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Sample records for iron nitrates

  1. Iron, nitrate uptake by phytoplankton, and mermaids

    NASA Astrophysics Data System (ADS)

    Banse, Karl

    1991-11-01

    The critique by Martin et al. (this issue) of my recalculation of rates of nitrate uptake, and hence of algal division, from the Gulf of Alaska is shown to be incorrect. Neither can iron deficiency, if any, be shown to be connected with the demise of mermen and mermaids, although for different reasons.

  2. Simultaneous removal of nitrate and heavy metals by iron metal.

    PubMed

    Hao, Zhi-Wei; Xu, Xin-Hua; Jin, Jian; He, Ping; Liu, Yong; Wang, Da-Hui

    2005-05-01

    Great attention should be paid now to simultaneously removing common pollutants, especially inorganic pollutants such as nitrate and heavy metals, as individual removal has been investigated extensively. Removing common pollutants simultaneously by iron metal is a very effective alternative method. Near neutral pH, heavy metals, such as copper and nickel, can be removed rapidly by iron metal, while nitrate removal very much slower than that of copper and nickel, and copper can accelerate nitrate removal when both are removed simultaneously. Even a little amount of copper can enhance nitrate removal efficiently. Different mechanisms of these contaminants removal by iron metal were also discussed.

  3. Reductive denitrification of nitrate by scrap iron filings.

    PubMed

    Hao, Zhi-Wei; Xu, Xin-Hua; Wang, Da-Hui

    2005-03-01

    Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.

  4. A new method to produce nanoscale iron for nitrate removal

    NASA Astrophysics Data System (ADS)

    Chen, Shiao-Shing; Hsu, Hong-Der; Li, Chi-Wang

    2004-12-01

    This article proposes a novel technology combining electrochemical and ultrasonic methods to produce nanoscale zero valent iron (NZVI). With platinum placed in the cathode and the presence of the dispersion agent, 0.2g/l cetylpyridinium chloride (CPC), a cation surfactant, in the solution, the nanoscale iron particle was successfully produced with diameter of 1-20 nm and specific surface area of 25.4m2/g. The produced NZVI was tested in batch experiments for nitrate removal. The results showed that the nitrate reduction was affected by pH. Al low pH, nitrate was shown faster decline and more reduction in term of g NO 3 - -N/g NZVI. The reaction was first order and kinetic coefficients for the four pHs were directly related to pH with R 2 >0.95. Comparing with microscale zero-valent iron (45μm, 0.183m2/g), microscale zero-valent iron converted nitrate to ammonia completely, but NZVI converted nitrate to ammonia partially from 36.2 to 45.3% dependent on pH. For mass balance of iron species, since the dissolved iron in the solution was very low (<1mg/l), Electron Spectroscopy for Chemical Analysis (ESCA) was used for identification of oxidation state of the surface species on the NZVI and Fe2O3 was recognized. Thus the reaction mechanisms can be determined.

  5. A bioinspired iron catalyst for nitrate and perchlorate reduction.

    PubMed

    Ford, Courtney L; Park, Yun Ji; Matson, Ellen M; Gordon, Zachary; Fout, Alison R

    2016-11-11

    Nitrate and perchlorate have considerable use in technology, synthetic materials, and agriculture; as a result, they have become pervasive water pollutants. Industrial strategies to chemically reduce these oxyanions often require the use of harsh conditions, but microorganisms can efficiently reduce them enzymatically. We developed an iron catalyst inspired by the active sites of nitrate reductase and (per)chlorate reductase enzymes. The catalyst features a secondary coordination sphere that aids in oxyanion deoxygenation. Upon reduction of the oxyanions, an iron(III)-oxo is formed, which in the presence of protons and electrons regenerates the catalyst and releases water. Copyright © 2016, American Association for the Advancement of Science.

  6. Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; Löscher, Carolin R.; Fiskal, Annika; Sommer, Stefan; Hensen, Christian; Lomnitz, Ulrike; Wuttig, Kathrin; Göttlicher, Jörg; Kossel, Elke; Steininger, Ralph; Canfield, Donald E.

    2016-11-01

    Iron is an essential element for life on Earth and limits primary production in large parts of the ocean. Oxygen-free continental margin sediments represent an important source of bioavailable iron to the ocean, yet little of the iron released from the seabed reaches the productive sea surface. Even in the anoxic water of oxygen minimum zones, where iron solubility should be enhanced, most of the iron is rapidly re-precipitated. To constrain the mechanism(s) of iron removal in anoxic ocean regions we explored the sediment and water in the oxygen minimum zone off Peru. During our sampling campaign the water column featured two distinct redox boundaries separating oxic from nitrate-reducing (i.e., nitrogenous) water and nitrogenous from weakly sulfidic water. The sulfidic water mass in contact with the shelf sediment contained elevated iron concentrations >300 nM. At the boundary between sulfidic and nitrogenous conditions, iron concentrations dropped sharply to <20 nM coincident with a maximum in particulate iron concentration. Within the iron gradient, we found an increased expression of the key functional marker gene for nitrate reduction (narG). Part of this upregulation was related to the activity of known iron-oxidizing bacteria. Collectively, our data suggest that iron oxidation and removal is induced by nitrate-reducing microbes, either enzymatically through anaerobic iron oxidation or by providing nitrite for an abiotic reaction. Given the important role that iron plays in nitrogen fixation, photosynthesis and respiration, nitrate-dependent iron oxidation likely represents a key-link between the marine biogeochemical cycles of nitrogen, oxygen and carbon.

  7. The nature of heme/iron-induced protein tyrosine nitration

    PubMed Central

    Bian, Ka; Gao, Zhonghong; Weisbrodt, Norman; Murad, Ferid

    2003-01-01

    Recently, substantial evidence has emerged that revealed a very close association between the formation of nitrotyrosine and the presence of activated granulocytes containing peroxidases, such as myeloperoxidase. Peroxidases share heme-containing homology and can use H2O2 to oxidize substrates. Heme is a complex of iron with protoporphyrin IX, and the iron-containing structure of heme has been shown to be an oxidant in several model systems where the prooxidant effects of free iron, heme, and hemoproteins may be attributed to the formation of hypervalent states of the heme iron. In the current study, we have tested the hypothesis that free heme and iron play a crucial role in NO2-Tyr formation. The data from our study indicate that: (i) heme/iron catalyzes nitration of tyrosine residues by using hydrogen peroxide and nitrite, a reaction that revealed the mechanism underlying the protein nitration by peroxidase, H2O2, and NO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{-}}}\\end{equation*}\\end{document}; (ii) H2O2 plays a key role in the protein oxidation that forms the basis for the protein nitration, whereas nitrite is an essential element that facilitates nitration by the heme(Fe), H2O2, and the NO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{2}^{-}}}\\end{equation*}\\end{document} system; (iii) the formation of a Fe(IV) hypervalent compound may be essential for heme(Fe)-catalyzed nitration, whereas O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage

  8. Anoxic Iron Cycling Bacteria from an Iron Sulfide- and Nitrate-Rich Freshwater Environment

    PubMed Central

    Haaijer, Suzanne C. M.; Crienen, Gijs; Jetten, Mike S. M.; Op den Camp, Huub J. M.

    2012-01-01

    In this study, both culture-dependent and culture-independent methods were used to determine whether the iron sulfide mineral- and nitrate-rich freshwater nature reserve Het Zwart Water accommodates anoxic microbial iron cycling. Molecular analyses (16S rRNA gene clone library and fluorescence in situ hybridization, FISH) showed that sulfur-oxidizing denitrifiers dominated the microbial population. In addition, bacteria resembling the iron-oxidizing, nitrate-reducing Acidovorax strain BrG1 accounted for a major part of the microbial community in the groundwater of this ecosystem. Despite the apparent abundance of strain BrG1-like bacteria, iron-oxidizing nitrate reducers could not be isolated, likely due to the strictly autotrophic cultivation conditions adopted in our study. In contrast an iron-reducing Geobacter sp. was isolated from this environment while FISH and 16S rRNA gene clone library analyses did not reveal any Geobacter sp.-related sequences in the groundwater. Our findings indicate that iron-oxidizing nitrate reducers may be of importance to the redox cycling of iron in the groundwater of our study site and illustrate the necessity of employing both culture-dependent and independent methods in studies on microbial processes. PMID:22347219

  9. AN EFFICIENT AND ECOFRIENDLY OXIDATION OF ALKENES USING IRON NITRATE AND MOLECULAR OXYGEN

    EPA Science Inventory

    An environmentally friendly solventless oxidation of alkenes is accomplished efficiently using relatively benign iron nitrate as catalyst in the pressence of molecular oxygen under pressurized conditions.

  10. Role of humic substances in promoting autotrophic growth in nitrate-dependent iron-oxidizing bacteria.

    PubMed

    Kanaparthi, Dheeraj; Conrad, Ralf

    2015-05-01

    Nitrate-dependent iron oxidation was discovered in 1996 and has been reported from various environments ever since. To date, despite the widespread nature of this process, all attempts to cultivate chemolithoautotrophic nitrate-dependent iron oxidizers have been unsuccessful. The present study was focused on understanding the influence of natural chelating agents of iron, like humic substances, on the culturability, activity, and enumeration, of these microorganisms. Pure culture studies conducted with Thiobacillus denitrificans showed a constant increase in cell mass with a corresponding nitrate-dependent iron oxidation activity only when Fe(II) was provided together with humic substances, compared to no growth in control incubations without humic substances. The presence of a relatively strong chelating agent, such as EDTA, inhibited the growth of Thiobacillus denitrificans. It was concluded that complex formation between humic substances and iron was required for chemolithoautotrophic nitrate-dependent iron oxidation. Most probable number enumerations showed that numbers of chemolithoautotrophic nitrate-dependent iron-oxidizing bacteria were one to three orders of magnitude higher in the presence of humic substances compared to media without. Similar results were obtained when potential nitrate-dependent iron oxidation activity was determined in soil samples. In summary, this study showed that humic substances significantly enhanced the growth and activity of autotrophic nitrate-dependent iron-oxidizing microorganisms, probably by chelation of iron. Copyright © 2015 Elsevier GmbH. All rights reserved.

  11. Nitrative and oxidative modifications of enolase are associated with iron in iron-overload rats and in vitro.

    PubMed

    Lu, Naihao; Li, Xueli; Li, Jinyang; Xu, Wenjing; Li, Hailing; Gao, Zhonghong

    2011-03-01

    Iron overload is one of the most common iron-related toxicities, and liver is the major organ that is injured. Although oxidative stress is well accepted in the pathological mechanism of iron overload, nitrative modification in liver and the role of iron are relatively unknown. In this work, the nitrative and oxidative stress in liver was investigated in an iron-overload rat model. It was found that after 15 weeks of iron dextran administration, consistent with the increase of iron content in rat liver, both protein tyrosine nitration and protein oxidation were clearly elevated. By means of immunoprecipitation analysis, it was found that enolase nitration and oxidation status were significantly increased in iron-overload liver, whereas both α-enolase expression and activity were clearly decreased. The effects of different forms of iron on NaNO(2)-H(2)O(2)- and peroxynitrite (ONOO(-))-dependent enolase nitration and oxidation were further investigated in vitro to elucidate the possible role of iron in enolase dysfunction in vivo. Compared with EDTA-Fe(III), ferric citrate, and ferritin, heme (hemin and hemoglobin) showed higher efficiency in catalyzing protein nitration in both models. Besides the major contribution of free iron (Fe(2+) and Fe(3+)) to catalyze protein oxidation, Fe(2+) also directly acted as a competitive inhibitor and produced a significant decrease in enzyme activity. These results suggest that the existence of various forms of iron is an important contributing factor to the elevated nitrative/oxidative modifications and diminished activity of α-enolase in the development and progress of iron-overload-associated syndromes.

  12. Influence of Microbial Iron and Nitrate Reduction on Subsurface Iron Biogeochemistry and Contaminant Metal Mobilization

    SciTech Connect

    Flynn W. Picardal

    2002-04-10

    Although toxic metal and radionuclide contaminants can not be destroyed, their toxicity and mobility can be dramatically altered by microbial activity. In addition to toxic metals, many contaminated sites contain both iron-containing minerals and co-contaminants such as nitrate NO{sub 3}{sup -}. Successful implementation of metal and radionuclide bioremediation strategies in such environments requires an understanding of the complex microbial and geochemical interactions that influence the redox speciation and mobility of toxic metals. Our specific objectives have been to (1) determine the effect of iron oxide mineral reduction on the mobility of sorbed, representative toxic metals (Zn{sup 2+}), (2) study the biogeochemical interactions that may occur during microbial reduction of NO{sub 3}{sup -} and iron oxide minerals, and (3) evaluate the kinetics of NO{sub 3}{sup -}-dependent, microbial oxidation of ferrous iron (Fe{sup 2+}).

  13. Perivascular iron deposits are associated with protein nitration in cerebral experimental autoimmune encephalomyelitis.

    PubMed

    Sands, Scott A; Williams, Rachel; Marshall, Sylvester; LeVine, Steven M

    2014-10-17

    Nitration of proteins, which is thought to be mediated by peroxynitrite, is a mechanism of tissue damage in multiple sclerosis (MS). However, protein nitration can also be catalyzed by iron, heme or heme-associated molecules independent of peroxynitrite. Since microhemorrhages and perivascular iron deposits are present in the CNS of MS patients, we sought to determine if iron is associated with protein nitration. A cerebral model of experimental autoimmune encephalomyelitis (cEAE) was utilized since this model has been shown to have perivascular iron deposits similar to those present in MS. Histochemical staining for iron was used together with immunohistochemistry for nitrotyrosine, eNOS, or iNOS on cerebral sections. Leakage of the blood-brain barrier (BBB) was studied by albumin immunohistochemistry. Iron deposits were colocalized with nitrotyrosine staining around vessels in cEAE mice while control animals revealed minimal staining. This finding supports the likelihood that nitrotyrosine formation was catalyzed by iron or iron containing molecules. Examples of iron deposits were also observed in association with eNOS and iNOS, which could be one source of substrates for this reaction. Extravasation of albumin was present in cEAE mice, but not in control animals. Extravasated albumin may act to limit tissue injury by binding iron and/or heme as well as being a target of nitration, but the protection is incomplete. In summary, iron-catalyzed nitration of proteins is a likely mechanism of tissue damage in MS.

  14. [Synchronous treatment of heavy metal ions and nitrate by zero-valent iron].

    PubMed

    Zhang, Zhen; Hao, Zhi-Wei; Liu, Wen-Li; Xu, Xin-Hua

    2009-03-15

    The wastewater which contains bivalent copper and nitrate, bivalent nickel and nitrate, hexavalent chromium and nitrate were simultaneously treated by the zero-valent iron (Fe(0)) system to investigate the feasibility of using Fe(0) for the remediation of contaminated groundwater. The experimental results indicate that nitrate has no obvious effect on the removal of heavy metals, and different heavy metal has different impacts on the removal of nitrate. Bivalent copper accelerates the nitrate removal percentage and the reaction rate. 50 mg x L(-1) bivalent copper made the nitrate removal percentage in 120 min increase from 38.2% to 95.0%, meanwhile made k(obs) of the nitrate reduction increase from 0.004 3 to 0.033 9 min(-1). And the more the concentrations of bivalent copper are, the higher the nitrate removal percentage and the reaction rate are. And it is the bivalent copper that makes the apparent activation energy of the nitrate reduction by Fe(0) decrease from 40.8 k x mol(-1) to 21.1 kJ x mol(-1), which leads to the increase of the reaction rate. When Fe(0) simultaneously treats the wastewater containing bivalent nickel and nitrate, they have no obvious effects on each other. When Fe(0) simultaneously treats the wastewater containing hexavalent chromium and nitrate, the results show the nitrate concentration remains unchanged, and prove that hexavalent chromium decreases the nitrate removal speed.

  15. Nitrate reduction and its effects on trichloroethylene degradation by granular iron.

    PubMed

    Lu, Qiong; Jeen, Sung-Wook; Gui, Lai; Gillham, Robert W

    2017-04-01

    Laboratory column experiments and reactive transport modeling were performed to evaluate the reduction of nitrate and its effects on trichloroethylene (TCE) degradation by granular iron. In addition to determining degradation kinetics of TCE in the presence of nitrate, the columns used in this study were equipped with electrodes which allowed for in situ measurements of corrosion potentials of the iron material. Together with Raman spectroscopic measurements the mechanisms of decline in iron reactivity were examined. The experimental results showed that the presence of nitrate resulted in an increase in corrosion potential and the formation of thermodynamically stable passive films on the iron surface which impaired iron reactivity. The extent of the decline in iron reactivity was proportional to the nitrate concentration. Consequently, significant decreases in TCE and nitrate degradation rates and migration of degradation profiles for both compounds occurred. Furthermore, the TCE degradation kinetics deviated from the pseudo-first-order model. The results of reactive transport modeling, which related the amount of a passivating iron oxide, hematite (α-Fe2O3), to the reactivity of iron, were generally consistent with the patterns of migration of TCE and nitrate profiles observed in the column experiments. More encouragingly, the simulations successfully demonstrated the differences in performances of three columns without changing model parameters other than concentrations of nitrate in the influent. This study could be valuable in the design of iron permeable reactive barriers (PRBs) or in the development of effective maintenance procedures for PRBs treating TCE-contaminated groundwater with elevated nitrate concentrations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. In vitro and in vivo biological activities of iron chelators and gallium nitrate against Acinetobacter baumannii.

    PubMed

    de Léséleuc, Louis; Harris, Greg; KuoLee, Rhonda; Chen, Wangxue

    2012-10-01

    We investigated the ability of compounds interfering with iron metabolism to inhibit the growth of Acinetobacter baumannii. Iron restriction with transferrin or 2,2-bipyridyl significantly inhibited A. baumannii growth in vitro. Gallium nitrate alone was moderately effective at reducing A. baumannii growth but became bacteriostatic in the presence of serum or transferrin. More importantly, gallium nitrate treatment reduced lung bacterial burdens in mice. The use of gallium-based therapies shows promise for the control of multidrug-resistant A. baumannii.

  17. NITRATE REDUCTION BY ZEROVALENT IRON: EFFECTS OF FORMATE, OXALATE, CITRATE, CHLORIDE, SULFATE, BORATE, AND PHOSPHATE

    EPA Science Inventory

    Recent studies have shown that zerovalent iron (Fe0) may potentially be used as a chemical medium in permeable reactive barriers (PRBs) for nitrate remediation in groundwater; however, the effects of commonly found organic and inorganic ligands in soil and sediments on nitrate re...

  18. NITRATE REDUCTION BY ZEROVALENT IRON: EFFECTS OF FORMATE, OXALATE, CITRATE, CHLORIDE, SULFATE, BORATE, AND PHOSPHATE

    EPA Science Inventory

    Recent studies have shown that zerovalent iron (Fe0) may potentially be used as a chemical medium in permeable reactive barriers (PRBs) for nitrate remediation in groundwater; however, the effects of commonly found organic and inorganic ligands in soil and sediments on nitrate re...

  19. Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control.

    PubMed

    Fan, Xiaomeng; Guan, Xiaohong; Ma, Jun; Ai, Hengyu

    2009-01-01

    Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions (dissolved oxygen or reaction pH) control, this work aimed at subjecting the kinetics of denitrification by microscale Fe0 (160-200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

  20. Ammonium nitrate and iron nutrition effects on some nitrogen assimilation enzymes and metabolites in Spirulina platensis.

    PubMed

    Esen, Merve; Ozturk Urek, Raziye

    2015-01-01

    The effect of various concentrations of ammonium nitrate (5-60 mM), an economical nitrogen source, on the growth, nitrate-ammonium uptake rates, production of some pigments and metabolites, and some nitrogen assimilation enzymes such as nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT) in Spirulina platensis (Gamont) Geitler was investigated. Ten millimolars of ammonium nitrate stimulated the growth, production of pigments and the other metabolites, and enzyme activities, whereas 30 and 60 mM ammonium nitrate caused inhibition. In the presence of 10 mM ammonium nitrate, different concentrations of iron were tried in the growth media of S. platensis. After achieving the best growth, levels of metabolite and pigment production, and enzyme activities in the presence of 10 mM ammonium nitrate as a nitrogen source, different iron concentrations (10-100 µM) were tried in the growth medium of S. platensis. The highest growth, pigment and metabolite levels, and enzyme activities were determined in the medium containing 50 µM iron and 10 mM ammonium nitrate. In this optimum condition, the highest dry biomass level, chlorophyll a, and pyruvate contents were obtained as 55.42 ± 3.8 mg mL(-1) , 93.114 ± 7.9 µg g(-1) , and 212.5 ± 18.7 µg g(-1) , respectively. The highest NR, NiR, GS, and GOGAT activities were 67.16 ± 5.1, 777.92 ± 52, 0.141 ± 0.01, and 44.45 ± 3.6, respectively. Additionally, 10 mM ammonium nitrate is an economical and efficient nitrogen source for nitrogen assimilation of S. platensis, and 50 µM iron is optimum for the growth of S. platensis. © 2014 International Union of Biochemistry and Molecular Biology, Inc.

  1. Remediation of Nitrate-contaminated Groundwater by a Mixture of Iron and Activated Carbon

    NASA Astrophysics Data System (ADS)

    Huang, Guoxin; Liu, Fei; Jin, Aifang; Qin, Xiaopeng

    2010-11-01

    Nitrate contamination in groundwater has become a major environmental and health problem worldwide. The aim of the present study is to remediate groundwater contaminated by nitrate and develop potential reactive materials to be used in PRBs (Permeable Reactive Barriers). A new approach was proposed for abiotic groundwater remediation by reactive materials of iron chips and granular activated carbon particles. Batch tests were conducted and remediation mechanisms were discussed. The results show that nitrate decreases from 86.31 to 33.79 mgṡL-1 under the conditions of near neutral pH and reaction time of 1h. The combination of iron chips and activated carbon particles is cost-effective and suitable for further use as denitrification media in PRBs. Nitrogen species don't change significantly with the further increase in reaction time (>1 h). The iron-activated carbon-water-nitrate system tends to be steady-state. Small amounts of ammonium and nitrite (0.033-0.039 and 0.14-3.54 mgṡL-1, respectively) appear at reaction time from 0 h to 5 h. There is no substantial accumulation of nitrogen products in the system. The removal rate of nitrate only reaches 16.11% by sole iron chips at reaction time of 5 h, while 63.57% by the mixture of iron chips and activated carbon particles. There is significantly synergistic and promotive effect of mixing the two different types of materials on nitrate treatment. Fe/C ratio (1/1.5-1/2.5) doesn't cause dramatically different residual nitrate concentrations (24.09-26.70 mgṡL-1). Nitrate can't be limitlessly decreased with decreasing Fe/C ratio. The concomitant occurrences of chemical reduction, galvanic cell reaction, electrophoretic accumulation, chemical coagulation, and physical adsorption are all responsible for the overall nitrate removal by iron allied with activated carbon. To accurately quantify various nitrogen species, further studies on adsorption mechanisms of nitrite and nitrate are needed.

  2. Selective decomposition of aqueous nitrate into nitrogen using iron deposited bimetals.

    PubMed

    Liou, Ya Hsuan; Lin, Chin Jung; Weng, Shih Chi; Ou, Hsin Hung; Lo, Shang Lien

    2009-04-01

    In the case of the reduction of nitrate in groundwater, the problem is how to convert nitrate [N(+V)] selectively to nontoxic dinitrogen [N(O)] and not to completely reduced ammonia [N(-III)]. Unfortunately, near 100% of the total nitrogen in nitrate is reductively converted to ammonia using naked zerovalent iron (ZVI) thus far reported. In this study, deposition of noble metals (Pt, Pd, and Au) and Cu on iron surface to offer favorable pathways for nitrate reduction was fabricated using either the complete mixing orthe successive method with spontaneous redox reactions. The prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy/energy disperse X-ray spectroscopy, and electrochemical analysis. The formation of N2 from the reduction of nitrate was confirmed by residual gas analyzer coupled to a high vacuum system. Based on the experimental results, the ZVI deposited Pd and Cu closely is suggested to promote the abstraction of oxygen from NOx by adsorbed atomic hydrogen on the Cu surface, and enhance N2 formation on the Pd surface. An optimum N2 selectivity of approximately 30% obtained in the alkaline solution containing nitrate using 0.3 wt.% Pd-0.5 wt% Cu/Fe is evident. For groundwater treatment, iron deposited Pd and Cu could facilitate the development of a process requiring neither a massive addition of chemicals nor complex equipment.

  3. Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Zhou, Xuefei; Dai, Chaomeng; Zhang, Weixian; Keller, Arturo A; Zhang, Yalei

    2014-09-15

    Nanoscale zerovalent iron (nZVI) is efficient for removing Pb(2+) and nitrate from water. However, the influence of nitrate, a common groundwater anion, on Pb(2+) removal by nZVI is not well understood. In this study, we showed that under excess Fe(0) conditions (molar ratio of Fe(0)/nitrate>4), Pb(2+) ions were immobilized more quickly (<5 min) than in nitrate-free systems (∼ 15 min) due to increasing pH. With nitrate in excess (molar ratio of Fe(0)/nitrate<4), nitrate stimulated the formation of crystal PbxFe3-xO4 (ferrite), which provided additional Pb(2+) removal. However, ∼ 7% of immobilized Pb(2+) ions were released into aqueous phase within 2h due to ferrite deformation. Oxidation-reduction potential (ORP) values below -600 mV correlated with excess Fe(0) conditions (complete Pb(2+) immobilization), while ORP values ≥-475 mV characterized excess nitrate conditions (ferrite process and Pb(2+) release occurrence). This study indicates that ORP monitoring is important for proper management of nZVI-based remediation in the subsurface to avoid lead remobilization in the presence of nitrate.

  4. Microbial reduction of nitrate in the presence of zero-valent iron and biochar.

    PubMed

    Oh, Seok-Young; Seo, Yong-Deuk; Kim, Beomseok; Kim, In Young; Cha, Daniel K

    2016-01-01

    The denitrification of nitrate (NO3(-)) by mixed cultures in the presence of zero-valent iron [Fe(0)] and biochar was investigated through a series of batch experiments. It was hypothesized that biochar may provide microbes with additional electrons to enhance the anaerobic biotransformation of nitrate in the presence of Fe(0) by facilitating electron transfer. When compared to the anaerobic transformation of nitrate by microbes in the presence of Fe(0) alone, the presence of biochar significantly enhanced anaerobic denitrification by microbes with Fe(0). Graphite also promoted the anaerobic microbial transformation of nitrate with Fe(0), and it was speculated that electron-conducting graphene moieties were responsible for the improvement. The results obtained in this work suggest that nitrate can be effectively denitrified by microbes with Fe(0) and biochar in natural and engineered systems.

  5. In Vitro and In Vivo Biological Activities of Iron Chelators and Gallium Nitrate against Acinetobacter baumannii

    PubMed Central

    Harris, Greg; KuoLee, Rhonda; Chen, Wangxue

    2012-01-01

    We investigated the ability of compounds interfering with iron metabolism to inhibit the growth of Acinetobacter baumannii. Iron restriction with transferrin or 2,2-bipyridyl significantly inhibited A. baumannii growth in vitro. Gallium nitrate alone was moderately effective at reducing A. baumannii growth but became bacteriostatic in the presence of serum or transferrin. More importantly, gallium nitrate treatment reduced lung bacterial burdens in mice. The use of gallium-based therapies shows promise for the control of multidrug-resistant A. baumannii. PMID:22825117

  6. SOLVENT FREE OXIDATION OF ALCOHOLS USING IRON (III) NITRATE NONAHYDRATE

    EPA Science Inventory

    Oxidation of alcohols have been conducted with metal nitrate reagents on various mineral supports such as clay, silica and zeolite etc. To circumvent the limitations of these supported reagents namely their preparation using solvents and short shelf-life, we explored the use of i...

  7. SOLVENT FREE OXIDATION OF ALCOHOLS USING IRON (III) NITRATE NONAHYDRATE

    EPA Science Inventory

    Oxidation of alcohols have been conducted with metal nitrate reagents on various mineral supports such as clay, silica and zeolite etc. To circumvent the limitations of these supported reagents namely their preparation using solvents and short shelf-life, we explored the use of i...

  8. Kinetic Study of Nitrate Removal from Aqueous Solutions Using Copper-Coated Iron Nanoparticles.

    PubMed

    Vilardi, Giorgio; Di Palma, Luca

    2017-03-01

    Nitrates are considered hazard compounds for human health due to their tendency to be reduced to nitrites, in particular in reducing environment. Nano zero valent iron (nZVI) represents an efficient and low-cost adsorbent/reductive agent for nitrate removal from groundwater and wastewaters and a little addition of a second metal species (Cu, Pd, Ni, Ag) has proven to increase process effectiveness, by enhancing stability and oxidation resistance of nanoparticles. In this work Cu/Fe nanoparticles were loaded in a NO3(-) solution (100 mg L(-1)) and the removal efficiency was tested by monitoring nitrate concentration at selected time intervals. Results showed that the nitrate removal process involves both reduction and adsorption processes: the removal mechanism has been investigated, and the pseudo-first-order and pseudo-second-order-adsorption kinetic models were successfully tested.

  9. Arsenic, nitrate, iron, and hardness in ground water, Fairbanks area, Alaska

    USGS Publications Warehouse

    Johnson, Paula R.; Wilcox, D.E.; Morgan, W.D.; Merto, Josephine; McFadden, Ruth

    1979-01-01

    Well water with concentrations of arsenic and nitrate exceeding U.S. Environmental Protection Agency standards occurs sporadically throughout the hills north of Fairbanks, Alaska. The arsenic contamination has not been correlated with placer or other mining activity. The high levels of nitrate do not generally appear related to septic waste contamination. Few wells in the Fairbanks area yield water with low concentrations of iron or low hardness. Iron concentrations are consistently greater than 3 mg/L on the flood plain. In the uplands, concentrations of both iron and hardness are lowest near the ridgetops and increase downslope. The report includes a map of the area showing the location of sampled wells and a table of chemical analysis. (Woodard-USGS)

  10. Changes in Ice Age Nitrate Consumption, Productivity, and Biological Pump Efficiency can be Explained by the Internal Cycling of Iron

    NASA Astrophysics Data System (ADS)

    Rafter, P. A.; Sigman, D. M.; Mackey, K. R.

    2016-12-01

    The biological pump—the surface-to-deep transport of marine organic carbon—is linked to "new" primary production fueled by upwelled nutrients such as nitrate, and incomplete nitrate consumption in High Nutrient, Low Chlorophyll (HNLC) regions limits the biological pump to 50% of its potential strength. Recent work shows that the intensity and temporal variability of nitrate consumption in iron-limited HNLC regions cannot be explained by the supply of iron or the iron-to-nitrate supply ratio. Instead, this nitrate consumption must be supported by vigorous iron recycling within the euphotic zone. Iron recycling explains observed variability in HNLC nitrate consumption as a function of upwelling water residence time, with slower upwelling rates allowing for more iron recycling. Applying these findings to sediment proxy records answers some outstanding questions about nitrate consumption, productivity, and biological pump efficiency in the equatorial Pacific and Southern Ocean HNLC regions. For example, we will discuss how variable upwelling strength explains changes in equatorial Pacific and Antarctic Zone nitrate consumption and productivity during the last glacial period.

  11. Iron overload-induced rat liver injury: Involvement of protein tyrosine nitration and the effect of baicalin.

    PubMed

    Zhang, Yan; Huang, Yi; Deng, Xiaorong; Xu, Yan; Gao, Zhonghong; Li, Hailing

    2012-04-05

    Baicalin has been reported to protect against liver injury in iron-overload mice, however, the mechanisms underlying the hepatoprotective properties of baicalin are poorly understood. In this study, we systematically studied the protective effect of baicalin on iron overload induced liver injury, as well as the underlying mechanism based on nitrative stress in rat model. We found that when iron overload rats (500mgiron/kg) were fed baicalin-containing diet (0.3% and 1% w/w) for 45days, baicalin dose dependently protected against iron overload induced liver injury, including alleviation of hepatic pathological damage, decrease of SOD activity, iron content, carbonyl content, and the thiobarbituric acid-reactive substances level in hepatic tissues. It also increased serum iron content, SH content and GPx activity, decreased serum ALT and AST activities. Immunohistochemistry and immunoprecipitation analysis revealed that baicalin could also inhibit iron overload induced protein tyrosine nitration in liver. Moreover, in iron overload rat liver, we found that baicalin decreased the iron overload increased level of glutathione-S-transferases (GSTs) expression, oxidation and nitration. These results suggest that not only oxidative stress, but also nitrative stress, is involved in iron overload induced liver injury, and the underlying mechanism might partially relate to the involvement of GSTs expression and post-translational modification. Baicalin can effectively prevent iron overload caused abnormality and can be a candidate medicine for iron overload diseases. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

    PubMed Central

    Kappler, A.; Johnson, C.M.; Crosby, H.A.; Beard, B.L.; Newman, D.K.

    2010-01-01

    Iron isotope fractionations produced during chemical and biological Fe(II) oxidation are sensitive to the proportions and nature of dissolved and solid-phase Fe species present, as well as the extent of isotopic exchange between precipitates and aqueous Fe. Iron isotopes therefore potentially constrain the mechanisms and pathways of Fe redox transformations in modern and ancient environments. In the present study, we followed in batch experiments Fe isotope fractionations between Fe(II)aq and Fe(III) oxide/hydroxide precipitates produced by the Fe(III) mineral encrusting, nitrate-reducing, Fe(II)-oxidizing Acidovorax sp. strain BoFeN1. Isotopic fractionation in 56Fe/54Fe approached that expected for equilibrium conditions, assuming an equilibrium Δ56FeFe(OH)3 – Fe(II)aq fractionation factor of +3.0 ‰. Previous studies have shown that Fe(II) oxidation by this Acidovorax strain occurs in the periplasm, and we propose that Fe isotope equilibrium is maintained through redox cycling via coupled electron and atom exchange between Fe(II)aq and Fe(III) precipitates in the contained environment of the periplasm. In addition to the apparent equilibrium isotopic fractionation, these experiments also record the kinetic effects of initial rapid oxidation, and possible phase transformations of the Fe(III) precipitates. Attainment of Fe isotope equilibrium between Fe(III) oxide/hydroxide precipitates and Fe(II)aq by neutrophilic, Fe(II)-oxidizing bacteria or through abiologic Fe(II)aq oxidation is generally not expected or observed, because the poor solubility of their metabolic product, i.e. Fe(III), usually leads to rapid precipitation of Fe(III) minerals, and hence expression of a kinetic fractionation upon precipitation; in the absence of redox cycling between Fe(II)aq and precipitate, kinetic isotope fractionations are likely to be retained. These results highlight the distinct Fe isotope fractionations that are produced by different pathways of biological and

  13. Bioinhibitory effect of hydrogenotrophic bacteria on nitrate reduction by nanoscale zero-valent iron.

    PubMed

    An, Yi; Dong, Qi; Zhang, Keqiang

    2014-05-01

    Hydrogenotrophic bacteria (HTB) were introduced into a nitrate removal system, which used nanoscale zero-valent iron (nZVI) as reductant, to investigate its bioinhibitory effect. Based on the results, it was noted that addition of HTB culture (10-50 mL) led to 58.9-91.4% decrease in the first observed rate constant (kobs1), which represented the nitrate removal rate by nZVI, and a reduction in the generated poisonous by-products from 94.9% to 38.5%. In other words, HTB had a significant inhibitory effect on nitrate reduction by nZVI. However, the pathway of this bioinhibition only prevented the occurrence of chemical reduction, but not competition for nitrate. Furthermore, FeOOH coating was observed on the surface of nZVI, instead of Fe3O4 or Fe2O3, which could prevent electron transmission from nZVI to nitrate. Considering that FeOOH was the product of iron corrosion, the result indicated that HTB could inhibit chemical reduction by enhancing the reaction between nZVI and water.

  14. Nanosized iron based permeable reactive barriers for nitrate removal - Systematic review

    NASA Astrophysics Data System (ADS)

    Araújo, Rui; Castro, Ana C. Meira; Santos Baptista, João; Fiúza, António

    2016-08-01

    It is unquestionable that an effective decision concerning the usage of a certain environmental clean-up technology should be conveniently supported. Significant amount of scientific work focussing on the reduction of nitrate concentration in drinking water by both metallic iron and nanomaterials and their usage in permeable reactive barriers has been worldwide published over the last two decades. This work aims to present in a systematic review of the most relevant research done on the removal of nitrate from groundwater using nanosized iron based permeable reactive barriers. The research was based on scientific papers published between 2004 and June 2014. It was performed using 16 combinations of keywords in 34 databases, according to PRISMA statement guidelines. Independent reviewers validated the selection criteria. From the 4161 records filtered, 45 met the selection criteria and were selected to be included in this review. This study's outcomes show that the permeable reactive barriers are, indeed, a suitable technology for denitrification and with good performance record but the long-term impact of the use of nanosized zero valent iron in this remediation process, in both on the environment and on the human health, is far to be conveniently known. As a consequence, further work is required on this matter, so that nanosized iron based permeable reactive barriers for the removal of nitrate from drinking water can be genuinely considered an eco-efficient technology.

  15. Peroxynitrite-induced nitration of tyrosine-34 does not inhibit Escherichia coli iron superoxide dismutase.

    PubMed Central

    Soulère, L; Claparols, C; Périé, J; Hoffmann, P

    2001-01-01

    The peroxynitrite anion is a potent oxidizing agent, formed by the diffusion-limited combination of nitric oxide and superoxide, and its production under physiological conditions is associated with the pathologies of a number of inflammatory and neurodegenerative diseases. Nitration of Escherichia coli iron superoxide dismutase (Fe-SOD) by peroxynitrite was investigated, and demonstrated by spectral changes and electrospray mass spectroscopic analysis. HPLC and mass studies of the tryptic digests of the mono-nitrated Fe-SOD indicated that tyrosine-34 was the residue most susceptible to nitration by peroxynitrite. Exclusive nitration of this residue occurred when Fe-SOD was exposed to a cumulative dose of 0.4 mM peroxynitrite. Unlike with human Mn-SOD, this single modification did not inactivate E. coli Fe-SOD at pH 7.4. When Fe-SOD was exposed to higher concentrations of peroxynitrite (7 mM), eight tyrosine residues per subunit of the protein, of the nine available, were nitrated without loss of catalytic activity of the enzyme. The pK(a) of nitrated tyrosine-34 was determined to be 7.95+/-0.15, indicating that the peroxynitrite-modified enzyme appreciably maintains its protonation state under physiological conditions. PMID:11736645

  16. Reduction of trichloroethylene and nitrate by zero-valent iron with peat.

    PubMed

    Min, Jee-Eun; Kim, Meejeong; Pardue, John H; Park, Jae-Woo

    2008-02-01

    The feasibility of using zero-valent iron (ZVI) and peat mixture as in situ barriers for contaminated sediments and groundwater was investigated. Trichloroethylene (TCE) and nitrate (NO(3)(-)), redox sensitive contaminants were reduced by ZVI and peat soil mixture under anaerobic condition. Peat was used to support the sorption of TCE, microbial activity for biodegradation of TCE and denitrification while TCE and nitrate were reduced by ZVI. Decreases in TCE concentrations were mainly due to ZVI, while peat supported denitrifying microbes and further affected the sorption of TCE. Due to the competition of electrons, nitrate reduction was inhibited by TCE, while TCE reduction was not affected by nitrate. From the results of peat and sterilized peat, it can be concluded that peat was involved in both dechlorination and denitrification but biological reduction of TCE was negligible compared to that of nitrate. The results from hydrogen and methane gas analyses confirmed that hydrogen utilization by microbes and methanogenic process had occurred in the ZVI-peat system. Even though effect of the peat on TCE reduction were quantitatively small, ZVI and peat contributed to the removal of TCE and nitrate independently. The 16S rRNA analysis revealed that viable bacterial diversity was narrow and the most frequently observed genera were Bacillus and Staphylococcus spp.

  17. Influence of compositional modifications on the corrosion of iron aluminides of molten nitrate salts

    SciTech Connect

    Tortorelli, P.F.; Bishop, P.S.

    1991-01-01

    The corrosion of iron-aluminum alloys by molten nitrate salt as a function of aluminum, chromium, and other minor elements has been studied as part of an alloy design effort aimed at the development of a strong, ductile, corrosion-resistant FeAl type of aluminide. Short- term weight change data were used to examine the compositional dependence of the corrosion processes that occurred upon exposure of iron aluminides to highly oxidizing nitrate salts of 650{degrees}C. Corrosion resistance was found to increase with increasing aluminum concentrations of the alloy up to approximately 30 at. % Al. Chromium additions to the aluminide were not detrimental and may have improved the corrosion behavior for certain aluminum concentrations. No effects of minor alloying additions (C, B, Ti, and Zr) could be determined. The best overall corrosion resistance as measured by weight change results were obtained for an Fe-35.8 at. % Al aluminide containing some chromium. Based on linear weight loss kinetics, the weight change measurements for the most resistant compositions predict corrosion rates of 300 {mu}m/year or less at 650{degrees}C. These rates are substantially better than typical nickel-based alloys and stainless steels. From a consideration of the weight changes; the microstructural, thermodynamic, and X-ray diffraction data; and the salt analyses, corrosion of iron aluminides by the molten nitrate salt appears to be controlled by oxidation of base metal components and a slow release of material from an aluminum-rich product layer into the salt. The rate of release was substantially lower than that previously found for iron and iron-based alloys. This would imply that corrosion of iron aluminides could be minimized by maximizing the surface coverage of this aluminum-rich layer either by alloying or by an appropriate preoxidation treatment.

  18. Influence of compositional modifications on the corrosion of iron aluminides of molten nitrate salts

    SciTech Connect

    Tortorelli, P.F.; Bishop, P.S.

    1991-01-01

    The corrosion of iron-aluminum alloys by molten nitrate salt as a function of aluminum, chromium, and other minor elements has been studied as part of an alloy design effort aimed at the development of a strong, ductile, corrosion-resistant FeAl type of aluminide. Short- term weight change data were used to examine the compositional dependence of the corrosion processes that occurred upon exposure of iron aluminides to highly oxidizing nitrate salts of 650{degrees}C. Corrosion resistance was found to increase with increasing aluminum concentrations of the alloy up to approximately 30 at. % Al. Chromium additions to the aluminide were not detrimental and may have improved the corrosion behavior for certain aluminum concentrations. No effects of minor alloying additions (C, B, Ti, and Zr) could be determined. The best overall corrosion resistance as measured by weight change results were obtained for an Fe-35.8 at. % Al aluminide containing some chromium. Based on linear weight loss kinetics, the weight change measurements for the most resistant compositions predict corrosion rates of 300 {mu}m/year or less at 650{degrees}C. These rates are substantially better than typical nickel-based alloys and stainless steels. From a consideration of the weight changes; the microstructural, thermodynamic, and X-ray diffraction data; and the salt analyses, corrosion of iron aluminides by the molten nitrate salt appears to be controlled by oxidation of base metal components and a slow release of material from an aluminum-rich product layer into the salt. The rate of release was substantially lower than that previously found for iron and iron-based alloys. This would imply that corrosion of iron aluminides could be minimized by maximizing the surface coverage of this aluminum-rich layer either by alloying or by an appropriate preoxidation treatment.

  19. Toxicity of xenobiotics during sulfate, iron, and nitrate reduction in primary sewage sludge suspensions.

    PubMed

    Elsgaard, Lars

    2010-05-01

    The effect and persistence of six organic xenobiotics was tested under sulfate-, iron-, and nitrate-reducing conditions in primary sewage sludge suspensions. The xenobiotics tested were acenaphthene, phenanthrene, di(2-ethylhexyl)phthalate (DEHP), 4-nonylphenol (4-NP), linear alkylbenzene sulfonate (LAS), and 1,2,4-trichlorobenzene (1,2,4-TCB) added to initial analytical concentrations of 54-117 mgL(-1). The suspensions were incubated at 30 degrees C for 15 weeks and rates of sulfate, iron, and nitrate reduction were estimated from the time course of hydrogen sulfide accumulation, Fe(II) accumulation, and nitrate depletion, respectively. Chemical analysis showed that the xenobiotics were persistent under the different electron acceptor regimes for the duration of the experiment. This was partly attributed to low bioavailability and microbial toxicity of the xenobiotics. Rates of anaerobic respiration in control suspensions (without added xenobiotics) showed a weekly reduction potential of 0.84 mM SO(4)(2-), 0.92 mM Fe(III), and 9.25 mM NO(3)(-). All three processes were completely inhibited by 1,2,4-TCB (54 mgL(-1)) whereas there was no significant (P<0.05) toxicity of phenanthrene (109 mgL(-1)) and DEHP (105 mgL(-1)). Sulfate reduction was inhibited completely by LAS (105 mgL(-1)), 76% by acenaphthene (54 mgL(-1)) and 57% by 4-NP (117 mgL(-1)), and likewise iron reduction was inhibited 62% by LAS and 55% by 4-NP (the latter though at P<0.10). Nitrate reduction was not significantly inhibited by acenaphthene and 4-NP and furthermore was resistant to LAS toxicity (105 mgL(-1)). Nitrate reduction also had the highest potential for mineralization of organic matter and thus was the most robust of the tested anaerobic processes in the sewage sludge suspensions. Copyright 2010 Elsevier Ltd. All rights reserved.

  20. Ligand effects on nitrate reduction by zero-valent iron: Role of surface complexation.

    PubMed

    Song, Xiaojie; Chen, Zhihao; Wang, Xiaomeng; Zhang, Shujuan

    2017-05-01

    Surface passivation is a key limiting factor in the application of zero-valent iron (ZVI) for water remediation. Addition of ligands is a useful approach to overcome this issue. In this work, a small amount of acetylacetone (AA) (0.5 mM) was found highly efficient to enhance the reduction of nitrate by ZVI at near neutral conditions (pH 6.0) with the formation of considerable black coating on ZVI. At an initial nitrate concentration of 20 mg N/L, the pseudo first-order reduction rate constant of nitrate in the ZVI-AA-NO3(-) system was 0.0991 h(-1), which was 52 times higher than that in the ZVI-NO3(-) system. Under otherwise identical conditions, the other five ligands, including EDTA, formate, acetate, oxalate, and phosphate, had negligible effects. Based on the pKa values of these ligands and the final species of iron, the ligand effects on nitrate reduction by ZVI were summarized from three aspects: (1) the ability to offer potentially dissociable protons from the ligands; (2) the complexation ability to eliminate iron (hydr)oxide precipitates from the surface of ZVI; and (3) the ability to lower down the redox potentials of iron species. The good performance of AA in these three aspects makes it advantage over the other ligands. A cycle test up to six runs demonstrates that AA could continuously take effect in the ZVI system. The results here point out the potential of AA as an effective ligand in ZVI system for enhanced contaminant transformation.

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

    PubMed

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

    2017-01-01

    Zero-valent iron has been intensively investigated in chemical reduction of nitrate in water, but the reduction requires acidic or weak acidic pH conditions and the product of the reduction is exclusively ammonium, an even more toxic substance. Zero-valent aluminum is a stronger reductant than iron, but its use for the reduction of aqueous nitrate requires considerably alkaline pH conditions. In this study, aluminum-iron alloys with an iron content of 10%, 20% and 58% (termed Al-Fe10, Al-Fe20 and Al-Fe58, respectively) were investigated for the reduction of aqueous nitrate. Al-Fe alloys were efficient to reduce nitrate in water in an entire pH range of 2-12 and the reduction proceeded in a pseudo-first order at near neutral pH conditions. The observed reaction rate constant (Kobs) of Al-Fe10 was 3 times higher than that of Fe and the Kobs of Al-Fe20 doubled that of Al-Fe10. The nitrogen selectivity of the reduction by Al-Fe10, Al-Fe20 and Al-Fe58 was 17.6%, 23.9% and 40.3%, respectively at pH 7 and the nitrogen selectivity by Al-Fe20 increased from 18.9% at pH 2-60.3% at pH 12. The enhanced selectivity and reactivity of Al-Fe alloys were likely due to the presence of an intermetallic Al-Fe compound (Al13Fe4).

  2. Mesophilic, Circumneutral Anaerobic Iron Oxidation as a Remediation Mechanism for Radionuclides, Nitrate and Perchlorate

    NASA Astrophysics Data System (ADS)

    Bose, S.; Thrash, J. C.; Coates, J. D.

    2008-12-01

    Iron oxidation is a novel anaerobic metabolism where microorganisms obtain reducing equivalents from the oxidization of Fe(II) and assimilate carbon from organic carbon compounds or CO2. Recent evidence indicates that in combination with the activity of dissimilatory Fe(III)-reducing bacteria, anaerobic microbial Fe(II) oxidation can also contribute to the global iron redox cycle. Studies have also proved that Fe(II)- oxidation is ubiquitous in diverse environments and produce a broad range of insoluble iron forms as end products. These biogenic Fe(III)-oxides and mixed valence Fe minerals have a very high adsorption capacity of heavy metals and radionuclides. Adsorption and immobilization by these biogenic Fe phases produced at circumneutral pH, is now considered a very effective mode of remediation of radionuclides like Uranium, especially under variable redox conditions. By coupling soluble and insoluble Fe(II) oxidation with nitrate and perchlorate as terminal electron acceptors in-situ, anaerobic Fe-oxidation can also be used for environmental cleanup of Fe through Fe-mineral precipitation, as well as nitrate and perchlorate through reduction. Coupling of Fe as the sole electron and energy source to the reduction of perchlorate or nitrate boosts the metabolism without building up biomass hence also taking care of biofouling. To understand the mechanisms by which microorganisms can grow at circumneutral pH by mesophilic, anaerobic iron oxidation and the ability of microorganisms to reduce nitrate and perchlorate coupled to iron oxidation recent work in our lab involved the physiological characterization of Dechlorospirillum strain VDY which was capable of anaerobic iron-oxidation with either nitrate or perchlorate serving as terminal electron acceptor. Under non-growth conditions, VDY oxidized 3mM Fe(II) coupled to nitrate reduction, and 2mM Fe(II) coupled to perchlorate reduction, in 24 hours. It contained a copy of the RuBisCO cbbM subunit gene which was

  3. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater

    NASA Astrophysics Data System (ADS)

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-07-01

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3-6 mmol/L in temperature range of 30-40 °C, 6-10 mmol/L in temperature range of 15-30 °C and 10-14 mmol/L in temperature range of 5-15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency.

  4. Rapid and controlled transformation of nitrate in water and brine by stabilized iron nanoparticles

    NASA Astrophysics Data System (ADS)

    Xiong, Zhong; Zhao, Dongye; Pan, Gang

    2009-05-01

    Highly reactive zero-valent iron (ZVI) nanoparticles stabilized with carboxymethyl cellulose (CMC) were tested for reduction of nitrate in fresh water and brine. Batch kinetic tests showed that the pseudo first-order rate constant ( k obs) with the stabilized nanoparticles was five times greater than that for non-stabilized counterparts. The stabilizer not only increased the specific surface area of the nanoparticles, but also increased the reactive particle surface. The allocation between the two reduction products, NH4 + and N2, can be manipulated by varying the ZVI-to-nitrate molar ratio and/or applying a Cu-Pd bimetallic catalyst. Greater CMC-to-ZVI ratios lead to faster nitrate reduction. Application of a 0.05 M HEPES buffer increased the k obs value by 15 times compared to that without pH control. Although the presence of 6% NaCl decreased k obs by 30%, 100% nitrate was transformed within 2 h in the saline water. The technology provides a powerful alternative for treating water with concentrated nitrate such as ion exchange brine.

  5. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater.

    PubMed

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-07-22

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3-6 mmol/L in temperature range of 30-40 °C, 6-10 mmol/L in temperature range of 15-30 °C and 10-14 mmol/L in temperature range of 5-15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency.

  6. Effects of Coating Materials and Mineral Additives on Nitrate Reduction by Zerovalent Iron

    NASA Astrophysics Data System (ADS)

    Kim, K. H.; Jeong, H. Y.; Lee, S.; Kang, N.; Choi, H. J.; Park, M.

    2015-12-01

    In efforts to facilitate nitrate removal, a variety of coating materials and mineral additives were assessed for their effects on the nitrate reduction by zerovalent iron (ZVI). Coated ZVIs were prepared by reacting Fe particles with Cr(III), Co(II), Ni(II), Cu(II), and S(-II) solutions under anoxic conditions, with the resultant materials named Cr/Fe, Co/Fe, Ni/Fe, Cu/Fe, and FeS/Fe, respectively. The mineral additives used, synthesized or purchased, included goethite, magnetite, and hydrous ferric oxide (HFO). Kinetic experiments were performed using air-tight serum vials containing 1.0 g Fe (uncoated or coated forms) in 15 mL of 100 mg NO3×N/L solutions with pH buffered at 7.0. To monitor the reaction progress, the solution phase was analyzed for NO3-, NO2-, and NH4+ on an ion chromatography, while the headspace was analyzed for H2, N2, and O2 on a gas chromatography. By uncoated Fe, ca. 60% of nitrate was reductively transformed for 3.6 h, with NH4+ being the predominant product. Compared with uncoated one, Cr/Fe, Co/Fe, and Cu/Fe showed faster removal rates of nitrate. The observed reactivity enhancement was thought to result from additional reduction of nitrate by H atoms adsorbed on the surface of Cr, Co, or Cu metal. In contrast, both Ni/Fe and FeS/Fe showed slower removal of nitrate than uncoated Fe. In both cases, the coating, which highly disfavors the adsorption of nitrate, would form on the Fe surface. When goethite, HFO, and magnetite were amended, the nitrate reduction by Fe was significantly increased, with the effect being most evident with HFO. Although not capable of reducing nitrate, the mineral additives would serve as crystal nuclei for the corrosion products of Fe, thus making the development of passivation layers on the Fe surface less. In the future, we will perform a kinetic modeling of the experimental data to assess the relative contribution of multiple reaction paths in the nitrate reduction by Fe.

  7. Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas

    PubMed Central

    Trick, Charles G.; Bill, Brian D.; Cochlan, William P.; Wells, Mark L.; Trainer, Vera L.; Pickell, Lisa D.

    2010-01-01

    Oceanic high-nitrate, low-chlorophyll environments have been highlighted for potential large-scale iron fertilizations to help mitigate global climate change. Controversy surrounds these initiatives, both in the degree of carbon removal and magnitude of ecosystem impacts. Previous open ocean enrichment experiments have shown that iron additions stimulate growth of the toxigenic diatom genus Pseudonitzschia. Most Pseudonitzschia species in coastal waters produce the neurotoxin domoic acid (DA), with their blooms causing detrimental marine ecosystem impacts, but oceanic Pseudonitzschia species are considered nontoxic. Here we demonstrate that the sparse oceanic Pseudonitzschia community at the high-nitrate, low-chlorophyll Ocean Station PAPA (50° N, 145° W) produces approximately 200 pg DA L−1 in response to iron addition, that DA alters phytoplankton community structure to benefit Pseudonitzschia, and that oceanic cell isolates are toxic. Given the negative effects of DA in coastal food webs, these findings raise serious concern over the net benefit and sustainability of large-scale iron fertilizations. PMID:20231473

  8. Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas.

    PubMed

    Trick, Charles G; Bill, Brian D; Cochlan, William P; Wells, Mark L; Trainer, Vera L; Pickell, Lisa D

    2010-03-30

    Oceanic high-nitrate, low-chlorophyll environments have been highlighted for potential large-scale iron fertilizations to help mitigate global climate change. Controversy surrounds these initiatives, both in the degree of carbon removal and magnitude of ecosystem impacts. Previous open ocean enrichment experiments have shown that iron additions stimulate growth of the toxigenic diatom genus Pseudonitzschia. Most Pseudonitzschia species in coastal waters produce the neurotoxin domoic acid (DA), with their blooms causing detrimental marine ecosystem impacts, but oceanic Pseudonitzschia species are considered nontoxic. Here we demonstrate that the sparse oceanic Pseudonitzschia community at the high-nitrate, low-chlorophyll Ocean Station PAPA (50 degrees N, 145 degrees W) produces approximately 200 pg DA L(-1) in response to iron addition, that DA alters phytoplankton community structure to benefit Pseudonitzschia, and that oceanic cell isolates are toxic. Given the negative effects of DA in coastal food webs, these findings raise serious concern over the net benefit and sustainability of large-scale iron fertilizations.

  9. Nitrate

    Integrated Risk Information System (IRIS)

    Nitrate ; CASRN 14797 - 55 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects

  10. REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

    EPA Science Inventory

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

  11. REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

    EPA Science Inventory

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

  12. Mechanism of enhanced nitrate reduction via micro-electrolysis at the powdered zero-valent iron/activated carbon interface.

    PubMed

    Luo, Jinghuan; Song, Guangyu; Liu, Jianyong; Qian, Guangren; Xu, Zhi Ping

    2014-12-01

    Nitrate reduction by zero-valent iron (Fe(0)) powder always works well only at controlled pH lower than 4 due to the formation of iron (hydr)oxides on its surface. Fe(0) powder combined with activated carbon (AC), i.e., Fe(0)/AC micro-electrolysis system, was first introduced to enhance nitrate reduction in aqueous solution. Comparative study was carried out to investigate nitrate reduction by Fe(0)/AC system and Fe(0) under near-neutral conditions, showing that the Fe(0)/AC system successfully reduced nitrate even at initial pH 6 with the reduction efficiency of up to 73%, whereas for Fe(0) only ∼10%. The effect of Fe(0) to AC mass ratio on nitrate reduction efficiency was examined. Easier nitrate reduction was achieved with more contact between Fe(0) and AC as the result of decreasing Fe(0) to AC mass ratio. Ferrous ion and oxidation-reduction potential were measured to understand the mechanism of enhanced nitrate reduction by Fe(0)/AC micro-electrolysis. The results suggest that a relative potential difference drives much more electrons from Fe(0) to AC, thus generating adsorbed atomic hydrogen which makes it possible for nitrate to be reduced at near-neural pH. Fe(0)/AC micro-electrolysis thus presents a great potential for practical application in nitrate wastewater treatment without excessive pH adjustment.

  13. Phenol Nitration Induced by an {Fe(NO)2}10 Dinitrosyl Iron Complex

    SciTech Connect

    N Tran; H Kalyvas; K Skodje; T Hayashi; P Moenne-Loccoz; P Callan; J Shearer; L Kirschenbaum; E Kim

    2011-12-31

    Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs have been postulated, their chemical functionality outside of NO transfer has not been demonstrated thus far. Here we report the unprecedented dioxygen reactivity of a N-bound {l_brace}Fe(NO){sub 2}{r_brace}{sup 10} DNIC, [Fe(TMEDA)(NO){sub 2}] (1). In the presence of O{sub 2}, 1 becomes a nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation of a putative iron-peroxynitrite [Fe(TMEDA)(NO)(ONOO)] (2) that is stable below -80 C. Iron K-edge X-ray absorption spectroscopy on 2 supports a five-coordinated metal center with a bound peroxynitrite in a cyclic bidentate fashion. The peroxynitrite ligand of 2 readily decays at increased temperature or under illumination. These results suggest that DNICs could have multiple physiological or deleterious roles, including that of cellular nitrating agents.

  14. Fine Iron Aerosols Are Internally Mixed with Nitrate in the Urban European Atmosphere.

    PubMed

    Dall'Osto, Manuel; Beddows, D C S; Harrison, Roy M; Onat, Burcu

    2016-04-19

    Atmospheric iron aerosol is a bioavailable essential nutrient playing a role in oceanic productivity. Using aerosol time-of-flight mass spectrometry (ATOFMS), the particle size (0.3-1.5 μm), chemical composition and mixing state of Fe-containing particles collected at two European urban sites (London and Barcelona) were characterized. Out of the six particle types accounting for the entire Fe-aerosol population, that arising from long-range transport (LRT) of fine Fe-containing particles (Fe-LRT, 54-82% across the two sites) was predominant. This particle type was found to be internally mixed with nitrate and not with sulfate, and likely mostly associated with urban traffic activities. This is in profound contrast with previous studies carried out in Asia, where the majority of iron-containing particles are mixed with sulfate and are of coal combustion origin. Other minor fine iron aerosol sources included mineral dust (8-11%), traffic brake wear material (1-17%), shipping/oil (1-6%), biomass combustion (4-13%) and vegetative debris (1-3%). Overall, relative to anthropogenic Asian Fe-sulfate dust, anthropogenic European dust internally mixed with additional key nutrients such as nitrate is likely to play a different role in ocean global biogeochemical cycles.

  15. Iron Corrosion Induced by Nonhydrogenotrophic Nitrate-Reducing Prolixibacter sp. Strain MIC1-1

    PubMed Central

    Ito, Kimio; Wakai, Satoshi; Tsurumaru, Hirohito; Ohkuma, Moriya; Harayama, Shigeaki

    2014-01-01

    Microbiologically influenced corrosion (MIC) of metallic materials imposes a heavy economic burden. The mechanism of MIC of metallic iron (Fe0) under anaerobic conditions is usually explained as the consumption of cathodic hydrogen by hydrogenotrophic microorganisms that accelerates anodic Fe0 oxidation. In this study, we describe Fe0 corrosion induced by a nonhydrogenotrophic nitrate-reducing bacterium called MIC1-1, which was isolated from a crude-oil sample collected at an oil well in Akita, Japan. This strain requires specific electron donor-acceptor combinations and an organic carbon source to grow. For example, the strain grew anaerobically on nitrate as a sole electron acceptor with pyruvate as a carbon source and Fe0 as the sole electron donor. In addition, ferrous ion and l-cysteine served as electron donors, whereas molecular hydrogen did not. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MIC1-1 was a member of the genus Prolixibacter in the order Bacteroidales. Thus, Prolixibacter sp. strain MIC1-1 is the first Fe0-corroding representative belonging to the phylum Bacteroidetes. Under anaerobic conditions, Prolixibacter sp. MIC1-1 corroded Fe0 concomitantly with nitrate reduction, and the amount of iron dissolved by the strain was six times higher than that in an aseptic control. Scanning electron microscopy analyses revealed that microscopic crystals of FePO4 developed on the surface of the Fe0 foils, and a layer of FeCO3 covered the FePO4 crystals. We propose that cells of Prolixibacter sp. MIC1-1 accept electrons directly from Fe0 to reduce nitrate. PMID:25548048

  16. Influence of zero-valent iron nanoparticles on nitrate removal by Paracoccus sp.

    PubMed

    Liu, Yan; Li, Shibin; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

    2014-08-01

    Nitrate contamination in drinking water is a major threat to public health. This study investigated the efficiency of denitrification of aqueous solutions in the co-presence of synthesized nanoscale zero-valent iron (nZVI; diameter: 20-80 nm) and a previously isolated Paracoccus sp. strain YF1. Various influencing factors were studied, such as oxygen, pH, temperature, and anaerobic corrosion products (Fe(2+), Fe(3+) and Fe3O4). With slight toxicity to the strain, nZVI promoted denitrification efficiency by providing additional electron sources under aerobic conditions. For example, 50 mg L(-1) nZVI increased the nitrate removal efficiency from 66.9% to 85.2%. However, a high concentration of nZVI could lead to increased production of Fe(2+), a toxic ion which could compromise the removal efficiency. Kinetic studies suggest that denitrification by both free cells, and nZVI-amended cells fitted well to the zero-order model. Temperature and pH are the major factors affecting nitrate removal and cell growth, with or without the presence of nZVI. In this study, nitrate removal and cell growth increased in the pH range of 6.5-8.0, and temperature range of 25-35 °C. These conditions favor the growth of the strain, which dominated denitrification in all scenarios involved. As for anaerobic corrosion products, compared with Fe(2+) and Fe(3+), Fe3O4 promoted denitrification by serving as an electron donor. Finally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed attachments of nZVI on the surface of the cell, and the formation of iron oxides. This study indicated that, as an electron donor source with minimal cellular toxicity, nZVI could be used to promote denitrification efficiency under biotic conditions.

