Particle mass yield from β-caryophyllene ozonolysis
1School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
2Division of Environment, Hong Kong University of Science and Technology, Hong Kong, China
3Department of Chemistry, Amherst College, Amherst, Massachusetts, USA
4Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
Abstract. The influence of second-generation products on the particle mass yield of β-caryophyllene ozonolysis was systematically tested and quantified. The approach was to vary the relative concentrations of first- and second-generation products by controlling ozone concentration, while observing the change in particle mass yield. For all organic particle mass concentrations Morg of this study (0.5 < Morg < 230 μg m−3), the data show that particle-phase organic material was in large part composed of second-generation products. For 0.5 < Morg <10 μg m−3, a range which overlaps with atmospheric concentrations, the particle mass yield was not sensitive to ozone exposure, implying that the constituent molecules were rapidly produced at all investigated ozone exposures. In contrast, for Morg > 10 μg m−3 the particle mass yield increased with ozone exposure. These different dependencies on ozone exposure with M org are explained by a combination of the ozonolysis lifetimes of the first-generation products and the volatility distribution of the resulting second-generation products. First-generation products that have short lifetimes produce low-volatility second-generation products whereas first-generation products that have long lifetimes produce high-volatility second-generation products. The ultimate particle mass yield was defined by mass-based stoichiometric yields α0 = 0.17 ± 0.05, α1 = 0.11 ± 0.17, and α2 = 1.03 ± 0.30 for corresponding saturation concentrations of 1, 10, and 100 μg m−3. Terms α0 and α1 had low sensitivity to the investigated range of ozone exposure whereas term α2 increased from 0.32 ± 0.13 to 1.03 ± 0.30 as the ozone exposure was increased. These findings potentially allow for simplified yet nevertheless accurate parameterizations in air quality and climate models that seek to represent the ozonolysis particle mass yield of certain classes of biogenic compounds.