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  • 301.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    Jönsson, Sofie
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Natural organic matter to enhance electrokinetic transport of PAHManuscript (preprint) (Other academic)
  • 302.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    Lifvergren, Thomas
    Örebro University, Department of Natural Sciences.
    Mercury contaminated soil remediation by iodide and electroreclamationManuscript (preprint) (Other academic)
  • 303.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    Lifvergren, Thomas
    Örebro University, Department of Natural Sciences.
    Mercury contaminated soil: remediation by the combination of iodide and electroreclamationManuscript (preprint) (Other academic)
  • 304.
    Suèr, Pascal
    et al.
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Multivariate evaluation of electrokinetic movement of heavy metals by systematic variation of the voltage, the soil composition and complexing agentsManuscript (preprint) (Other academic)
  • 305.
    Svensson, Margareta
    Örebro University, Department of Natural Sciences.
    Mercury immobilization: a requirement for permanent disposal of mercury waste in Sweden2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Swedish Government states that mercury in the Swedish industry and private use shall be collected and waste containing more than 1% of mercury shall be conditioned for permanent storage in proposed groundwater-saturated repository in deep bedrock. The owners of mercury waste in Sweden are responsible for finding ways to the conversion of the mercury waste to insoluble forms.

    The aim of this thesis was to investigate different low-cost immobilization methods for mercury. Choice of treatment method depends on the nature of the waste, such as the mercury concentration and matrix constituents. High-contaminated waste would be suitable to transform to chemically insoluble mercury forms, while low-contaminated wastes would be suitable to treat with an encapsulation method. The investigations assessed conditions favourable for the formation of HgS at room temperature from elemental mercury as well as from mercury oxide. Elemental sulphur in an alkaline anaerobic environment gave a yield of close to 100% mercury sulphide within two years.

    The stabilization/solidification (S/S) method was estimated as a suitable treatment method for low contaminated mercury waste (below 5%w/w). The lowest leaching rate was observed from slag monoliths with elemental sulphur as sulphur source. After one year the accumulated leaching amount was 0.008-0.013%w/w of the total mercury content of the monolith (1% of the monolith mass). This is about 100-150 times more than from monoliths that initially contained black meta-cinnabar.

    Apparent diffusion coefficients for Hg(II)(aq) were determined in cement monoliths with different constituents (10-14-10-15 m2/s), for a barrier of Standard Portland concrete (10-14 m2/s) and in quartz sand (10-13 m2/s). After some 60 d in the leaching test, the apparent diffusion coefficient was of the order 10-17-10-21 m2/s, which was indicative of a slow release rate of the remaining mercury that could represent the dissolution/transformation of HgS, which gradually was formed during curing of the cement (aged for one year). The apparent diffusion coefficient for Hg(0) could not be measured since the mercury species oxidizes in aerobic systems.

    List of papers
    1. Speciation and solubility of mercury in aerobic solutions
    Open this publication in new window or tab >>Speciation and solubility of mercury in aerobic solutions
    (English)Manuscript (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2969 (URN)
    Available from: 2006-01-13 Created: 2006-01-13 Last updated: 2017-10-18Bibliographically approved
    2. Formation of cinnabar: an estimation of favourable conditions
    Open this publication in new window or tab >>Formation of cinnabar: an estimation of favourable conditions
    2006 (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2970 (URN)
    Available from: 2006-01-13 Created: 2006-01-13 Last updated: 2017-10-18Bibliographically approved
    3. Formation of HgS: mixing HgO or elemental Hg with S, FeS or FeS2
    Open this publication in new window or tab >>Formation of HgS: mixing HgO or elemental Hg with S, FeS or FeS2
    2006 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 368, no 1, p. 418-423Article in journal (Refereed) Published
    Abstract [en]

    The aim of this study is to assess the feasibility for generation of the sparingly soluble solid HgS from HgO or elemental Hg by mixing with a suitable sulphur source under various conditions (dry, wet at different pH, and room temperature). The formation of mercury sulphide was confirmed in 14 of the 36 combinations of Hg and S sources. Mercury sulphide was generally formed under alkaline conditions. Almost 100% HgS was obtained in anaerobic systems at high pH in the presence of elemental sulphur after about two years. Thus, it is feasible to create an environment at room temperature that, with time, leads to the generation of HgS from elemental Hg or HgO. This is relevant for the design of a repository for permanent geologic disposal of mercury. Choosing wrong components and conditions can however lead to a reduction of Hg(II) to elemental mercury.

    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2971 (URN)10.1016/j.scitotenv.2005.09.040 (DOI)
    Note
    Selected papers from the 7th International Conference on Mercury as a Global Pollutant, Ljubljana, Slovenia June 27 - July 2, 2004Available from: 2006-01-13 Created: 2006-01-13 Last updated: 2017-12-14Bibliographically approved
    4. Leaching of mercury-containing cement monoliths aged for one year
    Open this publication in new window or tab >>Leaching of mercury-containing cement monoliths aged for one year
    2008 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 28, no 3, p. 597-603Article in journal (Refereed) Published
    Abstract [en]

    A directive from the Swedish Government states that waste containing more than 1% of mercury shall be permanently deposited. The stabilization of mercury by conversion to a sparingly soluble compound like the sulphide is crucial to ensure long-term immobilization in a permanent storage. Immobilization by the solidification/stabilization (S/S) method and possible formation of HgS from mercury oxide or elemental mercury by reaction with a sulphur source (S or FeS) is investigated by a modified version of the NEN 7345 Dutch tank-leaching test. The diffusion of mercury during 11 months from 1-year-old mercury containing monoliths of Portland and slag cement is demonstrated. In a geologic repository under conditions representative of deep granitic bedrock (bicarbonate buffered to pH 8.6), a favourable monolith combination is slag cement with addition of the iron sulphide troilite. The apparent diffusion coefficient of mercury is estimated.

    National Category
    Environmental Sciences Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2972 (URN)10.1016/j.wasman.2007.02.031 (DOI)000253097600016 ()17544639 (PubMedID)2-s2.0-37449015893 (Scopus ID)
    Available from: 2006-01-13 Created: 2006-01-13 Last updated: 2017-12-14Bibliographically approved
    5. Diffusion tests of mercury through concrete, bentonite-enhanced sand and sand
    Open this publication in new window or tab >>Diffusion tests of mercury through concrete, bentonite-enhanced sand and sand
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2973 (URN)
    Available from: 2006-01-13 Created: 2006-01-13 Last updated: 2017-10-18Bibliographically approved
  • 306.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Diffusion tests of mercury through concrete, bentonite-enhanced sand and sandManuscript (preprint) (Other academic)
  • 307.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Diffusion tests of mercury through concrete, bentonite-enhanced sand and sand2007In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 142, no 1-2, p. 463-467Article in journal (Refereed)
    Abstract [en]

    The transport by diffusion of Hg(II) and Hg(O) through a barrier of concrete or bentonite-enhanced sand was examined under aerobic conditions. Sand was used as a reference system parallel to the two systems. Speciation of mercury was performed with a purge and trap method, where dissolved Hg(O) was purged with nitrogen gas from the sample, through a trap for volatile oxidized mercury species and finally trapped in an oxidative solution. The apparent diffusion coefficient (from Fick's second law of diffusion) for oxidized mercury was 1 x 10(-14) m(2)/s in Standard Portland concrete and 4 x 10(-13) m(2)/s in quartz sand. The diffusion of Hg(O) seemed to be faster than for Hg(II), Hg(O) was however oxidized to Hg(H) under aerobic conditions, and after 45 months only 1-10% of the total mercury concentration was Hg(O). (c) 2006 Elsevier B.V. All rights reserved.

  • 308.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences. SAKAB AB, Kumla, Sweden.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Leaching of mercury-containing cement monoliths aged for one year2008In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 28, no 3, p. 597-603Article in journal (Refereed)
    Abstract [en]

    A directive from the Swedish Government states that waste containing more than 1% of mercury shall be permanently deposited. The stabilization of mercury by conversion to a sparingly soluble compound like the sulphide is crucial to ensure long-term immobilization in a permanent storage. Immobilization by the solidification/stabilization (S/S) method and possible formation of HgS from mercury oxide or elemental mercury by reaction with a sulphur source (S or FeS) is investigated by a modified version of the NEN 7345 Dutch tank-leaching test. The diffusion of mercury during 11 months from 1-year-old mercury containing monoliths of Portland and slag cement is demonstrated. In a geologic repository under conditions representative of deep granitic bedrock (bicarbonate buffered to pH 8.6), a favourable monolith combination is slag cement with addition of the iron sulphide troilite. The apparent diffusion coefficient of mercury is estimated.

  • 309.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Düker, Anders
    Örebro University, Department of Natural Sciences.
    Formation of HgS: mixing HgO or elemental Hg with S, FeS or FeS22006In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 368, no 1, p. 418-423Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to assess the feasibility for generation of the sparingly soluble solid HgS from HgO or elemental Hg by mixing with a suitable sulphur source under various conditions (dry, wet at different pH, and room temperature). The formation of mercury sulphide was confirmed in 14 of the 36 combinations of Hg and S sources. Mercury sulphide was generally formed under alkaline conditions. Almost 100% HgS was obtained in anaerobic systems at high pH in the presence of elemental sulphur after about two years. Thus, it is feasible to create an environment at room temperature that, with time, leads to the generation of HgS from elemental Hg or HgO. This is relevant for the design of a repository for permanent geologic disposal of mercury. Choosing wrong components and conditions can however lead to a reduction of Hg(II) to elemental mercury.

