OH radical-initiated oxidation of organic compounds in atmospheric water phases: part 1. Reactions of peroxyl radicals derived from 2-butoxyethanol in water
The aim of this series of two publications is to characterize important radical reactions of organic molecules in atmospheric water phases, such as cloud, fog, and rain droplets, or on wetted aerosols. In this first study the reactions occurring in a mixed peroxyl radical system generated from the OH radical attack on a model compound, 2-butoxyethanol, in oxygenated aqueous solution are investigated in the absence of trace compounds typically found in such natural waters. Using γ-radiation emitted from a <sup>60</sup>Co source, we have produced steady-state concentrations of O<sub>2</sub><sup>-</sup>/HO<sub>2</sub>- and OH radicals comparable to those predicted for daytime conditions in cloud or fog droplets. The reactions of the peroxyl radicals derived from 2-butoxyethanol (C<sub>4</sub>H<sub>9</sub>OCH<sub>2</sub>CH<sub>2</sub>OH) in oxygenated aqueous solution have been investigated by measuring detailed product distributions resulting from the oxidation process. The observed and quantified products are mainly esters, ketones, aldehydes and hydroperoxides and accounted for 83% of the removal of 2-butoxyethanol (expressed as a carbon balance). A mechanism for the formation of the reaction products is proposed. It includes the OH attack at four carbon centers of the molecule producing carbon centered radicals, the formation of peroxyl radicals by addition of oxygen to these radicals, the decay of the peroxyl radicals in a reaction system of six different peroxyl radicals and superoxide via bimolecular and unimolecular reactions and the reactions of intermediary produced oxyl radicals.
Transport of radiocobalt discharged by the Mühleberg
nuclear reactor in the aquatic systems of the Aare river
and Lake Biel (Switzerland). Transfert du radiocobalt rejeté par la centrale de Mühleberg dans les systèmes aquatiques de l'Aar et du lac de Bien
During the discharge of a radioactive effluent, a radioelement passes from
an artificial system in the storage tank, to a natural system. Its behaviour will not only
be governed by relatively simple chemical reactions, that can be reproduced in the
laboratory, but in addition by more complex, poorly known mechanisms, that control
natural systems. <BR/>
Cobalt, well studied because of the radioecological importance of <SUP>60</SUP>Co, represents an
example of a metal that participates in chemical reactions which play a role in aquatic
systems, particularly organic and inorganic complexation and adsorption on suspended
particles. On the basis of equilibrium constants and a simple surface complexation model
it is possible to estimate the importance of the different chemical species of cobalt.
The theoretical results are confronted with <I>in situ</I> measurements downstream of the
Mühleberg nuclear power plant, situated at close proximity to Berne. Here sampling
can be carried out in the river Aare and in Lake Biel, 18 km downstream of the power
plant. Sediment cores indicate that only a small percentage ( < 5 % ) of <SUP>60</SUP>Co is found in
riverine sediments, whereas the proportion found in Lake Biel sediments reaches
A transport model is necessary to simulate the evolution of the discharged water in
the two aquatic systems. Transport in the river is calculated on the basis of advection/dispersion
equations, transport in the lake is represented by the water residence
time and aquatic physical characteristics. <BR/>
Measurements have shown that the fraction of <SUP>60</SUP>Co adsorbed to particles < 0.5 μm
and to colloïds (0.5 μm to 5000 Dalton) rarely exceeds 20 %.<BR/>
These results enable evaluating the model variables, which are poorly known, such as
the concentration of organic ligands, the equilibrium constant for organic complexation
or the relation between particle mass and number of adsorption sites. <BR/>
lt must be remembered that this model, which is based on <I>in situ</I> measurements, can
only be directly applied to the Aare downstream of the Mühleberg reactor and Lake
The article deals with dreams of graduate students in environmental sciences. The dreams
were collected by a survey at the Department of Environmental Sciences at the Swiss Federal
Institute of Technology (ETH Zürich). For a systematic treatment, the amplification method introduced
by C.G.Jung is explained and applied. One dream is discussed in detail: "The transformation
of stuffed animals." Other dreams are presented in groups according to some main motives. -
Archetypal dreams, in particular, do not exclusively affect the individual dreamer, they also relate to
central cultural questions such as the "environmental problem". When adequately understood, they
may have an effect on dreamers' purposes and general intentions - besides their well-documented
role for problem solving and discoveries in science.
Mild steel coupons were incubated in cultures of three different aerobic bacteria, <I>viz. Rhodococcus</I> sp. C125, <I>Pseudomonas putida</I> mt2 and <I>Streptomyces pilosus</I> DSM 40714 and then exposed to a corrosive aqueous medium. A significant reduction in the corrosion rate was observed in a corrosive medium when the steel had been incubated in mineral media containing more than 2 mM phosphate with growing, biofilm- forming bacteria which had direct access to the steel surface, but not with the non biofilm-forming <I>S. pilosus</I> DSM 40714. <I>Rhodococcus</I> sp. C125 and <I>P. putida</I> mt2 induced a surface reaction, resulting in the formation of vivianite. This barely insoluble iron(II)-phosphate was found to be the cause of the corrosion inhibition. The surface reaction was always accompanied by an increase in the iron concentration in the medium. In contrast to biocorrosion processes known so far, iron release stopped after some days. The results suggest that bacterial activity may induce the inhibition of corrosion of mild steel.
Optimization of nutrient removal in the WWTP Zürich-Werhölzli
Optimization of nitrifying activated sludge plants towards nutrient removal (denitrification and enhanced P-removal) will lead to substantial reduction of operating costs and improves effluent and operating conditions. At the WWTP Zürich-Werdhölzli, initially designed for nitrification, an anoxic zone of 28% of total activated sludge volume was installed in the initially fully aerated activated sludge tanks and allowed with optimization of the sludge blanket in the secondary clarifiers a nitrogen elimination of 60-70%. Parallel, different small process alterations at the grit removal tank, the primary clarifiers and return sludge pumps reduced odour problems and oxygen input and improved denitrification. Separate treatment of the digester supernatant, that contains about 20% of the inlet nitrogen load, will increase nitrogen elimination to about 75% and allows partial enhanced biological O-removal in the activated sludge system which will reduce precipitant feed and excess sludge production.
