bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Hydraulic Fracturing Results Utilizing Microfrac Testing in a West Siberia Field
Authors: Karpov V. B. , Parshin N. V. , Ryazanov A. A. , Zheng Y. , Kornilov A. V. , Moiseenko A. A. 
Published: October 2017

Abstract
Identification and quantification of in-situ stress barriers is a crucial part of every hydraulic fracturing design and treatment programme. The absence of stress barriers may lead to significant vertical growth of the fracture, creating a channel between the oil-bearing intervals and potential undesirable water-bearing formations.
This paper presents a case study where the in-situ stress profile in a tight oilfield in West Siberia was re-calibrated. The original stress profile, which was based on core analysis, gamma ray and acoustic data, indicated the stress contrast was enough to contain the fracture within the producing layer. Unexpectedly, high water cut between 60 to 70 % was reported in the horizontal wells, where multi-stage hydraulic fracturing was performed and the source of water production was uncertain.
Consequently, straddle packer microfrac testing was conducted in one well to create a more detailed and better-constrained stress profile in the target oil-bearing formation as well as in the bounding shale above and below. The data obtained indicated very little stress contrast between the production layer and the surrounding shale layers. The revised stress model differed significantly from what was typically used in West Siberia. The updated hydraulic fracture model showed that excess height growth into the surrounding shale barriers was likely, and breakthrough into the water-bearing layer located 50 to 70 meters above could explain the high observed water cuts in the treated wells.
Assuming a uniform stress profile along the lateral, the hydraulic fracture design was then optimized to decrease the risk of breakthrough into the water zone. The optimized treatments involved low-viscosity fracturing fluid and also a reduced amount of proppant per stage used in the treatment. The optimized hydraulic fracture treatment was performed in several horizontal wells, which saw a reduction in the initial water cut to below 10%, and also experienced an increase in oil production. This demonstrates the importance of having reliable stress measurements for hydraulic fracturing design.
Multinuclear Magnetic Resonance Analysis of Two Humic Acid Fractions from Lowland Rice Soils
Authors: Mahieu N. , Olk D.C. , Randall E.W. 
Published: October 2017

ABSTRACTTo determine the effects of intensive cropping of tropical lowland rice (Oryza sativaL.) and the associated long‐term soil submergence on chemical properties of soil organic matter, we used solid‐state13C and15N and solution31P nuclear magnetic resonance (NMR) spectroscopy to analyze the labile mobile humic acid (MHA) and the more recalcitrant calcium humate (CaHA) fractions extracted from a series of soils supporting several long‐term field experiments in the Philippines. The soils varied mainly in degree of submergence and cropping intensity, ranging from a rainfed rice field without soil submergence to irrigated double‐ and triple‐cropped fields in which soil remains submerged almost all year long. As reported previously, all analyses associated increasing intensity of rice cropping with larger proportions of less humified material in the MHA and CaHA, such as diester phosphorus (P), amide nitrogen (N), and phenolic carbon (C). We established significant correlations between proportions of various spectral areas as well as between some spectral areas and other humic acid (HA) properties such as visible light absorption and free radical concentration (positive indices of humification) and hydrogen (H) concentration (negative index of humification). For example, spectral proportions of heterocyclic N were positively, and proportions of amide N and phenolic C negatively, correlated with visible light absorption and free radical concentration, and each of these spectral proportions had an opposite sign when correlated with H concentration. The correlations of N‐alkyl C proportions were the strongest with these properties and with other functional group proportions.
Enzymatic Transformation and Binding of Labeled 2,4,6‐Trinitrotoluene to Humic Substances during an Anaerobic/Aerobic Incubation
Authors: Thiele S. , Fernandes E. , Bollag J.‐M. 
Published: October 2017

