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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.
191

Method Development for Sample Preparation of Fish for Non-target Analysis of Hydrophobic Organic Pollutants

Björk Bæringsdóttir, Bergdís January 2020 (has links)
Monitoring methods for environmental pollutants are mostly performed with targeted analysis which relies on predetermined compounds. This can cause an underestimation of possible toxicants as it might not detect undiscovered compounds such as breakdown products of other chemicals. Non-target analysis (NTA) has gained more attraction due to increasing instrumental sensitivity and technological advancements. It attempts to analyze the whole matrix without a prior selection of specific compounds. The aim of this project was to develop a sample preparation method that allows for biomonitoring of organic pollutants in fish using NTA. The method included a broad range of compounds that are suitable for gas chromatography-mass spectrometry (GC-MS) analysis. Five extraction techniques and three clean-up methods were compared using wet weight fish samples and spiked blank samples. The effectiveness of these methods was evaluated based on a selection of 60 compounds that cover the log Kow range of 0.8 to 8.3. The method best equipped for NTA after evaluating recovery and matrix effects was sonication extraction (extracted with a mixture of n-hexane/dichloromethane (DCM)) combined with a deactivated silica clean-up (eluted with n-hexane and DCM). The average recoveries for wet weight fish samples were 99 % for log Kow <5, 65% for log Kow 5-7, and 54% for log Kow ≥7. Semi quantification of nine compounds detected in the non-spiked fish was carried out. The sonication extraction result was statistically similar to the open column extraction but used less solvent than the other sample preparation procedures and was less time consuming. Deactivated silica clean-up is more comprehensive than the commonly used multi-layered silica clean-up and therefore more likely not to discriminate unknown compounds. Further non-target studies using the proposed method is required to evaluate its effectiveness.
192

Polychlorinated Biphenyls in Major Foodstuffs on the Canadian Market

Hope, Kjell January 2018 (has links)
No description available.
193

Occurrence of major perfluoroalkyl substances (PFAS) in water samples from a transect of the Indian Ocean along the East African coast

Hope, Kjell January 2020 (has links)
No description available.
194

Study of new and old reference material to determine effects of age

Lindroos, Paul January 2020 (has links)
No description available.
195

Modifying Silica with Corannulene Derivatives : Preparing stationary phase using click reaction to separate fullerene mixtures

Ho-Thi, Thuy-Tran January 2020 (has links)
No description available.
196

Quantification of target per- and polyfluoroalkyl substances (PFASs) and extractable organic fluorine (EOF) in crayfish from Lake Vättern, Sweden.

Villbrand, Wilma January 2020 (has links)
Per- and polyfluorinated substances (PFASs) are a family of persistent organic pollutants in which the aliphatic carbon chains have been fluorinated, either completely or partially. One subclass of PFASs are perfluoroalkyl acids (PFAAs), in which perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) are two prominent groups. PFASs are toxic to the environment, as well as humans, and are found to have a developmental, neurological and immunological toxicity. They are also found to be possibly carcinogenic. In this study, the quantity of target PFASs was determined in 11 samples of hepatopancreas in crayfish from different locations in Lake Vättern, Sweden, using liquid chromatography coupled to tandem mass spectrometry. The hepatopancreas is the crayfish detoxification organ and therefore, it is also where persistent organic pollutants are possibly accumulated. Extractable organic fluorine concentration was also determined, using combustion ion chromatography to account for other fluorinated compounds not included in the target analysis of 31 PFASs. The amount of target PFASs was compared to the extractable organic fluorine concentration, giving an idea of how much of the extractable organic fluorine that consists of identified PFASs in relation to unidentified organic fluorine.  The measured concentrations of target PFASs were compared to measured concentrations in a previous study (2008) of PFASs in the hepatopancreas of crayfish from two different locations in Lake Vättern. Concentrations of the measured target PFASs were also related to if the sampling sites for each pooled sample was located close to a known point source, Karlsborg military airport. A sum of the average of PFHxS, PFOS, PFOA and PFNA for all sample sites were compared to a combined tolerable weekly intake (TWI) for these four compounds, established by the European Food Safety Authority (EFSA). As well as the intake of PFOS and PFOA compared individually against their TWI.
197

Trees on contaminated soil : IS THERE A CORRELATION BETWEEN BIOAVAILABLE COMPOUNDS AND UPTAKE IN BIRCHES?

