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  • 1
    Electronic Resource
    Electronic Resource
    Pore-water response on seasonal environmental changes in intertidal sediments of the Weser Estuary, Germany (1996)
    Springer
    Environmental geology 27 (1996), S. 362-369 
    Details
    ISSN: 1432-0495
    Keywords: Pore water ; Seasonal changes ; Intertidal sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In order to determine time-dependent changes in estuarine pore-water chemistry and flux variations across the sediment-water interface, sediment cores of an intertidal mud flat in the Weser Estuary were taken monthly over a one-year period. Sediment temperature, pH, Eh, Cl−, O2, NO 3 − , and SO 4 2− pore-water concentrations were measured and showed variations that relate to the changes of surface temperature and estuarine water composition. Fick's first law was applied to quantify diffusive fluxes from concentration gradients in the diffusive boundary layer and in the pore water. Total nitrate fluxes were calculated from flux chamber experiments. Diffusive oxygen fluxes increased from 5 mmol m−2 d−1 in winter to 18 mmol m−2 d−1 in early summer, while nitrate fluxes into the sediment increased from 3 mmol m−2 d−1 in winter to 60 mmol m−2 d−1 in early summer. Oxygen and nitrate fluxes into the sediment correlated linearly to sediment temperature. Sulfate fluxes increased from 0.5 mmol m−2 d−1 in winter to 10 mmol m−2 d−1 in August and September. Converted into carbon fluxes, the sum of these oxidants ranged from 10 mmol m−2 d−1 in winter to 80 mmol m−2 d−1 in summer. An estimation of the upper limit of the annual nitrate flux into the sediment showed that about 10% of the 250,000 t of nitrate discharged annually by the river may be decomposed within the inner Weser Estuary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00766706
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  • 2
    Electronic Resource
    Electronic Resource
    Evolution of heavy-metal profiles in river Weser Estuary sediments, Germany (1994)
    Springer
    Environmental geology 24 (1994), S. 223-232 
    Details
    ISSN: 1432-0495
    Keywords: Sediments ; Heavy metals ; Estuary ; River Weser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Studies of heavy metal concentrations in porewaters and in sediments from the Weser Estuary, Germany, indicate that the depth distribution of Mn, Cd, and Cu in the solid phase is predominantly influenced by the subsurface redox regime, while Ni shows only moderate alteration. Based on solid-phase heavy metal data from eight locations in the study area, linear regressions of Fe, Mn, Cu, Ni, and Cd on Al allowed differences between the initial metal concentration and the concentration preserved in the sediments to be predicted. We calculate that, due to early diagenetic processes, Mn is enriched to 145 percent, while Cu and Cd are depleted to 71 percent and 46 percent, respectively, of the initial metal concentration in the near-surface sediment. Maximum depletion of Cd (84 percent), Cu (68 percent), Mn (54 percent), and Ni (24 percent) concentrations in the sediment, observed at a restricted area downcore, indicate the importance of post-depositional processes to metal preservation in the sediment. Without knowledge of the quantitative effects of diagenetic reactions on the preservation of metal concentrations in sediments, the depth distribution of metals in sediment cores may be misinterpreted as the effect of human activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00766892
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  • 3
    Electronic Resource
    Electronic Resource
    The potential formation of acid mine drainage in pyrite-bearing hard-coal tailings under water-saturated conditions: an experimental approach (1997)
    Springer
    Environmental geology 31 (1997), S. 59-65 
    Details
    ISSN: 1432-0495
    Keywords: Key words Pyrite oxidation ; Acid mine drainage ; Tailings ; landfill ; Sealing ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Annually, an amount of approximately 13 million cubic meters of hard-coal tailings must be disposed of in the German Ruhr Valley. Besides the waste of land in a densily populated region, the disposal of the pyrite-bearing material under atmospheric conditions may lead to the formation of acid mine drainage (AMD). Therefore, alternative disposal opportunities are of increasing importance, one of which being the use of tailings under water-saturated conditions, such as in backfilling of abandoned gravel pits or in the construction of waterways. In this case, the oxidation of pyrite, and hence the formation of AMD, is controlled by the amount of oxygen dissolved in the pore water of tailings deposited under water. In case the advective percolation of water is suppressed by sufficient