bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Organic Acids on Selenite Sorption by Poorly Ordered Aluminum Hydroxides
Authors: Dynes J. J. , Huang P. M. 
Published: July 2010

AbstractCompetition between low molecular weight (LMW) organic acids and selenite for sorption sites on hydrous metal oxides is an important factor affecting the dynamics of Se in soils and associated environments. Equilibrium and kinetic studies on the competition between selenite and 12 LMW organic acids (acetic, aspartic, citric, formic, glycine, glycolic, p‐hydroxybenzoic, malic, oxalic, salicylic, succinic, and tartaric) for the sorption sites on short‐range ordered Al hydroxides were investigated using the batch method. The equilibrium and kinetic results showed that the influence of the organic acids on selenite sorption by Al hydroxides depended on the concentration, structure, and functionality of the organic acids. The competitiveness of the organic acids with selenite for the sorption sites increased with increasing organic acid concentration. Generally, the larger the stability constant of the Al‐organic solution complexes (KAl‐L), the more effective the organic acid was in competing with selenite for the sorption sites of the Al hydroxides. However, some of the organic acids competed less successfully than expected based on their KAl‐L values. This is attributed to the stereochemical and electrostatic effects originating from both the surface of the Al hydroxides and the organic acids, which lowered the ability of some organic acids to compete with selenite for the sorption sites of the Al hydroxides. Moreover, the kinetic results revealed that the organic acids competed with selenite for the sorption sites primarily in the early reaction period (<3 h), and subsequently, it was this period that was largely responsible for the equilibrium level of selenite sorbed by the Al hydroxides. The findings are of fundamental significance in understanding the role of organic acids in influencing the fate of Se in the environment.
Fractionation of Iron, Managanese, Aluminum, and Phosphorus in Selected Sandy Soils under Citrus Production
Authors: Zhang M. , Li Y. C. , Calvert D. V. , Alva A. K. 
Published: July 2010

AbstractThe sorption and downward transport of trace metals and phosphate in soils are dependent, in part, on the distribution of various forms of Fe, Al, and Mn. The objectives of this study were to investigate (i) the distribution of various forms (exchangeable, organically bound, associated with Mn oxide, amorphous, and associated with crystalline Fe oxide forms) of Fe, Mn, Al, and P in the surface horizons, and (ii) the distribution of these elements in different depth horizons in six soil series in Florida representing Spodosols, Alfisols, and Entisols. Variation in concentration of total Fe with depth of soil was significantly correlated with clay content. Greater than 60 and 80% of total Fe was present in the amorphous and crystalline Fe oxide forms in soils with pH ≤ 6.5 and pH > 6.5, respectively. Total concentration of Mn was lower than that of Fe or Al in all the soils, and it changed very little with depth of sampling. Manganese in the surface horizon was present predominantly as the organically bound form in the Spodosols and as organically bound, oxide, and amorphous forms in the Alfisols and Entisols. The distribution of total and oxalate‐extractable P was significantly related to the content of amorphous Al and Fe and crystalline Fe oxides in the soils. The distribution of various forms of the metals and P was significantly influenced by the soil pH and organic matter content. In the surface horizon soils, Mn and Al were present predominantly as organically bound forms at pH < 6.5 or as Mn oxide and amorphous associated forms at pH > 6.5.
Methods for Comparing Spatial Variability Patterns of Millet Yield and Soil Data
Authors: Stein A. , Brouwer J. , Bouma J. 
Published: July 2010

AbstractThis paper investigates methods to compare spatial patterns of pearl millet [Pennisetum glaucum (L.) R. Br.] yield with spatial patterns of soil variables in a farmer's 1‐ha field on an undulating sand plain in Niger near ICRISAT‐SC. Spatial pattern comparisons are important for precision farming applications. Methods included the correlation coefficient, linear regression, a distance measure to compare separate maps and the cross‐correlation function. Millet grain yield varied from 0 to 2885 kg ha‐1 on 5 by 5 m sub‐plots. Pearl millet yield was correlated with measured soil variables at three different depths, elevation, and crust formation for two successive years. Only 30% of the total variation in millet dry yield was explained by regressing yield against soil variables. Detrended elevation showed a significant negative relation with yield (r = −0.421). The cation‐exchange capacity (CEC) at all the depths showed a significant negative relation with yield (r of −0.238 to −0.290) because crusting and erosion increase with CEC extending to distances up to 30 to 40 m. Pattern comparison using the cross‐correlogram related local hillocks in the area with high yields and local dips with low yields at a distance of 15 to 20 m. From this study, we concluded that the cross‐correlogram was beneficial to compare data at various distances. Yield patterns are best explained by soil variables related to erosion as the major determinign factor in the area.
Sodicity and Clay Type: Influence on Decomposition of Added Organic Matter
Authors: Nelson Paul N. , Barzegar A. Rahman , Oades J. Malcolm 
Published: July 2010

