Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1995"

Microbial mediation as a possible mechanism for natural dolomite formation at low temperatures

Abstract: DOLOMITE (CaMg(CO3)2) is a common carbonate mineral which is found in much greater abundance in ancient rocks than in modern carbonate environments. Why this is so remains a mystery. Over the past 30 years, dolomite formation has been observed in several modern environments, and various thermodynamic, kinetic and hydrological factors have been proposed to explain its formation1,2. But attempts to precipitate dolomite at low temperatures in the laboratory have been unsuccessful3,4, and the 'dolomite problem' remains a source of controversy in sedimentary geology5-7. Here we describe experiments in which a ferroan dolomite with a fairly high degree of cation order was precipitated in the presence of sulphate-reducing bacteria from the Desulfovibrio group. We propose that the direct mediation of these anaerobes can overcome the kinetic barrier to dolomite nucleation, and that they may play an active role in the formation of this mineral in natural environments.

Transformation of phosphorus species in settling seston and during early sediment diagenesis

Abstract: Sequential P extraction was combined with electron microscop and X-ray spectroscopy to characterise various P species and to study their transformation in settling seston and in recent sediment. During early diagenesis most of the particulate P formed in the water was redissolved. No net transformation into species that would resist dissolution was observed. It was shown that

Mixing Mechanisms in Lakes

Abstract: Transport phenomena are among the most important processes in natural systems Chemical compounds, the constituents of biogeochemical systems, are in continual motion in all parts of the earth The thermal motion of atoms and molecules is perceived on the macroscopic level as molecular diffusion ie, as the slow but persistent movement “down along the concentration gradient” Although the average speed of the atoms is on the order of tens to hundreds of meters per second, the net transport is small, because the molecules do not maintain the same direction long enough Thus, typical molecular diffusion coefficients of solutes in water are approximately 10-9 m2s - 1 corresponding to characteristic annual transport distances of approximately 20 cm In solids the diffusion coefficients even drop to values as low as 10-14m2s-1 or less

The Ecological and Physiological Significance of the Growth of Heterotrophic Microorganisms with Mixtures of Substrates

Abstract: It has been estimated that globally some 500 × 1012 kg of carbon dioxide are assimilated into biomass by autotrophic organisms annually. More than 99% of this assimilated carbon is remineralized, keeping the global biogeochemical carbon cycle roughly in balance (Hedges, 1992). In both terrestrial and aquatic ecosystems the majority of this primary biomass is not consumed directly by herbivorous animals, but decays to detritus and serves as a nutritional basis for the growth of consumers (for an extensive discussion, see Fenchel and Jorgensen, 1977). There is now substantial evidence suggesting that a large part of the energy and nutrients contained in this primary biomass is processed via the microbial detritus food chain, and this mineralizing ability makes heterotrophic microorganisms an important link in the global carbon cycle (Fenchel and Jorgensen, 1977; Paul and Voroney, 1980; Wetzel, 1984; Cole et al., 1988; Mann, 1988). In addition, their ability to mineralize man-made xenobiotic organic chemicals has become increasingly important. This is illustrated by the fact that in industrialized countries the flux of synthetically produced organic material, much of which is ending up in the environment, has increased within the past two centuries to some 40 g C m−2 year−1. This figure is equivalent to approximately 15% of the net primary biomass production in these regions (Egli, 1992).

Polyphosphate in lake sediments: 31P NMR spectroscopy as a tool for its identification

Abstract: Variations in the nonreactive P content of lake sediments as a consequence of changing redox conditions suggest that microorganisms may contribute to uptake and release of P. In this study, 31-50% of the nonreactive P was identified as polyphosphate (poly-P) in NaOH extracts of sediments from eutrophic Lake Baldegg and oligo-mesotrophic Lake Lucerne by means of 31 P NMR spectroscopy. Poly-P was present in surface sediments but not in deeper sediment layers. In samples where poly-P was detected, analysis under a scanning transmission electron microscope equipped with energy-dispersive X-ray spectroscopy indicated the presence of sediment bacteria containing P-rich granules. Although poly-P is stable in pure NaOH solution, it partially hydrolyzes during and after sediment extraction with NaOH. Cracking of poly-P molecules to shorter fragments is, however, much slower if the sediment is pre-extracted with EDTA and NaOH is replaced by a mixture of NaOH/EDTA to extract nonreactive P from sediments.

