Lack of increased availability of root-derived C may explain the low N2O emission from low N-urine patches

Urine deposition on grassland causes significant N₂O losses, which in some cases may result from increased denitrification stimulated by labile compounds released from scorched plant roots. Two 12-day experiments were conducted in ¹³C- labelled grassland monoliths to investigate the link between N₂O production and carbon mineralization following application of low rates of urine-N. Measurements of N₂O and CO₂ emissions from the monoliths as well as C signal of evolved CO₂ were done on day −4, −1, 0, 1, 2, 4, 5, 6 and 7 after application of urine corresponding to 3.1 and 5.5 g N m⁻² in the first and second experiment, respectively. The C signal was also determined for soil organic matter, dissolved organic C and CO₂ evolved by microbial respiration. In addition, denitrifying enzyme activity (DEA) and nitrifying enzyme activity (NEA) were measured on day −1, 2 and 7 after the first urine application event. Urine did not affect DEA, whereas NEA was enhanced 2 days after urine application. In the first experiment, urine had no significant effect on the N₂O flux, which was generally low (−8 to g N₂O-N m⁻² h⁻¹). After the second application event, the N₂O emission increased significantly to g N₂O-N m⁻² h⁻¹ and the N₂O emission factor for the added urine-N was 0.18%. However, the associated ¹³C signal of soil respiration was unaffected by urine. Consequently, the increased N₂O emission from the simulated low N-urine patches was not caused by enhanced denitrification stimulated by labile compounds released from scorched plant roots.     

Selective oxidation of cyclohexane in supercritical carbon dioxide

A feasibility study into the novel concept of using molecular oxygen to carry out one-step catalytic oxidation of cyclohexane to adipic acid in supercritical carbon dioxide over two types of catalysts, namely and Ag polyoxometallate, the silver decamolybdodivanadophosphate was carried out. Poor activity and selectivity towards adipic acid were initially noted over the aqueous micellar catalyst for the cyclohexane oxidation in supercritical carbon dioxide while under comparable conditions, the same catalyst gave a high activity for alkylaromatics oxidation to corresponding acids. It was later found that the adipic acid, being the extremely polar oxidised products, was virtually insoluble in the supercritical phase, which was rapidly degraded to carbon oxides after its prolonged contact with catalyst and O₂. Thus, the one-step cyclohexane oxidation to adipic acid with good selectivity can only be achieved by modifying the solvent with acetic acid or methanol, which enabled isolation of the acid from further oxidation. On the other hand, , in methanol modified supercritical carbon dioxide gave an impressive selectivity for cyclohexane conversion to other oxygenates.     

Nitrogen transformations in a flooded soil in the presence and absence of rice plants: 2. Denitrification

Denitrification rates (d) in a flooded alkaline clay were measured following addition of either to the floodwater, by collecting evolved N₂ + N₂O in an enclosure in the absence or presence of rice plants. Similar estimates of d were obtained in the treatment when the isotopic composition of the enclosed atmosphere was determined using arc redistribution or direct mass spectrometric analysis. Approximately 90% of the gaseous products of denitrification were physically trapped in the soil five days after addition. Mechanical shaking of the soil-water system was an effective method for releasing entrapped gas. Denitrification showed a marked diurnal variation in both and treatments planted to rice, with higher rates during the day than at night. Measured rates of denitrification were higher in planted than in unplanted pots for both and treatments for normal gas sampling. However, evidence was obtained that this was not a real effect, but was due to release of entrapped gas. Denitrification losses corrected for gas entrapment were estimated at <5% of applied . The ¹⁵N mass balance indicated that a much larger amount of applied ammonium (15–25%) was lost by NH₃ volatilisation. The rate of denitrification corrected for gas entrapment was similar to the rate of nitrification estimated by inhibition of ammonium oxidation. Although the inhibitors 2-ethynylpyridine and acetylene prevented denitrification by effectively inhibiting nitrification of , the total recovery of ¹⁵N in the soil-plant system did not increase. The total recovery of was 7–9% higher in the presence than in the absence of rice.     