AbstractSodicity and clay type influence the decomposition of organic matter, and hence its accumulation in soil. In this study, the interaction of these two factors was examined. Two soils were prepared by mixing sand (57%) and silt (28%), separated from one soil, with clay (15%) separated from two soils. One clay type (Urrbrae) was composed mostly of illite and kaolimite, with a mean particle diameter of 1050 nm. The other (Claremont) was composed of smectite‐dominated materials, with a mean diameter of 104 nm. The prepared soils were brought to different values of exchangeable sodium percentage (ESP) by equilibration with solutions having sodium adsorption ratios (SAR) between 0 and 30. Pea (Pisum sativum L.) straw was added at 50 g kg−1 soil, and the samples were incubated moist. After 67 d, cumulative mineralization of C was 16% greater in the soils with Urrbrae clay than in those with Claremont clay. Sodicity had a slight negative effect on mineralization, but its interaction with clay type was not significant. Differences in the mineralization of C with time and between treatments were reflected in the chemical nature of the remaining C, as determined by 13C nuclear magnetic resonance (NMR) spectroscopy. The greater the loss of C, the lower the proportion of O‐alkyl C relative to other types of C. An implication of the findings is that, following a large addition of organic matter to a sodic soil, retention of organic C would not be improved by a prior reduction in ESP, irrespective of clay mineralogy.
Radiocarbon Dating for Determination of Soil Organic Matter Pool Sizes and Dynamics
Authors: Paul E. A. , Follett R. F. , Leavitt S. W. , Halvorson A. , Peterson G. A. , Lyon D. J. 
Published: July 2010

AbstractThe size and turnover rate of the resistant soil organic matter (SOM) fractions were measured by 14C dating and 13C/12C measurements. This involved soils archived in 1948, and recent samples, from a series of long‐term sites in the North American Great Plains. A reevaluation of C dates obtained in the 1960s expanded the study scope. The 14C ages of surface soils were modern in some native sites and near modern in the low, moist areas of the landscape. They were much older at the catena summits. The 14C ages were not related to latitude although this strongly influenced the total SOM content. Cultivation resulted in lower C contents and increased the 14C age by an average of 900 yr. The 10‐ to 20‐cm depths from both cultivated and native sites were 1200 yr older than the 0‐ to 10‐cm depth. The 90‐ to 120‐cm depth of a cultivated site at 7015 yr before present (BP) was 6000 yr older than the surface. The nonhydrolyzable C of this depth dated 9035 yr BP. The residue of 6 M HCl hydrolysis comprised 23 to 70% of the total soil C and was, on the average, 1500 yr older. The percentage of nonhydrolyzable C and its 14C age analytically identify the amount and turnover rate of the old resistant soil C.
Pedogenesis and Cementation in Calcareous Till in Indiana
Authors: McBurnett S. L. , Franzmeier D. P. 
Published: July 2010

AbstractGlacial till is extensive in the north central USA. In Indiana, it is calcareous and dense and has high strength and low hydraulic conductivity. It limits root growth and water movement. Its strength has been attributed to compression by thick glacial ice resting on till during deposition. It is not known if chemical cementation also contributes to its strength. In some soils, argillans coat the large prisms in the till‐derived C horizons, and in others, calcans coat the prisms. The objective of this study was to learn if the kind of cutans indicates how water moves through till and if some of the till's strength is due to chemical cementation. We sampled six pedons in Delaware County, Indiana, to a depth of 3 m. Soils with argillans in the till‐derived upper C horizon had outwash strata 2 to 3 m below the surface, and those with calcans lacked outwash. We postulate that argillans indicate that water moves through planar voids in the till and into outwash strata and calcans indicate that the planar voids end in the till. To look for possible cementing agents, we extracted soil samples with acid oxalate (o), citrate‐bicarbonate‐dithionite (d), and NaOH (n) and determined Fe, Al, and Si in the extracts. We also determined soil strength with a modulus of rupture test. Strength was higher in Cd horizons than in the solum, so strength was lost during soil formation. Strength was positively correlated with extractable Si (Sio, Sid, and/or Sin) and CaCO3 equivalent and was negatively correlated with clay and extractable Fe and Al. We conclude that the strength of the glacial till C horizons is due in part to weak cementation by silica, carbonates, or both.
Woody Debris Decomposition in the Atchafalaya River Basin of Louisiana following Hurricane Disturbance
Authors: Rice Michael D. , Lockaby B. G. , Stanturf J. A. , Keeland B. D. 
Published: July 2010

