Variability of fresh- and salt-water marshes characteristics on the west coast of France: a spatio-temporal assessment

The degradation of water quality and the multiple conflicts of interest between users make marsh restoration very important. A Water Quality Evaluation System (WQES) was developed for river systems by the European Water Framework Directive (WFD). Some form of biologically-based, habitat-specific reference standard seems absolutely essential for wise management and stewardship of marsh ecosystems. The goal of this study was to develop a statistical method to define and to characterize a water body typology for drained marshes of the Charente-Maritime wetlands on the French Atlantic coast, placing particular emphasis on environmental factors as hydraulic functioning, human activities and pedological substratum. The Charente-Maritime marshes represent a good field study because of his high diversity of types of marshes and of anthropogenic activities in a restrictive area thus erasing spatial climatic effect (latitude effect). The statistical method developed here had permitted to define and characterize 12 different water bodies, 7 in freshwater (F1 to F7) and 5 in salt water marshes for the Charente-Maritime area. This typology demonstrated an important link between the size catchment area, nitrate concentrations, and leaching of precipitation from cultured soils. Even though the Charente-Maritime marshes are strongly impacted by humans, they may still retain the ability to remove nitrate. The increasing gradient of water renewal in the freshwater marshes from F1 to F7 explained the decreasing gradient of eutrophication. A better management of the hydrodynamic of the marshes can avoid eutrophication risk on the coastal sea area. Reliance on the WFD parameter set necessarily placed limits on the kinds of interpretations that could be made and on the study’s potential contribution to the basic science of marshes. Ecologically-based insights regarding both external flows (links between ecosystems, meta-ecosystem theory) and internal flows (structure of the planktonic food web) seem an essential prerequisite for further advances in the study of marsh ecosystems.     

Evaluation of the performance of sulfonated esparto grass lignin as a plasticizer-water reducer for cement

The objective of the work described in this first paper of a series is an investigation of the preparation of a sulfonated esparto grass lignin (SEL) and its behavior as a plasticizing-water-reducing agent for cement-water systems. SEL is prepared by extracting the lignin from the black liquor of a soda esparto grass pulping process and then sulfonating it with a mixture of sodium sulfite and formaldehyde.Analyses and characterization of SEL carried out with high-performance size exclusion chromatography (HPSEC), reversed phase chromatography (RPC), infrared spectrometry and chemical methods show that both the molecular weight average and the combined sulfur content are relatively high. Moreover, HPSEC shows that SEL has a relatively more uniform molecular weight distribution (MWD) than the commercial products obtained from the sulfite wood pulping process. On the other hand, SEL could reduce the water content, improve the workability and compressive strength of mortars. SEL also permits a very low rate of slump loss of cements without excessive extension of the final set time.     

Selective access to novel aryl alkyl disulfonates via photosulfochlorination process: An eco-benign approach to a highly active class of surfactants

In this work we report the synthesis of a new family of surfactants based on aryl alkyl disulfonates; the latter compounds were derived from a mixture of linear alkylbenzene with the resulting disulfonate groups residing on the linear alkyl side-chain rather than the usual aromatic ring structure. The Reed sulfochlorination reaction was successfully utilized to selectively promote the formation of disulfonates on the alkyl group. A number of analytical methods in the form of liquid chromatography–mass spectrometry (LC–MS), gas chromatography–mass spectrometry (GC–MS), Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) were used to characterize the resulting compounds and intermediates. The critical micelle concentration, the surface tension at the critical micelle concentration, the surface excess concentration at surface tension, and the area per molecule were measured at different concentrations and temperatures. Thermodynamic parameters and Krafft temperature were also determined. The obtained results were compared to those of commercial n-dodecylbenzene sulfonates and linear alkylbenzene sulfonates surfactants, showing that these new synthesized surfactants present good surface properties.     

