| 441. |
- Pirzadeh, Pardis
(författare)
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Ecotoxicological assessment by microcosm tests on plankton communities
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to present a short-term plankton community toxicity test in laboratory microcosms, with which the effect of the test substance on species abundance and composition of the community is evaluated. This laboratory microcosm is an intermediate between single-species tests and outdoor mesocosm tests. The brominated flame retardant HBCDD was chosen as the reoccurring test substance in three experiments. It was applied at similar nominal exposure concentrations in toxicity experiments performed in test systems with different grades of complexity. One experiment was performed in an outdoor artificial pond in which cylinders were inserted to isolate replicate mesocosms. The other experiments were performed in a greenhouse environment in 10 L microcosms with sediment and water from a eutrophic lake and brackish water estuary. The short-time plankton community toxicity test proposed in this work was successful in detecting structural changes in plankton community composition due to exposure to anthropogenic chemicals. Several prerequisites for a sensitive community toxicity test were fulfilled. Ecological interactions, like competition and predation, were present and made detection of community level responses like secondary effects possible. The community which developed in the 10 L microcosms included many plankton species. This is important for a sensitive and representative evaluation of the toxic effect. The rich plankton community and a maintained balance between the autotroph and heterotroph communities during the course of the experiment were possible due to the sediment compartment. The sediment acts as a seed-bank from which plankton continuously hatch and enter the water volume. Lake water inoculation did not increase the species richness and made no change in plankton community composition. Using artificial water decreases both work-load and costs, considerably. Another important issue in the evaluation of toxicity tests is the variance of test endpoints between replicates. The minimal detectable difference from control (MDD) which mirrors the variability of test endpoints was compared between the mesocosm experiment and the two microcosm experiments. The three lowest MDD values were more or less in the same range between the experiments and ranged between 5-39%. A possible increase in MDD was observed with increased experimental duration. An exposure period of 7 days is considered optimal in detecting clear community level responses at a minimum time. The effects of the test compounds in the three experiments were evaluated with population level and community level metrics. Judging from the results, no single toxic endpoint was found to be the most sensitive one. This stresses the importance of analysing both community and population metrics.
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| 442. |
- Törneman, Niklas
(författare)
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Spatial variability linking carbon resource heterogeneity and microorganisms; causes and consequences
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic carbon and bacteria have a high variability at different scales in the soil, and organic carbon may be a limiting factor for growth of soil bacteria. Thus, it can be expected that these co-vary at different scales in the soil. In this thesis, I have studied the spatial interaction between soil bacteria and natural and contaminant (polycyclic aromatic hydrocarbon, PAH) organic carbon. The overall objective was to suggest reasons why there is an absence or presence of co-variation between them. The spatial patterns of PAHs at a creosote contaminated site were clearly related to their water solubility. The microbial community fingerprint (PLFA analysis) co-varied with PAH concentrations while microbial community diversity was positively correlated to PAH concentrations. Taken together it was demonstrated that a diverse gram-negative bacterial community with a patchy spatial distribution similar to the PAH spatial distribution dominated the creosote contaminated site. Catabolic genes for PAH degradation in bacteria had a more even distribution across the site although hotspots and/or cold spots of PAH concentrations and catabolic genes often coincided.Bacterial biomass and soil respiration was spatially autocorrelated and positively dependent on PAH concentrations. PAH biodegradation lacked a spatial pattern and was uncoupled from most microbial and abiotic soil properties. The results indicated that creosote rather than PAHs was a major carbon source for the microbial community and that PAH biodegradation was controlled by a multitude of soil properties simultaneously, each with its own spatial pattern.In soil peat cores, pore water flow rate had a significant non-linear effect on respiration and methane production while the amount and type of dissolved organic carbon (DOC) remained unimportant for respiration. In contrast, in carbon limited river water, both the quality and quantity of DOC had a clear effect on respiration and bacterial growth efficiency.The main factor determining microbial biomass, community composition, and activity were both the amount and the type of organic carbon regardless of any toxic effects of the carbon.
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| 443. |
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| 444. |
- Mukherjee, Sritama, et al.
(författare)
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Evaluating sustainability for water and wastewater treatment technologies
- 2023
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Ingår i: Technological Solutions for Water Sustainability. - : IWA Publishing. ; , s. 191-199
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- High-performance water and wastewater treatment have become feasible with the development of innovative and advanced technologies that may have the potential to have an impact on health and the environment. At the same time, they can be helpful in protecting the environment and meet specific social needs in a more sustainable way. New purification techniques have the potential to lead to the sustainable development of clean water, understand global environmental challenges and seek ways to improve them. Water treatment processes become more environmentally friendly by reducing energy consumption, removing toxic and essential substances and making products sustainable during the synthesis phase. This chapter discusses water treatment in the context of India, the necessity and methods of assessing sustainability, as well as examples of technological assessments for sustainability.
