https://www.peren-revues.fr/pollutionatmospherique/1850 Entrées d’index fr 0 https://www.peren-revues.fr/pollutionatmospherique/1547 Quarante et un capteurs passifs ont été installés au voisinage de la cimenterie Holcim-Oujda située dans le couloir Naima-El Aioun. Ces capteurs reçoivent les retombées de poussières qui se déposent par gravité. L’analyse de ces retombées par diffraction des rayons X (DRX) s’est avérée une méthode efficace pour détecter le traceur de l’impact des poussières émises par la cimenterie. En effet, elle permet la séparation et l’identification des poussières d’origine industrielle (cimenterie) et celles d’origine naturelle.La diffraction des rayons X a montré également que les poussières émises par la cheminée, déposées sur les plantes ou recueillies par les capteurs passifs installés à l’intérieur de l’usine, ne contiennent pas de ciment. Il faut souligner toutefois que leur principale composante minéralogique est la calcite. Quant aux poussières naturelles, elles sont plutôt caractérisées par le quartz (SiO2) en tant que principale composante minéralogique. Ainsi, le rapport calcite/quartz équivalent au rapport poussières industrielles/poussières naturelles peut être considéré comme un bon traceur qui permettra de suivre la dispersion de la pollution atmosphérique particulaire issue de la cimenterie dans l’environnement du couloir Naima-El Aioun. The Naima-El Aioun corridor is a semi-arid rural zone, characterized by a dusty atmosphere. Indeed, it includes the Holcim cement factory with its two raw material careers (limestone and clay). Furthermore, the very frequent winds remove easily the soil dusts of this area which contribute highly to the aerosols formation. Before this situation, the agriculturists are alarmed of the environment state in their territory and more especially the impact of the dusts emitted by the Holcim factory. In fact, in this type of industry dust can be emitted at each stage of the manufacturing cement process: mine shootings, extraction, transportation, storage, handling, production, etc. These types of dust can be emitted in significant quantities (170 tons on average per month during the year 2001 for example). Generally, these particular emissions are of mineral origin and might have some impacts on the receiving environments as air, water, soil and vegetation.The Portland cement produced in the Holcim-Oujda factory is constituted of a mixture of limestone (80%), clay (20%) and of other corrective materials in very few proportion such as, iron (Fe2O3), bauxites (Al2O3) and sand (SiO2) which are added often to the mixture to reach the wished chemical composition. The clinker is the fundamental matter of the cement. It results from the calcination of the pre-homogenized mixture at a very elevated temperature about 1450°C. The cement is obtained by grinding the nodules of the clinker and by addition of gypsum and other corrective componentsThe mineralogical analysis by X-rays diffraction shows that the mineralogical composition of the dusts emitted by the Holcim chimney is similar to the pre-homogenized mixture (clay + limestone), and that the composition of soils is similar to the clays used by the cement factory. In addition, the dusts given out by the Holcim chimney and those deposited on the plants and in the captor of the immediate neighbourhoods of the factory do not contain cement. They are relatively characterized by an elevated proportion of calcite CaCO3 and dolomite (CaMg)CO3. The total dust fell again deposited in the passive captor installed in rural townships neighbouring the cement factory have been also analyzed by XRD which proves that they are also deprived of cement and are characterized by a high proportion of quartz (SiO2) resulting from the soil re-mobilization. So the calcite/quartz ratio equivalent to industrial dust/natural dust could be used as a marker of the industrial particulate pollution due to the Holcim-Oujda factory.Besides of quartz, the principal mineral phase of the natural dusts collected by the passive captors are mainly composed by the dolomite and the calcite resulting from the Jurassic carbonate belt of Beni Snassen and Oujda Mountains, and by the plagioclases and feldspars coming from quaternary and Triassic basalts and of Sidi Soltane granite and by the argillaceous minerals (illite and kaolin) which are present in few proportions and originated from the quaternary soils and Palaeozoic schist. These mineral phases are enough constant in the total dust: they represent the background of the aerosols of the Naima-El Aioun corridor. jeu., 23 mai 2013 11:38:22 +0200 lun., 02 nov. 2015 14:45:37 +0100 https://www.peren-revues.fr/pollutionatmospherique/1547