bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anion Transport Involving Competitive Adsorption during Transient Water Flow in an Andisol
Authors: Katou Hidetaka , Clothier Brent E. , Green Steven R. 
Published: July 2010

AbstractAndisols containing allophane and other poorly crystalline materials, carry variable surface charge, and adsorb otherwise inert anions such as Cl− and NO−3. The objective of this study was to predict composition‐dependent, retarded transport of anions during unsteady water flow in an Andisol. One‐dimensional absorption experiments in Kannondai subsoil (Hydric Hapludand) columns were conducted with CaCl2, Ca(NO3)2, and mixed CaCl2‐Ca(NO3)2 solutions at different concentrations (0.00462‐0.115 mol L−1). Because of nonlinear, competitive adsorption of Cl− and NO−3 by the soil, the observed retardation of anion penetration depended on the total concentration and composition of the invading solution. Nitrate ion had a smaller affinity to the adsorption sites than Cl− (the selectivity coefficient Kv = 0.51) and showed a greater penetration in the presence of Cl−. The adsorption of Cl− and NO−3 much exceeded the concurrent SO2−4 desorption from the soil. This suggests that SO2−4 was so strongly adsorbed that exchange reaction with the invading anions proceeded only to a limited extent. Thus, the adsorption of the monovalent anions was largely due to the increase in the anion exchange capacity of the soil in response to an increase in the ionic strength of the bulk solution. An approximate theory was developed for anion transport involving competitive adsorption in which total monovalent anion adsorption, obeying a Langmuir‐type equation, is allocated via Kv to the adsorption of Cl− and NO−3. Employing the adsorption parameters determined from separate steady state leaching experiments, the theory successfully described the measured anion content profiles.
Quantifying the Diffusive Mass Transfer of Nonreactive Solutes in Columns of Fractured Saprolite using Flow Interruption
Authors: Reedy O. C. , Jardine P. M. , Wilson G. V. , Selim H. M. 
Published: July 2010

AbstractSubsurface transport processes of low‐level radioactive contaminants at hazardous waste sites are complex due to a nonuniform distribution of pore regions in heterogeneous media. During transport, contaminant mass is continuously transferred between the various pore regions via hydraulic and concentration gradients. Our objective was to quantify the diffusive mass transfer of a nonreactive solute between the matrix porosity and preferential flow paths in fractured subsurface media. A large, undisturbed soil column (41 cm long by 17 cm diameter) of weathered, fractured shale was acquired from a proposed waste site on the Oak Ridge Reservation in eastern Tennessee. We injected a nonreactive tracer, Br−, under saturated conditions, interrupting tracer flow for a designated time, and then reinitiating flow. Experiments considered tracer injection and displacement, variations in duration of flow interruption, and variations in flux. Transport of Br− through the undisturbed medium was characterized by asymmetric breakthrough curves (BTC), indicative of preferential flow coupled with movement into the matrix. Interrupting flow resulted in decreased and increased Br− concentrations during tracer infusion and displacement, respectively, when flow was reinitiated. More pronounced concentration perturbations were observed at high fluxes and long interrupt durations. These perturbations were driven by solute concentration gradients established between pore regions as a result of preferential flow. This confirmed the importance of a diffusion contribution to the overall physical nonequilibrium mechanism that affects solute transport. Observed effluent concentrations were adequately simulated with a two‐region flow interrupt model by using independently determined parameters and adjusting the mass transfer coefficient. Estimated mass transfer coefficients increased linearly with increased flux, probably due to enhanced nonequilibrium that was established between pore regions as flux increased.
Landscape‐Scale Variations in Leached Nitrate: Relationship to Denitrification and Natural Nitrogen‐15 Abundance
Authors: Farrell Richard E. , Sandercock Peter J. , Pennock Daniel J. , Van Kessel Chris 
Published: July 2010

