bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Quaternary Ammonium on Sorption of Selected Metal Cations onto Clinoptilolite Zeolite
Authors: Li Zhaohui , Alessi Daniel , Allen Lori
Published: June 2010

Clay minerals and zeolites have large cation exchange capacities, which enable them to be modified by cationic surfactant to enhance their sorption of organic and anionic contaminants. In this study, the influence of quaternary ammonium surfactants on sorption of five metal cations (Cs+, Sr2+, La3+, Pb2+, and Zn2+) onto a clinoptilolite zeolite was investigated. Generally, the metal cation sorption capacity and affinity for the zeolite decreased, indicating that presorbed cationic surfactants blocked sorption sites for metal cations, as the surfactant loading on the zeolite increased. Cesium and Pb2+ sorption was affected to a small extent, indicating that selective sorption for Cs+ and specific sorption for Pb2+ play an important role in addition to cation exchange. Sorption of cationic surfactants on zeolite preloaded with different metal cations showed a strong correlation with the chain length of the surfactant tail group, while the roles of the charges and types of the metal cations were minimal. As the chain length increases, the critical micelle concentration decreases and the surfactant molecules become more hydrophobic, resulting in progressive bilayer coverage. Desorption of presorbed metal cations by cationic surfactants was strongly affected by the surfactant chain length and metal type. More metal cations, particularly Sr2+ and Zn2+, desorbed with an increase in surfactant chain length. The results, in combination with those from organic and oxyanion sorption on surfactant‐modified zeolite, may be used for future surfactant modification to target sorption and desorption of a specific type of contaminant or a mixture of different types of contaminants.
Dendrochemical Analysis of Lead and Calcium in Southern Appalachian American Beech
Authors: Fisher Suzanne , Nicholas N.S. , Scheuerman Phillip R.
Published: June 2010

The health of the northern hardwood forest in the southern Appalachian Mountains of Tennessee, North Carolina, and Virginia has gained attention from the media and environmental stakeholders due to a purported decline in forest health at higher elevations. This project examined lead (Pb) and calcium (Ca) concentrations in growth rings of an important northern hardwood species, American beech (Fagus grandifolia Ehrh.) at Mount Rogers and Whitetop Mountain, Virginia and attempted to examine concentration relationships with stem growth patterns. Dominant and codominant trees were sampled from 16 research plots at two elevations. Tree cores were crossdated, divided into sections of 10‐yr periods, and analyzed using atomic absorption spectroscopy. Lead concentrations correlated negatively with ring width. Elevation and aspect were significantly associated with the Pb concentration, while Ca concentrations were only associated with aspect. Tree core samples taken from higher elevation plots contained higher Pb concentrations than samples collected from lower elevation plots, while the northwest and southwest aspects contained significantly higher amounts of Pb and Ca. Both Pb and Ca concentrations increased during the 1860s and again during the mid‐1900s.
Response of Turf and Quality of Water Runoff to Manure and Fertilizer
Authors: Gaudreau J.E. , Vietor D.M. , White R.H. , Provin T.L. , Munster C.L.
Published: June 2010

Manure applications can benefit turfgrass production and unused nutrients in manure residues can be exported through sod harvests. Yet, nutrients near the soil surface could be transported in surface runoff. Our research objective was to evaluate responses of bermudagrass [Cynodon dactylon (L.) Pers. var. Guymon] turf and volumes and P and N concentrations of surface runoff after fertilizer or composted manure applications. Three replications of five treatments were established on a Boonville fine sandy loam (fine, smectitic, thermic Vertic Albaqualf) that was excavated to create an 8.5% slope. Manure rates of 50 and 100 kg P ha−1 at the start of two monitoring periods were compared with P fertilizer rates of 25 and 50 kg ha−1 and an unfertilized control. Compared with initial soil tests, nitrate concentrations decreased and P concentrations increased after two manure or fertilizer applications and eight rain events over the two monitoring periods. The fertilizer sources of P and N produced 19% more dry weight and 21% larger N concentrations in grass clippings than manure sources. Yet, runoff volumes were similar between manure and fertilizer sources of P. Dissolved P concentration (30 mg L−1) in runoff during a rain event 3 d after application of 50 kg P ha−1 was five times greater for fertilizer than for manure P. Observations during both monitoring periods indicated that total P and N losses in runoff were no greater for composted manure than for fertilizer sources of P at relatively large P rates on a steep slope of turfgrass.
Relationship between Compost Stability and Extractable Organic Carbon
Authors: Wu L. , Ma L.Q.
Published: June 2010