Electrocatalytic activity of copper alloys for \hbox{NO}_{3}^{-} reduction in a weakly alkaline solution Part 1: Copper–zinc

A comparative study of the influence of an addition of Zn to Cu as the basic cathode material on electrocatalytic activity for reduction was performed. Potentiodynamic measurements using a rotating ring-disk electrode were carried out in an artificial solution simulating solution after regeneration of the ion-exchange column for removal in drinking water treatment. The results were verified by batch electrolysis experiments. An enhancement of the electrocatalytic activity was observed. Unfortunately, NH₃ was found to be the main reduction product. The highest electrocatalytic activity was obtained using an electrode containing 41 wt.% Zn.     

Evaluation of the N2O emissions from N in plant residues as affected by environmental and management factors

A review of the N₂O-N emission from crop residues was conducted based on new data published during the last decade. The result indicated that factors as type of crop, biochemical quality of residues, agricultural management, climate and season of the year, soil properties and soil moisture play a significant role in the rate of N₂O-N emissions. An emission factor (EF) equal to 1.055% of N applied in plant residues – derived from a simple linear regression of emitted N₂O-N (kg ha^?1) on N applied in crop residues (kg ha^?1) – represent an estimate that explains about 60% of emission variations. However, the EF of N applied in plant residues is not a constant but a variable coefficient that depends on environmental and management variables. The following two linear models – that estimate emitted N₂O-N (kg ha^?1) as a function of the variables N (kg ha^?1) applied in plant residues (NPR), rain (mm), temperature (°C) and temperature²(°C²) – were fitted to the dataset with 45 observations obtained from the reviewed literature. $$\hskip1.5pc\hbox{N}_{2}\hbox{O}\hbox{-}\hbox{N}=-4.154+0.00955\hbox{ NPR}+1.7278\hbox{ ApM}+0.003996\hbox{ Rain }+0.6242\hbox{ Tem }-0.0230\hbox{ Tem}^{2}$$ and $$\hbox{N}_{2}\hbox{O}\hbox{-}\hbox{N}= 0.6535 + [-0.0404 + 0.0078\hbox{ ApM }+ 0.000044\hbox{ Rain }+ 0.00567\hbox{ Tem }-0.0001975\hbox{ Tem}^{2}]\hbox{ NPR }$$ Both models provided almost equally good statistical fit to the data, with R ²=0.832 and R ²=0.829, respectively, and most regression coefficients being significant at $P < 0.01$ . Because of its internal structure, the second model is more appealing as it represents N₂O-N emission as a transformation that is affected by management and environmental variables. The following expression – that correspond to the quantities in the square bracket at the right hand side of the second model – is the coefficient for the variable N applied in crop residues, and represent the emission factor as a function of application method of plant residues, rain, temperature and temperature². $$\hskip3.5pc\hbox{EF }=-0.0404+0.0078\hbox{ ApM }+0.000044\hbox{Rain }+0.00567\hbox{ Tem }- 0.0001975\hbox{ Tem}^{2}$$ Standardization of research methodologies and data gathering and reporting, including kind of crop, N content of applied residues, agricultural management, length of the measuring period, climate, soils properties, soil temperature and water content, would facilitate further advances in studies oriented to increase the precision of N₂O-N emission estimates.     

Controlling Reaction Pathways for Alcohol Dehydration and Dehydrogenation over FeSBA-15 Catalysts

The iron location in FeSBA-15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated $\hbox{Fe}^{3+}The iron location in FeSBA-15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated species in the amorphous silica phase. At higher loading additional aggregated forms of iron oxide exist. Isolated species in the silica matrix imply Br?nsted acidity resulting in selective formation of ethylene, whereas clusters catalyze formation of ethylene and aldehyde.     

