Fractionnement et mobilité des métaux lourds dans un sol en amont des eaux usées de tanneries

La migration et la spéciation de Cr, de Cu et de Pb sont étudiées sur le sol d'une colonne alimentée par les eaux usées de tanneries. La localisation des métaux est évaluée à l'aide du schéma d'extractions sélectives préconisé par Legret et al. (1988). Les résultats ont montré que l'horizon superficiel renferme des teneurs en métaux très élevées. Parmi les métaux étudiés, le Cr s'avère retenu essentiellement dans la phase résiduelle mais il se présente aussi sous des formes plus mobiles. Le Cu est principalement associé avec la phase résiduelle et organique. Le Pb est lié aux phases acido-soluble et réductible. De ce fait, l'épandage des eaux usées de tanneries, sans aucun traitement préalable, peut être une source de contamination des sols et des eaux souterraines, notamment pour le Cr.In Morocco, the town of Marrakesh, as in other areas of the country, is subject to multiple daily aggressions generated by industrial pollution, in particular from tanneries. The tannery waste water is discharged directly into the aquatic and terrestrial ecosystems without any preliminary processing. In order to evaluate the danger that can be generated by tannery effluents in the receiving ecosystems, and to study the ecotoxicological and environmental impact resulting from that chemical treatment of these effluents, we determined, before and after treatment, the inhibitory effect of the two most polluted effluents originating from manufactured leather: liming-deliming and chromium tanning.The purpose of our investigation was thus to evaluate the acute toxicity of the chromium tanning and epilage-coat waste waters before and after chemical treatment. The invertebrate Daphnia pulex was used for the toxicity test and the toxicity due to these industrial waste waters was evaluated by regression analysis. The processing carried out on the chromium tanning waste water consisted of precipitation with sodium carbonate at different pH values. The treatment of liming-deliming wastewaters consisted of an elimination and recovery of the sulphide compounds without carrying out their degradation.The chromium level was determined by atomic absorption spectrophotometry with graphite furnace atomization. The results of the toxicity test showed that the investigated chromium tanning and liming-deliming effluents presented were toxic, with respective IC50-24h values of 0.15 and 3.36 (expressed as dilution ratios). This toxicity could be explained by high levels of chromium, sulphides and organic matter in these waste waters. It is however difficult to correlate the IC50 values obtained with those of the physical-chemical parameters. The tested effluents are very complex matrices. On the other hand, we noticed a notable difference between these two effluents. The mineral tanning effluent is contaminated with chromium and organic matter, whereas the second is especially rich in organic matter and sulphide.The total chromium concentration corresponding to the IC50-24h value of the raw chromium tanning effluent is lower than that which would be expected on the basis on the known toxicity of K2Cr2O7, showing the toxicity of raw chromium waste waters is due not only to chromium, but also to other chemicals used during the manufacturing process of leather. After processing by chemical precipitation, the IC50-24h values increased from 0.15 to 26.6 and from 3.36 to 11.1 respectively, for the chromium tanning and the epilage-coat effluents. Consequently, these treated sewages can be classified as low toxicity wastes. The comparison of the results is very difficult considering that the test conditions and the physicochemical and heavy metal characteristics of the effluents vary enormously over time, without forgetting the physicochemical composition of the experimental solution used by standard OECD (fresh water) and the standard ISO (synthetic water). From where necessity to vary tests for determining well the degree of an effluent toxicity which the effects appear differently at various levels trophic.The diminution observed in the toxicity of the effluents is linked to a reduction of suspended matter (95 %), COD (55 %), Cr (90 %) and sulphides (50 %). Hence, this treatment presents at least two advantages. The first is environmental as just mentioned. The second is economic since chromium can be recycled for reuse in leather tanning. The results suggest that the recovered chromium is similar to commercial tanning chromium. These results also show that the fixing of chromium does not depend on the nature of the treated skin. In fact, a technical and economic analysis showed that proposed treatment can be economically beneficial (3112,5 $ per 1000 tons of skins)

Impact écotoxicologique du traitement chimique des eaux usées de tanneries: Analyse technico-économique

