Geochemical evolution of active porphyry copper tailings impoundments : from alkaline deposition towards acidification

J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Thesis abstract Mine waste is the largest volume of materials handled in the world. The oxidation of sulfidic mine waste may result in the release of acid mine drainage (AMD) rich in heavy metals and arsenic to the environment, one of the major problems the mining industry is facing today. To control and reduce this environmental impact, it is crucial to identify the main geochemical and hydrological processes influencing contaminant liberation, transport, and retention. This thesis presents the results of a geochemical, mineralogical and stable isotope study (δ2H, δ18O, δ34S) from two active porphyry copper tailings impoundments in Mediterranean (Carén tailings impoundment, El Teniente mine, Central Chile) and hyper-arid climate (Talabre tailings impoundment, Chuquicamata, Northern Chile) from the deposition in alkaline environment (pH 10.5) towards acidification after several years of exposure. The major hydrological results were the identification of vertical contaminant and water transport in the uppermost, not water-saturated zone, triggered by capillary rise due to evaporation, and infiltration downwards due to new tailings deposition, and of horizontal transport in the groundwater zone. At the surface of the sedimented tailings, evaporation of pore water led to the precipitation of Na-Ca-Mg sulfates (e.g., gypsum, tenorite), in hyper-arid climate also halite. At the Carén tailings impoundment, renewed deposition in a 4-week interval inhibited a pH decrease below neutral values and the formation of an efflorescent salt crust. At the Talabre tailings impoundment, deposition breaks of several years resulted in the formation of acidic oxidation zones in the timeframe of less than 4 years. This process enabled the transport of liberated Cu, Zn, and Fe via capillary rise to the surface, where these metals precipitated as heavy-metal sulfates (e.g., devilline, krohnkite) and chlorides (eriochalcite, atacamite). Renewed depositing may dissolve efflorescent salts and transport liberated elements towards the groundwater zone. This zone was found to be highly dynamic due to infiltration and mixing with water from different sources, like groundwater, catchment water, and infiltration from superficial waters. There, Cu was found to be partially mobile due to complexation with Cl (in Cl-rich groundwater, Talabre) and dissolved organic matter (in zones with infiltration of catchment water rich in dissolved organic matter, Carén). A laboratory study on the isotopic fractionation of sulfur and oxygen of sulfate in different minerals groups (water-soluble sulfates, low- and high-crystalline Fe(III) oxyhydroxides) contributed to the use of stable isotopes as tracer of geochemical and transport processes for environmental studies. The results highlight that a detailed geochemical, stable isotope and mineralogical study permits the identification of contamination processes and pathways already during the deposition of mine tailings. This knowledge allows the early planning of adequate actions to reduce and control the environmental impact during tailings deposition and after the closing of the impoundment. J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Résumé de these Les déchets miniers constituent les plus grands volumes de matériel gérés dans le monde. L'oxydation des déchets miniers sulfuriques peut conduire à la libération de drainages miniers acides (DMA) riches en métaux et arsenic dans l'environnement, ce qui est l'un des principaux problèmes de l'industrie minière aujourd'hui. Pour contrôler et réduire ces impacts sur l'environnement, il est crucial d'identifier les principaux processus géochimiques et hydrologiques influençant la libération, le transport et la rétention des contaminants. Cette thèse présente les résultats d'une étude géochimique, minéralogique et des isotopes stables (δ2H, δ18O, δ34S) sur des déchets miniers de 2 sites de dépôt actifs en climat méditerranéen (Dépôt de déchets de Carén, mine de El Teniente, Centre du Chili) et en climat hyper-aride (Dépôt de déchets de Talabre, mine de Chuquicamata, Nord du Chili). L'objectif était d'étudier l'évolution des déchets de la déposition en milieu alcalin (pH = 10.5) vers l'acidification après plusieurs années d'exposition. Le principal résultat hydrologique a été l'identification de 2 types de transport : un transport vertical de l'eau et des contaminants dans la zone non saturée en surface, induit par la montée capillaire due à l'évaporation et par l'infiltration subséquente de la déposition de sédiments frais ; et un transport horizontal dans la zone des eaux souterraines. À la surface des déchets, l'évaporation de l'eau interstitielle conduit à la précipitation de sulfates de Na-Ca-Mg (ex. gypse, ténorite) et halite en climat hyper-aride. Dans le site de Carén, une nouvelle déposition de déchets frais à 4 semaines intervalle a empêché la baise du pH en deçà des valeurs neutres et la formation d'une croûte de sels efflorescentes en surface. Dans le site de Talabre, les fentes de dessiccation des dépôts ont entraîné la formation d'une zone d'oxydation à pH acide en moins de 4 ans. Ce processus a permis la libération et le transport par capillarité de Cu, Zn, Fe vers la surface, où ces éléments précipitent sous forme de sulfates de métaux lourds (ex., dévilline, krohnkite) de chlorures (ex. ériochalcite, atacamite). Une nouvelle déposition de sédiments frais pourrait dissoudre ces sels et les transporter vers la zone des eaux souterraines. Cette dernière zone était très dynamique en raison du mélange d'eaux provenant de différentes sources, comme les eaux souterraines, l'eau de captage et l'infiltration des eaux superficielles. Egalement dans cette zone, le cuivre était partiellement mobile à cause de la formation de complexe avec le chlore (dans les zone riche en Cl, Talabre) et avec la matière organique dissoute (dans les zones où s'infiltre l'eau de captage riche en matière organique, Carén). Une étude en laboratoire sur le fractionnement des isotopes stables de sulfure et d'oxygène des sulfates dans différents groupes de minéraux (sulfates hydrosolubles, sulfures de oxy-hydroxyde de Fe(III) faiblement ou fortement cristallins) a permis d'apporter une contribution à leur utilisation comme traceurs dans l'étude des processus géochimiques et de transport lors d'études environnementales. Les résultats montrent qu'une étude détaillée de la géochimie, des isotopes stables et de la minéralogie permet d'identifier les processus et les voies de contamination déjà pendant la période de dépôt des déchets miniers. Cette connaissance permet de planifier, dès le début de l'exploitation, des mesures adéquates pour réduire et contrôler l'impact sur l'environnement pendant la période de dépôts de déchets miniers et après la fermeture du site.

