bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial Characteristics through Drinking Water Aquifer Sand Material
Authors: Ibekwe A. M. , Lyon S. R. 
Published: February 2007

AbstractPublic health concerns about pathogens present in animal manure are emerging constraints to water supplies in many areas of the world. The objective of this study was to examine the microbial community composition in aquifer material impacted by contaminants from different sources. Total microbial community profiles were compared by using eubacterial primers to amplify 16S rRNA genes from total bacterial DNA and RNA. PCR and reverse transcriptase (RT) PCR were used to amplify 16S ribosomal RNA, and the products were subjected to denaturing gradient gel electrophoresis (DGGE). DGGE analysis of RT‐PCR products detected a subset of bands visible in the DNA‐based analysis, indicating that some dominantly detected bacterial populations did not have high levels of metabolic activity. The sequences detected by the RT‐PCR approach were, however, derived from a wide taxonomic range, suggesting that the activity in the aquifer sand material was not determined at broad taxonomic levels but rather was a strain‐ or species‐specific phenomenon. Comparative analysis of DGGE profiles grouped all DNA‐derived aquifer samples together in a cluster. At the end of the experimental period, the aquifer material entered a stable population state, which was characterized by a greater diversity of DNA‐based fingerprints compared to viable bacteria. Our data showed that the active members of the community are a sub‐population of that community that performs certain biological functions during water filtration through aquifer material. Therefore, recharging surface water through aquifer sand material may produce a microbial population quite different from the input source due to the availability of nutrients for bacterial growth.
Flood‐related channel change in an arid‐region river
Authors: Graf William L. 
Published: February 2007

AbstractA review of 112 years of change in the channel of the Salt River, central Arizona, U.S.A., shows that this arid‐region river has a main‐flow channel that has migrated laterally up to 1.6 km (1 mi) in response to floor events. Maps showing locational probabilities indicate that along the channel zones of relative locational stability alternate with zones of relative instability at a 3.2 km (2 mi) interval. Construction of upstream reservoirs has reduced sediment input into the main river but has not controlled floods. The channel width has not changed except for moderate fluctuations around mean values; the main‐flow channel has incised approximately 6 m (20 ft) over most of the 48 km (30 mi) study reach during six recent floods. Gradient has remained unchanged. During floods bed material was mobilized to a depth below the original bed level that was greater than the height of the water surface above the original bed. Calculations based on tractive force indicate a threshold discharge of instability that is equal to the flow with a five‐year return interval. The river exhibits remarkable stability with respect to gradient and sinuosity, irrespective of water and sediment discharges, but horizontal channel location exhibited selective instability. Over the record period of more than a century, the channel appears not to have been in equilibrium considering geometry, discharge, and sediment.
Spatial variation in solutional denudation and soil moisture over a hillslope hollow
Authors: Crabtree R. W. , Burt T. P. 
Published: February 2007

AbstractA spatial pattern of relative solutional denudation is described for a hillslope hollow and adjacent spurs at Bicknoller Combe, Somerset. The pattern was obtained from a network of micro‐weight loss rock tablets emplaced in the soil. The results show that the hollow is the main locus of solutional denudation. The soil moisture distribution over the hollow indicates that it is a transmission zone for acid soil water percolating from the adjacent spurs to the saturated wedge at the base of the hollow. The wetter acid soils in the hollow are responsible for the relatively higher solutional denudation taking place in the hollow.
Preliminary estimates of intertidal limestone erosion, one tree island, southern great barrier reef, australia
Authors: Trudgill Stephen T. 
Published: February 2007

AbstractEstimations of surface lowering of 0.2‐3.8 mm a−1 were gained from measurements of pedestal heights under sedentary organisms. The role of erosion by chitons, estimated at 0.2‐2.9 mm a−1 for home scars and 0.2‐0.7 mm a−1 for grazing, and other bioerosive organisms, is briefly discussed.
A note on the amount of wave energy transmitted over nearshore sand bars
Authors: Carter R. W. G. , Balsillie J. H. 
Published: February 2007

