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Sample records for chromium nitrates

  1. Chromium in aqueous nitrate plutonium process streams: Corrosion of 316 stainless steel and chromium speciation

    SciTech Connect

    Smith, W.H.; Purdy, G.M.

    1995-12-31

    This study was undertaken to determine if chromium(+6) could exist in plutonium process solutions under normal operating conditions. Four individual reactions were studied: the rate of dissolution of stainless steel, which is the principal source of chromium in process solutions; the rate of oxidation of chromium(+3) to chromium(+6) by nitric acid; and the reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel and with oxalic acid. The stainless steel corrosion rate was found to increase with increasing nitric acid concentration, increasing hydrofluoric acid concentration, and increasing temperature. Oxidation of chromium(+3) to chromium(+6) was negligible at room temperature and only became significant in hot concentrated nitric acid. The rate of reduction of chromium(+6) back to chromium(+3) by reaction with stainless steel or oxalic acid was found to be much greater than the rate of the reverse oxidation reaction. Based on these findings and taking into account normal operating conditions, it was determined that although there would be considerable chromium in plutonium process streams it would rarely be found in the (+6) oxidation state and would not exist in the (+6) state in the final process waste solutions.

  2. Treatability Testing of an In Situ Biostimulation Barrier for Nitrate and Chromium Treatment - 9126

    SciTech Connect

    Truex, Michael J.; Vermeul, Vincent R.; Fruchter, Jonathan S.

    2008-11-14

    An ongoing treatability test is evaluating in situ biostimulation at the 100-D Area of the Hanford Site in Richland, Washington. This test is part of a strategy to couple multiple technologies to accelerate cleanup of hexavalent-chromium contaminated groundwater discharging into the Columbia River. A permeable chemical reducing barrier was previously applied as the primary treatment to prevent the chromium plume from reaching the river at concentrations that exceed regulatory standards. In situ biostimulation is intended to provide supplemental treatment upgradient of this chemical treatment barrier by reducing the concentration of the primary oxidizing species in groundwater (i.e., nitrate and dissolved oxygen) and chromium, thereby increasing the longevity of the chemical barrier and helping to diminish the chromium plume.

  3. Inhibition of nitrate reduction by chromium (VI) in anaerobic soil microcosms

    SciTech Connect

    Kourtev, P. S.; Nakatsu, C. H.; Konopka, Allan

    2009-10-01

    Chromium (VI) is often found as a co-contaminant at sites polluted with organic compounds. We used microcosms amended with glucose or protein, nitrate and increasing concentrations of chromium to study nitrate reduction in Cr(VI) polluted soils. Organic carbon stimulated bacterial activity, but the addition of Cr(VI) caused a lag and then slower rates 5 of CO2 accumulation. Nitrate reduction only occurred after Cr(VI) had been reduced. Bacterial activity was again inhibited when Cr(VI) was added a second time; thus not all Cr-sensitive bacteria were removed in the first phase. Glucose and protein selected for relatively similar bacterial communities, as assayed by PCR-DGGE of the 16S rRNA gene; this selection was modified by the addition of 10 Cr(VI). Cr-resistant bacteria isolated from microcosms were closely related to members of Bacillus, Enterococcus and Propionibacterium sp. Our results indicate that carbon utilization and nitrate reduction in these soils in the presence of Cr(VI) are contingent upon the reduction of the added heavy metal by a limited subset of the bacterial community. The amount of Cr(VI) required to inhibit nitrate reduction was 10-fold less than for aerobic catabolism of the same 15 substrate. We hypothesize that the resistance level of a microbial process is directly related to the diversity of microbes capable of conducting it.

  4. Chromium.

    PubMed

    Barceloux, D G

    1999-01-01

    Chromium occurs primarily in the trivalent state (III), which is the most stable form, or in the hexavalent state (VI), which is a strong oxidizing agent. Elemental chromium (0) does not occur naturally on earth. Trivalent chromium (III) is an essential trace metal necessary for the formation of glucose tolerance factor and for the metabolism of insulin. Commercial applications of chromium compounds include tanning (III), corrosion inhibition, plating, glassware-cleaning solutions, wood preservatives (VI), manufacture of safety matches, metal finishing (VI), and the production of pigments (III, VI). Hexavalent chromium (VI) contaminated local soil when chromium waste slag was part of the fill material present in residential, public, and industrial areas. In some urban areas, about two-thirds of the chromium in air results from the emission of hexavalent chromium from fossil fuel combustion and steel production. The remaining chromium in air is the trivalent form. The residence time of chromium in air is < 10 days, depending on the particle size. Trivalent compounds generally have low toxicity and the gastrointestinal tract poorly absorbs these compounds. Hexavalent chromium is a skin and mucous membrane irritant and some of these hexavalent compounds are strong corrosive agents. Hexavalent chromium compounds also produce an allergic contact dermatitis characterized by eczema. Sensitivity to trivalent compounds is much less frequent, but some workers may react to high concentrations of these compounds. Hexavalent chromium is recognized by the International Agency for Research on Cancer and by the US Toxicology Program as a pulmonary carcinogen. The increased risk of lung cancer occurs primarily in workers exposed to hexavalent chromium dust during the refining of chromite ore and the production of chromate pigments. Although individual studies suggest the possibility of an excess incidence of cancer at sites outside the lung, the results from these studies are

  5. Mechanisms of Chromium and Uranium Toxicity in Pseudomonas stutzeri RCH2 Grown under Anaerobic Nitrate-Reducing Conditions

    PubMed Central

    Thorgersen, Michael P.; Lancaster, W. Andrew; Ge, Xiaoxuan; Zane, Grant M.; Wetmore, Kelly M.; Vaccaro, Brian J.; Poole, Farris L.; Younkin, Adam D.; Deutschbauer, Adam M.; Arkin, Adam P.; Wall, Judy D.; Adams, Michael W. W.

    2017-01-01

    Chromium and uranium are highly toxic metals that contaminate many natural environments. We investigated their mechanisms of toxicity under anaerobic conditions using nitrate-reducing Pseudomonas stutzeri RCH2, which was originally isolated from a chromium-contaminated aquifer. A random barcode transposon site sequencing library of RCH2 was grown in the presence of the chromate oxyanion (Cr[VI]O42−) or uranyl oxycation (U[VI]O22+). Strains lacking genes required for a functional nitrate reductase had decreased fitness as both metals interacted with heme-containing enzymes required for the later steps in the denitrification pathway after nitrate is reduced to nitrite. Cr[VI]-resistance also required genes in the homologous recombination and nucleotide excision DNA repair pathways, showing that DNA is a target of Cr[VI] even under anaerobic conditions. The reduced thiol pool was also identified as a target of Cr[VI] toxicity and psest_2088, a gene of previously unknown function, was shown to have a role in the reduction of sulfite to sulfide. U[VI] resistance mechanisms involved exopolysaccharide synthesis and the universal stress protein UspA. As the first genome-wide fitness analysis of Cr[VI] and U[VI] toxicity under anaerobic conditions, this study provides new insight into the impact of Cr[VI] and U[VI] on an environmental isolate from a chromium contaminated site, as well as into the role of a ubiquitous protein, Psest_2088. PMID:28848534

  6. Chromium

    USDA-ARS?s Scientific Manuscript database

    The effects of chromium (Cr) on glucose and insulin metabolism are well documented. Normal dietary intake of Cr appears to be suboptimal because several studies have reported beneficial effects of Cr in people with elevated blood glucose or type 2 diabetes eating conventional diets. Stresses that ...

  7. 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

  8. Enhanced sludge processing of HLW: Hydrothermal oxidation of chromium, technetium, and complexants by nitrate. 1997 mid-year progress report

    SciTech Connect

    Buelow, S.

    1997-06-01

    'Treatment of High Level Waste (HLW) is the second most costly problem identified by OEM. In order to minimize costs of disposal, the volume of HLW requiring vitrification and long term storage must be reduced. Methods for efficient separation of chromium from waste sludges, such as the Hanford Tank Wastes (HTW), are key to achieving this goal since the allowed level of chromium in high level glass controls waste loading. At concentrations above 0.5 to 1.0 wt.% chromium prevents proper vitrification of the waste. Chromium in sludges most likely exists as extremely insoluble oxides and minerals, with chromium in the plus III oxidation state [1]. In order to solubilize and separate it from other sludge components, Cr(III) must be oxidized to the more soluble Cr(VI) state. Efficient separation of chromium from HLW could produce an estimated savings of $3.4B[2]. Additionally, the efficient separation of technetium [3], TRU, and other metals may require the reformulation of solids to free trapped species as well as the destruction of organic complexants. New chemical processes are needed to separate chromium and other metals from tank wastes. Ideally they should not utilize additional reagents which would increase waste volume or require subsequent removal. The goal of this project is to apply hydrothermal processing for enhanced chromium separation from HLW sludges. Initially, the authors seek to develop a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions. The authors also wish to evaluate the potential of hydrothermal processing for enhanced separations of technetium and TRU by examining technetium and TRU speciation at hydrothermal conditions optimal for chromium dissolution.'

  9. Hexavalent chromium stress enhances the uptake of nitrate but reduces the uptake of ammonium and glycine in pak choi (Brassica chinensis L.).

    PubMed

    Ma, Qingxu; Cao, Xiaochuang; Ma, Jinzhao; Tan, Xiaoli; Xie, Yinan; Xiao, Han; Wu, Lianghuan

    2017-05-01

    Chromium (Cr) pollution affects plant growth and biochemical processes, so, the relative uptake of glycine, nitrate, and ammonium by pak choi (Brassica chinensis) seedlings in treatments with 0mgL(-1) and 10mgL(-1) Cr (VI) were detected by substrate-specific (15)N-labelling in a sterile environment. The short-term uptake of (15)N-labelled sources and (15)N-enriched amino acids were detected by gas chromatography mass spectrometry to explore the mechanism by which Cr stress affects glycine uptake and metabolism, which showing that Cr stress hindered the uptake of ammonium and glycine but increased significantly the uptake of nitrate. Cr stress did not decrease the active or passive uptake of glycine, but it inhibited the conversion of glycine to serine in pak choi roots, indicating that the metabolism of glycine to serine in roots, rather than the root uptake, was the limiting step in glycine contribution to total N uptake in pak choi. Since Cr affects the relative uptake of different N sources, a feasible way to reduce Cr-induced stress is application of selective fertilization, in particular nitrate, in pak choi cultivation on Cr-polluted soil. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Toxicity of chromium (VI) to two mussels and an amphipod in water-only exposures with or without a co-stressor of elevated temperature, zinc, or nitrate

    USGS Publications Warehouse

    Wang, Ning; Kunz, James L.; Ivey, Chris D.; Ingersoll, Christopher G.; Barnhart, M. Christopher; Glidewell, Elizabeth A.

    2017-01-01

    The objectives of the present study were to develop methods for propagating western pearlshell (Margaritifera falcata) for laboratory toxicity testing and evaluate acute and chronic toxicity of chromium VI [Cr(VI)] to the pearlshell and a commonly tested mussel (fatmucket, Lampsilis siliquoidea at 20 °C or in association with a co-stressor of elevated temperature (27 °C), zinc (50 µg Zn/L), or nitrate (35 mg NO3/L). A commonly tested invertebrate (amphipod, Hyalella azteca) also was tested in chronic exposures. Newly transformed pearlshell (~1 week old) were successfully cultured and tested in acute 96 h Cr exposures (control survival 100%). However, the grow-out of juveniles in culture for chronic toxicity testing was less successful and chronic 28-day Cr toxicity tests started with 4 month-old pearlshell failed due to low control survival (39–68%). Acute median effect concentration (EC50) for the pearlshell (919 µg Cr/L) and fatmucket (456 µg Cr/L) tested at 20 °C without a co-stressor decreased by a factor of > 2 at elevated temperature but did not decrease at elevated Zn or elevated NO3. Chronic 28-day Cr tests were completed successfully with the fatmucket and amphipod (control survival 83–98%). Chronic maximum acceptable toxicant concentration (MATC) for fatmucket at 20 °C (26 µg Cr/L) decreased by a factor of 2 at elevated temperature or NO3 but did not decrease at elevated Zn. However, chronic MATC for amphipod at 20 °C (13 µg Cr/L) did not decrease at elevated temperature, Zn, or NO3. Acute EC50s for both mussels tested with or without a co-stressor were above the final acute value used to derive United States Environmental Protection Agency acute water quality criterion (WQC) for Cr(VI); however, chronic MATCs for fatmucket at elevated temperature or NO3 and chronic MATCs for the amphipod at 20 °C with or without elevated Zn or NO3 were about equal to the chronic WQC. The results indicate that (1) the elevated temperature

  11. Pharmacokinetic Modeling of Trivalent and Hexavalent Chromium Based on Ingestion and Inhalation of Soluble Chromium Compounds.

    DTIC Science & Technology

    1991-12-01

    Toxic Hazards Research Unit (THRU), and was coordinated by Allen Vinegar , Ph.D., Manager of the Biological Simulation Program at the THRU. This...chromates and dichromates, chromium trioxide (Cr0 3), and the hydrated Cr(III) nitrate, chloride, acetate , and sulfate salts, are soluble or highly...associated principally with the manufacture of chromates, including chromate pigments; chromium electroplating, which generates aerosols of chromic acid

  12. 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.

  13. 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

  14. 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.

  15. Electroremediation of an industrial area contaminated by chromium.

    PubMed

    Merdoud, O; Akretche, Djamal E

    2008-07-01

    Remediation of soils contaminated by chromium near an industrial area in Algeria has been studied by means of electrokinetic process. Chromium behavior in the course of an electroremediation is studied as a function of the solution in both anolyte and catholyte. After speciation and experiments which consist of 20 days each, it is shown that the use of NaNO(3) in these compartments induces a chromium oxidation by nitrate anion and its removing only through the anion exchange membrane toward the anode. Other ions (Cl(-) and SO(4)(2-) give rise to ion transfer toward the two electrodes showing that the chromium is present at two oxidation states. The pH and the current behavior have also been examined in this work. Results have shown a contribution to the understanding of the removing mechanisms in the course of the electroremediation of a soil contaminated by chromium.

  16. Chromium - blood test

    MedlinePlus

    ... work in the following industries: Leather tanning Electroplating Steel manufacturing Decreased chromium level only occurs in people who receive all of their nutrition by vein (total parenteral nutrition or TPN) and do not get enough chromium.

  17. Chromium in diet

    MedlinePlus

    Chromium deficiency may be seen as impaired glucose tolerance. It occurs in older people with type 2 diabetes and in infants with protein-calorie malnutrition. Taking chromium supplements can help manage these conditions. However, ...

  18. Elemental speciation for chromium in chromium picolinate products

    NASA Astrophysics Data System (ADS)

    Ding, Hong; Olson, Lisa K.; Caruso, Joseph A.

    1996-12-01

    Chromium picolinate products have been examined for different forms of chromium, using chromatographic separation and inductively coupled plasma mass spectrometric detection. The brands we evaluated contained no detectable amount of elemental chromium(VI), the toxic form. Since chromium picolinate might have other chromium forms as impurities, different products may contain different forms of chromium species. Compared with ion-exchange, reversed-phase chromatography showed excellent chromium recovery based on the amount stated on the product label.

  19. [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.

  20. Chromium adsorption by lignin

    SciTech Connect

    Lalvani, S.B.; Huebner, A.; Wiltowski, T.S.

    2000-01-01

    Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the US Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.

  1. [Chromium and insulin resistance].

    PubMed

    Kleefstra, N; Bilo, H J; Bakker, S J; Houweling, S T

    2004-01-31

    Since as early as the 50s of the last century, it has been known that chromium is essential for normal glucose metabolism. Too little chromium in the diet may lead to insulin resistance. However, there is still no standard against which chromium deficiency can be established. Nevertheless, chromium supplements are becoming increasingly popular. Various systematic reviews have been unable to demonstrate any effects of chromium on glycaemic regulation (possibly due partly to the low dosages used), but there is a slight reduction in body weight averaging 1 kg. In a double-blind randomised placebo-controlled trial in a Chinese population with type-2 diabetes mellitus, supplementation with 1000 micrograms of chromium led to a fall in the glycosylated haemoglobin level (HbA1c) by 2%. Toxic effects of chromium are seldom seen; recently, however, the safety of one of the dosage forms of chromium, chromium picolinate, has been questioned. One should be aware that individual patients with type-2 diabetes mellitus may have an increased risk of hypoglycaemic episodes when taking chromium supplements as self-medication.

  2. Chromium and Genomic Stability

    PubMed Central

    Wise, Sandra S.; Wise, John Pierce

    2014-01-01

    Many metals serve as micronutrients which protect against genomic instability. Chromium is most abundant in its trivalent and hexavalent forms. Trivalent chromium has historically been considered an essential element, though recent data indicate that while it can have pharmacological effects and value, it is not essential. There are no data indicating that trivalent chromium promotes genomic stability and, instead may promote genomic instability. Hexavalent chromium is widely accepted as highly toxic and carcinogenic with no nutritional value. Recent data indicate that it causes genomic instability and also has no role in promoting genomic stability. PMID:22192535

  3. Sodium sulfur container with chromium/chromium oxide coating

    DOEpatents

    Ludwig, Frank A.; Higley, Lin R.

    1981-01-01

    A coating of chromium/chromium oxide is disclosed for coating the surfaces of electrically conducting components of a sodium sulfur battery. This chromium/chromium oxide coating is placed on the surfaces of the electrically conducting components of the battery which are in contact with molten polysulfide and sulfur reactants during battery operation.

  4. 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)

  5. The carcinogenicity of chromium

    PubMed Central

    Norseth, Tor

    1981-01-01

    The carcinogenicity of chromium compounds is reviewed with specific attention to the gaps in knowledge for risk estimation and research needs. The most important problems at present are whether trivalent chromium compounds cause cancer, and whether there is a difference in cancer causing effects between the soluble and the slightly soluble hexavalent compounds in the practical exposure situation. Dose estimates for risk estimation based on epidemiological investigations are also lacking. Present evidence indicates that the trivalent chromium compounds do not cause cancer although high concentrations in some in vitro systems have shown genetic toxicity. Hexavalent chromium compounds cause cancer in humans, in experimental animals and exert genetic toxicity in bacteria and in mammalian cells in vitro. Epidemiological evidence and animal experiments indicate that the slightly soluble hexavalent salts are the most potent carcinogens, but proper identification and characterization of exposure patterns in epidemiological work are lacking. Workers also tend to have mixed exposures. Soluble and slightly soluble salts are equally potent genotoxic agents in vitro. Further work for establishing dose estimates for risk evaluation in epidemiological work is important. In vitro systems should be applied for further identification of the mechanism of the carcinogenic effects, and animal experiments are urgent for comparison of the carcinogenic potency of the different hexavalent salts. Hexavalent chromium salts must be regarded as established carcinogens, and proper action should be taken in all industries with regard to such exposure. At present the carcinogenic risk to the general population caused by chromium compounds seems to be negligible, chromium in cigarettes, however, is an uncertainty in this respect. The amount of chromium and the type of chromium compounds inhaled from cigarettes is not known. PMID:7023928

  6. A Novel Nonelectrolytic Process for Chromium and Nickel Coating

    DTIC Science & Technology

    2015-06-01

    ABSTRACT (maximum 200 words) The use of hexavalent chromium in metal coating operations, as per electrolytic processing, is subject to increasingly...was that a version of the Reduction Expansion Synthesis (RES) process, previously used to produce submicron metal particles, could be developed to...create metal coating. This study involved the production of coatings by a variety of RES-like protocols, based on mixing metal nitrates, urea, and

  7. Mineral of the month: chromium

    USGS Publications Warehouse

    Papp, John F.

    2005-01-01

    Chromium is one of the most indispensable industrial metals and it plays an essential but hidden role in daily life. Chromium is used in many consumer and building products, and it contributes to a clean, efficient and healthy environment.

  8. Stabilized chromium oxide film

    DOEpatents

    Garwin, Edward L.; Nyaiesh, Ali R.

    1988-01-01

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  9. Chromium(VI)

    Integrated Risk Information System (IRIS)

    TOXICOLOGICAL REVIEW OF HEXAVALENT CHROMIUM ( CAS No . 18540 - 29 - 9 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) August 1998 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in accordance with U.S . Environme

  10. Chromium and aging

    USDA-ARS?s Scientific Manuscript database

    Aging is associated with increased blood glucose, insulin, blood lipids, and fat mass, and decreased lean body mass leading to increased incidences of diabetes and cardiovascular diseases. Improved chromium nutrition is associated with improvements in all of these variables. Insulin sensitivity de...

  11. Stabilized chromium oxide film

    DOEpatents

    Nyaiesh, A.R.; Garwin, E.L.

    1986-08-04

    Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

  12. Kinetics of chromium ion absorption by cross-linked polyacrylate films

    NASA Technical Reports Server (NTRS)

    May, C. E.

    1984-01-01

    Three cross-linked ion exchange membranes were studied as to their ability to absorb chromium ion from aqueous chromium III nitrate solutions. Attention was given to the mechanism of absorption, composition of the absorbed product, and the chemical bonding. The membranes were: calcium polyacrylate, polyacrylic acid, and a copolymer of acrylic acid and vinyl alcohol. For the calcium polyacrylate and the copolymer, parabolic kinetics were observed, indicating the formation of a chromium polyacrylate phase as a coating on the membrane. The rate of absorption is controlled by the diffusion of the chromium ion through this coating. The product formed in the copolymer involves the formation of a coordination complex of a chromium ion with 6 carboxylic acid groups from the same molecule. The absorption of the chromium ion by the polyacrylic acid membranes appears to be more complicated, involving cross-linking. This is due to the coordination of the chromium ion with carboxylic acid groups from more than one polymer molecule. The absorption rate of the chromium ion by the calcium salt membrane was found to be more rapid than that by the free polyacrylic acid membrane.

  13. Spectroscopic studies on the interaction of chromium (VI) and chromium (III) with keyhole limpet hemocyanin.

    PubMed

    Fan, Yulan; Zeng, Guidi; Liu, Jingyi; Chen, Huifang; Xue, Jun; Wu, Yongquan; Li, Xun

    2017-03-01

    The interactions of keyhole limpet hemocyanin (KLH) with chromium nitrate, potassium dichromate, and chromate were investigated using fluorescence, UV-vis absorption and circular dichroism (CD) spectroscopy under simulated physiological conditions. The experimental results showed that the different forms of chromium could quench the intrinsic fluorescence of KLH following a static quenching mechanism rather than by dynamic collision, which indicated that a Cr-KLH complex was formed. The Stern-Volmer quenching constants for the interaction indicated that the binding reaction of KLH with Cr(VI) was stronger the binding of KLH with Cr(III). The thermodynamic values for binding of Cr(VI) to KLH are ΔH > 0 and ΔS > 0. By contrast, the values for the interaction of Cr(III) with KLH are ΔH < 0 and ΔS < 0. The results of synchronous fluorescence, UV-vis absorption and CD spectroscopy showed that the α-helical secondary structure and conformation of KLH were altered by different forms of chromium. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  14. Studies of chromium gettering

    SciTech Connect

    Simpkins, J.E.; Mioduszewski, P.; Stratton, L.W.

    1982-01-01

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions.

  15. 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.

  16. Studies of chromium gettering

    NASA Astrophysics Data System (ADS)

    Simpkins, J. E.; Mioduszewski, P.; Stratton, L. W.

    1982-12-01

    Preliminary results have shown that hydrogen pumping by chromium is a surface effect. Unlike with titanium, the getter material used in many present day tokamaks, there is no significant diffusion into the bulk. This feature, which would minimize the tritium inventory, makes chromium a viable alternate to titanium gettering for future tokamaks. Additional experiments have been carried out to measure the basic characteristics of chromium films for gases of interest in tokamak research. These gases include deuterium, oxygen and nitrogen. A vacuum system is described which allowed precise control of the test gas, a constant wall temperature and determination of the projected getter surface area. A quadrupole mass spectrometer, rather than simply a total pressure gauge, was utilized to measure the partial pressure of the test gas as well as the residual gas composition in the system. A quartz crystal monitor was used to measure film thickness. Pumping speeds and sticking coefficients are given as a function of surface coverage for each test gas. A comparison will be made with titanium films deposited in the same vacuum system and under similar conditions.

  17. Bioconcentration and phytotoxicity of chromium in Eichhornia crassipes.

    PubMed

    Mishra, Kumkum; Gupta, Kiran; Rai, Upendra Nath

    2009-07-01

    Physico-chemical parameter and metal concentration in effluents of two industries i.e. Tannery industry, Jajmau, Kanpur and Electroplating industry, Scooter India Limited (SIL), Lucknow were determined to assess the toxicity of chromium. Metal accumulation in Eichhomia crassipes growing in these contaminated sites were also determined. For laboratory toxicity testing the plants were exposed to nutrient solution containing Cr concentration ranging from 0.01-10 microg ml(-1) for 24-96 hr. Accumulation of chromium was observed to be dependent on its concentration and time of exposure and was greater in roots (789.3 mg g(-1) d.wt.) than in leaves (335.6 mg g(-1) d.wt.) after 96 hrat 10 microg ml(-1) concentration. Under field conditions the accumulation of Cr was 1258 and 733.3 in roots and 94 and 53 microg g(-1) d.wt. in leaves of E. crassipes growing in Jajmau, Kanpur tanning industry and SIL effluents, respectively. It was found that lower doses (0.01-0.1 microg ml(-1)) of chromium had stimulatory effect on various metabolic activities in plants including chlorophyll a, b and total chlorophyll, protein, nitrate reductase and mitotic index. Whereas higher doses of chromium had inhibitory effect. The carotenoid content and number of micronuclei was found directly proportional to the concentration of chromium and increased with increase in concentration of chromium to which plants were exposed. It may be concluded from the present study that E. crassipes is tolerant to the elevated Cr concentration as there is no inhibition of chlorophyll and carotenoid up to 0.1 microg ml(-1) at 24 and 48 hr exhibiting phytotoxicity at higher concentration. Therefore, E. crassipes may be used as bioassay for biomonitoring and control of Cr pollution in the environment.

  18. 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.

  19. Electrochemical Destruction of Nitrates and Organics FY1995 Progress Report

    SciTech Connect

    Hobbs, D.T.

    1995-05-30

    Production of nuclear materials within the DOE complex has yielded large volumes of high-level waste containing hazardous species such as nitrate, nitrite, chromium, and mercury. Processes being developed for the permanent disposal of these wastes are aimed at separating the bulk of the radioactivity, primarily 137-Cs and 90-Sr, into a small volume for incorporation into a vitrified wasteform, with the remainder being incorporated into a low-level wasteform.

  20. Chromium-induced toxic hepatitis.

    PubMed

    Lança, Sara; Alves, Amanda; Vieira, Ana Isabel; Barata, José; de Freitas, João; de Carvalho, Alvaro

    2002-12-01

    A clinical case of acute hepatitis in a patient undergoing an alternative medicine weight-reduction regimen is reported. Chromium polynicotinate had been ingested in combination with vegetable extracts over a 5-month period. Liver biopsy was compatible with toxic hepatitis and greatly elevated hepatic chromium levels were found (>10x normal). The clinical picture regressed following suspension of the medication.

  1. 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. ...

  2. Groundwater contaminant by hexavalent chromium

    SciTech Connect

    Parsons, C.

    1995-11-01

    Oxidation of trivalent chromium to hexavalent chromium has been investigated as a function of total manganese in soils as well as various incubation conditions. Chromium and manganese contents were analyzed by atomic absorption (graphite furnace and flame emission respectively) following acid digestion. Total hexavalent chromium generation capacity was determined by addition of 0.001 M CrCL3, incubation, and analysis by s-diphenyl carbazide. Samples were then leached with CaSO{sub 4} and MgSO{sub 4} and incubated in various environments (oven, freeze-drier, field moist, ultrafreeze) to test for geogenic generation of Cr(IV). The degree of geogenic generation of hexavalent chromium was compared with total Mn and Cr content as well as hexavalent generational capacity.

  3. The effects of water rock interaction and the human activities on the occurrence of hexavalent chromium in waters. The case study of the Psachna basin, Central Euboea, Greece.

    NASA Astrophysics Data System (ADS)

    Vasileiou, Eleni; Perraki, Maria; Stamatis, George; Gartzos, Efthimios

    2014-05-01

    High concentrations of heavy metals, particularly of the toxic hexavalent chromium, are recorded in surface and ground waters in many areas, and constitute one of the most severe environmental problems nowadays. The natural genesis of chromium is associated with the geological environment (peridotites and serpentintites). Chromium is structured in many minerals, mainly in spinel (e.g. chromite), in silicate minerals such as phyllosilicate serpentine minerals, chlorite, talc and chain-silicate minerals of pyroxene and amphibole group. Chromium is found in two forms in soils, waters and rocks, the hexavalent and the trivalent one. The relation between Cr(III) and Cr(VI) strongly depends on pH and oxidative properties of the area; however, in most cases, Cr(III) is the dominating variant. The natural oxidation of trivalent to hexavalent chromium can be achieved by manganese oxides, H2O2, O2 gas and oxy-hydroxides of trivalent iron. Anthropogenic factors may also cause the process of chromium's oxidation. In the Psachna basin, Central Euboea, Greece, high concentrations of hexavalent chromium were recently measured in spring- and drill- waters. In this work, we study the effect of the geological environment and of the anthropogenic activities on the water quality with emphasis on chromium. A detailed geochemical, petrological and mineralogical study of rocks and soils was carried out by means of optical microscopy, XRF, XRD and SEM/EDS. Ground and surface water samples were physically characterized and hydrochemically studied by means of ICP and AAF. Combined result evaluation indicates a natural source for the trivalent chromium in waters, attributed to the alteration of Cr-bearing minerals of the ultramafic rocks. However the oxidation of trivalent to hexavalent chromium results from anthropogenic activities, mainly from intensive agricultural activities and the extensive use of fertilizers and pesticides causing nitrate pollution in groundwater. It has been shown

  4. Chromium toxicity in plants.

    PubMed

    Shanker, Arun K; Cervantes, Carlos; Loza-Tavera, Herminia; Avudainayagam, S

    2005-07-01

    Due to its wide industrial use, chromium is considered a serious environmental pollutant. Contamination of soil and water by chromium (Cr) is of recent concern. Toxicity of Cr to plants depends on its valence state: Cr(VI) is highly toxic and mobile whereas Cr(III) is less toxic. Since plants lack a specific transport system for Cr, it is taken up by carriers of essential ions such as sulfate or iron. Toxic effects of Cr on plant growth and development include alterations in the germination process as well as in the growth of roots, stems and leaves, which may affect total dry matter production and yield. Cr also causes deleterious effects on plant physiological processes such as photosynthesis, water relations and mineral nutrition. Metabolic alterations by Cr exposure have also been described in plants either by a direct effect on enzymes or other metabolites or by its ability to generate reactive oxygen species which may cause oxidative stress. The potential of plants with the capacity to accumulate or to stabilize Cr compounds for bioremediation of Cr contamination has gained interest in recent years.

  5. Hexavalent chromium monitor

    DOEpatents

    Tao, Shiquan; Winstead, Christopher B.

    2005-04-12

    A monitor is provided for use in measuring the concentration of hexavalent chromium in a liquid, such as water. The monitor includes a sample cell, a light source, and a photodetector. The sample cell is in the form of a liquid-core waveguide, the sample cell defining an interior core and acting as a receiver for the liquid to be analyzed, the interior surface of the sample cell having a refractive index of less than 1.33. The light source is in communication with a first end of the sample cell for emitting radiation having a wavelength of about and between 350 to 390 nm into the interior core of the waveguide. The photodetector is in communication with a second end of the waveguide for measuring the absorption of the radiation emitted by the light source by the liquid in the sample cell. The monitor may also include a processor electronically coupled to the photodetector for receipt of an absorption signal to determine the concentration of hexavalent chromium in the liquid.

  6. Chromium in metabolic and cardiovascular disease.

    PubMed

    Hummel, M; Standl, E; Schnell, O

    2007-10-01

    Chromium is an essential mineral that appears to have a beneficial role in the regulation of insulin action, metabolic syndrome, and cardiovascular disease. There is growing evidence that chromium may facilitate insulin signaling and chromium supplementation therefore may improve systemic insulin sensitivity. Tissue chromium levels of subjects with diabetes are lower than those of normal control subjects, and a correlation exists between low circulating levels of chromium and the incidence of type 2 diabetes. Controversy still exists as to the need for chromium supplementation. However, supplementation with chromium picolinate, a stable and highly bioavailable form of chromium, has been shown to reduce insulin resistance and to help reduce the risk of cardiovascular disease and type 2 diabetes. Since chromium supplementation is a safe treatment, further research is necessary to resolve the confounding data. The existing data suggest to concentrate future studies on certain forms as chromium picolinate and doses as at least 200 mcg per day.

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. Chromium isotopes as indicators of hexavalent chromium reduction

    SciTech Connect

    Johnson, Thomas M.

