| 1. |
- Chartrand, Michelle, et al.
(författare)
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Compound specific isotope analysis of hexachlorocyclohexane isomers : a method for source fingerprinting and field investigation of in situ biodegradation
- 2015
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Ingår i: Rapid Communications in Mass Spectrometry. - : John Wiley & Sons. - 0951-4198 .- 1097-0231. ; 29:6, s. 505-514
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Tidskriftsartikel (refereegranskat)abstract
- RATIONALE: The manufacturing and uses of hexachlorocyclohexane (HCH) have resulted in a serious environmentalchallenge and legacy. This study highlights the ability of compound specific isotope analysis (CSIA) to distinguishamong various HCH sources and to support the evaluation of the potential for in situ biodegradation in contaminatedgroundwater.METHODS: Tests were conducted to verify the absence of significant isotope fractionation during HCH sample preconcentrationincluding dichloromethane extraction, solvent exchange into iso-octane, and H2SO4 clean-up, and analysisby gas chromatography/combustion-isotope ratio mass spectrometry (GC/C-IRMS). The method was then applied tofour Technical Grade (TG) HCH mixtures procured from different sources and to groundwater samples from acontaminated site.RESULTS: The pre-concentration method enabled determination of carbon isotope ratios (δ13C values) of HCH isomerswith no significant isotopic fractionation. The TG-HCH mixtures had significantly different δ13C values. Moreover, forany given TG-HCH, all isomers had δ13C values within 1.1‰ of each other – a distinctly uniform fingerprint. At theHCH-contaminated field site, compared with source wells, downgradient wells showed significant (up to 5.1‰)enrichment in 13C and the δ13C values of the HCH isomers were significantly different from each other.CONCLUSIONS: A method was successfully developed for the CSIA of HCH isomers that showed potential for HCHsource differentiation and identification of HCH in situ biodegradation. At the HCH-contaminated site, the observedpreferential isotopic enrichment of certain isomers relative to others for a given source allows differentiation betweenbiodegraded and non-biodegraded HCH.
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| 2. |
- Bidleman, Terry F, et al.
(författare)
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Chiral Pesticides in Soil and Water and Exchange with the Atmosphere
- 2002
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Ingår i: TheScientificWorldJOURNAL. - : Hindawi Limited. ; 2, s. 357-373
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Tidskriftsartikel (refereegranskat)abstract
- The enantiomers of chiral pesticides are often metabolised at different rates in soil and water, leading to nonracemic residues. This paper reviews enantioselective metabolism of organochlorine pesticides (OCPs) in soil and water, and the use of enantiomers to follow transport and fate processes. Residues of chiral OCPs and their metabolites are frequently nonracemic in soil, although exceptions occur in which the OCPs are racemic. In soils where enantioselective degradation and/or metabolite formation has taken place, some OCPs usually show the same degradation preference — e.g., depletion of (+)trans-chlordane (TC) and (-)cis-chlordane (CC), and enrichment of the metabolite (+)heptachlor exo-epoxide (HEPX). The selectivity is ambivalent for other chemicals; preferential loss of either (+) or (-)o,p?-DDT and enrichment of either (+) or (-)oxychlordane (OXY) occurs in different soils. Nonracemic OCPs are found in air samples collected above soil which contains nonracemic residues. The enantiomer profiles of chlordanes in ambient air suggests that most chlordane in northern Alabama air comes from racemic sources (e.g., termiticide emissions), whereas a mixture of racemic and nonracemic (volatilisation from soil) sources supplies chlordane to air in the Great Lakes region. Chlordanes and HEPX are also nonracemic in arctic air, probably the result of soil emissions from lower latitudes. The (+) enantiomer of a-hexachlorocyclohexane (a-HCH) is preferentially metabolised in the Arctic Ocean, arctic lakes and watersheds, the North American Great Lakes, and the Baltic Sea. In some marine regions (the Bering and Chukchi Seas, parts of the North Sea) the preference is reversed and (-)a-HCH is depleted. Volatilisation from seas and large lakes can be traced by the appearance of nonracemic a-HCH in the air boundary layer above the water. Estimates of microbial degradation rates for a-HCH in the eastern Arctic Ocean and an arctic lake have been made from the enantiomer fractions (EFs) and mass balance in the water column. Apparent pseudo first-order rate constants in the eastern Arctic Ocean are 0.12 year-1 for (+)a-HCH, 0.030 year-1 for (-)a-HCH, and 0.037 year-1 for achiral ?-HCH. These rate constants are 3–10 times greater than those for basic hydrolysis in seawater. Microbial breakdown may compete with advective outflow for long-term removal of HCHs from the Arctic Ocean. Rate constants estimated for the arctic lake are about 3–8 times greater than those in the ocean.
