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Journal of the Cameroon Academy of Sciences

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Volcanic Ash from the 1999 Eruption of Mount Cameroon Volcano: Characterization and Implications to Health Hazards

MBS Atanga, AS Van der Meerve, EM Shemamg, CE Suh, W Kruger, MS Njome, NE Asobo

Abstract


Volcanic ash from the 1999 eruption of Mount Cameroon volcano has been characterized for its particle size and shape (by scanning electron microscopy, SEM), and mineralogy (by X-ray diffractometry, XRD). Also the total fluorine (F) content of the ash was determined by the selective ion electrode method. The results show that the Mount Cameroon ash particles have a variety of shapes including fibrous, rounded, subrounded, irregular, angular, eleongated and bladed. All the ash samples have a significant proportion (~ 30%) of ash < 4 ƒÊm in size and this
is classified in occupational medicine as 'thoracic' and 'respirable' ash that is considered harmful to health. The XRD patterns show that the ash contains plagioclase feldspar, enstatite, augite and chromite, which, if fine enough may cause irritation of the respiratory tract, but they are relatively insoluble in the alveolar region. The ash lacks free silica, the main mineral in volcanic ash responsible for causing silicosis. The F concentration in the ash ranges from 46 ƒÊg/ g to 189ƒÊg/g. This is high considering that the lethal dose of F is set internationally at ~ 100ƒÊg/g. This study forms the basis for a long term monitoring of volcanic ash risk and possible mitigation measures of the Mount Cameroon volcano.

Keywords: volcanic ash, Mt. Cameroon, health hazards

Cendre de Volcan de L'Eruption de 1999 du Mont Cameroun: Caracterisation et Implications aux Risques Sanitaires.
La cendre de volcan de l'eruption de 1999 du mont Cameroun a ete caracterisee pour la dimension et la forme de ces particules (en utilisant la microscopie electronique a balayant, SEM), et mineralogie (diffractometrie a rayon X, XRD). En outre toute la teneur en fluor (F) de la cendre a ete determinee par la methode selective d'electrode d'ion. Les resultats prouvent que les particules de cendre du mont Cameroun ont une variete de formes comprenant : les fibreux, les arrondies, les sous arrondies, les irreguliers, les angulaires et les ovales. Tous les echantillons de cendre
ont une proportion significative de (~ 30 %) de cendre ayant la taille < 4 m et ceci est classifie dans la medecine du travail comme la cendre 'thoracique' et 'respirable' qui est consideree nocif a la sante. Les modeles de XRD montre que la cendre contient le feldspath de plagioclase, l'enstatite, l'augite et la chromite qui, s'ils sont assez fins, peuvent produire l'irritation de la cavite nasale mais sont relativement insolubles dans la region d'aveolaire. La cendre manque de la silice libre, qui est le minerai principal de la cendre volcanique responsable d'engendrer la silicose. La concentration de F dans la cendre s'echelonne de 189 g/g. Ceci est eleve considerant que la dose mortelle de F est place internationalement aux environs de ~ 100 g/g. Cette etude forme la base pour une surveillance a long terme du risque volcanique et des mesures possibles de reduction du volcan de mont Cameroun.

Mots cles : cendre de volcan, Mont Cameroun, risques sanitaires




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