  17. Iron corrosion induced by nonhydrogenotrophic nitrate-reducing Prolixibacter sp. strain MIC1-1.

    PubMed

    Iino, Takao; Ito, Kimio; Wakai, Satoshi; Tsurumaru, Hirohito; Ohkuma, Moriya; Harayama, Shigeaki

    2015-03-01

    Microbiologically influenced corrosion (MIC) of metallic materials imposes a heavy economic burden. The mechanism of MIC of metallic iron (Fe(0)) under anaerobic conditions is usually explained as the consumption of cathodic hydrogen by hydrogenotrophic microorganisms that accelerates anodic Fe(0) oxidation. In this study, we describe Fe(0) corrosion induced by a nonhydrogenotrophic nitrate-reducing bacterium called MIC1-1, which was isolated from a crude-oil sample collected at an oil well in Akita, Japan. This strain requires specific electron donor-acceptor combinations and an organic carbon source to grow. For example, the strain grew anaerobically on nitrate as a sole electron acceptor with pyruvate as a carbon source and Fe(0) as the sole electron donor. In addition, ferrous ion and l-cysteine served as electron donors, whereas molecular hydrogen did not. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain MIC1-1 was a member of the genus Prolixibacter in the order Bacteroidales. Thus, Prolixibacter sp. strain MIC1-1 is the first Fe(0)-corroding representative belonging to the phylum Bacteroidetes. Under anaerobic conditions, Prolixibacter sp. MIC1-1 corroded Fe(0) concomitantly with nitrate reduction, and the amount of iron dissolved by the strain was six times higher than that in an aseptic control. Scanning electron microscopy analyses revealed that microscopic crystals of FePO4 developed on the surface of the Fe(0) foils, and a layer of FeCO3 covered the FePO4 crystals. We propose that cells of Prolixibacter sp. MIC1-1 accept electrons directly from Fe(0) to reduce nitrate.

  18. Development of an iron nitrate resistant injector valve for the Space Shuttle orbiter primary thruster

    NASA Technical Reports Server (NTRS)

    Wichmann, Horst; Marquardt, Kaiser; Goforth, Alyssa

    1993-01-01

    Design of a direct-acting valve (DAV) for a primary thruster which is fully interchangeable with a thruster equipped with pilot-operated valves is described. The DAV is based on a bellows to isolate propellants form the actuator for maximum resistance to iron nitrate and other contamination and to select optimum materials for the actuator. It provides improved seal performance under all operating conditions and insensitivity to pressure transients. As compared with the existing pilot-operated valve, the DAV design is much simpler, consists of fewer parts, and will be lower in cost.

  19. Development of an iron nitrate resistant injector valve for the Space Shuttle orbiter primary thruster

    NASA Technical Reports Server (NTRS)

    Wichmann, Horst; Marquardt, Kaiser; Goforth, Alyssa

    1993-01-01

    Design of a direct-acting valve (DAV) for a primary thruster which is fully interchangeable with a thruster equipped with pilot-operated valves is described. The DAV is based on a bellows to isolate propellants form the actuator for maximum resistance to iron nitrate and other contamination and to select optimum materials for the actuator. It provides improved seal performance under all operating conditions and insensitivity to pressure transients. As compared with the existing pilot-operated valve, the DAV design is much simpler, consists of fewer parts, and will be lower in cost.

  20. Analysis of flow decay potential on Galileo. [oxidizer flow rate reduction by iron nitrate precipitates

    NASA Technical Reports Server (NTRS)

    Cole, T. W.; Frisbee, R. H.; Yavrouian, A. H.

    1987-01-01

    The risks posed to the NASA's Galileo spacecraft by the oxidizer flow decay during its extended mission to Jupiter is discussed. The Galileo spacecraft will use nitrogen tetroxide (NTO)/monomethyl hydrazine bipropellant system with one large engine thrust-rated at a nominal 400 N, and 12 smaller engines each thrust-rated at a nominal 10 N. These smaller thrusters, because of their small valve inlet filters and small injector ports, are especially vulnerable to clogging by iron nitrate precipitates formed by NTO-wetted stainless steel components. To quantify the corrosion rates and solubility levels which will be seen during the Galileo mission, corrosion and solubility testing experiments were performed with simulated Galileo materials, propellants, and environments. The results show the potential benefits of propellant sieving in terms of iron and water impurity reduction.

  1. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    USGS Publications Warehouse

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Böhlke, J.K.

    2017-01-01

    weeks. Additionally, Fe(II)-oxidizing, nitrate-reducing microbial enrichment cultures were obtained from aquifer sediments. Growth experiments with the cultures sequentially produced nitrite and nitrous oxide from nitrate while simultaneously oxidizing Fe(II). Field and culture results suggest that nitrogen oxide reduction and Fe(II) oxidation in the aquifer are a complex interaction of coupled biotic and abiotic reactions. Overall, the results of this study demonstrate that anoxic nitrate-dependent iron oxidation can occur in groundwater; that it could control iron speciation; and that the process can impact the mobility of other chemical species (e.g., phosphate and arsenic) not directly involved in the oxidation–reduction reaction.

  2. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    NASA Astrophysics Data System (ADS)

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Böhlke, J. K.

    2017-01-01

    . Additionally, Fe(II)-oxidizing, nitrate-reducing microbial enrichment cultures were obtained from aquifer sediments. Growth experiments with the cultures sequentially produced nitrite and nitrous oxide from nitrate while simultaneously oxidizing Fe(II). Field and culture results suggest that nitrogen oxide reduction and Fe(II) oxidation in the aquifer are a complex interaction of coupled biotic and abiotic reactions. Overall, the results of this study demonstrate that anoxic nitrate-dependent iron oxidation can occur in groundwater; that it could control iron speciation; and that the process can impact the mobility of other chemical species (e.g., phosphate and arsenic) not directly involved in the oxidation-reduction reaction.

  3. The role of magnetite nanoparticles in the reduction of nitrate in groundwater by zero-valent iron.

    PubMed

    Cho, Dong-Wan; Song, Hocheol; Schwartz, Franklin W; Kim, Bokseong; Jeon, Byong-Hun

    2015-04-01

    Magnetite nanoparticles were used as an additive material in a zero-valent iron (Fe0) reaction to reduce nitrate in groundwater and its effects on nitrate removal were investigated. The addition of nano-sized magnetite (NMT) to Fe0 reactor markedly increased nitrate reduction, with the rate proportionally increasing with NMT loading. Field emission scanning electron microscopy analysis revealed that NMT aggregates were evenly distributed and attached on the Fe0 surface due to their magnetic properties. The rate enhancement effect of NMT is presumed to arise from its role as a corrosion promoter for Fe0 corrosion as well as an electron mediator that facilitated electron transport from Fe0 to adsorbed nitrate. Nitrate reduction by Fe0 in the presence of NMT proceeded much faster in groundwater (GW) than in de-ionized water. The enhanced reduction of nitrate in GW was attributed to the adsorption or formation of surface complex by the cationic components in GW, i.e., Ca2+ and Mg2+, in the Fe0-H2O interface that promoted electrostatic attraction of nitrate to the reaction sites. Moreover, the addition of NMT imparted superior longevity to Fe0, enabling completion of four nitrate reduction cycles, which otherwise would have been inactivated during the first cycle without an addition of NMT. The results demonstrate the potential applicability of a Fe0/NMT system in the treatment of nitrate-contaminated GW.

  4. Arsenic removal from geothermal waters with zero-valent iron--effect of temperature, phosphate and nitrate.

    PubMed

    Tyruvola, Konstantina; Nikolaidis, Nikolaus P; Veranis, Nikolaus; Kallithrakas-Kontos, Nikolaso; Koulouridakis, Pavlos E

    2006-07-01

    Field column studies and laboratory batch experiments were conducted in order to assess the performance of zero-valent iron in removing arsenic from geothermal waters in agricultural regions where phosphates and nitrates were present. A field pilot study demonstrated that iron filings could remove arsenic, phosphate and nitrate from water. In addition, batch studies were performed to evaluate the effect of temperature, phosphate and nitrate on As(III) and As(V) removal rates. All batch experiments were conducted at three temperatures (20, 30 and 40 degrees C). Pseudo-first-order reaction rate constants were calculated for As(III), As(V), phosphate, nitrate and ammonia for all temperatures. As(V) exhibited greater removal rates than As(III). The presence of phosphate and nitrate decreased the rates of arsenic removal. The temperature of the water played a dominant role on the kinetics of arsenic, phosphate and nitrate removal. Nitrate reduction resulted in the formation of nitrite and ammonia. In addition, the activation energy, Eact, and the constant temperature coefficient, theta were determined for each removal process.

  5. Transformation of vivianite by anaerobic nitrate-reducing iron-oxidizing bacteria.

    PubMed

    Miot, J; Benzerara, K; Morin, G; Bernard, S; Beyssac, O; Larquet, E; Kappler, A; Guyot, F

    2009-06-01

    In phosphate-rich environments, vivianite (Fe(II)(3)(PO(4))(2), 8H(2)O) is an important sink for dissolved Fe(II) and is considered as a very stable mineral due to its low solubility at neutral pH. In the present study, we report the mineralogical transformation of vivianite in cultures of the nitrate-reducing iron-oxidizing bacterial strain BoFeN1 in the presence of dissolved Fe(II). Vivianite was first transformed into a greenish phase consisting mostly of an amorphous mixed valence Fe-phosphate. This precipitate became progressively orange and the final product of iron oxidation consisted of an amorphous Fe(III)-phosphate. The sub-micrometer analysis by scanning transmission X-ray microscopy of the iron redox state in samples collected at different stages of the culture indicated that iron was progressively oxidized at the contact of the bacteria and at a distance from the cells in extracellular minerals. Iron oxidation in the extracellular minerals was delayed by a few days compared with cell-associated Fe-minerals. This led to strong differences of Fe redox in between these two types of minerals and finally to local heterogeneities of redox within the sample. In the absence of dissolved Fe(II), vivianite was not significantly transformed by BoFeN1. Whereas Fe(II) oxidation at the cell contact is most probably directly catalyzed by the bacteria, vivianite transformation at a distance from the cells might result from oxidation by nitrite. In addition, processes leading to the export of Fe(III) from bacterial oxidation sites to extracellular minerals are discussed including some involving colloids observed by cryo-transmission electron microscopy in the culture medium.

  6. Removal of added nitrate in the single, binary, and ternary systems of cotton burr compost, zerovalent iron, and sediment: Implications for groundwater nitrate remediation using permeable reactive barriers.

    PubMed

    Su, Chunming; Puls, Robert W

    2007-04-01

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe(0)) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and autotrophic denitrification in the Fe(0) system. Questions arise as whether the more expensive Fe(0) is more effective than the less expensive carbonaceous solid materials for groundwater nitrate remediation, and whether there is any synergistic effect of mixing the two different types of materials. We carried out batch tests to study the nature and rates of removal of added nitrate in the suspensions of single, binary, and ternary systems of cotton burr compost, Peerless Fe(0), and a sediment low in organic carbon. Cotton burr compost acted as both organic carbon source and supporting material for the growth of indigenous denitrifiers. Batch tests showed that cotton burr compost alone removed added nitrate at a greater rate than did Peerless Fe(0) alone on an equal mass basis with a pseudo-first-order rate constant k=0.0830+/-0.0031 h(-1) for cotton burr compost and a k=0.00223+/-0.00022 h(-1) for Peerless Fe(0); cotton burr compost also removed added nitrate at a faster rate than did cotton burr compost mixed with Peerless Fe(0) and/or the sediment. Furthermore, there was no substantial accumulation of ammonium ions in the cotton burr compost system, in contrast to the systems containing Peerless Fe(0) in which ammonium ions persisted as major products of nitrate reduction. It is concluded that cotton burr compost alone may be used as an excellent denitrification medium in a PRB for groundwater nitrate removal. Further study is needed to evaluate performance of its field applications.

  7. Long-term Fate of Arsenic under the Oxidation of Ferrous Iron by Nitrate.

    NASA Astrophysics Data System (ADS)

    Sun, J.; Prommer, H.; Siade, A. J.; Chillrud, S. N.; Mailloux, B. J.; Bostick, B. C.

    2015-12-01

    In situ precipitation of iron (Fe) minerals can be an effective means of remediating groundwater arsenic (As) contamination. Among different Fe minerals, magnetite is promising as a host-mineral for As in situ immobilization in that it is stable under a wide range of geochemical conditions, including Fe(III) reducing conditions under which As are often mobilized. Our previous laboratory studies suggest that the formation of nanoparticulate magnetite can be achieved by the oxidation of ferrous Fe with nitrate. Magnetite can incorporate As into its structure during formation, in which case desorption and As(V) reduction are less likely. Nanoparticulate magnetite, once formed, can also immobilize As by surface adsorption, and thus serve as a reactive filter when contaminated groundwater migrates through the treatment zone. In this study, a reactive transport model is develop for the magnetite based As immobilization strategy. The initial numerical model development was guided by experimental data and hypothesized processes from the laboratory one-dimensional column studies. Our modeling results suggest that the ratio between Fe(II) and nitrate in the injectant regulates the extent and distribution of magnetite and ferrihydrite formation, and thus regulates the long-term potential of As immobilization. Based on these results, two-dimensional field-scale model scenarios were developed to predict and compare the impact of chemical and operational parameters on the efficiency of the remediation technology. The modeling results, which suggest that long-term groundwater As removal is feasible, favor scenarios that rely on the chromatographic mixing of Fe(II) and nitrate after injection. This study highlights the importance of combining laboratory studies and reactive transport modeling for elucidating the complex hydro-biogeochemical processes that control the fate of As and for up-scaling of the technology.

  8. Inhibition of bacterial oxidation of ferrous iron by lead nitrate in sulfate-rich systems

    USGS Publications Warehouse

    Wang, Hongmei; Gong, Linfeng; Cravotta, Charles A.; Yang, Xiaofen; Tuovinen, Olli H.; Dong, Hailiang; Fu, Xiang

    2013-01-01

    Inhibition of bacterial oxidation of ferrous iron (Fe(II)) by Pb(NO3)2 was investigated with a mixed culture of Acidithiobacillus ferrooxidans. The culture was incubated at 30 °C in ferrous-sulfate medium amended with 0–24.2 mM Pb(II) added as Pb(NO3)2. Anglesite (PbSO4) precipitated immediately upon Pb addition and was the only solid phase detected in the abiotic controls. Both anglesite and jarosite (KFe3(SO4)2(OH)6) were detected in inoculated cultures. Precipitation of anglesite maintained dissolved Pb concentrations at 16.9–17.6 μM regardless of the concentrations of Pb(NO3)2 added. Fe(II) oxidation was suppressed by 24.2 mM Pb(NO3)2 addition even when anglesite was removed before inoculation. Experiments with 0–48 mM KNO3 demonstrated that bacterial Fe(II) oxidation decreased as nitrate concentration increased. Therefore, inhibition of Fe(II) oxidation at 24.2 mM Pb(NO3)2 addition resulted from nitrate toxicity instead of Pb addition. Geochemical modeling that considered the initial precipitation of anglesite to equilibrium followed by progressive oxidation of Fe(II) and the precipitation of jarosite and an amorphous iron hydroxide phase, without allowing plumbojarosite to precipitate were consistent with the experimental time-series data on Fe(II) oxidation under biotic conditions. Anglesite precipitation in mine tailings and other sulfate-rich systems maintains dissolved Pb concentrations below the toxicity threshold of A. ferrooxidans.

  9. Inhibition of bacterial oxidation of ferrous iron by lead nitrate in sulfate-rich systems.

    PubMed

    Wang, Hongmei; Gong, Linfeng; Cravotta, Charles A; Yang, Xiaofen; Tuovinen, Olli H; Dong, Hailiang; Fu, Xiang

    2013-01-15

    Inhibition of bacterial oxidation of ferrous iron (Fe(II)) by Pb(NO(3))(2) was investigated with a mixed culture of Acidithiobacillus ferrooxidans. The culture was incubated at 30 °C in ferrous-sulfate medium amended with 0-24.2 mM Pb(II) added as Pb(NO(3))(2). Anglesite (PbSO(4)) precipitated immediately upon Pb addition and was the only solid phase detected in the abiotic controls. Both anglesite and jarosite (KFe(3)(SO(4))(2)(OH)(6)) were detected in inoculated cultures. Precipitation of anglesite maintained dissolved Pb concentrations at 16.9-17.6 μM regardless of the concentrations of Pb(NO(3))(2) added. Fe(II) oxidation was suppressed by 24.2 mM Pb(NO(3))(2) addition even when anglesite was removed before inoculation. Experiments with 0-48 mM KNO(3) demonstrated that bacterial Fe(II) oxidation decreased as nitrate concentration increased. Therefore, inhibition of Fe(II) oxidation at 24.2 mM Pb(NO(3))(2) addition resulted from nitrate toxicity instead of Pb addition. Geochemical modeling that considered the initial precipitation of anglesite to equilibrium followed by progressive oxidation of Fe(II) and the precipitation of jarosite and an amorphous iron hydroxide phase, without allowing plumbojarosite to precipitate were consistent with the experimental time-series data on Fe(II) oxidation under biotic conditions. Anglesite precipitation in mine tailings and other sulfate-rich systems maintains dissolved Pb concentrations below the toxicity threshold of A. ferrooxidans. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. The effect of granular ferric hydroxide amendment on the reduction of nitrate in groundwater by zero-valent iron.

    PubMed

    Song, Hocheol; Jeon, Byong-Hun; Chon, Chul-Min; Kim, Yongje; Nam, In-Hyun; Schwartz, Franklin W; Cho, Dong-Wan

    2013-11-01

    The feasibility of using granular ferric hydroxide (GFH) with zero-valent iron (Fe(0)) for its potential utility in enhancing nitrate reduction was investigated. The addition of 10gL(-1) GFH to 25gL(-1) Fe(0) significantly enhanced nitrate removal, resulting in 93% removal of 52.2mg-NL(-1) in 36-h as compared to 23% removal with Fe(0) alone. Surface analyses of the reacted Fe(0)/GFH revealed the presence of magnetite on the Fe(0) surface, which probably served as an electron mediator for nitrate reduction. Addition of GFH to Fe(0) also resulted in lower solution pH compared to Fe(0). The rate enhancing effect of GFH on nitrate reduction was attributed to the combined effects of magnetite formation and pH buffering by GFH. GFH amendment (100gL(-1)) significantly increased reduction capacity and longevity of Fe(0) to complete several nitrate reduction cycles before inactivation, giving a total nitrate removal of 205mg-NL(-1), while unamended Fe(0) gave only 20mg-NL(-1) before inactivation during the first reduction cycle. The overall result demonstrated the potential utility of Fe(0)/GFH system that may be developed into a viable technology for removal of nitrate from groundwater.

  11. The effect of dissimilatory Iron reduction, Nitrate reduction and microbial growth electrical conductivity

    NASA Astrophysics Data System (ADS)

    Regberg, Aaron B.

    In this dissertation changes in measured electrical conductivity are related to measured changes in aqueous concentrations of ions. In previous work anomalous increases in electrical conductivity measured in and around contaminated aquifers have been associated with biogeochemical activity. The respiration and growth of micro-organisms has been suggested as a possible cause of these conductivity signals. However, a quantitative link between the activity of micro-organisms and electrical conductivity has not been established. Normally, the bulk electrical conductivity (σb) of a water-saturated sediment responds to changes in concentrations of ions in solution. If micro-organisms in the subsurface are catalyzing mineral dissolution or precipitation, σ b may be affected by changing concentration of ions in the pore fluids. In this dissertation changes in the fluid electrical conductivity (σ f) and ob are related to changes in chemical concentrations at multiple scales. Changes in of can be interpreted as reaction rates if the stoichiometry of the reaction is understood. Results from batch experiments demonstrate that measured changes in σf over time document rates of abiotic and biotic reduction of goethite. Rates of change in conductivity are related quantitatively to rates of reduction. In two column reactors packed with sediments from Oyster Virginia and fed with a flowing input containing dissolved acetate, measured changes in σ b initially document biogeochemical reaction rates of iron reduction or nitrate reduction in the sediment. Eventually, σb becomes decoupled from changes in chemical concentrations and increases significantly. Fe(II) adsorption does not cause σb to become decoupled from aqueous chemistry. Instead, this decoupling is attributed to the growth and presence of an electrically conductive biofilm. Reactive transport modeling is used to constrain the amount of biomass produced in each reactor. A value for electrical conductivity is

  12. Association of cardiac injury with iron-increased oxidative and nitrative modifications of the SERCA2a isoform of sarcoplasmic reticulum Ca(2+)-ATPase in diabetic rats.

    PubMed

    Li, Xueli; Li, Wenliang; Gao, Zhonghong; Li, Hailing

    2016-08-01

    The role of iron in the etiology of diabetes complications is not well established. Thus, this study was performed to test whether the iron-induced increase of oxidative/nitrative damage is involved in SERCA2a-related diabetic heart complication. Four randomly divided groups of rats were used: normal control group; iron overload group; diabetes group, and diabetic plus iron overload group. Iron supplementation stimulated cardiomyocyte hypertrophy and led to an increase in cardiac protein carbonyls, nitrotyrosine (3-NT) formation, and iNOS protein expression, thus resulting in abnormal myocardium calcium homeostasis of diabetic rats. The levels of SECA2a oxidation/nitration were significantly increased in the iron overload diabetic rats, along with a decrease in SECA2a expression and activity. In order to elucidate the possible role of iron in SERCA2a dysfunction, the effects of iron (Fe(3+) or hemin) on peroxynitrite (ONOO(-)) induced SERCA2a oxidation and nitration were further investigated in vitro. It was found that tyrosine nitration played more important role in SERCA2a inactivation than thiol oxidation. These results present a potential mechanism in which iron exacerbates the diabetes-induced oxidative/nitrative modification of SERCA2a, which may cause functional deficits in the myocyte associated with diabetic cardiac dysfunction. Our findings may help to further understand the role of iron in the pathogenesis of diabetic complications.

  13. Reductimetric determination of peroxydisulphate, hydrogen peroxide, sodium perborate, nitrate and nitrite in concentrated phosphoric acid medium with iron(II).

    PubMed

    Murty, N K; Satyanarayana, V; Rao, Y F

    1977-12-01

    A direct reductimetric method for the determination of peroxydisulphate, hydrogen peroxide, sodium perborate, nitrate and nitrite in fairly concentrated phosphoric acid medium with iron(II) has been developed, with both potentiometric and visual end-point detection. Cacotheline, Methylene Blue, thionine, Azure A, Azure B, Azure C, Toluidine Blue, new Methylene Blue, ferroin, N-phenylanthranilic acid, p-ethoxychrysoidine and barium diphenylaminesulphonate are used as indicators. The method is useful in the analysis of binary mixtures of peroxydisulphate and peroxide or perborate and in the estimation of the nitrate content of fertilizers.

  14. Iron availability, nitrate uptake, and exportable new production in the subarctic Pacific. [phytoplankton population growth support and atmospheric CO2 removal

    NASA Technical Reports Server (NTRS)

    Banse, Karl

    1991-01-01

    This paper presents a critique of experimental data and papers by Martin et al. (1989, 1990), who suggested that the phytoplankton growth is iron-limited and that, small additions of iron to large subarctic ocean areas might be a way of removing significant amounts of atmospheric CO2 by increasing phytoplancton growth. Data are presented to show that, in the summer of 1987, the phytoplankton assemblage as a whole was not iron limited, as measured by the bulk removal of nitrate or by the increase of chlorophyll. It is suggested that grazing normally prevents the phytoplankton from reaching concentrations that reduce the iron (and nitrate) to levels that depress division rates drastically.

  15. Iron availability, nitrate uptake, and exportable new production in the subarctic Pacific. [phytoplankton population growth support and atmospheric CO2 removal

    NASA Technical Reports Server (NTRS)

    Banse, Karl

    1991-01-01

    This paper presents a critique of experimental data and papers by Martin et al. (1989, 1990), who suggested that the phytoplankton growth is iron-limited and that, small additions of iron to large subarctic ocean areas might be a way of removing significant amounts of atmospheric CO2 by increasing phytoplancton growth. Data are presented to show that, in the summer of 1987, the phytoplankton assemblage as a whole was not iron limited, as measured by the bulk removal of nitrate or by the increase of chlorophyll. It is suggested that grazing normally prevents the phytoplankton from reaching concentrations that reduce the iron (and nitrate) to levels that depress division rates drastically.

  16. Simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewater by zero-valent iron.

    PubMed

    Yoshino, Hiroyuki; Tokumura, Masahiro; Kawase, Yoshinori

    2014-01-01

    The zero-valent iron (ZVI) wastewater treatment has been applied to simultaneous removal of nitrate, hydrogen peroxide and phosphate in semiconductor acidic wastewaters. The simultaneous removal occurs by the reactions performed due to the sequential transformation of ZVI under the acidic condition. Fortunately the solution pH of semiconductor acidic wastewaters is low which is effective for the sequential transformation of ZVI. Firstly the reduction of nitrate is taken place by electrons generated by the corrosion of ZVI under acidic conditions. Secondly the ferrous ion generated by the corrosion of ZVI reacts with hydrogen peroxide and generates ·OH radical (Fenton reaction). The Fenton reaction consists of the degradation of hydrogen peroxide and the generation of ferric ion. Finally phosphate precipitates out with iron ions. In the simultaneous removal process, 1.6 mM nitrate, 9.0 mM hydrogen peroxide and 1.0 mM phosphate were completely removed by ZVI within 100, 15 and 15 min, respectively. The synergy among the reactions for the removal of nitrate, hydrogen peroxide and phosphate was found. In the individual pollutant removal experiment, the removal of phosphate by ZVI was limited to 80% after 300 min. Its removal rate was considerably improved in the presence of hydrogen peroxide and the complete removal of phosphate was achieved after 15 min.

  17. Biochar composites with nano zerovalent iron and eggshell powder for nitrate removal from aqueous solution with coexisting chloride ions.

    PubMed

    Ahmad, Munir; Ahmad, Mahtab; Usman, Adel R A; Al-Faraj, Abdullah S; Abduljabbar, Adel S; Al-Wabel, Mohammad I

    2017-09-18

    Biochar (BC) was produced from date palm tree leaves and its composites were prepared with nano zerovalent iron (nZVI-BC) and hen eggshell powder (EP-BC). The produced BC and its composites were characterized by SEM, XRD, BET, and FTIR for surface structural, mineralogical, and chemical groups and tested for their efficiency for nitrate removal from aqueous solutions in the presence and absence of chloride ions. The incidence of graphene and nano zerovalent iron (Fe(0)) in the nZVI-BC composite was confirmed by XRD. The nZVI-BC composite possessed highest surface area (220.92 m(2) g(-1)), carbon (80.55%), nitrogen (3.78%), and hydrogen (11.09%) contents compared to other materials. Nitrate sorption data was fitted well to the Langmuir (R (2) = 0.93-0.98) and Freundlich (R (2) = 0.90-0.99) isotherms. The sorption kinetics was adequately explained by the pseudo-second-order, power function, and Elovich models. The nZVI-BC composite showed highest Langmuir predicted sorption capacity (148.10 mg g(-1)) followed by EP-BC composite (72.77 mg g(-1)). In addition to the high surface area, the higher nitrate removal capacity of nZVI-BC composite could be attributed to the combination of two processes, i.e., chemisorption (outer-sphere complexation) and reduction of nitrate to ammonia or nitrogen by Fe(0). The appearance of Fe-O stretching and N-H bonds in post-sorption FTIR spectra of nZVI-BC composite suggested the occurrence of redox reaction and formation of Fe compound with N, such as ferric nitrate (Fe(NO3)3·9H2O). Coexistence of chloride ions negatively influenced the nitrate sorption. The decrease in nitrate sorption with increasing chloride ion concentration was observed, which could be due to the competition of free active sites on the sorbents between nitrate and chloride ions. The nZVI-BC composite exhibited higher nitrate removal efficiency compared to other materials even in the presence of highest concentration (100 mg L(-1)) of coexisting

  18. Long-term trends in dissolved iron and DOC concentration linked to nitrate depletion in riparian soils

    NASA Astrophysics Data System (ADS)

    Musolff, Andreas; Selle, Benny; Fleckenstein, Jan H.; Oosterwoud, Marieke R.; Tittel, Jörg

    2016-04-01

    The instream concentrations of dissolved organic carbon (DOC) are rising in many catchments of the northern hemisphere. Elevated concentrations of DOC, mainly in the form of colored humic components, increase efforts and costs of drinking water purification. In this study, we evaluated a long-term dataset of 110 catchments draining into German drinking water reservoirs in order to assess sources of DOC and drivers of a potential long-term change. The average DOC concentrations across the wide range of different catchments were found to be well explained by the catchment's topographic wetness index. Higher wetness indices were connected to higher average DOC concentrations, which implies that catchments with shallow topography and pronounced riparian wetlands mobilize more DOC. Overall, 37% of the investigated catchments showed a significant long-term increase in DOC concentrations, while 22% exhibited significant negative trends. Moreover, we found that increasing trends in DOC were positively correlated to trends in dissolved iron concentrations at pH≤6 due to remobilization of DOC previously sorbed to iron minerals. Both, increasing trends in DOC and dissolve iron were found to be connected to decreasing trends and low concentrations of nitrate (below ~6 mg/L). This was especially observed in forested catchments where atmospheric N-depositions were the major source for nitrate availability. In these catchments, we also found long-term increases of phosphate concentrations. Therefore, we argue that dissolved iron, DOC and phosphate were jointly released under iron-reducing conditions when nitrate as a competing electron acceptor was too low in concentrations to prevent the microbial iron reduction. In contrast, we could not explain the observed increasing trends in DOC, iron and phosphate concentrations by the long-term trends of pH, sulfate or precipitation. Altogether this study gives strong evidence that both, source and long-term increases in DOC are

  19. Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers

    PubMed Central

    Melton, E. D.; Schmidt, C.; Kappler, A.

    2012-01-01

    The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e− donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105 cells·g−1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104 cells·g−1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e− donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the

  20. Effect of increased temperature, CO2, and iron on nitrate uptake and primary productivity in the coastal Ross Sea

    NASA Astrophysics Data System (ADS)

    Bronk, D. A.; Spackeen, J.; Sipler, R. E.; Bertrand, E. M.; Roberts, Q. N.; Xu, K.; Baer, S. E.; McQuaid, J.; Zhu, Z.; Walworth, N. G.; Hutchins, D. A.; Allen, A. E.

    2016-02-01

    Western Antarctic Seas are rapidly changing as a result of elevated concentrations of CO2 and rising sea surface temperatures. It is critical to determine how the structure and function of microbial communities will be impacted by these changes in the future because the Southern Ocean has seasonally high rates of primary production, is an important sink for anthropogenic CO2, and supports a diverse assemblage of higher trophic level organisms. During the Austral summer of 2013 and 2015, a collaborative research group conducted a series of experiments to understand how the individual and combined effects of temperature, CO2, and iron impact Ross Sea microorganisms. Our project used a variety of approaches, including batch experiments, semi-continuous experiments, and continuous-culturing over extended time intervals, to determine how future changes may shift Ross Sea microbial communities and how nutrient cycling and carbon biogeochemistry may subsequently be altered. Chemical and biological parameters were measured throughout the experiments to assess changes in community composition and nutrient cycling, including uptake rate measurements of nitrate and bicarbonate by different size fractions of microorganisms. Relative to the control, nitrate uptake rates significantly increased when temperature and iron were elevated indicating that temperature and iron are important physical drivers that influence nutrient cycling. Elevations in temperature and iron independently and synergistically produced higher rates than elevated CO2. Our nutrient uptake results also suggest that the physiology of large microorganisms will be more impacted by climate change variables than small microorganisms.

  1. Removal of nitrate by zero-valent iron and pillared bentonite.

    PubMed

    Li, Jianfa; Li, Yimin; Meng, Qingling

    2010-02-15

    The pillared bentonite prepared by intercalating poly(hydroxo Al(III)) cations into bentonite interlayers was used together with Fe(0) for removing nitrate in column experiments. The obvious synergetic effect on nitrate removal was exhibited through uniformly mixing the pillared bentonite with Fe(0). In such a mixing manner, the nitrate was 100% removed, and the removal efficiency was much higher than the simple summation of adsorption by the pillared bentonite and reduction by Fe(0). The influencing factors such as bentonite type, amount of the pillared bentonite and initial pH of nitrate solutions were investigated. In this uniform mixture, the pillared bentonite could adsorb nitrate ions, and facilitated the mass transfer of nitrate onto Fe(0) surface, then accelerated the nitrate reduction. The pillared bentonite could also act as the proton-donor, and helped to keep the complete nitrate removal for at least 10h even when the nitrate solution was fed at nearly neutral pH.

  2. Methods for accelerating nitrate reduction using zerovalent iron at near-neutral pH: effects of H2-reducing pretreatment and copper deposition.

    PubMed

    Liou, Y H; Lo, S L; Lin, C I; Hu, C Y; Kuan, W H; Weng, S C

    2005-12-15

    Both surface treatments, H2-reducing pretreatment at 400 degrees C and the deposition of copper as a catalyst, were attempted to enhance the removal of nitrate (40 (mg N) L(-1)) using zerovalent iron in a HEPES buffered solution at a pH of between 6.5 and 7.5. After the iron surface was pretreated with hydrogen gas, the removal of the passive oxide layers that covered the iron was indicated by the decline in the oxygen fraction (energy dispersive X-ray analysis) and the overlap of the cyclic polarization curves. The reaction rate was doubled, and the lag of the early period disappeared. Then, the deposition of copper onto freshly pretreated iron promoted nitrate degradation more effectively than that onto a nonpretreated iron surface, because of the high dispersion and small size of the copper particles. An optimum of 0.25-0.5% (w/w) Cu/Fe accelerated the rate by more than six times that of the nonpretreated iron. The aged 0.5% (w/w) Cu/Fe with continual dipping in nitrate solution for 20 days completely restored its reactivity by a regeneration process with H2 reduction. Hence, these two iron surface treatments considerably promoted the removal of nitrate from near-neutral water; the reactivity of Cu/Fe was effectively recovered.

  3. Nitrate reduction, sulfate reduction, and sedimentary iron isotope evolution during the Cenomanian-Turonian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Jenkyns, Hugh C.; Matthews, Alan; Tsikos, Harilaos; Erel, Yigal

    2007-09-01

    Organic carbon-rich shales from localities in England, Italy, and Morocco, which formed during the Cenomanian-Turonian oceanic anoxic event (OAE), have been examined for their total organic carbon (TOC) values together with their carbon, nitrogen, and iron isotope ratios. Carbon isotope stratigraphy (δ13Corg and δ13Ccarb) allows accurate recognition of the strata that record the oceanic anoxic event, in some cases allowing characterization of isotopic species before, during, and after the OAE. Within the black shales formed during the OAE, relatively heavy nitrogen isotope ratios, which correlate positively with TOC, suggest nitrate reduction (leading ultimately to denitrification and/or anaerobic ammonium oxidation). Black shales deposited before the onset of the OAE in Italy have unusually low bulk δ57Fe values, unlike those found in the black shale (Livello Bonarelli) deposited during the oceanic anoxic event itself: These latter conform to the Phanerozoic norm for organic-rich sediments. Pyrite formation in the pre-OAE black shales has apparently taken place via dissimilatory iron reduction (DIR), within the sediment, a suboxic process that causes an approximately -2‰ fractionation between a lithogenic Fe(III)oxide source and Fe(II)aq. In contrast, bacterial sulfate reduction (BSR), at least partly in the water column, characterized the OAE itself and was accompanied by only minor iron isotope fractionation. This change in the manner of pyrite formation is reflected in a decrease in the average pyrite framboid diameter from ˜10 to ˜7 μm. The gradual, albeit irregular increase in Fe isotope values during the OAE, as recorded in the Italian section, is taken to demonstrate limited isotopic evolution of the dissolved iron pool, consequent upon ongoing water column precipitation of pyrite under euxinic conditions. Given that evidence exists for both nitrate and sulfate reduction during the OAE, it is evident that redox conditions in the water column were

  4. [Iron content and electron donor specificity of the nitrate reductase from Ankistrodesmus].

    PubMed

    Zumft, W G; Spiller, H; Yeboah-Smith, I

    1972-09-01

    Nitrate reductase (EC 1.6.6.1-2) purified from nitrogen-deficient cells of Ankistrodesmus braunii has the same characteristics previously described for the enzyme from Chlorella fusca. Nitrogen-deficient cells were chosen as a source for nitrate reductase because of a pronounced rise of enzymatic activity after about 20 days of growth, which surpassed even the specific activity present in normal cells. This nitrate reductase exhibits a twofold specificity towards NADH and NADPH which shows a constant ratio during enzyme purification and cannot be separated by gelfiltration or density gradient centrifugation. By growing Ankistrodesmus in the presence of radioactive (55)Fe, the incorporation of this metal into the purified enzyme could be demonstrated. A scheme is presented for the enzymatic mechanism of nitrate reduction in green algae.

  5. Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles.

    PubMed

    Su, Yiming; Adeleye, Adeyemi S; Huang, Yuxiong; Sun, Xiaoya; Dai, Chaomeng; Zhou, Xuefei; Zhang, Yalei; Keller, Arturo A

    2014-10-15

    Nanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate or cadmium (Cd) contamination, but its efficiency for simultaneous removal of nitrate and Cd has not been investigated. This study evaluated the reactivity of nZVI to the co-contaminants and by-product formation, employed different catalysts to reduce nitrite yield from nitrate, and examined the transformation of nZVI after reaction. Nitrate reduction resulted in high solution pH, negatively charged surface of nZVI, formation of Fe3O4 (a stable transformation of nZVI), and no release of ionic iron. Increased pH and negative charge contributed to significant increase in Cd(II) removal capacity (from 40 mg/g to 188 mg/g) with nitrate present. In addition, nitrate reduction by nZVI could be catalyzed by Cd(II): while 30% of nitrate was reduced by nZVI within 2 h in the absence of Cd(II), complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. While nitrate was reduced mostly to ammonium when Cd(II) was not present or at Cd(II) concentrations ≥ 40 mg/L, up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. Among nZVI particles doped with 1 wt. % Cu, Ag, or Au, nZVI deposited with 1 wt. % Au reduced nitrite yield to less than 3% of the initial nitrate, while maintaining a high Cd(II) removal capacity.

  6. Biodegradation of pharmaceuticals and endocrine disruptors with oxygen, nitrate, manganese (IV), iron (III) and sulfate as electron acceptors

    NASA Astrophysics Data System (ADS)

    Schmidt, Natalie; Page, Declan; Tiehm, Andreas

    2017-08-01

    Biodegradation of pharmaceuticals and endocrine disrupting compounds was examined in long term batch experiments for a period of two and a half years to obtain more insight into the effects of redox conditions. A mix including lipid lowering agents (e.g. clofibric acid, gemfibrozil), analgesics (e.g. diclofenac, naproxen), beta blockers (e.g. atenolol, propranolol), X-ray contrast media (e.g. diatrizoic acid, iomeprol) as well as the antiepileptic carbamazepine and endocrine disruptors (e.g. bisphenol A, 17α-ethinylestradiol) was analyzed in batch tests in the presence of oxygen, nitrate, manganese (IV), iron (III), and sulfate. Out of the 23 selected substances, 14 showed a degradation of > 50% of their initial concentrations under aerobic conditions. The beta blockers propranolol and atenolol and the analgesics pentoxifylline and naproxen showed a removal of > 50% under anaerobic conditions. In particular naproxen proved to be degradable with oxygen and under most anaerobic conditions, i.e. with manganese (IV), iron (III), or sulfate. The natural estrogens estriol, estrone and 17β-estradiol showed complete biodegradation under aerobic and nitrate-reducing conditions, with a temporary increase of estrone during transformation of estriol and 17β-estradiol. Transformation of 17β-estradiol under Fe(III)-reducing conditions resulted in an increase of estriol as well. Concentrations of clofibric acid, carbamazepine, iopamidol and diatrizoic acid, known for their recalcitrance in the environment, remained unchanged.

  7. Potential application of microbial iron redox cycles in nitrate removal and their effects on clay mineral properties

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Dong, H.; Kukkadapu, R. K.; Briggs, B. R.; Zeng, Q.

    2014-12-01

    Phyllosilicates that are ubiquitous in subsurface can serve as an iron source for microbial respiration. The objective of this research is to determine the ability of the phyllosilicate Fe to remove nitrate in subsurface undergoing microbial-driven redox cycles. In this study, thus, a well-characterized reference clay (NAu-2; nontronite), was subjected to redox cycles in a system containing dissimilatory Fe(III)-reducing bacteria, Shewanella putrefaciens CN32, and nitrate-dependent Fe(II)-oxidizing bacteria, Pseudogulbenkiania sp. Strain 2002. Three redox cycles were conducted in bicarbonate- and PIPES-buffered medium. The extents of Fe(III) reduction, Fe(II) oxidation, nitrate reduction, and its various intermediate products were measured by wet chemical methods. For each cycle, Electron Energy Loss Spectroscopy and Mossbauer spectroscopy confirmed Fe oxidation state. Mineralogical changes were identified by using X-ray diffraction (XRD), 57Fe-Mössbauer spectroscopy, and infrared absorption spectroscopy. For all three cycles, nitrate was completely reduced to nitrogen gas under both bicarbonate- and PIPES- buffered conditions. As redox cycle increased, bio-reduction extents of Fe(III) in NAu-2 decreased by 33% and 48% in PIPES- and bicarbonate-buffered medium, respectively; however, bio-oxidation extents increased by 66% and 55% in the same medium, respectively. Despite the change of OH-stretching vibration band and OH-bending vibration bands in NAu-2 structure along Fe redox cycles, XRD data showed interlayer spacing of NAu-2 to be constant along the same Fe redox cycle. 57Fe-Mössbauer spectroscopy indicated complex reduction and re-oxidation pathways. For example, a distinct Fe(II) doublet and a Fe2.5+ feature due to interfacial Fe(II)-Fe(III) electron transfer on clay mineral are prominent in their RT spectra. Both these Fe(II) are partially oxidized by Fe(II)-oxidizing bacteria. The result of this study shows that Fe in biogenically reduced or oxidized NAu-2

  8. Biological Redox Cycling Of Iron In Nontronite And Its Potential Application In Nitrate Removal

    SciTech Connect

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K.; Zeng, Qiang; Edelmann, Richard E.; Pentrak, Martin; Agrawal, Abinash

    2015-05-05

    Redox cycling of structural Fe in phyllosilicates provides a potential method to remediate nitrate contamination in natural environment. Past research has only studied chemical redox cycles or a single biologically mediated redox cycle of Fe in phyllosilicates. The objective of this research was to study three microbially driven redox cycles of Fe in one phyllosilicate, nontronite (NAu-2). During the reduction phase structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacteria Shewanella putrefaciens CN32 as mediator in bicarbonate-buffered and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served an electron donor, nitrate as electron acceptor, and nitrate-dependent Fe(II)-oxidizing bacteria Pseudogulbenkiania sp. strain 2002 as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo 3 redox cycles without significant reductive or oxidative dissolution. X-ray diffraction and scanning and transmission electron microscopy revealed that NAu-2 was the dominant residual mineral throughout the 3 redox cycles with some dissolution textures but no significant secondary mineralization. Mössbauer spectroscopy revealed that Fe(II) in bio-reduced samples likely occurred in two distinct environments, at edges and the interior of the NAu-2 structure. Nitrate was completely reduced to nitrogen gas under both buffer conditions and this extent and rate did not change with Fe redox cycles. Mössbauer spectroscopy further revealed that nitrate reduction was coupled to predominant/preferred oxidation of edge Fe(II). These results suggest that structural Fe in phyllosilicates may represent a renewable source to continuously remove nitrate in natural environments.

  9. Synergistic Interaction of Light Alcohol Administration in the Presence of Mild Iron Overload in a Mouse Model of Liver Injury: Involvement of Triosephosphate Isomerase Nitration and Inactivation.

    PubMed

    Gao, Wanxia; Zhao, Jie; Gao, Zhonghong; Li, Hailing

    2017-01-01

    It is well known that iron overload promotes alcoholic liver injury, but the doses of iron or alcohol used in studies are usually able to induce liver injury independently. Little attention has been paid to the coexistence of low alcohol consumption and mild iron overload when either of them is insufficient to cause obvious liver damage, although this situation is very common among some people. We studied the interactive effects and the underlining mechanism of mild doses of iron and alcohol on liver injury in a mouse model. Forty eight male Kunming mice were randomly divided into four groups: control, iron (300 mg/kg iron dextran, i.p.), alcohol (2 g/kg/day ethanol for four weeks i.g.), and iron plus alcohol group. After 4 weeks of treatment, mice were sacrificed and blood and livers were collected for biochemical analysis. Protein nitration level in liver tissue was determined by immunoprecipitation and Western blot analysis. Although neither iron overload nor alcohol consumption at our tested doses can cause severe liver injury, it was found that co-administration of the same doses of alcohol and iron resulted in liver injury and hepatic dysfunction, accompanied with elevated ratio of NADH/NAD+, reduced antioxidant ability, increased oxidative stress, and subsequent elevated protein nitration level. Further study revealed that triosephosphate isomerase, an important glycolytic enzyme, was one of the targets to be oxidized and nitrated, which was responsible for its inactivation. These data indicate that even under low alcohol intake, a certain amount of iron overload can cause significant liver oxidative damage, and the modification of triosephosphate isomerasemight be the important underlining mechanism of hepatic dysfunction.

  10. Synergistic Interaction of Light Alcohol Administration in the Presence of Mild Iron Overload in a Mouse Model of Liver Injury: Involvement of Triosephosphate Isomerase Nitration and Inactivation

    PubMed Central

    Gao, Wanxia; Zhao, Jie; Gao, Zhonghong

    2017-01-01

    It is well known that iron overload promotes alcoholic liver injury, but the doses of iron or alcohol used in studies are usually able to induce liver injury independently. Little attention has been paid to the coexistence of low alcohol consumption and mild iron overload when either of them is insufficient to cause obvious liver damage, although this situation is very common among some people. We studied the interactive effects and the underlining mechanism of mild doses of iron and alcohol on liver injury in a mouse model. Forty eight male Kunming mice were randomly divided into four groups: control, iron (300 mg/kg iron dextran, i.p.), alcohol (2 g/kg/day ethanol for four weeks i.g.), and iron plus alcohol group. After 4 weeks of treatment, mice were sacrificed and blood and livers were collected for biochemical analysis. Protein nitration level in liver tissue was determined by immunoprecipitation and Western blot analysis. Although neither iron overload nor alcohol consumption at our tested doses can cause severe liver injury, it was found that co-administration of the same doses of alcohol and iron resulted in liver injury and hepatic dysfunction, accompanied with elevated ratio of NADH/NAD+, reduced antioxidant ability, increased oxidative stress, and subsequent elevated protein nitration level. Further study revealed that triosephosphate isomerase, an important glycolytic enzyme, was one of the targets to be oxidized and nitrated, which was responsible for its inactivation. These data indicate that even under low alcohol intake, a certain amount of iron overload can cause significant liver oxidative damage, and the modification of triosephosphate isomerasemight be the important underlining mechanism of hepatic dysfunction. PMID:28103293

  11. Nitrate and ammonium ions removal from groundwater by a hybrid system of zero-valent iron combined with adsorbents.

    PubMed

    Ji, Min-Kyu; Park, Won-Bae; Khan, Moonis Ali; Abou-Shanab, Reda A I; Kim, Yongje; Cho, Yunchul; Choi, Jaeyoung; Song, Hocheol; Jeon, Byong-Hun

    2012-04-01

    Nitrate (NO(3)(-)) is a commonly found contaminant in groundwater and surface water. It has created a major water quality problem worldwide. The laboratory batch experiments were conducted to investigate the feasibility of HCl-treated zero-valent iron (Fe(0)) combined with different adsorbents as hybrid systems for simultaneous removal of nitrate (NO(3)(-)) and ammonium (NH(4)(+)) ions from aqueous solution. The maximum NO(3)(-) removal in combined Fe(0)-granular activated carbon (GAC), Fe(0)-filtralite and Fe(0)-sepiolite systems was 86, 96 and 99%, respectively, at 45 °C for 24 h reaction time. The NO(3)(-) removal rate increased with the increase in initial NO(3)(-) concentration. The NO(3)(-) removal efficiency by hybrid systems was in the order of sepiolite > filtralite > GAC. The NH(4)(+) produced during the denitrification process by Fe(0) was successfully removed by the adsorbents, with the removal efficiency in the order of GAC > sepiolite > filtralite. Results of the present study suggest that the use of a hybrid system could be a promising technology for achieving simultaneous removal of NO(3)(-) and NH(4)(+) ions from aqueous solution.

  12. Enhanced and stabilized arsenic retention in microcosms through the microbial oxidation of ferrous iron by nitrate

    SciTech Connect

    Sun, Jing; Chillrud, Steven N.; Mailloux, Brian J.; Stute, Martin; Singh, Rajesh; Dong, Hailiang; Lepre, Christopher J.; Bostick, Benjamin C.

    2015-10-23

    Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. In this paper, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at pH 6–7 following nitrate-Fe(II) addition, and As-bearing magnetite was stable under reducing conditions. Scanning electron microscopy and X-ray diffraction indicated that nano-particulate magnetite was produced as coatings on fine sediments, and no aging effect was detected on morphology over the course of incubation. Finally, these results suggest that a magnetite based strategy may be a long-term remedial option for As-contaminated aquifers.

  13. Enhanced and stabilized arsenic retention in microcosms through the microbial oxidation of ferrous iron by nitrate

    DOE PAGES

    Sun, Jing; Chillrud, Steven N.; Mailloux, Brian J.; ...

    2015-10-23

    Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. In this paper, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated bymore » the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at pH 6–7 following nitrate-Fe(II) addition, and As-bearing magnetite was stable under reducing conditions. Scanning electron microscopy and X-ray diffraction indicated that nano-particulate magnetite was produced as coatings on fine sediments, and no aging effect was detected on morphology over the course of incubation. Finally, these results suggest that a magnetite based strategy may be a long-term remedial option for As-contaminated aquifers.« less

  14. Enhanced and stabilized arsenic retention in microcosms through the microbial oxidation of ferrous iron by nitrate.

    PubMed

    Sun, Jing; Chillrud, Steven N; Mailloux, Brian J; Stute, Martin; Singh, Rajesh; Dong, Hailiang; Lepre, Christopher J; Bostick, Benjamin C

    2016-02-01

    Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. Here, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II) (aq) (as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II) (aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at pH 6-7 following nitrate-Fe(II) addition, and As-bearing magnetite was stable under reducing conditions. Scanning electron microscopy and X-ray diffraction indicated that nano-particulate magnetite was produced as coatings on fine sediments, and no aging effect was detected on morphology over the course of incubation. These results suggest that a magnetite based strategy may be a long-term remedial option for As-contaminated aquifers. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Enhanced and Stabilized Arsenic Retention in Microcosms through the Microbial Oxidation of Ferrous Iron by Nitrate

    PubMed Central

    SUN, JING; CHILLRUD, STEVEN N.; MAILLOUX, BRIAN J.; STUTE, MARTIN; SINGH, RAJESH; DONG, HAILIANG; LEPRE, CHRISTOPHER J.; BOSTICK, BENJAMIN C.

    2016-01-01

    Magnetite strongly retains As, and is relatively stable under Fe(III)-reducing conditions common in aquifers that release As. Here, laboratory microcosm experiments were conducted to investigate a potential As remediation method involving magnetite formation, using groundwater and sediments from the Vineland Superfund site. The microcosms were amended with various combinations of nitrate, Fe(II)(aq)(as ferrous sulfate) and lactate, and were incubated for more than 5 weeks. In the microcosms enriched with 10 mM nitrate and 5 mM Fe(II)(aq), black magnetic particles were produced, and As removal from solution was observed even under sustained Fe(III) reduction stimulated by the addition of 10 mM lactate. The enhanced As retention was mainly attributed to co-precipitation within magnetite and adsorption on a mixture of magnetite and ferrihydrite. Sequential chemical extraction, X-ray absorption spectroscopy and magnetic susceptibility measurements showed that these minerals formed at pH 6 – 7 following nitrate-Fe(II) addition, and As-bearing magnetite was stable under reducing conditions. Scanning electron microscopy and X-ray diffraction indicated that nano-particulate magnetite was produced as coatings on fine sediments, and no aging effect was detected on morphology over the course of incubation. These results suggest that a magnetite based strategy may be a long-term remedial option for As-contaminated aquifers. PMID:26454120

  16. Biological redox cycling of iron in nontronite and its potential application in nitrate removal.

    PubMed

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K; Zeng, Qiang; Edelmann, Richard E; Pentrák, Martin; Agrawal, Abinash

    2015-05-05

    Biological redox cycling of structural Fe in phyllosilicates is an important but poorly understood process. The objective of this research was to study microbially mediated redox cycles of Fe in nontronite (NAu-2). During the reduction phase, structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens CN32 as mediator in bicarbonate- and PIPES-buffered media. During the oxidation phase, biogenic Fe(II) served as electron donor and nitrate as electron acceptor. Nitrate-dependent Fe(II)-oxidizing bacterium Pseudogulbenkiania sp. strain 2002 was added as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo three redox cycles without significant dissolution. Fe(II) in bioreduced samples occurred in two distinct environments, at edges and in the interior of the NAu-2 structure. Nitrate reduction to nitrogen gas was coupled with oxidation of edge-Fe(II) and part of interior-Fe(II) under both buffer conditions, and its extent and rate did not change with Fe redox cycles. These results suggest that biological redox cycling of structural Fe in phyllosilicates is a reversible process and has important implications for biogeochemical cycles of carbon, nitrogen, and other nutrients in natural environments.

  17. Inhibition of nitrate reduction by NaCl adsorption on a nano-zero-valent iron surface during a concentrate treatment for water reuse.

    PubMed

    Hwang, Yuhoon; Kim, Dogun; Shin, Hang-Sik

    2015-01-01

    Nanoscale zero-valent iron (NZVI) has been considered as a possible material to treat water and wastewater. However, it is necessary to verify the effect of the matrix components in different types of target water. In this study, different effects depending on the sodium chloride (NaCl) concentration on reductions of nitrates and on the characteristics of NZVI were investigated. Although NaCl is known as a promoter of iron corrosion, a high concentration of NaCl (>3 g/L) has a significant inhibition effect on the degree of NZVI reactivity towards nitrate. The experimental results were interpreted by a Langmuir-Hinshelwood-Hougen-Watson reaction in terms of inhibition, and the decreased NZVI reactivity could be explained by the increase in the inhibition constant. As a result of a chloride concentration analysis, it was verified that 7.7-26.5% of chloride was adsorbed onto the surface of NZVI. Moreover, the change of the iron corrosion product under different NaCl concentrations was investigated by a surface analysis of spent NZVI. Magnetite was the main product, with a low NaCl concentration (0.5 g/L), whereas amorphous iron hydroxide was observed at a high concentration (12 g/L). Though the surface was changed to permeable iron hydroxide, the Fe(0) in the core was not completely oxidized. Therefore, the inhibition effect of NaCl could be explained as the competitive adsorption of chloride and nitrate.

  18. Impact of orchard and tillage management practices on soil leaching of atrazine, potassium, magnesium, manganese, iron, ammonium, nitrates and phosphates

    NASA Astrophysics Data System (ADS)

    Szajdak, L.; Lipiec, J.; Siczek, A.; Kotowska, U.; Nosalewicz, A.

    2009-04-01

    The experiments were carried out on an Orthic Luvisol developed from loess, over limestone, at the experimental field of Lublin Agricultural University in Felin (51o15'N, 22o35'E), Poland. The investigation deals with the problems of leaching's rate of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,2,3-triazine), potassium, magnesium, manganese, iron, ammonium, nitrates and phosphates from two management systems of soil: (i) conventionally tilled field with main tillage operations including stubble cultivator (10 cm) + harrowing followed by mouldboard ploughing to 20 cm depth, and crop rotation including selected cereals, root crops and papillionaceous crops, (ii) 35-year-old apple orchard field (100x200m) with a permanent sward that was mown in the inter-rows during the growing season. The conventionally tilled plot was under the current management practice for approximately 30 years. Field sites were close to each other (about 150 m). Core samples of 100 cm3 volume and 5 cm diameter were taken from two depths 0-10 cm and 10-20 cm, and were used to determine the soil water characteristic curve. It was observed that management practices impacted on the physic-chemical properties of soils. pH (in H2O) in tilled soil ranged from 5.80 to 5.91. However soil of orchard soil revealed higher values of pH than tilled soil and ranged from 6.36 to 6.40. The content of organic carbon for tilled soil ranged from 1.13 to 1.17%, but in orchard soil from 1.59 to 1.77%. Tillled soil showed broader range of bulk density 1.38-1.62 mg m-3, than orchard soil 1.33-134 mg m-3. The first-order kinetic reaction model was fitted to the experimental atrazine, potassium, magnesium, manganese, iron, nitrates, ammonium and phosphates leaching vs. time data. The concentrations of leached chemical compounds revealed linear curves. The correlation coefficients ranged from -0.873 to -0.993. The first-order reaction constants measured for the orchard soils were from 3.8 to 19 times higher than

  19. Formation of single domain magnetite by green rust oxidation promoted by microbial anaerobic nitrate-dependent iron oxidation

    NASA Astrophysics Data System (ADS)

    Miot, Jennyfer; Li, Jinhua; Benzerara, Karim; Sougrati, Moulay Tahar; Ona-Nguema, Georges; Bernard, Sylvain; Jumas, Jean-Claude; Guyot, François

    2014-08-01

    Biomineralization of magnetite is a central geomicrobiological process that might have played a primordial role over Earth’s history, possibly leaving traces of life in the geological record or controlling trace metal(loid)s and organic pollutants mobility in modern environments. Magnetite biomineralization has been attributed to two main microbial pathways to date (namely magnetotactic bacteria and dissimilatory iron-reducing bacteria). Here, we uncover a new route of magnetite biomineralization involving the anaerobic nitrate-reducing iron(II) oxidizing bacterium Acidovorax sp. strain BoFeN1. Using transmission electron microscopy, scanning transmission X-ray microscopy, transmission Mössbauer spectroscopy and rock magnetic analyses, this strain is shown to promote the transformation of hydroxychloride green rust in equilibrium with dissolved Fe(II) to (1) periplasmic lepidocrocite (γ-FeOOH) and (2) extracellular magnetite, thus leading to strong redox heterogeneities at the nanometer scale. On the one hand, lepidocrocite was associated with protein moieties and exhibited an anisotropic texture, with the elongated axis parallel to the cell wall. On the other hand, magnetite crystals exhibited grain sizes and magnetic properties consistent with stable single domain particles. By comparison, abiotic controls led to a very slow (4 months vs. 2 days in BoFeN1 cultures) and incomplete oxidation of hydroxychloride green rust towards magnetite. As this abiotic magnetite exhibited the same size and magnetic properties (stable single domain particles) as magnetite produced in BoFeN1 cultures, only the co-occurrence of textured Fe(III)-oxides and magnetite, associated with the persistence of organic carbon molecules, might constitute valuable biosignatures to be looked for in the geological record. Our results furthermore contribute to a more complex picture of Fe redox cycling in the environment, providing an additional process of Fe(II)-bearing phase

  20. Penetration pathways induced by low-frequency sonophoresis with physical and chemical enhancers: iron oxide nanoparticles versus lanthanum nitrates.

    PubMed

    Lee, Sang Eun; Choi, Ki Ju; Menon, Gopinathan K; Kim, Hyun Jung; Choi, Eung Ho; Ahn, Sung Ku; Lee, Seung Hun

    2010-04-01

    Low-frequency sonophoresis (LFS) has been shown to disrupt the structure of stratum corneum (SC) lipid bilayers and enhance SC permeability. In this study, we examined the penetration pathway of lanthanum nitrate (LaNO(3)) tracer in viable epidermis after combined treatment of LFS and tape stripping (TS), as a physical enhancer, or oleic acid (OA) application, as a chemical enhancer, using transmission electron microscopy (TEM). As a positive control, we visualized the passive diffusion pathway of LaNO(3) and iron oxide (Fe(3)O(4)) nanoparticles after the incision of hairless mouse skin. Next, we applied LFS immediately after TS or OA application and visualized the penetration pathway of LaNO(3). Each treatment showed restricted penetration to the SC-stratum granulosum (SG) interface or upper SG layer. However, the additional application of LFS induced diffuse intracellular distribution of LaNO(3) throughout the viable epidermis. Quantitative analysis also revealed that combined treatment significantly increases LaNO(3) penetration into viable epidermis when compared with each treatment. Our ultrastructural findings show the synergistic effect of LFS and TS or OA application on transdermal drug delivery. We also found that this combined treatment enhances the penetration of LaNO(3) through the viable epidermis through an intracellular pathway.

  1. Nitrate reduction by mixed iron(II-III) hydroxycarbonate green rust in the presence of phosphate anions: the key parameters influencing the ammonium selectivity.