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| 3. |
- Okeme, Joseph, et al.
(författare)
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Gas chromatographic estimation of vapor pressures and octanol-air partition coefficients of semivolatile organic compounds of emerging concern
- 2020
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Ingår i: Journal of Chemical and Engineering Data. - Washington, DC, USA : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 65:5, s. 2467-2475
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Tidskriftsartikel (refereegranskat)abstract
- The subcooled liquid-phase vapor pressures (pL298/Pa) and octanol–air partition coefficients (KOA298) at T/K = 298, enthalpies of vaporization (ΔVAPH/kJ·mol–1), and internal energies of phase transfer from octanol to air (ΔOAU/kJ·mol–1) were estimated for synthetic musks, novel brominated flame retardants (N-BFR), organophosphate esters, and ultraviolet filters using the capillary gas chromatographic retention time (GC-RT) method. These compounds, which spanned approximately six and three orders of magnitude for pL298/Pa and KOA298, respectively, were co-chromatographed with one of three reference compounds to give initial estimates of properties at T/K = 298. The initial GC-RT property estimates were subsequently calibrated using 18 compounds that spanned 6 log units for pL298/Pa and 13 compounds covering 4 log units for KOA298. The calibrated log10pL298/Pa values estimated here ranged from 0.14 ± 0.19 to −9.19 ± 0.29 for cyclopentadecanone to syn-dechlorane plus (syn-DDC-CO), respectively, while the range of log10KOA298 values was 6.59 ± 0.26 to 11.40 ± 0.23 for cyclopentadecanone to 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99), respectively. The calibrated GC-RT-derived values were highly correlated with, and were within an average of 0.70 log units of, the literature data for compounds with well-established pL298/Pa and KOA298 measured or derived using non-GC-RT methods. Nonpolar compounds were used in this study to estimate the target polar compound data, which may introduce systematic errors. However, the comparison of our GC-RT results against the literature non-GC-RT values shows that the GC-RT methods performed similarly well for estimating both polar and nonpolar target compounds studied in this work.
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| 4. |
- Rodgers, Timothy F.M., et al.
(författare)
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Novel Bayesian Method to Derive Final Adjusted Values of Physicochemical Properties : Application to 74 Compounds
- 2021
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 55:18, s. 12302-12316
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Tidskriftsartikel (refereegranskat)abstract
- Accurate values of physicochemical properties are essential for screening semivolatile organic compounds for human and environmental hazard and risk. In silico approaches for estimation are widely used, but the accuracy of these and measured values can be difficult to ascertain. Final adjusted values (FAVs) harmonize literature-reported measurements to ensure consistency and minimize uncertainty. We propose a workflow, including a novel Bayesian approach, for estimating FAVs that combines measurements using direct and indirect methods and in silico values. The workflow was applied to 74 compounds across nine classes to generate recommended FAVs (FAVRs). Estimates generated by in silico methods (OPERA, COSMOtherm, EPI Suite, SPARC, and polyparameter linear free energy relationships (pp-LFER) models) differed by orders of magnitude for some properties and compounds and performed systematically worse for larger, more polar compounds. COSMOtherm and OPERA generally performed well with low bias although no single in silico method performed best across all compound classes and properties. Indirect measurement methods produced highly accurate and precise estimates compared with direct measurement methods. Our Bayesian method harmonized measured and in silico estimated physicochemical properties without introducing observable biases. We thus recommend use of the FAVRs presented here and that the proposed Bayesian workflow be used to generate FAVRs for SVOCs beyond those in this study.
