bluuebunny/crossref_metadata_2025_split huggingface dataset:
Packing of Sands for the Production of Homogeneous Porous Media
Authors: Oliviera I. B. , Demond A. H. , Salehzadeh A. 
Published: July 2010

AbstractMany studies of transport through soil assume that the laboratory columns used in the experiments are packed homogeneously. This research evaluated a variety of dry and wet packing techniques for their ability to produce uniform packings of clean sands without the use of specialized equipment. The best dry packing technique consisted of the deposition of 0.2‐cm layers followed by compaction with a metal pestle. For the sand used in this study, this technique resulted in a porosity of 0.325 ± 0.0020. The best wet packing technique consisted of the deposition of thin layers of saturated sand into water while vibrating the column. This technique resulted in a denser and more uniform packing, with the porosity equaling 0.315 ± 0.0018. No significant lateral particle‐size segregation was observed for either technique. Despite their success in producing homogeneous columns, the techniques proved time consuming, taking about 1 h per 5 cm of packed depth to pack a 15‐cm square column.
Alteration of Imogolite, Allophane, and Acidic Soil Clays by Chemical Extractants
Authors: Su Chunming , Harsh James B. 
Published: July 2010

AbstractPretreatment of soils to enable physical separation and purification of minerals may alter their structural or chemical composition and preclude meaningful surface charge characterization. A natural imogolite and allophane, a synthetic imogolite (Al/Si = 2.01) and allophane (Al/Si = 1.64), and clays from the Bs and BC horizons of a Spodosol containing imogolite were subjected to standard H2O2 treatments before and after extraction with buffered dithionite‐citrate‐bicarbonate (DCB) to determine if effects on their surface charge characteristics and bulk composition were reversible. The H2O2 slightly shifted the point of zero charge (PZC) determined by electrophoretic mobility (EM) of natural imogolite and allophane toward more positive values, probably by the partial oxidation of retained organics, whereas it had no effect on the PZC values of soil clays. Five DCB extractions removed the most Al and Si from the synthetic allophane and the least Al from the synthetic imogolite. More Si than Al was removed from the synthetic imogolite by five DCB extractions. Citrate retained on allophane and soil clays after DCB extraction was probably partially transformed to oxalate by subsequent H2O2 treatment. The EM in synthetic allophane could not be restored by oxidation of retained citrate following DCB treatment. Synthetic imogolite, after five DCB extractions, had only positive mobility up to pH 11.8. The DCB extraction, commonly used to remove Fe oxide from imogolite and allophane samples isolated from soils, irreversibly altered mineral surfaces and modified surface charge characteristics.
Modeling Competitive Adsorption of Arsenate with Phosphate and Molybdate on Oxide Minerals
Authors: Manning Bruce A. , Goldberg S. 
Published: July 2010

AbstractThe mobility of As in soils depends on several factors including redox potential, soil mineralogy, pH, and the presence of other oxyanions that compete with As for soil retention sites. We investigated the effects of pH and competing anions on the adsorption of arsenate [As(V)] on α‐FeOOH (goethite) and γ‐Al(OH)3(gibbsite). Batch equilibrium As(V) adsorption experiments were conducted with P and Mo as competing anions in order to produce single‐anion [As(V), P, and Mo] and binary‐anion [As(V)/P and As(V)/Mo] adsorption envelopes (adsorption vs. solution pH). Arsenate and P single‐anion adsorption envelopes were similar with substantial adsorption occurring across a wide pH range, including pH values above the points of zero charge of the oxides. Maximum Mo adsorption occurred across a narrower pH range (pH 4–6). On both oxides, equimolar P concentrations decreased As(V) adsorption within the pH range 2 to 11, whereas Mo decreased As(V) adsorption only below pH 6. The constant capacitance model was used to predict competitive surface complexation behavior between As(V)/P and As(V)/Mo using intrinsic equilibrium constants [Kanlon (int)] optimized from single‐anion data. In addition, the model was applied using one‐site (monodentate) and two‐site (monodentate + bidentate) conceptualizations of the oxide surface. The two approaches gave comparable fits to experimental adsorption data and were consistent with competitive adsorption observed in binary adsorption envelopes.
Characterization of the Hydrophobic Acid Fraction Isolated from a Wheat Straw Extract
Authors: Grossl Paul R. , Inskeep William P. 
Published: July 2010

