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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.
31

Human exposure to organohalogen compounds in the Faroe Islands

Fängström, Britta January 2005 (has links)
The Faroe Islands in the North Atlantic are part of the sub-Arctic region, a remote region far from industrial activity. In spite of this remoteness, the Islands are not a sanctuary: exposures and effects of environmental pollutants mar its natural beauty and wildlife. In the Arctic regions, fish, sea mammals and seabirds have shown to contain elevated levels of the classical persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), as well as more recent POPs such as the polybrominated diphenyl ethers (PBDEs). Human populations living in the Arctic regions are usually highly dependent on seafood and seabirds as food sources, and diet becomes their major source of exposures to POPs. As reported in the 1980’s, residents of the Faroe Islands were shown to have high concentrations of organohalogen substances (OHS) in their breast milk. Long-finned pilot whales (Globicephala melas) blubber and meat have been shown to be a major source of OHS exposure for some of the Faroe Islanders. The main objective of this thesis is to investigate the sources and concentrations of some POPs and their metabolites for the Faroese population. First, human milk and serum from pregnant women (mothers) and children were analyzed for PBDEs, PCBs, and polychlorinated biphenylols (OH-PCB), the major PCB metabolites. Second, POPs were measured in seabirds, i.e. PCBs in fulmars (Fulmarus glacialis) and guillemots (Uria algae), and PBDEs in fulmars to search for other potential sources of POPs exposure. The results reinforce previous findings that part of the Faroe Island population is highly exposed to OHS. Median concentrations (430 ng/g lipid weight (l.w.) of CB-153) in maternal serum (1994-95) are among the highest in the world. Serum concentrations of CB-153 in children (age 7, samples collected in the early 2000’s) were approximately 90% of those in the mothers, sampled 1994-95. Similarly high CB-153 concentrations (380 ng/g l.w.) were measured in samples of mother’s milk, collected in 1999. The OH-PCB concentrations were also high in segments of the population, with 2.9 ng/g fresh weight as the sum of five OH-PCBs. Except for 4-OH-CB107, concentrations of OH-PCBs were generally lower in children than in mothers. The ΣPBDE median concentrations in maternal serum and human milk (1999) are at the higher end of those reported in Europe, with levels of 9.5 and 8.2 ng/g l.w. respectively. ΣPBDE levels increase in human milk samples collected at three different time points (1987-1999), mainly due to increasing BDE-153 concentrations. The range of serum ΣPBDE concentrations in mothers and children are similar, although the congener patterns show differences. BDE-47 is the dominant congener in maternal serum, while BDE-153 is the major congener in children. The differences seen in PBDE congener patterns may arise differences in dates of sampling (7 years) for the two populations, maternal serum sampled in 1994-95 and children serum sampled in 2000-01, rather than from differences in uptake/metabolism or in contemporary exposures. PCB concentrations in fulmars and pilot whales show similar ranges. In contrast, PBDE concentrations are 100 times higher in pilot whales than in fulmars. Consequently, Faroese may be especially exposed to PCBs via consumption of fulmars and fulmar eggs, while the exposure to PBDEs is less pronounced. Results from this thesis highlight the pronounced exposures to PCBs, OH-PCBs, and PBDEs among residents of the Faroe Islands, a remote region in the Northern Atlantic far away from industrial and urban sources of pollution.
32

Acrylamide in food products : Identification, formation and analytical methodology

