboxic sediment, a portion of solid Fe is reduced and mobilized as soluble Fe(II) into interstitial water during the oxidation of organic matter. The presence of Fe and its oxidation state in oxic sediment provides insight into an important metabolic and mineral reaction pathway in subseafloor sediment. We recovered bulk sediment and interstitial water at western North Atlantic sites during Expedition 223 on the R/V Knorr in November, 2014. The expedition targeted regions with predominantly oxic sediment and regions with predominantly anoxic sediment, ideal for investigating redox Fe cycling between solid and aqueous phases. At Site 10 (14.4008N, 50.6209W, 4455m water depth), interstitial dissolved oxygen is depleted within the upper few meters of sediment. At Site 12 (29.6767N, 58.3285W, 5637m water depth), interstitial dissolved oxygen is present throughout the cored sediment column (10s of meters). Here we present total solid Fe concentration for 45 bulk sediment samples and total aqueous Fe and Mn concentrations for 50 interstitial water samples analyzed via ICP-ES. We additionally present Fe(II) and Fe(III) speciation results from 10 solid sediment samples determined by Mossbauer spectroscopy. We trace downcore fluctuations in Fe in solid and aqueous phases to understand Fe cycling in oxic, suboxic, and transitional regimes. Our preliminary data indicate that solid Fe concentration ranges from 4-6 wt % at the oxic site; aqueous Fe ranges from below detection to 20μM and aqueous Mn ranges from 1 to 125 μM at the anoxic site. In the anoxic sediment (Site 10), 86-90% of the total Fe is oxidized [Fe(III)] and 10-14% as reduced [Fe(II)], compared to 3-6% as reduced [Fe(II)] at the oxic site (Site 12), even in sediment as old as 25 million years.

Microbial Immobilization of Si, Mn, Fe, and Sr Ions in the Nacreous Layer of Sinohyliopsis schlegeli and Environmental Factors

NASA Astrophysics Data System (ADS)

Tazaki, Kazue; Morii, Issei

Environmental changes recorded in the shell nacre of Sinohyliopsis schlegeli were observed with elemental factors of characteristic water and nutrition for eight months in a cultivated drainage pond at Kanazawa University, Ishikawa Prefecture, Japan. Tetracycline as an indicator was injected into the shell nacre once every month from May to November in 2007. Water qualities such as the pH, redox potential, electrical conductivity, dissolved oxygen concentration, and water temperature were measured periodically, and the suspended solids in the water were removed by filtration for optical microscopy, X-ray fluorescence analysis, and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) observations. X-ray fluorescence chemical analysis of shell nacre indicated layers with strong tetracycline accumulation corresponding to high concentrations of Si, Mn, Fe, and Sr ions. The redox potential and dissolved oxygen concentration measurements supported the existence of layers in the nacre. The suspended materials in the drainage pond water comprised mainly of Si, Mn, and Fe elements, which were the same elements involved in microbial immobilization in the shell nacre during the summer of 2007. SEM-EDX analyses confirmed that the ions originated from diatoms, Siderocapsa sp. and Gallionella ferruginea in the stomach. There was little microbial immobilization of the ions in winter. The results suggested elemental immobilization in the layered shell nacre and indicated that Sinohyliopsis schlegeli fed on the ions, to grow the nacre during summer. Sinohyliopsis schlegeli with these biogenic oxides might contribute to the scavenging of heavy metals in natural water.

Dissolved organic matter degradation by sunlight coagulates organo-mineral colloids and produces low-molecular weight fraction of metals in boreal humic waters

NASA Astrophysics Data System (ADS)

Oleinikova, Olga V.; Drozdova, Olga Yu.; Lapitskiy, Sergey A.; Demin, Vladimir V.; Bychkov, Andrey Yu.; Pokrovsky, Oleg S.

2017-08-01

Photochemical degradation of dissolved organic matter (DOM) is recognized as the major driver of CO2 emission to the atmosphere from the inland waters of high latitudes. In contrast to numerous studies of photo-induced DOM transformation, the behavior of trace element (TE) during photodegradation of boreal DOM remains virtually unknown. Towards a better understanding of concentration, size fractionation and speciation change of DOM and TE in boreal waters subjected to solar radiation, we conducted on-site photo-degradation experiments in stream and bog water collected from a pristine zone of the Northern Karelia (Russian subarctic). 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 dissolved (<0.22 μm) Al and Fe concentration was observed in the boreal stream. A number of low-soluble TE linked to Fe-rich organo-mineral colloids followed the behavior of Fe during bog water exposure to sunlight: Al, P, Ti, V, Cr, As, Y, Zr, REEs, Hf, Th, Pb and U. The second group of elements (Li, B, Mg, Ca, Sr, Ba, Na, K, Rb, Si, Mn, Ni, Cu, Co, Cd, Sb) was indifferent to photodegradation of DOM and exhibited a non-systematic variation (±10-15% from the control) of <0.22 μm fraction in the course of sunlight exposure. The bog water insolation yielded a factor of 3 ± 1 increase of low molecular weight (LMW < 1 kDa) fraction of organic carbon, Al, Fe, U, Mg, Ca, Mn, Co, Ni, Sr, Cd and Ba after 200 h of sunlight exposure compared to the dark control. The LMW< 1 kDa fraction was preferentially enriched in Fe, Al, Ca, Mg and other divalent metals relative to Corg. The climate warming leading to water temperature rise in the boreal zone will intensify the Fe and Al hydroxide coagulation while increasing the production of LMW organic ligands and free metals and metal - organic complexes.

Sources of variability in livestock water quality over 5 years in the Northern Great Plains

USDA-ARS?s Scientific Manuscript database

Mineral content of livestock water grazing rangelands can be a source of minerals affecting health and drinkability. To estimate yearly variation in water mineral concentrations, 11 indicators of quality were measured (Ca, Cl, Fe, Fl, Mg, Mn, Na, NO3-N, pH, SO4, total dissolved solids (TDS) and temp...

Sulfide Melts and Chalcophile Element Behavior in High Temperature Systems

NASA Astrophysics Data System (ADS)

Wood, B. J.; Kiseeva, K.

2016-12-01

We recently found that partition coefficients (Di) of many weakly and moderately chalcophile elements (e.g., Cd, Zn, Co, Cr, Pb, Sb, In) between sulfide and silicate melts are simple functions of the FeO content of the silicate liquid: logDi A-Blog[FeO] where [FeO] is the FeO concentration in the silicate, A and B are constants and the latter is related to the valency of the element of interest. In contrast, some strongly chalcophile (e.g Cu, Ni, Ag) and lithophile elements (e.g Mn) show marked deviations from linearity on a plot of logDi vs log[FeO]. More recent experiments show that linear behavior is confined to elements whose affinities for S and O are similar to those of Fe. In the case of elements more strongly lithophile than Fe (Ti, U, REE, Zr, Nb, Ta, Mn) a plot of logDi versus log[FeO] describes a U-shape with the element partitioning strongly into the sulfide at very low FeO and again at very high FeO content of the silicate melt. In contrast, strongly chalcophile elements (Cu, Ni, Ag) describe an n-shape on the plot of logD vs log[FeO]. The result is that lithophile elements such as Nb become more "chalcophile" than Cu at very low and very high FeO contents of the silicate melt. The reasons for this surprising behavior are firstly that, at very low FeO contents the silicate melt dissolves substantial amounts of sulfur, which drives down the activity of FeO and, from mass-action "pulls" the lihophile element into the sulfide. At high FeO contents of the silicate the sulfide itself starts to dissolve substantial amounts of oxygen and lithophile elements follow the oxygen into the sulfide. Given the principles which we have established, we are able to describe the patterns of chalcophile element behavior during partial melting and fractional crystallisation on Earth and also on bodies such as Mercury and Mars which are, respectively, strongly reduced relative to Earth and more oxidised than Earth.

Geochemical behaviour of dissolved trace elements in a monsoon-dominated tropical river basin, Southwestern India.

PubMed

Gurumurthy, G P; Balakrishna, K; Tripti, M; Audry, Stéphane; Riotte, Jean; Braun, J J; Udaya Shankar, H N

2014-04-01

The study presents a 3-year time series data on dissolved trace elements and rare earth elements (REEs) in a monsoon-dominated river basin, the Nethravati River in tropical Southwestern India. The river basin lies on the metamorphic transition boundary which separates the Peninsular Gneiss and Southern Granulitic province belonging to Archean and Tertiary-Quaternary period (Western Dharwar Craton). The basin lithology is mainly composed of granite gneiss, charnockite and metasediment. This study highlights the importance of time series data for better estimation of metal fluxes and to understand the geochemical behaviour of metals in a river basin. The dissolved trace elements show seasonality in the river water metal concentrations forming two distinct groups of metals. First group is composed of heavy metals and minor elements that show higher concentrations during dry season and lesser concentrations during the monsoon season. Second group is composed of metals belonging to lanthanides and actinides with higher concentration in the monsoon and lower concentrations during the dry season. Although the metal concentration of both the groups appears to be controlled by the discharge, there are important biogeochemical processes affecting their concentration. This includes redox reactions (for Fe, Mn, As, Mo, Ba and Ce) and pH-mediated adsorption/desorption reactions (for Ni, Co, Cr, Cu and REEs). The abundance of Fe and Mn oxyhydroxides as a result of redox processes could be driving the geochemical redistribution of metals in the river water. There is a Ce anomaly (Ce/Ce*) at different time periods, both negative and positive, in case of dissolved phase, whereas there is positive anomaly in the particulate and bed sediments. The Ce anomaly correlates with the variations in the dissolved oxygen indicating the redistribution of Ce between particulate and dissolved phase under acidic to neutral pH and lower concentrations of dissolved organic carbon. Unlike other tropical and major world rivers, the effect of organic complexation on metal variability is negligible in the Nethravati River water.

Evaluating the potential of three Fe- and Mn-(nano)oxides for the stabilization of Cd, Cu and Pb in contaminated soils.

PubMed

Michálková, Zuzana; Komárek, Michael; Šillerová, Hana; Della Puppa, Loïc; Joussein, Emmanuel; Bordas, François; Vaněk, Aleš; Vaněk, Ondřej; Ettler, Vojtěch

2014-12-15

The potential of three Fe- and Mn-(nano)oxides for stabilizing Cd, Cu and Pb in contaminated soils was investigated using batch and column experiments, adsorption tests and tests of soil microbial activity. A novel synthetic amorphous Mn oxide (AMO), which was recently proposed as a stabilizing amendment, proved to be the most efficient in decreasing the mobility of the studied metals compared to nano-maghemite and nano-magnetite. Its application resulted in significant decreases of exchangeable metal fractions (92%, 92% and 93% decreases of Cd, Cu and Pb concentrations, respectively). The adsorption capacity of the AMO was an order of magnitude higher than those recorded for the other amendments. It was also the most efficient treatment for reducing Cu concentrations in the soil solution. No negative effects on soil microorganisms were recorded. On the other hand, the AMO was able to dissolve soil organic matter to some extent. Copyright © 2014 Elsevier Ltd. All rights reserved.

Water quality impacts of hydraulic-fracturing chemicals observed in a permeable, quartz-sand aquifer

NASA Astrophysics Data System (ADS)

Kent, D. B.; LeBlanc, D. R.; Smith, R. L.

2012-12-01

A pilot scale experiment was conducted on western Cape Cod, Massachusetts to test the use of hydraulic fracturing (HF) for emplacing permeable reactive barriers (PRB) where the water table is too far below land surface to use standard excavation methods. Two PRB were emplaced 24 to 36 meters below land surface in a plume with low concentrations of perchloroethylene in oxic, mildly acidic groundwater with low concentrations of dissolved salts. The granular aquifer sediments consist of permeable sands and gravels. Quartz comprises greater than 90% by weight of the aquifer sediments but chemical reactivity of the sediments is controlled by micrometer-scale chlorite and illite and nanometer-scale aluminum-substituted goethite. HF fluids contained guar gum (gelling agent), cellulose enzyme and acetic acid (breakers), sodium borate (cross-linker), potassium (K) carbonate (pH adjustor), and sodium (Na) chloride (tracer). Water-quality impacts within about 20 meters of the PRB were monitored over a 1.7-year period following HF. Arrival of HF-chemicals was marked by an increase in boron (B) from ambient concentrations of 6 uM to >800 uM. B concentrations rose for approximately 50 days, much longer than the 22-day period over which HF was conducted. B concentrations subsequently decreased but remained 2-3 times above background concentrations for almost one year. Elevated Na and K concentrations in the HF fluids drove sorption (including ion exchange) reactions resulting in transient increases in naturally occurring major, minor, and trace cations up to 20 to 50 times background concentrations. Increases in dissolved organic carbon (DOC) and decreases in dissolved oxygen (DO) concentrations were observed as B concentrations increased. DOC concentration subsequently decreased but remained significantly above background. DO concentrations remained below detection. Dissolved iron (Fe) and manganese (Mn) concentrations increased as DO concentrations decreased below detection and remained elevated 1.7 years after HF. Reactions with Fe in the PRB may have contributed to the observed Fe concentrations but Mn was likely released from the aquifer sediments. Fe and Mn concentrations remained elevated throughout the sampling period. Dissolved arsenic concentrations increased after anaerobic conditions were established from below detection to 0.3-0.5 uM. HF fluids contained only a subset of the chemicals used in typical HF stimulations and aquifer sediments were likely less reactive than aquifer solids at other sites. Despite these differences, several findings have applicability to other sites. B is a potentially useful tracer of intrusion of HF fluids into aquifers, but elevated concentrations may be short-lived. Sorption reactions driven by differences in dissolved salt concentrations between HF fluids and ambient groundwater result in changes in cation concentrations, including barium and strontium. Organic compounds in HF fluids may drive aerobic aquifers anaerobic. Anaerobic conditions may lead to mobilization of naturally occurring contaminants like arsenic, whose reduced forms are more mobile than oxidized forms.

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.

Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater

USGS Publications Warehouse

Bau, M.; Koschinsky, A.; Dulski, P.; Hein, J.R.

1996-01-01

In order to evaluate details of the partitioning behaviours of Y, rare earth elements (REEs), and Ti between inorganic metal oxide surfaces and seawater, we studied the distribution of these elements in hydrogenetic marine ferromanganese (Fe-Mn) crusts from the Central Pacific Ocean. Nonphosphatized Fe-Mn crusts display shale-normalized rare earths and yttrium (REYSN) patterns (Y inserted between Dy and Ho) that are depleted in light REEs (LREEs) and which show negative anomalies for YSN, and positive anomalies for LaSN, EuSN, GdSN, and in most cases, CeSN. They show considerably smaller Y/ Ho ratios than seawater or common igneous and clastic rocks, indicating that Y and Ho are fractionated in the marine environment. Compared to P-poor crusts, REYSN patterns of phosphatized Fe-Mn crusts are similar, but yield pronounced positive YSN anomalies, stronger positive LaSN anomalies, and enrichment of the HREEs relative to the MREEs. The data suggest modification of REY during phosphatization and indicate that studies requiring primary REY distributions or isotopic ratios should be restricted to nonphosphatized (layers of) Fe-Mn crusts. Apparent bulk coefficients, KMD, describing trace metal partitioning between nonphosphatized hydrogenetic Fe-Mn crusts and seawater, are similar for Pr to Eu and decrease for Eu to Yb. Exceptionally high values of KCeD, which are similar to those of Ti, result from oxidative scavenging of Ce and support previous suggestions that Ce(IV) is a hydroxide-dominated element in seawater. Yttrium and Gd show lower KD values than their respective neighbours in the REY series. Results of modelling the exchange equilibrium between REY dissolved in seawater and REY sorbed on hydrous Fe-Mn oxides corroborate previous studies that suggested the surface complexation of REY can be approximated by their first hydroxide binding constant. Negative "anomalies" occur for stabilities of bulk surface complexes of Gd, La, and particularly Y. The differences in inorganic surface complex stability between Y and Ho and between Gd and its REE neighbours are similar to those shown by the stabilities of complexes with aminocarboxylic acids and are significantly larger than those shown by stabilities of complexes with carboxylic acids. Hence, sorption of Y and REEs onto hydrous Fe-Mn oxides may contribute significantly to the positive YSN and GdSN anomalies in seawater.

Mechanisms involved in phosphorus mobility at sediment/water interface under redox oscillations in dam-reservoir context

NASA Astrophysics Data System (ADS)

Rapin, Anne; Grybos, Malgorzata; Rabiet, Marion; Kestens, Tim; Mourier, Brice; Deluchat, Veronique

2017-04-01

The construction of dams, in response to the growing human demand of water and electricity, leads to the perturbation of several natural biogeochemical cycles, including phosphorus (P). Given its high affinity for solid phases, P tends to accumulate with the sediments in dam-reservoirs. Since the sedimentary P may contribute to water eutrophication, attention should be paid to better understand the parameters, conditions and mechanisms controlling the release of P at the sediment/water interface in such a system. The mobility of P at sediment/water interface closely depends on bio-physico-chemical conditions (redox potential, pH, temperature). Champsanglard dam-reservoir (19.5 m height; 55 ha; Creuse, France) was constructed in 1982 and is annually subject to bathing bans caused by the development of cyanobacteria, although the surface water is classified by the EU Water Framework Directive as being of medium quality regarding total dissolved P. The sediments accumulated in this reservoir are relatively rich in P (1.81 ± 0.22 mgP/gDW), in the silt-sand fraction and characterized by high organic matter content (21 ± 0.1 %). The development of temporary anoxia during summer in hypolimnion and P distribution in the sediments (66% of P associated with amorphous Mn/Fe-oxy-hydroxydes) highlight the importance of the redox potential variation on P mobility. In this context, incubation experiments were conducted to evaluate the role of alternation between aerobic and anaerobic conditions on P sediment mobility. Surface sediments (Φ<2 mm) were incubated with a synthetic solution simulating the chemistry of Champsanglard reservoir water and submitted to two successive aerated and non-aerated phases. Physico-chemical composition (pH, Eh, P-PO43-, FeII, Mn, NO3-, SO42- and dissolved organic carbon (DOC)) and organic matter aromaticity (SUVA254) of the supernatant were monitored all along the incubation. The results showed that the development of anaerobic conditions (decrease of redox potential, NO3- and SO42- and increase of FeII and Mn concentrations) during the two non-aerated phases induces the release of P to the solution. However, during the second anaerobic phase, a higher release of 57 % P- PO43- was observed (8.7 ± 0.5 mgP/L for the second phase to 6.4 ± 0.5 mgP/L for the first one). During the first anaerobic phase, P-PO43- dynamic was correlated with the release of FeII and Mn suggesting that the reductive dissolution of Mn/Fe-oxy-hydroxydes was the main mechanism controlling the P mobility. However, in the second anaerobic phase, Mn and FeII concentrations were much lower (respectively of 24 % and 56 %) than in the first anaerobic phase. SUVA254 index showed that organic compounds released in the first cycle were less aromatic than in the second cycle and exhibited the geochemical characteristics of microbial metabolites (in opposition to humic substances in the second cycle). According to Pan et al. (2016), aromatic organic matter could limit reductive dissolution of Fe-oxyhydroxydes and involve competition for P sorption sites. This experiment highlighted that organic matter quality plays together with Mn/Fe-oxy-hydroxydes an important role in P mobility at sediment/water interface in dam-reservoirs. Keywords: Phosphorus; Sediment; Redox-oscillations; Dam reservoir; Mechanisms

Rates of zinc and trace metal release from dissolving sphalerite at pH 2.0-4.0

USGS Publications Warehouse

Stanton, M.R.; Gemery-Hill, P. A.; Shanks, Wayne C.; Taylor, C.D.

2008-01-01

High-Fe and low-Fe sphalerite samples were reacted under controlled pH conditions to determine nonoxidative rates of release of Zn and trace metals from the solid-phase. The release (solubilization) of trace metals from dissolving sphalerite to the aqueous phase can be characterized by a kinetic distribution coefficient, (Dtr), which is defined as [(Rtr/X(tr)Sph)/(RZn/X(Zn) Sph)], where R is the trace metal or Zn release rate, and X is the mole fraction of the trace metal or Zn in sphalerite. This coefficient describes the relationship of the sphalerite dissolution rate to the trace metal mole fraction in the solid and its aqueous concentration. The distribution was used to determine some controls on metal release during the dissolution of sphalerite. Departures from the ideal Dtr of 1.0 suggest that some trace metals may be released via different pathways or that other processes (e.g., adsorption, solubility of trace minerals such as galena) affect the observed concentration of metals. Nonoxidative sphalerite dissolution (mediated by H+) is characterized by a "fast" stage in the first 24-30 h, followed by a "slow" stage for the remainder of the reaction. Over the pH range 2.0-4.0, and for similar extent of reaction (reaction time), sphalerite composition, and surface area, the rates of release of Zn, Fe, Cd, Cu, Mn and Pb from sphalerite generally increase with lower pH. Zinc and Fe exhibit the fastest rates of release, Mn and Pb have intermediate rates of release, and Cd and Cu show the slowest rates of release. The largest variations in metal release rates occur at pH 2.0. At pH 3.0 and 4.0, release rates show less variation and appear less dependent on the metal abundance in the solid. For the same extent of reaction (100 h), rates of Zn release range from 1.53 ?? 10-11 to 5.72 ?? 10-10 mol/m2/s; for Fe, the range is from 4.59 ?? 10-13 to 1.99 ?? 10-10 mol/m2/s. Trace metal release rates are generally 1-5 orders of magnitude slower than the Zn or Fe rates. Results indicate that the distributions of Fe and Cd are directly related to the rate of sphalerite dissolution throughout the reaction at pH 3.0 and 4.0 because these two elements substitute readily into sphalerite. These two metals are likely to be more amenable to usage in predictive acid dissolution models because of this behavior. The Pb distribution shows no strong relation to sphalerite dissolution and appears to be controlled by pH-dependent solubility, most likely related to trace amounts of galena. The distribution of Cu is similar to that of Fe but is the most-dependent of all metals on its mole fraction ratio (Zn:Cu) in sphalerite. The Mn distributions suggest an increase in the rate of Mn release relative to sphalerite dissolution occurs in low Mn samples as pH increases. The Mn distribution in high Mn samples is nearly independent of pH and sphalerite dissolution at pH 2.0 but shows a dependence on these two parameters at higher pH (3.0-4.0).

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.

Manganese and iron as oxygen carriers to anoxie estuarine sediment

NASA Astrophysics Data System (ADS)

Brayner, F. M. M.; Matvienko, B.

2003-05-01

We studied the concentration of a series of transition metals including Mn and Fe in an estuarine fishpond. The pond is situated at latitude 8°10'S and longitude 34°55'W, in the Capibaribe River estuary, within the Recife city boundaries, which is located in Pernambuco, a state of the Brazilian Northeast Pond area is 1.5 ha and it bas a 0.5 m depth. It is separated from the river by dikes. Water temperature at 28° C is stable throughout the year. Light breezes keep the water aerated, but intense ongoing decomposition makes the sediment anoxie. The area, originally of mangrove type, has been changed by antropic action on its fauna and vegetation. The study focuses on changes in behaviour of heavy metals. Samples of bottom sediments wore collected by Eckman dredge sediment sampler and total metal concentration was determined by the lithium borate fusion method. Water, recent sediment, and consolidated sediment were examined in this fishpond where Mn and Fe are brought in periodically by water and then gradually go into the sediment at respective rates of 10.52 and 1332 mg m^{-2}a^{-1}. Strong bioturbation re-suspends sediment while simultaneously re-dissolution of these ions is going on fhrough reduction in the anoxie sédiment. As soluble species these ions migrate from sediment to water and are there continually oxidized by dissolved oxygen, becoming insoluble. With their precipitation, chemically bound oxygen is carried down to the sediment, constituting a parallel channel of transport in addition to migration into the sediment bydiffusion of the oxygen dissolved in the water. The estimated flow rates are 3.25 and 76 mg O2 m^{-2}a^{-1} due to Mn and Fe respectively. The rates were established using natural silicon as a tracer.

Phosphorus Release to Floodwater from Calcareous Surface Soils and Their Corresponding Subsurface Soils under Anaerobic Conditions.

PubMed

Jayarathne, P D K D; Kumaragamage, D; Indraratne, S; Flaten, D; Goltz, D

2016-07-01

Enhanced phosphorus (P) release from soils to overlying water under flooded, anaerobic conditions has been well documented for noncalcareous and surface soils, but little information is available for calcareous and subsurface soils. We compared the magnitude of P released from 12 calcareous surface soils and corresponding subsurface soils to overlying water under flooded, anaerobic conditions and examined the reasons for the differences. Surface (0-15 cm) and subsurface (15-30 cm) soils were packed into vessels and flooded for 8 wk. Soil redox potential and concentrations of dissolved reactive phosphorus (DRP) and total dissolved Ca, Mg, Fe, and Mn in floodwater and pore water were measured weekly. Soil test P was significantly smaller in subsurface soils than in corresponding surface soils; thus, the P release to floodwater from subsurface soils was significantly less than from corresponding surface soils. Under anaerobic conditions, floodwater DRP concentration significantly increased in >80% of calcareous surface soils and in about 40% of subsurface soils. The increase in floodwater DRP concentration was 2- to 17-fold in surface soils but only 4- to 7-fold in subsurface soils. With time of flooding, molar ratios of Ca/P and Mg/P in floodwater increased, whereas Fe/P and Mn/P decreased, suggesting that resorption and/or reprecipitation of P took place involving Fe and Mn. Results indicate that P release to floodwater under anaerobic conditions was enhanced in most calcareous soils. Surface and subsurface calcareous soils in general behaved similarly in releasing P under flooded, anaerobic conditions, with concentrations released mainly governed by initial soil P concentrations. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

In situ deployment of voltammetric, potentiometric, and amperometric microelectrodes from a ROV to determine dissolved O{sub 2}, Mn, Fe, S({minus}2), and pH in porewaters

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

Luther, G.W. III; Reimers, C.E.; Nuzzio, D.B.

1999-12-01

Solid-state microelectrodes have been used in situ in Raritan Bay, NJ to measure pore water profiles of dissolved O{sub 2}, Mn, Fe, and sulfide at (sub)millimeter resolution by voltammetric techniques. The voltammetric sensor was positioned with microprofiling instrumentation mounted on a small remote operated vehicle (ROV). This instrumentation and the sensor were controlled and monitored in real time from a research vessel anchored at the study site. The voltammetric analyzer was connected to the electrodes of the voltammetric cell with a 30 m cable which also bridged receiver-transmitter transducers to ensure signal quality along the cable. Single analyte O{sub 2},more » pH, and resistivity microsensors were operated alongside the voltammetric sensor. The authors report on the technology of the system and the concentration changes of redox species observed from 2 to 3 cm above to approximately 4 cm below the sediment-water interface during three deployments. O{sub 2} measurements from both Clark and voltammetric electrodes were in excellent agreement. The profiles obtained show that there is no detectable overlap of O{sub 2} and Mn{sup 2+} in the sediments which is similar to previous reports from other continental margin sediments which were cored and analyzed in the laboratory. These data indicate that O{sub 2} is not a direct oxidant for Mn{sup 2+} when diffusive (rather than advective) processes control the transport of solutes within the sediment. Subsurface Mn{sup 2+} peaks were observed at about 2 cm and coincide with a subsurface pH maximum. The data can be explained by organic matter decomposition with alternate electron acceptors and by the formation of authigenic phases containing reduced Mn at depth.« less

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.

Environmental effects on the aquatic system and metal discharge to the Mediterranean Sea from a near-neutral zinc-ferrous sulfate mine drainage

USGS Publications Warehouse

Frau, Franco; Medas, Daniela; Da Pelo, Stefania; Wanty, Richard B.; Cidu, Rosa

2015-01-01

After mine closure in the 1980s and subsequent shutdown of the dewatering system, groundwater rebound led to drainage outflow from the Casargiu gallery (Montevecchio mine, SW Sardinia, Italy) beginning in 1997. Mine drainage had pH 6.0 and dissolved concentrations of sulfate (5000 mg/L) and metals (e.g., 1000 mg/L Zn, 230 mg/L Fe, 150 mg/L Mn) much higher than those previously measured in groundwater under dewatering conditions. As compared with the first stages of rebound at Casargiu, a very high contamination level still persists after more than 15 years of flushing. Mine drainage (20–70 L/s; pH 6.0 ± 0.2; Zn-Mg-Ca-SO4 composition) flowed into the Rio Irvi. Abundant precipitation of amorphous Fe(III)-(oxy)hydroxides occurred. Moreover, sulfate-bearing green rust was observed to flocculate in the reach of the Rio Irvi where pH was still circumneutral. Water sampling along this stream for about 6 km almost to its mouth in the Mediterranean Sea showed a pH decrease from 6.0 to 4.0 and a significant removal of Fe (46 %) and As (96 %), while sulfate, Zn, Mn, Co, Ni, and Cd showed small variations downstream. Lead was initially adsorbed onto Fe(III)-(oxy)hydroxides, then desorbed as pH dropped below 5. The estimated amount of dissolved metals discharged into the Mediterranean Sea is significant (e.g., 900 kg/day Zn, 1.4 kg/day Cd, 5 kg/day Ni). In particular, a conservative estimation of the amount of Zn discharged to the sea is about 330 ton/year, which would correspond to 1.4 % of the global annual flux of dissolved Zn from uncontaminated rivers to the oceans.

Effect of Fe-Mn addition on microstructure and magnetic properties of NdFeB magnetic powders

NASA Astrophysics Data System (ADS)

Kurniawan, C.; Purba, A. S.; Setiadi, E. A.; Simbolon, S.; Warman, A.; Sebayang, P.

2018-03-01

In this paper, the effect of Fe-Mn alloy addition on microstructures and magnetic properties of NdFeB magnetic powders was investigated. Varied Fe-Mn compositions of 1, 5, and 10 wt% were mixed with commercial NdFeB type MQA powders for 15 minutes using shaker mill. The characterizations were performed by powder density, PSA, XRD, SEM, and VSM. The Fe-Mn addition increased the powder density of NdFeB/Fe-Mn powders. On the other side, particle size distribution slightly decreased as the Fe-Mn composition increases. Magnetic properties of NdFeB/Fe-Mn powders changed with the increasing of Fe-Mn content. SEM analysis showed the particle size of NdFeB/Fe-Mn powder was smaller as the Fe-Mn composition increases. It showed that NdFeB/Fe-Mn particles have different size and shape for NdFeB and Fe-Mn particles separately. The optimum magnetic properties of NdFeB/Fe-Mn powder was achieved on the 5 wt% Fe-Mn composition with remanence M r = 49.45 emu/g, coercivity H c = 2.201 kOe, and energy product, BH max = 2.15 MGOe.

Adsorption of Heavy Metals in Industrial Wastewater by Magnetic Nano-particles

NASA Astrophysics Data System (ADS)

Tu, Y.; You, C.

2010-12-01

Industrial wastewater containing heavy metals is of great concern because of their toxic impact to living species and environments. Removal of metal ions from industrial effluent using nano-particles is an area of extensive research. This study collected wastewaters and effluents from 11 industrial companies in tanning, electronic plating, printed circuit board manufacturing, semi-conductor, and metal surface treatment industry and studied in detailed the major and trace element compositions to develop potential fingerprinting technique for pollutant source identification. The results showed that electronic plating and metal surface treatment industry produce high Fe, Mn, Cr, Zn, Ni and Mo wastewater. The tanning industry and the printed circuit board manufacturing industry released wastewater with high Fe and Cr, Cu and Ni, respectively. For semi-conductor industry, significant dissolved In was detected in wastewater. The absorption experiments to remove heavy metals in waters were conducted using Fe3O4 nano-particles. Under optimal conditions, more than 99 % dissolved metals were removed in a few minutes.

Attenuation of dissolved metals in neutral mine drainage in the Zambian Copperbelt.

PubMed

Sracek, Ondra; Filip, Jan; Mihaljevič, Martin; Kříbek, Bohdan; Majer, Vladimír; Veselovský, František

2011-01-01

Behaviour of metals like Cu and Co was studied in nearly neutral (pH ≥ 6.4) mine drainage seepage in a stream downgradient of a tailing dam at Chambishi site in the Copperbelt of Zambia. They are attenuated by precipitation of ferruginous ochres that incorporate significant quantities of metals. Using chemical analysis, X-ray powder diffraction and Mössbauer spectroscopy, we show that the ochres are composed mostly of amorphous ferric hydroxide. Close to the seepage face, the total Fe content of ochres increases due to precipitation of amorphous ferric hydroxide, but total Fe in sediment decreases further downstream. The stream then flows through wetland (dambo) where the remaining fraction of metals is removed. During rainy periods, increased flow rate may result in re-suspension of ochres, increasing thus the mobility of metals. Major ions like sulphate are conservative at the start of the dry period (May), but gypsum may probably precipitate later at the end of the dry period. Sequential extractions of bulk sediments indicate that Mn behaves differently to Fe, with a trend of increasing Mn with distance from the tailing dam. There is much more Fe than Mn in residual (Aqua Regia) fraction, indicating that amorphous ferric hydroxides are transformed to more crystalline phases deeper in sediment. Environmental impact of mine drainage is relatively limited due to its neutral character.

Ground-water quality in east-central New Jersey, and a plan for sampling networks

USGS Publications Warehouse

Harriman, D.A.; Sargent, B.P.

1985-01-01

Groundwater quality was evaluated in seven confined aquifers and the water table aquifer in east-central New Jersey based on 237 analyses of samples collected in 1981-82, and 225 older analyses. Investigation of the effect of land use on water quality and several sampling network proposals for the region are reported. Generally, water in the confined aquifers is of satisfactory quality for human consumption and most other uses. Iron (Fe) and manganese (Mn) concentrations exceed U.S. EPA drinking water standards in some wells screened in the Potomac-Raritan-Magothy aquifer system. Sodium (Na) concentrations in samples from three wells more than 800 ft deep in the Englishtown aquifer exceed the standard. Iron and Mn concentrations in this aquifer may also exceed the standards. Iron concentrations in the Wenonah-Mount Laurel aquifer exceed the standard. Based on 15 analyses of water from the Vincetown aquifer, Mn is the only constituent that exceeds the drinking water standard. In the Manasquan aquifer, 4 of the 16 Na determinations exceed the standard, and 8 of 16 Fe determinations exceed the standard. Water quality in the Atlantic City 800-ft sand is generally satisfactory. However, 12 Fe and 1 of 12 Mn determinations exceed the standards. For the Rio Grande water-bearing zone, 1 of 3 Fe determinations exceed the standard. The Kirkwood-Cohansey aquifer system (the water table aquifer) was the most thoroughly sampled (249 chemical analyses from 209 wells). Dissolved solids, chloride, Fe, nitrate, and Mn concentrations exceed drinking water standards in some areas. The results of chi-square tests of constituent distributions based on analyses from 158 wells in the water table aquifer indicate that calcium is higher in industrial and commercial areas; and Mg, chloride, and nitrate-plus-nitrite is higher in residential areas. (Author 's abstract)

Partition of heavy metals in a tropical river system impacted by municipal waste.

PubMed

Duc, Trinh Anh; Loi, Vu Duc; Thao, Ta Thi

2013-02-01

A research program was established to identify the governing factors for the partition coefficient (K(D)) of heavy metals between suspended particulate and dissolved phases in the Day River system a tropical, highly alluvial aquatic system, in Vietnam. The targeted river system, draining an urbanized-industrialized catchment where discharged wastewater is mostly untreated, could be separated into the least impacted, pristine area, and the most impacted, polluted area. Organic matter degradation was shown to govern the variation of parameters like total organic carbon, biochemical oxygen demand, chemical oxygen demand, nutrients, conductivity, or redox potential. Heavy metals in both dissolved and particulate phases were enriched in severely polluted area because of wastewater inflow that contains concentrated metals and intensification of metal influx from sediment. Results show log K(D) in the order Mn < As < Zn < Hg < Ni < Cu < Cd < Co < Pb < Cr < Fe and As < Zn < Ni < Mn < Cr < Cu < Co < Fe in the polluted zone and the pristine zone, respectively. A decreasing tendency of partition coefficients of 11 heavy metals considered from the pristine to the impacted zones was observed. Three explanations for the difference are: (1) increase of solubility of most heavy metals in low redox potential, (2) competition for the binding sites with major and minor cations, and (3) complexation with dissolved organic matter concentrated in municipal waste impacted water. Apart from domestic waste impact, statistical analysis has contributed to identify the influence of climate condition and hydrological regime to the partition of heavy metals in the area.

Mechanisms of Mn(II) catalytic oxidation on ferrihydrite surfaces and the formation of manganese (oxyhydr)oxides

NASA Astrophysics Data System (ADS)

Lan, Shuai; Wang, Xiaoming; Xiang, Quanjun; Yin, Hui; Tan, Wenfeng; Qiu, Guohong; Liu, Fan; Zhang, Jing; Feng, Xionghan

2017-08-01

Oxidation of Mn(II) is an important process that controls the mobility and bioavailability of Mn, as well as the formation of Mn (oxyhydr)oxides in natural systems. It was found that the surfaces of minerals, such as iron (oxyhydr)oxides, can accelerate Mn(II) oxidation to a certain degree, but the underlying mechanism has not been clearly understood. This study explores the reaction pathways and mechanisms of Mn(II) oxidation on ferrihydrite surfaces at neutral pH, commonly found in natural environments, by comparisons with montmorillonite, amorphous Al(OH)3, goethite, and magnetite using macroscopic experiments and spectroscopic analyses. Results show that when Mn(II) concentrations are below 4 mM, macroscopic Mn(II) adsorption on the three iron (oxyhydr)oxide surfaces conforms well to the Langmuir equation, with ferrihydrite showing the highest adsorption capacity. With Mn(II) concentrations ranging within 6-24 mM, the adsorbed Mn(II) is mainly oxidized into manganite (γ-MnOOH) and/or feitknechtite (β-MnOOH) by dissolved O2, and Mn(II) removal on a unit mass basis in the presence of magnetite is the highest compared with ferrihydrite and goethite. Ferrihydrite, a semiconductor material, shows stronger catalytic ability for Mn(II) oxidation on the same surface area than insulator minerals (i.e., montmorillonite and amorphous Al(OH)3). Additionally, the products of Mn(II) oxidation in the presence of semiconductor iron (oxyhydr)oxides (i.e., ferrihydrite, goethite, or magnetite) at the same Fe/Mn molar ratio include both manganite and a small amount of Mn(IV) minerals, and the Mn average oxidation states (Mn AOSs) of these products follow the order: magnetite > goethite > ferrihydrite. Magnetite and goethite, with relatively smaller SSAs and lower band gap energies, exhibit greater catalysis for Mn(II) oxidation than ferrihydrite at the same Fe/Mn ratio, which goes against the conventional interfacial effect and is related to the electrochemical properties. Thus, the Mn(II) catalytic oxidation by O2 on ferrihydrite surfaces should include an electrochemical pathway, i.e., electron transfer (ET) in the Mn(II)-Conduction Band (CB)Ferrihydrite-O2 complexes, in addition to the conventional two interfacial catalytic pathways, i.e., ET in the Mn(II)-Fe(II, III)-O2 complexes and direct ET in the Mn(II)-O2 complexes. These results reveal new implications for understanding the processes and mechanisms of Mn(II) oxidation on iron (oxyhydr)oxide surfaces and the abiotic formation of Mn (oxyhydr)oxides in surface environments.

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.

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

Liu, Yulin; Huang, Gaoren; Sun, Yimeng; Zhang, Li; Huang, Zhenwei; Wang, Jijie; Liu, Chunzhong

2016-01-29

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.

Metal concentrations in water and sediments from tourist beaches of Acapulco, Mexico.

PubMed

Jonathan, M P; Roy, P D; Thangadurai, N; Srinivasalu, S; Rodríguez-Espinosa, P F; Sarkar, S K; Lakshumanan, C; Navarrete-López, M; Muñoz-Sevilla, N P

2011-04-01

A survey on the metal concentrations (As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V, Zn) in beach water and sediments is reported from the tourist destination of Acapulco city on the Pacific coast of Mexico. The concentration of dissolved trace metals (DTMs) in beach water and acid leachable trace metals (ALTMs) in sediments indicated that they are anthropogenic in nature due to the increased tourist activities in the crowded beach locations. The statistical analysis indicates Fe and Mn play a major role as metal scavengers in both the medium (water and sediment) and the higher value of other metals is site specific in the study area, indicating that they are transported from the local area. Comparison results suggest that the beach water quality has deteriorated more than the sediments and special care needs to be taken to restore the beach quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

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

Dissolved Mn(III) in water treatment works: Prevalence and significance.

PubMed

Johnson, Karen L; McCann, Clare M; Wilkinson, John-Luke; Jones, Matt; Tebo, Bradley M; West, Martin; Elgy, Christine; Clarke, Catherine E; Gowdy, Claire; Hudson-Edwards, Karen A

2018-09-01

Dissolved Mn(III) has been identified at all stages throughout a Water Treatment Works (WTW) receiving inflow from a peaty upland catchment in NE England. Ninety percent of the influent total manganese into the WTW is particulate Mn, in the form of Mn oxide (>0.2 μm). Approximately 9% (mean value, n = 22, range of 0-100%) of the dissolved (<0.2 μm) influent Mn is present as dissolved Mn(III). Mn(III) concentrations are highest (mean of 49% of total dissolved Mn; n = 26, range of 17-89%) within the WTW where water comes into contact with the organic-rich sludges which are produced as waste products in the WTW. These Mn(III)-containing wastewaters are recirculated to the head of the works and constitute a large input of Mn(III) into the WTW. This is the first report of Mn(III) being identified in a WTW. The ability of Mn(III) to act as both an oxidant and a reductant is of interest to the water industry. Understanding the formation and removal of Mn(III) within may help reduce Mn oxide deposits in pipe networks. Further understanding how the ratio of Mn(III) to Mn(II) can be used to optimise dissolved Mn removal would save the water industry significant money in reducing discoloration 'events' at the customers' tap. Copyright © 2018. Published by Elsevier Ltd.

Automation of high-frequency sampling of environmental waters for reactive species

NASA Astrophysics Data System (ADS)

Kim, H.; Bishop, J. K.; Wood, T.; Fung, I.; Fong, M.

2011-12-01

Trace metals, particularly iron and manganese, play a critical role in some ecosystems as a limiting factor to determine primary productivity, in geochemistry, especially redox chemistry as important electron donors and acceptors, and in aquatic environments as carriers of contaminant transport. Dynamics of trace metals are closely related to various hydrologic events such as rainfall. Storm flow triggers dramatic changes of both dissolved and particulate trace metals concentrations and affects other important environmental parameters linked to trace metal behavior such as dissolved organic carbon (DOC). To improve our understanding of behaviors of trace metals and underlying processes, water chemistry information must be collected for an adequately long period of time at higher frequency than conventional manual sampling (e.g. weekly, biweekly). In this study, we developed an automated sampling system to document the dynamics of trace metals, focusing on Fe and Mn, and DOC for a multiple-year high-frequency geochemistry time series in a small catchment, called Rivendell located at Angelo Coast Range Reserve, California. We are sampling ground and streamwater using the automated sampling system in daily-frequency and the condition of the site is substantially variable from season to season. The ranges of pH of ground and streamwater are pH 5 - 7 and pH 7.8 - 8.3, respectively. DOC is usually sub-ppm, but during rain events, it increases by an order of magnitude. The automated sampling system focuses on two aspects- 1) a modified design of sampler to improve sample integrity for trace metals and DOC and 2) remote controlling system to update sampling volume and timing according to hydrological conditions. To maintain sample integrity, the developed method employed gravity filtering using large volume syringes (140mL) and syringe filters connected to a set of polypropylene bottles and a borosilicate bottle via Teflon tubing. Without filtration, in a few days, the dissolved concentration of Fe and Mn in the ground and streamwater samples stored in low density polyethylene (LDPE) sample bags decreased by 89% and 97%, respectively. In some cases of groundwater, the concentration of Ca decreased by 25%, due to degassing of CO2. However, DOC of the samples in LDPE bags without filtration increased up to 50% in 2 weeks, suggesting contamination from the bag. Performance of the new design was evaluated using the Fe-Mn-spiked Rivendell samples and environmental water samples collected from 1) Rivendell, 2) the Strawberry Creek located at the University of California, Berkeley campus, and 3) the San Francisco Bay. The samples were filtered using the developed method and stored in room temperature in 2 - 3 weeks without further treatment. The method improved the sample integrity significantly; the average recovery rates of Fe, Mn, DOC, and Ca were 92%, 98%, 90%, and 97%, respectively.

THE WEATHERING OF A SULFIDE OREBODY: SPECIATION AND FATE OF SOME POTENTIAL CONTAMINANTS

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

Courtin-Nomade, Alexandra; Grosbois, Cecile; Marcus, Matthew A.

2010-07-16

Various potentially toxic trace elements such as As, Cu, Pb and Zn have been remobilized by the weathering of a sulfide orebody that was only partially mined at Leona Heights, California. As a result, this body has both natural and anthropogenically modified weathering profiles only 500 m apart. The orebody is located in a heavily urbanized area in suburban Oakland, and directly affects water quality in at least one stream by producing acidic conditions and relatively high concentrations of dissolved elements (e.g., {approx}500 mg/L Cu, {approx}3700 mg/L Zn). Micrometric-scale mineralogical investigations were performed on the authigenic metal-bearing phases (less thanmore » 10 {mu}m in size) using electron-probe micro-analysis (EPMA), micro-Raman, micro X-ray absorption spectroscopy (mXAS), scanning X-ray diffraction (mSXRD) and scanning X-ray fluorescence (mSXRF) mapping techniques. Those measurements were coupled with classical mineralogical laboratory techniques, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Authigenic metal-bearing phases identified are mainly sulfates (jarosite, epsomite, schwertmannite), Fe (oxy-)hydroxides (goethite, hematite and poorly crystalline Fe products) and poorly crystalline Mn (hydr-)oxides. Sulfates and Fe (oxy-)hydroxides are the two main secondary products at both sites, whereas Mn (hydr-) oxides were only observed in the samples from the non-mining site. In these samples, the various trace elements show different affinities for Fe or Mn compounds. Lead is preferentially associated with Mn (hydr-)oxides and As with Fe (oxy-)hydroxides or sulfates. Copper association with Mn and Fe phases is questionable, and the results obtained rather indicate that Cu is present as individual Cu-rich grains (Cu hydroxides). Some ochreous precipitates were found at both sites and correspond to a mixture of schwertmannite, goethite and jarosite containing some potentially toxic trace elements such as Cu, Pb and Zn. According to the trace element distribution and relative abundance of the unweathered sulfides, this orebody still represents a significant reservoir of potential contaminants for the watershed, especially in the non-mining site, as a much greater proportion of sulfides is left to react and because of the lower porosity in this site.« less

The weathering of a sulfide orebody: Speciation and fate of some potential contaminants

USGS Publications Warehouse

Courtin-Nomade, A.; Grosbois, C.; Marcus, M.A.; Fakra, S.C.; Beny, J.-M.; Foster, A.L.

2009-01-01

Various potentially toxic trace elements such as As, Cu, Pb and Zn have been remobilized by the weathering of a sulfide orebody that was only partially mined at Leona Heights, California. As a result, this body has both natural and anthropogeni- cally modified weathering profiles only 500 m apart. The orebody is located in a heavily urbanized area in suburban Oakland, and directly affects water quality in at least one stream by producing acidic conditions and relatively high concentrations of dissolved elements (e.g., ??500 ??g/L Cu, ??3700 ??g/L Zn). Micrometric-scale mineralogical investigations were performed on the authigenic metal-bearing phases (less than 10 ??m in size) using electron-probe micro-analysis (EPMA), micro-Raman, micro X-ray absorption spectroscopy (??XAS), scanning X-ray diffraction ((??SXRD) and scanning X-ray fluorescence (??-SXRF) mapping techniques. Those measurements were coupled with classical mineralogical laboratory techniques, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Authigenic metal-bearing phases identified are mainly sulfates (jarosite, epsomite, schwertmannite), Fe (oxy-)hydroxides (goethite, hematite and poorly crystalline Fe products) and poorly crystalline Mn (hydr-)oxides. Sulfates and Fe (oxy-)hydroxides are the two main secondary products at both sites, whereas Mn (hydr-) oxides were only observed in the samples from the non-mining site. In these samples, the various trace elements show different affinities for Fe or Mn compounds. Lead is preferentially associated with Mn (hydr-)oxides and As with Fe (oxy-)hydroxides or sulfates. Copper association with Mn and Fe phases is questionable, and the results obtained rather indicate that Cu is present as individual Cu-rich grains (Cu hydroxides). Some ochreous precipitates were found at both sites and correspond to a mixture of schwertmannite, goethite and jarosite containing some potentially toxic trace elements such as Cu, Pb and Zn. According to the trace element distribution and relative abundance of the unweathered sulfides, this orebody still represents a significant reservoir of potential contaminants for the watershed, especially at the non-mining site, as a much greater proportion of sulfides is left to react and because of the lower porosity at this site.

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.

[Evaluation of compounding EDTA and citric acid on remediation of heavy metals contaminated soil].

PubMed

Yin, Xue; Chen, Jia-Jun; Cai, Wen-Min

2014-08-01

As commonly used eluents, Na2EDTA (EDTA) and citric acid (CA) have been widely applied in remediation of soil contaminated by heavy metals. In order to evaluate the removal of arsenic, cadmium, copper, and lead in the contaminated soil collected in a chemical plant by compounding EDTA and CA, a series of stirring experiments were conducted. Furthermore, the changes in speciation distribution of heavy metals before and after washing were studied. The results showed that, adopting the optimal molar ratio of EDTA/CA (1:1), when the pH of the solution was 3, the stirring time was 30 min, the stirring rate was 150 r x min(-1) and the L/S was 5:1, the removal rates of arsenic, cadmium, copper and lead could reach 11.72%, 43.39%, 24.36% and 27.17%, respectively. And it was found that after washing, for arsenic and copper, the content of acid dissolved fraction rose which increased the percentage of available contents. Fe-Mn oxide fraction mainly contributed to the removal of copper. As for cadmium, the percentages of acid dissolved fraction, Fe-Mn oxide fraction and organic fraction also decreased. In practical projects, speciation changes would pose certain environmental risk after soil washing, which should be taken into consideration.

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.

Experimental determination of activities in FeTiO3-MnTiO3 ilmenite solid solution by redox reversals

NASA Astrophysics Data System (ADS)

Feenstra, A.; Peters, Tjerk

1996-12-01

Solid solutions of (Fe,Mn)TiO3 were synthesized, mostly at 0.10 XMn intervals, at 1 bar, 900°C and log f O 2 = 17.50. Analysis by EMP indicate an ideal stoichiometry for the Fe-Mn ilmenites with (Fe+Mn) = Ti = 1.000 when normalized to 3 oxygens. Their unit cell volume increases linearly with XMn. The composition of Fe-Mn ilmenite coexisting with metallic Fe and rutile was reversed at 1 bar, 700 900°C and fixed f O 2 in a gas-mixing furnace. Oxygen fugacity was controlled by mixing CO2 and H2 gas and was continuously monitored with an yttrium-stabilized zirconia electrolyte. Solution properties of Fe-Mn ilmenite were derived from the experimental data by mathematical programming (Engi and Feenstra, in preparation) including notably the results of Fe-Mn exchange experiments between ilmenite and garnet (Feenstra and Engi, submitted) and anchoring the standard state properties to the updated thermodynamic dataset of Berman and Aranovich (1996). The thermodynamic analysis resulted in positive deviations from ideality for (Fe,Mn)TiO3 ilmenite, which is well described by an asymmetric Margules model with WH FeFeMn = 9.703 and WH FeMnMn = 23.234 kJ/mol, WS FeFeMn = 19.65 and WS FeMnMn = 22.06 J/(K·mol). The excess free energy for Fe-Mn ilmenite derived from the redox reversals is larger than in the symmetric ilmenite model (WG FeMn = +2.2 kJ/mol) determined by O'Neill et al. from emf measurements on the assemblage iron-rutile-(Fe,Mn)ilmenite.

Reductive solubilization of arsenic in a mining-impacted river floodplain: Influence of soil properties and temperature.

PubMed

Simmler, Michael; Bommer, Jérôme; Frischknecht, Sarah; Christl, Iso; Kotsev, Tsvetan; Kretzschmar, Ruben

2017-12-01

Mining activities have contaminated many riverine floodplains with arsenic (As). When floodplain soils become anoxic under water-saturated conditions, As can be released from the solid phase. Several microbially-driven As solubilization processes and numerous influential factors were recognized in the past. However, the interplay and relative importance of soil properties and the influence of environmental factors such as temperature remain poorly understood, especially considering the (co)variation of soil properties in a floodplain. We conducted anoxic microcosm experiments at 10, 17.5, and 25 °C using 65 representative soils from the mining-impacted Ogosta River floodplain in Bulgaria. To investigate the processes of As solubilization and its quantitative variation we followed the As and Fe redox dynamics in the solid and the dissolved phase and monitored a range of other solution parameters including pH, Eh, dissolved organic C, and dissolved Mn. We related soil properties to dissolved As observed after 20 days of microcosm incubation to identify key soil properties for As solubilization. Our results evidenced reductive dissolution of As-bearing Fe(III)-oxyhydroxides as the main cause for high solubilization. The availability of nutrients, most likely organic C as the source of energy for microorganisms, was found to limit this process. Following the vertical nutrient gradient common in vegetated soil, we observed several hundred μM dissolved As after 1-2 weeks for some topsoils (0-20 cm), while for subsoils (20-40 cm) with comparable total As levels only minor solubilization was observed. While high Mn contents were found to inhibit As solubilization, the opposite applied for higher temperature (Q 10 2.3-6.1 for range 10-25 °C). Our results suggest that flooding of nutrient-rich surface layers might be more problematic than water-saturation of nutrient-poor subsoil layers, especially in summer floodings when soil temperature is higher than in winter or spring. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

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.

Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts

USGS Publications Warehouse

Conrad, T.A.; Nielsen, S.G.; Peucker-Ehrenbrink, Bernhard; Blusztajn, J.; Winslow, D.; Hein, James; Paytan, A.

2017-01-01

The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (± 0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss seamounts. At the Taney seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve towards more radiogenic values from 6.8 to 4.5 (± 0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (± 0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

Reconstructing the Evolution of the Submarine Monterey Canyon System From Os, Nd, and Pb Isotopes in Hydrogenetic Fe-Mn Crusts

NASA Astrophysics Data System (ADS)

Conrad, T. A.; Nielsen, S. G.; Peucker-Ehrenbrink, B.; Blusztajn, J.; Winslow, D.; Hein, J. R.; Paytan, A.

2017-11-01

The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using 187Os/188Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (±0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss Seamounts. At the Taney Seamounts, approximately 225 km farther offshore from Davidson Seamount, 187Os/188Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve toward more radiogenic values from 6.8 to 4.5 (±0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (±0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

Dissolved trace and minor elements in cryoconite holes and supraglacial streams, Canada Glacier, Antarctica

NASA Astrophysics Data System (ADS)

Fortner, Sarah K.; Lyons, W. Berry

2018-04-01

Here we present a synthesis of the trace element chemistry in melt on the surface Canada Glacier, Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica ( 78°S). The MDV is largely ice-free. Low accumulation rates, strong winds, and proximity to the valley floor make these glaciers dusty in comparison to their inland counterparts. This study examines both supraglacial melt streams and cryoconite holes. Supraglacial streams on the lower Canada Glacier have median dissolved (<0.4 µm) concentrations of Fe, Mn, As, Cu, and V of 71.5, 75.5, 3.7, 4.6, and 4.3 nM. All dissolved Cd concentrations and the vast majority of Pb values are below our analytical detection (i.e. 0.4 and 0.06 nM). Chemical behavior did not follow similar trends for eastern and western draining waters. Heterogeneity likely reflects distinctions eolian deposition, rock:water ratios, and hydrologic connectivity. Future increases in wind-delivered sediment will likely drive dynamic responses in melt chemistry. For elements above detection limits, dissolved concentrations in glacier surface melt are within an order of magnitude of concentrations observed in proglacial streams (i.e. flowing on the valley floor). This suggests that glacier surfaces are an important source of downstream chemistry. The Fe enrichment of cryoconite water relative to N, P, or Si exceeds enrichment observed in marine phytoplankton. This suggests that the glacier surface is an important source of Fe to downstream ecosystems.

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity.

PubMed

Semin, B К; Davletshina, L N; Seibert, M; Rubin, A B

2018-01-01

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2 Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH5.7) than at neutral pH (3Mn/RC are extracted at pH6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extract only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster. Also we found that the presence of Fe cations in a heteronuclear cluster (2Mn/2Fe) increases the resistance of the remaining Mn cations to H 2 Q action, since H 2 Q can extract Mn cations from homonuclear Mn clusters of PSII(-Ca,4Mn) and PSII(-Ca,2Mn) membranes but not from the heteronuclear cluster in PSII(-Ca,2Mn,2Fe) membranes. H 2 Q also cannot extract Mn from PSII membranes obtained by incubation of PSII(-Ca,4Mn) membranes with Fe(II) cations at pH5.7, which suggests the formation of a heteronuclear 3Mn/1Fe cluster in the OEC. Functional activity of PSII with a 3Mn/1Fe cluster was investigated. PSII preparations with a 3Mn/1Fe cluster in the OEC are able to photoreduce the exogenous electron acceptor 2,6-dichlorophenolindophenol, possibly due to incomplete oxidation of water molecules as is the case with PSII(-Ca,2Mn,2Fe) samples. However, in the contrast to PSII(-Ca,2Mn,2Fe) samples PSII(-Ca,3Mn,1Fe) membranes can evolve O 2 at a low rate in the presence of exogenous Ca 2+ (at about 27% of the rate of O 2 evolution in native PSII membranes). The explanation for this phenomenon (either water splitting and production of molecular O 2 by the 3Mn/1Fe cluster or apparent O 2 evolution due to minor contamination of PSII(3Mn,1Fe) samples with PSII(-Ca,4Mn) membranes) is discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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.

Stable isotope fractionation of tungsten during adsorption on Fe and Mn (oxyhydr)oxides

NASA Astrophysics Data System (ADS)

Kashiwabara, Teruhiko; Kubo, Sayuri; Tanaka, Masato; Senda, Ryoko; Iizuka, Tsuyoshi; Tanimizu, Masaharu; Takahashi, Yoshio

2017-05-01

The similar, but not identical chemical properties of W compared with Mo suggest that the stable isotope system of W could be a novel proxy to explore the modern and ancient ocean as is the case in the well-established utility of Mo isotopes. We experimentally investigated the isotopic fractionation of W during adsorption on Fe and Mn (oxyhydr)oxides (ferrihydrite and δ-MnO2), a key process in the global ocean budget of this element. Our adsorption experiments confirmed that W isotopes fractionate substantially on both ferrihydrite and δ-MnO2: lighter W isotopes are preferentially adsorbed on both oxides as a result of equilibrium isotopic exchange between dissolved and adsorbed species, and the obtained values of Δ186/183Wliquid-solid (= δ186Wdissolved - δ186Wadsorbed) are 0.76 ± 0.09‰ for ferrihydrite and 0.88 ± 0.21‰ for δ-MnO2 (2σ, n = 6). Compared with the case of Mo isotopes, fractionation of W isotopes is (i) of comparable magnitude between ferrihydrite and δ-MnO2, and (ii) much smaller than that of Mo on δ-MnO2. Our previous XAFS observations and newly-performed DFT calculations both indicate that the observed W isotopic fractionations are caused by the symmetry change from Td (tetrahedral) WO42- to distorted Oh (octahedral) monomeric W species via formation of inner-sphere complexes on both ferrihydrite and δ-MnO2. The similar isotopic fractionations between the two oxides relate to the strong tendency for W to form inner-sphere complexes, which causes the symmetry change, in contrast to the outer-sphere complex of Mo on ferrihydrite. The smaller isotopic fractionation of W compared with Mo on δ-MnO2 despite their similar molecular symmetry seems to be due to their different degrees of distortion of Oh species. Our findings imply that the isotopic composition of W in modern oxic seawater is likely to become heavier relative to the input by removal of lighter W isotopes via adsorption on ferromanganese oxides in analogy with the Mo isotope budget. In contrast, the isotopic composition of W in ancient seawater should have evolved in response to the extent of deposition of both Fe and Mn oxides; this is likely to be different compared with that of the Mo isotopes, which is strongly associated with the occurrence of Mn oxides relative to Fe oxides.

Photographic Processing Interpretation Facility Wastewater Conceptual Treatment Design.

DTIC Science & Technology

1983-03-01

Total Chromium (Cr) - - - ɘ.05 - Copper (Cu) - - - ɘ.05 - Iron (Fe) - - - - - Manganese (Mn) - - - ɘ.03 - Mercury (Hg) - - - ɘ.004 - Potassium (K...8.3 - Silver (Ag) 2.2 7.0 17 0.15 2.2 Sodium (Na) - - - 8.2 - Zinc (Zn) - - - 0.12 - Biochemical Oxygen " Demand (BOD_) - - - 40 - Sulfate (SO...nonconventional pollutants include boron, dissolved sol i halides, iron, ammonia, nitrogen, phenols, sulfate and TOC. ,P,, 99 percent of the 11,000

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.

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.

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.

Molecular orbital (SCF-X-α-SW) theory of Fe2+-Mn3+, Fe3+-Mn2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates

USGS Publications Warehouse

Sherman, David M.

1990-01-01

Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. 

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.

Structural Basis for Assembly of the MnIV/FeIII Cofactor in the Class Ic Ribonucleotide Reductase from Chlamydia trachomatis‡

PubMed Central

Dassama, Laura M.K.; Krebs, Carsten; Bollinger, J. Martin; Rosenzweig, Amy C.; Boal, Amie K.

2013-01-01

The class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) employs a MnIV/FeIII cofactor in each monomer of its β2 subunit to initiate nucleotide reduction. The cofactor forms by reaction of MnII/FeII-β2 with O2. Previously, in vitro cofactor assembly from apo β2 and divalent metal ions produced a mixture of two forms, with Mn in site 1 (MnIV/FeIII) or site 2 (FeIII/MnIV), of which the more active MnIV/FeIII product predominates. Here we have addressed the basis for metal site-selectivity by solving X-ray crystal structures of apo, MnII, and MnII/FeII complexes of Ct β2. A structure obtained anaerobically with equimolar MnII, FeII, and apo protein reveals exclusive incorporation of MnII in site 1 and FeII in site 2, in contrast to the more modest site-selectivity achieved previously. Site-specificity is controlled thermodynamically by the apo protein structure, as only minor adjustments of ligands occur upon metal binding. Additional structures imply that, by itself, MnII binds in either site. Together the structures are consistent with a model for in vitro cofactor assembly in which FeII specificity for site 2 drives assembly of the appropriately configured heterobimetallic center, provided that FeII is substoichiometric. This model suggests that use of an MnIV/FeIII cofactor in vivo could be an adaptation to FeII limitation. A 1.8 Å resolution model of the MnII/FeII-β2 complex reveals additional structural determinants for activation of the cofactor, including a proposed site for side-on (η2) addition of O2 to FeII and a short (3.2 Å) MnII-FeII interionic distance, promoting formation of the MnIV/FeIV activation intermediate. PMID:23924396

Martensitic Transformations and Mechanical and Corrosion Properties of Fe-Mn-Si Alloys for Biodegradable Medical Implants

NASA Astrophysics Data System (ADS)

Drevet, Richard; Zhukova, Yulia; Malikova, Polina; Dubinskiy, Sergey; Korotitskiy, Andrey; Pustov, Yury; Prokoshkin, Sergey

2018-03-01

The Fe-Mn-Si alloys are promising materials for biodegradable metallic implants for temporary healing process in the human body. In this study, three different compositions are considered (Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si, all in wt pct). The phase composition analysis by XRD reveals ɛ-martensite, α-martensite, and γ-austenite in various proportions depending on the manganese amount. The DSC study shows that the starting temperature of the martensitic transformation ( M s) of the alloys decreases when the manganese content increases (416 K, 401 K, and 323 K (143 °C, 128 °C, and 50 °C) for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively). Moreover, mechanical compression tests indicate that these alloys have a much lower Young's modulus ( E) than pure iron (220 GPa), i.e., 145, 133, and 118 GPa for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively. The corrosion behavior of the alloys is studied in Hank's solution at 310 K (37 °C) using electrochemical experiments and weight loss measurements. The corrosion kinetics of the Fe-Mn-Si increases with the manganese content (0.48, 0.59, and 0.80 mm/year for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively). The alloy with the highest manganese content shows the most promising properties for biomedical applications as a biodegradable and biomechanically compatible implant material.