  • 310.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Düker, Anders
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Formation of cinnabar: an estimation of favourable conditions2006Manuscript (preprint) (Other academic)
  • 311.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Düker, Anders
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Formation of cinnabar: estimation of favourable conditions in a proposed Swedish repository2006In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 136, no 3, p. 830-836Article in journal (Refereed)
    Abstract [en]

    A deep repository for permanent storage of mercury will be designed and built in Sweden. The preferred chemical state for mercury in such a repository would be the sulphide HgS (cinnabar), which is a highly insoluble and the dominating natural mercury mineral. The possible formation of HgS from HgO or Hg(0) by reaction with a sulphur source (S, FeS or FeS2) is discussed from thermodynamic considerations, and pe–pH-diagrams are constructed by using the computer code MEDUSA to illustrate under which conditions HgS would dominate. Calculations of the speciation (PHREEQE) under varying conditions (S/Hg-ratios, presence of chloride) are given.

    Long-term laboratory experiments are performed, where the formation of HgS from the basic components is demonstrated (after mixing under various conditions and storage at room temperature for up to 3 years).

    The feasibility of HgS-formation with time in a geologic repository under conditions representative of deep granitic bedrock (calcium-bicarbonate buffered to pH 7–8.5) is discussed, as well as effects of alkaline conditions (concrete environment, pH 10.5–12.5). Formation of soluble polysulphides is not expected as long as the S/Hg mole ratio is within 1–1.3 and pH is below 10.5–11. Concrete should be used with caution. Suitable ballast materials could be introduced that would reduce porewater-pH that otherwise would be above 12.

  • 312.
    Svensson, Margareta
    et al.
    Örebro University, Department of Natural Sciences.
    Hagelberg, Erik
    Düker, Anders
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Speciation and solubility of mercury in aerobic solutionsManuscript (Other academic)
  • 313.
    Sävenstrand, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Brosché, Mikael
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Regulation of gene expression by low levels of ultraviolet-B radiation in Pisum sativum: isolation of novel genes by suppression subtractive hybridisation2002In: Plant and Cell Physiology, ISSN 0032-0781, E-ISSN 1471-9053, Vol. 43, no 4, p. 402-410Article in journal (Refereed)
    Abstract [en]

    Suppression subtractive hybridisation was used to isolate genes differentially regulated by low levels (UV-B(BE,300) 0.13 W m(-2)) of ultraviolet-B radiation (UV-B; 290-320 nm) in Pisum sativum. Six genes were regulated, two of which were novel. The mRNA levels for these two (PsTSDC and PsUOS1) were increased and depressed by UV-B treatment, respectively. Domains in the PsTSDC translation product was similar to TIR (Toll-Interleukin-1 receptor-similar) domains and a NB-ARC domain (nucleotide-binding domain in APAF-1, R gene products and CED-4). The PsUOS1 translation product was similar to an open reading frame in Arabidopsis. Genes encoding embryo-abundant protein (PsEMB) and S-adenosyl-L-methionine synthase (PsSAMS) were induced by UV-B, whereas the transcript levels for genes encoding sucrose transport protein (PsSUT) or ribulose-5-phosphate 3-epimerase (PsR5P3E) were decreased. These regulation patterns are novel, and the PsEMB and PsR5P3E sequences are reported for the first time. The stress-specificity of regulation of these genes were tested by ozone fumigation (100 ppb O(3)). Qualitatively, the similarity of expression after both UV-B and ozone exposure suggests that, for these genes, similar stress-response pathways are in action.

  • 314.
    Sävenstrand, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Brosché, Mikael
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Ultraviolet-B signalling: Arabidopsis brassinosteroid mutants are defective in UV-B regulated defence gene expression2004In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 42, no 9, p. 687-694Article in journal (Refereed)
    Abstract [en]

    The involvement of brassinosteroids in signalling events in plants during UV-B stress (280-315 nm) was investigated in Arabidopsis thaliana. Brassinosteroids are involved in growth and development in plants and have also been shown to enhance stress tolerance. Three mutants deficient in the biosynthetic pathway of brassinolide (BL; det2, dim1 and cpd) and the BL insensitive mutant (bri1) were together with visible light irradiated with 3 or 9 h of UV-B radiation (biologically effective radiation normalised to 300 nm being 0.24 W m(-2)). Also, a small size control, irx1, and Columbia 0 (Col-0) wild-type plants were examined under identical conditions. Gene expression patterns were established for these mutants with a set of four molecular markers (the defence genes chalcone synthase (CHS), PYROA, pathogenesis-related protein PR-5, and a gene regulated by very low levels of UV-B, MEB5.2). Although the genes in the brassinodefective mutants were still induced by UV-B radiation, they all also showed reduced levels of mRNA transcripts compared with Col-0 and irx1. The bri1 and cpd were the mutants with lowest levels of molecular marker mRNA transcripts. The effects of impairment of brassinosteroid signalling also differed between the genes studied, indicating a need for a complete brassinosteroid pathway in UV-B signalling.

  • 315.
    Sävenstrand, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Olofsson, Marie
    Samuelsson, Maria
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Induction of early light-inducible protein gene expression in Pisum sativum after exposure to low levels of UV-B irradiation and other environmental stresses2004In: Plant Cell Reports, ISSN 0721-7714, E-ISSN 1432-203X, Vol. 22, no 7, p. 532-536Article in journal (Refereed)
    Abstract [en]

    Plants are constantly subjected to environmental changes and have developed various defence mechanisms to facilitate their continued existence. Pisum sativum plants were exposed to low levels of UV-B radiation and ELIP (early light-inducible proteins) mRNA, with a probable protective function, was rapidly and strongly induced during this type of stress. To our knowledge, this is the only photosynthetic gene that is up-regulated following exposure to UV-B, and this result has to be compared with studies predominantly reporting down-regulation by UV-B of genes encoding proteins localised in the plastid. The expression pattern of ELIP mRNA in pea was also investigated during salt, wounding and ozone stress. The transcript levels of ELIP were induced after the salt and wounding treatments but not during ozone fumigation.

  • 316.
    Sävenstrand, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    A Pisum sativum glyoxysomal malate dehydrogenase induced by cadmium exposure2004In: DNA Sequence, ISSN 1042-5179, E-ISSN 1029-2365, Vol. 15, no 3, p. 206-208Article in journal (Refereed)
    Abstract [en]

    The glyoxysomal malate dehydrogenase (gMDH) catalyses the formation of oxaloacetate from malate during beta-oxidation of fatty acids in the glyoxysome. A partial Pisum sativum L. (cv. Greenfeast) cDNA was first isolated from a suppression subtractive hybridisation cDNA library obtained from heavy metal stressed plants. The full length cDNA was then isolated by rapid amplification of cDNA ends. The translated sequence showed strong similarity to Cucumis sativus and Citrullus lanatus gMDH including a typical glyoxysome-targeting presequence comprising the PTS2 motif and a cleavage site for a cystein-directed protease. Exposure of pea plants to Cd2+ induced expression of the gMDH gene in mature pea leaves indicating that the enzyme is under environmental control in addition to the normal developmental regulation pattern.

  • 317.
    Sävenstrand, Helena
    et al.
    Örebro University, Department of Natural Sciences.
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Six genes strongly regulated by mercury in Pisum sativum roots2004In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 42, no 2, p. 135-142Article in journal (Refereed)
    Abstract [en]

    Suppression subtractive hybridisation was used to isolate heavy metal-induced genes from Pisum sativum roots hydroponically exposed to 5 microM HgCl2 and 10 microM EDTA. Six genes were induced out of which one, PsHMIP6B, was novel. The other genes (PsSAMT, PsI2'H, PsNDA, PsAPSR, PsPOD) had not previously been isolated from pea and sequenced. All six genes were also induced after exposure to 5 microM HgCl2 in the absence of EDTA. The induction pattern was in some cases different for the two Hg species, demonstrating a quicker response to-free Hg2+ than Hg-EDTA. The stress-specificity of the gene regulation was investigated by hydroponically adding 5 microM Cd2+. Most Hg-induced cDNAs were also induced by Cd2+ but to a smaller extent than after Hg exposure. In addition, the gene expression was also probed for tissue specificity, which showed that all six genes were expressed in roots and not in leaves.