AbstractThe wave energy loss as waves break on nearshore bars is an important geomorphological process as it controls the stability of the adjacent beaches and dunes. The effect is particularly important during storms as it serves to guard against severe shoreline erosion.Field measurements from Florida and Ireland of waves crossing both single and multiple bar bedforms, indicate that where bar‐breaking occurs, between 78 and 99 per cent of wave energy may be dissipated from individual waves. However, a further 20 per cent energy may reach the shore if wave frequencies increase during the reformation process. This latter effect was not noted at the multiple bar site where spilling mode breakers dominate. The level of energy dissipation is related to the time taken to cross that section of the submerged bar below the critical depth, d < 1.28H. In the field this may be approximated by the ratio of wave speed to the width of the bar breaker zone.
Periodic heat conduction in a non‐uniform soil
Authors: Wiltshire R. J. 
Published: February 2007

AbstractThe one dimensional heat conduction equation is applied to a non‐uniform soil in which harmonic boundary conditions are specified. The analytic solutions are derived for practical use and satisfy a law that the thermal diffusivity is proportional to the square of the speed of the temperature wave. Depending on the nature of this speed the solutions may be categorized as circular, parabolic, hyperbolic, or exponential. A practical example is given in which the damping depth and thermal capacity of the soil both vary with depth. It shows that there may be considerable differences between uniform and nonuniform soils as far as temperature is concerned. A case of a slowly varying soil layer is also examined and is compared with the constant soil solution.
Slope process change and colluvium deposition in Swaziland: An SEM analysis
Authors: Goudie Andrew , Bull Peter A. 
Published: February 2007

AbstractElectron microscope analysis of sixty samples taken from six colluvium sites in Swaziland has shown that the quartz grains exhibit marked edge abrasion in the uppermost beds of exposures. This edge abrasion is lacking in the lower beds in all sections examined and indicates slope process change during colluvium deposition. A model of slope evolution is provided, in which slope erosion progressively brings about more channelling and causes greater surface roughness because of the exhumation of more core stones and differentially weathered rock. This roughness causes increased edge abrasion.
Eolian dust deposition on the Giara di Gesturi basalt plateau, Sardinia
Authors: Sevink J. , Kummer E. A. 
Published: February 2007

AbstractMineralogical study of samples from depression fills on an isolated basalt plateau in Central Sardinia showed that, although the basalt is free of quartz and mica, fair amounts of these minerals occur in the finer fractions. Results from X‐ray analyses of silt fractions and morphoscopical analyses of sand fractions indicate that the bulk of the quartz and mica is of eolian origin.The eolian quartz is predominantly of medium and coarse silt size and, in the upper 10 cm of the depression fills, constitutes about 20 per cent of the soil mass (approx. 20 kg/m2). Eolian mica is present in smaller amounts and is of medium silt or smaller size.The provenance of the eolian material could not be established with certainty, although a local origin can be excluded.
Hydraulics of runoff and loess loam deposition
Authors: De Ploey J. 
Published: February 2007

AbstractOn many more or less loamy soils, rill erosion is reported to start on slopes that are equal to or steeper than 2–3°; critical Froude numbers for the start of rill wash on these slopes vary between 2·0 and 3·0. This explains why colluvial deposition often occurs on slopes below 2–3°, when water spreads out at the downslope extremities of the rills.The critical hydraulic conditions for loess loam deposition were tested in the laboratory for slopes of 0·5° and 2°, applying unit‐discharges (q) up to 10 cm2/s. It appeared from these experiments that for afterflow, without raindrop impact, deposition starts for critical load concentrations (ccr) varying between several g/1 and about 60 g/l. Under rain ccr amounts to a minimum value of 100–125 g/l and it increases when the runoff film becomes thinner. Nevertheless, deposition in pluvial runoff is also possible, as was the case during the Weichselian, according to data from quarries in Belgium and in The Netherlands.A modified Kalinske equation is proposed for ccr prediction, with the introduction of a typical empirical coefficient Cr and considering such factors as shear stress and mean particle size. Massive sedimentation may occur when it stops raining and afterflow starts, since ccr values are then much lower. It is shown from the Shields' diagram that loamy suspensions are more sensitive to sedimentation than sands in clear water.
Structures caused by repeated freezing and thawing in various loamy sediments: A comparison of active, fossil and experimental data
Authors: Van Vliet‐Lanoë Brigitte , Coutard Jean‐Pierre , Pissart Albert 
Published: February 2007

