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Sample records for hexavalent chromium delays

  1. Hexavalent Chromium Workshop

    EPA Science Inventory

    EPA is developing an updated IRIS assessment of hexavalent chromium. This assessment will evaluate the potential health effects of hexavalent chromium from oral and inhalation exposures. An important component of determining the cancer causing potential of ingested hexavalent chr...

  2. Dermatological toxicity of hexavalent chromium.

    PubMed

    Shelnutt, Susan R; Goad, Phillip; Belsito, Donald V

    2007-06-01

    Hexavalent chromium causes two types of dermatological toxicities: allergic contact dermatitis (ACD) and skin ulcers. This report reviews the etiology, prevalence, pathology, dose-response, and prognosis of both of these reactions. Reports in the literature indicate that repeated exposure to hexavalent chromium in concentrations of 4-25 ppm can both induce sensitization and elicit chromium ACD. Exposure to 20 ppm hexavalent chromium can cause skin ulcers in nonsensitized people. The prevalence of chromium sensitivity in cement workers, exposed to 10-20 ppm hexavalent chromium for years, is approximately 4-5%. Chromium ACD can be a chronic debilitating disease, perhaps because chromium is ubiquitous in foods and in the environment and is difficult to avoid. Due to the high rates of sensitization in populations chronically exposed to chromium and the chronic nature of chromium ACD, some investigators recommend reducing the hexavalent chromiumconcentrations in consumer products, such as detergents, to less than 5 ppm. PMID:17612952

  3. 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.

  4. 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.

  5. Lactational exposure to hexavalent chromium delays puberty by impairing ovarian development, steroidogenesis and pituitary hormone synthesis in developing Wistar rats

    SciTech Connect

    Banu, Sakhila K. Samuel, Jawahar B.; Arosh, Joe A.; Burghardt, Robert C.; Aruldhas, Michael M.

    2008-10-15

    Hexavalent chromium (Cr-VI) is used in a wide range of industries. Cr-VI from chromate industries and atmospheric emissions contribute to the Cr contamination in the environment. Cr is a reproductive metal toxicant that can traverse the placental barrier and cause a wide range of fetal effects including ovotoxicity. Therefore, the goal of this study was to investigate the basic mechanisms involved in Cr(VI)-induced ovotoxicity, and the protective role of vitamin C on ovarian follicular development and function in Cr(VI)-induced reproductive toxicity using both in vivo and in vitro approaches. Lactating rats received potassium dichromate (200 mg/L) with or without vitamin C (500 mg/L), through drinking water from postpartum days 1-21. During postnatal days (PND) 1-21 the pups received Cr(VI) via the mother's milk. Pups from both control and treatment groups were continued on regular diet and water from PND-21 onwards, and euthanized on PND-21, -45 and -65. Cr(VI) decreased steroidogenesis, GH and PRL, increased FSH and did not alter LH. Cr(VI) delayed puberty, decreased follicle number, and extended estrous cycle. Spontaneously immortalized rat granulosa cells were treated with 12.5 {mu}M (IC{sub 50}) potassium dichromate for 12 and 24 h, with or without vitamin C pre-treatment. Cr(VI) decreased the mRNA expressions of StAR, SF-1, 17{beta}-HSD-1, 17{beta}-HSD-2, FSHR, LHR, ER{alpha} and ER{beta}. Vitamin C pre-treatment protected ovary and granulosa cells from the deleterious effects of Cr(VI) toxicity, both in vivo and in vitro. Therefore, Cr(VI) toxicity could be a potential risk to the reproductive system in developing females, and vitamin C plays a protective role against Cr(VI)-induced ovotoxicity.

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. 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. PMID:26361854

  11. ACTIVATED CARBON PROCESS FOR TREATMENT OF WASTEWATERS CONTAINING HEXAVALENT CHROMIUM

    EPA Science Inventory

    The removal of hexavalent chromium, Cr(VI), from dilute aqueous solution by an activated carbon process has been investigated. Two removal mechanisms were observed; hexavalent chromium species were removed by adsorption onto the interior carbon surface and/or through reduction to...

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

    EPA Science Inventory

  1. 77 FR 61431 - Hexavalent Chromium Standards; Extension of the Office of Management and Budget's (OMB) Approval...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-09

    ... Occupational Safety and Health Administration Hexavalent Chromium Standards; Extension of the Office of...) approval of the information collection requirements specified in the Hexavalent Chromium Standards for... requirements specified in the Hexavalent Chromium (Cr(VI)) Standards for General Industry (29 CFR...

  2. The removal of hexavalent chromium from water by ferrous sulfate

    SciTech Connect

    Lin, C.J.J.; Vesilind, P.A.

    1995-12-31

    The redox reaction of hexavalent chromium and ferrous sulfate is investigated in his study. Hexavalent chromium, a highly toxic and mobile anion, could exist in raw water used as a public water supply due to the industrial chromium contamination of natural water or due to natural oxidation of trivalent chromium. Ferrous sulfate is one of the widely used coagulants in water treatment plants and has good reducing ability. Because of its reducing capacity, ferrous sulfate can be applied to remove hexavalent chromium from water. The required contact time to reach equilibrium, the effectiveness of Cr(VI) reduction at different initial pH, and the required ferrous sulfate dosage for complete reduction are investigated. The redox reaction can be completed within 10 minutes, allowing 30 mg/L of hexavalent chromium to react with stoichiometric dosage of ferrous sulfate in deionized water, regardless of the initial pH. The pH of the solution is depressed during the progress of the reaction due to the hydrolysis of the produced Fe(III) and Cr(III) ions from the reaction. Dissolved oxygen in water is found to interfere with the redox reaction by consuming ferrous ions when the initial pH of solutions is high. In deionized water, complete Cr(VI) reduction can be achieved by applying excess ferrous sulfate under the condition of this study. It is also achievable when the raw water from Durham Water Treatment Plant is used as the reaction medium, without additional dosage of ferrous sulfate. Based on the results, simultaneous removal of hexavalent chromium in water treatment by applying ferrous sulfate as the coagulant is theoretically feasible.

  3. IRIS TOXICOLOGICAL REVIEW OF HEXAVALENT CHROMIUM (INTERAGENCY SCIENCE CONSULTATION DRAFT)

    EPA Science Inventory

    On Septemeber 30, 2010, the draft Toxicological Review of Hexavalent Chromium and the charge to external peer reviewers were released for external peer review and public comment. The Toxicological Review and charge were reviewed internally by EPA and by other federal agenc...

  4. CUTICULAR LESIONS INDUCED IN GRASS SHRIMP EXPOSED TO HEXAVALENT CHROMIUM

    EPA Science Inventory

    Adult grass shrimp were exposed to four concentrations (0.5, 1.0, 2.0 and 4.0 ppm) of hexavalent chromium for 38 days. At the end of the exposure period, over 50% of the surviving shrimp possessed cuticular lesions that had many of the gross characteristics of 'shell disease.' Th...

  5. Potential of Live Spirulina platensis on Biosorption of Hexavalent Chromium and Its Conversion to Trivalent Chromium.

    PubMed

    Colla, Luciane Maria; Dal'Magro, Clinei; De Rossi, Andreia; Thomé, Antônio; Reinehr, Christian Oliveira; Bertolin, Telma Elita; Costa, Jorge Alberto Vieira

    2015-01-01

    Microalga biomass has been described worldwide according their capacity to realize biosorption of toxic metals. Chromium is one of the most toxic metals that could contaminate superficial and underground water. Considering the importance of Spirulina biomass in production of supplements for humans and for animal feed we assessed the biosorption of hexavalent chromium by living Spirulina platensis and its capacity to convert hexavalent chromium to trivalent chromium, less toxic, through its metabolism during growth. The active biomass was grown in Zarrouk medium diluted to 50% with distilled water, keeping the experiments under controlled conditions of aeration, temperature of 30°C and lighting of 1,800 lux. Hexavalent chromium was added using a potassium dichromate solution in fed-batch mode with the aim of evaluate the effect of several additions contaminant in the kinetic parameters of the culture. Cell growth was affected by the presence of chromium added at the beginning of cultures, and the best growth rates were obtained at lower metal concentrations in the medium. The biomass removed until 65.2% of hexavalent chromium added to the media, being 90.4% converted into trivalent chromium in the media and 9.6% retained in the biomass as trivalent chromium (0.931 mg.g(-1)). PMID:25436450

  6. 48 CFR 252.223-7008 - Prohibition of Hexava-lent Chromium.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  7. Hexavalent chromium in the ground and surface waters near Telluride, Colorado; preliminary data report

    USGS Publications Warehouse

    Grove, David B.; Miller, R.L.; Konikow, L.F.; O'Boyle, P. S.

    1979-01-01

    Data showing results of 38 groundwater and 25 surface-water samples analyzed for hexavalent chromium are presented. Most samples were taken within the Telluride, Colo., city limits during October 1978. Twenty-four of the 38 groundwater samples (63%) contained more than 50 micrograms per liter of hexavalent chromium. Excluding the mill tailings pond 6 of the 23 surface-water samples (26%) contained more than 50 micrograms per liter of hexavalent chromium. Hexavalent chromium concentrations in groundwaters ranged from 0 to 2700 micrograms per liter and in surface waters from 0 to 160 micrograms per liter. (USGS)

  8. Hexavalent chromium reduction by bacteria from tannery effluent.

    PubMed

    Batool, Rida; Yrjala, Kim; Hasnain, Shahida

    2012-04-01

    Chromium is generated from several industrial processes. It occurs in different oxidation states, but Cr(III) and Cr(VI) are the most common ones. Cr(VI) is a toxic, soluble environmental contaminant. Some bacteria are able to reduce hexavalent chromium to the insoluble and less toxic Cr(III), and thus chromate bioremediation is of considerable interest. An indigenous chromium-reducing bacterial strain, Rb-2, isolated from a tannery water sample, was identified as Ochrobactrum intermedium, on the basis of 16S rRNA gene sequencing. The influence of factors like temperature of incubation, initial concentration of Cr, mobility of bacteria, and different carbon sources were studied to test the ability of the bacterium to reduce Cr(VI) under variable environmental conditions. The ability of the bacterial strain to reduce hexavalent chromium in artificial and industrial sewage water was evaluated. It was observed that the mechanism of resistance to metal was not due to the change in the permeability barrier of the cell membrane, and the enzyme activity was found to be inductive. Intracellular reduction of Cr(VI) was proven by reductase assay using cell-free extract. Scanning electron microscopy revealed chromium precipitates on bacterial cell surfaces, and transmission electron microscopy showed the outer as well as inner distribution of Cr(VI). This bacterial strain can be useful for Cr(VI) detoxification under a wide range of environmental conditions. PMID:22534304

  9. FORMATION AND DESTRUCTION OF HEXAVALENT CHROMIUM IN A LABORATORY SWIRL FLAME INCINERATOR

    EPA Science Inventory

    The partitioning of chromium (Cr) in combustion systems was investigated theoretically and experimentally. Theoretical predictions were based on chemical equilibrium and suggested that hexavalent chromium [Cr(VI)] was favored by the presence of chlorine (Cl) and diminished by the...

  10. Reduction of hexavalent chromium in aqueous medium with zerovalent iron.

    PubMed

    Dutta, Ratnadeepa; Mohammad, S Saker; Chakrabarti, Sampa; Chaudhuri, Basab; Bhattacharjee, Sekhar; Dutta, Binay K

    2010-02-01

    Hexavalent chromium, emanating primarily from the tannery and electroplating industries, can be reduced to the less toxic trivalent variety by several methods, including reduction with metallic iron. In the present work, electrolytic-grade iron dust was used to reduce chromium(VI) in the form of potassium dichromate. Loading of iron dust was varied from 0.5 to 1.0 g in 50 mL of solution; the pH of the medium was varied from 1.5 to 3.5; and the initial concentration of the dichromate solution was varied from 50 to 125 mg/L. Under the specified experimental conditions, maximum removal of the hexavalent chromium achieved was approximately 90% of its original value. The time-concentration data followed a pseudo-first-order kinetic model. The conversion and rate of reduction increased with an increase in iron loading and acidity of the medium, whereas an increase in the initial concentration of chromium(VI) caused a decrease in the reduction. PMID:20183980

  11. 77 FR 39141 - Defense Federal Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... Acquisition Regulation Supplement: Applicability of Hexavalent Chromium Policy to Commercial Items (DFARS Case... material containing hexavalent chromium. DATES: Effective Date: June 29, 2012. FOR FURTHER INFORMATION... published a final rule (DFARS Case 2009-D004) in the Federal Register at 76 FR 25569 on May 5, 2011,...

  12. 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.... SUPPLEMENTARY INFORMATION: I. Background DoD published a final rule at in the Federal Register at 76 FR 25569...

  13. 75 FR 18041 - Defense Federal Acquisition Regulation Supplement; Minimizing Use of Hexavalent Chromium (DFARS...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-08

    ...DoD is proposing to amend the Defense Federal Acquisition Regulation Supplement (DFARS) to address requirements for minimizing the use of hexavalent chromium in defense weapon systems, subsystems, components, and other items. The proposed rule prohibits the delivery of items containing hexavalent chromium under DoD contracts unless an exception...

  14. ADVANCES IN HEXAVALENT CHROMIUM REMOVAL AT HANFORD

    SciTech Connect

    NESHEM DO; RIDDELLE J

    2012-01-30

    At the Hanford Site, chromium was used as a corrosion inhibitor in the reactor cooling water and was introduced into the groundwater as a result of planned and unplanned discharges from reactors during plutonium production since 1944. Beginning in 1995, groundwater treatment methods were evaluated leading to the use of pump and treat facilities with ion exchange using Dowex 21 K, a regenerable strong base anion exchange resin. This required regeneration of the resin, which is currently performed offsite. Resin was installed in a 4 vessel train, with resin removal required from the lead vessel approximately once a month. In 2007, there were 8 trains (32 vessels) in operation. In 2008, DOE recognized that regulatory agreements would require significant expansion in the groundwater chromium treatment capacity. Previous experience from one of the DOE project managers led to identification of a possible alternative resin, and the contractor was requested to evaluate alternative resins for both cost and programmatic risk reductions. Testing was performed onsite in 2009 and 2010, using a variety of potential resins in two separate facilities with groundwater from specific remediation sites to demonstrate resin performance in the specific groundwater chemistry at each site. The testing demonstrated that a weak base anion single-use resin, ResinTech SIR-700, was effective at removing chromium, had a significantly higher capacity, could be disposed of efficiently on site, and would eliminate the complexities and programmatic risks from sampling, packaging, transportation and return of resin for regeneration. This resin was installed in Hanford's newest groundwater treatment facility, called 100-DX, which began operations in November, 2010, and used in a sister facility, 100-HX, which started up in September of 2011. This increased chromium treatment capacity to 25 trains (100 vessels). The resin is also being tested in existing facilities that utilize Dowex 21 K for

  15. Genetic Predisposition for Dermal Problems in Hexavalent Chromium Exposed Population

    PubMed Central

    Sharma, Priti; Bihari, Vipin; Agarwal, Sudhir K.; Goel, Sudhir K.

    2012-01-01

    We studied the effect of genetic susceptibility on hexavalent chromium induced dermal adversities. The health status of population was examined from the areas of Kanpur (India) having the elevated hexavalent chromium levels in groundwater. Blood samples were collected for DNA isolation to conduct polymorphic determination of genes, namely: NQO1 (C609T), hOGG1 (C1245G), GSTT1, and GSTM1 (deletion). Symptomatic exposed subjects (n = 38) were compared with asymptomatic exposed subjects (n = 108) along with asymptomatic controls (n = 148) from a non contaminated reference community. Exposed symptomatic group consisted of 36.8% subjects who were GSTM1 null genotyped as compared to asymptomatic where only 19.4% subjects were null. The exposed subjects with GSTM1 null genotype were more susceptible to dermal adversities in comparison with wild genotyped subjects (OR = 2.42; 95% CI = 1.071–5.451). Age, smoking, gender or duration of residence were not found to have any confounding effect towards this association. Association with other genes was not statistically significant, nonetheless, possible contribution by these genes cannot be ruled out. In conclusion, variation in the polymorphic status of GSTM1 gene may influence dermal outcomes among residents from Cr(VI) contaminated areas. Further studies are therefore, needed to examine these observations among different population groups. PMID:22919465

  16. 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. PMID:26971177

  17. Determination of total and hexavalent chromium in bile after intravenous administration of potassium dichromate in rats

    SciTech Connect

    Cavalleri, A.; Minoia, C.; Richelmi, P.; Baldi, C.; Micoli, G.

    1985-08-01

    Total and hexavalent chromium were measured in bile samples obtained from cannulated bile ducts of male rats iv administered with potassium dichromate at various doses corresponding to 0.1, 0.5, and 1 mg of chromium. The evaluation of the hexavalent form was performed by separation with a liquid anion exchanger and electrothermal atomization-atomic absorption spectrophotometric determination. Within 2 hr 1.35-2.23% of the chromium injected was recovered in bile as total chromium, the hexavalent form accounting for less than 1% of the total chromium collected, which seems almost entirely excreted as trivalent chromium. Since Cr(VI) administered iv was quickly reduced to Cr(III) in blood, the possibility exists for chromium in trivalent form to penetrate into the liver cells and to be excreted in the bile, possibly by binding to a carrier such as the low-molecular-weight substances described by Yamamoto et al.

  18. Impairment of Bony Crypt Development Associated With Hexavalent Chromium Exposure During Tooth Eruption.

    PubMed

    Sánchez, Luciana M; Lewicki, Marianela; De Lucca, Romina C; Ubios, Ángela M

    2015-12-01

    Improperly treated hexavalent chromium-containing industrial wastes contaminate drinking water, potentially affecting children taking breast milk or baby bottles prepared with infant formula. Thus, the aim of the present work was to determine the effect of this toxic on bone activity in the developing alveolus during tooth eruption of suckling Wistar rats intoxicated with potassium dichromate. Experimental animals received a daily dose of 12.5mg/kg body weight of potassium dichromate by gavage for 10 days; controls received an equivalent volume of saline solution. Histologic and histomorphometric studies of the mandible were performed. The data were statistically analyzed using Student's t test; statistical significance was set at a value of p <0.05. Experimental animals exhibited delayed tooth eruption, decreased periodontal width and bone volume, a lower percentage of bone formation surfaces, and higher percentage of quiescent surfaces (p<0.05) compared to controls. The delay in tooth eruption observed after exposure to hexavalent chromium is the result of a lower rate of bone remodeling in the developing alveolus. The obtained results show the importance of controlling toxic substances in drinking water, since their effects may alter the growth and development of subjects who were exposed during early infancy. PMID:27095619

  19. Bioremediation of hexavalent chromium by a cyanobacterial mat

    NASA Astrophysics Data System (ADS)

    Shukla, Dhara; Vankar, Padma S.; Srivastava, Sarvesh Kumar

    2012-12-01

    The study comprises the use of cyanobacterial mat (collected from tannery effluent site) to remove hexavalent chromium. This mat was consortium of cyanobacteria/blue-green algae such as Chlorella sp., Phormidium sp. and Oscillatoria sp. The adsorption experiments were carried out in batches using chromium concentrations 2-10, 15-30 and 300 ppm at pH 5.5-6.2. The adsorption started within 15 min; however, 96 % reduction in metal concentration was observed within 210 min. The adsorption phenomenon was confirmed by Fourier transform-infrared spectroscopy and energy dispersive X-ray analysis. This biosorption fitted Freundlich adsorption isotherm very well. It was observed that the best adsorption was at 4 ppm, and at 25 ppm in the chosen concentration ranges. Scanning electron micrograph showed the physiology of mat, indicating sites for metal uptake. The main focus was collection of the cyanobacterial mat from local environments and its chromium removal potential at pH 5.5-6.2.

  20. Eolian transport of geogenic hexavalent chromium to ground water

    USGS Publications Warehouse

    Wood, W.W.; Clark, D.; Imes, J.L.; Councell, T.B.

    2010-01-01

    A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr+6) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 μg/L Cr+6) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr+3 in the minerals is oxidized to Cr+6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr+6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr+6 concentration in the aquifer.

  1. Polyaniline coating with various substrates for hexavalent chromium removal

    NASA Astrophysics Data System (ADS)

    Qiu, Bin; Xu, Cuixia; Sun, Dezhi; Wang, Qiang; Gu, Hongbo; Zhang, Xin; Weeks, Brandon L.; Hopper, Jack; Ho, Thomas C.; Guo, Zhanhu; Wei, Suying

    2015-04-01

    Hexavalent chromium (Cr(VI)) contamination is increasingly serious in surface water and groundwater, therefore, its removal attracts increasing attention due to its highly toxic to human health. The cost effective and sustainable adsorbents are urgently needed for the remediation of Cr(VI) pollution. Polyanline (PANI), a conductive polymer, has demonstrated a great performance on Cr(VI) removal. But the recycling is the challenge for its application due to its small size. The PANI coating with various substrates is an effective approach to solve this problem. The synthesis methods and applications of the PANI coated magnetic Fe3O4, carbon fabric and cellulose composites for the Cr(VI) removal were reviewed. Finally, this review analyzed the Cr(VI) removal mechanisms by the PANI composites considering the substrate and the PANI coating.

  2. Hexavalent chromium is cytotoxic and genotoxic to American alligator cells.

    PubMed

    Wise, Sandra S; Wise, Catherine; Xie, Hong; Guillette, Louis J; Zhu, Cairong; Wise, John Pierce; Wise, John Pierce

    2016-02-01

    Metals are a common pollutant in the aquatic ecosystem. With global climate change, these levels are anticipated to rise as lower pH levels allow sediment bound metals to be released. The American alligator (Alligator mississippiensis) is an apex predator in the aquatic ecosystem and is considered a keystone species; as such it serves as a suitable monitor for localized pollution. One metal of increasing concern is hexavalent chromium (Cr(VI)). It is present in the aquatic environment and is a known human carcinogen and reproductive toxicant. We measured the cytotoxicity and genotoxicity of Cr(VI) in American alligator cells derived from scute tissue. We found that particulate and soluble Cr(VI) are both cytotoxic and genotoxic to alligator cells in a concentration-dependent manner. These data suggest that alligators may be used as a model for assessing the effects of environmental Cr(VI) contamination as well as for other metals of concern. PMID:26730726

  3. Electrochemical reduction of hexavalent chromium in ground water

    SciTech Connect

    Bansal, S.

    1994-12-01

    Electrochemical reduction of hexavalent chromium (Cr{sup +6}) to its trivalent state (Cr{sup +3}) is showing promising results in treating ground water at Lawrence Livermore National Laboratory`s (LLNL`s) Main Site. An electrolytic cell using stainless-steel and brass electrodes has been found to offer the most efficient reduction while yielding the least amount of precipitate. Trials have successfully lowered concentrations of Cr{sup +6} to below 11 parts per billion (micrograms/liter), the California state standard. We ran several trials to determine optimal voltage for running the cell; each trial consisted of applying a voltage between 6V and 48V for ten minutes through samples obtained at Treatment Facility C(TFC). No conclusive data has been obtained yet.

  4. Hexavalent chromium stimulation of riboflavin synthesis in flavinogenic yeast.

    PubMed

    Fedorovych, D; Kszeminska, H; Babjak, L; Kaszycki, P; Koloczek, H

    2001-03-01

    Flavinogenic yeast overproduce riboflavin (RF) in iron-deprived media. In optimal growth media supplemented with Fe, hexavalent chromium 'Cr (VI)' treatment led to elevated RF synthesis in all cases of 37 flavinogenic strains studied. The level of RF production exceeded the rate observed at iron-deficient conditions. At sublethal Cr concentrations the RF oversynthesis over time correlated well with the growth-inhibitory adaptational period as manifested by the prolonged lag phase. The consecutive logarithmic biomass growth was accompanied by a drop in RF biosynthesis. Cr (VI)-induced RF overproduction was not a result of cellular iron level decrease. The treatment of yeast with Cr (VI) led to the stimulation of GTP-cyclohydrolase and RF-synthase activities, the key enzymes of the RF biosynthesis pathway. PMID:11368272

  5. Assessing uncertainty in published risk estimates using hexavalent chromium and lung cancer mortality as an example

    EPA Science Inventory

    Introduction: The National Research Council recommended quantitative evaluation of uncertainty in effect estimates for risk assessment. This analysis considers uncertainty across model forms and model parameterizations with hexavalent chromium [Cr(VI)] and lung cancer mortality a...

  6. Assessing model uncertainty using hexavalent chromium and lung cancer mortality as an example [Abstract 2015

    EPA Science Inventory

    Introduction: The National Research Council recommended quantitative evaluation of uncertainty in effect estimates for risk assessment. This analysis considers uncertainty across model forms and model parameterizations with hexavalent chromium [Cr(VI)] and lung cancer mortality a...

  7. Development of a new electrokinetic technique for decontamination of hexavalent chromium from low surface charged soils

    SciTech Connect

    Haran, B.S.; Popov, B.N.; Zheng, Guanghong; White, R.E.

    1996-12-31

    A new in-situ technique was developed for hexavalent chromium removal from sand. Imposition of constant potential gradient across the soil matrix through a graphite cathode and iron anode resulted in successful migration of chromate towards the anode. The hexavalent chromium ions are reduced to harmless trivalent form by chemical reaction with the anodic dissolution product, Fe{sup 2+}. 23 refs., 14 figs.

  8. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water.

    PubMed

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-01-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium. PMID:27502074

  9. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water

    PubMed Central

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-01-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium. PMID:27502074

  10. Fabrication of Unique Magnetic Bionanocomposite for Highly Efficient Removal of Hexavalent Chromium from Water

    NASA Astrophysics Data System (ADS)

    Zhong, Yunlei; Qiu, Xun; Chen, Dongyun; Li, Najun; Xu, Qingfeng; Li, Hua; He, Jinghui; Lu, Jianmei

    2016-08-01

    Biotreatment of hexavalent chromium has attracted widespread interest due to its cost effective and environmental friendliness. However, the difficult separation of biomass from aqueous solution and the slow hexavalent chromium bioreduction rate are bottlenecks for biotechnology application. In this approach, a core-shell structured functional polymer coated magnetic nanocomposite was prepared for enriching the hexavalent chromium. Then the nanocomposite was connected to the bacteria via amines on bacterial (Bacillus subtilis ATCC-6633) surface. Under optimal conditions, a series of experiments were launched to degrade hexavalent chromium from the aqueous solution using the as-prepared bionanocomposite. Results showed that B. subtilis@Fe3O4@mSiO2@MANHE (BFSM) can degrade hexavalent chromium from the water more effectively (a respectable degradation efficiency of about 94%) when compared with pristine B. subtilis and Fe3O4@mSiO2@MANHE (FSM). Moreover, the BFSM could be separated from the wastewater by magnetic separation technology conveniently due to the Fe3O4 core of FSM. These results indicate that the application of BFSM is a promising strategy for effective treating wastewater containing hexavalent chromium.

  11. EMISSIONS OF METALS, CHROMIUM AND NICKEL SPECIES, AND ORGANICS FROM MUNICIPAL WASTEWATER SLUDGE INCINERATORS - VOLUME II: SITE 5 EMISSION TEST REPORT - HEXAVALENT CHROMIUM METHOD EVALUATION

    EPA Science Inventory

    At Site 5, three candidate samplIng methods and two candIdate analytical methods for hexavalent chromium were assessed. he conversion of hexavalent chromium (Cr+8) to ther valence states of chromium during sampling and sample storage was of primary concern. ethod 5-type samples a...

  12. Hexavalent chromium induces chromosome instability in human urothelial cells.

    PubMed

    Wise, Sandra S; Holmes, Amie L; Liou, Louis; Adam, Rosalyn M; Wise, John Pierce

    2016-04-01

    Numerous metals are well-known human bladder carcinogens. Despite the significant occupational and public health concern of metals and bladder cancer, the carcinogenic mechanisms remain largely unknown. Chromium, in particular, is a metal of concern as incidences of bladder cancer have been found elevated in chromate workers, and there is an increasing concern for patients with metal hip implants. However, the impact of hexavalent chromium (Cr(VI)) on bladder cells has not been studied. We compared chromate toxicity in two bladder cell lines; primary human urothelial cells and hTERT-immortalized human urothelial cells. Cr(VI) induced a concentration- and time-dependent increase in chromosome damage in both cell lines, with the hTERT-immortalized cells exhibiting more chromosome damage than the primary cells. Chronic exposure to Cr(VI) also induced a concentration-dependent increase in aneuploid metaphases in both cell lines which was not observed after a 24h exposure. Aneuploidy induction was higher in the hTERT-immortalized cells. When we correct for uptake, Cr(VI) induces a similar amount of chromosome damage and aneuploidy suggesting that the differences in Cr(VI) sensitivity between the two cells lines were due to differences in uptake. The increase in chromosome instability after chronic chromate treatment suggests this may be a mechanism for chromate-induced bladder cancer, specifically, and may be a mechanism for metal-induced bladder cancer, in general. PMID:26908176

  13. Ecotoxicology of hexavalent chromium in freshwater fish: a critical review.

    PubMed

    Velma, Venkatramreddy; Vutukuru, S S; Tchounwou, Paul B

    2009-01-01

    Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Intense industrialization and other anthropogenic activities have led to the global occurrence of soluble hexavalent chromium Cr(VI), which is readily leached from soil to groundwater or surface water, in concentrations above permissible levels. The ecotoxicology of Cr(VI) is linked to its environmental persistence and the ability to induce a variety of adverse effects in biologic systems, including fish. In aquatic ecosystems, Cr(VI) exposure poses a significant threat to aquatic life. This paper reviews the fate and transport of Cr(VI) in the environment and its acute and chronic effects on fish. We also discuss Cr(VI) toxicity at the cellular, biochemical, and genetic levels. An attempt is made in this review to comprehend the staggered data on the toxic effects of Cr(VI) to various species of fish. Such data are extremely useful to the scientific community and public officials involved in health risk assessment and management of environmental contaminants as a guide to the best course of action to restore ecosystems and, in turn, to preserve human health. PMID:19658319

  14. Natural and induced reduction of hexavalent chromium in soil

    NASA Astrophysics Data System (ADS)

    Leita, Liviana; Margon, Alja; Sinicco, Tania; Mondini, Claudio; Valentini, Massimiliano; Cantone, Pierpaolo

    2013-04-01

    Even though naturally elevated levels of chromium can be found naturally in some soils, distressing amounts of the hexavalent form (CrVI) are largely restricted to sites contaminated by anthropogenic activities. In fact, the widespread use of chromium in various industries and the frequently associated inadequate disposal of its by-products and wastes have created serious environmental pollution problems in many parts of the world. CrVI is toxic to plants, animals and humans and exhibits also mutagenic effects. However, being a strong oxidant, CrVI can be readily reduced to the much less harmful trivalent form (CrIII) when suitable electron donors are present in the environment. CrIII is relatively insoluble, less available for biological uptake, and thus definitely less toxic for web-biota. Various electron donors in soil can be involved in CrVI reduction in soil. The efficiency of CrVI reducing abiotic agents such as ferrous iron and sulphur compounds is well documented. Furthermore, CrVI reduction is also known to be significantly enhanced by a wide variety of cell-produced monosaccharides, including glucose. In this study we evaluated the dynamics of hexavalent chromium (CrVI) reduction in contaminated soil amended or not with iron sulphate or/and glucose and assessed the effects of CrVI on native or glucose-induced soil microbial biomass size and activity. CrVI negatively affected both soil microbial activity and the size of the microbial biomass. During the incubation period, the concentration of CrVI in soil decreased over time whether iron sulphate or/and glucose was added or not, but with different reduction rates. Soil therefore displayed a natural attenuation capacity towards chromate reduction. Addition of iron sulphate or/and glucose, however, increased the reduction rate by both abiotic and biotic mechanisms. Our data suggest that glucose is likely to have exerted an indirect role in the increased rate of CrVI reduction by promoting growth of

  15. Mechanisms of hexavalent chromium resistance and removal by microorganisms.

    PubMed

    Joutey, Nezha Tahri; Sayel, Hanane; Bahafid, Wifak; El Ghachtouli, Naïma

    2015-01-01

    Chromium has been and is extensively used worldwide in multiple industrial processes and is routinely discharged to the environment from such processes. Therefore, this heavy metal is a potential threat to the environment and to public health, primarily because it is non-biodegradable and environmentally persistent. Chromium exists in several oxidation states, the most stable of which are trivalent Cr(Ill) and hexavalent Cr(VI) species. Each species possesses its own individual chemical characteristics and produces its own biological effects. For example, Cr (Ill) is an essential oligoelement for humans, whereas Cr(VI) is carcinogenic and mutagenic. Several chemical methods are used to remove Cr(VI) from contaminated sites. Each of these methods has advantages and disadvantages. Currently, bioremediation is often the preferred method to deal with Cr contaminated sites, because it is eco-friendly, cost-effective and is a "natural" technology. Many yeast, bacterial and fungal species have been assessed for their suitability to reduce or remove Cr(VI) contamination. The mechanisms by which these microorganisms resist and reduce Cr(VI) are variable and are species dependent. There are several Cr-resistance mechanisms that are displayed by microorganisms. These include active efflux of Cr compounds, metabolic reduction of Cr(VI) to Cr (ill), and either intercellular or extracellular prec1p1tation. Microbial Cr (VI) removal typically involves three stages: binding of chromium to the cell surface, translocation of chromium into the cell, and reduction of Cr(VI) to Cr (ill). Cr(VI) reduction by microorganisms may proceed on the cell surface, outside the cell, or intracellularly, either directly via chromate reductase enzymes, or indirectly via metabolite reduction of Cr(VI). The uptake of chromium ions is a biphasic process. The primary step is known as biosorption, a metabolic energyindependent process. Thereafter, bioaccumulation occurs, but is much slower, and is

  16. DETERMINING DISSOLVED HEXAVALENT CHROMIUM IN WATER AND WASTEWATER BY ELECTROTHERMAL ATOMIZATION

    EPA Science Inventory

    A procedure is described for separating dissolved hexavalent chromium (Cr(+6)) from trivalent chromium (Cr(+3)) and the water sample matrix by coprecipitation of lead chromate with lead sulfate in acetic acid solution. Precision and accuracy data are presented for tap water and v...