    PubMed

    Etique, Marjorie; Zegeye, Asfaw; Grégoire, Brian; Carteret, Cédric; Ruby, Christian

    2014-10-01

    The reduction of nitrate anions by a mixed Fe(II)-Fe(III) carbonated green rust (GR) in aqueous medium is studied as a function of the initial pH and the initial concentrations of iron, phosphate and nitrate. The influence of these parameters on the fraction of nitrate removed and the production of ammonium is investigated by the help of statistical experimental designs. The goal is to determine experimental conditions that maximize the fraction of NO3(-) removed and concomitantly minimize the production of NH4(+). Increasing the phosphate concentration relatively to the initial Fe(II) concentration inhibits the reduction of nitrate probably due to a surface saturation of the lateral sites of the GR crystals. The kinetics of the reaction is greatly enhanced by increasing the initial pH at 10.5, however it leads to a global increase of the NH4(+) production. A partial saturation of the surface sites by phosphate leads to a global decrease of selectivity of the reaction towards ammonium. The evolution of the ratio of the NH4(+) concentration to the Fe(II) concentration confirms that the NO3(-) species are only partially transformed into ammonium. Interestingly at an initial pH of 7.5, the selectivity of the reaction towards NH4(+) is often lower than ∼30%. The reduction of nitrate by carbonated GR differs from the behavior of other GRs incorporating Cl(-), F(-) and SO4(2-) anions that fully transform nitrate into ammonium. Finally, if GR is intended to be used during a passive water denitrification process, complementary dephosphatation and ammonium treatments should be considered. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Denitrification-Coupled Iron(II) Oxidation: A Key Process Regulating the Fate and Transport of Nitrate, Phosphate, and Arsenic in a Wastewater-Contaminated Aquifer

    NASA Astrophysics Data System (ADS)

    Smith, R. L.; Kent, D. B.; Repert, D. A.; Hart, C. P.

    2007-12-01

    Denitrification in the subsurface is often viewed as a heterotrophic process. However, some denitrifiers can also utilize inorganic electron donors. In particular, Fe(II), which is common in many aquifers, could be an important reductant for contaminant nitrate. Anoxic iron oxidation would have additional consequences, including decreased mobility for species like arsenic and phosphate, which bind strongly to hydrous Fe(III) oxide. A study was conducted in a wastewater contaminant plume on Cape Cod to assess the potential for denitrification- coupled Fe(II) oxidation. Previous changes in wastewater disposal upgradient of the study area had resulted in nitrate being transported into a portion of the anoxic zone of the plume and decreased concentrations of Fe(II), phosphate, and arsenic. A series of anoxic tracers (groundwater + nitrate + bromide) were injected into the unaffected, Fe(II)-containing zone under natural gradient conditions. Denitrification was stimulated within 1 m of transport (4 days) for both low and high (100 & 1000 μM) nitrate additions, initially producing stiochiometric quantities of nitrous oxide (>300 μM N) and trace amounts of nitrite. Subsequent injections at the same site reduced nitrate even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and this was accompanied by an increase in colloidal Fe(III) and decreases in pH, total arsenic, and phosphate concentrations. All plume constituents returned to background levels several weeks after the tracer tests were completed. Groundwater microorganisms collected on filters during the tracer test rapidly and immediately reduced nitrite and oxidized Fe(II) in 3-hr laboratory incubations. Several pure cultures of Fe(II)-oxidizing denitrifying bacteria were isolated from core material and subsequently characterized. All of the isolates were mixotrophic, simultaneously oxidizing organic carbon and Fe

  3. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study

    PubMed Central

    Sinha, Rashmi; Ward, Mary H; Graubard, Barry I; Inoue-Choi, Maki; Dawsey, Sanford M; Abnet, Christian C

    2017-01-01

    Objective To determine the association of different types of meat intake and meat associated compounds with overall and cause specific mortality. Design Population based cohort study. Setting Baseline dietary data of the NIH-AARP Diet and Health Study (prospective cohort of the general population from six states and two metropolitan areas in the US) and 16 year follow-up data until 31 December 2011. Participants 536 969 AARP members aged 50-71 at baseline. Exposures Intake of total meat, processed and unprocessed red meat (beef, lamb, and pork) and white meat (poultry and fish), heme iron, and nitrate/nitrite from processed meat based on dietary questionnaire. Adjusted Cox proportional hazards regression models were used with the lowest fifth of calorie adjusted intakes as reference categories. Main outcome measure Mortality from any cause during follow-up. Results An increased risk of all cause mortality (hazard ratio for highest versus lowest fifth 1.26, 95% confidence interval 1.23 to 1.29) and death due to nine different causes associated with red meat intake was observed. Both processed and unprocessed red meat intakes were associated with all cause and cause specific mortality. Heme iron and processed meat nitrate/nitrite were independently associated with increased risk of all cause and cause specific mortality. Mediation models estimated that the increased mortality associated with processed red meat was influenced by nitrate intake (37.0-72.0%) and to a lesser degree by heme iron (20.9-24.1%). When the total meat intake was constant, the highest fifth of white meat intake was associated with a 25% reduction in risk of all cause mortality compared with the lowest intake level. Almost all causes of death showed an inverse association with white meat intake. Conclusions The results show increased risks of all cause mortality and death due to nine different causes associated with both processed and unprocessed red meat, accounted for, in part, by

  4. 2′-Deoxymugineic acid promotes growth of rice (Oryza sativa L.) by orchestrating iron and nitrate uptake processes under high pH conditions

    PubMed Central

    Araki, Ryoichi; Kousaka, Kayoko; Namba, Kosuke; Murata, Yoshiko; Murata, Jun

    2015-01-01

    Poaceae plants release 2′-deoxymugineic acid (DMA) and related phytosiderophores to chelate iron (Fe), which often exists as insoluble Fe(III) in the rhizosphere, especially under high pH conditions. Although the molecular mechanisms behind the biosynthesis and secretion of DMA have been studied extensively, little information is known about whether DMA has biological roles other than chelating Fe in vivo. Here, we demonstrate that hydroponic cultures of rice (Oryza sativa) seedlings show almost complete restoration in shoot height and soil-plant analysis development (SPAD) values after treatment with 3–30 μm DMA at high pH (pH 8.0), compared with untreated control seedlings at normal pH (pH 5.8). These changes were accompanied by selective accumulation of Fe over other metals. While this enhanced growth was evident under high pH conditions, DMA application also enhanced seedling growth under normal pH conditions in which Fe was fairly accessible. Microarray and qRT-PCR analyses revealed that exogenous DMA application attenuated the increased expression levels of various genes related to Fe transport and accumulation. Surprisingly, despite the preferential utilization of ammonium over nitrate as a nitrogen source by rice, DMA application also increased nitrate reductase activity and the expression of genes encoding high-affinity nitrate transporters and nitrate reductases, all of which were otherwise considerably lower under high pH conditions. These data suggest that exogenous DMA not only plays an important role in facilitating the uptake of environmental Fe, but also orchestrates Fe and nitrate assimilation for optimal growth under high pH conditions. PMID:25393516

  5. 2'-Deoxymugineic acid promotes growth of rice (Oryza sativa L.) by orchestrating iron and nitrate uptake processes under high pH conditions.

    PubMed

    Araki, Ryoichi; Kousaka, Kayoko; Namba, Kosuke; Murata, Yoshiko; Murata, Jun

    2015-01-01

    Poaceae plants release 2'-deoxymugineic acid (DMA) and related phytosiderophores to chelate iron (Fe), which often exists as insoluble Fe(III) in the rhizosphere, especially under high pH conditions. Although the molecular mechanisms behind the biosynthesis and secretion of DMA have been studied extensively, little information is known about whether DMA has biological roles other than chelating Fe in vivo. Here, we demonstrate that hydroponic cultures of rice (Oryza sativa) seedlings show almost complete restoration in shoot height and soil-plant analysis development (SPAD) values after treatment with 3-30 μm DMA at high pH (pH 8.0), compared with untreated control seedlings at normal pH (pH 5.8). These changes were accompanied by selective accumulation of Fe over other metals. While this enhanced growth was evident under high pH conditions, DMA application also enhanced seedling growth under normal pH conditions in which Fe was fairly accessible. Microarray and qRT-PCR analyses revealed that exogenous DMA application attenuated the increased expression levels of various genes related to Fe transport and accumulation. Surprisingly, despite the preferential utilization of ammonium over nitrate as a nitrogen source by rice, DMA application also increased nitrate reductase activity and the expression of genes encoding high-affinity nitrate transporters and nitrate reductases, all of which were otherwise considerably lower under high pH conditions. These data suggest that exogenous DMA not only plays an important role in facilitating the uptake of environmental Fe, but also orchestrates Fe and nitrate assimilation for optimal growth under high pH conditions. © 2014 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

  6. Transformation of the pesticide 1,2-dibromo-3-chloropropane (DBCP) and nitrate by iron powder and by H{sub 2}/Pd/Al{sub 2}O{sub 3}

    SciTech Connect

    Siantar, D.P.; Schreier, C.G.; Reinhard, M.

    1995-12-01

    In this study, zero-valent iron powder (Fe{sup o}) was shown to reductively dehalogenate DBCP completely under sterile (abiotic) buffered and unbuffered conditions. DBCP transformation was evidenced by the appearance of bromide and chloride ions. The effect of pH, mass transport, iron content and of dissolved oxygen (O{sub 2}), sulfate (SO{sub 4}{sup 2-}), nitrate (NO{sub 3}{sup -}), and nitrite (NO{sub 2}{sup -}) on DBCP transformation was investigated. There was little effect on DBCP transformation rate between pH {approx}6 and 8. Mass transport was not limiting if the iron slurries in the batch system were shaken at >340 rpm. The rate of DBCP transformation was proportional to the amount of iron. The DBCP transformation rate decreased linearly with increasing oxygen content. Sulfate did not significantly affect the rate of DBCP transformation. The presence of nitrate appeared to temporarily inhibit DBCP transformation until the NO{sub 3} was removed. Nitrate was reduced by iron to nitrite. Nitrite was also removed by iron. This system appears to be able to effectively treat DBCP nitrate and/or nitrite containing water. Comparison of DBCP transformation in groundwater using the Fe{sup o} and H{sub 2}/Pd/Al{sub 2}O{sub 3} systems shows that the H{sub 2}/Pd/Al{sub 2}O{sub 3} system performs better in actual environmental conditions.

  7. Ardenticatena maritima gen. nov., sp. nov., a ferric iron- and nitrate-reducing bacterium of the phylum 'Chloroflexi' isolated from an iron-rich coastal hydrothermal field, and description of Ardenticatenia classis nov.

    PubMed

    Kawaichi, Satoshi; Ito, Norihiro; Kamikawa, Ryoma; Sugawara, Tatsuya; Yoshida, Takashi; Sako, Yoshihiko

    2013-08-01

    A novel thermophilic, chemoheterotrophic, Gram-negative-staining, multicellular filamentous bacterium, designated strain 110S(T), was isolated from an iron-rich coastal hydrothermal field in Japan. The isolate is facultatively aerobic and chemoheterotrophic. Phylogenetic analysis using 16S rRNA gene sequences nested strain 110S(T) in a novel class-level clone cluster of the phylum 'Chloroflexi'. The isolate grows by dissimilatory iron- and nitrate-reduction under anaerobic conditions, which is the first report of these abilities in the phylum 'Chloroflexi'. The organism is capable of growth with oxygen, ferric iron and nitrate as a possible electron acceptor, has a wide range of growth temperatures, and tolerates higher NaCl concentrations for growth compared to the other isolates in the phylum. Using phenotypic and phylogenetic data, strain 110S(T) (= JCM 17282(T) = NBRC 107679(T) = DSM 23922(T) = KCTC 23289(T) = ATCC BAA-2145(T)) is proposed as the type strain of a novel species in a new genus, Ardenticatena maritima gen. nov., sp. nov. In addition, as strain 110S(T) apparently constitutes a new class of the phylum 'Chloroflexi' with other related uncultivated clone sequences, we propose Ardenticatenia classis nov. and the subordinate taxa Ardenticatenales ord. nov. and Ardenticatenaceae fam. nov.

  8. Preservation of protein globules and peptidoglycan in the mineralized cell wall of nitrate-reducing, iron(II)-oxidizing bacteria: a cryo-electron microscopy study.

    PubMed

    Miot, J; Maclellan, K; Benzerara, K; Boisset, N

    2011-11-01

    Iron-oxidizing bacteria are important actors of the geochemical cycle of iron in modern environments and may have played a key role all over Earth's history. However, in order to better assess that role on the modern and the past Earth, there is a need for better understanding the mechanisms of bacterial iron oxidation and for defining potential biosignatures to be looked for in the geologic record. In this study, we investigated experimentally and at the nanometre scale the mineralization of iron-oxidizing bacteria with a combination of synchrotron-based scanning transmission X-ray microscopy (STXM), scanning transmission electron microscopy (STEM) and cryo-transmission electron microscopy (cryo-TEM). We show that the use of cryo-TEM instead of conventional microscopy provides detailed information of the successive iron biomineralization stages in anaerobic nitrate-reducing iron-oxidizing bacteria. These results suggest the existence of preferential Fe-binding and Fe-oxidizing sites on the outer face of the plasma membrane leading to the nucleation and growth of Fe minerals within the periplasm of these cells that eventually become completely encrusted. In contrast, the septa of dividing cells remain nonmineralized. In addition, the use of cryo-TEM offers a detailed view of the exceptional preservation of protein globules and the peptidoglycan within the Fe-mineralized cell walls of these bacteria. These organic molecules and ultrastructural details might be protected from further degradation by entrapment in the mineral matrix down to the nanometre scale. This is discussed in the light of previous studies on the properties of Fe-organic interactions and more generally on the fossilization of mineral-organic assemblies.

  9. The draft genome of the hyperthermophilic archaeon Pyrodictium delaneyi strain hulk, an iron and nitrate reducer, reveals the capacity for sulfate reduction.

    PubMed

    Demey, Lucas M; Miller, Caitlin R; Manzella, Michael P; Spurbeck, Rachel R; Sandhu, Sukhinder K; Reguera, Gemma; Kashefi, Kazem

    2017-01-01

    Pyrodictium delaneyi strain Hulk is a newly sequenced strain isolated from chimney samples collected from the Hulk sulfide mound on the main Endeavour Segment of the Juan de Fuca Ridge (47.9501 latitude, -129.0970 longitude, depth 2200 m) in the Northeast Pacific Ocean. The draft genome of strain Hulk shared 99.77% similarity with the complete genome of the type strain Su06(T), which shares with strain Hulk the ability to reduce iron and nitrate for respiration. The annotation of the genome of strain Hulk identified genes for the reduction of several sulfur-containing electron acceptors, an unsuspected respiratory capability in this species that was experimentally confirmed for strain Hulk. This makes P. delaneyi strain Hulk the first hyperthermophilic archaeon known to gain energy for growth by reduction of iron, nitrate, and sulfur-containing electron acceptors. Here we present the most notable features of the genome of P. delaneyi strain Hulk and identify genes encoding proteins critical to its respiratory versatility at high temperatures. The description presented here corresponds to a draft genome sequence containing 2,042,801 bp in 9 contigs, 2019 protein-coding genes, 53 RNA genes, and 1365 hypothetical genes.

  10. Genome-enabled studies of anaerobic, nitrate-dependent iron oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans

    PubMed Central

    Beller, Harry R.; Zhou, Peng; Legler, Tina C.; Chakicherla, Anu; Kane, Staci; Letain, Tracy E.; A. O’Day, Peggy

    2013-01-01

    Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. A transposon mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process. PMID:24065960

  11. Structural and Molecular Basis of the Peroxynitrite-mediated Nitration and Inactivation of Trypanosoma cruzi Iron-Superoxide Dismutases (Fe-SODs) A and B

    PubMed Central

    Martinez, Alejandra; Peluffo, Gonzalo; Petruk, Ariel A.; Hugo, Martín; Piñeyro, Dolores; Demicheli, Verónica; Moreno, Diego M.; Lima, Analía; Batthyány, Carlos; Durán, Rosario; Robello, Carlos; Martí, Marcelo A.; Larrieux, Nicole; Buschiazzo, Alejandro; Trujillo, Madia; Radi, Rafael; Piacenza, Lucía

    2014-01-01

    Trypanosoma cruzi, the causative agent of Chagas disease, contains exclusively iron-dependent superoxide dismutases (Fe-SODs) located in different subcellular compartments. Peroxynitrite, a key cytotoxic and oxidizing effector biomolecule, reacted with T. cruzi mitochondrial (Fe-SODA) and cytosolic (Fe-SODB) SODs with second order rate constants of 4.6 ± 0.2 × 104 m−1 s−1 and 4.3 ± 0.4 × 104 m−1 s−1 at pH 7.4 and 37 °C, respectively. Both isoforms are dose-dependently nitrated and inactivated by peroxynitrite. Susceptibility of T. cruzi Fe-SODA toward peroxynitrite was similar to that reported previously for Escherichia coli Mn- and Fe-SODs and mammalian Mn-SOD, whereas Fe-SODB was exceptionally resistant to oxidant-mediated inactivation. We report mass spectrometry analysis indicating that peroxynitrite-mediated inactivation of T. cruzi Fe-SODs is due to the site-specific nitration of the critical and universally conserved Tyr35. Searching for structural differences, the crystal structure of Fe-SODA was solved at 2.2 Å resolution. Structural analysis comparing both Fe-SOD isoforms reveals differences in key cysteines and tryptophan residues. Thiol alkylation of Fe-SODB cysteines made the enzyme more susceptible to peroxynitrite. In particular, Cys83 mutation (C83S, absent in Fe-SODA) increased the Fe-SODB sensitivity toward peroxynitrite. Molecular dynamics, electron paramagnetic resonance, and immunospin trapping analysis revealed that Cys83 present in Fe-SODB acts as an electron donor that repairs Tyr35 radical via intramolecular electron transfer, preventing peroxynitrite-dependent nitration and consequent inactivation of Fe-SODB. Parasites exposed to exogenous or endogenous sources of peroxynitrite resulted in nitration and inactivation of Fe-SODA but not Fe-SODB, suggesting that these enzymes play distinctive biological roles during parasite infection of mammalian cells. PMID:24616096

  12. Effects of iron and dissolved N:P stoichiometry on the uptake of bicarbonate, nitrate, and amino acids by a Ross Sea microbial community

    NASA Astrophysics Data System (ADS)

    Spackeen, J.; Sipler, R. E.; Bertrand, E. M.; Hutchins, D. A.; Allen, A. E.; Bronk, D. A.

    2016-02-01

    The Southern Ocean is seasonally one of the most productive regions of the ocean. Phytoplankton growth in the Southern Ocean is typically limited by iron (Fe), and Fe input is predicted to increase over the next century, which will likely enhance primary productivity. Dissolved concentrations of nitrogen (N) and phosphorus (P) may also change in the future due to both physical and biological drivers, translating to a difference in the stoichiometric N:P ratio of the water column. Increased Fe availability coupled with altered N:P ratios could impact rates of primary production and cause nutrient utilization by microorganisms to change. A natural microbial community was collected from the Ross Sea, amended with Fe, and grown under a range of N:P ratios for nine days to determine how Fe addition in combination with different N:P ratios impact uptake rates of carbon and N. Stable isotope tracer techniques were used to measure uptake rates of bicarbonate, nitrate, and amino acids by two size fractions (0.7-5.0 μm and >5.0 μm) of microorganisms. We found that the physiology of the larger microorganisms was less sensitive to changes in dissolved N:P stoichiometry than smaller microorganisms. Absolute uptake rates of nitrate by smaller microorganisms increased when dissolved N:P ratios were elevated above ambient levels, while uptake rates of bicarbonate initially increased with moderate elevations in N:P and then decreased. When dissolved N:P ratios were lowered, uptake rates of nitrate were not affected, however, uptake rates of bicarbonate decreased. The addition of Fe and the subsequent changes in dissolved N:P ratios in the Southern Ocean will impact the rates at which nitrate and bicarbonate are cycled by different microbial size fractions. This may alter the current biogeochemical balance between smaller and larger microorganisms.

  13. Iron

    MedlinePlus

    Iron is a mineral that our bodies need for many functions. For example, iron is part of hemoglobin, a protein which carries ... It helps our muscles store and use oxygen. Iron is also part of many other proteins and ...

  14. Genome-Enabled Studies of Anaerobic, Nitrate-Dependent Iron Oxidation in the Chemolithoautotrophic Bacterium Thiobacillus denitrificans

    NASA Astrophysics Data System (ADS)

    Beller, H. R.; Zhou, P.; Legler, T. C.; Chakicherla, A.; O'Day, P. A.

    2013-12-01

    Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe2+, and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c1-cytochrome subunit of the cytochrome bc1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. Of the transposon mutants defective in Fe(II) oxidation, one mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process.

  15. EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS

    DOEpatents

    Furman, N.H.; Mundy, R.J.

    1957-12-10

    An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

  16. Sustaining reactivity of Fe(0) for nitrate reduction via electron transfer between dissolved Fe(2+) and surface iron oxides.

    PubMed

    Han, Luchao; yang, Li; Wang, Haibo; Hu, Xuexiang; Chen, Zhan; Hu, Chun

    2016-05-05

    The mechanism of the effects of Fe(2+)(aq) on the reduction of NO3(-) by Fe(0) was investigated. The effects of initial pH on the rate of NO3(-) reduction and the Fe(0) surface characteristics revealed Fe(2+)(aq) and the characteristics of minerals on the surface of Fe(0) played an important role in NO3(-) reduction. Both NO3(-) reduction and the decrease of Fe(2+)(aq) exhibited similar kinetics and were promoted by each other. This promotion was associated with the types of the surface iron oxides of Fe(0). Additionally, further reduction of NO3(-) produced more surface iron oxides, supplying more active sites for Fe(2+)(aq), resulting in more electron transfer between Fe(2+) and surface iron oxides and a higher reaction rate. Using the isotope specificity of (57)Fe Mossbauer spectroscopy, it was verified that the Fe(2+)(aq) was continuously converted into Fe(3+) oxides on the surface of Fe(0) and then converted into Fe3O4 via electron transfer between Fe(2+) and the pre-existing surface Fe(3+) oxides. Electrochemistry measurements confirmed that the spontaneous electron transfer between the Fe(2+) and structural Fe(3+) species accelerated the interfacial electron transfer between the Fe species and NO3(-). This study provides a new insight into the interaction between Fe species and contaminants and interface electron transfer. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. 3-D analysis of bacterial cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using complementary microscopy tomography approaches.

    PubMed

    Schmid, G; Zeitvogel, F; Hao, L; Ingino, P; Floetenmeyer, M; Stierhof, Y-D; Schroeppel, B; Burkhardt, C J; Kappler, A; Obst, M

    2014-07-01

    The formation of cell-(iron)mineral aggregates as a consequence of bacterial iron oxidation is an environmentally widespread process with a number of implications for processes such as sorption and coprecipitation of contaminants and nutrients. Whereas the overall appearance of such aggregates is easily accessible using 2-D microscopy techniques, the 3-D and internal structure remain obscure. In this study, we examined the 3-D structure of cell-(iron)mineral aggregates formed during Fe(II) oxidation by the nitrate-reducing Acidovorax sp. strain BoFeN1 using a combination of advanced 3-D microscopy techniques. We obtained 3-D structural and chemical information on different cellular encrustation patterns at high spatial resolution (4-200 nm, depending on the method): more specifically, (1) cells free of iron minerals, (2) periplasm filled with iron minerals, (3) spike- or platelet-shaped iron mineral structures, (4) bulky structures on the cell surface, (5) extracellular iron mineral shell structures, (6) cells with iron mineral filled cytoplasm, and (7) agglomerations of extracellular globular structures. In addition to structural information, chemical nanotomography suggests a dominant role of extracellular polymeric substances (EPS) in controlling the formation of cell-(iron)mineral aggregates. Furthermore, samples in their hydrated state showed cell-(iron)mineral aggregates in pristine conditions free of preparation (i.e., drying/dehydration) artifacts. All these results were obtained using 3-D microscopy techniques such as focused ion beam (FIB)/scanning electron microscopy (SEM) tomography, transmission electron microscopy (TEM) tomography, scanning transmission (soft) X-ray microscopy (STXM) tomography, and confocal laser scanning microscopy (CLSM). It turned out that, due to the various different contrast mechanisms of the individual approaches, and due to the required sample preparation steps, only the combination of these techniques was able to provide a

  18. Nitrate reduction

    DOEpatents

    Dziewinski, Jacek J.; Marczak, Stanislaw

    2000-01-01

    Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

  19. Nitrate and periplasmic nitrate reductases

    PubMed Central

    Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

    2014-01-01

    The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

  20. A fabrication strategy for nanosized zero valent iron (nZVI)-polymeric anion exchanger composites with tunable structure for nitrate reduction.

    PubMed

    Jiang, Zhenmao; Zhang, Shujuan; Pan, Bingcai; Wang, Wenfeng; Wang, Xiaoshu; Lv, Lu; Zhang, Weiming; Zhang, Quanxing

    2012-09-30

    To reveal how the distribution of nanoscale zero-valent iron (nZVI) affect their reduction efficiency of its polymer-based composites and to further develop a simple strategy to tune the structure of the composites, we prepared four nZVI-polymerstyrene anion exchanger composites with similar nZVI loadings (13.5-14.4 Fe % in mass) but different distributions just through varying the concentration of NaBH(4) (0.9, 1.8, 3.6, and 7.2% in mass) solution during reduction of nZVI precursor (FeCl(4)(-) anions). As observed by SEM-EDX images, increasing the NaBH(4) concentration resulted in a more uniform nZVI distribution within the polymer, and thereto higher NH(4)(+)N production, faster reaction rate and more gaseous products during its reduction of nitrate and nitrite. nZVI distribution of the composites was suggested to greatly depend upon two processes, the hydrolyzation of anionic FeCl(4)(-) into cationic Fe(3+) and the reduction of both Fe(III) species by NaBH(4). Higher NaBH(4) concentration favored its faster diffusion into the inside polymer and in situ reduction of Fe(III) species into nZVI, causing a more uniform nZVI distribution. The results reported herein suggest that adjusting the NaBH(4) concentration was a simple and effective method to control the nZVI distribution in the supporting polymers, and indirectly tune the reactivity of the resultant nZVI hybrids.

  1. Nitrate tolerance.

    PubMed

    Parker, J O

    1987-11-16

    The organic nitrates are the most widely used agents in the management of patients with angina pectoris. When initially administered by the oral route, the nitrates produce profound changes in systemic hemodynamics and significant and prolonged improvement in exercise duration. It has been shown that during short periods of regular oral nitrate administration, the hemodynamic, antiischemic and antianginal effects of the nitrates are greatly reduced. Thus, when initially administered, oral isosorbide dinitrate prolongs exercise duration for a period of several hours, but during sustained 4-times-daily therapy, exercise tolerance is improved for only 2 hours after administration. Studies with transdermal preparations of isosorbide dinitrate and nitroglycerin also show improvement during short-term administration for up to 8 hours, but after several days of once-daily therapy, the effects of these agents are similar to placebo. It is apparent that nitrate tolerance is a clinically relevant problem. Although tolerance develops rapidly during nitrate therapy, it is reversed promptly during nitrate-free periods. Oral nitrates maintain their antianginal effects when given 2 or 3 times daily with provision of a nitrate-free period. Studies are currently underway to investigate the effects of intermittent administration schedules with transdermal nitrate preparations.

  2. Direct formation of thermally stabilized amorphous mesoporous Fe2O3/SiO2 nanocomposites by hydrolysis of aqueous iron III nitrate in sols of spherical silica particles.

    PubMed

    Khalil, Kamal M S; Mahmoud, Hatem A; Ali, Tarek T

    2008-02-05

    Nanocomposite materials containing 10% and 20% iron oxide/silica, Fe2O3/SiO2 (w/w), were prepared by direct hydrolysis of aqueous iron III nitrate solution in sols of freshly prepared spherical silica particles (Stöber particles) present in their mother liquors. This was followed by aging, drying, calcination up to 600 degrees C through two different ramp rates, and then isothermal calcinations at 600 degrees C for 3 h. The calcined and the uncalcined (dried at 120 degrees C) composites were characterized by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption techniques, and scanning electron microscopy as required. XRD patterns of the calcined composites showed no line broadening at any d-spacing positions of iron oxide phases, thereby reflecting the amorphous nature of Fe2O3 in the composite. The calcined composites showed nitrogen adsorption isotherms characterizing type IV isotherms with high surface area. Moreover, surface area increased with the increasing of the iron oxide ratio and lowering of the calcination ramp rate. Results indicated that iron oxide particles were dispersed on the exterior of silica particles as isolated and/or aggregated nanoparticles. The formation of the title composite was discussed in terms of the hydrolysis and condensation mechanisms of the inorganic FeIII precursor in the silica sols. Thereby, fast nucleation and limited growth of hydrous iron oxide led to the formation of nanoparticles that spread interactively on the hydroxylated surface of spherical silica particles. Therefore, a nanostructured composite of amorphous nanoparticles of iron oxide (as a shell) spreading on the surface of silica particles (as a core) was formed. This morphology limited the aggregation of Fe2O3 nanoparticles, prevented silica particle coalescence at high temperatures, and enhanced thermal stability.

  3. Nitrate reductase from Rhodopseudomonas sphaeroides.

    PubMed Central

    Kerber, N L; Cardenas, J

    1982-01-01

    The facultative phototroph Rhodopseudomonas sphaeroides DSM158 was incapable of either assimilating or dissimilating nitrate, although the organism could reduce it enzymatically to nitrite either anaerobically in the light or aerobically in the dark. Reduction of nitrate was mediated by a nitrate reductase bound to chromatophores that could be easily solubilized and functioned with chemically reduced viologens or photochemically reduced flavins as electron donors. The enzyme was solubilized, and some of its kinetic and molecular parameters were determined. It seemed to be nonadaptive, ammonia did not repress its synthesis, and its activity underwent a rapid decline when the cells entered the stationary growth phase. Studies with inhibitors and with metal antagonists indicated that molybdenum and possibly iron participate in the enzymatic reduction of nitrate. The conjectural significance of this nitrate reductase in phototrophic bacteria is discussed. PMID:6978883

  4. Characterization by electron paramagnetic resonance of the role of the Escherichia coli nitrate reductase (NarGHI) iron-sulfur clusters in electron transfer to nitrate and identification of a semiquinone radical intermediate.

    PubMed Central

    Magalon, A; Rothery, R A; Giordano, G; Blasco, F; Weiner, J H

    1997-01-01

    We have used Escherichia coli cytoplasmic membrane preparations enriched in wild-type and mutant (NarH-C16A and NarH-C263A) nitrate reductase (NarGHI) to study the role of the [Fe-S] clusters of this enzyme in electron transfer from quinol to nitrate. The spectrum of dithionite-reduced membrane bound NarGHI has major features comprising peaks at g = 2.04 and g = 1.98, a peak-trough at g = 1.95, and a trough at g = 1.87. The oxidized spectrum of NarGHI in membranes comprises an axial [3Fe-4S] cluster spectrum with a peak at g = 2.02 (g(z)) and a peak-trough at g = 1.99 (g(xy)). We have shown that in two site-directed mutants of NarGHI which lack the highest potential [4Fe-4S] cluster (B. Guigliarelli, A. Magalon, P. Asso, P. Bertrand, C. Frixon, G. Giordano, and F. Blasco, Biochemistry 35:4828-4836, 1996), NarH-C16A and NarH-C263A, oxidation of the NarH [Fe-S] clusters is inhibited compared to the wild type. During enzyme turnover in the mutant enzymes, a distinct 2-n-heptyl-4-hydroxyquinoline-N-oxide-sensitive semiquinone radical species which may be located between the hemes of NarI and the [Fe-S] clusters of NarH is observed. Overall, these studies indicate (i) the importance of the highest-potential [4Fe-4S] cluster in electron transfer from NarH to the molybdenum cofactor of NarG and (ii) that a semiquinone radical species is an important intermediate in electron transfer from quinol to nitrate. PMID:9260944

  5. Iron(III) complexes of 2-(1H-benzo[d]imidazol-2-yl)phenol and acetate or nitrate as catalysts for epoxidation of olefins with hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Dutta, Amit Kumar; Samanta, Suvendu; Dutta, Supriya; Lucas, C. Robert; Dawe, Louise N.; Biswas, Papu; Adhikary, Bibhutosh

    2016-07-01

    Cheap and environmentally friendly Fe(III) catalysts [Fe(L)2(CH3COO)] (1) and [Fe(L)2(NO3)]·2CH3OH (2) where HL = 2-(1H-benzo[d]imidazol-2-yl)phenol for epoxidation of olefins have been developed. The catalysts have been characterized by elemental analyses, IR, UV-Vis spectroscopy and by X-ray crystallography. The X-ray structures reveal mononuclear compounds having a bidentate acetate or nitrate in 1 and 2, respectively. Catalytic epoxidations of styrene and cyclohexene have been carried out homogeneously by using 30% aqueous hydrogen peroxide in acetonitrile in the presence of catalytic amounts of 1 or 2. Yields of the respective epoxides were fair (1) to good (2) and selectivities were good in all cases although 2 produced two to three times the yield, depending on the substrate, than 1 and higher selectivity as well. A hypothesis for these differences in catalytic efficacy between 1 and 2 that is consistent with mechanistic details of related enzymatic and biomimetic model systems is proposed. Herein we report [Fe(L)2(NO3)]·2CH3OH (2) as the first structurally characterized non-heme iron epoxidation catalyst with a bidentate nitrate ligand.

  6. Insensitive Ammonium Nitrate.

    DTIC Science & Technology

    is reduced by replacing the ammonium nitrate with a solid solution of potassium nitrate in form III ammonium nitrate wherein the potassium nitrate...constitutes from more than zero to less than 50 weight percent of the solid solution . (Author)

  7. Cloning and sequence of cymA, a gene encoding a tetraheme cytochrome c required for reduction of iron(III), fumarate, and nitrate by Shewanella putrefaciens MR-1.

    PubMed Central

    Myers, C R; Myers, J M

    1997-01-01

    The cymA gene, which encodes a tetraheme cytochrome c, was cloned from Shewanella putrefaciens MR-1. This gene complemented a mutant which had a TnphoA insertion in cymA and which was deficient in the respiratory reduction of iron(III), nitrate, fumarate, and manganese(IV). The 561-bp nucleotide sequence of cymA encodes a protein of 187 amino acids with a predicted molecular mass of 20.8 kDa. No N-terminal signal sequence was readily apparent; consistent with this, a cytochrome with a size of 21 kDa was detected in the wild type but was absent in the insertional mutant. The cymA gene is transcribed into an mRNA; the major transcript was approximately 790 bases, suggesting that it is not part of a multicistronic operon. This RNA transcript was not detected in the cymA mutant. The CymA protein was found in the cytoplasmic membrane and soluble fraction of MR-1, and it shares partial amino acid sequence homology with multiheme c-type cytochromes from other bacteria. These cytochromes are ostensibly involved in the transfer of electrons from the cytoplasmic membrane to acceptors in the periplasm. The localization of the fumarate and iron(III) reductases to the periplasm and outer membrane of MR-1, respectively, suggests the possibility of a similar electron transfer role for CymA. PMID:9023196

  8. Draft Genome Sequence of Ardenticatena maritima 110S, a Thermophilic Nitrate- and Iron-Reducing Member of the Chloroflexi Class Ardenticatenia

    PubMed Central

    Ward, Lewis M.; Pace, Laura A.; Fischer, Woodward W.

    2015-01-01

    We report here the draft genome sequence of Ardenticatena maritima 110S, the first sequenced member of class Ardenticatenia of the phylum Chloroflexi. This thermophilic organism is capable of a range of physiologies, including aerobic respiration and iron reduction. It also encodes a complete denitrification pathway with a novel nitric oxide reductase. PMID:26586887

  9. PREPARATION AND PROPERTIES OF SOME HYDROCARBON SOLUBLE CERIUM AND IRON COMPOUNDS

    DTIC Science & Technology

    REACTIONS, COMPLEX COMPOUNDS, HYDROCARBONS, INFRARED SPECTROSCOPY, IRON COMPOUNDS, LUMINESCENCE, MOLECULAR STRUCTURE, NITRATES, OXIDATION REDUCTION REACTIONS, SODIUM, SOLUBILITY, STABILIZATION, SYNTHESIS , TOLUENES.

  10. Characterization of toluene and ethylbenzene biodegradation under nitrate-, iron(III)- and manganese(IV)-reducing conditions by compound-specific isotope analysis.

    PubMed

    Dorer, Conrad; Vogt, Carsten; Neu, Thomas R; Stryhanyuk, Hryhoriy; Richnow, Hans-Hermann

    2016-04-01

    Ethylbenzene and toluene degradation under nitrate-, Mn(IV)-, or Fe(III)-reducing conditions was investigated by compound specific stable isotope analysis (CSIA) using three model cultures (Aromatoleum aromaticum EbN1, Georgfuchsia toluolica G5G6, and a Azoarcus-dominated mixed culture). Systematically lower isotope enrichment factors for carbon and hydrogen were observed for particulate Mn(IV). The increasing diffusion distances of toluene or ethylbenzene to the solid Mn(IV) most likely caused limited bioavailability and hence resulted in the observed masking effect. The data suggests further ethylbenzene hydroxylation by ethylbenzene dehydrogenase (EBDH) and toluene activation by benzylsuccinate synthase (BSS) as initial activation steps. Notably, significantly different values in dual isotope analysis were detected for toluene degradation by G. toluolica under the three studied redox conditions, suggesting variations in the enzymatic transition state depending on the available TEA. The results indicate that two-dimensional CSIA has significant potential to assess anaerobic biodegradation of ethylbenzene and toluene at contaminated sites.

  11. Effects of structure of nitrator on nitration reaction

    SciTech Connect

    Shiying, Yin; Benli, Yin

    1995-12-01

    It is well-known that nitration of dinitrotoluene (DNT) proceeds quite slowly. Unsatisfactory structure of nitrator could cause an incomplete nitration in the nitrator, and nitration continues in the separator. This, in turn, increases the temperature difference between nitrator and separator. It was found that the nitration degree of DNT in nitrator could be estimated by this temperature difference. We investigated the relationship between the nitrator`s structure and the above temperature difference, and based on the research results obtained we could make nitration complete in nitrator, improve the quality of trinitrotoluene (TNT), lower the consumption of raw materials, especially sulfuric acid, and increase the safety of production.

  12. Alkali metal nitrate purification

    DOEpatents

    Fiorucci, Louis C.; Morgan, Michael J.

    1986-02-04

    A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of purified alkali metal nitrates.

  13. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate and potassium nitrate. 181.33... nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued... potassium nitrite, in the production of cured red meat products and cured poultry products. ...

  14. The iron-oxidizing proteobacteria.

    PubMed

    Hedrich, Sabrina; Schlömann, Michael; Johnson, D Barrie

    2011-06-01

    The 'iron bacteria' are a collection of morphologically and phylogenetically heterogeneous prokaryotes. They include some of the first micro-organisms to be observed and described, and continue to be the subject of a considerable body of fundamental and applied microbiological research. While species of iron-oxidizing bacteria can be found in many different phyla, most are affiliated with the Proteobacteria. The latter can be subdivided into four main physiological groups: (i) acidophilic, aerobic iron oxidizers; (ii) neutrophilic, aerobic iron oxidizers; (iii) neutrophilic, anaerobic (nitrate-dependent) iron oxidizers; and (iv) anaerobic photosynthetic iron oxidizers. Some species (mostly acidophiles) can reduce ferric iron as well as oxidize ferrous iron, depending on prevailing environmental conditions. This review describes what is currently known about the phylogenetic and physiological diversity of the iron-oxidizing proteobacteria, their significance in the environment (on the global and micro scales), and their increasing importance in biotechnology.

  15. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  16. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  17. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  18. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  19. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

  20. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

  1. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

  2. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium... nitrite, with or without sodium or potassium nitrite, in the production of cured red meat products and...

  3. Cylodextrin Polymer Nitrate

    NASA Technical Reports Server (NTRS)

    Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis

    2000-01-01

    The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

  4. Thermochemical nitrate destruction

    DOEpatents

    Cox, John L.; Hallen, Richard T.; Lilga, Michael A.

    1992-01-01

    A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200.degree. C. to about 600.degree. C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  5. Nitrate leaching index

    USDA-ARS?s Scientific Manuscript database

    The Nitrate Leaching Index is a rapid assessment tool that evaluates nitrate (NO3) leaching potential based on basic soil and climate information. It is the basis for many nutrient management planning efforts, but it has considerable limitations because of : 1) an oversimplification of the processes...

  6. Corrosion of aluminides by molten nitrate salt

    SciTech Connect

    Tortorelli, P.F.; Bishop, P.S.

    1990-01-01

    The corrosion of titanium-, iron-, and nickel-based aluminides by a highly aggressive, oxidizing NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} has been studied at 650{degree}C. It was shown that weight changes could be used to effectively evaluate corrosion behavior in the subject nitrate salt environments provided these data were combined with salt analyses and microstructural examinations. The studies indicated that the corrosion of relatively resistant aluminides by these nitrate salts proceeded by oxidation and a slow release from an aluminum-rich product layer into the salt at rates lower than that associated with many other types of metallic materials. The overall corrosion process and resulting rate depended on the particular aluminide being exposed. In order to minimize corrosion of nickel or iron aluminides, it was necessary to have aluminum concentrations in excess of 30 at. %. However, even at a concentration of 50 at. % Al, the corrosion resistance of TiAl was inferior to that of Ni{sub 3}Al and Fe{sub 3}Al. At higher aluminum concentrations, iron, nickel, and iron-nickel aluminides exhibited quite similar weight changes, indicative of the principal role of aluminum in controlling the corrosion process in NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} salts. 20 refs., 5 figs., 3 tabs.

  7. Thermochemical nitrate destruction

    DOEpatents

    Cox, J.L.; Hallen, R.T.; Lilga, M.A.

    1992-06-02

    A method is disclosed for denitrification of nitrates and nitrites present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200 C to about 600 C, and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

  8. The Chilean nitrate deposits.

    USGS Publications Warehouse

    Ericksen, G.E.

    1983-01-01

    The nitrate deposits in the arid Atacama desert of northern Chile consist of saline-cemented surficial material, apparently formed in and near a playa lake that formerly covered the area. Many features of their distribution and chemical composition are unique. The author believes the principal sources of the saline constituents were the volcanic rocks of late Tertiary and Quaternary age in the Andes and that the nitrate is of organic origin. Possible sources of the nitrate, iodate, perchlorate and chromate are discussed. -J.J.Robertson

  9. Bioactivation of organic nitrates and the mechanism of nitrate tolerance.

    PubMed

    Klemenska, Emila; Beresewicz, Andrzej

    2009-01-01

    Organic nitrates, such as nitroglycerin, are commonly used in the therapy of cardiovascular disease. Long-term therapy with these drugs, however, results in the rapid development of nitrate tolerance, limiting their hemodynamic and anti-ischemic efficacy. In addition, nitrate tolerance is associated with the expression of potentially deleterious modifications such as increased oxidative stress, endothelial dysfunction, and sympathetic activation. In this review we discuss current concepts regarding the mechanisms of organic nitrate bioactivation, nitrate tolerance, and nitrate-mediated oxidative stress and endothelial dysfunction. We also examine how hydralazine may prevent nitrate tolerance and related endothelial dysfunction.

  10. Determination of intracellular nitrate.

    PubMed Central

    Romero, J M; Lara, C; Guerrero, M G

    1989-01-01

    A sensitive procedure has been developed for the determination of intracellular nitrate. The method includes: (i) preparation of cell lysates in 2 M-H3PO4 after separation of cells from the outer medium by rapid centrifugation through a layer of silicone oil, and (ii) subsequent nitrate analysis by ion-exchange h.p.l.c. with, as mobile phase, a solution containing 50 mM-H3PO4 and 2% (v/v) tetrahydrofuran, adjusted to pH 1.9 with NaOH. The determination of nitrate is subjected to interference by chloride and sulphate when present in the samples at high concentrations. Nitrite also interferes, but it is easily eliminated by treatment of the samples with sulphamic acid. The method has been successfully applied to the study of nitrate transport in the unicellular cyanobacterium Anacystis nidulans. PMID:2497740

  11. How iron controls iron.

    PubMed

    Kühn, Lukas C

    2009-12-01

    Cells regulate iron homeostasis by posttranscriptional regulation of proteins responsible for iron uptake and storage. This requires RNA-binding activity of iron-regulatory proteins, IRP1 and IRP2. Two studies recently published in Science by Vashisht et al. (2009) and Salahudeen et al. (2009) reveal how cells adjust IRP2 activity.

  12. Reactivity of Metal Nitrates.

    DTIC Science & Technology

    1982-07-20

    amines, where nitration would not be a competing process. Acetanilide . Despite the complexity encountered with aniline, the corresponding amide... acetanilide , though having an N-hydrogen atom, was nitrated without tar formation, although this was not accomplished efficiently. After reaction for 24 h... acetanilide , in the absence of a N-hydrogen atom. However, the reverse proved to be the case, for after one day at room temperature nearly 60% of starting

  13. Protein tyrosine nitration

    PubMed Central

    Chaki, Mounira; Leterrier, Marina; Barroso, Juan B

    2009-01-01

    Nitric oxide metabolism in plant cells has a relative short history. Nitration is a chemical process which consists of introducing a nitro group (-NO2) into a chemical compound. in biological systems, this process has been found in different molecules such as proteins, lipids and nucleic acids that can affect its function. This mini-review offers an overview of this process with special emphasis on protein tyrosine nitration in plants and its involvement in the process of nitrosative stress. PMID:19826215

  14. Thermochemical nitrate reduction

    SciTech Connect

    Cox, J.L.; Lilga, M.A.; Hallen, R.T.

    1992-09-01

    A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with {approximately}3 wt% NO{sub 3}{sup {minus}} solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200{degrees}C to 350{degrees}C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia {approx} methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics.

  15. Pumping Iron and Silica Bodybuilding

    NASA Astrophysics Data System (ADS)

    Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

    2016-02-01

    The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

  16. Nitrate behavior in ground water of the southeastern USA

    SciTech Connect

    Nolan, B.T.

    1999-10-01

    Principal components analysis (PCA) was performed with water-quality data from studies conducted during 1993 to 1995 to explore potential nitrate-attenuation processes in ground waters of the southeastern USA. Nitrate reduction is an important attenuation process in selected areas of the Southeast. A nitrate-reduction component explains 23% of the total variance in the data and indicates that nitrate and dissolved oxygen (DO) are inversely related to ammonium, iron, manganese, and dissolved organic carbon (DOC). Additional components extracted by PCA include calcite dissolution (18% of variance explained) and phosphate dissolution (9% of variance explained). Reducing conditions in ground waters of the region influence nitrate behavior through bacterially mediated reduction in the presence of organic matter, and by inhibition of nitrate formation in anoxic ground water beneath forested areas. Component scores are consistent with observed water-quality conditions in the region. For example, median nitrate concentration in ground-water samples from the Albemarle-Pamlico Drainage Basin (ALBE) Coastal Plain is {lt}0.05 mg L{sup {minus}1}, median DOC concentration is 4.2 mg L{sup {minus}1}, and median DO concentration is 2.1 mg L{sup {minus}1}, consistent with denitrification. Nitrate reduction does not occur uniformly throughout the Southeast. Median DO concentrations in ground-water samples from the Apalachicola-Chattahoochee-Flint River Basin (ACFB) are 6.2 to 7.1 mg L{sup {minus}1}, and median nitrate concentrations are 0.61 to 2.2 mg L{sup {minus}1}, inconsistent with denitrification. Similarly, median DO concentration in samples from the Georgia-Florida Coastal Plain (GAFL) is 6.0 mg L{sup {minus}1} and median nitrate concentration is 5.8 mg L{sup {minus}1}.

  17. TREATMENT OF 1,2-DIBROMO-3-CHLOROPROPANE AND NITRATE-CONTAMINATED WATER WITH ZERO-VALENT IRON OR HYDROGEN/PALLADIUM CATALYSTS. (R825689C054,R825689C078)

    EPA Science Inventory

    Abstract

    The abilities of zero-valent iron powder and hydrogen with a palladium catalyst (H2/Pd-alumina) to hydrodehalogenate 1,2-dibromo-3-chloropropane (DBCP) to propane under water treatment conditions (ambient temperature and circumneutral pH) were compa...

  18. Iron Chelation

    MedlinePlus

    ... iron overload and need treatment. What is iron overload? Iron chelation therapy is used when you have ... may want to perform: How quickly does iron overload happen? This is different for each person. It ...

  19. Bioremediation of nitrated organics

    SciTech Connect

    Stafford, D.A.; Lappin-Scott, H.; Jass, J.

    1994-12-31

    In the manufacture of nitrated aromatic and heterocyclic compounds intermediates are produced as well as the final products, e.g. TNT (trinitrotoluene), and RDX (cyclotri-methylene trinitramine). The red water produced is a dilute effluent containing TNT and other nitrated intermediates. Many of the intermediates are also to be found in contaminated land areas as well as the primary manufacturing products as contaminants in ground adjacent to production and storage areas. Two intermediates included as by-products are p-nitrophenol and resorcinol; both are hydroxylated aromatics and one (the former) is also nitrated. If these rings can be hydroxylated and oxidized by pure or mixed microbial cultures then the notion of using microbes for the detoxification of a wide range of nitrated aromatics and heterocyclics is possible. It is proposed in the study to accelerate this degradative process in the first instance for p-nitrophenol and resorcinol, and secondly for TNT and RDX. The use of microbes to degrade nitroaromatic compounds such as nitrobenzenes, and mono-nitro phenols, have been described. In order to determine how aromatic degrading bacteria can also degrade substituted and nitrated aromatics several pure and mixed cultures have been utilized to demonstrate enzyme adaptation.

  20. Nitrate in groundwater of the United States, 1991-2003

    USGS Publications Warehouse

    Burow, Karen R.; Nolan, Bernard T.; Rupert, Michael G.; Dubrovsky, Neil M.

    2010-01-01

    An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program. The well networks reflect the existing used resource represented by domestic wells in major aquifers (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations were highest in shallow groundwater beneath agricultural land use in areas with well-drained soils and oxic geochemical conditions. Nitrate concentrations were lowest in deep groundwater where groundwater is reduced, or where groundwater is older and hence concentrations reflect historically low N application rates. Classification and regression tree analysis was used to identify the relative importance of N inputs, biogeochemical processes, and physical aquifer properties in explaining nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm N fertilizer inputs, percent well-drained soils, and dissolved oxygen. Overall, nitrate concentrations in groundwater are most significantly affected by redox conditions, followed by nonpoint-source N inputs. Other water-quality indicators and physical variables had a secondary influence on nitrate concentrations.

  1. Nitrates and Nitrites TNC Presentation

    EPA Pesticide Factsheets

    The Nitrates and Nitrites Presentation gives an overview of nitrates and nitrites in drinking water, why it is important to monitor them and what to do in cases where the results exceed the maximum contaminant level (MCL).

  2. Nitrate Leaching Management

    USDA-ARS?s Scientific Manuscript database

    Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site’s hydrologic cycle, avoiding excess ...

  3. Draft Genome Sequence of a Potential Nitrate-Dependent Fe(II)-Oxidizing Bacterium, Aquabacterium parvum B6

    PubMed Central

    Zhang, Xiaoxin

    2016-01-01

    Aquabacterium parvum B6 is a potential nitrate-dependent Fe(II)-oxidizing bacterium. The genes related to its denitrifying mechanism and iron metabolisms were unknown. We present the draft genome of Aquabacterium parvum B6, which could provide further insight into the nitrate-dependent Fe(II)-oxidizing mechanism of strain B6. PMID:26823591

  4. Draft Genome Sequence of a Potential Nitrate-Dependent Fe(II)-Oxidizing Bacterium, Aquabacterium parvum B6.

    PubMed

    Zhang, Xiaoxin; Ma, Fang; Szewzyk, Ulrich

    2016-01-28

    Aquabacterium parvum B6 is a potential nitrate-dependent Fe(II)-oxidizing bacterium. The genes related to its denitrifying mechanism and iron metabolisms were unknown. We present the draft genome of Aquabacterium parvum B6, which could provide further insight into the nitrate-dependent Fe(II)-oxidizing mechanism of strain B6. Copyright © 2016 Zhang et al.

  5. Purification of alkali metal nitrates

    DOEpatents

    Fiorucci, Louis C.; Gregory, Kevin M.

    1985-05-14

    A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

  6. Ammonium nitrate explosive systems

    DOEpatents

    Stinecipher, Mary M.; Coburn, Michael D.

    1981-01-01

    Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

  7. Nitrate Storage and Dissimilatory Nitrate Reduction by Eukaryotic Microbes

    PubMed Central

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils; Stief, Peter

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described. A first compilation of intracellular nitrate inventories in various marine sediments is presented, indicating that intracellular nitrate pools vastly exceed porewater nitrate pools. The relative contribution by foraminifers to total sedimentary denitrification is estimated for different marine settings, suggesting that eukaryotes may rival prokaryotes in terms of dissimilatory nitrate reduction. Finally, this review article sketches some evolutionary perspectives of eukaryotic nitrate metabolism and identifies open questions that need to be addressed in future investigations. PMID:26734001

  8. Iron Test

    MedlinePlus

    ... are used together to detect and help diagnose iron deficiency or iron overload. In people with anemia , these ... help determine whether the condition is due to iron deficiency or another cause, such as chronic blood loss ...

  9. Presence of nitrate NO 3 a ects animal production, photocalysis is a possible solution

    NASA Astrophysics Data System (ADS)

    Barba-Molina, Heli; Barba-Ortega, J.; Joya, M. R.

    2016-02-01

    Farmers and ranchers depend on the successful combination of livestock and crops. However, they have lost in the production by nitrate pollution. Nitrate poisoning in cattle is caused by the consumption of an excessive amount of nitrate or nitrite from grazing or water. Both humans and livestock can be affected. It would appear that well fertilised pasture seems to take up nitrogen from the soil and store it as nitrate in the leaf. Climatic conditions, favour the uptake of nitrate. Nitrate poisoning is a noninfectious disease condition that affects domestic ruminants. It is a serious problem, often resulting in the death of many animals. When nitrogen fertilizers are used to enrich soils, nitrates may be carried by rain, irrigation and other surface waters through the soil into ground water. Human and animal wastes can also contribute to nitrate contamination of ground water. A possible method to decontaminate polluted water by nitrates is with methods of fabrication of zero valent iron nanoparticles (FeNps) are found to affect their efficiency in nitrate removal from water.

  10. Assimilatory nitrate reductase from the green alga Ankistrodesmus braunii.

    PubMed

    De la Rosa, M A

    1983-01-01

    Assimilatory nitrate reductase (NAD(P)H-nitrate oxidoreductase, EC 1.6.6.2) from the green alga Ankistrodesmus braunii can be purified to homogeneity by dye-ligand chromatography on blue-Sepharose. The purified enzyme, whose turnover number is 623 s-1, presents an optimum pH of 7.5 and Km values of 13 microM, 23 microM and 0.15 mM for NADH, NADPH and nitrate, respectively. The NADH-nitrate reductase activity exhibits an iso ping pong bi bi kinetic mechanism. The molecular weight of the native nitrate reductase is 467 400, while that of its subunits is 58 750. These values suggest an octameric structure for the enzyme, which has been confirmed by electron microscopy. As deduced from spectrophotometric and fluorimetric studies, the enzyme contains FAD and cytochrome b-557 as prosthetic groups. FAD is not covalently bound to the protein and is easily dissociated in diluted solutions from the enzyme. Its apparent Km value is 4 nM, indicative of a high affinity of the enzyme for FAD. The results of the quantitative analyses of prosthetic groups indicate that nitrate reductase contains four molecules of flavin, four heme irons, and two atoms of molybdenum. The three components act sequentially transferring electrons from reduced pyridine nucleotides to nitrate, thus forming a short electron transport chain along the protein. A mechanism is proposed for the redox interconversion of the nitrate reductase activity. Inactivation seems to occur by formation of a stable complex of reduced enzyme with cyanide or superoxide, while reactivation is a consequence of reoxidation of the inactive enzyme. Both reactions imply the transfer of only one electron.

  11. Surviving a High Nutrient-Low Chlorophyll (HNLC) region: insights to the internal cycling of nitrogen and iron in the eastern equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Rafter, P. A.; Mackey, K. R.; Rykaczewski, R. R.; Sigman, D. M.

    2016-02-01

    The marine nutrient nitrate is completely utilized in much of the global surface ocean, but persists in so-called High-Nutrient, Low chlorophyll (HNLC) regions where primary production is limited by iron. Accordingly, the addition of iron to equatorial Pacific HNLC waters increases nitrate utilization and therefore decreases nitrate concentrations [NO3-]. However, seasonal variability in HNLC surface [NO3-] occurs alongside changes in upper ocean upwelling and stratification despite little seasonality in the flux of iron. Here we use nitrate isotopes (δ15N and δ18O) to show that seasonal variability of eastern equatorial Pacific HNLC surface [NO3-] is caused by changes in the degree of nitrate utilization that cannot be explained by the available iron flux. The available iron can account for less than 3 μmol/kg of nitrate utilization (19% of source water [NO3-]) even though the observed nitrate drawdown ranges from 7 μmol/kg (during boreal fall when upwelling is strongest) to >11 μmol/kg (during boreal spring when upwelling is weakest). Based on these observations, we propose that the photosynthetic picoplankton (e.g., Prochlorococcus and Synechococcus) with a low iron / carbon requirement preferentially consume recycled N compounds and that much of the recycled iron fuels nitrate assimilation by larger phytoplankton (e.g., diatoms). Slower upwelling rates during boreal spring and El Niño events therefore allow for more internal cycling of iron and increased nitrate utilization, explaining the seasonal variability in surface nitrate concentrations.

  12. Assimilation of nitrate by yeasts.

    PubMed

    Siverio, José M

    2002-08-01

    Nitrate assimilation has received much attention in filamentous fungi and plants but not so much in yeasts. Recently the availability of classical genetic and molecular biology tools for the yeast Hansenula polymorpha has allowed the advance of the study of this metabolic pathway in yeasts. The genes YNT1, YNR1 and YNI1, encoding respectively nitrate transport, nitrate reductase and nitrite reductase, have been cloned, as well as two other genes encoding transcriptional regulatory factors. All these genes lie closely together in a cluster. Transcriptional regulation is the main regulatory mechanism that controls the levels of the enzymes involved in nitrate metabolism although other mechanisms may also be operative. The process involved in the sensing and signalling of the presence of nitrate in the medium is not well understood. In this article the current state of the studies of nitrate assimilation in yeasts as well as possible venues for future research are reviewed.

  13. Southern Ocean Iron Experiment (SOFex)

    SciTech Connect

    Coale, Kenneth H.

    2005-07-28

    The Southern Ocean Iron Experiment (SOFeX) was an experiment decades in the planning. It's implementation was among the most complex ship operations that SIO has been involved in. The SOFeX field expedition was successful in creating and tracking two experimentally enriched areas of the Southern Ocean, one characterized by low silicic acid, one characterized by high silicic acid. Both experimental sites were replete with abundant nitrate. About 100 scientists were involved overall. The major findings of this study were significant in several ways: (1) The productivity of the southern ocean is limited by iron availability. (2) Carbon uptake and flux is therefore controlled by iron availability (3) In spite of low silicic acid, iron promotes non-silicious phytoplankton growth and the uptake of carbon dioxide. (4) The transport of fixed carbon from the surface layers proceeds with a C:N ratio that would indicate differential remineralization of nitrogen at shallow depths. (5) These finding have major implications for modeling of carbon export based on nitrate utilization. (6) The general results of the experiment indicate that, beyond other southern ocean enrichment experiments, iron inputs have a much wider impact of productivity and carbon cycling than previously demonstrated. Scientific presentations: Coale, K., Johnson, K, Buesseler, K., 2002. The SOFeX Group. Eos. Trans. AGU 83(47) OS11A-0199. Coale, K., Johnson, K. Buesseler, K., 2002. SOFeX: Southern Ocean Iron Experiments. Overview and Experimental Design. Eos. Trans. AGU 83 (47) OS22D-01. Buesseler, K.,et al. 2002. Does Iron Fertilization Enhance Carbon Sequestration? Particle flux results from the Southern Ocean Iron Experiment. Eos. Trans. AGU 83 (47), OS22D-09. Johnson, K. et al. 2002. Open Ocean Iron Fertilization Experiments From IronEx-I through SOFeX: What We Know and What We Still Need to Understand. Eos. Trans. AGU 83 (47), OS22D-12. Coale, K. H., 2003. Carbon and Nutrient Cycling During the Southern

  14. Tubulin nitration in human gliomas.

    PubMed

    Fiore, Gabriella; Di Cristo, Carlo; Monti, Gianluca; Amoresano, Angela; Columbano, Laura; Pucci, Pietro; Cioffi, Fernando A; Di Cosmo, Anna; Palumbo, Anna; d'Ischia, Marco

    2006-02-06

    Immunohistochemical and biochemical investigations showed that significant protein nitration occurs in human gliomas, especially in grade IV glioblastomas at the level of astrocytes and oligodendrocytes and neurones. Enhanced alpha-tubulin immunoreactivity was co-present in the same elements in the glioblastomas. Proteomic methodologies were employed to identify a nitrated protein band at 55 kDa as alpha-tubulin. Peptide mass fingerprinting procedures demonstrated that tubulin is nitrated at Tyr224 in grade IV tumour samples but is unmodified in grade I samples and in non-cancerous brain tissue. These results provide the first characterisation of endogenously nitrated tubulin from human tumour samples.

  15. Nitration Studies in Oxynitrogen Systems.

    DTIC Science & Technology

    1986-08-01

    the starting pyrene quantities could be accounted for fully in the products. The pyrene nitration yielded a mixture of 1,6-, 1,8- DNP and 1,3,6...trinitropyrene, with a very small quantity of 1,3- DNP . 1-NP in contrast yielded roughly equal quantities of the 3 dinitropyrene isomers. This result clearly...20 El1-NP nitrated 10 / 1,3- DNP 1,6. DNP 1,8- DNP . 1,3,6-TNP Nitration Products JA-61 26-19 FIGURE 1 PRODUCTS OF NITRATION OF PYR ENE AND 1-NITROPYRENE

  16. Modeled Wet Nitrate Deposition

    EPA Pesticide Factsheets

    Modeled data on nitrate wet deposition was obtained from Dr. Jeff Grimm at Penn State Univ. Nitrate wet depostion causes acidification and eutrophication of surface water bodies. See below regarding decriptions on how original data was produced. These data will be part of future ReVA publications. The first, https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip, contains the variables used in this study (of which AGSL is one) and is freely available to the public. The second, www.waratah.com/region3edt is available to the general public to learn more about the ReVA program within EPA Region 3. The third, http://www.waratah.com/revanew/Welcome.asp, provides additional information about the tools and variables used in this program, but users must first obtain a user name and password to access it. A user name and password may be obtained from Vasu Kilaru at kilaru.vasu@epa.gov.