Establishing a simple yet reliable compost stability test is essential for a better compost quality control and utilization efficiency. The objective of this study was to examine the relationship between extractable organic carbon (OC) and compost stability based on 18 compost samples from five composting facilities. The compost samples were extracted sequentially with water for 2 h [water(2h)] and 0.1 M NaOH for 2 and 24 h [NaOH(2h) and NaOH(24h), respectively]. The extractable OC was further separated into fulvic acid (FA) and humic acid (HA) fractions by adjusting the pH to <2. The mass specific absorbance (MSA) of OC in the six fractions was measured. Compost stability was estimated with a CO2 evolution method. The extractable OC concentration was influenced by the total volatile solids and decreased with curing time for compost with a high level of extractable OC. The OC levels in each fraction were significantly correlated (p < 0.05) to each other except for the water(2h)–extractable HA. In addition, all the FA and HA fractions except for water(2h)–extractable HA were highly (P < 0.01) and linearly correlated to CO2 evolution, but multiple regression showed that NaOH(24h)–extractable OC was insignificant for CO2 evolution. The relatively high slope of NaOH(2h)–extractable FA versus CO2 evolution suggests that this fraction may contribute the most to compost CO2 evolution. The water(2h)– and/or NaOH(2h)–extractable FA tests are recommended for measuring compost stability because of their high correlation with CO2 evolution. This estimation can be obtained through a simple photometric method covering a wide range of carbon concentrations up to 4000 mg L−1
Uncertainty Analysis of the Water Balance Technique for Measuring Seepage from Animal Waste Lagoons
Authors: Ham J. M.
Published: June 2010

Water balance measurements can be used to estimate seepage rates from animal waste lagoons and earthen storages. This method requires detailed measurements of depth changes and cumulative evaporation during 5‐ to 10‐d periods. Quantifying the uncertainty surrounding the measurements is crucial if data from seepage tests are used to determine if lagoons are meeting engineering specifications and operating within regulatory guidelines. Uncertainty analyses, using a 95% confidence interval, were applied to field data collected during studies of animal waste lagoons in Kansas and Oklahoma. Changes in depth were measured with float‐based recorders and evaporation was estimated from meteorological observations. Results showed that rate changes in depth could be measured to within ±0.28 mm d−1 or better when wind speeds at the start and end of the test were less than 4 m s−1 Uncertainty in evaporation was the most significant factor affecting the seepage estimate, and surface temperature and relative humidity were the main sources of imprecision in the evaporation calculations. Evaporation could be estimated to within 10 to 20%, with the largest uncertainty occurring during windy conditions. Uncertainty in the calculated seepage rate increased as evaporation increased. When evaporation rates are low (e.g., <4 mm d−1), seepage can be estimated to within ±0.5 mm d−1 with 95% confidence. A precision of ±0.25 mm d−1 is possible when research‐grade instruments are deployed under favorable weather conditions. A measurement duration of 5 d is adequate for most water balance tests. In many cases, precision of the water balance technique will be sufficient in determining if a working lagoon is within regulatory guidelines.
Treatment of 2,4‐Dichlorophenol Polluted Soil with Free and Immobilized Laccase
Authors: Ahn Mi‐Youn , Dec Jerzy , Kim Jang‐Eok , Bollag Jean‐Marc
Published: June 2010

Enzyme treatment is currently considered for remediation of terrestrial systems polluted with organic compounds. In this study, two soils from Pennsylvania with 2.8 or 7.4% organic matter contents (Soils 1 and 2, respectively) were amended with 14C‐labeled 2,4‐dichlorophenol (2,4‐DCP) and incubated with a laccase from Trametes villosa (free or immobilized on montmorillonite). 2,4‐DCP was either transformed to methanol‐soluble polymeric products (11–32%) or covalently bound to soil organic matter (53–85%); unaltered 2,4‐DCP could be recovered from soil by methanol extraction (0–38%) at the completion of a 14‐d incubation period. In Soil 1, both free and immobilized laccase removed 100% of 2,4‐DCP without regard for moisture conditions. In Soil 2, immobilized laccase removed more 2,4‐DCP (about 95%, regardless of moisture conditions) than free enzyme (55, 75, and 90% at 30, 55, and 100% of maximum water‐holding capacity, respectively). Binding of 2,4‐DCP in the humin fraction was nearly the same for free and immobilized laccase. More 2,4‐DCP, however, was bound to humic and fulvic acids in the presence of immobilized laccase than in the presence of free laccase. In general, immobilized laccase performed better than free laccase. However, for practical applications, the higher activity of immobilized laccase is offset by a 23% loss in enzyme activity during immobilization, which approximates the 30% increase in free laccase needed to achieve the same level of remediation. Furthermore, immobilized laccase is more costly than free T. villosa laccase.
Natural Uranium and Thorium Distributions in Podzolized Soils and Native Blueberry
Authors: Morton L. S. , Evans C. V. , Estes G. O.
Published: June 2010

Plant uptake of radionuclides is one of many vectors for introduction of contaminants into the human food chain. Thus, it is critical to understand soil–plant relationships that control nuclide bioavailability. Our objectives in this study were to (i) determine the extent of U and Th uptake and cycling by blueberry (Vaccinium pallidum Aiton) in native habitat and (ii) identify the soil properties and processes that contribute most to U and Th bioavailability in this system. We collected composite samples of plant leaves and stems, and samples from surface (AE) horizons and from the upper part of the Bs horizon at two sites. Concentration ratios (CRs) for U and Th were calculated for all plant tissues, using both the AE and Bs horizons as the base. Soil concentrations of U ranged from 16 to 25 μg g−1, with a mean of 21.1 μg g−1 Soil concentrations of Th ranged from 14 to 97 μg g−1, with a mean of 41.8 μg g−1 Mean U concentrations were 8.65 × 10−3 μg g−1 in leaf tissue, and 7.95 × 10−3 μg g−1 in stem tissue. Mean Th concentrations were 1.59 × 10−1 μg g−1 in leaf tissue, and 9.10 × 10−2 μg g−1 in stem tissue. Blueberry plants are cycling both U and Th in this system, with Th cycling occurring to a greater extent than U. In addition, Th was translocated preferentially to plant leaves while U concentrations showed little preferential translocation. Uranium uptake, however, seemed more sensitive than Th uptake to soil properties.
Estimating Soil Phosphorus Requirements and Limits from Oxalate Extract Data
Authors: D'Angelo E. M. , Vandiviere M. V. , Thom W. O. , Sikora F.
Published: June 2010