Composition and genesis of ferromanganese deposits from the northern South China Sea

NASA Astrophysics Data System (ADS)

Zhong, Yi; Chen, Zhong; González, Francisco Javier; Hein, James R.; Zheng, Xufeng; Li, Gang; Luo, Yun; Mo, Aibin; Tian, Yuhang; Wang, Shuhong

2017-05-01

Marine ferromanganese (Fe-Mn) nodules and crusts are archives of past environmental conditions and potential mineral resources. Over the last 30 years, many have been discovered in the northern South China Sea (SCS). To determine the origin of the Fe-Mn deposits, a comprehensive laboratory analysis of physical properties, mineralogy and geochemistry was conducted on newly collected Fe-Mn nodule/crust samples. The results revealed that there are three types of Fe-Mn deposits: (1) Fe-rich nodules containing essentially goethite occur on the northeastern slope of the SCS, with high Fe, low Mn (Mn/Fe = 0.03) and low trace metals and rare earth elements concentrations; (2) Smooth Fe-Mn nodules and crusts composed of asbolane, todorokite and CFA occur along the northwestern marginal of the SCS that have similar Fe and Mn contents (Mn/Fe = 1.21), moderate trace metal enrichments, and a positive Ce anomaly; (3) Fe-Mn nodules and crusts composed of asbolane, todorokite and birnessite that occur in the central basin of the SCS have higher Mn and lower Fe contents (Mn/Fe = 1.45). This depositional pattern was associated with major changes in oceanographic conditions and tectonic regimes. The northeastern slope deposits occur in a contourite depositional system, are strongly enriched in Fe relative to Mn (average 38.7% and 0.96%, respectively), formed from the combination of hydrogenetic and diagenetic processes. We propose a new genetic model for Fe-Mn nodules, which formed through the oxidation of pyrite and pyrite-barite concretions that formed by rapid early diagenetic growth (average 3320 mm/Myr) on continental margins above the carbonate compensation depth, and dominated by hydrocarbon seep structures and strong erosive action of bottom currents along the northeastern slope. In contrast, the introduction of vigorous deep-water flow from the North Pacific promoted the slow growth (4-7 mm/Myr) of hydrogenetic Fe-Mn nodules and crusts along the northwestern margin. Finally, hydrogenetic growth of Fe-Mn nodules and crusts in the central basin may have been enhanced by volcanic processes. Our data provide new insights into the genesis and province characteristics of the Fe-Mn nodules and crusts of the northern SCS.

Substituting Fe for two of the four Mn ions in photosystem II-effects on water-oxidation.

PubMed

Semin, Boris K; Seibert, Michael

2016-06-01

We have investigated the interaction of Fe(II) cations with Ca-depleted PSII membranes (PSII[-Ca,4Mn]) in the dark and found that Fe(II) incubation removes 2 of 4 Mn ions from the tetranuclear Mn cluster of the photosynthetic O2-evolving complex (OEC). The reduction of Mn ions in PSII(-Ca,4Mn) by Fe(II) and the concomitant release of two Mn(II) cations is accompanied by the binding of newly generated Fe(III) in at least one vacated Mn site. Flash-induced chlorophyll (Chl) fluorescence yield measurements of this new 2Mn/nFe cluster (PSII[-Ca,2Mn,nFe]) show that charge recombination in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) occurs between Qa (-) and the remaining Mn/Fe cluster (but not YZ (●)) in the OEC, and extraction of 2 Mn occurs uniformly in all PSII complexes. No O2 evolution is observed, but the heteronuclear metal cluster in PSII(-Ca,2Mn,nFe) samples is still able to supply electrons for reduction of the exogenous electron acceptor, 2,6-dichlorophrenolindophenol, by photooxidizing water and producing H2O2 in the absence of an exogenous donor as seen previously with PSII(-Ca,4Mn). Selective extraction of Mn or Fe cations from the 2Mn/nFe heteronuclear cluster demonstrates that the high-affinity Mn-binding site is occupied by one of the iron cations. It is notable that partial water-oxidation function still occurs when only two Mn cations are present in the PSII OEC.

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.

Response of sediment microbial community structure in a freshwater reservoir to manipulations in oxygen availability.

PubMed

Bryant, Lee D; Little, John C; Bürgmann, Helmut

2012-04-01

Hypolimnetic oxygenation systems (HOx) are being increasingly used in freshwater reservoirs to elevate dissolved oxygen levels in the hypolimnion and suppress sediment-water fluxes of soluble metals (e.g. Fe and Mn) which are often microbially mediated. We assessed changes in sediment microbial community structure and corresponding biogeochemical cycling on a reservoir-wide scale as a function of HOx operations. Sediment microbial biomass as quantified by DNA concentration was increased in regions most influenced by the HOx. Following an initial decrease in biomass in the upper sediment while oxygen concentrations were low, biomass typically increased at all depths as the 4-month-long oxygenation season progressed. A distinct shift in microbial community structure was only observed at the end of the season in the upper sediment near the HOx. While this shift was correlated to HOx-enhanced oxygen availability, increased TOC levels and precipitation of Fe- and Mn-oxides, abiotic controls on Fe and Mn cycling, and/or the adaptability of many bacteria to variations in prevailing electron acceptors may explain the delayed response and the comparatively limited changes at other locations. While the sediment microbial community proved remarkably resistant to relatively short-term changes in HOx operations, HOx-induced variation in microbial structure, biomass, and activity was observed after a full season of oxygenation. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Ferromagnetic resonance investigation in as-prepared NiFe/FeMn/NiFe trilayer

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

Yuan, S. J.; Xu, K.; Yu, L. M.

2007-06-01

NiFe/FeMn/NiFe trilayer prepared by dc magnetron sputtering was systematically investigated by ferromagnetic resonance technique (FMR) at room temperature. For NiFe/FeMn/NiFe trilayer, there are two distinct resonance peaks both in in-plane and out-of-plane FMR spectra, which are attributed to the two NiFe layers, respectively. The isotropic in-plane resonance field shift is negative for the bottom NiFe layer, while positive for the top NiFe layer. And, such phenomena result from the negative interfacial perpendicular anisotropy at the bottom NiFe/FeMn interface and positive interfacial perpendicular anisotropy at the top FeMn/NiFe interface. The linewidth of the bottom NiFe layer is larger than that ofmore » the top NiFe layer, which might be related to the greater exchange coupling at the bottom NiFe/FeMn interface.« less

Binder-jetting 3D printing and alloy development of new biodegradable Fe-Mn-Ca/Mg alloys.

PubMed

Hong, Daeho; Chou, Da-Tren; Velikokhatnyi, Oleg I; Roy, Abhijit; Lee, Boeun; Swink, Isaac; Issaev, Ilona; Kuhn, Howard A; Kumta, Prashant N

2016-11-01

3D printing of various biomaterials including titanium and stainless steel has been studied for treating patients with cranio-maxillofacial bone defect. The potential long term complications with use of inert biometals have opened the opportunities for use of biodegradable metals in the clinical arena. The authors previously reported that binder-jet 3D printing technique enhanced the degradation rates of biodegradable Fe-Mn alloy by creating engineered micropores rendering the system attractive as biodegradable implantable devices. In the present study, the authors employed CALPHAD modeling to systematically study and modify the Fe-Mn alloy composition to achieve enhanced degradation rates. Accordingly, Ca and Mg addition to Fe-35wt% Mn solid solution predicted increase in degradation rates. In order to validate the CALPHAD results, Fe - (35-y)wt% Mn - ywt% X (X=Ca, Mg, and y=0, 1, 2) were synthesized by using high energy mechanical alloying (HEMA). Sintered pellets of Fe-Mn-Ca and Fe-Mn-Mg were then subjected to potentiodynamic polarization (PDP) and live/dead cell viability tests. Sintered pellets of Fe-Mn, Fe-Mn-Ca, and Fe-Mn-Mg also exhibited MC3T3 murine pre-osteoblast cells viability in the live/dead assay results. Fe-Mn and Fe-Mn-1Ca were thus accordingly selected for 3D printing and the results further confirmed enhanced degradation of Ca addition to 3D printed constructs validating the theoretical and alloy development studies. Live/dead and MTT cell viability results also confirmed good cytocompatibility of the 3D-printed Fe-Mn and Fe-Mn-1Ca constructs. Bone grafting is widely used for the treatment of cranio-maxillofacial bone injuries. 3D printing of biodegradable Fe alloy is anticipated to be advantageous over current bone grafting techniques. 3D printing offers the fabrication of precise and tailored bone grafts to fit the patient specific bone defect needs. Biodegradable Fe alloy is a good candidate for 3D printing synthetic grafts to regenerate bone tissue without eliciting complications. CALPHAD theoretical models were used to develop new Fe-Mn-Ca/Mg alloys to enhance the degradation rates of traditional Fe-Mn alloys. In vitro experimental results also showed enhanced degradation rates and good cytocompatibility of sintered Fe-Mn-Ca/Mg compacts. 3D printing of Fe-Mn and Fe-Mn-1Ca alloys further demonstrated their feasibility as potentially viable bone grafts for the future. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

Magnetic interactions in BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices

NASA Astrophysics Data System (ADS)

Xu, Qingyu; Sheng, Yan; Khalid, M.; Cao, Yanqiang; Wang, Yutian; Qiu, Xiangbiao; Zhang, Wen; He, Maocheng; Wang, Shuangbao; Zhou, Shengqiang; Li, Qi; Wu, Di; Zhai, Ya; Liu, Wenqing; Wang, Peng; Xu, Y. B.; Du, Jun

2015-03-01

The clear understanding of exchange interactions between magnetic ions in substituted BiFeO3 is the prerequisite for the comprehensive studies on magnetic properties. BiFe0.5Mn0.5O3 films and BiFeO3/BiMnO3 superlattices have been fabricated by pulsed laser deposition on (001) SrTiO3 substrates. Using piezoresponse force microscopy (PFM), the ferroelectricity at room temperature has been inferred from the observation of PFM hysteresis loops and electrical writing of ferroelectric domains for both samples. Spin glass behavior has been observed in both samples by temperature dependent magnetization curves and decay of thermo-remnant magnetization with time. The magnetic ordering has been studied by X-ray magnetic circular dichroism measurements, and Fe-O-Mn interaction has been confirmed to be antiferromagnetic (AF). The observed spin glass in BiFe0.5Mn0.5O3 films has been attributed to cluster spin glass due to Mn-rich ferromagnetic (FM) clusters in AF matrix, while spin glass in BiFeO3/BiMnO3 superlattices is due to competition between AF Fe-O-Fe, AF Fe-O-Mn and FM Mn-O-Mn interactions in the well ordered square lattice with two Fe ions in BiFeO3 layer and two Mn ions in BiMnO3 layer at interfaces.

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia.

PubMed

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH<4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4years post-reinundation). Acidic (pH3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Near shore groundwater acidification during and after a hydrological drought in the Lower Lakes, South Australia

NASA Astrophysics Data System (ADS)

Leyden, Emily; Cook, Freeman; Hamilton, Benjamin; Zammit, Benjamin; Barnett, Liz; Lush, Ann Marie; Stone, Dylan; Mosley, Luke

2016-06-01

An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH < 4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4 years post-reinundation). Acidic (pH 3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2 m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4 years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments.

A novel sandwich Fe-Mn damping alloy with ferrite shell prepared by vacuum annealing

NASA Astrophysics Data System (ADS)

Qian, Bingnan; Peng, Huabei; Wen, Yuhua

2018-04-01

To improve the corrosion resistance of high strength Fe-Mn damping alloys, we fabricated a novel sandwich Fe-17.5Mn damping alloy with Mn-depleted ferrite shell by vacuum annealing at 1100 °C. The formation behavior of the ferrite shell obeys the parabolic law for the vacuum annealed Fe-17.5Mn alloy at 1100 °C. The sandwich Fe-17.5Mn alloy with ferrite shell exhibits not only better corrosion resistance but also higher damping capacity than the conventional annealed Fe-17.5Mn alloy under argon atmosphere. The existence of only ferrite shell on the surface accounts for the better corrosion in the sandwich Fe-17.5Mn alloy. The better damping capacity in the sandwich Fe-17.5Mn alloy is owed to more stacking faults inside both ɛ martensite and γ austenite induced by the stress from ferrite shell. Vacuum annealing is a new way to improve the corrosion resistance and damping capacity of Fe-Mn damping alloys.

Weathering steel as a potential source for metal contamination: Metal dissolution during 3-year of field exposure in a urban coastal site.

PubMed

Raffo, Simona; Vassura, Ivano; Chiavari, Cristina; Martini, Carla; Bignozzi, Maria C; Passarini, Fabrizio; Bernardi, Elena

2016-06-01

Surface and building runoff can significantly contribute to the total metal loading in urban runoff waters, with potential adverse effects on the receiving ecosystems. The present paper analyses the corrosion-induced metal dissolution (Fe, Mn, Cr, Ni, Cu) from weathering steel (Cor-Ten A) with or without artificial patinas, exposed for 3 years in unsheltered conditions at a marine urban site (Rimini, Italy). The influence of environmental parameters, atmospheric pollutants and surface finish on the release of dissolved metals in rain was evaluated, also by means of multivariate analysis (two-way and three-way Principal Component Analysis). In addition, surface and cross-section investigations were performed so as to monitor the patina evolution. The contribution provided by weathering steel runoff to the dissolved Fe, Mn and Ni loading at local level is not negligible and pre-patination treatments seem to worsen the performance of weathering steel in term of metal release. Metal dissolution is strongly affected by extreme events and shows seasonal variations, with different influence of seasonal parameters on the behaviour of bare or artificially patinated steel, suggesting that climate changes could significantly influence metal release from this alloy. Therefore, it is essential to perform a long-term monitoring of the performance, the durability and the environmental impact of weathering steel. Copyright © 2016 Elsevier Ltd. All rights reserved.

Soft x-ray absorption spectroscopy study of the electronic structures of the MnFe Prussian blue analogs (RbxBay) Mn[3 -(x +2 y )]/2[Fe (CN) 6] H2O

NASA Astrophysics Data System (ADS)

Lee, Eunsook; Seong, Seungho; Kim, Hyun Woo; Kim, D. H.; Thakur, Nidhi; Yusuf, S. M.; Kim, Bongjae; Min, B. I.; Kim, Younghak; Kim, J.-Y.; de Groot, F. M. F.; Kang, J.-S.

2017-11-01

The electronic structures of Prussian blue analog (RbxBay) Mn[3 -(x +2 y )]/2[Fe (CN) 6] cyanides have been investigated by employing soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) at the Fe and Mn L (2 p ) edges. The measured XAS spectra have been analyzed with the configuration-interaction (CI) cluster model calculations. The valence states of the Fe and Mn ions are found to be Fe2 +-Fe3 + mixed valent, with an average valency of v (Fe )˜2.8 and nearly divalent (Mn2 +), respectively. Our Mn/Fe 2 p XMCD study supports that Mn2 + ions are in the high-spin states while Fe2 +-Fe3 + ions are in the low-spin states. The Fe and Mn 2 p XAS spectra are found to be essentially the same for 80 ≤T ≤ 300 K, suggesting that a simple charge transfer upon cooling from Fe3 +-CN -Mn2 + to Fe2 +-CN -Mn3 + does not occur in (RbxBay) Mn[3 -(x +2 y )]/2[Fe (CN) 6] . According to the CI cluster model analysis, it is necessary to take into account both the ligand-to-metal charge transfer and the metal-to-ligand charge transfer in describing Fe 2 p XAS, while the effect of charge transfer is negligible in describing Mn 2 p XAS. The CI cluster model analysis also shows that the trivalent Fe3 + ions have a strong covalent bonding with the C ≡N ligands and are under a large crystal-field energy of 10 D q ˜3 eV, in contrast to the weak covalency effect and a small 10 D q ˜0.6 eV for the divalent Mn2 + ions.

Kinetics and mechanism of diclofenac removal using ferrate(VI): roles of Fe3+, Fe2+, and Mn2.

PubMed

Zhao, Junfeng; Wang, Qun; Fu, Yongsheng; Peng, Bo; Zhou, Gaofeng

2018-06-01

In this study, the effect of Fe 3+ , Fe 2+ , and Mn 2+ dose, solution pH, reaction temperature, background water matrix (i.e., inorganic anions, cations, and natural organic matters (NOM)), and the kinetics and mechanism for the reaction system of Fe(VI)/Fe 3+ , Fe(VI)/Fe 2+ , and Fe(VI)/Mn 2+ were investigated systematically. Traces of Fe 3+ , Fe 2+ , and Mn 2+ promoted the DCF removal by Fe(VI) significantly. The pseudo-first-order rate constant (k obs ) of DCF increased with decreasing pH (9-6) and increasing temperature (10-30 °C) due to the gradually reduced stability and enhanced reactivity of Fe(VI). Cu 2+ and Zn 2+ ions evidently improved the DCF removal, while CO 3 2- restrained it. Besides, SO 4 2- , Cl - , NO 3 - , Mg 2+ , and Ca 2+ almost had no influence on the degradation of DCF by Fe(VI)/Fe 3+ , Fe(VI)/Fe 2+ , and Fe(VI)/Mn 2+ within the tested concentration. The addition of 5 or 20 mg L -1 NOM decreased the removal efficiency of DCF. Moreover, Fe 2 O 3 and Fe(OH) 3 , the by-products of Fe(VI), slightly inhibited the DCF removal, while α-FeOOH, another by-product of Fe(VI), showed no influence at pH 7. In addition, MnO 2 and MnO 4 - , the by-products of Mn 2+ , enhanced the DCF degradation due to catalysis and superposition of oxidation capacity, respectively. This study indicates that Fe 3+ and Fe 2+ promoted the DCF removal mainly via the self-catalysis for Fe(VI), and meanwhile, the catalysis of Mn 2+ and the effect of its by-products (i.e., MnO 2 and MnO 4 - ) contributed synchronously for DCF degradation. Graphical abstract ᅟ.

Manganese inhibition of microbial iron reduction in anaerobic sediments

USGS Publications Warehouse

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

1988-01-01

Potential mechanisms for the lack of Fe(II) accumulation in Mn(IV)-containing anaerobic sediments were investigated. The addition of Mn(IV) to sediments in which Fe(II) reduction was the terminal electron-accepting process removed all the pore-water Fe(II), completely inhibited net Fe(III) reduction, and stimulated Mn(IV) reduction. Results demonstrate that preferential reduction of Mn(IV) by FE(III)-reducing bacteria cannot completely explain the lack of Fe(II) accumulation in anaerobic, Mn(IV)-containing sediments, and indicate that Mn(IV) oxidation of Fe(II) is the mechanism that ultimately prevents Fe(II) accumulation. -Authors

The Mn-Fe negative correlation in olivines in ALHA 77257 ureilite

NASA Technical Reports Server (NTRS)

Miyamoto, M.; Furuta, T.; Fujii, N.; Mckay, D. S.; Lofgren, G. E.; Duke, M. B.

1993-01-01

An electron probe microanalyzer is used to measure the Mn, Fe, and oxygen zoning profiles of olivines in the ALHA 77257 ureilite. This is done to study the effects of reduction on the Mn-Fe value, as ureilite olivines exhibit thin reduced rims. Since the Mn content gradually increases toward the rim of ureilite olivines, while the Fa (= 100 x Fe/(Mg + Fe), mol percent) component decreases, the Mn-Fe content of olivine is likely related to redox conditions. The results of melting experiments suggest that the Mn-Fe positive correlation is related to temperature and that the negative correlation of Mn-Fe in olivine and low-Ca pyroxene is related to reduction.

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.

The lacustrine carbon cycle as illuminated by the waters and sediments of two hydrologically distinct headwater lakes in North-Central Minnesota, U.S.A

USGS Publications Warehouse

Dean, W.E.; Schwalb, A.

2002-01-01

The accumulation rates of CaCO3 and organic carbon (OC) in lake sediments are delicately balanced between production in the epilimnion and destruction in the hypolimnion. The cycling of these two forms of carbon makes a "carbon pump" that greatly affects the biogeochemical cycles of other elements. To further understand these biogeochemical dynamics, the lakes, streams, and wetlands of the Shingobee River headwater area of north-central Minnesota have been subjected to intensive hydrologic and biogeochemical studies. Williams Lake, situated close to the highest point in the regional flow system, is hydrologically closed, with no surface inlet or outlet, and ground water and precipitation as the only sources of water. Shingobee Lake, situated at the lowest point in the regional flow system, has the Shingobee River as an inlet and outlet. The surface waters of both lakes are oversaturated, and the bottom waters undersaturated, with respect to CaCO3 during the summer. The small amount of CaCO3 that is precipitated in the epilimnion of Williams Lake during the summer is dissolved in the undersaturated hypolimnion and sediments with the result that no CaCO3 is incorporated into the profundal surface sediments. Because of the high phytoplankton productivity of Shingobee Lake, sufficient CaCO3 is produced in the epilimnion that large amounts survive the corrosive hypolimnion and sediments, and an average of 46 wt. % accumulates in surface sediments. Another consequence of higher phytoplankton productivity in Shingobee Lake is that the hypolimnion becomes oxygen deficient within a month after overturn in both the spring and fall. Because of reducing conditions that develop in the hypolimnion of Shingobee Lake, high concentrations of dissolved Fe and Mn accumulate there during summer stratification. Precipitation of Fe and Mn oxyhydroxides during periods of fall and spring overturn results in high concentrations of Fe and Mn in surface sediments. In Williams Lake, high concentrations of Fe and Mn do not build up in the hypolimnion. The concentration of CaCO3 is about 80 wt. % in lower Holocene sediments of both lakes. The lower Holocene sediments in both lakes also contain high concentrations of Fe and Mn, and the lower Holocene sediments of Shingobee are laminated. The waters of both lakes had identical values of ??13C and ??18O during the early Holocene, but the waters of Williams Lake "evolved" during the early Holocene, increasing about 10??? in both ??13C and ??18O. Deposits of lacustrine marl occur as much as seven meters above the present elevation of Williams Lake, the highest of the two lakes. Taken together, these observations suggest that the lakes were once connected to form a larger lake called Lake Willobee with a hypolimnion that was anoxic, at least seasonally.

Arsenate uptake and arsenite simultaneous sorption and oxidation by Fe-Mn binary oxides: influence of Mn/Fe ratio, pH, Ca2+, and humic acid.

PubMed

Zhang, Gaosheng; Liu, Huijuan; Qu, Jiuhui; Jefferson, William

2012-01-15

Arsenate retention, arsenite sorption and oxidation on the surfaces of Fe-Mn binary oxides may play an important role in the mobilization and transformation of arsenic, due to the common occurrence of these oxides in the environment. However, no sufficient information on the sorption behaviors of arsenic on Fe-Mn binary oxides is available. This study investigated the influences of Mn/Fe molar ratio, solution pH, coexisting calcium ions, and humic acids have on arsenic sorption by Fe-Mn binary oxides. To create Fe-Mn binary oxides, simultaneous oxidation and co-precipitation methods were employed. The Fe-Mn binary oxides exhibited a porous crystalline structure similar to 2-line ferrihydrite at Mn/Fe ratios 1:3 and below, whereas exhibited similar structures to δ-MnO(2) at higher ratios. The As(V) sorption maximum was observed at a Mn/Fe ratio of 1:6, but As(III) uptake maximum was at Mn/Fe ratio 1:3. However, As(III) adsorption capacity was much higher than that of As(V) at each Mn/Fe ratio. As(V) sorption was found to decrease with increasing pH, while As(III) sorption edge was different, depending on the content of MnO(2) in the binary oxides. The presence of Ca(2+) enhanced the As(V) uptake under alkaline pH, but did not significantly influence the As(III) sorption by 1:9 Fe-Mn binary oxide; whereas the presence of humic acid slightly reduced both As(V) and As(III) uptake. These results indicate that As(III) is more easily immobilized than As(V) in the environment, where Fe-Mn binary oxides are available as sorbents and they represent attractive adsorbents for both As(V) and As(III) removal from water and groundwater. Copyright © 2011 Elsevier Inc. All rights reserved.

Critical evaluation of sequential leaching procedures for the determination of Ni and Mn species in welding fumes.

PubMed

Berlinger, B; Náray, M; Sajó, I; Záray, G

2009-06-01

In this work, welding fume samples were collected in a welding plant, where corrosion-resistant steel and unalloyed structural steel were welded by gas metal arc welding (GMAW) and manual metal arc welding (MMAW) techniques. The welding fumes were sampled with a fixed-point sampling strategy applying Higgins-Dewell cyclones. The following solutions were used to dissolve the different species of Ni and Mn: ammonium citrate solution [1.7% (m/v) diammonium hydrogen citrate and 0.5% (m/v) citric acid monohydrate] for 'soluble' Ni, 50:1 methanol-bromine solution for metallic Ni, 0.01 M ammonium acetate for soluble Mn, 25% acetic acid for Mn(0) and Mn(2+) and 0.5% hydroxylammonium chloride in 25% acetic acid for Mn(3+) and Mn(4+). 'Insoluble' Ni and Mn contents of the samples were determined after microwave-assisted digestion with the mixture of concentrated (cc). HNO(3), cc. HCl and cc. HF. The sample solutions were analysed by inductively coupled plasma quadrupole mass spectrometry and inductively coupled plasma atomic emission spectrometry. The levels of total Ni and Mn measured in the workplace air were different because of significant differences of the fume generation rates and the distributions of the components in the welding fumes between the welding processes. For quality control of the leaching process, dissolution of the pure stoichiometric Mn and Ni compounds and their mixtures weighing was investigated using the optimized leaching conditions. The results showed the adequacy of the procedure for the pure metal compounds. Based on the extraction procedures, the predominant oxidation states of Ni and Mn proved to be very different depending on the welding techniques and type of the welded steels. The largest amount of Mn in GMAW fumes were found as insoluble Mn (46 and 35% in case of corrosion-resistant steel and unalloyed structural steel, respectively), while MMAW fumes contain mainly soluble Mn, Mn(0) and Mn(2+) (78%) and Mn(3+) and Mn(4+) (54%) in case of corrosion-resistant steel and unalloyed structural steel, respectively. According to the results of the leaching procedures, GMAW fumes are rich in oxidic Ni (79%), while Ni compounds in welding fumes generated during MMAW are mainly in easily soluble form (44%). The crystalline phases were identified in each welding fume by X-ray powder diffraction (XRPD) technique as well. From the XRPD spectra, it is clear that GMAW fumes contain predominantly magnetite (FeFe(2)O(4)). In case of structural steel welding, there was a little amount of ferrite (alpha-Fe) also found. Welding fume generated during MMAW of structural steel contained a complex alkali-alkali earth fluoride phase (KCaF(3)-CaF(2)) and some magnetite and jakobsite (MnFe(2)O(4)). The XRPD results did not fully confirm the ones obtained from the extraction experiments. However, some results, for example the rate of soluble Ni and Mn compounds compared to the total, can be useful for further investigations of welding fumes.

Biological regeneration of manganese (IV) and iron (III) for anaerobic metal oxide-mediated removal of pharmaceuticals from water.

PubMed

Liu, Wenbo; Langenhoff, Alette A M; Sutton, Nora B; Rijnaarts, Huub H M

2018-05-18

Applying manganese(IV)- or iron(III)-(hydr)oxides to remove pharmaceuticals from water could be attractive, due to the capacity of these metal oxides to remove pharmaceuticals and be regenerated. As pharmaceutical removal under anaerobic conditions is foreseen, Mn(IV) or Fe(III) regeneration under anaerobic conditions, or with minimum oxygen dosage, is preferred. In this study, batch experiments are performed to investigate (1) Mn(IV) and Fe(III) regeneration from Mn(II) and Fe(II); (2) the pharmaceutical removal during biological Mn(IV) and Fe(III) regeneration; and (3) anaerobic abiotic pharmaceutical removal with different Mn(IV) or Fe(III) species. Results show that biological re-oxidation of reduced Mn(II) to Mn(IV) occurs under oxygen-limiting conditions. Biological re-oxidation of Fe(II) to Fe(III) is obtained with nitrate under anaerobic conditions. Both bio-regenerated Mn(IV)-oxides and Fe(III)-hydroxides are amorphous. The pharmaceutical removal is insignificant by Mn(II)- or Fe(II)-oxidizing bacteria during regeneration. Finally, pharmaceutical removal is investigated with various Mn(IV) and Fe(III) sources. Anaerobic abiotic removal using Mn(IV) produced from drinking water treatment plants results in 23% metoprolol and 44% propranolol removal, similar to chemically synthesized Mn(IV). In contrast, Fe(III) from drinking water treatment plants outperformed chemically or biologically synthesized Fe(III); Fe (III) from drinking water treatment can remove 31-43% of propranolol via anaerobic abiotic process. In addition, one of the Fe(III)-based sorbents tested, FerroSorp ® RW, can also remove propranolol (20-25%). Biological regeneration of Mn(IV) and Fe(III) from the reduced species Mn(II) and Fe(II) could be more effective in terms of cost and treatment efficiency. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.

PubMed

Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang

2014-05-01

Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Mn-oxidizing Bacteria in Oak Ridge, TN and the Potential for Mercury Remediation

NASA Astrophysics Data System (ADS)

Wright, K. L.; McNeal, K. S.; Han, F. X.

2012-12-01

East Fork Poplar Creek (EFPC) in Oak Ridge, TN was highly contaminated with elemental mercury in the 1950 and 1960. The area is still experiencing the effects of mercury contamination, and researchers are searching for ways to remediate the EFPC. One possible mechanism for bioremediation is the use of biogenic Mn oxides to remove heavy metals from water systems. Six native Pseudomonas bacteria species were isolated from the EFPC in order to examine biogenic Mn oxides production and bioremediation of Oak Ridge slurries. To investigate the biochemical interactions of Pseudomonas and the native microbial communities with Hg, Mn, Fe, S, six different slurry treatment groups were compared using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and cold vapor atomic absorption spectrometry (CVAAS). Oak Ridge slurries were autoclaved to inhibit microbial growth (group 1), autoclaved and amended with HgS (group 2), autoclaved and amended with Pseudomonas isolates and additional HgS (group 3), untreated slurry (group 4), normal slurry amended with HgS (group 5), and normal slurry amended with Pseudomonas isolates and additional HgS (group 6). The comparison of the autoclaved groups with the counterpart untreated and normal Oak Ridge slurries highlighted important microbial interactions. Also, the Pseudomonas isolates were grown separately in a MnSO4 media, and the individual bacteria were monitored for Mn-oxidization using ICP-AES and transmission electron microscopy (TEM). In the slurry sediments, the Pseudomonas isolates did produce Mn oxides which bound to mercury, and mercury bound to organic matter significantly decreased. However, after a significant decrease of dissolved mercury in the water, dissolved mercury was cycled back into the water system on day 10 of the study. Additionally, two individual native Oak Ridge Pseudomonas isolates demonstrated Mn-oxidization. Biogenic Mn oxides have the potential to decrease mercury cycling, however there is need for more in depth and long-term studies to confirm their sustained use as Hg bioremediators.

Multiple antiferromagnet/ferromagnet interfaces as a probe of grain-size-dependent exchange bias in polycrystalline Co/Fe 50Mn 50

NASA Astrophysics Data System (ADS)

Bolon, Bruce T.; Haugen, M. A.; Abin-Fuentes, A.; Deneen, J.; Carter, C. B.; Leighton, C.

2007-02-01

We have used ferromagnet/antiferromagnet/ferromagnet trilayers and ferromagnet/antiferromagnet multilayers to probe the grain size dependence of exchange bias in polycrystalline Co/Fe 50Mn 50. X-ray diffraction and transmission electron microscopy show that the Fe 50Mn 50 (FeMn) grain size increases with increasing FeMn thickness in the Co (30 Å)/FeMn system. Hence, in Co(30 Å)/FeMn( tAF Å)/Co(30 Å) trilayers the two Co layers sample different FeMn grain sizes at the two antiferromagnet/ferromagnet interfaces. For FeMn thicknesses above 100 Å, where simple bilayers have a thickness-independent exchange bias, we are therefore able to deduce the influence of FeMn grain size on the exchange bias and coercivity (and their temperature dependence) simply by measuring trilayer and multilayer samples with varying FeMn thicknesses. This can be done while maintaining the (1 1 1) orientation, and with little variation in interface roughness. Increasing the average grain size from 90 to 135 Å results in a fourfold decrease in exchange bias, following an inverse grain size dependence. We interpret the results as being due to a decrease in uncompensated spin density with increasing antiferromagnet grain size, further evidence for the importance of defect-generated uncompensated spins.

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.

Column studies to assess the effects of climate variables on redox processes during riverbank filtration.

PubMed

Rudolf von Rohr, Matthias; Hering, Janet G; Kohler, Hans-Peter E; von Gunten, Urs

2014-09-15

Riverbank filtration is an established technique used world-wide to produce clean drinking water in a reliable and cost-efficient way. This practice is, however, facing new challenges posed by climate change, as already observed during past heat waves with the local occurrence of anoxic conditions. In this study we investigated the effect of direct (temperature) and indirect (dissolved organic matter (DOM) concentration and composition, flow rate) climate change variables on redox processes (aerobic respiration, denitrification and Mn(III/IV)/Fe(III) reduction) by means of column experiments. Natural river water, modified river water and river water mixed with treated wastewater effluent were used as feed waters for the columns filled with natural sand from a river-infiltration system in Switzerland. Biodegradable dissolved organic matter was mainly removed immediately at the column inlet and particulate organic matter (POM) associated with the natural sand was the main electron donor for aerobic respiration throughout the column. Low infiltration rates (≤0.01 m/h) enhanced the oxygen consumption leading to anoxic conditions. DOM consumption did not seem to be sensitive to temperature, although oxygen consumption (i.e., associated with POM degradation) showed a strong temperature dependence with an activation energy of ∼70 kJmol(-1). Anoxic conditions developed at 30 °C with partial denitrification and formation of nitrite and ammonium. In absence of oxygen and nitrate, Mn(II) was mobilized at 20 °C, highlighting the importance of nitrate acting as a redox buffer under anoxic conditions preventing the reductive dissolution of Mn(III/IV)(hydr)oxides. Reductive dissolution of Fe(III)(hydr)oxides was not observed under these conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thickness dependence of exchange anisotropy for (0 0 1) oriented Mn 89Pt 11/NiFe and Mn 80Ir 20/NiFe bilayers

NASA Astrophysics Data System (ADS)

Kume, T.; Yamato, T.; Kato, T.; Tsunashima, S.; Iwata, S.

2007-03-01

Antiferromagnetic layer thickness dependences of exchange anisotropy for (0 0 1) oriented Mn 89Pt 11 ( tAF nm)/Ni 80Fe 20 (5 nm) and Mn 80Ir 20 ( tAF nm)/Ni 80Fe 20 (5 nm) were investigated. For Mn 89Pt 11/NiFe, the exchange bias field appeared at tAF⩾5 nm. This critical thickness was found to be thicker than that of Mn 80Ir 20/NiFe ( tAF=3 nm). The thickness dependence of exchange bias field agreed well with that of 1-fold Fourier amplitude estimated from in-plane torque curves. The large coercivity of about 100 Oe was found for Mn 89Pt 11/NiFe at tAF=30 nm compared to that of Mn 80Ir 20/NiFe. The large coercivity in Mn 89Pt 11/NiFe bilayers seems to result from the large 4-fold anisotropy in their torque curve.

Selective sequential precipitation of dissolved metals in mine drainage from coal mine

NASA Astrophysics Data System (ADS)

Yim, Giljae; Bok, Songmin; Ji, Sangwoo; Oh, Chamteut; Cheong, Youngwook; Han, Youngsoo; Ahn, Joosung

2017-04-01

In abandoned mines in Korea, a large amount of mine drainage continues to flow out and spread pollution. In purification of the mine drainage a massive amount of sludge is generated as waste. Since this metal sludge contains high Fe, Al and Mn oxides, developing the treatment method to recover homogeneous individual metal with high purity may beneficial to recycle waste metals as useful resources and reduce the amount of sludge production. In this regard, we established a dissolved metals selective precipitation process to treat Waryong Industry's mine drainage. The process that selectively precipitates metals dissolved in mine drainage is a continuous Fe-buffer-Al process, and each process consists of the neutralization tank, the coagulation tank, and the settling tank. Based on this process, this study verified the operational applicability of the Fe and Al selective precipitation. Our previous study revealed that high-purity Fe and Al precipitates could be recovered at a flow rate of 1.5 ton/day, while the lower purity was achieved when the rate was increased to about 3 ton/day due to the difficulty in reagent dosage control. In the current study was conducted to increase the capacity of the system to recover Fe and Al as high-purity precipitates at a flow rate of 10 ton/day with the ensured continuous operations by introducing an automatic reagent injection system. The previous study had a difficulty in controlling the pH and operating system continuously due to the manually controlled reagent injection system. To upgrade this and ensure the optimal pH in a stable way, a continuous reagent injection system was installed. The result of operation of the 10 ton/day system confirmed that the scaled-up process could maintain the stable recovery rates and purities of precipitates on site.

Kinetic dissolution of carbonates and Mn oxides in acidic water: Measurement of in situ field rates and reactive transport modeling

USGS Publications Warehouse

Brown, J.G.; Glynn, P.D.

2003-01-01

The kinetics of carbonate and Mn oxide dissolution under acidic conditions were examined through the in situ exposure of pure phase samples to acidic ground water in Pinal Creek Basin, Arizona. The average long-term calculated in situ dissolution rates for calcite and dolomite were 1.65??10-7 and 3.64??10-10 mmol/(cm2 s), respectively, which were about 3 orders of magnitude slower than rates derived in laboratory experiments by other investigators. Application of both in situ and lab-derived calcite and dolomite dissolution rates to equilibrium reactive transport simulations of a column experiment did not improve the fit to measured outflow chemistry: at the spatial and temporal scales of the column experiment, the use of an equilibrium model adequately simulated carbonate dissolution in the column. Pyrolusite (MnO2) exposed to acidic ground water for 595 days increased slightly in weight despite thermodynamic conditions that favored dissolution. This result might be related to a recent finding by another investigator that the reductive dissolution of pyrolusite is accompanied by the precipitation of a mixed Mn-Fe oxide species. In PHREEQC reactive transport simulations, the incorporation of Mn kinetics improved the fit between observed and simulated behavior at the column and field scales, although the column-fitted rate for Mn-oxide dissolution was about 4 orders of magnitude greater than the field-fitted rate. Remaining differences between observed and simulated contaminant transport trends at the Pinal Creek site were likely related to factors other than the Mn oxide dissolution rate, such as the concentration of Fe oxide surface sites available for adsorption, the effects of competition among dissolved species for available surface sites, or reactions not included in the model.

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.

Cu-Mn-Fe alloys and Mn-rich amphiboles in ancient copper slags from the Jabal Samran area, Saudi Arabia: With synopsis on chemistry of Fe-Mn(III) oxyhydroxides in alteration zones

NASA Astrophysics Data System (ADS)

Surour, Adel A.

2015-01-01

In the Jabal Samran area (western Saudi Arabia), secondary copper mineralization in a NE-trending shear zone in which the arc metavolcanic host rocks (dacite-rhyodacite) show conjugate fractures and extensive hydrothermal alteration and bleaching. The zones contain frequent Fe-Mn(III) oxyhydroxides (FeOH-MnOH) that resulted from oxidation of pyrite and Mn-bearing silicates. In the bleached part, the groundmass is represented by Fe-bearing interstratified illite-smectite with up to 4.02 wt% FeOt. FeOH-MnOH are pre-weathering phases formed by hydrothermal alteration in a submarine environment prior to uplifting. Five varieties of FeOH are distinguished, four of them are exclusively hydrothermal with ∼20 wt% H2O whereas the fifth contains ∼31-33 wt% H2O and might represent reworking of earlier hydrothermal FeOH phases by weathering. FeOH fills thin fractures in the form of veinlets and crenulated laminae or as a pseudomorph for pyrite, goethite and finally ferrihydrite, and this oxyhydroxide is characterized by positive correlation of Fe2O3 with SiO2 and Al2O3. On the other hand, MOH shows positive correlation between MnO2 and Al2O3 whereas it is negative between Fe2O3 and SiO2. Paratacamite is the most common secondary copper mineral that fills fractures and post-dates FeOH and MnOH. It is believed that Cl- in the structure of paratacamite represents inherited marine storage rather than from surfacial evaporates or meteoric water. The mineralogy of slags suggests a complicated mineral assemblage that includes native Cu prills, synthetic spinifixed Mn-rich amphiboles with 16.73 wt% MnO, brown glass and Ca-Mn-Fe phase close to the olivine structure. EMPA indicate that the some Cu prills have either grey discontinuous boarder zone of S-rich Mn-Cu alloy (with up to 21.95 wt% S and 19.45 wt% Mn) or grey Cu-Mn-Fe alloy (with up to 15.9 wt% Cu, 39. 12 wt% Mn and 61.64 wt% Fe). Mn in the Cu prills is expelled inward as Cu-Mn-Fe alloy inclusions whereas S is expelled outward as S-rich Mn-Cu alloy crust. Remains in the Samran smelter sites suggest the use of charcoal as a source of energy, quartzite as a flux and an air-cooling technique was used.

Enhancement of magnetic ordering temperature in iron substituted ytterbium manganate (YbMn{sub 1-x}Fe{sub x}O{sub 3})

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

Samal, S.L.; Magdaleno, T.; Ramanujachary, K.V.

Oxides of the type YbMn{sub 1-x}Fe{sub x}O{sub 3}; x<=0.3 showing multiferroic behavior have been synthesized by the solid state route. These oxides crystallize in the hexagonal structure known for the parent YbMnO{sub 3} with the c/a ratio increasing with Fe substitution. The distortion of the MnO{sub 5} polyhedra (tbp) decreases and the Mn-O-Mn bonds in the a-b plane become shorter with Fe-substitution. Magnetic ordering is observed from the low temperature neutron diffraction study. The compounds were found to be antiferromagnetic and the ordering temperature T{sub N} increased from 82 K for pure YbMnO{sub 3} to 95 K for YbMn{sub 0.7}Fe{submore » 0.3}O{sub 3}. Variable temperature dielectric measurements (15-110 K) show an anomaly in the dielectric constant at temperatures close to the antiferromagnetic ordering temperature for all the compositions, showing a unique correlation between the magnetic and electric field. The increase in the ordering temperature in YbMn{sub 1-x}Fe{sub x}O{sub 3} is explained on the basis of increase in covalence of Mn/Fe-O-Mn/Fe bonds (shorter) with iron substitution. - Graphical abstract: Hexagonal manganites of the type YbMn{sub 1-x}Fe{sub x}O{sub 3}; x<=0.3 have been synthesized by the solid state route. The distortion of the MnO{sub 5} polyhedra (tbp) decreases and the Mn-O-Mn bonds in the a-b plane become shorter with Fe-substitution. The compounds were found to be antiferromagnetic and the ordering temperature T{sub N} increased from 82 K for pure YbMnO{sub 3} to 95 K for YbMn{sub 0.7}Fe{sub 0.3}O{sub 3}. The increase in the ordering temperature in YbMn{sub 1-x}Fe{sub x}O{sub 3} is explained on the basis of increase in covalence of Mn/Fe-O-Mn/Fe bonds with iron substitution. Low temperature dielectric measurements show a unique correlation between the magnetic and electric fields for all compositions.« less

Kineococcus radiotolerans Dps forms a heteronuclear Mn-Fe ferroxidase center that may explain the Mn-dependent protection against oxidative stress.

PubMed

Ardini, Matteo; Fiorillo, Annarita; Fittipaldi, Maria; Stefanini, Simonetta; Gatteschi, Dante; Ilari, Andrea; Chiancone, Emilia

2013-06-01

The ferroxidase center of DNA-binding protein from starved cells (Dps) is a major player in the iron oxidation/detoxification process that leads to a decreased reactive oxygen species production. The possible Mn(II) participation in this process has been studied in Dps from Kineococcus radiotolerans, a radiation-resistant bacterium with a high cytosolic Mn/Fe ratio and a high capacity to survive ionizing and stress conditions. The X-ray structure of recombinant K. radiotolerans Dps loaded with Mn(II) has been solved at 2.0Å resolution. Mn(II) binding to K. radiotolerans Dps and its effect on Fe(II) oxidation have been characterized in spectroscopic measurements. In K. radiotolerans Dps, the Fe-Fe ferroxidase center can have a Mn-Fe composition. Mn(II) binds only at the high affinity, so-called A site, whereas Fe(II) binds also at the low affinity, so-called B site. The Mn-Fe and Fe-Fe centers behave distinctly upon iron oxidation by O2. A site-bound Mn(II) or Fe(II) plays a catalytic role, while B site-bound Fe(II) behaves like a substrate and can be replaced by another Fe(II) after oxidation. When H2O2 is the Fe(II) oxidant, single electrons are transferred to aromatic residues near the ferroxidase center and give rise to intra-protein radicals thereby limiting OH release in solution. The presence of the Mn-Fe center results in significant differences in the development of such intra-protein radicals. Mn(II) bound at the Dps ferroxidase center A site undergoes redox cycling provided the B site contains Fe. The results provide a likely molecular mechanism for the protective role of Mn(II) under oxidative stress conditions as it participates in redox cycling in the hetero-binuclear ferroxidase center. Copyright © 2013 Elsevier B.V. All rights reserved.

Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 2: Geochemical controls on constituent concentrations

USGS Publications Warehouse

Cravotta, C.A.

2008-01-01

Water-quality data for discharges from 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania reveal complex relations among the pH and dissolved solute concentrations that can be explained with geochemical equilibrium models. Observed values of pH ranged from 2.7 to 7.3 in the coal-mine discharges (CMD). Generally, flow rates were smaller and solute concentrations were greater for low-pH CMD samples; pH typically increased with flow rate. Although the frequency distribution of pH was similar for the anthracite and bituminous discharges, the bituminous discharges had smaller median flow rates; greater concentrations of SO4, Fe, Al, As, Cd, Cu, Ni and Sr; comparable concentrations of Mn, Cd, Zn and Se; and smaller concentrations of Ba and Pb than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by near-neutral or alkaline ground water; (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous SO4-complexation and surface-complexation (adsorption) reactions. The formation of AlSO4+ and AlHSO42 + complexes adds to the total dissolved Al concentration at equilibrium with Al(OH)3 and/or Al hydroxysulfate phases and can account for 10-20 times greater concentrations of dissolved Al in SO4-laden bituminous discharges compared to anthracite discharges at pH of 5. Sulfate complexation can also account for 10-30 times greater concentrations of dissolved FeIII concentrations at equilibrium with Fe(OH)3 and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3-5. In contrast, lower Ba concentrations in bituminous discharges indicate that elevated SO4 concentrations in these CMD sources could limit Ba concentrations by the precipitation of barite (BaSO4). Coprecipitation of Sr with barite could limit concentrations of this element. However, concentrations of dissolved Pb, Cu, Cd, Zn, and most other trace cations in CMD samples were orders of magnitude less than equilibrium with sulfate, carbonate, and/or hydroxide minerals. Surface complexation (adsorption) by hydrous ferric oxides (HFO) could account for the decreased concentrations of these divalent cations with increased pH. In contrast, increased concentrations of As and, to a lesser extent, Se with increased pH could result from the adsorption of these oxyanions by HFO at low pH and desorption at near-neutral pH. Hence, the solute concentrations in CMD and the purity of associated "ochres" formed in CMD settings are expected to vary with pH and aqueous SO4 concentration, with potential for elevated SO4, As and Se in ochres formed at low pH and elevated Cu, Cd, Pb and Zn in ochres formed at near-neutral pH. Elevated SO4 content of ochres could enhance the adsorption of cations at low pH, but decrease the adsorption of anions such as As. Such information on environmental processes that control element concentrations in aqueous samples and associated precipitates could be useful in the design of systems to reduce dissolved contaminant concentrations and/or to recover potentially valuable constituents in mine effluents.

Effect of Ir-Mn composition on exchange bias and thermal stability of spin valves with nano-oxide layers

NASA Astrophysics Data System (ADS)

Liu, Y. F.; Cai, J. W.; Lai, W. Y.; Yu, G. H.

2008-05-01

The Ir-Mn bottom-pinned spin valves with nano-oxide layers (NOLs), Ta /Ni81Fe19/Ir-Mn/Co90Fe10/NOL/Co90Fe10/Cu/Co90Fe10/NOL/Ta, were fabricated by dc magnetron sputtering. The magnetoresistance (MR), magnetization, and exchange bias have been studied as a function of Ir-Mn composition and annealing temperature. It was observed that the spin valves with the Ir-Mn layer containing relatively low Mn content (58.9-72.4at.% Mn) show the best thermal endurance. For these samples, the Mn diffusion is effectively hampered by the NOL with a large MR value of about 12.5% even after annealing at 300°C. On the other hand, the exchange bias field of the pinned CoFe layer shows a maximum at Mn content of about 72.4at.%, which is different from the widely adopted composition, Ir-80at.% Mn, optimized from the top-pinned NiFe /Ir-Mn system. Moreover, the blocking temperature of the Ir -Mn/CoFe system with 72.4at.% Mn is higher than that with 80.6at.% Mn. The present results suggest that the Ir -Mn/CoFe pinning system with Mn content at about 72% renders the most favorable exchange bias and the best thermal stability for the bottom-pinned specular spin valves.

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity

DOE PAGES

Semin, B. K.; Davletshina, L. N.; Seibert, M.; ...

2017-11-11

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH 5.7) than at neutral pH (3Mn/RC are extracted at pH 6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH 6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extractmore » only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster.« less

Creation of a 3Mn/1Fe cluster in the oxygen-evolving complex of photosystem II and investigation of its functional activity

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

Semin, B. K.; Davletshina, L. N.; Seibert, M.

Extraction of Mn cations from the oxygen-evolving complex (OEC) of Ca-depleted PSII membranes (PSII[-Ca,4Mn]) by reductants like hydroquinone (H 2Q) occurs with lower efficiency at acidic pH (2Mn/reaction center [RC] are extracted at pH 5.7) than at neutral pH (3Mn/RC are extracted at pH 6.5) [Semin et al. Photosynth. Res. 125 (2015) 95]. Fe(II) also extracts Mn cations from PSII(-Ca,4Mn), but only 2Mn/RC at pH 6.5, forming a heteronuclear 2Mn/2Fe cluster [Semin and Seibert, J. Bioenerg. Biomembr. 48 (2016) 227]. Here we investigated the efficiency of Mn extraction by Fe(II) at acidic pH and found that Fe(II) cations can extractmore » only 1Mn/RC from PSII(-Ca,4Mn) membranes at pH 5.7, forming a 3Mn/1Fe cluster.« less

Origin of stratiform sediment-hosted manganese carbonate ore deposits: Examples from Molango, Mexico, and TaoJiang, China

USGS Publications Warehouse

Okita, P.M.; Shanks, Wayne C.

1992-01-01

Carbonate and sulfide minerals from the Molango, Mexico, and TaoJiang, China, Mn deposits display similar and distinctive ??34S and ??13C patterns in intervals of manganese carbonate mineralization. ??13C-values for Mn-bearing carbonate range from -17.8 to +0.5??? (PDB), with the most negative values occurring in high-grade ore zones that are composed predominantly of rhodochrosite. In contrast, calcite from below, within and above Mn-carbonate zones at Molango has ??13C???0??? (PDB). Markedly negative ??13C data indicate that a large proportion of the carbon in Mn-carbonates was derived from organic matter oxidation. Diagenetic reactions using MnO2 and SO2-4 to oxidize sedimentary organic matter were the principle causes of such 12C enrichment. Pyrite content and sulfide ?? 34S-values also show distinctive variations. In unmineralized rocks, very negative ??34S-values (avg. < -21??? CDT) and abundant pyrite content suggest that pyrite formed from diagenetic, bacteriogenic sulfate reduction. In contrast, Mn-bearing horizons typically contain only trace amounts of pyrite (e.g., <0.5 wt% S with ??34S-values 34S-enriched, in some cases to nearly the value for contemporaneous seawater. 34S-enriched pyrite from the Mn-carbonate intervals indicates sulfide precipitation in an environment that underwent extensive SO2-4 reduction, and was largely a closed system with regard to exchange of sulfate and dissolved sulfide with normal seawater. The occasional occurrence of 34S-depleted pyrite within Mn-carbonate zones dominated by 34S-enriched pyrite is evidence that closed-system conditions were intermittent and limited to local pore waters and did not involve entire sedimentary basins. Mn-carbonate precipitation may have occluded porosity in the surficial sediments, thus establishing an effective barrier to SO2-4 exchange with overlying seawater. Similar isotopic and mineralogic characteristics from both the Molango and TaoJiang deposits, widely separated in geologic time and space, suggest they were formed similarly by MnO2 precipitation at the margins of dysaerobic to anoxic marine basins. Mn-carbonate formed predominantly by early-diagenetic reduction of Mn-oxides via oxidation of organic matter in near-surface sediments. In addition to MnCO3 precipitation, organic matter oxidation reactions resulted in oxidation of FeS to Fe-oxides such as magnetite, maghemite and hematite. The latter process explains anomalously low pyrite content and abundant Fe-oxide minerals in ore zones dominated by rhodochrosite. ?? 1992.

Iron-Oxidizing Bacteria: A Review of Corrosion Mechanisms in Fresh Water and Marine Environments

DTIC Science & Technology

2010-01-01

ABSTRACT Models for corrosion influenced by iron-oxidizing ba < v-~~/ •" *> combinations, i.e., 300 series stainless steel exposed to oxygenated...surrounding oxygenated cathode . Metal at the anode dissolves, forming metal cations that undergo hydrolysis and decrease pH. The extent of the pH...S, K, Ca and Mn in addition to Fe. The underside of the tubercle, the surface that had been in contact with the metal, was comprised of bacteria

The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers

USGS Publications Warehouse

Swarzenski, P.; Campbell, P.; Porcelli, D.; McKee, B.

2004-01-01

Natural concentrations of 238U and ??234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (???1 m) zones of Fe(III) - and, to a lesser degree, Mn(IV) - reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ??234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ??234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ??234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface complexation reactions. In the Fly River estuary, 238U appears to exhibit a reasonably conservative distribution as a function of salinity. The absence of observed U removal does not necessarily imply non-reactivity, but instead may record an integration of concurrent U removal and release processes. There is not a linear correlation between ??234U vs. 1/ 238U that would imply simple two component mixing. It is likely that resuspension of bottom sediments, prolonged residence times in the lower reaches of the Fly River, and energetic particle-colloid interactions contribute to the observed estuarine U distribution. The supply of uranium discharged from humid, tropical river systems to the sea appears to be foremost influenced by particle/water interactions that are ultimately governed by the particular physiographic and hydrologic characteristics of an estuary. ?? 2004 Elsevier Ltd. All rights reserved.

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.

Natural decrease of dissolved arsenic in a small stream receiving drainages of abandoned silver mines in Guanajuato, Mexico.

PubMed

Arroyo, Yann Rene Ramos; Muñoz, Alma Hortensia Serafín; Barrientos, Eunice Yanez; Huerta, Irais Rodriguez; Wrobel, Kazimierz; Wrobel, Katarzyna

2013-11-01

Arsenic release from the abandoned mines and its fate in a local stream were studied. Physicochemical parameters, metals/metalloids and arsenic species were determined. One of the mine drainages was found as a point source of contamination with 309 μg L(-1) of dissolved arsenic; this concentration declined rapidly to 10.5 μg L(-1) about 2 km downstream. Data analysis confirmed that oxidation of As(III) released from the primary sulfide minerals was favored by the increase of pH and oxidation reduction potential; the results obtained in multivariate approach indicated that self-purification of water was due to association of As(V) with secondary solid phase containing Fe, Mn, Ca.

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

Fe/Mn in olivine of carbonaceous meteorites

NASA Technical Reports Server (NTRS)

Steele, Ian M.

1993-01-01

Olivines in primitive meteorites show a range of Fe/Mn both within one grain and among grains suggesting that they have recorded changing conditions during or after growth. Because olivine should be an early forming phase, Fe/Mn is used here to infer these earliest conditions. Initial Fe/Mn in cores of isolated, euhedral forsterite in both C2 and C3 meteorites ranges from 25 to 35 but differs at grain edge. Murchison (C2) forsterites show Fe/Mn approaching 1.0 at the grain edge while Ornans Fe/Mn is near 60 at grain edge. These values are lower than the matrix Fe/Mn for both meteorites and the distinct difference in zoning profile indicates different processes operating during and after grain growth. The Fe/Mn of bulk samples from a particular source such as the Moon is nearly constant. Individual samples show variation suggesting that there is some fractionation of Mn from Fe. Minerals have their individual ranges of Fe/Mn which has been used to recognize different types of olivine within one meteorite. Extreme values of Fe/Mn below 1.0 occur in forsterite from some IDP's, UOC matrix, and C1 meteorites. There are apparently no detailed studies of Fe/Mn variation within single olivine grains. Forsterite grains in C2 and C3 carbonaceous chondrites show complex zoning, and the nearly pure forsterites (Fo greater than approximately 99.5) have high levels of some minor elements including Ti, Al, V, and Sc. There is disagreement on the original source of these grains and both chondrule and vapor growth have been proposed. In addition, there is clear evidence that diffusion has affected the outer margins but in some cases the whole grain. Within the cores, the FeO range is limited, and if growing under constant conditions, the Fe/Mn should be near constant as there is little fractionation of Mn from Fe by forsterite. Additionally, there are apparently no co-crystallizing phases as evidenced by a lack of common inclusions in the forsterites. These observations are now followed by analyses of isolated olivine grains in C2 and C3 meteorites.

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.

Fractionation and risk assessment of Fe and Mn in surface sediments from coastal sites of Sonora, Mexico (Gulf of California).

PubMed

Jara-Marini, Martín E; García-Camarena, Raúl; Gómez-Álvarez, Agustín; García-Rico, Leticia

2015-07-01

The aim of this study was to evaluate Fe and Mn distribution in geochemical fractions of the surface sediment of four oyster culture sites in the Sonora coast, Mexico. A selective fractionation scheme to obtain five fractions was adapted for the microwave system. Surface sediments were analyzed for carbonates, organic matter contents, and Fe and Mn in geochemical fractions. The bulk concentrations of Fe ranged from 10,506 to 21,918 mg/kg (dry weight, dry wt), and the bulk concentrations of Mn ranged from 185.1 to 315.9 mg/kg (dry wt) in sediments, which was low and considered as non-polluted in all of the sites. The fractionation study indicated that the major geochemical phases for the metals were the residual, as well as the Fe and Mn oxide fractions. The concentrations of metals in the geochemical fractions had the following order: residual > Fe and Mn oxides > organic matter > carbonates > interchangeable. Most of the Fe and Mn were linked to the residual fraction. Among non-residual fractions, high percentages of Fe and Mn were linked to Fe and Mn oxides. The enrichment factors (EFs) for the two metals were similar in the four studied coasts, and the levels of Fe and Mn are interpreted as non-enrichment (EF < 1) because the metals concentrations were within the baseline concentrations. According to the environmental risk assessment codes, Fe and Mn posed no risk and low risk, respectively. Although the concentrations of Fe and Mn were linked to the residual fraction, the levels in non-residual fractions may significantly result in the transference of other metals, depending on several physico-chemical and biological factors.

Development and Evaluation of a Manganese and Iron Food Frequency Questionnaire for Pediatrics

PubMed Central

Zipkin, Frida B; Falciglia, Grace A; Kuhnell, Pierce; Haynes, Erin N

2017-01-01

Manganese (Mn) is an essential nutrient, but overexposure can lead to neurotoxicity. Given the essentiality of Mn in the diet, particularly during children’s growth and development, it is imperative to quantify dietary Mn intake in populations that may be exposed to industrial sources of Mn. Dietary absorption of Mn is inversely associated with iron (Fe) stores, yet there is currently no food frequency questionnaire (FFQ) to assess dietary Mn and Fe intake. The study objective was to develop and evaluate the validity of a FFQ to measure dietary Mn and Fe intake in pediatrics by comparing the estimated intakes of Mn and Fe with biomarkers: Mn in blood and hair and Fe in serum. This study utilized a subset of the Communities Actively Researching Exposure Study (CARES) population residing in Guernsey County, Ohio. Dietary Mn was not correlated with either blood or hair Mn; however, dietary Mn and serum ferritin were significantly correlated, with a correlation coefficient of 0.51, p < 0.01. Moreover, dietary Fe and serum ferritin were also significantly correlated, with a correlation coefficient of 0.51, p < 0.01. This FFQ is a valid measurement tool for Fe intake as measured by serum ferritin; however, Mn intake did not correlate with either blood or hair Mn. PMID:28906436

Development and Evaluation of a Manganese and Iron Food Frequency Questionnaire for Pediatrics.

PubMed

Zipkin, Frida B; Falciglia, Grace A; Kuhnell, Pierce; Haynes, Erin N

2017-09-14

Manganese (Mn) is an essential nutrient, but overexposure can lead to neurotoxicity. Given the essentiality of Mn in the diet, particularly during children's growth and development, it is imperative to quantify dietary Mn intake in populations that may be exposed to industrial sources of Mn. Dietary absorption of Mn is inversely associated with iron (Fe) stores, yet there is currently no food frequency questionnaire (FFQ) to assess dietary Mn and Fe intake. The study objective was to develop and evaluate the validity of a FFQ to measure dietary Mn and Fe intake in pediatrics by comparing the estimated intakes of Mn and Fe with biomarkers: Mn in blood and hair and Fe in serum. This study utilized a subset of the Communities Actively Researching Exposure Study (CARES) population residing in Guernsey County, Ohio. Dietary Mn was not correlated with either blood or hair Mn; however, dietary Mn and serum ferritin were significantly correlated, with a correlation coefficient of 0.51, p < 0.01. Moreover, dietary Fe and serum ferritin were also significantly correlated, with a correlation coefficient of 0.51, p < 0.01. This FFQ is a valid measurement tool for Fe intake as measured by serum ferritin; however, Mn intake did not correlate with either blood or hair Mn.

Transition metal redox and Mn disproportional reaction in LiMn0.5Fe0.5PO4 electrodes cycled with aqueous electrolyte

NASA Astrophysics Data System (ADS)

Zhuo, Zengqing; Hu, Jiangtao; Duan, Yandong; Yang, Wanli; Pan, Feng

2016-07-01

We performed soft x-ray absorption spectroscopy (sXAS) and a quantitative analysis of the transition metal redox in the LiMn0.5Fe0.5PO4 electrodes upon electrochemical cycling. In order to circumvent the complication of the surface reactions with organic electrolyte at high potential, the LiMn0.5Fe0.5PO4 electrodes are cycled with aqueous electrolyte. The analysis of the transitional metal L-edge spectra allows a quantitative determination of the redox evolution of Mn and Fe during the electrochemical cycling. The sXAS analysis reveals the evolving Mn oxidation states in LiMn0.5Fe0.5PO4. We found that electrochemically inactive Mn2+ is formed on the electrode surface during cycling. Additionally, the signal indicates about 20% concentration of Mn4+ at the charged state, providing a strong experimental evidence of the disproportional reaction of Mn3+ to Mn2+ and Mn4+ on the surface of the charged LiMn0.5Fe0.5PO4 electrodes.

Spontaneous perpendicular exchange bias effect in L10-MnGa/FeMn bilayers grown by molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Zhao, X. P.; Lu, J.; Mao, S. W.; Yu, Z. F.; Wei, D. H.; Zhao, J. H.

2018-01-01

We report on the spontaneous perpendicular exchange bias effect in as-grown L10-MnGa/FeMn bilayers. An FeMn layer with different thicknesses is introduced as an antiferromagnetic layer to couple with single-crystalline ferromagnetic L10-MnGa, which is epitaxially grown on a GaAs (001) substrate by molecular-beam epitaxy. The perpendicular exchange bias shows a strong dependence on both the thickness of the FeMn layer and the measurement temperature. A large spontaneous perpendicular exchange bias up to 8.9 kOe is achieved in L10-MnGa/FeMn bilayers at 5 K without any external magnetic treatment. The corresponding effective interfacial exchange energy Jeff is estimated to be 1.4 mJ/m2. The spontaneous perpendicular exchange bias effect in the (001) textured L10-MnGa/FeMn bilayers paves the way for spintronic devices based on exchange biased perpendicularly magnetized materials.

Spray deposited MnFe2O4 thin films for detection of ethanol and acetone vapors

NASA Astrophysics Data System (ADS)

Nagarajan, V.; Thayumanavan, A.

2018-01-01

Spinel MnFe2O4 films were synthesized with the help of spray pyrolysis technique. The morphology study shows fine crushed sand grain morphology of the film. The structural investigation verifies the polycrystalline nature of prepared MnFe2O4 films, which possess the spinel structure. Crystalline size is found to be around 23.5 nm-37.4 nm morphology analyses. Energy dispersive spectroscopy validates the presence of oxygen, iron and manganese in MnFe2O4 film. The prepared MnFe2O4 film is extremely sensitive towards ethanol molecules at 300 K. The electrical resistance of MnFe2O4 thin film decreases quickly when ethanol and acetone vapor molecules are adsorbed on base material. The synthesized MnFe2O4 film is also highly sensitive towards acetone molecules at ambient temperature. The selectivity, sensing response, stability and recovery time of MnFe2O4 film towards acetone and ethanol detection are analyzed in the present work.

MWCNT-MnFe2O4 nanocomposite for efficient hyperthermia applications

NASA Astrophysics Data System (ADS)

Seal, Papori; Hazarika, Monalisa; Paul, Nibedita; Borah, J. P.

2018-04-01

In this work we present synthesis of multi-walled carbon nanotube (MWCNT)-Manganese ferrite (MnFe2O4) nanocomposite and its probable application in hyperthermia. MnFe2O4 nanoparticles were synthesized by co-precipitation method. X ray diffractogram (XRD) confirms the formation of cubic phase of MnFe2O4 with preferred crystallographic orientation along (311) plane. High resolution electron microscope (HRTEM) image of the composites confirms the presence of MnFe2O4 spherical nanoparticles on the surface of CNT which are bound strongly to the surface. MWCNT-MnFe2O4 nanocomposite were prepared after acid functionalization of MWCNT. Vibrational features of the synthesized samples were confirmed through Fourier transformed infra-red spectroscopy (FTIR). FTIR spectra of acid functionalized MWCNT shows a peak positioned at ˜1620cm-1 which corresponds to C=O functional group of carboxylic acid. Prepared MnFe2O4 nanoparticles and MWCNT-MnFe2O4 nanocomposites were subjected to hyperthermia studies.

