Zum Problem der Redoxpotentialmessung in Abwässern und Schlämmen     

G. Zimmermann  E. Tiedemann  H. Ludwig 《洁净——土壤、空气、水》1977,5(3):299-307

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Calculation of uncertainties of U-Pb isotope data     

Kenneth R. Ludwig 《Earth and Planetary Science Letters》1980,46(2):212-220

Equations are derived for the estimation of errors and error correlations for various types of U-Pb isotope data, taking into account ion-beam instabilities, run-to-run variability in mass-discrimination, uncertainties in Pb and U concentrations, and uncertainties in initial-Pb and blank-Pb amount and isotopic composition. Equations are also given for the calculation of concordia intercept errors.  相似文献   

Neue Gesichtspunkte zur Entstehung des Planetensystems     

Prof. Dr. Ludwig Biermann 《International Journal of Earth Sciences》1972,61(1):1-15

Ohne Zusammenfassung

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New views on the origin of the planetary system

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Nouveaux aperçus sur l'origine du système planétaire

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Vortrag anläßlich der 61. Jahrestagung der Geologischen Vereinigung 1971 in München.  相似文献   

Röntgenographische und Mikrochemische Kontrolluntersuchungen bei Geochemischen Analysen an Einzelmineralen     

Dr. Ludwig Hertel 《International Journal of Earth Sciences》1966,55(2):355-358

The substitution of certain strange elements in the crystal lattice changes the lattice. The lattice constant increases as it is shown for instance with sphalerite, or decreases as it is shown with the example of glenite. Accordingly, X-Ray diffraction controls, whether strange elements, found by chemical analysis, are real components of the tested individual minerals. Further possibilities of control are given by X-Ray spectrochemical and by micro-chemical analysis of polished sections of ores, when the purity of minerals is proved by microscopic testing.  相似文献   

Application of Ultrafiltration for Characterization of the DOC of Elbe River Water     

U. Ludwig  V. Neumann  T. Grischek  W. Nestler 《洁净——土壤、空气、水》1997,25(2):71-78

An ultrafiltration methodology and the results of its application on Elbe river water are presented. Compared with other methods, Ultrafiltration allows fractionation of the molecular-weight fractions of DOC for higher volumes of solution in a shorter time. To characterize the molecular-weight fractions, the sum parameter DOC (β(DOC)) and the absorption coefficient at 254 nm a₂₅₄ were measured, together with determination of a₂₅₄/ β(DOC) for further characterization of the DOC fractions and to provide information about changes in parts of the UV-active substances of the total dissolved organic material. In the period May 1992 to November 1994, the DOC molecular-weight composition of 65 samples of Elbe river water were determined. At two sampling locations (Torgau-East and Meissen), the DOC content β(DOC) was approximately 6 mg/L. The high-molecular weight fraction (> 10000 g/mol) gave a mean of 13% of the total DOC content β₀(DOC). The measurements showed that the molecular composition of DOC in the Elbe does not greatly differ. There was also no clear seasonal influence on the molecular-weight composition of the DOC content. During the period of investigation, the percentage part of β(DOC) and a₂₅₄/β(DOC) of the high-molecular weight fraction of the total dissolved organic material increased, while the a₂₅₄/β(DOC) values of the middle molecular-weight fraction remained fairly constant. The dependence of β(DOC) on discharge of the Elbe river is low. Changes in molecularweight composition of DOC were only observed during the steepest increase in river discharge during a flood event, with another spectrum of substances responsible for the increase in β(DOC) when compared with the β(DOC) for low or middle water level.  相似文献   

Behaviour of Different Molecular-weight Fractions of DOC of Elbe River Water during River Bank Infiltration     

U. Ludwig  T. Grischek  W. Nestler  V. Neumann 《洁净——土壤、空气、水》1997,25(3):145-150

This paper reports changes in dissolved organic carbon concentration β(DOC) and the relation between UV-active and non-UV-active components determined for Elbe river water and river bank infiltrate in the Torgau river basin between 1992 and 1994. Using an ultrafiltration method, the fractionation of the DOC content was obtained for the fractions > 10 000 g/mol, 1 000…10 000 g/mol, and < 1 000 g/mol. The spectral absorption coefficient at 254 nm a₂₅₄ of the molecular-weight fractions was also measured. The mean total DOC concentration of Elbe river water decreased from 6.0 mg/L to below 3.9 mg/L along two investigated flowpaths. Two thirds of the decrease occurred within the first few metres of the river bed and one third along the 350 m length of the groundwater flowpaths. The a₂₅₄ values showed a significant decrease from 14.8 1/m in Elbe river water to 7.8 1/m in the aquifer. Along a flowpath, the proportion of low-molecular weight fraction of DOC increased, the proportion of high-molecular weight fraction decreased, and the proportion of the 1 000…10 000 g/mol molecular-weight fraction remained relatively stable. The Elbe river water contained the main portion of UV-active compounds in the fraction 1 000…10 000 g/mol, and this was also the case for samples of river infiltrate. For the high-molecular weight fraction, mainly non-UV-active compounds were attenuated in the river bed sediment.  相似文献   

Geomorphological-sedimentological studies of landform types and modern placer deposits in the savanna (Southern Malawi)     

