The aim of this series of two publications is to characterize radical reactions of organic molecules, occurring in atmospheric water phases. In this second study, the reactions occurring in a mixed peroxyl radical system generated from the OH radical attack on a model compound, 2-butoxyethanol, in oxygenated aqueous solution are investigated in the presence of O₂^-/HO₂ radicals, H₂O₂, and of copper (I and II)- and iron (II and III) species. A general mechanism of the reactions occurring in such systems is discussed and compared to the formation of organic hydroperoxides and hydrogen peroxide from this oxidation reactions. The main features of the mechanism are as follows: (i) production of peroxyl radicals following OH-attack on the model compound; (ii) cycling of the transition metals between the oxidation states given above, arising from a reduction reaction with superoxide, O₂^-, and oxidation reactions by organic peroxyl radicals, organic hydroperoxides, superoxide, and oxygen; (iii) reactions of organic peroxyl radicals, in contrast to superoxide radicals, occur only with the reduced forms of the transition metals and lead to the formation of organic hydroperoxides; (iv) the reaction of organic peroxyl radicals with Cu (I) is fast (<I>k</I>>10⁸ M^-1 s^-1); (v) the reaction of organic hydroperoxides with Cu (I) can be much faster (2 orders of magnitude) than the analogous reaction of hydrogen peroxide and leads to the production of oxyl radicals; and (vi) oxalate, a strong ligand for Cu (II), reduces the activity of copper, owing to its stabilization of the copper (II) complex. The mechanism is discussed in relation to atmospheric conditions.

The aim of this series of two publications is to characterize important radical reactions of organic molecules in atmospheric water phases, such as cloud, fog, and rain droplets, or on wetted aerosols. In this first study the reactions occurring in a mixed peroxyl radical system generated from the OH radical attack on a model compound, 2-butoxyethanol, in oxygenated aqueous solution are investigated in the absence of trace compounds typically found in such natural waters. Using γ-radiation emitted from a ⁶⁰Co source, we have produced steady-state concentrations of O₂^-/HO₂- and OH radicals comparable to those predicted for daytime conditions in cloud or fog droplets. The reactions of the peroxyl radicals derived from 2-butoxyethanol (C₄H₉OCH₂CH₂OH) in oxygenated aqueous solution have been investigated by measuring detailed product distributions resulting from the oxidation process. The observed and quantified products are mainly esters, ketones, aldehydes and hydroperoxides and accounted for 83% of the removal of 2-butoxyethanol (expressed as a carbon balance). A mechanism for the formation of the reaction products is proposed. It includes the OH attack at four carbon centers of the molecule producing carbon centered radicals, the formation of peroxyl radicals by addition of oxygen to these radicals, the decay of the peroxyl radicals in a reaction system of six different peroxyl radicals and superoxide via bimolecular and unimolecular reactions and the reactions of intermediary produced oxyl radicals.

During the discharge of a radioactive effluent, a radioelement passes from an artificial system in the storage tank, to a natural system. Its behaviour will not only be governed by relatively simple chemical reactions, that can be reproduced in the laboratory, but in addition by more complex, poorly known mechanisms, that control natural systems. <BR/> Cobalt, well studied because of the radioecological importance of <SUP>60</SUP>Co, represents an example of a metal that participates in chemical reactions which play a role in aquatic systems, particularly organic and inorganic complexation and adsorption on suspended particles. On the basis of equilibrium constants and a simple surface complexation model it is possible to estimate the importance of the different chemical species of cobalt. The theoretical results are confronted with <I>in situ</I> measurements downstream of the Mühleberg nuclear power plant, situated at close proximity to Berne. Here sampling can be carried out in the river Aare and in Lake Biel, 18 km downstream of the power plant. Sediment cores indicate that only a small percentage ( < 5 % ) of <SUP>60</SUP>Co is found in riverine sediments, whereas the proportion found in Lake Biel sediments reaches 50±20%. <BR/> A transport model is necessary to simulate the evolution of the discharged water in the two aquatic systems. Transport in the river is calculated on the basis of advection/dispersion equations, transport in the lake is represented by the water residence time and aquatic physical characteristics. <BR/> Measurements have shown that the fraction of <SUP>60</SUP>Co adsorbed to particles < 0.5 μm and to colloïds (0.5 μm to 5000 Dalton) rarely exceeds 20 %.<BR/> These results enable evaluating the model variables, which are poorly known, such as the concentration of organic ligands, the equilibrium constant for organic complexation or the relation between particle mass and number of adsorption sites. <BR/> lt must be remembered that this model, which is based on <I>in situ</I> measurements, can only be directly applied to the Aare downstream of the Mühleberg reactor and Lake Biel.

1. In unshaded, nutrient-rich streams, prolific growth of stream macrophytes often results in flows that over-top the banks and in high primary production and respiration that may result in extreme diel variations in dissolved oxygen. Consequently, water protection authorities commonly remove macrophytes periodically.<br/> 2. We investigated the effect of plant removal on stream metabolism and oxygen balance in two Swiss streams with a high macrophyte biomass. We monitored the concentration of dissolved oxygen before and after macrophytes were removed by cutting and dredging, and calculated rates of gross primary production and ecosystem respiration by means of diel oxygen curves.<br/> 3. The removal of plants, which had reached a dry biomass of 320-420 g m^-2 immediately before plant removal, had a different impact on stream metabolism in the two streams. In the first (plants removed in May), neither primary production nor ecosystem respiration were significantly affected. In the second (plants removed in late July), gross primary production and ecosystem respiration were reduced by about 70%. In this latter stream gross primary production increased in the first 2 weeks after plant removal but never recovered to pre-disturbance levels.<br/> 4. The removal of plants coincided with only a moderate increase in nocturnal oxygen concentration (+1 mg L^-1). This, and the rapid partial recovery of stream metabolism in the second stream, suggests that an increase in the oxygen concentration after plant cutting is transient in unshaded, nutrient-rich streams.

Two different procedures were compared to isolate polycyclic aromatic hydrocarbon (PAH)-utilizing bacteria from PAH-contaminated soil and sludge samples, i.e., (i) shaken enrichment cultures in liquid mineral medium in which PAHs were supplied as crystals and (ii) a new method in which PAH degraders were enriched on and recovered from hydrophobic membranes containing sorbed PAHs. Both techniques were successful, but selected from the same source different bacterial strains able to grow on PAHs as the sole source of carbon and energy. The liquid enrichment mainly selected for <em>Sphingomonas</em>spp., whereas the membrane method exclusively led to the selection of<em>Mycobacterium</em> spp. Furthermore, in separate membrane enrichment set-ups with different membrane types, three repetitive extragenic palindromic PCR-related <em>Mycobacterium</em> strains were recovered. The new <em>Mycobacterium</em> isolates were strongly hydrophobic and displayed the capacity to adhere strongly to different surfaces. One strain, <em>Mycobacterium</em> sp. LB501T, displayed an unusual combination of high adhesion efficiency and an extremely high negative charge. This strain may represent a new bacterial species as suggested by 16S rRNA gene sequence analysis. These results indicate that the provision of hydrophobic sorbents containing sorbed PAHs in the enrichment procedure discriminated in favor of certain bacterial characteristics. The new isolation method is appropriate to select for adherent PAH-degrading bacteria, which might be useful to biodegrade sorbed PAHs in soils and sludge.

The experimental determination of liposome-water partition coefficients, <I>K</I>_lipw, of the neutral and charged species of ionogenic compounds is rather tedious because apparent distribution ratios have to be measured as a function of pH and ionic strength. The partition coefficients of the single species have to be extrapolated from the experimental data using an appropriate partition model. A number of new assay methods have been developed in the past years to facilitate and speed up the experimental procedure for the determination of <I>K</I>_lipw. Here we compare three proposed assay methods with the well-established equilibrium dialysis method, and we evaluate their applicability for ionogenic compounds. The potentiometric method was initially developed for the determination of octanol-water partitioning but was recently extended to liposome-water partitioning. The potentiometric method described here was found to yield satisfactory estimates of the <I>K</I>_lipw-values of both neutral and charged species, although manifestation of electrostatic saturation phenomena cannot be fully ruled out due to the relatively high concentrations of compounds that have to be used. Two further methods based on immobilization of lipid material on a solid support, which were initially developed for the estimation of <I>K</I>_lipw of neutral compounds, were tested here for their applicability to charged organic species. IAM (immobilized artificial membrane) chromatography was found not to be suitable for prediction of membrane-water partitioning of ionic compounds because the charges on the chromatographic support material are not sufficiently shielded. A model including free silica and free amine sites explained the experimental data very well. A new type of immobilized liposomes in the form of noncovalently coated large porous particles (TRANSIL) gave promising results with <I>K</I>_lipw-values that agree well with those determined with the traditional equilibrium dialysis method. The advent of these alternative methods for the determination of <I>K</I>_lipw of ionogenic compounds will facilitate the application of <I>K</I>_lipw as a descriptor for biological systems in quantitative structure activity relationships in environmental chemistry and toxicology.

Liposome-water systems are used increasingly in lieu of the octanol-water system to evaluate and describe the partitioning of organic compounds between biological systems and water. In particular, for hydrophobic ionogenic compounds (HIOCs), the liposome-water (and biological membrane-water) distribution ratios of the ionic species are generally much greater than the corresponding octanol-water distribution ratios, even at high electrolyte concentrations where ion pair formation increases the apparent distribution of the ionized species into octanol. In this paper,we describe a comprehensive model that allows one to describe the complete data set of experimental liposome- water distribution ratios <I>D</I>_lipw measured by equilibrium dialysis as a function of concentration, pH, and ionic strength. Test compounds included acids (chloro- and (alkyl-)nitrophenols) and bases (methylated amines) covering a wide range of hydrophobicity and acidity and including several compounds of environmental concern. The partitioning model features an electrostatic term to account for the build-up of a surface potential when charged species are sorbed to the lipid bilayer at the lipid-water interface. tonic strength dependence was fully accounted for by the interfacial electrostatics and the activity coefficients of the charged molecules in the aqueous phase. Activity coefficients were set to unity for neutral species and for all species in the membrane. No ion pair formation needed to be postulated to explain the experimental data in the proposed model. In addition liposome- water partition coefficients for the neutral and corresponding charged species of HIOCs can be deduced directly from the model parameters.