Longitudinal variations in exposed riverine sediments: a context for the ecology of the Fiume Tagliamento, Italy
1. A key component of physical habitat along braided river systems is the exposed riverine sediment within the active zone. The relatively unmanaged, gravel-bed Fiume Tagliamento, Italy, provides the focus for exploring two ecologically important properties of exposed riverine sediments: their within-patch and between-patch variability in calibre.<br/>
2. To characterize between-patch variation in exposed riverine sediments, replicate (within-patch) samples were obtained from three geomorphologically distinct locations along 130 km of the river: bar heads along the margin of the low-flow channel, the heads of major bars across the exposed surface of the active zone, and floodplain surfaces. A photographic technique enabled rapid and consistent field sampling of the coarse sediments at bar heads along the low-flow channel margin and on major bars across the dry bed.<br/>
3. A downstream decrease in particle size and an increase in within-patch heterogeneity in sediment size were observed within bar head sediments along the margin of the low-flow channel. Comparisons between major bar and low-flow channel samples revealed greatest within-patch variability in individual sediment size indices (<I>D</I><sub>50</sub>, A- and B-axes of the larger particles) at headwater sites, greatest between-patch variability in the three measured indices in the central reaches, and lowest between-patch variability at downstream sites. However, there was a distinct increase in the overall heterogeneity in particle size, which was sustained across all patches, in a downstream direction.<br/>
4. There was a clear downstream decrease in the size of floodplain sediments in the headwaters, but thereafter there was no distinct downstream trend in any of the calculated particle size indices.<br/>
5. The geomorphological controls on the observed patterns and the potential ecological significance of the patterns, particularly for plant establishment, are discussed in relation to the relative relief of the active zone, and the highly variable hydrological and climatic regime along the river.
DNA degradation by the mixture of copper and catechol is caused by DNA-copper-hydroperoxo complexes, probably DNA-Cu(I)OOH
Free hydroxyl radicals (free <sup><B>·</B></sup>OH), singlet oxygen (<SUP>1</SUP>O<SUB>2</SUB>), or <sup><B>·</B></sup>OH produced by DNA-copper-hydroperoxo complexes are possible DNA-damaging reactive oxygen species (ROS) in the reaction system containing copper, catechol, and DNA. para-Chlorobenzoic acid (pCBA) degradation studies revealed that CuCl<SUB>2</SUB> mixed with catechol produced free <sup><B>·</B></sup>OH. In the presence of DNA, however, inhibition of the pCBA degradation suggested that another ROS is responsible for the DNA degradation. Of a series of ROS scavengers investigated, only KI, NaN<SUB>3</SUB>, and Na-formate—all of the salts tested—strongly inhibited the DNA degradation, suggesting that the ionic strength rather than the reactivity of the individual scavengers could be responsible for the observed inhibition. The ionic strength effect was confirmed by increasing the concentration of phosphate buffer, which is a poor <sup><B>·</B></sup>OH scavenger, and was interpreted as the result of destabilization of DNA-copper-hydroperoxo complexes. Piperidine-labile site patterns in DNA degraded by copper and catechol showed that the mixture of Cu(II) and catechol degrades DNA via the intermediate formation of a DNA-copper-hydroperoxo complex. Replacement of guanine by 7-deazaguanine did not retard the DNA degradation, suggesting that the DNA-copper-hydroperoxo complexes do not bind to the guanine N-7 as proposed in the literature.
Exposure of rainbow trout (<I>Oncorhynchus mykiss</I>) to nonylphenol is associated with an increased chloride cell fractional surface area
Nonylphenol is a biodegradation product of a widely used group of non-ionic detergents. Because of its ubiquitous distribution and persistence, nonylphenol is present in surface waters as a pollutant. Little is known about its biological effects at environmentally relevant concentrations other than its action as a xenoestrogen. The goal of the present paper was to study the trout gill surface epithelium as the major interface between fish and water in view of possible morphological alterations due to exposure to monylphenol. Rainbow trout were intermitently exposed to 10 mu g/l nonylphenol and gill samples from experimental and control animals were investigated by scanning electron microscopy. Gill surface epithelium was scrutinised for changes in chloride cell density and their status regarding cell surface modifications. In addition, chloride cell fractional surface area (CCFA) was determined by morphometrical methods. Statistical analysis revealed a highly significant increase of CCFA in animals exposed to nonylphenol as compared to control animals (P = 0.0001). Semi-quantitative assessment of their parameters suggested a higher chloride cell density and a larger proportion of chloride cell density and a larger proportion of chloride cells bearing microvilli. Taken together, these results provide evidence that exposure of trout to nonylphenol is associated with a substantial increase in the active interface of chloride cells with water. We interpret these findings as being a means to further the fish's capacity for calcium exchange.
Sub sea floor boiling of Red Sea brines: new indication from noble gas data
Hydrothermal brines from the Atlantis II Deep, Red Sea, have been sampled in situ and analyzed for noble gases. The atmospheric noble gas concentrations (Ne, Ar<sub>atm</sub>, Kr, Xe) in the deepest layer (LCL) are depleted by 20 to 30% relative to the initial concentrations in ambient Red Sea Deep Water without a systematic mass fractionation between the different noble gases. Sub surface boiling during the hydrothermal circulation and subsequent phase separation is shown to be a consistent explanation for the observed depletion pattern. Using a conceptual model of phase separation under sub-critical conditions, in which gases are partitioned according to Henry’s Law, we reconstruct the fluid history before injection into the Atlantis II Deep: after having circulated through evaporites and young oceanic crust, where it becomes enriched in He<sub>MORB</sub> and Ar<sub>MORB</sub>, the ascending fluid boils, and the residual liquid becomes depleted in noble gas concentrations. The depleted fluid rises to the sediment surface and feeds the Atlantis II basin. The relatively low boiling degree of about 3% (i.e., the percentage of fluid removed as vapor) derived from the model indicates that the Atlantis II system represents an early stage of boiling with relatively small gas loss, in contrast to hydrothermal systems at sediment-free mid-ocean ridges.
