Showing papers on "Silt published in 2008"
TL;DR: In this article, the authors discuss the laws which govern sediment deposition, and consequently determine size-dependent compositional variability, using a theoretical approach based on robust datasets on major Alpine, Himalayan, and African sedimentary systems.
241 citations
TL;DR: Grain size analyses of three hilltop, primary eolian loess sequences in the Negev desert, southern Israel, show a bimodal grain-size distribution at 50-60 μm and 3-8 μm using analyses of mineralogy and OSL ages as discussed by the authors.
212 citations
TL;DR: In this paper, the authors investigated to what extent cheap and readily available ancillary information derived from digital elevation models and remote sensing data can be used to support soil mapping and to indicate soil characteristics on the landscape scale.
185 citations
TL;DR: In this paper, a subglacial till formed from a sandstone bedrock has a variable grain-size distribution which reflects its variable genesis, and the experiments indicate that most of the sand-sized till material formed as a result of crushing, while the silt is mainly the result of abrasion.
Abstract: A subglacial till formed from a sandstone bedrock has a variable grain-size distribution which reflects its variable genesis. Glacial comminution processes were simulated by artificial mill experiments with fragments of the sandstone bedrock. Pure crushing caused disintegration along mineral boundaries into separate minerals, most mineral grains retaining their primary size during the crushing process. Abrasion produced cracks across the minerals and resulted in silt-sized rock flour. The experiments indicate that most of the sand-sized till material formed as a result of crushing, while the silt is mainly the result of abrasion. The sand and silt are both regarded as components resistant to further glacial comminution, but are formed by different comminution processes. By considering also the coarser till material, the general principles of glacial breakdown of resistant rocks from boulders to sand or silt can be illustrated. A matrix index and an abrasion index based on the mill experiments distinguish well between genetically different subglacial till types
151 citations
Journal Article•
TL;DR: The present study was carried out to determine the physicochemical characteristics of water and sediment and the textural aspects of sediments in western mangroves of Kachchh-Gujarat, west coast of India, for a period of two years during 1999-2000.
Abstract: The present study was carried out to determine the physicochemical characteristics of water and sediment and the textural aspects of sediments in western mangroves of Kachchh-Gujarat, west coast of India, for a period of two years during 1999-2000. Surface water and sediment temperatures varied from 17 o C to 37 o C and from 18.4 o C to 37 o C respectively. Tidal amplitude varied from 0.03m to 3.78 m. Salinity varied from 34.0 to 44 ‰ and the pH in water and sediment ranged between 7.0 and 8.9 and 6.29 and 8.45 respectively. Variation in dissolved oxygen content was from 3.42 to 5.85 ml l -1 . Concentrations of nutrients viz. nitrate (0.23 to 7.26 4M), nitrite (0.04 to 0.874M), phosphate (0.13 to 3.12 4M) and reactive silicate (4.23 to 19.02 4M) also varied independently. Total organic carbon varied from 0.29% to 2.56% and the total inorganic phosphorus ranged between 0.12 mg g -1 and 1.97 mg g -1 . Total nitrogen varied from 0.02 mg g -1 to 1.95 mg g -1 . Sediment textures ranges in terms of % of sand, clay and silt were: 0.26-19.2; 7.6-47 and 47-87.4 respectively in all the 3 stations. The nature of soil texture is characterized by the abundance of silty loam, silty clay and silty clay loam.
149 citations
TL;DR: In this paper, an intertidal digital elevation model (DEM) using waterlines extracted from Landsat TM and in situ ground levelling data was proposed to estimate morphologic change from the generated DEMs.