ABSTRACTOrganic pollutants are degraded in soil and simultaneously non‐extractable residues are formed. However, proof is lacking that this fixation has a detoxifying effect. We investigated the transformation and binding of 2,4,6‐trinitrotoluene (TNT) with catechol or soil humic acid as cosubstrates. Carbon‐14‐labeled TNT and its reaction products were quantified by radiocounting; extractable compounds were identified by high performance liquid chromatography (HPLC). Bound and extractable residues of 15N‐labeled TNT and metabolites were studied by 15N nuclear magnetic resonance spectroscopy (15N NMR). Since TNT is not easily transformed under oxidizing conditions an anaerobic/aerobic treatment was used. Anaerobic microorganisms from cow manure were used to reduce TNT during the anaerobic phase and subsequently, a laccase from Trametes villosa was used in the aerobic phase to oxidatively couple the metabolites to humic matter. Seventy‐four percent of TNT was immobilized with catechol as cosubstrate, but only 25% with humic acid. With catechol the main extractable component was TNT, while with humic acid it was mostly the metabolite 4‐aminodinitrotoluene. For both co‐substrates, the spectra of immobilized metabolites obtained by solid‐state 15N‐cross polarization magic angle spinning (CPMAS) NMR spectroscopy showed signals in the chemical shift region for protonated aromatic amino compounds. However, in the presence of catechol, an additional signal from non‐extractable nitro groups was found, which could represent sequestered TNT. The partially reduced metabolites of TNT that formed non‐extractable residues in humic acid are not likely to be remobilized easily and are thus regarded as detoxified.
Imaging of Water Flow in Porous Media by Magnetic Resonance Imaging Microscopy
Authors: Deurer Markus , Vogeler Iris , Khrapitchev Alexander , Scotter Dave 
Published: October 2017

ABSTRACTMagnetic resonance imaging (MRI) was used to study the flow of water in a column 14 mm in diameter packed with glass beads. The sample was fully saturated and water was pumped through the column using a peristaltic pump, at flow rates of 125 and 250 mL h−1This corresponds to mean velocities of 0.5 and 1 mm s−1, given a porosity of 0.46 m3m−3Nuclear magnetic resonance (NMR) images of the proton density and velocities within a 2‐mm slice were taken at a spatial resolution of 0.15 × 0.15 × 2 mm3At a mean pore water velocity of 1 mm s−1we approximated hydrodynamic dispersion using NMR‐measured velocity distributions in a 2‐mm slice through the sample. Additionally, we conducted a step pulse tracer experiment with chloride through the same column and at identical initial and boundary conditions. We fitted the convection–dispersion equation to the breakthrough curve and compared the column scale dispersion of the tracer experiment with the respective NMR estimate derived at the slice scale.
Combination Effect of Light and Toxicity in Algal Tests
Authors: Cleuvers Michael , Altenburger Rolf , Ratte Hans Toni 
Published: October 2017

ABSTRACTThe sensitivity of Scenedesmus subspicatus against potassium dichromate is positively correlated to the photon flux density during the algal growth inhibition test. Low photon flux densities led to significantly reduced maximum effects and higher EC50 levels. To improve the testing of colored substances, we distinguished between the toxic effect (chemical part, represented by potassium dichromate) and the shading effect (physical part, simulated by reduced light intensities during the test) of a hypothetical light absorbing substance. The contribution of these single effects to the total inhibition varied greatly. At high concentrations of potassium dichromate (1.6 and 3.2 mg L−1) the physical part never exceeded 25% of the total inhibition, not even at strongest light reduction, while at low concentrations (0.2 and 0.4 mg L−1) the physical effect became more prominent when halving the amount of available light. Further, the combination effect of the chemical and the physical effect could be calculated well only by using the concept of independent action. Thus, if chemical and physical effects are measured in combination, as is the case in tests with dyestuffs, the current test protocol for the algal growth inhibition test may lead to incorrect estimations of the toxic potential.
Chemistry of Inorganic Arsenic in Soils
Authors: Smith E. , Naidu R. , Alston A. M. 
Published: October 2017