Mapping the architecture of glaciofluvial sediments with three-dimensional georadar

Abstract: Three-dimensional (3-D) ground-penetrating radar (georadar) mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units. To investigate the potential of this high-resolution technique and at the same time study the architecture of Quaternary glaciofluvial deposits, georadar data have been collected on a dense grid established across a sequence of braided-river gravels and sands in northeastern Switzerland. Results of this survey are striking 3-D images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data. Continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of (Approx.)15 m. Clearly defined are the dominant flow direction of the ancient braided-river system, the boundaries between different sedimentary facies, and the level of the ground-water table. Trough-fill sediments and subhorizontal channel deposits observed on 7-m-high quarry walls can be followed confidently in the subsurface. The orientation, shape, and size of the troughs and the strike and dip of the cross-bedding are all well resolved.

Organotins in freshwater harbors and rivers: Temporal distribution, annual trends and fate

Abstract: The occurrence of butyltin and phenyltin compounds in water, mussels, and sediment of freshwater boat harbors of Lake Lucerne, Switzerland, and six Swiss river systems was determined between 1991 and 1993 following the sales ban of organotin-containing antifouling paints. In harbor waters, average levels of tributyltin (TBT) were between 40 and 50 ng/L in 1993, which was one order of magnitude lower than in 1988. Residues of up to 9.2 μg/g TBT and 0.7 μg/g triphenyltin (TPT) occurred in zebra mussels (Dreissena polymorpha) and were related to the water concentrations. In a sediment core, high levels of TBT and TPT occurred in the upper 7 cm and 5.5 cm, respectively, with significant decreases below. Estimated sedimentation rates and the fact that transformation products did not increase with depth indicate that TBT and TPT are persistent in these sediments. In all rivers, di- and/or monobutyltin of up to 46 ng/L occurred consistently, and occasionally TBT and TPT of up to 26 and 11 ng/L, respectively. This study indicates that even though regulations were effective in reducing TBT and TPT levels in boat harbor water, contamination of surface fresh waters including rivers by organotin compounds is still widespread and has ecotoxicological consequences. Moreover, harbor sediments represent long-term reservoirs of these compounds.

Minimum 10Be exposure ages of early Pliocene for the Table Mountain plateau and the Sirius Group at Mount Fleming, Dry Valleys, Antarctica

Abstract: Using accelerator mass spectrometry (AMS), we have measured 10Be and 26Al in quartz from granites and sandstones from Table Mountain and Mount Fleming, Antarctica. Our data show that the plateau surface at Table Mountain had formed by early Pliocene time at the latest. Granites fringing but within the Sirius Group at Table Mountain give a minimum exposure age of 2.6 Ma for this deposit. A sandstone clast on the Ferrar dolerite surface just outside and below, and thus postdating, the Sirius Group has a minimum age of 2.9 Ma. Two samples from the Sirius Group at Mount Fleming have 10Be concentrations that have reached secular equilibrium. This deposit is at least 4.8 m.y. old. The Sirius Group at Mount Fleming cannot have been deposited after 3.0–2.5 Ma, as implied by biostratigraphic data. Our dates contradict the hypothesis that in the Pliocene East Antarctica was deglaciated and the climate was significantly warmer and wetter. The preservation of these surfaces indicates a continuous cold desert in the dry valleys since the beginning of the Pliocene. The high 10Be concentrations we have measured cannot be reconciled with uplift of the Transantarctic Mountains at a rate of 1 km/m.y. during the past 3 m.y.

Competition of copper and zinc for strong ligands in a eutrophic lake

Abstract: Free aquo copper ion and zinc ion concentrations were determined in water samples from eutrophic Lake Greifen by means of ligand exchange with catechol and cathodic stripping voltametry (for Cu) and ligand exchange with EDTA and anodic stripping voltametry (for Zn). The ratios of total dissolved Zn (1 O-40 nM) to dissolved Cu (7-20 nM) were [Zn] : [Cu] = 0.5-3 in samples taken at different seasons of a year; the ratios of the free aquo ion concentrations [Zn’-&] : [Cu2 i ] were - 1 06. pCu was in the range of 14.5-l 5.9 and pZn 8.6-9.5 at different times and depths. The release of Zn from electrochemically inert complexes upon addition of Cu suggested direct competition of Cu and Zn for ligands in all lake-water samples examined. The selectivity of the natural ligands for Cu over Zn was evaluated as the conditional constant for the reaction Cu2 k + ZnL, = Zn2 I + CuL,; K = (1.4-tO.9) x lo6 (average in the euphotic zone; pH 8). These highly selective ligands are probably of biological origin.