Abstract: The objectives of this study were: (a) to generate an intertidal digital elevation model (DEM) using waterlines extracted from Landsat TM and in situ ground levelling data; (b) to quantitatively estimate morphologic change from the generated DEMs for the years 1991 and 2000; and (c) to evaluate the chenier migration in the tidal flats of Gomso Bay, Korea. On extracting the waterlines, we considered the tidal flat environments, such as tidal conditions, remnant surface water, suspended sediment, and exposure time. Ground levelling was carried out along one line in 1991, and two lines in 2000. From the extracted waterlines and ground levelling data, we succeeded in generating intertidal DEMs with an accuracy of 10.9 cm r.m.s. overall, and 7.3 cm r.m.s. in the lower tidal flats. The morphologic changes estimated by subtracting the two DEMs showed an erosion rate of −9.0 cm over 9 yr that corresponds to an annual mean morphologic change budget of −309,865 m 3 /yr. Overall, the Gomso tidal flats can be defined as an erosion-dominant environment. The changes with respect to the sedimentary facies were also evaluated as: (a) the sandy silt flat had a sedimentation rate of −3.4 cm over 9 yr that corresponds to an annual mean budget of −52,552 m 3 /yr; (b) the silty sand flat had a sedimentation rate of −14.3 cm over 9 yr that corresponds to a mean erosion of −197,927 m 3 /yr; and (c) the sand flat had a sedimentation rate of −11.8 cm over 9 yr that corresponds to a mean change of −58,808 m 3 /yr. The results comply with the general rules of sedimentology. We also investigated the chenier migration, which is the most dynamic geomorphologic change in the tidal flats. Chenier is usually composed by sand and shell as a result of coastal progradation in sand, and it is dominantly fed by sediments transported by long-shore currents. The chenier was found to have migrated about 148 m landward over 6 yr. The results demonstrate that satellite remote sensing is an efficient and effective tool for a long-term morphologic change estimation in tidal flats.
131 citations
TL;DR: In this article, a modified version of the Morgan-Morgan-Finney model was proposed to account for vegetation cover in the process of erosion, transport and deposition of soil particles.
Abstract: Modifications are made to the revised Morgan–Morgan–Finney erosion prediction model to enable the effects of vegetation cover to be expressed through measurable plant parameters. Given the potential role of vegetation in controlling water pollution by trapping clay particles in the landscape, changes are also made to the way the model deals with sediment deposition and to allow the model to incorporate particle-size selectivity in the processes of erosion, transport and deposition. Vegetation effects are described in relation to percentage canopy cover, percentage ground cover, plant height, effective hydrological depth, density of plant stems and stem diameter. Deposition is modelled through a particle fall number, which takes account of particle settling velocity, flow velocity, flow depth and slope length. The detachment, transport and deposition of soil particles are simulated separately for clay, silt and sand. Average linear sensitivity analysis shows that the revised model behaves rationally. For bare soil conditions soil loss predictions are most sensitive to changes in rainfall and soil parameters, but with a vegetation cover plant parameters become more important than soil parameters. Tests with the model using field measurements under a range of slope, soil and crop covers from Bedfordshire and Cambridgeshire, UK, give good predictions of mean annual soil loss. Regression analysis of predicted against observed values yields an intercept value close to zero and a line slope close to 1·0, with a coefficient of efficiency of 0·81 over a range of values from zero to 38·6 t ha−1. Copyright © 2007 John Wiley & Sons, Ltd.
128 citations
TL;DR: The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi as discussed by the authors, where two sites, only 700m apart but with very different As concentrations, were compared.
124 citations
TL;DR: Li et al. as mentioned in this paper investigated the physicochemical properties of biological soil crusts (BSCs) and underlying topsoil (0-5 cm under BSCs) in Horqin Sand Land, Inner Mongolia, Northern China.