    2012-03-20

    This is the final report for a university research project which advanced development of a new technology for identifying chemical reduction of hexavalent chromium contamination in groundwater systems. Reduction renders mobile and toxic hexavalent chromium immobile and less toxic. The new method uses stable isotope ratio measurements, which are made using multicollector ICP-mass spectrometry. The main objectives of this project were completed during the project period and two peer-reviewed articles were published to disseminate the information gained.

  12. Is chromium pharmacologically relevant?

    PubMed

    Vincent, John B

    2014-10-01

    Recent research, combined with reanalysis of previous results, has revealed that chromium can no longer be considered an essential trace element. Clinical studies are ambiguous at best as to whether Cr has a pharmacological effect in humans. Observed effects of Cr on rodent models of insulin resistance and diabetes are best interpreted in terms of a pharmacological role for Cr. Studies on the effects of Cr on rat models of diabetes are reviewed herein and suggest Cr increases insulin sensitivity in peripheral tissues of the rodent models. The lack of effects in human studies may stem from humans receiving a comparably smaller dose than the rodent models. However, given the different responses to Cr in the rodent models, humans could potentially have different responses to Cr.

  13. Effect of Chromium(VI) Toxicity on Enzymes of Nitrogen Metabolism in Clusterbean (Cyamopsis tetragonoloba L.)

    PubMed Central

    Sangwan, Punesh; Joshi, U. N.

    2014-01-01

    Heavy metals are the intrinsic component of the environment with both essential and nonessential types. Their excessive levels pose a threat to plant growth and yield. Also, some heavy metals are toxic to plants even at very low concentrations. The present investigation (a pot experiment) was conducted to determine the affects of varying chromium(VI) levels (0.0, 0.5, 1.0, 2.0, and 4.0 mg chromium(VI) kg−1 soil in the form of potassium dichromate) on the key enzymes of nitrogen metabolism in clusterbean. Chromium treatment adversely affect nitrogenase, nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase in various plant organs at different growth stages as specific enzyme activity of these enzymes decreased with an increase in chromium(VI) levels from 0 to 2.0 mg chromium(VI) kg−1 soil and 4.0 mg chromium(VI) kg−1 soil was found to be lethal to clusterbean plants. In general, the enzyme activity increased with advancement of growth to reach maximum at flowering stage and thereafter decreased at grain filling stage. PMID:24744916

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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.

  19. 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.

  20. Evaluation of aquatic toxicities of chromium and chromium-containing effluents in reference to chromium electroplating industries.

    PubMed

    Baral, A; Engelken, R; Stephens, W; Farris, J; Hannigan, R

    2006-05-01

    This study evaluated aquatic toxicities of chromium and chromium-containing laboratory samples representative of effluents from chromium electroplating industries, and compared the aquatic environmental risks of hexavalent and trivalent chromium electroplating operations. Trivalent chromium electroplating has emerged as an acceptable alternative to hazardous hexavalent chromium electroplating. This process substitution has reduced the human health impact in the workplace and minimized the production of hazardous sludge regulated under the Resource Conservation and Recovery Act (RCRA). The thrust behind this research was to investigate whether trivalent chromium electroplating operations have lower adverse impacts on standardized toxicity test organisms. Ceriodaphnia dubia and Pimephales promelas were used to investigate toxicities of trivalent chromium (Cr (III)), hexavalent chromium (Cr (VI)), and industrial effluents. In agreement with previous studies, Cr (III) was found to be less toxic than Cr (VI). Despite having several organic and inorganic constituents in the effluents obtained from trivalent chromium plating baths, they exhibited less adverse effects to C. dubia than effluents obtained from hexavalent chromium electroplating baths. Thus, transition from hexavalent to trivalent chromium electroplating processes may be justified. However, because of the presence of organic constituents such as formate, oxalate, and triethylene glycol in effluents, trivalent chromium electroplating operations may face additional regulatory requirements for removal of total organic carbon.

  1. Chromium deficiency during total parenteral nutrition.

    PubMed

    Freund, H; Atamian, S; Fischer, J E

    1979-02-02

    Chromium is required for maintenance of normal glucose tolerance. After complete bowel resection and five months of total parenteral nutrition, severe glucose intolerance, weight loss, and a metabolic encephalopathy-like confusional state developed in a patient. Serum chromium levels were at the lowest normal level. Supplementation of 150 microgram of chromium per day reversed the glucose intolerance, reduced insulin requirements, and resulted in weight gain and the disappearance of encephalopathy. The low levels of chromium and response to chromium supplementation suggest that chromium deficiency can arise in long-term total parenteral nutrition.

  2. 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...

  3. The contemporary anthropogenic chromium cycle.

    PubMed

    Johnson, Jeremiah; Schewel, Laura; Graedel, T E

    2006-11-15

    Chromium is an essential engineering metal used in stainless and alloy steels, chemicals, and refractory products. Using material flow analysis, all major anthropogenic chromium flows are characterized for the year 2000, from mining through discard, on three spatial levels: fifty-four countries, nine world regions, and the planet. Included is the first detailed quantification of chromium in internationally traded finished products and diverse waste streams. Findings include (1) 78% of chromium flow entering final use is added as a net addition to stock on the global level; most countries are close to this figure; (2) the majority of mining occurs in Africa (2400 Gg Cr/yr) and the Commonwealth of Independent States (1090 Gg Cr/yr), while the major end-users are Asia, Europe, and North America at 1150, 1140, and 751 Gg Cr/yr, respectively; (3) waste flows of chromium are the greatest in Europe (420 Gg Cr/yr), Asia (370 Gg Cr/yr), and North America (290 Gg Cr/yr), but the composition of these waste flows varies greatly among the world regions; (4) releases of chromium by the global system, which total 2630 Gg Cr/yr, are nearly evenly divided among tailings, ferrochromium slag, downgraded scrap, and post-consumer losses; (5) many countries have a heavy foreign dependence on chromium in the all forms, as is demonstrated for the United States. The findings relating to in-use stock changes and finished product trade are relevant to industry, allowing for more accurate planning for future scrap availability. The quantification of releases due to discards and dissipation hold environmental and human health relevance, while the full life cycle international trade assessment addresses local scarcity.

  4. Antiferromagnetism in chromium

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    I present two experimental studies of the spin density wave antiferromagnetic order in elemental Chromium. The first addresses the response of the magnetic ground state to applied pressure. The spin and charge order parameters are probed at high pressure and low temperature in a diamond anvil cell using monochromatic X-ray diffraction. We find that the magnetism is suppressed exponentially with pressure, providing a canonical example of a weak-coupling, mean-field ground state, before terminating at a quantum phase transition. We confirm the harmonic relationship between the spin and charge degrees of freedom in the low temperature regime, and we identify the microscopic coupling between pressure and magnetism. The discovery of the long-sought-after quantum critical regime sets the stage for a complete study of antiferromagnetic quantum criticality in this clean model system. The second study addresses the thermodynamics and transport properties of antiferromagnetic domain structure. We find a robust thermal hysteresis in the longitudinal and Hall resistivities of sub-mm bulk Cr samples. The temperature limits of the hysteresis are correlated with domain wall fluctuations and freezing. The persistent sign of the hysteresis and the macroscopic return point memory warrant a new understanding of domain wall energetics. By combining electrical transport and X-ray microdiffraction measurements we are able to pinpoint the effects of antiferromagnetic domain walls on electron transport.

  5. Mare Chromium Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This crater, located in Mare Chromium, shows evidence of exterior modification, with little interior modification. While the rim is still visible, the ejecta blanket has been removed or covered. There is some material at the bottom of the crater, but the interior retains the bowl shape from the initial formation of the crater.

    Image information: VIS instrument. Latitude -34.4, Longitude 174.4 East (185.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  6. Mare Chromium Crater

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This crater, located in Mare Chromium, shows evidence of exterior modification, with little interior modification. While the rim is still visible, the ejecta blanket has been removed or covered. There is some material at the bottom of the crater, but the interior retains the bowl shape from the initial formation of the crater.

    Image information: VIS instrument. Latitude -34.4, Longitude 174.4 East (185.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  7. Evaluation of Cajanus cajan (pigeon pea) for phytoremediation of landfill leachate containing chromium and lead.

    PubMed

    Jerez Ch, José A; Romero, Rosaura M

    2016-11-01

    Landfill leachates containing heavy metals are important contaminants and a matter of great concern due to the effect that they might have on ecosystems. We evaluated the use of Cajanus cajan to remove chromium and lead from landfill leachates. Eight-week-old plants were submitted to varied tests to select the experimental conditions. Water assays with a solution (pH 6) containing leachate (25% v/v) were selected; the metals were added as potassium dichromate and lead (II) nitrate salts. Soil matrices that contained leachate (30% v/v) up to field capacity were used. For both water and soil assays, the metal concentrations were 10 mg kg(-1). C. cajan proved able to remove 49% of chromium and 36% of lead, both from dilute leachate. The plants also removed 34.7% of chromium from irrigated soil, but were unable to decrease the lead content. Removal of nitrogen from landfill leachate was also tested, resulting in elimination of 85% of ammonia and 70% of combined nitrite/nitrate species. The results indicate that C. cajan might be an effective candidate for the rhizofiltration of leachates containing chromium and lead, and nitrogen in large concentrations.

  8. Chromium-induced kidney disease

    SciTech Connect

    Wedeen, R.P. ); Qian, Lifen )

    1991-05-01

    Kidney disease is often cited as one of the adverse effects of chromium, yet chronic renal disease due to occupational or environmental exposure to chromium has not been reported. Occasional cases of acute tubular necrosis (ATN) following massive absorption of chromate have been described. Chromate-induced ATN has been extensively studied in experimental animals following parenteral administration of large doses of potassium chromate (hexavalent). The chromate is selectively accumulated in the convoluted proximal tubule where necrosis occurs. An adverse long-term effect of low-dose chromium exposure on the kidneys is suggested by reports of low molecular weight (LMW) proteinuria in chromium workers. Excessive urinary excretion of {beta}{sub 2}-microglobulin, a specific proximal tubule brush border protein, and retinol-binding protein has been reported among chrome palters and welders. However, LMW proteinuria occurs after a variety of physiologic stresses, is usually reversible, and cannot by itself be considered evidence of chromic renal disease. Chromate-induced ATN and LMW proteinuria in chromium workers, nevertheless, raise the possibility that low-level, long-term exposure may produce persistent renal injury. The absence of evidence of chromate-induced chromic renal disease cannot be interpreted as evidence of the absence of such injury.

  9. [Biological monitoring in chromium-plating industry].

    PubMed

    Madsen, S W; Krue, S; Bonde, J P

    1992-05-25

    The purpose of the present investigation was to evaluate the role of biological monitoring as a means of surveillance of exposure in the Danish chromium-plating industry. We collected spot urine samples from 47 employees in five electro-plating plants near Aarhus and compared the results wide 40 non-exposed workers. We found no increase of chromium in urine during a work shift (mean = 0.11 nmol chromium/mmol creatinine, p = .46). The mean urine chromium value among the chromium workers was twice the mean value of the referent population (p = 0.001). There was, however, a considerable overlap between the two populations. All of the urine chromium values were much lower than the proposed American biological exposure indices. The results do not indicate any need for implementation of biological monitoring in the Danish chromium-plating industry, but longitudinal studies concerning possible accumulation of chromium at present occupational exposure levels should be carried out.

  10. Diffusion of Chromium in Alpha Cobalt-Chromium Solid Solutions

    NASA Technical Reports Server (NTRS)

    Weeton, John W

    1951-01-01

    Diffusion of chromium in cobalt-chromium solid solutions was investigated in the range 0 to 40 atomic percent at temperatures of 1360 degrees, 1300 degrees, 1150 degrees, and 10000 degrees c. The diffusion coefficients were found to be relatively constant within the composition range covered by each specimen. The activation heat of diffusion was determined to be 63,000 calories per mole. This value agrees closely with the value of 63,400 calories per mole calculated by means of the Dushman-Langmuir equation.

  11. Precipitating Chromium Impurities in Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Salama, A. M.

    1982-01-01

    Two new treatments for silicon wafers improve solar-cell conversion efficiency by precipitating electrically-active chromium impurities. One method is simple heat treatment. Other involves laser-induced damage followed by similar heat treatment. Chromium is one impurity of concern in metallurgical-grade silicon for solar cells. In new treatment, chromium active centers are made electrically inactive by precipitating chromium from solid solution, enabling use of lower grade, lower cost silicon in cell manufacture.

  12. Precipitating Chromium Impurities in Silicon Wafers

    NASA Technical Reports Server (NTRS)

    Salama, A. M.

    1982-01-01

    Two new treatments for silicon wafers improve solar-cell conversion efficiency by precipitating electrically-active chromium impurities. One method is simple heat treatment. Other involves laser-induced damage followed by similar heat treatment. Chromium is one impurity of concern in metallurgical-grade silicon for solar cells. In new treatment, chromium active centers are made electrically inactive by precipitating chromium from solid solution, enabling use of lower grade, lower cost silicon in cell manufacture.

  13. Chromium at High Pressure

    NASA Astrophysics Data System (ADS)

    Jaramillo, Rafael

    2012-02-01

    Chromium has long served as the archetype of spin density wave magnetism. Recently, Jaramillo and collaborators have shown that Cr also serves as an archetype of magnetic quantum criticality. Using a combination of x-ray diffraction and electrical transport measurements at high pressures and cryogenic temperatures in a diamond anvil cell, they have demonstrated that the N'eel transition (TN) can be continuously suppressed to zero, with no sign of a concurrent structural transition. The order parameter undergoes a broad regime of exponential suppression, consistent with the weak coupling paradigm, before deviating from a BCS-like ground state within a narrow but accessible quantum critical regime. The quantum criticality is characterized by mean field scaling of TN and non mean field scaling of the transport coefficients, which points to a fluctuation-induced reconstruction of the critical Fermi surface. A comparison between pressure and chemical doping as means to suppress TN sheds light on different routes to the quantum critical point and the relevance of Fermi surface nesting and disorder at this quantum phase transition. The work by Jaramillo et al. is broadly relevant to the study of magnetic quantum criticality in a physically pure and theoretically tractable system that balances elements of weak and strong coupling. [4pt] [1] R. Jaramillo, Y. Feng, J. Wang & T. F. Rosenbaum. Signatures of quantum criticality in pure Cr at high pressure. Proc. Natl. Acad. Sci. USA 107, 13631 (2010). [0pt] [2] R. Jaramillo, Y. Feng, J. C. Lang, Z. Islam, G. Srajer, P. B. Littlewood, D. B. McWhan & T. F. Rosenbaum. Breakdown of the Bardeen-Cooper-Schrieffer ground state at a quantum phase transition. Nature 459, 405 (2009).

  14. Effects of Low Chromium(III) Concentration in Electrodeposition of Low Contraction Chromium

    DTIC Science & Technology

    1990-04-01

    AD TECHNICAL REPORT ARCCB-TR-90014 EFFECTS OF LOW CHROMIUM(III) CONCENTRA TION IN ELECTRODEPOSITION oo OF LOW CONTRACTION CHROMIUMcv) N M. D. MILLER...TYPE OF REPORT & PERIOD COVERED EFFECTS OF LOW CHROMIUM(III) CONCENTRATION IN Final ELECTRODEPOSITION OF LOW CONTRACTION CHROMIUM 6. PERFORMING ORG...effects of low chromium (Cr)(IIT) concentrations on the electrodeposition of low contraction (LC) chromium were studied. A systematic experiment was

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. Environmental biochemistry of chromium.

    PubMed

    Losi, M E; Amrhein, C; Frankenberger, W T

    1994-01-01

    Chromium is a d-block transitional element with many industrial uses. It occurs naturally in various crustal materials and is discharged to the environment as industrial waste. Although it can occur in a number of oxidation states, only 3+ and 6+ are found in environmental systems. The environmental behavior of Cr is largely a function of its oxidation state. Hexavalent Cr compounds (mainly chromates and dichromates) are considered toxic to a variety of terrestrial and aquatic organisms and are mobile in soil/water systems, much more so than trivalent Cr compounds. This is largely because of differing chemical properties: Hexavalent Cr compounds are strong oxidizers and highly soluble, while trivalent Cr compounds tend to form relatively inert precipitates at near-neutral pH. The trivalent state is generally considered to be the stable form in equilibrium with most soil/water systems. A diagram of the Cr cycle in soils and water is given in Fig. 6 (Bartlett 1991). This illustration provides a summary of environmentally relevant reactions. Beginning with hexavalent Cr that is released into the environment as industrial waste, there are a number of possible fates, including pollution of soil and surface water and leaching into groundwater, where it may remain stable and, in turn, can be taken up by plants or animals, and adsorption/precipitation, involving soil colloids and/or organic matter. Herein lies much of the environmental concern associated with the hexavalent form. A portion of the Cr(VI) will be reduced to the trivalent form by inorganic electron donors, such as Fe2+ and S2-, or by bioprocesses involving organic matter. Following this conversion, Cr3+ can be expected to precipitate as oxides and hydroxides or to form complexes with numerous ligands. This fraction includes a vast majority of global Cr reserves. Soluble Cr3+ complexes, such as those formed with citrate, can undergo oxidation when they come in contact with manganese dioxide, thus reforming

  20. 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

  1. 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

  2. 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.

  3. Modeling of chromium in ground water

    SciTech Connect

    Shen, Huiying; Nikolaidis, N.P.

    1995-12-01

    National Chromium is a metal-plating facility located in Putnam, Connecticut that has been in operation for 55 years. Chromium has dripped onto the wooden floor and leached into the groundwater. The process that affect the fate and transport of chromium in groundwater are aqueous complexation, adsorption/desorption, precipitation/dissolution, and solute transport. In addition, field data and laboratory studies using soil samples from this site indicate that a predominant retardation process is diffusion into the soil matrix. While aqueous complexation usually takes seconds or less, the time scales of chromium diffusion in soil matrix is years. A three-dimensional multicomponent solute transport model has been developed to study the fate, speciation and transport of chromium. The model has been applied to the National Chromium site in a hind casting to study (1) the interaction among the processes, (2) the implication of chromium diffusion in soil matrix on remediation technologies, and (3) the time scales of remediation.

  4. Chromium in the environment of Finland.

    PubMed

    Mukherjee, A B

    1998-06-30

    This paper focuses upon the use, import and release of chromium to the environment of Finland. In addition, the behavior of trivalent and hexavalent chromium in soils has been briefly reviewed. In Finland, consumption of chromium compounds occurs in the following pattern: stainless steel > leather tanning > metal plating > chemicals. The emission of chromium has decreased from 114 t in 1979 to 28 t in 1995. The highest release of chromium continues to be from ferrochromium and stainless steel plants. From these facilities, 85% of slag and dusts are used by a secondary facility to recover valuable metal. In the industrial areas, the oxidizing behavior of chromium (III) is still unknown. In this study, the leachability of chromium (VI) to ground water and its effects on terrestrial and aquatic species in Finland are discussed.

  5. [Worldwide cancer mortality among chromium platers].

    PubMed

    Hara, Toshiyuki; Takahashi, Ken

    2012-12-01

    The elevated risk of lung cancer among chromate-producing workers has been confirmed by many epidemiological studies. Although chromium has been most used in the chromium plating industry and many platers are employed in small-scale factories, cancer studies have been documented in only a few investigations. We have conducted several prospective cohort studies in Japanese chromium platers and recently extended them through 2003. We additionally surveyed epidemiological studies among chromium platers carried out in other parts of the world. Occupational chromium exposure through chromium plating work may be a risk factor for mortality not only from lung cancer but also malignant lymphoma and brain tumor. The age at first exposure to chromium may be a more important factor than the duration of exposure for an increased risk of lung cancer and malignant lymphoma.

  6. Chromium(III), insoluble salts

    Integrated Risk Information System (IRIS)

    TOXICOLOGICAL REVIEW OF TRIVALENT CHROMIUM ( CAS No . 16065 - 83 - 1 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) August 1998 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed in accordance with U.S . Environmen

  7. Malleable Chromium and Its Alloys

    DTIC Science & Technology

    1952-03-01

    Silicon o.161 Zirconium 0 Tantalum 42 Twenty-gram briquettes , made by mixing chromium powder and finely divided master alloys and pressing in a 3/4-inch...Coupons about 1/4 x I x 1/16 inch were sawed from hot rolled sheet, cleaned with No. I emery paper and degreased, After weighing, the specimens were

  8. Chromium-51 calibrating neutrino source

    SciTech Connect

    Demchenko, N.F.; Karasev, V.I.; Karelin, E.A.

    1993-12-31

    The problem for measurement of the sun neutrino flux is resolved at the specially made Baksansk neutrino telescope and calls for calibration of registration system. For this a man made neutrino source is required with the known yield of particles and intensity comparable with the intensity of the measured subject. The most suitable radionuclide for production of this source is chromium-51 the radionuclide decay of which is accompanied with neutrino radiation. At the Research Institute of Atomic Reactors (in Dimitrovgrad) the production technology is developed as well as the closed chromium-51 neutrino source is made of 4 x 10{sup 5} Ci activity. The parts of active source made in the form of core of metallic isotope-enriched chromium were irradiated in the high flux neutron trap of the SM-2 reactor. The sources were subsequently assembled at the shield cells with remote equipment application. The source was certificated as a special form radioactive material. Due to low half-life of chromium-51 (T 1/2 - 27 hours) all the operations on assembly, certification and delivery of source to the Baksansk Laboratory were performed at the earliest possible date (less than 3 days).

  9. The use of trivalent chromium bath to obtain a solar selective black chromium coating

    NASA Astrophysics Data System (ADS)

    Survilienė, S.; Češūnienė, A.; Juškėnas, R.; Selskienė, A.; Bučinskienė, D.; Kalinauskas, P.; Juškevičius, K.; Jurevičiūtė, I.

    2014-06-01

    Black chromium coatings were electrodeposited from a trivalent chromium bath using a ZnO additive as a second main component. Black chromium was electrodeposited on steel and copper plates and substrates plated with bright nickel prior to black chromium electrodeposition. The black chromium coatings were characterized by XRD and SEM. The XRD data suggest that the phase structure of black chromium may be defined as a zinc solid solution in chromium or a chromium solid solution in zinc depending on the chromium/zinc ratio in the deposit. The role of substrate finish was evaluated through the corrosion resistance and reflectance of black chromium. According to corrosion tests the samples plated with bright nickel prior to black chromium deposition have shown the highest corrosion resistance. The electrodeposited black chromium possesses good optical properties for the absorption of solar energy. The absorption coefficient of black chromium was found to be over 0.99 for the samples obtained without the Ni undercoat and below 0.99 for those obtained with the use of Ni undercoat. However, the use of nickel undercoat before black chromium plating is recommended because it remarkably improves the corrosion resistance of samples.

  10. Remediation of soils contaminated with chromium using citric and hydrochloric acids: the role of chromium fractionation in chromium leaching.

    PubMed

    Cheng, Shu-Fen; Huang, Chin-Yuan; Tu, Yao-Ting

    2011-01-01

    Acid washing is a common method for soil remediation, but is not always efficient for chromium-contaminated soil. Both soil particle size and the forms of chromium existing in the soil affect the efficiency of soil washing. Laboratory batch and column dissolution experiments were conducted to determine the efficiencies of citric and hydrochloric acids as agents to extract chromium from soils contaminated with chromium. The effects of soil particle size and chromium fractionation on Cr leaching were also investigated. About 90% of chromium in the studied soil existed either in residual form or bound to iron and manganese oxides, and Cr fraction distributions were similar for all soil particle sizes. Almost all exchangeable and carbonate-bound chromium was removed by washing once with 0.5 M HCl, whereas organic chromium was more effectively removed by washing with citric acid rather than with HCl solution of the same concentration. For chromium fractions that were either bound to Fe-Mn oxides or existed as residual forms, the efficiencies of acid washing were usually 20% or less, except for 0.5 M HCl solution, which had much higher efficiencies. Separation of the soil sample by particle size before the separate washing of the soil fractions had little improvement on the chromium removal.

  11. 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.

  12. Atmospheric releases of hexavalent chromium from hard chromium plating operations

    SciTech Connect

    Hall, M.S.; Dietz, J.D.; Cooper, C.D.; Wayson, R.L.; Bauman, D.

    1992-01-01

    The study represents an assessment of airborne fugitive hexavalent chromium concentrations at these facilities. In an effort to develop a model for stack emissions of Cr(VI), EPA data were reviewed and a correlation for chromium emissions was reported versus ampere-hours and plating bath volume. A modification of a stack sampling train was constructed to accommodate fugitive sampling efforts made at two hard chrome plating facilities. The levels found at both sites, for the most part, were below detection limits of 4 micrograms cu m and 6 micrograms cu m for the 1st and 2nd plant, respectively. The annual emission rates from Plants 1 and 2 are < 0.5 and < 1 lb Cr(VI) per year, respectively.

  13. Electrodeposition of cobalt-chromium alloy from trivalent chromium solutions

    SciTech Connect

    Dasarathy, H.; Riley, C.; Coble, H.D. . Dept. of Chemistry and Materials Science)

    1994-07-01

    Cobalt-chromium alloy was deposited from plating solutions containing cobalt(II) chloride and chromium(III) chloride at 3.5 pH. The deposits were obtained using both single and mixed complex solutions. Deposit morphology showed significant dependence on the complexing agent(s) used. Partitioning of the two components in the deposit as determined by energy dispersive spectroscopy depended on plating parameters such as concentration ratio of the two salts in the solution, complexing agent, type of current (both dc and pulsed current were studied), and current density. X-ray photoelectron spectroscopy spectra collected from as-deposited alloy revealed the presence of both oxides and metals. X-ray diffraction spectra for the alloy deposit indicated solid solution formation.

  14. Occurrences, uses, and properties of chromium.

    PubMed

    Barnhart, J

    1997-08-01

    Chromium is the 21st most abundant element in the Earth's crust with a mean concentration in United States soils of about 40 mg/kg. Although it exists in several oxidation states, the zero, trivalent, and hexavalent states are the most important in commercial products and the environment. Nearly all naturally occurring chromium is in the trivalent state, usually in combination with iron or other metal oxides. Although only about 15% of the chromium mined is used in the manufacture of chemicals, most applications of chromium utilize the chemistry of chromium. For instance, the "stainless" nature of stainless steel is due to the chemical properties of the chromium oxides which form on the surface of the alloy. Similarly, the protective properties of chrome plating of metals, chromated copper arsenate (CCA) treatment of wood, and chrome tanning of leather are all dependent on chromium chemistry. The key to these uses is that under typical environmental and biological conditions of pH and oxidation-reduction potential, the most stable form of chromium is the trivalent oxide. This form has very low solubility and low reactivity resulting in low mobility in the environment and low toxicity in living organisms. In this paper the chemical properties of chromium are discussed for the major commercial products in the context of the Eh-pH diagram for chromium.

  15. Quantification of total chromium and hexavalent chromium in UHT milk by ETAAS.

    PubMed

    Lameiras, J; Soares, M E; Bastos, M L; Ferreira, M

    1998-10-01

    Procedures for the quantification of total chromium and hexavalent chromium in UHT milk samples are presented. Total chromium was determined directly in milk with the addition of a surfactant and a mixture of Pd and Mg as a chemical modifier. For the selective separation of hexavalent chromium, the sample pre-treatment consisted in precipitation of proteins and elution of the supernatant through a Chromabond NH2 column. The metal was eluted with nitric acid. Both total chromium and hexavalent chromium were evaluated by atomic absorption spectrometry with electrothermal atomization using the same instrumental conditions. The detection limits were 0.2 and 0.15 microgram l-1 for total chromium and hexavalent chromium, respectively. The linearity ranges under the optimized conditions were 0.2-20 and 0.15-50 micrograms l-1. For total chromium the precision was 4.9 and 5.7% for the analytical and the over-all procedure, respectively, and for hexavalent chromium 4.3 and 4.9%, respectively. The validation of both procedures was performed by the standard additions method and the recoveries were higher than 93% in all cases. For total chromium, a certified reference material was also used to validate the methodology. The methods were applied to the determination of total chromium and hexavalent chromium in 60 UHT milk samples.

  16. Food Chromium Contents, Chromium Dietary Intakes And Related Biological Variables In French Free-Living Elderly

    USDA-ARS?s Scientific Manuscript database

    Chromium (Cr III), an essential trace element, functions in potentiating insulin sensitivity, regulating glucose homeostasis, improving lipid profile, and maintaining lean body mass. Glucose intolerance and chromium deficiency increase with age, and could be aggravating factors of the metabolic synd...

  17. Sonoassisted microbial reduction of chromium.

    PubMed

    Kathiravan, Mathur Nadarajan; Karthick, Ramalingam; Muthu, Naggapan; Muthukumar, Karuppan; Velan, Manickam

    2010-04-01

    This study presents sonoassisted microbial reduction of hexavalent chromium (Cr(VI)) using Bacillus sp. isolated from tannery effluent contaminated site. The experiments were carried out with free cells in the presence and absence of ultrasound. The optimum pH and temperature for the reduction of Cr(VI) by Bacillus sp. were found to be 7.0 and 37 degrees C, respectively. The Cr(VI) reduction was significantly influenced by the electron donors and among the various electron donors studied, glucose offered maximum reduction. The ultrasound-irradiated reduction of Cr(VI) with Bacillus sp. showed efficient Cr(VI) reduction. The percent reduction was found to increase with an increase in biomass concentration and decrease with an increase in initial concentration. The changes in the functional groups of Bacillus sp., before and after chromium reduction were observed with FTIR spectra. Microbial growth was described with Monod and Andrews model and best fit was observed with Andrews model.

  18. Welding of high chromium steels

    NASA Technical Reports Server (NTRS)

    Miller, W B

    1928-01-01

    A brief description is given of different groups of high chromium steels (rustless iron and stainless steels) according to their composition and more generally accepted names. The welding procedure for a given group will be much the same regardless of the slight variations in chemical composition which may exist within a certain group. Information is given for the tensile properties (yield point and ultimate strength) of metal sheets and welds before and after annealing on coupons one and one-half inches wide. Since welds in rustless iron containing 16 to 18 percent chromium and 7 to 12 percent nickel show the best combination of strength and ductility in the 'as welded' or annealed condition, it is considered the best alloy to use for welded construction.

  19. Nondestructive evaluation of electrodeposited chromium

    NASA Astrophysics Data System (ADS)

    Todaro, Mark E.

    1992-11-01

    Benet Laboratories is pursuing methods for nondestructively evaluating the quality and adhesion of electrodeposited chromium coatings on the bore of large caliber gun tubes. The Army currently has no suitable means for testing such coatings nondestructively. A poor quality or poorly adherent coating shows up only when several test rounds are fired through the tube, removing portions of the coating and exposing the steel underneath. Recent in-house work has investigated both photothermal and ultrasonic methods. The photothermal method involves briefly heating the surface of the chromium with a laser pulse. After the initial heating, the surface temperature decreases as heat diffuses into the coating and substrate. The characteristics of the coating, interface, and substrate affect the surface temperature profile in distinct ways. The temperature of the surface can be measured by observing the emitted infrared radiation with a focused detector or an infrared scanner. Although no experimental data using the photothermal technique has been obtained yet, a one-dimensional finite difference algorithm was used to model temperature changes on the surface of a chromium coating on steel due to an incident energy pulse. The model verifies that with a suitable choice of laser pulse width, one could measure the thermal characteristics of the coating and detect the presence of a thermal discontinuity at the interface.

  20. Nasal manifestations in chromium industry workers.

    PubMed

    Aiyer, R G; Kumar, Gaurav

    2003-04-01

    People working in mines, plating factories, cement industries are mainly exposed to chrome substances, IIexavalent chromium has been implicated for its toxic effect on the nasal mucosa. Hereby we present a rare study of 28 patients who attended out patient department of Otorhinolaryngology at SSG Hospital, Baroda from a nearby chromium industry. This study aims to present various nasal manifestations of toxic effects of prolonged chromium exposure.

  1. Bendability of aluminiumand steel-clad chromium plates

    NASA Astrophysics Data System (ADS)

    Yoshida, Fusahito; Okada, Tatsuo; Itoh, Misao; Harada, Yasunori; Ohmori, Masanobu

    1998-05-01

    The present paper describes how the cladding of chromium plate with dissimilar metals improves the plastic bendability of the chromium. Three-point bending tests at various temperatures were performed for three types of chromium specimens: a monolithic chromium plate, aluminium- and steel-clad chromium plate. The aluminium-clad chromium plate was bent at 343 K up to a bent angle of 90 degrees without failure, even when the chromium layer was located outside of the plate (tension side), while the monolithic chromium plate could be bent exclusively at temperatures above 403 K. When the chromium layer was located inside of the steel-clad chromium plate (compression side), the plate was successfully bent at 307 K. The FE stress analysis of bending proved that the cladding of chromium plates with proper metals of different kinds is effective to reduce the tensile stress in chromium induced during bending and also the residual stress existing after bending operation.