The transport of a selected set of bacteria able to degrade polycyclic aromatic hydrocarbons (PAHs) was investigated in saturated column experiments, using as packing materials either a clay-containing soil or the isolated soil constituents montmorillonite clay, sand, or soil humic acid-clay complexes. The bacterial strains studied were able to grow on phenanthrene, anthracene, fluorene, fluoranthrene, and pyrene and were characterized for cell size, aspect ratio, hydrophobicity, and zeta potential. Removal of bacteria from the transport solution was quantified by calculating relative adhesion efficiencies (α_t) for all combinations of bacteria and packing materials. Transport through soil varied from strain to strain. However, no clear relationship was observed between the studied physicochemical characteristics of the bacteria and their transport. The relative differences between strains observed in soil were conserved in column experiments with isolated clay. Coating the clay surfaces with two different soil humic acid fractions drastically increased the transport of all bacteria tested. The nonionic surfactant Triton X-100 facilitated transport of hydrophobic cells at concentrations above its critical micelle concentration but had no effect on the transport of hydrophilic bacteria. We suggest that clay is the main retarding agent of PAH-degrading bacteria in soil.

Mild steel coupons were incubated in cultures of three different aerobic bacteria, <I>viz. Rhodococcus</I> sp. C125, <I>Pseudomonas putida</I> mt2 and <I>Streptomyces pilosus</I> DSM 40714 and then exposed to a corrosive aqueous medium. A significant reduction in the corrosion rate was observed in a corrosive medium when the steel had been incubated in mineral media containing more than 2 mM phosphate with growing, biofilm- forming bacteria which had direct access to the steel surface, but not with the non biofilm-forming <I>S. pilosus</I> DSM 40714. <I>Rhodococcus</I> sp. C125 and <I>P. putida</I> mt2 induced a surface reaction, resulting in the formation of vivianite. This barely insoluble iron(II)-phosphate was found to be the cause of the corrosion inhibition. The surface reaction was always accompanied by an increase in the iron concentration in the medium. In contrast to biocorrosion processes known so far, iron release stopped after some days. The results suggest that bacterial activity may induce the inhibition of corrosion of mild steel.

<em>Pseudomonas oleovorans</em> ATCC 29347 was grown in chemostat culture at different dilution rates with mineral media varying in their ratios of octanoate to ammonia (C₀/N₀ ratio). At all dilution rates tested, three distinct growth regimes were observed: (i) carbon limitation with NH₄⁺ in excess at low C₀/N₀ ratios, (ii) purely nitrogen-limited growth conditions at high C₀/N₀ ratios with residual octanoate in the culture supernatant, and (iii) an intermediate zone of dual-nutrient-limited growth conditions where both the concentration of octanoate and that of ammonia were very low. The dual-nutrient-limited growth zone shifted to higher C₀/N₀ ratios with decreasing dilution rates, and the extension of the dual-nutrient-limited growth zone was inversely proportional to the growth rate. The cells accumulated the storage compound medium-chain-length poly[(<em>R</em>)-3-hydroxyalkanoate] (mcl-PHA) during dual (C and N)-nutrient-limited and N-limited growth conditions. Within the dual-nutrient-limited growth zone, the cellular mcl-PHA contents increased when the C₀/N₀ ratio in the feed was increased, whereas the cellular mcl-PHA level was independent from the feed C₀/N₀ ratio during N-limited growth. The monomeric composition of the accumulated mcl-PHA was independent of both the dilution rate and the feed C₀/N₀ ratio and consisted of 12 mol% 3-hydroxyhexanoic acid and 88 mol% 3-hydroxyoctanoic acid. Accumulation of mcl-PHA led to an increase in the cellular C/N ratio and to changes in elemental growth yields for nitrogen and carbon.

Wood storage within the active zone of the dynamic, gravel-bed, Fiume Tagliamento, Italy, was investigated at eight sites along the river's main stem. The quantity, nature, and mode of wood storage revealed a number of trends related to active zone morphology, cover type, and distance from the river's source. Relatively small quantities of wood were stored on open-gravel surfaces (estimates ranged from 1 to 21 t ha⁻¹), intermediate quantities were associated with established islands (24–186 t ha⁻¹), and large quantities were associated with pioneer islands (293–1664 t ha⁻¹). Thus, variations in the geomorphological style of the river, which are associated with changes in these three cover types, are reflected in variations in the amount of wood that is stored in different reaches. In addition, although wood was found in many locations within the active zone, it was preferentially stored in three specific locations: (i) bar crests (the main open-gravel location for wood accumulations and pioneer islands); (ii) the margins and (iii) surfaces of established islands. The proportion of the stored wood that was living (sprouting) increased downstream and was higher on the open gravel than in association with established islands. There was a downstream gradient in the dominant type of wood accumulation. Individual logs predominated at the most upstream site. Thereafter, on the open gravel, whole shrubs and trees dominated the more confined sites in the headwaters and middle reaches, whereas, jams were the most frequent form of accumulation in the downstream reaches. Jams were the most frequent type of accumulation associated with established islands throughout the river. In contrast to small streams, where debris dams constitute the major type of wood accumulation, complex patterns and trends of wood storage were revealed along the Tagliamento. Although further studies are needed, it is clear that erosion of woody vegetation, its subsequent transport and deposition, play a major role in structuring the geomorphological and ecological character of this relatively natural, large European river-system. Insight into the mechanisms underlying the observed spatial patterns will contribute to a better understanding of the dynamic processes involved, and is essential for more effective management of river ecosystems.

Optimization of nitrifying activated sludge plants towards nutrient removal (denitrification and enhanced P-removal) will lead to substantial reduction of operating costs and improves effluent and operating conditions. At the WWTP Zürich-Werdhölzli, initially designed for nitrification, an anoxic zone of 28% of total activated sludge volume was installed in the initially fully aerated activated sludge tanks and allowed with optimization of the sludge blanket in the secondary clarifiers a nitrogen elimination of 60-70%. Parallel, different small process alterations at the grit removal tank, the primary clarifiers and return sludge pumps reduced odour problems and oxygen input and improved denitrification. Separate treatment of the digester supernatant, that contains about 20% of the inlet nitrogen load, will increase nitrogen elimination to about 75% and allows partial enhanced biological O-removal in the activated sludge system which will reduce precipitant feed and excess sludge production.

The mechanism of significant nitrogen loss in an aerobic rotating biological contactor (RBC) treating ammonium-rich waste water could be identified with the aid of batch experiments, mathematical modeling and microbial analysis. It turned out that the aerobic ammonium and nitrite-oxidizing organisms (nitrosomonas and nitrobacter clusters) are dominant in the upper aerobic 100–200 μm of the biofilm. It is assumed that nitrite, appearing as an intermediate product close to the surface of the aerobic biofilm layer, diffuses into deeper anoxic layers of the biofilm. It is reduced anaerobically there in parallel with ammonium oxidized as described in the Anammox (anaerobic ammonium oxidation) process. This was confirmed in an anoxic batch test with suspended biofilm removed from the RBC. Unknown micro-organisms were detected, some of them similar to the Anammox organisms. A mathematical model which describes the kinetics of the aerobic ammonium-oxidizing, aerobic nitrite-oxidizing and anoxic ammonium-oxidizing micro-organisms was formulated and fitted into the AQUASIM biofilm compartment. The distribution of the populations within the biofilm as well as the ammonium, nitrite and nitrate degradation along the RBC in a steady state and during short-term experiments were modeled and compared with the experimental data.

1. A key component of physical habitat along braided river systems is the exposed riverine sediment within the active zone. The relatively unmanaged, gravel-bed Fiume Tagliamento, Italy, provides the focus for exploring two ecologically important properties of exposed riverine sediments: their within-patch and between-patch variability in calibre.<br/> 2. To characterize between-patch variation in exposed riverine sediments, replicate (within-patch) samples were obtained from three geomorphologically distinct locations along 130 km of the river: bar heads along the margin of the low-flow channel, the heads of major bars across the exposed surface of the active zone, and floodplain surfaces. A photographic technique enabled rapid and consistent field sampling of the coarse sediments at bar heads along the low-flow channel margin and on major bars across the dry bed.<br/> 3. A downstream decrease in particle size and an increase in within-patch heterogeneity in sediment size were observed within bar head sediments along the margin of the low-flow channel. Comparisons between major bar and low-flow channel samples revealed greatest within-patch variability in individual sediment size indices (<I>D</I>₅₀, A- and B-axes of the larger particles) at headwater sites, greatest between-patch variability in the three measured indices in the central reaches, and lowest between-patch variability at downstream sites. However, there was a distinct increase in the overall heterogeneity in particle size, which was sustained across all patches, in a downstream direction.<br/> 4. There was a clear downstream decrease in the size of floodplain sediments in the headwaters, but thereafter there was no distinct downstream trend in any of the calculated particle size indices.<br/> 5. The geomorphological controls on the observed patterns and the potential ecological significance of the patterns, particularly for plant establishment, are discussed in relation to the relative relief of the active zone, and the highly variable hydrological and climatic regime along the river.

Free hydroxyl radicals (free ^<B>·</B>OH), singlet oxygen (<SUP>1</SUP>O<SUB>2</SUB>), or ^<B>·</B>OH produced by DNA-copper-hydroperoxo complexes are possible DNA-damaging reactive oxygen species (ROS) in the reaction system containing copper, catechol, and DNA. para-Chlorobenzoic acid (pCBA) degradation studies revealed that CuCl<SUB>2</SUB> mixed with catechol produced free ^<B>·</B>OH. In the presence of DNA, however, inhibition of the pCBA degradation suggested that another ROS is responsible for the DNA degradation. Of a series of ROS scavengers investigated, only KI, NaN<SUB>3</SUB>, and Na-formate—all of the salts tested—strongly inhibited the DNA degradation, suggesting that the ionic strength rather than the reactivity of the individual scavengers could be responsible for the observed inhibition. The ionic strength effect was confirmed by increasing the concentration of phosphate buffer, which is a poor ^<B>·</B>OH scavenger, and was interpreted as the result of destabilization of DNA-copper-hydroperoxo complexes. Piperidine-labile site patterns in DNA degraded by copper and catechol showed that the mixture of Cu(II) and catechol degrades DNA via the intermediate formation of a DNA-copper-hydroperoxo complex. Replacement of guanine by 7-deazaguanine did not retard the DNA degradation, suggesting that the DNA-copper-hydroperoxo complexes do not bind to the guanine N-7 as proposed in the literature.

