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Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols
Abstract Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.
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Highlights We measured mass absorption coefficients for a number of different types of SOA. We estimated the rates of condensed-phase photochemical processes in SOA. These processes can potentially be as fast as oxidation of SOA by gas-phase radicals.
Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols
Abstract Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.
Graphical abstract Display Omitted
Highlights We measured mass absorption coefficients for a number of different types of SOA. We estimated the rates of condensed-phase photochemical processes in SOA. These processes can potentially be as fast as oxidation of SOA by gas-phase radicals.
Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols
Romonosky, Dian E. (author) / Ali, Nujhat N. (author) / Saiduddin, Mariyah N. (author) / Wu, Michael (author) / Lee, Hyun Ji (Julie) (author) / Aiona, Paige K. (author) / Nizkorodov, Sergey A. (author)
Atmospheric Environment ; 130 ; 172-179
2015-10-07
8 pages
Article (Journal)
Electronic Resource
English