| 1. |
- Assefa, Anteneh, 1983-
(författare)
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Tracing and apportioning sources of dioxins using multivariate pattern recognition techniques
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in edible fish in the Baltic Sea have raised health concerns in the Baltic region and the rest of Europe. Thus, there are urgent needs to characterize sources in order to formulate effective mitigation strategies. The aim of this thesis is to contribute to a better understanding of past and present sources of PCDD/Fs in the Baltic Sea environment by exploring chemical fingerprints in sediments, air, and biota. The spatial and temporal patterns of PCDD/F distributions in the Baltic Sea during the 20th century were studied in Swedish coastal and offshore sediment cores. The results showed that PCDD/F levels peaked in 1975 (± 7 years) in coastal and 1991 (± 5 years) in offshore areas. The time trends of PCDD/Fs in the sediment cores also showed that environmental half-lives of these pollutants have been shorter in coastal than in offshore areas (15 ± 5 and 29 ± 14 years, respectively). Consequently, there have been remarkable recoveries in coastal areas, but slower recovery in offshore areas with 81 ± 12% and 38 ± 11% reductions from peak levels, respectively.Source-to-receptor multivariate modeling by Positive Matrix Factorization (PMF) showed that six types of PCDD/F sources are and have been important for the Baltic Sea environment: PCDD/Fs related to i) atmospheric background, ii) thermal processes, iii) manufacture and use of tetra-chlorophenol (TCP) and iv) penta-chlorophenol (PCP), v) industrial use of elementary chlo- rine and the chloralkali-process (Chl), and vi) hexa-CDD sources. The results showed that diffuse sources (i and ii) have consistently contributed >80% of the total amounts in the Southern Baltic Sea. In the Northern Baltic Sea, where the biota is most heavily contaminated, impacts of local sources (TCP, PCP and Chl) have been higher, contributing ca. 50% of total amounts. Among the six sources, only Thermal and chlorophenols (ii-iv) have had major impacts on biota. The impact of thermal sources has, however, been declining as shown from source apportioned time-trend data of PCDD/Fs in Baltic herring. In contrast, impacts of chlorophenol-associated sources generally increased, remained at steady-state or slowly decreased during 1990-2010, suggesting that these sources have substantially contributed to the persistently high levels of PCDD/Fs in Baltic biota.Atmospheric sources of PCDD/Fs for the Baltic region (Northern Europe) were also investigated, and specifically whether the inclusion of parallel measurements of metals in the analysis of air would help back-tracking sources. PCDD/Fs and metals in high-volume air samples from a rural field station near the shore of the central Baltic Sea were measured. The study focused on the winter season and air from the S and E sectors, as these samples showed elevated levels of PCDD/Fs, particularly PCDFs. Several metals were found to correlate significantly with the PCDFs. The wide range of candidate metals as source markers for PCDD/F emissions, and the lack of an up-to-date extensive compilation of source characteristics for metal emission from vari- ous sources, limited the use of the metals as source markers. The study was not able to pin-point primary PCDD/F sources for Baltic air, but it demonstrated a new promising approach for source tracing of air emissions. The best leads for back-tracking primary sources of atmospheric PCDD/Fs in Baltic air were seasonal trends and PCDD/F congener patterns, pointing at non-industrial related thermal sources related to heating. The non-localized natures of the sources raise challenges for managing the emissions and thus societal efforts are required to better control atmospheric emissions of PCDD/Fs.
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| 2. |
- Larsson, Malin, 1981-
(författare)
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Computational methods for analyzing dioxin-like compounds and identifying potential aryl hydrocarbon receptor ligands : multivariate studies based on human and rodent in vitro data
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are omnipresent and persistent environmental pollutants. In particular, 29 congeners are of special concern, and these are usually referred to as dioxin-like compounds (DLCs). In the European Union, the risks associated with DLCs in food products are estimated by a weighted sum of the DLCs’ concentrations. These weights, also called toxic equivalency factors (TEFs), compare the DLCs’ potencies to the most toxic congener, 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2378- TCDD). The toxicological effects of PCDD/Fs and PCBs are diverse, ranging from chloracne and immunological effects in humans to severe weight loss, thymic atrophy, hepatotoxicity, immunotoxicity, endocrine disruption, and carcinogenesis in rodents.Here, the molecular structures of DLCs were used as the basis to study the congeneric differences in in vitro data from both human and rodent cell responses related to the aryl hydrocarbon receptor (AhR). Based on molecular orbital densities and partial charges, we developed new ways to describe DLCs, which proved to be useful in quantitative structure-activity relationship modeling. This thesis also provides a new approach, the calculation of the consensus toxicity factor (CTF), to condense information from a battery of screening tests. The current TEFs used to estimate the risk of DLCs in food are primarily based on in vivo information from rat and mouse experiments. Our CTFs, based on human cell responses, show clear differences compared to the current TEFs. For instance, the CTF of 23478-PeCDF is as high as the CTF for 2378-TCDD, and the CTF of PCB 126 is 30 times lower than the corresponding TEF. Both of these DLCs are common congeners in fish in the Baltic Sea. Due to the severe effects of DLCs and their impact on environmental and human health, it is crucial to determine if other compounds have similar effects. To find such compounds, we developed a virtual screening protocol and applied it to a set of 6,445 industrial chemicals. This protocol included a presumed 3D representation of AhR and the structural and chemical properties of known AhR ligands. This screening resulted in a priority list of 28 chemicals that we identified as potential AhR ligands.
