Adsorption des métaux lourds (Cu, Zn, Cd et Pb) par les sédiments superficiels d'un cours d'eau: rôle du pH, de la température et de la composition du sédiment

Une étude expérimentale concernant l'adsorption des métaux lourds Cu, Cd, Zn et Pb par des sédiments d'un cours d'eau pollué par des rejets industriels a été entreprise pour mettre en évidence l'importance de certains paramètres expérimentaux, notamment le pH, la masse de sédiments et la température. Elle a permis également d'analyser la nature des liens qui participent à la fixation des cations métalliques sur les différentes fractions sédimentaires déterminées selon la méthode de TESSIER et al. (1979) et d'interpréter les capacités d'adsorption relativement variables suivant la nature du métal. Les résultats confirment le rôle particulier des fractions réductible (oxydes de fer et de manganèse) et organique (substances humiques en particulier), dont les propriétés respectives d'échange d'ions et de complexation ont été souvent vérifiées. La capacité d'adsorption de ce sédiment a notamment pu être interprétée en termes d'isothermes d'adsorption en exploitant les modèles de Langmuir et de Freundlich et leurs équations linéarisées.In an experimental study of the adsorption of Cu, Cd, Zn and Pb by surface sediment in a small stream polluted by the industrial drain of electro-refinery, we have demonstrated the irnportance of some such experimental parameters as pH, sediment concentration and temperature. These experiments were conducted in batch systems at constant temperature with continuous agitation, using a mixture of sediment and metals at an adjusted pH; the quantity of metals remaining in solution was determined by a polarographic method. Adsorption percentages for the concentratons of sediment (200 and 1000 mg/L) and metals (1 mg/L) reached the following maximum values: Pb (99-l00%o), Zn (80-90 %), Cd (75-85 %) and Cu (70-80%). These variations in metal soprtion are attributed to differences in binding energy between the metallic cation and the sediment sites, when all other parameters are fixed. Based on metal partitioning among the different sedimentary fractions, as determined according to the sequential extraction method of TESSIER et al. (1979), it was possible to attribute metal adsorption to complexation, coprecipitation and complexation reactions respectively with organic matter, carbonates and Fe-Mn oxides or alumino-silicates. Our results highlight the specific roles played by the reducible Fe-Mn oxides and by humic substances. Fulvic and humic acids, which are considered as the stable fraction of sedimentary organic matter, can form complexes and participate in the fixation of metals on the sediments (GODFRIN and BLADEL, 1990; WILLIAM and HANSON, 1979; FITCH et al., 1968; BIZRI et al., 1985). The stability of these complexes depends on the variety of reaction sites in these macromolecules, which in turn determines the degree of fixation of the cations (specific adsorption). Concerning the iron-manganese oxides and the alumino-silicate compounds, their surface sites are engaged insurface complex formation by a mechanism of proton exchange in which humic substances can be also involved (BELZILE et al., l989a; BELZILE and TESSIER, 1900; BELZILE et al., 1989b).Adsorption kinetics for Cu, Zn and Cd were relatively fast with more than 50 % of the metal adsorbed in a few hours, followed by a partially reversible stage over the next few days leading to an equilibrium state. Reversibilty of Pb binding was not signifrcant (attributed to the chemical precipitation of Pb3(PO4)2). An enhancement of adsorption with increasing pH between 5 and 8 was noted for Cu, Zn and Cd. Several factors may contribute to this increase in the quantity of absorbed metals:-the M+ and MOH+ species berome more competitivethan H+ fortte adsorption sites on the sediment;- the number of adsorption sites increases;- the change in conformation of the humic substances, from aggregated to stretched forms, may render the metal complexing sites more accessible;- the rate of Fe(III) and Mn(IV) formation is more significant at higher pH values;- at higher pH, the precipitation of oxides, hydroxides and hydroxycarbonates becomes important as well as the adsorption on the suspended phases;- the degree of oxide crystallization is influenced by the pH value and hence the adsorption capacity of reducible phases is also affected.A decrease in metal adsorption was also observed as the temperature increased between 10°C and 40°C. The adsorption of metals was described using FREUNDLICH and LANGMUIR equations in their linear form

Effect of industrial effluents polluting the river nile on growth, metabolism and productivity of Triticium aestivumand Vicia fabaplants

