During the Fukushima Daiichi power plant incident sea water was used in an attempt to cool reactor Unit 3. Since sea water contains an excessive amount of chloride, 36Cl has likely been formed and spread in the environment. Because of the long residence time and the presumed high mobility in water there is an increased interest to learn more about the biogeochemical cycle of chlorine from a radiation risk assessment perspective. Chlorine occurs in inorganic form as chloride (Clin) or bound to organic matter as organic chlorine (Clorg) and is commonly found in the environment due to both anthropogenic and natural processes. Though there are still uncertainties regarding all of the components of the chlorine cycle in soil, the chlorination of organic matter has been exemplified by research. The reverse process, Clorg mineralizing into Clin, has however not been thoroughly investigated. For this study the objective was to observe at what rate Clorg mineralizes into Clin, this by using 36Cl as a tracer in forest soil. 36Cl was added to the soil and 36Clorg was formed over a period of approximately 100 days. After chlorination the samples were incubated in different conditions and the amount of 36Clorg was observed over a period of time (180 days). The result showed no evident dechlorination during the experiment period which indicates that Clorg can be stable in the organic horizon in forest soil.

No description available.

Water managers must balance the need for clean and safe drinking water with ever-increasing amounts of waste-water. A technique for treating and storing surface water called “managed aquifer recharge” (MAR) is frequently used to help maintain this balance. When MAR is used to produce drinking water, water managers must ensure that disease-causing microbial contaminants are removed from the water prior to its distribution. This thesis examined the processes responsible for removing a specific class of microbial contaminants called “enteric viruses” during MAR. Viruses are naturally removed in groundwater through adsorption and inactivation mechanisms. This thesis investigated how these virus removal mechanisms were affected by ionic strength (IS), dissolved organic carbon (DOC), and the age of the sand used in a MAR infiltration basin. This was done using batch and flow-through column experiments designed to mimic conditions characteristic of a basin infiltration MAR scheme in Uppsala, Sweden. Bacteriophage MS2 was used as a proxy for enteric viruses. All of the experiments were conducted at 4°C. Experimental data were modeled to describe the fate and transport of viruses in the infiltrated groundwater. Conventional least-squares optimization and generalized likelihood uncertainty estimation (GLUE) were compared as model fitting-approaches in order to determine how data uncertainty affects parameter estimates and model predictions. Results showed that the sand used in the infiltration basins accumulates adsorbed organic matter as it is exposed to infiltrating surface waters. This reduced the amount of MS2 that was removed due to adsorption and inactivation. Results from GLUE indicated that MS2 is more likely to inactivate in a time-dependent manner when in the presence of sand with high concentrations of organic matter. Both model fitting techniques indicated that virus attachment rates were significantly lower for sand with high organic carbon content. Neither methodology was capable of adequately capturing the kinetics of virus adsorption. Uncertainties in the experimental data had a large effect on the conclusions that could be drawn from fitted models. This study showed that the presence of natural organic matter reduces the value of the infiltration basin as a microbial barrier.

