Aroclor 1260

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Peter De B Harrington - One of the best experts on this subject based on the ideXlab platform.

  • determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid phase microextraction
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    : A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil.

  • Determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid-phase microextraction.
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was

Donna L Bedard - One of the best experts on this subject based on the ideXlab platform.

  • The Microbiology of Anaerobic PCB Dechlorination
    Organohalide-Respiring Bacteria, 2016
    Co-Authors: Jianzhong He, Donna L Bedard
    Abstract:

    The last few years have seen a great deal of progress in our understanding of microbial dechlorination of polychlorinated biphenyls (PCBs). Four new strains of Dehalococcoides mccartyi, representing all three phylogenetic subgroups, and a strain of “ Dehalobium chlorocoercia ” have been isolated and, together with two previously isolated strains of D. mccartyi , demonstrated to dechlorinate the commercial PCB mixture Aroclor 1260 . Complete genomes for five of these isolates have been published. In addition, members of the genera Dehalogenimonas and Dehalobacter have been implicated in the reductive dechlorination and respiration of PCBs. It is clear that D. mccartyi strains capable of dechlorinating Aroclor 1260 are widespread in freshwater environments, having been found in PCB-impacted sites in China, Germany, Singapore, and the USA. Pure strains of D. mccartyi that dechlorinate Aroclor 1260 by following different sets of dechlorination routes, i.e., PCB Dechlorination Processes H, N,Z, and variations of these are now available. A member of the Chloroflexi belonging to the m1/SF1 clade appears to be responsible for the dechlorination of Aroclor 1254 in a marine site. The discovery and characterization of the first three PCB reductive dehalogenases constitute a new milestone in the field. PcbA1 , PcbA4 , and PcbA5 dechlorinate Aroclor 1260 with distinct regiospecificities and prove that individual RDases can carry out the complex dechlorination of dozens of PCB congeners described by the PCB dechlorination processes . Each of these three PCB dechlorinases is bifunctional and can also dechlorinate tetrachloroethene (PCE ). PCB dechlorinators with such bifunctional PCB/PCE RDases can be selectively enriched, transferred repeatedly, and grown to high cell densities with PCE as the sole electron acceptor with no possibility of losing their ability to dechlorinate PCBs. This property makes them ideal candidates for use in bioremediation of PCBs.

  • dehalococcoides mccartyi strain jna in pure culture extensively dechlorinates Aroclor 1260 according to polychlorinated biphenyl pcb dechlorination process n
    Environmental Science & Technology, 2014
    Co-Authors: Sarah L Laroe, Ashwana D Fricker, Donna L Bedard
    Abstract:

    We isolated Dehalococcoides mccartyi strain JNA from the JN mixed culture which was enriched and maintained using the highly chlorinated commercial PCB mixture Aroclor 1260 for organohalide respiration. For isolation we grew the culture in minimal liquid medium with 2,2′,3,3′,6,6′-hexachlorobiphenyl (236–236-CB)(20 μM) as respiratory electron acceptor. We repeatedly carried out serial dilutions to extinction and recovered dechlorination activity from transfers of 10–7 and 10–8 dilutions. Fluorescence microscopy, DGGE and RFLP analysis of PCR amplified16S rRNA genes, and multilocus sequence typing of three housekeeping genes confirmed culture purity. No growth occurred on complex media. JNA dechlorinated most hexa- and heptachlorobiphenyls in Aroclor 1260 (50 μg/mL) leading to losses of 51% and 20%, respectively. Dechlorination was predominantly from flanked meta positions of 34-, 234-, 235-, 236-, 245-, 2345-, 2346-, and 2356-chlorophenyl rings, as indicated by the underscores. The major products were 24–...

