| 1. |
- Dahlén, Johan, et al.
(författare)
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Determination of the molecular weight of fulvic acids by UV/VIS spectroscopy
- 1999
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Ingår i: Chemosphere. - 0045-6535 .- 1879-1298. ; 38:4, s. 783-794
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Tidskriftsartikel (refereegranskat)abstract
- Partial least squares (PLS) modeling was applied to investigate number-average molecular weights (Mn) and weight-average molecular weights (Mw) of fulvic acids (FAs) in relation to the corresponding UVNIS spectra. The Mn and Mw values were determined by size exclusion chromatography (SEC). The impact of pH control, wavelength range and density as well as smoothing and derivation of spectra were tested. It was found that PLS models based on absorbance spectra can be a fast and powerful complement to existing techniques employed for determination of molecular weights of FAs. Control of pH of the FA solutions is important for the performance of the models. The models were also compared with the best univariate alternatives.
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| 2. |
- Engwall, Magnus, 1965-, et al.
(författare)
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Levels of dioxin-like compounds in sewage sludge determined with a bioassay based on EROD induction in chicken embryo liver cultures
- 1999
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Ingår i: Chemosphere. - 0045-6535 .- 1879-1298. ; 38:10, s. 2327-2343
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Tidskriftsartikel (refereegranskat)abstract
- A bioassay for the detection of dioxin-like compounds was used to estimate levels in sewage sludge from Swedish sewage treatment plants (STPs). The sludge extracts were HPLC-separated into three fractions containing a) monoaromatic/aliphatic, b) diaromatic (e.g. polychlorinated biphenyls [PCBs], polychlorinated dibenzodioxins and polychlorinated dibenzofurans [PCDDs/Fs]), and c) polyaromatic compounds (e.g. polycyclic aromatic hydrocarbons [PAHs]). The bioassay, which is based on EROD (7-ethoxyresorufin O-deethylase) induction in cultured chicken embryo livers detected dioxin-like activity in all unfractionated extracts and in the di- and polyaromatic fractions of all sludge extracts, but not in the monoatomatic/aliphatic fractions. The levels ranged between 6 and 109 pg bio-TEQ/g sludge (d.w.). In sediment samples from rural lakes in Sweden, levels of about 5 pg bio-TEQ/g (d.w.) have been found. The polyaromatic fractions of the sludge samples were potent in the bioassay, probably due to various PAHs and other polyaromatics in the sludge. The levels of six PAHs that are screened for in the sludge at Swedish STPs accounted for only 3-10% of the observed EROD-induction by the polyaromatic fractions. Consequently, many other polyaromatic EROD-inducing compounds were present in the sludge. Inclusion of a biological test like the chicken embryo liver bioassay in the screening of sludge would improve the ability to detect the presence of bioactive dioxin-like compounds. A theoretical estimation of bio-TEQ concentrations in farm-soil following long-term application of sludge with bio-TEQ concentrations similar to those observed in this investigation indicated that the bio-TEQ levels in soil would increase very slowly over time. The chicken embryo liver bioassay proved useful in assessing levels of dioxin-like compounds in sewage sludge and it gives valuable complementary information to chemical analysis data.
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| 3. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Patterns and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans found in soil and sediment samples in southern Mississippi
- 1996
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 32:3, s. 421-432
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Tidskriftsartikel (refereegranskat)abstract
- Using hierarchical cluster analysis and Principal Component Analysis (PCA), sediment and soil samples from the State of Mississippi were compared with the effluents of a pulp mill, a potential point source. Additionally, data of many known sources of PCDD/PCDF from the scientific literature were evaluated. Both methods were able to distinguish between different matrices with known PCDD/PCDF contamination (e.g. PCP, PCB, kraft pulp mill effluents). In some instances, a specific PCDD/PCDF source could be correlated to an environmental sample, e.g. the pattern of a U.S, brand of pentachlorophenate was found in sediment samples. None of the mathematical and statistical techniques could identify the pulp mill as the source of the PCDD/PCDF in the sediments and soils in the floodplain.