Abstract: This study was undertaken at Horqin Sand Land, Inner Mongolia, Northern China. Field samples of biological soil crusts (BSCs) and underlying topsoil (0–5 cm under BSC) were taken in areas of different dune stabilization stages, and their physicochemical properties were analyzed, including particle size distribution, bulk density, organic matter, nitrogen, phosphorus, electrical conductivity (EC), pH, and CaCO3 content. The results revealed that semi-mobile dunes, semi-fixed dunes and fixed dunes had developed a physical crust, algae crust and moss crust, respectively. The thickness, hardness, water content, fine fraction and nutrient contents of BSCs were gradually increasing along the dune stabilization gradient. Meanwhile, BSC establishment and development enhanced the bulk density, silt and clay content, and nutrients of the topsoil under it, in an increasing tend from semi-mobile dune to fixed dune. Organic matter concentrations and other nutrients in the 0–5 cm topsoil layer under BSCs were significantly higher compared to unconsolidated soil (control). Moreover, there were strong significant positive correlations between topsoil and BSCs’ organic matter, total nitrogen, available nitrogen, available phosphorus, CaCO3, and <0.05 mm particle content, suggesting that BSCs have an influence on some of the properties of the underlying topsoil.
121 citations
TL;DR: In this paper, a fractionation protocol comprising complete dispersion of the fraction > 50μm of the original soil sample, and subsequent size and density fraction of the sample, was developed.
114 citations
TL;DR: In this article, the authors presented results of studies on the valorisation of polluted river sediments from the North region of France, where treated sediments were used as a brick making raw material.
Journal Article•
TL;DR: In this article, the authors quantified the spatial variation of bulk density organic carbon, silt and clay contents for two soil depths (0-15 and 15-30 cm) in the agricultural farm of the Indian Agricultural Research Institute, New Delhi were quantified and the respective surface maps were prepared through ordinary kriging.
Abstract: Knowledge of spatial variation of soil properties is important in precision farming and environmental modelling. Spatial distribution of water content at field capacity (FC) and permanent wilting point (PWP) at different zones of a farm governs the available water for plant growth. These two soil hydraulic parameters play key roles in crop selection for different blocks of a farm, and in scheduling irrigation of crops in a field. In this study, spatial variation of bulk density organic carbon, silt and clay contents for two soil depths (0-15 and 15-30 cm) in the agricultural farm of the Indian Agricultural Research Institute, New Delhi were quantified and the respective surface maps were prepared through ordinary kriging. Particle size distribution shows better spatial correlation structure than bulk density and organic carbon content. Gaussian model fits well with experimental semivariogram of bulk density, and silt and clay contents. Hole-effect model was found to be the best to fit the experimental semivariogram of organic carbon content. Spatial correlation structure for both surface (0-15 cm) and subsurface (15-30 cm) soil layer remains the same, but the magnitude of spatial correlation differs. Cross-validation of the kriged map shows that spatial prediction of basic soil properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. Pedo-transfer functions were coupled with the surface map of basic soil properties to generate a map of water content at FC and PWP. Evaluation of spatial maps of θ FC and θ PWP showed reasonable accuracy of these two hydraulic parameters for farm-level or regional-scale application.
TL;DR: A soil survey was carried out on Byers and Hurd peninsulas to characterize the soils and investigate the processes of soil development as mentioned in this paper, which indicated that the main process involved in soil development was the mechanical disintegration of bedrock although there was also some leaching.
TL;DR: The results from a laboratory experimental study on silty sand are presented in this article, where undrained triaxial compression tests were performed on Nevada sand containing nonplastic silt.
Abstract: The results from a laboratory experimental study on silty sand are presented Undrained triaxial compression tests were performed on Nevada sand containing nonplastic silt All specimens underwent
TL;DR: In this article, the spatial and vertical distribution of nutrients and biogeochemical processes of the C, N, P and S in the Pichavaram mangrove ecosystem were analyzed for grain size distribution, nutrients and stable N isotope (δ15N) signatures.