  • 318. Takeuchi, A.
    et al.
    Yamaguchi, T.
    Hidema, Jun
    Strid, Åke
    Örebro University, Department of Natural Sciences.
    Kumagai, Tadashi
    Changes in synthesis and degradation of Rubisco and LHCII with leaf age in rice (Oryza sativa L.) growing under supplementary UV-B radiation2002In: Plant, Cell & Environment, ISSN 0140-7791, Vol. 25, no 6, p. 695-706Article in journal (Refereed)
    Abstract [en]

    The effects of supplementary ultraviolet-B (UV-B) radiation on the changes in synthesis and degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and light-harvesting chlorophyll a/b binding protein of PSII (LHCII) were examined, as well as mRNA levels for small and large subunits of Rubisco (rbcS and rbcL, respectively) and LHCII (cab) with leaf age in UVsensitive rice (Norin 1) and UV-resistant rice (Sasanishiki). Both Rubisco and LHCII were actively synthesized until the leaf had fully expanded, and then decreased with increasing leaf age. Synthesis of Rubisco, but not LHCII, was significantly suppressed by UV-B in Norin 1. The degradation of Rubisco was enhanced by UV-B around the time of leaf maturation in the two cultivars. The levels of rbcS and rbcL were reduced by UV-B at the early stages after leaf emergence in both cultivars. Cab transcripts were first present at high levels in the two cultivars, but drastically decreased due to UV-B treatment immediately after leaf emergence in Norin 1. It was shown that synthesis and degradation of Rubisco and LHCII greatly changed with leaf age: Rubisco synthesis was significantly suppressed by supplementary UV-B radiation at the transcription step during the early leaf stages. It was also suggested that the difference in UV-B sensitivity in Rubisco synthesis between the two rice cultivars might be due to specific suppression both transcriptionally and post-transcriptionally.

  • 319. Tejero, Ismael
    et al.
    Gonzalez-Lafont, Angels
    Lluch, José M.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Theoretical modeling of hydroxyl-radical-induced lipid peroxidation reactions2007In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 20, p. 5684-5693Article in journal (Refereed)
    Abstract [en]

    The OH-radical-induced mechanism of lipid peroxidation, involving hydrogen abstraction followed by O2 addition, is explored using the kinetically corrected hybrid density functional MPWB1K in conjunction with the MG3S basis set and a polarized continuum model to mimic the membrane interior. Using a small nonadiene model of linoleic acid, it is found that hydrogen abstraction preferentially occurs at the mono-allylic methylene groups at the ends of the conjugated segment rather than at the central bis-allylic carbon, in disagreement with experimental data. Using a full linoleic acid, however, abstraction is correctly predicted to occur at the central carbon, giving a pentadienyl radical. The Gibbs free energy for abstraction at the central C11 is 8 kcal/mol, compared to 9 kcal/mol at the end points (giving an allyl radical). Subsequent oxygen addition will occur at one of the terminal atoms of the pentadienyl radical fragment, giving a localized peroxy radical and a conjugated butadiene fragment, but is associated with rather high free energy barriers and low exergonicity at the CPCM-MPWB1K/MG3S level. The ZPE-corrected potential energy surfaces obtained without solvent effects, on the other hand, display considerably lower barriers and more exergonic reactions.

  • 320.
    Temnerud, Johan
    Örebro University, Department of Natural Sciences.
    Spatial variation of dissolved organic carbon along streams in Swedish boreal catchments2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis quantifies the small-scale spatial variation of dissolved organic carbon (DOC) concentrations, fluxes and character in two boreal catchments (subcatchments 0.01-78 km²) using ”snapshots” of summer base flow where samples were taken upstream and downstream from every node in the stream network. An order of magnitude variation was found in DOC-concentrations, and many other chemical parameters. The range was similar to that found in all of northern Sweden by the national stream survey in 2000. According to the official assessment tools used in Sweden, the entire range of environmental status for DOC, pH and human acidification influence existed within these two study catchments. A large variability in specific discharge had a major impact on the contribution of headwaters to downstream chemistry. The water chemistry parameters were relatively stable at catchment areas greater than 15 km². Sampling at that scale may be adequate if generalised values for the landscape are desired. However the chemistry of headwaters, where much of the stream length and aquatic ecosystem is found would not be characterized.

    Downstream DOC-concentrations, as well as many other chemical parameters, are the sum of headwater inputs, in combination with progressive downstream dilution by inflowing water with its own DOC-concentration and character. Superimposed upon this are in-stream and hyporheic processes, as well as discrete loci of DOC loss/transformation at lakes and stream junctions. At the landscape scale, this results in a decreased downstream variation in stream water chemistry and often, but not necessarily, lower average DOC-concentrations. Along stream reaches there was not a loss of DOC-concentration or a consistent change in character. While the importance of in-stream/hyporheic processes that consistently alter DOC-concentrations along the channel network cannot be ruled out, the differences between headwater and downstream DOC-concentrations and related parameters depend largely on the mosaic of landscape elements (mires, lakes and forest soil) contributing water to the channel network, combined with patterns of specific discharge and discrete loci of DOC loss. Assessment would be facilitated by map information that could predict spatial patterns. Multivariate models using maps, however, did not give satisfactory predictions.

    Appropriate procedures for dealing with spatial variation in the environmental assessment of surface waters are not yet established. An awareness of stream water chemistry’s natural spatial variability should be considered when planning aquatic and terrestrial management.

    List of papers
    1. Spatial variation of streamwater chemistry in two Swedish boreal catchments: implications for environmental assessment
    Open this publication in new window or tab >>Spatial variation of streamwater chemistry in two Swedish boreal catchments: implications for environmental assessment
    2005 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 6, p. 1463-1469Article in journal (Refereed) Published
    Abstract [en]

    To evaluate the scale-dependent spatial variability of water chemistry within two Swedish boreal catchments (subcatchment areas 0.01-78 km2), samples were taken at every junction in the stream network during June 2000 and August 2002. The values of most chemical constituents spanned more than an order of magnitude, and the range was similar to that found in all of Northern Sweden by the national stream survey in 2000. According to the official assessment tools used in Sweden, the entire range of environmental status (for pH, absorbance, alkalinity, dissolved organic carbon (DOC)) and human acidification influence existed within these two study catchments. The water chemistry parameters were relatively stable at catchment areas greater than 15 km2. Sampling at that scale may be adequate if generalized values for the landscape are desired. However the chemistry of headwaters, where much of the stream length and aquatic ecosystem is found would not be characterized. Map parameters correlated to the variability in a key chemical parameter, DOC, but the best predictive map parameters differed markedly between catchments. This study highlights the importance of accounting for headwater spatial variability in environmental assessments of running waters, even in relatively pristine areas. The nature of drainage networks with many headwaters and progressively fewer downstream watercourses makes this a considerable challenge.

    National Category
    Natural Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2827 (URN)10.1021/es040045q (DOI)
    Available from: 2005-05-04 Created: 2005-05-04 Last updated: 2017-12-14Bibliographically approved
    2. Spatial variation in concentrations and fluxes of dissolved organic carbon in a catchment network of boreal streams in northern Sweden
    Open this publication in new window or tab >>Spatial variation in concentrations and fluxes of dissolved organic carbon in a catchment network of boreal streams in northern Sweden
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences Natural Sciences
    Research subject
    Chemistry; Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2828 (URN)
    Available from: 2005-05-04 Created: 2005-05-04 Last updated: 2017-10-18Bibliographically approved
    3. Landscape scale patterns in the character of dissolved organic carbon in a boreal stream network
    Open this publication in new window or tab >>Landscape scale patterns in the character of dissolved organic carbon in a boreal stream network
    Show others...
    (English)Manuscript (Other academic)
    National Category
    Natural Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2829 (URN)
    Available from: 2005-05-04 Created: 2005-05-04 Last updated: 2017-10-18Bibliographically approved
    4. Modelling dissolved organic carbon concentration in Swedish boreal watercourses using map information
    Open this publication in new window or tab >>Modelling dissolved organic carbon concentration in Swedish boreal watercourses using map information
    Show others...
    (English)Manuscript (Other academic)
    National Category
    Natural Sciences
    Research subject
    Enviromental Science
    Identifiers
    urn:nbn:se:oru:diva-2830 (URN)
    Available from: 2005-05-04 Created: 2005-05-04 Last updated: 2017-10-18Bibliographically approved
  • 321.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Bishop, Kevin
    Spatial variation of streamwater chemistry in two Swedish boreal catchments: implications for environmental assessment2005In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 39, no 6, p. 1463-1469Article in journal (Refereed)
    Abstract [en]

    To evaluate the scale-dependent spatial variability of water chemistry within two Swedish boreal catchments (subcatchment areas 0.01-78 km2), samples were taken at every junction in the stream network during June 2000 and August 2002. The values of most chemical constituents spanned more than an order of magnitude, and the range was similar to that found in all of Northern Sweden by the national stream survey in 2000. According to the official assessment tools used in Sweden, the entire range of environmental status (for pH, absorbance, alkalinity, dissolved organic carbon (DOC)) and human acidification influence existed within these two study catchments. The water chemistry parameters were relatively stable at catchment areas greater than 15 km2. Sampling at that scale may be adequate if generalized values for the landscape are desired. However the chemistry of headwaters, where much of the stream length and aquatic ecosystem is found would not be characterized. Map parameters correlated to the variability in a key chemical parameter, DOC, but the best predictive map parameters differed markedly between catchments. This study highlights the importance of accounting for headwater spatial variability in environmental assessments of running waters, even in relatively pristine areas. The nature of drainage networks with many headwaters and progressively fewer downstream watercourses makes this a considerable challenge.

