932 resultados para Chemical quality


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Within the European water framework directive (WFD), the status assessment of littoral waters is based both on the chemical quality and on the ecological quality of each water body. Quality elements enabling to assess the ecological status of a water body are, among other things, biological quality elements (phytoplankton, macroalgae, angiosperms, benthic invertebrates, fish), for each of which the member states have developed quantitative indicators. This document is one of the deliverables of a multi-annual study intended to characterize the sensitivity of these biological indicators towards the various anthropogenic pressures exerted on the French Atlantic and Channel coast: ultimately, the goal is to establish a quantitative and predictive relationship, statistically robust, between the WFD indicators used along the French channel and Atlantic coastline, and various anthropogenic pressures acting on these coasts. The aim of the WFD is indeed to restore or maintain a good chemical and biological quality of coastal waters, and thus to limit the impact of human activities potentially responsible for the degradation of ecosystems. This understanding of the linkages and interactions existing between anthropogenic pressures and ecological status of water bodies is therefore essential to identify priorities for action (challenges, substances ...), prioritize actions to implement within restoration programs (technical, fiscal, financial), but also to be able to communicate constructively and persuasively in talks between managers and the various stakeholders of coastal regions. Using the DPSIR methodology, this literature analysis has permitted to identify, for each WFD biological quality element (except fish), which pressures (or pressure types) are potentially relevant in the light of their impact on the indicators of the ecological status of water bodies. Some metrics and indicators of anthropogenic pressures used in the literature to characterize the sensitivity of the biological quality elements, within quantitative approaches, were also identified. It is also clear from this review that the biological quality elements can be particularly sensitive to intrinsic environmental conditions, and therefore to certain changes related to natural phenomena occurring at large scales (e.g. climate change, paroxysmal climate episode...). Therefore, when one is interested in the sensitivity of biological indicators to different anthropogenic pressures, two factors can complicate the analysis and are likely to weaken the resulting statistical relationships: on the one hand, the variability of biological responses depending on the natural context and, on the other hand, interactions (so called synergistic effects) between different types of anthropogenic pressures and the alterations they can generate.

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Within the European water framework directive (WFD), the status assessment of littoral waters is based both on the chemical quality and on the ecological quality of each water body. Quality elements enabling to assess the ecological status of a water body are, among other things, biological quality elements (phytoplankton, macroalgae, angiosperms, benthic invertebrates, fish), for each of which member states have developed quantitative indicators. This document compiles three deliverables of a multi-annual study intended to characterize the sensitivity of these biological indicators regarding the various anthropogenic pressures exerted on the French Atlantic and Channel coast: ultimately, the goal is to establish a quantitative and predictive relationship, statistically robust, between the WFD indicators used along the French channel and Atlantic coastline, and various anthropogenic pressures acting on these coasts. These three deliverables are the following : - The reports of various interviews performed with French national referents for the biological quality elements used within the littoral part of the WFD in Channel and Atlantic (phytoplankton, subtidal and intertidal macroalgae, opportunistic blooming macroalgae, angiosperms and benthic invertebrates). These interviews aimed to specify, for each metric constitutive of the BQE indicator (if multi-metric), the "relevant" pressures, as well as the trend of this impact, - Sheets describing the "pressure" and "environment" data available, in order to characterize spatially and quantitatively these "relevant" anthropogenic pressures acting on French Channel and Atlantic coast, - A progress report dealing with the development of a database tool, for archiving quantitative data characterizing "relevant" littoral anthropogenic pressures.

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Vehicle emissions are a significant source of fine particles (Dp < 2.5 µm) in an urban environment. These fine particles have been shown to have detrimental health effects, with children thought to be more susceptible. Vehicle emissions are mainly carbonaceous in nature, and carbonaceous aerosols can be defined as either elemental carbon (EC) or organic carbon (OC). EC is a soot-like material emitted from primary sources while OC fraction is a complex mixture of hundreds of organic compounds from either primary or secondary sources (Cao et al., 2006). Therefore the ratio of OC/EC can aid in the identification of source. The purpose of this paper is to use the concentration of OC and EC in fine particles to determine the levels of vehicle emissions in schools. It is expected that this will improve the understanding of the potential exposure of children in a school environment to vehicle emissions.

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The object of this study was to determine the value of physical, bacteriological and chemical tests used to find out and compare the indices of quality of prawns stored at 0°C and at 18°C. pH value, nature of drip, the total bacterial count, presence or absence of tryptophan, trimethylamine content, glycogen, lactic acid, vitamins such as thiamin, riboflavin and niacin were estimated periodically to evaluate the quality of prawns stored at 0°C, whereas in addition to organoleptic changes, pH, bacterial count, nature of growth in peptone water, soluble protein in salt solution and loss of moisture, glycogen, lactic acid, and changes in vitamin B contents were noted periodically for prawns stored at -l8°C. Riboflavin and niacin were not affected appreciably but the retention of thiamin in prawns was very low.