Late-glacial pollen and diatom changes in response to two different environmental perturbations: volcanic eruption and Younger Dryas cooling

Abstract: A high-resolution pollen and diatom stratigraphy has been studied from late-glacial annually laminated sediments of Holzmaar (425 m a.s.l., Germany). The sediment sequence studied comprises 475 varves and includes two environmental perturbations of different type and duration: the short, abrupt deposition of the late Allerod tephra layer of the Laacher See volcano (LST, 11 000 yr B.P.), and the more gradual onset of the 'Younger Dryas climatic cooling. Numerical analyses involving (partial) redundancy analyses in connection with Monte Carlo permutation tests suggest that the deposition of 78 mm of Laacher See Tephra had a statistically significant effect on the pollen stratigraphy (percentage and accumulation rates), most probably because of the proximity of the site to the volcano. The diatom accumulation rates also show a statistically significant change, whereas the diatom percentage data do not change significantly. The between-sample rates-of-change in both biostratigraphies are higher at and just after the LST event than at the transition to the Younger Dryas biozone. Sequence splitting of pollen and diatom accumulation rate data also shows a clustering of significant splits at the LST event. A close correlation between changes in the pollen and diatom percentage data for the investigated time-interval suggests a common underlying climatic signal, whereas the accumulation rates of both biostratigraphies behave more individualistically and show more short-term variability due, in part, to the inherent noise in the two data sets. Variance partitioning shows that the local pollen and diatom assemblage zones explain much of the variance in the data-sets. Statistical modelling using redundancy analysis shows that the changes in the diatom assemblages are best predicted by the Younger Dryas biozone and the main changes in the pollen stratigraphy (as represented by the first PCA axis of the pollen data). The results suggest that the biostratigraphies studied at Holzmaar reflect generally stable systems which were disturbed by the deposition of the Laacher See Tephra. After a phase of recovery both systems again reached a new phase of stability prior to the long-term Younger Dryas climatic deterioration that perturbed the assemblages again. The very close and statistically significant parallelism between the major stratigraphical patterns in the pollen and diatom percentage data highlights the responses of the two biological systems to environmental perturbations at different temporal scales.

Environmental Processes Influencing the Rate of Abiotic Reduction of Nitroaromatic Compounds in the Subsurface

Abstract: Numerous synthetic chemicals contain one or several nitro groups that are bound to an aromatic ring. Figure 1 shows the structures of some prominent representatives of such nitroaromatic compounds (NACs). The high toxicity of some NACs, particularly the mutagenic and carcinogenic potential of some nitrated polycyclic aromatic hydrocarbons (PAHs), has led to considerable interest in the fate of such compounds in the environment. Due to their widespread use, NACs are ubiquitous contaminants, especially in aqueous environments. In addition to contamination originating from agricultural use, from production facilities, and waste disposal sites, diffuse input into the pedosphere via the atmosphere has been documented (21, 27, 36, 37, 59, 65, 69, 80, 81). Atmospheric production of significant quantities of NACs by photochemical processes has been reported (19, 29, 42, 80). Table 1 lists some typical concentrations of NACs that have been measured in various compartments of the environment. Very high concentrations of nitroaromatic explosives (2,4,6-trinitrotoluene (TNT) and by-products) have been found especially in soil and subsurface systems. At those sites, significant concentrations of substituted aromatic amines that may have been formed from the reduction of NACs are frequently encountered.

Modeling biofilm accumulation and mass transport in a porous medium under high substrate loading.