Long-term effects of inorganic fertilizers and manure on phosphorus reaction products in a Typic Ustochrept

Phosphorus availability from residual P sources in soil is virtually the chemistry of metastable P compounds, i.e., their solubility and interaction with other soil and plant components. Identification of these compounds in soils under long-term application of fertilizers and farmyard manure is unstated and is prerequisite to comprehend the processes of P transformations and cycling in soil-plant system. X-ray diffraction analysis of surface and subsurface soils fertilized for 32 years under a maize–wheat–cowpea (fodder) cropping sequence revealed that P reaction products in soil depends upon the kind of fertilizer added to the soil as well as on management practices. Precipitation of applied P occurred mainly as octa-calcium phosphate, hydroxy apatite and variscite. In addition to these compounds, precipitation as was also observed in soil receiving diammonium phosphate rather than super phosphate as a fertilizer P source. Continuous application of farmyard manure (FYM) for three decades inhibited the conversion of applied P to more stable forms such as variscite and hydroxy apatite. The different P reaction products govern the availability of residual soil-P to growing plants. The reaction products formed were associated only with the sand and silt fraction of soil. Phosphorus in the clay fraction is mainly P adsorbed on exchange complexes or entrapped in lattice of silicate minerals.     

A simple and efficient oxidation system for the oxidation of alcohols utilizing Oxone® as oxidant catalyzed by polymer-supported 2-iodobenzamide

$\begin{array}{l}{\hbox{R}^1\hbox{R}^2\hbox{CHOH}} \\ {\hbox{RCH}_2\hbox{OH} }\end{array} \dynrightarrow{Oxone}{\hbox{CH}_3\hbox{CN/H}_2\hbox{O}, 70^{\circ}\hbox{C}} \begin{array}{l}{\hbox{R}^1\hbox{R}^2\hbox{CO}} \\ {\hbox{RCOOH}} \end{array} A simple and environmentally friendly procedure for the oxidation of alcohols is presented utilizing Oxone^? (2KHSO₅ · KHSO₄ · K₂ SO₄) as oxidant and polymer-supported 2-iodobenzamide as catalyst in CH₃CN/H₂O mixed solvents.     

Promotional effects on a PtRu/C catalyst-electrode interfaced with aqueous electrolytes: electrochemical metal support interaction (EMSI) and electrochemical promotion of catalysis (EPOC)

The kinetics of the catalytic oxidation of H₂ on PtRu/C gas diffusion electrode (GDE) was studied by interfacing the electrode with aqueous electrolytes at different pH values. The conducting electrolytes were aqueous solutions of varying concentrations of KOH and HClO₄ so that the pH was ranging between 2 and 13. The open circuit catalytic reaction rates exhibit the lowest value at pH = 13, while the catalytic activity is progressively increasing with decreasing pH values. The enhancement of the open circuit catalytic reaction rate can be even an order of magnitude higher in the acidic solution with respect to the alkaline electrolyte. It is shown that the nature of the aqueous electrolyte plays the role of an active catalyst support for the PtRu/C electrode, which drastically affects its catalytic properties. This is substantiated through the electrochemical equilibrium charge transfer reactions at the catalyst-electrode/electrolyte interface:

Syntheses and Characterization of Diorganotin Derivatives of 2-Mercapto-5-methyl-1,3,4-thiadiazole: X-ray Crystal Structure of Polymeric (C3H3S2N2) [(n-C4H9)6Sn3O(OH)2](C3H3S2N2)

Diorganotin derivatives of 2-mercapto-5-methyl-1,3,4 -thiadiazole, (R = Me 1, n-Bu 2, Ph 3, PhCH₂ 4), have been synthesized and characterized by IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. Among them, polymer 2 was also characterized by X-ray crystallography diffraction analysis. This revealed that 2 showed a unique tricyclic structure consisting of a fused five-membered Sn₂ON₂ ring and a four-membered Sn₂O₂ ring. These formed a planar N₂Sn₃O₂ skeleton, with distorted trigonal bipyramidal coordination at the two tin centers and a distorted octahedral coordination at the other tin center. The supramolecular structure of polymer 2 was a 1D zig-zag polymeric chain stabilized by intermolecular O–H...S hydrogen bonds. An erratum to this article can be found at     

Electrochemical redox reactions of chromium and iron ions in molten NaCl–2CsCl eutectic for pyro-reprocessing of nuclear fuels