Abstract: Mangrove sediments play a pivotal role in the nutrient biogeochemical processes by behaving as both source and sink for nutrients and other materials Surface and core sediments were collected from various locations of the Pichavaram mangrove (India) and analyzed for grain size distribution, nutrients and stable N isotope (δ15N) signatures in order to understand the spatial and vertical distribution of nutrients and biogeochemical processes of the C, N, P and S in this ecosystem Sand is the dominant fraction followed by silt and clay Spatial distribution of nutrients is controlled by the external and internal loadings, whereas vertical distribution is largely driven by the in situ microbial activities Interior mangrove sediments contain higher concentrations of organic carbon (OC) than the estuarine sediments reflecting high rates of organic matter retention Finer fractions of sediment hold ∼60% OC due to high surface area At some sampling points, moderately high δ15N signatures were observed and this may be because of agricultural runoff and aquaculture effluents
TL;DR: In this paper, the root effect is incorporated into the soil erosion model through adapting the soil cohesion input value, which is based on a comparison of measured soil detachment rates for bare and root-permeated topsoil samples with predicted erosion rates under the same flow conditions.
Abstract: As organic root exudates cause soil particles to adhere firmly to root surfaces, roots significantly increase soil strength and therefore also increase the resistance of the topsoil to erosion by concentrated flow. This paper aims at contributing to a better prediction of the root effects on soil erosion rates in the EUROSEM model, as the input values accounting for roots, presented in the user manual, do not account for differences in root density or root architecture. Recent research indicates that small changes in root density or differences in root architecture considerably influence soil erosion rates during concentrated flow. The approach for incorporating the root effects into this model is based on a comparison of measured soil detachment rates for bare and for root-permeated topsoil samples with predicted erosion rates under the same flow conditions using the erosion equation of EUROSEM. Through backwards calculation, transport capacity efficiencies and corresponding soil cohesion values can be assessed for bare and root-permeated topsoils respectively. The results are promising and present soil cohesion values that are in accordance with reported values in the literature for the same soil type (silt loam). The results show that grass roots provide a larger increase in soil cohesion as compared with tap-rooted species and that the increase in soil cohesion is not significantly different under wet and dry soil conditions, either for fibrous root systems or for tap root systems. Power and exponential relationships are established between measured root density values and the corresponding calculated soil cohesion values, reflecting the effects of roots on the resistance of the topsoil to concentrated flow incision. These relationships enable one to incorporate the root effect into the soil erosion model EUROSEM, through adapting the soil cohesion input value. A scenario analysis shows that the contribution of roots to soil cohesion is very important for preventing soil loss and reducing runoff volume. The increase in soil shear strength due to the binding effect of roots on soil particles is two orders of magnitude lower as compared with soil reinforcement achieved when roots mobilize their tensile strength during soil shearing and root breakage. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors evaluated K and identified factors affecting K for calcareous soils in Hashtrood City, northwestern Iran, using the Universal Soil Loss Equation (USLE).
TL;DR: In this paper, the authors hypothesize that a more likely source for the silt-rich mantles is airborne dust from mainland California and Baja California, either from the Mojave Desert or from the continental shelf during glacial low stands of sea.
Abstract: There is an increasing awareness that dust plays important roles in climate change, biogeochemical cycles, nutrient supply to ecosystems, and soil formation. In Channel Islands National Park, California, soils are clay-rich Vertisols or Alfi sols and Mollisols with vertic properties. The soils are overlain by silt-rich mantles that contrast sharply with the underlying clay-rich horizons. Silt mantles contain minerals that are rare or absent in the volcanic rocks that dominate these islands. Immobile trace elements (Sc-Th-La and Ta-Nd-Cr) and rare-earth elements show that the basalt and andesite on the islands have a composition intermediate between upper-continental crust and oceanic crust. In contrast, the silt fractions and, to a lesser extent, clay fractions of the silt mantle have compositions closer to average upper-continental crust and very similar to Mojave Desert dust. Island shelves, exposed during the last glacial period, could have provided a source of eolian sediment for the silt mantles, but this is not supported by mineralogical data. We hypothesize that a more likely source for the silt-rich mantles is airborne dust from mainland California and Baja California, either from the Mojave Desert or from the continental shelf during glacial low stands of sea. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when “Santa Ana” conditions prevail, caused by a high-pressure cell centered over the Great Basin. The eolian silt mantles constitute an important medium of plant growth and provide evidence that abundant eolian silt and clay may be delivered to the eastern Pacifi c Ocean from inland desert sources.
