Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1990"

Isolation and characterization of a bacterium that mineralizes toluene in the absence of molecular oxygen.

Abstract: A bacterium tentatively identified as a Pseudomonas sp. was isolated from a laboratory aquifer column in which toluene was degraded under denitrifying conditions. The organism mineralized toluene in pure culture in the absence of molecular oxygen. In carbon balance studies using [ring-UL-14C]toluene, more than 50% of the radioactivity was recovered as 14CO2. Nitrate and nitrous oxide served as electron acceptors for toluene mineralization. The organism was also able to degrade m-xylene, benzoate, benzaldehyde, p-cresol, p-hydroxy-benzaldehyde, p-hydroxybenzoate and cyclohexanecarboxylic acid in the absence of molecular oxygen.

Dynamics of microbial growth and cell composition in batch culture

Abstract: Wha t does a batch growth curve look like? T~e answer to this quest ion seems straight forward and any microbiology text book will provide you with virtual!y the same s tandard growth curve as the one depicted in Fig. 1. It is obvious that exponential growth in a closed system cannot go on ad infinitum: sooner or later one of the essential nutrients will be exhausted and it is generally thought (and taught) that, no matter what the growth-l imit ing nutr ient is, growth s tops abruptly after its depletion. But is the answer really as clear-cut as has been taught for some seven decades since Buchanan's first review [1| on this subject? Here this question for the simple ease of a heterotrophic, aerobic microbe will be addressed and some of the effects caused by depletion of different nutrients on the dynamics of growth and

Kinetics of Trace Metal Complexation: Ligand-Exchange Reactions

Abstract: In this study, we have investigated rates of complex dissociation and ligand exchange for copper under environmentally relevant conditions of pH and metal and ligand concentrations. We have determined the predominant mechanistic pathways for exchange reactions with model ligands under such conditions, focusing on the effects of the relative concentrations of the competing ligands and of the metal-to-ligand ratios. We then examined the kinetics of ligand-exchange reactions of humate-bound copper. These reactions can be described in terms of the mechanisms applicable to the model ligands.

Interaction of trace metals with natural particle surfaces: comparison between adsorption experiments and field measurements.

Abstract: The distribution of the metal ions Zn and Pb between particulate and dissolved phase in river Glatt was studied by field measurements and compared with calculated simulations, using parameters obtained by adsorption experiments with natural suspended particulate material. Differences in distribution coefficients obtained from field data are observed in function of the sampling locations and of the composition of the particulate matter. Experiments in which metal ion solutions are titrated with a suspension of natural particles and analyzed by anodic stripping voltammetry, are interpreted in terms of binding capacities and conditional stability constants of Zn and Pb with the surface sites. Binding constants of a particular metal ion varied very little for all samples. We obtained mean values for the conditional average complex formation constants at pH 8 of: logcond K Pb = 9.44 ± 0.18 and logcond K Zn = 8.17 ± 0.20. At this pH, binding capacities of 5 ⋅ 10−3 – 1.7 ⋅ 10−2 mol/kg of particles were obtained for samples collected at different locations and times; organic material, iron and manganese oxides are considered to be the main components that control the adsorption to the particles. Distribution coefficients are calculated from the experimentally obtained binding capacities and conditional stability constants. Calculated distribution coefficients for Zn agree with those obtained from the field data and are not very sensitive to changes in the composition of the solution. Good agreement was obtained for lead as well; for some samples it was important to take two types of sites with different affinity into consideration.

Biogeochemistry of iron in an acidic lake.

Abstract: In this paper, the fate of iron in Lake Cristallina, an acidic lake in the Alps of Switzerland, is discussed. A simple conceptual model is developed in order to explain the observed diel variation in dissolved iron(II) concentration. Biotite weathering provides reduced iron that is oxidized and subsequently precipitated in the lake. The amorphous Fe(III)hydroxide (FeOOH ⋅xH2O), found in the sediments of Lake Cristallina, is an Fe(II) oxidation product. This oxygenation reaction is most probably catalyzed by bacteria surfaces, as indicated by the relatively high estimated oxidation rate compared to the oxidation rate of the homogeneous oxidation of inorganic Fe(II) species at the ambient pH of Lake Cristallina (pH 5.4 at 4 °C) and by the scanning electron micrograph pictures. Under the influence of light, these amorphous iron(III)hydroxide phases are reductively dissolved. The net concentration of Fe(II) reflects the balance of the reductive dissolution and the oxidation/precipitation reactions and tends to parallel the light intensity, leading to a diurnal variation in the Fe(II) concentration. The rate of the photochemical reductive dissolution of Lake Cristallina iron(III)hydroxides is greatly enhanced in situ and in the laboratory by addition of oxalate to the lake water.

Isolation and growth of a bacterium able to degrade nitrilotriacetic acid under denitrifying conditions.