Ab initio study of Fe{sub 2}MnZ (Al, Si, Ge) Heusler alloy using GGA approximation

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

Jain, Vivek Kumar, E-mail: vivek.jain129@gmail.com; Jain, Vishal, E-mail: vivek.jain129@gmail.com; Lakshmi, N., E-mail: vivek.jain129@gmail.com

Density functional theory based on FP-LAPW method used to investigate the electronic structure of Fe{sub 2}MnZ, shows that the total spin magnetic moment shows a trend consistent with the Slater–Pauling curve. The Fe and Mn magnetic moment depend on choice of Z element although the magnetic moment of Z element is negative and less than 0.1 μ{sub B}. Spin polarization calculations evidence 100% spin polarization for Fe{sub 2}MnSi. Fe{sub 2}MnAl and Fe{sub 2}MnGe show metallic behavior with 93%, 98% spin polarization.

Study of manganese binding to the ferroxidase centre of human H-type ferritin.

PubMed

Ardini, Matteo; Howes, Barry D; Fiorillo, Annarita; Falvo, Elisabetta; Sottini, Silvia; Rovai, Donella; Lantieri, Marco; Ilari, Andrea; Gatteschi, Dante; Spina, Gabriele; Chiancone, Emilia; Stefanini, Simonetta; Fittipaldi, Maria

2018-05-01

Ferritins are ubiquitous and conserved proteins endowed with enzymatic ferroxidase activity, that oxidize Fe(II) ions at the dimetal ferroxidase centre to form a mineralized Fe(III) oxide core deposited within the apo-protein shell. Herein, the in vitro formation of a heterodimetal cofactor constituted by Fe and Mn ions has been investigated in human H ferritin (hHFt). Namely, Mn and Fe binding at the hHFt ferroxidase centre and its effects on Fe(II) oxidation have been investigated by UV-Vis ferroxidation kinetics, fluorimetric titrations, multifrequency EPR, and preliminary Mössbauer spectroscopy. Our results show that in hHFt, both Fe(II) and Mn(II) bind the ferroxidase centre forming a Fe-Mn cofactor. Moreover, molecular oxygen seems to favour Mn(II) binding and increases the ferroxidation activity of the Mn-loaded protein. The data suggest that Mn influences the Fe binding and the efficiency of the ferroxidation reaction. The higher efficiency of the Mn-Fe heterometallic centre may have a physiological relevance in specific cell types (i.e. glia cells), where the concentration of Mn is the same order of magnitude as iron. Copyright © 2018 Elsevier Inc. All rights reserved.

Structural and magnetic characterization of Mn/NiFe bilayers with ion-beam-assisted deposition

NASA Astrophysics Data System (ADS)

Wu, Chun-Hsien; Zheng, Chao; Chiu, Chun-Cheng; Manna, Palash Kumar; van Lierop, Johan; Lin, Ko-Wei; Pong, Philip W. T.

2018-01-01

The exchange bias effect in ferromagnetic (FM)/antiferromagnetic (AF) bilayer structures has been widely investigated because its underlying principle is critical for spintronic applications. In this work, the effect of Ar+ beam bombardment on the microstructural and magnetic properties of the Mn/NiFe thin films was investigated. The in-situ Ar+ bombardment nontrivially promoted the Mn/NiFe intermixing and facilitated the formation of the FeMn phase, accompanied by a remarkable reduction of Mn and NiFe layer thickness. The enhanced Mn/NiFe intermixing greatly disordered the interfacial spins, inhibiting the interfacial exchange coupling and giving rise to a significant decrease of the exchange bias field (H ex). The facilitated Mn/NiFe intermixing effect also dramatically degraded the magnetocrystalline anisotropy of the NiFe crystallites, leading to a notable suppression of the coercivity (H c). These results indicate that both the exchange bias and coercivity of the Mn/NiFe bilayers can be directly affected by the in-situ Ar+ bombardment, offering an effective way to modify the magnetism of the exchange-bias systems.

Hybrid supercapacitor devices based on MnCo2O4 as the positive electrode and FeMn2O4 as the negative electrode

NASA Astrophysics Data System (ADS)

Nagamuthu, Sadayappan; Vijayakumar, Subbukalai; Lee, Seong-Hun; Ryu, Kwang-Sun

2016-12-01

MnCo2O4 nanosheets and FeMn2O4 nanospheres were synthesized using a hydrothermal method. Choline chloride was used as the capping agent during the preparation of the nanoparticles. XRD patterns confirmed the spinel structure of MnCo2O4 and FeMn2O4. XPS measurements were used to determine the oxidation state of the prepared spinel metal oxides. HRTEM images revealed the formation of hexagonal nanosheets of MnCo2O4 and nanospheres of FeMn2O4. Electrochemical measurements were made for both positive and negative electrodes using three electrode systems. MnCo2O4 Exhibits 282C g-1 and FeMn2O4 yields 110C g-1 at a specific current of 1 A g-1. Hybrid supercapacitor device was fabricated using MnCo2O4 as the positive and FeMn2O4 as the negative electrode material. The hybrid supercapacitor device was delivered a maximum power of 37.57 kW kg-1.

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.

Synthesis of α-Fe2O3 and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates

PubMed Central

Feng, Yuping; Fornell, Jordina; Zhang, Huiyan; Solsona, Pau; Barό, Maria Dolors; Suriñach, Santiago; Sort, Jordi

2018-01-01

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N2 atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe2O3) foams are obtained from the metallic iron slurry independently of the N2 flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N2 flow. While the main phases for a N2 flow rate of 180 L/h are α-Fe2O3 and FeMnO3, the predominant phase for high N2 flow rates (e.g., 650 L/h) is Fe2MnO4. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe2MnO4 foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N2 flow rate (i.e., the amount of Fe2MnO4) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids. PMID:29439450

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.

Reduction kinetics of hexavalent chromium in soils and its correlation with soil properties.

PubMed

Xiao, Wendan; Zhang, Yibin; Li, Tingqiang; Chen, Bao; Wang, Huan; He, Zhenli; Yang, Xiaoe

2012-01-01

The toxicity of chromium (Cr) to biota is related to its chemical forms and consequently to the redox conditions of soils. Hexavalent Cr[Cr(VI)] may undergo natural attenuation through reduction processes. In this study, the reduction kinetics of Cr(VI) in seven soils and its relationships with soil properties were investigated with laboratory incubation experiments. The results indicate that the reduction of Cr(VI) can be described by a first-order reaction. The reduction rates of Cr(VI) in the seven soils decreased in the order: Udic Ferrisols > Stagnic Anthrosols > Calcaric Regosols > Mollisol > Typic Haplustalf > Periudic Argosols > Ustic Cambosols. Simple correlation analysis revealed that the reduction of Cr(VI) in soils was positively related to organic matter content, dissolved organic matter content, Fe(II) content, clay fraction, and to the diversity index of the bacterial community but negatively correlated with easily reducible Mn content. Using stepwise regression, the reduction of Cr(VI) in soil could be quantitatively predicted by the measurement of dissolved organic matter content, Fe(II) content, pH, and soil particle size distribution, with a fitting level of 95.5%. The results indicated that the reduction of Cr(VI) in natural soils is not controlled by a single soil property but is the result of the combined effects of dissolved organic matter, Fe(II), pH, and soil particle size distribution. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

[Influence of sulfur on the bioavailability of arsenic uptake by rice (Oryza. sativa L. ) and its speciation in soil ].

PubMed

Yang, Shi-jie; Tang, Bing-pei; Wang, Dai-chang; Rao, Wei; Zhang, Ya-nan; Wang, Dan; Zhu, Yun-ji

2014-09-01

Pot experiments using exogenous arsenic-polluted paddy soils were carried out to investigate the influence of different forms of sulfur fertilizers (sulfur and gypsum) on As uptake by rice and its chemical speciation. Soil solution pH value ranged 7. 38-7. 45 in different growth period of rice, and the pH value of AsS0 and AsS1 treatments was higher than that of AsS2 treatment. Variation of Eh value in soil solution was about 200 mV and the Eh of AsS0 was higher than those of AsS1 and AsS2 treatments. From dry matter weight of root and stem and grain of rice, S-fertilizer applied by sulfur and gypsum could improve the amounts of dry matter in rice, while the effects of sulfur treatments and gypsum treatments were not significant. Concentrations of Fe and Mn in iron-manganese plaque on rice roots were 10-30 g.kg-1 and 0.1-1.3 g.kg-1, respectively. Contents of Fe-Mn plaque were mainly different in the tiller stage. Elemental S treatment could more greatly promote the formation of Fe-Mn plaque of rice root than gypsum treatment. Concentrations of As adsorbed by rice roots surface plaque were 583-719 mg.kg-' in tiller stage, 466-621 mg.kg-1 in boot stage, and 310-384 mg kg-1 in flower and matur stage. And it was consistent with the thickness of Fe-Mn plaque on rice root surface. Concentrations of As uptake in roots and stem and leaf and grain were significantly reduced by the application of S fertilizer, and it may be related to the amount of As adsorbed by Fe-Mn plaque at boot stage. According to chemical speciation of soil arsenic, As of non-specific and specific adsorption was most active, and their amounts of As adsorbed in AsS, treatment were significantly lower by 2.85 mg kg-~' than that in AsS2 treatment in tiller stage, and was 0.77 mg.kg- higher than that in AsS2 treatment in the flower stage. Perhaps soil arsenic was easily dissolved in the soil solution and the bioavailability of AsS, treatment was better than that of AsS, treatment.

Manganese in the shell of the bivalve Mytilus edulis: Seawater Mn or physiological control?

NASA Astrophysics Data System (ADS)

Freitas, Pedro S.; Clarke, Leon J.; Kennedy, Hilary; Richardson, Christopher A.

2016-12-01

Manganese in the shell calcite of marine bivalves has been suggested to reflect ambient seawater Mn concentrations, thus providing a high-resolution archive of past seawater Mn concentrations. However, a quantitative relationship between seawater Mn and shell Mn/Ca ratios, as well as clear understanding of which process(es) control(s) shell Mn/Ca, are still lacking. Blue mussels, Mytilus edulis, were grown in a one-year duration field experiment in the Menai Strait, U.K., to study the relationship between seawater particulate and dissolved Mn2+ concentrations and shell calcite Mn/Ca ratios. Shell Mn/Ca showed a well-defined intra-annual double-peak, with maximum values during early spring and early summer and low values during autumn and winter. Seawater particulate Mn peaked during winter and autumn, with a series of smaller peaks during spring and summer, whereas dissolved Mn2+ exhibited a marked single maximum during late-spring to early-summer, being low during the remainder of the year. Consequently, neither seawater particulate Mn nor dissolved Mn2+ concentrations explain the intra-annual variation of shell Mn/Ca ratios. A physiological control on shell Mn/Ca ratios is evident from the strong similarity and timing of the double-peaked intra-annual variations of Mn/Ca and shell growth rate (SGR), the latter corresponding to periods of increased metabolic activity (as indicated by respiration rate). It is thus likely that in M. edulis SGR influences shell Mn/Ca by altering the concentration or activity of Mn2+ within the extra-pallial fluid (EPF), by changing the flux of Mn into or the proportion of protein bound Mn within the EPF. By linking shell Mn/Ca ratios to the endogenous and environmental factors that determine growth and metabolic activity, this study helps to explain the lack of a consistent relationship between shell Mn/Ca in marine bivalve shell calcite and seawater particulate and dissolved Mn2+ concentrations. The use of Mn content from M. edulis shell calcite as a proxy for the dissolved and/or particulate Mn concentrations, and thus the biogeochemical processes that control them, remains elusive.

High pressure structural investigation on alluaudites Na{sub 2}Fe{sub 3}(PO{sub 4}){sub 3}-Na{sub 2}FeMn{sub 2}(PO{sub 4}){sub 3} system

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

Gao, Jing; Huang, Weifeng; Qin, Shan

Alluaudites are promising electrochemical materials benefited from the open structure. Structural variations of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) system have been studied by synchrotron radiation X-ray diffraction combined with diamond anvil cell technique up to ~10 GPa at room temperature. No phase transition is observed. The excellent structural stability is mainly due to the flexible framework plus strong covalent P-O bond. Mn{sup 2+} instead of Fe can be described as Na{sup +}+2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy. The replacement of Fe with larger Mn{sup 2+} is equivalentmore » to applying negative chemical pressure to the material. And it causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe. External pressure effect produces anisotropic lattice shrinkage. Structural considerations related to these variations and promising application prospects are discussed. - Graphical abstract: Figure 1 The crystal structure of alluaudites Na{sub 2}M{sub 3}(PO{sub 4}){sub 3} (M{sub 3}=Fe{sub 3}, Fe{sub 2}Mn and FeMn{sub 2}) projected along the c-axis. Alluaudites adopt a flexible framework plus strong covalent P-O bond, which contribute to excellent structural stability up to ~10 GPa. Mn{sup 2+} instead of Fe can be described as Na{sup ++}2Fe{sup 2+}→Mn{sup 2+}+Fe{sup 3+}+□ where □ represents a lattice vacancy, and it is equivalent to applying negative chemical pressure to the host. The substitution causes a more compressible b-axis, lattice expansion, structural compressibility and intensifies the core/electron-electron interactions of Fe.« less

New understanding on separation of Mn and Fe from ferruginous manganese ores by the magnetic reduction roasting process

NASA Astrophysics Data System (ADS)

Liu, Bingbing; Zhang, Yuanbo; Wang, Juan; Wang, Jia; Su, Zijian; Li, Guanghui; Jiang, Tao

2018-06-01

Magnetic reduction roasting followed by magnetic separation process is reported as a simple route to realize separation of Mn and Fe from ferruginous manganese ores (Fe-Mn ores). However, the separation and recovery of Mn and Fe oxides are not very effective. This work clarified the underlying reason for the poor separation and also proposed some suggestions for the magnetic reduction process. In this work, the effect of temperature on the magnetic reduction roasting - magnetic separation of Fe-Mn ore was investigated firstly. Then the reduction behaviors of MnO2-Fe2O3 system and MnO2-Fe2O3-10 wt.%SiO2 system under 10 vol.% CO-90 vol.% CO2 at 600-1000 °C were investigated by XRD, XPS, SEM-EDS, VSM, DSC and thermodynamics analyses. Reduction and separation tests showed that higher reduction temperature was beneficial to the recovery of iron while it's not in favor of the recovery of manganese when the temperature was over 800 °C. The formation of composite oxide MnxFe3-xO4 with strong magnetism between the interface of the MnO2 and Fe2O3 particles leaded to the poor separation of iron and manganese. In addition, the formation mechanism of MnxFe3-xO4 from MnO2 and Fe2O3 as well as the interface reaction reduced under 10 vol.% CO was discussed in this study. Finally, some suggestions were recommended for the magnetic reduction roasting for utilizing the Fe-Mn ores effectively.

Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

NASA Technical Reports Server (NTRS)

Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

1974-01-01

By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

Uptake of elements from seawater by ferromanganese crusts: Solid-phase associations and seawater speciation

USGS Publications Warehouse

Koschinsky, A.; Hein, J.R.

2003-01-01

Marine Fe-Mn oxyhydroxide crusts form by precipitation of dissolved components from seawater. Three hydrogenetic crust samples (one phosphatized) and two hydrothermal Mn-oxide samples were subjected to a sequential-leaching procedure in order to determine the host phases of 40 elements. Those host-phase associations are discussed with respect to element speciation in seawater. The partitioning of elements between the two major phases, Mn oxide and Fe oxyhydroxide, can in a first-order approximation be explained by a simple sorption model related to the inorganic speciation of the elements in seawater, as has been proposed in earlier models. Free and weakly complexed cations, such as alkali and alkaline earth metals, Mn, Co, Ni, Zn, T1(I), and partly Y, are sorbed preferentially on the negatively charged surface of the MnO2 in hydrogenetic crusts. The driving force is a strong coulombic interaction. All neutral or negatively charged chloro (Cd, Hg, T1), carbonate (Cu, Y, Pb, and U), and hydroxide (Be, Sc, Ti, Fe, Zr, Nb, In, Sn, Sb, Te, Hf, Ta, Bi, Th, and T1(III)) complexes and oxyanions (V, Cr, As, Se, Mo, and W) bind to the slightly positively charged surface of the amorphous FeOOH phase. While coulombic interaction can explain the sorption of the negatively charged species, the binding of neutral species is based on specific chemical interaction. Organic complexation of elements in deep-ocean water seems to be at most of minor importance. Surface oxidation can explain some strong metal associations, e.g. of Co and T1 with the MnO2 and Te with the FeOOH. Sorption reactions initially driven by coulombic forces are often followed by the formation of specific bonds between the adsorbate and the atoms of the oxide surface. Differences in the associations of some metals between the non-phosphatized and phosphatized hydrogenetic crusts and between the hydrogenetic and the hydrothermal samples reflect the different physico-chemical environments of formation and speciations in oxic seawater vs. less-oxic fluids, especially for the redox-sensitive metals such as Mo and V. These environmental-related differences indicate that the methodology of chemical speciation used here in combination with spectroscopic methods may allow for the detection of changes in paleoceanographic conditions recorded during the several tens of millions of years of crust growth. ?? 2003 Elsevier Science B.V. All rights reserved.

Sequestration of Tellurium From Seawater by Ferromanganese Crusts: A XANES/EXAFS Perspective

NASA Astrophysics Data System (ADS)

Hein, J. R.; Bargar, J.; Koschinsky, A.; Dunham, R.; Halliday, A. N.

2007-12-01

Marine iron-oxyhydroxide/manganese-oxide crusts (Fe-Mn crusts) provide the richest known source of tellurium (Te). Te averages about 50 ppm in Fe-Mn crusts distributed globally, with concentrations locally up to 210 ppm. The sorption of Te onto Fe-Mn crusts likely controls the dominant redox species and concentration of Te in the global ocean (Hein et al., 2003). However, little is known about the mechanisms by which Te is sequestered by Fe-Mn crusts and Fe-Mn colloids in the water column, and then stabilized in the Fe/Mn oxyhydroxide/oxide framework. Two primary hypotheses are being tested: (a) Te(IV) is initially the predominant adsorbed species, which is subsequently oxidized on the Fe-oxyhydroxide and/or Mn oxide phases in natural systems and in sorption experiments. (b) Once oxidized, Te(VI) remains tightly bound to the Fe phase in Fe-Mn crusts as adsorbed surface complexes. These hypotheses are being examined by using the Stanford Synchrotron Radiation Laboratory's (SSRL) synchrotron-based XANES (x-ray absorption near-edge structure) spectroscopy to assess Te oxidation state in natural samples and samples in which Te(IV) and Te(VI) were sorbed onto synthetic and natural FeOOH and Mn oxides. EXAFS (extended x-ray absorption fine structure) spectroscopy is being used to resolve the local molecular-scale structure around Te in these same samples. Data have thus far been obtained for six Fe-Mn crusts from a variety of geographic locations and water depths of occurrence, with differing chemical compositions; and two model compounds, Te(IV) sorbed on FeOOH and Te(IV) sorbed on MnO2. XANES data show that for all six Fe-Mn crust samples, 85 to 100 percent of the Te occurs as Te(VI). For the model compounds, about 65 percent of the Te(IV) sorbed onto the MnO2 had oxidized to Te(VI) by the time (one week) the sample was analyzed, whereas Te sorbed onto FeOOH remained at about 100 percent Te(IV). The most striking result from the EXAFS data is that all spectra for the six Fe-Mn crust samples are virtually identical, regardless of location, depositional conditions, or chemical and mineralogical compositions. This uniformity indicates that the local structure around Te is similar for all samples and, therefore, the mode of incorporation of Te into the Fe-Mn crusts does not vary despite varying environments of formation. This implies that a single set of processes applies throughout the global ocean to the incorporation of Te into Fe-Mn crusts. Hein, J.R., Koschinsky, A., and Halliday, A.N., 2003, Geochim. Cosmochim. Acta 67: 1117-1127.

Heavy metals content in acid mine drainage at abandoned and active mining area

NASA Astrophysics Data System (ADS)

Hatar, Hazirah; Rahim, Sahibin Abd; Razi, Wan Mohd; Sahrani, Fathul Karim

2013-11-01

This study was conducted at former Barite Mine, Tasik Chini and former iron mine Sungai Lembing in Pahang, and also active gold mine at Lubuk Mandi, Terengganu. This study was conducted to determine heavy metals content in acid mine drainage (AMD) at the study areas. Fourteen water sampling stations within the study area were chosen for this purpose. In situ water characteristic determinations were carried out for pH, electrical conductivity (EC), redox potential (ORP) and total dissolved solid (TDS) using multi parameter YSI 556. Water samples were collected and analysed in the laboratory for sulfate, total acidity and heavy metals which follow the standard methods of APHA (1999) and HACH (2003). Heavy metals in the water samples were determined directly using Inductive Coupled Plasma Mass Spectrometry (ICP-MS). Data obtained showed a highly acidic mean of pH values with pH ranged from 2.6 ± 0.3 to 3.2 ± 0.2. Mean of electrical conductivity ranged from 0.57 ± 0.25 to 1.01 ± 0.70 mS/cm. Redox potential mean ranged from 487.40 ± 13.68 to 579.9 ± 80.46 mV. Mean of total dissolved solids (TDS) in AMD ranged from 306.50 ± 125.16 to 608.14 ± 411.64 mg/L. Mean of sulfate concentration in AMD ranged from 32.33 ± 1.41 to 207.08 ± 85.06 mg/L, whereas the mean of total acidity ranged from 69.17 ± 5.89 to 205.12 ± 170.83 mgCaCO3/L. Heavy metals content in AMD is dominated by Fe, Cu, Mn and Zn with mean concentrations range from 2.16 ± 1.61 to 36.31 ± 41.02 mg/L, 0.17 ± 0.13 to 11.06 ± 2.85 mg/L, 1.12 ± 0.65 to 7.17 ± 6.05 mg/L and 0.62 ± 0.21 to 6.56 ± 4.11 mg/L, respectively. Mean concentrations of Ni, Co, As, Cd and Pb were less than 0.21, 0.51, 0.24, 0.05 and 0.45 mg/L, respectively. Significant correlation occurred between Fe and Mn, Cu, Zn, Co and Cd. Water pH correlated negatively with all the heavy metals, whereas total acidity, sulfate, total dissolved solid, and redox potential correlated positively. The concentration of heavy metals in the AMD appeared to be influenced by acidity and the formation of Fe, Mn oxide and hydroxide.

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.

Fabrication of Mg-X-O (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn) barriers for magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Yakushiji, K.; Kitagawa, E.; Ochiai, T.; Kubota, H.; Shimomura, N.; Ito, J.; Yoda, H.; Yuasa, S.

2018-05-01

We fabricated magnetic tunnel junctions with a 3d-transition material(X)-doped MgO (Mg-X-O) barrier, and evaluated the effect of the doping on magnetoresistance (MR) and microstructure. Among the variations of X (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn), X = Fe and Mn showed a high MR ratio of more than 100%, even at a low resistance-area product of 3 Ωμm2. The microstructure analysis revealed that (001) textured orientation formed for X = Fe and Mn despite substantial doping (about 10 at%). The elemental mappings indicated that Fe atoms in the Mg-Fe-O barrier were segregated at the interfaces, while Mn atoms were evenly involved in the Mg-Mn-O barrier. This suggests that MgO has high adaptability for Fe and Mn dopants in terms of high MR ratio.

A Multi-Pumping Flow System for In Situ Measurements of Dissolved Manganese in Aquatic Systems

PubMed Central

Meyer, David; Prien, Ralf D.; Dellwig, Olaf; Waniek, Joanna J.; Schuffenhauer, Ingo; Donath, Jan; Krüger, Siegfried; Pallentin, Malte; Schulz-Bull, Detlef E.

2016-01-01

A METals In Situ analyzer (METIS) has been used to determine dissolved manganese (II) concentrations in the subhalocline waters of the Gotland Deep (central Baltic Sea). High-resolution in situ measurements of total dissolved Mn were obtained in near real-time by spectrophotometry using 1-(2-pyridylazo)-2-naphthol (PAN). PAN is a complexing agent of dissolved Mn and forms a wine-red complex with a maximum absorbance at a wavelength of 562 nm. Results are presented together with ancillary temperature, salinity, and dissolved O2 data. Lab calibration of the analyzer was performed in a pressure testing tank. A detection limit of 77 nM was obtained. For validation purposes, discrete water samples were taken by using a pump-CTD system. Dissolved Mn in these samples was determined by an independent laboratory based method (inductively coupled plasma–optical emission spectrometry, ICP-OES). Mn measurements from both METIS and ICP-OES analysis were in good agreement. The results showed that the in situ analysis of dissolved Mn is a powerful technique reducing dependencies on heavy and expensive equipment (pump-CTD system, ICP-OES) and is also cost and time effective. PMID:27916898

Effects of Exogenous Gibberellic Acid3 on Iron and Manganese Plaque Amounts and Iron and Manganese Uptake in Rice

PubMed Central

Guo, Yue; Zhu, Changhua; Gan, Lijun; Ng, Denny; Xia, Kai

2015-01-01

Gibberellins (GA) regulate various components of plant development. Iron and Mn plaque result from oxiding and hydroxiding Fe and Mn, respectively, on the roots of aquatic plant species such as rice (Oryza sativa L.). In this study, we found that exogenous gibberellic acid3 (GA3) spray decreased Fe plaque, but increased Mn plaque, with applications of Kimura B nutrient solution. Similar effects from GA3, leading to reduced Fe plaque and increased Mn plaque, were also found by scanning electron microscopy and energy dispersive X-ray spectrometric microanalysis. Reduced Fe plaque was observed after applying GA3 to the groups containing added Fe2+ (17 and 42 mg•L-1) and an increasing trend was detected in Mn plaques of the Mn2+ (34 and 84 mg•L-1) added treatments. In contrast, an inhibitor of GA3, uniconazole, reversed the effects of GA3. The uptake of Fe or Mn in rice plants was enhanced after GA3 application and Fe or Mn plaque production. Strong synergetic effects of GA3 application on Fe plaque production were detected. However, no synergetic effects on Mn plaque production were detected. PMID:25710173

Structural, magnetic and dielectric properties of polyaniline/MnCoFe2O4 nanocomposites

NASA Astrophysics Data System (ADS)

Chitra, Palanisamy; Muthusamy, Athianna; Jayaprakash, Rajan

2015-12-01

Ferromagnetic PANI containing MnCoFe2O4 nanocomposites were synthesized by in-situ chemical polymerization of aniline incorporated MnCoFe2O4 nanoparticles (20%, 10% w/w of fine powders) with and without ultrasonic treatment. The MnCoFe2O4 nanoparticles were synthesized by auto combustion method. The PANI/MnCoFe2O4 nanocomposites were characterized with Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The average particle size of the resulting PANI/MnCoFe2O4 nanocomposites was confirmed from the TEM and XRD analysis. The structure and morphology of the composites were confirmed by FT-IR spectroscopy, XRD and SEM. In addition, the electrical and magnetic properties of the nanocomposites were investigated. The PANI/MnCoFe2O4 nanocomposites under applied magnetic field exhibited the hysteresis loops of ferromagnetic nature at room temperature. The variation of Dielectric constant, Dielectric loss, and AC conductivity of PANI/MnCoFe2O4 nanocomposites at room temperature as a function of frequency in the range 50 Hz-5 MHz has been studied. Effect of ultrasonication on the PANI/MnCoFe2O4 nanocomposites was also investigated.

The photochemistry of manganese and the origin of banded iron formations

NASA Technical Reports Server (NTRS)

Anbar, A. D.; Holland, H. D.

1992-01-01

The origin of the deposition of superior-type Precambrian banded iron formations (BIFs) is investigated in experiments where the effect of UV radiation on dissolved manganese was studied to determine if the commonly accepted photochemical model for BIF formation is consistent with the distribution of Mn in BIFs. Solutions containing 0.56 M NaCl and about 180 microM MnCl2, with or without 3 to 200 microM FeCl2 were irradiated with filtered and unfiltered UV light for up to 8 hrs; the solutions were deaerated and buffered to a pH of 7, and the experiments were conducted under oxygen-free atmosphere. Data on the rate of manganese photooxidation confirmed that a photochemical model for the origin of oxide facies BIFs is consistent with field observations.

Characterization of iron, manganese, and copper synthetic hydroxyapatites by electron paramagnetic resonance spectroscopy

NASA Technical Reports Server (NTRS)

Sutter, B.; Wasowicz, T.; Howard, T.; Hossner, L. R.; Ming, D. W.

2002-01-01

The incorporation of micronutrients (e.g., Fe, Mn, Cu) into synthetic hydroxyapatite (SHA) is proposed for slow release of these nutrients to crops in NASA's Advanced Life Support (ALS) program for long-duration space missions. Separate Fe3+ (Fe-SHA), Mn2+ (Mn-SHA), and Cu2+ (Cu-SHA) containing SHA materials were synthesized by a precipitation method. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the location of Fe3+, Mn2+, and Cu2+ ions in the SHA structure and to identify other Fe(3+)-, Mn(2+)-, and Cu(2+)-containing phases that formed during precipitation. The EPR parameters for Fe3+ (g=4.20 and 8.93) and for Mn2+ (g=2.01, A=9.4 mT, D=39.0 mT and E=10.5 mT) indicated that Fe3+ and Mn2+ possessed rhombic ion crystal fields within the SHA structure. The Cu2+ EPR parameters (g(z)=2.488, A(z)=5.2 mT) indicated that Cu2+ was coordinated to more than six oxygens. The rhombic environments of Fe3+ and Mn2+ along with the unique Cu2+ environment suggested that these metals substituted for the 7 or 9 coordinate Ca2+ in SHA. The EPR analyses also detected poorly crystalline metal oxyhydroxides or metal-phosphates associated with SHA. The Fe-, Mn-, and Cu-SHA materials are potential slow release sources of Fe, Mn, and Cu for ALS and terrestrial cropping systems.

Effect of chitosan coating on the structural and magnetic properties of MnFe2O4 and Mn0.5Co0.5Fe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Mdlalose, W. B.; Mokhosi, S. R.; Dlamini, S.; Moyo, T.; Singh, M.

2018-05-01

We report the influence of polymer coatings on structural and magnetic properties of MnFe2O4 and Mn0.5Co0.5Fe2O4 nanoferrites synthesized by glycol thermal technique and then coated with chitosan viz. CHI-MnFe2O4 and CHI-Mn0.5Co0.5Fe2O4. The compounds were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), high-resolution scanning electron microscopy (HRSEM), Mössbauer spectroscopy and magnetization measurements. The powder XRD patterns of naked nanoferrites confirmed single-phase spinel cubic structure with an average crystallite size of 13 nm, while the coated samples exhibited an average particle size of 15 nm. We observed a reduction in lattice parameters with coating. HRTEM results correlated well with XRD results. 57Fe Mössbauer spectra showed ordered magnetic spin states in both nanoferrites. This study shows that coatings have significant effects on the structural and magnetic properties of Mn-nanoferrites. Magnetization studies performed at room temperature in fields up to 14 kOe revealed the superparamagnetic nature of both naked and coated nanoparticles with spontaneous magnetizations at room temperature of 49.2 emu/g for MnFe2O4, 23.6 emu/g for coated CHI-MnFe2O4 nanoparticles, 63.2 emu/g for Mn0.5Co0.5Fe2O4 and 33.2 emu/g for coated CHI-Mn0.5Co0.5Fe2O4 nanoparticles. We observed reduction in coercive fields due to coating. Overall, chitosan-coated manganese and manganese-cobalt nanoferrites present as suitable candidates for biomedical applications owing to physicochemical, and magnetic properties exhibited.

Accumulation of Metals in Juvenile Carp (Cyprinus carpio) Exposed to Sublethal Levels of Iron and Manganese: Survival, Body Weight and Tissue.

PubMed

Harangi, Sándor; Baranyai, Edina; Fehér, Milán; Tóth, Csilla Noémi; Herman, Petra; Stündl, László; Fábián, István; Tóthmérész, Béla; Simon, Edina

2017-05-01

Many oxbows are contaminated by Fe and Mn as a consequence of the elemental concentration of sediment and water originating from the Upper Tisza Region of Hungary. The phenomenon is partly caused by anthropogenic activities and mainly due to the geochemical characteristics of the region. The effects of Fe and Mn on the aquatic ecosystem of these wetlands were investigated in a model experiments in this study. Survival, individual body weight and the elemental concentrations of organs were determined in common carp (Cyprinus carpio) juveniles reared in Fe and Mn contaminated media (treatment 1: Fe 0.57 mg L -1 , Mn 0.29 mg L -1 , treatment 2: Fe 0.57 mg L -1 , Mn 0.625 mg L -1 , treatment 3: Fe 1.50 mg L -1 , Mn 0.29 mg L -1 , treatment 4: Fe 1.50 mg L -1 , Mn 0.625 mg L -1 and control: Fe 0.005 mg L -1 , Mn 0.003 mg L -1 ), for rearing time of 49 days. The treatment with Fe and Mn did not have any effect on the survival data and individual body weight in the levels tested. The highest concentration of Fe and Mn was found in the liver and brain of carp juveniles, while the lowest concentration of these elements occurred in the muscular tissue and gills. The treatment where Fe and Mn were applied in the highest concentrations resulted in a statistically higher level of these elements in the brain, grills and muscle tissues. The treatment where only Mn was present in the highest concentration caused increased level of Mn only in the liver. We found metal accumulation in almost every organ; however, the applied concentrations and exposure time did not affect the survival and average body weight of carp juveniles.

Trace-element evidence for the origin of desert varnish by direct aqueous atmospheric deposition

NASA Astrophysics Data System (ADS)

Thiagarajan, Nivedita; Aeolus Lee, Cin-Ty

2004-07-01

Smooth rock surfaces in arid environments are often covered with a thin coating of Fe-Mn oxyhydroxides known as desert varnish. It is debated whether such varnish is formed (a) by slow diagenesis of dust particles deposited on rock surfaces, (b) by leaching from the underlying rock substrate, or (c) by direct deposition of dissolved constituents in the atmosphere. Varnishes collected from smooth rock surfaces in the Mojave Desert and Death Valley, California are shown here to have highly enriched and fractionated trace-element abundances relative to upper continental crust (UCC). They are highly enriched in Co, Ni, Pb and the rare-earth elements (REEs). In particular, they have anomalously high Ce/La and low Y/Ho ratios. These features can only be explained by preferential scavenging of Co, Ni, Pb and the REEs by Fe-Mn oxyhydroxides in an aqueous environment. High field strength elements (HFSEs: Zr, Hf, Ta, Nb, Th), however, show only small enrichments despite the fact that these elements should also be strongly scavenged by Fe-Mn oxyhydroxides. This suggests that their lack of enrichment is a feature inherited from a solution initially poor in HFSEs. The first two scenarios for varnish formation can be ruled out as follows. The high enrichment factors of Fe, Mn and many trace elements cannot be generated by mass loss associated with post-depositional diagenesis of dust particles because such a process predicts only a small increase in concentration. In addition, the highly fractionated abundance patterns of particle reactive element pairs (e.g., Ce/La and Y/Ho) rules out leaching of the rock substrate. This is because if leaching were to occur, varnishes would grow from the inside to the outside, and thus any particle-reactive trace element leached from the substrate would be quantitatively sequestered in the Fe-Mn oxyhydroxide layers, prohibiting any significant elemental fractionations. One remaining possibility is that the Fe, Mn and trace metals in varnish are derived from leaching of dust particles entrained in rain or fog droplets either in the atmosphere or during wet atmospheric deposition. The high trace metal enrichment factors require that most of the dust was physically removed before or during varnish formation. The remaining aqueous counterpart would be depleted in HFSEs and Th relative to the REEs, Co, Ni and Pb because the former are more insoluble and hence largely retained in the removed dust fraction. The high Ce/La ratios suggest that precipitation of trace metals may have been governed by equilibrium partitioning in an excess of wet atmospheric deposition. If varnishes are indeed derived from wet atmospheric deposition, they may provide a record of the aqueous component of atmospheric dust inputs to various environments.

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.

Laser photoelectron spectroscopy of MnH - and FeH - : Electronic structures of the metal hydrides, identification of a low-spin excited state of MnH, and evidence for a low-spin ground state of FeH

NASA Astrophysics Data System (ADS)

Stevens, Amy E.; Feigerle, C. S.; Lineberger, W. C.

1983-05-01

The laser photoelectron spectra of MnH- and MnD-, and FeH- and FeD- are reported. A qualitative description of the electronic structure of the low-spin and high-spin states of the metal hydrides is developed, and used to interpret the spectra. A diagonal transition in the photodetachment to the known high-spin, 7Σ+, ground state of MnH is observed. An intense off-diagonal transition to a state of MnH, at 1725±50 cm-1 excitation energy, is attributed to loss of an antibonding electron from MnH-, to yield a low-spin quintet state of MnH. For FeH- the photodetachment to the ground state is an off-diagonal transition, attributed to loss of the antibonding electron from FeH-, to yield a low-spin quartet ground state of FeH. A diagonal transition results in an FeH state at 1945±55 cm-1; this state of FeH is assigned as the lowest-lying high-spin sextet state of FeH. An additional excited state of MnH and two other excited states of FeH are observed. Excitation energies for all the states are reported; vibrational frequencies and bond lengths for the ions and several states of the neutrals are also determined from the spectra. The electron affinity of MnH is found to be 0.869±0.010 eV; and the electron affinity of FeH is determined to be 0.934±0.011 eV. Spectroscopic constants for the various deuterides are also reported.

Microbial reduction of manganese oxides - Interactions with iron and sulfur

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

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.

Efficient catalytic As(III) oxidation on the surface of ferrihydrite in the presence of aqueous Mn(II).

PubMed

Lan, Shuai; Ying, Hong; Wang, Xiaoming; Liu, Fan; Tan, Wenfeng; Huang, Qiaoyun; Zhang, Jing; Feng, Xionghan

2018-01-01

Arsenic is a carcinogenic element that exists primarily as arsenate [As(V)] and arsenite [As(III)] in the nature environment, with As(III) being more toxic and mobile of the two species. In addition, ferrihydrite, which is widely distributed in soils and aquatic environments, can catalyze the oxidation of Mn(II) and accelerate the formation of high-valence Mn, which can significantly influence the speciation, toxicity, and mobility of As when these species co-exist. In this context, we herein explored the mechanism of As(III) oxidation in the presence of ferrihydrite and Mn(II) using a kinetic approach combined with multiple spectroscopic techniques, including X-ray absorption near edge spectroscopy, in situ horizontal attenuated total-reflectance Fourier transform infrared spectroscopy, and in situ quick scanning X-ray absorption spectroscopy. Our results indicate that efficient As(III) oxidation by dissolved O 2 occurs on the surface of ferrihydrite in the presence of aqueous Mn(II). Compared with As(III) oxidation in the presence of ferrihydrite and Mn oxides (i.e., Mn oxides/hydroxides), the degree of As(III) oxidation in the ferrihydrite-Mn(II) system was significantly higher, and the majority of generated As(V) was adsorbed on the mineral (i.e., ferrihydrite) surface. Furthermore, As(III) oxidation was enhanced upon increasing both the molar ratio of Mn(II)/As(III) and the solution pH. The greater As(III) oxidation by O 2 in the ferrihydrite-Mn(II) system was mainly attributed to the formation of a strong oxidant of the instantaneous intermediate Mn(III) species via Mn(II) oxidation under catalysis by the ferrihydrite surface. Moreover, As(III) oxidation occurred mainly on the ferrihydrite surface and was accompanied by the regeneration of Mn(II), thereby rendering it recyclable. These results therefore provide new insights into the mechanism of As(III) oxidation on the surfaces of Fe oxides (i.e., Fe oxides/hydroxides) in the presence of aqueous Mn(II) as well as the new details regarding the electron transfer mechanisms between the As(III)-Mn(II, III)-O 2 species at the ferrihydrite surface, and could lead to novel approaches for As(III) contaminant remediation in the environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Increased concentrations of potassium in heartwood of trees in response to groundwater contamination

NASA Astrophysics Data System (ADS)

Vroblesky, Don A.; Yanosky, Thomas M.; Siegel, Frederic R.

1992-03-01

The wood of tuliptrees ( Liriodendron tulipifera L.) growing above groundwater contamination from a hazardous-waste landfill in Maryland contained elevated concentrations of potassium (K). The groundwater contamination also contained elevated concentrations of dissolved K, as well as arsenic (As), cadmium (Cd), chloride (Cl), iron (Fe), manganese (Mn), zinc (Zn), and organic solvents. The dissolved K is derived from disposed smoke munitions. The excess K in the tuliptrees is concentrated in the heartwood, the part of the xylem most depleted in K in trees growing outside of the contamination. These data show that the uptake and translocation of K by tuliptrees can be strongly influenced by the availability of K in groundwater contamination and suggest the utility of this species as an areal indicator of groundwater contamination.

Global occurrence of tellurium-rich ferromanganese crusts and a model for the enrichment of tellurium

USGS Publications Warehouse

Hein, J.R.; Koschinsky, A.; Halliday, A.N.

2003-01-01

Hydrogenetic ferromanganese oxyhydroxide crusts (Fe-Mn crusts) precipitate out of cold ambient ocean water onto hard-rock surfaces (seamounts, plateaus, ridges) at water depths of about 400 to 4000 m throughout the ocean basins. The slow-growing (mm/Ma) Fe-Mn crusts concentrate most elements above their mean concentration in the Earth's crust. Tellurium is enriched more than any other element (up to about 50,000 times) relative to its Earth's crustal mean of about 1 ppb, compared with 250 times for the next most enriched element. We analyzed the Te contents for a suite of 105 bulk hydrogenetic crusts and 140 individual crust layers from the global ocean. For comparison, we analyzed 10 hydrothermal stratabound Mn-oxide samples collected from a variety of tectonic environments in the Pacific. In the Fe-Mn crust samples, Te varies from 3 to 205 ppm, with mean contents for Pacific and Atlantic samples of about 50 ppm and a mean of 39 ppm for Indian crust samples. Hydrothermal Mn samples have Te contents that range from 0.06 to 1 ppm. Continental margin Fe-Mn crusts have lower Te contents than open-ocean crusts, which is the result of dilution by detrital phases and differences in growth rates of the hydrogenetic phases. Correlation coefficient matrices show that for hydrothermal deposits, Te has positive correlations with elements characteristic of detrital minerals. In contrast, Te in open-ocean Fe-Mn crusts usually correlates with elements characteristic of the MnO2, carbonate fluorapatite, and residual biogenic phases. In continental margin crusts, Te also correlates with FeOOH associated elements. In addition, Te is negatively correlated with water depth of occurrence and positively correlated with crust thickness. Q-mode factor analyses support these relationships. However, sequential leaching results show that most of the Te is associated with FeOOH in Fe-Mn crusts and ???10% is leached with the MnO2. Thermodynamic calculations indicate that Te occurs predominantly as H5TeO6- in ocean water. The speciation of Te in ocean water and charge balance considerations indicate that Te should be scavenged by FeOOH, which is in agreement with our leaching results. The thermodynamically more stable Te(IV) is less abundant by factors of 2 to 3.5 than Te(VI) in ocean water. This can be explained by preferential (not exclusive) scavenging of Te(IV) by FeOOH at the Fe-Mn crust surface and by Fe-Mn colloids in the water column. We propose a model in which the extreme enrichment of Te in Fe-Mn crusts is likely the result of an oxidation reaction on the surface of FeOOH. A similar oxidation process has been confirmed for Co, Ce, and Tl at the surface of MnO2 in crusts, but has not been suggested previously to occur in association with FeOOH in Fe-Mn crusts. Mass-balance considerations indicate that ocean floor Fe-Mn deposits are the major sink for Te in the oceans. The concentration and redox chemistry of Te in the global ocean are likely controlled by scavenging on Fe-Mn colloids in the water column and Fe-Mn deposits on the ocean floor, as is also the case for Ce. ?? 2003 Elsevier Science Ltd.

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.

Persistence of deeply sourced iron in the Pacific Ocean.

PubMed

Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

2015-02-03

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

238U-234U-230Th disequilibrium in hydrogenous oceanic Fe-Mn crusts: Palaeoceanographic record or diagenetic alteration?

USGS Publications Warehouse

Chabaux, F.; O'Nions, R. K.; Cohen, A.S.; Hein, J.R.

1997-01-01

A detailed TIMS study of (234Uexc/238U), (230Th/232Th), and Th/U ratios have been performed on the outermost margin of ten hydrogenous Fe-Mn crusts from the equatorial Pacific Ocean and west-central Indian Ocean. Th/U concentration ratios generally decrease from the crust's surface down to 0.5-1 mm depth and growth rates estimated by uranium and thorium isotope ratios are significantly different in Fe-Mn crusts from the Peru Basin and the west-central Indian Ocean. Fe-Mn crusts from the same geographical area define a single trend in plots of Ln (234Uexc/238U) vs. Ln(230Th/232Th) and Th/U ratios vs. age of the analysed fractions. Results suggest that (1) hydrogenous Fe-Mn crusts remain closed-systems after formation, and consequently (2) the discrepancy observed between the 230Th and 234U chronometers in Fe-Mn crusts, and the variations of the Th/U ratios through the margin of Fe-Mn crusts, are not due to redistribution of uranium and thorium isotopes after oxyhydroxide precipitation, but rather to temporal variations of both Th/U and initial thorium activity ratios recorded by the Fe-Mn layers. Implications of these observations for determination of Fe-Mn crust growth-rates are discussed. Variations of both Th/U and initial Th activity ratios in Fe-Mn crusts might be related to changes in particle input to seawater and/or changes in ocean circulation during the last 150 ka. Copyright ?? 1997 Elsevier Science Ltd.

Characteristics and origin of rock varnish from the hyperarid coastal deserts of northern Peru

NASA Astrophysics Data System (ADS)

Jones, Charles E.

1991-01-01

The characteristics of a new type of rock varnish from the hyperarid coastal deserts of northern Peru, combined with laboratory experiments on associated soil materials, provide new insights into the formation of rock varnish. The Peruvian varnish consists of an Fe-rich, Mn-poor component covering up to 95% of a varnished surface and a Fe-rich, Mn-rich component found only in pits and along cracks and ridges. The alkaline soils plus the catalytic Fe oxyhydroxides that coat much of the varnish surfaces make the Peruvian situation ideal for physicochemical precipitation of Mn. However, the low Mn content of the dominant Fe-rich, Mn-poor component suggests that such precipitation is minor. This, plus the presence of abundant bacteria in the Mn-rich varnish and the recorded presence of Mn-precipitating bacteria in varnish elsewhere, suggests that bacteria are almost solely responsible for Mn-precipitation in rock varnish. A set of experiments involving Peruvian soil samples in contact with water-CO 2 solutions indicates that natural fogs or dews release Mn but not Fe when they come in contact with eolian materials on rock surfaces. This mechanism may efficiently provide Mn to bacteria on varnishing surfaces. The lack of Fe in solution suggests that a large but unknown proportion of Fe in varnish may be in the form of insoluble Fe oxyhydroxides sorbed onto the clay minerals that form the bulk of rock varnish. The results of this study do not substantively change R. I. Dorn's paleoenvironmental interpretations of varnish Mn:Fe ratios, but they do suggest areas for further inquiry.

Density functional theory study on the structures, electronic and magnetic properties of the MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters

NASA Astrophysics Data System (ADS)

Li, Zhi; Zhao, Zhen; Wang, Qi; Yin, Xi-tao

2018-04-01

The structures, electronic and magnetic properties of the MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters are obtained by using the GGA-PBE functional. The results found that the CoFe3n‑1O4n (n = 1–3) clusters are more stable than the corresponding NiFe3n‑1O4n and MnFe3n‑1O4n clusters. The NiFe2O4, MnFe5O8 and CoFe5O8 clusters have higher kinetic stability than their neighbors. The average magnetic moments of MFe3n‑1O4n (n = 1–3) (M=Mn, Co and Ni) clusters are successively: NiFe3n‑1O4n > CoFe3n‑1O4n > MnFe3n‑1O4n. For NiFe3n‑1O4n and CoFe3n‑1O4n clusters, the average magnetic moments are decreased with the cluster size increasing while for MnFe3n‑1O4n, the opposite situation is occur. The difference of 3d orbital electrons of M (M=Mn, Co and Ni) atoms influence the magnetic properties of MFe3n‑1O4n clusters.

Reduction Behavior of Assmang and Comilog ore in the SiMn Process

NASA Astrophysics Data System (ADS)

Kim, Pyunghwa Peace; Holtan, Joakim; Tangstad, Merete

The reduction behavior of raw materials from Assmang and Comilog based charges were experimentally investigated with CO gas up to 1600 °C. Quartz, HC FeMn slag or limestone were added to Assmang or Comilog according to the SiMn production charge, and mass loss results were obtained by using a TGA furnace. The results showed that particle size, type of manganese ore and mixture have close relationship to the reduction behavior of raw materials during MnO and SiO2 reduction. The influence of particle size to mass loss was apparent when Assmang or Comilog was mixed with only coke (FeMn) while it became insignificant when quartz and HC FeMn slag (SiMn) were added. This implied that quartz and HC FeMn slag had favored the incipient slag formation regardless of particle size. This explained the similar mass loss tendencies of SiMn charge samples between 1200-1500 °C, contrary to FeMn charge samples where different particle sizes showed significant difference in mass loss. Also, while FeMn charge samples showed progressive mass loss, SiMn charge samples showed diminutive mass loss until 1500 °C. However, rapid mass losses were observed with SiMn charge samples in this study above 1500 °C, and they have occurred at different temperatures. This implied rapid reduction of MnO and SiO2 and the type of ore and addition of HC FeMn slag have significant influence determining these temperatures. The temperatures observed for the rapid mass loss were approximately 1503 °C (Quartz and HC FeMn slag addition in Assmang), 1543 °C (Quartz addition in Assmang) and 1580-1587 °C (Quartz and limestone addition in Comilog), respectively. These temperatures also showed indications of possible SiMn production at process temperatures lower than 1550 °C.

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

Yuping, Duan, E-mail: duanyp@dlut.edu.c; Jia, Zhang; Hui, Jing

Fe-doped MnO{sub 2} with a hollow sea urchin-like ball chain shape was first synthesized under a high magnetic field of 10 T. The formation mechanism was investigated and discussed in detail. The synthesized samples were characterized by XRD, SEM, TEM, EMPA, and vector network analysis. By doping MnO{sub 2} with Fe, the relative complex permittivity of MnO{sub 2} and its corresponding loss tangent clearly decreases, but its relative complex permeability and its corresponding loss tangent markedly increases. Moreover, the theoretically calculated values of reflection loss show that with increasing the Fe content, the as-prepared Fe-doped MnO{sub 2} exhibits good microwavemore » absorption capability. -- Graphical Abstract: Fe-doped MnO{sub 2} with a hollow sea urchin-like ball chain shape was first synthesized in a high magnetic field of 10 T via a simple chemical process. Display Omitted Highlights: {yields} Fe-doped MnO{sub 2} with a hollow sea urchin-like ball chain shape was first synthesized. {yields} We investigated formation mechanism and electromagnetic properties of the Fe-doped MnO{sub 2}. {yields} By doping MnO{sub 2} with Fe, the electromagnetic properties are improved obviously.« less

In vitro study on apoptotic cell death by effective magnetic hyperthermia with chitosan-coated MnFe2O4

NASA Astrophysics Data System (ADS)

Oh, Yunok; Lee, Nohyun; Kang, Hyun Wook; Oh, Junghwan

2016-03-01

Magnetic nanoparticles (MNPs) have been widely investigated as a hyperthermic agent for cancer treatment. In this study, thermally responsive Chitosan-coated MnFe2O4 (Chitosan-MnFe2O4) nanoparticles were developed to conduct localized magnetic hyperthermia for cancer treatment. Hydrophobic MnFe2O4 nanoparticles were synthesized via thermal decomposition and modified with 2,3-dimercaptosuccinic acid (DMSA) for further conjugation of chitosan. Chitosan-MnFe2O4 nanoparticles exhibited high magnetization and excellent biocompatibility along with low cell cytotoxicity. During magnetic hyperthermia treatment (MHT) with Chitosan-MnFe2O4 on MDA-MB 231 cancer cells, the targeted therapeutic temperature was achieved by directly controlling the strength of the external AC magnetic fields. In vitro Chitosan-MnFe2O4-assisted MHT at 42 °C led to drastic and irreversible changes in cell morphology and eventual cellular death in association with the induction of apoptosis through heat dissipation from the excited magnetic nanoparticles. Therefore, the Chitosan-MnFe2O4 nanoparticles with high biocompatibility and thermal capability can be an effective nano-mediated agent for MHT on cancer.

Impacts of Modification of Alloying Method on Inclusion Evolution in RH Refining of Silicon Steel.

PubMed

Li, Fangjie; Li, Huigai; Zheng, Shaobo; You, Jinglin; Han, Ke; Zhai, Qijie

2017-10-19

This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH) process of low-carbon silicon steel production. A more economical method, described as "pre-alloying", has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7-4) inclusions nucleate on the surface of pre-existing 3FeO·MnO. Spherical FeO·zMnO (z = 3-5) is further evolved from shelled 3FeO·MnO by diffusion. Because these MnO-FeO inclusions float up into the slag before degassing, the pre-alloying process does not affect the quality of the melt in the end. Both carbon content and inclusion size conform to industry standards.

MnFe2O4 as a gas sensor towards SO2 and NO2 gases

NASA Astrophysics Data System (ADS)

Rathore, Deepshikha; Mitra, Supratim

2016-05-01

The chemical co-precipitation method was used to synthesize MnFe2O4 nanoparticles. Single cubic phase formation of nanoparticles was confirmed by X-ray diffraction technique. The average particle size of MnFe2O4 nanoparticles was found to be 10.7 nm using Scherrer formula. The ultrafine powder of MnFe2O4 nanoparticles was pressed to design pellet of 10 mm diameter and 1mm thickness. Copper electrodes have been deposited on the surface of pellet using silver paste in the form of capacitor. Fabricated gas sensing device of MnFe2O4 nanoparticles was tested towards SO2 and NO2 gases. Cole-Cole plot of MnFe2O4 was investigated with the help of electrochemical workstation. The performance of the sensors including sensitivity, response and recovery time was also determined. It was observed that the MnFe2O4 nanoparticles are more sensible for NO2 gas as compared to SO2 gas.

Impacts of Modification of Alloying Method on Inclusion Evolution in RH Refining of Silicon Steel

PubMed Central

Li, Huigai; Zheng, Shaobo; You, Jinglin; Han, Ke; Zhai, Qijie

2017-01-01

This study explores the effect of introducing additional alloy elements not only in a different order but also at different stages of the Ruhrstahl-Heraeus (RH) process of low-carbon silicon steel production. A more economical method, described as “pre-alloying”, has been introduced. The evolution of MnO-FeO inclusions produced by pre-alloying was investigated. Results show that spherical 3FeO·MnO inclusions form first, then shelled FeO·zMnO (z = 0.7–4) inclusions nucleate on the surface of pre-existing 3FeO·MnO. Spherical FeO·zMnO (z = 3–5) is further evolved from shelled 3FeO·MnO by diffusion. Because these MnO-FeO inclusions float up into the slag before degassing, the pre-alloying process does not affect the quality of the melt in the end. Both carbon content and inclusion size conform to industry standards. PMID:29048379

Dissolution kinetics of iron-, manganese-, and copper-containing synthetic hydroxyapatites

NASA Technical Reports Server (NTRS)

Sutter, B.; Hossner, L. R.; Ming, D. W.

2005-01-01

Micronutrient-substituted synthetic hydroxyapatite (SHA) is being evaluated by the National Aeronautics and Space Administration's (NASA) Advanced Life Support (ALS) Program for crop production on long-duration human missions to the International Space Station or for future Lunar or Martian outposts. The stirred-flow technique was utilized to characterize Ca, P, Fe, Mn, and Cu release characteristics from Fe-, Mn-, and Cu-containing SHA in deionized (DI) water, citric acid, and diethylene-triamine-pentaacetic acid (DTPA). Initially, Ca and P release rates decreased rapidly with time and were controlled by a non-SHA calcium phosphate phase(s) with low Ca/P solution molar ratios (0.91-1.51) relative to solid SHA ratios (1.56-1.64). At later times, Ca/P solution molar ratios (1.47-1.79) were near solid SHA ratios and release rates decreased slowly indicating that SHA controlled Ca and P release. Substituted SHA materials had faster dissolution rates relative to unsubstituted SHA. The initial metal release rate order was Mn >> Cu > Fe which followed metal-oxide/phosphate solubility suggesting that poorly crystalline metal-oxides/phosphates were dominating metal release. Similar metal release rates for all substituted SHA (approximately 0.01 cmol kg-1 min-1) at the end of the DTPA experiment indicated that SHA dissolution was supplying the metals into solution and that poorly crystalline metal-oxide/phosphates were not controlling metal release. Results indicate that non-SHA Ca-phosphate phases and poorly crystalline metal-oxide/phosphates will contribute Ca, P, and metals. After these phases have dissolved, substituted SHA will be the source of Ca, P, and metals for plants.

Persistence of deeply sourced iron in the Pacific Ocean

PubMed Central

Horner, Tristan J.; Williams, Helen M.; Hein, James R.; Saito, Mak A.; Burton, Kevin W.; Halliday, Alex N.; Nielsen, Sune G.

2015-01-01

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe−Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface. PMID:25605900

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

Adsorption of multi-heavy metals Zn and Cu onto surficial sediments: modeling and adsorption capacity analysis.

PubMed

Li, Shanshan; Zhang, Chen; Wang, Meng; Li, Yu

2014-01-01

Improved multiple regression adsorption models (IMRAMs) was developed to estimate the adsorption capacity of the components [Fe oxides (Fe), Mn oxides (Mn), organic materials (OMs), residuals] in surficial sediments for multi-heavy metal Zn and Cu. IMRAM is an improved version over MRAM, which introduces a computer program in the model developing process. As MRAM, Zn(Cu) IMRAM, and Cu(Zn) IMRAM again confirmed that there is significant interaction effects that control the adsorption of compounded Zn and Cu, which was neglected by additional adsorption model. The verification experiment shows that the relative deviation of the IMRAMs is less than 13%. It is revealed by the IMRAMs that Mn, which has the greatest adsorption capability for compounded Zn and Cu (54.889 and 161.180 mg/l, respectively), follows by interference adsorption capacity of Fe/Mn (-1.072 and -24.591 mg/l respectively). Zn and Cu influence each other through different mechanisms. When Zn is the adsorbate, compounded Cu mainly affects the adsorption capacities of Fe/Mn and Fe/Mn/OMs; while when Cu is the adsorbate, compounded Zn mainly exerts its effect on Mn, Fe/Mn, and Mn/OMs. It also shows that the compounded Zn or Cu weakened the interference adsorption of Fe/Mn, and meanwhile, strengthened the interference adsorption of Mn/OMs.

Stable Water Oxidation in Acid Using Manganese-Modified TiO2 Protective Coatings.

PubMed

Siddiqi, Georges; Luo, Zhenya; Xie, Yujun; Pan, Zhenhua; Zhu, Qianhong; Röhr, Jason A; Cha, Judy J; Hu, Shu

2018-06-06

Accomplishing acid-stable water oxidation is a critical matter for achieving both long-lasting water-splitting devices and other fuel-forming electro- and photocatalytic processes. Because water oxidation releases protons into the local electrolytic environment, it becomes increasingly acidic during device operation, which leads to corrosion of the photoactive component and hence loss in device performance and lifetime. In this work, we show that thin films of manganese-modified titania, (Ti,Mn)O x , topped with an iridium catalyst, can be used in a coating stabilization scheme for acid-stable water oxidation. We achieved a device lifetime of more than 100 h in pH = 0 acid. We successfully grew (Ti,Mn)O x coatings with uniform elemental distributions over a wide range of manganese compositions using atomic layer deposition (ALD), and using X-ray photoelectron spectroscopy, we show that (Ti,Mn)O x films grown in this manner give rise to closer-to-valence-band Fermi levels, which can be further tuned with annealing. In contrast to the normally n-type or intrinsic TiO 2 coatings, annealed (Ti,Mn)O x films can make direct charge transfer to a Fe(CN) 6 3-/4- redox couple dissolved in aqueous electrolytes. Using the Fe(CN) 6 3-/4- redox, we further demonstrated anodic charge transfer through the (Ti,Mn)O x films to high work function metals, such as iridium and gold, which is not previously possible with ALD-grown TiO 2 . We correlated changes in the crystallinity (amorphous to rutile TiO 2 ) and oxidation state (2+ to 3+) of the annealed (Ti,Mn)O x films to their hole conductivity and electrochemical stability in acid. Finally, by combining (Ti,Mn)O x coatings with iridium, an acid-stable water-oxidation anode, using acid-sensitive conductive fluorine-doped tin oxides, was achieved.

UV Light-Driven Photodegradation of Methylene Blue by Using Mn0.5Zn0.5Fe2O4/SiO2 Nanocomposites

NASA Astrophysics Data System (ADS)

Indrayana, I. P. T.; Julian, T.; Suharyadi, E.

2018-04-01

The photodegradation activity of nanocomposites for 20 ppm methylene blue solution has been investigated in this work. Nanocomposites Mn0.5Zn0.5Fe2O4/SiO2 have been synthesized using coprecipitation method. The X-ray diffraction (XRD) pattern confirmed the formation of three phases in sample Mn0.5Zn0.5Fe2O4/SiO2 i.e., Mn0.5Zn0.5Fe2O4, Zn(OH)2, and SiO2. The appearance of SiO2 phase showed that the encapsulation process has been carried out. The calculated particles size of Mn0.5Zn0.5Fe2O4/SiO2 is greater than Mn0.5Zn0.5Fe2O4. Bonding analysis via vibrational spectra for Mn0.5Zn0.5Fe2O4/SiO2 confirmed the formation of bonds Me-O-Si stretching (2854.65 cm-1) and Si-O-Si asymmetric stretching (1026.13 cm-1). The optical gap energy of Mn0.5Zn0.5Fe2O4/SiO2 was smaller (2.70 eV) than Mn0.5Zn0.5Fe2O4 (3.04 eV) due to smaller lattice dislocation and microstrain that affect their electronic structure. The Mn0.5Zn0.5Fe2O4/SiO2 showed high photodegradation ability due to smaller optical gap energy and the appearance of SiO2 ligand that can easily attract dye molecules. The Mn0.5Zn0.5Fe2O4/SiO2 also showed high degradation activity even without UV light radiation. The result showed that photodegradation reaction doesn’t follow pseudo-first order kinetics.

Facile preparation of magnetic mesoporous MnFe2O4@SiO2-CTAB composites for Cr(VI) adsorption and reduction.

PubMed

Li, Na; Fu, Fenglian; Lu, Jianwei; Ding, Zecong; Tang, Bing; Pang, Jiabin

2017-01-01

Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe 2 O 4 @SiO 2 -CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area, and vibrating sample magnetometer were used to characterize MnFe 2 O 4 @SiO 2 -CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe 2 O 4 nanoparticles, which ensured the easy separation by an external magnetic field. The performance of MnFe 2 O 4 @SiO 2 -CTAB composites in Cr(VI) removal was far better than that of bare MnFe 2 O 4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe 2 O 4 @SiO 2 -CTAB composites: (1) mesoporous silica shell with abundant CTA + significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe 2 O 4 , followed by Cr(III) immobilized on MnFe 2 O 4 @SiO 2 -CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe 2 O 4 @SiO 2 -CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe 2 O 4 @SiO 2 -CTAB composites exhibited a great potential for the removal of Cr(VI) from water. Copyright © 2016 Elsevier Ltd. All rights reserved.

The effect of Mn and B on the magnetic and structural properties of nanostructured Fe60Al40 alloys produced by mechanical alloying.

PubMed

Rico, M M; Alcázar, G A Pérez; Zamora, L E; González, C; Greneche, J M

2008-06-01

The effect of Mn and B on the magnetic and structural properties of nanostructured samples of the Fe60Al40 system, prepared by mechanical alloying, was studied by 57Fe Mössbauer spectrometry, X-ray diffraction and magnetic measurements. In the case of the Fe(60-x)Mn(x)Al40 system, 24 h milling time is required to achieve the BCC ternary phase. Different magnetic structures are observed according to the temperature and the Mn content for alloys milled during 48 h: ferromagnetic, antiferromagnetic, spin-glass, reentrant spin-glass and superparamagnetic behavior. They result from the bond randomness behaviour induced by the atomic disorder introduced by the MA process and from the competitive interactions of the Fe-Fe ferromagnetic interactions and the Mn-Mn and Fe-Mn antiferromagnetic interactions and finally the presence of Al atoms acting as dilutors. When B is added in the Fe60Al40 alloy and milled for 12 and 24 hours, two crystalline phases were found: a prevailing FeAl BCC phase and a Fe2B phase type. In addition, one observes an additional contribution attributed to grain boundaries which increases when both milling time and boron composition increase. Finally Mn and B were added to samples of the Fe60Al40 system prepared by mechanical alloying during 12 and 24 hours. Mn content was fixed to 10 at.% and B content varied between 0 and 20 at.%, substituting Al. X-ray patterns show two crystalline phases, the ternary FeMnAl BCC phase, and a (Fe,Mn)2B phase type. The relative proportion of the last phase increases when the B content increases, in addition to changes of the grain size and the lattice parameter. Such behavior was observed for both milling periods. On the other hand, the magnetic hyperfine field distributions show that both phases exhibit chemical disorder, and that the contribution attributed to the grain boundaries is less important when the B content increases. Coercive field values of about 10(2) Oe slightly increase with boron content. Comparison with previous results on FeAIB alloys shows that Mn promotes the structural stability of the nanostructured powders.

