AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Characterization of Atmospherically Important Organic Radicals in the Gas and Particle Phase
STEVEN CAMPBELL, Chiara Giorio, Markus Kalberer, University of Cambridge
Abstract Number: 533 Working Group: Health Related Aerosols
Abstract When volatile organic compounds are oxidized in the atmosphere less volatile compounds form which partition into the condensed phase and contribute to organic aerosol mass. The formation and composition of secondary organic aerosol (SOA), is poorly understood (Hallquist et al., 2009).
Epidemiological studies showed close correlations between exposure to ambient aerosol and adverse health effects, although toxicological mechanisms are largely unknown. It is likely that particle-bound reactive oxygen species and especially organic radicals play a key role by promoting oxidative stress which can lead to various pulmonary diseases (Donaldson et al., 2003). In addition, the role of organic radicals in SOA formation and composition is entirely unknown. The analysis of these species represents an analytical challenge due to their characteristic high reactivity and low concentrations.
The aim of the present work was the development of a method to characterise atmospherically important organic radicals in the gas and the particle phase by stabilisation with spin traps (5,5-dimethyl-pyrroline N-oxide, DMPO and N-tert-butyl-alpha-phenylnitrone, PBN) to facilitate chemical analysis.
Gas phase and particle-bound organic radicals were generated in a flow tube by reacting oleic acid or alpha-pinene (two SOA model systems) with ozone and OH radicals. The radical intermediates formed during these reactions were then scavenged and stabilized in impingers containing the spin trap and characterised via Ultra-High Resolution Mass Spectrometry. A number of radical-spin trap adducts have been identified in the gas and particle phase. In the most simple system, the ozonolysis of alpha-pinene, only one radical-spin trap adduct was identified which is identical to the expected product.
The reaction with OH yields more complex mixtures of radical-spin trap adducts, which will be discussed and compared with theoretically expected radical formation.
References
Donaldson, et al., 2003. Free Radical. Biology., 34, 1369-1382.
Hallquist, et al., 2009. Atmos. Chem. Phys., 9, 5155-5236.