AbstractIn this paper, the authors present the results of both macroscopic and microscopic investigations on structure development created by repeated ice lensing in various loamy experiments. Experimental data are compared with observations performed on active forms in High Arctic and Alpine Mountain environments. Those observations are also compared with phenomena observed in fossil periglacial formations of Western Europe.Platy and short prismatic structure formation is bonded to the hydraulic and thermal conditions during ice segregation. When a long series of alternating freezing and thawing affects platy structures, the fabric evolves, also being influenced by slope and drainage conditions: cryoturbations, frostcreep, and gelifluction can appear. They are characterized by specific microfabrics which are better developed with an increasing number of cycles: this is clear in experiments where hydraulic and thermal parameters are better controlled.Vesicles are also a prominent characteristic of the surface horizon in experiments and arctic soils. The genesis of vesicles is discussed on the basis of new observations and is related to the mechanical collapse of frost‐created aggregates under the mechanical work of soil air escape during soil saturation by water at thaw.
Determination of dissolved organic matter in streamwater using visible spectrophotometry
Authors: Grieve Ian C. 
Published: February 2007

AbstractAbsorbance at 360 nm was measured on 44 filtered streamwater samples of different dissolved organic matter (DOM) contents. A regression equation of DOM on absorbance predicted DOM with a standard error of estimate of 1.26 mgl−1, Use of a published equation relating dissolved organic carbon (DOC) to absorbance gave DOC values for the samples which were consistent with measured DOM. The method offers considerable potential for rapid quantification of dissolved organic matter concentrations in streamwater.
Sediment yield estimated from reservoir siltation in the Ochil hills, Scotland
Authors: McManus John , Duck Robert W. 
Published: February 2007

AbstractMeasurements made on the floors of the temporarily‐drained Glenfarg and Glenquey Reservoirs indicate that sediments with wet volumes of 63.94 × 103 m3 and 12.64 × 103 m3 were deposited in 56 and 73 years respectively. These figures represent 2.5 per cent and 1.1 per cent losses of original storage capacity. When corrected for water, organic, and diatom skeleton contents, and reservoir trap efficiency inorganic sediment yields of at least 31.3 tonnes km−2 yr−1 and of 9.0 tonnes km−2 yr−1 are suggested. The difference is probably related to contrasts of land use.
Attainable standards of accuracy in the retrodiction of palaeodischarge from channel dimensions
Authors: Dury G. H. 
Published: February 2007

AbstractThe most easily measurable palaeodimension on underfit streams is the wavelength of valley meanders, whether on manifest or on Osage‐type underfits. Checks that use data for existing, streams, however, suggest that retrodiction from wavelength is likely to be less accurate than retrodiction from width, while this in turn is less accurate than retrodiction from cross‐sectional area, or from some combination of cross‐sectional area and slope. Against this, former width and cross‐sectional area can be difficult to determine with any precision. Even where dimensions are known, calculation of discharge from these alone seems likely to range between some 75 and 130 per cent of actual values at the 50 per cent confidence limits, and between some 45 and 225 per cent at the 95 per cent limits. Variation in the form ratio appears to make no contribution to the difference between observed and expected velocities through the cross‐section. Unless former roughness can be reconstructed, by some other means than appeal to the form ratio, or unless something can be done with sediment transport, the retrodiction of palaeodischarge appears likely to remain subject to much uncertainty.
Definition of subfossil meandering palaeochannels
Authors: Rotnicki Karol , Borówka Ryszard K. 
Published: February 2007