ABSTRACTThere are more than 10000 arsenic (As) contaminated sites in Australia. The ability of soils at these contaminated sites to sorb As is highly variable and appreciable amounts of As have been recorded in the subsurface soils. The potential risk of surface and ground water contamination by As at these sites is a major environmental concern. Factors that influence adsorption capacity of soils influence the bioavailability and subsequent mobility of As in soils. In the present study we investigated the effect of PO3−4 and Na+ and Ca2+ on the sorption of AsV and AsIII by an Oxisol, a Vertisol, and two Alfisols. The presence of P (0.16 mmol L−1) greatly decreased AsV sorption by soils containing low amounts of Fe oxides (<100 mmol kg−1), indicating competitive adsorption between P and AsV for sorption sites. In contrast, the presence of a similar amount of P had little effect on the amount of AsV adsorbed by soils with high Fe content (>800 mmol kg−1). However, AsV sorption substantially decreased from 0.63 to 0.37 mmol kg−1 as P concentration was increased from 0.16 to 3.2 mmol L−1 in selected soils. This suggests increased competition between P and AsV for soil sorption sites, through either the higher affinity or the effect of mass action of the increasing concentration of P in solution. A similar effect of P on AsIII sorption was observed in the low sorbing Alfisol and high affinity Oxisol. However, the amount of AsIII sorbed by the Oxisol was much greater than the Alfisol for all treatments. The presence of Ca2+ increased the amount of AsV sorbed compared with that of Na+ and was manifested through changes in the surface charge characteristics of the soils. A similar trend in AsIII sorption was recorded with changes in index cation, although the effect was not as marked as recorded for AsV
Dissolution Kinetics of Heavy Metals in Dutch Carbonate‐ and Sulfide‐Rich Freshwater Sediments
Authors: Buykx S. E. J. , van den Hoop M. A. G. T. , Loch J. P. G. 
Published: October 2017

ABSTRACTIn two sulfide‐rich freshwater sediments from the Biesbosch and Kromme Rijn River in the Netherlands differing in carbonate content and acid volatile sulfide (AVS) content, metal and sulfide dissolution kinetics were studied at different acid concentrations by varying both the procedure of acid addition and the extraction time. The establishment of equilibrium was monitored by measuring the pH in time, which reached a near constant value. The equilibrium pH was reached quickly when large amounts of acid were added and slowly when small amounts of acid were added. This observation was confirmed by the yield of extracted metals after either a 45‐min or 24‐h extraction over a pH range from 0 to 5. The pH factor seemed to be of more influence than time for the dissolution of metals. The amount of extracted metals was highly dependent on the metal itself due to its physico–chemical behavior. Although the sediments studied varied in carbonate content, acid volatile sulfide (AVS), and total metal content, the extracted fraction of metals compared with their total content in the sediment was similar for most metals. Finally, the AVS content as well as the ratio of simultaneously extracted metals (SEM; sum of Cd, Cu, Ni, Pb, and Zn) to AVS decreased with increasing pH. Because the SEM to AVS ratio may be used to set environmental quality criteria for the sediment compartment, this observation is of significance.
Concentration, pH, and Surface Charge Effects on Cadmium and Lead Sorption in Three Tropical Soils
Authors: Appel Chip , Ma Lena 
Published: October 2017

ABSTRACTReactions of heavy metals with soil are important in determining metal fates in the environment. Sorption characteristics of two heavy metals, Cd and Pb, in three tropical soils (Mollisol, Oxisol, and Ultisol) from Puerto Rico were assessed at varying metal concentrations (0 to 1.2 mM) and pH values (approximately 2 to 7). All soils sorbed more Pb than Cd. Sorption maxima were obtained for each metal for the Oxisol and Ultisol soils, but not the Mollisol. Sorption appeared to depend more on soil mineralogy than organic matter content. Sorption isotherms were linear within the sorption envelope with similar slopes for each soil–metal curve, when plotting metal sorption as a function of pH. Cadmium and Pb isotherms yielded average slopes of approximately 36 ± 1 and 28 ± 1 units (percent increase in metal sorption per 1‐unit increase in pH), respectively. Metal sorption depended more on metal type than soil composition. Cadmium sorption displayed a greater pH dependence than Pb. Cadmium sorption was less than or equal to the amount of negative surface charge except at pH values greater than the point of zero net charge (PZNC). This suggests that Cd was probably sorbed via electrostatic surface reactions and/or possible inner‐sphere complexation at pH > 3.7. However, the amount of Pb sorbed by the Oxisol was greater than the amount of negative surface charge, suggesting that Pb participates in inner‐sphere surface reactions. Lead was sorbed more strongly than Cd in our soils and poses less of a threat to underlying ground water systems due to its lower mobility and availability.
Rhizosphere Acidification and Cadmium Uptake by Strawberry Clover
Authors: Jauert P. , Schumacher T. E. , Boe A. , Reese R. N. 
Published: October 2017

