Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1996"
TL;DR: In this article, the authors proposed a management belief system that relies upon natural habitat restoration and maintenance, as opposed to artificial propagation, installation of artificial instream structures (river engineering) and predator control.
Abstract: Large catchment basins may be viewed as ecosystems in which natural and cultural attributes interact. Contemporary river ecology emphasizes the four-dimensional nature of the river continuum and the propensity for riverine biodiversity and bioproduction to be largely controlled by habitat maintenance processes, such as cut and fill alluviation mediated by catchment water yield. Stream regulation reduces annual flow amplitude, increases baseflow variation and changes temperature, mass transport and other important biophysical patterns and attributes. As a result, ecological connectivity between upstream and downstream reaches and between channels, ground waters and floodplains may be severed. Native biodiversity and bioproduction usually are reduced or changed and non-native biota proliferate. Regulated rivers regain normative attributes as distance from the dam increases and in relation to the mode of dam operation. Therefore, dam operations can be used to restructure altered temperature and flow regimes which, coupled with pollution abatement and management of non-native biota, enables natural processes to restore damaged habitats along the river’s course. The expectation is recovery of depressed populations of native species. The protocol requires: restoring peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilizing baseflows to revitalize food-webs in shallow water habitats; reconstituting seasonal temperature patterns (e.g. by construction of depth selective withdrawal systems on storage dams); maximizing dam passage to allow recovery of fish metapopulation structure; instituting a management belief system that relies upon natural habitat restoration and maintenance, as opposed to artificial propagation, installation of artificial instream structures (river engineering) and predator control; and, practising adaptive ecosystem management. Our restoration protocol should be viewed as an hypothesis derived from the principles of river ecology. Although restoration to aboriginal state is not expected, nor necessarily desired, recovering some large portion of the lost capacity to sustain native biodiversity and bioproduction is possible by management for processes that maintain normative habitat conditions. The cost may be less than expected because the river can do most of the work.
728 citations
TL;DR: In this article, the role of Fenton's reaction [oxidation of Fe(II) by hydrogen peroxide] in the catalytic cycle was examined, and a number of competing processes were observed in model systems.
Abstract: Iron redox cycling can catalyze the oxidation of humic substances and increase the rate of oxygen consumption in surface waters rich in iron and organic carbon. This study examines the role of Fenton`s reaction [oxidation of Fe(II) by hydrogen peroxide] in this catalytic cycle. A number of competing processes were observed in model systems containing dissolved Fe, hydrogen peroxide, and Suwannee River fulvic acid. First, the effective rate constant of Fenton`s reaction increased with increasing fulvic acid concentration, indicating the formation Fe(II)-fulvate complexes that react more rapidly with hydrogen peroxide than Fe(II)-aquo complexes. This effect was significant at pH 5 but negligible at pH 3. A second effect was scavenging of the HO{sup .} radical produced in Fenton`s reaction by fulvic acid, forming an organic radical. The organic radical reduced oxygen to HO{sub 2}{sup .}/O{sub 2}{sup .-}, which then regenerated hydrogen peroxide by reaction with Fe(II). Finally, Fe(III) was reduced by a dark reaction with fulvic acid, characterized by an initially fast reduction followed by slower processes. The behavior of Fe(II) and hydrogen peroxide over time in the presence of fulvic acid and oxygen could be described by a kinetic model taking all of these reactions into account. The netmore » result was an iron redox cycle in which hydrogen peroxide as well as oxygen were consumed (even though direct oxidation of Fe(II) by oxygen was not significant), and the oxidation of fulvic acid was accelerated. 56 refs., 7 figs., 1 tab.« less
354 citations
191 citations
TL;DR: The speciation of EDTA in sewage effluents leaving wastewater treatment plants determines its ultimate fate in natural surface waters, since only the Fe(III)-EDTA complex (FeEDTA) is quickly degraded by direct photolysis, whereas other EDTA species are very slowly transformed by biological or chemical processes as discussed by the authors.
175 citations
TL;DR: In this article, the behaviour of various persistent metabolites derived from nonylphenol polyethoxylate (NPnEO) surfactants was studied during infiltration of river water to groundwater at two field sites situated in the northern part of Switzerland (Glatt River and Sitter River).