  17. A laminar flow microfluidic fuel cell for detection of hexavalent chromium concentration.

    PubMed

    Ye, Dingding; Yang, Yang; Li, Jun; Zhu, Xun; Liao, Qiang; Zhang, Biao

    2015-11-01

    An electrochemical hexavalent chromium concentration sensor based on a microfluidic fuel cell is presented. The correlation between current density and chromium concentration is established in this report. Three related operation parameters are investigated, including pH values, temperature, and external resistance on the sensor performance. The results show that the current density increases with increasing temperature and the sensor produces a maximum regression coefficient at the catholyte pH value of 1.0. Moreover, it is found that the external resistance has a great influence on the linearity and current densities of the microfluidic sensor. Owing to the membraneless structure and the steady co-laminar flow inside the microchannel, the microfluidic sensor exhibits short response time to hexavalent chromium concentration. The laminar flow fuel cell sensor provides a new and simple method for detecting hexavalent chromium concentration in the industrial wastewater. PMID:26649130

  18. Sex hormones and semen quality in welders exposed to hexavalent chromium.

    PubMed

    Bonde, J P; Ernst, E

    1992-07-01

    Recent experimental studies in rodents document the spermatotoxic effects of water-soluble hexavalent chromium. Welders comprise, worldwide, a major occupational group with acknowledged exposure to chromium. This study examines the relationship between semen quality and chromium in the urine and blood of a population of 30 tungsten inert gas (TIG) stainless steel welders, 30 mild steel welders and 47 non-welding workers. Each subject provided two to three semen samples. The chromium concentration ranged from 0.17 to 4.74 nmol mmol1 creatinine (median 1.08) in post-shift spot urine and from 6.0 to 46.4 nmol l-1 in blood. None of several semen parameters deteriorated with increasing level of internal exposure to chromium. Low-level exposure to hexavalent chromium associated with TIG stainless steel and mild steel welding do not appear to be a major hazard for human spermatogenesis. PMID:1354973

  19. Biosorption of Hexavalent Chromium from Aqueous Medium with Opuntia Biomass

    PubMed Central

    2014-01-01

    The biosorption of hexavalent chromium from aqueous solutions by Opuntia cladodes and ectodermis from cactus fruits was investigated. Both types of biomass are considered low-cost, natural, and ecofriendly biosorbents. Batch experiments were carried out to determine Cr(VI) biosorption capacity and the efficiency of the biosorption process under different pH, initial Cr(VI) concentration, and sorbent dosage. The biosorption of Cr(VI) by Opuntia biomass was highly pH dependent, favoring higher metal uptake at low pH. The higher biosorption capacity was exhibited at pH 2. The optimal conditions were obtained at a sorbent dosage of 1 g L−1 and initial metal concentration of 10 mg L−1. Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The rate constant, the initial biosorption rate, and the equilibrium biosorption capacity were determined. The experimental equilibrium data obtained were analyzed using two-parameter isotherm models (Langmuir, Freundlich, and Temkin). The Langmuir maximum monolayer biosorption capacity (qmax) was 18.5 mg g−1 for cladodes and 16.4 mg g−1 for ectodermis. The results suggest that Opuntia biomass could be considered a promising low-cost biosorbent for the ecofriendly removal of Cr(VI) from aqueous systems. PMID:24982975

  20. Reduction of hexavalent chromium by ascorbic acid in aqueous solutions.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Li, Xiao-Yan; Gu, Ji-Dong

    2004-11-01

    Hexavalent chromium is a priority pollutant in the USA and many other countries. Reduction of Cr(VI) to Cr(III) is environmentally favorable as the latter species is not toxic to most living organisms and also has a low mobility and bioavailability. Reduction of Cr(VI) by ascorbic acid (vitamin C) as a reductant was studied using potassium dichromate solution as the model pollutant. Effects of concentration of vitamin C, pH, temperature, irradiation and reaction time on the reduction of Cr(VI) were examined. Cr(VI) might be reduced by vitamin C not only in acidic conditions but also in weakly alkaline solutions. The reduction of Cr(VI) by vitamin C might occur not only under irradiation but also in the dark. Vitamin C is an important biological reductant in humans and animals, and not toxic. It is water-soluble and can easily permeate through various types of soils. The results indicate that vitamin C could be used in effective remediation of Cr(VI)-contaminated soils and groundwater in a wide range of pH, with or without sunlight. PMID:15488923

  1. Reduction of hexavalent chromium by the thermophilic methanogen Methanothermobacter thermautotrophicus

    PubMed Central

    Singh, Rajesh; Dong, Hailiang; Liu, Deng; Zhao, Linduo; Marts, Amy R.; Farquhar, Erik; Tierney, David L.; Almquist, Catherine B.; Briggs, Brandon R.

    2015-01-01

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 µM h−1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature

  2. Reduction of hexavalent chromium by the thermophilic methanogen Methanothermobacter thermautotrophicus

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Dong, Hailiang; Liu, Deng; Zhao, Linduo; Marts, Amy R.; Farquhar, Erik; Tierney, David L.; Almquist, Catherine B.; Briggs, Brandon R.

    2015-01-01

    Despite significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70 °C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations using 1,5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to 1.9 μM h-1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature subsurface radioactive waste disposal

  3. Reduction of hexavalent chromium by the thermophilic methanogen Methanothermobacter thermautotrophicus

    DOE PAGESBeta

    Singh, Rajesh; Dong, Hailiang; Liu, Deng; Zhao, Linduo; Marts, Amy R.; Farquhar, Erik; Tierney, David L.; Almquist, Catherine B.; Briggs, Brandon R.

    2014-10-22

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions bymore » this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 μM h₋1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of this study demonstrate the ability of M. thermautotrophicus cells to reduce toxic Cr6+ to less toxic Cr3+ and its potential application in metal bioremediation, especially at high temperature

  4. Reduction of hexavalent chromium by the thermophilic methanogen Methanothermobacter thermautotrophicus

    SciTech Connect

    Singh, Rajesh; Dong, Hailiang; Liu, Deng; Zhao, Linduo; Marts, Amy R.; Farquhar, Erik; Tierney, David L.; Almquist, Catherine B.; Briggs, Brandon R.

    2014-10-22

    Despite the significant progress on iron reduction by thermophilic microorganisms, studies on their ability to reduce toxic metals are still limited, despite their common co-existence in high temperature environments (up to 70°C). In this study, Methanothermobacter thermautotrophicus, an obligate thermophilic methanogen, was used to reduce hexavalent chromium. Experiments were conducted in a growth medium with H2/CO2 as substrate with various Cr6+ concentrations (0.2, 0.4, 1, 3, and 5 mM) in the form of potassium dichromate (K2Cr2O7). Time-course measurements of aqueous Cr6+ concentrations with the 1, 5-diphenylcarbazide colorimetric method showed complete reduction of the 0.2 and 0.4 mM Cr6+ solutions by this methanogen. However, much lower reduction extents of 43.6%, 13.0%, and 3.7% were observed at higher Cr6+ concentrations of 1, 3 and 5 mM, respectively. These lower extents of bioreduction suggest a toxic effect of aqueous Cr6+ to cells at this concentration range. At these higher Cr6+ concentrations, methanogenesis was inhibited and cell growth was impaired as evidenced by decreased total cellular protein production and live/dead cell ratio. Likewise, Cr6+ bioreduction rates decreased with increased initial concentrations of Cr6+ from 13.3 to1.9 μM h₋1. X-ray absorption near-edge structure (XANES) spectroscopy revealed a progressive reduction of soluble Cr6+ to insoluble Cr3+ precipitates, which was confirmed as amorphous chromium hydroxide by X-ray diffraction and selected area electron diffraction pattern. However, a small fraction of reduced Cr occurred as aqueous Cr3+. Scanning and transmission electron microscope observations of M. thermautotrophicus cells after Cr6+ exposure suggest both extra- and intracellular chromium reduction mechanisms. Results of

  5. Hexavalent chromium-resistant bacteria isolated from river sediments.

    PubMed Central

    Luli, G W; Talnagi, J W; Strohl, W R; Pfister, R M

    1983-01-01

    Hexavalent chromium [Cr(VI)] is a known carcinogen and mutagen; however, the actual mechanisms of Cr toxicity are unknown. Two approaches were used to isolate Cr(VI)-resistant bacteria from metal-contaminated river sediments. Diluted sediments were plated directly onto a peptone-yeast extract (PYE) medium containing 0 to 100 micrograms of Cr(VI) ml-1. Approximately 8.4 x 10(5) CFU g-1 were recovered on 0 microgram of Cr(VI) ml-1, whereas 4.0 x 10(2) CFU g-1 were recovered on PYE plus 100 micrograms of Cr(VI) ml-1. Alternatively, continuous culture enrichment techniques were employed using PYE and 100 micrograms Cr(VI) ml-1 input at dilution rates of 0.02 and 0.10 h-1. After six residence periods, 10(9) CFU were recovered on PYE agar containing 0 microgram of Cr(VI) ml-1 and 10(7) CFU on PYE agar plus 100 micrograms of Cr(VI) ml-1. Of 89 isolates obtained by direct plating onto PYE, 47% were resistant to 100 micrograms of Cr(VI) ml-1, and 29% were resistant to 250 micrograms of Cr(VI) ml-1. When the same isolates were plated onto PYE containing Cr(III), 88% were resistant to 100 micrograms ml-1 but only 2% were resistant to 250 micrograms ml-1. Cr, Co, Sb, and Zn were found in significantly higher concentrations at an industry-related contaminated site than at a site 11 km downstream. Total Cr in the sediments at the contaminated site averaged 586 micrograms (dry weight) g-1, and the downstream site averaged 71 micrograms (dry weight) g-1. The Cr recovered from acid-digested Ottawa River sediment samples was predominantly hexavalent. Five acid digestion procedures followed by atomic absorption spectroscopy were compared and found to be 30 to 70% efficient for recovery of Cr relative to neutron activation analysis. A population of aerobic, heterotrophic bacteria was recovered from sediments containing elevated levels of Cr.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6639032

  6. Sister chromatid exchange analysis in lymphocytes of workers exposed to hexavalent chromium.

    PubMed Central

    Nagaya, T; Ishikawa, N; Hata, H

    1989-01-01

    To investigate the usefulness of sister chromatid exchange (SCE) analysis in lymphocytes as an indicator for mutagenic effects after in vivo exposure to hexavalent chromium (Cr), SCE frequency was analysed in lymphocytes of 44 Cr platers occupationally exposed to hexavalent Cr and 47 controls. Although urinary Cr analysis confirmed that the Cr platers were exposed to Cr, no effects of the exposure on SCE frequency were found. Smokers, both Cr platers and controls, had a significantly higher SCE frequency than non-smokers. These results suggest that SCE analysis in human lymphocytes is not a good indicator of possible mutagenic effects of exposure to hexavalent Cr. PMID:2920143

  7. Transport of trivalent and hexavalent chromium through different ion-selective membranes in acidic aqueous media

    SciTech Connect

    Costa, R.F.D.; Rodrigues, M.A.S.; Ferreira, J.Z.

    1998-06-01

    The aim of this work was to evaluate the transport of trivalent and hexavalent chromium through anion- and cation-selective membranes using two- and three-compartment electrodialysis cells. Tests were done with acidic solutions of trivalent chromium ions, Cr{sup 3+}, and hexavalent chromium ions, Cr{sub 2}O{sub 7}{sup 2{minus}}. In each situation the transport of metallic ions through the membrane was evaluated. In the tests with trivalent chromium, Nafion 417 and Selemion CMT cation-selective membranes were used, and in the tests with hexavalent chromium, Selemion AMT membrane was used. The influence of SO{sub 4}{sup 2{minus}} ions and of the concentration of H{sup +} ions in the solutions was also analyzed. Results showed the oxidation of the Cr{sup 3+} ion at the anode and the reduction of the Cr{sub 2}O{sub 7}{sup 2{minus}} ion at the cathode. The maximum yield in the process was reached when hexavalent chromium solutions were used in the absence of sulfate ions and a Selemion AMT membrane in a three-compartment cell.

  8. Acute toxicity by water containing hexavalent or trivalent chromium in native Brazilian fish, Piaractus mesopotamicus: anatomopathological alterations and mortality.

    PubMed

    Castro, Marcello Pardi; de Moraes, Flávio Ruas; Fujimoto, Rodrigo Yudi; da Cruz, Claudinei; Belo, Marco Antonio de Andrade; de Moraes, Julieta Rodini Engrácia

    2014-02-01

    This study evaluated the toxicity of hexavalent and trivalent compounds of chromium to the pacu, Piaractus mesopotamicus, in acute exposures of 96 h through mortality and histopathological responses. Hexavalent potassium dichromate was more toxic than trivalent compounds of chromium chloride, chromium oxide and chromium carbochelate. Sufficient mortalities occurred only with potassium dichromate to yield an LC50 value at 124.2 mg L(-1). Hexavalent chromium caused reversible and irreversible lesions, which may affect organ functionality. Histopathological evaluation showed that trivalent chromium caused lesions of lower severity. Pacu subjected to different concentrations of chromium carbochelate showed no histopathological changes in the kidneys, liver, skin and gills, being similar to those of the control fish. Among the three sources of Cr(3+), only chromium chloride at 200 mg L(-1) resulted in mortality, which reached 100 % within the first 18 h. These findings confirm that trivalent chromium, when administered within recommended levels, may be used safely in aquaculture. PMID:24346495

  9. Selecting Processes to Minimize Hexavalent Chromium from Stainless Steel Welding

    PubMed Central

    KEANE, M.; SIERT, A.; STONE, S.; CHEN, B.; SLAVEN, J.; CUMPSTON, A.; ANTONINI, J.

    2015-01-01

    Eight welding processes/shielding gas combinations were assessed for generation of hexavalent chromium (Cr6+) in stainless steel welding fumes. The processes examined were gas metal arc welding (GMAW) (axial spray, short circuit, and pulsed spray modes), flux cored arc welding (FCAW), and shielded metal arc welding (SMAW). The Cr6+ fractions were measured in the fumes; fume generation rates, Cr6+ generation rates, and Cr6+ generation rates per unit mass of welding wire were determined. A limited controlled comparison study was done in a welding shop including SMAW, FCAW, and three GMAW methods. The processes studied were compared for costs, including relative labor costs. Results indicate the Cr6+ in the fume varied widely, from a low of 2800 to a high of 34,000 ppm. Generation rates of Cr6+ ranged from 69 to 7800 μg/min, and Cr6+ generation rates per unit of wire ranged from 1 to 270 μg/g. The results of field study were similar to the findings in the laboratory. The Cr6+ (ppm) in the fume did not necessarily correlate with the Cr6+ generation rate. Physical properties were similar for the processes, with mass median aerodynamic diameters ranging from 250 to 336 nm, while the FCAW and SMAW fumes were larger (360 and 670 nm, respectively). Conclusion: The pulsed axial spray method was the best choice of the processes studied based on minimal fume generation, minimal Cr6+ generation, and cost per weld. This method is usable in any position, has a high metal deposition rate, and is relatively simple to learn and use. PMID:26690276

  10. Hexavalent chromium and its effect on health: possible protective role of garlic (Allium sativum Linn).

    PubMed

    Das, Kusal K; Dhundasi, Salim A; Das, Swastika N

    2011-01-01

    Hexavalent chromium or chromium (VI) is a powerful epithelial irritant and a confirmed human carcinogen. This heavy metal is toxic to many plants, aquatic animals, and bacteria. Chromium (VI) which consists of 10%-15% total chromium usage, is principally used for metal plating (H2Cr2O7), as dyes, paint pigments, and leather tanning, etc. Industrial production of chromium (II) and (III) compounds are also available but in small amounts as compared to chromium (VI). Chromium (VI) can act as an oxidant directly on the skin surface or it can be absorbed through the skin, especially if the skin surface is damaged. The prooxidative effects of chromium (VI) inhibit antioxidant enzymes and deplete intracellular glutathione in living systems and act as hematotoxic, immunotoxic, hepatotoxic, pulmonary toxic, and nephrotoxic agents. In this review, we particularly address the hexavalent chromium-induced generation of reactive oxygen species and increased lipid peroxidation in humans and animals, and the possible role of garlic (Allium sativum Linn) as a protective antioxidant. PMID:22865357

  11. Reduction of hexavalent chromium in water samples acidified for preservation

    USGS Publications Warehouse

    Stollenwerk, K.G.; Grove, D.B.

    1985-01-01

    Reduction of hexavalent chromium, Cr(VI), in water samples, preserved by standard techniques, was investigated. The standard preservation technique for water samples that are to be analyzed for Cr(VI) consists of filtration through a 0.45-??m membrane, acidification to a pH < 2, and storage in plastic bottles. Batch experiments were conducted to evaluate the effect of H+ concentration, NO2, temperature, and dissolved organic carbon (DOC) on the reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) to Cr(III) increased with increasing NO2, DOC, H+, and temperature. Reduction of Cr(VI) by organic matter occurred in some samples even though the samples were unacidified. Reduction of Cr(VI) is inhibited to an extent by storing the sample at 4??C. Stability of Cr(VI) in water is variable and depends on the other constituents present in the sample. Water samples collected for the determination of Cr(VI) should be filtered (0.45-??m membrane), refrigerated, and analyzed as quickly as possible. Water samples should not be acidified. Measurement of total Cr in addition to Cr(VI) can serve as a check for Cr(VI) reduction. If total Cr is greater than Cr(VI), the possibility that Cr(VI) reduction has occurred needs to be considered.The rate of reduction of Cr(VI) to Cr(III) increased with increasing NO//2, DOC, H** plus , and temperature. Reduction of Cr(VI) by organic matter occurred in some samples even though the samples were unacidified. Reduction of Cr(VI) is inhibited to an extent by storing the sample at 4 degree C. Stability of Cr(VI) in water is variable and depends on the other constituents present in the sample. Water samples collected for the determination of Cr(VI) should be filtered (0. 45- mu m membrane), refrigerated, and analyzed as quickly as possible. Water samples should not be acidified. Measurement of total Cr in addition to Cr(VI) can serve as a check for Cr(VI) reduction. If total Cr is greater than Cr(VI), the possibility that Cr

  12. MODELING HEXAVALENT CHROMIUM REDUCTION IN GROUNDWATER IN FIELD-SCALE TRANSPORT AND LABORATORY BATCH EXPERIMENTS

    EPA Science Inventory

    A plausible and consistent model is developed to obtain a quantitative description of the gradual disappearance of hexavalent chromium (Cr(VI)) from groundwater in a small-scale field tracer test and in batch kinetic experiments using aquifer sediments under similar chemical cond...

  13. Isolation, identification and characterization of indigenous fungi for bioremediation of hexavalent chromium, nickel and cobalt

    NASA Astrophysics Data System (ADS)

    Hernahadini, Nelis; Suhandono, Sony; Choesin, Devi N.; Chaerun, Siti K.; Kadarusman, Ade

    2014-03-01

    Waste from nickel mining of Sorowako in South Sulawesi contains hexavalent chromium, nickel and cobalt metals in high concentration and may have a negative impact to the environment. Common waste treatment systems such as chemical treatment using a reducing reagent may still have a negative impact. Bioremediation using fungi or bacteria becomes more popular because it is an environmentally friendly alternative. The purposes of this study are to isolate and identify indigenous fungi that are resistant to heavy metals (hexavalent chromium, nickel, and cobalt) and are capable of reducing the concentration of metals in mining wastes. Ten fungal isolates were successfully isolated from the soils and pond sediments in the area of nickel mining in Sorowako. Selection of superior isolate was carried out by growing all the isolates on PDA medium, which contained all of the three metals. One superior isolate was identified to be able to grow on medium with concentrations of 6400 ppm hexavalent chromium, 200 ppm nickel and 50 ppm cobalt. Molecular identification and phylogenetic studies of the isolate using fungal PCR primers developed to amplify the ITS (internal transcribed spacer) region showed that the isolate sequence was very close to Trichoderma atroviride with 99.8% similarity. Optimum incubation time for the uptake of hexavalent chromium was 3 days, nickel and cobalt was 5 days, respectively, with an optimum pH of 4.

  14. MODELING HEXAVALENT CHROMIUM REDUCTION IN GROUND- WATER IN FIELD-SCALE TRANSPORT AND LABORATORY BATCH EXPERIMENTS

    EPA Science Inventory

    A plausible and consistent model is developed to obtain a quantitative description of the gradual disappearance of hexavalent chromium (Cr(VI)) from groundwater in a small-scale field tracer test and in batch kinetic experiments using aquifer sediments under similar chemical cond...

  15. 76 FR 20349 - Draft Toxicological Review of Hexavalent Chromium: In Support of Summary Information on the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-12

    ... meetings@erg.com (reference the ``Hexavalent Chromium Peer Review Workshop'' and include your name, title... with disabilities, contact ERG, 110 Hartwell Avenue, Lexington, MA 02421-3136 by calling 781-674-7374... include your name and contact information), or sending an e-mail to meetings@erg.com (reference...

  16. Comparative toxicity of trivalent and hexavalent chromium to fungi

    SciTech Connect

    Babich, H.; Schiffenbauer, M.; Stotzky, G.

    1982-04-01

    Studies were conducted to determine whether the differential toxicities of the two valence states of Cr (+3 and +6) occur with fungi as they do with bacteria as noted in previous studies. It was found that mycelial growth rates were inhibited more by Cr/sup 6 +/ than by Cr/sup 3 +/. Hexavalent Cr was also more toxic than equivalent trivalent Cr to spore formation and spore germination of the fungi tested. The greater toxicity of hexavalent Cr than of trivalent Cr to fungi is in agreement with the results observed with the bacterial studies. (JMT)

  17. Determination of hexavalent chromium in traditional Chinese medicines by high-performance liquid chromatography with inductively coupled plasma mass spectrometry.

    PubMed

    Li, Peng; Li, Li-Min; Xia, Jing; Cao, Shuai; Hu, Xin; Lian, Hong-Zhen; Ji, Shen

    2015-12-01

    An analytical method that combined high-performance liquid chromatography with inductively coupled plasma mass spectrometry has been developed for the determination of hexavalent chromium in traditional Chinese medicines. Hexavalent chromium was extracted using the alkaline solution. The parameters such as the concentration of alkaline and the extraction temperature have been optimized to minimize the interconversion between trivalent chromium and hexavalent chromium. The extracted hexavalent chromium was separated on a weak anion exchange column in isocratic mode, followed by inductively coupled plasma mass spectrometry determination. To obtain a better chromatographic resolution and sensitivity, 75 mM NH4 NO3 at pH 7 was selected as the mobile phase. The linearity of the proposed method was investigated in the range of 0.2-5.0 μg L(-1) (r(2) = 0.9999) for hexavalent chromium. The limits of detection and quantitation are 0.1 and 0.3 μg L(-1) , respectively. The developed method was successfully applied to the determination of hexavalent chromium in Chloriti lapis and Lumbricus with satisfactory recoveries of 95.8-112.8%. PMID:26541101

  18. INJECTION OF A FERROUS SULFATE/SODIUM DITHIONITE REDUCTANT FOR IN-SITU TREATMENT OF HEXAVALENT CHROMIUM

    EPA Science Inventory

    An in situ pilot study was conducted to evaluate the performance of a ferrous iron-based reductant solution in treating hexavalent chromium within a saturated zone source area at a former industrial site in Charleston, South Carolina (USA). The hexavalent source area, consisting...

  19. USE OF TOXICITY IDENTIFICATION EVALUATION METHODS TO CHARACTERIZE IDENTIFY, AND CONFIRM HEXAVALENT CHROMIUM TOXICITY IN AN INDUSTRIAL EFFLUENT

    EPA Science Inventory

    A toxicity identification evaluation (TIE) was conducted on effluent from a major industrial discharger. Initial monitoring showed slight chronic toxicity to Ceriodaphnia dubia; later sample showed substantial toxicity to C. dubia. Chemical analysis detected hexavalent chromium ...

  20. Assessing uncertainty in published risk estimates using hexavalent chromium and lung cancer mortality as an example [Presentation 2015

    EPA Science Inventory

    Introduction: The National Research Council recommended quantitative evaluation of uncertainty in effect estimates for risk assessment. This analysis considers uncertainty across model forms and model parameterizations with hexavalent chromium [Cr(VI)] and lung cancer mortality a...

  1. Genesis and transport of hexavalent chromium in the system ophiolitic rocks - groundwater

    NASA Astrophysics Data System (ADS)

    Shchegolikhina, Anastasia; Guadagnini, Laura; Guadagnini, Alberto

    2015-04-01

    Our study aims at contributing to the quantification and characterization of chromium transport processes from host rocks and soil matrices to groundwater. We focus on dissolved hexavalent chromium detected in groundwaters of geological regions with ophiolitic rocks (ophiolites and serpentinites) inclusions due to its critical ecological impact. (Oze et al., 2004). Despite the large number of analyses on the occurrence of high concentrations of hazardous hexavalent chromium ions in natural waters, only few studies were performed with the objective of identifying and investigating the geochemical reactions which could occur in the natural system rock - groundwater - dissolved chromium (Fantoni et al., 2002, Stephen and James, 2004, Lelli et al., 2013). In this context, there is a need for integration of results obtained from diverse studies in various regions and settings to improve our knowledge repository. Our theoretical analyses are grounded and driven by practical scenarios detected in subsurface reservoirs exploited for civil and industrial use located in the Emilia-Romagna region (Italy). Available experimental datasets are complemented with data from other international regional-scale settings (Altay mountains region, Russia). Modeling of chromium transformation and migration particularly includes characterization of the multispecies geochemical system. A key aspect of our study is the analysis of the complex competitive sorption processes governing heavy metal evolution in groundwater. The results of the research allow assessing the critical qualitative features of the mechanisms of hexavalent chromium ion mobilization from host rocks and soils and the ensuing transformation and migration to groundwater under the influence of diverse environmental factors. The study is then complemented by the quantification of the main sources of uncertainty associated with prediction of heavy metal contamination levels in the groundwater system explored. Fantoni, D

  2. Effect of hexavalent chromium-treated sperm on in vitro fertilization and embryo development.

    PubMed

    Yoisungnern, Ton; Das, Joydeep; Choi, Yun-Jung; Parnpai, Rangsun; Kim, Jin-Hoi

    2016-09-01

    Hexavalent chromium (Cr(VI)) is an environmental contaminant that is associated with reproductive abnormalities in both humans and animals. In the present study, we evaluated the cytotoxic effect of Cr(VI) on sperm function and subsequent embryo development after in vitro fertilization (IVF). Sperm obtained from BDF1 male mice were treated with potassium dichromate (0, 3.125, 6.25, 12.5, 25, or 50 μM) for 3 h. Cr(VI) significantly decreased sperm viability and acrosome reaction with increasing dose. These Cr(VI)-treated sperms were further used for IVF of oocytes obtained from BDF1 female mice. Results showed that Cr(VI)-treated sperm caused a significant reduction in IVF success, higher developmental arrest at the two-cell stage of embryos, and delayed blastocyst formation with increasing dose. In particular, most blastocysts from the Cr(VI)-treated sperm resulted in hatching failure as well as decreased inner cell mass and trophectoderm (TE). Furthermore, blastocysts obtained from Cr(VI)-treated sperm showed lower expression of not only TE-associated genes (eomes, cdx2, and krt8) but also pluripotent marker genes (sox2, pou5f1, and klf4) that are responsible for further embryo development of blastocyst embryos. The results of our current study showed that Cr(VI)-treated sperm had negative effects on oocyte fertilization and subsequent embryo development. PMID:25903088

  3. Activated carbons and low cost adsorbents for remediation of tri- and hexavalent chromium from water.

    PubMed

    Mohan, Dinesh; Pittman, Charles U

    2006-09-21

    Hexavalent chromium is a well-known highly toxic metal, considered a priority pollutant. Industrial sources of Cr(VI) include leather tanning, cooling tower blowdown, plating, electroplating, anodizing baths, rinse waters, etc. The most common method applied for chromate control is reduction of Cr(VI) to its trivalent form in acid (pH approximately 2.0) and subsequent hydroxide precipitation of Cr(III) by increasing the pH to approximately 9.0-10.0 using lime. Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal. Far less attention has been paid to adsorption. Herein, we provide the first review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation. After an overview of chromium contamination is provided, more than 300 papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation. Efforts to establish the adsorption mechanisms of Cr(III) and Cr(VI) on various adsorbents are reviewed. Chromium's impact environmental quality, sources of chromium pollution and toxicological/health effects is also briefly introduced. Interpretations of the surface interactions are offered. Particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to other low cost alternatives, including an extensive table. PMID:16904258

  4. Detoxification of hexavalent chromium by Leucobacter sp. uses a reductase with specificity for dihydrolipoamide.

    PubMed

    Sarangi, Abhipsa; Krishnan, Chandraraj

    2016-02-01

    Leucobacter sp. belongs to the metal stressed community and possesses higher tolerance to metals including chromium and can detoxify toxic hexavalent chromium by reduction to less toxic trivalent chromium. But, the mechanism of reduction of hexavalent chromium by Leucobacter sp. has not been studied. Understanding the enzyme catalyzing reduction of chromium is important to improve the species for application in bioremediation. Hence, a soluble reductase catalyzing the reduction of hexavalent chromium was purified from a Leucobacter sp. and characterized. The pure chromate reductase was obtained from the cell-free extract through hydrophobic interaction and gel filtration column chromatographic methods. It was a monomeric enzyme and showed similar molecular weights in both gel filtration (∼68 KDa) and SDS-PAGE (64 KDa). It reduced Cr(VI) using both NADH and NADPH as the electron donor, but exhibited higher activity with NADH. The optimal activity was found at pH 5.5 and 30 °C. The K(m) and V(max) for Cr(VI) reduction with NADH were 46.57 μM and 0.37 μmol min(-1) (mg protein) (-1), respectively. The activity was inhibited by p-hydroxy mercury benzoate, Ag(2+) and Hg(2+) indicating the role of thiol groups in the catalysis. The spectrophotometric analysis of the purified enzyme showed the absence of bound flavin in the enzyme. The N-terminal amino acid sequence and LC/MS analysis of trypsin digested purified enzyme showed similarity to dihydrolipoyl dehydrogenase. The purified enzyme had dihydrolipoyl dehydrogenase activity with dihydrolipoamide as the substrate, which suggested that Leucobacter sp. uses reductase with multiple substrate specificity for reduction of Cr(VI) detoxification. PMID:26377775

  5. Modeling and evaluation on removal of hexavalent chromium from aqueous systems using fixed bed column.

    PubMed

    Chauhan, Divya; Sankararamakrishnan, Nalini

    2011-01-15

    Removal of hexavalent chromium by xanthated chitosan was investigated in a packed bed up-flow column. The experiments were conducted to study the effect of important design parameters such as bed height and flow rate. At a bed height of 20 cm and flow rate of 5 mL min(-1), the metal-uptake capacity of xanthated chitosan and plain chitosan flakes for hexavalent chromium was found to be 202.5 and 130.12 mg g(-1) respectively. The bed depth service time (BDST) model was used to analyze the experimental data. The computed sorption capacity per unit bed volume (N(0)) was 4.6 ± 0.3 and 78.3 ± 2.9 g L(-1) for plain and xanthated flakes respectively at 10% breakthrough concentration. The rate constant (K(a)) was recorded as 0.0507 and 0.0194 L mg(-1)h(-1) for plain and xanthated chitosan respectively. In flow rate experiments, the results confirmed that the metal uptake capacity and the metal removal efficiency of plain and xanthated chitosan decreased with increasing flow rate. The Thomas model was used to fit the column sorption data at different flow rates and model constants were evaluated. The column was successfully applied for the removal of hexavalent chromium from electroplating wastewater. Five hundred bed volumes of electroplating wastewater were treated in column experiments using this adsorbent, reducing the concentrations of hexavalent chromium from 10 mg L(-1) to 0.1 mg L(-1). PMID:20943316

  6. Absorption spectroscopy in the ultraviolet and visible spectral range of hexavalent chromium aqueous solutions

    NASA Astrophysics Data System (ADS)

    Mignani, Anna G.; Spadoni, Lorenzo

    1999-09-01

    In order to demonstrate the possibility of performing direct absorption spectroscopy of Hexavalent Chromium aqueous solutions, absorption measurements were performed at the dual- beam spectrophotometer in the 250 - 850 nm spectral range, with 10 mm and 100 mm path lengths. Low concentration (26 - 520 (mu) g/l) (and high concentration (2.6 - 52 mg/l) solutions were analyzed, showing that it is possible to implement a basic instrumentation for risk condition monitoring and a more advanced instrumentation for quantitative measurements.

  7. The detection of hexavalent chromium by organically doped sol-gels

    SciTech Connect

    Wong, P.W.; Mackenzie, J.D.

    1994-12-31

    The sol-gel process can be used to produce porous inorganic matrices that are doped with organic molecules. These doped gels can be used as a quantitative method for the spectrophotometric determination of trace concentrations of metallic ions. For the detection of hexavalent chromium, malachite green was used as the dopant. Preliminary results indicate concentrations on the order of 5 ppb are detectable using this method.

  8. Tolerance and accumulation of hexavalent chromium by two seaweed associated aspergilli.

    PubMed

    Vala, Anjana K; Anand, Nisha; Bhatt, Purva N; Joshi, H V

    2004-05-01

    Marine seaweed (Eucheuma sp.) associated strains of Aspergillus flavus and Aspergillus niger were tested for their Cr(VI) tolerance. Both the isolates showed luxuriant growth in different concentrations of Cr(VI), i.e., 25, 50 and 100 ppm. There was no marked variation in the dry weight of control and test isolates, which indicated that both the isolates can tolerate a wide range of hexavalent chromium and their application for bioremediation purpose can be envisaged as XRF data revealed both the isolates accumulated more than 25% of the chromium supplied. A. flavus invariably exhibited higher accumulation potential. PMID:15111047

  9. 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. PMID:27178267

  10. Development of a site-specific water quality criterion for hexavalent chromium

    SciTech Connect

    McIntyre, D.O.; Sticko, J.P.; Reash, R.J.

    1995-12-31

    The effluent of treated fly ash from a coal-fired power plant located on the Ohio River periodically exceeds its NPDES acute permit limit for hexavalent chromium of 15 {micro}g/L. The increased levels of hexavalent chromium in the effluent are a recent occurrence which are likely due to changes in coal blends burned in the generating units. Ohio EPA determined the use designation of the receiving stream (Limited Resource Water) was being attained and a one-year biomonitoring program of the effluent detected no acute toxicity to Ceriodaphnia dubia or Daphnia magna. The water-effect ratio (WER) procedure was selected to develop a site-specific criterion maximum concentration for hexavalent chromium for the effluent`s receiving stream. WER procedures followed those described in EPA`s ``Interim Guidance on Determination and Use of Water-Effect Ratios for Metals`` (1994). Site water used in the WER determinations was undiluted effluent since the receiving stream originates at the discharge point of the outfall. 48-hour acute D. magna and 96-hour acute fathead minnow toxicity tests were selected as the primary and secondary tests, respectively for use in three seasonal WER determinations. The results of the three WER determinations and the status of the regulatory process will be presented.

  11. Interferences in the spectrophotometric S-diphenylcarbazide determination of environmental hexavalent chromium in a chromium and zinc plating plant.