AbstractThe hydrophobic acid portion (WSE‐FA) was isolated from a water‐soluble extract of wheat (Triticum aestivum L.) straw and chemically characterized. This material was isolated and concentrated on a column containing Amberlite XAD‐8 resin. Chemical analysis of the WSE‐FA included elemental composition (C, O, H, N, S, P, and ash); titrametric evaluation of carboxylic acid and phenolic functional group content; molecular weight (MW) determination by vapor pressure osmometry (VPO); gel filtration and ultrafiltration; and UV‐visible, solid‐state cross‐polarization magic angle spinning 13C nuclear magnetic resonance (NMR), and Fourier‐transform infrared spectroscopy. The MW of the WSE‐FA was approximately 600 daltons. The 13C‐NMR spectrum, the low MW relative to other humic substances, high E4/E6 ratio, and the low N content suggested that the WSE‐FA was comprised of small, aromatic phenolic acids, oxidized polyphenols with exposed carboxyl groups, and saccharides that were condensed during senescence.
Sulfur Balances and Sulfur‐34 Abundance in a Long‐Term Fertilizer Experiment
Authors: Kirchmann H. , Pichlmayer F. , Gerzabek M. H. 
Published: July 2010

AbstractReduced SO2 emissions, increased use of non‐S‐containing fertilizers, and higher crop yields may lead to S deficiency in agricultural soils in the future. In a long‐term field experiment on a clay loam soil (Typic Eutrochrept) at Uppsala, Sweden, S balances were evaluated for plots under continuous fallow, plots receiving inorganic fertilizers [(NH4)2(SO4 or Ca(NO3)2; 80 kg N ha‐1 yr‐1], and plots receiving organic amendments (2000 kg C ha‐1 yr‐1) with the aim of estimating plant uptake, leaching losses, immobilization, and variations of δ34S in soil. Total N was correlated with total S concentrations in soil (R2 = 0.980), but organic C was less well correlated (R2 = 0.741). Total soil S decreased in all treatments where no organic material was added, the largest decrease occurring in the continuous fallow plots with a S mineralization rate of 6 kg ha‐1 yr‐1. Sulfur added through (NH4)2SO4 and sewage sludge was mainly leached, whereas SO4 leaching was reduced in the Ca(NO3)2‐treated plots as a result of increased crop uptake. Of the organic amendments, 26 to 54% of the S remained in the soil with a half‐life of 24 to 38 yr. Recoveries of S from organic amendments in soil were correlated with their initial C/S ratios (R2 = 0.999) excluding peat. A significant enrichment of 34S was found only in plots receiving peat. Peat was more highly enriched in 34S than the other organic materials studied and was more resistant to decomposition. The results indicate that shifts in soil δ34S cannot be used as a tool for quantitative determinations of S turnover. Nitrogen transformations were the main cause of acidification in the (NH4)2SO4‐treated plots, as opposed to S leaching in the sewage‐sludgetreated plots.
Comparing Two Approaches of Characterizing Soil Map Unit Behavior in Solute Transport
Authors: Finke P. A. , Wösten J. H. M. , Kroes J. G. 
Published: July 2010

AbstractSoil maps can be used in different ways to characterize spatial patterns of soil behavior. A first approach is to establish the behavior of a pedogenetically representative profile from each soil map unit (SMU); a second is to subsample each SMU and select from the sample a characteristic profile by its behavior with respect to water and solute transport. The first approach was tested against the second with data from a SMU in the Netherlands. The use of pedogenetically representative profiles resulted in biased estimations of five studied functional properties related to water and solute transport. These properties were (i) the number of days with good workability; (ii) the number of days with sufficient aeration; (iii) the elapsed time to 10% breakthrough of an inert tracer (Cl‐); (iv) the percentage break‐through after 1 yr of an adsorbing, inert contaminant (Cd); (v) the percentage breakthrough after 1 yr of an adsorbing, degrading herbicide (isoproturon [N‐(4‐isopropylphenyl)‐N′, N′‐dimethylurea]). Soil profiles that did not fit the definition of the SMU (impurities) were responsible for the occurrence of extreme values for four out of five properties, which implies that impurities must be sampled when risk assessments have to be made. In this case, probability sampling offers a valid approach.
Soil Properties and Genesis of Pans in Till‐Derived Andisols, Olympic Peninsula, Washington
Authors: Wilson M. A. , Burt R. , Engel R. J. , Sobecki T. M. , Hipple K. 
Published: July 2010

