Characterization of a second <I>tfd</I> gene cluster for chlorophenol and chlorocatechol metabolism on plasmid pJP4 in <I>Ralstonia eutropha</I> JMP134(pJP4)
Within the 5.9-kb DNA region between the <em>tfdR</em> and<em>tfdK</em> genes on the 2,4-dichlorophenoxyacetic acid (2,4-D) catabolic plasmid pJP4 from <em>Ralstonia eutropha</em> JMP134, we identified five open reading frames (ORFs) with significant homology to the genes for chlorocatechol and chlorophenol metabolism (<em>tfdCDEF</em> and <em>tfdB</em>) already present elsewhere on pJP4. The five ORFs were organized and assigned as follows: <em>tfdD</em><sub>II</sub><em>C</em><sub>II</sub><em>E</em><sub>II</sub><em>F</em><sub>II</sub> and <em>tfdB</em><sub>II</sub> (in short, the <em>tfd</em><sub>II</sub> cluster), by analogy to <em>tfdCDEF</em> and <em>tfdB</em> (the <em>tfd</em><sub>I</sub> cluster). Primer extension analysis of mRNA isolated from 2,4-D-grown <em>R. eutropha</em> JMP134 identified a single transcription start site in front of the first gene of the cluster, <em>tfdD</em><sub>II</sub>, suggesting an operon-like organization for the <em>tfd</em><sub>II</sub> genes. By expressing each ORF in <em>Escherichia coli</em>, we confirmed that <em>tfdD</em><sub>II</sub> coded for a chloromuconate cycloisomerase, <em>tfdC</em><sub>II</sub> coded for a chlorocatechol 1,2-dioxygenase, <em>tfdE</em><sub>II</sub> coded for a dienelactone hydrolase, <em>tfdF</em><sub>II</sub> coded for a maleylacetate reductase, and <em>tfdB</em><sub>II</sub> coded for a chlorophenol hydroxylase. Dot blot hybridizations of mRNA isolated from <em>R. eutropha</em> JMP134 showed that both <em>tfd</em><sub>I</sub> and <em>tfd</em><sub>II</sub> genes are transcribed upon induction with 2,4-D. Thus, the functions encoded by the <em>tfd</em><sub>II</sub> genes seem to be redundant with respect to those of the <em>tfd</em><sub>I</sub> cluster. One reason why the <em>tfd</em><sub>II</sub> genes do not disappear from plasmid pJP4 might be the necessity for keeping the regulatory genes for the 2,4-D pathway expression <em>tfdR</em> and <em>tfdS</em>.
Nonylphenol affects the granulation pattern of epidermal mucous cells in rainbow trout, <I>Oncorhynchus mykiss</I>
Nonylphenol is a biodegradation product of nonionic surfactants and has recently attracted considerable attention due to its estrogenic potential. Sexually mature male rainbow trout were repeatedly exposed (one to four periods of 10 days each) to environmentally relevant concentrations of nonylphenol (1 μg/L, 10 μg/L) and for comparison, trout were injected with estradiol. Since estrogens are known to induce structural changes within the fish skin, a similar effect of xenobiotics with estrogen-like activity was assumed. Samples of skin were evaluated by means of light and electron microscopy and histochemistry. In trout exposed to nonylphenol and to estradiol, the structure of the epidermis was altered: an irregular overall architecture was often accompanied by detached pavement cells, vacuolation of the cytoplasm, and severely deformed cell nuclei. However, the granulation pattern of the mucous cells was influenced exclusively after exposition to nonylphenol. The number of large and irregularly shaped mucosomes depended more on the exposure period than on the concentration of nonylphenol. Furthermore, this alteration has not yet been reported for any other pollutant or stressor and, thus, can be classified as an effect that would strongly indicate exposure to nonylphenol.
Cytochrome P4501A induction potencies of polycyclic aromatic hydrocarbons in a fish hepatoma cell line: demonstration of additive interactions
The relative CYP1A induction potencies, determined as ethoxyresorufin-<em>O</em>-deethylase (EROD) activity, and the cytotoxicities of 19 compounds with one to six benzene rings, mixtures of polycyclic aromatic hydrocarbons (PAHs), and contaminated landfill leachates have been determined in the permanent fish hepatoma cell line PLHC-1. No CYP1A induction was observed with benzene, naphthalene, anthracene, acenaphthene, benzo[<em>g,h,i</em>]perylene, and fluorene and low induction was found with fluoranthene and phenanthrene. All other PAHs with three and more benzene rings led to a concentration-related induction of CYP1A, with rebound decreases at high concentrations resulting in bell-shaped concentration–activity curves. Fish-related induction equivalency factors (IEFs) were estimated for all PAHs on the basis of EC50 values of their EROD activities and are reported here for the first time. The following order of decreasing IEFs was found: dibenz[<em>a,h</em>]anthracene > dibenzo[<em>a,i</em>]pyrene > benzo[<em>k</em>]fluoranthene > 3-methylcholanthrene > benzo[<em>a</em>]pyrene > benzo[<em>e</em>]pyrene > chrysene > 7,12-dimethylbenz[<em>a</em>]anthracene > perylene > benz[<em>a</em>]anthracene > pyrene. In contrast to the EROD activity, the immunodetectable protein content determined by ELISA showed a concentration-dependent increase. The interaction of PAHs in mixtures of up to eight individual compounds was additive based on their EROD activities. In landfill leachates, determined induction equivalents (IEQ) were significantly higher than calculated IEQs based on analytical measurements, which indicates additional unknown inducing compounds present in leachates. This study shows that the PLHC-1 cell in vitro system serves as an integrative bioanalytical tool in the ecotoxicological evaluation of aquatic environmental samples contaminated with CYP1A-inducing compounds.
Total lipid content of freshwater macroinvertebrates from different orders and with different life histories was investigated. Lipids were determined as HIP-extractable lipids (HIP = hexane: isopropanol). Macroinvertebrate taxa were assigned to different feeding guilds, and life histories for insect taxa: <I>Gammarus pulex</I> (Amphipoda/shredder), <I>Ecdyonurus</I> sp. (Ephemeroptera/hemimetabolous/grazer), <I>Perla</I> sp. (Plecoptera/hemimetabolous/predator), <I>Hydrophsyche</I> sp. (Trichoptera/holometaboious/ suspension feeder), and <I>Atherix ibis</I> (Diptera/holometabolous/predator). Animals were collected in two streams in Switzerland bimonthly between October 1994 and October 1995. Lipids, expressed as percent dry mass (dm), were estimated using two techniques: (1) as total lipid content, determined by the sulphophosphovanilline method; (2) as total fatty acids (= sum of fatty acids), determined by gas chromatography. The annual aver age total lipid contents for <I>G. pulex</I>, <I>Ecdyonurus</I> and <I>Perla</I> were 6.1 %, 7.0 % and 6.0 % dm, respectively. The two holometabolous insects, <I>Hydropsyche</I> (8.0 %) and <I>A. ibis</I> (9.3 %), exhibited the highest total lipid content. Total fatty acids as a percentage of total lipids was lowest in <I>G. pulex</I> (62 %), followed by <I>Ecdyonurus</I> (64 %), <I>Perla</I> (73 %), <I>Hydropsyche</I> (80 %), and <I>A. ibis</I> (85 %). The dry mass of holometabolous insects (<I>Hydropsyche</I> and <I>A. ibis</I>) related positively with lipids, indicating an increase in body concentration during larval growth. No or only a weak positive relationship with dry mass was found for the hemimetabolous <I>Ecdyonurus</I> and <I>Perla</I>. <I>Gammarus pulex</I>, in contrast, showed a negative relationship. Male <I>G. pulex</I> attained a larger size and contained less fat than juveniles and adult females. Seasonal changes in total lipid content were recognisable only as weak trends because of high variation among individuals. <I>Gammarus pulex</I> had higher total lipid content in spring, while <I>Perla</I> and <I>Hydropsyche maxima</I> occurred in summer. No seasonal trends in total lipid content could be observed in <I>Ecdyonurus</I> and <I>A. ibis</I>.