AbstractEvidence suggests that the natural 15N abundance (δ15N) of leached NO3 can be related to denitrification activity. In addition, spatial patterns for denitrification and leached NO3 are controlled by land‐scape‐scale interactions between topography and hillslope hydrology. Thus, this study was conducted to assess whether a landscape‐scale relationship exists between denitrification activity and the δ15N of deep‐leached (>120 cm) NO3 in an undulating landscape developed on silty glacio‐lacustrine sediments overlying a clay loam till of late Wisconsinan age, under semiarid conditions. The highest concentrations of NO3 occurred in shoulder and upper‐level landscape positions and the lowest concentrations in footslope and lower‐level positions. In areas of the landscape where water accumulation was at a maximum, denitrification rates were highest and there was no accumulation of NO3 in the upper 3 m of the solum. Conversely, in areas where water accumulation and denitrification activity were low, there was a buildup of NO3 below the root zone and within 3 m of the soil surface. The relationship between seasonal denitrification activity and the concentration of leached NO3 was characterized by a negative correlation (rs = −0.464**). Moreover, values of δ15N‐NO3 were highest in areas of the landscape where rates of denitrification were highest and there was a negative correlation (rs = −0.638***) between the concentration of deep‐leached NO3 and its δ15N. These data support the hypothesis that topographic and hydrologic controls on denitrification and leaching are reflected in the localized removal of NO3 from the soil profile, which is reflected in the δ15N value of leached NO3‐N.
Automated Chromatographic Analysis of Atmospheric Gases in Environmental Samples
Authors: McCarty G. W. , Blicher‐Mathiesen G. 
Published: July 2010

AbstractThe need for a single‐injection gas chromatographic procedure for detection of the principal atmospheric gases found in environmental samples has led to development of an automated system that permits measurement of CO2, N2O, O2‐Ar, and N2 in a single detector without interference from water vapor in samples. The injection of gas samples on the system was automated by interfacing a commercial headspace sampler with a gas chromatograph (GC) that was fitted with an ultrasonic detector and two automated multiport switching valves. The first switching valve was configured with short precolumns of Porapak Q (PQ) to retain and vent the water vapor in samples. The other valve was configured with two analytical columns connected in series that permit separation of the gas components. After water is removed by the precolumn, the gas sample flows onto a PQ column where CO2 and N2O are retained and separated while the composite peak of N2 and O2‐Ar elutes onto a molecular sieve (MS) column. The valve is then switched, causing reversal of the order of columns with respect to the gas flow without reversing the direction of flow through the columns. This allows the CO2 and N2O peaks to elute from the PQ column to the detector while the O2‐Ar and N2 components are separated on the MS column and later flow to the detector. The system has proven to be robust in that it permits routine, unattended analyses of moist gas samples with high sensitivity and without interference from water peaks. This, in conjunction with the highly controlled equilibrium conditions permitted by use of the headspace sampler, makes the system suitable for gas analysis of environmental samples including dissolved gas analysis of natural water samples.
Water and Solute Movement under Conventional Corn in Central Spain. II. Salt Leaching
Authors: Bustos A. , Roman R. , Caballero R. , Díez J. A. , Caballero A. , Cartagena M. C. , Vallejo A. 
Published: July 2010

AbstractLeaching of salts under field conditions may be addressed through a combination of the soil water balance and the drainage and concentration of salts in the soil profile. A field experiment was conducted in the 1991 growing season on a Typic Xerofluvent soil planted to corn (Zea mays L.) to assess the leaching pattern of Ca2+, Mg2+, Na+, K+, Cl+, SO2−4, CO3H−, and NO−3 under conventional cropping. River and well irrigation water were used with salinities of 680 and 1580 mg L−1, respectively. Sampling of the soil water solution throughout the growing season was done for soil profile layers using a permanent ceramic‐candle extraction system. Neutron probes and tensiometers allowed seasonal measurements of soil water content and water movement in the profile. Leaching of salts was calculated as the product of deep drainage amounts times the salt concentrations at the 1.4‐m soil depth. Total salt drainage for river and well was 0.34 and 0.38 kg m−2, respectively. Accumulation of salts to a depth of 1.4 m in the soil profile showed values of 0.02 and 0.21 kg m−2 in plots irrigated with river and well water, respectively. Soil water balance and concentration of salts in the soil solution indicated discharge of salts to the groundwater table with conventional cropping practices. Groundwater pollution was addressed by matching irrigation to the evapotranspiration and by minimizing the concentration of salts in irrigation water.
Partitioned Flow Domains of Three Wisconsin Soils
Authors: Hart G. L. , Lowery B. 
Published: July 2010