  • 322.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Duker, Anders
    Örebro University, Department of Natural Sciences.
    Karlsson, Stefan
    Örebro University, Department of Natural Sciences.
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Köhler, Stephan
    Dept. of Applied Geosciences, Technical University of Graz, Graz, Austria.
    Bishop, Kevin
    Dept. of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network2009In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 13, no 9, p. 1567-1582Article in journal (Refereed)
    Abstract [en]

    This paper defines landscape-scale patterns in the character of natural organic matter (NOM) and tests for relationships to catchment soil, vegetation and topography. The drainage network of a boreal catchment, subcatchment size 0.12-78 km(2), in Northern Sweden was sampled in August 2002 during a period of stable low water flow. The NOM was characterized with UV/Vis spectroscopy, fluorescence, XAD-8 fractionation (%humic substances), gel permeation chromatography (apparent molecular weight), and elemental composition (C:N). The largest spatial variation was found for C: N, absorbance ratio, and specific visible absorptivity. The lowest variation was in fluorescence index, %humic substances and molecular retention time. The variation in total organic carbon (TOC), iron and aluminium concentration was more than twice that of C: N. Between headwater and downstream sites no significant changes were distinguished in the NOM character. At stream reaches, junctions and lakes little change (<10%) in NOM character was observed. Common factor analysis and partial least squares regression (PLS) revealed that the spatial variation in surface coverage of lakes and mires could explain some of the variation of TOC and NOM character. Our suggestion is that the mosaic of landscape elements (different amounts of water from lakes, forest soil and mires) delivers NOM with varying characteristics to a channel network that mixes conservatively downstream, with possible small changes at some stream reaches, junctions and lakes.

  • 323.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Düker, Anders
    Karlsson, Stefan
    Allard, Bert
    Örebro University, Department of Natural Sciences.
    Köhler, Stephan
    Bishop, Kevin
    Landscape scale patterns in the character of dissolved organic carbon in a boreal stream networkManuscript (Other academic)
  • 324.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Düker, Anders
    Örebro University, School of Science and Technology.
    Karlsson, Stefan
    Örebro University, School of Science and Technology.
    Allard, Bert
    Örebro University, School of Science and Technology.
    Köhler, Stephan
    Dept. of Applied Geosciences, Technical University of Graz, Graz, Austria.
    Bishop, Kevin
    Dept. of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Landscape scale patterns in the character of natural organic matter in a Swedish boreal stream network2009Conference paper (Refereed)
  • 325.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Lindsjö, Anders
    Seibert, Jan
    Laudon, Hjalmar
    Buffam, Ishi
    Bishop, Kevin
    Modelling dissolved organic carbon concentration in Swedish boreal watercourses using map informationManuscript (Other academic)
  • 326.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Seibert, Jan
    Jansson, Mats
    Bishop, Kevin
    Spatial variation in concentrations and fluxes of dissolved organic carbon in a catchment network of boreal streams in northern SwedenManuscript (preprint) (Other academic)
  • 327.
    Temnerud, Johan
    et al.
    Örebro University, Department of Natural Sciences.
    Seibert, Jan
    Jansson, Mats
    Bishop, Kevin
    Spatial variation in discharge and concentrations of organic carbon in a catchment network of boreal streams in northern Sweden2007In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 342, no 1-2, p. 72-87Article in journal (Refereed)
    Abstract [en]

    Total organic carbon (TOC) is an important feature of water quality in Fenno-Scandia's till catchments. In this study we estimated the contribution of headwater streams to downstream TOC, tested the hypothesis that TOC-concentration decreases downstream and explored mechanisms for the observed patterns. The drainage network of a boreal catchment (66 sites) in northern Sweden, with subcatchment sizes 0.1178 km(2), was sampled in August 2002. In the headwaters there was a large variation in TOC-concentration (4-66 mg l(-1)) as well as other chemical parameters and specific discharge (0.13-8.21 s(-1) km(-2)). Further downstream there was less variation in both chemistry and specific discharge. Both flow and chemistry stabilized at catchment areas larger than 5 km2. No clear indication of in-stream processing effects on downstream TOC was observed, though there was TOC loss at takes and some stream junctions. To test whether the observed downstream decrease is different than that expected from conservative mixing along the stream network, we used a Monte Carlo approach to simulate downstream conservative mixing. The observed spatial variability was higher than the simulated, indicating that landscape-scale patterns are more than conservative mixing of random inputs. While the importance of in-stream processes that after TOC- concentrations cannot be ruled out, and loci of TOC loss do exist, we propose that headwater/ downstream patterns in TOC, and related parameters depend largely on the mosaic of landscape elements (mires, takes and forest) together with specific discharge. (c) 2007 Elsevier B.V. All. rights reserved.

  • 328.
    Tovesson, Fredrik
    Örebro University, Department of Natural Sciences.
    The neutron-induced fission cross section of 233Pa: and the quest for clean and safe nuclear energy2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Neutron-induced fission of 233Pa has been investigated between 1.0 and 8.5 MeV, and the reaction cross section was determined. Due to the short half-life of 233Pa for β-decay, fission events from the daughter product 233U affect the analysis of the protactinium experiment. In order to be able to correct for this contamination by ingrowing 233U, its fission cross section was measured as well in the same energy region.

    The result for the 233Pa(n,f) cross section is compared with previous theoretical evaluations and indirect cross section estimations extracted from fission probability data. The cross section data that were measured in this work are lower than all other values for this isotope. The 233U(n,f) cross section values are also compared to evaluations. The evaluations for the neutron-induced fission cross section of 233U(n,f) are based on a large set of experimental values, and are thus considered to be very accurate. A good agreement between the results obtained in this work and the evaluations is observed in this case.

    New model calculations, based on the statistical model for nuclear reactions, are compared to the experimental results for the 233Pa(n,f) cross section. These theoretical calculations describe the experimental results very accurately, and can be used to extract information about the fissioning system.

    The main motivation for this work is its relevance for the thorium-based nuclear fuel cycle, which has been proposed for advanced reactor facilities intended for safe power supply and transmutation of nuclear waste.

    List of papers
    1. Neutron-induced fission cross section of 233Pa between 1.0 and 3.0 MeV
    Open this publication in new window or tab >>Neutron-induced fission cross section of 233Pa between 1.0 and 3.0 MeV
    Show others...
    2002 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, no 6, p. 062502-Article in journal (Refereed) Published
    Abstract [en]

    The energy dependent neutron-induced fission cross section of 233Pa has for the first time been measured directly with monoenergetic neutrons. This nuclide is an important intermediary in a thorium based fuel cycle, and its fission cross section is a key parameter in the modeling of future advanced fuel and reactor concepts. A first experiment resulted in four cross section values between 1.0 and 3.0 MeV, establishing a fission threshold in excess of 1 MeV. Significant discrepancies were found with a previous indirect experimental determination and with model estimates.

    National Category
    Physical Sciences
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-3089 (URN)10.1103/PhysRevLett.88.062502 (DOI)11863801 (PubMedID)
    Available from: 2003-11-21 Created: 2003-11-21 Last updated: 2017-12-14Bibliographically approved
    2. The Pa-233 fission cross section
    Open this publication in new window or tab >>The Pa-233 fission cross section
    Show others...
    2002 (English)In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. Supplement 2, p. 210-213Article in journal (Refereed) Published
    Abstract [en]

    The energy dependent neutron-induced fission cross section of 233Pa has for the first time been measured directly with mono-energetic neutrons. This isotope is produced in the thorium fuel cycle and serves as an intermediate step between the 232Th source material and the 233U fuel material. Four neutron energies between 1.0 and 3.0 MeV have been measured in a first campaign. Some preliminary results are presented and compared to literature.

    National Category
    Physical Sciences
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-3090 (URN)
    Available from: 2003-11-21 Created: 2003-11-21 Last updated: 2017-12-14Bibliographically approved
    3. 233Pa(n, f) cross section up to En=8.5 MeV
    Open this publication in new window or tab >>233Pa(n, f) cross section up to En=8.5 MeV
    Show others...
    2004 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 733, no 1-2, p. 3-19Article in journal (Refereed) Published
    Abstract [en]

    The energy dependence of the neutron-induced fission cross section of 233Pa has been measured directly for the first time from the fission threshold up to En=8.5 MeV. This reaction plays an important role in the thorium-uranium fuel cycle, and is thus of interest for the design and modeling of advanced reactor and transmutation facilities. The existing information in the ENDF/B-VI and JENDL-3.3 evaluated nuclear data files differ by a factor of two for the 233Pa(n, f) cross section values and show different fission threshold energies. Our new experimental data give lower cross section values than both evaluations and resolves the question about the threshold energy. In addition to the experimental investigation, also a new theoretical calculation of the reaction cross section has been performed with the statistical model code STATIS, showing a good agreement with the experimental data.

