bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Cycling in Piedmont Vegetated Filter Zones: II. Subsurface Nitrate Removal
Authors: Verchot Louis V. , Franklin E. Carlyle , Gilliam J. Wendell 
Published: July 2010

AbstractSubsurface flow often constitutes the major pathway for movement of dissolved nutrients such as NO3‐N from agricultural fields. The objectives of this study were (i) to determine the changes in shallow groundwater chemistry along a piezometric gradient from agricultural fields, across grass‐vegetated field edges and through adjacent forest on two Piedmont watersheds and (ii) determine the relative importance of dilution, denitrification, and plant uptake in subsurface NO3 attenuation. We monitored changes in groundwater chemistry at three depths along a piezometric gradient from an agricultural field through a grass field edge and through a forested filter zone (FFZ). We measured marked decrease in nitrate concentrations from 8 to 10 mg L−1 at the field edge to almost 0 at the forest edge; Cl concentrations remained within the range of 8 to 10 mg L−1, suggesting that dilution was not an important factor in NO3 concentration reductions. At a third site, we introduced NO3‐N and a conservative tracer, bromide, into the soil profile at both the grass‐vegetated field border and the forested area, to determine mechanisms responsible for the observed decrease in NO3‐N concentrations. Using ion concentration ratios we determined that nitrate attenuation in the grass‐vegetated field edge was low compared to the forest. Nitrate loss in the forest was almost exclusively through denitrification; plant uptake was insignificant in these experiments. Although grass‐vegetated field borders were less effective than riparian forests at NO3‐N removal, considerable reductions were observed in these areas on the experimental watersheds. Similar reductions would be expected over shorter distances in riparian forests.
Agricultural Chemicals in Alluvial Aquifers in Missouri after the 1993 Flood
Authors: Heimann D. C. , Richards J. M. , Wilkison D. H. 
Published: July 2010

AbstractIntense rains produced flooding during the spring and summer of 1993 over much of the midwestern USA including many agricultural areas of Missouri. Because of potential contamination from floodwater, an investigation was conducted to determine the changes in concentrations of agricultural chemicals in water samples from alluvial wells in Missouri after the flood. Water samples from 80 alluvial wells with historical data were collected in March, July, and November 1994, and analyzed for dissolved herbicides, herbicide metabolites, and nitrate (NO3). There were no statistically significant differences in the distribution of alachlor ((2,chloro‐2′‐6′‐diethyl‐N‐[methoxymethyl]‐acetanilide), atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1, 3, 5 triazine), and nitrate concentrations between pre‐ and postflood samples (α = 0.05). The detection frequency of alachlor and atrazine in postflood samples was generally lower than the frequency in preflood samples. Analyses of agricultural chemicals in water samples from an intensely sampled well field indicate significant differences between the distribution of dissolved P concentrations in pre‐ and postflood samples (α = 0.05). However, no significant differences were detected between the pre‐ and postflood distributions of NO3 or ammonia concentrations. Because of the numerous sources of temporal variability and the relatively short record of water‐quality data for the study wells, a cause‐and‐effect relation between changes in agricultural chemical concentrations and a single factor of the 1993 flood is difficult to determine. Based on the results of this study, the 1993 flood did not cause widespread or long‐term significant changes in concentrations of agricultural chemicals in water from alluvial aquifers in Missouri.
Selenium Speciation of Marine Shales, Alluvial Soils, and Evaporation Basin Soils of California
Authors: Martens D. A. , Suarez D. L. 
Published: July 2010