  • Sediment-free anaerobic microbial enrichments with novel dechlorinating activity against highly chlorinated commercial PCBs
    Journal of Chemical Technology & Biotechnology, 2012
    Co-Authors: Vlasta Dudkova, Kateřina Demnerová, Donna L Bedard
    Abstract:

    BACKGROUND: Reductive dehalogenation by anaerobic bacteria is a promising method of detoxifying polychlorinated biphenyls (PCBs) in aquatic sediments. PCB-contaminated sediment from Str ´ a y ´ y Sewer river (Slovakia) was used as an inoculum to develop stable sediment-free enrichments with dechlorination activity directed against the commercial PCB mixture Aroclor 1260. RESULTS: Characterization of the PCBs at the site revealed that 45 mol% of the PCBs were dichlorobiphenyls and 62% of the chlorines were in the ortho-position. Both findings are characteristic of extensive dechlorination insitu. Sedimentfree enrichments with stable dechlorinating activity against Aroclor 1260 were developed by a series of transfers. These enrichments targeted hexa- through nonachlorobiphenyls and dechlorinated them to tri- through hexachlorobiphenyls by removal of flanked meta -a ndpara- chlorines when pyruvate or lactate was added as a carbon source. The known haloprimers: 4,4 � -dibromobiphenyl and 2,6-dibromobiphenyl did not influence the rate or pattern of dechlorination. The chlorophenyl rings targeted were 2,3,4,5,6- (23456-), 2346-, 2345-, 234- and 245-. CONCLUSION: The PCB dechlorination carried out by these enrichments is novel and does not correspond to any of the previously identified microbial PCB dechlorination processes or their combination. Natural attenuation processes may be under way at the Str ´ a y zsk ´ y Sewer river site. c � 2012 Society of Chemical Industry

  • dehalococcoides sp strain cbdb1 extensively dechlorinates the commercial polychlorinated biphenyl mixture Aroclor 1260
    Applied and Environmental Microbiology, 2009
    Co-Authors: Lorenz Adrian, Vlasta Dudkova, Katařina Demnerova, Donna L Bedard
    Abstract:

    “Dehalococcoides” sp. strain CBDB1 in pure culture dechlorinates a wide range of PCB congeners with three to eight chlorine substituents. Congener-specific high-resolution gas chromatography revealed that CBDB1 extensively dechlorinated both Aroclor 1248 and Aroclor 1260 after four months of incubation. For example, 16 congeners comprising 67.3% of the total PCBs in Aroclor 1260 were decreased by 64%. We confirmed the dechlorination of 43 different PCB congeners. The most prominent dechlorination products were 2,3′,5-chlorinated biphenyl (25-3-CB) and 24-3-CB from Aroclor 1248 and 235-25-CB, 25-25-CB, 24-25-CB, and 235-236-CB from Aroclor 1260. Strain CBDB1 removed flanked para chlorines from 3,4-, 2,4,5-, and 3,4,5-chlorophenyl rings, primarily para chlorines from 2,3,4,5-chlorophenyl rings, primarily meta chlorines from 2,3,4- and 2,3,4,6-chlorophenyl rings, and either meta or para chlorines from 2,3,4,5,6-chlorophenyl rings. The site of attack on the 2,3,4-chorophenyl ring was heavily influenced by the chlorine configuration on the opposite ring. This dechlorination pattern matches PCB Process H dechlorination, which was previously observed in situ both in the Acushnet Estuary (New Bedford, MA) and in parts of the Hudson River (New York). Accordingly, we propose that Dehalococcoides bacteria similar to CBDB1 are potential agents of Process H PCB dechlorination in the environment. This is the first time that a complex naturally occurring PCB dechlorination pattern has been reproduced in the laboratory using a single bacterial strain.

  • A case study for microbial biodegradation: anaerobic bacterial reductive dechlorination of polychlorinated biphenyls-from sediment to defined medium.
    Annual Review of Microbiology, 2008
    Co-Authors: Donna L Bedard
    Abstract:

    The history of anaerobic microbial polychlorinated biphenyl (PCB) dechlorination is traced over 20 years using a case study of PCB dechlorination in the Housatonic River (Massachusetts) as an example. The history progresses from the characterization of the PCBs in the sediment, to cultivation in sediment microcosms, to the identification of four distinct types of PCB dechlorination, to a successful field test, to the cultivation in defined medium of the organisms responsible for extensive dechlorination of Aroclor 1260, and finally to the identification of a Dehalococcoides population that links its growth to the dechlorination of Aroclor 1260. Other PCB dechlorinators have also been identified. Two bacterial strains, o-17 and DF-1, that link their growth to the dechlorination of several PCB congeners belong to a novel clade of putative dechlorinating bacteria within the phylum Chloroflexi. Dehalococcoides ethenogenes strain 195 also dechlorinates several PCB congeners when grown on chlorinated ethenes. E...

