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  1. Anaerobic Dehalogenation of Chloroanilines by Dehalococcoides mccartyi Strain CBDB1 and Dehalobacter Strain 14DCB1 via Different Pathways as Related to Molecular Electronic Structure.

    Science.gov (United States)

    Zhang, Shangwei; Wondrousch, Dominik; Cooper, Myriel; Zinder, Stephen H; Schüürmann, Gerrit; Adrian, Lorenz

    2017-02-24

    Dehalococcoides mccartyi strain CBDB1 and Dehalobacter strain 14DCB1 are organohalide-respiring microbes of the phyla Chloroflexi and Firmicutes, respectively. Here we report the transformation of chloroanilines by these two bacterial strains via dissimilar dehalogenation pathways, and discuss the underlying mechanism with quantum chemically calculated net atomic charges of the substrate Cl, H and C atoms. Strain CBDB1 preferentially removed Cl doubly flanked by two Cl or by one Cl and NH2, whereas strain 14DCB1 preferentially dechlorinated Cl that has an ortho H. For the CBDB1-mediated dechlorination, comparative analysis with Hirshfeld charges shows that the least negative Cl discriminates active from non-active substrates in 14 out of 15 cases, and may represent the preferred site of primary attack through cob(I)alamin. For the latter trend, 3 of 7 active substrates provide strong evidence, with partial support from 3 of the remaining 4 substrates. Regarding strain 14DCB1, the most positive carbon-attached H atom discriminates active from non-active chloroanilines in again 14 out of 15 cases. Here, regioselectivity is governed for 10 of the 11 active substrates by the most positive H attached to the highest-charge (most positive or least negative) aromatic C carrying the Cl to be removed. These findings suggest the aromatic ring H as primary site of attack through the supernucleophile Co(I), converting an initial H-bond to a full electron transfer as start of the reductive dehalogenation. For both mechanisms, one- and two-electron transfer to Cl (strain CBDB1) or H (strain 14DCB1) are compatible with the presently available data. Computational chemistry research into reaction intermediates and pathways may further add in understanding the bacterial reductive dehalogenation at the molecular level.

  2. Phylogenetically distinct bacteria involve extensive dechlorination of aroclor 1260 in sediment-free cultures.

    Directory of Open Access Journals (Sweden)

    Shanquan Wang

    Full Text Available Microbial reductive dechlorination of the persistent polychlorinated biphenyls (PCBs is attracting much attention in cleanup of the contaminated environment. Nevertheless, most PCB dechlorinating cultures require presence of sediment or sediment substitutes to maintain their dechlorination activities which hinders subsequent bacterial enrichment and isolation processes. The information on enriching sediment-free PCB dechlorinating cultures is still limited. In this study, 18 microcosms established with soils and sediments were screened for their dechlorination activities on a PCB mixture - Aroclor 1260. After one year of incubation, 10 out of 18 microcosms showed significant PCB dechlorination with distinct dechlorination patterns (e.g., Process H, N and T classified based on profiles of PCB congeners loss and new congeners formation. Through serial transfers in defined medium, six sediment-free PCB dechlorinating cultures (i.e., CW-4, CG-1, CG-3, CG-4, CG-5 and SG-1 were obtained without amending any sediment or sediment-substitutes. PCB dechlorination Process H was the most frequently observed dechlorination pattern, which was found in four sediment-free cultures (CW-4, CG-3, CG-4 and SG-1. Sediment-free culture CG-5 showed the most extensive PCB dechlorination among the six cultures, which was mediated by Process N, resulting in the accumulation of penta- (e.g., 236-24-CB and tetra-chlorobiphenyls (tetra-CBs (e.g., 24-24-CB, 24-25-CB, 24-26-CB and 25-26-CB via dechlorinating 30.44% hepta-CBs and 59.12% hexa-CBs after three months of incubation. For culture CG-1, dechlorinators mainly attacked double flanked meta-chlorines and partially ortho-chlorines, which might represent a novel dechlorination pattern. Phylogenetic analysis showed distinct affiliation of PCB dechlorinators in the microcosms, including Dehalogenimonas and Dehalococcoides species. This study broadens our knowledge in microbial reductive dechlorination of PCBs, and provides

  3. Effects of polychlorinated biphenyl congener concentration and sediment supplementation on rates of methanogenesis and 2,3,6-trichlorobiphenyl dechlorination in an anaerobic enrichment

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, A.W.; May, H.D. (Celgene Corp., Warren, NJ (United States)); Blake, C.K. (Medical Univ. of South Carolina, Charleston, SC (United States)); Price, W.A. (Princeton Research Center, Lawrenceville, NJ (United States))

    1993-09-01

    The release of polychlorinated biphenyls (PCBs) into the environment has caused public concern. PCBs are know known to be susceptible to biodegradation; PCBs in the Hudson river have been shown to be extensively dechlorinated, but the rate of dechlorination in anaerobic environments have been slow, over months or years. This study tested the effects of PCB concentration and sediment supplementation with 2,3,6-trichlorobiphenol, on the rate of PCB dechlorination and methanogenesis. The rates of meta dechlorination in sediment supplemented cultures were measured in the laboratory, including both the rate per bacterial cell and the rate of methanogenesis when dechlorination increases. 24 refs., 3 figs., 1 tab.

  4. A Chloroflexi bacterium dechlorinates polychlorinated biphenyls in marine sediments under in situ-like biogeochemical conditions.

    Science.gov (United States)

    Zanaroli, Giulio; Balloi, Annalisa; Negroni, Andrea; Borruso, Luigimaria; Daffonchio, Daniele; Fava, Fabio

    2012-03-30

    We investigated the reductive dechlorination of Aroclor 1254 PCBs by a coplanar PCB-dechlorinating microbial community enriched from an actual site contaminated marine sediment of the Venice lagoon in sterile slurry microcosms of the same sediment suspended in its site water, i.e., under biogeochemical conditions that closely mime those occurring in situ. The culture dechlorinated more than 75% of the penta- through hepta-chlorinated biphenyls to tri- and tetra-chlorinated congeners in 30 weeks. The dechlorination rate was reduced by the addition of H(2) and short chain fatty acids, which stimulated sulfate-reduction and methane production, and markedly increased by the presence of vancomycin or ampicillin. DGGE analysis of 16S rRNA genes on PCB-spiked and PCB-free cultures ruled out sulfate-reducing and methanogenic bacteria and revealed the presence of a single Chloroflexi phylotype closely related to the uncultured bacteria m-1 and SF1 associated to PCB dechlorination. These findings suggest that a single dechlorinator is responsible for the observed extensive dechlorination of Aroclor 1254 and that a Chloroflexi species similar to those already detected in freshwater and estuarine contaminated sediments mediates PCB dechlorination in the marine sediment adopted in this study under biogeochemical conditions resembling those occurring in situ in the Brentella Canal of Venice Lagoon.

  5. The impact of bioaugmentation on dechlorination kinetics and on microbial dechlorinating communities in subsurface clay till

    DEFF Research Database (Denmark)

    Bælum, Jacob; Scheutz, Charlotte; Chambon, Julie Claire Claudia

    2014-01-01

    A molecular study on how the abundance of the dechlorinating culture KB-1 affects dechlorination rates in clay till is presented. DNA extracts showed changes in abundance of specific dechlorinators as well as their functional genes. Independently of the KB-1 added, the microbial dechlorinator abu...

  6. Population dynamics of dechlorinators and factors affecting the level and products of PCB dechlorination in sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.S.; Sokol, R.C.; Liu, X.; Bethoney, C.M.; Rhee, G.Y. [State Univ. of New York and New York State Department of Health, Albany, NY (United States)

    1996-12-31

    Microbial dechlorination of polychlorinated biphenyls (PCBs) often stops although a significant number of removable chlorines remain. To determine the reason for the cessation, we investigated the limitation of organic carbon, PCB bioavailability, and inhibition by metabolic products. Enrichment with carbon sources did not induce additional chlorination, indicating the plateau was not due to depletion of organic carbon. The bioavailability was not limiting, since a subcritical micelle concentration of the surfactant, which enhanced desorption without inhibiting dechlorinating microorganisms, failed to lower the plateau. Neither was it due to accumulation of metabolites, since no additional dechlorination was detected when plateau sediments were incubated with fresh medium. Similarly, dechlorination was not inhibited in freshly spiked sediment slurries. Dechlorination ended up at the same level with nearly identical congener profiles, regardless of treatment. These results indicate that cessation of dechlorination was due to the accumulation of daughter congeners, which cannot be used as electron acceptors by microbes. To determine whether the decreasing availability affected the microorganisms, we determined the population dynamics of dechlorinators using the most probable number technique. The growth dynamics of the dechlorinators mirrored the time course of dechlorination. It started when the population increased by two orders of magnitude. Once dechlorination stopped the dechlorinating population also began to decrease. When dechlorinators were inoculated into PCB-free sediments, the population decreased over time. The decrease of the population as dechlorination ceased confirms that the diminishing availability of congeners was the reason for the incomplete dechlorination. Recent findings have shown that a second phase of dechlorination of certain congeners can occur after a long lag. 45 refs., 8 figs.

  7. Dechlorination of TCE with palladized iron

    Science.gov (United States)

    Fernando, Quintus; Muftikian, Rosy; Korte, Nic

    1997-01-01

    The present invention relates to various methods, such as an above-ground method and an in-ground method, of using a palladized iron bimetallic system for the dechlorination of chlorinated organic compounds from effluents containing the same. The use of palladized iron bimetallic system results in the dechlorination of the chlorinated organic compound into environmentally safe reaction products. The present invention also provides kits, devices, and other instruments that use the above-mentioned palladized iron bimetallic system for the dechlorination of chlorinated organic compounds.

  8. Reductive dechlorination of methoxychlor by bacterial species of environmental origin: evidence for primary biodegradation of methoxychlor in submerged environments.

    Science.gov (United States)

    Satsuma, Koji; Masuda, Minoru

    2012-02-29

    Methoxychlor [1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane] is an organochlorine insecticide that undergoes dechlorination in natural submerged environments. We investigated the ability to dechlorinate this compound in seven environmental bacterial species ( Aeromonas hydrophila , Enterobacter amnigenus , Klebsiella terrigena , Bacillus subtilis , Achromobacter xylosoxidans , Acinetobacter calcoaceticus , and Mycobacterium obuense ) and the enteric bacterium Escherichia coli as a positive control. In R2A broth at 25 °C under aerobic, static culture, all species except Ach. xylosoxidans were observed to convert methoxychlor to dechlorinated methoxychlor [1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane]. The medium was aerobic at first, but bacterial growth resulted in the consumption of oxygen and generated microaerobic and weakly reductive conditions. Replacement of the headspace of the culture tubes with nitrogen gas was found to decrease the dechlorination rate. Our findings suggest that extensive bacterial species ubiquitously inhabiting the subsurface water environment play an important role in the primary dechlorination of methoxychlor.

  9. MODELING THE ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE IN A GRANULAR GRAPHITE-PACKED REACTOR

    Science.gov (United States)

    A comprehensive reactor model was developed for the electrolytic dechlorination of trichloroethylene (TCE) at a granular-graphite cathode. The reactor model describes the dynamic processes of TCE dechlorination and adsorption, and the formation and dechlorination of all the major...

  10. EFFECTS OF REACTOR CONDITIONS ON ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODE.

    Science.gov (United States)

    Trichloroethylene (TCE) was electrochemically dechlorinated in aqueous environments using granular graphite cathode in a mixed reactor. Effects of pH, current, electrolyte type, and flow rate on TCE dechlorination rate were evaluated. TCE dechlorination rate constant and gas pr...

  11. DFT Studies of SN2 Dechlorination of Polychlorinated Biphenyls.

    Science.gov (United States)

    Krzemińska, Agnieszka; Paneth, Piotr

    2016-06-21

    Nucleophilic dechlorination of all 209 PCBs congeners by ethylene glycol anion has been studied theoretically at the DFT level. The obtained Gibbs free energies of activation are in the range 7-22 kcal/mol. The reaction Gibbs free energies indicate that all reactions are virtually irreversible. Due to geometric constrains these reactions undergo rather untypical attack with attacking oxygen atom being nearly perpendicular to the attacked C-Cl bond. The most prone to substitution are chlorine atoms that occupy ortho- (2, 2', 6, 6') positions. These results provide extensive information on the PEG/KOH dependent PCBs degradation. They can also be used in further developments of reaction class transition state theory (RC-TST) for description of complex reactive systems encountered for example in combustion processes.

  12. Dechlorination of hexachlorobenzene using ultrafine Ca-Fe composite oxides.

    Science.gov (United States)

    Ma, Xiaodong; Zheng, Minghui; Liu, Wenbin; Qian, Yong; Zhang, Bing; Liu, Wenxia

    2005-12-09

    Ca-Fe composite oxides with different Ca/Fe atomic ratios were synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy with elemental X-ray analysis (SEM-EDX) and inductively coupled plasma optical emission spectrometer (ICP-OES). Their dechlorination activities were evaluated using hexachlorobenzene (HCB) as a model compound. The results indicate that the dechlorination activity is related to the composition of metal oxides. Different compositions lead to the formation of different phases of Ca-Fe composite oxides. When Ca/Fe atomic ratio was 3.4, the dechlorination activity reached 97%, which was the highest in the dechlorination of HCB at 300 degrees C for 0.5 h. This may be related to the formation of Ca(2)Fe(2)O(5) phase and small agglomerate size of oxide crystal of about 1 microm. The effect of reaction time on HCB dechlorination and the pathway of dechlorination were investigated using the Ca-Fe composite oxide with the highest activity. It was found that hydrodechlorination took place in the destruction of HCB, the dechlorination efficiency is almost 100% after 2 h reaction. After reaction, quantitative measurement of chloride ion and qualitative analysis of CaCO(3) indicate besides hydrodechlorination, other degradation routes may be present. The mechanism of synergic dechlorination using Ca-Fe composite oxides was discussed.

  13. ELECTROCHEMICAL DECHLORINATION OF TRICHLOROETHYLENE USING GRANULAR-GRAPHITE ELECTRODES

    Science.gov (United States)

    Electrochemical dechlorination of TCE was conducted in a glass column using granular graphite as electrodes. A constant voltage of 15 volt was applied resulting in 60-62 mA of current. Approximately 4-6% of the TCE was dechlorinated. Among the reduced TCE, more than 95% was compl...

  14. Dechlorination of PCBs in the rhizosphere of switchgrass and poplar.

    Science.gov (United States)

    Meggo, Richard E; Schnoor, Jerald L; Hu, Dingfei

    2013-07-01

    Polychlorinated biphenyl (PCB) congeners (PCB 52, 77, and 153) singly and in mixture were spiked and aged in soil microcosms and subsequently planted with switchgrass (Panicum virgatum) or poplar (Populus deltoids x nigra DN34). The planted reactors showed significantly greater reductions in PCB parent compounds when compared to unplanted systems after 32 weeks. There was evidence of reductive dechlorination in both planted and unplanted systems, but the planted microcosms with fully developed roots and rhizospheres showed greater biotransformation than the unplanted reactors. These dechlorination products accounted for approximately all of the molar mass of parent compound lost. Based on the transformation products, reductive dechlorination pathways are proposed for rhizospheric biotransformation of PCB 52, 77, and 153. This is the first report of rhizosphere biotransformation pathways for reductive dechlorination in marginally aerobic, intermittently flooded soil as evidenced by a mass balance on transformation products.

  15. Dechlorination Technology Manual. Final report. [Utility cooling water discharge systems

    Energy Technology Data Exchange (ETDEWEB)

    Aschoff, A.F.; Chiesa, R.J.; Jacobs, M.H.; Lee, Y.H.; Mehta, S.C.; Meko, A.C.; Musil, R.R.; Sopocy, D.M.; Wilson, J.A.

    1984-11-01

    On November 19, 1982, the United States Environmental Protection Agency (EPA) promulgated regulations severely restricting chlorination practices as they relate to utility cooling water discharge systems. EPRI authorized the preparation of a manual on dechlorination technology to assist utilities in evaluating the various alternatives available to them to meet these new requirements. The Dechlorination Technology Manual emphasizes the engineering aspects involved in the selection and design of dechlorination systems. However, background information is included concerning chemistry, regulatory requirements, environmental considerations and aquatic impacts. There is also a brief discussion of the various alternatives to dechlorination. Case studies are given to acquaint the user with the use of the manual for the design of chlorination facilities given various site-related characteristics, such as salt versus fresh waters. Numerous graphs and tables are presented to facilitate the selection and design process. 207 references, 66 figures, 60 tables.

  16. Dechlorination by combined electrochemical reduction and oxidation

    Institute of Scientific and Technical Information of China (English)

    CONG Yan-qing; WU Zu-cheng; TAN Tian-en

    2005-01-01

    Chlorophenols are typical priority pollutants listed by USEPA (U.S. Environmental Protection Agency). The removal of chlorophenol could be carried out by a combination of electrochemical reduction and oxidation method. Results showed that it was feasible to degrade contaminants containing chlorine atoms by electrochemical reduction to form phenol, which was further degraded on the anode by electrochemical oxidation. Chlorophenol removal rate was more than 90% by the combined electrochemical reduction and oxidation at current of 6 mA and pH 6. The hydrogen atom is a powerful reducing agent that reductively dechlorinates chlorophenols. The instantaneous current efficiency was calculated and the results indicated that cathodic reduction was the main contributor to the degradation of chlorophenol.

  17. Reductive dechlorination of hexachlorocyclohexane (HCH) isomers in soil under anaerobic conditions

    NARCIS (Netherlands)

    Middeldorp, P.J.M.; Doesburg, van W.C.J.; Schraa, G.; Stams, A.J.M.

    2005-01-01

    The biological anaerobic reductive dechlorination of -hexachlorocyclohexane under methanogenic conditions was tested in a number of contaminated soil samples from two locations in the Netherlands. Soils from a heavily polluted location showed rapid dechlorination of -hexachlorocyclohexane to benzene

  18. Reductive dechlorination of hexachlorocyclohexane (HCH) isomers in soil under anaerobic conditions

    NARCIS (Netherlands)

    Middeldorp, P.J.M.; Doesburg, van W.C.J.; Schraa, G.; Stams, A.J.M.

    2005-01-01

    The biological anaerobic reductive dechlorination of -hexachlorocyclohexane under methanogenic conditions was tested in a number of contaminated soil samples from two locations in the Netherlands. Soils from a heavily polluted location showed rapid dechlorination of -hexachlorocyclohexane to benzene

  19. Review of reactive kinetic models describing reductive dechlorination of chlorinated ethenes in soil and groundwater

    DEFF Research Database (Denmark)

    Chambon, Julie Claire Claudia; Bjerg, Poul Løgstrup; Scheutz, Charlotte;

    2013-01-01

    Reductive dechlorination is a major degradation pathway of chlorinated ethenes in anaerobic subsurface environments, and reactive kinetic models describing the degradation process are needed in fate and transport models of these contaminants. However, reductive dechlorination is a complex biologi...

  20. IDENTIFICATION OF CHLOROMETHANE FORMATION PATHS DURING ELECTROCHEMICAL DECHLORINATION OF TCE USING GRAPHITE ELECTRODES

    Science.gov (United States)

    The purpose of this research is to investigate the formation of chloromethane during TCE dechlorination in a mixed electrochemical reactor using graphite electrodes. Chloromethane was the major chlorinated organic compound detected in previous dechlorination experiments. In order...

  1. Subculturing of a polychlorinated biphenyl-dechlorinating anaerobic enrichment on solid media

    Energy Technology Data Exchange (ETDEWEB)

    May, H.D.; Boyle, A.W.; Price, W.A. II.; Blake, C.K. (Celgene Corp., Warren, NJ (United States))

    1992-12-01

    An anaerobic culture capable of dechlorinating polychlorinated biphenyls was subcultured under strict anaerobic conditions on solid media containing sterilized river sediment. The dechlorination activity was transferred as a bacterial colony on a solid medium three times. After two transfers on solid medium, the culture was no longer methanogenic but still dechlorinated a mixture of tri- and tetrachlorobiphenyls. This demonstrates that anaerobic bacteria are responsible for the polychlorinated biphenyl dechlorination and can be grown without polychlorinated biphenyl on solid media.

  2. Reductive dechlorination of chlorinated ethenes by iron metal

    Energy Technology Data Exchange (ETDEWEB)

    Sivavec, T.M.; Horney, D.P. [GE Corp. Research and Development, Schenectady, NY (United States)

    1995-12-01

    Reduction of chlorinated ethenes in aqueous solution by iron metal was studied in batch and column systems under anaerobic and mildly aerobic conditions. The goal of this work was to gain a fundamental mechanistic understanding of the reaction chemistry and to determine the factors that affect dechlorination rate and long-term performance in groundwater treatment. Pseudo-first-order TCE, DCE and VC dechlorination rates and product mass balances (chloride ion and C2-C6 hydrocarbons) were measured for greater than twenty-five commercial iron metals. All experimental evidence was found to support a direct reduction mechanism in which electron transfer from Fe{sup o} to the adsorbed chloroethene occurs at the metal/water interface. XPS depth profile analysis was used to correlate Fe{sup o} surface concentration with observed dechlorination rates. A linear dependence of dechlorination rate on iron specific surface area was determined. Other factors that influence dechlorination rates will be discussed, including proton- and anion-promoted dissolution processes that remove surface iron oxides and yield new Fe{sup o} surfaces.

  3. Microbiome Dynamics of a Polychlorobiphenyl (PCB) Historically Contaminated Marine Sediment under Conditions Promoting Reductive Dechlorination

    Science.gov (United States)

    Matturro, Bruna; Ubaldi, Carla; Rossetti, Simona

    2016-01-01

    The toxicity of polychlorinated biphenyls (PCB) can be efficiently reduced in contaminated marine sediments through the reductive dechlorination (RD) process lead by anaerobic organohalide bacteria. Although the process has been extensively investigated on PCB-spiked sediments, the knowledge on the identity and metabolic potential of PCB-dechlorinating microorganisms in real contaminated matrix is still limited. Aim of this study was to explore the composition and the dynamics of the microbial communities of the marine sediment collected from one of the largest Sites of National Interest (SIN) in Italy (Mar Piccolo, Taranto) under conditions promoting the PCBs RD. A long-term microcosm study revealed that autochthonous bacteria were able to sustain the PCB dechlorination at a high extent and the successive addition of an external fermentable organic substrate (lactate) caused the further depletion of the high-chlorinated PCBs (up to 70%). Next Generation Sequencing was used to describe the core microbiome of the marine sediment and to follow the changes caused by the treatments. OTUs affiliated to sulfur-oxidizing ε-proteobacteria, Sulfurovum, and Sulfurimonas, were predominant in the original sediment and increased up to 60% of total OTUs after lactate addition. Other OTUs detected in the sediment were affiliated to sulfate reducing (δ-proteobacteria) and to organohalide respiring bacteria within Chloroflexi phylum mainly belonging to Dehalococcoidia class. Among others, Dehalococcoides mccartyi was enriched during the treatments even though the screening of the specific reductive dehalogenase genes revealed the occurrence of undescribed strains, which deserve further investigations. Overall, this study highlighted the potential of members of Dehalococcoidia class in reducing the contamination level of the marine sediment from Mar Piccolo with relevant implications on the selection of sustainable bioremediation strategies to clean-up the site.

  4. Polyphasic characterization of a PCP-to-phenol dechlorinating microbial community enriched from paddy soil

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Naoko [EcoTopia Science Institute, Nagoya University Nagoya 464-8603 (Japan)]. E-mail: ysd75@esi.nagoya-u.ac.jp; Yoshida, Yukina [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Handa, Yuko [Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kim, Hyo-Keun [Korea Ginseng and Tobacco Research Institute, Taejon 305-345 (Korea, Republic of); Ichihara, Shigeyuki [Faculty of Agriculture, Meijo University, Nagoya 468-8502 (Japan); Katayama, Arata [EcoTopia Science Institute, Nagoya University Nagoya 464-8603 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan)

    2007-08-01

    Dechlorination of PCP has been observed previously under anaerobic condition in paddy soil. However, there is poor information about the dechlorination pathway of PCP and the microbial community associated with the PCP dechlorination in paddy soil. In this study, an anaerobic microbial community dechlorinating PCP was enriched by serial transfers from a paddy soil using a medium containing PCP, lactate and the steam-sterilized paddy soil. The enriched microbial community dechlorinated PCP completely to phenol under the anaerobic condition by a dechlorinating pathway as follows; PCP {sup {yields}} 2,3,4,5-tetrachlorophenol {sup {yields}} 3,4,5-trichlorophenol {sup {yields}} 3,5-dichlorophenol {sup {yields}} 3-chlorophenol {sup {yields}} phenol. Intermediate products such as 3-chlorophenol were not accumulated, which were immediately dechlorinated to phenol. The enriched microbial community was characterized physiologically by testing the effects of electron donors and electron acceptors on the dechlorinating activity. The dechlorinating activity was promoted with lactate, pyruvate, and hydrogen as electron donors but not with acetate. Electron acceptors, nitrate and sulphate, inhibited the dechlorinating activity competitively but not iron (III). The microbial group associated with the anaerobic dechlorination was characterized by the effect of specific inhibitors on the PCP dechlorination. Effects of specific metabolic inhibitors and antibiotics indicated the involvement of Gram-positive spore-forming bacteria with the PCP dechlorinating activity, which was represented as bacteria of phylum Firmicutes. The structure of the microbial community was characterized by fluorescence in situ hybridization, quinone profiling, and PCR-DGGE (denaturing gel gradient electrophoresis). The combined results indicated the predominance of Clostridium species of phylum Firmicutes in the microbial community. Desulfitobacterium spp. known as anaerobic Gram-positive spore

  5. Studies on Dechlorination of DDT with Alkaline 2-propanol and Iron-Nickel (Fe-Ni) Catalyst.

    Science.gov (United States)

    Shareef, A.; Zaman, S. U.

    2009-05-01

    The Persistent Organic Pollutants (POPs) pesticides were previously extensively used in the cotton production and other agricultural activities in Pakistan and at least three thousand metric tons of obsolete pesticides have been stored under extreme hazardous conditions in more than thousand sites. Locally banned or severely restricted pesticides are easily available and DDT is continuously illegally imported and use in our country. Elimination of organochlorine pesticides (OCPs) waste has received considerable attention over the past two decades. Existing catalytic hydrodechlorinated techniques for disposing of OCPs are very costly due to the use of noble metals as catalysts. The aim of our study is to develop the cost effective and efficient method for the safe disposal of OCPs. This study is in continuation work on dechlorination of organochlorine pesticides with Fe-Ni catalyst in alkaline 2-propanol media. We turned our attention to the development of DDT disposal method for the third world countries. Herein, we report our first finding that in alkaline 2-propanol with Fe-Ni catalyst is an effective method for dechlorination of DDT. Catalytic dechlorination of DDT was carried out in an alkaline solution of NaOH and 2-propanol in the presence of catalyst at the temperature below 82 oC and end products were analyzed by using Gas Chromatography (GC-ECD) and Ion Chromatography (IC) techniques. Results obtained with initial concentration of DDT ranging between 10-100 μg/ml showed conversion of DDT to chlorine free product within 4 hrs.

  6. Direct electron transfer from electrode to electrochemically active bacteria in a bioelectrochemical dechlorination system.

    Science.gov (United States)

    Liu, Ding; Lei, Lecheng; Yang, Bin; Yu, Qingni; Li, Zhongjian

    2013-11-01

    Pentachlorophenol (PCP) was dechlorinated by electrochemically active bacteria using an electrode as the direct electron donor. Dechlorination efficiency and coulombic efficiency (CE) were investigated. When hydrogen evolution reaction was eliminated by controlling the potential, both dechlorination efficiency and CE increase as the potential decreases, which implied the dechlorination was stimulated by electric current rather than hydrogen gas. Further investigation of the cyclic voltammetry characterization of the medium revealed nearly no redox mediator secreted by the bacteria. Moreover, the comparison of dechlorination experiments carried out with filtered and unfiltered medium provided convincible evidence that the dominating electron transfer mechanism for the dechlorination is direct electron transfer. Additionally, 454 pyrosequencing technique was employed to gain a comprehensive understanding of the biocathodic microbial community. The results showed Proteobacteria, Bacteroidetes and Firmicutes were the three predominant groups. This paper demonstrated the direct electron transfer mechanism could be involved in PCP dechlorination with a biocathode. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Gratuitous dechlorination of chloroethanes by methanogenic granular sludge

    NARCIS (Netherlands)

    Eekert, van M.H.A.; Stams, A.J.M.; Field, J.A.; Schraa, G.

    1999-01-01

    The dechlorinating activity of a methanogenic granular sludge from a methanol-fed upflow anaerobic sludge blanket reactor was investigated with chlorinated ethanes. This unadapted methanogenic consortium degraded all chloroethanes tested. The product formation rates decreased with the number of chlo

  8. DDT, DDD, AND DDE DECHLORINATION BY ZERO-VALENT IRON

    Science.gov (United States)

    Traditionally, destruction of DDT [1,1,1-trichIoro-2,2-bis(p-chlorophenyl)ethane] for environmental remediation required high-energy processes such as incineration. Here, the capability of powdered zero-valent iron to dechlorinate DDT and related compounds at room tempera...

  9. The dechlorination of cyclodiene pesticides by methanogenic granular sludge

    NARCIS (Netherlands)

    Baczynski, T.H.; Grotenhuis, J.T.C.; Knipscheer, P.

    2004-01-01

    Cyclodiene pesticides: aldrin, isodrin, dieldrin and endrin were dechlorinated by methanogenic granular sludge in spiked batch tests. Initial pesticides concentration was 7 or 9 mg1(-1). Two monodechlorinated analogues were formed during the conversions of aldrin and isodrin. Dieldrin was

  10. Catalytic dechlorination of chlorobenzene in water by Pd/Fe bimetallic system

    Institute of Scientific and Technical Information of China (English)

    ZHOU Hong-yi; XU Xin-hua; WANG Da-hui

    2003-01-01

    Catalytic reductive dechlorination of monochlorobenzene(MCB) was carried out in the palladium/iron system. With low Pd loading(0.005%), 45% dechlorination efficiency was achieved within 5 h Pd as catalyst accelerated the reductive dechlorination reaction. Dechlorination mechanism and kinetics were discussed. The reaction took place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0071 min-1(KSA=8.0(10-3 L/(m2@h). The reduction product for MCB was benzene.

  11. Catalytic Dechlorination of Chlorobenzene in Water by Pd/Fe System

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Chlorobenzene was dechlorinated by Pd/Fe bimetallic system in water through catalytic reduction. The dechlorination rate increases with increase of bulk loading of Pd due to the increase of both the surface loading of the Pd and the total surface area. For conditions with 0.005% Pd/Fe, 45% dechlorination efficiency was achieved within 5 h. The dechlorinated reaction is believed to take place on the bimetal surface in a pseudo-first-order reaction, with the rate constant being 0.0043 min-1.

  12. Isolation of a bacterium that reductively dechlorinates tetrachloroethene to ethene

    Energy Technology Data Exchange (ETDEWEB)

    Maymo-Gatell, X.; Chien, Yueh-tyng; Zinder, S.H. [Cornell Univ., Ithaca, NY (United States)] [and others

    1997-06-06

    Tetrachloroethene is a prominent groundwater pollutant that can be reductively dechlorinated by mixed anaerobic microbial populations to the nontoxic product ethene. Strain 195, a coccoid bacterium that dechlorinates tetrachlorethene to ethene, was isolated and characterized. Growth of strain 195 with H{sub 2} and tetrachloroethene as the electron donor and acceptor pair required extracts from mixed microbial cultures. Growth of strain 195 was resistant to ampicillin and vancomycin; its cell wall did not react with a peptidoglycan-specific lectin and its ultrastructure resembled S-layers of Archaea. Analysis of the 16S ribosomal DNA sequence of strain 195 indicated that it is a eubacterium without close affiliation to any known groups. 24 refs., 4 figs., 1 tab.

  13. Reductive Dechlorination of p-Chlorophenol by Nanoscale Iron

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To investigate reductive dechlorination of 4-chlorophenol (4-CP) by nanoscale Fe0 under different conditions.Methods Nanoscale Fe0 was synthesized by using reductive method. 4-CP and its intermediate products were analyzed by HPLC. Chlorine ion was quantified with DX-100 ion chromatograph. Nano-iron particles were observed under a FEI Quanta 200 FEG environmental scanning electron microscope (ESEM).Results The size of the particles was in the range of 10-100 nm. The nano-iron particles could reduce 4-CP effectively. The initial concentration of 4-CP increased with the decrease of the relative degradation rate,whereas the reduced amount of 4-CP increased. Temperature could influence both the dechlorination rate and the reaction pathway. Moreover,the stability and durability of nanoscale Fe0 was evaluated through batch studies over extended periods of time.Conclusion The nanoscale Fe0 can be used for sustainable treatment of contaminants in groundwater.

  14. Reductive dechlorination of tetrachloroethylene (PCE) catalyzed by cyanocobalamin

    Energy Technology Data Exchange (ETDEWEB)

    Habeck, B.D.; Sublette, K.L. [Univ. of Tulsa, OK (United States)

    1995-12-31

    A biomimetic system has been developed for the reductive dechlorination of tetrachloroethylene (PCE). PCE was dechlorinated to trichloroethylene (TCE) and 1,2-dichloroethylene (DCE) in the presence of dithiothreitol or Ti (III) citrate and catalytic amounts of cyanocobalamin in both homogeneous reaction mixtures and packed bed reactor systems. In packed bed reactors with Ti (III) citrate as the reductant, PCE (0.18 mM) conversion averaged 55% at residence times of 1.75 and 3.5 h. The product distribution was 94% TCE and 6% DCE at the lower residence time. DCE formation increased to 45% at the higher residence time. No reduction of PCE was observed in the absence of cyanocobalamin. This system may be useful as a means of pretreatment of halogenated aliphatic hydrocarbons in advance of biological treatment.

  15. Guided cobalamin biosynthesis supports Dehalococcoides mccartyi reductive dechlorination activity

    Science.gov (United States)

    Yan, Jun; Im, Jeongdae; Yang, Yi; Löffler, Frank E.

    2013-01-01

    Dehalococcoides mccartyi strains are corrinoid-auxotrophic Bacteria and axenic cultures that require vitamin B12 (CN-Cbl) to conserve energy via organohalide respiration. Cultures of D. mccartyi strains BAV1, GT and FL2 grown with limiting amounts of 1 µg l−1 CN-Cbl quickly depleted CN-Cbl, and reductive dechlorination of polychlorinated ethenes was incomplete leading to vinyl chloride (VC) accumulation. In contrast, the same cultures amended with 25 µg l−1 CN-Cbl exhibited up to 2.3-fold higher dechlorination rates, 2.8–9.1-fold increased growth yields, and completely consumed growth-supporting chlorinated ethenes. To explore whether known cobamide-producing microbes supply Dehalococcoides with the required corrinoid cofactor, co-culture experiments were performed with the methanogen Methanosarcina barkeri strain Fusaro and two acetogens, Sporomusa ovata and Sporomusa sp. strain KB-1, as Dehalococcoides partner populations. During growth with H2/CO2, M. barkeri axenic cultures produced 4.2 ± 0.1 µg l−1 extracellular cobamide (factor III), whereas the Sporomusa cultures produced phenolyl- and p-cresolyl-cobamides. Neither factor III nor the phenolic cobamides supported Dehalococcoides reductive dechlorination activity suggesting that M. barkeri and the Sporomusa sp. cannot fulfil Dehalococcoides' nutritional requirements. Dehalococcoides dechlorination activity and growth occurred in M. barkeri and Sporomusa sp. co-cultures amended with 10 µM 5′,6′-dimethylbenzimidazole (DMB), indicating that a cobalamin is a preferred corrinoid cofactor of strains BAV1, GT and FL2 when grown with chlorinated ethenes as electron acceptors. Even though the methanogen and acetogen populations tested did not produce cobalamin, the addition of DMB enabled guided biosynthesis and generated a cobalamin that supported Dehalococcoides' activity and growth. Guided cobalamin biosynthesis may offer opportunities to sustain and enhance Dehalococcoides activity in contaminated

  16. Dechlorination of Aromatic Xenobiotic Compounds by Anaerobic Microorganisms

    Science.gov (United States)

    1988-07-01

    treatment. Furthermore, anaerobic processes can be more cost -effective than current technology. In our earlier work (References 2, 3), we screened more...radioactivity must be greater than can be accouted for by dechlorination of possible radioimpurities (( 1 percent). This means the samples must contain more...Wood Processing Industry." 1984. p. 668-676. In M.J. Klug and C.A. Reddy (eds.), Current Persctive Microbial Ecoloa . American Society for Microbiology

  17. Enhanced reductive dechlorination in columns treated with edible oil emulsion

    Science.gov (United States)

    Long, Cameron M.; Borden, Robert C.

    2006-09-01

    The effect of edible oil emulsion treatment on enhanced reductive dechlorination was evaluated in a 14 month laboratory column study. Experimental treatments included: (1) emulsified soybean oil and dilute HCl to inhibit biological activity; (2) emulsified oil only; (3) emulsified oil and anaerobic digester sludge; and (4) continuously feeding soluble substrate. A single application of emulsified oil was effective in generating strongly reducing, anaerobic conditions for over 14 months. PCE was rapidly reduced to cis-DCE in all three live columns. Bioaugmentation with a halorespiring enrichment culture resulted in complete dechlorination of PCE to ethene in the soluble substrate column (yeast extract and lactate). However, an additional treatment with a pulse of yeast extract and bioaugmentation culture was required to stimulate complete dechlorination in the emulsion treated columns. Once the dechlorinating population was established, the emulsion only column degraded PCE from 90-120 μM to below detection with concurrent ethene production in a 33 day contact time. The lower biodegradation rates in the emulsion treated columns compared to the soluble substrate column suggest that emulsified oil barriers may require a somewhat longer contact time for effective treatment. In the HCl inhibited column, partitioning of PCE to the retained oil substantially delayed PCE breakthrough. However, reduction of PCE to more soluble degradation products ( cis-DCE, VC and ethene) greatly reduced the impact of oil-water partitioning in live columns. There was only a small decline in the hydraulic conductivity ( K) of column #1 (low pH + emulsion, Kfinal/ Kinitial = 0.57) and column #2 (live + emulsion, Kfinal/ Kinitial = 0.73) indicating emulsion injection did not result in appreciable clogging of the clayey sand. However, K loss was greater in column #3 (sludge +emulsion, Kfinal/ Kinitial = 0.12) and column #4 (soluble substrate, Kfinal/ Kinitial = 0.03) indicating clogging due

  18. Metalloporphyrin solubility: a trigger for catalyzing reductive dechlorination of tetrachloroethylene.

    Science.gov (United States)

    Dror, Ishai; Schlautman, Mark A

    2004-02-01

    Metalloporphyrins are well known for their electron-transfer roles in many natural redox systems. In addition, several metalloporphyrins and related tetrapyrrole macrocycles complexed with various core metals have been shown to catalyze the reductive dechlorination of certain organic compounds, thus demonstrating the potential for using naturally occurring metalloporphyrins to attenuate toxic and persistent chlorinated organic pollutants in the environment. However, despite the great interest in reductive dechlorination reactions and the wide variety of natural and synthetic porphyrins currently available, only soluble porphyrins, which comprise a small fraction of this particular family of organic macrocycles, have been used as electron-transfer shuttles in these reactions. Results from the present study clearly demonstrate that metalloporphyrin solubility is a key factor in their ability to catalyze the reductive dechlorination of tetrachloroethylene and its daughter compounds. Additionally, we show that certain insoluble and nonreactive metalloporphyrins can be activated as catalysts merely by changing solution conditions to bring about their dissolution. Furthermore, once a metalloporphyrin is fully dissolved and activated, tetrachloroethylene transformation proceeds rapidly, giving nonchlorinated and less toxic alkenes as the major reaction products. Results from the present study suggest that if the right environmental conditions exist or can be created, specific metalloporphyrins may provide a solution for cleaning up sites that are contaminated with chlorinated organic pollutants.

  19. Effects of bioaugmentation on enhanced reductive dechlorination of 1,1,1-trichloroethane in groundwater - a comparison of three sites

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Durant, Neal D.; Broholm, Mette Martina

    2014-01-01

    , microcosms were amended with various concentrations of chloroethanes (TCA or monochloroethane [CA]) and/or chloroethenes (tetrachloroethene [PCE], trichloroethene [TCE], or 1,1-dichloroethene [1,1-DCE]). Results showed that combined electron donor addition and bioaugmentation stimulated dechlorination of TCA...... and 1,1-dichloroethane (1,1-DCA) to CA, and dechlorination of PCE, TCE, 1,1-DCE and cDCE to ethane. Dechlorination of CA was not observed. Bioaugmentation improved the rate and extent of TCA and 1,1-DCA dechlorination at two sites, but did not accelerate dechlorination at a third site where geochemical...... conditions were reducing and Dhc and Dhb were indigenous. TCA at initial concentrations of 5 mg/L inhibited (i.e., slowed the rate of) TCA dechlorination, TCE dechlorination, donor fermentation, and methanogenesis. 1 mg/L TCA did not inhibit dechlorination of TCA, TCE or cDCE. Moreover, complete...

  20. INFLUENCES OF PH AND CURRENT ON ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE AT A GRANULAR-GRAPHITE PACKED ELECTRODE

    Science.gov (United States)

    Electrolytic dechlorination using a granular-graphite packed cathode is an alternative method for the remediation of chlorinated organic compounds. Its effectiveness under various conditions needs experimental investigation. Dechlorination of trichloroethylene (TCE) was conducted...

  1. Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.

    Science.gov (United States)

    Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

    2015-02-01

    The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC

  2. Detection of sewage organic chlorination products that are resistant to dechlorination with sulfite

    Energy Technology Data Exchange (ETDEWEB)

    MacCrehan, W.A. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Analytical Chemistry Div.; Jensen, J.S.; Helz, G.R. [Univ. of Maryland, College Park, MD (United States). Dept. of Chemistry and Biochemistry

    1998-11-15

    Most of the 36 billion gal of treated sewage wastewater discharged daily into the environment in the United States is disinfected via chlorination. To minimize toxicity. dechlorination with sulfite or sulfur dioxide is often performed. Although dechlorination is considered instantaneous and complete, several studies have found residual toxicity of chlorinated/dechlorinated effluent to aquatic life. The authors investigated chlorination/dechlorination of the organic nitrogen components of sewage wastewater using both iodometric titration and a novel LC method. For LC, a postcolumn reaction with iodide rendered submicromolar chloramine concentrations detectable with amperometry. Using a gradient-elution LC separation, the retention and dechlorination behavior of a suite of model amines was determined, representing primary and secondary aliphatic, peptide, and protein-N. Chlorination/dechlorination experiments on freshly collected, tertiary-treated wastewater showed a fraction of the organic N-chloramines are dechlorinated slowly by sulfite with half-lives of >20 min. Chromatographic retention and kinetic behavior of the sewage N-chloramines was consistent with the behavior of the model peptides and proteins. Proteolytic hydrolysis markedly increased the peptide fraction observed upon chlorination of the wastewater. These results suggest that peptides and proteins contribute to slow dechlorination of sewage and may be a factor in the toxicity noted for chlorine-disinfected wastewater.

  3. An Experimental and Theoretical Approach to Visualize Dechlorinating Bacteria in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    McNab, Walt [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Salazar, Eddie [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jackson, Paul [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Detwiler, Russ [Univ. of California, Irvine, CA (United States)

    2010-03-25

    The goal of this study is to understand how anaerobic dechlorinating bacteria are distributed in porous media following injection, in the context of the issues listed above. To address this goal, a series of experiments were conducted involving KB-1, a commercial microbial consortium containing Dehalococcoides bacteria, the only genus of organisms known to completely dechlorinate TCE into the benign end product ethene.

  4. PALLADIUM-FACILITATED ELECTROLYTIC DECHLORINATION OF 2-CHLOROBIPHENYL USING A GRANULAR-GRAPHITE ELECTRODE.

    Science.gov (United States)

    Palladium-assisted electrocatalytic dechlorination of 2-chlorobiphenyl (2-Cl BP) in aqueous solutions was conducted in a membrane-separated electrochemical reactor with granular-graphite packed electrodes. The dechlorination took place at a granular-graphite cathode while Pd was ...

  5. Behavior and products of mechano-chemical dechlorination of polyvinyl chloride and poly (vinylidene chloride).

    Science.gov (United States)

    Xiao, Xiao; Zeng, Zigao; Xiao, Songwen

    2008-02-28

    The mechano-chemical (MC) dechlorination of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) was performed by mechanical milling PVC/PVDC powder with zinc powder in a planetary ball mill, and the products of dechlorination were characterized by Infrared spectra (IR), X-ray diffraction (XRD), Raman spectroscopy, gas chromatography-mass spectrometry (GC-MS), and 13C solid-state nuclear magnetic resonance (NMR). The experimental results show that PVC/PVDC can be easily dechlorinated by milling with zinc powder, and formed various kinds of inorganic and organic products. Inorganic compounds included Zn2OCl(2).2H2O, Zn5(OH)8Cl2.H2O etc., and organic products involved diamond-like carbon, carbyne fragment, polyacetylene etc. Organic products formed following the paths of dechlorination, dehydrochlorination, crosslink, and oxidation. The mechano-chemical dechlorination process of PVC/PVDC may be an effective approach for carbyne synthesizing in the appropriate condition.

  6. Effects of the nonionic surfactant tween 80 on microbial reductive dechlorination of chlorinated ethenes.

    Science.gov (United States)

    Amos, Benjamin K; Daprato, Rebecca C; Hughes, Joseph B; Pennell, Kurt D; Löffler, Frank E

    2007-03-01

    Recent field studies have indicated synergistic effects of coupling microbial reductive dechlorination with physicochemical remediation (e.g., surfactant flushing) of dense nonaqueous phase liquid (DNAPL) source zones. This study explored chlorinated ethene (e.g., tetrachloroethene [PCE]) dechlorination in the presence of 50-5000 mg/L Tween 80, a nonionic surfactant employed in source zone remediation. Tween 80 did not inhibit dechlorination by four pure PCE-to-cis-1,2-dichloroethene (cis-DCE) or PCE-to-trichloroethene (TCE) dechlorinating cultures. In contrast, cis-DCE-dechlorinating Dehalococcoides isolates (strain BAV1 and strain FL2) failed to dechlorinate in the presence of Tween 80. Bio-Dechlor INOCULUM (BDI), a PCE-to-ethene dechlorinating consortium, produced cis-DCE in the presence of Tween 80, further suggesting that Tween 80 inhibits dechlorination by Dehalococcoides organisms. Quantitative real-time PCR analysis applied to BDI revealed that the number of Dehalococcoides cells decayed exponentially (R(2) = 0.85) according to the Chick-Watson disinfection model (pseudo first-order decay rate of 0.13+/-0.02 day(-1)) from an initial value of 6.6 +/-1.5 x 10(8) to 1.3+/-0.8 x 10(5) per mL of culture after 58 days of exposure to 250 mg/L Tween 80. Although Tween 80 exposure prevented ethene formation and reduced Dehalococcoides cell numbers, Dehalococcoides organisms remained viable, and dechlorination activity pist cis-DCE was recovered following the removal of Tween 80. These findings suggest that sequential Tween 80 flushing followed by microbial reductive dechlorination is a promising strategy for remediation of chlorinated ethene-impacted source zones.

  7. Enhanced dechlorination of tetrachloroethylene by zerovalent silicon in the presence of polyethylene glycol under anoxic conditions.

    Science.gov (United States)

    Lee, Chun-Chi; Doong, Ruey-An

    2011-03-15

    The combination of zerovalent silicon (Si(0)) with polyethylene glycol (PEG) is a novel technique to enhance the dechlorination efficiency and rate of chlorinated hydrocarbons. In this study, the dechlorination of tetrachloroethylene (PCE) by Si(0) in the presence of various concentrations of PEG was investigated under anoxic conditions. Several surfactants including cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 were also selected for comparison. Addition of SDS and Tween 80 had little effect on the enhancement of PCE dechlorination, while CTAB and PEG significantly enhanced the dechlorination efficiency and rate of PCE by Si(0) under anoxic conditions. The Langmuir-Hinshelwood model was used to describe the dechlorination kinetics of PCE and could be simplified to pseudo-first-order kinetics at low PCE concentration. The rate constants (k(obs)) for PCE dechlorination were 0.21 and 0.36 h(-1) in the presence of CTAB and PEG, respectively. However, the reaction mechanisms for CTAB and PEG are different. CTAB could enhance the apparent water solubility of PCE in solution containing Si(0), leading to the enhancement of dechlorination efficiency and rate of PCE, while PEG prevented the formation of silicon dioxide, and significantly enhanced the dechlorination efficiency and rate of PCE at pH 8.3 ± 0.2. In addition, the dechlorination rate increased upon increasing PEG concentration and then leveled off to a plateau when the PEG concentration was higher than 0.2 μM. The k(obs) for PCE dechlorination by Si(0) in the presence of PEG was 106 times higher than that by Si(0) alone. Results obtained in this study would be helpful in facilitating the development of processes that could be useful for the enhanced degradation of cocontaminants by zerovalent silicon.

  8. Enhanced reductive dechlorination of polychlorinated biphenyl-contaminated soil by in-vessel anaerobic composting with zero-valent iron.

    Science.gov (United States)

    Long, Yu-Yang; Zhang, Chi; Du, Yao; Tao, Xiao-Qing; Shen, Dong-Sheng

    2014-03-01

    Anaerobic dechlorination is an effective degradation pathway for higher chlorinated polychlorinated biphenyls (PCBs). The enhanced reductive dechlorination of PCB-contaminated soil by anaerobic composting with zero-valent iron (ZVI) was studied, and preliminary reasons for the enhanced reductive dechlorination with ZVI were investigated. The results show that the addition of nanoscale ZVI can enhance dechlorination during in-vessel anaerobic composting. After 140 days, the average number of removed Cl per biphenyl with 10 mg g(-1) of added nanoscale ZVI was 0.63, enhancing the dechlorination by 34 % and improving the initial dechlorination speed. The ZVI enhances dechlorination by providing a suitable acid base environment, reducing volatile fatty acid inhibition and stimulating the microorganisms. The C/N ratios for treatments with the highest rate of ZVI addition were smaller than for the control, indicating that ZVI addition can promote compost maturity.

  9. Combination of aquifer thermal energy storage and enhanced bioremediation: resilience of reductive dechlorination to redox changes.

    Science.gov (United States)

    Ni, Zhuobiao; van Gaans, Pauline; Smit, Martijn; Rijnaarts, Huub; Grotenhuis, Tim

    2016-04-01

    To meet the demand for sustainable energy, aquifer thermal energy storage (ATES) is widely used in the subsurface in urban areas. However, contamination of groundwater, especially with chlorinated volatile organic compounds (CVOCs), is often being encountered. This is commonly seen as an impediment to ATES implementation, although more recently, combining ATES and enhanced bioremediation of CVOCs has been proposed. Issues to be addressed are the high water flow velocities and potential periodic redox fluctuation that accompany ATES. A column study was performed, at a high water flow velocity of 2 m/h, simulating possible changes in subsurface redox conditions due to ATES operation by serial additions of lactate and nitrate. The impacts of redox changes on reductive dechlorination as well as the microbial response of Dehalococcoides (DHC) were evaluated. The results showed that, upon lactate addition, reductive dechlorination proceeded well and complete dechlorination from cis-DCE to ethene was achieved. Upon subsequent nitrate addition, reductive dechlorination immediately ceased. Disruption of microorganisms' retention was also immediate and possibly detached DHC which preferred attaching to the soil matrix under biostimulation conditions. Initially, recovery of dechlorination was possible but required bioaugmentation and nutrient amendment in addition to lactate dosing. Repeated interruption of dechlorination and DHC activity by nitrate dosing appeared to be less easily reversible requiring more efforts for regenerating dechlorination. Overall, our results indicate that the microbial resilience of DHC in biosimulated ATES conditions is sensitive to redox fluctuations. Hence, combining ATES with bioremediation requires dedicated operation and monitoring on the aquifer geochemical conditions.

  10. Sulfentrazone dechlorination by iron-nickel bimetallic nanoparticles.

    Science.gov (United States)

    Nascimento, Mayra A; Lopes, Renata P; Cruz, Jean C; Silva, Antônio A; Lima, Claudio F

    2016-04-01

    The sulfentrazone dechlorination using bimetallic nanoparticles of Fe/Ni was studied. Different variables that could influence the sulfentrazone conversion were investigated, such as nitrogen atmosphere, pH and dosage of the nanoparticles and initial concentration of sulfentrazone. The best results were obtained using controlled pH (pH 4.0) and 1.0 g L(-1) of nanomaterials, resulting in 100 % conversion in only 30 min. Kinetic studies were also conducted, evaluating the influence of different nanoparticle dosages (1.0 to 4.0 g L(-1)), system temperatures (20 to 35 °C) and nickel levels in the composition of the nanomaterials (0.025 to 0.10 gNi/gFe). The mechanism of sulfentrazone conversion has changed due a direct reduction on the catalytic activity sites and indirect reduction by atomic hydrogen. Both mechanisms have followed pseudo-first order models. The conversion rate improved when the dosage of the nanomaterials, system temperature and nickel content in the composition of the nanocomposites were increased. Finally, the conversion products were elucidated by mass spectrometry and toxicity assays were performed using Daphnia Similis. The results showed that the dechlorination product is less toxic than sulfentrazone. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Optimization of electrochemical dechlorination of trichloroethylene in reducing electrolytes.

    Science.gov (United States)

    Mao, Xuhui; Ciblak, Ali; Baek, Kitae; Amiri, Mohammad; Loch-Caruso, Rita; Alshawabkeh, Akram N

    2012-04-15

    Electrochemical dechlorination of trichloroethylene (TCE) in aqueous solution is investigated in a closed, liquid-recirculation system. The anodic reaction of cast iron generates ferrous species, creating a chemically reducing electrolyte (negative ORP value). The reduction of TCE on the cathode surface is enhanced under this reducing electrolyte because of the absence of electron competition. In the presence of the iron anode, the performances of different cathodes are compared in a recirculated electrolysis system. The copper foam shows superior capability for dechlorination of aqueous TCE. Electrolysis by cast iron anode and copper foam cathode is further optimized though a multivariable experimental design and analysis. The conductivity of the electrolyte is identified as an important factor for both final elimination efficiency (FEE) of TCE and specific energy consumption. The copper foam electrode exhibits high TCE elimination efficiency in a wide range of initial TCE concentration. Under coulostatic conditions, the optimal conditions to achieve the highest FEE are 9.525 mm thick copper foam electrode, 40 mA current and 0.042 mol L(-1) Na(2)SO(4). This novel electrolysis system is proposed to remediate groundwater contaminated by chlorinated organic solvents, or as an improved iron electrocoagulation process capable of treating the wastewater co-contaminated with chlorinated compounds.

  12. Chlorination and dechlorination rates in a forest soil — A combined modelling and experimental approach

    Energy Technology Data Exchange (ETDEWEB)

    Montelius, Malin, E-mail: malin.montelius@liu.se [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden); Svensson, Teresia [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden); Lourino-Cabana, Beatriz [EDF, Laboratoire National d' Hydraulique et Environnement, 78401 Chatou (France); Thiry, Yves [Andra, Research and Development Division, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex (France); Bastviken, David [Department of Thematic Studies — Environmental Change, Linköping University, 581 83 Linköping (Sweden)

    2016-06-01

    Much of the total pool of chlorine (Cl) in soil consists of naturally produced organic chlorine (Cl{sub org}). The chlorination of bulk organic matter at substantial rates has been experimentally confirmed in various soil types. The subsequent fates of Cl{sub org} are important for ecosystem Cl cycling and residence times. As most previous research into dechlorination in soils has examined either single substances or specific groups of compounds, we lack information about overall bulk dechlorination rates. Here we assessed bulk organic matter chlorination and dechlorination rates in coniferous forest soil based on a radiotracer experiment conducted under various environmental conditions (additional water, labile organic matter, and ammonium nitrate). Experiment results were used to develop a model to estimate specific chlorination (i.e., fraction of Cl{sup −} transformed to Cl{sub org} per time unit) and specific dechlorination (i.e., fraction of Cl{sub org} transformed to Cl{sup −} per time unit) rates. The results indicate that chlorination and dechlorination occurred simultaneously under all tested environmental conditions. Specific chlorination rates ranged from 0.0005 to 0.01 d{sup −1} and were hampered by nitrogen fertilization but were otherwise similar among the treatments. Specific dechlorination rates were 0.01–0.03 d{sup −1} and were similar among all treatments. This study finds that soil Cl{sub org} levels result from a dynamic equilibrium between the chlorination and rapid dechlorination of some Cl{sub org} compounds, while another Cl{sub org} pool is dechlorinated more slowly. Altogether, this study demonstrates a highly active Cl cycling in soils. - Highlights: • Chlorination and dechlorination rates in soil were revealed by a radiotracer method. • Chlorination was hampered by nitrogen addition. • Both Cl{sup −} and many Cl{sub org} compounds are highly reactive in soils. • Some formed Cl{sub org} seem to be refractory.

  13. Microbial dechlorination activity during and after chemical oxidant treatment

    Energy Technology Data Exchange (ETDEWEB)

    Doğan-Subaşı, Eylem [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium); Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000 Gent (Belgium); Bastiaens, Leen, E-mail: leen.bastiaens@vito.be [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium); Boon, Nico [Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000 Gent (Belgium); Dejonghe, Winnie [Flemish Institute for Technological Research (VITO), Separation and Conversion Technology, Boeretang 200, 2400 Mol (Belgium)

    2013-11-15

    Highlights: • Combined treatment was possible below 0.5 g/L of KMnO{sub 4} and 1 g/L of Na{sub 2}S{sub 2}O{sub 8}. • By-products SO{sub 4}{sup 2−} and MnO{sub 2(s)} had inhibitory effects on dehalogenating bacteria. • Oxidation reduction potential (ORP) was identified as a crucial parameter for recovery of oxidant exposed cells. • Bioaugmentation is a necessity at 0.5 g/L of KMnO{sub 4} and 1 g/L of Na{sub 2}S{sub 2}O{sub 8} and above. -- Abstract: Potassium permanganate (PM) and sodium persulfate (PS) are used in soil remediation, however, their compatibility with a coinciding or subsequent biotreatment is poorly understood. In this study, different concentrations of PM (0.005–2 g/L) and PS (0.01–4.52 g/L) were applied and their effects on the abundance, activity, and reactivation potential of a dechlorinating enrichment culture were investigated. Expression of the tceA, vcrA and 16S rRNA genes of Dehalococcoides spp. were detected at 0.005–0.01 g/L PM and 0.01–0.02 g/L PS. However, with 0.5–2 g/L PM and 1.13–4.52 g/L PS no gene expression was recorded, neither were indicator molecules for total cell activity (Adenosine triphosphate, ATP) detected. Dilution did not promote the reactivation of the microbial cells when the redox potential was above −100 mV. Similarly, inoculated cells did not dechlorinate trichloroethene (TCE) above −100 mV. When the redox potential was decreased to −300 mV and the reactors were bioaugmented for a second time, dechlorination activity recovered, but only in the reactors with 1.13 and 2.26 g/L PS. In conclusion, our results show that chemical oxidants can be combined with a biotreatment at concentrations below 0.5 g/L PM and 1 g/L PS.

  14. Dechlorination of DDT, DDD and DDE in soil (slurry) phase using magnesium/palladium system.

    Science.gov (United States)

    Gautam, Sumit Kumar; Suresh, Sumathi

    2006-12-01

    Mg0/Pd4+ was able to dechlorinate >99% of extractable DDT (initial concentration of 10 mg DDT kg(-1) of soil) and >90% of extractable DDT (initial concentration of 50 mg DDT kg(-1) of soil) in soil slurry. Mg0/Pd4+ was also found to be effective in dechlorinating of 50 mg kg(-1) DDD and DDE, in soil aged for varying time periods. GC-MS analyses revealed the formation of 1,1-diphenylethane as an end product from DDT, DDE and DDD. To the best of our knowledge this is the first report describing the application Mg0/Pd4+ system for remediation of DDT, DDD and DDE contaminated soil. We conclude that reductive dechlorination reaction catalyzed by Mg0/Pd4+ may be a promising system to remediate soil contaminated with DDT and its dechlorinated products such as DDD and DDE.

  15. Effects of different electron donor feeding patterns on TCE reductive dechlorination performance.

    Science.gov (United States)

    Panagiotakis, I; Antoniou, K; Mamais, D; Pantazidou, M

    2015-03-01

    This study investigates how the feeding pattern of e(-) donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e(-) donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e(-) accepting process in all experiments, regardless the e(-) donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dechlorination and reduce methanogenic activity.

  16. Dechlorination of polychlorinated biphenyl-contaminated soil via anaerobic composting with pig manure.

    Science.gov (United States)

    Zhang, Chi; Du, Yao; Tao, Xiao-Qing; Zhang, Kun; Shen, Dong-Sheng; Long, Yu-Yang

    2013-10-15

    Anaerobic dechlorination is an effective degradation pathway of higher chlorinated polychlorinated biphenyls (PCBs). The efficiency of anaerobic composting remediation of PCB-contaminated soil using pig manure was determined. The results show that the dechlorination of PCB-contaminated soil via anaerobic composting with pig manure is feasible. PCB concentration is the most critical factor. Elevated PCB concentrations can inhibit dechlorination but does not disrupt the anaerobic fermentation process. At 1 mg kg(-1) PCBs, the degradation rate of five or more chlorinated biphenyls is 43.8%. The highest dechlorination performance in this experiment was obtained when the soil-to-organic waste ratio, carbon-to-nitrogen ratio, moisture content, and PCB concentration were 2:3, 20, 60%, and 1 mg kg(-1), respectively.

  17. Enhanced reductive dechlorination of PCE DNAPL with TBOS as a slow-release electron donor

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Seungho, E-mail: seunghoyu68@gmail.com [Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup, Jeonbuk 580-185 (Korea, Republic of); Semprini, Lewis [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR 97331 (United States)

    2009-08-15

    Tetrabutoxysilane (TBOS), which yields 1-butanol upon abiotic hydrolysis, was evaluated as a slow-release substrate for the reductive dechlorination of tetrachloroethylene (PCE) as a dense non-aqueous-phase liquid (DNAPL). Dechlorination was achieved using an anaerobic binary mixed (BM) culture, which consisted of the Pt. Mugu (PM) and the Evanite (EV) mixed cultures. In batch reactor experiments, TBOS was mixed with PCE DNAPL to achieve different PCE mol fractions (PCE mol/(PCE mol + TBOS mol)), and different PCE aqueous concentrations based on Raoult's Law. The reductive dechlorination activity was determined based on the amount of chloride ions released and the mass balances of the transformation products formed. The mass balances of the total chlorinated aliphatic hydrocarbons (CAHs) between water, NAPL and gas phases were performed using independently measured NAPL/water partition coefficients. The amounts of chloride released (directly measured in aqueous samples) agreed with the total chloride produced based on the mass balances. The abiotic rates of TBOS hydrolysis were first-order with respect to TBOS NAPL concentration. A higher electron transfer efficiency to dechlorination was correlated with lower rates of TBOS hydrolysis. The total amounts of PCE DNAPL and TBOS were important factors for the reductive dechlorination of PCE. The dechlorination activity was suppressed at high NAPL concentrations. Direct contact of the PCE/TBOS NAPL mixture may have caused toxicity to the dechlorinating bacteria. Decreases in pH likely lowered the microbial activity for reductive dechlorination due to the accumulation of acetate and/or butyrate. These studies showed the potential of TBOS as a slow-release substrate for enhancing bioremediation of DNAPL contaminated sites.