AbstractThe surface exposed shales of the Moreno and Kreyenhagen Formations are considered to be the sources of selenium (Se) that have enriched soils of the west‐central San Joaquin Valley of California. Although the total Se content for the source shales and the resulting alluvial, seleniferous soils has been reported, the distribution of Se oxidation states has not been determined in these materials. This study investigates the Se speciation trends in the seleniferous source shales, the adjacent alluvial soils, the San Luis Drain sediment to the Kesterson evaporation pond soils. The surface‐exposed Moreno shales (5.21 mg total Se kg−1) had half of the Se content of the less exposed Kreyenhagen shale (10.94 mg total Se kg−1). The elemental Se (Se0) concentration was similar in the two shales, but the selenate (Se + VI), selenite (Se + IV), and selenide (Se‐II) concentrations were lower in the Moreno shale as compared with the Kreyenhagen shale. The Se in the San Luis Drain sediment (83.8 mg total Se kg−1) was enriched in the Se0 and the Se‐II fractions (91.4% of Se inventory). The soils of the Kesterson evaporation pond 4 (47.8 mg total Se kg−1), 7 (6.7 mg total Se kg−1), and 11 (5.4 mg total Se kg−1) were also enriched in Se with 86, 76, and 48% of the Se inventory present in the Se0 and Se‐II fractions, respectively. The organic C content also decreased in the sequence, San Luis Drain, Kesterson pond 4, 7, and 11, from 33.3, 26.7, and 19.3 g C, to 15.1 g C kg−1 soil material, respectively, suggesting a relationship between Se concentrations and organic C levels. A linear relationship between the sum of (Se‐II and Se0)‐Se and organic C levels (R2 = 0.96*; significant at the 0.05 level) was noted for the analyzed San Luis Drain sediment and the Kesterson soils. For the nine soil materials, an exponential relationship (R2 = 0.96) was determined for the sum of (Se‐II and Se0)‐Se and organic C contents, suggesting that the Se in the materials tested was highly associated with the soil organic matter fraction. An additional 12 Se analyses and organic C contents from Se contaminated semiarid and irrigation drainage water evaporation basin soils obtained from the literature closely fit the exponential function established for the nine soil materials. The results suggest that an initial release of organic‐associated Se would be expected with increased C oxidation, along with a slower, long‐term release of the refractory Se, due to the reversion of the former Kesterson wetland evaporation pond ecosystem back to a native semiarid grassland.
Arsenic Transport in Contaminated Mine Tailings following Liming
Authors: Jones C. A. , Inskeep W. P. , Neuman D. R. 
Published: July 2010

AbstractThe practice of liming to remediate contaminated soils and mine tailings has the potential to mobilize arsenic (As), due to the pH dependence of As sorption reactions on oxide minerals and layer silicates. The objectives of this study were to determine the effects of liming on As mobility in mine tailings and identify possible mechanisms controlling As mobilization with increased pH. Six mine tailing samples obtained from an abandoned copper smelter near Anaconda, Montana were analyzed for total As and soluble constituents using saturated paste extractions. Concentrations of soluble As among the six samples did not correlate with total As, but were more closely related to pH. Saturation indices with respect to known metal arsenate solid phases suggested that metal arsenate solid phases were not controlling soluble As in these samples. Two low pH samples (pond tailings and reprocessed tailings) were chosen for more detailed chemical characterization and unsaturated column transport experiments before and after liming. Soluble As concentrations measured in column effluent increased by factors of 10 (reprocessed tailings, RT) to 400 (pond tailings, PT) following liming. Sequential extractions of these tailing samples showed that the PT contained significantly higher “labile” As relative to the RT, consistent with amounts of As mobilized after liming. Further characterization of these samples using scanning electron microscopy (SEM) and energy dispersive analysis of x‐rays (EDAX) suggested that these samples do not contain discrete metal arsenate solid phases. Based on this suite of experimental data, increased mobility of As with liming appears to be consistent with the pH dependence of sorption reactions of As on Fe oxide minerals rather than dissolution‐precipitation reactions involving As.
Aerobic Degradation Potential Assessment from Oxygen and Carbon Dioxide Soil Gas Concentrations in Roadside Soil
Authors: Ostendorf D. W. , DeGroot D. J. , Pollock S. J. , Long L. J. 
Published: July 2010

AbstractThe application of calcium magnesium acetate [CMA; Ca0.3Mg0.7‐(C2H3O2)2] to highways as a deicing agent induces aerobic acetate degradation by microorganisms in the capillary fringe, which may reduce O2 demand in the underlying groundwater. We assessed this aerobic degradation potential by computing the diffusive fluxes of O2 and CO2 from measured soil gas concentrations in the unsaturated zone of a mildly acidic roadside soil. The fluxes were relevant to the potential assessment because O2 is consumed and CO2 is generated by the aerobic degradation of organic substrates such as acetate. Soil gas O2 and CO2 were measured on a monthly basis in tubing clusters in the unsaturated zone over a 2‐yr period using portable meters. Quasi‐steady gaseous diffusion models were calibrated with the data, showing that O2 diffused into the fringe at a rate that was proportional to the exiting diffusive flux of CO2. The modeled fluxes were consistent with an independent estimate of acetate‐based microcosm reaction rates in the capillary fringe. Roadside soils have the potential to significantly degrade CMA under aerobic conditions before the deicing agent reaches the water table, thus reducing O2 demand in the groundwater.
Fate of Methabenzthiazuron in Calcareous Soils from Southeastern Spain
Authors: Romero T. E. , Barifouse M. M. , Rasero F. S. , Peña H. A. , de la Colina G. C. , Dios C. G. 
Published: July 2010