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Shark livers are considered as an important raw material providing a quality fish oil. It has been reported to aid white — blood-cell production and act as an active ingredient in hemorrhoid treatments. It is also reported that liver oil as a good supplement of vitamin A and poly-unsaturated fatty acids which are important to the development of brain cells in human. Freshness of livers is very important to extract better quality oil. In Sri Lanka, the annual shark production amounts to 8000t, however the quality of livers collected from landing sites has not being measured yet. Present study was conducted to evaluate the quality of silky (Charcarninus fakiformis) shark livers available in Negombo and Beruwala landing sites in the West Coast of Sri Lanka and also to study the relationship between organoleptic and bio-chemical correlation on freshness of shark livers. Liver samples which were collected from landing sites in the West coast of Sri Lanka, were evaluated for external and internal colour, texture and odour. Total volatile nitrogen (TVN), pH value, free fatty acid (FFA%) and peroxide (PV) values of livers were also determined to assess quality. According to the organoleptic scoring system 4.3% of liver samples were categorized as best in quality while 30.4%, 56.5% and 8.7% rated as good, medium and poor in quality respectively at the Negombo and Beruwala landing sites. Bio-chemical analysis showed that the better quality livers had the highest score for sensory evaluation and low values for TVN, FFA and peroxide value while low quality livers gave low score for sensory evaluation and high TVN, FFA, peroxide values. Correlation coefficient of organoleptic scores against total volatile nitrogen value, pH value, free fatty acid % and peroxide value of shark livers were determined by statistical analysis. Organoleptic score of shark livers was found to be highly.

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Protein powders were prepared from processing waste of prawns either by mechanically squeezing the shell and freeze drying the resultant aqueous extract or by treating the shell with 0.5% sodium hydroxide, filtering it and freeze drying the filtrate. Comparative studies on the proximate composition, amino acid profile, consumer acceptability and nutritional quality of the protein powders showed that the product prepared by freeze drying of the press liquor obtained by passing the waste through a hand operated expeller is better in all aspects studied than the product prepared by mild alkali extraction.

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A method of comparing data on protozoan communities with chemical parameters is presented. Using data from an extensive survey of the River Hanjiang in China, each species of protozoa has been given a species pollution value (SPV) related to its occurrence in waters with different degrees of pollution. A comprehensive chemical index is calculated for each site based on water quality standards for eight chemical parameters. The index is calculated from the relationship between the observed levels of each chemical at a site, compared with the limits of the drinking water quality standards of the People's Republic of China. From the distribution of each species at sites with differing chemical index values, a SPV is calculated. The SPV for each species is obtained by summing the logarithmic value of 10 times the chemical pollution divided by the number of chemical parameters, then divided by the stations where the species occurs. The community pollution value (CPV), which is the average SPVs of all protozoa at a site, is used to evaluate water quality. The CPV has been shown to have a close correlation with the degree of water pollution. It is not necessary for all the protozoa in a sample to have SPVs listed in this paper, provided at least 56% of the protozoa in a sample have an SPV value, the CPV will be applicable.

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High-quality Ge epilayer on Si(1 0 0) substrate with an inserted low-temperature Ge seed layer and a thin Si0.77Ge0.23 layer was grown by ultrahigh vacuum chemical vapor deposition. The epitaxial Ge layer with surface root-mean-square roughness of 0.7 nm and threading dislocation density of 5 x 10(5) cm(-2) was obtained. The influence of low temperature Ge seed layer on the quality of Ge epilayer was investigated. We demonstrated that the relatively higher temperature (350 degrees C) for the growth of Ge seed layer significantly improved the crystal quality and the Hall hole mobility of the Ge epilayer. (C) 2008 Elsevier B.V. All rights reserved.

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The effect of the growth temperature on the surface and interface quality for the GaN/AlN multiquantum well (MQW) layer grown by metal-organic vapour chemical deposition is investigated. The obtained GaN/AlN MQW structure is almost coherent to the underlying AlGaN layer at improved growth conditions. With a relatively low growth temperature, the GaN/AlN MQW growth rate increases, the surface roughness reduces considerably and no macro steps are observed, resulting in a better periodicity of MQW.