La toxicité des eaux usées du tannage au chrome et d'épilage-pelanage, avant et après traitement, a été évaluée par test Daphnia pulex. Cette évaluation a été déterminée à partir des équations de corrélation linéaires. Les résultats obtenus montrent que le tannage au chrome et l'épilage-pelanage présentent une toxicité élevée avec des valeurs des CI50 24h respectives de 0,15 et 3,36. Cette toxicité élevée pourrait être expliquée par la charge de ces effluents en chrome, en sulfures et en matière organique.Après traitement par précipitation chimique, la CI50 24h a connu une importante augmentation. Elle est passée de 0,15 à 26,58 et de 3,36 à 11,1 respectivement pour le tannage au chrome et l'épilage-pelanage. Par conséquent, ces effluents traités peuvent être classés comme rejets peu toxiques. Cette diminution de la toxicité est liée surtout à l'abattement des MES (95 %), de la DCO (55 %), de Cr (90 %) et des sulfures (50 %). Ce traitement a donc, un double intérêt; le premier est environnemental, le second est économique du fait de la possibilité de recyclage du chrome récupéré dans le tannage du cuir. En effet, l'application expérimentale du chrome dans le tannage a montré un résultat similaire à celui obtenu par le produit commercial. Ainsi, suite à une analyse technico-économique, le bénéfice réalisé par cette opération est estimé à 3112,50 $par 1000 tonnes par an.The purpose of our investigation was to evaluate the acute toxicity of chromium tanning and liming-deliming waste waters before and after chemical treatment. The invertebrate Daphnia pulex was used for toxicity test. The toxicity due to these industrial waste waters was revealed by the equations of the regression lines. The results of the toxicity test showed that the waste waters from chromium tanning and from dehairing presented higher toxicity, with respective 24-h IC50 values of 0.15 and 3.36. This toxicity could be explained by higher levels of chromium, sulphides and organic matter in these waste waters.After processing by chemical precipitation, 24-h IC50 values increased from 0.15 to 26.6 and from 3.4 to 11.1 respectively for the chromium tanning and the de-hairing waste waters. Consequently, these processed effluents can be classified as low toxic wastes. This diminution of the toxicity is linked to a reduction of suspended matter (95$ per 1000 tons per year)

Spectral element discretization of the vorticity, velocity and pressure formulation of the Stokes problem

We consider the Stokes problem provided with non standard boundary conditions which involve the normal component of the velocity and the tangential components of the vorticity. We write a variational formulation of this problem with three independent unknowns: the vorticity, the velocity and the pressure. Next we propose a discretization by spectral element methods which relies on this formulation. A detailed numerical analysis leads to optimal error estimates for the three unknowns and numerical experiments confirm the interest of the discretization

On the uniqueness for weak solutions of steady double-phase fluids

We consider a double-phase non-Newtonian fluid, described by a stress tensor which is the sum of a p-Stokes and a q-Stokes stress tensor, with 12 to justify calculations for weak solutions. Results are obtained through a careful use of the symmetries of the convective term and are also valid for rather general (even anisotropic) stress-tensors

Estudo analítico sobre os elementos didáticos

UIDB/00693/2020 UIDP/00693/2020No ano em que se assinalam 250 anos do nascimento de João José Baldi, o presente estudo revela a vertente pedagógica deste compositor português. Com o objetivo de identificar a presença de elementos didáticos nas suas obras para instrumentos de tecla, foi realizada uma pesquisa biográfica, um levantamento das respetivas obras e um estudo e comparação das fontes, bem como uma análise musical com base numa grelha elaborada a partir da Teoria da Sonata de Hepokoski & Darcy. O estudo permitiu descobrir informações biográficas inéditas e identificar a presença de elementos didáticos e de elementos musicais e extra-musicais que indiciam um propósito pedagógico na composição destas obras. In the year that marks 250 years since the birth of João José Baldi, the present study reveals the pedagogical strand of this Portuguese composer. In order to identify the presence of didactic elements in his works for keyboard instruments, a biographical research, a survey of the respective works and a study and comparison of the sources were performed, as well as a musical analysis based on a grid elaborated from the Sonata Theory of Hepokoski & Darcy. The study allowed to discover new biographical information and to identify the presence of didactic elements and of musical and extramusical elements that indicate a pedagogical purpose in the composition of these works.publishersversionpublishe