The reactivity of hypoiodous acid (HOI) is an important factor for the fate of iodine in oxidative drinking water treatment. The possible reactions of HOI are its disproportionation, its oxidation to iodate (IO₃ ^-), or the reaction with natural organic matter (NOM). The latter reaction may result in the formation of iodoorganic compounds which are frequently responsible for taste and odor problems. The acid dissociation constant (<I>pK</I>_a) of HOI has been determined spectrophotometrically as 10.4±0.1 (<I>T</I> = 25 °C; I = 50 mM). Kinetic constants and a new rate law for the disproportionation of HOI as catalyzed by hydrogencarbonate, carbonate, and borate are presented. In the pH range 7.6-11.1, the main uncatalyzed reactions are HOI+HOI (<I>k</I>₁ = 0.3 M^-1 s^-1) and HOI+OI^- (<I>k</I>₂ = 15 M^-1 s^-1). The buffer-catalyzed reaction step was found to be second-order in HOI and first-order in the buffer anion. The following rate constants were deduced: HOI+HOI+HCO₃ ^-: 50 M^-2 s^-1; HOI+HOI+CO₃ ^2-: 5000 M^-2 s^-1; HOI+HOI+B(OH)₄ ^-: 1700 M^-2 s^-1. All these rate constants result in half-lifes for HOI of 10-1000 days under typical drinking water conditions.

Nonylphenol is a biodegradation product of a widely used group of non-ionic detergents. Because of its ubiquitous distribution and persistence, nonylphenol is present in surface waters as a pollutant. Little is known about its biological effects at environmentally relevant concentrations other than its action as a xenoestrogen. The goal of the present paper was to study the trout gill surface epithelium as the major interface between fish and water in view of possible morphological alterations due to exposure to monylphenol. Rainbow trout were intermitently exposed to 10 mu g/l nonylphenol and gill samples from experimental and control animals were investigated by scanning electron microscopy. Gill surface epithelium was scrutinised for changes in chloride cell density and their status regarding cell surface modifications. In addition, chloride cell fractional surface area (CCFA) was determined by morphometrical methods. Statistical analysis revealed a highly significant increase of CCFA in animals exposed to nonylphenol as compared to control animals (P = 0.0001). Semi-quantitative assessment of their parameters suggested a higher chloride cell density and a larger proportion of chloride cell density and a larger proportion of chloride cells bearing microvilli. Taken together, these results provide evidence that exposure of trout to nonylphenol is associated with a substantial increase in the active interface of chloride cells with water. We interpret these findings as being a means to further the fish's capacity for calcium exchange.

In this paper, biochemical process equations are presented as a basis for water quality modelling in rivers under aerobic and anoxic conditions. These equations are not new, but they summarise parts of the development over the past 75 years. The primary goals of the presentation are to stimulate communication among modellers and field-oriented researchers of river water quality and of wastewater treatment, to facilitate practical application of river water quality modelling, and to encourage the use of elemental mass balances for the derivation of stoichiometric coefficients of biochemical transformation processes. This paper is part of a series of three papers. In the first paper, the general modelling approach is described; in the present paper, the biochemical process equations of a complex model are presented; and in the third paper, recommendations are given for the selection of a reasonable submodel for a specific application.

Der oligotrophe Brienzersee liegt in den Schweizer Voralpen und ist geprägt durch ein vergletschertes Einzugsgebiet. Durch die hohen glazialen Erosionsraten bringen die beiden Hauptzuflüsse Aare und Lütschine eine hohe Fracht an anorganischen Partikeln in den Brienzersee. Dies führt zum trüben, türkisfarbenen Erscheinungsbild des Sees. Es wird erwartet, dass sowohl die hohe Oberflächentrübung durch die Schwebstoffe als auch niedrige Konzentrationen an bioverfügbarem Phosphat limitierende Faktoren für die Primärproduktion im Brienzersee darstellen. Die Primärproduktion ist eine entscheidende Grösse im see-internen ökologischen System, da die Nahrungskette Phytoplankton – Zooplankton – Fisch in der Primärproduktion gründet.<br /> Aus Fischereikreisen wird vermutet, dass die Trübung im Brienzersee durch die hydroelektrische Nutzung im Einzugsgebiet der Aare angestiegen sei. Die jährliche Partikelfracht in den Brienzersee hat aber aufgrund der Stauseen im Grimselgebiet abgenommen. Die Oberflächentrübung könnte deshalb einzig durch einen vermehrten Eintrag von feinen Schwebstoffen in die Oberflächenschicht, aufgrund von veränderten Partikel- und Zuflussdynamiken der Aare, zugenommen haben.

Es gibt weltweit bereits mehrere verschiedene Modelle von solaren Kochern. Die Palette reicht von Kochern für Kleinfamilien bis hin zu solaren Grossküchen. Das Ziel dieser Arbeit ist es, ein solares Kochsystem für Gemeinschaftsküchen (max. ~50 Personen) zu testen, welches die Sonnenenergie mit einem Scheftler-Reflektor konzentriert and in einem massiven Eisenblock in Form von Wärme speichert. Zum Kochen wird die Energie aus dem Warmespeicher verwendet, indem über einen Verdampfer im Eisenblock Wasserdampf erzeugt wird. Der Dampf wird in den Hohlraum der Topfwand eines doppelwandigen Topfes geleitet; durch die bei der Kondensation freiwerdende Wärme erhitzt der Dampf das Kochgut. Weil die nötige Wärme aus einem Speicher und nicht direkt von der Sonne kommt, hat dieses Systetn den Vorteil, dass man auch zu Zeiten ohne Sonnenschein kochen kann. Bei den meisten anderen solaren Kochern wird der Kochvorgang durch Wolken verzögert<br /> oder unmöglich. Im Rahmen dieser Diplomarbeit wird das solare Kochsystem mit Wärmespeicher auf seine Eignung zum Kochen getestet und Ansatzpunkte für mögliche Verbesserungen werden erarbeitet. [...]

<em>Salmonella enterica</em> subspecies 1 serovar Typhimurium is a frequent cause of gastroenteritis and diarrhoea in humans. As diarrhoea is one of the major health problems in the world, it is of great interest to understand <em>Salmonella </em>pathogenesis and the factors controlling it. Upon infection of its host, S. Typhimurium enters epithelial cells. At the beginning of this process several effector proteins are translocated into the host cell through a type III secretion system encoded on the <em>Salmonella </em>pathogenicity island 1 (SPI-1). These virulence factors modulate signal transduction pathways inside the host cell and lead to the internalisation of the bacterial cell. Most of the virulence factors involved in this process have been identified, e.g. the SPI-1 type III secretion apparatus protein PrgH and the effector proteins SopE and SptP. However, little is known about the environmental growth factors controlling their expression and, in the case of effector proteins, their translocation.<br /> In this study the influence of different conditions on the expression of PrgH, SopE and SptP as well as on the secretion of the latter two was examined. <em>Salmonella enterica</em> subspecies 1 serovar Typhimurium was grown in batch cultures and in continuous culture at different dilution rates. Growth in Luria-Bertani (LB) broth containing different NaCl concentrations as well as in glucose- and ammonia limited mineral medium was examined. Furthermore, the influence of aerobic and anaerobic conditions during growth in LB was tested. In addition, carbon utilisation patterns were examined using Biolog microplates. The expression and secretion of proteins were analysed using sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blotting.<br /> In present study the main factor found controlling virulence factor expression was specific growth rate. At specific growth rates equal to or smaller than 0.2 h^-1 very little or no PrgH, SptP and SopE were produced in continuous cultures containing LB medium. They were strongly expressed and the effector proteins also secreted at fast specific growth rates (0.7, 1, 1.25 h^-1). The expression of PrgH and SopE but not of SptP was reduced again at a specific growth rate of 1.5 h^-1. These results indicate a maximal expression at intermediate to high specific growth rates and a repression at low or very high specific growth rates.<br /> In addition, these proteins were found earlier in the growth cycle and in higher amounts if LB batch cultures had been inoculated 1:20 with stationary cells than 1:100 with exponentially growing cells. Contradictory to some other studies, only a minor effect of high osmolarity conditions (0.3 M NaCl) in LB on the expression of virulence factors was seen and none of the examined proteins were expressed under obligate anaerobic conditions in LB batch cultures. However, a weak expression was found in anaerobic LB continuous cultures.<br /> Furthermore, it could be shown that some unidentified substances, which are vital for the expression of PrgH and SopE but not of SptP, are not available in glucose- and ammonialimited mineral medium.<br /> This study contributes to the knowledge about the regulation of virulence factors in S. Typhimurium by environmental factors. Starting from the observed crucial role of the specific growth rate, there is a chance that more detailed investigations might unravel the trigger which transforms S. Typhimurium in a (hyper)virulent state.

Die Studie befasst sich im weiteren Sinne mit der Beurteilung von Revitalisierungsmassnahmen bei Fliessgewässern, im engeren Sinne mit dem Testen einer Methodik für Erfolgskontrollen. Mit dieser Methodik soll die Qualität von Revitalisierungsprojekten messbar gemacht werden. Das Instrumentarium (nachfolgend Indikatorset genant) ist das vorläufige Produk der Arbeitsgruppe "Erfolgskontrolle" (AG Erfolgskontrolle) der Eidgenössischen Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz (EAWAG). Mit der vorliegenden Arbeit war zu untersuchen, ob dieses Indikatorset die Anforderungen aus Praxis und Wissenschaft erfüllt. [...]