  2. Removal of hexavalent chromium using distillery sludge.

    PubMed

    Selvaraj, K; Manonmani, S; Pattabhi, S

    2003-09-01

    Batch mode experiments were conducted to study the removal of hexavalent chromium from aqueous and industrial effluent using distillery sludge. Effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(VI) were studied. The data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity was found to be 5.7 mg/g. Freundlich constants K(f) and n were 2.05 [mg/g(L/mg)(n)] and 3.9, respectively. Desorption studies indicated the removal of 82% of the hexavalent chromium. The efficiency of adsorbent towards the removal of chromium was also tested using chromium-plating wastewater.

  3. 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).

  4. 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 ...

  5. Separation of chromium(III) and chromium(VI) by ion chromatography and an inductively coupled plasma mass spectrometer as element-selective detector.

    PubMed

    Hagendorfer, Harald; Goessler, Walter

    2008-07-30

    Due to its extensive use in industrial processes, large quantities of chromium compounds are discharged into the environment. Common approaches for the speciation of Cr employ the determination of Cr(VI) and total Cr. The focus of the present work was a separation of Cr(III) and Cr(VI) species, with a minimum of sample preparation, by keeping an eye on the more relevant and toxic Cr(VI). For the successful simultaneous separation of both chromium species we implemented a RSpak NN-814 4DP (PEEK, 4 mm x 150 mm) multi-mode column using an eluent containing 90 mM ammonium sulfate and 10 mM ammonium nitrate, adjusted to pH 3.5. At a flow of 0.3 mL min(-1) the separation of both Cr species was possible within 8 min. Further the octopole reaction system of the inductively coupled plasma mass spectrometer was systematically studied and optimised to reduce the influence of polyatomic interferences. The major advantage of the developed method compared to published methods is that a derivatisation of the Cr(III) species--an invasion in the speciation--is not required. With the used multi-mode column both chromium species are retained. Furthermore the pH of the mobile phase (pH 3.5) prevents reduction of Cr(VI) as well as precipitation of Cr(III) during the analysis. A limit of determination of approximately 0.5 microg L(-1) for both chromium species with an injection volume of 25 microL was obtained. The optimised method was successfully applied to the determination of Cr(VI) in cement samples as well as chromium speciation analysis in homeopathic drugs.

  6. [Chromium exposure biological indices and clinical findings in chromium plating industry (author's transl)].

    PubMed

    Franchini, I; Cavatorta, A; Mutti, A; Marcato, M; Bottazzi, D; Cigala, F

    1977-09-01

    According to the investigations carried out on workers of two chromium plating plants, the authors believe that chromium urinary excretion allows to determine the degree of its acute absorption. Moreover, the renal clearance of diffusible chromium allows the evaluation of chromium body burden and is related to the duration as well as to the severity of exposure. This interpretation is supported by the relation between the exposure biological indexes and the clinical and instrumental investigations which make possible the evaluation of lesions caused by chromium exposure, mostly concerning the respiratory system.

  7. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... by employees in the immediate release area, or by maintenance personnel, it is not an emergency. Employee exposure means the exposure to airborne chromium (VI) that would occur if the employee were not... employee exposure to chromium (VI) associated with a particular product or material or a specific process...

  8. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... days a year; (B) Experiencing signs or symptoms of the adverse health effects associated with chromium... symptoms of the adverse health effects associated with chromium (VI) exposure; (v) Within 30 days after... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  9. Environmental Durability of Electroplated Black Chromium

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1983-01-01

    Report describes tests of durability of electroplated black chromium coatings on solar-collector panels in rural, industrial, and seacoast environments for 60, 36, and 13 months, respectively. Black-chromium coating showed exceptionally-good optical durability in all three environments.

  10. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  11. REACTIVE SPUTTER DEPOSITION OF CHROMIUM NITRIDE COATINGS

    EPA Science Inventory

    The effect of substrate temperature and sputtering gas compositon on the structure and properties of chromium-chromium nitride films deposited on C-1040 steel using r.f. magnetron sputter deposition was investigated. X-ray diffraction analysis was used to determine the structure ...

  12. Environmental Durability of Electroplated Black Chromium

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1983-01-01

    Report describes tests of durability of electroplated black chromium coatings on solar-collector panels in rural, industrial, and seacoast environments for 60, 36, and 13 months, respectively. Black-chromium coating showed exceptionally-good optical durability in all three environments.

  13. 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.

  14. 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.

  15. 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

  16. [Bioremediation of chromium (VI) contaminated site by reduction and microbial stabilization of chromium].

    PubMed

    Zheng, Jia-Chuan; Zhang, Jian-Rong; Liu, Xi-Wen; Xu, Qian; Shi, Wei-Lin

    2014-10-01

    Chromium (VI) contaminated soil samples were collected from a chemical plant in Suzhou. Firstly, the reduced soil was prepared by adding reagent (Stone-sulfure reagent) into polluted soil to transfer most chromium (VI) into chromium (III), then a nutrient solution was introduced into the reduced soil, and the stabilized soil was obtained after 60 days culturing. The chromium (VI) content of the three kinds of soil was analyzed. The results showed that the chromium (VI) content in toxicity characteristic leaching liquid (TCLL) dropped by 96. 8% (from 8.26 mg · L(-1) to 0.26 mg · L(-1)), and the total chromium content dropped by 95.7% (from 14.66 mg · L(-1) to 0.63 mg · L(-1)) after bioremediation in 5% nutrient solution. Additionally, the durability of chromium stabilization was tested by potassium permanganate oxidation and sterilization of microbe-treated soil. After oxidation, the chromium (VI) content in TCLL of the reduced soil was increased from 8.26 mg · L(-1) to 14.68 mg · L(-1). However, the content after bioremediation was decreased to 2.68 mg · L(-1). The results of sterilization demonstrated that the death of microbe had no significant effect on the stabilization of chromium. Consequently, the research in this paper demonstrated the feasibility of bioremediation of chromium (VI) polluted soil through reduction followed by stabilization/soilidification, and provided a technique with low cost but high efficiency.

  17. Low-chromium reduced-activation chromium-tungsten steels

    SciTech Connect

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J.

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  18. 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.

  19. 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.

  20. 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

  1. Chromium is not an essential trace element for mammals: effects of a "low-chromium" diet.

    PubMed

    Di Bona, Kristin R; Love, Sharifa; Rhodes, Nicholas R; McAdory, DeAna; Sinha, Sarmistha Halder; Kern, Naomi; Kent, Julia; Strickland, Jessyln; Wilson, Austin; Beaird, Janis; Ramage, James; Rasco, Jane F; Vincent, John B

    2011-03-01

    Chromium was proposed to be an essential trace element over 50 years ago and has been accepted as an essential element for over 30 years. However, the studies on which chromium's status are based are methodologically flawed. Whether chromium is an essential element has been examined for the first time in carefully controlled metal-free conditions using a series of purified diets containing various chromium contents. Male Zucker lean rats were housed in specially designed metal-free cages for 6 months and fed the AIN-93G diet with no added chromium in the mineral mix component of the diet, the standard AIN-93G diet, the standard AIN-93G diet supplemented with 200 μg Cr/kg, or the standard AIN-93G diet supplemented with 1,000 μg Cr/kg. The chromium content of the diet had no effect on body mass or food intake. Similarly, the chromium content of the diet had no effect on glucose levels in glucose tolerance or insulin tolerance tests. However, a distinct trend toward lower insulin levels under the curve after a glucose challenge was observed with increasing chromium content in the diet; rats on the supplemented AIN-93G diets had significantly lower areas (P < 0.05) than rats on the low-chromium diet. The studies reveal that a diet with as little chromium as reasonably possible had no effect on body composition, glucose metabolism, or insulin sensitivity compared with a chromium-"sufficient" diet. Together with the results of other recent studies, these results clearly indicate that chromium can no longer be considered an essential element.

  2. 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.

  3. 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.

  4. Efficiency of silicon solar cells containing chromium

    NASA Technical Reports Server (NTRS)

    Salama, A. M. (Inventor)

    1982-01-01

    Efficiency of silicon solar cells containing about one quadrillon atoms cu cm of chromium is improved about 26% by thermal annealing of the silicon wafer at a temperature of 200 C to form chromium precipitates having a diameter of less than 1 Angstrom. Further improvement in efficiency is achieved by scribing laser lines onto the back surface of the wafer at a spacing of at least 0.5 mm and at a depth of less than 13 micrometers to preferentially precipitate chromium near the back surface and away from the junction region of the device. This provides an economical way to improve the deleterious effects of chromium, one of the impurities present in metallurgical grade silicon mateial.

  5. Potentiometry: A Chromium (III) -- EDTA Complex

    ERIC Educational Resources Information Center

    Hoppe, J. I.; Howell, P. J.

    1975-01-01

    Describes an experiment that involves the preparation of a chromium (III)-EDTA compound, a study of its infrared spectrum, and the potentiometric determination of two successive acid dissociation constants. (Author/GS)

  6. Efficiency of silicon solar cells containing chromium

    DOEpatents

    Frosch, Robert A. Administrator of the National Aeronautics and Space; Salama, Amal M.

    1982-01-01

    Efficiency of silicon solar cells containing about 10.sup.15 atoms/cm.sup.3 of chromium is improved about 26% by thermal annealing of the silicon wafer at a temperature of 200.degree. C. to form chromium precipitates having a diameter of less than 1 Angstrom. Further improvement in efficiency is achieved by scribing laser lines onto the back surface of the wafer at a spacing of at least 0.5 mm and at a depth of less than 13 micrometers to preferentially precipitate chromium near the back surface and away from the junction region of the device. This provides an economical way to improve the deleterious effects of chromium, one of the impurities present in metallurgical grade silicon material.

  7. Potentiometry: A Chromium (III) -- EDTA Complex

    ERIC Educational Resources Information Center

    Hoppe, J. I.; Howell, P. J.

    1975-01-01

    Describes an experiment that involves the preparation of a chromium (III)-EDTA compound, a study of its infrared spectrum, and the potentiometric determination of two successive acid dissociation constants. (Author/GS)

  8. OPTIMIZATION AND EVALUATION OF CHROMIUM COMPOSITES.

    DTIC Science & Technology

    COMPOSITE MATERIALS), (*CHROMIUM ALLOYS , POWDER METALLURGY, REINFORCING MATERIALS, TANTALUM ALLOYS , CARBON ALLOYS , OPTIMIZATION, TENSILE PROPERTIES...FRACTOGRAPHY, RUPTURE, DUCTILITY, CORROSION, EROSION, THERMOCOUPLES, PROTECTIVE COVERINGS, FLUIDICS, JET ENGINES, MAGNESIUM COMPOUNDS, OXIDES, VANADIUM ALLOYS , SILICON ALLOYS .

  9. Point Defect Properties in Iron Chromium Alloys

    DTIC Science & Technology

    2006-09-01

    evolution of macro scale behaviors such as void swelling, hardening, embrittlement , creep, stress corrosion cracking , the first-principles...PROPERTIES IN IRON CHROMIUM ALLOYS by Harun Đogo September 2006 Thesis Advisor: Craig Smith Second Reader: Xavier Maruyama...REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Point Defect Properties in Iron Chromium Alloys 6. AUTHOR(S) Harun Đogo 5

  10. Attenuation of chromium toxicity by bioremediation technology.

    PubMed

    Mohanty, Monalisa; Patra, Hemanta Kumar

    2011-01-01

    Chromium is an important toxic environmental pollutant. Chromium pollution results largely from industrial activities, but other natural and anthropogenic sources also contribute to the problem. Plants that are exposed to environmental contamination by chromium are affected in diverse ways, including a tendency to suffer metabolic stress. The stress imposed by Cr exposure also extends to oxidative metabolic stress in plants that leads to the generation of active toxic oxygen free radicals. Such active free radicals degrade essential biomolecules and distort plant biological membranes. In this chapter, we describe sources of environmental chromium contamination, and provide information about the toxic impact of chromium on plant growth and metabolism. In addition, we address different phytoremediation processes that are being studied for use worldwide, in contaminated regions, to address and mitigate Cr pollution. There has been a long history of attempts to successfully mitigate the toxic effects of chromium-contaminated soil on plants and other organisms. One common approach, the shifting of polluted soil to landfills, is expensive and imposes environmental risks and health hazards of its own. Therefore, alternative eco-friendly bioremediation approaches are much in demand for cleaning chromium-polluted areas. To achieve its cleaning effects, bioremediation utilizes living organisms (bacteria, algae, fungi, and plants) that are capable of absorbing and processing chromium residues in ways which amend or eliminate it. Phytoremediation (bioremediation with plants) techniques are increasingly being used to reduce heavy metal contamination and to minimize the hazards of heavy metal toxicity. To achieve this, several processes, viz., rhizofiltration, phytoextraction, phytodetoxification, phytostabilization, and phytovolatilization, have been developed and are showing utility in practice, or promise. Sources of new native hyperaccumulator plants for use at contaminated

  11. Trivalent chromium, in atherosclerosis and diabetes.

    PubMed

    Mossop, R T

    1991-11-01

    The known effects of trivalent chromium (Cr) in lowering blood levels of low density lipoproteins (LDL), raising high density lipoproteins (HDL) and improving glucose tolerance are summarised. Chromium deficiency cannot easily be established by direct means, but can be inferred by the reversal of symptoms and signs following the administration of trivalent chromium. This evidence can be supported by knowledge or suspicion of a deficiency in the diet, common in those who use highly refined cereal foods. It is considered that the beneficial effects of chromium repletion are now so well established and the trivalent form is so free of toxicity that it should now be used in clinical medicine for the benefit of those with some forms of diabetes and its complications and those suffering from atherosclerosis. Of perhaps more importance is the public health aspect, since most chromium is discarded in the cereal refinement process, we now have added evidence for a return to the diets in which complex carbohydrates predominated. In those who refuse or are unable to do this, possibly the addition of chromium to their drinking water may be of value.

  12. 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.

  13. 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

  14. 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.

  15. [Is chromium an essential trace element in human nutrition?].

    PubMed

    Yoshida, Munehiro

    2012-01-01

    It has been recognized that chromium is an essential trace element associated with carbohydrate metabolism, and chromium deficiency causes an impaired glucose tolerance. Recently, however, Vincent et al. have reported that chromium is not an essential trace element. In the present report, the author evaluated the nutritional essentiality of chromium by reviewing several previous reports. In almost all previous reports, the chromium concentration in the animal feed used was higher than 0.1 μg/g, and it is difficult to consider that the experimental animals were in a low-chromium state. In addition, the amount of chromium administered to the animals for the improvement of glucose tolerance was at a pharmacological level, and corresponded to a level that far exceeded the human daily chromium intake (20 to 80 μg/day). On the other hand, recent research has clearly shown that feeding with a severely low-chromium diet (0.016 μg/g) does not impair glucose tolerance. The amount of chromium absorbed in humans estimated from chromium intake (20 to 80 μg/day), chromium absorption rate (1%), and urinary chromium excretion (<1 μg/day) is less than 1 μg/day, which is much lower than those of other essential trace elements. In addition, because there is an inconsistency between the chromium concentration in food and chromium intake, chromium intake seems to be dependent on chromium contamination during food processing and cooking. It is concluded that there is a high possibility that chromium is not an essential trace element.

  16. 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.

  17. Bioremediation of chromium solutions and chromium containing wastewaters.

    PubMed

    Malaviya, Piyush; Singh, Asha

    2016-08-01

    Cr(VI) represents a serious threat to human health, living resources and ecological system as it is persistent, carcinogenic and toxic, whereas, Cr(III), another stable oxidation state of Cr, is less toxic and can be readily precipitated out of solution. The conventional methods of Cr(VI) removal from wastewaters comprise of chemical reduction followed by chemical precipitation. However, these methods utilize large amounts of chemicals and generate toxic sludge. This necessitates the need for devising an eco-technological strategy that would use the untapped potential of the biological world for remediation of Cr(VI) containing wastewaters. Among several viable approaches, biotransformation of Cr(VI) to relatively non-toxic Cr(III) by chromium resistant bacteria offers an economical- and environment-friendly option for its detoxification. Various studies on use of Cr(VI) tolerant viable bacterial isolates for treatment of Cr(VI) containing solutions and wastewater have been reported. Therefore, a detailed account of mechanisms and processes involved in bioreduction of Cr(VI) from solutions and wastewaters by bacterial isolates are the focus of this review article in addition to a discussion on toxicity of Cr(VI) on bacterial strains and various factors affecting Cr(VI) bioreduction.

  18. Cytotoxicity and oxidative mechanisms of different forms of chromium.

    PubMed

    Bagchi, Debasis; Stohs, Sidney J; Downs, Bernard W; Bagchi, Manashi; Preuss, Harry G

    2002-10-30

    Chromium exists mostly in two valence states in nature: hexavalent chromium [chromium(VI)] and trivalent chromium [chromium(III)]. Chromium(VI) is commonly used in industrial chrome plating, welding, painting, metal finishes, steel manufacturing, alloy, cast iron and wood treatment, and is a proven toxin, mutagen and carcinogen. The mechanistic cytotoxicity of chromium(VI) is not completely understood, however, a large number of studies demonstrated that chromium(VI) induces oxidative stress, DNA damage, apoptotic cell death and altered gene expression. Conversely, chromium(III) is essential for proper insulin function and is required for normal protein, fat and carbohydrate metabolism, and is acknowledged as a dietary supplement. In this paper, comparative concentration- and time-dependent effects of chromium(VI) and chromium(III) were demonstrated on increased production of reactive oxygen species (ROS) and lipid peroxidation, enhanced excretion of urinary lipid metabolites, DNA fragmentation and apoptotic cell death in both in vitro and in vivo models. Chromium(VI) demonstrated significantly higher toxicity as compared with chromium(III). To evaluate the role of p53 gene, the dose-dependent effects of chromium(VI) were assessed in female C57BL/6Ntac and p53-deficient C57BL/6TSG p53 mice on enhanced production of ROS, lipid peroxidation and DNA fragmentation in hepatic and brain tissues. Chromium(VI) induced more pronounced oxidative damage in multiple target organs in p53 deficient mice. Comparative studies of chromium(III) picolinate and niacin-bound chromium(III), two popular dietary supplements, reveal that chromium(III) picolinate produces significantly more oxidative stress and DNA damage. Studies have implicated the toxicity of chromium picolinate in renal impairment, skin blisters and pustules, anemia, hemolysis, tissue edema, liver dysfunction; neuronal cell injury, impaired cognitive, perceptual and motor activity; enhanced production of hydroxyl

  19. Lateral stress evolution in chromium sulfide cermets with varying excess chromium

    NASA Astrophysics Data System (ADS)

    Petel, O. E.; Appleby-Thomas, G. J.; Wood, D. C.; Capozzi, A.; Nabavi, A.; Goroshin, S.; Frost, D. L.; Hazell, P. J.

    2016-04-01

    The shock response of chromium sulfide-chromium, a cermet of potential interest as a matrix material for ballistic applications, has been investigated at two molar ratios. Using a combustion synthesis technique allowed for control of the molar ratio of the material, which was investigated under near-stoichiometric (cermet) and excess chromium (interpenetrating composite) conditions, representing chromium:sulfur molar ratios of 1.15:1 and 4:1, respectively. The compacts were investigated via the plate-impact technique, which allowed the material to be loaded under a one-dimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress in both materials. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time for the two molar ratio conditions. The two materials exhibited identical material strength despite variations in their excess chromium contents.

  20. Materials corrosion of high temperature alloys immersed in 600C binary nitrate salt.

    SciTech Connect

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-03-01

    Thirteen high temperature alloys were immersion tested in a 60/40 binary nitrate salt. Samples were interval tested up to 3000 hours at 600ÀC with air as the ullage gas. Chemical analysis of the molten salt indicated lower nitrite concentrations present in the salt, as predicted by the equilibrium equation. Corrosion rates were generally low for all alloys. Corrosion products were identified using x-ray diffraction and electron microprobe analysis. Fe-Cr based alloys tended to form mixtures of sodium and iron oxides, while Fe-Ni/Cr alloys had similar corrosion products plus oxides of nickel and chromium. Nickel based alloys primarily formed NiO, with chromium oxides near the oxide/base alloy interface. In625 exhibited similar corrosion performance in relation to previous tests, lending confidence in comparisons between past and present experiments. HA230 exhibited internal oxidation that consisted of a nickel/chromium oxide. Alloys with significant aluminum alloying tended to exhibit superior performance, due formation of a thin alumina layer. Soluble corrosion products of chromium, molybdenum, and tungsten were also formed and are thought to be a significant factor in alloy performance.

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

    SciTech Connect

    John F. Stolz

    2011-06-15

    A major challenge for the bioremediation of radionuclides (i.e., uranium, technetium) and metals (i.e., Cr(VI), Hg) is the co-occurrence of nitrate as it can inhibit metal transformation. Denitrification (nitrate reduction to dinitrogen gas) is considered the most important ecological process. For many metal and metalloid reducing bacteria, however, ammonia is the end product through respiratory nitrate reduction (RNRA). The focus of this work was to determine how RNRA impacts Cr(VI) transformation. The goal was to elucidate the specific mechanism(s) that limits Cr(VI) reduction in the presence of nitrate and to use this information to develop strategies that enhance Cr(VI) reduction (and thus detoxification). Our central hypothesis is that nitrate impacts the biotransformation of metals and metalloids in three ways 1) as a competitive alternative electron acceptor (inhibiting transformation), 2) as a co-metabolite (i.e., concomitant reduction, stimulating transformation), and 3) as an inducer of specific proteins and pathways involved in oxidation/reduction reactions (stimulating transformation). We have identified three model organisms, Geobacter metallireducens (mechanism 1), Sulfurospirillum barnesii, (mechasism 2), and Desulfovibrio desulfuricans (mechanisms 3). Our specific aims were to 1) investigate the role of Cr(VI) concentration on the kinetics of both growth and reduction of nitrate, nitrite, and Cr(VI) in these three organisms; 2) develop a profile of bacterial enzymes involved in nitrate transformation (e.g., oxidoreductases) using a proteomic approach; 3) investigate the function of periplasmic nitrite reductase (Nrf) as a chromate reductase; and 4) develop a strategy to maximize microbial chromium reduction in the presence of nitrate. We found that growth on nitrate by G. metallireducens was inhibited by Cr(VI). Over 240 proteins were identified by LC/MS-MS. Redox active proteins, outer membrane heavy metal efflux proteins, and chemotaxis sensory

  2. Microbial reduction of hexavalent chromium under vadose zone conditions.

    PubMed

    Oliver, Douglas S; Brockman, Fred J; Bowman, Robert S; Kieft, Thomas L

    2003-01-01

    Hexavalent chromium [Cr(VI)] is a common contaminant associated with nuclear reactors and fuel processing. Improper disposal at facilities in and and semiarid regions has contaminated underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those in the vadose zone, and to evaluate the potential for enhancing biological Cr(VI) reduction through nutrient addition. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic C (molasses). Nutrient amendments resulted in up to 87% reduction of the initial 67 mg L(-1) Cr(VI) in an unsaturated batch experiment. Molasses and nitrate additions to 15 cm long unsaturated flow columns receiving 65 mg L(-1) Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-d experiment. All of the immobilized Cr was in the form of Cr(III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy, and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  3. 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.

  4. 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.

  5. Diffusion of chromium in chrysoberyl

    NASA Astrophysics Data System (ADS)

    Ahn, Yong-Kil; Seo, Jin-Gyo; Park, Jong-Wan

    2009-07-01

    Cr 3+ diffusion in chrysoberyl (BeAl 2O 4) irradiated by H + ions and electrons has been studied and compared with diffusion in non-irradiated samples. Chrysoberyl crystals were irradiated with 6 MeV H + ions to fluencies of 1×10 16 cm -2 for 25 min and with 10 MeV electrons to fluencies of 2×10 17 cm -2 for 1 h. Three different types of samples, which were doped with Cr 3+, were annealed in horizontal alumina tube furnaces by 50 K intervals in the temperature range from 1773 to 1923 K for 200 h. Scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDX) was used to measure the diffusion. Arrhenius equations for the diffusion coefficient for Cr 3+ in the temperature range 1773-1923 K were developed: Electron beam irradiated chrysoberyls, Dcr=2.1×10 -5×exp (-482.3±18.2 kJ mol -1/ RT)m 2 s -1 Proton beam irradiated chrysoberyls, Dcr=2.3×10 -3×exp (-545.4±25.0 kJ mol -1/ RT)m 2 s -1 Natural non-irradiated chrysoberyls Dcr=2.2×10 -3×exp (-547.9±36.8 kJ mol -1/ RT)m 2 s -1 The results indicate that the chromium diffuses deepest into the electron beam irradiated chrysoberyls.

  6. Oral Chromium Exposure and Toxicity

    PubMed Central

    Sun, Hong; Brocato, Jason

    2015-01-01

    Hexavalent chromium [Cr(VI)] is a known carcinogen when inhaled. However, inhalational exposure to Cr(VI) affects only a small portion of the population, mainly by occupational exposures. In contrast, oral exposure to Cr(VI) is widespread and affects many people throughout the globe. In 2008, the National Toxicology Program (NTP) released a 2-year study demonstrating that ingested Cr(VI) was carcinogenic in rats and mice. The effects of Cr(VI) oral exposure is mitigated by reduction in the gut, however a portion evades the reductive detoxification and reaches target tissues. Once Cr(VI) enters the cell, it ultimately gets reduced to Cr(III), which mediates its toxicity via induction of oxidative stress during the reduction while Cr intermediates react with protein and DNA. Cr(III) can form adducts with DNA that may lead to mutations. This review will discuss the potential adverse effects of oral exposure to Cr(VI) by presenting up-to-date human and animal studies, examining the underlying mechanisms that mediate Cr(VI) toxicity, as well as highlighting opportunities for future research. PMID:26231506

  7. Chromium Recycling in the United States in 1998

    USGS Publications Warehouse

    Papp, John F.

    2001-01-01

    The purpose of this report is to illustrate the extent to which chromium was recycled in the United States in 1998 and to identify chromium-recycling trends. The major use of chromium was in the metallurgical industry to make stainless steel; substantially less chromium was used in the refractory and chemical industries. In this study, the only chromium recycling reported was that which was a part of stainless steel scrap reuse. In 1998, 20 percent of the U.S. apparent consumption of chromium was secondary (from recycling); the remaining 80 percent was based on net chromium commodity imports and stock adjustments. Chromite ore was not mined in the United States in 1998. In 1998, 75,300 metric tons (t) of chromium contained in old scrap was consumed in the United States; it was valued at $66.4 million. Old scrap generated contained 132,000 t of chromium. The old scrap recycling efficiency was 87 percent, and the recycling rate was 20 percent. About 18,000 t of chromium in old scrap was unrecovered. New scrap consumed contained 28,600 t of chromium, which yielded a new-to-old-scrap ratio of 28:72. U.S. chromium-bearing stainless steel scrap net exports were valued at $154 million and were estimated to have contained 41,000 t of chromium.

  8. Oral bioavailability of chromium from a specific site

    SciTech Connect

    Witmer, C.M.; Harris, R. ); Shupack, S.I. )

    1991-05-01

    Analysis of soil from a specific site in New Jersey indicated a low level of sodium and chromium present as a calcium compound. Chromium was then administered orally to young, mature male rats at a level of 240 {mu}g/kg for 14 days as chromium-contaminated soil, as CaCrO{sub 4}, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hours after the last dosing, and tissues were taken immediately for chromium analysis. Blood, muscle, and liver contained the highest levels of chromium in these animals, although kidney contained the highest concentration per gram of tissue. Total amount of chromium in the tissues was less than 2% of the administered chromium. In a study of the excretion of chromium, the animals were dosed orally for 8 days and the chromium in feces and urine was determined on days 1, 2, 7, and 8. The animals administered the chromium in soil had higher levels of chromium in both urine and feces on all days compared to the group fed the CaCrO{sub 4}. The total recovery of chromium in any of the 2-day periods was less than 50% of the chromium administered during that period.

  9. Production of Chromium Oxide from Turkish Chromite Concentrate Using Ethanol

    NASA Astrophysics Data System (ADS)

    Aktas, S.; Eyuboglu, C.; Morcali, M. H.; Özbey, S.; Sucuoglu, Y.

    2015-05-01

    In this study, the possibility of chromium extraction from Turkish chromite concentrate and the production of chromium oxide were investigated. For the conversion of chromium(III) into chromium(VI), NaOH was employed, as well as air with a rate of 20 L/min. The effects of the base amount, fusing temperature, and fusing time on the chromium conversion percentage were investigated in detail. The conversion kinetics of chromium(III) to chromium(VI) was also undertaken. Following the steps of dissolving the sodium chromate in water and filtering, aluminum hydroxide was precipitated by adjusting the pH level of the solution. The chromium(VI) solution was subsequently converted to Cr(III) by the combination of sulfuric acid and ethanol. Interestingly, it was observed that ethanol precipitated chromium as chromium(VI) at mildly acidic pH levels, although this effect is more pronounced for K2Cr2O7 than Na2Cr2O7. On the other hand, in the strongly acidic regime, ethanol acted as a reducing agent role in that chromium(VI) was converted into Cr(III) whereas ethanol itself was oxidized to carbon dioxide and water. Subsequently, chromium hydroxide was obtained by the help of sodium hydroxide and converted to chromium oxide by heating at 800 °C, as indicated in thermo gravimetric analysis (TGA).

  10. Reduction of hexavalent chromium collected on PVC filters.

    PubMed

    Shin, Y C; Paik, N W

    2000-01-01

    Chromium exists at various valences, including elemental, trivalent, and hexavalent chromium, and undergoes reduction-oxidation reactions in the environment. Since hexavalent chromium is known as a human carcinogen, it is most important to evaluate the oxidation-reduction characteristics of the hexavalent chromium species. Although hexavalent chromium can be reduced to trivalent state, the detailed information on this in workplace environments is limited. The purpose of this study was to investigate hexavalent chromium reduction in time in various conditions. A pilot chrome plating operation was prepared and operated in a laboratory for this study. There was evidence that the hexavalent chromium was reduced by time after mist generation. The percentage ratio (with 95% confidence intervals in parentheses) of hexavalent chromium to total chromium was almost 100% (99.1 approximately 102.3) immediately after mist generation, and was reduced to 87.4% (84.8 approximately 89.9) at 1 hour and 81.0% (78.3 approximately 83.5) at 2 hours, respectively. Another test indicated that hexavalent chromium collected on PVC filters was also reduced by time after sampling. Hexavalent chromium was reduced to 90.8% (88.2 approximately 93.3) at 2 hours after sampling. It also was found that hexavalent chromium was reduced during storage in air. It is recommended that air samples of hexavalent chromium be protected against reduction during storage.

  11. Chromium-induced skin damage among Taiwanese cement workers.

    PubMed

    Chou, Tzu-Chieh; Wang, Po-Chih; Wu, Jyun-De; Sheu, Shiann-Cherng

    2016-10-01

    Little research has been done on the relationships between chromium exposure, skin barrier function, and other hygienic habits in cement workers. Our purpose was to investigate chromium-induced skin barrier disruption due to cement exposure among cement workers. One hundred and eight cement workers were recruited in this study. Urinary chromium concentration was used to characterize exposure levels. The biological exposure index was used to separate high and low chromium exposure. Transepidermal water loss (TEWL) was used to assess the skin barrier function. TEWL was significantly increased in workers with high chromium exposure levels than those with low chromium exposure levels (p = 0.048). A positive correlation was also found between urinary chromium concentration and TEWL (R = 0.28, p = 0.004). After adjusting for smoking status and glove use, a significant correlation between urinary chromium concentrations and TEWL remained. Moreover, workers who smoked and had a high chromium exposure had significantly increased TEWL compared to nonsmokers with low chromium exposure (p = 0.01). Skin barrier function of cement workers may have been disrupted by chromium in cement, and smoking might significantly enhance such skin barrier perturbation with chromium exposure. Decreased chromium skin exposure and smoking cessation should be encouraged at work. © The Author(s) 2015.

  12. Phytotoxic lesions of chromium in maize.

    PubMed

    Sharma, D C; Sharma, C P; Tripathi, R D

    2003-04-01

    Chromium (Cr) is fairly abundant in the earth's crust and ranks fourth among the 29 elements of biological importance. Besides natural sources, Cr enters biotic components of the ecosystem in various ways. Of other major industrial sources, tanning and chrome-plating industries are prominent sources. Cr(VI) form of chromium is highly reactive and influences both plants and animals. Due to Mn present in soil, Cr(III) is oxidized to Cr(VI) which remains in soil for a long time and can affect plant growth and development. Since maize is an important food and fodder plant for human beings and cattle, a study was conducted to investigate the effects of Cr on some metabolic activities of maize (Zea mays L. cv. Ganga 5). Chromium caused visible lesions of interveinal chlorosis. Young leaves showed vein clearing. Also, a papery appearance was observed in leaves. Margins of leaves were curled and the leaves appeared pale at greater Cr exposure. Concentrations of both chlorophyll a and b were reduced by exposure to Cr, the activities of ribonuclease and phenyl phosphatase were greater while the activity of iron-porphyrin enzyme catalase was less and the activity of amylase was also much less in plants exposed to Cr. Chromium also caused retardation of soluble protein. Accumulation of Cr in roots was much at all the levels of chromium supply. Exposure to Cr resulted in reduction in grain production and quality.