    PubMed

    Carelli, G; La Bua, R; Rimatori, V; Porcelli, D; Iannaccone, A

    1981-03-01

    A study on the determination of environmental hexavalent chromium [Cr(VI)] was carried out in a chromium and zinc plating plant. The atmospheric particulate was collected both on glass wool filters and with an electrostatic sampler; Cr(VI) was determined by the S-diphenylcarbazide method. The filtered and electrostatically collected Cr(VI) was extracted with both 1.4% sulfuric acid and 7% sodium carbonate. Strong interference was observed when extraction was carried out with the acid medium. Alkaline extraction permits 95 +/- 6 (+/- SD)% recovery of the total chromium and has been shown to be suitable in releasing Cr(VI). The analyses of the alkaline samples were carried out with the standard addition method to compensate for a depressive interference of 26 +/- 8 (+/- SD)%. The absorbance decrease of the Cr-S-diphenylcarbazide complex is a time function, and it should be measured within a few minutes of the reagent addition. PMID:7313611

  12. Hexavalent chromium removal from wastewater using aniline formaldehyde condensate coated silica gel.

    PubMed

    Kumar, P Albino; Ray, Manabendra; Chakraborty, Saswati

    2007-05-01

    A resinous polymer, aniline formaldehyde condensate (AFC) coated on silica gel was used as an adsorbent in batch system for removal of hexavalent chromium from aqueous solution by considering the effects of various parameters like reaction pH, dose of AFC coated silica gel, initial Cr(VI) concentration and aniline to formaldehyde ratio in AFC synthesis. The optimum pH for total chromium [Cr(VI) and Cr(III)] adsorption was observed as 3. Total chromium adsorption was second order and equilibrium was achieved within 90-120 min. Aniline to formaldehyde ratio of 1.6:1 during AFC synthesis was ideal for chromium removal. Total chromium adsorption followed Freundlich's isotherm with adsorption capacity of 65 mg/g at initial Cr(VI) 200mg/L. Total chromium removal was explained as combinations of electrostatic attraction of acid chromate ion by protonated AFC, reduction of Cr(VI) to Cr(III) and bond formation of Cr(III) with nitrogen atom of AFC. Almost 40-84% of adsorbed chromium was recovered during desorption by NaOH, EDTA and mineral acids. AFC coated silica gel can be effectively used for treatment of chromium containing wastewaters as an alternative. PMID:17030417

  13. 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.

  14. Release of Hexavalent Chromium by Ash and Soils in Wildfire-Impacted Areas

    USGS Publications Warehouse

    Wolf, Ruth E.; Morman, Suzette A.; Plumlee, Geoffrey S.; Hageman, Philip L.; Adams, Monique

    2008-01-01

    The highly oxidizing environment of a wildfire has the potential to convert any chromium present in the soil or in residential or industrial debris to its more toxic form, hexavalent chromium, a known carcinogen. In addition, the highly basic conditions resulting from the combustion of wood and wood products could result in the stabilization of any aqueous hexavalent chromium formed. Samples were collected from the October 2007 wildfires in Southern California and subjected to an array of test procedures to evaluate the potential effects of fire-impacted soils and ashes on human and environmental health. Soil and ash samples were leached using de-ionized water to simulate conditions resulting from rainfall on fire-impacted areas. The resulting leachates were of high pH (10-13) and many, particularly those of ash from burned residential areas, contained elevated total chromium as much as 33 micrograms per liter. Samples were also leached using a near-neutral pH simulated lung fluid to model potential chemical interactions of inhaled particles with fluids lining the respiratory tract. High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry was used to separate and detect individual species (for example, Cr+3, Cr+6, As+3, As+5, Se+4, and Se+6). These procedures were used to determine the form of the chromium present in the de-ionized water and simulated lung fluid leachates. The results show that in the de-ionized water leachate, all of the chromium present is in the form of Cr+6, and the resulting high pH tends to stabilize Cr+6 from reduction to Cr+3. Analysis of the simulated lung fluid leachates indicates that the predominant form of chromium present in the near-neutral pH of lung fluid would be Cr+6, which is of concern due to the high possibility of inhalation of the small ash and soil particulates, particularly by fire or restoration crews.

  15. Transport of hexavalent chromium in porous media: Effect of an applied electrical field

    SciTech Connect

    McIntosh, K.R. |; Huang, C.P.

    1995-12-31

    Contamination of soil and groundwater by chromium has occurred in many industrial areas. In the natural aqueous environment chromium exists at significant levels in two oxidation states: trivalent (Cr[III]) and hexavalent (Cr[VI]). Furthermore, CR(VI) occurs as the oxyanions HCrO{sub 4}{sup {minus}} and CrO{sub 4}{sup 2{minus}} which are highly soluble and mobile in groundwater. Therefore, with respect to potential human exposures, the presence of Cr(VI) in soil and ground water is generally the primary concern at hazardous waste sites with chromium contamination. The investigations described herein focused on the potential removal of Cr(VI) from soil using an electrokinetic process.

  16. Toxicity of hexavalent chromium to the alveolar macrophage in vivo and in vitro. [Rats

    SciTech Connect

    Galvin, J.B.; Oberg, S.G.

    1984-02-01

    In vivo and in vitro systems were used to evaluate hexavalent chromium toxicity to alveolar macrophages. Rat alveolar macrophages were exposed to 2 ..mu..g calcium chromate (CaCrO/sub 4/, insoluble) or 2 ..mu..g chromium trioxide (CrO/sub 3/, soluble) in live animals, in vivo, and in tissue culture, in vitro, collected by lavage from the lung. Chemiluminescence and oxygen consumption were measured as indicators of toxicity. Trypan blue dye exclusion was used to determine macrophage viability. In vivo exposure of the macrophage to either chromium compound showed no toxic effects at a 2-..mu..g dose. Macrophages exposed in tissue culture, however, had values significantly different from controls. The untreated controls for both exposure methods were compared to evaluate differences resulting from methods alone.

  17. Hexavalent chromium emissions from aerospace operations: A case study

    SciTech Connect

    Chaurushia, A.; Bajza, C.

    1994-12-31

    Northrop Aircraft Division (NAD) is subject to several air toxic regulations such as EPA SARA Title 3, California Assembly Bill 2588 (AB2588), and Proposition 65 and is a voluntary participant in air toxic emissions reduction programs such as the EPA 33/50 and MERIT Program. To quantify emissions, NAD initially followed regulatory guidelines which recommend that emission inventories of air toxics be based on engineering assumptions and conservative emission factors in absence of specific source test data. NAD was concerned that Chromium VI emissions from NAD`s spray coating and chemical tank line operations were not representative due to these techniques. More recently, NAD has relied upon information from its ongoing source testing program to determine emission rates of Chromium VI. Based on these source test results, NAD revised emission calculations for use in Chromium VI inventories, impact assessments and control strategies. NAD has been successful in demonstrating a significant difference between emissions calculated utilizing the source test results and emissions based on the traditional mass balance using agency suggested methods.

  18. MODELING THE RATE-CONTROLLED SORPTION OF HEXAVALENT CHROMIUM.

    USGS Publications Warehouse

    Grove, D.B.; Stollenwerk, K.G.

    1985-01-01

    Sorption of chromium VI on the iron-oxide- and hydroxide-coated surface of alluvial material was numerically simulated with rate-controlled reactions. Reaction kinetics and diffusional processes, in the form of film, pore, and particle diffusion, were simulated and compared with experimental results. The use of empirically calculated rate coefficients for diffusion through the reacting surface was found to simulate experimental data; pore or particle diffusion is believed to be a possible rate-controlling mechanism. The use of rate equations to predict conservative transport and rate- and local-equilibrium-controlled reactions was shown to be feasible.

  19. Hexavalent chromium removal from aqueous solutions by a novel powder prepared from Colocasia esculenta leaves.

    PubMed

    Nakkeeran, E; Saranya, N; Giri Nandagopal, M S; Santhiagu, A; Selvaraju, N

    2016-08-01

    In this study, batch removal of hexavalent chromium from aqueous solutions by powdered Colocasia esculenta leaves was investigated. Batch experiments were conducted to study the effects of adsorption of Cr(VI) at different pH values, initial concentrations, agitation speeds, temperatures, and contact times. The biosorbent was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrometer analysis. The biosorptive capacity of the adsorbent was dependent on the pH of the chromium solution in which maximum removal was observed at pH 2. The adsorption equilibrium data were evaluated for various adsorption isotherm models, kinetic models, and thermodynamics. The equilibrium data fitted well with Freundlich and Halsey models. The adsorption capacity calculated was 47.62 mg/g at pH 2. The adsorption kinetic data were best described by pseudo-second-order kinetic model. Thus, Colocasia esculenta leaves can be considered as one of the efficient and cheap biosorbents for hexavalent chromium removal from aqueous solutions. PMID:26853060

  20. Toxic hexavalent chromium reduction by Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium

    NASA Astrophysics Data System (ADS)

    Rehman, Fatima; Faisal, Muhammad

    2015-05-01

    Three bacterial strains Bacillus pumilis, Cellulosimicrobium cellulans and Exiguobacterium were investigated when grown in Luria-Bertani (LB) medium at 500 μg/mL Cr(VI). The hexavalent chromium reduction was measured by growing the strains in DeLeo and Ehrlich (1994) medium at 200 and 400 μg/mL K2CrO4. The optimal Cr (VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 51%, 39%, and 41%, respectively, at an initial K2CrO4 concentration of 200 μg/mL at pH 3 and temperature 37°C. At an initial chromate concentration of 400 μg/mL, the Cr(VI) reduction by strains B. pumilis, Exigubacterium and C. cellulans was 24%, 19%, and 18%, respectively at pH 3 at 37°C after 24 h. These strains have ability to reduce toxic hexavalent chromium to the less mobile trivalent chromium at a wide range of different environmental conditions and can be useful for the treatment of contaminated wastewater and soils.

  1. Exposure to particulate hexavalent chromium exacerbates allergic asthma pathology

    SciTech Connect

    Schneider, Brent C.; Constant, Stephanie L.; Patierno, Steven R.; Jurjus, Rosalyn A.; Ceryak, Susan M.

    2012-02-15

    Airborne hexavalent chromate, Cr(VI), has been identified by the Environmental Protection Agency as a possible health threat in urban areas, due to the carcinogenic potential of some of its forms. Particulate chromates are produced in many different industrial settings, with high levels of aerosolized forms historically documented. Along with an increased risk of lung cancer, a high incidence of allergic asthma has been reported in workers exposed to certain inhaled particulate Cr(VI) compounds. However, a direct causal association between Cr(VI) and allergic asthma has not been established. We recently showed that inhaled particulate Cr(VI) induces an innate neutrophilic inflammatory response in BALB/c mice. In the current studies we investigated how the inflammation induced by inhaled particulate Cr(VI) might alter the pathology of an allergic asthmatic response. We used a well-established mouse model of allergic asthma. Groups of ovalbumin protein (OVA)-primed mice were challenged either with OVA alone, or with a combination of OVA and particulate zinc chromate, and various parameters associated with asthmatic responses were measured. Co-exposure to particulate Cr(VI) and OVA mediated a mixed form of asthma in which both eosinophils and neutrophils are present in airways, tissue pathology is markedly exacerbated, and airway hyperresponsiveness is significantly increased. Taken together these findings suggest that inhalation of particulate forms of Cr(VI) may augment the severity of ongoing allergic asthma, as well as alter its phenotype. Such findings may have implications for asthmatics in settings in which airborne particulate Cr(VI) compounds are present at high levels. -- Highlights: ► Allergic asthma correlated with exposure to certain inhaled particulate chromates. ► Direct causal association between Cr(VI) and allergic asthma not established. ► Cr exacerbated pathology and airway hyperresponsiveness in an OVA-challenged mouse. ► Particulate Cr

  2. Exposure to Particulate Hexavalent Chromium Exacerbates Allergic Asthma Pathology

    PubMed Central

    Schneider, Brent C.; Constant, Stephanie L.; Patierno, Steven R.; Jurjus, Rosalyn A.; Ceryak, Susan M.

    2011-01-01

    Airborne hexavalent chromate, Cr(VI), has been identified by the Environmental Protection Agency as a possible health threat in urban areas, due to the carcinogenic potential of some of its forms. Particulate chromates are produced in many different industrial settings, with high levels of aerosolized forms historically documented. Along with an increased risk of lung cancer, a high incidence of allergic asthma has been reported in workers exposed to certain inhaled particulate Cr(VI) compounds. However, a direct causal association between Cr(VI) and allergic asthma has not been established. We recently showed that inhaled particulate Cr(VI) induces an innate neutrophilic inflammatory response in BALB/c mice. In the current studies we investigated how the inflammation induced by inhaled particulate Cr(VI) might alter the pathology of an allergic asthmatic response. We used a well-established mouse model of allergic asthma. Groups of ovalbumin protein (OVA)-primed mice were challenged either with OVA alone, or with a combination of OVA and particulate zinc chromate, and various parameters associated with asthmatic responses were measured. Co-exposure to particulate Cr(VI) and OVA mediated a mixed form of asthma in which both eosinophils and neutrophils are present in airways, tissue pathology is markedly exacerbated, and airway hyperresponsiveness is significantly increased. Taken together these findings suggest that inhalation of particulate forms of Cr(VI) may augment the severity of ongoing allergic asthma, as well as alter its phenotype. Such findings may have implications for asthmatics in settings in which airborne particulate Cr(VI) compounds are present at high levels. PMID:22178736

  3. Removal of hexavalent chromium in tannery wastewater by Bacillus cereus.

    PubMed

    Zhao, Changqing; Yang, Qinhuan; Chen, Wuyong; Teng, Bo

    2012-01-01

    Bacillus cereus was used to remove chromium (Cr(VI)) from medium containing tannery wastewater under different conditions. The maximum rate of Cr(VI) removal was attained at a temperature of 37 °C, pH of 7.0-9.0, and biomass of 20 g/L when the initial Cr(VI) concentration was less than 50 mg/L. Under the optimum conditions, the Cr(VI) in tannery wastewater was treated with each cellular component of B. cereus to detect its ability to reduce Cr(VI). The results showed that the removal rate of Cr(VI) for the cell-free extracts could reach 92.70%, which was close to that of the whole cells (96.85%), indicating that the Cr(VI) reductase generated by B. cereus is primarily intracellular. Additionally, during continuous culture of the B. cereus, the strain showed good consecutive growth and removal ability. After treatment of 20 mg/L Cr(VI) for 48 h, the B. cereus was observed by SEM and TEM-EDX. SEM images showed that the B. cereus used to treat Cr(VI) grew well and had a uniform cellular size. TEM-EDX analysis revealed large quantities of chromium in the B. cereus cells used to treat Cr(VI). Overall, the results presented herein demonstrate that B. cereus can be used as a new biomaterial to remove Cr(VI) from tannery wastewater. PMID:22149215

  4. Lethal and sub-lethal effects on the Asian common toad Duttaphrynus melanostictus from exposure to hexavalent chromium.

    PubMed

    Fernando, Vindhya A K; Weerasena, Jagathpriya; Lakraj, G Pemantha; Perera, Inoka C; Dangalle, Chandima D; Handunnetti, Shiroma; Premawansa, Sunil; Wijesinghe, Mayuri R

    2016-08-01

    Chromium discharged in industrial effluents frequently occurs as an environmental pollutant, but the lethal and sub-lethal effects the heavy metal might cause in animals exposed to it have been insufficiently investigated. Selecting the amphibian Duttaphrynus melanostictus, we carried out laboratory tests to investigate the effects of short and long term exposure to hexavalent chromium (Cr(VI)) in both tadpoles and adult toads. The concentrations used were 0.002, 0.02, 0.2, 1.0 and 2.0mg/L, the first three corresponding to field levels. In vitro exposures were also carried out using toad erythrocytes and Cr(VI) concentrations of 0.0015, 0.003, 0.015, 0.03, 0.15mg/L. Mortality, growth retardation, developmental delays and structural aberrations were noted in the metal-treated tadpoles, with increasing incidence corresponding to increase in Cr(VI) level and duration of exposure. Many of the sub-lethal effects were evident with long term exposure to environmentally relevant levels of the toxicant. Changes in selected blood parameters and erythrocyte morphometry were also detected in Cr(VI) exposed toads, indicating anaemic and leucopenic conditions. In the genotoxicity study, DNA damage indicated by comet assay and increased micronuclei frequency, occurred at the low Cr(VI) concentrations tested. The multiple deleterious effects of exposure to chromium signal the need for monitoring and controlling the discharge of chromium to the environment. The dose-dependency and genotoxic effects observed in this widely distributed Asian toad indicates its suitability for monitoring heavy metal pollution in aquatic systems. PMID:27262939

  5. Lifetime and regeneration of immobilized titania for photocatalytic removal of aqueous hexavalent chromium.

    PubMed

    Tuprakay, Seree; Liengcharernsit, Winai

    2005-09-30

    Immobilized titania (TiO2) batch reactors reduced hexavalent chromium (Cr(VI)) in the form of potassium dichromate (K2Cr2O7) to trivalent chromium (Cr(III)) in aqueous solution at pH 3 under 171 W/m2 light intensity. The light source was a 125-W ultraviolet (UV) lamp. The Cr(VI) reduction showed zero-order kinetics (k0), while the Cr(VI) adsorption fitted with first-order kinetics (k(1st)). Adsorption capacity increased with increasing initial Cr(VI) concentration, and the area of immobilized TiO2 limited the reduction efficiency. The lifetime of fresh immobilized TiO2 was approximately 14 h. In addition, the regeneration of TiO2 with 3M sodium hydroxide (NaOH) was necessary to improve adsorption reaction. PMID:16046253

  6. Ecotoxicology of Hexavalent Chromium in Freshwater Fish: A Critical Review

    PubMed Central

    Velma, Venkatramreddy; Vutukuru, S.S.; Tchounwou, Paul B.

    2010-01-01

    Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Intense industrialization and other anthropogenic activities have led to the global occurrence of soluble Cr(VI), which is readily leached from soil to groundwater or surface water, in concentrations above permissible levels. The ecotoxicology of Cr(VI) is linked to its environmental persistence and the ability to induce a variety of adverse effects in biologic systems, including fish. In aquatic ecosystems, Cr(VI) exposure poses a significant threat to aquatic life. This paper reviews the fate and transport of Cr(VI) in the environment and its acute and chronic effects on fish. We also discuss Cr(VI) toxicity at the cellular, biochemical, and genetic levels. An attempt is made in this review to comprehend the staggered data on the toxic effects of Cr(VI) to various species of fish. Such data are extremely useful to the scientific community and public officials involved in health risk assessment and management of environmental contaminants as a guide to the best course of action to restore ecosystems and, in turn, to preserve human health. PMID:19658319

  7. Isotope evidence of hexavalent chromium stability in ground water samples.

    PubMed

    Čadková, Eva; Chrastný, Vladislav

    2015-11-01

    Chromium stable isotopes are of interest in many geochemical studies as a tool to identify Cr(VI) reduction and/or dilution in groundwater aquifers. For such studies the short term stability of Cr(VI) in water samples is required before the laboratory analyses can be carried out. Here the short term stability of Cr(VI) in groundwater samples was studied using an isotope approach. Based on commonly available methods for Cr(VI) stabilization, water samples were filtered and the pH value was adjusted to be equal to or greater than 8 before Cr isotope analysis. Based on our Cr isotope data (expressed as δ(53)CrNIST979), Cr(VI) was found to be unstable over short time periods in anthropogenically contaminated groundwater samples regardless of water treatment (e.g., pH adjustment, different storage temperatures). Based on our laboratory experiments, δ(53)CrNIST979 of the Cr(VI) pool was found to be unstable in the presence of dissolved Fe(II), Mn(IV) and/or SO2. Threshold concentrations of Fe(II) causing Cr(VI) reduction range between 10 mg L(-1) and 100 mg L(-1)and less than 1 mg L(-1) for Mn. Hence our isotope data show that water samples containing Cr(VI) should be processed on-site through anion column chemistry to avoid any isotope shifts. PMID:26037819

  8. Wastewater remediation using a spiral shaped reactor for photochemical reduction of hexavalent chromium.

    PubMed

    Machado, Tiele Caprioli; Lansarin, Marla Azário; Ribeiro, Camila Silva

    2015-03-01

    The hexavalent chromium contained in wastewater of some industries is toxic to most microorganisms and potentially harmful to human health. The application of photochemical reduction of Cr(VI) in the treatment of wastewater from the electroplating industry was studied, and a continuous reactor in spiral shape made of borosilicate was designed and constructed (SSR). The statistical model of a circumscribed central composite design (CCCD) was used to investigate the influence of the amount of ethanol and the initial concentration of hexavalent chromium on total Cr(VI) reduction. A total Cr(VI) reduction of 46.0% was achieved under the optimal conditions established by the experimental design, using a synthetic Cr(VI) solution. In addition, the photochemical reduction of Cr(VI) follows pseudo first-order kinetics. The SSR exhibited similar behavior to that of the plug flow reactor (PFR), and presented higher photonic efficiency than the batch reactor. Finally, the designed reactor was effective when applied to real wastewater, showing a total Cr(VI) reduction of 51.8%, and its configuration is suitable for scale up. PMID:25355488

  9. HISTOPATHOLOGICAL AND ULTRASTRUCTURAL CHANGES IN THE ANTENNAL GLAND, MIDGUT, HEPATOPANCREAS, AND GILL OF GRASS SHRIMP FOLLOWING EXPOSURE TO HEXAVALENT CHROMIUM

    EPA Science Inventory

    Grass shrimp, Palaemonetes pugio, were exposed for 1 month to subacute concentrations of hexavalent chromium (0.5, 1.0, 2.0, 4.0 ppm) after which the gills, midgut, hepatopancreas, and antennal glands were examined for histopathological and ultrastructural changes. Pathological c...

  10. Chronic occupational exposure to hexavalent chromium causes DNA damage in electroplating workers

    PubMed Central

    2011-01-01

    Background Occupational exposure to chromium compounds may result in adverse health effects. This study aims to investigate whether low-level hexavalent chromium (Cr(VI)) exposure can cause DNA damage in electroplating workers. Methods 157 electroplating workers and 93 control subjects with no history of occupational exposure to chromium were recruited in Hangzhou, China. Chromium levels in erythrocytes were determined by graphite furnace atomic absorption spectrophotometer. DNA damage in peripheral lymphocytes was evaluated with the alkaline comet assay by three parameters: Olive tail moment, tail length and percent of DNA in the comet tail (tail DNA%). Urinary 8-OHdG levels were measured by ELISA. Results Chromium concentration in erythrocytes was about two times higher in electroplating workers (median: 4.41 μg/L) than that in control subjects (1.54 μg/L, P < 0.001). The medians (range) of Olive tail moment, tail length and tail DNA% in exposed workers were 1.13 (0.14-6.77), 11.17 (3.46-52.19) and 3.69 (0.65-16.20), and were significantly higher than those in control subjects (0.14 (0.01-0.39), 3.26 (3.00-4.00) and 0.69 (0.04-2.74), P < 0.001). Urinary 8-OHdG concentration was 13.65 (3.08-66.30) μg/g creatinine in exposed workers and 8.31 (2.94-30.83) μg/g creatinine in control subjects (P < 0.001). The differences of urinary 8-OHdG levels, Olive tail moment, tail length and tail DNA% between these two groups remained significant (P < 0.001) even after stratification by potential confounding factors such as age, gender, and smoking status. Chromium exposure was found to be positively associated with chromium levels in erythrocytes, urinary 8-OHdG levels, Olive tail moment, tail length and tail DNA%. Positive dose-response associations were also found between chromium levels in erythrocytes and Olive tail moment, tail length and tail DNA%. Conclusion The findings in this study indicated that there was detectable chromium exposure in electroplating workers

  11. Synergy between hexavalent chromium ions and TiO2 nanoparticles inside TUD-1 in the photocatalytic oxidation of propane, a spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hamdy, Mohamed S.

    2016-02-01

    Siliceous TUD-1 mesoporous material was bi-functionalized by titanium dioxide nanoparticles and hexavalent chromium ions. The synthesis was carried out by one-pot procedure based on sol-gel technique. The photocatalytic performance of the prepared material was evaluated in the oxidation of propane under the illumination of ultraviolet light (wavelength = 360 nm) and monitored by in situ Fourier transform infrared spectroscopy. The photocatalytic activity of the prepared material exhibited an extra-ordinary activity than the reference samples that contain either hexavalent chromium ions or titanium dioxide nanoparticles only, confirming the true synergy between hexavalent chromium and tetravalent titanium ions of titanium dioxide nanoparticles.

  12. An evaluation of in vivo models for toxicokinetics of hexavalent chromium in the stomach

    SciTech Connect

    Sasso, A.F. Schlosser, P.M.

    2015-09-15

    Hexavalent chromium (Cr6) is a drinking water contaminant that has been detected in most of the water systems throughout the United States. In 2-year drinking water bioassays, the National Toxicology Program (NTP) found clear evidence of carcinogenic activity in male and female rats and mice. Because reduction of Cr6 to trivalent chromium (Cr3) is an important detoxifying step in the gastrointestinal (GI) tract prior to systemic absorption, models have been developed to estimate the extent of reduction in humans and animals. The objective of this work was to use a revised model of ex vivo Cr6 reduction kinetics in gastric juice to analyze the potential reduction kinetics under in vivo conditions for mice, rats and humans. A published physiologically-based pharmacokinetic (PBPK) model was adapted to incorporate the new reduction model. This paper focuses on the toxicokinetics of Cr6 in the stomach compartment, where most of the extracellular Cr6 reduction is believed to occur in humans. Within the range of doses administered by the NTP bioassays, neither the original nor revised models predict saturation of stomach reducing capacity to occur in vivo if applying default parameters. However, both models still indicate that mice exhibit the lowest extent of reduction in the stomach, meaning that a higher percentage of the Cr6 dose may escape stomach reduction in that species. Similarly, both models predict that humans exhibit the highest extent of reduction at low doses. - Highlights: • We outline a new in vivo model for hexavalent chromium reduction in the stomach. • We examine in vivo reduction for mice, rats, and humans under varying conditions. • Species differences in toxicokinetics may explain susceptibility. • We show that a simplified stomach reduction model is adequate for extrapolation. • Internal dose uncertainties still exist.

  13. Genotoxicity of tri- and hexavalent chromium compounds in vivo and their modes of action on DNA damage in vitro.

    PubMed

    Fang, Zhijia; Zhao, Min; Zhen, Hong; Chen, Lifeng; Shi, Ping; Huang, Zhiwei

    2014-01-01

    Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo. PMID:25111056

  14. Genotoxicity of Tri- and Hexavalent Chromium Compounds In Vivo and Their Modes of Action on DNA Damage In Vitro

    PubMed Central

    Fang, Zhijia; Zhao, Min; Zhen, Hong; Chen, Lifeng; Shi, Ping; Huang, Zhiwei

    2014-01-01

    Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo. PMID:25111056

  15. Automated Ground-Water Sampling and Analysis of Hexavalent Chromium using a “Universal” Sampling/Analytical System

    PubMed Central

    Burge, Scott R.; Hoffman, Dave A.; Hartman, Mary J.; Venedam, Richard J.

    2005-01-01

    The capabilities of a “universal platform” for the deployment of analytical sensors in the field for long-term monitoring of environmental contaminants were expanded in this investigation. The platform was previously used to monitor trichloroethene in monitoring wells and at groundwater treatment systems (1,2). The platform was interfaced with chromium (VI) and conductivity analytical systems to monitor shallow wells installed adjacent to the Columbia River at the 100-D Area of the Hanford Site, Washington. A groundwater plume of hexavalent chromium is discharging into the Columbia River through the gravels beds used by spawning salmon. The sampling/analytical platform was deployed for the purpose of collecting data on subsurface hexavalent chromium concentrations at more frequent intervals than was possible with the previous sampling and analysis methods employed a the Site.

  16. Removal of hexavalent chromium by biosorption process in rotating packed bed.

    PubMed

    Panda, M; Bhowal, A; Datta, S

    2011-10-01

    Removal of hexavalent chromium ions from an aqueous solution by crude tamarind (Tamarindus indica) fruit shell was examined in a rotating packed bed contactor by continuously recirculating a given volume of solution through the bed. Reduction of Cr(VI) to Cr(III) within the biosorbent appeared to be the removal mechanism. Depletion rate of Cr(VI) from, and release of reduced Cr(III) ions into the aqueous phase, was influenced by mass transfer resistance besides pH and packing depth. A mathematical model considering the reduction reaction to be irreversible and incorporating intraparticle and external phase mass transfer resistances represented the experimental data adequately. The study indicated that the limitations of fixed bed contactor operating under terrestrial gravity in intensifying mass transfer rates for this system can be overcome with rotating packed bed due to liquid flow under centrifugal acceleration. PMID:21819035

  17. Hexavalent chromium (CrVI) field analytical method for bioenvironmental engineers. Final report

    SciTech Connect

    Carlton, G.N.; Chaloux, L.; Reichert, J.M.; England, E.C.; Greebon, K.

    1999-04-01

    The Industrial Hygiene Branch, in a collaborative effort with the National Institute for Occupational Safety and Health (NIOSH), developed a field analytical method to measure hexavalent chromium (CrVI, chromate) levels in air. The method uses ultrasonic extraction of sampling filters, solid-phase extraction of chromates from the extracted solution, and determination of chromate concentrations by spectrophotometry. It is an alternative to NIOSH methods 7300 and 7600 and overcomes some of the disadvantages of these methods. The chromate field method is relatively easy to use, specific for CrVI, has a lower detection limit than NIOSH 7600, and allow analysis before there is a chance for significant sample degradation. The method is intended for use by Bioenvironmental Engineers. Although all Bioenvironmental Engineering shops will benefit from use of the method, those shops that take a lot of chromate samples or have significant chromate exposure problems will derive the most benefit from the method.

  18. Removal of hexavalent chromium from aqueous solution by calcined Zn/Al-LDHs.

    PubMed

    Yang, Hui-Duo; Zhao, Yun-Peng; Li, Shi-Feng; Fan, Xing; Wei, Xian-Yong; Zong, Zhi-Min

    2016-01-01

    In this study, Zn/Al-layered double hydroxides (Zn/Al-LDHs) were synthesized by a co-precipitation method and characterized with X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then the hexavalent chromium Cr(VI) adsorption experiments on calcined Zn/Al-LDHs were carried out to analyze the effects of pH, temperature, adsorption time, initial Cr(VI) concentration and adsorbent dosage on the removal of Cr(VI) from aqueous solutions. The maximum adsorption capacity for Cr(VI) on calcined Zn/Al-LDHs under optimal conditions was found to be over 120 mg/g. The kinetic and isotherm of Cr(VI) adsorption on calcined Zn/Al-LDHs can be described with the pseudo-second-order kinetic model and Langmuir isotherm, respectively. PMID:27387001

  19. Hexavalent Chromium-Induced Apoptosis in Rat Uterus: Involvement of Oxidative Stress.

    PubMed

    Marouani, Neila; Tebourbi, Olfa; Mokni, Moncef; Yacoubi, Mohamed Tahar; Sakly, Mohsen; Benkhalifa, Moncef; Rhouma, Khémais Ben

    2015-01-01

    The present study is designed to test the hypothesis that oxidative stress mediates hexavalent chromium (VI)-induced apoptosis in uterus. Female Wistar rats received an intraperitoneal (i.p.) injection of potassium dichromate at doses of 1 and 2 mg/kg. Superoxide anion production was assessed by determination of the reduction of cytochrome c and iodonitrotetrazolium (INT), lipid peroxidation (LPO), metallothioneins (MTs), and catalase (CAT) activity. The expression of Bax and Bcl-2 proteins was investigated. After 15 days of treatment, an increase of LPO and MT levels occurred, whereas CAT activity decreased. Intense apoptosis was observed in endometriotic stromal cells of Cr-exposed rats. Bax protein expression was induced in endometriotic stromal cells with 1 mg of Cr(VI)/kg, and in stromal and epithelial cells at the higher dose. These results clearly suggest that Cr(VI) subacute treatment causes oxidative stress in rat uterus, leading to endometriotic stromal cells apoptosis. PMID:24965329

  20. Assessment of Hexavalent Chromium Natural Attenuation for the Hanford Site 100 Area

    SciTech Connect

    Truex, Michael J.; Szecsody, James E.; Qafoku, Nikolla P.; Sahajpal, Rahul; Zhong, Lirong; Lawter, Amanda R.; Lee, Brady D.

    2015-09-01

    Hexavalent chromium (Cr(VI)) plumes are present in the 100 Area at the Hanford Site. Remediation efforts are under way with objectives of restoring the groundwater to meet the drinking-water standard (48 µg/L) and protecting the Columbia River by ensuring that discharge of groundwater to the river is below the surface-water quality standard (10 µg/L). Current remedies include application of Pump-and-Treat (P&T) at the 100-D, 100-H, and 100-K Areas and Monitored Natural Attenuation (MNA) at the 100-F/IU Area. Remedy selection is still under way at the other 100 Areas. Additional information about the natural attenuation processes for Cr(VI) is important in all of these cases. In this study, laboratory experiments were conducted to demonstrate and quantify natural attenuation mechanisms using 100 Area sediments and groundwater conditions.

  1. Use of behavioral responses of rainbow trout Oncorhynchus mykiss in identifying sublethal exposure to hexavalent chromium.

    PubMed

    Svecevicius, Gintaras

    2009-05-01

    Laboratory tests were conducted in a flow-through apparatus on 1-year-old rainbow trout Oncorhynchus mykiss to evaluate the sensitivity of a number of their behavioral responses to hexavalent chromium (Cr(6+)). Test fish were exposed to Cr(6+) concentrations corresponding to 0.001-1 parts of the rainbow trout 96-h LC50 (0.029-28.5 mg Cr/L, respectively) in short-term (15 min) tests. Sensitivity parameter responses could be arranged into the following sequence: latent period of detection response = locomotor activity > gill ventilation frequency > coughing rate. All the rainbow trout responses were sensitive behavioral indicators of sublethal exposure. Behavioral responses meet the criteria as rapid tools for bioassay testing and could be easily standardized using Cr(6+) as a reference toxicant. PMID:19190838

  2. AN IN-SITU PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM AND TRICHLOROETHYLENE IN GROUNDWATER: VOLUME 3 MULTICOMPONENT REACTIVE TRANSPORT MODELING

    EPA Science Inventory

    Reactive transport modeling has been conducted to describe the performance of the permeable reactive barrier at the Coast Guard Support Center near Elizabeth City, NC. The reactive barrier was installed to treat groundwater contaminated by hexavalent chromium and chlorinated org...

  3. 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...