From May to July 2005, the effects of solar ultraviolet radiation (UVR) on periphyton accrual and photosynthetic performance were studied in two alpine streams (2050 m a.s.l.) in the Swiss Alps. Ambient UV levels were manipulated using UV-opaque and UV-transparent Plexiglas screens. Chlorophyll a, ash-free dry mass, and the photosynthetic performance of periphyton growing on artificial substrata and exposed to the two different UV treatments were measured 3, 6 and 9 weeks after the beginning of the experiment. Periphyton biomass was significantly lower under UV-protection. Concomitantly, higher densities of grazing mayflies (<em>Baetis alpinus</em>) were found in the absence of UVR, indicating that these grazers were more sensitive to UVR than periphyton (e.g., a solar cascade of indirect UVR effects). Photosynthetic parameters (ETR_max, photosynthetic efficiency, light saturation and maximum quantum yield) measured with a pulse amplitude fluorometer were not affected by the presence of UVR. The results suggest that periphyton in alpine streams is adapted to naturally high UVR levels. Rather, the overall low photosynthetic performance indicates that periphyton is constrained more from relative harsh environmental conditions such as phosphorus limitation, low temperature, and grazing pressure than from the direct impact by UVR.<br /><br /> Zwischen Mai und Juli, wurde der Einfluss der ultravioletten Strahlung (UVR) auf Wachstum und Photosynthese von Periphyton zweier alpiner Bäche (2050 m a.s.l.) im Val Roseg (Schweiz) untersucht. Die natürliche UV-Strahlung wurde mit UV-undurchlässigem Plexiglas manipuliert. Chlorophyll a, Asche freies Trockengewicht und Photosynthese von auf künstlichen Substrat wachsenden Periphyton wurden 3, 6 und 9 Wochen nach Beginn des Experimentes gemessen. Die Periphytonbiomasse war signifikant höher auf UV-exponierten Substraten. Gleichzeitig war die Abundanz herbivore Eintagsfliegen (<em>Baetis alpinus</em>) deutlich grösser in Abwesenheit von UVR. Dieses Resultat deutet an, dass die herbivoren Invertebraten empfindlicher gegenüber UV-Strahlung sind als Periphyton („solar cascade of indirect UVR effects“). Die mit einem „Pulse Amplitude Modulation Fluorometer“ gemessenen photosynthetischen Parameter (maximaler Elektronentransport, Effizienz der Photosynthese, Lichtsättigung der Photosynthese und maximale Quantenausbeute) wurden durch UVR nicht beeinträchtigt. Das Resultat zeigt, dass Periphyton an die hohen natürlichen UV Intensitäten angepasst ist. Die allgemein tiefen Photosyntheseleistungen weisen darauf hin, dass Periphyton eher durch Umwelteinflüsse wie Phosphormangel, Weidedruck und tiefe Wassertemperaturen beeinträchtigt wird, als durch die direkte Wirkung von UVR.

<em>Escherichia coli</em> occupies two different habitats: the primary habitat is the intestine of warm-blooded animals and human, and secondary habitat is water and soil. The primary habitat is characterized by copiotrophic conditions with an excess of carbonaceous nutrients but limited oxygen availability, whereas the secondary habitats are oligotrophic environments where cells need to adapt to nutrient-poor and mostly oxic conditions. Of particular interest to drinking water microbiology is the ability of <em>E. coli</em> to survive and proliferate in aqueous environments because this bacterium is generally used as an indicator for faecal contamination.<br />The preferred method used here to study growth under nutrient-limited conditions was carbon/energy-limited continuous culture. Populations of <em>E. coli</em> cultivated in glucoselimited continuous culture exhibit a two-step adaptation to such conditions: A short-term adaptation (10-50 generations), which is characterized by a constant affinity to glucose (Ks ～ 400 μg l^-1), and a long-term adaptation (&gt; 200 generations), which is characterized by the selection of a population of mutants with increased affinity to glucose (K_s ～ 30-50 μg l^-1). Transcriptome analysis of short- and long-term glucose-adapted populations reveals an up-regulation of many transport genes and a rearrangement of the central metabolism. Generally, in long-term adapted cells the same pattern of gene expression is observed as that monitored in the short-term response, except that genes belonging to the general (RpoS-dependent) stress response regulon are down-regulated. This downregulation is due to attenuation of RpoS. Increased glucose affinity in long-term adapted cells results from a massive up-regulation of the maltose and galactose high affinity systems. [...]

Metal uptake and accumulation from freshwater systems can lead to toxicity effects in organisms when either essential trace element concentrations (Zn, Mn, Cu, Co) are above nutritional level, or when non-essential metals exhibit detrimental effects at already low concentrations (Cd, Ag, Pb, Hg). In order to assess the toxicity of a given metal it is not sufficient to know the total metal concentration, but also its bioavailability which is controlled by the speciation of the metal in water.<br />Cadmium is known to compete with other cations for uptake into organisms and is toxic at low concentrations. The goals of this work were to study factors determining Cd uptake and accumulation in Scenedesmus vacuolatus, a freshwater algal species, under conditions relevant for metal uptake in freshwaters, and to link the Cd accumulation with chemical speciation measurements of Cd in the water. Therefore, Cd accumulation and speciation was investigated in synthetic solutions and in freshwater samples. [...]<br /><br />Die Aufnahme und Akkumulation von Metallen aus Süßwassersystemen ist für Organismen toxisch, wenn die Konzentration von essentiellen Spurenelementen den Nährstoffbedarf deutlich übersteigt (z.B. bei Zn, Mn, Cu, Co) oder wenn ein nicht-essentielles Metall bereits bei geringen Konzentrationen schädliche Einflüsse zeigt (z.B. Cd, Ag, Pb, Hg). Um die Toxizität eines Metalls zu beurteilen, ist die Kenntnis seiner totalen Konzentration nicht ausreichend, da die tatsächliche Bioverfügbarkeit von der Speziierung des Metalls im Wasser abhängt.<br />Kadmium ist bereits in sehr geringen Konzentrationen giftig und konkurriert mit anderen Kationen um die Aufnahme in Organismen. Ziel dieser Arbeit war es, die wesentlichen Faktoren für die Kadmiumakkumulation in die Süsswasseralge Scenedesmus vacuolatus unter Bedingungen zu bestimmen, wie sie für die Metallaufnahme aus Gewässern relevant sind. Weiterhin wurde die beobachtete Cd-Akkumulation in Beziehung zur chemischen Speziierung von Cd im Wasser gesetzt. Dazu wurden Cd-Akkumulation und -speziierung in verschiedenen synthetischen Medien und Gewässerproben untersucht. [...]

Antimony is an element widely used in industrial products. The main applications are in flame retardant formulations and in lead alloys for lead-acid batteries and ammunition. Very little is known about its toxicity and geochemistry but it is assumed to have a similar behavior to Arsenic (As). In the aquatic environment, the oxidation states Sb(III) and Sb(V) commonly occur. Under oxic conditions, the more soluble species Sb(V) predominates and is present as Sb(OH)₆^-. It appears that Sb(III) has a stronger affinity for Al, Mn and Fe (hydr)oxides and that its oxide (Sb₂O₃) is less soluble than that of Sb(V). This indicates that oxidation processes may lead to the mobilization of Sb in the environment and that an understanding of Sb(III) oxidation reactions is important in order to assess the risk posed to humans and the environment. [...]<br /><br />Antimon (Sb) ist ein toxisches Element mit ähnlichen chemischen Eigenschaften wie Arsen. Der Einsatz von Sb in industriellen Produkten, insbesondere in Flammschutzmitteln und als Additiv in Bleilegierungen, z.B. in Batterien und Munition gewinnt zunehmend an Bedeutung. In der Umwelt kommt Sb in den zwei Oxidationszuständen Sb(III) und Sb(V) vor. In aquatischen Systemen ist Sb(V) die vorherrschende Spezies, welche als Hydroxidkomplex Sb(OH)₆^- vorliegt. Nur ein kleiner Teil des gelösten Sb liegt im dreiwertigen Zustand als neutraler Hydroxidkomplex Sb(OH)₃ vor. Es wird vermutet, dass die Löslichkeit von Sb(III) entweder durch die Sorption an Fe-, Mn- und Al-Oxiden oder durch die Ausfällung als Oxid stärker als für Sb(V) kontrolliert wird. Daher kann Sb durch Oxidationsprozesse in der Umwelt mobilisiert werden. Ein besseres Verständnis der Bedingungen, unter welchen Sb oxidiert, ist daher notwendig um potentielle Risiken für Mensch und Umwelt beurteilen zu können. [...]

Lake Ohrid is comparably large (surface area A ~358 km²), deep (maximal depth z_max ~289 m) and one of the most voluminous (volume V ~55 km³) lakes in Europe. It is a transboundary lake, with two-thirds in Macedonia and one-third in Albania. Including the underground karst connection to upstream Lake Prespa (A ~254 km², z_max ~48 m, V ~3.6 km³), the watershed of Lake Ohrid extends into Greece. The overall karst groundwater inflow – recharged by Lake Prespa and local precipitation – contributes more than 50 % to the lake’s water balance. Because of the comparably small watershed and the dry climate, water exchange is slow with a mean residence time of ~70 years.<br />While a groundwater-fed, large water body in Mediterranean climate is exceptional in itself, the most outstanding quality of Lake Ohrid is its endemism (&gt; 200 species). During the estimated two to five million years of existence, species covering the whole food chain have evolved or persisted in the lake. Given its importance as a global hotspot of biodiversity and being the only ancient, long-lived lake in Europe, Lake Ohrid was declared a UNESCO world heritage site in 1979.<br />However, the unique ecosystem could be jeopardized by human impacts. A particular concern is potential eutrophication of the currently oligotrophic lake from population growth. It is feared that eutrophication could threaten the endemic flora and fauna, which has adapted to nutrient-poor conditions. However, assessment of eutrophication is not straight forward: Because of the long water residence time, changes will be slow. Moreover, expected variations in nutrient conditions are in the range of measurement error because of the low present-day concentrations. As there is a lack in high-quality, long-term data, different measurement schemes must be combined to assess eutrophication. [...]<br /><br />Der Ohridsee ist ein grosser, tiefer und einer der volumenreichsten Seen Europas (Oberfläche A ~358 km², maximale Tiefe z_max ~289 m, Volumen V~55 km³). Die Oberfläche des Grenzsees teilen sich die Länder Mazedonien und Albanien im Verhältnis zwei zu eins. Durch die Karstverbindung zum höher gelegenen Prespasee (A ~254 km², z_max ~48 m, V ~3.6 km³) erstreckt sich das Einzugsgebiet zusätzlich bis nach Griechenland. Die vom Prespasee und lokalem Niederschlag gespeisten Karst-Grundwasserzuflüsse bilden auch den grössten Beitrag zur Wasserbilanz des Ohridsees (&gt; 50%). Aufgrund des relativ kleinen Einzugsgebietes, sowie des trockenen, mediterranen Klimas ist der Gesamtzufluss allerdings gering, was zu einer langen Wasseraufenthaltszeit von durchschnittlich ca. 70 Jahren führt.<br />Ein grundwassergespeister See dieser Grössenordnung im trockenen südeuropäischen Klima ist an sich schon erstaunlich. Der herausragendste Aspekt des Ohridsees ist aber seine endemische Flora und Fauna (&gt; 200 Arten). Während seiner geschätzten zwei bis fünf Millionen jährigen Geschichte haben Tier- und Pflanzenarten der gesamten Nahrungskette im Ohridsee überdauert und sich weiterentwickelt. Die Bedeutung des Ohridsees als einziger Ursee Europas und globales Biodiversitäts-Zentrum wurde 1979 durch seine Aufnahme als Weltnaturerbe der UNESCO unterstrichen.<br />Das einzigartige Ökosystem ist allerdings verschiedenen menschlichen Einflüssen ausgesetzt. Insbesondere wird als Resultat des regionalen Bevölkerungswachstums eine Eutrophierung des momentan oligotrophen Sees befürchtet. Diese könnte ihrerseits die endemischen Arten gefährden, welche sich im Laufe ihrer Entwicklung an nährstoffarme Bedingungen angepasst haben. Die Frage, ob der See sich in einem Eutrophierungsprozess befindet ist allerdings nicht einfach zu beantworten. Einerseits bewirkt die lange Wasseraufenthaltszeit eine verzögerte Reaktion auf Veränderungen. Andererseits liegen erwartete Konzentrationsschwankungen im nährstoffarmen See im Bereich des analytischen Messfehlers. Wegen einem Mangel an langfristigen, qualitativ hochwertigen Seemonitoring-Daten müssen daher verschiedene Messungen kombiniert werden, um etwas über eine potentielle Eutrophierung aussagen zu können. [...]