How do migrating daphnids cope with fish predation risk in the epilimnion under anoxic conditions in the hypolimnion?
The vertical distribution of <I>Daphnia</I> in experimental tubes is influenced by fish kairomone concentration in the 'epilimnion' and oxygen conditions in the 'hypolimnion'. Daphnids trade off reduced predation mortality in a refuge against disadvantages due to unfavourable oxygen conditions.
Influence of carbonate on the ozone/hydrogen peroxide based advanced oxidation process for drinking water treatment
The influence of carbonate on the ozone/hydrogen peroxide process has been investigated. Carbonate radicals, which are formed from the reaction of bicarbonate/carbonate with OH radicals, act as a chain carrier for ozone decomposition due to their reaction with hydrogen peroxide. The efficiency of bicarbonate/carbonate as a promoter for the radical-based chain reaction in presence of hydrogen peroxide has been calibrated and compared to a well-known chain promoter (methanol) and an inhibitor (tert-butanol). Relative to tert-butanol, the hydrogen peroxide induced ozone decomposition is accelerated by bicarbonate/carbonate. Relative to methanol, bicarbonate/carbonate in presence of hydrogen peroxide is less effective as a promoter under comparable experimental conditions.<br/>
In the O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> process, the consumption of hydrogen peroxide is proportional to the fraction by which bicarbonate+carbonate contributes to the total rate of OH radical scavenging. In drinking water treatment this is important if the organic matter content of the water is low (≤1 mg/L). The overall OH radical oxidation capacity is not affected by the reaction of carbonate radicals with H<sub>2</sub>O<sub>2</sub>. However, the rate of the oxidation of a micropopulant can be significantly increased in presence of H<sub>2</sub>O<sub>2</sub> if the bicarbonate/carbonate fraction on the overall scavenging gets more important. The rate of ozone decomposition increases in such conditions, resulting in a smaller ozone oxidation capacity and less disinfection.<br/>
The experimental findings (ozone decomposition, OH radical oxidation capacity and hydrogen peroxide consumption) could be reproduced by kinetic modeling using a standard set of rate constants from the literature. This further supports our proposed mechanism for the processes in the Advanced Oxidation Process (AOP) O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> in presence of bicarbonate/carbonate.
Bestimmungsschlüssel für die Larven und Puppen der in der Schweiz, in Österreich und in Deutschland vorkommenden Netzflügelmücken (Diptera: Blephariceridae), mit Hinweisen zu ihrer Verbreitung und Phänologie
Eight blepharicerid species and subspecies occur in Switzerland, Austria and Germany. <I>Hapalothrix lugubris</I> LOEW, <I>Liponeura cinerascens minor</I> BISCHOFF, <I>Liponeura cordata</I> VIMMER, <I>Liponeura decipiens</I> BEZZI and <I>Blepharicera fasciata fasciata</I> (WESTWOOD) are found in all three countries. <I>Hapalothrix lugubris</I> and L. cinerascens minor are restricted to alpine areas. In contrast, <I>Liponeura cinerascens cinerascens</I> LOEW is found only outside of the Alps. In Switzerland and Austria, <I>B. fasciata fasciata</I> is restricted to southern areas. In Germany some isolated populations of <I>B. fasciata fasciata</I> exist in Bavaria. <I>Liponeura vimmeri</I> MANNHEIMS is absent from Switzerland, and <I>L. brevirostris</I> LOEW occurs only in Germany. The altitudinal distributions of the different species overlap substantially, except for <I>B. fasciata fasciata</I> which is limited to low altitudes. <I>L. cinerascens minor</I> and <I>H. lugubris</I> (and probably <I>L. brevirostris</I>) reach the highest altitudes of all species. Postembryonic development of <I>L. cinerascens cinerascens</I> and <I>H. lugubris</I> takes place during the cold season (late summer to spring), whereas all other species develop during spring and summer. Blepharicerid larvae and pupae colonize torrential streams, where they adhere to stabile substrata. Standard sampling methods like "kick-sampling" etc. are ineffective collecting techniques, but blepharicerids can be easily sampled from large stones from high velocity areas. <BR/>
All species can be identified as pupae. Larval identification is possible for <I>B. fasciata fasciata, H. lugubris, L. cinerascens</I> s.l. and <I>L. cordata</I>. Larvae of <I>L. brevirostris, L. decipiens</I> and <I>L. vimmeri</I> cannot be separated if they originate from sites where two or three species coexist. Separation between <I>L. cinerascens minor</I> and <I>L. cinerascens cinerascens</I> is usually possible because they only coexist in some very restricted areas and differ substantially in their life-cycle.
Response of climate to solar forcing recorded in a 6000-year δ<SUP>18</SUP>O time-series of Chinese peat cellulose
Previous studies have shown that the oxygen isotope ratio (δ<SUP>18</SUP>O) of plant cellulose can serve as a sensitive proxy indicator of past climate, but its application has mainly been restricted to tree-rings. Here we present a 6000-year high- resolution δ<SUP>18</SUP>O record of peat plant cellulose from northeastern China. The δ<SUP>18</SUP>O Variation is interpreted as reflecting changes in regional surface air temperature. The climate events inferred from the isotope data agree well with archaeological and historic evidence. The record shows a striking correspondence of climate events to nearly all of the apparent solar activity changes characterized by the atmospheric radiocarbon in tree-rings over the past 6000 years. Spectral analysis of the δ<SUP>18</SUP>O record reveals the periodicities of around 86, 93, 101, 110, 127, 132, 140, 155, 207, 245, 311, 590, 820 and 1046 years, which are similar to those detected in the solar excursions. We consider these observations as further evidence for a close relationship between solar activity and climate variations on timescales of decades to centuries. Our results also have implications for distinguishing between natural and anthropogenic contributions to future climate change.
Determination of diffusion coefficients of humic substances by fluorescence correlation spectroscopy: role of solution conditions
Fluorescence correlation spectroscopy (FCS) was used to determine diffusion coefficients (D) of the Suwannee River fulvic and humic acids (SRFA and SRHA) and to measure the effects of pH, ionic strength, Ca, and humic substance (HS) concentration on the value of D. For these HS, average diffusion coefficients were in the range of (2-3) x 10<sup>-10</sup> m<sup>2</sup> s<sup>-1</sup> (corresponding to hydrodynamic diameters of approximately 1.5-2.1 nm). Small, but significant, decreases in the diffusion coefficients were observed with decreasing pH, most likely indicating that a small degree of aggregation (formation of dimers and trimers) was occurring. The effect of ionic strength (up to 100 mM) was either small or insignificant, but, where a change occurred, there was a tendency toward a reduction in the diffusion coefficient with increasing salt concentration. No effect of HS concentration (1-50 mg L<sup>-1</sup>) or hydration time (1-14 days) was observed. There were no observable effects of Ca in comparison to Na, at an ionic strength of 5 mM. For all conditions studied, SRFA had a higher diffusion coefficient than SRHA which is in agreement with literature data on their respective molar masses. Since this is the first application of FCS to HS, the technique was systematically tested for artifacts, in particular photobleaching and the effect of fluorescence excitation wavelength. Despite a small amount of photobleaching due to the intense laser excitation, FCS was found to be suitable for use with fulvic or humic acids.