Allele-specific silencing of mutant huntingtin in rodent brain and human stem cells.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder resulting from polyglutamine expansion in the huntingtin (HTT) protein and for which there is no cure. Although suppression of both wild type and mutant HTT expression by RNA interference is a promising therapeutic strategy, a selective silencing of mutant HTT represents the safest approach preserving WT HTT expression and functions. We developed small hairpin RNAs (shRNAs) targeting single nucleotide polymorphisms (SNP) present in the HTT gene to selectively target the disease HTT isoform. Most of these shRNAs silenced, efficiently and selectively, mutant HTT in vitro. Lentiviral-mediated infection with the shRNAs led to selective degradation of mutant HTT mRNA and prevented the apparition of neuropathology in HD rat's striatum expressing mutant HTT containing the various SNPs. In transgenic BACHD mice, the mutant HTT allele was also silenced by this approach, further demonstrating the potential for allele-specific silencing. Finally, the allele-specific silencing of mutant HTT in human embryonic stem cells was accompanied by functional recovery of the vesicular transport of BDNF along microtubules. These findings provide evidence of the therapeutic potential of allele-specific RNA interference for HD.

Fate of the herbicide glyphosate and its metabolite AMPA in soils and their transfer to surface waters: A multi-scale approach in the Lavaux vineyards, western Switzerland