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| 445. |
- Kong, Xiangrui
(författare)
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Molecular investigations of atmospherically relevant interface processes: ice formation and water accommodation on ice and organic surfaces
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Clouds and aerosols play important roles in the climate system by affecting on atmospheric chemistry, the radiation budget of the atmosphere, and the water cycle including the formation of precipitation. Climate models with predictive power require quantitative descriptions of aerosols and clouds, but several key processes remain to be fully understood. One important example is the formation and growth of ice particles in clouds. Organic compounds also form secondary organic aerosol and coatings on existing particles including ice nuclei and ice cloud particles, which further complicate the description of cloud processes. To improve the understanding of these processes, some fundamental investigations of atmospherically relevant interface interactions are carried out, and the results and findings are summarized and discussed in this thesis. The investigations use a newly developed environmental molecular beam (EMB) technique as the main experimental method. The principle, design and demonstration of the EMB method are described in detail. The method allows for ice surface investigations at temperatures up to 213 K, and it is employed to study gas-surface interactions under conditions relevant to the troposphere. The main findings of this thesis are related to three research themes: (1) Ice formation via deposition mode nucleation on hydrophobic and hydrophilic surfaces is characterized. The critical supersaturation required to activate nucleation on various surfaces increases rapidly with decreasing temperature below 200 K, and adsorbed organic compounds are observed to influence the nucleation, structure and growth rate of ice. (2) Water uptake by bare ice and coated ice surfaces is investigated. The accommodation and desorption kinetics for water on bare ice is quantitatively described by a precursor model. Coatings on ice have a significant impact on water uptake, and adsorption of acids commonly found in the atmosphere tends to enhance water accommodation. (3) Water interactions with surfaces on condensed organic phases and organic coatings on graphite are characterized. Bulk accommodation is inefficient on solid organic surfaces, while water uptake is efficient on liquid phases. The surface layer on condensed n-butanol is shown to change gradually from solid to liquid over a 10 K temperature span around the bulk melting temperature, with major implications for water uptake. The thesis includes the development of new experimental methods and an improved molecular-level understanding of processes at gas-solid and gas-liquid interfaces, and thereby contributes to a better description of cloud and aerosol processes in the environment.
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| 446. |
- Sveinbjörnsson, Kári
(författare)
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Preparation and Characterization of Lead Halide Perovskites : Towards sustainable, cost-effective and upscalable solar cell manufacture
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The perovskite solar cell (PSC) is a recent contender within the photovoltaic research field. In a matter of a few years, the power conversion efficiency (PCE) of the PSC has catapulted from 4% to above 22%, which represents one of the fastest developments in the field. The PSC band-gap tunability makes them interesting for use in tandem solar cells with other established solar cell technologies. This thesis focuses on exploring the photophysics of the perovskite material as well as the development of different perovskite preparation processes and materials for potential use in large-scale manufacture and tandem solar cell applications.First, the photoconductivity of a perovskite film deposited on different metal oxide nanoparticle layers is investigated. The results show that the perovskite can generate free charge carriers without the presence of an electron acceptor.Secondly, we constructed PSCs with a conducting carbon-nanotube film, as a replacement for both the hole-selective layer and the metallic back electrode, which yielded a PCE of 15.5%. Furthermore, we explored the preparation of semitransparent PSCs for tandem solar cells by using atomic-layer deposition (ALD) for depositing a thin electron-selective metal-oxide layer. We were successful using ALD directly on a perovskite layer without damage to the perovskite. Although the PSCs did not yield high PCE, the study marks a step in further development for direct ALD deposition onto the perovskite.Finally, we developed two different methods concerning sustainable manufacture of PSCs. The first method was based on the synthesis of the mixed-ion (FAPbI3)0.87(MAPbBr3)0.17 perovskite in ambient air, which had hitherto only been possible in inert atmosphere. The best PSC was obtained by depositing the perovskite onto a 50°C warm substrate in ambient air yielding a PCE of 17.7%. In the second method, only non-hazardous solvents, water and isopropanol, were used in the synthesis of Cs0.1FA0.9Pb(I0.83Br0.17)3. It is the first publication of mixed inorganic and organic cation perovskite synthesis using a two-step preparation procedure with only non-hazardous solvents and the process yielded a PCE of 13.0%. The method allows for complete ionic control of the perovskite and further variation and improvements are therefore possible.