  17. Analytical Chemistry and Materials Characterization Results for Debris Recovered from Nitrate Salt Waste Drum S855793

    SciTech Connect

    Martinez, Patrick Thomas; Chamberlin, Rebecca M.; Schwartz, Daniel S.; Worley, Christopher Gordon; Garduno, Katherine; Lujan, Elmer J. W.; Borrego, Andres Patricio; Castro, Alonso; Colletti, Lisa Michelle; Fulwyler, James Brent; Holland, Charlotte S.; Keller, Russell C.; Klundt, Dylan James; Martinez, Alexander; Martin, Frances Louise; Montoya, Dennis Patrick; Myers, Steven Charles; Porterfield, Donivan R.; Schake, Ann Rene; Schappert, Michael Francis; Soderberg, Constance B.; Spencer, Khalil J.; Stanley, Floyd E.; Thomas, Mariam R.; Townsend, Lisa Ellen; Xu, Ning

    2015-09-16

    Solid debris was recovered from the previously-emptied nitrate salt waste drum S855793. The bulk sample was nondestructively assayed for radionuclides in its as-received condition. Three monoliths were selected for further characterization. Two of the monoliths, designated Specimen 1 and 3, consisted primarily of sodium nitrate and lead nitrate, with smaller amounts of lead nitrate oxalate and lead oxide by powder x-ray diffraction. The third monolith, Specimen 2, had a complex composition; lead carbonate was identified as the predominant component, and smaller amounts of nitrate, nitrite and carbonate salts of lead, magnesium and sodium were also identified. Microfocused x-ray fluorescence (MXRF) mapping showed that lead was ubiquitous throughout the cross-sections of Specimens 1 and 2, while heteroelements such as potassium, calcium, chromium, iron, and nickel were found in localized deposits. MXRF examination and destructive analysis of fragments of Specimen 3 showed elevated concentrations of iron, which were broadly distributed through the sample. With the exception of its high iron content and low carbon content, the chemical composition of Specimen 3 was within the ranges of values previously observed in four other nitrate salt samples recovered from emptied waste drums.

  18. Iron-stimulated toxin production in Microcystis aeruginosa.

    PubMed Central

    Utkilen, H; Gjølme, N

    1995-01-01

    Nitrate- and phosphate-limited conditions had no effect on toxin production by Microcystis aeruginosa. In contrast, iron-limited conditions influenced toxin production by M. aeruginosa, and iron uptake was light dependent. A model for production of toxin by M. aeruginosa is proposed. PMID:7574617

  19. Nitrate reduction in water by aluminum alloys particles.

    PubMed

    Bao, Zunsheng; Hu, Qing; Qi, Weikang; Tang, Yang; Wang, Wei; Wan, Pingyu; Chao, Jingbo; Yang, Xiao Jin

    2017-07-01

    Nano zero-valent iron (NZVI) particles have been extensively investigated for nitrate reduction in water. However, the reduction by NZVI requires acidic pH conditions and the final product is exclusively ammonium, leading to secondary contamination. In addition, nanomaterials have potential threats to environment and the transport and storage of nanomaterials are of safety concerns. Aluminum, the most abundant metal element in the earth's crust, is able to reduce nitrate, but the passivation of aluminum limits its application. Here we report Al alloys (85% Al) with Fe, Cu or Si for aqueous nitrate reduction. The Al alloys particles of 0.85-0.08 mm were inactivate under ambient conditions and a simple treatment with warm water (45 °C) quickly activated the alloy particles for rapid reduction of nitrate. The Al-Fe alloy particles at a dosage of 5 g/L rapidly reduced 50 mg-N/L nitrate at a reaction rate constant (k) of 3.2 ± 0.1 (mg-N/L)(1.5)/min between pH 5-6 and at 4.0 ± 0.1 (mg-N/L)(1.5)/min between pH 9-11. Dopping Cu in the Al-Fe alloy enhanced the rates of reduction whereas dopping Si reduced the reactivity of the Al-Fe alloy. The Al alloys converted nitrate to 20% nitrogen and 80% ammonium. Al in the alloy particles provided electrons for the reduction and the intermetallic compounds in the alloys were likely to catalyze nitrate reduction to nitrogen. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Aniline-induced nitrosative stress in rat spleen: Proteomic identification of nitrated proteins

    SciTech Connect

    Fan Xiuzhen; Wang Jianling; Soman, Kizhake V.; Ansari, G.A.S.; Khan, M. Firoze

    2011-08-15

    Aniline exposure is associated with toxicity to the spleen which is characterized by splenomegaly, hyperplasia, fibrosis, and a variety of sarcomas on chronic exposure in rats. However, mechanisms by which aniline elicits splenotoxic responses are not well understood. Earlier we have shown that aniline exposure leads to increased nitration of proteins in the spleen. However, nitrated proteins remain to be characterized. Therefore, in the current study using proteomic approaches, we focused on characterizing the nitrated proteins in the spleen of aniline-exposed rats. Aniline exposure led to increased tyrosine nitration of proteins, as determined by 2D Western blotting with anti-3-nitrotyrosine specific antibody, compared to the controls. The analyzed nitrated proteins were found in the molecular weight range of 27.7 to 123.6 kDa. A total of 37 nitrated proteins were identified in aniline-treated and control spleens. Among them, 25 were found only in aniline-treated rats, 11 were present in both aniline-treated and control rats, while one was found in controls only. The nitrated proteins identified mainly represent skeletal proteins, chaperones, ferric iron transporter, enzymes, nucleic acids binding protein, and signaling and protein synthesis pathways. Furthermore, aniline exposure led to significantly increased iNOS mRNA and protein expression in the spleen, suggesting its role in increased reactive nitrogen species formation and contribution to increased nitrated proteins. The identified nitrated proteins provide a global map to further investigate alterations in their structural and functional properties, which will lead to a better understanding of the role of protein nitration in aniline-mediated splenic toxicity. - Highlights: > Proteomic approaches are used to identify nitrated proteins in the spleen. > Twenty five nitrated proteins were found only in the spleen of aniline-treated rats. > Aniline exposure led to increased iNOS mRNA and protein expression in

  1. TREATMENT OF AMMONIUM NITRATE SOLUTIONS

    DOEpatents

    Boyer, T.W.; MacHutchin, J.G.; Yaffe, L.

    1958-06-10

    The treatment of waste solutions obtained in the processing of neutron- irradiated uranium containing fission products and ammonium nitrate is described. The object of this process is to provide a method whereby the ammonium nitrate is destroyed and removed from the solution so as to permit subsequent concentration of the solution.. In accordance with the process the residual nitrate solutions are treated with an excess of alkyl acid anhydride, such as acetic anhydride. Preferably, the residual nitrate solution is added to an excess of the acetic anhydride at such a rate that external heat is not required. The result of this operation is that the ammonium nitrate and acetic anhydride react to form N/sub 2/ O and acetic acid.

  2. Some History of Nitrates

    NASA Astrophysics Data System (ADS)

    Barnum, Dennis W.

    2003-12-01

    The history of saltpeter is an interesting combination of chemistry, world trade, technology, politics, and warfare. Originally it was obtained from the dirt floors of stables, sheep pens, pigeon houses, caverns, and even peasants' cottages; any place manure and refuse accumulated in soil under dry conditions. When these sources became inadequate to meet demand it was manufactured on saltpeter plantations, located in dry climates, where piles of dirt, limestone, and manure were allowed to stand for three to five years while soil microbes oxidized the nitrogen to nitrate—an example of early bioengineering. Extensive deposits of sodium nitrate were mined in the Atacama Desert in northern Chile from 1830 until the mid 1920s when the mines were displaced by the Haber Ostwald process.

  3. Nitrate transport system in Neurospora crassa.

    PubMed

    Schloemen, R H; Garrett, R H

    1974-04-01

    Nitrate uptake in Neurospora crassa has been investigated under various conditions of nitrogen nutrition by measuring the rate of disappearance of nitrate from the medium and by determining mycelial nitrate accumulation. The nitrate transport system is induced by either nitrate or nitrite, but is not present in mycelia grown on ammonia or Casamino Acids. The appearance of nitrate uptake activity is prevented by cycloheximide, puromycin, or 6-methyl purine. The induced nitrate transport system displays a K(m) for nitrate of 0.25 mM. Nitrate uptake is inhibited by metabolic poisons such as 2,4-dinitrophenol, cyanide, and antimycin A. Furthermore, mycelia can concentrate nitrate 50-fold. Ammonia and nitrite are non-competitive inhibitors with respect to nitrate, with K(i) values of 0.13 and 0.17 mM, respectively. Ammonia does not repress the formation of the nitrate transport system. In contrast, the nitrate uptake system is repressed by Casamino Acids. All amino acids individually prevent nitrate accumulation, with the exception of methionine, glutamine, and alanine. The influence of nitrate reduction and the nitrate reductase protein on nitrate transport was investigated in wild-type Neurospora lacking a functional nitrate reductase and in nitrate non-utilizing mutants, nit-1, nit-2, and nit-3. These mycelia contain an inducible nitrate transport system which displays the same characteristics as those found in the wild-type mycelia having the functional nitrate reductase. These findings suggest that nitrate transport is not dependent upon nitrate reduction and that these two processes are separate events in the assimilation of nitrate.

  4. Influence of Nitrate on the Hanford 100D Area In Situ Redox Manipulation Barrier Longevity

    SciTech Connect

    Szecsody, Jim E.; Phillips, Jerry L.; Vermeul, Vince R.; Fruchter, Jonathan S.; Williams, Mark D.

    2005-07-15

    The purpose of this laboratory study is to determine the influence of nitrate on the Hanford 100D Area in situ redox manipulation (ISRM) barrier longevity. There is a wide spread groundwater plume of 60 mg/L nitrate upgradient of the ISRM barrier with lower nitrate concentrations downgradient, suggestive of nitrate reduction occurring. Batch and 1-D column experiments showed that nitrate is being slowly reduced to nitrite and ammonia. These nitrate reduction reactions are predominantly abiotic, as experiments with and without bactericides present showed no difference in nitrate degradation rates. Nitrogen species transformation rates determined in experiments covered a range of ferrous iron/nitrate ratios such that the data can be used to predict rates in field scale conditions. Field scale reaction rate estimates for 100% reduced sediment (16 C) are: (a) nitrate degradation = 202 {+-} 50 h (half-life), (b) nitrite production = 850 {+-} 300 h, and (c) ammonia production = 650 {+-} 300 h. Calculation of the influence of nitrate reduction on the 100D Area reductive capacity requires consideration of mass balance and reaction rate effects. While dissolved oxygen and chromate reduction rates are rapid and essentially at equilibrium in the aquifer, nitrate transformation reactions are slow (100s of hours). In the limited (20-40 day) residence time in the ISRM barrier, only a portion of the nitrate will be reduced, whereas dissolved oxygen and chromate are reduced to completion. Assuming a groundwater flow rate of 1 ft/day, it is estimated that the ISRM barrier reductive capacity is 160 pore volumes (with no nitrate), and 85 pore volumes if 60 mg/L nitrate is present (i.e., a 47% decrease in the ISRM barrier longevity). Zones with more rapid groundwater flow will be less influenced by nitrate reduction. For example, a zone with a groundwater flow rate of 3 ft/day and 60 mg/L nitrate will have a reductive capacity of 130 pore volumes. Finally, long-term column experiments

  5. Nitrate concentrations under irrigated agriculture

    USGS Publications Warehouse

    Zaporozec, A.

    1983-01-01

    In recent years, considerable interest has been expressed in the nitrate content of water supplies. The most notable toxic effect of nitrate is infant methemoglobinemia. The risk of this disease increases significantly at nitrate-nitrogen levels exceeding 10 mg/l. For this reason, this concentration has been established as a limit for drinking water in many countries. In natural waters, nitrate is a minor ionic constituent and seldom accounts for more than a few percent of the total anions. However, nitrate in a significant concentration may occur in the vicinity of some point sources such as septic tanks, manure pits, and waste-disposal sites. Non-point sources contributing to groundwater pollution are numerous and a majority of them are related to agricultural activities. The largest single anthropogenic input of nitrate into the groundwater is fertilizer. Even though it has not been proven that nitrogen fertilizers are responsible for much of nitrate pollution, they are generally recognized as the main threat to groundwater quality, especially when inefficiently applied to irrigated fields on sandy soils. The biggest challenge facing today's agriculture is to maintain the balance between the enhancement of crop productivity and the risk of groundwater pollution. ?? 1982 Springer-Verlag New York Inc.

  6. Nitrate photolysis in salty snow

    NASA Astrophysics Data System (ADS)

    Donaldson, D. J.; Morenz, K.; Shi, Q.; Murphy, J. G.

    2016-12-01

    Nitrate photolysis from snow can have a significant impact on the oxidative capacity of the local atmosphere, but the factors affecting the release of gas phase products are not well understood. Here, we report the first systematic study of the amounts of NO, NO2, and total nitrogen oxides (NOy) emitted from illuminated snow samples as a function of both nitrate and total salt (NaCl and Instant Ocean) concentration. We show that the release of nitrogen oxides to the gas phase is directly related to the expected nitrate concentration in the brine at the surface of the snow crystals, increasing to a plateau value with increasing nitrate, and generally decreasing with increasing NaCl or Instant Ocean (I.O.). In frozen mixed nitrate (25 mM) - salt (0-500 mM) solutions, there is an increase in gas phase NO2 seen at low added salt amounts: NO2 production is enhanced by 35% at low prefreezing [NaCl] and by 70% at similar prefreezing [I.O.]. Raman microscopy of frozen nitrate-salt solutions shows evidence of stronger nitrate exclusion to the air interface in the presence of I.O. than with added NaCl. The enhancement in nitrogen oxides emission in the presence of salts may prove to be important to the atmospheric oxidative capacity in polar regions.

  7. Properties of a thermostable nitrate reductase from the hyperthermophilic archaeon Pyrobaculum aerophilum.

    PubMed

    Afshar, S; Johnson, E; de Vries, S; Schröder, I

    2001-10-01

    The nitrate reductase of the hyperthermophilic archaeon Pyrobaculum aerophilum was purified 137-fold from the cytoplasmic membrane. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, the enzyme complex consists of three subunits with apparent molecular weights of 130,000, 52,000, and 32,000. The enzyme contained molybdenum (0.8-mol/mol complex), iron (15.4-mol/mol complex) and cytochrome b (0.49-mol/mol complex) as cofactors. The P. aerophilum nitrate reductase distinguishes itself from nitrate reductases of mesophilic bacteria and archaea by its very high specific activity using reduced benzyl viologen as the electron donor (V(max) with nitrate, 1,162 s(-1) (326 U/mg); V(max) with chlorate, 1,348 s(-1) (378 U/mg) [assayed at 75 degrees C]). The K(m) values for nitrate and chlorate were 58 and 140 microM, respectively. Azide was a competitive inhibitor and cyanide was a noncompetitive inhibitor of the nitrate reductase activity. The temperature optimum for activity was > 95 degrees C. When incubated at 100 degrees C, the purified nitrate reductase had a half-life of 1.5 h. This study constitutes the first description of a nitrate reductase from a hyperthermophilic archaeon.

  8. Abiotic process for Fe(II) oxidation and green rust mineralization driven by a heterotrophic nitrate reducing bacteria (Klebsiella mobilis).

    PubMed

    Etique, Marjorie; Jorand, Frédéric P A; Zegeye, Asfaw; Grégoire, Brian; Despas, Christelle; Ruby, Christian

    2014-04-01

    Green rusts (GRs) are mixed Fe(II)-Fe(III) hydroxides with a high reactivity toward organic and inorganic pollutants. GRs can be produced from ferric reducing or ferrous oxidizing bacterial activities. In this study, we investigated the capability of Klebsiella mobilis to produce iron minerals in the presence of nitrate and ferrous iron. This bacterium is well-known to reduce nitrate using an organic carbon source as electron donor but is unable to enzymatically oxidize Fe(II) species. During incubation, GR formation occurred as a secondary iron mineral precipitating on cell surfaces, resulting from Fe(II) oxidation by nitrite produced via bacterial respiration of nitrate. For the first time, we demonstrate GR formation by indirect microbial oxidation of Fe(II) (i.e., a combination of biotic/abiotic processes). These results therefore suggest that nitrate-reducing bacteria can potentially contribute to the formation of GR in natural environments. In addition, the chemical reduction of nitrite to ammonium by GR is observed, which gradually turns the GR into the end-product goethite. The nitrogen mass-balance clearly demonstrates that the total amount of ammonium produced corresponds to the quantity of bioreduced nitrate. These findings demonstrate how the activity of nitrate-reducing bacteria in ferrous environments may provide a direct link between the biogeochemical cycles of nitrogen and iron.

  9. Nitrogen photofixation on nanostructured iron titanate films.

    PubMed

    Rusina, Olga; Linnik, Oksana; Eremenko, Anna; Kisch, Horst

    2003-01-20

    A nanostructured iron titanate thin film has been prepared by a sol-gel method from iron(III) chloride and titanium tetraisopropylate. Energy-dispersive X-ray analysis and Mössbauer spectroscopy suggest the presence of a Fe(2)Ti(2)O(7) phase, which was previously obtained as an intermediary phase upon heating ilmenite. In the presence of ethanol or humic acids and traces of oxygen, the novel film photocatalyzes the fixation of dinitrogen to ammonia (17 microM) and nitrate (45 microM). In the first observable reaction step, hydrazine is produced and then undergoes further photoreduction to ammonia. Oxidation of the latter by oxygen affords nitrate as the final product. Since the reaction occurs also in air and with visible light (lambda>455 nm), and since the iron titanate phase may be formed by the weathering of ilmenite minerals, it may be a model for mutual nonenzymatic nitrogen fixation in nature.

  10. Nitrosative Stress and Apoptosis by Intravenous Ferumoxytol, Iron Isomaltoside 1000, Iron Dextran, Iron Sucrose, and Ferric Carboxymaltose in a Nonclinical Model.

    PubMed

    Toblli, J E; Cao, G; Giani, J F; Dominici, F P; Angerosa, M

    2015-07-01

    Iron is involved in the formation as well as in the scavenging of reactive oxygen and nitrogen species. Thus, iron can induce as well as inhibit both oxidative and nitrosative stress. It also has a key role in reactive oxygen and nitrogen species-mediated apoptosis. We assessed the differences in tyrosine nitration and caspase 3 expression in the liver, heart, and kidneys of rats treated weekly with intravenous ferumoxytol, iron isomaltoside 1000, iron dextran, iron sucrose and ferric carboxymaltose (40 mg iron/kg body weight) for 5 weeks. Nitrotyrosine was quantified in tissue homogenates by Western blotting and the distribution of nitrotyrosine and caspase 3 was assessed in tissue sections by immunohistochemistry. Ferric carboxymaltose and iron sucrose administration did not result in detectable levels of nitrotyrosine or significant levels of caspase 3 vs. control in any of the tissue studied. Nitrotyrosine and caspase 3 levels were significantly (p<0.01) increased in all assessed organs of animals treated with iron dextran and iron isomaltoside 1000, as well as in the liver and kidneys of ferumoxytol-treated animals compared to isotonic saline solution (control). Nitrotyrosine and caspase 3 levels were shown to correlate positively with the amount of Prussian blue-detectable iron(III) deposits in iron dextran- and iron isomaltoside 1000-treated rats but not in ferumoxytol-treated rats, suggesting that iron dextran, iron isomaltoside 1000 and ferumoxytol induce nitrosative (and oxidative) stress as well as apoptosis via different mechanism(s).

  11. Development of hydraulic properties and nitrate turnover processes in minerotrophic fen soil on differnet scales

    NASA Astrophysics Data System (ADS)

    Kleimeier, Christian; Lennartz, Bernd

    2014-05-01

    Generally, it is recommended to remove the uppermost highly degraded peat layer from fens prior to rewetting to eliminate a potential source of organic pollutants for downstream water bodies. We investigated this material as a potential medium for denitrifying filters to further use the organic material. We are aiming to remove nitrate from tile drainage runoff at the outlet drainage dominated catchments to fullfill the requirements of the European Water Framework Directive. In a lysimeter scale long term mesocosm experiments we were aiming to reveal the peats behavior after disturbing and rewetting under constant flow conditions. Tracer experiments revealed a restructuring of the peat ending up at 20/80 percentage of mobile immobile pore volume. Additionally we observed the nitrate turnover. The turnover rate was determined by the hydraulic load. Absolute turnover rates were equal at lower and higher concentrations as well as flow rates, whereas the turnover reached higher percentages at lower concentrations. To further reveal the nitrate turnover processes flow through rector experiments were conducted in an anaerobic environment. We found that strongly reducing conditions can be created in peat even at the presence of nitrate. Thus we can conclude that the minerotrophic peat with its high iron and sulfur concentrations also enables autotrophic denitrification oxidizing iron and sulfur. While the conditions are favorable to re-reduce iron and sulfur,thus an electron shuttling system developed transporting electrons from the organic material as initial e- donor to nitrate as terminal e- acceptor.

  12. Molten nitrate salt technology development

    NASA Astrophysics Data System (ADS)

    Carling, R. W.; Kramer, C. M.; Bradshaw, R. W.; Nissen, D. A.; Goods, S. H.; Mar, R. W.; Munford, J. W.; Karnowsky, M. M.; Biefeld, R. N.; Norem, N. J.

    1981-03-01

    Of the fluids proposed for heat transfer and energy storage, molten nitrate salts offer significant economic advantages. The nitrate salt of most interest is a binary mixture of NaNO3 and KNO3. Although nitrate/nitrite mixtures were used for decades as heat transfer and heat treatment fluids the use was at temperatures of about 4500 C and lower. In solar thermal power systems the salts will experience a temperature range of 350 to 6000 C. Because central receiver applications place more rigorous demands and higher temperatures on nitrate salts a comprehensive experimental program was developed to examine what effects, if any, the new demands and temperatures have on the salts. The experiments include corrosion testing, environmental cracking of containment materials, and determinations of physical properties and decomposition mechanisms.

  13. Ammonium nitrate cold pack ingestion.

    PubMed

    Challoner, K R; McCarron, M M

    1988-01-01

    Disposable ammonium nitrate cold packs are widely used in emergency departments instead of ice bags. Five confused or suicidal patients who tore open a pack and ingested from 64 to 234 grams of ammonium nitrate in a single dose, and another patient who attempted to do so, are reported. It is known that chronic ingestion of 6 to 12 grams/day of ammonium nitrate may cause gastritis, acidosis, isosmotic diuresis, and nitrite toxicity manifesting as methemoglobinemia or vasodilatation. None of these patients developed severe toxicity, although three had symptoms of gastritis, three had slight methemoglobinemia, and two had mild hypotension. The product was removed from the stomach promptly in three of the five patients. None had pre-existing renal or intestinal dysfunction, which are known to enhance ammonium nitrate toxicity.

  14. The "silver-nitrate-oma".

    PubMed

    McBride, T J; Rand, B; Dhillon, S S

    2012-01-01

    This case report demonstrates and emphasises the unusual radiographic appearance of silver nitrate treatment in a 30-year-old patient, who subsequently underwent excision biopsy of a presumed potentially malignant lesion.

  15. Enhanced removal of nitrate from water using nZVI@MWCNTs composite: synthesis, kinetics and mechanism of reduction.

    PubMed

    Babaei, Ali Akbar; Azari, Ali; Kalantary, Roshanak Rezaei; Kakavandi, Babak

    2015-01-01

    Herein, multi-wall carbon nanotubes (MWCNTs) were used as the carrier of nano-zero valent iron (nZVI) particles to fabricate a composite known as nZVI@MWCNTs. The composite was then characterized and applied in the nitrate removal process in a batch system under anoxic conditions. The influential parameters such as pH, various concentrations of nitrate and composite were investigated within 240 min of the reaction. The mechanism, kinetics and end-products of nitrate reduction were also evaluated. Results revealed that the removal nitrate percentage for nZVI@MWCNTs composite was higher than that of nZVI and MWCNTs alone. Experimental data from nitrate reduction were fitted to the Langmuir-Hinshelwood kinetic model. The values of observed rate constant (kobs) decreased with increasing the initial concentration of nitrate. Our experiments proved that the nitrate removal efficiency was favorable once both high amounts of nZVI@MWCNTs and low concentrations of nitrate were applied. The predominant end-products of the nitrate reduction were ammonium (84%) and nitrogen gas (15%). Our findings also revealed that ZVI@MWCNTs is potentially a good composite for removal/reduction of nitrate from aqueous solutions.

  16. Effect of water quality improvement on the remediation of river sediment due to the addition of calcium nitrate.

    PubMed

    Liu, Xiaoning; Tao, Yi; Zhou, Kuiyu; Zhang, Qiqi; Chen, Guangyao; Zhang, Xihui

    2017-01-01

    In situ sediment remediation technique is commonly used to control the release of pollutants from sediment. Addition of calcium nitrate to sediment has been applied to control the release of phosphorus from sediments. In this study, laboratory experiments were conducted to investigate the effect of water quality improvement on the remediation of river sediment with the addition of calcium nitrate. The results demonstrated that the redox-potential of sediments increased from -282mV to -130mV after 28days of calcium nitrate treatment. The acid volatile sulphide in the sediments significantly decreased (by 54.9% to 57.1%), whereas the total organic carbon decreased by 9.7% to 10.2%. However, the difference between these and water quality improvement was not significant. Due to the addition of calcium nitrate, low phosphate concentration in the water column and interstitial phosphate in the sediment were observed, indicating that the calcium nitrate was beneficial to controlling the release of phosphorus from river sediment. The decrease in phosphorus release could be attributed to the fixation of iron-phosphorus and calcium-phosphorus due to the addition of calcium nitrate. The addition of calcium nitrate to sediment caused the oxidation of sulphide to sulphate, hence resulting in high nitrate and sulphate concentrations in the water column, and high interstitial nitrate and sulphate concentrations in the sediment. The results also showed that only the water quality improvement had a significant effect on the interstitial nitrate and sulphate concentrations in the sediment.

  17. Vasodilator Therapy: Nitrates and Nicorandil.

    PubMed

    Tarkin, Jason M; Kaski, Juan Carlos

    2016-08-01

    Nitrates have been used to treat symptoms of chronic stable angina for over 135 years. These drugs are known to activate nitric oxide (NO)-cyclic guanosine-3',-5'-monophasphate (cGMP) signaling pathways underlying vascular smooth muscle cell relaxation, albeit many questions relating to how nitrates work at the cellular level remain unanswered. Physiologically, the anti-angina effects of nitrates are mostly due to peripheral venous dilatation leading to reduction in preload and therefore left ventricular wall stress, and, to a lesser extent, epicardial coronary artery dilatation and lowering of systemic blood pressure. By counteracting ischemic mechanisms, short-acting nitrates offer rapid relief following an angina attack. Long-acting nitrates, used commonly for angina prophylaxis are recommended second-line, after beta-blockers and calcium channel antagonists. Nicorandil is a balanced vasodilator that acts as both NO donor and arterial K(+) ATP channel opener. Nicorandil might also exhibit cardioprotective properties via mitochondrial ischemic preconditioning. While nitrates and nicorandil are effective pharmacological agents for prevention of angina symptoms, when prescribing these drugs it is important to consider that unwanted and poorly tolerated hemodynamic side-effects such as headache and orthostatic hypotension can often occur owing to systemic vasodilatation. It is also necessary to ensure that a dosing regime is followed that avoids nitrate tolerance, which not only results in loss of drug efficacy, but might also cause endothelial dysfunction and increase long-term cardiovascular risk. Here we provide an update on the pharmacological management of chronic stable angina using nitrates and nicorandil.

  18. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not exceed...

  19. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified... sablefish, smoked, cured salmon, and smoked, cured shad, so that the level of sodium nitrate does not exceed...

  20. Peroxynitrite-mediated nitration of the stable free radical tyrosine residue of the ribonucleotide reductase small subunit.

    PubMed

    Guittet, O; Decottignies, P; Serani, L; Henry, Y; Le Maréchal, P; Laprévote, O; Lepoivre, M

    2000-04-25

    Ribonucleotide reductase activity is rate-limiting for DNA synthesis, and inhibition of this enzyme supports cytostatic antitumor effects of inducible NO synthase. The small R2 subunit of class I ribonucleotide reductases contains a stable free radical tyrosine residue required for activity. This radical is destroyed by peroxynitrite, which also inactivates the protein and induces nitration of tyrosine residues. In this report, nitrated residues in the E. coli R2 protein were identified by UV-visible spectroscopy, mass spectrometry (ESI-MS), and tryptic peptide sequencing. Mass analysis allowed the detection of protein R2 as a native dimer with two iron clusters per subunit. The measured mass was 87 032 Da, compared to a calculated value of 87 028 Da. Peroxynitrite treatment preserved the non-heme iron center and the dimeric form of the protein. A mean of two nitrotyrosines per E. coli protein R2 dimer were obtained at 400 microM peroxynitrite. Only 3 out of the 16 tyrosines were nitrated, including the free radical Tyr122. Despite its radical state, that should favor nitration, the buried Tyr122 was not nitrated with a high yield, probably owing to its restricted accessibility. Dose-response curves for Tyr122 nitration and loss of the free radical were superimposed. However, protein R2 inactivation was higher than nitration of Tyr122, suggesting that nitration of the nonconserved Tyr62 and Tyr289 might be also of importance for peroxynitrite-mediated inhibition of E. coli protein R2.

  1. Fe(III) oxides accelerate microbial nitrate reduction and electricity generation by Klebsiella pneumoniae L17.

    PubMed

    Liu, Tongxu; Li, Xiaomin; Zhang, Wei; Hu, Min; Li, Fangbai

    2014-06-01

    Klebsiella pneumoniae L17 is a fermentative bacterium that can reduce iron oxide and generate electricity under anoxic conditions, as previously reported. This study reveals that K. pneumoniae L17 is also capable of dissimilatory nitrate reduction, producing NO2(-), NH4(+), NO and N2O under anoxic conditions. The presence of Fe(III) oxides (i.e., α-FeOOH, γ-FeOOH, α-Fe2O3 and γ-Fe2O3) significantly accelerates the reduction of nitrate and generation of electricity by K. pneumoniae L17, which is similar to a previous report regarding another fermentative bacterium, Bacillus. No significant nitrate reduction was observed upon treatment with Fe(2+) or α-FeOOH+Fe(2+), but a slight facilitation of nitrate reduction and electricity generation was observed upon treatment with L17+Fe(2+). This result suggests that aqueous Fe(II) or mineral-adsorbed Fe(II) cannot reduce nitrate abiotically but that L17 can catalyze the reduction of nitrate and generation of electricity in the presence of Fe(II) (which might exist as cell surface-bound Fe(II)). To rule out the potential effect of Fe(II) produced by L17 during microbial iron reduction, treatments with the addition of TiO2 or Al2O3 instead of Fe(III) oxides also exhibited accelerated microbial nitrate reduction and electricity generation, indicating that cell-mineral sorption did account for the acceleration effect. However, the acceleration caused by Fe(III) oxides is only partially attributed to the cell surface-bound Fe(II) and cell-mineral sorption but may be driven by the iron oxide conduction band-mediated electron transfer from L17 to nitrate or an electrode, as proposed previously. The current study extends the diversity of bacteria of which nitrate reduction and electricity generation can be facilitated by the presence of iron oxides and confirms the positive role of Fe(III) oxides on microbial nitrate reduction and electricity generation by particular fermentative bacteria in anoxic environments.

  2. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  3. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  4. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  5. 46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Ammonium nitrate and ammonium nitrate fertilizers. 148... Materials § 148.205 Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to the stowage and transportation in bulk of ammonium nitrate and the following fertilizers composed of...

  6. Nitrate transport and signalling.

    PubMed

    Miller, Anthony J; Fan, Xiaorong; Orsel, Mathilde; Smith, Susan J; Wells, Darren M

    2007-01-01

    Physiological measurements of nitrate (NO(3)(-)) uptake by roots have defined two systems of high and low affinity uptake. In Arabidopsis, genes encoding both of these two uptake systems have been identified. Most is known about the high affinity transport system (HATS) and its regulation and yet measurements of soil NO(3)(-) show that it is more often available in the low affinity range above 1 mM concentration. Several different regulatory mechanisms have been identified for AtNRT2.1, one of the membrane transporters encoding HATS; these include feedback regulation of expression, a second component protein requirement for membrane targeting and phosphorylation, possibly leading to degradation of the protein. These various changes in the protein may be important for a second function in sensing NO(3)(-) availability at the surface of the root. Another transporter protein, AtNRT1.1 also has a role in NO(3)(-) sensing that, like AtNRT2.1, is independent of their transport function. From the range of concentrations present in the soil it is proposed that the NO(3)(-)-inducible part of HATS functions chiefly as a sensor for root NO(3)(-) availability. Two other key NO(3)(-) transport steps for efficient nitrogen use by crops, efflux across membranes and vacuolar storage and remobilization, are discussed. Genes encoding vacuolar transporters have been isolated and these are important for manipulating storage pools in crops, but the efflux system is yet to be identified. Consideration is given to how well our molecular and physiological knowledge can be integrated as well to some key questions and opportunities for the future.

  7. Sodium nitrate ingestion increases skeletal muscle nitrate content in humans.

    PubMed

    Nyakayiru, Jean; Kouw, Imre W K; Cermak, Naomi M; Senden, Joan M; van Loon, Luc J C; Verdijk, Lex B

    2017-09-01

    Nitrate ([Formula: see text]) ingestion has been shown to have vasoactive and ergogenic effects that have been attributed to increased nitric oxide (NO) production. Recent observations in rodents suggest that skeletal muscle tissue serves as an endogenous [Formula: see text] "reservoir." The present study determined [Formula: see text] contents in human skeletal muscle tissue in a postabsorptive state and following ingestion of a sodium nitrate bolus (NaNO3). Seventeen male, type 2 diabetes patients (age 72 ± 1 yr; body mass index 26.5 ± 0.5 kg/m(2); means ± SE) were randomized to ingest a dose of NaNO3 (NIT; 9.3 mg [Formula: see text]/kg body wt) or placebo (PLA; 8.8 mg NaCl/kg body wt). Blood and muscle biopsy samples were taken before and up to 7 h following [Formula: see text] or placebo ingestion to assess [Formula: see text] [and plasma nitrite ([Formula: see text])] concentrations. Additionally, basal plasma and muscle [Formula: see text] concentrations were assessed in 10 healthy young (CON-Y; age 21 ± 1 yr) and 10 healthy older (CON-O; age 75 ± 1 yr) control subjects. In all groups, baseline [Formula: see text] concentrations were higher in muscle (NIT, 57 ± 7; PLA, 61 ± 7; CON-Y, 80 ± 10; CON-O, 54 ± 6 µmol/l) than in plasma (NIT, 35 ± 3; PLA, 32 ± 3; CON-Y, 38 ± 3; CON-O, 33 ± 3 µmol/l; P ≤ 0.011). Ingestion of NaNO3 resulted in a sustained increase in plasma [Formula: see text], plasma [Formula: see text], and muscle [Formula: see text] concentrations (up to 185 ± 25 µmol/l) in the NIT group (time effect P < 0.001) compared with PLA (treatment effect P < 0.05). In conclusion, basal [Formula: see text] concentrations are substantially higher in human skeletal muscle tissue compared with plasma. Ingestion of a bolus of dietary [Formula: see text] increases both plasma and muscle [Formula: see text] contents in humans.NEW & NOTEWORTHY Literature of the pharmacokinetics following dietary nitrate ingestion is usually limited to the changes

  8. Nitrate attenuation in the Missoula Flood Deposits Aquitard (Willamette Silt) of the Willamette Valley, Oregon

    NASA Astrophysics Data System (ADS)

    Arighi, L.; Haggerty, R.; Myrold, D. D.; Iverson, J.; Baham, J. E.; Madin, I. P.; Arendt, J.

    2005-12-01

    Low-permeability geologic units may offer significant chemical and hydraulic protection of adjacent aquifers, and are important for managing groundwater quality, especially in areas with significant non-point source contamination. Nitrate in the Willamette Valley is attenuated across the Willamette Silt, a semi-confining unit overlying a regionally important aquifer. To quantify the main mechanism responsible for nitrate attenuation, soil cores were taken at 19 locations, and profiles of nitrate concentrations were constructed for each site. In 7 locations a sharp, major geochemical transition - a "redoxcline" - is present near the base of the Willamette Silt; this redoxcline is characterized by a color change from red-brown to blue-gray, an increase in iron(II) concentration, a rise in pH, and the appearance of carbonate minerals. At all sites where a significant surface input of nitrate was detected, the nitrate signal was attenuated before reaching the base of the silt. Denitrifier Enzyme Activity assays from one site show no denitrification potential in the profile, suggesting that a non-biological mechanism is responsible. We suggest that iron(II) is reducing the nitrate abiotically to nitrite, and that the blue-gray reducing zone of Willamette Silt is indicative of the presence of sufficient iron(II) for the reaction to go forward. To increase the usefulness of this study to regional water management agencies, a thickness isopach map of the reduced zone was created both for the northern and southern Willamette Valley to help determine areas where nitrate is most likely to be attenuated.

  9. Simultaneous removal of nitrate and arsenic from drinking water sources utilizing a fixed-bed bioreactor system.

    PubMed

    Upadhyaya, Giridhar; Jackson, Jeff; Clancy, Tara M; Hyun, Sung Pil; Brown, Jess; Hayes, Kim F; Raskin, Lutgarde

    2010-09-01

    A novel bioreactor system, consisting of two biologically active carbon (BAC) reactors in series, was developed for the simultaneous removal of nitrate and arsenic from a synthetic groundwater supplemented with acetic acid. A mixed biofilm microbial community that developed on the BAC was capable of utilizing dissolved oxygen, nitrate, arsenate, and sulfate as the electron acceptors. Nitrate was removed from a concentration of approximately 50 mg/L in the influent to below the detection limit of 0.2 mg/L. Biologically generated sulfides resulted in the precipitation of the iron sulfides mackinawite and greigite, which concomitantly removed arsenic from an influent concentration of approximately 200 ug/L to below 20 ug/L through arsenic sulfide precipitation and surface precipitation on iron sulfides. This study showed for the first time that arsenic and nitrate can be simultaneously removed from drinking water sources utilizing a bioreactor system. Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings

    NASA Technical Reports Server (NTRS)

    Warner, R. L.; Huffaker, R. C.

    1989-01-01

    Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

  11. Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings.

    PubMed

    Warner, R L; Huffaker, R C

    1989-01-01

    Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

  12. Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings

    NASA Technical Reports Server (NTRS)

    Warner, R. L.; Huffaker, R. C.

    1989-01-01

    Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

  13. Aniline-induced nitrosative stress in rat spleen: proteomic identification of nitrated proteins.

    PubMed

    Fan, Xiuzhen; Wang, Jianling; Soman, Kizhake V; Ansari, G A S; Khan, M Firoze

    2011-08-15

    Aniline exposure is associated with toxicity to the spleen which is characterized by splenomegaly, hyperplasia, fibrosis, and a variety of sarcomas on chronic exposure in rats. However, mechanisms by which aniline elicits splenotoxic responses are not well understood. Earlier we have shown that aniline exposure leads to increased nitration of proteins in the spleen. However, nitrated proteins remain to be characterized. Therefore, in the current study using proteomic approaches, we focused on characterizing the nitrated proteins in the spleen of aniline-exposed rats. Aniline exposure led to increased tyrosine nitration of proteins, as determined by 2D Western blotting with anti-3-nitrotyrosine specific antibody, compared to the controls. The analyzed nitrated proteins were found in the molecular weight range of 27.7 to 123.6kDa. A total of 37 nitrated proteins were identified in aniline-treated and control spleens. Among them, 25 were found only in aniline-treated rats, 11 were present in both aniline-treated and control rats, while one was found in controls only. The nitrated proteins identified mainly represent skeletal proteins, chaperones, ferric iron transporter, enzymes, nucleic acids binding protein, and signaling and protein synthesis pathways. Furthermore, aniline exposure led to significantly increased iNOS mRNA and protein expression in the spleen, suggesting its role in increased reactive nitrogen species formation and contribution to increased nitrated proteins. The identified nitrated proteins provide a global map to further investigate alterations in their structural and functional properties, which will lead to a better understanding of the role of protein nitration in aniline-mediated splenic toxicity.

  14. Aniline-induced nitrosative stress in rat spleen: Proteomic identification of nitrated proteins

    PubMed Central

    Fan, Xiuzhen; Wang, Jianling; Soman, Kizhake V.; Ansari, G. A. S.; Khan, M. Firoze

    2011-01-01

    Aniline exposure is associated with toxicity to the spleen which is characterized by splenomegaly, hyperplasia, fibrosis, and a variety of sarcomas on chronic exposure in rats. However, mechanisms by which aniline elicits splenotoxic responses are not well understood. Earlier we have shown that aniline exposure leads to increased nitration of proteins in the spleen. However, nitrated proteins remain to be characterized. Therefore, in the current study using proteomic approaches, we focused on characterizing the nitrated proteins in the spleen of aniline-exposed rats. Aniline exposure led to increased tyrosine nitration of proteins, as determined by 2D Western blotting with anti-3-nitrotyrosine specific antibody, compared to the controls. The analyzed nitrated proteins were found in the molecular weight range of 27.7 to 123.6 kDa. A total of 37 nitrated proteins were identified in aniline-treated and control spleens. Among them, 25 were found only in aniline-treated rats, 11 were present in both aniline-treated and control rats, while one was found in controls only. The nitrated proteins identified mainly represent skeletal proteins, chaperones, ferric iron transporter, enzymes, nucleic acids binding protein, and signaling and protein synthesis pathways. Furthermore, aniline exposure led to significantly increased iNOS mRNA and protein expression in the spleen, suggesting its role in increased reactive nitrogen species formation and contribution to increased nitrated proteins. The identified nitrated proteins provide a global map to further investigate alterations in their structural and functional properties, which will lead to a better understanding of the role of protein nitration in aniline-mediated splenic toxicity. PMID:21708182

  15. Reduction of nitrate in Shewanella

    SciTech Connect

    Gao, Haichun; Yang, Zamin Koo; Barua, Sumitra; Reed, SB; Nealson, Kenneth H.; Fredrikson, JK; Tiedje, James; Zhou, Jizhong

    2009-01-01

    In the genome of Shewanella oneidensis, a napDAGHB gene cluster encoding periplasmic nitrate reductase (NapA) and accessory proteins and an nrfA gene encoding periplasmic nitrite reductase (NrfA) have been identified. These two systems seem to be atypical because the genome lacks genes encoding cytoplasmic membrane electron transport proteins, NapC for NAP and NrfBCD/NrfH for NRF, respectively. Here, we present evidence that reduction of nitrate to ammonium in S. oneidensis is carried out by these atypical systems in a two-step manner. Transcriptional and mutational analyses suggest that CymA, a cytoplasmic membrane electron transport protein, is likely to be the functional replacement of both NapC and NrfH in S. oneidensis. Surprisingly, a strain devoid of napB encoding the small subunit of nitrate reductase exhibited the maximum cell density sooner than the wild type. Further characterization of this strain showed that nitrite was not detected as a free intermediate in its culture and NapB provides a fitness gain for S. oneidensis to compete for nitrate in the environments. On the basis results from mutational analyses of napA, napB, nrfA and napBnrfA in-frame deletion mutants, we propose that NapB is able to favor nitrate reduction by routing electrons to NapA exclusively.

  16. Anaerobic, nitrate-dependent oxidation of pyrite nanoparticles by Thiobacillus denitrificans.

    PubMed

    Bosch, Julian; Lee, Keun-Young; Jordan, Guntram; Kim, Kyoung-Woong; Meckenstock, Rainer U

    2012-02-21

    Pyrite is a key mineral in the global biogeochemical cycles of sulfur and iron, yet its anaerobic microbial oxidation has eluded geochemists and microbiologists for decades. Recent reports indicated that anaerobic oxidation of pyrite is occurring, but the mechanism remains unclear. Here, we provide evidence for the capability of Thiobacillus denitrificans to anaerobically oxidize a putatively nanosized pyrite particle fraction with nitrate as electron acceptor. Nanosized pyrite was readily oxidized to ferric iron and sulfate with a rate of 10.1 μM h(-1). The mass balance of pyrite oxidation and nitrate reduction revealed a closed recovery of the electrons. This substantiates a further "missing lithotrophy" in the global cycles of sulfur and iron and emphasizes the high reactivity of nanominerals in the environment.

  17. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    PubMed Central

    Mackey, Katherine R. M.; Chien, Chia-Te; Paytan, Adina

    2014-01-01

    Coastal California is a dynamic upwelling region where nitrogen (N) and iron (Fe) can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13–30 μ M) in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 μ M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts. PMID:25477873

  18. Iron refractory iron deficiency anemia

    PubMed Central

    De Falco, Luigia; Sanchez, Mayka; Silvestri, Laura; Kannengiesser, Caroline; Muckenthaler, Martina U.; Iolascon, Achille; Gouya, Laurent; Camaschella, Clara; Beaumont, Carole

    2013-01-01

    Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in adulthood. The disease is refractory to oral iron treatment but shows a slow response to intravenous iron injections and partial correction of the anemia. To date, 40 different Matriptase-2 mutations have been reported, affecting all the functional domains of the large ectodomain of the protein. In vitro experiments on transfected cells suggest that Matriptase-2 cleaves Hemojuvelin, a major regulator of hepcidin expression and that this function is altered in this genetic form of anemia. In contrast to the low/undetectable hepcidin levels observed in acquired iron deficiency, in patients with Matriptase-2 deficiency, serum hepcidin is inappropriately high for the low iron status and accounts for the absent/delayed response to oral iron treatment. A challenge for the clinicians and pediatricians is the recognition of the disorder among iron deficiency and other microcytic anemias commonly found in pediatric patients. The current treatment of iron refractory iron deficiency anemia is based on parenteral iron administration; in the future, manipulation of the hepcidin pathway with the aim of suppressing it might become an alternative therapeutic approach. PMID:23729726

  19. Removal of Selenium and Nitrate in Groundwater Using Organic Carbon-Based Reactive Mixtures

    NASA Astrophysics Data System (ADS)

    An, Hyeonsil; Jeen, Sung-Wook

    2016-04-01

    Treatment of selenium and nitrate in groundwater was evaluated through column experiments. Four columns consisting of reactive mixtures, either organic carbon-limestone (OC-LS) or organic carbon-zero valent iron (OC-ZVI), were used to determine the removal efficiency of selenium with different concentrations of nitrate. The source waters were collected from a mine site in Korea or were prepared artificially based on the mine drainage water or deionized water, followed by spiking of elevated concentrations of Se (40 mg/L) and nitrate (100 or 10 mg/L as NO3-N). The results for the aqueous chemistry showed that selenium and nitrate were effectively removed both in the mine drainage water and deionized water-based artificial input solution. However, the removal of selenium was delayed when selenium and nitrate coexisted in the OC-LS columns. The removal of selenium was not significant when the influent nitrate concentration was 100 mg/L as NO3-N, while most of nitrate was gradually removed within the columns. In contrast, 94% of selenium was removed when the influent nitrate concentration was reduced to 10 mg/L as NO3-N. In the OC-ZVI column, selenium and nitrate was removed almost simultaneously and completely even with the high nitrate concentration; however, a high concentration of ammonia was produced as a by-product of abiotic reaction between ZVI and nitrate. The elemental analysis for the solid samples after the termination of the experiments showed that selenium was accumulated in the reactive materials where removal of aqueous-phase selenium mostly occurred. The X-ray absorption near-edge structure (XANES) study indicated that selenium existed in the forms of SeS2 and Se(0) in the OC-LS column, while selenium was present in the forms of FeSe, SeS2 and absorbed Se(IV) in the OC-ZVI column. This study shows that OC-based reactive mixtures have an ability to remove selenium and nitrate in groundwater. However, the removal of selenium was influenced by the high

  20. Autotrophic denitrification using hydrogen generated from metallic iron corrosion.

    PubMed

    Sunger, Neha; Bose, Purnendu

    2009-09-01

    Hydrogenotrophic denitrification was demonstrated using hydrogen generated from anoxic corrosion of metallic iron. For this purpose, a mixture of hydrogenated water and nitrate solution was used as reactor feed. A semi-batch reactor with nitrate loading of 2000 mg m(-3) d(-1) and hydraulic retention time (HRT) of 50 days produced effluent with nitrate concentration of 0.27 mg N L(-1) (99% nitrate removal). A continuous flow reactor with nitrate loading of 28.9 mg m(-3) d(-1) and HRT of 15.6 days produced effluent with nitrate concentration of approximately 0.025 mg N L(-1) (95% nitrate removal). In both cases, the concentration of nitrate degradation by-products, viz., ammonia and nitrite, were below detection limits. The rate of denitrification in the reactors was controlled by hydrogen availability, and hence to operate such reactors at higher nitrate loading rates and/or lower HRT than reported in the present study, hydrogen concentration in the hydrogenated water must be significantly increased.

  1. Histochemical localization of nitrate reductase.

    PubMed

    Vaughn, K C; Duke, S O

    1981-01-01

    NADH-dependent nitrate reductase (E.C. 1.6.6.1) was ultrastructurally localized in norflurazon-treated and control soybean cotyledons [Glycine max (L.) Merr.] by a method based upon the increase in osmiophilia due to the formation of an azo dye. The reaction product was observed in small vesicles throughout the cytoplasm. An apparent transport of nitrite to the plastid, the site of nitrite reduction, may occur through fusion of the nitrite-containing vesicles with the chloroplast envelope. Plants grown in tungstate lacked nitrate reductase activity as measured by standard assay procedures, and showed no increase in osmiophilia, suggesting a degree of specificity of this cytochemical procedure.

  2. Nitrate Trends in Minnesota Rivers

    USGS Publications Warehouse

    Wall, Dave; Christopherson, Dave; Lorenz, Dave; Martin, Gary

    2013-01-01

    The objective of this study was to assess long-term trends (30 to 35 years) of flow-adjusted concentrations of nitrite+nitrate-N (hereinafter referred to as nitrate) in a way that would allow us to discern changing trends. Recognizing that these trends are commonly different from one river to another river and from one part of the state to another, our objective was to examine as many river monitoring sites across the state as possible for which sufficient long term streamflow and concentration data were available.

  3. Serum iron test

    MedlinePlus

    ... test if you have: Signs of low iron (iron deficiency) Signs of too much iron Anemia caused by ... Brittenham GM. Disorders of iron homeostasis: iron deficiency and ... Basic Principles and Practice . 6th ed. Philadelphia, PA: ...

  4. Nitrate transport and signalling in Arabidopsis.

    PubMed

    Krapp, Anne; David, Laure C; Chardin, Camille; Girin, Thomas; Marmagne, Anne; Leprince, Anne-Sophie; Chaillou, Sylvain; Ferrario-Méry, Sylvie; Meyer, Christian; Daniel-Vedele, Françoise

    2014-03-01

    Plants have developed adaptive responses allowing them to cope with nitrogen (N) fluctuation in the soil and maintain growth despite changes in external N availability. Nitrate is the most important N form in temperate soils. Nitrate uptake by roots and its transport at the whole-plant level involves a large panoply of transporters and impacts plant performance. Four families of nitrate-transporting proteins have been identified so far: nitrate transporter 1/peptide transporter family (NPF), nitrate transporter 2 family (NRT2), the chloride channel family (CLC), and slow anion channel-associated homologues (SLAC/SLAH). Nitrate transporters are also involved in the sensing of nitrate. It is now well established that plants are able to sense external nitrate availability, and hence that nitrate also acts as a signal molecule that regulates many aspects of plant intake, metabolism, and gene expression. This review will focus on a global picture of the nitrate transporters so far identified and the recent advances in the molecular knowledge of the so-called primary nitrate response, the rapid regulation of gene expression in response to nitrate. The recent discovery of the NIN-like proteins as master regulators for nitrate signalling has led to a new understanding of the regulation cascade.

  5. Short-term effects of a high nitrate diet on nitrate metabolism in healthy individuals.

    PubMed

    Bondonno, Catherine P; Liu, Alex H; Croft, Kevin D; Ward, Natalie C; Puddey, Ian B; Woodman, Richard J; Hodgson, Jonathan M

    2015-03-12

    Dietary nitrate, through the enterosalivary nitrate-nitrite-NO pathway, can improve blood pressure and arterial stiffness. How long systemic nitrate and nitrite remain elevated following cessation of high nitrate intake is unknown. In 19 healthy men and women, the time for salivary and plasma nitrate and nitrite to return to baseline after 7 days increased nitrate intake from green leafy vegetables was determined. Salivary and plasma nitrate and nitrite was measured at baseline [D0], end of high nitrate diet [D7], day 9 [+2D], day 14 [+7D] and day 21 [+14D]. Urinary nitrite and nitrate was assessed at D7 and +14D. Increased dietary nitrate for 7 days resulted in a more than fourfold increase in saliva and plasma nitrate and nitrite (p < 0.001) measured at [D7]. At [+2D] plasma nitrite and nitrate had returned to baseline while saliva nitrate and nitrite were more than 1.5 times higher than at baseline levels. By [+7D] all metabolites had returned to baseline levels. The pattern of response was similar between men and women. Urinary nitrate and nitrate was sevenfold higher at D7 compared to +14D. These results suggest that daily ingestion of nitrate may be required to maintain the physiological changes associated with high nitrate intake.

  6. Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton

    PubMed Central

    Botebol, Hugo; Lesuisse, Emmanuel; Šuták, Robert; Six, Christophe; Lozano, Jean-Claude; Schatt, Philippe; Vergé, Valérie; Kirilovsky, Amos; Morrissey, Joe; Léger, Thibaut; Camadro, Jean-Michel; Gueneugues, Audrey; Bowler, Chris; Blain, Stéphane; Bouget, François-Yves

    2015-01-01

    In large regions of the open ocean, iron is a limiting resource for phytoplankton. The reduction of iron quota and the recycling of internal iron pools are among the diverse strategies that phytoplankton have evolved to allow them to grow under chronically low ambient iron levels. Phytoplankton species also have evolved strategies to cope with sporadic iron supply such as long-term storage of iron in ferritin. In the picophytoplanktonic species Ostreococcus we report evidence from observations both in the field and in laboratory cultures that ferritin and the main iron-binding proteins involved in photosynthesis and nitrate assimilation pathways show opposite diurnal expression patterns, with ferritin being maximally expressed during the night. Biochemical and physiological experiments using a ferritin knock-out line subsequently revealed that this protein plays a central role in the diel regulation of iron uptake and recycling and that this regulation of iron homeostasis is essential for cell survival under iron limitation. PMID:26553998

  7. Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton.

    PubMed

    Botebol, Hugo; Lesuisse, Emmanuel; Šuták, Robert; Six, Christophe; Lozano, Jean-Claude; Schatt, Philippe; Vergé, Valérie; Kirilovsky, Amos; Morrissey, Joe; Léger, Thibaut; Camadro, Jean-Michel; Gueneugues, Audrey; Bowler, Chris; Blain, Stéphane; Bouget, François-Yves

    2015-11-24

    In large regions of the open ocean, iron is a limiting resource for phytoplankton. The reduction of iron quota and the recycling of internal iron pools are among the diverse strategies that phytoplankton have evolved to allow them to grow under chronically low ambient iron levels. Phytoplankton species also have evolved strategies to cope with sporadic iron supply such as long-term storage of iron in ferritin. In the picophytoplanktonic species Ostreococcus we report evidence from observations both in the field and in laboratory cultures that ferritin and the main iron-binding proteins involved in photosynthesis and nitrate assimilation pathways show opposite diurnal expression patterns, with ferritin being maximally expressed during the night. Biochemical and physiological experiments using a ferritin knock-out line subsequently revealed that this protein plays a central role in the diel regulation of iron uptake and recycling and that this regulation of iron homeostasis is essential for cell survival under iron limitation.

  8. Enhanced sensitivity of oceanic CO2 uptake to dust deposition by iron-light colimitation

    NASA Astrophysics Data System (ADS)

    Nickelsen, Levin; Oschlies, Andreas

    2015-01-01

    The iron hypothesis suggests that in large areas of the ocean phytoplankton growth and thus photosynthetic CO2 uptake is limited by the micronutrient iron. Phytoplankton requires iron in particular for nitrate uptake, light harvesting, and electron transport in photosynthesis, suggesting a tight coupling of iron and light limitation. One important source of iron to the open ocean is dust deposition. Previous global biogeochemical modeling studies have suggested a low sensitivity of oceanic CO2 uptake to changes in dust deposition. Here we show that this sensitivity is increased significantly when iron-light colimitation, i.e., the impact of iron bioavailability on light-harvesting capabilities, is explicitly considered. Accounting for iron-light colimitation increases the shift of export production from tropical and subtropical regions to the higher latitudes of subpolar regions at high dust deposition and amplifies iron limitation at low dust deposition. Our results reemphasize the role of iron as a key limiting nutrient for phytoplankton.

  9. The addition of organic carbon and nitrate affects reactive transport of heavy metals in sandy aquifers.

    PubMed

    Satyawali, Yamini; Seuntjens, Piet; Van Roy, Sandra; Joris, Ingeborg; Vangeel, Silvia; Dejonghe, Winnie; Vanbroekhoven, Karolien

    2011-04-25

    Organic carbon introduction in the soil to initiate remedial measures, nitrate infiltration due to agricultural practices or sulphate intrusion owing to industrial usage can influence the redox conditions and pH, thus affecting the mobility of heavy metals in soil and groundwater. This study reports the fate of Zn and Cd in sandy aquifers under a variety of plausible in-situ redox conditions that were induced by introduction of carbon and various electron acceptors in column experiments. Up to 100% Zn and Cd removal (from the liquid phase) was observed in all the four columns, however the mechanisms were different. Metal removal in column K1 (containing sulphate), was attributed to biological sulphate reduction and subsequent metal precipitation (as sulphides). In the presence of both nitrate and sulphate (K2), the former dominated the process, precipitating the heavy metals as hydroxides and/or carbonates. In the presence of sulphate, nitrate and supplemental iron (Fe(OH)(3)) (K3), metal removal was also due to precipitation as hydroxides and/or carbonates. In abiotic column, K4, (with supplemental iron (Fe(OH)(3)), but no nitrate), cation exchange with soil led to metal removal. The results obtained were modeled using the reactive transport model PHREEQC-2 to elucidate governing processes and to evaluate scenarios of organic carbon, sulphate and nitrate inputs.

  10. Biological denitrification of high concentration nitrate waste

    DOEpatents

    Francis, Chester W.; Brinkley, Frank S.

    1977-01-01

    Biological denitrification of nitrate solutions at concentrations of greater than one kilogram nitrate per cubic meter is accomplished anaerobically in an upflow column having as a packing material a support for denitrifying bacteria.

  11. 76 FR 62311 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-07

    ... to best notify agents (AN Agents) when ammonium nitrate purchasers (AN Purchasers) submit those AN... directly to ammonium nitrate sellers (AN Sellers) when it is not possible for an AN Seller to verify the...

  12. Inert Reassessment Document for Ammonium Nitrate

    EPA Pesticide Factsheets

    Magnesium nitrate is used in preservation. Other uses for magnesium nitrate include use as a catalyst in the manufacture of petrochemicals, as a densensitizer for lithographic plates and in pyrotechnics.

  13. Dietary nitrate and cardiovascular health

    USGS Publications Warehouse

    Ahluwalia, A.; Gladwin, M.T.; Harman, Jane L.; Ward, M.H.; Nolan, Bernard T.

    2014-01-01

    The National Heart, Lung, and Blood Institute convened this workshop to discuss the results of recent research on the effects of inorganic nitrate and nitrite on the cardiovascular system, possible long term effects of these compounds in the diet and drinking water, and future research needs including population-wide effects examined through epidemiological studies.

  14. Anaerobic, Nitrate-Dependent Fe(II) Oxidation Under Advective Flow

    NASA Astrophysics Data System (ADS)

    Weber, K. A.; Coates, J. D.

    2005-12-01

    Microbially-catalyzed nitrate-dependent Fe(II) oxidation has been identified as a ubiquitous biogeochemical process contributing to anaerobic iron redox cycling in sedimentary environments. Most probable number enumeration revealed nitrate-dependent Fe(II) oxidizing microbial communities in groundwater and subsurface sediments in the order of 0 - 2.04 x 103 cells mL-1 and 2.39 x 102 - 1.17 x 103 cells (g wet sediment)-1, respectively. The efficacy of nitrate-dependent Fe(II) oxidation under advective flow was evaluated in a meso-scale column reactor packed with sterile low iron sand amended with subsurface sediments collected from the NABIR FRC background field site (10% mass/mass). Continuous flow of minimal medium mimicked the natural groundwater. Periodic FeCl2 and nitrate injections over a period of 49 days resulted in the retention of 95% of the iron (290 mmol). Extraction of solid-phase Fe revealed a net increase in Fe(III) of 160 mmol above background Fe(III) content indicating that 55% of the injected Fe(II) was oxidized. Differential solubility analysis of 0.5M HCl-extractable Fe and 3M HCl-extractable Fe indicated that the oxidation product was crystalline in nature as only 20% was soluble in 0.5M HCl. This formation of crystalline biogenic Fe(III) oxides is consistent with previous studies. Periodic injections of nitrate and acetate did not result in significant changes in Fe(II) or Fe(III) throughout a control column. Together these results demonstrate that native subsurface sediments harbor microbial communities capable of nitrate-dependent Fe(II) oxidation under advective flow. The biogenic formation of reactive Fe(III) oxide minerals capable of immobilizing heavy metals and radionuclides presents a plausible bioremediative strategy for contaminated subsurface environments.