Excessive fertilizer and manure phosphorus (P) inputs to soils elevates P in soil solution and surface runoff, which can lead to freshwater eutrophication. Runoff P can be related to soil test P and P sorption saturation, but these approaches are restricted to a limited range of soil types or are difficult to determine on a routine basis. The purpose of this study was to determine whether easily measurable soil characteristics were related to the soil phosphorus requirements (Preq, the amount of P sorbed at a particular solution P level). The Preq was determined for 18 chemically diverse soils from sorption isotherm data (corrected for native sorbed P) and was found to be highly correlated to the sum of oxalate‐extractable Al and Fe (R2 > 0.90). Native sorbed P, also determined from oxalate extraction, was subtracted from the Preq to determine soil phosphorus limits (PL, the amount of P that can be added to soil to reach Preq). Using this approach, the PL to reach 0.2 mg P L−1 in solution ranged between −92 and 253 mg P kg−1 Negative values identified soils with surplus P, while positive values showed soils with P deficiency. The results showed that P, Al, and Fe in oxalate extracts of soils held promise for determining PL to reach up to 10 mg P L−1 in solution (leading to potential runoff from many soils). The soil oxalate extraction test could be integrated into existing best management practices for improving soil fertility and protecting water quality.
Fate of Urine Nitrogen in Three Soils throughout a Grazing Season
Authors: Decau M. L. , Simon J. C. , Jacquet A.
Published: June 2010

The fate of 15N‐labeled cattle (Bos taurus) urine (52 g N m−2), applied to a 0.4‐m2 surface area on three dates between May and October to three different pasture soils, was studied using 2‐m2 lysimeters. Over a period of two years, the sward recovered most of the 15N, but the amount recovered decreased with application date (62% in spring to 17% in fall). However, N uptake by ryegrass (Lolium perenne L.) in Year 2 showed that some nitrogen came from the previous year's urine application. The largest leaching losses of urine N resulted from the late application date. These losses mainly occurred during the first winter despite the small amount of water drainage. Soil type largely determined 15N losses. The granitic Brunisol was the most freely draining and had the greatest leaching (up to 35% recovery of urinary N). In contrast, leaching in the silty loam Neoluvisol remained under 4% of 15N applied. The Calcosol appeared to be susceptible to all kinds of N losses with intermediate unaccounted‐for N pool and leaching fractions and lesser utilization of urinary N by grass. Immobilization in soil organic matter, roots and litter, and stubble pools were not markedly influenced by the date of application or soil type. They amounted to 25 to 33, 2, and 2% of N applied as urine, respectively. In these climatic conditions with moderate drainage, leaching of water poor in quality for nitrate only occurred for late‐season grazing or on the granitic Brunisol, which was very vulnerable to leaching.
Herbicide Retention in Soil as Affected by Sugarcane Mulch Residue
Authors: Selim H. M. , Zhou L. , Zhu H.
Published: June 2010

Reducing surface and subsurface losses of herbicides in the soil and thus their potential contamination of water resources is a national concern. This study evaluated the effectiveness of sugarcane (Saccharum spp.) residue (mulch cover) in reducing nonpoint‐source contamination of applied herbicides from sugarcane fields. Specifically, the effect of mulch residue on herbicide retention was quantified. Two main treatments were investigated: a no‐till treatment and a no‐mulch treatment. The amounts of extractable atrazine [2‐chloro‐4‐(isopropylamino)‐6‐ethylamino‐s‐triazine], metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one], and pendimethalin [N‐(ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitroaniline] from the mulch residue and the surface soil layer were quantified during the 1999 and 2000 growing seasons. Significant amounts of applied herbicides were intercepted by the mulch residue. Extractable concentrations were at least one order of magnitude higher for the mulch residue compared with that retained by the soil. Moreover, the presence of mulch residue on the sugarcane rows was highly beneficial in minimizing runoff losses of the herbicides applied. When the residue was not removed, a reduction in runoff‐effluent concentrations, as much as 50%, for atrazine and pendimethalin was realized. Moreover, the presence of mulch residue resulted in consistently lower estimates for rates of decay or disappearance of atrazine and pendimethalin in the surface soil.
Pilot‐Scale Treatment of RDX‐Contaminated Soil with Zerovalent Iron
Authors: Comfort S. D. , Shea P. J. , Machacek T. A. , Satapanajaru T.
Published: June 2010