Growth kinetics of <I>Escherichia coli</I> with galactose and several other sugars in carbon-limited chemostat culture
Kinetic models for microbial growth describe the specific growth rate (µ) as a function of the concentration of the growth-limiting nutrient (s) and a set of parameters. A typical example is the model proposed by Monod, where µ is related to s using substrate affinity (K<SUB>s</SUB>) and the maximum specific growth rate (µ<SUB>max</SUB>). The preferred method to determine such parameters is to grow microorganisms in continuous culture and to measure the concentration of the growth-limiting substrate as a function of the dilution rate. However, owing to the lack of analytical methods to quantify sugars in the microgram per litre range, it has not been possible to investigate the growth kinetics of <I>Escherichia coli</I> in chemostat culture. Using an HPLC method able to determine steady-state concentrations of reducing sugars, we previously have shown that the Monod model adequately describes glucose-limited growth of <I>E. coli</I> ML30. This has not been confirmed for any other sugar. Therefore, we carried out a similar study with galactose and found steady-state concentrations between 18 and 840 µ g.L<SUP>-1</SUP> for dilution rates between 0.2 and 0.8.h<SUP>-1</SUP>, respectively. With these data the parameters of several models giving the specific growth rate as a function of the substrate concentration were estimated by nonlinear parameter estimation, and subsequently, the models were evaluated statistically. From all equations tested, the Monod model described the data best. The parameters for galactose utilisation were µ<SUB>max</SUB> = 0.75.h<SUP>-1</SUP> and K<SUB>s</SUB> = 67 µ g.L<SUP>-1</SUP>. The results indicated that accurate K<SUB>s</SUB> values can be estimated from a limited set of steady-state data when employing µ<SUB>max</SUB> measured during balanced growth in batch culture. This simplified procedure was applied for maltose, ribose, and fructose. For growth of <I>E. coli</I> with these sugars, µ<SUB>max</SUB> and K<SUB>s</SUB> were for maltose 0.87.h<SUP>-1</SUP>, 100 µ g.L<SUP>-1</SUP>; for ribose 0.57.h<SUP>-1</SUP>, 132 µ g.L<SUP>-1</SUP>, and for fructose 0.70.h<SUP>-1</SUP>, 125 µ g.L<SUP>-1</SUP>.
Dynamics of mixed bottom boundary layers and its implications for diapycnal transport in a stratified, natural water basin
Here we report on two field experiments from Lake Alpnach (surface area: 4.8 km<sup>2</sup>; maximum depth: 34 m) that were designed to study the process of boundary mixing and to estimate its efficiency, the ratio between the turbulent kinetic energy converted into potential energy and dissipated into heat, for diapycnal tracer transport. Lake Alpnach is particularly suited for this purpose because it is known from earlier experiments that (1) its currents follow a regular oscillatory pattern, associated with basin-wide standing internal waves (seiches, period ∼0.5 days and 1 day, respectively), and (2) diapycnal tracer transport is mainly caused by boundary mixing. During one of the experiments reported here, strong seiches were excited regularly and damped on a timescale of the order of 3 days; during the other experiment seiching motion was comparably weak. If seiching is excited regularly, we find a persistent well-mixed bottom layer of 4–5 m height at the deepest part of the lake. In the absence of regular seiching the layer disappears within 10–20 days. On the sloping bottom boundaries the well-mixed layers (1) are of much more transient nature, (2) exhibit different thermal structure, and (3) decrease in thickness toward shallower depth inversely proportionally to the stability at the same depth in the lake interior. Their reduced thickness is possibly the result of repeatedly occurring intrusions of boundary mixed water masses that are observed to extend horizontally ∼100–200 m into the lake interior. As a consequence of repeated generation of intrusions, mixing on the sloping boundaries is expected to be considerably more efficient compared to mixing over flat bottom boundaries. The observed mixing efficiency, the ratio of the rate of change of potential energy below depth z caused by turbulence to the energy loss by bottom friction below depth z, increases indeed from 0.01±0.01 in the deepest well-mixed layers to 0.15±0.04 in the upper pycnocline.
North Atlantic palaeointensity stack since 75 ka (NAPIS-75) and the duration of the Laschamp event
Six relative palaeointensity records from the north Atlantic Ocean were stacked together to produce a new record for the last 75 kyr (NAPIS-75). Five of these records have been previously correlated at millennial scale and placed on the GISP2 age scale, the sixth record was tied to the others using magnetic susceptibility. From 75 ka the field strength exhibits some oscillations, with a first minimum <I>ca.</I> 65 ka, followed by a progressive increase to a broad maximum centred at <I>ca.</I> 48 ka. There is then a well-marked low at 40 ka, corresponding to the directional anomaly of the Laschamp event. Another intensity low, observed at <I>ca.</I> 34 ka, corresponds in age to the Mono Lake event. After a high at 33 ka and two lows at 30 and 24 ka with a broad maximum between, the field strength seems to slowly increase to the upper limit of the studied interval. In the 10- 20 kyr interval some differences exist between individual records, and fine-scale details are not always resolved. In the 20 75 kyr interval, on the other hand, well-resolved millennial-scale features are superimposed to the broader trends. The duration of the Laschamp event, which is recorded directionally in five cores, appears to be about 1500 years, consistent with a recent suggestion on the origin of geomagnetic excursions.
Environmental engineering education at the Swiss Federal Institute of Technology in Zürich
A revised ten-semester curriculum in environmental engineering was introduced at the Swiss Federal Institute of Technology in 1998 which is based on 10 years of experience with a previous less focused curriculum. The scope of the new curriculum is rather broad and includes sanitary engineering, water resources management, soil pollution control and resource and waste management. Air pollution is not fully developed yet. Based on broad basic studies (first four semesters) the professional studies (semesters 5 to 9) require the students to choose two out of four possible areas of specialization. These studies are followed in credit groups which combine advanced courses and extensive project work designed to reach scientific depth in an exemplary fashion. There is an exchange of teaching units between Environmental Engineering and Environmental Natural Sciences but the two curricula are quite different and lead to significantly different professional profiles.
Light within algal cultures; Implications from light intensities within a lens
Continuous, homogeneous lighting conditions are fiction. The form of the culture vessel, as well as the light source and the culture density, influence the light field within a culture. What actually happens is due to the alteration of light within an optical lens. This also applies to the usual exposition devices used for studying primary production. In the worst case, with a point source and without any precautions, as much as 10% of the lens (vessel) volume is shaded by optical effects, whereas light is concentrated along a focus within the lens. Stirring of algal cultures introduces time, so focusing is transformed into flickering. A solution is to immerse the vessel in a water bath of rectangular shape.
Hormonaktive Stoffe in Gewässern: Auch eine Gefahr fürs Trinkwasser?
Hormone active compounds («endocrine disruptors») have been detected in wastewater, surface water but also in some drinking water samples in Germany, Israel, U.K. and the USA. Mainly natural and synthetic steroid hormones, but also some weakly estrogenic chemicals (nonylphenol, bisphenol A, DDT etc.) have been found. These compounds may have importance as they may negatively influence gonadal development, fertility and reproduction. Estrogenic effects have been documented in various studies in fish exposed to waste-water and contaminated freshwater and estuaries, but effects on humans remain elusive. In this overview environmental concentrations are given and effects on wildlife described. Effects are mainly associated with contaminated wastewater. Only little is known about residues of hormone active compounds in drinking water. However, a hazard seems rather unlikely.