    National Category
    Subatomic Physics
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-3091 (URN)10.1016/j.nuclphysa.2003.11.054 (DOI)
    Available from: 2003-11-21 Created: 2003-11-21 Last updated: 2017-12-14Bibliographically approved
    4. Fission fragment properties and the problem of the pulse height defect
    Open this publication in new window or tab >>Fission fragment properties and the problem of the pulse height defect
    2002 (English)In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. Supplement 2, p. 673-676Article in journal (Refereed) Published
    Abstract [en]

    The pulse height defect (PHD) has been investigated for three different counting gases commonly used in ionization chambers. The PHD introduces an underestimation of the kinetic energy of a charged particle detected with an ionization chamber. Thus, in some cases it is of crucial importance to correct for this effect, e.g. when studying fission fragment properties. A now method was used, applying a waveform digitizer, to study the PHD. The fission fragment properties from spontaneous fission of 252Cf where determined using different counting gases and different ways of correcting for the PHD were evaluated.

    National Category
    Physical Sciences
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-3092 (URN)
    Available from: 2003-11-21 Created: 2003-11-21 Last updated: 2017-12-14Bibliographically approved
    5. Calculation of the neutron-induced fission cross section of 233Pa
    Open this publication in new window or tab >>Calculation of the neutron-induced fission cross section of 233Pa
    Show others...
    2004 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 69, no 2, p. 021604-Article in journal (Refereed) Published
    Abstract [en]

    Since very recently, experimental data for the energy dependence of the 233Pa(n,f) cross section are finally available. This has stimulated a new, self-consistent cross section evaluation for the system n+233Pa in the incident neutron energy range 0.01–6 MeV. The results are quite different compared to earlier evaluation attempts. Since 233Pa is an important intermediary in the thorium based fuel cycle, its neutron reaction cross sections are key parameters in the modeling of future advanced reactor concepts.

    National Category
    Physical Sciences
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-3093 (URN)10.1103/PhysRevC.69.021604 (DOI)
    Available from: 2003-11-21 Created: 2003-11-21 Last updated: 2017-12-14Bibliographically approved
  • 329.
    Tovesson, Fredrik
    et al.
    Örebro University, Department of Natural Sciences.
    Birgersson, E.
    Örebro University, Department of Natural Sciences.
    Flenéus, M.
    Örebro University, Department of Natural Sciences.
    Fogelberg, B.
    Fritsch, V.
    Gustafsson, C.
    Örebro University, Department of Natural Sciences.
    Hambsch, F.-J.
    Oberstedt, Andreas
    Örebro University, Department of Natural Sciences.
    Oberstedt, Stephan
    Ramström, E.
    Tudora, A.
    Vladuca, G.
    233Pa(n, f) cross section up to En=8.5 MeV2004In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 733, no 1-2, p. 3-19Article in journal (Refereed)
    Abstract [en]

    The energy dependence of the neutron-induced fission cross section of 233Pa has been measured directly for the first time from the fission threshold up to En=8.5 MeV. This reaction plays an important role in the thorium-uranium fuel cycle, and is thus of interest for the design and modeling of advanced reactor and transmutation facilities. The existing information in the ENDF/B-VI and JENDL-3.3 evaluated nuclear data files differ by a factor of two for the 233Pa(n, f) cross section values and show different fission threshold energies. Our new experimental data give lower cross section values than both evaluations and resolves the question about the threshold energy. In addition to the experimental investigation, also a new theoretical calculation of the reaction cross section has been performed with the statistical model code STATIS, showing a good agreement with the experimental data.

  • 330.
    Tovesson, Fredrik
    et al.
    Örebro University, Department of Natural Sciences.
    Hambsch, F.-J.
    Oberstedt, Andreas
    Örebro University, Department of Natural Sciences.
    Fogelberg, B.
    Ramström, E.
    Oberstedt, Stephan
    Neutron-induced fission cross section of 233Pa between 1.0 and 3.0 MeV2002In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 88, no 6, p. 062502-Article in journal (Refereed)
    Abstract [en]

    The energy dependent neutron-induced fission cross section of 233Pa has for the first time been measured directly with monoenergetic neutrons. This nuclide is an important intermediary in a thorium based fuel cycle, and its fission cross section is a key parameter in the modeling of future advanced fuel and reactor concepts. A first experiment resulted in four cross section values between 1.0 and 3.0 MeV, establishing a fission threshold in excess of 1 MeV. Significant discrepancies were found with a previous indirect experimental determination and with model estimates.

  • 331.
    Tovesson, Fredrik
    et al.
    Örebro University, Department of Natural Sciences.
    Hambsch, F.-J.
    Oberstedt, Andreas
    Örebro University, Department of Natural Sciences.
    Fogelberg, B.
    Ramström, E.
    Oberstedt, Stephan
    The Pa-233 fission cross section2002In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. Supplement 2, p. 210-213Article in journal (Refereed)
    Abstract [en]

    The energy dependent neutron-induced fission cross section of 233Pa has for the first time been measured directly with mono-energetic neutrons. This isotope is produced in the thorium fuel cycle and serves as an intermediate step between the 232Th source material and the 233U fuel material. Four neutron energies between 1.0 and 3.0 MeV have been measured in a first campaign. Some preliminary results are presented and compared to literature.

  • 332.
    Tovesson, Fredrik
    et al.
    Örebro University, Department of Natural Sciences.
    Hambsch, Franz-Josef
    Oberstedt, Stephan
    Bax, Hugo
    Fission fragment properties and the problem of the pulse height defect2002In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. Supplement 2, p. 673-676Article in journal (Refereed)
    Abstract [en]

    The pulse height defect (PHD) has been investigated for three different counting gases commonly used in ionization chambers. The PHD introduces an underestimation of the kinetic energy of a charged particle detected with an ionization chamber. Thus, in some cases it is of crucial importance to correct for this effect, e.g. when studying fission fragment properties. A now method was used, applying a waveform digitizer, to study the PHD. The fission fragment properties from spontaneous fission of 252Cf where determined using different counting gases and different ways of correcting for the PHD were evaluated.

  • 333.
    van Hees, Patrick A. W.
    et al.
    Örebro University, Department of Natural Sciences.
    Johansson, Emma M.
    Örebro University, Department of Natural Sciences.
    Jones, D. L.
    Dynamics of simple carbon compounds in two forest soils as revealed by soil solution concentrations and biodegradation kinetics2008In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 310, no 1-2, p. 11-23Article in journal (Refereed)
    Abstract [en]

    Simple compounds in soil such as organic acids, amino acids and monosaccharides are believed to be important in regulating many aspects of terrestrial ecosystem functioning (e.g. C cycling, nutrient acquisition). Understanding the fate and dynamics of these low molecular weight (MW) compounds is therefore essential for predicting ecosystem responses to disturbance. Our aim was to quantify the amounts of these compounds in two podzolic forest soil profiles (O, E, Bs and C horizons) and to quantify their contribution to total soil respiration. The total concentration of organic acids, amino acids and monosaccharides in soil solution comprised on average 15 +/- 10% of the total dissolved organic C (DOC), with declining concentrations in the deeper soil layers. Dissolved organic N (DON) was the dominant form of N in soil solution and free amino acids contributed to 34% of this pool. The mineralization behaviour of glucose and galactose was described by parabolic (Michaelis-Menten) type kinetics with V-max and K (M) values in the range of < 1-250 mu mol kg(-1) h(-1) and 15-1,100 mu M, respectively. Assuming that (1) microbially mediated substrate turnover follows Michaelis-Menten kinetics, and (2) steady state soil solution concentrations, we calculated the rate of CO2 efflux attributable to the mineralisation of the three classes of low MW compounds. Our results indicated that in the O horizon, the turnover of these substrates could comprise similar to 100% of the basal, heterotrophic, soil respiration. In contrast, in the deeper mineral soil < 20% of total soil respiration could be attributable to the mineralization of these compounds. Our compound-specific approach has identified the main substrates contributing to soil respiration in forest topsoils. However, our results also suggest that soil respiration in subsoils may be attributable to compounds other than organic acids, amino acids and monosaccharides.

  • 334.
    van Hees, Patrick A. W.
    et al.
    Örebro University, Department of Natural Sciences.
    Rosling, A.
    Lundstrom, U. S.
    Finlay, R. D.
    The biogeochemical impact of ectomycorrhizal conifers on major soil elements (Al, Fe, K and Si)2006In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 136, no 1-2, p. 364-377Article in journal (Refereed)
    Abstract [en]

    Mobilisation of nutrients and dissolution of minerals are of key importance for plant growth and soil formation, as well as long term ecosystem sustainability. The effects of Pinus sylvestris seedlings, ectomycorrhizal colonisation and potassium supply on the mobilisation of Al, Fe, K and Si were studied in a soil column experiment. Budgets were constructed considering amounts in drainage water, accumulation in plants and changes in the pools of exchangeable ions (BaCl2 extractions). Drainage was the most important sink under the experimental conditions imposed, but the other two pools were also of quantitative significance. Plants had a significant positive effect on the total quantities of all elements mobilized. Mycorrhizal colonisation had limited quantitative impact on the mobilization, probably because the chosen mycorrhizal fungi did not cause any growth promotion in this experiment. Despite this, a multivariate analysis (PCA) showed a clear separate grouping of mycorrhizal, non-mycorrhizal and no-plant treatments, and in particular Si and K mobilization was related to soil biological variables which in turn were affected by the presence of mycorrhiza. When K was omitted from the watering solution, plants were able to mobilise significantly more K, which was reflected in plant uptake and a potential replenishment of the exchangeable pool. Up-scaling of total Al, K and Si mobilization to field conditions resulted in rates between equal to and up to 10 times higher than the average historical weathering rate. (c) 2006 Elsevier B.V. All rights reserved.

