bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solubility Relationships of Fluorine Minerals in Soils
Authors: Elrashidi M. A. , Lindsay W. L. 
Published: July 2010

AbstractPredictive models for the solubility of F minerals were developed and compared to the F solubility measurements made on 109 soils. The experimental findings indicate that AlF3(c) may be the solid phase controlling F solubility in strongly acid soils, CaF2 (fluorite) in slightly acid soils, and KMg3AlSi3O10F2 (fluorophlogopite) in neutral and alkaline soils. Although Ca5(PO4)3F (fluorapatite) alone or in combination with hydroxyapatite is theoretically able to lower F activity in soils below that controlled by any of the aforementioned minerals, solubility measurements on all soils indicate supersaturation with respect to these apatite minerals.
Effect of Aluminum Substitution in Goethite on Phosphorus Adsorption: I. Adsorption and Isotopic Exchange
Authors: Ainsworth C. C. , Sumner M. E. , Hurst V. J. 
Published: July 2010

AbstractThree sets of goethite samples, pure (α‐FeOOH) and aluminum substituted (α‐[Fe,Al]OOH), were made using different synthesis techniques. Specific surface area ranged from 6.8 to 28.4 × 104 m2 kg−1. Adsorption isotherms were carried out on a surface area basis at pH values ranging from 2.6 to 7.6 for up to 120 h. The specific surface area (determined by Brunauer, Emmett, and Teller N2 adsorption [BET]) depended on the method of synthesis. Phosphate adsorption and isotopic exchange rates were dependent upon mode of synthesis, aluminum substitution, and pH. These results and the accompanying transmission electron micrographs indicate that the chemico‐physical environment during synthesis is a prime determinant of goethite's phosphate adsorption capacity. Aluminum substitution affects specific surface area and extent of phosphate adsorption as greatly as does the synthesis process. The Al samples had faster isotopic exchange rates than their pure counterparts. The rate of exchange increased with increasing surface area (smaller crystal size).
Effect of Aluminum Substitution in Goethite on Phosphorus Adsorption: II. Rate of Adsorption
Authors: Ainsworth C. C. , Sumner M. E. 
Published: July 2010

AbstractThe effects of initial pH, P concentration, Al substitution and method of synthesis on the rate of phosphate adsorption by a series of α‐FeOOH samples containing up to 30 mol % Al were investigated. The results, plotted as first‐order reactions with respect to phosphate disappearance, were characterized by an initial fast phase followed by a pseudo‐first‐order reaction. An approximation of the magnitude of the fast phase was made by extrapolating the first‐order line back to zero time. The difference between the initial and zero time first‐order concentration was then considered to be the magnitude of the rapid phase of the reaction. Phosphate concentration, initial pH, and method of synthesis influenced this parameter. Al substitution had little effect. However, Al substitution did affect the pseudo‐first‐order rate constant at all pH levels and lower P concentrations. It is postulated that Al substitution may sterically hinder the sorption of phosphate. The various synthesis methods affected the magnitude of the fast phase and the pseudo‐first‐order rate. This may be due to the apparent change in the number of active sites related to changes in synthesis as discussed in part 1.
High Humidity‐induced Increase in Water Repellency in Some Sandy Soils
Authors: Jex G. W. , Bleakley B. H. , Hubbell D. H. , Munro L. L. 
Published: July 2010

AbstractThe degree of resistance to water penetration of diverse water repellent soils was found to be controlled by their moisture states. Repellency was found to increase sharply when samples were incubated at 100% relative humidity and to decline when wetted or when incubated at humidities < 90%. A soil which was nonwater‐repellent in the field did not become repellent at 100% relative humidity. A Florida soil (St. Lucie series, hyperthermic, uncoated Typic Quartzipsamments) was used for detailed study. Repellency increase in this sand was temperature dependent and could be eliminated by gamma irradiation, indicating the biological nature of the process. Application of antibiotics prior to incubation suggested that prokaryotic organisms were essential to repellency increase. A dilution study of the St. Lucie soil incubated at 100% relative humidity for various periods revealed that the actinomycete population correlated best with the repellency increase. When incubated St. Lucie sand was investigated by electron microscopy, actinomycetes were found to dominate the visual field. A model for repellency increase and decline, based on soil humidity, is offered.
Scanning Electron Microscopy of Humic Matter as Influenced by Methods of Preparation
Authors: Tan K. H. 
Published: July 2010

