Comparison of fractional bed-material load computation methods in sand-bed channels
This paper presents a comparison of different fractional bed-material load computation methods in sand-bed channels. These methods include the direct computation by size fraction approach of Einstein, Laursen and Toffaleti; the bed material fraction
(BMF) approach using equations of Engelund and Hansen, Ackers and White, Yang, and Karim's modified BMF method; and the transport capacity fraction (TCF) approach. Statistical analysis and graphical comparison are utilized to demonstrate the performance
Fractionation mechanism of stable isotope in evaporating water body
This study quantificationally analyses the interaction between evaporating water body and atmosphere, and the influences of different factors on the evaporation by probing into the fractionation mechanism of stable isotope as water body is vaporized
under kinetic non-equilibrium and by comparing the kinetic fractionation model with the Rayleigh equilibrium model.
La fraction fine des débris de gélifraction expérimentale
Cryoclastie ; Experimentation de laboratoire ; Fraction fine ; Granulométrie ; Géographie physique ; Périglaciaire ; Sédimentologie
The amount of fine fraction given by frost shattering depends on the facies: chalk, marls, clayey limestones argillites and weathered rocks yield a large volume| massive limestones, sandstones, schists and slightly weathered granites furnish little
silt. The granulometric curve of the fine fraction is logarithmic or parabolic| only weathered rocks, certain soft schists, argillites and marls give a noteworthy amount of particles smaller than 0.2 micron.
Working a fraction and making a fraction work : a rough guide for geographers in the academy
Enquête auprès de géographes exerçant des emplois fractionnés dans les institutions d'enseignement supérieur au Royaume-Uni. Considérations sur la place de ce type de travail dans le discours dominant autour du travail rémunéré, des problèmes de
Verification of a simple gravity technique for separation of particle size fractions suitable for mineral magnetic analysis
Techniques for the separation of sediment samples into size fractions are reviewed and the use of repeated decantations to provide samples for mineral magnetic analysis is described. Results from a series of trials are presented and compared
Weathering of the sand fraction of surface wash on a low-angled slope near Bloemfontein
Sediments from five sets of wash traps on a low-angled slope were screened into 11 sand fractions. The analysis showed that dolerite particles weathered faster than siltstone. - (AJC)
The accuracy of gravimetric fractionation as a means of obtaining size fractions from marine sediments has been explored. Analysis of the particle size distribution and sediment properties of fractions obtained using this method was undertaken
. This has highlighted the extent to which experimental artefacts rather than variations in sediment characteristics may adversely affect the efficiency of the fractionation process.
Etudie une méthode de nomenclature des sols d'après la distribution fractionnelle| diagramme ternaire pour la nature, la quantité et la distribution des fractions.
Mineralisation and changes in the fractions of soil organic matter in soils of the permafrost region, Qinghai-Tibet Plateau, China
To determine the relationship between soil organic matter (SOM) decomposition and chemistry in the permafrost region of the Qinghai-Tibet Plateau (QTP), 300-day laboratory incubations at 25°C and chemical fractionation were performed to characterise
the mineralisation dynamics of organic carbon from soils under 5 vegetation conditions. The respiration rates in wet meadows were the highest. After the incubation period, all 4 fractions of SOM (non-polarity soluble, water soluble, holocellulose and lignin contents
on the changes in chemical fractions of organic matter, it could be determined that soils with higher water-soluble fractions had higher rates of carbon mineralisation, while the mechanisms involved in the respiration of different chemical fractions
The effects of grain abrasion and disaggregation on 137 Cs concentrations in different size fractions of soils developed on three different rock types
of disaggregation and grain abrasion on the distribution of 137 Cs with respect to particle size fractions were studied in soils derived from the 3 different rock types of the Tarago catchment.
The character of the fine fractions of the bottom sediments of the Bohemian part of the Labe (Elbe) river
of the river catchment geological setting, of its relief and of weathering on the composition of the particulate bed material. As it is generally accepted that the smaller grain-size of the sediment fraction binds the greatest amount of trace toxic elements
A continuous spatial characterization of textural fractions and CaCO3 content of the topsoil of the Polder region of Northwest East-Flanders, Belgium
at small distance lags, several levels of spatial variability of the textural fractions ranging from within-a-field to polder scale were identified. This structure was best represented by nested semivariograms.
Determination of vegetation cover fraction by inversion of a four-parameter model based on isoline parametrization
Estimation de la fraction de la couverture végétale en utilisant un modèle à 4 paramètres combinant les réflectances dans le rouge et l'infrarouge proche. L'étalonnage des paramètres est faite en utilisant les simulations de Verhoef sur la
Variation in radiocarbon ages of soil organic matter fractions from late Quaternary buried soils
This study highlights the inconsistencies among the radiocarbon ages of the three organic fractions usually extracted by laboratories and addresses the problem of interlaboratory variation in radiocarbon ages for paired samples.
Les fractions sableuses des sols sont relativement peu affectées par les processus pédogénétiques postérieurs à la pédimentation de versant de colline. Pour la fraction gravillonnaire, discontinuité lithologique entre la nappe de gravats et la
couverture fine. Etude de l'évolution en profondeur de la fraction fine et évolution en fonction de la position géomorphologique. - (HN)
Phosphorus fractionation in lowland tropical rainforest soils in central Panama
Here the AA. report data from a reconnaissance survey of soil phosphorus fractions for contrasting soil types under lowland tropical forest on Barro Colorado Island, Republic of Panama. These soils have developed under uniform vegetation and climate
, but on contrasting lithology and topography, so they are subject to distinct mineralogy and weathering regimes. By studying these soils, the AA. aimed to explore the extent to which soil phosphorus fractions and phosphorus availability vary with local-scale