La confrérie Madaniyya

Issu d’une enquête de terrain réalisée en 2003, cet article étudie, en profondeur, les pratiques d’une confrérie soufie en France. Il démontre que ces pratiques remplissent, hormis la fonction rituelle, d’autres fonctions d’ordre social et symbolique : sociabilité, reproduction collective de la réalité et fédération. Cependant, ces mécanismes de fédération génèrent, au sein même de cette organisation, des luttes pour le pouvoir, agitant cette minorité. L’enjeu théorique de cet article est d’esquisser une théorie de conflits dans l’Islam des minorités en France.Originated within the framework of a field study realized in 2003, this article analyses in depth the practices of a Sufi brotherhood in France. It demonstrates that these practices fulfil, besides a ritual function, other functions of social and symbolic order: sociability, collective reproduction of the reality and federation. However, the mechanisms of federation are generating power struggles inside of the organization which shatter this minority. The theoretical challenge of this article is to outline a theory of conflicts within the Islam of minorities in France

Overview on Mediterranean Shark’s Fisheries: Impact on the Biodiversity

Bibliographic analysis shows that the Mediterranean Sea is a hot spot for cartilaginous species biodiversity, including sharks, rays, and chimaeras; 49 sharks and 36 rays were recorded in this region. However, they are by far the most endangered group of marine fish in the Mediterranean Sea. The IUCN Red List shows clearly the vulnerability of elasmobranchs and the lack of data; 39 species (53% of 73 assessed species) are critically endangered, endangered, or vulnerable. The biological characteristics of elasmobranchs (low fecundity, late maturity, and slow growth) make them more vulnerable to fishing pressure than most teleost fish. Overfishing, the wide use of nonselective fishing practices, and habitat degradation are leading to dramatic declines of these species in the Mediterranean Sea. In general, elasmobranchs are not targeted but are caught incidentally. In many fisheries, they are, however, often landed and marketed. A decline in cartilaginous fish species landings has been observed while fishing effort has generally increased. Better understanding of the composition of incidental and targeted catches of sharks by commercial fisheries are fundamentally important for the conservation of these populations. Moreover, problems encountered by elasmobranchs in the area are highlighted, and conservation measures are suggested

Biología reproductiva de Mustelus punctulatus (Risso, 1826) (Condrictios: Triakidae) del Golfo de Gabès, Mediterráneo central

Specimens of Mustelus punctulatus were collected between January 2002 and December 2005 from commercial fisheries in the Gulf of Gabès (central Mediterranean Sea). Males and females reached a maximum total length (TL) of 111 and 122 cm respectively. Males matured between 76 and 88.5 cm TL, with a size at maturity (TL50) of 81.4 cm TL. Females matured between 88 and 100 cm TL with a TL50 of 95.6 cm. Females had an annual reproductive cycle. Mating occurred through late-May and June. Ovulation occurred from early July to mid-August with parturition occurring from mid-May to early June, after a gestation period of 11 months. The size at birth was estimated to be 24.5 to 30.5 cm TL. Positive linear relationships were detected between the TL of mature females and ovarian and uterine fecundities. Mustelus punctulatus is an opportunistic predator that consumes a wide range of demersal and benthic prey items. It preys mainly on crustaceans, teleosts and molluscs. Polychaetes, sipunculids, echinoderms and tunicates are also consumed. The species change their main food item as they grow, from crustaceans to teleosts then to molluscs.Entre enero de 2002 y diciembre de 2005 se recolectaron ejemplares de Mustelus punctulatus, a partir de las pesquerías comerciales del Golfo de Gabès (Mediterráneo central). Los machos y las hembras alcanzaron una longitud total (LT) de 111 y 122 cm, respectivamente. Los machos maduran entre 76 y 88.5 cm LT, con una talla de primera madurez (LT50) de 81.4 cm. Las hembras maduran entre 88 y 100 cm de LT, con una LT50 de 95.6 cm. Las hembras tuvieron un ciclo reproductivo anual. El apareamiento tiene lugar desde finales de mayo y a lo largo de junio. La ovulación ocurre desde principios de julio hasta mediados de agosto y el parto desde mitad de mayo hasta principios de junio, después de un periodo de gestación de 11 meses. La talla de nacimiento se estimó en 24.5-30.5 cm LT. Se detectó una relación lineal positiva entre la LT de las hembras maduras y la fecundidad ovárica y uterina. Mustelus punctulatus es un depredador oportunista, que consume un amplio rango de presas bentónicas y demersales. Se alimenta principalmente de crustáceos, teleósteos y moluscos. También consume poliquetos, sipuncúlidos, equinodermos y tunicados. Al crecer, la especie cambia su principal alimento, de crustáceos a teleósteos y posteriormente, moluscos