AbstractPreferential flow mechanisms have been the subject of increasing research interest because these phenomena contribute to solute transport. Commonly, preferential flow paths are associated with macropores or highly structured soils. Sandy soils are typically weakly structured or structureless. However, they exhibit rapid drainage, which may mimic the hydrology and solute transport effects of macropores. We tested whether a flow domain partitioning scheme could be applied on two sandy soils, by collecting drainage data with time domain reflectometry across small time increments and implementing analytical models using a nonlinear iterative fitting procedure. The analysis was applied to both observed and Leaching Estimation and Chemistry Water Model (LEACHW) drainage of Sparta (mesic, uncoated, Typic Quartzipsamments) and Plainfield sand (mixed, mesic, Typic Udipsamment), as well as strongly structured Dubuque silt loam (fine‐silty, mixed, mesic, Typic Hapludalf), where water content was measured with a neutron meter. We found significant differences (P < 0.05) between soils and profile depths relating macropore and matrix flow domains of observed data. Maximum hydrologically effective macropore volumes ranged from 0.018 (1.8%) in Dubuque silt loam to 0.294 (29.4%) in Sparta sand. Mixed results were obtained with flow domain partitioning of drainage simulated with LEACHW. In 5 of 15 cases, macropore and micropore parameter estimates failed to converge. Best agreement of micropore and macropore parameter estimates between observed and modeled drainage was observed in Dubuque soil and poorest concordance in Sparta sand. This analytical scheme may be applied to a wide range of soils if appropriate data describing the hydrological character were available.
Analytical Solution for Two‐Region Diffusion with Two Well‐Mixed End Chambers
Authors: El‐Farhan Y. H. , Rolston D. E. , Petersen L. W. , Glauz R. D. 
Published: July 2010

AbstractMany methods have been developed for determining the effective gaseous diffusion coefficient (Dp) in soils. Some commonly used methods are the one‐ and two‐chamber apparatuses. In addition, laboratory apparatuses for the study of vapor diffusion, sorption, and biodegradation may consist of soil and vapor chambers. Existing analytical solutions for such apparatuses cannot accommodate diffusion through regions containing two distinct layers of differing porosity and diffusion coefficient. Such dual porosities can represent stagnant air layers, or crusting‐compaction at core ends. We developed an analytical solution for gaseous diffusion in a four‐region chamber system. The system consists of two diffusion regions (with two different porosities), and a well‐mixed end chamber attached at either end. The solution was used to simulate one‐dimensional gas diffusion in an apparatus consisting of two diffusion regions with constant‐concentration boundary conditions. The solution was also used to quantify errors made in estimating Dp using the one‐chamber apparatus when the air chamber is not mixed, or when a stagnant air layer exists above the soil surface. Errors due to non‐mixing decreased with time and increased with water content and air‐chamber size when analysis was done using concentrations at a point close to the soil surface. Analysis of the effects of a stagnant air layer showed that errors increased with time and air‐chamber size and decreased with increasing water content. Analysis done to test the effects of soil crusting on diffusion showed that, despite the thinness of the soil crust, large estimation errors in Dp are possible.
Secondary Carbonates in Three Fine and Fine‐loamy Alfisols in Michigan
Authors: Schaetzl Randall J. , Frederick William E. , Tornes Lawrence 
Published: July 2010