159 citations
TL;DR: Physical/chemical elimination of ammonium from digester supernatant with magnesium-ammonium-phosphate precipitation and with air stripping is investigated in pilot scale as discussed by the authors.
152 citations
TL;DR: In this article, an overview on the contamination of these media is given, and the behavior of organotins in the treatment process is described in raw municipal wastewater of the city of Zurich, Switzerland, mono- (MBT), di- (DBT), and tributyltin (TBT) were detected in the range of 140-560, 130-1030, and 60-220 ng/l, respectively.
150 citations
TL;DR: In this article, the termination of the Younger Dryas is dated to 10,920±132 yr B.P. This is younger than the recently published Greenland ice core dates but in accordance with, for example, the central European dendrochronology.
146 citations
TL;DR: Results suggest the involvement of specific enzymes for the degradation of each enantiomer in Sphingomonas herbicidovorans MH, as oxygen consumption was strongly dependent on the growth substrate.
Abstract: Sphingomonas herbicidovorans MH (previously designated Flavobacterium sp. strain MH) was able to utilize the chiral herbicide (RS)-2-(4-chloro-2-methylphenoxy)propionic acid (mecoprop) as the sole carbon and energy source. When strain MH was offered racemic mecoprop as the growth substrate, it could degrade both the (R) and the (S) enantiomer to completion, as shown by biomass formation, substrate consumption, and stoichiometric chloride release. However, the (S) enantiomer disappeared much faster from the culture medium than the (R) enantiomer. These results suggest the involvement of specific enzymes for the degradation of each enantiomer. This view was substantiated by the fact that resting cells of strain MH grown on (S)-mecoprop were able to degrade the (S) but not the (R) enantiomer of mecoprop. Accordingly, resting cells of strain MH grown on (R)-mecoprop preferentially metabolized the (R) enantiomer. Nevertheless, such cells could transform (S)-mecoprop at low rates. Oxygen uptake rates with resting cells confirmed the above view, as oxygen consumption was strongly dependent on the growth substrate. Cells grown on (R)-mecoprop showed oxygen uptake rates more than two times higher upon incubation with the (R) than upon incubation with the (S) enantiomer and vice versa.
143 citations
TL;DR: In this paper, the authors extended Schulthess et al.'s model with the consumption of organic substrate and with nitrification to predict the nitrous oxide (N2O) accumulation in continuously fed full scale waste water treatment plants.
141 citations
TL;DR: In this article, the authors highlight the uses and limitations of thermodynamic calculations in the planning of leach tests in the laboratory or for research in the field and highlight the limitations of such calculations.
TL;DR: Homology comparisons indicated that the chlorobenzene dioxygenase and dehydrogenase originated from a toluene or benzene degradation pathway, probably by horizontal gene transfer, and left its traces as short gene fragments directly outside the tcbAB coding regions.
TL;DR: In this article, the authors evaluated the dominant processes that control periphyton biomass, measured data were compared with a set of simulations from an empirical dynamic perphyton model, and different combinations of process hypotheses were systematically activated and deactivated to assess their importance.
Abstract: 1 Periphyton chlorophyll a was measured at weekly or 2 weekly intervals from October 1992 to March 1994 at four sites in a Swiss prealpine gravel bed river that was frequently disturbed by unpredictable spates
2 To evaluate the dominant processes that control periphyton biomass, measured data were compared with a set of simulations from an empirical dynamic periphyton model Different combinations of process hypotheses were systematically activated and deactivated in order to assess their importance
3 The simplest model leading to an acceptable agreement with measured data employs a biomass-dependent growth rate, a detachment rate directly proportional to discharge and biomass, and a catastrophic loss rate during bed moving spates Terms describing light or temperature dependence had a minor effect on the model fit
4 The model describes the temporal pattern of the periphyton biomass as a series of growth curves periodically truncated by spates Within the uncertainties of the measurements, mainly caused by the spatial heterogeneity of periphyton, the biomass recovered along deterministic trajectories
5 Sensitivity analyses with respect to model parameters and model structure showed that site-specific model parameters could not be unequivocally determined, and that the model yields similar results with slightly different formulations of processes This indicates that the data base with respect to periphyton biomass was too small for a unique identification of model details but that the main conclusions on the significance of processes did not depend on arbitrary choices of the model formulation
TL;DR: In this paper, the authors address the issue of uncertainty and subjectivity in modelling and relate bias to different perspectives, and introduce the methodology of multiple model routes, which are reflections of different perceptions of reality and various policy preferences.