The use of herbicides in agriculture may lead to environmental problems, such as surface water pollution, with a potential risk for aquatic organisms. The herbicide glyphosate is the most used active ingredient in the world and in Switzerland. In the Lavaux vineyards it is nearly the only molecule applied. This work aimed at studying its fate in soils and its transfer to surface waters, using a multi-scale approach: from molecular (10-9 m) and microscopic scales (10-6 m), to macroscopic (m) and landscape ones (103 m). First of all, an analytical method was developed for the trace level quantification of this widely used herbicide and its main by-product, aminomethylphosphonic acid (AMPA). Due to their polar nature, their derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) was done prior to their concentration and purification by solid phase extraction. They were then analyzed by ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The method was tested in different aqueous matrices with spiking tests and validated for the matrix effect correction in relevant environmental samples. Calibration curves established between 10 and 1000ng/l showed r2 values above 0.989, mean recoveries varied between 86 and 133% and limits of detection and quantification of the method were as low as 5 and 10ng/l respectively. At the parcel scale, two parcels of the Lavaux vineyard area, located near the Lutrive River at 6km to the east of Lausanne, were monitored to assess to which extent glyphosate and AMPA were retained in the soil or exported to surface waters. They were equipped at their bottom with porous ceramic cups and runoff collectors, which allowed retrieving water samples for the growing seasons 2010 and 2011. Results revealed that the mobility of glyphosate and AMPA in the unsaturated zone was likely driven by the precipitation regime and the soil characteristics, such as slope, porosity structure and layer permeability discrepancy. Elevated glyphosate and AMPA concentrations were measured at 60 and 80 cm depth at parcel bottoms, suggesting their infiltration in the upper parts of the parcels and the presence of preferential flow in the studied parcels. Indeed, the succession of rainy days induced the gradual saturation of the soil porosity, leading to rapid infiltration through macropores, as well as surface runoff formation. Furthermore, the presence of more impervious weathered marls at 100 cm depth induced throughflows, the importance of which for the lateral transport of the herbicide molecules was determined by the slope steepness. Important rainfall events (>10 mm/day) were clearly exporting molecules from the soil top layer, as indicated by important concentrations in runoff samples. A mass balance showed that total loss (10-20%) mainly occurred through surface runoff (96%) and, to a minor extent, by throughflows in soils (4%), with subsequent exfiltration to surface waters. Observations made in the Lutrive River revealed interesting details of glyphosate and AMPA dynamics in urbanized landscapes, such as the Lavaux vineyards. Indeed, besides their physical and chemical properties, herbicide dynamics at the catchment level strongly depend on application rates, precipitation regime, land use and also on the presence of drains or constructed channels. Elevated concentrations, up to 4970 ng/l, observed just after the application, confirmed the diffuse export of these compounds from the vineyard area by surface runoff during main rain events. From April to September 2011, a total load of 7.1 kg was calculated, with 85% coming from vineyards and minor urban sources and 15% from arable crops. Small vineyard surfaces could generate high concentrations of herbicides and contribute considerably to the total load calculated at the outlet, due to their steep slopes (~10%). The extrapolated total amount transferred yearly from the Lavaux vineyards to the Lake of Geneva was of 190kg. At the molecular scale, the possible involvement of dissolved organic matter (DOM) in glyphosate and copper transport was studied using UV/Vis fluorescence spectroscopy. Combined with parallel factor (PARAFAC) analysis, this technique allowed characterizing DOM of soil and surface water samples from the studied vineyard area. Glyphosate concentrations were linked to the fulvic-like spectroscopic signature of DOM in soil water samples, as well as to copper, suggesting the formation of ternary complexes. In surface water samples, its concentrations were also correlated to copper ones, but not in a significant way to the fulvic-like signature. Quenching experiments with standards confirmed field tendencies in the laboratory, with a stronger decrease in fluorescence intensity for fulvic-like fluorophore than for more aromatic ones. Lastly, based on maximum concentrations measured in the river, an environmental risk for these compounds was assessed, using laboratory tests and ecotoxicity data from the literature. In our case and with the methodology applied, the risk towards aquatic species was found negligible (RF<1).

Functional expression of PHO1 to the Golgi and trans-Golgi network and its role in export of inorganic phosphate.

