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  • Articles  (444)
  • Geosciences  (444)
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  • Articles  (444)
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  • 1
    Electronic Resource
    Electronic Resource
    Spectroscopic properties of dissolved humic substances - a reflection of land use history in a fen area (1999)
    Springer
    Biogeochemistry 47 (1999), S. 219-238 
    Details
    ISSN: 1573-515X
    Keywords: dissolved humic substances ; FTIR spectroscopy ; land use history ; peat ; synchronous fluorescence spectroscopy ; UV/VIS spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The elemental composition and spectroscopic properties of dissolved fulvic acids isolated from different sampling media (topsoil, ground and surface water) of a natural fen area (high portion of organic soils) were examined to reveal the effects of land use history. These effects need to be known if dissolved humic substances are to be a major factor in identifying the impact of present and future changes in land use. Dissolved fulvic acids (topsoil, groundwater) from highly degraded peatlands (due to a long-term agricultural use) exhibit lower C/N ratios, higher absorption in the UV spectra, and higher absorption at 1,620 cm−1 in the FTIR spectra compared with fulvic acids from relatively intact peatlands. These properties illustrate that long-term agricultural use with high inputs results in increased aromatic structures and a further humification of dissolved fulvic acids due to very strong peat decomposition compared with relatively intact peatlands. Synchronous fluorescence spectra also indicate the higher level of aromatic structures within fulvic acids isolated from sites with long-term agricultural use (high peat decomposition) compared with a land use history resulting in a lower peat decomposition. The different sources of fulvic acids in surface water (precipitation, runoff, interflow, groundwater) are the main reason for these effects not being detected in fulvic acids isolated from surface water. Short-term changes in land use characterized by a transition from crop farming to an unimproved grassland were found not to affect the spectroscopic properties of dissolved fulvic acids. A humification index deduced from the synchronous fluorescence spectra is proposed. We have strong evidence that dissolved humic substances indicate changes in the environmental conditions (both anthropogenic and natural) of wetlands with a high proportion of organic soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006134214244
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  • 2
    Electronic Resource
    Electronic Resource
    Spectroscopic properties of dissolved humic substances — a reflection of land use history in a fen area (1999)
    Springer
    Biogeochemistry 47 (1999), S. 219-238 
    Details
    ISSN: 1573-515X
    Keywords: dissolved humic substances ; FTIR spectroscopy ; land use history ; peat ; synchronous fluorescence spectroscopy ; UV/VIS spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The elemental composition and spectroscopic properties of dissolved fulvic acids isolated from different sampling media (topsoil, ground and surface water) of a natural fen area (high portion of organic soils) were examined to reveal the effects of land use history. These effects need to be known if dissolved humic substances are to be a major factor in identifying the impact of present and future changes in land use. Dissolved fulvic acids (topsoil, groundwater) from highly degraded peatlands (due to a long-term agricultural use) exhibit lower C/N ratios, higher absorption in the UV spectra, and higher absorption at 1,620 cm−1 in the FTIR spectra compared with fulvic acids from relatively intact peatlands. These properties illustrate that long-term agricultural use with high inputs results in increased aromatic structures and a further humification of dissolved fulvic acids due to very strong peat decomposition compared with relatively intact peatlands. Synchronous fluorescence spectra also indicate the higher level of aromatic structures within fulvic acids isolated from sites with long-term agricultural use (high peat decomposition) compared with a land use history resulting in a lower peat decomposition. The different sources of fulvic acids in surface water (precipitation, runoff, interflow, groundwater) are the main reason for these effects not being detected in fulvic acids isolated from surface water. Short-term changes in land use characterized by a transition from crop farming to an unimproved grassland were found not to affect the spectroscopic properties of dissolved fulvic acids. A humification index deduced from the synchronous fluorescence spectra is proposed. We have strong evidence that dissolved humic substances indicate changes in the environmental conditions (both anthropogenic and natural) of wetlands with a high proportion of organic soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00994924
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  • 3
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    Spectroscopic properties of dissolved humic substances ? a reflection of land use history in a fen area (1999)
    Springer
    Details
    Publication Date: 1999-11-01
    Print ISSN: 0168-2563
    Electronic ISSN: 1573-515X
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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    PAPER CURRENT
  • 4
    Electronic Resource
    Electronic Resource
    Electromagnetic fields of a vertical magnetic dipole above a laterally inhomogeneous thin layer of conductive overburden (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 181-197 
    Details
    ISSN: 1420-9136
    Keywords: Electromagnetic field ; Vertical magnetic dipole ; Thin conductive sheet ; Lateral conductivity variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An analytical formulation is developed for the resultant electromagnetic field of an oscillating vertical magnetic dipole located over a thin conductive sheet of infinite extent. The sheet is characterized by a conductivity-thickness product or conductance σd that may be a function of the horizontal coordinates. The system of integral equations arising in the general formulation is simplified greatly when azimuthal symmetry prevails. Numerical results for a Gaussian variation of σd in the radial direction are presented for the case of a symmetrically located source. These results are for the fields at the level of the source dipole over the conductive sheet. It is shown that the quadrature response of the sheet is enhanced when there is rapid variation of the conductance. The null in the resultant wave tilt is also found to be shifted toward the direction of increasing conductance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878992