Transition-Metal Mixing and Redox Potentials in Li x (M 1–y M' y )PO 4 (M, M' = Mn, Fe, Ni) Olivine Materials from First-Principles Calculations

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

Snydacker, David H.; Wolverton, Chris

The performance of olivine cathode materials can be improved using core/shell structures such as LiMnPO 4/LiFePO 4 and LiMnPO 4/LiNiPO 4. We use density functional theory to calculate the energetics, phase stability, and voltages of transition-metal mixing for a series of olivine phosphate materials. For LiMn 1–yFe yPO 4, LiFe 1–yNi yPO 4, and LiMn 1–yNi yPO 4, we find phase-separating tendencies with (mean-field) maximum miscibility gap temperatures of 120, 320, and 760 K respectively. At room temperature, we find that Mn is completely miscible in LiFePO 4, whereas Mn solubility in LiNiPO 4 is just 0.3%. Therefore, we suggestmore » that core/shell LiMnPO 4/LiNiPO 4 particles could be more effective at containing Mn in the particle core and limiting Mn dissolution into the electrolyte relative to LiMnPO 4/LiFePO 4 particles. We calculate shifts in redox potentials for dilute transition metals, M, substituted into Li xM'PO 4 host materials. Unmixed Li xMnPO 4 exhibits a redox potential of 4.0 V, but we find that dilute Mn in a LiNiPO 4 shell exhibits a redox potential of 4.3 V and therefore remains redox inactive at lower cathode potentials. We find that strain plays a large role in the redox potentials of some mixed systems (Li xMn 1–yFe yPO 4) but not others (Li xMn 1–yNi yPO 4).« less

One-pot hydrothermal synthesis, characterization, and electrochemical properties of rGO/MnFe2O4 nanocomposites

NASA Astrophysics Data System (ADS)

Kotutha, Isara; Swatsitang, Ekaphan; Meewassana, Worawat; Maensiri, Santi

2015-06-01

In this work, a simple facile route for preparing an rGO/MnFe2O4 nanocomposite through a one-pot hydrothermal approach was demonstrated. Graphite oxide (GO) was prepared from graphite powder by a modified Hummers method. Fe(NO3)2 • 9H2O and Mn(NO3)2 • H2O were used as the precursors for the preparation of the rGO/MnFe2O4 nanocomposite. The formation of the rGO/MnFe2O4 nanocomposite was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Rama spectroscopy (Raman). The specific surface area of the prepared composite obtained by Brunauer-Emmett-Teller (BET) analysis was lower than that of pure rGO but higher than that of pure MnFe2O4. Consequently, the electrochemical performance was investigated by using a three-electrode cell system in 6.0 M KOH. The results show that the specific capacitance was determined to be 190.3, 276.9, and 144.5 F/g at a scan rate of 10 mV/s, and 194.9, 274.6, and 134.4 F/g at a current density of 5.0 A/g for rGO, rGO/(5 mmol) MnFe2O4, and rGO/(10 mmol) MnFe2O4, respectively. These results suggest that the composite of MnFe2O4 nanoparticles on an rGO nanosheet can improve the capacitive behavior of the fabricated electrode, but the electrochemical properties are reduced when the MnFe2O4 concentration ratio is high.

Preparation of a nanosized as(2)o(3)/mn(0.5)zn(0.5)fe(2)o(4) complex and its anti-tumor effect on hepatocellular carcinoma cells.

PubMed

Zhang, Jia; Zhang, Dongsheng

2009-01-01

Manganese-zinc-ferrite nanoparticles (Mn(0.5)Zn(0.5)Fe(2)O(4), MZF-NPs) prepared by an improved co-precipitation method and were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Then thermodynamic testing of various doses of MZF-NPs was performed in vitro. The cytotoxicity of the Mn(0.5)Zn(0.5)Fe(2)O(4) nanoparticles in vitro was tested by the MTT assay. A nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex was made by an impregnation process. The complex's shape, component, envelop rate and release rate of As(2)O(3) were measured by SEM, EDS and atom fluorescence spectrometry, respectively. The therapeutic effect of nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex combined with magnetic fluid hyperthermia (MFH) on human hepatocelluar cells were evaluated in vitro by an MTT assay and flow cytometry. The results indicated that Mn(0.5)Zn(0.5)Fe(2)O(4) and nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex were both prepared successfully. The Mn(0.5)Zn(0.5)Fe(2)O(4) nanoparticles had powerful absorption capabilities in a high-frequency alternating electromagnetic field, and had strong magnetic responsiveness. Moreover, Mn(0.5)Zn(0.5)Fe(2)O(4) didn't show cytotoxicity in vitro. The therapeutic result reveals that the nanosized As(2)O(3)/Mn(0.5)Zn(0.5)Fe(2)O(4) complex can significantly inhibit the growth of hepatoma carcinoma cells.

Dissimilatory Fe(III) and Mn(IV) reduction.

PubMed Central

Lovley, D R

1991-01-01

The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process. PMID:1886521

Two Reactive Zones within Riverbank Aquifers Impact the Accumulation of Arsenic within Permeable Natural Reactive Barrier

NASA Astrophysics Data System (ADS)

Knappett, P.; Myers, K.; Jewell, K.; Berube, M.; Datta, S.; Hossain, A.; Hosain, A.; Lipsi, M.; Ahmed, K. M.

2017-12-01

River stage fluctuations drives river water, rich oxidants, into riverbanks aquifers. When these aquifers are rich in dissolved iron (Fe), iron oxides (FeOOH) precipitate, creating a reactive surface upon which toxic elements such as arsenic (As) may sorb. These Permeable Natural Reactive Barriers (PNRBs) have been studied on the Meghna River. The lack of understanding of what controls their formation and fate could result in dangerous consequences. Pumping of riverbank aquifers for irrigation could re-mobilize toxic concentrations of As into drinking water aquifers. It is important to understand the hydrological, geochemical and biological processes controlling the properties of PNRBs. To this end, monitoring wells and drive-point piezometers were installed orthogonal to the Meghna River in Bangladesh. The dimensions of the shallow aquifer was mapped with Electrical Resistivity Tomography (ERT). The monitoring wells and a river gage were instrumented with pressure transducers to record water level fluctuations. Groundwater flows towards the river for most of the year but reverses under the influence of local irrigation pumping in the late dry season and rapidly rising river stage in the early monsoon. Semi-diurnal tides in the dry season have an amplitude of 80 cm. Declining concentrations of conservative dissolved ions towards the river indicated a zone of dilution from river water extending up to 50 m from the river's dry season edge. Dissolved As was produced as groundwater passed through this dilution zone until the final 20 m where As was abruptly removed from solution. This location coincided with a PNRB with enriched solid-phase Fe and Mn within the upper 3 m of sediment. 16S bacterial community DNA was sequenced from the wells and drive-point piezometers to map the distribution of Fe and As reducers and oxidizers. The richest overall biodiversity was found within the PNRB zone. It contained the most oxidizing and reducing species. This evidence suggests that transient river levels drive mixing between oxidizing and reducing agents in Hyporheic Zones (HZs). When the shallow aquifers are rich in dissolved concentrations of Fe and As, this mixing results in the accumulation of solid-phase Fe and As. This is likely a general process affecting other oxide-forming metals and toxic elements they bind.

FeOOH-loaded MnO2 nano-composite: An efficient emergency material for thallium pollution incident.

PubMed

Chen, Meiqing; Wu, Pingxiao; Yu, Langfeng; Liu, Shuai; Ruan, Bo; Hu, Haihui; Zhu, Nengwu; Lin, Zhang

2017-05-01

A FeOOH-loaded MnO 2 nano-composite was developed as an emergency material for Tl(I) pollution incident. Structural characterizations showed that FeOOH successfully loaded onto MnO 2 , the nanosheet-flower structure and high surface area (191 m 2  g -1 ) of material contributed to the excellent performance for Tl(I) removal. FeOOH-loaded MnO 2 with a Fe/Mn molar ratio of 1:2 exhibited a noticeable enhanced capacity for Tl(I) removal compared to that of pure MnO 2 . The outstanding performance for Tl(I) removal involves in extremely high efficiency (achieved equilibrium and drinking water standard within 4 min) and the large maximum adsorption capacity (450 mg g -1 ). Both the control-experiment and XPS characterization proved that the removal mechanism of Tl(I) on FeOOH-loaded MnO 2 included adsorption and oxidation: the oxidation of MnO 2 played an important role for Tl(I) removal, and the adsorption of FeOOH loaded on MnO 2 enhanced Tl(I) purification at the same time. In-depth purification of Tl(I) had reach drinking water standards (0.1 μg L -1 ) at pH above 7, and there wasn't security risk produced from the dissolution of Mn 2+ and Fe 2+ . Moreover, the as-prepared material could be utilized as a recyclable adsorbent regenerated by using NaOH-NaClO binary solution. Therefore, the synthesized FeOOH-loaded MnO 2 in this study has the potential to be applied as an emergency material for thallium pollution incident. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

First-principles study on the ferrimagnetic half-metallic Mn{sub 2}FeAs alloy

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

Qi, Santao; Zhang, Chuan-Hui, E-mail: zhangch@ustb.edu.cn; Chen, Bao

2015-05-15

Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn{sub 2}FeAs full-Heusler alloy have been investigated in detail. The Hg{sub 2}CuTi-type Mn{sub 2}FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational latticemore » constants. We expect that our calculated results may trigger Mn{sub 2}FeAs applying in the future spintronics field. - Graphical abstract: The d orbitals of Mn and Fe atoms split into multi-degenerated levels which create new bonding and nonbonding states. These exchange splitting shift the Fermi level to origin band gap.▪ - Highlights: • The electronic structure and magnetic properties of Mn{sub 2}FeAs full-Heusler alloy were studied. • A total magnetic moment of 3μ{sub B} was obtained for Mn{sub 2}FeAs alloy, following the SP rule M{sub t}=Z{sub t}−24. • The origin of ferrimagnetism and half-metallic character in Mn{sub 2}FeAs were discussed.« less

Structural and dielectric characteristics of double perovskite La2(NiFe)1/2MnO6

NASA Astrophysics Data System (ADS)

Nasir, Mohd.; Kandasami, Asokan; Sen, Somaditya

2018-05-01

Recently, La2NiMnO6 has drawn significant interest because large magnetic field induced changes in dielectric properties makes this compound a promising material for potential spintronic device applications. In the present study, the structural and dielectric characteristics of sol-gel prepared La2(Ni1/2Fe1/2)MnO6 double perovskite ceramics were evaluated. La2(Ni1/2Fe1/2)MnO6 was crystallized in the monoclinic P21/n structure with ordered Ni2+/Fe2+ and Mn4+ cations. A giant dielectric constant with relaxor-like behavior was observed, which was attributed to the dipolar effects arising from hopping between Ni2+/Fe2+ and Mn4+ ions.

Enhanced magnetic fluid hyperthermia by micellar magnetic nanoclusters composed of Mn(x)Zn(1-x)Fe(2)O(4) nanoparticles for induced tumor cell apoptosis.

PubMed

Qu, Yang; Li, Jianbo; Ren, Jie; Leng, Junzhao; Lin, Chao; Shi, Donglu

2014-10-08

Monodispersed MnxZn1-xFe2O4 magnetic nanoparticles of 8 nm are synthesized and encapsulated in amphiphilic block copolymer for development of the hydrophilic magnetic nanoclusters (MNCs). These MNCs exhibit superparamagnetic characteristics, high specific absorption rate (SAR), large saturation magnetization (Ms), excellent stability, and good biocompatibility. MnFe2O4 and Mn0.6Zn0.4Fe2O4 are selected as optimum compositions for the MNCs (MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC) and employed for magnetic fluid hyperthermia (MFH) in vitro. To ensure biosafety of MFH, the parameters of alternating magnetic field (AMF) and exposure time are optimized with low frequency, f, and strength of applied magnetic field, Happlied. Under optimized conditions, MFH of MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC result in cancer cell death rate up to 90% within 15 min. The pathway of cancer cell death is identified as apoptosis, which occurs in mild hyperthermia near 43 °C. Both MnFe2O4/MNC and Mn0.6Zn0.4Fe2O4/MNC show similar efficiencies on drug-sensitive and drug-resistant cancer cells. On the basis of these findings, those MnxZn1-xFe2O4 nanoclusters can serve as a promising candidate for effective targeting, diagnosis, and therapy of cancers. The multimodal cancer treatment is also possible as amphiphilic block copolymer can encapsulate, in a similar fashion, different nanoparticles, hydrophobic drugs, and other functional molecules.

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

Lin, Xiaomei; Lv, Xin; Wang, Limin

Graphical abstract: - Highlights: • Effect of CTAB on the morphology and crystallization of MnFe{sub 2}O{sub 4}. • The lowest coercivity of MnFe{sub 2}O{sub 4} polyhedron is 11.9 Oe. • MnFe{sub 2}O{sub 4} as anode for LIB shows good reversible capacity and cycle performances. - Abstract: The uniform different morphologies MnFe{sub 2}O{sub 4}, including cube, truncated cube, polyhedron and octahedron, were successfully synthesized via a solvothermal route using cetyltrimethylammonium bromide. The results of control experiments revealed that the concentration of cetyltrimethylammonium bromide was an important factor, which affected the morphology and crystallization of MnFe{sub 2}O{sub 4} submicro-crystals. All the preparedmore » samples exhibited soft-magnetic behavior at room temperature. Especially, the coercivity of MnFe{sub 2}O{sub 4} polyhedron with 200 nm diameter was 11.9 Oe, which was among the lowest values reported so far. Moreover, MnFe{sub 2}O{sub 4} submicro-crystals with special morphologies demonstrated higher reversible capacity (about 1000 mAh g{sup −1}) and different cycle performances. After 50 cycles, polyhedron structure remained 428 mAh/g. The MnFe{sub 2}O{sub 4} would have a potential application as anode material for lithium ion batteries.« less

Distribution and speciation of trace elements in iron and manganese oxide cave deposits

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

Frierdich, Andrew J.; Catalano, Jeffrey G.

2012-10-24

Fe and Mn oxide minerals control the distribution and speciation of heavy metals and trace elements in soils and aquatic systems through chemical mechanisms involving adsorption, incorporation, and electron transfer. The Pautler Cave System in Southwest Illinois, an analog to other temperate carbonate-hosted karst systems, contains Fe and Mn oxide minerals that form in multiple depositional environments and have high concentrations of associated trace elements. Synchrotron-based micro-scanning X-ray fluorescence ({mu}-SXRF) shows unique spatial distributions of Fe, Mn, and trace elements in mineral samples. Profile maps of Mn oxide cave stream pebble coatings show Fe- and As-rich laminations, indicating dynamic redoxmore » conditions in the cave stream. {mu}-SXRF maps demonstrate that Ni, Cu, and Zn correlate primarily with Mn whereas As correlates with both Mn and Fe; As is more enriched in the Fe phase. Zn is concentrated in the periphery of Mn oxide stream pebble coatings, and may be an indication of recent anthropogenic surface activity. X-ray absorption fine structure spectroscopy measurements reveal that As(V) occurs as surface complexes on Mn and Fe oxides whereas Zn(II) associated with Mn oxides is adsorbed to the basal planes of phyllomanganates in a tetrahedral coordination. Co(III) and Se(IV) are also observed to be associated with Mn oxides. The observation of Fe, Mn, and trace element banding in Mn oxide cave stream pebble coatings suggests that these materials are sensitive to and document aqueous redox conditions, similar to ferromanganese nodules in soils and in marine and freshwater sediments. Furthermore, speciation and distribution measurements indicate that these minerals scavenge trace elements and limit the transport of micronutrients and contaminants in karst aquifer systems while also potentially recording changes in anthropogenic surface activity and land-use.« less

The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China.

PubMed

Ren, Huimin; Liu, Huijuan; Qu, Jiuhui; Berg, Michael; Qi, Weixiao; Xu, Wei

2010-01-01

The role of colloids in estuarine and marine systems has been studied extensively in recent years, whereas less is known about the polluted freshwater system. Yongdingxin River is one of the major recipients of industrial effluents in Tianjin. This article evaluates the role of colloids in controlling geochemical behavior of Cu, Zn, Fe, Mn, Hg and Cr at the confluences between Yongdingxin River and its major tributaries Beijing Drainage River, Jinzhong River and Beitang Drainage River. Based on the distribution of metal partitioning among particulate (>0.22mum), colloidal (1kDa to 0.22mum) and truly dissolved (<1kDa) fractions, the metals can be assigned to the following groups: Group 1 - organic colloidal pool-borne elements Cu and Cr; Group 2 - inorganic colloidal pool-borne metals Fe and Mn; Group 3 - Zn and Hg characterized by varying complexation patterns. The distribution of metal partitioning among particulate, colloidal and truly dissolved fractions was influenced by anthropogenic input. In addition, the theoretical concentrations of elements in case of conservative mixing between the waters of Yongdingxin River and the waters of its tributaries were compared with the measured values to evaluate the geochemical role of colloids. The result showed that all of the metals presented a non-conservative mixing behavior. Addition of colloids resulted in the removal of metals from the water column to bed sediment during river water mixing, which was furthermore confirmed by the similar partition coefficient of metal concentration between colloid and sediment. Copyright 2009 Elsevier Ltd. All rights reserved.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

PubMed

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

Synthesis Gas Conversion over Rh-Based Catalysts Promoted by Fe and Mn

DOE PAGES

Liu, Yifei; Göeltl, Florian; Ro, Insoo; ...

2017-06-13

Rh/SiO2 catalysts promoted with Fe and Mn are selective for synthesis gas conversion to oxygenates and light hydrocarbons at 523 K and 580 psi. Selective anchoring of Fe and Mn species on Rh nanoparticles was achieved by controlled surface reactions and was evidenced by ultraviolet–visible absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The interaction between Rh and Fe promotes the selective production of ethanol through hydrogenation of acetaldehyde and enhances the selectivity toward C2 oxygenates, which include ethanol and acetaldehyde. The interaction between Rh and Mn increases the overall reaction rate and the selectivitymore » toward C2+ hydrocarbons. The combination of Fe and Mn on Rh/SiO2 results in trimetallic Rh-Fe-Mn catalysts that surpass the performance of their bimetallic counterparts. The highest selectivities toward ethanol (36.9%) and C2 oxygenates (39.6%) were achieved over the Rh-Fe-Mn ternary system with a molar ratio of 1:0.15:0.10, as opposed to the selectivities obtained over Rh/SiO2, which were 3.5% and 20.4%, respectively. The production of value-added oxygenates and C2+ hydrocarbons over this trimetallic catalyst accounted for 55% of the total products. X-ray photoelectron spectroscopy measurements suggest that significant fractions of the Fe and Mn species exist as metallic iron and manganese oxides on the Rh surface upon reduction. These findings are rationalized by density functional theory (DFT) calculations, which reveal that the exact state of metals on the surfaces is condition-dependent, with Mn present as Mn(I) and Mn(II) oxide on the Rh (211) step edges and Fe present as Fe(I) oxide on the step edge and metallic subsurface iron on both Rh steps and terraces. CO Fourier transform infrared spectroscopy and DFT calculations suggest that the binding of CO to Rh (211) step edges modified by Fe and/or manganese oxide is altered in comparison to CO adsorption on a clean Rh (211) surface. These results suggest that Mn2Ox species and Fe and Fe2O modify bonding at Rh step edges and shift reaction selectivity away from CH4.« less

Genetic and biochemical effects induced by iron ore, Fe and Mn exposure in tadpoles of the bullfrog Lithobates catesbeianus.

PubMed

Veronez, Alexandra Caroline da Silva; Salla, Rômulo Victor; Baroni, Vinícius Dadalto; Barcarolli, Indianara Fernanda; Bianchini, Adalto; Dos Reis Martinez, Claudia Bueno; Chippari-Gomes, Adriana Regina

2016-05-01

For decades, the extraction of minerals has intensified in order to meet the demand of industry. Iron ore deposits are important sources of metals, such as iron (Fe) and manganese (Mn). The particulate ores can be dispersed during extraction, transport and storage, with potential to induce biological impacts. Amphibians are very sensitive to environmental stressors. Therefore, the present study aimed to assess the effects of iron ore, Fe and Mn exposure during the metamorphosis of Lithobates catesbeianus. Endpoints analyzed included morphological (biometrical and developmental analyses), whole body Fe and Mn concentration in, plasma ferritin concentration, erythrocyte DNA damage (measured through comet assay and micronucleus test) and liver activity of enzymes involved in oxidative status [glutathione S-transferase (GST) and catalase (CAT)]. Tadpoles were kept under control condition (no contaminant addition) or exposed to iron ore (3.79mg/L as fine particulate matter); Fe (nominal concentration: 0.51mg/L Fe as C10H12FeN2NaO8; Fe-EDTA); and Mn (nominal concentration: 5.23mg/L Mn as 4H2O.MnCl2) for 30 days. Virtually, no mortality was observed, except for one tadpole found dead in the iron ore treatment. However, tadpoles exposed to iron ore had longer tail than those kept under control conditions while tadpoles exposed to manganese chloride showed higher body length than control ones. Exposure to Fe and Mn induced a delay in tadpole metamorphosis, especially when these metals are presented not as a mixture (iron ore). Tadpoles exposed to iron ore had increased whole body Fe and Mn while those exposed to Fe and Mn accumulated each metal individually. Tadpoles exposed to any of the contaminants tested showed a significant increase in erythrocyte DNA damage and frequency of micronuclei. In addition, they showed higher liver GST activity respect with those kept under control conditions. Plasma ferritin concentration and liver CAT activity were higher only in tadpoles exposed to iron ore. These findings indicated that tadpoles accumulated Fe and Mn at the whole body level after exposure to the single metals or to their mixture as iron ore. In addition, they indicate that Fe and Mn accumulation can induce oxidative stress with consequent significant developmental, genotoxic and biochemical effects in L. catesbeianus tadpoles. Copyright © 2016 Elsevier B.V. All rights reserved.

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

Kim, S.H.; Song, B.

The reoxidation behavior of steels by slag in the secondary steelmaking process was addressed by investigating the thermodynamic equilibria between the liquid iron containing Mn and P and CaO-MgO-SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}-MnO-Fe{sub t}O ladle slag at 1873 K. The activity coefficient of Fe{sub t}O shows a maximum value in the vicinity of the basicity ((X{sub CaO} + X{sub MgO} + X{sub MnO})/(X{sub SiO{sub 2}} + X{sub Al{sub 2}O{sub 3}} + XP{sub 2}O{sub 5})) = 2.5 at the specific mole fraction range of Fe{sub t}O, while that of MnO seems to increase gradually with increasing the basicity. However, themore » values of {gamma}{sub Fe{sub t}O} and {gamma}{sub MnO} showed minima with respect to P{sub 2}O{sub 5} content of slag. In addition, the values of {gamma}{sub Fe{sub t}O} and {gamma}{sub MnO} increased as (pct CaO)/(pct Al{sub 2}O{sub 3}) ratio increased at given SiO{sub 2}, MgO, and P{sub 2}O{sub 5} contents. The conversion equations between the Fe{sub t}O and MnO activities and their calculated activities via regular solution model were derived by the correlation between the measured and calculated activities over the limited ranges of Fe{sub t}O and MnO contents. The regular solution model was used to estimate the oxygen potential in the slag. For MgO saturated slags, a{sub Fe{sub t}O{sub (l)}} = 0.864a{sub FeO{sub (R.S.)}}, a{sub MnO{sub (l)}} = 6.38a{sub MnO{sub (R.S.)}}. For Al{sub 2}O{sub 3} saturated slags, a{sub Fe{sub t}O{sub (l)}} = 2.086a{sub FeO{sub (R.S.)}}, a{sub MnO{sub (l)}} = 14.39a{sub MnO{sub (R.S.)}}.« less

Crystallographic and magnetic properties of sol-gel synthesized T xCo 1-xFe 2O 4 (T=Mn and Cr) thin films

NASA Astrophysics Data System (ADS)

Kim, Kwang Joo; Kyung Kim, Hee; Ran Park, Young; Choi, Seung-li; Eun Kim, Sung; Jung Lee, Hee; Yun Park, Jae; Jin Kim, Sam

Effects of Mn and Cr substitution for Co on crystallographic and magnetic properties of inverse-spinel CoFe 2O 4 thin films were investigated. The crystal structure of the samples remain cubic for x<1 with the lattice constant ( a0) increasing with x for Mn doping and remaining constant for Cr doping. Tetrahedral Fe 2+ ions were detected in Cr xCo 1-xFe 2O 4 by Mössbauer spectroscopy while no such ions existed in Mn xCo 1-xFe 2O 4. The appearance of the tetrahedral Fe 2+ ions can be explained in terms of the Cr 3+ substitution for the octahedral Co 2+ sites with the resultant charge imbalance being compensated by a reduction of the tetrahedral Fe 3+ into Fe 2+. The observed variation in a0 and magnetic properties can be partly explained in terms of Mn 2+ and Cr 3+ substitution of octahedral sites in Mn xCo 1-xFe 2O 4 and Cr xCo 1-xFe 2O 4, respectively.

Oxoiron(IV) complexes as synthons for the assembly of heterobimetallic centers such as the Fe/Mn active site of Class Ic ribonucleotide reductases.

PubMed

Zhou, Ang; Crossland, Patrick M; Draksharapu, Apparao; Jasniewski, Andrew J; Kleespies, Scott T; Que, Lawrence

2018-01-01

Nonheme oxoiron(IV) complexes can serve as synthons for generating heterobimetallic oxo-bridged dimetal complexes by reaction with divalent metal complexes. The formation of Fe III -O-Cr III and Fe III -O-Mn III complexes is described herein. The latter complexes may serve as models for the Fe III -X-Mn III active sites of an emerging class of Fe/Mn enzymes represented by the Class 1c ribonucleotide reductase from Chlamydia trachomatis and the R2-like ligand-binding oxidase (R2lox) found in Mycobacterium tuberculosis. These synthetic complexes have been characterized by UV-Vis, resonance Raman, and X-ray absorption spectroscopy, as well as electrospray mass spectrometry. The Fe III -O-Cr III complexes exhibit a three-band UV-Vis pattern that differs from the simpler features associated with Fe III -O-Fe III complexes. The positions of these features are modulated by the nature of the supporting polydentate ligand on the iron center, and their bands intensify dramatically in two examples upon the binding of an axial cyanate or thiocyanate ligand trans to the oxo bridge. In contrast, the Fe III -O-Mn III complexes resemble Fe III -O-Fe III complexes more closely. Resonance Raman characterization of the Fe III -O-M III complexes reveals an 18 O-sensitive vibration in the range of 760-890 cm -1 . This feature has been assigned to the asymmetric Fe III -O-M III stretching mode and correlates reasonably with the Fe-O bond distance determined by EXAFS analysis. The likely binding of an acetate as a bridging ligand to the Fe III -O-Mn III complex 12 lays the foundation for further efforts to model the heterobimetallic active sites of Fe/Mn enzymes.

Evidence That the [beta] Subunit of Chlamydia trachomatis Ribonucleotide Reductase Is Active with the Manganese Ion of Its Manganese(IV)/Iron(III) Cofactor in Site 1

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

Dassama, Laura M.K.; Boal, Amie K.; Krebs, Carsten

2014-10-02

The reaction of a class I ribonucleotide reductase (RNR) begins when a cofactor in the {beta} subunit oxidizes a cysteine residue {approx}35 {angstrom} away in the {alpha} subunit, generating a thiyl radical. In the class Ic enzyme from Chlamydia trachomatis (Ct), the cysteine oxidant is the Mn{sup IV} ion of a Mn{sup IV}/Fe{sup III} cluster, which assembles in a reaction between O{sub 2} and the Mn{sup II}/Fe{sup II} complex of {beta}. The heterodinuclear nature of the cofactor raises the question of which site, 1 or 2, contains the Mn{sup IV} ion. Because site 1 is closer to the conserved locationmore » of the cysteine-oxidizing tyrosyl radical of class Ia and Ib RNRs, we suggested that the Mn{sup IV} ion most likely resides in this site (i.e., {sup 1}Mn{sup IV}/{sup 2}Fe{sup III}), but a subsequent computational study favored its occupation of site 2 ({sup 1}Fe{sup III}/{sup 2}Mn{sup IV}). In this work, we have sought to resolve the location of the Mn{sup IV} ion in Ct RNR-{beta} by correlating X-ray crystallographic anomalous scattering intensities with catalytic activity for samples of the protein reconstituted in vitro by two different procedures. In samples containing primarily Mn{sup IV}/Fe{sup III} clusters, Mn preferentially occupies site 1, but some anomalous scattering from site 2 is observed, implying that both {sup 1}Mn{sup II}/{sup 2}Fe{sup II} and {sup 1}Fe{sup II}/{sup 2}Mn{sup II} complexes are competent to react with O{sub 2} to produce the corresponding oxidized states. However, with diminished Mn{sup II} loading in the reconstitution, there is no evidence for Mn occupancy of site 2, and the greater activity of these 'low-Mn' samples on a per-Mn basis implies that the {sup 1}Mn{sup IV}/{sup 2}Fe{sup III}-{beta} is at least the more active of the two oxidized forms and may be the only active form.« less

Preparation and characterization of highly water-soluble magnetic Fe3O4 nanoparticles via surface double-layered self-assembly method of sodium alpha-olefin sulfonate

NASA Astrophysics Data System (ADS)

Li, Honghong; Qin, Li; Feng, Ying; Hu, Lihua; Zhou, Chunhua

2015-06-01

A kind of double-layered self-assembly sodium alpha-olefin sulfonate (AOS) capped Fe3O4 magnetic nanoparticles (Fe3O4-AOS-MN) with highly water-solubility was prepared by a wet co-precipitation method with a pH of 4.8. The resulting Fe3O4-AOS-MN could be dispersed into water to form stable magnetic fluid without other treatments. The result of X-ray diffraction (XRD) indicated that the Fe3O4-AOS-MN maintained original crystalline structure and exhibited a diameter of about 7.5 nm. The iron oxide phase of nanoparticles determined by Raman spectroscopy is Fe3O4. Transmission electron microscopy (TEM) analysis confirmed that the Fe3O4-AOS-MN with spherical morphology were uniformly dispersed in water. FT-IR spectroscopy (FT-IR) and thermo-gravimetric analysis (TGA) verified the successful preparation of Fe3O4-AOS-MN capped with double-layered self-assembled AOS. The corresponding capacities of monolayer chemical absorption and the second-layer self-assembly absorption were respectively 4.07 and 14.71 wt% of Fe3O4-MN, which were much lower than those of other surfactants. Vibrating sample magnetometer (VSM) test result showed Fe3O4-AOS-MN possessed superparamagnetic behavior with the saturation magnetization value of about 44.45 emu/g. The blocking temperature TB of Fe3O4-AOS-MN capped with double-layered AOS is 170 K.

Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 Systems

NASA Astrophysics Data System (ADS)

Kang, Youn-Bae; Jung, In-Ho

2017-06-01

A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2SiO4-Mn2SiO4) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3-FeSiO3) and braunite (Mn7SiO_{12} with excess Mn2O3) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3O4) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.

Advanced Nanofiber-Based Lithium-Ion Battery Cathodes

NASA Astrophysics Data System (ADS)

Toprakci, Ozan

Among various energy storage technologies, rechargeable lithium-ion batteries have been considered as effective solution to the increasing need for high-energy density electrochemical power sources. Rechargeable lithium-ion batteries offer energy densities 2 - 3 times and power densities 5 - 6 times higher than conventional Ni-Cd and Ni-MH batteries, and as a result, they weigh less and take less space for a given energy delivery. However, the use of lithium-ion batteries in many large applications such as electric vehicles and storage devices for future power grids is hindered by the poor thermal stability, relatively high toxicity, and high cost of lithium cobalt oxide (LiCoO2) powders, which are currently used as the cathode material in commercial lithium-ion batteries. Recently, lithium iron phosphate (LiFePO 4) powders have become a favorable cathode material for lithium-ion batteries because of their low cost, high discharge potential (around 3.4 V versus Li/Li+), large specific capacity (170 mAh g -1), good thermal stability, and high abundance with the environmentally benign and safe nature. As a result, there is a huge demand for the production of high-performance LiFePO4. However, LiFePO4 also has its own limitation such as low conductivity (˜10-9 S cm -1), which results in poor rate capability. To address this problem, various approaches can be used such as decreasing particle size of LiFePO 4, doping LiFePO4 with metal ions or coating LiFePO 4 surface with carboneous materials. Formation of conductive layer on LiFePO4 and decreasing particle size are promising approaches due to their superior contribution to electrical conductivity and electrochemical performance of LiFePO4. Although different approaches can be used for surface coating and particle size decrement, electrospinning can be potentially considered as an efficient, simple and inexpensive way. In this study, LiFePO 4/carbon and carbon nanotube- and graphene-loaded electrospun LiFePO 4/carbon composite nanofibers were synthesized by using a combination of sol-gel and electrospinning. During the material preparation, polyacrylonitrile (PAN) was used as an electrospinning media and a carbon source. LiFePO 4 precursor materials and/or conductive materials (carbon nanotubes and graphene) and PAN were dissolved in N,N-dimethylformamide separately and they were mixed before electrospinning. LiFePO4 precursor/PAN fibers were heat treated, during which LiFePO4 precursor transformed to energy-storage LiFePO4 material and PAN was converted to carbon. The surface morphology, microstructure and electrochemical performance of the materials were analyzed. Compared with conventional powder based positive electrodes, the novel LiFePO4/C composite nanofiber cathodes possess better electrochemical performance. Furthermore, the newly developed LiFePO 4/C composite nanofibers are easy to fabricate, highly controllable, and can be used in practical Lithium-ion battery applications. In addition to LiFePO4, more recent efforts have been directed to mixed form of layered lithiummetal oxides (Li-Ni-Mn-Co). Nickel and manganese are of importance because of their lower cost, safety and higher abundance in nature. These new cathodes offer noticeable improvement in the capacity and cycling behavior. In these cathodes, LiNi1/3Co1/3Mn 1/3O2 attracted significant interest because of its good electrochemical properties such as high capacity, prolonged cycling life, and so on. On the other hand, it has some disadvantages such as instability at high voltages and high current densities. To overcome these problems, synthesis of layered Li-rich composite materials such as xLi2MnO3˙(1-x)LiCo 1/3Ni1/3Mn1/3O2 can be a promising approach. In this study, various xLi2MnO3˙(1-x)LiCo 1/3Ni1/3Mn1/3O2 (x=0.1, 0.2, 0.3, 0.4, 0.5) composite cathode materials were prepared by a one-step sol-gel route. Morphology, microstructure and electrochemical behavior of these cathode materials were evaluated. The resultant cathode material shows good electrochemical performance. Relatively low cost and simple preparation route make new xLi2MnO3˙(1-x)LiMn1/3Ni 1/3Co1/3O2 composite materials possible to use as potential cathode candidate for lithium-ion batteries.

[Adsorption of Cu on Core-shell Structured Magnetic Particles: Relationship Between Adsorption Performance and Surface Properties].

PubMed

Li, Qiu-mei; Chen, Jing; Li, Hai-ning; Zhang, Xiao-lei; Zhang, Gao-sheng

2015-12-01

In order to reveal the relationship between the adsorption performance of adsorbents and their compositions, structure, and surface properties, the core-shell structured Fe₃O₄/MnO2 and Fe-Mn/Mn₂2 magnetic particles were systematically characterized using multiple techniques and their Cu adsorption behaviors as well as mechanism were also investigated in details. It was found that both Fe₃O4 and Fe-Mn had spinel structure and no obvious crystalline phase change was observed after coating with MnO₂. The introduction of Mn might improve the affinity between the core and the shell, and therefore enhanced the amount and distribution uniformity of the MnO₂ coated. Consequently, Fe-Mn/MnO₂ exhibited a higher BET specific surface area and a lower isoelectric point. The results of sorption experiments showed that Fe-Mn had a higher maximal Cu adsorption capacity of 33.7 mg · g⁻¹ at pH 5.5, compared with 17.5 mg · g⁻¹ of Fe₃O4. After coating, the maximal adsorption capacity of Fe-Mn/MnO₂ was increased to 58.2 mg · g⁻¹, which was 2.6 times as high as that of Fe₃O₄/MnO₂ and outperformed the majority of magnetic adsorbents reported in literature. In addition, a specific adsorption of Cu occurred at the surface of Fe₃O₄/MnO₂ or Fe-Mn/MnO₂ through the formation of inner-sphere complexes. In conclusion, the adsorption performance of the magnetic particles was positively related to their compositions, structure, and surface properties.

Magnetic and structural properties of ferromagnetic Fe 5PB 2 and Fe 5SiB 2 and effects of Co and Mn substitutions

DOE PAGES

McGuire, Michael A.; Parker, David S.

2015-10-22

Crystallographic and magnetic properties of Fe 5PB 2, Fe 4CoPB 2, Fe 4MnPB 2, Fe 5SiB 2, Fe 4CoSiB 2, and Fe 4MnSiB 2 are reported. All adopt the tetragonal Cr 5B 3 structure-type and are ferromagnetic at room temperature with easy axis of magnetization along the c-axis. The spin reorientation in Fe 5SiB 2 is observed as an anomaly in the magnetization near 170 K, and is suppressed by substitution of Co or Mn for Fe. The silicides are found to generally have larger magnetic moments than the phosphides, but the data suggests smaller magnetic anisotropy in the silicides.more » Cobalt substitution reduces the Curie temperatures by more than 100 K and ordered magnetic moments by 16-20%, while manganese substitution has a much smaller effect. This suggests Mn moments align ferromagnetically with the Fe and that Co does not have an ordered moment in these structures. Anisotropic thermal expansion is observed in Fe 5PB 2 and Fe 5SiB 2, with negative thermal expansion seen along the c-axis of Fe 5SiB 2. First principles calculations of the magnetic properties of Fe 5SiB 2 and Fe 4MnSiB 2 are reported. The results, including the magnetic moment and anisotropy, and are in good agreement with experiment.« less

Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density Functional Theory

DTIC Science & Technology

2013-08-20

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--13-9479 Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using ...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density...structure associated with Fe, Mn, and Mg water complexes using time-dependent density functional theory (TD-DFT). Calculation of excited state resonance

The role of biological uptake in iron and manganese cycling in Lake Baikal

USGS Publications Warehouse

Granina, L.Z.; Callender, E.

2006-01-01

The role of biological uptake in the internal cycling of Fe and Mn in Lake Baikal was quantified. Biological uptake, sedimentation consisting of the biogenic and lithogenic fluxes, and remineralization have been evaluated. The results of calculations show that about 5-10% of Fe and Mn accumulated in the lake are annually taken up by biota. More than 80% of this amount is again recycled after remineralization of biological material. At this, the biogenic fluxes of Fe and Mn are 2-4 times less compared to lithogenic ones. Thus not only is oxidation of Fe and Mn within the water column highly enriched in the oxygen that results in settling of Fe and Mn oxides, but also intensive biological uptake of these elements contributes to their fast removal from internal cycling. However, essential remineralization makes this process of minor importance to Fe and Mn cycling in Lake Baikal. ?? Springer 2006.

Temperature dependence of exchange anisotropy for (0 0 1) oriented Mn 89Pt 11/ferromagnetic bilayers

NASA Astrophysics Data System (ADS)

Yamato, T.; Kume, T.; Kato, T.; Tsunashima, S.; Iwata, S.

Temperature dependence of the exchange anisotropy was investigated for (0 0 1)-oriented top-type Mn 89Pt 11 ( tAF nm)/Ni 80Fe 20 (5 nm) and bottom-type Ni 80Fe 20 (3 nm)/Mn 89Pt 11 (30 nm) and Co 90Fe 10 (3 nm)/Mn 89Pt 11 (30 nm) bilayers. The top-type MnPt/NiFe bilayers exhibited both 1 and 4-fold anisotropies in their in-plane torque curves at 80 K. For tAF=3 nm, rapid decrease of 1-fold component and gradual decrease of 4-fold component were observed with increasing temperature. While for tAF=30 nm, the 1 and 4-fold anisotropies decreased similarly with temperature. In the bottom-type bilayers, by using CoFe ferromagnetic layer, the 4-fold anisotropy was found to become twice as that of the NiFe/MnPt bilayer.

The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

NASA Technical Reports Server (NTRS)

Hwang, S. K.; Morris, J. W., Jr.

1979-01-01

An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (alpha + gamma) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196 C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (gamma). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated alpha-prime martensitic structure and absence of epsilon martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained.

Developmental manganese exposure in combination with developmental stress and iron deficiency: Effects on behavior and monoamines.

PubMed

Amos-Kroohs, Robyn M; Davenport, Laurie L; Gutierrez, Arnold; Hufgard, Jillian R; Vorhees, Charles V; Williams, Michael T

2016-01-01

Manganese (Mn) is an essential element but neurotoxic at higher exposures, however, Mn exposure seldom occurs in isolation. It often co-occurs in populations with inadequate dietary iron (Fe) and limited resources that result in stress. Subclinical FeD affects up to 15% of U.S. children and exacerbates Mn toxicity by increasing Mn bioavailability. Therefore, we investigated Mn overexposure (MnOE) in rats in combination with Fe deficiency (FeD) and developmental stress, for which we used barren cage rearing. For barren cage rearing (BAR), rats were housed in cages with a wire grid floor or standard bedding material (STD) from embryonic day (E)7 through postnatal day (P)28. For FeD, dams were fed a 90% Fe-deficient NIH-07 diet from E15 through P28. Within each litter, different offspring were treated with 100mg/kg Mn (MnOE) or vehicle (VEH) by gavage every other day from P4-28. Behavior was assessed at two ages and consisted of: open-field, anxiety tests, acoustic startle response (ASR) with prepulse inhibition (PPI), sociability, sucrose preference, tapered beam crossing, and the Porsolt's forced swim test. MnOE had main effects of decreasing activity, ASR, social preference, and social novelty. BAR and FeD transiently modified MnOE effects. BAR groups weighed less and showed decreased anxiety in the elevated zero maze, had increased ASR and decreased PPI, and exhibited reduced sucrose preference compared with the STD groups. FeD animals also weighed less and had increased slips on the tapered beam. Most of the monoamine effects were dopaminergic and occurred in the MnOE groups. The results showed that Mn is a pervasive developmental neurotoxin, the effects of which are modulated by FeD and/or BAR cage rearing. Copyright © 2016 Elsevier Inc. All rights reserved.

Galvanostatically deposited Fe: MnO2 electrodes for supercapacitor application

NASA Astrophysics Data System (ADS)

Dubal, D. P.; Kim, W. B.; Lokhande, C. D.

2012-01-01

The present investigation describes the addition of iron (Fe) in order to improve the supercapacitive properties of MnO2 electrodes using galvanostatic mode. These amorphous worm like Fe: MnO2 electrodes are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and wettability test. The supercapacitive properties of MnO2 and Fe: MnO2 electrodes are investigated using cyclic voltammetry, chronopotentiometry and impedance techniques. It is seen that the supercapacitance increases with increase in Fe doping concentration and achieved a maximum of 173 F g-1 at 2 at% Fe doping. The maximum supercapacitance obtained is 218 F g-1 for 2 at% Fe: MnO2 electrode. This hydrous binary oxide exhibited ideal capacitive behavior with high reversibility and high pulse charge-discharge property between -0.1 and +0.9 V/SCE in 1 M Na2SO4 electrolyte indicating a promising electrode material for electrochemical supercapacitors.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

NASA Astrophysics Data System (ADS)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-10-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

Solid state 31phosphorus nuclear magnetic resonance of iron-, manganese-, and copper-containing synthetic hydroxyapatites

NASA Technical Reports Server (NTRS)

Sutter, B.; Taylor, R. E.; Hossner, L. R.; Ming, D. W.

2002-01-01

The incorporation of micronutrients into synthetic hydroxyapatite (SHA) is proposed for slow release of these nutrients to crops in the National Aeronautics and Space Administration's (NASA's) Advanced Life Support (ALS) program for Lunar or Martian outposts. Solid state 31P nuclear magnetic resonance (NMR) was utilized to examine the paramagnetic effects of Fe3+, Mn2+, and Cu2+ to determine if they were incorporated into the SHA structure. Separate Fe3+, Mn2+, and Cu2+ containing SHA materials along with a transition metal free SHA (pure-SHA) were synthesized using a precipitation method. The proximity (<1 nm) of the transition metals to the 31P nuclei of SHA were apparent when comparing the integrated 31P signal intensities of the pure-SHA (87 arbitrary units g-1) with the Fe-, Mn-, and Cu-SHA materials (37-71 arbitrary units g-1). The lower integrated 31P signal intensities of the Fe-, Mn-, and Cu-SHA materials relative to the pure-SHA suggested that Fe3+, Mn2+, and Cu2+ were incorporated in the SHA structure. Further support for Fe3+, Mn2+, and Cu2+ incorporation was demonstrated by the reduced spin-lattice relaxation constants of the Fe-, Mn-, and Cu-SHA materials (T'=0.075-0.434s) relative to pure-SHA (T1=58.4s). Inversion recovery spectra indicated that Fe3+, Mn2+, and Cu2+ were not homogeneously distributed about the 31P nuclei in the SHA structure. Extraction with diethylene-triamine-penta-acetic acid (DTPA) suggested that between 50 and 80% of the total starting metal concentrations were incorporated in the SHA structure. Iron-, Mn-, and Cu-containing SHA are potential slow release sources of Fe, Mn, and Cu in the ALS cropping system.

Increased concentrations of potassium in heartwood of trees in response to groundwater contamination

USGS Publications Warehouse

Vroblesky, D.A.; Yanosky, T.M.; Siegel, F.R.

1992-01-01

The wood of tuliptrees (Liriodendron tulipifera L.) growing above groundwater contamination from a hazardous-waste landfill in Maryland contained elevated concentrations of potassium (K). The groundwater contamination also contained elevated concentrations of dissolved K, as well as arsenic (As), cadmium (Cd), chloride (Cl), iron (Fe), manganese (Mn), zinc (Zn), and organic solvents. The dissolved K is derived from disposed smoke munitions. The excess K in the tuliptrees is concentrated in the heartwood, the part of the xylem most depleted in K in trees growing outside of the contamination. These data show that the uptake and translocation of K by tuliptrees can be strongly influenced by the availability of K in groundwater contamination and suggest the utility of this species as an areal indicator of groundwater contamination. ?? 1992 Springer-Verlag New York Inc.

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.

Thermodynamic Simulation of Carbonate Cements-Water-Carbon Dioxide Equilibrium in Sandstone for Prediction of Precipitation/Dissolution of Carbonate Cements

PubMed Central

Zhong, Xinyan; Shang, Ruishu; Huang, Lihong

2016-01-01

Carbonate cements, such as calcite, dolomite, ferrocalcite and ankerite, play important roles in the formation of pores in sandstones: precipitation of carbonate cements modifies pores and inhibits compaction, while dissolution creates secondary pores. This work proposed a precipitation-dissolution model for carbonate cements-CO2-H2O system by means of ion equilibrium concentration ([M2+], M = Ca, Mg, Fe or Mn) with different factors, such as temperature, depth, pH, PCO2, variable rock composition and overpressure. Precipitation-dissolution reaction routes were also analyzed by minimization of the total Gibbs free energy (ΔG). Δ[M2+], the variation of [Ca2+], [Fe2+], [Mg2+] or [Mn2+] for every 100 m of burial depths, is used to predict precipitation or dissolution. The calculation results indicate that the increasing temperature results in decrease of equilibrium constant of reactions, while the increasing pressure results in a relatively smaller increase of equilibrium constant; As a result, with increasing burial depth, which brings about increase of both temperature and pressure, carbonate cements dissolve firstly and produces the maximal dissolved amounts, and then precipitation happens with further increasing depth; For example, calcite is dissolving from 0.0 km to 3.0 km with a maximal value of [Ca2+] at depth of 0.8 km, and then precipitates with depth deeper than 3.0 km. Meanwhile, with an increasing CO2 mole fraction in the gaseous phase from 0.1% to 10.0% in carbonate systems, the aqueous concentration of metal ions increases, e.g., dissolved amount of CaFe0.7Mg0.3(CO3)2 increases and reaches maximum of 1.78 mmol·L-1 and 8.26 mmol·L-1 at burial depth of 0.7 km with CO2 mole fraction of 0.1% and 10.0%, respectively. For the influence of overpressure in the calcite system, with overpressure ranging from 36 MPa to 83 MPa, pH reaches a minimum of 6.8 at overpressure of 51 MPa; meanwhile, Δ[Ca2+] increases slightly from -2.24 mmol·L-1 to -2.17 mmol·L-1 and remains negative, indicating it is also a precipitation process at burial depth of 3.9 km where overpressure generated. The method used in this study can be applied in assessing burial precipitation-dissolution processes and predicting possible pores in reservoirs with carbonate cement-water-carbon dioxide. PMID:27907043

Thermodynamic Simulation of Carbonate Cements-Water-Carbon Dioxide Equilibrium in Sandstone for Prediction of Precipitation/Dissolution of Carbonate Cements.

PubMed

Duan, Yiping; Feng, Mingshi; Zhong, Xinyan; Shang, Ruishu; Huang, Lihong

2016-01-01

Carbonate cements, such as calcite, dolomite, ferrocalcite and ankerite, play important roles in the formation of pores in sandstones: precipitation of carbonate cements modifies pores and inhibits compaction, while dissolution creates secondary pores. This work proposed a precipitation-dissolution model for carbonate cements-CO2-H2O system by means of ion equilibrium concentration ([M2+], M = Ca, Mg, Fe or Mn) with different factors, such as temperature, depth, pH, [Formula: see text], variable rock composition and overpressure. Precipitation-dissolution reaction routes were also analyzed by minimization of the total Gibbs free energy (ΔG). Δ[M2+], the variation of [Ca2+], [Fe2+], [Mg2+] or [Mn2+] for every 100 m of burial depths, is used to predict precipitation or dissolution. The calculation results indicate that the increasing temperature results in decrease of equilibrium constant of reactions, while the increasing pressure results in a relatively smaller increase of equilibrium constant; As a result, with increasing burial depth, which brings about increase of both temperature and pressure, carbonate cements dissolve firstly and produces the maximal dissolved amounts, and then precipitation happens with further increasing depth; For example, calcite is dissolving from 0.0 km to 3.0 km with a maximal value of [Ca2+] at depth of 0.8 km, and then precipitates with depth deeper than 3.0 km. Meanwhile, with an increasing CO2 mole fraction in the gaseous phase from 0.1% to 10.0% in carbonate systems, the aqueous concentration of metal ions increases, e.g., dissolved amount of CaFe0.7Mg0.3(CO3)2 increases and reaches maximum of 1.78 mmol·L-1 and 8.26 mmol·L-1 at burial depth of 0.7 km with CO2 mole fraction of 0.1% and 10.0%, respectively. For the influence of overpressure in the calcite system, with overpressure ranging from 36 MPa to 83 MPa, pH reaches a minimum of 6.8 at overpressure of 51 MPa; meanwhile, Δ[Ca2+] increases slightly from -2.24 mmol·L-1 to -2.17 mmol·L-1 and remains negative, indicating it is also a precipitation process at burial depth of 3.9 km where overpressure generated. The method used in this study can be applied in assessing burial precipitation-dissolution processes and predicting possible pores in reservoirs with carbonate cement-water-carbon dioxide.

Differential coordination demands in Fe vs Mn water-soluble cationic metalloporphyrins translates into remarkably different aqueous redox chemistry and biology

PubMed Central

Tovmasyan, Artak; Weitner, Tin; Sheng, Huaxin; Lu, MiaoMiao; Rajic, Zrinka; Warner, David S.; Spasojevic, Ivan; Reboucas, Julio S.; Benov, Ludmil; Batinic-Haberle, Ines

2013-01-01

The different biological behavior of cationic Fe and Mn pyridylporphyrins in Escherichia coli and mouse studies prompted us to revisit and compare their chemistry. For that purpose the series of ortho and meta isomers of Fe(III) meso-tetrakis-N-alkylpyridylporphyrins, alkyl being methyl to n-octyl, were synthesized and characterized by elemental analysis, UV/vis spectroscopy, mass spectrometry, lipophilicity, protonation equilibria of axial waters, metal-centered reduction potential, E1/2 for MIIIP/MIIP redox couple (M = Fe, Mn, P=porphyrin), kcat for the catalysis of O2•− dismutation, stability towards peroxide-driven porphyrin oxidative degradation (produced in the catalysis of ascorbate oxidation by MP), ability to affect growth of SOD-deficient E. coli and toxicity to mice. Electron-deficiency of the metal site is modulated by the porphyrin ligand, which renders Fe(III) porphyrins ≥ 5 orders of magnitude more acidic than the analogous Mn(III) porphyrins, as revealed by the pKa1 of axially coordinated waters. The 5 log units difference in the acidity between the Mn and Fe sites in porphyrin translates into the predominance of tetracationic (OH)(H2O)FeP complexes relative to pentacationic (H2O)2MnP species at pH ~7.8. This is evidenced in large differences in the thermodynamic parameters - pKa of axial waters and E1/2 of MIII/MII redox couple. The presence of hydroxo ligand labilizes trans-axial water which results in higher reactivity of Fe- relative to Mn center. The differences in the catalysis of O2•− dismutation (log kcat) between Fe and Mn porphyrins is modest, 2.5-5-fold, due to predominantly outer-sphere, with partial inner-sphere character of two reaction steps. However, the rate constant for the inner-sphere H2O2-based porphyrin oxidative degradation is 18-fold larger for (OH)(H2O)FeP than for (H2O)2MnP. The in vivo consequences of the differences between the Fe- and Mn porphyrins were best demonstrated in SOD-deficient E. coli growth. Based on fairly similar log kcat(O2.− values, very similar effect on the growth of SOD-deficient E. coli was anticipated by both metalloporphyrins. Yet, while MnTE-2-PyP5+ was fully efficacious at ≥20 μM, the Fe analog, FeTE-2-PyP5+ supported SOD-deficient E. coli growth at 200-fold lower doses in the range of 0.1 to 1 μM. Moreover the pattern of SOD-deficient E. coli growth was different with Mn- and Fe porphyrins. Such results suggested different mode of action of these metalloporphyrins. Further exploration demonstrated that: (1) 0.1 μM FeTE-2-PyP5+ provided similar growth stimulation as 0.1 μM Fe salt, while 20 μM Mn salt provides no protection to E. coli; and (2) 1 μM Fe porphyrin is fully degraded by 12 hours in E. coli cytosol and growth medium; while Mn porphyrin is not. Stimulation of the aerobic growth of SOD-deficient E. coli by the Fe porphyrin is therefore due to iron acquisition. Our data suggest that in vivo, redox-driven degradation of Fe porphyrins resulting in Fe release plays a major role in their biological action. Possibly, iron reconstitutes enzymes bearing [4Fe-4S] clusters as active sites. Under same experimental conditions, (OH)(H2O)FePs do not cause mouse arterial hypotension, whereas (H2O)2MnPs do, which greatly limits the application of Mn porphyrins in vivo. PMID:23646875

Magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3

NASA Astrophysics Data System (ADS)

Mihalik, Matúš; Mihalik, Marián; Hoser, Andreas; Pajerowski, Daniel M.; Kriegner, Dominik; Legut, Dominik; Lebecki, Kristof M.; Vavra, Martin; Fitta, Magdalena; Meisel, Mark W.

2017-10-01

The magnetic structure of the mixed antiferromagnet NdMn0.8Fe0.2O3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k =(000 ) and with the magnetic structure (Ax,Fy,Gz ) for 1.6 K

Spatial and temporal characterization of trace elements and nutrients in the Rawal Lake Reservoir, Pakistan using multivariate analysis techniques.

PubMed

Malik, Riffat Naseem; Nadeem, Muhammad

2011-12-01

Rawal Lake Reservoir is renowned for its ecological significance and is the sole source of drinking water of the third largest city of Pakistan. However, fish kill in recent years and anthropogenic impacts from human-related activities in its catchment area have resulted in deterioration of its surface water quality. This study aims to characterize spatial and temporal variations in surface water quality, identify contaminant sources, and compare their levels with quality guidelines. Surface water samples were collected from 10 sites and analyzed for 27 physicochemical parameters for a period of 2 years on a seasonal basis. Concentration of metals in surface water in pre-monsoon were in the order: Fe > Mg > Ca > Mn > Zn > Ni > Cr > Cu > Co > Pb, whereas in post-monsoon, the order of elemental concentrations was: Ca > Mg > Na > Fe > K > Zn > Cr > Li > Pb > Co > Ni > Cu > Mn > Cd. Metals (Ni, Fe, Zn, and Ca), pH, electrical conductivity (EC), dissolved oxygen (DO), chemical oxygen demand (COD), and nutrients (PO (4) (3-) , NO(3)-N, and SO (4) (2-) ) were measured higher in pre-monsoon, whereas concentration of Cu, Mn, Cr, Co, Pb, Cd, K, Na, Mg, Li, Cl(-), and NH(4)-N were recorded higher in post-monsoon. Results highlighted serious metal pollution of surface water. Mean concentration of Zn, Cd, Ni, Cu, Fe, Cr, and Pb in both seasons and Mn in post-monsoon were well above the permissible level of surface water quality criteria. Results stress the dire need to reduce heavy-metal input into the lake basin and suggest that heavy-metal contamination should be considered as an integral part of future planning and management strategies for restoration of water quality of the lake reservoir.

Synthesis and characterization of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO nanocomposites from waste batteries for photocatalytic, electrochemical and thermal studies

NASA Astrophysics Data System (ADS)

Mylarappa, M.; Venkata Lakshmi, V.; Vishnu Mahesh, K. R.; Nagaswarupa, H. P.; Raghavendra, N.

2017-11-01

In the present paper, Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO composites recovered from waste batteries using acid dissolution and ferrite processing were studied. The recovered Mn-ZnFe2O4 nanocomposites were decorated onto rGO using the facile hydrothermal method. The recovered material was characterized using x-ray powder diffraction to study the particle size and crystallinity. The morphology of the composites was analyzed using scanning electron microscopy, and elements present in the materials were studied using energy dispersive x-ray analysis. The functional groups attached were observed using a Fourier transform infrared spectrometer. Furthermore, the recovered composites were evaluated in thermal studies using thermal gravimetric analysis, differential scanning calorimetry and dynamic thermal analysis. The material was used as a photocatalyst for the removal of acid orange 88 dye, and as an electrocatalyst. The decreased band gap energy for the Mn-ZnFe2O4/rGO composite was displayed in better photocatalytic activity for a given reaction. The electrochemical properties of Mn-ZnFe2O4 and Mn-ZnFe2O4/rGO have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with a paste-type electrode. The CV indicated the reversibility of the electrode reaction, and the EIS revealed that a decrease in the charge transfer resistance increases the double layer capacitance of the rGO/Mn-ZnFe2O4 electrode.

Periodic table of 3d-metal dimers and their ions.

PubMed

Gutsev, G L; Mochena, M D; Jena, P; Bauschlicher, C W; Partridge, H

2004-10-08

The ground states of the mixed 3d-metal dimers TiV, TiCr, TiMn, TiFe, TiCo, TiNi, TiCu, TiZn, VCr, VMn, VFe, VCo, VNi, VCu, VZn, CrMn, CrFe, CrCo, CrNi, CrCu, CrZn, MnFe, MnCo, MnNi, MnCu, MnZn, FeCo, FeNi, FeCu, FeZn, CoNi, CoCu, CoZn, NiCu, NiZn, and CuZn along with their singly negatively and positively charged ions are assigned based on the results of computations using density functional theory with generalized gradient approximation for the exchange-correlation functional. Except for TiCo and CrMn, our assignment agrees with experiment. Computed spectroscopic constants (r(e),omega(e),D(o)) are in fair agreement with experiment. The ground-state spin multiplicities of all the ions are found to differ from the spin multiplicities of the corresponding neutral parents by +/-1. Except for TiV, MnFe, and MnCu, the number of unpaired electrons, N, in a neutral ground-state dimer is either N(1)+N(2) or mid R:N(1)-N(2)mid R:, where N(1) and N(2) are the numbers of unpaired 3d electrons in the 3d(n)4s(1) occupation of the constituent atoms. Combining the present and previous results obtained at the same level of theory for homonuclear 3d-metal and ScX (X=Ti-Zn) dimers allows one to construct "periodic" tables of all 3d-metal dimers along with their singly charged ions.

Ability of rabbit alveolar macrophages to dissolve metals.

PubMed

Lundborg, M; Lind, B; Camner, P

1984-01-01

Manganese dioxide particles, 0.1-0.5 micron, were added to samples of 2-3 X 10(6) rabbit alveolar macrophages. The amount of manganese added and dissolved from the particles, over periods of 0, 1, 3, and 5 days, was determined by flame atomic absorption spectrophotometry. Macrophages from six rabbits received about 10 micrograms of Mn, macrophages from two rabbits about 30 micrograms, and macrophages from another two rabbits about 100 micrograms. Over periods of 1, 3, and 5 days the macrophages in all three dose groups dissolved two to three times more Mn than was dissolved in control experiments. In control experiments solubility was studied in the medium without macrophages. Macrophages cultivated 3 days before the addition of MnO2 dissolved the particles within another 2 days to an extent similar to that in the control experiments. The ability of the macrophages to dissolve MnO2 particles might be related to the low pH values in the phagosomes. Studies of the ability of macrophages from various species to dissolve metal particles as well as of pH values in their phagosomes might lead to a better understanding of alveolar clearance of metal particles.

How does organic matter occurrence set limit onto the use of Ce anomaly as a reliable proxy of redox conditions in shallow groundwaters?

NASA Astrophysics Data System (ADS)

Dia, A.; Gruau, G.; Davranche, M.; Vidy, A.; Henin, O.; Petitjean, P.; Le Coz-Bouhnik, M.

2003-04-01

This study is dedicated to the effects of organic matter on the hydrochemistry of Rare Earth Elements (REE) and the ability of using the Ce anomaly as a reliable proxy of redox conditions in surface waters when organic matter occurs. The data include a : i) two-year survey of SREE and Ce anomalies in organic-rich waters recovered from a catchment located in Brittany (western Europe) and (ii) experimental incubation of organic soils from this catchment set under controlled conditions, as well as, (iii) a REE speciation calculation in both the natural organic-rich waters from the wetlands and the experimental solutions. Field and experimental data appear to be extremely coherent, displaying good correlation between the SREE, the Dissolved Organic Carbon (DOC) contents and the redox state. The field data show a strong increase of the SREE and DOC concentrations in soil waters when the environment becomes more reducing. The onset of DOC and SREE contents is seen to be in phase with the increase of dissolved Fe and Mn. The role of Fe-, Mn-oxyhydroxides is confirmed by the experimental data as the maximum of DOC and SREE content is reached when Fe2+ reaches a maximum in the soil solution, suggesting that reductive dissolution of Fe, Mn-oxyhydroxides happens. Despite the strong redox changes and the known redox sensitive behaviour of Ce as compared to other REE, none Ce anomaly variation is observed during either, the experimental procedure, or the field survey through time. Speciation calculations were performed showing that in both such pH range and moderately oxidizing waters in DOC-rich waters, REE should have an organic speciation. Such an organic speciation prevents the formation of Ce(IV) and therefore the development of any Ce anomaly. However, since the studied waters are highly oxidizing (high nitrate contents), the nitrates impose the redox formation of Ce(IV) and a Ce anomaly should appear. Therefore, Ce(IV) is not formed in these waters either because (i) the reaction kinetic might be so slow that the anomaly has no time to ever happen in the field, or (ii) Ce(IV) might be linked to the organic colloidal fraction. Since the thermodynamic modelling does not help getting information, further experimental kinetics or ultrafiltration studies will be required to clarify these latter points. This has to be fixed to be able to use the Ce anomaly as a reliable proxy of redox conditions in organic-rich environment.

Ab initio investigation of competing antiferromagnetic structures in low Si-content FeMn(PSi) alloy

NASA Astrophysics Data System (ADS)

Li, Guijiang; Eriksson, Olle; Johansson, Börje; Vitos, Levente

2016-06-01

The antiferromagnetic structures of a low Si-content FeMn(PSi) alloy were investigated by first principles calculations. One possible antiferromagnetic structure in supercell along the c-axis was revealed in FeMnP0.75Si0.25 alloy. It was found that atomic disorder occupation between Fe atom on 3f and Mn atoms on 3g sites is responsible for the formation of antiferromagnetic structures. Furthermore the magnetic competition and the coupling between possible AFM supercells along the c and a-axis can promote a non-collinear antiferromagnetic structure. These theoretical investigations help to deeply understand the magnetic order in FeMn(PSi) alloys and benefit to explore the potential magnetocaloric materials in Fe2P-type alloys.

Flavins in Coastal Marine Sediments: New Perspectives on Diagenetic Electron Transfer

NASA Astrophysics Data System (ADS)

Monteverde, D.; Berelson, W.; Baronas, J. J.; Sanudo-Wilhelmy, S. A.

