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Träfflista för sökning "AMNE:(NATURVETENSKAP Kemi Miljökemi) srt2:(2000-2004)"

Sökning: AMNE:(NATURVETENSKAP Kemi Miljökemi) > (2000-2004)

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1.
  • Dario, Mårten, et al. (författare)
  • Effects of cement additives on radionuclide mobility
  • 2004
  • Ingår i: Scientific basis for radioactive waste management XXVII. - Warrendale, Pa : Materials Research Society. - 1558997520 ; , s. 639-644
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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  • Dario, Mårten, 1970- (författare)
  • Metal distribution and mobility under alkaline conditions
  • 2004
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The adsorption of an element, expressed as its distribution between liquid (aquatic) and solid phases in the biogeosphere, largely determines its mobility and transport properties. This is of fundamental importance in the assessment of the performance of e.g. geologic repositories for hazardous elements like radionuclides. Geologic repositories for low and intermediate level nuclear waste will most likely be based on concrete constructions in a suitable bedrock, leading to a local chemical environment with pH well above 12. At this pH metal adsorption is very high, and thus the mobility is hindered. Organic complexing agents, such as natural humic matter from the ground and in the groundwater, as well as components in the waste (cleaning agents, degradation products from ion exchange resins and cellulose, cement additives etc.) would affect the sorption properties of the various elements in the waste. Trace element migration from a cementitious repository through the pH- and salinity gradient created around the repository would be affected by the presence and creation of particulate matter (colloids) that may serve as carriers that enhance the mobility. The objective of this thesis was to describe and quantify the sorption of some selected elements representative of spent nuclear fuel (Eu, Am) and other heavy metals (Zn, Cd, Hg) in a clay/cement environment (pH 10-13) and in the pH-gradient outside this environment. The potential of organic complexing agents and colloids to enhance metal migration was also investigated. It was shown that many organic ligands are able to reduce trace metal sorption under these conditions. It was not possible to calculate the effect of well-defined organic ligands on the metal sorption in a cement environment by using stability constants from the literature. A simple method for comparing the effect of different complexing agents on metal sorption is, however, suggested. The stability in terms of the particle size of suspended colloidal matter (clays and an iron hydroxide) was measured by photon correlation spectroscopy. In the absence of large amounts of organic material, the present colloids will, in most cases, not enhance metal migration in a cementitious environment due to agglomeration of the colloidal phase at high pH and salinities.
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  • Backe, Cecilia (författare)
  • Persistent organic pollutants in the atmosphere - spatial and temporal variations
  • 2001
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In these thesis I have studied the spatial and temporal variations of PCBs in the atmosphere and in precipitation in southern Sweden. Further, soil-air exchange processes of PCBs were investigated. Finally, the long-range transport of PCBs and DDT was studied in the Baltic Sea region and in a tropical vs. a temporal region. On the regional scale there were significant differences in PCB concentration in the atmosphere, in precipitation and in soil between nearby sampling-areas. Differences in PCB concentrations between areas probably originated from varying geographical and meteorological conditions that affected exchange processes between air and soil/vegetation surfaces. Temporal variations in PCB concentration in atmosphere and precipitation were also found. For PCBs in the air, a systematic pattern in the deviation from the yearly median value for the region was observed. Wind direction played an important role for PCB concentration in precipitation in coastal areas, while at the inland sites this variable seemed to have a minor influence. To examine the intensity of precipitation scavenging, the total washout ratios were calculated and the highest ratios were observed at the two sites where PCB concentration in the air was high. Further, high concentrations of PCB in precipitation correlated with a composition of highly chlorinated PCB congeners, as shown by principal component analysis. For most of the sites there was a significant negative relationship between PCB concentration and rain volume. Soil type and soil organic matter content was found to be important for the variations in PCB concentration between nearby areas. Highest concentrations were found at two sites with sandy soils, one with an extremely high organic carbon content. Soils with similar soil textures (i.e. sandy silt moraine) did not show any significant differences in PCB concentrations. PCB congener composition was shown to differ between sites, with site-specific congener patterns. No significant relationships were found between air and soil concentrations of PCBs, or between deposition and soil concentrations. From fugacity quotient calculations it was shown that the soil- and air compartments for most of the sampling-areas were close to equilibrium. However, for some areas there was an outgassing of PCBs from the soil and at one site a tendency for a transport of PCBs from the air to the soil was observed. Within the Baltic Sea region a latitudinal gradient of PCBs in the atmosphere was revealed, with higher levels in the south. Further evidence of the global distillation theory was shown in a study with higher atmospheric levels of DDT in a tropical region in comparison with DDT levels in a temperate region. In accordance with the theory, DDT levels were high in fish from the temperate region, but low in fish from the tropical region.
