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| 2. |
- Oesterle, Pierre, 1990-
(författare)
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Exploring the fate of emerging contaminants during hydrothermal regeneration of carbonaceous adsorbents
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wastewater from households and industries commonly contain emerging contaminants that are not easily removed by most wastewater treatment plants. These contaminants can be removed through adsorption onto adsorbents, such as activated carbon or biochars. Previously, attention has been given to waste residues from the agriculture and forestry industry as potential raw materials for activated biochars, which could replace coal and coconut, common feedstocks for activated carbon production. This thesis investigates the factors governing the adsorption efficiencies of these activated biochars and explores the potential of hydrothermal regeneration as a post-treatment. The adsorption experiments showed that iron-doped (i.e., magnetic) activated biochar had two times more adsorption capacity than non-doped activated biochar (i.e., non-magnetic). However, the adsorption capacity of magnetic activated biochar was still inferior to activated carbon for removing sulfamethoxazole (8 mg/g vs. 42 mg/g) and caffeine (40 vs. 56 mg/g). Of the three conditions tested (i.e., salts, humic acids, and pH), only pH had a significant influence on the adsorption of the three selected contaminants onto activated biochars, and the biochars preferentially adsorbed neutral species. This observation is most likely explained by the π-π bonds. Hydrothermal regeneration effectively degraded trimethoprim, sulfamethoxazole, and caffeine at temperatures above 240 °C in the absence of adsorbent. Only trimethoprim generated transformation products that could be identified and quantified from non-targeted analysis. In presence of adsorbent, caffeine was not completely degraded at 280 or even 320 °C, suggesting that the activated biochars adsorb and to some extent shelter the contaminants from degradation.After hydrothermal regeneration, the activated biochars had an enhanced adsorption capacity for sulfamethoxazole, whereas lower adsorption capacity was observed for trimethoprim and caffeine. These changes in performance are believed to be related to the alteration of surface characteristics of activated biochar induced by the adsorbed contaminants during the hydrothermal reaction. Overall, the regeneration efficiency for the activated biochars was found to exceed 50 %. After three regeneration cycles, the regeneration efficiency was as high as 320 %. The results of this thesis suggest that activated biochars could remove emerging contaminants in water and hydrothermal regeneration could degrade most of the emerging contaminants, allowing the spent adsorbent to be reused.
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| 3. |
- Luong, N. Tan, 1995-
(författare)
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Water film-mediated mineralogical transformations and photocatalytic reactions
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mineral particles capture water vapor in the atmosphere in the form of water films that are only few monolayers thick. Water films form nanoscale hydration environments that mediate a wide range of important reactions in nature and technology. This thesis explored two important phenomena that commonly occur within the confines of water films: mineralogical transformations (Topic 1) and photocatalytic decomposition of organics (Topic 2). These transformations were chiefly identified by vibrational spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and (Transmission and Scanning) electron microscopy. Interpretations of reaction mechanisms were partially supported by chemometrics, kinetic and thermodynamic modeling, as well as molecular simulations.Mineralogical transformations (Topic 1) resolved in this thesis involved the hydroxylation (Papers I, II) and carbonation (Paper III) of periclase (MgO), and the oxidation of rhodochrosite (MnCO3) (Paper IV). Two types of MgO nanocubes with contrasting physical properties were used to resolve nucleation- and diffusion-limited hydroxylation reactions to brucite and carbonation reactions to amorphous magnesium carbonate (AMC). While nucleation-limited reactions completely transformed (8 nm) small and aggregated MgO nanocubes to brucite, the reactions became diffusion-limited in larger (32 nm) monodispersed MgO nanocubes because of brucite surface nanocoatings (Paper I). Additionally, brucite nanosheets grew under (GPa-level) crystallization pressures because of the important volumetric expansion of the reaction, which took place in a complex network of microporosity between the small and within the larger MgO nanocubes. Brucite stacking mechanisms, explored in Paper II, focused on the early stages of MgO-water interaction in water films of different thicknesses. These were suggested to involve the stacking and (epitaxial-like) growth of precursor Mg(OH)2 nanosheets in water films. Carbonation reactions explored in Paper III completely hampered hydroxylation reactions studied in Papers I and II, and produced AMC nanocoatings grown over an unreacted MgO core. Finally, oxidation-driven reactions involving rhodochrosite in Paper IV produced MnO2, Mn3O4, and MnOOH nanocoatings with growth rates being scaled with water loadings.Photocatalytic decomposition reactions of organics (Topic 2) were focused on the case of oxalate bound to TiO2 nanoparticles (Paper V). Photodecomposition rates scaled with humidity in oxygenated water films, and were explained by the combination of hole transfer (HT), ligand-to-metal charge transfer (LMCT), and the formation of hydroxyl radicals and reactive oxygen species. Decreasing rates in oxygen-free water films were, on the other hand, explained by water-driven charge localization, which eventually limited radical production and charge transfers via HT and LMCT. The reactions involved limited HT and LMCT processes which also competed with a charge recombination process across all humidity ranges.This thesis provides new insight into two key types of transformations mediated by water films on minerals. This knowledge can be used to understand the reactivity of mineral (nano)particles exposed to variations in atmospheric humidity and oxygen content, which are both highly relevant to a wide range of settings in nature and technology. It can also advance new ideas in the study of mineral growth, especially within the confines of nanometer-thick water films.