Abstract: A packed bed biofilm reactor inoculated with pure culture Pseudomonas aeruginosa was run under high substrate loading and constant flow rate conditions. The 3.1-cm-diameter cylindrical reactor was 5 cm in length and packed with 1-mm glass beads. Daily observations of biofilm thickness, influent and effluent glucose substrate concentration, and effluent dissolved and total organic carbon were made during the 13-day experiment. Biofilm thickness appeared to rech quasi-steady-state condition after 10 days. A published biofilm process simulation program (AQUASIM) was used to analyze experimental data. Comparison of observed and simulated variables revealed three distinct phases of biofilm accumulation during the experiment: an initial phase, a growth phase, and a mature biofilm phase. Different combinations of biofilm and mass transport process variables were found to be important during each phase. Biofilm detachment was highly correlated with shear at the biofilm surface during all three phases of biofilm development. © 1995 John Wiley & Sons, Inc.

Short‐term exposure to triphenyltin affects the swimming and feeding behavior of tadpoles

Abstract: Triphenyltin compounds are used globally in agriculture as fungicides for a wide variety of crops. Their persistence in aquatic habitats and toxicity make them of special concern to amphibian species using temporary ponds or lakes for critical life-history functions. The effects of short-term exposure to three concentrations (5, 10, 20 μg/L) of triphenyltin chloride (TPT) were assessed for the swimming and feeding behavior of tadpoles of the European frog, Rana esculenta. The proportion of time spent swimming declined 33.8% with increasing TPT level. Treatments also had a significant effect on the proportion of time spent feeding, initially increasing in the acetone and lowest TPT treatments, but thereafter declining 19.6% with increasing TPT level. Tadpoles also compensated for reduced swimming by spending an increased proportion of activity time on feeding, but even this compensation declined at the highest TPT levels. Reduced swimming activity and food intake are likely to result in decreased growth and development as well as negatively influence adult traits such as size at maturity, survival to first reproduction, and fecundity.

Evidence for enhanced 10Be deposition in Mediterranean sediments 35 kyr BP

Abstract: In this letter, we report the profiles (∼160 samples) of 10Be, 9Be, Zn in a Mediterranean sediment core spanning the last 60 kyr. We show the existence of a 10Be peak, whose absolute age is estimated to be 34±3 kyr BP, based on its stratigraphic position between two tephra layers originating from two volcanic eruptions (Campanian Ignimbrite and Citara), dated by K-Ar, 40Ar-39Ar and 14C methods. This peak is similar to the increase in the 10Be concentration observed in Vostok and Dome C ice cores at the same age. The increase with approximately similar amplitude in both ice and sediment cores at different latitudes and hemispheres cannot be explained by changes in the archives. The present result supports the view of a well defined global enhancement of the 10Be flux, related to an increase of the 10Be production rate and not to a redistribution of the 10Be fallout between different latitudes.

Cloud model experiments of the effect of iron and copper on tropospheric ozone under marine and continental conditions

Abstract: We have used a multi-phase cloud photochemistry model to investigate the influence of dissolved iron (Fe) and copper (Cu) on the in-cloud production and loss of ozone and ozone-related species. Comparison of the results of our simulations with and without Fe and Cu reactions for three different photochemical scenarios (marine, averaged continental and polluted continental) indicate that Fe and Cu reactions, depending upon the scenario considered, can either increase or decrease the predicted rate of loss of ozone and ozone related species. For the marine and averaged continental scenarios the rate of loss of ozone in the aqueous-phase was decreased by as much as 45% and 70%, respectively, when Fe and Cu reactions were considered. For polluted continental conditions, the rate of loss of ozone in the aqueous phase increased with a factor 2 for low metal concentrations up to a factor 20 for high metal concentrations. In all three scenarios inclusion of the Fe and Cu reactions results in cloud droplets becoming more efficient sinks for gas-phase HO2 and also enhances OH production. The net effect of the decreased losses of ozone from the aqueous phase and the effect of the cloud droplets on HO2 and OH determine the overall impact on ozone and ozone related species, for each of the situations considered. Overall, when Fe and Cu reactions were included the marine cloud was found to be a less efficient sink for ozone, and averaged continental and polluted continental clouds were more efficient sinks for ozone (O3 losses doubled in the averaged continental scenario). The higher OH flux in the aqueous phase also enhances the rate at which organic compounds, such as formaldehyde and formic acid, are oxidized in the cloud.