  13. The enriched chromium neutrino source for GALLEX

    SciTech Connect

    Hartmann, F.X.; Hahn, R.L.

    1991-01-18

    The preparation and study of an intense source of neutrinos in the form of neutron irradiated materials which are enriched in Cr-50 for use in the GALLEX solar neutrino experiment are discussed. Chromyl fluoride gas is enriched in the Cr-50 isotope by gas centrifugation and subsequently converted to a very stable form of chromium oxide. The results of neutron activation analyses of such chromium samples indicate low levels of any long-lived activities, but show that short-lived activities, in particular Na-24, may be of concern. These results show that irradiating chromium oxide enriched in Cr-50 is preferable to irradiating either natural chromium or argon gas as a means of producing a neutrino source to calibrate the GALLEX detector. These results of the impurity level analysis of the enriched chromyl fluoride gas and its conversion to the oxide are also of interest to work in progress by other members of the Collaboration investigating an alternative conversion of the enriched gas to chromium metal. 35 refs., 12 figs., 5 tabs.

  14. [Occupational exposure to chromium(VI) compounds].

    PubMed

    Skowroń, Jolanta; Konieczko, Katarzyna

    2015-01-01

    This article discusses the effect of chromium(VI) (Cr(VI)) on human health under conditions of acute and chronic exposure in the workplace. Chromium(VI) compounds as carcinogens and/or mutagens pose a direct danger to people exposed to them. If carcinogens cannot be eliminated from the work and living environments, their exposure should be reduced to a minimum. In the European Union the proposed binding occupational exposure limit value (BOELV) for chromium(VI) of 0.025 mg/m³ is still associated with high cancer risk. Based on the Scientific Commitee of Occupational Exposure Limits (SCOEL) document chromium(VI) concentrations at 0.025 mg/m³ increases the risk of lung cancer in 2-14 cases per 1000 exposed workers. Exposure to chromium(VI) compounds expressed in Cr(VI) of 0.01 mg Cr(VI)/m3; is responsible for the increased number of lung cancer cases in 1-6 per 1000 people employed in this condition for the whole period of professional activity.

  15. Natural Attenuation of Hexavalent Chromium in Groundwater and Soils

    EPA Pesticide Factsheets

    Concerns about the impact of chromium on human health and the environment require an evaluation of the potential risk of chromium entering the groundwater flow system and being transported beyond compliance boundaries.

  16. 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.

  17. 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.

  18. 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.

  19. Efficacy of dietary chromium (III) supplementation on tissue chromium deposition in finishing pigs.

    PubMed

    Wang, Min-Qi; Li, Hui; He, Yu-Dan; Wang, Chao; Tao, Wen-Jing; Du, Yong-Jie

    2012-09-01

    The study was conducted to evaluate the efficacy of different forms of trivalent chromium (Cr) supplementation on tissue chromium deposition in finishing pigs. A total of 96 pigs with an initial average body mass 65.57±1.05 kg were blocked by body mass and randomly assigned to four treatments with three replicates. Pigs were offered one of four diets including a control diet or the control diet supplemented with 200 μg/kg chromium from either chromium chloride (CrCl(3)), chromium picolinate (CrPic) or chromium nanocomposite (CrNano) for 40 days. During the trial, all pigs were given free access to feed and water. After feeding trial, eight pigs from each treatment were slaughtered for samples collection. The results showed that supplemental CrNano increased Cr content in blood, longissimus muscle, heart, liver, kidney, jejunum, and ileum (P<0.05). Supplemental Cr from three sources increased Cr excretion from all feces (P<0.05). Urinary Cr excretion was increased by CrNano or CrPic supplementation significantly. These results suggested that chromium nanocomposite exhibited more effective on tissue Cr deposition in pigs, which indicated higher absorption compared with CrCl(3) and CrPic.

  20. Unusual reactivity in a commercial chromium supplement compared to baseline DNA cleavage with synthetic chromium complexes.

    PubMed

    Chaudhary, Shveta; Pinkston, Joel; Rabile, M Mohamed; Van Horn, J David

    2005-03-01

    Commercially available chromium supplements were tested for their DNA cleavage ability compared with synthetic chromium(III) complexes, including chromium(III) tris-picolinate [Cr(pic)3], basic chromium acetate [Cr3O(OAc)6]+, model complexes, and recently patented Cr-complexes for use in supplements or therapy. Four different supplements (P1-P4) were tested for their DNA cleaving activity in the presence and the absence of H2O2, dithiothreitol (DTT) or ascorbate. One supplement, P1, showed nicking of DNA in the absence of oxidant or reductant at 120 microM metal concentration. Different lot numbers of P1 were also tested for DNA cleavage activity with similar results. Commercial supplements containing Cr(pic)3 nicked DNA at 120 microM metal concentrations in the presence of 5 mM ascorbate or with excess hydrogen peroxide, analogous to reactions with synthetic Cr(pic)3 reported elsewhere. Another chromium (non-Cr(pic)3) supplement, P2, behaves in a comparable manner to simple Cr(III) salts in the DNA nicking assay. Chromium(III) malonate [Cr(mal)2] and chromium(III) acetate [Cr(OAc)] can nick DNA in the presence of ascorbate or hydrogen peroxide, respectively, only at higher metal concentrations. The Cr(III) complexes of histidine, succinate or N-acetyl-L-glutamate do not nick DNA to a significant degree.

  1. 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.

  2. 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...

  3. 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...

  4. In vivo effects of chromium.

    PubMed Central

    Witmer, C; Faria, E; Park, H S; Sadrieh, N; Yurkow, E; O'Connell, S; Sirak, A; Schleyer, H

    1994-01-01

    The production of reactive oxygen species on addition of hexavalent chromium (potassium dichromate, K2Cr2O7) to lung cells in culture was studied using flow cytometer analysis. A Coulter Epics Profile II flow cytometer was used to detect the formation of reactive oxygen species after K2Cr2O7 was added to A549 cells grown to confluence. The cells were loaded with the dye, 2',7'-dichlorofluorescein diacetate, after which cellular esterases removed the acetate groups and the dye was trapped intracellularly. Reactive oxygen species oxidized the dye, with resultant fluorescence. Increased doses of Cr(VI) caused increasing fluorescence (10-fold higher than background at 200 microM). Addition of Cr(III) compounds, as the picolinate or chloride, caused no increased fluorescence. Electron paramagnetic resonance (EPR) spectroscopic studies indicated that three (as yet unidentified) spectral "signals" of the free radical type were formed on addition of 20, 50, 100, and 200 microM Cr(VI) to the A549 cells in suspension. Two other EPR "signals" with the characteristics of Cr(V) entities were seen at field values lower than the standard free radical value. Liver microsomes from male Sprague-Dawley rats treated intraperitoneally with K2Cr2O7 (130 mumole/kg every 48 hr for six treatments) had decreased activity of cytochromes P4503A1 and/or 3A2, and 2C11. Hepatic microsomes from treated female Sprague-Dawley rats, in contrast, had increased activities of these isozymes. Lung microsomes from male Sprague-Dawley rats had increased activity of P4502C11. Images Figure 4. Figure 6. PMID:7843092

  5. Phytoremediation of chromium by model constructed wetland.

    PubMed

    Mant, Catherine; Costa, Sylvia; Williams, John; Tambourgi, Elias

    2006-10-01

    Chromium is a pollutant present in tannery wastewater, its removal is necessary for protection of the environment. Penisetum purpureum, Brachiaria decumbens and Phragmites australis were grown hydroponically in experimental gravel beds to determine their potential for the phytoremediation of solutions containing 10 and 20 mg Cr dm(-3). These concentrations, similar to tannery wastewater after initial physico-chemical treatment were used with the aim of developing an economic secondary treatment to protect the environment. All the systems achieved removal efficiencies of 97-99.6% within 24 h. P. purpureum and B. decumbens removed 78.1% and 68.5% respectively within the first hour. Both P. purpureum and B. decumbens were tolerant of the concentrations of chromium applied, but P. purpureum showed the greatest potential because its faster growth and larger biomass achieved a much greater chromium removal over the whole length of time of the experiment.

  6. [Occupational asthma caused by chromium and nickel].

    PubMed

    Cruz, María Jesus; Costa, Roser; Marquilles, Eduard; Morell, Ferran; Muñoz, Xavier

    2006-06-01

    We report the case of a 40-year-old woman who developed occupational asthma following exposure to chromium and nickel in the nickel-plating section of a metalworks company. Skin prick tests for specific antibodies proved positive for nickel chloride at a concentration of 1 mg/mL and negative for potassium dichromate. The specific bronchial provocation test confirmed the diagnosis of occupational asthma due to exposure to chromium and nickel. The patient presented a late positive reaction to nickel chloride (0.1 mg/mL) and an immediate positive reaction to a 10 mg/mL solution of potassium dichromate. These results indicate a dual response to nickel and chromium in this patient.

  7. Hexavalent Chromium IV-Free Primer Development

    NASA Technical Reports Server (NTRS)

    Alldredge, Michael J.; Buck, Amy L.

    2015-01-01

    Primer materials provide corrosion protection for metal parts as well as an increased adhesion between metallic substrates and thermal protection systems (TPSs). Current primers for use in cryogenic applications contain hexavalent chromium. This hexavalent chromium provides excellent corrosion protection even in a cryogenic environment, but it is a carcinogen that requires special equipment and waste control procedures to use. The hazardous nature of hexavalent chromium makes it an obsolescence risk in the future. This study included two phases of evaluation. Thirteen primers were initially identified as candidates and twelve of those primers were tested in phase 1. Four of the best performing candidates from phase 1 continued into phase 2 testing. Phase 1 testing consisted mostly of liquid constituent and physical property testing. Cryoflex and salt fog testing were included in phase 1 because of their importance to the overall success of a candidate material. Phase 2 consisted of physical, thermal, and mechanical properties for nominally processed and fabricated specimens.

  8. Chromium picolinate supplementation for diabetes mellitus.

    PubMed

    Fox, G N; Sabovic, Z

    1998-01-01

    Chromium picolinate is a widely available nutritional supplement marketed for a plethora of afflictions. There is some evidence, including results from human studies, that it has a role in glucose homeostasis. We report the case of a 28-year-old woman with an 18-year history of type 1 diabetes mellitus whose glycosylated hemoglobin (Hb A1c) declined from 11.3% to 7.9% 3 months after initiation of chromium picolinate, 200 micrograms 3 times daily. Chromium picolinate continues to fall squarely within the scope of "alternative medicine," with both unproven benefits and unknown risks. It deserves closer scrutiny with additional prospective, randomized, double-blind, placebo-controlled trials to evaluate its efficacy in improving outcomes in patients with diabetes. A brief review of the literature was done to assist physicians who are being called upon to counsel and treat patients who are engaging in alternative therapies.

  9. 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.

  10. 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.

  11. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens shall conform in identify and specifications to the requirements of § 73.1327 (a)(1) and (b). (b) Uses and restrictions. The color additive chromium oxide greens...

  12. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens shall conform in identify and specifications to the requirements of § 73.1327 (a)(1) and (b). (b) Uses and restrictions. The color additive chromium oxide greens...

  13. 75 FR 67100 - Superalloy Degassed Chromium From Japan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-01

    ... COMMISSION Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission... chromium from Japan. SUMMARY: The Commission hereby gives notice that it has instituted a review pursuant... revocation of the antidumping duty order on superalloy degassed chromium from Japan would be likely to lead...

  14. Avoidance behavior of young black ducks treated with chromium

    USGS Publications Warehouse

    Heinz, G.H.; Haseltine, S.D.

    1981-01-01

    Pairs of adult black ducks (Anas rubripes) were fed a diet containing 0, 20, or 200 ppm chromium in the form of chromium potassium sulfate. Ducklings from these pairs were fed the same diets as adults and were tested for their avoidance responses to a fright stimulus. Neither level of chromium had a significant effect on avoidance behavior.

  15. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium oxide greens. 73.1327 Section 73.1327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color...

  16. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  17. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (JUN 2013) (a) Definitions. As used...

  18. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 1 2013-04-01 2013-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  19. Hexavalent and trivalent chromium in leather: What should be done?

    PubMed

    Moretto, Angelo

    2015-11-01

    Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions.

  20. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  1. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium oxide greens. 73.1327 Section 73.1327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color...

  2. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (MAY 2011) (a) Definitions. As used...

  3. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium hydroxide green. 73.1326 Section 73.1326... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide...

  4. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 1 2012-04-01 2012-04-01 false Chromium oxide greens. 73.1327 Section 73.1327... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color...

  5. 48 CFR 252.223-7008 - Prohibition of Hexavalent Chromium.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Chromium. 252.223-7008 Section 252.223-7008 Federal Acquisition Regulations System DEFENSE ACQUISITION... of Provisions And Clauses 252.223-7008 Prohibition of Hexavalent Chromium. As prescribed in 223.7306, use the following clause: Prohibition of Hexavalent Chromium (MAY 2011) (a) Definitions. As used...

  6. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  7. 21 CFR 73.3111 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Chromium oxide greens. 73.3111 Section 73.3111... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Medical Devices § 73.3111 Chromium oxide greens. (a) Identity and specifications. The color additive chromium oxide greens (chromic oxide) (CAS Reg. No....

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. 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.

  13. 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.

  14. The Neel temperatures of nanocrystalline chromium

    SciTech Connect

    Fitzsimmons, M.R.; Robinson, R.A.; Eastman, J.A.; Lynn, J.W.

    1994-07-01

    Wide-angle neutron diffraction measurements at temperatures from 6 to 250 K indicate that the major portion of a nanocrystalline chromium sample with a mean grain size of 73 nm becomes antiferromagnetically ordered at 119 {plus_minus} 10 K. The remainder of the sample has a Neel temperature above 250 K, as expected for coarse-grained chromium. No evidence for antiferromagnetic order in a second sample with a mean grain size of 11 nm was observed, even to temperatures as low as 6 K.

  15. Strategies for chromium bioremediation of tannery effluent.

    PubMed

    Garg, Satyendra Kumar; Tripathi, Manikant; Srinath, Thiruneelakantan

    2012-01-01

    Bioremediation offers the possibility of using living organisms (bacteria, fungi, algae,or plants), but primarily microorganisms, to degrade or remove environmental contaminants, and transform them into nontoxic or less-toxic forms. The major advantages of bioremediation over conventional physicochemical and biological treatment methods include low cost, good efficiency, minimization of chemicals, reduced quantity of secondary sludge, regeneration of cell biomass, and the possibility of recover-ing pollutant metals. Leather industries, which extensively employ chromium compounds in the tanning process, discharge spent-chromium-laden effluent into nearby water bodies. Worldwide, chromium is known to be one of the most common inorganic contaminants of groundwater at pollutant hazardous sites. Hexavalent chromium poses a health risk to all forms of life. Bioremediation of chromium extant in tannery waste involves different strategies that include biosorption, bioaccumulation,bioreduction, and immobilization of biomaterial(s). Biosorption is a nondirected physiochemical interaction that occurs between metal species and the cellular components of biological species. It is metabolism-dependent when living biomass is employed, and metabolism-independent in dead cell biomass. Dead cell biomass is much more effective than living cell biomass at biosorping heavy metals, including chromium. Bioaccumulation is a metabolically active process in living organisms that works through adsorption, intracellular accumulation, and bioprecipitation mechanisms. In bioreduction processes, microorganisms alter the oxidation/reduction state of toxic metals through direct or indirect biological and chemical process(es).Bioreduction of Cr6+ to Cr3+ not only decreases the chromium toxicity to living organisms, but also helps precipitate chromium at a neutral pH for further physical removal,thus offering promise as a bioremediation strategy. However, biosorption, bioaccumulation, and

  16. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  17. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

  18. Chromium isotopic anomalies in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.

    1986-01-01

    Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

  19. Magnetic properties of cobalt and chromium clusters

    NASA Astrophysics Data System (ADS)

    Payne, Forrest William

    We have used the Stern-Gerlach deflection technique to study magnetism in cobalt clusters of 13-187 atoms and chromium clusters with between 20-133 atoms. These clusters were observed at temperatures ranging from 60K to 250K and at magnetic field gradients up to 360 T/m. Using superparamagnetic theory we have determined the moment per atom for each cluster size and find enhanced magnetism due to reduced dimensionality of the clusters. Remarkably, we find that we are capable of making chromium clusters in two magnetically distinguishable forms for each cluster size with ≥34 atoms. We attribute this observation to the presence of structural isomers.

  20. Chromium levels in spices and aromatic herbs.

    PubMed

    Garcia, E; Cabrera, C; Lorenzo, M L; López, M C

    2000-02-28

    We determined the presence of chromium in a total of 72 samples of 17 different spices and aromatic herbs. Electrothermal atomization atomic absorption spectrometry (ETA-AAS) was used to determine Cr content in the samples mineralized with HNO3 and V2O5. The analytical characteristics of the proposed method were tested, and the accuracy and precision was also verified against an NBS-certified reference material. Chromium concentrations ranged from not detectable to 1.42 micrograms/g (dry wt.) and Cr presence was detected in 95% of samples. Spices and aromatic herbs are widely consumed in the Spanish diet and in the Mediterranean diet, in general.

  1. Nitrate to ammonia and ceramic (NAC) bench scale stabilization studies. Final technical progress report, May 1995--May 1996

    SciTech Connect

    1996-05-01

    The Department of Energy (DOE) has large quantities of sodium-nitrate based liquid wastes. Around 1 billion liters of high level waste tank supernatant are present at Hanford, Savannah River Plant, Rocky Flats Plant, Idaho National Engineering Laboratory, and Oak Ridge National Laboratory. The largest quantity of these wastes is in the 149 single shell tanks at Hanford which hold up to 1 million gallons each. These tank waste are typically 4 to 5 molar in nitrate and contain radionuclides, various salts, and heavy metals. INEL high-level waste tank supernatant contains about 0.7 and 0.6 grams per liter of chromium and mercury, respectively. SRP high-level waste tank supernatant contains about 0.2 g/L of chromium. Other heavy metals could well be present at lower levels in theses tank wastes. The major components present in these wastes are summarized in Appendix A. These wastes are currently regulated and managed by the DOE. Under the Federal Facility Compliance Act (FFCA) DOE is subject to RCRA, which would apply to these tank supernatants. Stabilization of this waste is difficult because nitrates are very mobile. Additionally, vitrification of these wastes produces large quantities of hard-to-manage NO{sub x} emissions. The conversion of sodium nitrate to ammonia is discussed.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Removal of chromium from wastewater by reverse osmosis

    NASA Astrophysics Data System (ADS)

    Çimen, Aysel

    2015-07-01

    Removal of chromium from wastewaters has been studied and the optimal process conditions were determined. The reverse osmosis (RO) technique, the sea water high rejection (SWHR) and high rejection brackish water (AG, SE, and SG) membranes were used. The chromium rejection depended on membrane type, pH of the feed water and operating pressure. The removal of chromium was most effective when the feed water pH 3. The rejection efficiency of the membranes increased in the order AG > SWHR > SG > SE. RO method can be efficiently used (with >91% rejection) for the removal of chromium from wastewater of chromium coating processes.

  7. The Preparation of Chromium by the Thermal Decomposition of Chromium Iodide

    DTIC Science & Technology

    2014-05-15

    chromium with iodine vapor, the sublimation of the chromium iodide, and its subsequent decomposition on a hot tungsten filament, all in an evacuated...heated with a gas burner while iodine from the bulb was vaporized and passed over it. As the iodine vapor passed over the hot metal, a condensate was v...of iodine was exhausted, the apparatus was broken ~pen and the contents examined. The reaction product was very hygro- scopic, forming a green

  8. Environmental Analysis Focusing on Nitrate and Phosphate of Lake Merced, San Francisco, California

    NASA Astrophysics Data System (ADS)

    Chavez, A.; de La Cruz, C.; Diaz, R.; Snell, J.; Bissell, M.; Rawley, A.; Kirwin, J. P.

    2007-12-01

    Lake Merced is located in the southwest region of San Francisco. The lake is used for recreation by many San Francisco residents, is home to many animals and plants and is an emergency water source for the City of San Francisco. We analyzed the lake for nitrate and phosphate concentrations to determine the ecological health of the lake. High levels of these chemicals increase the risk of eutrophication. Our study finds that the amount of each chemical is below maximum contaminant levels (MCLs). We tested for arsenic, chromium, copper, lead and zinc and found that only arsenic and lead were above the MCL. Additionally, we identified the soils and sands, tested the soil for nitrate and phosphate levels at two sites near large amount of wildlife. We also identified the native and invasive plants around the lake and found that the lake contains a majority of invasive plants. Our overall results show that the lake is healthy but could be improved.

  9. 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.

  10. Chromium(III) and chromium(VI) surface treated galvanized steel for outdoor constructions: environmental aspects.

    PubMed

    Lindström, David; Hedberg, Yolanda; Odnevall Wallinder, Inger

    2010-06-01

    The long-term degradation of chromium(III) (Zn-Cr(III)) and chromium(VI)-based (Zn-Cr(VI)) surface treatments on galvanized steel and their capacities to hinder the release of zinc induced by atmospheric corrosion at nonsheltered urban and marine exposure conditions for 2 years are investigated. Compared to bare zinc sheet, both surface treatments revealed high corrosion protection abilities and capacities to hinder the release of zinc, still evident after 2 years of exposure. The zinc barrier properties of the thinner Zn-Cr(VI) (10 nm) treatment were during the first 100 days of urban exposure slightly improved compared with Zn-Cr(III) (35 nm). However, their long-term protection capacities were inverse. Released concentrations of total chromium correspond to annual release rates less than 0.000032 (Zn-Cr(III)) and 0.00014 g Cr m(-2) yr(-1) (Zn-Cr(VI)) after 1 year of urban exposure. Aging by indoor storage of the surface treatments prior to outdoor exposure reduced the released Cr concentrations from the surface treatments. No Cr(VI) was released from the aged surfaces but from the freshly exposed Zn-Cr(VI). Marine exposure conditions resulted in a faster reduction of chromate to chromium(III)oxide compared with urban conditions, and a significantly lower amount of both chromium(III) and chromium(VI) released from Zn-Cr(VI) at the marine site compared with the urban site.

  11. Biological groundwater treatment for chromium removal at low hexavalent chromium concentrations.

    PubMed

    Mamais, Daniel; Noutsopoulos, Constantinos; Kavallari, Ioanna; Nyktari, Eleni; Kaldis, Apostolos; Panousi, Eleni; Nikitopoulos, George; Antoniou, Kornilia; Nasioka, Maria

    2016-06-01

    The objective of this work is to develop and evaluate biological groundwater treatment systems that will achieve hexavalent chromium reduction and total chromium removal from groundwater at hexavalent chromium (Cr(VI)) groundwater concentrations in the 0-200 μg/L range. Three lab-scale units operated, as sequencing batch reactors (SBR) under aerobic, anaerobic and anaerobic-aerobic conditions. All systems received groundwater with a Cr(VI) content of 200 μg/L. In order to support biological growth, groundwater was supplemented with milk, liquid cheese whey or a mixture of sugar and milk to achieve a COD concentration of 200 mg/L. The results demonstrate that a fully anaerobic system or an anaerobic-aerobic system dosed with simple or complex external organic carbon sources can lead to practically complete Cr(VI) reduction to Cr(III). The temperature dependency of maximum Cr(VI) removal rates can be described by the Arrhenius relationship. Total chromium removal in the biological treatment systems was not complete because a significant portion of Cr(III) remained in solution. An integrated system comprising of an anaerobic SBR followed by a sand filter achieved more than 95% total chromium removal thus resulting in average effluent total and dissolved chromium concentrations of 7 μg/L and 3 μg/L, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Trivalent Chromium Conversion Coatings for Aluminum

    DTIC Science & Technology

    1993-09-27

    salts corrosion. This is without any hexavalent chromium in the bath. The absence of Cr+ 6 was determined by analysis of the bath by atomic absorption spectroscopy and...coating was determined by dissolving the films 5 minutes in 25% (vol.) HC1 at 250 C and analyzing for Cr 20 by atomic absorption spectroscopy . The solution

  13. The role of mitochondria in chromium carcinogenesis

    SciTech Connect

    Rossi, S.C. )

    1987-01-01

    The uptake and reduction of chromium(VI) compounds are crucial to their carcinogenicity. Many cellular systems have been shown to reduce chromium(VI). The ability of mitochondria to reduce chromate in vitro was investigated using rat liver submitochondrial particles (SMPs), which contain the electron transport chain, and isolated rat liver mitochondria. SMPs with NADH as substrate reduced chromate as shown by EPR and UV-VIS spectroscopic studies. Chromate was reduced to a chromium(V) species, which was detectable by EPR. SMPs with succinate as substrate were less effective in reducing chromate relative to NADH-driven chromate-reductase activity. SMPs show a higher rate of oxygen depletion with NADH as substrate as compared to succinate as substrate. In SMPs with NADH as substrate, rotenone, antimycin and cyanide all produced a {approx}40% inhibition of chromate-reductase activity. In SMPs with succinate as substrate, cyanide and antimycin produced {approx}50% inhibition of chromate-reductase activity and rotenone caused no detectable inhibition. In vivo studies of rats injected with sodium dichromate spiked with {sup 51}Cr showed that after 24 hr, chromium was bound preferentially to mitochondrial DNA relative to nuclear DNA by a factor of {approximately}1500.

  14. Chemical behavior of acidified chromium (3) solutions

    SciTech Connect

    Terman, D.K.

    1981-05-01

    A unique energy-storage system has been developed at NASA's Lewis Research Center called REDOX. This NASA-REDOX system is an electrochemical storage device that utilized the oxidation and reduction of two fully soluble redox couples for charging and discharging. The redox couples now being investigated are acidified chloride solutions of chromium (Cr(+2)/Cr(+3)) and iron (Fe(+2)/Fe(+3)).

  15. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... action level for 30 or more days a year; (B) Experiencing signs or symptoms of the adverse health effects...) Whenever an employee shows signs or symptoms of the adverse health effects associated with chromium (VI... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  16. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  17. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... or more days a year; (B) Experiencing signs or symptoms of the adverse health effects associated with... symptoms of the adverse health effects associated with chromium (VI) exposure; (v) Within 30 days after... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  18. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  19. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  20. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... action level for 30 or more days a year; (B) Experiencing signs or symptoms of the adverse health effects...) Whenever an employee shows signs or symptoms of the adverse health effects associated with chromium (VI... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  1. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... or more days a year; (B) Experiencing signs or symptoms of the adverse health effects associated with... symptoms of the adverse health effects associated with chromium (VI) exposure; (v) Within 30 days after... Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED...

  2. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  3. 29 CFR 1910.1026 - Chromium (VI).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... or more days a year; (B) Experiencing signs or symptoms of the adverse health effects associated with... symptoms of the adverse health effects associated with chromium (VI) exposure; (v) Within 30 days after... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  4. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... action level for 30 or more days a year; (B) Experiencing signs or symptoms of the adverse health effects...) Whenever an employee shows signs or symptoms of the adverse health effects associated with chromium (VI... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  5. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... action level for 30 or more days a year; (B) Experiencing signs or symptoms of the adverse health effects...) Whenever an employee shows signs or symptoms of the adverse health effects associated with chromium (VI... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  6. 29 CFR 1926.1126 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  7. 29 CFR 1915.1026 - Chromium (VI).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... of the adverse health effects associated with chromium (VI) exposure; or (C) Exposed in an emergency... additional examination; (iv) Whenever an employee shows signs or symptoms of the adverse health effects... Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR...

  8. Effects of chromium on the immune system.

    PubMed

    Shrivastava, Richa; Upreti, R K; Seth, P K; Chaturvedi, U C

    2002-09-06

    Chromium is a naturally occurring heavy metal found commonly in the environment in trivalent, Cr(III), and hexavalent, Cr(VI), forms. Cr(VI) compounds have been declared as a potent occupational carcinogen among workers in chrome plating, stainless steel, and pigment industries. The reduction of Cr(VI) to Cr(III) results in the formation of reactive intermediates that together with oxidative stress oxidative tissue damage and a cascade of cellular events including modulation of apoptosis regulatory gene p53, contribute to the cytotoxicity, genotoxicity and carcinogenicity of Cr(VI)-containing compounds. On the other hand, chromium is an essential nutrient required to promote the action of insulin in body tissues so that the body can use sugars, proteins and fats. Chromium is of significant importance in altering the immune response by immunostimulatory or immunosuppressive processes as shown by its effects on T and B lymphocytes, macrophages, cytokine production and the immune response that may induce hypersensitivity reactions. This review gives an overview of the effects of chromium on the immune system of the body.

  9. Hygienic behaviour in chromium plating industries.

    PubMed

    Lumens, M E; Ulenbelt, P; Géron, H M; Herber, R F

    1993-01-01

    The impact of hygienic behaviour on the uptake of chromium has been studied in two small chromium plating factories. The correlation between the environmental monitoring measure (Cr-A) and the biological monitoring measure (Cr-U) varied between the two factories. In one factory (I) the correlation between Cr-U and Cr-A was 0.68 (P < 0.001), while in the other factory (II) it was negative (r = -0.64, P = 0.03). However, in both populations a significant impact of hygienic behaviour on the variance in Cr-U levels could be detected. In factory I, explained variance could be enhanced to R2 = 0.94 (P < 0.001) when considering expressions of hygienic behaviour. In factory II, a strong relation proved to exist between Cr-U and dermal uptake. For the various questions referring to skin problems and possible dermal uptake, the correlation with Cr-U is up to 0.70 (P = 0.03). When comparing the results for the two factories, it is shown that in addition to individual differences in hygienic behaviour, general hygienic conditions also have an impact on uptake of chromium. In factory II, where many efforts were made to prevent exposure to chromium, Cr-U was significantly lower than in factory I (P < 0.001).

  10. Dermatitis from a chromium dental plate.

    PubMed

    Hubler, W R; Hubler, W R

    1983-09-01

    Systemic absorption of metal or metallic salts from dental and orthopedic surgical implants can produce a cutaneous allergic dermatitis in susceptible individuals. Mercury, nickel and cobalt are the most common metals to elicit such systemic allergic reactions from chronic internal exposure. A case is presented of a generalized eczematoid dermatitis apparently caused by allergy to chromium liberated from a metal dental plate.

  11. Method for welding chromium molybdenum steels

    DOEpatents

    Sikka, Vinod K.

    1986-01-01

    Chromium-molybdenum steels exhibit a weakening after welding in an area adjacent to the weld. This invention is an improved method for welding to eliminate the weakness by subjecting normalized steel to a partial temper prior to welding and subsequently fully tempering the welded article for optimum strength and ductility.

  12. Nickel-chromium-silicon brazing filler metal

    DOEpatents

    Martini, Angelo J.; Gourley, Bruce R.

    1976-01-01

    A brazing filler metal containing, by weight percent, 23-35% chromium, 9-12% silicon, a maximum of 0.15% carbon, and the remainder nickel. The maximum amount of elements other than those noted above is 1.00%.

  13. The microstructure of chromium-tungsten steels

    NASA Astrophysics Data System (ADS)

    Klueh, R. L.; Maziasz, P. J.