TL;DR: In this article, the HYDRUS-1D mobile-immobile water model was used to evaluate the transport of fecal coliforms, Salmonella bacteriophage, and Br in 10 soils.
Abstract: The HYDRUS-1D mobile‐immobile water model (MIM) was used to evaluate the transport of fecal coliforms, Salmonella bacteriophage, and Br in 10 soils. At a fl ux of 5 mm h −1 , a pulse of dairy shed effl uent was applied to 30 large undisturbed lysimeters, followed by water irrigation. Soil types included clayey gley soil, clay loam, silt loam, silt loam over gravels, fi ne sandy loam, dune sand soil, pumice soil, and allophanic soil. Except for dune sand, modeling results showed lower mobile water contents and dispersivities for microbes than for Br, indicating the exclusion of microbes from smaller pores. The MIM-derived removal rates were in the order: volcanic soils > greywacke-derived silt loams > granular young sandy soils, and were the most variable in clayey gley loam and silt loam over gravels. Microbial reduction was 100% in allophanic soil, 16 to 18 log m −1 in pumice soil (where the unit log is the log 10 reduction in maximum concentration compared with the original concentration), and was lowest in clayey gley soil (0.1‐2 log m −1 ). For most of the other soils, the reduction was 2 to 3 log m −1 , except for 9 to 10 log m −1 for fecal coliforms in a fi ne sandy loam. The detachment rate was only 1% of the attachment rate, indicating irreversible attachment of microbes. Soil structure (macroporosity) appeared to play the most important role in the transport of microbes and Br, while soil lithology had the greatest infl uence on attenuation and mass exchange. The general pattern of predicted mobile water content agrees with the measured macroporosity, which is positively related to leaching vulnerability but negatively related to dispersivity.
TL;DR: In this paper, the physical, chemical and microclimatological properties of soils along a High Arctic glacier foreland and adjacent moraine in relation to the development of biological soil crusts were examined.
Abstract: This study explores the physical, chemical and microclimatological properties of soils along a High Arctic glacier foreland and adjacent moraine in relation to the development of biological soil crusts. We examine various edaphic properties: soil temperature, volumetric water content, organic carbon content, and texture in surface samples (∼1 cm) with and without a cover of biological soil crust as well as changes in nitrogen, phosphorus, potassium, organic carbon, pH, volumetric water content, bulk density, and texture in crusted surfaces (<1 cm) and soil cores (5 cm) along a chronosequence following deglaciation. Soil crusts developed within four years of deglaciation and subsequent peaks in crust cover and thickness coincided with an accumulation of nitrogen and organic carbon in the crust. Crusted surfaces had significantly higher volumetric water content, organic carbon, a greater silt and clay fraction, and lower temperature compared to uncrusted soils. A steady supply of water from glacier...
TL;DR: In this paper, a planar infinite slope model was used to investigate mass movement processes on thawing ice-rich slopes, and measured pore pressures were used in slope stability analyses.
TL;DR: In this paper, a scanning electron microscope (SEM) was used to investigate the effect of depositional method and silt content on the performance of a laboratory experimental study on silty sand.
Abstract: The results from a laboratory experimental study on silty sand are presented. A scanning electron microscope (SEM) was used to investigate the effect of depositional method and silt content on the ...
TL;DR: Wang et al. as mentioned in this paper investigated the relationship between soil and crop yield in terraced catenas with contrasting soil textures cropped with wet rice and found significant correlations between rice yield and silt as well as total nitrogen content.
TL;DR: A review of sediment dispersal processes in the Strait of Georgia, based on marine geological studies, finds that far-field sediment accumulation is controlled by local morphology and sediment dynamics, and some parts of the basin floor are characterized by bottom sediment reworking and erosion.