AbstractThe determination of the bottom of a subfossil meandering palaeochannel is important for investigations of the palaeohydrology of valley bottoms, and crucial for the quantitative estimation of past river discharges. The authors present a procedure on the basis of which the bottom of a palaeochannel can be precisely determined. It is based on an analysis of the stratigraphic variability of such features of deposits as: mean diameter, standard deviation of the grain‐size composition, the percentage of sand, and ignition loss.
A factor analytic approach to the identification of geomorphic processes from soil particle size characteristics
Authors: East Thomas J. 
Published: February 2007

AbstractQ‐mode factor analysis of soil particle size data is used to identify the three dominant geomorphic processes responsible for the spatial variability of particle size in a catchment on the basaltic Darling Downs landsurface. Three factors are shown to account for 95 per cent of the textural variability of a suite of transported and sedentary materials. The spatial characteristics of groups of samples associated with the three factors suggests that the three factors are associated with suspended sediment transport and deposition, weathering, and bedload transport and deposition respectively. These interpretations are supported by the detailed graphical analysis of the cumulative particle size curves. The spatially variable influence of the three factors and related processes is given by their respective factor loadings which are mappable for the surface layer materials.
Genesis of late pleistocene cross‐valley moraine ridges, South—Central Ulster, Northern Ireland
Authors: Dardis George F. 
Published: February 2007

AbstractFour genetic varieties of ice‐marginal cross‐valley moraine ridge have been identified in south‐central Ulster, Northern Ireland. Type I ridges are flat topped, composed of stratified, water‐lain sediments and formed by coalescence of a series of supraaquatic deltas. Type II ridges are sharp crested, composed of stratified, water‐lain sediments and formed by coalescence of a series of subaquatic deltas. Type III ridges show mixed morphological and sedimentological characteristics of type I and II ridges. Type IV ridges are sharp crested or hummocky, composed of poorly‐sorted and poorly‐stratified water‐lain sediments and formed by coalescence of a series of subaquatic sediment gravity flow cones. Field evidence indicates that cross‐valley moraine ridges in south‐central Ulster were deposited in proglacial lacustrine environments. Ridge type depended principally on (1) the nature of the proglacial bedrock slope; (2) the manner in which meltwater entered the proglacial zone; and (3) ice‐sheet behaviour during deglaciation, particularly within the ice‐sheet terminus zone.
Corroded cobbles in Southern Death Valley: Their relationship to honeycomb weathering and lake shorelines
Authors: Butler Paul R. , Mount Jeffrey F. 
Published: February 2007

AbstractIn southern Death Valley, pits similar in morphology to honeycomb weathering (herein referred to as corrosion pits) occur on the surfaces of cobbles that are associated with wave‐produced benches. The pitted cobbles include a variety of igneous, metamorphic, and siliciclastic rocks; corrosion pits are rare to absent in limestones or dolomites. Pit morphology is controlled by cobble lithology. In massive rocks the pits are arcuate, elongate, and gently tapering; corrosion of laminated or foliated rocks has produced irregular, more jagged pits. The presence of desert varnish has strongly inhibited the corrosion process.The corroded cobbles are inferred to reflect both chemical and physical weathering of rocks along Pleistocene lacustrine strandlines. Corrosion took place through salt‐weathering and/or heat‐moisture expansion processes and through chemical dissolution of selected minerals as a result of splash‐zone wetting and drying. The ancient lake waters may have had high pH and high total dissolved solids contents. The recognition of corroded cobbles may be important in the reconstruction of the position of ancient shorelines for certain types of alkaline lakes and in the reconstruction of their ancient chemistries.
Semi‐variograms for modelling the spatial pattern of landform and soil properties
Authors: Oliver Margaret A. , Webster R. 
Published: February 2007