    1989-03-01

    Chromium-tungsten steels are being developed to replace the Cr-Mo steels for fusion-reactor applications. Eight experimental steels were produced and examined by optical and electron microscopy. Chromium concentrations of 2.25, 5, 9 and 12 pct were used. Steels with these chromium compositions and with 2 pct W and 0.25 pct V were produced. To determine the effect of tungsten and vanadium, three other 2.25Cr steels were produced as follows: an alloy with 2 pct W and 0 pct V and alloys with 0 and 1 pct W and 0.25 pct V. A 9Cr steel containing 2 pct W, 0.25 pct V, and 0.07 pct Ta also was studied. For all alloys, carbon was maintained at 0.1 pct. Two pct tungsten was required in the 2.25Cr steels to produce 100 pct bainite (no polygonal ferrite). The 5Cr and 9Cr steels were 100 pct martensite, but the 12Cr steel contained about 25 pct delta-ferrite. Precipitate morphology and precipitate types varied, depending on the chromium content. For the 2.25Cr steels, M3C and M7C3 were the primary precipitates; for the 9Cr and 12Cr steels, M23C6 was the primary precipitate. The 5Cr steel contained M7C3 and M23C6. All of the steels with vanadium also contained MC.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Chromium(II) and chromium(II) tri-tert-butoxysiloxy complexes

    SciTech Connect

    Terry, K.W.; Gantzel, P.K.; Tilley, T.D. )

    1993-11-10

    The authors have been exploring the structure, bonding, and chemistry of transition-metal and main-group complexes that possess oxygen-rich alkoxysiloxy ligands such as [minus]OSi(O[sup t]Bu)[sub 3]. A primary focus of these studies is the development of molecular, single-source precursors to homogeneous, ultrapure metal silicates. The authors have found that titanium, zirconium, hafnium, and aluminum derivatives of [minus]OSi(O[sup t]Bu)[sub 3] thermally decompose at low temperatures (100-200[degrees]C) with elimination of isobutylene and water to give metal-containing silicates. Previous observations suggested the possible use of this methodology in new syntheses of supported catalysts, particularly since chemical reactivities and selectivities are known to be very sensitive to the size and shape of the supported metal catalyst particles. Silica- and aluminosilica-supported chromium catalysts are used widely for the catalytic polymerization of ethylene. To examine alkoxysiloxy derivatives of chromium as precursors to chromium-supported catalysts, the authors have begun to explore synthetic routes to Cr-OSi(O[sup t]Bu)[sub 3] complexes. On the basis of previously reported routes to siloxide and alkoxide complexes of chromium, approaches based on either the silanol HOSi(O[sup t]Bu)[sub 3] or alkali metal derivatives MOSi(O[sup t]Bu)[sub 3] (M = Li, Na, K) as starting materials seem possible. The authors report two siloxide complexes which result from the reaction of Cr(NEt[sub 2])[sub 4] with HOSi(O[sup t]Bu)[sub 3]. While this reaction does not provide a high yield of a single product that can be used in a convenient route to chromium silicate materials, it does offer the opportunity to closely compare analogous chromium(II) and chromium(III) siloxide complexes Cr[OSi(O[sup t]Bu)[sub 3

  19. Chromium supplementation improved post-stroke brain infarction and hyperglycemia.

    PubMed

    Chen, Wen-Ying; Mao, Frank Chiahung; Liu, Chia-Hsin; Kuan, Yu-Hsiang; Lai, Nai-Wei; Wu, Chih-Cheng; Chen, Chun-Jung

    2016-04-01

    Hyperglycemia is common after acute stroke and is associated with a worse outcome of stroke. Thus, a better understanding of stress hyperglycemia is helpful to the prevention and therapeutic treatment of stroke. Chromium is an essential nutrient required for optimal insulin activity and normal carbohydrate and lipid metabolism. Beyond its nutritional effects, dietary supplement of chromium causes beneficial outcomes against several diseases, in particular diabetes-associated complications. In this study, we investigated whether post-stroke hyperglycemia involved chromium dynamic mobilization in a rat model of permanent focal cerebral ischemia and whether dietary supplement of chromium improved post-stroke injury and alterations. Stroke rats developed brain infarction, hyperglycemia, hyperinsulinemia, glucose intolerance, and insulin resistance. Post-stroke hyperglycemia was accompanied by elevated secretion of counter-regulatory hormones including glucagon, corticosterone, and norepinephrine, decreased insulin signaling in skeletal muscles, and increased hepatic gluconeogenesis. Correlation studies revealed that counter-regulatory hormone secretion showed a positive correlation with chromium loss and blood glucose increased together with chromium loss. Daily chromium supplementation increased tissue chromium levels, attenuated brain infarction, improved hyperglycemia, and decreased plasma levels of glucagon and corticosterone in stroke rats. Our findings suggest that stroke rats show disturbance of tissue chromium homeostasis with a net loss through urinary excretion and chromium mobilization and loss might be an alternative mechanism responsible for post-stroke hyperglycemia.

  20. 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.

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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...

  7. 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...

  8. 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...

  9. Analytical Characterization of the Thorium Nitrate Stockpile

    SciTech Connect

    Mattus, CH

    2003-12-30

    For several years, Oak Ridge National Laboratory (ORNL) has been supporting the Defense Logistics Agency-Defense National Stockpile Center with stewardship of a thorium nitrate (ThN) stockpile. The effort for fiscal year 2002 was to prepare a sampling and analysis plan and to use the activities developed in the plan to characterize the ThN stockpile. The sampling was performed in June and July 2002 by RWE NUKEM with oversight by ORNL personnel. The analysis was performed by Southwest Research Institute of San Antonio, Texas, and data validation was performed by NFT, Inc., of Oak Ridge, Tennessee. Of the {approx} 21,000 drums in the stockpile, 99 were sampled and 53 were analyzed for total metals composition, radiological constituents (using alpha and gamma spectrometry), and oxidizing characteristics. Each lot at the Curtis Bay Depot was sampled. Several of the samples were also analyzed for density. The average density of the domestic ThN was found to be 1.89 {+-} 0.08 g/cm{sup 3}. The oxidizer test was performed following procedures issued by the United Nations in 1999. Test results indicated that none of the samples tested was a Division 5.1 oxidizer per Department of Transportation definition. The samples were analyzed for total metals following the U.S. Environmental Protection Agency methods SW-846-6010B and 6020 (EPA 2003) using a combination of inductively coupled plasma--atomic emission spectroscopy and inductively coupled plasma--mass spectroscopy techniques. The results were used to compare the composition of the eight Resource Conservation and Recovery Act metals present in the sample (arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver) to regulatory limits. None of the samples was found to be hazardous for toxicity characteristics. The radiological analyses confirmed, when possible, the results obtained by the inductively coupled plasma analyses. These results--combined with the historical process knowledge acquired on the material

  10. Production of basic chromium sulfate by using recovered chromium from ashes of thermally treated leather.

    PubMed

    Dettmer, Aline; Nunes, Keila Guerra Pacheco; Gutterres, Mariliz; Marcílio, Nilson Romeu

    2010-04-15

    Leather wastes tanned with chromium are generated during the production process of leather, hence the wastes from hand crafted goods and footwear industries are a serious environmental problem. The thermal treatment of leather wastes can be one of the treatment options because the wastes are rich in chromium and can be used as a raw material for sodium chromate production and further to obtain several chromium compounds. The objective of this study was to utilize the chromium from leather wastes via basic chromium sulfate production to be subsequently applied in a hide tanning. The obtained results have shown that this is the first successful attempt to achieve desired base properties of the product. The result was achieved when the following conditions were applied: a molar ratio between sodium sulfite and sodium dichromate equal to 6; reaction time equal to 5 min before addition of sulfuric acid; pH of sodium dichromate solution equal to 2. Summarizing, there is an opportunity to utilize the dangerous wastes and reused them in the production scheme by minimizing or annulling the environmental impact and to attend a sustainable process development concept. 2009 Elsevier B.V. All rights reserved.

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

  18. 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.

  19. 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...

  20. 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.

  1. 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...

  2. 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…

  3. 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…

  4. 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...

  5. 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.

  6. Issues in the risk assessment of chromium.

    PubMed Central

    Albert, R E

    1991-01-01

    Although hexavalent chromium is well established as a human carcinogen by the inhalation route, there are significant uncertainties in the quantitative estimation of cancer risk. One of the important uncertainties is the assumption that the carcinogenic potency, determined under conditions of occupational exposure where most workers were cigarette smokers, applies to the nonsmoking individual in the general population. There is substantial evidence that carcinogenicity is a function of the rate of cell turnover in the target tissue. The chromate worker would be expected to have a relatively high rate of cell proliferation in the bronchial mucosa due to airborne irritants and smoking. The potency of chromium might therefore be relatively high under conditions of occupational exposure. This problem in quantitative risk assessment applies equally well to another important indoor pollutant, radon. PMID:1935856

  7. Interactions of chromium with microorganisms and plants.

    PubMed

    Cervantes, C; Campos-García, J; Devars, S; Gutiérrez-Corona, F; Loza-Tavera, H; Torres-Guzmán, J C; Moreno-Sánchez, R

    2001-05-01

    Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.

  8. Distribution and significance of chromium in meteorites

    NASA Technical Reports Server (NTRS)

    Bunch, T. E.; Olsen, E.

    1975-01-01

    Chromium is present as a minor element in all meteorite types. Depending on the meteorite type it is lithophile (most frequent), chalcophile (less frequent), or siderophile (rare). Chromium is an indicator of physical and chemical conditions of meteorite formation, especially of the state of oxidation. The Cr contents of meteoritic chromites are related to classification and can be used to distinguish among meteorite types that contain this mineral. The distribution of Cr between coexisting pyroxenes may indicate the degree of equilibration of this mineral pair. Siderophile Cr appears to result from primitive condensation processes rather than secondary reduction processes. The lack of much experimental data on Cr in silicate systems limits the interpretation of the occurrences of Cr-silicate phases, ureyite and krinovite, in the meteorite type in which they occur.

  9. Lateral stress evolution in Chromium Sulfide

    NASA Astrophysics Data System (ADS)

    Petel, Oren; Appleby-Thomas, Gareth; Hameed, Amer; Capozzi, Alexander; Frost, David; Hazell, Paul

    2013-06-01

    In this paper the shock response of chromium sulfide, a cermet of potential interest as a matrix material for ballistic applications, has been investigated. Compacts with a Chromium:Sulfur ratio of 1.15:1 were investigated via the plate-impact technique. These experiments allowed the material to be loaded under a one-dimensional state of strain. Embedded manganin stress gauges were employed to monitor the temporal evolution of longitudinal and lateral components of stress. Comparison of these two components has allowed assessment of the variation of material shear strength both with impact pressure/strain-rate and time. Interestingly tentative evidence of what appeared to be an elastic-plastic transition was noted on the lateral traces, despite the absence of a lateral shock.

  10. International strategic minerals inventory summary report; chromium

    USGS Publications Warehouse

    DeYoung, J.H.; Lee, M.P.; Lipin, B.R.

    1984-01-01

    Major world resources of chromium, a strategic mineral commodity, are described in this summary report of information in the International Strategic Minerals Inventory {ISMI}. ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, and the United States of America. This report, designed to be of benefit to policy analysts, contains two parts. Part I presents an overview of the resources and potential supply of chromium on the basis of inventory information. Part II contains tables of some of the geologic information and mineral-resource and production data that were collected by ISMI participants.

  11. New mixed aluminium–chromium diarsenate

    PubMed Central

    Bouhassine, Mohamad Alem; Boughzala, Habib

    2017-01-01

    Potassium chromium aluminium diarsenate, KCr1/4Al3/4As2O7, was prepared by solid-state reaction. The structure consists of (Cr1/4/Al3/4)O6 octa­hedra and As2O7 diarsenate groups sharing corners to build up a three-dimensional anionic framework. The potassium cations are located in wide channels running along the c-axis direction. The crystal structure is isostructural with the triclinic A I M III X 2O7 (A I = alkali metal; M III = Al, Cr, Fe; X = As, P) compounds. However, the M III octa­hedrally coordinated site is 25% partially occupied by chromium and 75% by aluminium. PMID:28316805

  12. Speciation and recovery of chromium from chromite ore processing residues.

    PubMed

    Sreeram, K J; Ramasami, T

    2001-10-01

    The processing of chromite ore is associated with the generation of large quantities of solid wastes containing chromium, which have been disposed of as landfill for many years. The mobilization and operational speciation of chromium contained in soils contaminated with metal salts are important in terms of the environment. Several methods have been employed for the extraction and recovery of solid wastes. Chromium contained in contaminated soils and solid wastes can be categorized as exchangeable, oxidizable, carbonate-bound, reducible and residual. The results from this study indicate a need for efficient leaching methodologies in chromite ore processing plants to decrease the non-detrital fractions of chromium in the residue. Aggressive methodologies are required to recover chromium from the detrital fractions. The potential benefits of employing sodium peroxide for the complete recovery of chromium from chromite residue have been demonstrated, and the need to ensure the safety of the process has been emphasized.

  13. X-616 Chromium Sludge Lagoons pictorial overview, Piketon, Ohio

    SciTech Connect

    Not Available

    1992-10-01

    The Portsmouth Gaseous Diffusion Plant uses large quantities of water for process cooling. The X-616 Liquid Effluent Control Facility was placed in operation in December 1976 to treat recirculation cooling water blowdown from the process cooling system. A chromium-based corrosion inhibitor was used in the cooling water system. A chromium sludge was produced in a clarifier to control chromium levels in the water. Chromium sludge produced by this process was stored in two surface impoundments called the X-616 Chromium Sludge Lagoons. The sludge was toxic due to its chromium concentration and therefore required treatment. The sludge was treated, turning it into a sanitary waste, and buried in an Ohio EPA approved landfill. The plant's process cooling water system has changed to a more environmentally acceptable phosphate-based inhibitor. Closure activities at X-616 began in August 1990, with all construction activities completed in June 1991, at a total cost of $8.0 million.

  14. 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.

  15. The Use of Chromium(III) to Supercharge Peptides by Protonation at Low Basicity Sites

    NASA Astrophysics Data System (ADS)

    Feng, Changgeng; Commodore, Juliette J.; Cassady, Carolyn J.

    2015-02-01

    The addition of chromium(III) nitrate to solutions of peptides with seven or more residues greatly increases the formation of doubly protonated peptides, [M + 2H]2+, by electrospray ionization. The test compound heptaalanine has only one highly basic site (the N-terminal amino group) and undergoes almost exclusive single protonation using standard solvents. When Cr(III) is added to the solution, abundant [M + 2H]2+ forms, which involves protonation of the peptide backbone or the C-terminus. Salts of Al(III), Mn(II), Fe(III), Fe(II), Cu(II), Zn (II), Rh(III), La(III), Ce(IV), and Eu(III) were also studied. Although several metal ions slightly enhance protonation, Cr(III) has by far the greatest ability to generate [M + 2H]2+. Cr(III) does not supercharge peptide methyl esters, which suggests that the mechanism involves interaction of Cr(III) with a carboxylic acid group. Other factors may include the high acidity of hexa-aquochromium(III) and the resistance of Cr(III) to reduction. Nitrate salts enhance protonation more than chloride salts and a molar ratio of 10:1 Cr(III):peptide produces the most intense [M + 2H]2+. Cr(III) also supercharges numerous other small peptides, including highly acidic species. For basic peptides, Cr(III) increases the charge state (2+ versus 1+) and causes the number of peptide molecules being protonated to double or triple. Chromium(III) does not supercharge the proteins cytochrome c and myoglobin. The ability of Cr(III) to enhance [M + 2H]2+ intensity may prove useful in tandem mass spectrometry because of the resulting overall increase in signal-to-noise ratio, the fact that [M + 2H]2+ generally dissociate more readily than [M + H]+, and the ability to produce [M + 2H]2+ precursors for electron-based dissociation techniques.

  16. The Use of Chromium(III) to Supercharge Peptides by Protonation at Low Basicity Sites

    PubMed Central

    Feng, Changgeng; Commodore, Juliette J.; Cassady, Carolyn J.

    2014-01-01

    The addition of chromium(III) nitrate to solutions of peptides with seven or more residues greatly increases the formation of doubly protonated peptides, [M+2H]2+, by electrospray ionization. The test compound heptaalanine has only one highly basic site (the N-terminal amino group) and undergoes almost exclusive single protonation using standard solvents. When Cr(III) is added to the solution, abundant [M+2H]2+ forms, which involves protonation of the peptide backbone or the C-terminus. Salts of Al(III), Mn(II), Fe(III), Fe(II), Cu(II), Zn (II), Rh(III), La(III), Ce(IV), and Eu(III) were also studied. While several metal ions slightly enhance protonation, Cr(III) has by far the greatest ability to generate [M+2H]2+. Cr(III) does not supercharge peptide methyl esters, which suggests that the mechanism involves interaction of Cr(III) with a carboxylic acid group. Other factors may include the high acidity of hexaaquochromium(III) and the resistance of Cr(III) to reduction. Nitrate salts enhance protonation more than chloride salts and a molar ratio of 10:1 Cr(III):peptide produces the most intense [M+2H]2+. Cr(III) also supercharges numerous other small peptides, including highly acidic species. For basic peptides, Cr(III) increases the charge state (2+ versus 1+) and causes the number of peptide molecules being protonated to double or triple. Chromium(III) does not supercharge the proteins cytochrome c and myoglobin. The ability of Cr(III) to enhance [M+2H]2+ intensity may prove useful in tandem mass spectrometry because of the resulting overall increase in signal-to-noise ratio, the fact that [M+2H]2+ generally dissociate more readily than [M+H]+, and the ability to produce [M+2H]2+ precursors for electron-based dissociation techniques. PMID:25395012

  17. Chromium Toxicity: Reductive Enzymes in Humans.

    DTIC Science & Technology

    2007-11-02

    internal organs (e.g. lungs, liver, kidneys) [24,27,64], pulmonary fibrosis and chronic bronchitis [2], skin ulcers and allergic dermatitis [2], and...cross the skin [2] and are readily transported across cell membranes [18] via an anion carrier [6]. Cr compounds are also mutagenic [67], and the bulk of...reduced nicotinamide adenine dinucleotide phosphate-cytochrome P450 oxidoreductase- dependent chromium(VI) reduction. Analyst 120:935-938. 42. Miura, A

  18. Method for welding chromium molybdenum steels

    SciTech Connect

    Sikka, V.K.

    1986-09-16

    A process is described for welding chromium-molybdenum steels which consist of: subjecting the steel to normalization by heating to above the transformation temperature and cooling in air; subjecting the steel to a partial temper by heating to a temperature less than a full temper; welding the steel using an appropriate filler metal; subjecting the steel to a full temper by heating to a temperature sufficient to optimize strength, reduce stress, increase ductility and reduce hardness.

  19. Laser action in chromium-doped forsterite

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.; Yamagishi, Kiyoshi; Anzai, H.

    1988-01-01

    This paper reports on pulsed laser operation obtained in chromium-activated forsterite Cr(3+):Mg2SiO4 at room temperature. The spectrum of the free-running laser peaks at 1235 nm and a bandwidth of about 22 nm. The spectral range of the laser emission is expected to extend from 850 to 1300, provided the parasitic impurity absorption may be minimized by improved crystal growth techique.

  20. Observational Approach to Chromium Site Remediation - 13266

    SciTech Connect

    Scott Myers, R.

    2013-07-01

    Production reactors at the U.S. Department of Energy's (DOE) Hanford Site in Richland, Washington, required massive quantities of water for reactor cooling and material processing. To reduce corrosion and the build-up of scale in pipelines and cooling systems, sodium dichromate was added to the water feedstock. Spills and other releases at the makeup facilities, as well as leaks from miles of pipelines, have led to numerous areas with chromium-contaminated soil and groundwater, threatening fish populations in the nearby Columbia River. Pump-and-treat systems have been installed to remove chromium from the groundwater, but significant contamination remain in the soil column and poses a continuing threat to groundwater and the Columbia River. Washington Closure Hanford, DOE, and regulators are working on a team approach that implements the observational approach, a strategy for effectively dealing with the uncertainties inherent in subsurface conditions. Remediation of large, complex waste sites at a federal facility is a daunting effort. It is particularly difficult to perform the work in an environment of rapid response to changing field and contamination conditions. The observational approach, developed by geotechnical engineers to accommodate the inherent uncertainties in subsurface conditions, is a powerful and appropriate method for site remediation. It offers a structured means of quickly moving into full remediation and responding to the variations and changing conditions inherent in waste site cleanups. A number of significant factors, however, complicate the application of the observational approach for chromium site remediation. Conceptual models of contamination and site conditions are difficult to establish and get consensus on. Mid-stream revisions to the design of large excavations are time-consuming and costly. And regulatory constraints and contract performance incentives can be impediments to the flexible responses required under the observational

  1. Laser action in chromium-doped forsterite

    NASA Technical Reports Server (NTRS)

    Petricevic, V.; Gayen, S. K.; Alfano, R. R.; Yamagishi, Kiyoshi; Anzai, H.

    1988-01-01

    This paper reports on pulsed laser operation obtained in chromium-activated forsterite Cr(3+):Mg2SiO4 at room temperature. The spectrum of the free-running laser peaks at 1235 nm and a bandwidth of about 22 nm. The spectral range of the laser emission is expected to extend from 850 to 1300, provided the parasitic impurity absorption may be minimized by improved crystal growth techique.

  2. Effects of hexavalent chromium on performance and microbial community of an aerobic granular sequencing batch reactor.

    PubMed

    Wang, Zichao; Gao, Mengchun; She, Zonglian; Jin, Chunji; Zhao, Yangguo; Yang, Shiying; Guo, Liang; Wang, Sen

    2015-03-01

    The performance and microbial community of an aerobic granular sequencing batch reactor (GSBR) were investigated at different hexavalent chromium (Cr(VI)) concentrations. The COD and NH4 (+)-N removal efficiencies decreased with the increase in Cr(VI) concentration from 0 to 30 mg/L. The specific oxygen utilization rate (SOUR) decreased from 34.86 to 12.18 mg/(g mixed liquor suspended sludge (MLSS)·h) with the increase in Cr(VI) concentration from 0 to 30 mg/L. The specific ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), and specific nitrate reduction rate (SNRR) decreased with the increase in Cr(VI) concentration, whereas the SNRR was always higher than the sum of SAOR and SNOR at 0-30 mg/L Cr(VI). The scanning electron micrographs (SEM) showed some undefined particles on the surface of filamentous bacteria that might be the chelation of chromium and macromolecular organics at 30 mg/L Cr(VI). The denaturing gradient gel electrophoresis (DGGE) profiles revealed that some microorganisms adapting to high Cr(VI) concentration gradually became the predominant bacteria, while others without Cr(VI)-tolerance capacity tended to deplete or weaken. Some bacteria could tolerate the toxicity of high Cr(VI) concentration in the aerobic GSBR, such as Propionibacteriaceae bacterium, Ochrobactrum anthropi, and Micropruina glycogenica.

  3. Chromium oxidation state mapping in human cells

    NASA Astrophysics Data System (ADS)

    Ortega, R.; Fayard, B.; Salomé, M.; Devès, G.; Susini, J.

    2003-03-01

    The widespread use of chromium in industrial applications such as chemical production of pigments, refractory brick production, tanning, metallurgy, electroplating, and combustion of fuels has lead to human occupational exposure and to its increased introduction into the environment. Hexavalent chromium compounds are established carcinogens but their mechanism of cell transformation is not known. Up to now, no microanalytical technique was sensitive enough to allow the observation of chromium distribution, and oxidation state identification, within isolated cells at carcinogenic concentrations. In this experiment, we used successfully the ID-21 X-ray microscope to map Cr(VI) and total Cr distributions in cells exposed in vitro to soluble, and insoluble, Cr(VI) compounds. Exposure to soluble compounds, weak carcinogens, resulted in a homogeneous intracellular distribution of Cr, confirming by in situ measurement that Cr is present in the cell nucleus. Cr(VI) was never detected in cells which suggests a mechanism of rapid intracellular reducticn. On the other hand, exposure to insoluble compounds, strong carcinogens, also resulted in a homogeneous distribution of reduced forms of Cr in cells, and their nucleus. However, in this case, Cr(VI)-rich structures were observed into the cells suggesting that carcinogenicity is enhanced when oxidation reactions due to Cr(VI) chronic exposure are associated to Cr-DNA alterations.

  4. Comparative kinetics of bacterial reduction of chromium

    SciTech Connect

    Schmieman, E.A.; Yonge, D.R.; Rege, M.A.; Petersen, J.N.; Johnstone, D.L.; Turick, C.E.; Apel, W.A.

    1998-05-01

    Most previous studies of bacterial reduction of chromium have been done with pure cultures that are not likely to be found in ground water, and at hexavalent chromium concentrations much greater than typically present in contaminated ground water. Further, most previous work has been performed with complex laboratory substrates that would not be suitable for in situ application. In this study, mixed cultures were enriched from three diverse soil sources: surface soil, subsurface soil, and river sediment. The enrichment medium contained 10 mg Cr{sup 6+}/L and sucrose as the carbon source. The three mixed cultures obtained from the diverse soil samples were transferred to batch reactors and exhibited similar chromium reduction enzyme kinetics at stationary phase. The maximum specific reduction rates were between 0.98 and 3.3 mg Cr{sup 6+}/(g dry cells {center_dot} h) and the half velocity constants were between 0.39 and 1.48 mg Cr{sup 6+}/L. The relatively narrow range of values for kinetic parameters suggests that a conservative engineering design for in situ remediation could be applied over a wide range of contaminated sites at the Cr(VI) concentrations examined.

  5. Dimensionally Controlled Lithiation of Chromium Oxide

    SciTech Connect

    Fister, Tim T.; Hu, Xianyi; Esbenshade, Jennifer; Chen, Xiao; Wu, Jinsong; Dravid, Vinayak; Bedzyk, Michael; Long, Brandon; Gewirth, Andrew A.; Shi, Bing; Schlepütz, Christian M.; Fenter, Paul

    2016-01-12

    Oxide conversion reactions are an alternative approach for high capacity lithium ion batteries but are known to suffer from structural irreversibility associated with the phase separation and reconstitution of reduced metal species and Li2O. In particular, the morphology of the reduced metal species is thought to play a critical role in the electrochemical properties of a conversion material. Here we use a model electrode with alternating layers of chromium and chromium oxide to better understand and control these phase changes in real-time and at molecular length scales. Despite lacking crystallinity at the atomic scale, this superstructure is observed (with X-ray reflectivity, XR) to lithiate and delithiate in a purely one-dimensional manner, preserving the layered structure. The XR data show that the metal layers act as nucleation sites for the reduction of chromium in the conversion reaction. Irreversibility during delithiation is due to the formation of a ternary phase, LiCrO2, which can be further delithiated at higher potentials. The results reveal that the combination of confining lithiation to nanoscale sheets of Li2O and the availability of reaction sites in the metal layers in the layered structure is a strategy for improving the reversibility and mass transport properties that can be used in a wide range of conversion materials.

  6. Magnetism in chromium and terbium clusters

    NASA Astrophysics Data System (ADS)

    Deng, Jun

    We report the results of Stem-Gerlach type molecular beam deflection experiments on the magnetic properties of chromium and terbium clusters. We find that chromium clusters of 13 to 156 atoms exhibit non-zero magnetic moments at temperatures between 63 K and 123 K. The internal magnetic moments of these clusters are very much size-dependent. These clusters are also found to have two or more magnetic isomers with great differences in magnetism. These chromium clusters provide the first observation of strong magnetic responses in clusters composed of a material that is antiferromagnetic in the bulk. We also report magnetic properties of terbium clusters of 2 to 36 atoms. At certain temperature, the clusters are either superparamagnetic or locked-moment, or semilocked- moment. The magnetic responses of clusters depend greatly on the temperature and cluster size. The observation of the reduced magnetic moments compared to the bulk value, along with the increasing magnetic moment with increasing temperature for superparamagnetic clusters indicates that the spin canting diminishes with increasing temperature.

  7. Robust Ferromagnetism of Chromium Nanoparticles Formed in Superfluid Helium.

    PubMed

    Yang, Shengfu; Feng, Cheng; Spence, Daniel; Al Hindawi, Aula M A A; Latimer, Elspeth; Ellis, Andrew M; Binns, Chris; Peddis, Davide; Dhesi, Sarnjeet S; Zhang, Liying; Zhang, Yafei; Trohidou, Kalliopi N; Vasilakaki, Marianna; Ntallis, Nikolaos; MacLaren, Ian; de Groot, Frank M F

    2017-01-01

    Chromium nanoparticles are formed using superfluid helium droplets as the nanoreactors, which are strongly ferromagnetic. The transition from antiferromagentism to ferromagnetism is attributed to atomic-scale disorder in chromium nanoparticles, leading to abundant unbalanced surface spins. Theoretical modeling confirms a frustrated aggregation process in superfluid helium due to the antiferromagnetic nature of chromium. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Chromium coatings to reduce radiation buildup. Final report

    SciTech Connect

    Galbraith, G.T.; Asay, R.H.; Asay, D.J.

    1995-12-01

    For the past several years, the Electric Power Research Institute (EPRI) has been intensively investigating new methods to mitigate radiation buildup on out-of-core surfaces in light water reactors to reduce occupational radiation exposure. As a result of this work, a new surface preconditioning method termed stabilized chromium has been developed for pretreatment of reactor piping and other components. This treatment method has been shown to be highly effective in retarding radiation buildup. Initial coupon tests of stabilized chromium treatment, an EPRI patented process, showed very favorable results. EPRI is now sponsoring additional development and testing of this preconditioning technique. The specific goals of this project were to investigate the effects of various chromium plating bath compositions, define acceptable chromium plating parameters, and demonstrate the benefit of stabilized chromium treatment by preconditioning actual plant components. Presently, two steam generator manway diaphragms installed at Millstone-2 have been treated with stabilized chromium and are being exposed to primary coolant. After exposure for one fuel cycle the stabilized chromium surfaces had approximately ten times less activity buildup than electropolished-only reference surfaces. Two pipes in the residual heat removal system of Diablo Canyon Unit 2 have also been treated with stabilized and non-stabilized chromium. Initial gamma spectroscopy measurements of these pipes showed the pipe treated with stabilized chromium had the lowest activity buildup. Additional tests of stabilized and non-stabilized chromium films applied to coupon specimens were also conducted at the Doel-2 reactor to evaluate the effect of chromium film thickness on activity buildup. These tests showed thin stabilized chromium films (ca. 3,000 {angstrom}) to be highly effective in retarding activity buildup with reduction factors ranging from 100--150 in comparison to electropolished-only coupons.

  9. Contingency plans for chromium utilization. Publication NMAB-335

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The United States depends entirely on foreign sources for the critical material, chromium, making it very vulnerable to supply disruptions. The effectiveness of programs such as stockpiling, conservation, and research and development for substitutes to reduce the impact of disruption of imports of chromite and ferrochromium are discussed. Alternatives for decreasing chromium consumption also are identified for chromium-containing materials in the areas of design, processing, and substitution.

  10. Purification of spent chromium bath by membrane electrolysis.

    PubMed

    Korzenowski, C; Rodrigues, M A S; Bresciani, L; Bernardes, A M; Ferreira, J Z

    2008-04-15

    The present study deals with the purification of spent chromium bath contaminated by trivalent chromium, iron and aluminum. The ionic transfer of Fe(III) depends on the presence of chloride ions on the pH while aluminum transfer is not affected by chromium(III) chloride. Five different commercial cation-exchange membranes were used. Nafion and PC-SK membranes showed the best results for trivalent iron and aluminum transfer.

  11. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 27 2014-07-01 2014-07-01 false Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces XII Appendix XII to Part 266... Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  12. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 28 2012-07-01 2012-07-01 false Nickel or Chromium-Bearing Materials... FACILITIES Pt. 266, App. XII Appendix XII to Part 266—Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery Furnaces A. Exempt Nickel or Chromium-Bearing Materials...

  13. 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

  14. 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

  15. 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.

  16. Studies on the essentiality of chromium in ruminants

    SciTech Connect

    Samsell, L.J.; Spears, J.W.

    1986-03-01

    Although chromium has been established as an essential trace element for certain animal species, no requirement has been shown for ruminants. Sixteen female lambs (35 kg) were used in an attempt to determine if chromium is essential in the ruminant. Animals were individually housed in all plastic pens and fed twice daily either a low chromium (100 ppb) torula yeast based diet or the basal diet supplemented with 10 ppm chromium as CrCl/sub 3/. Blood samples obtained prior to the morning feeding and 2 and 6 hr post-feeding on days 28 and 56 indicated no significant treatment differences in plasma glucose or serum free fatty acids. By day 56, serum cholesterol tended to be lower in chromium supplemented lambs (60.9 vs 71.7 mg/dl). Lambs in the chromium supplemented treatment also tended to gain more efficiently through 56 days (.130 vs .118 gain/fed). On day 84, lambs were bled after a 48 hr fast, refed, then bled again at 2 and 6 hr post-feeding. Plasma glucose and serum free fatty acids were not affected by chromium at the end of the 48 hr fast or when lambs were refed following fasting. At 84 days both total serum cholesterol and HDL-cholesterol were lower in lambs receiving supplemental chromium. These results suggest that chromium may have a biological role in the ruminant.

  17. Stabilization and solidification of chromium-contaminated soil

    SciTech Connect

    Cherne, C.A.; Thomson, B.M.; Conway, R.

    1997-11-01

    Chromium-contaminated soil is a common environmental problem in the United States as a result of numerous industrial processes involving chromium. Hexavalent chromium [Cr(VI)] is the species of most concern because of its toxicity and mobility in groundwater. One method of diminishing the environmental impact of chromium is to reduce it to a trivalent oxidation state [Cr(III)], in which it is relatively insoluble and nontoxic. This study investigated a stabilization and solidification process to minimize the chromium concentration in the Toxicity Characteristic Leaching Procedure (TCLP) extract and to produce a solidified waste form with a compressive strength in the range of 150 to 300 pounds per square inch (psi). To minimize the chromium in the TCLP extract, the chromium had to be reduced to the trivalent oxidation state. The average used in this study was an alluvium contaminated with chromic and sulfuric acid solutions. The chromium concentration in the in the in situ soil was 1212 milligrams per kilogram (mg/kg) total chromium and 275 mg/kg Cr(VI). The effectiveness of iron, ferrous sulfate to reduce Cr(VI) was tested in batch experiments.