<em>Introduction</em><br />A large number of substances, contained in pharmaceuticals, personal care products and other household chemicals, are comfortably disposed of in sanitary appliances. Collected in the sewer system and partly eliminated in wastewater treatment plants they are then released to a certain extent into the aquatic environment. Many of these compounds belong to the category of micropollutants, which can have adverse effects on living organisms already in very low concentrations. Since no clear causal relationship between observed changes of ecosystems and the presence of micropollutants could be established, scientists combine monitoring with laboratory data. While experiments in the laboratory can be performed under controlled conditions it is very difficult to assess the complex situation in the environment. It is not only a hand full of micropollutants, but rather hundreds. To measure environmental concentrations of all these compounds over a relevant period of time is impossible. Therefore, predictive models are needed to forecast environmental concentrations. The input to these kinds of models, are emission data. Their acquisition is a tedious task. [...]<br /><br /><em>Einleitung</em><br />Medikamente, Körperpflegemittel und viele andere Haushaltprodukte enthalten eine grosse Anzahl chemischer Substanzen. Diese werden nach ihrer Anwendung bequem in sanitären Einrichtungen wie Toilette, Bad, Geschirrspül- oder Waschmaschine entsorgt. Mit dem Abwasser werden sie in der Kanalisation gesammelt und in die Kläranlagen transportiert. Einige werden gut eliminiert, andere hingegen können nur teilweise oder gar nicht abgebaut werden und gelangen so in die natürlichen Gewässer. Viele dieser chemischen Verbindungen gehören zu Kategorie der so genannten „Mikroverunreinigungen“, welche bereits in tiefsten Konzentrationen negative Auswirkung auf aquatische Lebewesen haben können. Bis heute konnten keine eindeutigen Zusammenhänge zwischen dem Auftreten von Mikroverun-reinigungen und beobachteten Veränderungen aquatischer Populationen aufgezeigt werden. Deshalb kombinieren Wissenschaftler Laborergebnisse mit Umweltdaten. Während Labor-experimente unter weitest gehend kontrollierten Bedingungen durchgeführt werden können, ist es äusserst schwierig, die komplexe Situation in der Umwelt zu erfassen. Es handelt sich bei den Mikroverunreinigungen nicht nur um eine Hand voll, sondern eher um hunderte von kritischen Substanzen. Das Messen von Umweltkonzentrationen all dieser Stoffe über eine genügend lange Periode ist unmöglich. Darum braucht es Modelle, um diese Umwelt konzentrationen abschätzen zu können. Die Eingangsgrössen zu solchen Modellen sind Emissionsdaten. Diese zu erheben ist eine mühsame Aufgabe. [...]

<em>Thema</em> dieser Arbeit sind kognitive Prozesse, welche Merkmale von Situationen als Hinweise interpretieren lassen, welche dann das in diesen Situationen gezeigte Verhalten beeinflussen. Weiter geht es um die Wirkung dieser kognitiven Veränderungen auf das Verhalten und Massnahmen zur gezielten Beeinflussung von Verhalten, welche diese kognitiven Prozesse nutzen. Konkret geht es um Gewohnheiten, Erinnerungshilfen, Vorsätze, Selbstverpflichtungen und situative Normen.<br />Im Rahmen dieser Arbeit wurden Befunde aus den Forschungsbereichen Handlungstheorien, Einstellungen, Normen, prospektives Gedächtnis, Gewohnheiten und Vorsatzbildung zu einem <em>theoretischen Modell</em> integriert, welches die kognitiven Prozesse der Entstehung von situativen Hinweisreizen und deren Wirkung zu erklären vermag. Dieses Modell zeigt, dass die verschiedenen im Rahmen dieser Arbeit untersuchten Phänomene auf die gleichen psychologischen Prozesse zurückgeführt werden können. Es wird aber auch gezeigt, dass die Wirkung so einfacher Massnahmen wie von Erinnerungshilfen oder Vorsatzbildungen eine Vielzahl von Prozessen voraussetzen wie z.B. die Interpretation der Situation, Konditionierungsprozesse oder die Entstehung und Wirkung kognitiver Spannungszustände. [...]<br /><br />This thesis <em>focuses </em>on cognitive processes that turn situational attributes into cues, which then influence the behavior executed in this situation. The effects of these cognitive changes on behavior performance are also investigated together with measures that use these effects to influence behavior in a purposeful way. More specifically, the thesis is about habits, memory aids, implementation intentions, self-commitment and situational norms.<br />In this thesis, a <em>theoretical model </em>was developed that integrates findings from the research areas of behavior selection, attitudes, norms, prospective memory, habits and implementation intentions, and explains the cognitive processes of the emergence of situational cues and their effects. The model shows that the various phenomena investigated in this thesis can be ascribed to the same psychological processes. But it also shows that the effects of such simple measures as memory aids or implementation intentions require many different processes, such as the interpretation of the situation, conditioning processes or the emergence and effect of cognitive tension states. [...]

A knowledge of past climatic and environmental changes is of great interest because it allows us to view the recent, probably anomalous, climate change within a broader context, which should improve our ability to predict future climate. Existing climate reconstructions agree on major climatic episodes (e.g. the Little Ice Age and the Medieval Warm Period), but differ substantially with respect to the reconstructed absolute temperature amplitudes. New climate proxies and innovative reconstruction techniques are therefore in great demand.<br />Sediments from high-altitude lakes are known to respond especially sensitively to climatic and environmental changes. Lake Sils and Lake Silvaplana are located at an altitude of about 1800 m a.s.l. in the Upper Engadine region of south-eastern Switzerland. A detailed seismic survey of these lakes, based on a total of 32 km of seismic proiles, was used to determine optimum coring positions, and to study sediment volumes and distribution. In Lake Sils, 22 short cores were taken, and in Lake Silvaplana, a total of 16 short cores and two freeze cores.<br />Due to the absence of varves, the chronology of the 1300-year-long recovered sediment record of Lake Sils was determined using ¹³⁷Cs, ²¹⁰Pb, and ¹⁴C AMS dating. The average sedimentation rate in Lake Sils (40 mg cm^-2yr^-1) is only 20% of that in Lake Silvaplana (200 mg cm^-2yr^-1). This is because its surface area is 40% greater than that of Lake Silvaplana, while its catchment area is 60% smaller and its glaciated area 40% smaller. The impact of the late Little Ice Age (A.D. 1550 - 1850) on the sediments of Lake Sils is clearly apparent, with anomalously low concentrations of organic carbon and biogenic silica, but anomalously high values of median grain-size and mica content. In contrast, the period A.D. 800 - 1550 (partly coinciding with the Medieval Warm Period, A.D. 800 - 1300) is characterized by poorly sorted silici-clastics, high C/N ratios and high biogenic silica values, indicating major glacier recessions. The very recent sediments of both Lake Sils and Lake Silvaplana are signiicantly inluenced by waste water from the adjacent villages. Several steep, stepwise increases in organic carbon and biogenic silica concentrations have occurred since approximately A.D. 1900 in Lake Sils and A.D. 1960 in Lake Silvaplana. [...]

Diarrhoea is one of the major causes of childhood death in developing countries. In this research project, we studied factors that presumably affect the incidence of diarrhoea among young children in urban slums: consumption of safe drinks, hygiene behaviour, cleanliness of household surroundings and the quality of raw water. Beliefs concerning the causes of diarrhoea were also related to health-improving behaviour, namely the application of the water-treatment method SODIS (solar water disinfection) and hygiene behaviour. We conducted a survey in Kibera, a huge shantytown in Nairobi, Kenya. Field workers interviewed a random sample of 500 households. Analysis with regression models revealed that two out of the four postulated factors (mentioned above) were significant: children have a lower risk of contracting diarrhoea when they consume high percentages of safe drinks and live in households with good hygiene behaviour. As regards beliefs, we found that biomedical knowledge of children’s diarrhoea as well as the perceived social norm for treating water are associated with the use of SODIS and good hygiene behaviour. These findings underline the importance of water treatment at household level and safe hygiene practices for protecting the health of young children growing up in urban slum settlements. Our data suggest that these measures are more important for diarrhoea prevention than efforts focussing on cleaning up neighbourhoods.