  18. Graphene oxide-mediated rapid dechlorination of carbon tetrachloride by green rust

    DEFF Research Database (Denmark)

    Huang, Li-Zhi; Hansen, Hans Christian B.; Daasbjerg, Kim

    2017-01-01

    Graphene-based nanomaterials can mediate environmentally relevant abiotic redox reactions of chlorinated aliphatic hydrocarbons. In this study as low amounts as ∼0.007 % of graphene oxide (GO) was found to catalyze the reduction of carbon tetrachloride by layered Fe(II)-Fe(III) hydroxide (Green....... This study indicates that traces of graphene oxide can affect reaction pathways as well as kinetics for dechlorination processes in anoxic sediments by facilitating a partial dechlorination....

  19. Enhanced reductive dechlorination in clay till contaminated with chlorinated solvents

    DEFF Research Database (Denmark)

    Damgaard, Ida

    Chlorinated solvents are among the most frequently found contaminants in groundwater. In fractured media, chlorinated ethenes and ethanes are transported downwards through preferential pathways with subsequent diffusion into the sediment matrix. Due to slow back diffusion it can serve as a long...... term secondary source that can leach to the underlying aquifer. As some of the chlorinated solvents and their degradation products are toxic and carcinogenic, remediation technologies applicable in low permeability settings are needed. Enhanced reductive dechlorination (ERD) has been proven efficient...... and ethanes in clay till (Vadsbyvej) revealed a very complex system where diffusion, biotic and abiotic degradation processes occurred simultaneously. High resolution sub sampling with combined use of chemical analysis, molecular microbial tools and CSIA was necessary to identify both biotic and abiotic...

  20. Reductive dechlorination of 2,4-dichlorophenol using nanoscale Fe0: influencing factors and possible mechanism

    Institute of Scientific and Technical Information of China (English)

    CHENG Rong; WANG JianLong; ZHANG WeiXian

    2007-01-01

    Nanoscale Fe0 was synthesized through a reductive method in this paper. The experiments were performed to investigate the reduction of 2,4-dichlorophenol (2,4-DCP) by nanoscale Fe0 under different conditions. The pathways for the reduction of 2,4-DCP by nanoscale Fe0 were discussed. Batch studies demonstrated that the mechanism includes adsorption, dechlorination and cleavage of the benzene ring. Dechlorination, which occurs after 2,4-DCP molecule is adsorbed on the interface of Fe particle, is an interfacial reaction. One or two chlorine atom can be removed from 2,4-DCP to form 2-chlorophenol, 4-chlorophenol or phenol. As the concentration of 2,4-DCP increased, the relative dechlorination ratio decreased. However, the reduced quantities of 2,4-DCP increased. Temperature can influence dechlorination rate and pathway. Dechlorination is prior to cleavage of the benzene ring at a higher temperature, but at a lower temperature, adsorption may be the main pathway, and cleavage of the benzene ring may be prior to dechlorination.

  1. Reductive dechlorination of 2,4-dichlorophenol using nanoscale Fe~0:influencing factors and possible mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nanoscale Fe0 was synthesized through a reductive method in this paper. The experiments were per-formed to investigate the reduction of 2,4-dichlorophenol (2,4-DCP) by nanoscale Fe0 under different conditions. The pathways for the reduction of 2,4-DCP by nanoscale Fe0 were discussed. Batch studies demonstrated that the mechanism includes adsorption, dechlorination and cleavage of the benzene ring. Dechlorination, which occurs after 2,4-DCP molecule is adsorbed on the interface of Fe particle, is an interfacial reaction. One or two chlorine atom can be removed from 2,4-DCP to form 2-chlorophenol, 4-chlorophenol or phenol. As the concentration of 2,4-DCP increased, the relative dechlorination ratio decreased. However, the reduced quantities of 2,4-DCP increased. Temperature can influence dechlo-rination rate and pathway. Dechlorination is prior to cleavage of the benzene ring at a higher tempera-ture, but at a lower temperature, adsorption may be the main pathway, and cleavage of the benzene ring may be prior to dechlorination.

  2. Dechlorination of polychlorinated biphenyls in industrial transformer oil by radiolytic and photolytic methods.

    Science.gov (United States)

    Jones, Cynthia G; Silverman, Joseph; Al-Sheikhly, Mohamad; Neta, Pedatsur; Poster, Dianne L

    2003-12-15

    Used electrical transformer oils containing low or high concentrations of polychlorinated biphenyls (PCBs) were treated using electron, gamma, and ultraviolet radiation, and the conditions for complete dechlorination were developed. Dechlorination was determined by analysis of the inorganic chloride formed and the concentrations of remaining PCBs. Transformer oil containing approximately 95 microg g(-1) PCB (approximately 3.5 mmol L(-1) Cl) is completely dechlorinated by irradiation with 600 kGy after the addition of 10% triethylamine (TEA). Transformer oil containing >800,000 microg g(-1) PCB (17.7 mol L(-1) Cl) requires an additional solvent to prevent solidification. When this oil is diluted with 2-propanol (2-PrOH) and TEA (v/v/v, 1/79/20), complete dechlorination is achieved with a dose of 2500 kGy. Ultraviolet photolysis of the same oil/2-PrOH/TEA solutions led to 90% dechlorination after exposure for 120 h in our experimental setup. Such yields were obtained by radiolysis with a dose of 2000 kGy (300 h in our Gammacell). Replacing TEA with KOH in 2-PrOH solutions greatly increases the yield of dechlorination in both the radiolytic and the photolytic experiments, demonstrating that a chain reaction plays a role in both of these treatment methods and suggesting that both methods deserve further consideration for large-scale application.

  3. Dechlorination of chlorinated hydrocarbons by bimetallic Ni/Fe immobilized on polyethylene glycol-grafted microfiltration membranes under anoxic conditions.

    Science.gov (United States)

    Parshetti, Ganesh K; Doong, Ruey-an

    2012-01-01

    In this study, the dechlorination of chlorinated hydrocarbons including trichloroethylene (TCE), tetrachloroethylene (PCE) and carbon tetrachloride (CT) by bimetallic Ni/Fe nanoparticles immobilized on four different membranes was investigated under anoxic conditions. Effects of several parameters including the nature of membrane, initial concentration, pH value, and reaction temperature on the dechlorination efficiency were examined. The scanning electron microscopic images showed that the Ni/Fe nanoparticles were successfully immobilized inside the four membranes using polyethylene glycol as the cross-linker. The agglomeration of Ni/Fe were observed in poly(vinylidene fluoride), Millex GS and mixed cellulose ester membranes, while a relatively uniform distribution of Ni/Fe was found in nylon-66 membrane because of its hydrophilic nature. The immobilized Ni/Fe nanoparticles exhibited good reactivity towards the dechlorination of chlorinated hydrocarbons, and the pseudo-first-order rate constant for TCE dechlorination by Ni/Fe in nylon-66 were 3.7-11.7 times higher than those in other membranes. In addition, the dechlorination efficiency of chlorinated hydrocarbons followed the order TCE>PCE>CT. Ethane was the only end product for TCE and PCE dechlorination, while dichloromethane and methane were found to be the major products for CT dechlorination, clearly indicating the involvement of reactive hydrogen species in dechlorination. In addition, the initial rate constant for TCE dechlorination increased upon increasing initial TCE concentrations and the activation energy for TCE dechlorination by immobilized Ni/Fe was 34.9 kJ mol(-1), showing that the dechlorination of TCE by membrane-supported Ni/Fe nanoparticles is a surface-mediated reaction.

  4. Complete dechlorination of DDE/DDD using magnesium/palladium system.

    Science.gov (United States)

    Gautam, Sumit Kumar; Suresh, Sumathi

    2007-04-01

    Kinetic studies on the dechlorination of 1,1-dichloro-2,2 bis (4,-chlorophenyl) ethane (DDD) and 1,1,dichloro-2,2 bis (4,-chlorophenyl) ethylene (DDE) in 0.05% biosurfactant revealed that the reaction follows second-order kinetics. The rate of reaction was dependent on the presence of acid, initial concentrations of the target compound, and zerovalent magnesium/tetravalent palladium. Gas chromatography-mass spectrometry analyses of DDE dechlorination revealed the formation of a completely dechlorinated hydrocarbon skeleton, with diphenylethane as the end product, thereby implying the removal of all four chlorine atoms of DDE. In the case of DDD, we identified two partially dechlorinated intermediates [namely, 1,1-dichloro-2, 2 bis (phenyl) ethane and 1, chloro-2, 2 bis (phenyl) ethane] and diphenylethane as the end product. On the basis of products formed from DDD dehalogenation, we propose the removal of aryl chlorine atoms as a first step. Our investigation reveals that biosurfactant may be an attractive solubilizing agent for DDT and its residues. The magnesium/palladium system is a promising option because of its high reactivity and ability to achieve complete dechlorination of DDE and DDD.

  5. [Effect of composting organic fertilizer supplies on hexachlorobenzene dechlorination in paddy soils].

    Science.gov (United States)

    Liu, Cui-Ying; Jiang, Xin

    2013-04-01

    A rice pot experiment was conducted in two soils, Hydragric Acrisols (Ac) and Gleyi-Stagnic Anthrosols (An). Three treatments including control and additions of 1% or 2% composting organic fertilizer were designed for each soil. The objective of this research was to evaluate the reductive dechlorination of hexachlorobenzene (HCB) as affected by organic fertilizer supplies in planted paddy soils, and to analyze the relationship between methane production and HCB dechlorination. The results showed that the HCB residues were decreased by 28.6%-30.1% of the initial amounts in Ac, and 47.3% -61.0% in An after 18 weeks of experiment. The amount of HCB and its metabolite uptake by rice plants was only a few thousandths of the initial HCB amount in soils. The main product of HCB dechlorination was pentachlorobenzene (PeCB). The rates of HCB dechlorination in An were higher than those in Ac, which was mainly attributed to the higher pH and dissolved organic carbon (DOC) content of An. The applications of both 1% and 2% composting organic fertilizer showed significant inhibition on PeCB production after the 6th and 10th week in Ac and An, respectively. In both tested soils, no significant difference of PeCB production rates was observed between the applications of 1% and 2% composting organic fertilizer. The role of methanogenic bacteria in HCB dechlorination was condition-dependent.

  6. Mixtures of Vegetable Oil and Xanthan as a Substrate for Biological Dechlorination

    Science.gov (United States)

    Zhong, L.; Macbeth, T.; Truex, M. J.; Yan, X.

    2012-12-01

    In situ anaerobic biological processes are widely applied for dechlorination of chlorinated solvents in groundwater. A wide range of organic substrates have been tested and applied to support the dechlorination processes. Key factors considered in substrate selection are the induced dechlorination kinetics, geochemical impacts such as pH decreases, longevity of the substrate, and ability to distribute the substrate in the subsurface. Vegetable oils are a promising substrate and have been shown to induce effective dechlorination, have limited geochemical impacts, and good longevity. Distribution of vegetable oil in the subsurface, because it is a non-aqueous phase material, has typically been addressed by creating emulsified oil solutions. In this study, inexpensive waste vegetable oils were tested in laboratory microcosm experiments and induced dechlorination reactions with minor geochemical impacts and good longevity. Additional testing showed that mixtures of waste vegetable oil and Xanthan, a biopolymer with shear-thinning properties, produced stable suspensions of the oil as micron-scale droplets. The mixture rheology retains shear-thinning properties that would facilitate improved uniformity of substrate distribution in heterogeneous aquifers. Soil column tests were conducted as a first step in quantifying the transport of the oil droplets in the mixture through porous media. Results show that the mixture of vegetable oil and Xanthan is a potential substrate for supporting in situ anaerobic bioremediation for some subsurface settings.

  7. Dechlorination and decomposition of chloroform induced by glow discharge plasma in an aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongjun, E-mail: lyjglow@sohu.com [College of Environmental Science & Engineering, Dalian Maritime University, Dalian 116026 (China); Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States); Crittenden, John C. [Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States); Wang, Lei [College of Environmental Science & Engineering, Xiamen University of Technology, Xiamen 361024 (China); Liu, Panliang [Brook Byers Institute for Sustainable Systems, Georgia Institute of Technology, Atlanta 30332 (United States)

    2016-05-05

    Highlights: • Hydrated electrons played an important role for chloroform decomposition. • Oxygen enhanced hydrolyses are critical for the chloroform mineralization. • Energy efficiency of GDP is higher than those of the typical competitive processes. - Abstract: In this study, efficient dechlorination and decomposition of chloroform (CF) induced by glow discharge plasma (GDP) in contact with a sodium sulfate solution was investigated. Intermediate byproducts were determined by ionic chromatography and headspace gas chromatography, respectively. Results showed that CF can be effectively dechlorinated and decomposed under the action of GDP. Both removal and dechlorination of CF increased with increasing pH and with addition of hydroxyl radical scavengers to the solution. Addition of H{sub 2}O{sub 2} to the solution slightly decreased the CF removal. Formic acid, oxalic acid and dichloromethane were determined as the major intermediate byproducts. Final products were carbon dioxide and hydrochloric acid. Hydrated electrons were the most likely active species responsible for initiation of the dechlorination, and hydroxyl radicals may be the ones for the oxidation of the organic intermediate byproducts. Hydrolyses of the chloromethyl radicals contributed much in the mineralization of the organic chlorine. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts.

  8. Behavior and products of mechano-chemical dechlorination of polyvinyl chloride and poly (vinylidene chloride)

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Xiao [College of Metallurgical Science and Engineering, Central South University, Changsha 410083 (China); Changsha Research Institute of Mining and Metallurgy, Changsha 410012 (China); Zeng Zigao [Changsha Research Institute of Mining and Metallurgy, Changsha 410012 (China); Xiao Songwen [Changsha Research Institute of Mining and Metallurgy, Changsha 410012 (China)], E-mail: swinxiao@yahoo.com.cn

    2008-02-28

    The mechano-chemical (MC) dechlorination of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) was performed by mechanical milling PVC/PVDC powder with zinc powder in a planetary ball mill, and the products of dechlorination were characterized by Infrared spectra (IR), X-ray diffraction (XRD), Raman spectroscopy, gas chromatography-mass spectrometry (GC-MS), and {sup 13}C solid-state nuclear magnetic resonance (NMR). The experimental results show that PVC/PVDC can be easily dechlorinated by milling with zinc powder, and formed various kinds of inorganic and organic products. Inorganic compounds included Zn{sub 2}OCl{sub 2}.2H{sub 2}O, Zn{sub 5}(OH){sub 8}Cl{sub 2}.H{sub 2}O etc., and organic products involved diamond-like carbon, carbyne fragment, polyacetylene etc. Organic products formed following the paths of dechlorination, dehydrochlorination, crosslink, and oxidation. The mechano-chemical dechlorination process of PVC/PVDC may be an effective approach for carbyne synthesizing in the appropriate condition.

  9. Visualizing microbial dechlorination processes in underground ecosystem by statistical correlation and network analysis approach.

    Science.gov (United States)

    Yamazawa, Akira; Date, Yasuhiro; Ito, Keijiro; Kikuchi, Jun

    2014-03-01

    Microbial ecosystems are typified by diverse microbial interactions and competition. Consequently, the microbial networks and metabolic dynamics of bioprocesses catalyzed by these ecosystems are highly complex, and their visualization is regarded as essential to bioengineering technology and innovation. Here we describe a means of visualizing the variants in a microbial community and their metabolic profiles. The approach enables previously unidentified bacterial functions in the ecosystems to be elucidated. We investigated the anaerobic bioremediation of chlorinated ethene in a soil column experiment as a case study. Microbial community and dechlorination profiles in the ecosystem were evaluated by denaturing gradient gel electrophoresis (DGGE) fingerprinting and gas chromatography, respectively. Dechlorination profiles were obtained from changes in dechlorination by microbial community (evaluated by data mining methods). Individual microbes were then associated with their dechlorination profiles by heterogenous correlation analysis. Our correlation-based visualization approach enables deduction of the roles and functions of bacteria in the dechlorination of chlorinated ethenes. Because it estimates functions and relationships between unidentified microbes and metabolites in microbial ecosystems, this approach is proposed as a control-logic tool by which to understand complex microbial processes.

  10. Dechlorination of pentachlorophenol by grinding at low rotation speed in short time

    Institute of Scientific and Technical Information of China (English)

    Zhi Xu; Xiaoyu Zhang; Qingzhi Fei

    2015-01-01

    In order to apply grinding method for degradation of pentachlorophenol (PCP) to an industrial scale, the propor-tion of different materials [CaO, SiO2 and CO(NH2)2] and the size of grinding balls were examined. For saving en-ergy and increasing dechlorination efficiency, the rotation speed and grinding time were maintained at relatively low values. At a mass ratio of grinding bal s to materials (40:1), PCP was added into a big steel jar (300 ml) with other materials to grind at 300 r·min−1 for 5 h. The results indicated that when PCP was mixed with CaO and SiO2 in a molar ratio of 1:60:60, the best dechlorination of 58.4%was achieved. CO(NH2)2 could not be used as hydro-gen donor in the dehalogenation by mechanochemical reaction, since it restrained the dechlorination process. The size of grinding balls has significant effect on the reaction. The experiment with 5 mm steel balls indicates that the weight is too light to provide appropriate energy for the reaction, while steel balls of 10 and 15 mm could give better dechlorination reaction. It indicates that dechlorination depends on the mass of balls and fill rate.

  11. A conceptual model linking functional gene expression and reductive dechlorination rates of chlorinated ethenes in clay rich groundwater sediment

    DEFF Research Database (Denmark)

    Bælum, Jacob; Chambon, Julie Claire Claudia; Scheutz, Charlotte

    2013-01-01

    We used current knowledge of cellular processes involved in reductive dechlorination to develop a conceptual model to describe the regulatory system of dechlorination at the cell level; the model links bacterial growth and substrate consumption to the abundance of messenger RNA of functional gene...

  12. Effects of Aqueous Film-Forming Foams (AFFFs) on Trichloroethene (TCE) Dechlorination by a Dehalococcoides mccartyi-Containing Microbial Community.

    Science.gov (United States)

    Harding-Marjanovic, Katie C; Yi, Shan; Weathers, Tess S; Sharp, Jonathan O; Sedlak, David L; Alvarez-Cohen, Lisa

    2016-04-05

    The application of aqueous film-forming foams (AFFFs) to extinguish chlorinated solvent-fueled fires has led to the co-contamination of poly- and perfluoroalkyl substances (PFASs) and trichloroethene (TCE) in groundwater and soil. Although reductive dechlorination of TCE by Dehalococcoides mccartyi is a frequently used remediation strategy, the effects of AFFF and PFASs on TCE dechlorination are not well-understood. Various AFFF formulations, PFASs, and ethylene glycols were amended to the growth medium of a D. mccartyi-containing enrichment culture to determine the impact on dechlorination, fermentation, and methanogenesis. The community was capable of fermenting organics (e.g., diethylene glycol butyl ether) in all AFFF formulations to hydrogen and acetate, but the product concentrations varied significantly according to formulation. TCE was dechlorinated in the presence of an AFFF formulation manufactured by 3M but was not dechlorinated in the presence of formulations from two other manufacturers. Experiments amended with AFFF-derived PFASs and perfluoroalkyl acids (PFAAs) indicated that dechlorination could be inhibited by PFASs but that the inhibition depends on surfactant concentration and structure. This study revealed that the fermentable components of AFFF can stimulate TCE dechlorination, while some of the fluorinated compounds in certain AFFF formulations can inhibit dechlorination.

  13. Removal and reductive dechlorination of triclosan by Chlorella pyrenoidosa.

    Science.gov (United States)

    Wang, Shujuan; Wang, Xian; Poon, Karen; Wang, Yini; Li, Shangfu; Liu, Hongxia; Lin, Shuhai; Cai, Zongwei

    2013-09-01

    Triclosan that is widely used as antimicrobial agent has been detected as contaminant in various aquatic environments. In this work, removal and biodegradation of triclosan in water by using a ubiquitous green alga, Chlorella pyrenoidosa was investigated. When C. pyrenoidosa was exposed to a series concentration of triclosan from 100 to 800ngmL(-1), more than 50% of triclosan was eliminated by algal uptake from the culture medium during the first 1h exposure and reached equilibrium after the 6h treatment. In the biodegradation experiments, a removal percentage of 77.2% was obtained after C. pyrenoidosa was cultivated with 800ngmL(-1) triclosan for 96h. A major metabolite from the reductive dechlorination of triclosan was identified by using liquid chromatography coupled with electrospray ionization-mass spectrometry. The ultrastructural morphology of algal cells grown in the presence of triclosan was observed by using transmission electron microscopy and the growth of algal cells was detected. It was found that the trilcosan treatment resulted in the disruption of the chloroplast and the release of organic material into aquatic environment, which indicated that triclosan may affect membrane metabolism.

  14. Biosupported Bimetallic Pd Au Nanocatalysts for Dechlorination of Environmental Contaminants

    Energy Technology Data Exchange (ETDEWEB)

    De Corte, S.; Fitts, J.; Hennebel, T.; Sabbe, T.; Bliznuk, V.; Verschuere, S.; van der Lelie, D.; Verstraete, W.; Boon, N.

    2011-08-30

    Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichloroethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L{sup -1} and reduced simultaneously by Shewanella oneidensis in the presence of H{sub 2}, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.

  15. Cathodic Hydrogen as Electron Donor in Enhanced Reductive Dechlorination

    Institute of Scientific and Technical Information of China (English)

    张瑞玲; 路晓霞; 焦刚珍; 秦松岩

    2013-01-01

    In situ capping is an attractive and cost-effective method for remediation of contaminated sediments, but few studies on enhancing contaminant degradation in sediment caps have been reported, especially for chlorin-ated benzenes. Electrically enhanced bioactive barrier is a new process for in situ remediation for reducible com-pounds in soil or sediments. The primary objective of this study is to determine if electrodes in sediment could cre-ate a redox gradient and provide electron acceptor/donor to stimulate degradation of chlorinated contaminant. The results demonstrate that graphite electrodes lead to sustainable evolution of hydrogen, displaying zero-order kinetics in the initial stages with different voltages. The constant rates of hydrogen evolution at 3, 4, and 5 V are 1.05, 2.54, and 4.3 nmol·L-1·d-1, respectively. Even higher voltage can produce more hydrogen, but it could not keep long time because the over potentials on electrode surfaces prevent its function. The study shows that 4 V is more appropriate for hydrogen evolution. The measured and evaluated concentration of 1,2,3,5-tetrachlorobenzene in pore water of sediment and concentration of sulfate show that dechlorination is inhibited at higher concentration of sulfate.

  16. Modeling multi-component transport and enhanced anaerobic dechlorination processes in a single fracture-clay matrix system

    DEFF Research Database (Denmark)

    Chambon, Julie Claire Claudia; Broholm, Mette Martina; Binning, Philip John;

    2010-01-01

    and the contaminant flux out of the clay system are assessed for different distributions of microbial degradation. Results from a set of scenarios show that time to remove 90% of the initial mass is halved when dechlorination occurs in a 5 cm reaction zone in the clay at the fracture-matrix interface (from 419 to 195...... to the physical processes, mainly diffusion in the matrix, than to the biogeochemical processes, when dechlorination is assumed to take place in a limited reaction zone only. The inclusion of sequential dechlorination in clay fracture transport models is crucial, as the contaminant flux to the aquifer...... of a contaminant in a single fracture-clay matrix system coupled with a reactive model for anaerobic dechlorination. The model takes into account microbially driven anaerobic dechlorination, where sequential Monod kinetics with competitive inhibition is used to model the reaction rates, and degradation...

  17. Biogenic FeS accelerates reductive dechlorination of carbon tetrachloride by Shewanella putrefaciens CN32.

    Science.gov (United States)

    Huo, Ying-Chao; Li, Wen-Wei; Chen, Chang-Bin; Li, Chen-Xuan; Zeng, Raymond; Lau, Tai-Chu; Huang, Tian-Yin

    2016-12-01

    Dissimilatory metal reducing bacteria (DMRB) widely exist in the subsurface environment and are involved in various contaminant degradation and element geochemical cycling processes. Recent studies suggest that DMRB can biosynthesize metal nanoparticles during metal reduction, but it is unclear yet how such biogenic nanomaterials would affect their decontamination behaviors. In this study, we found that the dechlorination rates of carbon tetrachloride (CT) by Shewanella putrefaciens CN32 was significantly increased by 8 times with the formation of biogenic ferrous sulfide (FeS) nanoparticles. The pasteurized biogenic FeS enabled 5 times faster dechlorination than abiotic FeS that had larger sizes and irregular structure, confirming a significant contribution of the biogenic FeS to CT bioreduction resulting from its good dispersion and relatively high dechlorination activity. This study highlights a potentially important role of biosynthesized nanoparticles in environmental bioremediation. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Biochar as an electron shuttle for reductive dechlorination of pentachlorophenol by Geobacter sulfurreducens

    Science.gov (United States)

    Yu, Linpeng; Yuan, Yong; Tang, Jia; Wang, Yueqiang; Zhou, Shungui

    2015-11-01

    The reductive dechlorination of pentachlorophenol (PCP) by Geobacter sulfurreducens in the presence of different biochars was investigated to understand how biochars affect the bioreduction of environmental contaminants. The results indicated that biochars significantly accelerate electron transfer from cells to PCP, thus enhancing reductive dechlorination. The promotion effects of biochar (as high as 24-fold) in this process depend on its electron exchange capacity (EEC) and electrical conductivity (EC). A kinetic model revealed that the surface redox-active moieties (RAMs) and EC of biochar (900 °C) contributed to 56% and 41% of the biodegradation rate, respectively. This work demonstrates that biochars are efficient electron mediators for the dechlorination of PCP and that both the EC and RAMs of biochars play important roles in the electron transfer process.

  19. A remediation performance model for enhanced metabolic reductive dechlorination of chloroethenes in fractured clay till

    DEFF Research Database (Denmark)

    Manoli, Gabriele; Chambon, Julie C.; Bjerg, Poul L.;

    2012-01-01

    ). The model is tested on lab batch experiments and applied to describe sediment core samples from a TCE-contaminated site. Model simulations compare favorably to field observations and demonstrate that dechlorination may be limited to narrow bioactive zones in the clay matrix around fractures and sand......A numerical model of metabolic reductive dechlorination is used to describe the performance of enhanced bioremediation in fractured clay till. The model is developed to simulate field observations of a full scale bioremediation scheme in a fractured clay till and thereby to assess remediation...... efficiency and timeframe. A relatively simple approach is used to link the fermentation of the electron donor soybean oil to the sequential dechlorination of trichloroethene (TCE) while considering redox conditions and the heterogeneous clay till system (clay till matrix, fractures and sand stringers...

  20. Biochar as an electron shuttle for reductive dechlorination of pentachlorophenol by Geobacter sulfurreducens

    Science.gov (United States)

    Yu, Linpeng; Yuan, Yong; Tang, Jia; Wang, Yueqiang; Zhou, Shungui

    2015-01-01

    The reductive dechlorination of pentachlorophenol (PCP) by Geobacter sulfurreducens in the presence of different biochars was investigated to understand how biochars affect the bioreduction of environmental contaminants. The results indicated that biochars significantly accelerate electron transfer from cells to PCP, thus enhancing reductive dechlorination. The promotion effects of biochar (as high as 24-fold) in this process depend on its electron exchange capacity (EEC) and electrical conductivity (EC). A kinetic model revealed that the surface redox-active moieties (RAMs) and EC of biochar (900 °C) contributed to 56% and 41% of the biodegradation rate, respectively. This work demonstrates that biochars are efficient electron mediators for the dechlorination of PCP and that both the EC and RAMs of biochars play important roles in the electron transfer process. PMID:26592958

  1. Influential factors of 2-chlorobiphenyl reductive dechlorination by highly dispersed bimetallic nanoparticles

    Directory of Open Access Journals (Sweden)

    Jiang Junrong

    2016-01-01

    Full Text Available Highly dispersed Pd-Fe0 bimetallic nanoparticles were prepared in the presence of 40 kHz ultrasonic irradiation in order to enhance disparity and reactivity, and simultaneously avoid agglomeration. Influential factors of 2-chlorobiphenyl (2-Cl BP reductive dechlorination by highly dispersed Pd-Fe0 nanoparticles were investigated. Experimental results showed that highly dispersed Pd-Fe0 nanoparticles prepared in the in the presence of ultrasound could further improve the dechlorination efficiency of 2-Cl BP, meanwhile the biphenyl (BP formation rates increased obviously and increased from 47.4% (in the absence of ultrasound to 95.3% (in the presence of ultrasound within 300 min. The catalytic reductive dechlorination effciency of 2-Cl BP was dependent on Pd-Fe0 nanoparticles prepared methods, Pd-Fe0 nanoparticles dosage, Pd loading percentage over Fe0 and initial pH values

  2. Oxygen controlled product formation in CCl{sub 4} dechlorination using zero-valent iron

    Energy Technology Data Exchange (ETDEWEB)

    Helland, B.R.; Alvarez, P.J.J.; Schnoor, J.L. [Univ. of Iowa, Iowa City, IA (United States)

    1995-12-01

    Carbon tetrachloride (CCl{sub 4}) was abiotically dechlorinated using zero-valent iron powder (Fe{sup o}) to yield chloroform (CHCl{sub 3}) and methylene chloride (CH{sub 2}Cl{sub 2}), which did not undergo further dechlorination. Dechlorination was rapid and approximated first-order kinetics in the range of concentrations tested (CCl{sub 4}: 1.5 to 5.5 {mu}M; Fe{sup o}: 1 to 10 g per 265 mL distilled deionized water). Initial dechlorination rate coefficients for anoxic batch reactors (0.290 {plus_minus} 0.009 hr{sup -1} for 1 g Fe{sup o}; 1.723 {plus_minus} 0.078 hr{sup -1} for 10 g Fe{sup o}) increased with iron surface area (initially 2.4 {plus_minus} 0.2 m{sup 2}/g). Dechlorination also occurred under oxic conditions, although rates were significantly slower (e.g., 0.085 {plus_minus} 0.041 hr{sup -1} for 1 g Fe{sup o} and 7.4 mg/L initial dissolved oxygen). Rate coefficients increased with time, probably due to an increase in reactive surface area from pitting and dissolution of the iron surface. A rapid pH increase was synchronous to dissolved oxygen consumption, and the pH remained constant after oxygen depletion. This was attributed to the proton and oxygen consuming aerobic corrosion of the Fe{sup o} surface. Recalcitrant CH{sub 2}Cl{sub 2} was decreased in the presence of dissolved oxygen, which reacted with dechlorinated intermediates to yield less environmentally onerous products such as formic acid and carbon monoxide.

  3. [Effects of EDTA on the Reductive Dechlorination of 2,4-D by Pd/Fe].

    Science.gov (United States)

    Zhou, Hong-yi; Nie, Ya-zhong; Chen, Yong; Lei, Shuang-jian

    2016-02-15

    In Pd/Fe system, zero-valent iron (ZVI) passivation layer is easily formed on the particle surface during the catalytic reductive dechlorination of chlorinated organics, hindering further dechlorination of target contaminants. In this paper, the passivation layer on the Pd/Fe particle surfaces could be eliminated by the chelation of disodium edetate (EDTA) with Fe2+, Fe3+, making the reductive dechlorination continue. The experiment investigated the effects of EDTA addition manner and dosage, pH, Pd loading and temperature on dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) by Pd/Fe. The conclusions can be summarized as follows: (1) Phenoxyacetic acid (PA) generation ratio reached 90. 7% within 20 min with EDTA concentration of 25.0 mmol x L(-1) and flow rate of 20 mL x h(-1), while it was only 74.5% after 210 min in the system without EDTA. (2) The EDTA could chelate the Fe2+ and Fe3+ generated from the process of 2,4-D dechlorination by Pd/Fe, preventing or slowing down the formation of passivation layer, and accelerating the reduction efficiency. (3) The appropriate experimental parameters for 2,4-D removal were as follows: EDTA flow rate of 20 mL x h(-1), CEDTA of 25.0 mmol x L(-1), Pd loading of 0.050%, 200 r x min(-1), pH 4.2 and 30.0 degrees C. The removal percentage of 20.0 mg x L(-1) 2,4-D reached nearly up to 100% within 210 min under these conditions. (4) The intermediates of 2, 4-D catalytic dechlorination included 2-chlorophenoxvacetic acid (2-CPA) and trace 4-chloronhenoxyacetic acid (4-CPA), and the end product was PA.

  4. Rapid dechlorination of chlorophenols in aqueous solution by [Ni|Cu] microcell

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Lifeng, E-mail: yinlifeng@gmail.com [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Dai, Yunrong, E-mail: daiyunrong@mail.bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Niu, Junfeng, E-mail: junfengn@bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Bao, Yueping, E-mail: baoyueping@mail.bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Shen, Zhenyao, E-mail: zyshen@bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China)

    2012-03-30

    Highlights: Black-Right-Pointing-Pointer Rapid dechlorination of chlorophenols in aqueous solution can be achieved by [Ni|Cu] mixture. Black-Right-Pointing-Pointer The decomposition rates of chlorophenols by [Ni|Cu] were decuple of that by [Fe|Ni], [Fe|Cu], [Zn|Cu], or [Sn|Cu]. Black-Right-Pointing-Pointer Ni{sup 0} acts as an indirect reductant and catalyst in dechlorination reaction. Black-Right-Pointing-Pointer The H* corridor mechanism from Ni to Cu is proposed based on hydrogen spillover. - Abstract: The [Ni|Cu] microcell was prepared by mixing the Ni{sup 0} and Cu{sup 0} particles. The composition and crystal form were characterized by X-ray diffraction (XRD) and scanning electron microscope. The results evidenced the zero-valence metals Ni and Cu were exposed on the surface of particles mixture. The [Ni|Cu] microcell was employed to decompose chlorophenols in aqueous solution by reductive dechlorination. The dechlorination rates of chlorophenols by [Ni|Cu] were >10 times faster than those by [Fe|Cu], [Zn|Cu], [Sn|Cu], and [Fe|Ni] mixtures under the same conditions. [Ni|Cu] is different from other zero valent metals (ZVMs) in that it performed the best at neutral pH. The main products of chlorophenol dechlorination were cyclohexanol and cyclohexanone. The reduction kinetics was between pseudo zero-order and first-order, depending on the pH, concentration, and temperature. These results, combined with electrochemical analysis, suggested that Ni{sup 0} acted as a reductant and catalyst in dechlorination reaction. The H* corridor mechanism from Ni{sup 0} to Cu{sup 0} was also proposed based on hydrogen spillover. The inhibition on the release of Ni{sup 2+} by adding natural organic matters and adjusting pH was investigated.

  5. Factors Influencing TCE Anaerobic Dechlorination Investigated via Simulations of Microcosm Experiments

    Science.gov (United States)

    Mao, X.; Harkness, M.; Lee, M. D.; Mack, E. E.; Dworatzek, S.; Acheson, C.; McCarty, P.; Barry, D. A.; Gerhard, J. I.

    2006-12-01

    SABRE (Source Area BioREmediation) is a public-private consortium whose charter is to determine if enhanced anaerobic bioremediation can result in effective and quantifiable treatment of chlorinated solvent DNAPL source areas. The focus of this 4-year, $5.7 million research project is a field site in the United Kingdom containing a TCE DNAPL source area. In preparation, a microcosm study was performed to determine the optimal combination of factors to support reductive dechlorination of TCE in site soil and groundwater. The study consisted of 168 bottles distributed between four laboratories (Dupont, GE, SiREM, and Terra Systems) and tested the impact of six carbon substrates (lactate, acetate, methanol, SRS (soybean oil), hexanol, butyl acetate), bioaugmentation with KB-1 bacterial culture, three TCE levels (100 mg/L, 400 mg/L, and 800 mg/L) and two sulphate levels (200 mg/L, >500 mg/L) on TCE dechlorination. This research presents a numerical model designed to simulate the main processes occurring in the microcosms, including substrate fermentation, sequential dechlorination, toxic inhibition, and the influence of sulphate concentration. In calibrating the model to over 60 of the microcosm experiments, lumped parameters were employed to quantify the effect of key factors on the conversion rate of each chlorinated ethene in the TCE degradation sequence. Results quantify the benefit (i.e., increased stepwise dechlorination rate) due to both bioaugmentation and the presence of higher sulphate concentrations. Competitive inhibition is found to increase in significance as TCE concentrations increase; however, inclusion of Haldane inhibition is not supported. Over a wide range of experimental conditions and dechlorination steps, SRS appears to induce relatively little hydrogen limitation, thereby facilitating relatively quick conversion of TCE to ethene. In general, hydrogen limitation is found to increase with increasing TCE concentration and with bioaugmentation, and

  6. Desorption, partitioning, and dechlorination characteristics of PCBs in sediments in interaction with reactive activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Hyeok, E-mail: hchoi@uta.edu [Department of Civil Engineering, The University of Texas at Arlington, 416 Yates Street, Arlington, TX 76019-0308 (United States); Environmental and Earth Sciences Program, The University of Texas at Arlington, 500 Yates Street, Arlington, TX 76019-0049 (United States); Lawal, Wasiu [Environmental and Earth Sciences Program, The University of Texas at Arlington, 500 Yates Street, Arlington, TX 76019-0049 (United States); Al-Abed, Souhail R. [National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr., Cincinnati, OH 45268 (United States)

    2015-04-28

    Highlights: • Problematic aged real PCBs-contaminated sediment (WHS) was examined. • Performance of reactive activated carbon (RAC) impregnated with Pd–ZVI was tested. • Fate and transport of PCBs bound to WHS in the presence of RAC was fully traced. • Direct mixing configuration was compared with compartment configuration. • Results reflected real world complexities associated with slow desorption of PCBs. - Abstract: Sediment (WHS) in Waukegan Harbor, Illinois, heavily contaminated and aged with polychlorinated biphenyls (PCBs), was treated with reactive activated carbon (RAC) impregnated with palladized iron nanoparticles. Lab test proceeded in a direct mixing configuration of RAC and WHS. A compartment configuration, where RAC was physically separated from WHS, was also designed to trace the sequential transport and fate of PCBs, including desorption, adsorption, dechlorination, and re-partitioning. PCBs, once desorbed from WHS, were immediately sequestrated to RAC and subject to dechlorination. Direct mixing of WHS with RAC was one-order of magnitude more effective for dechlorination than compartment configuration. Compared to their desorption-followed by-adsorption route, direct physical contact of RAC with PCBs bound to WHS exhibited negligible contribution to the availability of PCBs for dechlorination reaction. Addition of RAC even in compartment configuration facilitated PCBs desorption from WHS. However, slow desorption of PCBs limited overall performance, resulting in a five-order of magnitude lower dechlorination yield when compared with treatment of purely aqueous PCBs. The low dechlorination yield reflected real world complexities in treating 3.19% organic carbon-containing WHS aged with PCBs for 40 years. These observations were further supported when compared with results on clean Cesar Creek sediment spiked with 2-chlorinated biphenyls.

  7. Dechlorination of Hexachloroethane in Water Using Iron Shavings and Amended Iron Shavings: Kinetics and Pathways

    Directory of Open Access Journals (Sweden)

    D. L. Wu

    2014-01-01

    Full Text Available In contrast to previous studies which employed zero-valent iron powder, this paper investigated reductive dechlorination of hexachloroethane (HCA using iron shavings and bimetallic iron shavings modified with Cu, Ag, or Pd. Results clearly show that iron shavings offer superior reductive dechlorination of HCA. In addition, surface-normalized pseudo first-order dechlorination rates of 0.0073 L·m−2·h−1, 0.0136 L·m−2·h−1, 0.0189 L·m−2·h−1, and 0.0084 L·m−2·h−1 were observed in the presence of iron shavings (Fe0 and the bimetallic iron shavings Cu/Fe, Ag/Fe, and Pd/Fe, respectively. Bimetallic iron shavings consisting of Cu/Fe and Ag/Fe could greatly enhance the reductive reaction rate; Pd/Fe was used to achieve complete dechlorination of HCA within 5 hours. The additives of Ag and Pd shifted product distributions, and the reductive dechlorination of HCA occurred via β reductive elimination and sequential hydrogenolysis in the presence of all iron shavings. This study consequently designed a reaction pathway diagram which reflected the reaction pathway and most prevalent dechlorination products. Iron shavings are a common byproduct of mechanical processing plants. While the purity of such Fe metals may be low, these shavings are readily available at low costs and could potentially be used in engineering applications such as contamination control technologies.

  8. Rapid dechlorination of chlorinated organic compounds by nickel/iron bimetallic system in water

    Institute of Scientific and Technical Information of China (English)

    TONG Shao-ping; WEI Hong; MA Chun-an; LIU Wei-ping

    2005-01-01

    Detoxification of chlorinated organic compounds via reaction with nickel/iron powder was implemented in aqueous solution. Compared to iron, nickel/iron bimetallic powder had higher hydrodechlorination activities for both atrazine (ATR) and p-chlorophenol (pCP); nickel/iron (2.96%, w/w) was shown to have the largest specific surface area and the optimum proportion for the dechlorination of both ATR and pCP. Electrochemical measurements showed that the adsorbed hydrogen atom on the nickel must have been the dominant reductive agent for the dechlorination of both ATR andpCP in this system.

  9. Establishment of a polychlorinated biphenyl-dechlorinating microbial consortium, specific for doubly flanked chlorines, in a defined, sediment-free medium

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Q.; Sowers, K.R.; May, H.D.

    2000-01-01

    Estuarine sediment from Charleston Harbor, South Carolina, was used as inoculum for the development of an anaerobic enrichment culture that specifically dechlorinates doubly flanked chlorines (i.e., chlorines bound to carbon that are flanked on both sides by other chlorine-carbon bonds) of polychlorinated biphenyls (PCBs). Dechlorination was restricted to the para chlorine in cultures enriched with 10 mM fumarate, 50 ppm (173 {micro}M) 2,3,4,5-tetrachlorobiphenyl, and no sediment. Initially the rate of dechlorination decreased upon the removal of sediment from the medium. However, the dechlorinating activity was sustainable, and following sequential transfer in a defined, sediment-free estuarine medium, the activity increased to levels near that observed with sediment. The culture was nonmethanogenic, and molybdate, ampicillin, chloramphenicol, neomycin, and streptomycin inhibited dechlorination activity; bromethanesulfonate and vancomycin did not. Addition of 17 PCB congeners indicated that the culture specifically removes double flanked chlorines, preferably in the para position, and does not attack ortho chlorines. This is the first microbial consortium shown to para or meta dechlorinate a PCB congener in a defined sediment-free medium. It is the second PCB-dechlorinating enrichment culture to be sustained in the absence of sediment, but its dechlorinating capabilities are entirely different from those of the other sediment-free PCB-dechlorinating culture, an ortho-dechlorinating consortium, and do not match any previously published Aroclor-dechlorinating patterns.

  10. Thermal dechlorination of heavily PCB-contaminated soils from a sealed site of PCB-containing electrical equipment.

    Science.gov (United States)

    Gao, Xingbao; Ji, Bingjing; Huang, Qifei

    2016-08-01

    A large amount of soils are contaminated by leakage of polychlorinated biphenyls (PCBs) from sealed-up PCB-containing electrical equipment in China. Thermal dechlorination of soils contaminated with PCBs at a level of 108 mg g(-1) and PCB77 (3,3',4,4'-tetrachlorobiphenyl) as a model isomer in conjunction with calcium oxide was investigated in this study. The PCB dechlorination rate improved with increased temperature and time. The highest dechlorination rate was 85.3 %, and temperature was the main influencing factor. Pentachlorobiphenyl and tetrachlorobiphenyl in soils decreased or disappeared in response to treatment at 350 and 400 °C for 4 h, while monochlorinated biphenyl and biphenyl were detected after the reaction, indicating the presence of a dechlorination/hydrogenation pathway. Discrepancy in chlorine balance was observed after low-temperature thermal dechlorination. The species of dechlorination products were identified as amorphous carbon containing a crystalline graphite plane structure and a carbonyl group-containing polymerized product, demonstrating the existence of a dechlorination/polymerization pathway. The yield of amorphous carbon and high-molecular-weight intermediates increased with heating time. The results showed that the discrepancy in chlorine balance was because of the generation of polymerized products and undetected intermediates.

  11. Study on the Effect of Electrochemical Dechlorination Reduction of Hexachlorobenzene Using Different Cathodes

    Science.gov (United States)

    Wang, Yingru; Lu, Xiaohua

    2014-01-01

    Hexachlorobenzene (HCB) is a persistent organic pollutant and poses great threat on ecosystem and human health. In order to investigate the degradation law of HCB, a RuO2/Ti material was used as the anode, meanwhile, zinc, stainless steel, graphite, and RuO2/Ti were used as the cathode, respectively. The gas chromatography (GC) was used to analyze the electrochemical products of HCB on different cathodes. The results showed that the cathode materials significantly affected the dechlorination efficiency of HCB, and the degradation of HCB was reductive dechlorination which occurred only on the cathode. During the reductive process, chlorine atoms were replaced one by one on various intermediates such as pentachlorobenzene, tetrachlorobenzene, and trichlorobenzene occurred; the trichlorobenzene was obtained when zinc was used as cathode. The rapid dechlorination of HCB suggested that the electrochemical method using zinc or stainless steel as cathode could be used for remediation of polychlorinated aromatic compounds in the environment. The dechlorination approach of HCB by stainless steel cathode could be proposed. PMID:24995145

  12. Impact Of Organic Solvents And Common Anions On 2-Chlorobiphenyl Dechlorination Kinetics With Pd/Mg

    Science.gov (United States)

    The current study evaluates Pd/Mg performance for 2-chlorobiphenyl (2-CB) dechlorination in the presence of naturally abundant anions such as sulfate, chloride, nitrate, hydroxide and carbonates and organic solvents that are used for ex-situ PCB extraction or may accompany PCB co...

  13. PCB 77 dechlorination products modulate pro-inflammatory events in vascular endothelial cells.

    Science.gov (United States)

    Eske, Katryn; Newsome, Bradley; Han, Sung Gu; Murphy, Margaret; Bhattacharyya, Dibakar; Hennig, Bernhard

    2014-05-01

    Persistent organic pollutants such as polychlorinated biphenyls (PCBs) are associated with detrimental health outcomes including cardiovascular diseases. Remediation of these compounds is a critical component of environmental policy. Although remediation efforts aim to completely remove toxicants, little is known about the effects of potential remediation byproducts. We previously published that Fe/Pd nanoparticles effectively dechlorinate PCB 77 to biphenyl, thus eliminating PCB-induced endothelial dysfunction using primary vascular endothelial cells. Herein, we analyzed the toxic effects of PCB congener mixtures (representative mixtures of commercial PCBs based on previous dechlorination data) produced at multiple time points during the dechlorination of PCB 77 to biphenyl. Compared with pure PCB 77, exposing endothelial cells to lower chlorinated PCB byproducts led to improved cellular viability, decreased superoxide production, and decreased nuclear factor kappa B activation based on duration of remediation. Presence of the parent compound, PCB 77, led to significant increases in mRNA and protein inflammatory marker expression. These data implicate that PCB dechlorination reduces biological toxicity to vascular endothelial cells.

  14. Pentachlorophenol dechlorination and simultaneous Cr6+ reduction by Pseudomonas putida SKG-1 MTCC (10510): characterization of PCP dechlorination products, bacterial structure, and functional groups.

    Science.gov (United States)

    Garg, Satyendra Kumar; Tripathi, Manikant; Singh, Santosh Kumar; Singh, Anamika

    2013-04-01

    It is the first report in which a novel psychrotrophic Pseudomonas putida SKG-1 strain was evaluated for simultaneous bioremediation of pentachlorophenol and Cr(6+) under various cultural and nutritional conditions. Pentachlorophenol (PCP) dechlorination products, bacterial structure, and functional groups were characterized by gas chromatography and mass spectrometry (GC-MS), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDS), and Fourier-transform infrared (FTIR) techniques. The strain was extremely tolerant to excessively higher individual concentration of PCP (1,400 mg l(-1)) and Cr(6+) (4,300 mg l(-1)). Increasing concentration of PCP and Cr(6+) exerted inhibitory effect on bacterial growth and toxicants' removal. The strain exhibited growth, and concomitantly remediated both the pollutants simultaneously over a broad pH (7.0-9.0) and temperature (28-32 °C) range; maximum growth, PCP dechlorination (87.5%), and Cr(6+) removal (80.0%) occurred at optimum pH 8.0 and 30 °C (from initial PCP 100 mg l(-1) and Cr(6+) 500 mg l(-1)) under shaking (150 rpm) within 72 h incubation. Optimization of agitation (125 rpm) and aeration (0.4 vvm) in bioreactor further enhanced PCP dechlorination by ~10% and Cr(6+) removal by 2%. A direct correlation existed between growth and bioremediation of both the toxicants. Among other heavy metals, mercury exerted maximum and cobalt minimum inhibitory effect on PCP dechlorination and Cr(6+) removal. Chromate reductase activity was mainly associated with the supernatant and cytosolic fraction of bacterial cells. GC-MS analysis revealed the formation of tetrachloro-p-hydroquinone, 2,4,6-trichlorophenol, and 2,6-dichlorophenol as PCP dechlorination products. FTIR spectrometry indicated likely involvement of carbonyl and amide groups in Cr(3+) adsorption, and SEM-EDS showed the presence of chromium on P. putida surface. Thus, our promising isolate can be ecofriendly employed for biotreatment of various

  15. Distribution of Dechlorinating Bacteria between the Aqueous and Solid Phases

    Science.gov (United States)

    Cápiro, N. L.; Hatt, J. K.; Wang, Y.; Loeffler, F. E.; Pennell, K. D.

    2010-12-01

    Microbial monitoring of aquifers relies on nucleic acid biomarker analysis, which is typically performed with biomass recovered from groundwater samples; however, it is unclear what fraction of the target population(s) is associated with groundwater (i.e., planktonic cells) or is attached to solid phases (i.e., biofilms). Understanding how the titer of target organism(s) in groundwater correlates with the true cell titers of the target organism in the aquifer (i.e., planktonic plus attached cells) is critical for a meaningful interpretation of the data, the prediction of bioremediation performance, and the implementation of site management strategies. To evaluate the distribution of active cells between resident solid phase and the aqueous phase, one-dimensional columns were packed under water-saturated conditions with Bio-Dechlor INOCULUM, a PCE-to ethene-dechlorinating bacterial consortium containing both multiple Dehalococcoides (Dhc) strains and Geobacter lovleyi strain SZ (GeoSZ). The columns were packed with two distinct solid matrices: a low organic content sandy Federal Fine Ottawa soil or Appling soil with higher organic matter content. Influent reduced mineral salts medium supplied at a groundwater pore-water velocity of 0.3 m/day contained both 10 mM lactate as electron donor and 0.33 mM PCE as electron acceptor. Routine collection of biomass from column side ports and effluent samples measured the titers of target cells in the aqueous phase and determined when steady state conditions had been reached. A second set of column experiments evaluated delivery and filtration effects by the solid matrix (i.e., Federal Fine Ottawa sand versus Appling soil) under the same conditions except that electron donor or acceptor were omitted (no growth conditions). Quantitative real-time PCR (qPCR) analysis using Dhc and GeoSZ 16S rRNA gene-targeted primer and probe sets determined the planktonic cell counts, and destructive sampling of the columns allowed measurement

  16. [Microbial reductive dechlorination of TCE with nano iron serving as electron donor].

    Science.gov (United States)

    Xiu, Zong-Ming; Li, Tie-Long; Jin, Zhao-Hui; Alvarez, Pedro J

    2009-06-15

    A trichloroethylene (TCE) dechlorinating enrichment (Dehalococcoides spp.), which was isolated from soil of chlorinated ethene contaminated site, was used to investigate whether nano-scale zero valent iron (NZVI) could serve as electron donor for this consortium via cathodic H2 production during anaerobic corrosion. The results show that in the presence of methanol serving as electron donor, dechlorinating culture of 25 fold dilution [(2.0 +/- 0.44) x 10(5) cell/mL] degraded 20 mg/L TCE completely in 96 h, which was accompanied by the production of 2.706 micromol ethene in 190 h. Methanol-free control caused partial degradation of TCE to primarily cis-DCE in 96 h, with only 0.159 micromol ethene produced in 190 h. This indicates bacteria cannot reduce TCE to ethene without electron donor. But when 4 g/L NZVI was added as sole electron donor, this dechlorinating culture degraded 20 mg/L TCE into ethene and vinyl chloride (VC) in 131 h at a speed higher than that by NZVI alone. Compared to 2.706 micromol ethene produced by Dehalococcoides spp. with methanol added as the electron donor, there was only 1.187 micromol ethene produced by bacteria with NZVI serving as the electron donor, which means NZVI has a potential toxicity on Dehalococcoides spp.. At the meantime, 0.109 micromol acetylene was produced in 190 h, which was relatively lower than 0.161 micromol produced by NZVI alone, indicating bacteria competed with NZVI under electron deficient condition. In conclusion, NZVI could serve as electron donor and support dechlorination activity for Dehalococcoides spp. which could enhance the application of NZVI and usage of dechlorinating culture as a polishing strategy in future ground water remediation.

  17. Development and Characterization of PCE-to-Ethene Dechlorinating Microcosms with Contaminated River Sediment.

    Science.gov (United States)

    Lee, Jaejin; Lee, Tae Kwon

    2016-01-01

    An industrial complex in Wonju, contaminated with trichloroethene (TCE), was one of the most problematic sites in Korea. Despite repeated remedial trials for decades, chlorinated ethenes remained as sources of down-gradient groundwater contamination. Recent efforts were being made to remove the contaminants of the area, but knowledge of the indigenous microbial communities and their dechlorination abilities were unknown. Thus, the objectives of the present study were (i) to evaluate the dechlorination abilities of indigenous microbes at the contaminated site, (ii) to characterize which microbes and reductive dehalogenase genes were responsible for the dechlorination reactions, and (iii) to develop a PCE-to-ethene dechlorinating microbial consortium. An enrichment culture that dechlorinates PCE to ethene was obtained from Wonju stream, nearby a trichloroethene (TCE)-contaminated industrial complex. The community profiling revealed that known organohalide-respiring microbes, such as Geobacter, Desulfuromonas, and Dehalococcoides grew during the incubation with chlorinated ethenes. Although Chloroflexi populations (i.e., Longilinea and Bellilinea) were the most enriched in the sediment microcosms, those were not found in the transfer cultures. Based upon the results from pyrosequencing of 16S rRNA gene amplicons and qPCR using TaqMan chemistry, close relatives of Dehalococcoides mccartyi strains FL2 and GT seemed to be dominant and responsible for the complete detoxification of chlorinated ethenes in the transfer cultures. This study also demonstrated that the contaminated site harbors indigenous microbes that can convert PCE to ethene, and the developed consortium can be an important resource for future bioremediation efforts.

  18. Role of metalloporphyrin core metals in the mediated reductive dechlorination of tetrachloroethylene.

    Science.gov (United States)

    Dror, Ishai; Schlautman, Mark A

    2003-03-01

    A promising approach to abiotically dechlorinate a variety of chlorinated organic contaminants under reducing conditions is to utilize porphyrins or other tetrapyrrole macrocycles as electron transfer mediators/shuttles for catalyzing their reduction. In this study, various experimental approaches were used to elucidate the role of porphyrin core metals in the reductive dechlorination of tetrachloroethylene (PCE). The importance of specific core metals for the reactivity of a porphyrin and its mediated reaction mechanisms was demonstrated by inserting different metals into metallo tetrakis (N-methyl-4-4 pyridiniumyl) porphyrin (TMPyP). No PCE dechlorination was observed when the free-base (i.e., no core metal) and iron core metal forms of TMPyP were utilized. When using nickel or cobalt TMPyP, reductive dechlorination of PCE occurred but appeared to follow different pathways for the two metals based on product analyses. Physical (e.g., steric) considerations suggest that direct contact between a porphyrin core metal and PCE may be limited and therefore that the entire metalloporphyrin molecule should be viewed as a functional system in which the organic macrocycle has an active part in reductive dechlorination reactions. This view is supported by the fact that slight changes in the functional groups on a porphyrin macrocycle, particularly those far removed from the core metal itself, greatly affected the reactivity and mechanism of the porphyrin. Solution conditions also had a major effect on porphyrin reactivities, to the extent that a nonreactive metalloporphyrin could be activated merely by adjusting the pH of the solution or by adding a small amount of cosolvent. The collective results of this study suggest that fine tuning of naturally occurring metalloporphyrin complexes and/or their environments can enhance the catalyzed detoxification of chlorinated contaminants in many natural and engineered environmental systems.

  19. Dechlorination of polychlorinated biphenyls in transformer oil using UV and visible light.

    Science.gov (United States)

    Kong, Jiansong; Achari, Gopal; Langford, Cooper H

    2013-01-01

    A study on dechlorination of PCB138 in transformer oil (TO) and 2-propanol (IPA) using 254 nm ultraviolet (UV) light as well as dye sensitized visible light has been conducted. Studies on dechlorination of polychlorinated biphenyls (PCBs) in TO using visible light in the presence of methylene blue (MB) and triethylamine (TEA) (providing a 'photocatalytic' cycle) in both deaerated and aerated conditions have been conducted to determine effects of TO, MB and TEA on reaction rates. The results show that photolytic methods are effective in treating PCBs in TO, and that the oil plays a limited adverse role. Under UV irradiation, PCB 138 can be >99% dechlorinated in the presence 0.06% (w/w) TO in IPA within 1 h with a rate constant of 0.0853 min(-1), while 47% of PCB138 can be dechlorinated in 92.1% (w/w) TO in IPA within 2 h with a rate constant of 0.0051 min(-1). In the 'photocatalytic' system, 94% reduction of PCB 138 was achieved within 30 min with a rate constant of 0.0968 min(-1) when the solvent was 60.70% (w/w) TO in IPA, while 71% dechlorination of PCB138 was achieved within 30 min with a rate constant of 0.0382 min(-1) when 81.62% (w/w) TO was present. In treatment of 30-73 ppm PCBs in TO, the optimal concentration of MB and TEA were found to be 0.5 g/L and 58.08 g/L respectively. Because of quenching by oxygen, deaeration of the solution is necessary for an efficient reaction. The photocatalytic system is especially adapted for treating lower concentration of PCBs in TO.

  20. Batch reactor kinetic studies on the reductive dechlorination of chlorinated ethylenes by tetrakis-(4-sulfonatophenyl)porphyrin cobalt.

    Science.gov (United States)

    Barnett, Brandon R; Evans, Alexandra L; Roberts, Courtney C; Fritsch, Joseph M

    2011-01-01

    Tetrakis-(4-sulfonatophenyl)porphyrin cobalt was identified as a highly-active reductive dechlorination catalyst for chlorinated ethylenes. Through batch reactor kinetic studies, degradation of chlorinated ethylenes proceeded in a step-wise fashion with the sequential replacement of Cl by H. For perchloroethylene (PCE) and trichloroethylene (TCE), the dechlorination products were quantified and the C₂ mass was accounted for. Degradation of the chlorinated ethylenes was found to be first-order in substrate. Dechlorination trials with increasing catalyst concentration showed a linearly increasing pseudo first-order rate constant which yielded rate laws for PCE and TCE degradation that are first-order in catalyst. The dechlorination activity of this catalyst was compared to that of another water-soluble cobalt porphyrin under the same reaction conditions and found to be comparable for PCE and TCE. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. In Situ Redox Manipulation of Subsurface Sediments from Fort Lewis, Washington: Iron Reduction and TCE Dechlorination Mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Fruchter, Jonathan S.; Sklarew, Deborah S.; Evans, John C.

    2000-03-17

    The feasibility of chemically treating sediments from the Ft. Lewis, Washington, Logistics Center to develop a permeable barrier for dechlorination of TCE was investigated in a series of laboratory experiments.

  2. Concurrent ethene generation and growth of Dehalococcoides containing vinyl chloride reductive dehalogenase genes during an enhanced reductive dechlorination field demonstration

    DEFF Research Database (Denmark)

    Scheutz, Charlotte; Durant, N. D.; Dennis, P.;

    2008-01-01

    Dehalococcoides bacteria that produce catabolic vinyl chloride (VC) reductive dehalogenase enzymes have been implicated as a requirement for successful biological dechlorination of VC to ethene in groundwater systems. Therefore, the functional genes in Dehalococcoides that produce VC reductase (e...

  3. The corrinoid cofactor of reductive dehalogenases affects dechlorination rates and extents in organohalide-respiring Dehalococcoides mccartyi.

    Science.gov (United States)

    Yan, Jun; Şimşir, Burcu; Farmer, Abigail T; Bi, Meng; Yang, Yi; Campagna, Shawn R; Löffler, Frank E

    2016-05-01

    Corrinoid auxotrophic organohalide-respiring Dehalococcoides mccartyi (Dhc) strains are keystone bacteria for reductive dechlorination of toxic and carcinogenic chloroorganic contaminants. We demonstrate that the lower base attached to the essential corrinoid cofactor of reductive dehalogenase (RDase) enzyme systems modulates dechlorination activity and affects the vinyl chloride (VC) RDases BvcA and VcrA differently. Amendment of 5,6-dimethylbenzimidazolyl-cobamide (DMB-Cba) to Dhc strain BAV1 and strain GT cultures supported cis-1,2-dichloroethene-to-ethene reductive dechlorination at rates of 107.0 (±12.0) μM and 67.4 (±1.4) μM Cl(-) released per day, respectively. Strain BAV1, expressing the BvcA RDase, reductively dechlorinated VC to ethene, although at up to fivefold lower rates in cultures amended with cobamides carrying 5-methylbenzimidazole (5-MeBza), 5-methoxybenzimidazole (5-OMeBza) or benzimidazole (Bza) as the lower base. In contrast, strain GT harboring the VcrA RDase failed to grow and dechlorinate VC to ethene in medium amended with 5-OMeBza-Cba or Bza-Cba. The amendment with DMB to inactive strain GT cultures restored the VC-to-ethene-dechlorinating phenotype and intracellular DMB-Cba was produced, demonstrating cobamide uptake and remodeling. The distinct responses of Dhc strains with BvcA versus VcrA RDases to different cobamides implicate that the lower base exerts control over Dhc reductive dechlorination rates and extents (that is, detoxification), and therefore the dynamics of Dhc strains with discrete reductive dechlorination capabilities. These findings emphasize that the role of the corrinoid/lower base synthesizing community must be understood to predict strain-specific Dhc activity and achieve efficacious contaminated site cleanup.