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| 4. |
- Josefsson, Sarah, 1976-, et al.
(författare)
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Capping efficiency of various carbonaceous and mineral materials for in situ remediation of marine sediments contaminated with PCDD/Fs, OCS and HCB
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The efficiency of various thin-layer capping materials in reducing the sediment-to-water flux and benthic organism bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), hexachlorobenzene (HCB) and octachlorostyrene (OCS) was investigated in a boxcosm experiment. The influence of cap layer thickness (0.5-5 cm) and different cap materials were tested using a three-factor experimental design. The capping materials consisted of a passive carrier (coarse or fine limestone material, or a marine clay sediment), and an active material (activated carbon (AC) or kraft lignin) to sequester the contaminants and decrease their bioavailability. Macrofauna was added to the boxes to get a semi-natural bioturbation. The sediment-to-water flux was measured using passive (SPMD) samplers, and the bioaccumulation by the surface-dwelling gastropod Hinia reticulata and the deep-burrowing polychaetes Nereis spp. was determined. Results showed substantial decreases in both flux and bioaccumulation as a result of thin-layer capping. The thickness of the capping layer and the choice of active material were important factors, while the use of different types of passive materials was not statistically significant for any of the observed endpoints. Flux and bioaccumulation decreased with increased cap thickness, and could be further decreased with addition of active material. Activated carbon was more efficient than lignin, and a ~90% reduction of the flux and bioaccumulation, compared to uncapped control sediment, could be achieved with 3 cm caps with 3.3% AC (g C/g ww clay). The reduction was generally larger in the surface-dwelling H. reticulata than in Nereis spp., and the magnitude of the reduction was frequently similar between Nereis spp. and sediment-to-water fluxes. The latter was interpreted to indicate a link between Nereis spp. bioirrigation and sediment-to-water fluxes. Furthermore, the reduction in sediment-to-water flux was dependent on the hydrophobicity of the congeners, with less hydrophobic congeners achieving a larger reduction than more hydrophobic congeners.
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| 5. |
- Buckland, Philip I, et al.
(författare)
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SEAD : Strategic Environmental Archaeology Database, planning report
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This document lays out a strategy for the development of SEAD – A Strategic Environmental Archaeology Database, which will facilitate the digitisation and accessibility augmentation of MAL’s existing data from nearly thirty years of work in the fields of archaeology and environmental science. SEAD will also provide a framework for the entry of data from all future research and consultancy work at MAL, and allow guest researchers and external partners to contribute to, and work with the same data. The planned system will be implemented at both local and internet levels, and be designed with an aim towards broadening its scope with external partners in the future. SEAD will be made available online in order to increase the ease of access to environmental archaeology data and encourage an expansion of both the discipline and Sweden’s role in it. This is inline with current EU strategies on enhancing research infrastructure, and providing a greater insight into human-environment interactions for long term planning.