  4. 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

  5. Evaluation for Early Life Stage Fall Chinook Salmon Exposed to Hexavalent Chromium from a Contaminated Groundwater Source

    SciTech Connect

    Patton, Gregory W.; Dauble, Dennis D.; McKinstry, Craig A.

    2007-09-01

    We conducted a laboratory evaluation to assess the risk to early life stage (i.e., eyed egg to swim up) fall Chinook salmon (Oncorhynchus tshawytscha) for exposure to hexavalent chromium from a contaminated groundwater source. Local populations of fall Chinook salmon were exposed to Hanford Site source groundwater that was diluted with Columbia River water. Specific endpoints included survival, development rate, and growth. Tissue burdens of fish were also measured to estimate uptake and elimination rates of chromium. Survival, development, and growth of early life stage fall Chinook salmon were not adversely affected by extended exposures (i.e., 98 day) to hexavalent chromium ranging from 0.79 to 260 μg/L. Survival for all treatment levels and controls exceeded 98% at termination of the test. In addition, there were no differences among the mean lengths and weights of fish among all treatment groups. Whole-body concentrations of chromium in early life stage fall Chinook salmon had a typical dose-response pattern; i.e., those subjected to highest exposure concentrations and longest exposure intervals had higher tissue concentrations. Given the spatial extent of chromium concentrations at the Hanford Site, and the dynamics of the groundwater - river water interface, the current cleanup criterion of 10 µg/L chromium appear adequate to protect fall Chinook salmon populations.

  6. An evaluation of in vivo models for toxicokinetics of hexavalent chromium in the stomach.

    PubMed

    Sasso, A F; Schlosser, P M

    2015-09-15

    Hexavalent chromium (Cr6) is a drinking water contaminant that has been detected in most of the water systems throughout the United States. In 2-year drinking water bioassays, the National Toxicology Program (NTP) found clear evidence of carcinogenic activity in male and female rats and mice. Because reduction of Cr6 to trivalent chromium (Cr3) is an important detoxifying step in the gastrointestinal (GI) tract prior to systemic absorption, models have been developed to estimate the extent of reduction in humans and animals. The objective of this work was to use a revised model of ex vivo Cr6 reduction kinetics in gastric juice to analyze the potential reduction kinetics under in vivo conditions for mice, rats and humans. A published physiologically-based pharmacokinetic (PBPK) model was adapted to incorporate the new reduction model. This paper focuses on the toxicokinetics of Cr6 in the stomach compartment, where most of the extracellular Cr6 reduction is believed to occur in humans. Within the range of doses administered by the NTP bioassays, neither the original nor revised models predict saturation of stomach reducing capacity to occur in vivo if applying default parameters. However, both models still indicate that mice exhibit the lowest extent of reduction in the stomach, meaning that a higher percentage of the Cr6 dose may escape stomach reduction in that species. Similarly, both models predict that humans exhibit the highest extent of reduction at low doses. PMID:26123277

  7. NOM and alkalinity interference in trace-level hexavalent chromium analysis.

    PubMed

    Parks, Jeffrey L; McNeill, Laurie; Edwards, Marc

    2014-12-01

    Three analytical methods were evaluated for hexavalent and trivalent chromium analyses in the presence of natural organic matter (NOM) and alkalinity. Each method was tested using a simulated tap water with 1 μg L(-1) Cr(VI) and 0.8 μg L(-1) Cr(III) and several concentrations of NOM and/or alkalinity. An ion chromatograph with post column reaction cell conforming to USEPA Method 218.7 could accurately quantify Cr(VI) in the presence of up to 8 mg CL(-1) NOM and up to 170 mg L(-1) as CaCO3 alkalinity, and no oxidation of chromium was observed when 0.8 μg L(-1) Cr(III) was also present. A high-performance liquid chromatography coupled with inductively coupled plasma (HPLC-ICPMS) method and a field speciation method were also evaluated. Each of these methods was unaffected by the presence of alkalinity; however, the presence of NOM created issues. For the HPLC-ICPMS method, as the concentration of NOM increased the recovery of Cr(VI) decreased, resulting in a 'false negative' for Cr(VI). However, for the field speciation method, Cr(III) was complexed by NOM and carried through the ion exchange column, resulting in a 'false positive' for Cr(VI). PMID:25159403

  8. Reduction of hexavalent chromium by Sphaerotilus natans a filamentous micro-organism present in activated sludges.

    PubMed

    Caravelli, Alejandro H; Giannuzzi, Leda; Zaritzky, Noemí E

    2008-08-15

    Wastewaters produced by various industries may contain undesirable amounts of hexavalent chromium (Cr(VI)), as chromate and dichromate, a hazardous metal affecting flora and animals of aquatic ecosystems as well as human health. One removal strategy comprises the microbial reduction of Cr(VI) to Cr(III), a less soluble chemical species that is less toxic than Cr(VI). In this work, the ability to reduce Cr(VI) of Sphaerotilus natans, a filamentous bacterium usually found in activated sludge systems, was evaluated. In aerobic conditions, S. natans was able to efficiently reduce Cr(VI) to Cr(III) from dichromate solutions ranging between 4.5 and 80 mg Cr(VI)l(-1) in the presence of a carbonaceous source. A simultaneous evaluation of the microbial respiratory activity inhibition was also carried out to analyze the toxic effect of Cr(VI). Cr(VI) reduction by S. natans was mathematically modeled; chromium(VI) reduction rate depended on both Cr(VI) concentration and active biomass concentration. Although it is known that S. natans removes heavy metal cations such as Cr(III) by biosorption, the ability of this micro-organism to reduce Cr(VI), which behaves as an oxyanion in aqueous solutions, is a novel finding. The distinctive capacity to reduce Cr(VI) to Cr(III) than remain soluble or precipitated becomes S. natans a potential micro-organism to decontaminate wastewaters. PMID:18215460

  9. Removal of hexavalent chromium from aqueous solution by granular and powdered Peganum Harmala

    NASA Astrophysics Data System (ADS)

    Khosravi, Rasoul; Fazlzadehdavil, Mehdi; Barikbin, Behnam; Taghizadeh, Ali Akbar

    2014-02-01

    In this paper, batch removal of hexavalent chromium from aqueous solutions by granular and powdered seeds of Peganum Harmala was investigated. The Peganum Harmala seeds were collected and after beating slowly, separating and cleaning the Harmala seeds done using a sieve. Batch adsorption studies were performed in 100 ml Erlenmeyer flasks inside an incubator container. The main process parameters considered were pH, initial Cr(VI) concentration for PPH and GPH, adsorbent dose, and contact time. Cr(VI) was measured at a wavelength of 540 nm using a UV-vis T80+ spectrophotometer. The adsorption data were fitted well by Freundlich isotherm. The result shows that the maximum removal of Cr(VI) was observed at pH 1.5 for both adsorbents. Also, by increase adsorption dose, adsorption capacity of Cr(VI) decreased but the chromium adsorption rate increased. The mount of adsorbed Cr(VI) onto both adsorbents increased with an increase in the contact time but by increases initial concentration of Cr(VI), the mount of adsorbed Cr(VI) onto both adsorbents decreased. The results indicate that the powdered Peganum Harmala can be effective adsorbent than the granular Peganum Harmala for the removal of Cr(VI) from aqueous solution.

  10. Removal of hexavalent chromium from wastewater using a new composite chitosan biosorbent.

    PubMed

    Boddu, Veera M; Abburi, Krishnaiah; Talbott, Jonathan L; Smith, Edgar D

    2003-10-01

    A new composite chitosan biosorbent was prepared by coating chitosan, a glucosamine biopolymer, onto ceramic alumina. The composite bioadsorbent was characterized by high-temperature pyrolysis, porosimetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Batch isothermal equilibrium and continuous column adsorption experiments were conducted at 25 degrees C to evaluate the biosorbent for the removal of hexavalent chromium from synthetic as well as field samples obtained from chrome plating facilities. The effect of pH, sulfate, and chloride ion on adsorption was also investigated. The biosorbent loaded with Cr(VI) was regenerated using 0.1 M sodium hydroxide solution. A comparison of the results of the present investigation with those reported in the literature showed that chitosan coated on alumina exhibits greater adsorption capacity for chromium(VI). Further, experimental equilibrium data were fitted to Langmuir and Freundlich adsorption isotherms, and values of the parameters of the isotherms are reported. The ultimate capacity obtained from the Langmuir model is 153.85 mg/g chitosan. PMID:14572099

  11. Hexavalent Chromium Removal by a Paecilomyces sp. Fungal Strain Isolated from Environment

    PubMed Central

    Cárdenas-González, Juan F.; Acosta-Rodríguez, Ismael

    2010-01-01

    A resistant and capable fungal strain in removing hexavalent chromium was isolated from an environment near of Chemical Science Faculty, located in the city of San Luis Potosí, Mexico. The strain was identified as Paecilomyces sp., by macro- and microscopic characteristics. Strain resistance of the strain to high Cr (VI) concentrations and its ability to reduce chromium were studied. When it was incubated in minimal medium with glucose, another inexpensive commercial carbon source like unrefined and brown sugar or glycerol, in the presence of 50 mg/L of Cr (VI), the strain caused complete disappearance of Cr (VI), with the concomitant production of Cr (III) in the growth medium after 7 days of incubation, at 28°C, pH 4.0, 100 rpm, and an inoculum of 38 mg of dry weight. Decrease of Cr (VI) levels from industrial wastes was also induced by Paecilomyces biomass. These results indicate that reducing capacity of chromate resistant filamentous fungus Cr (VI) could be useful for the removal of Cr (VI) pollution. PMID:20634988

  12. High-capacity adsorption of dissolved hexavalent chromium using amine-functionalized magnetic corn stalk composites.

    PubMed

    Song, Wen; Gao, Baoyu; Zhang, Tengge; Xu, Xing; Huang, Xin; Yu, Huan; Yue, Qinyan

    2015-08-01

    Easily separable amine-functionalized magnetic corn stalk composites (AF-MCS) were employed for effective adsorption and reduction of toxic hexavalent chromium [Cr(VI)] to nontoxic Cr(III). The saturated magnetization of AF-MCS reached 6.2emu/g, and as a result, it could be separated from aqueous solution by a magnetic process for its superparamagnetism. The studies of various factors influencing the sorption behavior indicated that the optimum AF-MCS dosage for Cr(VI) adsorption was 1g/L, and the maximum adsorption capacity was observed at pH 3.0. The chromium adsorption perfectly fitted the Langmuir isotherm model and pseudo second order kinetic model. Furthermore, characterization of AF-MCS was investigated by means of XRD, SEM, TEM, FT-IR, BET, VSM and XPS analysis to discuss the uptake mechanism. Basically, these results demonstrated that AF-MCS prepared in this work has shown its merit in effective removal of Cr(VI) and rapid separation from effluents simultaneously. PMID:25690680

  13. Two fold modified chitosan for enhanced adsorption of hexavalent chromium from simulated wastewater and industrial effluents.

    PubMed

    Kahu, S S; Shekhawat, A; Saravanan, D; Jugade, R M

    2016-08-01

    Ionic solid (Ethylhexadecyldimethylammoniumbromide) impregnated phosphated chitosan (ISPC) was synthesized and applied for enhanced adsorption of hexavalent chromium from industrial effluent. The compound obtained was extensively characterized using instrumental techniques like FT-IR, TGA-DTA, XRD, SEM, BET and EDX. ISPC showed high adsorption capacity of 266.67mg/g in accordance with Langmuir isotherm model at pH 3.0 due to the presence of multiple sites which contribute for ion pair and electrostatic interactions with Cr(VI) species. The sorption kinetics and thermodynamic studies revealed that adsorption of Cr(VI) followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. Applicability of ISPC for higher sample volumes was discerned through column studies. The real chrome plating industry effluent was effectively treated with total chromium recovery of 94%. The used ISPC was regenerated simply by dilute ammonium hydroxide treatment and tested for ten adsorption-desorption cycles with marginal decrease in adsorption efficiency. PMID:27112874

  14. Field screening for hexavalent chromium in soil: A fast-turnaround field method based on water extraction

    SciTech Connect

    McCain, R.G.; Baechler, M.A.

    1994-01-01

    Sodium dichromate has been identified as a contaminant of concern at several waste sites on the Hanford Site. Although chromium standards for soil are typically stated in terms of total chrome, much of the toxicity and carcinogenicity are attributed to the hexavalent state, which typically exists as a relatively mobile anion. Investigation and removal of crushed drums potentially containing residual sodium dichromate required a field test for hexavalent chromium to support characterization and remediation activities. Previous experience with a commercially available field test kit had been unsuccessful. This stimulated an effort to determine potential sources of error in the field test and led to a number of modifications that significantly improved the reliability of the test.

  15. Sorptive removal of trivalent and hexavalent chromium from binary aqueous solutions by composite alginate-goethite beads.

    PubMed

    Lazaridis, N K; Charalambous, Ch

    2005-11-01

    In this study, the removal of hexavalent and trivalent chromium ions from binary aqueous solutions by composite alginate-goethite beads was investigated in a batch mode. Equilibrium sorption experiments were carried out at different temperatures and pH values. The data were correlated with Langmuir and Freundlich equations. The thermodynamic parameters calculated were: change in free energy, in enthalpy, in entropy and the heat of adsorption. The influence of mixing rate, sorbent concentration and sorbent particle size was studied at kinetic runs. The effective diffusion coefficients were evaluated by employing the homogeneous diffusion model and the shrinking core model for hexavalent and trivalent chromium, respectively. Desorption experiments were conducted by employing various eluants showed that the loaded material could be regenerated satisfactorily. PMID:16233908

  16. On the removal of hexavalent chromium from a Class F fly ash.

    PubMed

    Huggins, F E; Rezaee, M; Honaker, R Q; Hower, J C

    2016-05-01

    Coarse and fine samples of a Class F fly ash obtained from commercial combustion of Illinois bituminous coal have been exposed to two long-term leaching tests designed to simulate conditions in waste impoundments. ICP-AES analysis indicated that the coarse and fine fly ash samples contained 135 and 171mg/kg Cr, respectively. Measurements by XAFS spectroscopy showed that the ash samples originally contained 5 and 8% of the chromium, respectively, in the hexavalent oxidation state, Cr(VI). After exposure to water for more than four months, the percentage of chromium as Cr(VI) in the fly-ash decreased significantly for the coarse and fine fly-ash in both tests. Combining the XAFS data with ICP-AES data on the concentration of chromium in the leachates indicated that, after the nineteen-week-long, more aggressive, kinetic test on the coarse fly ash, approximately 60% of the Cr(VI) had been leached, 20% had been reduced to Cr(III) and retained in the ash, and 20% remained as Cr(VI) in the ash. In contrast, during the six-month-long baseline test, very little Cr was actually leached from either the coarse or the fine fly-ash (<0.1mg/kg); rather, about 66% and 20%, respectively, of the original Cr(VI) in the coarse and fine fly-ash was retained in the ash in that form, while the remainder, 34% and 80%, respectively, was reduced and retained in the ash as Cr(III). The results are interpreted as indicating that Cr(VI) present in Class F fly-ash can be reduced to Cr(III) when in contact with water and that such chemical reduction can compete with physical removal of Cr(VI) from the ash by aqueous leaching. PMID:26951722

  17. Reduction of hexavalent chromium using Aerva lanata L.: elucidation of reduction mechanism and identification of active principles.

    PubMed

    Poonkuzhali, K; Rajeswari, V; Saravanakumar, T; Viswanathamurthi, P; Park, Seung-Moon; Govarthanan, M; Sathishkumar, P; Palvannan, T

    2014-05-15

    The effluent discharge treatment for controlling the environment from non biodegradable metal contaminants using plant extract is an efficient technique. The reduction of hexavalent chromium by abundantly available weed, Aerva lanata L. was investigated using batch equilibrium technique. The variables studied were Cr(VI) concentration, Aerva lanata L. dose, contact time, pH, temperature and agitation speed. Cyclic voltammetry and ICP-MS analysis confirmed the reduction of Cr(VI) to Cr(III). Electrochemical analysis proved that, the chromium has not been degraded and the valency of the chromium has only been changed. ICP-MS analysis shows that 100ng/L of hexavalent chromium was reduced to 97.01ng/L trivalent chromium. These results suggest that components present in the Aerva lanata L. are responsible for the reduction of Cr(VI) to Cr(III). The prime components ferulic acid, kaempherol and β-carboline present in the Aerva lanata L. may be responsible for the reduction of Cr(VI) as evident from LC-MS analysis. PMID:24681590

  18. Evaluation of extraction methods for hexavalent chromium determination in dusts, ashes, and soils

    USGS Publications Warehouse

    Wolf, Ruth E.; Wilson, Stephen A.

    2010-01-01

    One of the difficulties in performing speciation analyses on solid samples is finding a suitable extraction method. Traditional methods for extraction of hexavalent chromium, Cr(VI), in soils, such as SW846 Method 3060A, can be tedious and are not always compatible with some determination methods. For example, the phosphate and high levels of carbonate and magnesium present in the U.S. Environmental Protection Agency (USEPA) Method 3060A digestion for Cr(VI) were found to be incompatible with the High Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry (HPLC-ICP-MS) detection method used by our laboratory. Modification of Method 3060A by eliminating the use of the phosphate buffer provided improved performance with the detection method, however dilutions are still necessary to achieve good chromatographic separation and detection of Cr(VI). An ultrasonic extraction method using a 1 mM Na2CO3 - 9 mM NaHCO3 buffer solution, adapted from Occupational Safety and Health Administration (OSHA) Method ID215, has been used with good results for the determination of Cr(VI) in air filters. The average recovery obtained for BCR-545 - Welding Dust Loaded on Filter (IRMM, Belgium) using this method was 99 percent (1.2 percent relative standard deviation) with no conversion of Cr(VI) to Cr(III) during the extraction process. This ultrasonic method has the potential for use with other sample matrices, such as ashes and soils. Preliminary investigations using NIST 2701 (Hexavalent Chromium in Contaminated Soil) loaded onto quartz filters showed promising results with approximately 90 percent recovery of the certified Cr(VI) value. Additional testing has been done using NIST 2701 and NIST 2700 using different presentation methods. Extraction efficiency of bulk presentation, where small portions of the sample are added to the bottom of the extraction vessel, will be compared with supported presentation, where small portions of the sample are loaded onto a

  19. Selected science: an industry campaign to undermine an OSHA hexavalent chromium standard.

    PubMed

    Michaels, David; Monforton, Celeste; Lurie, Peter

    2006-01-01

    While exposure to hexavalent chromium (Cr(VI)) has been associated with increased lung cancer risk for more than 50 years, the chemical is not currently regulated by the U.S. Occupational Safety and Health Administration (OSHA) on the basis of its carcinogenicity. The agency was petitioned in 1993 and sued in 1997 and 2002 to lower the workplace Cr(VI) exposure limit, resulting in a court order to issue a final standard by February 2006. Faced with the threat of stronger regulation, the chromium industry initiated an effort to challenge the scientific evidence supporting a more protective standard. This effort included the use of "product defense" consultants to conduct post hoc analyses of a publicly-funded study to challenge results viewed unfavorably by the industry. The industry also commissioned a study of the mortality experience of workers at four low-exposure chromium plants, but did not make the results available to OSHA in a timely manner, despite multiple agency requests for precisely these sorts of data. The commissioned study found a statistically significant elevation in lung cancer risk among Cr(VI)-exposed workers at levels far below the current standard. This finding changed when the multi-plant cohort was divided into two statistically underpowered components and then published separately. The findings of the first paper published have been used by the chromium industry to attempt to slow OSHA's standard setting process. The second paper was withheld from OSHA until it was accepted for publication in a scientific journal, after the rulemaking record had closed. Studies funded by private sponsors that seek to influence public regulatory proceedings should be subject to the same access and reporting provisions as those applied to publicly funded science. Parties in regulatory proceedings should be required to disclose whether the studies were performed by researchers who had the right to present their findings without the sponsor's consent or

  20. Hexavalent chromium removal and bioelectricity generation by Ochrobactrum sp. YC211 under different oxygen conditions.

    PubMed

    Chen, Chih-Yu; Cheng, Chiu-Yu; Chen, Ching-Kuo; Hsieh, Min-Chi; Lin, Ssu-Ting; Ho, Kuo-Ying; Li, Jo-Wei; Lin, Chia-Pei; Chung, Ying-Chien

    2016-01-01

    Bioremediation is an environmentally friendly method of reducing heavy metal concentration and toxicity. A chromium-reducing bacterial strain, isolated from the vicinity of an electroplate factory, was identified as Ochrobactrum sp. YC211. The efficiency and capacity per time of Ochrobactrum sp. YC211 for hexavalent chromium (Cr(VI)) removal under anaerobic conditions were superior to those under aerobic conditions. An acceptable removal efficiency (96.5 ± 0.6%) corresponding to 30.2 ± 0.8 mg-Cr (g-dry cell weight-h)(-1) was achieved by Ochrobactrum sp. YC211 at 300 mg L(-1) Cr(VI). A temperature of 30°C and pH 7 were the optimal parameters for Cr(VI) removal. By examining reactivated cells, permeabilized cells, and cell-free extract, we determined that Cr(VI) removal by Ochrobactrum sp. YC211 under anaerobic conditions mainly occurred in the soluble fraction of the cell and can be regarded as an enzymatic reaction. The results also indicated that an Ochrobactrum sp. YC211 microbial fuel cell (MFC) with an anaerobic anode was considerably superior to that with an aerobic anode in bioelectricity generation and Cr(VI) removal. The maximum power density and Cr(VI) removal efficiency of the MFC were 445 ± 3.2 mW m(-2) and 97.2 ± 0.3%, respectively. Additionally, the effects of coexisting ions (Cu(2+), Zn(2+), Ni(2+), SO4(2-), and Cl(-)) in the anolyte on the MFC performance and Cr(VI) removal were nonsignificant (P > 0.05). To our knowledge, this is the first report to compare Cr(VI) removal by different cells and MFC types under aerobic and anaerobic conditions. PMID:26889692

  1. Hexavalent chromium removal in contaminated water using reticulated chitosan micro/nanoparticles from seafood processing wastes.

    PubMed

    Dima, Jimena Bernadette; Sequeiros, Cynthia; Zaritzky, Noemi E

    2015-12-01

    Chitosan particles (CH) were obtained from seafood processing wastes (shrimp shells) and physicochemically characterized; deacetylation degree of CH was measured by Infrared Spectroscopy (FTIR) and potentiometric titration; polymer molecular weight was determined by intrinsic viscosity measurements. Reticulated micro/nanoparticles of chitosan (MCH) with an average diameter close to 100nm were synthesized by ionic gelation of chitosan using tripolyphosphate (TPP), and characterized by SEM, size distribution and Zeta-potential. Detoxification capacities of CH and MCH were tested analyzing the removal of hexavalent chromium Cr(VI) from contaminated water, at different initial chromium concentrations. The effect of pH on adsorption capacity of CH and MCH was experimentally determined and analyzed considering the Cr(VI) stable complexes (anions) formed, the presence of protonated groups in chitosan particles and the addition of the reticulating agent (TPP). Chitosan crosslinking was necessary to adsorb Cr(VI) at pH<2 due to the instability of CH particles in acid media. Langmuir isotherm described better than Freundlich and Temkin equations the equilibrium adsorption data. Pseudo-second order rate provided the best fitting to the kinetic data in comparison to pseudo-first order and Elovich equations. Chemical analysis to determine the oxidation state of the adsorbed Cr, showed that Cr(VI) was adsorbed on CH particles without further reduction; in contrast Cr(VI) removed from the solution was reduced and bound to the MCH as Cr(III). The reduction of toxic Cr(VI) to the less or nontoxic Cr(III) by the reticulated chitosan micro/nanoparticles can be considered a very efficient detoxification technique for the treatment of Cr(VI) contaminated water. PMID:26151484

  2. A chronic oral reference dose for hexavalent chromium-induced intestinal cancer.

    PubMed

    Thompson, Chad M; Kirman, Christopher R; Proctor, Deborah M; Haws, Laurie C; Suh, Mina; Hays, Sean M; Hixon, J Gregory; Harris, Mark A

    2014-05-01

    High concentrations of hexavalent chromium [Cr(VI)] in drinking water induce villous cytotoxicity and compensatory crypt hyperplasia in the small intestines of mice (but not rats). Lifetime exposure to such cytotoxic concentrations increases intestinal neoplasms in mice, suggesting that the mode of action for Cr(VI)-induced intestinal tumors involves chronic wounding and compensatory cell proliferation of the intestine. Therefore, we developed a chronic oral reference dose (RfD) designed to be protective of intestinal damage and thus intestinal cancer. A physiologically based pharmacokinetic model for chromium in mice was used to estimate the amount of Cr(VI) entering each intestinal tissue section (duodenum, jejunum and ileum) from the lumen per day (normalized to intestinal tissue weight). These internal dose metrics, together with corresponding incidences for diffuse hyperplasia, were used to derive points of departure using benchmark dose modeling and constrained nonlinear regression. Both modeling techniques resulted in similar points of departure, which were subsequently converted to human equivalent doses using a human physiologically based pharmacokinetic model. Applying appropriate uncertainty factors, an RfD of 0.006 mg kg(-1) day(-1) was derived for diffuse hyperplasia-an effect that precedes tumor formation. This RfD is protective of both noncancer and cancer effects in the small intestine and corresponds to a safe drinking water equivalent level of 210 µg l(-1). This concentration is higher than the current federal maximum contaminant level for total Cr (100 µg l(-1)) and well above levels of Cr(VI) in US drinking water supplies (typically ≤ 5 µg l(-1)). PMID:23943231

  3. [Determination of trivalent chromium and hexavalent chromium in dried edible fungi by microwave ashing-liquid chromatography with inductively coupled plasma mass spectrometry].

    PubMed

    Ni, Zhanglin; Tang, Fubin; Qu, Minghua; Mo, Runhong

    2014-02-01

    An analytical method using liquid chromatography with inductively coupled plasma mass spectrometry (LC-ICP-MS) for the determination of trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) in dried edible fungi was established. Edible fungi sample was ashed by a microwave ashing system and Na2 EDTA was added to the ashing sample to stabilize the Cr(III). An anion exchange column (250 mm x 4.6 mm, 10 microm) with a 60 mmol/L nitric acid (pH 9.3) solution as mobile phase was used for the separation and using ICP-MS as a detector for the determination of trivalent chromium and hexavalent chromium. The calibration curves were linear in the range of 0.5-50 microg/L and the correlation coefficients were 0. 999 9 for Cr(III) and Cr(VI). The average recoveries of Cr(III) and Cr(VI) ranged from 78.0% to 90.7% with the relative standard deviations (RSDs, n = 6) less than 4%. The limits of quantification (LOQ) of Cr(III) and Cr(VI) were 0.5 microg/L. The method is efficient, reliable and sensitive, and can meet the requirement for the determination of Cr(III) and Cr(VI) in dried edible fungi. PMID:24822453

  4. Inhalation cancer risk assessment of hexavalent chromium based on updated mortality for Painesville chromate production workers

    PubMed Central

    Proctor, Deborah M; Suh, Mina; Mittal, Liz; Hirsch, Shawn; Valdes Salgado, Raydel; Bartlett, Chris; Van Landingham, Cynthia; Rohr, Annette; Crump, Kenny

    2016-01-01

    The exposure-response for hexavalent chromium (Cr(VI))-induced lung cancer among workers of the Painesville Ohio chromate production facility has been used internationally for quantitative risk assessment of environmental and occupational exposures to airborne Cr(VI). We updated the mortality of 714 Painesville workers (including 198 short-term workers) through December 2011, reconstructed exposures, and conducted exposure-response modeling using Poisson and Cox regressions to provide quantitative lung cancer risk estimates. The average length of follow-up was 34.4 years with 24,535 person-years at risk. Lung cancer was significantly increased for the cohort (standardized mortality ratio (SMR)=186; 95% confidence interval (CI) 145–228), for those hired before 1959, those with >30-year tenure, and those with cumulative exposure >1.41 mg/m3-years or highest monthly exposures >0.26 mg/m3. Of the models assessed, the linear Cox model with unlagged cumulative exposure provided the best fit and was preferred. Smoking and age at hire were also significant predictors of lung cancer mortality. Adjusting for these variables, the occupational unit risk was 0.00166 (95% CI 0.000713–0.00349), and the environmental unit risk was 0.00832 (95% CI 0.00359–0.0174), which are 20% and 15% lower, respectively, than values developed in a previous study of this cohort. PMID:26669850

  5. Factors affecting chemical and biological reduction of hexavalent chromium in soil

    SciTech Connect

    Losi, M.E.; Amrhein, C.; Frankenberger, W.T. Jr. . Dept. of Soil and Environmental Sciences)

    1994-11-01

    Hexavalent chromium [Cr(VI)] is a common environmental pollutant that is mobile in soils and is a known mutagen. The trivalent form [Cr(III)] has not known mutagenic properties and is highly insoluble and immobile above pH 5.5. Reduction to the trivalent state thus represents an effective mechanism for detoxification and immobilization of Cr(VI) in soil/water systems. In this study, the authors conducted experiments to examine various parameters involving aerobic reduction of Cr(VI) in a field soil. They found that organic matter content, bioactivity, and oxygen status were important factors. Under optimum conditions, the soil reduced 96% of added Cr(VI) under aerobic, field-moist conditions. The pH of the system was shown to have little effect. Both biological and nonbiological processes were influential, and, of 20 chromate-resistant bacterial cultures isolated from soils, 9 were found to actively reduce Cr(VI) to Cr(III) in liquid media. Their study suggests that organic-amended soils can readily reduce Cr(VI) and could promote excellent removal efficiency either as a primary treatment technique, or in conjunction with bioreactor-type wastewater treatment systems.

  6. Preparation of Silk Sericin/Lignin Blend Beads for the Removal of Hexavalent Chromium Ions.

    PubMed

    Kwak, Hyo Won; Shin, Munju; Yun, Haesung; Lee, Ki Hoon

    2016-01-01

    In the present study, novel adsorbents having high adsorption capability and reusability were prepared using agricultural by-products: silk sericin and lignin. Silk sericin and lignin blend beads were successfully prepared using simple coagulation methods for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. A 1 M lithium chloride (LiCl)/dimethyl sulfoxide (DMSO) solvent system successfully dissolved both sericin and lignin and had sufficient viscosity for bead preparation. Compared to the conventional sericin bead adsorbent, sericin/lignin blend beads showed higher Cr(VI) adsorption capacity. The amount of lignin added to the adsorbent greatly affected the adsorption capacity of the beads, and a 50:50 sericin/lignin blend ratio was optimal. Adsorption behavior followed the Freundlich isotherm, which means the adsorption of Cr(VI) occurred on the heterogeneous surface. Cr(VI) adsorption capability increased with temperature because of thermodynamic-kinetic effects. In addition, over 90% of Cr(VI) ions were recovered from the Cr(VI) adsorbed sericin/lignin beads in a 1 M NaOH solution. The adsorption-desorption recycling process was stable for more than seven cycles, and the recycling efficiency was 82%. It is expected that the sericin/lignin beads could be successfully applied in wastewater remediation especially for hazardous Cr(VI) ions in industrial wastewater. PMID:27598142

  7. Hexavalent chromium damages chamomile plants by alteration of antioxidants and its uptake is prevented by calcium.

    PubMed

    Kováčik, Jozef; Babula, Petr; Hedbavny, Josef; Klejdus, Bořivoj

    2014-05-30

    Toxicity of low (3μM) and high (60 and 120μM) concentrations of hexavalent chromium/Cr(VI) in chamomile plants was studied. Fluorescence staining confirmed reduction of Cr(VI) to Cr(III). Cr was mainly accumulated in the roots with translocation factor <0.007. Notwithstanding this, both shoots and roots revealed increase in oxidative stress and depletion of glutathione, total thiols, ascorbic acid and activities of glutathione reductase and partially ascorbate peroxidase mainly at 120μM Cr. Though some protective mechanisms were detected (elevation of nitric oxide, enhancement of GPX activity and increase in phenols and lignin), this was not sufficient to counteract the oxidative damage. Consequently, soluble proteins, tissue water content and biomass production were considerably depleted. Surprising increase in some mineral nutrients in roots (Ca, Fe, Zn and Cu) was also detected. Subsequent experiment confirmed that exogenous calcium suppressed oxidative symptoms and Cr uptake but growth of chamomile seedlings was not improved. Alteration of naturally present reductants could be a reason for Cr(III) signal detected using specific fluorescence reagent: in vitro assay confirmed disappearance of ascorbic acid in equimolar mixture with dichromate (>96% at pH 4 and 7) while such response of glutathione was substantially less visible. PMID:24727012

  8. Assessment of polyphenol coated nano zero valent iron for hexavalent chromium removal from contaminated waters.

    PubMed

    Mystrioti, C; Sparis, D; Papasiopi, N; Xenidis, A; Dermatas, D; Chrysochoou, M

    2015-03-01

    Alternative plant extracts were examined as raw materials for the synthesis of nZVI from ferric solutions. Four plants were selected for evaluation, i.e. Camellia sinensis (green tea, GT), Syzygium aromaticum (clove, CL), Mentha spicata (spearmint, SM) and Punica granatum (pomegranate, PG). Based on the results obtained, it was concluded that the reduction of Fe(III) with the herb extracts is not complete. Using the GT extract, approximately 28 mM of the initial 66 mM of Fe (42.4 %) are reduced to the elemental state Fe(0). The highest reduction of Fe(III), about 53 %, was achieved with PG and the lowest, only 15.6 %, with the SM extract. Additional batch experiments have been carried out to evaluate the effectiveness of nZVI, synthesized with GT, CL, SM and PG, for the removal of hexavalent chromium from a 0.96 mM solution. The highest reduction of Cr(VI) (96 %) was obtained using the nZVI suspension produced with PG juice. The other three nZVI suspensions, i.e. CL-nZVI, GT-nZVI, and SM-nZVI, had a comparable effectiveness corresponding to 70 % reduction of chromate. PMID:25512186

  9. Inhalation cancer risk assessment of hexavalent chromium based on updated mortality for Painesville chromate production workers.