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Rutherford backscattering and channeling is combined with X-ray diffraction to study the depth dependence of crystalline quality in InN layers grown by metalorganic chemical vapor deposition on sapphire substrate. The poorest crystalline quality in InN layer is produced at the intermediate region over 100 nm away from the InN/sapphire interface. With increasing layer thickness the crystalline quality improves to a certain degree dependent on the growth temperature. The InN sample grown at 450 degrees C is found to be more homogeneous than the sample grown at 550 degrees C. The difference in the defect profile is explained by the temperature-dependent growth modes. The inhomogeneity of structural quality and related properties such as carrier concentration and strain field is possibly the reason to observe a high energy wing in PL spectrum of the InN sample grown at 550 degrees C. (c) 2006 Elsevier B.V All rights reserved.

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HF etching followed by relatively low temperature (almost-equal-to 600-degrees-C) pretreatment is shown to provide a suitable substrate for the heteroepitaxial growth of GaAs on Si(100) by CBE using TEGa and AsH3 as sources. Rutherford backscattering (RBS), photoluminescence (PL), transmission electron microscopy (TEM), and Raman measurements show the low-defect nature of the GaAs epilayer.

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Chemical Imaging (CI) is an emerging platform technology that integrates conventional imaging and spectroscopy to attain both spatial and spectral information from an object. Vibrational spectroscopic methods, such as Near Infrared (NIR) and Raman spectroscopy, combined with imaging are particularly useful for analysis of biological/pharmaceutical forms. The rapid, non-destructive and non-invasive features of CI mark its potential suitability as a process analytical tool for the pharmaceutical industry, for both process monitoring and quality control in the many stages of drug production. This paper provides an overview of CI principles, instrumentation and analysis. Recent applications of Raman and NIR-CI to pharmaceutical quality and process control are presented; challenges facing Cl implementation and likely future developments in the technology are also discussed. (C) 2007 Elsevier B.V. All rights reserved.

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Industrial activities are the major sources of pollution in all environments. Depending on the type of industry, various levels of organic and inorganic pollutants are being continuously discharged into the environment. Although, several kinds of physical, chemical, biological or the combination of methods have been proposed and applied to minimize the impact of industrial effluents, few have proved to be totally effective in terms of removal rates of several contaminants, toxicity reduction or amelioration of physical and chemical properties. Hence, it is imperative to develop new and innovative methodologies for industrial wastewater treatment. In this context nanotechnology arises announcing the offer of new possibilities for the treatment of wastewaters mainly based on the enhanced physical and chemical proprieties of nanomaterials (NMs), which can remarkably increase their adsorption and oxidation potential. Although applications of NMs may bring benefits, their widespread use will also contribute for their introduction into the environment and concerns have been raised about the intentional use of these materials. Further, the same properties that make NMs so appealing can also be responsible for producing ecotoxicological effects. In a first stage, with the objective of selecting NMs for the treatment of organic and inorganic effluents we first assessed the potential toxicity of nanoparticles of nickel oxide (NiO) with two different sizes (100 and 10-20 nm), titanium dioxide (TiO2, < 25 nm) and iron oxide (Fe2O3, ≈ 85x425 nm). The ecotoxicological assessment was performed with a battery of assays using aquatic organisms from different trophic levels. Since TiO2 and Fe2O3 were the NMs that presented lower risks to the aquatic systems, they were selected for the second stage of this work. Thus, the two NMs pre-selected were tested for the treatment of olive mill wastewater (OMW). They were used as catalyst in photodegradation systems (TiO2/UV, Fe2O3/UV, TiO2/H2O2/UV and Fe2O3/H2O2/UV). The treatments with TiO2 or Fe2O3 combined with H2O2 were the most efficient in ameliorating some chemical properties of the effluent. Regarding the toxicity to V. fischeri the highest reduction was recorded for the H2O2/UV system, without NMs. Afterwards a sequential treatment using photocatalytic oxidation with NMs and degradation with white-rot fungi was applied to OMW. This new approach increased the reduction of chemical oxygen demand, phenolic content and ecotoxicity to V. fischeri. However, no reduction in color and aromatic compounds was achieved after 21 days of biological treatment. The photodegradation systems were also applied to treat the kraft pulp mill and mining effluents. For the organic effluent the combination NMs and H2O2 had the best performances in reduction the chemical parameters as well in terms of toxicity reduction. However, for the mine effluent the best (TiO2/UV and Fe2O3/UV) were only able to significantly remove three metals (Zn, Al and Cd). Nonetheless the treatments were able of reducing the toxicity of the effluent. As a final stage, the toxicity of solid wastes formed during wastewater treatment with NMs was assessed with Chironomus riparius larvae, a representative species of the sediment compartment. Certain solid wastes showed the potential to negatively affect C. riparius survival and growth, depending on the type of effluent treated. This work also brings new insights to the use of NMs for the treatment of industrial wastewaters. Although some potential applications have been announced, many evaluations have to be performed before the upscaling of the chemical treatments with NMs.