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Modeling Secondary Organic Aerosol Formation from Fuel Combustion and Evaporation, Using Box Model and Primary and Secondary Source Apportionment of Fine Particulate Matter, Using PMF Receptor Model

Esmaeilirad, Sepideh | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52774 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hosseini, Vahid; Shamloo, Amir
  7. Abstract:
  8. Focus of the present research is on the study and cognition of sources of carbonaceous compounds present in PM2.5, particularly secondary organic carbon. For this purpose, two different approaches were used. The first approach investigates the SOA formation from internal combustion engines exhaust and unburned fuel (bottom-up approach). The second approach studies the contribution of each of the primary and secondary sources to PM2.5 mass, whereby secondary organic carbon share is obtained (top-down approach). Modeling SOA formation from vehicles exhaust showed that diesel vehicles have greater SOA formation potential than gasoline vehicles, due to large amount of S/IVOCs present in their exhaust gases. However, SOA mass yields for newer gasoline vehicles are higher than both older gasoline vehicles and diesel vehicles and this is due to the low level of NO emitted from newer gasoline vehicles. Among common carburetor motorcycles, those with 150 cc and 200 cc engine volume have the highest SOA formation potential. While, SOA emission factor (based on fuel consumption and traveled distance) is higher for 125 cc motorcycles. Average SOA formation from carburetor motorcycles is 60 times higher than direct emission of particles from a Euro IV passenger car and 20 times higher than direct emission of PM from Euro II (or better standard) motorcycles. In the second approach, the concentration of carbonaceous compounds, metallic elements and organic markers was measured for 24-hour PM2.5 samples, from two residential urban sites in Tehran. Then, Positive matrix factorization model (PMF) was applied to this dataset whereby primary and secondary sources of PM2.5 were determined. These sources include: traffic exhaust, biomass burning, industries, nitrate-rich, sulfate-rich, dust, traffic non-exhaust and heavy fuel combustion. Results showed that traffic exhaust has an annual contribution of 42.2% to total quantified PM2.5 mass. Sulfate and nitrate factors, which are linked to secondary aerosol formation, were the next major contributors. A survey of the correlations of different factors between the two sites revealed that traffic exhaust and biomass burning are local sources, while dust, heavy fuel combustion and industrial emissions are regional sources. In addition, investigating water soluble organic carbon measurements and the amount of OC apportioned by nitrate-rich and sulfate-rich factors showed that almost 20% of organic carbon in PM2.5 samples is water-soluble and is most probably produced by secondary photo-oxidation processes in the atmosphere. By converting secondary OC to secondary OM, SOA contribution to total PM2.5 mass is anticipated to be less than 10%. Results of this study indicate that gas- and particle-phase pollutants emitted from fossil fuel combustion (mobile and stationary) are the principal origin of both primary and secondary fine aerosols
  9. Keywords:
  10. Particulate Matter Less than 2.5 mm ; Volatile Organic Compound (VOC) ; Sources Apportionment ; Positive Matrix Factorization (PMF) ; Organic Molecular Markers ; Metallic Elements ; Secondary Organic Aerosols (SOA) ; Semi-Volatile Organic Compounds ; Gas/Particle Partitioning ; Effective Saturation Vapor Concentration ; Volatility Basis Set (VBS)Approach ; Chemical Speciation

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