Cool glacial temperatures and changes in moisture source recorded in Oman groundwaters
Concentrations of atmospheric noble gases (neon, argon, krypton, and xenon) dissolved in groundwaters from northern Oman indicate that the average ground temperature during the Late Pleistocene (15,000 to 24,000 years before present) was 6.5° ± 0.6°C lower than that of today. Stable oxygen and hydrogen isotopic groundwater data show that the origin of atmospheric water vapor changed from a primarily southern, Indian Ocean source during the Late Pleistocene to a dominantly northern, Mediterranean source today. The reduced northern water vapor source is consistent with a drier Last Glacial Maximum through much of northern Africa and Arabia.
Variability of photosynthesis-irradiance curves and ecosystem respiration in a small river
1. We investigated photosynthesis-irradiance relationships (<I>P-I</I> curves; <I>P</I> = oxygen production rate due to photosynthesis, <I>I</I> = light irradiance rate at the water surface) and ecosystem respiration in a 9 km long reach of a river that is characterised by light conditions favouring primary production, high ambient nutrient concentrations, a high reaeration rate, and frequent spates. We addressed the question of how disturbances (spates) and season influence photosynthesis and ecosystem respiration.<br/>
2. We used an oxygen mass-balance model of the river to identify ecosystem respiration rates and the two parameters of a hyperbolic <I>P-I</I> function (<I>P</I><sub>max</sub> = maximum oxygen production rate due to photosynthesis, α = the initial slope of the <I>P-I</I> function). The model was fitted to dissolved oxygen concentrations quasi-continuously recorded at the end of the reach. We estimated parameters for 137 three-day periods (during the years 1992-97) and subsequently explored the potential influence of season and disturbances (spates) on <I>P</I><sub>max</sub>, α and ecosystem respiration using stepwise regression analysis.<br/>
3. Photosynthesis-irradiance relationships and ecosystem respiration were subject to distinct seasonal variation. Only a minor portion of the variability of <I>P-I</I> curves could be attributed to disturbance (spates), while ecosystem respiration did not correlate with disturbance related parameters. Regular seasonal variation in photosynthesis and ecosystem respiration apparently prevailed due to the absence of severe disturbances (a lack of significant bedload transport during high flow).
Description of <I>Sphingomonas xenophaga </I>sp nov for strains BN6<SUP>T</SUP> and N,N which degrade xenobiotic aromatic compounds
The taxonomic position of two bacterial strains, BN6<SUP>T</SUP> and N,N, with the ability to degrade xenobiotic aromatic compounds (naphthalenesulfonates or N,N-dimethylaniline) was investigated. The 16S rRNA gene sequence, the G+C content of the DNA (62-63 mol%) and the detection of ubiquinone Q-10,2- hydroxymyristic acid and the sphingoglycolipid present clearly placed the two strains into the genus <I>Sphingomonas</I>, Both strains are representatives of one species according to the level of DNA relatedness (70.7%). The strains could be separated from all validly described taxa of the genus <I>Sphingomonas</I>, according to the 16S rRNA gene sequence (the highest sequence similarity observed was 96% to <I>Sphingomonas yanoikuyae</I>), the pattern of the polar lipids and physiological characteristics. Therefore, the new species <I>Sphingomonas xenophaga</I> is proposed to accommodate strains BN6<SUP>T</SUP> (= DSM 6383<SUP>T</SUP>) and N,N(= DSM 8566).
<I>p</I>-Toluenesulfonate in landfill leachates: leachability from foundry sands and aerobic biodegradation
<I>p</I>-Toluenesulfonate (pTS) was found at concentrations between 9.6 and 48.8 mg/L in leachates from two Swiss landfill sections where foundry wastes are stored. pTS represented less than or equal to 33% of the nonpurgable organic carbon (NPOC) in the leachates. A standard test showed that PTS is easily leached from foundry sands that contained 1% (w/w) of a technical hardener consisting of toluenesulfonates. Hence, the hardener is a likely source of pTS in the landfill leachates. Furthermore, analyses using liquid chromatography coupled to mass spectrometry and UV absorption detection indicated that the hardener also was the source for toluene-2,4-disulfonate, benzenesulfonate and <I>o</I>- and <I>m</I>-toluenesulfonate, all of which were detected in the landfill leachates. Modified OECD screening tests with pure pTS or hardener as carbon source and landfill leachate as inoculum indicated that aerobic bacteria using pTS for growth are present in the landfill leachates. The intermediates <I>p</I>-sulfobenzyl alcohol and <I>p</I>-sulfobenzoate gives strong evidence for a degradation pathway common to <I>Comamonas testosteroni</I>.
Characterization of total organic carbon in solid residues provides insight into sludge incineration processes
In this paper, an analytical method is presented to determine the concentrations of elemental carbon (EC) and organic carbon (OC) in incinerator residues. This method is applied to sewage sludge incinerators with different combustion technologies. The results show that the OC concentrations are below the detection limit of 0.01 g/kg of dry matter (DM) and that the EC concentrations are lower than 0.3 g/kg of DM in the solid residues of the investigated stationary fluidized-bed furnace and of the multiple-hearth furnace. The OC concentrations in the investigated rotary kiln are lower than 2.5 g/kg of DM, and the EC concentrations are between 20 and 35 g/kg of DM in the rotary kiln bottom ash. Information on processes occurring in the rotary kiln are obtained by determining the EC and OC concentrations in different particle size classes of the bottom ash as well as by sampling the bottom ash during the turn-off of the rotary kiln and determining the EC and OC concentrations in these samples. By combining the results with the process parameters, it is concluded that the OC/EC ratio is a viable indicator for the temperatures within the furnace bed, while the EC concentration indicates the oxygen supply into the furnace bed.