Basic electrochemical and spectroscopic properties of Cr³⁺, Cr²⁺, Fe³⁺, and Fe²⁺ were studied to analyze the cyclic redox reactions of Cr and Fe, which may decrease the current efficiency of the electro-winning method using NaCl–2CsCl melts. The formal redox potentials of the and couples, and , in NaCl–2CsCl melts at 923 K were spectroelectrochemically determined to be −0.648 ± 0.005 V and , respectively. These values were determined by measuring electromotive force and UV–VIS absorption spectra at varying concentration ratios of trivalent and divalent ions. Cyclic voltammetry was also carried out to examine the characteristics of the voltammograms for the and couples in NaCl–2CsCl melts. The determined by the spectroelectrochemical method was close to that determined by cyclic voltammetry . The effect of temperature on the in NaCl–2CsCl melts was studied by cyclic voltammetry in the range from 823 to 1,023 K . Diffusion coefficients of Cr³⁺ and Cr²⁺, and , were determined between 823 and 1,023 K to be and , respectively. Molar absorptivities of Cr³⁺ and Cr²⁺ in NaCl–2CsCl melts at 923 K were determined to be 77.8 ± 2.4 M⁻¹ cm⁻¹ at 17,670 cm⁻¹ and 48.0 ± 1.4 M⁻¹ cm⁻¹ at 9,170 cm⁻¹, respectively. In addition, the effects of these ions on the cyclic redox reaction of the pyro-reprocessing process were discussed.     

The titanium/hydrogen system as the solid-state reference in high-temperature proton conductor-based hydrogen sensors

It has been demonstrated that a mixture of the solid solutions of hydrogen in -titanium and -titanium may be applied as a solid-state hydrogen reference electrode in conjunction with the high-temperature proton-conducting solid electrolyte . The design and preparation of a sensor that incorporates this type of reference electrode are described, and coulometric titration experiments as well as cell voltage measurements are presented and discussed. The activity of the residual oxygen in the reference material has been identified as a critical parameter that needs to be controlled in order to ensure reliable and reproducible sensor performance. The impact of other impurities in the reference material is also considered.     

Stability of the electrodeposition process for CoPt alloy formation

The stability of the process for electrodeposition of CoPt alloys from ammonium citrate electrolytes containing [Pt(NO₂)₂(NH₃)₂]⁰ as the source of Pt was studied. Voltammetric monitoring of the anodic oxidation of the electrolyte and deposition of CoPt on the cathode showed the effect of the changes of the nature of the Pt complex on the performance of the plating bath. Anodic oxidation of the Pt complex was shown to involve mainly the oxidation of and to some extent NH₃ ligands. The cathodic process is accompanied by reduction of free The reduction of this anion in the bound form is highly inhibited. In contrast, its oxidation at the anode proceeds almost as readily in the bound form as that in the free form.     

The inhibition of copper–nickel alloy corrosion under controlled hydrodynamic condition in seawater

A comparative study of the corrosion resistance of a bare Cu–10 Ni alloy and a Cu–10 Ni alloy protected by sodium-diethyl-dithiocarbamate (NaEt₂dtc) has been undertaken. The experimental conditions varied from quiescent natural seawater to seawater subjected to jet impingement of different fluid velocities. The mechanism of inhibitor action has been suggested that includes the formation of a surface chelate compound between the dissolving metal ion and the (Et₂dtc)⁻ ligand, as well as formation of a 3-D ternary surface complex. The surface layer that incorporates both the inhibitor and the cuprous oxide, represented by the structure: has shown an excellent protective performance with efficiency > 90% under stagnant and fluid impingement conditions.     

A spatially explicit methodology to quantify soil nutrient balances and their uncertainties at the national level

A soil nutrient balance is a commonly used indicator to assess changes in soil fertility. In this paper, an earlier developed methodology by Stoorvogel and Smaling to assess the soil nutrient balance is given a major overhaul, based on growing insights and advances in data availability and modelling. The soil nutrient balance is treated as the net balance of five inflows (mineral fertilizer, organic inputs, atmospheric deposition, nitrogen fixation and sedimentation) and five outflows (crop products, crop residues, leaching, gaseous losses and erosion). This study aims to improve the existing methodology by making it spatially explicit, improving various transfer functions, and by modelling explicitly the uncertainties in the estimations. Spatially explicit modelling has become possible through a novel methodology to create a simulated land use map on the basis of the principles of traditional qualitative land evaluation. New literature data on the various inputs and outputs allowed improvement of the estimations of deposition, sedimentation, leaching, and erosion. Moreover, the uncertainty of the calculated soil nutrient balances was assessed. To illustrate the improved methodology, we applied it to Burkina Faso and revealed that nutrient depletion is occurring throughout the country at rates of , and . The resulting spatial soil nutrient balances at the national level can constitute the basis for targeting soil fertility policies at lower levels.     

