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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Isotopic Disequilibrium for Assessment of Radionuclide Transport in Peat Lands : Uranium-Thorium Series Nuclides in a Core from Klarebäcksmossen, Oskarshamn, Sweden

Lidman, Fredrik January 2005 (has links)
<p>In order to assess the risks that are associated with a deep repository of nuclear waste, it is important to know how different radionuclides behave in different environments. Since some of the most critical radionuclides in nuclear waste such as Ra-226 occur naturally in the environment, it is possible to study their behaviour directly. Peat lands are thought to be one of the most critical ecosystems due to their capability of accumulating large amounts of radioactivity and the possible exposure pathways to man.</p><p>Klarebäcksmossen is a peat land situated close to the nuclear power plant in Oskarshamn, which is one of two areas in Sweden where site investigations for a future deep repository are being conducted. In this study a complete peat-gyttja-clay profile from Klarebäcksmossen has been analysed for a large number of both natural and artificial radionuclides using gamma spectrometry. The degree of isotopic disequilibrium between different nuclides in the uranium-thorium series has been used to assess radionuclide migration and accumulation throughout the core.</p><p>The measurements indicate that uranium has been accumulated in the gyttja, but mobilised from the clay. Radium, on the other hand, has been leached from the gyttja layers, and the strikingly low Ra-226/Pb-210 ratios show that it might have been very recently. Alternatively, there is a very extensive migration of Rn-222.</p><p>In the peat low levels of radioactivity were found for most radionuclides, but with clear differences between minerotrophic and ombrotrophic peat. This may indicate that the uptake of radionuclides by peat mainly is passive. The accumulation rate for the peat has also been determined using Pb-210 dating.</p>
2

Leaching Test with Sawdust from Different Tree Species : Appropriateness of using them as adsorption media in wastewater and in stormwater treatment

Svensson, Henric January 2010 (has links)
Abstract   Bio energy in form of woodchips and sawdust is today commonly stored outdoors in heaps on hardened surfaces, exposed to weather and wind. Any water leaching from these heaps have the potential to be toxic to the environment. This paper examines the quality of the water leaching from heaps of four different tree species (oak, pine, maple and beech), by analysing different parameters such as pH, conductivity, colour, COD, BOD7, tannins &amp; lignins (T&amp;L) and phenols. The results show significant higher leaching values of COD, phenols, T&amp;L and colour from oak compared to the other tree species (pine, maple and beech). These leached substances from woodchips and sawdust were shown in the BOD7 tests and BOD7/COD ratio values to be hard to biodegrade and are therefore not easily removed from the water. Hence it is important that wood-based fuel storage conditions are considered in bio energy generation schemes to ensure that the environmental benefits of using woodchips and sawdust instead of traditional fuel are not offset by the potential harm of inappropriate storage. The investigation further showed that leaching of highly toxic substances such as phenols can be up to 10 times higher for one tree type (oak) than another (pine, beech and maple). This difference could potentially be found for other tree species not characterized in this study.  Therefore, it is important to consider the constitution of the heaps to be able to apply appropriate storage conditions to avoid these toxic substances in the leached water reaching sensitive watercourses. As some of these substances are hard to biodegrade the treatment applied need a long retention time. Another problem is the carbon: nutrient ratio, this water has a high carbon content compared to phosphorus and nitrogen content which might prevent an efficient biodegradation. Adjusting C:N:P ratio with low cost amendments might raise the performance of the biodegradation in for instance, a constructed wetland.
3