  • 335. van Leeuwen, Stefan P. J.
    et al.
    Kärrman, Anna
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    de Boer, Jacob
    Lindström, Gunilla
    Örebro University, Department of Natural Sciences.
    Struggle for quality in determination of perfluorinated contaminants in environmental and human samples2006In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 40, no 24, p. 7854-7860Article in journal (Refereed)
    Abstract [en]

    The first worldwide interlaboratory study on the analyses of 13 perfluorinated compounds (PFCs) in three environmental and two human samples indicates a varying degree of accuracy in relation to the matrix or analyte determined. The ability of 38 participating laboratories from 13 countries to determine the analytes in the various matrices was evaluated by calculation of z-scores according to the Cofino model. The PFCs which were reported most frequently by the laboratories, and assessed with the most satisfactory agreement, were perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In general, the level of agreement between the participating laboratories decreased in the following order: PFC standard solution (76% satisfactory z-scores of <[2]1 for PFOS) < human blood (67%) < human plasma (63%) < fish liver extract (55%) < water (31%) < fish tissue (17%). This shows that relative good agreement between laboratories was obtained for the study of standard and human matrices. For the fish extract, most laboratories underestimated the actual PFOS concentration due to matrix effects. The results for the fish tissue and water are also poor, indicating that the extraction and cleanup steps require further improvement. It was concluded that the PFC determinations in various matrices are not yet fully mastered.

  • 336. Vladuca, G.
    et al.
    Hambsch, F.-J.
    Tudora, A.
    Oberstedt, S.
    Oberstedt, Andreas
    Örebro University, Department of Natural Sciences.
    Tovesson, F.
    Örebro University, Department of Natural Sciences.
    Filipescu, D.
    Calculation of the neutron-induced fission cross section of 233Pa up to 20 MeV2004In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 740, no 1-2, p. 3-19Article in journal (Refereed)
    Abstract [en]

    Since very recently, direct measurements of the 233Pa(n,f) cross-section are available in the energy range from 1.0 to 8.5 MeV. This has stimulated a new, self-consistent, neutroncross-section evaluation for the n+233Pa system, in the incident neutron energy range 0.01–20MeV. Since higher fission chances are involved also the lighter Pa-isotopes had to be re-evaluated in a consistent manner. The results are quite different compared to earlier evaluation attempts. Since 233Pa is a key isotope in the thorium based fuel cycle the quality of its reaction cross-sections is important for the modeling of future advanced fuel and reactor concepts. The present status of the evaluated libraries is that they differ by a factor of two in the absolute fissioncross-section and also in the threshold energy value.

  • 337. Vladuca, G.
    et al.
    Hambsch, F.-J.
    Tudora, A.
    Oberstedt, Stephan
    Tovesson, Fredrik
    Örebro University, Department of Natural Sciences.
    Oberstedt, Andreas
    Örebro University, Department of Natural Sciences.
    Filipescu, D.
    Calculation of the neutron-induced fission cross section of 233Pa2004In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 69, no 2, p. 021604-Article in journal (Refereed)
    Abstract [en]

    Since very recently, experimental data for the energy dependence of the 233Pa(n,f) cross section are finally available. This has stimulated a new, self-consistent cross section evaluation for the system n+233Pa in the incident neutron energy range 0.01–6 MeV. The results are quite different compared to earlier evaluation attempts. Since 233Pa is an important intermediary in the thorium based fuel cycle, its neutron reaction cross sections are key parameters in the modeling of future advanced reactor concepts.

  • 338. von Hofsten, J.
    et al.
    Larsson, A.
    Örebro University, Department of Natural Sciences.
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Novel steroidogenic factor-1 homolog (ff1d) is coexpressed with anti-Mullerian hormone (AMH) in zebrafish2005In: Developmental Dynamics, ISSN 1058-8388, E-ISSN 1097-0177, Vol. 233, no 2, p. 595-604Article in journal (Refereed)
    Abstract [en]

    ff1d is a novel zebrafish FTZ-F1 gene with sequence characteristics indicating similar basic regulatory mechanisms as the previously characterized ff1 based on the presence of an FTZ-F1 box in the DNA binding domain and an interactive domain (I-Box) and an AF-2 in the ligand binding domain. The highest sequence similarity was found between ff1d and ff1b (NR5A4), a gene previously shown to be a functional homolog to the steroidogenic factor 1 (SF-1). The expression pattern of ff1d was comparable to ff1b both in brain and gonads in adults and in the pituitary and interrenal cells in embryos. SF-1 is crucial in mammalian steroidogenesis and in sex determination by regulating the anti-Mullerian hormone (AMH). In fish, AMH has not been described previously. In this study, we cloned a partial zebrafish AMH. AMH was detected in growing oocytes, the ovarian follicular layer and testicular Sertoli cells, similar to the mammalian pattern, suggesting a conserved role between zebrafish and mammalian AMH. Teleosts lack a gene homolog to SRY, which constitute the universal testis-determining factor in mammalian sex determination. Comparison of sequences and expression patterns indicate that ff1d is a new candidate for sex determination and differentiation in a way similar to SF-1, possibly involving AMH.

  • 339. von Hofsten, J.
    et al.
    Modig, Carina
    Örebro University, Department of Natural Sciences.
    Larsson, A.
    Örebro University, Department of Natural Sciences.
    Karlsson, J.
    Örebro University, Department of Natural Sciences.
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Determination of the expression pattern of the dual promoter of zebrafish fushi tarazu factor-1a following microinjections into zebrafish one cell stage embryos2005In: General and Comparative Endocrinology, ISSN 0016-6480, E-ISSN 1095-6840, Vol. 142, no 1-2, p. 222-226Article in journal (Refereed)
    Abstract [en]

    The zebrafish fushi tarazu factor-1a (ff1a) is a transcription factor belonging to the NR5A subgroup of nuclear receptors. The NR5A receptors bind DNA as monomers and are considered to be orphans due to their ability to promote transcription of downstream genes without ligands. In zebrafish, four ff1 homologues (Ff1a, Ff1b, Ff1c, and Ff1d) have been identified so far. The gene coding for Ff1a is driven by two separate promoters, and give rise to four splice variants. Ff1a is expressed in the somites and pronephric ducts during somitogenesis and in the brain, liver, and mandibular arch during later embryonic stages. In adults the gene is highly expressed in gonads, liver, and intestine, but can be detected in most tissues. The broad variety of embryonic expression domains indicates several important developmental features. One of the mammalian fushi tarazu factor-1 genes, steroidogenic factor-1 (SF-1), is essential for the development of gonads and adrenals. SF-1 is together with Sox9, WT1, and GATA4 a positive transcriptional regulator of human anti-mullerian hormone (AMH) and thereby linked to the male sex-determining pathway. The zebrafish ff1a dual promoter contains several GATA binding sites and E-boxes, a site for DR4, XFD2, MyoD, Snail, HNF3, S8, and an HMG-box recognition site for Sox9. In a first attempt to dissect the ff1a promoter in vivo we have produced first generation transgenes in order to determine the correlation between the expression of the endogenous ff1a gene and the microinjected ff1a dual promoter coupled to the pEGFP reporter vector. Our results show that the microinjected constructs are expressed in the correct tissues.

  • 340. von Hofsten, Jonas
    et al.
    Karlsson, Johnny
    Örebro University, Department of Natural Sciences.
    Jones, Iwan
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Expression and regulation of fushi tarazu factor-1 and steroidogenic genes during reproduction in Arctic char (Salvelinus alpinus)2002In: Biology of Reproduction, ISSN 0006-3363, E-ISSN 1529-7268, Vol. 67, no 4, p. 1297-1304Article in journal (Refereed)
    Abstract [en]

    Teleost fushi tarazu factor-1 (FTZ-F1) is a potential regulator of steroidogenesis. The present study shows sex-specific regulation of Arctic char fushi tarazu factor-1 (acFF1) and steroidogenic genes during reproductive maturation and in response to hormone treatment. A link between gonadal expression of acFF1, steroidogenic acute regulatory protein (StAR), and cytochrome P450-11A (CYP11A), was observed in the reproductive maturation process, as elevated acFF1 mRNA and protein levels preceded increased StAR and CYP11A transcription. Sex-specific differences were observed as estrogen treatment resulted in down-regulated levels of acFF1 mRNA in testis and male head kidney, whereas no significant effect was observed in females. 11-Ketotestosterone (11-KT) down-regulated CYP11A and 3beta-hydroxysteroid dehydrogenase (3betaHSD) in head kidney and up-regulated CYP11A in testis. StAR remained unaffected by hormone treatment. This suggests that acFF1 is controlled by 17beta-estradiol, whereas the effects on CYP11A and 3betaHSD are mediated by 11-KT. Coexpression of acFF1, StAR, and CYP11A was observed in head kidney, in addition to gonads, indicating correlation between these steroidogenic genes. StAR and acFF1 were also coexpressed in liver, suggesting a potential role in cholesterol metabolism. Although these results indicate conserved steroidogenic functions for FTZ-F1 among vertebrates, they also raise the question of additional roles for FTZ-F1 in teleosts.

