OH- and O3-initiated atmospheric degradation of camphene: product yields and mechanisms

ELIZABETH GAONA COLMÁN, MARÍA B. BLANCO, IAN BARNES AND MARIANO A. TERUEL

San Francisco

Congreso; Atmospheric Chemical Mechanisms; 2016

Camphene (2, 2-dimethyl-3-methylenebicyclo[2.2.1]heptane) is a bicyclic monoterpene, which is emitted to the atmosphere by vegetation. It is one of the most abundant monoterpene emitted from plants such as Pinus sylvestris (Komenda and Koppmann. 2002), Abies alba (Moukhtar et al. 2006) and Echinacea species (Mazza and Cottrel. 1999). Volatile organic compounds release from vegetation can have several functions such as attract pollinators, serve as signaling between plants and as a defense mechanism against herbivores (Kesselmeier and Staudt.1999; Baldwin et al. 2006; Metlen et al. 2009; Novoplansky. 2009; Holopainen and Gershenzon. 2010; War et al. 2012). ). Once in the atmosphere, this monoterpene reacts with trace oxidants (OH and NO3 radicals, and O3 molecules) leading to the formation of wide variety of oxygenated compounds and secondary organic aerosol (SOA) (Calogirou et al. 1999; Atkinson and Arey. 2003. In this sense, product studies have been performed at (298 ± 2) K and 760 Torr of synthetic air for the OH reactions in the absence and presence of NOx, and for O3 molecules at (298 ± 2) K and 750 Torr of synthetic air. For OH reaction the obtained molar products yields were: acetone (10 ± 2) % and (33 ± 6) %, and formaldehyde (3.6 ± 0.7) % and (10 ± 2) % in the absence and presence of NOx, respectively. Formaldehyde was the unique product quantified due to O3 reaction obtaining a yield of (29 ± 6) %. The experiments were performed in an atmospheric chamber coupled with a FTIR spectroscopy at 298 K and atmospheric pressure. Taking into account that monoterpenes are the main emitted biogenic compounds together with isoprene (Guenther el al. 1995 and Zhihui et al. 2003), a well-established experimental study of their atmospheric reaction pathways are fundamental for assessing the oxidative capacity of the atmosphere and secondary aerosol formation (SOA) and also contribute with experimental data for atmospheric modeling.