Arabidopsis thaliana PHO1 is primarily expressed in the root vascular cylinder and is involved in the transfer of inorganic phosphate (Pi) from roots to shoots. To analyze the role of PHO1 in transport of Pi, we have generated transgenic plants expressing PHO1 in ectopic A. thaliana tissues using an estradiol-inducible promoter. Leaves treated with estradiol showed strong PHO1 expression, leading to detectable accumulation of PHO1 protein. Estradiol-mediated induction of PHO1 in leaves from soil-grown plants, in leaves and roots of plants grown in liquid culture, or in leaf mesophyll protoplasts, was all accompanied by the specific release of Pi to the extracellular medium as early as 2-3 h after addition of estradiol. Net Pi export triggered by PHO1 induction was enhanced by high extracellular Pi and weakly inhibited by the proton-ionophore carbonyl cyanide m-chlorophenylhydrazone. Expression of a PHO1-GFP construct complementing the pho1 mutant revealed GFP expression in punctate structures in the pericycle cells but no fluorescence at the plasma membrane. When expressed in onion epidermal cells or in tobacco mesophyll cells, PHO1-GFP was associated with similar punctate structures that co-localized with the Golgi/trans-Golgi network and uncharacterized vesicles. However, PHO1-GFP could be partially relocated to the plasma membrane in leaves infiltrated with a high-phosphate solution. Together, these results show that PHO1 can trigger Pi export in ectopic plant cells, strongly indicating that PHO1 is itself a Pi exporter. Interestingly, PHO1-mediated Pi export was associated with its localization to the Golgi and trans-Golgi networks, revealing a role for these organelles in Pi transport.

Impact of mycelia on the accessibility of fluorene to PAH-degrading bacteria.

Mycelia have been recently shown to actively transport polycyclic aromatic hydrocarbons (PAH) in water-unsaturated soil over the range of centimeters, thereby efficiently mobilizing hydrophobic PAH beyond their purely diffusive transport in air and water. However, the question if mycelia-based PAH transport has an effect on PAH biodegradation was so far unsolved. To address this, we developed a laboratory model microcosm mimicking air-water interfaces in soil. Chemical analyses demonstrated transport of the PAH fluorene (FLU) by the mycelial oomycete Pythium ultimum that was grown along the air-water interfaces. Furthermore, degradation of mycelia-transported FLU by the bacterium Burkholderia sartisoli RP037-mChe was indicated. Since this organism expresses eGFP in response to a FLU flux to the cell, it was also as a bacterial reporter of FLU bioavailability in the vicinity of mycelia. Confocal laser scanning microscopy (CLSM) and image analyses revealed a significant increase of eGFP expression in the presence of P. ultimum compared to controls without mycelia or FLU. Hence, we could show that physically separated FLU becomes bioavailable to bacteria after transport by mycelia. Experiments with silicon coated glass fibers capturing mycelia-transported FLU guided us to propose a three-step mechanism of passive uptake, active transport and diffusion-driven release. These experiments were also used to evaluate the contributions of these individual steps to the overall mycelial FLU transport rate.

Biased diffusion in confined media: Test of the Fick-Jacobs approximation and validity criteria

We study biased, diffusive transport of Brownian particles through narrow, spatially periodic structures in which the motion is constrained in lateral directions. The problem is analyzed under the perspective of the Fick-Jacobs equation, which accounts for the effect of the lateral confinement by introducing an entropic barrier in a one-dimensional diffusion. The validity of this approximation, based on the assumption of an instantaneous equilibration of the particle distribution in the cross section of the structure, is analyzed by comparing the different time scales that characterize the problem. A validity criterion is established in terms of the shape of the structure and of the applied force. It is analytically corroborated and verified by numerical simulations that the critical value of the force up to which this description holds true scales as the square of the periodicity of the structure. The criterion can be visualized by means of a diagram representing the regions where the Fick-Jacobs description becomes inaccurate in terms of the scaled force versus the periodicity of the structure.