  15. Nitrate removal by Fe0/Pd/Cu nano-composite in groundwater.

    PubMed

    Liu, Hongyuan; Guo, Min; Zhang, Yan

    2014-01-01

    Nitrate pollution in groundwater shows a great threat to the safety of drinking water. Chemical reduction by zero-valent iron is being considered as a promising technique for nitrate removal from contaminated groundwater. In this paper, Fe0/Pd/Cu nano-composites were prepared by the liquid-phase reduction method, and batch experiments of nitrate reduction by the prepared Fe0/Pd/Cu nano-composites under various operating conditions were carried out. It has been found that nano-Fe0/Pd/Cu composites processed dual functions: catalytic reduction and chemical reduction. The introduction of Pd and Cu not only improved nitrate removal rate, but also reduced the generation of ammonia. Nitrate removal rate was affected by the amount of Fe0/Pd/Cu, initial nitrate concentration, solution pH, dissolved oxygen (DO), reaction temperature, the presence of anions, and organic pollutant. Moreover, nitrate reduction by Fe0/Pd/Cu composites followed the pseudo-first-order reaction kinetics. The removal rate of nitrate and total nitrogen were about 85% and 40.8%, respectively, under the reaction condition of Fe-6.0%Pd-3.0%Cu amount of 0.25 g/L, pH value of 7.1, DO of 0.42 mg/L, and initial nitrate concentration of 100 mg/L. Compared with the previous studies with Fe0 alone or Fe-Cu, nano-Fe-6%Pd-3%Cu composites showed a better selectivity to N2.

  16. The case for iron

    SciTech Connect

    Martin, J.H.; Gordon, R.M.; Fitzwater, S.E. )

    1991-12-01

    Excess major nutrients occur in offshore areas ranging from the tropical equatorial Pacific to the polar Antarctic. In spite of the great ecological differences in these environments, the authors believe they share a common trait: iron deficiency. Here they present the case of iron; they point out that all of these areas are far from Fe-rich terrestrial sources and that atmospheric dust loads in these regions are among the lowest in the world. The authors summarize experiments performed in three nutrient-rich areas: The Gulf of Alaska, the Ross Sea, and the equatorial Pacific. In general, populations without added Fe doubled at rates 11-40% of the expected maxima at various temperatures. The additions of nanomole quantities of Fe increased these doubling rates by factors of 2-3. In spite of the lack of Fe, tightly coupled phytoplankton/zooplankton communities seem to inhabit these major nutrient-rich areas. Since Fe is required for the synthesis of chlorophyll and nitrate reductase, little chlorophyll is found and NH{sub 3} is the favored N source. Normal rate values of specific productivity indicate that these populations are healthy, but limited by the insufficient Fe supply. When Fe becomes available either artificially in bottle experiments or in the environment as Fe-rich land masses are approached, diatoms quickly bloom, chlorophyll levels increase, and nutrient stocks are rapidly depleted. These combined results indicate that Fe availability is the primary factor controlling phytoplankton production in nutrient-rich areas of the open sea.

  17. A Novel Chemical Nitrate Destruction Process

    SciTech Connect

    Dziewinski, J.; Marczak, S.

    1999-03-01

    Nitrates represent one of the most significant pollutant discharged to the Baltic Sea by the Sliiamae hydrometallurgical plant. This article contains a brief overview of the existing nitrate destruction technologies followed by the description of a new process developed by the authors. The new chemical process for nitrate destruction is cost effective and simple to operate. It converts the nitrate to nitrogen gas which goes to the atmosphere.

  18. Plasma nitrate and nitrite are increased by a high nitrate supplement, but not by high nitrate foods in older adults

    PubMed Central

    Miller, Gary D.; Marsh, Anthony P.; Dove, Robin W.; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S. Bruce; Kim-Shapiro, Daniel

    2012-01-01

    Little is known about the effect of dietary nitrate on the nitrate/nitrite/NO (nitric oxide) cycle in older adults. We examined the effect of a 3-day control diet vs. high nitrate diet, with and without a high nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics, and blood pressure using a randomized four period cross-over controlled design. We hypothesized that the high nitrate diet would show higher levels of plasma nitrate/nitrite and blood pressure compared to the control diet, which would be potentiated by the supplement. Participants were eight normotensive older men and women (5 female, 3 male, 72.5±4.7 yrs) with no overt disease or medications that affect NO metabolism. Plasma nitrate and nitrite levels and blood pressure were measured prior to and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet+supplement (p<0.001 and =0.017 for nitrate and nitrite, respectively) and high nitrate diet+supplement (p=0.001 and 0.002), but not for control diet (p=0.713 and 0.741) or high nitrate diet (p=0.852 and 0.500). Blood pressure decreased from the morning baseline measure to the three 2 hr post-meal follow-up time-points for all treatments, but there was no main effect for treatment. In healthy older adults, a high nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction. PMID:22464802

  19. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  20. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  1. 49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation Other Regulations Relating to... nitrate and ammonium nitrate mixtures. (a) This section prescribes requirements to be observed...

  2. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

  3. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

  4. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing...

  5. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium nitrate. 172.160 Section 172.160 Food... ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent in the processing of cod...

  6. 21 CFR 172.160 - Potassium nitrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium nitrate. 172.160 Section 172.160 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used...

  7. 21 CFR 172.170 - Sodium nitrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate. 172.170 Section 172.170 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified foods in accordance with the...

  8. 76 FR 47238 - Ammonium Nitrate From Russia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-04

    ... COMMISSION Ammonium Nitrate From Russia Determination On the basis of the record \\1\\ developed in the subject... order on ammonium nitrate from Russia would be likely to lead to continuation or recurrence of material... Commission are contained in USITC Publication 4249 (August 2011), entitled Ammonium Nitrate from...

  9. Efflux Of Nitrate From Hydroponically Grown Wheat

    NASA Technical Reports Server (NTRS)

    Huffaker, R. C.; Aslam, M.; Ward, M. R.

    1992-01-01

    Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

  10. 76 FR 11273 - Ammonium Nitrate From Russia

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-01

    ... COMMISSION Ammonium Nitrate From Russia AGENCY: United States International Trade Commission. ACTION: Institution of a five-year review concerning the suspended investigation on ammonium nitrate from Russia... investigation on ammonium nitrate from Russia would be likely to lead to continuation or recurrence of...

  11. Method of producing thin cellulose nitrate film

    DOEpatents

    Lupica, S.B.

    1975-12-23

    An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent.

  12. Modeling nitrate removal in a denitrification bed

    USDA-ARS?s Scientific Manuscript database

    Denitrification beds are being promoted to reduce nitrate concentrations in agricultural drainage water to alleviate the adverse environmental effects associated with nitrate pollution in surface water. In this system, water flows through a trench filled with a carbon media where nitrate is transfor...

  13. Nitration of Naphthol: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Mowery, Dwight F.

    1982-01-01

    Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

  14. Nitration of Naphthol: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Mowery, Dwight F.

    1982-01-01

    Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

  15. Post-translational Regulation of Nitrate Reductase

    USDA-ARS?s Scientific Manuscript database

    Nitrate reductase (NR) catalyzes the reduction of nitrate to nitrite, which is the first step in the nitrate assimilation pathway, but can also reduce nitrite to nitric oxide (NO), an important signaling molecule that is thought to mediate a wide array of of developmental and physiological processes...

  16. Efflux Of Nitrate From Hydroponically Grown Wheat

    NASA Technical Reports Server (NTRS)

    Huffaker, R. C.; Aslam, M.; Ward, M. R.

    1992-01-01

    Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

  17. Dissimilatory Iron Reduction in Microorganisms Growing Near 100 C

    NASA Astrophysics Data System (ADS)

    Feinberg, L.; Holden, J.

    2006-12-01

    Dissimilatory iron reduction for microbial energy-generation has been well studied in mesophilic bacteria, such as Geobacter and Shewanella, but has only recently been found in organisms that grow optimally above 80°C, namely hyperthermophilic archaea. Dissimilatory iron reduction at high temperatures is likely to be widespread in high-temperature, anoxic environments such as deep-sea hydrothermal vents and terrestrial hot springs. Understanding the physiological mechanisms of microbe-metal interactions will help us to interpret the interplay between microorganisms and their geochemical environment. Our studies sought to characterize iron reduction in members of the hyperthermophilic genus Pyrobaculum (Topt 100°C) and the constraints associated with it and alternative terminal electron accepting processes. P. aerophilum and P. islandicum grew on soluble (Fe(III) citrate) and insoluble (Fe(III) oxide hydroxide) forms of iron. In P. aerophilum, ferric reductase and nitrate reductase activities and nitrate reductase abundances varied in iron- and nitrate-grown cultures suggesting that dissimilatory iron and nitrate reduction are regulated. P. aerophilum grew on Fe(III) oxide hydroxide that was separated from the cells by a dialysis membrane (12,000-14,000 MWCO). This suggests that direct contact with insoluble iron was not necessary for growth and that the organism may use an extracellular mediator for iron reduction. A hydroquinone-like molecule (MW = 234 Da) was identified by LC-MS in spent medium from cultures grown on insoluble Fe(III) oxide hydroxide that was far less abundant in spent media with other electron acceptors. P. aerophilum produced c- type cytochromes but genome analyses showed that the organism lacks polyheme c-type cytochromes, which are required for iron reduction in Geobacter and Shewanella species. There were significant differences between Pyrobaculum species with respect to pH and reduction potential preference of the media, which may have

  18. Rates and potential mechanism of anaerobic nitrate-dependent microbial pyrite oxidation.

    PubMed

    Bosch, Julian; Meckenstock, Rainer U

    2012-12-01

    Pyrite (FeS2) is a major iron- and sulfur-containing mineral phase in the environment. Oxidation of pyrite by aerobic micro-organisms has been well investigated. However, the reactivity of pyrite under anoxic conditions is still an open question. In the present paper, we summarize field and laboratory data on this chemolithotrophic respiration process with nitrate as terminal electron acceptor. Geochemical and stable isotope field data indicate that this process is occurring. Laboratory studies are more ambiguous, but recent positive results provide evidence that anaerobic microbial pyrite oxidation can, in fact, occur with nitrate as electron acceptor.

  19. Nitrate- and nitrite-dependent anaerobic oxidation of methane.

    PubMed

    Welte, Cornelia U; Rasigraf, Olivia; Vaksmaa, Annika; Versantvoort, Wouter; Arshad, Arslan; Op den Camp, Huub J M; Jetten, Mike S M; Lüke, Claudia; Reimann, Joachim

    2016-12-01

    Microbial methane oxidation is an important process to reduce the emission of the greenhouse gas methane. Anaerobic microorganisms couple the oxidation of methane to the reduction of sulfate, nitrate and nitrite, and possibly oxidized iron and manganese minerals. In this article, we review the recent finding of the intriguing nitrate- and nitrite-dependent anaerobic oxidation of methane (AOM). Nitrate-dependent AOM is catalyzed by anaerobic archaea belonging to the ANME-2d clade closely related to Methanosarcina methanogens. They were named 'Candidatus Methanoperedens nitroreducens' and use reverse methanogenesis with the key enzyme methyl-coenzyme M (methyl-CoM) reductase for methane activation. Their major end product is nitrite which can be taken up by nitrite-dependent methanotrophs. Nitrite-dependent AOM is performed by the NC10 bacterium 'Candidatus Methylomirabilis oxyfera' that probably utilizes an intra-aerobic pathway through the dismutation of NO to N2 and O2 for aerobic methane activation by methane monooxygenase, yet being a strictly anaerobic microbe. Environmental distribution, physiological and biochemical aspects are discussed in this article as well as the cooperation of the microorganisms involved. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  20. SEPARATION OF SCANDIUM VALUES FORM IRON VALUES BY SOLVENT EXTRACTION

    DOEpatents

    Kuhlman, C.W. Jr.; Lang, G.P.

    1961-12-19

    A process is given for separating scandium from trivalent iron values. In this process, an aqueous nitric acid solution is contacted with a water- immiscible alkyl phosphate solution, the aqueous solution containing the values to be separated, whereby the scandium is taken up by the alkyl phosphate. The aqueous so1ution is preferably saturated with magnesium nitrate to retain the iron in the aqueous solution. (AEC)

  1. Decomposition and Stability Studies of TAGN (Triaminoguanidium Nitrate)

    DTIC Science & Technology

    1988-12-01

    and atomic absorption spectroscopy . TAGN (Triaminoquanidinium Nitrate), DAGN (Diaminoquanidinium Nitrate), Thermal analysis, Mass Spectroscopy, RDX (Trinitrotriazacyclohexane), Decomposition chemistry.

  2. METABOLISM OF IRON STORES

    PubMed Central

    SAITO, HIROSHI

    2014-01-01

    ABSTRACT Remarkable progress was recently achieved in the studies on molecular regulators of iron metabolism. Among the main regulators, storage iron, iron absorption, erythropoiesis and hepcidin interact in keeping iron homeostasis. Diseases with gene-mutations resulting in iron overload, iron deficiency, and local iron deposition have been introduced in relation to the regulators of storage iron metabolism. On the other hand, the research on storage iron metabolism has not advanced since the pioneering research by Shoden in 1953. However, we recently developed a new method for determining ferritin iron and hemosiderin iron by computer-assisted serum ferritin kinetics. Serum ferritin increase or decrease curves were measured in patients with normal storage iron levels (chronic hepatitis C and iron deficiency anemia treated by intravenous iron injection), and iron overload (hereditary hemochromatosis and transfusion dependent anemia). We thereby confirmed the existence of two iron pathways where iron flows followed the numbered order (1) labile iron, (2) ferritin and (3) hemosiderin in iron deposition and mobilization among many previously proposed but mostly unproven routes. We also demonstrated the increasing and decreasing phases of ferritin iron and hemosiderin iron in iron deposition and mobilization. The author first demonstrated here the change in proportion between pre-existing ferritin iron and new ferritin iron synthesized by removing iron from hemosiderin in the course of iron removal. In addition, the author disclosed the cause of underestimation of storage iron turnover rate which had been reported by previous investigators in estimating storage iron turnover rate of normal subjects. PMID:25741033

  3. Surplus Photosynthetic Antennae Complexes Underlie Diagnostics of Iron Limitation in a Cyanobacterium

    PubMed Central

    Schrader, Paul S.; Milligan, Allen J.; Behrenfeld, Michael J.

    2011-01-01

    Chlorophyll fluorescence from phytoplankton provides a tool to assess iron limitation in the oceans, but the physiological mechanism underlying the fluorescence response is not understood. We examined fluorescence properties of the model cyanobacterium Synechocystis PCC6803 and a ΔisiA knock-out mutant of the same species grown under three culture conditions which simulate nutrient conditions found in the open ocean: (1) nitrate and iron replete, (2) limiting-iron and high-nitrate, representative of natural high-nitrate, low-chlorophyll regions, and (3) iron and nitrogen co-limiting. We show that low variable fluorescence, a key diagnostic of iron limitation, results from synthesis of antennae complexes far in excess of what can be accommodated by the iron-restricted pool of photosynthetic reaction centers. Under iron and nitrogen co-limiting conditions, there are no excess antennae complexes and variable fluorescence is high. These results help to explain the well-established fluorescence characteristics of phytoplankton in high-nutrient, low-chlorophyll ocean regions, while also accounting for the lack of these properties in low-iron, low-nitrogen regions. Importantly, our results complete the link between unique molecular consequences of iron stress in phytoplankton and global detection of iron stress in natural populations from space. PMID:21533084

  4. Submerged membrane adsorption hybrid system using four adsorbents to remove nitrate from water.

    PubMed

    Kalaruban, Mahatheva; Loganathan, Paripurnanda; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

    2017-04-05

    Nitrate contamination of ground and surface waters causes environmental pollution and human health problems in many parts of the world. This study tests the nitrate removal efficiencies of two ion exchange resins (Dowex 21K XLT and iron-modified Dowex 21K XLT (Dowex-Fe)) and two chemically modified bio-adsorbents (amine-grafted corn cob (AG corn cob) and amine-grafted coconut copra (AG coconut copra)) using a dynamic adsorption treatment system. A submerged membrane (microfiltration) adsorption hybrid system (SMAHS) was used for the continuous removal of nitrate with a minimal amount of adsorbents. The efficiency of membrane filtration flux and replacement rate of adsorbent were studied to determine suitable operating conditions to maintain the effluent nitrate concentration below the WHO drinking standard limit of 11.3 mg N/L. The volume of water treated and the amount of nitrate adsorbed per gramme of adsorbent for all four flux tested were in the order Dowex-Fe > Dowex > AG coconut copra > AG corn cob. The volumes of water treated (L/g adsorbent) were 0.91 and 1.85, and the amount of nitrate removed (mg N/g adsorbent) were 9.8 and 22.2 for AG corn cob and Dowex-Fe, respectively, at a flux of 15 L/(m(2)/h).

  5. Continuous flow nitration in miniaturized devices

    PubMed Central

    2014-01-01

    Summary This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

  6. Nitrated fatty acids: Synthesis and measurement

    PubMed Central

    Woodcock, Steven R.; Bonacci, Gustavo; Gelhaus, Stacy L.; Schopfer, Francisco J.

    2012-01-01

    Nitrated fatty acids are the product of nitrogen dioxide reaction with unsaturated fatty acids. The discovery of peroxynitrite and peroxidase-induced nitration of biomolecules led to the initial reports of endogenous nitrated fatty acids. These species increase during ischemia reperfusion, but concentrations are often at or near the limits of detection. Here, we describe multiple methods for nitrated fatty acid synthesis, sample extraction from complex biological matrices, and a rigorous method of qualitative and quantitative detection of nitrated fatty acids by LC-MS. In addition, optimized instrument conditions and caveats regarding data interpretation are discussed. PMID:23200809

  7. Nitrated fatty acids: synthesis and measurement.

    PubMed

    Woodcock, Steven R; Bonacci, Gustavo; Gelhaus, Stacy L; Schopfer, Francisco J

    2013-06-01

    Nitrated fatty acids are the product of nitrogen dioxide reaction with unsaturated fatty acids. The discovery of peroxynitrite and peroxidase-induced nitration of biomolecules led to the initial reports of endogenous nitrated fatty acids. These species increase during ischemia/reperfusion, but concentrations are often at or near the limits of detection. Here, we describe multiple methods for nitrated fatty acid synthesis and sample extraction from complex biological matrices and a rigorous method of qualitative and quantitative detection of nitrated fatty acids by liquid chromatography-mass spectrometry. In addition, optimized instrument conditions and caveats regarding data interpretation are discussed.

  8. Biological Oxidation of Fe(II) in Reduced Nontronite Coupled with Nitrate Reduction by Pseudogulbenkiania sp. Strain 2002

    SciTech Connect

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi K.; Agrawal, A.; Liu, Deng; Zhang, Jing; Edelmann, Richard E.

    2013-10-15

    Nitrate contamination in soils, sediments, and water bodies is a significant issue. Although much is known about nitrate degradation in these environments, especially via microbial pathways, a complete understanding of all degradation processes, especially in clay mineral-rich soils, is still lacking. The objective of this study was to study the potential of removing nitrate contaminant using structural Fe(II) in clay mineral nontronite. Specifically, the coupled processes of microbial oxidation of Fe(II) in microbially reduced nontronite (NAu-2) and nitrate reduction by Pseudogulbenkiania species strain 2002 was investigated. Bio-oxidation experiments were conducted in bicarbonate-buffered medium under both growth and nongrowth conditions. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in nontronite. The bio-oxidation extent under growth and nongrowth conditions reached 93% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Magnetite was a mineral product of nitrate-dependent Fe(II) oxidation, as evidenced by XRD data and TEM diffraction patterns. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate removal in soils.

  9. Nitrosative stress and apoptosis in non-anemic healthy rats induced by intravenous iron sucrose similars versus iron sucrose originator.

    PubMed

    Toblli, Jorge E; Cao, Gabriel; Angerosa, Margarita

    2015-04-01

    Iron can both induce and inhibit nitrosative stress. Intracellular iron levels play an important role in nitric oxide (NO(•)) signaling mechanisms. Depending on various factors, such as the cell's redox state and transition metal levels, NO(•) generation may lead to lipid peroxidation and DNA damage as well as both anti- and pro-apoptotic effects. Administration of intravenous iron sucrose originator (IS(ORIG)) has been shown not to cause significant tyrosine nitration or significantly increased caspase 3 levels in non-anemic rats. In this study, the potential of several marketed iron sucrose similars (ISSs) to induce tyrosine nitration and caspase 3 expression in non-anemic rats was assessed. Although the physico-chemical properties of most of the analyzed ISSs complied with the United States Pharmacopeia for iron sucrose injection, all ISSs resulted in higher levels of tyrosine nitration and increased the expression of caspase 3 versus IS(ORIG). Moreover, significant differences were detected in tissue iron distribution between IS(ORIG)- and ISS-treated animals. In general, ISORIG resulted in higher levels of ferritin deposits versus ISSs whereas ISSs showed higher Prussian blue-stainable iron(III) deposits than IS(ORIG). This result suggests that some iron from ISSs bypassed the tightly regulated pathway through resident macrophages of the liver, spleen and bone marrow thus, ending up in the cellular compartment that favors oxidative and or nitrosative stress as well as apoptosis. The results also confirm that polynuclear iron(III)-oxyhydroxide carbohydrates, such as iron sucrose, cannot be fully characterized by physico-chemical methods alone.

  10. Pollution of drinking water with nitrate

    SciTech Connect

    Cabel, B.; Kozicki, R.; Lahl, U.; Podbielshi, A.; Stachel, B.; Struss, S.

    1982-01-01

    The main sources of nitrate in man are food and drinking water. The legislature in West Germany intends to lower the permitted level of nitrate in drinking water from the present 90 mg/l to 50 mg/l in 1982. The European Community has issued a directive that recommends a level of only 25 mg/l, and for babies 10 mg/l nitrate should not be exceeded. At present, nitrate cannot be removed from raw water at an acceptable cost. The problem of high nitrate content is mainly one of drinking water generation from ground water. Several analyses indicate rising concentrations of nitrate in ground water in different regions of West Germany, especially in the last few years. The following sources of nitrate-contamination of ground water aquifers in West are discussed: natural sources; over-manuring of agricultural areas with natural organic fertilizers; over-manuring of agricultural areas with synthetic fertilizers.

  11. Nitrate Utilization by the Diatom Skeletonema costatum

    PubMed Central

    Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

    1978-01-01

    Nitrate uptake has been studied in nitrogen-deficient cells of the marine diatom Skeletonema costatum. When these cells are incubated in the presence of nitrate, this ion is quickly taken up from the medium, and nitrite is excreted by the cells. Nitrite is excreted following classical saturation kinetics, its rate being independent of nitrate concentration in the incubation medium for nitrate concentration values higher than 3 micromolar. Nitrate uptake shows mixed-transfer kinetics, which can be attributed to the simultaneous contributions of mediated and diffusion transfer. Cycloheximide and p-hydroxymercuribenzoate inhibit the carrier-mediated contribution to nitrate uptake, without affecting the diffusion component. When cells are preincubated with nitrate, the net nitrogen uptake is increased. PMID:16660652

  12. Molten nitrate salt technology development

    NASA Astrophysics Data System (ADS)

    Carling, R. W.

    1981-04-01

    This paper presents an overview of the experimental programs underway in support of the Thermal Energy Storage for Solar Thermal Applications (TESSTA) program. The experimental programs are concentrating on molten nitrate salts which have been proposed as heat transfer and energy storage medium. The salt composition of greatest interest is drawsalt, nominally a 50-50 molar mixture of NaNO3 and KNO3 with a melting point of 220 C. Several technical uncertainties have been identified that must be resolved before nitrate based solar plants can be commercialized. Research programs at Sandia National Laboratories, universities, and industrial suppliers have been implemented to resolve these technical uncertainties. The experimental programs involve corrosion, decomposition, physical properties, and environmental cracking. Summaries of each project and how they impact central receiver applications such as the repowering/industrial retrofit and cogeneration program are presented.

  13. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, M.; Yoo, C. S.

    2014-05-01

    Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

  14. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  15. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  16. 49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 Transportation Other... requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers. (a) Except as... Captain of the Port (COTP). (1) Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more...

  17. Molten nitrate salt materials studies

    NASA Astrophysics Data System (ADS)

    Carling, R. M.

    1981-03-01

    An overview of the experimental programs underway in support of the Thermal Energy Storage for Solar Thermal Applications (TESSTA) program is presented. The experimental programs are concentrating on molten nitrate salts which were proposed as heat transfer and energy storage medium. The experimental programs involve corrosion, decomposition, physical properties, and environmental cracking. Summaries of each project and how they impact central receiver applications are presented.

  18. High performance ammonium nitrate propellant

    NASA Technical Reports Server (NTRS)

    Anderson, F. A. (Inventor)

    1979-01-01

    A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

  19. Catalyzed reduction of nitrate in aqueous solutions

    SciTech Connect

    Haas, P.A.

    1994-08-01

    Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH{sub 3}, hydrazine, or organic compounds containing oxygen would be advantageous for reduction of nitrate in sodium nitrate solutions. Objective of this seed money study was to determine minimum conditions for reduction. Proposed procedure was batchwise heating of aqueous solutions in closed vessels with monitoring of temperatures and pressures. A simple, convenient apparatus and procedure were demonstrated for observing formation of gaseous products and collecting samples for analyses. The test conditions were 250{degree}C and 1000 psi max. Any useful reduction of sodium nitrate to sodium hydroxide as the primary product was not found. The nitrate present at pHs < 4 as HNO{sub 3} or NH{sub 4}NO{sub 3} is easily decomposed, and the effect of nitromethane at these low pHs was confirmed. When acetic acid or formic acid was added, 21 to 56% of the nitrate in sodium nitrate solutions was reduced by methanol or formaldehyde. With hydrazine and acetic acid, 73 % of the nitrate was decomposed to convert NaNO{sub 3} to sodium acetate. With hydrazine and formic acid, 36% of the nitrate was decomposed. If these products are more acceptable for final disposal than sodium nitrate, the reagents are cheap and the conversion conditions would be practical for easy use. Ammonium acetate or formate salts did not significantly reduce nitrate in sodium nitrate solutions.

  20. Biogeochemical modelling of the tropical Pacific Ocean. II: Iron biogeochemistry

    NASA Astrophysics Data System (ADS)

    Christian, J. R.; Verschell, M. A.; Murtugudde, R.; Busalacchi, A. J.; McClain, C. R.

    A coupled physical-biogeochemical model of the tropical Pacific Ocean with simultaneous iron and nitrogen limitation was developed to study questions of iron biogeochemistry, its effects on upper ocean production, and ultimately the biogeochemical cycles of the other elements. The model results suggest that iron limitation is ubiquitous in the equatorial Pacific, and extends further west than is generally believed unless there are significant inputs of geothermal iron at quite shallow depths. Most model parameters (e.g., iron solubility, scavenging rates, Fe : N ratios) must be near the limit of their generally accepted range of values in order to prevent elevated surface nitrate concentrations from spreading further into the warm pool than is observed. Transport of geothermal iron in the equatorial undercurrent (EUC) provides a possible mechanism for limiting surface nitrate in the warm pool, but the source must be near the upper boundary of the EUC to provide iron to the surface west of the dateline. Accumulations of ammonium in the western Pacific appear to result from the exhaustion of iron in upwelled water before nitrogen. The realism of the simulation is limited primarily by lack of information about the abundance and distribution of dissolved iron; the assumption of constant Fe : N ratios and the magnitude, distribution and solubility of the aeolian iron flux are also important sources of uncertainty. The sensitivity of the simulation to the way that iron is initialized in the western Pacific thermocline emphasizes the importance of the equatorial undercurrent throughout the tropical Pacific and the need for iron observations in this region.

  1. [Nitrate storage and transport within a typical karst aquifer system in the paralleled ridge-valley of east Sichuan].

    PubMed

    Yang, Ping-Heng; Yuan, Dao-Xian; Ren, You-Rong; Xie, Shi-You; He, Qiu-Fang; Hu, Xiao-Feng

    2012-09-01

    In order to investigate the nitrate storage and transport in the karst aquifer system, the hydrochemical dynamics of Qingmuguan underground river system was monitored online by achieving high-resolution data during storm events and monthly data in normal weather. The principal component analysis was employed to analyze the karst water geochemistry. Results showed that nitrate in Jiangjia spring did not share the same source with soluble iron, manganese and aluminum, and exhibited different geochemical behaviors. Nitrate was derived from land surface and infiltrated together with soil water, which was mainly stored in fissure, pore and solution crack of karst unsaturated zone, whereas soluble iron, manganese and aluminum were derived from soil erosion and directly recharged the underground river through sinkholes and shafts. Nitrate transport in the karst aquifer system could be ideally divided into three phases, including input storage, fast output and re-inputting storage. Under similar external conditions, the karstification intensity of vadose zone was the key factor to determine the dynamics of nitrate concentrations in the groundwater during storm events. Nitrate stored in the karst vadose zone was easily released, which would impair the aquatic ecosystem and pose seriously threats to the local health. Thus, to strengthen the management of ecological system, changing the land-use patterns and scientifically applying fertilizer could effectively make a contribution to controlling mass nutrient input from the surface.

  2. Effect of nitrate on microbial perchlorate reduction

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Coates, J. D.

    2007-12-01

    Over the last decade perchlorate has been recognized as an important emerging water contaminant that poses a significant public health threat. Because of its chemical stability, low ionic charge density, and significant water solubility microbial remediation has been identified as the most feasible method for its in situ attenuation. Our previous studies have demonstrated that dissimilatory perchlorate reducing bacteria (DPRB) capable of the respiratory reduction of perchlorate into innocuous chloride are ubiquitous in soil and sedimentary environments. As part of their metabolism these organisms reduce perchlorate to chlorite which is subsequently dismutated into chloride and molecular oxygen. These initial steps are mediated by the perchlorate reductase and chlorite dismutase enzymes respectively. Previously we found that the activity of these organisms is dependent on the presence of molybdenum and is inhibited by the presence of oxygen and to different extents nitrate. However, to date, there is little understanding of the mechanisms involved in the regulation of perchlorate reduction by oxygen and nitrate. As a continuation of our studies into the factors that control DPRB activity we investigated these regulatory mechanisms in more detail as a model organism, Dechloromonas aromatica strain RCB, transitions from aerobic metabolism through nitrate reduction to perchlorate reduction. In series of growth transition studies where both nitrate and perchlorate were present, preference for nitrate to perchlorate was observed regardless of the nitrate to perchlorate ratio. Even when the organism was pre-grown anaerobically in perchlorate, nitrate was reduced prior to perchlorate. Using non-growth washed cell suspension, perchlorate- grown D. aromatica was capable of reducing both perchlorate and nitrate concomitantly suggesting the preferentially utilization of nitrate was not a result of enzyme functionality. To elucidate the mechanism for preferential utilization of

  3. Sorptive removal of technetium from heavy metals sludge filtrate containing nitrate ion

    SciTech Connect

    Bostick, W.D.; Evans-Brown, B.S.

    1988-01-01

    We have found that cross-linked polyvinylpyridine (PVP) resin is more efficient than strongly basic anion-exchange resin for removal of technetium in wastes containing high concentrations of nitrate ion. Resin loading by nitrate is greatly reduced, and PVP resins are very stable with respect to chemical and radiological degradation. We have also found that the inexpensive inorganic reagents, elemental iron and ferrous sulfide, are very efficient for the removal of technetium and soluble mercury from aqueous nitrate wastes. The spent reactant and sorbent occupies a much smaller volume (per unit of technetium removed) than does organic resin, and the spent reactant can be immobilized into grout, with a very low leach rate for technetium. 30 refs., 5 figs., 13 tabs.

  4. Total iron binding capacity

    MedlinePlus

    ... iron supplies are low. This can occur with: Iron deficiency anemia Pregnancy (late) Lower-than-normal TIBC may ... Brittenham GM. Disorders of iron homeostasis: iron deficiency and ... Basic Principles and Practice . 6th ed. Philadelphia, PA: ...

  5. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, Jean-Francois; Peeters, Jozef; Stavrakou, Trisevgeni

    2014-05-01

    We show that photolysis is, by far, the major atmospheric sink of isoprene-derived carbonyl nitrates. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as the likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photorates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methylvinylketone nitrates strongly supports our assumptions of large cross section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications, as carbonyl nitrates constitute an important component of the total organic nitrate pool over vegetated areas: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  6. Skeletal muscle as an endogenous nitrate reservoir

    PubMed Central

    Piknova, Barbora; Park, Ji Won; Swanson, Kathryn M.; Dey, Soumyadeep; Noguchi, Constance Tom; Schechter, Alan N

    2015-01-01

    The nitric oxide synthase (NOS) family of enzymes form nitric oxide (NO) from arginine in the presence of oxygen. At reduced oxygen availability NO is also generated from nitrate in a two step process by bacterial and mammalian molybdopterin proteins, and also directly from nitrite by a variety of five-coordinated ferrous hemoproteins. The mammalian NO cycle also involves direct oxidation of NO to nitrite, and both NO and nitrite to nitrate by oxy-ferrous hemoproteins. The liver and blood are considered the sites of active mammalian NO metabolism and nitrite and nitrate concentrations in the liver and blood of several mammalian species, including human, have been determined. However, the large tissue mass of skeletal muscle had not been generally considered in the analysis of the NO cycle, in spite of its long-known presence of significant levels of active neuronal NOS (nNOS or NOS1). We hypothesized that skeletal muscle participates in the NO cycle and, due to its NO oxidizing heme protein, oxymyoglobin, has high concentrations of nitrate ions. We measured nitrite and nitrate concentrations in rat and mouse leg skeletal muscle and found unusually high concentrations of nitrate but similar levels of nitrite, when compared to the liver. The nitrate reservoir in muscle is easily accessible via the bloodstream and therefore nitrate is available for transport to internal organs where it can be reduced to nitrite and NO. Nitrate levels in skeletal muscle and blood in nNOS−/− mice were dramatically lower when compared with controls, which support further our hypothesis. Although the nitrate reductase activity of xanthine oxidoreductase in muscle is less than that of liver, the residual activity in muscle could be very important in view of its total mass and the high basal level of nitrate. We suggest that skeletal muscle participates in overall NO metabolism, serving as a nitrate reservoir, for direct formation of nitrite and NO, and for determining levels of nitrate

  7. Bacteria associated with iron seeps in a sulfur-rich, neutral pH, freshwater ecosystem.

    PubMed

    Haaijer, Suzanne C M; Harhangi, Harry R; Meijerink, Bas B; Strous, Marc; Pol, Arjan; Smolders, Alfons J P; Verwegen, Karin; Jetten, Mike S M; Op den Camp, Huub J M

    2008-12-01

    The freshwater nature reserve De Bruuk is an iron- and sulfur-rich minerotrophic peatland containing many iron seeps and forms a suitable habitat for iron and sulfur cycle bacteria. Analysis of 16S rRNA gene-based clone libraries showed a striking correlation of the bacterial population of samples from this freshwater ecosystem with the processes of iron reduction (genus Geobacter), iron oxidation (genera Leptothrix and Gallionella) and sulfur oxidation (genus Sulfuricurvum). Results from fluorescence in situ hybridization analyses with a probe specific for the beta-1 subgroup of Proteobacteria, to which the genera Leptothrix and Gallionella belong, and newly developed probes specific for the genera Geobacter and Sulfuricurvum, supported the clone library data. Molecular data suggested members of the epsilonproteobacterial genus Sulfuricurvum as contributors to the oxidation of reduced sulfur compounds in the iron seeps of De Bruuk. In an evaluation of anaerobic dimethyl sulfide (DMS)-degrading activity of sediment, incubations with the electron acceptors sulfate, ferric iron and nitrate were performed. The fastest conversion of DMS was observed with nitrate. Further, a DMS-oxidizing, nitrate-reducing enrichment culture was established with sediment material from De Bruuk. This culture was dominated by dimorphic, prosthecate bacteria, and the 16S rRNA gene sequence obtained from this enrichment was closely affiliated with Hyphomicrobium facile, which indicates that the Hyphomicrobium species are capable of both aerobic and nitrate-driven DMS degradation.

  8. Iron and alloys of iron. [lunar resources

    NASA Technical Reports Server (NTRS)

    Sastri, Sankar

    1992-01-01

    All lunar soil contains iron in the metallic form, mostly as an iron-nickel alloy in concentrations of a few tenths of 1 percent. Some of this free iron can be easily separated by magnetic means. It is estimated that the magnetic separation of 100,000 tons of lunar soil would yield 150-200 tons of iron. Agglutinates contain metallic iron which could be extracted by melting and made into powder metallurgy products. The characteristics and potential uses of the pure-iron and iron-alloy lunar products are discussed. Processes for working iron that might be used in a nonterrestrial facility are also addressed.

  9. Nitrate Enhanced Microbial Cr(VI) Reduction-Final Report

    SciTech Connect

    John F. Stolz

    2011-06-15

    proteins (Gmet_2478 and Gmet_1641) were up-regulated with exposure to Cr(VI). A nine-heme cytochrome C was purified that could reduce nitrite and could be oxidized by Cr(VI). For D. desulfuricans, we found that confirmed that Cr(VI) induced a prolonged lag period when Cr(VI) was reduced. Over three hundred proteins were unequivocally identified by LC/MS-MS and a significant number of down-regulated proteins for which the levels were changed >2 fold compared to control. Sulfite reductase levels were similar, however, nitrate and nitrite reductase were down-regulated. The supernatant of spent cultures was found to contain a filterable, heat stable compound that rapidly reduced Cr(VI). In addition, desulfoviridin was purified from nitrate grown cells and shown to have nitrite reductase activity that was inhibited by Cr(VI). For S. barnesii, periplasmic nitrate reductase (Nap), nitrite reductase (Nrf), and the metalloid reductase (Rar) were purified and characterized. The supernatant of spent cultures was also found to contain a filterable, heat stable compound that rapidly reduced Cr(VI) but that Rar also reduced Cr(VI). Our results from specific aims 1 through 3 indicate that for G. metallireducens, Cr(VI) inhibits nitrate respiration as it oxidizes cytochromes involved in nitrate respiration. Iron reduction is apparently not affected and the inhibitory affects of Cr(VI) may be attenuated by the addition of sufficient Fe(III) to generate Fe(II) that abiotically reduces the chromium. For S. barnesii, although the enzyme assays indicate that the components of the respiratory pathway for nitrate (e.g. Nap and Nrf) are inhibited by chromate, the organism has a mechanism to prevent this from actually occurring. Our current hypothesis is that the non-specific metalloid reductase (Rar) is providing resistance by reducing the Cr(VI). The strategy here would be to enhance its growth and metabolism in the natural setting. Lactate is a suitable electron donor for S. barnesii but other

  10. Autotrophic denitrification by nitrate-dependent Fe(II) oxidation in a continuous up-flow biofilter.

    PubMed

    Zhou, Jun; Wang, Hongyu; Yang, Kai; Ji, Bin; Chen, Dan; Zhang, Huining; Sun, Yuchong; Tian, Jun

    2016-02-01

    A continuous-upflow biofilter packed with sponge iron was constructed for nitrate removal under an anaerobic atmosphere. Microbacterium sp. W5, a nitrate reducing and Fe(II) oxidizing strain, was added to the biofilter as an inoculum. The best results were achieved when NO3 (-)-N concentration was 30 mg/L and Fe(2+) was 800 mg/L. Nitrite in influent would inhibit nitrate removal and aqueous Fe(2+) resulted in encrustation. Fe(II)EDTA would prevent cells from encrustation and the maximum nitrogen removal efficiency was about 90 % with Fe(II)EDTA level of 1100 mg/L. Nitrate reduction followed first-order reaction kinetics. Characteristics of biofilms were analyzed by X-ray fluorescence spectroscopy.

  11. Nitrates

    MedlinePlus

    ... or interactions with other medicines and vitamin or herbal supplements. This information should not be used as medical ... your doctor about every medicine and vitamin or herbal supplement that you are taking, so he or she ...

  12. Applicability of anaerobic nitrate-dependent Fe(II) oxidation to microbial enhanced oil recovery (MEOR).

    PubMed

    Zhu, Hongbo; Carlson, Han K; Coates, John D

    2013-08-06

    Microbial processes that produce solid-phase minerals could be judiciously applied to modify rock porosity with subsequent alteration and improvement of floodwater sweep in petroleum reservoirs. However, there has been little investigation of the application of this to enhanced oil recovery (EOR). Here, we investigate a unique approach of altering reservoir petrology through the biogenesis of authigenic rock minerals. This process is mediated by anaerobic chemolithotrophic nitrate-dependent Fe(II)-oxidizing microorganisms that precipitate iron minerals from the metabolism of soluble ferrous iron (Fe(2+)) coupled to the reduction of nitrate. This mineral biogenesis can result in pore restriction and reduced pore throat diameter. Advantageously and unlike biomass plugs, these biominerals are not susceptible to pressure or thermal degradation. Furthermore, they do not require continual substrate addition for maintenance. Our studies demonstrate that the biogenesis of insoluble iron minerals in packed-bed columns results in effective hydrology alteration and homogenization of heterogeneous flowpaths upon stimulated microbial Fe(2+) biooxidation. We also demonstrate almost 100% improvement in oil recovery from hydrocarbon-saturated packed-bed columns as a result of this metabolism. These studies represent a novel departure from traditional microbial EOR approaches and indicate the potential for nitrate-dependent Fe(2+) biooxidation to improve volumetric sweep efficiency and enhance both the quality and quantity of oil recovered.

  13. Silver nitrate based gel dosimeter

    NASA Astrophysics Data System (ADS)

    Titus, D.; Samuel, E. J. J.; Srinivasan, K.; Roopan, S. M.; Madhu, C. S.

    2017-05-01

    A new radiochromic gel dosimeter based on silver nitrate and a normoxic gel dosimeter was investigated using UV-Visible spectrophotometry in the clinical dose range. Gamma radiation induced the synthesis of silver nanoparticles in the gel and is confirmed from the UV-Visible spectrum which shows an absorbance peak at around 450 nm. The dose response function of the dosimeter is found to be linear upto12Gy. In addition, the gel samples were found to be stable which were kept under refrigeration.

  14. Genetics Home Reference: iron-refractory iron deficiency anemia

    MedlinePlus

    ... Conditions iron-refractory iron deficiency anemia iron-refractory iron deficiency anemia Printable PDF Open All Close All Enable ... view the expand/collapse boxes. Description Iron-refractory iron deficiency anemia is one of many types of anemia , ...

  15. Iron and iron derived radicals

    SciTech Connect

    Borg, D.C.; Schaich, K.M.

    1987-04-01

    We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fastexclamation Think smallexclamation In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab.

  16. Measurement of isoprene nitrates by GCMS

    NASA Astrophysics Data System (ADS)

    Mills, Graham P.; Hiatt-Gipson, Glyn D.; Bew, Sean P.; Reeves, Claire E.

    2016-09-01

    According to atmospheric chemistry models, isoprene nitrates play an important role in determining the ozone production efficiency of isoprene; however this is very poorly constrained through observations as isoprene nitrates have not been widely measured. Measurements have been severely restricted largely due to a limited ability to measure individual isoprene nitrate isomers. An instrument based on gas chromatography/mass spectrometry (GCMS) and the associated calibration methods are described for the speciated measurements of individual isoprene nitrate isomers. Five of the primary isoprene nitrates which formed in the presence of NOx by reaction of isoprene with the hydroxyl radical (OH) in the Master Chemical Mechanism are identified using known isomers on two column phases and are fully separated on the Rtx-200 column. Three primary isoprene nitrates from the reaction of isoprene with the nitrate radical (NO3) are identified after synthesis from the already identified analogous hydroxy nitrate. A Tenax adsorbent-based trapping system allows the analysis of the majority of the known hydroxy and carbonyl primary isoprene nitrates, although not the (1,2)-IN isomer, under field-like levels of humidity and showed no impact from typical ambient concentrations of NOx and ozone.

  17. Groundwater nitrate contamination: Factors and indicators

    PubMed Central

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-01-01

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation. PMID:22906701

  18. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, J.-F.; Peeters, J.; Stavrakou, T.

    2013-11-01

    Photolysis is shown to be a major sink for isoprene-derived carbonyl nitrates, which constitute an important component of the total organic nitrate pool over vegetated areas. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as the likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photorates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methylvinylketone nitrates strongly supports our assumptions of large cross section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  19. Fast photolysis of carbonyl nitrates from isoprene

    NASA Astrophysics Data System (ADS)

    Müller, J.-F.; Peeters, J.; Stavrakou, T.

    2014-03-01

    Photolysis is shown to be a major sink for isoprene-derived carbonyl nitrates, which constitute an important component of the total organic nitrate pool over vegetated areas. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of α-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as a likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photo rates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methyl vinyl ketone nitrates strongly supports our assumptions of large cross-section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~ 3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

  20. Trend Analyses of Nitrate in Danish Groundwater

    NASA Astrophysics Data System (ADS)

    Hansen, B.; Thorling, L.; Dalgaard, T.; Erlandsen, M.

    2012-04-01

    This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends and trend reversals in the groundwater nitrate concentration. Secondly, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Thirdly, groundwater recharge CFC (Chlorofluorocarbon) age determination allows linking of the first two dataset. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark. Are the Danish groundwater monitoring strategy obtimal for detection of nitrate trends? Will the nitrate concentrations in Danish groundwater continue to decrease or are the Danish nitrate concentration levels now appropriate according to the Water Framework Directive?

  1. Groundwater nitrate contamination: factors and indicators.

    PubMed

    Wick, Katharina; Heumesser, Christine; Schmid, Erwin

    2012-11-30

    Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation.

  2. Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.

    ERIC Educational Resources Information Center

    Bretherick, Leslie

    1989-01-01

    Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

  3. Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.

    ERIC Educational Resources Information Center

    Bretherick, Leslie

    1989-01-01

    Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

  4. Phase Diagram of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-06-01

    Ammonium Nitrate (AN) has often been subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood - resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety, in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN, in different chemical environments, at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 15 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 673 K. The present study has been supported by the U.S. DHS under Award Number 2008-ST-061-ED0001.

  5. REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER

    EPA Science Inventory

    The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 “Determination of Nitrate-Nitrite by Automated Colorimetry,” employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

  6. Challenges with nitrate therapy and nitrate tolerance: prevalence, prevention, and clinical relevance.

    PubMed

    Thadani, Udho

    2014-08-01

    Nitrate therapy has been an effective treatment for ischemic heart disease for over 100 years. The anti-ischemic and exercise-promoting benefits of sublingually administered nitrates are well established. Nitroglycerin is indicated for the relief of an established attack of angina and for prophylactic use, but its effects are short lived. In an effort to increase the duration of beneficial effects, long-acting orally administered and topical applications of nitrates have been developed; however, following their continued or frequent daily use, patients soon develop tolerance to these long-acting nitrate preparations. Once tolerance develops, patients begin losing the protective effects of the long-acting nitrate therapy. By providing a nitrate-free interval, or declining nitrate levels at night, one can overcome or reduce the development of tolerance, but cannot provide 24-h anti-anginal and anti-ischemic protection. In addition, patients may be vulnerable to occurrence of rebound angina and myocardial ischemia during periods of absent nitrate levels at night and early hours of the morning, and worsening of exercise capacity prior to the morning dose of the medication. This has been a concern with nitroglycerin patches but not with oral formulations of isosorbide-5 mononitrates, and has not been adequately studied with isosorbide dinitrate. This paper describes problems associated with nitrate tolerance, reviews mechanisms by which nitrate tolerance and loss of efficacy develop, and presents strategies to avoid nitrate tolerance and maintain efficacy when using long-acting nitrate formulations.

  7. REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER

    EPA Science Inventory

    The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 “Determination of Nitrate-Nitrite by Automated Colorimetry,” employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

  8. Arabidopsis Nitrate Transporter NRT1.9 Is Important in Phloem Nitrate Transport[W][OA

    PubMed Central

    Wang, Ya-Yun; Tsay, Yi-Fang

    2011-01-01

    This study of the Arabidopsis thaliana nitrate transporter NRT1.9 reveals an important function for a NRT1 family member in phloem nitrate transport. Functional analysis in Xenopus laevis oocytes showed that NRT1.9 is a low-affinity nitrate transporter. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.9 is a plasma membrane transporter expressed in the companion cells of root phloem. In nrt1.9 mutants, nitrate content in root phloem exudates was decreased, and downward nitrate transport was reduced, suggesting that NRT1.9 may facilitate loading of nitrate into the root phloem and enhance downward nitrate transport in roots. Under high nitrate conditions, the nrt1.9 mutant showed enhanced root-to-shoot nitrate transport and plant growth. We conclude that phloem nitrate transport is facilitated by expression of NRT1.9 in root companion cells. In addition, enhanced root-to-shoot xylem transport of nitrate in nrt1.9 mutants points to a negative correlation between xylem and phloem nitrate transport. PMID:21571952

  9. Arabidopsis nitrate transporter NRT1.9 is important in phloem nitrate transport.

    PubMed

    Wang, Ya-Yun; Tsay, Yi-Fang

    2011-05-01

    This study of the Arabidopsis thaliana nitrate transporter NRT1.9 reveals an important function for a NRT1 family member in phloem nitrate transport. Functional analysis in Xenopus laevis oocytes showed that NRT1.9 is a low-affinity nitrate transporter. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.9 is a plasma membrane transporter expressed in the companion cells of root phloem. In nrt1.9 mutants, nitrate content in root phloem exudates was decreased, and downward nitrate transport was reduced, suggesting that NRT1.9 may facilitate loading of nitrate into the root phloem and enhance downward nitrate transport in roots. Under high nitrate conditions, the nrt1.9 mutant showed enhanced root-to-shoot nitrate transport and plant growth. We conclude that phloem nitrate transport is facilitated by expression of NRT1.9 in root companion cells. In addition, enhanced root-to-shoot xylem transport of nitrate in nrt1.9 mutants points to a negative correlation between xylem and phloem nitrate transport.

  10. Trichloroethylene, tetrachloroethylene, nitrates, and other chemicals in well water in the Fresno-Clovis Metropolitan Area.

    PubMed

    Kloos, H

    1997-01-01

    In this study, the author examined the spatial and temporal distribution of tetrachloroethylene, trichloroethylene, nitrate, and several other organic and inorganic chemicals in large community wells in the Fresno-Clovis Metropolitan Area and estimated the lifetime cancer risk associated with exposure to tetrachloroethylene and trichloroethylene. By 1992-1993, investigators found the industrial solvent tetrachloroethylene in 34 wells and found trichloroethylene in 16 wells. All wells had detectable levels of nitrate. In addition, investigators found radon, arsenic, cadmium, iron, manganese, trihalomethanes, and several other volatile organic chemicals in the wells, but only radon and arsenic posed a significant health risk. In 1995, 16 wells were closed because chemicals were found in them. Twenty-six of 248 (10.5%) active wells and 24 of 43 (55.8%) closed wells contained multiple contaminants, excluding nitrate. Between 1988 and 1993, concentrations of trichloroethylene, tetrachloroethylene, and nitrates increased in selected wells. Daily, monthly, and bimonthly variations in the concentrations of tetrachloroethylene, trichloroethylene, and nitrate were often considerable. Granulated activated carbon filtration reduced trichloroethylene levels in well water by 91%-95%, and the author examined its usefulness as a remedial measure. Estimated lifetime cancer risks for tetrachloroethylene and trichloroethylene were 1 excess cancer death per 9.5 million people and 1 excess death per 250 million, respectively. The author also included recommendations for the conduct of further epidemiological and environmental studies.

  11. Electrochemical removal of nitrate using ZVI packed bed bipolar electrolytic cell.

    PubMed

    Jeong, Joo-Young; Kim, Han-Ki; Kim, Jung-Hwan; Park, Joo-Yang

    2012-09-01

    The present study investigates the performance of the zero valent iron (ZVI, Fe(0)) packed bed bipolar electrolytic cell for nitrate removal. The packing mixture consists of ZVI as electronically conducting material and silica sand as non-conducting material between main cathode and anode electrodes. In the continuous column experiments for the simulated groundwater (initial nitrate and electrical conductivity of about 30 mg L(-1) as N and 300 μS cm(-1), respectively), above 99% of nitrate was removed at the applied potential of 600 V with the main anode placed on the bottom of reactor. The influx nitrate was converted to ammonia (20% to maximum 60%) and nitrite (always less than 0.5 mg L(-1) as N in the effluent). The optimum packing ratio (v/v) of silica sand to ZVI was found to be 1:1-2:1. Magnetite was observed on the surface of the used ZVI as corrosion product. The reduction at the lower part of the reactor in acidic condition and adsorption at the upper part of the reactor in alkaline condition are the major mechanism of nitrate removal.

  12. Effects of microbial redox cycling of iron on cast iron pipe corrosion in drinking water distribution systems.

    PubMed

    Wang, Haibo; Hu, Chun; Zhang, Lili; Li, Xiaoxiao; Zhang, Yu; Yang, Min

    2014-11-15

    Bacterial characteristics in corrosion products and their effect on the formation of dense corrosion scales on cast iron coupons were studied in drinking water, with sterile water acting as a reference. The corrosion process and corrosion scales were characterized by electrochemical and physico-chemical measurements. The results indicated that the corrosion was more rapidly inhibited and iron release was lower due to formation of more dense protective corrosion scales in drinking water than in sterile water. The microbial community and denitrifying functional genes were analyzed by pyrosequencing and quantitative polymerase chain reactions (qPCR), respectively. Principal component analysis (PCA) showed that the bacteria in corrosion products played an important role in the corrosion process in drinking water. Nitrate-reducing bacteria (NRB) Acidovorax and Hydrogenophaga enhanced iron corrosion before 6 days. After 20 days, the dominant bacteria became NRB Dechloromonas (40.08%) with the protective corrosion layer formation. The Dechloromonas exhibited the stronger corrosion inhibition by inducing the redox cycling of iron, to enhance the precipitation of iron oxides and formation of Fe3O4. Subsequently, other minor bacteria appeared in the corrosion scales, including iron-respiring bacteria and Rhizobium which captured iron by the produced siderophores, having a weaker corrosion-inhibition effect. Therefore, the microbially-driven redox cycling of iron with associated microbial capture of iron caused more compact corrosion scales formation and lower iron release.

  13. Regulation of nitrate assimilation in cyanobacteria.

    PubMed

    Ohashi, Yoshitake; Shi, Wei; Takatani, Nobuyuki; Aichi, Makiko; Maeda, Shin-ichi; Watanabe, Satoru; Yoshikawa, Hirofumi; Omata, Tatsuo

    2011-02-01

    Nitrate assimilation by cyanobacteria is inhibited by the presence of ammonium in the growth medium. Both nitrate uptake and transcription of the nitrate assimilatory genes are regulated. The major intracellular signal for the regulation is, however, not ammonium or glutamine, but 2-oxoglutarate (2-OG), whose concentration changes according to the change in cellular C/N balance. When nitrogen is limiting growth, accumulation of 2-OG activates the transcription factor NtcA to induce transcription of the nitrate assimilation genes. Ammonium inhibits transcription by quickly depleting the 2-OG pool through its metabolism via the glutamine synthetase/glutamate synthase cycle. The P(II) protein inhibits the ABC-type nitrate transporter, and also nitrate reductase in some strains, by an unknown mechanism(s) when the cellular 2-OG level is low. Upon nitrogen limitation, 2-OG binds to P(II) to prevent the protein from inhibiting nitrate assimilation. A pathway-specific transcriptional regulator NtcB activates the nitrate assimilation genes in response to nitrite, either added to the medium or generated intracellularly by nitrate reduction. It plays an important role in selective activation of the nitrate assimilation pathway during growth under a limited supply of nitrate. P(II) was recently shown to regulate the activity of NtcA negatively by binding to PipX, a small coactivator protein of NtcA. On the basis of accumulating genome information from a variety of cyanobacteria and the molecular genetic data obtained from the representative strains, common features and group- or species-specific characteristics of the response of cyanobacteria to nitrogen is summarized and discussed in terms of ecophysiological significance.

  14. Iron-refractory iron deficiency anemia (IRIDA).

    PubMed

    Heeney, Matthew M; Finberg, Karin E

    2014-08-01

    Iron deficiency anemia is a common global problem whose etiology is typically attributed to acquired inadequate dietary intake and/or chronic blood loss. However, in several kindreds multiple family members are affected with iron deficiency anemia that is unresponsive to oral iron supplementation and only partially responsive to parenteral iron therapy. The discovery that many of these cases harbor mutations in the TMPRSS6 gene led to the recognition that they represent a single clinical entity: iron-refractory iron deficiency anemia (IRIDA). This article reviews clinical features of IRIDA, recent genetic studies, and insights this disorder provides into the regulation of systemic iron homeostasis.

  15. Role for Fe(III) minerals in nitrate-dependent microbial U(IV) oxidation

    USGS Publications Warehouse

    Senko, John M.; Mohamed, Yasser; Dewers , Thomas A.; Krumholz, Lee R.

    2005-01-01

    Microbiological reduction of soluble U(VI) to insoluble U(IV) is a means of preventing the migration of that element in groundwater, but the presence of nitrate in U(IV)-containing sediments leads to U(IV) oxidation and remobilizaton. Nitrite or iron(III) oxyhydroxides may oxidize U(IV) under nitrate-reducing conditions, and we determined the rate and extent of U(IV) oxidation by these compounds. Fe(III) oxidized U(IV) at a greater rate than nitrite (130 and 10 μM U(IV)/day, respectively). In aquifer sediments, Fe(III) may be produced during microbial nitrate reduction by oxidation of Fe(II) with nitrite, or by enzymatic Fe(II) oxidation coupled to nitrate reduction. To determine which of these mechanisms was dominant, we isolated a nitrate-dependent acetate- and Fe(II)-oxidizing bacterium from a U(VI)- and nitrate-contaminated aquifer. This organism oxidized U(IV) at a greater rate and to a greater extent under acetate-oxidizing (where nitrite accumulated to 50 mM) than under Fe(II)-oxidizing conditions. We show that the observed differences in rate and extent of U(IV) oxidation are due to mineralogical differences between Fe(III) produced by reaction of Fe(II) with nitrite (amorphous) and Fe(III) produced enzymatically (goethite or lepidocrocite). Our results suggest the mineralogy and surface area of Fe(III) minerals produced under nitrate-reducing conditions affect the rate and extent of U(IV) oxidation. These results may be useful for predicting the stability of U(IV) in aquifers.

  16. Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why?

    PubMed Central

    Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.

    2014-01-01

    Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This

  17. Iron speciation and dynamics during SERIES, a mesoscale iron enrichment experiment in the NE Pacific

    NASA Astrophysics Data System (ADS)

    Wong, C. S.; Johnson, W. K.; Sutherland, N.; Nishioka, J.; Timothy, D. A.; Robert, M.; Takeda, S.

    2006-10-01

    During the Sub-arctic Ecosystem Response to Iron Enrichment Study (SERIES), the addition of ferrous iron to high-nitrate low-chlorophyll (HNLC) waters near Ocean Station PAPA (OSP: 50°N, 145°W) produced a phytoplankton bloom and CO 2 drawdown, as evidenced by decreasing CO 2 fugacity ( fCO 2). We analyzed five fractions or phases of iron: soluble (<0.03 μm), dissolved (<0.22 μm), total dissolved (acidified dissolved, <0.22 μm), labile (unfiltered), and total (acidified, unfiltered). From these, we also calculated non-labile iron, colloidal iron (0.03-0.22 μm), and both labile and non-labile particulate iron (>0.22 μm). Here, we describe iron distributions and the evolution of iron phases in the upper ocean during the experiment. We also present an iron budget accounting for horizontal and vertical dilution. At the time of our first sampling eight hours after fertilization was completed, total iron reached 8.6 nmol L -1 and dissolved iron was approximately 3 nmol L -1. Early in the experiment the dissolved iron phase decreased the most rapidly and by late day 6 the integrated dissolved iron (8.6 μmol m -2) represented less than 10% of the initial addition (90-95 μmol m -2). However at this same time the total integrated iron at the centre of the patch was still 52 μmol m -2 or almost 60% of the calculated initial addition. By day 12,45% of the added iron (from both injections) could be accounted for in the patch. The half-life of total iron in the patch for the first injection was estimated to be less than 5 days if dilution is not considered, but more than 13 days if dilution is taken into account. The most notable change in iron percentages from one form to another occurred early in the first week of the experiment where the predominant phase shift was from the colloidal portion of dissolved iron to labile particulate iron that could have been biologically induced or simply aggregation of oxyhydroxides. This was immediately followed by a physical event

  18. Iron supply and demand in the upper ocean

    SciTech Connect

    Fung, I.Y.; Meyn, S.K.; Tegen, I.; Doney, S.C.; John, J.; Bishop, J.

    1999-09-29

    Iron is hypothesized to be a limiting micronutrient for ocean primary production. This paper presents an analysis of the iron budget in the upper ocean. The global distribution of annual iron assimilation by phytoplankton was estimated from distributions of satellite-derived oceanic primary production and measured (Fe:C)(cellular) ratios. The distributions of iron supply by upwelling/mixing and aeolian deposition were obtained by applying (Fe:NO3)(dissolved) ratios to the nitrate supply and by assuming the soluble fraction of mineral aerosols. A lower bound on the rate of iron recycling in the photic zone was estimated as the difference between iron assimilation and supply. Global iron assimilation by phytoplankton for the open ocean was estimated to be 12 x 10(9) mol Fe yr(-1). Atmospheric deposition of total Fe is estimated to be 96 x 10(9) mol Fe yr(-1) in the open ocean, with the soluble Fe fraction ranging between 1 and 10 percent (or 1-10 x 10(9) mol Fe yr(-1)). By comparison, the upwelling/entrainment supply of dissolved Fe to the upper ocean is small, similar to 0.7 x 10(9) mol Fe yr(-1). Uncertainties in the aeolian flux and assimilation may be as large as a factor of 5-10 but remain difficult to quantify, as information is limited about the form and transformation of iron from the soil to phytoplankton incorporation. An iron stress index, relating the (Fe:N) demand to the (Fe:N) supply, confirms the production in the high-nitrate low-chlorophyll regions is indeed limited by iron availability.

  19. The contributions of nitrate uptake and efflux to isotope fractionation during algal nitrate assimilation

    NASA Astrophysics Data System (ADS)

    Karsh, K. L.; Trull, T. W.; Sigman, D. M.; Thompson, P. A.; Granger, J.