Soils in Technical Area 16 at Los Alamos National Laboratory (LANL) are severely contaminated from past explosives testing and research. Our objective was to conduct laboratory and pilot‐scale experiments to determine if zerovalent iron (Fe0) could effectively transform RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) in two LANL soils that differed in physicochemical properties (Soils A and B). Laboratory tests indicated that Soil A was highly alkaline and needed to be acidified [with H2SO4, Al2(SO4)3, or CH3COOH] before Fe0 could transform RDX. Pilot‐scale experiments were performed by mixing Fe0 and contaminated soil (70 kg), and acidifying amendments with a high‐speed mixer that was a one‐sixth replica of a field‐scale unit. Soils were kept unsaturated (soil water content = 0.30–0.34 kg kg−1) and sampled with time (0–120 d). While adding CH3COOH improved the effectiveness of Fe0 to remove RDX in Soil A (98% destruction), CH3COOH had a negative effect in Soil B. We believe that this difference is a result of high concentrations of organic matter and Ba. Adding CH3COOH to Soil B lowered pH and facilitated Ba release from BaSO4 or BaCO3, which decreased Fe0 performance by promoting flocculation of humic material on the iron. Despite problems encountered with CH3COOH, pilot‐scale treatment of Soil B (12100 mg RDX kg−1) with Fe0 or Fe0 + Al2(SO4)3 showed high RDX destruction (96–98%). This indicates that RDX‐contaminated soil can be remediated at the field scale with Fe0 and soil‐specific problems (i.e., alkalinity, high organic matter or Ba) can be overcome by adjustments to the Fe0 treatment.
Modeling Surface Water Critical Loads with PROFILE
Authors: Rapp L. , Bishop K.
Published: June 2010

The critical load concept has become a valuable tool for policymakers in the European negotiations on emission reductions. Despite the international acceptance, ongoing validation of critical load methodology is of the utmost importance to avoid a situation where the calculation results are difficult to defend. In this paper we explore the potential of using the steady state soil chemistry model PROFILE as an alternative to the Steady State Water Chemistry (SSWC) method for calculating critical loads of acidity. The hypothesis is that the uncertainty in prediction of preindustrial leaching of base cations is reduced when soil properties instead of lake chemistry are used as input data. Paleolimnological reconstructions of preindustrial lake chemistry are used to test PROFILE. As PROFILE requires soil data that are not generally available on a catchment level, we used distributions of crucial parameters from soil survey data within the vicinity of five lakes for which paleoecological pH reconstructions were available. An important concern is the characterization of catchment hydrology. A calibration of the “effective” soil depth, needed to give PROFILE predictions that coincided with paleolimnology, suggested that approximately 0.6 m of the total soil depth was hydrologically active in supplying acid neutralizing capacity (ANC) to runoff through weathering. At present, there is insufficient evidence to either recommend or reject the PROFILE model for surface water critical loads. Before such a judgement can be made, the approach presented here has to be tested for other regions, and the definition of catchment hydrology needs to be investigated further.
Solute Movement through an Allophanic Soil
Authors: Magesan G. N. , Vogeler I. , Clothier B. E. , Green S. R. , Lee R.
Published: June 2010

Allophanic soils are widespread around the world, but little research has been done on their transport properties. This study reveals the effect of two soil water potential heads and two water‐flow regimes of continuous and intermittent flow on solute transport through undisturbed soil columns of Horotiu silt loam (Typic Hapludand), an allophanic soil. Two different methods—breakthrough curves (BTCs) and time domain reflectometry (TDR)—were employed to determine the extent of preferential solute transport in the topsoil. The TDR data were also used to look at the depth dependence of the transport properties. The convection–dispersion equation (CDE) with the appropriate boundary conditions adequately described the movement of both Br and Cl under the various flow conditions. Although no preferential flow was found under the imposed unsaturated flow conditions, the flow of water and transport of solute became more uniform with depth. The results show that both Br and Cl are retarded in this allophanic soil. Retardation values range from 1.5 to 1.9, and, as the TDR data showed, increase from the depth of 5.0 to 10.0 cm. Intermittent leaching results showed that there was no effect on solute concentrations in the leachate following no‐flow periods. This suggests that water and solute transport in this soil were either relatively uniform or that transverse mixing during flow was already fast enough to eliminate concentration gradients between regions of different “mobility.”
Impact of Genetically Modified Crops and Their Management on Soil Microbially Mediated Plant Nutrient Transformations
Authors: Motavalli P. P. , Kremer R. J. , Fang M. , Means N. E.
Published: June 2010