AbstractSubsoil pans regarded as cemented are present in certain Andisols of the Olympic Peninsula region of western Washington. Soils formed in basalt‐derived alluvium or colluvium over Pleistocene‐aged compact alpine till. Theories of pan formation include pedogenic cementation by silica, allophane, or humic‐metal complexes; or geogenic till compaction with no subsequent cementation. We examined the properties of three pedons with compacted and cemented subsoil horizons to better understand the genesis of these soils and pan horizons. Pan horizons, designated as Cm, are very brittle, nearly impossible to dig with hand tools, and massive in structure. Soils are acidic, with pH(H2O) for all horizons ranging from 3.7 to 6.0. Crystalline phyllosilicates identified are gibbsite, kaolinite, chlorite, vermiculite, and hydroxy‐interlayered vermiculite. Allophane was detected in most mineral horizons, including Cm horizons, and allophane Al/Si molar ratios vary from 1.2 to 3.4. Low NaOH‐extractable Si, low Si/Al molar ratios from NaOH extracts, high rainfall, and the presence of gibbsite decrease the likelihood of pedogenic opal as a cementing agent in pans. Limited organo‐metallic deposition, low organic C, and low pyrophosphate‐extractable Fe and Al in pan horizons suggest that podzolization processes related to ortstein formation are not responsible for Cm horizon cementation. Micromorphologic examination of Cm horizons detected a light brown to nearly colorless substance that appears to be allophane around mineral grains and in pore channels. Soil chemistry data support allophane as the primary cementing agent in these pan horizons, with kaolinite, gibbsite, and Fe oxides acting as possible accessory agents. Glacial compaction, parent material mineralogy, and cycles of wetting and drying are important factors affecting cementation of these pans.
Sediment and Chemical Load Reduction by Grass and Riparian Filters
Authors: Daniels R. B. , Gilliam J. W. 
Published: July 2010

AbstractVegetated filter strips help reduce non‐point source pollution from agricultural areas. Even though they are an accepted and highly promoted practice, little quantitative data exist on their effectiveness under field conditions. The objective of this research was to determine the amount of nutrients and sediment removed by natural and planted filters. This was achieved by collecting and analyzing runoff at field edges and at various locations in vegetated buffers. Total weight of sediment and nutrients in runoff from North Carolina agricultural fields showed that the grass and riparian filter strips studied reduced runoff load by 50 to 80%. Total sediment decrease through the filters was about 80% for both grass and riparian vegetation. The reduction in the chemical load depended on the nutrient and its form. Filters reduced total P load by 50%, but 80% of the soluble PO4‐P arriving at the field edge frequently passed through the filters. The filters retained 20 to 50% of the NH4 and approximately 50% of the total Kjeldahl N and NO3. High‐volume flows commonly overwhelmed both grass and riparian filters next to cultivated fields. Forested ephemeral channels had little vegetation and were effective sediment sinks during the dry season but were ineffective during large storm events because there was little resistance to flow. When possible, drainageways should be designed to hold sediment and to disperse the discharge into a riparian area.
A Method for Studying the Effects of Soil Aggregate Size and Density
Authors: De Freitas P. L. , Zobel R. W. , Snyder V. A. 
Published: July 2010

AbstractSoil macroproperties, such as bulk density, porosity, water conductivity, and aeration, have been utilized in order to evaluate soil structure effects on crop yields. It has been suggested that many of the limitations to crop growth can be explained by the physical properties of the aggregates. To explore some aspects of this, a method to simulate soil aggregates of different sizes and densities was developed and tested. A Collamer silt loam soil (fine‐silty, mixed, mesic Glossoboric Hapludalf) was dried, crushed, sieved, and compressed to different densities (1.4, 1.6, and 1.8 Mg m‐3). The resulting 25‐ and 50‐mm‐thick cylindrical soil slices were cut to two different cubical sizes (25‐ and 50‐mm sides). Cylinders with continuous horizontal and vertical macropores were assembled from these artificial aggregates to make six different treatment combinations of aggregate size and density. Corn (Zea mays L.) seedlings were transplanted into the cylinders and grown in a growth chamber for 27 d. Results show that high aggregate density limits crop growth and that, at intermediate densities, aggregate size assumes more significance as a limiting factor.
Pedogenesis of a Vernal Pool Entisol‐Alfisol‐Vertisol Catena in Southern California
Authors: Weitkamp W. A. , Graham R. C. , Anderson M. A. , Amrhein C. 
Published: July 2010