Eriksson, Sune January 2005 (has links)
The aim of this thesis was to verify the indicated occurrence of acrylamide formation in heating of food, to identify factors affecting the formation, and to identify important sources of acrylamide exposure from food. As a prerequisite for the studies, gas- and liquid-chromatographic methods with mass spectrometric detection were developed for the analysis of acrylamide in food. The developed methods showed a high correlation coefficient (0.99), high sensitivity and reproducibility. Acrylamide was demonstrated to occur in heated food products, with unexpectedly high levels in potato products (up to mg/kg level in potato crisps) and in beetroot. The identity of acrylamide was confirmed by the developed methods. With potato as a food model, different factors affecting the acrylamide formation were tested. It was shown that the addition of asparagine and fructose, as well as heating temperature and time had a large impact on the formation. Other factors affecting the acrylamide content were pH, addition of other amino acids apart from asparagine, protein and other reducing sugars. No significant effects were observed from addition of neither antioxidant nor radical initiators. It was discovered that acrylamide could be formed during heating of biological materials similar to food, also at temperatures below 100 ˚C. Furthermore, it was demonstrated that a fraction of acrylamide evaporates during heating, similar to conditions for cooking in household kitchens, and during dry matter determinations in laboratories (65-130 ˚C). This constitutes an earlier unobserved source of exposure to acrylamide. The method for extraction of food was studied with regard to yield of acrylamide. It was shown that the yield at pH ≥12 increases 3 - 4 times compared to normal water extraction for some foods products. Extraction at acidic pH or with enzymatic treatment was also tested, showing no effect on yield. In a study with mice the bioaviability of acrylamide extracted with the normal water extration and at alkaline pH was compared. It was shown that the extra acrylamide released at alkaline pH gave insignificant contributions to the in vivo dose, measured by hemoglobin adducts.
33

Polychlorinated biphenyls and their metabolites in human blood : Method development, identification and quantification

Hofvander, Lotta January 2006 (has links)
PCBs are well known environmental pollutants. They are also precursors to metabolites, as the hydroxy-PCBs and the methylsulfonyl-PCBs. This thesis presents a validated methodology for analysis of PCB metabolites and a structural identification of 38 hydroxy-PCBs in human blood. Further methodological development resulted in an identification of a similar number of methylsulfonyl-PCBs. The analytical method has been applied in two extensive studies of humans, consisting of maternal and cord blood from Dutch women and of blood from humans living in Slovakia. The Dutch shows that the relative transfer of hydroxy-PCBs from the mother to the foetus is higher compared to the PCBs. Even though the chemical plant in Michalovce in Slovakia had been shut down for over 20 years, the concentrations of PCB and its metabolites were among the highest detected in European human blood.
34

Human exposure to persistent organic pollutants : Illustrated by four case studies in Europe

Weiss, Jana January 2006 (has links)
An extensive use of chemicals in countless consumer products has resulted in human exposure to several persistent organic pollutants (POPs). Sufficient knowledge about their chemical composition properties and environmental faith is required, to be able to proper risk assess and regulate the substances. Significant data gaps exist regarding knowledge of actual exposure to humans and toxicological effect data. The objective of this thesis was to add human exposure data of a few POPs from four case studies. The analytes discussed in this thesis are polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD). Three European populations were studied. Milk was analysed from a group of women, who were accidentally exposed to high levels of 2,3,7,8-TetraCDD (TCDD) in Seveso, 1976. Still today, twice as high TCDD levels were recorded in the milk, compared to background concentrations. Serum was analysed from mothers and their infants from The Netherlands. Cord serum contained equal amounts of POPs as in mother’s blood, indicating non-hindered placenta transfer. Serum analysed from Swedish men and women with a high fish intake had elevated PCB and PCB metabolite (OH-PCB) levels. Additionally, butter was collected worldwide and shown to be a suitable matrix for dairy product survey of POPs. The exposure levels in the four papers were compared to recently reported exposure levels in Europe. It is indicated in the thesis that the PCDDs/PCDFs and PCBs toxic equivalency (TEQ) levels are of concern, i.e. the ratio between threshold levels for adverse health effects and TEQ exposure levels is lower than requested margin of safety. Average levels of PBDE/HBCDD in the European population are estimated to be of no concern today, but for individuals with intakes at the 95th percentile are the current margins of safety small.
35

Modeling the global fate and transport of perfluoroalkylated substances (PFAS)