Molecular diversity of plasmids bearing genes that encode toluene and xylene metabolism in <I>Pseudomonas</I> strains isolated from different contaminated sites in Belarus
Twenty different <em>Pseudomonas</em> strains utilizing<em>m</em>-toluate were isolated from oil-contaminated soil samples near Minsk, Belarus. Seventeen of these isolates carried plasmids ranging in size from 78 to about 200 kb (assigned pSVS plasmids) and encoding the <em>meta</em> cleavage pathway for toluene metabolism. Most plasmids were conjugative but of unknown incompatibility groups, except for one, which belonged to the IncP9 group. The organization of the genes for toluene catabolism was determined by restriction analysis and hybridization with <em>xyl</em> gene probes of pWW0. The majority of the plasmids carried <em>xyl</em>-type genes highly homologous to those of pWW53 and organized in a similar manner (M. T. Gallegos, P. A. Williams, and J. L. Ramos, J. Bacteriol. 179:5024–5029, 1997), with two distinguishable <em>meta</em>pathway operons, one upper pathway operon, and three<em>xylS</em>-homologous regions. All of these plasmids also possessed large areas of homologous DNA outside the catabolic genes, suggesting a common ancestry. Two other pSVS plasmids carried only one<em>meta</em> pathway operon, one upper pathway operon, and one copy each of <em>xylS</em> and <em>xylR</em>. The backbones of these two plasmids differed greatly from those of the others. Whereas these parts of the plasmids, carrying the <em>xyl</em> genes, were mostly conserved between plasmids of each group, the noncatabolic parts had undergone intensive DNA rearrangements. DNA sequencing of specific regions near and within the <em>xylTE</em> and <em>xylA</em>genes of the pSVS plasmids confirmed the strong homologies to the<em>xyl</em> genes of pWW53 and pWW0. However, several recombinations were discovered within the upper pathway operons of the pSVS plasmids and pWW0. The main genetic mechanisms which are thought to have resulted in the present-day configuration of the<em>xyl</em> operons are discussed in light of the diversity analysis carried out on the pSVS plasmids.
In vitro ATP regeneration from polyphosphate and AMP by polyphosphate:AMP phosphotransferase and adenylate kinase from <I>Acinetobacter johnsonii</I> 210A
In vitro enzyme-based ATP regeneration systems are important for improving yields of ATP-dependent enzymatic reactions for preparative organic synthesis and biocatalysis. Several enzymatic ATP regeneration systems have been described but have some disadvantages. We report here on the use of polyphosphate:AMP phosphotransferase (PPT) from<em>Acinetobacter johnsonii</em> strain 210A in an ATP regeneration system based on the use of polyphosphate (polyP) and AMP as substrates. We have examined the substrate specificity of PPT and demonstrated ATP regeneration from AMP and polyP using firefly luciferase and hexokinase as model ATP-requiring enzymes. PPT catalyzes the reaction polyP<sub><em>n</em></sub> + AMP → ADP + polyP<sub><em>n</em>−1</sub>. The ADP can be converted to ATP by adenylate kinase (AdK). Substrate specificity with nucleoside and 2′-deoxynucleoside monophosphates was examined using partially purified PPT by measuring the formation of nucleoside diphosphates with high-pressure liquid chromatography. AMP and 2′-dAMP were efficiently phosphorylated to ADP and 2′-dADP, respectively. GMP, UMP, CMP, and IMP were not converted to the corresponding diphosphates at significant rates. Sufficient AdK and PPT activity in <em>A. johnsonii</em> 210A cell extract allowed demonstration of polyP-dependent ATP regeneration using a firefly luciferase-based ATP assay. Bioluminescence from the luciferase reaction, which normally decays very rapidly, was sustained in the presence of <em>A. johnsonii</em> 210A cell extract, MgCl<sub>2</sub>, polyP<sub><em>n</em>=35</sub>, and AMP. Similar reaction mixtures containing strain 210A cell extract or partially purified PPT, polyP, AMP, glucose, and hexokinase formed glucose 6-phosphate. The results indicate that PPT from <em>A. johnsonii</em> is specific for AMP and 2′-dAMP and catalyzes a key reaction in the cell-free regeneration of ATP from AMP and polyP. The PPT/AdK system provides an alternative to existing enzymatic ATP regeneration systems in which phosphoenolpyruvate and acetylphosphate serve as phosphoryl donors and has the advantage that AMP and polyP are stabile, inexpensive substrates.
Transport of Cu, Zn and Cd in a small agricultural catchment
Concentrations of dissolved and particulate metals (Cu, Zn and Cd) were determined in water samples collected during several rain events from the River Kleine Aa, a first order tributary to Lake Sempach (Central Switzerland). Metal contents were also measured in soil cores obtained from fertilized and unfertilized areas of the catchment and in liquid manure samples. The contribution of farming activities to the metal loads was evaluated.<br/>
Because total metal concentrations were linearly related to water discharge, rain events significantly contribute to the yearly metal load. During such events, metals were predominantly associated to particles, but dissolved copper constituted up to half of the Cu load at low flow rates. Dissolved Cu concentrations exceeded dissolved Zn concentrations at low discharge rates, and in experimental water extracts of the grassland soil. The dynamic behavior of dissolved metals and dissolved organic carbon were linked in the river water and in the soil extracts. Metal concentration of suspended particles decreased with increasing discharge to a constant level with Cu and Zn contents similar to those of the grassland topsoil. Their Cd content was, however, lower than in the soil. These observations suggest that the grassland topsoil is the main source of dissolved and particulate trace metals in the river water.<br/>
Farming activities have caused metal accumulation, since the metal contents in the grassland soil were highest at the surface and higher than in the forest soil at any depth. Based on a metal budget of the drainage area and on metal profiles of forest and grassland soil, it is concluded that frequent application of liquid manure with high metal concentrations was mainly responsible for the high Cu and Zn content of the soil and the elevated loss rates to the river, whereas air pollution mainly explained the elevated Cd load of the drainage basin and the river water.