    2014-05-01

    In order to strengthen environmental application of nitrate N and O isotopes, we measured the N and O isotopic fractionation associated with cellular nitrate uptake and efflux in the nitrate-assimilating marine diatom Thalassiosira weissflogii. We isolated nitrate uptake and efflux from nitrate reduction by growing the cells in the presence of tungsten, which substitutes for molybdenum in assimilatory nitrate reductase, yielding an inactive enzyme. After growth on ammonium and then N starvation, cells were exposed to nitrate. Numerical models fit to the evolution of intracellular nitrate concentration and N and O isotopic composition yielded distinct N isotope effects (15ɛ) for nitrate uptake and nitrate efflux (2.0 ± 0.3‰ and 1.2 ± 0.4‰, respectively). The O isotope effects (18ɛ) for nitrate uptake and nitrate efflux were indistinguishable (2.8 ± 0.6‰), yielding a ratio of O to N isotopic fractionation for uptake of 1.4 ± 0.4 and for efflux of 2.3 ± 0.9. The 15ɛ for nitrate uptake can account for at most 40% of the organism-level N isotope effect (15ɛorg) measured in laboratory studies of T. weissflogii and in the open ocean (typically 5‰ or greater). This observation supports previous evidence that most isotope fractionation during nitrate assimilation is due to intracellular nitrate reduction, with nitrate efflux allowing the signal to be communicated to the environment. An O to N fractionation ratio (18ɛorg:15ɛorg) of ˜1 has been measured for nitrate assimilation in algal cultures and linked to the N and O isotope effects of nitrate reductase. Our results suggest that the ratios of O to N fractionation for both nitrate uptake and efflux may be distinct from a ratio of 1, to a degree that could cause the net 18ɛorg:15ɛorg to rise appreciably above 1 when 15ɛorg is low (e.g., yielding a ratio of 1.1 when 15ɛorg is 5‰). However, field and culture studies have consistently measured nearly equivalent fractionation of N and O isotopes in

  20. 76 FR 46907 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-03

    ... comments. SUMMARY: This proposed rule would implement anti-terrorism measures to better secure the homeland... purpose of preventing the use of ammonium nitrate in an act of terrorism. This proposed rule seeks comment... Regulations Addressing Ammonium Nitrate a. Chemical Facility Anti-Terrorism Standards b. U.S. Coast...

  1. Bacterial nitrate assimilation: gene distribution and regulation.

    PubMed

    Luque-Almagro, Víctor M; Gates, Andrew J; Moreno-Vivián, Conrado; Ferguson, Stuart J; Richardson, David J; Roldán, M Dolores

    2011-12-01

    In the context of the global nitrogen cycle, the importance of inorganic nitrate for the nutrition and growth of marine and freshwater autotrophic phytoplankton has long been recognized. In contrast, the utilization of nitrate by heterotrophic bacteria has historically received less attention because the primary role of these organisms has classically been considered to be the decomposition and mineralization of dissolved and particulate organic nitrogen. In the pre-genome sequence era, it was known that some, but not all, heterotrophic bacteria were capable of growth on nitrate as a sole nitrogen source. However, examination of currently available prokaryotic genome sequences suggests that assimilatory nitrate reductase (Nas) systems are widespread phylogenetically in bacterial and archaeal heterotrophs. Until now, regulation of nitrate assimilation has been mainly studied in cyanobacteria. In contrast, in heterotrophic bacterial strains, the study of nitrate assimilation regulation has been limited to Rhodobacter capsulatus, Klebsiella oxytoca, Azotobacter vinelandii and Bacillus subtilis. In Gram-negative bacteria, the nas genes are subjected to dual control: ammonia repression by the general nitrogen regulatory (Ntr) system and specific nitrate or nitrite induction. The Ntr system is widely distributed in bacteria, whereas the nitrate/nitrite-specific control is variable depending on the organism.

  2. NITRATE CONTAMINATION OF GROUND WATER (GW-761)

    EPA Science Inventory

    The occurrence of nitrate and related compounds in ground water is discussed from the perspectives of its natural as well as anthropogenic origins. A brief explanation of the nitrogen cycle touches on the production as well as utilization of ammonia, nitrite, nitrate, and nitrog...

  3. Dietary Nitrate, Nitric Oxide, and Cardiovascular Health.

    PubMed

    Bondonno, Catherine P; Croft, Kevin D; Hodgson, Jonathan M

    2016-09-09

    Emerging evidence strongly suggests that dietary nitrate, derived in the diet primarily from vegetables, could contribute to cardiovascular health via effects on nitric oxide (NO) status. NO plays an essential role in cardiovascular health. It is produced via the classical L-arginine-NO-synthase pathway and the recently discovered enterosalivary nitrate-nitrite-NO pathway. The discovery of this alternate pathway has highlighted dietary nitrate as a candidate for the cardioprotective effect of a diet rich in fruit and vegetables. Clinical trials with dietary nitrate have observed improvements in blood pressure, endothelial function, ischemia-reperfusion injury, arterial stiffness, platelet function, and exercise performance with a concomitant augmentation of markers of NO status. While these results are indicative of cardiovascular benefits with dietary nitrate intake, there is still a lingering concern about nitrate in relation to methemoglobinemia, cancer, and cardiovascular disease. It is the purpose of this review to present an overview of NO and its critical role in cardiovascular health; to detail the observed vascular benefits of dietary nitrate intake through effects on NO status as well as to discuss the controversy surrounding the possible toxic effects of nitrate.

  4. Intravesical silver nitrate for refractory hemorrhagic cystitis

    PubMed Central

    Montgomery, Brian D.; Boorjian, Stephen A.; Ziegelmann, Matthew J.; Joyce, Daniel D.; Linder, Brian J.

    2016-01-01

    Objective Hemorrhagic cystitis is a challenging clinical entity with limited evidence available to guide treatment. The use of intravesical silver nitrate has been reported, though supporting literature is sparse. Here, we sought to assess outcomes of patients treated with intravesical silver nitrate for refractory hemorrhagic cystitis. Material and methods We identified nine patients with refractory hemorrhagic cystitis treated at our institution with intravesical silver nitrate between 2000–2015. All patients had failed previous continuous bladder irrigation with normal saline and clot evacuation. Treatment success was defined as requiring no additional therapy beyond normal saline irrigation after silver nitrate instillation prior to hospital discharge. Results Median patient age was 80 years (IQR 73, 82). Radiation was the most common etiology for hemorrhagic cystitis 89% (8/9). Two patients underwent high dose (0.1%–0.4%) silver nitrate under anesthesia, while the remaining seven were treated with doses from 0.01% to 0.1% via continuous bladder irrigation for a median of 3 days (range 2–4). All nine patients (100%) had persistent hematuria despite intravesical silver nitrate therapy, requiring additional interventions and red blood cell transfusion during the hospitalization. There were no identified complications related to intravesical silver nitrate instillation. Conclusion Although well tolerated, we found that intravesical silver nitrate was ineffective for bleeding control, suggesting a limited role for this agent in the management of patients with hemorrhagic cystitis. PMID:27635296

  5. COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS

    EPA Science Inventory

    A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

  6. COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS

    EPA Science Inventory

    A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

  7. Aerosol-spray diverse mesoporous metal oxides from metal nitrates

    PubMed Central

    Kuai, Long; Wang, Junxin; Ming, Tian; Fang, Caihong; Sun, Zhenhua; Geng, Baoyou; Wang, Jianfang

    2015-01-01

    Transition metal oxides are widely used in solar cells, batteries, transistors, memories, transparent conductive electrodes, photocatalysts, gas sensors, supercapacitors, and smart windows. In many of these applications, large surface areas and pore volumes can enhance molecular adsorption, facilitate ion transfer, and increase interfacial areas; the formation of complex oxides (mixed, doped, multimetallic oxides and oxide-based hybrids) can alter electronic band structures, modify/enhance charge carrier concentrations/separation, and introduce desired functionalities. A general synthetic approach to diverse mesoporous metal oxides is therefore very attractive. Here we describe a powerful aerosol-spray method for synthesizing various mesoporous metal oxides from low-cost nitrate salts. During spray, thermal heating of precursor droplets drives solvent evaporation and induces surfactant-directed formation of mesostructures, nitrate decomposition and oxide cross-linking. Thirteen types of monometallic oxides and four groups of complex ones are successfully produced, with mesoporous iron oxide microspheres demonstrated for photocatalytic oxygen evolution and gas sensing with superior performances. PMID:25897988

  8. Aerosol-spray diverse mesoporous metal oxides from metal nitrates.

    PubMed

    Kuai, Long; Wang, Junxin; Ming, Tian; Fang, Caihong; Sun, Zhenhua; Geng, Baoyou; Wang, Jianfang

    2015-04-21

    Transition metal oxides are widely used in solar cells, batteries, transistors, memories, transparent conductive electrodes, photocatalysts, gas sensors, supercapacitors, and smart windows. In many of these applications, large surface areas and pore volumes can enhance molecular adsorption, facilitate ion transfer, and increase interfacial areas; the formation of complex oxides (mixed, doped, multimetallic oxides and oxide-based hybrids) can alter electronic band structures, modify/enhance charge carrier concentrations/separation, and introduce desired functionalities. A general synthetic approach to diverse mesoporous metal oxides is therefore very attractive. Here we describe a powerful aerosol-spray method for synthesizing various mesoporous metal oxides from low-cost nitrate salts. During spray, thermal heating of precursor droplets drives solvent evaporation and induces surfactant-directed formation of mesostructures, nitrate decomposition and oxide cross-linking. Thirteen types of monometallic oxides and four groups of complex ones are successfully produced, with mesoporous iron oxide microspheres demonstrated for photocatalytic oxygen evolution and gas sensing with superior performances.

  9. Vinegar-amended anaerobic biosand filter for the removal of arsenic and nitrate from groundwater.

    PubMed

    Snyder, Kathryn V; Webster, Tara M; Upadhyaya, Giridhar; Hayes, Kim F; Raskin, Lutgarde

    2016-04-15

    The performance of a vinegar-amended anaerobic biosand filter was evaluated for future application as point-of-use water treatment in rural areas for the removal of arsenic and nitrate from groundwater containing common ions. Due to the importance of sulfate and iron in arsenic removal and their variable concentrations in groundwater, influent sulfate and iron concentrations were varied. Complete removal of influent nitrate (50 mg/L) and over 50% removal of influent arsenic (200 μg/L) occurred. Of all conditions tested, the lowest median effluent arsenic concentration was 88 μg/L. Iron removal occurred completely when 4 mg/L was added, and sulfate concentrations were lowered to a median concentration <2 mg/L from influent concentrations of 22 and 50 mg/L. Despite iron and sulfate removal and the establishment of reducing conditions, arsenic concentrations remained above the World Health Organization's arsenic drinking water standard. Further research is necessary to determine if anaerobic biosand filters can be improved to meet the arsenic drinking water standard and to evaluate practical implementation challenges. Copyright © 2016. Published by Elsevier Ltd.

  10. 70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  11. Nitrate removal from drinking water -- Review

    SciTech Connect

    Kapoor, A.; Viraraghavan, T.

    1997-04-01

    Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that ion exchange and biological denitrification are more acceptable for nitrate removal than reverse osmosis. Ion exchange is more viable for ground water while biological denitrification is the preferred alternative for surface water. This paper reviews the developments in the field of nitrate removal processes.

  12. Dietary nitrates, nitrites, and cardiovascular disease.

    PubMed

    Hord, Norman G

    2011-12-01

    Dietary nitrate (NO(3)), nitrite (NO(2)), and arginine can serve as sources for production of NO(x) (a diverse group of metabolites including nitric oxide, nitrosothiols, and nitroalkenes) via ultraviolet light exposure to skin, mammalian nitrate/nitrite reductases in tissues, and nitric oxide synthase enzymes, respectively. NO(x) are responsible for the hypotensive, antiplatelet, and cytoprotective effects of dietary nitrates and nitrites. Current regulatory limits on nitrate intakes, based on concerns regarding potential risk of carcinogenicity and methemoglobinemia, are exceeded by normal daily intakes of single foods, such as soya milk and spinach, as well as by some recommended dietary patterns such as the Dietary Approaches to Stop Hypertension diet. This review includes a call for regulatory bodies to consider all available data on the beneficial physiologic roles of nitrate and nitrite in order to derive rational bases for dietary recommendations.

  13. Use of nitrates in ischemic heart disease.

    PubMed

    Giuseppe, Cocco; Paul, Jerie; Hans-Ulrich, Iselin

    2015-01-01

    Short-acting nitrates are beneficial in acute myocardial ischemia. However, many unresolved questions remain about the use of long-acting nitrates in stable ischemic heart disease. The use of long-acting nitrates is weakened by the development of endothelial dysfunction and tolerance. Also, we currently ignore whether lower doses of transdermal nitroglycerin would be better than those presently used. Multivariate analysis data from large nonrandomized studies suggested that long-acting nitrates increase the incidence of acute coronary syndromes, while data from another multivariate study indicate that they have positive effects. Because of methodological differences and open questions, the two studies cannot be compared. A study in Japanese patients with vasospastic angina has shown that, when compared with calcium antagonists, long-acting nitrates do not improve long-term prognosis and that the risk for cardiac adverse events increases with the combined therapy. We have many unanswered questions.

  14. Methemoglobinemia: nitrate toxicity in rural America

    SciTech Connect

    Kross, B.C.; Ayebo, A.D.; Fuortes, L.J. )

    1992-07-01

    Nitrates are frequently found in vegetables and ground water. Nitrate levels in ground water have increased over the past two decades because of the heightened use of nitrogenous fertilizers. Following ingestion, nitrates are converted to nitrites by fecal organisms. Nitrites are absorbed and form methemoglobin, which interferes with the oxygen-carrying capacity of hemoglobin. Infants are particularly susceptible to nitrate poisoning because fetal hemoglobin is more readily oxidized to methemoglobin. In infants, the most common source of nitrate exposure is well water, which is mixed with infant formula. Affected infants may present with asymptomatic cyanosis, which can progress to dyspnea and lethargy or coma. Blood methemoglobin concentrations are elevated. Treatment consists of the administration of oxygen and intravenous and oral methylene blue.24 references.

  15. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(-)-myrtenol nitrate.

    PubMed

    Bew, Sean P; Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a 'halide for nitrate' substitution. Employing readily available starting materials, reagents and Horner-Wadsworth-Emmons chemistry the synthesis of easily separable, synthetically versatile 'key building blocks' (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, 'off the shelf' materials. Exploiting their reactivity we have studied their ability to undergo an 'allylic halide for allylic nitrate' substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates ('isoprene nitrates') in 66-80% overall yields. Using NOESY experiments the elucidation of the carbon-carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our 'halide for nitrate' substitution chemistry we outline the straightforward transformation of (1R,2S)-(-)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(-)-myrtenol nitrate.

  16. Transdermal iron replenishment therapy.

    PubMed

    Modepalli, Naresh; Shivakumar, H N; Kanni, K L Paranjothy; Murthy, S Narasimha

    2015-01-01

    Iron deficiency anemia is one of the major nutritional deficiency disorders. Iron deficiency anemia occurs due to decreased absorption of iron from diet, chronic blood loss and other associated diseases. The importance of iron and deleterious effects of iron deficiency anemia are discussed briefly in this review followed by the transdermal approaches to deliver iron. Transdermal delivery of iron would be able to overcome the side effects associated with conventional oral and parenteral iron therapy and improves the patient compliance. During preliminary investigations, ferric pyrophosphate and iron dextran were selected as iron sources for transdermal delivery. Different biophysical techniques were explored to assess their efficiency in delivering iron across the skin, and in vivo studies were carried out using anemic rat model. Transdermal iron delivery is a promising approach that could make a huge positive impact on patients suffering with iron deficiency.

  17. [Iron dysregulation and anemias].

    PubMed

    Ikuta, Katsuya

    2015-10-01

    Most iron in the body is utilized as a component of hemoglobin that delivers oxygen to the entire body. Under normal conditions, the iron balance is tightly regulated. However, iron dysregulation does occasionally occur; total iron content reductions cause iron deficiency anemia and overexpression of the iron regulatory peptide hepcidin disturbs iron utilization resulting in anemia of chronic disease. Conversely, the presence of anemia may ultimately lead to iron overload; for example, thalassemia, a common hereditary anemia worldwide, often requires transfusion, but long-term transfusions cause iron accumulation that leads to organ damage and other poor outcomes. On the other hand, there is a possibility that iron overload itself can cause anemia; iron chelation therapy for the post-transfusion iron overload observed in myelodysplastic syndrome or aplastic anemia improves dependency on transfusions in some cases. These observations reflect the extremely close relationship between anemias and iron metabolism.

  18. Pharmacology of Iron Transport

    PubMed Central

    Byrne, Shaina L.; Krishnamurthy, Divya; Wessling-Resnick, Marianne

    2013-01-01

    Elucidating the molecular basis for the regulation of iron uptake, storage, and distribution is necessary to understand iron homeostasis. Pharmacological tools are emerging to identify and distinguish among different iron transport pathways. Stimulatory or inhibitory small molecules with effects on iron uptake can help characterize the mechanistic elements of iron transport and the roles of the transporters involved in these processes. In particular, iron chelators can serve as potential pharmacological tools to alleviate diseases of iron overload. This review focuses on the pharmacology of iron transport, introducing iron transport membrane proteins and known inhibitors. PMID:23020294

  19. Pharmacology of iron transport.

    PubMed

    Byrne, Shaina L; Krishnamurthy, Divya; Wessling-Resnick, Marianne

    2013-01-01

    Elucidating the molecular basis for the regulation of iron uptake, storage, and distribution is necessary to understand iron homeostasis. Pharmacological tools are emerging to identify and distinguish among different iron transport pathways. Stimulatory or inhibitory small molecules with effects on iron uptake can help characterize the mechanistic elements of iron transport and the roles of the transporters involved in these processes. In particular, iron chelators can serve as potential pharmacological tools to alleviate diseases of iron overload. This review focuses on the pharmacology of iron transport, introducing iron transport membrane proteins and known inhibitors.

  20. PREPARATION OF DIBASIC ALUMINUM NITRATE

    DOEpatents

    Gresky, A.T.; Nurmi, E.O.; Foster, D.L.; Wischow, R.P.; Savolainen, J.E.

    1960-04-01

    A method is given for the preparation and recovery of basic aluminum nltrates having an OH: Al ratio of at least two, comprising two steps. First, metallic aluminum is dissolved in aqueous Al(NO/sub 3/)/sub 3/, in the presence of a small quantity of elemental or ionic mercury, to increase its Al: NO/sub 3/ ratio into the range 1 to 1.2. The resulting aqueous solution is then added to an excess of a special organic solvent, typically a mixture of five parts methanol and six parts diethyl ether, whereupon the basic aluminum nitrate, e.g. Al/sub 6/(OH)/sub 13/-(NO/sub 3/)/sub 5/, recoverably precipitates.

  1. Bacterial Nitration of 4-Chlorobiphenyl

    PubMed Central

    Sylvestre, Michel; Massé, Robert; Messier, François; Fauteux, Johanne; Bisaillon, Jean-Guy; Beaudet, Réjean

    1982-01-01

    In the course of a study dealing with the biodegradation of 4-chlorobiphenyl by strain B-206, we noticed that the gram-negative bacterium accumulated different metabolic intermediates depending on the nitrogen source of the medium. Hence, in the presence of nitrate, strain B-206 produced four compounds which were identified as 2- and 4-hydroxy-4′-chlorobiphenyl and 2- and 4-hydroxy-mononitro-4′-chlorobiphenyl. The accumulation of these compounds in the culture medium indicated the presence of a monooxygenase in strain B-206 leading to the production of arene oxide intermediates. The possible transformation of 4-chlorobiphenyl to an arene oxide by this bacterial strain is a matter of concern because of the high reactivity of these arene oxides with biological material. PMID:16346111

  2. Global distribution of peroxyacetyl nitrate

    NASA Technical Reports Server (NTRS)

    Singh, H. B.; Salas, L. J.; Viezee, W.

    1986-01-01

    Peroxyacetyl nitrate (PAN) atmospheric concentration samples were collected hourly from an ocean vessel 50 mi off the continental coast traveling from Seattle to Chile in 1984. Air concentration data for PAN and light hydrocarbons (LHC) were also taken by aircraft in the same period over Wyoming and Colorado and over the eastern Pacific. The PAN concentrations were higher and more variable in the Northern Hemisphere than in the Southern Hemisphere, increased with altitude, and were higher in the winter than in summer. The summer PAN concentrations were higher in the continental troposphere than in the marine troposphere. The results show that photochemical models of the atmosphere which do not account for the reaction between nonmethane hydrocarbons and PAN will probably overestimate the abundances of NO(x) and HNO3. The collection of further PAN concentration data is recommended as a means to characterizing the moderating role of PAN in the photochemistry of the troposphere.

  3. Phase diagram of ammonium nitrate

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-01

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  4. Nitrate Transport, Sensing, and Responses in Plants.

    PubMed

    O'Brien, José A; Vega, Andrea; Bouguyon, Eléonore; Krouk, Gabriel; Gojon, Alain; Coruzzi, Gloria; Gutiérrez, Rodrigo A

    2016-06-06

    Nitrogen (N) is an essential macronutrient that affects plant growth and development. N is an important component of chlorophyll, amino acids, nucleic acids, and secondary metabolites. Nitrate is one of the most abundant N sources in the soil. Because nitrate and other N nutrients are often limiting, plants have developed sophisticated mechanisms to ensure adequate supply of nutrients in a variable environment. Nitrate is absorbed in the root and mobilized to other organs by nitrate transporters. Nitrate sensing activates signaling pathways that impinge upon molecular, metabolic, physiological, and developmental responses locally and at the whole plant level. With the advent of genomics technologies and genetic tools, important advances in our understanding of nitrate and other N nutrient responses have been achieved in the past decade. Furthermore, techniques that take advantage of natural polymorphisms present in divergent individuals from a single species have been essential in uncovering new components. However, there are still gaps in our understanding of how nitrate signaling affects biological processes in plants. Moreover, we still lack an integrated view of how all the regulatory factors identified interact or crosstalk to orchestrate the myriad N responses plants typically exhibit. In this review, we provide an updated overview of mechanisms by which nitrate is sensed and transported throughout the plant. We discuss signaling components and how nitrate sensing crosstalks with hormonal pathways for developmental responses locally and globally in the plant. Understanding how nitrate impacts on plant metabolism, physiology, and growth and development in plants is key to improving crops for sustainable agriculture. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

  5. Use of Ferrihydrite-Coated Pozzolana and Biogenic Green Rust to Purify Waste Water Containing Phosphate and Nitrate

    SciTech Connect

    Ruby, Christian; Naille, Sébastien; Ona-Nguema, Georges; Morin, Guillaume; Mallet, Martine; Guerbois, Delphine; Barthélémy, Kévin; Etique, Marjorie; Zegeye, Asfaw; Zhang, Yuhai; Boumaïza, Hella; Al-Jaberi, Muayad; Renard, Aurélien; Noël, Vincent; Binda, Paul; Hanna, Khalil; Despas, Christelle; Abdelmoula, Mustapha; Kukkadapu, Ravi; Sarrias, Joseph; Albignac, Magali; Rocklin, Pascal; Nauleau, Fabrice; Hyvrard, Nathalie; Génin, Jean-Marie

    2016-06-27

    The activated sludge treatments combined to the addition of ferric chloride is commonly used to eliminate nitrate and phosphate from waste water in urban area. These processes that need costly infrastructures are not suitable for rural areas and passive treatments (lagoons, reed bed filters…) are more frequently performed. Reed bed filters are efficient for removing organic matter but are not suitable for treating phosphate and nitrate as well. Passive water treatments using various materials (hydroxyapatite, slag…) were already performed, but those allowing the elimination of both nitrate and phosphate are not actually available. The goal of this work is to identify the most suitable iron based materials for such treatments and to determine their optimal use conditions, in particular in hydrodynamic mode. The reactivity of the iron based minerals was measured either by using free particles in suspension or by depositing these particles on a solid substrate. Pouzzolana that is characterized by a porous sponge-like structure suits for settling a high amount of iron oxides. The experimental conditions enabling to avoid any ammonium formation when green rust encounters nitrate were determined within the framework of a full factorial design. The process is divided into two steps that will be performed inside two separated reactors. Indeed, the presence of phosphate inhibits the reduction of nitrate by green rust and the dephosphatation process must precede the denitrification process. In order to remove phosphate, ferrihydrite coated pouzzolana is the best materials. The kinetics of reaction of green rust with nitrate is relatively slow and often leads to the formation of ammonium. The recommendation of the identified process is to favor the accumulation of nitrite in a first step, these species reacting much more quickly with green rust and do not transform into ammonium.

  6. Sedimentary nitrate reduction and its effect on the N-isotopic composition of oceanic nitrate

    NASA Astrophysics Data System (ADS)

    Lehmann, M. F.; Sigman, D. M.; McCorkle, D. C.

    2005-12-01

    A prerequisite for assessing denitrification fluxes in a specific environment using water column nitrate N isotope ratios is the knowledge of the expressed N isotope effects of water column and/or benthic denitrification in this environment. Here, we aim at assessing the effects of benthic nitrogen cycling on the N isotopic composition of the oceanic nitrate pool in deep-sea sediments, which are believed to harbour a large portion of the global benthic denitrification. We report 15N/14N ratios of pore water nitrate in pelagic sediments from the deep Bering Sea, where benthic nitrate reduction has previously been identified as a significant sink of fixed nitrogen. Porewater profiles from multicores indicate strong 15N enrichment in porewater nitrate at all stations, as one goes deeper in the sediments and nitrate concentrations decrease (δ15N generally reached 25-35‰). Our data are consistent with variable biological isotope effect (ɛ) for dissimilatory nitrate reduction ranging between 13 to 30 ‰. A one-dimensional diffusion-reaction model including organic matter degradation, nitrification, and denitrification indicates that, although denitrification leads to a pore water nitrate pool that is enriched in 15N, N isotope fractionation is poorly expressed at the scale of sediment-water nitrate exchange, independent of whether sediments are a net sink or a net source of nitrate. The apparent nitrate isotope effect of sedimentary denitrification on nitrate in overlying waters is generally below 2‰, as a result of diffusive transport limitation into, and within, the sediments and/or the production of light nitrate during nitrification. Thus, our data suggest that the low expressed isotope effect of benthic denitrification observed previously in reactive shelf sediments also applies to deep-sea sediments. However, where ammonium fluxes out of the sediments, it is enriched in 15-N, and may ultimately lead to an N-isotopic enrichment of the water-column nitrate

  7. Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants.

    PubMed

    Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

    2013-05-01

    In fungi, transcriptional activation of genes involved in NO3(-) assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an "autoregulation control" model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show "pseudo-constitutivity" due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest that

  8. Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants

    PubMed Central

    Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

    2013-01-01

    In fungi, transcriptional activation of genes involved in NO3- assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an “autoregulation control” model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show “pseudo-constitutivity” due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest

  9. Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface

    SciTech Connect

    Wu, Weimin; Carley, Jack M; Green, Stefan; Luo, Jian; Kelly, Shelly D; Van Nostrand, Joy; Lowe, Kenneth Alan; Mehlhorn, Tonia L; Carroll, Sue L; Boonchayanant, Dr. Benjaporn; Loeffler, Frank E; Jardine, Philip M; Criddle, Craig

    2010-06-01

    The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H{sub 2}S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 {mu}M.

  10. 'Low-acid' sulfide oxidation using nitrate-enriched groundwater

    NASA Astrophysics Data System (ADS)

    Donn, Michael; Boxall, Naomi; Reid, Nathan; Meakin, Rebecca; Gray, David; Kaksonen, Anna; Robson, Thomas; Shiers, Denis

    2016-04-01

    where pH remains neutral. The "low-acid" oxidation of sulfides with nitrate as an electron acceptor has been demonstrated at the laboratory scale. In 90-day microcosm respirometry experiments, we exposed a mixture of pulverized quartz and pyrite -rich ore to natural, high-nitrate groundwater and inoculated the microcosms with a culture of aerobic and anaerobic nitrate-dependent iron and sulfur-oxidising microorganisms, which were enriched from ore, groundwater and activated waste water. Incubations were performed under both oxic and anoxic conditions, in addition to abiotic controls. Initial results show that oxidation of the sulfides under nitrate-rich and microbially enhanced conditions does produce less acid than the same material under oxic conditions, and to some degree can match the models as long as oxygen ingress can be controlled. These results are the focus of further research into how this process can be enhanced and whether it can be applied in the field. Nitrate-driven oxidation of sulfides could potentially be used as a new approach to reduce acid generation and leaching of contaminants from waste dumps, in a passive or actively managed process designed to deplete and/or ameliorate (i.e. through surface passivation) the mineralogical hazard. Developing our understanding of biological aspects of these processes may also allow testing of longer-term "bio-caps" for various tailings and dump materials.

  11. Iron and Your Child

    MedlinePlus

    ... get iron by eating foods like meat and dark green leafy vegetables. Iron is also added to ... tofu dried beans and peas dried fruits leafy dark green vegetables iron-fortified breakfast cereals, breads, and ...

  12. Iron metabolism and toxicity

    SciTech Connect

    Papanikolaou, G.; Pantopoulos, K. . E-mail: kostas.pantopoulos@mcgill.ca

    2005-01-15

    Iron is an essential nutrient with limited bioavailability. When present in excess, iron poses a threat to cells and tissues, and therefore iron homeostasis has to be tightly controlled. Iron's toxicity is largely based on its ability to catalyze the generation of radicals, which attack and damage cellular macromolecules and promote cell death and tissue injury. This is lucidly illustrated in diseases of iron overload, such as hereditary hemochromatosis or transfusional siderosis, where excessive iron accumulation results in tissue damage and organ failure. Pathological iron accumulation in the liver has also been linked to the development of hepatocellular cancer. Here we provide a background on the biology and toxicity of iron and the basic concepts of iron homeostasis at the cellular and systemic level. In addition, we provide an overview of the various disorders of iron overload, which are directly linked to iron's toxicity. Finally, we discuss the potential role of iron in malignant transformation and cancer.

  13. CARBON-BASED REACTIVE BARRIER FOR NITRATE ...

    EPA Pesticide Factsheets

    Nitrate (NO3-) is a common ground water contaminant related to agricultural activity, waste water disposal, leachate from landfills, septic systems, and industrial processes. This study reports on the performance of a carbon-based permeable reactive barrier (PRB) that was constructed for in-situ bioremediation of a ground water nitrate plume caused by leakage from a swine CAFO (concentrated animal feeding operation) lagoon. The swine CAFO, located in Logan County, Oklahoma, was in operation from 1992-1999. The overall site remediation strategy includes an ammonia recovery trench to intercept ammonia-contaminated ground water and a hay straw PRB which is used to intercept a nitrate plume caused by nitrification of sorbed ammonia. The PRB extends approximately 260 m to intercept the nitrate plume. The depth of the trench averages 6 m and corresponds to the thickness of the surficial saturated zone; the width of the trench is 1.2 m. Detailed quarterly monitoring of the PRB began in March, 2004, about 1 year after construction activities ended. Nitrate concentrations hydraulically upgradient of the PRB have ranged from 23 to 77 mg/L N, from 0 to 3.2 mg/L N in the PRB, and from 0 to 65 mg/L N hydraulically downgradient of the PRB. Nitrate concentrations have generally decreased in downgradient locations with successive monitoring events. Mass balance considerations indicate that nitrate attenuation is dominantly from denitrification but with some component of

  14. CARBON-BASED REACTIVE BARRIER FOR NITRATE ...

    EPA Pesticide Factsheets

    Nitrate (NO3-) is a common ground water contaminant related to agricultural activity, waste water disposal, leachate from landfills, septic systems, and industrial processes. This study reports on the performance of a carbon-based permeable reactive barrier (PRB) that was constructed for in-situ bioremediation of a ground water nitrate plume caused by leakage from a swine CAFO (concentrated animal feeding operation) lagoon. The swine CAFO, located in Logan County, Oklahoma, was in operation from 1992-1999. The overall site remediation strategy includes an ammonia recovery trench to intercept ammonia-contaminated ground water and a hay straw PRB which is used to intercept a nitrate plume caused by nitrification of sorbed ammonia. The PRB extends approximately 260 m to intercept the nitrate plume. The depth of the trench averages 6 m and corresponds to the thickness of the surficial saturated zone; the width of the trench is 1.2 m. Detailed quarterly monitoring of the PRB began in March, 2004, about 1 year after construction activities ended. Nitrate concentrations hydraulically upgradient of the PRB have ranged from 23 to 77 mg/L N, from 0 to 3.2 mg/L N in the PRB, and from 0 to 65 mg/L N hydraulically downgradient of the PRB. Nitrate concentrations have generally decreased in downgradient locations with successive monitoring events. Mass balance considerations indicate that nitrate attenuation is dominantly from denitrification but with some component of

  15. Modeling nitrate removal in a denitrification bed.

    PubMed

    Ghane, Ehsan; Fausey, Norman R; Brown, Larry C

    2015-03-15

    Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12 μg N m(-2) min(-1)) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2 mg N L(-1). We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality.

  16. Vertical Nitrate Fluxes in the Oligotrophic Ocean

    NASA Astrophysics Data System (ADS)

    Lewis, Marlon R.; Harrison, W. Glen; Oakey, Neil S.; Hebert, David; Platt, Trevor

    1986-11-01

    The vertical flux of nitrate across the thermocline in the upper ocean imposes a rigorous constraint on the rate of export of organic carbon from the surface layer of the sea. This export is the primary means by which the oceans can serve as a sink for atmospheric carbon dioxide. For the oligotrophic open ocean regions, which make up more than 75% of the world's ocean, the rate of export is currently uncertain by an order of magnitude. For most of the year, the vertical flux of nitrate is that due to vertical turbulent transport of deep water rich in nitrate into the relatively impoverished surface layer. Direct measurements of rates of turbulent kinetic energy dissipation, coupled with highly resolved vertical profiles of nitrate and density in the oligotrophic eastern Atlantic showed that the rate of transport, averaged over 2 weeks, was 0.14 (0.002 to 0.89, 95% confidence interval) millimole of nitrate per square meter per day and was statistically no different from the integrated rate of nitrate uptake as measured by incorporation of 15N-labeled nitrate. The stoichiometrically equivalent loss of carbon from the upper ocean, which is the relevant quantity for the carbon dioxide and climate question, is then fixed at 0.90 (0.01 to 5.70) millimole of carbon per square meter per day. These rates are much lower than recent estimates based on in situ changes in oxygen over annual scales; they are consistent with a biologically unproductive oligotrophic ocean.

  17. Significant mixed layer nitrification in a natural iron-fertilized bloom of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Fripiat, F.; Elskens, M.; Trull, T. W.; Blain, S.; Cavagna, A.-J.; Fernandez, C.; Fonseca-Batista, D.; Planchon, F.; Raimbault, P.; Roukaerts, A.; Dehairs, F.

    2015-11-01

    Nitrification, the microbially mediated oxidation of ammonium into nitrate, is generally expected to be low in the Southern Ocean mixed layer. This paradigm assumes that nitrate is mainly provided through vertical mixing and assimilated during the vegetative season, supporting the concept that nitrate uptake is equivalent to the new primary production (i.e., primary production which is potentially available for export). Here we show that nitrification is significant (~40-80% of the seasonal nitrate uptake) in the naturally iron-fertilized bloom over the southeast Kerguelen Plateau. Hence, a large fraction of the nitrate-based primary production is regenerated, instead of being exported. It appears that nitrate assimilation (light dependent) and nitrification (partly light inhibited) are spatially separated between the upper and lower parts, respectively, of the deep surface mixed layers. These deep mixed layers, extending well below the euphotic layer, allow nitrifiers to compete with phytoplankton for the assimilation of ammonium. The high contributions of nitrification to nitrate uptake are in agreement with both low export efficiency (i.e., the percentage of primary production that is exported) and low seasonal nitrate drawdown despite high nitrate assimilation.

  18. Groundwater Head Control of Catchment Nitrate Export

    NASA Astrophysics Data System (ADS)

    Musolff, A.; Schmidt, C.; Rode, M.; Fleckenstein, J. H.

    2014-12-01

    Elevated nutrient fluxes from agricultural catchments affect downstream water resources. A method to assess nutrient fluxes is the evaluation of the export regime. The export regime classifies the relation between concentration and discharge and integrates mobilization as well as retention processes. Solutes can be exported chemostatically (variance of concentration << variance of discharge) or chemodynamically (variance of concentration ≥ variance of discharge). Starting point of this study is the evaluation of export regimes of nitrate in a series of neighboring sub-catchments of the Central German River Bode catchment. We found an accretion pattern of nitrate with increasing concentration when discharge is increasing and thus a chemodynamic export regime. Here we follow a nested approach and have a closer look at the controls of nitrate export in the small (1.4 km2) headwater catchment of the Sauerbach stream. The Sauerbach catchment is dominated by agricultural land use and is characterized by tile drains. We hypothesize that discharge as well as nitrate export is controlled by the groundwater head variability over time. To that end we follow a joint data analysis of discharge, groundwater heads and nitrate concentrations in groundwater, tile drains and surface water. At the gauging station the nitrate export is chemodynamic exhibiting the typical accretion pattern also found at the larger scale. Our data analysis shows that nitrate export regime is in two ways controlled by the depth to groundwater and the groundwater head variability: Discharge increases with increasing groundwater heads due to the activation of tile drains. On the other hand, depth to groundwater and passage through the unsaturated zone is the major control of aquifer nitrate concentration. At wells with larger depth to groundwater nitrate concentrations are significantly lower than at more shallow wells indicating retention processes in the unsaturated zone. Therefore the concentration in

  19. Photodegradation of Paracetamol in Nitrate Solution

    SciTech Connect

    Meng Cui; Qu Ruijuan; Liang Jinyan; Yang Xi

    2010-11-24

    The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

  20. Photodegradation of Paracetamol in Nitrate Solution

    NASA Astrophysics Data System (ADS)

    Meng, Cui; Qu, Ruijuan; Liang, Jinyan; Yang, Xi

    2010-11-01

    The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

  1. Effect of nitrate injection on the bacterial community in a water-oil tank system analyzed by PCR-DGGE.

    PubMed

    Jurelevicius, Diogo; von der Weid, Irene; Korenblum, Elisa; Valoni, Erika; Penna, Mônica; Seldin, Lucy

    2008-04-01

    Sulfide production by sulfate-reducing bacteria (SRB) is a major concern for the petroleum industry since it is toxic and corrosive, and causes plugging due to the formation of insoluble iron sulfides (reservoir souring). In this study, PCR followed by denaturing gradient gel electrophoresis (PCR-DGGE) using two sets of primers based on the 16S rRNA gene and on the aps gene (adenosine-5-phosphosulfate reductase) was used to track changes in the total bacterial and SRB communities, respectively, present in the water-oil tank system on an offshore platform in Brazil in which nitrate treatment was applied for 2 months (15 nitrate injections). PCR-DGGE analysis of the total bacterial community showed the existence of a dominant population in the water-oil tank, and that the appearance and/or the increase of intensity of some bands in the gels were not permanently affected by the introduction of nitrate. On the other hand, the SRB community was stimulated following nitrate treatment. Moreover, sulfide production did not exceed the permissible exposure limit in the water-oil separation tank studied treated with nitrate. Therefore, controlling sulfide production by treating the produced water tank with nitrate could reduce the quantity of chemical biocides required to control microbial activities.

  2. Calcium nitrate addition to control the internal load of phosphorus from sediments of a tropical eutrophic reservoir: microcosm experiments.

    PubMed

    Yamada, T M; Sueitt, A P E; Beraldo, D A S; Botta, C M R; Fadini, P S; Nascimento, M R L; Faria, B M; Mozeto, A A

    2012-12-01

    The main objective of this study was to perform laboratory experiments on calcium nitrate addition to sediments of a tropical eutrophic urban reservoir (Ibirité reservoir, SE Brazil) to immobilize the reactive soluble phosphorus (RSP) and to evaluate possible geochemical changes and toxic effects caused by this treatment. Reductions of 75 and 89% in the concentration of RSP were observed in the water column and interstitial water, respectively, after 145 days of nitrate addition. The nitrate application increased the rate of autotrophic denitrification, causing a consumption of 98% of the added nitrate and oxidation of 99% of the acid volatile sulfide. As a consequence, there were increases in the sulfate and iron (II) concentrations in the sediment interstitial water and water column, as well as changes in the copper speciation in the sediments. Toxicity tests initially indicated that the high concentrations of nitrate and nitrite in the sediment interstitial water (up to 2300 mg L(-1) and 260 mg L(-1), respectively) were the major cause of mortality of Ceriodaphnia silvestrii and Chironomus xanthus. However, at the end of the experiment, the sediment toxicity was completely removed and a reduction in the 48 h-EC50 of the water was also observed. Based on these results we can say that calcium nitrate treatment proved to be a valuable tool in remediation of eutrophic aquatic ecosystems leading to conditions that can support a great diversity of organisms after a restoration period.

  3. Parenteral iron therapy options.

    PubMed

    Silverstein, Scott B; Rodgers, George M

    2004-05-01

    Parenteral iron therapy is occasionally necessary for patients intolerant or unresponsive to oral iron therapy, for receiving recombinant erythropoietin therapy, or for use in treating functional iron deficiency. There are now three parenteral iron products available: iron dextran, ferric gluconate, and iron sucrose. We summarize the advantages and disadvantages of each product, including risk of anaphylaxis and hypersensitivity, dosage regimens, and costs. The increased availability of multiple parenteral iron preparations should decrease the need to use red cell transfusions in patients with iron-deficiency anemia.

  4. Iron and vegetarian diets.

    PubMed

    Saunders, Angela V; Craig, Winston J; Baines, Surinder K; Posen, Jennifer S

    2013-08-19

    Vegetarians who eat a varied and well balanced diet are not at any greater risk of iron deficiency anaemia than non-vegetarians. A diet rich in wholegrains, legumes, nuts, seeds, dried fruits, iron-fortified cereals and green leafy vegetables provides an adequate iron intake. Vitamin C and other organic acids enhance non-haem iron absorption, a process that is carefully regulated by the gut. People with low iron stores or higher physiological need for iron will tend to absorb more iron and excrete less. Research to date on iron absorption has not been designed to accurately measure absorption rates in typical Western vegetarians with low ferritin levels.

  5. Effects of nitrate addition on water column methylmercury in Occoquan Reservoir, Virginia, USA.

    PubMed

    Beutel, Marc W; Duvil, Ricardi; Cubas, Francisco J; Grizzard, Thomas J

    2017-03-01

    Mercury bioaccumulation in aquatic biota poses a widespread threat to human and environmental health. Methylmercury (MeHg), the toxic form of mercury, tends to build up under anaerobic conditions in the profundal zones of lakes. In this study we performed a two-year assessment of spatial and temporal patterns of dissolved oxygen, nitrate, MeHg, manganese (Mn) and iron (Fe) in Occoquan Reservoir, a large run-of-the-river drinking water reservoir in Virginia, USA. A tributary to the reservoir receives input of nitrate-rich tertiary-treated wastewater that enhances the oxidant capacity of bottom water. Multiple lines of evidence supported the hypothesis that the presences of nitrate and/or oxygen in bottom water correlated with low MeHg in bottom water. Bottom water MeHg was significantly lower in a nitrate-rich tributary (annual mean of 0.05 ng/L in both 2012 and 2013) compared to a nitrate-poor tributary (annual mean of 0.58 ng/L in 2012 and 0.21 ng/L in 2013). The presence of nitrate and oxygen in bottom water corresponded with significantly lower bottom water MeHg at an upstream station in the main reservoir (0.05 versus 0.11 ng/L in 2013). In 2012 the reservoir exhibited a longitudinal gradient with nitrate and oxygen decreasing and MeHg and Mn increasing downstream. In both study years, there was a clear threshold of oxygen equivalent (3-5 mg/L), a metric that combines the oxidant capacity of nitrate and oxygen, above which MeHg (<0.05 ng/L), Mn (<0.3 mg/L) and Fe (<0.5 mg/L) were low. Results indicated that the addition of nitrate-rich tertiary-treated wastewater to the bottom of anaerobic reservoirs can reduce MeHg concentrations, and potentially decrease mercury bioaccumulation, while increasing the safe water yield for potable use. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Treatment of Selenium and Nitrate in Acid Mine Drainage: A Column Study

    NASA Astrophysics Data System (ADS)

    An, H.; Jeen, S. W.

    2015-12-01

    Treatment efficiency of selenium and nitrate in acid mine drainage (AMD) by two types of reactive mixtures, i.e., organic carbon-limestone (OC-LS) and organic carbon-zero valent iron (OC-ZVI), was evaluated through column experiments. The influent AMD, collected at an abandoned metal mine site in Korea, had pH of 2.9 and contained 1600 mg/ L of SO42- and elevated concentrations of metals (e.g., Al, Cd, Co, Cu, Fe, Zn). Selenium (40 mg/L) and nitrate (100 mg/L as NO3-N initially and 10 mg/L as NO3-N after 55 days) were spiked into the AMD. The columns were operated for a total of 90 days. The results showed the increase of pH from 2.9 to 7.0 and the decreases in concentrations of most of major ions including selenium and nitrate in both the OC-LS and OC-ZVI columns. The OC-ZVI column had higher removal rates of selenium and nitrate and created a more reduced environment than the OC-LS column due to the abiotic reactions of ZVI. However, a notable amount of ammonia was produced as a reaction product in the OC-ZVI column, while the OC-LS produced a minimum amount of ammonia, suggesting formation of N2 by denitrification. In both columns, removal rates of selenium were substantially increased when the influent NO3-N concentration was changed from 100 mg/L to 10 mg/L. Sulfate was reduced as much as 390 mg/L, as indicated by detection of hydrogen sulfide. The reduction of most metals is considered to be due to precipitation of metal-containing secondary minerals (e.g., sulfides, hydroxides, carbonates). This study shows that treatment of selenium and nitrate in AMD can be achievable using organic carbon-based reactive mixtures through reduction of selenium and nitrate. However, the use of ZVI is not recommended when selenium and nitrate coexist in AMD because of production of ammonia by abiotic reaction between ZVI and nitrate. This study also shows that concentration of nitrate in AMD is an important factor to determine the rate of selenium removal.

  7. Interaction of inorganic anions with iron-mineral adsorbents in aqueous media--a review.

    PubMed

    Kumar, Eva; Bhatnagar, Amit; Hogland, William; Marques, Marcia; Sillanpää, Mika

    2014-01-01

    A number of inorganic anions (e.g., nitrate, fluoride, bromate, phosphate, and perchlorate) have been reported in alarming concentrations in numerous drinking water sources around the world. Their presence even in very low concentrations may cause serious environmental and health related problems. Due to the presence and significance of iron minerals in the natural aquatic environment and increasing application of iron in water treatment, the knowledge of the structure of iron and iron minerals and their interactions with aquatic pollutants, especially inorganic anions in water are of great importance. Iron minerals have been known since long as potential adsorbents for the removal of inorganic anions from aqueous phase. The chemistry of iron and iron minerals reactions in water is complex. The adsorption ability of iron and iron minerals towards inorganic anions is influenced by several factors such as, surface characteristics of the adsorbent (surface area, density, pore volume, porosity, pore size distribution, pHpzc, purity), pH of the solution, and ionic strength. Furthermore, the physico-chemical properties of inorganic anions (pore size, ionic radius, bulk diffusion coefficient) also significantly influence the adsorption process. The aim of this paper is to provide an overview of the properties of iron and iron minerals and their reactivity with some important inorganic anionic contaminants present in water. It also summarizes the usage of iron and iron minerals in water treatment technology. © 2013.

  8. Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, S.; Ward, B. A.; Monteiro, F.; Follows, M. J.

    2012-03-01

    We examine the interplay between iron supply, iron concentrations and phytoplankton communities in the Pacific Ocean. We present a theoretical framework which considers the competition for iron and nitrogen resources between phytoplankton to explain where nitrogen fixing autotrophs (diazotrophs, which require higher iron quotas, and have slower maximum growth) can co-exist with other phytoplankton. The framework also indicates that iron and fixed nitrogen concentrations can be strongly controlled by the local phytoplankton community. Together with results from a three-dimensional numerical model, we characterize three distinct biogeochemical provinces: 1) where iron supply is very low diazotrophs are excluded, and iron-limited nondiazotrophic phytoplankton control the iron concentrations; 2) a transition region where nondiazotrophic phytoplankton are nitrogen limited and control the nitrogen concentrations, but the iron supply is still too low relative to nitrate to support diazotrophy; 3) where iron supplies increase further relative to the nitrogen source, diazotrophs and other phytoplankton coexist; nitrogen concentrations are controlled by nondiazotrophs and iron concentrations are controlled by diazotrophs. The boundaries of these three provinces are defined by the rate of supply of iron relative to the supply of fixed nitrogen. The numerical model and theory provide a useful tool to understand the state of, links between, and response to changes in iron supply and phytoplankton community structure that have been suggested by observations.

  9. The impact of ocean deoxygenation on iron release from continental margin sediments

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; McManus, James; Mix, Alan C.; Hensen, Christian; Schneider, Ralph R.

    2014-06-01

    In the oceans' high-nitrate-low-chlorophyll regions, such as the Peru/Humboldt Current system and the adjacent eastern equatorial Pacific, primary productivity is limited by the micronutrient iron. Within the Peruvian upwelling area, bioavailable iron is released from the reducing continental margin sediments. The magnitude of this seafloor source could change with fluctuations in the extension or intensity of the oxygen minimum zones. Here we show that measurements of molybdenum, uranium and iron concentrations can be used as a proxy for sedimentary iron release, and use this proxy to assess iron release from the sea floor beneath the Peru upwelling system during the past 140,000 years. We observe a coupling between levels of denitrification, as indicated by nitrogen isotopes, trace metal proxies for oxygenation, and sedimentary iron concentrations. Specifically, periods with poor upper ocean oxygenation are characterized by more efficient iron retention in the sediment and a diminished iron supply to the water column. We attribute efficient iron retention under more reducing conditions to widespread sulphidic conditions in the surface sediment and concomitant precipitation of iron sulphides. We argue that iron release from continental margin sediments is most effective in a narrow redox window where neither oxygen nor sulphide is present. We therefore suggest that future deoxygenation in the Peru upwelling area would be unlikely to result in increased iron availability, whereas in weaker oxygen minimum zones partial deoxygenation may enhance the iron supply.

  10. Impact of mineral dust on nitrate, sulfate, and ozone in transpacific Asian pollution plumes

    NASA Astrophysics Data System (ADS)

    Fairlie, T. D.; Jacob, D. J.; Dibb, J. E.; Alexander, B.; Avery, M. A.; van Donkelaar, A.; Zhang, L.

    2009-11-01

    We use a 3-d global chemical transport model (GEOS-Chem) to interpret aircraft observations of nitrate and sulfate partitioning in transpacific dust plumes during the INTEX-B campaign of April-May 2006. The model includes explicit transport of size-resolved mineral dust and its alkalinity, nitrate, and sulfate content. The observations show that particulate nitrate is primarily associated with dust, sulfate is primarily associated with ammonium, and Asian dust remains alkaline across the Pacific. This can be reproduced in the model by using a reactive uptake coefficient for HNO3 on dust (γ(HNO3)~10-3) much lower than commonly assumed in models and likely reflecting limitation of uptake by dust dissolution. The model overestimates gas-phase HNO3 by a factor of 2-3, typical of previous model studies; we show that this cannot be corrected by uptake on dust. We find that the fraction of aerosol nitrate on dust in the model increases from ~30% in fresh Asian outflow to 80-90% over the Northeast Pacific, reflecting in part the volatilization of ammonium nitrate and the resulting transfer of nitrate to the dust. Consumption of dust alkalinity by uptake of acid gases in the model is slow relative to the lifetime of dust against deposition, so that dust in general does not acidify. This argues against the hypothesis that dust iron released by acidification could become bio-available upon dust deposition. Observations in INTEX-B show no detectable ozone depletion in Asian dust plumes, consistent with the model. Uptake of HNO3 by dust, suppressing its recycling to NOx, reduces Asian pollution influence on US surface ozone in the model by 10-15% or up to 1 ppb.

  11. Impact of mineral dust on nitrate, sulfate, and ozone in transpacific Asian pollution plumes

    NASA Astrophysics Data System (ADS)

    Fairlie, T. D.; Jacob, D. J.; Dibb, J. E.; Alexander, B.; Avery, M. A.; van Donkelaar, A.; Zhang, L.

    2010-04-01

    We use a 3-D global chemical transport model (GEOS-Chem) to interpret aircraft observations of nitrate and sulfate partitioning in transpacific dust plumes during the INTEX-B campaign of April-May 2006. The model includes explicit transport of size-resolved mineral dust and its alkalinity, nitrate, and sulfate content. The observations show that particulate nitrate is primarily associated with dust, sulfate is primarily associated with ammonium, and Asian dust remains alkaline across the Pacific. This can be reproduced in the model by using a reactive uptake coefficient for HNO3 on dust (γ(HNO3) ~10-3) much lower than commonly assumed in models and possibly reflecting limitation of uptake by dust dissolution. The model overestimates gas-phase HNO3 by a factor of 2-3, typical of previous model studies; we show that this cannot be corrected by uptake on dust. We find that the fraction of aerosol nitrate on dust in the model increases from ~30% in fresh Asian outflow to 80-90% over the Northeast Pacific, reflecting in part the volatilization of ammonium nitrate and the resulting transfer of nitrate to the dust. Consumption of dust alkalinity by uptake of acid gases in the model is slow relative to the lifetime of dust against deposition, so that dust does not acidify (at least not in the bulk). This limits the potential for dust iron released by acidification to become bio-available upon dust deposition. Observations in INTEX-B show no detectable ozone depletion in Asian dust plumes, consistent with the model. Uptake of HNO3 by dust, suppressing its recycling to NOx, reduces Asian pollution influence on US surface ozone in the model by 10-15% or up to 1 ppb.

  12. Metallocorroles as cytoprotective agents against oxidative and nitrative stress in cellular models of neurodegeneration.

    PubMed

    Kupershmidt, Lana; Okun, Zoya; Amit, Tamar; Mandel, Silvia; Saltsman, Irena; Mahammed, Atif; Bar-Am, Orit; Gross, Zeev; Youdim, Moussa B H

    2010-04-01

    Water-soluble iron, and manganese(III) complexes of corroles and porphyrins were examined with regard to their neuroprotective/neurorescue activities by using various neuronal cytotoxic models of oxidative and nitrative stress. The present study demonstrates that the metallocorroles significantly protect human neuroblastoma SH-SY5Y and mouse motor neuron-neuroblastoma fusion NSC-34 cell lines against neurotoxicity induced by either the peroxynitrite donor 3-morpholinosydnonimine or the parkinsonism-related neurotoxin 6-hydroxydopamine. The neuronal survival effect is further reflected by the prevention of 3-morpholinosydnonimine-induced protein nitration, inhibition of caspase 3 activation, as well as attenuation of 6-hydroxydopamine-mediated decrease in growth associated protein-43 levels. The iron(III) corrole, but not manganese (III) corrole, also significantly promotes neuronal survival of hydrogen peroxide (H(2)O(2))-impaired SH-SY5Y and NSC-34 cells. A substantial superiority of the metallocorroles relative to the corresponding porphyrin complexes is revealed in all examined aspects. These results highlight the large potential of corrole complexes as novel agents for therapeutic approaches in degenerative disorders of the central and peripheral nervous systems, where oxidative and nitrative stresses are involved.

  13. 77 FR 65532 - Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice of Rescission of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-29

    ... International Trade Administration Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice... the antidumping duty order on solid fertilizer grade ammonium nitrate (ammonium nitrate) from the... Administrative Review: Solid Fertilizer Grade Ammonium Nitrate (Ammonium Nitrate) from the Russian...

  14. Global distribution of peroxyacetyl nitrate.

    PubMed

    Singh, H B; Salas, L J; Viezee, W

    Nitrogen oxides (NOx) have a central role in the chemistry of the atmosphere, especially in key processes relating to ozone, hydroxyl-radical (OH) and acid formation. High reactivity of NOx (lifetime of 0.5-2 days) precludes hemispheric-scale transport and it has been proposed that non-methane hydrocarbons present in the troposphere can transform NOx into its organic forms principally as peroxyacetyl nitrate (PAN). PAN is highly stable in the colder regions of the middle and upper troposphere and can provide a mechanism for NOx storage and transport. Once transported, PAN and its homologues can easily release free NOx in warmer atmospheric conditions. PAN is probably ubiquitous and its concentrations could exceed those of NOx in clean tropospheric conditions. Here we present the first view of the global distribution of PAN based on extensive shipboard and aircraft measurements. PAN is more abundant in the Northern than in the Southern Hemisphere and in the continental than in the marine troposphere. In contrast to its behaviour in polluted atmospheres, PAN mixing ratios in winter greatly exceed those in summer. These measurements provide a basis for assessing the significance of PAN as a reservoir of NOx and for extending and validating reactive nitrogen chemistry theory in the troposphere.

  15. The pharmacology of aminoadamantane nitrates.

    PubMed

    Wang, Yuqiang; Eu, Jerry; Washburn, Mark; Gong, Tong; Chen, H-S Vincent; James, W Larrick; Lipton, Stuart A; Stamler, Jonathan S; Went, Gregory T; Porter, Seth

    2006-07-01

    Memantine, an aminodamantane, has recently been approved to treat moderate-to-severe Alzheimer's disease in the US after over 20 years on the market in Europe for treatment of Parkinson's disease. The unique properties of Memantine allow for its selective inhibition of abnormally active NMDA receptor channels while preserving normal glutamate activity and healthy neuronal function. Recently, it has been shown that compounds such as nitroglycerin, used for years for ischemic coronary disease, can also regulate the NMDA receptor channel. Novel compounds have been synthesized in an attempt to combine these activities, in an attempt to synergistically improve upon the activities of both nitrates and aminoadamantanes. We have subjected these compounds to several laboratory tests to compare their ability to affect the function of the NMDA receptor and to dilate blood vessels. These tests provide an initial indication of which of the compounds may have enhanced activity relative to memantine. The results also provide guidance for the synthesis of additional compounds that are likely to have the properties that are being sought.

  16. Technical Report on Hydroxylamine Nitrate

    SciTech Connect

    Harlow, Donald G.; Felt, Rowland E.; Agnew, Steve; Barney, G. Scott; McKibben, J. Malvyn; Garber, Robert; Lewis, Margie

    1998-02-01

    This report presents the chemical properties and safe conditions for handling and storing solutions of hydroxylamine nitrate (HAN, NH2OH•HNO3 or NH3OH+) in nitric acid (HNO3). Section 1.0 summarizes the accidents experienced within the Department of Energy (DOE) weapons complex involving HAN or hydroxylamine sulfate (HAS), a chemical with similar properties. Section 2.0 describes past and current uses of HAN by DOE, the U.S. Military and foreign countries. Section 3.0 presents the basic chemistry of HAN, including chemical reaction and energy content equations. Section 4.0 provides experience and insights gained from previous uncontrolled reactions involving HAN and experimental data from Hanford & Savannah River Site (SRS). This information was used to develop safe conditions for the storage and handling of HAN as presented in Section 5.0. Section 6.0 summarizes recommendations for safe facility operations involving HAN and future research needs.

  17. Phase diagram of ammonium nitrate

    SciTech Connect

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2013-12-07

    Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ′} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

  18. Iron-Refractory Iron Deficiency Anemia

    PubMed Central

    Yılmaz Keskin, Ebru; Yenicesu, İdil

    2015-01-01

    Iron is essential for life because it is indispensable for several biological reactions, such as oxygen transport, DNA synthesis, and cell proliferation. Over the past few years, our understanding of iron metabolism and its regulation has changed dramatically. New disorders of iron metabolism have emerged, and the role of iron as a cofactor in other disorders has begun to be recognized. The study of genetic conditions such as hemochromatosis and iron-refractory iron deficiency anemia (IRIDA) has provided crucial insights into the molecular mechanisms controlling iron homeostasis. In the future, these advances may be exploited to improve treatment of both genetic and acquired iron disorders. IRIDA is caused by mutations in TMPRSS6, the gene encoding matriptase-2, which downregulates hepcidin expression under conditions of iron deficiency. The typical features of this disorder are hypochromic, microcytic anemia with a very low mean corpuscular volume of erythrocytes, low transferrin saturation, no (or inadequate) response to oral iron, and only a partial response to parenteral iron. In contrast to classic iron deficiency anemia, serum ferritin levels are usually low-normal, and serum or urinary hepcidin levels are inappropriately high for the degree of anemia. Although the number of cases reported thus far in the literature does not exceed 100, this disorder is considered the most common of the “atypical” microcytic anemias. The aim of this review is to share the current knowledge on IRIDA and increase awareness in this field. PMID:25805669

  19. Iron-refractory iron deficiency anemia.

    PubMed

    Yılmaz Keskin, Ebru; Yenicesu, İdil

    2015-03-05

    Iron is essential for life because it is indispensable for several biological reactions, such as oxygen transport, DNA synthesis, and cell proliferation. Over the past few years, our understanding of iron metabolism and its regulation has changed dramatically. New disorders of iron metabolism have emerged, and the role of iron as a cofactor in other disorders has begun to be recognized. The study of genetic conditions such as hemochromatosis and iron-refractory iron deficiency anemia (IRIDA) has provided crucial insights into the molecular mechanisms controlling iron homeostasis. In the future, these advances may be exploited to improve treatment of both genetic and acquired iron disorders. IRIDA is caused by mutations in TMPRSS6, the gene encoding matriptase-2, which downregulates hepcidin expression under conditions of iron deficiency. The typical features of this disorder are hypochromic, microcytic anemia with a very low mean corpuscular volume of erythrocytes, low transferrin saturation, no (or inadequate) response to oral iron, and only a partial response to parenteral iron. In contrast to classic iron deficiency anemia, serum ferritin levels are usually low-normal, and serum or urinary hepcidin levels are inappropriately high for the degree of anemia. Although the number of cases reported thus far in the literature does not exceed 100, this disorder is considered the most common of the "atypical" microcytic anemias. The aim of this review is to share the current knowledge on IRIDA and increase awareness in this field.

  20. Prevention of iron deficiency.

    PubMed

    Hallberg, L

    1994-12-01

    This chapter discusses different methods to prevent iron deficiency--to reduce iron losses (e.g. reducing menstrual iron losses by using a contraceptive pill or combating of hookworm infestation) or to increase iron absorption. Iron absorption can be increased (1) by modifying the composition of meals--increasing the content of dietary factors enhancing iron absorption (e.g. meat and ascorbic acid) or reducing the content of factors inhibiting iron absorption such as phytate and iron-binding phenolic compounds, (2) by increasing the iron content of the diet by fortification with iron, or by (3) supplementation with iron tablets. Several factors to consider in the choice of strategy are discussed such as the importance of the bioavailability of the diet for the efficacy of iron fortification, the choice of vehicle for iron fortification that is compatible with the iron compound used, the feasibility to increase the bioavailability of the dietary iron by modification of the composition of the diet and the short time available in pregnancy to ensure a sufficient supply of the extra iron needed limiting the effective measures available to supplementation with iron tablets.