Pot experiments using loamy soil were conducted to evaluate the effect of irrigation with industrial effluents on growth, uptake on growth, uptake of nutrients and yield of wheat (Triticum aestivumGiza 164) as a monocot and faba beans (Vicia fabaGiza 461) as a dicot plant. Also, irrigation by industrial effluents in combination with vesicular-arbuscular mycorrhiza (VAM) was used in trying to use a biological control to overcome the harmful effects of heavy metals pollution. Irrigation of plants with industrial effluents leads to marked changes in growth criteria depending on plant and/or the stage of growth. Industrial wastewater led also to marked changes in total carbohydrates and nitrogen in both shoots and roots. On the other hand, combination of industrial waste water with VAM caused an increase in the total carbohydrates and total nitrogen in shoots and roots of both wheat and bean plants. The yield components in wheat and bean were significantly increased with industrial effluents, but the biochemical concentrations were different. In wheat, the carbohydrate concentrations were increased, but protein- N and total-N were decreased, however mineral contents, especially ZN were increased. The reverse response was recorded with VAM. For bean the opposite occurred. Generally, bean plants were more sensitive to pollution with heavy metals, than those of wheat however this could influence be overcome by using VAM with irrigation

Gibberellic acid effects on protein pattern, hydrolytic enzyme activities and ionic uptake during germination of Vicia faba in sea water

The germination and water uptake of Vicia faba seeds were suppressed in response to the treatments with the different concentrations of sea water (5%, 25% and 50%). The following parameters were increased: the osmotic potential, Na+, Cl, proline and protease activity. While K+, K+/Na+ ratio, Ca2+, amylase activity and total soluble sugars were decreased. Gibberellic acid treatments to the seeds counteracted the harmful effect which were induced by sea water treatments. In turn the germination percentage, water uptake, K+, K+/Na+ ratio, Ca2+, total soluble sugars, a-amylase and protease activities were increased, while Na+, Cl, and proline were decreased. The changes in protein banding pattern in Vicia faba germinated seeds in sea water were investigated. Salinization induced de novo synthesis of some salt responsive proteins. The salt responsive proteins might be osmotin (M wt 23.39 and 26.86 KDa), dehydrin (36.79 and 40.63 KDa) and ubiquitin (8.81 KDa) which were apparent in Vicia faba seeds. The seeds priming soaking in GA and germinated in sea water induced de novo synthesis of some responsive proteins. This indicated that gibberellic acid had a synergistic effect on the induction of the salt gene which is responsible for the synthesis of the mentioned proteins

Is Khat (Catha edulis) chewing a risk factor for periodontal diseases? : a systematic review

Background: Khat (Catha edulis) chewing is a highly prevalent habit in the Arabian Peninsula and East Africa, and has recently spread to Western countries. The association between khat chewing and oral mucosal lesions is well documented in the literature. However, there is no concrete evidence on the association between khat chewing and periodontal disease. The purpose of this systematic review was to analyze the influence of khat chewing on periodontal health. Material and methods: A literature search of PubMed, Scopus and Web of Sciences databases was carried out to identify relevant articles published from 1990 to May 2017. The inclusion criteria were all clinical studies that assessed the relationship between khat chewing and periodontal disease. Results: The search yielded 122 articles, of which 10 were included in this systematic review. Most of the studies exhibited a positive correlation between khat chewing and periodontal disease. Conclusions: Altogether, the analysis of the current evidence reveals that khat chewing is destructive to the periodontium and enhances the risk of periodontal disease progression. However, due to variability of studies, more longitudinal case-controlled studies are highly warranted to establish a causal relation between khat chewing and periodontal disease

Evaluating potential of diatomite as anti clogging agent for porous asphalt mixture

Clogging is a major problem that occurs throughout the service life of porous asphalt due to the open nature of the mixture itself. Diatomite with characteristic of abrasiveness and porous structure seems to have potential in order to remove the clogging materials that mainly consists of soils. This study aims to investigate the effects of diatomite as anti-clogging agent on the permeability rate and strength of porous asphalt. The porous asphalt samples were prepared using Malaysia aggregate gradation and polymer modified bitumen of PG76 was used as the binder. This study focuses on clay as the clogging material at different concentration. A fixed amount of 0.5 g/L diatomite was applied to the porous asphalt samples as an anti-clogging agent prior to clogging cycles. The permeability test and resilient modulus were then conducted at different clogging concentrations (0.5, 1.0, 1.5 g/L) and cycles, with and without diatomite. It was found that samples with diatomite have a higher permeability rate compared to those without any application of diatomite after a few clogging cycles. As the clogging cycles increase, the clogging materials have trapped and filled up the voids in the porous asphalt samples and increase the resilient modulus result

Impacts of tea tree or lemongrass essential oils supplementation on growth, immunity, carcass traits, and blood biochemical parameters of broilers reared under different stocking densities