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| 447. |
- Sörengård, Mattias
(författare)
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Stabilization remediation of soils contaminated with per- and polyfluoroalkyl substances (PFASs)
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Per- and polyfluoroalkyl substances (PFASs) are a major global concern in pollution of drinking water sources and aquatic environments. Due to the high persistence and mobility of these compounds, remediation methods for PFAS-contaminated soils are urgently needed to protect the surrounding environment and drinking water source areas. This is particularly important at firefighter training sites, due to the historical usage and release of PFAS-containing aqueous foams causing high levels of soil contamination, with high potential for leaching to groundwater and nearby environments. This thesis assessed the efficacy of stabilization remediation methodologies in mitigating PFAS leaching from contaminated soils. Screening of 44 PFAS sorbent materials showed that activated carbons (ACs) (granulated and pulverised, n = 5) were the best sorbent (mean removal efficiency >99.9%) for PFASs in aqueous solution. Based on these results, a commercially available injectable colloidal AC product (PlumeStop®) for soil stabilization was systematically assessed for PFAS retention efficiency. The best treatment efficiency for 10 different soils (fortified with 17 PFASs) treated with colloidal AC was observed for perfluorooctanoic acid (PFOA), 6:2 fluorotelomer sulfonate (6:2 FTSA) and perfluorohexane sulfonate (PFHxS), resulting in sorption increases of >80%. Assessment was also performed of a stabilization-solidification (S/S) technique that uses cementitious material to chemically stabilise PFASs and solidify the soil, decreasing hydraulic conductivity and thereby reducing PFAS leaching potential. The S/S technique was tested on PFAS-spiked soil using a cost-efficient cementitious material with a soil:binder ratio of 9:1 and seven different additives (including ACs) to 0.2% of dry weight (dw). In conservative leaching tests, treatment efficiency was highest for AC additive amended S/S remediation (e.g. >99.9% for longer-chain PFASs such as perfluorooctane sulfonate (PFOS)). To further assess the applicability and long-term stability of S/S treatment, a pilot-scale experiment was set up treating over six tons of field-contaminated soil using 15% cementitious binder and 0.2% dw mass-granulated AC. An artificial irrigation system was used to apply the equivalent of six years of precipitation. The treatment efficiency was >97% for four dominant PFASs homologues (perfluorohexanoic acid (PFHxA), PFOA, PFHxS and PFOS), but low (3%) for shortchain perfluoropentanoic acid (PFPeA). Ultimately, based on laboratory- and pilot-scale experiments, it can be concluded that stabilization remediation of PFAS-contaminated soils can be an efficient technique, in particular for longer-chain PFASs.
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| 448. |
- Teknetzi, Ioanna, 1992
(författare)
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Recycling of CIGS solar cells: environmentally friendly approaches for silver and indium recovery
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increase in electricity produced by solar energy is expected to create an end-of-life photovoltaics (PV) waste problem in the following decades, while their manufacturing waste is already a reality. However, their recycling is still at a primitive stage. Among the other PV types, Copper Indium Gallium diSelenide (CIGS) thin film technology can achieve high energy conversion efficiencies, while consuming small amounts of materials. However, the use of critical, precious and toxic elements in this PV technology is a considerable drawback due to risk on sustainable material supply and environmental concerns. Thus, the waste should be treated properly. The scientific literature on waste recycling of indium (In) and silver (Ag) from CIGS solar cells, which is very limited, suggests that their dissolution is accomplished through leaching in acid solutions with high concentrations and, many times, at high temperatures. However, such conditions are not environmentally friendly and can also be costly for the industry. Another challenge on the recycling is the contamination issues from other elements that are usually ignored when recycling of real CIGS PV is investigated. The main focus of this thesis is the recycling of Ag and In (although other elements are studied as well) from flexible CIGS solar cells, using mild leaching conditions. Two processes were tested, both at room temperature: a) a method for leaching of the cell with nitric acid (HNO3) of relatively low concentrations for recovery of Ag and In and b) a method for recovery of Ag and Indium Tin Oxide (ITO) particles using ultrasonic (US) assisted leaching. 100% recovery of Ag and 85% of In was achieved within 24 h when leaching with 2 M HNO3 and surface area to liquid ratio (A:L) equal to 1:3 cm2/ml. However, these results were improved with the second method for a complete recovery of both Ag 95 wt% pure and ITO 70.5 wt% pure. For that, a two-step US-leaching process with 0.1 M HNO3 and A:L equal to 1:3 cm2/ml was used. Both methods offer the advantage of achieving 100% recovery of Ag using relatively benign conditions. Especially the improved US-leaching approach opens up a new path for possible direct reuse of the Ag and ITO particles in the manufacturing of new PVs, after further purification, with an impressively low need for chemicals.
