Maha Harhash
Assistant Lecturer
Astronomy and Meteorology Dept., Faculty of Science, Cairo University (email)
Seasonality of major aerosol species and their transformations in Cairo megacity
- Citation:
- Favez, O., H. Cachier, jean Sciare, S. C. Alfaro, T. M. El-Araby, M. A. Harhash, and M. M. Abdelwahab, "Seasonality of major aerosol species and their transformations in Cairo megacity", Atmospheric Environment, vol. 42, no. 7, pp. 1503 - 1516, 2008.
Abstract:
Bulk aerosols sampled on a weekly basis at two Cairo (Egypt) urban sites from January 2003 to May 2006 were analysed for their chemical composition of major aerosol species (elemental carbon, water soluble/insoluble organic carbon, nitrate, sulphate, ammonium, chloride, sodium and calcium). Data subsequently obtained constitute one of the longest and more detailed dataset related to Cairo aerosols, and offer the opportunity to investigate seasonal trends. Dust aerosols (derived from calcium measurements) displayed maximum concentrations in spring and winter, due to frequent dust storms, but also high background concentration levels (∼50μgm−3) all year long. Within these particles, about 40% on average of Ca2+ was found to be associated with SO42−, NO3− and/or Cl−, pointing out “dust anthropization” processes and their subsequent climatic impact on a regional scale. Seasonal variations of non-dust aerosols, equally distributed between carbonaceous aerosols and ions, were also observed, with concentrations of the order of 100μgm−3 in autumn and winter, and of 60μgm−3 in spring and summer. High concentration levels of non-sea-salt chloride (up to 15μgm−3 on a monthly basis), likely of industrial origin, were observed in autumn and winter. During the autumn “Black Cloud” event, biomass burning aerosols originating from rice straw burning in the Nile Delta have shown to account for 12%, 35% and 50% of Cairo EC, WIOC and WSOC mass concentrations, respectively. Finally, relatively low WSOC/OC ratios (∼1/3) were obtained all the year long, calling for more investigation on the water-solubility of organic aerosols originating from the burning of agricultural waste, and on that of secondary organic aerosols formed in dry urban atmospheres.
Notes:
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