Herbicides runoff in vegetative filter strips: evaluation and validation of a recent rainfall return period model

Vegetative filter strips reduce herbicide runoff from cultivated fields owing to the ability of vegetation to delay surface runoff, promote infiltration, and adsorb herbicides. Previous research has shown that the annual runoff of each herbicide is typically less than 1 g ha^?1. A model for the detection of the return period of rainfall events was recently proposed for a site in the north-eastern Po Valley, Italy. The return period model suggested that most of the herbicide loss by runoff (about 98%) is caused by a few, or even just one, extreme rainfall event with a return period of about 25–27 years, whereas ordinary events (4–5 each year) account for the rest. The present study aims to validate that model by comparing model predictions with the experimental results obtained in the 2010–2011 sampling season (independent test data), and to evaluate the effectiveness of the VFS. In addition, a 7-yr dataset of metolachlor and terbuthylazine concentration in real runoff events is summarised in order to highlight the medium-term magnitude of the pollution. Results show that on the Po Valley plain, 3–4 runoff events of low intensity are expected in spring–summer and that the consequent annual runoff of the herbicides metolachlor and terbuthylazine is about 0.5–0.7 g ha^?1 yr^?1. A summary shows that, owing to their chemical-physical properties, concentrations of the two herbicides are similar, both varying from about 0.01–300 μg l^?1, with a potential pulse-like exposure risk for aquatic communities in waterways. This study showed that vegetative filter strips can reduce herbicide transfer to surface water by 90–98%, and should be suggested for environmental schemes at field and catchment scale.     

Synchrotron investigations of electronic and atomic-structure peculiarities for silicon-oxide films’ surface layers containing silicon nanocrystals

Films obtained using molecular-beam deposition of SiO powder on c-Si (111) substrates for the purpose of SiO2 system formation with silicon nanocrystals were investigated before and after 900–1100°C annealing by photoluminescence, ultrasoft X-ray emission spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption near-edge structure spectroscopy, and X-ray diffraction. The appearance of (111)-oriented luminescent silicon nanoclusters in considerable amounts upon annealing at T = 1000–1100°C is established in the investigated films. An anomalous phenomenon of X-ray absorption quantum yield intensity reversal for the L _2,3 elementary silicon edge is detected. Models for this phenomenon are suggested.     

Experimental observation of anisometric structures in solutions with a low gelator content

Gelators with a molecular mass of 200 Da are synthesized, and the mechanisms of the formation of anisotropic supramolecular structures during the gelation of N-trifluoroacetyl derivatives of amino alcohols are discussed. The conditions of their stability are identified and the thresholds of gelation of the alcohols in various solvents are determined. It is shown that the gels are formed at concentrations of 10⁻²–10⁻³ M, values substantially lower the percolation threshold for isotropic molecules. An analysis of possible topological structures formed in the gel phase is performed.     

Compaction of intermolecular bonds in the macroscopic chiral phase of strings

The microstructure of a cured state characteristic of a wide variety of low-concentration homochiral solutions in comparison with that of the condensed phase formed in achiral solutions is studied using optical and atomic force microscopy and X-ray diffraction analysis.     

Production of insoluble exopolysaccharide of Agrobacterium sp. (ATCC 31749 and IFO 13140)

Agrobacterium isolated from soil samples produced two extracellular polysaccharides: succinoglycan, an acidic soluble polymer, and curdlan gum, a neutral, insoluble polymer. Maize glucose, cassava glucose, and maize maltose were used in fermentation medium to produce insoluble polysaccharide. Two Agrobacterium sp. strains which were used (ATCC 31749 and IFO 13140) in the production of insoluble exopolysaccharide presented equal or superior yields compared to the literature. The strain ATCC 31749 yielded better production when using maize maltose, whose yield was 85%, whereas strain IFO 13140 produced more when fed maize glucose, producing a yield of 50% (on reducing sugars).     

The effect of microwave radiation on dissolved elemental sulfur in the presence of ionic liquids

The products of transformation of elemental sulfur in benzene solutions in the presence of ionic liquids under microwave irradiation have been studied by NMR. It has been shown that some ionic liquids can cease to be chemically inert and react with elemental sulfur.     

Characterization and utilization of Candida rugosa lipase immobilized on controlled pore silica

Candida rugosa lipase was immobilized by covalent binding on controlled poresilica (CPS) using glutaraldehyde ascross-linking agent under aqueous and nonaqueous conditions. The immobilized C. rugosa was more active when the coupling procedure was performed in the presence of a nonpolar solvent, hexane. Similar optima pH (7.5–8.0) was found for both free and immobilized lipase. The optimum temperature for the immobilized lipase was about 10°C higher than that for the free lipase. The thermal stability of the CPS lipase was alsogreater than the original lipase preparation. Studies on the operational stability of CPS lipase revealed good potential for recycling under aqueous (olive-oil hydrolysis) and nonaqueous (butyl butyrate synthesis) conditions.     

Experimental and numerical study of the stability of a pre-separated flow on an airfoil

The problem of the origin and evolution of two-dimensional waves of unstable disturbances in the boundary layer on an airfoil in the region of adverse pressure gradient in the preseparation flow region is solved numerically. The stability of the experimental velocity profiles, including the inflected profiles, is studied. As a result of the calculations, the boundaries of the instability region and the parameters of the maximally unstable disturbances (frequency, growth rate, wavelength, and propagation velocity) are determined for each velocity profile. The characteristics obtained in the present work are in good agreement with the real experimental parameters of instability waves. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 1, pp. 126–132, January–February, 1999.     

Transformations of Imidazolium Ionic Liquids under the Influence of 60Co Gamma Radiation

Doklady Physical Chemistry - The comparative stability of ionic liquids containing alkyl-substituted imidazolium and phosphonium cations on exposure to gamma radiation (60Co source) under the same...     

Molecular inclusion of butylated hydroxyanisole (BHA) into alpha and beta cyclodextrins

BHA (butylated hydroxyanisole) was complexed with ??- and ??-cyclodextrins with the objective of characterizing the thermal stability. From phase solubility diagrams, the association constants for the complexes of ??-CD:BHA and ??-CD:BHA were found as 49.3 and 585 L mol^?1, respectively. To increase the thermal stability of BHA, its molecular encapsulation in ??-CD and ??-CD, was tested using molar ratios of 1:1 and 1:2 (BHA:CD) and the complex preparation techniques of kneading and physical mixture. The products of complexation were characterized by differential scanning calorimetry and thermogravimetry, indicating the formation of a BHA:??-CD complex and showing that the release of the complexed BHA occurs in the temperature range of 280?C350 °C, well above the temperature at which BHA sublimates. Dissolution tests have shown that the BHA: ??-CD complex produced by kneading has high efficiency of dissolution and partition coefficient experiments demonstrated that the presence of ??-CD leads to higher concentration of BHA in the organic phase.