The effects of tea tree essential oil (TTEO) and lemongrass essential oil (LGEO) with different stocking densities on the growth performance, biochemical markers, antioxidants, and immunity state of broiler chickens were studied. Birds were housed at stocking densities of 25, 30, 35, and 40 kg/m2. The treatments were, basal diet without any supplementation, the second and third groups were supplemented with 300 mg TTEO/kg feed, and 300 mg LGEO/kg feed, respectively. Results revealed that increasing stocking density from 25 to 40 kg/m2 significantly reduced body weight and daily weight gain at different ages. The phagocytic index and activity were significantly higher under the lower stocking density (25 kg/m2). Serum amyloid A (SAA), serum or liver transferrin (TRF), or C-reactive protein (CRP) were significant decreased when decreasing stocking density. Increasing stocking density from 25 to 40 kg/m2 resulted in a significant increase in the serum urea, creatinine, uric acid, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), and catalase (CAT) levels. However, there was a significant reduction in antioxidant enzyme activity, including glutathione peroxidase (GPx) and superoxide dismutase (SOD), as stocking density increased. The supplementation of TTEO produced significantly higher body weight and daily weight gain followed by LGEO. Additionally, the mortality rates were reduced in TTEO (27.4%) and LGEO (25%) groups. TTEO or LGEO supplementation significantly improved meat constituents and cellular immunity and reduced serum total lipids, serum and meat cholesterol, and triglycerides, SAA, TRF, and CRP. For all these measured parameters, superior results were obtained when TTEO was used compared to LGEO. TTEO or LGEO supplementation also significantly reduced serum urea, creatinine, uric acid, and the enzymatic activities of LDH, ALT, AST, MDA, and CAT (but not GPx and SOD) in comparison to the control treatment. Overall, our results showed the superiority of TTEO over LGEO as a feed supplement in broiler diets. In conclusion, TTEO treatment offers a better solution for raising broiler chickens in high stocking density

Structural and Functional adaptation of the lingual papillae of the Egyptian fruit bat (Rousettus aegyptiacus): Specific Adaptive feeding Strategies

The current investigation was directed to clarify the correlations between the feeding strategy and lingual structure of the Egyptian fruit bat captured from the Egyptian east desert. The current work depends on twelve adult Egyptian fruit bats that observed grossly and with the help of the stereo, light, and scanning electron microscope. There were three types of the lingual papillae; one mechanical filiform and two gustatory (fungiform and circumvallate). There were seven subtypes of filiform papillae were recognized on the seven lingual regions. There were scanty numbers of fungiform papillae distributed among the filiform papillae on the lingual tip and two lateral parts of apex and body while fungiform papillae completely absent in the median part. There were three circumvallate papillae. The central bulb of circumvallate papillae surrounded by one layer of two segmented circular annular bad. The lingual tip had cornflower-like and diamond-shaped filiform papillae. Histochemical results revealed that the lingual glands were a stronger AB-positive reaction and gave dark blue color, while the reaction for the PAS-stain was negative. Also, the glands exhibited a blue color as an indication of positive AB reactivity with combined AB-PAS staining

Citrus flavonoids in preventing cardiovascular diseases

Citrus, belonging to the family of Rutaceae is a genus of the flowering plants and shrubs. They originated in the tropical and subtropical regions of Southeast Asia. Citrus fruits are highly produced in China, Brazil, USA, India, Mexico, and Spain. Among Citrus species, sweet oranges (Citrus sinensis) are the most widely spread and valued throughout the world. Citrus fruits are rich in flavonoids, mainly hesperidin and naringin that are known to have benefit in the avoidance of long-term diseases. Based on the in vivo and epidemiological studies done previously, the potential biological properties of Citrus flavonoids in Citrus fruits are beneficial for the prevention of cardiovascular diseases (CVDs) by acting as antihypertensive, anti-hypercholesterolemia, and antidiabetic. However, the mechanisms of action are still uncertain and not clearly defined. Citrus contains some phytochemicals that can give beneficial effects to human’s health through several biological properties. Thus, Citrus fruits can be a new discovery of natural prevention of chronic diseases around the globe with regard to their high production each year. This chapter provides a comprehensive information on the phytochemical constituents found in Citrus fruits and their biological properties in preventing cardiovascular diseases

Characterization of industrial by-products as asphalt paving material

Most of the recent research is focusing on the utilization of industrial by-products in road construction. The intention is not only to mitigate the problem of waste being dumped to the landfills but to encourage their use as construction material without compromising quality and performance of the road. Steel slag and bottom ash are the industrial by-products generated in large quantity by industry. This study investigates the characteristics of steel slag and bottom ash to be utilized as aggregate in asphalt pavement. Both materials were characterized in terms of physical, chemical and morphological characteristics compared to the conventional granite aggregate. The results revealed that both materials have much potential to be used as aggregate in asphalt mix. The bottom ash was observed weaker in terms of strength, but the steel slag was found much stronger than the granite. The morphological structure of bottom ash and steel slag disclosed that these are made up of porous and rough-edged granular particles with slightly higher water absorption