42 research outputs found
Potential of Opuntia ficus-indica for air pollution biomonitoring : a lead isotopic study
Opuntia ficus-indica (Ofi) is a long-domesticated cactus that is widespread throughout arid and semiarid regions. Ofi is grown for both its fruits and edible cladodes, which are flattened photosynthetic stems. Young cladodes develop from mother cladodes, thus forming series of cladodes of different ages. Therefore, successive cladodes may hold some potential for biomonitoring over several years the local atmospheric pollution. In this study, cladodes, roots, dust deposited onto the cladodes, and soil samples were collected in the vicinity of three heavily polluted sites, i.e., a fertilizer industry, the road side of a highway, and mine tailings. The lead content was analyzed using atomic absorption spectroscopy (AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) was used to characterize the cladode surfaces and the nature of dust deposit, and the lead isotopes were analyzed to identify the origin of Pb. The results show that (i) Ofi readily bioaccumulates Pb, (ii) the lead isotopic composition of cladodes evidences a foliar pathway of lead into Ofi and identifies the relative contributions of local Pb sources, and (iii) an evolution of air quality is recorded with successive cladodes, which makes Ofi a potential biomonitor to be used in environmental and health studies
Utilisation de la coagulation - floculation pour la dépollution des eaux de surface au Liban
Ibrahim et Ghadir sont deux riviĂšres cĂŽtiĂšres localisĂ©es aux environs de Beyrouth et exposĂ©es Ă des impacts anthropiques diffĂ©rents. L'Ă©limination des MatiĂšres en Suspension MES des eaux de ces riviĂšres a Ă©tĂ© Ă©tudiĂ©e par simple jar test couplĂ© Ă des mesures de turbiditĂ© au niveau du surnageant, et Ă une mesure de volumes des sĂ©diments. Les caractĂ©ristiques physico-chimiques des eaux avant et aprĂšs traitement sont dĂ©terminĂ©es par absorption atomique et chromatographie ionique. Les jars tests montrent que la prĂ©hydrolyse des sels d'aluminium avant leur ajout dans l'eau permet l'utilisation de plus faibles quantitĂ©s en Al pour la coagulation-floculation des eaux qui Ă©limine prĂ©fĂ©rentiellement les MatiĂšres en Suspension. Plus la turbiditĂ© initiale des eaux Ă traiter est faible, plus la concentration optimale en aluminium est moindre. L'Ă©limination des MES par coagulation-floculation est plus efficace pour la riviĂšre Ibrahim, oĂč les rejets anthropiques directs dans son cours d'eau sont moindres que ceux dans la riviĂšre Ghadir. La restabilisation dans les jars tests est marquĂ©e dans tous les essais de la riviĂšre Ibrahim. Dans les deux cas, un Ă©change cationique avec les polycations Al13 au niveau des sĂ©diments marque la libĂ©ration du calcium et l'augmentation de sa concentration dans le surnageant
Trace element carriers in combined sewer during dry and wet weather: an electron microscope investigation
International audienceThe nature of trace element carriers contained in sewage and combined sewer overflow (CSO) was investigated by TEM-EDX-Electron diffraction and SEM-EDX. During dry weather, chalcophile elements were found to accumulate in sewer sediments as early diagenetic sulfide phases. The sulfurization of some metal alloys was also evidenced. Other heavy metal carriers detected in sewage include metal alloys, some iron oxihydroxide phases and neoformed phosphate minerals such as anapaite. During rain events, the detailed characterization of individual mineral species allowed to differentiate the contributions from various specific sources. Metal plating particles, barite from automobile brake, or rare earth oxides from catalytic exhaust pipes, originate from road runoff, whereas PbSn alloys and lead carbonates are attributed to zinc-works from roofs and paint from building siding. Soil contribution can be traced by the presence of clay minerals, iron oxihydroxides, zircons and rare earth phosphates. However, the most abundant heavy metal carriers in CSO samples were the sulfide particles eroded from sewer sediments. The evolution of relative abundances of trace element carriers during a single storm event, suggests that the pollution due to the âfirst flushâ effect principally results from the sewer stock of sulfides and previously deposited metal alloys, rather than from urban surface runoff
Speciation of Organic Matter and Heavy Metals in Urban Wastewaters from an Emerging Country
International audienc
Clarification of municipal sewage with ferric chloride: the nature of coagulant species
International audienceThe nature of coagulant species formed in the system ferric chloride/municipal sewage was explored with Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (TEM-EDXS) and Fe K-edge X-ray Absorption spectroscopy. Jar-test data combined with chemical analysis of supernatant (dissolved organic carbon, iron, and phosphorus) and Fourier-Transform-Infrared spectroscopy (FTIR) of freeze-dried sediment, provided a detailed description of sewage clarification. The results showed that the nature of coagulant species evolves with Fe concentration. Up to the optimum turbidity removal, mainly iron dimers linked with one phosphate anion are detected. At higher dosages, polymers of hydrolyzed Fe appear even though PO4 still participates in the formation of coagulant species. TEM observation of freeze-dried sediments corroborates such an evolution of Fe speciation. EDXS analyses reveal that minute amounts of sulfur, silicon, aluminum, and calcium, are associated with the coagulant species. Even though the coagulant species change with Fe concentration, the destabilization mechanism, inferred from electrophoretic mobility of aggregates and the evolution of floc size under cyclic changes of stirring conditions, is equivalent with a charge neutralization of sewage colloids in the whole range of coagulant concentration