AbstractScanning electron microscopy (SEM) has recently been used to study the macromolecular structure of fulvic (FA) and humic acids (HA). Differences in soils and sample preparations are believed to produce different results, but little is known to confirm the latter. This investigation was initiated to study the effect of different sample preparations on SEM of humic matter extracted from Omega, Mascotte, Onaway, and Cecil soil series. Using air dry specimens, SEM showed massive sheets of FA and HA with granular surfaces observable at high magnification, similar to those obtained by transmission electron microscopy (TEM). The individual spheres of FA and HA reported in earlier TEM studies appeared in the present SEM analysis only after the samples had been frozen at 0°C in a freezer. Use of a modified liquid‐N procedure, to provide a simpler and faster method, yielded similar tissue‐like structures for FA and HA as with the freon‐liquid‐N method on mica strips. Fulvic acid (pH 3.0) was composed of fiber‐like tissue, whereas HA (pH 7.0) had the appearance of shredded sheets. In both FA and HA, the sheets became prevalent at higher pH values. No effect was noticed by differences in concentration, but differences in soils had a definite influence on the SEM of the humic fractions. The fibers of FA from the Omega soil were coarse and thick, compared to those of the Mascotte soil where they were very fine. In the Onaway series, the FA fibers were medium in size. Fulvic acid from the Cecil soil, on the other hand, had the appearance of shredded or perforated sheets. Six types of structures were distinguished, e.g., fibrous, spheroids connected by fibers, sheets interwoven by fibers, perforated sheets, bladed, and shredded sheets. They were believed to be the result of the method of freezing.
Factors Affecting Oxidation‐reduction Processes in an Oxisol with a Seasonal Water Table
Authors: Couto W. , Sanzonowicz C. , Barcellos A. de O. 
Published: July 2010

AbstractThe weekly fluctuation of the water table was recorded for a period of 2 yr at five sites along a transect of a high plateau area in the Cerrados of Brazil characterized by minimal variation in soil morphology, color, and texture. The soil studied was a Red‐Yellow Latosol, a member of the clayey, oxidic, isohyperthermic family of Typic Acrustoxes. The soil profile to a depth of 200 cm did not show mottling or color chromas of 2 or less at any site. However, the water table was within 0.4 to 2.0 m of the soil surface at some sites for more than 90 d yr−1. Bright platinum electrodes installed at three sites showed only a moderate range of Eh values (700‐500 mV) indicating that no reduction took place in the soil at any depth, in spite of the standing water table. Soil samples taken at the 0‐ to 20‐, 20‐ to 40‐, 40‐ to 60‐ and 60‐ to 80‐cm depth, and subjected to different treatments, were incubated for 90 d at approximately 30 kPa water tension or under waterlogged conditions. Treatments consisted of nutrients, nutrients plus lime, and sucrose at two rates, 0 and 10 g kg−1 of soil. The Fe (II) content measured in moist samples at the end of the incubation period showed that intensive reduction took place under all treatments in soil samples taken from the 0‐ to 20‐ and 20‐ to 40‐cm depths. Samples taken below 40 cm contained a high Fe (II) content only when sucrose was applied. These data suggest that reduction does not occur in the field in the lower part of the soil profile even when a high water table is present due to the lack of a source of energy for microbial activity. It is suggested that the organic matter present in the lower part of the soil profile is too stable and/or too low in available nutrients for the reduction process to take place during the water logging period.
Biotite Kaolinization in Virginia Piedmont Soils: I. Extent, Profile Trends, and Grain Morphological Effects
Authors: Harris W. G. , Zelazny L. W. , Baker J. C. , Martens D. C. 
Published: July 2010