Abstract: A Gram-negative bacterium was isolated from river sediment which was able to grow with nitrilotriacetic acid as a combined carbon, nitrogen and energy source in the absence of molecular oxygen using nitrate as the terminal electron acceptor. Batch growth parameters and mass balances are reported for growth under both aerobic and denitrifying conditions.

The past 5000 Years History of Solar Modulation of Cosmic Radiation from $^{10}$Be and $^{14}$C Studies

Abstract: 10 Be is produced in a similar way as 14 C by the interaction of cosmic radiation with the nuclei in the atmosphere. Assuming that the 10 Be and 14 C variation are proportional and considering the different behaviour in the Earth system, the 10 Be concentrations in ice cores can be compared with the 14 C variations in tree rings. A high correlation is found for the short-term variations ( 14 C-Suess-wiggles). They reflect with a high probability production rate variations. More problematic is the interpretation of the long-term trends of 14 C and 10 Be. Several explanations are discussed. The reconstructed CO 2 concentrations in ice cores indicate a rather constant value (280 ± 10 p.p.m. by volume) during the past few millenia. Measurements on the ice core from Byrd Station, Antarctica, during the period 9000 to 6000 years BP indicate a decrease that might be explained by the extraction of CO 2 from the atmosphere-ocean system to build the terrestrial biomass pool during the climatic optimum.

Heavy metals in the Dead Sea and their coprecipitation with halite

Abstract: After a prolongued period of stratification (about 300 years) the Dead Sea overturned in 1979 and again in 1982. Its waters became saturated with respect to halite and the massive precipitation of halite which occurred in winter 1982/83 has been monitored. We followed the fate of the heavy metals during this period of physical and chemical changes.

Use of dual-beam acoustic technique for detecting young whitefish, Coregonus sp., juveniles : first experiments in an enclosure

Abstract: We tested the possibility of using a high-frequency, BioSonics, dual-beam, acoustic system with an upwards-looking transducer to detect very young whitefish, Coregonus sp., juveniles. These first experiments were conducted in an enclosure with 100 fish (20–30 mm total length). Observations over 24-h periods showed wide variations of the fish vertical distribution (> 5 m) and two typical aggregation patterns in near-surface waters at dawn and dusk. No direct relationship was found between light intensity and distribution of the fish during the day. The mean target strength of young whitefish juveniles was found to be – 56 dB when fish were staying near the surface and – 63 dB as they were moving up- or downwards.

Ökotoxikologie am Beispiel der Rheinverschmutzung durch den Chemie-Unf all bei Sandoz in Basel

Abstract: A fire at a chemical manufacturing plant at Schweizerhalle (near Basel) in November 1986 and the subsequent release of toxic agrochemicals into the Rhine river is taken as a basis to discuss some problems and needs in ecotoxicological research. Especially serious is the lack of knowledge about chronic effects of mixtures of chemicals to individuals and whole ecosystems. There is an urgent need for generally applicable principles and concepts. A discussion of the relationship between toxic effects to fish, exposure time, and concentration provides some hints about the direction towards which research should proceed. Finally, eight theses pertaining to ecotoxicology summarize what can be learned from the analysis of a chemical spill.

Von der Industriellen Revolution zu den Grenzen des Wachstums

Abstract: Heute ist der 11.11, es ist 1108 h, in 3 Minuten beginnt die Fasnacht. Die Fasnacht war einst ein Ventil gegen die strikten Regeln der Kirche und der Gesellschaft, das wir heute nicht mehr notig zu haben scheinen, leben wir doch in einer Gesellschaft ohne Tabus und Autoritat. Und doch erfreut sich die Fasnacht zunehmender Beliebtheit (es soll sogar eine Fasnacht in Zurich geben!). Mag da etwa mitspielen, dass wir die Verkleidung vermehrt dazu brauchen, vor uns selbst, vor unserem im Wohlstand ertrinkenden und daher beangstigenden Leben Distanz zu gewinnen?

Flux Measurements over Prairie Grasslands in Northern Colorado

Abstract: The fluxes of nitrogen oxides and ozone have been measured over the prairie grassland of Northern Colorado by eddy correlation. The deposition velocity of ozone varied diurnally. The ozone maximum deposition velocity occurred at around midday, Vd = 0.4 cm s-1, and was zero overnight. The net flux of nitrogen oxides was upward, with a diurnal and a seasonal variation. In early spring there was an upward flux during the day, and zero or a slight downward flux overnight. The daytime NOx fluxes increased from the spring to early summer, as the soil temperature increased. During the summer, moderate rainfall after a few days drought initiated large bursts of upward NOx flux. The average NO2 flux for the period March — July was 1.7 ng N m-2s-l (peak 8.8 ng N m-2s-1), and the average NOx flux for June and July was 5.1 ng N m-2s-l (peak 17.3 ng N m-2s-1).