2016-02-01

Coastal marine sediments play a critical role in the global cycling of metals and nutrients, many of which undergo diagenetic alteration. Central to these transformations are redox reactions where electron-rich organic matter is oxidized via transfer to terminal electron acceptors (NO3-, MnOx, FeOx, SO42-). The flavins (flavin adenine dinucleotide [FAD], flavin mononucleotide [FMN], and riboflavin [B2]) are microbially synthesized organic coenzymes that perform both single and double electron transfer and are known to mediate reduction of insoluble metal oxides. Culture experiments have found high rates of flavin excretion in metal-reducing Shewanella and Geobacter species, however environmental measurements of these highly labile molecules have not been previously reported. Here we present porewater measurements of FAD, FMN, and B2 from San Pedro Basin. This California Borderland basin is silled, suboxic, 900 m deep, and experiences high sedimentation. Flavin concentrations ranged from pico- (FAD: 0- 60 pM; B2: 40 - 90 pM) to nanomolar (FMN: 0.4 - 1.2 nM). The concentration cascade of FMN>B2>FAD fits well within culture experiments. Interestingly, profiles of all three flavins show a near linear increase with depth from 0-30 cm and a relatively steady concentration from 30-45 cm, supporting likely in situ production. Additionally, the flavins showed a negative correlation with dissolved Fe (R2 = 0.7 for FMN, 0.8 for FAD, and 0.9 for B2), which decreased linearly with depth from 160µM to 65µM. We discuss hypothesized mechanisms controlling flavin concentrations based on a suite of sediment geochemical parameters (dissolved Fe, Mn, TCO2, δ13C, NH3, DOM, and SO42-) as well as implications for microbial redox syntrophy. These data provide a critical link between the extensive culture-based mechanistic understanding of flavin function and the sedimentary environment. Furthermore, these results demonstrate that flavins likely serve as a significant electron transfer intermediaries in the marine sediment carbon cycle.

Cyanide-bridged Fe(III)-Mn(III) bimetallic complexes with dimeric and chain structures constructed from a newly made mer-Fe tricyanide: structures and magnetic properties.

PubMed

Kim, Jae Il; Kwak, Hyun Young; Yoon, Jung Hee; Ryu, Dae Won; Yoo, In Young; Yang, Namgeun; Cho, Beong Ki; Park, Je-Geun; Lee, Hyosug; Hong, Chang Seop

2009-04-06

Four cyanide-linked Fe(III)-Mn(III) complexes were prepared by reacting Mn Schiff bases with a new molecular precursor (PPh(4))[Fe(qcq)(CN)(3)] [1; qcq = 8-(2-quinolinecarboxamido)quinoline anion]. They include a dimeric molecule, [Fe(qcq)(CN)(3)][Mn(3-MeOsalen)(H(2)O)] x 2 H(2)O [2 x 2 H(2)O; 3-MeOsalen = N,N'-ethylenebis(3-methoxysalicylideneiminato) dianion], and three 1D zigzag chains, [Fe(qcq)(CN)(3)][Mn(5-Clsalen)] x 3 H(2)O [3 x 2 MeOH; 5-Clsalen = N,N'-ethylenebis(5-chlorosalicylideneiminato) dianion], [Fe(qcq)(CN)(3)][Mn(5-Brsalen)] x 2 MeOH [4 x 2 MeOH; 5-Brsalen = N,N'-ethylenebis(5-bromosalicylideneiminato) dianion], and Fe(qcq)(CN)(3)][Mn(salen)].MeCN x H(2)O [5 x MeCN; salen = N,N'-ethylenebis(salicylideneiminato) dianion]. The complexes consist of extensive hydrogen bonding and pi-pi stacking interactions, generating multidimensional structures. Magnetic studies demonstrate that antiferromagnetic couplings are operative between Fe(III) and Mn(III) centers bridged by cyanide ligands. On the basis of an infinite chain model, magnetic coupling parameters of 2-5 range from -9.3 to -14.1 cm(-1). A long-range order is observed at 2.3 K for 3 and 2.2 K for 4, while compound 5 shows spin glass behavior possibly coupled with magnetic ordering.

Fe-Mn bi-metallic oxides loaded on granular activated carbon to enhance dye removal by catalytic ozonation.

PubMed

Tang, Shoufeng; Yuan, Deling; Zhang, Qi; Liu, Yameng; Zhang, Qi; Liu, Zhengquan; Huang, Haiming

2016-09-01

A Fe-Mn bi-metallic oxide supported on granular activated carbon (Fe-Mn GAC) has been fabricated by an impregnation-desiccation method and tested in the catalytic ozonation of methyl orange (MO) degradation and mineralization. X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy characterizations revealed that Fe-Mn oxides were successfully loaded and uniformly distributed on the GAC, and nitrogen adsorption isotherms showed that the supported GAC retained a large surface area and a high pore volume compared with the pristine GAC. The catalytic activity was systematically assessed by monitoring the MO removal efficiencies at different operational parameters, such as catalyst dosage, initial solution pH, and ozone flow rate. The Fe-Mn GAC exhibited better catalytic activity relative to ozone alone and GAC alone, improving the TOC removal by 24.5 and 11.5 % and COD removal by 13.6 and 7.3 %, respectively. The reusability of the hybrid was examined over five consecutive cyclic treatments. The Fe-Mn GAC catalytic activity was only a slight loss in the cycles, showing good stability. The addition of Na2CO3 as hydroxyl radicals (•OH) scavengers proved that the catalytic ozonation mechanism was the enhanced generation of •OH by the Fe-Mn GAC. The above results render the Fe-Mn GAC an industrially promising candidate for catalytic ozonation of dye contaminant removal.

Attenuation of landfill leachate by UK Triassic sandstone aquifer materials. 1. Fate of inorganic pollutants in laboratory columns

NASA Astrophysics Data System (ADS)

Thornton, Steven F.; Tellam, John H.; Lerner, David N.

2000-05-01

The attenuation of inorganic contaminants in acetogenic and methanogenic landfill leachate by calcareous and carbonate-deficient, oxide-rich Triassic sandstone aquifer materials from the English Midlands was examined in laboratory columns. Aqueous equilibrium speciation modelling, simple transport modelling and chemical mass balance approaches are used to evaluate the key processes and aquifer geochemical properties controlling contaminant fate. The results indicate that leachate-rock interactions are dominated by ion-exchange processes, acid-base and redox reactions and sorption/precipitation of metal species. Leachate NH 4 is attenuated by cation exchange with the aquifer sediments; however, NH 4 migration could be described with a simple model using retardation factors. Organic acids in the acetogenic leachate buffered the system pH at low levels during flushing of the calcareous aquifer material. In contrast, equilibrium with Al oxyhydroxide phases initially buffered pH (˜4.5) during flushing of the carbonate-deficient sandstone with methanogenic leachate. This led to the mobilisation of sorbed and oxide-bound heavy metals from the aquifer sediment which migrated as a concentrated pulse at the leachate front. Abiotic reductive dissolution of Mn oxyhydroxides on each aquifer material by leachate Fe 2+ maintains high concentrations of dissolved Mn and buffers the leachate inorganic redox system. This feature is analogous to the Mn-reducing zones found in leachate plumes and in the experiments provides a sink for the leachate Fe load and other heavy metals. The availability of reactive solid phase Mn oxyhydroxides limits the duration of redox buffering and Fe attenuation by these aquifer sediments. Aquifer pH and redox buffering capacity exert a fundamental influence on leachate inorganic contaminant fate in these systems. The implications for the assessment of aquifer vulnerability at landfills are discussed and simple measurements of aquifer properties which may improve the prediction of contaminant attenuation are outlined.

Iron and Arsenic Speciation During As(III) Oxidation by Manganese Oxides in the Presence of Fe(II): Molecular-Level Characterization Using XAFS, Mössbauer, and TEM Analysis

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

Wu, Yun; Kukkadapu, Ravi K.; Livi, Kenneth J. T.

The redox state and speciation of metalloid arsenic (As) determine its toxicity and mobility. Knowledge of biogeochemical processes influencing the As redox state is therefore important to understand and predict its environmental behavior. Many previous studies examined As(III) oxidation by various Mn-oxides, but little is known the environmental influences (e.g. co-existing ions) on such process. In this study, we investigated the mechanisms of As(III) oxidation by a poorly crystalline hexagonal birnessite (δ-MnO2) in the presence of Fe(II) using X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS). As K-edge X-ray absorption nearmore » edge spectroscopy (XANES) analysis revealed that, at low Fe(II) concentration (100 μM), As(V) was the predominant As species on the solid phase, while at higher Fe(II) concentration (200-1000 μM), both As(III) and As(V) were sorbed on the solid phase. As K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) analysis showed an increasing As-Mn/Fe distance over time, indicating As prefers to bind with the newly formed Fe(III)-(hydr)oxides. As adsorbed on Fe(III)-(hydr)oxides as a bidentate binuclear corner-sharing complex. Both Mössbauer and TEM-EDS investigations demonstrated that the oxidized Fe(III) products formed during Fe(II) oxidation by δ-MnO2 were predominantly ferrihydrite, goethite, and ferric arsenate like compounds. However, Fe EXAFS analysis also suggested the formation of a small amount of lepidocrocite. The Mn K-edge XANES data indicated that As(III) and Fe(II) oxidation occurs as a two electron transfer with δ-MnO2 and the observed Mn(III) is due to conproportionation of surface sorbed Mn(II) with Mn(IV) in δ-MnO2 structure. This study reveals that the mechanisms of As(III) oxidation by δ-MnO2 in the presence of Fe(II) are very complex, involving many simultaneous reactions, and the formation of Fe(III)-(hydr)oxides plays a very important role in reducing As mobility.« less

Combined effects of Bi deficiency and Mn substitution on the structural transformation and functionality of BiFeO{sub 3} films

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

Chen, Jingyi; Wang, Yao, E-mail: wang-yao@buaa.edu.cn; Deng, Yuan, E-mail: dengyuan@buaa.edu.cn

2014-11-07

Mn-doped BiFeO{sub 3} films with Mn contents of 5 and 10 mol. % were prepared via a chemical route. A carefully controlled amount of Bi deficiency was introduced to further tune the lattice structure and the functionality of multiferroic BiFeO{sub 3}. The crystal structure of Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{sub 3} films was investigated by X-ray diffraction and Raman spectra; a rhombohedral-to-orthorhombic phase transition was revealed. The observed double hysteresis loops and two capacitance maxima from polarization vs electric field and capacitance-voltage measurements indicate an antiferroelectric-like behavior. Additionally, the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases in Bi{sub 1−δ}Fe{sub 1−x}Mn{sub x}O{submore » 3} films was revealed from the domain structures obtained by piezoelectric force microscopy. The effects of Mn substitution in conjunction with Bi deficiency on the FE-AFE phase transition and electrical behavior of BiFeO{sub 3} films are discussed in detail. Meanwhile, magnetic and photoluminescence measurements on the films illustrate that Mn substitution gives rise to the net magnetic moment and the defects induced by both Bi deficiency and Mn substitution influence the electronic structure of BiFeO{sub 3} films. This study thus shows a simple and effective way to control the functionalities of BiFeO{sub 3} films.« less

Phase transformation and magnetic properties of MnAl powders prepared by elemental-doping and salt-assisted ball milling

NASA Astrophysics Data System (ADS)

Qian, Hui-Dong; Si, Ping-Zhan; Choi, Chul-Jin; Park, Jihoon; Cho, Kyung Mox

2018-05-01

The effects of elemental doping of Si and Fe on the ɛ→τ phase transformation and the magnetic properties of MnAl were studied. The magnetic powders of Si- and Fe-doped MnAl were prepared by using induction melting followed by water-quenching, annealing, and salt-assisted ball-milling. The Fe-doped MnAl powders are mainly composed of the L10-structured τ-phase, while the Si-doped MnAl are composed of τ-phase and a small fraction of γ2- and β-phases. A unique thin leaves-like morphology with thickness of several tens of nanometers and diameter size up to 500 nm were observed in the Si-doped MnAl powders. The Fe-doped MnAl powders show irregular shape with much larger dimensions in the range from several to 10 μm. The morphology difference of the samples was ascribed to the variation of the mechanical properties affected by different doping elements. The phase transformation temperatures of the ɛ-phase of the samples were measured. The doping of Fe decreases the onset temperature of the massive phase transformation in MnAl, while the Si-doping increases the massive phase transformation temperature. Both Fe and Si increase the Curie temperature of MnAl. A substantially enhanced coercivity up to 0.45 T and 0.42 T were observed in the ball-milled MnAl powders doped with Si and Fe, respectively.

Study of the Thermodynamics of Chromium(III) and Chromium(VI) Binding to Fe3O4 and MnFe2O4 nanoparticles

PubMed Central

Luther, Steven; Brogfeld, Nathan; Kim, Jisoo; Parsons, J.G.

2013-01-01

Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4 ± 0.9 nm (Fe3O4) and 15.5 ± 0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative. PMID:23558081

Magnetic and conventional shape memory behavior of Mn-Ni-Sn and Mn-Ni-Sn(Fe) alloys

NASA Astrophysics Data System (ADS)

Turabi, A. S.; Lázpita, P.; Sasmaz, M.; Karaca, H. E.; Chernenko, V. A.

2016-05-01

Magnetic and conventional shape memory properties of Mn49Ni42Sn9(at.%) and Mn49Ni39Sn9Fe3(at.%) polycrystalline alloys exhibiting martensitic transformation from ferromagnetic austenite into weakly magnetic martensite are characterized under compressive stress and magnetic field. Magnetization difference between transforming phases drastically increases, while transformation temperature decreases with the addition of Fe. Both Mn49Ni42Sn9 and Mn49Ni39Sn9Fe3 alloys show remarkable superelastic and shape memory properties with recoverable strain of 4% and 3.5% under compression at room temperature, respectively. These characteristics can be counted as extraordinary among the polycrystalline NiMn-based magnetic shape memory alloys. Critical stress for phase transformation was increased by 34 MPa in Mn49Ni39Sn9Fe3 and 21 MPa in Mn49Ni42Sn9 at 9 T, which can be qualitatively understood in terms of thermodynamic Clausius-Clapeyron relationships and in the framework of the suggested physical concept of a volume magnetostress.

Anthropogenic sources and environmentally relevant concentrations of heavy metals in surface water of a mining district in Ghana: a multivariate statistical approach.

PubMed

Armah, Frederick A; Obiri, Samuel; Yawson, David O; Onumah, Edward E; Yengoh, Genesis T; Afrifa, Ernest K A; Odoi, Justice O

2010-11-01

The levels of heavy metals in surface water and their potential origin (natural and anthropogenic) were respectively determined and analysed for the Obuasi mining area in Ghana. Using Hawth's tool an extension in ArcGIS 9.2 software, a total of 48 water sample points in Obuasi and its environs were randomly selected for study. The magnitude of As, Cu, Mn, Fe, Pb, Hg, Zn and Cd in surface water from the sampling sites were measured by flame Atomic Absorption Spectrophotometry (AAS). Water quality parameters including conductivity, pH, total dissolved solids and turbidity were also evaluated. Principal component analysis and cluster analysis, coupled with correlation coefficient analysis, were used to identify possible sources of these heavy metals. Pearson correlation coefficients among total metal concentrations and selected water properties showed a number of strong associations. The results indicate that apart from tap water, surface water in Obuasi has elevated heavy metal concentrations, especially Hg, Pb, As, Cu and Cd, which are above the Ghana Environmental Protection Agency (GEPA) and World Health Organisation (WHO) permissible levels; clearly demonstrating anthropogenic impact. The mean heavy metal concentrations in surface water divided by the corresponding background values of surface water in Obuasi decrease in the order of Cd > Cu > As > Pb > Hg > Zn > Mn > Fe. The results also showed that Cu, Mn, Cd and Fe are largely responsible for the variations in the data, explaining 72% of total variance; while Pb, As and Hg explain only 18.7% of total variance. Three main sources of these heavy metals were identified. As originates from nature (oxidation of sulphide minerals particularly arsenopyrite-FeAsS). Pb derives from water carrying drainage from towns and mine machinery maintenance yards. Cd, Zn, Fe and Mn mainly emanate from industry sources. Hg mainly originates from artisanal small-scale mining. It cannot be said that the difference in concentration of heavy metals might be attributed to difference in proximity to mining-related activities because this is inconsistent with the cluster analysis. Based on cluster analysis SN32, SN42 and SN43 all belong to group one and are spatially similar. But the maximum Cu concentration was found in SN32 while the minimum Cu concentration was found in SN42 and SN43.

Accelerated Oxygen Atom Transfer and C-H Bond Oxygenation by Remote Redox Changes in Fe3 Mn-Iodosobenzene Adducts.

PubMed

de Ruiter, Graham; Carsch, Kurtis M; Gul, Sheraz; Chatterjee, Ruchira; Thompson, Niklas B; Takase, Michael K; Yano, Junko; Agapie, Theodor

2017-04-18

We report the synthesis, characterization, and reactivity of [LFe 3 (PhPz) 3 OMn( s PhIO)][OTf] x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene-metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, 57 Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe III 2 Fe II Mn II vs. Fe III 3 Mn II ) influence oxygen atom transfer in tetranuclear Fe 3 Mn clusters. In particular, a one-electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Secular variations of iron isotopes in ferromanganese crusts: evidences for deeply sourced iron in the Pacific Ocean?

NASA Astrophysics Data System (ADS)

Rouxel, O. J.; Gueguen, B.

2016-12-01

Ferromanganese (Fe-Mn) crusts are potential archive of the Fe isotope composition of deep seawater through time. Here, we report Fe isotope composition of two pairs of Fe-Mn crusts collected on two volcanic seamounts from the Northern Pacific Ocean (Apuupuu Seamount, Hawaii) and the Southern Pacific Ocean (near Rurutu Island, Austral archipelago of French Polynesia). This approach allows (a) a direct comparison of the Fe isotope record in Fe-Mn crusts from the same seamount in order to address local effects, and (b) a comparison of geochemical composition of crusts between North and South Pacific in order to address the effect of more global geochemical processes. The results show that, despite different growth rates, diagenetic history, textures and geochemical patterns, Fe-Mn crusts from both North and South Pacific Oceans have fairly homogenous Fe isotope compositions over the last 17 Ma, yielding average δ56Fe values of -0.22 ± 0.20‰ (1sd, n = 54). The results also show striking correlations between Fe and Pb isotope ratios, indicating that local mixing between water masses is the main factor controlling Fe isotope composition in FeMn crusts. Recently, Horner et al. (2015) reported a range of δ56Fe values from -1.12‰ to 1.54‰ along a 76 Ma-old FeMn crust from the central pacific. However, secular variations of Fe isotopes inferred from other FeMn crusts in the Central North Pacific and Western Pacific (Yang and Rouxel, unpublished) show different patterns over the last 40 Ma, with δ56Fe ranging from -0.07 to -0.61‰ (n=81). Hence, the application of Fe isotopes as paleoceanographic proxies to trace deeply sourced iron at the scale of oceanic basins should be used with caution, prompting for an integrative approach combining diverse yet complimentary geochemical proxies.

Syntheses, structures, and properties of trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)], constructed with the complexed bridging ligand [M(bpca)(2)] [M, M' = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone].

PubMed

Kamiyama, Asako; Noguchi, Tomoko; Kajiwara, Takashi; Ito, Tasuku

2002-02-11

Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.

Levels and predictors of airborne and internal exposure to manganese and iron among welders.

PubMed

Pesch, Beate; Weiss, Tobias; Kendzia, Benjamin; Henry, Jana; Lehnert, Martin; Lotz, Anne; Heinze, Evelyn; Käfferlein, Heiko Udo; Van Gelder, Rainer; Berges, Markus; Hahn, Jens-Uwe; Mattenklott, Markus; Punkenburg, Ewald; Hartwig, Andrea; Brüning, Thomas

2012-01-01

We investigated airborne and internal exposure to manganese (Mn) and iron (Fe) among welders. Personal sampling of welding fumes was carried out in 241 welders during a shift. Metals were determined by inductively coupled plasma mass spectrometry. Mn in blood (MnB) was analyzed by graphite furnace atom absorption spectrometry. Determinants of exposure levels were estimated with multiple regression models. Respirable Mn was measured with a median of 62 (inter-quartile range (IQR) 8.4-320) μg/m(3) and correlated with Fe (r=0.92, 95% CI 0.90-0.94). Inhalable Mn was measured with similar concentrations (IQR 10-340 μg/m(3)). About 70% of the variance of Mn and Fe could be explained, mainly by the welding process. Ventilation decreased exposure to Fe and Mn significantly. Median concentrations of MnB and serum ferritin (SF) were 10.30 μg/l (IQR 8.33-13.15 μg/l) and 131 μg/l (IQR 76-240 μg/l), respectively. Few welders were presented with low iron stores, and MnB and SF were not correlated (r=0.07, 95% CI -0.05 to 0.20). Regression models revealed a significant association of the parent metal with MnB and SF, but a low fraction of variance was explained by exposure-related factors. Mn is mainly respirable in welding fumes. Airborne Mn and Fe influenced MnB and SF, respectively, in welders. This indicates an effect on the biological regulation of both metals. Mn and Fe were strongly correlated, whereas MnB and SF were not, likely due to higher iron stores among welders.

Molybdenum isotopes in modern marine hydrothermal Fe/Mn deposits: Implications for Archean and Paleoproterozoic Mo cycles

NASA Astrophysics Data System (ADS)

Goto, K. T.; Hein, J. R.; Shimoda, G.; Aoki, S.; Ishikawa, A.; Suzuki, K.; Gordon, G. W.; Anbar, A. D.

2016-12-01

Molybdenum isotope (δ98/95Mo) variations recorded in Archean and Paleoproterozoic Fe/Mn-rich sediments have been used to constrain ocean redox conditions at the time of deposition (Canfield et al., 2013 PNAS; Planavsky et al., 2014 Nat. Geo.; Kurzweil et al., 2015 GCA). However, except for hydrogenous Fe-Mn crusts (Siebert et al., 2003), δ98/95Mo variation of modern Fe and Mn oxide deposits has been poorly investigated. Marine hydrothermal systems are thought to be the major source of Fe and Mn in Archean and Paleoproterozoic Fe- and Mn-rich sediments. Hence, to accurately interpret Mo isotope data of those ancient sedimentary rocks, it is important to evaluate the possible influence of hydrothermally derived Mo on δ98/95Mo of modern Fe- and Mn-rich sediments. In this study, we analyzed Mo isotopic compositions of one hydrothermal Fe oxide and 15 Mn oxides from five different hydrothermal systems in the modern ocean. The Fe oxide is composed mainly of goethite, and has a δ98/95Mo of 0.7‰, which is 1.4‰ lighter than that of present-day seawater. The observed offset is similar to isotope fractionation observed during adsorption experiments of Mo on goethite (Δ98/95Mogoethite-solution = -1.4 ± 0.5%; Goldberg et al., 2009 GCA). The 15 hydrothermal Mn oxides show large variations in δ98/95Mo ranging from -1.7 to 0.5‰. However, most of the values are similar to those of modern hydrogenous Fe-Mn crusts (Siebert et al., 2003 EPSL), and fall within the range of estimated δ98/95Mo of Mn oxides precipitated from present-day seawater using the isotope offset reported from adsorption experiments (Δ98/95Mo = -2.7 ± 0.3‰; Wasylenki et al., 2008 GCA). These findings indicate that seawater is the dominant source of Mo for modern hydrothermal Fe and Mn deposits. However, the observed large variation indicates that the contribution Mo from local hydrothermal systems is not negligible. The oceanic Mo inventory during the Archean and Paleoproterozoic is thought to be much smaller than that of present-day (Scott et al., 2008 Nature). Hence, δ98/95Mo of Archean and Paleoproterozoic Fe- and Mn-rich sediments could be strongly influenced by hydrothermally derived Mo, which may contrast to modern hydrothermal deposits. Possible Archean and Paleoproterozoic Mo cycles constrained by these data will also be discussed.

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.

MnFe{sub 2}O{sub 4} as a gas sensor towards SO{sub 2} and NO{sub 2} gases

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

Rathore, Deepshikha, E-mail: deep.nano@gmail.com; Mitra, Supratim

2016-05-06

The chemical co-precipitation method was used to synthesize MnFe{sub 2}O{sub 4} nanoparticles. Single cubic phase formation of nanoparticles was confirmed by X-ray diffraction technique. The average particle size of MnFe{sub 2}O{sub 4} nanoparticles was found to be 10.7 nm using Scherrer formula. The ultrafine powder of MnFe{sub 2}O{sub 4} nanoparticles was pressed to design pellet of 10 mm diameter and 1mm thickness. Copper electrodes have been deposited on the surface of pellet using silver paste in the form of capacitor. Fabricated gas sensing device of MnFe{sub 2}O{sub 4} nanoparticles was tested towards SO{sub 2} and NO{sub 2} gases. Cole-Cole plot of MnFe{submore » 2}O{sub 4} was investigated with the help of electrochemical workstation. The performance of the sensors including sensitivity, response and recovery time was also determined. It was observed that the MnFe{sub 2}O{sub 4} nanoparticles are more sensible for NO{sub 2} gas as compared to SO{sub 2} gas.« less

Synthesis and characterization of polymer-coated manganese ferrite nanoparticles as controlled drug delivery

NASA Astrophysics Data System (ADS)

Wang, Guangshuo; Zhao, Dexing; Ma, Yingying; Zhang, Zhixiao; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Zhang, Zheng

2018-01-01

In this study, monodisperse and superparamagnetic manganese ferrite (MnFe2O4) nanoparticles have been synthesized by a one-pot sonochemical method using polyvinylpyrrolidone (PVP) as stabilizer. The as-prepared MnFe2O4 nanoparticles were investigated systematically by TEM, XRD, FTIR, XPS, SQUID and MTT. The TEM observation showed that the PVP-coated MnFe2O4 nanoparticles had uniform dispersion with narrow particle size distribution. The magnetization curves demonstrated superparamagnetic properties of the coated MnFe2O4 nanoparticles with good hydrophilicity at room temperature. The in vitro cytotoxicity experiments exhibited negligible cytotoxicity of the obtained PVP-coated MnFe2O4 nanoparticles even at the high concentration of 150 μg/mL after 24 h treatment. More importantly, anti-cancer model drug of doxorubicin hydrochloride (DOX) was loaded on the surface of MnFe2O4 nanoparticles. The drug loading capacity of the developed nanocarrier reached 0.45 mg/mg and the loaded DOX exhibited interesting pH-dependent release behavior. In conclusion, the as-prepared PVP-coated MnFe2O4 nanoparticles were proposed as a potential candidate for controlled drug delivery.

Mössbauer studies of a martensitic transformation and of cryogenic treatments of a D2 tool steel

NASA Astrophysics Data System (ADS)

Costa, B. F. O.; Blumers, M.; Kortmann, A.; Theisen, W.; Batista, A. C.; Klingelhöfer, G.

2013-04-01

A D2 tool steel X153CrVMo12 with composition C1.53 Cr12 V0.95 Mo0.80 Mn0.40(wt% Fe balanced) was studied by use of Mössbauer spectroscopy and X-ray diffraction. It was observed that the study of carbides by X-ray diffraction was difficult while Mössbauer spectroscopy gives some light on the process occurring during cryogenic treatment. With the increase of the martensitic phase the carbides decrease and are dissolved in solid solution of martensite as well as the chromium element.

Dominance of cyanobacterial and cryptophytic assemblage correlated to CDOM at heavy metal contamination sites of Gujarat, India.

PubMed

Patidar, Shailesh Kumar; Chokshi, Kaumeel; George, Basil; Bhattacharya, Sourish; Mishra, Sandhya

2015-01-01

Industrial clusters of Gujarat, India, generate high quantity of effluents which are received by aquatic bodies such as estuary and coastal water. In the present study, microalgal assemblage, heavy metals, and physico-chemical variables were studied from different habitats. Principal component analysis revealed that biovolume of cyanobacterial and cryptophytic community positively correlated with the heavy metal concentration (Hg, As, Zn, Fe, Mo, Ni, and Co) and chromophoric dissolved organic matter (CDOM) under hypoxic environment. Green algae and diatoms dominated at comparatively lower nitrate concentration which was positively associated with Pb and Mn.

Enhancement of exchange coupling interaction of NdFeB/MnBi hybrid magnets

NASA Astrophysics Data System (ADS)

Nguyen, Truong Xuan; Nguyen, Khanh Van; Nguyen, Vuong Van

2018-03-01

MnBi ribbons were fabricated by melt - spinning with subsequent annealing. The MnBi ribbons were ground and mixed with NdFeB commercial Magnequench powders (MQA). The hybrid powder mixtures were subjected thrice to the annealing and ball-milling route. The hybrid magnets (100 - x)NdFeB/xMnBi, x=0, 30, 40, 50 and 100 wt% were in-mold aligned in an 18 kOe magnetic field and warm compacted at 290 °C by 2000 psi uniaxial pressure for 10 min. An enhancement of the exchange coupling of NdFeB/MnBi hybrid magnets was obtained by optimizing the magnets' microstructures via annealing and ball-milling processes. The magnetic properties of prepared NdFeB/MnBi hybrid magnets were studied and discussed in details.

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

Chu, Heng-Hsuan; Car, Suzana; Socha, Amanda L.

Understanding how seeds obtain and store nutrients is key to developing crops with higher agronomic and nutritional value. We have uncovered unique patterns of micronutrient localization in seeds using synchrotron X-ray fluorescence (SXRF). Although all four members of the Arabidopsis thaliana Mn-CDF family can transport Mn, here we show that only mtp8-2 has an altered Mn distribution pattern in seeds. In an mtp8-2 mutant, Mn no longer accumulates in hypocotyl cortex cells and sub-epidermal cells of the embryonic cotyledons, but rather accumulates with Fe in the cells surrounding the vasculature, a pattern previously shown to be determined by the vacuolarmore » transporter VIT1. We also show that MTP8, unlike the other three Mn-CDF family members, can transport Fe and is responsible for localization of Fe to the same cells that store Mn. When both the VIT1 and MTP8 transporters are non-functional, there is no accumulation of Fe or Mn in specific cell types; rather these elements are distributed amongst all cell types in the seed. Finally, disruption of the putative Fe binding sites in MTP8 resulted in loss of ability to transport Fe but did not affect the ability to transport Mn.« less

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

Chu, Heng-Hsuan; Car, Suzana; Socha, Amanda L.

Understanding how seeds obtain and store nutrients is key to developing crops with higher agronomic and nutritional value. We have uncovered unique patterns of micronutrient localization in seeds using synchrotron X-ray fluorescence (SXRF). Although all four members of the Arabidopsis thaliana Mn-CDF family can transport Mn, here we show that only mtp8-2 has an altered Mn distribution pattern in seeds. In an mtp8-2 mutant, Mn no longer accumulates in hypocotyl cortex cells and sub-epidermal cells of the embryonic cotyledons, but rather accumulates with Fe in the cells surrounding the vasculature, a pattern previously shown to be determined by the vacuolarmore » transporter VIT1. We also show that MTP8, unlike the other three Mn-CDF family members, can transport Fe and is responsible for localization of Fe to the same cells that store Mn. When both the VIT1 and MTP8 transporters are non-functional, there is no accumulation of Fe or Mn in specific cell types; rather these elements are distributed amongst all cell types in the seed. Disruption of the putative Fe binding sites in MTP8 resulted in loss of ability to transport Fe but did not affect the ability to transport Mn.« less

Origin of middle rare earth element enrichments in acid waters of a Canadian high Arctic lake.

NASA Astrophysics Data System (ADS)

Johannesson, Kevin H.; Zhou, Xiaoping

1999-01-01

-Middle rare earth element (MREE) enriched rock-normalized rare earth element (REE) patterns of a dilute acidic lake (Colour Lake) in the Canadian High Arctic, were investigated by quantifying whole-rock REE concentrations of rock samples collected from the catchment basin, as well as determining the acid leachable REE fraction of these rocks. An aliquot of each rock sample was leached with 1 N HNO 3 to examine the readily leachable REE fraction of each rock, and an additional aliquot was leached with a 0.04 M NH 2OH · HCl in 25% (v/v) CH 3COOH solution, designed specifically to reduce Fe-Mn oxides/oxyhydroxides. Rare earth elements associated with the leachates that reacted with clastic sedimentary rock samples containing petrographically identifiable Fe-Mn oxide/oxyhydroxide cements and/or minerals/amorphous phases, exhibited whole-rock-normalized REE patterns similar to the lake waters, whereas whole-rock-normalized leachates from mafic igneous rocks and other clastic sedimentary rocks from the catchment basin differed substantially from the lake waters. The whole-rock, leachates, and lake water REE data support acid leaching or dissolution of MREE enriched Fe-Mn oxides/oxyhydroxides contained and identified within some of the catchment basin sedimentary rocks as the likely source of the unique lake water REE patterns. Solution complexation modelling of the REEs in the inflow streams and lake waters indicate that free metal ions (e.g., Ln 3+, where Ln = any REE) and sulfate complexes (LnSO 4+) are the dominant forms of dissolved REEs. Consequently, solution complexation reactions involving the REEs during weathering, transport to the lake, or within the lake, cannot be invoked to explain the MREE enrichments observed in the lake waters.

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).

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.

Iron, manganese and phosphorus partitioning during high flow events: impacts of land cover and seasonality

NASA Astrophysics Data System (ADS)

Schroth, A. W.

2015-12-01

Metals and phosphorous are essential micro and macronutrients in aquatic ecosystems, and redox sensitive colloidal and particulate metal (oxy)hydroxide phases can be particularly reactive carriers of solid phase P, as well as other nutrients and/or pollutants in riverine chemical loads. High flow events driven by storms and/or snow or glacial melt often dominate the annual load of such constituents, yet remain poorly understood from a biogeochemical perspective. Our research examines the biogeochemical nature of riverine metal and P loads during targeted high flow events to determine to what extent, and under what environmental conditions, are the concentration and biogeochemical composition of riverine loads of P, Fe, and Mn disproportionately high and relatively reactive v. inert. We present a suite of biogeochemical data derived from water and suspended sediment samples that were collected during these events in multiple catchments and over different seasons within the hydrologic year. We examine the size partitioning (particulate, colloidal, 'truly dissolved') of riverine Fe, Mn, and P during events in glaciated, boreal-forested, and agriculturalized catchments of Vermont and Alaska. Suspended sediment loads are also characterized by relative redox sensitivity to examine the potential reactivity of Fe, Mn, and P in sediment transported during particular events. We demonstrate that metal and P concentration, size partitioning, and redox sensitivity differs both seasonally and by land cover, which is due to different source environments and flow paths that are preferentially activated during high discharge. The conceptual model herein developed is critical to understanding the biogeochemical nature of event-based riverine loads, and how this could evolve with changing frequency and severity of high flow events or land cover associated with climate change and landscape management.

The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

NASA Technical Reports Server (NTRS)

Schuon, S. R.

1982-01-01

The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

Electrical control of antiferromagnetic metal up to 15 nm

NASA Astrophysics Data System (ADS)

Zhang, PengXiang; Yin, GuFan; Wang, YuYan; Cui, Bin; Pan, Feng; Song, Cheng

2016-08-01

Manipulation of antiferromagnetic (AFM) spins by electrical means is on great demand to develop the AFM spintronics with low power consumption. Here we report a reversible electrical control of antiferromagnetic moments of FeMn up to 15 nm, using an ionic liquid to exert a substantial electric-field effect. The manipulation is demonstrated by the modulation of exchange spring in [Co/Pt]/FeMn system, where AFM moments in FeMn pin the magnetization rotation of Co/Pt. By carrier injection or extraction, the magnetic anisotropy of the top layer in FeMn is modulated to influence the whole exchange spring and then passes its influence to the [Co/Pt]/FeMn interface, through a distance up to the length of exchange spring that fully screens electric field. Comparing FeMn to IrMn, despite the opposite dependence of exchange bias on gate voltages, the same correlation between carrier density and exchange spring stiffness is demonstrated. Besides the fundamental significance of modulating the spin structures in metallic AFM via all-electrical fashion, the present finding would advance the development of low-power-consumption AFM spintronics.

Interfacial magnetic coupling in hetero-structure of Fe/double-perovskite NdBaMn2O6 single crystal

NASA Astrophysics Data System (ADS)

Lin, W. C.; Tsai, C. L.; Ogawa, K.; Yamada, S.; Gandhi, Ashish C.; Lin, J. G.

2018-04-01

The interfacial magnetic coupling between metallic Fe and the double-perovskite NdBaMn2O6 single crystal was investigated in the heterostructure of 4-nm Pd/10-nm Fe/NdBaMn2O6. A considerable magnetic coupling effect was observed in the temperature range coincident with the magnetic phase transition of NdBaMn2O6. When the temperature was elevated above 270 K, NdBaMn2O6 transformed from a state of antiferromagnetic fluctuating domains to a superparamagnetism-like (ferromagnetic fluctuation) state with high magnetic susceptibility. Concurrently, the interfacial magnetic coupling between the Fe layer and the NdBaMn2O6 crystal was observed, as indicated by the considerable squareness reduction and coercivity enhancement in the Fe layer. Moreover, the presence of the Fe layer changed the magnetic structure of NdBaMn2O6 from conventional 4-fold symmetry to 2-fold symmetry. These observations offer applicable insights into the mutual magnetic interaction in the heterostructures of metallic ferromagnetism/perovskite materials.

Synthesis of α-Fe₂O₃ and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates.

PubMed

Feng, Yuping; Fornell, Jordina; Zhang, Huiyan; Solsona, Pau; Barό, Maria Dolors; Suriñach, Santiago; Pellicer, Eva; Sort, Jordi

2018-02-11

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N₂ atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe₂O₃) foams are obtained from the metallic iron slurry independently of the N₂ flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N₂ flow. While the main phases for a N₂ flow rate of 180 L/h are α-Fe₂O₃ and FeMnO₃, the predominant phase for high N₂ flow rates (e.g., 650 L/h) is Fe₂MnO₄. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe₂MnO₄ foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N₂ flow rate (i.e., the amount of Fe₂MnO₄) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids.

Magnetic structure of the mixed antiferromagnet NdMn 0.8 Fe 0.2 O 3

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

Mihalik, Matus; Mihalik, Marian; Hoser, Andreas

The magnetic structure of the mixed antiferromagnet NdMn 0.8Fe 0.2O 3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k=(000) and with the magnetic structure (A x, F y, G z) for 1.6 K N(≈ 59 K). The Nd sublattice has a (0, f y, 0) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T 1 ≈ 13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at T N but no additional structural phase transitionsmore » from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO 3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn 0.8Fe 0.2O 3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO 3 and NdFeO 3. Lastly, this result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.« less

Magnetic structure of the mixed antiferromagnet NdMn 0.8 Fe 0.2 O 3

DOE PAGES

Mihalik, Matus; Mihalik, Marian; Hoser, Andreas; ...

2017-10-27

The magnetic structure of the mixed antiferromagnet NdMn 0.8Fe 0.2O 3 was resolved. Neutron powder diffraction data definitively resolve the Mn sublattice with a magnetic propagation vector k=(000) and with the magnetic structure (A x, F y, G z) for 1.6 K N(≈ 59 K). The Nd sublattice has a (0, f y, 0) contribution in the same temperature interval. The Mn sublattice undergoes a spin-reorientation transition at T 1 ≈ 13 K while the Nd magnetic moment abruptly increases at this temperature. Powder x-ray diffraction shows a strong magnetoelastic effect at T N but no additional structural phase transitionsmore » from 3 to 300 K. Density functional theory calculations confirm the magnetic structure of the undoped NdMnO 3 as part of our analysis. Taken together, these results show that the magnetic structure of the Mn sublattice in NdMn 0.8Fe 0.2O 3 is a combination of the Mn and Fe parent compounds, but the magnetic ordering of the Nd sublattice spans a broader temperature interval than in the case of NdMnO 3 and NdFeO 3. Lastly, this result is a consequence of the fact that the Nd ions do not order independently, but via polarization from the Mn/Fe sublattice.« less

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.

Influence of depositional environment in fossil teeth: a micro-XRF and XAFS study

NASA Astrophysics Data System (ADS)

Zougrou, I. M.; Katsikini, M.; Pinakidou, F.; Papadopoulou, L.; Tsoukala, E.; Paloura, E. C.

2014-04-01

The formation of metal-rich phases during the fossilization of vertebrate fossil teeth, recovered from various deposition environments in northern Greece, is studied by means of synchrotron radiation X-ray fluorescence (SR-XRF) as well as Fe and Mn K edge X-ray absorption fine structure (XAFS) spectroscopy. XRF line-scans from the samples' cross-sections revealed different contamination paths for Mn and Fe. The two-dimensional XRF maps illustrate the spatial distribution of P, Ca, Mn and Fe as well as the precipitation of Fe-rich phases in cementum, dentin and dentinal tubules. Goethite, lepidocrocite and ferrihydrite were detected in the samples' cross-section by means of Fe K edge EXAFS spectroscopy. Moreover the Fe and Mn K edge EXAFS revealed the presence of vivianite and birnessite (MnO2) on the external surface of two samples.

Constraints on the utility of MnO2 cartridge method for the extraction of radionuclides: A case study using 234Th

USGS Publications Warehouse

Baskaran, M.; Swarzenski, P.W.; Biddanda, B.A.

2009-01-01

[1] Large volume (102-103 L) seawater samples are routinely processed to investigate the partitioning of particle reactive radionuclides and Ra between solution and size-fractionated suspended particulate matter. One of the most frequently used methods to preconcentrate these nuclides from such large volumes involves extraction onto three filter cartridges (a prefilter for particulate species and two MnO2-coated filters for dissolved species) connected in series. This method assumes that the extraction efficiency is uniform for both MnO2-coated cartridges, that no dissolved species are removed by the prefilter, and that any adsorbed radionuclides are not desorbed from the MnO2-coated cartridges during filtration. In this study, we utilized 234Th-spiked coastal seawater and deionized water to address the removal of dissolved Th onto prefilters and MnO2-coated filter cartridges. Experimental results provide the first data that indicate (1) a small fraction of dissolved Th (<6%) can be removed by the prefilter cartridge; (2) a small fraction of dissolved Th (<5%) retained by the MnO2 surface can also be desorbed, which undermines the assumption of uniform extraction efficiency for Th; and (3) the absolute and relative extraction efficiencies can vary widely. These experiments provide insight on the variability of the extraction efficiency of MnO 2-coated filter cartridges by comparing the relative and absolute efficiencies and recommend the use of a constant efficiency on the combined activity from two filter cartridges connected in series for future studies of dissolved 234Th and other radionuclides in natural waters using sequential filtration/extraction methods. ?? 2009 by the American Geophysical Union.

Morphology-controlled synthesis and novel microwave electromagnetic properties of hollow urchin-like chain Fe-doped MnO 2 under 10 T high magnetic field

NASA Astrophysics Data System (ADS)

Yuping, Duan; Jia, Zhang; Hui, Jing; Shunhua, Liu

2011-05-01

Fe-doped MnO 2 with a hollow sea urchin-like ball chain shape was first synthesized under a high magnetic field of 10 T. The formation mechanism was investigated and discussed in detail. The synthesized samples were characterized by XRD, SEM, TEM, EMPA, and vector network analysis. By doping MnO 2 with Fe, the relative complex permittivity of MnO 2 and its corresponding loss tangent clearly decreases, but its relative complex permeability and its corresponding loss tangent markedly increases. Moreover, the theoretically calculated values of reflection loss show that with increasing the Fe content, the as-prepared Fe-doped MnO 2 exhibits good microwave absorption capability.

Geochemical Constraints on Core-Mantle Interaction from Fe/Mn Ratios

NASA Astrophysics Data System (ADS)

Humayun, M.; Qin, L.

2003-12-01

The greater density of liquid iron alloy, and its immiscibility with silicate, maintains the physical separation of the core from the mantle. There are no a priori reasons, however, why the Earth's mantle should be chemically isolated from the core. Osmium isotopic variations in mantle plumes have been interpreted in terms of interaction between outer core and the source regions of deep mantle plumes. If chemical transport occurs across the core-mantle boundary its mechanism remains to be established. The Os isotope evidence has also been interpreted as the signatures of subducted Mn-sediments, which are known to have relatively high Pt/Os. In the mantle, Fe occurs mainly as the divalent ferrous ion, and Mn occurs solely as a divalent ion, and both behave in a geochemically coherent manner because of similarity in ionic charge and radius. Thus, the Fe/Mn ratio is a planetary constant insensitive to processes of mantle differentiation by partial melting. Two processes may perturb the ambient mantle Fe/Mn of 60: a) the subduction of Mn-sediments should decrease the Fe/Mn ratio in plume sources, while b) chemical transport from the outer core may increase the Fe/Mn ratio. The differentiation of the liquid outer core to form the solid inner core may increase abundances of the light element constituents (FeS, FeO, etc.) to the point of exsolution from the core at the CMB. The exact rate of this process is determined by the rate of inner core growth. Two end-member models include 1) inner core formation mainly prior to 3.5 Ga with heat release dominated by radioactive sources, or 2) inner core formation occurring mainly in the last 1.5 Ga with heat release dominated by latent heat. This latter model would imply large fluxes of Fe into the sources of modern mantle plumes. Existing Fe/Mn data for Gorgona and Hawaiian samples place limits on both these processes. We describe a new procedure for the precise determination of the Fe/Mn ratio in magmatic rocks by ICP-MS. This high-resolution study of the Fe/Mn of mantle-derived samples offers a new set of chemical constraints on the rates of inner core differentiation and the viability of Os isotope interpretations.

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.

Catalytic conversion of syngas to mixed alcohols over Zn-Mn promoted Cu-Fe based catalyst

DOE PAGES

Lu, Yongwu; Yu, Fei; Hu, Jin; ...

2012-04-12

Zn-Mn promoted Cu-Fe based catalyst was synthesized by the co-precipitation method. Mixed alcohols synthesis from syngas was studied in a half-inch tubular reactor system after the catalyst was reduced. Zn-Mn promoted Cu-Fe based catalyst was characterized by SEM-EDS, TEM, XRD, and XPS. The liquid phase products (alcohol phase and hydrocarbon phase) were analyzed by GC-MS and the gas phase products were analyzed by GC. The results showed that Zn-Mn promoted Cu-Fe based catalyst had high catalytic activity and high alcohol selectivity. The maximal CO conversion rate was 72%, and the yield of alcohol and hydrocarbons were also very high. Cumore » (111) was the active site for mixed alcohols synthesis, Fe 2C (101) was the active site for olefin and paraffin synthesis. The reaction mechanism of mixed alcohols synthesis from syngas over Zn-Mn promoted Cu-Fe based catalyst was proposed. Here, Zn-Mn promoted Cu-Fe based catalyst can be regarded as a potential candidate for catalytic conversion of biomass-derived syngas to mixed alcohols.« less

Vapor-Liquid Partitioning of Iron and Manganese in Hydrothermal Fluids: An Experimental Investigation with Application to the Integrated Study of Basalt-hosted Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Pester, N. J.; Seyfried, W. E.

2010-12-01

The chemistry of deep-sea hydrothermal vent fluids, expressed at the seafloor, reflects a complex history of physicochemical reactions. After three decades of field and experimental investigations, the processes of fluid-mineral equilibria that transform seawater into that of a typical “black smoker” are generally well described in the literature. Deep crustal fluids, when encountering a given heat source that ultimately drives hydrothermal circulation, routinely intersect the two-phase boundary. This process results in the nearly ubiquitous observations of variable salinity in vent fluids and is often a secondary driver of circulation via the evolution of a more buoyant (i.e. less saline) phase. Phase separation in chemically complex fluids results in the partitioning of dissolved species between the two evolved phases that deviates from simple charge balance calculations and these effects become more prominent with increasing temperature and/or decreasing pressure along the two-phase envelope. This process of partitioning has not been extensively studied and the interplay between the effects of phase separation and fluid-mineral equilibrium are not well understood. Most basalt-hosted hydrothermal systems appear to enter a steady state mode wherein fluids approach the heat source at depth and rise immediately once the two-phase boundary is met. Thus, venting fluids exhibit only modest deviations from seawater bulk salinity and the effects of partitioning are likely minor for all but the most volatile elements. Time series observations at integrated study sites, however, demonstrate dynamic changes in fluid chemistry following eruptions/magmatic events, including order of magnitude increases in gas concentrations and unexpectedly high Fe/Cl ratios. In this case, the time dependence of vapor-liquid partitioning relative to fluid-mineral equilibrium must be considered when attempting to interpret changes in subsurface reaction conditions. The two-phase region of vent fluids (as modeled by the NaCl-H2O system) represents challenging experimental conditions due to the extreme sensitivity to pressure and temperature. Using a novel flow through system that allows pressure and temperature to be controlled within 0.5 bars and 1°C, respectively, we have derived vapor-liquid partition coefficients for several species, including Fe and Mn. Divalent cations partition more drastically into the liquid phase than monovalent species and the demonstrated temperature sensitivity of equilibrium Fe/Mn ratios in basalt alteration experiments make these two elements excellent candidates when attempting to interpret time series changes in the aftermath of eruptions. Our experiments demonstrate that with decreasing vapor salinity, the Fe/Mn ratio can effectively double, relative to the bulk fluid composition, as the vapors approach the extremely low dissolved Cl concentrations observed at both EPR, 9°N and Main Endeavour, JdFR. Our results suggest that phase separation can easily account for the observed deviation from apparent Fe-Mn equilibrium in these fluids and further suggests that it may take more than a year for these hydrothermal systems to return to steady state.

Time-Resolved Investigations of Heterobimetallic Cofactor Assembly in R2lox Reveal Distinct Mn/Fe Intermediates.

PubMed

Miller, Effie K; Trivelas, Nicholas E; Maugeri, Pearson T; Blaesi, Elizabeth J; Shafaat, Hannah S

2017-07-05

The assembly mechanism of the Mn/Fe ligand-binding oxidases (R2lox), a family of proteins that are homologous to the nonheme diiron carboxylate enzymes, has been investigated using time-resolved techniques. Multiple heterobimetallic intermediates that exhibit unique spectral features, including visible absorption bands and exceptionally broad electron paramagnetic resonance signatures, are observed through optical and magnetic resonance spectroscopies. On the basis of comparison to known diiron species and model compounds, the spectra have been attributed to (μ-peroxo)-Mn III /Fe III and high-valent Mn/Fe species. Global spectral analysis coupled with isotopic substitution and kinetic modeling reveals elementary rate constants for the assembly of Mn/Fe R2lox under aerobic conditions. A complete reaction mechanism for cofactor maturation that is consistent with experimental data has been developed. These results suggest that the Mn/Fe cofactor can perform direct C-H bond abstraction, demonstrating the potential for potent chemical reactivity that remains unexplored.

Speciation analysis of Mn(II)/Mn(VII) using Fe3O4@ionic liquids-β-cyclodextrin polymer magnetic solid phase extraction coupled with ICP-OES.

PubMed

Chen, Songqing; Qin, Xingxiu; Gu, Weixi; Zhu, Xiashi

2016-12-01

Ionic liquids-β-cyclodextrin polymer (ILs-β-CDCP) was attached on Fe 3 O 4 nanoparticles to prepare magnetic solid phase extraction agent (Fe 3 O 4 @ILs-β-CDCP). The properties and morphology of Fe 3 O 4 @ILs-β-CDCP were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction(XRD), size distribution and magnetic analysis. A new method of magnetic solid phase extraction (MSPE) coupled to ICP-OES for the speciation of Mn(II)/Mn(VII) in water samples was established. The results showed that Mn(VII) and total manganese [Mn(II)+Mn(VII)] were quantitatively extracted after adjusting aqueous sample solution to pH 6.0 and 10.0, respectively. Mn(II) was calculated by subtraction of Mn(VII) from total manganese. Fe 3 O 4 @ILs-β-CDCP showed a higher adsorption capacity toward Mn(II) and Mn(VII). Several factors, such as the pH value, extraction temperature and sample volume, were optimized to achieve the best extraction efficiency. Moreover, the adsorption ability of Fe 3 O 4 @ILs-β-CDCP would not be significantly lower after reusing of 10 times. The accuracy of the developed method was confirmed by analyzing certified reference materials (GSB 07-1189-2000), and by spiking spring water, city water and lake water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

A study of cytocompatibility and degradation of iron-based biodegradable materials.

PubMed

Oriňaková, Renáta; Oriňak, Andrej; Giretová, Mária; Medvecký, L'ubomír; Kupková, Miriam; Hrubovčáková, Monika; Maskal'ová, Iveta; Macko, Ján; Kal'avský, František

2016-02-01

Biodegradable metallic implants are of significant importance in the replacement of bones or the repair of bone defects. Iron-phosphate-coated carbonyl iron powder (Fe/P) was prepared by the phosphating method. Moreover, Fe/P-Mn alloy was produced by sintering the Fe/P powder mixed with manganese powder. Bare carbonyl iron samples and the Fe/P and Fe/P-Mn sintered samples were evaluated for their microstructure, cytotoxicity, and hemocompatibility. The microstructure of the sintered samples was examined using an optical microscope and scanning electron microscopic analysis. Corrosion behavior was evaluated by potentiodynamic polarization in Hank's solution. The in vitro biocompatibilities were investigated by cytotoxicity and hemolysis tests. The results obtained demonstrate that the addition of Mn resulted in higher surface inhomogeneity, porosity and roughness as well as in increased cytotoxicity. The phosphate coating has a moderately negative effect on the cytotoxicity. The corrosion rates determined from Tafel diagrams were ordered in the following sequence: Fe/P-Mn, Fe, Fe/P from high to low. The hemocompatibility of experimental samples was ordered in the following sequence: Fe/P, Fe/P-Mn, Fe from high to low. All samples were found to be hemocompatible. © The Author(s) 2015.

Reduction of Mn-oxides by ferrous iron in a flow system: column experiment and reactive transport modeling

NASA Astrophysics Data System (ADS)

Postma, D.; Appelo, C. A. J.

2000-04-01

The reduction of Mn-oxide by Fe2+ was studied in column experiments, using a column filled with natural Mn-oxide coated sand. Analysis of the Mn-oxide indicated the presence of both Mn(III) and Mn(IV) in the Mn-oxide. The initial exchange capacity of the column was determined by displacement of adsorbed Ca2+ with Mg2+. Subsequently a FeCl2 solution was injected into the column causing the reduction of the Mn-oxide and the precipitation of Fe(OH)3. Finally the exchange capacity of the column containing newly formed Fe(OH)3 was determined by injection of a KBr solution. During injection of the FeCl2 solution into the column, an ion distribution pattern was observed in the effluent that suggests the formation of separate reaction fronts for Mn(III)-oxide and Mn(IV)-oxide travelling at different velocities through the column. At the proximal reaction front, Fe2+ reacts with MnO2 producing Fe(OH)3, Mn2+ and H+. The protons are transported downstream and cause the disproportionation of MnOOH at a separate reaction front. Between the two Mn reaction fronts, the dissolution and precipitation of Fe(OH)3 and Al(OH)3 act as proton buffers. Reactive transport modeling, using the code PHREEQC 2.0, was done to quantify and analyze the reaction controls and the coupling between transport and chemical processes. A model containing only mineral equilibria constraints for birnessite, manganite, gibbsite, and ferrihydrite, was able to explain the overall reaction pattern with the sequential appearance of Mn2+, Al3+, Fe3+, and Fe2+ in the column outlet solution. However, the initial breakthrough of a peak of Ca2+ and the observed pH buffering indicated that exchange processes were of importance as well. The amount of potential exchangers, such as birnessite and ferrihydrite, did vary in the course of the experiment. A model containing surface complexation coupled to varying concentrations of birnessite and ferrihydrite and a constant charge exchanger in addition to mineral equilibria provided a satisfactory description of the distribution of all solutes in time and space. However, the observed concentration profiles are more gradual than indicated by the equilibrium model. Reaction kinetics for the dissolution of MnO2 and MnOOH and dissolution of Al(OH)3 were incorporated in the model, which explained the shape of the breakthrough curves satisfactorily. The results of this study emphasize the importance of understanding the interplay between chemical reactions and transport in addition to interactions between redox, proton buffering, and adsorption processes when dealing with natural sediments. Reactive transport modeling is a powerful tool to analyze and quantify such interactions.

Trace-Element Evidence for an Aqueous Atmospheric Origin of Desert Varnish: implications for the aqueous atmospheric input flux into the ocean

NASA Astrophysics Data System (ADS)

Thiagarajan, N.; Lee, C.

2003-12-01

Desert varnish is a slow-growing dark patina commonly found on rock surfaces in arid environments. Varnishes consist of about 30% Mn and Fe oxides accompanied by oxides of Si, Al, Mg, K and Ca, which occur primarily in the form of clays. Although it is generally agreed that varnishes have an atmospheric origin, their exact formation mechanism remains highly debated. Two endmember hypotheses are gradual accumulation of wind-blown dust followed by diagenesis, and direct chemical precipitation of dissolved elements from atmospheric aerosols. To rule out one of these hypotheses, we investigated the trace-element systematics of varnishes, in particular, focusing on those elements that have contrasting solubilities in aqueous environments. If our trace element analyses are consistent with the varnishes being derived from dissolved atmospheric constituents then the data can be used to quantify the paleofluxes of the soluble fraction of atmospheric aerosols to various depositional environments. For example, this will have implications for the transport of metals to the ocean that are immediately biologically available. We collected varnishes deposited on smooth basaltic lava flow surfaces in the Cima Volcanic Field (Mojave Desert) and in Death Valley, California. The chosen lava flows retain original flow surface structure and are topographical highs; the effects of erosion are hence minimal. Varnishes were scraped off with a quartz rod to minimize trace element contamination and the trace element compositions were then determined by ICP-MS using an external synthetic standard for calibration. Our analyses show that the rare-earth elements (REEs), Co, Ni, and Pb are enriched 1.5 to 10 times relative to the upper continental crust (UCC) and that Nb, Ti, Ta, Hf, Th, Rb and Cs are depleted to varying degrees relative to UCC and the REEs. These fractionations can be explained by their differing chemical behaviors in aqueous environments. The extreme depletion in Rb and Cs reflect their high solubilities and tendency to be progressively leached out by rain water. Nb, Ti, Ta, Hf and Th are present only in detrital concentrations, reflecting their high insolublities and their probable depletion in the Fe- and Mn-rich components of the varnish. Co, Ni, Pb and Ce are soluble but readily coprecipitate with Mn oxides hence their 10-fold enrichments. Enrichments caused by diagenesis of dust accreted on the varnish substrate cannot achieve the 10-fold enrichments of some elements observed here, indicating that the aqueous component must be derived directly from the atmosphere. Remarkably, we find that ferro-manganese crusts produced by hydrogenous processes in the marine environment have trace-element abundance patterns nearly identical to those of varnishes. Relative to the upper continental crust, they are enriched in REEs, Co, Ni, and Pb, depleted in Nb, Ti, Ta, Hf, Th, Rb and Cs and are anomalously high in Ce. These unexpected similarities provide additional evidence that desert varnishes represent the direct precipitation of aqueous components in the atmosphere. It may be possible to estimate the aqueous atmospheric input of such trace elements as the REEs into the ocean. For example, multiplying the Nd/Fe and Nd/Mn ratios of the varnishes by estimates of modern day Fe and Mn wet deposition inputs to the ocean yields an oceanic input of 4 to 15 x 107 moles of Nd/year. This is slightly larger than the amount of dissolved Nd entering the oceans each year (2.4 x 106 moles/yr) via rivers, hence, there is a significant atmospheric input of REEs into the ocean in aqueous form.

Mn(2+)-mediated homogeneous Fenton-like reaction of Fe(III)-NTA complex for efficient degradation of organic contaminants under neutral conditions.

PubMed

Li, Yifan; Sun, Jianhui; Sun, Sheng-Peng

2016-08-05

In this work, we report a novel Mn(2+)-mediated Fenton-like process based on Fe(III)-NTA complex that is super-efficient at circumneutral pH range. Kinetics experiments showed that the presence of Mn(2+) significantly enhanced the effectiveness of Fe(III)-NTA complex catalyzed Fenton-like reaction. The degradation rate constant of crotamiton (CRMT), a model compound, by the Fe(III)- NTA_Mn(2+) Fenton-like process was at least 1.6 orders of magnitude larger than that in the absence of Mn(2+). Other metal ions such as Ca(2+), Mg(2+), Co(2+) and Cu(2+) had no impacts or little inhibitory effect on the Fe(III)-NTA complex catalyzed Fenton-like reaction. The generation of hydroxyl radical (HO) and superoxide radical anion (O2(-)) in the Fe(III)-NTA_Mn(2+) Fenton-like process were suggested by radicals scavenging experiments. The degradation efficiency of CRMT was inhibited significantly (approximately 92%) by the addition of HO scavenger 2-propanol, while the addition of O2(-) scavenger chloroform resulted in 68% inhibition. Moreover, the results showed that other chelating agents such as EDTA- and s,s-EDDS-Fe(III) catalyzed Fenton-like reactions were also enhanced significantly by the presence of Mn(2+). The mechanism involves an enhanced generation of O2(-) from the reactions of Mn(2+)-chelates with H2O2, indirectly promoting the generation of HO by accelerating the reduction rate of Fe(III)-chelates to Fe(II)- chelates. Copyright © 2016 Elsevier B.V. All rights reserved.

On the nature of the Fe-bearing particles influencing hard anodizing behavior of AA 7075 extrusion products

NASA Astrophysics Data System (ADS)

Mukhopadhyay, A. K.

1998-03-01

The deleterious effects of Fe-bearing constituent particles on the fracture toughness of wrought A1 alloys have been known. Recent studies have shown that the presence of Fe-bearing, constituent particles is also determental to the nature and growth of the hard anodic oxide coating formed on such materials. The present study, using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA), was made to examine the influence of the nature of the Fe-bearing particles on the hard anodizing behavior of AA 7075 extrusion products containing varying amounts of Si, Mn, and Fe impurities. It was found that, in the alloy containing 0.25 wt pct Si, 0.27 wt pct Mn, and 0.25 wt pct Fe, the Fe-bearing constituent particles are based on the Al12(FeMn)3Si phase (bcc with α=1.260 nm). These particles survive the hard anodizing treatment, add resistance to the electrical path, causing a rapid rise in the bath voltage with time, and cause a nonuniform growth of the anodic oxide film. In the materials containing 0.05 wt pct Si, 0.04 wt pct Mn, and 0.18 wt pct Fe, on the other hand, the formation of the Al12(FeMn)3Si-based phase is suppressed, and two different Fe-bearing phases, based on Al-Fe-Cu-Mn-based (simple cubic with a=1.265 nm) and Al7Cu2Fe, respectively form. Neither the Al-Fe-Cu-Mn-based phase nor the Al7Cu2Fe-based phase survive the hard anodizing treatment, and this results in a steady rise in the bath voltage with time and a relatively uniform growth of the anodic oxide film. Consideration of the size of the Fe-bearing, particles reveals that the smaller the particle, the more uniform the growth of the anodic oxide film.

Effect of Iron(II) on Arsenic Sequestration by δ-MnO 2 : Desorption Studies Using Stirred-Flow Experiments and X-Ray Absorption Fine-Structure Spectroscopy

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

Wu, Yun; Li, Wei; Sparks, Donald L.

2015-10-18

Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems and have high sorptive capacities for many trace metals, including As. Although numerous studies have studied the effects of As adsorption and desorption onto Fe and Mn oxides individually, the fate of As within mixed systems representative of natural environments has not been resolved. In this research, As(III) was initially reacted with a poorly crystalline phyllomanganate (δ-MnO 2) in the presence of Fe(II)more » prior to desorption. This initial reaction resulted in the sorption of both As(III) and As(V) on mixed Fe/Mn-oxides surfaces. A desorption study was carried out using two environmentally significant ions, phosphate (PO 4 3–) and calcium (Ca 2+). Both a stirred-flow technique and X-ray absorption fine-structure spectroscopy (XAFS) analysis were used to investigate As desorption behavior. Results showed that when As(III)/Fe(II) = 1:1 in the initial reaction, only As(V) was desorbed, agreeing with a previous study showing that As(III) is not associated with the Fe/Mn-oxides. When As(III)/Fe(II) = 1:10 in the initial reaction, both As(III) and As(V) can be desorbed from the Fe/Mn-oxide surface, and more As(III) is desorbed than As(V). Neither of the desorbents used in this study completely removed As(III) or As(V) from the Fe/Mn-oxides surface. However, the As desorption fraction decreases with increasing Fe(II) concentration in the initial reactions.« less

Effect of Iron(II) on Arsenic Sequestration by δ-MnO2: Desorption Studies Using Stirred-Flow Experiments and X-Ray Absorption Fine-Structure Spectroscopy.

PubMed

Wu, Yun; Li, Wei; Sparks, Donald L

2015-11-17

Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems and have high sorptive capacities for many trace metals, including As. Although numerous studies have studied the effects of As adsorption and desorption onto Fe and Mn oxides individually, the fate of As within mixed systems representative of natural environments has not been resolved. In this research, As(III) was initially reacted with a poorly crystalline phyllomanganate (δ-MnO2) in the presence of Fe(II) prior to desorption. This initial reaction resulted in the sorption of both As(III) and As(V) on mixed Fe/Mn-oxides surfaces. A desorption study was carried out using two environmentally significant ions, phosphate (PO4(3-)) and calcium (Ca(2+)). Both a stirred-flow technique and X-ray absorption fine-structure spectroscopy (XAFS) analysis were used to investigate As desorption behavior. Results showed that when As(III)/Fe(II) = 1:1 in the initial reaction, only As(V) was desorbed, agreeing with a previous study showing that As(III) is not associated with the Fe/Mn-oxides. When As(III)/Fe(II) = 1:10 in the initial reaction, both As(III) and As(V) can be desorbed from the Fe/Mn-oxide surface, and more As(III) is desorbed than As(V). Neither of the desorbents used in this study completely removed As(III) or As(V) from the Fe/Mn-oxides surface. However, the As desorption fraction decreases with increasing Fe(II) concentration in the initial reactions.

Divergent assembly mechanisms of the manganese/iron cofactors in R2lox and R2c proteins.