  18. Safety assessment of chromium by exposure from cosmetic products.

    PubMed

    Hwang, Myungsil; Yoon, Eun Kyung; Kim, Ja Young; Son, Bo Kyung; Yang, Seong Jun; Yun, Mi Ok; Choi, Sang Sook; Jang, Dong Deuk; Yoo, Tae Moo

    2009-02-01

    Low level impurities often reside in cosmetic products. The aim of the present study was to estimate the human exposure to chromium from cosmetic products purchased at a local market in South Korea, and to assess the risk on public health. Hexavalent chromium is an impurity substance that contaminates cosmetic products during manufacture. The potential for chromium to induce and elicit allergic contact dermatitis, as well as the degree of chromium exposure from cosmetic products, were assessed. Chromium exposure was estimated using the chromium concentrations found in cosmetic samples taken from the local market along with the expected user pattern data that was taken from the literature. Of the cosmetics we tested and available for purchase on the Korean market, seven had chromium contents above the detection limit of 0.1 ppm (0.1 microg/mL), ranging from 0.2 to 3.15 ppm. In risk assessment, scientifically defensible dose-response relationships must be established for the end points of concern. In the case of chromium contaminated cosmetic products, this includes conducting dose-response assessments for allergic contact dermatitis following dermal exposure. This dose-response information can then be integrated with site-specific exposure assessments to regulate consumer safety by use of these products. We found that dermal exposure to chromium concentrations ranging from 0.0002 to 0.003 microg/cm(2) does not appear to cause concern for eliciting allergic contact dermatitis.

  19. Chromium: is it essential, pharmacologically relevant, or toxic?

    PubMed

    Vincent, John B

    2013-01-01

    Over fifty years ago, the element chromium (as the trivalent ion) was proposed to be an essential element for mammals with a role in maintaining proper carbohydrate and lipid metabolism. Evidence for an essential role came from dietary studies with rodents, studies on the effects of chromium on subjects on total parenteral nutrition, and studies of the absorption and transport of chromium. Over the next several decades, chromium-containing nutritional supplements became so popular for weight loss and muscle development that sales were second only to calcium among mineral supplements. However, the failure to identify the responsible biomolecules(s) that bind chromium(III) and their mode of action, particularly a postulated species named glucose tolerance factor or GTF, resulted in the status of chromium being questioned in recent years, such that the question of its being essential needs to be formally readdressed. At the same time as chromium(III)'s popularity as a nutritional supplement was growing, concerns over its safety appeared. While chromium has been conclusively shown not to have beneficial effects on body mass or composition and should be removed from the list of essential trace elements, chromium(III) compounds are generally nontoxic and have beneficial pharmacological effects in rodents models of insulin insensitivity, although human studies have not conclusively shown any beneficial effects. Mechanisms have been proposed for these pharmacological effects, but all suffer from a lack of consistent supporting evidence.

  20. Chromium recycling of tannery waste through microbial fermentation.

    PubMed

    Katsifas, E A; Giannoutsou, E; Lambraki, M; Barla, M; Karagouni, A D

    2004-02-01

    An Aspergillus carbonarius isolate, selected from an established microbial culture collection, was used to study the biodegradation of chromium shavings in solid-state fermentation experiments. Approximately 97% liquefaction of the tannery waste was achieved and the liquid obtained from long-term experiments was used to recover chromium. The resulting alkaline chromium sulfate solution was useful in tanning procedures. A proteinaceous liquid was also obtained which has potential applications as a fertilizer or animal feed additive and has several other industrial uses. The A. carbonarius strain proved to be a very useful tool in tannery waste-treatment processes and chromium recovery in the tanning industries.

  1. Method of trivalent chromium concentration determination by atomic spectrometry

    DOEpatents

    Reheulishvili, Aleksandre N.; Tsibakhashvili, Neli Ya.

    2006-12-12

    A method is disclosed for determining the concentration of trivalent chromium Cr(III) in a sample. The addition of perchloric acid has been found to increase the atomic chromium spectrometric signal due to Cr(III), while leaving the signal due to hexavalent chromium Cr(VI) unchanged. This enables determination of the Cr(III) concentration without pre-concentration or pre-separation from chromium of other valences. The Cr(III) concentration may be measured using atomic absorption spectrometry, atomic emission spectrometry or atomic fluorescence spectrometry.

  2. 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.

  3. 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

  4. Determination of chromium in estuarine waters by catalytic cathodic stripping voltammetry using a vibrating silver amalgam microwire electrode.

    PubMed

    Espada-Bellido, Estrella; Bi, Zhaoshun; van den Berg, Constant M G

    2013-02-15

    Chromium (Cr(VI)) in water can be determined by adsorptive catalytic cathodic stripping voltammetry in the presence of diethylenetriaminepentaacetic acid (DTPA) and nitrate on the hanging mercury drop electrode (HMDE). Predominately Cr(VI) is detected and the water is UV-digested to convert all Cr to Cr(VI) prior to analysis. We develop here an alternative to the HMDE by using a silver amalgam electrode based on a vibrating microwire. The microwire electrodes were 12.5 μm in diameter and electrochemically coated with mercury, and were stable for a week. Conditions were re-optimised, and we used a DTPA concentration of 5mM, 30 mM acetate pH buffer (pH 5.5 in seawater and pH 5.8 in pure water), and 1.5M nitrate solution. The microwire was reactivated prior to each scan by applying a negative potential (-3V) for 2s which removed all deposited Cr. The detection limit for chromium in pH buffer was found to be 0.2 nM Cr(VI) and in seawater 0.3 nM Cr(VI) at a deposition time of 30s. The response increased linearly with the concentration of Cr(VI) up to 60 nM Cr(VI) in seawater. The limit of detection is less good than using the HMDE, but the linear range is good and the microwire electrode could form the basis of apparatus for flow-analysis. The method was successfully tested on water samples from the estuary of the river Mersey (Liverpool Bay) giving chromium concentrations between 1.48 nM and 2.29 nM. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. 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.

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. 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.

  11. 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.

  12. 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.

  13. A potentiometric rhodamine-B based membrane sensor for the selective determination of chromium ions in wastewater.

    PubMed

    Hassan, Saad S M; El-Shahawi, M S; Othman, A M; Mosaad, M A

    2005-06-01

    The construction and performance characteristics of a novel chromate ion-selective membrane sensor are described and used for determining chromium(III) and chromium(VI) ions. The sensor is based on the use of a rhodamine-B chromate ion-associate complex as an electroactive material in a poly(vinyl chloride) membrane plasticized with o-nitrophenyloctyl ether as a solvent mediator. In a phosphate buffer solution of pH 6 - 7, the sensor displays a stable, reproducible and linear potential response over the concentration range of 1 x 10(-1) - 5 x 10(-6) mol l(-1) with an anionic Nernstian slope of 30.8 +/- 0.5 mV decade(-1) and a detection limit of 1 x 10(-6) mol l(-1) Cr(VI). High selectivity for Cr(VI) is offered over many common anions (e.g., I-, Br-, Cl-, IO4-, CN-, acetate, oxalate, citrate, sulfate, phosphate, thiosulfate, selenite, nitrate) and cations (e.g., Ag+, Ca2+, Sr2+, Co2+, Ni2+, Cu2+, Mn2+, Fe2+, Zn2+, Cd2+, Al3+, Cr3+). The sensor is used for determining Cr(VI) and/or Cr(III) ions in separate or mixed solutions after the oxidation of Cr(III) into Cr(VI) with H2O2. As low as 0.2 microg ml(-1) of chromium is determined with a precision of +/-1.2%. The chromium contents of some wastewater samples were accurately assessed, and the results agreed fairly well with data obtained by atomic absorption spectrometry.

  14. 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

  15. 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.

  16. Chromium adsorption and Cr(VI) reduction to trivalent chromium in aqueous solutions by soya cake.

    PubMed

    Daneshvar, N; Salari, D; Aber, S

    2002-09-02

    Chromium as Cr(VI) is a industrially produced pollutant. Hexavalent chromium can be reduced to the trivalent state using various reductive agents or it can be removed from solution by surface-active adsorbents. In this study, both of these methods were evaluated using soya cake. A high efficiency for reduction of Cr(VI) to trivalent chromium was observed at pH < 1. Increasing the temperature, also increased the yield. Experimentally, the optimum time and soya cake mass were 5h and 0.7 g, respectively. In the second treatment method, a high efficiency for adsorption of chromium was also observed at pH < 1. The favorable temperature for adsorption was found to be 20 degrees C. Experimentally, the best time was 1h and with increasing soya cake mass up to 30 g, the adsorption efficiency was increased. Dissolution of LiCl in the experimental solutions, increased the efficiency of adsorption, however, this effect was not observed in the case of KCl. Langmuir isotherm constants, Q and b, for ground soybeans, were found to be 2.8 x 10(-4)mg/mg and 0.623, respectively. Freundlich isotherm constants, K(f) and n, were found to be 1.4 x 10(-4) and 4.99, respectively.

  17. A Laboratory Procedure for the Reduction of Chromium(VI) to Chromium(III).

    ERIC Educational Resources Information Center

    Lunn, George; Sansone, Eric B.

    1989-01-01

    Chromium(VI) compounds are classified as oxidizers and must be specially packaged and transported for disposal while Cr(III) compounds are considered nonoxidizers. A process which reduces Cr(VI) to Cr(III) by adding sodium metabisulfite followed by neutralization with magnesium hydroxide is explored. (MVL)

  18. A Laboratory Procedure for the Reduction of Chromium(VI) to Chromium(III).

    ERIC Educational Resources Information Center

    Lunn, George; Sansone, Eric B.

    1989-01-01

    Chromium(VI) compounds are classified as oxidizers and must be specially packaged and transported for disposal while Cr(III) compounds are considered nonoxidizers. A process which reduces Cr(VI) to Cr(III) by adding sodium metabisulfite followed by neutralization with magnesium hydroxide is explored. (MVL)

  19. COST EFFECTIVE CONTROL OF HEXAVALENT CHROMIUM AIR EMISSIONS FROM FUNCTIONAL CHROMIUM ELECTROPLATING

    EPA Science Inventory

    This paper will summrize thie pollution prevention (p2) method to control stack emissions from hard chromium plating operations performed by the USEPA's National Risk Management Research Laboratory (NRMRL) over the last four years. During literature research and user surveys, it...

  20. COST EFFECTIVE CONTROL OF HEXAVALENT CHROMIUM AIR EMISSIONS FROM FUNCTIONAL CHROMIUM ELECTROPLATING

    EPA Science Inventory

    This paper will summrize thie pollution prevention (p2) method to control stack emissions from hard chromium plating operations performed by the USEPA's National Risk Management Research Laboratory (NRMRL) over the last four years. During literature research and user surveys, it...

  1. Ultra low nanowear in novel chromium/amorphous chromium carbide nanocomposite films

    NASA Astrophysics Data System (ADS)

    Yate, Luis; Martínez-de-Olcoz, Leyre; Esteve, Joan; Lousa, Arturo

    2017-10-01

    In this work, we report the first observation of novel nanocomposite thin films consisting of nanocrystalline chromium embedded in an amorphous chromium carbide matrix (nc-Cr/a-CrC) with relatively high hardness (∼22,3 GPa) and ultra low nanowear. The films were deposited onto silicon substrates using a magnetic filtered cathodic arc deposition system at various negative bias voltages, from 50 to 450 V. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) suggested the co-existence of chromium and chromium carbide phases, while high resolution transmission electron microscopy (HRTEM) confirmed the presence of the nc-Cr/a-CrC structure. The friction coefficient measured with the ball-on disk technique and the nanowear results showed a strong correlation between the macro and nano-tribological properties of the samples. These novel nanocomposite films show promising properties as solid lubricant and wear resistant coatings with relatively high hardness, low friction coefficient and ultra low nanowear.

  2. Electronic and magnetic structure of chromium surfaces and chromium monolayers on iron

    SciTech Connect

    Victora, R.H.; Falicov, L.M.

    1985-05-01

    Chromium surfaces and Cr monolayers atop Fe have greatly enhanced magnetizations relative to bulk. The Cr (100) surface is ferromagnetic with a spin polarization of 3.00; the (110) surface is antiferromagnetic. A Cr monolayer is ferromagnetic atop either the (100) or (110) Fe surfaces; the former has a large polarization of 3.63.

  3. Diffusion of hexavalent chromium in chromium-containing slag as affected by microbial detoxification.

    PubMed

    Wang, Yunyan; Yang, Zhihui; Chai, Liyuan; Zhao, Kun

    2009-09-30

    An electrochemical method was used to determine the diffusion coefficient of chromium(VI) in chromium-containing slag. A slag plate was prepared from the original slag or the detoxified slag by Achromobacter sp. CH-1. The results revealed that the apparent diffusion coefficient of Cr(VI) was 4.4 x 10(-9)m(2)s(-1) in original slag and 2.62 x 10(-8)m(2)s(-1) in detoxified slag. The results implied that detoxification of chromium-containing slag by Achromobacter sp. CH-1 could enhance Cr(VI) release. Meanwhile, the results of laboratory experiment showed that the residual total Cr(VI) in slag decreased from an initial value of 6.8 mg g(-1) to 0.338 mg g(-1) at the end of the detoxification process. The Cr(VI) released from slag was also reduced by Achromobacter sp. CH-1 strain since water soluble Cr(VI) in the leachate was not detected after 4 days. Therefore, Achromobacter sp. CH-1 has potential application for the bio-detoxification of chromium-containing slag.

  4. 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

  5. Urinary chromium concentrations in humans following ingestion of safe doses of hexavalent and trivalent chromium: Implications for biomonitoring

    SciTech Connect

    Finley, B.L.; Scott, P.K.; Norton, R.L.

    1996-08-09

    This study evaluates the significance of increased urinary chromium concentrations as a marker of chromium exposure and potential health risk. Six human volunteers ingested trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)] at doses that are known to be safe but higher than typical levels. The following dosing regimen was used: d 1-7, 200 {mu}g/d chromium picolinate; d 8-10, Cr(VI) ingestion at the U.S. Environmental Protection Agency (EPA) reference dose (RfD) of 0.005 mg/kg/d; d 11-13, no dose; d 14-16, Cr(III) ingestion at the U.S. EPA RfD of 1.0 mg/kg/d; and 17-18, postdose. Findings are as follows: (1) ingestion of 200 {mu}g/d of chromium picolinate yielded significantly elevated urine concentrations such that each participant routinely exceeded background, (2) ingestion of the Cr(VI) RfD (0.005 mg/kg/d) yielded individual mean urinary chromium levels (1.2-2.3 {mu}g/L) and a pooled mean urinary chromium level (2.4 {mu}g/L) that significantly exceeded background, and (3) ingestion of the Cr(III) RfD yielded no significantly exceeded background, and (3) ingestion of the Cr(III) RfD yielded no significant increase in urinary chromium concentrations, indicating that little, if any, absorption occurred. Our work identified three critical issues that need to be accounted for in any future studies that will use urinary chromium as a marker of exposure. First, a minimum urinary chromium concentration of approximately 2 {mu}g/L should be used as a screening level to critically identify individuals who may have experienced elevated exposures to chromium. Second, if Cr(III) levels in soils are known to be less than 80,000 ppm and the Cr(III) is insoluble, urinary chromium concentrations are not an appropriate marker of exposure. Third, newer forms of chromium supplements that contain organic forms of Cr(III) must be considered potential confounders and their contribution to residential chromium uptake must be carefully evaluated. 19 refs., 7 figs., 3 tabs.

  6. ALUMINUM AND CHROMIUM LEACHING WORKSHOP WHITEPAPER

    SciTech Connect

    McCabe, D; Jeff Pike, J; Bill Wilmarth, B

    2007-04-25

    A workshop was held on January 23-24, 2007 to discuss the status of processes to leach constituents from High Level Waste (HLW) sludges at the Hanford and Savannah River Sites. The objective of the workshop was to examine the needs and requirements for the HLW flowsheet for each site, discuss the status of knowledge of the leaching processes, communicate the research plans, and identify opportunities for synergy to address knowledge gaps. The purpose of leaching of non-radioactive constituents from the sludge waste is to reduce the burden of material that must be vitrified in the HLW melter systems, resulting in reduced HLW glass waste volume, reduced disposal costs, shorter process schedules, and higher facility throughput rates. The leaching process is estimated to reduce the operating life cycle of SRS by seven years and decrease the number of HLW canisters to be disposed in the Repository by 1000 [Gillam et al., 2006]. Comparably at Hanford, the aluminum and chromium leaching processes are estimated to reduce the operating life cycle of the Waste Treatment Plant by 20 years and decrease the number of canisters to the Repository by 15,000-30,000 [Gilbert, 2007]. These leaching processes will save the Department of Energy (DOE) billions of dollars in clean up and disposal costs. The primary constituents targeted for removal by leaching are aluminum and chromium. It is desirable to have some aluminum in glass to improve its durability; however, too much aluminum can increase the sludge viscosity, glass viscosity, and reduce overall process throughput. Chromium leaching is necessary to prevent formation of crystalline compounds in the glass, but is only needed at Hanford because of differences in the sludge waste chemistry at the two sites. Improving glass formulations to increase tolerance of aluminum and chromium is another approach to decrease HLW glass volume. It is likely that an optimum condition can be found by both performing leaching and improving

  7. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b) Specifications...

  8. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... area of the eye. (d) Labeling requirements. The label of the color additive and of any mixtures... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O...

  9. 21 CFR 73.1327 - Chromium oxide greens.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1327 Chromium oxide greens. (a) Identity. (1) The color additive chromium oxide greens is principally chromic sesquioxide (Cr2O3). (2) Color additive... subpart as safe and suitable for use in color additive mixtures for coloring drugs. (b) Specifications...

  10. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and specifications.The color additive chromium hydroxide green shall conform in identity and specifications to the... in coloring externally applied cosmetics, including those intended for use in the area of the eye, in...

  11. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and specifications.The color additive chromium hydroxide green shall conform in identity and specifications to the... in coloring externally applied cosmetics, including those intended for use in the area of the eye, in...

  12. 21 CFR 73.1326 - Chromium hydroxide green.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... area of the eye. (d) Labeling requirements. The label of the color additive and of any mixtures... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1326 Chromium hydroxide green. (a) Identity. (1) The color additive chromium hydroxide green is principally hydrated chromic sesquioxide (Cr2O3·XH2O...

  13. Hydrogel coated fiber Bragg grating based chromium sensor

    NASA Astrophysics Data System (ADS)

    Kishore, P. V. N.; Madhuvarasu, Sai Shankar; Putha, Kishore; Moru, Satyanarayana; Gobi, K. Vengatajalabathy

    2016-04-01

    The present article reports a hydrogel coated Fiber Bragg Grating (FBG) based sensor for chromium metal ion detection. The presence of chromium metal ion in environmental water causes many toxic effects both on humans and animals. The inability of sensing traces of chromium ions is still remains a challenging problem for decades, as the Chromium exists in the environment in different oxidation states. This Paper discusses a chemo-mechanical-optical sensing approach for sensing harmful Chromium ions in environmental water. Fiber Bragg Grating is functionalized with a stimulus responsive hydrogel which swells or deswells depending on ambient chromium ion concentrations. This volume change of the hydrogels causes a bragg shift of the FBG peak. Different peak shifting's, corresponding to different concentrations of the Cr ion concentrations, can be considered as a measure for quantifying traces of chromium ions. Hydrogel network cross-linked with (3-Acrylamidopropyl)-trimethylammonium chloride (ATAC) was synthesized and coated on FBG by dip coating method. Chromium ion concentrations up to ppm (parts per million) can be sensed by this technique.

  14. IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft)

    EPA Science Inventory

  1. Safety, absorption, and antioxidant effects of chromium histidine

    USDA-ARS?s Scientific Manuscript database

    Supplemental chromium has been shown to be involved in the alleviation of the metabolic syndrome, glucose intolerance, polycystic ovary syndrome, depression, excess body fat, and gestational, steroid-induced, and type 2 diabetes. Chromium amino acid complexes that contained histidine displayed cons...

  2. IRIS Toxicological Review of Hexavalent Chromium (2010 External Review Draft)

    EPA Science Inventory

  1. Determination of chromium in treated crayfish, Procambarus clarkii, by electrothermal ASS: study of chromium accumulation in different tissues

    SciTech Connect

    Hernandez, F.; Diaz, J.; Medina, J.; Del Ramo, J.; Pastor, A.

    1986-06-01

    In the present study, the authors investigated the accumulation of chromium in muscle, hepatopancreas, antennal glands, and gills of Procambarus clarkii (Girard) from Lake Albufera following Cr(VI)-exposure. Determinations of chromium were made by using Electrothermal Atomic Absorption Spectroscopy and the standard additions method.

  2. Reaction of chromium(VI) with glutathione or with hydrogen peroxide: Identification of reactive intermediates and their role in chromium(VI)-induced DNA damage

    SciTech Connect

    Aiyar, J.; Berkovits, H.J.; Wetterhahn, K.E. ); Floyd, R.A. )

    1991-05-01

    The types of reactive intermediates generated upon reduction of chromium (VI) by glutathione or hydrogen peroxide and the resulting DNA damage have been determined. In vitro, reaction of chromium (VI) with glutathione led to formation of two chromium (V) complexes and the glutathione thiyl radical. When chromium (VI) was reacted with DNA in the presence of glutathione, chromium-DNA adducts were obtained, with no DNA strand breakage. The level of chromium-DNA adduct formation correlated with chromium (V) formation. Reaction of chromium (VI) with hydrogen peroxide led to formation of hydroxyl radical. No chromium (V) was detectable at 24 C (297 K); however, low levels of the tetraperoxochromium (V) complex were detected at 77 K. Reaction of chromium (VI) with DNA in the presence of hydrogen peroxide produced significant DNA strand breakage and the 8-hydroxydeoxyguanosine adduct, whose formation correlated with hydroxyl radical production. No significant chromium-DNA adduct formation was detected. Thus, the nature of chromium (VI)-induced DNA damage appears to be dependent on the reactive intermediates, i.e., chromium (V) or hydroxyl radical, produced during the reduction of chromium (VI).

  3. 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.

  4. Thermophysical Properties and Corrosion Characterization of Low Cost Lithium Containing Nitrate Salts Produced in Northern Chile for Thermal Energy Storage

    SciTech Connect

    Fernandez, Angel G.; Gomez, Judith C.; Galleguillos, Hector; Fuentealba, Edward

    2016-05-31

    In recent years, lithium containing salts have been studied for thermal energy storage (TES) systems applications, because of their optimal thermophysical properties. In solar power plants, lithium is seen as a way to improve the properties of molten salts used today. Lithium nitrate is a good candidate for sensible heat storage, due to its ability to increase the salt mixture's working temperature range. In the present research, thermophysical properties characterization of lithium nitrate containing salts, produced in Chile, have been carried out. Corrosion evaluations of carbon and low chromium steels were performed at 390 degrees C for 1000 hours. Thermophysical properties of the salt mixtures, such as thermal stability and heat capacity, were measured before and after corrosion tests. Chemical composition of the salts was also determined and an estimation of Chilean production costs is reported. Results showed that purity, thermal stability and heat capacity of the salts were reduced, caused by partial thermal decomposition and incorporation of corrosion products from the steel.

  5. Treatment tests for ex situ removal of chromate, nitrate, and uranium (VI) from Hanford (100-HR-3) groundwater. Final report

    SciTech Connect

    Beck, M.A.; Duncan, J.B.

    1993-11-15

    This report describes batch and anion exchange column laboratory-scale studies investigating ex situ methods to remove chromate (chromium [VI]), nitrate (NO{sub 3}), and uranium (present as uranyl (uranium [VI]) carbonato anionic species) from contaminated Hanford Site groundwaters. The technologies investigated include chemical precipitation or coprecipitation to remove chromate and uranium, and anion exchange to remove chromate, uranium, and nitrate. The technologies investigated were specified in the 100-HR-3 Groundwater Treatability Test Plan (DOE-RL 1993). The goal of these tests was to determine the best method to remove selected contaminants to below the concentration of the project performance goals. The raw data and observations made during these tests can be found in the Westinghouse Hanford Company (WHC) laboratory notebooks (Beck 1992, Herting 1993). The method recommended for future study is anion exchange with Dowex 21K resin.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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?

  11. 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.

  12. Speciation of chromium in Australian fly ash.

    PubMed

    Narukawa, Tomohiro; Riley, Kenneth W; French, David H; Chiba, Koichi

    2007-08-15

    The concentrations of chromium (III) and (VI) in fly ash from nine Australian coal fired power stations were determined. Cr(VI) was completely leached by extraction with 0.01 M NaOH solution and the concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). This was confirmed by determining Cr(III) and Cr(VI) in the extracts of fly ash that had been spiked with chromium salts. These analytical measurements were done using a combination of ion-exchange chromatography and ICP-AES. The elutant was 0.05 M HNO(3) containing 0.5%-CH(3)OH. When the column was operated at a flow rate of 1.2 ml min(-1) and samples were injected by use of a sample loop with a volume of 100 microl, Cr(III) and Cr(VI) in sample solution was exclusively separated within approximately 10 min. The detection limits (3sigma) were 5 ng for Cr(III) (0.050 mg l(-1)) and 9 ng for Cr(VI) (0.090 mg l(-1)), respectively. A relative standard deviation of 1.9% (n=6) was obtained for the determination by IC-ICP-AES of 0.25 mg l(-1) Cr(III) and Cr(VI).

  13. Occupational asthma induced by chromium salts.

    PubMed

    Olaguibel, J M; Basomba, A

    1989-01-01

    Five patients with asthma related to exposure to chromium salts, in their work area, are presented. All of them were non atopics and presented a history of contact dermatitis, with positive patch tests to potassium dichromate, previous to the onset of bronchial asthma. Solutions of K2Cr2O5 were prepared in normal saline at 0.01, 0.1 and 1 mg/ml for skin prick tests (SPT) and bronchial provocation tests (BPT). Immediate cutaneous reaction by SPT was negative for controls and patients. BPT were performed by the tidal breathing method, with positive results in all subjects. A negative response was recorded in 4 control unexposed asthmatics. An attempt to inhibit BPT with sodium cromoglycate was unsuccessful. The diversity of reactions (immediate, dual and late) registered in BPT, support that bronchial reactivity can be induced specifically by inhalation of chromium salts. The data of follow-up indicates a good prognosis, provided that patients remain out of exposure. The lack of facts suggesting an IgE-mediated reaction puts forward for consideration other pathophysiologic mechanisms.

  14. Toxicity of chromium to activated sludge.

    PubMed

    Vanková, S; Kupec, J; Hoffmann, J

    1999-01-01

    The work deals with the toxicity of hexavalent and trivalent chromium to activated sludge. Cr(VI) was added as K2Cr2O7, and Cr(III) as Cr2(SO4)3. Toxicity is expressed as the inhibition of respiratory activity of microorganisms present in activated sludge. Respiration was measured by two methods, by means of an oximeter with an oxygen electrode and by means of a manometric apparatus permitting continuous observation of biological oxygen demand (BOD). The equation of the normal distribution function was used to construct inhibition curves and to calculate effective concentration (EC50). The influence of exposure time was observed as was the influence of concentration of activated sludge on the value of EC50. The 1-h EC50 for Cr(VI) by the ISO method was determined to be in the range of 40-90 mg/liter. A greater scatter of measured values, 46-201mg/liter, was found for the first hour of exposure by the manometric method. In the case of Cr(III) only combined inhibition by chromium ions and pH was determined. The 0.5-h EC50 was 49 mg/liter. Copyright 1999 Academic Press.

  15. Chromium(VI) bioremediation by probiotics.

    PubMed

    Younan, Soraia; Sakita, Gabriel Z; Albuquerque, Talita R; Keller, Rogéria; Bremer-Neto, Hermann

    2016-09-01

    Chromium is a common mineral in the earth's crust and can be released into the environment from anthropogenic sources. Intake of hexavalent chromium (Cr(VI)) through drinking water and food causes toxic effects, leading to serious diseases, and is a commonly reported environmental problem. Microorganisms can mitigate or prevent the toxic effects caused by heavy metals in addition to having effective resistance mechanisms to prevent cell damage and bind to these metals, sequestering them from the cell surface and removing them from the body. Species of Lactobacillus, Streptococcus, Bacillus and Bifidobacterium present in the human mouth and gut and in fermented foods have the ability to bind and detoxify some of these substances. This review address the primary topics related to Cr(VI) poisoning in animals and humans and the use of probiotics as a way to mitigate or prevent the toxic effects caused by Cr(VI). Further advances in the genetic knowledge of such microorganisms may lead to discoveries which will clarify the most active microorganisms that act as bioprotectants in bodies exposed to Cr(VI) and are an affordable option for people and animals intoxicated by the oral route. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  16. Chromium toxicity. (Latest citations from the Life Sciences Collection data base). Published Search

    SciTech Connect

    Not Available

    1992-10-01

    The bibliography contains citations concerning the biological effects of chromium exposure. Topics include the effects on protein metabolism and kidney and liver functions, chromium antigenicity, and the role of chromium as a carcinogenic agent. Sources of chromium contamination are discussed, including occupational exposure and pollution. Methods of analysis are also described. (Contains 250 citations and includes a subject term index and title list.)

  17. 76 FR 71926 - Defense Federal Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-21

    ... Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to Commercial Items (DFARS Case... hexavalent chromium. DATES: Comment Date: Comments on the proposed rule should be submitted in writing to the... chromium. Hexavalent chromium is a chemical that has been used in numerous DoD weapons systems...

  18. 75 FR 65067 - National Emission Standards for Hazardous Air Pollutant Emissions: Hard and Decorative Chromium...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-21

    ... Decorative Chromium Electroplating and Chromium Anodizing Tanks; Group I Polymers and Resins; Marine Tank...: Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks; Group I Polymers and Resins... Tanks. Group I Polymers and Resins Production.. Scott Throwe, (202) 564-7013, throwe.scott@epa.gov...

  19. 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)

  20. 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)

  1. 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.

  2. 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 ...

  3. 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.

  4. 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 ...

  5. 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

  6. 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.

  7. Chromium nanoparticle exhibits higher absorption efficiency than chromium picolinate and chromium chloride in Caco-2 cell monolayers.

    PubMed

    Zha, L-Y; Xu, Z-R; Wang, M-Q; Gu, L-Y

    2008-04-01

    This study was conducted to determine whether chromium nanoparticle (CrNano) exhibited higher absorption efficiency and possessed unique absorption mechanism in comparison to chromium picolinate (CrPic) and chromium chloride (CrCl(3)), as was postulated by previous reports. Twenty-one-day-old Caco-2 cell monolayers grown on semipermeable membranes in Snapwell tissue culture bichambers were incubated with CrNano, CrPic or CrCl(3) to examine their transport and uptake respectively. In the concentration range of 0.2-20 micromol/l, transport of CrNano, CrPic and CrCl(3) across Caco-2 monolayers both in apical-to-basolateral and basolateral-to-apical direction was concentration-, and time-dependent, and temperature independent. The apparent permeability coefficient (P(app)) of CrNano was between 5.89 and 7.92 x 10(-6) cm/s and that of CrPic and CrCl(3) was between 3.52 and 5.31 x 10(-6) cm/s and between 0.97 and 1.37 x 10(-6) cm/s respectively. Uptake of CrNano, CrPic and CrCl(3) by both apical and basolateral membranes was concentration- and time-dependent. Uptake of CrNano by apical membrane was significantly (p < 0.05) decreased when the incubation temperature was reduced from 37 degrees C to 4 degrees C. The transport efficiency of CrNano, CrPic and CrCl(3) after incubation for 120 min at 37 degrees C was 15.83% +/- 0.76%, 9.08% +/- 0.25% and 2.11% +/- 0.53% respectively. The uptake efficiency of CrNano, CrPic and CrCl(3) was 10.08% +/- 0.76%, 4.73% +/- 0.60% and 0.88% +/- 0.08% respectively. It was concluded that the epithelial transport of CrNano, CrPic and CrCl(3) across the Caco-2 cell monolayers was mainly via passive transport pathways. In addition, CrNano exhibited considerably higher absorption efficiency than both CrPic and CrCl(3) in Caco-2 cell monolayers.

  8. Workshop on effects of chromium coating on Nb{sub 3}Sn superconductor strand: Proceedings

    SciTech Connect

    Not Available

    1994-04-12

    This report discusses the following topics: Chromium coating on superconductor strand -- an overview; technology of chromium plating; comparison of wires plated by different platers; search for chromium in copper; strand manufactures` presentations; chromium plating at the Lawrence Livermore National Laboratory; a first look at a chromium plating process development project tailored for T.P.X. and I.T.E.R. strand; and influence of chromium diffusion and related phenomena on the reference ratios of bare and chromium plated Nb{sub 3}Sn strand.