Steady-state modelling of biogeochemical processes in columns with aquifer material: 2. Dynamics of iron-sulfur interactions
Serial data from column experiments were used to develop a dynamic model to describe the evolution of concentration profiles of redox-sensitive chemical components such as iron(II), sulfate/sulfide, FeOOH(s), and FeS(s). The experimental results were gained from a study with a laboratory column filled with aquifer sand and operated in a water-saturated state. "Reduction of sulfate", "reduction of FeOOH(s)", "formation of FeS(s)" and "precipitation of FeS(s)" were identified as slow nonequilibrium reactions. The rate coefficients of these processes were determined by using an extended version of the program STEADYQL in combination with the parameter optimisation program SUFI. Based on this kinetic information it is possible to carry out prognostic modelling of the propagation of a sulfide plume in an anaerobic aquifer if the main characteristics of the solids' surfaces are known.<br/>
The major sink for sulfide turned out to be FeOOH(s) that is gradually transformed into FeS(s). The Ti(III)EDTA-extractable fraction of FeOOH(s) appeared to be a good measure for the overall sulfide-immobilisation capacity. Under the prevailing experimental conditions with a flow velocity of approximately 1 m/day and a dissolved sulfate concentration in the inflow of 215 μM, the calculated sulfide front migrates in the order of 1 m/year. These model findings indicate that even in aquifers, where strongly reducible conditions are predominant, sulfide immobilisation by iron may lead to a sulfide-free groundwater for a long period.
Larch needle breakdown in contrasting streams of an alpine glacial floodplain
Larch (<I>Larex decidua</I> Mill.) is an early successional tree species of glacial sediments and valley side-slopes at treeline in the Swiss Alps. In such areas, the needles from this deciduous conifer are a dominant source of particulate organic matter to springs and streams of glacial floodplains. We examined the breakdown of larch needles in 5 stream types of a glacial floodplain in the Swiss Alps in relation to macroinvertebrates, aquatic fungi, and litter nutrient concentrations. The 5 streams ranged from a physically harsh pro-glacial (kryal) stream that lacked significant input of terrestrially derived particulate organic matter to a stable side-slope springbrook that flowed through a mixed larch/pine forest with alder also present in the riparian zone. We hypothesized that needle breakdown (as a surrogate of ecosystem function) would be significantly faster in the springbrook than in the other streams, reflecting differences in macroinvertebrate and fungal assemblages present among streams. Although needle breakdown was generally slow, especially relative to alder leaves, parameters of litter breakdown were indeed higher in the springbrook than in the other streams. Concentrations of nutrients (N and P) found in decomposing needles were 2 to 4× higher in the springbrook than in the other streams. Ergosterol levels (a measure of fungal biomass) in needles were 4× greater in the springbrook than for needles in the kryal and main channel sites. Last, abundances of macroinvertebrates colonizing needle packs, shredders in particular, were higher in the springbrook and a side-channel site than in the other stream types. The results emphasize the importance of trophic linkages in the successional development and function of lotic ecosystems.
Ozonation of bromide-containing drinking waters: a delicate balance between disinfection and bromate formation
The occurrence of <I>Cryptosporidium</I> in raw waters and bromate formation during ozonation of bromide-containing waters leads to a difficult optimisation of ozonation processes. On the one hand inactivation of <I>Cryptosporidium</I> requires high ozone exposures, on the other hand under these conditions bromate formation is favored. In order to overcome this problem we need information about (i) the oxidant concentrations (ozone and OH radicals) during an ozonation process, (ii) kinetics of the inactivation of <I>Cryptosporidium</I>, (iii) kinetics and mechanism of bromate formation, and (iv) the reactor hydraulics. The strong temperature dependence of the inactivation of <I>Cryptosporidium</I> which results in a higher ozone exposure (time-integrated action of ozone) at low temperatures makes it more difficult to fulfil disinfection and bromate standards at low temperatures. Under these conditions control options for bromate formation can be applied. Depression of pH and addition of ammonia have been selected to be the best options. For a given ozone exposure both measures lead to a reduction of bromate formation in the order of 50%.
Determination of solar cycle length variations using the continuous wavelet transform
The length of the sunspot cycle determined by Friis-Christensen & Lassen (1991) correlates well with indicators of terrestrial climate, but has been criticized as being subjective. In the present paper we present a more objective and general cycle- length determination. Objectivity is achieved by using the continuous wavelet transform based on Morlet wavelets and carrying out a careful error analysis. Greater generality comes from the application of this technique to different records of solar activity, e.g. sunspot number, sunspot area, plage area or Be-10 records. The use of different indicators allows us to track cycle length variations back to the 15th century. All activity indicators give cycle length records which agree with each other within the error bars, whereby the signal due to the solar cycle is weaker within Be-10 than in the other indicators. <BR/>
In addition, all records exhibit cycle length variations which are, within the error bars, in accordance with the record originally proposed by Friis-Christensen & Lassen (1991). In the 16th century, however, the Be-10 record suggests a much longer cycle than the auroral record used by Friis- Christensen & Lassen. Also, the presence of a distinct 11-year cycle in the Be-10 record during the Maunder Minimum is confirmed. By combining the results from all the indicators a composite of the solar cycle length is constructed, which we expect to be more reliable than the length derived from individual records.
Surface turbulence in natural waters: a comparison of large eddy simulations with microstructure observations
Turbulent properties of the surface layer of stratified lakes have been quantified from temperature microstructure measurements made during convective conditions. Large eddy simulations have been performed using corresponding surface boundary conditions. We compare rates of dissipation of turbulent kinetic energy and dissipation of temperature variance obtained from observations with those obtained from large eddy simulations. While profiles of the rate of dissipation of turbulent kinetic energy can be reproduced very well by the model, the rate of dissipation of temperature variance exhibits smaller values in the calculations. Other statistical characteristics of turbulence agree for both properties. We show that part of the discrepancy derives from large-scale lateral advection, which is not represented by the model, while turbulence on the microscale is reproduced well.
Chlorine 36 fallout in the Summit Greenland Ice Core Project ice core
The natural cosmogenic radioisotope <sup>36</sup>Cl has been measured in the Greenland Ice Core Project ice core from Summit, Greenland. Generally, a good correlation between <sup>36</sup>Cl and δ<sup>18</sup>O was found, even in glacial periods with strong δ<sup>18</sup>O oscillations. The <sup>36</sup>Cl flux is calculated assuming an exponential relationship between accumulation rate and δ<sup>18</sup>O. A prominent excursion is detected between 35 and 40 kyr B.P., which coincides with a similar <sup>10</sup>Be peak measured in the same samples. This sheds light on possible causes of this excursion. In the lowest part of the ice core the flux decreases smoothly. This can be interpreted as radioactive decay of <sup>36</sup>Cl (<em>T</em><sub>1/2</sub>=300 kyr).
