Measurements of Secondary Organic Aerosol from Oxidation of Cycloalkenes, Terpenes, and m-Xylene Using an Aerodyne Aerosol Mass Spectrometer

Abstract

The Aerodyne aerosol mass spectrometer (AMS) was used to characterize physical and chemical properties of secondary organic aerosol (SOA) formed during ozonolysis of cycloalkenes and biogenic hydrocarbons and photo-oxidation of m-xylene. Comparison of mass and volume distributions from the AMS and differential mobility analyzers yielded estimates of "effective" density of the SOA in the range of 0.64-1.45 g/cm3, depending on the particular system. Increased contribution of the fragment at m/z 44, C02+ ion fragment of oxygenated organics, and higher "delta" values, based on ion series analysis of the mass spectra, in nucleation experiments of cycloalkenes suggest greater contribution of more oxygenated molecules to the SOA as compared to those formed under seeded experiments. Dominant negative "delta" values of SOA formed during ozonolysis of biogenics indicates the presence of terpene derivative structures or cyclic or unsaturated oxygenated compounds in the SOA. Evidence of acid-catalyzed heterogeneous chemistry, characterized by greater contribution of higher molecular weight fragments to the SOA and corresponding changes in "delta" patterns, is observed in the ozonolysis of alpha-pinene. Mass spectra of SOA formed during photooxidation of m-xylene exhibit features consistent with the presence of furandione compounds and nitro organics. This study demonstrates that mixtures of SOA compounds produced from similar precursors result in broadly similar AMS mass spectra. Thus, fragmentation patterns observed for biogenic versus anthropogenic SOA may be useful in determining the sources of ambient SOA.

Characterization of aerosol associated with enhanced small particle number concentrations in a suburban forested environment

“…The greater contribution of smaller fragments again indicates the aerosols observed by Cottrell et al [2008] were more oxidized. The D patterns for both studies are similar to those observed for chamber-derived SOA from oxidation of a-pinene [Bahreini et al, 2005] and biogenic SOA produced in a chamber with live plant emissions [Kiendler-Scharr et al, 2009], suggesting that BVOC played a role in the formation of SOA at the Duke Forest site but not discounting influence from regional and potentially anthropogenic sources.…”

Real Time In Situ Detection of Organic Nitrates in Atmospheric Aerosols

“…Total particle mass was calculated from the SMPS data assuming a particle density of 1.2 g cm −3 which is similar to that reported in a number of studies for high-NO x SOA of terpenes (39)(40)(41)(42)(43)(44). Particle number distributions were typically centered at 100 -150 nm.…”

Secondary organic aerosol (SOA) formation from reaction of isoprene with nitrate radicals (NO<sub>3</sub>)

“…In calculating SOA yield (defined as the ratio of the organic aerosol mass formed to the mass of parent hydrocarbon reacted), knowledge of the SOA density is required. By comparing volume distributions from the DMA and mass distributions from the Q-AMS, the effective density for the SOA formed can be estimated (Bahreini et al, 2005;Alfarra et al, 2006).…”