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| 4. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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PCDD, PCDF, and PCB in farm-raised catfish from southeast United States - Concentrations, sources, and CYP1A induction
- 1998
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 37:9-12, s. 1645-1656
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Tidskriftsartikel (refereegranskat)abstract
- Nine catfish fillets, three catfish nuggets, two feed samples, and one pond sediment were analyzed for PCDD, PCDF, and-PCB. Farm-raised catfish from Mississippi, Alabama, and Arkansas contained significant levels of 2,3,7,8-substituted PCDD and PCDF. In addition, a large number of non-2,3,7,8-substituted congeners were present in all samples. The catfish fillets and catfish nuggets also contained high concentrations of dioxin-like PCB, as well as a number of non-dioxin-like PCB. The TEQ based on PCDD and PCDF ranged from 9.5 to 43.0 pg/g lipid and the TEQ based on PCB ranged from 0.45 to 4.9 pg/g lipid for all catfish samples. The dioxin-like PCB contributed 4-16% to the total TEQ (PCDD/PCDF/PCB) for the catfish samples. The major source for the PCDD, PCDF, and PCB appears to be from feed and not from pond sediment. Immunoreactive CYP1A protein was elevated 2.5 fold in the pond-raised catfish compared to the aquarium-raised one. The results of this study suggest that the PCDD/PCDF are more important than the PCB in the CYP1A induction.
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| 5. |
- Fiedler, Heidelore, 1953-, et al.
(författare)
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Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) in food samples collected in southern Mississippi, USA
- 1997
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 34:5-7, s. 1411-1419
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Tidskriftsartikel (refereegranskat)abstract
- n 1994, we analyzed 43 foodstuff samples from local supermarkets in southern Mississippi, USA, for PCDD/PCDF. 2,3,7,8-Cl4DD could be quantified in 31 of these samples. On a lipid basis, levels in meat (0.53-1.10 pg I-TEQ/g) and dairy products (0.42-1.10 pg I-TEQ/g) were slightly lower than those reported from other industrialized countries. While levels in dairy samples from the United States and Europe are comparable, there is a difference in the contribution of individual congeners to the I-TEQ: for example, in milk samples from Germany approximately 40% of the I-TEQ is due to the presence of 2,3,4,7,8-Cl5DF while in the Mississippi samples this congener only contributes 16%. The highest concentrations of PCDD/PCDF in our study were detected in the farm-raised catfish (10.2-27.8 pg I-TEQ/g). A unique finding was that in addition to the 2,3,7,8-substituted PCDD/PCDF the catfish samples contained many non-2,3,7,8-substituted congeners. This is unusual because vertebrate animals selectively eliminate or metabolize the non-2,3,7,8-substituted congeners.
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| 6. |
- Fiedler, Heidelore, 1953-
(författare)
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Sources of PCDD/PCDF and impact on the environment
- 1996
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 32:1, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- PCDD/PCDF can be formed in a variety of industrial and thermal processes. Especially the combustion sources contribute to the ambient air levels. In addition to the well-investigated emissions from municipal waste incinerators dioxins were measured in the flue gases of other thermal emitters. It was found that some recycling plants can emit high concentrations of PCDD/PCDF. Ambient air concentrations monitored over several years have shown a clear seasonal trend with higher PCDD/PCDF levels in winter and lower concentrations during summer. Thus, results from short-term measurements cannot be used to calculate annual means for ambient air concentations or deposition rates. Dioxins, once concentrated in sewage sludge and compost can re-enter the environment when these ''reservoirs'' are applied onto agricultural and horticultural soils.
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| 7. |
- Lau, C., et al.
(författare)
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Levels of selected organic compounds in materials for candle production and human exposure to candle emissions
- 1997
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 34:5-7, s. 1623-1630
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) selected chlorinated pesticides, polycyclic aromatic hydrocarbons (PAH) and some volatile organic compounds (VOC) were analysed in the exhaust fumes of candles made from different waxes and finishing materials. To guarantee defined burning conditions a chamber was developed for the sampling of the exhaust fumes, Using a simple exposure model, the inhalative uptake of PCDD/PCDF by an adult person was calculated for different scenarios. It was shown that additional uptake of PCDD/PCDF caused by candle emissions does not contribute significantly to the total daily intake of these compounds. Emissions of PCDD/PCDF, benzo(a)pyrene and the VOC were then compared to limit value for working places. Even when many candles would be burnt at the same time in a small room, concentrations of the compounds investigated stay below 1 % of the tolerable limit values.
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| 8. |
- Rappe, Christoffer, et al.