compaction of the tailings, oxygen transport can be reduced to diffusive processes, which are limited by the diffusive flux of dissolved oxygen in equilibrium with the atmospheric pO2. Calculations of the duration of pyrite oxidation based on laboratory experiments have shown that the reduction of oxygen is mainly controlled by the content of organic substance rather than the pyrite content, a fact that is supported by results from oxidation experiments with nitrate. A "worst case" study has lead to the result that the complete oxidation of a 1.5-m layer of hard-coal tailings deposited under water-saturated conditions would take as much as several hundred thousand years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540050164
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  • 4
    Electronic Resource
    Electronic Resource
    Computer simulation of deep sulfate reduction in sediments of the Amazon Fan (2000)
    Springer
    International journal of earth sciences 88 (2000), S. 641-654 
    Details
    ISSN: 1437-3262
    Keywords: Key words Amazon Fan ; Sulfate reduction ; Mackinawite ; Numerical model ; Operator splitting ; PHREEQC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Pore water concentration profiles of sediments at a site on the Amazon Fan were investigated and simulated with the numerical model CoTReM (column transport and reaction model) to reveal the biogeochemical processes involved. The pore water profiles for gravity core GeoB 4417-7 showed a distinct sulfate–methane transition zone in which deep sulfate reduction occurs. Only a small sulfide peak could be observed at the reaction zone. Due to high amounts of iron minerals, the produced sulfide is instantaneously precipitated in form of iron sulfides. We present a simulation which starts from a steady state system with respect to pore water profiles for methane and sulfate. Furthermore, sulfide, iron, pH, pE, calcium and total inorganic carbon (TIC) were included in the simulation. The program calculated mineral equilibria to mackinawite, iron sulfides (more stable than mackinawite), iron hydroxides and calcite via saturation indices (SI) by a module incorporating the program PHREEQC (Parkhurst 1995). The measured sulfide and iron profiles are obtained in the simulation output by using a constant SI (=0) for mackinawite and calcite, while a depth dependent SI distribution is applied for the PHREEQC phases “Pyrite” and “Fe(OH)3(a)”, representing a composition and the kinetics of different iron sulfides and iron hydroxides. These SI distributions control the results of sulfide and iron pore water profiles, especially conserving the sulfide profile at the reaction zone during the simulation. The results suggest that phases of iron hydroxides are dissolved, mackinawite is precipitated within, and other iron sulfides are precipitated below the reaction zone. The chemical reactivity of iron hydroxides corresponds to the rate of sulfide production. The system H2O–CO2–CaCO3 is generally successfully maintained during the simulation. Deviations to the measured pH profile suggest that further processes are active which are not included in the simulation yet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050294
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  • 5
    Electronic Resource
    Electronic Resource
    A comparative study of iron and manganese diagenesis in continental slope and deep sea basin sediments off Uruguay (SW Atlantic) (2000)
    Springer
    International journal of earth sciences 88 (2000), S. 619-629 
    Details
    ISSN: 1437-3262
    Keywords: Key words Iron ; Manganese ; Early diagenesis ; Redox cycling ; Surface sediment ; Argentine Basin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Pore water and solid phase from surface sediments of the continental slope off Uruguay and from the Argentine Basin (southwestern Atlantic) were investigated geochemically to ascribe characteristic early diagenetic reactions of iron and manganese. Solid-phase iron speciation was determined by extractions as well as by Mössbauer spectroscopy. Both methods showed good agreement ( 〈6% deviation) for total-Fe speciation. The proportion of easy reducible iron oxyhydroxide relative to total-Fe oxides decreased from the continental slope to the deep sea which is attributed to an increase in crystallinity during transport as well as to a general decrease of iron mobilization. The product of iron reoxidation is Fe oxyhydroxide which made up less than 5% of total Fe. In addition to this fraction, a proportion of smectite bound iron was found to be redox reactive. This fraction made up to 10% of total Fe in sediments of the Argentine Basin and was quantitatively extracted by 1 N HCl. The redox reactive Fe(+II) fraction of smectite was almost completely reoxidized within 24 h under air atmosphere and may