Seasonality of major aerosol species and their transformations in Cairo megacity

摘要: 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 nitrate, sulphate, ammonium, chloride, sodium and calcium). Data subsequently obtained constitute one the longest more detailed dataset related aerosols, offer opportunity investigate seasonal trends. Dust (derived calcium measurements) displayed maximum concentrations in spring winter, due frequent dust storms, but also high background concentration levels (∼50 μg m −3 ) all year long. Within these particles, about 40% average Ca 2+ was found be associated with SO 4 2− , NO 3 − and/or Cl pointing out “dust anthropization” processes subsequent climatic impact regional scale. Seasonal variations non-dust equally distributed between carbonaceous ions, observed, order 100 μg m autumn 60 μg m summer. High non-sea-salt chloride (up 15 μg m monthly basis), likely industrial origin, observed winter. During “Black Cloud” event, biomass burning originating rice straw Nile Delta have shown account 12%, 35% 50% EC, WIOC WSOC mass concentrations, respectively. Finally, relatively low WSOC/OC ratios (∼1/3) long, calling investigation water-solubility agricultural waste, that secondary formed dry atmospheres.