Ängmyren, Elisabeth January 2017 (has links)
In this thesis a method of dry-ashing wood, sequential leaching of soil and analysis with ICP-QMS is tested as a possible way for establishing a correlation between bioavailable compounds in soil and uptake to birches. The total amount of trace elements (V, Sr, Cd, Pb and U) in stem wood and contaminated soils were analysed. The total concentration of metals in the soil was extracted using HCl and HNO3 in warm water bath. Biological availability of inorganic compounds in the soil were established using sequential leaching. The total concentration of metals in stem wood of birches were determined with the use of tree core samples, dry ashing and analysis with ICP-QMS. A rough estimation of each trees’ first 10 years through counting annual tree rings was also made, to be able to see when the tree accumulate most bioavailable elements. No correlation between the bioavailable concentration of elements in the soil and uptake to the birches could be found. Some deductions about where in the tree different elements appear could be done but more samples is needed to make a significant judgement.
198

PFAS in Gullspångsälvens catchment area

Lindblom, Karin January 2017 (has links)
Gullspångsälvens catchment area starts in the county of Dalarna and ends in the lake Vänern. On the way the water passes a couple of villages and small towns. The aim of the project is to identify point sources of PFAS and see their influence on the PFAS levels in the systems surface water. In the area some point sources have been identified. The villages and towns have waste water treatment plants and there are also a couple of landfills. Sampling have been carried out at expected point sources as well as in the surface water close to human activities. The samples have been extracted with SPE and analysed with LCMS-MS. Results show that the levels of PFAS is increasing through the system and that the expected point sources release PFAS to the environment. It was also possible to identify an earlier unknown point source. Compared with levels in other parts of Sweden (S-EPA, 2016) the levels of PFAS in the system is within a normal range except for the levels close to the until now unknown point source.
199

Global Priority Perfluoroalkyl Substances in Surface Waters:Establishing Baseline Levels on Regional Basis.

