Fragmentation vs. functionalization: chemical aging and organic aerosol formation Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
25 Oct 2011
Received: 19 Apr 2011 – Published in Atmos. Chem. Phys. Discuss.: 05 May 2011 Abstract. The transformation process that a carbon backbone undergoes in the
atmosphere is complex and dynamic. Understanding all these changes for all
the species in detail is impractical; however, choosing different molecules
that resemble progressively higher stages of oxidation or aging and studying
them can give us an insight into general characteristics and mechanisms.
Here we determine secondary organic aerosol (SOA) mass yields of two
sequences of molecules reacting with the OH radical at high NOx. Each
sequence consists of species with similar vapor pressures, but a succession
of oxidation states. The first sequence consists of n-pentadecane,
n-tridecanal, 2-, 7-tridecanone, and pinonaldehyde. The second sequence
consists of n-nonadecane, n-heptadecanal and cis-pinonic acid. Oxidized molecules
tend to have lower relative SOA mass yields; however, oxidation state alone
was not enough to predict how efficiently a molecule forms SOA. Certain
functionalities are able to fragment more easily than others, and even the
position of these functionalities on a molecule can have an effect.
n-Alkanes tend to have the highest yields, and n-aldehydes the lowest.
n-Ketones have slightly higher yields when the ketone moiety is located on the
side of the molecule and not in the center. In general, oxidation products
remain efficient SOA sources, though fragmentation makes them less effective
than comparable alkanes.
Revised: 16 Sep 2011 – Accepted: 23 Sep 2011 – Published: 25 Oct 2011
Citation: Chacon-Madrid, H. J. and Donahue, N. M.: Fragmentation vs. functionalization: chemical aging and organic aerosol formation, Atmos. Chem. Phys., 11, 10553-10563, doi:10.5194/acp-11-10553-2011, 2011.