Measurement of non-volatile particle number size distribution

• Κύριος συγγραφέας: Γκατζέλης, Γεώργιος
• Άλλοι συγγραφείς: Πανδής, Σπύρος
• Μορφή: Thesis
• Γλώσσα: English
• Έκδοση: 2015
• Θέματα: Thermodenuders; Non-volatilte particles; Θερμοαπογυμνωτές; Μη πτητικά σωματίδια; 551.56

A new experimental methodology was developed to measure the non-volatile particle number concentration, using a thermodenuder (TD). The TD was coupled with a high resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (98 %) of secondary organic aerosol (SOA) as well as freshly nucleated particles, using the TD temperature of 400 C. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of non-volatile particles from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80% of the particles survived the intense heating, suggesting that nearly all biomass burning particles had a non-volatile core. These particles consisted mostly from black carbon (BC), while organic aerosol (OA) were responsible for another 40 %. Organics that survived through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) that had not evaporated, contributing 90% of the organic mass concentration, while the other 10% was hydrocarbon-like OA (HOA) and cooking OA (COA). For periods that traffic contribution was dominant, mostly during the rush hour, 50-60% of the particles had a non-volatile core, while the rest evaporated at 400 0C. The remaining particles consisted mostly from BC, with an 80% contribution, while organics were responsible for another 15-20 %. Organics were mostly HOA and OOA, with a contribution of >95% to the organic mass concentration, while <5% was from BBOA and COA.