Influence of acidification and liming on metals in lake sediments

Wällstedt, Teresia January 2005 (has links)
<p>Emission and precipitation of acidifying substances and metals has caused severe acidification and increased metal concentrations in lakes and streams in Sweden as well as many other countries during the last decades. To counteract the negative effects of acidification, liming has been used extensively in Sweden since the 1970’s, a treatment that has been called one of the largest man-maid manipulations of aquatic ecosystems ever.</p><p>The aim of this thesis is to investigate the influence of acidification and liming on deposition of metals to lake sediments, and to look at the fate of metals in sediments during a possible reacidification process because of terminated liming.</p><p>Studies of both surface sediments and dated sediment profiles sampled from limed lakes and non-limed reference lakes indicated that liming causes increased sedimentation of many metals. Increased deposition to the sediments was found for Al, Cd, Co, Ni, Fe, Mn and Zn, probably as a direct result of the increased pH. Liming was also found to increase the deposition of As and Cr, but that was probably due to the secondary effect of association to Fe and Mn complexes. No influence of lime treatment on the deposition of Hg, Pb and V to lake sediments could be demonstrated. The studies also indicated that acidification can decrease the deposition of Cd, Fe, Mn and possibly also Co and Zn to the sediments.</p><p>The contribution from the used lime products to the metal load in sediments of lakes limed directly on the lake surface was also evaluated. The lime products were found to be an important source for Al, Cu and Ni and a relatively important source for Co, Cr, Hg and V, but did not seem to contribute much to the content of As, Cd, Pb or Zn in lake sediments.</p><p>An experimental study of reacidification showed that (re)mobilisation of metals, e.g Al, Cd, Mn and Zn, from sediments may occur and that reacidification of formerly lime treated lakes may contribute to increased concentrations of these metals in the lake water. Cu, Fe and Pb are less affected by pH changes and the concentrations of these metals will probably not increase in lake water during reacidification.</p><p>Altogether, the thesis shows that lime treatment causes increased deposition of many metals to the lake sediments, whereas reacidification may lead to remobilisation of some metals from the sediments with increased concentrations in the water phase as a result.</p>
4

Measurement and source apportionment of ubiquitous soot black carbon in sediments

Elmquist, Marie January 2007 (has links)
<p>The pyrogenic particles formed from incomplete combustion of organic matter are often termed black carbon (BC) and they partake in many important biogeochemical processes. For instance, BC in water and sediment affects the solid-water partitioning of hydrophobic organic pollutants reducing their bioavailability.</p><p>The key objective of this thesis was to test the chemothermal oxidation method (CTO) to quantify soot-BC in sediments. In the CTO method, sedimentary BC is isolated by removing non-pyrogenic organic matter through thermal combustion at 375°C under active airflow and subsequent removal of inorganic carbonates by adding hydrochloric acid. The CTO method was here shown to work well for quantifying the thermally more stable soot-BC phase.</p><p>Another objective was to study sediment samples to measure the historical and spatial distribution of combustion products. First, historical fluxes of BC and polycyclic aromatic hydrocarbons (PAH) were investigated in a Swedish lake sediment. Increasing fluxes of BC and PAH were seen in sediment dated to the industrial revolution in the 1850s, the high coal usage in the early 1900s lead to a 5 time increase in BC flux relative to the pre-industrial flux, and the switch from coal to oil usage in the 1950s lead to a 46 time increase in PAH flux relative to the pre-industrial flux. Further, lower fluxes came from stricter emission controls in the 1960s, improvements in combustion technology and the usage of catalytic filters from mid-1980s. Modern sediment measured 20% lower BC flux and 5 times higher PAH flux relative to the pre-industrial fluxes.</p><p>Secondly, the spatial distribution and sources of sedimentary soot-BC were studied in rivers in the Arctic region. The estimated BC flux was highest in the McKenzie (99 kton yr<sup>-1)</sup> whereas it was lowest in Yukon (1.1 kton yr<sup>-1</sup>). Contemporary biomass-derived BC was detected for the Yenisey, whereas fossil fuel derived BC was found for the Lena, Yukon and McKenzie.</p>
5