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| 5. |
- Wong, Fiona, et al.
(författare)
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Air-Water Exchange of Anthropogenic and Natural Organohalogens on International Polar Year (IPY) Expeditions in the Canadian Arctic
- 2011
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Ingår i: Environmental Science and Technology. - : AMER CHEMICAL SOC. - 0013-936X .- 1520-5851. ; 45:3, s. 876-881
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Tidskriftsartikel (refereegranskat)abstract
- Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L-1) were as follows: alpha-hexachlorocyclohexane (alpha-HCH) 465-1013, gamma-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: alpha-HCH 7.5-48, gamma-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of alpha-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The alpha-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 +/- 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 +/- 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic alpha-HCH from surface water (EF = 0.457 +/- 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means +/- SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: alpha-HCH 6.8 +/- 3.2 (2.7-13), gamma-HCH 0.76 +/- 0.40 (0.26-1.4), HCB -9.6 +/- 2.7 (-6.1 to -15), DBA 1.2 +/- 0.69 (0.04-2.0), and TBA 0.46 +/- 1.1 ng m(-2) d(-1) (-1.6 to 2.0).
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| 6. |
- Wong, Fiona, et al.
(författare)
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Comparison of micrometeorological and two-film estimates of air-water gas exchange for alpha-hexachlorocyclohexane in the Canadian archipelago
- 2012
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 19:6, s. 1908-1914
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Tidskriftsartikel (refereegranskat)abstract
- The air-sea gas exchange of alpha-hexachlorocyclohexane (alpha-HCH) in the Canadian Arctic was estimated using a micrometeorological approach and the commonly used Whitman two-film model. Concurrent shipboard measurements of alpha-HCH in air at two heights (1 and 15 m) and in surface seawater were conducted during the Circumpolar Flaw Lead study in 2008. Sampling was carried out during eight events in the early summer time when open water was encountered. The micrometeorological technique employed the vertical gradient in air concentration and the wind speed to estimate the flux; results were corrected for atmospheric stability using the Monin-Obukhov stability parameter. The Whitman two-film model used the concentrations of alpha-HCH in surface seawater, in bulk air at 1 and 15 m above the surface, and the Henry's law constant adjusted for temperature and salinity to derive the flux. Both approaches showed that the overall net flux of alpha-HCH was from water to air. Mean fluxes calculated using the micrometeorological technique ranged from -3.5 to 18 ng m(-2) day(-1) (mean 7.4), compared to 3.5 to 14 ng m(-2) day(-1) (mean 7.5) using the Whitman two-film model. Flux estimates for individual events agreed in direction and within a factor of two in magnitude for six of eight events. For two events, fluxes estimated by micrometeorology were zero or negative, while fluxes estimated with the two-film model were positive, and the reasons for these discrepancies are unclear. Improvements are needed to shorten air sampling times to ensure that stationarity of meteorological conditions is not compromised over the measurement periods. The micrometeorological technique could be particularly useful to estimate fluxes of organic chemicals over water in situations where no water samples are available.
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| 7. |
- Bidleman, Terry Frank, et al.