  4. Efficacy of zero-valent copper (Cu(0)) nanoparticles and reducing agents for dechlorination of mono chloroaromatics.

    Science.gov (United States)

    Raut, Sandesh S; Kamble, Sanjay P; Kulkarni, Prashant S

    2016-09-01

    The zero-valent copper (Cu(0)) nanoparticles were prepared by chemical reduction method. The morphology of nanoparticles was investigated by using X ray diffraction, scanning electron microscopy-energy dispersive X ray, UV-visible spectrophotometer and Brunauer-Emmett-Teller surface area analyser. The Cu(0) nanoparticles along with reducing agents, NaBH4/5% acidified alcohol were used for the dechlorination of chloroaromatics at room temperature. Chlorobenzene (Cl-B), chlorotoluene (Cl-T), chloropyridine (Cl-Py) and chlorobiphenyl (Cl-BPh) were selected as the contaminants. The effect of various operating parameters such as pH, concentration of the catalyst and reducing agent (NaBH4), and recycling of the catalyst on dechlorination were studied. Nearly complete dechlorination of all the chloroaromatics were achieved in the presence of Cu(0) nanoparticles (2.5 g L(-1)) and NaBH4 (1.0 g L(-1)) within 12 h. On the contrary, approximately 70% of dechlorination was observed in the presence of 5% acidified alcohol at similar experimental conditions. The dechlorination mechanism highlighted the importance of Cu(0) nanoparticles as a surface mediator. The kinetics of the dechlorination of chloroaromatics was investigated and compared with chloroaliphatics. The dechlorination rate differed from 0.23 h(-1) (Cl-B) to 0.15 h(-1) (Cl-BPh) in the presence of Cu(0) nanoparticles and NaBH4. The effectiveness of Cu(0) nanoparticles with NaBH4 (1 g L(-1)) and 5% acidified alcohol as electron donors were studied by oxidation-reduction potential and observed to be -1016 mV and -670 mV, respectively. Final products of the dechlorination were benzene, toluene, pyridine and biphenyl, as identified by gas chromatograph mass spectrometer and nuclear magnetic resonance spectroscopy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Reductive dechlorination of tetrachloroethylene and trichloroethylene by mackinawite (FeS) in the presence of metals: reaction rates.

    Science.gov (United States)

    Jeong, Hoon Y; Hayes, Kim F

    2007-09-15

    Reductive dechlorination by mackinawite (FeS) is an important transformation pathway for chloroethylenes in anoxic environments. Yet, the impact of metals on reductive dechlorination is not well understood, despite their frequent cooccurrence with chloroethylenes. Fe(II), Co(II), Ni(II), and Hg(II) were evaluated for their impact on the dechlorination rates of PCE and TCE by FeS. Compared with unamended FeS batches, the dechlorination rates of both chloroethylenes decreased by addition of 0.01 M Fe(II). Relative to 0.01 M Fe(II)-added FeS batches, the dechlorination rates increased in FeS batches amended with 0.01 M of Co(II) and Hg(II), whereas the rates decreased in 0.01 M Ni(II)-added batches. While significantly impacting the dechlorination rates, the amended metals were quantitatively sequestered by FeS mainly because of formation of metal sulfides. Comparison of the dechlorination rates between metal-added FeS batches and metal sulfide batches suggests that discrete metal sulfides do not form in metal-added FeS batches. The observed exceptionally high reactivity of CoS suggests that it may be useful in reactive permeable barrier applications because of its stability in anoxic waters. The dechlorination rates of PCE and TCE significantly varied with Fe(ll) amendment concentrations (Fe(II)0), indicating the presence of different types of solid-bound Fe phases with Fe(II)o.

  6. Dechlorination of chlorinated phenols by subnanoscale Pd{sup 0}/Fe{sup 0} intercalated in smectite: pathway, reactivity, and selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Hanzhong; Wang, Chuanyi, E-mail: jiahz0143@aliyun.com

    2015-12-30

    Graphical abstract: Dechlorination process of pentachlorophenol (PCP) by smectite-templated Pd{sup 0}/Fe{sup 0}. - Highlights: • Smectite was employed as templated matrix to prepare subnanoscale Pd{sup 0}/Fe{sup 0} particles. • Dechlorination rate depends linearly on the Pd content as its loadings <0.065 wt.%. • Dechlorination rates correlate with the total charge of C on chlorinated phenols. • The dechlorination selectivity relies on charges of individual C in aromatic ring. - Abstract: Smectite clay was employed as templated matrix to prepare subnanoscale Pd{sup 0}/Fe{sup 0} particles, and their components as well as intercalated architectures were well characterized by X-ray energy dispersive spectroscopy (X-EDS) and X-ray diffraction (XRD). Furthermore, as-prepared Pd{sup 0}/Fe{sup 0} subnanoscale nanoparticles were evaluated for their dechlorination effect using chlorinated phenols as model molecules. As a result, pentachlorophenol (PCP) is selectively transformed to phenol in a stepwise dechlorination pathway within 6 h, and the dechlorination rate constants show linearly relationship with contents of Pd as its loadings <0.065%. Comparing with PCP, other chlorinated phenols display similar degradation pattern but within much shorter time frame. The dechlorination rate of chlorinated phenols increases with decreasing in number of -Cl attached to aromatic ring, which can be predicted by the total charge of the aromatic ring, exhibiting an inversely linear relationship with the dechlorination rates. While the selectivity of dechlorination depends on the charges associated with the individual aromatic carbon. Chloro-functional groups at the ortho-position are easier to be dechlorinated than that at meta- and para- positions yielding primarily 3,4,5-TCP as intermediate from PCP, further to phenol. The effective dechlorination warrants their potential utilizations in development of in-situ remediation technologies for organic pollutants in contaminated

  7. Enhanced abiotic and biotic contributions to dechlorination of pentachlorophenol during Fe(III) reduction by an iron-reducing bacterium Clostridium beijerinckii Z

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yan [College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058 (China); He, Yan, E-mail: yhe2006@zju.edu.cn [College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058 (China); Feng, Xiaoli [College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058 (China); Liang, Luyi [Experiment Teaching Center for Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Xu, Jianming, E-mail: jmxu@zju.edu.cn [College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058 (China); Brookes, Philip C.; Wu, Jianjun [College of Environmental and Natural Resource Sciences, Zhejiang Provincial Key Laboratory of Subtropical Soil and Plant Nutrition, Zhejiang University, Hangzhou 310058 (China)

    2014-03-01

    A novel Fe(III) reducing bacterium, Clostridium beijerinckii Z, was isolated from glucose amended paddy slurries, and shown to dechlorinate pentachlorophenol (PCP). Fifty percent of added PCP was removed by C. beijerinckii Z alone, which increased to 83% in the presence of both C. beijerinckii Z and ferrihydrite after 11 days of incubation. Without C. beijerinckii Z, the surface-bound Fe(II) also abiotically dechlorinated more than 40% of the added PCP. This indicated that the biotic dechlorination by C. beijerinckii Z is a dominant process causing PCP transformation through anaerobic dechlorination, and that the dechlorination rates can be accelerated by simultaneous reduction of Fe(III). A biochemical electron transfer coupling process between sorbed Fe(II) produced by C. beijerinckii Z and reductive dehalogenation is a possible mechanism. This finding increases our knowledge of the role of Fe(III) reducing genera of Clostridium in dechlorinating halogenated organic pollutants, such as PCP, in anaerobic paddy soils. - Highlights: • A novel Fe(III) reducing bacterium Clostridium beijerinckii Z was isolated and could dechlorinate pentachlorophenol. • Anaerobic transformation of PCP by C. beijerinckii Z could be accelerated by simultaneous reduction of Fe(III). • Biochemical electron transfer coupling between Fe redox cycling and reductive dechlorination was the mechanism involved. • The finding increases our knowledge of Clostridium sp. regarding their multiple functions for dechlorinating pollutants.

  8. Catalytic dechlorination of o-cllorophenol by nanoscale Pd/Fe

    Institute of Scientific and Technical Information of China (English)

    WEI Jian-jun; XU Xin-hua; WANG Da-hui

    2004-01-01

    Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20-100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder( <100 mesh) has a specific surface area of just 0.49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

  9. Abiotic dechlorination in rock matrices impacted by long-term exposure to TCE.

    Science.gov (United States)

    Schaefer, Charles E; Towne, Rachael M; Lippincott, David R; Lacombe, Pierre J; Bishop, Michael E; Dong, Hailiang

    2015-01-01

    Field and laboratory tests were performed to evaluate the abiotic reaction of trichloroethene (TCE) in sedimentary rock matrices. Hydraulically conductive fractures, and the rock directly adjacent to the hydraulically conductive fractures, within a historically contaminated TCE bedrock aquifer were used as the basis for this study. These results were compared to previous work using rock that had not been exposed to TCE (Schaefer et al., 2013) to assess the impact of long-term TCE exposure on the abiotic dechlorination reaction, as the longevity of these reactions after long-term exposure to TCE was hitherto unknown. Results showed that potential abiotic TCE degradation products, including ethane, ethene, and acetylene, were present in the conductive fractures. Using minimally disturbed slices of rock core at and near the fracture faces, laboratory testing on the rocks confirmed that abiotic dechlorination reactions between the rock matrix and TCE were occurring. Abiotic daughter products measured in the laboratory under controlled conditions were consistent with those measured in the conductive fractures, except that propane also was observed as a daughter product. TCE degradation measured in the laboratory was well described by a first order rate constant through the 118-d study. Observed bulk first-order TCE degradation rate constants within the rock matrix were 1.3×10(-8) s(-1). These results clearly show that abiotic dechlorination of TCE is occurring within the rock matrix, despite decades of exposure to TCE. Furthermore, these observed rates of TCE dechlorination are expected to have a substantial impact on TCE migration and uptake/release from rock matrices.

  10. Efficient dechlorination of carbon tetrachloride by hydrophobic green rust intercalated with dodecanoate anions

    DEFF Research Database (Denmark)

    Ayala Luis, Karina Barbara; Ginette Anneliese Cooper, Nicola; Bender Koch, Christian

    2012-01-01

    The reductive dechlorination of carbon tetrachloride (CT) by Fe-II-Fe-III hydroxide (green rust) intercalated with dodecanoate, (Fe4Fe2III)-Fe-II (OH)(12)(C12H23O2)(2)center dot gamma H2O (designated GR(C12)), at pH similar to 8 and at room temperature was investigated. CT at concentration levels...

  11. Reductive dechlorination of chlorinated solvents by zero-valent iron, iron oxide and iron sulfide minerals

    Energy Technology Data Exchange (ETDEWEB)

    Sivavec, T.M.; Horney, D.P. [GE Corporate Research and Development, Schenectady, NY (United States)

    1996-10-01

    The degradation of chlorinated solvents by reduction at the surface of zero-valent metals and bimetallic systems has emerged as an important approach to the in-situ remediation of ground water. Reduction by iron metal was studied in batch and column systems to develop a mechanistic understanding of the reaction chemistry and to determine the factors that affect dechlorination rate and long term performance in field applications.

  12. Isolation and characterization of tetrachloroethylene- and cis-1,2-dichloroethylene-dechlorinating propionibacteria.

    Science.gov (United States)

    Chang, Young-Cheol; Ikeutsu, Kaori; Toyama, Tadashi; Choi, Dubok; Kikuchi, Shintaro

    2011-10-01

    Two rapidly growing propionibacteria that could reductively dechlorinate tetrachloroethylene (PCE) and cis-1,2-dichloroethylene (cis-DCE) to ethylene were isolated from environmental sediments. Metabolic characterization and partial sequence analysis of their 16S rRNA genes showed that the new isolates, designated as strains Propionibacterium sp. HK-1 and Propionibacterium sp. HK-3, did not match any known PCE- or cis-DCE-degrading bacteria. Both strains dechlorinated relatively high concentrations of PCE (0.3 mM) and cis-DCE (0.52 mM) under anaerobic conditions without accumulating toxic intermediates during incubation. Cell-free extracts of both strains catalyzed PCE and cis-DCE dechlorination; degradation was accelerated by the addition of various electron donors. PCE dehalogenase from strain HK-1 was mediated by a corrinoid protein, since the dehalogenase was inactivated by propyl iodide only after reduction by titanium citrate. The amounts of chloride ions (0.094 and 0.103 mM) released after PCE (0.026 mM) and cis-DCE (0.05 mM) dehalogenation using the cell-free enzyme extracts of both strains, HK-1 and HK-3, were stoichiometrically similar (91 and 100%), indicating that PCE and cis-DCE were fully dechlorinated. Radiotracer studies with [1,2-¹⁴C] PCE and [1,2-¹⁴C] cis-DCE indicated that ethylene was the terminal product; partial conversion to ethylene was observed. Various chlorinated aliphatic compounds (PCE, trichloroethylene, cis-DCE, trans-1,2-dichloroethylene, 1,1-dichloroethylene, 1,1-dichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, and vinyl chloride) were degraded by cell-free extracts of strain HK-1.

  13. Acetylene fuels TCE reductive dechlorination by defined Dehalococcoides/Pelobacter consortia

    Science.gov (United States)

    Mao, Xinwei; Oremland, Ronald S.; Liu, Tong; Landers, Abigail A; Baesman, Shaun; Alvarez-Cohen, Lisa

    2017-01-01

    Acetylene (C2H2) can be generated in contaminated groundwater sites as a consequence of chemical degradation of trichloroethene (TCE) by in situ minerals, and C2H2 is known to inhibit bacterial dechlorination. In this study, we show that while high C2H2 (1.3 mM) concentrations reversibly inhibit reductive dechlorination of TCE by Dehalococcoides mccartyi isolates as well as enrichment cultures containing D. mccartyi sp., low C2H2 (0.4 mM) concentrations do not inhibit growth or metabolism of D. mccartyi. Cocultures of Pelobacter SFB93, a C2H2-fermenting bacterium, with D. mccartyi strain 195 or with D. mccartyi strain BAV1 were actively sustained by providing acetylene as the electron donor and carbon source while TCE or cis-DCE served as the electron acceptor. Inhibition by acetylene of reductive dechlorination and methanogenesis in the enrichment culture ANAS was observed, and the inhibition was removed by adding Pelobacter SFB93 into the consortium. Transcriptomic analysis of D. mccartyi strain 195 showed genes encoding for reductive dehalogenases (e.g., tceA) were not affected during the C2H2-inhibition, while genes encoding for ATP synthase, biosynthesis, and Hym hydrogenase were down-regulated during C2H2 inhibition, consistent with the physiological observation of lower cell yields and reduced dechlorination rates in strain 195. These results will help facilitate the optimization of TCE-bioremediation at contaminated sites containing both TCE and C2H2.

  14. Characterization of four TCE-dechlorinating microbial enrichments grown with different cobalamin stress and methanogenic conditions.

    Science.gov (United States)

    Men, Yujie; Lee, Patrick K H; Harding, Katie C; Alvarez-Cohen, Lisa

    2013-07-01

    To investigate the important supportive microorganisms responsible for trichloroethene (TCE) bioremediation under specific environmental conditions and their relationship with Dehalococcoides (Dhc), four stable and robust enrichment cultures were generated using contaminated groundwater. Enrichments were maintained under four different conditions exploring two parameters: high and low TCE amendments (resulting in inhibited and uninhibited methanogenic activity, respectively) and with and without vitamin B₁₂ amendment. Lactate was supplied as the electron donor. All enrichments were capable of reductively dechlorinating TCE to vinyl chloride and ethene. The dechlorination rate and ethene generation were higher, and the proportion of electrons used for dechlorination increased when methanogenesis was inhibited. Biologically significant cobalamin biosynthesis was detected in the enrichments without B₁₂ amendment. Comparative genomics using a genus-wide microarray revealed a Dhc genome similar to that of strain 195 in all enrichments, a strain that lacks the major upstream corrin ring biosynthesis pathway. Seven other bacterial operational taxonomic units (OTUs) were detected using clone libraries. OTUs closest to Pelosinus, Dendrosporobacter, and Sporotalea (PDS) were most dominant. The Clostridium-like OTU was most affected by B₁₂ amendment and active methanogenesis. Principal component analysis revealed that active methanogenesis, rather than vitamin B₁₂ limitation, exerted a greater effect on the community structures even though methanogens did not seem to play an essential role in providing corrinoids to Dhc. In contrast, acetogenic bacteria that were abundant in the enrichments, such as PDS and Clostridium sp., may be potential corrinoid providers for Dhc.

  15. Phreatophyte influence on reductive dechlorination in a shallow aquifer contaminated with trichloroethene (TCE)

    Science.gov (United States)

    Lee, R.W.; Jones, S.A.; Kuniansky, E.L.; Harvey, G.; Lollar, B.S.; Slater, G.F.

    2000-01-01

    Phytoremediation uses the natural ability of plants to degrade contaminants in groundwater. A field demonstration designed to remediate aerobic shallow groundwater contaminated with trichloroethene began in April 1996 with the planting of cottonwood trees, a short-rotation woody crop, over an approximately 0.2-ha area at the Naval Air Station, Fort Worth, Texas. The project was developed to demonstrate capture of contaminated groundwater and degradation of contaminants by phreatophytes. Analyses from samples of groundwater collected from July 1997 to June 1998 indicate that tree roots have the potential to create anaerobic conditions in the groundwater that will facilitate degradation of trichloroethene by microbially mediated reductive dechlorination. Organic matter from root exudates and decay of tree roots probably stimulate microbial activity, consuming dissolved oxygen. Dissolved oxygen concentrations, which varied across the site, were smallest near a mature cottonwood tree (about 20 years of age and 60 meters southwest of the cottonwood plantings) where degradation products of trichloroethene were measured. Oxidation of organic matter is the primary microbially mediated reaction occurring in the groundwater beneath the planted trees whereas near the mature cottonwood tree, data indicate that methanogenesis is the most probable reaction occurring. Reductive dechlorination in groundwater either is not occurring or is not a primary process away from the mature tree. Carbon-13 isotope values for trichloroethene are nearly identical at locations away from the mature tree, further confirming that dechlorination is not occurring at the site.

  16. Dechlorination kinetics of TCE at toxic TCE concentrations: Assessment of different models.

    Science.gov (United States)

    Haest, P J; Springael, D; Smolders, E

    2010-01-01

    The reductive dechlorination of trichloroethene (TCE) in a TCE source zone can be self-inhibited by TCE toxicity. A study was set up to examine the toxicity of TCE in terms of species specific degradation kinetics and microbial growth and to evaluate models that describe this self-inhibition. A batch experiment was performed using the TCE dechlorinating KB-1 culture at initial TCE concentrations ranging from 0.04mM to saturation (8.4mM). Biodegradation activity was highest at 0.3mM TCE and no activity was found at concentrations from 4 to 8mM. Species specific TCE and cis-DCE (cis-dichloroethene) degradation rates and Dehalococcoides numbers were modeled with Monod kinetics combined with either Haldane inhibition or a log-logistic dose-response inhibition on these rates. The log-logistic toxicity model appeared the most appropriate model and predicts that the species specific degradation activities are reduced by a factor 2 at about 1mM TCE, respectively cis-DCE. However, the model showed that the inhibitive effects on the time for TCE to ethene degradation are a complex function of degradation kinetics and the initial cell densities of the dechlorinating species. Our analysis suggests that the self-inhibition on biodegradation cannot be predicted by a single concentration threshold without information on the cell densities.

  17. Kinetics and Mechanism of Dechlorination of o-Chlorophenol by Nanoscale Pd/Fe

    Institute of Scientific and Technical Information of China (English)

    WEI Jian-jun; XU Xin-hua; LIU Yong

    2004-01-01

    Nanoscale Pd/Fe bimetallic particles were synthesized with an efficient method to dechlorinate o-chlorophenol. The nanoscale Pd/Fe particles were determined by transmission electron microscopy and BET specific surface area analysis. Most of the particles are in the size range of 20-100 nm. The BET specific surface area of synthesized nanoscale Pd/Fe particles is 12.4 m2/g. In contrast, a commercially available fine iron powder(<100 mesh) has a specific surface area of 0.49 m2/g. Batch studies demonstrated that the nanoscale particles can effectively dechlorinate o-chlorophenol. The dechlorination reaction takes place on the surface of synthesized nanoscale Pd/Fe bimetallic particles in a pseudo-first order reaction. The surface-area-normalized rate coefficients(kSA) are comparable to those reported in the literature for chlorinated ethenes. The observed reaction rate constants(kobs) are dominated by the mass fraction of Pd and the mass concentration of the nanoscale Pd/Fe particles.

  18. Kinetics of 2-chlorobiphenyl Reductive Dechlorination by Pd-fe0 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jiang Junrong

    2016-01-01

    Full Text Available Kinetics of 2-chlorobiphenyl (2-Cl BP catalytic reductive dechlorination by Pd-Fe0 nanoparticles were investigated. Experimental results showed that ultrafine bimetallic Pd-Fe0e nanoparticles were synthesized in the presence of 40 kHz ultrasound in order to enhance disparity and avoid agglomeration. The application of ultrasonic irradiation during the synthesis of Pd-Fe0 nanoparticles further accelerated the dechlorinated removal ratio of 2-Cl BP. Up to 95.0% of 2-Cl BP was removed after 300 min reaction with the following experimental conditions: initial 2-Cl BP concentration 10 mg L-1, Pd content 0.8 wt. %, bimetallic Pd-Fe0 nanoparticles prepared in the presence of ultrasound available dosage 7g L-1, initial pH value in aqueous solution 3.0, and reaction temperature 25°C. The catalytic reductive dechlorination of 2-Cl BP followed pseudo-first-order kinetics and the apparent pseudo-first-order kinetics constant was 0.0143 min-1.

  19. Flowpath independent monitoring of reductive dechlorination potential in a fractured rock aquifer

    Science.gov (United States)

    Bradley, P.M.; Lacombe, P.J.; Imbrigiotta, T.E.; Chapelle, F.H.; Goode, D.J.

    2009-01-01

    The flowpath dependent approaches that are typically employed to assess biodegradation of chloroethene contaminants in unconsolidated aquifers are problematic in fractured rock settings, due to difficulties defining discrete groundwater flowpaths in such systems. In this study, the variation in the potential for chloroethene biodegradation with depth was evaluated in a fractured rock aquifer using two flowpath independent lines of field evidence: (1) the presence of the three biochemical prerequisites [electron donor(s), chloroethene electron acceptor(s), and chlororespiring microorganism(s)] for efficient chloroethene chlororespiration and (2) the in situ accumulation of chloroethene reductive dechlorination daughter products. The validity of this approach was assessed by comparing field results with the results of [1, 2- 14C] cis-DCE microcosm experiments. Microcosms were prepared with depth-specific core material, which was crushed and emplaced in discrete packer intervals for 1 year to allow colonization by the indigenous microbial community. Packer intervals characterized by significant electron donor concentrations, elevated numbers of chlororespiring microorganisms, and high reductive dechlorination product to parent contaminant ratios correlated well with the production of 14C-labeled reductive dechlorination products in the microcosm experiments. These results indicate that, in the absence of information on discrete groundwater flowpaths, a modified approach emphasizing flowpath independent lines of evidence can provide insight into the temporal and spatial variability of contaminant biodegradation in fractured rock systems. ?? 2009 National Ground Water Association.

  20. Enhanced dechlorination of 2,4-dichlorophenol by recoverable Ni/Fe-Fe3O4 nanocomposites.

    Science.gov (United States)

    Xu, Cancan; Liu, Rui; Chen, Lvjun; Tang, Jialu

    2016-10-01

    Ni/Fe-Fe3O4 nanocomposites were synthesized for dechlorination of 2,4-dichlorophenol (2,4-DCP). The effects of the Ni content in Ni/Fe-Fe3O4 nanocomposites, solution pH, and common dissolved ions on the dechlorination efficiency were investigated, in addition to the reusability of the nanocomposites. The results showed that increasing content of Ni in Ni/Fe-Fe3O4 nanocomposites, from 1 to 5wt.%, greatly increased the dechlorination efficiency; the Ni/Fe-Fe3O4 nanocomposites had much higher dechlorination efficiency than bare Ni/Fe nanoparticles. Ni content of 5wt.% and initial pH below 6.0 was found to be the optimal conditions for the catalytic dechlorination of 2,4-DCP. Both 2,4-DCP and the intermediate product 2-chlorophenol (2-CP) were completely removed, and the concentration of the final product phenol was close to the theoretical phenol production from complete dechlorination of 20mg/L of 2,4-DCP, after 3hr reaction at initial pH value of 6.0, 3g/L Ni/Fe-Fe3O4, 5wt.% Ni content in the composite, and temperature of 22°C. 2,4-DCP dechlorination was enhanced by Cl(-) and inhibited by NO3(-) and SO4(2-). The nanocomposites were easily separated from the solution by an applied magnetic field. When the catalyst was reused, the removal efficiency of 2,4-DCP was almost 100% for the first seven uses, and gradually decreased to 75% in cycles 8-10. Therefore, the Ni/Fe-Fe3O4 nanocomposites can be considered as a potentially effective tool for remediation of pollution by 2,4-DCP.

  1. Catalytic dechlorination of 2,4-dichlorophenol by Pd/Fe bimetallic nanoparticles in the presence of humic acid.

    Science.gov (United States)

    Zhang, Zhen; Shen, Qiaohui; Cissoko, Naman; Wo, Jingjing; Xu, Xinhua

    2010-10-15

    Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products--phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82-91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10 wt.%, 0.15 wt.% to 0.20 wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300 min, respectively, the nitrate (NO(3)(-)) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl(-), o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP. 2010 Elsevier B.V. All rights reserved.

  2. Identification of Multiple Dehalogenase Genes Involved in Tetrachloroethene-to-Ethene Dechlorination in a Dehalococcoides-Dominated Enrichment Culture

    Directory of Open Access Journals (Sweden)

    Mohamed Ismaeil

    2017-01-01

    Full Text Available Chloroethenes (CEs are widespread groundwater toxicants that are reductively dechlorinated to nontoxic ethene (ETH by members of Dehalococcoides. This study established a Dehalococcoides-dominated enrichment culture (designated “YN3” that dechlorinates tetrachloroethene (PCE to ETH with high dechlorination activity, that is, complete dechlorination of 800 μM PCE to ETH within 14 days in the presence of Dehalococcoides species at 5.7±1.9×107 copies of 16S rRNA gene/mL. The metagenome of YN3 harbored 18 rdhA genes (designated YN3rdhA1–18 encoding the catalytic subunit of reductive dehalogenase (RdhA, four of which were suggested to be involved in PCE-to-ETH dechlorination based on significant increases in their transcription in response to CE addition. The predicted proteins for two of these four genes, YN3RdhA8 and YN3RdhA16, showed 94% and 97% of amino acid similarity with PceA and VcrA, which are well known to dechlorinate PCE to trichloroethene (TCE and TCE to ETH, respectively. The other two rdhAs, YN3rdhA6 and YN3rdhA12, which were never proved as rdhA for CEs, showed particularly high transcription upon addition of vinyl chloride (VC, with 75±38 and 16±8.6 mRNA copies per gene, respectively, suggesting their possible functions as novel VC-reductive dehalogenases. Moreover, metagenome data indicated the presence of three coexisting bacterial species, including novel species of the genus Bacteroides, which might promote CE dechlorination by Dehalococcoides.

  3. Acetylene fuels reductive dechlorination of TCE by Dehalococcoides/Pelobacter-containing microbial consortia

    Science.gov (United States)

    Oremland, R. S.; Mao, X.; Mahandra, C.; Baesman, S. M.; Gushgari, S.; Alvarez-Cohen, L.; Liu, T.

    2015-12-01

    Groundwater contamination by trichloroethene (TCE) poses a threat to health and leads to the generation of vinyl chloride (VC), a carcinogen. Dehalococcoides mccartyi is the only bacterium that can completely dechlorinate TCE to ethene (C2H4). Acetylene (C2H2) occurs in TCE-contaminated sites as a consequence of chemical degradation of TCE. Yet acetylene inhibits a variety of microbial processes including methanogesis and reductive dechlorination. Pelobacter acetylenicus and related species can metabolize acetylene via acetylene hydratase and acetaldehyde dismutatse thereby generating acetate and H2 as endproducts, which could serve as electron donor and carbon source for growth of D. mccartyi. We found that 1mM acetylene (aqueous) inhibits growth of D. mccartyi strain 195 on 0.3 mM TCE, but that the inhibition was removed after 12 days with the addition of an acetylene-utilizing isolate from San Francisco Bay, Pelobacter strain SFB93. TCE did not inhibit the growth of this Pelobacter at the concentrations tested (0.1-0.5 mM) and TCE was not consumed by strain SFB93. Co-cultures of strain 195 with strain SFB93 at 5% inoculation were established in 120 mL serum bottles containing 40 mL defined medium. TCE was supplied at a liquid concentration of 0.1 mM, with 0.1 mM acetylene and N2/CO2 (90:10 v/v) headspace at 34 °C. Co-cultures were subsequently transferred (5% vol/vol inoculation) to generate subcultures after 20 μmol TCE was reduced to VC and 36 μmol acetylene was depleted. Aqueous H2 ranged from 114 to 217 nM during TCE-dechlorination, and the cell yield of strain 195 was 3.7 ±0.3 × 107 cells μmol-1 Cl- released. In a D. mccartyi-containing enrichment culture (ANAS) under the same conditions as above, it was found that inhibition of dechlorination by acetylene was reversed after 19 days by adding SFB93. Thus we showed that a co-culture of Pelobacter SFB93 and D. mccartyi 195 could be maintained with C2H2 as the electron donor and carbon source while TCE

  4. Enhanced reductive dechlorination of tetrachloroethene by nano-sized mackinawite with cyanocobalamin in a highly alkaline condition.

    Science.gov (United States)

    Kim, Sangwoo; Park, Taehyung; Lee, Woojin

    2015-03-15

    In this study, we characterize the reductive dechlorination of tetrachloroethene (PCE) by nano-sized mackinawite (nFeS) with cobalamin (Cbl(III)) at a high pH and investigate the effects of environmental factors, including the concentrations of the target contaminant, reductant, and catalyst and suspension ions on the dechlorination kinetics of PCE. Ninety five percent of the PCE was degraded by nFeS with Cbl(III) in 15 h. Cyclic voltammetry conducted with regard to the reductive dechlorination showed a higher redox potential of mackinawite under a high-pH condition (-1.01 V), suggesting that the oxidation state of the central cobalt ion in the cobalamin could be reduced to Cbl(I). The change of cobalamin species on the nFeS surface was verified under different pH conditions by UV-vis spectroscopy. The rate constant of PCE dechlorination increased from 0.1582 to 0.4284 h(-1) due to the increase in the nFeS content (2.085-20.85 g/L). As the concentration of Cbl(III) increased from 0 to 0.5 mM, the dechlorination kinetics of PCE was accelerated (0-1.4091 h(-1)) but reached a state of equilibrium from 0.5 to 1 mM. The increase in the initial PCE concentration (0.035-1.0 mM) slowed down the dechlorination kinetics (0.2036-0.0962 h(-1)). The dechlorination kinetics was enhanced by 1.5-11 times when 10 mM of ions (Na(+), K(+), Mg(2+), Ca(2+), CO3(2-), SO4(2-), and NO3(-)) were added, while an addition of HCO3 decelerated it by 10 times. This study can provide background knowledge pertaining to the PCE dechlorination by a natural reductant under a high-pH condition and the effect of environmental factors on the dechlorination kinetics for the development of novel remediation technologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Electrocatalytic dechlorination of 2,3,5-trichlorophenol on palladium/carbon nanotubes-nafion film/titanium mesh electrode.

    Science.gov (United States)

    Sun, Zhirong; Ma, Xiaoyue; Hu, Xiang

    2017-06-01

    Palladium/carbon nanotubes-nafion film-modified titanium mesh electrode (Pd/CNTs-nafion film/Ti electrode) was prepared and used for catalytic dechlorination of 2,3,5-trichlorophenol (2,3,5-TCP). The influences of factors, such as Pd(2+) concentration, plating solution pH, and electrodeposition time and current, on the preparation of the electrode were studied by cyclic voltammetry (CV) to establish the optimal electrode preparation conditions. Additionally, the CV results highlighted that the addition of the CNTs-nafion film could enhance the electrochemical performance of the electrode. The Pd/CNTs-nafion film/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The electrode exhibited good stability and high catalytic dechlorination capacity on 2,3,5-TCP-100 mg L(-1) 2,3,5-TCP was completely dechlorinated within 100 min at a dechlorination current of 5 mA and an initial solution pH of 2.3. High-performance liquid chromatography (HPLC) was used to detect the chlorinated phenolic intermediates, and the results revealed that the final products were mainly phenol. The kinetics studies revealed that the dechlorination of 2,3,5-TCP followed two-stage mixed order kinetics, and a possible degradation pathway for 2,3,5-TCP was proposed.

  6. Effect of AQDS Accelerating Anaerobic Dechlorination of DDT in Hydragric Acrisols%AQDS加速红壤性水稻土中DDT厌氧脱氯效应研究

    Institute of Scientific and Technical Information of China (English)

    刘翠英; 王壮; 徐向华; 罗雪顶

    2016-01-01

    电子供体基质和电子穿梭体对电子转移过程有重要影响,进而可能影响厌氧反应体系中2,2-双(4-氯苯基)-1,1,1-三氯乙烷(DDT)还原脱氯降解。为了阐明电子供体基质正丁酸与电子穿梭体蒽醌-2,6-二磺酸盐(AQDS)对红壤性水稻土中DDT还原脱氯效果的影响,本研究采用厌氧土壤培养试验并设定以下5个处理:①灭菌对照,②对照,③正丁酸,④AQDS,⑤正丁酸+AQDS。结果表明,厌氧培养20 d后,土壤中DDT可提取态残留量减少了85.2%~96.3%。DDT厌氧脱氯降解的主要产物为2,2-双(4-氯苯基)-1,1-二氯乙烷DDD。添加正丁酸在培养前8d显著提高产CH4速率,而对DDT脱氯降解无显著促进作用,第8天之后,随着产CH4速率降低,添加正丁酸处理的DDT脱氯速率逐渐升高。添加AQDS显著增强土壤还原性并加速三价铁氧化物还原生成电子供体二价铁,进而显著促进DDT还原脱氯降解。同时添加正丁酸和AQDS对促进DDT还原脱氯的效果最佳,但是正丁酸和AQDS对加速DDT还原脱氯无显著交互作用。本研究结果对于制定DDT污染土壤的高效原位修复技术方案具有指导意义。%1,1,1-Trichoro-2,2-bis(p-chlorophenyl)ethane(DDT)is one of the most extensively used organochlorine pesticides worldwide. As a result,DDT can be detected in various environmental compartments in recent years,and its concentration is much higher in the soil than in the air and water. Therefore,it is of great significance to develop an efficient technology to remedy DDT contaminated soils. Reductive dechlorination seems to be a crucial pathway for DDT degradation under anaerobic conditions, because the five electrophonic chlorine substitients in a DDT molecule make aerobic oxidative degradation difficult. However,reductive dechlorination requires the addition of two electrons for each chlorine removed. Therefore,the existence of electron donor

  7. Use of statistical tools to evaluate the reductive dechlorination of high levels of TCE in microcosm studies.

    Science.gov (United States)

    Harkness, Mark; Fisher, Angela; Lee, Michael D; Mack, E Erin; Payne, Jo Ann; Dworatzek, Sandra; Roberts, Jeff; Acheson, Carolyn; Herrmann, Ronald; Possolo, Antonio

    2012-04-01

    A large, multi-laboratory microcosm study was performed to select amendments for supporting reductive dechlorination of high levels of trichloroethylene (TCE) found at an industrial site in the United Kingdom (UK) containing dense non-aqueous phase liquid (DNAPL) TCE. The study was designed as a fractional factorial experiment involving 177 bottles distributed between four industrial laboratories and was used to assess the impact of six electron donors, bioaugmentation, addition of supplemental nutrients, and two TCE levels (0.57 and 1.90 mM or 75 and 250 mg/L in the aqueous phase) on TCE dechlorination. Performance was assessed based on the concentration changes of TCE and reductive dechlorination degradation products. The chemical data was evaluated using analysis of variance (ANOVA) and survival analysis techniques to determine both main effects and important interactions for all the experimental variables during the 203-day study. The statistically based design and analysis provided powerful tools that aided decision-making for field application of this technology. The analysis showed that emulsified vegetable oil (EVO), lactate, and methanol were the most effective electron donors, promoting rapid and complete dechlorination of TCE to ethene. Bioaugmentation and nutrient addition also had a statistically significant positive impact on TCE dechlorination. In addition, the microbial community was measured using phospholipid fatty acid analysis (PLFA) for quantification of total biomass and characterization of the community structure and quantitative polymerase chain reaction (qPCR) for enumeration of Dehalococcoides organisms (Dhc) and the vinyl chloride reductase (vcrA) gene. The highest increase in levels of total biomass and Dhc was observed in the EVO microcosms, which correlated well with the dechlorination results.

  8. Humic acid and metal ions accelerating the dechlorination of 4-chlorobiphenyl by nanoscale zero-valent iron

    Institute of Scientific and Technical Information of China (English)

    Yu Wang; Dongmei Zhou; Yujun Wang; Xiangdong Zhu; Shengyang Jin

    2011-01-01

    Transformation of polychlorinated biphenyls (PCBs) by zero-valent iron represents one of the latest innovative technologies for environmental remediation.The dechlorination of 4-chlorobiphenyl (4-C1BP) by nanoscale zero-valent iron (NZVI) in the presence of humic acid or metal ions was investigated.The results showed that the de chlorination of 4-CIBP by NZVI increased with decreased solution pH.When the initial pH value was 4.0,5.5,6.8,and 9.0,the de chlorination efliciencies of 4-C1BP after 48 hr were 53.8%,47.8%,35.7%,and 35.6%,respectively.The presence of humic acid inhibited the reduction of 4-ClBP in the first 4 hr,and then significantly accelerated the dechlorination by reaching 86.3% in 48 hr.Divalent metal ions,Co2+,Cu2+,and Ni2+,were reduced and formed bimetals with NZVI,thereby enhanced the dechlorination of 4-CIBP.The dechlorination percentages of 4-CIBP in the presence of 0.1 mmol/L Co2+,Cu2+ and Ni2+ were 66.1%,66.0% and 64.6% in 48 hr,and then increased to 67.9%,71.3% and 73.5%,after 96 hr respectively.The dechlorination kinetics of 4-CIBP by the NZVI in all cases followed pseudo-first order model.The results provide a basis for better understanding of the dechlorination mechanisms of PCBs in real environment.

  9. Ecology and distribution of a new biomarker linked to 1,2-dichloropropane dechlorination in subsurface environments

    Science.gov (United States)

    Padilla-Crespo, E.; Loeffler, F. E.

    2011-12-01

    Reductive dechlorination plays a major role in the transformation and detoxification of chlorinated solvents, including chlorinated ethenes. Molecular biological tools are being applied at contaminated sites in order to assess the process-specific biomarkers that impact site performance, and to monitor the progress of bioremediation approaches. The few current biomarker genes in use provide an incomplete picture of the reductively dechlorinating bacterial community; this is a limitation for implementing enhanced bioremediation and monitored natural attenuation as cleanup strategies at chlorinated solvent contaminated sites. Reductively dehalogenating organisms, particularly Dehalococcoides (Dhc) strains, possess multiple reductive dehalogenase (RDase) genes, which are promising targets to specifically monitor dehalogenation processes of interest. Dehalococcoides populations in two highly enriched cultures (RC and KS) have been implicated in the reductive dechlorination of dechlorination of 1,2-dichloropropane (1,2-D), a widespread halogenated organic pollutant, to the non-toxic propene. Using a combined approach of transcription, expression and molecular analysis a new biomarker linked to 1,2-dichloropropane has been identified in Dhc strains RC and KS providing for the first time, convincing evidence of a specific RDase implicated in 1,2-D dechlorination to propene. Further analyses imply that new biomarker is in a "mobile DNA segment", a genomic island (GI) of horizontal gene transfer origin. A valid quantitative PCR approach was designed to detect and enumerate this gene in cultures and environmental samples; this will be a useful to bioremediation practitioners to more efficiently implement reductive dechlorination as a remediation tool. The new biomarker has been identified in fresh water sediment samples from different geographical locations in Europe, North and South America. Further research aims to shed light on RDase gene dissemination and the adaptation

  10. Accelerated anaerobic dechlorination of DDT in slurry with Hydragric Acrisols using citric acid and anthraquinone-2,6-disulfonate (AQDS).

    Science.gov (United States)

    Liu, Cuiying; Xu, Xianghua; Fan, Jianling

    2015-12-01

    The application of electron donor and electron shuttle substances has a vital influence on electron transfer, thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)ethane (DDT) in anaerobic reaction systems. To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate (AQDS) in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide, a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of (1) control, (2) citric acid, (3) AQDS, and (4) citric acid+AQDS. Results showed that DDT residues decreased by 78.93%-92.11% of the initial quantities after 20days of incubation, and 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane (DDD) was the dominant metabolite. The application of citric acid accelerated DDT dechlorination slightly in the first 8days, while the methanogenesis rate increased quickly, and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased. The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe(III) oxides to generate Fe(II), which was an efficient electron donor, thus enhancing the reductive dechlorination rate of DDT. The addition of citric acid+AQDS was most efficient in stimulating DDT dechlorination, but no significant interaction between citric acid and AQDS on DDT dechlorination was observed. The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites. Copyright © 2015. Published by Elsevier B.V.

  11. Toxicokinetic model assessment on the dechlorination of dietary toxaphene CHB-62 into CHB-44 in Atlantic salmon (Salmo salar L.).

    Science.gov (United States)

    Berntssen, M H G; Lock, E J; Zeilmaker, M J; Van Eijkeren, J C H

    2013-01-01

    European Union legislation on the upper limits of toxaphene in feed and food include the congeners CHB-26, CHB-62 and CHB-50 and is set at 50 µg kg⁻¹ feed for the sum of these three congeners. However, due to their elevated presence in fish, the congeners CHB-40 and CHB-41, CHB-44, and CHB-42 should also be included according to the European Food Safety Authority (EFSA) in 2005. Earlier trials with model zebra fish have shown in vivo dechlorination of dietary CHB-62 to CHB-44 and, to a lesser degree, of CHB-50 to CHB-40. Biomagnification patterns of Atlantic salmon, fed with technical toxaphene-enriched feeds, indicated that Atlantic salmon have a similar dechlorination. In the present study, a serial one-compartment physiological kinetic model, which includes differentiated growth of body components, is used to quantify the contribution of dechlorination to the congener-specific fillet accumulation of a mixture of dietary toxaphene congeners in Atlantic salmon. The model is assessed from experimental uptake and elimination kinetics of Atlantic salmon smolt fed with technical toxaphene for 122 days followed by a depuration period of 75 days in which the fish were fed toxaphene-free control feed. The serial one-compartment model shows that about 31% of CHB-44 that accumulated in the fillet originated from dietary CHB-62. In contrast, dechlorination of CHB-50 into CHB-40 is not significant. The results show that previously demonstrated in vivo dechlorination of CHB-62 into CHB-44 in zebra fish also occurs in the farmed fish species Atlantic salmon. This dechlorination can at least partly explain the relatively elevated CHB-44 observed in toxaphene fish surveys.

  12. Stable carbon isotope monitoring of in situ bioaugmentation for enhanced reductive dechlorination of halogenated hydrocarbons

    Science.gov (United States)

    Bill, M.; Conrad, M. E.; Sorenson, K.; Wymore, R.; Lamar, M.; Chamberlain, S.; Trotsky, J.

    2009-12-01

    Injection of electron donor to stimulate reductive dechlorination of trichloroethene (TCE) has been demonstrated to be an effective strategy for remediation of contaminated groundwater. At a number of sites, however, complete reductive dechlorination of TCE to ethene is not attained because the appropriate microbial community is not present. Addition of Dehalococcoides spp. to groundwater to achieve complete reductive dechlorination of TCE is being tested at Naval Weapons Station Seal Beach, CA. To help assess the effectiveness of this process, the stable carbon isotope compositions of TCE and its byproducts, cis-dichloroethene (cDCE), vinyl chloride (VC) and ethene are being measured during the experiment. Two different methods of bioremediation are being tested. In the “active” cell groundwater is continuously pumped from downgradient wells and re-injected into two upgradient wells. Electron donor (1-3% Na-lactate) has been added to the injection line either weekly or monthly. In the “passive” cell, no circulation of groundwater is done, but electron donor is added to three injection wells monthly. When reducing conditions were reached in the groundwater (late 2008), the bioaugmentation culture was added to both experimental cells with the electron donor. In the active cell, addition of electron donor prior to introduction of the bioaugmentation culture stimulated significant increases in the concentrations of cDCE, but only trace VC and ethene. In the passive cell, production of cDCE was observed, but at lower levels. The δ13C values of TCE ranged from -20‰ to 28‰ (averaging -24‰). The δ13C values of cDCE were generally 1-2‰ per mil lower than those of the TCE, representing fractionation during the biological conversion from TCE to cDCE. Following bioaugmentation, significant production of VC has been observed in the active cell, with corresponding increases in δ13C values of TCE and cDCE. In several wells, the δ13C values of the cDCE have

  13. Mineralization of 2-chlorophenol by sequential electrochemical reductive dechlorination and biological processes

    Energy Technology Data Exchange (ETDEWEB)

    Arellano-González, Miguel Ángel; González, Ignacio [Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Química, Av. San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D.F. (Mexico); Texier, Anne-Claire, E-mail: actx@xanum.uam.mx [Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Biotecnología, Av. San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico, D.F. (Mexico)

    2016-08-15

    Highlights: • Dechlorination of 2-chlorophenol to phenol was 100% efficient on Pd-Ni/Ti electrode. • An ECCOCEL reactor was efficient and selective to obtain phenol from 2-chlorophenol. • Phenol was totally mineralized in a coupled denitrifying biorreactor. • Global time of 2-chlorophenol mineralization in the combined system was 7.5 h. - Abstract: In this work, a novel approach was applied to obtain the mineralization of 2-chlorophenol (2-CP) in an electrochemical-biological combined system where an electrocatalytic dehydrogenation process (reductive dechlorination) was coupled to a biological denitrification process. Reductive dechlorination of 2-CP was conducted in an ECCOCEL-type reactor on a Pd-Ni/Ti electrode at a potential of −0.40 V vs Ag/AgCl{sub (s)}/KCl{sub (sat)}, achieving 100 percent transformation of 2-CP into phenol. The electrochemically pretreated effluent was fed to a rotating cylinder denitrifying bioreactor where the totality of phenol was mineralized by denitrification, obtaining CO{sub 2} and N{sub 2} as the end products. The total time required for 2-CP mineralization in the combined electrochemical-biological process was 7.5 h. This value is close to those previously reported for electrochemical and advanced oxidation processes but in this case, an efficient process was obtained without accumulation of by-products or generation of excessive energy costs due to the selective electrochemical pretreatment. This study showed that the use of electrochemical reductive pretreatment combined with biological processes could be a promising technology for the removal of recalcitrant molecules, such as chlorophenols, from wastewaters by more efficient, rapid, and environmentally friendly processes.

  14. Reductive dechlorination of tetrachloroethene in marine sediments: Biodiversity and dehalorespiring capabilities of the indigenous microbes.

    Science.gov (United States)

    Matturro, B; Presta, E; Rossetti, S

    2016-03-01

    Chlorinated compounds pose environmental concerns due to their toxicity and wide distribution in several matrices. Microorganisms specialized in leading anaerobic reductive dechlorination (RD) processes, including Dehalococcoides mccartyi (Dhc), are able to reduce chlorinated compounds to harmless products or to less toxic forms. Here we report the first detailed study dealing with the RD potential of heavy polluted marine sediment by evaluating the biodegradation kinetics together with the composition, dynamics and activity of indigenous microbial population. A microcosm study was conducted under strictly anaerobic conditions on marine sediment collected near the marine coast of Sarno river mouth, one of the most polluted river in Europe. Tetrachloroethene (PCE), used as model pollutant, was completely converted to ethene within 150 days at reductive dechlorination rate equal to 0.016 meq L(-1) d(-1). Consecutive spikes of PCE allowed increasing the degradation kinetics up to 0.1 meq L(-1)d(-1) within 20 days. Strictly anaerobiosis and repeated spikes of PCE stimulated the growth of indigenous Dhc cells (growth yield of ~7.0 E + 07 Dhc cells per μM Cl(-1) released). Dhc strains carrying the reductive dehalogenase genes tceA and vcrA were detected in the original marine sediment and their number increased during the treatment as demonstrated by the high level of tceA expression at the end of the microcosm study (2.41 E + 05 tceA gene transcripts g(-1)). Notably, the structure of the microbial communities was fully described by Catalysed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) as wells as the dynamics of the dechlorinating bacteria during the microcosms operation. Interestingly, a direct role of Dhc cells was ascertained suggesting the existence of strains adapted at salinity conditions. Additionally, non-Dhc Chloroflexi were retrieved in the original sediment and were kept stable over time suggesting their likely flanking role of the RD

  15. Molecular Biomarker-Based Biokinetic Modeling of a PCE-Dechlorinating and Methanogenic Mixed Culture

    Energy Technology Data Exchange (ETDEWEB)

    Heavner, Gretchen L. W.; Rowe, Annette R.; Mansfeldt, Cresten B.; Pan, Ju Khuan; Gossett, James M.; Richardson, Ruth E.

    2013-04-16

    Bioremediation of chlorinated ethenes via anaerobic reductive dechlorination relies upon the activity of specific microbial population-most notably Dehalococcoides (DHC) strains. In the lab and field Dehalococcoides grow most robustly in mixed communities which usually contain both fermenters and methanogens. Recently, researchers have been developing quantitative molecular biomarkers to aid in field site diagnostics and it is hoped that these biomarkers could aid in the modeling of anaerobic reductive dechlorination. A comprehensive biokinetic model of a community containing Dehalococcoides mccartyi (formerly D. ethenogenes) was updated to describe continuously fed reactors with specific biomass levels based on quantitative PCR (qPCR)-based population data (DNA and RNA). The model was calibrated and validated with subsets of chemical and molecular biological data from various continuous feed experiments (n = 24) with different loading rates of the electron acceptor (1.5 to 482 μeeq/L-h), types of electron acceptor (PCE, TCE, cis-DCE) and electron donor to electron acceptor ratios. The resulting model predicted the sum of dechlorination products vinyl chloride (VC) and ethene (ETH) well. However, VC alone was under-predicted and ETH was over predicted. Consequently, competitive inhibition among chlorinated ethenes was examined and then added to the model. Additionally, as 16S rRNA gene copy numbers did not provide accurate model fits in all cases, we examined whether an improved fit could be obtained if mRNA levels for key functional enzymes could be used to infer respiration rates. The resulting empirically derived mRNA “adjustment factors” were added to the model for both DHC and the main methanogen in the culture (a Methanosaeta species) to provide a more nuanced prediction of activity. Results of this study suggest that at higher feeding rates competitive inhibition is important and mRNA provides a more accurate indicator of a population’s instantaneous

  16. Chloroethene dechlorination in acidic groundwater: Implications for combining fenton's treatment with natural attenuation

    Science.gov (United States)

    Bradley, Paul M.; Singletary , Michael A.; Chapelle, Francis H.

    2007-01-01

    A sulfuric acid leak in 1988 at a chloroethene-contaminated groundwater site at the Naval Air Station Pensacola has resulted in a long-term record of the behavior of chloroethene contaminants at low pH and a unique opportunity to assess the potential impact of source area treatment technologies, which involve acidification of the groundwater environment (e.g., Fenton's-based in situ chemical oxidation), on downgradient natural attenuation processes. The greater than 75 percent decrease in trichloroethene (TCE) concentrations and the shift in contaminant composition toward predominantly reduced daughter products (dichloroethene [DCE] and vinyl chloride [VC]) that were observed along a 30-m groundwater flow path characterized by highly acidic conditions (pH = 3.5 ± 0.4) demonstrated that chloroethene reductive dechlorination can continue to be efficient under persistent acidic conditions. The detection of Dehalococcoides-type bacteria within the sulfuric acid/chloroethene co-contaminant plume was consistent with biotic chloroethene reductive dechlorination. Microcosm studies conducted with 14C-TCE and 14C-VC confirmed biotic reductive dechlorination in sediment collected from within the sulfuric acid/chloroethene co-contaminant plume. Microcosms prepared with sediment from two other locations within the acid plume, however, demonstrated only a limited mineralization to 14CO2 and 14CO, which was attributed to abiotic degradation because no significant differences were observed between experimental and autoclaved control treatments. These results indicated that biotic and abiotic mechanisms contributed to chloroethene attenuation in the acid plume at NAS Pensacola and that remediation techniques involving acidification of the groundwater environment (e.g., Fenton's-based source area treatment) do not necessarily preclude efficient chloroethene degradation.

  17. Inhibition of iron (III) minerals and acidification on the reductive dechlorination of trichloroethylene.

    Science.gov (United States)

    Paul, Laiby; Smolders, Erik

    2014-09-01

    Reductive dechlorination of chlorinated ethenes is inhibited by acidification and by the presence of Fe (III) as a competitive electron acceptor. Synergism between both factors on dechlorination is predicted as reductive dissolution of Fe (III) minerals is facilitated by acidification. This study was set-up to assess this synergism for two common aquifer Fe (III) minerals, goethite and ferrihydrite. Anaerobic microbial dechlorination of trichloroethylene (TCE) by KB-1 culture and formate as electron donor was investigated in anaerobic batch containers at different solution pH values (6.2-7.2) in sand coated with these Fe minerals and a sand only as control. In the absence of Fe, lowering substrate pH from 7.2 to 6.2 increased the time for 90% TCE degradation from 14±1d to 42±4d. At pH 7.2, goethite did not affect TCE degradation time while ferrihydrite increased the degradation time to 19±1d compared to the no Fe control. At pH 6.2, 90% degradation was at 78±1 (ferrihydrite) or 131±1d (goethite). Ferrous iron production in ferrihydrite treatment increased between pH 7.2 and 6.5 but decreased by further lowering pH to 6.2, likely due to reduced microbial activity. This study confirms that TCE is increasingly inhibited by the combined effect of acidification and bioavailable Fe (III), however no evidence was found for synergistic inhibition since Fe reduction did not increase as pH decreases. To the best of our knowledge, this is the first study where effect of pH and Fe (III) reduction on TCE was simultaneously tested. Acid Fe-rich aquifers need sufficient buffering and alkalinity to ensure swift degradation of chlorinated ethenes.

  18. A stepwise dechlorination/cross-coupling strategy to diversify the vancomycin 'in-chloride'.

    Science.gov (United States)

    Wadzinski, Tyler J; Gea, Katherine D; Miller, Scott J

    2016-02-01

    In an effort to rapidly access vancomycin analogues bearing diverse functionality at the 6c-Cl (the 'in-chloride') position, a two-step dechlorination/cross-coupling protocol was developed. Conditions for efficient cross-coupling of the relatively unreactive 6c-Cl group were found that ensure high conversion with minimal product decomposition. A set of 2c-dechloro-6c-functionalized vancomycin derivatives was prepared, and antibiotic activities of the compounds were evaluated against a panel of vancomycin-resistant and vancomycin-susceptible strains. Results from biological testing further underscore the steric sensitivity of vancomycin's binding pocket.

  19. Impact of estuarine gradients on reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin in river sediment enrichment cultures.

    Science.gov (United States)

    Dam, Hang T; Häggblom, Max M

    2017-02-01

    Polychlorinated dibenzo-p-dioxins (PCDDs) are among the most persistent organic pollutants. Although the total input of PCDDs into the environment has decreased substantially over the past four decades, their input via non-point sources is still increasing, especially in estuarine metropolitan areas. Here we report on the microbially mediated reductive dechlorination of PCDDs in anaerobic enrichment cultures established from sediments collected from five locations along the Hackensack River, NJ and investigate the impacts of sediment physicochemical characteristics on dechlorination activity. Dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) and abundance of Dehalococcoides spp. negatively correlated with salinity and sulfate concentration in sediments used to establish the cultures. 1,2,3,4-TeCDD was dechlorinated to a lesser extent in cultures established from sediments from the tidally influenced estuarine mouth of the river. In cultures established from low salinity sediments, 1,2,3,4-TeCDD was reductively dechlorinated with the accumulation of 2-monochlorodibenzo-p-dioxin as the major product. Sulfate concentrations above 2 mM inhibited 1,2,3,4-TecDD dechlorination activity. Consecutive lateral- and peri- dechlorination took place in enrichment cultures with a minimal accumulation of 2,3-dichlorodibenzo-p-dioxin in active cultures. A Dehalococcoides spp. community was enriched and accounted for up to 64% of Chloroflexi detected in these sediment cultures. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. ADVANCEMENT OF NUCLEIC ACID-BASED TOOLS FOR MONITORING IN SITU REDUCTIVE DECHLORINATION

    Energy Technology Data Exchange (ETDEWEB)

    Vangelas, K; ELIZABETH EDWARDS, E; FRANK LOFFLER, F; Brian02 Looney, B

    2006-11-17

    Regulatory protocols generally recognize that destructive processes are the most effective mechanisms that support natural attenuation of chlorinated solvents. In many cases, these destructive processes will be biological processes and, for chlorinated compounds, will often be reductive processes that occur under anaerobic conditions. The existing EPA guidance (EPA, 1998) provides a list of parameters that provide indirect evidence of reductive dechlorination processes. In an effort to gather direct evidence of these processes, scientists have identified key microorganisms and are currently developing tools to measure the abundance and activity of these organisms in subsurface systems. Drs. Edwards and Luffler are two recognized leaders in this field. The research described herein continues their development efforts to provide a suite of tools to enable direct measures of biological processes related to the reductive dechlorination of TCE and PCE. This study investigated the strengths and weaknesses of the 16S rRNA gene-based approach to characterizing the natural attenuation capabilities in samples. The results suggested that an approach based solely on 16S rRNA may not provide sufficient information to document the natural attenuation capabilities in a system because it does not distinguish between strains of organisms that have different biodegradation capabilities. The results of the investigations provided evidence that tools focusing on relevant enzymes for functionally desired characteristics may be useful adjuncts to the 16SrRNA methods.

  1. Reductive dechlorination of trichloroethene DNAPL source zones: source zone architecture versus electron donor availability

    Science.gov (United States)

    Krol, M.; Kokkinaki, A.; Sleep, B.

    2014-12-01

    The persistence of dense-non-aqueous-phase liquids (DNAPLs) in the subsurface has led practitioners and regulatory agencies to turn towards low-maintenance, low-cost remediation methods. Biological degradation has been suggested as a possible solution, based on the well-proven ability of certain microbial species to break down dissolved chlorinated ethenes under favorable conditions. However, the biodegradation of pure phase chlorinated ethenes is subject to additional constraints: the continuous release of electron acceptor at a rate governed by mass transfer kinetics, and the temporal and spatial heterogeneity of DNAPL source zones which leads to spatially and temporally variable availability of the reactants for reductive dechlorination. In this work, we investigate the relationship between various DNAPL source zone characteristics and reaction kinetics using COMPSIM, a multiphase groundwater model that considers non-equilibrium mass transfer and Monod-type kinetics for reductive dechlorination. Numerical simulations are performed for simple, homogeneous trichloroethene DNAPL source zones to demonstrate the effect of single source zone characteristics, as well as for larger, more realistic heterogeneous source zones. It is shown that source zone size, and mass transfer kinetics may have a decisive effect on the predicted bio-enhancement. Finally, we evaluate the performance of DNAPL bioremediation for realistic, thermodynamically constrained, concentrations of electron donor. Our results indicate that the latter may be the most important limitation for the success of DNAPL bioremediation, leading to reduced bio-enhancement and, in many cases, comparable performance with water flooding.

  2. DETECTING AND QUANTIFYING REDUCTIVE DECHLORINATION DURING MONITORED NATURAL ATTENUATION AT THE SAVANNAH RIVER CBRP SITE

    Energy Technology Data Exchange (ETDEWEB)

    Vangelas, K; JACK D. ISTOK, J; JENNIFER A. FIELD, J; ERIC RAES, E; Margaret Millings, M; AARON D. PEACOCK, A; Brian02 Looney, B

    2007-01-02

    Various attenuation mechanisms control the destruction, stabilization, and/or removal of contaminants from contaminated subsurface systems. Measuring the rates of the controlling attenuation mechanisms is a key to employing mass balance as a means to evaluate and monitor the expansion, stability and subsequent shrinkage of a contaminant plume. A team of researchers investigated the use of push-pull tests for measuring reductive dechlorination rates in situ at sites with low chlorinated solvent concentrations (<1 ppm). The field research also examined the synergistic use of a suite of geochemical and microbial assays. Previous push-pull tests applied to environmental remediation objectives focused on general hydrological characterization or on designing bioremediation systems by examining the response of the subsurface to stimulation. In this research, the push-pull technique was tested to determine its ''low-range'' sensitivity and uncertainty. Can these tests quantify relatively low attenuation rates representative of natural attenuation? The results of this research indicate that push-pull testing will be useful for measurement of in situ reductive dechlorination rates for chlorinated solvents at ''Monitored Natural Attenuation'' (MNA) sites. Further, using principal component analysis and other techniques, the research confirmed the usefulness of multiple lines of evidence in site characterization and in upscaling measurements made in individual wells--especially for sites where there is a geochemical gradient or varying geochemical regimes within the contaminant plume.

  3. Evaluation of redox indicators for determining sulfate-reducing and dechlorinating conditions.

    Science.gov (United States)

    Jones, Brian D; Ingle, James D

    2005-11-01

    An in situ methodology based on covalently bonded redox indicators has been developed for determining when sulfate-reducing conditions exist in environmental samples. Three immobilized redox indicators [thionine (Thi, formal potential at pH 7 (E(0')7) equals 52 mV), cresyl violet (CV, E(0')7 = -81 mV), and phenosafranine (PSaf, E(0')7 = -267 mV)] were tested for their response to sulfide in synthetic solutions and under sulfate-reducing conditions in wastewater slurries. The byproduct of the sulfate-reducing process, sulfide, was found to couple well to CV in the concentration range of 1-100 microM total sulfide ([S(-II)]) and the pH range of 6-8. Thi, the indicator with the highest formal potential, reacts rapidly with sulfide at levels well below 1 microM while PSaf, the indicator with the lowest formal potential, does not couple to sulfide at levels in excess of 100 microM [S(-II)]. The degree of reduction of the indicators (i.e., the fraction of cresyl violet oxidized) in contact with a given level of sulfide can be modeled qualitatively with an equilibrium expression for [S(-II)]-indicator based on the Nernst equation assuming that rhombic sulfur is the product of sulfide oxidation. In a groundwater sample with dechlorinating microbes, reduction of Thi and partial reduction of CV correlated with dechlorination of TCE to cis-DCE.