One of the potential environmental effects of the recent rapid increase in the global agricultural area cultivated with transgenic crops is a change in soil microbially mediated processes and functions. Among the many essential functions of soil biota are soil organic matter decomposition, nutrient mineralization and immobilization, oxidation–reduction reactions, biological N fixation, and solubilization. However, relatively little research has examined the direct and indirect effects of transgenic crops and their management on microbially mediated nutrient transformations in soils. The objectives of this paper are to review the available literature related to the environmental effects of transgenic crops and their management on soil microbially mediated nutrient transformations, and to consider soil properties and climatic factors that may affect the impact of transgenic crops on these processes. Targeted genetic traits for improved plant nutrition include greater plant tolerance to low Fe availability in alkaline soils, enhanced acquisition of soil inorganic and organic P, and increased assimilation of soil N. Among the potential direct effects of transgenic crops and their management are changes in soil microbial activity due to differences in the amount and composition of root exudates, changes in microbial functions resulting from gene transfer from the transgenic crop, and alteration in microbial populations because of the effects of management practices for transgenic crops, such as pesticide applications, tillage, and application of inorganic and organic fertilizer sources. Possible indirect effects of transgenic crops, including changes in the fate of transgenic crop residues and alterations in land use and rates of soil erosion, deserve further study. Despite widespread public concern, no conclusive evidence has yet been presented that currently released transgenic crops, including both herbicide and pest resistant crops, are causing significant direct effects on stimulating or suppressing soil nutrient transformations in field environments. Further consideration of the effects of a wide range of soil properties, including the amount of clay and its mineralogy, pH, soil structure, and soil organic matter, and variations in climatic conditions, under which transgenic crops may be grown, is needed in evaluating the impact of transgenic crops on soil nutrient transformations. Future environmental evaluation of the impact of the diverse transgenic crops under development could lead to an improved understanding of soil biological functions and processes.
Impact of Glyphosate on the Bradyrhizobium japonicum Symbiosis with Glyphosate‐Resistant Transgenic Soybean: A Minireview
Authors: Zablotowicz Robert M. , Reddy Krishna N.
Published: June 2010

Glyphosate‐resistant (GR) soybean [Glycine max (L.) Merr.] expressing an insensitive 5‐enolpyruvylshikimic acid‐3‐phosphate synthase (EPSPS) gene has revolutionized weed control in soybean production. The soybean nitrogen fixing symbiont, Bradyrhizobium japonicum, possesses a glyphosate‐sensitive enzyme and upon exposure to glyphosate accumulates shikimic acid and hydroxybenzoic acids such as protocatechuic acid (PCA), accompanied with B. japonicum growth inhibition and death at high concentrations. In a series of greenhouse and field experiments, glyphosate inhibited nodulation and nodule leghemoglobin content of GR soybean. Glyphosate accumulated in nodules of field‐grown GR soybean, but its effect on nitrogenase activity of GR soybean was inconsistent in field studies. In greenhouse studies, nitrogenase activity of GR soybean following glyphosate application was transiently inhibited especially in early growth stages, with the greatest inhibition occurring under moisture stress. Studies using bacteroid preparations showed that the level of glyphosate inhibition of bacteroid nitrogenase activity was related to in vitro glyphosate sensitivity of the B. japonicum strains. These studies indicate the potential for reduced nitrogen fixation in the GR soybean system; however, yield reductions due to this reduced N2 fixation in early stages of growth have not been demonstrated.
Reduced Biodegradation of Benzonitrile in Soil Containing Wheat‐Residue‐Derived Ash
Authors: Zhang Ping , Sheng Guangyao , Wolf Duane C. , Feng Yucheng
Published: June 2010

Burning of crop residues is a common agricultural practice that incorporates the resulting particulate matter (ash) of high adsorptivity into soils. To investigate the effect of ash on the biodegradation of pesticides in soils, we measured the sorption, desorption, and biodegradation of benzonitrile in a silt loam in the presence and absence of an ash resulting from burning of wheat (Triticum aestivum L.) residue. Biodegradation experiments were conducted by inoculating sorbent slurries with a pure culture of benzonitrile‐degrading bacteria (Nocardia sp.). Both liquid‐ and sorbed‐phase benzonitrile concentrations were quantified over time. The ash was approximately 2000 times more effective per unit mass than the soil in sorbing benzonitrile. Amendment of the soil with 1% ash (by weight) resulted in a 10‐fold increase in sorption. Sorption of benzonitrile by the ash significantly decreased the solution‐phase concentration in the slurries of ash and ash‐amended soil. Desorption of benzonitrile from the ash required approximately 60 min to complete, whereas approximately 20 min were required for desorption from the soil. Benzonitrile in the extracts of various sorbents and soil slurry was completely degraded within 500 min. However, the degradation was substantially reduced in the presence of the ash. At 2000 min, only 20% of benzonitrile in ash slurry and only 44% in ash‐amended soil slurry were degraded. An acclimation period of approximately 100 min was observed in extracts and slurries containing the ash. Substantial reduction in the biodegradation of benzonitrile in the presence of wheat ash was apparently due to sorption of benzonitrile by the ash, slow desorption from the ash, and the increased acclimation period. Our results suggest that the presence of crop‐residue‐derived ash may increase the persistence of pesticides in agricultural soils.
Stream Nitrate Variations Explained by Ground Water Head Fluctuations in a Pyrite‐Bearing Aquifer
Authors: Grimaldi C. , Viaud V. , Massa F. , Carteaux L. , Derosch S. , Regeard A. , Fauvel Y. , Gilliet N. , Rouault F.
Published: June 2010