PubMed

Kutin, Yuri; Srinivas, Vivek; Fritz, Matthieu; Kositzki, Ramona; Shafaat, Hannah S; Birrell, James; Bill, Eckhard; Haumann, Michael; Lubitz, Wolfgang; Högbom, Martin; Griese, Julia J; Cox, Nicholas

2016-09-01

A manganese/iron cofactor which performs multi-electron oxidative chemistry is found in two classes of ferritin-like proteins, the small subunit (R2) of class Ic ribonucleotide reductase (R2c) and the R2-like ligand-binding oxidase (R2lox). It is unclear how a heterodimeric Mn/Fe metallocofactor is assembled in these two related proteins as opposed to a homodimeric Fe/Fe cofactor, especially considering the structural similarity and proximity of the two metal-binding sites in both protein scaffolds and the similar first coordination sphere ligand preferences of Mn II and Fe II . Using EPR and Mössbauer spectroscopies as well as X-ray anomalous dispersion, we examined metal loading and cofactor activation of both proteins in vitro (in solution). We find divergent cofactor assembly mechanisms for the two systems. In both cases, excess Mn II promotes heterobimetallic cofactor assembly. In the absence of Fe II , R2c cooperatively binds Mn II at both metal sites, whereas R2lox does not readily bind Mn II at either site. Heterometallic cofactor assembly is favored at substoichiometric Fe II concentrations in R2lox. Fe II and Mn II likely bind to the protein in a stepwise fashion, with Fe II binding to site 2 initiating cofactor assembly. In R2c, however, heterometallic assembly is presumably achieved by the displacement of Mn II by Fe II at site 2. The divergent metal loading mechanisms are correlated with the putative in vivo functions of R2c and R2lox, and most likely with the intracellular Mn II /Fe II concentrations in the host organisms from which they were isolated. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility

NASA Astrophysics Data System (ADS)

Bösch, Dominik; Pogatscher, Stefan; Hummel, Marc; Fragner, Werner; Uggowitzer, Peter J.; Göken, Mathias; Höppel, Heinz Werner

2015-03-01

Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed α-Al15(Fe,Mn)3Si2 phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the α-Al15(Fe,Mn)3Si2 phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys.

Comparison on the Surface Structure Properties along with Fe(II) and Mn(II) Removal Characteristics of Rice Husk Ash, Inactive Saccharomyces cerevisiae Powder, and Rice Husk

PubMed Central

Jiang, Zhao; Cao, Bo; Su, Guangxia; Lu, Yan; Zhao, Jiaying; Shan, Dexin; Zhang, Xiuyuan; Wang, Ziyi

2016-01-01

This study selected solid wastes, such as rice husk ash (RHA), inactive Saccharomyces cerevisiae powder (ISP), and rice husk (RH), as the potential adsorbents for the removal of Fe(II) and Mn(II) in aqueous solution. The structural characteristics, functional groups, and elemental compositions were determined by scanning electron microscope (SEM) and Fourier translation infrared spectrum (FT-IR) analyses, respectively. Then the influence on the Fe(II) and Mn(II) removing efficiency by the factors, such as pH, adsorbent dosage, initial Fe(II) and Mn(II) concentration, and contact time, was investigated by the static batch test. The adsorption isotherm study results show that Langmuir equation can better fit the Fe(II) and Mn(II) adsorption process by the three adsorbents. The maximum adsorption amounts for Fe(II) were 6.211 mg/g, 4.464 mg/g, and 4.049 mg/g by RHA, ISP, and RH and for Mn(II) were 3.016 mg/g, 2.229 mg/g, and 1.889 mg/g, respectively. The adsorption kinetics results show that the pseudo-second-order kinetic model can better fit the Fe(II) and Mn(II) adsorption process. D-R model and thermodynamic parameters hint that the adsorption processes of Fe(II) and Mn(II) on the three adsorbents took place physically and the processes were feasible, spontaneous, and exothermic. PMID:28042571

Mechanism of γ-irradiation induced phase transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics

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

Jagadeesha Angadi, V.; Anupama, A.V.; Choudhary, Harish K.

The structural, infrared absorption and magnetic property transformations in nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} samples irradiated with different doses (0, 15, 25 and 50 kGy) of γ-irradiation were investigated in this work and a mechanism of phase transformation/decomposition is provided based on the metastable nature of the Mn-atoms in the spinel lattice. The nano-powder sample was prepared by solution combustion route and the pellets of the sample were exposed to γ-radiation. Up to a dose of 25 kGy of γ-radiation, the sample retained the single phase cubic spinel (Fd-3m) structure, but the disorder in the sample increased. On irradiatingmore » the sample with 50 kGy γ-radiation, the spinel phase decomposed into new stable phases such as α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases along with amorphous MnO phase, leading to a change in the surface morphology of the sample. Along with the structural transformations the magnetic properties deteriorated due to breakage of the ferrimagnetic order with higher doses of γ-irradiation. Our results are important for the understanding of the stability, durability and performance of the Mn-Zn ferrite based devices used in space applications. - Graphical abstract: The nanocrystalline Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramic sample transforms to crystalline α-Fe{sub 2}O{sub 3} and ZnFe{sub 2}O{sub 4} phases (and amorphous MnO phase) at a γ-irradiation dose of 50 kGy, as MnO goes out of the spinel lattice. The high energy γ-irradiation causes structural damage to the nanomaterials leading to change in morphology of the sample as seen in the SEM images. - Highlights: • Mn atoms are more unstable in the Mn-Zn ferrite spinel lattice than Zn-atoms. • Displacement of Mn atoms by γ-radiation from the lattice renders phase transformation. • In Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}, Mn-ferrite cell transforms to crystalline α-Fe{sub 2}O{sub 3} and amorphous MnO. • The stable ZnFe{sub 2}O{sub 4} phase retains its structure even after 50 KGy γ-irradiation. • The γ-irradiation degrades the magnetic properties of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} ceramics.« less

Drastic effect of the Mn-substitution in the strongly correlated semiconductor FeSb2.

NASA Astrophysics Data System (ADS)

Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

2017-06-01

We report the effects of Mn substitution, corresponding to hole doping, on the electronic properties of the narrow gap semiconductor, FeSb2, using single crystals of Fe1- x Mn x Sb2 grown by the Sb flux method. The orthorhombic Pnnm structure was confirmed by powder X-ray diffraction (XRD) for the pure and Mn-substituted samples. Their crystal structure parameters were refined using the Rietveld method. The chemical composition was investigated by wavelength-dispersive X-ray spectroscopy (WDX). The solubility limit of Mn in FeSb2 is x max ˜ 0.05 and the lattice constants change monotonically with increasing the actual Mn concentration. A drastic change from semiconducting to metallic electronic transports was found at very low Mn concentration at x ˜ 0.01. Our experimental results and analysis indicate that the substitution of a small amount of Mn changes drastically the electronic state in FeSb2 as well as the Co-substitution does: closing of the narrow gap and emergence of the density of states (DOS) at the Fermi level.

Anaerobic biodegradation of BTEX using Mn(IV) and Fe(III) as alternative electron acceptors.

PubMed

Villatoro-Monzón, W R; Mesta-Howard, A M; Razo-Flores, E

2003-01-01

Anaerobic BTEX biodegradation was tested in batch experiments using an anaerobic sediment as inoculum under Fe(III) and Mn(IV) reducing conditions. All BTEX were degraded under the conditions tested, specially under Mn(IV) reducing conditions, where benzene was degraded at a rate of 0.8 micromol l(-1) d(-1), significantly much faster than Fe(III) reducing conditions. Under Fe(III) reducing conditions, ethylbenzene was the compound that degraded at the faster rate of 0.19 micromol l(-1) d(-1). Mn(IV) reducing conditions are energetically more favourable than Fe(III), therefore, BTEX were more rapidly degraded under Mn(IV) reducing conditions. These results represent the first report of the degradation of benzene with Mn(IV) as the final electron acceptor. Amorphous manganese oxide is a natural widely distributed metal in groundwater, where it can be microbiologically reduced, leading to the degradation of monoaromatic compounds.

Charge ordering and multiferroicity in Fe{sub 3}BO{sub 5} and Fe{sub 2}MnBO{sub 5} oxyborates

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

Maignan, A., E-mail: antoine.maignan@ensicaen.fr; Lainé, F.; Guesdon, A.

2017-02-15

The comparison of Fe{sub 3}BO{sub 5} and Fe{sub 2}MnBO{sub 5} reveals that the 2Fe{sup 2+}: Fe{sup 3+} charge ordering of the former is suppressed in the latter. Spin dynamics probed by ac susceptibility are strongly affected by the substitution, inducing superparamagnetism at low temperature in Fe{sub 2}MnBO{sub 5}. Interestingly, for both oxyborates, glassiness is observed in the dielectric properties at low temperature, but only Fe{sub 3}BO{sub 5} shows a magnetodielectric effect close to its lower magnetic transition. A change in the electrical polarization, measured by pyroelectric current integration, is observed in Fe{sub 3}BO{sub 5} and is even more pronounced inmore » Fe{sub 2}MnBO{sub 5}. Such results suggest that these oxyborates behave like antiferromagnetic relaxor ferroelectrics. These features are proposed to be related to the distribution of the species (Fe{sup 3+}, Fe{sup 2+} and Mn{sup 2+}) over the four transition metal sites forming the ludwigite structure. - Graphical abstract: 90 K [010] electron diffraction patterns of Fe{sub 3}BO{sub 5}. The yellow arrows in the pattern indicate the extra-spots corresponding to the superstructure induced by the charge ordering. - Highlights: • The TEM (ED) study of the Fe{sub 3}BO{sub 5} oxyborate at 90 K reveals a superstructure related to a Fe{sup 2+}/Fe{sup 3+} ordering. • The Fe{sub 2}MnBO{sub 5}, Mn-substituted counterpart, does not show such ordering. • Our magnetic and electric measurements demonstrate that these magnetic ferrites exhibit glassiness in their charges (relaxor-type) with additional superparamagnetism at low T for Fe{sub 2}MnBO{sub 5} and magnetodielectric coupling near T{sub N2}=72 K in Fe{sub 3}BO{sub 5}. • The pyroelectric measurements confirm the existence of a ferroelectric behavior in these antiferromagnets. Accordingly, our results open the route to the study of other large class of the M{sub 2}{sup 2+}M’{sup 3+}BO{sub 5} ludwigites and to their complex magnetism and its relationship to relaxor ferroelectricity.« less

Groundwater chemistry and occurrence of arsenic in the Meghna floodplain aquifer, southeastern Bangladesh

USGS Publications Warehouse

Zahid, A.; Hassan, M.Q.; Balke, K.-D.; Flegr, M.; Clark, D.W.

2008-01-01

Dissolved major ions and important heavy metals including total arsenic and iron were measured in groundwater from shallow (25-33 m) and deep (191-318 m) tube-wells in southeastern Bangladesh. These analyses are intended to help describe geochemical processes active in the aquifers and the source and release mechanism of arsenic in sediments for the Meghna Floodplain aquifer. The elevated Cl- and higher proportions of Na+ relative to Ca2+, Mg2+, and K+ in groundwater suggest the influence by a source of Na+ and Cl-. Use of chemical fertilizers may cause higher concentrations of NH 4+ and PO 43- in shallow well samples. In general, most ions are positively correlated with Cl-, with Na+ showing an especially strong correlation with Cl-, indicating that these ions are derived from the same source of saline waters. The relationship between Cl-/HCO 3- ratios and Cl- also shows mixing of fresh groundwater and seawater. Concentrations of dissolved HCO 3- reflect the degree of water-rock interaction in groundwater systems and integrated microbial degradation of organic matter. Mn and Fe-oxyhydroxides are prominent in the clayey subsurface sediment and well known to be strong adsorbents of heavy metals including arsenic. All five shallow well samples had high arsenic concentration that exceeded WHO recommended limit for drinking water. Very low concentrations of SO 42- and NO 3- and high concentrations of dissolved Fe and PO 43- and NH 4+ ions support the reducing condition of subsurface aquifer. Arsenic concentrations demonstrate negative co-relation with the concentrations of SO 42- and NO 3- but correlate weakly with Mo, Fe concentrations and positively with those of P, PO 43- and NH 4+ ions. ?? 2007 Springer-Verlag.

Establishing the environmental risk of metal contaminated river bank sediments

NASA Astrophysics Data System (ADS)

Lynch, Sarah; Batty, Lesley; Byrne, Patrick

2016-04-01

Climate change predictions indicate an increase in the frequency and duration of flood events along with longer dry antecedent conditions, which could alter patterns of trace metal release from contaminated river bank sediments. This study took a laboratory mesocosm approach. Chemical analysis of water and sediment samples allowed the patterns of Pb and Zn release and key mechanisms controlling Pb and Zn mobility to be determined. Trace metal contaminants Pb and Zn were released throughout flooded periods. The highest concentrations of dissolved Pb were observed at the end of the longest flood period and high concentrations of dissolved Zn were released at the start of a flood. These concentrations were found to exceed environmental quality standards. Key mechanisms controlling mobility were (i) evaporation, precipitation and dissolution of Zn sulphate salts, (ii) anglesite solubility control of dissolved Pb, (iii) oxidation of galena and sphalerite, (iv) reductive dissolution of Mn/Fe hydroxides and co-precipitation/adsorption with Zn. In light of climate change predictions these results indicate future scenarios may include larger or more frequent transient 'pulses' of dissolved Pb and Zn released to river systems. These short lived pollution episodes could act as a significant barrier to achieving the EU Water Framework Directive objectives.

Dietary Manganese Modulates PCB126 Toxicity, Metal Status, and MnSOD in the Rat

PubMed Central

Wang, Bingxuan; Klaren, William D.; Wels, Brian R.; Simmons, Donald L.; Olivier, Alicia K.; Wang, Kai; Robertson, Larry W.; Ludewig, Gabriele

2016-01-01

PCB126 (3,3′,4,4′,5-pentachlorobiphenyl) is a potent aryl hydrocarbon receptor agonist and induces oxidative stress. Because liver manganese (Mn) levels decrease in response to PCB126, a Mn dietary study was designed to investigate the role of Mn in PCB126 toxicity. Male Sprague Dawley rats received diets containing 0, 10, or 150 ppm added Mn for 3 weeks, followed by a single ip injection of corn oil or PCB126 (5 µmol/kg body weight). After 2 weeks, Mn, Cu, Zn, and Fe levels in the heart, liver, and liver mitochondria, and Mn-containing superoxide dismutase (MnSOD) and metallothionein mRNA, MnSOD protein, and MnSOD activity were determined. Mn levels in liver, heart, and liver mitochondria were strongly decreased by the Mn-deficient diet. Small effects on Fe levels and a stepwise increase in MnSOD activity with dietary Mn were also visible. PCB126 caused profound changes in Cu (up), Zn, Fe, and Mn (down) in liver, but not in heart, and differing effects (Cu, Zn, and Fe up, Mn down) in liver mitochondria. Liver MnSOD and metallothionein mRNA levels and MnSOD protein were increased but MnSOD activity was decreased by PCB126. PCB126-induced liver enlargement was dose-dependently reduced with increasing dietary Mn. These changes in metals homeostasis and MnSOD activity in liver but not heart may be a/the mechanism of PCB126 liver-specific toxicity. Specifically, transport of Fenton metals (Cu, Fe) into and Mn out of the mitochondria, a probable mechanism for lower MnSOD activity, may be a/the cause of PCB126-induced oxidative stress. The role of metallothioneins needs further evaluation. Dietary Mn slightly alleviated PCB126-induced toxicities. PMID:26660635

As(III) oxidation by MnO2 during groundwater treatment.

PubMed

Gude, J C J; Rietveld, L C; van Halem, D

2017-03-15

The top layer of natural rapid sand filtration was found to effectively oxidise arsenite (As(III)) in groundwater treatment. However, the oxidation pathway has not yet been identified. The aim of this study was to investigate whether naturally formed manganese oxide (MnO 2 ), present on filter grains, could abiotically be responsible for As(III) oxidation in the top of a rapid sand filter. For this purpose As(III) oxidation with two MnO 2 containing powders was investigated in aerobic water containing manganese(II) (Mn(II)), iron(II) (Fe(II)) and/or iron(III) (Fe(III)). The first MnO 2 powder was a very pure - commercially available - natural MnO 2 powder. The second originated from a filter sand coating, produced over 22 years in a rapid filter during aeration and filtration. Jar test experiments showed that both powders oxidised As(III). However, when applying the MnO 2 in aerated, raw groundwater, As(III) removal was not enhanced compared to aeration alone. It was found that the presence of Fe(II)) and Mn(II) inhibited As(III) oxidation, as Fe(II) and Mn(II) adsorption and oxidation were preferred over As(III) on the MnO 2 surface (at pH 7). Therefore it is concluded that just because MnO 2 is present in a filter bed, it does not necessarily mean that MnO 2 will be available to oxidise As(III). However, unlike Fe(II), the addition of Fe(III) did not hinder As(III) oxidation on the MnO 2 surface; resulting in subsequent effective As(V) removal by the flocculating hydrous ferric oxides. Copyright © 2016 Elsevier Ltd. All rights reserved.

Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

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

Gubbiotti, G., E-mail: gubbiotti@fisica.unipg.it; Tacchi, S.; Del Bianco, L.

2015-05-07

Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence ofmore » the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.« less

Origins of giant biquadratic coupling in CoFe/Mn/CoFe sandwich structures (abstract)

NASA Astrophysics Data System (ADS)

Koon, Norman C.

1996-04-01

Recently Filipkowski et al. reported extremely strong, near 90 degree coupling of 2.5 erg/cm2 for epitaxial sandwiches of CoFe/Mn/CoFe, where the CoFe composition was chosen to be a good lattice match to Mn. Both CoFe and Mn have the bcc structure, but Mn is antiferromagnetic while CoFe is ferromagnetic. It was found that the data were very well described by a simple model due to Slonczewski, in which the interlayer coupling is given by Fc=C+(φ1-φ2)2+C-(φ1-φ2-π)2. While this model describes the data much better than the usual biquadratic form, it still does not connect directly to the microscopic origins of the effect. In the present work we seek to explain the results in terms of normal bilinear exchange and magnetocrystalline anisotropy, together with reasonable assumptions about the structure of the interfaces. We obtain excellent agreement with both the experimental results and the Slonczewski model under the assumptions that at least one of the two CoFe/Mn interfaces is smooth (i.e., atomically flat) on a length scale comparable to or greater than the thickness of the Mn layer and at least one interface is rough on a scale less than approximately a domain wall thickness.

The corrosion behavior of Fe-Mn-Al weld metals

NASA Astrophysics Data System (ADS)

Aidun, Daryush K.

2001-02-01

The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.

Self-templated fabrication of FeMnO3 nanoparticle-filled polypyrrole nanotubes for peroxidase mimicking with a synergistic effect and their sensitive colorimetric detection of glutathione.

PubMed

Chi, Maoqiang; Chen, Sihui; Zhong, Mengxiao; Wang, Ce; Lu, Xiaofeng

2018-06-05

A self-templated approach has been developed for the preparation of FeMnO3 nanoparticles filled in the hollow core of polypyrrole (PPy) nanotubes by an in situ polymerization process accompanied by the etching of FeMnO3 nanofibers. The prepared FeMnO3@PPy nanotubes exhibited a superior peroxidase-like activity. The catalytic reaction system has been used for the sensitive colorimetric detection of glutathione with a low detection limit and good selectivity.

NASICON-related Na3.4Mn0.4Fe1.6(PO4)3

PubMed Central

Yatskin, Michael M.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Ogorodnyk, Ivan V.; Slobodyanik, Nikolay S.

2012-01-01

The solid solution, sodium [iron(III)/manganese(II)] tris­(orthophosphate), Na3.4Mn0.4Fe1.6(PO4)3, was obtained using a flux method. Its crystal structure is related to that of NASICON-type compounds. The [(Mn/Fe)2(PO4)3] framework is built up from an (Mn/Fe)O6 octa­hedron (site symmetry 3.), with a mixed Mn/Fe occupancy, and a PO4 tetra­hedron (site symmetry .2). The Na+ cations are distributed over two partially occupied sites in the cavities of the framework. One Na+ cation (site symmetry -3.) is surrounded by six O atoms, whereas the other Na+ cation (site symmetry .2) is surrounded by eight O atoms. PMID:22807697

Fe and Mn removal from mining drainage using goaf filling materials obtained from coal mining process.

PubMed

Zhang, Liping; Chen, Aolei; Qu, Hongbin; Xu, Shouqiang; Zhang, Xue; He, Xuwen

2015-01-01

Coal gangue, sandy soil and clay (mass ratio 45:4:1) as goaf filling materials acquired from coal mining processes were applied to remove Fe and Mn effectively from mining drainage. The results of an adsorption kinetic study showed that the Fe adsorption equation was y=21.454y+8.4712, R2=0.9924 and the Mn adsorption equation was y=7.5409x+0.905, R2=0.9957. Meanwhile, the goaf filling materials had low desorption capacity (Fe 6.765 μg/g, Mn 1.52 μg/g) and desorption ratio (Fe 8.98%, Mn 11.04%). Experiments demonstrated that Fe and Mn from mining drainage could be removed stably at a flow rate of 1.2 L/min, Fe inlet concentration of less than 40 mg/L, Mn inlet concentration of less than 2 mg/L and neutral or alkaline conditions. During a procedure of continuous experiments, the effluent quality could meet the requirement of the 'Code for Engineering Design of Sewage Regeneration-GB503352-2002'. A real-application project using goaf filling materials to treat mining drainage in Shendong coal mine showed that the average cost per ton of mining drainage was about 0.55 RMB, which could bring about considerable economic benefit for coal mining enterprises.

Graphene oxide/manganese ferrite nanohybrids for magnetic resonance imaging, photothermal therapy and drug delivery.

PubMed

Yang, Yan; Shi, Haili; Wang, Yapei; Shi, Benzhao; Guo, Linlin; Wu, Dongmei; Yang, Shiping; Wu, Huixia

2016-01-01

Superparamagnetic manganese ferrite (MnFe2O4) nanoparticles have been deposited on graphene oxide (GO) by the thermal decomposition of manganese (II) acetylacetonate and iron (III) acetylacetonate precursors in triethylene glycol. The resulting GO/MnFe2O4 nanohybrids show very low cytotoxicity, negligible hemolytic activity, and imperceptible in vivo toxicity. In vitro and in vivo magnetic resonance imaging experiments demonstrate that GO/MnFe2O4 nanohybrids could be used as an effective T2 contrast agent. The strong optical absorbance in the near-infrared (NIR) region and good photothermal stability of GO/MnFe2O4 nanohybrids result in the highly efficient photothermal ablation of cancer cells. GO/MnFe2O4 nanohybrids can be further loaded with doxorubicin (DOX) by π-π conjugate effect for chemotherapy. DOX release from GO/MnFe2O4 is significantly influenced by pH and can be triggered by NIR laser. The enhanced cancer cell killing by GO/MnFe2O4/DOX composites has been achieved when irradiated with near-infrared light, suggesting that the nanohybrids could deliver both DOX chemotherapy and photothermal therapy with a synergistic effect. © The Author(s) 2015.

Arsenic mobilization in the Brahmaputra plains of Assam: groundwater and sedimentary controls.

PubMed

Sailo, Lalsangzela; Mahanta, Chandan

2014-10-01

Arsenic (As) mobilization to the groundwater of Brahmaputra floodplains was investigated in Titabor, Jorhat District, located in the North Eastern part of India. The groundwater and the aquifer geochemistry were characterized in the study area. The range of As concentration in the groundwater varies from 10 to 440 μg/l with mean concentration 210 μg/l. The groundwaters are characterized by high dissolved Fe, Mn, and HCO₃(-) and low concentrations of NO₃(-) and SO₄(2-) indicating the reduced conditions prevailing in the groundwater. In order to understand the actual mobilization processes in the area, six core drilling surrounding the two target tube wells (T1 and T2) with high As concentration (three drill-cores surrounds each tube well closely) was done. The sediment was analyzed its chemical, mineralogical, and elemental compositions. A selective sequential extraction suggested that most of the As in the sediment is bound to Fe oxides fractions (32 to 50%) and the competition for adsorption site by anions (PO₄(3-)) also accounts to significant fractions of the total arsenic extracted. High variability in the extraction as well as properties of the sediment was observed due to the heterogeneity of the sediment samples with different chemical properties. The SEM and EDX results indicate the presence of Fe, Mn coating along with As for most of the sample, and the presence of As associated minerals were calculated using PHREEQC. The mobilization of As into the groundwater was anticipated to be largely controlled by the reductive dissolution of Fe oxides and partly by the competitive anions viz. PO₄(3-).

New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

NASA Astrophysics Data System (ADS)

Laurila, Tea E.; Hannington, Mark D.; Leybourne, Matthew; Petersen, Sven; Devey, Colin W.; Garbe-Schönberg, Dieter

2015-12-01

The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main "ore" minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

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.

Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

PubMed Central

Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

2017-01-01

Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

Mn-Cr isotopic systematics of Chainpur chondrules and bulk ordinary chondrites

NASA Technical Reports Server (NTRS)

Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Bansal, B.; Shih, C.-Y.; Mittlefehldt, D.; Martinez, R.; Wentworth, S.

1994-01-01

We report on ongoing study of the Mn-Cr systematics of individual Chainpur (LL3.4) chondrules and compare the results to those for bulk ordinary chondrites. Twenty-eight chondrules were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by INAA. Twelve were chosen for SEM/EDX and high-precision Cr-isotopic studies on the basis of LL-chondrite-normalized Mn(LL), Sc(LL), (Mn/Fe)(LL), and (Sc/Fe)(LL) as well as their Mn/Cr ratios. Classification into textural types follows from SEM/EDX examination of interior surfaces.

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.

Semiconductor Ceramic Mn0.5Fe1.5O3-Fe2O3 from Natural Minerals as Ethanol Gas Sensors

NASA Astrophysics Data System (ADS)

Aliah, H.; Syarif, D. G.; Iman, R. N.; Sawitri, A.; Sanjaya WS, M.; Nurul Subkhi, M.; Pitriana, P.

2018-05-01

In this research, Mn and Fe-based ceramic gas sensing were fabricated and characterized. This research used natural mineral which is widely available in Indonesia and intended to observe the characteristics of Mn and Fe-based semiconducting material. Fabricating process of the thick films started by synthesizing the ceramic powder of Fe(OH)3 and Mn oxide material using the precipitation method. The deposition from precipitation method previously was calcined at a temperature of 800 °C to produce nanoparticle powder. Nanoparticle powder that contains Mn and Fe oxide was mixed with an organic vehicle (OV) to produce a paste. Then, the paste was layered on the alumina substrate by using the screen printing method. XRD method was utilized to characterize the thick film crystal structure that has been produced. XRD spectra showed that the ceramic layer was formed from the solid Mn0.5Fe1.5O3 (bixbyite) and Fe2O3. In addition, the electrical properties (resistance) examination was held in the room that contains air and ethanol to determine the sensor sensitivity of ethanol gas. The sensor resistance decreases as the ethanol gas was added, showing that the sensor was sensitive to ethanol gas and an n-type semiconductor. Gas sensor exhibit sensitive characterization of ethanol gas on the concentration of (100 to 300) ppm at a temperature of (150 to 200) °C. This showed that the Mn0.5Fe1.5O3-Fe2O3 ceramic semiconductor could be utilized as the ethanol gas detector.

Metal dynamics in Lake Vanda (Wright Valley, Antarctica)

NASA Technical Reports Server (NTRS)

Green, W. J.; Ferdelman, T. G.; Canfield, D. E.; DeVincenzi, D. L. (Principal Investigator)

1989-01-01

Data are reported for Mn, Fe, Co, Ni, Cu and Cd in the Onyx River, and for Mn, Co, Ni, Cu and Cd in Lake Vanda, a closed-basin Antarctic lake. Oxic water concentrations for Co, Ni, Cu and Cd were quite low and approximate pelagic ocean values. Scavenging of these metals by sinking particles is strongly indicated. Deep-lake profiles reveal a sharp peak in the concentrations of Mn, Fe and Co at the oxic-anoxic boundary at 60 m. Maxima for Ni, Cu and Cd occur higher in the water column, in the vicinity of a Mn submaximum, suggesting early release of these metals from sinking manganese oxide-coated particles. A rough steady-state model leads to the conclusion that there is a large downward flux of Mn into the deep lake and that this flux is sufficient to explain the annual loss of Co, Ni, Cu and Cd. A pronounced geochemical separation between Fe and Mn apparently occurs in this system--Fe being best lost in near-shore environments and Mn being lost in deeper waters. Comparison of metal residence times in Lake Vanda with those in the oceans shows that in both systems Mn, Fe and Co are much more reactive than Ni, Cu and Cd. Energetically favorable inclusion of the more highly charged metals, Mn(IV), Fe(III) and Co(III), into oxide-based lattices is a plausible explanation.

Damping studies in Ni-Mn-Ga-Fe/PU polymer composites

NASA Astrophysics Data System (ADS)

Saranya, C.; Kumar, S. Vinodh; Seenithurai, S.; Pandyan, R. Kodi; Munieswaran, P.; Mahendran, M.

2015-06-01

Ni-Mn-Ga-Fe/PU polymer composite is prepared to investigate the damping behavior by using an indigenous experimental setup. The excellent damping properties of Ni-Mn-Ga-Fe alloys bonded with polymer matrix makes possible to develop new damping materials which are effective, less expensive and easier than bulk Ni-Mn-Ga. At low frequency, the stress amplitude increases and then smoothly decreases on increasing the frequency.

The Arabidopsis MTP8 transporter determines the localization of manganese and iron in seeds

DOE PAGES

Chu, Heng-Hsuan; Car, Suzana; Socha, Amanda L.; ...

2017-09-08

Understanding how seeds obtain and store nutrients is key to developing crops with higher agronomic and nutritional value. We have uncovered unique patterns of micronutrient localization in seeds using synchrotron X-ray fluorescence (SXRF). Although all four members of the Arabidopsis thaliana Mn-CDF family can transport Mn, here we show that only mtp8-2 has an altered Mn distribution pattern in seeds. In an mtp8-2 mutant, Mn no longer accumulates in hypocotyl cortex cells and sub-epidermal cells of the embryonic cotyledons, but rather accumulates with Fe in the cells surrounding the vasculature, a pattern previously shown to be determined by the vacuolarmore » transporter VIT1. We also show that MTP8, unlike the other three Mn-CDF family members, can transport Fe and is responsible for localization of Fe to the same cells that store Mn. When both the VIT1 and MTP8 transporters are non-functional, there is no accumulation of Fe or Mn in specific cell types; rather these elements are distributed amongst all cell types in the seed. Finally, disruption of the putative Fe binding sites in MTP8 resulted in loss of ability to transport Fe but did not affect the ability to transport Mn.« less

Heavy metal flows in aquatic systems of the Don and Kuban river deltas

NASA Astrophysics Data System (ADS)

Tkachenko, A. N.; Tkachenko, O. V.; Lychagin, M. Yu.; Kasimov, N. S.

2017-05-01

This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013-2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.

Dissimilatory Fe(III) reduction by the marine microorganism Desulfuromonas acetoxidans

USGS Publications Warehouse

Roden, E.E.; Lovley, D.R.

1993-01-01

The ability of the marine microorganism Desulfuromonas acetoxidans to reduce Fe(III) was investigated because of its close phylogenetic relationship with the freshwater dissimilatory Fe(III) reducer Geobacter metallireducens. Washed cell suspensions of the type strain of D. acetoxidans reduced soluble Fe(III)-citrate and Fe(III) complexed with nitriloacetic acid. The c-type cytochrome(s) of D. acetoxidans was oxidized by Fe(III)- citrate and Mn(IV)-oxalate, as well as by two electron acceptors known to support growth, colloidal sulfur and malate. D. acetoxidans grew in defined anoxic, bicarbonate-buffered medium with acetate as the sole electron donor and poorly crystalline Fe(III) or Mn(IV) as the sole electron acceptor. Magnetite (Fe3O4) and siderite (FeCO3) were the major end products of Fe(III) reduction, whereas rhodochrosite (MnCO3) was the end product of Mn(IV) reduction. Ethanol, propanol, pyruvate, and butanol also served as electron donors for Fe(III) reduction. In contrast to D. acetoxidans, G. metallireducens could only grow in freshwater medium and it did not conserve energy to support growth from colloidal S0 reduction. D. acetoxidans is the first marine microorganism shown to conserve energy to support growth by coupling the complete oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). Thus, D. acetoxidans provides a model enzymatic mechanism for Fe(III) or Mn(IV) oxidation of organic compounds in marine and estuarine sediments. These findings demonstrate that 16S rRNA phylogenetic analyses can suggest previously unrecognized metabolic capabilities of microorganisms.

Diel variations in stream chemistry and isotopic composition of dissolved inorganic carbon, upper Clark Fork River, Montana, USA

USGS Publications Warehouse

Parker, Stephen R.; Gammons, Christopher H.; Poulson, Simon R.; DeGrandpre, Michael D.

2007-01-01

Many rivers undergo diel (24-h) concentration fluctuations of pH, dissolved gases, trace metals, nutrients, and other chemical species. A study conducted in 1994 documented such behavior in the upper Clark Fork River, Montana, a stream whose headwaters have been severely impacted by historic metal mining, milling, and smelting. The purpose of the present investigation was to expand on these earlier findings by conducting simultaneous diel samplings at two sites on the upper Clark Fork River separated by 2.5 h of stream travel time. By monitoring two stations, it was possible to more closely examine the processes that control temporal and spatial gradients in stream chemistry. Another objective was to examine diel changes in the δ13C composition of dissolved inorganic C (DIC) and their relationship to biological activity in the stream. The most important findings of this study include: (1) concentrations of dissolved and particulate heavy metals increased during the night and decreased during the day, in agreement with previous work; (2) these changes were positively correlated to diel changes in pH, dissolved O2, and water temperature; (3) dissolved concentrations increased during the night at the lower site, but showed the opposite behavior at the upper site; and (4) diel changes in δ13C-DIC were noted at both sites, although the timing and magnitudes of the cycles differed. Hypotheses to explain the first two observations include: cyclic co-precipitation of divalent metals with carbonate minerals; pH- and temperature-dependent sorption of metal cations onto the streambed and suspended particles; or photosynthetically enhanced oxidation and removal of Fe and Mn oxides at biofilm surfaces during the daytime. The latter model explains the majority of the field observations, including night-time increases in particulate forms of Fe and other elements.

Metal Tolerance Protein 8 Mediates Manganese Homeostasis and Iron Reallocation during Seed Development and Germination.

PubMed

Eroglu, Seckin; Giehl, Ricardo F H; Meier, Bastian; Takahashi, Michiko; Terada, Yasuko; Ignatyev, Konstantin; Andresen, Elisa; Küpper, Hendrik; Peiter, Edgar; von Wirén, Nicolaus

2017-07-01

Metal accumulation in seeds is a prerequisite for germination and establishment of plants but also for micronutrient delivery to humans. To investigate metal transport processes and their interactions in seeds, we focused on METAL TOLERANCE PROTEIN8 (MTP8), a tonoplast transporter of the manganese (Mn) subclade of cation diffusion facilitators, which in Arabidopsis ( Arabidopsis thaliana ) is expressed in embryos of seeds. The x-ray fluorescence imaging showed that expression of MTP8 was responsible for Mn localization in subepidermal cells on the abaxial side of the cotyledons and in cortical cells of the hypocotyl. Accordingly, under low Mn availability, MTP8 increased seed stores of Mn, required for efficient seed germination. In mutant embryos lacking expression of VACUOLAR IRON TRANSPORTER1 ( VIT1 ), MTP8 built up iron (Fe) hotspots in MTP8 -expressing cells types, suggesting that MTP8 transports Fe in addition to Mn. In mtp8 vit1 double mutant seeds, Mn and Fe were distributed in all cell types of the embryo. An Fe transport function of MTP8 was confirmed by its ability to complement Fe hypersensitivity of a yeast mutant defective in vacuolar Fe transport. Imbibing mtp8-1 mutant seeds in the presence of Mn or subjecting seeds to wet-dry cycles showed that MTP8 conferred Mn tolerance. During germination, MTP8 promoted reallocation of Fe from the vasculature. These results indicate that cell type-specific accumulation of Mn and Fe in seeds depends on MTP8 and that this transporter plays an important role in the generation of seed metal stores as well as for metal homeostasis and germination efficiency under challenging environmental conditions. © 2017 American Society of Plant Biologists. All Rights Reserved.

Metal Tolerance Protein 8 Mediates Manganese Homeostasis and Iron Reallocation during Seed Development and Germination1[OPEN

PubMed Central

Takahashi, Michiko; Terada, Yasuko

2017-01-01

Metal accumulation in seeds is a prerequisite for germination and establishment of plants but also for micronutrient delivery to humans. To investigate metal transport processes and their interactions in seeds, we focused on METAL TOLERANCE PROTEIN8 (MTP8), a tonoplast transporter of the manganese (Mn) subclade of cation diffusion facilitators, which in Arabidopsis (Arabidopsis thaliana) is expressed in embryos of seeds. The x-ray fluorescence imaging showed that expression of MTP8 was responsible for Mn localization in subepidermal cells on the abaxial side of the cotyledons and in cortical cells of the hypocotyl. Accordingly, under low Mn availability, MTP8 increased seed stores of Mn, required for efficient seed germination. In mutant embryos lacking expression of VACUOLAR IRON TRANSPORTER1 (VIT1), MTP8 built up iron (Fe) hotspots in MTP8-expressing cells types, suggesting that MTP8 transports Fe in addition to Mn. In mtp8 vit1 double mutant seeds, Mn and Fe were distributed in all cell types of the embryo. An Fe transport function of MTP8 was confirmed by its ability to complement Fe hypersensitivity of a yeast mutant defective in vacuolar Fe transport. Imbibing mtp8-1 mutant seeds in the presence of Mn or subjecting seeds to wet-dry cycles showed that MTP8 conferred Mn tolerance. During germination, MTP8 promoted reallocation of Fe from the vasculature. These results indicate that cell type-specific accumulation of Mn and Fe in seeds depends on MTP8 and that this transporter plays an important role in the generation of seed metal stores as well as for metal homeostasis and germination efficiency under challenging environmental conditions. PMID:28461400

Redox-controlled release dynamics of thallium in periodically flooded arable soil.

PubMed

Antić-Mladenović, Svetlana; Frohne, Tina; Kresović, Mirjana; Stärk, Hans-Joachim; Savić, Dubravka; Ličina, Vlado; Rinklebe, Jörg

2017-07-01

To our knowledge, this is the first work to mechanistically study the impact of the redox potential (E H ) and principal factors, such as pH, iron (Fe), manganese (Mn), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), chlorides (Cl - ) and sulfates (SO 4 2- ), on the release dynamics of thallium (Tl) in periodically flooded soil. We simulated flooding using an automated biogeochemical microcosm system that allows for systematical control of pre-defined redox windows. The E H value was increased mechanistically at intervals of approximately 100 mV from reducing (-211 mV) to oxidizing (475 mV) conditions. Soluble Tl levels (0.02-0.28 μg L -1 ) increased significantly with increases in E H (r = 0.80, p < 0.01, n = 30). Thallium mobilization was found to be related to several simultaneous processes involving the gradual oxidation of Tl-bearing sulfides, reductive dissolution of Fe-Mn oxides and desorption from mineral sorbents. Manganese oxides did not appear to have a considerable effect on Tl retention under oxidizing conditions. Before conducting the microcosm experiment, Tl geochemical fractionation was assessed using the modified BCR sequential extraction procedure. The BCR revealed a majority of Tl in the residual fraction (77.7%), followed by reducible (13.3%) and oxidizable fractions (5.9%). By generating high levels of Tl toxicity at low doses, Tl released under oxidizing conditions may pose an environmental threat. In the future, similar studies should be conducted on various soils along with a determination of the Tl species and monitoring of the Tl content in plants to achieve more detailed insight into soluble Tl behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

Elucidating the Role of Carbon Sources on Abiotic and Biotic Release of Arsenic into Cambodian Aquifers

NASA Astrophysics Data System (ADS)

Koeneke, M.

2017-12-01

Arsenic (As) is a naturally occurring contaminant in Cambodia that has been contaminating well-water sources of millions of people. Commonly, studies look into the biotic factors that cause the arsenic to be released from aquifer sediments to groundwater. However, abiotic release of As from sediments, though little studied, may also play key roles in As contamination of well water. The goal of this research is to quantitatively compare organic-carbon mediated abiotic and biotic release of arsenic from sediments to groundwater. Batch anaerobic incubation experiments under abiotic (sodium azide used to immobilize microbes) and biotic conditions were conducted using Cambodian aquifer sediments, four different organic carbon sources (sodium lactate, sodium citrate, sodium oxalate, and humic acid), and six different carbon concentrations (0, 1, 2.5, 5, 10, 25mg C/L). Dissolved arsenic, iron(Fe), and manganese(Mn) concentrations in the treatments were measured 112 days . In addition, sediment and solution carbon solution was measured . Collectively, these show how different carbon sources, different carbon concentrations, and how abiotic and biotic factors impact the release of arsenic from Cambodian sediments into aquifers. Overall, an introduction of organic carbon to the soil increases the amount of As released from the sediment. The biotic + abiotic and abiotic conditions seemed to play a minimal role in the amount of As released. Dissolved species analysis showed us that 100% of the As was As(V), Our ICP-MS results vary due to the heterogeneity of samples, but when high levels are Fe are seen in solution, we also see high levels of As. We also see higher As concentrations when there is a smaller amount of Mn in solution.

Spatial variations of community structures and methane cycling across a transect of Lei-Gong-Hou mud volcanoes in eastern Taiwan.

PubMed

Wang, Pei-Ling; Chiu, Yi-Ping; Cheng, Ting-Wen; Chang, Yung-Hsin; Tu, Wei-Xain; Lin, Li-Hung

2014-01-01

This study analyzed cored sediments retrieved from sites distributed across a transect of the Lei-Gong-Hou mud volcanoes in eastern Taiwan to uncover the spatial distributions of biogeochemical processes and community assemblages involved in methane cycling. The profiles of methane concentration and carbon isotopic composition revealed various orders of the predominance of specific methane-related metabolisms along depth. At a site proximal to the bubbling pool, the methanogenic zone was sandwiched by the anaerobic methanotrophic zones. For two sites distributed toward the topographic depression, the methanogenic zone overlaid the anaerobic methanotrophic zone. The predominance of anaerobic methanotrophy at specific depth intervals is supported by the enhanced copy numbers of the ANME-2a 16S rRNA gene and coincides with high dissolved Fe/Mn concentrations and copy numbers of the Desulfuromonas/Pelobacter 16S rRNA gene. Assemblages of 16S rRNA and mcrA genes revealed that methanogenesis was mediated by Methanococcoides and Methanosarcina. pmoA genes and a few 16S rRNA genes related to aerobic methanotrophs were detected in limited numbers of subsurface samples. While dissolved Fe/Mn signifies the presence of anaerobic metabolisms near the surface, the correlations between geochemical characteristics and gene abundances, and the absence of aerobic methanotrophs in top sediments suggest that anaerobic methanotrophy is potentially dependent on iron/manganese reduction and dominates over aerobic methanotrophy for the removal of methane produced in situ or from a deep source. Near-surface methanogenesis contributes to the methane emissions from mud platform. The alternating arrangements of methanogenic and methanotrophic zones at different sites suggest that the interactions between mud deposition, evaporation, oxidation and fluid transport modulate the assemblages of microbial communities and methane cycling in different compartments of terrestrial mud volcanoes.

Advanced transition metal phosphide materials from single-source molecular precursors

NASA Astrophysics Data System (ADS)

Colson, Adam Caleb

In this thesis, the feasibility of employing organometallic single-source precursors in the preparation of advanced transition metal pnictide materials such as colloidal nanoparticles and films has been investigated. In particular, the ternary FeMnP phase was targeted as a model for preparing advanced heterobimetallic phosphide materials, and the iron-rich Fe3P phase was targeted due to its favorable ferromagnetic properties as well as the fact that the preparation of advanced Fe3P materials has been elusive by commonly used methods. Progress towards the synthesis of advanced Fe2--xMn xP nanomaterials and films was facilitated by the synthesis of the novel heterobimetallic complexes FeMn(CO)8(mu-PR1R 2) (R1 = H, R2 = H or R1 = H, R2 = Ph), which contain the relatively rare mu-PH2 and mu-PPhH functionalities. Iron rich Fe2--xMnxP nanoparticles were obtained by thermal decomposition of FeMn(CO)8(mu-PH 2) using solution-based synthetic methods, and empirical evidence suggested that oleic acid was responsible for manganese depletion. Films containing Fe, Mn, and P with the desired stoichiometric ratio of 1:1:1 were prepared using FeMn(CO)8(mu-PH2) in a simple low-pressure metal-organic chemical vapor deposition (MOCVD) apparatus. Although the elemental composition of the precursor was conserved in the deposited film material, spectroscopic evidence indicated that the films were not composed of pure-phase FeMnP, but were actually mixtures of crystalline FeMnP and amorphous FeP and Mn xOy. A new method for the preparation of phase-pure ferromagnetic Fe 3P films on quartz substrates has also been developed. This approach involved the thermal decomposition of the single-source precursors H 2Fe3(CO)9PR (R = tBu or Ph) at 400 °C. The films were deposited using a simple home-built MOCVD apparatus and were characterized using a variety of analytical methods. The films exhibited excellent phase purity, as evidenced by X-ray diffraction, X-ray photoelectron spectroscopy, and field-dependent magnetization measurements, the results of which were all in good agreement with measurements obtained from bulk Fe3P. As-deposited Fe3P films were found to be amorphous, and little or no magnetic hysteresis was observed in plots of magnetization versus applied field. Annealing the Fe3P films at 550 °C resulted in improved crystallinity as well as the observation of magnetic hysteresis.

Density functional theory study of lithium diffusion at the interface between olivine-type LiFePO4 and LiMnPO4

NASA Astrophysics Data System (ADS)

Shi, Jianjian; Wang, Zhiguo; Qing Fu, Yong

2016-12-01

Coating LiMnPO4 with a thin layer of LiFePO4 shows a better electrochemical performance than the pure LiFePO4 and LiMnPO4, thus it is critical to understand Li diffusion at their interfaces to improve the performance of electrode materials. Li diffusion at the (1 0 0)\\text{LiFeP{{\\text{O}}4}} //(1 0 0)\\text{LiMnP{{\\text{O}}4}} , (0 1 0)\\text{LiFeP{{\\text{O}}4}} //(0 1 0)\\text{LiMnP{{\\text{O}}4}} , and (0 0 1)\\text{LiFeP{{\\text{O}}4}} //(0 0 1)\\text{LiMnP{{\\text{O}}4}} interfaces between LiFePO4 and LiMnPO4 was investigated using density functional theory. The calculated diffusion energy barriers are 0.55 eV for Li to diffuse along the (0 0 1) interface, 0.44 and 0.49 eV for the Li diffusion inside the LiMnPO4 and along the (1 0 0) interface, respectively. When Li diffuses from the LiFePO4 to LiMnPO4 by passing through the (0 1 0) interfaces, the diffusion barriers are 0.45 and 0.60 eV for the Li diffusions in both sides. The diffusion barriers for Li to diffuse in LiMnPO4 near the interfaces decrease compared with those in the pure LiMnPO4. The calculated diffusion coefficient of Li along the (1 0 0) interface is in the range of 3.65  ×  10-11-5.28  ×  10-12 cm2 s-1, which is larger than that in the pure LiMnPO4 with a value of 7.5  ×  10-14 cm2 s-1. Therefore, the charging/discharging rate performance of the LiMnPO4 can be improved by surface coating with the LiFePO4.

Iron, Manganese and Copper Release from Synthetic Hydroxyapatite

NASA Technical Reports Server (NTRS)

Sutter, B.; Hossner, L. R.; Ming, Douglas W.

1999-01-01

Kinetic stir-flow dissolution experiments were performed on iron- (Fe-SHA), manganese- (Mn-SHA), and copper- (Cu-SHA) containing synthetic hydroxyapatites. Solution treatments consisted of de-ionized water, citric acid and DTPA. Initially, Mn concentrations were higher than Cu concentrations and Fe concentrations were the lowest in all treatments. At later times Mn and Cu concentrations dropped in the DTPA treatment while Fe rose to the concentration similar to Mn and Cu. At all times, metal release concentrations in the water and citric acid treatments followed the trend of Mn>Cu>Fe. Rietveld analysis of x-ray diffraction data and ^31P NMR indicated that the metals substituted for Ca in the SHA structure. However, EPR data suggested that a metal (hydr)oxide phase existed either on the SHA surface or between the SHA crystallites. The metal concentration trend of Mn>Cu>Fe suggested that the initial solution metal concentrations are dependent on the dissolution of (hydr)oxides from SHA surfaces or between SHA crystallites. Similar metal concentrations at later times in the DTPA experiments suggests that metal concentrations were controlled by the release of Mn, Cu, or Fe from the SHA structure.

Tailoring magnetic behavior of CoFeMnNiX (X = Al, Cr, Ga, and Sn) high entropy alloys by metal doping

DOE PAGES

Zuo, Tingting; Gao, Michael C.; Ouyang, Lizhi; ...

2017-03-07

Magnetic materials with excellent performances are desired for functional applications. Based on the high-entropy effect, a system of CoFeMnNiX (X = Al, Cr, Ga, and Sn) magnetic alloys are designed and investigated. The dramatic change in phase structures from face-centered-cubic (FCC) to ordered body-centered-cubic (BCC) phases, caused by adding Al, Ga, and Sn in CoFeMnNiX alloys, originates from the potent short-range chemical order in the liquid state predicted by ab initio molecular dynamics (AIMD) simulations. This phase transition leads to the significant enhancement of the saturation magnetization (M s), e.g., the CoFeMnNiAl alloy has M s of 147.86 Am 2/kg.more » In conclusion, first-principles density functional theory (DFT) calculations on the electronic and magnetic structures reveal that the anti-ferromagnetism of Mn atoms in CoFeMnNi is suppressed especially in the CoFeMnNiAl HEA because Al changes the Fermi level and itinerant electron-spin coupling that lead to ferromagnetism.« less

Crystal Structure, Magnetic and Optical Properties of Mn-Doped BiFeO₃ by Hydrothermal Synthesis.

PubMed

Zhang, Ning; Wei, Qinhua; Qin, Laishun; Chen, Da; Chen, Zhi; Niu, Feng; Wang, Jiangying; Huanag, Yuexiang

2017-01-01

In this paper, Mn doped BiFeO₃ were firstly synthesized by hydrothermal process. The influence of Mn doping on structural, optical and magnetic properties of BiFeO₃ was studied. The different amounts of Mn doping in BiFeO₃ were characterized by X-ray diffraction, Scanning Electron Microscope, Energy Dispersive X-ray Spectroscope, UV-Vis diffuse reflectance spectroscopy and magnetic measurements. The X-ray diffraction (XRD) patterns confirmed the formation of pure phase rhombohedral structure in BiFe(1−x) Mn (x) O₃ (x = 0.01, 0.03, 0.05, 0.07) samples. The morphologies and chemical compositions of as-prepared samples could be observed by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscope (EDS). A relative large saturated magnetization (Ms) of 0.53 emu/g for x = 0.07 sample was obtained at room temperature, which is considered to be Mn ions doping. UV-Vis diffuse reflectance spectroscopy showed strong absorption of light in the range of 200–1000 nm, indicating the optical band gap in the visible region for these samples. This implied that BiFe(1−x) Mn(x)O₃ may be a potential photocatalyst for utilizing solar energy.

Arsenic removal in aqueous solution by a novel Fe-Mn modified biochar composite: Characterization and mechanism.

PubMed

Lin, Lina; Qiu, Weiwen; Wang, Di; Huang, Qing; Song, Zhengguo; Chau, Henry Wai

2017-10-01

The aim of this study was to develop a cost-effective method for As removal from aqueous systems. To this end, pristine biochar (BC) was impregnated with Fe-Mn oxides and a comparative analysis was conducted on the adsorption capacities of BC, Fe-Mn binary oxide (FMO), and Fe/Mn modified biochar (FMBC). The ferromanganese oxides increased the specific surface areas of BC. FMBC presented greater adsorption of As (Q max = 8.25mgg -1 ) than FMO and BC. Energy dispersive spectrometer analysis and electron microscope scanning revealed numerous pores of FMBC with the existence of Fe-Mn oxide using. Distinguished binding energy shifting of the As3d, Fe2p, O1s, and Mn2p3/2 regions after As sorption were found, indicating that Mn(III) oxidation and interaction of oxygen-containing function groups in the FMBC promoted the conversion of As(III) to As(V). Furthermore, chemisorption was found to be the main mechanism for As sorption on FMBC. Thus, the results suggest that FMBC could be used as an inexpensive and highly efficient adsorbent for As removal from water environment. Copyright © 2017 Elsevier Inc. All rights reserved.

Magnetic interactions in La0.7Sr0.3Mn1-xMexO3 (Me=Ga, Fe, Cr) manganites

NASA Astrophysics Data System (ADS)

Troyanchuk, I. O.; Bushinsky, M. V.; Karpinsky, D. V.; Tereshko, N. V.; Dobryansky, V. M.; Többens, D. M.; Sikolenko, V.; Efimov, V.

2015-11-01

Magnetic properties and crystal structure of La0.7Sr0.3Mn1-xMexO3 (Me=Ga, Fe, Cr; x≤0.3) have been studied by neutron powder diffraction and magnetization measurements. It is shown that substitution of manganese ions by chromium or gallium ions (x=0.3) leads to phase separation into antiferromagnetic and ferromagnetic phases whereas replacement by Fe ions stabilizes spin glass state (x=0.3). Ferromagnetic interactions in Cr-substituted compounds are much more pronounced than in Fe- and Ga-doped ones. Magnetic properties are discussed in the model assuming a dominance of superexchange interactions. It is considered that ferromagnetism in the Cr-substituted compositions is associated with nearly equal contributions from positive and negative components of the superexchange interaction between Mn3+ and Cr3+ ions as well as to mixed valence of chromium ions. The spin glass state observed for the Fe-doped sample (x=0.3) is associated with strong antiferromagnetic superexchange between Fe3+-O-Fe3+ and Fe3+-O-(Mn3+, Mn4+).

Large-scale phase separation with nano-twin domains in manganite spinel (Co,Fe,Mn){sub 3}O{sub 4}

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

Horibe, Y., E-mail: horibe@post.matsc.kyutech.ac.jp; Takeyama, S.; Mori, S.

The effect of Mn concentration on the formation of nano-domain structures in the spinel oxide (Co,Fe,Mn){sub 3}O{sub 4} was investigated by electron diffraction, bright-, and dark-field imaging technique with transmission electron microscopy. Large scale phase separation with nano-twin domains was observed in Co{sub 0.6}Fe{sub 1.0}Mn{sub 1.4}O{sub 4}, in contrast to the highly aligned checkerboard nano-domains in Co{sub 0.6}Fe{sub 0.9}Mn{sub 1.5}O{sub 4}. Diffusion of the Mn{sup 3+} ions with the Jahn-Teller distortions is suggested to play an important role in the formation of checkerboard nano-domain structure.

Enhanced Stability of the Fe(II)/Mn(II) State in a Synthetic Model of Heterobimetallic Cofactor Assembly.

PubMed

Kerber, William D; Goheen, Joshua T; Perez, Kaitlyn A; Siegler, Maxime A

2016-01-19

Heterobimetallic Mn/Fe cofactors are found in the R2 subunit of class Ic ribonucleotide reductases (R2c) and R2-like ligand binding oxidases (R2lox). Selective cofactor assembly is due at least in part to the thermodynamics of M(II) binding to the apoprotein. We report here equilibrium studies of Fe(II)/Mn(II) discrimination in the biomimetic model system H5(F-HXTA) (5-fluoro-2-hydroxy-1,3-xylene-α,α'-diamine-N,N,N',N'-tetraacetic acid). The homobimetallic F-HXTA complexes [Fe(H2O)6][1]2·14H2O and [Mn(H2O)6][2]2·14H2O (1 = [Fe(II)2(F-HXTA)(H2O)4](-); 2 = [Mn(II)2(F-HXTA)(H2O)4](-)) were characterized by single crystal X-ray diffraction. NMR data show that 1 retains its structure in solution (2 is NMR silent). Metal exchange is facile, and the heterobimetallic complex [Fe(II)Mn(II)(F-HXTA)(H2O)4](-) (3) is formed from mixtures of 1 and 2. (19)F NMR was used to quantify 1 and 3 in the presence of excess M(II)(aq) at various metal ratios, and equilibrium constants for Fe(II)/Mn(II) discrimination were calculated from these data. Fe(II) is preferred over Mn(II) with K1 = 182 ± 13 for complete replacement (2 ⇌ 1). This relatively modest preference is attributed to a hard-soft acid-base mismatch between the divalent cations and the polycarboxylate ligand. The stepwise constants for replacement are K2 = 20.1 ± 1.3 (2 ⇌ 3) and K3 = 9.1 ± 1.1 (3 ⇌ 1). K2 > K3 demonstrates enhanced stability of the heterobimetallic state beyond what is expected for simple Mn(II) → Fe(II) replacement. The relevance to Fe(II)/Mn(II) discrimination in R2c and R2lox proteins is discussed.

Study of As(III) and As(V) Oxoanion Adsorption onto Single and Mixed Ferrite and Hausmannite Nanomaterials

PubMed Central

Garcia, Sandra; Sardar, Saima; Maldonado, Stephanie; Garcia, Velia; Tamez, C.; Parsons, J. G.

2014-01-01

The removal of arsenic(III) and arsenic(V) from an aqueous solution through adsorption on to Fe3O4, MnFe2O4, 50% Mn substituted Fe3O4, 75% Mn substituted Fe3O4, and Mn3O4 nanomaterials was investigated. Characterization of the nanomaterials using XRD showed only pure phases for Mn3O4, MnFe2O4, and Fe3O4. The 50% and 75% substituted nanomaterials were found to be mixtures of Mn3O4 and Fe3O4. From batch studies the optimum binding pH of arsenic(III) and arsenic(V) to the nanomaterials was determined to be pH 3. The binding capacity for As(III) and As(VI) to the various nanomaterials was determined using Isotherm studies. The binding capacity of Fe3O4 was determined to be 17.1 mg/g for arsenic(III) and 7.0 mg/g for arsenic(V). The substitution of 25% Mn into the Fe3O4 lattice showed a slight increase in the binding capacity for As(III) and As(VI) to 23.8 mg/g and 7.9 mg/g, respectively. The 50% substituted showed the maximum binding capacity of 41.5 mg/g and 13.9 mg/g for arsenic(III) and arsenic(V). The 75% Mn substituted Fe3O4 capacities were 16.7 mg/g for arsenic(III) and 8.2 mg/g for arsenic(V). The binding capacity of the Mn3O4 was determined to be 13.5 mg/g for arsenic(III) and 7.5 mg/g for arsenic(V). In addition, interference studies on the effects of SO2−4, PO3−4, Cl−, and NO−3 investigated. All the interferences had very minimal effects on the As(III) and As(V) binding never fell below 20% even in the presence of 1000 ppm interfering ions. PMID:25097269

Unsymmetrical Bimetallic Complexes with MII–(μ-OH)–MII Cores (MIIMIII = FeIIFeIII, MnIIFeIII, MnIIMnIII): Structural, Magnetic, and Redox Properties

PubMed Central

Sano, Yohei; Weitz, Andrew C.; Ziller, Joseph W.; Hendrich, Michael P.; Borovik, A.S.

2013-01-01

Heterobimetallic cores are important unit within the active sites of metalloproteins, but are often difficult to duplicate in synthetic systems. We have developed a synthetic approach for the preparation of a complex with a MnII–(μ-OH)–FeIII core, in which the metal centers have different coordination environments. Structural and physical data support the assignment of this complex as a heterobimetallic system. Comparison with the analogous homobimetallic complexes, those containing MnII–(μ-OH)–MnIII and FeII–(μ-OH)–FeIII cores, further supports this assignment. PMID:23992041

Oxidative removal of Mn(II) from solution catalysed by the γ-FeOOH (lepidocrocite) surface

NASA Astrophysics Data System (ADS)

Sung, Windsor; Morgan, James J.

1981-12-01

A laboratory study was undertaken to ascertain the role of surface catalysis in Mn(II) oxidative removal. γ-FeOOH, a ferric oxyhydroxide formed by O2 oxidation of ferrous iron in solution, was studied in the following ways: surface charge characteristics by acid base titration, adsorption of Mn(II) and surface oxidation of Mn(II). A rate law was formulated to account for the effects of pH and the amount of surface on the surface oxidation rate of Mn(II). The presence of milli-molar levels of γ-FeOOH was shown to reduce significantly the half-life of Mn(II) in 0.7 M NaCl from hundreds of hours to hours. The numerical values of the surface rate constants for the γ-FeOOH and that reported for colloidal MnO2 are comparable in order of magnitude.

Caries prevalence and manganese and iron levels of drinking water in school children living in a rural/semi-urban region of North-Eastern Greece.

PubMed

Tsanidou, Eirini; Nena, Evangelia; Rossos, Alexandros; Lendengolts, Zhanna; Nikolaidis, Christos; Tselebonis, Athanasios; Constantinidis, Theodoros C

2015-11-01

The aim of this study was to correlate different combinations of manganese (Mn) and iron (Fe) concentration in drinking water with prevalence of dental caries in both primary and permanent dentition, among school children with similar socio-demographic characteristics. Evros region, in North-Eastern Greece, was divided into four areas, according to combinations of levels of Mn and Fe in drinking water (High Mn-high Fe; High Mn-low Fe; Low Mn-high Fe; Low Mn-low Fe). Children of similar socio-economic background, attending either first or sixth grade (primary or permanent dentition, respectively) of elementary schools, were clinically assessed for caries by three dentists. Caries was defined by the use of dmft/DMFT index. A questionnaire answered by the parents was also analysed. 573 children were included. Caries prevalence was high in both age groups (64.2 % with mean dmft 3.3 ± 3.6 in primary and 60.7 % with mean DMFT 2.3 ± 2.5 in permanent dentition, respectively). Residence in a high Mn-low Fe area was associated with a significant OR for caries in both age groups [OR (95 % CIs) for primary and permanent dentition was, respectively, 3.75 (1.68-8.37), p = 0.001 and 3.09 (1.48-6.44), p = 0.003], independently of factors like sugar consumption or brushing frequency. Prevalence of caries was high in general, and was associated with the combination of high Mn/low Fe levels in drinking water, independently of various socio-demographic factors.

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.

Diurnal variations of dissolved and colloidal organic carbon and trace metals in a boreal lake during summer bloom.

PubMed

Pokrovsky, O S; Shirokova, L S

2013-02-01

This work describes variation of element concentration in surface water of a subarctic organic-rich lake during the diurnal cycle of photosynthesis. An unusually hot summer 2010 in European part of subarctic Russia produced elevated surface water temperature (28-30 °C) and caused massive cyanobacterial bloom. Diurnal variation of ~40 dissolved macro and trace elements and organic carbon were recorded in the humic Lake Svyatoe in the White Sea drainage basin. Two days continuous measurements with 3 h sampling steps at the surface (0.5 m) allowed tracing cyanobacterial activity via pH and O₂ measurement and revealed constant concentrations (within ±20-30%) of all major elements (Na, Mg, Cl, SO₄, K, Ca), organic and inorganic carbon and most trace elements (Li, B, Sc, Ti, Ni, Cu, Ga, As, Rb, Sr, Y, Zr, Mo, Sb, medium and heavy REEs, Hf, Pb, Th, U). The concentration of Mn demonstrated a factor of 3 decrease during the day following Mn adsorption onto cyanobacterial cells due to ~1 pH unit raise during the photosynthesis and Mn release during the night due to desorption from the cell surface. The role of Mn(II) photo-oxidation by reactive oxygen species could be also pronounced, although its contribution to Mn diurnal variation was much smaller than the adsorption at the cell surfaces. Similar pattern, but with much lesser variations (c.a., 10-20%), was recorded for Ba and Fe. On-site ultrafiltration technique allowed to distinguish between low molecular weight (LMW) complexes (<1 kDa) and high molecular weight (HMW) colloids (1 kDa-0.22 μm) and to assess their diurnal pattern. Colloidal Al and Fe were the highest during the night, when the contribution of HMW allochthonous colloids was maximal. Typical insoluble trivalent and tetravalent elements exhibited constant complexation (>80-90%) with HMW allochthonous organics, independent on the diel photosynthetic cycle. Finally, biologically-relevant metals (Cu, Co, Cr, V, and Ni) demonstrated significant variations of colloidal fractions (from 10 to 60%) not directly related to the photosynthesis. The majority of possible metal nutrients, being strongly associated with organic and organo-mineral colloids do not exhibit any measurable concentration variation during photosynthesis. The two types of element behavior during cyanobacterial bloom in the water column--constant concentration and sinusoidal variations--likely depend on element speciation in solution and their relative affinity to surfaces of aquatic microorganisms and complexation with authochthonous and allochthonous organic matter. Copyright © 2012 Elsevier Ltd. All rights reserved.

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.