<em>Overview</em><br />In this dissertation several factors influencing litter decomposition in streams were studied separately or, in some cases, in combination. All factors involved anthropogenic influences on ecosystems and thus tackled different topics of environmental relevance at a broad scale. The factors considered in the experiments reported here were dissolved nutrient concentrations in stream water (eutrophication), stream chemistry as affected by liming, functional litter diversity, and litter quality as affected by elevated concentrations of CO₂ in the atmosphere. [...]<br /><br /><em>Überblick</em><br />In dieser Dissertation wurden verschiedene Faktoren untersucht, die den Abbau von Laubstreu in Fliessgewässern beeinflussen. Die gewählten Faktoren spiegeln primär anthropogene Einflüsse auf Ökosysteme wider, die von grosser Bedeutung für die Umwelt sind. Konkret wurden die Einflüsse erhöhter Nährstoffkonzentrationen (Eutrophierung), pH-Werte und Wasserhärte, der funktionellen Laubstreudiversität sowie erhöhter atmosphärischer CO₂-Konzentrationen auf den Abbau von Laubstreu untersucht. [...]

Granular activated carbon (GAC) filters have been used for decades to remove various kinds of organic micropollutants (MP), disinfectant by-products and taste and odor (T&amp;O) compounds from water by adsorption. In recent years chemical oxidation by ozonation was implemented in many treatment plants before GAC filtration. During ozonation a substantial fraction of the natural organic matter (NOM) present in surface waters is oxidized to smaller and biodegradable compounds thus giving rise to elevated assimilable organic carbon (AOC) concentrations. This fraction is readily metabolized by the biomass present in the GAC filter. To date, the removal processes occurring in GAC filters are not completely understood and therefore most GAC filters have been designed empirically. Improved drinking water quality requirements (regulations of European Union and U.S. Environmental Protection Agency) and the availability of innovative treatment technologies make it necessary to rethink the role of activated carbon applications in water works. This necessitates gaining a more detailed understanding of simultaneously occurring processes in GAC filters, in particular with regard to adsorption and microbiological processes. [...]<br /><br />Granulierte Aktivkohle (GAK) wird seit Jahrzehnten in der Trinkwasseraufbereitung eingesetzt, um verschiedene organische Spurenstoffe, Desinfektionsnebenprodukte und Geruchs- und Geschmackstoffe durch Adsorption zu entfernen. In den letzten Jahren wurde in vielen Trinkwasserwerken die Ozonung als Vorstufe zur GAK Filtration eingeführt. Ein beträchtlicher Teil des im Zulauf, d.h. in Oberflächengewässern enthaltenen, natürlichen organischen Materials (NOM) wird während der Ozonung zu kleineren und biologisch abbaubaren Verbindungen oxidiert. Dies führt zu einer signifikanten Zunahme an assimilierbarem organischen Kohlenstoff (AOC), der durch die im GAK Filter etablierte Biomasse leicht abgebaut wird. Da die Entfernungsprozesse in GAK Filtern bisher nicht vollständig verstanden sind, werden GAK Filter in der Regel empirisch dimensioniert. Erhöhte Anforderungen an die Trinkwasserqualität (Regelungen der European Union und U.S. Environmental Protection Agency) sowie die Verfügbarkeit innovativer Behandlungstechnologien bedingen ein Überdenken der Rolle von GAK in der Trinkwasseraufbereitung. Dies macht ein detailliertes Verständnis der im GAK Filter zeitgleich stattfindenden Prozesse, insbesondere der Adsorptions- und mikrobiologischen Prozesse, erforderlich. [...]

Most of the wastewater generated worldwide is discharged untreated into aquatic systems, thus leading to water pollution and loss of valuable nutrients. Furthermore, since most of the nutrient load finding its way into water bodies cannot be recovered for food production, artificial fertilisers must cover the agricultural nutrient demand. Production of artificial nitrogen fertiliser is energyintensive and phosphate rocks have to be mined for the production of phosphorus fertilisers. Phosphorus reserves are, however, likely to be depleted in the near future. To secure water and phosphorus reserves for future generations, new environmental sanitation concepts are required to promote the saving and reuse of limited resources and preserve the environment.<br />The material flow analysis (MFA) method can be used to develop such concepts by simulating for example the impact of different types of sanitation infrastructure, consumption patterns and agricultural reuse practices on resource consumption and environmental pollution. However, application of this method in developing countries is constrained by limited data availability and data collection means. [...]<br /><br />Das Management von Ressourcen wie Wasser und Nährstoffen im konventionellen Siedlungswasser- und Abfallwirtschaftssystem ist nicht nachhaltig. Folglich müssen neue Konzepte entwickelt werden, welche Ressourcen schonen und die Umwelt schützen. Die Methode der Stoffflussanalyse (MFA) unterstützt das Erarbeiten solcher Konzepte. Sie erlaubt es, die Auswirkungen von verschiedenen Abfall- und Abwasserbehandlungstechniken, Konsumverhalten und landwirtschaftlichen Wiederverwertungspraktiken auf Ressourcenverbrauch und Umweltverschmutzung zu simulieren. Die Anwendung dieser Methode in Entwicklungsländern ist aber durch die begrenzte Datenverfügbarkeit und fehlende Mittel für Datenerhebung eingeschränkt. Die vorliegende Dissertation präsentiert deshalb einen Ansatz zur Entwicklung und Kalibrierung von zuverlässigen Stoffflussmodellen trotz begrenzter Datenverfügbarkeit. Weiter wird in dieser Arbeit das Verständnis des Nährstoffverhaltens im Siedlungswasser- und Abfallwirtschaftssystem vertieft.<br />Ein Instrument für die Planung von Siedlungswasser- und Abfallwirtschaftssystemen wurde aufgebaut. Es erlaubt, die Auswirkungen von verschiedenen Szenarien auf Wasser- und Nährstoffverbrauch, Nährstoffeinleitung in die Umwelt sowie Nährstoffwiederverwertung für die Nahrungsmittelproduktion zu evaluieren. Es besteht im Wesentlichen aus einem stochastischen Modell, welches Güter-, Stickstoff- und Phosphorflüsse in einem regionalen Siedlungswasser-, Abfall- und Landwirtschaftssystem beschreibt. Das Instrument integriert auch Konzepte zur Unsicherheitsanalyse und Plausibilitätsprüfung in die MFA-Methode. Es enthält weiter eine Datenbank mit Default-Werten für verschiedene Modellparameter und für Plausibilitätskriterien. Ein Microsoft Excel®-Programm erlaubt es, die verschiedenen Elemente des Instruments umzusetzen. Dieses wurde im Rahmen einer Fallstudie in Hanoi, Vietnam, getestet. [...]

Endocrine disrupting chemicals (EDCs) are exogenous substances that can disrupt the endocrine system of organisms by acting as hormone agonists or antagonists. EDCs are ingested mainly via food, air and water and bioaccumulate in the body. Effects suspected of being caused by bioaccumulated EDCs (internal exposure) are found in all taxa of organisms around the world. However, specific EDCs as the causative agent have not yet been identified for all these effects. The fact that it is not possible to identify EDCs using their chemical structure alone makes the search for EDCs more difficult. [...]<br /><br />Chemikalien mit hormonaktiver Wirkung (EDCs) sind Substanzen, welche das endokrine System nachteilig beeinflussen können, indem sie eine ähnliche Wirkung wie endogene Hormone zeigen oder ihnen entgegenwirken. Nahezu alle Lebewesen sind ihnen heutzutage in mehr oder weniger starkem Ausmass, durch kontaminierte Nahrung, Luft und Wasser, ausge-setzt und reichern sie im Körper an. Gesundheitliche Auswirkungen, die in Verdacht stehen, durch bioakkumulierte EDCs (interne Exposition) hervorgerufen zu sein, sind über die Art-grenzen hinaus bereits auf der ganzen Welt entdeckt worden, wobei noch nicht alle Effekte spezifischen EDCs haben zugeordnet werden können. Die Ursache liegt unter anderem darin, dass die Gesamtheit der EDCs nicht bekannt und eine Identifizierung durch die Tatsache erschwert ist, dass die chemische Struktur einer Substanz keine eindeutige Bestimmung als EDC zulässt. [...]

Pollution of natural resources is a core problem related to the current syndromes of global change. In particular, major rivers in developing and emerging countries suffer increasingly severe water degradation. The conventional approach to <em>address river water pollution</em> is based on mathematical models, such as QUAL2E, WASP or MIKE11, which allow simulating hydrodynamic and water quality transformation processes within the river water. These models focus on the points where pollution is discharged into the main river but they do not investigate into the actual origins and the processes generating the pollution. The simulated mitigation scenarios are generalized and lead to strategy plans that fail to clearly identify and prioritize effective water quality remediation measures.<br />With the current research, a <em>mathematical Material Flow Analysis (MMFA)</em> is conducted as an alternative approach to address river water pollution. Nutrient pollution (nitrogen and phosphorus) in the <em>Thachin River Basin</em> in Central Thailand is presented as a case-study. Using available data and system knowledge, a simple stationary MFA model is established. The simulations give an overview over the origins, flow paths and relative importance of nutrient loads from the various pollution sources in the basin. The orders of magnitude of nutrient loads which can be expected from the various sources are quantified, their influential parameters identified and effective mitigation measures evaluated. Based on an uncertainty and sensitivity analysis, needs for further investigations are specified.<br />According to the model simulations AQUACULTURE is <em>currently </em>the most critical nutrient pollution source in the Thachin River Basin, followed by RICE and PIG production. INDUSTRIES could produce similar nutrient loads, if the uncertainty range of our simulations is considered. The remaining pollution sources of HOUSEHOLDS, FIELDCROPS, FRUIT &amp; VEGETABLES, POULTRY production and WATER PLANTS are of moderate or low significance. The relative importance of the various pollution sources shifts when <em>down-scaling the model</em> to the provincial level, thus highlighting the necessity of discussing remediation measures on a provincial scale. Simulations of selected mitigation <em>scenarios </em>show that a significant reduction of the basin’s nutrient loads could be achieved by, e.g., an improved management of AQUACULTURE wastewater, lower fertilizer application rates in RICE farming or an optimum managment of PIG farms.<br />Cross-checks with local and international data show that our model results are in a<em> plausible</em> range, despite the high uncertainty of some variables. Comparing the simulated nutrient loads with <em>water quality and flow measurements</em> in the river system, however, a large discrepancy is apparent. This indicates a significant nutrient <em>retention </em>within and/or loss from the river system. Considering the “bathtub” character of the Thachin River Basin, with its warm water temperature, slow flow velocites, partially closed water gates and its widespread coverage by aquatic plants, such high retentions and losses are indeed plausible: as sedimentation, within the stagnant canal system, via uptake by/harvest of aquatic plants or as N emission to the atmosphere.<br />Once established, the MFA model can now serve as an alternative <em>scientific basis for decisionmaking</em> towards effective river water quality remediation in the Thachin River Basin. Concrete measures can be evaluated amongst concerned stakeholders and existing action plans and projects revised.<br />Based on the findings of the current MFA model, average per-unit nutrient loads from the various pollution sources (<em>transfer functions</em>) are specified. These can be used for a first broad quantification of nutrient pollution loads in <em>comparable river basins</em>, by extrapolating these figures according to available statistical figures (population numbers, land use areas, etc).

