Aerosol complexity in megacities: From size-resolved chemical composition to optical properties of the Beijing atmospheric particles
Résumé
Megacities need adapted tools for the accurate modeling of aerosol impacts. For this purpose a new experimental data processing has been worked out for Beijing aerosols as case study. Size-resolved aerosol particles were extensively sampled during winter and summer 2003 and subsequently fully chemically characterized. The product is an aerosol model presenting a new particle pattern (mode number, size and chemistry) without any prerequisite constrain either on the mode number or on each mode chemical composition. Six modes were found and five of them consistently appear as internally mixed particles organized around a black carbon or a dust core coated by organic and/or inorganic material. Data were checked by robust comparisons with other experimental data (particle number, sunphotometer-derived derived data). We found the presence of two accumulation modes in different internal mixing and optical calculations show that the Beijing aerosol single scattering albedo (ωo # 0.90) is significantly higher than expected. Such an approach would allow realistic modeling of atmospheric particle impacts under complex situations.
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