AbstractBiotite kaolinization was examined for acidic, well‐drained Virginia Piedmont soils with respect to extent, profile trends, and grain morphological effects. Fifty‐eight samples from 16 profiles were treated to remove Fe‐oxides, fractionated by particle size, and examined mineralogically using optical microscopy and x‐ray diffraction (XRD). Selected samples were examined by infrared (IR) spectroscopy, differential scanning calorimetric (DSC), scanning electron microscopy (SEM), and Hg‐intrusion porosimetry. All profiles contained kaolinized biotite sand grains and had kaolinite‐dominated clay fractions. Vermiculite was a minor component of most samples. Kaolinization increased with decreasing particle size and, for some profiles, with decreasing depth. Individual sand‐sized grains commonly contained both biotite and kaolinite. Kaolinized grains had lighter colored, duller (001) cleavage surfaces, and more pores than unaltered biotite grains. Pores extended from the edges inward, exposing new surfaces to soil solution thereby fostering continued kaolinite encroachment. The pore volume difference between kaolinite and biotite specimens was only slightly greater than the calculated difference based on a 1:1 layer‐for‐layer replacement of biotite by kaolinite.
Weathering Assessment of Quartz Grains: A Semiquantitative Approach
Authors: Darmody R. G. 
Published: July 2010

AbstractThis paper details the development of a technique to assess the relative weathering state of quartz grains as revealed by scanning electron microscopy (SEM). This approach considers the criticisms leveled against environmental assessments based on SEM observations. The method uses only one size fraction of grains to eliminate size dependent surface texture variability. Operator bias is removed by coding specimens. A semiquantitative approach is used: five grain surface features indicative of “weathering” and five indicative of “freshness” are observed on each grain. A binary scoring system is used where a negative point is assigned for the presence of a weathering feature and a positive point is assigned for the presence of a freshness feature. A zero is assigned for each absent indicator feature. Summing the points gives the weathering class (WC) for a grain. The mean WC for 15 to 30 grains is the weathering classification for a sample. This systematic approach is an improvement over qualitative assessments and allows for statistical analysis of the data.
Determining Soil Hydraulic Properties from One‐step Outflow Experiments by Parameter Estimation: II. Experimental Studies
Authors: Parker J. C. , Kool J. B. , van Genuchten M. Th. 
Published: July 2010

AbstractUnsaturated hydraulic properties of four soils of varying particle size distributions were evaluated by determining values of the five parameters in van Genuchten's (1980) hydraulic model. Saturated conductivities (Ks) and saturated water contents (θs) were directly measured and values of residual water content (θr) and the parameters α and n were evaluated by a nonlinear inversion method to minimize various objective functions. Method I uses an objective function involving sums of squared deviations between measured cumulative outflow with time Q(t) for one‐step pressure desorption and numerically simulated outflow from saturation to a final pressure head h = − 10 m. Method II supplements Q(t) data with the measured equilibrium water content θ at h = − 150 m, while Method III employs equilibrium θ(h) data only. Method I yields the most accurate description of Q(t) and the independently determined hydraulic diffusivity D(θ). A fair description of θ(h) is obtained within the range of the one‐step experiment but at lower θ predictions are less reliable especially for finer‐textured soil. Method II extends the range of validity of the predicted θ(h) to lower θ with generally small effects on predicted D(θ) and Q(t). Method III gives the best description of θ(h) but at the expense of accuracy in Q(t) and D(θ). Implications for routine evaluation of soil hydraulic properties are discussed.
Effects of Drying Treatments on Porosity of Soil Materials
Authors: Thompson Michael L. , McBride John F. , Horton Robert 
Published: July 2010