A stepwise recovery of metals from hybrid cathodes of spent Li-ion batteries with leaching-flotation-precipitation process

NASA Astrophysics Data System (ADS)

Huang, Yanfang; Han, Guihong; Liu, Jiongtian; Chai, Wencui; Wang, Wenjuan; Yang, Shuzhen; Su, Shengpeng

2016-09-01

The recovering of valuable metals in spent lithium-ion battery cathodes brings about economic and environmental benefits. A stepwise leaching-flotation-precipitation process is adopted to separate and recover Li/Fe/Mn from the mixed types of cathode materials (hybrid wastes of LiFePO4 and LiMn2O4). The optimal operating conditions for the stepwise recovery process are determined and analyzed by factorial design, thermodynamics calculation, XRD and SEM characterization in this study. First, Li/Fe/Mn ions are released from the cathode using HCl assisted with H2O2 in the acid leaching step. The leachability of metals follows the series Li > Fe > Mn in the acidic environment. Then Fe3+ ions are selectively floated and recovered as FeCl3 from the leachate in the flotation step. Finally, Mn2+/Mn3+ and Li+ ions are sequentially precipitated and separated as MnO2/Mn2O3 and Li3PO4 using saturated KMnO4 solution and hot saturated Na3PO4 solution, respectively. Under the optimized and advisable conditions, the total recovery of Li, Fe and Mn is respectively 80.93 ± 0.16%, 85.40 ± 0.12% and 81.02 ± 0.08%. The purity for lithium, ferrum and manganese compounds is respectively 99.32 ± 0.07%, 97.91 ± 0.05% and 98.73 ± 0.05%. This stepwise process could provide an alternative way for the effective separation and recovery of metal values from spent Li-ion battery cathodes in industry.

Complete oxidation of solid phase sulfides by manganese and bacteria in anoxic marine sediments

NASA Astrophysics Data System (ADS)

Aller, Robert C.; Rude, Peter D.

1988-03-01

During the physical or biological reworking of surficial marine sediments, metal oxides are often brought into contact with both solid and dissolved sulfides. Experiments simulating these mixing processes demonstrate that in natural sediments Mn-oxides can completely oxidize solid phase sulfides to SO 4- under anoxic conditions. The major source of sulfur is probably acid volatile sulfide. Minerals containing Mn +4 are apparently more effective than Mn +3 in driving the oxidation. There is slight or no evidence for complete sulfide oxidation by Fe-oxides under similar conditions. The reaction is inhibited by DNP (dinitrophenol) and azide, implying biological mediation by a group of chemolithotrophic bacteria such as the thiobacilli, having a well-organized cytochrome system, oxidative phosphorylation coupled with sulfide oxidation, and possibly aulolrophic CO 2 fixation. Lack of sensitivity to chlorate suggests that a No 3- reductase complex is not involved. Because of metal reduction and the overall stoichiometry of reaction, this sulfide oxidation causes a rise in pH in contrast to oxidation by O 2. Alkalinity is also simultaneously depeleted by Mn, Ca carbonate precipitation. Both manganoan kutnahorite and manganoan calcite are observed to form rapidly (days) during Mn reduction. The oxidation of sulfides by Mn-oxides is likely to be important, but highly variable, in organic-rich shelf sediments and environments such as hydrothermal vents where sulfidic plumes contact oxidized metals. A substantial Proportion of sedimentary sulfide may be oxidized and Mn reduced by this pathway, particularly in bioturbated sediments. The relative roles of lithotrophic (S) and heterotrophic (C) Mn-reduction in marine sediments are presently unknown.

Hydrogenetic Ferromanganese Crusts of the California Continental Margin

NASA Astrophysics Data System (ADS)

Conrad, Tracey A.

Hydrogenetic Ferromanganese (Fe-Mn) crusts grow from seawater and in doing so sequester elements of economic interest and serve as archives of past seawater chemistry. Ferromanganese crusts have been extensively studied in open-ocean environments. However, few studies have examined continent-proximal Fe-Mn crusts especially from the northeast Pacific. This thesis addresses Fe-Mn crusts within the northeast Pacific California continental margin (CCM), which is a dynamic geological and oceanographic environment. In the first of three studies, I analyzed the chemical and mineralogical composition of Fe-Mn crusts and show that continental-proximal processes greatly influence the chemistry and mineralogy of CCM Fe-Mn crusts. When compared to global open-ocean Fe-Mn crusts, CCM crusts have higher concentrations of iron, silica, and thorium with lower concentrations of many elements of economic interest including manganese, cobalt, and tellurium, among other elements. The mineralogy of CCM Fe-Mn crusts is also unique with more birnessite and todorokite present than found in open-ocean samples. Unlike open-ocean Fe-Mn crusts, carbonate-fluorapatite is not present in CCM crusts. This lack of phosphatization makes CCM Fe-Mn crusts excellent candidates for robust paleoceanography records. The second and third studies in this thesis use isotope geochemistry on select CCM Fe-Mn crusts from four seamounts in the CCM to study past terrestrial inputs into the CCM and sources and behavior of Pb and Nd isotopes over the past 7 million years along the northeast Pacific margin. The second study focuses on riverine inputs into the Monterey Submarine Canyon System and sources of the continental material. Osmium isotopes in the crusts are compared to the Cenozoic Os seawater curve to develop an age model for the samples that show the crusts range in age of initiation of crust growth from approximately 20 to 6 Myr. Lead and neodymium isotopes measured in select Fe-Mn crusts show that large amounts of terrestrial material entered the CCM via the Monterey Canyon from prior to 6.8+/-0.5 until 4.5 +/-0.5 Myr ago. These data combined with reconstructions of the paleo-coastline indicate that incision of the modern Monterey Canyon started around 7 Myr ago. Isotope plots of potential source regions indicate that the source of the material is the border of the southern Sierra Nevada and western Basin and Range. This answers a long-standing and fundamental question about the timing and formation of the Monterey Canyon, the dominant feature of the Monterey Bay. The third study presented here uses the differences in lead and neodymium isotopic values in CCM Fe-Mn crusts over time compared to open-ocean Pacific, North Pacific, and Arctic Ocean Fe-Mn crusts to identify regional time-series trends and sources for these important oceanographic tracers. I found that sediment fluxes and inputs of terrestrial material from North American rivers effects the lead and neodymium isotope composition of regional seawater.

Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

DOE PAGES

Tong, Yang; Jin, Ke; Bei, Hongbin; ...

2018-05-26

Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). Furthermore, the origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

Local lattice distortion in NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys investigated by synchrotron X-ray diffraction

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

Tong, Yang; Jin, Ke; Bei, Hongbin

Severe lattice distortion is presumptively considered as a core effect of high-entropy alloys, but quantitative measurements are still missing. Here, we demonstrate that the lattice distortion in high-entropy alloys can be quantitatively analyzed based on pair distribution function obtained from synchrotron X-ray diffraction. By applying this method to equiatomic NiCoCr, FeCoNiCr and FeCoNiCrMn concentrated alloys, we found that the local lattice distortion in the NiCoCr (0.23%) and FeCoNiCrMn (0.24%) alloys are comparable while negligible in the FeCoNiCr alloy (0.04%). Furthermore, the origin of local lattice distortion in the NiCoCr and FeCoNiCrMn concentrated alloys was discussed.

Transformation of metals speciation in a combined landfill leachate treatment.

PubMed

Wu, Yanyu; Zhou, Shaoqi; Chen, Dongyu; Zhao, Rong; Li, Huosheng; Lin, Yiming

2011-04-01

Landfill leachate was treated by a combined sequential batch reactor (SBR), coagulation, Fenton oxidation and biological aerated filter (BAF) technology. The metals in treatment process were fractionated into three fractions: particulate and colloidal (size charge filtration), free ion/labile (cation exchange) and non-labile fractions. Fifty percent to 66% Cu, Ni, Zn, Mn, Pb and Cd were present as particulate/colloidal matter in raw leachate, whereas Cr was present 94.9% as non-labile complexes. The free ion/labile fractions of Ni, Zn, Mg, Mn, Pb and Cd increased significantly after treatment except Cr. Fifty-nine percent to 100% of Al was present mainly as particulate/colloidal matter >0.45 μm and the remaining portions were predicted as non-labile complexes except in coagulation effluent. The speciation of Fe varied significantly in various individual processes. Visual MINTEQ simulation showed that 95-100% colloidal species for Cu, Cd and Pb were present as metal-humic complexes even with the lower dissolved organic carbon. Optimum agreements for the free ion/labile species were within acidic solution, whereas under-estimated in alkaline effluents. Overestimated particulate/colloidal fraction consisted with the hypothesis that a portion of colloids in fraction <0.45 μm were considered as dissolved. Copyright © 2011 Elsevier B.V. All rights reserved.

Temporal and spatial variability of Fe and Mn in perched groundwater flowing through weathered argillite underlying a steep forested hillslope

NASA Astrophysics Data System (ADS)

Kim, H.; Bishop, J. K.

2013-12-01

Groundwater flowing through weathered bedrock dictates the runoff chemistry to streams in many catchments yet; its chemical evolution has been rarely documented. In particular, observations of Fe and Mn dynamics in groundwater are extremely challenging due to their high reactivity. To preserve the sample integrity for these elements we have developed a new sampling scheme that is applicable to autosamplers; a gravitational filtration system (GFS). GFS is capable of filtering samples by gravity within 30 minutes after the sampling. The GFS samples showed a good agreement with reference samples, which were collected following the standard sampling method for trace metals (i.e. immediate filtration and acidification). Since October 2011, GFS has been employed to monitor Fe and Mn in perched groundwater that moves through weathered argillite in an intensively instrumented hillslope (Rivendell), in the Angelo Coast Range Reserve. The study site is located at the headwaters of the Eel River, northern California, characterized by a typical coastal Californian Mediterranean climate. We collected groundwater samples at 3 wells along the hillslope (upslope (W10), mid-slope (W3) and near the creek (W1)) with 1-3 day intervals. Additionally, rainwater and throughfall samples were collected at a meadow near the hillslope and at the middle of the hillslope, respectively. The results from our observations indicate that Fe and Mn exhibit distinct spatial and temporal behavior under variable hydrologic conditions. The concentrations of Fe in throughfall vs. rainwater were similar (0.45μM vs. 0.49μM), but Mn in throughfall was 10-fold higher than that in rainwater (1.2 μM vs. 0.1 μM). In the early rainy season, W10's water table was deep (-18m) and Fe and Mn in W10 were 30-150 nM and 1-2 μM, respectively. As the rainy season proceeds, W10's water table rose by 4-6m, indicating the arrival of new water. At this time, Mn in W10 decreased to ~0.1 μM, synchronizing with the water table rise, and remained unchanged throughout the season. In contrast, Fe slowly declined to <10nM for this high water table regime. During the summer recession limb, Fe and Mn concentrations in W10 began to increase. During the dry summer, the concentrations of Fe and Mn at W3 were 2-3μM and 15-20 μM, respectively. At the beginning of the rainy seasons, the W3 water table slowly rose (<1 m) and both Fe and Mn decreased by 10-fold. The concentrations of Fe and Mn decreased to 20-70nM and 0.1 μM, respectively, when W3's water table became highly dynamic and fluctuated about 4 m. At W1, Fe and Mn remained in the 50-100nM and 5-10 μM ranges, respectively; however, the water table was extremely responsive to rainfall inputs. Mn in W1 was briefly diluted to <0.1 μM during large rainstorms and rebounded within several days. In the late summer of 2012, Fe and Mn in W1 increased up to 2-6 μM and 80 μM, respectively. These high-frequency observations of Fe and Mn will provide insight into the biogeochemical cycles of redox sensitive elements in upland terrains, allowing for better quantitative estimation of these elemental fluxes.

Factors affecting the partitioning of Cu, Zn and Pb in boulder coatings and stream sediments in the vicinity of a polymetallic sulfide deposit

USGS Publications Warehouse

Filipek, L.H.; Chao, T.T.; Carpenter, R.H.

1981-01-01

A sequential extraction scheme is utilized to determine the geochemical partitioning of Cu, Zn and Pb among hydrous Mn- and Fe-oxides, organics and residual crystalline silicates and oxides in the minus-80-mesh ( Fe-oxides > Mn-oxides; Zn, Mn-oxides {reversed tilde equals} organics > Fe-oxides; Pb, Fe-oxides > organics > Mn-oxides. In the sediments, organics are the most efficient scavengers of all three ore metals. These results emphasize the importance of organics as sinks for the ore metals, even in environments with high concentrations of Mn- and Fe-oxides. Of the ore metals, Zn appears to be the most mobile, and is partitioned most strongly into the coatings. However, anomaly contrast for hydromorphic Zn, normalized to the MnFe-oxide or organic content, is similar in sediments and coatings. Cu shows the highest anomaly on the boulder coatings, probably due to precipitation of a secondary Cu mineral. In contrast, detrital Pb in the pan concentrates shows a better anomaly than any hydromorphic Pb component. ?? 1981.

Photochemical Decoration of Silver Nanocrystals on Magnetic MnFe2O4 Nanoparticles and Their Applications in Antibacterial Agents and SERS-Based Detection

NASA Astrophysics Data System (ADS)

Huy, Le Thanh; Tam, Le Thi; Van Son, Tran; Cuong, Nguyen Duy; Nam, Man Hoai; Vinh, Le Khanh; Huy, Tran Quang; Ngo, Duc-The; Phan, Vu Ngoc; Le, Anh-Tuan

2017-06-01

In this study, multifunctional nanocomposites consisting of silver nanoparticles and manganese ferrite nanoparticles (Ag-MnFe2O4) were successfully synthesized using a two-step chemical process. The formation of Ag-MnFe2O4 nanocomposites were analyzed by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy measurements. Noticeable antibacterial activity of the Ag-MnFe2O4 nanocomposites was demonstrated against two Gram-negative bacteria, Salmonella enteritidis and Klebsiella pneumoniae. A direct-drop diffusion method can be an effective way to investigate the antibacterial effects of nanocomposite samples. Interestingly, we also demonstrated the use of Ag-MnFe2O4 nanocomposites as a surface-enhanced Raman scattering (SERS) platform to detect and quantify trace amounts of organic dye in water solutions. The combination of Ag and MnFe2O4 nanoparticles opens opportunities for creating advantages such as targeted bactericidal delivery, recyclable capability, and sensitive SERS-based detection for advanced biomedicine and environmental monitoring applications.

Improvement of Superplasticity in High-Mg Aluminum Alloys by Sacrifice of Some Room Temperature Formability

NASA Astrophysics Data System (ADS)

Jin, H.; Amirkhiz, B. Shalchi; Lloyd, D. J.

2018-03-01

The mechanical properties of fully annealed Al-4.6 wt pct Mg alloys with different levels of Mn and Fe have been characterized at room and superplastic forming (SPF) temperatures. The effects of Mn and Fe on the intermetallic phase, grain structure, and cavitation were investigated and correlated to the formability at different temperatures. Although both Mn and Fe contribute to the formation of Al6(Mn,Fe) phase, which refines the grain structure by particle-stimulated nucleation and Zener pinning, their effects are different. An increasing Mn reduces the room temperature formability due to the increasing number of intermetallic particles, but significantly improves the superplasticity by fine grain size-induced grain boundary sliding. Meanwhile, the Fe makes the constituent particles very coarse, resulting in reduced formability at all temperatures due to extensive cavitation. A combination of high Mn and low Fe is therefore beneficial to SPF, while low levels of both elements are good for cold forming. Consequently, the superplasticity of high-Mg aluminum alloys can be significantly improved by modifying the chemical composition with sacrifice of some room temperature formability.

The enhancement in dielectric and magnetic property in Na and Mn co substituted lanthanum ferrite

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

Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K., E-mail: akt@iitp.ac.in; Centre for Energy and Environment Indian Institute of Technology Patna 800013 India

2016-05-06

Nanocrystalline solid solutions of La{sub 1-x}Na{sub x}Fe{sub 1-y}Mn{sub y}O{sub 3} (x=y=0.00 and 0.25) were prepared via modified Pechini route. No evidence of secondary or impurity phase has been detected up to the detection of error limit of high power X-ray diffractometer. Dielectric property of the samples has been investigated in the frequency range 100 Hz-4MHz at temperature ranging 300–450K. The value of relative permittivity (ε{sub r}) increases drastically and shows colossal dielectric response (∼10{sup 4}) by cosubstitution of Na and Mn as compared to pure LaFeO{sub 3}. Dielectric relaxation peak in loss tangent in both samples have been found and shiftmore » towards higher frequency region as temperature increases. Magnetization-Field (M-H) loop of the calcined sample have been recorded at room temperature (300K) at field ±60kOe. Magnetic property also enhanced by co substitution of Na and Mn. The change in Fe/Mn-O-Fe/Mn angle by co-substitution of Na and Mn in LaFeO{sub 3} and indirect exchange interaction between two different magnetic sub lattices Fe and Mn might be responsible for drastic change. Saturation/maximum magnetic moment increase ∼four times in LNFM25 (5.335emu/g) as compared to pure LaFeO{sub 3} (1.302emu/g).« less

Oscillatory oxidation of Mn(II) ions by hexacyanoferrates(III) and bistability in the reductions of MnO 2 by hexacyanoferrates(II) in a CSTR

NASA Astrophysics Data System (ADS)

Olexová, Anna; Melicherčík, Milan; Treindl, L'udovít

1997-04-01

A new transition metal oscillator based on the oxidation of Mn 2+ ions by Fe(CN) 3-6 ions in a CSTR has been found. As well as the oscillations of the absorbance of the Mn(IV) species, pH-oscillations have been observed. In the reduction of manganese dioxide by Fe(CN) 4-6 ions a kinetic bistability has been described. A skeleton mechanism described recently for Mn(II)H 2O 2 and Mn(II)Br 2 oscillators has been applied here and further developed by the idea of the catalytic activity of colloidal particles and of the assistance of the pH-value change of both main processes, i.e. of the Mn(II) oxidation by Fe(CN) 3-6 ions and of the Mn(IV) reduction by Fe(CN) 4-6 ions. This appears to be the first case where both sides of a reversible reaction are autocatalytic.

Synthesis and magnetic properties of the thin film exchange spring system of MnBi/FeCo

NASA Astrophysics Data System (ADS)

Sabet, S.; Hildebrandt, E.; Alff, L.

2017-10-01

Manganese bismuth thin films with a nominal thickness of ∼40 nm were grown at room temperature onto quartz glass substrate in a DC magnetron sputtering unit. In contrast to the usual multilayer approach, the MnBi films were deposited using a single sputtering target with a stoichiometry of Mn55Bi45 (at. %). A subsequent in-situ annealing step was performed in vacuum in order to form the ferromagnetic LTP of MnBi. X-ray diffraction confirmed the formation of a textured LTP MnBi hard phase after annealing at 330 °C. This film shows a maximum saturation magnetization of 530 emu/cm3, high out-of-plane coercivity of 15 kOe induced by unreacted bismuth. The exchange coupling effect was investigated by deposition of a second layer of FeCo with 1 nm and 2 nm thickness onto the LTP MnBi films. The MnBi/FeCo double layer showed as expected higher saturation magnetization with increasing thickness of the FeCo layer while the coercive field remained constant. The fabrication of the MnBi/FeCo double layer for an exchange spring magnet was facilitated by deposition from a single stoichiometric target.

Structural, dielectric and gas sensing behavior of Mn substituted spinel MFe2O4 (M=Zn, Cu, Ni, and Co) ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Ranjith Kumar, E.; Siva Prasada Reddy, P.; Sarala Devi, G.; Sathiyaraj, S.

2016-01-01

Spinel ferrite (MnZnFe2O4, MnCuFe2O4, MnNiFe2O4 and MnCoFe2O4) nanoparticles have been prepared by evaporation method. The annealing temperature plays an important role on changing particle size of the spinel ferrite nanoparticles was found out by X-ray diffraction and transmission electron microscopy. The role of manganese substitution in the spinel ferrite nanoparticles were also analyzed for different annealing temperature. The substitution of Mn also creates a vital change in dielectric properties have been measured in the frequency range of 100 kHz to 5 MHz. These spinel ferrites are decomposed to α-Fe2O3 after annealing above 550 °C in air. Through the characterization of the prepared powder, the effect of annealing temperature, chemical composition and preparation technique on the microstructure, particle size and dielectric properties of the Mn substituted spinel ferrite nanoparticles are discussed. Furthermore, Conductance response of Mn substituted MFe2O4 ferrite nanoparticles were measured by exposing the materials to reducing gas like liquefied petroleum gas (LPG).

Engineered in situ bioremediation of a petroleum hydrocarbon-contaminated aquifer: assessment of mineralization based on alkalinity, inorganic carbon and stable carbon isotope balances

NASA Astrophysics Data System (ADS)

Hunkeler, Daniel; Höhener, Patrick; Bernasconi, Stefano; Zeyer, Josef

1999-04-01

A concept is proposed to assess in situ petroleum hydrocarbon mineralization by combining data on oxidant consumption, production of reduced species, CH 4, alkalinity and dissolved inorganic carbon (DIC) with measurements of stable isotope ratios. The concept was applied to a diesel fuel contaminated aquifer in Menziken, Switzerland, which was treated by engineered in situ bioremediation. In the contaminated aquifer, added oxidants (O 2 and NO 3-) were consumed, elevated concentrations of Fe(II), Mn(II), CH 4, alkalinity and DIC were detected and the DIC was generally depleted in 13C compared to the background. The DIC production was larger than expected based on the consumption of dissolved oxidants and the production of reduced species. Stable carbon isotope balances revealed that the DIC production in the aquifer originated mainly from microbial petroleum hydrocarbon mineralization, and that geochemical reactions such as carbonate dissolution produced little DIC. This suggests that petroleum hydrocarbon mineralization can be underestimated if it is determined based on concentrations of dissolved oxidants and reduced species.

Preparation of Superparamagnetic Zn0.5Mn0.5Fe2O4 Particle by Coprecipitation-Sonochemical Method for Radar Absorbing Material

NASA Astrophysics Data System (ADS)

Taufiq, A.; Bahtiar, S.; Sunaryono; Hidayat, N.; Hidayat, A.; Mufti, N.; Diantoro, M.; Fuad, A.; Munasir; Rahmawati, R.; Adi, W. A.; Pratapa, S.; Darminto

2017-05-01

One of many applications of spinel ferrite nanoparticles is related to their performance as radar absorbing materials. In this work, we report developing synthesis method through combined coprecipitation-sonochemical routes in preparing Zn0.5Mn0.5Fe2O4 nanoparticle from iron sand in Indonesia as a vital raw material. The structure, size, morphology, and elements of the Zn0.5Mn0.5Fe2O4 nanoparticle were investigated via X-Ray diffractometry and Transmission/Scanning Electron Microscopy (TEM/SEM) combining Energy Dispersive Spectroscopy (EDS). The magnetic properties of the Zn0.5Mn0.5Fe2O4 nanoparticle were characterized by using Vibrating Sample Magnetometer (VSM). Furthermore, the reflection loss character of the Zn0.5Mn0.5Fe2O4 nanoparticle was determined via Vector Network Analyzer (VNA). From the qualitative and quantitative analysis of the XRD data, it can be identified that the Zn0.5Mn0.5Fe2O4 particle formed a spinel cubic structure in a single phase with the lattice parameter of approximately 8.401 Å. It is known from the TEM image that the Zn0.5Mn0.5Fe2O4 particle had a size of about 9.7 nm and tended to agglomerate. Furthermore, the data analysis of the M(H) curve presented that the Zn0.5Mn0.5Fe2O4 nanoparticle has a superparamagnetic behavior with the saturation magnetization of approximately 43 emu/g. Finally, the data analysis of the reflection loss as a function of frequency showed that the Zn0.5Mn0.5Fe2O4 nanoparticle performs as a radar absorbing material with the absorption performance of approximately -11.0 dB at the frequency of 10.8 GHz

Synthesis of Ferromagnetic Fe0.6 Mn0.4 O Nanoflowers as a New Class of Magnetic Theranostic Platform for In Vivo T1 -T2 Dual-Mode Magnetic Resonance Imaging and Magnetic Hyperthermia Therapy.

PubMed

Liu, Xiao Li; Ng, Cheng Teng; Chandrasekharan, Prashant; Yang, Hai Tao; Zhao, Ling Yun; Peng, Erwin; Lv, Yun Bo; Xiao, Wen; Fang, Jie; Yi, Jia Bao; Zhang, Huan; Chuang, Kai-Hsiang; Bay, Boon Huat; Ding, Jun; Fan, Hai Ming

2016-08-01

Uniform wüstite Fe0.6 Mn0.4 O nanoflowers have been successfully developed as an innovative theranostic agent with T1 -T2 dual-mode magnetic resonance imaging (MRI), for diagnostic applications and therapeutic interventions via magnetic hyperthermia. Unlike their antiferromagnetic bulk counterpart, the obtained Fe0.6 Mn0.4 O nanoflowers show unique room-temperature ferromagnetic behavior, probably due to the presence of an exchange coupling effect. Combined with the flower-like morphology, ferromagnetic Fe0.6 Mn0.4 O nanoflowers are demonstrated to possess dual-modal MRI sensitivity, with longitudinal relaxivity r1 and transverse relaxivity r2 as high as 4.9 and 61.2 mm(-1) s(-1) [Fe]+[Mn], respectively. Further in vivo MRI carried out on the mouse orthotopic glioma model revealed gliomas are clearly delineated in both T1 - and T2 -weighted MR images, after administration of the Fe0.6 Mn0.4 O nanoflowers. In addition, the Fe0.6 Mn0.4 O nanoflowers also exhibit excellent magnetic induction heating effects. Both in vitro and in vivo magnetic hyperthermia experimentation has demonstrated that magnetic hyperthermia by using the innovative Fe0.6 Mn0.4 O nanoflowers can induce MCF-7 breast cancer cell apoptosis and a complete tumor regression without appreciable side effects. The results have demonstrated that the innovative Fe0.6 Mn0.4 O nanoflowers can be a new magnetic theranostic platform for in vivo T1 -T2 dual-mode MRI and magnetic thermotherapy, thereby achieving a one-stop diagnosis cum effective therapeutic modality in cancer management. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mn-Cr isotopic systematics of individual Chainpur chondrules. [Abstract only

NASA Technical Reports Server (NTRS)

Nyquist, L.; Lindstrom, D.; Wiesmann, H.; Martinez, R.; Bansal, B.; Mittlefehldt, D.; Shih, C.-Y.; Wentworth, S.

1994-01-01

Twenty-eight chondrules separated from Chainpur (LL3.4) were surveyed for abundances of Mn, Cr, Na, Fe, Sc, Hf, Ir, and Zn by Instrumental Neutron Activation Analysis (INAA). Six, weighting 0.6-1.5 mg each, were chosen for Scanning Electron Microscopy (SEM)/Energy Dispersive X-ray (EDX) and high-precision Ce-isotopic studies. LL-chondrite-normalized (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) were found to be useful in categorizing them. Five chondrules (CH-16, -17, -18, -23, and -28) were in the range 0.5 less than (Mn/Fe)(sub LL) less than 1. 4 and 0.5 less than (Sc/Fe)(sub LL) less than 1.4. The sixth (CH-25) had (Mn/Fe)(sub LL) and (Sc/Fe)(sub LL) ratios of 0.40 and 8.1, respectively, and was enriched in the refractory lithophile elements Sc and Hf and the refractory siderophile element Ir by 2.7 and 4.4x LL abundances respectively. SEM/EDX of exterior surfaces of the chondrules showed they consisted of varying proportions of low- and high-Ca pyroxenes, olivine, glass, kamacite/taenite, and Fe-sulfides. Chromium-53/chromium-52 for the six chondrules and bulk Chainpur (WR) are presented. Chromium-54/chromium-52 is close to terrestrial and does not correlate with Mn/Cr. We provisionally ignore the possibility of initial Cr isotopic heterogeneities among the chondrules. Omitting both the CH-25 and WR data, a linear regression gives initial (Mn-53/Mn-55)(sub I) = 8 +/- 4 x 10(exp -6), corresponding to chondrule formation at Delta(t)(sub LEW) = -9 +/- 4 Ma prior to igneous crystallization of the LEW 86010 angrite. If initial (Mn-53/Mn-55)(sub 0) in the solar system were as high as approximately 4.4 x 10(exp -5) when Allende CAI formed, our data suggest Chainpur chondrules formed approximately 9 Ma later, in qualitative agreement with 'late' I-Xe formation ages for most Chainpur chondrules.

Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters.

PubMed

Bai, Yaohui; Chang, Yangyang; Liang, Jinsong; Chen, Chen; Qu, Jiuhui

2016-12-01

High concentrations of iron (Fe(II)) and manganese (Mn(II)) often occur simultaneously in groundwater. Previously, we demonstrated that Fe(II) and Mn(II) could be oxidized to biogenic Fe-Mn oxides (BFMO) via aeration and microbial oxidation, and the formed BFMO could further oxidize and adsorb other pollutants (e.g., arsenic (As(III)) and antimony (Sb(III))). To apply this finding to groundwater remediation, we established four quartz-sand columns for treating groundwater containing Fe(II), Mn(II), As(III), and Sb(III). A Mn-oxidizing bacterium (Pseudomonas sp. QJX-1) was inoculated into two parallel bioaugmented columns. Long-term treatment (120 d) showed that bioaugmentation accelerated the formation of Fe-Mn oxides, resulting in an increase in As and Sb removal. The bioaugmented columns also exhibited higher overall treatment effect and anti-shock load capacity than that of the non-bioaugmented columns. To clarify the causal relationship between the microbial community and treatment effect, we compared the biomass of active bacteria (reverse-transcribed real-time PCR), bacterial community composition (Miseq 16S rRNA sequencing) and community function (metagenomic sequencing) between the bioaugmented and non-bioaugmented columns. Results indicated that the QJX1 strain grew steadily and attached onto the filter material surface in the bioaugmented columns. In general, the inoculated strain did not significantly alter the composition of the indigenous bacterial community, but did improve the relative abundances of xenobiotic metabolism genes and Mn oxidation gene. Thus, bioaugmentation intensified microbial degradation/utilization for the direct removal of pollutants and increased the formation of Fe-Mn oxides for the indirect removal of pollutants. Our study provides an alternative method for the treatment of groundwater containing high Fe(II), Mn(II) and As/Sb. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modulation of Jahn-Teller effect on magnetization and spontaneous electric polarization of CuFeO2

NASA Astrophysics Data System (ADS)

Xiao, Guiling; Xia, Zhengcai; Wei, Meng; Huang, Sha; Shi, Liran; Zhang, Xiaoxing; Wu, Huan; Yang, Feng; Song, Yujie; Ouyang, Zhongwen

2018-03-01

CuFe0.99Mn0.01O2 and CuFe0.99Co0.01O2 single crystal samples are grown by a floating zone technique and their magnetization and spontaneous electric polarization have been investigated. Similarly with pure CuFeO2, an obviously anisotropic magnetization and spontaneous electric polarization were observed in the both doped samples, and their phase transition critical fields and temperatures are directly doping ion dependent. Considering the different d-shell configuration and ionic size between Mn3+, Co3+ and Fe3+ ions, in which the Mn3+ ion with Jahn-Teller (J-T) effect has different distortion on the geometry frustration from both of Fe3+ and Co3+ ion. Since for Mn3+ ion, the orbital splitting results from the low-symmetry J-T distortion in a crystal-field environment leads to a distorted MnO6 octahedron, which different from undistorted FeO6 and CoO6 octahedrons. The strain between distorted and undistorted octahedrons produces different effects on the spin reorientation transition and spontaneous electric polarization. Although the pure CuFeO2 has a very strong and robust frustration, the presence of the strain due to the random distribution of distorted MnO6 octahedron and undistorted CoO6 (FeO6) octahedrons leads to its spin reorientation transitions and spontaneous electric polarization different from CuFeO2.

Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens

USGS Publications Warehouse

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

1989-01-01

The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.

The enhancement in dielectric and magnetic property in Na and Mn co substituted lanthanum ferrite

NASA Astrophysics Data System (ADS)

Rai, Atma; Thakur, Awalendra K.

2016-05-01

Nanocrystalline solid solutions of La1-xNaxFe1-yMnyO3 (x=y=0.00 and 0.25) were prepared via modified Pechini route. No evidence of secondary or impurity phase has been detected up to the detection of error limit of high power X-ray diffractometer. Dielectric property of the samples has been investigated in the frequency range 100 Hz-4MHz at temperature ranging 300-450K. The value of relative permittivity (ɛr) increases drastically and shows colossal dielectric response (˜104) by cosubstitution of Na and Mn as compared to pure LaFeO3. Dielectric relaxation peak in loss tangent in both samples have been found and shift towards higher frequency region as temperature increases. Magnetization-Field (M-H) loop of the calcined sample have been recorded at room temperature (300K) at field ±60kOe. Magnetic property also enhanced by co substitution of Na and Mn. The change in Fe/Mn-O-Fe/Mn angle by co-substitution of Na and Mn in LaFeO3 and indirect exchange interaction between two different magnetic sub lattices Fe and Mn might be responsible for drastic change. Saturation/maximum magnetic moment increase ˜four times in LNFM25 (5.335emu/g) as compared to pure LaFeO3 (1.302emu/g).

3D hierarchical flower-like nickel ferrite/manganese dioxide toward lead (II) removal from aqueous water.

PubMed

Xiang, Bo; Ling, Dong; Lou, Han; Gu, Hongbo

2017-03-05

A functionalized magnetic nickel ferrite/manganese dioxide (NiFe 2 O 4 /MnO 2 ) with 3D hierarchical flower-like and core-shell structure was synthesized by a facile hydrothermal approach and applied for the removal of Pb(II) ions from aqueous solutions. Batch adsorption experiments were conducted to study the effect of solution pH, initial Pb(II) concentration, and dose of absorbents on the Pb(II) removal by NiFe 2 O 4 /MnO 2 . The NiFe 2 O 4 /MnO 2 nanocomposites showed the fast Pb(II) adsorption performance with the maximum adsorption capacity of 85.78mgg -1 . The adsorption kinetics of Pb(II) onto NiFe 2 O 4 /MnO 2 obeyed a pseudo-second-order model. The isothermal experimental results indicated that the Langmuir model was fitted better than the Freundlich model, illustrating a monolayer adsorption process for Pb(II) onto NiFe 2 O 4 /MnO 2 . Meanwhile, the NiFe 2 O 4 /MnO 2 was easily separated from the solution by an external magnet within a short period of time and still exhibited almost 80% removal capacity after six regenerations. The NiFe 2 O 4 /MnO 2 is expected to be a new promising adsorbent for heavy metal removal. Copyright © 2016 Elsevier B.V. All rights reserved.

Elemental Mercury Oxidation over Fe-Ti-Mn Spinel: Performance, Mechanism, and Reaction Kinetics.

PubMed

Xiong, Shangchao; Xiao, Xin; Huang, Nan; Dang, Hao; Liao, Yong; Zou, Sijie; Yang, Shijian

2017-01-03

The design of a high-performance catalyst for Hg 0 oxidation and predicting the extent of Hg 0 oxidation are both extremely limited due to the uncertainties of the reaction mechanism and the reaction kinetics. In this work, Fe-Ti-Mn spinel was developed as a high-performance catalyst for Hg 0 oxidation, and the reaction mechanism and the reaction kinetics of Hg 0 oxidation over Fe-Ti-Mn spinel were studied. The reaction orders of Hg 0 oxidation over Fe-Ti-Mn spinel with respect to gaseous Hg 0 concentration and gaseous HCl concentration were approximately 1 and 0, respectively. Therefore, Hg 0 oxidation over Fe-Ti-Mn spinel mainly followed the Eley-Rideal mechanism (i.e., the reaction of gaseous Hg 0 with adsorbed HCl), and the rate of Hg 0 oxidation mainly depended on Cl • concentration on the surface. As H 2 O, SO 2 , and NO not only inhibited Cl • formation on the surface but also interfered with the interface reaction between gaseous Hg 0 and Cl • on the surface, Hg 0 oxidation over Fe-Ti-Mn spinel was obviously inhibited in the presence of H 2 O, SO 2 , and NO. Furthermore, the extent of Hg 0 oxidation over Fe-Ti-Mn spinel can be predicted according to the kinetic parameter k E-R , and the predicted result was consistent with the experimental result.

Serrated Flow and Dynamic Strain Aging in Fe-Mn-C TWIP Steel

NASA Astrophysics Data System (ADS)

Lan, Peng; Zhang, Jiaquan

2018-01-01

The tensile behavior, serrated flow, and dynamic strain aging of Fe-(20 to 24)Mn-(0.4 to 0.6)C twinning-induced plasticity (TWIP) steel have been investigated. A mathematical approach to analyze the DSA and PLC band parameters has been developed. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with a theoretical ordering index (TOI) between 0.1 and 0.3, DSA can occur at the very beginning of plastic deformation and provide serrations during work hardening, while for TOI less than 0.1 the occurrence of DSA is delayed and twinning-dominant work hardening remains relatively smooth. The critical strain for the onset of DSA and PLC bands in Fe-Mn-C TWIP steels decreases as C content increases, while the numbers of serrations and bands increase. As Mn content increases, the critical strain for DSA and PLC band varies irregularly, but the numbers of serrations and bands increase. For Fe-(20 to 24)Mn-(0.4 to 0.6)C TWIP steel with grain size of about 10 to 20 μm, the twinning-induced work hardening rate is about 2.5 to 3.0 GPa, while the DSA-dominant hardening rate is about 2.0 GPa on average. With increasing engineering strain from 0.01 to 0.55 at an applied strain rate of 0.001s-1, the cycle time for PLC bands in Fe-Mn-C TWIP steel increases from 6.5 to 162 seconds, while the band velocity decreases from 4.5 to 0.5 mm s-1, and the band strain increases from 0.005 to 0.08. Increasing applied strain rate leads to a linear increase of band velocity despite composition differences. In addition, the influence of the Mn and C content on the tensile properties of Fe-Mn-C TWIP steel has been also studied. As C content increases, the yield strength and tensile strength of Fe-Mn-C TWIP steel increase, but the total elongation variation against C content is dependent on Mn content. As Mn content increases, the yield strength and tensile strength decrease, while the total elongation increases, despite C content. Taking both tensile properties and serrated flow behavior into consideration, Fe-22Mn-0.4C TWIP steel shows excellent mechanical performance with a high product of tensile strength and total elongation and a slightly serrated stress-strain response. To suppress the negative effect of DSA in Fe-Mn-C TWIP steels on the stability of tensile behavior, a TOI lower than 0.1 is strongly suggested.

Exceptional effect of glassy lithium fluorophosphate on Mn-rich olivine cathode material for high-performance Li ion batteries

NASA Astrophysics Data System (ADS)

Kim, Jongsoon; Kim, Hyungsub; Myung, Seung-Taek; Yoo, Jung-Keun; Lee, Seongsu

2018-01-01

Mn-rich olivine LiFe0.3Mn0.7PO4 is homogenously encapsulated by an ∼3-nm-thick conductive nanolayer composed of the glassy lithium fluorophosphate through simple non-stoichiometric synthesis using additives of small amounts of LiF and a phosphorus source. The coating of the glassy lithium fluorophosphate nanolayer is clearly verified using transmission electron microscopy and X-ray photoelectron spectroscopy. It enables significant decrease in charge transfer resistance of LiFe0.3Mn0.7PO4 and improvement of its sluggish Li diffusion. At a rate of 10C, the LiFe0.3Mn0.7PO4 encapsulated by conductive glassy lithium fluorophosphate (LiFe0.3Mn0.7PO4-GLFP) electrode delivers a capacity of ∼130 mAh g-1, which is ∼77% of its theoretical capacity (∼170 mAh g-1) and ∼1.5 times higher than that of the pristine counterpart at 10C. Furthermore, LiFe0.3Mn0.7PO4-GLFP achieves outstanding cycle stability (∼75% retention of its initial capacity over 500 cycles at 1C). The proposed olivine LiFe0.3Mn0.7PO4-GLFP battery is thus expected to be a promising candidate for large-scale energy storage applications.

Impact of a long term fire retardant (Fire Trol 931) on the leaching of Na, Al, Fe, Mn, Cu and Si from a Mediterranean forest soil: a short-term, lab-scale study.

PubMed

Koufopoulou, Sofia; Michalopoulos, Charalampos; Tzamtzis, Nikolaos; Pappa, Athina

2014-06-01

Long term fire retardant (LTR) application for forest fire prevention purposes as well as wildland fires can result in chemical leaching from forest soils. Large quantities of sodium (Na), aluminium (Al), iron (Fe), manganese (Mn), copper (Cu) and silicon (Si) in leachates, mainly due to ammonium (one of the major LTR components) soil deposition, could affect the groundwater quality. The leaching of Na, Al, Fe, Mn, Cu and Si due to nitrogen based LTR application (Fire Trol 931) was studied at laboratory scale. The concentrations of Na(+), Al(3+), Fe(3+)/Fe(2+), Mn(2+), Cu(2+) and Si(4+) were measured in the resulting leachates from pots with forest soil and pine trees alone and in combination with fire. The leaching of Na, Fe and Si from treated pots was significantly greater than that from control pots. The leaching of Al, Mn and Cu was extremely low.

Accelerated Oxygen Atom Transfer and C-H Bond Oxygenation by Remote Redox Changes in Fe 3Mn-Iodosobenzene Adducts

DOE PAGES

de Ruiter, Graham; Carsch, Kurtis M.; Gul, Sheraz; ...

2017-03-24

In this paper, we report the synthesis, characterization, and reactivity of [LFe 3(PhPz) 3OMn( sPhIO)][OTf] x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene–metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, 57Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe III 2Fe IIMn II vs. Fe III 3Mn II) influence oxygen atom transfer in tetranuclear Fe 3Mn clusters. Finally, in particular, a one-electron redox change atmore » a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude.« less

Kinetics of abiotic nitrous oxide production via oxidation of hydroxylamine by particulate metals in seawater

NASA Astrophysics Data System (ADS)

Cavazos, A. R.; Taillefert, M.; Glass, J. B.

2016-12-01

The oceans are a significant of nitrous oxide (N2O) to the atmosphere. Current models of global oceanic N2­O flux focus on microbial N2O cycling and often ignore abiotic reactions, such as the thermodynamically favorable oxidation of the nitrification intermediate hydroxylamine (NH2OH) by Mn(IV) or Fe(III). At circumneutral pH, NH2OH oxidation is more thermodynamically favorable via Mn(IV) than Fe(III) reduction. We characterized the kinetics of NH2OH oxidation in synthetic ocean water at pH 5.1-8.8 using microsensor electrodes to measure real-time N2O production. N2O production rates and yield were greater when NH2OH was oxidized by Mn(IV) than Fe(III). Accordingly, the reduction of Mn(IV) was first order with respect to NH2OH whereas the reduction of Fe(III) was zero order with respect to NH2OH. Interestingly, the order of the reaction with respect to Mn(IV) appears to be negative whereas the reaction is second order with respect to Fe(III). The inverse order with respect to Mn(IV) may be due to the aggregation of particles in seawater, which decreases their surface area and changes their reactivity. Finally, the reaction is first order with respect to protons with Fe(III) as the oxidant but zero order with Mn(IV). The stronger effect of the pH on the reaction with Fe(III) as the oxidant compared to Mn(IV) reflects the stoichiometry of these two reactions, as each mole of N2O produced by Fe(III) reduction consumes eight protons while each mole of N2O produced with Mn(IV) as the oxidant requires only four protons. Our data show that abiotic NH2OH oxidation by Mn(IV) or Fe(III) particles may represent a significant source of N2O in seawater. These findings suggest that abiotic N2O production in marine waters may be significant in areas of the oceans where particulate metals originating from aerosols, dust, or rivers may react with NH2OH released from ammonia-oxidizing microorganisms.

Effects of Co and Mn doping in K0.8Fe2-ySe2 revisited.

PubMed

Zhou, Tingting; Chen, Xiaolong; Guo, Jiangang; Jin, Shifeng; Wang, Gang; Lai, Xiaofang; Ying, Tianping; Zhang, Han; Shen, Shijie; Wang, Shunchong; Zhu, Kaixing

2013-07-10

Accumulated evidence indicates that phase separation occurs in potassium intercalated iron selenides, a superconducting phase coexisting with the antiferromagnetic phase K2Fe4Se5, the so-called '245 phase'. Here, we report a comparative study of substitution effects by Co and Mn for Fe sites in K0.8Fe2-ySe2 within the phase separation scenario. Our results demonstrate that Co and Mn dopants have distinct differences in occupancy and hence in the suppression mechanism of superconductivity upon doping of Fe sites. In K0.8Fe2-xCoxSe2, Co prefers to occupy the lattice of the superconducting phase and suppresses superconductivity very quickly, obeying the magnetic pair-breaking mechanism or the collapse of the Fermi surface nesting mechanism. In contrast, in K0.8Fe1.7-xMnxSe2, Mn shows no preferential occupancy in the superconducting phase or the 245 phase. The suppression of superconductivity can be attributed to restraining of the superconducting phase and meanwhile inducing another non-superconducting phase by Mn doping.

Recrystallization of Manganite (γ-MnOOH) and Implications for Trace Element Cycling.

PubMed

Hens, Tobias; Brugger, Joël; Cumberland, Susan A; Etschmann, Barbara; Frierdich, Andrew J

2018-02-06

The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II) aq ) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with Manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II) aq under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a 62 Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the Manganite crystal structure during reactions in 1 mM Mn(II) aq and in Mn(II)-free solutions. XAS spectra show that Ni is initially sorbed on the Manganite mineral surface and is progressively incorporated into the mineral structure over time (13% after 51 days) even in the absence of dissolved Mn(II). The amount of Ni incorporation significantly increases to about 40% over a period of 51 days when Mn(II) aq is present in solution. Similarly, Mn(II) aq promotes Ni exchange between Ni-substituted Manganite and dissolved Ni(II), with around 30% of Ni exchanged at pH 7.5 over the duration of the experiment. No new mineral phases are detected following recrystallization as determined by X-ray diffraction and XAS. Our results reveal that Mn(II)-catalyzed mineral recrystallization partitions Ni between Mn oxides and aqueous fluids and can therefore affect Ni speciation and mobility in the environment.

Development of Novel Faster-Dissolving Microneedle Patches for Transcutaneous Vaccine Delivery

PubMed Central

Ono, Akihiko; Ito, Sayami; Sakagami, Shun; Saito, Mio; Quan, Ying-Shu; Kamiyama, Fumio; Hirobe, Sachiko; Okada, Naoki

2017-01-01

Microneedle (MN) patches are promising for transcutaneous vaccination because they enable vaccine antigens to physically penetrate the stratum corneum via low-invasive skin puncturing, and to be effectively delivered to antigen-presenting cells in the skin. In second-generation MN patches, the dissolving MNs release the loaded vaccine antigen into the skin. To shorten skin application time for clinical practice, this study aims to develop novel faster-dissolving MNs. We designed two types of MNs made from a single thickening agent, carboxymethylcellulose (CMC) or hyaluronan (HN). Both CMC-MN and HN-MN completely dissolved in rat skin after a 5-min application. In pre-clinical studies, both MNs could demonstrably increase antigen-specific IgG levels after vaccination and prolong antigen deposition compared with conventional injections, and deliver antigens into resected human dermal tissue. In clinical research, we demonstrated that both MNs could reliably and safely puncture human skin without any significant skin irritation from transepidermal water loss measurements and ICDRG (International Contact Dermatitis Research Group) evaluation results. PMID:28771172

Sorption of Ferric Iron from Ferrioxamine B to Synthetic and Biogenic Layer Type Manganese Oxides

NASA Astrophysics Data System (ADS)

Duckworth, O.; John, B.; Sposito, G.

2006-12-01

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effects of predominantly Mn(IV) oxides, we studied the sorption reaction of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(III, IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over at pH 8. After 72 hours equilibration time, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the EXAFS spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to into the mineral structure at multiple sites with no evidence of DFOB complexation, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron in marine and terrestrial environments.

Sulfides of Bottom Sediments in the Northeastern Part of the Black Sea

NASA Astrophysics Data System (ADS)

Rozanov, A. G.

2018-03-01

A study of bottom sediments conducted on the 100th cruise of R/V Professor Shtokman in the northeastern part of the Black Sea along the section from the Kerch Strait to the deep-sea depression allowed estimation of Holocene sulfide sedimentation and consideration of the accompanying diagenetic processes, which involve reactions with C, N, and P. The behavior of dissolved forms of Mn and Fe is considered from the viewpoint of their different solubility and formation of sulfides. The redox system of the Black Sea sediments can significantly be expanded at the expense of the migration methane and hydrogen, which accompanies its anaerobic oxidation.

Sorption of Ferrioxime B to Synthetic and Biogenic layer type Mn Oxides

NASA Astrophysics Data System (ADS)

Duckworth, O. W.; Bargar, J. R.; Sposito, G.

2005-12-01

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effect of solid-phase Mn(IV), we studied the sorption reaction of ferrioxamine B [principally the species, Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore, desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over the pH range between 5 and 9. After 72 h equilibration time at pH 8, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-Ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the X-ray absorption spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed with DFOB, but instead is incorporated into the mineral structure, thus implying that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron.

Surface Charge Development on Transition Metal Sulfides: An Electrokinetic Study

NASA Astrophysics Data System (ADS)

Bebie, Joakim; Schoonen, Martin A. A.; Fuhrmann, Mark; Strongin, Daniel R.

1998-02-01

The isoelectric points, pH i.e.p., of ZnS, PbS, CuFeS 2, FeS, FeS 2, NiS 2, CoS 2, and MnS 2 in NaCl supported electrolyte solutions are estimated to be between pH 3.3 and 0.6, with most of the isoelectric points below pH 2. The first electrokinetic measurements on NiS 2, CoS 2, and MnS 2 are reported here. Below pH i.e.p. the metal-sulfide surfaces are positively charged, above pH i.e.p. the surfaces are negatively charged. The addition of Me 2+ ions shifts the pH i.e.p. and changes the pH dependence considerably. The isoelectric points of the measured transition metal sulfides in the absence of metal ions or dissolved sulfide (H 2S or HS -) are in agreement with those found in earlier studies. The pH range of observed isoelectric points for metal sulfides (0.6-3.3) is compared to the considerably wider pH i.e.p. range (2-12) found for oxides. The correlation between pH i.e.p. and the electronegativities of the metal sulfides suggests that all metal sulfides will have an isoelectric point between pH 0.6 and 3.3. Compared to metal oxides, sulfides exhibit an isoelectric point that is largely independent of the nature of the metal cation in the solid.

Heavy metals in water, sediments, plants and fish of Kali Nadi U. P. (India)

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

Ajmal, M.; Uddin, R.; Khan, A.U.

1988-01-01

The distribution of heavy metals viz., Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, plants and fish samples collected from the Kali Nadi (India) have been determined. The studies have shown that there was considerable variation in the concentration of heavy metals from one sampling station to the other which may be due to the variation in the quality of industrial and sewage wastes being added to the river at different places. The orders of the concentration of heavy metals in water, sediments, plants (Eicchornia crassipes) and fish (Heteropnuestes fossilis) were Fe > Znmore » > Cu > Mn > Cr > Ni > Pb > Co > Cd; Fe > Zn > Mn > Ni > Cr > Co > Cu > Pb > Cd; Fe > Mn > Zn > Cu > Ni > Co > Pb > Cr > Cd and Fe > Zn > Mn > Ni > Pb >Co > Cr > Cu > Cd, respectively.« less

Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

NASA Technical Reports Server (NTRS)

Nowotny, H.; Wayne, S.; Schuster, J. C.

1982-01-01

The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

MnFe2O4: Synthesis, morphology and electrochemical properties

NASA Astrophysics Data System (ADS)

Kulkarni, Shrikant; Thombare, Balu; Patil, Shankar

2017-05-01

MnFe2O4 has been synthesized by simple ammonia assisted co-precipitation method to obtain nanocrystalline powder. X-ray diffraction studies confirmed its crystallinity and phase purity. The MnFe2O4 calcined at 1000°C for 4 h has spinel crystal structure with Fd3m space group and lattice constant 8.511 Å. The electrode was prepared by dip coating method on stainless steel substrate and fired at 600°C for 2 h. Random shape grains of 0.2 to 1.5 micron with pores of 1-2 micron dimensions were observed in SEM images. The electrochemical studies of MnFe2O4 were carried out with 1 mole Na2SO4 electrolyte. The MnFe2O4 electrode shows highest specific capacitance of 27.53 F.g-1 and interfacial capacitance of 0.83 F.cm-2.

Accurate solid solution range of BiMnxFe3-xO6 and low temperature magnetism

NASA Astrophysics Data System (ADS)

Jiang, Pengfei; Yue, Mufei; Cong, Rihong; Gao, Wenliang; Yang, Tao

2017-11-01

BiMnxFe3-xO6 (x = 1) represents a new type of oxide structure containing Bi3+ and competing magnetic super-exchanges. In literature, multiple magnetic states were realized at low temperatures in BiMnFe2O6, and the hypothetical parent compounds (BiMn3O6, BiFe3O6) were predicted to be different in magnetism. Herein, we performed a careful study on the syntheses of BiMnxFe3-xO6 at ambient pressure, and the solid solution range was determined to be 0.9 ≤ x ≤ 1.3 by Rietveld refinements on high-quality powder X-ray diffraction data. Due to the very similar cationic size of Mn3+ and Fe3+, and possibly the structural rigidity, there was no significant structure change in the whole range of solid solution. The magnetic behavior of BiMnxFe3-xO6 (x = 1.2, 1.22, 1.26, 1.28 and 1.3) was generally similar to BiMnFe2O6, while the relative higher concentration of Mn3+ led to the decreasing of the antiferromagnetic ordering temperature.

Biodegradable FeMnSi Sputter-Coated Macroporous Polypropylene Membranes for the Sustained Release of Drugs

PubMed Central

Fornell, Jordina; Soriano, Jorge; Guerrero, Miguel; Sirvent, Juan de Dios; Ferran-Marqués, Marta; Ibáñez, Elena; Barrios, Leonardo; Baró, Maria Dolors; Suriñach, Santiago; Nogués, Carme; Sort, Jordi; Pellicer, Eva

2017-01-01

Pure Fe and FeMnSi thin films were sputtered on macroporous polypropylene (PP) membranes with the aim to obtain biocompatible, biodegradable and, eventually, magnetically-steerable platforms. Room-temperature ferromagnetic response was observed in both Fe- and FeMnSi-coated membranes. Good cell viability was observed in both cases by means of cytotoxicity studies, though the FeMnSi-coated membranes showed higher biodegradability than the Fe-coated ones. Various strategies to functionalize the porous platforms with transferrin-Alexa Fluor 488 (Tf-AF488) molecules were tested to determine an optimal balance between the functionalization yield and the cargo release. The distribution of Tf-AF488 within the FeMnSi-coated PP membranes, as well as its release and uptake by cells, was studied by confocal laser scanning microscopy. A homogeneous distribution of the drug within the membrane skeleton and its sustained release was achieved after three consecutive impregnations followed by the addition of a layer made of gelatin and maltodextrin, which prevented exceedingly fast release. The here-prepared organic-inorganic macroporous membranes could find applications as fixed or magnetically-steerable drug delivery platforms. PMID:28672792

Mineralogical and chemical characterization of iron-, manganese-, and copper-containing synthetic hydroxyapatites.

PubMed

Sutter, B; Ming, D W; Clearfield, A; Hossner, L R

2003-01-01

The National Aeronautics and Space Administration's (NASA) Advanced Life Support (ALS) Program is evaluating the use of Fe-, Mn-, and Cu-containing synthetic hydroxyapatite (SHA) as a slow release fertilizer for crops that might be grown on the International Space Station or at Lunar and Martian outposts. Separate Fe-, Mn-, and Cu-containing SHA materials along with a transition-metal free SHA (pure-SHA) were synthesized using a precipitation method. Chemical and mineralogical analyses determined if and how Fe, Mn, and Cu were incorporated into the SHA structure. X-ray diffraction (XRD), Rietveld refinement, and transmission electron microscopy (TEM) confirmed that SHA materials with the apatite structure were produced. Chemical analyses indicated that the metal containing SHA materials were deficient in Ca relative to pure-SHA. The shift in the infrared PO4-mu 3 vibrations, smaller unit cell parameters, smaller particle size, and greater structural strain for Fe-, Mn-, and Cu-containing SHA compared with pure-SHA suggested that Fe, Mn, and Cu were incorporated into SHA structure. Rietveld analyses revealed that Fe, Mn, and Cu substituted into the Ca2 site of SHA. An Fe-rich phase was detected by TEM analyses and backscattered electron microscopy in the Fe-containing SHA material with the greatest Fe content. The substitution of metals into SHA suggests that metal-SHA materials are potential slow-release sources of micronutrients for plant uptake in addition to Ca and P.

Mineralogical and chemical characterization of iron-, manganese-, and copper-containing synthetic hydroxyapatites

NASA Technical Reports Server (NTRS)

Sutter, B.; Ming, D. W.; Clearfield, A.; Hossner, L. R.

2003-01-01

The National Aeronautics and Space Administration's (NASA) Advanced Life Support (ALS) Program is evaluating the use of Fe-, Mn-, and Cu-containing synthetic hydroxyapatite (SHA) as a slow release fertilizer for crops that might be grown on the International Space Station or at Lunar and Martian outposts. Separate Fe-, Mn-, and Cu-containing SHA materials along with a transition-metal free SHA (pure-SHA) were synthesized using a precipitation method. Chemical and mineralogical analyses determined if and how Fe, Mn, and Cu were incorporated into the SHA structure. X-ray diffraction (XRD), Rietveld refinement, and transmission electron microscopy (TEM) confirmed that SHA materials with the apatite structure were produced. Chemical analyses indicated that the metal containing SHA materials were deficient in Ca relative to pure-SHA. The shift in the infrared PO4-mu 3 vibrations, smaller unit cell parameters, smaller particle size, and greater structural strain for Fe-, Mn-, and Cu-containing SHA compared with pure-SHA suggested that Fe, Mn, and Cu were incorporated into SHA structure. Rietveld analyses revealed that Fe, Mn, and Cu substituted into the Ca2 site of SHA. An Fe-rich phase was detected by TEM analyses and backscattered electron microscopy in the Fe-containing SHA material with the greatest Fe content. The substitution of metals into SHA suggests that metal-SHA materials are potential slow-release sources of micronutrients for plant uptake in addition to Ca and P.

Giant magnetoresistance enhancement in spin valves with nano-oxide layers

NASA Astrophysics Data System (ADS)

Lai, Chih-Huang; Chen, C. J.; Chin, T. S.

2001-06-01

The magnetoresistance (MR) ratio is enhanced by 35% by inserting the nano-oxide layer (NOL) at the Ta/Co interface in the FeMn-based top spin valves (Ta/NOL/Co/Cu/Co/FeMn/Ta). The enhancement is attributed to specular reflection, resulting in a large resistance change and small sheet resistance. However, the formation of NOL at the interface of Ta/Co suppresses the (111) texture, resulting in small exchange fields. Top spin valves with NOLs show good thermal stability up to 200 °C annealing. The MR ratio is further increased after annealing at temperatures below 200 °C. Enhancement of the MR ratio by 61% can be achieved by annealing at 150 °C. For bottom spin valves (Ta/NiFe/FeMn/Co/Cu/NiFe/Ta), NOLs formed at FeMn/Co and NiFe/Ta interfaces increase MR ratios, but NOLs at Co/Cu or Cu/NiFe deteriorate the differential spin scattering and significantly reduce MR ratios.

Modifying exchange bias effects of Mn/NiFe bilayers by in-situ Ar+ bombardment

NASA Astrophysics Data System (ADS)

Causer, G. L.; Manna, P. K.; Chiu, C.-C.; van Lierop, J.; Ionescu, M.; Lin, K.-W.; Klose, F.

2017-10-01

In this work, we present a procedure to modify the exchange bias (EB) properties of antiferromagnetic Mn/ferromagnetic NiFe bilayers by in-situ low energy Ar+ bombardment of the Mn layer during sample deposition. We present structural and magnetic results for unassisted and Ar+ assisted Mn/NiFe bilayers. X-ray diffraction, transmission electron microscopy and electron diffraction results establish different preferred Mn orientation directions between the two samples as a result of the Ar+ bombardment process. Hysteresis loops taken over several temperatures reveal that samples assisted with Ar+ ions during the Mn layer deposition had suppressed EB properties at low temperature as compared to samples grown without Ar+ assistance.

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

USGS Publications Warehouse

Hein, J.R.; Schulz, M.S.; Dunham, R.E.; Stern, R.J.; Bloomer, S.H.

2008-01-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 ?? and 7 ?? manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean-8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along, the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms. Copyright 2008 by the American Geophysical Union.

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

NASA Astrophysics Data System (ADS)

Hein, James R.; Schulz, Marjorie S.; Dunham, Rachel E.; Stern, Robert J.; Bloomer, Sherman H.

2008-08-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 Å and 7 Å manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean 8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms.

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

Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Bae, Jae Wung; Moon, Jongun; Jang, Min Ji; Ahn, Dong-Hyun; Joo, Soo-Hyun; Jung, Jaimyun; Yim, Dami; Kim, Hyoung Seop

2017-09-01

Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.

Thermal expansion and cation partitioning of MnFe2O4 (Jacobsite) from 1.6 to 1276 K studied by using neutron powder diffraction

NASA Astrophysics Data System (ADS)

Levy, Davide; Pastero, Linda; Hoser, Andreas; Viscovo, Gabriele

2015-01-01

MnFe2O4 is a low-cost and stable magnetic spinel ferrite. In this phase, the influence of the inversion degree on the magnetic properties is still not well understood. To understand this relationship, Mn-ferrite was synthesized by a chemical co-precipitation method modified in our laboratory and studied by using the Neutron Powder Diffraction from 1.6 K to 1243 K. A full refinement of both crystal and magnetic structures was performed in order to correlate the high-temperature cation partitioning, the Curie transition and the structure changes of the Mn-ferrite. In this work three main temperature intervals are detected, characterized by different Mn-ferrite behaviors: first, ranging from 1.6 K to 573 K, where MnFe2O4 is magnetic; second, from 573 K to 623 K, where MnFe2O4 becomes paramagnetic without cation partitioning; and lastly, from 673 K to 1243 K, where cation partitioning occurs.

AC conductivity, magnetic and shielding effectiveness studies on polyaniline embedded Co0.5Mn0.5Fe2O4 nanoparticles for electromagnetic interference suppression

NASA Astrophysics Data System (ADS)

Gurusiddesh, M.; Madhu, B. J.; Shankaramurthy, G. J.

2018-05-01

Electrically conducting Polyaniline (PANI)/Co0.5Mn0.5Fe2O4 nanocomposites are synthesized by in situ polymerization of aniline monomer in the presence of Co0.5Mn0.5Fe2O4 nanoparticles. Structural studies on the synthesized samples have been carried out using X-ray diffraction technique, Field emission scanning electron microscopy and Energy dispersive X-ray spectroscopy. Frequency dependent ac conductivity studies on the prepared samples revealed that conductivity of the composite is high compared to Co0.5Mn0.5Fe2O4 nanoparticles. Further, both the samples exhibited hysteresis behavior under the applied magnetic field. Electromagnetic interference (EMI) shielding effectiveness of both the samples decreases with increase in the applied frequency in the studied frequency range. Maximum shielding effectiveness (SE) of 31.49 dB and 62.84 dB were obtained for Co0.5Mn0.5Fe2O4 nanoparticles and PANI/Co0.5Mn0.5Fe2O4 nanocomposites respectively in the studied frequency range. Observed higher EMI shielding in the composites was attributed to its high electrical conductivity.

Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

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

Ohno, S.; Shimakura, H.; Tahara, S.

The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquidmore » Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.« less

Electrochemical characterization of FeMnO3 microspheres as potential material for energy storage applications

NASA Astrophysics Data System (ADS)

Saravanakumar, B.; Ramachandran, S. P.; Ravi, G.; Ganesh, V.; Guduru, Ramesh K.; Yuvakkumar, R.

2018-01-01

In this study, uniform iron manganese trioxide (FeMnO3) microspheres were characterized as electrode for supercapacitor applications. The microspheres were synthesized by hydrothermal method in the presence of different molar ratios of sucrose. X-ray diffraction pattern confirmed that the obtained microsphere has body-centered lattice structure of space group 1213(199). The Raman peak observed at 640 cm-1 might be attributed to the stretching mode of vibration of Mn-O bonds perpendicular to the direction of MnO6 octahedral double chains. The photoluminescence peak at the 536 nm corresponded to Fe2+ ions in FeMnO3 lattice point of body-centered cubic structure. The characteristic strong infrared (IR) bands observed at 669 cm-1 corresponded to Fe-O stretching. The electrochemical characterization of the obtained FeMnO3 products could be understood by carrying out cyclic voltammeter, electroimpedance spectra, and galvanostatic charging and discharge studies in a three-cell setup that demonstrates the exceptional specific capacitance of 773.5 F g-1 at a scan rate of 10 mV s-1 and 763.4 F g-1 at a current density of 1 A g-1.

Bioaccumulation of metals in fish species from water and sediments in macrotidal Ennore creek, Chennai, SE coast of India: A metropolitan city effect.