Predator-mediated plasticity in morphology, life history, and behavior of <I>Daphnia</I>: the uncoupling of responses
We studied the way 12 traits responded to fish kairomones in a set of 16 <I>Daphnia magna</I> clones derived from four different habitats-two where daphnids co-occur with fish and two without fish. These clones differed widely in their response to predator kairomones, with none of the clones showing a significant response in all traits and all clones showing a response for at least one trait. Most of the clones showed a significant response in one to four traits, with no evidence for an association between different traits. Clones from fish habitats were slightly more responsive to the presence of fish kairomones than clones from fishless locations. We conclude that most clones show an induced response to the presence of their predators (fish) but that there is a large genetic variability with respect to the traits for which clones show a response. Our results indicate that the major distinction is not between inducible and noninducible genotypes but rather that the genotypes differ in the combination of traits for which they show inducible responses.
Benzene- and naphthalenesulfonates in leachates and plumes of landfills
Benzene- and naphthalenesulfonates (BS, NS) are xenobiotic, highly water-soluble chemical compounds that are used for the production of many consumer products such as fluorescent whitening agents, dyes, or concrete plasticizers, and for various applications in industrial processes. They are mainly introduced into ambient waters by industrial or municipal wastewater directly or following municipal sewage treatment. In order to characterize an additional pathway for BS and NS into the environment, leachates and groundwater samples collected from the pollution plumes of four Swiss landfills were investigated. The samples were analyzed using ion-pair liquid chromatography with UV absorption and fluorescence detection. Liquid chromatography coupled to mass spectrometry was performed for the selective identification of aromatic monosulfonates. The results show that landfill sites are point sources for BS and NS in the aquatic environment. BS and NS were measured in the leachates at a wide concentration range from a few μg l<sup>-1</sup> up to several mg l<sup>-1</sup>, depending on the composition of the deposited material. Their contribution to the leachate DOC was from below 1‰ up to around 30%. BS and NS were also found in groundwater samples contaminated by percolating leachates. The concentrations, which contributed less than 1‰ to the groundwater DOC, ranged from a few ng l<sup>-1</sup> to several μg l<sup>-1</sup>.
Degradation of metal-EDTA complexes by resting cells of the bacterial strain DSM 9103
Ethylenediaminetetraacetate (EDTA), an industrially important chelating agent, forms very stable complexes with di- and trivalent metal ions, and in both wastewater and natural waters it is normally present in the metal-associated form. Therefore, the influence of EDTA speciation on its utilization by the EDTA-degrading bacterial strain DSM 9103 was investigated. EDTA-grown cells harvested from the exponential phase of a batch culture were incubated with 1 mM of various EDTA species and the EDTA concentration in the assay was monitored as a function of time. Uncomplexed EDTA as well as complexes with low stability constants (MgEDTA<SUP>2-</SUP>, CaEDTA<SUP>2-</SUP>, and MnEDTA<SUP>2-</SUP>, stability constant < 10<SUP>16</SUP>) were found to be readily degraded to completion at a constant rate. For more stable EDTA chelates (i.e. chelates of Co<SUP>2+</SUP>, Cu<SUP>2+</SUP>, Zn<SUP>2+</SUP>, and Pb<SUP>2+</SUP>) the data suggest that these complexes were not used directly by the cells but that they had to dissociate prior to degradation. The rate of this dissociation step possibly determined the microbial degradation of these complexes. CdEDTA<SUP>2-</SUP> and Fe(III)EDTA<SUP>-</SUP> were not degraded within 48 h. in case of CdEDTA<SUP>2-</SUP> the toxicity of freed Cd<SUP>2+</SUP> ions most likely prevented a significant degradation of the complex, whereas in case of Fe(III)EDTA<SUP>-</SUP> a combination of metal or complex toxicity and the very slow dissociation of the complex might explain the absence of degradation.
Quality of roof runoff for groundwater infiltration
The assumption that roof runoff can be considered as non-polluted stormwater that can be discharged directly into natural water bodies without impairing their quality and use was examined in a field study.<br/>
Concentrations of major ions; total C, N, and P; heavy metals (Cu, Zn, Pb, Cd, Cr, Mn, Fe) and pesticides (triazines, acetamides, phenoxy acids) were measured in runoff from an inclined tile roof, an inclined polyester roof and a flat gravel roof. Runoff from the first two roofs showed initially very high concentrations declining rapidly to lower constant levels. This first-flush effect was modelled using a first-order rate law (wash-off function). For most constituents, concentrations were in the range of the wet deposition after the first few mm runoff depth and total loads in the runoff corresponded approximately to the total (dry and wet) atmospheric deposition load. The flat gravel roof depicted a different behaviour. Rainwater was first retained before it overflowed. Consequently gravel will be weathered and most pollutants were partially retained in the gravel layer. However, corrosion of Cu in drains (rate about 5 g m<sup>-2</sup> y<sup>-1</sup>) produced such high Cu concentrations that direct disposal of runoff is questionable.
Predator-induced life-history changes and the coexistence of five taxa in a <I>Daphnia</I> species complex
Interspecific hybridization is common in water fleas of the <I>Daphnia galeata</I> species complex (e.g. <I>D. galeata</I>, <I>D. cucullata</I>, <I>D. hyalina</I> and their interspecific hybrids). We studied the effect of fish on the life histories of live taxa of this species complex originating from the Plußsee, northern Germany. Using four clones per taxon, we found that fish kairomones reduce size at birth and size at maturity significantly. For size at maturity larger taxa showed a significantly stronger reaction to fish kairomones than the smaller taxa. With respect to the intrinsic rate of increase, <I>r</I>, we compared two predation regimes (positive size selective and not selective). We found that under the fish predation regime most clones had a higher <I>r</I> when cultured with fish kairomones, leading to a higher <I>r</I>, and a stronger reaction for the smaller taxa. We conclude that fish predation might be an important factor influencing the co-occurrence of <I>Daphnia</I> parental taxa with their hybrids.