Initialement émis lors des essais nucléaires atmosphériques, le tritium (3H) est l’un des principaux radionucléides rejetés par les installations nucléaires. Il est présent dans toutes les composantes environnementales sous différentes formes, libres (HT, HTO, CH3T) ou liée à la matière organique (TOL). Le tritium suit les mêmes dynamiques d’incorporation et de dégradation dans les organismes que l’hydrogène et se met rapidement à l’équilibre avec le milieu ambiant. Des études ont montré un déséquilibre TOL/HTO dans différents compartiments et matrices environnementales. Ce travail vise à expliquer la variabilité des concentrations en 3H et l’origine des déséquilibres observés en se basant sur l’hypothèse de la rémanence. Une approche multi-échelles axée sur le rôle du transfert différé de la matière organique entre les compartiments environnementaux a été menée. Les résultats acquis ont permis d’établir des gammes de concentrations en HTO dans des cours d’eau non influencés par des rejets tritiés et d’identifier les principaux paramètres liés à la variabilité observée. Les résultats ont aussi permis de comprendre l’origine du TOL à partir d’analyses statistiques, qui tendent à confirmer que des zones de rémanence en TOL issus des essais nucléaires, peuvent conduire à des déséquilibres significatifs entre formes libre et liée. De plus, l’étude d’une archive sédimentaire a montré l’existence d’un pic de concentrations en TOL en profondeur, provenant vraisemblablement des retombées de ces essais. Enfin, l’instrumentation d’un site atelier, à proximité d’installations nucléaires, a permis de confirmer l’existence d’un marquage de la matière organique et la rémanence du TOL. / Initially emitted in the environment by atmospheric nuclear weapons tests, tritium (3H) is one of the main radionuclide released by nuclear facilities. It is present in all environmental media in several different forms, bound to organic matter (OBT) or in free forms (HT, HTO, CH3T). Furthermore, 3H follows the same dynamics of incorporation and degradation in living organisms as the hydrogen and is quickly balanced with the surrounding environment. Numerous studies have shown disequilibrium of OBT/HTO in different environmental compartments and matrices. This research work aims to explain the variability of 3H concentrations and the origin of disequilibrium of OBT/HTO based on the persistence hypothesis. In this study, a multi-scale approach was used, focusing on the role of delayed transfer of organic matter between natural compartments. The main results have established the ranges of HTO concentrations in several rivers that are not influenced by atmospheric releases from nuclear facilities, and also identified key environmental parameters linked to the observed variability. The results also made it possible to understand the origin of OBT using statistical analyses. The results tend to confirm that atmospheric nuclear tests led to areas of persistence of OBT, and can lead to significant disequilibrium between bound and free forms. Moreover, the study of a sediment core has shown a peak of OBT at depth, in all likelihood from the global fallout associated with atmospheric nuclear weapons tests. Also, a study site impacted by industrial releases of tritium for the last fifty years has confirmed the persistence of OBT in organic matter, especially in abiotic matrices.