In the context of agricultural nitrogen excesses in northwestern France, pyrite‐bearing weathered schist aquifers represent important hydrological compartments due to their capacity to eliminate nitrate NO3− Under oxygen‐free conditions, nitrate is reduced simultaneously with the oxidation of pyrite leading to the release of sulfate SO42− The aim of the present study is to identify the hydrological conditions under which the weathered schist ground water influences the stream water chemistry, leading to a decrease in NO3− concentration. We measured the ground water head on a small catchment over weathered schist, near the bank and under the streambed, and analyzed the chemical composition of the ground water as well as the stream water on both seasonal and storm‐event timescales. Using SO42− as a tracer of the weathered schist ground water, we showed that ground water inflow caused a decrease of NO3− concentration in the stream during the autumn as well as during storm events in spring and summer. In summer, the NO3− concentration was controlled by the sources of the stream, and in winter by the shallow ground water inflow. The effect of the weathered schist ground water on the NO3− depletion remained relatively limited in time. This effect persisted into late autumn as long as the NO3−–rich shallow ground water did not feed the stream. The duration and intensity of the effect would be extended by decreasing the shallow ground water inflow, which depends on climate as well as the presence of landscape features such as hedges and buffer zones.
Herbicide Selection of Italian Ryegrass under Different Levels of UVB Radiation
Authors: Martínez‐Ghersa M. Alejandra , Aiub Martín M. Vila , Ghersa Claudio M. , Gundel Pedro , Satorre Emilio H.
Published: June 2010

Ultraviolet‐B radiation is an environmental stress for plants and this situation could become aggravated in the next decades. In this study we used Italian ryegrass (Lolium multiflorum Lam.) as a model system to test whether an environmental stress derived from global change, such as UVB, can influence the efficacy of control procedures and evolution toward herbicide resistance. We grew three generations of Italian ryegrass plants with and without UVB light and subjected them to a series of diclofop‐methyl {(±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy] propanoic acid, methyl ester} doses. The effect of selection history was tested with herbicide dose response. The effect of herbicide application on plant survival and biomass varied significantly among herbicide doses and with absence or presence of UVB light. In the absence of herbicide, the decrease in individual fecundity with increasing plant density was similar under both no‐UVB and UVB light treatments. Only plants growing without UVB light increased production of reproductive structures in response to the decrease in density caused by herbicide application. Our study shows that UVB light was a weak stress factor for the ryegrass plants. However, when herbicide selection pressure was high, UVB light reduced the evolution toward herbicide tolerance. When selection pressure on the parental plants was lower, the two stress factors had a synergistic effect, causing changes in herbicide efficacy that in turn had demographic and evolutionary consequences. In the field, these interactions between stress factors might be of significance for annual weeds in which seed output is a major determinant in fitness.
Automated and Continuous Redox Potential Measurements in Soil
Authors: Vorenhout Michel , van der Geest Harm G. , van Marum Daan , Wattel Kees , Eijsackers Herman J. P.
Published: June 2010

Redox potential (Eh) describes the electrical state of a matrix. In soils, Eh is an important parameter controlling the persistence of many organic and inorganic compounds. A popular, but also criticized, manual measuring method makes use of a small tip of Pt placed on a copper wire that is placed in the soil; a reference electrode is placed in the same soil at a fixed distance. Fluctuations in redox potential values measured in the soil can be very large and depth‐dependent. This will be overlooked when making single‐point measurements. We developed the datalogger Hypnos 2.0 for continuous redox potential and temperature measurements at various depths in the soil and without disturbance of the site. Hypnos is field‐deployable, relatively cheap, and runs on batteries. The datalogger can use a “sleep mode” between sampling events. In sleep mode, there is no constant voltage on the Pt wire or the reference electrode, but there is only a short pulse during sampling. We did not measure an effect of this short pulse on the measured redox potential. In sandy soils in mesocosms and in a salt marsh soil we measured changes in the Eh as large as from −400 to +100 mV within 4 d, and daily cycles of 200 mV. Both absolute redox potential values and their diurnal variations were depth‐dependent. Because single redox measurements are insufficient in describing redox conditions in some soil systems, Hypnos can be a powerful tool when studying the effects of fluctuating redox conditions on metal availability and pollutant degradation.
An Improved Description of Pesticide Volatilization
Authors: Wolters André , Klein Michael , Vereecken Harry
Published: June 2010

The consideration of pesticide volatilization from soil surfaces as an integral component of pesticide fate models is of importance, especially as part of the Predicted Environmental Concentrations (PEC) models used in the registration procedures for pesticides. The Pesticide Leaching Model (PELMO), which is used in the European registration process, was modified to allow for a reliable prediction of volatilization from soil. The previous PELMO version was upgraded by improving the spatiotemporal discretization at the soil surface, improving the empirical description of temperature dependence of Henry's law constants and including increased sorption of pesticides in dry soils. Comparison of predictions with experimental findings revealed the improvements of PELMO to contribute to a more realistic reflection of measurements, particularly at initial stages of the studies. The broad range of literature values of Henry's law constants was shown to have a significant effect on predicted volatilization fluxes. As a main refinement, the tendency of pesticides toward enhanced volatilization under moist conditions was correctly calculated by the improved model. Variations between model predictions and measurements were due to a lack of experimental data on soil sorption under dry conditions and indicated the need for further calibration of the model. The description of water content in the top layer was subject to uncertainty, which was exemplified by an overestimation of soil moisture during the last days of the field study. Thus, future model improvement will be dependent on experimental support to obtain more detailed information on soil–air–water partitioning of pesticides in the top soil layer.
Forecasting the Number of Soil Samples Required to Reduce Remediation Cost Uncertainty
Authors: Demougeot‐Renard Hélène , de Fouquet Chantal , Renard Philippe
Published: June 2010