Concentrations of the antifouling compound Irgarol 1051 and of organotins in water and sediments of German North and Baltic Sea marinas
A survey of 2-methylthio-4-<em>tert</em>-butylamino-6-cyclopropylamino-<em>s</em>-triazine (Irgarol 1051) and organotins, used as biocides in antifouling paints, was carried out in German marinas of the North and Baltic Sea. Highest levels of the <em>s</em>-triazine herbicide were found in Baltic Sea marinas where water exchange was restricted (water up to 440 ng/l; sediment about 220 ng/g dry weight), while in the North Sea marinas with higher water exchange rates lower concentrations were encountered (water 11–170 ng/l; sediment 3–25 ng/g dry weight). Although the application of the antifouling agent tributyltin (TBT) was banned for small vessels (<25 m) in Germany and other countries in 1989, significant levels of TBT between 570 to 17 000 ng/g dry weight, lower concentrations of triphenyltin (TPT) of up to 3800 ng/g as well as the TBT degradation products dibutyltin and monobutyltin occurred in sediment samples of the Baltic Sea marinas. In the North Sea marinas with stronger water exchange the TBT sediment levels ranged from about 80 to 720 ng/g dry weight. This study shows parallel contamination patterns of Irgarol and organotins in North and Baltic Sea marinas and the persistence of several organotins in these sediments about eight years after the ban. A seasonal dependence of Irgarol 1051 concentrations was found both in the water and sediment samples, with maxima during the periods March–May/July–September, while during the winter period December–January low values were encountered though measurable amounts remained in the sediment. A mean value of the partitioning coefficient log <em>K</em><sub>OC</sub>=3.3±0.72 was inferred from the water and sediment concentrations determined in seven Baltic Sea marinas.
Behavior of aliphatic alcohol polyethoxylates and their metabolites under standardized aerobic biodegradation conditions
Aerobic biodegradation of aliphatic alcohol polyethoxylates (AEs) was tested under screening test conditions (Organization for Economic Cooperation and Development [OECD] 301E protocol) using recently developed analytic methodologies for the specific determination of AEs and their neutral (polyethylene glycols [PEGs]) and carboxylic (carboxylated PEGs and AEs) aerobic metabolites. Biodegradation screening tests were performed under the same conditions on three typical, commercial AE blends and an individual, linear AE ethoxymer. The linear and monobranched AEs underwent a fast primary biodegradation, whereas the multibranched AEs underwent a slower biodegradation. Based on the formation and oligomeric distribution of PEGs and the lack of detection of other biointermediates before the formation of PEGs, the central cleavage of the AE molecule appeared to be the mechanism for primary biodegradation of the linear and monobranched AEs in the tested commercial blends. As a result, the shorter AE ethoxymers biodegraded faster than the longer ones. No PEGs were detected during biodegradation of the multibranched AEs. In addition, PEGs biodegraded more slowly than the parent AEs and were removed by hydrolysis, thus leading to shorter PEG oligomers, and by oxidative hydrolysis, thus forming carboxylated PEGs.
Photolytic transformation of organic pollutants on soil surfaces - an experimental approach
Photolysis on soil surfaces is an important degradation pathway for many agro chemicals. Although the investigation of photochemical pesticide transformation on soil surfaces is required by registration authorities, knowledge of the relevant processes is limited. The quantification of photolysis on soil surfaces is of higher complexity than it is in solutions. In experiments, carried out on soil layers, the observed overall degradation rate is nor only determined by photolysis itself but is also a function of the layer thickness and in many cases of transport processes. In this article we describe a theoretical framework to understand combined effects of these different processes, and we present an experimental setup that allows a separate quantification of actual photolysis and diffusive transport processes. For the two compounds <I>p</I>-nitroanisole and trifluralin we performed experiments on kaolinite layers of variable thickness and evaluated the results using a mathematical model. Thus, we were able to determine the actual photolysis rate constants which are independent of layer thickness and transport kinetics. The proposed theoretical and experimental concept contributes to the development of a standardized laboratory method.
Atmospheric water: transformation of ozone into OH-radicals by sensitized photoreactions or black carbon
In droplets of clouds and fog the transformation of ozone (O<sub>3</sub>) to secondary oxidants, such as hydroxyl radicals (OH<sup><B>·</B></sup>), is an important process. As demonstrated by experiments on model solutions, chromophoric compounds, represented by ubiquitous iron(III)-oxalato complexes, act as primary photoreactants. Upon photolysis these compounds produce peroxide anion (O<sub>2</sub><sup><B>·</B>-</sup>). O<sub>2</sub><sup><B>·</B>-</sup> reacts with aqueous ozone. This transforms aqueous O<sub>3</sub> into OH<sup><B>·</B></sup>. As estimates show, the quick equilibration with the gas-phase maintains aqueous O<sub>3</sub> in droplets of clouds at about 1 nM. But already in the presence of ubiquitous traces of dissolved copper at 1 nM, O<sub>2</sub><sup><B>·</B>-</sup> rather reduces copper(II) to copper(I) than reacts with ozone. Therefore, it is rather an indirect loop in which Cu(I) acts as a further chain carrier to convert O<sub>3</sub> to OH<sup><B>·</B></sup>. Ubiquitous aqueous formate and formaldehyde then convert a fraction of non-selective OH<sup><B>·</B></sup> to highly selective HO<sub>2</sub><sup><B>·</B></sup> and O<sub>2</sub><sup><B>·</B>-</sup>, i.e. to O<sub>2</sub>(-I). Either directly or indirectly this O<sub>2</sub>(-I) reacts with further O<sub>3</sub> to produce further OH<sup><B>·</B></sup>. However, ubiquitous acetate and some other types of solutes, such as bisulfite, scavenge OH<sup><B>·</B></sup> without recycling O<sub>2</sub>(-I). Experimental calibrations on model solutions showed that acetate limits the kinetic length of the O<sub>3</sub> converting chain reaction just in proportion to its concentration relative to that of formate and formaldehyde. As demonstrated by further experiments, a similar aqueous O<sub>2</sub>(-I)-O<sub>3</sub>-OH<sup><B>·</B></sup> radical-type chain reaction can also be initiated when some aqueous O<sub>3</sub> reacts on black carbon particles. Black carbon was thereby studied as a surrogate for soot. Within cloud droplets the sum of all these O<sub>3</sub> promoted aqueous-phase radical-type chain reactions increases the flux of aqueous-phase OH<sup><B>·</B></sup> and its oxidation processes.
Simultaneous quantification of acetanilide herbicides and their oxanilic and sulfonic acid metabolites in natural waters
This paper describes a procedure for simultaneous enrichment, separation, and quantification of acetanilide herbicides and their major ionic oxanilic acid (OXA) and ethanesulfonic acid (ESA) metabolites in groundwater and surface water using Carbopack B as a solid-phase extraction (SPE) material. The analytes adsorbed on Carbopack B were eluted selectively from the solid phase in three fractions containing the parent compounds (PCs), their OXA metabolites, and their ESA metabolites, respectively. The complete separation of the three compound classes allowed the analysis of the neutral PCs (acetochlor, alachlor, and metolachlor) and their methylated OXA metabolites by gas chromatography/mass spectrometry, The ESA compounds were analyzed by high-performance liquid chromatography with UV detection. The use of Carbopack B resulted in good recoveries of the polar metabolites even from large sample volumes (1 L). Absolute recoveries from spiked surface and groundwater samples ranged between 76 and 100% for the PCs, between 41 and 91% for the OXAs, and between 47 and 96% for the ESAs. The maximum standard deviation of the absolute recoveries was 12%, The method detection limits are between 1 and 8 ng/L for the PCs, between 1 and 7 ng/L for the OXAs, and between 10 and 90 ng/L for the ESAs.