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| 3. |
- Røyne, Frida, 1985-
(författare)
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Exploring the relevance of uncertainty in the life cycle assessment of forest products
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The role of forest biomass as a replacement for fossil fuels and products is becoming increasingly prominent as a means to mitigate climate change. To guide a sustainable transition towards a forest-based bio-economy, it is important that advantages and disadvantages of forest products are assessed, to ensure that the products deliver environmental impact reduction. Life Cycle Assessment (LCA) has become heavily relied upon for assessing the environmental impact of bio-based products. However, LCAs of similar product systems can lead to results that differ considerably, and the method is, thus, associated with uncertainties. It is, therefore, necessary to explore the relevance of uncertainties, to build knowledge about enablers and challenges in using LCA for assessing forest products.Three important challenges in the context of uncertainty in LCA are the focus of this thesis: 1) system boundaries, 2) climate impact assessment practice, and 3) allocation. More specifically, the relevance of a) including and excluding life cycle phases, b) potentially important climate aspects, and c) applying different allocation methods, was assessed. Case studies involved a chemical industry cluster, a biorefinery, and single product value chains for a plastic box, a fuel, and a building.In summary, the thesis demonstrates that:A major share of the environmental impact related to the production of an industry cluster can occur outside the cluster gates, so when strategies involving a transition to forest biomass feedstock are developed and evaluated, a life cycle perspective reveals the full environmental impact reduction potential.For bio-based products differing in functional properties from the fossil products they are meant to replace, material deterioration in the use phase can contribute substantially to overall environmental performance. This is acknowledged if all life cycle phases are regarded.As climate aspects commonly not assessed in forest product LCAs could influence results greatly, and even affect the outcome of comparisons between forest and non-forest products, the climate impact of forest products is uncertain. It is, therefore, important that this uncertainty is acknowledged and communicated, and that appropriate methods and guidelines are developed.The choice of allocation method in the LCA of biorefinery products can have a major influence on results, especially for physically non-dominant products and in consequential studies. In these cases, scenario analysis is especially valuable to show the possible range of results.LCA provides useful guidance for forest product development and production as the life cycle approach reveals causes of environmental impact throughout the product value chain. Proper identification, estimation, and management of uncertainties strengthen the provision of reliable decision support.
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| 4. |
- Östman, Marcus, 1987-
(författare)
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Antimicrobials in sewage treatment plants : occurrence, fate and resistance
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The World Health Organization (WHO) has identified antibiotic resistance as a major threat to human health. The environment has been suggested to play an important role in the emergence of antibiotic resistant bacteria. The external environment can act as a source of resistance genes that could potentially be transferred into human pathogens. It is also an important route for the dissemination of antibiotic resistance genes and bacteria. Sewage treatment plants (STPs) are among the most important routes by which antibiotics and antibiotic resistance genes enter the environment. It has been suggested that STPs are hotspots for the development of antibiotic resistance because they contain relatively high concentrations of antibiotics as well as both human and environmental bacteria. Further complicating matters, there is evidence that other substances with antimicrobial properties, such as biocides and metals, can cause antibiotic resistance due to co- and cross-resistance.This thesis contributes new knowledge on the concentrations, mass flows, and removal efficiencies of antimicrobials in STPs and their connections to the emergence of antibiotic resistance. Paper I presents data on the levels of 40 different antimicrobials in the incoming wastewater, treated effluent, and digested sludge of eleven different STPs. Although not previously detected in STPs, chlorhexidine is shown to be ubiquitous in such plants. In Paper II, mass flows and removal efficiencies are calculated for eleven antimicrobials over various treatment steps in three STPs, showing that polar antimicrobials were inefficiently removed from the wastewater. In Paper III, the minimum selective concentration (MSC) for the antibiotic tetracycline was determined in a complex bacterial aquatic biofilm using both phenotypic and genotypic endpoints. It was found that 10 µg/L selected for phenotypic resistance, and 1 µg/L selected for certain resistance genes. Paper VI used metagenomics to determine whether there is selection for antibiotic-resistant bacteria in STPs and whether the extent of this selection can be correlated to the concentrations of antimicrobial compounds. No clear evidence for selection was identified. Paper V evaluates advanced wastewater treatment techniques for removing antimicrobial compounds using ozonation and granular activated carbon (GAC). The identity of the GAC material was found to strongly affect removal efficiency, and GAC was more efficient than ozonation for most compounds at the tested concentrations.
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