Armitage, James M. January 2009 (has links)
Perfluoroalkylated substances (PFAS) are persistent contaminants that are widely distributed in the global environment. Despite the fact that these chemicals have been manufactured and used for over 50 years, there has been little scientific and regulatory interest until very recently. An important research priority over the past decade has been to gain a better understanding of the mechanisms and pathways explaining the presence of these compounds in remote regions. One explanation is related to the use and release of volatile precursor compounds which undergo atmospheric transport and are also susceptible to degradation to PFAS through gas phase reactions with radical species. The main purpose of this doctoral thesis was to investigate an alternative explanation, namely the long-range transport (LRT) of PFAS themselves, which have been released into the environment in substantial quantities during manufacturing and product use. Papers I – III explore the LRT potential of perfluorocarboxylic acids and perfluorocarboxylates and demonstrate that both oceanic and atmospheric transport are efficient pathways of dispersion from source to remote regions of the Northern Hemisphere. Oceanic transport of perfluorooctane sulfonate (PFOS) was shown to be an important process in Paper IV as well. The role of precursor transport and degradation to PFOS was also examined in this paper. The most interesting aspect of the fate and transport of PFOS precursors is the rapid response in ambient concentrations exhibited by these compounds in the model simulations following production phase-out. Since precursor compounds are known to degrade to PFOS in vivo, the modeling results demonstrate that this exposure pathway is a plausible explanation for the declining trends in PFOS concentrations reported for marine mammals in some remote environments.
36

Modelling Chlorine Transport in Temperate Soils

Ibikunle, Olatunde Idris January 2007 (has links)
Microbes have been suggested to have a strong impact on the transportation of chlorine in soils. There are speculations about environmental factors limiting microbial effect on chlorine movement and retention. For this study, a numerical hydrochemical model was built to describe microbial transformation of chlorine in a laboratory lysimeter experiment. Undisturbed soil cores used to set-up the experiment were collected from a coniferous forest soil in southeast Sweden. The lysimeters were modelled in groups depending on their different water and chloride treatments. Microbial transformation of chlorine was better described under high water residence times and high chloride loads compared to low water residence times and low chloride loads. Microbial activity was also shown to properly account for a sudden shift from net-chlorine retention to net chlorine release in most of the lysimeters. Oxygen proved to be very important in accounting for the short-term shift from chloride retention to release in all the lysimeters. Model outcome revealed that 0.02– 0.10 mg Cl- could be available per day in a coniferous soil depending on season and other soil conditions. This study shows that modeling enable a better understanding of chlorine biogeochemistry. It also confirms the speculated importance of microbial activities on chloride availability in soils.
37

Organic chlorine in soilwater : Influence of Clear-cuttning and Nitrogen

Fredriksson, Maria January 2007 (has links)
Chlorine is one of most common element on earth and it is essential in every living organism, but can also cause problems in the environment. Chlorine can exist both as inorganic (Clin) and organically bound (Clorg). Earlier was the common opinion that Clorg only occurs from anthropogenic sources, but the last years, research has shown that chlorine is a part of the biogeochemical cycle and Clorg also can have natural sources. Many chlorinated substances are poisonous, so the fact that they have a natural source created attention. Fertilizations with nitrogen in forest areas have shown unexpected consequences, such as an increase leakage of nitrogen to ground and surface water. Clear-cutting is a disturbance on the ecosystem and the environment is sensitive for disturbances. Because of the fact that both chlorine and fertilization can be environmental problems and that clear-cutting is a big disturbance in the nature, this study will investigate if there are changes of organic chlorine (Clorg) in soil water after clear-cutting and if fertilization with nitrogen has any influence on the concentration of Clorg. This study was made in a forest area in Värmland, Sweden (Hagfors). Chemical analyses were made in the laboratory though measuring AOX (absorbable organic halogens). The result of this study showed that clear-cutting probably has some effect on the Clorg concentration and that nitrogen doesn’t have any influence.
38

Effect of Khartoum City for Water Quality : chemical analyses / تأثير مدينة الخرطوم علي نوعية مياه نهر النيل : تحاليل كيميائيه