AbstractThe effects of three drying techniques on total porosity and pore size distribution of soil materials were studied by Hg intrusion porosimetry. The three soils investigated had different clay contents (21%, 35%, and 44%), but the clay fraction of each was dominated by montmorillonite. Some samples were dried in an oven at 40°C for 7 d; some samples were quick‐frozen in liquid N and lyophilized; some samples were dried by acetone vapor exchange and immersion, followed by evaporation of the acetone. Both undisturbed and compacted samples were investigated. The three drying techniques caused a reduction in sample total porosity ranging from 3 to 52%. Freeze drying usually caused the least change in total porosity. Although materials highest in clay shrank the most, there was no other discernible relationship between shrinkage and clay content. Freeze‐dried samples had the greatest volume of porosity in the 0.2‐ to 2‐ µm equivalent pore radius (epr) range, whereas acetone‐dried samples had the greatest volume of porosity in the 0.02‐ to 0.2‐ and 0.2‐ to 2‐µm epr ranges. Pore size distributions of oven‐dried samples varied from soil to soil. The consistency of pore size distributions in freeze‐dried materials strongly suggests that pores were deformed by ice crystals either during or after freezing of the samples. In the epr range of 0.002 to 0.02 µm, acetone‐dried samples had porosities similar to oven‐dried samples.
Boron Adsorption on Aluminum and Iron Oxide Minerals
Authors: Goldberg Sabine , Glaubig R. A. 
Published: July 2010

AbstractBoron adsorption behavior was investigated on various crystalline and x‐ray amorphous Al and Fe oxide minerals. Adsorption increased at low pH, exhibited a peak in the pH range 7 to 8, and decreased at high pH. The magnitude of B adsorption was much greater for the x‐ray amorphous materials. Since B adsorbs specifically on Al and Fe oxide minerals, the constant capacitance model containing a ligand exchange mechanism was used to describe its adsorption behavior. The constant capacitance model was able to represent B adsorption on all minerals over the entire pH range studied (3–12) using the same set of surface complexation constants. With the exception of amorphous Al oxide, B adsorption on these oxide minerals could be successfully described by optimizing only the B surface complexation constant. Other nonexperimental parameters were held fixed at values identical to those previously used in modeling phosphate, silicate, and selenite adsorption on Al and Fe oxide minerals.
Ethylene Biosynthesis in Soil: II. Kinetics and Thermodynamics in the Conversion of 1‐aminocyclopropane‐1‐carboxylic Acid to Ethylene
Authors: Frankenberger W. T. , Phelan Patrick J. 
Published: July 2010

AbstractKinetic analyses were performed to characterize the conversion of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) to ethylene (C2H4) in soils. Application of three linear transformations of the Michaelis‐Menten equation indicated that the Km values varied slightly among soils, but were similar in magnitude. By using the Lineweaver‐Burk plot, the Km values in three soils ranged from 2.7 to 6.1 (avg = 4.8) mM and Vmax values ranged from 3.9 to 16.5 mmol of C2H4 released kg−1 soil 48 h−1. The activation energy (Ea) and enthalpy of activation (ΔH*) values, expressed in kJ mol−1, ranged from 35.4 to 70.5 (avg = 49.4) and 32.8 to 67.9 (avg = 46.8), respectively. The Q10 values within a temperature range of 5 to 50°C ranged from 1.52 to 2.60. A direct relationship was established between soil pH of 20 unbuffered surface soils and ACC enhanced‐C2H4 production, but no such relationship was found with any other soil parameter tested including organic C, total N, CEC, and texture. Antibiotic treatments of soils revealed that both fungistatic and bacteriostatic agents were effective in inhibiting (25–82%) ACC derived‐C2H4 production in soils indicating that both major groups are active C2H4 producers.
Puddling Influence on Soil, Rice Development, and Yield
Authors: Sharma P. K. , De Datta S. K. 
Published: July 2010