Biodiversity of Collembola in urban soils and their use as bioindicators for pollution

The objective of this work was to evaluate the effects of pollutants on the abundance and diversity of Collembola in urban soils. The research was carried out in three parks (Cişmigiu, Izvor and Unirea) in downtown Bucharest, where the intense car traffic accounts for 70% of the local air pollution. One site in particular (Cişmigiu park) was highly contaminated with Pb, Cd, Zn and Cu at about ten times the background levels of Pb. Collembola were sampled in 2006 (July, September, November) using the transect method: 2,475 individuals from 34 species of Collembola were collected from 210 samples of soil and litter. Numerical densities differed significantly between the studied sites.The influence of air pollutants on the springtail fauna was visible at the species richness diversity and soil pollution levels. Species richness was lowest in the most contaminated site (Cismigiu, 11 species), which presented an increase in springtails abundances, though. Some species may become resistant to pollution and occur in high numbers of individuals in polluted sites, which makes them a good bioindicator of pollutants.

Translocation of cyanogenic glycosides in rubber tree crown clones resistant to South American leaf blight

The objective of this work was to assess the possible transport of cyanogenic glycosides from leaves of rubber tree crown clones (Hevea spp.) resistant to South American leaf blight to the trunk of the panel clones in which they are grafted. The cyanogenic potential (HCNp) of the crown clones was determined in the trunk bark, at different distances from the cambium, and its gradient was evaluated along the trunk. The correlation between the HCNp of the crown leaves and that of the trunk bark was also evaluated. HCNp determined in leaves showed a wide range variation in the species studied as crown clones, with the lowest values registered in H. nitida clones, and the highest ones in H. rigidifolia. In the trunk bark, the tissue layer nearer the cambium showed higher HCNp values. A positive basipetal gradient was observed along the trunk, i.e., there was an increase in HCNp from the apex toward the base. Although the grafted crowns influence the cyanogenic potential of the trunk bark of panel clones, the absence of correlation between the HCNp of the leaves and trunk bark indicates that the crown is not the main source of the cyanogenic glycosides found in the trunk.

Dissection of hormone-responsive plasma membrane to nucleus signaling of Bravis Radix : its role in vascular differentiation and root meristem growth

AbstractPlants continuously grow during their complete life span and understanding the mechanisms that qualitatively regulate their traits remains a challenging topic in biology. The hormone auxin has been identified as a crucial molecule for shaping plant growth, as it has a role in most developmental processes. In the root, the directional, so-called polar transport of auxin generates a peak of concentration that specifies and maintains the stem cell niche and a subsequent gradient of decreasing concentration that also regulates cell proliferation and differentiation. For these reasons, auxin is considered the main morphogen of the root, as it is fundamental for its organization and maintenance. Recently, in Arabidopsis thaliana, a natural variation screen allowed the discovery of BREVIS RADIX (BRX) gene as a limiting factor for auxin responsive gene expression and thus for root growth.In this study, we discovered that BRX is a direct target of auxin that positively feeds back on auxin signaling, as a transcriptional co-regulator, through interaction with the Auxin Response Factor (ARF) MONOPTEROS (MP), modulating the auxin gene response magnitude during the transition between division and differentiation