Bastway Mohammed, Omer Abdalrahim January 2007 (has links)
This thesis assesses the water quality of the River Nile around the city Khartoum in Khartoum State, Sudan Republic, and investigates eventual influences of the city on the River Nile by analysis of the following parameters: temperature, pH, and conductivity, and Adsorbable Organic Halogen (AOX), cadmium (Cd), lead (Pb), chromium (Cr), Total Organic Carbon(TOC) and Nitrate (NO3− ). A survey of the area is also included. It was concluded that the city Khartoum added small but legible concentrations of cadmium, lead, chromium and TOC to the river Nile. However, the resulting concentrations were all within acceptable levels. Also, the observed results showed that the Blue and White Nile, which merge together upstream on the outskirts of Khartoum, had concentrations of AOX resp. chromium, which were not suitable for drinking water.
39

Organohalogen contaminants in Greenland shark (Somniosus microcephalus)

Strid, Anna January 2010 (has links)
The remote sub-Arctic/Arctic environment has due to human activities become a sink for organohalogen contaminants (OHCs). These OHC include traditional contaminants such as polychlorinated biphenyls (PCBs), DDTs and technical mixtures of polybrominated diphenyl ethers (PBDEs), all included in the Stockholm Convention list of persistent organic pollutants (POPs). Other OHCs, currently under evaluation to be included among the POPs i.e. short chain chlorinated paraffins (SCCPs) and hexabromocyclododecane (HBCDD) are also found in these environments as well as a whole range of other OHCs. The main objective of this thesis is to increase the knowledge about the presence of OHCs in a high trophic Arctic shark species, the Greenland shark (Somniosus microcephalus). The Greenland shark is an opportunistic feeder, occasionally feeding at the top of the Arctic marine food chain. Furthermore may this species have a life span in excess of 100 years and is probably among the oldest of any fish species. These traits make the shark prone to accumulate elevated concentrations of OHCs. This has shown to be true for the Greenland sharks studied and most of the targeted OHCs were determined in the species. The highest concentrations were observed for the DDTs, ranging up to 26 μg/g fat. Other OHCs reported that are of special interest are SCCPs and brominated flame retardants used as replacement products to PBDEs; pentabromoethylbenzene (PBEB) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE). Also a range of OHCs whose origin is assumed to be natural, were shown to be present in Greenland sharks. This thesis is stressing the fact that even though the use of certain OHCs has been banned for decades they are still present at high concentrations in the deep waters of the Arctic. Therefore it is of major importance to continue to monitor the fate of traditional and emerging OHCs in the environment, and for this purpose the Greenland shark is an excellent species. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
40

Kväve i Östra Mälaren : hur kunskap förvaltas och används i tillståndsprocesser / Nitrogen in Eastern Lake Mälaren : How Knowledge is Managed and Applied in Permitting Processes