  4. [Degradation of 2, 4-D by combined catalytic dechlorination and biological oxidation].

    Science.gov (United States)

    Zhou, Hong-yi; Zeng, Si-si; Liang, Si; Han, Jian

    2014-09-01

    In this paper, Pd/Fe nanoparticles were used to degrade 2,4-D. Then the resulted solution of 2,4-D dechlorination was biological oxidized by activated sludge. And the effects of initial pH, activated sludge volume, initial contaminant concentration and temperature on the removal of PA were studied. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) was used to study microbial community structure. And High Performance Liquid Chromatography (HPLC) was employed to determine and analyze the degradation process of target pollutant. The conclusions can be summarized as follows: (1) Pd/Fe can degrade 2,4-D efficiently, 2-CPA was the intermediate product, and the end product was PA. (2) Compared with 2,4-D, the dechlorination product PA has lower biological toxicity, and can be more easily degraded by activated sludges. (3) pH = 7, 50 mL activated sludge/200 mL solution, PA initial concentration of 14. 6 mg L-1 and 30°C favored the PA removal. Under suitable conditions, the removal rate of PA can reach to 84. 3% after 96 hours.

  5. Dechlorination of chlorinated ethylenes by a photochemically generated iron(0) complex.

    Science.gov (United States)

    Pelton, Emily J; Blank, David A; McNeill, Kristopher

    2013-07-28

    The reactivity of Fe(0) toward chlorinated ethylenes was examined utilizing a photochemically generated, highly reactive Fe(0) complex. Irradiation of (dmpe)2FeH2 (dmpe = Me2PCH2CH2PMe2) with 360 nm light generated a 16-e(-), Fe(0) intermediate that reacted to dechlorinate chlorinated ethylenes in a stepwise fashion, consistent with a hydrogenolysis dechlorination pathway. The source of the hydrogen atoms in the hydrogenolysis were the hydride ligands of an additional equivalent of (dmpe)2FeH2, as evidenced by deuterium labeling experiments. The reaction was observed to be first-order in (dmpe)2FeH2, chlorinated ethylene substrate, and the intensity of 360 nm radiation. The rate of chlorinated ethylene substrate decay increased with increasing substrate chlorination in the order CH2=CHCl < cis-CHCl=CHCl < trans-CHCl=CHCl < CCl2=CHCl. A mechanism of reaction was proposed that accounts for the reaction kinetics, the observed intermediates, and the origin of hydrogen atoms incorporated into reaction products.

  6. Impacts of microbial community composition on isotope fractionation during reductive dechlorination of tetrachloroethylene.

    Science.gov (United States)

    Dong, Yiran; Butler, Elizabeth C; Philp, R Paul; Krumholz, Lee R

    2011-04-01

    Isotope fractionation has been used with increasing frequency as a tool to quantify degradation of chlorinated aliphatic pollutants in the environment. The objective of this research was to determine if the electron donor present in enrichment cultures prepared from uncontaminated sediments influenced the extent of isotope fractionation of tetrachloroethylene (PCE), either directly, or through its influence on microbial community composition. Two PCE-degrading enrichment cultures were prepared from Duck Pond (DP) sediment and were incubated with formate (DPF) or H(2) (DPH) as electron donor. DPF and DPH were significantly different in both product distribution and extent of isotope fractionation. Chemical and isotope analyses indicated that electron donors did not directly affect the product distribution or the extent of isotope fractionation for PCE reductive dechlorination. Instead, restriction fragment length polymorphism (RFLP) and sequence analysis of the 16S rRNA clone libraries of DPF and DPH identified distinct microbial communities in each enrichment culture, suggesting that differences in microbial communities were responsible for distinct product distributions and isotope fractionation between the two cultures. A dominant species identified only in DPH was closely related to known dehalogenating species (Sulfurospirillum multivorans and Sulfurospirillum halorespirans) and may be responsible for PCE degradation in DPH. Our study suggests that different dechlorinators exist at the same site and can be preferentially stimulated by different electron donors, especially over the long-term (i.e., years), typical of in-situ ground water remediation.

  7. Catalytic dechlorination of diclofenac by biogenic palladium in a microbial electrolysis cell

    Science.gov (United States)

    Gusseme, Bart De; Soetaert, Maarten; Hennebel, Tom; Vanhaecke, Lynn; Boon, Nico; Verstraete, Willy

    2012-01-01

    Summary Diclofenac is one of the most commonly detected pharmaceuticals in wastewater treatment plant (WWTP) effluents and the receiving water bodies. In this study, biogenic Pd nanoparticles (‘bio‐Pd’) were successfully applied in a microbial electrolysis cell (MEC) for the catalytic reduction of diclofenac. Hydrogen gas was produced in the cathodic compartment, and consumed as a hydrogen donor by the bio‐Pd on the graphite electrodes. In this way, complete dechlorination of 1 mg diclofenac l−1 was achieved during batch recirculation experiments, whereas no significant removal was observed in the absence of the biocatalyst. The complete dechlorination of diclofenac was demonstrated by the concomitant production of 2‐anilinophenylacetate (APA). Through the addition of −0.8 V to the circuit, continuous and complete removal of diclofenac was achieved in synthetic medium at a minimal HRT of 2 h. Continuous treatment of hospital WWTP effluent containing 1.28 µg diclofenac l−1 resulted in a lower removal efficiency of 57%, which can probably be attributed to the affinity of other environmental constituents for the bio‐Pd catalyst. Nevertheless, reductive catalysis coupled to sustainable hydrogen production in a MEC offers potential to lower the release of micropollutants from point‐sources such as hospital WWTPs. PMID:22221490

  8. Mineralization of 2-chlorophenol by sequential electrochemical reductive dechlorination and biological processes.

    Science.gov (United States)

    Arellano-González, Miguel Ángel; González, Ignacio; Texier, Anne-Claire

    2016-08-15

    In this work, a novel approach was applied to obtain the mineralization of 2-chlorophenol (2-CP) in an electrochemical-biological combined system where an electrocatalytic dehydrogenation process (reductive dechlorination) was coupled to a biological denitrification process. Reductive dechlorination of 2-CP was conducted in an ECCOCEL-type reactor on a Pd-Ni/Ti electrode at a potential of -0.40V vs Ag/AgCl(s)/KCl(sat), achieving 100 percent transformation of 2-CP into phenol. The electrochemically pretreated effluent was fed to a rotating cylinder denitrifying bioreactor where the totality of phenol was mineralized by denitrification, obtaining CO2 and N2 as the end products. The total time required for 2-CP mineralization in the combined electrochemical-biological process was 7.5h. This value is close to those previously reported for electrochemical and advanced oxidation processes but in this case, an efficient process was obtained without accumulation of by-products or generation of excessive energy costs due to the selective electrochemical pretreatment. This study showed that the use of electrochemical reductive pretreatment combined with biological processes could be a promising technology for the removal of recalcitrant molecules, such as chlorophenols, from wastewaters by more efficient, rapid, and environmentally friendly processes.

  9. Organometallic copper I, II or III species in an intramolecular dechlorination reaction

    KAUST Repository

    Poater, Albert

    2013-03-15

    The present paper gives insight into an intramolecular dechlorination reaction involving Copper (I) and an ArCH2Cl moiety. The discussion of the presence of a CuIII organometallic intermediate becomes a challenge, and because of the lack of clear experimental detection of this proposed intermediate, and due to the computational evidence that it is less stable than other isomeric species, it can be ruled out for the complex studied here. Our calculations are completely consistent with the key hypothesis of Karlin et al. that TMPA-CuI is the substrate of intramolecular dechlorination reactions as well as the source to generate organometallic species. However the organometallic character of some intermediates has been refused because computationally these species are less stable than other isomers. Thus this study constitutes an additional piece towards the full understanding of a class of reaction of biological relevance. Further, the lack of high energy barriers and deep energy wells along the reaction pathway explains the experimental difficulties to trap other intermediates. © Springer-Verlag Berlin Heidelberg 2013.

  10. Evidence for polychlorinated biphenyls dechlorination in the sediments of Sado Estuary, Portugal.

    Science.gov (United States)

    Gil, O; Vale, C

    2001-06-01

    Sediment gravity cores and grab samples were collected in the Sado Estuary and in its coastal area. The cores were sliced on board and the percentage of weight loss on ignition was determined in the laboratory, and analysed for polychlorinated biphenyl (PCB) congeners. PCB contents were higher in samples from the North Channel of the estuary, nearby the industrial zone (max. 114 ng g-1 dry weight), while levels in the coastal area were lower than 4.9 ng g-1. The concentrations of the quantified congeners varied irregularly with sediment depth in the estuary, but showed two opposite distribution patterns in cores from the coastal area: the proportions of lower chlorinated congeners increased with depth, while congeners with higher number of chlorines decreased. This suggests a dechlorination of the most chlorinated congeners into less toxic compounds, under reductive conditions of the sediment. Though measurements were done in natural environment it appears that dechlorination was not entirely dependent on chlorine position in the phenyl rings.

  11. Pd/C-catalyzed dechlorination of polychlorinated biphenyls under hydrogen gas-free conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, Shinji [Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-1 Daigaku-nishi, Gifu 501-1196 (Japan); Ido, Akiko [Laboratory of Health Sciences, Gifu Pharmaceutical University, 1-25-1 Daigaku-nishi, Gifu 501-1196 (Japan); Monguchi, Yasunari [Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-1 Daigaku-nishi, Gifu 501-1196 (Japan); Nagase, Hisamitsu [Laboratory of Health Sciences, Gifu Pharmaceutical University, 1-25-1 Daigaku-nishi, Gifu 501-1196 (Japan); Sajiki, Hironao, E-mail: sajiki@gifu-pu.ac.jp [Laboratory of Organic Chemistry, Gifu Pharmaceutical University, 1-25-1 Daigaku-nishi, Gifu 501-1196 (Japan)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer PCBs were completely decomposed at room temperature under H{sub 2} gas-free conditions. Black-Right-Pointing-Pointer 10% Pd/C, Mg, and MeOH are only required. Black-Right-Pointing-Pointer Aroclors 1242, 1248, 1254 and used PCBs are applicable to the degradation method. Black-Right-Pointing-Pointer A single electron transfer from Pd{sup 0} species to the aromatic ring would be involved. - Abstract: The simultaneous use of catalytic amount of palladium on carbon (Pd/C) and Mg metal (1.5-2.0 equiv vs. Cl numbers of the substrates) in MeOH achieved the complete dechlorination of a variety of aryl chlorides at room temperature under a nitrogen atmosphere in the absence of hydrogen gas. The present method could be successfully used for the detoxification of PCBs based on the dechlorinaton reaction. Both virgin PCBs, such as Aroclors 1242, 1248 and 1254, and used PCBs as a high-tension capacitor oil, were smoothly dechlorinated into harmless biphenyl without any byproducts within 2 h at rt. The distinctive features of this method are convenience and safety due to no needs for the pretreatment of catalyst and Mg and complete degradation of PCBs under mild conditions without hydrogen gas.

  12. Evaluation of biodegradable plastics as solid hydrogen donors for the reductive dechlorination of fthalide by Dehalobacter species.

    Science.gov (United States)

    Yoshida, Naoko; Ye, Lizhen; Liu, Fengmao; Li, Zhiling; Katayama, Arata

    2013-02-01

    Biodegradable plastics (BPs) were evaluated for their applicability as sustainable and solid H(2) donors for microbial reductive dechlorination of 4,5,6,7-tetrachlorophthalide (fthalide). After a screening test of several BPs, the starch-based plastic (SP) that produced the highest levels of H(2) was selected for its use as the sole H(2) donor in this reaction. Fthalide dechlorination was successfully accomplished by combining an H(2)-producing SP culture and a KFL culture containing Dehalobacter species, supplemented with 0.13% and 0.5% SP, respectively. The efficiency of H(2) use in dechlorination was evaluated in a combined culture containing the KFL culture and strain Clostridium sp. Ma13, a new isolate that produces H(2) from SP. Results obtained with this culture indicated increased H(2)-fraction for fthalide dechlorination much more in this culture than in compared with a KFL culture supplemented with 20mM lactate, which are 0.75 H(2)·glucose(-1) and 0.015 H(2)·lactate(-1) in mol ratio, respectively.

  13. Dechlorination of Aromatic Chlorides in Aqueous System Catalyzed by Functionalized MontK10 Supported Palladium-tin

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A novel bisupporter bimetal catalyst PVP-PdCl2-SnCl4/MontK10-PEG400, using for dehalogenation of insoluable aromatic halides in aqueous system, has shown high dechlorination activity and selectivity, without any organic solvent or phase transfer catalyst. The conversion of aromatic chlorides can reach 100%. The catalyst is easy to prepare and has good reusability.

  14. Coupling between Pentachlorophenol Dechlorination and Soil Redox As Revealed by Stable Carbon Isotope, Microbial Community Structure, and Biogeochemical Data.

    Science.gov (United States)

    Xu, Yan; He, Yan; Zhang, Qian; Xu, Jianming; Crowley, David

    2015-05-05

    Carbon isotopic analysis and molecular-based methods were used in conjunction with geochemical data sets to assess the dechlorination of pentachlorophenol (PCP) when coupled to biogeochemical processes in a mangrove soil having no prior history of anthropogenic contamination. The PCP underwent 96% dechlorination in soil amended with acetate, compared to 21% dehalogenation in control soil. Carbon isotope analysis of residual PCP demonstrated an obvious enrichment of 13C (εC, -3.01±0.1%). Molecular and statistical analyses demonstrated that PCP dechlorination and Fe(III) reduction were synergistically combined electron-accepting processes. Microbial community analysis further suggested that enhanced dechlorination of PCP during Fe(III) reduction was mediated by members of the multifunctional family of Geobacteraceae. In contrast, PCP significantly suppressed the growth of SO4(2-) reducers, which, in turn, facilitated the production of CH4 by diversion of electrons from SO4(2-) reduction to methanogenesis. The integrated data regarding stoichiometric alterations in this study gives direct evidence showing PCP, Fe(III), and SO4(2-) reduction, and CH4 production are coupled microbial processes during changes in soil redox.

  15. Complete dechlorination of 2,4-dichlorophenol in aqueous solution on palladium/polymeric pyrrole-cetyl trimethyl ammonium bromide/foam-nickel composite electrode

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhirong, E-mail: zrsun@bjut.edu.cn [College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Wei, Xuefeng; Han, Yanbo; Tong, Shan [College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Hu, Xiang, E-mail: huxiang99@163.com [College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2013-01-15

    Highlights: ► Pd/PPy-CTAB/foam-Ni electrode with high surface area and low Pd content was prepared. ► The composite electrode was applied to dechlorination of 2,4-DCP in aqueous solution. ► Complete dechlorination of 2,4-DCP was achieved with higher current efficiency. ► Removal efficiency kept 100% after 10 times dechlorination on the stable electrode. ► The electrochemically reductive activation energy was 25.8 kJ mol{sup −1} in this system. -- Abstract: The electrochemically reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) in aqueous solution on palladium/polymeric pyrrole-cetyl trimethyl ammonium bromide/foam-nickel electrode (Pd/PPy-CTAB/foam-Ni electrode) was investigated in this paper. Pd/PPy-CTAB/foam-Ni electrode was prepared and characterized by cyclic voltammetry (CV), scanning electron microscope (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) adsorption and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The influences of some experimental factors such as the dechlorination current, dechlorination time and the initial pH on the removal efficiency and the current efficiency of 2,4-DCP dechlorination on Pd/PPy-CTAB/foam-Ni electrode were studied. Complete removal of 2,4-DCP was achieved and the current efficiency of 47.4% could be obtained under the conditions of the initial pH of 2.2, the dechlorination current of 5 mA and the dechlorination time of 50 min when the initial 2,4-DCP concentration was 100 mg L{sup −1}. The analysis of high performance liquid chromatography (HPLC) identified that the intermediate products were 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP). The final products were mainly phenol. Its further reduction product cyclohexanone was also detected. The electrocatalytic dechlorination pathways of 2,4-DCP on Pd/PPy-CTAB/foam-Ni electrode were discussed. The stability of the electrode was favorable that it could keep dechlorination efficiency at 100% after having been reused

  16. Effect of TCE concentration and dissolved groundwater solutes on NZVI-promoted TCE dechlorination and H2 evolution.

    Science.gov (United States)

    Liu, Yueqiang; Phenrat, Tanapon; Lowry, Gregory V

    2007-11-15

    Nanoscale zero-valent iron (NZVI) is used to remediate contaminated groundwater plumes and contaminant source zones. The target contaminant concentration and groundwater solutes (NO3-, Cl-, HCO3-, SO4(2-), and HPO4(2-)) should affect the NZVI longevity and reactivity with target contaminants, but these effects are not well understood. This study evaluates the effect of trichloroethylene (TCE) concentration and common dissolved groundwater solutes on the rates of NZVI-promoted TCE dechlorination and H2 evolution in batch reactors. Both model systems and real groundwater are evaluated. The TCE reaction rate constant was unaffected by TCE concentration for [TCE] TCE concentration up to water saturation (8.4 mM). For [TCE] > or = 0.46 mM, acetylene formation increased, and the total amount of H2 evolved at the end of the particle reactive lifetime decreased with increasing [TCE], indicating a higher Fe0 utilization efficiency for TCE dechlorination. Common groundwater anions (5mN) had a minor effect on H2 evolution but inhibited TCE reduction up to 7-fold in increasing order of Cl- TCE reduction but increased acetylene production and decreased H2 evolution. NO3- present at > 3 mM slowed TCE dechlorination due to surface passivation. NO3- present at 5 mM stopped TCE dechlorination and H2 evolution after 3 days. Dissolved solutes accounted for the observed decrease of NZVI reactivity for TCE dechlorination in natural groundwater when the total organic content was small (< 1 mg/L).

  17. Dechlorination of pentachlorophenol (PCP) in aqueous solution on novel Pd-loaded electrode modified with PPy-SDBS composite film.

    Science.gov (United States)

    Sun, Zhirong; Wei, Xuefeng; Zhang, Huan; Hu, Xiang

    2015-03-01

    Pentachlorophenol (PCP) is a persistent pollutant and a suspected human carcinogen. It can be found in the air, water, and soil and enters the environment through evaporation from treated wood surfaces, industrial spills, and disposal at uncontrolled hazardous waste sites. Ecotoxicity of PCP necessitates the development of rapid and reliable remediation techniques. Electrocatalytic hydrogenolysis (ECH) has been proven as a promising method for detoxification of halogenated wastes, due to its rapid reaction rate, low apparatus cost, mild reaction conditions, and absence of secondary contaminants. Challenge for the application of ECH is to prepare a Pd-coated cathode with high stability, high catalytic activity, and low Pd loading level. In this work, Pd/polypyrrole-sodium dodecyl benzene sulfonate/meshed Ti (Pd/PPy-SDBS/Ti) electrode was prepared and was characterized by cyclic voltammetry, scanning electron microscopy, X-ray diffraction, and inductively coupled plasma-atomic emission spectrometry. Electrochemically reductive dechlorination of PCP on the Pd/PPy-SDBS/Ti electrode in aqueous solution was investigated. Pd microparticles were uniformly dispersed on PPy-SDBS film which was previously electrodeposited on the meshed Ti supporting electrode. The loading of Pd on the electrode was 0.72 mg cm(-2). Electrocatalytic dechlorination of PCP was performed in a two-compartment cell separated by cation-exchange membrane. The PCP removal on the Pd/PPy-SDBS/Ti electrode could reach 100 % within 70 min with dechlorination current 3 mA when PCP initial concentration was 10 mg L(-1) and initial pH was 2.4. Conversion of PCP on the Pd/PPy-SDBS/Ti electrode followed pseudo-first-order kinetics, and the apparent activation energy was 13.0 kJ mol(-1). The removal of PCP still kept 100 % after 70 min dechlorination when the Pd/PPy-SDBS/Ti cathode was reused ten times. The electrode exhibited promising dechlorination potential with high electrocatalytic activity, good stability

  18. Dechlorination of PCBs in the simulative transformer oil by microwave-hydrothermal reaction with zero-valent iron involved.

    Science.gov (United States)

    Liu, Xitao; Zhao, Wei; Sun, Ke; Zhang, Guixiang; Zhao, Ye

    2011-01-01

    The conventional hydrothermal reaction with iron powder, NaOH and H(2)O as reactants was reported to occur at temperature above 423K, and iron oxides (Fe(3)O(4) and NaFeO(2)) and hydrogen were produced. In this study, microwave heating was adopted to take the place of conventional heating to induce the hydrothermal reaction. Under microwave irradiation, NaOH and H(2)O absorbed microwave energy by space charge polarization and dipolar polarization and instantly converted it into thermal energy, which initiated the hydrothermal reaction that involved with zero-valent iron. X-ray diffraction (XRD) analysis found Fe(3)O(4)/NaFeO(2) and confirmed the occurrence of microwave-induced hydrothermal reaction. The developed microwave-hydrothermal reaction was employed for the dechlorination of PCBs. Hexadecane containing 100mgL(-1) of Aroclor1254 was used as simulative transformer oil, and the dechlorination of PCBs was evaluated by GC/ECD, GC/MS and ion chromatography. For PCBs in 10mL simulative transformer oil, almost complete dechlorination was achieved by 750W microwave irradiation for 10min, with 0.3g iron powder, 0.3g NaOH and 0.6mL H(2)O added. The effects of important factors including microwave power and the amounts of reactants added, on the dechlorination degree were investigated, moreover, the dechlorination mechanism was suggested. Microwave irradiation combined with the common and cheap materials, iron powder, NaOH and H(2)O, might provide a fast and cost-effective method for the treatment of PCBs-containing wastes.

  19. Comment on 'evaluation of dechlorination mechanisms during anaerobic fermentation of blached kraft mill effluent by W.J. Parker, E.R. Hall and G.J. Farquhar'

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.

    Comment on "Evaluation of dechlorination mechanisms during anaerobic fermentation of bleached kraft mill effluent", is put forth. The data reproduced in Table 1 does not seem to be authentic as the method of preprationo of the chlorinated organic...

  20. Reductive dechlorination of trichloroethylene (TCE) in competition with Fe and Mn oxides – observed dynamics in H2-dependent terminal electron accepting processes

    DEFF Research Database (Denmark)

    Paul, Laiby; Jakobsen, Rasmus; Smolders, Erik;

    2016-01-01

    The determination of hydrogen (H2) concentration together with the products of microbial reduction reactions in a trichloroethylene dechlorinating system is conducted to delineate the ongoing predominant terminal electron accepting processes (TEAP). Formate was used as electron donor and synthetic...

  1. Combining Chemical Oxidation and Enhanced Reductive Dechlorination for DNAPL Source Area Treatment at a Danish Megasite

    DEFF Research Database (Denmark)

    Christophersen, Mette; Christensen, Jørgen F; Durant, Neal D

    beneath two of the waste pits (Pits 1 and 2). Technologies included in the bench test were chemical oxidation using modified Fenton’s reagent, MFR (hydrogen peroxide + chelated Fe2+), chemical oxidation using activated sodium persulfate (ASP) and biological enhanced reductive dechlorination (ERD) via......) consists of a closed-loop groundwater recirculation cell (25 m long) in which electron donor (lactate and ethanol) is delivered to the treatment zone via forced gradient flow field. Performance is monitored in a series of wells located between the injection and extraction wells. Results. Despite very high...... contaminant concentrations, soil samples collected after the 2nd MFR injection event in Pit 1 showed a significant reduction in contaminant concentrations. Water analyses showed that the concentrations of organic contaminants still are very high and that metals were mobilized. Lead and copper were found...

  2. Temperature of hydrogen radio frequency plasma under dechlorination process of polychlorinated biphenyls

    Science.gov (United States)

    Inada, Y.; Abe, K.; Kumada, A.; Hidaka, K.; Amano, K.; Itoh, K.; Oono, T.

    2014-10-01

    It has been reported that RF (radio frequency) hydrogen plasmas promote the dechlorination process of PCBs (polychlorinated biphenyls) under irradiation of MW (microwave). A relative emission intensity spectroscope system was used for single-shot imaging of two-dimensional temperature distributions of RF hydrogen plasmas generated in chemical solutions with several mixing ratios of isopropyl alcohol (IPA) and insulation oil under MW irradiation. Our experimental results showed that the plasma generation frequencies for the oil-contaminating solutions were higher than that for the pure IPA solution. In addition, the plasma temperature in the compound liquids including both oil and IPA was higher than that in the pure IPA and oil solutions. A combination of the plasma temperature measurements and plasma composition analysis indicated that the hydrogen radicals generated in a chemical solution containing the equal volumes of IPA and oil were almost the same amounts of H and H+, while those produced in the other solutions were mainly H.

  3. Efficient oxidative dechlorination and aromatic ring cleavage of chlorinated phenols catalyzed by iron sulfophthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, A.; Meunier, B. [Laboratoire de Chimie de Coordination du CNRS, Toulouse (France); Seris, J.L. [Elf-Aquitaine, Artix (France)

    1995-05-26

    An efficient method has been developed for the catalytic oxidation of pollutants that are not easily degraded. The products of the hydrogen peroxide (H{sub 2}O{sub 2}) oxidation of 2,4,6-trichlorophenol (TCP) catalyzed by the iron complex 2,9,16,23-tetrasulfophthalocyanine (FePcS) were observed to be chloromaleic, chlorofumaric, maleic, and fumaric acids from dechlorination and aromatic cycle cleavage, as well as additional products that resulted from oxidative coupling. Quantitative analysis of the TCP oxidation reaction revealed that up to two chloride ions were released per TCP molecule. This chemical system, consisting of an environmentally safe oxidant (H{sub 2}O{sub 2}) and an easily accessible catalyst (FePcS), can perform several key steps in the oxidative mineralization of TCP, a paradigm of recalcitrant pollutants. 20 refs., 4 figs., 2 tabs.

  4. Enhanced CAH dechlorination in a low permeability, variably-saturated medium

    Science.gov (United States)

    Martin, J.P.; Sorenson, K.S.; Peterson, L.N.; Brennan, R.A.; Werth, C.J.; Sanford, R.A.; Bures, G.H.; Taylor, C.J.; ,

    2002-01-01

    An innovative pilot-scale field test was performed to enhance the anaerobic reductive dechlorination (ARD) of chlorinated aliphatic hydrocarbons (CAHs) in a low permeability, variably-saturated formation. The selected technology combines the use of a hydraulic fracturing (fracking) technique with enhanced bioremediation through the creation of highly-permeable sand- and electron donor-filled fractures in the low permeability matrix. Chitin was selected as the electron donor because of its unique properties as a polymeric organic material and based on the results of lab studies that indicated its ability to support ARD. The distribution and impact of chitin- and sand-filled fractures to the system was evaluated using hydrologic, geophysical, and geochemical parameters. The results indicate that, where distributed, chitin favorably impacted redox conditions and supported enhanced ARD of CAHs. These results indicate that this technology may be a viable and cost-effective approach for remediation of low-permeability, variably saturated systems.

  5. Self-regeneration of activated carbon modified with palladium catalyst for electrochemical.dechlorination

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Catalyst regeneration and the retention of high catalytic activity are still the critical issues in environmental application. A novel fluidized gas-liquid-solid electrochemical reactor was developed to simultaneously remove chlorinated pollutants and in situ regenerate the spent catalyst. Activated carbon modified with palladium catalyst (AC-Pd) was prepared for electrochemical dechlorination. For the 4-chlorophenol wastewater of initial concentration 200 mg L-1, the removal efficiency could nearly reach 100% in less than 30 min. Catalytic activity of AC-Pd catalyst was preserved effectively even in consecutive cycling run without special regeneration. *OH radicals, generated by electrochemical reaction, played a critical role in self-regeneration of AC-Pd. High catalytic activity of spent AC-Pd catalyst provided an attractive alternative in wastewater treatment.

  6. Degradation of atrazine by Frankia alni ACN14a: gene regulation, dealkylation, and dechlorination.

    Science.gov (United States)

    Rehan, Medhat; Kluge, Martin; Fränzle, Stefan; Kellner, Harald; Ullrich, René; Hofrichter, Martin

    2014-07-01

    Atrazine is transformed to N-isopropylammelide through hydroxyatrazine as an intermediate as indicated by high-performance liquid chromatography/mass spectroscopy in culture filtrates of Frankia alni ACN14a and Frankia sp. EuI1c. Both Frankia strains have the ability to degrade atrazine via dechlorination and dealkylation and, subsequently, may be using it as a nitrogen and carbon source as detected here by increasing their growth patterns. Bioinformatic analysis of the Frankia genomes revealed that a potential gene cluster involved in atrazine decomposition contains three genes, namely, trzN (FRAAL1474 and FraEuI1c_5874), atzB (FRAAL1473 and FraEuI1c_5875), and atzR (FRAAL1471). The relative messenger RNA gene expression of the former genes was examined by qRT-PCR. The LysR-type transcriptional regulator atzR (FRAAL1471), which is expected to control the cluster expression, showed a 13-fold increase in the expression level under atrazine stress. Moreover, the putative adenosine aminohydrolase 3 atzB (FRAAL1473), which is expected to dealkylate the N-ethyl group of atrazine, showed also an increased expression by factor 16 with increased exposure. Eventually, the trzN (FRAAL1474) gene, which is predicted to encode a putative amidohydrolase catalyzing atrazine dechlorination, exhibited 31-fold increased expression. To our best knowledge, this is the first report about adenosine aminohydrolase 3 function in the dealkylation of the N-ethyl group from atrazine.

  7. Complete dechlorination of pentachlorophenol using palladized bacterial cellulose in a rotating catalyst contact reactor.

    Science.gov (United States)

    Patel, Upendra D; Suresh, Sumathi

    2008-03-15

    A rotating catalyst contact reactor (RCCR) was developed which consisted of palladized bacterial cellulose immobilized on acrylic discs for hydrodechlorination of pentachlorophenol (PCP). More than 99% of 40 mg L(-1) PCP was dechlorinated to phenol in the presence of hydrogen in batch mode at initial pH values of 5.5 and 6.5 within 2 h of reaction with stoichiometric release of free chloride. The rate of PCP dechlorination was found to be independent of rotational speed of discs. PCP (40 mg L(-1)) hydrodechlorination experiments were also conducted using RCCR in continuous flow mode at hydraulic retention times of 1 and 2 h. The average outlet PCP concentrations revealed that liquid phase in RCCR closely resembled that of a continuous flow complete mix reactor (CFMR). Approximately 12 and 11 L of 40 mg L(-1) PCP (pH 6.5) could be treated in RCCR with 99 and 80% efficiencies in batch and continuous flow modes, respectively without any appreciable loss of the catalytic activity. These results suggested reusability of palladized bacterial cellulose which in turn is expected to substantially reduce the cost of treatment process. Thus RCCR seems to have high potential for treatment of ground water contaminated with chlorinated organic compounds. Dried palladized bacterial cellulose has been used as a material for electrodes in a fuel cell. However, its application as a hydrodechlorination catalyst in a reactor operating under room temperature and atmospheric pressure has not been reported to the best of our knowledge. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analyses suggested the irreversible deposition of palladium (Pd 0) particles on the bacterial cellulose fibrils.

  8. Occurrence, distribution, and dechlorination of polychlorinated biphenyls and health risk assessment in Selangor River basin.

    Science.gov (United States)

    Sakai, Nobumitsu; Dayana, Emmy; Abu Bakar, Azizi; Yoneda, Minoru; Nik Sulaiman, Nik Meriam; Ali Mohd, Mustafa

    2016-10-01

    Polychlorinated biphenyls (PCBs) were monitored in surface water collected in the Selangor River basin, Malaysia, to identify the occurrence, distribution, and dechlorination process as well as to assess the potential adverse effects to the Malaysian population. Ten PCB homologs (i.e., mono-CBs to deca-CBs) were quantitated by using gas chromatography-mass spectrometry (GC/MS). The total concentration of PCBs in the 10 sampling sites ranged from limit of detection to 7.67 ng L(-1). The higher chlorinated biphenyls (tetra-CBs to deca-CBs) were almost not detected in most of the sampling sites, whereas lower chlorinated biphenyls (mono-CBs, di-CBs, and tri-CBs) dominated more than 90 % of the 10 homologs in all the sampling sites. Therefore, the PCB load was estimated to be negligible during the sampling period because PCBs have an extremely long half-life. The PCBs, particularly higher chlorinated biphenyls, could be thoroughly dechlorinated to mono-CBs to tri-CBs by microbial decomposition in sediment or could still be accumulated in the sediment. The lower chlorinated biphenyls, however, could be resuspended or desorbed from the sediment because they have faster desorption rates and higher solubility, compared to the higher chlorinated biphenyls. The health risk for the Malaysia population by PCB intake that was estimated from the local fish consumption (7.2 ng kg(-1) bw day(-1)) and tap water consumption (1.5 × 10(-3)-3.1 × 10(-3) ng kg(-1) bw day(-1)) based on the detected PCB levels in the surface water was considered to be minimal. The hazard quotient based on the tolerable daily intake (20 ng kg(-1) bw day(-1)) was estimated at 0.36.

  9. [Dechlorination degradation of 2,4-D by nanoscale Fe3O4].

    Science.gov (United States)

    Fang, Guo-Dong; Si, You-Bin

    2010-06-01

    Reductive transformation of 2,4-Dichlorophenoxyacetic acid (2,4-D) by nanoscale Fe3O4 was studied, and the effects of 2,4-D initial concentration, the dosage of nanoscale Fe3O4, pH and temperature on degradation rate of 2,4-D were investigated. The results showed that 48% 2,4-D with initial concentration of 10 mg/L was transformed within 48 h in the presence of 300 mg/L nanoscale Fe3O4. The degradation of 2,4-D was a reductive dechlorination process, and the concentration of chloride ion increased sharply with the degration of the 2,4-D. Disappearance of parent species and formation of reaction intermediates and products were analyzed by LC/MS. The transformation of 2,4-D followed a primary pathway of its complete reduction to phenol and a secondary pathway of sequential reductive hydrogenolysis to 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) or 2-chlorophenol (2-CP) and phenol. The degradation equations of 2,4-D by nanoscale Fe3O4 conformed to pseudo-first-order kinetics, and the reaction rate constant (K) of 4-CP, 2,4-DCP and phenol were 0.0043 h(-1), 0.0026 h(-1) and 0.0032 h(-1), respectively. The degradation rate increased with an increase in initial concentration of 2,4-D from 0 mg/L to 10 mg/L, and increasing the dosage of nanoscale Fe3O4 from 0 mg/L to 300 mg/L. The pH of reaction solution significantly influenced reductive degradation of 2,4-D, and the optimum pH value was 3.0. Besides, high temperature could improve dechlorination rate of 2,4-D.

  10. Effect of heterogeneity on enhanced reductive dechlorination: Analysis of remediation efficiency and groundwater acidification

    Science.gov (United States)

    Brovelli, A.; Lacroix, E.; Robinson, C. E.; Gerhard, J.; Holliger, C.; Barry, D. A.

    2011-12-01

    Enhanced reductive dehalogenation is an attractive in situ treatment technology for chlorinated contaminants. The process includes two acid-forming microbial reactions: fermentation of an organic substrate resulting in short-chain fatty acids, and dehalogenation resulting in hydrochloric acid. The accumulation of acids and the resulting drop of groundwater pH are controlled by the mass and distribution of chlorinated solvents in the source zone, type of electron donor, alternative terminal electron acceptors available and presence of soil mineral phases able to buffer the pH (such as carbonates). Groundwater acidification may reduce or halt microbial activity, and thus dehalogenation, significantly increasing the time and costs required to remediate the aquifer. In previous work a detailed geochemical and groundwater flow simulator able to model the fermentation-dechlorination reactions and associated pH change was developed. The model accounts for the main processes influencing microbial activity and groundwater pH, including the groundwater composition, the electron donor used and soil mineral phase interactions. In this study, the model was applied to investigate how spatial variability occurring at the field scale affects dechlorination rates, groundwater pH and ultimately the remediation efficiency. Numerical simulations were conducted to examine the influence of heterogeneous hydraulic conductivity on the distribution of the injected, fermentable substrate and on the accumulation/dilution of the acidic products of reductive dehalogenation. The influence of the geometry of the DNAPL source zone was studied, as well as the spatial distribution of soil minerals. The results of this study showed that the heterogeneous distribution of the soil properties have a potentially large effect on the remediation efficiency. For examples, zones of high hydraulic conductivity can prevent the accumulation of acids and alleviate the problem of groundwater acidification. The

  11. CATALYTIC DECHLORINATION OF m-DCB IN WATER BY Pd/Fe%Pd/Fe双金属对水中m-二氯苯的催化脱氯

    Institute of Scientific and Technical Information of China (English)

    周红艺; 徐新华; 汪大翚

    2004-01-01

    Pd/Fe bimetallic catalysts were synthesized via chemical deposition and used to treat m-DCB.Batch experiments demonstrated that the Pd/Fe bimetallic particles could effectively dechlorinate m-DCB.The dechlorination efficiency reached 90% at a Pd/Fe loading ratio of 0.02% (mass) and metal to solution ratio 4g : 75ml in 90 min. Dechlorination was affected by several factors such as reaction temperature,pH, Pd/Fe ratio, and the induction of Pd/Fe catalysts. Chlorobenzene represents the partially stable dechlorinated intermediate in the generation of the final product (i. e. , benzene), while part of m-DCB was dechlorinated to benzene directly. The dechlorination reaction was believed to take place mainly on the active surface sites of the Pd/Fe bimetallic particles via a pseudo-first order reaction, and the activation energy of this reaction was found to be 96.6 kJ · mo1-1.

  12. Coupling the dechlorination of aqueous 4-CP with the mechanochemical destruction of solid PCNB using Fe–Ni–SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Teng [State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084 (China); Department of Environmental Engineering, Beijing Jiaotong University, Beijing 100044 (China); Huang, Jun [State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084 (China); Zhang, Wang [State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084 (China); Department of Environmental Engineering, Beijing General Research Institute of Milling and Metallurgy, Beijing 100070 (China); Yu, Yunfei; Deng, Shubo; Wang, Bin [State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084 (China); Yu, Gang, E-mail: yg-den@tsinghua.edu.cn [State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084 (China)

    2013-04-15

    Highlights: ► Toxic PCNB was completely destroyed by ball milling using Fe–Ni–SiO{sub 2}. ► Nonhazardous destruction residue can effectively dechlorinate the 4-CP in water. ► Dechlorination mechanism involving reactions on 3 interfaces (Fe–Ni, Fe–C and Fe–C–Ni) was proposed. -- Abstract: A novel combined process was developed for mechanochemical destruction of pentachloronitrobenzene (PCNB) in solid waste, coupled with the dechlorination of aqueous 4-chlorophenol (4-CP) using the nonhazardous residue from the solid-phase destruction step. Using the mixture of iron powder, nickel powder and quartz sand as the additives in a planetary ball mill under the room temperature, the mechanochemical reaction was induced and a complete destruction of PCNB was realized. The resulting solid residue was characterized by various measures including X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS), which suggested that main components were carbon, chloride besides excess additives. Such nonhazardous residue was then used to effectively dechlorinate aqueous 4-CP. The residue achieving over 93% dechlorination rate was selected as the optimized content. With a series of verification experiments, a possible dechlorination mechanism was proposed, involving the reactions occurred on three interfaces (i.e. Fe/Ni, Fe/C and Fe/C/Ni)

  13. Science Letters:Dechlorination mechanism of 2,4-dichlorophenol by Ni/Fe nanoparticles in the presence of humic acid

    Institute of Scientific and Technical Information of China (English)

    Jing-jing WO; Zhen ZHANG; Xin-hua XU

    2009-01-01

    To understand the feasibility of its application to the in situ remediation of contaminated groundwater, the dechlori-nation of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe nanoparticles in the presence of humic acid (HA) was investigated. We found that, as high performance liquid chromatography (HPLC) was used, the 2,4-DCP was first quickly reduced to o-chlorophenol (o-CP) andp-chlorophenol (p-CP), and then reduced to phenol as the final product. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Ni/Fe nanoparticles, as the HA concentration increased, the removal rate decreased evidently. It also demonstrated that 2,4-DCP was reduced more easily to o-CP than to p-CP, and that the sequence of the tendency in dechlorination of intermediates was p-CP>o-CP. Transmission electron microscope (TEM) showed that HA could act as an adsorbate to compete reactive sites on the surface of Ni/Fe nanoparticles to decrease the dechlorination rate. Also we con-cluded that the dechlorination reaction of 2,4-DCP over Ni/Fe nanoparticles progressed through catalytic reductive dechlorination.

  14. Dechlorination of Trichloroacetic Acid Using a Noble Metal-Free Graphene-Cu Foam Electrode via Direct Cathodic Reduction and Atomic H.

    Science.gov (United States)

    Mao, Ran; Li, Ning; Lan, Huachun; Zhao, Xu; Liu, Huijuan; Qu, Jiuhui; Sun, Meng

    2016-04-05

    A three-dimensional graphene-copper (3D GR-Cu) foam electrode prepared by chemical vapor deposition method exhibited superior electrocatalytic activity toward the dechlorination of trichloroacetic acid (TCAA) as compared to the Cu foam electrode. The cyclic voltammetry and electrochemical impedance spectra analysis confirmed that GR accelerated the electron transfer from the cathode surface to TCAA. With the applied cathode potential of -1.2 V (vs SCE), 95.3% of TCAA (500 μg/L) was removed within 20 min at pH 6.8. TCAA dechlorination at the Cu foam electrode was enhanced at acidic pH, while a slight pH effect was observed at the GR-Cu foam electrode with a significant inhibition for Cu leaching. The electrocatalytic dechlorination of TCAA was accomplished via a combined stepwise and concerted pathway on both electrodes, whereas the concerted pathway was efficiently promoted on the GR-Cu foam electrode. The direct reduction by electrons was responsible for TCAA dechlorination at Cu foam electrode, while at GR-Cu foam electrode, the surface-adsorbed atomic H* also contributed to TCAA dechlorination owing to the chemical storage of hydrogen in the GR structure. Finally, the potential applicability of GR-Cu foam was revealed by its stability in the electrocatalytic dechlorination over 25 cycles.

  15. Kinetics and inhibition of reductive dechlorination of trichloroethene, cis-1,2-dichloroethene and vinyl chloride in a continuously fed anaerobic biofilm reactor.

    Science.gov (United States)

    Popat, Sudeep C; Deshusses, Marc A

    2011-02-15

    Anaerobic bioreactors containing Dehalococcoides spp. can be effective for the treatment of trichloroethene (TCE) contamination. However, reductive dehalogenation of TCE often results in partial conversion to harmless ethene, and significant production of undesired cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) is frequently observed. Here, a detailed modeling study was conducted focusing on the determination of biokinetic constants for the dechlorination of TCE and its reductive dechlorination intermediates cis-DCE and VC as well as any biokinetic inhibition that may exist between these compounds. Dechlorination data from an anaerobic biotrickling filter containing Dehalococcoides spp. fed with single compounds (TCE, cis-DCE, or VC) were fitted to the model to determine biokinetic constants. Experiments with multiple compounds were used to determine inhibition between the compounds. It was found that the Michaelis-Menten half-saturation constants for all compounds were higher than for cells grown in suspended cultures, indicating a lower enzyme affinity in biofilm cells. It was also observed that TCE competitively inhibited the dechlorination of cis-DCE and had a mild detrimental effect on the dechlorination of VC. Thus, careful selection of biotreatment conditions, possibly with the help of a model such as the one presented herein, is required to minimize the production of partially dechlorinated intermediates.

  16. Reductive dechlorination of chlorinated hydrocarbons as non-aqueous phase liquid (NAPL): Preliminary investigation on effects of cement doses

    Energy Technology Data Exchange (ETDEWEB)

    Do, Si-Hyun, E-mail: sihyun2@hanyang.ac.kr [Department of Chemical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Batchelor, Bill [Zachry Department of Civil Engineering, Texas A and M University, College Station, TX 77843 (United States)

    2012-07-15

    The reactivities of various types of iron mixtures to degrade chlorinated hydrocarbons (PCE, TCE and 1,1,1-TCA) in the form of non-aqueous phase liquids were investigated. The iron mixtures included a mixture of Fe(II) and Portland cement (Fe(II)-C), a mixture of Fe(II), Fe(III) and Ca(OH){sub 2} (Fe(II/III)-L), and a mixture of Fe(II), Fe(III), Ca(OH){sub 2}, and Portland cement (Fe(II/III)-C). When the same amount of Fe(II) was used, Fe(II)-C was more reactive with chlorinated ethylenes (i.e. PCE and TCE) than Fe(II/III)-L. The reductive pathway for high concentrations of total PCE (i.e. above solubility) with Fe(II)-C was determined to be a combination of two-electron transfer, {beta}-elimination and hydrogenolysis. Increasing the cement dose from 5% to 10% in Fe(II)-C did not affect PCE dechlorination rates, but it did favor the {beta}-elimination pathway. In addition, when Fe(II/III)-C with 5%C was used, PCE dechlorination was similar to that by Fe(II)-C, but this mixture did not effectively degrade TCE. A modified second-order kinetic model was developed and shown to appropriately describe degradation of TCE at high concentrations. Fe(II/III)-L effectively degraded high concentrations of 1,1,1-TCA at rates that were similar to those obtained with Fe(II)-C using 10% C. Moreover, both increasing cement doses and the presence of Fe(III) increased dechlorination rates of 1,1,1-TCA, which was mainly through the hydrogenolysis pathway. The reactivity of Fe(II/III)-L was strongly dependent on the target compound (i.e. less reactivity with TCE, more with 1,1,1-TCA). Therefore, Fe(II/III)-L could be a potential mixture for degrading 1,1,1-TCA, but it should be modified to degrade TCE more effectively. - Highlights: Black-Right-Pointing-Pointer TCE yield indicated that PCE dechlorination was through hydrogenolysis and {beta}-elimination. Black-Right-Pointing-Pointer {beta}-elimination, especially PCE to dichloroacetylene, was favored with the higher cement doses. Black

  17. Electrospun and functionalized PVDF/PAN nanocatalyst-loaded composite for dechlorination and photodegradation of pesticides in contaminated water.

    Science.gov (United States)

    Nthumbi, Richard M; Ngila, Jane C

    2016-10-01

    A novel approach for the electrospinning and functionalization of nanocatalyst-loaded polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) composite grafted with acrylic acid (AA; which form polyacrylic acid (PAA) brush) and decorated with silver (Ag/PAN/PVDF-g-PAA-TiO2/Fe-Pd) designed for the dechlorination and photodegradation of pesticides was carried out. PAN was used both as a nitrogen dopant as well as a co-polymer. Smooth nanofibers were obtained by electrospinning a solution of 12:2 wt.% PVDF/PAN blend using dimethylformamide (DMF) as solvent. The nanofibers were grafted with AA by free-radical polymerization using 2,2'azobis(2-methylpropionitrile) (AIBN) as initiator. Both bimetallic iron-palladium (Fe-Pd) and titania (TiO2) nanoparticles (NP) were anchored on the grafted nanofibers via the carboxylate groups by in situ and ex situ synthesis. The Fe-Pd and nitrogen-doped TiO2 nanoparticles were subsequently used for dechlorination and oxidation of target pollutants (dieldrin, chlorpyrifos, diuron, and fipronil) to benign products. Structural and chemical characterizations of the composites were done using various techniques. These include surface area and porosity analyzer (ASAP) using the technique by Brunner Emmett Teller (BET), Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM) analyses were done. After dechlorination, the transformation products (TPs) for dieldrin, chlorpyrifos, diuron, and fipronil were obtained and identified using two-dimensional gas chromatography (time-of-flight) with a mass spectrometer detector (GCxGC-TOFMS). Analysis of total organic carbon (TOC) was carried out and used to extrapolate percentage mineralization. Experimental results showed that dechlorination efficiencies of 96, 93, 96, and 90 % for 1, 2, 2, and 3 h treatment period were respectively achieved for 5 ppm solutions of dieldrin, chlorpyrifos, diuron, and fipronil. The

  18. Validation of an integrative methodology to assess and monitor reductive dechlorination of chlorinated ethenes in contaminated aquifers

    Directory of Open Access Journals (Sweden)

    Sonia-Estelle eTarnawski

    2016-02-01

    Full Text Available Bioremediation of tetra-and trichloroethene-contaminated aquifers is frequently hampered due to incomplete dechlorination to the more toxic dichloroethene (DCE and vinyl chloride (VC, indicating insufficient knowledge about the biological mechanisms related to aquifer functioning. A methodology based on the joint analysis of geochemical and microbiological datasets was developed to assess the presence of the biochemical potential for complete reductive dechlorination to harmless ethene and to explain the reasons for which degradation often stalls at the more toxic intermediates. This methodology is composed of three successive steps, with i the acquisition of geochemical data including chlorinated ethenes, ii the detailed analysis of the bacterial community structures as well as the biochemical potential for complete dechlorination using microcosms and molecular detection of organohalide-respiring bacteria and key reductive dehalogenases, and iii a statistical Multiple Factor Analysis combining the above mentioned abiotic and biotic variables in a functional modelling of the contaminated aquifer. The methodology was validated by analyzing two chlorinated ethenes-contaminated sites. Results from the first site showed that the full biochemical potential for ethene production was present in situ. However, redox potential was overall too high and locally manganese reduction out-competed chlorinated ethenes reduction, explaining the reasons for the local accumulation of DCE and VC to a lesser extent. The second contaminated aquifer was under bioremediation by successive cheese whey injections. Analysis demonstrated that cheese whey additions led to increasingly reduced redox conditions and that hampered reductive dechlorination was not due to competition with other anaerobic respiration processes. Complete reductive dechlorination to ethene was preferentially occurring under methanogenic conditions. DCE and VC accumulation was probably induced first

  19. [Influence of the interaction between iron oxide and electron donor substances on 1,1,1-trichloro- 2, 2-bis (p-chlorophenyl) ethane ( DDT) reductive dechlorination in hydragric acrisols].

    Science.gov (United States)

    Liu, Cui-Ying; Xu, Xiang-Hua; Wang, Zhuang; Yao, Tong-Yan

    2014-11-01

    The interaction between iron oxide and electron donor substance have significant influences on electron transfer and the growth of iron-reducing bacteria, which may affect the reductive dechlorination of polychlorinated organic compounds in soil. Anaerobic soil incubation experiment was conducted to study the effect and its mechanism of iron oxide (goethite), electron donor substances (butyrate and ethanol), and their interaction on DDT reductive dechlorination in Hydragric Acrisols. Results showed that after 6 weeks of anaerobic incubation, the extractable residues of DDT were between 1.29% and 2.01% of initial DDT amounts in soils, which was attributed to the dechlorinated degradation of DDT and formation of bound residues of DDT and its dechlorinated products. The main product of DDT anaerobic dechlorination was 1,1-dichloro-2,2-bis (p-chloro-phenyl) ethane (DDD). During the prophase of incubation, the application of butyrate or ethanol led to the decreased pH and increased Eh for reaction system, thus inhibited DDT dechlorination. The applications of only goethite or goethite and electron donor substances resulted in the increased soil pH, decreased soil Eh and increased Fe( II ) contents, thus accelerated DDT dechlorination. There was no significant interaction between butyrate and iron oxide on DDT dechlorination, whereas there was antagonistic action between ethanol and iron oxide on DDT dechlorination. The results will be of great significance for developing efficient and in-situ remediation technology of DDT contaminated soil.

  20. Dechlorination of 3-Chlorobiphenyl by nZVI Particles Prepared in the Presence of 20 kHz Ultrasonic Irradiation

    Directory of Open Access Journals (Sweden)

    Deming Zhao

    2013-05-01

    Full Text Available Nanoscale zero-Valent Iron (nZVI particles were prepared in the presence of 20 kHz ultrasonic irradiation in order to enhance disparity and reactivity and simultaneously avoid agglomeration. Dechlorination of 3-chlorobiphenyl (3-Cl BP by nZVI particles was investigated to understand its feasibility for an in situ remediation of contaminated groundwater. Experimental results showed that the induction of ultrasound during the preparation of nZVI further enhanced the removal efficiency of 3-Cl BP, meanwhile the Biphenyl (BP formation rates increased obviously. The dechlorination rate was dependent on various factors including nZVI dosage, reaction temperature and initial pH values. The degradation of 3-Cl BP followed pseudo-first-order kinetics reaction.

  1. Dechlorination of three tetrachlorobenzene isomers by contaminated harbor sludge-derived enrichment cultures follows thermodynamically favorable reactions

    NARCIS (Netherlands)

    Lu, Yue; Ramiro-Garcia, Javier; Vandermeeren, Pieter; Herrmann, Steffi; Cichocka, Danuta; Springael, Dirk; Atashgahi, Siavash; Smidt, Hauke

    2016-01-01

    Dechlorination patterns of three tetrachlorobenzene isomers, 1,2,3,4-, 1,2,3,5-, and 1,2,4,5-TeCB, were studied in anoxic microcosms derived from contaminated harbor sludge. The removal of doubly, singly, and un-flanked chlorine atoms was noted in 1,2,3,4- and 1,2,3,5-TeCB fed microcosms, whereas

  2. Session 6: Hydro-dechlorination of Carbon Tetrachloride: Study of the Deactivation and Regeneration of Pt Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Garetto, T.F.; Borgna, A. [Instituto de Investigaciones en Catalisis y Petroquimica-INCAPE. (UNL-CONICET), Santa Fe (Argentina); Montoya, J.A.; Acosta, D. [Zaragoza Univ., Dept. de Ingenieria Quimica y Tecnologias del Medio Ambiente. Facultad de Ciencias (Spain); Monzon, A. [Instituto Mexicano del Petroleo, D.F. (Mexico)

    2004-07-01

    The aim of this work is to get more insight on the deactivation-regeneration process of supported metal catalysts during CTC hydro-dechlorination. In this contribution we report a kinetic analysis on the deactivation-regeneration of Pt/Al{sub 2}O{sub 3} catalysts and the effect of the regeneration conditions. Particularly, the effectiveness of the regeneration treatment under different atmospheres is analyzed. (authors)

  3. Role of bicarbonate as a pH buffer and electron sink in microbial dechlorination of chloroethenes

    Directory of Open Access Journals (Sweden)

    Delgado Anca G

    2012-09-01

    Full Text Available Abstract Background Buffering to achieve pH control is crucial for successful trichloroethene (TCE anaerobic bioremediation. Bicarbonate (HCO3− is the natural buffer in groundwater and the buffer of choice in the laboratory and at contaminated sites undergoing biological treatment with organohalide respiring microorganisms. However, HCO3− also serves as the electron acceptor for hydrogenotrophic methanogens and hydrogenotrophic homoacetogens, two microbial groups competing with organohalide respirers for hydrogen (H2. We studied the effect of HCO3− as a buffering agent and the effect of HCO3−-consuming reactions in a range of concentrations (2.5-30 mM with an initial pH of 7.5 in H2-fed TCE reductively dechlorinating communities containing Dehalococcoides, hydrogenotrophic methanogens, and hydrogenotrophic homoacetogens. Results Rate differences in TCE dechlorination were observed as a result of added varying HCO3− concentrations due to H2-fed electrons channeled towards methanogenesis and homoacetogenesis and pH increases (up to 8.7 from biological HCO3− consumption. Significantly faster dechlorination rates were noted at all HCO3− concentrations tested when the pH buffering was improved by providing 4-(2-hydroxyethyl-1-piperazineethanesulfonic acid (HEPES as an additional buffer. Electron balances and quantitative PCR revealed that methanogenesis was the main electron sink when the initial HCO3− concentrations were 2.5 and 5 mM, while homoacetogenesis was the dominant process and sink when 10 and 30 mM HCO3− were provided initially. Conclusions Our study reveals that HCO3− is an important variable for bioremediation of chloroethenes as it has a prominent role as an electron acceptor for methanogenesis and homoacetogenesis. It also illustrates the changes in rates and extent of reductive dechlorination resulting from the combined effect of electron donor competition stimulated by HCO3− and the changes in pH exerted by

  4. Comparison of reactors for oxygen-sensitive reactions: reductive dechlorination of chlorophenols by vitamin b(12s).

    Science.gov (United States)

    Smith, M H; Woods, S L

    1994-11-01

    Serum bottles are frequently used for studies of reductive dechlorination by vitamin B(12), but reducing conditions can be maintained only for several days. This time period is inadequate for evaluating the reductive dechlorination of some slow-reacting aromatic compounds. Sealed glass ampoules maintain reducing conditions for many months, but this method has the disadvantage of disallowing subsampling of the reaction mixture. A glass serum tube was modified for these experiments which not only maintained anoxic conditions for several days but also allowed subsamples to be removed during experiments. The modification was a restriction placed in the middle of the tube by heating in a flame, creating two chambers separated by a narrow neck. The lower chamber contained the oxygen-sensitive reaction mixture. The upper chamber, sealed with a septum and screw cap, was purged with purified nitrogen or argon introduced and vented through fused silica capillaries. Reductive dechlorination of chlorophenols by vitamin B(12) reduced with Ti(III) citrate was monitored in all three reactor types. Sealed ampoules maintained reducing conditions for up to 12 months. The two-chambered reactor maintained reducing conditions longer than the serum vials when frequent samples were taken.

  5. Enhanced dechlorination of carbon tetrachloride by Geobacter sulfurreducens in the presence of naturally occurring quinones and ferrihydrite.

    Science.gov (United States)

    Doong, Ruey-an; Lee, Chun-chi; Lien, Chia-min

    2014-02-01

    The effect of naturally occurring quinones including lawsone (LQ), ubiquinone (UQ), juglone (JQ), and 1,4-naphthoquinone (NQ) on the biotransformation of carbon tetrachloride (CT) in the presence of Geobacter sulfurreducens and ferrihydrite was investigated. AQDS was used as the model compound for comparison. The reductive dissolution of ferrihydrite by G. sulfurreducens was enhanced by AQDS, NQ, and LQ. However, addition of UQ and JQ had little enhancement effect on Fe(II) production. The bioreduction efficiency and rate of ferrihydrite was highly dependent on the natural property and concentration of quinone compounds and the addition of low concentrations of LQ and NQ significantly accelerated the biotransformation rate of CT. The pseudo-first-order rate constants for CT dechlorination (kobsCT) in AQDS-, LQ- and NQ-amended batches were 5.4-5.8, 4.6-7.4 and 2.4-5.8 times, respectively, higher than those in the absence of quinone. A good relationship between kobsCT for CT dechlorination and bioreduction ratio of ferrihydrite was observed, indicating the important role of biogenic Fe(II) in dechlorination of CT under iron-reducing conditions. Spectroscopic analysis showed that AQDS and NQ could be reduced to semiquinones and hydroquinones, while only hydroquinones were generated in LQ-amended batches.

  6. Novel iron metal matrix composite reinforced by quartz sand for the effective dechlorination of aqueous 2-chlorophenol.

    Science.gov (United States)

    Zhang, Yunfei; Yang, Bo; Han, Yanni; Jiang, Chaojin; Wu, Deli; Fan, Jinhong; Ma, Luming

    2016-03-01

    In this work, we tested a novel iron metal matrix composite (MMC) synthesized by mechanically introducing quartz sand (SiO2) into an iron matrix (denoted as SiO2-Fe MMC). The pseudo-first-order reaction rate constant of the SiO2-Fe MMC (initial pH 5.0) for 20 mg/L of 2-chlorophenol (2-CP) was 0.051 × 10(-3) L/m(2)/min, which was even higher than that of some reported Pd/Fe bimetals. This extraordinary high activity was promoted by the quick iron dissolution rate, which was caused by the formation of Fe-C internal electrolysis from carbonization of process control agent (PCA) and the active reinforcement/metal interfaces during the milling process. In addition, pH has slight effect on the dechlorination rate. The SiO2-Fe MMC retained relatively stable activity, still achieving 71% removal efficiency for 2-CP after six consecutive cycles. The decrease in dechlorination efficiency can be attributed to the rapid consumption of Fe(0). A dechlorination mechanism using the SiO2-Fe MMC was proposed by a direct electron transfer from Fe(0) to 2-CP at the quartz sand/iron interface.

  7. Microbially enhanced dissolution and reductive dechlorination of PCE by a mixed culture: Model validation and sensitivity analysis

    Science.gov (United States)

    Chen, Mingjie; Abriola, Linda M.; Amos, Benjamin K.; Suchomel, Eric J.; Pennell, Kurt D.; Löffler, Frank E.; Christ, John A.

    2013-08-01

    Reductive dechlorination catalyzed by organohalide-respiring bacteria is often considered for remediation of non-aqueous phase liquid (NAPL) source zones due to cost savings, ease of implementation, regulatory acceptance, and sustainability. Despite knowledge of the key dechlorinators, an understanding of the processes and factors that control NAPL dissolution rates and detoxification (i.e., ethene formation) is lacking. A recent column study demonstrated a 5-fold cumulative enhancement in tetrachloroethene (PCE) dissolution and ethene formation (Amos et al., 2009). Spatial and temporal monitoring of key geochemical and microbial (i.e., Geobacter lovleyi and Dehalococcoides mccartyi strains) parameters in the column generated a data set used herein as the basis for refinement and testing of a multiphase, compositional transport model. The refined model is capable of simulating the reactive transport of multiple chemical constituents produced and consumed by organohalide-respiring bacteria and accounts for substrate limitations and competitive inhibition. Parameter estimation techniques were used to optimize the values of sensitive microbial kinetic parameters, including maximum utilization rates, biomass yield coefficients, and endogenous decay rates. Comparison and calibration of model simulations with the experimental data demonstrate that the model is able to accurately reproduce measured effluent concentrations, while delineating trends in dechlorinator growth and reductive dechlorination kinetics along the column. Sensitivity analyses performed on the optimized model parameters indicate that the rates of PCE and cis-1,2-dichloroethene (cis-DCE) transformation and Dehalococcoides growth govern bioenhanced dissolution, as long as electron donor (i.e., hydrogen flux) is not limiting. Dissolution enhancements were shown to be independent of cis-DCE accumulation; however, accumulation of cis-DCE, as well as column length and flow rate (i.e., column residence time

  8. Anaerobic reductive dechlorination of tetrachloroethene: how can dual Carbon-Chlorine isotopic measurements help elucidating the underlying reaction mechanism?