AbstractAdsorption, incubation, and soil column experiments with methabenzthiazuron [1‐(1,3‐benzothiazol‐2‐yl‐)‐1,3‐dimethylurea] (MBT) were carried out on soils from the surrounding fertile plain of Granada (southeast Spain). The isotherms of MBT adsorption followed the Freundlich model. Due to the similar physico‐chemical and mineralogical properties of the soils from this area, the Kf values were only correlated with soil clay content, smectite content, and soil surface area. Methabenzthiazuron degradation did not occur in the soils, under our experimental conditions, for incubation periods of up to 42 d. Methabenzthiazuron was not detected in the eluates from the clay and silt loam soil columns; it was retained in the first 3‐cm layer and the retardation factor values, R, were 24 and 14, respectively. A computation model simulating a uniform flow of water and instantaneous adsorption‐desorption equilibrium is suitable for the description of MBT in the G‐8 soil but showed an overestimation in the G‐11 soil column.
Field Assessment of Sludge Metal Bioavailability to Crops: Sludge Rate Response
Authors: Logan T. J. , Lindsay B. J. , Goins L. E. , Ryan J. A. 
Published: July 2010

AbstractWe conducted a field study (1991–1995) of trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations in two crops, corn (Zea mays L.) and lettuce (Lactuca sativa L.) as affected by a one‐time application of an anaerobically digested sewage sludge to Miamian silt loam (fine, mixed, mesic Typic Hapludalf) in Columbus, OH to determine the nature of the uptake response over a wide range of sludge application rates (0, 7.5, 15, 30, 60, 90, 120, 150, 188, 225, and 300 Mg/ha dry solids). Cadmium, Cu, Ni, Pb, and Zn sludge concentrations were 46, 433, 67, 185, and 2334 mg/kg, respectively. Soil pH did not vary significantly with sludge application (6.1–7.5), while electrical conductivity, total C and total organic N increased linearly with sludge application and declined over time. Soil metals extracted with 0.005 M EDTA in 0.01 M Ca(NO3)2 increased linearly with total soil concentration and generally declined over time. Cadmium, Cu and Zn concentrations in corn increased significantly with sludge application, while Ni and Pb levels were low compared to the control. Cadmium, Cu, and Zn concentrations in corn exhibited a plateau‐type response that could be modeled with the Mitscherlich equation. Lettuce concentrations increased linearly with sludge application for Cd, Cu, and Zn in all years, and linear regression slopes generally declined and stabilized after the first 2 yr.
Automated Gas Chromatographic System for Rapid Analysis of the Atmospheric Trace Gases Methane, Carbon Dioxide, and Nitrous Oxide
Authors: Loftfield N. , Flessa H. , Augustin J. , Beese F. 
Published: July 2010

AbstractTo study the fluxes of the radiative active trace gases CH4, CO2, and N2O, a gas sampling and analytical device was developed. It is a useful tool for accurate gas sampling in the field and enables the subsequent fully automated analysis of the gas samples in the laboratory. The computer‐controlled analytical system consists of a gas chromatograph equipped with a flame ionization detector (FID), an electron capture detector (ECD), and a pressure‐controlled autosampler for 64 sample containers. The system automates sample injection, the analysis of CH4, CO2, and N2O in each sample and the subsequent evacuation of the sample containers. It is equipped with a second alternative sample inlet for manual syringe injection. This inlet is suitable for analyzing small volumes of gas samples (3 mL). The gas sampling system for use in the field consists of evacuated sample bottles (100 mL) with Teflon cocks combined with a small battery‐driven field sampler with a pressure sensor. This device enables an on‐site control of the vacuum integrity of the sample bottles during sampling and purging of the dead volumes between the sampler induction pipe and the sample container.
Atrazine Sorption at the Field Scale in Relation to Soils and Landscape Position
Authors: Novak J. M. , Moorman T. B. , Cambardella C. A. 
Published: July 2010