TL;DR: In this paper, a series of unsaturated soil triaxial tests were performed on four soils including sand, silt, and a low plasticity clay, and the feasibility of estimating unsaturated property functions from saturated soil properties, SWCCs and gradation data, is demonstrated.
Abstract: A series of unsaturated soil triaxial tests were performed on four soils including sand, silt, and a low plasticity clay Attempts were made to correlate unsaturated soil properties from these tests and data from the literature with soil-water characteristics curve (SWCC), soil gradation, and saturated soil properties The feasibility of estimating unsaturated soil property functions from saturated soil properties, SWCCs and gradation data, is demonstrated A hyperbolic model for estimation of the unsaturated soil parameter, Φ b , versus matric suction is presented Shear induced volume change behavior was also studied, and results are included in this paper Although not correlated with soil index properties, these shear-induced volume change data are important to complete stress-deformation analyses, and represent a significant addition to the existing data base of unsaturated soil properties
TL;DR: In this article, a series of undrained torsional shear tests with constant α and b-values were conducted by hollow cylindrical Torsional Shear (HCTS) apparatus on Firoozkuh sand containing a wide range of silt percentage.
TL;DR: In three excavations in the southern Netherlands and northern Belgium, the Weichselian convolutions in fine sand, silt and clay deposits were investigated, and an attempt was made towards a semi-quantitative approach to some sediment parameters as mentioned in this paper.
Abstract: In three excavations in the southern Netherlands and northern Belgium, the Weichselian convolutions in fine sand, silt and clay deposits were investigated, and an attempt was made towards a semi-quantitative approach to some sediment parameters. This, together with a detailed field survey, enabled interpretation of the deformations as forms of periglacial loadcasting. They originated from the time of permafrost degradation when large quantites of water were available. The amplitude of the involutions can be related to the depth of the permafrost table at that time. During the weichselian, two periods occurred in which this involution process could have been active
TL;DR: In this article, the impact of stover removal on micro-scale soil properties was investigated in continuous corn systems in a Rayne silt loam (RSL) with 10% slope, Celina silt leam (CSL) (fine, mixed, active, mesic Aquic Hapludalfs) with 2% slope and Hoytville clays (HCL) with < 1% slope in Ohio.
TL;DR: In this paper, the redistribution of pore water during diffusion of earthquake-induced excess pore pressures in a sand slope with embedded silt layers was studied using a 9m-radius centrifuge.
Abstract: This paper presents analyses of a test conducted on a 9-m-radius centrifuge to study the redistribution of pore water during diffusion of earthquake-induced excess pore pressures in a sand slope with embedded silt layers. The centrifuge model developed large postshaking deformations associated with shear strain localization at the interface between the sand and silt layers. Dense arrays of pore pressure transducers provided detailed measurements of pore pressure variations in time and space within the slope. A new data analysis approach is presented in which measured pore-pressures are used to compute flow rates and volumetric strains as a function of time and position throughout the slope. Hydraulic gradients were calculated by numerical differentiation of measured pore-pressure distributions with respect to position. Flow rates that were based on Darcy's law were then integrated with respect to time to obtain flow quantities, from which volumetric strains were computed. A second data analysis approach that computes volumetric strains on the basis of soil compressibility and changes in pore pressure provided an independent computation of strains in consolidating zones. Results using these data analysis procedures confirm that a dilating (loosening) zone of significant thickness developed in the sand immediately beneath an embedded silt layer that had impeded the drainage of high pore pressures. These results support the hypothesis that the dilating zone corresponds to regions where the mobilized friction angle exceeds the critical state friction angle and that the dilating zone can be initially relatively thick before its size diminishes to the thickness of a thin shear band after the peak friction angle is mobilized. Quantification of the evolution of the size of the dilating zone is a key to understanding the magnitude of deformations associated with void redistribution.
TL;DR: In this paper, a new stabilizing agent (SEU-2) was developed to improve the mechanical performance and applicability of silt in road, which has high early strength, small shrinkage deformation, and high entire stiffness.