    Science.gov (United States)

    Badin, Alice; Buttet, Géraldine; Maillard, Julien; Holliger, Christof; Hunkeler, Daniel

    2014-05-01

    Chlorinated ethenes (CEs) such as tetrachloroethene (PCE) are common persistent groundwater contaminants. Among clean-up strategies applied to sites affected by such pollution, bioremediation has been considered with a growing interest as it represents a cost-effective, environmental friendly approach. This technique however sometimes leads to an incomplete and slow biodegradation of CEs resulting in an accumulation of toxic metabolites. Understanding the reaction mechanisms underlying anaerobic reductive dechlorination would thus help assessing PCE biodegradation in polluted sites. Stable isotope analysis can provide insight into reaction mechanisms. For chlorinated hydrocarbons, carbon (C) and chlorine (Cl) isotope data (δ13C and δ37Cl) tend to show a linear correlation with a slope (m ≡ ɛC/ɛCl) characteristic of the reaction mechanism [1]. This study hence aims at exploring the potential of a dual C-Cl isotope approach in the determination of the reaction mechanisms involved in PCE reductive dechlorination. C and Cl isotope fractionation were investigated during anaerobic PCE dechlorination by two bacterial consortia containing members of the Sulfurospirillum genus. The specificity in these consortia resides in the fact that they each conduct PCE reductive dechlorination catalysed by one different reductive dehalogenase, i.e. PceADCE which yields trichloroethene (TCE) and cis-dichloroethene (cDCE), and PceATCE which yields TCE only. The bulk C isotope enrichment factors were -3.6±0.3 o for PceATCE and -0.7±0.1o for PceADCE. The bulk Cl isotope enrichment factors were -1.3±0.2 o for PceATCE and -0.9±0.1 o for PceADCE. When applying the dual isotope approach, two m values of 2.7±0.1 and 0.7±0.2 were obtained for the reductive dehalogenases PceATCE and PceADCE, respectively. These results suggest that PCE can be degraded according to two different mechanisms. Furthermore, despite their highly similar protein sequences, each reductive dehalogenase seems

  9. Research advances in microbial dechlorination of polychlorinated biphenyls%多氯联苯微生物脱氯研究进展

    Institute of Scientific and Technical Information of China (English)

    陈晨; 崔静岚; 秦智慧; 俞春娜; 陈曦; 沈超峰; 陈英旭

    2012-01-01

    Polychlorinated biphenyls ( PCBs) are the typical persistent organic pollutants ( POPs) in the environment. As a ubiquitous attenuation course of chlorinated organic compounds in anoxic environment, the microorganism-mediated reductive dechlorination process plays an important role in PCBs transformation, especially the transformation of higher chlorinated PCBs. The higher chlorinated PCBs can be dechlorinated in anaerobic condition, and thus, their persistence and toxicity can be decreased. The resultant lower chlorinated PCBs from the dechlorination can be further degraded and completely mineralized in aerobic condition. This paper summarized the research advances of PCBs microbial reductive dechlorination, introduced the mechanisms and characteristics of the dechlorination and the related specific microorganisms, and approached the affecting factors of PCBs bio-dechlorination, as well as the significances of anaerobic dechlorination coupling with aerobic degradation. The future research directions, including the complex metabolic networks of dechlorinating microbial populations, the screening of novel specific dechlorinators and their practical applications in the remediation of PCBs contaminated sites were also prospected.%多氯联苯(polychlorinated biphenyls,PCBs)是环境中典型的氯代持久性有机污染物.微生物脱氯是一种氯代有机物自然降解模式,对全球PCBs特别是高氯代同系物消减起到至关重要的作用.厌氧条件下高氯代PCBs能够发生脱氯反应,使其毒性大大降低,脱氯后形成的低氯代化合物可以进一步好氧降解,直至完全矿化.本文综述了PCBs生物脱氯的研究进展,介绍了微生物脱氯反应的机理和特征、参与微生物脱氯过程的专性脱氯菌等,探讨了该微生物过程的影响因素及厌氧脱氯与好氧降解耦合的意义,并对脱氯微生物群落的复杂代谢网络研究、专性脱氯新菌种筛选及其污染地实际修复应用等未来研究方向进行了展望.

  10. Implementing heterogeneous catalytic dechlorination technology for remediating TCE-contaminated groundwater.

    Science.gov (United States)

    Davie, Matthew G; Cheng, Hefa; Hopkins, Gary D; Lebron, Carmen A; Reinhard, Martin

    2008-12-01

    To transition catalytic reductive dechlorination (CRD) into practice, it is necessary to demonstrate the effectiveness, robustness, and economic competitiveness of CRD-based treatment systems. A CRD system scaled up from previous laboratory studies was tested for remediating groundwater contaminated with 500-1200 microg L(-1) trichloroethylene (TCE) at Edwards Air Force Base (AFB), California. Groundwater was pumped from a treatment well at 2 gal min(-1), amended with hydrogen to 0.35 mg L(-1) and contacted for 2.3 min with 20 kg eggshell-coated Pd on alumina beads (2% Pd by wt) packed in a fixed-bed reactor, and then returned to the aquifer. Operation was continuous for 23 h followed a 1 h regeneration cycle. After regeneration, TCE removal was 99.8% for 4 to 9 h and then declined to 98.3% due to catalyst deactivation. The observed catalyst deactivation was tentatively attributed to formation of sulfidic compounds; modeling of catalyst deactivation kinetics suggests the presence of sulfidic species equivalent to 2-4 mg L(-1) hydrogen sulfide in the reactor water. Over the more than 100 day demonstration period, TCE concentrations in the treated groundwater were reduced by >99% to an average concentration of 4.1 microg L(-1). The results demonstrate CRD as a viable treatment alternative technically and economically competitive with activated carbon adsorption and other conventional physicochemical treatmenttechnologies.

  11. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Hui [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan [College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); Shi, Xiangyang, E-mail: xshi@dhu.edu.cn [State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai 201620 (China); CQM - Centro de Quimica da Madeira, Universidade da Madeira, Campus da Penteada, 9000-390 Funchal (Portugal)

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants.

  12. Diverse Reductive Dehalogenases Are Associated with Clostridiales-Enriched Microcosms Dechlorinating 1,2-Dichloroethane

    KAUST Repository

    Merlino, Giuseppe

    2015-03-06

    The achievement of successful biostimulation of active microbiomes for the cleanup of a polluted site is strictly dependent on the knowledge of the key microorganisms equipped with the relevant catabolic genes responsible for the degradation process. In this work, we present the characterization of the bacterial community developed in anaerobic microcosms after biostimulation with the electron donor lactate of groundwater polluted with 1,2-dichloroethane (1,2-DCA). Through a multilevel analysis, we have assessed (i) the structural analysis of the bacterial community; (ii) the identification of putative dehalorespiring bacteria; (iii) the characterization of functional genes encoding for putative 1,2-DCA reductive dehalogenases (RDs). Following the biostimulation treatment, the structure of the bacterial community underwent a notable change of the main phylotypes, with the enrichment of representatives of the order Clostridiales . Through PCR targeting conserved regions within known RD genes, four novel variants of RDs previously associated with the reductive dechlorination of 1,2-DCA were identified in the metagenome of the Clostridiales-dominated bacterial community.

  13. Effects of electron donors on the microbial reductive dechlorination of hexachlorocyclohexane and on the environment.

    Science.gov (United States)

    Cui, Zhaojie; Meng, Fanli; Hong, Jinglan; Li, Xiangzhi; Ren, Xiaohua

    2012-06-01

    The reductive biotransformation of α-, β-, γ-, and δ-hexachlorocyclohexane isomers was investigated using five alternative electron donors (i.e., glucose plus methanol, glucose only, methanol only, acetate, and ethanol) in a batch assay of an HCH-dechlorinating anaerobic culture. In addition, a life cycle assessment was conducted using the IMPACT2002+ method to evaluate the environmental effects of HCH bioremediation with the aforementioned electron donors. Results showed that the electron donors methanol plus glucose, ethanol, glucose, and methanol can significantly enhance the biotransformation of each HCH isomer. However, the amended electron donors and the byproduct of the anoxic/anaerobic systems may negatively affect the environment (e.g., respiratory inorganic, land occupation, global warming, and non-renewable energy categories). These effects are attributed to the electron donor production processes. To avoid secondary pollutants, a linear relationship between the upper bound electron donor applications and HCH concentration was observed from an environmental perspective. Results indicated that the methanol scenario was the most suitable option for the current research.

  14. Reductive dechlorination of methoxychlor and DDT by human intestinal bacterium Eubacterium limosum under anaerobic conditions.

    Science.gov (United States)

    Yim, You-Jin; Seo, Jiyoung; Kang, Su-Il; Ahn, Joong-Hoon; Hur, Hor-Gil

    2008-04-01

    Methoxychlor [1,1,1-trichloro-2,2-bis(p-methoxyphenyl)ethane], a substitute for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), is a compound of environmental concern because of potential long-term health risks related to its endocrine-disrupting and carcinogenic potency. In order to determine the metabolic fate of methoxychlor and DDT in the human intestinal gut, Eubacterium limosum (ATCC 8486), a strict anaerobe isolated from the human intestine that is capable of O-demethylation toward O-methylated isoflavones, was used as a model intestinal microbial organism. Under anaerobic incubation conditions, E. limosum completely transformed methoxychlor and DDT in 16 days. Based on gas chromatography-mass chromatography analyses, the metabolites produced from methoxychlor and DDT by E. limosum were confirmed to be 1,1-dichloro-2,2-bis(p-methoxyphenyl)ethane (methoxydichlor) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), respectively. This study suggests that E. limosum in the human intestinal gut might be a participant in the reductive dechlorination of methoxychlor to the more antiandrogenic active methoxydichlor.

  15. The oxidative p-dichlorobenzene dechlorinating in the presence of copper (ΙΙ complexes and nitrogen (ΙΙ, ΙV oxides

    Directory of Open Access Journals (Sweden)

    Valentina Yemelyanova

    2012-12-01

    Full Text Available The results of dechlorination in the solution CuCl2–TBP–NaNO2–О2–Н2О kinetics research are presented in the article. All system components influence to the dechlorination process is studied and quantitatively described. The composition of copper intermediate complexes participating in reaction is studied by the instrumentality of UV-spectroscopy. Established part of binuclear copper complexes in the catalytic intermediate complex constants of formation were estimated and compared with the kinetic and spectrophotometric methods. The composition of the intermediate complexes responsible for process is defined, the mechanism scheme is offered, the p-dichlorobenzene dechlorination limiting stage including redox-disintegration of the intermediate complex consisting of dimeric complex of copper (II, I chloride, nitrogen oxide and p-dichlorobenzene is defined.

  16. Electrochemical dechlorination of chloroform in neutral aqueous solution on palladium/foam-nickel and palladium/polymeric pyrrole film/foam-nickel electrodes

    Institute of Scientific and Technical Information of China (English)

    SUN Zhirong; LI Baohua; HU Xiang; SHI Min; HOU Qingnan; PENG Yongzhen

    2008-01-01

    Electrochemical dechlonnafion of chloroform in neutral aqueous solution was investigated using palladium-loaded electrodes at ambient temperature.Palladium/foam-nickel (Pd/foam-Ni) and palladium/polymeric pyrrole film/foam-nickel (Pd/PPy/foam-Ni)composite electrodes which provided catalytic surface for reductive dechiorination of chloroform in aqueous solution were prepared using an electrodepositing method.Scanning electron microscope (SEM) micrographs showed that polymeric pyrrole film modified the electrode-surface characteristics and resulted in the uniform dispersion of needle-shaped palladium particles on foam-Ni supporting electrode.The experimental results of dechlorination indicated that the removal efficiency of chloroform and current efficiency in neutral aqueous solution on Pd/PPy/foam-Ni electrode could be up to 36.8% and 33.0% at dechlorination current of 0.1 mA and dechlorination time of 180 rain,which is much higher than that of Pd/foam-Ni electrode.

  17. Efficient photocatalytic reductive dechlorination of 4-chlorophenol to phenol on {0 0 1}/{1 0 1} facets co-exposed TiO{sub 2} nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Guodong; Wei, Meng; Yuan, Songdong [College of Chemistry and chemical engineering, Hubei Collaborative Innovation Center for High Efficient Utilization of Solar Energy, Hubei University of Technology, Wuhan 430068 (China); Chang, Qing, E-mail: changqinghust@163.com [Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science, South-Central University for Nationalities, Wuhan 430074 (China)

    2016-01-30

    Graphical abstract: - Highlights: • 4-Chlorophenol is dechlorinated over {0 0 1}/{1 0 1} co-exposed TiO{sub 2} nanocrystals. • Photo-electrons are accumulated on {1 0 1} facets due to surface heterojunction. • Fluorine will trap photoelectrons to depress the dechlorination performance. • Sufficient isopropanol promotes the dechlorination activity and selectivity. - Abstract: 4-chlorophenol could be efficiently photoreductively dechlorinated over anatase TiO{sub 2} nanocrystals with co-exposed {0 0 1} and {1 0 1} facets, which were synthesized and further characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Although fluorine could adsorb on {0 0 1} facets to decrease their surface energy, enabling TiO{sub 2} to expose high energy {0 0 1} facets, the surface bonded fluorine might depress the photoreductive dechlorination efficiency of 4-chlorophenol, attributed to the electron trapping role of surface ≡Ti−F groups. Due to the formation of a surface heterojunction between {1 0 1} and {0 0 1} facets in a single TiO{sub 2} nanocrystal, electrons and holes were spontaneously self-separated and selectively migrate to {1 0 1} and {0 0 1} facets, respectively. Electron trapping experiments demonstrated that photogenerated electrons are the responsible for the reductive dechlorinaton of 4-chlorophenol to phenol. To avoid the oxidative degradation of 4-chlorophenol by holes and ensure sufficient electrons to reductively dechlorinate the substrate, moderate scavengers were required in the reaction system and dissolved oxygen, which might deplete electron on TiO{sub 2}, also should be removed. With the optimal scavengers, the conversion efficiency of 4-chlorophenol (4-CP) achieved 97.5% and the selectivity for phenol was 92.5%, which were much higher than that of commercial TiO{sub 2} P25.

  18. Modeling and Decision Support Tools Based on the Effects to Sediment Geochemistry and Microbial Populations on Contaminant Reactions in Sediments

    Science.gov (United States)

    2011-09-01

    chlorocoercia DF-1 o-17 RFLP17 PCB-dechlorinating bacter ium O HudCHL072 HudCHL069 HudCHL003 HudCHL088 GraCHL024 GraCHL040 GraCHL005 HudCHL047 GraCHL009...HudBac055-G7 HudBac074-B10 HudBac088-H11 Dehalobium chlorocoercia DF-1 o-17 unidentified eubacterium Uncultured Chloroflexi bacter i Dehalococcoides...ethenogenes st Dehalococcoides sp. CBDB1 AF23 Uncultured bacterium SHD-197 A HudBac095-G12 Uncul tured bacter ium SHD-245 A Uncultured bacterium SJA-131

  19. Comparison Of A Laboratory Consortium That Dechlorinates TCE To Ethene To The Field Community From Which It Was Derived

    Energy Technology Data Exchange (ETDEWEB)

    T. Wood; K. S. Sorenson; D. E. Cummings

    2004-12-01

    Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of bacterial amplicons was predominated by those from members of the class Clostridia (57 of 93 clones), of which a phylotype most similar to that of the homoacetogen Acetobacterium sp. strain HAAP-1 was most abundant (32 of 93 clones). The remaining Bacteria consisted of phylotypes affiliated with Sphingobacteria, Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria and candidate divisions OP11 and OP3. The two proteobacterial phylotypes were most similar to those of the known dechlorinators Trichlorobacter thiogenes and Sulfurospirillum multivorans. Although not represented by the bacterial clones generated with broad-specificity bacterial primers, a Dehalococcoides-like phylotype was identified with genus-specific primers. Only four distinct phylotypes were detected in the groundwater archaeal library, including predominantly a clone affiliated with the strictly acetoclastic methanogen Methanosaeta concilii (24 of 43 clones). A mixed culture that completely dechlorinates TCE to ethene was enriched from this groundwater, and both communities were characterized by terminal restriction fragment length polymorphism (T-RFLP). According to T-RFLP, the laboratory enrichment community was less diverse overall than the groundwater community, with 22 unique phylotypes as opposed to 43 and a higher percentage of Clostridia, including the Acetobacterium population. Bioreactor archaeal structure was very similar to that of the groundwater community, suggesting that methane is

  20. A Dechlorinating Community Resulting From In Situ Biostimulation of a TCE-contaminated Deep Fracture Basalt Aquifer

    Energy Technology Data Exchange (ETDEWEB)

    T. Wood; D. E. Cummings

    2004-12-01

    Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of bacterial amplicons was predominated by those from members of the class Clostridia (57 of 93 clones), of which a phylotype most similar to that of the homoacetogen Acetobacterium sp. strain HAAP-1 was most abundant (32 of 93 clones). The remaining Bacteria consisted of phylotypes affiliated with Sphingobacteria, Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria and candidate divisions OP11 and OP3. The two proteobacterial phylotypes were most similar to those of the known dechlorinators Trichlorobacter thiogenes and Sulfurospirillum multivorans. Although not represented by the bacterial clones generated with broad-specificity bacterial primers, a Dehalococcoides-like phylotype was identified with genus-specific primers. Only four distinct phylotypes were detected in the groundwater archaeal library, including predominantly a clone affiliated with the strictly acetoclastic methanogen Methanosaeta concilii (24 of 43 clones). A mixed culture that completely dechlorinates TCE to ethene was enriched from this groundwater, and both communities were characterized by terminal restriction fragment length polymorphism (T-RFLP). According to T-RFLP, the laboratory enrichment community was less diverse overall than the groundwater community, with 22 unique phylotypes as opposed to 43 and a higher percentage of Clostridia, including the Acetobacterium population. Bioreactor archaeal structure was very similar to that of the groundwater community, suggesting that methane is

  1. Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene.

    Science.gov (United States)

    Kyung, Daeseung; Sihn, Youngho; Kim, Sangwoo; Bae, Sungjun; Amin, Muhammad Tahir; Alazba, Abdulrahman Ali; Lee, Woojin

    2016-07-01

    Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k(obs-PCE)=0.57 h(-1)) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO2, Al2O3, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005-0.1 mM), cement ratio (0.05-0.2), and suspension pH (11.5-13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

  2. O-Demethylation and successive oxidative dechlorination of methoxychlor by Bradyrhizobium sp. strain 17-4, isolated from river sediment.

    Science.gov (United States)

    Satsuma, Koji; Masuda, Minoru; Sato, Kiyoshi

    2012-08-01

    O-Demethylation of insecticide methoxychlor is well known as a phase I metabolic reaction in various eukaryotic organisms. Regarding prokaryotic organisms, however, no individual species involved in such reaction have been specified and characterized so far. Here we successfully isolated a bacterium that mediates oxidative transformation of methoxychlor, including O-demethylation and dechlorination, from river sediment. The isolate was found to be closely related to Bradyrhizobium elkanii at the 16S rRNA gene sequence level (100% identical). However, based on some differences in the physiological properties of this bacterium, we determined that it was actually a different species, Bradyrhizobium sp. strain 17-4. The isolate mediated O-demethylation of methoxychlor to yield a monophenolic derivative [Mono-OH; 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(4-methoxyphenyl)ethane] as the primary degradation product. The chiral high-performance liquid chromatography (HPLC) analysis revealed that the isolate possesses high enantioselectivity favoring the formation of (S)-Mono-OH (nearly 100%). Accompanied by the sequential O-demethylation to form the bis-phenolic derivative Bis-OH [1,1,1-trichloro-2,2-bis(4-hydroxyphenyl)ethane], oxidative dechlorination of the side chain proceeded, and monophenolic carboxylic acid accumulated, followed by the formation of multiple unidentified polar degradation products. The breakdown proceeded more rapidly when reductively dechlorinated (dichloro-form) methoxychlor was applied as the initial substrate. The resultant carboxylic acids and polar degradation products are likely further biodegraded by ubiquitous bacteria. The isolate possibly plays an important role for complete degradation (mineralization) of methoxychlor by providing the readily biodegradable substrates.

  3. Selective utilization of exogenous amino acids by Dehalococcoides ethenogenes strain 195 and its effects on growth and dechlorination activity.

    Science.gov (United States)

    Zhuang, Wei-Qin; Yi, Shan; Feng, Xueyang; Zinder, Stephen H; Tang, Yinjie J; Alvarez-Cohen, Lisa

    2011-11-01

    Bacteria of the genus Dehalococcoides are important members of bioremediation communities because of their ability to detoxify chloroethenes to the benign end product ethene. Genome-enabled studies conducted with Dehalococcoides ethenogenes 195 have revealed that two ATP-binding cassette (ABC)-type amino acid transporters are expressed during its exponential growth stages. In light of previous findings that Casamino Acids enhanced its dechlorination activity, we hypothesized that strain 195 is capable of importing amino acids from its environment to facilitate dechlorination and growth. To test this hypothesis, we applied isotopomer-based dilution analysis with (13)C-labeled acetate to differentiate the amino acids that were taken up by strain 195 from those synthesized de novo and to determine the physiological changes caused by the significantly incorporated amino acids. Our results showed that glutamate/glutamine and aspartate/asparagine were almost exclusively synthesized by strain 195, even when provided in excess in the medium. In contrast, phenylalanine, isoleucine, leucine, and methionine were identified as the four most highly incorporated amino acids, at levels >30% of respective proteinogenic amino acids. When either phenylalanine or all four highly incorporated amino acids were added to the defined mineral medium, the growth rates, dechlorination activities, and yields of strain 195 were enhanced to levels similar to those observed with supplementation with 20 amino acids. However, genes for the putative ABC-type amino acids transporters and phenylalanine biosynthesis exhibited insignificant regulation in response to the imported amino acids. This study also demonstrates that using isotopomer-based metabolite analysis can be an efficient strategy for optimizing nutritional conditions for slow-growing microorganisms.

  4. Dechlorination/Solidification of LiCl waste by using a synthetic inorganic composite with different compositions

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Na Young; Cho, In Hak; Park, Hwan Seo; Ahn, Do Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-09-15

    Waste salt generated from a pyro-processing for the recovery of uranium and transuranic elements has high volatility at vitrification temperature and low compatibility in conventional waste glasses. For this reason, KAERI (Korea Atomic Energy Research Institute) suggested a new method to de-chlorinate waste salt by using an inorganic composite named SAP (SiO{sub 2}-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5}). In this study, the de-chlorination behavior of waste salt and the microstructure of consolidated form were examined by adding B{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} to the original SAP composition. De-chlorination behavior of metal chloride waste was slightly changed with given compositions, compared with that of original SAP. In the consolidated forms, the phase separation between Si-rich phase and P-rich phase decreases with the amount of Al{sub 2}O{sub 3} or B{sub 2}O{sub 3} as a connecting agent between Si and P-rich phase. The results of PCT (Product Consistency Test) indicated that the leach-resistance of consolidated forms out of reference composition was lowered, even though the leach-resistance was higher than that of EA (Environmental Assessment) glass. From these results, it could be inferred that the change in the content of Al or B in U-SAP affected the microstructure and leach-resistance of consolidated form. Further studies related with correlation between composition and characteristics of wasteform are required for a better understanding.

  5. Enhancement of Degradation and Dechlorination of Trichloroethylene via Supporting Palladium/Iron Bimetallic Nanoparticles onto Mesoporous Silica

    Directory of Open Access Journals (Sweden)

    Jianjun Wei

    2016-07-01

    Full Text Available This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688 m2/g was prepared and used as the host of Pd/Fe nanoparticles. The Pd/Fe nanoparticles were deposited onto or into the mesoporous silica by reduction of ferrous ion and hexachloropalladate ion in aqueous phase. Batch degradation and dechlorination reactions of trichloroethylene were conducted with initial trichloroethylene concentration of 23.7 mg/L, iron loading of 203 or 1.91 × 103 mg/L and silica loading of 8.10 g/L at 25 °C. Concentration of trichloroethylene occurs on the supported Pd/Fe nanoparticles, with trichloroethylene degrading to 56% and 59% in 30 min on the supported Pd/Fe nanoparticles with weight percentage of palladium to iron at 0.075% and 0.10% respectively. The supported Pd/Fe nanoparticles exhibit better dechlorination activity. When the supported Pd/Fe nanoparticles with a weight percentage of palladium to iron of 0.10% were loaded much less than the bare counterpart, the yield of ethylene plus ethane in 10 h on them was comparable, i.e., 19% vs. 21%. This study offers a future approach to efficiently combine the reactivity of supported Pd/Fe nanoparticles and the adsorption ability of mesoporous silica.

  6. Improved dechlorinating performance of upflow anaerobic sludge blanket reactors by incorporation of Dehalospirillum multivorans into granular sludge

    DEFF Research Database (Denmark)

    Hörber, Christine; Christiansen, Nina; Arvin, Erik

    1998-01-01

    .5 mM acetate and were operated under sterile conditions. In the test reactor, an average of 93% (mole/mole) of the effluent chloroethenes was dichloroethene (DCE), compared to 99% (mole/mole) in the Ri reactor. The R2 reactor, with no inoculation, produced only trichloroethene (TCE), averaging 43......% (mole/mole) of the effluent chloroethenes. No dechlorination of PCE was observed in an abiotic control consisting of sterile granules without inoculum, During continuous operation with stepwise-reduced hydraulic retention times (HRTs), both the test reactor and the R1 reactor showed conversion of PCE...

  7. An interesting biochar effect that suppressed dechlorination of pentachlorophenol while promoted iron/sulfate reduction and methanogenesis in flooded soil

    Science.gov (United States)

    He, Yan; Zhu, Min

    2017-04-01

    Biochar has received increasing attention for its many environmental impacts in recent years, but there is still a lack of comprehensive understanding of its effects on the fate of reducible organic pollutants and soil biogeochemical processes under anaerobic environments. In this study, anaerobic batch experiments were conducted to explore the effect of biochar on reductive transformation of PCP and other soil redox processes in anaerobic incubation environment. Results showed that biochar had little impact on the system Eh and pH, both of which decreased gradually to a stable value during the incubation. Dissimilatory iron reduction and sulfate reduction were significantly enhanced following biochar addition, with the promoting effect more prominent in the treatment with 1% (w/w) than that with 5% biochar added. In addition, biochar accelerated the formation of carbon dioxide and methane, but there was no difference in the final content of these two greenhouse gases at the end of incubation between biochar amended and control treatments. Unexpectedly, compared to biochar-free controls, the reductively dechlorinated degradation of PCP was inhibited following biochar addition, with the inhibition extent increased with the increase of biochar amount. These revealed an interesting biochar effect that suppressed the dechlorination of PCP, but promoted the iron/sulfate reduction and accelerated the methanogenesis. It might be simultaneously mediated by the functional microbial groups that responded sensitively to the addition of biochar and/or PCP, including the potential dechlorinators, the potential iron/sulfate reducers, and the typical methanogenic archaea. Specific function of biochar as electron shuttle was also likely involved in underpinning this interesting effect, since biochar would be capable of splitting the limited electrons from the inferior electron acceptors (in our case, the PCP) to the dominant more competitive ones (in our case, Fe(III) and SO42

  8. Reductive Dechlorination of Trichloroethene by Zero-valent Iron Nanoparticles: Reactivity Enhancement through Sulfidation Treatment.

    Science.gov (United States)

    Han, Yanlai; Yan, Weile

    2016-12-06

    Zero-valent iron nanoparticles (nZVI) synthesized in the presence of reduced sulfur compounds have been shown to degrade trichloroethene (TCE) at significantly higher rates. However, the applicability of sulfidation as a general means to enhance nZVI reactivity under different particle preparation conditions and the underlying cause for this enhancement effect are not well understood. In this study, the effects of sulfidation reagent, time point of sulfidation, and sulfur loading on the resultant particles were assessed through TCE degradation experiments. Up to 60-fold increase in TCE reaction rates was observed upon sulfidation treatment, with products being fully dechlorinated hydrocarbons. While the reactivity of these sulfur-treated nZVI (S-nZVI) was relatively unaffected by the sulfidation reagent (viz., sodium sulfide, dithionite, or thiosulfate) or the sequence of sulfidation relative to iron reduction, TCE reaction rates were found to depend strongly on sulfur to iron ratio. At a low sulfur loading, TCE degradation was accelerated with increasing sulfur dose. The rate constant reached a limiting value, however, as the sulfur to iron mole ratio was greater than 0.025. Different from previous propositions that iron sulfidation leads to more efficient TCE or tetrachloroethene (PCE) degradation by enabling depassivation of iron surface, affording catalytic pathways, or facilitating electron transfer, we show that the role of sulfur in nZVI lies essentially in its ability to poison hydrogen recombination, which drives surface reactions to favor reduction by atomic hydrogen. This implies that the reactivity of S-nZVI is contaminant-specific and is selective against the background reaction of water reduction. As the effect of sulfur manifests through surface processes, sulfidation represents a broadly applicable surface modification approach to modulate or increase the reactivity of nZVI for treating TCE and other related contaminants.

  9. Influence of nitrate and sulfate reduction in the bioelectrochemically assisted dechlorination of cis-DCE.

    Science.gov (United States)

    Lai, Agnese; Verdini, Roberta; Aulenta, Federico; Majone, Mauro

    2015-04-01

    This paper investigated the reductive dechlorination (RD) of cis-dichloroethylene (cis-DCE) (average influent 14.2±0.7 μM) by a bioelectrochemical system (BES), in the presence of real contaminated groundwater containing high levels of nitrate and sulfate. The BES enhanced both the RD and competing reactions, such as nitrate and sulfate reductions, which occurred with neither an external organic carbon source nor any inoculum other than the indigenous microbial consortia in the real groundwater. In preliminary batch tests, RD and full nitrate removal occurred after a short lag phase, whereas sulfate reduction occurred slowly and alongside the RD. Under continuous flow conditions (hydraulic retention time, HRT, 1.4 d), the competition of different electron acceptors was strongly affected by the cathodic potential in the range -550 to -750 mV vs. standard hydrogen electrode (SHE). Nitrate reduction was driven to completion at all tested cathodic potentials, whereas sulfate reduction and the RD rate increased as the cathodic potential became more negative. At -750 mV vs. SHE, strong methanogenesis was also observed and became the most important sink of electrons. The overall coulombic efficiency decreased while the potential became more negative. The RD contribution was always less than 1%. Hence, greater energy consumption was required to obtain higher RD rate and better conversion. Anodic oxidation was only observed at -750 mV vs. SHE where almost 39% of residual vinyl chloride (VC) was oxidized and the sulfate was formed back from sulfide (further contributing to electric waste).

  10. Low and high acetate amendments are equally as effective at promoting complete dechlorination of trichloroethylene (TCE).

    Science.gov (United States)

    Wei, Na; Finneran, Kevin T

    2013-06-01

    Experiments with trichloroethylene-contaminated aquifer material demonstrated that TCE, cis-DCE, and VC were completely degraded with concurrent Fe(III) or Fe(III) and sulfate reduction when acetate was amended at stoichiometric concentration; competing TEAPs did not inhibit ethene production. Adding 10× more acetate did not increase the rate or extent of TCE reduction, but only increased methane production. Enrichment cultures demonstrated that ~90 μM TCE or ~22 μM VC was degraded primarily to ethene within 20 days with concurrent Fe(III) or Fe(III) + sulfate reduction. The dechlorination rates were comparable between the low and high acetate concentrations (0.36 vs 0.34 day(-1), respectively), with a slightly slower rate in the 10× acetate amended incubations. Methane accumulated to 13.5 (±0.5) μmol/tube in the TCE-degrading incubations with 10× acetate, and only 1.4 (±0.1) μmol/tube with low acetate concentration. Methane accumulated to 16 (±1.5) μmol/tube in VC-degrading enrichment with 10× acetate and 2 (±0.1) μmol/tube with stoichiometric acetate. The estimated fraction of electrons distributed to methanogenesis increased substantially when excessive acetate was added. Quantitative PCR analysis indicated that 10× acetate did not enhance Dehalococcoides biomass but rather increased the methanogen abundance by nearly one order of magnitude compared to that with stoichiometric acetate. The data suggest that adding low levels of substrate may be equally if not more effective as high concentrations, without producing excessive methane. This has implications for field remediation efforts, in that adding excess electron donor may not benefit the reactions of interest, which in turn will increase treatment costs without direct benefit to the stakeholders.

  11. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    Science.gov (United States)

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Impact of the morphology and reactivity of nanoscale zero-valent iron (NZVI) on dechlorinating bacteria.

    Science.gov (United States)

    Rónavári, Andrea; Balázs, Margit; Tolmacsov, Péter; Molnár, Csaba; Kiss, István; Kukovecz, Ákos; Kónya, Zoltán

    2016-05-15

    Nanoscale zero-valent iron (NZVI) is increasingly used for reducing chlorinated organic contaminants in soil or groundwater. However, little is known about what impact the particles will have on the biochemical processes and the indigenous microbial communities. Nanoiron reactivity is affected by the structure and morphology of nanoparticles that complicates the applicability in bioremediation. In this study, the effect of precursors (ferrous sulfate and ferric chloride) and reducing agents (sodium dithionite and sodium borohydride) on the morphology and the reactivity of NZVIs was investigated. We also studied the impact of differently synthesized NZVIs on microbial community, which take part in reductive dechlorination. We demonstrated that both the applied iron precursor and the reducing agent had influence on the structure of the nanoparticles. Spherical nanoparticles with higher Fe(0) content (>90%) was observed by using sodium borohydride as reducing agent, while application of sodium dithionite as reducing agent resulted nanostructures with lower Fe(0) content (between 68,7 and 85,5%). To determine the influence of differently synthesized NZVIs on cell viability anaerobic enriched microcosm were used. NVZI was used in 0.1 g/L concentration in all batch experiments. Relative amount of Dehalococcoides, sulfate reducers (SRBs) and methanogens were measured by quantitative PCR. We found that the relative amount of Dehalococcoides slowly decreased in all experiments independently from the precursor and reducing agent, whereas the total amount of microbes increased. The only clear distinction was in relative amount of sulfate reducers which were higher in the presence of NZVIs synthesized from sodium dithionite. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Dechlorination of disinfection by-product monochloroacetic acid in drinking water by nanoscale palladized iron bimetallic particle

    Institute of Scientific and Technical Information of China (English)

    CHEN Chao; WANG Xiangyu; CHANG Ying; LIU Huiling

    2008-01-01

    Nanoscale palladized iron (Pd/Fe) bimetallic particles were prepared by reductive deposition method. The particles were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM), and Brunauer-Emmett-Teller-nitrogen (BET-N2) method. Data obtained from those methods indicated that nanoscale Pd/Fe bimetallic particles contained α-Fe0. Detected Pd to Fe ratio by weight (PFRW) was close to theoretical PFRW. Spherical granules with diameter of 47±11.5 nm connected with one another to form chains and the chains composed nanoscale Pd/Fe bimetallic particles. Specific surface area of particles was 51 m2/g. Factors, such as species of reductants, PFRW, dose of nanoscale Pd/Fe bimetallic particles added into solutions, solution initial pH, and a variety of solvents were studied. Dechlorination effect of monochloroacetic acid (MCAA) by different reductants followed the trend: nanoscale Pd/Fe bimetallic particles of 0.182% PFRW > nanoscale Fe > reductive Fe. When PFRW was lower than 0.083%, increasing PFRW would increase dechlorination efficiency (DE) of MCAA. But when the PFRW was higher than 0.083%, increasing PFRW caused decrease in DE. Adding more nanoscale Pd/Fe bimetallic particles to solution would enhance DE. The DE of MCAA decreased as initial pH of solution increased.

  14. Exploring the Genome and Proteome of Desulfitobacterium hafniense DCB2 for its Protein Complexes Involved in Metal Reduction and Dechlorination

    Energy Technology Data Exchange (ETDEWEB)

    Sang-Hoon, Kim; Hardzman, Christina; Davis, John k.; Hutcheson, Rachel; Broderick, Joan B.; Marsh, Terence L.; Tiedje, James M.

    2012-09-27

    Desulfitobacteria are of interest to DOE mission because of their ability to reduce many electron acceptors including Fe(III), U(VI), Cr(VI), As(V), Mn(IV), Se(VI), NO3- and well as CO2, sulfite, fumarate and humates, their ability to colonize more stressful environments because they form spores, fix nitrogen and they have the more protective Gram positive cell walls. Furthermore at least some of them reductively dechlorinate aromatic and aliphatic pollutants. Importantly, most of the metals and the organochlorine reductions are coupled to ATP production and support growth providing for the organism's natural selection at DOE's contaminant sites. This work was undertaken to gain insight into the genetic and metabolic pathways involved in dissimilatory metal reduction and reductive dechlorination, (ii) to discern the commonalities among these electron-accepting processes, (iii) to identify multi-protein complexes catalyzing these functions and (iv) to elucidate the coordination in expression of these pathways and processes.

  15. Synthesis of granular activated carbon/zero valent iron composites for simultaneous adsorption/dechlorination of trichloroethylene.

    Science.gov (United States)

    Tseng, Hui-Hsin; Su, Jhih-Gang; Liang, Chenju

    2011-08-30

    The coupling adsorption and degradation of trichloroethylene (TCE) through dechlorination using synthetic granular activated carbon and zerovalent iron (GAC-ZVI) composites was studied. The GAC-ZVI composites were prepared from aqueous Fe(2+) solutions by impregnation with and without the use of a PEG dispersant and then heated at 105°C or 700°C under a stream of N(2). Pseudo-first-order rate constant data on the removal of TCE demonstrates that the adsorption kinetics of GAC is similar to those of GAC-ZVI composites. However, the usage of GAC-ZVI composites liberated a greater amount of Cl than when ZVI was used alone. The highest degree of reductive dechlorination of TCE was achieved using a GAC-ZVI700P composite (synthesized using PEG under 700°C). A modified Langmuir-Hinshelwood rate law was employed to depict the behavior of Cl liberation. As a result, a zero-order Cl liberation reaction was observed and the desorption limited TCE degradation rate constant decreased as the composite dosage was increased. The GAC-ZVI composites can be employed as a reactive GAC that is not subject to the limitations of using GAC and ZVI separately.

  16. Isolation and characterization of Desulfitobacterium dehalogenans gen. nov., sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds.

    Science.gov (United States)

    Utkin, I; Woese, C; Wiegel, J

    1994-10-01

    An organism that is able to reductively ortho-dechlorinate 2,4-dichlorophenol and 3-chloro-4-hydroxyphenylacetate (3-Cl-4-OHPA) was isolated from a methanogenic lake sediment. This organism, an anaerobic, motile, Gram-type-positive, rod-shaped bacterium, grew in the presence of 0.1% yeast extract when pyruvate, lactate, formate, or hydrogen was used as the electron donor for reductive dehalogenation of 3-Cl-4-OHPA. Sulfite, thiosulfate, and sulfur were reduced to sulfide, nitrate was reduced to nitrite, and fumarate was reduced to succinate. Dissimilatory reduction of sulfate could not be demonstrated, and no adenylylsulfate reductase was detected with an immunoassay. The organism fermented two pyruvate molecules to one lactate molecule, one acetate molecule, and one carbon dioxide molecule. The pH and temperature optima for both growth and dechlorination of 3-Cl-4-OHPA were 7.5 and 38 degrees C, respectively. The doubling time under these conditions was approximately 3.5 h. On the basis of the results of a 16S rRNA analysis and the inability of the organism to use sulfate as an electron acceptor, strain JW/IU-DC1 is described as the type strain of the new taxon Desulfitobacterium dehalogenans gen. nov., sp. nov.

  17. Characterization of natural anaerobic dechlorination of TCE and 1,1,1-TCA in clay till including isotope fractionation and molecular biological tools

    DEFF Research Database (Denmark)

    Damgaard, Ida; Bælum, J.; Hunkeler, D.;

    2010-01-01

    One of the major challenges when using enhanced reductive dechlorination (ERD) as a remediation technology at clay till sites is to obtain good contact between added agents such as donor, bacteria and the contamination. It is unclear whether degradation only takes place in fractures and/or sand l...

  18. Dynamics of the microbial community and Fe(III)-reducing and dechlorinating microorganisms in response to pentachlorophenol transformation in paddy soil.

    Science.gov (United States)

    Chen, Manjia; Liu, Chengshuai; Chen, Pengcheng; Tong, Hui; Li, Fangbai; Qiao, Jiangtao; Lan, Qing

    2016-07-15

    Soil microorganisms play crucial roles in the fates of pollutants, and understanding the behaviour of these microorganisms is critical for the bioremediation of PCP-contaminated soil. However, shifts remain unclear in the community structure and Fe(III)-reducing and dechlorinating microorganisms during PCP transformation processes, especially during the stages from the lag to the dechlorination phase and from the dechlorination to the stationary phase. Here, a set of lab-scale experiments was performed to investigate the microbial community dynamics accompanying PCP transformation in paddy soil. 19μM of PCP was biotransformed completely in 10days for all treatments. T-RFLP analysis of the microbial community confirmed that Veillonellaceae and Clostridium sensu stricto were the dominant groups during PCP transformation, and the structures of the microbial communities changed due to the degree of biotransformation and the addition of lactate and AQDS. However, similar temporal dynamics of the microbial communities were obtained among all treatments. Furthermore, as revealed by quantitative PCR, the dynamics of Fe(III)-reducing and dechlorinating microorganisms, including Geobacter sp., Shewanella sp., and Dehalobacter sp., were consistent with the transformation kinetics of PCP, suggesting the critical roles played by these microorganisms in PCP transformation. These findings are valuable for making predictions of and proposing methods for the microbial detoxification of residual organochlorine pesticides in paddy soil. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra- and trichloroethene in an anaerobic respiration

    NARCIS (Netherlands)

    Holliger, C; Hahn, D; Harmsen, H; Ludwig, W; Schumacher, W; Tindall, B; Vazquez, F; Weiss, N; Zehnder, AJB

    The highly enriched anaerobic bacterium that couples the reductive dechlorination of tetrachloroethene to growth, previously referred to as PER-K23, was obtained in pure culture and characterized. The bacterium, which does not form spores, is a small, gram-negative rod with one lateral flagellum. It

  20. Reductive dechlorination of trichloroethylene (TCE) in competition with Fe and Mn oxides – observed dynamics in H2-dependent terminal electron accepting processes

    DEFF Research Database (Denmark)

    Paul, Laiby; Jakobsen, Rasmus; Smolders, Erik

    2016-01-01

    Fe minerals or environmental samples were used as the substrata. Iron(III) and Mn(IV) reduction limited microbial dechlorination by the mixed anaerobic culture by decreasing the level of H2 in the system. The H2 measurements indicated that the H2 concentration at which different TEAPs occur can...

  1. Introduction of a De Novo Bioremediation Ability, Aryl Reductive Dechlorination, into Anaerobic Granular Sludge by Inoculation of Sludge with Desulfomonile tiedjei

    DEFF Research Database (Denmark)

    Ahring, Birgitte Kiær; Christiansen, Nina; Mathrani, Indra Madan

    1992-01-01

    Methanogenic upflow anaerobic granular-sludge blanket (UASB) reactors treat wastewaters at a high rate while simultaneously producing a useful product, methane; however, recalcitrant environmental pollutants may not be degraded. To impart 3-chlorobenzoate (3-CB)-dechlorinating ability to UASB rea...

  2. Inhibition of Geobacter dechlorinators at elevated trichloroethene concentrations is explained by a reduced activity rather than by an enhanced cell decay.

    Science.gov (United States)

    Philips, Jo; Haest, Pieter Jan; Springael, Dirk; Smolders, Erik

    2013-02-05

    Microbial dechlorination of trichloroethene (TCE) is inhibited at elevated TCE concentrations. A batch experiment and modeling analysis were performed to examine whether this self-inhibition is related to an enhanced cell decay or a reduced dechlorination activity at increasing TCE concentrations. The batch experiment combined four different initial TCE concentrations (1.4-3.0 mM) and three different inoculation densities (4.0 × 10(5) to 4.0 × 10(7)Geobacter cells·mL(-1)). Chlorinated ethene concentrations and Geobacter 16S rRNA gene copy numbers were measured. The time required for complete conversion of TCE to cis-DCE increased with increasing initial TCE concentration and decreasing inoculation density. Both an enhanced decay and a reduced activity model fitted the experimental results well, although the reduced activity model better described the lag phase and microbial decay in some treatments. In addition, the reduced activity model succeeded in predicting the reactivation of the dechlorination reaction in treatments in which the inhibiting TCE concentration was lowered after 80 days. In contrast, the enhanced decay model predicted a Geobacter cell density that was too low to allow recovery for these treatments. Conclusively, our results suggest that TCE self-inhibition is related to a reduced dechlorination activity rather than to an enhanced cell decay at elevated TCE concentrations.

  3. Influence of physical factors and geochemical conditions on groundwater acidification during enhanced reductive dechlorination

    Science.gov (United States)

    Brovelli, A.; Barry, D. A.; Robinson, C.; Gerhard, J.

    2010-12-01

    Enhanced reductive dehalogenation is an attractive in situ treatment technology for chlorinated contaminants. The process includes two acid-forming microbial reactions: fermentation of an organic substrate resulting in short-chain fatty acids, and dehalogenation resulting in hydrochloric acid. The accumulation of acids and the resulting drop of groundwater pH are controlled by the mass and distribution of chlorinated solvents in the source zone, type of electron donor, availability of alternative terminal electron acceptors and presence of soil mineral phases able to buffer the pH (such as carbonates). Groundwater acidification may reduce or halt microbial activity, and thus dehalogenation, significantly increasing the time and costs required to remediate the aquifer. For this reason, research in this area is gaining increasing attention. In previous work (Robinson et al., 2009 407:4560, Sci. Tot. Environ, Robinson and Barry, 2009 24:1332, Environ. Model. & Software, Brovelli et al., 2010, submitted), a detailed geochemical and groundwater flow model able to predict the pH change occurring during reductive dehalogenation was developed. The model accounts for the main processes influencing groundwater pH, including the groundwater composition, the electron donor used and soil mineral phase interactions. In this study, the model was applied to investigate how spatial variability occurring at the field scale affects groundwater pH and dechlorination rates. Numerical simulations were conducted to examine the influence of heterogeneous hydraulic conductivity on the distribution of the injected, fermentable substrate and on the accumulation/dilution of the acidic products of reductive dehalogenation. The influence of the geometry of the DNAPL source zone was studied, as well as the spatial distribution of soil minerals. The results of this study showed that the heterogeneous distribution of the soil properties have a potentially large effect on the remediation efficiency

  4. Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Kyung, Daeseung [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Sihn, Youngho [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Kim, Sangwoo [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Bae, Sungjun [Department of Environmental Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029 (Korea, Republic of); Amin, Muhammad Tahir; Alazba, Abdulrahman Ali [Alamoudi Water Chair, King Saud University, Riyadh 11451 (Saudi Arabia); Lee, Woojin, E-mail: woojin_lee@kaist.ac.kr [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of)

    2016-07-05

    Highlights: • Complete degradation of PCE was observed in nFeS-Cbl(III)-cement at pH 12. • PCE was completely degraded to non-chlorinated organic compounds by this system. • Co redox couple and Ca species in cement played a pivotal role for PCE reduction. • Increases in Cbl(III) concentration, cement ratio, and pH enhanced PCE degradation. • Efficiency of the system for PCE reduction was good even at high concentration of PCE. - Abstract: Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k{sub obs-PCE} = 0.57 h{sup −1}) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO{sub 2}, Al{sub 2}O{sub 3}, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005–0.1 mM), cement ratio (0.05–0.2), and suspension pH (11.5–13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

  5. PRELIMINARY RESEARCH ON DECHLORINATION OF 2,4-DICHLOROPHENOL BY NANOSCALE Pd/Fe%纳米级钯/铁作用下2,4-二氯苯酚脱氯反应初探

    Institute of Scientific and Technical Information of China (English)

    卫建军; 徐新华; 刘永; 汪大翚

    2004-01-01

    @@ 1 INTRODUCTION Zero valent iron has been used to dechlorinate chlorinated organic compounds (COCs) in water and groundwater. The studies were concerned with compounds such as carbon tetrachloride and trichloroethene[1-3].

  6. Journal of Agricultural Extension

    African Journals Online (AJOL)

    Mission Statement The mission of the "Journal of Agricultural Extension" is to publish ... diffusion and adoption of innovations; extension communication models and ... Socio-Economic Determinants of Cocoyam Farmer's Strategies for Climate ...

  7. Experimental Study on Dechlorination and Leaching of Zinc-Oxide Powder%锌氧粉脱氯及浸出试验研究

    Institute of Scientific and Technical Information of China (English)

    杨体昌

    2011-01-01

    The high temperature calcination removal method of zinc - oxide powder dechlorination and defluoridation, as well as the alkaline washing dechlorination method are researched by experiment, and the direct leaching of zinc-oxide powder and using it as the neutralizer is explored too in the experiment, So the operating condition of direct leaching zinc-oxide powder by electrolyte waste liquid is proposed.%试验研究了锌氧粉脱除氟和氯的高温焙烧脱除法和碱洗除氯法;并对锌氧粉的直接浸出和作为中和剂进行了探索,提出用电解废液直接浸出锌氧粉的操作条件.

  8. The ecotoxic potential of a new zero-valent iron nanomaterial, designed for the elimination of halogenated pollutants, and its effect on reductive dechlorinating microbial communities.

    Science.gov (United States)

    Schiwy, Andreas; Maes, Hanna M; Koske, Daniel; Flecken, Mirkko; Schmidt, Kathrin R; Schell, Heico; Tiehm, Andreas; Kamptner, Andre; Thümmler, Silke; Stanjek, Helge; Heggen, Marc; Dunin-Borkowski, Rafal E; Braun, Jürgen; Schäffer, Andreas; Hollert, Henner

    2016-09-01

    The purpose of this study was to assess the ecotoxic potential of a new zero-valent iron nanomaterial produced for the elimination of chlorinated pollutants at contaminated sites. Abiotic dechlorination through the newly developed nanoscale zero-valent iron material and its effects on dechlorinating bacteria were investigated in anaerobic batch and column experiments. The aged, i.e. oxidized, iron material was characterization with dynamic light scattering, transmission electron microscopy and energy dispersive x-ray analysis, x-ray diffractometry and cell-free reactive oxygen measurements. Furthermore, it was evaluated in aerobic ecotoxicological test systems with algae, crustacean, and fish, and also applied in a mechanism specific test for mutagenicity. The anaerobic column experiments showed co-occurrence of abiotic and biological dechlorination of the common groundwater contaminant perchloroethene. No prolonged toxicity of the nanomaterial (measured for up to 300 days) towards the investigated dechlorinating microorganism was observed. The nanomaterial has a flake like appearance and an inhomogeneous size distribution. The toxicity to crustacean and fish was calculated and the obtained EC50 values were 163 mg/L and 458 mg/L, respectively. The nanomaterial showed no mutagenicity. It physically interacted with algae, which had implications for further testing and the evaluation of the results. Thus, the newly developed iron nanomaterial was slightly toxic in its reduced state but no prolonged toxicity was recorded. The aquatic tests revealed a low toxicity with EC50 values ≥ 163 mg/L. These concentrations are unlikely to be reached in the aquatic environment. Hence, this nanomaterial is probably of no environmental concern not prohibiting its application for groundwater remediation. Copyright © 2016. Published by Elsevier Ltd.

  9. Type Safe Extensible Programming

    Science.gov (United States)

    Chae, Wonseok

    2009-10-01

    Software products evolve over time. Sometimes they evolve by adding new features, and sometimes by either fixing bugs or replacing outdated implementations with new ones. When software engineers fail to anticipate such evolution during development, they will eventually be forced to re-architect or re-build from scratch. Therefore, it has been common practice to prepare for changes so that software products are extensible over their lifetimes. However, making software extensible is challenging because it is difficult to anticipate successive changes and to provide adequate abstraction mechanisms over potential changes. Such extensibility mechanisms, furthermore, should not compromise any existing functionality during extension. Software engineers would benefit from a tool that provides a way to add extensions in a reliable way. It is natural to expect programming languages to serve this role. Extensible programming is one effort to address these issues. In this thesis, we present type safe extensible programming using the MLPolyR language. MLPolyR is an ML-like functional language whose type system provides type-safe extensibility mechanisms at several levels. After presenting the language, we will show how these extensibility mechanisms can be put to good use in the context of product line engineering. Product line engineering is an emerging software engineering paradigm that aims to manage variations, which originate from successive changes in software.

  10. Torque-wrench extension

    Science.gov (United States)

    Peterson, D. H.

    1981-01-01

    Torque-wrench extension makes it easy to install and remove fasteners that are beyond reach of typical wrenches or are located in narrow spaces that prevent full travel of wrench handle. At same time, tool reads applied torque accurately. Wrench drive system, for torques up to 125 inch-pounds, uses 2 standard drive-socket extensions in aluminum frame. Extensions are connected to bevel gear that turns another bevel gear. Gears produce 1:1 turn ratio through 90 degree translation of axis of rotation. Output bevel has short extension that is used to attach 1/4-inch drive socket.

  11. Motile Geobacter dechlorinators migrate into a model source zone of trichloroethene dense non-aqueous phase liquid: Experimental evaluation and modeling

    Science.gov (United States)

    Philips, Jo; Miroshnikov, Alexey; Haest, Pieter Jan; Springael, Dirk; Smolders, Erik

    2014-12-01

    Microbial migration towards a trichloroethene (TCE) dense non-aqueous phase liquid (DNAPL) could facilitate the bioaugmentation of TCE DNAPL source zones. This study characterized the motility of the Geobacter dechlorinators in a TCE to cis-dichloroethene dechlorinating KB-1™ subculture. No chemotaxis towards or away from TCE was found using an agarose in-plug bridge method. A second experiment placed an inoculated aqueous layer on top of a sterile sand layer and showed that Geobacter migrated several centimeters in the sand layer in just 7 days. A random motility coefficient for Geobacter in water of 0.24 ± 0.02 cm2·day- 1 was fitted. A third experiment used a diffusion-cell setup with a 5.5 cm central sand layer separating a DNAPL from an aqueous top layer as a model source zone to examine the effect of random motility on TCE DNAPL dissolution. With top layer inoculation, Geobacter quickly colonized the sand layer, thereby enhancing the initial TCE DNAPL dissolution flux. After 19 days, the DNAPL dissolution enhancement was only 24% lower than with an homogenous inoculation of the sand layer. A diffusion-motility model was developed to describe dechlorination and migration in the diffusion-cells. This model suggested that the fast colonization of the sand layer by Geobacter was due to the combination of random motility and growth on TCE.

  12. First evidence on the occurrence and dynamics of Dehalococcoides mccartyi PCB-dechlorinase genes in marine sediment during Aroclor1254 reductive dechlorination.

    Science.gov (United States)

    Matturro, B; Di Lenola, M; Ubaldi, C; Rossetti, S

    2016-11-15

    The present study evaluates the PCB-dehalorespiring capabilities and dynamics of indigenous Dehalococcoides mccartyi population in a PCB contaminated marine sediment. Specialized PCB-dechlorinase genes pcbA1, pcbA4 and pcbA5 previously characterized in pure cultures of D. mccartyi, were here found for the first time in environmental samples. Reductive dechlorination was stimulated by spiking Aroclor1254 to the sediment and by imposing strictly anaerobic conditions both with and without bioaugmentation with a Dehalococcoides mccartyi enrichment culture. In line with the contaminant dechlorination kinetics, Dehalococcoides population increased during the entire incubation period showing growth yields of 4.94E+07 Dehalococcoides per μmolCl(-1) and 7.30E+05 Dehalococcoides per μmolCl(-1) in the marine sediment with and without bioaugmentation respectively. The pcbA4 and pcbA5 dechlorinase genes, and to a lesser extent pcbA1 gene, were enriched during the anaerobic incubation suggesting their role in Aroclor1254 dechlorination under salinity conditions.

  13. Kentucky's Urban Extension Focus

    Science.gov (United States)

    Young, Jeffery; Vavrina, Charles

    2014-01-01

    Defining the success of Urban Extension units is sometimes challenging. For those Extension agents, specialists, administrators, and others who have worked to bring solid, research-based programming to urban communities, it is no surprise that working in these communities brings its own unique and sometimes difficult challenges. Kentucky's Urban…

  14. Metagenomic and Metatranscriptomic Analyses Reveal the Structure and Dynamics of a Dechlorinating Community Containing Dehalococcoides mccartyi and Corrinoid-Providing Microorganisms under Cobalamin-Limited Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Men, Yujie; Yu, Ke; Bælum, Jacob; Gao, Ying; Tremblay, Julien; Prestat, Emmanuel; Stenuit, Ben; Tringe, Susannah G.; Jansson, Janet; Zhang, Tong; Alvarez-Cohen, Lisa; Liu, Shuang-Jiang

    2017-02-10

    ABSTRACT

    The aim of this study is to obtain a systems-level understanding of the interactions betweenDehalococcoidesand corrinoid-supplying microorganisms by analyzing community structures and functional compositions, activities, and dynamics in trichloroethene (TCE)-dechlorinating enrichments. Metagenomes and metatranscriptomes of the dechlorinating enrichments with and without exogenous cobalamin were compared. Seven putative draft genomes were binned from the metagenomes. At an early stage (2 days), more transcripts of genes in theVeillonellaceaebin-genome were detected in the metatranscriptome of the enrichment without exogenous cobalamin than in the one with the addition of cobalamin. Among these genes, sporulation-related genes exhibited the highest differential expression when cobalamin was not added, suggesting a possible release route of corrinoids from corrinoid producers. Other differentially expressed genes include those involved in energy conservation and nutrient transport (including cobalt transport). The most highly expressed corrinoidde novobiosynthesis pathway was also assigned to theVeillonellaceaebin-genome. Targeted quantitative PCR (qPCR) analyses confirmed higher transcript abundances of those corrinoid biosynthesis genes in the enrichment without exogenous cobalamin than in the enrichment with cobalamin. Furthermore, the corrinoid salvaging and modification pathway ofDehalococcoideswas upregulated in response to the cobalamin stress. This study provides important insights into the microbial interactions and roles played by members of dechlorinating communities under cobalamin-limited conditions.

    IMPORTANCEThe key

  15. Algebraic extensions of fields

    CERN Document Server

    McCarthy, Paul J

    1991-01-01

    ""...clear, unsophisticated and direct..."" - MathThis textbook is intended to prepare graduate students for the further study of fields, especially algebraic number theory and class field theory. It presumes some familiarity with topology and a solid background in abstract algebra. Chapter 1 contains the basic results concerning algebraic extensions. In addition to separable and inseparable extensions and normal extensions, there are sections on finite fields, algebraically closed fields, primitive elements, and norms and traces. Chapter 2 is devoted to Galois theory. Besides the fundamenta

  16. Cotorsion Pair Extensions

    Institute of Scientific and Technical Information of China (English)

    De Xu ZHOU

    2009-01-01

    Assume that S is an almost excellent extension of R. Using functors Hom R(S,-) and -(×)R S, we establish some connections between classes of modules (L)R and (L)S, cotorsion pairs ((A)R, (A)R)and ((A)S, (B)S). If (L)S is a T-extension or (and) H-extension of (L)R, we show that (L)S is a (resp., monomorphic, epimorphic, special) preenveloping class if and only if so is (L)R. If (S, S) is a TH-extension of ((A)R,(B)R), we obtain that ((A)S,(B)S) is complete (resp., of finite type, of cofinite type, hereditary, perfect, n-tilting) if and only if so is ((A)R,(B)R).

  17. Type extension trees

    DEFF Research Database (Denmark)

    Jaeger, Manfred

    2006-01-01

    We introduce type extension trees as a formal representation language for complex combinatorial features of relational data. Based on a very simple syntax this language provides a unified framework for expressing features as diverse as embedded subgraphs on the one hand, and marginal counts...... of attribute values on the other. We show by various examples how many existing relational data mining techniques can be expressed as the problem of constructing a type extension tree and a discriminant function....

  18. Type extension trees

    DEFF Research Database (Denmark)

    Jaeger, Manfred

    2006-01-01

    We introduce type extension trees as a formal representation language for complex combinatorial features of relational data. Based on a very simple syntax this language provides a unified framework for expressing features as diverse as embedded subgraphs on the one hand, and marginal counts...... of attribute values on the other. We show by various examples how many existing relational data mining techniques can be expressed as the problem of constructing a type extension tree and a discriminant function....

  19. EXTENSIVE READING IN CHINA

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    IntroductionMost teachers and students in China are quite familiar with the term‘extensive reading’,but how itshould be taught still remains a problem.This paper covers the aims of extensive reading and the methodsand materials used in the course.Then some practical suggestions will be given to make the course moreinteresting and efficient.According to Dzao(1990).extensive reading is‘the course where other reading skills-speed,predictionand making inference-can be developed,’and‘where there is practice in geting the gist,in summarisingmain ideas,in understanding the author’s purpose and theme...’.So the aims of this course are todevelop general reading skills,the ability,to read quickly and to grasp the main ideas of the text.Toachieve these,students must enlarge their vocabulary,so this is also regarded as one of the aims.

  20. Android Access Control Extension

    Directory of Open Access Journals (Sweden)

    Anton Baláž

    2015-12-01

    Full Text Available The main objective of this work is to analyze and extend security model of mobile devices running on Android OS. Provided security extension is a Linux kernel security module that allows the system administrator to restrict program's capabilities with per-program profiles. Profiles can allow capabilities like network access, raw socket access, and the permission to read, write, or execute files on matching paths. Module supplements the traditional Android capability access control model by providing mandatory access control (MAC based on path. This extension increases security of access to system objects in a device and allows creating security sandboxes per application.

  1. Recent extensions to GALPROP

    CERN Document Server

    Strong, A W

    2015-01-01

    Some recent extensions to the GALPROP cosmic-ray propagation package are described. The enhancements include: an accurate solution option, improved convection formulation, alternative spatial boundary conditions, polarized synchrotron emission, new magnetic field models, updated gamma-ray production cross-sections, free-free radio emission and absorption, primary positrons, additional injection spectral breaks, deuterium production by pp fusion, hadronic energy losses, improved HEALPix skymap format, compatibility with latest HEALPix release, and various bug fixes. The Explanatory Supplement has been extensively updated, including details of these enhancements. A compatible plot package GALPLOT for GALPROP output is also provided, as well as other related software.

  2. Acidification due to microbial dechlorination near a trichloroethene DNAPL is overcome with pH buffer or formate as electron donor: experimental demonstration in diffusion-cells.

    Science.gov (United States)

    Philips, Jo; Maes, Nele; Springael, Dirk; Smolders, Erik

    2013-04-01

    Acidification due to microbial dechlorination of trichloroethene (TCE) can limit the bio-enhanced dissolution of TCE dense non-aqueous phase liquid (DNAPL). This study related the dissolution enhancement of a TCE DNAPL to the pH buffer capacity of the medium and the type of electron donor used. In batch systems, dechlorination was optimal at pH7.1-7.5, but was completely inhibited below pH6.2. In addition, dechlorination in batch systems led to a smaller pH decrease at an increasing pH buffer capacity or with the use of formate instead of lactate as electron donor. Subsequently, bio-enhanced TCE DNAPL dissolution was quantified in diffusion-cells with a 5.5 cm central sand layer, separating a TCE DNAPL layer from an aqueous top layer. Three different pH buffer capacities (2.9 mM-17.9 mM MOPS) and lactate or formate as electron donor were applied. In the lactate fed diffusion-cells, the DNAPL dissolution enhancement factor increased from 1.5 to 2.2 with an increase of the pH buffer capacity. In contrast, in the formate fed diffusion-cells, the DNAPL dissolution enhancement factor (2.4±0.3) was unaffected by the pH buffer capacity. Measurement of the pore water pH confirmed that the pH decreased less with an increased pH buffer capacity or with formate instead of lactate as electron donor. These results suggest that the significant impact of acidification on bio-enhanced DNAPL dissolution can be overcome by the amendment of a pH buffer or by applying a non acidifying electron donor like formate. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Molecular characterization of a dechlorinating community resulting from in situ biostimulation in a trichloroethene-contaminated deep, fractured basalt aquifer and comparison to a derivative laboratory culture.