AbstractVernal pools are seasonal wetlands that have unique plant and animal species. More than 10 vernal pools are found on the basaltcapped mesas of the Santa Rosa Plateau Ecological Preserve in southern Riverside County, California. In this study, one vernal pool catena was investigated to determine the relationships between soil morphology, soil chemical properties, and water movement. Soils on the summit and backslope are shallow and coarse‐loamy, and are maintained as Entisols by extensive burrowing by rodents and their predators. Footslope soils are clayey Alfisols with strong prismatic structure. The basin and toeslope soils are Vertisols with strong angular blocky structure and slickensides. Iron oxides are concentrated in the upper slope soils, imparting 5YR hues and high chromas. Because Mn oxides are soluble at higher redox potential than Fe oxides, Mn has been preferentially dissolved, transported downslope with throughflow, and precipitated as oxides in the lower slope soils, which have 10YR hues and low chromas. Water infiltrates readily through the upper slope soils and moves downslope along the soil‐basalt bedrock contact and within the vesicular basalt. In the basin, the Vertisols are wetted unevenly as water moves downward through soil cracks and upward from throughflow in the underlying vesicular basalt.
Soil Mass, Surface, and Spectral Fractal Dimensions Estimated from Thin Section Photographs
Authors: Anderson A. N. , McBratney A. B. , FitzPatrick E. A. 
Published: July 2010

AbstractAspects of fractal geometry have been used to give quantitative measurements of soil structure. Fractal dimensions measured were the mass fractal dimension (Dm), surface fractal dimension (Ds), and the spectral dimension (d). We investigated the fractal component of a computer program, STRUCTURA, which measures the fractal dimension of soil from images of soil thin sections. Six thin sections, each showing different structural characteristics, were analyzed in order to obtain a range of fractal dimensions. The dimensions, in particular Dm and d, were shown to discriminate the different structures. The values of Dm and d ranged from 1.682 to 1.852 and 1.236 to 1.668, respectively. A further objective was to use these results, together with fractal theory, to show the potential fractal geometry has in predicting physical processes such as diffusion within the soil. To assist with the interpretation of fractal dimensions, the dimensions of different soil samples with the same porosity were compared.
Two‐Dimensional Model for Water, Heat, and Solute Transport in Furrow‐Irrigated Soil: II. Field Evaluation
Authors: Noborio K. , McInnes K. J. , Heilman J. L. 
Published: July 2010

AbstractTo maintain crop production in areas where irrigation water or soil contains a large amount of salt, proper management of water and soil is required. A model simulating salt movement in the field may be helpful for developing improved management practices. We developed a two‐dimensional Galerkin finite element model to simulate transport of water, heat, and solute in furrow‐irrigated soil. In this model, we considered the interaction of soil water content, temperature, and solute concentration on transport of water, heat, and solute. An energy balance equation was applied to each node along the simulated ridge‐furrow soil surface to provide boundary conditions for water and heat transport. The model was compared with field measurements acquired in a loamy sand plot near College Station, TX. In the soil profile, distributions of water content and electrical conductivity were measured with time domain reflectometry, and distributions of temperature were measured with thermocouples. Solute concentration was estimated from electrical conductivity. The overall performance of the developed model was favorable when simulating distributions of water content, temperature, and solute concentration.
Soil Textural Control on Decomposition and Soil Organic Matter Dynamics
Authors: Scott Neal A. , Cole C. Vernon , Elliott Edward T. , Huffman Steve A. 
Published: July 2010