therefore considerably contribute to iron redox cycling if bioturbation occurs. In the case of the slope sediments we found concurrent iron and manganese release to pore water. It is not clear whether this is caused by dissimilatory iron and manganese reduction at the same depth or dissimilatory iron reduction alone inducing Mn(+IV) reduction by (abiotic) reaction with released Fe2+. The Argentine Basin sediment showed a significant manganese solid-phase enrichment above the denitrification depth despite the absence of a distinct pore-water gradient of Mn. This implies a recent termination of manganese mobilization and thus a non-steady-state situation with respect to sedimentation or to organic carbon burial rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050292
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  • 6
    Electronic Resource
    Electronic Resource
    Über die Natur eines Teilchens auffallend hoher Radioaktivität im atmosphärischen Niederschlag (1959)
    Springer
    Naturwissenschaften 46 (1959), S. 139-140 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00622667
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of tau decays into three charged pions (1986)
    Springer
    The European physical journal 33 (1986), S. 7-12 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report a study of the decay τ−→τ−τ+τ− v τ using the ARGUS detector at the DORIS II storage ring. Tau pairs were produced bye + e − annihilation at centre-of-mass energies near 10 GeV. We have observed about 1,700 events, corresponding to a branching ratio for τ−→τ−τ+τ− v τ of (5.6±0.7)%. The dominant mode for this decay is observed to beρ 0π− in aJ p =1+ spin state. Theρ 0π− mass spectrum shows a broad enhancement near 1.10 GeV/c2, which has the properties expected for theA 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410447
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  • 8
    Electronic Resource
    Electronic Resource
    The hadronic transitions from Υ(2S) to Υ(1S) (1987)
    Springer
    The European physical journal 35 (1987), S. 283-293 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the ARGUS detector at DORIS, we have investigated the hadronic transitions of the Υ(2S) to the Υ(1S). The decays to Υ(1S)π+π−, Υ(1S)π0π0 and Υ(1S)η where the Υ(1S) subsequently decays intoe + e − and Υ(1S)η have been investigated. The transition via two charged pions has also been studied inclusively. We obtain branching ratios of the Υ(2S) into Υ(1S)π+π− of (18.1±0.5±1.0)%, into Υ(1S)π0π0 of (9.5±1.9±1.9)% and into Υ(1S)η of less than 0.5% with 90% confidence. From the exclusive events we find the leptonic branching ratios of the Υ(1S) to beB ee=(2.42±0.14±0.14)% andB μμ=(2.30±0.25±0.13)%. Kinematical parameters of the two pion transitions have been investigated in detail and found to be consistent with current algebra and colour-field multipole expansion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570762
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  • 9
    Electronic Resource
    Electronic Resource
    Exclusive hadronic decays ofB mesons (1990)
    Springer
    The European physical journal 48 (1990), S. 543-551 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the ARGUS detector at thee + e − storage ring DORIS II, we have measuredB decays into exclusive final states containing aD orD * meson plus several pions, or containing aJ/ψ or ψ′ meson plus a strange particle. Some of these channels have not been seen before, while others represent updated measurements of previous results. The branching ratios are compared with the predictions of the model of Bauer, Stech and Wirbel. Using the cleanest decay channels, the mass of the charged and neutralB meson are found to bem B −=(5280.5±1.0±2.0) MeV/c2 andm B 0=(5279.6±0.7±2.0) MeV/c2 respectively, yielding a mass differencem B 0−m B − =(−0.9±1.2±0.5) MeV/c2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01614687
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  • 10
    Electronic Resource
    Electronic Resource
    Search for charm production in direct decays of the ϒ(1S) resonance (1992)
    Springer
    The European physical journal 55 (1992), S. 25-31 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production ofD *(2010)+ andJ/ψ mesons and prompt leptons has been investigated ine + e − interactions at the Ψ(1S) resonance energy. The data were collected at the storage ring DORIS II at DESY with the ARGUS detector. We obtain upper limits of BRdir (ϒ (1S)→D *(2010)±+X)〈0.019 (forx p 〉0.2) and BRdir (ϒ(1S)→J/ψ+X)〈0.68×10−3, both at the 90% confidence level. From the prompt lepton analysis, a model dependent limit of BRdir (ϒ(1S)→Y c +X)〈0.034 (Y c denoting a charm-containing particle) is derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01558286
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