Inter-annual patterns in macroinvertebrate communities of wilderness streams in Idaho, U.S.A.
This study examined the inter-annual variation in macroinvertebrate assemblages in six wilderness streams in central Idaho over a 6-year period (1990-1995). Benthic macroinvertebrates and associated environmental correlates were sampled during baseflow each summer. Little environmental change, as assessed using coefficients of variation (CVs) for substrate size and embeddedness, width, depth and periphyton standing crops, occurred in the streams over the period of study. There was also little temporal change in macroinvertebrate assemblages based on the relative abundance of the 10 most abundant taxa, all shredder taxa and all plecopteran taxa. CVs for individual taxa were substantially greater than those of most community measures, with rare taxa contributing 30-50% of the variation for any one stream. Frequency distributions for taxa CVs excluding rare taxa were more normally distributed. Differences in assemblage structure among streams were attributed to stream size (shift in shredder assemblages) and temperature (shift in plecopteran taxa). These data indicate a long-term (multi-year) persistence in the macroinvertebrate composition of these pristine streams, thus supporting the premise that such streams are excellent references for use in long-term biomonitoring programs.
Integrated Urban Water Systems (IUWS) - an international postgraduate course
In this paper we describe the background, the concept and the current status of an international postgraduate course on the subject of integrated urban water systems. The course aims to overcome the typical fragmentation of the engineering curricula in that field. Hence, the objective is to give a comprehensive overview on the total urban water and pollutant cycle, thus hoping to provide the students with a wider perspective on the problem. The course is structured into 22 modules that can also be taught in certain combinations. Emphasis is given to engineering problem solving and modeling.
Seasonal effects of disturbance on a lake outlet algal assemblage
Streams flowing from lakes typically have high standing crops of filamentous algae and associated diatoms. Most outlet streams show more constant environmental conditions than other comparably-sized streams, as the lake ameliorates extreme fluctuations in flow, temperature, and water chemistry. We examined the recovery dynamics of periphyton following disturbance in a low elevation lake outlet in spring, summer, and winter. In each season, replicated 1 m<sup>2</sup> areas were disturbed every 0 (not disturbed), 5, 10, and 30 days. After 30 days, each area was sampled and assessed for periphyton biomass, relative abundance of common algal tars or groups (e.g. <I>Cladaphora glomerata</I> (L.) Kütz., pennate diatoms), and diatom composition. Periphyton biomass of undisturbed areas was 4x greater in spring and winter than in summer, probably due to seasonal changes in ambient light (i.e, canopy coverage) and temperature. Response to disturbance varied seasonally with recovery fastest in summer (30 days). Recovery primarily reflected increases in periphyton standing crops (i.e. growth of <I>Cladophora</I>) and seasonal changes in the abundance of some diatom species (e.g. <I>Cocconeis placentula</I> var. <I>euglypta</I> (Ehr.) Cl., <I>Achnanthes minutissima</I> Kütz., and <I>Nitzschia dissipata</I> (Kütz.) (Grun.)). Principal components analysis revealed that other diatom species also showed a change in abundance to frequent disturbance in spring and winter, but not in summer. Our results indicate that recovery of lake outlet periphyton assemblages following disturbance reflects seasonal differences in the abundances of specific taxa. The interplay between algal life histories and seasonal changes in environmental conditions play a strong role in the recovery dynamics of algal communities to physical disturbance.
Distribution patterns of benthic crustaceans in a formerly meromictic lake with changing trophic conditions (Lake Piburg, Tyrol, Austria)
The change of the crustacean fauna in the soft sediment of an Alpine lake (Lake Piburg) due to reoligotrophication is investigated. Samples were taken with a Core-Sampler (Kajak-type) along two transects from 5 m to the maximum depth of the lake (24 m) in November 1994 and May 1995, and compared to a study from 20 years ago. The crustacean fauna typically consisted of Cladocera, Copepoda, and Ostracoda with benthic, planktonic and diapausing representatives. Density and biomass of crustaceans showed high variation with water depth and season. The average density of crustaceans in the soft sediment reached 105,289 ind. m<sup>-2</sup> with a biomass of 409.9 mg DW m<sup>-2</sup> in November; in May these values were much lower (25,333 ind. m<sup>-2</sup> and 66.1 mg DW m<sup>-2</sup>). Comparisons with an earlier study, when the hypolimnion was anoxic, suggest that changes in distribution patterns, densities, and species composition were due to a change in trophic state. The recovery of the hypolimnion reflected a trend towards oligotrophy. In contrast, the crustacean community in the hypolimnion still indicates eutrophy.
Neue Konzepte und Methoden für die mikrobiologische Qualitätssicherung des Trinkwassers
Microbial testing of drinking water has not significantly changed during almost one hundred years. Nevertheless the concept of using indicator organisms is still valid. But especially for treated drinking water, adaptation of the testing is needed. A lot can be learned in this respect from the food industry, where this problem has been solved by the HACCP (hazard assessment and critical control points) concept. Routine detection of pathogens in the finished drinking water using molecular methods will not improve safety of drinking water. These methods will, however, be of extreme value for the study of outbreaks.
Genetic markers, genealogies and biogeographic patterns in the cladocera
Cladoceran crustaceans are an important component of zooplankton in a wide range of freshwater habitats. Although the ecological characteristics of several cladoceran species have been well studied, biogeographical studies have been hampered by problematic taxonomic affiliations. However, recently developed molecular techniques, provide a powerful tool to subject aquatic taxa to comparative analyses. Here we highlight recent molecular approaches in aquatic ecology by presenting a simple method of DNA preparation and PCR amplification of the mitochondrial DNA (16S rDNA) in species from nine different families within the cladocera. On a broad taxonomic scale, sequence analysis of this mtDNA fragment has been used to produce the first molecular based phylogeny of the cladocera. This analysis clustered the cladoceran families in a fashion similar to that suggested by previous systematic classifications. In a more detailed analysis of the family Daphniidae, nuclear randomly amplified polymorphic DNA (RAPD), mitochondrial restriction fragment length polymorphism (RFLP) and morphological analyses were combined to identify species and interspecific hybrids within the <I>Daphnia galeata</I> species complex across 50 lakes in 13 European countries and one lake in Africa. The study revealed interspecific hybridization and backcrossing between some taxa (<I>D. cucullata</I> and <I>D. galeata</I>) to be widespread, and species and hybrids to frequently occur in sympatry. Genetic, as well as morphological information, suggests the occurrence of <I>D. hyalina</I> outside the Holarctic.
