Utilisation des lichens comme bio-indicateurs de la pollution atmosphérique par le plomb, cadmium et zinc de la région de Rabat-Sale-Zemmour-Zaêr (Maroc)

Au Nord-Ouest du Maroc, la région de Rabat-Salé-Zemmour-Zaêr présente une importance socioéconomique pour le royaume. En effet, elle est sujette à deux sources de pollution; le trafic routier et les rejets des poteries. Considérant le risque de contamination métallique de l’Homme et de l’environnement, une étude a été conduite pour évaluer la pollution métallique de l’atmosphère. Elle a porté sur les bioindicateurs lichens (Xanthoria Parietina). C’est ainsi que des échantillons de thalle de Xanthoria Parietina ont été prélevés au cours de la période située entre janvier et juillet 2007 et trois éléments métalliques Plomb(Pb), Cadmium(Cd) et Zinc(Zn) ont été détectés. Les résultats de suivi spatial obtenus au niveau des quatre stations étudiées (Kamra, Centre ville, Oulja et Allal Behraoui) ont révélé des concentrations moyennes mensuelles dépassant les normes requises à l’exception de la station de Allal Behraoui. Les résultats de suivi temporel obtenus au niveau des lichens montrent que la variation saisonnière atmosphérique des métaux est très marquée avec des teneurs plus élevées en hiver et plus basses en été.Mots-clés : métaux lourds, lichens, plomb, cadmium, zinc, Rabat, salé, Zemmour, Zaêr, Maroc

Bacterial adhesion and inactivation on Ag decorated TiO-nanotubes under visible light Effect of the nanotubes geometry on the photocatalytic activity

International audienceThis study investigates the effect of the diameter of TiO nanotubes and silver decorated nanotubes on optical properties and photocatalytic inactivation of Escherichia coli under visible light. The TiO nanotubes (TiO-NTs) were prepared using the electrochemical method varying the anodization potential starting from 20 V until 70 V. The Ag nanoparticles were carried out using the photoreduction process under the same experimental conditions. The diameter size was determined using the scanning electronic microscopy (SEM). TiO-NTs diameter reached ∼100 nm at 70 V. Transmission electronic microscopy (TEM) imaging confirmed the TiO-NTs surface decoration by silver nanoparticles. The Ag-NPs average size was found to be equal to 8 nm. The X-Ray diffraction (XRD) analysis confirm that all TiO-NTs crystallize in the anatase phases regardless the used anodization potential. The decrease of the photoluminescence (PL) intensity of Ag NPs decorated TiO-NTs indicates the decrease of the specific area when the nanotubes diameter increases. The UV-vis absorbance show that the absorption edges was bleu shifted with the increasing of nanotubes diameter, which can be explained by the increase of the crystallites average size. The bacterial adhesion and inactivation tests were carried in the dark and under light. Bacteria were seen to adhere on TiO-NTs in the dark; however, under light the bacteria were killed before they establish a strong contact with the TiO-NTs and Ag/TiO-NTs surfaces. Bacterial inactivation kinetics were faster when the anodizing potential of the NTs-preparation increases. A total bacterial inactivation was obtained on ∼100 nm nanotubes diameter within 90 min. This result was attributed to the enhancement of the TNTs crystallinity leading to reduced surface defects. Redox catalysis was seen to occur under light on the TiO-NTs and Ag/TiO-NTs. the photo-induced antibacterial activity on the AgO/AgO decorated TiO-NTs was attributed to the interfacial charge transfer mechanism (IFCT)

Relativistic quantum mechanical calculations of electron-impact broadening for spectral lines in Be-like ions

Aims. We present relativistic quantum mechanical calculations of electron-impact broadening of the singlet and triplet transition 2s3s <- 2s3p in four Be-like ions from N IV to Ne VII. Methods. In our theoretical calculations, the K-matrix and related symmetry information determined by the colliding systems are generated by the DARC codes. Results. A careful comparison between our calculations and experimental results shows good agreement. Our calculated widths of spectral lines also agree with earlier theoretical results. Our investigations provide new methods of calculating electron-impact broadening parameters for plasma diagnostics.Astronomy & AstrophysicsSCI(E)EI2ARTICLEnull54

Electron-impact broadening parameters for Be II, Sr II, and Ba II spectral lines

Aims. We present results of the electron-impact broadening parameters (i.e., widths and shifts) of spectral lines in singly ionized Be II, Sr II, and Ba II ions, calculated by using our relativistic quantum mechanical methods. Methods. In these calculations, Dirac R-matrix methods were used to solve (N + 1)-electron colliding systems to obtain the required scattering matrices. The dimensionless collision strength Omega(epsilon) is calculated as a function of incident electron energies epsilon. Results. The present line-broadening parameters are required for future spectral analysis by means of state-of-the-art nonlocal thermodynamic equilibrium atmospheres, which is now hampered largely by the paucity of reliable atomic and accurate line-broadening data tables. Our results for the spectral line-broadening parameters in the case of three ions obtained for a set of electron temperatures at an electron density 10(17) cm(-3) show very good agreement with other theoretical calculations, and are much closer to the available experimental measurements.Astronomy & AstrophysicsSCI(E)EI2ARTICLEnull55