Synthesis and characterization of highly polybrominated diphenyl ethers

Teclechiel, Daniel January 2008 (has links)
<p>Polybrominated diphenyl ethers (PBDEs) make up an important class of brominated flame retardants. The present production is mainly concentrated to DecaBDE but until recently also a significant production of PentaBDE and OctaBDE took place, leaving us with a large number of different PBDE congeners. The PBDEs have become widespread pollutants abiotically and in biota, particularly in high trophic level wildlife and in humans. Accordingly, pure authentic reference standards have been required to promote high quality exposure assessments of wildlife and humans and analysis of abiotic matrices, to study both chemical and physical properties of the PBDEs and to allow toxicological studies. The objective of this thesis was to develop methods for synthesis of polybrominated diphenyl ether (PBDE) congeners and to characterize them. Further, some octabrominated DEs were determined with x-ray crystallography. Main focus has been to prepare highly brominated PBDE congeners, i.e. PBDEs substituted with six to nine bromine atoms.</p><p>A total number of twenty-three PBDE congeners were synthesized via reduction of decabromodiphenyl ether receiving nonaBDEs; perbromination and bromination of mono- and diaminodiphenyl ethers followed by diazotization of the amino group(s) and reduction of the diazonium ion(s) receiving octaBDEs and nonaBDEs; selective bromination of diaminodiphenyl ethers followed by diazotization of the amino groups and insertion of bromine receiving hexaBDEs and heptaBDEs; bromination of the latter PBDEs giving octaBDEs; and an improved coupling of symmetrical diphenyliodonium salts with bromophenols yielding tetraBDEs to octaBDEs. To enable these compounds to be synthesized three hexabromodiphenyl iodonium salts were prepared: 2,2’,3,3’,4,4’-, 2,2’,4,4’,5,5’- and 2,2’,4,4’,6,6’ - hexabromodiphenyliodonium salts. These iodonium salts are described for the first time which made it possible to synthesize PBDE congeners with 2,3,4-, 2,4,5- and 2,4,6-tribromo substitution in the phenyl rings originating from the diphenyliodonium salts. Among the PBDE congeners 18 are synthesized for the first time. The thesis includes an improved methodology for synthesis of polybromodiphenyl iodonium salts which is based on improved solubilization of both one of the reactants and the product formed. The present work on PBDE synthesis adds useful methods for synthesis of the most highly brominated diphenyl ether congeners.</p>
6

Synthesis of highly brominated diphenyl ethers and aspects on photolysis and indoor spreading

Christiansson, Anna January 2008 (has links)
<p>Adding chemicals to materials to decrease flammability can be dated back to as early as 450 BC when the Egyptians used alum to reduce flammability of wood. Almost 2500 years later brominated flame retardants (BFRs) are used to prevent ignition of textiles, electronics and polymers. BFRs in major use today are polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA), including derivatives. There have been three industrial PBDE mixtures produced. Extensive scientific reporting has shown increasing concentrations of PBDEs in wildlife and in humans. This in combination with reports on their physico-chemical characteristics and chemical reactivity have led to that two of the PBDE products have been classified as being persistent, bioaccumulative and toxic, which has led to legislative measures, in e.g. EU, Norway and the USA.</p><p>The availability of pure reference standards is a prerequisite for much toxicologically related research. Hence the main objective of this thesis was to develop additional methods for synthesis of highly brominated diphenyl ethers. Further, to quantify and identify photolysis products of decabromodiphenyl ether (decaBDE) and to perform a case study regarding PBDE exposure in aircrafts.</p><p>Synthesis of highly brominated BDE congeners by perbromination of mono- or diaminodiphenyl ethers followed by diazotization of the amino group(s) and introduction of hydrogen(s) in the molecules is a convenient route for synthesis of some octaBDEs and all nonaBDEs. Selective bromination of diaminodiphenyl ether, followed by diazotization of the amino groups and substitution with bromines yielded a hexaBDE or a heptaBDE which were then further brominated to octaBDE congeners.</p><p>Even though several studies have been performed on photolysis of decaBDE a new study with a more quantitative approach was performed as part of this thesis. Debrominated PBDE products were identified and quantified and a marker PBDE for UV degradation of DecaBDE was identified i.e., 2,2’,3,3’,5,5’,6,6-octabromodiphenyl ether (BDE-202). Polybrominated dibenzofuranes, methoxlated brominated dibenzofuranes, pentabromophenol and hydroxylated bromobenzenes were also detected. The PBDEs accounted for approximately 90% of the total amount of substances in each sample and the PBDFs for about 10%. Also, a case study on potential exposure to PBDEs in humans travelling long distances by aircraft was done. It was shown that PBDE concentrations in dust onboard aircrafts may be high and increased PBDE serum levels were indicated in a majority of the travellers.</p><p>The present thesis has contributed to make higher brominated diphenyl ethers available as reference standards, allowing better quantitative assessments possible regarding both abiotic studies and exposure assessments. New toxicological testing can also be pursued.</p>
7