  9. 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.

  10. Mode of occurrence of chromium in four US coals

    USGS Publications Warehouse

    Huggins, Frank E.; Shah, N.; Huffman, G.P.; Kolker, A.; Crowley, S.; Palmer, C.A.; Finkelman, R.B.

    2000-01-01

    The mode of occurrence of chromium in three US bituminous coals and one US subbituminous has been examined using both X-ray absorption fine structure (XAFS) spectroscopy and a selective leaching protocol supplemented by scanning electron microscopy (SEM) and electron microprobe measurements. A synthesis of results from both methods indicates that chromium occurs principally in two forms in the bituminous coals: the major occurrence of chromium is associated with the macerals and is not readily leached by any reagent, whereas a second, lesser occurrence, which is leachable in hydrofluoric acid (HF), is associated with the clay mineral, illite. The former occurrence is believed to be a small particle oxyhydroxide phase (CrO(OH)). One coal also contained a small fraction (<5%) of the chromium in the form of a chromian magnetite, and the leaching protocol indicated the possibility of a similar small fraction of chromium in sulfide form in all three coals. There was little agreement between the two techniques on the mode of occurrence of chromium in the subbituminous coal; however, only a limited number of subbituminous coals have been analyzed by either technique. The chromium in all four coals was trivalent as no evidence was found for the Cr6+ oxidation state in any coal.

  11. Kinetics of chromium(VI) reduction by ferrous iron

    SciTech Connect

    Batchelor, B.; Schlautman, M.; Hwang, I.; Wang, R.

    1998-09-01

    Chromium is a primary inorganic contaminant of concern at the Pantex Plant. Chromium concentrations have been found to be two orders of magnitude higher than the drinking water standards, particularly in certain wells in the perched aquifer below Zone 12. In situ reduction of a mobile form of chromium, Cr(VI) to an immobile form, Cr(III), was examined as a viable option to active soil restoration. Successfully immobilizing chromium in the vadose zone as Cr(III) will reduce the amount of chromium that reaches the groundwater table. The results from the solution experiments indicated that chromium was rapidly and stoichiometrically reduced by Fe(II) in solution. Also, the slurry experiments showed that the aquifer solids removed Fe(II) from solution, but a portion of the iron removed remained available for reaction with Cr(VI), but at a slower rate. A model to predict different amounts of iron pseudo-components was developed, which allowed prediction of iron amounts required to reduce chromium under in situ conditions.

  12. Lipid peroxidation in workers exposed to hexavalent chromium.

    PubMed

    Huang, Y L; Chen, C Y; Sheu, J Y; Chuang, I C; Pan, J H; Lin, T H

    1999-02-26

    The aim of this study was to investigate whether exposure to hexavalent chromium induces lipid peroxidation in human. This study involved 25 chrome-plating factory workers and a reference group of 28 control subjects. The whole-blood and urinary chromium concentrations were determined by graphite furnace atomic absorption spectrophotometry. Malondialdehyde (MDA), the product of lipid peroxidation, was determined by high-performance liquid chromatography, and the activities of protective enzymes were measured by ultraviolet-visible spectrophotometry. In the chrome-plating workers, the mean concentrations of chromium in blood and urine were 5.98 microg/L and 5.25 microg/g creatinine, respectively; the mean concentrations of MDA in blood and urine were 1.7 micromol/L and 2.24 micromol/g creatinine. The concentrations of both chromium and MDA in blood and urine were significantly higher in the chromium-exposed workers. The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were not markedly different between control and exposed workers. Data suggest that MDA may be used as a biomarker for occupational chromium exposure. Antioxidant enzymic activities are not a suitable marker for chromium exposure.

  13. Bioavailability of a potato chromium complex to the laboratory rat

    SciTech Connect

    Gilbert, H.K.

    1985-01-01

    Research objectives were to study the effect of food source, preparation method and chemical form on bioavailability of chromium. Chromium concentration in potatoes was determined and tubers labeled either intrinsically or extrinsically with radioactive chromate. A labeled chromium complexes was isolated from preparations of raw, baked or fried potatoes and chromatographed on gel permeation media. Availability of the potato chromium complex to the rat was examined in three feeding studies. Animals were dosed with radioactive extrinsically or intrinsically labeled potato extract or with chromate. A labeled chromium complex was isolated from gastrointestinal contents of rats and chromatographed. Potato pulp and peel contained 1.63 and 2.70 ..mu..g Cr/g tissue respectively. True and apparent absorption from extrinsically labeled feedings were 33.4 +/- 4.7 and 29.8 +/- 11.2% respectively, and no differences existed between absorption from raw and cooked potatoes. Absorption from the extrinsic labeled potatoes differed significantly from absorption of inorganic chromatium. Apparent absorption of raw (11.1 +/- 7.9%) and cooked (-0.7 +/- 2.8%) intrinsically labeled feedings differed significantly. Absorption of inorganic chromium was 17.8% (true) and 11.5% (apparent). Examination of the chromium complex isolated from gastrointestinal tract contents showed enlargement of the complex in the stomach after consumption.

  14. Removal of chromium from tannery effluents by adsorption.

    PubMed

    Fadali, O A; Magdy, Y H; Daifullah, A A M; Ebrahiem, E E; Nassar, M M

    2004-01-01

    Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.

  15. Controlling diabetes by chromium complexes: The role of the ligands.

    PubMed

    Peng, Mei; Yang, Xiaoping

    2015-05-01

    Diabetes, particularly type II diabetes, is a severe disease condition which affects human health worldwide, with a dramatically increasing trend in Asian countries including China. Currently, no efficient drugs other than those with observable side effects are available. Chromium complexes, with the most known representative chromium picolinate, have been listed as one of most attractive health supplements to attenuate this disease condition in western countries. Recent efforts have been made to develop new chromium complexes with novel ligands. Although fair amounts of reviews have been published to emphasize the biological activity, preclinical and clinical information of chromium picolinate, this mini-review is trying to cover the entire picture of updated research efforts on various chromium complexes highlighting the role of ligands. Chromium phenylalanine sensitizes insulin cell signaling pathway via the activation of phosphorylation of Akt (protein kinase B (PKB)) and/or AMPK (AMP-activated protein kinase). The biological activities, toxicity, pharmacological features and clinical implications, including the effect of anti-oxidative capacities, protective effect on obese-induced heart dysfunction, and efficacy and safety of chromium supplementation in diabetes are discussed as well.

  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. Chromium supplementation for menstrual cycle-related mood symptoms.

    PubMed

    Brownley, Kimberly A; Girdler, Susan S; Stout, Anna L; McLeod, Malcolm N

    2013-12-01

    Premenstrual dysphoric disorder (PMDD) afflicts ~7% of reproductive-age women resulting in impaired relationships, diminished overall quality of life, and disability-adjusted life years lost on par with other major psychiatric disorders. Response to pharmacological treatment is inadequate in ~50% of women with PMDD. The goal of the present study is to evaluate the effects of a novel approach-short-term chromium supplementation-on menstrual cycle-related mood and physical symptoms. Five women were studied under single-blind conditions in a private clinical setting (2 of them were referred specifically for treatment-resistant menstrual-related symptoms); 6 women completed a double-blind crossover study of chromium plus placebo versus chromium plus sertraline in a university clinical research setting. Treatments were administered from mid-cycle to onset of menses in 1-month intervals. Symptom ratings were obtained by self-report, using daily symptom checklists, and by clinical assessment, using the Hamilton Psychiatric Rating Scale for Depression (HAM-D) and the Clinical Global Impressions (CGI) scale. Overall, chromium treatment was associated with reduced mood symptoms and improved overall health satisfaction in most participants. In some cases, chromium alone was associated with marked clinical improvement; in others, chromium plus an antidepressant resulted in greater improvement than either chromium alone or an antidepressant alone. These preliminary observations suggest that chromium may be a useful monotherapy or adjunctive therapy for women suffering from significant menstrual cycle-related symptoms. Larger, controlled studies are needed to evaluate the efficacy of chromium treatment in this patient population.

  18. Oral bioaccessibility of trivalent and hexavalent chromium in soil by simulated gastric fluid.

    PubMed

    Skowronski, G A; Seide, M; Abdel-Rahman, M S

    2001-07-06

    Chromium is found in soil from natural sources and anthropogenic activities. The ingestion of soil contaminated with chromium especially by children can have toxic consequences. Therefore, it is important to quantify the oral bioaccessibility of chromium in chromium in contaminated soil. In this study, chromium-51 as chromic (III) chloride and sodium chromate (VI), was mixed with an Atsion sandy soil and a Keyport clay soil and stored for 4 mo at either 21-25 degrees C or 2-4 degrees C. Utilizing simulated gastric conditions, the oral bioaccessibility of chromium in soil was determined. When the effects of soil on the bioaccessibility of chromium were compared, the data revealed the the bioaccessibility of chromium (III) from the clay soil was significantly lower than from the sandy at 21-25 degrees C. However, at 2-4 degrees C, more chromium (III) was extracted by synthetic gastric fluid from the clay soil than from the sandy soil. Temperature was also a factor as evidenced by the higher bioaccessibility of chromium (IV) in the sandy soil at 2-4 degrees C and of both chromium species in the clay soil at the same temperature. Reduction of the soluble chromium (VI) chemical to the nonsoluble chromium (III) compound in the acidic soils by naturally occurring organic matter in soil would explain the lower bioaccessibilty of chromium (VI) at 21-25 degrees C. At 2-4 degrees C, the data indicate that the rate of chromium (VI) reduction to chromium (III) was slowed. Although the results of this study are limited to one low concentration of chromium (III) and chromium (VI) and indicate that the bioaccessibility of chromium in soil can range between 18% and 72%, the data also suggest that there may be a potential health hazard from oral exposure to chromium in heavily contaminated sites. Therefore, more extensive research should be conducted to determine if thes findings can be extended to environmentally relevant concentrations.

  19. Chromium isotopes and the fate of hexavalent chromium in the environment

    USGS Publications Warehouse

    Ellis, Andre S.; Johnson, Thomas M.; Bullen, Thomas D.

    2002-01-01

    Measurements of chromium (Cr) stable-isotope fractionation in laboratory experiments and natural waters show that lighter isotopes reacted preferentially during Cr(VI) reduction by magnetite and sediments. The 53Cr/52Cr ratio of the product was 3.4 ± 0.1 per mil less than that of the reactant.53Cr/52Cr shifts in water samples indicate the extent of reduction, a critical process that renders toxic Cr(VI) in the environment immobile and less toxic.

  20. 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

  1. 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...

  2. 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.

  3. 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...

  4. 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.

  5. 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

  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. 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...

  8. Chromium environmental risk assessment. Interim report, April 1996--October 1997

    SciTech Connect

    Vermulen, E.K.; May, L.M.; Hoffman-Till, T.A.; Prince, J.K.; Lurker, P.A.

    1997-11-01

    A review of chromium environmental criteria, supporting scientific studies and recent research activities was conducted to determine the implications of evolving observations on cancer risk to DoD environmental clean-up programs. Public concern over the occupational cancer risk of hexavalent chromium is influencing a new assessment of the risk data. Toxicology literature on the human health hazards, cancer and non-cancer, was reviewed. On-going epidemiology efforts were unavailable for a thorough assessment. Data gaps in the literature were noted as support for research recommendations. Alternatives to chromium speciation at environmental clean-up sites were recommended as an interim measure. An extensive bibliography is provided.

  9. Cancer hazards caused by nickel and chromium exposure

    SciTech Connect

    Norseth, T.

    1980-09-01

    An increased risk of cancer associated with nickel refining and with chromate production has been known for some decades. The occupational exposure pattern of both nickel and chromium is very complex. Nickel subsulfide may be the most potent carcinogen among the different nickel compounds. A correlation between lung cancer and exposure to chromates has been shown in several studies. Hexavalent chromium has been suggested as the causative carcinogen among platers and ferrochromium workers. There is an urgent need for careful dose registration before a quantitative cancer risk analysis can be performed for the nickel and chromium industry.

  10. [Blood and urine chromium: compared values between chromium exposed workers and common people].

    PubMed

    Provenzani, A; Verso, M G; Picciotto, D

    2008-01-01

    Aim of present study is the valutation and quantification of chromium in blood and urine. We compared 3 groups of persons formed by building workers, in particular masons, because cement contains potassium chromate that is dangerous for health, and by common people: urban population and outside the town population. In fact, exposure to CrVI risk is high for people who live near chromate industries. We maked a medical examination, blood and instrumental tests, chromium measuring in blood (recent exposure indicator) and urine (recent and previous indicator). Then we used statistical methods to estimate obtained values of blood and urine chromium among professional exposed people and common people. At the end we think that preventive measures in working environment reduced exposure to CrVI but environmental exposure (for example road dust from catalytic converter erosion, from brake lining erosion, cement dust and tobacco smoke), in the last years, has increased. So there are no difference between urban population and outside the town population and there are also no difference with professional exposed people for work prevention according to law in force, that let down professional risk using safe limits.

  11. Microbial Diversity of Chromium-Contaminated Soils and Characterization of Six Chromium-Removing Bacteria.

    PubMed

    He, Zhiguo; Hu, Yuting; Yin, Zhen; Hu, Yuehua; Zhong, Hui

    2016-06-01

    Three soil samples obtained from different sites adjacent to a chromium slag heap in a steel alloy factory were taken to examine the effect of chromium contamination on soil bacterial diversity as determined by construction of 16S rDNA clone libraries and sequencing of selected clones based on restriction fragment length polymorphism (RFLP) analysis. Results revealed that Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Alphaproteobacteria occurred in all three soil samples, although the three samples differed in their total diversity. Sample 1 had the highest microbial diversity covering 12 different classes, while Sample 3 had the lowest microbial diversity. Strains of six different species were successfully isolated, one of which was identified as Zobellella denitrificans. To our knowledge, this is the first report of a strain belonging to the genus Zobellella able to resist and reduce chromium. Among all isolates studied, Bacillus odysseyi YH2 exhibited the highest Cr(VI)-reducing capability, with a total removal of 23.5 % of an initial Cr(VI) concentration of 350 mg L(-1).

  12. Microbial Diversity of Chromium-Contaminated Soils and Characterization of Six Chromium-Removing Bacteria

    NASA Astrophysics Data System (ADS)

    He, Zhiguo; Hu, Yuting; Yin, Zhen; Hu, Yuehua; Zhong, Hui

    2016-06-01

    Three soil samples obtained from different sites adjacent to a chromium slag heap in a steel alloy factory were taken to examine the effect of chromium contamination on soil bacterial diversity as determined by construction of 16S rDNA clone libraries and sequencing of selected clones based on restriction fragment length polymorphism (RFLP) analysis. Results revealed that Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Alphaproteobacteria occurred in all three soil samples, although the three samples differed in their total diversity. Sample 1 had the highest microbial diversity covering 12 different classes, while Sample 3 had the lowest microbial diversity. Strains of six different species were successfully isolated, one of which was identified as Zobellella denitrificans. To our knowledge, this is the first report of a strain belonging to the genus Zobellella able to resist and reduce chromium. Among all isolates studied, Bacillus odysseyi YH2 exhibited the highest Cr(VI)-reducing capability, with a total removal of 23.5 % of an initial Cr(VI) concentration of 350 mg L-1.

  13. Laboratory evaluation of the hydrogen sulfide gas treatment approach for remediation of chromate-, uranium(VI)-, and nitrate-contaminated soils

    SciTech Connect

    Thornton, E.C.; Baechler, M.A.; Beck, M.A.; Amonette, J.E.

    1994-08-01

    Bench-scale soil treatment tests were conducted as part of an effort to develop and implement an in situ chemical treatment approach to the remediation of metal and radionuclide contaminated soils through the use of reactive gases. In general, > 90% immobilization of chromium and > 50% immobilization of uranium was achieved. Leach test results indicate that the treatment process is irreversible for chromium but partially reversible for uranium indicates that immobilization for this contaminant is more readily achieved in organic rich soils. This observation is ascribed to the reducing nature of organic matter. Additional tests were also conducted with soils contaminated to the 5,000 ppm level with nitrate. Nitrate was not found to interfere significantly with treatment of the contaminants. Nitrite was observed in the leachate samples obtained from tests with an organic-rich soil containing clay, however. Leachate chemistries suggested that no other significantly hazardous byproducts were generated by the treatment process and that soil alteration effects were minimal. Test results also suggest that treatment effectiveness is somewhat lower in very dry soils but still able to immobilize chromium and uranium to an acceptable degree. Results of these testing activities indicate that the concentration of hydrogen sulfide in the gas mixture is not a limited factor in treatment as long as a sufficient volume of the mixture is delivered to the soil to achieve a mole ratio of hydrogen sulfide to contaminant of at least 10.

  14. 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

  15. Evaluation of chromium in red blood cells as an indicator of exposure to hexavalent chromium: An in vitro study.

    PubMed

    Devoy, Jérôme; Géhin, Antoine; Müller, Samuel; Melczer, Mathieu; Remy, Aurélie; Antoine, Guillaume; Sponne, Isabelle

    2016-07-25

    Chromium(VI) compounds are classified as carcinogenic to humans. Whereas chromium measurements in urine and whole blood (i.e., including plasma) are indicative of recent exposure, chromium in red blood cells (RBC) is attributable specifically to Cr(VI) exposure. Before recommending Cr in RBC as a biological indicator of Cr(VI) exposure, in-vitro studies must be undertaken to assess its reliability. The present study examines the relationship between the chromium added to a blood sample and that subsequently found in the RBC. After incubation of total blood with chromium, RBC were isolated, counted and their viability assessed. Direct analysis of chromium in RBC was conducted using Atomic Absorption Spectrometry. Hexavalent, but not trivalent Cr, was seen to accumulate in the RBC and we found a strong correlation between the Cr(VI) concentration added to a blood sample and the amount of Cr in RBC. This relationship appears to be independent of the chemical properties of the human blood samples (e.g., different blood donors or different reducing capacities). Even though in-vivo studies are still needed to integrate our understanding of Cr(VI) toxicokinetics, our findings reinforce the idea that a single determination of the chromium concentration in RBC would enable biomonitoring of critical cases of Cr(VI) exposure.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Possible adverse effect of chromium in occupational exposure of tannery workers.

    PubMed

    Kornhauser, Carlos; Wróbel, Katarzyna; Wróbel, Kazimierz; Malacara, Juan Manuel; Nava, Laura Eugenia; Gómez, Leobardo; González, Rita

    2002-04-01

    Our aim was to investigate the adverse effects of occupational exposure to trivalent chromium. We measured chromium and iron levels in serum and urine and hemoglobin levels in tannery workers and unexposed persons. We studied three groups of subjects. Group 1 included 15 non-smoking male tannery workers highly exposed to chromium from tanning and retanning departments. Group 2 included 14 non-smoking male tannery workers with moderate chromium exposure from dying, drying and finishing departments. Group 3 included 11 healthy, non-smoking male subjects without direct chromium exposure. Higher serum chromium levels were observed in groups 1 and 2 with respect to group 3 (mean values respectively: 0.43; 0.25 and 0.13 microg x l(-1)). Urine chromium levels in group 1 were higher than those in controls (mean values: 1.78 and 1.35 microg x l(-1)). In group 1 an inverse association was found between serum chromium and urine iron (-0.524), urine chromium and hemoglobin (-0.594) and between the urine chromium to iron ratio and hemoglobin (-0.693, p<0.05). The results suggest a chromium adverse effect on iron metabolism, possibly associated with excessive body chromium accumulation. In conclusion, chromium urine test could be recommended for diagnosis of chromium adverse effect on iron metabolism. Further studies are needed to quantify the relationship between urine chromium and hemoglobin metabolism.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. Chromium and nickel in roadside grapes.

    PubMed

    Pertoldi Marletta, G; Gabrielli Favretto, L; Favretto, L

    1989-01-01

    Chromium and nickel concentration in roadside unwashed wine grapes and leaves is considered as a function of the distance from the suspected source, an isolated straight road. The analyses were performed with electrothermal atomization in a graphite furnace. The decrease in the concentration of the element can be described by means of a three-parameter exponential function c = A + (B - A)exp(-Cd), which allows the determination of the asymptotic level far from the emitting source (C infinity) and the pollution level (C0) at the edge of the road (d = 0). Least-squares nonlinear regression gives the estimation of the parameters A, B, and C. The results indicate that an effect is detectable up to a distance of about 50 m.

  8. Chromium detoxification by fixed-film bioreactors

    SciTech Connect

    Chirwa, E.M.N.; Wang, Y.T.

    1996-11-01

    In this study, completely mixed, continuous flow bioreactors were utilized to detoxify chromium. Glass beads were incorporated as a support medium for two strains of bacteria, Bacillus sp. and Pseudomonas fluorescens LB300 (LB300), growing aerobically in two separate reactors. Aerobic conditions were maintained in the reactors by continuously supplying fresh air to the liquid through gas exchange chambers installed on the recycle line of the bioreactors. Results obtained showed that near complete removal of chromate was possible for influent concentrations up to 200 mg/L for Bacillus sp., and up to 100 mg/L for LB300 at 24 hours liquid detention time. Similar results were obtained for corresponding loading rates at 12 hours and 6 hours liquid detention time.

  9. Nitridation of chromium powder in ammonia atmosphere

    NASA Astrophysics Data System (ADS)

    Li, Ling; Zhen, Qiang; Li, Rong

    2015-03-01

    CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different temperatures. Chromium nitride formed at 7002-1200°C under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000°C for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).

  10. Self-Lubricating Composite Containing Chromium Oxide

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher (Inventor); Edmonds, Brian J. (Inventor)

    1999-01-01

    A self lubricating. friction and wear reducing composite material useful over a wide temperature range of from cryogenic temperature up to about 900 C. contains 60 80 wt. % of particulate Cr2O3, dispersed in a metal binder of a metal alloy containing Cr and at least 50 wt. % of Ni, Cr or a mature of Ni and Cr. It also contains 5-20 wt. % of a fluoride of at least one Group I, Group II or rare earth metal and. optionally, 5-20 wt. % of a low temperature lubricant metal, such as Ag. Au, Pt, Pd, Rh and Cu. This composite exhibits less oxidation instability and less abrasiveness than composites containing chromium carbide, is readily applied using plasma spray and can be ground and polished with a silicon carbide abrasive.

  11. TiC reinforced cast chromium steels

    SciTech Connect

    Dogan, Omer N.; Rawers, James C.; Hawk, Jeffrey A.; Schrems, Karol K.

    2003-11-01

    A series of new titanium carbide reinforced cast chromium steels were developed for wear applications. Objective of the program was to enhance wear resistant alloys and, if possible, improve mechanical properties. The new steels which were melted in a vacuum induction furnace contained 12 Cr, 3-5 Ti, 1-2 C in weight percent. Alloying with Ti changed the precipitate microstructure from Cr carbide to TiC dispersed in a martensitic matrix. Yield strength and impact resistance improved with Ti alloying. Wear rates of the cast Cr/TiC steels, (determined from high- and low-stress abrasion tests, erosion test, and scratch tests) were generally lower than both the as-cast and heat-treated AISI type 440°C steel and were often further reduced by increasing the Ti alloy concentration. The exceptions were the erosion test for which all materials had similar wear rate.

  12. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Generated by Manufacturers or Users of Nickel, Chromium, or Iron Baghouse bags Raney nickel catalyst Floor... Nickel, chromium, and iron catalysts Nickel-cadmium and nickel-iron batteries Filter cake from...

  13. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Generated by Manufacturers or Users of Nickel, Chromium, or Iron Baghouse bags Raney nickel catalyst Floor... Nickel, chromium, and iron catalysts Nickel-cadmium and nickel-iron batteries Filter cake from...

  14. 40 CFR Appendix Xii to Part 266 - Nickel or Chromium-Bearing Materials that may be Processed in Exempt Nickel-Chromium Recovery...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Generated by Manufacturers or Users of Nickel, Chromium, or Iron Baghouse bags Raney nickel catalyst Floor... Nickel, chromium, and iron catalysts Nickel-cadmium and nickel-iron batteries Filter cake from...

  15. 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

  16. Chromium concentrations in ruminant feed ingredients.

    PubMed

    Spears, J W; Lloyd, K E; Krafka, K

    2017-02-22

    Chromium (Cr), in the form of Cr propionate, has been permitted for supplementation to cattle diets in the United States at levels up to 0.50 mg of Cr/kg of DM since 2009. Little is known regarding Cr concentrations naturally present in practical feed ingredients. The present study was conducted to determine Cr concentrations in feed ingredients commonly fed to ruminants. Feed ingredients were collected from dairy farms, feed mills, grain bins, and university research farms. Mean Cr concentrations in whole cereal grains ranged from 0.025 mg/kg of DM for oats to 0.041 mg/kg of DM for wheat. Grinding whole samples of corn, soybeans, and wheat through a stainless steel Wiley mill screen greatly increased analyzed Cr concentrations. Harvested forages had greater Cr concentrations than concentrates, and alfalfa hay or haylage had greater Cr concentrations than grass hay or corn silage. Chromium in alfalfa hay or haylage (n = 13) averaged 0.522 mg/kg of DM, with a range of 0.199 to 0.889 mg/kg of DM. Corn silage (n = 21) averaged 0.220 mg of Cr/kg of DM with a range of 0.105 to 0.441 mg of Cr/kg of DM. By-product feeds ranged from 0.040 mg of Cr/kg of DM for cottonseed hulls to 1.222 mg of Cr/kg of DM for beet pulp. Of the feed ingredients analyzed, feed grade phosphate sources had the greatest Cr concentration (135.0 mg/kg). Most ruminant feedstuffs and feed ingredients had less than 0.50 mg of Cr/kg of DM. Much of the analyzed total Cr in feed ingredients appears to be due to Cr contamination from soil or metal contact during harvesting, processing, or both.

  17. 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

  18. 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

  19. Daily intake of heavy metals and nitrate through greenhouse cucumber and bell pepper consumption and potential health risks for human.

    PubMed

    Khoshgoftarmanesh, Amir H; Aghili, Forough; Sanaeiostovar, Azadeh

    2009-01-01

    Limited information is available on the health quality of greenhouse vegetables. Lead, cadmium, nickel, chromium, and nitrate (NO3-) concentrations in greenhouse cucumber (Cucumis sativa L.) and bell pepper (Capsicum annuum L.) and their dietary intakes were determined. The non-cancer risk for NO3- was determined using the non-cancer hazard quotient. Lead non-cancer risk in children was calculated using the Integrated Exposure-Uptake Biokinetic model. Higher concentrations of cadmium, lead, and chromium were found in bell pepper than cucumber. The mean NO3- concentration in the greenhouse cucumber was about 2.7 times higher than the World Health Organization standard limit. Cadmium, lead, nickel, and chromium daily intake for different populations groups through consumption of the vegetables were < 0.01-0.04, 0.35-1.00, 0.03-0.24, and 0.05-0.27 microg/g, respectively. The dietary intake of NO3- for adult was greater than children. Elevated lead and NO3- concentrations in the greenhouse vegetables are important concerns for consumers. Potential health quality problems in greenhouse products have to be considered.

  20. Effects of Chromium(VI) and Chromium(III) on Desulfovibrio vulgaris Cells

    SciTech Connect

    M.E. Clark; A. Klonowska; S.B. Thieman; B. Giles; J.D. Wall; and M.W. Fields

    2007-04-19

    Desulfovibrio vulgaris ATCC 29579 is a well studied sulfate reducer that has known capabilities of reducing heavy metals and radionuclides, like chromium and uranium. Cultures grown in a defined medium (i.e. LS4D) had a lag period of approximately 40 h when exposed to 50 μMof Cr(VI). Substrate analysis revealed that although chromium is reduced within the first 5 h, growth does not resume for another 35 h. During this time, small amounts of lactate are still utilized but the reduction of sulfate does not occur. Sulfate reduction occurs concurrently with the accumulation of acetate approximately 40 h after inoculation, when growth resumes. Similar amounts of hydrogen are produced during this time compared to hydrogen production by cells not exposed to Cr(VI); therefore an accumulation of hydrogen cannot account for the utilization of lactate. There is a significant decrease in the carbohydrate to protein ratio at approximately 25 h, and this result indicated that lactate is not converted to glycogen. Most probable number analysis indicated that cell viability decreased steadily after inoculation and reached approximately 6 x 104 cells/ml 20 h post-chromium exposure. Regeneration of reducing conditions during chromium exposure does not induce growth and in fact may make the growth conditions even more unfavorable. This result suggested that an increase in Eh was not solely responsible for the decline in viability. Cell pellets collected 10 h after chromium-exposure were unable to resume growth when suspended into fresh medium. Supernatants from these pellets were able to support cell growth upon re- inoculation. D. vulgaris cells treated with a non-dose dependent addition of ascorbate at the same time of Cr(VI) addition did not enter a lag period. Ascorbate added 3 h post-Cr(VI) exposure did not prevent the growth lag. These results indicated that Desulfovibrio utilized lactate to reduce Cr(VI) without the reduction of sulfate, that the decline in cell viability and

  1. Deposition of nanocrystalline nonstoichiometric chromium oxide coatings on the surface of multiwalled carbon nanotubes by chromium acetylacetonate vapor pyrolysis

    NASA Astrophysics Data System (ADS)

    Kremlev, K. V.; Ob'edkov, A. M.; Ketkov, S. Yu.; Kaverin, B. S.; Semenov, N. M.; Gusev, S. A.; Andreev, P. V.

    2017-04-01

    Nanocrystalline coatings of nonstoichiometric chromium oxide have been obtained for the first time on the surface of multiwalled carbon nanotubes (MWCNTs) by the method of metalorganic chemical-vapor deposition using chromium acetylacetonate as a precursor. The new hybrid nanomaterial (Cr2O2.4/MWCNT) has been characterized by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. It is established that oxidation of the hybrid nanomaterial in air under soft conditions (at 380°C) leads to the formation of nanocrystalline chromium oxide (Cr2O3) on the surface of MWCNTs.

  2. Isolation and characterization of hexavalent chromium-reducing rhizospheric bacteria from a wetland.

    PubMed

    Mauricio Gutiérrez, Amparo; Peña Cabriales, Juan José; Maldonado Vega, María

    2010-01-01

    Scirpus americanus Pers. occurs naturally in "San Germán," a pond that serves as a receptor of industrial wastewater in Guanajuato, México. This plant accumulates metals mainly in the root: concentrations (mg/kg) of Cr, As, Cd and Se were 970, 49, 41, and 85 respectively. Analysis of rhizosphere samples indicated bacterial population of 10(8) cfu g(-1) in media with 0.2 mM Cr(VI) and 10 mM sodium gluconate. Thirteen isolates were obtained and phylogenetic analyses (16S rRNA) indicated they corresponded to genera of Agrobacterium, Arthrobacter, Microbacterium, Curtobacterium, Rhodococcus, Xanthomonas and Pseudomonas. Cr(VI) reduction was evaluated using the diphenyl carbazide method. The isolates accomplished 5-40% (20 microM) of reduction in assays of resting cell and tolerated 0.5-5.0 mM Cr(VI). Eight strains used nitrate and thirteen used iron and chromium as electron acceptors to grow under anaerobic conditions. Cr(VI) reduction by five strains occurred at pH values (7-9) and NaCl concentrations (0.5-1.0 M) in basal medium. A mixed culture of strains (S17 and S28) reached a chromium removal of 100% at 0.2 mM Cr(VI) initial concentration. Aerobically, this consortium was capable of 93.8% Cr(VI) reduction of 81 microg L(-1) Cr(VI) of the industrial effluent, indicating their possible use in environmental cleanup.

  3. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... the solution obtained by boiling 10 grams of the chromium-cobalt-aluminum oxide for 15 minutes in 50..., and set by annealing. (2) The quantity of the color additive does not exceed 2 percent by weight of...

  4. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... the solution obtained by boiling 10 grams of the chromium-cobalt-aluminum oxide for 15 minutes in 50..., and set by annealing. (2) The quantity of the color additive does not exceed 2 percent by weight of...

  5. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... the solution obtained by boiling 10 grams of the chromium-cobalt-aluminum oxide for 15 minutes in 50..., and set by annealing. (2) The quantity of the color additive does not exceed 2 percent by weight of...

  6. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... the solution obtained by boiling 10 grams of the chromium-cobalt-aluminum oxide for 15 minutes in 50..., and set by annealing. (2) The quantity of the color additive does not exceed 2 percent by weight of...

  7. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... the solution obtained by boiling 10 grams of the chromium-cobalt-aluminum oxide for 15 minutes in 50..., and set by annealing. (2) The quantity of the color additive does not exceed 2 percent by weight of...