Oxidation of phenols by triplet aromatic ketones in aqueous solution
Aromatic ketones efficiently mediate the photo-oxidative degradation of phenols in aerated aqueous solution, a process likely to be relevant in sunlit natural waters. Absolute bimolecular rate constants for the quenching of three model ketone triplets by nine phenols bearing various substituents, from electron-donating alkyl and alkoxy groups to the electron-withdrawing cyano group, were measured by nanosecond laser flash photolysis. Triplet benzophenone (BP) is quenched at nearly diffusion-controlled rates (2.6−5.6 × 10<sup>9</sup> M<sup>-1</sup> s<sup>-1</sup>). Triplet state quenching of 3‘-methoxyacetophenone (3‘-MAP) and 2-acetonaphthone (2-AN) by the same set of phenols occurs more selectively, with rate constants spanning a range of 1 and more than 2 orders of magnitude, respectively. Quenching rate constants obey a Rehm−Weller relationship to the free energy of electron transfer from the phenol to the ketone triplet. By comparison of the quenching constants with overall photo-oxidation rates obtained by stationary irradiation in air-saturated aqueous solution, phenols bearing electron-donating substituents were found to be depleted with quantum yields generally exceeding 0.5, whereas parent phenol and, presumably, acceptor-substituded phenols are transformed at only ∼0.1 efficiency. The present quenching data were used to interpret the efficiency of photosensitized oxidation of phenols by dissolved natural organic matter (DNOM), an important sunlight absorber present in surface waters. The effective reduction potential of reactive excited triplet states in DNOM was estimated to be at least 1.36 V vs NHE.
Degradation kinetics of atrazine and its degradation products with ozone and OH radicals: a predictive tool for drinking water treatment
The present study investigates the degradation of atrazine (2- chloro-4-(ethylamino)-6-isopropylamino-s-triazine) by ozone and OH radicals during ozonation and advanced oxidation processes, with the identification of the main degradation products. Besides the dealkylated and amide degradation products(6-amino- 2-chloro-4-isopropylamino-s-triazine, 6-amino-2-chloro-4- (ethylamino)-s-triazine, 4-acetamido-2-chloro-6-isopropylamino- s-triazine, 4-acetamido-6-amino-2-chloro-s-triazine, and chlorodiamino-striazine), two new degradation products with an imine group were identified (2-chloro-4-ethylimino-6- isopropylamino-s-triazine and 6-amino-2-chloro-4-ethylimino-s- triazine). The contribution of the different pathways (direct ozone and OH radical reaction) to the overall degradation process has been quantified, and the rate constants of the reactions of atrazine and its main degradation products with both oxidants have been measured. The ethyl group is more reactive than the isopropyl group (i.e. 19 times during ozonation and four times during OH radical attack). The ethyl group reacts in higher proportion through oxidation to acetamide or imine derivates than to dealkylation. In contrast, the isopropyl group reacts mainly through dealkylation to the free amino group. Acetamido and imino groups a re found to be resistant to chemical oxidation. These reactivities were corroborated by the measured values of the rate constants with both oxidants. A combination of product distribution and the kinetic parameters together with ozone and OH radical concentrations allowed us to calculate the evolution of the concentration of the degradation products for a given ozonation process.
HbpR, a new member of the XylR/DmpR subclass within the NtrC family of bacterial transcriptional activators, regulates expression of 2-hydroxybiphenyl metabolism in <I>Pseudomonas azelaica</I> HBP1
The regulation of 2-hydroxybiphenyl and 2,2′-dihydroxybiphenyl degradation in <em>Pseudomonas azelaica</em> is mediated by the regulatory gene, <em>hbpR</em>. The <em>hbpR</em> gene encodes a 63-kDa protein belonging to the NtrC family of prokaryotic transcriptional activators and having the highest homology to members of the XylR/DmpR subclass. Disruption of the <em>hbpR</em> gene in <em>P. azelaica</em> and complementation in <em>trans</em> showed that the HbpR protein was the key regulator for 2-hydroxybiphenyl metabolism. Induction experiments with <em>P. azelaica</em> and <em>Escherichia coli</em> containing<em>luxAB</em>-based transcriptional fusions revealed that HbpR activates transcription from a promoter (P<sub><em>hbpC</em></sub>) in front of the first gene for 2-hydroxybiphenyl degradation, <em>hbpC</em>, and that 2-hydroxybiphenyl itself is the direct effector for HbpR-mediated activation. Of several compounds tested, only the pathway substrates 2-hydroxybiphenyl and 2,2′-dihydroxybiphenyl and structural analogs like 2-aminobiphenyl and 2-hydroxybiphenylmethane were effectors for HbpR activation. HbpR is therefore, to our knowledge, the first regulator of the XylR/DmpR class that recognizes biaromatic but not monoaromatic structures. Analysis of a spontaneously occurring mutant, <em>P. azelaica</em> HBP1 Prp, which can grow with the non-wild-type effector 2-propylphenol, revealed a single mutation in the <em>hbpR</em> gene (T613C) leading to a Trp→Arg substitution at amino acid residue 205. <em>P. azelaica</em> HBP1 derivative strains without a functional <em>hbpR</em> gene constitutively expressed the genes for 2-hydroxybiphenyl degradation when complemented in <em>trans</em> with the <em>hbpR</em>-T613C gene. This suggests the importance of this residue, which is conserved among all members of the XylR/DmpR subclass, for interdomain repression.
The Sun is by far the most important driving force of the climate system. However, only little is known how variable this force is acting on different time scales ranging from minutes to millennia and how the climate system reacts to changes in this forcing. Changes of the global insolation can be related to the nuclear fusion in the core of the Sun, the energy transport through the radiative zone and the convection zone, the emission of radiation from the photosphere, and the distance between Sun and Earth. Satellite based measurements over two decades show a clear correlation between the solar irradiance and the 11-year sunspot cycle. The irradiance amplitude is about 0.1%. This is too small to affect significantly the climate. However, there are indications that, on longer time scales, solar variability coluld be much larger. The analysis of cosmogenic nuclides stored in natural archives provides a means to extend our knowledge of solar variability over much longer time periods.<br/>
The response of the climate system to solar forcing depends not only on the amount of radiation, but also on its spectral composition (e.g. UV contribution), seasonal distribution over the globe, and feedback mechanisms connected with clouds, water vapour, ice cover, atmospheric and oceanic transport and other terrestrial processes. It is therefore difficult to establish a quantitative relationship between observed climate changes in the past and reconstructed solar variability. However, there is growing evidence that periods of low solar activity (so called minima) coincide with advances of glaciers, changes in lake levels, and sudden changes of climatic conditions. These findings point to an active role of the Sun in past climate changes beside other geophysical factors, internal variability of the climate system, and greenhouse gases. In fact a non-linear regression model to separate natural and anthropogenic forcing since 1850 is consistent with a solar contribution of about 40% to the global warming during the last 140 years.
A discrete, allometric approach to the modeling of ecosystem dynamics
This work focuses on a special type of generic ecosystem model that allows for the investigation of the dynamics of ecological networks. The emphasis lies on patterns that arise from within the system and their dependency on environmental factors, and the relationship between network structure. organization and performance. The model which has been built to simulate these patterns is a highly abstracted representation of nutrient flows in a food web. It is based on allometric relationships for the physiological rates and the diversity of time scales present in the system. The functional response of predator to prey abundance is defined as a two dimensional extension of a Holling type III function. A comparison of the most commonly used predation functions reveals that neither prey- nor ratio-dependent functions can account for the different responses for very high/very low predator and prey densities. Only by employing predator and prey dependence can unrealistic behavior, as displayed by one-dimensional functions, be avoided. Finally, we show an example of the model's capability to make statements about general rules connecting ecosystem structure, organization and performance. It is found that a system's nutrient efficiency is correlated both to its functional diversity and to its temporal organization of nutrient hows. In a large number of differently structured food webs and under varying environmental conditions, the diversity of temporal and functional niches enhances the efficiency of nutrient utilization.
A conceptual model for alpine proglacial river channel evolution under changing climatic conditions
This paper integrates concepts derived from the literature to focus upon interactions between riparian vegetation and river channel dynamics in alpine glacier basins. Discussion of the nature and variability of discharge and sediment regimes of alpine glacier-fed rivers; downstream variations in the physical character of the river channel and corridor; consequent downstream variations in lateral processes; and regional variations in alpine glacier dynamics, lead to the proposal of a conceptual model of proglacial river channel–riparian vegetation interactions under changing climatic conditions.