Abstract: In the context of Integrated assessment, the authors address the Issue of uncertainty and subjectivity in modelling In relating bias to different perspectives, the authors introduce the methodology of multiple model routes, which are reflections of different perceptions of reality and various policy preferences As heuristic they use three perspectives, which are distinguished In cultural theory The article describes case studies on the population and climate issue in order to illustrate the possibilities of their approach The article concludes with discussing the achievements and limitations
TL;DR: It is now proven that, besides toluene, benzene and ethylbenzene can be oxidized under anaerobic redox conditions.
TL;DR: The 94% drop in DTDMAC concentrations in digested sludges is due to the replacement of this substance and is a clear result of the producers' voluntary ban on its use in Europe.
Abstract: To study the phasing-out of the quaternary ammonium surfactant ditallowdimethylammonium cation (DTDMAC), concentrations of the cation in anaerobically stabilized sewage sludges were determined before and after its replacement by better degradable compounds. DTDMAC was quantitatively extracted from digested sludges using 380 atm of supercritical CO2 modified with 30% methanol at 100 °C. Determination of DTDMAC was performed by normal-phase HPLC with postcolumn ion-pair formation and extraction with no sample cleanup. Mean concentrations of DTDMAC in sludges from five different municipal sewage treatment plants in Switzerland decreased from 3.67 g/kg (in 1991) to 0.96, 0.47, and 0.21 g/kg of dry sludge in 1992, 1993, and 1994, respectively. The precision of the method in digested sludge for 0.1−6.0 g/kg of dry matter, as indicated by the relative standard deviation, was typically 7%. The influence of the sample matrix was studied by performing supercritical fluid extraction (SFE) in coastal marine sediments...
TL;DR: It is proposed that the product of the tfdR gene (or its identical twin, tfdS), located elsewhere on plasmid pJP4, can successfully take over the regulation of tfdCDEF expression, implying cross-activation by chromosomally encoded regulatory elements in R. eutropha JMP134(pJP4).
Abstract: The tfdT gene is located upstream of and transcribed divergently from the tfdCDEF chlorocatechol-degradative operon on plasmid pJP4 of Ralstonia eutropha (formerly Alcaligenes eutrophus) JMP134. It is 684 bp long and encodes a 25-kDa protein. On the basis of its predicted amino acid sequence, the TfdT protein could be classified as a LysR-type transcriptional regulator. It has the highest degree of similarity with the proteins TcbR, ClcR, and TfdR, which are involved in the regulation of chloroaromatic breakdown. Despite this homology, the TfdT protein failed to activate the expression of its presumed target operon, tfdCDEF. This failure could be attributed to the inability of TfdT to bind the tfdC promoter region, an absolute requirement for transcriptional activation. Sequence analysis downstream of the tfdT gene revealed the presence of an insertion element-like element. We postulate that this element disrupted the tfdT open reading frame, leading to a premature termination and the production of a truncated, disfunctional TfdT protein. As an alternative to the inactivated TfdT protein, we propose that the product of the tfdR gene (or its identical twin, tfdS), located elsewhere on plasmid pJP4, can successfully take over the regulation of tfdCDEF expression. The TfdR protein was capable of binding to the tfdC promoter region and activated tfdCDEF gene expression by a factor of 80 to 100 when provided in cis as a tfdR-tfdCDEF hybrid regulon. Although to a lesser extent, induction of tfdCDEF expression was also observed when no functional TfdR protein was provided, implying cross-activation by chromosomally encoded regulatory elements in R. eutropha JMP134(pJP4).