  • 341. von Hofsten, Jonas
    et al.
    Karlsson, Johnny
    Örebro University, Department of Natural Sciences.
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus)2003In: General and Comparative Endocrinology, ISSN 0016-6480, E-ISSN 1095-6840, Vol. 132, no 1, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.

  • 342. Wiberg, Karin
    et al.
    Andersson, Patrik L.
    Berg, Håkan
    Örebro University, Department of Natural Sciences.
    Olsson, Per-Erik
    Örebro University, Department of Natural Sciences.
    Haglund, Peter
    The fate of chiral organochlorine compounds and selected metabolites in intraperitoneally exposed arctic char (Salvelinus alpinus)2006In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 25, no 6, p. 1465-1473Article in journal (Refereed)
    Abstract [en]

    The fate of chiral organochlorine compounds (OCs) and selected metabolites in exposed Arctic char (Salvelinus alpinus) was investigated. The contaminants alpha-hexachlorocyclohexane (alpha-HCH), cis-chlordane, 13C4-heptachlor, o,p'-DDT, and the atropisomeric chlorinated biphenyls (CBs) 95, 132, 136, 149, and 174 were solved in peanut oil and injected into the peritoneal cavity. The exposed fish were sampled three times during a five-week period, and the OC residues and detected metabolites (heptachlorexo-epoxide) were quantified in muscle and liver tissues by chiral and achiral gas chromatography-mass spectrometry and gas chromatography-electron-capture detection. Peak concentrations were reached after one to two weeks, and thereafter, the levels declined. At the end of the experiment, liver concentrations had decreased 76 to 92% relative to peak concentrations, whereas muscle concentrations showed a moderate decline (5-38%), with the exception of alpha-HCH (91%). Hydrophobicity and steric hindrance were shown to influence the assimilation process, and a significant linear relationship between the product of the steric hindrance coefficients and the inverse of the octanol-water partition coefficients (Kow) versus peak concentration was found for the CBs (r2 = 0.86, p = 0.02). The assimilation of the contaminants into muscle and liver tissues generally resulted in racemic mixtures, whereas elimination was enantioselective for alpha-HCH, cis-chlordane, o,p'-DDT, CB-132, and CB-136. The chiral heptachlor metabolite 13C4-heptachlor-exo-epoxide was formed in the fish. The enantiomeric composition of the formed metabolite indicated racemic formation, whereas the elimination process appeared to be enantioselective.

  • 343.
    Wide, Peter
    et al.
    Örebro University, Department of Technology.
    Schellwat, Holger
    Örebro University, Department of Natural Sciences.
    Implementation of a Genetic Algorithm for Routing an Autonomous Robot1997In: Robotica (Cambridge. Print), ISSN 0263-5747, E-ISSN 1469-8668, Vol. 15, no 2, p. 207-211Article in journal (Refereed)
    Abstract [en]

    A practical implementation of a genetic algorithm for routing a real autonomous robot through a changing environment is described. Moving around in a production plant the robot collects information about its environment and stores it in a temporal map, which is virtually a square grid, taking account of changing obstacles. The evolutional optimizer continuously searches for short paths in this map using string representations of paths as chromosomes. The main features of the implementation include physical realization, random walk exploration, temporal mapping, and dedicated genetic operators.

  • 344. Wolkers, H.
    et al.
    Lydersen, C.
    Kovacs, K. M.
    Burkow, I.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Accumulation, metabolism, and food-chain transfer of chlorinated and brominated contaminants in subadult white whales (Delphinapterus leucas) and narwhals (Monodon monoceros) from Svalbard, Norway2006In: Archives of Environmental Contamination and Toxicology, ISSN 0090-4341, E-ISSN 1432-0703, Vol. 50, no 1, p. 69-78Article in journal (Refereed)
    Abstract [en]

    The concentrations and patterns of polychlorinated biphenyls (PCBs), chlorinated pesticides, and polybrominated diphenyl ethers (PBDEs) were studied in white whales (Delphinapterus leucas) and narwhals (Monodon monoceros) from Svalbard, Norway. In addition, their main food items were included in the study. In the whales, a broad range of pollutants was found in relatively high concentrations. PCBs and pesticides were approximately 3000 and 8000 ng/g lipid, respectively, for white whales and three times higher for narwhals. PBDEs 47 were approximately 70 ng/g lipid for white whales and 170 ng/g lipid for narwhals. Compared with other marine mammals from the same area, contaminant levels are among the highest levels ever measured. These high levels are likely in part because of a decreased capacity to metabolize contaminants. Metabolic indices indicated that most compounds accumulate to the same degree in white whales and narwhals, but for some toxaphenes and chlordanes, narwhals might have a decreased metabolism and consequently a higher accumulation. The three-times-higher contaminant levels in blubber of narwhals was further explained by substantially higher contaminant levels in their more benthic diet. The high levels and broad pattern of accumulating pollutants make white whales and narwhals excellent indicators for a wide range of contaminants in the Arctic.

  • 345. Wolkers, Hans
    et al.
    Corkeron, Peter J.
    van Parijs, Sofie M.
    Similä, Tiu
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Accumulation and transfer of contaminants in killer whales (Orcinus orca) from Norway: indications for contaminant metabolism2007In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 26, no 8, p. 1582-1590Article in journal (Refereed)
    Abstract [en]

    Blubber tissue of one subadult and eight male adult killer whales was sampled in Northern Norway in order to assess the degree and type of contaminant exposure and transfer in the herring-killer whale link of the marine food web. A comprehensive selection of contaminants was targeted, with special attention to toxaphenes and polybrominated diphenyl ethers (PBDEs). In addition to assessing exposure and food chain transfer, selective accumulation and metabolism issues also were addressed. Average total polychlorinated biphenyl (PCB) and pesticide levels were similar, approximately 25 microg/g lipid, and PBDEs were approximately 0.5 microg/g. This makes killer whales one of the most polluted arctic animals, with levels exceeding those in polar bears. Comparing the contamination of the killer whale's diet with the diet of high-arctic species such as white whales reveals six to more than 20 times higher levels in the killer whale diet. The difference in contaminant pattern between killer whales and their prey and the metabolic index calculated suggested that these cetaceans have a relatively high capacity to metabolize contaminants. Polychlorinated biphenyls, chlordanes, and dichlorodiphenyldichloro-ethylene (DDE) accumulate to some degree in killer whales, although toxaphenes and PBDEs might be partly broken down.

  • 346. Wolkers, Hans
    et al.
    Hammill, Mike O.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Tissue-specific accumulation and lactational transfer of polychlorinated biphenyls, chlorinated pesticides, and brominated flame retardants in hooded seals (Cistophora cristata) from the Gulf of St. Lawrence: applications for monitoring.2006In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 142, no 3, p. 476-486Article in journal (Refereed)
    Abstract [en]

    Accumulation and mother-pup transfer of halogenated organic contaminants was studied in hooded seal tissues from eastern Canada. Blubber polychlorinated biphenyl (PCB) and total pesticide concentrations were relatively high, possibly due to their high trophic level and demersal feeding habits. Blood plasma showed the lowest contaminant concentrations compared to blubber and liver, possibly due to a lower affinity of these compounds to lipoproteins in blood plasma. Total contaminant body burden correlated well with blubber, liver, and milk contaminants, but not with blood plasma contaminants, indicating that blood plasma might be less suitable to monitor contaminants in hooded seals. Lactational transfer favored less lipophilic contaminants and was associated with relatively high blood plasma PCB and polybrominated diphenyl ether concentrations in females. Despite lactational transfer, females did not show significantly lower blubber contaminant concentrations or burdens than males. This might be caused by their low blubber, and thus contaminant, loss during lactation compared to other species.