    Science.gov (United States)

    Macbeth, Tamzen W; Cummings, David E; Spring, Stefan; Petzke, Lynn M; Sorenson, Kent S

    2004-12-01

    Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of bacterial amplicons was predominated by those from members of the class Clostridia (57 of 93 clones), of which a phylotype most similar to that of the homoacetogen Acetobacterium sp. strain HAAP-1 was most abundant (32 of 93 clones). The remaining Bacteria consisted of phylotypes affiliated with Sphingobacteria, Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria and candidate divisions OP11 and OP3. The two proteobacterial phylotypes were most similar to those of the known dechlorinators Trichlorobacter thiogenes and Sulfurospirillum multivorans. Although not represented by the bacterial clones generated with broad-specificity bacterial primers, a Dehalococcoides-like phylotype was identified with genus-specific primers. Only four distinct phylotypes were detected in the groundwater archaeal library, including predominantly a clone affiliated with the strictly acetoclastic methanogen Methanosaeta concilii (24 of 43 clones). A mixed culture that completely dechlorinates TCE to ethene was enriched from this groundwater, and both communities were characterized by terminal restriction fragment length polymorphism (T-RFLP). According to T-RFLP, the laboratory enrichment community was less diverse overall than the groundwater community, with 22 unique phylotypes as opposed to 43 and a higher percentage of Clostridia, including the Acetobacterium population. Bioreactor archaeal structure was very similar to that of the groundwater community, suggesting that methane is

  4. Mobile Applications for Extension

    Science.gov (United States)

    Drill, Sabrina L.

    2012-01-01

    Mobile computing devices (smart phones, tablets, etc.) are rapidly becoming the dominant means of communication worldwide and are increasingly being used for scientific investigation. This technology can further our Extension mission by increasing our power for data collection, information dissemination, and informed decision-making. Mobile…

  5. Extensions of tempered representations

    NARCIS (Netherlands)

    Opdam, E.; Solleveld, M.

    2013-01-01

    Let π, π′ be irreducible tempered representations of an affine Hecke algebra H with positive parameters. We compute the higher extension groups Ext nH(π,π′) explicitly in terms of the representations of analytic R-groups corresponding to π and π′. The result has immediate applications to the computa

  6. Extending Extensive Reading

    Science.gov (United States)

    Day, Richard R.

    2015-01-01

    The April 2015 issue of "Reading in a Foreign Language" featured a discussion forum on extensive reading (ER). Most of the authors, recognized authorities on ER, discussed their views of the principles of ER, particularly in establishing and conducting ER programs. The purpose of this discussion is to review developments in the practice…

  7. Molecular Characterization of a Dechlorinating Community Resulting from In Situ Biostimulation in a Trichloroethene-Contaminated Deep, Fractured Basalt Aquifer and Comparison to a Derivative Laboratory Culture

    OpenAIRE

    Macbeth, Tamzen W.; Cummings, David E; Spring, Stefan; Petzke, Lynn M.; Sorenson, Kent S.

    2004-01-01

    Sodium lactate additions to a trichloroethene (TCE) residual source area in deep, fractured basalt at a U.S. Department of Energy site have resulted in the enrichment of the indigenous microbial community, the complete dechlorination of nearly all aqueous-phase TCE to ethene, and the continued depletion of the residual source since 1999. The bacterial and archaeal consortia in groundwater obtained from the residual source were assessed by using PCR-amplified 16S rRNA genes. A clone library of...

  8. Complete anaerobic mineralization of pentachlorophenol (PCP) under continuous flow conditions by sequential combination of PCP-dechlorinating and phenol-degrading consortia.

    Science.gov (United States)

    Li, Zhiling; Yang, Suyin; Inoue, Yasushi; Yoshida, Naoko; Katayama, Arata

    2010-12-01

    Complete mineralization of 50 µM of pentachlorophenol (PCP) was achieved anaerobically under continuous flow conditions using two columns connected in series with a hydraulic retention time of 14.2 days, showing the highest reported mineralization rate yet of 3.5 µM day(-1). The first column, when injected with a reductive PCP dechlorinating consortium, dechlorinated PCP to mainly phenol and traces of 3-chlorophenol (3-CP) using lactate supplied continuously as an electron donor. The second column, with an anaerobic phenol degrading consortium, decomposed phenol and 3-CP under iron-reducing conditions with substantial fermentative degradation of organic compounds. When 20 mM of lactate was introduced into the first column, the phenol degradation activity of the second column was lost in a short period of time, because the amorphous Fe(III) oxide (FeOOH) that had been packed in the column before use was depleted by lactate metabolites, such as acetate and propionate, flowing into the second column from the first column. The complete mineralization of PCP was maintained for a long period by reducing the lactate concentration to 4 mM, effectively extending the longevity of second-column activity with no depletion of FeOOH for more than 200 pore volumes (corresponding to 3,000 days). The carbon balance showed that 50 µM PCP and 4 mM lactate in the influent had transformed to CO(2) (81%) and CH(4) (3%) and had contributed to biomass growth (8%). A comparison of the microbial consortia introduced into the columns and those flowing out from the columns suggested that the introduced population did not flow out during the experiments, although the microbial composition of the phenol column was considered to be affected by the inflow of microbes from the PCP dechlorination column. These results suggest that a sequential combination of reductive dechlorinating and anaerobic oxidizing consortia is useful for anaerobic remediation of chlorinated aromatic compounds in

  9. Simulation Of Enhanced Reductive Dechlorination For Remediation Of Tce In A Fractured Clay System: A New Model Approach And Application To Field Site

    DEFF Research Database (Denmark)

    Manoli, Gabriele; Chambon, Julie Claire Claudia; Christiansen, Camilla Maymann;

    2010-01-01

    with interspersed sand lenses and stringers. The transport model couples diffusion dominated transport in the clay matrix, with advective‐dispersive transport in the fractures and higher permeability sand lenses. The reactive model calculates sequential reductive dechlorination of TCE (trichloroethylene) to its...... a contamination of trichloroethylene located in a fractured clay till. The site is simulated using the model developed. Fracture geometry, site parameters and degradation rates are based on observations from the site and lab studies. The risk for drinking water is assessed and cleanup times are simulated using...

  10. Treatment of radioactive waste salt by using synthetic silica-based phosphate composite for de-chlorination and solidification

    Science.gov (United States)

    Cho, In-Hak; Park, Hwan-Seo; Lee, Ki-Rak; Choi, Jung-Hun; Kim, In-Tae; Hur, Jin Mok; Lee, Young-Seak

    2017-09-01

    In the radioactive waste management, waste salts as metal chloride generated from a pyrochemical process to recover uranium and transuranic elements are one of problematic wastes due to their intrinsic properties such as high volatility and low compatibility with conventional glasses. This study reports a method to stabilize and solidify LiCl waste via de-chlorination using a synthetic composite, U-SAP (SiO2-Al2O3-B2O3-Fe2O3-P2O5) prepared by a sol-gel process. The composite was reacted with alkali metal elements to produce some metal aluminosilicates, aluminophosphates or orthophosphate as a crystalline or amorphous compound. Different from the original SAP (SiO2-Al2O3-P2O5), the reaction product of U-SAP could be successfully fabricated as a monolithic wasteform without a glassy binder at a proper reaction/consolidation condition. From the results of the FE-SEM, FT-IR and MAS-NMR analysis, it could be inferred that the Si-rich phase and P-rich phase as a glassy grains would be distributed in tens of nm scale, where alkali metal elements would be chemically interacted with Si-rich or P-rich region in the virgin U-SAP composite and its products was vitrified into a silicate or phosphate glass after a heat-treatment at 1150 °C. The PCT-A (Product Consistency Test, ASTM-1208) revealed that the mass loss of Cs and Sr in the U-SAP wasteform had a range of 10-3∼10-1 g/m2 and the leach-resistance of the U-SAP wasteform was comparable to other conventional wasteforms. From the U-SAP method, LiCl waste salt was effectively stabilized and solidified with high waste loading and good leach-resistance.

  11. Modal extension rule

    Institute of Scientific and Technical Information of China (English)

    WU Xia; SUN Jigui; LIN Hai; FENG Shasha

    2005-01-01

    Modal logics are good candidates for a formal theory of agents. The efficiency of reasoning method in modal logics is very important, because it determines whether or not the reasoning method can be widely used in systems based on agent. In this paper,we modify the extension rule theorem proving method we presented before, and then apply it to P-logic that is translated from modal logic by functional transformation. At last, we give the proof of its soundness and completeness.

  12. EXTENSIONS OF SOME INEQUALITIES

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By using a simple analytic method the following inequalities are proved:(bx+y-ax+y)/(bx-ax)≥[(x+y)/x][(a+b)/2]y,for 0<a<b,x≥1,y>0,x+y≥2;(bx+y-ax+y)/(bx-ax)<[(x+y)/x][(a+b)/2]y,for0<a<b,0<x<1,y>0,x+y≤2.These inequalities are the extensions of inequalities of Qi Feng, Xu Senlin and Zheng Lin. And a conjection of Qi Feng is proved not true.

  13. Extensive air showers

    CERN Document Server

    Rao, M V S

    1997-01-01

    Ultrahigh energy cosmic rays carry information about their sources and the intervening medium apart from providing a beam of particles for studying certain features of high energy interactions currently inaccessible at man-made accelerators. They can at present be studied only via the extensive air showers (EAS's) they generate while passing through the Earth's atmosphere, since their fluxes are too low for the experiments of limited capability flown in balloons and satellites. The EAS is generated by a series of interactions of the primary cosmic ray and its progeny with the atmospheric nucle

  14. Quotient Semigroups and Extension Semigroups

    Indian Academy of Sciences (India)

    Rong Xing; Changguo Wei; Shudong Liu

    2012-08-01

    We discuss properties of quotient semigroup of abelian semigroup from the viewpoint of *-algebra and apply them to a survey of extension semigroups. Certain interrelations among some equivalence relations of extensions are also considered.

  15. The BGAN extension programme

    Science.gov (United States)

    Rivera, Juan J.; Trachtman, Eyal; Richharia, Madhavendra

    2005-11-01

    Mobile satellite telecommunications systems have undergone an enormous evolution in the last decades, with the interest in having advanced telecommunications services available on demand, anywhere and at any time, leading to incredible advances. The demand for braodband data is therefore rapidly gathering pace, but current solutions are finding it increasingly difficult to combine large bandwidth with ubiquitous coverage, reliability and portability. The BGAN (Broadband Global Area Network) system, designed to operate with the Inmarsat-4 satellites, provides breakthrough services that meet all of these requirements. It will enable broadband connection on the move, delivering all the key tools of the modern office. Recognising the great impact that Inmarsat's BGAN system will have on the European satellite communications industry, and the benefits that it will bring to a wide range of European industries, in 2003 ESA initiated the "BGAN Extension" project. Its primary goals are to provide the full range of BGAN services to truly mobile platforms, operating in aeronautical, vehicular and maritime environments, and to introduce a multicast service capability. The project is supported by the ARTES Programme which establishes a collaboration agreement between ESA, Inmarsat and a group of key industrial and academic institutions which includes EMS, Logica, Nera and the University of Surrey (UK).

  16. A Classification of BPEL Extensions

    Directory of Open Access Journals (Sweden)

    Oliver Kopp

    2011-10-01

    Full Text Available The Business Process Execution Language (BPEL has emerged as de-facto standard for business processes implementation. This language is designed to be extensible for including additional valuable features in a standardized manner. There are a number of BPEL extensions available. They are, however, neither classified nor evaluated with respect to their compliance to the BPEL standard. This article fills this gap by providing a framework for classifying BPEL extensions, a classification of existing extensions, and a guideline for designing BPEL extensions.

  17. Effectiveness of Agricultural Extension Activities

    Directory of Open Access Journals (Sweden)

    Ali AL-Sharafat

    2012-01-01

    Full Text Available Problem statement: Jordans agricultural extension service is seriously under-staffed and its effectiveness is consequently compromised. Reservations are being expressed about the performance and capability of the agricultural extension system in Jordan. The performance of this sector has been disappointing and has failed to transfer agricultural technology to the farmers. The main objective of this study is to assess the effectiveness of Jordans agricultural extension services. Approach: The effect of extension services on olive productivity in the study area was investigated. A total number of 60 olive producers were selected to be interviewed for this study. This number was enough to achieve the study objectives. The interviewed producers were distributed almost equally within olive production locations in the study area. The sample obtained through the simple random sampling technique. The two groups had been chosen and distributed randomly into an experimental group (30 farmers; 10 for each source of extension service and control group (30 farmers. The experimental group received extension services and the control group received no extension services. Two interview-cum-structured questionnaires were designed and used to collect information and data for this study. The first instrument was designed for farmers who received extension services and the second from farmers who received no extension services. Another questionnaire was designed for administrators of extension organizations concerned with providing extension services to farmers. To find the differences that may exist between two studied groups, One Way Analysis of Variance (ANOVA, t-test and LSD test via Statistical Package for Social Sciences software (SPSS were used. The average net profit obtained from an area of one dynamo of olive farm was the main item to be considered in determining the effectiveness of agricultural extension activities. Results and Conclusion: The results of

  18. Reductive dechlorination of TCE by chemical model systems in comparison to dehalogenating bacteria: insights from dual element isotope analysis (13C/12C, 37Cl/35Cl).

    Science.gov (United States)

    Cretnik, Stefan; Thoreson, Kristen A; Bernstein, Anat; Ebert, Karin; Buchner, Daniel; Laskov, Christine; Haderlein, Stefan; Shouakar-Stash, Orfan; Kliegman, Sarah; McNeill, Kristopher; Elsner, Martin

    2013-07-02

    Chloroethenes like trichloroethene (TCE) are prevalent environmental contaminants, which may be degraded through reductive dechlorination. Chemical models such as cobalamine (vitamin B12) and its simplified analogue cobaloxime have served to mimic microbial reductive dechlorination. To test whether in vitro and in vivo mechanisms agree, we combined carbon and chlorine isotope measurements of TCE. Degradation-associated enrichment factors ε(carbon) and ε(chlorine) (i.e., molecular-average isotope effects) were -12.2‰ ± 0.5‰ and -3.6‰ ± 0.1‰ with Geobacter lovleyi strain SZ; -9.1‰ ± 0.6‰ and -2.7‰ ± 0.6‰ with Desulfitobacterium hafniense Y51; -16.1‰ ± 0.9‰ and -4.0‰ ± 0.2‰ with the enzymatic cofactor cobalamin; -21.3‰ ± 0.5‰ and -3.5‰ ± 0.1‰ with cobaloxime. Dual element isotope slopes m = Δδ(13)C/ Δδ(37)Cl ≈ ε(carbon)/ε(chlorine) of TCE showed strong agreement between biotransformations (3.4 to 3.8) and cobalamin (3.9), but differed markedly for cobaloxime (6.1). These results (i) suggest a similar biodegradation mechanism despite different microbial strains, (ii) indicate that transformation with isolated cobalamin resembles in vivo transformation and (iii) suggest a different mechanism with cobaloxime. This model reactant should therefore be used with caution. Our results demonstrate the power of two-dimensional isotope analyses to characterize and distinguish between reaction mechanisms in whole cell experiments and in vitro model systems.

  19. Developing Extension Professionals to Develop Extension Programs: A Case Study for the Changing Face of Extension

    Directory of Open Access Journals (Sweden)

    Scott R. Cummings

    2015-06-01

    Full Text Available Development of Cooperative Extension programs depends upon the skills and abilities of competent Extension professionals. The most effective manner of building program development competencies in these Extension professionals is through professional development. A wide variety of competencies are necessary for Extension professionals to develop programs, including strong interpersonal skills. Differences exist between the professional development efforts of Extension institutions and are highlighted herein. Major challenges to delivery of professional development include time and budget, but these can be overcome through planning and innovation and use of online or hybrid methods. Professional development for program development is essential to furthering Extension’s mission, especially during times of rapid change.

  20. ALGEBRAIC EXTENSION OF *-A OPERATOR

    Institute of Scientific and Technical Information of China (English)

    左红亮; 左飞

    2014-01-01

    In this paper, we study various properties of algebraic extension of∗-A operator. Specifically, we show that every algebraic extension of∗-A operator has SVEP and is isoloid. And if T is an algebraic extension of∗-A operator, then Weyl’s theorem holds for f (T ), where f is an analytic functions on some neighborhood of σ(T ) and not constant on each of the components of its domain.

  1. Anaerobic transformation of chlorinated dioxins by microorganisms

    Energy Technology Data Exchange (ETDEWEB)

    Adrian, L. [Fachgebiet Technische Biochemie, Technische Univ. Berlin (Germany); Lechner, U. [Inst. fuer Mikrobiologie, Martin-Luther-Univ. Halle-Wittenberg (Germany)

    2004-09-15

    Mixed bacterial cultures catalyze diverse chlorodioxin-dehalogenation pathways. Some of these pathways lead to relatively harmless end products, which can undergo further biological degradation e.g. by aerobic bacteria. However, the possible formation of highly toxic products is a critical problem for a bioremediation approach but also for untreated sites where such dechlorination reactions can occur. Bioaugmentation with suitable pure or mixed cultures is promising. This has recently been demonstrated in a tetrachloroethene-contaminated groundwater using a Dehalococcoidescontaining inoculum that almost completely converted tetrachloroethene to ethene without accumulation of the toxic intermediate vinyl chloride. With Dehalococcoides sp. strain CBDB1 the first bacterium is now known, that grows by dehalorespiration with dioxins. Learning from the physiology and biochemistry of this bacterium will help us to understand the role of these bacteria in the environment and to predict the fate of dioxin pollution.

  2. Think - Baltic Extension / Kalle Kask

    Index Scriptorium Estoniae

    Kask, Kalle

    2002-01-01

    Tallinna TÜ Rehabilitatsiooni tehnoloogia keskus korraldas pressikonverentsi, kus tutvustati osalemist EL V raamprogrammis Think - Baltic Extension, mis on suunatud puuetega inimeste tööhõive tagamisele

  3. Think - Baltic Extension / Kalle Kask

    Index Scriptorium Estoniae

    Kask, Kalle

    2002-01-01

    Tallinna TÜ Rehabilitatsiooni tehnoloogia keskus korraldas pressikonverentsi, kus tutvustati osalemist EL V raamprogrammis Think - Baltic Extension, mis on suunatud puuetega inimeste tööhõive tagamisele

  4. Multilayer Multidimensional Extension Set Theory

    Institute of Scientific and Technical Information of China (English)

    CAO Shao-zhong; YANG Guo-wei; TU Xu-yan

    2006-01-01

    In order to study the contradiction problem of multilayer multidimensional complex systems, the concepts of extension field and stable field of intersection and union of multilayer multidimensional extension set are given. Then the related operations and properties are discussed. The results of study expand the concepts of intersection and union of extension set to a general situation, and provide the theoretical basis for production of the concepts of intersection and union of multilayer multidimensional matter element system extension set. In this way, it will be possible that matter element system theory is used to creative designs of complex systems.

  5. Reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) using palladium or palladium/iron nanoparticles and assessment of the reduction in toxic potency in vascular endothelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Venkatachalam, Karthik [Department of Chemistry, University of Kentucky, Lexington, KY 40506 (United States); Arzuaga, Xabier [Molecular and Cell Nutrition Laboratory, College of Agriculture, University of Kentucky, KY 40506 (United States); Chopra, Nitin; Gavalas, Vasilis G. [Department of Chemistry, University of Kentucky, Lexington, KY 40506 (United States); Xu, Jian; Bhattacharyya, Dibakar [Department of Chemical Engineering, University of Kentucky, Lexington, KY 40506 (United States); Hennig, Bernhard [Molecular and Cell Nutrition Laboratory, College of Agriculture, University of Kentucky, KY 40506 (United States); Bachas, Leonidas G. [Department of Chemistry, University of Kentucky, Lexington, KY 40506 (United States)], E-mail: bachas@uky.edu

    2008-11-30

    Palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films; or (2) immobilized Fe/Pd nanoparticles within polyvinylidene fluoride microfiltration membranes. For the first approach, the polypyrrole film was electrochemically formed in the presence of perchlorate ions that were incorporated into the film to counter-balance the positive charges of the polypyrrole chain. The film was then incubated in a solution containing tetrachloropalladate ions, which were exchanged with the perchlorate ions within the film. During this exchange, reduction of tetrachloropalladate by polypyrrole occurred, which led to the formation of palladium nanoparticles within the film. For the second approach, the membrane-supported Fe/Pd nanoparticles were prepared in three steps: polymerization of acrylic acid in polyvinylidene fluoride microfiltration membrane pores was followed by ion exchange of Fe{sup 2+}, and then chemical reduction of the ferrous ions bound to the carboxylate groups. The membrane-supported iron nanoparticles were then soaked in a solution of tetrachloropalladate resulting in the deposition of Pd on the Fe surface. The nanoparticles prepared by both approaches were employed in the dechlorination of PCB77. The presence of hydrogen was required when the monometallic Pd nanoparticles were employed. The results indicate the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and ultimately biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the dechlorination system used in this study markedly reduced the proinflammatory activity of PCB77, a persistent organic pollutant.

  6. Frames and extension problems I

    DEFF Research Database (Denmark)

    Christensen, Ole

    2014-01-01

    In this article we present a short survey of frame theory in Hilbert spaces. We discuss Gabor frames and wavelet frames and set the stage for a discussion of various extension principles; this will be presented in the article Frames and extension problems II (joint with H.O. Kim and R.Y. Kim)....

  7. Extension and the Practicing Veterinarian

    Science.gov (United States)

    Meyerholz, G. W.

    1974-01-01

    In order for Extension programs of veterinary medicine to succeed, good relationships are needed among university veterinarians, practicing local veterinarians, county Extension agents and the clientele. This author attempts to define some roles and relationships and offer some suggestions for the improvement of relationships to increase…

  8. An extension of heat hierarchy

    OpenAIRE

    Wang, Joe S.

    2014-01-01

    We propose a formally completely integrable extension of heat hierarchy based on the space of symmetries isomorphic to the Weyl algebra $\\mathcal{A}_1$. The extended heat hierarchy will be the basic model for the analysis of the extension of KP hierarchy, and other integrable equations.

  9. Extensive Reading Coursebooks in China

    Science.gov (United States)

    Renandya, Willy A.; Hu, Guangwei; Xiang, Yu

    2015-01-01

    This article reports on a principle-based evaluation of eight dedicated extensive reading coursebooks published in mainland China and used in many universities across the country. The aim is to determine the extent to which these coursebooks reflect a core set of nine second language acquisition and extensive reading principles. Our analysis shows…

  10. Learning Joomla! 3 extension development

    CERN Document Server

    Plummer, Tim

    2013-01-01

    A practical guide with step-by-step examples that build on each other so you can learn by doing and get hands-on knowledge about creating your plugins, modules, and components in Joomla.""Learning Joomla! 3 Extension Development, Third Edition"" is for developers who want to create their own Joomla extensions. It is assumed you will have some basic PHP, HTML, and CSS knowledge, but you don't need any prior Joomla programming experience. This book will also be useful to people who just want to make minor customizations to existing Joomla extensions and build on the work of others in the open so

  11. Programming Reactive Extensions and LINQ

    CERN Document Server

    Liberty, Jesse

    2011-01-01

    Pro Reactive Extensions and LINQ is a deep dive into the next important technology for .NET developers: Reactive Extensions. This in-depth tutorial goes beyond what is available anywhere else to teach how to write WPF, Silverlight, and Windows Phone applications using the Reactive Extensions (Rx) to handle events and asynchronous method calls. Reactive programming allows you to turn those aspects of your code that are currently imperative into something much more event-driven and flexible. For this reason, it's sometimes referred to as LINQ for Events. Reactive programming hinges on the concep

  12. Dechlorination of Zinc Sulfate Solution by Bismuth Oxide%氧化铋法从硫酸锌溶液中除氯的研究

    Institute of Scientific and Technical Information of China (English)

    封志敏; 宁顺明; 王文娟; 佘宗华; 万洪强; 吴江华

    2015-01-01

    Processing parameters for dechlorination of zinc sulfate solution by bismuth oxide were investigated, and the results show that dechlorination can be accomplished after 2 h reaction in a pulp with pH value of 2. 0 at 50 ℃ by bismuth oxide with weight 1. 5 times the theoretically calculated dosage. The chlorine concentration can be reduced to 0.28 g/L with the residue bismuth concentration at 0.96 mg/L. The conversion conditions of bismuth oxychloride were also studied and optimized as follows: initial alkali concentration at 1 mol/L, twofold calculated NaOH dosage, 4 h reaction at room temperature, with which, good conversion effect can be achieved as the conversion rate amounted to 93.97% with the residue bismuth concentration around 2.35 mg/L. A six⁃period commercial test was conducted, leading to results consistent with that from laboratory tests. This processing technique is easy to operate, with which chlorine concentration in zinc sulfate solution can be effectively reduced with less loss of bismuth.%以硫酸锌溶液为研究对象,研究了氧化铋脱除硫酸锌溶液中氯的工艺条件,结果表明,较佳的工艺条件为:pH值约2.0,50℃,氧化铋用量为理论计算值的1.5倍,反应时间2 h,此条件下除氯后溶液中Cl含量为0.28 g/L,Bi含量为0.96 mg/L。同时研究了氯氧铋转化的工艺参数条件,较佳的工艺条件为:NaOH用量为计算值2倍当量,初始碱浓度1 mol/L,反应时间4 h,常温,在此条件下可达到转化率93.97%、余铋浓度约2.35 mg/L的较好转化效果。进行了6周期工业实验,与模似实验结果重现性好。本工艺操作简单,能有效降低硫酸锌溶液中氯的浓度,且铋损失较小。

  13. Dechlorination of HCB by Bimetals Based on Zero Valent Iron%基于零价铁的双金属体系对六氯苯还原脱氯研究

    Institute of Scientific and Technical Information of China (English)

    曾宪委; 刘建国; 聂小琴

    2013-01-01

    利用Ag、Pb和Cu作为催化金属与微米级铁粉制成不同的双金属体系还原脱氯六氯苯(hexachlorobenzene,HCB),探讨不同催化金属种类、不同双金属添加量以及不同离子强度3种因素对HCB脱氯效率的影响,并剖析双金属催化条件下HCB的脱氯规律.结果表明,微米级铁粉对HCB几乎无还原脱氯效果,添加Ag、Pb和Cu对HCB均具有良好的催化脱氯能力,当Ag/Fe、Pb/Fe和Cu/Fe的最佳比例分别为0.2%、0.5%和1%时,反应2h后HCB的脱氯率分别达到93.5%、88.5%和49.6%;同时,由于催化金属均匀附着在零价铁表面可以形成更多的微型原电池,故增加双金属投加量可有效提高HCB脱氯速率,0.1 g Pb/Fe对HCB脱氯率为38.3%,而0.8 g Pb/Fe对HCB脱氯率可达到88.6%;另外,离子强度增大对HCB的脱氯也有一定促进作用,在Na2SO4浓度分别为0、0.05和0.5 mol· L-1的3个反应器中,反应2h后HCB脱氯率分别达到93.5%、98.O%和98.9%.%Based on the reducing capacity of zero valent iron, the study investigated the behavior of dechlorination of hexachlorobenzene by bimetals synthetized using Fe with Ag, Pb or Cu as catalysts,respectively. The results showed that bimetals could dechlorinate HCB faster than Fe(0) did, the optimal ratios of Ag/Fe, Pb/Fe and Cu/Fe were 0.2% , 0.5% and 1%. After reacting 2 hours, the dechlorination rates of HCB by Ag/Fe, Pb/Fe and Cu/Fe were 93.5%, 88.5% and 49.6% respectively. The catalyst metal distribution had a great effect on the reductive dechlorination capacity of the bimetal systems, due to more galvanic cells produced by well-distributed catalyst metal and iron. Increasing the amount of bimetal was an effective way to promote HCB dechlorination rate, 88.6% HCB was degraded in 2 h by 0.8 g Pb/Fe while only 38.3% HCB was degraded by 0. 1 g Pb/Fe. Besides, HCB dechlorination could be enhanced a little with increasing ionic strength, the HCB dechlorination rates were 93.5% , 98.0% and 98

  14. Physiological characterization of a microbial consortium that reductively dechlorinates 1,1-dichloroethane to chloroethane%1,1-二氯乙烷微生物降解菌群的生理学鉴定

    Institute of Scientific and Technical Information of China (English)

    杨锐; 孙宝林

    2009-01-01

    An anaerobic microbial consortium reductively dechlorinating 1,1-dichloroethane (DCA) to chloroethane (CA) was enriched from the sediment of Hudson River, New York. The consortium used hydrogen, formate, acetate, benzoate and fumarate as electron donors for reductive dechlorination. Pyruvate fermentation occurred in the enrichment culture, although this compound was not used as an electron donor for dechlorination. Among other halogenated compounds tested, only DCA was reductively dechlorinated. Sulfite could completely inhibit DCA dechlorination, whereas sulfate, nitrate or fumarate had no effect. Growth by reductive dechlorination with hydrogen as electron donor was revealed by a cell yield of (4.402±1.241)g of cells (dry weight) per mole of chloride released. Sequence analysis of 16S rRNA gene amplified from a highly enriched culture with H2 as electron donor suggests that Dehalobacter species dominated the enrichment culture under dechlorination conditions.%从纽约哈得逊河河底淤泥样品中富集分离得到的微生物菌群,在厌氧条件下,可将1,1-二氯乙烷通过还原脱氯的呼吸代谢方式降解生成一氯乙烷.这个微生物菌群可以利用氢气、甲酸、乙酸、苯甲酸和延胡索酸作为电子供体进行还原脱氯生长,并能以丙酮酸发酵的呼吸方式生长,但丙酮酸不能用来作为电子供体进行还原脱氯.通过对其他氯代化合物是否能作为电子受体的实验,发现只有1,1-二氯乙烷能被脱氯.在培养基中加入亚硫酸盐可完全抑制二氯乙烷的还原脱氯,但硫酸盐、硝酸盐和延胡索酸盐的加入却不影响还原脱氯.在以氢气作为电子供体进行还原脱氯时,每摩尔氯原子的还原相应地使细胞干重增加(4.402±1.241)g.同时对富集分离的菌群进行16S rRNA基因序列分析发现,在脱氯生长方式下,该微生物菌群中Dehalobacter细菌占主导地位.

  15. Extension agents and conflict narratives

    DEFF Research Database (Denmark)

    Bond, Jennifer Lauren

    2016-01-01

    conflict. Originality: This work contributes to a growing body of literature interested in the role of extension agents in conflict management. By applying Q methodology, this work has shown that while extension agents are involved in conflict management, their perceptions of these conflicts are subjective......Purpose: This work investigated the narratives of development extensionists in relation to natural resource conflict, in order to understand the competing discourses surrounding the wicked problems of natural resource management in Laikipia County, Kenya. Methodology: Q methodology was used...... to elicit the conflict narratives present among extension professionals. A concourse of 221 statements were devised from interviews and group discussions with key informants and a final sample of 49 statements was used for the sorting. Thirteen Q-sorts were undertaken with among rural extension...

  16. Decentralizing Agricultural Extension: Alternative Strategies.

    Science.gov (United States)

    Rivera, William M.

    1997-01-01

    Examines government strategies for decentralizing agricultural extension, concluding that such changes are largely determined by the country's constitutional status. Reviews decentralization guidelines for structural and fiscal reforms and participatory management systems. (SK)

  17. Frames and extension problems II

    DEFF Research Database (Denmark)

    Christensen, Ole; Kim, Hong Oh; Kim, Rae Young

    2014-01-01

    This article is a follow-up on the article Frames and Extension Problems I. Here we will go into more recent progress on the topic and also present some open problems.......This article is a follow-up on the article Frames and Extension Problems I. Here we will go into more recent progress on the topic and also present some open problems....

  18. COCLEFT EXTENSIONS OF HOPF ALGEBRAS

    Institute of Scientific and Technical Information of China (English)

    祝家贵

    2006-01-01

    Let B and H be finitely generated projective Hopf algebras over a commutative ring R,with B cocommutative and H commutative. In this paper we investigate cocleft extensions of Hopf algebras, and prove that the isomorphism classes of cocleft Hopf algebras extensions of B by H are determined uniquely by the group C(B, H) = ZC(B, H)/d(B, H) .

  19. Preferred extensions as stable models

    OpenAIRE

    2008-01-01

    Given an argumentation framework AF, we introduce a mapping function that constructs a disjunctive logic program P, such that the preferred extensions of AF correspond to the stable models of P, after intersecting each stable model with the relevant atoms. The given mapping function is of polynomial size w.r.t. AF. In particular, we identify that there is a direct relationship between the minimal models of a propositional formula and the preferred extensions of an argumentation framework by w...

  20. Boiler-turbine life extension

    Energy Technology Data Exchange (ETDEWEB)

    Natzkov, S. [TOTEMA, Ltd., Sofia (Bulgaria); Nikolov, M. [CERB, Sofia (Bulgaria)

    1995-12-01

    The design life of the main power equipment-boilers and turbines is about 105 working hours. The possibilities for life extension are after normatively regulated control tests. The diagnostics and methodology for Boilers and Turbines Elements Remaining Life Assessment using up to date computer programs, destructive and nondestructive control of metal of key elements of units equipment, metal creep and low cycle fatigue calculations. As well as data for most common damages and some technical decisions for elements life extension are presented.

  1. COMPATIBLE EXTENSIONS OF FUZZY RELATIONS

    Institute of Scientific and Technical Information of China (English)

    Irina GEORGESCU

    2003-01-01

    In 1930 Szpilrajn proved that any strict partial order can be embedded in a strict linear order.This theorem was later refined by Dushnik and Miller (1941), Hansson (1968), Suzumura (1976),Donaldson and Weymark (1998), Bossert (1999). Particularly Suzumura introduced the important concept of compatible extension of a (crisp) relation. These extension theorems have an important role in welfare economics. In particular Szpilrajn theorem is the main tool for proving a known theorem of Richter that establishes the equivalence between rational and congruous consumers. In 1999 Duggan proved a general extension theorem that contains all these results. In this paper we introduce the notion of compatible extension of a fuzzy relation and we prove an extension theorem for fuzzy relations. Our result generalizes to fuzzy set theory the main part of Duggan's theorem. As applications we obtain fuzzy versions of the theorems of Szpilrajn, Hansson and Suzumura. We also prove that an asymmetric and transitive fuzzy relation has a compatible extension that is total, asymmetric and transitive.Our results can be useful in the theory of fuzzy consumers. We can prove that any rational fuzzyconsumer is congruous, extending to a fuzzy context a part of Richter's theorem. To prove that acongruous fuzzy consumer is rational remains an open problem. A proof of this result can somehowuse a fuzzy version of Szpilrajn theorem.

  2. Extensive fitness and human cooperation.

    Science.gov (United States)

    van Hateren, J H

    2015-12-01

    Evolution depends on the fitness of organisms, the expected rate of reproducing. Directly getting offspring is the most basic form of fitness, but fitness can also be increased indirectly by helping genetically related individuals (such as kin) to increase their fitness. The combined effect is known as inclusive fitness. Here it is argued that a further elaboration of fitness has evolved, particularly in humans. It is called extensive fitness and it incorporates producing organisms that are merely similar in phenotype. The evolvability of this mechanism is illustrated by computations on a simple model combining heredity and behaviour. Phenotypes are driven into the direction of high fitness through a mechanism that involves an internal estimate of fitness, implicitly made within the organism itself. This mechanism has recently been conjectured to be responsible for producing agency and goals. In the model, inclusive and extensive fitness are both implemented by letting fitness increase nonlinearly with the size of subpopulations of similar heredity (for the indirect part of inclusive fitness) and of similar phenotype (for the phenotypic part of extensive fitness). Populations implementing extensive fitness outcompete populations implementing mere inclusive fitness. This occurs because groups with similar phenotype tend to be larger than groups with similar heredity, and fitness increases more when groups are larger. Extensive fitness has two components, a direct component where individuals compete in inducing others to become like them and an indirect component where individuals cooperate and help others who are already similar to them.

  3. Preferred extensions as stable models

    CERN Document Server

    Nieves, Juan Carlos; Cortés, Ulises

    2008-01-01

    Given an argumentation framework AF, we introduce a mapping function that constructs a disjunctive logic program P, such that the preferred extensions of AF correspond to the stable models of P, after intersecting each stable model with the relevant atoms. The given mapping function is of polynomial size w.r.t. AF. In particular, we identify that there is a direct relationship between the minimal models of a propositional formula and the preferred extensions of an argumentation framework by working on representing the defeated arguments. Then we show how to infer the preferred extensions of an argumentation framework by using UNSAT algorithms and disjunctive stable model solvers. The relevance of this result is that we define a direct relationship between one of the most satisfactory argumentation semantics and one of the most successful approach of non-monotonic reasoning i.e., logic programming with the stable model semantics.

  4. Fish Culture Economics and Extension

    Directory of Open Access Journals (Sweden)

    E.N. Ogamba

    2012-12-01

    Full Text Available Fish culture economics and extension was reviewed to enable fish culturist plan effectively before involved in fish culture and practices. The cost and benefits of fish culture need be known before participation in the business. There is need for cross-link between research and the fishing community. Prior to introduction of any new innovation in fisheries extension and evaluation of such programmers, the agency responsible for such exercise should have full knowledge of the existing farming practice/techniques and the reasons behind them. In assessing or evaluating the impact of any new techniques or programmers, consideration should be given to such factors as natural conditions, local infrastructures, socio cultural setting, farmers’ production aims and labor economics. The study reviews the types of feasibility study, a typical feasibility study and report on a fish farm project and detail analysis of culture extension to enable fish culturist plan effectively before involved in fish culture and practices.

  5. On extensions of Leibniz algebras

    Science.gov (United States)

    Rakhimov, I. S.; Said Husain, Sh. K.; Mohammed, M. A.

    2017-09-01

    This paper is dedicated to the study extensions of Leibniz algebras using the annihilator approach. The extensions methods have been used earlier to classify certain classes of algebras. In the paper we first review and adjust theoretical background of the method for Leibniz algebras then apply it to classify four-dimensional Leibniz algebras over a field K. We obtain complete classification of four-dimensional nilpotent Leibniz algebras. The main idea of the method is to transfer the “base change” action to an action of automorphism group of the algebras of smaller dimension on cocycles constructed by the annihilator extensions. The method can be used to classify low-dimensional Leibniz algebras over other finite fields as well.

  6. On Nilpotent Extensions of Algebras

    Institute of Scientific and Technical Information of China (English)

    Adam W. Marczak; Jerzy Plonka

    2007-01-01

    In this paper, we investigate essentially n-ary term operations of nilpotent extensions of algebras. We detect the connection between term operations of an original algebra and its nilpotent extensions. This structural point of view easily leads to the conclusion that the number of distinct essentially n-ary term operations of a proper algebraic nilpotent extension (ひ) of an algebra (ワ) is given by the formula pn(ひ)={pn(ワ)+1 for n=1,{pn(ワ) otherwise. We show that in general the converse theorem is not true. However, we suppose that if a variety V is uniquely determined by its pn-sequences, the converse theorem is also satisfied. In the second part of the paper, we characterize generics of nilpotent shifts of varieties and describe cardinalities of minimal generics. We give a number of examples and pose some problems.

  7. Stable extensions by line bundles

    CERN Document Server

    Teixidor-i-Bigas, M

    1997-01-01

    Let C be an algebraic curve of genus g. Consider extensions E of a vector bundle F'' of rank n'' by a vector bundle F' of rank n'. The following statement was conjectured by Lange: If 0extensions like this with E stable. We prove this result for the generic curve when F' is a line bundle. Our method uses a degeneration argument to a reducible curve.

  8. Extension Resources for International Trade

    Science.gov (United States)

    Seal, Susan D.

    2016-01-01

    With the opening of additional trade partnerships, the reduction of global transportation and communication costs, and the increase in demand for U.S. agricultural products and services, international trade is an area of great importance to more and more Extension clients and stakeholders. This article provides information about the primary…

  9. Unramified extensions of quadratic fields

    Institute of Scientific and Technical Information of China (English)

    Wei Li; Dong Yang; Xianke Zhang

    2008-01-01

    Let K be a global quadratic field, then every unramified abelian extension of K is proved to be absolutely Galois when K is a number field or under some natural conditions when K is a function field. The absolute Galois group is also determined explicitly.

  10. Equivalence Relations of -Algebra Extensions

    Indian Academy of Sciences (India)

    Changguo Wei

    2010-04-01

    In this paper, we consider equivalence relations of *-algebra extensions and describe the relationship between the isomorphism equivalence and the unitary equivalence. We also show that a certain group homomorphism is the obstruction for these equivalence relations to be the same.

  11. EXTENSIONS OF EULER HARMONIC SUMS

    Directory of Open Access Journals (Sweden)

    Djurdje Cvijović

    2012-10-01

    Full Text Available Three new closed-form summation formulae involving harmonic numbers are established using simple arguments and they are very general extensions of Euler’s famous harmonic sum identity. Some illustrative special cases as well as immediate consequences of the main results are also considered.

  12. Longest Common Extensions in Trees

    DEFF Research Database (Denmark)

    Bille, Philip; Gawrychowski, Pawel; Gørtz, Inge Li;

    2015-01-01

    The longest common extension (LCE) of two indices in a string is the length of the longest identical substrings starting at these two indices. The LCE problem asks to preprocess a string into a compact data structure that supports fast LCE queries. In this paper we generalize the LCE problem to t...

  13. Protective coatings on extensible biofibres

    Science.gov (United States)

    Holten-Andersen, Niels; Fantner, Georg E.; Hohlbauch, Sophia; Waite, J. Herbert; Zok, Frank W.

    2007-09-01

    Formulating effective coatings for use in nano- and biotechnology poses considerable technical challenges. If they are to provide abrasion resistance, coatings must be hard and adhere well to the underlying substrate. High hardness, however, comes at the expense of extensibility. This property trade-off makes the design of coatings for even moderately compliant substrates problematic, because substrate deformation easily exceeds the strain limit of the coating. Although the highest strain capacity of synthetic fibre coatings is less than 10%, deformable coatings are ubiquitous in biological systems. With an eye to heeding the lessons of nature, the cuticular coatings of byssal threads from two species of marine mussels, Mytilus galloprovincialis and Perna canaliculus, have been investigated. Consistent with their function to protect collagenous fibres in the byssal-thread core, these coatings show hardness and stiffness comparable to those of engineering plastics and yet are surprisingly extensible; the tensile failure strain of P. canaliculus cuticle is about 30% and that of M. galloprovincialis is a remarkable 70%. The difference in extensibility is attributable to the presence of deformable microphase-separated granules within the cuticle of M. galloprovincialis. The results have important implications in the design of bio-inspired extensible coatings.

  14. NACRE Update and Extension Project

    Science.gov (United States)

    Aikawa, Masayuki; Arai, Koji; Arnould, Marcel; Takahashi, Kohji; Utsunomiya, Hiroaki

    2006-04-01

    NACRE, the `nuclear astrophysics compilation of reaction rates', has been widely utilized in stellar evolution and nucleosynthesis studies since its publication in 1999. We describe here the current status of a Konan-Université Libre de Bruxelles (ULB) joint project that aims at its update and extension.

  15. Selections, Extensions and Collectionwise Normality

    CERN Document Server

    Gutev, Valentin

    2008-01-01

    We demonstrate that the classical Michael's selection theorem for l.s.c. mappings with a collectionwise normal domain can be reduced only to compact-valued mappings modulo the Dowker's extension theorem for such spaces. The technique developed to achieve this result is applied to construct selections for set-valued mappings whose point images are in completely metrizable absolute retracts.

  16. Homomorphisms between $C^*$-Algebra Extensions

    Indian Academy of Sciences (India)

    Changguo Wei

    2010-02-01

    In this paper we consider the question when a homomorphism between two extension algebras preserves the essential ideal in the corresponding extension. Some conditions of two essential extensions being isomorphic are given. We also describe the relationship between the induced extensions and the Kasparov products and give the completely positive liftings of the induced extensions.

  17. 2-氯酚在超临界水-NaOH体系中的脱氯特性%Dechlorination characteristics of o-chlorophenol in supercritical water-sodium hydroxide system

    Institute of Scientific and Technical Information of China (English)

    孙治荣; 马林; 韩延波

    2012-01-01

    The dechlorination characteristics of o-chlorophenol in supercritical water-sodium hydroxide system were studied.The conversion of o-chlorophenol,the yield of chloride ion and the dechlorination selectivity were investigated in the presence of sodium hydroxide.Results indicated that sodium hydroxide could significantly improve the conversion of o-chlorophenol,the yield of chloride ion and the dechlorination selectivity.The conversion of o-chlorophenol was improved with the increase of the additive amount of sodium hydroxide.o-chlorophenol conversed completely at residence time of 27 s under the conditions of 460 ℃,25 MPa,and the molar ratio of sodium hydroxide to o-chlorophenol of 1 to 1.%研究了2-氯酚在超临界水-NaOH体系中的脱氯特性,考察了NaOH添加对2-氯酚转化率、Cl-生成率、脱氯选择性等的影响。实验结果表明,NaOH的添加能够显著提高2-氯酚的转化率、Cl-的生成率和脱氯选择性。2-氯酚的转化率随着NaOH添加量的增大而增大,460℃、25 MPa条件下,NaOH添加量与2-氯酚的摩尔比为1∶1时,停留时间27 s时可实现2-氯酚的完全转化。

  18. Building an Extension Network in Vietnam.

    Science.gov (United States)

    Poussard, H.

    1999-01-01

    Agricultural extension in Vietnam is in transition as the economy moves to a market orientation. The national extension service created in 1993 is constrained by lack of funding, staff, and access to current extension knowledge. (SK)

  19. Use of Fixed-Film Bioreactors, in Situ Microcosms, and Molecular Biological Analyses to Evaluate Bioremediation of Chlorinated Benzenes By Indigenous Bacteria and a Bioaugmented Dechlorinating Consortium

    Science.gov (United States)

    Lorah, M. M.; Teunis, J. A.

    2014-12-01

    Evaluation of bioremediation is complicated by contaminant mixtures, high concentrations, variable site conditions, and multiple possible degradation pathways. In this study, fixed-film bioreactor experiments, in situ microcosms, and microbial analyses were utilized to evaluate both anaerobic and aerobic biodegradation processes for tri- and dichlorobenzene isomers, monochlorobenzene, and benzene in a wetland. Biofilm-based bioreactors provide a robust assessment tool because of their typically high degree of stability, even with major and repeated perturbations. Two bioreactor units seeded with an anaerobic dechlorinating consortium (WBC-2) and one unit seeded only with bacteria indigenous to the site were operated under flow-through conditions to compare biougmentation and natural attenuation. Electron donor levels were varied to fluctuate between anaerobic and aerobic conditions, and inflow concentrations of total chlorobenzenes were transitioned from 1-10 mg/L to 50-100 mg/L. Biodegradation resulted in removal efficiencies of 80 to 99 percent for the different compounds and inflow concentrations. Degradation efficiency in the native bioreactor was not impacted by cycling between anaerobic and aerobic conditions, although removal rates for monochlorobenzene and benzene increased under aerobic conditions. In situ microcosms were incubated below the wetland surface in sets of 3 treatments—unamended, biostimulated (lactate addition), and bioaugmented (WBC-2 and lactate). Additional treatment sets contained 13C-labeled contaminants to monitor for production of 13C-containing carbon dioxide and cellular material. Microcosm results verified that WBC-2 bioaugmentation can enhance biodegradation, with complete mineralization of chlorobenzene and benzene in bioaugmented and native treatments. Microbial analyses using QuantArrayTM for functional and taxonomic genes indicated potential for co-occurrence of anaerobic and aerobic biodegradation. Compared to the unamended

  20. NURBS curve blending using extension

    Institute of Scientific and Technical Information of China (English)

    Yong-jin LIU; Rong-qi QIU; Xiao-hui LIANG

    2009-01-01

    Curve and surface blending is an important operation in CAD systems, in which a non-uniform rational B-spline (NURBS) has been used as the de facto standard. In local comer blending, two curves intersecting at that comer are first made disjoint, and then the third blending curve is added-in to smoothly join the two curves with G1-or G2-continuity. In this paper we present a study to solve the joint problem based on curve extension. The following nice properties of this extension algorithm are exploited in depth: (1) The parameterization of the original shapes does not change; (2) No additional fragments are created.Various examples are presented to demonstrate that our solution is simple and efficient.

  1. Linear programming foundations and extensions

    CERN Document Server

    Vanderbei, Robert J

    2001-01-01

    Linear Programming: Foundations and Extensions is an introduction to the field of optimization. The book emphasizes constrained optimization, beginning with a substantial treatment of linear programming, and proceeding to convex analysis, network flows, integer programming, quadratic programming, and convex optimization. The book is carefully written. Specific examples and concrete algorithms precede more abstract topics. Topics are clearly developed with a large number of numerical examples worked out in detail. Moreover, Linear Programming: Foundations and Extensions underscores the purpose of optimization: to solve practical problems on a computer. Accordingly, the book is coordinated with free efficient C programs that implement the major algorithms studied: -The two-phase simplex method; -The primal-dual simplex method; -The path-following interior-point method; -The homogeneous self-dual methods. In addition, there are online JAVA applets that illustrate various pivot rules and variants of the simplex m...

  2. Mosaic: Policy Homomorphic Network Extension

    CERN Document Server

    Li, L Erran; Yang, Y R

    2010-01-01

    With the advent of large-scale cloud computing infrastructure, network extension and migration has emerged as a major challenge in the management of modern enterprise networks. Many enterprises are considering extending or relocating their network components, in whole or in part, to remote, private and public data centers, in order to attain scalability, failure resilience, and cost savings for their network applications. In this paper, we conduct a first rigorous study on the extension and migration of an enterprise network while preserving its performance and security requirements, such as layer 2/layer 3 reachability, and middle-box traversal through load balancer, intrusion detection and ACLs. We formulate this increasingly important problem, present preliminary designs, and conduct experiments to validate the feasibility of our designs.

  3. Process of Petri Nets Extension

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    To describe the dynamic semantics for the network computing, the concept on process is presented based on the semantic model with variable, resource and relation. Accordingly, the formal definition of process and the mapping rules from the specification of Petri nets extension to process are discussed in detail respectively. Based on the collective concepts of process, the specification of dynamic semantics also is constructed as a net system. Finally, to illustrate process intuitively, an example is specified completely.

  4. Mechanical heterogeneities and lithospheric extension

    Science.gov (United States)

    Duretz, Thibault; Petri, Benoit; Mohn, Geoffroy; Schenker, Filippo L.; Schmalholz, Stefan

    2016-04-01

    Detailed geological and geophysical studies of passive margins have highlighted the multi-stage and depth-dependent aspect of lithospheric thinning. Lithospheric thinning involves a variety of structures (normal faults, low angle detachments, extensional shear zones, extraction faults) and leads to a complex architecture of passive margins (with e.g. necking zone, mantle exhumation, continental allochthons). The processes controlling the generation and evolution of these structures as well as the impact of pre-rift inheritance are so far incompletely understood. In this study, we investigate the impact of pre-rift inheritance on the development of rifted margins using two-dimensional thermo-mechanical models of lithospheric thinning. To first order, we represent the pre-rift mechanical heterogeneities with lithological layering. The rheologies are kept simple (visco-plastic) and do not involve any strain softening mechanism. Our models show that mechanical layering causes multi-stage and depth-dependent extension. In the initial rifting phase, lithospheric extension is decoupled: as the crust undergoes thinning by brittle (frictional-plastic) faults, the lithospheric mantle accommodates extension by symmetric ductile necking. In a second rifting phase, deformation in the crust and lithospheric mantle is coupled and marks the beginning of an asymmetric extension stage. Low angle extensional shear zones develop across the lithosphere and exhume subcontinental mantle. Furthemore, crustal allochthons and adjacent basins develop coevally. We describe as well the thermal evolution predicted by the numerical models and discuss the first-order implications of our results in the context of the Alpine geological history.

  5. Extension of the Schrodinger equation

    Science.gov (United States)

    Somsikov, Vyacheslav

    2017-03-01

    Extension of the Schrodinger equation is submitted by removing its limitations appearing due to the limitations of the formalism of Hamilton, based on which this equation was obtained. For this purpose the problems of quantum mechanics arising from the limitations of classical mechanics are discussed. These limitations, in particular, preclude the use of the Schrodinger equation to describe the time symmetry violation. The extension of the Schrodinger equation is realized based on the principle of duality symmetry. According to this principle the dynamics of the systems is determined by the symmetry of the system and by the symmetry of the space. The extension of the Schrodinger equation was obtained from the dual expression of energy, represented in operator form. For this purpose the independent micro - and macro-variables that determine respectively the dynamics of quantum particle system relative to its center of mass and the movement of the center of mass in space are used. The solution of the extended Schrodinger equation for the system near equilibrium is submitted. The main advantage of the extended Schrodinger equation is that it is applicable to describe the interaction and evolution of quantum systems in inhomogeneous field of external forces.

  6. Organelle Extensions in Plant Cells

    Institute of Scientific and Technical Information of China (English)

    Jaideep Mathur; Alena Mammone; Kiah A.Barton

    2012-01-01

    Cell walls lock each cell in a specific position within the supraorganization of a plant.Despite its fixed location,each cell must be able to sense alterations in its immediate environment and respond rapidly to ensure the optimal functioning,continued growth and development,and eventual long-term survival of the plant.The ultra-structural detail that underlies our present understanding of the plant cell has largely been acquired from fixed and processed material that does not allow an appreciation of the dynamic nature of sub-cellular events in the cell.In recent years,fluorescent proteinaided imaging of living plant cells has added to our understanding of the dynamic nature of the plant cell.One of the major outcomes of live imaging of plant cells is the growing appreciation that organelle shapes are not fixed,and many organelles extend their surface transiently in rapid response to environmental stimuli.In many cases,the extensions appear as tubules extending from the main organelle.Specific terms such as stromules from plastids,matrixules from mitochondria,and peroxules from peroxisomes have been coined to describe the extensions.Here,we review our present understanding of organelle extensions and discuss how they may play potential roles in maintaining cellular homeostasis in plant cells.

  7. Coal Combustion Products Extension Program

    Energy Technology Data Exchange (ETDEWEB)

    Tarunjit S. Butalia; William E. Wolfe

    2003-12-31

    The primary objective of the CCP Extension Program is to promote the responsible uses of Ohio CCPs that are technically sound, environmentally safe, and commercially competitive. A secondary objective is to assist other CCP generating states (particularly neighboring states) in establishing CCP use programs within their states. The goal of the CCP extension program at OSU is to work with CCP stakeholders to increase the overall CCP state utilization rate to more than 30% by the year 2005. The program aims to increase FGD utilization for Ohio to more than 20% by the year 2005. The increased utilization rates are expected to be achieved through increased use of CCPs for highway, mine reclamation, agricultural, manufacturing, and other civil engineering uses. In order to accomplish these objectives and goals, the highly successful CCP pilot extension program previously in place at the university has been expanded and adopted by the university as a part of its outreach and engagement mission. The extension program is an innovative technology transfer program with multiple sponsors. The program is a collaborative effort between The Ohio State University (College of Engineering and University Extension Service), United States Department of Energy's National Energy Technology Laboratory, Ohio Department of Development's Coal Development Office, and trade associations such as the American Coal Ash Association as well as the Midwest Coal Ash Association. Industry co-sponsors include American Electric Power, Dravo Lime Company, and ISG Resources. Implementation of the proposed project results in both direct and indirect as well as societal benefits. These benefits include (1) increased utilization of CCPs instead of landfilling, (2) development of proper construction and installation procedures, (3) education of regulators, specification-writers, designers, construction contractors, and the public, (4) emphasis on recycling and decrease in the need for landfill

  8. The Geometric Invariants of Group Extensions Part I: Finite Extensions

    CERN Document Server

    Koban, Nic

    2011-01-01

    In this note, we compute the {\\Sigma}^1(G) invariant when 1 {\\to} H {\\to} G {\\to} K {\\to} 1 is a short exact sequence of finitely generated groups with K finite. As an application, we construct a group F semidirect Z_2 where F is the R. Thompson's group F and show that F semidirect Z_2 has the R-infinity property while F is not characteristic. Furthermore, we construct a finite extension G with finitely generated commutator subgroup G' but has a finite index normal subgroup H with infinitely generated H'.

  9. 48 CFR 570.405 - Lease extensions.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Lease extensions. 570.405... Requirements 570.405 Lease extensions. (a) This section applies to extension of the term of a lease to provide for continued occupancy on a short-term basis. (b) If the value of a lease extension will exceed...

  10. Coal Combustion Products Extension Program

    Energy Technology Data Exchange (ETDEWEB)

    Tarunjit S. Butalia; William E. Wolfe

    2006-01-11

    This final project report presents the activities and accomplishments of the ''Coal Combustion Products Extension Program'' conducted at The Ohio State University from August 1, 2000 to June 30, 2005 to advance the beneficial uses of coal combustion products (CCPs) in highway and construction, mine reclamation, agricultural, and manufacturing sectors. The objective of this technology transfer/research program at The Ohio State University was to promote the increased use of Ohio CCPs (fly ash, FGD material, bottom ash, and boiler slag) in applications that are technically sound, environmentally benign, and commercially competitive. The project objective was accomplished by housing the CCP Extension Program within The Ohio State University College of Engineering with support from the university Extension Service and The Ohio State University Research Foundation. Dr. Tarunjit S. Butalia, an internationally reputed CCP expert and registered professional engineer, was the program coordinator. The program coordinator acted as liaison among CCP stakeholders in the state, produced information sheets, provided expertise in the field to those who desired it, sponsored and co-sponsored seminars, meetings, and speaking at these events, and generally worked to promote knowledge about the productive and proper application of CCPs as useful raw materials. The major accomplishments of the program were: (1) Increase in FGD material utilization rate from 8% in 1997 to more than 20% in 2005, and an increase in overall CCP utilization rate of 21% in 1997 to just under 30% in 2005 for the State of Ohio. (2) Recognition as a ''voice of trust'' among Ohio and national CCP stakeholders (particularly regulatory agencies). (3) Establishment of a national and international reputation, especially for the use of FGD materials and fly ash in construction applications. It is recommended that to increase Ohio's CCP utilization rate from 30% in 2005 to

  11. Rhinomaxillary mucormycosis with cerebral extension

    Directory of Open Access Journals (Sweden)

    Goel Shikha

    2009-01-01

    Full Text Available Mucormycosis is a rare opportunistic infection caused by fungus belonging to the order Mucorales. A case of a controlled diabetic male with rhino maxillary mucormycosis, with cerebral extension, is described. The patient presented with hemifacial swelling, a nasal twang in his voice, fever, ocular signs, gross tissue destruction, and was sluggish. Early recognition of mucormycosis is necessary to limit the spread of infection, which can lead to high morbidity and mortality. Therefore, health practitioners should be familiar with the signs and symptoms of the disease.

  12. The Catalytic Reductive Dechlorination of Ni/Fe Nano-alloy to Trichloro Ethylene(TCE)in Water%纳米Ni/Fe合金对水中三氯乙烯(TCE)的催化还原脱氯

    Institute of Scientific and Technical Information of China (English)

    张卫华; 张春华; 陈保国

    2016-01-01

    利用纳米Ni/Fe合金粉末对水中TCE进行催化还原脱氯研究,结果表明,纳米Ni/Fe合金对水中TCE具有较好的脱氯作用.在Ni含量5wt%、初始pH值为6.5、Ni/Fe粉末投加量为0.4g/L的条件下,TCE的脱氯率在60min内达72%;合金中较高Ni含量、较低初始pH、较大的粉末投加量均有利于脱氯反应;脱氯产物为丁烷、丁烯和乙烷等,可推测该反应是发生在双金属合金表面的加氢脱氯.%Dechlorination rate of TCE is up to 72%within 60 minutes under conditions of 5 wt%Ni,initial pH value 6.5 and 0.4g/L Ni/Fe powder. With the higher Ni content,the lower initial pH value and the more Ni/Fe powder,the Ni/Fe nano-alloy powder can better dechlorinate TCE in the water and produce butane,butene and ethane. This hy-drodechlorination occurrs on the surface of Ni/Fe alloy.

  13. Maximal right smooth extension chains

    CERN Document Server

    Huang, Yun Bao

    2010-01-01

    If $w=u\\alpha$ for $\\alpha\\in \\Sigma=\\{1,2\\}$ and $u\\in \\Sigma^*$, then $w$ is said to be a \\textit{simple right extension}of $u$ and denoted by $u\\prec w$. Let $k$ be a positive integer and $P^k(\\epsilon)$ denote the set of all $C^\\infty$-words of height $k$. Set $u_{1},\\,u_{2},..., u_{m}\\in P^{k}(\\epsilon)$, if $u_{1}\\prec u_{2}\\prec ...\\prec u_{m}$ and there is no element $v$ of $P^{k}(\\epsilon)$ such that $v\\prec u_{1}\\text{or} u_{m}\\prec v$, then $u_{1}\\prec u_{2}\\prec...\\prec u_{m}$ is said to be a \\textit{maximal right smooth extension (MRSE) chains}of height $k$. In this paper, we show that \\textit{MRSE} chains of height $k$ constitutes a partition of smooth words of height $k$ and give the formula of the number of \\textit{MRSE} chains of height $k$ for each positive integer $k$. Moreover, since there exist the minimal height $h_1$ and maximal height $h_2$ of smooth words of length $n$ for each positive integer $n$, we find that \\textit{MRSE} chains of heights $h_1-1$ and $h_2+1$ are good candidates t...

  14. Reductive Dechlorination of 1,2,4-Trichlorobenzene and Its Metabolites at a Contaminated Site in Nanjing, China: Concordance between Field and Microcosm Data

    Science.gov (United States)

    Qiao, W.; Lomheim, L.; Luo, F.; Ye, S.; Wu, J.; Edwards, E.