Mengliang Zhang - One of the best experts on this subject based on the ideXlab platform.

  • determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid phase microextraction
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    : A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil.

  • Determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid-phase microextraction.
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was

Kevin R Sowers - One of the best experts on this subject based on the ideXlab platform.

  • enhanced reductive dechlorination of polychlorinated biphenyl impacted sediment by bioaugmentation with a dehalorespiring bacterium
    Environmental Science & Technology, 2011
    Co-Authors: Rayford B Payne, Kevin R Sowers
    Abstract:

    Anaerobic reductive dehalogenation of commercial PCBs such as Aroclor 1260 has a critical role of transforming highly chlorinated congeners to less chlorinated congeners that are then susceptible to aerobic degradation. The efficacy of bioaugmentation with the dehalorespiring bacterium Dehalobium chlorocoercia DF1 was tested in 2-L laboratory mesocosms containing sediment contaminated with weathered Aroclor 1260 (1.3 ppm) from Baltimore Harbor, MD. Total penta- and higher chlorinated PCBs decreased by approximately 56% (by mass) in bioaugmented mesocosms after 120 days compared with no activity observed in unamended controls. Bioaugmentation with DF-1 enhanced the dechlorination of doubly flanked chlorines and stimulated the dechlorination of single flanked chlorines as a result of an apparent synergistic effect on the indigenous population. Addition of granulated activated carbon had a slight stimulatory effect indicating that anaerobic reductive dechlorination of PCBs at low concentrations was not inhib...

  • Effects of bioaugmentation on indigenous PCB dechlorinating activity in sediment microcosms
    Water Research, 2011
    Co-Authors: Sonja K Fagervold, Joy E. M. Watts, Kevin R Sowers
    Abstract:

    Bioaugmentation is an attractive mechanism for reducing recalcitrant pollutants in sediments, especially if this technology could be applied in situ. To examine the potential effectiveness of a bioaugmentation strategy for PCB contamination, PCB dehalorespiring populations were inoculated into Baltimore Harbor sediment microcosms. A culture containing the two most predominant indigenous PCB dehalorespiring microorganisms and a culture containing a strain with a rare ortho dechlorination activity and a non-indigenous strain that attacks double-flanked chlorines, were inoculated into sediment microcosms amended with 2,2',3,5,5',6-hexachlorobiphenyl (PCB 151) and Aroclor 1260. Although we observed a similar reduction in the concentration of PCB 151 in all microcosms at day 300, a reduced lag time for dechlorination activity was observed only in the bioaugmented microcosms and the pattern of dechlorination was altered depending on the initial combination of microorganisms added. Dechlorination of Aroclor 1260 was most extensive when dehalorespiring microorganisms were added to sediment. Overall numbers of dehalorespiring microorganisms in both bioaugmented and non-bioaugmented microcosms increased 100- and 1000-fold with PCB 151 and Aroclor 1260, respectively, and they were sustained for the full 300 days of the experiments. The ability of bioaugmentation to redirect dechlorination reactions in the sediment microcosms indicates that the inoculated PCB dehalorespiring microorganisms effectively competed with the indigenous microbial populations and cooperatively enhanced or altered the specific pathways of PCB dechlorination. These observations indicate that bioaugmentation with PCB dehalorespiring microorganisms is a potentially tractable approach for in situ treatment of PCB impacted sites.