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| 449. |
- Bardakov, Roman, 1992-
(författare)
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Transport and chemical processing of trace gases in deep convective clouds
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deep convective clouds can efficiently transport trace gases from the planetary boundary layer to the upper troposphere. Once there, some gases will contribute to new particle formation and growth, eventually producing aerosols that are large enough to influence cloud properties, the radiative budget of the Earth, and climate. The magnitude and exact pathways of the convective transport of many organic and inorganic compounds are, however, still unclear. This dissertation presents a framework to study vertical transport of gas mixtures by deep convective clouds. The method consists of a chemical box model that is driven by cloud air parcel trajectory data generated by large-eddy simulation. This combination allows us to examine detailed gas-cloud interactions as well as complex systems of gas-phase chemical reactions. A large ensemble of simulated cloud trajectories was used to identify and characterize convective up- and downdrafts in the Amazon region. The analysis showed that air parcels starting close to the surface (at 0.5 km) experienced a substantially larger probability of reaching the upper troposphere (above 10 km) than parcels starting at the top of the boundary layer. Furthermore, the framework was used to estimate the vertical transport of isoprene, isoprene oxidation products, ammonia, and several non-reactive trace gases. We found that a typical Amazonian deep convective cloud can transport around 30% of the boundary layer isoprene to the cloud outflow if the efficiency of the gas uptake on ice is high and there is no lightning within the cloud. If the efficiency of gas uptake on ice is low and lightning within the cloud is extensive, all isoprene will be oxidized. Several low-volatility isoprene oxidation products will then have relatively high concentrations in the outflow, which potentially could lead to new particle formation and growth. Another result was that up to 10% of the boundary layer ammonia can reach the cloud outflow, where it in some environments can nucleate synergistically with nitric and sulfuric acid. A key uncertainty in our estimates is the efficiency of gas uptake by ice particles.
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| 450. |
- Pohl, Johannes
(författare)
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Effects of ozonated sewage effluents and pharmaceuticals in zebrafish (Danio rerio)
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aquatic environment is the main destination for many organic pollutants originating from human activity. Pharmaceuticals are significant contributors to this pollutant cocktail. One major route of pharmaceuticals into the aquatic environment is through discharges from sewage treatment plants (STPs) with inadequate pharmaceutical removal capacity. Adverse effects in aquatic organisms exposed to pharmaceuticals have been illustrated in a multitude of studies. Advanced sewage treatment technologies are therefore being evaluated as potential methods for improving pharmaceutical removal, for example whole-effluent ozonation. However, it remains important to assess how the ozonation treatment modulates the biological effect in aquatic organisms exposed to the STP effluent due to the formation of ozonation by-products (OBPs). This thesis aimed to investigate outcomes of ozonation treatment of STP effluents with a special focus on pharmaceuticals, by combining chemical analysis and in vivo testing using zebrafish (Danio rerio). Firstly the effects of an ozonated STP effluent on reproduction and behavior of adult zebrafish were evaluated at a Swedish STP (Knivsta municipal STP) with a full-scale ozonation step. Fish exposed over 21 days to the ozonated STP effluent spawned significantly more eggs than fish exposed to the nonozonated effluent and tap water. Vitellogenin induction (a biomarker for estrogenic pollutants) and a possible anxiety-related behavior were also observed in fish exposed to the ozonated STP effluent. Chemical analysis of the pre- and post ozonated STP effluent was used to screen for the presence of 105 pharmaceuticals, of which 24 could be detected. The average ozone removal efficiency of these pharmaceuticals was 77%. The thesis work then focused on how ozonation would affect zebrafish embryotoxicity of three pharmaceuticals detected in the Knivsta STP effluent (i.e. carbamazepine, diclofenac, and oxazepam). While embryotoxicity of diclofenac was eliminated, exposure to oxazepam and carbamazepine induced embryotoxic responses following ozonation, suggesting formation of OBPs. The thesis therefore proceeded to investigate the toxicities of isolated carbamazepine OBPs. It was revealed that two carbamazepine OBPs, BQM and BQD, were the drivers of ozonated carbamazepine embryotoxicity. The thesis concludes that the formation of specific pharmaceutical OBPs explains adverse biological outcomes of effluent ozonation. The results add valuable information for the continuing efforts to improve STP effluent treatment.
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