    PubMed

    Proctor, Deborah M; Suh, Mina; Mittal, Liz; Hirsch, Shawn; Valdes Salgado, Raydel; Bartlett, Chris; Van Landingham, Cynthia; Rohr, Annette; Crump, Kenny

    2016-01-01

    The exposure-response for hexavalent chromium (Cr(VI))-induced lung cancer among workers of the Painesville Ohio chromate production facility has been used internationally for quantitative risk assessment of environmental and occupational exposures to airborne Cr(VI). We updated the mortality of 714 Painesville workers (including 198 short-term workers) through December 2011, reconstructed exposures, and conducted exposure-response modeling using Poisson and Cox regressions to provide quantitative lung cancer risk estimates. The average length of follow-up was 34.4 years with 24,535 person-years at risk. Lung cancer was significantly increased for the cohort (standardized mortality ratio (SMR)=186; 95% confidence interval (CI) 145-228), for those hired before 1959, those with >30-year tenure, and those with cumulative exposure >1.41 mg/m(3)-years or highest monthly exposures >0.26 mg/m(3). Of the models assessed, the linear Cox model with unlagged cumulative exposure provided the best fit and was preferred. Smoking and age at hire were also significant predictors of lung cancer mortality. Adjusting for these variables, the occupational unit risk was 0.00166 (95% CI 0.000713-0.00349), and the environmental unit risk was 0.00832 (95% CI 0.00359-0.0174), which are 20% and 15% lower, respectively, than values developed in a previous study of this cohort. PMID:26669850

  10. LUNG INJURY, INFLAMMATION AND AKT SIGNALING FOLLOWING INHALATION OF PARTICULATE HEXAVALENT CHROMIUM

    PubMed Central

    Beaver, Laura M.; Stemmy, Erik J.; Constant, Stephanie L.; Schwartz, Arnold; Little, Laura G.; Gigley, Jason P.; Chun, Gina; Sugden, Kent D.; Ceryak, Susan M.; Patierno, Steven R.

    2013-01-01

    Certain particulate hexavalent chromium [Cr(VI)] compounds are human respiratory carcinogens that release genotoxic soluble chromate, and are associated with fibrosis, fibrosarcomas, adenocarcinomas and squamous cell carcinomas of the lung. We postulate that inflammatory processes and mediators may contribute to the etiology of Cr(VI) carcinogenesis, however the immediate (0–24 hours) pathologic injury and immune responses after exposure to particulate chromates have not been adequately investigated. Our aim was to determine the nature of the lung injury, inflammatory response, and survival signaling responses following intranasal exposure of BALB/c mice to particulate basic zinc chromate. Factors associated with lung injury, inflammation and survival signaling were measured in airway lavage fluid and in lung tissue. A single chromate exposure induced an acute immune response in the lung, characterized by a rapid and significant increase in IL-6 and GRO-α levels, an influx of neutrophils, and a decline in macrophages in lung airways. Histological examination of lung tissue in animals challenged with a single chromate exposure revealed an increase in bronchiolar cell apoptosis and mucosal injury. Furthermore, chromate exposure induced injury and inflammation that progressed to alveolar and interstitial pneumonitis. Finally, a single Cr(VI) challenge resulted in a rapid and persistent increase in the number of airways immunoreactive for phosphorylation of the survival signaling protein Akt, on serine 473. These data illustrate that chromate induces both survival signaling and an inflammatory response in the lung, which we postulate may contribute to early oncogenesis. PMID:19109987

  11. Hexavalent chromium reduction and energy recovery by using dual-chambered microbial fuel cell.

    PubMed

    Gangadharan, Praveena; Nambi, Indumathi M

    2015-01-01

    Microbial fuel cell (MFC) technology is utilized to treat hexavalent chromium (Cr(VI)) from wastewater and to generate electricity simultaneously. The Cr(VI) is bioelectrochemically reduced to non-toxic Cr(III) form in the presence of an organic electron donor in a dual-chambered MFC. The Cr(VI) as catholyte and artificial wastewater inoculated with anaerobic sludge as anolyte, Cr(VI) at 100 mg/L was completely removed within 48 h (initial pH value 2.0). The total amount of Cr recovered was 99.87% by the precipitation of Cr(III) on the surface of the cathode. In addition to that 78.4% of total organic carbon reduction was achieved at the anode chamber within 13 days of operation. Furthermore, the maximum power density of 767.01 mW/m² (2.08 mA/m²) was achieved by MFCs at ambient conditions. The present work has successfully demonstrated the feasibility of using MFCs for simultaneous energy production from wastewater and reduction of toxic Cr(VI) to non-toxic Cr(III). PMID:25714633

  12. Adsorption and desorption of hexavalent chromium in an alluvial aquifer near Telluride, Colorado

    USGS Publications Warehouse

    Stollenwerk, K.G.; Grove, D.B.

    1985-01-01

    A laboratory investigation of reactions between hexavalent chromium [Cr(VI)] and alluvium was conducted to evaluate reactions of Cr(VI) contaminating an alluvial aquifer near Telluride, CO and to determine the mechanisms responsible for these reactions. Uncontaminated alluvium and groundwater (spiked with CrO42-) from the study site were used in batch and column experiments. Results of these experiments show that Cr(VI) was adsorbed by the alluvium. Distribution coefficients from batch experiments ranged from 52 L/kg at an equilibrium CrO42- concentration of 0.4 ??mol/L to 1.7 L/kg at an equilibrium concentration of 1400 ??mol/L. The zero point of charge for the alluvium was approximately 8.3, and the alluvium had a positive net charge at the groundwater pH of 6.8. Visual and chemical evidence indicated that Fe oxide and hydroxide coatings on the alluvial particles principally were responsible for the absorption of Cr(VI). During column experiments, Cr(VI) initially was desorbed easily from the alluvium by Cr-free groundwater; however, the rate of desorption decreased rapidly, and > 60 pore volumes of groundwater were required to decrease the effluent concentration of Cr(VI) to 3 ??mol/L [drinking water standard for Cr(VI) = 1 ??mol/L]. The quantity of Cr(VI) adsorbed varied with the type and concentration of other anions in solution.

  13. Application of phytogenic zerovalent iron nanoparticles in the adsorption of hexavalent chromium

    NASA Astrophysics Data System (ADS)

    Madhavi, Vemula; Prasad, T. N. V. K. V.; Reddy, Ambavaram Vijaya Bhaskar; Ravindra Reddy, B.; Madhavi, Gajulapalle

    2013-12-01

    Zerovalent iron nanoparticles (ZVNI) were synthesized using a rapid, single step and completely green synthetic method from the leaf extracts of Eucalyptus globules and were characterized using the techniques Scanning Electron Microscopy (SEM), UV-Vis Spectroscopy, Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD) and Zeta potential measurement. The FT-IR analysis reveals that the polyphenolic compounds present in the leaf extract may be responsible for the reduction and stabilization of the ZVNI. These nanoparticles were utilized for the adsorption of hexavalent chromium (Cr (VI)) and the concentration of Cr (VI) was determined using UV-Vis spectrometer after treating with ZVNI. Response and surface contour plots were drawn with the help of Mini-tab software to explain the adsorption of Cr (VI). The adsorption efficiency of Cr (VI) reaches to the highest value (98.1%) when the reaction time was about 30 min. and the ZVNI dosage was 0.8 g/L. The effective parameters such as adsorbent (ZVNI) dosage, initial Cr (VI) concentration and the kinetics were also examined.

  14. Assessment of hexavalent chromium release in Malaysian electric arc furnace steel slag for fertilizer usage

    NASA Astrophysics Data System (ADS)

    Bankole, L. K.; Rezan, S. A.; Sharif, N. M.

    2014-03-01

    This study investigates the leaching of hexavalent chromium (Cr (VI)) from electric arc furnace steel slag as Cr (VI) is classified as human carcinogen. Batch leaching tests were performed for 16 days. The lixiviants used were alkaline, de-ionized and rain water. After 16 days, Cr (VI) was found to be highest in alkaline water (0.03 mg/L) and lowest in de-ionized water (0.01 mg/L). Besides the lixiviants used, slag stirring speed and liquid to solid ratio also affect Cr (VI) released. The experimental work was complimented with slag characterization using XRF, XRD and SEM/EDX analysis. The leaching process was also simulated via Factsage software to calculate isothermal pourbaix diagrams. The Cr (VI) released was low and below the threshold of 0.1 mg/L set for public water systems. Recycle the slag as fertilizer should be considered safe as it does not exceed the safety limit set for Cr (VI) dissolution.

  15. Biosorption of hexavalent chromium from aqueous solutions by Macadamia nutshell powder

    NASA Astrophysics Data System (ADS)

    Pakade, Vusumzi Emmanuel; Ntuli, Themba Dominic; Ofomaja, Augustine Enakpodia

    2016-04-01

    Macadamia nutshell biosorbents treated in three different activating agents [raw Macadamia nutshell powder (RMN), acid-treated Macadamia nutshell (ATMN) and base-treated Macadamia nutshell (BTMN)] were investigated for the adsorption of hexavalent chromium [Cr(VI)] from aqueous solutions. Fourier transform infrared spectroscopy spectra of free and Cr(VI)-loaded sorbents as well as thermogravimetric analysis revealed that the acid and base treatments modified the surface properties of the sorbent. Surface characteristics were also evaluated by the scanning electron microscopy and surface area analyzer. The optimum conditions for the adsorption of Cr(VI) by sorbents were pH 2, contact time 10 h, adsorbent mass 0.2 g and concentration 100 mg L-1. The equilibrium data were fitted into the Langmuir, Freundlich, Redlich-Peterson and Sips isotherms, and no single model could clearly explain the sorption mechanism. Maximum binding capacities of 45.23, 44.83 and 42.44 mg g-1 for RMN, ATMN and BTMN, respectively, were obtained. The kinetic data were analyzed using the pseudo-first, pseudo-second and Elovich kinetic models, and it was observed that the pseudo-second-order model produced the best fit for the experimental data. Macadamia nutshell sorbents showed potential as low-cost adsorbent for the removal of Cr(VI) from aqueous solution.

  16. Hexavalent chromium removal performance of anionic functionalized monolithic polymers: column adsorption, regeneration and modelling.

    PubMed

    Barlik, Necla; Keskinler, Bülent; Kocakerim, M Muhtar

    2016-01-01

    Anionic functionalized monolithic macro-porous polymers were used for the removal of hexavalent chromium(VI) anions from aqueous solution in column experiments. At a flux of 1.0 cm min and 30 mg Cr(VI) L(-1) feed concentration, breakthrough capacity and apparent capacity were 0.066 g Cr(VI) g(-1) anionic monolith and 0.144 g Cr(VI) g(-1) anionic monolith, respectively. The degree of column utilization was found to lie in the range 41-46%. Two kinetic models, theoretical and Thomas models, were applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. The simulation of the whole breakthrough curve was effective with the models. At a flux of 1.0 cm min and 30 mg Cr(VI) L(-1) feed concentration, the dispersion coefficient and adsorption equilibrium constant (K) were 3.14 × 10(-7) m s(-1) and 3,840, respectively. Also, Thomas model parameters k1 (rate constant of adsorption) and qm (equilibrium solid-phase concentration of sorbed solute) were 1.08 × 10(-3) L mg(-1) min(-1) and 0.124 g g(-1), respectively. After reaching equilibrium adsorption capacity, the monoliths were regenerated using 1 N HCl and were subsequently re-tested. It was found that the regeneration efficiency reduced from 98% after second usage to 97% after the third usage. PMID:27003067

  17. Morphological and transcriptional responses of Lycopersicon esculentum to hexavalent chromium in agricultural soil.

    PubMed

    Li, Shi-Guo; Hou, Jing; Liu, Xin-Hui; Cui, Bao-Shan; Bai, Jun-Hong

    2016-07-01

    The carcinogenic, teratogenic, and mutagenic effects of hexavalent chromium (Cr[VI]) on living organisms through the food chain raise the immediate need to assess the potential toxicological impacts of Cr(VI) on human health. Therefore, the concentration-dependent responses of 12 Cr(VI)-responsive genes selected from a high-throughput Lycopersicon esculentum complementary DNA microarray were examined at different Cr concentrations. The results indicated that most of the genes were differentially expressed from 0.1 mg Cr/kg soil, whereas the lowest-observable-adverse-effect concentrations of Cr(VI) were 1.6 mg Cr/kg soil, 6.4 mg Cr/kg soil, 3.2 mg Cr/kg soil, and 0.4 mg Cr/kg soil for seed germination, root elongation, root biomass, and root morphology, respectively, implying that the transcriptional method was more sensitive than the traditional method in detecting Cr(VI) toxicity. Dose-dependent responses were observed for the relative expression of expansin (p = 0.778), probable chalcone-flavonone isomerase 3 (p = -0.496), and 12S seed storage protein CRD (p = -0.614); therefore, the authors propose the 3 genes as putative biomarkers in Cr(VI)-contaminated soil. Environ Toxicol Chem 2016;35:1751-1758. © 2015 SETAC. PMID:26627465

  18. Reduction of hexavalent chromium by a novel Ochrobactrum sp. - microbial characteristics and reduction kinetics.

    PubMed

    Narayani, M; Vidya Shetty, K

    2014-04-01

    A Gram negative hexavalent chromium (Cr(VI)) reducing bacteria, Ochrobactrum sp. Cr-B4 (genbank accession number: JF824998) was isolated from the aerator water of an activated sludge process of a wastewater treatment facility of a dye and pigment based specialty chemical industry. It showed a resistance for 1000 mg L(-1) Cr(VI). It exhibited resistance against other heavy metal ions like Ni(2+) (900 mg L(-1) ), Cu(2+) (500 mg L(-1) ), Pb(2+) (800 mg L(-1) ), and Cd(2+) (250 mg L(-1) ), Zn(2+) (700 mg L(-1) ), Fe(3+) (800 mg L(-1) ), and against selected antibiotics. Cr-B4 could efficiently reduce 200 mg L(-1) Cr(VI) completely in nutrient and LB media and could convert Cr(VI) to Cr(III) efficiently. Cr(VI) reduction in nutrient media followed allosteric enzyme kinetics with Km values of 59.39 mg L(-1) and Vmax values of 47.03 mg L(-1)  h(-1) . The reduction in LB media followed Michaelis-Menten kinetics with Km values of 99.52 mg L(-1) and Vmax of 77.63 mg L(-1)  h(-1) . Scanning electron micrograms revealed the presence of extracellular polymeric secretions. PMID:23553414

  19. Hexavalent chromium induces apoptosis in male somatic and spermatogonial stem cells via redox imbalance

    PubMed Central

    Das, Joydeep; Kang, Min-Hee; Kim, Eunsu; Kwon, Deug-Nam; Choi, Yun-Jung; Kim, Jin-Hoi

    2015-01-01

    Hexavalent chromium [Cr(VI)], an environmental toxicant, causes severe male reproductive abnormalities. However, the actual mechanisms of toxicity are not clearly understood and have not been studied in detail. The present in vitro study aimed to investigate the mechanism of reproductive toxicity of Cr(VI) in male somatic cells (mouse TM3 Leydig cells and TM4 Sertoli cells) and spermatogonial stem cells (SSCs) because damage to or dysfunction of these cells can directly affect spermatogenesis, resulting in male infertility. Cr(VI) by inducing oxidative stress was cytotoxic to both male somatic cells and SSCs in a dose-dependent manner, and induced mitochondria-dependent apoptosis. Although the mechanism of Cr(VI)-induced cytotoxicity was similar in both somatic cells, the differences in sensitivity of TM3 and TM4 cells to Cr(VI) could be attributed, at least in part, to cell-specific regulation of P-AKT1, P-ERK1/2, and P-P53 proteins. Cr(VI) affected the differentiation and self-renewal mechanisms of SSCs, disrupted steroidogenesis in TM3 cells, while in TM4 cells, the expression of tight junction signaling and cell receptor molecules was affected as well as the secretory functions were impaired. In conclusion, our results show that Cr(VI) is cytotoxic and impairs the physiological functions of male somatic cells and SSCs. PMID:26355036

  20. Protective effects of pine bark extract on hexavalent chromium-induced dermatotoxicity in rats.

    PubMed

    Lee, In-Chul; Kim, Sung-Hwan; Shin, In-Sik; Moon, Changjong; Park, Soo-Hyun; Kim, Sung-Ho; Park, Seung-Chun; Kim, Hyoung-Chin; Kim, Jong-Choon

    2012-10-01

    The present study investigated the protective effects of pine bark extract (PBE) against hexavalent chromium [Cr(VI)]-induced dermatotoxicity in rats. Skin reactions were evaluated by visual inspection, histopathological changes and oxidative stress parameters. Topical application of Cr(VI) produced a significant increase in the incidence and severity of erythema and edema upon visual inspection. Histopathological examination showed moderate to severe necrosis and desquamation in the epidermis and inflammation and hemorrhage in the dermis. In addition, an increased malondialdehyde (MDA) concentration, and decreased glutathione (GSH), catalase, superoxide dismutase, glutathione-S-transferase (GST) and glutathione reductase of the skin were observed in the Cr(VI) group. On the contrary, concomitant administration with PBE significantly improved Cr(VI)-induced dermatotoxicity, evidenced by a decrease in the incidence and severity of skin irritation and histopathological lesions in a dose-dependent manner. Moreover, PBE treatment reduced MDA concentrations and increased catalase and GST activities in skin tissues, indicating that concomitant administration with PBE effectively prevents Cr(VI)-induced oxidative damage in rats. The results indicate that PBE has a protective effect against Cr(VI)-induced dermatotoxicity and is useful as a protective agent against various dermal lesions induced by oxidative stress. PMID:22344852

  1. Reduction of hexavalent chromium: photocatalysis and photochemistry and their application in wastewater remediation.

    PubMed

    Machado, Tiele Caprioli; Lansarin, Marla Azário; Matte, Natália

    2014-01-01

    Hexavalent chromium present in wastewater discharge of galvanic industries is toxic to most microorganisms and potentially harmful to human health. This work examines the photochemical reduction of Cr(VI) with ethanol under ultraviolet (UV) and visible radiation, and photocatalytic reduction of Cr(VI) with TiO2 in the presence of ethanol under UV radiation. By means of different experimental designs, this study investigates the influence of the initial pH, ethanol amount, catalyst concentration and initial Cr(VI) concentration on total Cr(VI) reduction. The results obtained showed that photochemistry with ethanol under UV radiation (96.10%) was more efficient than photochemistry with ethanol under visible light (48.07%). Furthermore, photocatalysis with TiO2 in the presence of ethanol under UV radiation showed high values of total Cr(VI) reduction: 94.15%, under the optimal conditions established by the experimental design. Finally, experiments were carried out with wastewater discharge from an electroplating plant in its original concentration, and higher values of total Cr(VI) reduction were observed. PMID:25026579

  2. Lung injury, inflammation and Akt signaling following inhalation of particulate hexavalent chromium

    SciTech Connect

    Beaver, Laura M.; Stemmy, Erik J.; Constant, Stephanie L.; Schwartz, Arnold; Little, Laura G.; Gigley, Jason P.; Chun, Gina; Sugden, Kent D.

    2009-02-15

    Certain particulate hexavalent chromium [Cr(VI)] compounds are human respiratory carcinogens that release genotoxic soluble chromate, and are associated with fibrosis, fibrosarcomas, adenocarcinomas and squamous cell carcinomas of the lung. We postulate that inflammatory processes and mediators may contribute to the etiology of Cr(VI) carcinogenesis, however the immediate (0-24 h) pathologic injury and immune responses after exposure to particulate chromates have not been adequately investigated. Our aim was to determine the nature of the lung injury, inflammatory response, and survival signaling responses following intranasal exposure of BALB/c mice to particulate basic zinc chromate. Factors associated with lung injury, inflammation and survival signaling were measured in airway lavage fluid and in lung tissue. A single chromate exposure induced an acute immune response in the lung, characterized by a rapid and significant increase in IL-6 and GRO-{alpha} levels, an influx of neutrophils, and a decline in macrophages in lung airways. Histological examination of lung tissue in animals challenged with a single chromate exposure revealed an increase in bronchiolar cell apoptosis and mucosal injury. Furthermore, chromate exposure induced injury and inflammation that progressed to alveolar and interstitial pneumonitis. Finally, a single Cr(VI) challenge resulted in a rapid and persistent increase in the number of airways immunoreactive for phosphorylation of the survival signaling protein Akt, on serine 473. These data illustrate that chromate induces both survival signaling and an inflammatory response in the lung, which we postulate may contribute to early oncogenesis.

  3. Investigation of Hexavalent Chromium Flux to Groundwater at the 100-C-7:1 Excavation Site

    SciTech Connect

    Truex, Michael J.; Vermeul, Vincent R.; Fritz, Brad G.; Mackley, Rob D.; Horner, Jacob A.; Johnson, Christian D.; Newcomer, Darrell R.

    2012-11-16

    Deep excavation of soil has been conducted at the 100-C-7 and 100-C-7:1 waste sites within the 100-BC Operable Unit at the Department of Energy (DOE) Hanford Site to remove hexavalent chromium (Cr(VI)) contamination with the excavations reaching to near the water table. Soil sampling showed that Cr(VI) contamination was still present at the bottom of the 100-C-7:1 excavation. In addition, Cr(VI) concentrations in a downgradient monitoring well have shown a transient spike of increased Cr(VI) concentration following initiation of excavation. Potentially, the increased Cr(VI) concentrations in the downgradient monitoring well are due to Cr(VI) from the excavation site. However, data were needed to evaluate this possibility and to quantify the overall impact of the 100-C-7:1 excavation site on groundwater. Data collected from a network of aquifer tubes installed across the floor of the 100-C-7:1 excavation and from temporary wells installed at the bottom of the entrance ramp to the excavation were used to evaluate Cr(VI) releases into the aquifer and to estimate local-scale hydraulic properties and groundwater flow velocity.

  4. Removal of hexavalent chromium by using red mud activated with cetyltrimethylammonium bromide.

    PubMed

    Li, Deliang; Ding, Ying; Li, Lingling; Chang, Zhixian; Rao, Zhengyong; Lu, Ling

    2015-01-01

    The removal of hexavalent chromium [Cr(VI)] from aqueous solution by using red mud activated with cetyltrimethylammonium bromide (CTAB) was studied. The optimum operation parameters, such as CTAB concentration, pH values, contact time, and initial Cr(VI) concentration, were investigated. The best concentration of CTAB for modifying red mud was found to be 0.50% (mCTAB/VHCl,0.6 mol/L). The lower pH (<2) was found to be much more favourable for the removal of Cr(VI). Red mud activated with CTAB can greatly improve the removal ratio of Cr(VI) as high as four times than that of original red mud. Adsorption equilibrium was reached within 30 min under the initial Cr(VI) concentration of 100 mg L(-1). The isotherm data were analysed using Langmuir and Freundlich models. The adsorption of Cr(VI) on activated red mud fitted well to the Langmuir isotherm model, and the maximum adsorption capacity was estimated as 22.20 mg g(-1) (Cr/red mud). The adsorption process could be well described using the pseudo-second-order model. The result shows that activated red mud is a promising agent for low-cost water treatment. PMID:25299348

  5. Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag.

    PubMed

    Han, Chong; Jiao, Yanan; Wu, Qianqian; Yang, Wangjin; Yang, He; Xue, Xiangxin

    2016-08-01

    Basic oxygen furnace slag (BOFS) has the potential to remove hexavalent chromium (Cr(VI)) from wastewater by a redox process due to the presence of minerals containing Fe(2+). The effects of the solution pH, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system and X-ray diffractometer (XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe(2+) released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe(2+) responsible for Cr(VI) removal was primarily derived from the dissolution of FeO and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum (CaSO4·2H2O) could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe(2+) and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps. PMID:27521937

  6. Biodegradation of the metallic carcinogen hexavalent chromium Cr(VI) by an indigenously isolated bacterial strain

    PubMed Central

    Mishra, Susmita

    2010-01-01

    Background: Hexavalent chromium [Cr(VI)], a potential mutagen and carcinogen, is regularly introduced into the environment through diverse anthropogenic activities, including electroplating, leather tanning, and pigment manufacturing. Human exposure to this toxic metal ion not only causes potential human health hazards but also affects other life forms. The World Health Organization, the International Agency for Research on Cancer, and the Environmental Protection Agency have determined that Cr(VI) compounds are known human carcinogens. The Sukinda valley in Jajpur District, Orissa, is known for its deposit of chromite ore, producing nearly 98% of the chromite ore in India and one of the prime open cast chromite ore mines in the world (CES, Orissa Newsletter). Materials and Methods: Our investigation involved microbial remediation of Cr(VI) without producing any byproduct. Bacterial cultures tolerating high concentrations of Cr were isolated from the soil sample collected from the chromite-contaminated sites of Sukinda, and their bioaccumulation properties were investigated. Strains capable of growing at 250 mg/L Cr(VI) were considered as Cr resistant. Results: The experimental investigation showed the maximum specific Cr uptake at pH 7 and temperature 30°C. At about 50 mg/L initial Cr(VI) concentrations, uptake of the selected potential strain exceeded 98% within 12 h of incubation. The bacterial isolate was identified by 16S rRNA sequencing as Brevebacterium casei. Conclusion: Results indicated promising approach for microbial remediation of effluents containing elevated levels of Cr(VI). PMID:20976016

  7. Mitigation of Hexavalent Chromium in Storm Water Resulting from Demolition of Large Concrete Structure at the East Tennessee Technology Park - 12286

    SciTech Connect

    Britto, Ronnie; Brown, Bridget; Hale, Timothy B.; Hensley, Janice L.; Johnson, Robert T.; Patel, Madhu; Emery, Jerry A.; Gaston, Clyde; Queen, David C.

    2012-07-01

    American Recovery and Reinvestment Act (ARRA) funding was provided to supplement the environmental management program at several DOE sites, including the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee. Demolition of the ETTP K-33 Building, the largest building to be demolished to date in Oak Ridge, was awarded to LSRS in FY-2010 under the ARRA program. The K-33 building was an 82 foot tall 2-story structure covering approximately 32 acres. Once this massive building was brought down to the ground, the debris was segregated and consolidated into piles of concrete rubble and steel across the remaining pad. The process of demolishing the building, tracking across concrete debris with heavy equipment, and stockpiling the concrete rubble caused it to become pulverized. During and after storm events, hexavalent chromium leached from the residual cement present in the large quantities of concrete. Storm water control measures were present to preclude migration of contaminants off-site, but these control measures were not designed to control hexavalent chromium dissolved in storm water from reaching nearby receiving water. The following was implemented to mitigate hexavalent chromium in storm water: - Steel wool was distributed around K-33 site catch basins and in water pools as an initial step in addressing hexavalent chromium. - Since the piles of concrete were too massive and unsafe to tarp, they were placed into windrows in an effort to reduce total surface area. - A Hach colorimetric field meter was acquired by the K-33 project to provide realtime results of hexavalent chromium in site surface water. - Three hexavalent chromium treatment systems were installed at three separate catch basins that receive integrated storm water flow from the K-33 site. Sodium bisulfite is being used as a reducing agent for the immobilization of hexavalent chromium while also assisting in lowering pH. Concentrations initially were 310 - 474 ppb of hexavalent chromium in

  8. Reduction And Immobilization Of Hexavalent Chromium By Microbially Reduced Fe-bearing Clay Minerals

    SciTech Connect

    Bishop, Michael E.; Glasser, Paul; Dong, Hailiang; Arey, Bruce W.; Kovarik, Libor

    2014-05-15

    Hexavalent chromium (Cr6+) is a major contaminant in the environment. As a redox-sensitive element, the fate and toxicity of chromium is controlled by reduction-oxidation (redox) reactions. Previous research has shown the ability of structural Fe(II) in naturally present and chemically reduced clay minerals to reduce Cr6+ to Cr(III) as a way of immobilization and detoxification. However, it is still poorly known whether or not structural Fe(II) in biologically reduced clay minerals exhibits a similar reactivity and if so, what the kinetics and mechanisms of Cr6+ reduction are. The objective of this study was to determine the kinetics and possible mechanisms of Cr6+ reduction by structural Fe(II) in microbially reduced clay minerals and the nature of reduced Cr(III). Structural Fe(III) in nontronite (NAu-2), montmorillonite (SWy-2), chlorite (CCa-2), and clay-rich sediments from the Ringold Formation of the Hanford site of Washington State, USA was first bioreduced to Fe(II) by an iron-reducing bacterium Geobacter sulfurreducens with acetate as the sole electron donor and anthraquinone-2,6-disulfate (AQDS) as electron shuttle in synthetic groundwater (pH 7). Biogenic Fe(II) was then used to reduce aqueous Cr6+ at three different temperatures, 10°, 20°, and 30°C, in order to determine the temperature dependence of the redox reaction between Cr6+ and clay-Fe(II). The results showed that nontronite and montmorillonite were most effective in reducing aqueous Cr6+ at all three temperatures. In contrast, most Fe(II) in chlorite was not reactive towards Cr6+ reduction at 10°C, though at 30°C there was some reduction. For all the clay minerals, the ratio of total Fe(II) oxidized to Cr6+ reduced was close to the expected stoichiometric value of 3. Characterization of the Cr-clay reaction product with scanning electron microscopy with focused ion beam and transmission electron microscopy with electron energy loss spectroscopy revealed that reduced chromium was possibly

  9. Reduction and immobilization of hexavalent chromium by microbially reduced Fe-bearing clay minerals

    NASA Astrophysics Data System (ADS)

    Bishop, Michael E.; Glasser, Paul; Dong, Hailiang; Arey, Bruce; Kovarik, Libor

    2014-05-01

    Hexavalent chromium (Cr6+) is a major contaminant in the environment. As a redox-sensitive element, the fate and toxicity of chromium is controlled by reduction-oxidation (redox) reactions. Previous research has shown the ability of structural Fe(II) in naturally present and chemically reduced clay minerals to reduce Cr6+ to Cr(III) as a way of immobilization and detoxification. However, it is still poorly known whether or not structural Fe(II) in biologically reduced clay minerals exhibits a similar reactivity and if so, what the kinetics and mechanisms of Cr6+ reduction are. The objective of this study was to determine the kinetics and possible mechanisms of Cr6+ reduction by structural Fe(II) in microbially reduced clay minerals and the nature of reduced Cr(III). Structural Fe(III) in nontronite (NAu-2), montmorillonite (SWy-2), chlorite (CCa-2), and clay-rich sediments from the Ringold Formation of the Hanford site of Washington State, USA was first bioreduced to Fe(II) by an iron-reducing bacterium Geobacter sulfurreducens with acetate as the sole electron donor and anthraquinone-2,6-disulfonate (AQDS) as electron shuttle in synthetic groundwater (pH 7). Biogenic Fe(II) was then used to reduce aqueous Cr6+ at three different temperatures, 10, 20, and 30 °C, in order to determine the temperature dependence of the redox reaction between Cr6+ and clay-Fe(II). The results showed that nontronite and montmorillonite were most effective in reducing aqueous Cr6+ at all three temperatures. In contrast, most Fe(II) in chlorite was not reactive towards Cr6+ reduction at 10 °C, though at 30 °C there was some reduction. For all the clay minerals, the ratio of total Fe(II) oxidized to Cr6+ reduced was close to the expected stoichiometric value of 3. Characterization of the Cr-clay reaction product with scanning electron microscopy with focused ion beam and transmission electron microscopy with electron energy loss spectroscopy revealed that reduced chromium was possibly

  10. Removing hexavalent chromium from subsurface waters with anion-exchange resin

    SciTech Connect

    Torres, R.A.

    1995-06-01

    Some subsurface waters at Lawrence Livermore National Laboratory (LLNL) are contaminated with volatile organic compounds (VOCs). Hexavalent chromium, Cr(VI), is also present in the ground water; however, the source of the Cr(VI) may be natural. The Cr(VI) still must be treated if brought to the surface because its concentration exceeds discharge standards. We are planning facilities for removing the VOCs and Cr(VI) to a level below the discharge standards. The planned treatment includes the following steps: (1) Pumping the water to the surface facility. (2) Purging the VOCs with air and absorbing them on activated carbon. The VOCs in LLNL`s subsurface waters are primarily chlorinated organic solvents, such as dichloroethylene (DCE), trichloroethylene (TCE), perchloroethylene (PCE), and chloroform (CHCl{sub 3}). Contamination levels range from tens to thousands of parts per billion. (3) Filtering the water. (4) Passing the water through anion-exchange resin to remove the Cr. The Cr in LLNL subsurface waters occurs almost entirely as Cr(VI), which exists as the chromate anion, CrO{sub 4}{sup 2-}, at environmental pH. Cr levels range from tens to hundreds of parts per billion. (5) Discharging the treated water into the local arroyos. The relevant discharge criteria are 5 ppb total VOCs, 11 ppb Cr(VI), and pH between 6.5 and 8.5, inclusive. This report describes laboratory experiments undertaken to learn how the proposed treatment facility can be expected to operate. The laboratory results are expected to supply vendors with the detailed performance specifications needed to prepare bids on the Cr removal portion of the treatment facility. The treatment facility is expected to process 60 gallons per minute (gpm) of water by stripping VOCs with 720 standard cubic feet per minute (scfm) of air and removing Cr(VI) with 60 ft{sup 3} of resin.

  11. Hexavalent Chromium Is Cytotoxic and Genotoxic to Hawksbill Sea Turtle Cells

    PubMed Central

    Wise, Sandra S.; Xie, Hong; Fukuda, Tomokazu; Thompson, W. Douglas; Wise, John Pierce

    2014-01-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5 μg/cm2 lead chromate induced 108, 79, 54, and 7 percent relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5 μg/cm2 lead chromate induced damage in 4, 10, 15, 26, and 36 percent of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate induced 84, 69, 46, 25, and 3 percent relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29 percent of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general. PMID:24952338

  12. Prolonged Particulate Hexavalent Chromium Exposure Suppresses Homologous Recombination Repair in Human Lung Cells.

    PubMed

    Browning, Cynthia L; Qin, Qin; Kelly, Deborah F; Prakash, Rohit; Vanoli, Fabio; Jasin, Maria; Wise, John Pierce

    2016-09-01

    Genomic instability is one of the primary models of carcinogenesis and a feature of almost all cancers. Homologous recombination (HR) repair protects against genomic instability by maintaining high genomic fidelity during the repair of DNA double strand breaks. The defining step of HR repair is the formation of the Rad51 nucleofilament, which facilitates the search for a homologous sequence and invasion of the template DNA strand. Particulate hexavalent chromium (Cr(VI)), a human lung carcinogen, induces DNA double strand breaks and chromosome instability. Since the loss of HR repair increases Cr(VI)-induced chromosome instability, we investigated the effect of extended Cr(VI) exposure on HR repair. We show acute (24 h) Cr(VI) exposure induces a normal HR repair response. In contrast, prolonged (120 h) exposure to particulate Cr(VI) inhibited HR repair and Rad51 nucleofilament formation. Prolonged Cr(VI) exposure had a profound effect on Rad51, evidenced by reduced protein levels and Rad51 mislocalization to the cytoplasm. The response of proteins involved in Rad51 nuclear import and nucleofilament formation displayed varying responses to prolonged Cr(VI) exposure. BRCA2 formed nuclear foci after prolonged Cr(VI) exposure, while Rad51C foci formation was suppressed. These results suggest that particulate Cr(VI), a major chemical carcinogen, inhibits HR repair by targeting Rad51, causing DNA double strand breaks to be repaired by a low fidelity, Rad51-independent repair pathway. These results further enhance our understanding of the underlying mechanism of Cr(VI)-induced chromosome instability and thus, carcinogenesis. PMID:27449664

  13. Adsorption characteristics of hexavalent chromium on HCB/TiO2

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhang, Yonggang

    2014-10-01

    Sol-gel method was adopted to prepare HCB/TiO2 and its adsorption ability of hexavalent chromium, Cr(VI), and removal from aqueous solution were investigated. The samples were characterized by Power X-ray diffraction (XRD) and a transmission electron microscope (TEM) which showed that the TiO2 was deposited on the surface of HCB. FTIR was used to identify the changes of the surface functional groups before and after adsorption. Potentiometric titration method was used to characterize the zero charge (pHpzc) characteristics of the surface of HCB/TiO2 which showed more acidic functional groups containing. Batch experiments showed that initial pH, absorbent dosage, contact time and initial concentration of Cr(VI) were important parameters for the Cr(VI) adsorption studies. The Freundlich isotherm model better reflected the experimental data better. Cr(VI) adsorption process followed the pseudo-second order kinetic model, which illustrated chemical adsorption. The thermodynamic parameters, such as Gibbs free energy (ΔG), changes in enthalpy change (ΔH) and changes in entropy change (ΔS) were also evaluated. Negative value of free energy occurred at temperature range of 25-45 °C, so Cr(VI) adsorption by HCB/TiO2 is spontaneous. Desorption results showed that the adsorption capacity could maintain 80% after five cycles. The maximum adsorption capacity for Cr(VI) was at 27.33 mg g-1 in an acidic medium, of which the value is worth comparable with other low-cost adsorbents.