AbstractSecondary pedogenic carbonates are usually associated with ustic or drier soil moisture regimes; when found elsewhere, their interpretation can be troublesome. We studied three Alfisol pedons in Michigan that contained secondary carbonates on ped faces. The purpose of the research was to (i) characterize these accumulations, (ii) examine possible genetic explanations for the accumulations, (iii) determine if these soils have calcic horizons, given the recent redefinition of this diagnostic horizon, and (iv) evaluate how current “k horizon” nomenclature might apply to these soils. Three different drainage classes and two soil temperature regimes were represented in the sampled pedons: a fine, mixed Glossic Eutroboralf; a fine, illitic, mesic Aquic Hapludalf; and a fine‐loamy, mixed, mesic Aeric Endoaqualf. All three pedons had thin (<50 cm) leached zones near the surface, and carbonate coatings (calcans) on ped faces within the lower B and/or upper C horizons. Two of the three pedons had horizons that met calcic horizon criteria. Horizons of preferential carbonate accumulation sometimes occurred near subtle textural breaks in the lower solum. Some B horizons in one pedon contained carbonate accumulations in amounts that exceeded that of the presumed parent material. The calcans have probably resulted both from vertical translocation of carbonates, followed by precipitation at depth, as well as internal redistribution of carbonates from ped interiors to ped faces. Use of the k subscript is warranted for some horizons in these soils. We recommend that its usage should be similar to t or s, i.e., horizons with evidence of secondary carbonates merit the k subscript.
Soil Morphology of Canopy and Intercanopy Sites in a Piñon‐Juniper Woodland
Authors: Davenport David W. , Wilcox Bradford P. , Breshears David D. 
Published: July 2010

AbstractPiñon‐juniper woodlands in the semiarid western USA have expanded as much as fivefold during the last 150 yr, often accompanied by losses of understory vegetation and increasing soil erosion. We conducted this study to determine the differences in soil morphology between canopy and intercanopy locations within a piñon (Pinus edulis Engelm.)‐juniper [Juniperus monosperma (Engelm.) Sarg.] woodland with uniform parent material, topography, and climate. The woodland studied, located near Los Alamos, NM, has a mean tree age of 135 yr. We examined soil morphology by augering 135 profiles in a square grid pattern and comparing soils under piñon and juniper canopies with intercanopy soils. Only two of the 17 morphological properties compared showed significant differences. The B horizons make up a slightly greater proportion of total profile thickness in intercanopy soils, and there are higher percentages of coarse fragments in the lower portions of canopy soil profiles. Canopy soils have lower mean pH and higher mean organic C than intercanopy soils. Regression analysis showed that most soil properties did not closely correspond with tree size, but total soil thickness and B horizon thickness are significantly greater under the largest piñon trees, and soil reaction is lower under the largest juniper trees. Our findings suggest that during the period in which piñon‐juniper woodlands have been expanding, the trees have had only minor effects on soil morphology.
Characterization of Phosphorus in a Spruce‐Fir Spodosol by Phosphorus‐31 Nuclear Magnetic Resonance Spectroscopy
Authors: Dai K'o H. , David Mark B. , Vance George F. , Krzyszowska Anna J. 
Published: July 2010

AbstractFactors affecting the distribution and biogeochemical cycling of soil P are only partially understood. Many previous studies have focused on P distribution within surface mineral soils and cycling of inorganic P. Few data are available on organic forms of P in forest floor and mineral horizons of forest soils. Therefore, we used 31P nuclear magnetic resonance (31P‐NMR) to characterize the P compounds in NaOH‐ethylenediaminetetraacetic acid (EDTA) extracts of three Spodosol profiles. The NaOH‐EDTA extracted most of the P in the three organic horizons (87, 83, and 69% of total P in Oi, Oe, and Oa horizons, respectively) and 39 to 67% in the Bhs horizon. Major P species detected in all horizons were inorganic orthophosphate and orthophosphate monoesters and diesters that ranged from 11 to 53%, 12 to 52%, and 13 to 45% of total P extracted, respectively. As is typical in Spodosol chemistry, considerable variation was found for organic P distribution in the organic horizons of the three profiles. However, on average, distribution patterns of P forms with depth were observed, including a decrease in the proportion of inorganic orthophosphate with greater decomposition in the forest floor (Oi > Oe > Oa), followed by an increase in the Bhs horizons. Pyrophosphate (5–19% of total P) and polyphosphates (5–13% of total P) were found mainly in the forest floor horizons, except for one profile where pyrophosphate had evidently accumulated in the Bhs horizon. Traces (≈2%) of phosphonates occurred only in the Oa horizon. Results suggest that biological activity, extractable Fe concentration, structural characteristics of P compounds, and pH are probably responsible for the distribution of P species in these Spodosols.
Organic Matter Decomposition following Harvesting and Site Preparation of a Forested Wetland
Authors: Trettin C. C. , Davidian M. , Jurgensen M. F. , Lea R. 
Published: July 2010