Supported lipid bilayers (SLBs) are one of the most common model membranes used in the field of cell membrane biology as they provide a well-defined model membrane platform for determination of molecular-level interactions between different biomolecules (e.g. proteins, peptides) and lipid membrane. Compared to model organisms, the use of SLB is preferable since it mimics cell plasma membrane in a very simple and well-controlled way. Therefore, molecular structure of membrane and experimental conditions (e.g. solution chemistry, temperature, and pH) can be easily adjusted to the required conditions of any systematic research. In addition, SLBs are typically easy to form, cheap and very reproducible and they are compatible with different surface characterization techniques, such as quartz crystal microbalance with dissipation (QCM-D), ellipsometry and atomic force microscopy (AFM). This study demonstrates that QCM-D analysis of SLBs serve as powerful tool to investigate and characterize the mechanisms of interactions between lipid membrane and gold nanoparticles (NPs), environmentally relevant polymers, and disease-inducing peptides. Due to many critical applications of gold NPs in drug delivery and diagnostics, understanding of membrane-NP interactions is crucial especially for determination of NPs cytotoxicity. In this study we focus on membrane disruption as one of the different mechanisms by which metal NPs induce cytotoxicity. The use of SLB is beneficial for this goal as it elucidates the unique mechanism of membrane disruption without interference of other mechanisms taking place simultaneously in biological cells. For NP-membrane interaction studies, a SLB composed of L-α-phosphatidylcholine (egg PC) was formed on a SiO2-coated crystal and QCM-D analysis was performed to obtain information about mass and viscoelastic changes of SLB resulting from interactions with gold NPs. For better understanding of the mechanisms of NP-membrane interactions, we systematically changed the NPs properties and the experimental conditions. In order to understand the effect of NP size, gold NPs with diameters of 2,5,10, and 40 nm were tested and compared to each other. NPs were tested in their citric acid-stabilized state as well as in the presence of poly (methacrylic acid) (PMAA), representing an organic coating that could become associated with NPs in the environment. The results indicated that when dissolved in water, gold NPs with the dimeters of 2, 5, 10, and 40 nm did not perturb the membrane, but in the presence of environmentally relevant polymer, the larger nanoparticles were found to disrupt the membrane. In order to elucidate the effect of surface chemistry, 10 nm - gold NPs with various functionalizations (i.e. anionic, cationic and non-ionic ligands) were tested. Control experiments were designed to test the effect of NPs in the absence of humic substances which means the NPs were dissolved in water. In these cases, regardless of the type of NP functionalization, no substantial bilayer mass changes were observed. This suggests that the charge and chemistry of the ligands had a minor effect on NP-membrane interactions. Furthermore, in both the control and humic acid experiments, there were small dissipation changes (less than 1 unit) indicating that the overall membrane structure was not perturbed. In order to mimic environmentally-relevant conditions, mass and viscoelasticity of SLB was characterized in the presence of four different natural polymers, also known as natural organic materials (NOMs): Fulvic and humic acids extracted from Suwannee River (SRFA and SRHA), which had relatively lower molecular weights and a commercial humic acid (HA) and the humic acid extracted from Elliott soil (ESHA) with higher molecular weight. The results showed that NOMs with lower molecular weights, adsorbed to the bilayer, while higher molecular weight components, did not induce any changes to the bilayers. In addition, the NPs in SRFA and SRHA increased the mass of the bilayer by 20-30 ng, while the NPs in HA and ESHA changed the mass of the bilayer by < 10 ng. It was concluded that the presence of humic substances as well as their physical and chemical properties exert a direct impact on the interactions between cell membrane and the nanoparticles. In addition to the field of NP toxicity, SLBs play a pivotal role in the field of neurodegenerative diseases, such as Alzheimer’s disease (AD), in which the pathological cascade of events starts from interactions of a misfolded peptide with cell membrane. In this thesis, we confirm the validity of QCM-D analysis of SLB as an important platform for investigation of amyloid β (the peptide associated with AD) interactions with lipid membrane. Adsorption of Aβ peptide to cell membrane is known to take place on the so-called “lipid raftâ€� which are membrane microdomains enriched with cholesterol, sphingomyelin and ganglioside. The formation of SLBs containing lipid rafts is not only important for the field of AD research, but also it is important for other in vitro studies of cell biology as the lipid rafts are responsible for a variety of biological functions such as association of some membrane proteins and cellular signaling. However, the presence of lipid raft components such as sphingomyelin and cholesterol makes the formation of the bilayer more challenging which leads to adsorption of intact vesicles on the substrate without formation of the bilayer. In this study, the formation of lipid bilayer composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl- sn-glycero-3-phospho-L-serine (DOPS), cholesterol (Chol), sphingomyelin (SM), and ganglioside (GM) was investigated using QCM-D. A challenge was that the raft-containing vesicles remained intact on the SiO2 crystal. Therefore, different experimental conditions were tested to induce vesicle fusion, such as pH, temperature, osmotic pressure, and vesicle size. The key parameter in forming the bilayer was found to be applying osmotic pressure to the vesicles by having the vesicles exterior concentration of NaCl higher than interior concentration. When this concentration gradient was applied to the vesicles before flowing them on the substrate, vesicle rupture was favored and formation of a complete bilayer could occur. Here, we report the effects of each tested variable on the adsorption and fusion of the raft-containing vesicles, and the results are discussed based on the mechanisms of vesicle-vesicle and vesicle-substrate interactions.After developing the robust method for formation of SLB with lipid rafts, we used that as a template to characterize the mechanism of interactions between Aβ peptide and cell membrane which leads to onset of AD. The mechanism of Aβ toxicity leading to AD has not fully discovered yet, due to the complexity of the process including several steps of Aβ peptide adsorption on membrane, conformational change from disordered in solution to a membrane-bound α-helix structure and then formation of β-sheet aggregates that serve as fibrillation seeds. In this study, we showed that QCM-D technique as a promising tool to conduct systematic studies on the mechanism of interactions between Aβ peptide with lipid membrane. To our knowledge, this was the first time QCM-D was utilized for characterization of Aβ fibrillation starting from monomer states until formation of mature fibrils. The data indicated that peptide-membrane interactions follow a two-step kinetic pathway starting with the adsorption of small (low-n) oligomers until covering all the adsorption sites on the surface. In the second step, the membrane structure is destabilized as the result of interaction with oligomers which leads to lipid loss from the surface. Consistency of the results with the data obtained via other techniques substantiates QCM-D technique as a robust approach to answer the remaining unanswered questions in the field of Alzheimer’s disease.