in the root meristem. Moreover, we provide evidence that BRX is activated at the plasma membrane level as an associated protein before moving into the nucleus to modulate cellular growth.To investigate the discrepancy between the auxin concentration and the expression pattern of its downstream targets, we combined experimental and computational approaches. Expression profiles deviating from the auxin gradient could only be modeled after intersection of auxin activity with the observed differential endocytosis pattern and with positive auto- regulatory feedback through plasma- membrane-to-nucleus transfer of BRX. Because BRX is required for expression of certain auxin response factor targets, our data suggest a cell-type-specific endocytosis-dependent input into transcriptional auxin perception. This input sustains expression of a subset of auxin-responsive genes across the root meristem's division and transition zones and is essential for meristem growth. Thus, the endocytosis pattern provides specific positional information to modulate auxin response. RésuméLes plantes croissent continuellement tout au long de leur cycle de vie. Comprendre et expliquer les mécanismes impliqués dans ce phénomène reste à l'heure actuelle, un défi. L'hormone auxine a été identifiée comme une molécule essentielle à la régulation de la croissance des plantes, car impliquée dans la plupart des processus développementaux. Dans la racine, le transport polaire de l'auxine, par la génération d'un pic de concentration, spécifie et maintient la niche de cellules souches, et par la génération d'un gradient de concentration, contrôle la prolifération et la différentiation cellulaire. Puisque l'auxine est essentielle pour l'organisation et la maintenance du système racinaire, il est considéré comme son principal morphogène. Récemment, dans la plante modèle, Arabidopsis thalinana, un criblage des variations génétique a permis d'identifier le gène Brevis radix (BRX) comme facteur limitant l'expression des gènes de réponse à l'auxine et par là même, la croissance de la racine.Dans ce travail, nous avons découvert que BRX est une cible direct de l'auxine qui rétroactive positivement le signalement de l'hormone, agissant ainsi comme un régulateur transcriptionnel à travers l'interaction avec la protéine Monopteros (MP) de la famille des facteurs de réponse à l'auxine (Auxin Responsive Factor, ARF), et modulant ainsi la magnitude de la réponse des gènes reliés à l'auxine durant la division et la différentiation cellulaire dans le méristème de la racine. De plus, nous fournissons des preuves que BRX est activées au niveau de la membrane plasmique, tel une protéine associée se déplaçant à l'intérieur du noyau et modulant la croissance cellulaire.Pour mener à bien l'investigation des divergences entre la concentration de l'auxine et les schémas d'expression de ses propres gènes cibles, nous avons combiné les approches expérimentales et computationnelles. Les profiles d'expressions déviant du gradient d'auxine pourraient seulement être modéliser après intersection de l'activité de l'auxine avec les schémas différentiels d'endocytose observés et les boucles de rétroaction positives et autorégulatrices par le transfert de BRX de la membrane plasmique au noyau. Puisque BRX est requis pour l'expression de certains gènes cibles des facteurs de réponse à l'auxine, nos données suggèrent une contribution dépendante d'une endocytose spécifique au type de cellule dans la perception transcriptionnelle à l'auxine Cette contribution soutient l'expression d'un sous-set de gène de réponse à l'auxine dans la division du méristème racinaire et la zone de transition, et par conséquent, est essentielle pour la croissance méristematique. Ainsi, le schéma d'endocytose fournit des informations positionnelles spécifiques à la modulation de la réponse à l'auxine.