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6.
  • Karlsson, Daniel (författare)
  • Airborne Isocyanates, Aminoisocyanates and Amines
  • 2001
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Isocyanates are used in the production of polyurethane (PUR). Exposure to isocyanates is associated with respiratory disorders and may occur during production or processing of PUR. During thermal degradation of PUR, amines and aminoisocyanates are formed in addition to isocyanates. Some isocyanates and several aromatic amines are sensitizers and listed as carcinogens. A liquid chromatography mass spectrometry (LC-MS) method for simultaneous determination of isocyanates, aminoisocyanates and amines in gas and particle phase was developed. Air samples were collected in midget impinger flasks, containing di-n-butylamine (DBA) in toluene, and glass fibre filters in series to form specific DBA-isocyanate derivatives. Amines were derivatized with ethyl chloroformate. Derivatives were characterized using both LC-MS and LC-chemiluminescent nitrogen detection. Gas chromatography with MS and thermionic specific detection was also used. LC-MS detection resulted in a highly sensitive measurement of isocyanates equivalent to 1/2000 of the Swedish threshold limit value (for TDI in a 5 L air sample). In air samples from spray painting operations, aliphatic isocyanates that have not been reported previously were revealed. In car repair shops, during work operations such as welding in PUR-coated metal sheets, isocyanates, aminoisocyanates and amines were observed at high concentrations in both gas and particle phase. Compounds with high volatility were efficiently collected in the impinger flask, whereas compounds with low volatility were mainly found on the filter. Isocyanic acid (ICA) and methyl isocyanate (MIC) were among the most dominating compounds present. ICA and MIC could also be observed when urea-based resins were thermally degraded.
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8.
  • Sjödin, Andreas, 1971- (författare)
  • Occupational and dietary exposure to organohalogen substances, with special emphasis on polybrominated diphenyl ethers
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis is aimed at widening the current knowledge base about human exposure to brominated flame retardants (BFRs), particularly polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA). Data on exposures to some of the traditional organohalogen substances (OHS) have been included for comparative reasons. BFRs are produced and applied in large quantities for fire prevention purposes in our society today. The ongoing production and use may lead to a dramatic pollution problem in the future unless they are used with care. Human exposure to BFRs must also be understood, assessed and measures based on the scientific knowledge should be taken when necessary.Ambient air measurements of BFRs at an electronics dismantling plant showed significantly higher levels of hexa- to decabrominated diphenyl ethers (hexaBDE-decaBDE), tetrabromobisphenol A (TBBPA) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) than in any other indoor facilities, including IT intensive work environments. Serum PBDE levels in workers at a dismantling plant were found to have significantly elevated concentrations of hepta- to decaBDEs, compared to a non-exposed group of women, comprised of cleaners. Results were obtained that unambiguously show that decaBDE is bioavailable, even though it has a molecular mass of 959 and previously was regarded as not being bioavailable. The decaBDE is present both in the workers and in persons from the control group. The decaBDE has however also been shown to be much less persistent than other PBDE congeners, with a half-life in humans of approximately 7 days, while a heptaBDE was shown to have a half-life of almost 3 months. TBBPA was also shown at low levels in human blood and to have a short half-life. Human exposure to OHS via intake of contaminated fish has been studied in a group of Latvian and Swedish men with highly interindividual consumption of fatty Baltic Sea fish. The OHS levels observed in serum were significantly related to both age and fish consumption for PCB and DDE but not for 2,2',4,4'-tetrabromodiphenyl ether, representing traditionally studied and newer OHS, respectively.Methods for reliable analysis of PBDEs, TBBPA and other BFRs have been developed. Improvements have been made in the clean-up procedure to minimize interferences, avoid adsorption to glass and to apply a highly specific identification mass spectrometric method. The instrumental analyses have been improved by making changes in sample application to the gas chromatographic system and choice of column for the separations. With these methods, it has also been possible to detect and quantify compounds with high molecular weights, e.g. decaBDE in both air and serum samples. A more relevant presentation of concentration data is suggested, based on molar mass instead of weight.
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9.