AbstractThe contribution of woody debris to some biogeochemical functions of forested wetlands was examined in the Atchafalaya River Basin in Louisiana following disturbance by Hurricane Andrew. Woody debris decomposition processes were characterized in terms of mass, C, N, and P dynamics. These were compared between different diameters of debris, areas recieving different intensities of disturbance, and between different positions relative to the soil. Disturbance intensity (as defined by canopy closure) had little effect on decomposition processes when compared with soil orientation (i.e., whether in contact with or suspended above the soil). Rates of mass loss varied between 0.055 and 0.068 for suspended and ground‐contact coarse woody debris, respectively. Fine woody debris rate coefficients averaged 0.060 and 0.085 for the same respective orientations. In general, woody debris displayed strong source activity for P but a greater tendency toward sink behavior for N. In terms of biogeochemical transformations, these data suggest that woody debris might act as a phosphate source during sheet flow events but could provide short‐term retention of inorganic N associated with floodwaters.
Reaction of Nitric Oxide with Acetylene and Oxygen: Implications for Denitrification Assays
Authors: McKenney D. J. , Wang S. W. , Drury C. F. 
Published: July 2010

AbstractNitric oxide reacts with C2H2 at ambient temperature under aerobic conditions with relatively large quantities of O2 present. We used a gas‐flow system at 20°C to determine the extent, if any, of reaction of NO with C2H2 under nearly anaerobic conditions with addition of trace (<500 µL L−1) quantities of O2, and to determine whether the process could account for the apparent C2H2 inhibition of NO production in soil. Results showed that reaction occurred only when critical trace quantities of O2 were present. For example, if [NO] was in the range 0.5 to 2.5 µL L−1, which is typical of concentrations in our soil studies, approximately 200 to 300 µL O2 L−1 was required before measurable NO loss was observed. The reaction was first order with respect to NO and variable order, becoming zero order, with respect to O2 when [O2] exceeded ≈400 µL L−1 and maximum NO depletion rates (≈0.01–0.06 µL L−1 s−1) were obtained. The effect of C2H2 on NO production with addition of O2 (≈20–730 µL L−1) in Brookston clay loam (fine‐loamy, mixed, mesic Typic Argiaquoll) and Fox sandy loam (fine‐loamy over sandy or sandy‐skeletal, mixed, mesic Typic Hapludalf) under conditions similar to the gas‐phase studies was also investigated. Depletion of NO in the presence of C2H2 vs. [O2] followed the same pattern with similar rates as the gasphase process. A simplified C2H2‐catalyzed scheme for the oxidation of NO to NO2 provides a plausible, partial explanation for these results. Since NO depletion requires only trace amounts of O2, the results suggest that in many previous studies involving assays of NO or N2O production based on C2H2 inhibition, significant gas‐phase reaction may have occurred leading to serious errors of interpretation.
Equilibrium and Kinetic Study of Ammonium Adsorption and Fixation in Sodium‐Treated Vermiculite
Authors: Shen Siyuan , Tu Shu‐I , Kemper W. Doral 
Published: July 2010