Structure function relationships of ENaC and its role in sodium handling.

The epithelial sodium channel (ENaC) in the apical membrane of polarized epithelial cells is the rate-limiting step for Na entry into the cell; in series with the basolateral Na pump, it allows the vectorial transepithelial transport of Na ions. ENaC is expressed in different epithelia like the distal nephron or colon, and the airways epithelium. In the lung ENaC controls the composition and the amount of pulmonary fluid, whereas in the distal nephron ENaC under the control of aldosterone and vasopressin, is essential to adapt the amount of Na+ reabsorbed with the daily sodium intake. Activating mutations of ENaC cause severe disturbances of Na+ homeostasis leading to hypertension in human and in mouse models. Functional expression of ENaC in different cell systems allowed the identification of structural domains of the protein that are essential for channel function and/or modulation of channel activity. Site-directed mutations in specific domains of the channel protein lead to channel hyperactivity or channel loss of function. Knowledge about ENaC structure-function relationships opens new opportunities for development of pharmacological tools for controlling ENaC activity, such as channel activators of potential benefit in the treatment of pulmonary edema, or highly potent ENaC blockers with natriuretic effects.

Aqueous photocatalytic oxidation of steroid estrogens

Concerns have increased regarding the detection of endocrine-disrupting compounds in the effluents of sewage treatment plants (STPs). These compounds are able to disrupt normal function of the endocrine system of living organisms even at trace concentrations. Natural and synthetic steroid estrogens (SEs) are believed to be responsible for the majority of the endocrine-disrupting effects. Municipal sewage, the main source of SEs in the environment, is a complex mixture of a wide range of pollutants at concentrations much higher than those of SEs. Low concentrations of SEs in the presence of copollutants thus make their removal problematic. The main objectives of the present work were to study the potential of photocatalytic oxidation (PCO) to effectively treat SE-containing aqueous solutions and to identify the optimum conditions for such treatment. The results showed that SEs can be effectively degraded photocatalytically. Due to the adsorption properties of SEs on the TiO2 photocatalyst surface alkaline medium was found to be beneficial for SE oxidation despite the presence of co-pollutants in concentrations characteristic for the sanitary fraction of municipal sewage. The potential of PCO to selectively oxidise SEs was examined in the presence of copollutants of the sanitary fraction of sewage - urea, saccharose and human urine. The impact of ethanol, often used as a solvent in the preparation of SE stock solutions, was also studied and the results indicated the need to use organic solvent-free solutions for the study of SE behaviour. Photocatalytic oxidation of SEs appeared to be indifferent towards the presence of urea in concentrations commonly found in domestic sewage. The effect of other co-pollutants under consideration was far weaker than could be expected from their concentrations, which are from one hundred to a few thousands times higher than those of the SEs. Although higher concentrations can dramatically slow down the PCO of SEs, realistic concentrations of co-pollutants characteristic for the sanitary fraction of domestic sewage allowed selective removal of SEs. This indicates the potential of PCO to be a selective oxidation method for SE removal from the separate sanitary fraction of municipal sewage.

Tracing of the Rhône River, wastewater, and mixing within Lake Geneva : stable isotope compositions of water and dissolved inorganic carbon

This study presents an evaluation of the stable isotopic composition of water (hydrogen and oxygen) and dissolved inorganic carbon (DIC) of Lake Geneva, a deep, peri-alpine lake situated at the border between Switzerland and France. The research goal is to apply vertical and seasonal variations of the isotope compositions to evaluate mixing processes of pollutants, nutrients and oxygen. Depth profiles were sampled at different locations throughout Lake Geneva on a monthly and seasonal basis over the course of three years (2009-2011). The results of the oxygen isotopic composition indicate a Rhône River interflow, which can be traced for about 55 km throughout the lake during summer. The Rhône River interflow is 7 to 15 m thick and the molar fraction of Rhône water is estimated to amount up to 37 %. Calculated density of the water and measured isotopic compositions demonstrate that the interflow depth changes in conjunction with the density gradient in the water column during fall. Partial pressure of CO2 indicates that the epilimnion is taking up CO2 from the atmosphere between spring and fall. The epilimnion is most enriched in 13CDIC in September and a progressive depletion of 13CDIC can be observed in the metalimnion from spring to late fall. This stratification is dependent on the local density stratification and the results demonstrate that parameters, which are indicating photosynthesis, are not necessarily linked to δ13CDIC values. In addition, the amount of primary production shows a strong discrepancy between summer 2009 and 2010, but δ13CDIC values of the epilimnion and metalimnion do not indicate variations. In the hypolimnion of the deep lake δ13CDIC values are constant and the progressive depletion allows tracing remineralization processes. The combination of stable carbon and oxygen isotopic compositions allows furthermore tracing Rhône River water fractions, as well as wastewater, stormwater and anthropogenic induced carbon in the water column of the shallow Bay of Vidy. In combination with the results of measured micropollutants, the study underlines that concentrations of certain substances may be related to the Rhône River interflow and/or remineralization of particulate organic carbon. Water quality monitoring and research should therefore be extended to the metalimnion as well as sediment water interface.