(författare)
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PCDD and PCDF contamination in catfish feed from Arkansas, USA
- 1998
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 36:13, s. 2705-2720
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Tidskriftsartikel (refereegranskat)abstract
- One combined catfish feed sample from Arkansas, USA, and its eight ingredients were analyzed for PCDDs and PCDFs. One of the ingredients, soybean meal, was highly contaminated by PCDDs, especially the toxic 2,3,7,8-substituted congeners, e.g. 7.3 pg/g dry weight or 370 pg/g lipid for the 2,3,7,8-tetra CDD. The I-TEQ value for the soybean meal was 11.4 pg/g dry weight or 576 pg/g fat. The corresponding values for the combined catfish feed concentrations were approximately 3 times lower. The congener pattern, the congener profile and the ratio Sigma PCDDs/Sigma PCDFs for the soybean meal were quite unique. We are not aware of any environmental sample or technical product with similar characteristics. As a result, natural formation of the PCDDs found in the soybean meal cannot be ruled out.
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| 9. |
- Rappe, C., et al.
(författare)
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PCDDs and PCDFs in municipal sewage sludge and effluent from POTW in the State of Mississippi, USA
- 1998
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 36:2, s. 315-328
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Tidskriftsartikel (refereegranskat)abstract
- During the summer 1995, we collected sewage sludge and effluent samples from 17 publicly-owned treatment works (POTW) in the State of Mississippi, USA. Most PCDDs and PCDFs were detected in the sludge, and the hepta- and octaCDD congeners typically were dominant. One plant had an octaCDD value in sludge exceeding 400,000 pg/g d.m. The primary source probably is pentachlorophenol. An earlier US EPA finding of 116 pg/g d.m. 2,3,7,8-tetraCDD in sludge from the Corinth POTW was not confirmed in this study, where only 0.3 pg/g d.m. was measured. Most effluent samples were below the detection limit of approximately 10 pg/L for the tetra- through hexachlorinated congeners. The New Augusta POTW had the highest octaCDD value in effluent (2500 pg/L). This plant is a point source to the Leaf River.
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| 10. |
- Rappe, C., et al.
(författare)
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PCDDs and PCDFs in soil and river sediment samples from a rural area in the United States of America
- 1997
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 34:5-7, s. 1297-1314
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Tidskriftsartikel (refereegranskat)abstract
- In 1994, we collected 36 soil samples and 61 sediment samples from southern Mississippi, USA. Each sample was analyzed for PCDDs and PCDFs by HRMS using either a polar or a non-polar HRGC column. Although most Cl-4 - Cl-8 PCDDs and PCDFs were detected in each sample, PCDD levels (particularly Cl-7 - Cl-8) were higher in sediment than soil samples. The PCDF pattern in two sediment samples indicated a possible PCB source. The concentrations of 2,3,7,8-tetra CDD and 2,3,7,8-tetra CDF were somewhat higher upstream of a pulp mill than downstream from the mill.
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| 11. |
- Yazawa, Akira, et al.
(författare)
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Thermodynamic evaluations on the formation of dioxins and furans in combustion gas
- 1999
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Ingår i: Chemosphere. - 0045-6535 .- 1879-1298. ; 39:14, s. 2419-2432
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Tidskriftsartikel (refereegranskat)abstract
- The formation of toxic PCDD/Fs are discussed thermodynamically for C---O---H---Cl quaternary combustion gas to elucidate the effects of temperature and gas composition. In most cases, these toxic gases are formed at a temperature below 400°C, representing the isomers of furans and tetra dioxin (4CDD) in similar amounts, but those of other dioxin isomers are much lower.The amounts of PCDD/Fs species formed depend greatly on the gas composition, but are always associated with the formation of chlorobenzenes. When the system contains excess oxygen such as O/C > 1, PCDD/Fs decrease sharply.Hydrogen and water vapor are quite effective in decomposing dioxins and furans to form benzene and hydrocarbons. The derived amounts of PCDD/Fs are much higher than those observed in practice because of kinetic reasons. Taking account of kinetic factors, reasonable amounts of these toxic gases are derived.Especially, the reaction of carbon deposition has always been neglected in thermodynamic calculation of PCDD/Fs because of kinetic reason, but both of solid carbon and PCDD/Fs must be coexisting in small amounts.
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