PubMed

Jayaprakash, M; Kumar, R Senthil; Giridharan, L; Sujitha, S B; Sarkar, S K; Jonathan, M P

2015-10-01

Accumulation of trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were investigated in water, sediment (n=20) along with six fish of diverse feeding guilds (Sillago sihama, Liza parsia, Etroplus suratensis, Oreochromis mossambicus, Arius parkii and Gerres oyena) from the Ennore creek, northern part of Chennai metropolitan megacity, southeast coast of India. Dissolved trace metals (DTMs) in surface water samples and total trace metals (TTMs) in surface sediments (top 0-10cm) indicate that concentration pattern of metals was higher in the discharge point of the river/channels entering the main creek. The maximum mean values of DTMs exhibited the following decreasing order (expressed in µg/L): Fe (1698)>Mn (24)>Zn (14.50)>Pb (13.89)>Ni (6.73)>Cu (3.53)>Co (3.04)>Cr (2.01) whereas the trend is somewhat different in sediments (µgg(-1)): Fe (4300)>Mn (640)>Cr (383)>Zn (155)>Cu (102)>Ni (35)>Pb (32)>Cd (0.51) are mainly due to the industrial complexes right on the banks of the river/channels. Species-specific heterogeneous patterns of tissue metal loads were apparent and the overall metal enrichment exhibited the following decreasing order (expressed in µgg(-1)): Cu (7.33)>Fe (6.53)>Zn (4.91)>Cr (1.67)>Pb (1.33)>Ni (0.44)>Mn (0.43)>Co (0.36)>Cd (0.11). This indicates that metals are absorbed onto the different organs, which is also endorsed by the calculated values of bioaccumulation factor (BAFs) (avg. muscle 117, gill 126, liver 123, intestine 118) in fishes. The high calculated biota sediment accumulation factor (BSAF) (0.437) for the species Arius parkii is considered to be a potential bioindicator in this region. The enrichment of trace metals is also supported by the association of metals in water, sediments and different body organs (muscle, gill, liver, intestine) of fish samples. Comparative studies with other coastal regions indicate considerable enrichment of DTMs & TTMs in sediments as well as in various organs of fish samples. Holistic spatial, temporal monitoring and comprehensive regional strategies are required to prevent health risks and ensure nutritional safety conditions. Copyright © 2015 Elsevier Inc. All rights reserved.

Influence of Fe doped on the magnetocaloric behavior of La_{{2}/{3}} Ca_{{1}/{3}} Mn1-x Fe x O3 compounds: a Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Alzate-Cardona, J. D.; Barco-Rios, H.; Restrepo-Parra, E.

2018-02-01

The magnetocaloric behavior of La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 for x  =  0.00, 0.02, 0.03, 0.05, 0.07, 0.08 and 0.10 under the influence of an external magnetic field was simulated and analyzed. Simulations were carried out using the Monte Carlo method and the classical Heisenberg model under the Metropolis algorithm. These mixed valence manganites are characterized by having three types of magnetic ions corresponding to Mn4+≤ft(S=\\frac{3}{2}\\right) , which are bonded with Ca2+ , and Mneg3+ and Mneg\\prime3+ (S=2) , related to La3+ . The Fe ions were randomly included, replacing Mn ions. With this model, the magnetic entropy change, Δ S , in an isothermal process was determined. -Δ Sm showed maximum peaks around the paramagnetic-ferromagnetic transition temperature, which depends on Fe doping. Relative cooling power was computed for different Fe concentrations varying the magnetic applied field. Our model and results show that the Fe doping decreases the magnetocaloric effect in the La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3, making this a bad candidate for magnetic refrigeration. The strong dependence of the magnetocaloric behavior on Fe doping and the external magnetic field in La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 can boost these materials for the future technological applications.

The role of the (111) texture on the exchange bias and interlayer coupling effects observed in sputtered NiFe/IrMn/Co trilayers

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

Castro, I. L.; Nascimento, V. P.; Passamani, E. C.

2013-05-28

Magnetic properties of sputtered NiFe/IrMn/Co trilayers grown on different seed layers (Cu or Ta) deposited on Si (100) substrates were investigated by magnetometry and ferromagnetic resonance measurements. Exchange bias effect and magnetic spring behavior have been studied by changing the IrMn thickness. As shown by X-ray diffraction, Ta and Cu seed layers provoke different degrees of (111) fcc-texture that directly affect the exchange bias and indirectly modify the exchange spring coupling behavior. Increasing the IrMn thickness, it was observed that the coupling angle between the Co and NiFe ferromagnetic layers increases for the Cu seed system, but it reduces formore » the Ta case. The results were explained considering (i) different anisotropies of the Co and IrMn layers induced by the different degree of the (111) texture and (ii) the distinct exchange bias set at the NiFe/IrMn and IrMn/Co interfaces in both systems. The NiFe and Co interlayer coupling angle is strongly correlated with both exchange bias and exchange magnetic spring phenomena. It was also shown that the highest exchange bias field occurs when an unstressed L1{sub 2} IrMn structure is stabilized.« less

Environmental impact of coal ash on tributary streams and nearshore water of Lake Erie. Progress report, June 1, 1975--December 31, 1975. [Cd, Zn, Cu, Cr, Fe, Mn

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

Wood, K.

The principal study site is the landfill of the Niagara Mohawk Power Corp., Dunkirk, N.Y. Concentrations of dissolved metals are determined in the waters from the site and aquatic invertebrates from ponds and streams at the site are being identified and analyzed for trace metals. Elevated levels of Fe and Mn occur in the runoff from the site and in the aquatic invertebrates. The metals Cd, Zn, Cu, and Cr are found at low levels (ppB range) in the waters and in variable, generally low concentrations in the biota. Taxonomic study is focused primarily on the Chironomidae (10 general) andmore » Ephemeroptera (6 genera) with detailed studies in progress. The rate of leaching of metals from coal ash is also being studied in the laboratory by two methods. Sediments from Lake Erie at Dunkirk, N.Y., are being assessed for textural classification and composition. Attempts are being made to distinguish between coal wastes and other sediment in the silt and finer size range. The dump site is being evaluated for groundwater, surface water, and geological structure, so that trace element cycling can be evaluated.« less

Phytoremediation of domestic wastewaters in free water surface constructed wetlands using Azolla pinnata.

PubMed

Akinbile, Christopher O; Ogunrinde, Temitope A; Che Bt Man, Hasfalina; Aziz, Hamidi Abdul

2016-01-01

Two constructed wetlands, one with Azolla pinnata plant (CW1) and the other without (CW2) for treating domestic wastewaters were developed. Fifteen water parameters which include: Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Total Suspended Solid (TSS), Total Phosphorus (TP), Total Nitrogen (TN), Ammoniacal Nitrogen (NH3N), Turbidity, pH, Electrical Conductivity (EC), Iron (Fe), Magnesium (Mg), Manganese (Mn), and heavy metals such as Lead (Pb) and Zinc (Zn) were analyzed using standard laboratory procedures. The experiments were conducted in two (dry and wet) seasons simultaneously. Results showed considerable reductions in all parameters and metals including Zn in CW1 compared with CW2 in the two seasons considered while Pb and Mn were not detected throughout the study. Zn concentration levels reduced significantly in both seasons just as removal efficiencies of 70.03% and 64.51% were recorded for CW1 while 35.17% and 33.45% were recorded for CW2 in both seasons. There were no significant differences in the removal efficiencies of Fe in both seasons as 99.55%, 59.09%, 88.89%, and 53.56% were recorded in CW1 and CW2 respectively. Azolla pinnata has proved effective in domestic wastewater phytoremediation studies.

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.

Cultural Meromixis: the Influence of Road Salt Deicers on Two Urban Kettle Lakes

NASA Astrophysics Data System (ADS)

Koretsky, C.; Sibert, R.; Wyman, D. A.; Griffey, D.; Krishnamurthy, R. V.

2014-12-01

The increasing global use of road salt deicers has led to an influx of salts, particularly NaCl and CaCl2, into urban surface waters. This influx has led to documented salinization of drinking water supplies, as well as damage to ecosystems. There is an increasing recognition that the influx of road salt deciers may also influence the physical mixing of lakes, with dramatic consequences for lake biogeochemistry. In this study, the water column chemistry of two kettle lakes in urban Kalamazoo, MI, USA was monitored for over a year. Woods Lake, an ~9.7 ha, 14 m max depth lake, receives most water from storm water sewers, whereas nearby Asylum Lake, an ~19.8 ha, 15.8 m max depth lake, is primarily groundwater fed. The water columns of both lakes are strongly redox stratified, but exhibit some significant differences in water chemistry. The input of road salt has caused Woods Lake to transition to meromixis, with permanently anoxic bottom waters and significant accumulations of dissolved Mn(II), Fe(II), NH3, PO4-3 and sometimes HS- in the hypolimnion. In contrast, Asylum Lake appears to be monomictic, with turnover occurring in fall, but not spring. During most seasons, the hypolimnion of Asylum Lake has significant levels of dissolved Mn(II), NH3, PO4-3, and sometimes HS-, but dissolved Fe(II) remains below detection limits. A comparison of δ18O and δD with the local meteoric water line demonstrates that both lakes undergo significant evaporation. Woods Lake is considerably more influenced by evaporation than Asylum Lake, presumably due to the longer residence time of water in Woods Lake. The longer residence time, together with the smaller volume of water in Woods Lake, likely explains the more rapid transition to meromixis compared to Asylum Lake. This study demonstrates that road salt deicers can significantly influence the biogeochemistry and physical function of urban lakes, and in some cases can result in dimictic lakes transitioning to cultural meromixis.

The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

DOE PAGES

Li, Boyan; Zhang, Lei; Li, Chengliang; ...

2018-04-18

The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« less

The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

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

Li, Boyan; Zhang, Lei; Li, Chengliang

The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« 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.

Coexistence of Fe(II)- and Mn(II)-oxidizing bacteria govern the formation of deep sea umber deposits

NASA Astrophysics Data System (ADS)

Peng, Xiaotong; Ta, Kaiwen; Chen, Shun; Zhang, Lijuan; Xu, Hengchao

2015-11-01

The genesis of umber deposits has remained controversial for several decades. Recently, microbial Fe(II) oxidation associated with low-temperature diffuse venting has been identified as a key process for the formation of umber deposits, but the exact biogeochemical mechanisms involved to the precipitation of Mn oxides in umber deposits still remain unknown. Here, we used nano secondary ion mass spectrometer, synchrotron-based X-ray absorption spectroscopy, electron microscopy, and molecular techniques to demonstrate the coexistence of two types of metal-oxidizing bacteria within deep-sea hydrothermal umber deposits at the South Mid-Atlantic Ridge, where we found unique spheroids composed of biogenic Fe oxyhydroxides and Mn oxides in the deposits. Our data show that Fe oxyhydroxides and Mn oxides are metabolic by-products of lithotrophic Fe(II)-oxidizing bacteria and heterotrophic Mn(II)-oxidizing bacteria, respectively. The hydrothermal vents fuel lithotrophic microorganisms, which constitute a trophic base that might support the activities of heterogenic Mn(II)-oxidizing bacteria. The biological origin of umber deposits shed light on the importance of geomicrobiological interaction in triggering the formation of metalliferous deposits, with important implications for the generation of submarine Mn deposits and crusts.

Understanding temperature and magnetic-field actuated magnetization polarity reversal in the Prussian blue analogue Cu 0.73 Mn 0.77 [Fe(CN) 6 ]. z H 2 O, using XMCD

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

Lahiri, Debdutta; Choi, Yongseong; Yusuf, S. M.

2016-02-23

We have investigated the microscopic origin of temperature and magnetic-field actuated magnetization reversal in Cu0.73Mn0.77[Fe(CN)(6)]center dot zH(2)O, using XMCD. Our results show a fair deviation from the mean-field-theory in the form of different ordering temperatures of Fe and Mn sublattices. A preferential sign reversal of Mn spin under magnetic field and different spin cant angles for the two sublattices have also been observed. An antiferromagnetic coupling between the Fe and Mn sublattices along with different ordering temperatures (sublattice decoupling) for these sublattices explain the temperature-dependent magnetization reversal. Whereas, Mn spin reversal alone (under external magnetic field) is responsible for themore » observed field-dependent magnetization reversal. The dissimilar magnetic behavior of Fe and Mn sublattices in this cubic 3d-orbital system has been understood by invoking disparity and competition among inter-sublattice magnetic control parameters, viz. magnetic Zeeman energy, exchange coupling constant and magnetic anisotropy constant. Our results have significant design implications for future magnetic switches, by optimizing the competition among these magnetic control parameters.« less

Arsenic transformation and adsorption by iron hydroxide/manganese dioxide doped straw activated carbon

NASA Astrophysics Data System (ADS)

Xiong, Ying; Tong, Qiang; Shan, Weijun; Xing, Zhiqiang; Wang, Yuejiao; Wen, Siqi; Lou, Zhenning

2017-09-01

Iron hydroxide/manganese dioxide doped straw activated carbon was synthesized for As(III) adsorption. The Fe-Mn-SAc adsorbent has two advantages, on the one hand, the straw active carbon has a large surface area (1360.99 m2 g-1) for FeOOH and MnO2 deposition, on the other hand, the manganese dioxide has oxidative property as a redox potential of (MnO2 + H+)/Mn2+, which could convert As(III) into As(V). Combined with the arsenic species after reacting with Fe-Mn-SAc, the As(III) transformation and adsorption mechanism was discussed. H2AsO4-oxidized from As(III) reacts with the Fe-Mn-SAc by electrostatic interaction, and unoxidized As(III) as H3AsO3 reacts with SAc and/or iron oxide surface by chelation effect. The adsorption was well-described by Langmuir isotherms model, and the adsorption capacity of As(III) was 75.82 mg g-1 at pH 3. Therefore, considering the straw as waste biomass material, the biosorbent (Fe-Mn-SAc) is promising to be exploited for applications in the treatment of industrial wastewaters containing a certain ratio of arsenic and germanium.

Recent advances on Fe- and Mn-based cathode materials for lithium and sodium ion batteries

NASA Astrophysics Data System (ADS)

Zhu, Xiaobo; Lin, Tongen; Manning, Eric; Zhang, Yuancheng; Yu, Mengmeng; Zuo, Bin; Wang, Lianzhou

2018-06-01

The ever-growing market of electrochemical energy storage impels the advances on cost-effective and environmentally friendly battery chemistries. Lithium-ion batteries (LIBs) are currently the most critical energy storage devices for a variety of applications, while sodium-ion batteries (SIBs) are expected to complement LIBs in large-scale applications. In respect to their constituent components, the cathode part is the most significant sector regarding weight fraction and cost. Therefore, the development of cathode materials based on Earth's abundant elements (Fe and Mn) largely determines the prospects of the batteries. Herein, we offer a comprehensive review of the up-to-date advances on Fe- and Mn-based cathode materials for LIBs and SIBs, highlighting some promising candidates, such as Li- and Mn-rich layered oxides, LiNi0.5Mn1.5O4, LiFe1-xMnxPO4, NaxFeyMn1-yO2, Na4MnFe2(PO4)(P2O7), and Prussian blue analogs. Also, challenges and prospects are discussed to direct the possible development of cost-effective and high-performance cathode materials for future rechargeable batteries.

Synthesis of KMnO4-treated magnetic graphene oxide nanocomposite (Fe3O4@GO/MnO x ) and its application for removing of Cu2+ ions from aqueous solution

NASA Astrophysics Data System (ADS)

Zhang, Huining; Chang, Qing; Jiang, Yu; Li, Huili; Yang, Yahong

2018-04-01

A magnetic KMnO4-treated graphene-oxide-based nanocomposite, Fe3O4@GO/MnO x , was synthesized through a facile hydrothermal technique. The properties of the Fe3O4@GO/MnO x nanocomposite were characterized by SEM, XRD and FTIR. Batch experiments showed that the maximum adsorption capacity calculated by the Langmuir model for Cu2+ was 62.65 mg g-1 at T = 303.15 K. Kinetics and XPS analysis also revealed that the mechanism of Cu2+ removal was mainly a chemical adsorption process involving both the MnO x particles and oxygen functional groups. The prepared Fe3O4@GO/MnO x was found to be an ideal adsorbent for the removal of Cu2+ ions due to the MnO x particle coating, and was easily separated using a magnetic field after utilization. Reusability studies imply that Fe3O4@GO/MnO x is a suitable material for heavy metal ion removal from aqueous solutions in real applications.

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

Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan

Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe{sub 2}O{sub 4}, MgFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} respectively, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe{sub 2}O{sub 4} powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates andmore » aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M{sub s} of 68.9 emu/g at 10 kOe were observed for the samples of MnFe{sub 2}O{sub 4}. - Abstract: Nanocrystalline spinel ferrite MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac){sub 3}, M(acac){sub 3} (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} samples contain nanoparticles, whereas the MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe{sub 2}O{sub 4} sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe{sub 2}O{sub 4}, MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} exhibit a superparamagnetic behavior.« less

The concentration of manganese, iron and strontium in bone of red fox Vulpes vulpes (L. 1758).

PubMed

Budis, Halina; Kalisinska, Elzbieta; Lanocha, Natalia; Kosik-Bogacka, Danuta I

2013-12-01

The aims of the study were to determine manganese (Mn), iron (Fe) and strontium (Sr) concentrations in fox bone samples from north-western Poland and to examine the relationships between the bone Mn, Fe and Sr concentrations and the sex and age of the foxes. In the studied samples of fox cartilage, cartilage with adjacent compact bone, compact bone and spongy bone, the concentrations of the analysed metals had the following descending order: Fe > Sr > Mn. The only exception was in compact bone, in which the concentrations were arranged in the order Sr > Fe > Mn. Manganese concentrations were significantly higher in cartilage, compact bone and cartilage with compact bone than in spongy bone. Iron concentrations were higher in cartilage and spongy bone compared with compact bone. Strontium concentrations were greater in compact bone than in cartilage and spongy bone. The manganese, iron and strontium concentrations in the same type of bone material in many cases correlated with each other, with the strongest correlation (r > 0.70) between Mn and Fe in almost all types of samples. In addition, concentrations of the same metals in different bone materials were closely correlated for Mn and Fe in cartilage and cartilage with adjacent compact bone, and for Sr in compact bone and cartilage with compact bone. In the fox from NW Poland, there were no statistically significant differences in Mn, Fe and Sr in any of the types of bone material between the sexes and immature and adult foxes.

The Effect of Contact Non-equilibrium Plasma on Structural and Magnetic Properties of Mn Х Fe3 - X О4 Spinels.

PubMed

Frolova, L A; Derhachov, M P

2017-08-23

Nano-sized manganese ferrites Mn х Fe 3 - х О 4 (х = 0-1.3) were prepared using contact non-equilibrium plasma (CNP) in two different pH (11.5 and 12.5). The influence of synthesis conditions (e.g., cation ratio and initial pH) on phase composition, crystallite size, and magnetic properties were investigated employing X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurement techniques. The formation of monodispersed faceted ferrite particles at х = 0-0.8 was shown. The FTIR spectra revealed reflection in region 1200-1700 cm -1 caused by the presence of water adsorbed on the surface of Fe 3 - x Mn x O 4 micro-granules or embedded into their crystal lattice. The most sensitivity of reflection spectra to the composition changes takes place within a 400-1200 cm -1 range, typical to the stretching vibrations of Fe(Mn)-O (up to 700 cm -1 ), Fe(Mn)-OH, and Fe(Mn)-OH 2 bonds (over 700 cm -1 ). The XRD results showed that the nanocrystalline Mn х Fe 3 - х О 4 (0 < x < 1.0) had cubic spinel crystal structure with average crystallite size 48-49 A. The decrease of crystalline size with the x increase was also observed.

Developmental manganese neurotoxicity in rats: Cognitive deficits in allocentric and egocentric learning and memory.

PubMed

Amos-Kroohs, Robyn M; Davenport, Laurie L; Atanasova, Nina; Abdulla, Zuhair I; Skelton, Matthew R; Vorhees, Charles V; Williams, Michael T

Manganese (Mn) is an essential element but neurotoxic at higher exposure levels. The effects of Mn overexposure (MnOE) on hippocampal and striatal-dependent learning and memory in rats were tested in combination with iron deficiency (FeD) and developmental stress that often co-occur with MnOE. Moderate FeD affects up to 15% of U.S. children and developmental stress is common in lower socio-economic areas where MnOE occurs. Pregnant Sprague-Dawley rats and their litters were housed in cages with or without (barren cage (BAR)) standard bedding from embryonic day (E)7 to postnatal day (P)28. Dams were fed a 90% FeD or iron sufficient (FeS) diet from E15-P28. Within each litter, separate offspring were treated with 100mg/kg Mn (MnOE) or vehicle (VEH) by gavage on alternate days from P4-28. Offspring were tested as adults in the Morris and Cincinnati water mazes. FeD and developmental stress interactively impaired spatial learning in the Morris water maze. Developmental stress and MnOE impaired learning and memory in both mazes. MnOE resulted in reduced CA1 hippocampal long-term potentiation (LTP) and increased levels of α-synuclein. Preweaning MnOE resulted in cognitive deficits on multiple domains of learning and memory accompanied by impaired LTP and α-synuclein changes, effects worsened by developmental stress. Copyright © 2016 Elsevier Inc. All rights reserved.

Coating effect of LiFePO4 and Al2O3 on Li1.2Mn0.54Ni0.13Co0.13O2 cathode surface for lithium ion batteries

NASA Astrophysics Data System (ADS)

Seteni, Bonani; Rapulenyane, Nomasonto; Ngila, Jane Catherine; Mpelane, Siyasanga; Luo, Hongze

2017-06-01

Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 and Al2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The scanning electron microscopy shows the agglomeration of the materials and their nanoparticle size ∼100 nm. The transmission electron microscopy confirms that LiFePO4 forms a rough mat-like surface and Al2O3 remain as islandic particles on the surface of the Li1.2Mn0.54Ni0.13Co0.13O2 material. The Li1.2Mn0.54Ni0.13Co0.13O2 coated with LiFePO4 and Li1.2Mn0.54Ni0.13Co0.13O2 coated with Al2O3 exhibits improved electrochemical performance. The initial discharge capacity is enhanced to 267 mAhg-1 after the LiFePO4 coating and 285 mAhg-1 after the Al2O3 coating compared to the as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 material that has an initial discharge capacity of 243 mAhg-1. Galvanostatic charge-discharge tests at C/10 display longer activation of Li2MnO3 phase and higher capacity retention of 88% after 20 cycles for Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3 of 80% after 20 cycles and LMNC of 80% after 20 cycles. Meanwhile Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 also shows higher rate capability compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3.

Conditions for the formation of pure birnessite during the oxidation of Mn(II) cations in aqueous alkaline medium

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

Boumaiza, Hella; Laboratoire de Chimie Physique et Microbiologie pour l'Environnement; Département de Génie Biologique et Chimique, Institut National des Sciences Appliquées et de Technologies

Birnessite was synthetized through redox reaction by mixing MnO{sub 4}{sup -}, Mn{sup 2+} and OH{sup -} solutions. The Mn(VII): Mn(II) ratio of 0.33 was chosen and three methods were used consisting in a quick mixing under vigorous stirring of two of the three reagents and then on the dropwise addition of the third one. The obtained solids were characterized by XRD, FTIR and XPS spectroscopies. Their average oxidation states were determined from ICP and CEC measurements while their surface properties were investigated by XPS. This study provides an increased understanding of the importance of dissolved oxygen in the formation ofmore » birnessite and hausmannite and shows the ways to obtain pure birnessite. The role of counter-ion ie. Na{sup +} or K{sup +} was also examined. - Graphical abstract: Pathways of birnessite formation. - Highlights: • Pure birnessite is prepared through a redox reaction. • Hausmannite formation is prevented by controlling dissolved O2. • The employed counterion influences the purity of birnessite. • Initial Mn(OH){sub 2} is oxidized by both MnO{sub 4}{sup -} and dissolved O{sub 2}.« less

Comparison of methods for the removal of organic carbon and extraction of chromium, iron and manganese from an estuarine sediment standard and sediment from the Calcasieu River estuary, Louisiana, U.S.A.

USGS Publications Warehouse

Simon, N.S.; Hatcher, S.A.; Demas, C.

1992-01-01

U.S. National Bureau of Standards (NBS) estuarine sediment 1646 from the Chesapeake Bay, Maryland, and surface sediment collected at two sites in the Calcasieu River estuary, Louisiana, were used to evaluate the dilute hydrochloric acid extraction of Cr, Fe and Mn from air-dried and freeze-dried samples that had been treated by one of three methods to remove organic carbon. The three methods for the oxidation and removal of organic carbon were: (1) 30% hydrogen peroxide; (2) 30% hydrogen peroxide plus 0.25 mM pyrophosphate; and (3) plasma oxidation (low-temperature ashing). There was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the percent of organic carbon removed by the three methods. Generally, there was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the concentration of Cr, Fe and Mn that was extracted, regardless of the extraction technique that was used. Hydrogen peroxide plus pyrophosphate removed the most organic carbon from sediment collected at the site in the Calcasieu River that was upstream from industrial outfalls. Plasma oxidation removed the most organic carbon from the sediment collected at a site in the Calcasieu River close to industrial outfalls and from the NBS estuarine sediment sample. Plasma oxidation merits further study as a treatment for removal of organic carbon. Operational parameters can be chosen to limit the plasma oxidation of pyrite which, unlike other Fe species, will not be dissolved by dilute hydrochloric acid. Preservation of pyrite allows the positive identification of Fe present as pyrite in sediments. ?? 1992.

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.

Manganese speciation of laboratory-generated welding fumes

PubMed Central

Andrews, Ronnee N.; Keane, Michael; Hanley, Kevin W.; Feng, H. Amy; Ashley, Kevin

2015-01-01

The objective of this laboratory study was to identify and measure manganese (Mn) fractions in chamber-generated welding fumes (WF) and to evaluate and compare the results from a sequential extraction procedure for Mn fractions with that of an acid digestion procedure for measurement of total, elemental Mn. To prepare Mn-containing particulate matter from representative welding processes, a welding system was operated in short circuit gas metal arc welding (GMAW) mode using both stainless steel (SS) and mild carbon steel (MCS) and also with flux cored arc welding (FCAW) and shielded metal arc welding (SMAW) using MCS. Generated WF samples were collected onto polycarbonate filters before homogenization, weighing and storage in scintillation vials. The extraction procedure consisted of four sequential steps to measure various Mn fractions based upon selective solubility: (1) soluble Mn dissolved in 0.01 M ammonium acetate; (2) Mn (0,II) dissolved in 25 % (v/v) acetic acid; (3) Mn (III,IV) dissolved in 0.5% (w/v) hydroxylamine hydrochloride in 25% (v/v) acetic acid; and (4) insoluble Mn extracted with concentrated hydrochloric and nitric acids. After sample treatment, the four fractions were analyzed for Mn by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). WF from GMAW and FCAW showed similar distributions of Mn species, with the largest concentrations of Mn detected in the Mn (0,II) and insoluble Mn fractions. On the other hand, the majority of the Mn content of SMAW fume was detected as Mn (III,IV). Although the concentration of Mn measured from summation of the four sequential steps was statistically significantly different from that measured from the hot block dissolution method for total Mn, the difference is small enough to be of no practical importance for industrial hygiene air samples, and either method may be used for Mn measurement. The sequential extraction method provides valuable information about the oxidation state of Mn in samples and allows for comparison to results from previous work and from total Mn dissolution methods. PMID:26345630

Manganese speciation of laboratory-generated welding fumes.

PubMed

Andrews, Ronnee N; Keane, Michael; Hanley, Kevin W; Feng, H Amy; Ashley, Kevin

The objective of this laboratory study was to identify and measure manganese (Mn) fractions in chamber-generated welding fumes (WF) and to evaluate and compare the results from a sequential extraction procedure for Mn fractions with that of an acid digestion procedure for measurement of total, elemental Mn. To prepare Mn-containing particulate matter from representative welding processes, a welding system was operated in short circuit gas metal arc welding (GMAW) mode using both stainless steel (SS) and mild carbon steel (MCS) and also with flux cored arc welding (FCAW) and shielded metal arc welding (SMAW) using MCS. Generated WF samples were collected onto polycarbonate filters before homogenization, weighing and storage in scintillation vials. The extraction procedure consisted of four sequential steps to measure various Mn fractions based upon selective solubility: (1) soluble Mn dissolved in 0.01 M ammonium acetate; (2) Mn (0,II) dissolved in 25 % (v/v) acetic acid; (3) Mn (III,IV) dissolved in 0.5% (w/v) hydroxylamine hydrochloride in 25% (v/v) acetic acid; and (4) insoluble Mn extracted with concentrated hydrochloric and nitric acids. After sample treatment, the four fractions were analyzed for Mn by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). WF from GMAW and FCAW showed similar distributions of Mn species, with the largest concentrations of Mn detected in the Mn (0,II) and insoluble Mn fractions. On the other hand, the majority of the Mn content of SMAW fume was detected as Mn (III,IV). Although the concentration of Mn measured from summation of the four sequential steps was statistically significantly different from that measured from the hot block dissolution method for total Mn, the difference is small enough to be of no practical importance for industrial hygiene air samples, and either method may be used for Mn measurement. The sequential extraction method provides valuable information about the oxidation state of Mn in samples and allows for comparison to results from previous work and from total Mn dissolution methods.

Recovery of Manganese Ore Tailings by High-Gradient Magnetic Separation and Hydrometallurgical Method

NASA Astrophysics Data System (ADS)

Zhang, Xiufeng; Tan, Xiumin; Yi, Yuejun; Liu, Weizao; Li, Chun

2017-11-01

With the depletion of high-grade manganese ores, Mn ore tailings are considered valuable secondary resources. In this study, a process combining high-gradient magnetic separation (HGMS) with hydrometallurgical methods is proposed to recycle fine-grained Mn tailings. The Mn tailings were treated by HGMS at 12,500 G to obtain a Mn concentrate of 30% Mn with the recovery efficiency of 64%. The Mn concentrate could be used in the ferromanganese industry. To recover Mn further, the nonmagnetic fraction was leached by SO2 in an H2SO4 solution. Hydrogen peroxide was added to the leachate to oxidize Fe2+ to Fe3+, and the solution pH was adjusted to 5.0-5.5 with ammonia to remove Al, Fe, and Si impurities. The purified solution was reacted with NH4HCO3, and a saleable product of MnCO3 with 97.9% purity was obtained. The combined process can be applied to Mn recovery from finely dispersed weakly magnetic Mn ores or tailings.

Influence of off-stoichiometry on magnetoresistance characteristics of Co2MnSi/Ag-based current-perpendicular-to-plane spin valves

NASA Astrophysics Data System (ADS)

Inoue, Masaki; Hu, Bing; Moges, Kidist; Inubushi, Kazuumi; Nakada, Katsuyuki; Yamamoto, Masafumi; Uemura, Tetsuya

2017-08-01

The influence of off-stoichiometry of Co2MnSi (CMS) spin sources on giant magnetoresistance characteristics was investigated for CMS/Ag-based current-perpendicular-to-plane spin valves prepared with various Mn compositions α in Co2MnαSi0.82 electrodes. The magnetoresistance ratio of the prepared CMS/Co50Fe50 (CoFe) (1.1 nm)/Ag/CoFe (1.1)/CMS spin valves systematically increased with α from 11.4% for Mn-deficient α = 0.62 to 20.7% for Mn-rich α = 1.45 at 290 K. This result suggests that increasing α from a Mn-deficient to Mn-rich value increases the spin polarization by suppressing CoMn antisites harmful to the half-metallicity. Thus, our results demonstrate that appropriately controlling the film composition toward a Mn-rich one is highly effective for enhancing the half-metallicity of CMS in CMS-based spin valves, as it is in CMS-based magnetic tunnel junctions.

Formation of Deep Sea Umber Deposits Linked to Microbial Metal Oxidation at the South Atlantic Ridge

NASA Astrophysics Data System (ADS)

Peng, Xiaotong; Ta, Kaiwen; Chen, Shun; Zhang, Lijuan; Xu, Hengchao

2015-04-01

Umber deposits are important metalliferous deposits, which occur in off-axis half-graben structures at ancient and modern ocean floor. The genesis of umber deposits has remained controversial for several decades. Recently, microbial Fe(II) oxidation associated with low-temperature diffuse venting has been identified as a key process for the formation of umber deposits, but the exact biochemical mechanisms involved to the precipitation of Mn oxides and co-precipitation of Fe oxyhydroxides and Mn oxides in umber deposits still remain unknown. Here, we used nano secondary ion mass spectrometer, synchrotron-based X-ray absorption spectroscopy, electron microscopy, and molecular techniques to demonstrate the coexistence of two types of metal-oxidizing bacteria within deep-sea hydrothermal umber deposits at the South Atlantic Ridge, where we found unique spheroids composed of biogenic Fe oxyhydroxides and Mn oxides in the deposits. Our data suggest that Fe oxyhydroxides and Mn oxides are metabolic by-products of lithotrophic Fe(II)-oxidizing bacteria and heterotrophic Mn(II)-oxidizing bacteria, respectively. The hydrothermal vents fuel lithotrophic Fe(II)-oxidizing bacteria, which constitute a trophic base that may support the activities of heterotrophic Mn(II)-oxidizing bacteria. The biological origin of umber deposits underscore the importance of geomicrobiologcial interaction in triggering the formation of deep-sea deposits, with important implications for the generation of submarine Mn deposits and crusts.

Sorption and precipitation of Mn2+ by viable and autoclaved Shewanella putrefaciens: Effect of contact time

NASA Astrophysics Data System (ADS)

Chubar, Natalia; Visser, Tom; Avramut, Cristina; de Waard, Helen

2013-01-01

The sorption of Mn(II) by viable and inactivated cells of Shewanella putrefaciens, a non-pathogenic, facultative anaerobic, gram-negative bacterium characterised as a Mn(IV) and Fe(III) reducer, was studied under aerobic conditions, as a function of pH, bacterial density and metal loading. During a short contact time (3-24 h), the adsorptive behaviour of live and dead bacteria toward Mn(II) was sufficiently similar, an observation that was reflected in the studies on adsorption kinetics at various metal loadings, effects of pH, bacteria density, isotherms and drifting of pH during adsorption. Continuing the experiment for an additional 2-30 days demonstrated that the Mn(II) sorption by suspensions of viable and autoclaved cells differed significantly from one another. The sorption to dead cells was characterised by a rapid equilibration and was described by an isotherm. In contrast, the sorption (uptake) to live bacteria exhibited a complex time-dependent uptake. This uptake began as adsorption and ion exchange processes followed by bioprecipitation, and it was accompanied by the formation of polymeric sugars (EPS) and the release of dissolved organic substances. FTIR, EXAFS/XANES and XPS demonstrated that manganese(II) phosphate was the main precipitate formed in 125 ml batches, which is the first evidence of the ability of microbes to synthesise manganese phosphates. XPS and XANES spectra did not detect Mn(II) oxidation. Although the release of protein-like compounds by the viable bacteria increased in the presence of Mn2+ (and, by contrast, the release of carbohydrates did not change), electrochemical analyses did not indicate any aqueous complexation of Mn(II) by the organic ligands.

Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

NASA Astrophysics Data System (ADS)

Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

2016-05-01

Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

Synthesis and electrochemical properties of Na-rich Prussian blue analogues containing Mn, Fe, Co, and Fe for Na-ion batteries

NASA Astrophysics Data System (ADS)

Bie, Xiaofei; Kubota, Kei; Hosaka, Tomooki; Chihara, Kuniko; Komaba, Shinichi

2018-02-01

Electrochemical performance of Prussian blue analogues (PBAs) as positive electrode materials for non-aqueous Na-ion batteries is known to be highly dependent on their synthesis conditions according to the previous researches. Na-rich PBAs, NaxM[Fe(CN)6]·nH2O where M = Mn, Fe, Co, and Ni, are prepared via precipitation method under the same condition. The structure, chemical composition, morphology, valence of the transition metals, and electrochemical property of these samples are comparatively researched. The PBA with Mn shows large reversible capacity of 126 mAh g-1 in 2.0-4.2 V at a current density of 30 mA g-1 and the highest working voltage owning to high redox potential of Mn2+/3+ in MnN6 and Fe2+/3+ in FeC6. While, the PBA with Ni exhibits the best cyclability and rate performance though only 66 mAh g-1 is delivered. The significant differences in electrochemical behaviors of the PBAs originate from the various properties depending on different transition metals.

Mechanism of selenite removal by a mixed adsorbent based on Fe-Mn hydrous oxides studied using X-ray absorption spectroscopy.

PubMed

Chubar, Natalia; Gerda, Vasyl; Szlachta, Małgorzata

2014-11-18

Selenium cycling in the environment is greatly controlled by various minerals, including Mn and Fe hydrous oxides. At the same time, such hydrous oxides are the main inorganic ion exchangers suitable (on the basis of their chemical nature) to sorb (toxic) anions, separating them from water solutions. The mechanism of selenite adsorption by the new mixed adsorbent composed of a few (amorphous and crystalline) phases [maghemite, MnCO3, and X-ray amorphous Fe(III) and Mn(III) hydrous oxides] was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy [supported by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data]. The complexity of the porous adsorbent, especially the presence of the amorphous phases of Fe(III) and Mn(III) hydrous oxides, is the main reason for its high selenite removal performance demonstrated by batch and column adsorption studies shown in the previous work. Selenite was bound to the material via inner-sphere complexation (via oxygen) to the adsorption sites of the amorphous Fe(III) and Mn(III) oxides. This anion was attracted via bidentate binuclear corner-sharing coordination between SeO3(2-) trigonal pyramids and both FeO6 and MnO6 octahedra; however, the adsorption sites of Fe(III) hydrous oxides played a leading role in selenite removal. The contribution of the adsorption sites of Mn(III) oxide increased as the pH decreased from 8 to 6. Because most minerals have a complex structure (they are seldom based on individual substances) of various crystallinity, this work is equally relevant to environmental science and environmental technology because it shows how various solid phases control cycling of chemical elements in the environment.

Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation

USGS Publications Warehouse

Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

2007-01-01

The major element relationships in ferromanganese (Fe-Mn) crusts from Afanasiy-Nikitin seamount (ANS), eastern equatorial Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the ANS Fe-Mn crusts are distinct from Pacific seamount Fe-Mn crusts, and reflect region-specific chemical characteristics. The platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au in ANS Fe-Mn crusts are derived from seawater and are mainly of terrestrial origin, with a minor cosmogenic component. The Ru/Rh (0.5-2) and Pt/Ru ratios (7-28) are closely comparable to ratios in continental basalts, whereas Pd/Ir ratios exhibit values ( 0.75) correlations between water depth and Mn/Co, Fe/Co, Ce/Co, Co, and the PGEs. Fractionation of the PGE-Au from seawater during colloidal precipitation of the major-oxide phases is indicated by well-defined linear positive correlations (r > 0.8) of Co and Ce with Ir, Ru, Rh, and Pt; Au/Co with Mn/Co; and by weak or no correlations of Pd with water depth, Co-normalized major-element ratios, and with the other PGE (r < 0.5). The strong enrichment of Pt (up to 1 ppm) relative to the other PGE and its positive correlations with Ce and Co demonstrate a common link for the high concentrations of all three elements, which likely involves an oxidation reaction on the Mn-oxide and Fe-oxyhydroxide surfaces. The documented fractionation of PGE-Au and their positive association with redox sensitive Co and Ce may have applications in reconstructing past-ocean redox conditions and water masses.

Review of Manganese Processing for Production of TRIP/TWIP Steels, Part 2: Reduction Studies

NASA Astrophysics Data System (ADS)

Elliott, R.; Coley, K.; Mostaghel, S.; Barati, M.

2018-02-01

Production of ultrahigh-manganese steels is expected to result in significant increase in demand for low-carbon (LC) ferromanganese (FeMn) and silicomanganese (SiMn). Current manganese processing techniques are energy intensive and typically yield a high-carbon product. The present work therefore reviews available literature regarding carbothermic reduction of Mn oxides and ores, with the objective of identifying opportunities for future process development to mitigate the cost of LC FeMn and SiMn. In general, there is consensus that carbothermic reduction of Mn oxides and ores is limited by gasification of carbon. Conditions which enhance or bypass this step (e.g., by application of CH4) show higher rates of reduction at lower temperatures. This phenomenon has potential application in solid-state reduction of Mn ore. Other avenues for process development include optimization of the prereduction step in conventional FeMn production and metallothermic reduction as a secondary reduction step.

The Enhancement of Mg Corrosion Resistance by Alloying Mn and Laser-Melting

PubMed Central

Yang, Youwen; Wu, Ping; Wang, Qiyuan; Wu, Hong; Liu, Yong; Deng, Youwen; Zhou, Yuanzhuo; Shuai, Cijun

2016-01-01

Mg has been considered a promising biomaterial for bone implants. However, the poor corrosion resistance has become its main undesirable property. In this study, both alloying Mn and laser-melting were applied to enhance the Mg corrosion resistance. The corrosion resistance, mechanical properties, and microstructure of rapid laser-melted Mg-xMn (x = 0–3 wt %) alloys were investigated. The alloys were composed of dendrite grains, and the grains size decreased with increasing Mn. Moreover, Mn could dissolve and induce the crystal lattice distortion of the Mg matrix during the solidification process. Mn ranging from 0–2 wt % dissolved completely due to rapid laser solidification. As Mn contents further increased up to 3 wt %, a small amount of Mn was left undissolved. The compressive strength of Mg-Mn alloys increased first (up to 2 wt %) and then decreased with increasing Mn, while the hardness increased continuously. The refinement of grains and the increase in corrosion potential both made contributions to the enhancement of Mg corrosion resistance. PMID:28773342

Band structure of the quaternary Heusler alloys ScMnFeSn and ScFeCoAl

NASA Astrophysics Data System (ADS)

Shanthi, N.; Teja, Y. N.; Shaji, Shephine M.; Hosamani, Shashikala; Divya, H. S.

2018-04-01

In our quest for materials with specific applications, a theoretical study plays an important role in predicting the properties of compounds. Heusler alloys or compounds are the most studied in this context. More recently, a lot of quaternary Heusler compounds are investigated for potential applications in fields like Spintronics. We report here our preliminary study of the alloys ScMnFeSn and ScFeCoAl, using the ab-initio linear muffin-tin orbital method within the atomic sphere approximation (LMTO-ASA). The alloy ScMnFeSn shows perfect half-metallicity, namely, one of the spins shows a metallic behaviour and the other spin shows semi-conducting behaviour. Such materials find application in devices such as the spin-transfer torque random access memory (STT-MRAM). In addition, the alloy ScMnFeSn is found to have an integral magnetic moment of 4 µB, as predicted by the Slater-Pauling rule. The alloy ScFeCoAl does not show half-metallicity.

Tungsten in the environment: A geochemical and mineralogical investigation of an emerging contaminant

NASA Astrophysics Data System (ADS)

Datta, S.; Hobson, C.; Mohajerin, T. J.; Johannesson, K. H.; Tappero, R.; Telfeyan, K.; Witten, M. L.; Sheppard, P. R.

2012-12-01

Interest in tungsten (W) research has increased in the past several years, as it may have previously unrecognized human toxicological and environmentally degrading effects [1][2]. In 2002, the Center for Disease Control (CDC) investigated several clusters of acute lymphatic leukemia in both Nevada and in Arizona. The study found residents had urinary W levels above the 95th percentile for the US [1][3]. After this, the EPA classified W as an emerging contaminant. Field studies have shown that W is mobile in the environment [1][4], but there is still a paucity of knowledge about the actual behavior of W in groundwater flow systems and the processes that control W concentration and transport. Here the hypothesis being tested is that physical and chemical changes from chemical weathering, mineral dissolution and precipitation, and redox reactions catalyzed by microbial activity control W transport and sequestration. Sediment samples have been collected from three different localities with elevated W. Fallon, NV is the first site being analyzed, along with Sierra Vista, AZ and Cheyenne Bottoms refuge near Hoisington, KS. The first few centimeters of the sediment profile are scraped aside and then sediment core samples are collected at incremental depths of approximately two feet, starting with a near surface sample. The sediment cores are being studied for total extractability of W from the sediments and then the mineral associations within the sediments are studied by petrographic observations and FESEM assisted single grain mapping (also to understand the association of W to Fe, Mn and S in these sediments). Various extraction techniques of the sediment samples including sequential extractions (assisted by microwave digestion) are done along with solid state synchrotron analyses (by acquiring μXRF maps and having specific hotspots analyzed for μXRD and μXANES). This elucidates valuable information about W's oxidation state, concentration, and where it is bound in the sediment fractions. The μXRF results from both Fallon and Cheyenne Bottoms have shown different elemental correlations. In Fallon, W shows good correlation with Cu and Zn but not with Fe or Mn, whereas they themselves correlate well with each other. In Cheyenne Bottoms W does not correlate with any particular element, while Cu and Zn now correlate well with Fe and Mn. All locations have shown discrete hot spots of high W concentration, rather than a dispersed uniform distribution. In Fallon, W has predominately been shown to be in W (VI) oxidation state. Water sample analyses from Hoisington (the only water samples collected thus far) does not seem to contain high levels of dissolved W. The dissolved species in the water samples displays different trends in concentration from one sample to another. Some elements (Fe, Pb, Zn, Cu, As) displayed similar patterns in change in concentration as W. Other elements/anions (K, Mn, Mg, Ca, SO4, U, Ni) show a different trend from W. [1]Seiler, Stollenwerk, Garbarino (2005) App. GeoChem 20, 423-441. [2] Strigul, Koutsospyros, Arienti, Christodoulatos, Dermatas, Braida (2005) Chemo 61, 248-258. [3] Koutsospyros, Braida, Christodoulatos, Dermatas, Strigul (2006) J. Hazard. Mat. 136, 1-19.[4] Johannesson, Tang (2009) J. Hydro 378, 13-28.

Synthesis, structural and optical properties of (ALa)(FeMn)O6 (A = Ba and Sr) double perovskites

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Sudarshan, V.; Singh, Akhilesh Kumar

2018-05-01

Here, we report structural and optical properties of ALaFeMnO6 (A = Ba and Sr) double perovskite synthesized via auto-combustion followed by calcinations process. Rietveld refinement of structure using x-ray diffraction data reveals that BaLaFeMnO6 crystallizes into cubic crystal structure with space group Pm-3m while SrLaFeMnO6 crystallizes into rhombohedral crystal structure having space group R-3c. The absorption spectrum measurement using UV-Vis spectroscopy reveals that these samples are prefect insulator having energy band gap between conduction and valence band of the order of 6 eV.

Nanostructured Mn-Fe Binary Mixed Oxide: Synthesis, Characterization and Evaluation for Arsenic Removal.

PubMed

Pillewan, Pradnya; Mukherjee, Shrabanti; Bansiwal, Amit; Rayalu, Sadhana

2014-07-01

Adsorption of arsenic on bimetallic Mn and Fe mixed oxide was carried out using both field as well as simulated water. The material was synthesized using hydrothermal method and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Langmuir and Freundlich adsorption isotherms were computed using batch adsorption studies to determine the adsorption capacity of Mn-Fe binary mixed oxide for arsenic. Adsorption capacity for MFBMO obtained from Freundlich model was found to be 2.048 mg/g for simulated water and 1.084 mg/g for field water. Mn-Fe binary mixed oxide was found to be effective adsorbent for removal of arsenic from water.

Coating magnetic CuFe2O4 nanoparticles with OMS-2 for enhanced degradation of organic pollutants via peroxymonosulfate activation

NASA Astrophysics Data System (ADS)

Ye, Peng; Wu, Deming; Wang, Manye; Wei, Yi; Xu, Aihua; Li, Xiaoxia

2018-01-01

A heterogeneous magnetic CuFe2O4@OMS-2 catalyst was fabricated through a facile solvent-free process using Mn(CH3COO)2 and KMnO4 in the presence of CuFe2O4. It was found that the BET surface area of OMS-2 as well as the ratio of low-valent manganese species significantly increased in the hybrid catalyst, due to interactions between CuFe2O4 and the precursor of amorphous manganese oxide. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the CuFe2O4@OMS-2 catalyst within 30 min in the presence of peroxymonosulfate (PMS), while CuFe2O4 and OMS-2 showed no significant activity for the reaction. The hybrid catalyst also exhibited excellent long-term stability and could be easily recovered with the assistance of an external magnetic field. A possible degradation mechanism for the synergistic effects of different valent metal species and reactive radicals was proposed, which involved the electron transfer from Mn(III) or Mn(II) species to PMS with the generation of sulfate and hydroxyl radicals, and from AO7 and Cu(I) in CuFe2O4 to Mn(IV) and Mn(III) to reduce these Mn species.

Survival of the fittest: phosphorus burial in the sulfidic deep Black Sea

NASA Astrophysics Data System (ADS)

Kraal, Peter; Dijkstra, Nikki; Behrends, Thilo; Slomp, Caroline

2016-04-01

The Black Sea is characterized by permanently anoxic and sulfidic deep waters. Studies of the mechanisms of P burial in such a setting can be used to improve our understanding of P cycling in modern coastal systems undergoing eutrophication and ancient oceans during periods of anoxia in Earth's past. Here, we present phosphorus and iron (Fe) pools as determined in surface sediments along a transect from oxic shallow waters to sulfidic deep waters in the northwestern Black Sea, using a combination of bulk chemical analyses and micro-scale X-ray fluorescence (μXRF) and X-ray absorption spectroscopy (μXAS). We show that under oxic bottom water conditions, ferric iron oxides (Fe(III)ox) in surficial sediment efficiently scavenge dissolved phosphate from pore waters. Under these conditions, Fe(III)ox-bound P constitutes the main P pool at the sediment surface, but rapidly declines with depth in the sediment due to anoxic diagenesis. The transition from shallow (oxic) to deep (sulfidic) waters along the depth transect is reflected in a slight increase in the fraction of organic P. We also show evidence for authigenic calcium phosphate formation under sulfidic conditions at relatively low dissolved PO4 concentrations. Furthermore, we provide spectroscopic evidence for the presence of Fe(II)-Mn(II)-Mg-P minerals in sediments of the sulfidic deep basin. We hypothesize that these minerals are formed as a result of input of Fe(III)ox-P from shallower waters and subsequent transformation in either the water column or sediment. This finding suggests an unexpected strength of Fe-P shuttling from the shelf to the deep basin. While the presence of Fe-P species in such a highly sulfidic environment is remarkable, further analysis suggests that this P pool may not be quantitatively significant. In fact, our results indicate that some of the P that is interpreted as Fe-bound P based on chemical extraction may in fact be Ca-associated PO4 consisting of a combination of fish debris and adsorbed P.

Do manganese nodules grow or dissolve after burial? Results from the Central Indian Ocean Basin

NASA Astrophysics Data System (ADS)

Pattan, J. N.; Parthiban, G.

2007-07-01

Fifty buried manganese nodules at different depth intervals were recovered in 12 sediment cores from the Central Indian Ocean Basin (CIOB). A maximum of 15 buried nodules were encountered in one sediment core (AAS-22/GC-07) and the deepest nodule was recovered at 5.50 m below seafloor in core AAS-04/GC-5A. Approximately 80% of the buried nodules are small in size (˜2 cm diameter) in contrast to the Atlantic Ocean and Peru Basin (Pacific Ocean) where the majority of the buried nodules are large, ˜8 cm and >6 cm, respectively. Buried nodule size decreases with core depth and this distribution appears to be similar to the phenomenon of "Brazil Nut Effect". Buried nodules exhibit both smooth and rough surface textures and are ellipsoidal, elongated, rounded, sub rounded, irregular and polynucleated. Buried nodules from siliceous ooze are enriched in Mn, Cu, Ni, Zn, Mo, Ga, V and Rb whereas those from red clay are enriched in Fe, Co, Ti, U, Th, Y, Cr, Nb and Rare Earth Elements (REE). Buried nodules from siliceous ooze suggest their formation under hydrogenetic, early digenetic and diagenetic processes whereas those from red clay are of hydrogenetic origin. REE are enriched more than 1.5 times in buried nodules from red clay compared to siliceous ooze. However, the mode of incorporation of REE into buried nodules from both sedimentary environments is by a single authigenic phase consisting of Fe-Ti-P. Shale-normalized REE patterns and Ce anomalies suggest that nodules from siliceous ooze formed under more oxidizing conditions than those from red clay. Nodules buried at depths between 1.5 and 2.5 m are diagenetic (Mn/Fe ratio 10-15), formed in highly oxic environments (large positive Ce anomalies) and record aeolian dust (high Eu anomalies). Chemical composition, surface texture and morphology of buried nodules are similar to those of surface nodules from the same basin. Furthermore, buried nodule compositions do not exhibit any distinct patterns within the core depth, suggesting that buried nodules neither grow nor dissolve after their burial in the sediment column.

Enhanced catalytic performance for methane combustion of 3DOM CoFe2O4 by co-loading MnOx and Pd-Pt alloy nanoparticles

NASA Astrophysics Data System (ADS)

Li, Xiangyu; Liu, Yuxi; Deng, Jiguang; Xie, Shaohua; Zhao, Xingtian; Zhang, Yang; Zhang, Kunfeng; Arandiyan, Hamidreza; Guo, Guangsheng; Dai, Hongxing

2017-05-01

Three-dimensionally ordered macroporous (3DOM) CoFe2O4, zMnOx/3DOM CoFe2O4 (z = 4.99-12.30 wt%), and yPd-Pt/6.70 wt% MnOx/3DOM CoFe2O4 (y = 0.44-1.81 wt%; Pd/Pt molar ratio = 2.1-2.2) have been prepared using the polymethyl methacrylate microspheres-templating, incipient wetness impregnation, and bubble-assisted polyvinyl alcohol-protected reduction strategies, respectively. All of the samples were characterized by means of various techniques. Catalytic performance of the samples was measured for methane combustion. It is shown that the as-prepared samples exhibited a high-quality 3DOM structure (103 ± 20 nm in pore size) and a surface area of 19-28 m2/g, and the noble metal or alloy nanoparticles (NPs) with a size of 2.2-3.0 nm were uniformly dispersed on the macropore wall surface of 3DOM CoFe2O4. The loading of MnOx on CoFe2O4 gave rise to a slight increase in activity, however, the dispersion of Pd-Pt NPs on 6.70MnOx/3DOM CoFe2O4 significantly enhanced the catalytic performance, with the 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 sample showing the highest activity (T10% = 255 °C, T50% = 301 °C, and T90% = 372 °C at a space velocity of 20,000 mL/(g h)). We believe that the excellent catalytic activity of 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 was related to its well-dispersed Pd-Pt alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between MnOx or Pd-Pt NPs and 3DOM CoFe2O4.

Influence of film thickness and Fe doping on LPG sensing properties of Mn3O4 thin film grown by SILAR method

NASA Astrophysics Data System (ADS)

Belkhedkar, M. R.; Ubale, A. U.

2018-05-01

Nanocrystalline Fe doped and undoped Mn3O4 thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates using MnCl2 and NaOH as cationic and anionic precursors. The grazing incidence X-ray diffraction (GIXRD) and field emission scanning electron microscopy (FESEM)) have been carried out to analyze structural and surface morphological properties of the films. The LPG sensing performance of Mn3O4thin films have been studied by varying temperature, concentration of LPG, thickness of the film and doping percentage of Fe. The LPG response of the Mn3O4thin films were found to be enhances with film thickness and decreases with increased Fe doping (0 to 8 wt. %) at 573 K temperature.

A novel method for vanadium slag comprehensive utilization to synthesize Zn-Mn ferrite and Fe-V-Cr alloy.

PubMed

Liu, Shi-Yuan; Li, Shu-Jin; Wu, Shun; Wang, Li-Jun; Chou, Kuo-Chih

2018-07-15

Vanadium slag is a by-product from steelmaking process of vanadium-titanium magnetite, which mainly contains FeO, MnO, V 2 O 3 , and Cr 2 O 3 , The elements Fe and Mn are major components of Mn-Zn ferrite. The elements V and Cr are major components of V-Cr alloy. In view of the potential application in these study, a Mn 0.8 Zn 0.2 Fe 2 O 4 of high saturation magnetization (Ms = 68.6 emu/g) and low coercivity (Hc = 3.3 Oe) was successfully synthesized from the leaching solutions of vanadium slag by adding appropriate chemical reagents, ZnCl 2 and MnCl 2 ·4H 2 O, via roasting at 1300 °C for 1 h. The minor components (CaO and SiO 2 ) in the leaching solution of vanadium slag segregated to the grain boundaries resulting in increasing the resistivity of ferrite. The value of DC resistivity of Mn 0.8 Zn 0.2 Fe 2 O 4 at 25 °C reached 1230.7Ω m. The residue containing Fe, V and Cr was chlorinated by AlCl 3 and the Fe 3+ , V 3+ , and Cr 3+ ions were released into the NaCl-KCl eutectic. The current-time curve for the electrolysis of molten salt was investigated. Alloy (Fe, V, and Cr) of granular shape was obtained. The residue can be used to produce the mulite. This process provided a new approach to utilize slag from steelmaking. Copyright © 2018 Elsevier B.V. All rights reserved.

Degradable and porous Fe-Mn-C alloy for biomaterials candidate

NASA Astrophysics Data System (ADS)

Pratesa, Yudha; Harjanto, Sri; Larasati, Almira; Suharno, Bambang; Ariati, Myrna

2018-02-01

Nowadays, degradable implants attract attention to be developed because it can improve the quality of life of patients. The degradable implant is expected to degrade easily in the body until the bone healing process already achieved. However, there is limited material that could be used as a degradable implant, polymer, magnesium, and iron. In the previous study, Fe-Mn-C alloys had succesfully produced austenitic phase. However, the weakness of the alloy is degradation rate of materials was considered below the expectation. This study aimed to produce porous Fe-Mn-C materials to improve degradation rate and reduce the density of alloy without losing it non-magnetic properties. Potassium carbonate (K2CO3) were chosen as filler material to produce foam structure by sintering and dissolution process. Multisteps sintering process under argon gas environment was performed to generate austenite phase. The product showed an increment of the degradation rate of the foamed Fe-Mn-C alloy compared with the solid Fe-Mn-C alloy without losing the Austenitic Structure

Effect of sputtering condition and heat treatment in Co/Cu/Co/FeMn spin valve

NASA Astrophysics Data System (ADS)

Kim, Hong Jin; Bae, Jun Soo; Lee, Taek Dong; Lee, Hyuck Mo

2002-03-01

The exchange field of Cu(50 Å)/FeMn(50 Å)/Co(50 Å) sputtered on Si substrate was studied in terms of surface roughness and phase formation of γ-FeMn under a variety of Ar pressures and powers in sputtering. It was found that the exchange field is stronger when the surface is smoother and the FeMn layer forms better. The exchange bias field increased by more than three times after heat treatment. The effect of heat treament on magnetoresistance (MR) and resistance of the top spin valve, substrate/Co(30 Å)/Cu(30 Å)/Co(30 Å)/FeMn(150 Å), was studied. It was observed that the MR started to increase with annealing temperature and the effect was significant at 150°C. The heat treatment led to the disappearance of the intermixed layer between Co and Cu, and the concentration profile of Cu became flat and smooth at this temperature.

Synthesis of magnetically recyclable MnFe2O4@SiO2@Ag nanocatalyst: Its high catalytic performances for azo dyes and nitro compounds reduction

NASA Astrophysics Data System (ADS)

Kurtan, U.; Amir, Md.; Yıldız, A.; Baykal, A.

2016-07-01

In this study, magnetically recycable MnFe2O4@SiO2@Ag nanocatalyst (MnFe2O4@SiO2@Ag MRCs) has been synthesized through co-precipition and chemical reduction method. XRD analysis confirmed the synthesis of single phase nanoproduct with crystallite size of 10 nm. VSM measurements showed the superparamagnetic property of the product. Catalytic studies showed that MnFe2O4@SiO2@Ag MRC could catalyze the reduction of the various azo compounds like methyl orange (MO), methylene blue (MB), eosin Y (EY), and rhodamine B (RhB) and also aromatic nitro compounds such as 4-nitrophenol (4-NP), 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA). Moreover, the magnetic nanocatalyst showed an excellent reusability properties that remained unchanged after several cycles. Therefore, MnFe2O4@SiO2@Ag is the potential candidate for the application of organic pollutants for wastewater treatment.

Data on xylem sap proteins from Mn- and Fe-deficient tomato plants obtained using shotgun proteomics.

PubMed

Ceballos-Laita, Laura; Gutierrez-Carbonell, Elain; Takahashi, Daisuke; Abadía, Anunciación; Uemura, Matsuo; Abadía, Javier; López-Millán, Ana Flor

2018-04-01

This article contains consolidated proteomic data obtained from xylem sap collected from tomato plants grown in Fe- and Mn-sufficient control, as well as Fe-deficient and Mn-deficient conditions. Data presented here cover proteins identified and quantified by shotgun proteomics and Progenesis LC-MS analyses: proteins identified with at least two peptides and showing changes statistically significant (ANOVA; p ≤ 0.05) and above a biologically relevant selected threshold (fold ≥ 2) between treatments are listed. The comparison between Fe-deficient, Mn-deficient and control xylem sap samples using a multivariate statistical data analysis (Principal Component Analysis, PCA) is also included. Data included in this article are discussed in depth in the research article entitled "Effects of Fe and Mn deficiencies on the protein profiles of tomato ( Solanum lycopersicum) xylem sap as revealed by shotgun analyses" [1]. This dataset is made available to support the cited study as well to extend analyses at a later stage.

Effect of Fe doping on the electrochemical capacitor behavior of MnO2 nanocrystals

NASA Astrophysics Data System (ADS)

Poonguzhali, R.; Shanmugam, N.; Gobi, R.; Senthilkumar, A.; Viruthagiri, G.; Kannadasan, N.

2015-10-01

In this work, the influence of Fe doping on the capacitance behavior of MnO2 nanoparticles synthesized by chemical precipitation was investigated. During the doping process the concentration of Fe was increased from 0.025 M to 0.125 M in steps of 0.025 M. The products obtained were characterized by X-ray diffraction, Fourier infrared spectroscopy, scanning electron microscopy and N2 adsorption-desorption isotherms. To demonstrate the suitability of Fe-doped MnO2 for capacitor applications, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance were recorded. Among the different levels of doping, the specific capacitance of 912 F/g was delivered by 0.075 M of Fe-doped MnO2 at a scan rate of 10 mV/s, which is almost more than fourfold that of the bare MnO2 electrode (210 F/g). Moreover, for the same concentration the charge, discharge studies revealed the highest specific capacitance of 1084 F/g at a current density of 10 A/g.

Stability of half-metallic behavior with lattice variation for Fe2MnZ (Z = Si, Ge, Sn) Heusler alloy

NASA Astrophysics Data System (ADS)

Jain, Vivek Kumar; Lakshmi, N.; Jain, Rakesh

2018-05-01

The electronic structure and magnetic properties with variation of lattice constant for Fe2MnZ (Z = Si, Ge, Sn) Heusler alloys have been studied. Optimized lattice constant are found to be 5.59, 5.69, 6.00 Å for Z= Si, Ge and Sn respectively. Total magnetic moments of the alloys are ˜3 µB as predicted by the Slater Pauling rule and is maintained over a wide range of lattice variation for all three alloys. Half metallic ferromagnetic nature with 100% spin polarization is observed for Fe2MnSi for a lattice range from 5.40-5.70 Å. Fe2MnGe and Fe2MnSn show ferromagnetic and metallic natures with more than 90% spin polarization over a wide range of lattice constant. Due to the stability of half metallic character of these alloys with respect to variation in the lattice parameters, they are promising robust materials suitable for spintronics device applications.

Impact of diatom growth on trace metal dynamics (Mn, Mo, V, U)

NASA Astrophysics Data System (ADS)

Osterholz, Helena; Simon, Heike; Beck, Melanie; Maerz, Joeran; Rackebrandt, Siri; Brumsack, Hans-Jürgen; Feudel, Ulrike; Simon, Meinhard

2014-03-01

In order to examine the specific role of diatoms in cycling of the trace metals manganese (Mn), molybdenum (Mo), vanadium (V), and uranium (U) Thalassiosira rotula, Skeletonema marinoi, Chaetoceros decipiens, and Rhizosolenia setigera were grown in batch cultures axenically and inoculated with three different bacterial strains isolated from the North Sea. Algal and bacterial growth, concentrations of trace metals and dissolved organic carbon (DOC) were monitored over time and showed that Mn and V were removed from the dissolved phase whereas Mo and U were not. R. setigera and T. rotula exhibited lowest growth and lowest removal whereas S. marinoi grew best and removed highest fractions of Mn and V. The high potential of Mn removal by S. marinoi was also evident from its 7 × higher Mn/P elemental ratio relative to T. rotula. The presence of bacteria modified the timing of the growth of S. marinoi but not directly trace metal removal whereas bacteria enhanced trace metal removal in the cultures of T. rotula and C. decipiens. Modeling of phytoplankton growth, concentrations of Mn and DOC fraction in axenic T. rotula cultures indicated that processes of binding and desorption of Mn to excreted organic components are important to explain the varying proportions of dissolved Mn and thus must be considered as an active component in Mn cycling. The results show distinct differences in the potential of the diatoms in the removal of Mn and V and that bacteria can play an active role in this context. S. marinoi presumably is an important player in Mn and V dynamics in coastal marine systems.

Effect of citric acid and rhizosphere bacteria on metal plaque formation and metal accumulation in reeds in synthetic acid mine drainage solution.

PubMed

Guo, Lin; Cutright, Teresa J

2014-06-01

Many of regions in the world have been affected by acid mine drainage (AMD). The study assessed the effect of rhizosphere bacteria and citric acid (CA) on the metal plaque formation and heavy metal uptake in Phragmites australis cultured in synthetic AMD solution. Mn and Al plaque were not formed, but Fe plaque which was mediated by rhizosphere iron oxidizing bacteria (Fe(II)OB) was observed on the root system of reeds. Fe plaque did not significantly influence the uptake of Fe, Al and Mn into tissues of reeds. CA significantly (p<0.01) inhibited the growth of Fe(II)OB and decreased the formation of Fe plaque. CA also significantly improved (p<0.05) the accumulation of Fe, Mn and Al in all the tissues of reeds. Roots and rhizomes were the main organs to store metals. The roots contained 0.08±0.01mg/g Mn, 2.39±0.26mg/g Fe and 0.19±0.02mg/g Al, while the shoots accumulated 0.04±0.00mg/g Mn, 0.20±0.01mg/g Fe, 0.11±0.00mg/g Al in reeds cultured in solution amended with 2.101g/l CA and without inoculation of rhizosphere bacteria. Copyright © 2014 Elsevier Inc. All rights reserved.