Sampling scheme design is an important step in the management of polluted sites. It largely controls the accuracy of remediation cost estimates. In practice, however, sampling is seldom designed to comply with a given level of remediation cost uncertainty. In this paper, we present a new technique that allows one to estimate of the number of samples that should be taken at a given stage of investigation to reach a forecasted level of accuracy. The uncertainty is expressed both in terms of volume of polluted soil and overall cost of remediation. This technique provides a flexible tool for decision makers to define the amount of investigation worth conducting from an environmental and financial perspective. The technique is based on nonlinear geostatistics (conditional simulations) to estimate the volume of soil that requires remediation and excavation and on a function allowing estimation of the total cost of remediation (including investigations). The geostatistical estimation accounts for support effect, information effect, and sampling errors. The cost calculation includes mainly investigation, excavation, remediation, and transportation. The application of the technique on a former smelting work site (lead pollution) demonstrates how the tool can be used. In this example, the forecasted volumetric uncertainty decreases rapidly for a relatively small number of samples (20–50) and then reaches a plateau (after 100 samples). The uncertainty related to the total remediation cost decreases while the expected total cost increases. Based on these forecasts, we show how a risk‐prone decision maker would probably decide to take 50 additional samples while a risk‐averse decision maker would take 100 samples.
Development of a Phosphorus Index for Pastures Fertilized with Poultry Litter—Factors Affecting Phosphorus Runoff
Authors: DeLaune Paul B. , Moore Philip A. , Carman Dennis K. , Sharpley Andrew N. , Haggard Brian E. , Daniel Tommy C.
Published: June 2010

Currently, several state and federal agencies are proposing upper limits on soil test phosphorus (P), above which animal manures cannot be applied, based on the assumption that high P concentrations in runoff are due to high soil test P. Recent studies show that other factors are more indicative of P concentrations in runoff from areas where manure is being applied. The original P index was developed as an alternative P management tool incorporating factors affecting both the source and transport of P. The objective of this research was to evaluate the effects of multiple variables on P concentrations in runoff water and to construct a P source component of a P index for pastures that incorporates these effects. The evaluated variables were: (i) soil test P, (ii) soluble P in poultry litter, (iii) P in poultry diets, (iv) fertilizer type, and (v) poultry litter application rate. Field studies with simulated rainfall showed that P runoff was affected by the amount of soluble P applied in the fertilizer source. Before manure applications, soil test P was directly related to soluble P concentrations in runoff water. However, soil test P had little effect on P runoff after animal manure was applied. Unlike most other P indices, weighting factors of the P source components in the P index for pastures are based on results from runoff studies conducted under various management scenarios. As a result, weighting factors for the P source potential variables are well justified. A modification of the P index using scientific data should strengthen the ability of the P index concept to evaluate locations and management alternatives for P losses.
Associated Release of Magnesium and Phosphorus from Active and Abandoned Dairy Soils
Authors: Josan M. S. , Nair V. D. , Harris W. G. , Herrera D.
Published: June 2010

Dairy manure application to soils can result in phosphorus (P)‐related degradation of water quality. The P in these manure‐impacted soils can be labile even years after abandonment and under conditions normally associated with high P stability. Failure of P to stabilize with time compounds the environmental consequences of dairy manure disposal, especially on sandy soils. The objectives of this study were to compare chemical characteristics of active and abandoned dairy manure–impacted soils and minimally impacted soils and to assess the continuous release of P in relation to sparingly soluble salts using repeated water extractions, X‐ray diffraction, and speciation modeling of column leachates. Soil samples from Ap horizons were collected from nine highly manure‐impacted (total P > 1000 mg P kg−1 soil) areas on four active and five abandoned dairies and four minimally impacted soils (total P < 200 mg P kg−1 soil). Soil extracts were analyzed for electrical conductivity (EC), soluble reactive phosphorus (SRP), Ca, Mg, Na, and K. The EC of the soil solutions decreased as active dairy > abandoned dairy > minimally impacted soils. Release of Mg and SRP were significantly correlated (r2 = 0.68) and did not decline after abandonment; Ca release was not correlated with SRP (r2 = 0.01), and declined significantly (p < 0.05) after abandonment. Speciation data from column leachates suggested that Mg‐P phases and/or the most soluble Ca‐P phases could control P solution activities. An implication of this study is that P stabilization via crystallization of calcium phosphates (even at near‐neutral pH) may be preempted by Mg‐P association. Thus, mechanisms to minimize P release may require P‐retaining soil amendments or management of animal rations to eliminate Mg‐P formation.
Prediction of Zinc, Cadmium, Lead, and Copper Availability to Wheat in Contaminated Soils Using Chemical Speciation, Diffusive Gradients in Thin Films, Extraction, and Isotopic Dilution Techniques
Authors: Nolan Annette L. , Zhang Hao , McLaughlin Mike J.
Published: June 2010