  14. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells.

    PubMed

    Wise, Sandra S; Xie, Hong; Fukuda, Tomokazu; Douglas Thompson, W; Wise, John Pierce

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5μg/cm(2) lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general. PMID:24952338

  15. Characteristics of a novel Acinetobacter sp. and its kinetics in hexavalent chromium bioreduction.

    PubMed

    Narayani, M; Vidya Shetty, K

    2012-05-01

    Cr-B2, a Gram-negative hexavalent chromium [Cr(VI)] reducing bacteria, was isolated from the aerator water of an activated sludge process in the wastewater treatment facility of a dye and pigment based chemical industry. Cr- B2 exhibited a resistance for 1,100 mg/l Cr(VI) and, similarly, resistance against other heavy metal ions such as Ni2+ (800 mg/l), Cu2+ (600 mg/l), Pb2+ (1,100 mg/l), Cd2+ (350 mg/l), Zn2+ (700 mg/l), and Fe3+ (1,000 mg/l), and against selected antibiotics. Cr-B2 was observed to efficiently reduce 200 mg/l Cr(VI) completely in both nutrient and LB media, and could convert Cr(VI) to Cr(III) aerobically. Cr(VI) reduction kinetics followed allosteric enzyme kinetics. The Km values were found to be 43.11 mg/l for nutrient media and 38.05 mg/l for LB media. Vmax values of 13.17 mg/l/h and 12.53 mg/l/h were obtained for nutrient media and LB media, respectively, and the cooperativity coefficients (n) were found to be 8.47 and 3.49, respectively, indicating positive cooperativity in both cases. SEM analysis showed the formation of wrinkles and depressions in the cells when exposed to an 800 mg/l Cr(VI) concentration. The organism was seen to exhibit pleomorphic behavior. Cr-B2 was identified on the basis of morphological, biochemical, and partial 16S rRNA gene sequencing chracterizations and found to be Acinetobacter sp. PMID:22561865

  16. Hexavalent chromium-induced multiple biomarker responses in liver and kidney of goldfish, Carassius auratus.

    PubMed

    Velma, Venkatramreddy; Tchounwou, Paul B

    2011-11-01

    Hexavalent chromium [Cr (VI)] is a constituent of chromite ore. Although it is known to have several industrial and technological applications, its release into the aquatic environment as a result of chemical spill or inadequate waste discharge may hamper the health of aquatic organisms. In this study, we have investigated the effects of Cr (VI) on multiple biomarkers responses in goldfish under subchronic exposure conditions. Laboratory-acclimatized fish were exposed to 4.25 ppm and 8.57 ppm Cr (VI) for four weeks using a continuous flow-through system. During exposure, fish samples were collected on a weekly basis and analyzed for multiple biomarkers including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), metallothionein (MT), and total protein in liver and kidney. Study results indicated that the CAT activity and total protein levels in Cr (VI) - treated goldfish did not significantly differ (P > 0.05) from their respective controls during experimentation. However, highly significant up-regulations (P < 0.05) of SOD, GPx, and MT expression in Cr (VI) - treated goldfish were recorded at different exposure times depending on Cr (VI) concentration, test organ, and/or biomarker of interest. For example, significantly higher liver GPx levels were found at weeks 2 and 3 in the 4.25 ppm concentration, and at weeks 3 and 4 in the 8.57 ppm, while kidney GPx levels were significantly higher at weeks 1, 2 and 3 in the 4.25 ppm concentration, and at weeks 2, 3 and 4 in the 8.57 ppm concentration. In summary, Cr (VI)-induced oxidative stress was characterized by statistically significant increases in SOD, GPx, and MT expression in goldfish tissues; with the kidney showing a relatively higher sensitivity to Cr (VI) toxicity compared with the liver. PMID:20549632

  17. Photocatalytic reduction of hexavalent chromium with illuminated amorphous FeOOH.

    PubMed

    Samarghandi, Mohammad-Reza; Yang, Jae-Kyu; Giahi, Omid; Shirzad-Siboni, Mehdi

    2015-01-01

    In this study, photocatalytic reduction of hexavalent chromium [Cr(VI)] by amorphous FeOOH was investigated with variations in FeOOH dosage, pH, initial Cr(VI) concentration, purging gas, organic compounds and initial hydrogen peroxide concentration. Reduction and adsorption were identified as important processes for the removal of Cr(VI). FeOOH dosage was also an important parameter for the removal of Cr(VI). As the FeOOH dosage increased up to 0.5 g/L, the removal of Cr(VI) was continuously enhanced and then decreased above 0.5 g/L due to increased blockage of the incident UV light. The removal efficiency of Cr(VI) decreased with increasing pH, initial Cr(VI) concentration and initial hydrogen peroxide concentration. While the removal efficiency of Cr(VI) increased with purging of nitrogen gas compared to that of oxygen gas because of less competition between dissolved oxygen and Cr(VI) with the electron in the conduction band of FeOOH. The photocatalytic reduction of Cr(VI) was increased in the presence of citric acid and phenol, while it was decreased in the presence of EDTA and oxalic acid. The reaction rate constant (kobs) was decreased from 0.2141 to 0.0026 1/min and the value of electrical energy per order (EEo) was increased from 22.41 to 1846.15 (kWh/m3) with increasing initial Cr(VI) concentration from 10 to 50 mg/L, respectively. Finally, proper photocatalytic activity was maintained even after five successive cycles. PMID:25367257

  18. Hexavalent chromium is cytotoxic and genotoxic to hawksbill sea turtle cells

    SciTech Connect

    Wise, Sandra S.; Xie, Hong; Fukuda, Tomokazu; Douglas Thompson, W.; and others

    2014-09-01

    Sea turtles are a charismatic and ancient ocean species and can serve as key indicators for ocean ecosystems, including coral reefs and sea grass beds as well as coastal beaches. Genotoxicity studies in the species are absent, limiting our understanding of the impact of environmental toxicants on sea turtles. Hexavalent chromium (Cr(VI)) is a ubiquitous environmental problem worldwide, and recent studies show it is a global marine pollutant of concern. Thus, we evaluated the cytotoxicity and genotoxicity of soluble and particulate Cr(VI) in hawksbill sea turtle cells. Particulate Cr(VI) was both cytotoxic and genotoxic to sea turtle cells. Concentrations of 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced 108, 79, 54, and 7% relative survival, respectively. Additionally, concentrations of 0, 0.1, 0.5, 1, and 5 μg/cm{sup 2} lead chromate induced damage in 4, 10, 15, 26, and 36% of cells and caused 4, 11, 17, 30, and 56 chromosome aberrations in 100 metaphases, respectively. For soluble Cr, concentrations of 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate induced 84, 69, 46, 25, and 3% relative survival, respectively. Sodium chromate induced 3, 9, 9, 14, 21, and 29% of metaphases with damage, and caused 3, 10, 10, 16, 26, and 39 damaged chromosomes in 100 metaphases at concentrations of 0, 0.25, 0.5, 1, 2.5, and 5 μM sodium chromate, respectively. These data suggest that Cr(VI) may be a concern for hawksbill sea turtles and sea turtles in general. - Highlights: • Particulate Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Soluble Cr(VI) is cytotoxic and clastogenic to hawksbill sea turtle cells. • Cr(VI) may be a risk factor for hawksbill sea turtle health.

  19. Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities

    PubMed Central

    Yuan, Tong; Podar, Mircea; Phelps, Tommy J.; Brown, Steven D.; Yang, Zamin K.; Hazen, Terry C.; Arkin, Adam P.; Palumbo, Anthony V.; Van Nostrand, Joy D.; Zhou, Jizhong; Elias, Dwayne A.

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure. PMID:24376771

  20. Modulation of histone methylation and MLH1 gene silencing by hexavalent chromium

    SciTech Connect

    Sun Hong; Zhou Xue; Chen Haobin; Li Qin; Costa, Max

    2009-06-15

    Hexavalent chromium [Cr(VI)] is a mutagen and carcinogen, and occupational exposure can lead to lung cancers and other adverse health effects. Genetic changes resulting from DNA damage have been proposed as an important mechanism that mediates chromate's carcinogenicity. Here we show that chromate exposure of human lung A549 cells increased global levels of di- and tri-methylated histone H3 lysine 9 (H3K9) and lysine 4 (H3K4) but decreased the levels of tri-methylated histone H3 lysine 27 (H3K27) and di-methylated histone H3 arginine 2 (H3R2). Most interestingly, H3K9 dimethylation was enriched in the human MLH1 gene promoter following chromate exposure and this was correlated with decreased MLH1 mRNA expression. Chromate exposure increased the protein as well as mRNA levels of G9a a histone methyltransferase that specifically methylates H3K9. This Cr(VI)-induced increase in G9a may account for the global elevation of H3K9 dimethylation. Furthermore, supplementation with ascorbate, the primary reductant of Cr(VI) and also an essential cofactor for the histone demethylase activity, partially reversed the H3K9 dimethylation induced by chromate. Thus our studies suggest that Cr(VI) may target histone methyltransferases and demethylases, which in turn affect both global and gene promoter specific histone methylation, leading to the silencing of specific tumor suppressor genes such as MLH1.

  1. Hexavalent Chromium Reduction under Fermentative Conditions with Lactate Stimulated Native Microbial Communities

    SciTech Connect

    Somenahally, Anil C; Mosher, Jennifer J; Yuan, Tong; Phelps, Tommy Joe; Brown, Steven D; Yang, Zamin Koo; Hazen, Terry C; Arkin, Adam; Palumbo, Anthony Vito; Van Nostrand, Dr. Joy D.; Zhou, Jizhong; Elias, Dwayne A

    2013-01-01

    Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.

  2. Hexavalent Chromium-Induced Multiple Biomarker Responses in Liver and Kidney of Goldfish, Carassius auratus

    PubMed Central

    Velma, Venkatramreddy; Tchounwou, Paul B.

    2010-01-01

    Hexavalent chromium [Cr (VI)] is a constituent of chromite ore. Although it is known to have several industrial and technological applications, its release into the aquatic environment as a result of chemical spill or inadequate waste discharge may hamper the health of aquatic organisms. In this study, we have investigated the effects of Cr (VI) on multiple biomarkers responses in goldfish under sub-chronic exposure conditions. Laboratory-acclimatized fish were exposed to 4.25 ppm and 8.57 ppm Cr (VI) for four weeks using a continuous flow-through system. During exposure, fish samples were collected on a weekly basis and analyzed for multiple biomarkers including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), metallothionein (MT), and total protein in liver and kidney. Study results indicated that the CAT activity and total protein levels in Cr (VI) – treated goldfish did not significantly differ (p>0.05) from their respective controls during experimentation. However, highly significant up-regulations (p<0.05) of SOD, GPx, and MT expression in Cr (VI) – treated goldfish were recorded at different exposure times depending on Cr (VI) concentration, test organ, and/or biomarker of interest. For example, significantly higher liver GPx levels were found at weeks 2 and 3 in the 4.25 ppm concentration, and at weeks 3 and 4 in the 8.57 ppm, while kidney GPx levels were significantly higher at weeks 1, 2 and 3 in the 4.25 ppm concentration, and at weeks 2, 3 and 4 in the 8.57 ppm concentration. In summary, Cr (VI)-induced oxidative stress was characterized by statistically significant increases in SOD, GPx, and MT expression in goldfish tissues; with the kidney showing a relatively higher sensitivity to Cr (VI) toxicity compared to the liver. PMID:20549632

  3. Dispersion modeling of particulate matter containing hexavalent chromium during high winds in southern Iraq.

    PubMed

    Zannetti, Paolo; Daly, Aaron D; Freedman, Frank R

    2015-02-01

    The aim of this paper is to describe a scientific methodology (i.e., the combination of different well-established modeling techniques) and its application to a real case scenario of contaminated dust emissions in high winds. This scenario addresses potential air pollution problems at the water treatment plant (WTP) at Qarmat-Ali, Basra, Iraq, during 2003. Workplace practices at the WTP before 2003 resulted in sodium dichromate contamination in the area. Looting at the site in early 2003 also contributed to this contamination. Individuals who were assigned to provide security at the site in 2003 have claimed adverse health effects caused by exposure to dust containing hexavalent chromium [Cr(VI)]. This report presents our modeling study with respect to these claims in relation to (1) amount of Cr(VI) present in the soil, (2) wind erosion episodes, and (3) possible long-term (e.g., annual average) Cr(VI) concentrations inhaled by different people while at the site. Our modeling approach included (1) the analysis of Cr(VI) soil measurements to assess the degree of contamination in different areas of the plant at different times; (2) the use of DUSTRAN model equations to calculate the emission rate of particulate matter (PM) less than 10 µm in diameter (PM10) during high-wind episodes; (3) the use of the U.S. Environmental Protection Agency (EPA) AERMOD modeling system to estimate Cr(VI) concentrations at the site; and (4) the calculation of modeling results in the form of both contour lines of average Cr(VI) concentrations at the site, and specific concentration values for selected individuals, based upon their recollection of their visits to the site. PMID:25947053

  4. Total and hexavalent chromium removal in a subsurface horizontal flow (h-SSF) constructed wetland operating as post-treatment of textile wastewater for water reuse.

    PubMed

    Fibbi, D; Doumett, S; Colzi, I; Coppini, E; Pucci, S; Gonnelli, C; Lepri, L; Del Bubba, M

    2011-01-01

    In this study we investigated total and hexavalent chromium removal in an h-SSF constructed wetland (CW) planted with Phragmites australis and operating as post-treatment of effluent wastewater from an activated sludge plant serving the textile industrial district of Prato (Italy). Two measurement campaigns were carried out in 2006 and 2008-2010 in which more than 950 inlet and outlet samples were analyzed. When inlet and outlet concentrations were compared one to the other, the latter were found to be significantly lower than the former (p < 0.001); during the entire period of investigation, removal of hexavalent chromium equal to about 70% was achieved. Outlet concentrations ranged between values lower than the quantification limit (0.5 microg L(-1)) and 4.5 microg L(-1), and in all cases were therefore lower than the limit indicated for hexavalent chromium in the Italian regulation for water reuse (5 microg L(-1)). The comparison of the removal efficiencies achieved for hexavalent and trivalent chromium during the two campaigns suggested that the removal of the former can be sustained in the long term, while for the latter, the treatment efficiency is more sensitive to the age of the CW, being that it is it based on trivalent chromium retention in the reed bed. PMID:22097067

  5. An evaluation of welding processes to reduce hexavalent chromium exposures and reduce costs by using better welding techniques.

    PubMed

    Keane, Michael J

    2014-01-01

    A group of stainless steel arc welding processes was compared for emission rates of fume and hexavalent chromium, and costs per meter length of weld. The objective was to identify those with minimal emissions and also compare relative labor and consumables costs. The selection included flux-cored arc welding (FCAW), shielded-metal arc welding (SMAW), and multiple gas metal arc welding (GMAW) processes. Using a conical chamber, fumes were collected, and fume generation rates and hexavalent chromium (Cr(6+)) were measured. GMAW processes used were short-circuit (SC) and pulsed-spray modes. Flux-cored welding used gas shielding. Costs were estimated per meter of a 6.3-mm thick horizontal butt weld. Emission rates of Cr(6+) were lowest for GMAW processes and highest for SMAW; several GMAW processes had less than 2% of the SMAW generation rate. Labor and consumable costs for the processes studied were again highest for SMAW, with those of several GMAW types about half that cost. The results show that use of any of the GMAW processes (and flux-cored welding) could substantially reduce fume and Cr(6+) emissions, and greatly reduce costs relative to SMAW. PMID:25574138

  6. An Evaluation of Welding Processes to Reduce Hexavalent Chromium Exposures and Reduce Costs by Using Better Welding Techniques

    PubMed Central

    Keane, Michael J

    2014-01-01

    A group of stainless steel arc welding processes was compared for emission rates of fume and hexavalent chromium, and costs per meter length of weld. The objective was to identify those with minimal emissions and also compare relative labor and consumables costs. The selection included flux-cored arc welding (FCAW), shielded-metal arc welding (SMAW), and multiple gas metal arc welding (GMAW) processes. Using a conical chamber, fumes were collected, and fume generation rates and hexavalent chromium (Cr6+) were measured. GMAW processes used were short-circuit (SC) and pulsed-spray modes. Flux-cored welding used gas shielding. Costs were estimated per meter of a 6.3-mm thick horizontal butt weld. Emission rates of Cr6+ were lowest for GMAW processes and highest for SMAW; several GMAW processes had less than 2% of the SMAW generation rate. Labor and consumable costs for the processes studied were again highest for SMAW, with those of several GMAW types about half that cost. The results show that use of any of the GMAW processes (and flux-cored welding) could substantially reduce fume and Cr6+ emissions, and greatly reduce costs relative to SMAW. PMID:25574138

  7. Hexavalent chromium reduction in contaminated soil: A comparison between ferrous sulphate and nanoscale zero-valent iron.

    PubMed

    Di Palma, L; Gueye, M T; Petrucci, E

    2015-01-01

    Iron sulphate (FeSO4) and colloidal nano zero-valent iron (nZVI) as reducing agents were compared, with the aim of assessing their effectiveness in hexavalent chromium [Cr(VI)] removal from a contaminated industrial soil. Experiments were performed on soil samples collected from an industrial site where a nickel contamination, caused by a long-term productive activity, was also verified. The influence of reducing agents amount with respect to chromium content and the effectiveness of deoxygenation of the slurry were discussed. The soil was fully characterized before and after each test, and sequential extractions were performed to assess chemico-physical modifications and evaluate metals mobility induced by washing. Results show that both the reducing agents successfully lowered the amount of Cr(VI) in the soil below the threshold allowed by Italian Environmental Regulation for industrial reuse. Cr(VI) reduction by colloidal nZVI proved to be faster and more effective: the civil reuse of soil [Cr(VI)<2mg/kg] was only achieved using colloidal nZVI within 60min adopting a nZVI/Cr(VI) molar ratio of 30. The reducing treatment resulted in an increase in the amount of chromium in the oxide-hydroxide fraction, thus confirming a mechanism of chromium-iron hydroxides precipitation. In addition, a decrease of nickel (Ni) and lead (Pb) content in soil was also observed when acidic conditions were established. PMID:25139286

  8. Cancer mortality in a Chinese population exposed to hexavalent chromium in drinking water

    USGS Publications Warehouse

    Beaumont, J.J.; Sedman, R.M.; Reynolds, S.D.; Sherman, C.D.; Li, L.-H.; Howd, R.A.; Sandy, M.S.; Zeise, L.; Alexeeff, G.V.

    2008-01-01

    BACKGROUND: In 1987, investigators in Liaoning Province, China, reported that mortality rates for all cancer, stomach cancer, and lung cancer in 1970-1978 were higher in villages with hexavalent chromium (Cr)-contaminated drinking water than in the general population. The investigators reported rates, but did not report statistical measures of association or precision. METHODS: Using reports and other communications from investigators at the local Jinzhou Health and Anti-Epidemic Station, we obtained data on Cr contamination of groundwater and cancer mortality in 9 study regions near a ferrochromium factory. We estimated:(1) person-years at risk in the study regions, based on census and population growth rate data, (2) mortality counts, based on estimated person-years at risk and previously reported mortality rates, and (3) rate ratios and 95% confidence intervals. RESULTS: The all-cancer mortality rate in the combined 5 study regions with Cr-contaminated water was negligibly elevated in comparison with the rate in the 4 combined study regions without contaminated water (rate ratio = 1.13; 95% confidence interval = 0.86-1.46), but was somewhat more elevated in comparison with the whole province (1.23; 0.97-1.53). Stomach cancer mortality in the regions with contaminated water was more substantially elevated in comparison with the regions without contaminated water (1.82; 1.11-2.91) and the whole province (1.69; 1.12-2.44). Lung cancer mortality was slightly elevated in comparison with the unexposed study regions (1.15; 0.62-2.07), and more strongly elevated in comparison with the whole province (1.78; 1.03-2.87). Mortality from other cancers combined was not elevated in comparison with either the unexposed study regions (0.86; 0.53-1.36) or the whole province (0.92; 0.58-1.38). CONCLUSIONS: While these data are limited, they are consistent with increased stomach cancer risk in a population exposed to Cr in drinking water. ?? 2008 Lippincott Williams & Wilkins, Inc.

  9. Double shroud delivery of silica precursor for reducing hexavalent chromium in welding fume.

    PubMed

    Wang, Jun; Kalivoda, Mark; Guan, Jianying; Theodore, Alexandros; Sharby, Jessica; Wu, Chang-Yu; Paulson, Kathleen; Es-Said, Omar

    2012-01-01

    The welding process yields a high concentration of nanoparticles loaded with hexavalent chromium (Cr(6+)), a known human carcinogen. Previous studies have demonstrated that using tetramethylsilane (TMS) as a shielding gas additive can significantly reduce the Cr(6+) concentration in welding fume particles. In this study, a novel insulated double shroud torch (IDST) was developed to further improve the reduction of airborne Cr(6+) concentration by separating the flows of the primary shielding gas and the TMS carrier gas. Welding fumes were collected from a welding chamber in the laboratory and from a fixed location near the welding arc in a welding facility. The Cr(6+) content was analyzed with ion chromatography and X-ray photoelectron spectroscopy (XPS). Results from the chamber sampling demonstrated that the addition of 3.2 ≈ 5.1% of TMS carrier gas to the primary shielding gas resulted in more than a 90% reduction of airborne Cr(6+) under all shielding gas flow rates. The XPS result confirmed complete elimination of Cr(6+) inside the amorphous silica shell. Adding 100 ≈ 1000 ppm of nitric oxide or carbon monoxide to the shielding gas could also reduce Cr(6+) concentrations up to 57% and 35%, respectively; however, these reducing agents created potential hazards from the release of unreacted agents. Results of the field test showed that the addition of 1.6% of TMS carrier gas to the primary shielding gas reduced Cr(6+) concentration to the limitation of detection (1.1 μg/m(3)). In a worst-case scenario, if TMS vapor leaked into the environment without decomposition and ventilation, the estimated TMS concentration in the condition of field sampling would be a maximum 5.7 ppm, still well below its flammability limit (1%). Based on a previously developed cost model, the use of TMS increases the general cost by 3.8%. No visual deterioration of weld quality caused by TMS was found, although further mechanical testing is necessary. PMID:23113576

  10. Transcriptomic analysis of cultured whale skin cells exposed to hexavalent chromium [Cr(VI)].

    PubMed

    Pabuwal, Vagmita; Boswell, Mikki; Pasquali, Amanda; Wise, Sandra S; Kumar, Suresh; Shen, Yingjia; Garcia, Tzintzuni; Lacerte, Carolyne; Wise, John Pierce; Wise, John Pierce; Warren, Wesley; Walter, Ronald B

    2013-06-15

    Hexavalent chromium Cr(VI) is known to produce cytotoxic effects in humans and is a highly toxic environmental contaminant. Interestingly, it has been shown that free ranging sperm whales (Phyester macrocephalus) may have exceedingly high levels of Cr in their skin. Also, it has been demonstrated that skin cells from whales appear more resistant to both cytotoxicity and clastogenicity upon Cr exposure compared to human cells. However, the molecular genetic mechanisms employed in whale skin cells that might lead to Cr tolerance are unknown. In an effort to understand the underlying mechanisms of Cr(VI) tolerance and to illuminate global gene expression patterns modulated by Cr, we exposed whale skin cells in culture to varying levels of Cr(VI) (i.e., 0.0, 0.5, 1.0 and 5.0 μg/cm²) followed by short read (100 bp) next generation RNA sequencing (RNA-seq). RNA-seq reads from all exposures (≈280 million reads) were pooled to generate a de novo reference transcriptome assembly. The resulting whale reference assembly had 11K contigs and an N50 of 2954 bp. Using the reads from each dose (0.0, 0.5, 1.0 and 5.0 μg/cm²) we performed RNA-seq based gene expression analysis that identified 35 up-regulated genes and 19 down-regulated genes. The experimental results suggest that low dose exposure to Cr (1.0 μg/cm²) serves to induce up-regulation of oxidative stress response genes, DNA repair genes and cell cycle regulator genes. However, at higher doses (5.0 μg/cm²) the DNA repair genes appeared down-regulated while other genes that were induced suggest the initiation of cytotoxicity. The set of genes identified that show regulatory modulation at different Cr doses provide specific candidates for further studies aimed at determination of how whales exhibit resistance to Cr toxicity and what role(s) reactive oxygen species (ROS) may play in this process. PMID:23584427

  11. Estimating historical occupational exposure to airborne hexavalent chromium in a chromate production plant: 1940--1972.

    PubMed

    Proctor, D M; Panko, J P; Liebig, E W; Paustenbach, D J

    2004-11-01

    This article presents a retrospective exposure assessment for 493 workers who were occupationally exposed to airborne hexavalent chromium, Cr(VI), at a Painesville, Ohio, chromate production plant from 1940-1972. Exposure estimates were reconstructed using a job-exposure matrix approach that related job titles with area monitoring data from 21 industrial hygiene surveys conducted from 1943 to 1971. No personal monitoring data were collected. Specifically, airborne Cr(VI) concentration profiles for 22 areas of the plant, termed job-exposure group (JEG) areas, were constructed for three distinct time periods (1940-1949, 1950-1964, and 1965-1972), with cut points based on known major plant and process changes. Average airborne Cr(VI) concentrations were the highest for the bridge crane operators (5.5 mg/m3) prior to 1965, although only four cohort members held this job title. Airborne concentrations for the rest of the production areas of the plant ranged from 1.9 mg/m3 for packers in the 1940s to 0.012 mg/m3 for ore mill operators after 1964. For nearly all JEG areas, exposures decreased over time, particularly after 1964. For example, average airborne concentrations in production areas of the plant decreased from 0.72 mg/m3 in the 1940s to 0.27 mg/m3 from 1950 to 1964, and the average was 0.039 mg/m3 after 1964. Former workers were interviewed to determine activity patterns in the plant by job title. This information was combined with Cr(VI) monitoring data to calculate cumulative occupational exposure for each worker. Cumulative exposures ranged from 0.003 to 23 (mg/m3) x years. The highest monthly 8-hour average exposure concentration for each worker ranged from 0.003 to 4.1 mg/m3. These exposure estimates have been combined with mortality data for this cohort to assess the lung cancer risk associated with inhaled Cr(VI), and a positive dose-response relationship was observed for increases in lung cancer mortality with measures of cumulative exposure and highest

  12. Reduction of Hexavalent Chromium by Human Cytochrome b5: Generation of Hydroxyl Radical and Superoxide

    PubMed Central

    Borthiry, Griselda R.; Antholine, William E.; Kalyanaraman, B.; Myers, Judith M.; Myers, Charles R.

    2007-01-01

    The reduction of hexavalent chromium, Cr(VI), can generate reactive Cr intermediates and various types of oxidative stress. The potential role of human microsomal enzymes in free radical generation was examined using reconstituted proteoliposomes (PLs) containing purified cytochrome b5 and NADPH:P450 reductase. Under aerobic conditions, the PLs reduced Cr(VI) to Cr(V) which was confirmed by ESR using isotopically pure 53Cr(VI). When 5-Diethoxyphos-phoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) was included as a spin trap, a very prominent signal for the hydroxyl radical (HO•) adduct was observed as well as a smaller signal for the superoxide (O2•−) adduct. These adducts were observed even at very low Cr(VI) concentrations (10 μM). NADPH, Cr(VI), O2 and the PLs were all required for significant HO• generation. Superoxide dismutase eliminated the O2• − adduct and resulted in a 30% increase in the HO• adduct. Catalase largely diminished the HO• adduct signal indicating its dependence on H2O2. Some sources of catalase were found to have Cr(VI)-reducing contaminants which could confound results, but a source of catalase free of these contaminants was used for these studies. Exogenous H2O2 was not needed, indicating that it was generated by the PLs. Adding exogenous H2O2, however, did increase the amount of DEPMPO/HO• adduct. The inclusion of formate yielded the carbon dioxide radical adduct of DEPMPO, and experiments with dimethylsulfoxide (DMSO) plus the spin trap α-phenyl-N-tert-butylnitrone (PBN) yielded the methoxy and methyl radical adducts of PBN, confirming the generation of HO•. Quantification of the various species over time was consistent with a stoichiometric excess of HO• relative to the net amount of Cr(VI) reduced. This also represents the first demonstration of a role for cytochrome b5 in the generation of HO•. Overall, the simultaneous generation of Cr(V) and H2O2 by the PLs and the resulting generation of HO• at low Cr

  13. Measurement of Soluble and Total Hexavalent Chromium in the Ambient Airborne Particles in New Jersey

    PubMed Central

    Huang, Lihui; Yu, Chang Ho; Hopke, Philip K.; Lioy, Paul J.; Buckley, Brian T.; Shin, Jin Young; Fan, Zhihua (Tina)

    2015-01-01

    Hexavalent chromium (Cr(VI)) in ambient airborne particulate matter (PM) is a known pulmonary carcinogen and may have both soluble and insoluble forms. The sum of the two forms is defined as total Cr(VI). Currently, there were no methods suitable for large-scale monitoring of total Cr(VI) in ambient PM. This study developed a method to measure total Cr(VI) in ambient PM. This method includes PM collection using a Teflon filter, microwave extraction with 3% Na2CO3-2% NaOH at 95°C for 60 minutes, and Cr(VI) analysis by 1,5-diphenylcarbazide colorimetry at 540 nm. The recoveries of total Cr(VI) were 119.5 ± 10.4% and 106.3 ± 16.7% for the Cr(VI)-certified reference materials, SQC 012 and SRM 2700, respectively. Total Cr(VI) in the reference urban PM (NIST 1648a) was 26.0 ± 3.1 mg/kg (%CV = 11.9%) determined by this method. The method detection limit was 0.33 ng/m3. This method and the one previously developed to measure ambient Cr(VI), which is soluble in pH ~9.0 aqueous solution, were applied to measure Cr(VI) in ambient PM10 collected from three urban areas and one suburban area in New Jersey. The total Cr(VI) concentrations were 1.05–1.41 ng/m3 in the winter and 0.99–1.56 ng/m3 in the summer. The soluble Cr(VI) concentrations were 0.03–0.19 ng/m3 in the winter and 0.12–0.37 ng/m3 in the summer. The summer mean ratios of soluble to total Cr(VI) were 14.3–43.7%, significantly higher than 4.2–14.4% in the winter. The winter concentrations of soluble and total Cr(VI) in the suburban area were significantly lower than in the three urban areas. The results suggested that formation of Cr(VI) via atmospheric chemistry may contribute to the higher soluble Cr(VI) concentrations in the summer. PMID:26120324

  14. The role of EDTA in phytoextraction of hexavalent and trivalent chromium by two willow trees.

    PubMed

    Yu, Xiao-Zhang; Gu, Ji-Dong

    2008-04-01

    Effects of the synthetic chelator ethylenediamine tetraacetate (EDTA) on uptake and internal translocation of hexavalent and trivalent chromium by plants were investigated. Two different concentrations of EDTA were studied for enhancing the uptake and translocation of Cr from the hydroponic solution spiked with K(2)CrO(4) or CrCl(3) maintained at 24.0 +/- 1 degrees C. Faster removal of Cr(3+) than Cr(6+) by hybrid willows (Salix matsudana Koidz x Salix alba L.) from the plant growth media was observed. Negligible effect of EDTA on the uptake of Cr(6+) was found, but significant decrease of the Cr concentration in roots was measured. Although the translocation of Cr(6+) within plant materials was detected in response to EDTA concentration, the amount of Cr(6+) translocated to the lower stems was considerably small. EDTA in the nutrient media showed a negative effect on the uptake of Cr(3+ )by hybrid willows; the removal rates of Cr(3+ )were significantly decreased. Translocation of Cr(3+) into the stems and leaves was undetectable, but roots were the exclusive sink for Cr(3+) accumulation. Weeping willows (Salix babylonica L.) showed lower removal rates for both chemical forms of Cr than hybrid willows. Although EDTA had a minor effect on Cr(6+ )uptake by weeping willows, positive effect on Cr(6+ )translocation within plant materials was observed. It was also determined that EDTA in plant growth media significantly decreased the amount of Cr(3+) taken up by plants, but significantly increased Cr(3+) mobilization from roots to stems. Results indicated that EDTA was unable to increase the uptake of Cr(6+) by both plant species, but translocation of Cr(6+)-EDTA within plant materials was possible. Addition of EDTA in the nutrient media showed a strong influence on the uptake and translocation of Cr(3+) in both willows. Cr(3+)-EDTA in tissues of weeping willows was more mobile than that in hybrid willows. The information has important implications for the use of metal

  15. AN IN SITU PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM AND TRICHLOROETHYLENE IN GROUNDWATER:VOLUME 2 PERFORMANCE MONITORING

    EPA Science Inventory

    A 46 m long, 7.3 m deep, and 0.6 m wide permeable subsurface reactive wall was installed at the U.S. Coast Guard (USCG) Support Center, near Elizabeth City, North Carolina, in June 1996. The reactive wall was designed to remediate hexavalent chromium [Cr(VI)] contaminated ground ...