  1. New methods of nitrate removal from water.

    PubMed

    Shrimali, M; Singh, K P

    2001-01-01

    Nitrate contamination in groundwater resources originates mainly from the excessive use of fertilisers and uncontrolled land discharges of treated wastewater. This can cause potential health hazards to infants and pregnant women, thus limiting the direct use of the groundwater resources for the human consumption in several parts of the world, including India. The conventional processes used to eliminate nitrate from water are ion exchange, reverse osmosis and electro-dialysis. The utility of these processes has been limited due to their expensive operation and subsequent disposal problem of the generated nitrate waste brine. This paper presents a comprehensive account of the methods/techniques used for the removal of nitrate ion from water during the last 10 years with special reference to the biological denitrification and fate of the metals in decontamination processes.

  2. Qualitative Determination of Nitrate with Triphenylbenzylphosphonium Chloride.

    ERIC Educational Resources Information Center

    Berry, Donna A.; Cole, Jerry J.

    1984-01-01

    Discusses two procedures for the identification of nitrate, the standard test ("Brown Ring" test) and a new procedure using triphenylbenzylphosphonium chloride (TPBPC). Effectiveness of both procedures is compared, with the TPBPC test proving to be more sensitive and accurate. (JM)

  3. 76 FR 70366 - Ammonium Nitrate Security Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-14

    ...- accessible Internet access could obtain the access necessary to register online. 3. How to best notify... ammonium nitrate sellers (AN Sellers) when it is not possible for an AN Seller to verify the identity of...

  4. Freezing-Enhanced Dissolution of Iron Oxides: Effects of Inorganic Acid Anions.

    PubMed

    Jeong, Daun; Kim, Kitae; Min, Dae Wi; Choi, Wonyong

    2015-11-03

    Dissolution of iron from mineral dust particles greatly depends upon the type and amount of copresent inorganic anions. In this study, we investigated the roles of sulfate, chloride, nitrate, and perchlorate on the dissolution of maghemite and lepidocrocite in ice under both dark and UV irradiation and compared the results with those of their aqueous counterparts. After 96 h of reaction, the total dissolved iron in ice (pH 3 before freezing) was higher than that in the aqueous phase (pH 3) by 6-28 times and 10-20 times under dark and UV irradiation, respectively. Sulfuric acid was the most efficient in producing labile iron under dark condition, whereas hydrochloric acid induced the most dissolution of the total and ferrous iron in the presence of light. This ice-induced dissolution result was also confirmed with Arizona Test Dust (AZTD). In the freeze-thaw cycling test, the iron oxide samples containing chloride, nitrate, or perchlorate showed a similar extent of total dissolved iron after each cycling while the sulfate-containing sample rapidly lost its dissolution activity with repeating the cycle. This unique phenomenon observed in ice might be related to the freeze concentration of protons, iron oxides, and inorganic anions in the liquid-like ice grain boundary region. These results suggest that the ice-enhanced dissolution of iron oxides can be a potential source of bioavailable iron, and the acid anions critically influence this process.

  5. Confirmation of iron limitation of phytoplankton photosynthesis in the equatorial Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Behrenfeld, Michael J.; Bale, Anthony J.; Kolber, Zbigniew S.; Aiken, James; Falkowski, Paul G.

    1996-10-01

    THE eastern equatorial Pacific Ocean is one of only three open-ocean regions where low phytoplankton chlorophyll biomass persists despite perennially high nitrate and phosphate nutrient concentrations1. In 1993, an area within this region was artificially enriched with a single dose of soluble iron to test whether phytoplankton are physiologically prevented from utilizing the available nutrients by the low natural iron concentrations2,3. Although photosynthesis was stimulated4, the observed lack of a bloom or a significant decrease in nutrient concentrations could not be attributed unequivocally to zooplankton grazing5-7, further iron limitation or secondary nutrient limitation2,4. In 1995, a second iron-enrichment experiment (IronEx II) was conducted in which the same total dosage of iron was added, but over eight days8. A massive phytoplankton bloom developed, significantly reducing surface-water nutrient and CO2 concentrations8-10. Here we report in situ measurements of fluorescence during IronEx II, which show that the iron enrichment triggered biophysical alterations of the phytoplankton's photosynthetic apparatus, resulting in increased photosynthetic capacities throughout the experiment and, hence, the observed bloom. These results unequivocally establish physiological limitation of phytoplankton by iron as the cause of the high-nitrate, low-chlorophyll phenomenon in this ocean region.

  6. Nitrate inhibition of legume nodule growth and activity. II. Short term studies with high nitrate supply

    SciTech Connect

    Streeter, J.G.

    1985-02-01

    Soybean plants (Glycine max (L.) Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reduction) activity by 80% whether or not Rhizobium japonicum bacteroids had nitrate reductase (NR) activity. The pattern of nitrite accumulation in nodules formed by NR/sup +/ rhizobia was inversely related to the decrease and recovery of nitrogenase activity. However, nitrite concentration in nodules formed by NR/sup -/ rhizobia appeared to be too low to explain the inhibition of nitrogenase. Nodules on plants treated with 15 millimolar nitrate contained higher concentrations of amino N and, especially, ureide N than control nodules and, after withdrawal of nitrate, reduced N content of treated and control nodules returned to similar levels. The accumulation of N/sub 2/ fixation products in nodules in response to high nitrate treatment was observed with three R. japonicum strains, two NR/sup +/ and one NR/sup -/.

  7. New insights into bioactivation of organic nitrates, nitrate tolerance and cross-tolerance.

    PubMed

    Daiber, A; Wenzel, P; Oelze, M; Münzel, T

    2008-01-01

    Organic nitrates still represent a group of very effective anti-ischemic drugs used for the treatment of patients with stable angina, acute myocardial infarction and chronic congestive heart failure. Long-term therapy with organic nitrates, however, results in a rapid development of nitrate tolerance blunting their hemodynamic and antiischemic efficacy. Recent studies revealed that mitochondrial reactive oxygen species (ROS) formation and a subsequent oxidative inactivation of nitrate reductase, the mitochondrial aldehyde dehydrogenase (ALDH-2), play an important role for the development of nitrate and crosstolerance. The present review focuses firstly on the role of ALDH-2 for organic nitrate bioactivation and secondly on the role of oxidative stress in the development of tolerance and cross-tolerance (endothelial dysfunction) in response to various organic nitrates. Finally, we would like to draw the reader's attention to the protective properties of the organic nitrate pentaerithrityl tetranitrate (PETN), which, in contrast to all other organic nitrates, is able to upregulate enzymes with a strong antioxidative capacity thereby preventing tolerance and the development of endothelial dysfunction.

  8. Organic nitrates and nitrate tolerance--state of the art and future developments.

    PubMed

    Daiber, Andreas; Münzel, Thomas; Gori, Tommaso

    2010-01-01

    The hemodynamic and antiischemic effects of nitroglycerin (GTN) are lost upon chronic administration due to the rapid development of nitrate tolerance. The mechanism of this phenomenon has puzzled several generations of scientists, but recent findings have led to novel hypotheses. The formation of reactive oxygen and nitrogen species in the mitochondria and the subsequent inhibition of the nitrate-bioactivating enzyme mitochondrial aldehyde dehydrogenase (ALDH-2) appear to play a central role, at least for GTN, that is, bioactivated by ALDH-2. Importantly, these findings provide the opportunity to reconcile the two "traditional" hypotheses of nitrate tolerance, that is, the one postulating a decreased bioactivation and the concurrent one suggesting a role of oxidative stress. Furthermore, recent animal and human experimental studies suggest that the organic nitrates are not a homogeneous group but demonstrate a broad diversity with regard to induction of vascular dysfunction, oxidative stress, and other side effects. In the past, attempts to avoid nitrate-induced side effects have focused on administration schedules that would allow a "nitrate-free interval"; in the future, the role of co-therapies with antioxidant compounds and of activation of endogeneous protective pathways such as the heme oxygenase 1 (HO-1) will need to be explored. However, the development of new nitrates, for example, tolerance-free aminoalkyl nitrates or combination of nitrate groups with established cardiovascular drugs like ACE inhibitors or AT(1)-receptor blockers (hybrid molecules) may be of great clinical interest.

  9. Nitrate reduction in Haloferax alexandrinus: the case of assimilatory nitrate reductase.

    PubMed

    Kilic, Volkan; Kilic, Gözde Aydoğan; Kutlu, Hatice Mehtap; Martínez-Espinosa, Rosa María

    2017-05-01

    Haloferax alexandrinus Strain TM JCM 10717(T) = IFO 16590(T) is an extreme halophilic archaeon able to produce significant amounts of canthaxanthin. Its genome sequence has been analysed in this work using bioinformatics tools available at Expasy in order to look for genes encoding nitrate reductase-like proteins: respiratory nitrate reductase (Nar) and/or assimilatory nitrate reductase (Nas). The ability of the cells to reduce nitrate under aerobic conditions was tested. The enzyme in charge of nitrate reduction under aerobic conditions (Nas) has been purified and characterised. It is a monomeric enzyme (72 ± 1.8 kDa) that requires high salt concentration for stability and activity. The optimum pH value for activity was 9.5. Effectiveness of different substrates, electron donors, cofactors and inhibitors was also reported. High nitrite concentrations were detected within the culture media during aerobic/microaerobic cells growth. The main conclusion from the results is that this haloarchaeon reduces nitrate aerobically thanks to Nas and may induce denitrification under anaerobic/microaerobic conditions using nitrate as electron acceptor. The study sheds light on the role played by haloarchaea in the biogeochemical cycle of nitrogen, paying special attention to nitrate reduction processes. Besides, it provides useful information for future attempts on microecological and biotechnological implications of haloarchaeal nitrate reductases.

  10. Preformed Nitrate in the Glacial North Atlantic

    NASA Astrophysics Data System (ADS)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  11. The UK Nitrate Time Bomb (Invited)

    NASA Astrophysics Data System (ADS)

    Ward, R.; Wang, L.; Stuart, M.; Bloomfield, J.; Gooddy, D.; Lewis, M.; McKenzie, A.

    2013-12-01

    The developed world has benefitted enormously from the intensification of agriculture and the increased availability and use of synthetic fertilizers during the last century. However there has also been unintended adverse impact on the natural environment (water and ecosystems) with nitrate the most significant cause of water pollution and ecosystem damage . Many countries have introduced controls on nitrate, e.g. the European Union's Water Framework and Nitrate Directives, but despite this are continuing to see a serious decline in water quality. The purpose of our research is to investigate and quantify the importance of the unsaturated (vadose) zone pathway and groundwater in contributing to the decline. Understanding nutrient behaviour in the sub-surface environment and, in particular, the time lag between action and improvement is critical to effective management and remediation of nutrient pollution. A readily-transferable process-based model has been used to predict temporal loading of nitrate at the water table across the UK. A time-varying nitrate input function has been developed based on nitrate usage since 1925. Depth to the water table has been calculated from groundwater levels based on regional-scale observations in-filled by interpolated river base levels and vertical unsaturated zone velocities estimated from hydrogeological properties and mapping. The model has been validated using the results of more than 300 unsaturated zone nitrate profiles. Results show that for about 60% of the Chalk - the principal aquifer in the UK - peak nitrate input has yet to reach the water table and concentrations will continue to rise over the next 60 years. The implications are hugely significant especially where environmental objectives must be achieved in much shorter timescales. Current environmental and regulatory management strategies rarely take lag times into account and as a result will be poorly informed, leading to inappropriate controls and conflicts

  12. Microbial uranium immobilization independent of nitrate reduction.

    PubMed

    Madden, Andrew S; Smith, April C; Balkwill, David L; Fagan, Lisa A; Phelps, Tommy J

    2007-09-01

    At many uranium processing and handling facilities, including sites in the US Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in situ strategies involving the stimulation of metal-reducing bacteria are hindered by low-pH environments and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This work investigated the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 5.7-6.2 using methanol or glycerol as a carbon source. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.2) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and terminal-restriction fragment length polymorphism (T-RFLP) profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

  13. Protein Nitration in Placenta – Functional Significance

    PubMed Central

    Webster, RP; Roberts, VHJ; Myatt, L

    2009-01-01

    Crucial roles of the placenta are disrupted in early and mid-trimester pregnancy loss, preeclampsia, eclampsia and intrauterine growth restriction. The pathophysiology of these disorders includes a relative hypoxia of the placenta, ischemia/reperfusion injury, an inflammatory response and oxidative stress. Reactive oxygen species including nitric oxide (NO), carbon monoxide and superoxide have been shown to participate in trophoblast invasion, regulation of placental vascular reactivity and other events. Superoxide, which regulates expression of redox sensitive genes, has been implicated in up-regulation of transcription factors, antioxidant production, angiogenesis, proliferation and matrix remodeling. When superoxide and nitric oxide are present in abundance, their interaction yields peroxynitrite a potent pro-oxidant, but also alters levels of nitric oxide, which in turn affect physiological functions. The peroxynitrite anion is extremely unstable thus evidence of its formation in vivo has been indirect via the occurrence of nitrated moieties including nitrated lipids and nitrotyrosine residues in proteins. Formation of 3-nitrotyrosine (protein nitration) is a “molecular fingerprint” of peroxynitrite formation. Protein nitration has been widely reported in a number of pathological states associated with inflammation but is reported to occur in normal physiology and is thought of as a prevalent, functionally relevant post-translational modification of proteins. Nitration of proteins can give either no effect, a gain or a loss of function. Nitration of a range of placental proteins is found in normal pregnancy but increased in pathologic pregnancies. Evidence is presented for nitration of placental signal transduction enzymes and transporters. The targets and extent of nitration of enzymes, receptors, transporters and structural proteins may markedly influence placental cellular function in both physiologic and pathologic settings. PMID:18851882

  14. Synthesis of a new energetic nitrate ester

    SciTech Connect

    Chavez, David E

    2008-01-01

    Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

  15. Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise.

    PubMed

    Flueck, Joelle Leonie; Bogdanova, Anna; Mettler, Samuel; Perret, Claudio

    2016-04-01

    Dietary nitrate has been reported to lower oxygen consumption in moderate- and severe-intensity exercise. To date, it is unproven that sodium nitrate (NaNO3(-); NIT) and nitrate-rich beetroot juice (BR) have the same effects on oxygen consumption, blood pressure, and plasma nitrate and nitrite concentrations or not. The aim of this study was to compare the effects of different dosages of NIT and BR on oxygen consumption in male athletes. Twelve healthy, well-trained men (median [minimum; maximum]; peak oxygen consumption: 59.4 mL·min(-1)·kg(-1) [40.5; 67.0]) performed 7 trials on different days, ingesting different nitrate dosages and placebo (PLC). Dosages were 3, 6, and 12 mmol nitrate as concentrated BR or NIT dissolved in plain water. Plasma nitrate and nitrite concentrations were measured before, 3 h after ingestion, and postexercise. Participants cycled for 5 min at moderate intensity and further 8 min at severe intensity. End-exercise oxygen consumption at moderate intensity was not significantly different between the 7 trials (p = 0.08). At severe-intensity exercise, end-exercise oxygen consumption was ~4% lower in the 6-mmol BR trial compared with the 6-mmol NIT (p = 0.003) trial as well as compared with PLC (p = 0.010). Plasma nitrite and nitrate concentrations were significantly increased after the ingestion of BR and NIT with the highest concentrations in the 12-mmol trials. Plasma nitrite concentration between NIT and BR did not significantly differ in the 6-mmol (p = 0.27) and in the 12-mmol (p = 0.75) trials. In conclusion, BR might reduce oxygen consumption to a greater extent compared with NIT.

  16. Atmospheric Transport and Input of Iron to the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Tindale, N. W.

    2002-12-01

    While Australia is not generally considered to be a major source of mineral dust to the atmosphere, at least compared to Asian and African desert regions, it does appear to be the main source of mineral material to the Southern Ocean region south of Australia and New Zealand. In common with most of the greater Southern Ocean, this region contains high nitrate, low chlorophyll (HNLC) waters. Recent open ocean iron enrichment experiments in this region have demonstrated that phytoplankton growth and biomass are limited by iron availability. However the flux of atmospheric iron to this open ocean region is poorly known with very few direct measurements of mineral aerosol levels and input. Using mineral aerosol samples collected on Macquarie Island and at Cape Grim, together with other chemical data, air mass trajectories and satellite data, the spatial and temporal variability of aerosol iron transport and input to the Southern Ocean region south of Australia is estimated.

  17. Study of Nitrate Stress in Desulfovibrio vulgaris Hildenborough Using iTRAQ Proteomics

    SciTech Connect

    Redding, A.M.; Mukhopadhyay, A.; Joyner, D.; Hazen, T.C.; Keasling, J.D.

    2006-10-12

    The response of Desulfovibrio vulgaris Hildenborough (DvH),a sulphate-reducing bacterium, to nitrate stress was examined usingquantitative proteomic analysis. DvH was stressed with 105 m M sodiumnitrate(NaNO3), a level that caused a 50 percent inhibition in growth.The protein profile of stressed cells was compared with that of cellsgrown in the absence of nitrate using the iTRAQ peptide labellingstrategy and tandem liquid chromatography separation coupled with massspectrometry (quadrupoletime-of-flight) detection. A total of 737 uniqueproteins were identified by two or more peptides, representing 22 percentof the total DvH proteome and spanning every functional category. Theresults indicate that this was a mild stress, as proteins involved incentral metabolism and the sulphate reduction pathway were unperturbed.Proteins involved in the nitrate reduction pathway increased. Increasesseen in transport systems for proline, glycine^ betaineandglutamateindicate that the NaNO3 exposure led to both salt stress and nitratestress.Up-regulation observed in oxidative stress response proteins (Rbr,RbO, etc.) and a large number of ABC transport systems as well as in iron^ sulphur -cluster-containing proteins, however, appear to be specific tonitrate exposure. Finally, a number of hypothetical proteins were amongthe most significant changers, indicating that there may be unknownmechanisms initiated upon nitrate stress in DvH.

  18. Performance Evaluation of In-Situ Iron Reactive Barriers at the Oak Ridge Y-12 Site

    SciTech Connect

    Watson, D.B.

    2003-12-30

    In November 1997, a permeable iron reactive barrier trench was installed at the S-3 Ponds Pathway 2 Site located at the Y-12 Plant, Oak Ridge, Tennessee. The overall goal of the project is to evaluate the ability of permeable reactive barrier technology to remove uranium, nitrate, and other inorganic contaminants in groundwater and to assess impacts of biogeochemical interactions on long-term performance of the treatment system. Zero-valent iron (Fe0) was used as the reactive medium, which creates a localized zone of reduction or low oxidation reduction potential (ORP), elevated pH, and dissolved H{sub 2} as Fe{sup 0} corrodes in groundwater. These conditions favor the removal of metals and radionuclides (such as uranium and technetium) through redox-driven precipitation and/or sorption to iron corrosion byproducts, such as iron oxyhydroxides. The technology is anticipated to be economical and low in maintenance as compared with conventional pump-and-treat technology. Groundwater monitoring results indicate that the iron barrier is effectively removing uranium and technetium, the primary contaminants of concern, as anticipated from our previous laboratory studies. In addition to uranium and technetium, nitrate, sulfate, bicarbonate, calcium, and magnesium are also found to be removed, either partially or completely by the iron barrier. Elevated concentrations of ferrous ions and sulfide, and pH were observed within the iron barrier. Although ferrous iron concentrations were initially very high after barrier installation, ferrous ion concentrations have decreased to low to non-detectable levels as the pH within the iron has increased over time (as high as 9 or 10). Iron and soil core samples were taken in February 1999 and May 2000 in order to evaluate the iron surface passivation, morphology, mineral precipitation and cementation, and microbial activity within and in the vicinity of the iron barrier. Results indicate that most of the iron filings collected in cores

  19. Protein tyrosine nitration in the cell cycle

    SciTech Connect

    Jia, Min; Mateoiu, Claudia; Souchelnytskyi, Serhiy

    2011-09-23

    Highlights: {yields} Enrichment of 3-nitrotyrosine containing proteins from cells synchronized in different phases of the cell cycle. {yields} Identification of 76 tyrosine nitrated proteins that change expression during the cell cycle. {yields} Nineteen identified proteins were previously described as regulators of cell proliferation. -- Abstract: Nitration of tyrosine residues in proteins is associated with cell response to oxidative/nitrosative stress. Tyrosine nitration is relatively low abundant post-translational modification that may affect protein functions. Little is known about the extent of protein tyrosine nitration in cells during progression through the cell cycle. Here we report identification of proteins enriched for tyrosine nitration in cells synchronized in G0/G1, S or G2/M phases of the cell cycle. We identified 27 proteins in cells synchronized in G0/G1 phase, 37 proteins in S phase synchronized cells, and 12 proteins related to G2/M phase. Nineteen of the identified proteins were previously described as regulators of cell proliferation. Thus, our data indicate which tyrosine nitrated proteins may affect regulation of the cell cycle.

  20. Compartmental model of nitrate retention in streams

    NASA Astrophysics Data System (ADS)

    Faulkner, B. R.; Campana, M. E.

    2007-02-01

    A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first-order reaction terms to represent nitrate uptake in the free stream and denitrification in the storage regions. In the context of a short-term nitrate injection we define nitrate assimilative capacity as 1 - ?, where the attenuation factor, ?, is the fraction of injected nitrate mass that is flushed past the outlet of stream. Net exchange with groundwater is modeled by allowing free stream discharge to vary from one reach section to the next. A Monte Carlo simulation was used to compare results of the compartmental model with the OTIS numerical model. Out of 350 Monte Carlo simulations of a stream consisting of five reach sections the highest relative percent difference was 15%, most being well below 10%, as determined using moment analysis on breakthrough curves. Moment analysis on published experimental breakthrough curves showed assimilative capacities did not differ from those determined with the compartmental model by more than about 0.035 and were well within the uncertainty due to possible errors in measured stream metrics and net exchange with groundwater. The results show that the compartmental modeling approach, commonly used in analysis of groundwater data, can also be useful in evaluating nitrate retention in streams.

  1. Process for decomposing nitrates in aqueous solution

    DOEpatents

    Haas, Paul A.

    1980-01-01

    This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.degree.-200.degree. C.

  2. Suppression of erythropoiesis by dietary nitrate.

    PubMed

    Ashmore, Tom; Fernandez, Bernadette O; Evans, Colin E; Huang, Yun; Branco-Price, Cristina; Griffin, Julian L; Johnson, Randall S; Feelisch, Martin; Murray, Andrew J

    2015-03-01

    In mammals, hypoxia-triggered erythropoietin release increases red blood cell mass to meet tissue oxygen demands. Using male Wistar rats, we unmask a previously unrecognized regulatory pathway of erythropoiesis involving suppressor control by the NO metabolite and ubiquitous dietary component nitrate. We find that circulating hemoglobin levels are modulated by nitrate at concentrations achievable by dietary intervention under normoxic and hypoxic conditions; a moderate dose of nitrate administered via the drinking water (7 mg NaNO3/kg body weight/d) lowered hemoglobin concentration and hematocrit after 6 d compared with nonsupplemented/NaCl-supplemented controls. The underlying mechanism is suppression of hepatic erythropoietin expression associated with the downregulation of tissue hypoxia markers, suggesting increased pO2. At higher nitrate doses, however, a partial reversal of this effect occurred; this was accompanied by increased renal erythropoietin expression and stabilization of hypoxia-inducible factors, likely brought about by the relative anemia. Thus, hepatic and renal hypoxia-sensing pathways act in concert to modulate hemoglobin in response to nitrate, converging at an optimal minimal hemoglobin concentration appropriate to the environmental/physiologic situation. Suppression of hepatic erythropoietin expression by nitrate may thus act to decrease blood viscosity while matching oxygen supply to demand, whereas renal oxygen sensing could act as a brake, averting a potentially detrimental fall in hematocrit.

  3. Groundwater nitrate pollution in intensively farmed regions

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-12-01

    Intensified agricultural practices that have developed during the past century have helped improve food security for many people but have also added to nitrate pollution in water supply. Balancing the water needs for agriculture with the need for clean groundwater for drinking requires understanding factors such as the routes by which nitrate enters the water supply and how long nitrate remains in the water. The Thames River catchment provides a good study example because the water quality in the river, which supplies drinking water to millions of people, has been monitored for the past 140 years, and the region has undergone significant agricultural development over the past century. Howden et al. studied nitrate transport from agricultural land to water in the Thames basin using a simple model that considers an estimate of the amount of nitrate that could leach the groundwater based on land use practices along with an algorithm that determines the route nitrate would take to reach surface water or groundwater from agricultural areas.

  4. Stimulating nitrate removal processes of restored wetlands.

    PubMed

    Ballantine, Kate A; Groffman, Peter M; Lehmann, Johannes; Schneider, Rebecca L

    2014-07-01

    The environmental and health effects caused by nitrate contamination of aquatic systems are a serious problem throughout the world. A strategy proposed to address nitrate pollution is the restoration of wetlands. However, although natural wetlands often remove nitrate via high rates of denitrification, wetlands restored for water quality functions often fall below expectations. This may be in part because key drivers for denitrification, in particular soil carbon, are slow to develop in restored wetlands. We added organic soil amendments that range along a gradient of carbon lability to four newly restored wetlands in western New York to investigate the effect of carbon additions on denitrification and other processes of the nitrogen cycle. Soil carbon increased by 12.67-63.30% with the use of soil amendments (p ≤ 0.0001). Soil nitrate, the carbon to nitrogen ratio, and microbial biomass nitrogen were the most significant predictors of denitrification potential. Denitrification potential, potential net nitrogen nitrification and mineralization, and soil nitrate and ammonium, were highest in topsoil-amended plots, with increases in denitrification potential of 161.27% over control plots. While amendment with topsoil more than doubled several key nitrogen cycling processes, more research is required to determine what type and level of amendment application are most effective for stimulating removal of exogenous nitrate and meeting functional goals within an acceptable time frame.

  5. Characterization of Atmospheric Organic Nitrates in Particles

    NASA Astrophysics Data System (ADS)

    Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

    2008-12-01

    Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

  6. Weekly cycles in fine particulate nitrate

    NASA Astrophysics Data System (ADS)

    Millstein, Dev E.; Harley, Robert A.; Hering, Susanne V.

    Atmospheric responses to changes in emissions are a complex but central issue in control strategy design for pollutants such as ozone and particulate matter. Here, we investigate fine particle nitrate response to weekly cycles in emissions, which includes a large decrease in diesel NO x emissions among other changes. Nitrate concentrations were measured at 10-min time resolution for a year or longer at four US urban sites: Fresno and Claremont in California, St. Louis, and Pittsburgh. Weekly minima in nitrate concentrations were observed at Fresno, Claremont, and St. Louis, with mean reductions of 21-29% below weekly average values on Sundays or Mondays. The day of week with lowest nitrate varied with site and season. No significant day-of-week variations in nitrate were observed at Pittsburgh. Analysis of ammonium and sulfate measurements at Pittsburgh indicates that weekend sulfate reductions observed at this site during spring/summer months do not increase ammonia availability, but rather lead to more complete neutralization of S(VI). Fine particle nitrate measurements at Claremont were resolved into three size ranges (0.07-0.45, 0.45-1.0, and 1.0-2.5 μm); similar weekly reductions were seen for each size range.

  7. Iron fertilization of the Subantarctic ocean during the last ice age.

    PubMed

    Martínez-García, Alfredo; Sigman, Daniel M; Ren, Haojia; Anderson, Robert F; Straub, Marietta; Hodell, David A; Jaccard, Samuel L; Eglinton, Timothy I; Haug, Gerald H

    2014-03-21

    John H. Martin, who discovered widespread iron limitation of ocean productivity, proposed that dust-borne iron fertilization of Southern Ocean phytoplankton caused the ice age reduction in atmospheric carbon dioxide (CO2). In a sediment core from the Subantarctic Atlantic, we measured foraminifera-bound nitrogen isotopes to reconstruct ice age nitrate consumption, burial fluxes of iron, and proxies for productivity. Peak glacial times and millennial cold events are characterized by increases in dust flux, productivity, and the degree of nitrate consumption; this combination is uniquely consistent with Subantarctic iron fertilization. The associated strengthening of the Southern Ocean's biological pump can explain the lowering of CO2 at the transition from mid-climate states to full ice age conditions as well as the millennial-scale CO2 oscillations.

  8. Formation of Stable and Metastable Porphyrin- and Corrole-Iron(IV) Complexes and Isomerizations to Iron(III) Macrocycle Radical Cations

    PubMed Central

    Pan, Zhengzheng; Harischandra, Dilusha N.; Newcomb, Martin

    2009-01-01

    Oxidations of three porphyrin-iron(III) complexes (1) with ferric perchlorate, Fe(ClO4)3, in acetonitrile solutions at −40 °C gave metastable porphyrin-iron(IV) diperchlorate complexes (2) that isomerized to known iron(III) diperchlorate porphyrin radical cations (3) when the solutions were warmed to room temperature. The 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetramesitylporphyrin (TMP), and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) systems were studied by UV-visible spectroscopy. Low temperature NMR spectroscopy and effective magnetic moment measurements were possible with the TPP and TMP iron(IV) complexes. Reactions of two corrole systems, 5,10,15-tris(pentafluorophenyl)corrole (TPFC) and 5,15-bis(pentafluorophenyl)-10-p-methoxyphenylcorrole (BPFMC), also were studied. The corrole-iron(IV) chlorides reacted with silver salts to give corrole-iron(IV) complexes. The corrole-iron(IV) nitrate complexes were stable at room temperature. (TPFC)-iron(IV) toslyate, (TPFC)-iron(IV) chlorate, and (BPFMC)-iron(IV) chlorate were metastable and rearranged to their electronic isomers iron(III) corrole radical cations at room temperature. (TPFC)-iron(III) perchlorate corrole radical cation was the only product observed from reaction of the corrole-iron(IV) chloride with silver perchlorate. For the metastable iron(IV) species, the rates of isomerizations to the iron(III) macrocycle radical cation electronic isomers in dilute acetonitrile solutions were relatively insensitive to electron demands of the macrocyclic ligand but reflected the binding strength of the ligand to iron. Kinetic studies at varying temperatures and concentrations indicated that the mechanisms of the isomerization reactions are complex, involving mixed order reactivity. PMID:19013647

  9. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress

    PubMed Central

    2015-01-01

    Abstract Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3′,-5′-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed. Antioxid. Redox Signal. 23, 899–942. PMID:26261901

  10. Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate-Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress.

    PubMed

    Daiber, Andreas; Münzel, Thomas

    2015-10-10

    Organic nitrates, such as nitroglycerin (GTN), isosorbide-5-mononitrate and isosorbide dinitrate, and pentaerithrityl tetranitrate (PETN), when given acutely, have potent vasodilator effects improving symptoms in patients with acute and chronic congestive heart failure, stable coronary artery disease, acute coronary syndromes, or arterial hypertension. The mechanisms underlying vasodilation include the release of •NO or a related compound in response to intracellular bioactivation (for GTN, the mitochondrial aldehyde dehydrogenase [ALDH-2]) and activation of the enzyme, soluble guanylyl cyclase. Increasing cyclic guanosine-3',-5'-monophosphate (cGMP) levels lead to an activation of the cGMP-dependent kinase I, thereby causing the relaxation of the vascular smooth muscle by decreasing intracellular calcium concentrations. The hemodynamic and anti-ischemic effects of organic nitrates are rapidly lost upon long-term (low-dose) administration due to the rapid development of tolerance and endothelial dysfunction, which is in most cases linked to increased intracellular oxidative stress. Enzymatic sources of reactive oxygen species under nitrate therapy include mitochondria, NADPH oxidases, and an uncoupled •NO synthase. Acute high-dose challenges with organic nitrates cause a similar loss of potency (tachyphylaxis), but with distinct pathomechanism. The differences among organic nitrates are highlighted regarding their potency to induce oxidative stress and subsequent tolerance and endothelial dysfunction. We also address pleiotropic effects of organic nitrates, for example, their capacity to stimulate antioxidant pathways like those demonstrated for PETN, all of which may prevent adverse effects in response to long-term therapy. Based on these considerations, we will discuss and present some preclinical data on how the nitrate of the future should be designed.

  11. Iron and Your Child

    MedlinePlus

    ... vegetarian diet might also need added iron. What's Iron Deficiency? Iron deficiency is when a person's body doesn't have ... fact, many teenage girls are at risk for iron deficiency — even if they have normal periods — if their ...

  12. Iron stress in plants.

    PubMed

    Connolly, Erin L; Guerinot, Mary

    2002-07-30

    Although iron is an essential nutrient for plants, its accumulation within cells can be toxic. Plants, therefore, respond to both iron deficiency and iron excess by inducing expression of different gene sets. Here, we review recent advances in the understanding of iron homeostasis in plants gained through functional genomic approaches

  13. Microbially catalyzed nitrate-dependent metal/radionuclide oxidation in shallow subsurface sediments

    NASA Astrophysics Data System (ADS)

    Weber, K.; Healy, O.; Spanbauer, T. L.; Snow, D. D.

    2011-12-01

    Anaerobic, microbially catalyzed nitrate-dependent metal/radionuclide oxidation has been demonstrated in a variety of sediments, soils, and groundwater. To date, studies evaluating U bio-oxidation and mobilization have primarily focused on anthropogenically U contaminated sites. In the Platte River Basin U originating from weathering of uranium-rich igneous rocks in the Rocky Mountains was deposited in shallow alluvial sediments as insoluble reduced uranium minerals. These reduced U minerals are subject to reoxidation by available oxidants, such nitrate, in situ. Soluble uranium (U) from natural sources is a recognized contaminant in public water supplies throughout the state of Nebraska and Colorado. Here we evaluate the potential of anaerobic, nitrate-dependent microbially catalyzed metal/radionuclide oxidation in subsurface sediments near Alda, NE. Subsurface sediments and groundwater (20-64ft.) were collected from a shallow aquifer containing nitrate (from fertilizer) and natural iron and uranium. The reduction potential revealed a reduced environment and was confirmed by the presence of Fe(II) and U(IV) in sediments. Although sediments were reduced, nitrate persisted in the groundwater. Nitrate concentrations decreased, 38 mg/L to 30 mg/L, with increasing concentrations of Fe(II) and U(IV). Dissolved U, primarily as U(VI), increased with depth, 30.3 μg/L to 302 μg/L. Analysis of sequentially extracted U(VI) and U(IV) revealed that virtually all U in sediments existed as U(IV). The presence of U(IV) is consistent with reduced Fe (Fe(II)) and low reduction potential. The increase in aqueous U concentrations with depth suggests active U cycling may occur at this site. Tetravalent U (U(IV)) phases are stable in reduced environments, however the input of an oxidant such as oxygen or nitrate into these systems would result in oxidation. Thus co-occurrence of nitrate suggests that nitrate could be used by bacteria as a U(IV) oxidant. Most probable number

  14. Effect of nitrate enrichment and diatoms on the bioavailability of Fe(III) oxyhydroxide colloids in seawater.

    PubMed

    Liu, Feng-Jiao; Huang, Bang-Qin; Li, Shun-Xing; Zheng, Feng-Ying; Huang, Xu-Guang

    2016-03-01

    The photoconversion of colloidal iron oxyhydroxides was a significant source of bioavailable iron in coastal systems. Diatoms dominate phytoplankton communities in coastal and upwelling regions. Diatoms are often exposed to eutrophication. We investigated the effects of different species of diatom, cell density, illumination period, and nitrate additions on the bioavailability of Fe(III) oxy-hydroxide colloids in seawaters. With the increase of illumination period from 1 to 4 h, the ratios of concentrations of total dissolved Fe (DFe) to colloidal iron oxyhydroxides and Fe(II) to DFe increased up to 24.3% and 23.9% for seawater without coastal diatoms, 45.6% and 30.2% for Skeletonema costatum, 44.3% and 29.7% for Thalassiosira weissflogii, respectively. The photochemical activity of coastal diatoms themselves (excluding the dissolved organic matter secreted by algae) on the species transformation of iron in seawater (including the light-induced dissolution of Fe(III) oxyhydroxide colloids and the photo-reduction of Fe(III) into Fe(II)) was confirmed for the first time. There was no significant difference of the ability of S. costatum and Thalassiosira weissflogii on the photoconversion of colloidal iron oxyhydroxides. The photoproduction of dissolved Fe(II) and DFe in the seawater with or without diatoms could be depressed by the nitrate addition.

  15. Degradation of pentaerythritol tetranitrate (PETN) by granular iron.

    PubMed

    Zhuang, Li; Gui, Lai; Gillham, Robert W

    2008-06-15

    Pentaerythritol tetranitrate (PETN), a nitrate ester, is used primarily as an explosive. It is of environmental concern, posing a threat to aquatic organisms with an estimated EC50 five times greater than that of RDX. This study evaluated the kinetics and products of PETN degradation in the presence of granular iron. PETN transformation in columns containing 100% granular iron and 30% iron mixed with 70% silica sand followed pseudo first-order kinetics, with average half-lives of 0.26 and 1.58 min, respectively. The reduction pathway was proposed to be sequential denitration, in which PETN was stepwise reduced to pentaerythritol with the formation of pentaerythritol trinitrate and pentaerythritol dinitrate as intermediates. The intermediate of pentaerythritol mononitrate was not detected; however, the nearly 100% nitrogen mass recovery supported complete denitration. Nitrite was released in each denitration step and was subsequently reduced to ammonium by iron. Nitrate was not detected during the experiment suggesting that hydrolysis was not involved in PETN degradation. Batch experiments showed that when solid-phase PETN is present, dissolution is the rate-limiting factorfor PETN mass removal. Using 50% methanol as a cosolvent PETN solubility was enhanced and thus the removal efficiency was improved. The results demonstrate excellent potential of using iron to remediate PETN-contaminated water.

  16. Parenteral iron dextran therapy.

    PubMed

    Kumpf, V J; Holland, E G

    1990-02-01

    Parenteral iron therapy is indicated in patients with iron-deficiency anemia associated with conditions that interfere with the ingestion or absorption of oral iron. Replacement doses of iron required to replenish iron stores are based on body weight and the observed hemoglobin value. Methods of administering iron dextran are reviewed, including intramuscular and intravenous injections of the undiluted drug, intravenous infusion of a diluted preparation, and as an addition to parenteral nutrition solutions. The overall incidence of adverse reactions associated with the parenteral administration of iron is low, but the potential for an anaphylactic reaction requires that an initial test dose be given followed by careful patient observation.

  17. Iron Deficiency Anemia.

    PubMed

    DeLoughery, Thomas G

    2017-03-01

    Iron deficiency is one of the most common causes of anemia. The 2 main etiologies of iron deficiency are blood loss due to menstrual periods and blood loss due to gastrointestinal bleeding. Beyond anemia, lack of iron has protean manifestations, including fatigue, hair loss, and restless legs. The most efficient test for the diagnosis of iron deficiency is the serum ferritin. Iron replacement can be done orally, or in patients in whom oral iron is not effective or contraindicated, with intravenous iron. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Iron status of vegetarians.

    PubMed

    Craig, W J

    1994-05-01

    An appropriately planned well-balanced vegetarian diet is compatible with an adequate iron status. Although the iron stores of vegetarians may be reduced, the incidence of iron-deficiency anemia in vegetarians is not significantly different from that in omnivores. Restrictive vegetarian diets (eg, macrobiotic) are associated with more widespread iron-deficiency anemia. Western vegetarians who consume a variety of foods have a better iron status than do those in developing countries who consume a limited diet based on unleavened, unrefined cereals. Whereas phytates, polyphenolics, and other plant constituents found in vegetarian diets inhibit nonheme-iron absorption, vitamin C, citric acid, and other organic acids facilitate nonheme-iron absorption.

  19. Historical Tracking of Nitrate in Contrasting Vineyard Using Water Isotopes and Nitrate Depth Profiles

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Erhardt, M.; Riedel, M.; Weiler, M.

    2015-12-01

    The European Water Framework Directive (EWFD) aims to achieve a good chemical status for the groundwater bodies in Europe by the year 2015. Despite the effort to reduce the nitrate pollution from agriculture within the last two decades, there are still many groundwater aquifers that exceed nitrate concentrations above the EWFD threshold of 50 mg/l. Viticulture is seen as a major contributor of nitrate leaching and sowing of a green cover was shown to have a positive effect on lowering the nitrate loads in the upper 90 cm of the soil. However, the consequences for nitrate leaching into the subsoil were not yet tested. We analyzed the nitrate concentrations and pore water stable isotope composition to a depth of 380 cm in soil profiles under an old vineyard and a young vineyard with either soil tillage or permanent green cover in between the grapevines. The pore water stable isotopes were used to calibrate a soil physical model, which was then used to infer the age of the soil water at different depths. This way, we could relate elevated nitrate concentrations below an old vineyard to tillage processes that took place during the winter two years before the sampling. We further showed that the elevated nitrate concentration in the subsoil of a young vineyard can be related to the soil tillage prior to the planting of the new vineyard. If the soil is kept bare due to tillage, a nitrate concentration of 200 kg NO3--N/ha is found in 290 to 380 cm depth 2.5 years after the installation of the vineyard. The amount of nitrate leaching is considerably reduced due to a seeded green cover between the grapevines that takes up a high share of the mobilized nitrate reducing a potential contamination of the groundwater.

  20. Parenteral iron supplementation.

    PubMed

    Kumpf, V J

    1996-08-01

    Indications for the use of parenteral iron are limited to conditions in which the oral supplementation of iron is not possible or fails. An overview of iron balance and iron requirements is presented to describe situations in which iron supplementation may be required. When parenteral iron supplementation is required, careful attention to proper dosing and administration is necessary to optimize efficacy and safety. The purpose of this article is to review the literature regarding the clinical use of parenteral iron therapy and provide guidelines on dosing and administration. Methods of iron dextran administration, including the IV and intramuscular injection of undiluted drug and total dose infusion, are compared. Complications associated with the use of parenteral iron are also be reviewed. Finally, the use of iron supplementation in patients receiving parenteral nutrition care explored.

  1. Laboratory Evaluation of Sulfur Modified Iron for Use as a Filter Material to Treat Agricultural Drainage Waters

    NASA Astrophysics Data System (ADS)

    Allred, B. J.

    2009-12-01

    Where subsurface drainage practices are employed, fertilizer nutrients and pesticides applied on farm fields and municipal locations are commonly intercepted by the buried drainage pipes and then discharged into local streams and lakes, oftentimes producing adverse environmental impacts on these surface water bodies. On-site water filter treatment systems can be employed to prevent the release of agricultural nutrients/pesticides into adjacent waterways. Sulfur modified iron is a relatively unknown industrial product that may have promise for use as a filter material to remove contaminants from subsurface drainage waters. Sulfur modified iron (SMI) is a high surface area iron powder (zero valent iron) that has been altered via chemical reaction with pure sulfur to produce a sulfur/iron surface coating on the iron particles. A laboratory investigation was conducted with contaminant removal batch tests, saturated falling-head hydraulic conductivity tests, and saturated solute transport column experiments to evaluate the feasibility for using SMI to treat subsurface drainage waters. Contaminant removal batch tests showed that three SMI samples were much more effective removing nitrate (> 94% nitrate removed) than three zero valent iron samples (< 10% nitrate removed). Batch test results additionally showed that SMI removed greater that 94% of dissolved phosphate, but was not particularly effective removing the pesticide, atrazine (< 37% atrazine removed). Hydraulic conductivity tests indicated that all three SMI samples that were evaluated had sufficient hydraulic conductivity, much greater than the 1 x 10-3 cm/s standard used for stormwater sand filters. The saturated solute transport tests confirmed that SMI can be effective removing nitrate and phosphate from drainage waters. Analysis of column effluent also showed that the large majority of nitrate removed by SMI was converted to ammonium. Consequently, these laboratory findings support the use of SMI in

  2. Modeling iron limitation of primary production in the coastal Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Fiechter, Jerome; Moore, Andrew M.; Edwards, Christopher A.; Bruland, Kenneth W.; Di Lorenzo, Emanuele; Lewis, Craig V. W.; Powell, Thomas M.; Curchitser, Enrique N.; Hedstrom, Kate

    2009-12-01

    A lower trophic level NPZD ecosystem model with explicit iron limitation on nutrient uptake is coupled to a three-dimensional coastal ocean circulation model to investigate the regional ecosystem dynamics of the northwestern coastal Gulf of Alaska (CGOA). Iron limitation is included in the NPZD model by adding governing equations for two micro-nutrient compartments: dissolved iron and phytoplankton-associated iron. The model has separate budgets for nitrate (the limiting macro-nutrient in the standard NPZD model) and for iron, with iron limitation on nitrate uptake being imposed as a function of the local phytoplankton realized Fe:C ratio. While the ecosystem model represents a simple approximation of the complex lower trophic level ecosystem of the northwestern CGOA, simulated chlorophyll concentrations reproduce the main characteristics of the spring bloom, high shelf primary production, and "high-nutrient, low-chlorophyll" (HNLC) environment offshore. Over the 1998-2004 period, model-data correlations based on spatially averaged, monthly mean chlorophyll concentrations are on average 0.7, with values as high as 0.9 and as low as 0.5 for individual years. The model also provides insight on the importance of micro- and macro-nutrient limitation on the shelf and offshore, with the shelfbreak region acting as a transition zone where both nitrate and iron availability significantly impact phytoplankton growth. Overall, the relative simplicity of the ecosystem model provides a useful platform to perform long-term simulations to investigate the seasonal and interannual CGOA ecosystem variability, as well as to conduct sensitivity studies to evaluate the robustness of simulated fields to ecosystem model parameterization and forcing. The ability of the model to differentiate between nitrate-limited, and iron-limited growth conditions, and to identify their spatial and temporal occurrences, is also a first step towards understanding the role of environmental gradients in

  3. Biological oxidation of Fe(II) in reduced nontronite coupled with nitrate reduction by Pseudogulbenkiania sp. Strain 2002

    NASA Astrophysics Data System (ADS)

    Zhao, Linduo; Dong, Hailiang; Kukkadapu, Ravi; Agrawal, Abinash; Liu, Deng; Zhang, Jing; Edelmann, Richard E.

    2013-10-01

    The importance of microbial nitrate-dependent Fe(II) oxidation to iron biogeochemistry is well recognized. Past research has focused on oxidation of aqueous Fe2+ and structural Fe(II) in oxides, carbonates, and phosphate, but the importance of structural Fe(II) in phyllosilicates in this reaction is only recently studied. However, the effect of clay mineralogy on the rate and the mechanism of the reaction, and subsequent mineralogical end products are still poorly known. The objective of this research was to study the coupled process of microbial oxidation of Fe(II) in clay mineral nontronite (NAu-2), and nitrate reduction by Pseudogulbenkiania species strain 2002, and to determine mineralogical changes associated with this process. Bio-oxidation experiments were conducted using Fe(II) in microbially reduced nontronite as electron donor and nitrate as electron acceptor in bicarbonate-buffered medium under both growth and nongrowth conditions to investigate cell growth on this process. The extents of Fe(II) oxidation and nitrate reduction were measured by wet chemical methods. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and 57Fe-Mössbauer spectroscopy were used to observe mineralogical changes associated with Fe(III) reduction and Fe(II) oxidation in NAu-2. The bio-oxidation extent under growth and nongrowth conditions reached 67% and 57%, respectively. Over the same time period, nitrate was completely reduced under both conditions to nitrogen gas (N2), via an intermediate product nitrite. Abiotic oxidation by nitrite partly accelerated Fe(II) oxidation rate under the growth condition. The oxidized Fe(III) largely remained in the nontronite structure, but secondary minerals such as vivianite, ferrihydrite, and magnetite formed depending on specific experimental conditions. The results of this study highlight the importance of iron-bearing clay minerals in the global nitrogen cycle with potential applications in nitrate

  4. Coagulation and flocculation study of iron ore fines

    SciTech Connect

    Singh, B.P.; Besra, L.; Ravi Prasad, A.

    1999-03-01

    A comparative study of the flocculation and coagulation response of an iron ore fines suspension has been carried out, and the extent of flocculation has been assessed by measurement of electrophoretic mobility, supernatant clarity, and settling rate. Of the several commercial flocculants and polyelectrolyte studied, the combination of medium molecular weight anionic flocculants Magnafloc 1011 and Rishfloc 258 (1:1), and coagulant aluminum nitrate was most effective in terms of enhancing settling rate and supernatant clarity.

  5. Performance of nitrate-dependent anaerobic ferrous oxidizing (NAFO) process: a novel prospective technology for autotrophic denitrification.

    PubMed

    Zhang, Meng; Zheng, Ping; Li, Wei; Wang, Ru; Ding, Shuang; Abbas, Ghulam

    2015-03-01

    Nitrate-dependent anaerobic ferrous oxidizing (NAFO) is a valuable biological process, which utilizes ferrous iron to convert nitrate into nitrogen gas, removing nitrogen from wastewater. In this work, the performance of NAFO process was investigated as a nitrate removal technology. The results showed that NAFO system was feasible for autotrophic denitrification. The volumetric loading rate (VLR) and volumetric removal rate (VRR) under steady state were 0.159±0.01 kg-N/(m(3) d) and 0.073±0.01 kg-N/(m(3) d), respectively. In NAFO system, the effluent pH was suggested as an indicator which demonstrated a good correlation with nitrogen removal. The nitrate concentration was preferred to be less than 130 mg-N/L. Organic matters had little influence on NAFO performance. Abundant iron compounds were revealed to accumulate in NAFO sludge with peak value of 51.73% (wt), and they could be recycled for phosphorus removal, with capacity of 16.57 mg-P/g VS and removal rate of 94.77±2.97%, respectively.

  6. Iron-mediated changes in phytoplankton photosynthetic competence during SOIREE

    NASA Astrophysics Data System (ADS)

    Boyd, P. W.; Abraham, E. R.

    Active fluorescence (fast repetition rate fluorometry, FRRF) was used to follow the photosynthetic response of the phytoplankton community during the 13-day Southern Ocean Iron RElease Experiment (SOIREE). This in situ iron enrichment was conducted in the polar waters of the Australasian-Pacific sector of the Southern Ocean in February 1999. Iron fertilisation of these high nitrate low chlorophyll (HNLC) waters resulted in an increase in the photosynthetic competence ( Fv/ Fm) of the resident cells from around 0.20 to greater than 0.60 (i.e. close to the theoretical maximum) by 10/11 days after the first enrichment. Although a significant iron-mediated response in Fv/ Fm was detected as early as 24 h after the initial fertilisation, the increase in Fv/ Fm to double ambient levels took 6 days. This response was five-fold slower than observed in iron enrichments (in situ and in vitro) in the HNLC waters of the subarctic and equatorial Pacific. Although little is known about the relationship between water temperature and Fv/ Fm, it is likely that low water temperatures — and possibly the deep mixed layer — were responsible for this slow response time. During SOIREE, the photosynthetic competence of the resident phytoplankton in iron-enriched waters increased at dissolved iron levels above 0.2 nM, suggesting that iron limitation was alleviated at this concentration. Increases in Fv/ Fm of cells within four algal size classes suggested that all taxa displayed a photosynthetic response to iron enrichment. Other physiological proxies of algal iron stress (such as flavodoxin levels in diatoms) exhibited different temporal trends to iron-enrichment than Fv/ Fm during the time-course of SOIREE. The relationship between Fv/ Fm, algal growth rate and such proxies in Southern Ocean waters is discussed.

  7. Effect of molybdenum treatment on molybdenum concentration and nitrate reduction in maize seedlings.

    PubMed

    Kovács, Béla; Puskás-Preszner, Anita; Huzsvai, László; Lévai, László; Bódi, Éva

    2015-11-01

    Since 1940 molybdenum has been known as an essential trace element in plant nutrition and physiology. It has a central role in nitrogen metabolism, and its deficiency leads to nitrate accumulation in plants. In this study, we cultivated maize seedlings (Zea mays L. cv. Norma SC) in nutrient solution and soil (rhizoboxes) to investigate the effect of molybdenum treatment on the absorption of molybdenum, sulfur and iron. These elements have been previously shown to play important roles in nitrate reduction, because they are necessary for the function of the nitrate reductase enzyme. We also investigated the relationship between molybdenum treatments and different nitrogen forms in maize. Molybdenum treatments were 0, 0.96, 9.6 and 96 μg kg(-1) in the nutrition solution experiments, and 0, 30, 90, 270 mg kg(-1) in the rhizobox experiments. On the basis of our results, the increased Mo level produced higher plant available Mo concentration in nutrient solution and in soil, which resulted increased concentration of Mo in shoots and roots of maize seedlings. In addition it was observed that maize seedlings accumulated more molybdenum in their roots than in their shoots at all treatments. In contrast, molybdenum treatments did not affect significantly either iron or sulfur concentrations in the plant, even if these elements (Mo, S and Fe) play alike important roles in nitrogen metabolism. Furthermore, the physiological molybdenum level (1× Mo = 0.01 μM) reduced NO3-N and enhanced the NH4-N concentrations in seedlings, suggesting that nitrate reduction was more intense under a well-balanced molybdenum supply.

  8. Suppression of erythropoiesis by dietary nitrate

    PubMed Central

    Ashmore, Tom; Fernandez, Bernadette O.; Evans, Colin E.; Huang, Yun; Branco-Price, Cristina; Griffin, Julian L.; Johnson, Randall S.; Feelisch, Martin; Murray, Andrew J.

    2015-01-01

    In mammals, hypoxia-triggered erythropoietin release increases red blood cell mass to meet tissue oxygen demands. Using male Wistar rats, we unmask a previously unrecognized regulatory pathway of erythropoiesis involving suppressor control by the NO metabolite and ubiquitous dietary component nitrate. We find that circulating hemoglobin levels are modulated by nitrate at concentrations achievable by dietary intervention under normoxic and hypoxic conditions; a moderate dose of nitrate administered via the drinking water (7 mg NaNO3/kg body weight/d) lowered hemoglobin concentration and hematocrit after 6 d compared with nonsupplemented/NaCl-supplemented controls. The underlying mechanism is suppression of hepatic erythropoietin expression associated with the downregulation of tissue hypoxia markers, suggesting increased pO2. At higher nitrate doses, however, a partial reversal of this effect occurred; this was accompanied by increased renal erythropoietin expression and stabilization of hypoxia-inducible factors, likely brought about by the relative anemia. Thus, hepatic and renal hypoxia-sensing pathways act in concert to modulate hemoglobin in response to nitrate, converging at an optimal minimal hemoglobin concentration appropriate to the environmental/physiologic situation. Suppression of hepatic erythropoietin expression by nitrate may thus act to decrease blood viscosity while matching oxygen supply to demand, whereas renal oxygen sensing could act as a brake, averting a potentially detrimental fall in hematocrit.—Ashmore, T., Fernandez, B. O., Evans, C. E., Huang, Y., Branco-Price, C., Griffin, J. L., Johnson, R. S., Feelisch, M., Murray, A. J. Suppression of erythropoiesis by dietary nitrate. PMID:25422368

  9. Nitrate loss associated with Federal Reference Method

    NASA Astrophysics Data System (ADS)

    Jin, L.; Serve, A.; Brown, N. J.

    2014-12-01

    The 24-h PM2.5 mass, measured by the Federal Reference Method (FRM) designated by EPA, reports the bulk PM2.5 mass retained on a single channel sampler with Teflon or Quartz filters. Semivolatile species such as nitrate can be lost from the Teflon filter during sampling and equilibration processes, and the FRM measurements may not reflect true ambient concentrations of total PM2.5. Consequently, FRM PM2.5 can be problematic when used for evaluating the fidelity of air quality models, especially for domains where particulate nitrate is a dominant contributor. In order to account for this discrepancy, a thermodynamic adjustment method was developed by EPA to determine the retained nitrate based upon the temperature (T) and relative humidity (RH). The nitrate adjustment method was evaluated for the eastern US where summertime is characterized by hot and humid weather and sulfate particles are the dominant inorganic contributor. Potential differences exist for applications to California due to its different PM2.5 composition and meteorology. In this study we, (1) evaluate EPA's nitrate adjustment method for California where particulate nitrate is a major contributor to total PM2.5 mass and (2) apply this method to adjusting simulated PM2.5 by the Community Multiscale Air Quality Model(CMAQ) over the California domain. The adjusted CMAQ outputs are then compared to the observed total PM2.5. The positive biases between CMAQ and observed PM2.5 can be largely explained by evaporative loss of nitrate on filters.

  10. Nitrate in aquifers beneath agricultural systems

    USGS Publications Warehouse

    Burkart, M.R.; Stoner, J.D.; ,

    2007-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as

  11. Nitrate in aquifers beneath agricultural systems.

    PubMed

    Burkart, M R; Stoner, J D

    2007-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as

  12. FeCycle: Attempting an iron biogeochemical budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters

    NASA Astrophysics Data System (ADS)

    Boyd, P. W.; Law, C. S.; Hutchins, D. A.; Abraham, E. R.; Croot, P. L.; Ellwood, M.; Frew, R. D.; Hadfield, M.; Hall, J.; Handy, S.; Hare, C.; Higgins, J.; Hill, P.; Hunter, K. A.; Leblanc, K.; Maldonado, M. T.; McKay, R. M.; Mioni, C.; Oliver, M.; Pickmere, S.; Pinkerton, M.; Safi, K.; Sander, S.; Sanudo-Wilhelmy, S. A.; Smith, M.; Strzepek, R.; Tovar-Sanchez, A.; Wilhelm, S. W.

    2005-12-01

    An improved knowledge of iron biogeochemistry is needed to better understand key controls on the functioning of high-nitrate low-chlorophyll (HNLC) oceanic regions. Iron budgets for HNLC waters have been constructed using data from disparate sources ranging from laboratory algal cultures to ocean physics. In summer 2003 we conducted FeCycle, a 10-day mesoscale tracer release in HNLC waters SE of New Zealand, and measured concurrently all sources (with the exception of aerosol deposition) to, sinks of iron from, and rates of iron recycling within, the surface mixed layer. A pelagic iron budget (timescale of days) indicated that oceanic supply terms (lateral advection and vertical diffusion) were relatively small compared to the main sink (downward particulate export). Remote sensing and terrestrial monitoring reveal 13 dust or wildfire events in Australia, prior to and during FeCycle, one of which may have deposited iron at the study location. However, iron deposition rates cannot be derived from such observations, illustrating the difficulties in closing iron budgets without quantification of episodic atmospheric supply. Despite the threefold uncertainties reported for rates of aerosol deposition (Duce et al., 1991), published atmospheric iron supply for the New Zealand region is ˜50-fold (i.e., 7- to 150-fold) greater than the oceanic iron supply measured in our budget, and thus was comparable (i.e., a third to threefold) to our estimates of downward export of particulate iron. During FeCycle, the fluxes due to short term (hours) biological iron uptake and regeneration were indicative of rapid recycling and were tenfold greater than for new iron (i.e. estimated atmospheric and measured oceanic supply), giving an "fe" ratio (uptake of new iron/uptake of new + regenerated iron) of 0.17 (i.e., a range of 0.06 to 0.51 due to uncertainties on aerosol iron supply), and an "Fe" ratio (biogenic Fe export/uptake of new + regenerated iron) of 0.09 (i.e., 0.03 to 0.24).

  13. Nitrate removal and denitrification affected by soil characteristics in nitrate treatment wetlands.

    PubMed

    Lin, Ying-Feng; Jing, Shuh-Ren; Lee, Der-Yuan; Chang, Yih-Feng; Shih, Kai-Chung

    2007-03-01

    Several small-scale surface flow constructed wetlands unplanted and planted (monoculture) with various macrophytes (Phragmites australis, Typha orientalis, Pennisetum purpureum, Ipomoea aquatica, and Pistia stratiotes) were established to continuously receive nitrate-contaminated groundwater. Soil characteristics and their effects on nitrate removal and soil denitrification were investigated. The results showed that planted wetland cells exhibited significantly higher (P < 0.05) nitrate removal efficiencies (70-99%) and soil denitrification rates (3.78-15.02 microg N2O-N/g dry soil/h) than an unplanted covered wetland cell (1%, 0.11 microg N2O-N/g/h). However, the unplanted uncovered wetland cell showed a nitrate removal efficiency (55%) lower than but a soil denitrification rate (9.12 microg N2O-N/g/h) comparable to the planted cells. The nitrate removal rate correlated closely and positively with the soil denitrification rate for the planted cells, indicating that soil denitrification is an important process for removing nitrate in constructed wetlands. The results of nitrogen budget revealed that around 68.9-90.7% of the overall nitrogen removal could be attributed to the total denitrification. The soil denitrification rate was found to correlate significantly (P < 0.01) with the extractable organic carbon, organic matter, and in situ-measured redox potential of wetland soil, which accordingly were concluded as suitable indicators of soil denitrification rate and nitrate removal rate in nitrate treatment wetlands.

  14. Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors.

    PubMed

    Krishna Mohan, Tulasi Venkata; Renu, Kadali; Nancharaiah, Yarlagadda Venkata; Satya Sai, Pedapati Murali; Venugopalan, Vayalam Purath

    2016-02-01

    A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy.

  15. Extraction of lanthanide(III) and yttrium nitrates by trialkylmethylammonium nitrate from multicomponent solutions

    SciTech Connect

    Pyartman, A.K.; Kopyrin, A.A.; Puzikov, E.A.

    1995-07-01

    The extraction of lanthanide(III) and yttrium nitrates from multicomponent solutions by trialkylmethylammonium nitrate at 298.15 K and pH 2 is examined. Physicochemical and mathematical models describing the distributions of lanthanide(III) (Pr-Lu) and Y in multicomponent solutions as a function of the total metal concentration in the aqueous phase and concentrate composition are presented.

  16. An unexpected truth: increasing nitrate loading can decrease nitrate export from watersheds

    NASA Astrophysics Data System (ADS)

    Askarizadeh Bardsiri, A.; Grant, S. B.; Rippy, M.