Dissolved organic matter (DOM) plays a vital role in biogeochemical processes and can flux CO2 to the atmosphere when labile fractions are degraded, hence DOM degradation is increasingly studied. Some studies have suggested that fluorescence-derived substrate characteristics are useful metrics for estimating bioavailability (as prerequisite condition for biodegradability), however, recent findings on soil organic matter emphasize the importance of ecosystem scale factors such as physical separation of substrate from soil microbial communities and soil physiochemical cycles driving organic matter stability. I extend this principle to soil derived DOM and hypothesize that such environmental conditions, covariant with season, land use and landscape position, impact the composition of soil DOM and activity and abundance of the microbial community, which together govern DOM biodegradability. As a result, DOM bioavailability may not reliably be predicted using substrate characteristics alone. To test these hypotheses, I assessed aqueous soil extracts for water extractable organic carbon (WEOC) content, biodegradability, microbial biomass and fluorescence spectroscopy on water extractable organic matter (WEOM) across a range of environmental conditions in northern Vermont, USA. My results indicate that changes in environmental conditions affect composition, quantity, and biodegradability of DOM. WEOC concentrations were highest in the fall and lowest in the summer, while no significant differences were found between land covers or landscape position, however, DOM biodegradability was significantly higher in the agricultural (AG) site across seasons. Despite a shift in utilized substrate from less aromatic DOM in summer to more aromatic DOM in winter, biodegradability was similar for all seasons. The only exception were cold temperature incubations where microbial activity was depressed, and processing was halted. These results indicate that bioavailability cannot be reliably predicted based on fluorescence-based metric alone, rather, my core findings illustrate a complex picture of how environmental conditions, landscape characteristics, and substrate composition interact to drive the biodegradability of labile carbon pools in the soil environment. This thesis includes i) a background and comprehensive review of literature to inform the reader of any relevant topics, ii) a paper submitted for publication to Biogeochemistry (Chapter 2), and iii) supplemental information containing figures and tables pertinent to the paper.

Stable carbon isotope ratios of soils, roots and litter along transects stretching from nearly monospecific stands of Ceratoides lanata , a species possessing c3 photosynthesis, to nearly monospecific stands of Atriplex confertifolia, a species possessing c4 photosynthesis, were analyzed to determine i f changes in the relative dominance of the shrubs have occurred in salt-desert communities. The a13c value , which reflects the proportion of 12c and 13c in a sample of plant tissue, can be used to distinguish between c3 and c4 species. Atriolex confertifolia and Ceratoides lanata have a13c values of -13.0 ofoo and - 25 ofoo, respectively. The a13c value of litter and roots was used as a measure of current community dominance. The a13c value of soil organic matter was employed as a measure of past community dominance . The differential between a13c values of roots and soils was consistently about 3.0 ofoo in Ceratoides- dominated stands. Root a13c values were always more negative than soil a13c values. The striking uniformity in the rootsoil differential l in Ceratuitles- duninateci stands is most likely the result of fractionation of carbon isotopes during decomposition. The differential between a13c values of roots and soils in Atriplexdominated stands was more variable. This most likely indicates a lack of long- term community stability in areas na The distribution of a13c values in relation to depth and among soil organic matter fractions was also studied. There was a trend for a13c values to become slightly less negative with depth . The a13c value of humic acid was most similar to the o13c value of the dominant vegetation. Fulvic acid was isotopically heavier than humic acid in all analyses. The implications of these trends are discussed.

Membrane processes are increasingly used in water treatment. Experiments were performed using stirred cell equipment, polymeric membranes and synthetic surface water containing natural organics, inorganic colloids and their aggregates, and cations. All processes could remove a significant amount of natural organics. Pretreatment with ferric chloride was required to achieve significant organic removal with MF and high MWCO UF. Additionally, fouling mechanisms for the three processes were investigated. Crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics. In MF, fouling by pore plugging was most severe. Variations in solution chemistry changed the aggregation state of the colloids and/or natural organic matter and dramatically affected rejection and fouling behaviour. UF membrane fouling was mainly influenced by pore adsorption and could improve natural organics rejection significantly. Coagulant addition shifted fouling mechanism from pore adsorption to cake formation. Aggregate structure was most significant for flux decline. In NF, rejection of natural organics involved both size and charge exclusion. Fouling was caused by precipitation of a calcium-organic complex. Fouling could be avoided by pretreatment with metal salt coagulants. Thorough chemical characterisation of the organics used demonstrated that only size and aromaticity can be related to fouling. The study is concluded with a process comparison based on a water quality parameter and a cost comparison. Treatment cost of microfiltration with chemical pretreatment was similar to that of nanofiltration at a comparable natural organics rejection.

