bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorus Mobilization from Various Sediment Pools in Response to Increased pH and Silicate Concentration
Authors: Koski‐Vähälä J. , Hartikainen H. , Tallberg P. 
Published: June 2010

ABSTRACTPhosphorus (P) release from sediment particles to the interstitial water has been studied extensively, but the contribution of different inorganic P pools in sediment under differing environmental conditions is not fully understood. This study was undertaken to get more detailed information about the chemical mobilization mechanisms. Phosphorus mobilization from reserves bound by Al, Fe, and Ca compounds in response to increased pH and to inorganic silicon (Si) enrichments was investigated using a sequential fractionation analysis and an isotope‐labeling technique. The aerobic sediment of Lake Vesijärvi had a high P retention capacity, and Fe‐bound P was the largest inorganic P pool as well as the main source of released P. High Si addition (47 mg Si L−1 sediment) released more P to the interstitial water than did the elevation of pH from 6.6 to 9.5, since Si lowered the resorption of released P onto hydrated Al oxides. This finding reveals that P equilibrium between Fe‐bound and Al‐bound P in sediments regulates P net mobilization to the interstitial water under aerobic conditions. Furthermore, elevated pH combined with high Si enrichment had a positive synergistic effect, resulting in the most substantial P mobilization. This synergism may cause a self‐fueled increase in the internal loading of P. It accentuates the effect of diatom sedimentation on P fluxes in eutrophic lakes with high pH and may favor the appearance of bloom‐forming cyanobacteria.
Monitoring Nitrate Leaching from Submerged Drains
Authors: de Vos J.A. 
Published: June 2010

ABSTRACTMonitoring nitrate N (NO3–N) leaching is important in order to judge the effect that agricultural practices have on the quality of ground water and surface water. Measuring drain discharge rates and NO3–N concentrations circumvents the problem of spatial variability encountered by other methods used to quantify NO3–N leaching in the field. A new flow‐proportional drainage water sampling method for submerged drains has been developed to monitor NO3–N leaching. Both low and high discharge rates can be measured accurately, and are automatically compensated for fluctuations in ditch‐water levels. The total amount of NO3–N leached was 10.6 kg N ha−1 for a tile‐drained silt‐loam soil during the 114‐d monitoring period. The NO3–N concentrations fluctuated between 5 mg L−1 at deep ground water levels and 15 mg L−1 at shallow levels, due to variations in water flow. A flow‐proportional drainage water sampling method is required to measure NO3–N leaching accurately under these conditions. Errors of up to 43% may occur when NO3–N concentrations in the drainage water are only measured at intervals of 30 d and when the precipitation excess is used to estimate cumulative NO3–N leaching. Measurements of NO3–N concentrations in ground water cannot be used to accurately estimate NO3–N leaching in drained soils.
Kinetic Modeling of Bioavailability for Sorbed‐Phase 2,4‐Dichlorophenoxyacetic Acid
Authors: Park Jeong‐Hun , Kay Denise , Zhao Xianda , Boyd Stephen A. , Voice Thomas C. 
Published: June 2010

ABSTRACTThe degradation rate of 2,4‐dichlorophenoxyacetic acid (2,4‐D) was studied in silica–slurry systems to evaluate the bioavailability of sorbed‐phase contaminant. After the silica particles were saturated with 2,4‐D, the system was inoculated with the 2,4‐D–degrading microorganism Flavorbacterium sp. strain FB4. The disappearance rate of 2,4‐D was found to be greater than the rate predicted based upon liquid‐phase 2,4‐D concentrations. A kinetic formulation, termed the enhanced bioavailability model, was developed to describe the desorption and biodegradation processes in this batch system. The approach assumes that 2,4‐D resides in both the liquid and solid phases and degradation occurs via both suspended and attached biomass. All biomass can degrade liquid‐phase 2,4‐D at one rate, while only attached biomass can degrade sorbed 2,4‐D at another rate. An enhanced transformation factor (Ef) was introduced to express the increased biodegradation rate over that expected from the liquid phase only. This approach was able to account for the increased degradation rates observed experimentally. The results provide evidence that desorption to the bulk solution is not prerequisite to degradation, and that sorbed substrate may be available for degradation.
Influence of Quaternary Ammonium on Sorption of Selected Metal Cations onto Clinoptilolite Zeolite
Authors: Li Zhaohui , Alessi Daniel , Allen Lori 
Published: June 2010

ABSTRACTClay 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

ABSTRACTThe 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

ABSTRACTManure 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

ABSTRACTEstablishing 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

ABSTRACTWater 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

ABSTRACTEnzyme 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

ABSTRACTPlant 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

ABSTRACTExcessive 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

ABSTRACTThe 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

ABSTRACTReducing 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

ABSTRACTSoils 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.