Particle Phase Acidity and Oligomer Formation in Secondary Organic Aerosol

Abstract

A series of controlled laboratory experiments are carried out in dual Teflon chambers to examine the presence of oligomers in secondary organic aerosols (SOA) from hydrocarbon ozonolysis as well as to explore the effect of particle phase acidity on SOA formation. In all seven hydrocarbon systems studied (i.e., alpha-pinene, cyclohexene, 1-methyl cyclopentene, cycloheptene, 1-methyl cyclohexene, cyclooctene, and terpinolene), oligomers with MW from 250 to 1600 are present in the SOA formed, both in the absence and presence of seed particles and regardless of the seed particle acidity. These oligomers are comparable to, and in some cases, exceed the low molecular weight species (MW < 250) in ion intensities in the ion trap mass spectra, suggesting they may comprise a substantial fraction of the total aerosol mass. It is possible that oligomers are widely present in atmospheric organic aerosols, formed through acid- or base-catalyzed heterogeneous reactions. In addition, as the seed particle acidity increases, larger oligomers are formed more abundantly in the SOA; consequently, the overall SOA yield also increases. This explicit effect of particle phase acidity on the composition and yield of SOA may have important climatic consequences and need to be considered in relevant models.

Natural Background Visibility and Regional Haze Goals in the Southeastern United States

“…[33][34][35][36][37][38][39][40] The exact role of VOCs in the nucleation process is a subject of debate, although the fact that biogenic VOCs are much more reactive than anthropogenic VOCs 41 suggests that they play a role from the outset. Also, the acidity of seed particles appears to enhance the formation of SOA, [42][43][44] which may mean that current organic particle formation rates from natural emissions are greater than they would be under natural conditions because of the presence today of global anthropogenic inorganic acidic pollution.…”

High-molecular-weight esters in &lt;i&gt;α&lt;/i&gt;-pinene ozonolysis secondary organic aerosol: structural characterization and mechanistic proposal for their formation from highly oxygenated molecules

“…Gao et al (2004) assigned the MW 358 α-pinene/O 3 compound to a dehydration product formed between the gem-diol forms of two norpinonic acid molecules. Iinuma et al (2004) reported MW 354 and 370 α-pinene/O 3 products that were enhanced in acidic conditions and tentatively assigned them to reaction products between the gem-diol of pinonaldehyde and pinonaldehyde, and between pinonaldehyde and hydroxypinonaldehyde, respectively.…”

Terpenylic acid and related compounds: precursors for dimers in secondary organic aerosol from the ozonolysis of α- and β-pinene

“…Higher-MW products either correspond to non-covalent dimers between monomeric carboxylic acids that are held together by hydrogen bonds (e.g., Hoffmann et al, 1998;Claeys et al, 2009) or to covalent dimers between monomeric carboxylic acids that are connected through covalent bonds, such as, esters (e.g., Hamilton et al, 2006;Szmigielski et al, 2007;Müller et al, 2008) and oligomers formed through gem-diol intermediates (e.g., Gao et al, 2004;Iinuma et al, 2004;Tolocka et al, 2004;Docherty et al, 2005) or aldol condensation reactions (e.g., Tolocka et al, 2004). These heterogeneous processes are consistent 9384 F. Yasmeen et al: Terpenylic acid and related compounds: precursors for dimers in secondary organic aerosol with the observation that sulfuric acid seed aerosol catalyzes the formation of SOA (e.g., Jang et al, 2002Jang et al, , 2003Czoschke et al, 2003;Iinuma et al, 2004).…”