(författare)
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Chiral Chemicals as Tracers of Atmospheric Sources and Fate Processes in a World of Changing Climate
- 2013
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Ingår i: Mass Spectrometry. - 2186-5116. ; 2:19, Special Issue: Proceedings of 19th International Mass Spectrometry Conference, s. S0019-
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Tidskriftsartikel (refereegranskat)abstract
- Elimination of persistent organic pollutants (POPs) under national and international regulations reduces “primary” emissions, but “secondary” emissions continue from residues deposited in soil, water, ice and vegetation during former years of usage. In a future, secondary source controlled world, POPs will follow the carbon cycle and biogeochemical processes will determine their transport, accumulation and fate. Climate change is likely to affect mobilisation of POPs through e.g., increased temperature, altered precipitation and wind patterns, flooding, loss of ice cover in polar regions, melting glaciers, and changes in soil and water microbiology which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their ability to distinguish racemic (newly released or protected from microbial attack) and nonracemic (microbially degraded) sources. This paper discusses the rationale for this approach and suggests applications where chiral POPs could aid investigation of climate-mediated exchange and degradation processes. Multiyear measurements of two chiral POPs, trans-chlordane and α-HCH, at a Canadian Arctic air monitoring station show enantiomer compositions which cycle seasonally, suggesting varying source contributions which may be under climatic control. Large-scale shifts in the enantioselective metabolism of chiral POPs in soil and water might influence the enantiomer composition of atmospheric residues, and it would be advantageous to include enantiospecific analysis in POPs monitoring programs.
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| 8. |
- Bidleman, Terry F, et al.
(författare)
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Chiral persistent organic pollutants as tracers of atmospheric sources and fate : review and prospects for investigating climate change influences
- 2012
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Ingår i: Atmospheric Pollution Research. - 1309-1042. ; 3:4, s. 371-382
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Tidskriftsartikel (refereegranskat)abstract
- Elimination of persistent organic pollutants (POPs) under national and international controls reduces “primary” emissions, but “secondary” emissions continue from residues deposited in soil, water, ice and vegetation during former years of high usage. Secondary sources are expected to dominate in the future, when POPs transport and accumulation will be controlled by air–surface exchange and the biogeochemical cycle of organic carbon. Climate change is likely to affect mobilization of POPs through, e.g., increased temperature, loss of ice cover in polar regions, melting glaciers and changes in soil and water microbiology which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their ability to distinguish racemic (newly released or protected from microbial attack) and nonracemic (microbially altered) sources. Here we explain the rationale for this approach and suggest applications where chiral POPs could aid investigation of climate–mediated exchange and degradation processes. Examples include distinguishing agricultural vs. non–agricultural and recently used vs. residual pesticides, degradation and sequestration processes in soil, historical vs. recent atmospheric deposition, sources in arctic air and influence of ice cover on volatilization.
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| 9. |
- Bidleman, Terry F., et al.
(författare)
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Is There Still “New” DDT in North America? An Investigation Using Proportions of DDT Compounds
- 2013
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Ingår i: Occurrence, fate and impact of atmospheric pollutants on environmental and human health. - Washington, DC : American Chemical Society (ACS). - 9780841228900 - 9780841228917 ; , s. 153-181
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Bokkapitel (refereegranskat)abstract