AbstractThe effects of puddling on soil physical properties, percolation losses of water and nutrients, and nutrient uptake and grain yield of IR36 rice (Oryza sativa L.) in an Andaqueptic Haplaquoll and a Lithic Hapludoll were evaluated in a field experiment. Puddling decreased the bulk densities of both soils in the top 0.1‐m layer by about 30%, but the differences in bulk density between puddled and nonpuddled soil narrowed with time. In the first soil, mechanical strength at 1 d after transplanting (DT) and at 60 DT was the same for both puddled and nonpuddled soils and was <0.3 MPa in the top 0.15‐m layer. In the second soil, it was significantly lower in puddled plots at 1 DT, but the differences between puddled and nonpuddled plots were not significant at 60 DT. Puddling decreased percolation rate by > 70% in the second soil but its effect on percolation rate was negligible in the first. It decreased seasonal water losses by percolation by about 0.03 m in the first soil and by 0.48 m in the second. Puddling decreased significantly the saturated hydraulic conductivities (Ks) of the surface layer in the second soil. In the top 0.15‐m layer, puddling decreased maximum temperatures and diurnal temperature amplitudes in the second soil, but caused no measurable differences in the first. Puddling decreased the redox potential (Eh) of both soils and increased Fe and Mn solubilities. In puddled soil, at the 0.3‐m depth, soil‐solution concentrations of Mn and Fe were higher and those of NH+4‐N, P, K, and Zn comparable to those in nonpuddled soil. The concentration of NO‐3‐N in puddled soil was either comparable to or lower than that in nonpuddled soil. In the first soil, puddling significantly decreased leaching losses of NO‐3‐N; in the second, it decreased leaching losses of NO‐3‐N, NH+4‐N, P, K, and Zn. Puddling significantly increased grain yield in both soils. Total nutrient uptake by rice increased significantly with puddling in both soils. Higher percolation rates did not improve soil productivity, but increased leaching losses of water and plant nutrients. Bulk density and soil strength were the main factors affecting grain yield.
Comparative Effects of an Organic and Inorganic Nitrogen Source in Flooded Soils
Authors: Westcott M. P. , Mikkelsen D. S. 
Published: July 2010

AbstractThe availability of N from organic and inorganic sources in soils is controlled by contrasting microbiological processes. Nitrogen from an added organic source is made gradually available through mineralization whereas immobilization and N loss mechanisms act to decrease inorganic‐N availability with time. To define these initial processes, it is necessary to trace the availability of N from both added and native sources and to measure biological activity while varying a controlling factor such as temperature. A laboratory incubation study was designed to compare (NH4)2SO4 and vetch as added N sources in a flooded soil (Clear Lake clay, Typic Pelloxererts, fine, montmorillonitic, thermic). Nitrogen‐15 labeled materials were added at rates of 0, 50, or 100 µg N/g in factorial combination to 50 g samples of soil and placed in vessels forming columns 10‐ to 12‐cm deep. Temperature regimes of 20, 25, and 30°C were utilized. Available (soluble and exchangeable) NH+4‐N and CO2 production were periodically measured over a 30‐d incubation time. Vetch‐N underwent a gradual mineralization paralleling that of soil‐N. Levels of total NH+4‐N in the vetch treatments were positively affected by temperature and showed a highly significant correlation with CO2 production. Levels of total (labeled + unlabeled) NH+4‐N were consistently higher throughout the incubation period in the (NH4)2SO4 treatments as compared to vetch treatments at equal rates of addition. Labeled (NH4)2SO4‐N rapidly disappeared from the available form, however, and a simultaneous “priming effect” on soil—N mineralization occurred. These two events were quantitatively correlated. The priming effect was not correlated with CO2 production. These findings support the concept that the priming effect of labeled fertilizer‐N on soil‐N mineralization is an apparent effect due to the interchange of labeled available‐N with unlabeled organic‐N with no net effect on N mineralization.
Geophysical Techniques for Reconnaissance Investigations of Soils and Surficial Deposits in Mountainous Terrain
Authors: Olson C. G. , Doolittle J. A. 
Published: July 2010

AbstractTwo geophysical techniques—ground‐penetrating radar (GPR) and seismic refraction—were assessed for their capabilities in reconnaissance studies of soil characteristics, depth to the water table, and depth to bedrock beneath surficial deposits in mountainous terrain. Ground‐penetrating radar had the best near‐surface resolution in the upper 2 m of the profile and provided continuous interpretable imagery of soil profiles and bedrock surfaces. Where thick colluvium blankets side slopes, the GPR could not consistently define the bedrock interface. In areas with clayey or shaley sediments, the GPR is also more limited in defining depth and is less reliable. Seismic refraction proved useful in determining the elevation of the water table and depth to bedrock, regardless of thickness of overlying material, but could not distinguish soil‐profile characteristics. Although both techniques provide adequate information for reconnaissance purposes, these techniques have a greater probability of success in areas where there is some subsurface information. Independent use of any one method is advised only where ground control is well documented.