Water–Gas Shift Reaction Over Aluminum Promoted Cu/CeO2 Nanocatalysts Characterized by XRD, BET, TPR and Cyclic Voltammetry (CV)

A series of aluminum promoted Cu/CeO₂ nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H₂-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content at first, but then decreases with the further increase of aluminum content. Hereinto, Cu/CeO₂ catalyst doped with 1 wt.% of aluminum shows the highest catalytic activity (CO conversion reaches 84.4% at 200 °C) and thermal stability for WGS reaction. Correlation to the results from above characterization, it is found that the variation of catalytic activity is in very agreement with that of the surface area, the area of peak γ (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C₂ and in cyclic voltammetry process), respectively. Enough evidence was found for the fact that the metallic copper (Cu⁰) interacted with surface oxygen vacancies on ceria is the active site for WGS reaction over Cu/CeO₂ catalysts.     

Absolute potential measurements in solid and aqueous electrochemistry using two Kelvin probes and their implications for the electrochemical promotion of catalysis

  The concept of absolute electrode potential in aqueous and solid electrochemistry is discussed in light of the first experimental investigation utilizing a two Kelvin probe system which allows for direct in situ measurement of the work functions of both the, emersed or spillover modified, working and reference electrodes. In both cases, i.e. emersed electrodes in aqueous electrochemistry and spillover-modified electrodes in solid electrochemistry, it is found that the following two equations relate the working–reference electrode potential difference, U _WR, and the work functions, Φ_W and Φ_R of the emersed or spillover-modified working and reference electrodes:

Ferrocenyl Monomers and Polymers of <Emphasis Type="Italic">N</Emphasis>-Allyl and <Emphasis Type="Italic">N</Emphasis>-Acrylatenaphthalimides

A series of N-allyl, N-ethylmethacrylate and N-phenylmethacrylatenaphthalimide monomers have been prepared with –C=CFc, –C≡CFc and –C≡CSiMe₃ substituents at the 4-position of the naphthalimide ring. All have been characterised by elemental analysis and spectroscopy; the X-ray structure of N-allyl-4-ethenylferrocenylnapththalimide is also reported. Free-radical polymerisation of these monomers gave homopolymers, random co- and terpolymers with polydispersities ranging from 1.7 to 3.2. Incorporation into a polymer matrix has no effect on the spectroscopic and electrochemical properties of the naphthalimide or ferrocenyl components. The ferrocenyl polymers are electrochromic and when oxidised give naphthalimide charge-transfer bands in the NIR; this electrochromism was examined by OTTLE techniques.     

Bifunctional N-Oxides of Alkyldiamidoamines

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)ethyl]-amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylethylenediamine followed by oxidation with an aqueous solution of hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ _CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), standard free energies of adsorption and micellization

Effects of SiC and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles on the electrodeposition of Zn,Co and ZnCo. I. Electrodeposition in the absence of SiC and Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Electrodeposition of Zn, Co and ZnCo from acid sulfate solutions onto steel was investigated in this first part of a study of the effects of SiC or Al₂O₃ particles on these processes and the formation of ZnCo–SiC and ZnCo–Al₂O₃ electrocomposites. Zn electrodeposition shows a well-defined pre-bulk region, where the hydrogen evolution reaction (HER) and Zn underpotential deposition (upd) compete. Zn bulk electrodeposition begins with primary nucleation and diffusion-controlled growth, strongly dependent on conditions favoring previous Zn upd against HER. It is assumed that this first bulk process takes place over the upd Zn. Zn bulk electrodeposition is followed by secondary nucleation and growth. Co electrodeposition begins with a slow reduction in parallel with HER, followed by a faster reduction. strongly hinders the initial reduction. The ZnCo and Zn electrodeposition curves are initially similar, retaining features of pre-bulk and bulk Zn electrodeposition.