  8. Structure and magnetic properties of chromium doped cobalt molybdenum nitrides

    NASA Astrophysics Data System (ADS)

    Guskos, Niko; Żołnierkiewicz, Grzegorz; Typek, Janusz; Guskos, Aleksander; Adamski, Paweł; Moszyński, Dariusz

    2016-09-01

    Four nanocomposites containing mixed phases of Co3Mo3N and Co2Mo3N doped with chromium have been prepared. A linear fit is found for relation between Co2Mo3N and chromium concentrations. The magnetization in ZFC and FC modes at different temperatures (2-300 K) and in applied magnetic fields (up to 70 kOe) have been investigated. It has been detected that many magnetic characteristics of the studied four nanocomposites correlate not with the chromium concentration but with nanocrystallite sizes. The obtained results were interpreted in terms of magnetic core-shell model of a nanoparticle involving paramagnetic core with two magnetic sublattices and a ferromagnetic shell related to chromium doping.

  9. The effect of chromium oxyhydroxide on solid oxide fuel cells.

    SciTech Connect

    Krumpelt, M.; Cruse, T. A.; Ingram, B. J.; Routbort, J. L.; Wang, S.; Salvador, P. A.; Chen, G.; Carnegie Mellon Univ.; NETL; Ohio Univ.

    2010-01-01

    Hexavalent chromium species like the oxyhydroxide, CrO{sub 2}(OH){sub 2}, or hexoxide, CrO{sub 3}, are electrochemically reduced to Cr{sub 2}O{sub 3} in solid oxide fuel cells and adversely affect the cell operating potentials. Using a narrowly focused beam from the Advanced Photon Source, such chromium oxide deposits were unequivocally identified in the active region of the cathode by X-ray diffraction, suggesting that the triple phase boundaries were partially blocked. Under fuel cell operating conditions, the reaction has an equilibrium potential of about 0.9 V and the rate of chromium oxide deposition is therefore dependent on the operating potential of the cell. It becomes diffusion limited after several hours of steady operation. At low operating potentials, lanthanum manganite cathodes begin to be reduced to MnO, which reacts with the chromium oxide to form the MnCr{sub 2}O{sub 4} spinel.

  10. [Occupational diseases caused by chromium and its compounds].

    PubMed

    Hassmanová, V; Vanĕcková, J; Bousová, K

    2000-01-01

    The present paper demonstrates by documentary evidence occupational diseases caused by chromium and its compounds. Perforations of the nasal septum were diagnosed in 20 males and 9 females, the last one in 1980. Most of them worked in chromium-plating shops. Other diseases, including bronchial asthma, allergic rhinitis, and contact allergic eczemas, were examined in 1985-1999. Bronchial asthma was reported in a textile dyer who was in contact with chromium dyes for 32 years and two allergic rhinitides (a welder and an electroplater) were reported in 1987 as "other damage to health resulting from work." Out of 103 contact allergic eczemas, only 24 diseases, i.e. less than one quarter, were healed in 1999. Improvements were observed in 59 of them and 20 diseases persist. There was an exceptional finding of a chromium ulcer (pigeonneaux) on the lower extremity of a builder.

  11. Chromium plating pollution source reduction by plasma source ion implantation

    SciTech Connect

    Chen, A.; Sridharan, K.; Dodd, R.A.; Conrad, J.R.; Qiu, X.; Hamdi, A.H.; Elmoursi, A.A.; Malaczynski, G.W.; Horne, W.G.

    1995-12-31

    There is growing concern over the environmental toxicity and workers` health issues due to the chemical baths and rinse water used in the hard chromium plating process. In this regard the significant hardening response of chromium to nitrogen ion implantation can be environmentally beneficial from the standpoint of decreasing the thickness and the frequency of application of chromium plating. In this paper the results of a study of nitrogen ion implantation of chrome plated test flats using the non-line-of-sight Plasma Source Ion Implantation (PSII) process, are discussed. Surface characterization was performed using Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), and Electron Spectroscopy for Chemical Analysis (ESCA). The surface properties were evaluated using a microhardness tester, a pin-on-disk wear tester, and a corrosion measurement system. Industrial field testing of nitrogen PSII treated chromium plated parts showed an improvement by a factor of two compared to the unimplanted case.

  12. IRIS Toxicological Review of Hexavalent Chromium (Peer Review Plan)

    EPA Science Inventory

    EPA is conducting a peer review of the scientific basis supporting the human health hazard and dose-response assessment of hexavalent chromium that will appear on the Integrated Risk Information System (IRIS) database.

  13. Chromium and Polyphenols from Cinnamon and Insulin Sensitivity

    USDA-ARS?s Scientific Manuscript database

    Factors that improve insulin sensitivity usually lead to improvements in risk factors associated with the metabolic syndrome, diabetes, and cardiovascular diseases. Naturally occurring bioactive compounds that have been shown to improve insulin sensitivity include chromium and polyphenols found in ...

  14. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  15. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  16. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  17. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  18. 21 CFR 73.2326 - Chromium hydroxide green.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2326 Chromium hydroxide green. (a) Identity and... in coloring externally applied cosmetics, including those intended for use in the area of the eye,...

  19. 21 CFR 73.2327 - Chromium oxide greens.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... COLOR ADDITIVES EXEMPT FROM CERTIFICATION Cosmetics § 73.2327 Chromium oxide greens. (a) Identity and... may be safely used in externally applied cosmetics, including cosmetics intended for use in the...

  20. Molecular Mechanisms of Chromium in Alleviating Insulin Resistance

    PubMed Central

    Hua, Yinan; Clark, Suzanne; Ren, Jun; Sreejayan, Nair

    2011-01-01

    Type 2 diabetes is often associated with obesity, dyslipidemia, and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance. PMID:22423897

  1. Extended followup of a cohort of chromium production workers.

    PubMed

    Gibb, Herman Jones; Lees, Peter St John; Wang, Jing; Grace O'Leary, Keri

    2015-08-01

    The current study evaluates the mortality of 2,354 workers first employed at a Baltimore chromate production plant between 1950 and 1974. The National Death Index (NDI Plus) was used to determine vital status and cause of death. Cumulative chromium (VI) exposure and nasal and skin irritation were evaluated as risk factors for lung cancer mortality. There are 91,186 person-years of observation and 217 lung cancer deaths. Cumulative chromium (VI) exposure, nasal irritation, nasal perforation, nasal ulceration, and other forms of irritation (e.g., skin irritation) were associated with lung cancer mortality. Cumulative chromium (VI) exposure was a risk factor for lung cancer death. Cancer deaths, other than lung cancer, were not significantly elevated. Irritation may be a possible mechanism for chromium (VI)-induced lung cancer. © 2015 The Authors. American Journal of Industrial Medicine Published by Wiley Periodicals, Inc.

  2. IRIS Toxicological Review of Hexavalent Chromium (Peer Review Plan)

    EPA Science Inventory

    EPA is conducting a peer review of the scientific basis supporting the human health hazard and dose-response assessment of hexavalent chromium that will appear on the Integrated Risk Information System (IRIS) database.

  3. USE OF FUME SUPPRESSANTS IN HARD CHROMIUM BATHS - QUALITY TESTING

    EPA Science Inventory

    The EPA Common Sense Initiative (CSI) is a cooperative effort of government, industry, environmental and other stakeholder groups to find "cleaner, cheaper, smarter" approaches to environmental management in industrial sectors. The purpose of the project is to help hard chromium ...

  4. USE OF FUME SUPPRESSANTS IN HARD CHROMIUM BATHS - QUALITY TESTING

    EPA Science Inventory

    The EPA Common Sense Initiative (CSI) is a cooperative effort of government, industry, environmental and other stakeholder groups to find "cleaner, cheaper, smarter" approaches to environmental management in industrial sectors. The purpose of the project is to help hard chromium ...

  5. Chromium (V) compounds as cathode material in electrochemical power sources

    DOEpatents

    Delnick, F.M.; Guidotti, R.A.; McCarthy, D.K.

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca/sub 5/(CrO/sub 4/)/sub 3/Cl, Ca/sub 5/(CrO/sub 4/)OH, and Cr/sub 2/O/sub 5/. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

  6. Lessons Learned in Implementing Hexavalent Chromium and other Material Restrictions

    DTIC Science & Technology

    2011-05-01

    Lead and Lead Compounds – Mercury – Methylene Chloride – Methyl Ethyl Ketone – Nickel and Nickel Compounds – Polychlorinated Biphenyls (PCBs...targeted materials across DoD programs for new programs – Asbestos, Cadmium, Hexavalent Chromium, Mercury , + ?? • Consider life cycle risk based analysis...Use existing framework when possible – Is RoHs compliant good enough in specific cases? [RoHS; .1 % lead, .1% mercury , .1% hexavalent chromium, .1

  7. Sludge Generation from Ferrous/Sulfide Chromium Treatment.

    DTIC Science & Technology

    1984-08-01

    sodium bisulfite , sulfur dioxide, and sodium sulfide. While all these chemicals produce a satisfactory effluent, the quantity of sludge produced by the...34Treatment of Toxic Metal Wastewaters by Alkaline Ferrous Sulfate and Sodium Sulfied for Chromium Reduction, Precipitation and Coagulation," Pro... sodium sulfide and ferrous chloride (9:1 ratio) at pH 8.0 rapidly reduced hexavalent chromium and produced approximately one-fourth the sludge (on a

  8. SCIENCE AND TECHNOLOGY ACTIVITIES FOR CHROMIUM IN THE 100 AREAS

    SciTech Connect

    PETERSEN SW

    2009-07-02

    {sm_bullet} Primary Objective: Protect the Columbia River - Focus is control and treatment of contamination at or near the shoreline, which is influenced by bank storage {sm_bullet} Secondary Objective: Reduce hexavalent chromium to <48 parts per billion (ppb) in aquifer (drinking water standard) - Large plumes with isolated areas of high chromium concentrations (> 40,000 ppb), - Unknown source location(s); probably originating in reactor operation areas

  9. Electrodeposition of amorphous ternary nickel-chromium-phosphorus alloy

    DOEpatents

    Guilinger, Terry R.

    1990-01-01

    Amorphous ternary nickel-chromium-phosphorus alloys are electrodeposited from a bath comprising a nickel salt, a chromium salt, a phosphorus source such as sodium hypophosphite, a complexing agent for the nickel ions, supporting salts to increase conductivity, and a buffering agent. The process is carried out at about room temperature and requires a current density between about 20 to 40 A/dm.sup.2.

  10. Chromium (V) compounds as cathode material in electrochemical power sources

    DOEpatents

    Delnick, Frank M.; Guidotti, Ronald A.; McCarthy, David K.

    1985-01-01

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca.sub.5 (CrO.sub.4).sub.3 Cl, Ca.sub.5 (CrO.sub.4).sub.3 OH, and Cr.sub.2 O.sub.5. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

  11. Chromium Ions Improve Moisure Resistance of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

    1986-01-01

    Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

  12. Chromium Ions Improve Moisure Resistance of Epoxy Resins

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; St. Clair, T. L.; Stoakley, D. M.; Singh, J. J.; Sprinkle, D. R.

    1986-01-01

    Broad spectrum of thermosetting epoxy resins used on commercial and military aircraft, primarily as composite matrices and adhesives. In new technique, chromium-ion containing epoxy with improved resistance to moisture produced where chromium ions believed to prevent absorption of water molecules by coordinating themselves to hydroxyl groups on epoxy chain. Anticipated that improved epoxy formulation useful as composite matrix resin, adhesive, or casting resin for applications on commercial and advanced aircraft. Improvement made without sacrifice in mechanical properties of polymer.

  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. Nitrated metalloporphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1994-01-18

    Compositions of matter comprising nitro-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has nitro groups attached thereto in meso and/or [beta]-pyrrolic positions.

  18. Nitrated metalloporphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1994-01-01

    Compositions of matter comprising nitro-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has nitro groups attached thereto in meso and/or .beta.-pyrrolic positions.

  19. Chromium contamination in Army face masks. Final report

    SciTech Connect

    Not Available

    1989-01-01

    The National Research Council's Committee on Toxicology's Subcommittee on Chromium Contamination in Army Face Masks reviewed the possible health risks to soldiers associated with exposure to U.S. Army gas-mask canisters containing activated charcoal impregnated with hexavalent chromium, a carcinogen. The canisters are attached to masks used to detoxify toxic gases, such as hydrogen chloride and cyanogen chloride. In 1982, reports surfaced of dark smudges on the faces of mask users; the smudges were traced to leaking of activated charcoal fines from canisters. The carbon smudging was also associated with some exposure to hexavalent chromium. The subcommittee's review of data provided by the Army on the amounts of chromium released during tests of gas-mask canisters indicated that the amounts of insoluble hexavalent chromium--chromium (VI)--found in the C2 canister (developed by the Canadian Army) and in the field-fixed and redesigned M10Al canisters are well within the limits implied by standards set by the National Institute for Occupational Safety and Health under worst-case mask use conditions.

  20. Environmental monitoring of chromium in air, soil, and water.

    PubMed

    Vitale, R J; Mussoline, G R; Rinehimer, K A

    1997-08-01

    Historical uses of chromium have resulted in its widespread release into the environment. In recent years, a significant amount of research has evaluated the impact of chromium on human health and the environment. Additionally, numerous analytical methods have been developed to identify and quantitate chromium in environmental media in response to various state and federal mandates such as CERCLA, RCRA, CWA, CAA, and SWDA. Due to the significant toxicity differences between trivalent [Cr(III)] and hexavalent [Cr(VI)] chromium, it is essential that chromium be quantified in these two distinct valence states to assess the potential risks to exposure to each in environmental media. Speciation is equally important because of their marked differences in environmental behavior. As the knowledge of risks associated with each valence state has grown and regulatory requirements have evolved, methods to accurately quantitate these species at ever-decreasing concentrations within environmental media have also evolved. This paper addresses the challenges of chromium species quantitation and some of the most relevant current methods used for environmental monitoring, including ASTM Method D5281 for air, SW-846 Methods 3060A, 7196A and 7199 for soils, sediments, and waste, and U.S. EPA Method 218.6 for water.

  1. Lime enhanced chromium removal in advanced integrated wastewater pond system.

    PubMed

    Tadesse, I; Isoaho, S A; Green, F B; Puhakka, J A

    2006-03-01

    The removal of trivalent chromium from a combined tannery effluent in horizontal settling tanks and subsequent Advanced Integrated Wastewater Pond System (AIWPS) reactors was investigated. The raw combined effluent from Modjo tannery had pH in the range of 11.2-12. At this pH, a trivalent chromium removal of 46-72% was obtained in the horizontal settling tanks after a one-day detention time. Trivalent chromium precipitated as chromium hydroxide, Cr(OH)3. 58-95% Cr(III) was removed in the advanced facultative pond (AFP) where the water column pH of 7.2-8.4 was close to pH 8, which is the optimum precipitation pH for trivalent chromium. Chromium removals in the secondary facultative pond (SFP) and maturation pond (MP) were 30-50% and 6-16%, respectively. With Cr(III) concentration of 0.2-0.8 mg/l in the final treated effluent, the AIWPS preceded by horizontal settling tanks produced effluent that could easily meet most of the current Cr(III) discharge limits to receive water bodies.

  2. Carcinogenicity of chromium and chemoprevention: a brief update

    PubMed Central

    Gu, Yuanliang; Song, Xin; Zhao, Jinshun

    2017-01-01

    Chromium has two main valence states: hexavalent chromium (Cr[VI]) and trivalent chromium (Cr[III]). Cr(VI), a well-established human carcinogen, can enter cells by way of a sulfate/phosphate anion-transport system, and then be reduced to lower-valence intermediates consisting of pentavalent chromium (Cr[V]), tetravalent chromium (Cr[IV]) or Cr(III) via cellular reductants. These intermediates may directly or indirectly result in DNA damage or DNA–protein cross-links. Although Cr(III) complexes cannot pass easily through cell membranes, they have the ability to accumulate around cells to induce cell-surface morphological alteration and result in cell-membrane lipid injuries via disruption of cellular functions and integrity, and finally to cause DNA damage. In recent years, more research, including in vitro, in vivo, and epidemiological studies, has been conducted to evaluate the genotoxicity/carcinogenicity induced by Cr(VI) and/or Cr(III) compounds. At the same time, various therapeutic agents, especially antioxidants, have been explored through in vitro and in vivo studies for preventing chromium-induced genotoxicity/carcinogenesis. This review aims to provide a brief update on the carcinogenicity of Cr(VI) and Cr(III) and chemoprevention with different antioxidants. PMID:28860815

  3. Method for fabricating cermets of alumina-chromium systems

    DOEpatents

    Morgan, Chester S.

    1983-01-01

    Cermet insulators resistant to thermal and mechanical shock are prepared from alumina-chromium systems by providing an Al.sub.2 O.sub.3 material of about 0.5 to 7.0 micron size with a solid-hydrocarbon overcoating by slurring an effective amount of said solid hydrocarbon in a solvent mixture containing said Al.sub.2 O.sub.3 and thereafter evaporating said solvent, contacting said coated Al.sub.2 O.sub.3 with a solution of chromium precursor compound, heating the resulting mixture in a reducing environment to a temperature above the decomposition temperature of said chromium precursor compound but less than the melting temperature of the Al.sub.2 O.sub.3 or chromium for sufficient duration to yield a particulate compound having chromium essentially dispersed throughout the Al.sub.2 O.sub.3, and then densifying said particulate to provide said cermet characterized by a theoretical density in excess of 96% and having 0.1 to 10.0 vol.% elemental chromium metal present therein as a dispersed phase at the boundaries of the Al.sub.2 O.sub.3 material. Cermet components prepared thereby are useful in high temperature equipment, advanced heat engines, and nuclear-related equipment applications where electrical or thermal insulators are required.

  4. Evaluating trivalent chromium toxicity on wild terrestrial and wetland plants.

    PubMed

    Lukina, A O; Boutin, C; Rowland, O; Carpenter, D J

    2016-11-01

    Elevated chromium levels in soil from mining can impact the environment, including plants. Mining of chromium is concentrated in South Africa, several Asian countries, and potentially in Northern Ontario, Canada, raising concerns since chromium toxicity to wild plants is poorly understood. In the first experiment, concentration-response tests were conducted to evaluate effects of chromium on terrestrial and wetland plants. Following established guidelines using artificial soil, seeds of 32 species were exposed to chromium (Cr(3+)) at concentrations simulating contamination (0-1000 mg kg(-1)). This study found that low levels of chromium (250 mg kg(-1)) adversely affected the germination of 22% of species (33% of all families), while higher levels (500 and 1000 mg kg(-1)) affected 69% and 94% of species, respectively, from 89% of the families. Secondly, effects on seedbanks were studied using soil collected in Northern Ontario and exposed to Cr(3+) at equivalent concentrations (0-1000 mg kg(-1)). Effects were less severe in the seedbank study with significant differences only observed at 1000 mg kg(-1). Seeds exposed to Cr(3+) during stratification were greatly affected. Seed size was a contributing factor as was possibly the seed coat barrier. This study represents an initial step in understanding Cr(3+) toxicity on wild plants and could form the basis for future risk assessments.

  5. The chemistry of chromium and some resulting analytical problems.

    PubMed Central

    Shupack, S I

    1991-01-01

    Chromium, named for its many-colored compounds, exists in the oxidation states of -2 to +6 inclusively. The compounds exhibit a wide range of geometries including square planar, tetrahedral, octahedral, and various distorted geometries. Chromium is found in nature principally as the chromite ore FeCr2O4 in which chromium is in the +3 state. The existence of a particular oxidation state is dependent on many factors including pH, redox potentials, and kinetics. Thermodynamically, +3 and +2 are the most stable states, while the +3 and +6 oxidation states are the most common ones found in aqueous solution. Kinetically, chromium +3 is substitutionally inert: for water exchange k(sec-1) = 2.5 x 10(-6), due to the presence of the half-filled d(t2g)3.4A2g state. On the other hand, protonation/deprotonation is quite rapid. Polymerization is very slow but is promoted at higher pHs; acid cleavage of the protonated oligomers is also quite slow. Chromium +6 as the chromate ion is strongly oxidizing at low pHs and less so in basic solution. The chromate ion does form some polyacids and polyanions. These factors must be considered in analyzing samples for total chromium and for the amounts of each oxidation state. Images FIGURE 1. PMID:1935853

  6. Removal of chromium from industrial waste by using eucalyptus bark.

    PubMed

    Sarin, Vikrant; Pant, K K

    2006-01-01

    Several low cost biomaterials such as baggase, charred rice husk, activated charcoal and eucalyptus bark (EB) were tested for removal of chromium. All the experiments were carried out in batch process with laboratory prepared samples and wastewater obtained from metal finishing section of auto ancillary unit. The adsorbent, which had highest chromium(VI) removal was EB. Influences of chromium concentration, pH, contact time on removal of chromium from effluent was investigated. The adsorption data were fitted well by Freundlich isotherm. The kinetic data were analyzed by using a first order Lagergren kinetic. The Gibbs free energy was obtained for each system and was found to be -1.879 kJ mol(-1) for Cr(VI) and -3.885 kJ mol(-1) for Cr(III) for removal from industrial effluent. The negative value of deltaG0 indicates the feasibility and spontaneous nature of adsorption. The maximum removal of Cr(VI) was observed at pH 2. Adsorption capacity was found to be 45 mg/g of adsorbent, at Cr(VI) concentration in the effluent being 250 mg/l. A waste water sample containing Cr(VI), Cr(III), Mg, and Ca obtained from industrial unit showed satisfactory removal of chromium. The results indicate that eucalyptus bark can be used for the removal of chromium.

  7. Cytokine detection for the diagnosis of chromium allergy*

    PubMed Central

    Martins, Luis Eduardo Agner Machado; dos Reis, Vitor Manoel Silva

    2013-01-01

    BACKGROUND Patch testing remains the gold standard method for the identification of the etiologic agent of allergic contact dermatitis. However, it is a subjective, time-consuming exam whose technique demands special care and which presents some contraindications, which hamper its use. In a recent study, we showed that the proliferation assay can suitably replace patch testing for the diagnosis of chromium allergy, which had been previously demonstrated only for nickel allergy. In this study, we try to refine the method by reducing the incubation period of cultures for lymphocyte proliferation assays in response to chromium. OBJECTIVE Develop an alternative or complementary diagnostic test for chromium allergic contact dermatitis. METHODS We compared the production of 9 cytokines (IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17 and RANTES) between 18 chromium-allergic patients and 19 controls. RESULTS Chromium increased the production of IFN-y, IL-5, IL-2 and IL-13 in allergic patients, but only IL-2 and especially IL-13 helped discriminate allergic patients from controls. The sensitivity, specificity and accuracy found with IL-13 were about 80%. CONCLUSIONS IL-13 and IL-2 detection may be used to diagnose chromium allergy in 2-day cultures. However, in general, the 6-day cultures seem to be superior for this purpose. PMID:24173176

  8. Stabilization of carbon dioxide and chromium slag via carbonation.

    PubMed

    Wu, Xingxing; Yu, Binbin; Xu, Wei; Fan, Zheng; Wu, Zucheng; Zhang, Huimin

    2017-08-01

    As the main greenhouse gas, CO2 is considered as a threat in the context of global warming. Many available technologies to reduce CO2 emission was about CO2 separation from coal combustion and geological sequestration. However, how to deal with the cost-effective storage of CO2 has become a new challenge. Moreover, chromium pollution, the treatment of which requires huge energy consumption, has attracted people's widespread attention. This study is aimed to develop the sequestration of CO2 via chromium slag. A dynamic leaching experiment of chromium slag was designed to testify the ability of CO2 adsorption onto chromium slag and to release Cr(VI) for stabilization. The results showed that the accumulative amounts of Cr(VI) were ca. 2.6 mg/g released from the chromium slag after 24 h of leaching. In addition, ca. 89 mg/g CO2 was adsorbed by using pure CO2 in the experiment at 12 h. Calcite is the only carbonate species in the post-carbonated slag analyzed by powder X-ray diffraction and thermal analysis. The approach provides the feasibility of the utilization of chromium slag and sequestration of the carbon dioxide at the same time at ordinary temperatures and pressures.

  9. Chromium Exposure and Hygienic Behaviors in Printing Workers in Southern Thailand

    PubMed Central

    Decharat, Somsiri

    2015-01-01

    Objectives. The main objective of this study was to assess the chromium exposure levels in printing workers. The study evaluated the airborne, serum, and urinary chromium levels and determines any correlation between level of chromium in specimen and airborne chromium levels. Material and Methods. A cross-sectional study was conducted with 75 exposed and 75 matched nonexposed subjects. Air breathing zone was measured by furnace atomic absorption spectrophotometer. Serum and urine samples were collected to determine chromium levels by graphite furnaces atomic absorption spectrometer chromium analyzer. Results and Discussion. The printing workers' urinary chromium levels (6.86 ± 1.93 μg/g creatinine) and serum chromium levels (1.24 ± 1.13 μg/L) were significantly higher than the control group (p < 0.001 and p < 0.001). Work position, duration of work, personal protective equipment (PPE), and personal hygiene were significantly associated with urinary chromium level and serum chromium levels (p < 0.001 and p < 0.001). This study found a correlation between airborne chromium levels and urinary chromium levels (r = 0.247, p = 0.032). A multiple regression model was constructed. Significant predictors of urinary and serum chromium levels were shown in this study. Conclusion. Improvements in working conditions, occupational health training, and PPE use are recommended to reduce chromium exposure. PMID:26448746

  10. 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

  11. 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.

  12. 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.

  13. Establishment of a reference value for chromium in the blood for biological monitoring among occupational chromium workers.

    PubMed

    Li, Ping; Li, Yang; Zhang, Ji; Yu, Shan-Fa; Wang, Zhi-Liang; Jia, Guang

    2016-10-01

    The concentration of chromium in the blood (CrB) has been confirmed as a biomarker for occupational chromium exposure, but its biological exposure indices (BEIs) are still unclear, so we collected data from the years 2006 and 2008 (Shandong Province, China) to analyze the relationship between the concentration of chromium in the air (CrA) of the workplaces and CrB to establish a reference value of CrB for biological monitoring of occupational workers. The levels of the indicators for nasal injury, kidney (β2 microglobulin (β2-MG)), and genetic damages (8-hydroxy-deoxyguanosine (8-OHdG) and micronucleus (MN)) were measured in all subjects of the year 2011 (Henan Province, China) to verify the protective effect in this reference value of CrB. Compared with the control groups, the concentrations of CrA and CrB in chromium exposed groups were significantly higher (P < 0.05). Positive correlations were found between CrA and CrB in chromium exposed groups (r 2006 = 0.60, r 2008 = 0.35) in the years 2006 and 2008. According to the occupational exposure limitation of CrA (50 μg/m(3), China), the reference value of CrB was recommended to 20 μg/L. The levels of nasal injury, β2-MG, 8-OhdG, and MN were not significantly different between the low chromium exposed group (CrB ≤ 20 μg/L) and the control group, while the levels of β2-MG, 8-OHdG, and MN were statistically different in the high chromium exposed group than that in the control group. This research proved that only in occupational workers, CrB could be used as a biomarker to show chromium exposure in the environment. The recommended reference value of CrB was 20 μg/L. © The Author(s) 2015.

  14. Chromium Isotopic Fractionation During Biogeochemical Cr (IV) Reduction in Hanford Sediment Column Experiments with Native Aquifer Microbial Communities

    NASA Astrophysics Data System (ADS)

    Qin, L.; Christensen, J. N.; Brown, S. T.; Yang, L.; Conrad, M. E.; Sonnenthal, E. L.; Beller, H. R.

    2010-12-01

    Hexavalent Chromium contamination in groundwater within the DOE complex, including the Hanford 100D and 100H sites has been a long-standing issue. It has been established that certain bacteria (including denitrifying and sulfate-reducing bacteria) harbor enzymes that catalyze Cr(VI) reduction to relatively nontoxic Cr(III). Microbial reduction of Cr(VI) also occurs indirectly by products of microbial respiration, such as sulfide and Fe(II). Chromium isotopes can be fractionated during Cr(VI) reduction and provides a potential basis for characterizing and discriminating between different microbial metabolic and geochemical pathways associated with Cr(VI) reductive immobilization. Addition of electron donor to contaminated groundwater systems to create conditions favorable for reductive metal immobilization has become a widely utilized remediation practice. We conducted a series of small-scale column experiments with homogenized material from the Hanford 100H aquifer to examine the effects of differing electron acceptors on local microbial communities. All columns have a continuous inflow of solutions with constant concentrations of Cr(VI), lactate (electron donor), and the appropriate electron acceptor (e.g. nitrate or sulfate). The Cr isotopic composition in the effluent was measured using a 50-54 double-spike technique and a Triton TIMS. Cr concentration measurements showed that the greatest Cr(VI) reduction occurred in the sulfate columns. Our preliminary Cr isotopic data show that under these conditions the delta 53Cr value increased from close to 0 to 4 per mil while the Cr concentration decreased from 260 ppb to 30 ppb in the effluent. This yields an apparent fractionation factor of 0.9979 (2.1 per mil). A decrease in Cr concentration from 260 ppb to 190 ppb in a nitrate-reducing column was accompanied by an increase of 1 per mil in delta 53Cr. Further Cr isotopic data will be presented and the effects of differing flow rates and electron acceptors will be

  15. Complete genome sequence of Pseudomonas stutzeri strain RCH2 isolated from a Hexavalent Chromium [Cr(VI)] contaminated site

    DOE PAGES

    Chakraborty, Romy; Woo, Hannah; Dehal, Paramvir; ...

    2017-02-08

    Hexavalent Chromium [Cr(VI)] is a widespread contaminant found in soil, sediment, and ground water in several DOE sites, including Hanford 100 H area. In order to stimulate microbially mediated reduction of Cr(VI) at this site, a poly-lactate hydrogen release compound was injected into the chromium contaminated aquifer. The targeted enrichment of dominant nitrate-reducing bacteria post injection resulted in the isolation of Pseudomonas stutzeri strain RCH2. P. stutzeri strain RCH2 was isolated using acetate as the electron donor and is a complete denitrifier. Experiments with anaerobic washed cell suspension of strain RCH2 revealed it could reduce Cr(VI) and Fe(III). We sequencedmore » the genome of strain RCH2 using a combination of Illumina and 454 sequencing technologies and contained a circular chromosome of 4.6 Mb and three plasmids. Furthermore, global genome comparisons of strain RCH2 with six other fully sequenced P. stutzeri strains revealed most genomic regions are conserved, however strain RCH2 has an additional 244 genes, some of which are involved in chemotaxis, Flp pilus biogenesis and pyruvate/2-oxogluturate complex formation.« less

  16. Chromium released from leather - I: exposure conditions that govern the release of chromium(III) and chromium(VI).

    PubMed

    Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

    2015-04-01

    Approximately 1-3% of the adult population in Europe is allergic to chromium (Cr). A new restriction in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) based on the ISO 17075 standard has recently been adopted in the EU to limit Cr(VI) in consumer and occupational leather products. The aim of this study was to critically assess key experimental parameters in this standard on the release of Cr(III) and Cr(VI) and their relevance for skin exposure. Four differently tanned, unfinished, leather samples were systematically investigated for their release of Cr(III) and Cr(VI) in relation to surface area, key exposure parameters, temperature, ultraviolet irradiation, and time. Although the total release of Cr was largely unaffected by all investigated parameters, except exposure duration and temperature, the Cr oxidation state was highly dynamic, with reduced amounts of released Cr(VI) with time, owing to the simultaneous release of reducing agents from the leather. Significantly more Cr(III) than Cr(VI) was released from the Cr-tanned leather for all conditions tested, and it continued to be released in artificial sweat up to at least 1 week of exposure. Several parameters were identified that influenced the outcome of the ISO 17075 test. © 2015 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.

  17. Chromium released from leather – I: exposure conditions that govern the release of chromium(III) and chromium(VI)

    PubMed Central

    Hedberg, Yolanda S; Lidén, Carola; Odnevall Wallinder, Inger

    2015-01-01

    Background Approximately 1–3% of the adult population in Europe is allergic to chromium (Cr). A new restriction in REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) based on the ISO 17075 standard has recently been adopted in the EU to limit Cr(VI) in consumer and occupational leather products. Objectives The aim of this study was to critically assess key experimental parameters in this standard on the release of Cr(III) and Cr(VI) and their relevance for skin exposure. Material and methods Four differently tanned, unfinished, leather samples were systematically investigated for their release of Cr(III) and Cr(VI) in relation to surface area, key exposure parameters, temperature, ultraviolet irradiation, and time. Results Although the total release of Cr was largely unaffected by all investigated parameters, except exposure duration and temperature, the Cr oxidation state was highly dynamic, with reduced amounts of released Cr(VI) with time, owing to the simultaneous release of reducing agents from the leather. Significantly more Cr(III) than Cr(VI) was released from the Cr-tanned leather for all conditions tested, and it continued to be released in artificial sweat up to at least 1 week of exposure. Conclusions Several parameters were identified that influenced the outcome of the ISO 17075 test. PMID:25653094

  18. 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...

  19. 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.

  20. 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.