Influence of acidification and liming on metals in lake sediments

Wällstedt, Teresia January 2005 (has links)
Emission and precipitation of acidifying substances and metals has caused severe acidification and increased metal concentrations in lakes and streams in Sweden as well as many other countries during the last decades. To counteract the negative effects of acidification, liming has been used extensively in Sweden since the 1970’s, a treatment that has been called one of the largest man-maid manipulations of aquatic ecosystems ever. The aim of this thesis is to investigate the influence of acidification and liming on deposition of metals to lake sediments, and to look at the fate of metals in sediments during a possible reacidification process because of terminated liming. Studies of both surface sediments and dated sediment profiles sampled from limed lakes and non-limed reference lakes indicated that liming causes increased sedimentation of many metals. Increased deposition to the sediments was found for Al, Cd, Co, Ni, Fe, Mn and Zn, probably as a direct result of the increased pH. Liming was also found to increase the deposition of As and Cr, but that was probably due to the secondary effect of association to Fe and Mn complexes. No influence of lime treatment on the deposition of Hg, Pb and V to lake sediments could be demonstrated. The studies also indicated that acidification can decrease the deposition of Cd, Fe, Mn and possibly also Co and Zn to the sediments. The contribution from the used lime products to the metal load in sediments of lakes limed directly on the lake surface was also evaluated. The lime products were found to be an important source for Al, Cu and Ni and a relatively important source for Co, Cr, Hg and V, but did not seem to contribute much to the content of As, Cd, Pb or Zn in lake sediments. An experimental study of reacidification showed that (re)mobilisation of metals, e.g Al, Cd, Mn and Zn, from sediments may occur and that reacidification of formerly lime treated lakes may contribute to increased concentrations of these metals in the lake water. Cu, Fe and Pb are less affected by pH changes and the concentrations of these metals will probably not increase in lake water during reacidification. Altogether, the thesis shows that lime treatment causes increased deposition of many metals to the lake sediments, whereas reacidification may lead to remobilisation of some metals from the sediments with increased concentrations in the water phase as a result.
8

Measurement and source apportionment of ubiquitous soot black carbon in sediments

Elmquist, Marie January 2007 (has links)
The pyrogenic particles formed from incomplete combustion of organic matter are often termed black carbon (BC) and they partake in many important biogeochemical processes. For instance, BC in water and sediment affects the solid-water partitioning of hydrophobic organic pollutants reducing their bioavailability. The key objective of this thesis was to test the chemothermal oxidation method (CTO) to quantify soot-BC in sediments. In the CTO method, sedimentary BC is isolated by removing non-pyrogenic organic matter through thermal combustion at 375°C under active airflow and subsequent removal of inorganic carbonates by adding hydrochloric acid. The CTO method was here shown to work well for quantifying the thermally more stable soot-BC phase. Another objective was to study sediment samples to measure the historical and spatial distribution of combustion products. First, historical fluxes of BC and polycyclic aromatic hydrocarbons (PAH) were investigated in a Swedish lake sediment. Increasing fluxes of BC and PAH were seen in sediment dated to the industrial revolution in the 1850s, the high coal usage in the early 1900s lead to a 5 time increase in BC flux relative to the pre-industrial flux, and the switch from coal to oil usage in the 1950s lead to a 46 time increase in PAH flux relative to the pre-industrial flux. Further, lower fluxes came from stricter emission controls in the 1960s, improvements in combustion technology and the usage of catalytic filters from mid-1980s. Modern sediment measured 20% lower BC flux and 5 times higher PAH flux relative to the pre-industrial fluxes. Secondly, the spatial distribution and sources of sedimentary soot-BC were studied in rivers in the Arctic region. The estimated BC flux was highest in the McKenzie (99 kton yr-1) whereas it was lowest in Yukon (1.1 kton yr-1). Contemporary biomass-derived BC was detected for the Yenisey, whereas fossil fuel derived BC was found for the Lena, Yukon and McKenzie.
9