    2016-12-01

    Chlorinated benzenes (CBs) are widespread contaminants at many industrial sites, posing a threat to human health and the environment. Bioremediation has the advantage of using natural biological processes to possibly completely destroy target pollutants. A three-year site investigation was conducted from 2012 to 2014 at a former chemical plant in Nanjing, China, which was contaminated by chlorobenzenes (CBs) and benzene. The aquifer was located within a silty clay and clayey silt with extremely low permeability. Soil and groundwater sample analyses revealed that the main contaminants were 1,2,4-tichlorobenzene (TCB) with highest concentration of 7300ug/L, dichlorobenzene (DCB) isomers, monochlorobenzene (MCB) and benzene. The contaminants were mainly located in the vicinity of a former wastewater basin and production facilities of chemical products. TCB was used as a solvent and leaked during the plant manufacturing processes. It is assumed that DCB isomers, MCB and benzene were derived from the anaerobic subsequent dehalogenation of 1,2,4-TCB. A corresponding lab microcosm study was conducted to prove the assumption of indigenous CBs biodegradation. The contaminated soil and groundwater from the site were used to conduct the lab microcosms study to keep the lab experimental conditions the same as the site and to be comparable with the site investigation results. The lab microcosms study results demonstrated that 1,4-DCB, 1,2-DCB and 1,3-DCB were the anaerobic dechlorination product of 1,2,4-TCB, and 1,2-DCB, 1,3-DCB can be transformed to MCB, and benzene can be degraded to CO2 under sulfate reducing condition. The lab microcosms study results were consistent with the site investigation results, which will provide a theoretical proposition on site remediation strategy making. This research method of combing the site investigation with the lab study can be applied and transferable to any other contaminated sites of concern. The site investigation and lab study can

  15. Extensible Numerical Library in JAVA

    Institute of Scientific and Technical Information of China (English)

    T.Aso; H.Okazawa; 等

    2001-01-01

    In this paper,we present the current status of the project for developing the numerical librayr in JAVA.We have presented how object-oriented techniques improve usage and also development of numerical libraries compared with the conventional way at previous conference,we need many functions for data analysis which is not provided within JAVA language,for example,good random number generators.special functions and so on.Our development strategy is focused on easiness of implementation and adding new features by users themselves not only by developers.In HPC filed,there are other focus efforts to develop numerical libraries in JAVA,However,their focus is on the performance of execution.not easiness of extension.Following the strategy,we have degigned and implemented more classes for random number generators and so on .

  16. Extensive Renovation of Heritage Buildings

    DEFF Research Database (Denmark)

    Rasmussen, Torben Valdbjørn; Møller, Eva B.; Buch-Hansen, Thomas Cornelius

    2015-01-01

    In the debate on whether or not heritage buildings should be included in work to mitigate climate change impacts, it is important to assess the impact of these buildings. Therefore the results of an extensive energy upgrading of a listed complex was studied. Climate change and measures to mitigate...... its effects have been a global priority for more than a decade. Efforts to mitigate climate change have focused on reducing greenhouse gas emissions, especially CO2. As a consequence, there is an increased interest in reducing the energy consumption and increase the indoor climate standard of many...... feasible energy-upgrading measures for implementation including measures to provide an acceptable indoor climate. The energy savings as well as the reduction of CO2 emissions are calculated. Furthermore, it is discussed how measures can affect the durability of a heritage building, as measures may create...

  17. Longest Common Extensions via Fingerprinting

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Kristensen, Jesper

    2012-01-01

    . The LCE problem can be solved in linear space with constant query time and a preprocessing of sorting complexity. There are two known approaches achieving these bounds, which use nearest common ancestors and range minimum queries, respectively. However, in practice a much simpler approach with linear......(n,σ)) preprocessing time, where sort(n,σ) is the time it takes to sort n numbers from σ. Though this solution is asymptotically strictly worse than the asymptotically best previously known algorithms, it outperforms them in practice in average case and is almost as fast as the simple linear time algorithm. On worst......The longest common extension (LCE) problem is to preprocess a string in order to allow for a large number of LCE queries, such that the queries are efficient. The LCE value, LCE s (i,j), is the length of the longest common prefix of the pair of suffixes starting at index i and j in the string s...

  18. Industrial extension, the Oklahoma way

    Science.gov (United States)

    Farrell, Edmund J.

    1994-03-01

    Oklahoma has established a customer-driven industrial extension system. A publicly-chartered, private non-profit corporation, the Oklahoma Alliance for Manufacturing Excellence, Inc. (`the Alliance') coordinates the system. The system incorporates principles that Oklahoma manufacturers value: (1) decentralization and local accessibility; (2) coordinated existing resources; (3) comprehensive help; (4) interfirm cooperation; (5) pro-active outreach; (6) self- help and commitment from firms; (7) customer governance; and (8) performance accountability. The Oklahoma system consists of: (1) a network of locally-based broker/agents who work directly with manufacturers to diagnose problems and find appropriate assistance; (2) a group of industry sector specialists who collect and disseminate sector specific technological and market intelligence to the broker/agents and their clients; (3) all the specialized public and private sector resources coordinated by the system; and (4) a customer- driven coordination and evaluation mechanism, the Alliance.

  19. Analysis of Extension Categorical Data Mining Process for the Extension Interior Designing

    Institute of Scientific and Technical Information of China (English)

    Hui Ma; Guangtian Zou

    2016-01-01

    On the basis of extension architectonics, this paper researches the process of extension categorical data mining for extension interior design. In accordance with the theory of extension data mining, the extension categorical data mining for the extension interior design can be divided into data preparation, the operation of mining and knowledge application. The paper expatiates the main content and cohesive relations of each link, and emphatically discusses extension acquisition, analysis extension, categorical mining extension, knowledge application extension and other several core nodes that are related with data. Through the knowledge fusion of extension architectonics and data mining, the paper discusses the process of knowledge requirements with multiple classification under different mining targets. The purpose of this paper is to explore a whole categorical data mining process of interior design from extension design data to the design of knowledge discovery and extension application.

  20. Competency Modeling in Extension Education: Integrating an Academic Extension Education Model with an Extension Human Resource Management Model

    Science.gov (United States)

    Scheer, Scott D.; Cochran, Graham R.; Harder, Amy; Place, Nick T.

    2011-01-01

    The purpose of this study was to compare and contrast an academic extension education model with an Extension human resource management model. The academic model of 19 competencies was similar across the 22 competencies of the Extension human resource management model. There were seven unique competencies for the human resource management model.…

  1. On transfinite extension of asymptotic dimension

    OpenAIRE

    Radul, Taras

    2006-01-01

    We prove that a transfinite extension of asymptotic dimension asind is trivial. We introduce a transfinite extension of asymptotic dimension asdim and give an example of metric proper space which has transfinite infinite dimension.

  2. Extensions of cutting problems: setups

    Directory of Open Access Journals (Sweden)

    Sebastian Henn

    2013-08-01

    Full Text Available Even though the body of literature in the area of cutting and packing is growing rapidly, research seems to focus on standard problems in the first place, while practical aspects are less frequently dealt with. This is particularly true for setup processes which arise in industrial cutting processes whenever a new cutting pattern is started (i.e. a pattern is different from its predecessor and the cutting equipment has to be prepared in order to meet the technological requirements of the new pattern. Setups involve the consumption of resources and the loss of production time capacity. Therefore, consequences of this kind must explicitly be taken into account for the planning and control of industrial cutting processes. This results in extensions to traditional models which will be reviewed here. We show how setups can be represented in such models, and we report on the algorithms which have been suggested for the determination of solutions of the respective models. We discuss the value of these approaches and finally point out potential directions of future research.

  3. Presentation Extensions of the SOAP

    Science.gov (United States)

    Carnright, Robert; Stodden, David; Coggi, John

    2009-01-01

    A set of extensions of the Satellite Orbit Analysis Program (SOAP) enables simultaneous and/or sequential presentation of information from multiple sources. SOAP is used in the aerospace community as a means of collaborative visualization and analysis of data on planned spacecraft missions. The following definitions of terms also describe the display modalities of SOAP as now extended: In SOAP terminology, View signifies an animated three-dimensional (3D) scene, two-dimensional still image, plot of numerical data, or any other visible display derived from a computational simulation or other data source; a) "Viewport" signifies a rectangular portion of a computer-display window containing a view; b) "Palette" signifies a collection of one or more viewports configured for simultaneous (split-screen) display in the same window; c) "Slide" signifies a palette with a beginning and ending time and an animation time step; and d) "Presentation" signifies a prescribed sequence of slides. For example, multiple 3D views from different locations can be crafted for simultaneous display and combined with numerical plots and other representations of data for both qualitative and quantitative analysis. The resulting sets of views can be temporally sequenced to convey visual impressions of a sequence of events for a planned mission.

  4. Effective Ways of Extensive Reading Teaching

    Institute of Scientific and Technical Information of China (English)

    杨柳

    2012-01-01

    COmpared with intensive reading; extenSiVe reading Can arouse Students' interest in reading, and enrich their back- ground knowledge about western COuntries. Therefore, we Should improve both and pay Special attention tO the extensive reading So that students' reading ability can be enhanced: The following points Should be noticed when teaching extensive reading.

  5. Inductions and coinductions for Hopf extensions

    Institute of Scientific and Technical Information of China (English)

    Freddy Van Oystaeyen; 许永华; 张印火

    1996-01-01

    The induction and coinduction functors for the two types of Hopf extensions (Hopf Galois extensions and dual to Hopf Galois extension) and the symmetry between them are studied; by using the theory of separable functors further links between these two classes are provided.

  6. 78 FR 57790 - Extension of Time Limits

    Science.gov (United States)

    2013-09-20

    ... International Trade Administration 19 CFR Part 351 RIN 0625-AA94 Extension of Time Limits AGENCY: Import... Department of Commerce (the Department) is modifying its regulation concerning the extension of time limits... clarifies that parties may request an extension of time limits before any time limit established under...

  7. 7 CFR 15b.27 - Extension education.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Extension education. 15b.27 Section 15b.27 Agriculture... Education § 15b.27 Extension education. (a) General. A recipient to which this subpart applies that provides extension education may not, on the basis of handicap, exclude qualified handicapped persons. A recipient...

  8. 铁氧化物与电子供体基质交互作用对红壤性水稻土中DDT 还原脱氯影响%Influence of the Interaction Between Iron Oxide and Electron Donor Substances on 1, 1, 1-Trichloro- 2, 2-bis(p-chlorophenyl)ethane(DDT)Reductive Dechlorination in Hydragric Acrisols

    Institute of Scientific and Technical Information of China (English)

    刘翠英; 徐向华; 王壮; 姚童言

    2014-01-01

    铁氧化物与电子供体基质交互作用对电子转移及具有脱氯功能的铁还原菌生长有重要影响,进而可能影响土壤中多氯代有机物的还原脱氯降解.本研究采用土壤厌氧培养实验,分析铁氧化物(针铁矿)和电子供体基质(正丁酸和乙醇)及其交互作用对红壤性水稻土中 DDT 脱氯的影响及其机制.结果表明,由于 DDT 脱氯降解,DDT 及其降解产物与土壤形成结合态残留,厌氧培养6周后,土壤中 DDT 可提取态残留量仅为初始量的1.29%~2.01%. DDT 厌氧脱氯降解的主要产物为 DDD.在培养前期,加入正丁酸和乙醇使反应体系的 pH 降低 Eh 增加,进而不利于 DDT 还原脱氯降解.添加针铁矿或者同时添加针铁矿和电子供体基质均使反应体系的 pH 增加 Eh 降低,并且增加土壤中二价铁的量,从而促进 DDT 还原脱氯降解.正丁酸和铁氧化物对 DDT 还原脱氯无显著交互作用,而乙醇和铁氧化物对 DDT 还原脱氯具有拮抗作用.本研究结果对于制定 DDT 污染土壤的高效原位修复技术方案具有重要意义.%The interaction between iron oxide and electron donor substance have significant influences on electron transfer and the growth of iron-reducing bacteria, which may affect the reductive dechlorination of polychlorinated organic compounds in soil. Anaerobic soil incubation experiment was conducted to study the effect and its mechanism of iron oxide (goethite), electron donor substances (butyrate and ethanol), and their interaction on DDT reductive dechlorination in Hydragric Acrisols. Results showed that after 6 weeks of anaerobic incubation, the extractable residues of DDT were between 1. 29% and 2. 01% of initial DDT amounts in soils, which was attributed to the dechlorinated degradation of DDT and formation of bound residues of DDT and its dechlorinated products. The main product of DDT anaerobic dechlorination was 1,1-dichloro- 2,2-bis ( p-chloro-phenyl) ethane ( DDD

  9. Reorganization of Agricultural Extension toward Green Agriculture

    Directory of Open Access Journals (Sweden)

    Mohammad S. Allahyari

    2009-01-01

    Full Text Available Problem statement: Considering unsustainable agricultural conditions of Iran and organizational recession and inability of current extension organization to achieve sustainability, it seems that extension systems require a new organizational structure to achieve sustainability objectives. The purpose of the present study was to identify the most appropriate characteristics for extension organization toward green agriculture in Iran context. Approach: To fulfill this objective, a sample of 120 respondents was selected through simple random sampling technique. A survey study was applied as a methodology of research. A mailed questionnaire was used to collect the data. The response rate of questionnaire was 65.83% (N = 79. Appropriate descriptive statistics such as mean scores, standard deviations and variation ratio were used. Results: Extension experts believed that among important organizational characteristics of extension system for supporting green agriculture collaboration among research, extension, education organizations, farmers' associations, NGOs, rural credit agencies, transportation companies, considering local groups and learning organization had very high importance for supporting green agriculture. According to factor analysis, the implications for extension organization were categorized into two groups consisting: (1 Holistic organizations (2 Participatory organizations that those factors explained 67.54% of the total variance of the research variables. Conclusion: Identifying suitable extension mechanisms had important role for developing extension system. Therefore, identifying extension organizational characteristics for supporting green agriculture of Iran is one of the major approaches needs to be carefully thought and accurately implemented for the extension system development.

  10. 乙腈溶剂中三氯化苄在银阴极上的脱氯反应%Dechlorination of Benzenyltrichloride in CH3CN Solvent at a Silver Cathode

    Institute of Scientific and Technical Information of China (English)

    徐颖华; 马红星; 蔡倩倩; 朱英红; 马淳安

    2013-01-01

      用常规循环伏安(CV)法和恒电位电解法研究了含0.1 mol·L-1四丁基高氯酸铵(TBAP)乙腈溶剂中三氯化苄在银电极上的还原脱氯机理;用以银和氯离子的氧化还原反应为基础的阳极区拓宽CV法探测了还原脱氯反应生成氯离子在银电极上的吸附情况.循环伏安实验表明:(1)银电极对三氯化苄的电还原脱氯反应具有比汞电极更优良的电催化活性;(2)三氯化苄在低扫描速率(v)下得到的第一个还原峰对应反应受吸附控制,电子转移系数约为0.25,遵守协同电子转移机理;(3)三氯化苄还原脱氯反应生成氯离子在银电极上的吸附电位为-0.75--1.75 V (vs Ag/Ag+).电解实验表明,通过改变银电极电位可以有效控制三氯化苄还原反应的电解产物.%The reductive dechlorination mechanism of benzenyltrichloride at an Ag cathode was investigated using cyclic voltammetry (CV) and potentiostatic electrolysis, in CH3CN solvent containing 0.1 mol·L-1 tetrabutylammonium perchlorate (TBAP). The adsorption of Cl- generated during dechlorination was detected using wide anode region CV, based on its anodic reaction with Ag. The CV results indicated that:(1) Ag exhibited better electrocatalytic activity than Hg for the dechlorination; (2) the first reduction peak, which was divided from the reduction peak of benzenyltrichloride at-1.19 V (vs Ag/Ag+) when the scan rate was≤50 mV·s-1, is an adsorption control ed process and its electron transfer occurred in a concerted way, and the electron transfer coefficient is approximately 0.25; (3) the potential region where departing Cl-adsorbed on Ag ranged from-0.75 to-1.75 V (vs Ag/Ag +). The electrolysis results indicated that dechlorination product selectivity was strongly dependent on the Ag electrode potential.

  11. Development of an integrated in-situ remediation technology. Topical report for Task {number_sign}3.2 entitled, ``Modeling and iron dechlorination studies`` (September 26, 1994--August 31, 1997)

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, A.P.; Sivavec, T.M.; Principe, J.M. [General Electric Research and Development, Schenectady, NY (United States)

    1997-11-01

    Contamination in low-permeability soils poses a significant technical challenge to in-situ remediation efforts. Poor accessibility to the contaminants and difficulty in delivery of treatment reagents have rendered existing in-situ treatments such as bioremediation, vapor extraction, and pump and treat rather ineffective when applied to low-permeability soils present at many contaminated sites. The technology is an integrated in-situ treatment in which established geotechnical methods are used to install degradation zones directly in the contaminated soil, and electro-osmosis is utilized to move the contaminants back and forth through those zones until the treatment is complete. The present Topical Report for Task {number_sign}3.2 summarizes the modeling and dechlorination research conducted by General Electric Research and Development.

  12. Optimizing control to reduce sodium sulfite consumption in dechlorination of electrolytic system%通过优化控制降低电解脱氯系统亚硫酸钠消耗

    Institute of Scientific and Technical Information of China (English)

    刘江泽; 李永全; 董建刚; 祝辉年; 俞刚山

    2015-01-01

    A facility newly started up for production of ion-exchange membrane caustic soda was intro-duced as well its running situations. Excess sodium chloride was consumed in dechlorination at the early stage of start-up. Improvement measures to reduce sodium sulfite consumption were proposed.%介绍了新开车的离子膜法烧碱生产装置及其运行情况,针对装置开车初期脱氯系统亚硫酸钠消耗偏高的情况,提出了降低脱氯系统亚硫酸钠消耗的改进措施.

  13. Electrochemically reductive dechlorination of six dichlorophenol isomers:comparison of apparent kinetics%6种二氯酚电催化还原脱氯:表观动力学过程比较

    Institute of Scientific and Technical Information of China (English)

    赵思思; 魏学锋; 孙治荣

    2015-01-01

    采用自制的钯/聚吡咯(十二烷基苯磺酸钠)/钛(Pd/PPy(SDBS)/Ti)电极对二氯酚(DCP)的6种同分异构体进行了电化学还原脱氯研究。探讨了脱氯电流、溶液初始pH和污染物初始浓度对2,5-DCP脱氯过程的影响。在脱氯电流5 mA、溶液初始pH 2.5、温度25℃、污染物初始浓度100 mg·L−1的条件下对2,3-DCP、2,4-DCP、2,5-DCP、2,6-DCP、3,4-DCP和3,5-DCP的脱氯过程进行了比较。6种DCP的脱氯产物均以苯酚为主,有少量的单氯酚产生,脱氯反应速率常数依次为4.735×10−2、4.609×10−2、4.845×10−2、4.317×10−2、3.973×10−2、3.770×10−2 min−1。推测 DCP 的降解速率受 pKa、质子化效应和溶液 pH 等因素的影响,降解难度由小到大依次为2,4-DCP<2,3-DCP<2,5-DCP<2,6-DCP<3,4-DCP<3,5-DCP。%Chlorophenols are persistent organic pollutants with high toxicity. Dichlorophenols (DCPs) include six isomers due to differentsubstituted position of chlorine atoms. Self-made Pd/polypyrrole(sodium dodecylbenzene sulfonate)/Ti electrode(Pd/PPy(SDBS)/Ti electrode) was employed to dechlorinate six DCP isomers. The effects of electrolysis current, initial pH and the initial concentration of target pollutant on the dechlorination process of 2,5-DCP were investigated. Under the selected conditions,i.e., applied current of 5 mA, initial pH of 2.5 and temperature of 25℃, dechlorination experiments of 2,3-DCP, 2,5-DCP, 2,4-DCP, 2,6-DCP, 3,4-DCP and 3,5-DCP with the same DCP concentration of 100 mg·L−1 were conducted, respectively. Phenol was the main product and a small amount of monochlorophenol could be detected during the dechlorination of six DCPs. The reaction rate constants of six DCPs were 4.735×10−2min−1, 4.609×10−2min−1, 4.845×10−2min−1, 4.317×10−2min−1, 3.973× 10−2min−1and 3.770×10−2min−1, respectively. It showed that the degradationrates of DCPs were affected by pKa, protonation and pH. The degradation difficulty

  14. 探究海绵铁/银脱氯还原降解二噁英的方法%Explore the Sponge Iron/Silver De-chlorination Method of Reduction Degradation of Dioxins

    Institute of Scientific and Technical Information of China (English)

    杨蒙蒙; 穆乃花

    2014-01-01

    This paper,taking OCDF and 1 2378-PeCDF as example,explores the sponge iron reduction degrada-tion dioxin de-chlorination method as well as a comparison of ultrasound,sponge iron+ultrasound,sponge iron/Ag+ultrasonic three treatments dioxin experimental methods.And Optimization sponge/Ag+ultrasonic treatment conditions,concentration of dioxins treatment,sponge iron dosage and time ultrasound conditions were optimized to explore the sponge method of dioxin treatment.Experimental results show that the sponge iron/Ag+ultrasound sys-tem conditions can not restore degraded de-chlorination of dioxins,which needs further inquiry.%以OCDF和12378-PeCDF为例,探究了海绵铁脱氯还原降解二英的方法。对比了超声、海绵铁+超声、海绵铁/银+超声三种处理二英的实验方法,并对海绵铁/银+超声处理方法中二英浓度、海绵铁投加量以及超声时间等条件进行了优化,探索海绵铁处理二英的方法。实验结果表明,在海绵铁/银+超声的体系条件下还不能脱氯还原降解二英,还需要做进一步深入的探究。

  15. Longitudinally extensive optic neuritis in pediatric patients.

    Science.gov (United States)

    Graves, Jennifer; Kraus, Verena; Soares, Bruno P; Hess, Christopher P; Waubant, Emmanuelle

    2015-01-01

    Extensive optic nerve demyelinating lesions on magnetic resonance imaging (MRI) in adults could indicate a diagnosis other than multiple sclerosis with worse prognosis such as neuromyelitis optica. We report the frequency of longitudinally extensive lesions in children with first events of optic neuritis. Subjects had brain or orbit MRI within 3 months of onset and were evaluated at the University of California, San Francisco, Pediatric Multiple Sclerosis Center. Lesion length, determined by T2 hyperintensity or contrast enhancement, was blindly graded as absent, focal or longitudinally extensive (at least 2 contiguous segments of optic nerve). Of 25 subjects, 9 (36%) had longitudinally extensive optic neuritis. Extensive lesions were not associated with non-multiple sclerosis versus multiple sclerosis diagnosis (P = 1.00). No association between age and lesion extent was observed (P = .26). Prospective studies are needed to determine if longitudinally extensive optic neuritis can predict visual outcome.

  16. DERIVATIONS AND EXTENSIONS OF LIE COLOR ALGEBRA

    Institute of Scientific and Technical Information of China (English)

    Zhang Qingcheng; Zhang Yongzheng

    2008-01-01

    In this article, the authors obtain some results concerning derivations of fi-nitely generated Lie color algebras and discuss the relation between skew derivation space SkDer(L) and central extension H2(L, F) on some Lie color algebras. Meanwhile, they generalize the notion of double extension to quadratic Lie color algebras, a sufficient con-dition for a quadratic Lie color algebra to be a double extension and further properties are given.

  17. On extensions of ALGOL-like languages

    DEFF Research Database (Denmark)

    Skyum, Sven

    1974-01-01

    In this paper we introduce the notion of a level grammar and a level language. We define an extension to the extended definable sets and we characterize ALGOL-like languages, extended definable sets, and extensions of those as languages generated by level grammars with different kinds of restrict......In this paper we introduce the notion of a level grammar and a level language. We define an extension to the extended definable sets and we characterize ALGOL-like languages, extended definable sets, and extensions of those as languages generated by level grammars with different kinds...

  18. Extension - A Risk Taken in the Revolution

    Science.gov (United States)

    McNeil, Donald R.

    1970-01-01

    Extension institutions should take a risk and pool their resources with those of vocational-technical institutes, high schools, private schools, outside industries or government to advise the best possible educational programs for all the people. Extension needs money, support, commitment, and the will to take risks now. (DM)

  19. Extension Excellence in the Information Age.

    Science.gov (United States)

    Patton, Michael Quinn

    1985-01-01

    The author suggests that the business of extension is getting people to apply knowledge and use information. He makes observations concerning people and their use of information and knowledge. He presents five characteristics upon which future extension programs should be built. (CT)

  20. Effective Use of Facebook for Extension Professionals

    Science.gov (United States)

    Mains, Mark; Jenkins-Howard, Brooke; Stephenson, Laura

    2013-01-01

    As the use of social media increases, Extension is challenged to stay relevant with cliental by using digital tools. This article illustrates how Facebook can be part of Extension's repertoire of methods for communication, program implementation, education, and marketing. This allows professionals to build social networking capacity with…

  1. Farmer Experience of Pluralistic Agricultural Extension, Malawi

    Science.gov (United States)

    Chowa, Clodina; Garforth, Chris; Cardey, Sarah

    2013-01-01

    Purpose: Malawi's current extension policy supports pluralism and advocates responsiveness to farmer demand. We investigate whether smallholder farmers' experience supports the assumption that access to multiple service providers leads to extension and advisory services that respond to the needs of farmers. Design/methodology/approach: Within a…

  2. CANONICAL EXTENSIONS OF SYMMETRIC LINEAR RELATIONS

    NARCIS (Netherlands)

    Sandovici, Adrian; Davidson, KR; Gaspar, D; Stratila, S; Timotin, D; Vasilescu, FH

    2006-01-01

    The concept of canonical extension of Hermitian operators has been recently introduced by A. Kuzhel. This paper deals with a generalization of this notion to the case of symmetric linear relations. Namely, canonical regular extensions of symmetric linear relations in Hilbert spaces are studied. The

  3. Unifiability in extensions of K4

    NARCIS (Netherlands)

    Gencer, Ç.; de Jongh, D.

    2009-01-01

    We extend and generalize the work on unifiability of [8]. We give a semantic characterization for unifiability and non-unifiability in the extensions of K4. We apply this in particular to extensions of KD4, GL and K4.3 to obtain a syntactic characterization and give a concrete decision procedure for

  4. Effective Use of Facebook for Extension Professionals

    Science.gov (United States)

    Mains, Mark; Jenkins-Howard, Brooke; Stephenson, Laura

    2013-01-01

    As the use of social media increases, Extension is challenged to stay relevant with cliental by using digital tools. This article illustrates how Facebook can be part of Extension's repertoire of methods for communication, program implementation, education, and marketing. This allows professionals to build social networking capacity with…

  5. Meckel's cave tuberculoma with unusual infratemporal extension.

    Science.gov (United States)

    Kesavadas, Chandrasekharan; Somasundaram, S; Rao, Ravi M; Radhakrishnan, V V

    2007-07-01

    The authors describe a rare case of intracranial tuberculoma of the Meckel's cave and cavernous sinus with extension into the infratemporal fossa causing widening of the foramen ovale and adjacent bone destruction. The rarity of the lesion and the unusual extension of the lesion are presented with a brief review of literature.

  6. Paravertebral neurinoma associated with aggressive intravertebral extension

    Energy Technology Data Exchange (ETDEWEB)

    Inaoka, T.; Takahashi, Koji; Hanaoka, Hideto; Aburano, Tamio [Dept. of Radiology, Asahikawa Medical College (Japan); Tokusashi, Yoshihiko [Div. of Surgical Pathology, Asahikawa Medical Coll. (Japan); Matsuno, Takeo [Dept. of Orthopedics, Asahikawa Medical Coll. (Japan); Sugimoto, Hideharu [Dept. of Radiology, Showa Univ. Fujigaoka Hospital, Tokyo (Japan); Furuse, Makoto [Department of Radiology, Jichi Medical School, Tochigi (Japan)

    2001-05-01

    Neurinomas are relatively common benign tumors thought to arise from nerve sheath cells. Although intraosseous neurinomas may destroy the bone, extraosseous neurinomas with extensive destruction and invasion of bone are considered rare. We present two unusual cases of a benign extraosseous neurinoma that extensively invaded the vertebral body through the nutrient canal. (orig.)

  7. Plagiarism within Extension: Origin and Current Effects

    Science.gov (United States)

    Rollins, Dora

    2011-01-01

    Extension publication editors from around the United States are finding cases of plagiarism within manuscripts that Extension educators submit as new public education materials. When editors confront such educators with the problem, some don't understand it as such, rationalizing that reproducing published information for a new purpose qualifies…

  8. An extension theorem for conformal gauge singularities

    CERN Document Server

    Tod, Paul

    2007-01-01

    We analyse conformal gauge, or isotropic, singularities in cosmological models in general relativity. Using the calculus of tractors, we find conditions in terms of tractor curvature for a local extension of the conformal structure through a cosmological singularity and prove a local extension theorem.

  9. Extensive Reading: Students' Performance and Perception

    Science.gov (United States)

    Fernandez de Morgado, Nelly

    2009-01-01

    Reading is thought to be a crucial skill in the EFL learning process, and Extensive Reading a very useful strategy. However, very few teachers implement it on a regular basis. The process of introducing Extensive Reading (ER) is considered far too expensive, complicated, and time-consuming. One way to encourage its use would be to more deeply…

  10. Extension Sustainability Camp: Design, Implementation, and Evaluation

    Science.gov (United States)

    Brain, Roslynn; Upton, Sally; Tingey, Brett

    2015-01-01

    Sustainability Camps provide an opportunity for Extension educators to be in the forefront of sustainability outreach and to meet the growing demand for sustainability education. This article shares development, implementation, and evaluation of an Extension Sustainability Camp for youth, grades 4-6. Camp impact was measured via daily pre-and…

  11. An Extension to the Weibull Process Model

    Science.gov (United States)

    1981-11-01

    Subt5l . TYPE OF REPORT & PERIOD COVERED AN EXTENSION+TO THE WEIBULL PROCESS MODEL 6. PERFORMING O’G. REPORT NUMBER I. AuTHOR() S. CONTRACT OR GRANT...indicatinq its imrportance to applications. 4 AN EXTENSION TO TE WEIBULL PROCESS MODEL 1. INTRODUCTION Recent papers by Bain and Engelhardt (1980)1 and Crow

  12. Taxonomy for Assessing Evaluation Competencies in Extension

    Science.gov (United States)

    Rodgers, Michelle S.; Hillaker, Barbara D.; Haas, Bruce E.; Peters, Cheryl

    2012-01-01

    Evaluation of public service programming is becoming increasingly important with current funding realities. The taxonomy of evaluation competencies compiled by Ghere et al. (2006) provided the starting place for Taxonomy for Assessing Evaluation Competencies in Extension. The Michigan State University Extension case study described here presents a…

  13. Extension Learners' Use of Electronic Technology

    Science.gov (United States)

    Guenthner, Joseph F.; Swan, Benjamin G.

    2011-01-01

    Extension clientele use electronic technology for entertainment, communication, and business. Educational programs that use electronic technology can enhance learning. To learn more about use of electronic technology among Extension clientele, we surveyed 80 university students and 135 potato farmers. We found that the farmers were likely to use…

  14. Creating Teams Increases Extension Educator Productivity

    Science.gov (United States)

    Chalker-Scott, Linda; Daniels, Catherine H.; Martini, Nicole

    2016-01-01

    The Garden Team at Washington State University is a transdisciplinary group of faculty, staff, and students with expertise in applied plant and soil sciences and an interest in Extension education. The team's primary mission is to create current, relevant, and peer-reviewed materials as Extension publications for home gardeners. The average yearly…

  15. Extension Sustainability Camp: Design, Implementation, and Evaluation

    Science.gov (United States)

    Brain, Roslynn; Upton, Sally; Tingey, Brett

    2015-01-01

    Sustainability Camps provide an opportunity for Extension educators to be in the forefront of sustainability outreach and to meet the growing demand for sustainability education. This article shares development, implementation, and evaluation of an Extension Sustainability Camp for youth, grades 4-6. Camp impact was measured via daily pre-and…

  16. Tennessee Extension Agents' Perceptions of Performance Appraisal

    Science.gov (United States)

    Donaldson, Joseph L.; French, Russell L.

    2013-01-01

    Performance appraisal is necessary for summative decisions about employees, such as merit pay and promotion. The research reported here describes Extension agent perceptions of their performance appraisal system. The population studied consisted of all Tennessee Extension agents (N = 312). Surveys were completed by 218 respondents, for a completed…

  17. 10 CFR 905.33 - Extension formula.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Extension formula. 905.33 Section 905.33 Energy DEPARTMENT OF ENERGY ENERGY PLANNING AND MANAGEMENT PROGRAM Power Marketing Initiative § 905.33 Extension... an appropriate public process. (d) The formula set forth in paragraph (a) of this section also...

  18. Invariant properties of representations under cleft extensions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The main aim of this paper is to give the invariant properties of representations of algebras under cleft extensions over a semisimple Hopf algebra. Firstly, we explain the concept of the cleft extension and give a relation between the cleft extension and the crossed product which is the approach we depend upon. Then, by making use of them, we prove that over an algebraically closed field k, for a finite dimensional Hopf algebra H which is semisimple as well as its dual H*, the representation type of an algebra is an invariant property under a finite dimensional H-cleft extension . In the other part, we still show that over an arbitrary field k, the Nakayama property of a k-algebra is also an invariant property under an H -cleft extension when the radical of the algebra is H-stable.

  19. The Brazilian Experience with Agroecological Extension: A Critical Analysis of Reform in a Pluralistic Extension System

    Science.gov (United States)

    Diesel, Vivien; Miná Dias, Marcelo

    2016-01-01

    Purpose: To analyze the Brazilian experience in designing and implementing a recent extension policy reform based on agroecology, and reflect on its wider theoretical implications for extension reform literature. Design/methodology/approach: Using a critical public analysis we characterize the evolution of Brazilian federal extension policy…

  20. Agricultural Extension: Farm Extension Services in Australia, Britain and the United States.

    Science.gov (United States)

    Williams, Donald B.

    By analyzing the scope and structure of agricultural extension services in Australia, Great Britain, and the United States, this work attempts to set guidelines for measuring progress and guiding extension efforts. Extension training, agricultural policy, and activities of national, international, state, and provincial bodies are examined. The…

  1. Extension Approach for an Effective Fisheries and Aquaculture Extension Service in India

    Science.gov (United States)

    Kumaran, M.; Vimala, D. Deboral; Chandrasekaran, V. S.; Alagappan, M.; Raja, S.

    2012-01-01

    Purpose: Public-funded fisheries extension services have been blamed as poor and responsible for the slow pace of aquaculture development in India. The present investigation aimed to find concrete interventions to streamline the extension service by understanding the research-extension-farmer linkage indirectly in terms of information sources of…

  2. Examining eXtension: Diffusion, Disruption, and Adoption among Iowa State University Extension and Outreach Professionals

    Science.gov (United States)

    Taylor, Cayla; Miller, Greg

    2016-01-01

    As eXtension unveils its new membership model, Iowa State University Extension and Outreach must determine how best to support professionals and clientele using the technology. This article reports on a study that used the diffusion of innovations and disruptive innovation theories to assess Iowa Extension professionals' adoption and perceptions…

  3. Extensions and Pullbacks in QB-rings

    OpenAIRE

    Ara, Pere; Pedersen, Gert K.; Perera, Francesc

    2001-01-01

    We prove a new extension result for $QB-$rings that allows us to examine extensions of rings where the ideal is purely infinite and simple. We then use this result to explore various constructions that provide new examples of $QB-$rings. More concretely, we show that a surjective pullback of two $QB-$rings is usually again a $QB-$ring. Specializing to the case of an extension of a semi-prime ideal $I$ of a unital ring $R$, the pullback setting leads naturally to the study of rings whose multi...

  4. Extension versus Bending for Continuum Robots

    Directory of Open Access Journals (Sweden)

    George Grimes

    2008-11-01

    Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.

  5. The Effects of Leader-Member Exchanges on the Relationships Between Extension Agents and County Extension Directors in Florida

    National Research Council Canada - National Science Library

    Matt Benge; Amy Harder

    2017-01-01

    .... Understanding the interactions between Extension agents and County Extension Directors is critical to maintaining positive relationships and providing adequate support to Extension supervisors...

  6. Offshore extension of Gomati river, Dwarka

    Digital Repository Service at National Institute of Oceanography (India)

    Vora, K.H.; Naik, D.K.; Ganesan, P.; Moraes, C.

    ) at National Institute of Oceanography (NIO), Goa, India since 1984. Based on about 40 line-kilometres of echosounding, Side Scan Sonar and Shallow Seismic Profiling carried out in December 1989, underwater extension of the river Gomati has been mapped...

  7. Robustness of Equations Under Operational Extensions

    CERN Document Server

    Mosses, Peter D; Reniers, Michel A; 10.4204/EPTCS.41.8

    2010-01-01

    Sound behavioral equations on open terms may become unsound after conservative extensions of the underlying operational semantics. Providing criteria under which such equations are preserved is extremely useful; in particular, it can avoid the need to repeat proofs when extending the specified language. This paper investigates preservation of sound equations for several notions of bisimilarity on open terms: closed-instance (ci-)bisimilarity and formal-hypothesis (fh-)bisimilarity, both due to Robert de Simone, and hypothesis-preserving (hp-)bisimilarity, due to Arend Rensink. For both fh-bisimilarity and hp-bisimilarity, we prove that arbitrary sound equations on open terms are preserved by all disjoint extensions which do not add labels. We also define slight variations of fh- and hp-bisimilarity such that all sound equations are preserved by arbitrary disjoint extensions. Finally, we give two sets of syntactic criteria (on equations, resp. operational extensions) and prove each of them to be sufficient for...

  8. Integrated Composite Rocket Nozzle Extension Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ORBITEC proposes to develop and demonstrate an Integrated Composite Rocket Nozzle Extension (ICRNE) for use in rocket thrust chambers. The ICRNE will utilize an...

  9. ERP extension - Supply Chain Management (SCM

    Directory of Open Access Journals (Sweden)

    Vasile LUPSE

    2006-01-01

    Full Text Available This article presents an extension of a ERP (Enterprise Resource Planning, more precisely the Supply Chain Management (SCM, together with some personal considerations and contributions of the authors, regarding the presented concepts.

  10. Controleum - an independently extensible control system

    DEFF Research Database (Denmark)

    Jensen, Martin Lykke Rytter

    2014-01-01

    While the extensibility of many software systems has been greatly improved during the past two decades, nontrivial control systems remain to be a category of software systems that are remarkably difficult for independent parties to extend. Support for independent extension is the ability...... be resolved automatically. Typical control system components are concerned with the way in which actuators are controlled. Combining mutually unaware control system components that share interest in the same actuators are likely to lead to complex conflicts, thus making control systems a particularly...... challenging kind of system to design for independent extension. This thesis presents two new software technologies that improve the extensibility of control systems: First, the concept of dynamic links is introduced and Decouplink – an implementation of dynamic links for Java - is presented. Dynamic links...

  11. Absaloka Mine South Extension NPDES Permit

    Science.gov (United States)

    Under NPDES permit MT-0030783, Westmoreland Resources, Inc. is authorized to discharge mine drainage from outfalls associated with the Absaloka Mine South Extension on the Crow Indian reservation near Hardin, Montana to Middle Fork of Sarpy Creek.

  12. Communication for extension: developing country experience.

    Science.gov (United States)

    Meyer, A J

    1985-01-01

    This paper characterizes several major approaches to the use of communication in support of agricultural extension and suggests directions for change. The approaches discussed include: direct farmer contact, farmer forums, open broadcasting, advertising and social marketing, print media, multiple channel systems (campaigns and distance teaching), and comprehensive communication systems. Although all programs should be able to use media in interaction with training and the coordination of other inputs, this approach has not been comprehensively implemented in extension programs. There are few examples of cases where multiple methods have been brought together under a comprehensive communications strategy and institutionalized as part of an ongoing extension system. Lessons from social marketing in other sectors have not been exploited, while lessons from distance teaching have been underutilized. In addition, the networking and feedback functions of communication in extenson have not been given adequate attention. There is substantial potential for increasing the coverage and impact of agricultural extension through the more systematic and comprehensive use of communication.

  13. Extension's Role in a Global World.

    Science.gov (United States)

    Phelan, J.

    1998-01-01

    Trends in farming and farm household incomes in Ireland are presented in the context of global competitiveness. Addresses the issue of extension's dilemma in providing fee-based service while relying on public monies. (SK)

  14. South African Journal of Agricultural Extension

    African Journals Online (AJOL)

    The South African Journal of Agricultural Extensionaims to: * advance and apply the science of extension and of rural development as scientific discipline by ... collaboration in agricultural innovation systems amongst stakeholders in the North ...

  15. Extensive lichenoid sarcoidosis intermingled with white papules.

    OpenAIRE

    Nakahigashi, Kyoko; Miyachi, Yoshiki; Utani, Atsushi

    2011-01-01

    Cutaneous sarcoidosis is classified into nodular, plaque, diffuse infiltrative, and lichenoid types and others . Herein, we report an extensive case of rare lichenoid sarcoidosis with unusual small white macules representing early lesions of its typical red papules.

  16. Study on Reductive Dechlorination of PCBs in Groundwater by Fe/Zn Bimetal%Fe/Zn双金属对地下水中PCBs的还原脱氯研究

    Institute of Scientific and Technical Information of China (English)

    刘园园; 张兰英; 邱明英; 任何军; 杜军

    2012-01-01

    [ Objective] The research aimed to study reductive dechlorination effect of PCBs in groundwater by Fe/Zn bimetal. [ Method] Fe/ Zn bimetal as reduction system, PCBs degradation ratio as inspected index .degradation effect of PCBs by Fe/Zn bimetallic system when adding self-made hydroxypropyl-β-cyclodextrin (HP-β-CD) was studied. Meanwhile,we investigated the influences of loading ratio and Fe-Zn dosage on the dechlorination of PCBs. [ Result] PCBs was significantly solubilized by the synthesized HP-3-CD. With increase of the HP-β-CD concentration, the apparent solubility of PCBs increased linearly,forming 1:1 inclusion complex. When Fe-Zn dosage was 10 g.and mass fraction of Zn was 7% ,the dechilorination efficiency of PCBs with 321 μg/L was 47,6% after degrading for 7 d at 10 ℃, [Conclusion] The research provided theoretical guiding for in situ remediation of the groundwater contaminated by PCBs.%[目的]研究Fe/Zn双金属对地下水中PCBs的还原脱氯效果.[方法]以Fe、Zn构建二元金属还原体系,以PCBs降解率为考察指标,研究了添加羟丙基-β-环糊精(HP-β-CD)时,Fe/Zn双金属对PCBs的降解效果,同时考察了负载率、金属投加量对PCBs脱氯的影响.[结果]合成的HP-β-CD对PCBs有很好的增溶作用,PCBs表观溶解度随HP-β-CD浓度增加而线性增加,形成1∶1的包结物;10℃下,当混合金属投加量为10 g,Zn质量分数为7%时,321 μg/LPCBs降解7d后的去除率为47.6%.[结论]该研究为PCBs污染的地下水原位修复提供了理论指导.

  17. Strategies for Teaching English Extensive Reading

    Institute of Scientific and Technical Information of China (English)

    娄立国

    2008-01-01

    Extensive reading can make a major difference in student reading development over time.To endure that the students benefit most from extensive reading class,a few strategies must be adopted for teaching. The teacher is advised to attach importance to the significance of reading to language learning.Choosing understandable materials, protecting the students’enthusiasm, engaging the students in after-class reading,and playing a good role model are four important strategies discussed in the article.

  18. Selfadjoint extensions of multipoint singular differential operators

    Directory of Open Access Journals (Sweden)

    Zameddin I. Ismailov

    2013-10-01

    Full Text Available This article describes all selfadjoint extensions of the minimal operator generated by a linear singular multipoint symmetric differential-operator expression for first order in the direct sum of Hilbert spaces of vector-functions. This description is done in terms of the boundary values, and it uses the Everitt-Zettl and the Calkin-Gorbachuk methods. Also the structure of the spectrum of these extensions is studied.

  19. Decidable extensions of Hennessy-Milner Logic

    DEFF Research Database (Denmark)

    Mardare, Radu Iulian; Priami, Corrado

    2006-01-01

    R. Mardare, C. Priami. Decidable extensions of Hennessy-Milner Logic. In Proc. of the International Conference on Formal Methods for Networked and Distributed Systems (FORTE 2006), Lecture Notes in Computer Science 4229:196-211, Springer, 2006......R. Mardare, C. Priami. Decidable extensions of Hennessy-Milner Logic. In Proc. of the International Conference on Formal Methods for Networked and Distributed Systems (FORTE 2006), Lecture Notes in Computer Science 4229:196-211, Springer, 2006...

  20. Magnetic translation groups as group extension

    OpenAIRE

    Florek, Wojciech

    1998-01-01

    Extensions of a direct product T of two cyclic groups Z_n1 and Z_n2 by an Abelian (gauge) group G with the trivial action of T on G are considered. All possible (nonequivalent) factor systems are determined using the Mac Lane method. Some of resulting groups describe magnetic translation groups. As examples extensions with G=U(1) and G=Z_n are considered and discussed.

  1. Upper Stage Engine Composite Nozzle Extensions

    Science.gov (United States)

    Valentine, Peter G.; Allen, Lee R.; Gradl, Paul R.; Greene, Sandra E.; Sullivan, Brian J.; Weller, Leslie J.; Koenig, John R.; Cuneo, Jacques C.; Thompson, James; Brown, Aaron; hide

    2015-01-01

    Carbon-carbon (C-C) composite nozzle extensions are of interest for use on a variety of launch vehicle upper stage engines and in-space propulsion systems. The C-C nozzle extension technology and test capabilities being developed are intended to support National Aeronautics and Space Administration (NASA) and United States Air Force (USAF) requirements, as well as broader industry needs. Recent and on-going efforts at the Marshall Space Flight Center (MSFC) are aimed at both (a) further developing the technology and databases for nozzle extensions fabricated from specific CC materials, and (b) developing and demonstrating low-cost capabilities for testing composite nozzle extensions. At present, materials development work is concentrating on developing a database for lyocell-based C-C that can be used for upper stage engine nozzle extension design, modeling, and analysis efforts. Lyocell-based C-C behaves in a manner similar to rayon-based CC, but does not have the environmental issues associated with the use of rayon. Future work will also further investigate technology and database gaps and needs for more-established polyacrylonitrile- (PAN-) based C-C's. As a low-cost means of being able to rapidly test and screen nozzle extension materials and structures, MSFC has recently established and demonstrated a test rig at MSFC's Test Stand (TS) 115 for testing subscale nozzle extensions with 3.5-inch inside diameters at the attachment plane. Test durations of up to 120 seconds have been demonstrated using oxygen/hydrogen propellants. Other propellant combinations, including the use of hydrocarbon fuels, can be used if desired. Another test capability being developed will allow the testing of larger nozzle extensions (13.5- inch inside diameters at the attachment plane) in environments more similar to those of actual oxygen/hydrogen upper stage engines. Two C-C nozzle extensions (one lyocell-based, one PAN-based) have been fabricated for testing with the larger

  2. An Educational Extension Service in India

    Science.gov (United States)

    Krichevsky, M. I.

    2001-12-01

    A strength of US education is interaction with the public under the Land Grant University program. The public benefits from outreach through extension services which evolved for communication with end users, e.g., farmers, homemakers, public health providers, schoolchildren and entrepreneurs i.e., the public with problems and the extension agents who advise on solutions. Further, the agents can seek specialized advice from university faculty. No such system exists in India. The University of Pune (UP), Bionomics International (BI), and WorldSpace Foundation (WSF) will use digital radio broadcasts to facilitate educational extension services. The UP (350,000 students, 250 campuses, among dispersed communities) is a useful institutional setting to demonstrate the value of an outreach system in India. The UP will coordinate development of the broadcast content and the teaching faculty. The campuses will be focal points for outreach. BI will consult on development of the extension structure. WSF will provide the facilities and technical expertise for use of the digital system under the terms of an agreement with Bionomics International. Digital radios (&$slash75-150 each) and PCs will be at each campus and community. The major components of the Extension Service are broadcast of 1) University lecture and examination material in many disciplines; 2) outreach to the general population with of "canned" presentations and talks, skits, songs, games. The steps are: 1) Enhance communication among the campuses by use of satellite digital audio and multimedia broadcasts with feedback by telephone, mail, fax, etc. 2) Develop course material for training of extension personnel. 3) Train extension personnel to interface between the faculty of the University and the local population. 4) Extend digital radio services to population centers for communication of locally useful information. 5) Utilize extension personnel for system maintenance, motivating use of the broadcast

  3. Approximation of Bivariate Functions via Smooth Extensions

    Science.gov (United States)

    Zhang, Zhihua

    2014-01-01

    For a smooth bivariate function defined on a general domain with arbitrary shape, it is difficult to do Fourier approximation or wavelet approximation. In order to solve these problems, in this paper, we give an extension of the bivariate function on a general domain with arbitrary shape to a smooth, periodic function in the whole space or to a smooth, compactly supported function in the whole space. These smooth extensions have simple and clear representations which are determined by this bivariate function and some polynomials. After that, we expand the smooth, periodic function into a Fourier series or a periodic wavelet series or we expand the smooth, compactly supported function into a wavelet series. Since our extensions are smooth, the obtained Fourier coefficients or wavelet coefficients decay very fast. Since our extension tools are polynomials, the moment theorem shows that a lot of wavelet coefficients vanish. From this, with the help of well-known approximation theorems, using our extension methods, the Fourier approximation and the wavelet approximation of the bivariate function on the general domain with small error are obtained. PMID:24683316

  4. Dechlorination of the dietary nona-chlorinated toxaphene congeners 62 and 50 into the octa-chlorinated toxaphene congeners 44 and 40 in zebrafish (Danio rerio) and Atlantic salmon (Salmo salar)

    Energy Technology Data Exchange (ETDEWEB)

    Berntssen, M.H.G., E-mail: marc.berntssen@nifes.no [National Institute of Nutrition and Seafood Research (NIFES), Postbox 2029 Nordnes, 5817 Bergen (Norway); Lundebye, A.-K.; Hop-Johannessen, L.; Lock, E.-J. [National Institute of Nutrition and Seafood Research (NIFES), Postbox 2029 Nordnes, 5817 Bergen (Norway)

    2012-05-15

    Graphical abstract: - Abstract: The relative feed-to-fish accumulation and possible biotransformation of the nona-chlorinated toxaphene congeners currently included in EU-legislation (CHB-50 and -62) and the octa-chlorinated congeners recommended by the European Food Safety Authority to be included in future surveillance of fish samples (CHB-40, 41, and 44) were investigated in the present study. Model fish Danio rerio were fed either (a) diets spiked with a combination as well as the pure individual toxaphene congeners CHB-50 or 62 or (b) diets spiked with the combination of CHB N-Ary-Summation 50 + 62 and/or CHB N-Ary-Summation 40 + 41 + 44. In addition, seawater adapted Atlantic salmon smolts were fed technical toxaphene enriched feeds for 62 days. Zebrafish fed a diet containing CHB-50 and CHB-62 accumulated newly formed CHB-40 and 41 and CHB-44, respectively. The biomagnifications factors (BMF) of the toxaphene congeners in Atlantic salmon muscle from the feeds spiked with technical toxaphene were significantly correlated with their relative lipophilicity (expressed as log K{sub ow}). An exception was CHB-44 which had a higher BMF than could be expected from its specific log K{sub ow}, reflecting that CHB-44 is a metabolite formed under dietary exposure to CHB-62. This paper reports the in vivo dechlorination of nona-chlorinated toxaphene congeners into octa-chlorinated congeners in feeding trials with a model fish (zebrafish) and an oily food fish (Atlantic salmon).

  5. Dechlorination of the dietary nona-chlorinated toxaphene congeners 62 and 50 into the octa-chlorinated toxaphene congeners 44 and 40 in zebrafish (Danio rerio) and Atlantic salmon (Salmo salar).

    Science.gov (United States)

    Berntssen, M H G; Lundebye, A-K; Hop-Johannessen, L; Lock, E-J

    2012-05-15

    The relative feed-to-fish accumulation and possible biotransformation of the nona-chlorinated toxaphene congeners currently included in EU-legislation (CHB-50 and -62) and the octa-chlorinated congeners recommended by the European Food Safety Authority to be included in future surveillance of fish samples (CHB-40, 41, and 44) were investigated in the present study. Model fish Danio rerio were fed either (a) diets spiked with a combination as well as the pure individual toxaphene congeners CHB-50 or 62 or (b) diets spiked with the combination of CHB ∑50+62 and/or CHB ∑40+41+44. In addition, seawater adapted Atlantic salmon smolts were fed technical toxaphene enriched feeds for 62 days. Zebrafish fed a diet containing CHB-50 and CHB-62 accumulated newly formed CHB-40&41 and CHB-44, respectively. The biomagnifications factors (BMF) of the toxaphene congeners in Atlantic salmon muscle from the feeds spiked with technical toxaphene were significantly correlated with their relative lipophilicity (expressed as logK(ow)). An exception was CHB-44 which had a higher BMF than could be expected from its specific logK(ow), reflecting that CHB-44 is a metabolite formed under dietary exposure to CHB-62. This paper reports the in vivo dechlorination of nona-chlorinated toxaphene congeners into octa-chlorinated congeners in feeding trials with a model fish (zebrafish) and an oily food fish (Atlantic salmon).

  6. On Central Extensions of Associative Dialgebras

    Science.gov (United States)

    Rakhimov, Isamiddin S.

    2016-03-01

    The concept of central extensions plays an important in constructing extensions of algebras. This technique has been successfully used in the classification problem of certain classes of algebras. In 1978 Skjelbred and Sund reduced the classification of nilpotent Lie algebras in a given dimension to the study of orbits under the action of automorphism group on the space of second degree cohomology of a smaller Lie algebra with coefficients in a trivial module. Then W. de Graaf applied the Skjelbred and Sund method to the classification problem of low-dimensional nilpotent Lie and associative algebras over some fields. The main purpose of this note is to establish elementary properties of central extensions of associative dialgebras and apply the above mentioned method to the classification of low dimensional nilpotent associative dialgebras.

  7. Introduction to Special Section: Magmatism and Extension

    Science.gov (United States)

    Metcalf, Rodney V.; Smith, Eugene I.

    1995-06-01

    The relationship between magmatism and the formation of continental rift zones is the subject of much controversy. In particular, the cause and effect relationships between magmatism and extension and the mode of generation of magma during the process of extension are still hotly debated. This controversy served as the theme of a symposium on "Cenozoic Magmatism in the Colorado River Extensional Corridor and Adjacent Areas" and a field trip held as part of the Geological Society of America Cordilleran/Rocky Mountain Section meeting in Reno, Nevada [Metcalf et al., 1993]. It was clear from data presented at the symposium that a considerable amount of new information has become available regarding magmatism and extension since the last special section on this topic published by the Journal of Geophysical Research (June 1989).

  8. Improved Approximations for Some Polymer Extension Models

    CERN Document Server

    Petrosyan, Rafayel

    2016-01-01

    We propose approximations for force-extension dependencies for the freely jointed chain (FJC) and worm-like chain (WLC) models as well as for extension-force dependence for the WLC model. Proposed expressions show less than 1% relative error in the useful range of the corresponding variables. These results can be applied for fitting force-extension curves obtained in molecular force spectroscopy experiments. Particularly they can be useful for cases where one has geometries of springs in series and/or in parallel where particular combination of expressions should be used for fitting the data. All approximations have been obtained following the same procedure of determining the asymptotes and then reducing the relative error of that expression by adding an appropriate term obtained from fitting its absolute error.

  9. Symmetric Functional Model for Extensions of Hermitian

    CERN Document Server

    Ryzhov, V

    2006-01-01

    This paper offers the functional model of a class of non-selfadjoint extensions of a Hermitian operator with equal deficiency indices. The explicit form of dilation of a dissipative extension is offered and the symmetric form of Sz.Nagy-Foia\\c{s} model as developed by B.~Pavlov is constructed. A variant of functional model for a general non-selfadjoint non-dissipative extension is formulated. We illustrate the theory by two examples: singular perturbations of the Laplace operator in~$L_2(\\Real^3)$ by a finite number of point interactions, and the Schr\\"odinger operator on the half axis~$(0, \\infty)$ in the Weyl limit circle case at infinity.

  10. Extensive bullous lichen sclerosus et atrophicus*

    Science.gov (United States)

    Vukicevic, Jelica

    2016-01-01

    Lichen sclerosus et atrophicus is a chronic disease of unknown etiology characterized by atrophic and sclerotic plaques in both genital and extragenital regions. Extensive bullous lichen sclerosus et atrophicus (BLSA) is a severe variant of the disease with no widely accepted treatment. We present a 63-year-old woman with extensive extragenital, ivory-colored, atrophic plaques on her trunk and extremities and disseminated hemorrhagic bullae. The patient was unsuccessfully treated with standard topical corticosteroid therapy, doxycycline and chloroquine. According to the literature, there is little evidence of the efficacy of doxycycline and hydroxychloroquine in the treatment of BLSA. We report a rare case of extensive BLSA that is unresponsive to these drugs.

  11. Scientific contributions of extensive biodiversity monitoring.

    Science.gov (United States)

    Couvet, Denis; Devictor, Vincent; Jiguet, Frédéric; Julliard, Romain

    2011-05-01

    To develop a complete and informative biodiversity observation system, it is necessary to compare the strengths and limits of various monitoring schemes. In this article, we examine the various advantages of extensively monitoring fine-grained spatial variations of biodiversity, where the prominent traits of many species within a community (abundance, phenology, etc.) are regularly recorded at numerous sites over a large territory, usually via human observation networks. Linking these variations with environmental factors sheds lights on the major mechanisms leading to changes in biodiversity, thus increasing our knowledge of macroecology and community ecology. This extensive monitoring allows us to assess diffuse effects, contributing to the sound use of the precautionary principle. Combined with site-focused monitoring, information gathered from extensive monitoring provides the raw material necessary to build biodiversity scenarios.

  12. Supersymmetric extension of the Snyder algebra

    Energy Technology Data Exchange (ETDEWEB)

    Gouba, L., E-mail: lgouba@ictp.it [Abdus Salam International Centre for Theoretical Physics (ICTP), Strada Costiera 11, 34014 Trieste (Italy); Stern, A., E-mail: astern@bama.ua.edu [Dept. of Physics and Astronomy, Univ. of Alabama, Tuscaloosa, Al 35487 (United States)

    2012-04-11

    We obtain a minimal supersymmetric extension of the Snyder algebra and study its representations. The construction differs from the general approach given in Hatsuda and Siegel ( (arXiv:hep-th/0311002)) and does not utilize super-de Sitter groups. The spectra of the position operators are discrete, implying a lattice description of space, and the lattice is compatible with supersymmetry transformations. -- Highlights: Black-Right-Pointing-Pointer A new supersymmetric extension of the Snyder algebra is constructed. Black-Right-Pointing-Pointer The extension is minimal and the construction does not involve supersymmetric de Sitter algebras. Black-Right-Pointing-Pointer An involution is defined for the system and discrete representations are constructed. Black-Right-Pointing-Pointer The representations imply a spatial lattice and the lattice spacing is half that of the bosonic case. Black-Right-Pointing-Pointer A differential operator representation is given for fields on super-momentum space.

  13. abc: An extensible AspectJ compiler

    DEFF Research Database (Denmark)

    Avgustinov, Pavel; Christensen, Aske Simon; Hendren, Laurie

    2005-01-01

    Research in the design of aspect-oriented programming languages requires a workbench that facilitates easy experimentation with new language features and implementation techniques. In particular, new features for AspectJ have been proposed that require extensions in many dimensions: syntax, type...... checking and code generation, as well as data flow and control flow analyses. The AspectBench Compiler (abc) is an implementation of such a workbench. The base version of abc implements the full AspectJ language. Its frontend is built, using the Polyglot framework, as a modular extension of the Java...... language. The use of Polyglot gives flexibility of syntax and type checking. The backend is built using the Soot framework, to give modular code generation and analyses. In this paper, we outline the design of abc, focusing mostly on how the design supports extensibility. We then provide a general overview...

  14. Rough Sets, Their Extensions and Applications

    Institute of Scientific and Technical Information of China (English)

    Qiang Shen; Richard Jensen

    2007-01-01

    Rough set theory provides a useful mathematical foundation for developing automated computational systems that can help understand and make use of imperfect knowledge. Despite its recency, the theory and its extensions have been widely applied to many problems, including decision analysis, data mining, intelligent control and pattern recognition. This paper presents an outline of the basic concepts of rough sets and their major extensions, covering variable precision, tolerance and fuzzy rough sets. It also shows the diversity of successful applications these theories have entailed, ranging from financial and business, through biological and medicine, to physical, art, and meteorological.

  15. Timeability in Extensive-Form Games

    DEFF Research Database (Denmark)

    Jakobsen, Sune K.; Sørensen, Troels Bjerre; Conitzer, Vincent

    2016-01-01

    Extensive-form games constitute the standard representation scheme for games with a temporal component. But do all extensive-form games correspond to protocols that we can implement in the real world? We often rule out games with imperfect recall, which prescribe that an agent forget something...... to time the game, some information will leak to the agents that they are not supposed to have. We say such a game is not exactly timeable. We provide easy-to-check necessary and sufficient conditions for a game to be exactly timeable. Most of the technical depth of the paper concerns how to approximately...

  16. Mathematics for common entrance three (extension) answers

    CERN Document Server

    Alexander, Serena

    2015-01-01

    This book contains answers to all exercises featured in the accompanying textbook Mathematics for Common Entrance Three (Extension) , which provides essential preparation for Level 3 of the ISEB 13+ Mathematics exam, as well as for CASE and other scholarship exams. - Clean, clear layout for easy marking. - Includes examples of high-scoring answers with diagrams and workings. Also available to purchase from the Galore Park website www.galorepark.co.uk :. - Mathematics for Common Entrance Three (Extension). - Mathematics for Common Entrance One. - Mathematics for Common Entrance One Answers. - M

  17. Extensibility enables locomotion under isotropic drag

    CERN Document Server

    Pak, On Shun

    2011-01-01

    Anisotropic viscous drag is usually believed to be a requirement for the low Reynolds number locomotion of slender bodies such as flagella and cilia. Here we show that locomotion under isotropic drag is possible for extensible slender bodies. After general considerations, a two-ring swimmer and a model dinoflagellate flagellum are studied analytically to illustrate how extensibility can be exploited for self-propulsion without drag anisotropy. This new degree of freedom could be useful for some complex swimmer geometries and locomotion in complex fluid environments where drag anisotropy is weak or even absent.

  18. Extensive keloidal healing of pemphigus vulgaris

    Directory of Open Access Journals (Sweden)

    Khanna Neena

    1997-01-01

    Full Text Available Bullae of pemphigus vulgaris heal without scarring. We here report a patient of pemphigus vulgaris whose lesions healed with a one-month history of extensive flaccid bullae and uninfected erosions on the trunk and extremities along with superficial erosions in the oral mucosa. The clinical suspicion of pemphigus vulgaris was confirmed by histopathological and immunohistological examination. Pulse therapy with monthly parenteral dexamethasone and cyclophosphamide pulse was instituted. The cutaneous lesions on healing formed extensive keloidal scars despite high dose of monthly corticosteroid therapy.