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| 6. |
- Gutensohn, Mareike Franziska, 1992-
(författare)
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Unraveling the importance of thiol compounds on mercury speciation, uptake and transformation by the iron-reducer Geobacter sulfurreducens
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The biogenic methylation of inorganic, divalent mercury (Hg(II)) by methylating microorganisms leads to formation and bioaccumulation of monomethyl mercury (MeHg) in the environment and can cause severe damage to ecosystems and human health. Diverse microorganisms carry the gene sequence hgcAB and are able to methylate Hg(II) intracellularly. The interplay of biological, chemical and physical parameters is driving mercury (Hg) transformation by microorganisms. The chemical speciation of Hg(II) with thiol compounds, both with dissolved low molecular mass (LMM) thiols and thiols present on microbial membrane surfaces, is one key factor for Hg availability and transformation. In this work the role of thiol compounds with respect to Hg speciation, uptake and transformation was studied by the iron-reducing model organisms Geobacter sulfurreducens. The turnover of dissolved thiols and the role of outer and inner membrane thiols was studied with novel experimental strategies.In Paper I and II the formation of thiol compounds was studied under varying nutrient conditions. It was shown that the formation of LMM-thiol compounds was impacted by divalent iron, Fe(II). Furthermore, we showed the turnover of the small LMM-thiol cysteine to the branched LMM-thiol penicillamine, which was further amplified by the addition of exogenous cysteine or nutrients. This turnover of small to branched LMM-thiols impacted the Hg(II) speciation in methylation assays and the relative contribution between cysteine and penicillamine was important for Hg(II) availability, uptake and methylation. In addition, the partition of Hg(II) between the cell-adsorbed and dissolved phase was shifted towards the latter at higher LMM-thiol concentrations. Nutrient concentrations impacted cell physiology due to a shift to an active metabolism and a faster metabolization of LMM-thiols. We concluded that the interplay between thiol metabolism, Hg(II) speciation and cell physiology are key parameters for Hg(II) methylation by G. sulfurreducens. In Paper III The outer and inner membrane was characterized independently by two X-ray absorption spectroscopy techniques. The determination of the Hg speciation by both X-ray absorption spectroscopy techniques showed coherent results for both the outer and inner membrane of G. sulfurreducens. The concentration of thiol membrane groups was higher on the inner compared to the outer membrane. The differences between the outer and inner membrane suggested that thiol concentration and Hg coordination environment likely impact the Hg(II) internalization. The role of membrane thiols for Hg(II) uptake and transformation was further investigated in Paper IV by selectively blocking these functional groups. Partitioning and uptake of Hg was not affected by blocking the outer and inner membrane thiols of whole cell and spheroplast samples, respectively. However, the Hg(II) methylation was decreased by blocking thiols at the outer membrane, but no effect was observed by blocking thiols at the inner membrane. Blocking of membrane surface thiols changed the physiology in whole cells but not in spheroplasts. This result suggested weaknesses of the applied blocking approach. In addition, Hg(II) reduction was studied on the outer and inner membrane and showed the formation of liquid and gaseous elemental Hg, Hg(0), in Paper III and IV, respectively.Overall, this work showed the central role of dissolved and cell-associated thiol compounds for Hg(II) uptake and the transformation reactions. Herby, concentration, compositions and distribution of thiols are crucial and impact the Hg(II) speciation, partitioning, uptake and availability for Hg(II) methylation and reduction. In addition, cell physiology is impacting the methylation potential and the turnover of LMM-thiol compounds. The role of membrane surface thiols for Hg(II) uptake was not fully identified, however such thiols were for the first time characterized selectively for the outer and inner membrane by X-ray absorption spectroscopy.
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| 8. |
- Blum, Kristin, 1989-
(författare)
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Targeted and untargeted analysis of organic contaminants from on-site sewage treatment facilities : Removal, fate and environmental impact
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- On-site sewage treatment facilities (OSSFs) are widely used all over the world to treat wastewater when large-scale sewage treatment plants (STPs) are not economically feasible. Although there is great awareness that the release of untreated wastewater into the environment can lead to water-related diseases and eutrophication, little is known about organic contaminants and their removal by OSSFs, environmental load and fate. Thus, this PhD thesis aims to improve the knowledge about treatment efficiencies in current OSSFs, the environmental impact and fate of contaminants released from OSSFs, as well as how biochar fortification in sand filter (soil beds) OSSFs might increase removal of these contaminants. State-of-the-art analytical techniques for untargeted and targeted analyses were used and the results evaluated with univariate and multivariate statistics.Environmentally-relevant contaminants discharged from OSSFs were identified using untargeted analysis with two-dimensional gas chromatography mass spectrometry (GC×GC-MS) and a MS (NIST) library search in combination with a prioritization strategy based on environmental relevance. A method was successfully developed for the prioritized contaminants using solid phase extraction and GC×GC-MS, and the method was also applicable to untargeted analysis. This method was applied to several studies. The first study compared treatment efficiencies between STP and soil beds and showed that treatment efficiencies are similar or better in soil beds, but the removal among the same type of treatment facilities and contaminants varied considerably. Hydrophilic contaminants were generally inadequately removed in both types of treatment facilities and resulted in effluent levels in the nanogram per liter range.Additionally, several prioritized and sometimes badly removed compounds were found to be persistent, mobile, and bioavailable and two additional, untargeted contaminants identified by the NIST library search were potentially mobile. These contaminants were also found far from the main source, a large-scale STP, at Lake Ekoln, which is part of the drinking water reservoir Lake Mälaren, Sweden. The study also showed that two persistent, mobile and bioavailable contaminants were additionally bioaccumulating in perch. Sampling for this study was carried out over several seasons in the catchment of the River Fyris. Parts of this catchment were affected by OSSFs, other parts by STPs. Potential ecotoxicological risks at these sites were similar or higher at those affected by STPs compared to those affected by OSSFs. Mass fluxes per capita were calculated from these levels, which were higher at STP-affected than at OSSF-affected sites in summer and autumn, but not in winter. Possibly, the diffuse OSSF emissions occur at greater average distances from the sampling sites than the STP point emissions, and OSSF-affected sites may consequently be more influenced by fate processes.The studies carried out suggested that there is a need to improve current treatment technologies for the removal of hydrophilic contaminants. Thus, the final study of this thesis investigated char-fortified sand filters (soil beds) as potential upgrades for OSSFs using a combination of advanced chemical analysis and quantitative structure-property relationship modeling. Removal efficiencies were calculated from a large variety of contaminants that were identified by untargeted analysis using GC×GC-MS and liquid chromatography ion mobility mass spectrometry as well as library searches (NIST and Agilent libraries). On average, char-fortified sand filters removed contaminants better than sand, partly due to an enhanced removal of several hydrophilic contaminants with heteroatoms. After a two-year runtime, sorption and particularly biodegradation must have contributed to the removal of these compounds.Generally, the combination of targeted and untargeted analysis has proven valuable in detecting a large variety of organic contaminants, as well as unexpected ones. The results imply that OSSFs have similar or better removal efficiencies, similar or lower environmental risks and similar or lower mass fluxes per capita, compared to STPs. Biochar fortification can improve the removal of organic contaminants in soil beds, but further research is needed to find technologies that reduce the discharge of all types of organic contaminants.