AbstractMany geomorphic properties can be treated as spatially‐dependent random variables. Some are second‐order stationary, others appear to vary without bound. In these circumstances their variation is best described by the semi‐variogram. In most instances the semi‐variogram can be modelled by a simple mathematical function, which itself is bounded for a stationary variable and unbounded otherwise. The function must be conditional negative semi‐definite to be permissible. More complex variation can be represented by combining two or more permissible models.Sample semi‐variograms of several landform and soil properties illustrate the common types of semi‐variogram. Their form and parameters are interpreted in physical terms.
Coincidence and spatial variability of geology, soils, and vegetation, mill run watershed, Virginia
Authors: Olson C. G. , Hupp C. R. 
Published: February 2007

AbstractThe Mill Run watershed is a structurally‐controlled synclinal basin on the eastern limb of the Massanutten Mountain complex of northwestern Virginia. Bedrock contacts are obscured by coarse sandstone debris from exposures near basin divides. Colluvium blankets more than half the basin, masking geomorphic surfaces, affecting vegetation patterns, and contributing to the convexity of the alluvial, terrace, pediment and erosion surfaces. Examination of the bedrock geology, geomorphology, soils and vegetation shows distinct distributional correspondences. Vegetation is strongly interdependent with geomorphology, bedrock geology, and soils. On convex colluvial slopes, mixed hardwood forests are most common. In concave coves and deep gorges, mixed hardwoods are replaced by conifers. In thin colluvium, in poorly developed soils, and on blockfields, chestnut oak is singularly prevalent. Conifers dominate shaley bedrock areas. Soils and surficial sediments have a major effect on near‐surface hydrology. During wet seasons, cemented horizons in the subsurface cause temporary saturation in the superjacent horizons; lateral movement of soil‐water effectively eliminates a vertical component of ground‐water recharge. Vegetation is strongly dependent on water availability and thus reflects the distribution of subsurface barriers and sediment‐soil fades changes.
A rapid method for simulating three‐dimensional fluvial terrain
Authors: Griffin Mark W. 
Published: February 2007

AbstractA rapid, computer‐based method of simulating ‘geomorphologically‐sensible’ three‐dimensional terrain data by modelling landform morphology is presented. For some engineering applications such an approach, even in a simple form, is preferable to the synthesis of terrain data by purely stochastic methods, and additionally can be useful where real data sets are difficult to obtain.The approach adopted utilizes a computer program which models landscape evolution by establishing a stream network on a tilted surface, with accompanying fluvial downcutting and slope adjustment. This is achieved by an iterative mechanism that combines deterministic and stochastic processes with geomorphological theory.The end‐product is a matrix of high‐resolution altitude data that has been used as the terrain model for a vehicle simulation exercise.
Theoretical investigation of the time variation of drainage density
Authors: Kashiwaya Kenji 
Published: February 2007

AbstractA theoretical equation was developed to express the time variation of drainage density in a basin or geomorphic surface: magnified image Di(t, T) is the drainage density at time T on the i‐th basin or geomorphic surface, which was formed at time t; β(τ) is a factor related to the erosional force causing the development of the rivers of the basin or surface at time τ; δi is the maximum drainage density; and Di is the initial drainage density on the i‐th geomorphic surface or basin. The equation is based on the assumption that the drainage density increases with time until it reaches a specific upper limit δi(t)), the maximum drainage density, which is related to certain physical properties of the basin. The equations for various dated basins or geomorphic surfaces can be combined into one modified equation if the same relative erosional forces have acted on those basins or surfaces (β(t) = β(t) and if the basins or surfaces have the same physical properties δi(t) = δi(t), (Di = D0). The application of this equation to coastal terraces and glacial tills shows that the model is compatible with observed drainage densities on various dated basins or surfaces.
Lake‐ice collapse trenches in Wisconsin, U.S.A.
Authors: Clayton Lee , Attig John W. 
Published: February 2007

AbstractA series of trenches about a metre deep, 20 to 30 m wide, and as much as 2 km in length occurs in central Wisconsin, along the east shore of proglacial Lake Wisconsin. They are interpreted to be collapse trenches formed when shore ice melted after being buried beneath an expanding outwash plain.