Lakes are recognized for their effective removal of nitrogen from aquatic systems and for their potential global significance as a long-term sink of organic carbon. Processes in the surface sediment determine the degradation state of organic matter (OM) and thus the extent of OM that will be preserved in deeper sediments. The aim of this thesis was to identify and quantify mineralization pathways in surface sediments of lakes with different trophic status. Since biogeochemical processes are most intense in a narrow layer just below the sediment surface, a microscale approach was used to measure accurately concentration profiles in the sediment porewater.<br />A promising analytical tool is the application of chemical microsensors. Hence, LISA, a profiling lander system was optimized to study biogeochemical processes in situ at the sediment-water interface of deep lakes (depth of up to 200 m). This device was equipped with up to 18 microelectrodes connected to a stepping motor that allowed sub-millimetre vertical resolution. The different ionselective sensors allowed new observation possibilities in studying OM mineralization in freshwater sediments. [...]<br /><br />Seen eliminieren Stickstoff effektiv aus aquatischen Systemen und stellen langfristig wahrscheinlich eine global wichtige Senke für organischen Kohlenstoff dar. Prozesse im Oberflächensediment bestimmen den Zersetzungsgrad organischen Materials (OM) und somit auch das Ausmass von OM, das in tieferen Sedimentschichten konserviert wird. Das Ziel der vorliegenden Arbeit war es, die Mineralisationswege in Oberflächensedimenten von Seen mit unterschiedlichen Trophiegraden zu identifizieren und zu quantifizieren. Da die biogeochemischen Prozesse in einer dünnen Schicht direkt unter der Sedimentoberfläche am intensivsten sind, wurde ein feinskaliger Ansatz gewählt, um Konzentrationsprofile im Porenwasser möglichst genau zu messen.<br />Eine vielversprechende analytische Methode ist die Anwendung chemischer Mikrosensoren. Dafür wurde ein Profiling Lander System (LISA) optimiert, um biogeochemische Vorgänge direkt am Seegrund von tiefen Seen (bis zu 200 m) messen zu können. Dieses Gerät wurde mit bis zu 18 Mikroelektroden und einem Schrittmotor ausgerüstet, der eine vertikale Auflösung im Submillimeterbereich ermöglichte. Die verschiedenen ionenselektiven Sensoren eröffneten neue Möglichkeiten, um die Mineralisation von OM in Süsswasser-Sedimenten zu untersuchen. [...]

Aquatic environments retain a large quantity of carbon and have a significant influence on the global carbon and nitrogen cycles. It is therefore essential to understand the mechanisms responsible for the transformation and accumulation of organic material and to characterize its composition. During the last few decades, environmental conditions like anoxia, nature and origin of contributed material, sedimentation regime, and adsorption to mineral particles were identified as important factors for carbon accumulation. Furthermore, some specific environments are considered to accumulate carbon more efficiently than others, as for instance, anoxic and iimnic systems. Although progress has been made in characterizing organic compounds, rather large fractions of the organic matter in aquatic systems still remain unidentified. [...]<br /><br />Gli ambicnti acquatiei ritengono un'enormc quantità di carbonio cd lianno quindi un'innuen/a rilcvantc sui cicli globali di carbonio cd a/oto. Risulta dunque fondamentale comprendcrc i mcccanismi rcsponsabili dclle traslbrma/ioni e delTaecumulazione della materia organiea e eonoscerne la composizionc. Purtroppo, nonostantc la presen/a di numcrosi studi, gran parte della materia organiea non c ancora stata identificata. Lsistono degli ambienti speeifici, in cui la materia organiea è aecumulata in modo parlicolarmente efficiente, per esempio, in sistemi anossici c in sistemi lacustri. Le cause delTaecumulazione più efficiente sono ancora incerte, tutlavia csistono diverse ipotesi che suggeriscono un inllusso da parle dell'anossia, della natura della materia di sedimentazione, del regime di sedimenta/ione e dell'adsorbimento a materia inorganica. [...]

Riverine floodplains are complex ecosystems that undergo cycles of expansion, contraction, and fragmentation along the longitudinal, lateral, and vertical dimensions. They can be conceptualized as a three dimensional shifting habitat mosaic. Thus, they can serve as model ecosystems to investigate the linkage between environmental heterogeneity and ecosystem functioning.<br />The primary goal of the study was to assess environmental heterogeneity at the habitat and landscape level in a floodplain ecosystem and to link this environmental heterogeneity with ecosystem processes. The focus was on respiration as a key process in the carbon cycle that integrates the energy flow through the biotic compartments of aquatic and terrestrial ecosystems. [...]<br /><br />Schwemmebenen sind komplexe Ökosysteme, die einem Kreislauf von Expansion, Kontraktion und Fragmentierung entlang der longitudinalen, vertikalen und lateralen Dimension unterlegen sind und können somit als dreidimensionale, sich verändernde Habitatmosaike betrachtend werden. Aus diesem Grund stellen sie Modellökosyteme zur Untersuchung der Wechselwirkungen zwischen der Heterogenität und dem Funktionieren von Ökosystemen dar.<br />Das Hauptziel dieser Arbeit war, die Heterogenität einer Schwemmebene sowohl auf Habitat als auch auf Landschaftsebene zu untersuchen und den Zusammenhang zwischen Heterogenität und Ökosystemprozessen aufzuzeigen. Insbesondere wurde die Respiration untersucht, ein Schlüsselprozess im Kohlenstoffkreislauf aquatischer und terrestrischer Ökosysteme. [...]

The discovery of an extraordinarily abundant and diverse viral community in oceans and lakes has profoundly reshaped ideas about global carbon, nutrient fluxes, food web dynamics, and maintenance of microbial biodiversity. These impacts are exerted through the massive viral impact on the population dynamics of heterotrophic bacterioplankton and primary producers. The general objectives of this doctoral research were to determine the dynamic and composition of benthic and pelagic viral communities in aquatic ecosystems by using qualitative fingerprinting (Pulsed Field Gel Electrophoresis) and quantitative methods (transmission electron microscopy, epifluorescence microscopy, flow cytometry). A “mosaic approach” was used to gain insight into viruses and their ecological roles in both freshwater and marine ecosystems. Specifically, I aimed to estimate the viral distribution and viral induced bacterial mortality in different benthic habitats in the littoral zone of a lake (Chapter 1), to determine the total viral genome distribution in benthic and pelagic systems (Chapter 2), to assess the degree of temporal and horizontal spatial variation in viral abundance in a lake (Chapter 3), and to detect climate change effects on viral abundance and infectivity (Chapter 4). Studies were conducted in a Swiss lake and in freshwater, brackish and marine ecosystems in Denmark. [...]<br /><br />La scoperta di una comunità virale straordinariamente abbondante e diversa in oceani e laghi, ha portato a riformulare le idee sui flussi di carbonio e nutrimenti, sulle dinamiche delle reti alimentari e sul mantenimento della biodiversità microbiologica. Infatti, i virus hanno un ruolo fondamentale sulle dinamiche delle popolazioni di batterioplancton e di produttori primari.<br />Gli obiettivi generali di questo dottorato sono quelli di determinare la dinamica e la composizione delle comunità virali del dominio bentonico e pelagico in ecosistemi acquatici tramite l’impiego di tecniche di fingerprinting (elettroforesi in campo pulsato; PFGE) e metodi quantitativi (microscopio elettronico a trasmissione, microscopio a epifluorescenza, citometria a flusso). Per chiarire la distribuzione dei virus, la loro ecologia e il loro ruolo nei sistemi marini e lacustri é stato utilizzato un “approccio a mosaico”. Nello specifico, nel primo capitolo, si é determinata la distribuzione dei virus e il tasso di mortalità che questi provocano sui batteri in differenti substrati bentonici che caratterizzano una zona litorale. Nel secondo si é studiato la distribuzione dell’intero genoma virale in sistemi bentonici e pelagici. La variazione temporale (giornaliera e stagionale) e quella spaziale dell’abbondanza virale é stata esaminata nel terzo capitolo. Per finire, nel quarto capitolo sono stati valutati gli effetti del cambiamento climatico sull’abbondanza e infettività virale. Queste ricerche sono state effettuate in un lago svizzero e in diversi ecosistemi acquatici in Danimarca: sistemi lacustri, marini e salmastri. [...]