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| 9. |
- Zheng, Ziye, 1992-
(författare)
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Improving alternatives assessment of plastic additives : exploring in silico tools to identify less hazardous flame retardants
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Alternatives assessment is applied for replacing hazardous chemicals with viable, safer substitutes. High quality experimental hazard data, however, are usually unavailable for this purpose, and obtaining in silico data is the only approach to fill in data gaps. In silico tools also have the advantage of providing a large amount of data with much lower cost and time requirements.The aim of this PhD project was to explore the use of in silico tools for alternatives assessment, and develop practical tools for alternatives assessment of organic plastic additives. For this purpose, flame retardants were used as case chemicals. The major results were:1. Quantitative structure-activity relationship (QSAR) models for endocrine disruption were developed and explored (Paper I and II). These developed models were able to identify chemical properties that impact the binding affinities of brominated organic chemicals with estrogen-related receptor γ (Paper I), and to predict the androgen receptor activity of several organic chemicals, including flame retardants (Paper II);2. A hazard ranking tool was developed for alternatives assessment based on the hazard properties of persistence (P), bioaccumulation (B), mobility in the aquatic environment (M) and toxicity (T). The flame retardant decabromodiphenyl ether (decaBDE) and 16 of its alternatives were taken as case chemicals to develop the tool. From a comparison of experimental and in silico data for these case chemicals, hazard data predicted by in silico tools were identified as the more suitable data source for the hazard ranking tool as the experimental data were confounded by large data gaps (Paper III);3. The inclusion of chemical transformation products for the hazard ranking tool were studied with the case of decaBDE and its alternatives. Several in silico tools were used to predict transformation products, and a strategy for prioritizing chemical transformations with high occurrence potential in the environment was developed (Paper IV);4. Multicriteria decision analysis (MCDA) tools were used to evaluate diverse P, B, M and T endpoints of parent compounds (Paper III) and their transformation products (Paper IV) simultaneously based on in silico data. Three different MCDA methods were explored, and one of them was developed to include the consideration of uncertainties of in silico data;5. In the studied case of decaBDE alternatives, the three different MCDA methods generally agreed on the most and least hazardous alternatives. With the consideration of hazard for the studied flame retardants and their in silico predicted transformation products, two alternatives, melamine and bis(2-ethylhexyl) tetrabromophthalate, were identified as the least hazardous of considered alternatives for decaBDE (Paper III and IV);6. It is critical for the exposure aspect of alternatives assessment to identify the key properties that influence the emission process. For this, a fast measuring method for the emission of polymer additives was developed based on a Quartz Crystal Microbalance (QCM). Empirical linear models were applied to describe the emission patterns (Weibull model) to better understand the chemical mechanism behind the emissions of organophosphate flame retardants from various polymers. The results showed that the octanol-water partitioning coefficient and molecular size are key parameters for the emission process, but also showed that the emission process is complex and is likely driven by a combination of both polymer and additive properties, as well as their interactions (Paper V).This research shows how alternatives assessment can make more effective use of in silico tools. and it also highlights current challenges in the use of these in silico tools that require further development. The next steps to make a holistic alternatives assessment would include an exposure assessment procedure based on the work in Paper V, and combining this with the hazard ranking tools (developed in Paper III and IV), including information on technical feasibilities, economic feasibilities, and also life cycle impacts. The MCDA methods for hazard ranking in Paper III and IV can be further adapted for the decision component of such a more complete alternatives assessment for specific uses of chemicals.
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| 10. |
- Harju, Mikael, 1968-
(författare)
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Analysis of PCBs with special emphasis on comprehensive two-dimensional gas chromatography of atropisomers
- 2003
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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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