Photocatalytic oxidation of humic substances and lignins in aqueous solutions

Tässä tutkimuksessa tarkastellaan kahden yleisen, veden ympäristökuormitusta aiheuttavan kemikaaliryhmän, ligniinin ja humusaineiden, fotokatalyyttistahapetusta (photocatalytic oxidation, PCO) vesiliuoksessa. Fotokatalyyttina käytettiin titaanidioksidia, jota säteilytettiin ultraviolettivalolla. Työssä selvitettiin useiden eri olosuhdeparametrien vaikutusta fotokatalyysiin. Tutkittavia parametreja olivat mm. kontaminanttien alkukonsentraatio, pH, vetyperoksidilisäys, rauta-ionien lisäys, fotokatalyysimenetelmä, fotokatalyytin pintakonsentraatioja titaanidioksidin määrä lasisissa mikropartikkeleissa. Ultraviolettivalon lähteinä käytettiin sekä keinovaloa että auringonvaloa. Katalyytin kantoaineena käytettiin huokoisia lasisia mikropartikkeleita, joiden pintaan kiinnittynyt titaanidioksidi pystyi hyvin vähentämään kontaminanttien määrää vedessä. Fotokatalyysin tehokkuus kasvoi humusaine- ja ligniinikonsentraatioiden kasvaessa. Korkeimmat hapetustehokkuudet kumallakin kontaminantilla saavutettiin neutraaleissa jalievästi emäksisissä olosuhteissa huolimatta siitä, että paras adsorboituminen tapahtui happamissa olosuhteissa. Tämän perusteella voidaan olettaa, että humusaineiden ja ligniinin hapetus tapahtuu pääosin radikaalimekanismilla. Vetyperoksidin lisääminen humusaineliuokseen lisäsi hapettumisnopeutta, vaikka näennäinen hapetustehokkuus ei muuttunut. Tämän perusteella vetyperoksidi hapetti myös humusaineita referenssinäytteessä. Ligniinin fotokatalyyttinen hapettuminen parani vetyperoksidilisäyksellä happamissa olosuhteissa johtuen lisääntyneestä OH-radikaalien muodostumisesta. Ligniini ei hapettunut vetyperoksidilla, jos fotokatalyyttiä ei¿ollut läsnä. Rauta-ionit eivät lisänneet humushappojen fotokatalyyttistähapettumista, mutta Fe2+-ionien lisäys aina konsentraatioon 0.05 mM johti ligniinin hapettumistehokkuuden voimakkaaseen kasvuun. Rauta-ionikonsentraation kasvattaminen edelleen johti ligniinin hapetustehokkuuden alenemiseen.

Investigations of GaAs based heterostructures for spintronics

In the present work are reported investigations of structural, magnetic and electronic properties of GaAs/Ga1-xInxAs/GaAs quantum wells (QW) having a 0.5 - 1.8 monolayer thick Mn layer, separated from the quantum well by a 3 nm thick spacer. The structure of the samples is analyzed in details by photoluminescence and high-resolution X-ray difractometry and reflectometry, confirming that Mn atoms are practically absent from the QW. Transport properties and crystal structure are analyzed for the first time for this type of QW structures with so high mobility. Observedconductivity and the Hall effect in quantizing magnetic fields in wide temperature range, defined by transport of holes in the quantum well, demonstrate properties inherent to ferromagnetic systems with spin polarization of charge carriersin the QW. Investigation of the Shubnikov ¿ de Haas and the Hall effects gave the possibility to estimate the energy band parameters such as cyclotron mass andFermi level and calculate concentrations and mobilities of holes and show the high-quality of structures. Magnetic ordering is confirmed by the existence of the anomalous Hall effect.

Testing of Access Network's Internet Protocol Television Features

Testaus on tänä päivänä olennainen osa tuotekehitysprosessia koko tuotteen elinkaaren ajan, myös tietoliikennetekniikassa. Tietoverkoille asetetut tiukat vaatimukset ympärivuorokautisen toimivuuden suhteen nostavatmyös niiden testauksen tason ja laadun merkitystä. Erityisesti verkkojen uudet toiminnallisuudet, joilla ei ole vielä vuosia kestäneen käytön ja kehityksen tuomaa varmuus- ja laatutasoa, tuovat haasteita testauksen toteutukselle. Televisiokuvan välityksen Internetin yli mahdollistavat ominaisuudet ovat esimerkki tällaisista toiminnallisuuksista. Tässä diplomityössä käsitellään Tellabs Oy:n tuotekehitysosastolla vuosina 2005 ja 2006 toteutetun, erään operaattorin laajakaistaliityntäverkon päivitysprojektin testausosuutta. Kattavamman tarkastelun kohteena ovat erityisesti verkkoon lisättyjen laajakaistatelevisio- eli IPTV-toiminnallisuuksien integraatio- ja systeemitestausmenetelmät.