AbstractSoil texture affects litter decomposition by altering soil water availability, pore size distribution, nutrient availability, and surface area. We examined the direct and indirect effects of soil texture on litter decomposition and soil organic matter mineralization during 91‐d laboratory incubations. Treatments included texture (73, 55, and 40% sand), soil water pressure (−0.012, −0.033, and −0.30 MPa), and nutrient availability (with or without additional N and P). Wheat litter (Triticum aestivum L.) was placed on the surface or incorporated into the soil. Soil texture had no effect on litter decomposition (P >‐ 0.23). Litter decomposition was fastest for the −0.012 MPa treatment across all soil types (P < 0.01), and the difference between water pressure treatments was greatest in the loam (40% sand) soil. The effects of texture and soil water pressure could be combined into one variable (percentage water‐filled pore space), which accounted for more of the variability in litter decomposition and native soil C mineralization than either texture or soil water pressure alone. Surface‐applied litter decomposed significantly faster than incorporated litter, but the effect was not consistent across different soils (P = 0.04). Litter addition stimulated the mineralization of native soil C, the greatest effect occurring when litter was incorporated into the fine‐textured soil.
Soil Phosphorus Dynamics during Seventeen Years of Continuous Cultivation: Fractionation Analyses
Authors: Schmidt J. P. , Buol S. W. , Kamprath E. J. 
Published: July 2010

AbstractExcluding fertilizer P, a finite quantity of soil P exists for plant uptake. To improve our understanding of sinks and sources of long‐term plant‐available P, soil P fractions to a depth of 30 cm were determined in soils under a continuous cropping system prior to fertilization (1975), after 10 yr of P fertilization (1985), and 6 yr after the last P fertilization (1992). Soil types for two study sites were Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult) and Davidson clay loam (clayey, kaolinitic, thermic Rhodic Paleudult). Superphosphate was applied from 1975 to 1986 at rates of 0, 10, 20, and 40 kg P ha−1 yr−1. Average removal of P, via corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] cropping, was between 10 and 20 kg P ha−1 yr−1 from 1975 to 1992. Resin‐extractable soil P increased in the Norfolk soil with annual P applications that were in excess of crop removal and decreased with annual P applications that were less than crop P removal. Resin‐extractable soil P decreased to below 3 mg P kg−1 in the Davidson soil regardless of P application or removal rate. Inorganic soil P extracted with NaHCO3 and NaOH increased with excess P additions and decreased with deficient P additions for both soils. Organic soil P in the Norfolk soil extracted with NaOH represented a P sink at the 40 kg P ha−1 yr−1 treatment in 1985, but subsequently mineralized by 1992. In both soils, inorganic P extracted in the resin, NaHCO3, and NaOH fractions, and organic P in the NaOH fraction of the Norfolk soil, represented the biologically dynamic P.
Spatial Characteristics of Soil Properties along an Elevational Gradient in a Carolina Bay Wetland
Authors: Reese Rachel E. , Moorhead Kevin K. 
Published: July 2010

AbstractSoil chemistry gradients exist in wetlands but information on the spatial variability of wetland soil properties is limited. Soils were collected from a small, depressional wetland (Carolina bay) in South Carolina to determine spatial patterns along an elevational gradient. The bay was divided into four quadrants and a transect was established in each quadrant. Plots were sampled at every 10‐cm rise in elevation along the four transects. Samples from the A and B horizons were analyzed for soil texture, organic carbon (OC), pH, cation‐exchange capacity (CEC), and exchangeable Ca, Mg, and K. Significant difference were noted for OC, clay content, CEC, and base saturation for the A horizon across the elevational gradient. The OC content of the A horizon decreased from 4.7% in the center of the bay to 2.7% near the rim. The CEC decreased from 26.0 cmolc kg−1 in the center to 13.9 cmolc kg−1 near the rim. Significant differences also were observed for pH, OC, CEC, sand, silt, clay, exchangeable Mg, Ca, and base saturation among the four transects. In the B horizon, there were no significant differences for any parameter across the elevational gradient, or among the four transects. The clay content of the B horizon was about 20%, compared with <10% in the A horizon. The differences in soil parameters in the A horizon may be a reflection of vegetation patterns or hydrology of the bay. Sampling protocol for soils of depressional wetlands may require an evaluation of elevation, hydrology, and vegetation patterns to determine spatial patterns of nutrient cycling.