Baabish, Abeer January 2019 (has links)
Perfluorooctane sulfonic acid (PFOS) has been regulated under Stockholm Convention in 2009, perfluorooctanoic acid (PFOA) was listed in 2019. Perfluorohexane sulfonic acid (PFHxS) is under review and could be included in 2021. There are still permitted uses of these three chemicals, but it is expected that the production and application will decrease as a result of the international regulation and the environmental concentrations of PFOS, PFOA and PFHxS are expected to decline. However, without a reference point, it is difficult to judge if the levels are decreasing or not. Therefore, baseline levels of PFOS, PFOA and PFHxS in one of United Nations Environment Programme (UNEP) core matrices, surface water, were established with the support of samples collected from Africa (n=34), Asia (n=11), Group of Latin America and Caribbean (GRULAC) (n=35) and Pacific Islands (n=25) under a period of two years. The baseline levels were set as the median concentration (ng/L) in each region (interquartile range) based on a variance test (Kruskal-Wallis) and descriptive statistical testing. Baseline levels for ΣPFOS, PFOA and PFHxS including all countries in Africa (n=6) was set at 0.38 (0.18 – 0.54) ng/L, 0.26 (0.13 – 0.80) ng/L and 0.042 (0.02 - 0.09) ng/L respectively, and excluding Kenya and Tunisia (n=4) at 0.22 (0.10 – 0.38) ng/L for ΣPFOS , 0.18 (0.10 – 0.25) ng/L for PFOA and 0.031 (0.02 – 0.04) ng/L for PFHxS. In Pacific Islands the baseline levels for ΣPFOS, PFOA and PFHxS were established at 0.15 (0.04 – 1.24) ng/L, 0.046 (0.03 – 0.11) ng/L and 0.055 (0.01 – 0.63) ng/L including all countries (n=7), and 0.053 (0.03 – 0.15) ng/L, 0.033 (0.03 – 0.04) ng/L and 0.012 (0.01 – 0.05) ng/L excluding Vanuatu and Kiribati (n=5). In Asia and Group of Latin America samples were in similar concentrations range within the region, so baseline levels for ΣPFOS, PFOA and PFHxS in Asia were set at 0.048 (0.04 - 0.12) ng/L, 0.11 (0.07 – 0.19) ng/L and 0.018 (0.01-0.03) ng/L, and in GRULAC at 1.31(0.39 – 1.88) ng/L, 0.50 (0.28 – 0.71) ng/L and 0.14 (0.06 – 0.44) ng/L for the three priority PFASs respectively. The importance of the three PFASs in relation to other measured Σ73 PFASs were assessed in selected samples (n=12) including six samples from Sweden. The results showed a contribution of 10% to 48% of the sum of the three priority PFASs to all 27 detected PFASs.It is not clear whether a total of 73 PFASs is enough to explain the environmental contamination of PFASs and therefore the extractable organofluorine (EOF) was measured in selected samples (n=12). Due to the high EOF levels in procedural blanks, only two out of twelve samples were used to assess the contribution of detected PFASs to EOF. The contribution of 27 detected PFASs to EOF were 3% for Vanuatu and 5% for Sweden (Svartån). The contribution of the sum of the three PFASs to EOF accounted for 1.1% for Vanuatu and 1.4% for Svartån. Nevertheless, within the organofluorine fraction, a major percentage 95% to 97% of fluorine remains unknown in water samples, suggesting the occurrence of other organofluorine substances. At the same time, some newly identified PFAS (novel PFASs) that are known to replace PFOS and PFOA in different applications were detected in surface water samples collected from Sweden (n=6) and from developing countries under UNEP/GMP2 project (n=6). Perfluoroethylcyclohexane sulfonate (PFECHS) was detected in four samples in concentrations ranging between 0.03 and 0.14 ng/L. Perfluoro-2-propoxypropanoic acid (HFPO-DA) was detected in three samples in the concentration range 0.03-0.06 ng/L.
200

Temporal and spatial variations of microplastic concentrations in surface waters in Gothenburg, Sweden.

Vigren, David January 2019 (has links)
Temporal and spatial variations of microlitter (ML) concentrations in Gothenburg were measured by sampling surface water. ML was divided into three main categories; microplastics (MP), fibers (F) and other anthropogenic particles (OA). Samples were collected using a pump installed with 300 μm and 50 μm stainless mesh filters, during three separate field sampling campaigns during the fall and early winter of 2017. Samples were treated with H2O2 digestion for removing organic material. Microlitter were then visually counted and categorized for all samples under light microscope. In the 300 μm fraction, F was most prevalent at 84.6 %, MP at 12.9 % and OA at 2.5 %. Concentrations of MP varied from 0.1 to 22 MP/m3 in the 300 μm size fraction and from 0 to 81 MP/m3 in the 50 μm size fraction. MP concentrations collected on the 50 μm size filter were higher compared to the 300 μm size filter in all but two samples. MP from the 300 μm size fraction was further subcategorized as particle/fragment (71 %), film (14 %), filament (9 %), expanded cellstructure (3 %) and pellets (3 %). MP concentrations found in Gothenburg surface water are comparable to what has been found in other urban cities of Sweden, but higher compared to studies measuring MP concentrations along the Swedish east, west and southern coastline. The polymeric structure of MP particles from the 300 μm size fraction was analyzed with Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) and were identified as polyethylene (46.5 %), polypropylene (17.2 %), polystyrene (9.0 %), polyethylene terephthalate (3.1 %), polyamide (1.2 %), and 23 % were unmatched. Possible correlating factors such as precipitation and ML concentrations were explored but the data was insufficient for any decisive conclusions to be made. Flow rate, the volume of water passing per time unit in the water course was shown to have an inverse correlation with concentration. Large temporal variation was observed at most of the sampling sites. It is not possible to pin point or quantify any particular source of ML pollution with this data, however it can be stated that ML’s from various urban sources indeed do contribute to ML pollution, and that the pollution from these sources vary over time based on factors that are not yet known.

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