AbstractAmmonium fixation in vermiculite affects the movement of N in many soils. The effects of particle size, solution concentration, pH, and associated anions on NH+4 fixation in vermiculite are also important information for reducing N leaching from soils. In this study, the retention of NH+4 on the exchangeable and nonexchangeable sites of Montana vermiculite was determined in batch experiments. In the NH+4‐K+ exchange isotherm, the exchangeable sites of the vermiculite exhibited a preference for K+ to NH+4, while the nonexchangeable sites preferred NH+4 to K+. The nonexchangeable sites of the sand fraction had a higher preference for NH+4 at lower solution NH+4 concentration and a lower preference at higher NH+4 concentration. An opposite case was observed for the NH+4 concentration effect on the preference of nonexchangeable sites in the clay fraction. The retention isotherm of total NH+4 in the vermiculite exhibited S‐shape curves that can be described by the “two‐surface” Langmuir‐Freundlich equation. In the kinetic study, the clay fraction adsorbed the largest amount of exchangeable NH+4, but the silt fraction fixed the most NH+4 on its nonexchangeable sites. The retention of NH+4 in vermiculite increased with solution NH+4 concentration. Ammonium adsorption on the exchangeable sites increased at low solution pH, while NH+4 fixation was unaffected by pH change. The effect of associated anions was insignificant, except they caused a pH difference in solution.
Approximating the Impact of Sorption on Biodegradation Kinetics in Soil‐Water Systems
Authors: Gamerdinger A. P. , Achin R. S. , Traxler R. W. 
Published: July 2010

AbstractNaphthalene sorption and biodegradation were quantified in three soils of varying organic C content using miscible displacement and batch incubation techniques. As anticipated, sorption increased with organic C content; the sorption rate coefficient and equilibrium sorption constant (Kd) were inversely related. Organic matter in solution (NOM) from the high‐organic‐matter soil decreased apparent sorption, which was also quantified using methanol as a cosolvent. A cosolvency power of 3.8 or 4.1 was determined. The initial biodegradation rate decreased with increasing sorption and was a function of naphthalene concentration in solution. The extent of biodegradation was greatest in the high‐organic‐matter soil and decreased when NOM was removed from the system. The observed dependence of biodegradation kinetics on sorption (this study and in the literature) prompted us to develop a simple approach for approximating a biodegradation rate constant for soil‐water systems. This approach combines independently determined sorption parameters with the biodegradation rate constant determined for aqueous (soil‐free) solution. The approach was applied to our data and to published data where sorption was shown to control naphthalene biodegradation. The approximated biodegradation rate constant was within 10% of the measured values for three cases, 20% for a fourth case, and was underestimated by five‐to sevenfold for the high‐organic‐matter soil. The approach will be useful when applying management models for predicting contaminant fate and transport that require a degradation rate constant, or for estimating biodegradation rates in situations where cultured organisms are introduced for biodegradation.
Flow Velocity Effects on the Retardation of FD&C Blue no. 1 Food Dye in Soil
Authors: Perillo Catherine A. , Gupta Satish C. , Nater Edward A. , Moncrief John F. 
Published: July 2010

AbstractDyes are often used as tracers of water and solute flow in soil. However, there has been little published research on the effects of flow velocity on the relative movement of dye and wetting fronts. Recently, the FD&C Blue no. 1 dye has been used as a tracer of preferential water flow paths in soils, and has attractive properties suggesting it will be used increasingly in the future. The objective of this study was to characterize the effects of flow velocity on the adsorption characteristics of the FD&C Blue no. 1. We performed a series of laboratory experiments on the characterization of the equilibrium adsorption isotherm as well as the effect of flow velocity on adsorption characteristics of the FD&C Blue no. 1 in three horizons of Verndale sandy loam (coarse‐loamy over sandy, mixed, frigid Udic Argiboroll). Batch equilibration (24 h) measurements resulted in linearized Freundlich distribution coefficients (Kd) of 4.33, 23.95, and 4.59 L kg−1 for the Ap, Bt, and C horizons, respectively. Neither organic C nor clay content differences accounted for the variation between horizons. Leaching experiments with a 1 g L−1 dye solution and repacked soil columns containing either Ap, Bt, or C horizon material showed that the dye was retarded relative to the wetting front, and that the extent of retardation was inversely related to the time period during which dye solution was applied. Therefore, this dye (and perhaps others) should not be used to make inferences about the movement of water or other solutes until the effect of the application rate is evaluated for the flow conditions in the system(s) of interest.
Surface Roughness Related Processes of Runoff and Soil Loss: A Flume Study
Authors: Helming K. , Römkens M. J. M. , Prasad S. N. 
Published: July 2010