Halling, Nina January 2006 (has links)
The nitrogen cycle in freshwater bodies is complex and consists of many separate processes affected by a number of important factors for example oxygen concentration in the water, temperature and circulation. Knowledge of the different components of the nitrogen cycle exists; however, a complete and comprehensive picture is difficult conceptually as well as theoretically. The available literature illustrates that the research on nitrogen and the related freshwater processes is still associated with high uncertainty of how much of the supplied nitrogen from the catchment is transported with the water versus and how much is lost due to denitrification, sedimentation or uptake by plants. This report is an interdisciplinary survey of Nitrogen discharge permitting. The research focuses in particular on the decision-making process, the levels of scientific standard and the administrative framework. Application for Nitrogen discharge permits are decided by the Environmental Court with council from their own experts as well as relevant government authorities and organisations. The court bases their decisions largely on a report that is produced by a third party with direct input from the permit applicant. With the goal aimed at cheapest production of report results in a situation where data is incomparable and discontinuous and hinders consistent rulings. Where there is a lack of knowledge, decisions are based on assumptions, estimations and intuition. To be able to make profitable decision for the society in environmental questions concerning Nitrogen there has to be an adequate basis. It has also pushed the Environmental Court to use the Precautionary Principle since threshold values become general and are not context specific. This has resulted in court rulings that, in hindsight, are uneconomical both for the applicant and broader society. The permitting process must consider a range of directives and regulations. The basis for Swedish environmental law, and more specifically Nitrogen permitting, includes Miljöbalken, the Council Directive concerning urban waste-water treatment, the Council Directive concerning the protection of waters against pollution caused by nitrates from agricultural sources and the Water Policy Directive. Furthermore, the Broviken area investigated in this report is classified as a Natura 2000 in which some portions are slated to switch over to nature reserve status. In addition to all these directives and regulations, Nitrogen permitting must also take into consideration the 15 Environmental Goals declared by the Swedish Government. / Kvävets kretslopp i limniska miljöer är ett komplext förlopp bestående av flera processer vilka påverkas av en rad omgivande faktorer. Kännedom finns om de olika delprocesserna men exakt kunskap och en täckande helhetsbild är svår att få. Vid litteratursökning och samtal med verksamma inom området framkommer en bild av att forskning bedrivits med fokus på kväve och dess processer men har under 1990-talet stannat av och inriktats mer på andra områden och ämnen. Man vet för tillfället till exempel inte med säkerhet hur stor del av det kväve som tillförs vattnet som transporteras vidare och hur står del som denitrifieras, sedimenterar eller tas upp av växter. Detta skapar en osäkerhet i massbalansberäkningar och olika analyser och beräkningar av kvävets transport och påverkan på sin omgivning. I miljödomstolens arbete att bedöma en ansökan om kväveutsläpp för en verksamhet ber de utöver sina egna experter olika myndigheter och organisationer om synpunkter. Dessa hämtar fakta för sina utlåtande från rapporter om miljöstatus i området. Ofta baseras olika myndigheter och organisationers uttalanden på samma rapport, en rapport som sökanden indirekt varit med att framställa genom ett vattenvårdsförbund. Då vattenvårdsförbundet genom påtryckning från sina medlemmar söker den billigaste lösningen av uppgiften miljöövervakning låter man de som tar minst betalt framställa en rapport och utföra arbetet. Detta har lett till byte mellan utförare av analys, miljöövervakning och rapportsammanställning vilket gett en diskontinuitet i data då provtagning inte skett på samma sätt. Underlagen blir osäkra och svåra att jämföra med tidigare analyser, långsiktiga trender blir svåra att se. Gränsvärden blir inte platsspecifika utan generella vilket kan leda till ekonomiskt olönsamma beslut både för den sökande och för samhället. Kunskap är nyckeln till framgång. Det gäller inom många områden och så även när det kommer till kvävets processer i limniska miljöer. Vid bristande kunskap fattas beslut som baseras på antaganden, uppskattning eller känsla. För att kunna fatta samhällsekonomiskt lönsamma beslut om miljöfrågor krävs det att man har adekvata underlag. Det finns många direktiv och förordningar att ta hänsyn till vid en tillståndsprocess. Till grund för miljölagstiftningen som berör kväveutsläpp ligger miljöbalken, avloppsdirektiv, nitratdirektiv och ramdirektivet för vatten. Broviken, som är en del av det geografiskt undersökta området i Mälarens avrinningsområde, är ett Natura 2000 område i vilket delar även kommer att bli naturreservat. Utöver dessa bestämmelser ska hänsyn till de av regeringen uppsatta 15 miljömålen tas vid tillståndsansökan. Hur dessa ska implementeras i lagstiftningen är dock osäkert. Detta arbete är en tvärvetenskaplig kartläggning av de processer som leder till ett tillstånd för kväveutsläpp. Arbetet fokuserar på tillståndsprocessen, kunskapsnivån och vem som förvaltar kunskapen. Arbetet visar på svårigheter med många olika direktiv och mål utan klarhet i hur de ska följas och hur brist på vetenskapligt adekvata underlag leder till en stor osäkerhet i miljöstatus och en situation där utvecklingen av kvävehantering står still.

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