Can secondary organic aerosol formed in an atmospheric simulation chamber continuously age? |
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Authors: | Li Qi Shunsuke Nakao Quentin Malloy Bethany Warren David R Cocker |
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Institution: | 1. Department of Chemistry & Biochemistry, Old Dominion University, Norfolk, VA 23529, USA;2. Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA |
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Abstract: | This work investigates the oxidative aging process of SOA derived from select aromatic (m-xylene) and biogenic (α-pinene) precursors within an environmental chamber. Simultaneous measurements of SOA hygroscopicity, volatility, particle density, and elemental chemical composition (C:O:H) reveal only slight particle aging for up to the first 16 h of formation. The chemical aging observed is consistent with SOA that is decreasing in volatility and increasing in O/C and hydrophilicity. Even after aging, the O/C (0.25 and 0.40 for α-pinene and m-xylene oxidation, respectively) was below the OOAI and OOAII ambient fractions measured by high-resolution aerosol mass spectra coupled with Positive Matrix Factorization (PMF). The rate of increase in O/C does not appear to be sufficient to achieve OOAI or OOAII levels of oxygenation within regular chamber experiment duration. No chemical aging was observed for SOA during dark α-pinene ozonolysis with a hydroxyl radical scavenger present. This finding is consistent with observations by other groups that SOA from this system is comprised of first generation products. |
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