  19. EXTENSION EDUCATION SYMPOSIUM: reinventing extension as a resource--what does the future hold?

    Science.gov (United States)

    Mirando, M A; Bewley, J M; Blue, J; Amaral-Phillips, D M; Corriher, V A; Whittet, K M; Arthur, N; Patterson, D J

    2012-10-01

    The mission of the Cooperative Extension Service, as a component of the land-grant university system, is to disseminate new knowledge and to foster its application and use. Opportunities and challenges facing animal agriculture in the United States have changed dramatically over the past few decades and require the use of new approaches and emerging technologies that are available to extension professionals. Increased federal competitive grant funding for extension, the creation of eXtension, the development of smartphone and related electronic technologies, and the rapidly increasing popularity of social media created new opportunities for extension educators to disseminate knowledge to a variety of audiences and engage these audiences in electronic discussions. Competitive grant funding opportunities for extension efforts to advance animal agriculture became available from the USDA National Institute of Food and Agriculture (NIFA) and have increased dramatically in recent years. The majority of NIFA funding opportunities require extension efforts to be integrated with research, and NIFA encourages the use of eXtension and other cutting-edge approaches to extend research to traditional clientele and nontraditional audiences. A case study is presented to illustrate how research and extension were integrated to improve the adoption of AI by beef producers. Those in agriculture are increasingly resorting to the use of social media venues such as Facebook, YouTube, LinkedIn, and Twitter to access information required to support their enterprises. Use of these various approaches by extension educators requires appreciation of the technology and an understanding of how the target audiences access information available on social media. Technology to deliver information is changing rapidly, and Cooperative Extension Service professionals will need to continuously evaluate digital technology and social media tools to appropriately integrate them into learning and

  20. Computer Anxiety Levels of Virginia Extension Personnel.

    Science.gov (United States)

    Martin, Brenda L.; Stewart, Daisy L.; Hillison, John

    2001-01-01

    Survey responses from 402 Virginia extension personnel showed that secretaries and younger staff had the lowest computer anxiety, technicians and older staff the highest. Time spent using computers, age, and years of employment were somewhat associated with anxiety. Training recommendations were made. (SK)

  1. Disaster Preparedness and the Cooperative Extension Service

    Science.gov (United States)

    Black, Lynette

    2012-01-01

    This past decade has recorded an increase in catastrophic events that have led to dramatic changes for Americans. The wake of these disasters has resulted in many lessons being learned. These lessons have been captured by Homeland Security in the First Edition of the National Preparedness Goal. Extension is uniquely positioned to assist with…

  2. Does Extensive Reading Promote Reading Speed?

    Science.gov (United States)

    He, Mu

    2014-01-01

    Research has shown a wide range of learning benefits accruing from extensive reading. Not only is there improvement in reading, but also in a wide range of language uses and areas of language knowledge. However, few research studies have examined reading speed. The existing literature on reading speed focused on students' reading speed without…

  3. Catastrophic failure of polymer melts during extension

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.

    2013-01-01

    Numerical flow modeling has been applied to study the break of monodisperse polymer melts during extension. These continuum mechanical based computations are within the ideas of the microstructural ’interchain pressure’ theory. Calculated breaks, a result of small initial sample imperfections, ag...

  4. 75 FR 20561 - Patent Term Extension

    Science.gov (United States)

    2010-04-20

    ... Patent and Trademark Office Patent Term Extension ACTION: Proposed collection; comment request. SUMMARY: The United States Patent and Trademark Office (USPTO), as part of its continuing effort to reduce... the Chief Information Officer, United States Patent and Trademark Office, P.O. Box 1450,...

  5. 78 FR 31885 - Patent Term Extension

    Science.gov (United States)

    2013-05-28

    ... Patent and Trademark Office Patent Term Extension ACTION: Proposed collection; comment request. SUMMARY: The United States Patent and Trademark Office (USPTO), as part of its continuing effort to reduce...: Susan K. Fawcett, Records Officer, Office of the Chief Information Officer, United States Patent...

  6. Characteristics of Noncredit University Extension Students.

    Science.gov (United States)

    Dow, June Barth

    Characteristics of noncredit University Extension enrollees of 1964 were studied further to explore Houle's typology of the continuous learner. A structured questionnaire composed of 47 items was presented to 24 participants in interview sessions. It was found that most participants did not fit Houle's classification of being activity-oriented; a…

  7. A Graph Library Extension of SVG

    DEFF Research Database (Denmark)

    Nørmark, Kurt

    2007-01-01

    be aggregated as a single node, and an entire graph can be embedded in a single node. In addition, a number of different graph animations are described. The starting point of the SVG extension is a library that provides an exact of mirror of SVG 1.1 in the functional programming language Scheme. Each element...

  8. Particle Swarm Optimisation with Spatial Particle Extension

    DEFF Research Database (Denmark)

    Krink, Thiemo; Vesterstrøm, Jakob Svaneborg; Riget, Jacques

    2002-01-01

    In this paper, we introduce spatial extension to particles in the PSO model in order to overcome premature convergence in iterative optimisation. The standard PSO and the new model (SEPSO) are compared w.r.t. performance on well-studied benchmark problems. We show that the SEPSO indeed managed...

  9. Extension Leads Model City Litter Fight

    Science.gov (United States)

    Magnuson, Doris

    1971-01-01

    A three-year war on litter is in effect in the Portland, Maine, area, as a result of the University of Maine's enlisting the county extension service to help the local Model Cities program clean up the inner city. Article details problems and progress in meeting the objectives. (PD)

  10. Substantial Life Extension and Meanings of Life

    NARCIS (Netherlands)

    Derkx, P.H.J.M.

    2009-01-01

    Substantial extension of the human lifespan has become a subject of lively debate. One reason for this is the completion of the Human Genome Project in 2001 and the experimental avenues for biogerontological research the project enables. Another is recent theoretical progress in biogerontology (Aust

  11. Does Extensive Reading Promote Reading Speed?

    Science.gov (United States)

    He, Mu

    2014-01-01

    Research has shown a wide range of learning benefits accruing from extensive reading. Not only is there improvement in reading, but also in a wide range of language uses and areas of language knowledge. However, few research studies have examined reading speed. The existing literature on reading speed focused on students' reading speed…

  12. Principles Guiding Vocabulary Learning through Extensive Reading

    Science.gov (United States)

    Nation, Paul

    2015-01-01

    Extensive reading is one of a range of activities that can be used in a language learning course. Ideally, the choice of activities to go into a course should be guided by principles which are well supported by research. Similarly, the way each of those activities is used should be guided by well-justified principles. In this article, we look at…

  13. Effectively Communicating Science to Extension Audiences

    Science.gov (United States)

    Robinson, Patrick

    2013-01-01

    This article discusses the concept of "framing" within the context of relevant communication and psychological research and considers its potential applicability to Extension science communication. Examples of research-based support for the framing of scientific issues are presented, along with a literature-based discussion of the…

  14. Substantial Life Extension and Meanings of Life

    NARCIS (Netherlands)

    Derkx, P.H.J.M.

    2009-01-01

    Substantial extension of the human lifespan has become a subject of lively debate. One reason for this is the completion of the Human Genome Project in 2001 and the experimental avenues for biogerontological research the project enables. Another is recent theoretical progress in biogerontology

  15. Extensible Markup Language Data Mining System Model

    Institute of Scientific and Technical Information of China (English)

    李炜; 宋瀚涛

    2003-01-01

    The existing data mining methods are mostly focused on relational databases and structured data, but not on complex structured data (like in extensible markup language(XML)). By converting XML document type description to the relational semantic recording XML data relations, and using an XML data mining language, the XML data mining system presents a strategy to mine information on XML.

  16. EXTENSION OF THE PROGRESSIVE RETIREMENT PROGRAMME

    CERN Multimedia

    Human Resources Division

    2002-01-01

    In accordance with the provisions agreed by the Finance Committee and Council in March and June 2000, respectively, the Director-General has approved the extension of the Progressive Retirement Programme with effect from 1 April 2001, for one year. Human Resources Division Tel. 72808/74128

  17. Communication for Strengthening Agricultural Extension and Rural ...

    African Journals Online (AJOL)

    chrischisoni

    and rural development programs are quite complex, but as this study found, ... Development (C4D), an emerging body of knowledge for addressing problems, such as participation, integration and ..... as community radio, can expand extension's reach to deep into the rural hinterland as the African .... Delhi, India: B. R..

  18. Longest Common Extensions in Sublinear Space

    DEFF Research Database (Denmark)

    Bille, Philip; Gørtz, Inge Li; Knudsen, Mathias Bæk Tejs;

    2015-01-01

    The longest common extension problem (LCE problem) is to construct a data structure for an input string T of length n that supports LCE(i,j) queries. Such a query returns the length of the longest common prefix of the suffixes starting at positions i and j in T. This classic problem has a well-kn...

  19. A Graph Library Extension of SVG

    DEFF Research Database (Denmark)

    Nørmark, Kurt

    2007-01-01

    be aggregated as a single node, and an entire graph can be embedded in a single node. In addition, a number of different graph animations are described. The starting point of the SVG extension is a library that provides an exact of mirror of SVG 1.1 in the functional programming language Scheme. Each element...

  20. Home Food Preservation Training for Extension Educators

    Science.gov (United States)

    Goard, Linnette Mizer; Hill, Melinda; Shumaker, Katharine; Warrix, Marisa

    2013-01-01

    During times of economic downturn, there has been an increased interest in home food preservation. As the primary resource for current research-based recommendations, a team of Extension Family and Consumer Sciences educators with specialization in food safety and food preservation responded to this demand by developing a standardized food…

  1. Introducing Extension/Outreach Education in Tajikistan

    Science.gov (United States)

    Albrecht, Julie A.; Prochaska-Cue, Kathleen; Rockwell, S. Kay; Pulatov, Pulat A.

    2010-01-01

    University of Nebraska-Lincoln (UNL) and Khujand branch of the Technological University of Tajikistan (KbTUT) collaborated on the development of an Extension/outreach program in Tajikistan. Fifteen KbTUT administrators, faculty, and students from textiles, food science, and management engaged in training sessions at UNL on entrepreneurship, adult…

  2. Maintaining extensivity in evolutionary multiplex networks

    CERN Document Server

    Antonopoulos, Chris G

    2015-01-01

    In this Letter, we explore the role of network topology on its extensive character. We study analytically and numerically how the topology contributes to maintaining extensivity of entropy in multiplex networks, i.e. networks of subnetworks, by means of the sum of the positive Lyapunov exponents, $H_{KS}$, a quantity related to entropy. We show that extensivity relies not only on the interplay between the coupling strengths of the dynamics associated to the intra (short-range) and inter (long-range) interactions, but also on the sum of the intra-degrees of the nodes of the subnetworks. For the analytically treated networks of size $N$, if the sum of the intra-degrees (and the sum of inter-degrees) scales as $N^{\\theta+1}$, extensivity can be maintained if the intra-coupling (and the inter-coupling) strength scales as $N^{-\\theta}$, when evolution is driven by the maximization of $H_{KS}$. We then verify our analytical result by doing numerical simulations in multiplex networks formed by electrically and chemi...

  3. Strategic Opportunities for Cooperative Extension. Executive Summary

    Science.gov (United States)

    National Association of State Universities and Land-Grant Colleges, 2007

    2007-01-01

    In this new century, opportunities exist to help advance America's greatness in the midst of many challenges. Energy, water, food, environment, health, economic productivity, global competitiveness, and the quality of the living environments are all paramount to the future. Extension is, as a part of higher education, prepared to create new…

  4. Extensive Air Showers in the Classroom

    Science.gov (United States)

    Badala, A.; Blanco, F.; La Rocca, P.; Pappalardo, G. S.; Pulvirenti, A.; Riggi, F.

    2007-01-01

    The basic properties of extensive air showers of particles produced in the interaction of a high-energy primary cosmic ray in the Earth's atmosphere are discussed in the context of educational cosmic ray projects involving undergraduate students and high-school teams. Simulation results produced by an air shower development code were made…

  5. Tools for Creating Mobile Applications for Extension

    Science.gov (United States)

    Drill, Sabrina L.

    2012-01-01

    Considerations and tools for developing mobile applications for Extension include evaluating the topic, purpose, and audience. Different computing platforms may be used, and apps designed as modified Web pages or implicitly programmed for a particular platform. User privacy is another important consideration, especially for data collection apps.…

  6. Modeling the Forced Extension of Nicked DNA

    Science.gov (United States)

    Balaeff, Alexander; Craig, Stephen; Beratan, David

    2007-03-01

    The design and study of DNA-based nanodevices has been a topic of considerable interest in the last decade. While the applications of classical continuous DNA structures have been thoroughly studied, nicked DNA structures, i.e., ones that contains breaks (``nicks'') in one or both DNA backbone chains, have received much less attention. Recently, Kersey et al. (JACS, 2004) reported the force spectroscopy of long DNA chains with periodic nicks, self-assembled from short DNA oligomers. We attempt to model the experimental force-extension profiles in a series of steered molecular dynamics simulations. The simulated all-atom model of a basic unit of the long self-assembled chain, a 16bp-long DNA segment with a nick in the middle of one strand, is extended by applying either a constant force or a moving harmonic potential to the DNA ends. The computed force-extension profiles are compared to those for a non-nicked DNA; the dynamics of structural changes in the nicked DNA during the forced extension is discussed. A theoretical framework is established to link the extension and rupture in the simulated basic unit to the corresponding events in the long self-assembled chain.

  7. Entrepreneurial Extension Conducted via Social Media

    Science.gov (United States)

    Cornelisse, Sarah; Hyde, Jeffrey; Raines, Christopher; Kelley, Kathleen; Ollendyke, Dana; Remcheck, James

    2011-01-01

    The widespread availability of and access to the Internet have led to the development of new forms of communication. Collectively termed "social media," these new communication tools have created vast opportunities for Extension professionals in how they perform their work and how businesses interact with consumers. This article outlines currently…

  8. On free ring extensions of degree n

    Directory of Open Access Journals (Sweden)

    George Szeto

    1981-01-01

    Full Text Available Nagahara and Kishimoto [1] studied free ring extensions B(x of degree n for some integer n over a ring B with 1, where xn=b, cx=xρ(c for all c and some b in B(ρ=automophism of  B, and {1,x…,xn−1} is a basis. Parimala and Sridharan [2], and the author investigated a class of free ring extensions called generalized quaternion algebras in which b=−1 and ρ is of order 2. The purpose of the present paper is to generalize a characterization of a generalized quaternion algebra to a free ring extension of degree n in terms of the Azumaya algebra. Also, it is shown that a one-to-one correspondence between the set of invariant ideals of B under ρ and the set of ideals of B(x leads to a relation of the Galois extension B over an invariant subring under ρ to the center of B.

  9. Coherent radiation from extensive air showers

    NARCIS (Netherlands)

    Scholten, Olaf; de Vries, Krijn D.; Werner, Klaus

    2012-01-01

    The generic properties of the emission of coherent radiation from a moving charge distribution are discussed. The general structure of the charge and current distributions in an extensive air shower are derived. These are subsequently used to develop a very intuitive picture for the properties of th

  10. 78 FR 13333 - Agency Information Collection Extension

    Science.gov (United States)

    2013-02-27

    ... Request Title: Natural Gas Imports and Exports; (3) Type of Request: Three-year extension; (4) Purpose... reporting sections for the collection and identification of new types of natural gas transactions related to...-746R, ``Natural Gas Imports and Exports.'' Comments are invited on: (a) Whether the proposed...

  11. 40 CFR 52.1078 - Extensions.

    Science.gov (United States)

    2010-07-01

    ... generation On-board Diagnostics (OBD-II) equipped motor vehicles as part of its inspection and maintenance (I/M) program. As a result of this deadline extension, Maryland must now incorporate mandatory OBD-II checks (for 1996-and-newer OBD-II equipped vehicles) as an element of the Commonwealth's I/M program...

  12. 75 FR 38091 - Agency Information Collection Extension

    Science.gov (United States)

    2010-07-01

    ... Program, OMB Control Number 1910-5127. The proposed collection will collect information on the status of... collect information on the status of grantee activities, expenditures, and results, to ensure that program... Information Collection Extension AGENCY: U.S. Department of Energy. ACTION: Submission for Office...

  13. Emergency Food Programs: Untapped Opportunities for Extension?

    Science.gov (United States)

    Mobley, Amy R.

    2012-01-01

    This article reports results from a questionnaire that assessed the frequency and type of nutrition questions asked at emergency food programs to determine if Extension professionals need to increase direct outreach efforts. Emergency food program workers (n = 460) were recruited via mail to complete a self-administered survey. More than one-third…

  14. Integrating Reading and Writing through Extensive Reading

    Science.gov (United States)

    Park, Jeongyeon

    2016-01-01

    This study explores whether an extensive reading (ER) approach can enhance L2 learners' writing performance in an English for Academic Purposes context. Two classes were compared in terms of writing improvement after one semester: a 'traditional' writing class primarily focused on writing practice and grammar instruction, and an ER class in which…

  15. On Viviani's Theorem and Its Extensions

    Science.gov (United States)

    Abboud, Elias

    2010-01-01

    Viviani's theorem states that the sum of distances from any point inside an equilateral triangle to its sides is constant. Here, in an extension of this result, we show, using linear programming, that any convex polygon can be divided into parallel line segments on which the sum of the distances to the sides of the polygon is constant. Let us say…

  16. MECHANICAL PRODUCT EXTENSIVE INTELLIGENT CONCEPTUAL DESIGN

    Institute of Scientific and Technical Information of China (English)

    Zhang Guoquan; Zhong Yifang; Zhang Weiguo

    2004-01-01

    Based on extenics, an extensive functional information model (function-behavioral action-structure-environmental constraint) of the mechanical product intelligent conceptual design is developed, and the mechanism of theoretic structure solutions is produced, the mapping relations between function-behavior and behavior-structure are analyzed.The model is applied to the filling material system's conceptual design to verify validity.

  17. Playing extensive form games in parallel

    NARCIS (Netherlands)

    S. Ghosh; R. Ramanujam; S. Simon

    2010-01-01

    Consider a player playing against different opponents in two extensive form games simultaneously. Can she then have a strategy in one game using information from the other? The famous example of playing chess against two grandmasters simultaneously illustrates such reasoning. We consider a simple dy

  18. Agent Turnovers in Ohio State University Extension.

    Science.gov (United States)

    Rousan, Laith M.; Henderson, Janet L.

    1996-01-01

    Responses from 61 of 67 Ohio State University extension agents who left between 1990-94 showed they were primarily female (66%), white (90%), and untenured (98%). They were most likely to leave due to other priorities, insufficient pay, family obligations, too many work responsibilities, or the opportunity to make more money elsewhere. (SK)

  19. Differential Krull dimension in differential polynomial extensions

    OpenAIRE

    Smirnov, Ilya

    2011-01-01

    We investigate the differential Krull dimension of differential polynomials over a differential ring. We prove a differential analogue of Jaffard's Special Chain Theorem and show that differential polynomial extensions of certain classes of differential rings have no anomaly of differential Krull dimension.

  20. Trials and Triumphs of Expanded Extension Programs.

    Science.gov (United States)

    Leavengood, Scott; Love, Bob

    1998-01-01

    Oregon extension faced challenges in presenting programs in the wood products industry. Several traditional tactics, revised to suit a new audience, have proved successful: personal coaching, building partnerships, and providing a high level of service. Newer methods, such as database marketing and distance learning, are also proving to be…

  1. Stories and Storytelling in Extension Work

    Science.gov (United States)

    Peters, Scott; Franz, Nancy K.

    2012-01-01

    Deep budget cuts, increased accountability, and the growth of anti-government and anti-intellectual sentiments place Extension systems in a defensive position. In response, we're engaging in organizational change exercises, restructuring, regionalizing, rewriting mission statements, and developing strategic plans. We're spending…

  2. STARTCL -- Starlink Extensions to Tcl & Tk

    Science.gov (United States)

    Terrett, D. L.

    The STARTCL package is a set of extensions to the Tcl/Tk language to enable Tcl and Tk applications to display Starlink graphics inside widgets embedded in the application, send and receive ADAM messages and access ADAM noticeboards. This document will be of interest to programmers writing graphics user interfaces for Starlink applications in Tcl/Tk.

  3. Workplace Issues in Extension--A Delphi Study of Extension Educators

    Science.gov (United States)

    Kroth, Michael; Peutz, Joey

    2011-01-01

    Using the Delphi technique, expert Extension educators identified and prioritized those workplace issues they believe will be the most important to attract, motivate, and retain Extension educators/agents over the next 5 to 7 years. Obtaining and then utilizing a talented, highly motivated workforce during a period when many will be retiring will…

  4. Tampa Bay Extension Agents’ Views of Urban Extension: Philosophy and Program Strategies

    Directory of Open Access Journals (Sweden)

    Amy Harder

    2017-06-01

    Full Text Available The purpose of this article was to explore the concept of urban Extension as perceived by Extension agents within the Tampa Bay area, one of Florida’s fastest growing metropolitan areas. From a theoretical perspective, it is critical to understand Extension agents’ beliefs about urban Extension because behaviors are directly related to attitudes (Ajzen, 2012. In 2016, a qualitative investigation was undertaken to explore the perspectives of 23 agents working within the Tampa Bay area. Results showed the majority of agents believed that context and client needs are unique for urban Extension, and that to a lesser extent, unique agent expertise is required. Further, these beliefs impacted how agents reported their approach to programming, with an emphasis on providing convenience and seeking partnerships. Difficulties were identified related to identifying the role of Extension in a resource-rich environment of service providers, which contributed to the existence of a perceived disconnect between urban audiences and Extension. Opportunities exist for Extension leadership to provide strategic organizational support that will enhance agents’ abilities to succeed in the metropolitan environment.

  5. Hypoallergenicity of an extensively hydrolyzed whey formula.

    Science.gov (United States)

    Giampietro, P G; Kjellman, N I; Oldaeus, G; Wouters-Wesseling, W; Businco, L

    2001-04-01

    Several different protein hydrolysate-based infant formulas have been promoted as hypoallergenic and considered suitable for the dietary management of cow's milk allergy (CMA). Accepting that none of the hydrolysate-based products is completely safe, the American Academy of Pediatrics (AAP) recommends that these formulas should be tested in a double-blind placebo-controlled setting and tolerated by at least 90% of children with proven CMA. In principle, this recommendation is also endorsed by the European Society of Paediatric Gastroenterology and Nutrition (ESPGAN) and the European Society of Paediatric Allergy and Clinical Immunology (ESPACI). In this two-center study, 32 children with proven CMA were tested with the extensive hydrolysate whey formula Nutrilon Pepti, for comparison with Profylac (extensive) and Nan HA (partial) whey hydrolysate products. Skin-prick tests (SPTs) were, respectively, positive to the three hydrolysate formulas in 19%, 15%, and 32% of children. After oral challenge it was concluded that 97% (95% CI: 85-100%) of the children tolerated Nutrilon Pepti, 94% (95% CI: 75-100%) tolerated Profylac, and 64% (95% CI: 37-81%) tolerated Nan HA. This study demonstrates that the extensive hydrolysates Nutrilon Pepti and Profylac are well tolerated in a population of children with proven CMA and that both products can be considered safe for their intended use. This study confirms that a very small number of children react even to extensively hydrolyzed formulas. SPT prior to oral exposure to the hydrolysate-based formulas can indicate whether a child is at risk of showing reactions to the product. Introduction of new products to these children should be carried out under a doctor's supervision. However, the majority of the SPT-positive children did tolerate the two extensively hydrolyzed whey-based formulas tested.

  6. Evaluation of mechanical tractor pedal extensions.

    Science.gov (United States)

    Kelso, S A; Stangherlin, A M; Mann, D D

    2008-10-01

    Many farmers with disabilities choose to modify their work environments to accommodate their personal abilities; however, modified tractors may present greater risk to the operator as they are often one-of-a-kind designs that have not been subjected to rigorous safety testing. The objective of this research was to evaluate mechanical tractor pedal , extensions from a safety perspective. This objective was achieved by identifying potential hazards associated with the introduction of a pedal extension into the cab environment so that both existing and novel designs could be compared using a common methodology. Based on review of the published literature, 19 potential hazards associated with the introduction of a pedal extension into the cab of a tractor were identified. A hazard self-assessment worksheet (HSAW), created based on the 19 hazards, was validated through a pilot study. The overall inter-rater reliability and concurrent criterion validity proved to be acceptable. With the use of the HSAW six pedal extensions (three existing designs and three novel designs) were evaluated by 14 experts. Statistical analysis of the results did not identify a "best" design; however, several important trends were observed. Four of the six designs tended to block access to the exit path. The two designs that did not block access to the exit path might be considered to be the best designs for the tractors used in this study, but other designs likely would have been acceptable if they had been custom-fit for these tractors. The results of this research suggest that custom fabrication of pedal extensions for each specific tractor will likely yield the safest work environment for those who choose to use this assistive technology.

  7. Xyloglucan endotransglucosylase and cell wall extensibility.

    Science.gov (United States)

    Miedes, E; Zarra, I; Hoson, T; Herbers, K; Sonnewald, U; Lorences, E P

    2011-02-15

    Transgenic tomato hypocotyls with altered levels of an XTH gene were used to study how XET activity could affect the hypocotyl growth and cell wall extensibility. Transgenic hypocotyls showed significant over-expression (line 13) or co-suppression (line 33) of the SlXTH1 in comparison with the wild type, with these results being correlated with the results on specific soluble XET activity, suggesting that SlXTH1 translates mainly for a soluble XET isoenzyme. A relationship between XET activity and cell wall extensibility was found, and the highest total extensibility was located in the apical hypocotyl segment of the over-expressing SlXTH1 line, where the XET-specific activity and hypocotyl growth were also highest compared with the wild line. Also, in the co-suppression SlXTH1 line, total extensibility values were lower than in the wild type line. The study of linkages between cell wall polysaccharides by FTIR showed that hypocotyls over-expressing SlXTH1 and having a higher XET-specific activity, were grouped away from the wild line, indicating that the linkages between pectins and between cellulose and xyloglucans might differ. These results suggested that the action of the increased XET activity in the transgenic line could be responsible for the cell wall structural changes, and therefore, alter the cell wall extensibility. On the other hand, results on xyloglucan oligosaccharides composition of the xyloglucan by MALDI TOF-MS showed no differences between lines, indicating that the xyloglucan structure was not affected by the XET action. These results provide evidences that XTHs from group I are involved mainly in the restructuring of the cell wall during growth and development, but they are not the limiting factor for plant growth.

  8. 78 FR 52505 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2013-08-23

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... National Institute of Standards and Technology (NIST) announces that the Manufacturing Extension... FURTHER INFORMATION CONTACT: Karen Lellock, Manufacturing Extension Partnership, National Institute...

  9. 75 FR 19941 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2010-04-16

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... announces that the Manufacturing Extension Partnership (MEP) Advisory Board, National Institute of Standards..., 2010. FOR FURTHER INFORMATION CONTACT: Karen Lellock, Manufacturing Extension Partnership,...

  10. 76 FR 53666 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2011-08-29

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... National Institute of Standards and Technology (NIST) announces that the Manufacturing Extension...: Karen Lellock, Manufacturing Extension Partnership, National Institute of Standards and Technology,...

  11. 77 FR 50469 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2012-08-21

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY...: The National Institute of Standards and Technology (NIST) announces that the Manufacturing Extension... Lellock, Manufacturing Extension Partnership, National Institute of Standards and Technology, 100...

  12. 77 FR 20790 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2012-04-06

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... announces that the Manufacturing Extension Partnership (MEP) Advisory Board, National Institute of Standards... INFORMATION section below. FOR FURTHER INFORMATION CONTACT: Karen Lellock, Manufacturing Extension...

  13. 76 FR 22674 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2011-04-22

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... announces that the Manufacturing Extension Partnership (MEP) Advisory Board, National Institute of Standards... than May 2, 2011. FOR FURTHER INFORMATION CONTACT: Karen Lellock, Manufacturing Extension...

  14. 75 FR 50749 - Manufacturing Extension Partnership Advisory Board

    Science.gov (United States)

    2010-08-17

    ... National Institute of Standards and Technology Manufacturing Extension Partnership Advisory Board AGENCY... announces that the Manufacturing Extension Partnership (MEP) Advisory Board, National Institute of Standards... INFORMATION CONTACT: Karen Lellock, Manufacturing Extension Partnership, National Institute of Standards...

  15. Extensible Technology-Agnostic Runtime Verification

    Directory of Open Access Journals (Sweden)

    Christian Colombo

    2013-02-01

    Full Text Available With numerous specialised technologies available to industry, it has become increasingly frequent for computer systems to be composed of heterogeneous components built over, and using, different technologies and languages. While this enables developers to use the appropriate technologies for specific contexts, it becomes more challenging to ensure the correctness of the overall system. In this paper we propose a framework to enable extensible technology agnostic runtime verification and we present an extension of polyLarva, a runtime-verification tool able to handle the monitoring of heterogeneous-component systems. The approach is then applied to a case study of a component-based artefact using different technologies, namely C and Java.

  16. Subintegrality, invertible modules and Laurent polynomial extensions

    Indian Academy of Sciences (India)

    Vivek Sadhu

    2015-05-01

    Let ⊆ be a commutative ring extension. Let $\\mathcal{I}$(, ) be the multiplicative group of invertible -submodules of . In this article, we extend a result of Sadhu and Singh by finding a necessary and sufficient condition on an integral birational extension ⊆ of integral domains with dim ≤ 1, so that the natural map $\\mathcal{I}$(, ) $→$ $\\mathcal{I}(A[X,X^{-1}],B[X,X^{-1}])$ is an isomorphism. In the same situation, we show that if dim ≥ 2, then the condition is necessary but not sufficient. We also discuss some properties of the cokernel of the natural map $\\mathcal{I}(A,B)→ \\mathcal{I}[X,X^{-1}], B[X,X^{-1}])$ in the general case.

  17. States On Orthocomplemented Difference Posets (Extensions)

    Science.gov (United States)

    Hroch, Michal; Pták, Pavel

    2016-08-01

    We continue the investigation of orthocomplemented posets that are endowed with a symmetric difference (ODPs). The ODPs are orthomodular and, therefore, can be viewed as "enriched" quantum logics. In this note, we introduced states on ODPs. We derive their basic properties and study the possibility of extending them over larger ODPs. We show that there are extensions of states from Boolean algebras over unital ODPs. Since unital ODPs do not, in general, have to be set-representable, this result can be applied to a rather large class of ODPs. We then ask the same question after replacing Boolean algebras with "nearly Boolean" ODPs (the pseudocomplemented ODPs). Making use of a few results on ODPs, some known and some new, we construct a pseudocomplemented ODP, P, and a state on P that does not allow for extensions over larger ODPs.

  18. Study on Extension Strategy-Tactics-Planning

    Institute of Scientific and Technical Information of China (English)

    YangChunyan; ZhangYongjun; ZhuDongmei

    2004-01-01

    Extension strategy-tactics-planning (ESTP), based upon the science of Extenics, is established for the purpose of solving contradictory problems. In this paper, the fundamental thoughts, theories and methods of ESTP are introduced concisely. The highlights of ESTP are that the techniques, used in the case of tackling such problems as how to generate the ideas of strategy-tactics-planning, how to completely analyze the resources, how to exploit extension resources, how to transfer the incompatible into the compati-ble, and how to transfer the opposite into the co-existent, are developed in a formalized way. And regarding the practices of ESTP, the applications of ESTP in resource integration, project, market development, and the prevention and handling crises are presented.

  19. Extensive cortical involvement in leptomeningeal carcinomatosis.

    Science.gov (United States)

    Ayzenberg, I; Börnke, C; Tönnes, C; Ziebarth, W; Lavrov, A; Lukas, C

    2012-12-01

    We present a 77-year-old previously well patient with facial asymmetry and progressive weakness of the lower extremities. An initial MRI revealed slight contrast enhancement of the meninges. Three consecutive cerebrospinal fluid examinations demonstrated low glucose concentration, marked elevation of total protein and moderate pleocytosis. No tumor cells, fungi, acid-fast bacilli or mycobacterial DNA were found. The patient's level of consciousness deteriorated dramatically, and follow-up MRI showed widespread extensive cortical hyperintensities. The lesions showed restricted diffusion on diffusion-weighted images as well as low values on the corresponding apparent diffusion coefficient maps, the changes consistent with diffuse cytotoxic edema. Neuropathological examination findings were of leptomeningeal carcinomatosis (LMC) with diffuse continuous infiltration of the cerebral cortex, cerebellum and spinal cord. The autopsy revealed a subcentimetre adenocarcinoma of the lung. To our knowledge, this is the first report demonstrating extensive cortical involvement in adenocarcinomatous LMC.

  20. A giant frontoethmoid mucocele with intracranial extension.

    Science.gov (United States)

    Işık, Abdülcemal Ümit; Arslan, Selçuk; Arslan, Erhan; Baykal, Süleyman

    2015-02-01

    Mucoceles are mucus-containing cysts lined by epithelium. Although benign, they may show expansive growth and remain undiagnosed until symptoms due to compression of surrounding structures arise. We report a rare case of frontoethmoid mucocele with intracranial extension in an 80-year-old woman with complaints of headache, right diplopia and proptosis. A right frontoorbital craniotomy was performed, and a mucocele in the frontal sinus extending into the frontal lobe and orbit was totally removed. The patient was successfully treated without any complication. The two-year follow-up results were satisfactory. Magnetic resonance imaging excluded any recurrence of the mucocele. Combined intranasal and transcranial approach is necessary to treat giant frontoetmoid mucoceles with intracranial extension. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  1. Traumatic knee extension deficit (the locked knee)

    DEFF Research Database (Denmark)

    Helmark, I C; Neergaard, K; Krogsgaard, M R

    2007-01-01

    In the present study we investigated the validity of magnetic resonance imaging (MRI) and arthroscopy in knees with acute, traumatic extension deficit (the "locked knee"), and evaluated whether arthroscopy of knees with no mechanical pathology could be avoided by MRI evaluation. The study consisted...... of 50 patients who had an acute, traumatic extension deficit of the knee. All patients were submitted to MRI prior to arthroscopy. Following MRI and surgery, standardized forms were filled out, attempting to objectify the findings. The orthopaedic surgeon was not aware of the MRI result prior to surgery......, the following results were calculated for the overall appearance of a lesion able to cause locking: Positive predictive value = 0.85, negative predictive value = 0.77, sensitivity = 0.95, specificity = 0.53. Two knees were erroneously evaluated with no mechanical locking at MRI (one bucket-handle lesion and one...

  2. Chordal Loewner chains with quasiconformal extensions

    OpenAIRE

    2015-01-01

    In 1972, Becker [J. Reine Angew. Math. 255 (1972), 23-43] discovered a construction of quasiconformal extensions making use of the classical radial Loewner chains. In this paper we develop a chordal analogue of Becker's construction. As an application, we establish new sufficient conditions for quasiconformal extendibility of holomorphic functions and give a simplified proof of one well-known result by Becker and Pommerenke for functions in the half-plane [J. Reine Angew. Math. 354 (1984), 74...

  3. Stable Extensions with(out) Gravity

    DEFF Research Database (Denmark)

    Antipin, Oleg; Krog, Jens; Mojaza, Matin

    2014-01-01

    We investigate the vacuum stability as well as the gravitational corrections in extensions of the Standard Model featuring a new complex scalar, and two Dirac fermions for different choices of the hypercharge of the scalar and one of the two fermions. The neutral fermion acquires loop-induced mag...... and discover that the models can be compatible with the asymptotically safe gravity scenario at the price of a heavier Higgs and lighter top mass...

  4. Extension in Mona Passage, Northeast Caribbean

    Science.gov (United States)

    Chaytor, J.D.; ten Brink, U.S.

    2010-01-01

    As shown by the recent Mw 7.0 Haiti earthquake, intra-arc deformation, which accompanies the subduction process, can present seismic and tsunami hazards to nearby islands. Spatially-limited diffuse tectonic deformation within the Northeast Caribbean Plate Boundary Zone likely led to the development of the submerged Mona Passage between Puerto Rico and the Dominican Republic. GPS geodetic data and a moderate to high level of seismicity indicate that extension within the region is ongoing. Newly-collected high-resolution multibeam bathymetry and multi-channel seismic reflection profiles and previously-collected samples are used here to determine the tectonic evolution of the Mona Passage intra-arc region. The passage is floored almost completely by Oligocene-Pliocene carbonate platform strata, which have undergone submarine and subaerial erosion. Structurally, the passage is characterized by W- to NNW-trending normal faults that offset the entire thickness of the Oligo-Pliocene carbonate platform rocks. The orientation of these faults is compatible with the NE-oriented extension vector observed in GPS data. Fault geometry best fits an oblique extension model rather than previously proposed single-phase, poly-phase, bending-moment, or rotation extension models. The intersection of these generally NW-trending faults in Mona Passage with the N-S oriented faults of Mona Canyon may reflect differing responses of the brittle upper-crust, along an arc-forearc rheological boundary, to oblique subduction along the Puerto Rico trench. Several faults within the passage, if ruptured completely, are long enough to generate earthquakes with magnitudes on the order of Mw 6.5-7. ?? 2010.

  5. Emergence of Extensively Drug Resistant Tuberculosis

    Centers for Disease Control (CDC) Podcasts

    2007-03-01

    Extensively drug-resistant tuberculosis (XDR TB) outbreaks have been reported in South Africa, and strains have been identified on 6 continents. Dr. Peter Cegielski, team leader for drug-resistant TB with the Division of Tuberculosis Elimination at CDC, comments on a multinational team's report on this emerging global public health threat.  Created: 3/1/2007 by Emerging Infectious Diseases.   Date Released: 3/26/2007.

  6. Esthesioneuroblastoma With Poor Outcome Despite Extensive Treatment.

    Science.gov (United States)

    Niyaz, Leyla; Gunduz, Kaan; Meco, Cem; Kankaya, Duygu

    2015-10-01

    Esthesioneuroblastoma is a rare malignant tumor of neuroectodermal origin. It usually presents with nonspecific symptoms, such as nasal obstruction, epistaxis, and pain, but has an aggressive course if the treatment is delayed. The authors report a case of esthesioneuroblastoma in a 47-year-old woman, treated with extensive surgical resection, radiotherapy, and chemotherapy. Despite intensive treatment, the patient developed a local recurrence with systemic metastasis and succumbed 4 months later.

  7. Invariant holomorphic extension in several complex variables

    Institute of Scientific and Technical Information of China (English)

    ZHOU; Xiangyu

    2006-01-01

    Two fundamental problems on the invariant holomorphic extensions have been posed, which are naturally arose from our solution of the extended future tube conjecture and closely and deeply related to the general theory of Stein manifolds due to Cartan-Serre. In this paper, the relationship is presented between the two problems, the motivation of considering the problems, and the methods to approach the problems. We have also posed some questions and conjectures related to this two problems.

  8. Valgus Extension Overload in Baseball Players.

    Science.gov (United States)

    Paulino, Franklin E; Villacis, Diego C; Ahmad, Christopher S

    2016-01-01

    Repetitive throwing, such as in baseball pitching, applies massive stress on the elbow. This can often lead to a predictable constellation of elbow injuries, such as valgus extension overload syndrome (VEO). The following review of VEO provides an understanding of relevant anatomy, explanation of pathomechanics, key aspects to clinical evaluation, effective treatment options, and indications for surgery. In addition, we provide the senior author's (CSA) preferred arthroscopic technique for cases of VEO refractory to conservative management.

  9. New Mechanism for Multiagent Extensible Negotiations

    OpenAIRE

    Aknine, Samir

    2014-01-01

    Multiagent negotiation mechanisms advise original solutions to several problems for which usual problem solving methods are inappropriate. Mainly negotiation models are based on agents' interactions through messages. Agents interact in order to reach an agreement for solving a specific problem. In this work, we study a new variant of negotiations, which has not yet been addressed in existing works. This negotiation form is denoted extensible negotiation. In contrast with current negotiation m...

  10. The simplest extension of Starobinsky inflation

    CERN Document Server

    van de Bruck, Carsten

    2015-01-01

    We consider the simplest extension to the Starobinsky model, by allowing an extra scalar field to help drive inflation. We perform our analysis in the Einstein frame and calculate the power spectra at the end of inflation to second order in the slow--roll parameters. We find that the model gives predictions in great agreement with the current Planck data without the need for fine-tuning. Our results encourage current efforts to embed the model in a supergravity setting.

  11. Extensive Green Roof Ecological Benefits in Latvia

    OpenAIRE

    Rušenieks, Rihards; Kamenders, Agris

    2013-01-01

    Extensive green roof ecological benefits are studiedin this paper. The research contains a brief explanation aboutgreen roof technology and green roof ecological benefits. Greenroof capability to retain rainwater runoff by accumulating it instorage layers and conducting it back into the atmospherethrough evapotranspiration is studied and modeled. Modeling isdone in Stormwater Management Model 5.0 software. The modelis based on an existing warehouse-type building located in Rigaand hourly Riga...

  12. Learning PrimeFaces extensions development

    CERN Document Server

    Jonna, Sudheer

    2014-01-01

    This book provides a step by step approach that explains the most important extension components and their features. All the major features are explained by using the JobHub application with supporting screenshots.If you are an intermediate to advanced level user (or developer) who already has a basic working knowledge of PrimeFaces, then this book is for you.The only thing you need to know is Java Server Faces(JSF).

  13. Mucocele and pyocele with marked intracranial extension

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, Kazuhiro; Machida, Tohru; Iio, Masahiro

    1984-08-01

    Two cases are presented with frontal sinus pyocele and fronto-ethmoid sinus mucocele in which marked intracranial extension is shown. Their intracranial part appeared as a large biconvex mass, which showed iso or slightly low density homogeneously and had gross calcification in the posterior rim. The findings of the paranasal sinuses and the orbit in tomograms and CT scans are thought to be useful in the differential diagnosis of chronic subdural hematoma.

  14. British Men Opt for Penis Extensions

    Institute of Scientific and Technical Information of China (English)

    向勃

    2003-01-01

    选注者言:cosmetic surgery,即“整容手术;整容外科”,英国男士和女士的所谓 “整容”已经大大超出了我们所理解的“面部”范畴。男士:penis extension(阴茎 伸长扩大);女士:liposuction(吸脂)or breast enlargement(隆胸)

  15. Muonic footprint of simulated extensive air showers

    Energy Technology Data Exchange (ETDEWEB)

    Erfani, Mona; Risse, Markus; Yushkov, Alexey [University of Siegen (Germany)

    2015-07-01

    The number of muons at ground is one of the major parameters in extensive air showers to discriminate hadronic showers from photon ones. There are already numerous studies focusing on this matter and on using the muon content in combination with other parameters. In our study, we use CORSIKA showers for photon and proton primaries at E=10{sup 18} eV without thinning of shower muons to analyze the structure of the muonic footprint at different core distances.

  16. [Physical rehabilitation in extensively burned patients].

    Science.gov (United States)

    Martín Martínez, V; Díez Sanz, Ma J; Corona Fernández, O; García Aragón, A; González Fraile, L

    2014-02-01

    The rehabilitation of the extensively burned patient aims to prevent and minimize consequences of the own lesion this is supported by three pillars: 1) postural treatment to prevent contractures; 2) kinesiotherapy to maintain/restore joint range of movement and muscle strength; 3) functional recovery. Physical therapy is essential in the multidisciplinary team. A coordinated team assures better results and positively influences the quality of life of the patients.

  17. Constraints on Extensions of a Default Theory

    Institute of Scientific and Technical Information of China (English)

    SU Kaile

    2001-01-01

    In this paper, the representability of a family of theories as the set of extensions of a default theory is studied. First, a new necessary condition is given for the representability by means of general default theories; then a sufficient one is presented. The families of theories represented by default theories are also fully characterized. Finally, the paper gives an example of denumerable families of mutually inconsistent theories that are represented by a default theory but not by normal ones.

  18. Translation Invariant Extensions of Finite Volume Measures

    Science.gov (United States)

    Goldstein, S.; Kuna, T.; Lebowitz, J. L.; Speer, E. R.

    2017-02-01

    We investigate the following questions: Given a measure μ _Λ on configurations on a subset Λ of a lattice L, where a configuration is an element of Ω ^Λ for some fixed set Ω , does there exist a measure μ on configurations on all of L, invariant under some specified symmetry group of L, such that μ _Λ is its marginal on configurations on Λ ? When the answer is yes, what are the properties, e.g., the entropies, of such measures? Our primary focus is the case in which L=Z^d and the symmetries are the translations. For the case in which Λ is an interval in Z we give a simple necessary and sufficient condition, local translation invariance ( LTI), for extendibility. For LTI measures we construct extensions having maximal entropy, which we show are Gibbs measures; this construction extends to the case in which L is the Bethe lattice. On Z we also consider extensions supported on periodic configurations, which are analyzed using de Bruijn graphs and which include the extensions with minimal entropy. When Λ subset Z is not an interval, or when Λ subset Z^d with d>1, the LTI condition is necessary but not sufficient for extendibility. For Z^d with d>1, extendibility is in some sense undecidable.

  19. Applications and extensions of degradation modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, F.; Subudhi, M.; Samanta, P.K. (Brookhaven National Lab., Upton, NY (United States)); Vesely, W.E. (Science Applications International Corp., Columbus, OH (United States))

    1991-01-01

    Component degradation modeling being developed to understand the aging process can have many applications with potential advantages. Previous work has focused on developing the basic concepts and mathematical development of a simple degradation model. Using this simple model, times of degradations and failures occurrences were analyzed for standby components to detect indications of aging and to infer the effectiveness of maintenance in preventing age-related degradations from transforming to failures. Degradation modeling approaches can have broader applications in aging studies and in this paper, we discuss some of the extensions and applications of degradation modeling. The application and extension of degradation modeling approaches, presented in this paper, cover two aspects: (1) application to a continuously operating component, and (2) extension of the approach to analyze degradation-failure rate relationship. The application of the modeling approach to a continuously operating component (namely, air compressors) shows the usefulness of this approach in studying aging effects and the role of maintenance in this type component. In this case, aging effects in air compressors are demonstrated by the increase in both the degradation and failure rate and the faster increase in the failure rate compared to the degradation rate shows the ineffectiveness of the existing maintenance practices. Degradation-failure rate relationship was analyzed using data from residual heat removal system pumps. A simple linear model with a time-lag between these two parameters was studied. The application in this case showed a time-lag of 2 years for degradations to affect failure occurrences. 2 refs.

  20. Applications and extensions of degradation modeling

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, F.; Subudhi, M.; Samanta, P.K. [Brookhaven National Lab., Upton, NY (United States); Vesely, W.E. [Science Applications International Corp., Columbus, OH (United States)

    1991-12-31

    Component degradation modeling being developed to understand the aging process can have many applications with potential advantages. Previous work has focused on developing the basic concepts and mathematical development of a simple degradation model. Using this simple model, times of degradations and failures occurrences were analyzed for standby components to detect indications of aging and to infer the effectiveness of maintenance in preventing age-related degradations from transforming to failures. Degradation modeling approaches can have broader applications in aging studies and in this paper, we discuss some of the extensions and applications of degradation modeling. The application and extension of degradation modeling approaches, presented in this paper, cover two aspects: (1) application to a continuously operating component, and (2) extension of the approach to analyze degradation-failure rate relationship. The application of the modeling approach to a continuously operating component (namely, air compressors) shows the usefulness of this approach in studying aging effects and the role of maintenance in this type component. In this case, aging effects in air compressors are demonstrated by the increase in both the degradation and failure rate and the faster increase in the failure rate compared to the degradation rate shows the ineffectiveness of the existing maintenance practices. Degradation-failure rate relationship was analyzed using data from residual heat removal system pumps. A simple linear model with a time-lag between these two parameters was studied. The application in this case showed a time-lag of 2 years for degradations to affect failure occurrences. 2 refs.

  1. Translation Invariant Extensions of Finite Volume Measures

    Science.gov (United States)

    Goldstein, S.; Kuna, T.; Lebowitz, J. L.; Speer, E. R.

    2016-08-01

    We investigate the following questions: Given a measure μ _Λ on configurations on a subset Λ of a lattice L, where a configuration is an element of Ω ^Λ for some fixed set Ω , does there exist a measure μ on configurations on all of L, invariant under some specified symmetry group of L, such that μ _Λ is its marginal on configurations on Λ ? When the answer is yes, what are the properties, e.g., the entropies, of such measures? Our primary focus is the case in which L=Z^d and the symmetries are the translations. For the case in which Λ is an interval in Z we give a simple necessary and sufficient condition, local translation invariance (LTI), for extendibility. For LTI measures we construct extensions having maximal entropy, which we show are Gibbs measures; this construction extends to the case in which L is the Bethe lattice. On Z we also consider extensions supported on periodic configurations, which are analyzed using de Bruijn graphs and which include the extensions with minimal entropy. When Λ subset Z is not an interval, or when Λ subset Z^d with d>1 , the LTI condition is necessary but not sufficient for extendibility. For Z^d with d>1 , extendibility is in some sense undecidable.

  2. An $OSp$ extension of Canonical Tensor Model

    CERN Document Server

    Narain, Gaurav

    2015-01-01

    Tensor models are generalizations of matrix models, and are studied as discrete models of quantum gravity for arbitrary dimensions. Among them, the canonical tensor model (CTM for short) is a rank-three tensor model formulated as a totally constrained system with a number of first-class constraints, which have a similar algebraic structure as the constraints of the ADM formalism of general relativity. In this paper, we formulate a super-extension of CTM as an attempt to incorporate fermionic degrees of freedom. The kinematical symmetry group is extended from $O(N)$ to $OSp(N,\\tilde N)$, and the constraints are constructed so that they form a first-class constraint super-Poisson algebra. This is a straightforward super-extension, and the constraints and their algebraic structure are formally unchanged from the purely bosonic case, except for the additional signs associated to the order of the fermionic indices and dynamical variables. However, this extension of CTM leads to the existence of negative norm state...

  3. LIMB Demonstration Project Extension and Coolside Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Goots, T.R.; DePero, M.J.; Nolan, P.S.

    1992-11-10

    This report presents results from the limestone Injection Multistage Burner (LIMB) Demonstration Project Extension. LIMB is a furnace sorbent injection technology designed for the reduction of sulfur dioxide (SO[sub 2]) and nitrogen oxides (NO[sub x]) emissions from coal-fired utility boilers. The testing was conducted on the 105 Mwe, coal-fired, Unit 4 boiler at Ohio Edison's Edgewater Station in Lorain, Ohio. In addition to the LIMB Extension activities, the overall project included demonstration of the Coolside process for S0[sub 2] removal for which a separate report has been issued. The primary purpose of the DOE LIMB Extension testing, was to demonstrate the generic applicability of LIMB technology. The program sought to characterize the S0[sub 2] emissions that result when various calcium-based sorbents are injected into the furnace, while burning coals having sulfur content ranging from 1.6 to 3.8 weight percent. The four sorbents used included calcitic limestone, dolomitic hydrated lime, calcitic hydrated lime, and calcitic hydrated lime with a small amount of added calcium lignosulfonate. The results include those obtained for the various coal/sorbent combinations and the effects of the LIMB process on boiler and plant operations.

  4. Mixed views about radical life extension

    Directory of Open Access Journals (Sweden)

    Allen Alvarez

    2015-05-01

    Full Text Available Background: Recent studies on public attitudes toward life extension technologies show a mix of ambivalence toward and support for extending the human lifespan (Partridge 2009; Dragojlovic 2013; Funk et al. 2013. Attitudes toward genetic modification of organisms and technological enhancements may be used to categorize individuals according to political or ideological orientation such as technoprogressive or conservative (Hughes 2010 and it could be easy to assume that these categories are related to more general categorizations related to culture, e.g. between Traditional and Secular-rational values in the World Values Survey (Ingelhart & Welzel 2010. This paper discusses how attitudes toward aspects of radical life extension may be related to cultural values as revealed in an online deliberative survey among university students conducted between January 2012 to January 2013. Survey results suggest that attitudes toward radical life extension tend to be mixed among groups categorized as Traditional, Secular-rational, Survivalist, and Self-expressionist. The study explored the relation between responses of 326 university students to 5 key questions on radical life extension (RLE and the cultural values they tend to favor as indicated by their response to 20 statements from the World Values Survey. Design and Method: The survey consisted of 3 stages: an online pre-discussion survey, face-to-face discussion, and post-discussion survey. After completing the 5 main survey questions in stage 1, participants were presented two additional questionnaires: one on cultural attitudes using 20 statements from the 2004-2008 World Values Survey (WVS and another on health attitudes with 12 statements from Dutta-Bergman’s 2004 study. In stage 2, participants were engaged in a face-to-face discussion in class focusing on their responses to the five key questions. After the discussion, they were invited to reconsider the choices and reasons they posted in stage

  5. Carbon sequestration potential of extensive green roofs.

    Science.gov (United States)

    Getter, Kristin L; Rowe, D Bradley; Robertson, G Philip; Cregg, Bert M; Andresen, Jeffrey A

    2009-10-01

    Two studies were conducted with the objective of quantifying the carbon storage potential of extensive green roofs. The first was performed on eight roofs in Michigan and four roofs in Maryland, ranging from 1 to 6 years in age. All 12 green roofs were composed primarily of Sedum species, and substrate depths ranged from 2.5 to 12.7 cm. Aboveground plant material was harvested in the fall of 2006. On average, these roofs stored 162 g C x m(-2) in aboveground biomass. The second study was conducted on a roof in East Lansing, MI. Twenty plots were established on 21 April 2007 with a substrate depth of 6.0 cm. In addition to a substrate only control, the other plots were sown with a single species of Sedum (S. acre, S. album, S. kamtshaticum, or S. spurium). Species and substrate depth represent typical extensive green roofs in the United States. Plant material and substrate were harvested seven times across two growing seasons. Results at the end of the second year showed that aboveground plant material storage varied by species, ranging from 64 g C x m(-2) (S. acre) to 239 g C x m(-2) (S. album), with an average of 168 g C x m(-2). Belowground biomass ranged from 37 g C x m(-2) (S. acre) to 185 g C x m(-2) (S. kamtschaticum) and averaged 107 g C x m(-2). Substrate carbon content averaged 913 g C x m(-2), with no species effect, which represents a sequestration rate of 100 g C x m(-2) over the 2 years of this study. The entire extensive green roof system sequestered 375 g C x m(-2) in above- and belowground biomass and substrate organic matter.

  6. A Model for Evaluating eXtension Communities of Practice

    Science.gov (United States)

    Kelsey, Kathleen D.; Stafne, Eric T.

    2012-01-01

    As Americans shift their work and leisure activities online, Extension seeks to remain viable by delivering programs through a website known as eXtension. eXtension is predicated on the voluntary labor of Extension specialists and educators who form Communities of Practice to create and deliver content through the website. Evaluation of eXtension…

  7. An Assessment of Extension Education Curriculum at Land Grant Universities

    Science.gov (United States)

    Harder, Amy; Mashburn, Diane; Benge, Matt

    2009-01-01

    A critical assessment of extension education is needed to ensure there are adequate opportunities for students to study extension education and that the curriculum is relevant to today's Cooperative Extension Service. This descriptive study was conducted to assess extension education curriculum by identifying and comparing the courses being taught…

  8. 11 CFR 100.55 - Extension of credit.

    Science.gov (United States)

    2010-01-01

    ... substantially similar to extensions of credit to nonpolitical debtors that are of similar risk and size of... 11 Federal Elections 1 2010-01-01 2010-01-01 false Extension of credit. 100.55 Section 100.55... Contribution (2 U.S.C. 431(8)) § 100.55 Extension of credit. The extension of credit by any person is...

  9. A CART extension using Quadratic Decision Borders

    DEFF Research Database (Denmark)

    Hartelius, Karsten

    1999-01-01

    In this article we put forward an extention to the hierarchical CART classification method which uses quadratic decision borders. The original CART applies univariate splits on individual variables as well as splits on combinations of variables to recursively partition the feature......-space into subsets which are successively more class-homogeneous. Guided by the fact that class-distributions in feature-space are very often hyper-elliptical shaped, we give an extension to the original CART which also uses quadratic shaped decision borders which can be modelled by a mean-vector and a dispersion...

  10. A timed extension for AltaRica

    OpenAIRE

    Cassez, Franck; Pagetti, Claire; Roux, Olivier

    2004-01-01

    International audience; In this paper we present a timed extension of the AltaRica formalism. Following previous works, we first extend the semantics of AltaRica with time and define timed components and timed nodes. Moreover we lift the priority features of AltaRica to the timed case. We obtain a timed version of AltaRica, called Timed AltaRica. Finally we give a translation of a Timed AltaRica specification into a usual timed automaton. These are the semantic foundations of a high-level hie...

  11. Software extension and integration with type classes

    DEFF Research Database (Denmark)

    Lämmel, Ralf; Ostermann, Klaus

    2006-01-01

    expressiveness, by using the language concept of \\emph{type classes}, as it is available in the functional programming language Haskell. A detailed comparison with related work shows that type classes provide a powerful framework in which solutions to known software extension and integration problems can......The abilities to extend a software module and to integrate a software module into an existing software system without changing existing source code are fundamental challenges in software engineering and programming-language design. We reconsider these challenges at the level of language...

  12. Extensive Epidermoid Cyst and Breathing Difficulty

    Directory of Open Access Journals (Sweden)

    Ciro Dantas Soares

    2015-01-01

    Full Text Available Epidermoid cysts are common cystic lesions in the skin, ovaries, and testicles, but their occurrence in the oral cavity is uncommon. They consist of cysts delimited by a fibrous capsule without cutaneous annexes and are lined by stratified squamous epithelium. The differential diagnosis includes ranula, dermoid cysts, and lingual thyroid. Despite their benign presentation, these cysts can cause functional limitations, requiring special clinical attention for extensive lesions located in regions that preserve vital structures. This paper aims to report a case of epidermoid cyst in patient with swallowing and breathing difficulty, highlighting the clinical and surgical planning.

  13. Central extensions of Lax operator algebras

    Science.gov (United States)

    Schlichenmaier, M.; Sheinman, O. K.

    2008-08-01

    Lax operator algebras were introduced by Krichever and Sheinman as a further development of Krichever's theory of Lax operators on algebraic curves. These are almost-graded Lie algebras of current type. In this paper local cocycles and associated almost-graded central extensions of Lax operator algebras are classified. It is shown that in the case when the corresponding finite-dimensional Lie algebra is simple the two-cohomology space is one-dimensional. An important role is played by the action of the Lie algebra of meromorphic vector fields on the Lax operator algebra via suitable covariant derivatives.

  14. Central extensions of Lax operator algebras

    OpenAIRE

    Schlichenmaier, Martin; Sheinman, Oleg K.

    2007-01-01

    Lax operator algebras were introduced by Krichever and Sheinman as a further development of I.Krichever's theory of Lax operators on algebraic curves. These are almost-graded Lie algebras of current type. In this article local cocycles and associated almost-graded central extensions are classified. It is shown that in the case that the corresponding finite-dimensional Lie algebra is simple the two-cohomology space is one-dimensional. An important role is played by the action of the Lie algebr...

  15. Extensive spinal epidural abscess complicated with hydrocephalus

    Directory of Open Access Journals (Sweden)

    Balan Corneliu

    2015-12-01

    Full Text Available Spinal epidural abscess is a rare but severe infection requiring prompt recognition in order to have a favorable outcome and appropriate treatment, mainly surgical. We present one of the largest extensions of such abscess in literature, involving the whole spine. No surgical treatment was tempted due to the involvement of 19 levels but antibiotics. The evolution of the lesion was complicated with hydrocephalus, by mechanism of cervical block of CSF flow, and needed first external derivation and later ventriculo-peritoneal drainage.

  16. High energy hadrons in extensive air showers

    Science.gov (United States)

    Tonwar, S. C.

    1985-01-01

    Experimental data on the high energy hadronic component in extensive air showers of energies approx. 10 to the 14 to 10 to the 16 eV when compared with expectations from Monte Carlo simulations have shown the observed showers to be deficient in high energy hadrons relative to simulated showers. An attempt is made to understand these anomalous features with more accurate comparison of observations with expectations, taking into account the details of the experimental system. Results obtained from this analysis and their implications for the high energy physics of particle interactions at energy approx. 10 to the 15 eV are presented.

  17. The Profound and Extensive Chinese Tea Culture

    Institute of Scientific and Technical Information of China (English)

    刘航

    2014-01-01

    Anyone who knows a little bit about Chinese culture usualy knows about Chinese tea culture.Chinese tea culture has a history of more than 4,000 years and stil emerges fresh and vigorous from the test of history. Chinese tea culture has played an important and indispensable role in Chinese culture. The extensiveness and profoundness of Chinese tea culture is unpaneled. Its importance to Chinese people is noticeable. Tea has surprising functions: it can not only refresh the body but also the mind. Tea is prevalent in and out of China and is loved by people throughout the world.

  18. Analytic extension of the nuclear algebraic potential

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenthaeler, R. (Departamento de Fisica Nuclear, Laboratorio do Pelletron, Universidade de Sao Paulo, Caixa Postal 20516, 01452-990 Sao Paulo, Sao Paulo (Brazil)); Gomes, L.C. (Grupo de Fisica Nuclear Teorica e Fenomenologia de Particulas Elementares Instituto de Fisica Universidade de Sao Paulo, Caixa Postal 20516, 01498-970 Sao Paulo, Sao Paulo (Brazil))

    1994-12-01

    An analytic extension of the nuclear algebraic potential in the complex energy and angular momentum planes is discussed and an approximation for the algebraic potential in agreement with the known analytic properties of the [ital S]-matrix is proposed. The invariance of the energy spectrum of the Coulomb part of the interaction is established. The results are applied to the Regge pole analysis of the [sup 12]C+[sup 24]Mg elastic collision at [ital E][sub [ital l][ital a][ital b

  19. Extensive Variation in Chromatin States Across Humans

    KAUST Repository

    Kasowski, M.

    2013-10-17

    The majority of disease-associated variants lie outside protein-coding regions, suggesting a link between variation in regulatory regions and disease predisposition. We studied differences in chromatin states using five histone modifications, cohesin, and CTCF in lymphoblastoid lines from 19 individuals of diverse ancestry. We found extensive signal variation in regulatory regions, which often switch between active and repressed states across individuals. Enhancer activity is particularly diverse among individuals, whereas gene expression remains relatively stable. Chromatin variability shows genetic inheritance in trios, correlates with genetic variation and population divergence, and is associated with disruptions of transcription factor binding motifs. Overall, our results provide insights into chromatin variation among humans.

  20. Generic modules for trivial extension algebras

    Institute of Scientific and Technical Information of China (English)

    杜先能

    1995-01-01

    Let A be a finite-dimensional algebra over an algebraically closed field. An indecomposable (right) ,4-module M is called generic provided M is infinite k-dimensional but finite length as (left) EndA(M)-module. Let R = A DA be the trivial extension algebra of A- Generic R-modules are constructed from generic A-modules using some functors between Mod A and Mod R. it is also proved that if A is a tame hereditary algebra, then R has only two generic modules.