Synthesis and characterization of highly polybrominated diphenyl ethers

Teclechiel, Daniel January 2008 (has links)
Polybrominated diphenyl ethers (PBDEs) make up an important class of brominated flame retardants. The present production is mainly concentrated to DecaBDE but until recently also a significant production of PentaBDE and OctaBDE took place, leaving us with a large number of different PBDE congeners. The PBDEs have become widespread pollutants abiotically and in biota, particularly in high trophic level wildlife and in humans. Accordingly, pure authentic reference standards have been required to promote high quality exposure assessments of wildlife and humans and analysis of abiotic matrices, to study both chemical and physical properties of the PBDEs and to allow toxicological studies. The objective of this thesis was to develop methods for synthesis of polybrominated diphenyl ether (PBDE) congeners and to characterize them. Further, some octabrominated DEs were determined with x-ray crystallography. Main focus has been to prepare highly brominated PBDE congeners, i.e. PBDEs substituted with six to nine bromine atoms. A total number of twenty-three PBDE congeners were synthesized via reduction of decabromodiphenyl ether receiving nonaBDEs; perbromination and bromination of mono- and diaminodiphenyl ethers followed by diazotization of the amino group(s) and reduction of the diazonium ion(s) receiving octaBDEs and nonaBDEs; selective bromination of diaminodiphenyl ethers followed by diazotization of the amino groups and insertion of bromine receiving hexaBDEs and heptaBDEs; bromination of the latter PBDEs giving octaBDEs; and an improved coupling of symmetrical diphenyliodonium salts with bromophenols yielding tetraBDEs to octaBDEs. To enable these compounds to be synthesized three hexabromodiphenyl iodonium salts were prepared: 2,2’,3,3’,4,4’-, 2,2’,4,4’,5,5’- and 2,2’,4,4’,6,6’ - hexabromodiphenyliodonium salts. These iodonium salts are described for the first time which made it possible to synthesize PBDE congeners with 2,3,4-, 2,4,5- and 2,4,6-tribromo substitution in the phenyl rings originating from the diphenyliodonium salts. Among the PBDE congeners 18 are synthesized for the first time. The thesis includes an improved methodology for synthesis of polybromodiphenyl iodonium salts which is based on improved solubilization of both one of the reactants and the product formed. The present work on PBDE synthesis adds useful methods for synthesis of the most highly brominated diphenyl ether congeners.
10

Synthesis of highly brominated diphenyl ethers and aspects on photolysis and indoor spreading

Christiansson, Anna January 2008 (has links)
Adding chemicals to materials to decrease flammability can be dated back to as early as 450 BC when the Egyptians used alum to reduce flammability of wood. Almost 2500 years later brominated flame retardants (BFRs) are used to prevent ignition of textiles, electronics and polymers. BFRs in major use today are polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA), including derivatives. There have been three industrial PBDE mixtures produced. Extensive scientific reporting has shown increasing concentrations of PBDEs in wildlife and in humans. This in combination with reports on their physico-chemical characteristics and chemical reactivity have led to that two of the PBDE products have been classified as being persistent, bioaccumulative and toxic, which has led to legislative measures, in e.g. EU, Norway and the USA. The availability of pure reference standards is a prerequisite for much toxicologically related research. Hence the main objective of this thesis was to develop additional methods for synthesis of highly brominated diphenyl ethers. Further, to quantify and identify photolysis products of decabromodiphenyl ether (decaBDE) and to perform a case study regarding PBDE exposure in aircrafts. Synthesis of highly brominated BDE congeners by perbromination of mono- or diaminodiphenyl ethers followed by diazotization of the amino group(s) and introduction of hydrogen(s) in the molecules is a convenient route for synthesis of some octaBDEs and all nonaBDEs. Selective bromination of diaminodiphenyl ether, followed by diazotization of the amino groups and substitution with bromines yielded a hexaBDE or a heptaBDE which were then further brominated to octaBDE congeners. Even though several studies have been performed on photolysis of decaBDE a new study with a more quantitative approach was performed as part of this thesis. Debrominated PBDE products were identified and quantified and a marker PBDE for UV degradation of DecaBDE was identified i.e., 2,2’,3,3’,5,5’,6,6-octabromodiphenyl ether (BDE-202). Polybrominated dibenzofuranes, methoxlated brominated dibenzofuranes, pentabromophenol and hydroxylated bromobenzenes were also detected. The PBDEs accounted for approximately 90% of the total amount of substances in each sample and the PBDFs for about 10%. Also, a case study on potential exposure to PBDEs in humans travelling long distances by aircraft was done. It was shown that PBDE concentrations in dust onboard aircrafts may be high and increased PBDE serum levels were indicated in a majority of the travellers. The present thesis has contributed to make higher brominated diphenyl ethers available as reference standards, allowing better quantitative assessments possible regarding both abiotic studies and exposure assessments. New toxicological testing can also be pursued.

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