  16. AN IN-SITU PERMEABLE REACTIVE BARRIER FOR THE TREATMENT OF HEXAVALENT CHROMIUM AND TRICHLOROETHYLENE IN GROUND WATER: VOLUME 1 DESIGN AND INSTALLATION

    EPA Science Inventory

    A 46 m long, 7.3 m deep, and 0.6 m wide permeable subsurface reactive wall was installed at the U.S. Coast Guard (USCG) Support Center, near Elizabeth City, North Carolina, in June 1996. The reactive wall was designed to remediate hexavalent chromium [Cr(VI)] contaminated ground ...

  17. TREATMENT OF A SATURATED ZONE HEXAVALENT CHROMIUM SOURCE AREA USING A FERROUS SULFATE/SODIUM DITHIONITE MIXTURE: A FIELD PILOT STUDY

    EPA Science Inventory

    A field pilot study was conducted to evaluate the performance of a combined ferrous sulfate/sodium dithionite solution for in situ treatment of a saturated zone hexavalent chromium source area at a former ferrochromium alloy production facility in Charleston, S.C. The saturate...

  18. TREATMENT OF HEXAVALENT CHROMIUM IN CHROMITE ORE PROCESSING SOLID WASTE USING A MIXED REDUCTANT SOLUTION OF FERROUS SULFATE AND SODIUM DITHIONITE

    EPA Science Inventory

    We developed a method for disseminating ferrous iron in the subsurface to enhance chemical reduction of hexavalent chromium (Cr(VI)) in a chromite ore processing solid waste derived from the production of ferrochrome alloy. The method utilizes ferrous sulfate (FeSO4) in combinati...

  19. A post-remediation assessment in Jersey City of the association of hexavalent chromium in house dust and urinary chromium in children.

    PubMed

    Black, Kathleen; Gochfeld, Michael; Lioy, Paul J; Fan, Zhi-Hua Tina; Yu, Chang Ho; Jeitner, Chris; Hernandez, Marta; Einstein, Stephanie A; Stern, Alan H

    2015-01-01

    Although all chromite ore processing residue (COPR) sites near residential neighborhoods in Jersey City, New Jersey have undergone remediation, recent studies found widespread, but low levels of hexavalent chromium (Cr(+6)) in house dust both in Jersey City and in communities with no known sources of Cr(+6). This study was designed as a follow-up to determine whether there is an association between current Cr(+6) levels in house dust and urinary chromium concentrations in young children. Dust samples (N=369) were collected from 123 homes. The median Cr(+6) concentration was 3.3 μg/g (mean±SD 5.2±7.5) and the median Cr(+6) loading was 1.1 μg/m(2) (1.9±3.1). These levels were not elevated compared with previously reported levels in background communities (median concentration=3.5 μg/g; median loading=2.8 μg/m(2)). Urinary chromium concentrations were measured in spot urine samples collected from 150 children, ages 3 months to 6 years. The median uncorrected urinary chromium concentration was 0.19 μg/l (0.22±0.16). Current urinary chromium concentrations were significantly lower than those previously reported before and during remediation (t-test; P<0.001). Urinary chromium concentrations were not significantly higher in homes with high (75th or 90th percentile) Cr(+6) dust levels (concentration or loading) compared with other homes. Multiple linear regression was used to examine the relationship between Cr(+6) levels (concentration and loading) in house dust and urinary chromium concentrations (uncorrected and specific gravity corrected). Contrary to pre-remediation studies, we did not find a positive association between Cr(+6) levels in house dust and urinary chromium concentrations. The findings indicate that current Cr(+6) levels in house dust are not positively associated with children's chromium exposure as measured by urinary chromium, and the children's exposure to Cr(+6) in house dust is below the level that could be identified by urine

  20. A revised model of ex-vivo reduction of hexavalent chromium in human and rodent gastric juices

    SciTech Connect

    Schlosser, Paul M. Sasso, Alan F.

    2014-10-15

    Chronic oral exposure to hexavalent chromium (Cr-VI) in drinking water has been shown to induce tumors in the mouse gastrointestinal (GI) tract and rat oral cavity. The same is not true for trivalent chromium (Cr-III). Thus reduction of Cr-VI to Cr-III in gastric juices is considered a protective mechanism, and it has been suggested that the difference between the rate of reduction among mice, rats, and humans could explain or predict differences in sensitivity to Cr-VI. We evaluated previously published models of gastric reduction and believe that they do not fully describe the data on reduction as a function of Cr-VI concentration, time, and (in humans) pH. The previous models are parsimonious in assuming only a single reducing agent in rodents and describing pH-dependence using a simple function. We present a revised model that assumes three pools of reducing agents in rats and mice with pH-dependence based on known speciation chemistry. While the revised model uses more fitted parameters than the original model, they are adequately identifiable given the available data, and the fit of the revised model to the full range of data is shown to be significantly improved. Hence the revised model should provide better predictions of Cr-VI reduction when integrated into a corresponding PBPK model. - Highlights: • Hexavalent chromium (Cr-VI) reduction in gastric juices is a key detoxifying step. • pH-dependent Cr-VI reduction rates are explained using known chemical speciation. • Reduction in rodents appears to involve multiple pools of electron donors. • Reduction appears to continue after 60 min, although more slowly than initial rates.

  1. Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study.

    PubMed

    Blade, L M; Yencken, M Story; Wallace, M E; Catalano, J D; Khan, A; Topmiller, J L; Shulman, S A; Martinez, A; Crouch, K G; Bennett, J S

    2007-08-01

    The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries to characterize workers' exposures to hexavalent chromium-containing airborne particulate and to evaluate existing technologies for controlling these exposures. Hexavalent chromium Cr(VI) is a respiratory irritant and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full work shift, personal breathing-zone (PBZ) air samples for Cr(VI), measurement of ventilation system parameters, and documentation of processes and work practices. This study emphasized evaluation of engineering exposure control measures, so PBZ exposures were measured on the outside of personal protective equipment, for example, respirators. Field surveys were conducted in two chromium electroplating facilities, including one where full-shift PBZ exposures to Cr(VI) ranged from 3.0 to 16 times the 1 micro g/m(3)NIOSH recommended exposure limit (REL) despite several engineering controls on the plating tanks. At a painting and coating facility that used Cr(VI)-containing products, full-shift exposures of painters and helpers (2.4 to 55 micro g/m(3)) exceeded the REL, but LEV effectiveness was limited. Other operations evaluated included welding in construction; metal cutting operations on chromium-containing materials in ship breaking; chromate-paint removal with abrasive blasting; atomized alloy-spray coating; foundry operations; printing; and the manufacture of refractory brick, colored glass, prefabricated concrete products, and treated wood products. NIOSH researchers concluded that, in many of the evaluated processes, Cr(VI) exposures at or below the current NIOSH REL are achievable. However, for some processes, it is unclear whether controlling exposures to this range is consistently achievable without respirator use. Some operations involving the application of coatings and finishes may be among those most difficult to control to this

  2. Mesoporous BaTiO₃@SBA-15 derived via solid state reaction and its excellent adsorption efficiency for the removal of hexavalent chromium from water.

    PubMed

    Kumari, Vandana; Sasidharan, Manickam; Bhaumik, Asim

    2015-01-28

    We report the synthesis of a barium-titanate/mesoporous silica nanocomposite material BaTiO3@SBA-15 via aerosol assisted solid state reaction using SBA-15 as a hard template. Hexavalent chromium is one of the most harmful contaminants of industrial waste-water. We have used BaTiO3@SBA-15 nanocomposite as an adsorbent for the removal of chromium(vi)-contaminated water and it showed an adsorption capacity of 98.2 wt% within only 40 min contact time in a batch reactor. This mesoporous composite has retained this excellent adsorption efficiency of hexavalent chromium for several repetitive cycles, suggesting its future potential for the remediation of water contaminated with Cr(vi). PMID:25490743

  3. The toxic effects on the stress and immune responses in juvenile rockfish, Sebastes schlegelii exposed to hexavalent chromium.

    PubMed

    Kim, Jun-Hwan; Kang, Ju-Chan

    2016-04-01

    Juvenile Sebastes schlegelii (mean length 13.7±1.7cm, and mean weight 55.6±4.8g) were exposed for 4 weeks with the different levels of dietary chromium (Cr(6+)) concentration (0, 30, 60, 120 and 200mg/L). The plasma cortisol and heat shock protein 70 was evaluated as stress indicators. Plasma cortisol was significantly increased in response to the dietary chromium exposure over 120mg/kg at 2 and 4 weeks. Heat shock protein 70 was also notably increased over 120mg/kg at 2 weeks and over 60mg/kg at 4 weeks. In the immune response, immunoglobulin M was considerably increased in the concentration of 240mg/kg at 2 weeks and over 120mg/kg at 4 weeks. Lysozyme activity was considerably induced by the dietary hexavalent chromium exposure. A significant increase in plasma lysozyme activity was observed at 240mg/kg after 2 weeks and over 60mg/kg after 4 weeks, kidney lysozyme was also increased over 120mg/kg at 2 and 4 weeks. The results demonstrate that dietary Cr exposure can induce a significant stress and immune stimulation. PMID:26991846

  4. Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

    NASA Astrophysics Data System (ADS)

    Yokoyama, Seiji; Okazaki, Kohei; Sasano, Junji; Izaki, Masanobu

    2014-02-01

    Hexavalent chromium (Cr(VI)) is well-known to be a strong oxidizer, and is recognized as a carcinogen. Therefore, it is regulated for drinking water, soil, groundwater and sea by the environmental quality standards all over the world. In this study, it was attempted to remove Cr(VI) ion in a carbonic acid solution by the oxidizing slag that was discharged from the normal steelmaking process in an electric arc furnace. After the addition of the slag into the aqueous solution contained Cr(VI) ion, concentrations of Cr(VI) ion and total chromium (Cr(VI) + trivalent chromium (Cr(III)) ions decreased to lower detection limit of them. Therefore, the used slag could reduce Cr(VI) and fix Cr(III) ion on the slag. While Cr(VI) ion existed in the solution, iron did not dissolve from the slag. From the relation between predicted dissolution amount of iron(II) ion and amount of decrease in Cr(VI) ion, the Cr(VI) ion did not react with iron(II) ion dissolved from the slag. Therefore, Cr(VI) ion was removed by the reductive reaction between Cr(VI) ion and the iron(II) oxide (FeO) in the slag. This reaction progressed on the newly appeared surface of iron(II) oxide due to the dissolution of phase composed of calcium etc., which existed around iron(II) oxide grain in the slag.

  5. Bionanocomposites based on layered silicates and cationic starch as eco-friendly adsorbents for hexavalent chromium removal.

    PubMed

    Koriche, Yamina; Darder, Margarita; Aranda, Pilar; Semsari, Saida; Ruiz-Hitzky, Eduardo

    2014-07-21

    Functional bionanocomposites based on two layered silicates, the commercial montmorillonite known as Cloisite®Na and a natural bentonite from Algeria, were prepared by intercalation of cationic starch, synthesized with two different degrees of substitution, 0.85 and 0.55. After characterization of the prepared bionanocomposites by XRD and zeta potential measurements, batch studies were conducted to evaluate the adsorption capacity of hexavalent chromium anions from aqueous solution. The adsorption isotherms, adsorption kinetics, and the effect of pH on the process were studied. The removal efficiency was evaluated in the presence of competing anions such as NO3(-), ClO4(-), SO4(2-) and Cl(-). In order to regenerate the adsorbent for its repeated use, the regeneration process was studied in two different extractant solutions, 0.1 M NaCl at pH 10 and 0.28 M Na2CO3 at pH 12. PMID:24658793

  6. Efficiencies and Optimization of Weak Base Anion Ion-Exchange Resin for Groundwater Hexavalent Chromium Removal at Hanford

    SciTech Connect

    Nesham, Dean O.; Ivarson, Kristine A.; Hanson, James P.; Miller, Charles W.; Meyers, P.; Jaschke, Naomi M.

    2014-02-03

    The U.S. Department of Energy’s (DOE’s) contractor, CH2M HILL Plateau Remediation Company, has successfully converted a series of groundwater treatment facilities to use a new treatment resin that is delivering more than $3 million in annual cost savings and efficiency in treating groundwater contamination at the DOE Hanford Site in southeastern Washington State. During the production era, the nuclear reactors at the Hanford Site required a continuous supply of high-quality cooling water during operations. Cooling water consumption ranged from about 151,417 to 378,541 L/min (40,000 to 100,000 gal/min) per reactor, depending on specific operating conditions. Water from the Columbia River was filtered and treated chemically prior to use as cooling water, including the addition of sodium dichromate as a corrosion inhibitor. Hexavalent chromium was the primary component of the sodium dichromate and was introduced into the groundwater at the Hanford Site as a result of planned and unplanned discharges from the reactors starting in 1944. Groundwater contamination by hexavalent chromium and other contaminants related to nuclear reactor operations resulted in the need for groundwater remedial actions within the Hanford Site reactor areas. Beginning in 1995, groundwater treatment methods were evaluated, leading to the use of pump-and-treat facilities with ion exchange using Dowex™ 21K, a regenerable, strong-base anion exchange resin. This required regeneration of the resin, which was performed offsite. In 2008, DOE recognized that regulatory agreements would require significant expansion for the groundwater chromium treatment capacity. As a result, CH2M HILL performed testing at the Hanford Site in 2009 and 2010 to demonstrate resin performance in the specific groundwater chemistry at different waste sites. The testing demonstrated that a weak-base anion, single-use resin, specifically ResinTech SIR-700 ®, was effective at removing chromium, had a significantly

  7. Role of Bacillus subtilis error prevention oxidized guanine system in counteracting hexavalent chromium-promoted oxidative DNA damage.

    PubMed

    Santos-Escobar, Fernando; Gutiérrez-Corona, J Félix; Pedraza-Reyes, Mario

    2014-09-01

    Chromium pollution is potentially detrimental to bacterial soil communities, compromising carbon and nitrogen cycles that are essential for life on earth. It has been proposed that intracellular reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] may cause bacterial death by a mechanism that involves reactive oxygen species (ROS)-induced DNA damage; the molecular basis of the phenomenon was investigated in this work. Here, we report that Bacillus subtilis cells lacking a functional error prevention oxidized guanine (GO) system were significantly more sensitive to Cr(VI) treatment than cells of the wild-type (WT) strain, suggesting that oxidative damage to DNA is involved in the deleterious effects of the oxyanion. In agreement with this suggestion, Cr(VI) dramatically increased the ROS concentration and induced mutagenesis in a GO-deficient B. subtilis strain. Alkaline gel electrophoresis (AGE) analysis of chromosomal DNA of WT and ΔGO mutant strains subjected to Cr(VI) treatment revealed that the DNA of the ΔGO strain was more susceptible to DNA glycosylase Fpg attack, suggesting that chromium genotoxicity is associated with 7,8-dihydro-8-oxodeoxyguanosine (8-oxo-G) lesions. In support of this notion, specific monoclonal antibodies detected the accumulation of 8-oxo-G lesions in the chromosomes of B. subtilis cells subjected to Cr(VI) treatment. We conclude that Cr(VI) promotes mutagenesis and cell death in B. subtilis by a mechanism that involves radical oxygen attack of DNA, generating 8-oxo-G, and that such effects are counteracted by the prevention and repair GO system. PMID:24973075

  8. Role of Bacillus subtilis Error Prevention Oxidized Guanine System in Counteracting Hexavalent Chromium-Promoted Oxidative DNA Damage

    PubMed Central

    Santos-Escobar, Fernando; Gutiérrez-Corona, J. Félix

    2014-01-01

    Chromium pollution is potentially detrimental to bacterial soil communities, compromising carbon and nitrogen cycles that are essential for life on earth. It has been proposed that intracellular reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] may cause bacterial death by a mechanism that involves reactive oxygen species (ROS)-induced DNA damage; the molecular basis of the phenomenon was investigated in this work. Here, we report that Bacillus subtilis cells lacking a functional error prevention oxidized guanine (GO) system were significantly more sensitive to Cr(VI) treatment than cells of the wild-type (WT) strain, suggesting that oxidative damage to DNA is involved in the deleterious effects of the oxyanion. In agreement with this suggestion, Cr(VI) dramatically increased the ROS concentration and induced mutagenesis in a GO-deficient B. subtilis strain. Alkaline gel electrophoresis (AGE) analysis of chromosomal DNA of WT and ΔGO mutant strains subjected to Cr(VI) treatment revealed that the DNA of the ΔGO strain was more susceptible to DNA glycosylase Fpg attack, suggesting that chromium genotoxicity is associated with 7,8-dihydro-8-oxodeoxyguanosine (8-oxo-G) lesions. In support of this notion, specific monoclonal antibodies detected the accumulation of 8-oxo-G lesions in the chromosomes of B. subtilis cells subjected to Cr(VI) treatment. We conclude that Cr(VI) promotes mutagenesis and cell death in B. subtilis by a mechanism that involves radical oxygen attack of DNA, generating 8-oxo-G, and that such effects are counteracted by the prevention and repair GO system. PMID:24973075

  9. Ion-exchange resin for removing hexavalent chromium from ground water at treatment facility C: Data on removal capacity, regeneration efficiency, and operation

    SciTech Connect

    Bahowick, S.; Dobie, D.; Kumamoto, G.

    1996-12-31

    Lawrence Livermore National Laboratory (LLNL) is operated for the Department of Energy by the University of California. In July 1987, LLNL was placed on the National Priorities List based on the presence of volatile organic compounds (VOCs) in ground water. The July 1992 Record of Decision stipulates air stripping for treatment of VOCs and ion-exchange to treat chromium in the ground water for Treatment Facility C (TFC). TFC, which was activated in October 1993, was designed to treat influent ground water at 60 gpm with concentrations of hexavalent chromium averaging 30 ppb. The ion exchange system removes the hexavalent chromium to below its limit of detection (2 ppb). The resin used is a strongly basic Type I quaternary ammonium anion exchange resin with a styrene-divinylbenzene copolymer gel matrix. The total hexavalent chromium removed from the ground water as of October 8, 1995 was 660 grams. An initial operating capacity was achieved of 6.4 grams CrO{sub 4}{sup 2{minus}} removal per ft{sup 3} of resin, but this was observed to vary over the next two years. Variation was observed in the rate of breakthrough. The regeneration process was optimized to minimize waste produced and maximize regeneration of the resin. Elevated levels of chloride, sulfate, nitrate, potassium 40 and uranium have been observed in the regeneration waste. Because of the potassium and uranium content, the regenerated waste had to be disposed of as mixed waste.

  10. LABORATORY AND FIELD EVALUATIONS OF METHODOLOGY FOR DETERMINING HEXAVALENT CHROMIUM EMISSIONS FROM STATIONARY SOURCES

    EPA Science Inventory

    Development of methodology for sampling and analysis of chromium to support stationary source regulations was initiated in 1984. his study was initiated to determine whether chromium emissions should be regulated under Section 112 of the Clean Air Act National Emissions Standards...

  11. Determination of hexavalent chromium in cosmetic products by ion chromatography and postcolumn derivatization.

    PubMed

    Kang, Eun Kyung; Lee, Somi; Park, Jin-Hee; Joo, Kyung-Mi; Jeong, Hye-Jin; Chang, Ih Seop

    2006-05-01

    Chromium hydroxide green [Cr(2)O(OH)(4)] and chromium oxide green (Cr(2)O(3)) are colouring agents for use in cosmetic products. These colourants may contain chromium (VI), which cause skin allergies through percutaneous adsorption on the skin. Eye shadow is a representative cosmetic product in which significant colourants are used. We analysed the chromium (VI) in the eye shadows by ion chromatography and post column derivatization. We optimize conditions of chromium (VI) analysis in eye shadows. During the pretreatment procedure, there are no exchange of chromium (III) to chromium (VI). This method has a limit of quantification for chromium (VI) of 1.0 microg l(-1), recovery rate of 100 +/- 3% and analysis time less than 10 min. This result is 300 times more sensitive than the high-performance liquid chromatography method. We applied the optimized method to analyse 22 eye shadows and 6 colouring agents. 2 out of 22 of the products contained more than 5 mg l(-1). In our previous work, 5 mg l(-1) of Cr represented a threshold level. There was much more Cr(VI) in the colouring agents. The Cr(VI) in one of the colouring agents was 97.6 mg l(-1). PMID:16689807

  12. A revised model of ex-vivo reduction of hexavalent chromium in human and rodent gastric juices.

    PubMed

    Schlosser, Paul M; Sasso, Alan F

    2014-10-15

    Chronic oral exposure to hexavalent chromium (Cr-VI) in drinking water has been shown to induce tumors in the mouse gastrointestinal (GI) tract and rat oral cavity. The same is not true for trivalent chromium (Cr-III). Thus reduction of Cr-VI to Cr-III in gastric juices is considered a protective mechanism, and it has been suggested that the difference between the rate of reduction among mice, rats, and humans could explain or predict differences in sensitivity to Cr-VI. We evaluated previously published models of gastric reduction and believe that they do not fully describe the data on reduction as a function of Cr-VI concentration, time, and (in humans) pH. The previous models are parsimonious in assuming only a single reducing agent in rodents and describing pH-dependence using a simple function. We present a revised model that assumes three pools of reducing agents in rats and mice with pH-dependence based on known speciation chemistry. While the revised model uses more fitted parameters than the original model, they are adequately identifiable given the available data, and the fit of the revised model to the full range of data is shown to be significantly improved. Hence the revised model should provide better predictions of Cr-VI reduction when integrated into a corresponding PBPK model. PMID:25151221

  13. Cytotoxicity and Genotoxicity of Hexavalent Chromium in Human and North Atlantic Right Whale (Eubalaena glacialis) Lung Cells

    PubMed Central

    Chen, Tânia Li; Wise, Sandra S.; Holmes, Amie; Shaffiey, Fariba; Wise, John Pierce; Thompson, W. Douglas; Kraus, Scott; Wise, John Pierce

    2009-01-01

    Humans and cetaceans are exposed to a wide range of contaminants. In this study, we compared the cytotoxic and genotoxic effects of a metal pollutant, hexavalent chromium [Cr(VI)], which has been shown to cause damage in lung cells from both humans and North Atlantic right whales. Our results show that Cr induces increased cell death and chromosome damage in lung cells from both species with increasing intracellular Cr ion levels. Soluble Cr(VI) induced less of a cytotoxic and genotoxic effect on administered dose in right whale (Eubalaena glacialis) cells than in human (Homo sapiens) cells. Whereas, particulate Cr(VI) induced a similar cytotoxic effect but less of a genotoxic effect based on administered dose in right whale cells than in human cells. Differences in chromium ion uptake explained some but not all of the soluble chromate-induced cell death and chromosome damage. Uptake differences of lead ions could explain the differences in particulate chromate-induced toxicity. The data show that both forms of Cr(VI) are less genotoxic to right whale than human lung cells, and that soluble Cr(VI) induces a similar cytotoxic effect in both right whale and human cells, while particulate Cr(VI) is more cytotoxic to right whale lung cells. PMID:19632355

  14. Elevated Frequencies of Micronuclei and other Nuclear Abnormalities of Chrome Plating Workers Occupationally Exposed to Hexavalent Chromium

    PubMed Central

    Sudha, S; Kripa, SK; Shibily, P; Shyn, J

    2011-01-01

    Background Biomonitoring provides a useful tool to estimate the genetic risk from exposure to genotoxic agents. The aim of this study was to assess the potential cytogenetic damage associated with occupational exposure to hexavalent chromium by using micronuclei (MN) as a biomarker. Methods This was a cross-sectional study and all participants were males. Both the exposed and control individuals were selected from Coimbatore, Southern India. Exfoliated buccal cells from 44 chrome plating workers and 40 age and sex matched control subjects were examined for MN frequency and nuclear abnormalities (NA) other than micronuclei, such as binucleates, broken eggs, karyorrhexis, karyolysis and pyknosis. Results Results showed statistically significant difference between chrome plating workers and control groups. MN and NA frequencies in chrome plating workers were significantly higher than those in control groups (p < 0.05) and also significantly related to smoking habit (P < 0.05). A significant difference in NA was observed in workers exposed to chromium for longer duration. In addition to this, a higher degree of NA was observed among smokers. Conclusion MN and other NA reflect genetic changes, events associated with carcinogenesis. Therefore the results of this study indicate that chrome plating workers are under risk of significant cytogenetic damage. Therefore, there is a need to educate those who work with heavy metals about the potential hazard of occupational exposure and the importance of using protective measures. PMID:26328050

  15. Removal of hexavalent chromium [Cr(VI)] from aqueous solutions by the diatomite-supported/unsupported magnetite nanoparticles.

    PubMed

    Yuan, Peng; Liu, Dong; Fan, Mingde; Yang, Dan; Zhu, Runliang; Ge, Fei; Zhu, JianXi; He, Hongping

    2010-01-15

    Diatomite-supported/unsupported magnetite nanoparticles were prepared by co-precipitation and hydrosol methods, and characterized by X-ray diffraction, nitrogen adsorption, elemental analysis, differential scanning calorimetry, transmission electron microscopy and X-ray photoelectron spectroscopy. The average sizes of the unsupported and supported magnetite nanoparticles are around 25 and 15 nm, respectively. The supported magnetite nanoparticles exist on the surface or inside the pores of diatom shells, with better dispersing and less coaggregation than the unsupported ones. The uptake of hexavalent chromium [Cr(VI)] on the synthesized magnetite nanoparticles was mainly governed by a physico-chemical process, which included an electrostatic attraction followed by a redox process in which Cr(VI) was reduced into trivalent chromium [Cr(III)]. The adsorption of Cr(VI) was highly pH-dependent and the kinetics of the adsorption followed a pseudo-second-order model. The adsorption data of diatomite-supported/unsupported magnetite fit well with the Langmuir isotherm equation. The supported magnetite showed a better adsorption capacity per unit mass of magnetite than unsupported magnetite, and was more thermally stable than their unsupported counterparts. These results indicate that the diatomite-supported/unsupported magnetite nanoparticles are readily prepared, enabling promising applications for the removal of Cr(VI) from aqueous solution. PMID:19748178

  16. Exposure to Hexavalent Chromium Resulted in Significantly Higher Tissue Chromium Burden Compared With Trivalent Chromium Following Similar Oral Doses to Male F344/N Rats and Female B6C3F1 Mice

    PubMed Central

    Collins, Bradley J.; Stout, Matthew D.; Levine, Keith E.; Kissling, Grace E.; Fennell, Timothy R.; Walden, Ramsey; Abdo, Kamal; Pritchard, John B.; Fernando, Reshan A.; Burka, Leo T.; Hooth, Michelle J.

    2010-01-01

    In National Toxicology Program 2-year studies, hexavalent chromium [Cr(VI)] administered in drinking water was clearly carcinogenic in male and female rats and mice, resulting in small intestine epithelial neoplasms in mice at a dose equivalent to or within an order of magnitude of human doses that could result from consumption of chromium-contaminated drinking water, assuming that dose scales by body weight3/4 (body weight raised to the 3/4 power). In contrast, exposure to trivalent chromium [Cr(III)] at much higher concentrations may have been carcinogenic in male rats but was not carcinogenic in mice or female rats. As part of these studies, total chromium was measured in tissues and excreta of additional groups of male rats and female mice. These data were used to infer the uptake and distribution of Cr(VI) because Cr(VI) is reduced to Cr(III) in vivo, and no methods are available to speciate tissue chromium. Comparable external doses resulted in much higher tissue chromium concentrations following exposure to Cr(VI) compared with Cr(III), indicating that a portion of the Cr(VI) escaped gastric reduction and was distributed systemically. Linear or supralinear dose responses of total chromium in tissues were observed following exposure to Cr(VI), indicating that these exposures did not saturate gastric reduction capacity. When Cr(VI) exposure was normalized to ingested dose, chromium concentrations in the liver and glandular stomach were higher in mice, whereas kidney concentrations were higher in rats. In vitro studies demonstrated that Cr(VI), but not Cr(III), is a substrate of the sodium/sulfate cotransporter, providing a partial explanation for the greater absorption of Cr(VI). PMID:20843897

  17. Distribution and mass balance of hexavalent and trivalent chromium in a subsurface, horizontal flow (SF-h) constructed wetland operating as post-treatment of textile wastewater for water reuse.

    PubMed

    Fibbi, Donatella; Doumett, Saer; Lepri, Luciano; Checchini, Leonardo; Gonnelli, Cristina; Coppini, Ester; Del Bubba, Massimo

    2012-01-15

    In this study, during a two-year period, we investigated the fate of hexavalent and trivalent chromium in a full-scale subsurface horizontal flow constructed wetland planted with Phragmites australis. The reed bed operated as post-treatment of the effluent wastewater from an activated sludge plant serving the textile industrial district and the city of Prato (Italy). Chromium speciation was performed in influent and effluent wastewater and in water-suspended solids, at different depths and distances from the inlet; plants were also analyzed for total chromium along the same longitudinal profile. Removals of hexavalent and trivalent chromium equal to 72% and 26%, respectively were achieved. The mean hexavalent chromium outlet concentration was 1.6 ± 0.9 μg l(-1) and complied with the Italian legal limits for water reuse. Chromium in water-suspended solids was in the trivalent form, thus indicating that its removal from wastewater was obtained by the reduction of hexavalent chromium to the trivalent form, followed by accumulation of the latter inside the reed bed. Chromium in water-suspended solids was significantly affected by the distance from the inlet. Chromium concentrations in the different plant organs followed the same trend of suspended solids along the longitudinal profile and were much lower than those found in the solid material, evidencing a low metal accumulation in P. australis. PMID:22104764

  18. Airborne exposure to inhalable hexavalent chromium in welders and other occupations: Estimates from the German MEGA database.

    PubMed

    Pesch, Beate; Kendzia, Benjamin; Hauptmann, Kristin; Van Gelder, Rainer; Stamm, Roger; Hahn, Jens-Uwe; Zschiesche, Wolfgang; Behrens, Thomas; Weiss, Tobias; Siemiatycki, Jack; Lavoué, Jerome; Jöckel, Karl-Heinz; Brüning, Thomas

    2015-07-01

    This study aimed to estimate occupational exposure to inhalable hexavalent chromium (Cr(VI)) using the exposure database MEGA. The database has been compiling Cr(VI) concentrations and ancillary data about measurements at German workplaces. We analysed 3659 personal measurements of inhalable Cr(VI) collected between 1994 and 2009. Cr(VI) was determined spectrophotometrically at 540 nm after reaction with diphenylcarbazide. We assigned the measurements to pre-defined at-risk occupations using the information provided about the workplaces. Two-thirds of the measurements were below the limit of quantification (LOQ) and multiply imputed according to the distribution above LOQ. The 75th percentile value was 5.2 μg/m(3) and the 95th percentile was 57.2 μg/m(3). We predicted the geometric mean for 2h sampling in the year 2000, and the time trend of Cr(VI) exposure in these settings with and without adjustment for the duration of measurements. The largest dataset was available for welding (N = 1898), which could be further detailed according to technique. The geometric means were above 5 μg/m(3) in the following situations: spray painting, shielded metal arc welding, and flux-cored arc welding if applied to stainless steel. The geometric means were between 1 μg/m(3) and 5 μg/m(3) for gas metal arc welding of stainless steel, cutting, hard-chromium plating, metal spraying and in the chemical chromium industry. The exposure profiles described here are useful for epidemiologic and industrial health purposes. Exposure to Cr(VI) varies not only between occupations, but also within occupations as shown for welders. In epidemiologic studies, it would be desirable to collect exposure-specific information in addition to the job title. PMID:25979374

  19. Hexavalent chromium reduction by chromate-resistant haloalkaliphilic Halomonas sp. M-Cr newly isolated from tannery effluent

    PubMed Central

    Mabrouk, Mona E.M.; Arayes, Mervat A.; Sabry, Soraya A.

    2014-01-01

    The current study aimed to isolate and characterize a chromate-resistant bacterium from tannery effluent, able to reduce Cr(VI) aerobically at high pH and salinity. Environmental contamination by hexavalent chromium, Cr(VI), presents a serious public health problem. Enrichment led to the isolation of 12 bacteria displaying different degrees of chromate reduction. Phenotypic characterization and phylogenetic analysis based on 16S rDNA sequence comparison indicated that the most potent strain belonged to the genus Halomonas. The new strain designated as Halomonas sp. M-Cr was able to reduce 82% of 50 mg L−1 Cr(VI) in 48 h, concomitant with discolouring of yellow colour of the medium and formation of white insoluble precipitate of Cr(III). It exhibited growth up to 3500 mg L−1 Cr(VI), 20% NaCl and showed strong Cr(VI) reduction under alkaline condition, pH 10. Scanning electron microscopy revealed precipitation of chromium hydroxide on bacterial cell surfaces, which showed characteristic peak of chromium in energy-dispersive X-ray analysis. Plackett–Burman design was used to evaluate the influence of related parameters for enhancing Cr(VI) reduction. Glucose, yeast extract and KH2PO4 were confirmed as significant variables in the medium. Data suggest Halomonas sp. M-Cr as a promising candidate for bioremediation of Cr(VI) contaminated effluents particularly in saline and alkaline environments. Up to our knowledge, this is the first report on isolation of haloalkaliphilic Halomonas sp. from tannery effluent. PMID:26740769

  20. Effect of culture conditions and mother's age on the sensitivity of Daphnia magna Straus 1820 (Cladocera) neonates to hexavalent chromium.

    PubMed

    Martínez-Jerónimo, Fernando; Martínez-Jerónimo, Laura; Espinosa-Chávez, Félix

    2006-04-01

    Daphnia magna is a freshwater cladoceran used worldwide as test organism in aquatic toxicity assays. In Mexico there is a test protocol for this species; nevertheless, some aspects of the controlled neonate production, as well as the possible consequences of the reproducers' culture conditions on the response of neonates to the toxic substance, are not completely known. In the present study, we evaluated the effect of temperature and photoperiod on the acute toxicity of CrVI in D. magna neonates, aimed at providing useful information on the Median Lethal Concentration (LC50) to this heavy metal, which is used as reference toxicant in some laboratories. D. magna was cultured at 20 and 25 degrees C, in combination with two photoperiod values: 16:8 and 12:12 (light:dark) during 40 days; the green microalga Ankistrodesmus falcatus (4x10(5) cells ml(-1)) was supplied as food. Once the reproduction began, the neonates were removed and acute toxicity bioassays at 20 and 25 degrees C were performed, by exposing them to hexavalent chromium. We also determined changes in neonates' size at 20 and 25 degrees C. Chromium toxicity increased along with increasing temperatures, and LC50 values were slightly lower for the first and last clutches in the observed period, but these findings are not conclusive because of the large variability recorded. The average LC50's were 0.2076+/-0.0164 mg l(-1) (at 20 degrees C) and 0.1544+/-0.0175 mg l(-1) (at 25 degrees C). The reproducers' culture temperature had no effect on neonates' sensitivity to chromium, in spite of performing the tests at temperatures either lower or higher than those at which the neonates had been obtained. The length of neonates produced during the first two clutches (<1.25 mm) was significantly lower than that measured in neonates of following reproductions (>1.3 mm), and were smaller at 25 degrees C; however, this did not seem to affect their sensitivity to chromium. PMID:16570207

  1. Toxic and genotoxic effects of hexavalent chromium in environment and its bioremediation strategies.

    PubMed

    Mishra, Sandhya; Bharagava, Ram Naresh

    2016-01-01

    Chromium is one of the major inorganic environmental pollutants, which is added in the environment through various natural and anthropogenic activities and exists mainly in two forms: Cr(III) and Cr(VI). Cr(VI) is considered to be more toxic than Cr(III) due to its high solubility and mobility. It is a well-reported occupational carcinogen associated with lung, nasal, and sinus cancers. Thus, this review article provides the detailed information on the occurrence, sources of chromium contamination in the environment and their toxicological effects in human, animal, plants as well as in microorganisms, and bioremediation strategies to minimize the toxic effects. PMID:26398402

  2. Determination and evaluation of hexavalent chromium in power plant coal combustion by-products and cost-effective environmental remediation solutions using acid mine drainage.