ABSTRACTStrawberry clover (Trifolium fragiferum L.) is a hardy legume found in indigenous or introduced populations throughout the world. Tolerance to saline and alkaline soils, flooding, and heavy metals make it a good prospect for reclamation projects. The research, described here, was conducted to: (i) characterize the morphological variation in plants from available seed sources, (ii) evaluate cadmium uptake and tolerances over a wide range of morphological variants, and (iii) elucidate the variability in the effects of roots on rhizosphere pH and the relationship to cadmium uptake. Seeds from selected accessions were planted in the greenhouse for comparison of morphological variation. The accessions examined had a mean height of 10.7 ± 7 cm. Accessions 254916 and 237925 are tall with high rhizosphere pH values and might be useful in phytoremediation. Strawberry clover accessions were also grown hydroponically to examine differences in cadmium uptake. The ability of strawberry clover roots to change rhizosphere pH and take up cadmium was examined using culture tubes containing nutrient agar, a moderate level of cadmium, and a pH indicator dye. The results provided evidence for a negative correlation between rhizosphere pH and cadmium uptake.
Fate of Nitrate and Bromide in an Unsaturated Zone of a Sandy Soil under Citrus Production
Authors: Paramasivam S. , Alva A. K. , Fares A. , Sajwan K. S. 
Published: October 2017

ABSTRACTUnderstanding water and nutrient transport through the soil profile is important for efficient irrigation and nutrient management to minimize excess nutrient leaching below the rootzone. We applied four rates of N (28, 56, 84, and 112 kg N ha−1; equivalent to one‐fourth of annual N rates being evaluated in this study for bearing citrus trees), and 80 kg Br− ha−1 to a sandy Entisol with >25‐yr‐old citrus trees to (i) determine the temporal changes in NO3–N and Br− distribution down the soil profile (2.4 m), and (ii) evaluate the measured concentrations of NO3–N and Br− at various depths with those predicted by the Leaching Estimation and Chemistry Model (LEACHM). Nitrate N and Br− concentrations approached the background levels by 42 and 214 d, respectively. Model‐predicted volumetric water content and concentrations of NO3–N and Br− at various depths within the entire soil profile were very close to measured values. The LEACHM data showed that 21 to 36% of applied fertilizer N leached below the root zone, while tree uptake accounted for 40 to 53%. Results of this study enhance our understanding of N dynamics in these sandy soils, and provide better evaluation of N and irrigation management to improve uptake efficiency, reduce N losses, and minimize the risk of ground water nitrate contamination from soils highly vulnerable to nutrient leaching.
Microcosm Wetlands for Wastewater Treatment with Different Hydraulic Loading Rates and Macrophytes
Authors: Jing Shuh‐Ren , Lin Ying‐Feng , Wang Tze‐Wen , Lee Der‐Yuan 
Published: October 2017

ABSTRACTConstructed wetlands (CW) usually require large land areas for treating wastewater. This study evaluated the feasibility of applying CW with less land requirement by operating a group of microcosm wetlands at a hydraulic retention time (HRT) of less than 4 d in southern Taiwan. An artificial wastewater, simulating municipal wastewater containing 200 mg L−1 of chemical oxygen demand (COD), 20 mg L−1 of NH+4–N (AN), and 20 mg L−1 of PO3−4–P (OP), was the inflow source. Three emergent plants [reed, Phragmites australis (Cav.) Trin. ex Steud.; water primrose, Ludwigia octovalvis (Jacq.) P.H. Raven; and dayflower, Commelina communis L.] and two floating plants [water spinach, Ipomoea aquatica Forssk.; and water lettuce, Pistia stratiotes L.] plants were tested. The planted systems showed more nutrient removal than unplanted systems; however, the type of macrophytes in CW did not make a major difference in treatment. At the HRTs of 2 to 4 d, the planted system maintained greater than 72, 80, and 46% removal for COD, AN, and OP, respectively. For AN and OP removal, the highest efficiencies occurred at the HRT of 3 d, whereas maximum removal rates for AN and OP occurred at the HRT of 2 d. Both removal rates and efficiencies were reduced drastically at the HRT of 1 d. Removals of COD, OP, and AN followed first‐order reactions within the HRTs of 1 to 4 d. The efficient removals of these constituents obtained with HRT between 2 and 4 d indicated the possibility of using a CW system for waste‐water treatment with less land requirement.
A Time‐Saving Method for Higher Plant Tests in Hydroculture
Authors: Andersohn Cornelia , Fuchs Maike , Seyed‐Mansouri Regina , Fleischmann Susanne , Wilke Berndt‐Michael 
Published: October 2017