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  • 5
    Electronic Resource
    Electronic Resource
    Process-based interpretation of tracer tests in carbonate aquifers (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Ground water 43 (2005), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: A tracer test in a carbonate aquifer is analyzed using the method of moments and two analytical advection-dispersion models (ADMs) as well as a numerical model. The numerical model is a coupled continuum-pipe flow and transport model that accounts for two different flow components in karstified carbonate aquifers, i.e., rapid and often turbulent conduit flow and Darcian flow in the fissured porous rock. All techniques employed provide reasonable fits to the tracer breakthrough curve (TBC) measured at a spring. The resulting parameter estimates are compared to investigate how each conceptual model of flow and transport processes that forms the basis of the analyses affects the interpretation of the tracer test. Numerical modeling results suggest that the method of moments and the analytical ADMs tend to overestimate the conduit volume because part of the water discharged at the spring is wrongly attributed to the conduit system if flow in the fissured porous rock is ignored. In addition, numerical modeling suggests that mixing of the two flow components accounts for part of the dispersion apparent in the measured TBC, while the remaining part can be attributed to Taylor dispersion. These processes, however, cannot reasonably explain the tail of the TBC. Instead, retention in immobile-fluid regions as included in a nonequilibrium ADM provides a possible explanation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2005.0033.x
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  • 6
    Electronic Resource
    Electronic Resource
    TRANSIENT ELECTROMAGNETIC RESPONSE NEAR A FAULT ZONE (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 20 (1972), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Recent improvements in instrumentation and field techniques have made time domain electromagnetic methods more acceptable. This acceptance has prompted further theoretical work for use in the interpretation of field data.The asymptotic solutions for the transient electromagnetic field components in the vicinity of a fault zone separating two media of high resistivity contrast are obtained for low frequency or late time. Excitation is by normally incident plane waves at the earth's surface. Because of the slow convergence of the asymptotic time series expansions, a numerical polygonal inversion is performed on the real part, or in-phase term, of the time-harmonic surface expressions for the electric and magnetic field components.For both impulsive and step excitation the transient electric field normal to the contact is more sensitive to changes in the structural attitude of the fault plane than the transient electric field parallel to the contact. The transient anomalous vertical magnetic field for either impulsive or step excitation appears to be most diagnostic of dip angle, although waveform shape does not seem to be significantly dependent on the slope of the fault. For dip angles greater than 90 degrees, as measured on the poorly conducting side of the contact, all field components become more insensitive as indicators of the structural attitude. The results presented here should be useful in obtaining several geologic parameters descriptive of a fault zone or lateral resistivity inhomogeneity from transient electromagnetic soundings; they should also provide an aid to differentiating with available geological information between layering effects on transient electromagnetic responses and effects largely due to lateral changes in resistivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1972.tb00669.x
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  • 7
    Electronic Resource
    Electronic Resource
    A New Small-Angle X-ray Scattering Instrument on the French CRG Beamline at the ESRF Multiwavelength Anomalous Scattering/Diffraction Beamline (D2AM) (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 30 (1997), S. 900-904 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A new small-angle X-ray scattering instrument has been set up on the D2AM-ESRF beamline. This modular instrument, which has the capacity to handle different sample environments (variable temperature and pressure), is designed for easy wavelength changes, i.e. for anomalous-scattering studies. This paper describes its design and discusses in some detail its positioning and alignment with respect to the focusing optics. The mirrors were found to be a major source of diffuse scattering, which was eliminated by rearrangement of the slit positions and refocusing of the optics. The present configuration yields a high flux (1010photons s−1) and allows measurements down to q = 0.005 Å−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897001684
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  • 8
    Electronic Resource
    Electronic Resource
    The Hoher List observations of the occultation of 28 Sagittarii by Titan (1991)
    Springer
    Earth, moon and planets 52 (1991), S. 83-86 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Observations of the occultation of 28 Sgr by Titan are presented. Apparently being located close to the central line of the occultation track, a double peaked central flash was observed. Some characteristic times of the phenomenon are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00113833
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  • 9
    Electronic Resource
    Electronic Resource
    Die mesozoische Magnafazies-Abfolge in den nördlichen Anden (Peru, Ekuador, Kolumbien) (1980)
    Springer
    International journal of earth sciences 69 (1980), S. 875-891 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Over 100 sedimentary formations and groups are known from the epicontinental to continental Mesozoic (“Oriente Andino” sensu H.Bürgl) in the Andean region of Peru, Ecuador and Colombia. These lithostratigraphic (or facial) complexes are attached to 6 magnafacies-units which follow each other chronologically, thereby clearly evidencing a uniform paleogeographic-sedimentary development in the mentioned areas, although the geological structure of the Western respectively Coastal Cordilleras of the North (Colombia, Ecuador) is fundamentally different from that of the Southern ones (Peru, Chile).