TL;DR: In this paper, the effects of decreasing lead emissions from gasoline on a lake sediment, profiles of lead concentrations and 206Pb/207P... were studied. But the results were limited to a single lake.
Abstract: In Switzerland, unleaded gasoline was introduced in 1985. In order to study the effects of decreasing lead emissions from gasoline on a lake sediment, profiles of lead concentrations and 206Pb/207P...
TL;DR: The mechanism explains why the rate order generally coincides with the metal valence, and why there is a similarity between rates of water ligand lability in dissolved complexes and rates of mineral dissolution and metal desorption, and establishes a close consistency between reactions at surfaces and ligand-exchange reactions in solution.
Abstract: THE exchange of metal ions between an oxide mineral surface and water occurs in a wide range of processes, including corrosion1, the breakdown of inhaled dusts2,3, soil formation4 and the cycling of toxic substances in the environment5. In studies of the mechanisms of dissolution, the measured rate-law order with respect to protons6–15 cannot be reconciled with the number of protons needed to form any reasonable assumed activated complex. Here we suggest that this discrepancy can be avoided if one takes into account the number of protonation and deprotonation steps leading to detachment of the hydrated metal ion. We show that the experimental proton rate order reflects a net balance of protons removed and attached in these steps. Our mechanism explains why the rate order generally coincides with the metal valence8,9,11,12,16–18, and why there is a similarity between rates of water ligand lability in dissolved complexes and rates of mineral dissolution19–22 and metal desorption23. It eliminates the need to invoke catalysis by protons, and establishes a close consistency between reactions at surfaces and (better understood) ligand-exchange reactions in solution.
TL;DR: In this article, surface and sub-surface infiltration systems for road run-off at two sites in Switzerland were investigated by sampling and analysing the runoff sludge and soil found in the systems.
TL;DR: Fluorescent whitening agents (FWAs) used in laundry detergents were determined in aqueous samples from sewage treatment plants and rivers using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with post-column UV irradiation and fluorescence detection as discussed by the authors.
Abstract: Fluorescent whitening agents (FWAs) used in laundry detergents were determined in aqueous samples from sewage treatment plants and rivers using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with post-column UV irradiation and fluorescence detection. FWAs were extracted from 10−200-mL water samples with C18 bonded- phase silica extraction disks and eluted with methanol-containing tetrabutylammonium ion-pairing reagent. No further sample cleanup steps were necessary due to the sensitive and selective fluorescence detection. Recovery of FWAs from raw sewage, primary effluent, secondary effluent, and river water ranged from 76 to 96%. The overall precision of the method, indicated by the relative standard deviation, ranged from 1 to 11%. The limit of quantification was less than 30 ng/L. The concentrations of the two most frequently used FWAs ranged from 7 to 21 μg/L in primary effluent, from 2.6 to 8.9 μg/L in secondary effluent, and from 0.04 to 0.57 μg/L in river water. FWA...
TL;DR: In this paper, the development of sediment trap techniques and hydrodynamics are briefly reviewed, with special emphasis on the experimental and in-situ trap calibration, and the ongoing controversy within the trap community on the validity of flux data obtained by sediment traps can only be overcome by understanding the effects of hydrogynamics on the entrapping of settling particles in turbulent waters.
Abstract: This article is aimed at established sediment trap specialists as well as young learning scientists. The development of sediment trap techniques and hydrodynamics are briefly reviewed, with special emphasis on the experimental and in-situ trap calibration. The ongoing controversy within the trap community on the validity of flux data obtained by sediment traps can only be overcome by understanding the effects of hydrodynamics on the entrapping of settling particles in turbulent waters. A proper trap protocol is still missing. Also, the problems of entering swimmers and preservatives are not yet fully solved. Innovative ideas and robust data are needed to improve our knowledge on trapping efficiency, particle settling flux data, and the interpretation of lake and oceanic nutrient cycles. It is emphasized that controversial papers should be published when based on documented experiments and/or theory applied.
TL;DR: In this paper, the results from the water columns of some eutrophic and oligotrophic lakes are presented and compared to small acid lakes, indicating that Cu complexing ligands are specific organic compounds.
