Journal Article PreJuSER-5758

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Isoprene oxidation by nitrate radical: alkyl nitrate and secondary organic aerosol yields

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2009
EGU Katlenburg-Lindau

Atmospheric chemistry and physics 9, 6685 - 6703 ()

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Abstract: Alkyl nitrates and secondary organic aerosol (SOA) produced during the oxidation of isoprene by nitrate radicals has been observed in the SAPHIR ( Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) chamber. A 16 h dark experiment was conducted with temperatures at 289-301 K, and maximum concentrations of 11 ppb isoprene, 62.4 ppb O-3 and 31.1 ppb NOX. We find the yield of nitrates is 70 +/- 8% from the isoprene + NO3 reaction, and the yield for secondary dinitrates produced in the reaction of primary isoprene nitrates with NO3 is 40 +/- 20%. We find an effective rate constant for reaction of NO3 with the group of first generation oxidation products to be 7 x 10(-14) molecule(-1) cm(3) s(-1). At the low total organic aerosol concentration in the chamber (max=0.52 mu g m(-3)) we observed a mass yield (Delta SOA mass/Delta isoprene mass) of 2% for the entire 16 h experiment. However a comparison of the timing of the observed SOA production to a box model simulation of first and second generation oxidation products shows that the yield from the first generation products was <0.7% while the further oxidation of the initial products leads to a yield of 14% ( defined as Delta SOA/Delta isoprene(2X) where Delta isoprene(2X) is the mass of isoprene which reacted twice with NO3). The SOA yield of 14% is consistent with equilibrium partitioning of highly functionalized C-5 products of isoprene oxidation.

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Note: The Berkeley authors were supported by NSF ATM-0639847 and NSF ATM-0511829. The authors would like to thank the SAPHIR NO<INF>3</INF> intercomparison campaign team for organizing and administering the experiments in June 2007 at Forschungszentrum Julich. This work was a joint activity of the European Community Network of Excellence ACCENT, grant no. GOCE CT-2004-505337 and the EUROCHAMP project.

Research Program(s):
  1. Atmosphäre und Klima (P22)

Appears in the scientific report 2009
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