To predict the availability of metals to plants, it is important to understand both solution‐ and solid‐phase processes in the soil, including the kinetics of metal release from its binding agent (ligand and/or particle). The present study examined the speciation and availability of Zn, Cd, Pb, and Cu in a range of well‐equilibrated metal‐contaminated soils from diverse sources using several techniques as a basis for predicting metal uptake by plants. Wheat (Triticum aestivum L.) was grown in 13 metal‐contaminated soils and metal tissue concentrations (Zn, Cd, Pb, and Cu) in plant shoots were compared with total soil metal concentrations, total soluble metal, and free metal activities (pM2+) in soil pore waters, 0.01 M CaCl2–extractable metal concentrations, E values measured by isotope dilution, and effective metal concentrations, CE, measured by diffusive gradients in thin films (DGT). In the DGT technique, ions are dynamically removed by their diffusion through a gel to a binding resin, while E values represent the isotopically exchangeable (labile) metal pools. Free metal activities (Zn2+, Cd2+, and Pb2+) in soil pore waters were determined using a Donnan dialysis technique. Plant Zn and Cd concentrations were highly related to CE, while relationships for Zn and Cd with respect to the other measures of metals in the soils were generally lower, except for CaCl2–extractable Cd. These results suggest that the kinetically labile solid‐phase pool of metal, which is included in the DGT measurement, played an important role in Zn and Cd uptake by wheat along with the labile metal in soil solution. Plant Pb concentrations were highly related to both soil pore water concentrations and CE, indicating that supply from the solid phase may not be so important for Pb. Predictions of Cu uptake by wheat from these soils by the various measures of Cu were generally poor, except surprisingly for total Cu.
On Delegation in Contests and the Survival of Payoff Maximizing Behavior
Authors: Possajennikov Alex
Published: June 2010

In two-player contests, optimal delegation involves giving the agent incentives to maximize the principal's payoff while in contests with more than two players incentives will be different from the principal's payoff maximization. These results are related to the evolutionary stability of payoff-maximizing preferences in the model of indirect evolution in general symmetric games, which depends on the slope of the reaction function being zero at equilibrium. Further examples of the relationship are also discussed.
A study on the microstructure of a nitrate ester plasticized polyether propellant dissolved in HCl and KOH solutions
Authors: Liu Yong , Wang Luoxin , Tuo Xinlin , Li Songnian , Yang Weimin
Published: June 2010

Understanding of how the properties and performance of nitrate ester plasticized polyether (NEPE) propellants relate to microstructure is complicated by numerous components that have different characteristics. One approach to alleviating these complications is to observe a microstructure that has lost one or several components. This article examines the dissolution process, mass loss and change of the ion concentration of propellants in acid and alkali solutions. A scanning electron microscope was used to observe the dissolved residual of the propellants. The results revealed that the main constituents of NEPE propellant have different dissolving properties in solutions of HCl and KOH. By monitoring the dissolution process of NEPE propellant in HCl and KOH solutions, it was found that the microstructure of the propellant is generally compact and the polymer binder not only binds all the other components, but also protects the inner part of the propellant in solution.
Intravenous Sedation with Low-Dose Dexmedetomidine: Its Potential for Use in Dentistry
Authors: Ogawa Sachie , Seino Hiroaki , Ito Hiroshi , Yamazaki Shinya , Ganzberg Steven , Kawaai Hiroyoshi
Published: June 2010

This study investigated the physiologic and sedative parameters associated with a low-dose infusion of dexmedetomidine (Dex). Thirteen healthy volunteers were sedated with Dex at a loading dose of 6 mcg/kg/h for 5 minutes and a continuous infusion dose of 0.2 mcg/kg/h for 25 minutes. The recovery process was observed for 60 minutes post infusion. The tidal volume decreased significantly despite nonsignificant changes in respiratory rate, minute ventilation, oxygen saturation, and end-tidal carbon dioxide. The mean arterial pressure and heart rate also decreased significantly but within clinically acceptable levels. Amnesia to pin prick was present in 69% of subjects. A Trieger dot test plot error ratio did not show a significant change at 30 minutes post infusion despite a continued significant decrease in bispectral index. We conclude that sedation with a low dose of Dex appears to be safe and potentially efficacious for young healthy patients undergoing dental procedures.
Phosphorus Uptake and Utilization Efficiency in Peanut1
Authors: Krishna K. R.
Published: June 2010

Cultivars of a crop can differ genetically with respect to their uptake, translocation, accumulation, and use of phosphorus. The objective of this paper was to evaluate genetic variation for P uptake and utilization among peanut (Arachis hypogaea L.) genotypes. Several traits contribute to the total P efficiency of the genotype, including root length, rate of P uptake per unit root length, leaf and pod characters such as P accumulation, and dry matter/yield produced per unit P absorbed [i.e., P efficiency ratio (PER)]. Peanut genotypes with increased P uptake and higher PER were identified. Some genotypes sustained higher PER at both low and high soil P availabilities.