  • microbial reductive dechlorination of Aroclor 1260 in baltimore harbor sediment microcosms is catalyzed by three phylotypes within the phylum chloroflexi
    Applied and Environmental Microbiology, 2007
    Co-Authors: Sonja K Fagervold, Kevin R Sowers
    Abstract:

    The specific dechlorination pathways for Aroclor 1260 were determined in Baltimore Harbor sediment microcosms developed with the 11 most predominant congeners from this commercial mixture and their resulting dechlorination intermediates. Most of the polychlorinated biphenyl (PCB) congeners were dechlorinated in the meta position, and the major products were tetrachlorobiphenyls with unflanked chlorines. Using PCR primers specific for the 16S rRNA genes of known PCB-dehalogenating bacteria, we detected three phylotypes within the microbial community that had the capability to dechlorinate PCB congeners present in Aroclor 1260 and identified their selective activities. Phylotype DEH10, which has a high level of sequence identity to Dehalococcoides spp., removed the double-flanked chlorine in 234-substituted congeners and exhibited a preference for para-flanked meta-chlorines when no double-flanked chlorines were available. Phylotype SF1 had similarity to the o-17/DF-1 group of PCB-dechlorinating bacteria. Phylotype SF1 dechlorinated all of the 2345-substituted congeners, mostly in the double-flanked meta position and 2356-, 236-, and 235-substituted congeners in the ortho-flanked meta position, with a few exceptions. A phylotype with 100% sequence identity to PCB-dechlorinating bacterium o-17 was responsible for an ortho and a double-flanked meta dechlorination reaction. Most of the dechlorination pathways supported the growth of all three phylotypes based on competitive PCR enumeration assays, which indicates that PCB-impacted environments have the potential to sustain populations of these PCB-dechlorinating microorganisms. The results demonstrate that the variation in dechlorination patterns of congener mixtures typically observed at different PCB impacted sites can potentially be mediated by the synergistic activities of relatively few dechlorinating species.

  • microbial reductive dechlorination of Aroclor 1260 in anaerobic slurries of estuarine sediments
    Applied and Environmental Microbiology, 1998
    Co-Authors: Qingzhong Wu, Kevin R Sowers
    Abstract:

    Reductive dechlorination of Aroclor 1260 was investigated in anaerobic slurries of estuarine sediments from Baltimore Harbor (Baltimore, Md.). The sediment slurries were amended with 800 ppm Aroclor 1260 with and without the addition of 350 μM 2,3,4,5-tetrachlorobiphenyl (2,3,4,5-CB) or 2,3,5,6-tetrachlorobiphenyl (2,3,5,6-CB) and incubated in triplicate at 30°C under methanogenic conditions in an artificial estuarine medium. After 6 months, extensive meta dechlorination and moderate ortho dechlorination of Aroclor 1260 occurred in all incubated cultures except for sterilized controls. Overall, total chlorines per biphenyl decreased by up to 34%. meta chlorines per biphenyl decreased by 65, 55, and 45% and ortho chlorines declined by 18, 12, and 9%, respectively, when 2,3,4,5-CB, 2,3,5,6-CB, or no additional congener was supplied. This is the first confirmed report of microbial ortho dechlorination of a commercial polychlorinated biphenyl mixture. In addition, compared with incubated cultures supplied with Aroclor 1260 alone, the dechlorination of Aroclor 1260 plus 2,3,4,5-CB or 2,3,5,6-CB occurred with shorter lag times (31 to 60 days versus 90 days) and was more extensive, indicating that the addition of a single congener stimulated the dechlorination of Aroclor 1260.

Jennifer R Bowman - One of the best experts on this subject based on the ideXlab platform.

  • determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid phase microextraction
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    : A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil.

  • Determination of Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid-phase microextraction.
    IEEE Journal of Solid-state Circuits, 2014
    Co-Authors: Mengliang Zhang, Glen P Jackson, Natalie A Kruse, Jennifer R Bowman, Peter De B Harrington
    Abstract:

    A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid-phase microextraction. Nonequilibrium headspace solid-phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9-65.7%. Two-way extracted ion chromatogram data were used to construct calibration curves. The relative error was