- Usage of DDT ceased over four decades ago in Canada and the United States, and since 2000 in Mexico. Potential sources in the North American atmosphere today include emissions of legacy residues from soils and long-range transport from other countries where DDT is still used or recently banned. Distinction of source types is investigated here using proportions of p,p'-DDT, o,p'-DDT, p,p'-DDE and p,p'-DDD. The relative volatilization of DDT compounds can be accurately described by their subcooled liquid vapor pressures (PO; e.g., (p,p'-DDT/p,p'-DDE)AIR = (p,p'-DDT/p,p'-DDE)son. x PL, (DDT)/P-L,P-DDE. Using this model, the expected proportions in air due to volatilization from technical DDT and from soils in Canada, the U.S.A. and Mexico were estimated and expressed as the fractions F-DDTE = p,p'-DDT/(p,p'-DDT + P,P'-DDE), F-DDTO = p,p1-DDT/(p,p'-DDT + o,p'-DDT), and FDDTD = p,p1-DDT/(p,p'-DDT + p,p1-DDD). FDDTE, FDDTO and FDDTD predicted from soil emissions were compared to compound fractions in ambient air sampled at the Integrated Atmospheric Deposition Network (IADN) of stations on the Great Lakes between Canada and the U.S.A., and at arctic monitoring stations. FDDTE in air at IADN stations on lakes Erie, Ontario, Michigan and Huron were lower than in technical DDT vapor. This is consistent with emissions of aged residues from agricultural land and urban centers near these lakes. By comparison, FDDTE values were higher at stations on Lake Superior where atmospheric DDT is likely due to long-range transport rather than regional soil emissions. FDDTE increased from the early 1990s to 2005 at the Lake Superior stations and at the Canadian arctic station Alert between 2002-2005, whereas a significant decline in FDDTE was observed at the Norwegian arctic station Zeppelin Mountain. The mean FDDTO in air at IADN stations were consistent with either soil emissions or technical DDT composition, but annual values showed significant downward trends at two Canadian stations, and also decreased with time at Zeppelin Mountain (but not at Alert). These trends might signify contribution from dicofol-type DDT sources, which have a lower FDDTO than technical DDT or soil emissions, or preferential degradation of p,p'-DDT vs. o,p'-DDT over time. FDDTD in air at IADN stations were lower than in technical DDT vapor, showing the influence of soil sources. The enantiomer proportions of the chiral compounds o,p'-DDT and o,p1-DDD were nonracemic in some soils and ambient air, but enantiospecific analysis has not been done for IADN air samples. It is suggested that isomer, parent/metabolite and enantiomer composition information be incorporated into air monitoring programs to help identify sources.
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| 10. |
- Bidleman, Terry Frank, et al.
(författare)
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Scavenging amphipods : sentinels for penetration of mercury and persistent organic chemicals into food webs of the deep arctic ocean
- 2013
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Ingår i: Environmental Science and Technology. - Washington : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 47:11, s. 5553-5561
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Tidskriftsartikel (refereegranskat)abstract
- Archived specimens of the scavenging amphipod Eurythenes gryllus, collected from 2075 to 4250 m below the surface on five expeditions to the western and central Arctic Ocean between 1983 and 1998, were analyzed for total mercury (∑Hg), methyl mercury (MeHg), polychlorinated biphenyls (PCBs) and other industrial or byproduct organochlorines (chlorobenzenes, pentachloroanisole, octachlorostyrene), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). Median ∑Hg concentrations ranged from 70 to 366 ng g(-1) wet weight (ww). MeHg concentrations (3.55 to 23.5 ng g(-1) ww) accounted for 1.7 to 20.1% (median 3.7%) of ∑Hg. ∑Hg and MeHg were positively and significantly correlated with ww (∑Hg r(2) = 0.18, p = 0.0004, n = 63; MeHg r(2) = 0.42, p = 0.0004, n = 25), but not significantly with δ(13)C nor δ(15)N. Median concentrations of total persistent organic pollutants (POPs) ranged from 9750 to 156 000 ng g(-1) lipid weight, with order of abundance: ∑TOX (chlorobornanes quantified as technical toxaphene) > ∑PCBs > ∑DDTs > ∑chlordanes > ∑mirex compounds > ∑BDEs ∼ ∑chlorobenzenes ∼ octachlorostyrene > α-hexachlorocyclohexane ∼ hexachlorobenzene ∼ pentachloroanisole. Enantioselective accumulation was found for the chiral OCPs o,p'-DDT, cis- and trans-chlordane, nonachlor MC6 and oxychlordane. Lipid-normalized POPs concentrations were elevated in amphipods with lipid percentages ≤10%, suggesting that utilization of lipids resulted in concentration of POPs in the remaining lipid pool. Multidimensional Scaling (MDS) analysis using log-transformed physiological variables and lipid-normalized organochlorine concentrations distinguished amphipods from the central vs western arctic stations. This distinction was also seen for PCB homologues, whereas profiles of other compound classes were more related to specific stations rather than central-west differences.
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