The oxidative stress-sensitive <I>yap1</I> null strain of <I>Saccharomyces cerevisiae</I> becomes resistant due to increased carotenoid levels upon the introduction of the <I>Chlamydomonas reinhardtii</I> cDNA, coding for the 60S ribosomal protein L10a
The <em>Saccharomyces cerevisiae yap1</em> null strain was transformed with a <em>Chlamydomonas reinhardtii</em> cDNA expression library. A 688-bp cDNA fragment, coding for the 60S ribosomal protein L10a (RPL10a), restored the capacity of the <em>S. cerevisiae yap1</em> null strain to resist oxidative stress. The <em>rpl10a</em> gene is a single-copy gene in <em>C. reinhardtii</em> and encodes a constitutively produced 1.35-kb mRNA. The deduced 214-residue amino acid sequence was highly related with RPL10a proteins from eukarya (between 46.1 and 63.7% identity) and archaea (between 24.5 and 29.2% identity). Resistant transformants were pink, due to increased carotenoid levels, with the same chemical structure as torularhodin, the main carotenoid of the pink yeast <em>Rhodotorula mucilaginosa.</em> The pink transformants showed high resistance levels against H<sub>2</sub>O<sub>2</sub>, paraquat, menadione, and UV light. Partial inhibition of the carotenoid synthesis by diphenylamine reduced the resistance levels, demonstrating the role of excess carotenoid synthesis in the resistance mechanism.
Cytochrome P4501A induction and porphyrin accumulation in PLHC-1 fish cells exposed to sediment and oil shale extracts
The present study describes the use of a fish hepatoma cell line (PLHC-1) in monitoring the biological effects of sediments collected from recipient waters of the oil shale industry. Sampling sites were located in River Purtse and River Kohtla in northeast Estonia. The effects of pure oil shale on the PLHC-1 cells were also studied. The cells were exposed to <i>n</i>-hexane–extracted samples in 48-well plates for 24 h, and 7-ethoxyresorufin <i>O</i>-deethylase (EROD) activity, total protein, and porphyrin content were measured in the exposed cells. Polycyclic aromatic hydrocarbon (PAH) contents in the samples were measured by high-performance liquid chromatography (HPLC). All the sediment and oil shale samples induced CYP1A activity and led to porphyrin accumulation in the cells. The most potent inducers were the sediments collected near the oil shale processing plants (site Lüganuse in River Purtse and Kohtla in River Kohtla), as well as those at the most downstream site in River Purtse (Purtse). These samples possessed high total PAH contents, ranging from 4,270 to nearly 150,000 μg/kg dry sediment. The presence of other lipophilic organic contaminants in the samples was not determined in this study. Both EROD activity and porphyrin content exhibited biphasic induction curves, and the ED<sub>50</sub><sup>1</sup> values for EROD activity were lower than the ED<sub>50</sub>s for porphyrin content. 2,3,7,8-Tetrachlorodibenzo-<i>p</i>-dioxin induction equivalents (TCDD-EQs) calculated from EROD induction potencies correlated well with total PAHs (<i>r</i><sup>2</sup> = 0.827 and p = 0.003 for log-transformed data) and also with individual PAHs. TCDD-EQs for porphyrin content did not correlate significantly with total PAHs (log-log r<sup>2</sup> = 0.785, <i>p</i> = 0.116). The biological potency and PAH contamination of the samples showed the same rank order, except at Lüganuse, where sediment extracts induced CYP1A and porphyrins more than could have been expected based on PAH contents. Bioassay-derived induction EQs (normalized to dibenz(<i>a</i>,<i>h</i>)anthracene) were 20- to 3,200-fold greater than EQs calculated from the concentrations of five PAHs, suggesting important contributions from other compounds or nonadditive effects. The PLHC-1 cells proved to be a sensitive bioanalytical tool for sediments contaminated with PAH-type pollutants in the oil shale processing area. We suggest further use of this bioassay in screening and monitoring waters with similar background of pollution as in northeast Estonia.
The use of lake water as drinking water resource involves a multistage treatment procedure. Food-related laws and regulations, in particular the food ordinance and the hygiene ordinance, require the identification and assessment of health risks, and thus the assessment of critical treatment and processing steps by the Swiss waterworks. Ozonation is used as an example to show how the oxidising and disinfecting effect can be estimated in an ozonation reactor.
Propagation of waves and dissolved compounds in sewer
The phenomenon of the surface wave propagating faster than the fluid. that induced it is studied experimentally and numerically. The study focuses on the importance of the wave phenomenon for the urban hydrology system, where it can determine the impact of combined sewer overflows on the environment and the operation of a novel urine (anthropogenic nutrient solution) separation system. Urine would be stored decentrally and released during the night hours so that a wave would form in the sewer. The full-scale experiments were carried out in a 2-km section of a main sewer. The wave was induced with the aid of fire hydrant water traced by salt. Five measurements and sampling stations were operated downstream through which the transport of both fluid and compounds were analyzed. Numerical simulations of the results are discussed focusing on the reliability of friction approaches and dispersion prediction. Although difficult to model with commercial tools, it was shown that the wave phenomenon has no adverse effects on the practicability of the urine separation system, but can lead to the release of undiluted wastewater during a rain event.
Different expression patterns of heat shock proteins hsp 60 and hsp 70 in zebra mussels (<I>Dreissena polymorpha</I>) exposed to copper and tributyltin
To investigate the dose–response relationship of the expression of heat shock proteins hsp 60 and hsp 70 following exposure to environmentally-relevant contaminants, zebra mussels (<I>Dreissena polymorpha</I>) were exposed to sublethal concentrations of copper and tributyltin (TBT). Mussels were exposed to Cu (0–500 μg/l) or TBT (0–75 μg/l) for 24 h. Hsp 60 and hsp 70 expression relative to the controls was analyzed by western blotting and densitometry. Contaminant concentrations in the exposure medium and mussel tissues were measured by atomic absorption spectroscopy (AAS) or high resolution gas chromatography with flame photometric detection (HRGC-FPD) for Cu and TBT, respectively. Following copper exposure, hsp 60 showed a biphasic expression pattern, with a maximal expression of three times control levels at 22 μg Cu/g dry wt., while hsp 70 concentrations reached a plateau of approximately 2.5 times control levels after crossing an induction threshold at tissue concentrations of less than 29 μg Cu/g dry wt. In contrast, concentrations of both hsp 60 and hsp 70 were increased to approximately 2.5–3 times control levels in TBT-exposed mussels at all tested doses. The results of this study demonstrate that the nature of the dose–response curves depend on both the form of stress protein investigated (hsp 60 or hsp 70) and on the contaminant. The implications for the use of hsp 60 and hsp 70 as biomarkers in ecotoxicological research are discussed.
A contaminated site investigation: comparison of information gained from geophysical measurements and hydrogeological modeling
The investigation of contaminated sites is usually a long and expensive process. It is therefore desirable to use a combination of methodologies in an integrative approach that can reduce redundant information gathering. The objective of this study was to examine the usefulness of 2 non-intrusive exploration techniques in a contaminated site investigation. Borehole positioning based on geophysical measurements was compared to positioning based on the Bayesian expert system for flow-field modeling. The goal set at the field site was the assessment of the type and load of contaminants transported from the landfill site to the adjacent aquifer and the extent of leachate plumes within the groundwater. The two methods made different demands on information gathering and were found to be complementary. The geophysical approach focused attention on the waste compartments at the site and on mixing plumes in the adjacent aquifer but could not, without prior information, provided information on the flow field. The Bayesian approach to flow-field modeling determined areas of greatest model uncertainty at the model boundaries. The model highlighted areas of greatest uncertainty that might otherwise have been overlooked and provided information on the most likely mean direction of the leachate plumes, it was concluded that both methods contribute to a site investigation and should be used before additional drilling is carried out.