AbstractUnderstanding the spatial variation of herbicide sorption in soils is important in determining the potential for leaching at the field scale. Our objectives were to determine the spatial variability of atrazine sorption (6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) at the field scale and to relate sorption partition coefficients (Kd) to landscape position and soil survey map units. Atrazine sorption was measured on 241 surface samples from a 6.25‐ha field using batch‐equilibration methods. Field‐scale variability in atrazine sorption coefficients was described using spherical semivariograms. Less than 20% of the total semivariance in atrazine Kd values was found at lag distances <10 m, indicating there was relatively little variability at this scale. Multiple regression analyses using pooled data revealed that atrazine sorption was influenced by soil organic C, pH, and, to a lesser extent, soil clay. We also evaluated the relationship of atrazine sorption to landscape position and soil series. Less atrazine was sorbed by soils from upland shoulder slopes than by soil in level and depressional areas (potholes). Soils from foot slope and back slope landscape positions were intermediate in atrazine sorption. The magnitude of atrazine sorption by soils in different landscape positions was also related to variations in soil organic C content, pH, and clay content. The greater sorption of atrazine by soils in the pothole depressions may reduce transport of this herbicide to tile lines that commonly drain these soils. Field‐scale maps of atrazine sorption based on landscape position more effectively predicted the actual distribution of the Kd values determined by kriging, than did maps based on soil series.
Modeling Alachlor Transport in Saturated Soils from No‐till and Conventional Tillage Systems
Authors: Xue S. K. , Chen Shulin , Selim H. M. 
Published: July 2010

AbstractBatch and transport experiments with alachlor were conducted in soils from no‐till and conventional tillage systems. Alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] adsorption was described with equilibrium and multireaction models (MRM), and alachlor transport was evaluated with a multireaction transport model (MRTM) in undisturbed soils. In batch experiments, alachlor retention was greater in no‐till soil, based on the parameters of equilibrium adsorption models, than in soil with conventional tillage. This is due to the increase in organic matter. The MRM improved fitting of adsorption data compared with the equilibrium model. Preferential flow in no‐till led to earlier tritium and alachlor breakthrough and higher hydrodynamic dispersion coefficients, compared with conventional tillage. The breakthrough concentrations in no‐till soils are spread more widely over time than in conventional tillage soils, which showed a steady high peak concentration. The MRTM adequately described alachlor transport in soils of both systems. There was no significant difference in alachlor retention capacity between undisturbed soils of no‐till and conventional tillages, and among different cover crops, based on overall parameters fitted from alachlor breakthrough curves (BTCs) in undisturbed soil columns. The higher recovery and lack of irreversible reaction indicated that no‐till soils may have reduced bound alachlor residue during transport.
Temperature Dependence of Linuron Sorption to Three Different Agricultural Soils
Authors: Brücher Jörg , Bergström Lars 
Published: July 2010

AbstractThe temperature dependence of sorption of the herbicide linuron (N′‐(3,4‐dichlorophenyl)‐N‐methoxy‐N‐methylurea) was investigated in three texturally different soils (two sandy soils and one clay soil), each of which had been divided into three layers (0–30, 30–60, and 60–90 cm). Four different temperatures were used, ranging from 277 to 296 K (4–23°C). The sorption tests were conducted according to the Organization for Economic Cooperation and Development (OECD) standard batch‐equilibrium method, in which sieved soil was gently shaken with aqueous linuron solution for 16 to 25 h. In most cases, the sorption isotherms obtained could be described satisfactorily with the Freundlich sorption function. Analyses based on the derived isotherms and calculated Kd values revealed some general patterns: (i) sorption changed significantly (Kd values changed by a factor up to 15 at low linuron concentrations) over the investigated temperature range in all soils; (ii) the nonlinearity of the isotherms increased with decreasing temperature in the sandy soils, but decreased in the clay soil; and (iii) the temperature dependence of sorption was generally stronger at lower linuron concentrations. Based on the sorption data, the free energy and heat of sorption were calculated. These results were then used to describe sorption at any temperature and concentration within the ranges investigated.
Management Practices to Conserve Soil Nitrate in Maize Production Systems
Authors: Zhou Xiaomin , MacKenzie Angus F. , Madramootoo Chandra A. , Kaluli J. Wambua , Smith Donald L. 
Published: July 2010