  • Söderström, Maria, 1960- (författare)
  • Local and global contaminants in Swedish waters : studies on PCBs, DDTs, 4,5,6-trichloroguaiacol and their transformation products in fish and sediments
  • 2002
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis is focused on studies on the environmental fate and methodological improvements for determination of the global contaminants, PCBs and DDTs, and locally discharged phenolics, e.g. 4,5,6-trichloroguaiacol (4,5,6-TCG), and their transformation products.4,5,6-TCG is released from bleached pulp mills, and was chosen as a model substance, to study its fate and effects in aquatic environments. In a brackish water model ecosystem, 4,5,6-TCG was shown to be transformed via demethylation, dechlorination, and methylation reactions. Marine periphyton exposed to 4,5,6-TCG was shown to form demethylated, brominated and dimeric metabolites. Several of these metabolites were identified and quantified. Also more tightly bound chlorophenolics were recovered from the substrate, after harsh extraction procedures had been applied. Conjugates of chlorophenols in fish bile were determined as useful tracers for monitoring effluents from bleached pulp mills, even in areas far from the discharge point. To facilitate calculations of water concentrations, bile to water bioconcentration factors (bBCF-values) were determined for several phenolics, including also alkali-labile chlorocatechols.PCBs and DDTs, were assessed in Swedish lakes with background exposure of these global contaminants. A methodological study focus on the contamination risks of airborne PCBs, during freeze-drying and storage of dry sediment samples. Eutrophication has been proposed to cause lower levels of pollutants in biota in lakes due to biomass dilution but in this thesis examples of higher levels of PCBs in sediment traps, sediment and in perch, and also in higher fluxes of PCBs to the sediment, were observed. Phytoplankton are supposed to be responsible for most of the transport of the contaminants. The composition of DDTs in soil, sediment traps and in dated sediment cores was studied in some detail. PCBs, DDTs, HCB and HCHs were measured in sediments from 100 reference lakes included in the National Swedish Environmental Program. The lakes have a large variation in lake characteristics, representative for different areas in Sweden. A gradient was observed for sPCB with decreasing levels from the south west towards the north. The results suggests that longrange transport is the dominating mechanism for distribution of the contaminants analysed. In this study the levles of PCBs and DDTs were lower in eutrophic lakes than in oligotrophic lakes, in an area with similar atmospheric exposure.
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10.
  • Harju, Mikael, 1968- (författare)
  • Analysis of PCBs with special emphasis on comprehensive two-dimensional gas chromatography of atropisomers
  • 2003
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • There are 209 PCB congeners, 136 of which have been found in technical PCB mixtures and hence may be found in the environment as a result of either intentional or unintentional release. The identification and quantification of the congeners are difficult due to analytical bias from coeluting PCBs and other persistent organic pollutants. Among the 209 possible PCB congeners, 19 tri- and tetra-ortho chlorinated congeners exist in stable atropisomeric conformations. The racemization barrier were determined for twelve of the nineteen atropisomers and was found to be between 176-185 kJ × mol-1 and ca. 250 kJ × mol-1 for tri- and tetra-ortho PCB, respectively. Further, a buttressing effect of 6.4 kJ × mol-1 was observed for congeners with vicinal ortho-meta chlorines. Comprehensive two-dimensional gas chromatography (GC×GC) was used to analyze the atropisomers and other PCBs. A Longitudinally Modulated Cryogenic System (LMCS) was used with liquid CO2 as cryogen. The LMCS was optimized for semi-volatile organic substances, primarily PCBs. The trap temperature was shown to be an important factor for the trapping and desorption efficiency, as was the thermal mass of the column used in the modulator region. A number of column sets were tested and the separation efficiency, congener resolution and analysis time was evaluated. Good separation of non- and mono-ortho PCBs and “bulk” PCBs (in a technical PCB) was obtained within 8 min using a smectic liquid crystal column (LC50) as the first and a nonpolar column as the second dimension column. Using a second column, an efficient nonpolar (DB-XLB) column, which separates many PCB congeners, were combined with a polar (cyanopropyl) or shape selective (LC50) second dimension column. As a maximum, 181 of the 209 congeners and 126 of the 136 Aroclor PCBs were resolved. The seven frequently measured PCBs (PCBs 28, 52, 101, 118, 138, 153 and 180) and all WHO-PCBs were separated from all other Aroclor PCBs. Chiral PCBs are released into the environment as racemic mixtures. However, organisms have been shown to enantiomerically enrich many of the atropisomers, suggesting that enantioselective biotransformations occur. Non-racemic PCB enrichment has also been seen in mammalians including humans, which is of particular concern because of the potential health risk. An analytical procedure were therefore developed and used to determine the levels of atropisomeric PCBs, planar-PCBs (WHO-PCBs) and total PCBs in seals with different health status. GC×GC was used to separate the target PCBs from other PCBs and potential interferences. A chiral column (permethylated â-cyclodextrin) was used in combination with a polar or shape selective column and enantiomeric fractions (EFs) were determined for five atropisomeric PCBs, i.e. CBs 91, 95, 132, 149 and 174. Some atropisomers had EF that deviated largely from racemic. The deviation was larger in liver than blubber, indicating enantioselective metabolism. However, there was no selective passage of the studied atropisomeric PCBs across placenta and no selective blood-brain barrier. Similarly, no correlation between EFs and health status was observed, although there was a correlation between total PCBs and health status.
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