Environmental stress and local adaptation in <I>Daphnia magna</I>
The effects of fish kairomones, crowding chemicals, and day length on the life-history traits of a set of 16 <I>Daphnia magna</I> clones, derived from four populations that differ in fish-predation pressure, were studied. Significant among-population differences were observed, the differences being in concordance with the hypothesis of local adaptation. The among-population genetic differences were not mediated through a change in response to fish kairomones, but through an overall smaller body size, smaller eggs, and a higher number of eggs in clones derived from habitats in which fish are present. Using a model, we show that the observed changes in life-history characteristics may lead to differences in fitness under different predation regimes, such that populations from habitats with fish have highest fitness under fish-predation regimes and populations without a fish background have higher fitness values under invertebrate predation regimes.
Hydroxyhydroquinone reductase, the initial enzyme involved in the degradation of hydroxyhydroquinone (1,2,4-trihydroxybenzene) by <I>Desulfovibrio inopinatus</I>
The recently isolated sulfate reducer Desulfovibrio inopinatus oxidizes hydroxyhydroquinone (1,2,4-trihydroxybenzene; HHQ) to 2 mol acetate and 2 mol CO<sub>2</sub> (mol substrate)<sup>-1</sup>, with stoichiometric reduction of sulfate to sulfide. None of the key enzymes of fermentative HHQ degradation, i.e. HHQ-1,2,3,5-tetrahydroxybenzene transhydroxylase or phloroglucinol reductase, were detected in cell-free extracts of D. inopinatus, indicating that this bacterium uses a different pathway for anaerobic HHQ degradation. HHQ was reduced with NADH in cell-free extracts to a nonaromatic compound, which was identified as dihydrohydroxyhydroquinone by its retention time in HPLC separation and by HPLC-mass spectrometry. The compound was identical with the product of chemical reduction of HHQ with sodium borohydride. Dihydrohydroxyhydroquinone was converted stoichiometrically to acetate and to an unknown coproduct. HHQ reduction was an enzymatic activity which was present in the cell-free extract at 0.25-0.30 U (mg protein)<sup>-1</sup>, with a pH optimum at 7.5. The enzyme was sensitive to sodium chloride, potassium chloride, EDTA, and o-phenanthroline, and exhibited little sensitivity towards sulfhydryl group reagents, such as copper chloride or p-chloromercuribenzoate.
Nutrient addition accelerates leaf breakdown in an alpine springbrook
This study assessed the effect of nutrient enrichment on organic matter breakdown in an alpine springbrook, using alder leaf packs to which phosphorus and nitrogen were added in the form of slow-release fertilizer briquettes. The breakdown of leaf packs with nutrients added (<I>k</I>=0.0284 day<sup>-1</sup>) was significantly faster than that of unfertilized packs (<I>k</I>=0.0137 day<sup>-1</sup>), resulting in a 30% higher mass loss after 42 days. Unfertilized leaves enclosed in fine-mesh bags broke down at an even slower rate (<I>k</I>=0.0062 day<sup>-1</sup>). Phosphorus and nitrogen concentrations were initially higher in leaf packs with nutrients added, but this difference disappeared within 3 weeks. Fungal biomass developing in decomposing leaves was substantial (<I>c</I>. 55 mg dry mass per 1 g leaf dry mass) although similar between fertilized and unfertilized packs, as was the sporulation activity of aquatic hyphomycetes. There was a significantly greater number and higher biomass of macroinvertebrates (shredding nemourid stoneflies in particular) on the fertilized packs, suggesting that the increased leaf mass loss was brought about by shredder feeding.
Structure of a glutathione peroxidase homologous gene involved in the oxidative stress response in <I>Chlamydomonas reinhardtii</I>
The organisation and nucleotide sequence of the single copy glutathione peroxidase homologous gene <I>gpxh</I> from <I>Chlamydomonas reinhardtii</I> is reported. The <I>gpxh</I> gene consists of five exons and four introns, and encodes a predicted protein (GPXH) of 162 amino acids. GPXH belongs to the family of glutathione peroxidase (GPX)-like proteins and showed high homology with the deduced amino acid sequences of <I>gpx</I>-related genes from yeast (67-78% similarity) and from plants (60-65% similarity). The GPXH from <I>C. reinhardtii</I> differs from the well characterized mammalian cytosolic GPX (GPX1) in that it contains a normal cysteine residue instead of a selenocysteine, that the residues responsible for glutathione binding at the reactive center in GPX1 are not present, and that two amino acid stretches important for the tetramerisation of GPX1 are absent. Northern blot experiments revealed a single 1.3 kb mRNA of which the cellular concentration is elevated strongly upon exposure to chemicals causing oxidative stress. In addition, salt stress did cause a weak increase in mRNA concentration. This indicates that <I>gpxh</I> is an oxidative stress responding gene rather than a general stress responsive gene.
Calibration of full-scale ozonation systems with conservative and reactive tracers
A full-scale ozonation reactor was characterised with respect to the overall oxidation budget by coupling laboratory kinetics with reactor hydraulics. The ozone decomposition kinetics and the ratio of the OK radical to the ozone concentration were determined in laboratory batch experiments. With the computer model AQUASIM these parameters could be coupled with the hydraulics of the ozonation reactor which allowed the prediction of the behaviour of ozone, chlorine, and micropollutants (e.g. atrazine) in the reactor. The comparison of measured and modelled concentration showed an excellent agreement. The present study summarises a general approach of how full scale ozonation reactors can be calibrated to assess disinfection, oxidation and minimise disinfection by-products, such as bromate.