    2015-12-01

    The discharge of anthropogenic nitrate (e.g., from partially treated sewage, return flows from agricultural irrigation, and runoff from animal feeding operations) to streams can negatively impact both human and ecosystem health. Managing these many point and non-point sources to achieve some specific end-point—for example, reducing the annual mass of nitrate exported from a watershed—can be a challenge, particularly in rapidly growing urban areas. Adding to this complexity is the fact that streams are not inert: they too can add or remove nitrate through assimilation (e.g., by stream-associated plants and animals) and microbially-mediated biogeochemical reactions that occur in streambed sediments (e.g., respiration, ammonification, nitrification, denitrification). By coupling a previously published correlation for in-stream processing of nitrate [Mulholland et al., Nature, 2008, 452, 202-205] with a stream network model of the Jacksons Creek watershed (Victoria, Australia) I demonstrate that managing anthropogenic sources of stream nitrate without consideration of in-stream processing can result in a number of non-intuitive "surprises"; for example, wastewater effluent discharges that increase nitrate loading but decrease in-stream nitrate concentrations can reduce the mass of nitrate exported from a watershed.

  17. Perspectives on iron absorption.

    PubMed

    Hallberg, Leif; Hulthén, Lena

    2002-01-01

    Newly established relationships between dietary iron absorption and serum ferritin and between serum ferritin and iron stores permit calculation of amounts of stored iron under different conditions at steady states when absorption equals losses. The rate of growth of stores can also be calculated. All calculations are based on observations and require no model assumptions. Present analyses demonstrated an effective control of iron absorption preventing development of iron overload in otherwise healthy subjects even if the diet is fortified with iron and even if meat intake is high. There are strong relationships between iron requirements, bioavailability of dietary iron, and amounts of stored iron. Our observations that a reduction in iron stores and a calculated decrease of hemoglobin iron had the same increasing effect on iron absorption suggest that the control of iron absorption is mediated from a common cell, which may register both size of iron stores and hemoglobin iron deficit. We suggest that the hepatocyte is that cell. Nutritional iron deficiency is especially critical in menstruating women, in the latter third of pregnancy, during adolescence for both girls and boys, and in the weaning period from 4 to 6 months to 2 years of age. The body possesses remarkable, potential control systems of probable very ancient origin capable of preventing both iron deficiency and iron overload. Present problems with iron deficiency being the most frequent deficiency disorder are related to nonbiological changes in our societies over the most recent 10,000 years. This perspective on iron homeostasis or iron balance is mainly based on studies in humans of clinical and epidemiological observations, trying to understand why iron deficiency is the most frequent deficiency disorder in the world in spite of the ingenious mechanisms in the body that should prevent it. Withdrawal of iron fortification of flour in Sweden in 1994 led to a significant increase in iron deficiency

  18. Contribution of atmospheric nitrate deposition to nitrate loading in the Chesapeake Bay. Final report

    SciTech Connect

    Tyler, M.

    1988-12-01

    Recent studies have suggested that nitrate introduced into the Chesapeake Bay via atmospheric deposition may be a significant source of excess nutrients. In order to determine if concerns about atmospheric deposition are justified, modeled estimates of wetfall nitrate deposition over the Chesapeake Bay basin, based on monitoring data collected in 1984, were used to estimate basin-wide nitrate loading (1.38 x 10/sup 8/ kg) over the land area of the basin. Estimates of transfer coefficients and nitrate loadings to the Bay for various land-use categories were also calculated, using figures developed by the EPA Chesapeake Bay Program. The conservative nature of assumptions made in developing these figures suggests that the actual percentage contribution of atmospheric nitrate deposition may be lower than the estimated value.

  19. Dietary inorganic nitrate mobilizes circulating angiogenic cells.

    PubMed

    Heiss, Christian; Meyer, Christian; Totzeck, Matthias; Hendgen-Cotta, Ulrike B; Heinen, Yvonne; Luedike, Peter; Keymel, Stefanie; Ayoub, Nassim; Lundberg, Jon O; Weitzberg, Eddie; Kelm, Malte; Rassaf, Tienush

    2012-05-01

    Nitric oxide (NO) was implicated in the regulation of mobilization and function of circulating angiogenic cells (CACs). The supposedly inert anion nitrate, abundant in vegetables, can be stepwise reduced in vivo to form nitrite, and consecutively NO, representing an alternative to endogenous NO formation by NO synthases. This study investigated whether inorganic dietary nitrate influences mobilization of CACs. In a randomized double-blind fashion, healthy volunteers ingested 150 ml water with 0.15 mmol/kg (12.7 mg/kg) of sodium nitrate, an amount corresponding to 100-300 g of a nitrate-rich vegetable, or water alone as control. Mobilization of CACs was determined by the number of CD34(+)/KDR(+) and CD133(+)/KDR(+) cells using flow cytometry and the mobilization markers stem cell factor (SCF) and stromal cell-derived factor-1a (SDF-1α) were determined in plasma via ELISA. Nitrite and nitrate were measured using high-performance liquid chromatography and reductive gas-phase chemiluminescence, respectively. NOS-dependent vasodilation was measured as flow-mediated vasodilation. Further mechanistic studies were performed in mice after intravenous application of nitrite together with an NO scavenger to identify the role of nitrite and NO in CAC mobilization. Nitrate ingestion led to a rise in plasma nitrite together with an acute increase in CD34(+)/KDR(+) and CD133(+)/KDR(+)-CACs along with increased NOS-dependent vasodilation. This was paralleled by an increase in SCF and SDF-1α and the maximal increase in plasma nitrite correlated with CD133(+)/KDR(+)-CACs (r=0.73, P=0.016). In mice, nitrate given per gavage and direct intravenous injection of nitrite led to CAC mobilization, which was abolished by the NO scavenger cPTIO, suggesting that nitrite mediated its effect via formation of NO. Dietary inorganic nitrate acutely mobilizes CACs via serial reduction to nitrite and NO. The nitrate-nitrite-NO pathway could offer a novel nutritional approach for regulation of

  20. The δ15N of nitrate in the Southern Ocean: Consumption of nitrate in surface waters

    NASA Astrophysics Data System (ADS)

    Sigman, D. M.; Altabet, M. A.; McCorkle, D. C.; Francois, R.; Fischer, G.

    1999-12-01

    We report nitrogen isotope data for nitrate from transects of hydrocast and surface samples collected in the eastern Indian and Pacific sectors of the Southern Ocean, focusing here on the data from the upper water column to study the effect of nitrate consumption by phytoplankton. The δ15N of nitrate increases by 1-2‰ from deep water into the Antarctic summertime surface layer, due to kinetic isotopic fractionation during nitrate uptake. Estimation of the nitrate uptake isotope effect from Antarctic depth profiles yields values in the range of 5-6‰ in east Indian sector and 4-5‰ in the east Pacific sector. Surface transect data from the Pacific sector also yield values of 4-5‰. The major uncertainty in the profile-based estimation of the isotope effect involves the δ15N of nitrate from the temperature minimum layer below the summertime Antarctic surface layer, which deviates significantly from the predictions of simple models of isotope fractionation. For the Subantarctic surface, it is possible to distinguish between nitrate supplied laterally from the surface Antarctic and nitrate supplied vertically from the Subantarctic thermocline because of the distinctive relationships between the δ15N and concentration of nitrate in these two potential sources. Our Subantarctic samples, collected during the summer and fall, indicate that nitrate is supplied to the Subantarctic surface largely by northward transport of Antarctic surface water. Isotopic data from the Pacific sector of the Subantarctic suggest an isotope effect of 4.5‰, indistinguishable from the Antarctic estimates in this sector.

  1. Microbial Reduction of Chromate in the Presence of Nitrate by Three Nitrate Respiring Organisms

    PubMed Central

    Chovanec, Peter; Sparacino-Watkins, Courtney; Zhang, Ning; Basu, Partha; Stolz, John F.

    2012-01-01

    A major challenge for the bioremediation of toxic metals is the co-occurrence of nitrate, as it can inhibit metal transformation. Geobacter metallireducens, Desulfovibrio desulfuricans, and Sulfurospirillum barnesii are three soil bacteria that can reduce chromate [Cr(VI)] and nitrate, and may be beneficial for developing bioremediation strategies. All three organisms respire through dissimilatory nitrate reduction to ammonia (DNRA), employing different nitrate reductases but similar nitrite reductase (Nrf). G. metallireducens reduces nitrate to nitrite via the membrane bound nitrate reductase (Nar), while S. barnesii and D. desulfuricans strain 27774 have slightly different forms of periplasmic nitrate reductase (Nap). We investigated the effect of DNRA growth in the presence of Cr(VI) in these three organisms and the ability of each to reduce Cr(VI) to Cr(III), and found that each organisms responded differently. Growth of G. metallireducens on nitrate was completely inhibited by Cr(VI). Cultures of D. desulfuricans on nitrate media was initially delayed (48 h) in the presence of Cr(VI), but ultimately reached comparable cell yields to the non-treated control. This prolonged lag phase accompanied the transformation of Cr(VI) to Cr(III). Viable G. metallireducens cells could reduce Cr(VI), whereas Cr(VI) reduction by D. desulfuricans during growth, was mediated by a filterable and heat stable extracellular metabolite. S. barnesii growth on nitrate was not affected by Cr(VI), and Cr(VI) was reduced to Cr(III). However, Cr(VI) reduction activity in S. barnesii, was detected in both the cell free spent medium and cells, indicating both extracellular and cell associated mechanisms. Taken together, these results have demonstrated that Cr(VI) affects DNRA in the three organisms differently, and that each have a unique mechanism for Cr(VI) reduction. PMID:23251135

  2. Nitrate radical oxidation of γ-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields

    NASA Astrophysics Data System (ADS)

    Slade, Jonathan H.; de Perre, Chloé; Lee, Linda; Shepson, Paul B.

    2017-07-01

    Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield = 4(+1/-3) %, total ON yield = 14(+3/-2) %, and SOA yield ≤ 10 % under atmospherically relevant particle mass loadings, similar to those for α-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography-mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest.

  3. Light-dependent nitration of bacteriorhodopsin

    SciTech Connect

    Lam, E.; Seltzer, S.; Katsura, T.; Packer, L.

    1983-11-01

    Purple membranes were treated with tetranitromethane to modify tyrosine residues of bacteriorhodopsin. At pH 8.0, nitration is shown to be affected by illumination during the modification. Amino acid analysis revealed about 0.7 residues nitrated if reaction was in the dark while about 2.0 tyrosines were modified if illumination greater than 540 nm was provided. Tryptophan was unaffected under both conditions. Light-dependent nitration caused a blue shift of the absorbance maximum of bacteriorhodopsin from 568 to 530 nm while no chromophore shift was observed for the dark-modified preparation. Both preparations show an absorption band at 360 nm indicative of the presence of nitrotyrosines. Reduction by dithionite eliminated the pH-dependent changes associated with the 360-nm nitrotyrosine band. Circular dichroism spectra indicate that interactions between neighboring chromophores are altered concomitant with the blue shift of the absorbance maximum by nitration. These studies show that light is required for the nitration of the tyrosine residue is probably responsible for the blue shift of the absorbance maximum. The intrinsic fluorescence and photocycle kinetics of the tyrosine-modified preparation and reduction of nitrotyrosine by dithionite were studied. In dark modification, only pH-dependent dithionite-reducible nitrotyrosines were produced. It is concluded that surface tyrosines probably do not directly participate in the proton-translocation events coupled to the photocycle of bacteriorhodopsin.

  4. Exclusion of Nitrate from Frozen Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Marrocco, H. A.; Michelsen, R. R.

    2013-12-01

    Reactions occurring at the surface of ice, sea ice, and snow in Earth's cryosphere have an impact on the composition of the overlying atmosphere. In order to elucidate reaction mechanisms and model their contributions to atmospheric processes, the morphology of frozen aqueous surfaces and amounts of reactants contained therein must be determined. To this end, the exclusion of nitrate ions to the surface of frozen aqueous solutions has been studied by attenuated total reflection infrared spectroscopy (ATR-IR). In this technique the near-surface region of the frozen films are interrogated to a depth of a few hundred nanometers from the film-crystal interface. Aqueous solutions (0.001 to 0.01 M) of sodium nitrate (NaNO3), magnesium nitrate (Mg(NO3)2), and nitric acid (HNO3) were quickly frozen on the germanium ATR crystal and observed at a constant temperature of about -18°C. In addition to ice and the solutes, liquid water in varying amounts was observed in the spectra. The amount of nitrate in the surface liquid is three to four orders of magnitude higher than in the unfrozen solution. While all the nitrate salts exhibit exclusion to the unfrozen surface, the dynamics are different for different counter-ions. Results are compared to freezing point depression data and the predictions of equilibrium thermodynamics.

  5. Vulnerability of streams to legacy nitrate sources

    USGS Publications Warehouse

    Tesoriero, Anthony J.; Duff, John H.; Saad, David A.; Spahr, Norman E.; Wolock, David M.

    2013-01-01

    The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI).

  6. Vulnerability of streams to legacy nitrate sources.

    PubMed

    Tesoriero, Anthony J; Duff, John H; Saad, David A; Spahr, Norman E; Wolock, David M

    2013-04-16

    The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI).

  7. Nitrate transceptor(s) in plants.

    PubMed

    Gojon, Alain; Krouk, Gabriel; Perrine-Walker, Francine; Laugier, Edith

    2011-04-01

    The availability of mineral nutrients in the soil dramatically fluctuates in both time and space. In order to optimize their nutrition, plants need efficient sensing systems that rapidly signal the local external concentrations of the individual nutrients. Until recently, the most upstream actors of the nutrient signalling pathways, i.e. the sensors/receptors that perceive the extracellular nutrients, were unknown. In Arabidopsis, increasing evidence suggests that, for nitrate, the main nitrogen source for most plant species, a major sensor is the NRT1.1 nitrate transporter, also contributing to nitrate uptake by the roots. Membrane proteins that fulfil a dual nutrient transport/signalling function have been described in yeast and animals, and are called 'transceptors'. This review aims to illustrate the nutrient transceptor concept in plants by presenting the current evidence indicating that NRT1.1 is a representative of this class of protein. The various facets, as well as the mechanisms of nitrate sensing by NRT1.1 are considered, and the possible occurrence of other nitrate transceptors is discussed.

  8. Structure and Function of Metal- and Nitrate-reducing Microbial Communities in the FRC Subsurface

    SciTech Connect

    Akob, Denise M.; Mills, Heath J.; Kerkhof, Lee; Gihring, Thomas M.; Kostk, Joel E.

    2006-04-05

    The overall goal of this study is to evaluate structure-function relationships of sedimentary microbial communities likely to regulate U(VI) reduction and immobilization in the subsurface of Area 2 at the Field Research Center (FRC), Oak Ridge, TN. Microcosm experiments were conducted under near in situ conditions with FRC subsurface materials cocontaminated with high levels of U(VI) and nitrate. The activity, abundance, and community composition of microorganisms was determined in microcosm samples, stimulated with ethanol or glucose, and compared to those from sediment cores and unamended controls. Activity was assessed by monitoring terminal electron accepting processes (TEAPs; nitrate, sulfate, uranium, and iron reduction) as well as electron donor utilization. Microbial functional groups, nitrate- and iron(III)-reducing bacteria, were enumerated during the nitrate- and metal-reduction phases of the incubation and in sediment core samples using a most probable number (MPN) serial dilution assay. U(VI) and Fe(III) were reduced concurrently in the glucose but not the ethanol treatments. In ethanol-amended microcosms, U(VI) was reduced during a 4-day lag phase between nitrate- and Fe(III)-reduction phases. Biostimulation resulted in 3 to 5 orders of magnitude higher counts of Fe(III)-reducing bacteria, whereas populations of nitrate-reducers were enhanced by 1 to 3 orders of magnitude. One to 2 orders of magnitude more Fe(III)-reducers were observed in ethanol- as compared to glucose-amended treatments in parallel with enhanced U(VI) removal in ethanol treatments. Cultivatable Fe(III)-reducing bacteria in the ethanol treatments were dominated by Geobacter sp. while those cultured on glucose were dominated by fermentative organisms, i.e., Tolumonas sp. Currently, carbon substrate utilization is being examined through HPLC analysis of microcosm porewaters. In addition, changes in the overall microbial community composition are being assessed using cultivation

  9. Effect of promoter and noble metals and suspension pH on catalytic nitrate reduction by bimetallic nanoscale Fe(0) catalysts.

    PubMed

    Bae, Sungjun; Hamid, Shanawar; Jung, Junyoung; Sihn, Youngho; Lee, Woojin

    2016-01-01

    Experiments were conducted to investigate the effect of experimental factors (types of promotor and noble metals, H2 injection, and suspension pH) on catalytic nitrate reduction by bimetallic catalysts supported by nanoscale zero-valent iron (NZVI). NZVI without H2 injection showed 71% of nitrate reduction in 1 h. Cu/NZVI showed the almost complete nitrate reduction (96%) in 1 h, while 67% of nitrate was reduced by Ni/NZVI. The presence of noble metals (Pd and Pt) on Cu/NZVI without H2 injection resulted in the decrease of removal efficiency to 89% and 84%, respectively, due probably to the electron loss of NZVI for formation of metallic Pd and Pt. H2 injection into Cu-Pd/NZVI suspension significantly improved both catalytic nitrate reduction (>97% in 30 min) and N2 selectivity (18%), indicating that adsorbed H on active Pd sites played an important role for the enhanced nitrate reduction and N2 selectivity. The rapid passivation of NZVI surface resulted in a dramatic decrease in nitrate reduction (79-28%) with an increase in N2 selectivity (8-66%) as the suspension pH increased from 8 to 10.

  10. Nitrate destruction in an elutriated fluid-bed calciner

    SciTech Connect

    Cowan, R.G.; Cash, R.J.; Owen, T.J.; Shook, G.E.

    1987-09-01

    Nitrate destruction was demonstrated using an elutriated fluid-bed calciner process developed for nuclear fuel mixed-oxide conversion. Testing was directed to treatment of sodium nitrate, a major waste component at the Hanford Site. One test was also performed with copper nitrate. All tests produced low concentrations of NO/sub x/ in the offgas. The chemistry developed for uranium and plutonium nitrate appears to apply to other metal nitrates. The copper nitrate test was successful, with over 90% of the nitrate converted to elemental nitrogen and water and with recovery of a granular, free-flowing copper product. Tests with sodium nitrate were not successful due to fusion of sodium carbonate in the calciner bed and plugging of the calciner. Further development of the elutriated fluid-bed system would be required to process high sodium nitrate waste solutions.

  11. Catalytic effect of different forms of iron in purification of single-walled carbon nanotubes.

    PubMed

    Suzuki, Tomoko; Inoue, Sakae; Ando, Yoshinori

    2010-06-01

    In the arc plasma jet (APJ) method, a large amount of soot including single wall carbon nanotubes (SWNTs) can be produced in a short time. However, as-grown soot contains a lot of impurities, such as metallic particles used as catalyst and amorphous carbon. Hence it is necessary to purify the soot to obtain pure SWNTs. The biggest problem in purifying APJ-SWNTs is how to remove the thick amorphous carbon covering the catalyst metal particles. By refluxing APJ-SWNTs in hydrogen peroxide using iron particle as catalyst, it can be purified. The added fine particle of pure iron is found to be effective. Then, we examine whether SWNTs can be purified more effectively by adding solution containing the Fe ion instead of the iron particle. We used iron (III) nitrate nonahydrate, hydrogen peroxide decomposing agent which contains catalase and ammonium iron (II) sulfate hexahydrate. In the case of iron (III) nitrate and catalase, purification effect is not obvious. Under these conditions hydrogen peroxide was decomposed into H2O and O2, and the hydroxyl radical was not generated. On the other hand, ammonium iron (II) sulfate is effective. Because of existence of Fe2+ in solution Fenton's reaction takes place. Reaction rate is increased at high temperature. Therefore, APJ-SWNT is purified more effectively if refluxed in hydrogen peroxide using ammonium iron (II) sulfate as catalyst.

  12. Molecular Components of Nitrate and Nitrite Efflux in Yeast

    PubMed Central

    Cabrera, Elisa; González-Montelongo, Rafaela; Giraldez, Teresa; de la Rosa, Diego Alvarez

    2014-01-01

    Some eukaryotes, such as plant and fungi, are capable of utilizing nitrate as the sole nitrogen source. Once transported into the cell, nitrate is reduced to ammonium by the consecutive action of nitrate and nitrite reductase. How nitrate assimilation is balanced with nitrate and nitrite efflux is unknown, as are the proteins involved. The nitrate assimilatory yeast Hansenula polymorpha was used as a model to dissect these efflux systems. We identified the sulfite transporters Ssu1 and Ssu2 as effective nitrate exporters, Ssu2 being quantitatively more important, and we characterize the Nar1 protein as a nitrate/nitrite exporter. The use of strains lacking either SSU2 or NAR1 along with the nitrate reductase gene YNR1 showed that nitrate reductase activity is not required for net nitrate uptake. Growth test experiments indicated that Ssu2 and Nar1 exporters allow yeast to cope with nitrite toxicity. We also have shown that the well-known Saccharomyces cerevisiae sulfite efflux permease Ssu1 is also able to excrete nitrite and nitrate. These results characterize for the first time essential components of the nitrate/nitrite efflux system and their impact on net nitrate uptake and its regulation. PMID:24363367

  13. Limited role of biochars in nitrogen fixation through nitrate adsorption.

    PubMed

    Yang, Jing; Li, Hao; Zhang, Di; Wu, Min; Pan, Bo

    2017-08-15

    Nitrate cycling is essential in sustaining soil systems. Excessive application of N-fertilizers and the associated underground water contamination have attracted a great deal of research attention. Sorption is efficient and environmentally friendly in nitrate fixation. A debate was noted in literature regarding whether biochars have potential to fix nitrate through sorption. In this study, biochars produced from different biomasses as well as biomass compositions were chosen as the absorbents to evaluate their potential efficiencies in nitrate fixation. Increased sorption to nitrate was observed for biochars with increased pyrolysis temperature, but the increasing extent varied with biomass. The surface base functional groups and surface charges of biochars could not well explain nitrate sorption. The significant positive correlation between nitrate sorption and biochar surface areas suggested that surface area was the controlling parameter for nitrate sorption. The pre-coating of tannic acid (TA) on biochars decreased but did not completely inhibit nitrate sorption. This observation suggested that nitrate sorption on biochars may be further decreased after their interactions with natural organic matter. Nitrate sorption was compared among various adsorbents, including biochars, soil particles, clay minerals, engineered particles, as well as humic substances. Soil particles generally showed high sorption to nitrate over biochars. This result suggested that biochars investigated in this work may play a limited role in nitrate fixation through sorption after their massive application. Nitrogen fixation through nitrate adsorption on biochars should be carefully evaluated taking into consideration of biochar feedstocks and properties.

  14. Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age.

    PubMed

    Wang, Xingchen Tony; Sigman, Daniel M; Prokopenko, Maria G; Adkins, Jess F; Robinson, Laura F; Hines, Sophia K; Chai, Junyi; Studer, Anja S; Martínez-García, Alfredo; Chen, Tianyu; Haug, Gerald H

    2017-03-28

    The Southern Ocean regulates the ocean's biological sequestration of CO2 and is widely suspected to underpin much of the ice age decline in atmospheric CO2 concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the (15)N/(14)N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher (15)N/(14)N across the Southern Ocean during the Last Glacial Maximum (LGM), 18-25 thousand years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the surface Antarctic Zone, respectively.

  15. Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age

    NASA Astrophysics Data System (ADS)

    Wang, Xingchen Tony; Sigman, Daniel M.; Prokopenko, Maria G.; Adkins, Jess F.; Robinson, Laura F.; Hines, Sophia K.; Chai, Junyi; Studer, Anja S.; Martínez-García, Alfredo; Chen, Tianyu; Haug, Gerald H.

    2017-03-01

    The Southern Ocean regulates the ocean’s biological sequestration of CO2 and is widely suspected to underpin much of the ice age decline in atmospheric CO2 concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the 15N/14N of fossil-bound organic matter in the stony deep-sea coral Desmophyllum dianthus, a tool for reconstructing surface ocean nutrient conditions. The central robust observation is of higher 15N/14N across the Southern Ocean during the Last Glacial Maximum (LGM), 18-25 thousand years ago. These data suggest a reduced summer surface nitrate concentration in both the Antarctic and Subantarctic Zones during the LGM, with little surface nitrate transport between them. After the ice age, the increase in Antarctic surface nitrate occurred through the deglaciation and continued in the Holocene. The rise in Subantarctic surface nitrate appears to have had both early deglacial and late deglacial/Holocene components, preliminarily attributed to the end of Subantarctic iron fertilization and increasing nitrate input from the surface Antarctic Zone, respectively.

  16. Inorganic nitrate and the cardiovascular system.

    PubMed

    Kapil, V; Webb, A J; Ahluwalia, A

    2010-11-01

    Fruit and vegetable-rich diets reduce blood pressure and risk of ischaemic stroke and ischaemic heart disease. While the cardioprotective effects of a fruit and vegetable-rich diet are unequivocal, the exact mechanisms of this effect remain uncertain. Recent evidence has highlighted the possibility that dietary nitrate, an inorganic anion found in large quantities in vegetables (particularly green leafy vegetables), may have a part to play. This beneficial activity lies in the processing in vivo of nitrate to nitrite and thence to the pleiotropic molecule nitric oxide. In this review, recent preclinical and clinical evidence identifying the mechanisms involved in nitrate bioactivity, and the evidence supporting the potential utility of exploitation of this pathway for the prevention and/or treatment of cardiovascular diseases are discussed.

  17. Organic nitrates: past, present and future.

    PubMed

    França-Silva, Maria S; Balarini, Camille M; Cruz, Josiane C; Khan, Barkat A; Rampelotto, Pabulo H; Braga, Valdir A

    2014-09-24

    Nitric oxide (NO) is one of the most important vasodilator molecules produced by the endothelium. It has already been established that NO/cGMP signaling pathway deficiencies are involved in the pathophysiological mechanisms of many cardiovascular diseases. In this context, the development of NO-releasing drugs for therapeutic use appears to be an effective alternative to replace the deficient endogenous NO and mimic the role of this molecule in the body. Organic nitrates represent the oldest class of NO donors that have been clinically used. Considering that tolerance can occur when these drugs are applied chronically, the search for new compounds of this class with lower tolerance potential is increasing. Here, we briefly discuss the mechanisms involved in nitrate tolerance and highlight some achievements from our group in the development of new organic nitrates and their preclinical application in cardiovascular disorders.

  18. Ammonium and nitrate tolerance in lichens.

    PubMed

    Hauck, Markus

    2010-05-01

    Since lichens lack roots and take up water, solutes and gases over the entire thallus surface, these organisms respond more sensitively to changes in atmospheric purity than vascular plants. After centuries where effects of sulphur dioxide and acidity were in the focus of research on atmospheric chemistry and lichens, recently the globally increased levels of ammonia and nitrate increasingly affect lichen vegetation and gave rise to intense research on the tolerance of lichens to nitrogen pollution. The present paper discusses the main findings on the uptake of ammonia and nitrate in the lichen symbiosis and to the tolerance of lichens to eutrophication. Ammonia and nitrate are both efficiently taken up under ambient conditions. The tolerance to high nitrogen levels depends, among others, on the capability of the photobiont to provide sufficient amounts of carbon skeletons for ammonia assimilation. Lowly productive lichens are apparently predisposed to be sensitive to excess nitrogen. Copyright 2010 Elsevier Ltd. All rights reserved.

  19. Plasma nitrate and nitrite are increased by a high-nitrate supplement but not by high-nitrate foods in older adults.

    PubMed

    Miller, Gary D; Marsh, Anthony P; Dove, Robin W; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S Bruce; Kim-Shapiro, Daniel

    2012-03-01

    Little is known about the effect of dietary nitrate on the nitrate/nitrite/nitric oxide cycle in older adults. We examined the effect of a 3-day control diet vs high-nitrate diet, with and without a high-nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics and blood pressure using a randomized 4-period crossover controlled design. We hypothesized that the high-nitrate diet would show higher levels of plasma nitrate/nitrite and lower blood pressure compared with the control diet, which would be potentiated by the supplement. Participants were 8 normotensive older men and women (5 female, 3 male, 72.5 ± 4.7 years old) with no overt disease or medications that affect nitric oxide metabolism. Plasma nitrate and nitrite levels and blood pressure were measured before and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet + supplement (P < .001 and P = .017 for nitrate and nitrite, respectively) and high-nitrate diet + supplement (P = .001 and P = .002), but not for control diet (P = .713 and P = .741) or high-nitrate diet (P = .852 and P = .500). Blood pressure decreased from the morning baseline measure to the three 2-hour postmeal follow-up time points for all treatments, but there was no main effect for treatment. In healthy older adults, a high-nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction.

  20. Iron deficiency in Europe.

    PubMed

    Hercberg, S; Preziosi, P; Galan, P

    2001-04-01

    In Europe, iron deficiency is considered to be one of the main nutritional deficiency disorders affecting large fractions of the population, particularly such physiological groups as children, menstruating women and pregnant women. Some factors such as type of contraception in women, blood donation or minor pathological blood loss (haemorrhoids, gynaecological bleeding...) considerably increase the difficulty of covering iron needs. Moreover, women, especially adolescents consuming low-energy diets, vegetarians and vegans are at high risk of iron deficiency. Although there is no evidence that an absence of iron stores has any adverse consequences, it does indicate that iron nutrition is borderline, since any further reduction in body iron is associated with a decrease in the level of functional compounds such as haemoglobin. The prevalence of iron-deficient anaemia has slightly decreased in infants and menstruating women. Some positive factors may have contributed to reducing the prevalence of iron-deficiency anaemia in some groups of population: the use of iron-fortified formulas and iron-fortified cereals; the use of oral contraceptives and increased enrichment of iron in several countries; and the use of iron supplements during pregnancy in some European countries. It is possible to prevent and control iron deficiency by counseling individuals and families about sound iron nutrition during infancy and beyond, and about iron supplementation during pregnancy, by screening persons on the basis of their risk for iron deficiency, and by treating and following up persons with presumptive iron deficiency. This may help to reduce manifestations of iron deficiency and thus improve public health. Evidence linking iron status with risk of cardiovascular disease or cancer is unconvincing and does not justify changes in food fortification or medical practice, particularly because the benefits of assuring adequate iron intake during growth and development are well established

  1. Iron, nutrient, and phytoplankton distributions in Oregon coastal waters

    NASA Astrophysics Data System (ADS)

    Chase, Zanna; van Geen, Alexander; Kosro, P. Michael; Marra, John; Wheeler, Patricia A.

    2002-10-01

    The relationship between iron and nitrate concentrations was examined off the coast of Oregon during the upwelling season. Surface Fe and N (nitrate + nitrite) concentrations measured underway by flow injection analysis ranged from <0.3 to 20 nmol L-1 and <0.1 to 30 μmol L-1, respectively. Total dissolvable Fe concentrations, measured in unfiltered, acidified samples in surface waters and in vertical profiles, ranged from <0.3 to 300 nmol L-1. Surface water Fe and N concentrations were highly variable and uncoupled. Our observations indicate two dominant sources of Fe to Oregon coastal waters: Slope or shelf sediments and the Columbia River. Sedimentary iron, probably largely in the particulate form, appears to be added to surface waters through wind-induced vertical mixing during strong winds, through thickening of the bottom mixed layer during relaxation or downwelling favorable wind conditions, and through outcropping of shelf bottom waters during upwelling events. The existence of multiple iron sources and the generally high iron concentrations may explain why the distribution of phytoplankton, measured both remotely (by Sea-viewing Wide Field-of-view Sensor) and underway (by in vivo fluorescence), appeared to be driven primarily by physical dynamics and was not strongly linked to the distribution of iron. Nevertheless, at some offshore stations where underway Fe concentrations were <0.3 nmol L-1, underway measurements of the physiological state of phytoplankton by fast repetition rate fluorometry were consistent with mild iron stress, and cross-shelf nutrient distributions were consistent with iron regulation of the magnitude of phytoplankton blooms.

  2. Techniques for Measurement of Nitrate Movement in Soils

    NASA Technical Reports Server (NTRS)

    Broadbent, F. E.

    1971-01-01

    Contamination of surface and ground waters with nitrate usually involves leaching through soil of nitrate produced by mineralization of soil organic matter, decomposition of animal wastes or plant residues, or derived from fertilizers. Nitrate concentrations in the soil solution may be measured by several chemical procedures or by the nitrate electrode. since nitrate is produced throughout the soil mass it is difficult to identify a source of nitrate contamination by conventional means. This problem can be solved by use of N-15-enriched or N-15-depleted materials as tracers. The latter is particularly attractive because of the negligible possibility of the tracer hazardous to health.

  3. Techniques for Measurement of Nitrate Movement in Soils

    NASA Technical Reports Server (NTRS)

    Broadbent, F. E.

    1971-01-01

    Contamination of surface and ground waters with nitrate usually involves leaching through soil of nitrate produced by mineralization of soil organic matter, decomposition of animal wastes or plant residues, or derived from fertilizers. Nitrate concentrations in the soil solution may be measured by several chemical procedures or by the nitrate electrode. since nitrate is produced throughout the soil mass it is difficult to identify a source of nitrate contamination by conventional means. This problem can be solved by use of N-15-enriched or N-15-depleted materials as tracers. The latter is particularly attractive because of the negligible possibility of the tracer hazardous to health.

  4. Comparison of four methods for determining nitrate utilization by cryptococci.

    PubMed Central

    Rhodes, J C; Roberts, G D

    1975-01-01

    This study evaluated the following methods for determining nitrate utilization: Wickerham broth, a special nitrate broth, Delft plate, and nitrate strip. With 236 isolates of cryptococci as test organisms, the special nitrate broth method gave 99% correct results and the Wickerham broth method gave 98%. The nitrate strip and Delft plate methods gave correct results in 94 and 86% of tests, respectively. The special nitrate broth method is judged superior because it provides accurate results within 48 h, compared to 14 days with the Wickerham broth method. PMID:1100649

  5. [Nitrates in the drinking water and cancer].

    PubMed

    Leclerc, H; Vincent, P; Vandevenne, P

    1991-12-01

    Nitrates originating from food and particularly from water are supposedly precursors of carcinogenic N-nitroso compound (NOC) formed within the organism. According to Correa and al. these transformations could be a consequence of bacterial gastric pullulation resulting from certain hypochlorhydric conditions. Much epidemiological research has tried to establish a relationship between exposure to nitrates in drinking water and cases of gastric cancer. The present article deals with research into this relationship in France, in a region where the rate of nitrates in water supplies is among the highest. Death statistics (from cancers of the digestive and urinal tracts) are issued by INSERM and these of the population by INSEE. Towns are classified according to nitrate concentration and the number of deaths is established according to tumour detection by sex and age. Research into death rate divergencies is found by chi 2 and the correlated coefficient. The average relative risk for any age group is calculated for all types of cancer. Research on frequency is carried out from tumour records. Comparative frequency rates are established by direct standardisation according to the structural age of any one European population. Results are analysed in relation to (1) mortality rates and (2) incidence rates. (1) None of the cancers studied, of the digestive or urinary systems, whatever the age on sex, is significantly linked to the quantity of nitrates in water supplies. When all these cancers are taken into account, the death rate does not vary significantly for increasing concentration of nitrates. Towns exceeding the maximum concentration permitted by law do not have a higher mortality rate than other towns.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Nitrate in aquifers beneath agricultural systems

    USGS Publications Warehouse

    Burkart, M.R.; Stoner, J.D.

    2002-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWOA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and shallow carbonate aquifers provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The agricultural system of corn, soybeans, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems, although mean nitrate concentrations in counties with dairy, poultry, cattle and grains, and horticulture systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of

  7. Nitrate postdeposition processes in Svalbard surface snow

    NASA Astrophysics Data System (ADS)

    Björkman, Mats P.; Vega, Carmen P.; Kühnel, Rafael; Spataro, Francesca; Ianniello, Antonietta; Esposito, Giulio; Kaiser, Jan; Marca, Alina; Hodson, Andy; Isaksson, Elisabeth; Roberts, Tjarda J.

    2014-11-01

    The snowpack acts as a sink for atmospheric reactive nitrogen, but several postdeposition pathways have been reported to alter the concentration and isotopic composition of snow nitrate with implications for atmospheric boundary layer chemistry, ice core records, and terrestrial ecology following snow melt. Careful daily sampling of surface snow during winter (11-15 February 2010) and springtime (9 April to 5 May 2010) near Ny-Ålesund, Svalbard reveals a complex pattern of processes within the snowpack. Dry deposition was found to dominate over postdeposition losses, with a net nitrate deposition rate of (0.6 ± 0.2) µmol m-2 d-1 to homogeneous surface snow. At Ny-Ålesund, such surface dry deposition can either solely result from long-range atmospheric transport of oxidized nitrogen or include the redeposition of photolytic/bacterial emission originating from deeper snow layers. Our data further confirm that polar basin air masses bring 15N-depleted nitrate to Svalbard, while high nitrate δ(18O) values only occur in connection with ozone-depleted air, and show that these signatures are reflected in the deposited nitrate. Such ozone-depleted air is attributed to active halogen chemistry in the air masses advected to the site. However, here the Ny-Ålesund surface snow was shown to have an active role in the halogen dynamics for this region, as indicated by declining bromide concentrations and increasing nitrate δ(18O), during high BrO (low-ozone) events. The data also indicate that the snowpack BrO-NOx cycling continued in postevent periods, when ambient ozone and BrO levels recovered.

  8. Electrolytic removal of nitrate from crop residues.

    PubMed

    Colon, G; Sager, J C

    2001-01-01

    The Controlled Ecological Life Support System (CELSS) resource recovery system, which is a waste-processing system,uses aerobic and anaerobic bioreactors to recover plants nutrients and secondary foods from the inedible biomass. Crop residues contain a significant amount of nitrate. There are actually two major problems concerning nitrate: 1) both CELSS biomass production and resource recovery consume large quantities of nitric acid, and 2) nitrate causes a variety of problems in both aerobic and anaerobic bioreactors. The nitrate anion causes several problems in the resource recovery system in such a way that removal prior to the process is highly desirable. The technique proposed to remove nitrate from potato inedible biomass leachate and to satisfy the nitric acid demand was a four-compartment electrolytic cell. In order to establish the electrolytic cell performance variables, experiments were carried out using potato crop residue aqueous leachate as the diluate solution. The variables studied were the potato biomass leachate composition and electrical properties, preparation of compartment solutions to be compatible with the electrolytic system, limiting current density, nutrients removal rates as a function of current density, fluid hydrodynamic conditions, applied voltage, and process operating time during batch recirculation operation. Results indicated that the limiting current density (maximum operating current density) was directly proportional to the solution electrical conductivity an a power function of the linear fluid velocity in the range between 0.083 and 0.403 m/s. During the electrolytic cell once-through operation, the nitrate, potassium, and other nutrient removal rates were proportional to the current density and were inversely proportional to fluid velocity. The removal of monovalent ions was found to be higher than divalent ones. Under batch recirculation operation at constant applied voltage of 4.5 and 8.5 V, it was found that the nutrient

  9. Nitrate in aquifers beneath agricultural systems.

    PubMed

    Burkart, M R; Stoner, J D

    2002-01-01

    Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWOA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and shallow carbonate aquifers provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional concentrations of groundwater nitrate than all other agricultural systems, although mean nitrate concentrations in counties with dairy, poultry, cattle and grains, and horticulture systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of this practice.

  10. The role of nitrate reductase in the regulation of the nitrate assimilation pathway in the yeast Hansenula polymorpha.

    PubMed

    Navarro, Francisco J; Perdomo, Germán; Tejera, Paula; Medina, Braulio; Machín, Félix; Guillén, Rosa Maria; Lancha, Ana; Siverio, José M

    2003-11-01

    The role of nitrate reductase (NR) in the regulation of the nitrate assimilation pathway was evaluated in the yeast Hansenula polymorpha. Posttranscriptional regulation of NR in response to reduced nitrogen sources and the effect of a heterologous NR on the transcriptional regulation of nitrate-assimilatory gene expression was examined. The strain bearing YNR1 (nitrate reductase gene) under the control of the methanol-induced MOX (methanol oxidase) promoter showed that NR is active in the presence of reduced nitrogen sources. In cells incubated with glutamine plus nitrate, rapamycin abolished nitrogen catabolite repression, NR activity being very similar to that in cells induced by nitrate alone. This reveals the involvement of the Tor-signalling pathway in the transcriptional regulation of H. polymorpha nitrate assimilation genes. To assess the role of NR in nitrate-assimilatory gene expression, different strains lacking YNR1, or both YNR1 and YNT1 (high-affinity nitrate transporter) genes, or expressing the tobacco NR under the YNR1 promoter, were used. Tobacco NR abolished the constitutive nitrate-assimilatory gene induction shown by an NR gene disruptant strain. Moreover, in strains lacking the high-affinity nitrate transporter and NR this deregulation disappeared. These facts discard the role of NR protein in the transcriptional induction of the nitrate-assimilatory genes and point out the involvement of the high-affinity nitrate transporter as a part of the nitrate-signalling pathway.

  11. Accumulation of nitrate and nitrite in chilled leaves of rice seedlings is induced by high root temperature.

    PubMed

    Suzuki, Kensaku; Ohmori, Yukimi; Nagao, Manabu

    2013-11-01

    We previously found a novel type of chilling injury in the leaves of rice seedlings (Oryza sativa L. cv. Akitakomachi). The damage was only observed when the roots were not chilled (10 °C/25 °C, shoots/roots), but not when the whole seedling was chilled (10 °C/10 °C). In this report, we show that the chilling injury induced by high root temperature required nitrate and potassium together with a trace amount of iron, manganese or both in the nutrient solution during the treatment, and that the injury was increased by nitrogen starvation before chilling. Both nitrate and nitrite accumulated in the 10 °C/25 °C leaves when the nutrient solution contained nitrate. The nitrate accumulation in the 10 °C/25 °C leaves was highest at the end of the first light period, and was followed by a decrease with a concomitant increase in nitrite during the first dark period. The photosynthetic electron transport was completely lost in both PSII and PSI in the 10 °C/25 °C leaves when the nutrient solution contained nitrate. However, the activities in the leaves of the 10 °C/25 °C plants treated with the nutrient solution lacking nitrate remained at approximately half those in the 10 °C/10°C leaves. The photochemical quenching of Chl fluorescence and the P700 oxidation state were also intermediate between those in the 10 °C/25 °C and 10 °C/10°C leaves of plants supplied with the complete nutrients. Thus, the chilling injury was closely linked to the accumulation of nitrate and nitrite, as well as to a malfunction of photosynthesis in the 10 °C/25 °C leaves.

  12. Iron aluminides and nickel aluminides as materials for chemical air separation

    DOEpatents

    Kang, Doohee

    1991-01-01

    The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

  13. Iron aluminides and nickel aluminides as materials for chemical air separation

    DOEpatents

    Kang, D.

    1991-01-29

    The present invention is directed to a chemical air separation process using a molten salt solution of alkali metal nitrate and nitrite wherein the materials of construction of the containment for the process are chosen from intermetallic alloys of nickel and/or iron aluminide wherein the aluminum content is 28 atomic percent or greater to impart enhanced corrosion resistance.

  14. [Nitrate contents in autumn vegetables and assessment of nitrate intake in Shanghai].

    PubMed

    Guo, Kai-Xiu; Yao, Chun-Xia; Chen, Yi; Yang, Ye-Feng; Lu, Li-Min

    2011-04-01

    To analyze and assess the nitrate contents in Autumn vegetables and nitrate intake in Shanghai resident 25 groups and 439 various vegetables were collected and analyzed from the green houses and outdoors in Songjiang, Fengxian, Jinshan and Pudong of Shanghai during Sep.-Nov., 2009. Nitrate contents were analyzed by UV-spectrophotometer. The results showed that the prevalence of severe contamination was 41.46%, the prevalence of heavy and medium contamination was 30.53%, the prevalence of mild contamination was 28.02%; the content of nitrate in vegetables was in the following descent order: leafy vegetables, root and stem vegetables, melons, egg plants, beans, the nitrate contents in different species differed greatly; the nitrate contents in leafy, root and stem vegetables with green-house planting were less than that of outdoor planting in Fengxian and Songjiang except Pudong and Jinshan. According to the assessment of nitrate intake, the average daily intake of local resident is 445.22 mg which exceeds ADI 38.42%, so limited standard and control are urgently needed.

  15. Excess nitrate loads to coastal waters reduces nitrate removal efficiency: mechanism and implications for coastal eutrophication.

    PubMed

    Lunau, Mirko; Voss, Maren; Erickson, Matthew; Dziallas, Claudia; Casciotti, Karen; Ducklow, Hugh

    2013-05-01

    Terrestrial ecosystems are becoming increasingly nitrogen-saturated due to anthropogenic activities, such as agricultural loading with artificial fertilizer. Thus, more and more reactive nitrogen is entering streams and rivers, primarily as nitrate, where it is eventually transported towards the coastal zone. The assimilation of nitrate by coastal phytoplankton and its conversion into organic matter is an important feature of the aquatic nitrogen cycle. Dissolved reactive nitrogen is converted into a particulate form, which eventually undergoes nitrogen removal via microbial denitrification. High and unbalanced nitrate loads to the coastal zone may alter planktonic nitrate assimilation efficiency, due to the narrow stochiometric requirements for nutrients typically shown by these organisms. This implies a cascade of changes for the cycling of other elements, such as carbon, with unknown consequences at the ecosystem level. Here, we report that the nitrate removal efficiency (NRE) of a natural phytoplankton community decreased under high, unbalanced nitrate loads, due to the enhanced recycling of organic nitrogen and subsequent production and microbial transformation of excess ammonium. NRE was inversely correlated with the amount of nitrate present, and mechanistically controlled by dissolved organic nitrogen (DON), and organic carbon (Corg) availability. These findings have important implications for the management of nutrient runoff to coastal zones.

  16. Isolating nitrated and aromatic aerosols and nitrated aromatic gases as sources of ultraviolet light absorption

    NASA Astrophysics Data System (ADS)

    Jacobson, Mark Z.

    1999-02-01

    Measurements in 1973 and 1987 showed that downward ultraviolet (UV) irradiances within the boundary layer in Los Angeles were up to 50% less than those above the boundary layer. Downward total solar irradiances were reduced by less than 14% in both studies. It is estimated that standard gas and particulate absorbers and scatterers accounted for only about 52-62% of the observed UV reductions at Claremont and Riverside. It is hypothesized that absorption by nitrated and aromatic aerosol components and nitrated aromatic gases caused at least 25-30% of the reductions (with aerosols accounting for about 4/5 of this percent). The remaining reductions are still unaccounted for. Absorbing aerosol components include nitrated aromatics, benzaldehydes, benzoic acids, aromatic polycarboxylic acids, phenols, polycyclic aromatic hydrocarbons, and nitrated inorganics. Many of these species have been observed to date in atmospheric particles, and absorption coefficient data indicate many are strong absorbers at long UV wavelengths. Since aerosols containing nitrated or aromatic aerosols have been observed widely in many areas aside from Los Angeles the finding may account for a portion of UV extinction in those regions as well. In Los Angeles, the finding may be important for predicting smog evolution, since UV reductions associated with high aerosol loadings were estimated to cause a 5-8% decrease in ozone mixing ratios in August 1987. Further laboratory and field studies are needed to quantify better the extent of UV absorption due to nitrated and aromatic aerosols and nitrated aromatic gases.

  17. Nitrate stimulation of indigenous nitrate-reducing, sulfide-oxidising bacterial community in wastewater anaerobic biofilms.

    PubMed

    Garcia-de-Lomas, Juan; Corzo, Alfonso; Carmen Portillo, M; Gonzalez, Juan M; Andrades, Jose A; Saiz-Jimenez, Cesáreo; Garcia-Robledo, Emilio

    2007-07-01

    The role of the nitrate-reducing, sulfide-oxidising bacteria (NR-SOB) in the nitrate-mediated inhibition of sulfide net production by anaerobic wastewater biofilms was analyzed in two experimental bioreactors, continuously fed with the primary effluent of a wastewater treatment plant, one used as control (BRC) and the other one supplemented with nitrate (BRN). This study integrated information from H(2)S and pH microelectrodes, RNA-based molecular techniques, and the time course of biofilm growth and bioreactors water phase. Biofilms were a net source of sulfide for the water phase (2.01 micromol S(2-)(tot)m(-2)s(-1)) in the absence of nitrate dosing. Nitrate addition effectively led to the cessation of sulfide release from biofilms despite which a low rate of net sulfate reduction activity (0.26 micromol S(2-)(tot)m(-2)s(-1)) persisted at a deep layer within the biofilm. Indigenous NR-SOB including Thiomicrospira denitrificans, Arcobacter sp., and Thiobacillus denitrificans were stimulated by nitrate addition resulting in the elimination of most sulfide from the biofilms. Active sulfate reducing bacteria (SRB) represented comparable fractions of total metabolically active bacteria in the libraries obtained from BRN and BRC. However, we detected changes in the taxonomic composition of the SRB community suggesting its adaptation to a higher level of NR-SOB activity in the presence of nitrate.

  18. Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

    PubMed Central

    Hiatt-Gipson, Glyn D; Mills, Graham P; Reeves, Claire E

    2016-01-01

    Summary Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a ’halide for nitrate’ substitution. Employing readily available starting materials, reagents and Horner–Wadsworth–Emmons chemistry the synthesis of easily separable, synthetically versatile ‘key building blocks’ (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, ’off the shelf’ materials. Exploiting their reactivity we have studied their ability to undergo an ‘allylic halide for allylic nitrate’ substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates (‘isoprene nitrates’) in 66–80% overall yields. Using NOESY experiments the elucidation of the carbon–carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our ‘halide for nitrate’ substitution chemistry we outline the straightforward transformation of (1R,2S)-(−)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(−)-myrtenol nitrate. PMID:27340495

  19. [Nitrates in drinking water and cancer].

    PubMed

    Leclerc, H; Vincent, P; Vandevenne, P

    1991-04-01

    Nitrates originating from food and particularly from water are supposedly precursors of carcinogenic N-nitroso compound (NOC) formed within the organism. According to Correa and al. these transformations could be a consequence of bacterial gastric pollution resulting from certain hypochlorhydric conditions. Much epidemiological research has tried to establish a relationship between exposure to nitrates in drinking water and cases of gastric cancer. The present article deals with research into this relationship in France, in a region where the rate of nitrates in water supplies is among the highest. Death statistics (from cancers of the digestive and urinal tracts) are issued by INSERM and these of the population by INSEE. Towns are classified according to nitrate concentration and the number of deaths is established according to tumour detection by sex and age. Research into death rate divergencies is found by chi 2 and the correlated coefficient. The average relative risk for any age group is calculated for all types of cancer. Research on frequency is carried out from tumour records. Comparative frequency rates are established by direct standardisation according to the structural age of any one European population. Results are analysed in relation to (1) mortality rates and (2) incidence rates. (1) None of the cancers studied, be they of the digestive or urinary systems, whatever the age on sex, is significantly linked to the quantity of nitrates in water supplies. When all these cancers are taken into account, the death rate does not vary significantly for increasing concentration of nitrates. Towns exceeding the maximum concentration permitted by law do not have a higher mortality rate than other towns. The overall can incidence rate in the Nord-Pas-de-Calais regions of France is 11.8 per 100,000 inhabitants. The average European rate is 18.3 per 100,000 for men in the Nord region and 20.5 in the Pas-de-Calais; for women, 5.9 and 7.2 respectively. These rates

  20. SEPARATION OF URANYL NITRATE BY EXTRACTION

    DOEpatents

    Stoughton, R.W.; Steahly, F.L.

    1958-08-26

    A process is presented for obtaining U/sup 233/ from solutions containing Pa/sup 233/. A carrier precipitate, such as MnO/sub 2/, is formed in such solutions and carries with it the Pa/sup 233/ present. This precipitate is then dissolved in nitric acid and the solution is aged to allow decay of the Pa/ sup 233/ into U/sup 233/. After a sufficient length of time the U/sup 233/ bearing solution is made 2.5 to 4.5 Molar in manganese nitrate by addition thereof, and the solution is then treated with ether to obtain uranyl nitrate by solvent extraction techniques.

  1. Methylhydrazinium nitrate. [rocket plume deposit chemistry

    NASA Technical Reports Server (NTRS)

    Lawton, E. A.; Moran, C. M.

    1983-01-01

    Methylhydrazinium nitrate was synthesized by the reaction of dilute nitric acid with methylhydrazine in water and in methanol. The white needles formed are extremely hygroscopic and melt at 37.5-40.5 C. The IR spectrum differs from that reported elsewhere. The mass spectrum exhibited no parent peak at 109 m/z, and thermogravimetric analysis indicated that the compound decomposed slowly at 63-103 C to give ammonium and methylammonium nitrate. The density is near 1.55 g/cu cm.

  2. Interaction of uranium with nitrate melts

    SciTech Connect

    Denisov, V.P.; Korobeinikov, I.V.; Kutyrev, K.N.; Pyatkov, V.I.; Raspopin, S.P.

    1987-07-01

    Interaction of metallic uranium with a eutectic mixture of KNO/sub 3/-NaNO/sub 3/ melt at 234-510/sup 0/C in an inert atmosphere is studied. It is shown that the degree of uranium oxidation depends on the melt temperature. At 236-367/sup 0/C uranium dioxide is formed; the latter undergoes oxidation to diuranate at a higher temperature. The interaction is accompanied by accumulation of alkali metal nitrates in a nitrate melt and by NO/sub 2/ evolution.

  3. A Reservoir of Nitrate Beneath Desert Soils

    USGS Publications Warehouse

    Walvoord, M.A.; Phillips, F.M.; Stonestrom, D.A.; Evans, R.D.; Hartsough, P.C.; Newman, B.D.; Striegl, R.G.

    2003-01-01

    A large reservoir of bioavailable nitrogen (upto ???104 kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of and regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for warm deserts and arid shrublands worldwide and by 3 to 16% globally. Subsoil nitrate accumulation indicates long-term leaching from desert soils, impelling further evaluation of nutrient dynamics in xeric ecosystems. Evidence that subsoil accumulations are readily mobilized raises concern about groundwater contamination after land-use or climate change.

  4. Insight into the evolution of the iron oxidation pathways.

    PubMed

    Ilbert, Marianne; Bonnefoy, Violaine

    2013-02-01

    Iron is a ubiquitous element in the universe. Ferrous iron (Fe(II)) was abundant in the primordial ocean until the oxygenation of the Earth's atmosphere led to its widespread oxidation and precipitation. This change of iron bioavailability likely put selective pressure on the evolution of life. This element is essential to most extant life forms and is an important cofactor in many redox-active proteins involved in a number of vital pathways. In addition, iron plays a central role in many environments as an energy source for some microorganisms. This review is focused on Fe(II) oxidation. The fact that the ability to oxidize Fe(II) is widely distributed in Bacteria and Archaea and in a number of quite different biotopes suggests that the dissimilatory Fe(II) oxidation is an ancient energy metabolism. Based on what is known today about Fe(II) oxidation pathways, we propose that they arose independently more than once in evolution and evolved convergently. The iron paleochemistry, the phylogeny, the physiology of the iron oxidizers, and the nature of the cofactors of the redox proteins involved in these pathways suggest a possible scenario for the timescale in which each type of Fe(II) oxidation pathways evolved. The nitrate dependent anoxic iron oxidizers are likely the most ancient iron oxidizers. We suggest that the phototrophic anoxic iron oxidizers arose in surface waters after the Archaea/Bacteria-split but before the Great Oxidation Event. The neutrophilic oxic iron oxidizers possibly appeared in microaerobic marine environments prior to the Great Oxidation Event while the acidophilic ones emerged likely after the advent of atmospheric O(2). This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems.

  5. The relevance of iron in the pathogenesis of Parkinson's disease.

    PubMed

    Sian-Hülsmann, Jeswinder; Mandel, Silvia; Youdim, Moussa B H; Riederer, Peter

    2011-09-01

    Alterations of iron levels in the brain has been observed and documented in a number of neurodegenerative disorders including Parkinson's disease (PD). The elevated nigral iron levels observed in PD may reflect a dysfunction of brain iron homeostasis. Under normal physiological conditions excess iron can be sequestrated in ferritin and neuromelanin. Alternatively, the excess iron may represent a component of brain iron deposition associated with ageing. The aetiology of idiopathic PD largely remains an enigma. However, intensive investigations have provided a host of putative mechanisms that might contribute to the pathogenesis underlying the characteristic degeneration of the dopaminergic neurons in the substantia nigra (SN). The mechanisms proposed include oxidative (and nitrative) stress, inflammation, excitotoxicity, mitochondrial dysfunction, altered proteolysis and finally apoptotic induced cell death. Iron-mediated cellular destruction is mediated primarily via reactive oxygen or/and nitrogen species induced oxidative stress. Furthermore, these pathogenic mechanisms appear to be closely interlinked to the cascade of events leading to cellular death. There are conflicting reports about the stage during disease progression at which nigral iron change occurs in PD. Some have found that there are no changes in iron content SN in asymptomatic incidental Lewy body disease, suggesting it may represent a secondary event in the cascade of neuronal degeneration. In contrast, others have found an elevation of iron in SN in pre-clinical stages. These discrepancies may be attributed to the occurrence of different sub-groups of the disease. This concurs with the notion that PD represents a group of related diseases with a number of potential pathogenic pathways.

  6. Immobilisation of arsenic by iron(II)-oxidizing bacteria

    NASA Astrophysics Data System (ADS)

    Kappler, A.; Hohmann, C.; Winkler, E.; Muehe, M.; Morin, G.

    2008-12-01

    Arsenic-contaminated groundwater is an environmental problem that affects about 1-2% of the world's population. As arsenic-contaminated water is also used for irrigating rice fields, the uptake of arsenic via rice is in some cases even higher than via drinking water. Arsenic is often of geogenic origin and in many cases bound to iron(III) minerals. Microbial iron(III) reduction leads to dissolution of Fe(III) minerals and thus the arsenic bound to these minerals is released to the environment. In turn, iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II) oxidation followed by iron(III) mineral formation. Here, we present work on arsenic co-precipitation and immobilization by anaerobic and aerobic iron(II)-oxidizing bacteria. Co-precipitation batch experiments with pure cultures of nitrate-dependent, phototrophic, and microaerophilic Fe(II)-oxidizing bacteria are used to quantify the amount of arsenic that can be immobilized during microbial iron mineral precipitation. Iron and arsenic speciation and redox state are determined by X- ray diffraction and synchrotron-based X-ray absorption methods (EXAFS, XANES). Microcosm experiments are set-up either with liquid media or with rice paddy soil amended with arsenic. Rice paddy soil from arsenic contaminated rice fields in China that include a natural population of Fe(II)-oxidizing microorganisms is used as inoculum. Dissolved and solid-phase arsenic and iron are quantified, Arsenic speciation is determined and the iron minerals are identified. Additionally, Arsenic uptake into the rice plant is quantified and a gene expression pattern in rice (Oryza sativa cv Gladia) is determined by microarrays as a response to the presence of Fe(II)-oxidizing bacteria.

  7. The feasibility study of autotrophic denitrification with iron sludge produced for sulfide control.

    PubMed

    Wei, Yangyang; Dai, Ji; Mackey, Hamish R; Chen, Guang-Hao

    2017-10-01

    Ferric iron is widely dosed in wastewater treatment plants dealing with sulfide for septicity control, which generates a great amount of iron-rich chemical sludge that is challenging and costly to dispose. This study investigates the feasibility of using this iron sludge as the electron donor for autotrophic denitrification, not only realizing high nitrogen removal efficiency without additional carbon source requirement, but also partially mitigating iron-rich chemical sludge disposal and reduce sludge production by enriching low-yield autotrophic denitrifiers in the system. Both batch tests and performance monitoring of a lab-scale up-flow anaerobic sludge blanket reactor with a more than 300 days of operation were conducted. All the results confirmed the feasibility of using iron sludge as electron donor for autotrophic denitrification. The nitrate reduction rate with iron sludge was highly influenced by the type of ferrous electron donor and the electron donor/acceptor ratio. Ferrous hydroxide had significantly higher nitrate reduction rate than ferrous sulfide at the same electron donor/acceptor ratio. The nitrate reduction rate also accelerated with the increase of the electron donor/acceptor ratio. However, if the total surface area of the iron sludge is considered for comparison, it was shown that ferrous hydroxide and ferrous sulfide provided similar nitrate reduction rates of around 0.02 mmol N/m(2)/d in this study, indicating total surface area would be the key parameter for denitrification efficiency for the solid phase electron donor. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate via Aerosol Chemistry

    NASA Technical Reports Server (NTRS)

    Riffel, Brent G.; Michelsen, Rebecca R.; Iraci, Laura T.

    2004-01-01

    The liquid phase acid catalyzed reaction of methanol with nitric acid to yield methyl nitrate under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This nitration reaction is expected to occur in acidic aerosol particles found in the upper troposphere/lower stratosphere as highly soluble methanol and nitric acid diffuse into these aerosols. Gaseous methyl nitrate is released upon formation, suggesting that some fraction of NO(x) may he liberated from nitric acid (methyl nitrate is later photolyzed to NO(x)) before it is removed from the atmosphere by wet deposition. Thus, this reaction may have important implications for the NO(x) budget. Reactions have been initiated in 45-62 wt% H2SO4 solutions at 10.0 C. Methyl nitrate production rates increased exponentially with acidity within the acidity regime studied. Preliminary calculations suggest that the nitronium ion (NO2(+) is the active nitrating agent under these conditions. The reaction order in methanol appears to depend on the water/methanol ratio and varies from first to zeroth order under conditions investigated. The nitration is first order in nitronium at all acidities investigated. A second order rate constant, kappa(sub 2), has been calculated to be 1 x 10(exp 8)/ M s when the reaction is first order in methanol. Calculations suggest the nitration is first order in methanol under tropospheric conditions. The infinitesimal percentage of nitric acid in the nitronium ion form in this acidity regime probably makes this reaction insignificant for the upper troposphere; however, this nitration may become significant in the mid stratosphere where colder temperatures increase nitric acid solubility and higher sulfuric acid content shifts nitric acid speciation toward the nitronium ion.

  9. Effect of temperature & salt concentration on salt tolerant nitrate-perchlorate reducing bacteria: Nitrate degradation kinetics.

    PubMed

    Ebrahimi, Shelir; Nguyen, Thi Hau; Roberts, Deborah J

    2015-10-15

    The sustainability of nitrate-contaminated water treatment using ion-exchange processes can be achieved by regenerating the exhausted resin several times. Our previous study shows that the use of multi-cycle bioregeneration of resin enclosed in membrane is an effective and innovative regeneration method. In this research, the effects of two independent factors (temperature and salt concentration) on the biological denitrification rate were studied. The results of this research along with the experimental results of the previous study on the effect of the same factors on nitrate desorption rate from the resin allow the optimization of the bio