    Abstract: Resumen Más de 100 grupos y formaciones sedimentarios des »Oriente Andino« (sensu H.Bürgl) en los Andes septentrionales (PerÚ, Ecuador, Colombia) están asociados a 6 unidades magnafaciales que se suceden cronológicamente. Este »Oriente Andino« abarca las cuencas sedimentarias de tipo epicontiental a continental de la época mesozoica. Se bosqueja así claramente, en las áreas mencionadas, una evolución paleogeográfica-sedimentológica bastante uniforme, aunque las estructuras geológicas de las Cordilleras Occidentales (o Costeras, respectivamente) de la parte septentrional (Colombia, Ecuador) se diferencian fundamentalmente de las del Sur (PerÚ, Chile).
    Notes: Zusammenfassung Die weit über 100 sedimentären Formationen und Gruppen im mesozoischen epikontinentalen bis kontinentalen „Oriente Andino“ der nördlichen Anden (Peru, Ekuador und Kolumbien) werden 6 zeitlich aufeinanderfolgenden Magnafazies-Einheiten zugeordnet. Dabei zeichnet sich deutlich eine einheitliche paläogeographisch-sedimentäre Entwicklung in den genannten Räumen ab, obwohl sich der geologische Bau der andinen West- bzw. Küstenkordilleren im Norden (Kolumbien, Ekuador) grundsätzlich vom Süden (Peru, Chile) unterscheidet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02104651
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  • 10
    Electronic Resource
    Electronic Resource
    Zur faziellen Entwicklung des subbetischen Juras in Südspanien (1967)
    Springer
    International journal of earth sciences 56 (1967), S. 973-992 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The facies development of the Jurassic in the subbetic realm of Spain shows many common features on the whole in spite of differences in detail. “Neritic limestone facies“ may be distinguished from “Nodular limestone facies“ and “Limestone-marl-facies“. This paper deals with the stratigraphie range of red nodular limestones and “Limonite Crusts“ as equivalents of the celtiberic “Boundary Oolites“. The occurrence ofNucleata, Pygope andPosidonia in the Subbetic is discussed. There are certain facies relations to the Jurassic of the adjacent celtiberic area and especially to the Jurassic of the Western and Southern Alps.
    Abstract: Résumé Les faciès dans le Jurassique subbétique montrent, malgré des différences dans les détails beaucoup de traits communs. Il faut cependant distinguer entre le « faciès des calcaires néritiques», le « faciès des calcaires noduleux» et le « faciès des marnes et calcaires». La distribution stratigraphique des calcaires noduleux rouges et des « croutes de limonite», qui représentent les équivalents des «oolites limitrophes» celtibériques, est discuté. On commente alors l'existence deNucleata, Pygope etPosidonia dans le Subbétique. On peut constater des relations plus ou moins nettes non seulement avec le Jurassique celtibérique, mais aussi, avant tout, avec le Jurassique alpin occidental et méridional.
    Notes: Zusammenfassung Die fazielle Entwicklung des subbetischen Juras weist trotz Differenzierung im einzelnen viele gemeinsame Züge auf. Grundsätzlich ist aber zwischen einer „Neritischen Kalk-Fazies“ einer „Knollenkalk-Fazies“ und einer „Kalk-MergelFazies“ zu unterscheiden. Auf die stratigraphische Verbreitung der Roten Knollenkalke und die „Limonitkrusten“ als Äquivalente der keltiberischen „Grenzoolithe“ wird näher eingegangen, das Auftreten vonNucleata, Pygope undPosidonia im subbetisehen Jura besprochen. Sowohl zum benachbarten keltiberischen Jura als auch zum west- und südalpinen Jura sind mehr oder weniger deutliche Beziehungen vorhanden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01848775
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