Natural organic matter (NOM) occurs ubiquitously in drinking water supplies and is problematic since it serves as a precursor to disinfection by-products (DBPs) formation. Stricter DBP regulations will drive utilities to consider advanced treatment processes for DBP control through NOM removal. Herein, the transformation of NOM in homogeneous (UVA/H2O2 and UVA/Fe/H2O2) and heterogeneous (UVA/TiO2) Advanced Oxidation Processes (AOPs) were studied. Organic matter from three different sources was investigated in this work, specifically a commercial humic acid, and two Australian surface water sources. The transformation of the organic matter as a result of oxidation was investigated through multiple analytical techniques, such as UV-Vis spectroscopy, DOC analysis, high performance size exclusion chromatography (HPSEC), resin fractionation, liquid chromatography with organic carbon detection (LC-OCD) and disinfection byproducts formation potential. The multi-analysis approach is required due to the complex and heterogeneous nature of NOM. Each analytical technique provides complementary information on different properties of NOM, leading to a comprehensive understanding on how AOPs transform the chemical and physical properties of NOM. Both homogeneous and heterogeneous AOPs were found to be effective for NOM removal. However, complete mineralisation was not achieved, even under prolonged irradiation. Large aromatic and hydrophobic organics were degraded into lower molecular weight hydrophilic compounds, which had weak UV absorbance at 254 nm. In the UVA/TiO2 treatment, multi-wavelength HPSEC analysis demonstrated the formation of low molecular weight compounds with strong absorbance at wavelength lower than 230 nm. These residual organic compounds, though recalcitrant, had a low reactivity to chlorine to form THMs, and were identified to be low molecular weight acids and neutral compounds from LC-OCD analysis. Finally, the current work reports the novel synthesis of magnetic photocatalyst for NOM oxidation from low cost precursors to solve the separation problem of nano-sized particles. Magnetite particles were coated with a layer of protective silica from sodium silicate precursor. Photoactive titanium dioxide was then deposited onto the silica coated particles using titanium tetrachloride precursor. The as-prepared magnetic photocatalyst exhibited excellent stability and durability. Although the photoactivity of the magnetic photocatalyst is lower than commercial TiO2 photocatalyst, it can be easily recovered by magnetic field.

In Belgium, the Boom Clay is currently studied as the reference host formation for the disposal of high-level and long-lived radioactive waste. In case of direct disposal of spent fuel, uranium isotopes are important contributors along with their daughters to the dose rate at very long term. Therefore, it is essential to study the migration of uranium in the host formation. The present work contributes to improve the knowledge of uranium speciation in the Boom Clay, U(IV) versus U(VI), and of the mechanisms controlling the uranium mobility such as solubility, sorption and complexation by organic matter. The information necessary to interpret the migration behaviour is derived from the study of naturally occurring uranium in the rock and from laboratory experiments conducted under conditions representative for the Boom Clay. Uranium naturally present in the Boom Clay is concentrated in detrital heavy minerals and in authigenic iron(II)-bearing minerals such as siderite and glauconite. Despite its reducing capacity, pyrite is surprisingly depleted in uranium relative to the mean content. Furthermore, uranium is also associated with the surfaces of clay minerals. The clayey fraction contains about 4 ppm uranium and is the main contributor to the total uranium content of the Boom Clay since it constitutes up to 60 wt. % of the rock. The correlation observed on the field between uranium and organic matter suggests that uranium is reduced, likely during the early diagenesis process of bacterially-mediated sulphate reduction. If hexavalent oxidation state of uranium predominates as predicted by geochemical calculations based on the most recent thermodynamic data of the Nuclear Energy Agency (NEA), less than 5% of uranium is complexed by humic acids in the Boom Clay pore water. The U(VI) speciation is dominated by the inorganic carbonate complexes, merely UO2(CO3)34-. The conditional constant determined for the complexation of U(VI) by humic acids under in situ Boom Clay conditions is log exp = 12.4. However, experimental studies show that UO2(CO3)34- is reduced by interaction with pyrite, the main reducing mineral present in the rock, and precipitates as a mixed oxide of U(IV)/U(VI), i.e. UO2+x. Moreover, electromigration experiments suggest that U(VI) is not stable in the Boom Clay: U(VI) is reduced and precipitates as U(IV) oxy-hydroxides. The experimentally measured solubility of U(IV) amorphous oxide, UO2(am), in Boom Clay pore water is about 10 8 mol•l 1. This solubility value is not increased by complexation of U(IV) with dissolved organic matter. The dominant effect of organic matter on the dissolution of UO2(am) is the stabilisation of U(IV) real colloids which increase the uranium concentration by three orders of magnitude. However, the mobility of these colloids is expected to be very limited because of the compaction level of the Boom Clay and its ultra-filtrating feature. The diffusive transport of dissolved uranium is furthermore retarded by significant sorption onto clay minerals. In conclusion, the presence of organic matter in the Boom Clay has no negative effect on the uranium retention which is dominated by the solubility and sorption of U(IV) species