    PubMed

    Kingston, H M Skip; Cain, Randy; Huo, Dengwei; Rahman, G M Mizanur

    2005-09-01

    The chromium species leaching from a coal combustion fly ash landfill has been characterized as well as a novel approach to treat leachates rich in hexavalent chromium, Cr(VI), by using another natural waste by-product, acid mine drainage (AMD), has been investigated during this study. It is observed that as much as 8% (approximately 10 microg g(-1) in fly ash) of total chromium is converted to the Cr(VI) species during oxidative combustion of coal and remains in the resulting ash as a stable species, however, it is significantly mobile in water based leaching. Approximately 1.23 +/- 0.01 microg g(-1) of Cr(VI) was found in the landfill leachate from permanent deposits of aged fly ash. This study also confirmed the use of AMD, which often is in close proximity to coal combustion by-product landfills, is an extremely effective and economical remediation option for the elimination of hexavalent chromium in fly ash generated leachate. Speciated isotope dilution mass spectrometry (SIDMS), as described in EPA Method 6800, was used to analytically evaluate and validate the field application of the ferrous iron and chromate chemistry in the remediation of Cr(VI) runoff. PMID:16121270

  3. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... claim of confidentiality only to the extent permitted by section 14 of TSCA and 40 CFR part 2, subpart B... water treatment chemicals to prevent unreasonable risks associated with human exposure to air emissions... chromium air emissions increases the risk of lung cancer. Federal Law prohibits use of this substance...

  4. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... claim of confidentiality only to the extent permitted by section 14 of TSCA and 40 CFR part 2, subpart B... water treatment chemicals to prevent unreasonable risks associated with human exposure to air emissions... chromium air emissions increases the risk of lung cancer. Federal Law prohibits use of this substance...

  5. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... claim of confidentiality only to the extent permitted by section 14 of TSCA and 40 CFR part 2, subpart B... water treatment chemicals to prevent unreasonable risks associated with human exposure to air emissions... chromium air emissions increases the risk of lung cancer. Federal Law prohibits use of this substance...

  6. 40 CFR 749.68 - Hexavalent chromium-based water treatment chemicals in cooling systems.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... claim of confidentiality only to the extent permitted by section 14 of TSCA and 40 CFR part 2, subpart B... water treatment chemicals to prevent unreasonable risks associated with human exposure to air emissions... chromium air emissions increases the risk of lung cancer. Federal Law prohibits use of this substance...

  7. TOXIC EFFECTS OF HEXAVALENT CHROMIUM ON BROOK TROUT ('SALVELINUS FONTINALIS') AND RAINBOW TROUT ('SALMO GAIRDNERI')

    EPA Science Inventory

    Exposing brook trout to various concentrations of chromium (Cr(VI)) for up to 22 months (including reproduction) significantly increased alevin mortality at 0.35 mg Cr/l and retarded growth of young brook trout at the lowest concentration tested (0.01 mg Cr/l). Eight month exposu...

  8. Adsorption behavior comparison of trivalent and hexavalent chromium on biochar derived from municipal sludge.

    PubMed

    Chen, Tan; Zhou, Zeyu; Xu, Sai; Wang, Hongtao; Lu, Wenjing

    2015-08-01

    In this work, static equilibrium experiments were conducted to distinguish the adsorption performance between the two valence states of chromium on biochar derived from municipal sludge. The removal capacity of Cr(VI) is lower than 7mg/g at the initial chromium concentration range of 50-200mg/L, whereas that of Cr(III) higher than 20mg/g. It indicates that Cr(III) is much easier to be stabilized than Cr(VI). No significant changes in the biochar surface functional groups are observed before and after the adsorption equilibrium, demonstrating the poor contribution of organic matter in chromium adsorption. The main mechanism of heavy metal adsorption by biochar involves (1) surface precipitation through pH increase caused by biochar buffer ability, and (2) exchange between cations in solution (Cd(2+)) and in biochar matrix (e.g. Ca(2+) and Mg(2+)). The reduction of Cr(VI) to Cr(III) is necessary to improve removal efficiency of chromium. PMID:25978792

  9. Hexavalent chromium reduction by aerobic heterotrophic bacteria indigenous to chromite mine overburden

    PubMed Central

    Dey, Satarupa; Paul, A.K.

    2013-01-01

    Microbiological analysis of overburden samples collected from chromite mining areas of Orissa, India revealed that they are rich in microbial density as well as diversity and dominated by Gram-negative (58%) bacteria. The phenotypically distinguishable bacterial isolates (130) showed wide degree of tolerance to chromium (2–8 mM) when tested in peptone yeast extract glucose agar medium. Isolates (92) tolerating 2 mM chromium exhibited different degrees of Cr+6 reducing activity in chemically defined Vogel Bonner (VB) broth and complex KSC medium. Three potent isolates, two belonging to Arthrobacter spp. and one to Pseudomonas sp. were able to reduce more than 50 and 80% of 2 mM chromium in defined and complex media respectively. Along with Cr+6 (MIC 8.6–17.8 mM), the isolates showed tolerance to Ni+2, Fe+3, Cu+2 and Co+2 but were extremely sensitive to Hg+2 followed by Cd+2, Mn+2 and Zn+2. In addition, they were resistant to antibiotics like penicillin, methicillin, ampicillin, neomycin and polymyxin B. During growth under shake-flask conditions, Arthrobacter SUK 1201 and SUK 1205 showed 100% reduction of 2 mM Cr+6 in KSC medium with simultaneous formation of insoluble precipitates of chromium salts. Both the isolates were also equally capable of completely reducing the Cr+6 present in mine seepage when grown in mine seepage supplemented with VB concentrate. PMID:24159321

  10. Hexavalent chromium [Cr(VI)] removal by the electrochemical ion-exchange process.

    PubMed

    Dharnaik, Amit Shivputra; Ghosh, Pranab Kumar

    2014-01-01

    In the present investigation, the performance of a laboratory-scale plate and frame-type electrochemical ion-exchange (EIX) cell on removal ofhexavalent chromium from synthetic wastewater containing 5 mg/l of Cr(VI) was evaluated under varying applied voltages. Ruthenium dioxide-coated titanium plate (RuO2/Ti) was used as anode and stainless steel plates as cathode. The EIX cell was run at different hydraulic retention time (HRT). Before using in the electrochemical cell, the capacity of ion-exchange resin was evaluated through kinetic and isotherm equilibrium tests in batch mode. The batch kinetic study result showed that the equilibrium time for effective ion exchange with resin is 2 h. The isotherm equilibrium data fit well to both Freundlich and Langmuir isotherms. Maximum capacity (qm) of resin calculated from Langmuir isotherm was 71.42 mg/g. Up to 99% of chromium removal was noticed in the EIX cell containing fresh resin at applied voltages of 10 V and higher. Migration of chromium ion to anode chamber was not noticed while performing the experiment with fresh resin. As high as 50% removal of chromium was observed from the middle chamber containing exhausted resin at an applied voltage of 25 V when the influent flow rate was maintained at 45 min of HRT. The performance of the reactor was increased to 72% when the influent flow rate was decreased to maintain at 90 min of HRT. Build-up of chromium in the anode chamber took place when exhausted resin was used in the process. PMID:25145180

  11. Effect of NaX zeolite-modified graphite felts on hexavalent chromium removal in biocathode microbial fuel cells.

    PubMed

    Wu, Xiayuan; Tong, Fei; Yong, Xiaoyu; Zhou, Jun; Zhang, Lixiong; Jia, Honghua; Wei, Ping

    2016-05-01

    Two kinds of NaX zeolite-modified graphite felts were used as biocathode electrodes in hexavalent chromium (Cr(VI))-reducing microbial fuel cells (MFCs). The one was fabricated through direct modification, and the other one processed by HNO3 pretreatment of graphite felt before modification. The results showed that two NaX zeolite-modified graphite felts are excellent bio-electrode materials for MFCs, and that a large NaX loading mass, obtained by HNO3 pretreatment (the HNO3-NaX electrode), leads to a superior performance. The HNO3-NaX electrode significantly improved the electricity generation and Cr(VI) removal of the MFC. The maximum Cr(VI) removal rate increased to 10.39±0.28 mg/L h, which was 8.2 times higher than that of the unmodified control. The improvement was ascribed to the strong affinity that NaX zeolite particles, present in large number on the graphite felt, have for microorganisms and Cr(VI) ions. PMID:26852205

  12. Effects of hexavalent chromium on microtubule organization, ER distribution and callose deposition in root tip cells of Allium cepa L.

    PubMed

    Eleftheriou, Eleftherios P; Adamakis, Ioannis-Dimosthenis S; Melissa, Pelagia

    2012-04-01

    The subcellular targets of hexavalent chromium [Cr(VI)] were examined in Allium cepa root tips with confocal laser scanning microscopy. Cr(VI) exerted dose- and time-dependent negative effects on root growth rate, the mitotic index and microtubule (MT) organization during cell division cycle. Interphase MTs were more resistant than the mitotic ones, but when affected they were shorter, sparse and disoriented. The preprophase band of MTs became poorly organized, branched or with fragmented MTs, whilst neither a perinuclear array nor a prophase spindle was formed. Metaphase spindles converged to eccentric mini poles or consisted of dissimilar halves and were unable to correctly orient the chromosomes. Anaphase spindles were less disturbed, but chromatids failed to separate; neither did they move to the poles. At telophase, projecting, lagging or bridging chromosomes and micronuclei also occurred. Phragmoplasts were unilaterally developed, split, located at unexpected sites and frequently dissociated from the branched and misaligned cell plates. Chromosomal aberrations were directly correlated with MT disturbance. The morphology and distribution of endoplasmic reticulum was severely perturbed and presumably contributed to MT disassembly. Heavy callose apposition was also induced by Cr(VI), maybe in the context of a cellular defence reaction. Results indicate that MTs are one of the main subcellular targets of Cr(VI), MT impairment underlies chromosomal and mitotic aberrations, and MTs may constitute a reliable biomonitoring system for Cr(VI) toxicity in plants. PMID:21633932

  13. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination.

    PubMed

    Wang, Guey-Horng; Cheng, Chiu-Yu; Liu, Man-Hai; Chen, Tzu-Yu; Hsieh, Min-Chi; Chung, Ying-Chien

    2016-01-01

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125-0.3 mg/L and 0.3-5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen. PMID:27537887

  14. Determination of optimum range for hexavalent chromium Cr(VI) removal using ageratum conyzoide leaf powder (ACLP)

    NASA Astrophysics Data System (ADS)

    Ezechi, Ezerie Henry; Kutty, Shamsul Rahman bin Mohamed; Malakahmad, Amirhossein; Salihi, Ibrahim Umar; Aminu, Nasiru

    2015-07-01

    The optimum range of process parameters for hexavalent chromium Cr(VI) removal were determined in a batch study using Ageratum conyzoide leaf powder (ACLP) as adsorbent. The process parameters were varied in the range 2-10 for Initial solution pH, 135-400 mg/L for initial concentration, 30-180 minutes for contact time and 0.1-0.6 g for adsorbent weight. Solution pH was adjusted using 0.1 M H2S04 and NaOH respectively. Results show that initial solution pH was vital for Cr(VI) removal. At low initial solution pH (pH 2), Cr(VI) removal was high but decreased when the solution was increased from pH 4 to 10. Cr(VI) removal decreased when initial solution concentration was increased and increased when contact time and adsorbent weight was increased. At initial solution concentration of 135 mg/L, residual Cr (VI) concentration was about 53.7 mg/L (61 % removal efficiency) at optimum range of pH 2, adsorbent weight 0.3 g and contact time 120 minutes. Ageratum conyzoide leaf powder (ACLP) could be a potential adsorbent for Cr(VI) removal from wastewater.

  15. Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed.

    PubMed

    Xu, Fei; Liu, Xu; Chen, Yijiao; Zhang, Ke; Xu, Heng

    2016-01-01

    A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 500 mg/L initial concentration of Cr(VI), respectively. Results indicated that the metal removal was dependent on dosage of adsorbent, particle diameter and treatment time. The experimental data obtained from the biosorption process was successfully correlated with Freundlich isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that self-assembly modified Pleurotus Cornucopiae material could be applied for the removal of heavy metal from wastewater in continuous fluidized bed process. PMID:27188258

  16. Determination of hexavalent chromium in plastic certified reference materials by X-ray absorption fine structure analysis

    NASA Astrophysics Data System (ADS)

    Ohata, Masaki; Matsubayashi, Nobuyuki

    X-ray absorption fine structure (XAFS) analysis with transmission mode was used to determine the percentages of hexavalent chromium {Cr(VI)} in total Cr in plastic certified reference materials (CRMs). Cr-K edge X-ray absorption near-edge structure (XANES) spectra were observed and the normalized pre-edge peaks of the spectrum where absorption data was summed was acquired for the determination of Cr(VI). Examination of different number of data point and range of photon energy for summed absorption of the pre-edge peak resulted in reproducible absorption data, though the measurements were carried out at different beam time and beam line. The concentrations of Cr(VI) in the plastic CRMs were also estimated from both the certified value of total Cr and the determined percentage of Cr(VI). The analytical procedure and the estimated concentrations can be useful for the determination of Cr(VI) in plastics with respect to RoHS (restriction of the use of hazardous substances in electrical and electronics equipment) directive.

  17. Application of Fe-Cu binary oxide nanoparticles for the removal of hexavalent chromium from aqueous solution.

    PubMed

    Khan, Saif Ullah; Zaidi, Rumman; Hassan, Saeikh Z; Farooqi, I H; Azam, Ameer

    2016-01-01

    The adsorption process has been used as an effective technique for the removal of metal ions from aqueous solutions. Groundwater remediation by nanoparticles has received interest in recent years. In the present study, a binary metal oxide of Fe-Cu was prepared and used for the removal of hexavalent chromium from aqueous solution. Batch experiments were performed to investigate the effects of initial Cr (VI) concentration, dose of adsorbent, and pH of solution on the removal efficiency of Cr (VI). The prepared nanostructured Fe-Cu binary oxides were able to reduce the concentration of Cr (VI) in aqueous solution. Binary metal oxides nanoparticle exhibited an outstanding ability to remove Cr (VI) due to high surface area, low particle size, and high inherent activity. The percentage removal efficiency of Cr (VI) increased with nanoparticles doses (0.1 g L(-1)-2.5 g L(-1)), whereas it decreased with initial Cr (VI) concentration (1 mg L(-1)-25 mg L(-1)) and with pH (3-9). The Freundlich model was found to be the better fit for adsorption isotherm. The prepared nanomaterial was characterized using powder X-ray diffraction, scanning electron microscopy (SEM), and ultraviolet (UV)-visible spectroscopy. It showed that the Fe-Cu binary oxides were formed in single phase. SEM micrograph showed aggregates with many nano-sized particles. UV-visible spectroscopy showed quantum confinement effect. PMID:27386994

  18. Adsorption of hexavalent chromium from synthetic and electroplating effluent on chemically modified Swietenia mahagoni shell in a packed bed column.

    PubMed

    Rangabhashiyam, S; Nandagopal, M S Giri; Nakkeeran, E; Selvaraju, N

    2016-07-01

    Packed bed column studies were carried out to evaluate the performance of chemically modified adsorbents for the sequestration of hexavalent chromium from synthetic and electroplating industrial effluent. The effects of parameters such as bed height (3-9 cm), inlet flow rate (5-15 mL/min), and influent Cr(VI) concentration (50-200 mg/L) on the percentage removal of Cr(VI) and the adsorption capacity of the adsorbents in a packed bed column were investigated. The breakthrough time increased with increasing bed height and decreased with the increase of inlet flow rate and influent Cr(VI) concentration. The adsorption column models such as Thomas, Adams-Bohart, Yoon-Nelson, and bed depth service time (BDST) were successfully correlated with the experimental data. The Yoon-Nelson and BDST model showed good agreement with the experimental data for all the studied parameter conditions. Results of the present study indicated that the chemically modified Swietenia mahagoni shell can be used as an adsorbent for the removal of Cr(VI) from industrial wastewater in a packed bed column. PMID:27312254

  19. Removal of hexavalent chromium from aqueous solutions using micro zero-valent iron supported by bentonite layer.

    PubMed

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

    Hexavalent chromium Cr(VI) is of particular environmental concern due to its toxicity, mobility, and challenging removal from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. Moreover, it does not form insoluble compounds in aqueous solutions; therefore, separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are the opposite and, like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI)-Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. Permeable reactive barriers (PRBs) with zero-valent iron (ZVI) have been used to remediate contaminated groundwater with metals, but using ZVI in remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation, and difficulty in separation of iron from the treated solution. Thus, the technology used in the present study is developed to address these problems by placing a layer of bentonite after the PRB layer to remove iron from the treated water. The removal rates of Cr(VI) under different values of pH were investigated, and the results indicated the highest adsorption capacity at low pH. PMID:25768212

  20. Effects of Dentifrice Containing Hydroxyapatite on Dentinal Tubule Occlusion and Aqueous Hexavalent Chromium Cations Sorption: A Preliminary Study

    PubMed Central

    Liu, Jing; Hou, Yarong; Zhu, Manqun; Huang, Jiansheng; Xu, Pingping

    2012-01-01

    In order to endow environmental protection features to dentifrice, hydroxyapatite (HA) was added to ordinary dentifrice. The effects on dentinal tubule occlusion and surface mineralization were compared after brushing dentine discs with dentifrice with or without HA. The two types of dentifrice were then added to 100 µg/ml of hexavalent chromium cation (Cr6+) solution in order to evaluate their capacities of adsorbing Cr6+ from water. Our results showed that the dentifrice containing HA was significantly better than the ordinary dentifrice in occluding the dentinal tubules with a plugging rate greater than 90%. Moreover, the effect of the HA dentifrice was persistent and energy-dispersive spectrometer (EDS) revealed that the atomic percentages of calcium and phosphorus on the surface of dentine discs increased significantly. Adding HA to ordinary dentifrice significantly enhanced the ability of dentifrice to adsorb Cr6+ from water with the removal rate up to 52.36%. In addition, the sorption was stable. Our study suggests that HA can be added to ordinary dentifrice to obtain dentifrice that has both relieving dentin hypersensitivity benefits and also helps to control environmental pollution. PMID:23300511

  1. Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed

    PubMed Central

    Xu, Fei; Liu, Xu; Chen, Yijiao; Zhang, Ke; Xu, Heng

    2016-01-01

    A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 500 mg/L initial concentration of Cr(VI), respectively. Results indicated that the metal removal was dependent on dosage of adsorbent, particle diameter and treatment time. The experimental data obtained from the biosorption process was successfully correlated with Freundlich isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that self-assembly modified Pleurotus Cornucopiae material could be applied for the removal of heavy metal from wastewater in continuous fluidized bed process. PMID:27188258

  2. Simultaneous decontamination of hexavalent chromium and methyl tert-butyl ether by UV/TiO2 process.

    PubMed

    Xu, Xiang-Rong; Li, Hua-Bin; Gu, Ji-Dong

    2006-04-01

    Hexavalent chromium and methyl tert-butyl ether (MTBE) are two important environmental pollutants. Simultaneous decontamination of Cr(VI) and MTBE was studied by UV/TiO2 process. The influences of pH and the concentrations of pollutants on the kinetics of the photocatalytic reactions were evaluated. Dark adsorption tests showed that the acidic pH favored the adsorption of Cr(VI) while neutral pH favored the adsorption of MTBE. Under UV irradiation, Cr(VI) reduction was observed in Cr(VI)/TiO2 system, and MTBE oxidation was observed in MTBE/TiO2 system. The system containing Cr(VI) and MTBE by UV/TiO2 process demonstrated the synergistic effect between oxidation of MTBE and reduction of Cr(VI). The results demonstrated that two pollutants Cr(VI) and MTBE could be eliminated simultaneously by UV/TiO2 process. tert-Butyl formate, tert-butyl alcohol and acetone were identified as primary degradation products of MTBE by gas chromatography-mass spectrometry in the degradation of MTBE by UV/TiO2 process. PMID:16169572

  3. Simultaneously photocatalytic treatment of hexavalent chromium (Cr(VI)) and endocrine disrupting compounds (EDCs) using rotating reactor under solar irradiation.

    PubMed

    Kim, Youngji; Joo, Hyunku; Her, Namguk; Yoon, Yeomin; Sohn, Jinsik; Kim, Sungpyo; Yoon, Jaekyung

    2015-05-15

    In this study, simultaneous treatments, reduction of hexavalent chromium (Cr(VI)) and oxidation of endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and 17β-estradiol (E2), were investigated with a rotating photocatalytic reactor including TiO₂ nanotubes formed on titanium mesh substrates under solar UV irradiation. In the laboratory tests with a rotating type I reactor, synergy effects of the simultaneous photocatalytic reduction and oxidation of inorganic (Cr(VI)) and organic (BPA) pollutants were achieved. Particularly, the concurrent photocatalytic reduction of Cr(VI) and oxidation of BPA was higher under acidic conditions. The enhanced reaction efficiency of both pollutants was attributed to a stronger charge interaction between TiO₂ nanotubes (positive charge) and the anionic form of Cr(VI) (negative charge), which are prevented recombination (electron-hole pair) by the hole scavenging effect of BPA. In the extended outdoor tests with a rotating type II reactor under solar irradiation, the experiment was extended to examine the simultaneous reduction of Cr(VI) in the presence of additional EDCs, such as EE2 and E2 as well as BPA. The findings showed that synergic effect of both photocatalytic reduction and oxidation was confirmed with single-component (Cr(VI) only), two-components (Cr(VI)/BPA, Cr(VI)/EE2, and Cr(VI)/E2), and four-components (Cr(VI)/BPA/EE2/E2) under various solar irradiation conditions. PMID:25698573

  4. Self-assembly modified-mushroom nanocomposite for rapid removal of hexavalent chromium from aqueous solution with bubbling fluidized bed

    NASA Astrophysics Data System (ADS)

    Xu, Fei; Liu, Xu; Chen, Yijiao; Zhang, Ke; Xu, Heng

    2016-05-01

    A self-assembled modified Pleurotus Cornucopiae material (SMPM) combined with improved Intermittent Bubbling Fluidized Bed (IBFB) was investigated to remove the hexavalent chromium ions in aqueous solution. After the modification, the powder-like raw material gradually self-assembled together to SMPM, which had crinkly porous structure, improved the Cr-accommodation ability in a sound manner. Optimized by Taguchi method, Cr(VI) removal efficiency was up to 75.91% and 48.01% for 100 mg/L and 500 mg/L initial concentration of Cr(VI), respectively. Results indicated that the metal removal was dependent on dosage of adsorbent, particle diameter and treatment time. The experimental data obtained from the biosorption process was successfully correlated with Freundlich isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that self-assembly modified Pleurotus Cornucopiae material could be applied for the removal of heavy metal from wastewater in continuous fluidized bed process.

  5. Hexavalent chromium-induced apoptosis of granulosa cells involves selective sub-cellular translocation of Bcl-2 members, ERK1/2 and p53

    SciTech Connect

    Banu, Sakhila K.; Stanley, Jone A.; Lee, JeHoon; Stephen, Sam D.; Arosh, Joe A.; Hoyer, Patricia B.; Burghardt, Robert C.

    2011-03-15

    Hexavalent chromium (CrVI) has been widely used in industries throughout the world. Increased usage of CrVI and atmospheric emission of CrVI from catalytic converters of automobiles, and its improper disposal causes various health hazards including female infertility. Recently we have reported that lactational exposure to CrVI induced a delay/arrest in follicular development at the secondary follicular stage. In order to investigate the underlying mechanism, primary cultures of rat granulosa cells were treated with 10 {mu}M potassium dichromate (CrVI) for 12 and 24 h, with or without vitamin C pre-treatment for 24 h. The effects of CrVI on intrinsic apoptotic pathway(s) were investigated. Our data indicated that CrVI: (i) induced DNA fragmentation and increased apoptosis, (ii) increased cytochrome c release from the mitochondria to cytosol, (iii) downregulated anti-apoptotic Bcl-2, Bcl-XL, HSP70 and HSP90; upregulated pro-apoptotic BAX and BAD, (iv) altered translocation of Bcl-2, Bcl-XL, BAX, BAD, HSP70 and HSP90 to the mitochondria, (v) upregulated p-ERK and p-JNK, and selectively translocated p-ERK to the mitochondria and nucleus, (vi) activated caspase-3 and PARP, and (vii) increased phosphorylation of p53 at ser-6, ser-9, ser-15, ser-20, ser-37, ser-46 and ser-392, increased p53 transcriptional activation, and downregulated MDM-2. Vitamin C pre-treatment mitigated CrVI effects on apoptosis and related pathways. Our study, for the first time provides a clear insight into the effect of CrVI on multiple pathways that lead to apoptosis of granulosa cells which could be mitigated by vitamin C.

  6. Phytotoxicity and phytoaccumulation of trivalent and hexavalent chromium in brake fern.

    PubMed

    Su, Yi; Han, Fengxiang X; Sridhar, B B Maruthi; Monts, David L

    2005-08-01

    A recently recognized hyperaccumulator plant, Chinese brake fern (Pteris vittata), has been found to extract very high concentration of arsenic from arsenic-contaminated soil. Chromium usually is a coexisting contaminant with arsenic in most contaminated soils. The potential application of ferns for phytoremediation of chromium(III)- and chromium(VI)-contaminated soils and their phytotoxicity to ferns has not been studied before. In this study, chromium distribution and phytotoxicity at the plant and cellular levels of brake ferns were studied using chemical analyses and scanning electron microscopy. The results show a higher phytotoxicity of Cr from Cr(VI)-contaminated soil to Chinese brake fern than from Cr(III)-contaminated soil. Phytotoxicity symptoms included significant decreases both in fresh biomass weight and relative water content (RWC), and also in leaf chlorosis during the late stage of growing. At higher concentrations (500 mg/kg Cr[VI] and 1,000 mg/kg Cr[III] addition), plants showed reduction in the number of palisade and spongy parenchyma cells in leaves. Compared with other plant species reported for phytoremediation of Cr(VI)-contaminated soil, brake fern took up and accumulated significant amounts of Cr (up to 1,145 mg/kg in shoots and 5,717 mg/kg in roots) and did not die immediately from phytotoxicity. Our study suggests that Chinese brake fern is a potential candidate for phytoremediation of Cr(VI)-contaminated soils, even though plants showed severe phytotoxic symptoms at higher soil Cr concentrations. PMID:16152975

  7. A plan for study of hexavalent chromium, CR(VI) in groundwater near a mapped plume, Hinkley, California, 2016

    USGS Publications Warehouse

    Izbicki, John A.; Groover, Krishangi

    2016-01-01

    The Pacific Gas and Electric Company (PG&E) Hinkley compressor station, in the Mojave Desert 80 miles northeast of Los Angeles, is used to compress natural gas as it is transported through a pipeline from Texas to California. Between 1952 and 1964, cooling water used at the compressor station was treated with a compound containing chromium to prevent corrosion. After cooling, the wastewater was discharged to unlined ponds, resulting in contamination of soil and groundwater in the underlying alluvial aquifer (Lahontan Regional Water Quality Control Board, 2013). Since 1964, cooling-water management practices have been used that do not contribute chromium to groundwater.In 2007, a PG&E study of the natural background concentrations of hexavalent chromium, Cr(VI), in groundwater estimated average concentrations in the Hinkley area to be 1.2 micrograms per liter (μg/L), with a 95-percent upper-confidence limit of 3.1 μg/L (CH2M-Hill, 2007). The 3.1 μg/L upper-confidence limit was adopted by the Lahontan Regional Water Quality Control Board (RWQCB) as the maximum background concentration used to map the plume extent. In response to criticism of the study’s methodology, and an increase in the mapped extent of the plume between 2008 and 2011, the Lahontan RWQCB (Lahontan Regional Water Quality Control Board, 2012) agreed that the 2007 PG&E background-concentration study be updated.The purpose of the updated background study is to evaluate the presence of natural and man-made Cr(VI) near Hinkley, Calif. The study also is to estimate natural background Cr(VI) concentrations in the aquifer upgradient and downgradient from the mapped Cr(VI) contamination plume, as well as in the plume and near its margins. The study was developed by the U.S. Geological Survey (USGS) in collaboration with a technical working group (TWG) composed of community members, the Independent Review Panel (IRP) Manager (Project Navigator, Ltd.), the Lahontan RWQCB, PG&E, and consultants for PG&E.&E.

  8. Assessment of the removal mechanism of hexavalent chromium from aqueous solutions by olive stone.

    PubMed

    Martín-Lara, María Ángeles; Calero de Hoces, Mónica; Ronda Gálvez, Alicia; Pérez Muñoz, Antonio; Trujillo Miranda, Ma Carmen

    2016-01-01

    The objectives of this study were to study the removal mechanism of Cr(VI) by natural olive stone (OS) and to present a sequential-batch process for the removal of total chromium (original Cr(VI) and Cr(III) derived from reduction of Cr(VI) during biosorption at acidic conditions). First, experiments were conducted varying pH from 1 to 4, and showed that a combined effect of biosorption and reduction is involved in the Cr(VI) removal. Then, X-ray photoelectron spectroscopy and desorption tests were employed to verify the oxidation state of the chromium bound to OS and to elucidate the removal mechanism of Cr(VI) by this material. The goal of these tests was to confirm that Cr(III) is the species mainly absorbed by OS. Finally, the possibility of total chromium removal by biosorption in a sequential-batch process was analyzed. In the first stage, 96.38% of Cr(VI) is removed by OS and reduced to Cr(III). In the second stage, approximately 31% of the total Cr concentration was removed. However, the Cr(III) released in the first stage is not completely removed, and it could suggest that the Cr(III) could be in a hydrated compound or a complex, which could be more difficult to remove under these conditions. PMID:27232404

  9. Reduction and immobilization of hexavalent chromium with coal- and humate-based sorbents.

    PubMed

    Janos, Pavel; Hůla, Václav; Bradnová, Petra; Pilarová, Vera; Sedlbauer, Josef

    2009-05-01

    Two kinds of the commercially available sorbents containing humic acids as active constituents were used for Cr(VI) reduction and removal, namely oxihumolite (naturally occurring weathered young brown coal) and iron humate (IH) (waste material produced during industrial manufacturing of humic substances). The mechanisms of the chromium removal involve the reduction of Cr(VI) (by humic substances or by Fe(II) ions) and subsequent binding of Cr(III) to a humic acid matrix. Other metal-binding mechanisms possibly effective in the process of Cr(VI) removal, e.g., coprecipitation or surface precipitation of Fe(III)/Cr(III) hydroxides, are also discussed. Oxihumolite was able to remove Cr(VI) from strongly acidic solutions with pH below ca. 2. IH, on the other hand, exhibited a maximum sorption capability in slightly acidic solutions with pH above ca. 3. Over the whole examined range (pH 1-5), however, IH was able to reduce Cr(VI) almost completely to its less toxic trivalent state. A sufficiently high sorption capacity (20 mg g(-1)) was found for chromium removal with IH in an unbuffered system, where the "natural" pH values governed by the buffering capacity of the sorbent itself ranged from 3.9 to 4.6. It follows from extraction studies with the loaded (spent) sorbents that chromium is bound strongly to the sorbent, and thus risks of its subsequent liberation into the environment are minimized. Similarity in the extraction behavior of the Cr(III)-loaded and Cr(VI)-loaded sorbents supported the above-mentioned mechanisms of the Cr(VI) removal. PMID:19215962

  10. Cytotoxic and clastogenic effects of soluble and insoluble compounds containing hexavalent and trivalent chromium.

    PubMed Central

    Levis, A. G.; Majone, F.

    1981-01-01

    Cr(III) and Cr(VI) compounds of varying solubilities have been tested in vitro for their ability to inhibit cell growth and nucleic acid and protein syntheses in BHK cells, to induce alterations in the mitotic cycle in HEp cells, and to increase the frequency of chromosomal aberrations and sister chromatid exchanges (SCE) in CHO cells. All Cr(VI) compounds, and particularly those containing soluble Cr(VI), such as potassium dichromate and zinc yellow, differentially inhibit macromolecular syntheses in BKH cells, that of DNA being always the most affected. Among Cr(III) compounds, which generally have very low cytotoxicity, chromite is particularly active, and inhibits cell growth and DNA synthesis even more than the poorly soluble Cr(VI) compounds. Preincubation in growth medium, with or without metabolizing cell cultures, solubilizes considerable amounts of Cr(VI) from zinc yellow and chromite, but significant amounts are also obtained from the most insoluble Cr(VI) pigments. When BHK cells are treated with such preincubated solutions, reduction of soluble Cr(VI) to Cr(III) by cell metabolites is seen with all Cr(VI) compounds, accompanied by decreased cytotoxicity. The same differences between Cr(VI) and Cr(III) compounds apply to the cytotoxic effects on mitosis of HEp cells and the clastogenic effects on CHO cells. The activity of chromite, the only Cr(III) pigment capable of significantly increasing the frequency of SCE, is due to contamination with soluble Cr(VI). In contrast to the very low cytotoxicity of Cr(III), much higher chromium levels are detected in the cells incubated with soluble Cr(III) than with the same concentrations of soluble Cr(VI). 50% and 75% of chromium accumulated in the cells during treatments with Cr(VI) and Cr(III) respectively remains firmly bound to the cells, even when they are incubated for up to 48 h in normal growth medium. Chromium accumulated in the cells after treatment with Cr(III) is most probably bound to the cell