Abstract: [Cu2+] and Cu complexation parameters in some selected freshwater systems in Switzerland were determined by the technique of ligand-exchange and DPCSV. Results from the water columns of some eutrophic and oligotrophic lakes are presented and compared to small acid lakes. Cu is strongly complexed by organic ligands which with very high stability constants at low concentrations are probably biologically produced, as indicated by the seasonal variations in the eutrophic lakes and by the relationship between Cu complexation and algal activity in the eutrophic (pCu=15−16), oligotrophic (pCu=13−14) and acidic (pCu=9−10) lakes. The extent of Cu complexation in river waters was generally lower than in the eutrophic lakes, at similar DOC levels. No obvious correlation between Cu complexation and DOC was observed, indicating that Cu complexing ligands are specific organic compounds.
TL;DR: In this paper, a thermodynamic model is suggested for predicting aqueous solubility of C-S-H as a function of the Ca/Si ratio based on a solid solution−aqueous solution (SSAS) subregular equilibrium model for a binary non-ideal mixing of the end-member phases calcium hydroxide and calcium silicate.
Abstract: The major component in cementitious waste solidification/stabilization (S/S) systems is an amorphous calcium silicate hydroxide hydrate phase (C-S-H) phase according to cement chemistry nomenclature), but the behavior of this gel phase in aqueous solution is not well understood. In this paper, a thermodynamic model is suggested for predicting aqueous solubility of C-S-H as a function of the Ca/Si ratio based on a solid solution−aqueous solution (SSAS) subregular equilibrium model for a binary non-ideal mixing of the end-member phases calcium hydroxide and calcium silicate, with known pK values and a miscibility gap at Ca/Si > 3. A maximum in Gibbs free energy of mixing (GM) of −3.2 kJ/mol is predicted to occur at a Ca/Si ratio of 1.5. Predicted Ca and Si solubility, pH, and solid Ca/Si values agree with experimental data on C-S-H solubility reported from the literature. The thermodynamic basis of this SSAS model is superior to those based on empirical Ksp values vs Ca/Si ratio relationships or on ideal so...
TL;DR: In this article, the authors address the issue of uncertainty and subjectivity in modelling and introduce the methodology of multiple model routes, which are reflections of different perceptions of reality and various policy preferences.
Abstract: In the context of integrated assessment, the authors address the issue of uncertainty and subjectivity in modelling. In relating bias to different perspectives, the authors introduce the methodology of multiple model routes, which are reflections of different perceptions of reality and various policy preferences. As heuristic they use three perspectives, which are distinguished in cultural theory. The article describes case-studies on the population and health controversy in order to illustrate the possibilities of their approach. The article concludes with discussing the lessons learned by applying this methodology.
TL;DR: The results indicate that cytotoxicity assays using this metabolically active hepatoma cell line are a promising tool in the first evaluation and toxicity screening of chemicals prone to contaminate aquatic systems.
TL;DR: The results indicate that Cd(II) and Cu( II) in particular may affect the CYP1A system of the liver of fish at low concentrations through direct inhibition of the CYp1A enzyme activity.
Abstract: The interactions in vitro of heavy metals Cd(II), Co(II), Cu(II), Ni(II), Pb(II), and Zn(II) with cytochrome P4501A (CYP1A) induction response and enzyme activity were studied in fish hepatoma cells PLHC-1. Cells were simultaneously exposed to heavy metals and to 3-methylcholanthrene (3-MC), an inducer of CYP1A. Heavy metals were added to the cells in different concentrations. Cytotoxicity were measured in the neutral red (NR) assay, relative CYP1A protein contents in an enzyme-linked immunosorbent assay (ELISA), and CYP1A activities in the ethoxyresorufin-O-deethylase (EROD) assay. All metals had a more pronounced effect on EROD activity than on CYP1A protein content and cytotoxicity. For the most active metal Cd(II), a 50% inhibition of EROD activity was observed at significantly lower concentrations (2.2 x 10(-5) M) than a 50% reduction of CYP1A protein (5.3 x 10(-5) M), and a 50% cytotoxicity (1.4 x 10(-4) M). The inhibitory potency of the metals had the following order: Cd(II) > Ni(II) > Cu(II) > Co(II) = Zn(II) > Pb(II). In a second set of experiments, lysates of 3-MC-induced cells were exposed to heavy metals. Cd(II) and Cu(II) caused a 50% inhibition of EROD activity at significantly lower concentrations than in the experiments with living cells, at 8.2 x 10(-6) M and 1.3 x 10(-5) M, respectively, whereas the effect by Co(II) occurred at a significantly higher concentration (8.2 x 10(-4) M). The results indicate that Cd(II) and Cu(II) in particular may affect the CYP1A system of the liver of fish at low concentrations through direct inhibition of the CYP1A enzyme activity. CYP1A induction response in fish liver is increasingly being used in biomonitoring programs. In the environment, interactions of CYP1A-inducing and CYP1A-inhibiting components (such as heavy metals) can be expected and must be taken into consideration.