ABSTRACTFor higher plant tests in hydroculture we developed a method to unify the usually separately performed germination and growth testing. This method renders unnecessary the time‐consuming and laborious installation of the germinated plants into the growth system.
Ascomicetes (Fungi: Ascomycota) del Parque Estatal Agua Blanca, Macuspana, Tabasco, México
Authors: Ávalos Lázaro Abisag Antonieta , Rosique Gil José Edmundo , Cappello García Silvia , Villarruel Ordaz José Luis 
Published: October 2017

Antecedentes y Objetivos: La diversidad de los ascomicetos macroscópicos que se conoce actualmente en el Parque Estatal Agua Blanca, Tabasco, es el resultado de varias investigaciones previas sobre todos los macromicetos a nivel estatal. Como no existe un estudio específico sobre los ascomicetos del parque antes mencionado, en este trabajo se reunieron los registros anteriores con los resultados de nuevas exploraciones de este proyecto.Métodos: El Parque Estatal Agua Blanca se ubica en la región Oeste y Noreste del estado de Tabasco, México. Se realizaron 28 recorridos entre diciembre del 2011 y julio del 2015. El material recolectado se depositó en el herbario UJAT para su preservación e identificación. La identificación de las muestras se realizó siguiendo las técnicas convencionales de micología.Resultados clave: Se revisaron 129 especímenes, los cuales permitieron la determinación de 22 especies pertenecientes a dos clases, tres órdenes, cinco familias y ocho géneros. Los géneros Scutellinia y Rosellinia se reportan por primera vez para el estado. El género Xylaria es el más diverso con 10 especies, mientras que los géneros Ophiocordyceps, Scutellinia, Hypoxylon y Rosellinia son los menos diversos con una especie cada uno.Conclusiones: De las 22 especies determinadas, 12(55%) fueron nuevas citas para Tabasco y 18(82%) lo son para la zona de estudio, mientras que 10(45%) ya se habían encontrado previamente en Tabasco y 4(18%) en el parque. Finalmente, este estudio muestra un mayor número de especies evaluadas en comparación con lo reportado en trabajos previos.
Disparity between Nephrologists’ Opinions and Contemporary Practices for Community Follow-Up after AKI Hospitalization
Authors: Karsanji Divya J. , Pannu Neesh , Manns Braden J. , Hemmelgarn Brenda R. , Tan Zhi , Jindal Kailash , Scott-Douglas Nairne , James Matthew T. 
Published: October 2017

Background and objectives
Recent guidelines suggest that patients should be evaluated after AKI for resolution versus progression of CKD. There is uncertainty as to the role of nephrologists in this process. The objective of this study was to compare the follow-up recommendations from nephrologists with contemporary processes of care for varying scenarios of patients hospitalized with AKI.

Design, setting participants, & measurements
We surveyed Canadian nephrologists using a series of clinical vignettes of patients hospitalized with severe AKI and asked them to rank their likelihood of recommending follow-up for each patient after hospital discharge. We compared these responses with administrative health data on rates of community follow-up with nephrologists for patients hospitalized with AKI in Alberta, Canada between 2005 and 2014.

Results
One hundred forty-five nephrologists participated in the survey (46% of the physician membership of the Canadian Society of Nephrology). Nephrologists surveyed indicated that they would definitely or probably re-evaluate patients in 87% of the scenarios provided, with a higher likelihood of follow-up for patients with a history of preexisting CKD (89%), heart failure (92%), receipt of acute dialysis (91%), and less complete recovery of kidney function (98%). In contrast, only 24% of patients with similar characteristics were seen by a nephrologist in Alberta within 1 year after a hospitalization with AKI, with a trend toward lower rates of follow-up over more recent years of the study. Follow-up with a nephrologist was significantly less common among patients over the age of 80 years old (20%) and more common among patients with preexisting CKD (43%) or a nephrology consultation before or during AKI hospitalization (78% and 41%, respectively).

Conclusions
There is a substantial disparity between the opinions of nephrologists and actual processes of care for nephrology evaluation of patients after hospitalization with severe AKI.