AbstractResidual soil N following maize (Zea mays L.) harvest is susceptible to leaching over winter. There is no available information regarding the combination of intercropping system and water table control to conserve soil N in maize production systems. A 2‐yr study was conducted to examine the effects of cropping systems (monocrop maize, and maize intercropped with annual Italian ryegrass [Lolium multiflorum Lam.]) and water table controls (free drainage, or subirrigation to establish water table depths at 70 and 80 cm below the soil surface) on conserving soil N, under climatic and soil conditions of southwestern Québec. The resulting six treatments were fertilized in the spring with 270 kg N ha−1. The effects of adding fertilizer at 0, 180, and 270 kg N ha−1 on monocrop maize with free drainage were also investigated. Soil cores of 1 m in depth were collected in the spring and fall of 1993 and 1994. In 1993, intercropping decreased the amount of NO−3‐N in the top 1 m of the soil profile by 47% (92.3 kg N ha−1) relative to monocropped maize at harvest time. Water table depth had less effect on soil NO−3‐N content than cropping system. Both increasing water table depth and monocrop maize enhanced downward movement of NO−3‐N during the growing season and following spring. More NO−3‐N was present in freely drained subsoil under maize given 270 kg N ha−1 than under maize given 180 kg N ha−1.
Correction of Limed‐Biosolid Induced Manganese Deficiency on a Long‐Term Field Experiment
Authors: Brown Sally , Angle J. S. , Chaney R. L. 
Published: July 2010

AbstractLand application of lime‐stabilized biosolids has been reported to cause Mn deficiency in wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.]. Deficiencies were observed on a long‐term biosolid research experiment in Beltsville, MD, that had been established on a Galestown sand (sandy, siliceous, mesic Psammentic Hapludult) in 1976 with lime‐stabilized biosolids applied at 224 and 448 Mg ha−1. For the present study, a randomized complete block experiment was set up in plot areas of the original study. Soil amendments included MnO at 50, 100, and 200 kg ha−1, and MnSO4 at 200 kg ha−1. Plots were split with random half plots receiving a foliar application of MnSO4 at 0.5 kg ha−1 Mn. Soybean and wheat were double cropped for two seasons (1993–1995). Measured indexes of deficiency included youngest emerged blade (YEB) and grain Mn, plant chlorophyll, and yield. Wheat exhibited severe Mn deficiency for both seasons in the 224 Mg ha−1 biosolid plots. Only plants grown in the MnSO4‐amended soils were not deficient in Mn. Foliar Mn spray also alleviated Mn deficiency. Although soybean plants were not Mn deficient, plants in the MnSO4‐treated plots had higher YEB Mn concentrations. Soil extractions to reflect phytoavailable Mn, including Mehlich 1 (M1), Mehlich 3 (M3), and DTPA were conducted on moist soils. Results from M3 and DTPA extractions mirrored plant response. The M1 extraction did not predict plant response indicating that this extraction is not appropriate for predicting Mn deficiency in coarse‐textured high pH soils.
Phytoextraction of Cadmium and Zinc from a Contaminated Soil
Authors: Ebbs S. D. , Lasat M. M. , Brady D. J. , Cornish J. , Gordon R. , Kochian L. V. 
Published: July 2010

AbstractTo identify populations with the ability to accumulate heavy metals, approximately 300 accessions pertaining to 30 plant species were grown for 4 wk in a hydroponic media that approximated the nutrient and heavy metal composition of a soil contaminated with moderate levels of cadmium (Cd), copper (Cu), and zinc (Zn). The results indicated that several Brassica spp. exhibited moderately enhanced Zn and Cd accumulation. Selected accessions of Brassica juncea (L.) Czern, B. napus L., and B. rapa L. were then grown in pots with heavy metal‐contaminated soil to compare the Zn and Cd phytoextraction by these species to that of Thlaspi caerulescens J. & C. Presl, a known Zn and Cd hyperaccumulator, and two grass species, Agrostis capillaris L. and Festuca rubra L. The three Brassica spp. were the most effective in removing Zn from the contaminated soil, primarily because they produced more than 10 times the shoot biomass produced by T. caerulescens. When the soil was amended with Gro‐Power, a commercial soil amendment that improves soil structure and fertility, removal of Zn by plant shoots doubled to more than 30 000 mg Zn pot−1 (4.5 kg). The results suggest that for phytoremediation of metal‐polluted soils to be successful, a strategy should be considered that combines rapid screening of plant species possessing the ability to tolerate and accumulate heavy metals with agronomic practices that enhance shoot biomass production and/or increase metal bioavailability in the rhizosphere.