TL;DR: It is indicated that TPTAc negatively affects rainbow trout in a concentration range that might be present in aquatic environments and in severe cases, cell necrosis was evident.
Abstract: To evaluate the toxic effects of sublethal concentrations of the fungicide triphenyltinacetate (TPTAc), a prolonged toxicity study was made on rainbow trout (Oncorhynchus mykiss). Fish were exposed to TPTAc concentrations ranging from 1 to 6 μg TPTAc/L for 28 and 18 days, respectively, using a flow-through exposure system. Hematological findings included an increase of the total number of erythrocytes and an elevated incidence of erythrocyte degradation stages at 4 μg TPTAc/L and higher. The hemoglobin content and the packed-cell volume increased as well at 4 and 1 μg TPTAc/L. Whereas the total number of leucocytes increased in fish exposed to 1 μg TPTAc/L, the number of leucocytes tended to decrease at higher concentrations. The percentage of lymphocytes within the differential blood cell count decreased. The histopathological examination of TPTAc-exposed fish showed a dose-related lymphocytic depletion of the spleen, accompanied by a proliferation of reticuloendothelial cells and an increased erythrophagia even at the lowest TPTAc concentration. In severe cases, cell necrosis was evident. In liver tissue, a depletion of the glycogen deposits within the hepatocytes could be detected in fish exposed to 4 and 6 μg TPTAc/L. The analysis of the phenyltin compounds within various organs of fish by HRGC-FPD revealed remarkable concentrations of triphenyltin of up to 16.1 μg/g with the following order of residue levels: liver > kidney > spleen > gills > muscle. Di- and monophenyltin were found only in traces of 1–109 ng/g in these organs. The present study indicates that TPTAc negatively affects rainbow trout in a concentration range that might be present in aquatic environments.
TL;DR: In this article, a numerical model for predicting the flow in secondary clarifiers is presented which accounts for density-affected and turbulent flow as well as for the settling of activated sludge, and the reliability of the two-dimensional model is demonstrated through verification by means of a laboratory experiment which was specially designed for this purpose.
TL;DR: In this article, Nitrous oxide (N{sub 2}O) production at the sediment surface of eutrophic Lake Baldegg was quantified with three independent methods: pore-water samplers, benthic chambers, and mass balances of the aerated-oxygenated hypolimnion.
Abstract: Nitrous oxide (N{sub 2}O) production at the sediment surface of eutrophic Lake Baldegg was quantified with three independent methods: pore-water samplers, benthic chambers, and mass balances of the aerated-oxygenated hypolimnion. N{sub 2}O production at the sediment surface was the most important source in this lake and led to an accumulation in the hypolimnion during summer stratification. Highest rates of N{sub 2}O emission to the atmosphere (24 {mu}mol m{sup {minus}2} d{sup {minus}1}) were observed after the onset of winter overturn, when hypolimnetic water enriched in N{sub 2}O came in contact with the atmosphere. During summer stratification N{sub 2}O emissions to the atmosphere decreased to {approximately}4 {mu}mol m{sup {minus}2} d {sup {minus}1}. The winter fluxes are close to the highest reported N{sub 2}O emissions from marine systems. 23 refs., 4 figs., 2 tabs.