Ozonolysis of b-pinene at conditions relevant for indoor environments: Influence of temperature on the composition of secondary organic aerosol.

Ubiquitous use of fragrances and air fresheners in the indoor environment may pose health implications for consumers because of the reaction of terpenes with ozone, which generates not only harmful gas phase products, such as formaldehyde, but also secondary organic aerosol (SOA) consisting of nanometer-sized particles. In outdoor air, SOA formation is strongly linked to biogenic emissions and may play a role in climate change. In order to gain information relevant for the modelling of nano-particle formation indoors as well as outdoors, the composition of SOA from beta-pinene (170-400 ppbV) and ozone (60-120 ppbV) was studied over a broad temperature range (278-307 K). Within less than 5 min of reaction time a nucleation burst of SOA particles appeared in all experiments (5-7 x 10(5) particles per cm(3)) measurable down to a diameter of 6 nm. As the reactions proceeded, the nano-particles grew in diameter by condensation and coagulation and reached the size of 400-600 nm within 30 min. This caused a steady increase in the particle mass concentration of up to several hundreds mu g/m(3). SOA formation tended to decrease with temperature in the order of 1.3% per degree K. Thirteen reaction products were quantified in SOA, most of which being multifunctional carboxylic acids and carbonyls. Cis-pinic acid was the most abundant compound followed by isomers of hydroxypinonic acid, pinolic acid, and pinaketone (no-pinone). The SOA composition varied with temperature consistent with a Clausius-Clapeyron type temperature dependence of the reaction products' partition coefficients.