  • 347. Wölz, Jan
    et al.
    Engwall, Magnus
    Örebro University, Department of Natural Sciences.
    Maletz, Sibylle
    Olsman Takner, Helena
    Örebro University, Department of Natural Sciences.
    van Bavel, Bert
    Örebro University, Department of Natural Sciences.
    Kammann, Ulrike
    Klempt, Martin
    Weber, Roland
    Braunbeck, Thomas
    Hollert, Henner
    Changes in toxicity and Ah receptor agonist activity of suspended particulate matter during flood events at the rivers Neckar and Rhine - a mass balance approach using in vitro methods and chemical analysis2008In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 15, no 7, p. 536-553Article in journal (Refereed)
    Abstract [en]

    Background, aim, and scope  As a consequence of flood events, runoff and remobilized sediments may cause an increase of ecotoxicologically relevant effects from contaminant reservoirs. Aquatic and terrestrial organisms as well as cattle and areas of settlement are exposed to dislocated contaminants during and after flood events. In this study, the impacts of two flood events triggered by intense rain at the rivers Neckar and Rhine (Southern Germany) were studied. Effects in correlation to flood flow were assessed at the river Neckar using samples collected at frequent intervals. River Rhine suspended particulate matter (SPM) was sampled over a longer period at normal flow and during a flood event. Three cell lines (H4L1.1c4, GPC.2D.Luc, RTL-W1) were used to compare Ah receptor agonist activity in different biotest systems. Multilayer fractionation was performed to identify causative compounds, focusing on persistent organic contaminants. Materials and methods  Native water and SPM of flood events were collected at the river Neckar and at the monitoring station (Rheinguetestation, Worms, Germany) of the river Rhine. Water samples were XAD-extracted. SPM were freeze-dried and Soxhlet-extracted using acetone and finally dissolved in dimethyl sulfoxide. Resulting crude extracts were analyzed for cytotoxicity with the neutral red assay. Aryl hydrocarbon receptor (AhR) agonist activity was measured in a set of biological test systems (DR-CALUX, GPC.2D, and ethoxyresorufin-O-deethylase (EROD) assay) and different cell lines. In addition, crude extracts were fractionated using a combined method of multilayer (sequence of acidified silica layers) and carbon fractionation. Fractions from the multilayer fractionation contained persistent organic compounds (polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and some polycyclic aromatic hydrocarbon (PAHs)); fractions from the carbon fractionation were separated into a PCDD/F and a PCB fraction. Dioxin-like activity of multilayer and carbon fractions was determined in the EROD assay and expressed as biological toxicity equivalency concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (bio-TEQs). The calculation of chemical equivalency concentrations (chem-TEQs) and comparison to bio-TEQ values allowed the determination of the contribution of the analyzed persistent compounds to the total biological effects measured. Results  Soluble compounds in native and extracted water samples resulted in no or minor activity in the toxicity tests, respectively. Filter residues of native water caused increased AhR-mediated activity at the peak of the flood. Activities of SPM of the river Neckar correlated well with the flow rate indicating a flood-dependent increase of toxicity culminating at the peak of flow. River Rhine SPM showed a decrease of activity regarding an SPM sample of the flood event compared to a long-term sample. Excellent correlations with AhR agonistic activity were determined for DR-CALUX and EROD assay, while the GPC.2D assay did not correlate with both other biotests. The activity of persistent dioxin-like acting compounds in multilayer and carbon fractionated PCDD/F and PCB fractions was low if compared to corresponding crude extracts. The congener pattern of PCDD/F revealed that the contaminations mainly originated from products and productions of the chlorine and organochlorine industries. Discussion  Native and extracted water samples could be shown to contain little or no cytotoxic or AhR agonistic compounds. In contrast, particle-bound compounds were shown to be the relevant effect-causing fraction, as indicated by the activities of filter residues of native water and SPM. Compounds other than fractionated persistent PCBs and PCDD/Fs were more relevant to explain AhR-mediated activities of crude flood SPM at both rivers assessed. Biologically detected activities could at least in part be traced back to chemically analyzed and quantified compounds. Conclusions  The calculation of the portion of persistent PCBs and PCDD/Fs in multilayer fractions causing the high inductions in the EROD assay in combination with chemical analysis provides a suitable tool to assess dioxin-like activity of persistent compounds in SPM sampled over the course of flood events. Depending on the catchment area and annual course of flood events, end points may either indicate an increase or a decrease of activity. In order to determine the ecological hazard potential of mobilized contaminants during flood events, the focus should be set on particle-bound pollutants. Furthermore, PCDD/Fs and PCBs, commonly expected to be the most relevant pollutants in river systems, could be shown to contribute only to a minor portion of the overall AhR-mediated activity. However, they might be most relevant for human exposure when considering persistence and bioaccumulation–biomagnification in the food chain. Recommendations and perspectives  As a consequence of climate change, flood events will increase in frequency and intensity at least in some regions such as Central Europe. Thus, it is crucial to identify the potential hazard of (re-)mobilized contaminants from reservoirs dislocated via floods and threatening especially aquatic organisms and cattle grazing in flood plains. Since other less persistent compounds seem to be more relevant to explain AhR-mediated activities in flood SPM, nonconventional PAHs and more polar compounds also need to be considered for risk assessment. Effect-directed analysis using broad-range fractionation methods taking into account compounds from polar to nonpolar should be applied for identification of pollutants causing biological effects, thus integrating biological and chemical parameters.

  • 348. Zhang, Ru bo
    et al.
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Effects of OH radical addition on proton transfer in the guanine-cytosine base pair2007In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, no 23, p. 6571-6576Article in journal (Refereed)
    Abstract [en]

    Double proton transfer (PT) reactions in guanine-cytosine OH radical adducts are studied by the hybrid density functional B3LYP approach. Concerted and stepwise proton-transfer processes are explored between N1(H) on guanine (G) and N3 on cytosine (C), and between N4(H) on C and O6 on G. All systems except GC6OH display a concerted mechanism. 8OHGC has the highest dissociation energy and is 1.2 kcal/mol more stable than the nonradical GC base pair. The origin of the interactions are investigated through the estimation of intrinsic acid-basic properties of the *OH-X monomer (X = G or C). Solvent effects play a significant role in reducing the dissociation energy. The reactions including *OH-C adducts have significantly lower PT barriers than both the nonradical GC pair and the *OH-G adducts. All reactions are endothermic, with the GC6OH --> GC6OHPT reaction has the lowest reaction energy (4.6 kcal/mol). In accordance with earlier results, the estimated NBO charges show that the G moiety carries a slight negative charge (and C a corresponding positive one) in each adduct. The formation of a partial ion pair may be a potential factor leading to the PT reactions being thermodynamically unfavored.

  • 349. Zhang, Ru Bo
    et al.
    Gao, Feng xin
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Radical-induced damage in 3'dTMP: Insights into a mechanism for DNA strand cleavage2007In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 3, no 3, p. 803-810Article in journal (Refereed)
    Abstract [en]

    DNA strand scission and base release in 3‘dTMP, induced by H and OH radical addition to thymine, is studied at the DFT B3LYP/6-31+G(d,p) level in the gas phase and in solution. In particular the mechanism of H atom transfer subsequent to radical formation, from C2‘ on the sugar to the C6 site on the base, is explored. Bulk solvation is found to lower the barrier by up to 5 kcal mol-1 and the reaction energy by up to 12 kcal mol-1 for the hydroxyl radical adducts. The strengths of the N1−C1‘(N1-glycosidic bond) and C3‘−O(P) bonds are calculated, showing that homolytic bond breaking processes are largely favored in both cases. The barrier for C3‘−O(P) bond rupture is approximately 18.2 kcal mol-1, and its breakage is preferred by 10−15 kcal mol-1 over that of N1-glycosidic bond cleavage in both the gas phase and solvents, which is consistent with the changes in C3‘−O(P) and N1−C1‘ bond lengths during the H transfer reactions. Mulliken spin densities, NPA charges, and vertical electron affinities are calculated to clarify the reactive properties of the intramolecular H-transfer radicals.

  • 350. Zhang, Ru Bo
    et al.
    Zhang, Ke
    Eriksson, Leif A.
    Örebro University, Department of Natural Sciences.
    Theoretical studies of damage to 3'-uridine monophosphate induced by electron attachment2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 9, p. 2850-2856Article in journal (Refereed)
    Abstract [en]

    Low-energy electrons (LEE) are well known to induce nucleic acid damage. However, the damage mechanisms related to charge state and structural features remain to be explored in detail. In the present work, we have investigated the N1-glycosidic and C3'-O(P) bond ruptures of 3'-UMP (UMP=uridine monophosphate) and the protonated form 3'-UMPH with -1 and zero charge, respectively, based on hybrid density functional theory (DFT) B3 LYP together with the 6-31+G(d,p) basis set. The glycosidic bond breakage reactions of the 3'UMP and 3'UMPH electron adducts are exothermic in both cases, with barrier heights of 19-20 kcal mol(-1) upon inclusion of bulk solvation. The effects of the charge state on the phosphate group are marginal, but the C2'-OH group destabilizes the transition structure of glycosidic bond rupture of 3'-UMPH in the gas phase by approximately 5.0 kcal mol(-1). This is in contrast with the C3'-O(P) bond ruptures induced by LEE in which the charge state on the phosphate influences the barrier heights and reaction energies considerably. The barrier towards C3'-O(P) bond dissociation in the 3'UMP electron adduct is higher in the gas phase than the one corresponding to glycosidic bond rupture and is dramatically influenced by the C2'-OH group and bulk salvation, which decreases the barrier to 14.7 kcal mol(-1). For the C3'-O(P) bond rupture of the 3'UMPH electron adduct, the reaction is exothermic and the barrier is even lower, 8.2 kcal mol(-1), which is in agreement with recent results for 3'-dTMPH and 5'-dTMPH (dTMPH=deoxythymidine monophosphate). Both the Mulliken atomic charges and unpaired-spin distribution play significant roles in the reactions

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