Durch ein geplantes Projekt zur Verminderung der Stoffbelastung aus der Landwirtschaft (Blum et al., 2003) kann die Zufuhr von Gesamtphosphor in den Zugersee um ca. 2 t a-1 reduziert werden. Es soll im Folgenden bestimmt werden, wie der Phosphorinhalt des Zugersees auf diese Änderung in der Zufuhr reagiert. Dazu werden die Phosphorkonzentrationen im Stationärzustand [mg-P m-3] berechnet, sowie die Zeitskala, innerhalb welcher der Stationärzustand erreicht wird. Es werden die folgenden Szenarien betrachtet: Derzeitige Zufuhr (Gesamtphosphor ca. 15 t a-1, gelöster Phosphor ca. 8.1 t a-1; einschliesslich Niederschlag). Reduzierte Zufuhr aufgrund des geplanten Phosphorprojektes (Gesamtphosphor ca. 13 t a-1, gelöster Phosphor ca. 6.6 t a-1). Zufuhr reduziert um ein Drittel (Gesamtphosphor ca. 10 t a-1, gelöster Phosphor ca. 5.4 t a-1).
Einfluss von Aufweitungen auf das Temperaturregime der Thur
Um Land zu gewinnen und die Thurebene vor Überschwemmungen zu schützen, wurde im 19. Jahrhundert eine tief greifende Korrektion am Mittel- und Unterlauf der Thur durchgeführt. Der Fluss wurde abgesenkt und erhielt ein begradigtes Flussbett. Durch den monotonen Flussverlauf hat die Thur in der Folge ihre ökologische Vielfalt und landschaftliche Eigenart weitgehend verloren. Mehrere Hochwasserereignisse im 20. Jahrhundert (1910, 1965, 1966, 1974, 1977, 1978 und 1999) mit Dammbrüchen und zum Teil grossen Überschwemmungen haben gezeigt, dass der Hochwasserschutz an der Thur Lücken aufweist. Nach dem Ereignis von 1978 wurde in den Kantonen Thurgau und Zürich mit Planungen für eine weitere Thurkorrektion begonnen. Seit 1987 sind im Kanton Zürich, seit 1993 im Kanton Thurgau, Bauarbeiten zur Verbesserung des Hochwasserschutzes im Gange. Die kantonalen Behörden wollen in diesen Projekten den Hochwasserschutz möglichst ökologisch verträglich gestalten. Gemäss den modernen Hochwasserschutz-Konzepten werden dazu die Dämme verstärkt, gleichzeitig aber auch Überflutungs- und Rückhaltezonen geschaffen, womit eine Revitalisierung angestrebt wird.
Phosphorhaushalt des Greifensees: Belastung und seeinterne Umsätze. Zusammenhang zwischen Belastung und Seezustand
Der Greifensee, ein eutropher Mittellandsee in dicht besiedeltem Umland, ist noch immer einer hohen Nährstoffbelastung ausgesetzt. Trotz grosser Verbesserungen bei Kanalisierung und Abwasserreinigung liegt die Konzentration an Phosphor weit über dem Zielwert eines mesotrophen Zustands. Als Folge des intensiven Algenwachstums wird der Sauerstoff im Tiefenwasser des Greifensees im Verlauf des Sommers komplett aufgebraucht. Gemäss Gewässerschutzverordnung sind die Kantone verpflichtet, Zuströmbereiche zum Schutz der Wasserqualität oberirdischer Gewässer zu bezeichnen, wenn das Wasser durch Nährstoffe verunreinigt ist. Das Amt für Abfall, Wasser, Energie und Luft des Kantons Zürich (AWEL) möchte daher im Einzugsgebiet des Greifensees die Ursachen sowie das Ausmass der Belastung ermitteln und die Wirksamkeit möglicher Sanierungsmassnahmen bewerten. Als Teil dieses Projekts wurde die EAWAG beauftragt, den Einfluss der Phosphorbelastung auf den Greifensee zu untersuchen.
Ressourcenwirtschaftliche Bedeutung der Zementindustrie in der Schweiz - eine langzeitliche Betrachtung. Bericht zu Handen des Kt. Aargaus, 2002 mit Korrekturen Seiten 9 bis 11 von 2006
Es ist davon auszugehen, dass in der Schweiz auch im 21. Jahrhundert vorwiegend mit Beton gebaut wird. Das Bindemittel Zement behält damit seine Bedeutung. Das im Bauwerk Schweiz gespeicherte Lager ist inzwischen so gross, dass alleine der Unterhalt Zementnachschub in der Grössenordnung der heutigen Schweizer Produktion erfordert. Zudem sind energiesparsamere Ersatzneubauten auch aus ökologischen Erwägungen erstrebenswert. Zement geht beim Recycling als Kies/Sand-Ersatz in den Beton. D.h. selbst bei forciertem Recycling muss neuer Zement nachgeschoben werden. Die derzeit bewilligten Reserven für Kalk/Mergel reichen schweizweit für ca. 40 Jahre. Die frühzeitige Evaluation neuer Abbaustandorte ist damit auch von gesamtvolkswirtschaftlicher Dringlichkeit. Bei Berücksichtigung des gesamten Lebenspfades des Zementes zeigt sich, dass zumindest rein energetische Erwägungen es durchaus erlauben würden, sich bei der Standortwahl für den Abbau mehr Flexibilität bezüglich Transportdistanzen und Abbautechnik offenzuhalten. Die Zementindustrie ist in ihrer Rolle als Technologieträger und in zunehmendem Mass als Entsorger von grosser nationaler Bedeutung. Eine Verlagerung der Zementproduktion ins Ausland wäre deshalb ein grosser Verlust. In Anbetracht des hohen Ressourcenpotenzials im bestehenden Siedlungsraum Schweiz sind Symbiosen, wie sie bei der Koppelung von Ver- und Entsorgung in der Zementindustrie am Entstehen sind, eine grosse Chance für die Zukunft.
Kolmation. Methoden zur Erkennung und Bewertung. Schlussbericht
Die Sohle von Fliessgewässern wird vorwiegend durch fluviale Ablagerungen aus kiesigem bis schottrigem Material aufgebaut. Der Abfluss transportiert unterschiedliche Feststoffmengen in Schweb oder als Geschiebe gerinneabwärts. Dringt Oberflächenwasser in die poröse Gewässersohle, so werden die Wasserinhaltstoffe (Schwebstoffe) ausfiltriert. Dieser Ablagerungsprozess findet massgebend in der obersten Schicht oder bereits auf der Gewässersohle statt. Die Ablagerung der Feinpartikel im Porenraum der Sohle wird als innere Kolmation und diejenige auf der Gewässersohle als äussere Kolmation bezeichnet. Durch die innere Kolmation wird die Sohle verdichtet, der Porenraum verkleinert, die Durchlässigkeit reduziert und damit die Sauerstoffzufuhr verringert. Die äussere Kolmation führt zu einem instabilen Substrat und zu einer Abnahme der Durchlässigkeit mit entsprechend verringerter Sauerstoffzufuhr.