AbstractOrganic matter accumulation is an important process that affects ecosystem function in many northern wetlands. The cotton strip assay (CSA) was used to measure the effect of harvesting and two different site preparation treatments, bedding and trenching, on organic matter decomposition in a forested wetland. A Latin square experimental design was used to determine the effect of harvesting, site preparation, and relative position within the wetland on organic matter decomposition at soil depths of 5, 10, and 20 cm. Repeated measures analysis of variance was used to test for treatment effects on organic matter decomposition, soil temperature, and soil oxidation depth. Cellulose decomposition increased at each soil depth as site disturbance increased, with bedding > trenching > whole‐tree harvest > reference. The cellulose decomposition response was correlated with changes in soil temperature; the temperature coefficient Q10 equaled 6.0, which is greater than previously reported values. Position within the wetland relative to an adjoining river affected the decomposition and soil oxidation depth. Because the rate of decomposition is strongly controlled by temperature, higher rates of organic matter decay are expected to continue on harvested and regenerated sites until canopy closure reduces soil temperature.
The Thermodynamic Theory of Ion Exchange: A Single‐Phase Mixture Formulation
Authors: Snyder V. A. , Cavallaro N. 
Published: July 2010

AbstractA longstanding problem in the thermodynamic theory of ion exchange has been lack of a general method for measuring activities of solid‐ion complexes or exchanger species. Existing theory, based on integrating the Gibbs‐Duhem relation for a solid exchanger phase immersed in an electrolyte solution, is often subject to uncertainties due to indeterminate amounts of solvent and electrolytes adsorbed onto the exchanger surface. We remove these difficulties by treating ion exchange systems as simple mixtures of solvent, electrolytes, and exchanger species, with no formal partitioning into phases. Through judicious choice of components, an integrable Gibbs‐Duhem relation is obtained that can be solved for the activity of any arbitrary exchanger species, requiring only reversibility of the system and measurable solvent and electrolyte activities. The theory is very general in principle and is applicable to variable‐ and permanent‐charge solid exchangers with positive and negative surface charge sites, in electrolyte environments containing any number of competing cation and anion species. In preliminary tests, the theory was used to calculate exchanger species activities and equilibrium constants from published data on binary and ternary NH4+‐Ba2+‐La3+ exchange in aqueous montmorillonite suspensions, for constant water potential conditions where the conventional two‐phase theory is also considered applicable. Results obtained with the mixture theory exhibited good internal consistency and were generally comparable to results obtained with the two‐phase theory.
Sulfate Retention by Kaolinitic Alfisols from Nigerian Savanna
Authors: Agbenin John O. 
Published: July 2010

AbstractThe low amount of available SO4 in savanna Alfisols necessitates investigation of mechanism of SO4 retention and availability in these soils. The study examines the mechanism and SO4 retention capacity of kaolinitic Alfisols from Nigerian savanna. Soil samples from 0‐ to 20‐cm depth from three cultivated plots and a native site were equilibrated with varying amounts of SO4 (0–0.003 M) in three supporting electrolytes, 0.01 M CaCl2, KCl, and NaCl, and three ionic strengths, 0.0 1, 0.1, and 0.2 M KCl at pH 5.6 ± 0.2, above the point of zero salt effect (PZSE) and point of zero net charge (PZNC) of the soils determined by potentiometric titration and ion adsorption method, respectively. The results of the study indicated that the soils had high SO4 retention capacity ranging from 15 to 17 mmol kg−1 soil, and the sorption isotherms were described by a modified Freundlich equation. Sulfate sorption was, however, not significantly affected by ionic composition and strength. If the forces of SO4 adsorption were simply electrostatic, increasing ionic strength would have significantly decreased SO4 adsorption above the PZSE or PZNC of the soils. The study suggested that SO4 retention by kaolinitic Alfisols might involve inner‐sphere complexation despite the difficulty of making mechanistic, molecular level interpretation from gross solution data of whole soils.