H.G. Dill  R.-R. Ludwig 《Ore Geology Reviews》2008,33(3-4):411-434

Semi-arid climatic conditions were responsible for the evolution of the vast savanna that stretches across central Africa and for the evolution of placers in this area that carry gemstones, rare earth element minerals and zircon- and titanium-bearing minerals. In combination with a polystage peneplanation, chemical weathering contributed to the emplacement of four different types of placer deposits during the Cenozoic in Malawi. Eight landform types have been defined by their geomorphological form, geometry, grain size parameters, stratification, fabric and rock contacts. Each type describes the landscape of the savanna and can be related to the emplacement of placer types within this morphoclimatic zone. Residual to eluvial placers, represented geomorphologically by landform type V, came into existence under strong chemical weathering during a period of alternating peneplanation and valley incision into soil and saprolite. Gentle valley-side slopes or elongated interfluves have a low gradient favorable for the formation and preservation of eluvial to colluvial placers (landform type Ic). Fluvial placers become economic only on outwash plains of tributaries near the confluence with their trunk rivers, beyond the point of inflection (landform types III, II). In the lower reaches of fluvial drainage systems around shallow lakes, fluvio-deltaic placers evolved during periods of rapid uplift and regression of the lake (landform type IV). Other landform types established throughout this study are cast in the role of ‘ore guides’ or, alternatively, have a negative impact on the likelihood of placer formation. The key associations of landforms discussed in this paper may be used as a geomorphological-sedimentological tool in search of modern continental placer deposits in areas where semi-arid climatic conditions occur(red) during the Cenozoic.  相似文献   

Late Pleistocene Climatic Variations at Achenheim, France, Based on a Magnetic Susceptibility and TL Chronology of Loess     

Denis-Didier Rousseau  Ludwig Zöller  Jean-Pierre Valet 《Quaternary Research》1998,49(3):255-263

New field investigations of the Achenheim sequence (Alsace, France) allow for the characterization of variations in the low-field magnetic susceptibility over most of the last climatic cycle, i.e., the past 130,000 yr. New stratigraphic data and thermoluminescence measurements permit reassessment of the previous chronological interpretation of the Upper Pleistocene at Achenheim. A high-resolution analysis of magnetic susceptibility discloses the occurrence of a fine-grained “marker” horizon which was also found recently in another section. This horizon is interpreted as a small-scale dust layer deposited prior to the main interval of loess deposition. The horizon, deposited at the marine isotope stage (MIS) 5/4 boundary, has been found in other loess sequences and is especially prevalent in central Europe. It is characterized by low susceptibility values and a grayish color. New thermoluminescence dates indicate that the loess deposition took place after the MIS 5/4 boundary, i.e., after 70,000 yr. These results are consistent with the Greenland GRIP ice-core dust record which also demonstrates a dusty atmosphere after 72,000 yr ago. On a more regional scale, the Achenheim loess sequence demonstrates a reliable correlation between the western side of the Eurasian loess belt and the dust record of the Greenland ice cores.  相似文献   

Die Bewegung der Kontinente in der Wegenerschen Theorie     

Ludwig Becker 《International Journal of Earth Sciences》1939,30(3):304-308

Ohne Zusammenfassung  相似文献   

A chronological and palaeoenvironmental re-evaluation of two loess-palaeosol records in the northern Harz foreland,Germany, based on innovative modelling tools     

Christoph Schmidt  Christian Zeeden  Lydia Krauß  Frank Lehmkuhl  Ludwig Zöller 《Boreas: An International Journal of Quaternary Research》2021,50(3):746-763

The continuing development of analytical methods for investigating sedimentary records calls for iterative re-examination of existing data sets obtained on loess-palaeosol sequences (LPS) as archives of palaeoenvironmental change. Here, we re-investigate two LPS (Hecklingen, Zilly) in the northern Harz foreland, Germany, being of interest due to their proximity to the Scandinavian Ice Sheet (SIS) and the position between oceanic climatic influence further west and continental influence towards the east. First, we established new quartz OSL and polymineral IRSL chronologies. Both methods show concordant ages in the upper part of the Hecklingen profile (~20–40 ka), but in the lower part IRSL underestimates OSL ages by up to ~15 ka for the period 40–60 ka. Interpretations hence refer to the OSL data set. Second, we applied Bayesian age-depth modelling to data sets from Hecklingen to resolve inversions in the original ages, also reducing averaged 1σ uncertainty by ~19% (OSL) and ~12% (IRSL). Modelled chronologies point out phases of increased (MIS 2, early MIS 3) and reduced (middle and late MIS 3) sedimentation, but interpretation of numerical rates is problematic because of intense erosion and slope wash particularly during MIS 3. Finally, previously obtained grain-size data were re-investigated by end member modelling analyses. Three fundamental grain-size distributions (loadings) explain the measured data sets and offer information on intensity and – combined with modelled OSL ages – timing of geomorphic processes. We interpret the loadings to represent (i) primary loess accumulation, (ii) postdepositional pedogenesis and/or input of aeolian fine fractions, and (iii) input of coarse aeolian material and/or slope wash. The applied modelling tools facilitate detailed understanding of site-formation through time, allowing us to correlate a strong peak in mean grain size at ~26–24 ka to the maximum extent of the SIS and increased influence of easterly winds.  相似文献