Phosphorbilanz von Sempachersee und Baldeggersee. Teil I: Eintrag durch Zuflüsse
Der Phosphorinhalt des Baldeggersees und des Sempachersees nahm in den vergangenen 20 Jahren deutlich ab. Trotzdem liegt er für beide Seen noch immer über dem Zielwert eines mesotrophen Zustandes. Seit den 1970er-Jahren konnte vor allem der Eintrag von Phosphor aus häuslichen Abwässern reduziert werden. Andererseits wurde die landwirtschaftliche Nutzung intensiviert. Deshalb macht die Abschwemmung aus landwirtschaftlich genutzten Böden heute den Grossteil der Phosphorfracht in die beiden Seen aus. Auf Bundes- und Kantonsebene wurden verschiedene Massnahmen ergriffen, um eine gewässerschonende Bodenbewirtschaftung zu fördern (siehe z. B. Kanton Luzern, 2000). Die Auswirkung solcher Massnahmen auf den Phosphoreintrag und damit auf den Phosphorhaushalt des Sees ist jedoch nicht direkt erkennbar: Einerseits wirken die Böden als Reservoir und reagieren nur langsam auf eine Reduktion des Düngereintrags (Gächter und Müller, 1999). Andererseits werden Nährstoffe vor allem bei Hochwasserereignissen abgeschwemmt (Gächter et al. 1996), weshalb der jährliche Phosphoreintrag stark vom Niederschlag abhängt und somit die zeitliche Entwicklung nur schwer zu erkennen ist. Aus diesen Gründen beauftragte das Amt für Umweltschutz des Kantons Luzern (AfU LU) die Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz (EAWAG), Überlegungen zur zeitlichen Entwicklung der Fracht anzustellen und Möglichkeiten aufzuzeigen, wie Fehler in den Zuflussdaten reduzieren werden können. Dabei sollten die folgenden Fragen beantwortet werden: Lassen sich in den seit 1986 gemessenen Phosphoreinträgen zeitliche Trends erken-nen? Über welchen Zeitraum müssen die Daten betrachtet werden, um einen mass-nahmenbezogenen Trend zu sehen? Wie können die mit den Daten verbundenen Fehler reduziert werden, und welcher Aufwand ist damit verbunden? Kann zwischen Variationen des Abflusses und Variationen des Abschwemmens un-terschieden werden? Kann die Abnahme des Seeinhalts des Phosphors im letzten Jahrzehnt mit Änderungen der C-Q-Beziehungen belegt und erklärt werden? Zur Beantwortung dieser Fragen werden im Kapitel 2 dieses Berichts die Ansätze zur Bestimmung der Phosphorfracht vorgestellt, und es wird erläutert, wie sich die Wahl des Ansatzes auf das Resultat auswirkt. Um die natürlichen Variationen im Abfluss von Veränderungen in der Phosphor-Abschwemmung zu trennen, wird in Kapitel 3 eine Methode vorgestellt, um die zeitliche Entwicklung der Jahresfracht unter Annahme eines unveränderten Abflusses zu bestimmen. In Kapitel 4 wird die vom AfU LU durchgeführte Fehlerrechnung überprüft, und es werden Überlegungen zur Verminderung der Fehler angestellt. Schliesslich wird in Kapitel 5 aufgezeigt, wie stark die Jahresfrachten des Phosphors streuen, wenn die Anzahl der Messpunkte bei Hoch- bzw. Niedrigwasser verändert wird. Die Resultate sowie die daraus abgeleiteten Schlussfolgerungen werden in Kapitel 6 zusammengefasst.
Phosphorbilanz von Sempachersee und Baldeggersee. Teil II: Phosphorbilanzen während der künstlichen Belüftung des Sempacher- und Baldeggersees
Der Bericht ist folgendermassen aufgebaut: In Kapitel 2 wird die jährliche Phosphorbilanz der beiden Seen erstellt, und es werden Netto- und Bruttosedimentation bestimmt. Da die einzelnen Werte der jährlichen Bilanz stark streuen, wird eine Bilanz mit gemittelten monatlichen Werten erstellt, und es werden die verschiedenen Faktoren, welche die Nettosedimentation beeinflussen, erläutert. In Kapitel 3 wird mit Hilfe eines Ein-Box-Modells bestimmt, welchem Stationärzustand sich die beiden Seen unter verschiedenen Randbedingungen nähern. Es werden die Zeitkonstanten der Veränderung ermittelt, sowie die maximal tolerierbare Belastung zum Erreichen eines mesotrophen Zustands hergeleitet. In Kapitel 4 wird der Einfluss der Seenbelüftung auf den Phosphorhaushalt erörtert, und in Kapitel 5 wird ein Vorschlag gemacht, die Nettosedimentation genauer zu bestimmen. Der damit verbundene Aufwand wird angegeben. Schliesslich werden in Kapitel 6 die Resultate zusammengefasst.
La désinfection de l'eau par irradiation solaire. Rapport de recherche 2004 réalisé à l'Eawag, Dübendorf
In developing countries, due to the Jack of money, drinking water is scarce. Diarrheal epidemics, caused by consumption of unsafe drinking water can be lethal. That is why an alternative approach self-sustaining have been proposed and tested in the field. A simple method, called SODIS (for Solar Disinfection), has been developed to disinfect drinking water. It is proved that a synergic effect of UV-A radiation and temperature can inactivate pathogens causing diarrhea. Up to now, most of the experiments, mainly aimed at developing and improving the methodology. Most of experiments use cells in exponential growth phase for disinfection experiments. But bacteria are more resistant in stationary phase and we found that sensitivity of cells to UV and temperature strongly depends on their growth state. Several experiments with different pathogenic enterobacteria have been conducted in the laboratory and the field to investigate the sensitivity and the behaviour of cells. Now, we know the range of sensitivity at different temperatures for pathogenic strains and the range of UV dose of the sun necessary to inactivate cells. We studied physiological as well as genetic changes in response to SODIS treatment. Some preliminary experiments about regrowth and recovery after treatment have been carried out. These first results revealed that no regrowth or recovery was observed after 48h. It is known that bacteria produce reactive oxygen species (ROS) (OH", 0 2·, Oi , H10 2) in stress conditions. Therefore, they have developed ways for quenching ROS. Enzymes involved in the detoxification of ROS are superoxide dismutase, peroxide and catalase. Activity of catalase has been measured and catalase was observed to play a role in the response. But experiments with mutants of E. coli exposed to the sunlight demonstrated a minor role in protection against UV radiation damage. To know which ways are involved in the mechanism of inactivation, we used mutants of E. coli and we have shown that RpoS, the "starvation" sigma factor, is very important in response against the sunlight. To compare cells exposed and no stress cells, a gene array will be done.
Wärmerückgewinnung aus Abwassersystemen: Schlussbericht
Wastewater contains large amounts of heat energy which can be recovered by means of a heat pump and a heat exchanger installed in the sewer system. Practical problems, which may arise and have been investigated in this research project, are the reduction of the heat transfer efficiency due to heat exchanger fouling and the reduction of the nitrification capacity of downstream wastewater treatment plants due to lower wastewater temperatures. A mathematical model was developed by which the decrease of the wastewater temperature in the treatment plant influent can be determined as a function of the amount of heat energy gathered from the wastewater in the sewer system. By this model the variation in time and space of the wastewater temperature in a sewer pipe is calculated for given hydraulics, geometry and environmental conditions. By analysis of data from a large wastewater treatment plant and simulations with a calibrated model, the effect of lowered influent temperatures on nitrification safety, total nitrogen removal efficiency and ammonium effluent concentrations could be quantified. A procedure is suggested by which the reserve nitrification capacity of an existing treatment plant and the increase of the ammonium effluent concentration resulting from a permanent decrease of the wastewater influent temperature can be estimated. By experiments with a pilot scale heat exchanger in a small wastewater channel, the significance of parameters known to have an effect on fouling was investigated and measures to reduce fouling were tested. The measures tested included controlled variation of the wastewater flow velocity (flushing), coatings and finish of the heat exchanger surface and obstacles mounted on the surface. The best results were obtained by regular short term increases of the flow velocity. By this measure, the efficiency of the fouled heat exchanger, which on the average was 60% of the efficiency of the clean heat exchanger, could repeatedly be raised to an average of 83% again.