Population persistence in temporary streams can result via local adaptation (specialization) or adaptive phenotypic plasticity in response to stream drying. If populations lack an adaptive response to stream drying, local population extinctions can occur, and apparent population persistence results from colonization from other streams, resulting in source-sink metapopulation dynamics. This thesis consists of four studies that investigated life history plasticity, gene flow, and population genetic structure of an alpine caddisfly (<em>Allogamus uncatus </em>Brauer) that inhabits permanent and temporary streams in the Swiss Alps. Two studies were conducted to assess whether populations show an adaptive strategy to seasonal time constraints, and two studies were conducted to quantify gene flow between stream types, and determine the genetic consequences of population extinction and recolonization.<br />The first study used a common garden experiment to assess whether males and females from both stream types differed in their life history responses to photoperiod and hydroperiod time constraint cues. I found that populations exhibited life history plasticity, although the responses varied by time constraint cue and sex. Larvae from both stream types developed faster in the ‘late season’ photoperiod, and males developed faster and emerged at a smaller size than females. Permanent stream larvae had lower growth rates when stressed by hydroperiod, but higher growth rates when stressed by both time constraints. Temporary stream females also had higher growth rates when stressed by both time constraints, whereas temporary stream males did not respond to hydroperiod. Contrary to my prediction, temporary stream insects did not develop faster and emerge earlier than permanent stream insects. [...]<br /><br />Das Überleben von Populationen in unbeständigen Habitaten kann durch lokale Adaptation (Spezialisierung) oder adaptive phänotypische Plastizität sichergestellt werden. Wenn Populationen nicht über eine adaptive Antwort auf z. B. das Austrocknen eines Baches verfügen, kann dies zum lokalen Aussterben führen und das weitere Existieren der Population wird nur durch erneute Wiederbesidlung aus anderen Populationen gewährleistet-, es bildet sich eine Metapopulationsdynamik.<br />Diese Dissertation besteht aus vier Abschnitten, die sich mit „life history“ Plastizität, Genfluss und der populationsgenetischen Struktur der alpinen Köcherfliege <em>Allogamus uncatus </em>Brauer befassen, die in solchen temporären Bächen in den Schweizer Alpen vorkommt. Zwei Arbeiten befassen sich dabei mit der Frage, ob die Populationen eine adaptive Antwort auf saisonale Zeitbeschränkungen zeigen. Zwei weitere Arbeiten versuchen Genfluss zwischen Populationen aus temporären und dauerhaften Habitaten zu quantifizieren und damit auch die genetischen Konsequenzen von Extinktion und Rekolonisierung aufzuzeigen.<br />Die erste Studie versuchte mittels eines “common garden”-Experiments zu klären, ob Reaktionen in den „life-history“-Parametern bei Reizen kurzer Photoperiode und Trockenstress zu beobachten waren und ob Männchen und Weibchen sich in dieser Reaktion unterschieden. Ich konnte bestätigen, dass die untersuchten Populationen plastischen reagiert haben. Allerdings unterschieden sich die Ergebnisse in Abhängigkeit des Reizes und des Geschlechts. Männchen entwickelten sich generell schneller und waren beim Schlüpfen kleiner als Weibchen. Larven von beiden Bachtypen (temporär und dauerhaft) entwickelten sich aber unter Herbstphotoperiode schneller. Larven aus dauerhaften Bächen wuchsen langsamer unter Trockenstress, wuchsen aber unter einer Kombination von Trockenstress und Herbstphotoperiode schneller. Weibchen aus temporären Bächen zeigten eine ähnliche Reaktion gegenüber beiden Stressquellen, während Männchen aus temporären Bächen keine Reaktion auf Trockenstress zeigten. Entgegen meiner Erwartung schlüpften Tiere aus den temporären Bächen aber nicht generell früher als Tiere aus dauerhaften Bächen. [...]

Cosmogenic radionuclide data retrieved from natural archives, such as ice cores, are excellent tools to use for reconstruction of past solar activity and geomagnetic eld intensity, and to study past climate changes. To interpret the data correctly, however, it is essential to separate these di erent signals. The physics of the production rate of the cosmogenic radionuclides as a function of solar and geomagnetic activity is known, but their transport from the atmosphere into natural archives is not well understood. The main goal of this thesis is to ll this gap and to improve our understanding of the atmospheric transport of the cosmogenic radionuclides ¹⁰Be and ⁷Be. This was made using new observational data and performing modeling experiments with the ECHAM5-HAM general circulation model. This model is a three-dimensional atmospheric circulation model that includes aerosol physics and chemistry. [...]<br /><br />Kosmogene Radionuklide stellen wertvolle Tracer in den Umweltwissenschaften dar, die aus natürlichen Archiven, wie z.B. polarem Eis gewonnen werden konnen. Sie liefern Informationen über die Sonnenaktivität, die Stärke des Erdmagnetfeldes und das Klima in der Vergangenheit. Um diese Daten richtig interpretieren zu konnen, ist es wichtig, die unterschliedlichen Komponenten in den Messdaten zu trennen. Die Produktion kosmogener Radionuklide als Funktion der Sonnenaktivität und der Stärke des Erdmagnetfeldes ist gut bekannt, aber der Transport der Radionuklide in der Atmosphäre jedoch ist weniger gut verstanden. In dieser Arbeit wird der atmosphärische Transport der kosmogenen Radionuklide ¹⁰Be und ⁷Be untersucht. Dies geschieht mit Hilfe gemessener Daten wie auch Modellstudien mit dem allgemeinen Zirkulationsmodell ECHAM5-HAM. Dieses Modell ist ein dreidimensionales atmosphärisches Zirkulationsmodell, das auch Aerosolphysik und -chemie beschreibt. [...]

Decomposition of leaf litter is a key process in stream ecosystems and one that has been the focus of a considerable body of research. Much of this research has found that decomposition is sensitive to many common human activities and recently ecologists have suggested that decomposition rates could prove useful as a process-based means of assessing the condition of stream ecosystems. In order to be effective in detecting anthropogenic impacts, knowledge of the spatial variability of this process is needed so that natural variability can be distinguished from human impacts on decomposition rate. This dissertation, presented in 5 chapters, describes spatial patterns of variability in leaf decomposition rates in streams, and implicates some of its causes. [...]<br /><br />Die Zersetzung von Laubstreu ist ein Schlüsselprozess in Fliessgewässer-Ökosystemen und Gegenstand intensiver Untersuchungen. Viele der derzeit vorliegenden Forschungsergebnisse zeigen, dass der Streuzersetzungsprozess empfindliche auf menschliche Aktivitäten reagiert. Ökologen haben deshalb jüngst vorgeschlagen, dass die<br />Bestimmung von Abbauraten ein nützliches prozessbasiertes Mittel für die ökologische Zustandsbewertung von Fliessgewässern darstellen könnte. Um die Auswirkungen menschlicher Eingriffe auf Ökosysteme effektiv erkennen zu können, muss die räumliche Variabilität der Abbauraten bekannt sein, da nur so zwischen natürlicher Variabilität und anthropogenen Einflüssen differenziert werden kann. Die vorliegende Dissertation, die sich in 5 Kapitel gliedert, beschreibt die räumlichen Variabilitätsmuster des Streuabbau in Fliessgewässern und zeigt einige Gründe für die beobachteten Unterschiede auf. [...]

Herbicides are widely applied in the environment to prevent the development of weeds in crop production. In creeks and rivers, the input of certain herbicides occurs in pulse following rain events rather than in continuous exposure. As a consequence, non-target aquatic organisms, such as algae, might be repeatedly exposed to high concentrations following field application. Indeed, these peak concentrations were shown to surpass, several times during field application season, the suggested chronic water quality criteria (CQC) for Switzerland, which is set to protect the aquatic environment on the long-term.<br /><em>The scope of this thesis was to assess the effects on algae of time-varying exposure to herbicides, with a focus on the estimation of the effects caused by peak and sequential peak exposures. </em>[...]<br /><br />Les herbicides sont utilisés en agriculture pour lutter contre le développement de mauvaises herbes. Lors d’événements pluvieux, plusieurs d’entre eux peuvent être transportés par le ruissellement de surface, générant ainsi des pics de concentrations dans les cours d’eau récepteurs. Par conséquent, des organismes non-cibles sensibles aux herbicides, comme les algues, se trouvent potentiellement exposés à de fortes concentrations pouvant dépasser le critère de qualité chronique (CQC) proposé en Suisse et visant une protection à long-terme des organismes aquatiques.<br /><em>L’objectif de ce travail est d’évaluer les effets de fluctuations de concentrations d’herbicides sur les algues, et en particulier les effets liés à des pics d’exposition et des expositions séquencées.</em> [...]

The influence of the hydrodynamics in a seiche driven prealpine lake on the oxygen transport into and across the bottom boundary layer and the resulting response of the solute dynamics in the sediment were the main focus of this thesis.<br />Previous studies have shown that a diffusive boundary layer existed in the investigated lake which correlated well with the turbulence level in the bottom boundary layer. In order to characterize the hydrodynamics in the vicinity of this diffusive sublayer at the last cm above the sediment a novel flow sensor for in situ measurements was used. This sensor could cope with the very low flow velocities close at the sediment water interface. It was thoroughly tested for its suitability as an in situ device. Its signal dependence on pressure, temperature and flow direction was analyzed and the necessary algorithms for the signal postprocessing of the in situ measurements were developed. The recorded flow profiles showed the collapsing turbulence close to the sediment water interface and the transition of the viscous boundary layer into a logarithmic layer. The obtained results compared also well with the horizontal velocities recorded simultaneously with an acoustic Doppler velocimeter. [...]<br /><br />Die vorliegende Arbeit befasst sich hauptsächlich mit dem Einfluss der Seiche induzierten Strömung auf den Sauerstofftransport in die und innerhalb der Bodengrenzschicht und der daraus resultierenden Reaktion gelöster Stoffe im Sediment in einem Voralpensee.<br />Ausgangspunkt der Studie war eine frühere Arbeit, die gezeigt hat, dass im untersuchten See ein starker Zusammenhang zwischen diffusiver Grenzschicht und dem Turbulenzniveau der Bodengrenzschicht besteht. Um die Strömungsverhältnisse in der Nähe der dieser diffusiven Schicht genauer zu untersuchen wurden Messungen innerhalb der letzten Zentimeter über dem Sediment mit einem neuartigen Strömungssensor durchgeführt. Dieser Sensor kann auch extrem niedrige Strömungsgeschwindigkeiten, wie sie in der Nähe der Sediment Wasser Grenzschicht auftreten, bestimmen. Ausführliche Tests erwiesen die Eignung des Gerätes für die in situ Anwendung am 35 m tief gelegenen Seegrund. Die im See gemessenen Strömungsprofile zeigten dass die Turbulenz in der Nähe der Sediment Wasser Grenzschicht zusammenbricht. Der Übergang der viskosen in die logarithmische Grenzschicht wurde ebefalls beobachtet. Parallele Vergleichsmessungen mit einem Acoustic Doppler Velocimeter stimmten sehr gut mit den Daten des Flussensors überein. [...]