The pressure-induced mechanical and optoelectronic behavior of cubic perovskite PbSnO3 via ab-initio investigations

The density functional theory based full-potential linear-augmented-plane-wave plus local-orbital method has been used to study the physical properties of PbSnO₃ in hypothetical cubic perovskite. An external pressure up to 40?GPa has been applied on PbSnO₃ to realize the variation in its electronic band structure and the subsequent optical properties. The stability of the PbSnO₃ has been investigated by the mechanical properties, the enthalpy of formation and Goldschmidt tolerance factor. Moreover, the Born criteria have been adopted to justify the mechanical stability of the PbSnO₃ perovskite. We show that the electronic bandgap of PbSnO₃ can be tailored from indirect to direct band gap at high symmetry (X-X) direction at an external pressure of magnitude ~ 26?GPa. The effect of pressure on the optical properties has been studied in terms of dielectric function, absorption, refraction, reflection, and optical loss factor. The application of hydrostatic pressure has shifted the maximum absorption toward the visible range, revealing that PbSnO₃ can be used for high- pressure optoelectronic applications.     

Root-mediated effects in carrot resistance to the carrot fly,Psila rosae

Field experiments on two different soil types in Ireland assessed the extent and mechanisms of resistance toPsila rosae (F.), the carrot fly, with emphasis on the role of the carrot root. Ten carrot cultivars gave consistent results in terms of resistant and susceptible cultivars. Nonpreference oviposition was confirmed as a mechanism, and the use of egg traps, providing differential exposure of the main root, showed this was regulated by root factors, probably chemical constituents. Independent main root resistance to the larva was also confirmed, and this effect was established as consistent with a chemically mediated nonpreference. Antibiosis by the root was demonstrated. Such effects in three different modes indicate that main root properties are crucial in carrot resistance toPsila and suggest a pervasive influence of root chemicals on such resistance.     

Photo‐induced hydrogen on iron hexagonal mesoporous silica (Fe‐HMS) photo‐catalyst

The iron hexagonal mesoporous silica (Fe‐HMS)‐n photocatalyst, where n is the molar ratio Si/Fe in the precursor gel (=50), has been successfully synthesized at an ambient temperature using hexadecylamine as template agent. The material was characterized by X‐ray diffraction, N₂ adsorption measurement Brunauer, Emmet, Taller (BET) and Barrett–Joyner–Halenda theory, UV–Vis spectroscopy, high‐resolution transmission electron microscopy and electron spin resonance. The electrical conductivity follows an Arrhenius‐type law with activation energy of 0.04 eV. Fe₂O₃ is uniformly dispersed on the HMS surface; it works synergistically to make Fe‐HMS photoelectrochemically active. The flat band potential (?0.75 V_SCE) is higher than the potential of hydrogen generation (?0.50 V_SCE at pH~7), and the material shows high efficiency for hydrogen evolution upon visible light. The photoactivity in Na₂SO₄ and Na₂SO₃ (0.1 M) solution was found to be 136 and 175 µmol g^‐1 min^‐1, respectively under full light (29 mW cm^‐2). The tendency to saturation, observed only in SO₃^2‐ electrolyte, is ascribed to the competitive reduction of the end product, namely S₂O₆^2‐ with the water reduction. Copyright © 2011 John Wiley & Sons, Ltd.     

Heat Recovery of a Diammonium Phosphates Drying Unit

Solid product drying is a widely used unit operation in the chemical industry. It is highly energy intensive, requiring hot, dry air streams at high temperatures to dry a wide range of products. Exhaust air from a dryer is usually vented to the atmosphere with little or no heat recovery. In the present work, a study was performed to analyze the performance of an absorption heat transformer (AHT) applied to the evaluation of thermal rejections of drying unit of diammonium phosphates (DAP). First, a basic AHT system is described and the operating sequence is explained. Next, an application of the AHT system to an industrial company is analyzed. A numerical simulation of the system using Aspen Plus software was performed to determine the effect of different parameters on the AHT system performance and the results are presented in graphical form.