AbstractSoil surface roughness greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. This study tested the hypothesis that runoff distribution and flow concentration differ with roughness and affect the amount of soil loss. Sequences of four rainstorms of constant rainfall amount but decreasing intensity (60, 45, 30, and 15 mm h−1) were applied to the Ap horizon material of a loess soil (Glossic Fragiudalf) packed into a 0.6 by 3.7 m flume. Rough, medium, and smooth soil surfaces were studied at 17, 8, and 2% slope steepness. Surface roughness and flow pathways were visualized with digital elevation maps obtained from laser microrelief measurements. On the smooth surfaces, runoff was uniformly distributed during the first two rainstorms and soil losses were 0.23, 0.07, and 0.12 kg m−2 for the first and 2.26, 0.35, and 0.2 kg m−2 for the second storm at 17, 8, and 2% slope steepness, respectively. On the rough and medium surfaces, flow concentrated in pathways between clods and soil losses were up to eight and three times that on the smooth surfaces during the first and second storms, respectively. During the last two storms, flow concentrated also on the smooth surfaces and soil losses were similar for the three initially different surface configurations. Surface roughness effects on runoff amount were minor, but roughness affected the spatial distribution of runoff, thereby affecting the amount of soil loss.
Retardation of Fluorobenzoate Tracers in Highly Weathered Soil and Groundwater Systems
Authors: Seaman John C. 
Published: July 2010

AbstractFluorobeuzoate (FBA) compounds have been used extensively as hydrologic tracers based on the assumption that they are not significantly sorbed or degraded in most soil and groundwater environments. However, previous batch studies have indicated that such compounds may be readily sorbed by organic matter and hydrous Fe oxides, such as goethite. This study was conducted to evaluate the transport properties of FBA tracers within the highly weathered sediments of the southeastern Coastal Plain. Repacked columns of coarse‐textured alluvial soil and aquifer sediments were leached with tracer solutions (pH ≈5.0) containing various fluorobenzoates with negative logs of the acid dissociation constants (pKas) ranging from 3.83 to 2.85. Bromide was included in many of the solutions to evaluate the influence of ionic strength and competition for anion‐exchange sites on FBA mobility. Despite possible differences in the mechanisms of sorption, retardation within surface and subsurface materials increased with increasing pKa of a given FBA compound. Retardation was attributed to partitioning to the organic fraction for the surface soil and to sorption by Fe oxides for the subsurface sample. For the transport of mixed‐benzoate solutions through surface soil, 2,6‐di‐FBA, 2,3,4,5‐tetra‐FBA, and Br− yielded transport velocities consistent with those observed for 3H; however, 3,4,5‐tri‐FBA and 3,4‐di‐FBA were significantly retarded, most likely due to partitioning to the organic fraction. For the subsurface sample, all of the FBA tracers and Br− were retarded compared with 3H, with FBA retardation increasing with pKa. At higher ionic strengths, retardation was reduced in the subsurface sample due to competition with Br− for anion sorption sites.
Soil Organic Matter Recovery on Conservation Reserve Program Fields in Southeastern Wyoming
Authors: Robles Marcos D. , Burke Ingrid C. 
Published: July 2010

AbstractSoil C and N changes following cessation of cultivation in semiarid soils is not well understood. We hypothesized that returning cultivated fields in southeastern Wyoming to perennial grasses through the Conservation Reserve Program (CRP) would (i) increase labile pools of soil organic matter (SOM), and (ii) increase small‐scale heterogeneity of SOM. Carbon and N in labile and passive pools of SOM were measured in CRP fields seeded with perennial grasses intermediate wheatgrass (Elytrigia intermedia [Host] Nevski ssp. intermedia), pubescent wheatgrass (Elytrigia intermedia [Schur.] A. Löve ssp. barbulata) and smooth brome (Bromus inermis Leysser), and in winter wheat (Triticum aestivum L.)‐fallow fields. Mineralizable C increased from 0.37 g m−2 d−1 in wheat‐fallow fields to 0.99 g m−2 d−1 in CRP fields; mineralizable N and coarse particulate C were consistently but not significantly higher in CRP fields. Fine particulate and total soil C and N were not significantly different between CRP and wheat‐fallow. Within CRP fields, mineralizable C was significantly higher under grasses than in interspaces (1.96 vs. 0.73 g m−2 d−1, respectively), and mineralizable N and coarse particulate C and N were consistently but not significantly higher under grasses than in interspaces. Soil C and N have increased only slightly after 6 yr of CRP management, and future changes in land use management on these CRP fields, including grazing and cropping, may accrue some small benefits associated with improved soil fertility status.